HK1138302B - Aromatic amic acid composition and method of preparing the same, and endless tubular polyimide film and method of preparing the same - Google Patents

Description

Aromatic amic acid composition, process for producing the same, endless tubular polyimide film, and process for producing the same

The application date of the present case is2004, 10 months and 8 daysApplication No. is200480042932.7The invention is named asEndless tubular polyimide filmDivisional application of

Technical Field

The present invention relates to an improved electrically non-conductive or semiconductive endless tubular polyimide film and a method for producing the same. Semiconductive endless tubular polyimide films are used, for example, as intermediate transfer belts of electrophotographic systems used in color printers, color copiers, and the like.

Background

The electrically nonconductive tubular polyimide film is generally processed into a tape shape, and is known to be used as a conveyor belt for heating an article or as a fixing belt for an electrophotographic method, for example.

A semiconductive tubular polyimide film is obtained by mixing and dispersing conductive carbon black in a nonconductive tubular polyimide film, and is used as an intermediate transfer belt for a copying machine, a printer, a facsimile machine, and a printer, for example.

As a method for producing such a non-conductive and semiconductive tubular polyimide film, a method of temporarily molding a predetermined molding material into a flat film, then connecting both ends of the film to process the film into a tubular shape, and a method of molding the film into an endless tubular film at one time by centrifugal injection molding are known. For example, the applicant of the present application also describes a method of molding by performing the centrifugal injection molding substantially without a centrifugal force in Japanese patent laid-open No. 2000-263568.

As a material for forming these tubular polyimide films, a polyamic acid (or polyamic acid) solution having a high molecular weight (usually, a number average molecular weight of about 10000 to 30000) is generally used as a polymer precursor of polyimide.

The polyamic acid solution is specifically produced by, for example, subjecting an aromatic tetracarboxylic dianhydride, such as 1, 2, 4, 5-benzenetetracarboxylic dianhydride, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride, 3 ', 4, 4' -benzophenonetetracarboxylic dianhydride, or 2, 3, 6, 7-naphthalenetetracarboxylic dianhydride, to which an acid anhydride group is bonded at a point-symmetrical position, to a polycondensation reaction with an aromatic diamine, such as p-phenylene diamine, 4, 4 '-diaminodiphenyl ether, or 4, 4' -diaminodiphenylmethane, in an equimolar amount in an organic polar solvent at a low temperature at which imidization does not occur.

The polyimide film is generally produced by 3 steps: a polyamic acid solution as a molding raw material was prepared, and the polyamic acid solution was molded into a polyamic acid film, and finally imidized to obtain a polyimide film.

However, the polyamic acid solution obtained by the above-mentioned molding method has a pot life (pot life), and therefore has a disadvantage that partial gelation is likely to occur gradually during storage. This gelation is more likely to proceed with higher temperatures and proceeds with time even at low temperatures, and even a very small amount of gelation adversely affects the physical properties of the polyimide film as the final product, and of course, causes deterioration in planarity. In particular, in the film mixed with conductive carbon black, the variability of the resistance is increased.

Further, there is a disadvantage that the solubility of the polyamic acid resin in an organic polar solvent is limited and the polyamic acid resin cannot be made to have a high concentration (the concentration of the nonvolatile component in the solution is at least 25% by weight).

Further, when carbon black is added to the polyamic acid solution, the viscosity is greatly increased, and dispersion of carbon black by impact force between balls in a dispersing machine such as a ball mill may be difficult. In general, in order to uniformly disperse carbon black in a polyamic acid solution, it is necessary to carry out pulverization of carbon black by a dispersing machine with an interfacial phenomenon called "wetting" of the disassembled carbon black by a solvent. Therefore, a method of uniformly dispersing carbon black by adding a large amount of an organic polar solvent has been adopted. However, as a result, only a low-concentration masterbatch solution containing a high concentration of carbon black can be obtained with a nonvolatile concentration of 16 wt% or less.

Moreover, the low-concentration polyamic acid solution has the following disadvantages: it is difficult to form a thick film at a time, and a large amount of solvent is required and a long time is required for the solvent to evaporate and remove.

Further, since 3 steps are required as described above, the time and cost required for the entire steps are still in the room for improvement from the viewpoint of efficiency and economy.

However, JP-A-10-182820 discloses a molding method using a polyimide precursor composition mainly composed of a monomer obtained by mixing an aromatic tetracarboxylic acid component and an aromatic diamine component in approximately equimolar amounts, and the aromatic tetracarboxylic acid component mainly composed of an asymmetric aromatic tetracarboxylic acid or an ester thereof (specifically, 2, 3, 3 ', 4' -biphenyltetracarboxylic acid or an ester thereof is 60 mol% or more). Further, Japanese unexamined patent publication Hei 10-182820 discloses a method of forming a polyimide film by applying and casting the polyimide precursor composition onto a glass plate and heating (stepwise raising the temperature between 80 and 350 ℃) the composition, wherein silver powder, copper powder, carbon black or the like can be mixed and used as a conductive paste.

However, in recent years, when the semiconductive polyimide film obtained by the above molding method is used for an electrophotographic intermediate transfer belt or the like used in a color printer, a color copier or the like, which is required to have high accuracy, there is room for further improvement in characteristics such as electric resistance.

Disclosure of Invention

In view of the problems of the prior art described above, it is an object of the present invention to provide a high-quality non-conductive or semiconductive endless (seamless) tubular polyimide film and a method for producing the film simply, efficiently, and economically.

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that: an aromatic tetracarboxylic acid component comprising a specific amount of an asymmetric aromatic tetracarboxylic acid or an ester thereof and a specific amount of a symmetric aromatic tetracarboxylic acid or an ester thereof, and an aromatic diamine component are mixed in an approximately equimolar amount to form a substantially monomer-state mixed solution, and the mixed solution is formed into a tube by a rotational molding method and is heat-treated to imidize the tube, whereby a high-quality endless tubular polyimide film can be produced.

Namely, the present invention provides the following non-conductive or semiconductive endless tubular polyimide film.

(1) An endless tubular polyimide film characterized in that,

comprising a polyimide comprising 2 or more kinds of aromatic tetracarboxylic acid components and aromatic diamine components, wherein the aromatic tetracarboxylic acid components are a mixture of 15 to 55 mol% of an asymmetric aromatic tetracarboxylic acid component and 85 to 45 mol% of a symmetric aromatic tetracarboxylic acid component,

its yield strength (sigma)_Y)120 MPa or more, and a ratio (sigma) of breaking strength to yield strength_cr/σ_Y) Is 1.10 or more.

(2) A semiconductive endless tubular polyimide film comprising a polyimide comprising a mixture of at least 2 aromatic tetracarboxylic acid components and an aromatic diamine component, the mixture comprising 15 to 55 mol% of an asymmetric aromatic tetracarboxylic acid component and 85 to 45 mol% of a symmetric aromatic tetracarboxylic acid component, and carbon black dispersed therein, the polyimide film having a surface resistivity of 10³～10¹⁵Ω/□。

(3) The semiconductive endless tubular polyimide film according to (2), wherein a standard deviation of logarithmic conversion values of surface resistivity is within 0.2, a standard deviation of logarithmic conversion values of volume resistivity is within 0.2, and a difference between the logarithmic conversion values of surface resistivity and backside resistivity is within 0.4.

The present invention has the above-described features, and more specifically, includes the following first to fourth inventions.

A. First invention

The present inventors have found that a semiconductive polyimide film of high quality can be produced by dispersing a specific amount of carbon black in a substantially monomer-state mixed solution in which an aromatic tetracarboxylic acid component comprising a specific amount of an asymmetric aromatic tetracarboxylic acid or an ester thereof and a specific amount of a symmetric aromatic tetracarboxylic acid or an ester thereof and an aromatic diamine component are mixed in substantially equimolar amounts, molding the semiconductive polyimide precursor composition obtained by the dispersion into a tube by a rotational molding method, and performing heat treatment to effect imidization.

The present inventors have further studied based on this finding, and as a result, the present invention (hereinafter also referred to as "first invention") has been completed.

That is, the first invention provides the following non-conductive or semiconductive endless tubular polyimide film and a method for producing the same.

(4) A method for producing an endless tubular polyimide film, characterized in that a substantially monomer-state mixed solution in which an aromatic tetracarboxylic acid component comprising 15 to 55 mol% of an asymmetric aromatic tetracarboxylic acid or an ester thereof and 85 to 45 mol% of a symmetric aromatic tetracarboxylic acid or an ester thereof and an aromatic diamine component are mixed in substantially equimolar amounts is formed into a tubular article by a rotational molding method, and the tubular article is subjected to heat treatment and imidization.

(5) A method for producing a semiconductive endless tubular polyimide film, characterized in that in a substantially monomer-state mixed solution in which an aromatic tetracarboxylic acid component comprising 15 to 55 mol% of an asymmetric aromatic tetracarboxylic acid or an ester thereof and 85 to 45 mol% of a symmetric aromatic tetracarboxylic acid or an ester thereof and an aromatic diamine component are mixed in substantially equimolar amounts, 1 to 35 parts by weight of carbon black is dispersed relative to 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the aromatic diamine component, and the resulting semiconductive monomer mixed solution is formed into a tubular product by a rotational molding method, and is subjected to heat treatment and imidization.

(6) A semiconductive endless tubular polyimide film for an intermediate transfer belt for an electrophotographic system, which is produced by the production method described in (5).

B. Second invention

The present inventors have further studied to solve the above problems, and as a result, they have found that: the semiconductive endless tubular polyimide film having a uniform resistivity can be obtained by heat-treating an aromatic tetracarboxylic acid component and an aromatic diamine component to substantially cause a partial polycondensation reaction to obtain a mixed solution containing an aromatic amic acid oligomer (an aromatic amic acid having a number average molecular weight of about 1000 to 7000), mixing conductive carbon black in the mixed solution, followed by rotational molding and imidization. The present inventors have further developed the present invention based on this finding (hereinafter also referred to as "second invention").

That is, the second invention provides the following semiconductive aromatic amic acid composition and a method for producing the same, and a semiconductive endless tubular polyimide film using the semiconductive aromatic amic acid composition and a method for producing the same.

(7) A semiconductive aromatic amic acid composition comprising an aromatic amic acid oligomer obtained by polycondensation of at least 2 aromatic tetracarboxylic acid components and an aromatic diamine in substantially equimolar amounts, carbon black and an organic polar solvent.

(8) The semiconductive aromatic amic acid composition according to item (7) above, wherein the aromatic amic acid oligomer is obtained by polycondensation of at least 2 aromatic tetracarboxylic dianhydrides and aromatic diamines in substantially equimolar amounts in an organic polar solvent at a temperature of about 80 ℃ or less.

(9) The semiconductive aromatic amic acid composition according to item (8) above, wherein the 2 or more aromatic tetracarboxylic dianhydrides are a mixture of 15 to 55 mol% of asymmetric aromatic tetracarboxylic dianhydrides and 85 to 45 mol% of symmetric aromatic tetracarboxylic dianhydrides.

(10) The semiconductive aromatic amic acid composition according to item (7) above, wherein said aromatic amic acid oligomer is obtained by polycondensation of at least 2 aromatic tetracarboxylic acid diesters and aromatic diamines in substantially equimolar amounts in an organic polar solvent at a temperature of about 90 to 120 ℃.

(11) The semiconductive aromatic amic acid composition according to item (10) above, wherein the 2 or more aromatic tetracarboxylic acid diesters are a mixture of 15 to 55 mol% of an asymmetric aromatic tetracarboxylic acid diester and 85 to 45 mol% of a symmetric aromatic tetracarboxylic acid diester.

(12) The semiconductive aromatic amic acid composition according to item (7), wherein the aromatic amic acid oligomer has a number average molecular weight of about 1000 to 7000.

(13) The semiconductive aromatic amic acid composition according to item (7), wherein the amount of carbon black blended is about 3 to 30 parts by weight per 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the aromatic diamine.

(14) A process for producing a semiconductive endless tubular polyimide film, which comprises subjecting the semiconductive aromatic amic acid composition described in (7) to rotational molding and heat treatment.

(15) A semiconductive endless tubular polyimide film for an intermediate transfer belt for an electrophotographic system, which is produced by the production method described in (14).

(16) A process for producing a semiconductive aromatic amic acid composition, which comprises subjecting an aromatic tetracarboxylic acid component and an aromatic diamine component of at least 2 species in an approximately equimolar amount to partial polycondensation in an organic polar solvent to form an aromatic amic acid oligomer solution, and uniformly mixing the aromatic amic acid oligomer solution with a conductive carbon black powder.

C. Third invention

The present inventors have conducted intensive studies to solve the above problems and, as a result, have found that: a mixed solution obtained by dissolving 2 or more kinds of aromatic tetracarboxylic acid diesters and aromatic diamines in an organic polar solvent in approximately equimolar amounts to form a nylon salt type monomer solution and mixing a predetermined high molecular weight polyimide precursor solution or high molecular weight polyamideimide solution with the nylon salt type monomer solution is excellent in dispersion stability of carbon black. Moreover, it was found that: by using a semiconductive polyimide precursor composition obtained by uniformly mixing the above-mentioned mixed solution and carbon black, and carrying out rotational molding and subsequent imidization treatment, a semiconductive endless tubular polyimide film having a uniform resistivity can be obtained. The present inventors have further developed the present invention (hereinafter also referred to as "third invention").

That is, the third invention provides the following semiconductive polyimide precursor composition and a method for producing the same, and a semiconductive endless tubular polyimide film using the semiconductive polyimide precursor composition and a method for producing the same.

(17) A semiconductive polyimide precursor composition characterized by mixing a high molecular weight polyimide precursor solution or a high molecular weight polyamideimide solution with a nylon salt type monomer solution prepared by dissolving 2 or more kinds of aromatic tetracarboxylic acid diesters and aromatic diamines in an approximately equimolar amount in an organic polar solvent to prepare a mixed solution, and uniformly dispersing carbon black in the mixed solution.

(18) The semiconductive polyimide precursor composition according to (17), wherein the 2 or more aromatic tetracarboxylic acid diesters are a mixture of 10 to 55 mol% of an asymmetric aromatic tetracarboxylic acid diester and 90 to 45 mol% of a symmetric aromatic tetracarboxylic acid diester.

(19) The semiconductive polyimide precursor composition according to claim 17, wherein the 2 or more aromatic tetracarboxylic acid diesters are a mixture of 10 to 55 mol% of an asymmetric 2, 3, 3 ', 4' -biphenyltetracarboxylic acid diester and 90 to 45 mol% of a symmetric 3, 3 ', 4, 4' -biphenyltetracarboxylic acid diester.

(20) The semiconductive polyimide precursor composition according to (17), wherein the high molecular weight polyimide precursor solution is a polyamic acid solution having a number average molecular weight of 10000 or more, and the high molecular weight polyamideimide solution is a polyamideimide solution having a number average molecular weight of 10000 or more.

(21) The semiconductive polyimide precursor composition according to claim 20, wherein the polyamic acid solution having a number average molecular weight of 10000 or more is prepared by reacting biphenyltetracarboxylic dianhydride and diaminodiphenyl ether in an organic polar solvent in substantially equimolar amounts.

(22) The semiconductive polyimide precursor composition according to the item (20), wherein the polyamideimide solution having a number average molecular weight of 10000 or more is produced by reacting an acid anhydride comprising trimellitic anhydride and benzophenonetetracarboxylic dianhydride with an aromatic isocyanate in an organic polar solvent in an approximately equimolar amount.

(23) A method for producing a semiconductive endless tubular polyimide-based film, characterized in that the semiconductive polyimide-based precursor composition of (17) is formed into a tubular article by a rotational molding method, and is subjected to heat treatment to effect imidization.

(24) A surface resistivity of 10 manufactured by the manufacturing method of (23)⁷～10¹⁴Omega/□, semiconducting endless tubular polyimide-based film for an intermediate transfer belt for electrophotographic systems.

(25) A process for producing a semiconductive polyimide precursor composition, characterized by mixing a high-molecular-weight polyimide precursor solution or a high-molecular-weight polyamideimide solution with a nylon salt type monomer solution in which at least 2 aromatic tetracarboxylic acid diesters and at least 2 aromatic diamines are dissolved in an organic polar solvent in approximately equimolar amounts to prepare a mixed solution, and uniformly dispersing carbon black in the mixed solution.

D. Fourth invention

The present inventors have conducted intensive studies to solve the above problems and, as a result, have found that: the semiconductive high-concentration polyimide precursor composition having excellent dispersibility of carbon black can be prepared by dissolving an aromatic tetracarboxylic acid diester and an aromatic diamine in substantially equimolar amounts in a carbon black dispersion liquid in which carbon black is uniformly dispersed in an organic polar solvent. Moreover, it was found that: by performing rotational molding using a semiconductive high-concentration polyimide precursor composition, followed by imidization treatment, a semiconductive endless tubular polyimide film having homogeneous resistivity can be obtained. The present inventors have further developed the present invention (hereinafter, also referred to as "fourth invention")

That is, the fourth invention provides the following semiconductive high-concentration polyimide precursor composition and a method for producing the same, and a semiconductive endless tubular polyimide film using the semiconductive high-concentration polyimide precursor composition and a method for producing the same.

(26) A process for producing a semiconductive high-concentration polyimide precursor composition, characterized by dissolving an aromatic tetracarboxylic acid diester and an aromatic diamine in substantially equimolar amounts in a carbon black dispersion liquid obtained by uniformly dispersing carbon black in an organic polar solvent.

(27) The process for producing a semiconductive high-concentration polyimide precursor composition according to (26), wherein the aromatic tetracarboxylic acid diester is a mixture of 10 to 55 mol% of an asymmetric aromatic tetracarboxylic acid diester and 90 to 45 mol% of a symmetric aromatic tetracarboxylic acid diester.

(28) The process for producing a semiconductive high-concentration polyimide precursor composition according to (26), wherein the aromatic tetracarboxylic acid diester is a mixture of 10 to 55 mol% of an asymmetric 2, 3, 3 ', 4' -biphenyltetracarboxylic acid diester and 90 to 45 mol% of a symmetric 3, 3 ', 4, 4' -biphenyltetracarboxylic acid diester.

(29) The process for producing a semiconductive high-concentration polyimide precursor composition according to (26), wherein the amount of carbon black is about 5 to 35 parts by weight based on 100 parts by weight of the total amount of the aromatic tetracarboxylic acid diester and the aromatic diamine.

(30) A semiconductive high-concentration polyimide precursor composition produced by the production method described in (26).

(31) A process for producing a semiconductive endless tubular polyimide film, which comprises subjecting a semiconductive high-concentration polyimide precursor composition as described in (30) to rotational molding to form a tubular article, and subjecting the tubular article to heat treatment to effect imidization.

(32) A surface resistivity of 10 manufactured by the manufacturing method of (31)⁷～10¹⁴Omega/□, a semi-conductive endless tubular polyimide film for an intermediate transfer belt for electrophotographic processes.

Detailed Description

Hereinafter, the present invention will be described in detail in terms of "a. first invention", "b. second invention", "c. third invention", and "d. fourth invention".

A. First invention

A-1. endless tubular polyimide film

The endless tubular polyimide film (hereinafter also referred to as "tubular PI film") of the present invention is produced by using a specific aromatic tetracarboxylic acid component and an aromatic diamine component as molding raw materials. Specifically, the nonconductive tubular PI film of the present invention is produced from a specific aromatic tetracarboxylic acid component and an aromatic diamine component as molding materials, and the semiconductive tubular PI film of the present invention is produced from a predetermined amount of carbon black (hereinafter also referred to as "CB") in addition to the molding materials described above for imparting conductivity.

Aromatic tetracarboxylic acid component

As the aromatic tetracarboxylic acid component as the raw material for molding, a mixture of an asymmetric aromatic tetracarboxylic acid component (at least one of asymmetric aromatic tetracarboxylic acids or esters thereof) and a symmetric aromatic tetracarboxylic acid component (at least one of symmetric aromatic tetracarboxylic acids or esters thereof) is used.

So-called asymmetric aromatic hydrocarbonExamples of the aromatic tetracarboxylic acid include compounds in which 4 carboxyl groups are bonded to non-point-symmetrical positions on a monocyclic or polycyclic aromatic ring (benzene ring, naphthalene ring, biphenyl ring, anthracene ring), or compounds in which 2 monocyclic aromatic rings (benzene ring) are bonded with-CO-, -CH-₂-、-SO₂Compounds in which 4 carboxyl groups are bonded in non-point-symmetrical positions, in compounds crosslinked by iso-or single bonds.

Specific examples of the asymmetric aromatic tetracarboxylic acid include 1, 2, 3, 4-benzenetetracarboxylic acid, 1, 2, 6, 7-naphthalenetetracarboxylic acid, 2, 3, 3 ', 4' -biphenyltetracarboxylic acid, 2, 3, 3 ', 4' -benzophenonetetracarboxylic acid, 2, 3, 3 ', 4' -diphenylethertetracarboxylic acid, 2, 3, 3 ', 4' -diphenylmethane tetracarboxylic acid, and 2, 3, 3 ', 4' -diphenylsulfonetetracarboxylic acid.

The asymmetric aromatic tetracarboxylic acid ester used in the present invention includes diesters (half-esters) of the asymmetric aromatic tetracarboxylic acids, and specifically includes compounds in which 2 carboxyl groups are esterified in 4 carboxylic acids of the asymmetric tetracarboxylic acids and one of 2 carboxyl groups adjacent to each other on the aromatic ring is esterified.

Examples of the 2-ester of the asymmetric aromatic tetracarboxylic acid diester include a di-lower alkyl ester, preferably a di-C ester such as dimethyl ester, diethyl ester or dipropyl ester_1-3Alkyl esters (in particular dimethyl esters).

Among the asymmetric aromatic tetracarboxylic diesters, dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid and diethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid are preferably used, and dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid is particularly preferably used.

The asymmetric aromatic tetracarboxylic acid diester can be produced by a commercially available method or a known method. For example, by mixing 1 part of the corresponding asymmetric aromatic tetracarboxylic dianhydride and 2 parts (molar ratio) of the corresponding alcohol (lower alcohol, preferably C)_1-3Alcohol, etc.) can be easily produced by a known method. By such a method, the acid anhydride as the raw material is reacted with the alcohol to be ring-opened, whereby the ring-opening reaction can be carried outIt is possible to produce diesters (half-esters) having an ester group and a carboxyl group on adjacent carbons of an aromatic ring, respectively.

The symmetric aromatic tetracarboxylic acid includes compounds in which 4 carboxyl groups are bonded to point-symmetric positions on monocyclic or polycyclic aromatic rings (benzene ring, naphthalene ring, biphenyl ring, anthracene ring), or compounds in which 2 monocyclic aromatic rings (benzene ring, etc.) are bonded to a group of-CO-, -O-, -CH-₂-、-SO₂Compounds in which 4 carboxyl groups are bonded in point-symmetrical positions on compounds crosslinked by an iso-or single bond.

Specific examples of the symmetrical aromatic tetracarboxylic acid include 1, 2, 4, 5-benzenetetracarboxylic acid, 2, 3, 6, 7-naphthalenetetracarboxylic acid, 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, 3, 3 ', 4, 4' -benzophenonetetracarboxylic acid, 3, 3 ', 4, 4' -diphenylethertetracarboxylic acid, 3, 3 ', 4, 4' -diphenylmethane tetracarboxylic acid, 3, 3 ', 4, 4' -diphenylsulfonetetracarboxylic acid, and the like.

The symmetric aromatic tetracarboxylic acid ester used in the present invention includes diesters (half-esters) of the above symmetric aromatic tetracarboxylic acids, and specifically includes compounds in which 2 carboxyl groups are esterified in 4 carboxylic acids of the above symmetric tetracarboxylic acids and one of 2 carboxyl groups adjacent to each other on the aromatic ring is esterified.

Examples of the 2-membered ester of the above symmetric aromatic tetracarboxylic acid diester include a di-lower alkyl ester, preferably C such as dimethyl ester, diethyl ester and dipropyl ester_1-3Alkyl esters (in particular dimethyl esters).

Among the above symmetrical aromatic carboxylic acid diesters, dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, diethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid and dimethyl 2, 3, 5, 6-benzenetetracarboxylic acid are preferably used, and dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid is particularly preferably used.

The symmetric aromatic tetracarboxylic acid diester can be produced by a commercially available method or a known method. For example, by reacting 1 part of the corresponding symmetric aromatic tetracarboxylic dianhydride with 2 parts (molar ratio) of the correspondingAlcohol (lower alcohol, preferably C)_1-3Alcohol, etc.) can be easily produced by a known method. By such a method, the acid anhydride as the raw material reacts with the alcohol to open the ring, and a diester (half-ester) having an ester group and a carboxyl group on adjacent carbons on the aromatic ring can be produced.

The mixing ratio of the asymmetric and symmetric aromatic tetracarboxylic acids or esters thereof is particularly specified to be about 15 to 55 mol% (preferably 20 to 50 mol%) of the asymmetric aromatic tetracarboxylic acid or ester thereof, and about 85 to 45 mol% (preferably 80 to 50 mol%) of the symmetric aromatic tetracarboxylic acid or ester thereof. In particular, the asymmetric aromatic tetracarboxylic acid diester is preferably used in an amount of about 20 to 50 mol% and the symmetric aromatic tetracarboxylic acid diester is preferably used in an amount of about 80 to 50 mol%.

The reason why the above-mentioned asymmetric and symmetric aromatic tetracarboxylic acid component must be blended is as follows. When only the symmetric aromatic tetracarboxylic acid or ester thereof is used, the polyimide film exhibits crystallinity, and therefore the film is pulverized during the heat treatment and cannot be formed into a film. On the other hand, when only asymmetric aromatic tetracarboxylic acid or ester thereof is used, an endless tubular PI film can be formed, but the obtained film has a low yield strength and low elastic modulus, and when it is used as a rotating belt, it has problems such as poor responsiveness during driving and elongation of the rotating belt at an initial stage.

On the other hand, when the aromatic tetracarboxylic acid or ester thereof having the above mixing ratio is used, a semiconductive endless tubular PI film having a high yield strength and a high elastic modulus can be obtained while extremely high film-forming properties (moldability) are obtained.

Further, the applicant considered that addition of an asymmetric aromatic tetracarboxylic acid or ester thereof can bend the polyamic acid molecule to impart flexibility.

The coexistence effect of the symmetric and asymmetric aromatic tetracarboxylic acids or esters thereof can be most effectively exhibited at the mixing ratio of the two as described above.

Aromatic diamine component

Examples of the aromatic diamine component include compounds having 2 amino groups on one aromatic ring (benzene ring, etc.), and compounds having 2 or more aromatic rings (benzene ring, etc.) and containing-O-, -S-, -CO-, -CH₂-、-SO-、-SO₂Compounds with 2 amino groups, crosslinked by an iso-or single bond. Specifically, for example, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, 4 '-diaminodiphenyl ether, 4' -diaminodiphenyl sulfide, 4 '-diaminodiphenylcarbonyl, 4' -diaminodiphenylmethane, 1, 4-bis (4-aminophenoxy) benzene, and the like. Among them, 4' -diaminodiphenyl ether is particularly preferable. This is because the use of these aromatic diamine components allows the reaction to proceed more smoothly and also allows a film to be produced which is stronger and has higher heat resistance.

Organic polar solvent

The organic polar solvent used in the substantially monomer-state mixed solution is preferably an aprotic organic polar solvent, and examples thereof include N-methyl-2-pyrrolidone (hereinafter referred to as "NMP"), N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, and 1, 3-dimethyl-2-imidazolidinone. One or a mixed solution of two or more of them may be used. NMP is particularly preferred. The amount of the organic polar solvent to be used may be about 65 to 300 parts by weight (preferably about 80 to 230 parts by weight, and more preferably about 100 to 200 parts by weight) based on 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the aromatic diamine component as the raw materials.

Carbon Black (CB)

In the production of the semiconductive tubular PI film of the present invention, CB powder is used in addition to the above components to impart resistance characteristics. The reason why carbon black is used is that the mixing dispersibility and stability (change with time after mixing dispersion) of the mixture with the prepared monomer mixed solution are excellent as compared with other generally known conductive materials of metal and metal oxide, and the polycondensation reaction is not adversely affected.

The CB powder has various physical properties (resistance, volatile matter, specific surface area, particle diameter, pH, DBP oil absorption, etc.) depending on the production raw material (natural gas, acetylene gas, tar, etc.) and the production conditions (combustion conditions). The conductive index is high (this is mostly CB powder produced from acetylene gas) due to the developed structure, and a predetermined resistance can be obtained with a relatively small filling amount, but the mixing dispersibility is not good. Although the conductivity index is not high, the oxidation-treated CB powder having a low pH and the CB powder containing a large amount of volatile matter require a relatively large amount of filling to achieve a predetermined resistance, but are excellent in mixing dispersibility and storage stability, and a tape having a uniform resistance can be easily obtained.

The conductive CB powder has an average particle diameter of usually about 15 to 65nm, and particularly preferably about 20 to 40nm when used for an intermediate transfer belt of an electrophotographic system used for a color printer, a color copier and the like.

Examples thereof include channel black and furnace black subjected to oxidation treatment. Specific examples thereof include Special Black 4(pH3, volatile matter content 14%, particle size 25nm) and Special Black 5(pH3, volatile matter content 15%, particle size 20nm) manufactured by Degusa corporation.

The amount of the CB powder to be added is preferably about 1 to 35 parts by weight (preferably about 5 to 25 parts by weight) based on 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the aromatic diamine component as the molding raw materials in the substantially monomer-state mixed solution.

The reason why the CB powder is used in the above range is to impart volume resistivity (Ω · cm) (VR) and surface resistivity (Ω/□) (SR) in the semiconductive region to the film. The lower limit of about 1 part by weight or more is because an amount of such an extent is necessary in order to obtain sufficient conductivity; the reason why the upper limit is about 35 parts by weight or less is to exhibit lower electric resistance and to prevent the deterioration of the physical properties of the film itself while maintaining moldability.

Preparation of monomer Mixed solution

The aromatic tetracarboxylic acid component, the aromatic diamine component and the organic polar solvent are mixed in predetermined amounts to prepare a mixed solution (hereinafter, also referred to as "monomer mixed solution") in a substantially monomer state for molding. The nonconductive tubular PI film and the semiconductive tubular PI film of the present invention are prepared under the same conditions as the monomer mixed solution as the molding material, except that there is a difference in the presence or absence of CB powder. The modulation order thereof is not particularly limited. The aromatic tetracarboxylic acid component used in the present invention is advantageous in that it does not substantially react with the diamine component at a low temperature (for example, 30 to 40 ℃ C. or lower) unlike the case of using an aromatic tetracarboxylic dianhydride having high reactivity, and thus a monomer mixture solution is prepared.

The monomer mixture solution is prepared by mixing and dissolving the aromatic tetracarboxylic acid component and the aromatic diamine component in an organic polar solvent at a reaction ratio of approximately equimolar amounts. These components are monomers, and therefore, they are easily dissolved in an organic polar solvent, and can be uniformly dissolved at a high concentration, and the obtained solution can substantially maintain a monomer state. The present invention uses the monomer-state mixed solution as a molding material.

The substantially equimolar amount is a reaction ratio at which the polycondensation reaction of the aromatic tetracarboxylic acid component and the aromatic diamine component proceeds smoothly and a polyimide having a predetermined high molecular weight is obtained. The substantially monomer state means that all the components in the mixed solution are in a monomer state, but the low-molecular polycondensation reaction product may be contained in a small amount to the extent that it does not adversely affect the present invention.

The amount of the organic polar solvent to be used may be about 65 to 300 parts by weight (preferably about 80 to 230 parts by weight, and more preferably about 100 to 200 parts by weight) based on 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the aromatic diamine component as the raw materials. Since the mixed solution substantially in a monomer state to be produced is easily dissolved in the organic polar solvent, there is an advantage that the amount of the solvent to be used can be reduced as much as possible.

Next, a method for preparing a monomer mixture solution is exemplified.

As example 1, first, the above-mentioned predetermined mole% of the symmetric and asymmetric aromatic tetracarboxylic acid components are mixed and dissolved in an organic polar solvent. An aromatic diamine component is added to the solution in an amount of approximately equimolar to the aromatic tetracarboxylic acid component while stirring, and the mixture is uniformly dissolved to form a monomer mixture solution for molding.

As example 2, a solution comprising the above-mentioned predetermined amount of a symmetric aromatic tetracarboxylic acid component and an aromatic diamine component substantially equimolar thereto, and a solution comprising the predetermined amount of an asymmetric aromatic tetracarboxylic acid component and an aromatic diamine component substantially equimolar thereto were prepared. The respective solutions were mixed so that the 2 kinds of aromatic tetracarboxylic acid components were in a predetermined mol% to obtain a monomer mixture solution for molding.

As example 3, a uniform monomer mixture solution was prepared by adding predetermined amounts of a symmetric and asymmetric aromatic tetracarboxylic acid component and an aromatic diamine component to an organic polar solvent at the same time.

The conventional polyimide acid solution can be used up to 25% by weight, whereas the nonvolatile content of the monomer mixture solution of the present invention can be as high as about 45% by weight (particularly 30 to 45% by weight). The "nonvolatile concentration" used herein means the concentration measured by the method described in the examples. By using a high-concentration monomer mixed solution, the polycondensation reaction proceeds rapidly, and the molding time can be shortened. Further, a film having a thick film can be easily produced, and the amount of solvent used is small, so that evaporation and removal of the solvent can be facilitated while suppressing the cost.

In addition, additives such as imidazole compounds (2-methylimidazole, 1, 2-dimethylimidazole, 2-methyl-4-methylimidazole, 2-ethyl-4-ethylimidazole, 2-phenylimidazole), surfactants (fluorine-based surfactants, etc.) may be added to the monomer mixture solution within a range not adversely affecting the effect of the present invention.

In the production of a semiconductive tubular PI film, a semiconductive monomer mixture solution in which carbon black is dispersed in a monomer mixture solution is used. The mixing method of mixing the CB powder into the monomer mixed solution is not particularly limited, and any known method such as stirring may be used. In the stirring, a ball mill is preferably used, so that a semiconductive monomer mixture solution for molding in which CB is uniformly dispersed can be obtained.

The amount of carbon black used is, as described above, 1 to 35 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the aromatic diamine component.

A-2. method for producing endless tubular polyimide film

Next, a method for forming a tubular PI film using the prepared monomer mixture solution or semiconductive monomer mixture solution will be described. Hereinafter, a molding method using a monomer mixture solution will be described, and a molding method using a semiconductive monomer mixture solution can be similarly performed.

The molding method employs a rotary molding method using a rotary cylinder (drum). First, the monomer mixture solution was poured into the inner surface of a rotating cylinder and uniformly spread over the entire inner surface.

The injection-casting method is, for example, a method in which a monomer mixture solution in an amount equivalent to a final film thickness is injected into a rotating cylinder which is stopped, and then the rotating speed is gradually increased until a speed at which a centrifugal force acts, and the entire inner surface is uniformly cast by the centrifugal force. Alternatively, injection-casting may be performed without using a centrifugal force. For example, a horizontally long slit-shaped nozzle is disposed on the inner surface of a cylinder, and the cylinder is rotated slowly and continuously, and the nozzle is also rotated (at a speed higher than the rotation speed). Then, the monomer mixture solution for molding is uniformly sprayed from the nozzle to the entire inner surface of the cylinder. The cylinder is mounted on a rotating roller and can be indirectly rotated by the rotation of the roller.

The heating is indirect heating from the outside by disposing a heat source such as a far infrared heater around the cylinder. The size of the cylinder depends on the size of the semiconducting tubular PI film desired.

The inner surface of the cylinder is heated to a temperature of about 100 to 190 ℃ and preferably about 110 to 130 ℃ at first (heating stage 1). The temperature rise rate is, for example, about 1 to 2 ℃/min. Maintaining the temperature for 30-120 min to evaporate more than half of the solvent and form self-supporting tubular film. However, when the polyimide is initially heated at such a high temperature, the polyimide is highly crystallized, which affects the dispersion state of CB, and a strong film cannot be formed. Therefore, in the 1 st heating stage, the upper limit temperature is controlled to about 190 ℃ at the maximum, and the polycondensation reaction is terminated at this temperature, whereby a strong tubular PI film is obtained.

After this stage, the second heating stage 2 is performed at a temperature of about 280 to 400 ℃ (preferably about 300 to 380 ℃) for completing the imidization. In this case, it is also preferable that the temperature is gradually increased to the temperature, rather than being suddenly increased from the temperature in the 1 st heating stage.

The 2 nd heating stage may be performed in a state where the endless tubular film is attached to the inner surface of the rotating cylinder as it is, or may be performed by heating the endless tubular film to 280 to 400 ℃ by providing another heating means for imidization after the 1 st heating stage by peeling the endless tubular film off the rotating cylinder and taking it out. The time for the imidization is usually about 2 to 3 hours. Therefore, the time required for the entire steps of the 1 st and 2 nd heating stages is usually about 4 to 7 hours.

Thus, the non-conductive (or semiconductive) PI film of the present invention is manufactured. The thickness of the film is not particularly limited, but is usually about 30 to 200 μm, preferably about 60 to 120 μm. Particularly, when used as an intermediate transfer belt for an electrophotographic system, it is preferably about 75 to 100 μm.

In the case of a semiconductive PI film, the semiconductivity of the film is a resistance characteristic determined by both volume resistivity (Ω · cm) (VR) and surface resistivity (Ω/□) (SR), which is imparted by the mixing and dispersion of CB powder. The range of the resistance can be changed by the amount of the CB powder to be mixed. As the resistivity range of the film of the present invention, VR: 10²～10¹⁴，SR：10³～10¹⁵As a preferable range, VR: 10⁶～10¹³，SR：10⁷～10¹⁴. These resistivity ranges can be easily achieved by using the above-mentioned CB powder blending amount. The content of CB in the film of the present invention is usually about 5 to 25 wt%, preferably about 8 to 20 wt%.

The semiconductive PI film of the present invention has a very homogeneous resistivity. That is, the semiconductive PI film of the present invention is characterized in that the variability of logarithmic conversion values of the surface resistivity SR and the volume resistivity VR is small, and the standard deviation of the respective logarithmic conversion values at all measurement points in the film is within 0.2, preferably within 0.15. Further, the difference between the surface resistivities (logarithmic conversion values) of the front surface and the back surface of the film is small, and the difference is preferably 0.4 or less, more preferably 0.2 or less. Further, the present invention has the following features: the log conversion value LogSR of the surface resistivity minus the log conversion value LogVR of the volume resistivity can be maintained at a high value of 1.0 to 3.0, preferably 1.5 to 3.0.

The semiconductive PI film of the present invention has various applications because of its excellent functions such as resistance characteristics. For example, as requiredImportant applications of the charging characteristics include electrophotographic intermediate transfer belts used in color printers, color copiers, and the like. The tape has a required semiconductivity (resistivity), for example, VR of 10⁹～10¹²SR of 10¹⁰～10¹³The semiconductive endless tubular PI film of the present invention can be suitably applied.

The non-conductive or semiconductive PI film of the present invention has excellent performance as a tape and has a high yield strength (σ)_Y) And breaking strength (. sigma.)_cr). Yield strength (sigma)_Y) At 120MPa or more, particularly 120 to 160MPa, the ratio (σ) of the breaking strength and the yield strength_cr/σ_Y) Is 1.10 or more, particularly about 1.10 to 1.35.

B. Second invention

The semiconductive endless tubular polyimide film (hereinafter also referred to as a "semiconductive tubular PI film") of the present invention is produced by subjecting a semiconductive aromatic amic acid composition containing an aromatic amic acid oligomer, conductive carbon black (hereinafter also referred to as "CB") and an organic polar solvent to rotational molding and amidation treatment.

B-1 semiconductive aromatic amic acid composition

The semiconductive aromatic amic acid composition of the present invention is prepared by partially polycondensing 2 or more aromatic tetracarboxylic acid components and aromatic diamine components in approximately equimolar amounts in an organic polar solvent to form an aromatic amic acid oligomer (aromatic amic acid having a number average molecular weight of about 1000 to 7000) solution, and uniformly mixing the solution with conductive carbon black powder.

(1) Aromatic tetracarboxylic acid component

As the 2 or more kinds of aromatic tetracarboxylic acid components as the molding raw material, a mixture of at least one asymmetric aromatic tetracarboxylic acid derivative and at least one symmetric aromatic tetracarboxylic acid derivative is used.

Asymmetric aromatic tetracarboxylic acid derivatives

In the present invention, examples of the asymmetric aromatic tetracarboxylic acid derivative include asymmetric aromatic tetracarboxylic dianhydride and asymmetric aromatic tetracarboxylic diester (half ester).

Here, the asymmetric aromatic tetracarboxylic acid includes compounds in which 4 carboxyl groups are bonded to non-point-symmetric positions on monocyclic or polycyclic aromatic rings (benzene ring, naphthalene ring, biphenyl ring, anthracene ring), or compounds in which 2 monocyclic aromatic rings (benzene ring, etc.) are bonded to-CO-, -CH-, - -O-or-CO- (-CH-) -)₂-、-SO₂Compounds in which 4 carboxyl groups are bonded in non-point-symmetrical positions, in compounds crosslinked by iso-or single bonds.

Specific examples of the asymmetric aromatic tetracarboxylic acid include 1, 2, 3, 4-benzenetetracarboxylic acid, 1, 2, 6, 7-naphthalenetetracarboxylic acid, 2, 3, 3 ', 4' -biphenyltetracarboxylic acid, 2, 3, 3 ', 4' -benzophenonetetracarboxylic acid, 2, 3, 3 ', 4' -diphenylethertetracarboxylic acid, 2, 3, 3 ', 4' -diphenylmethane tetracarboxylic acid, and 2, 3, 3 ', 4' -diphenylsulfonetetracarboxylic acid.

Examples of the asymmetric aromatic tetracarboxylic dianhydride used in the present invention include the asymmetric aromatic tetracarboxylic dianhydride described above, and specifically, a compound in which adjacent carboxyl groups on an aromatic ring in the asymmetric tetracarboxylic dianhydride form 2 acid anhydrides. Among them, 2, 3, 3 ', 4' -biphenyltetracarboxylic dianhydride, 1, 2, 6, 7-naphthalenetetracarboxylic dianhydride and the like are preferably used, and 2, 3, 3 ', 4' -biphenyltetracarboxylic dianhydride is particularly preferably used.

Examples of the asymmetric aromatic tetracarboxylic acid diester (half ester) used in the present invention include diesters (half esters) of the asymmetric aromatic tetracarboxylic acids, and specifically include compounds in which 2 carboxyl groups are esterified in 4 carboxylic acids of the asymmetric tetracarboxylic acids and one of 2 carboxyl groups adjacent to each other on the aromatic ring is esterified.

Examples of the 2-ester in the asymmetric aromatic tetracarboxylic acid diester include a di-lower alkyl ester, preferably a di-C ester such as dimethyl ester, diethyl ester or dipropyl ester_1-3Alkyl esters (in particular dimethyl esters).

Among the above symmetrical aromatic carboxylic acid diesters, dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid and diethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid are preferably used, and dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid is particularly preferably used.

The asymmetric aromatic tetracarboxylic acid diester can be produced by a commercially available method or a known method. For example, by mixing 1 part of the corresponding asymmetric aromatic tetracarboxylic dianhydride and 2 parts (molar ratio) of the corresponding alcohol (lower alcohol, preferably C)_1-3Alcohol, etc.) can be easily produced by a known method such as a reaction. By such a method, the acid anhydride as the raw material reacts with the alcohol to open the ring, and a diester (half-ester) having an ester group and a carboxyl group on the adjacent carbons of the aromatic ring can be produced.

Symmetrical aromatic tetracarboxylic acid derivatives

In the present invention, examples of the symmetric aromatic tetracarboxylic acid derivative include symmetric aromatic tetracarboxylic dianhydride and symmetric aromatic tetracarboxylic diester (half ester).

Here, the symmetric aromatic tetracarboxylic acid includes compounds in which 4 carboxyl groups are bonded to point-symmetric positions on monocyclic or polycyclic aromatic rings (benzene ring, naphthalene ring, biphenyl ring, anthracene ring), or compounds in which 2 monocyclic aromatic rings (benzene ring, etc.) are bonded to a point-symmetric position with-CO-, -O-, -CH-, - -CO-, -O-, -CH-O-or-O-groups₂-、-SO₂Compounds in which 4 carboxyl groups of the compounds crosslinked by an iso-or single bond are bonded in point-symmetrical positions.

Specific examples of the symmetrical aromatic tetracarboxylic acid include 1, 2, 4, 5-benzenetetracarboxylic acid, 2, 3, 6, 7-naphthalenetetracarboxylic acid, 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, 3, 3 ', 4, 4' -benzophenonetetracarboxylic acid, 3, 3 ', 4, 4' -diphenylethertetracarboxylic acid, 3, 3 ', 4, 4' -diphenylmethane tetracarboxylic acid, 3, 3 ', 4, 4' -diphenylsulfonetetracarboxylic acid, and the like.

The symmetric aromatic tetracarboxylic dianhydride used in the present invention includes a dianhydride of the above symmetric aromatic tetracarboxylic acid, and specifically includes a compound in which adjacent carboxyl groups in the above symmetric tetracarboxylic acid form 2 acid anhydrides. Among them, 1, 2, 4, 5-benzenetetracarboxylic dianhydride and 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride are preferably used, and 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride is particularly preferably used. This is because the obtained film can be made to function well in terms of strength formation and the like.

The symmetric tetracarboxylic acid diester (half-ester) used in the present invention includes diesters (half-esters) of the asymmetric aromatic tetracarboxylic acids, and specifically includes compounds in which 2 carboxyl groups are esterified in 4 carboxylic acids of the symmetric tetracarboxylic acids and one of 2 carboxyl groups adjacent to each other on the aromatic ring is esterified.

Examples of the 2-membered ester of the symmetric aromatic tetracarboxylic acid diester include a di-lower alkyl ester, preferably C such as dimethyl ester, diethyl ester and dipropyl ester_1-3Alkyl esters (in particular dimethyl esters).

Among the above symmetrical aromatic carboxylic acid diesters, dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, diethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid and dimethyl 2, 3, 5, 6-benzenetetracarboxylic acid are preferably used, and dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid is particularly preferably used.

The symmetric aromatic tetracarboxylic acid diester can be produced by a commercially available method or a known method. For example, by reacting 1 part of the corresponding symmetric aromatic tetracarboxylic dianhydride with 2 parts (molar ratio) of the corresponding alcohol (lower alcohol, preferably C)_1-3Alcohol, etc.) can be easily produced by a known method such as a reaction. By such a method, the acid anhydride as the raw material is reacted with the alcohol to open the ring, thereby producing the aromatic ring having an ester group and a carboxyl group on the adjacent carbons of the aromatic ringDiesters (half esters) of the radicals.

Mixing ratio

The mixing ratio of the asymmetric and symmetric aromatic tetracarboxylic acid derivatives is particularly specified to be about 10 to 55 mol% (preferably 15 to 55 mol%, more preferably 20 to 50 mol%) of the asymmetric aromatic tetracarboxylic acid derivative, and about 90 to 45 mol% (preferably 85 to 45 mol%, more preferably 80 to 50 mol%) of the symmetric aromatic tetracarboxylic acid derivative. In particular, it is preferable that the asymmetric aromatic tetracarboxylic dianhydride is used in an amount of about 20 to 50 mol% and the symmetric aromatic tetracarboxylic dianhydride is used in an amount of about 80 to 50 mol%.

The reason why the above-mentioned symmetric and asymmetric aromatic tetracarboxylic acid components must be blended is as follows. When only the symmetric aromatic tetracarboxylic acid derivative is used, the polyimide film exhibits crystallinity, and therefore the film is pulverized during the heat treatment and cannot be formed into a film. On the other hand, when only the asymmetric aromatic tetracarboxylic acid derivative is used, although the film can be formed into an endless tubular PI film, the obtained film has a low yield strength and a low elastic modulus, and when the film is used as a rotating belt, the film is not only poor in response during driving but also has problems such as elongation of the rotating belt at an initial stage.

On the other hand, when the aromatic tetracarboxylic acid derivative having the above mixing ratio is used, a semiconductive endless tubular PI film having a high yield strength and a high elastic modulus can be obtained while having an extremely high film-forming property (moldability).

Further, the applicant considered that addition of an asymmetric aromatic tetracarboxylic acid derivative can bend the polyamic acid molecule to impart flexibility.

The coexistence effect of the symmetric and asymmetric aromatic tetracarboxylic acid derivatives can be most effectively exhibited at the mixing ratio of the two compounds as described above.

(2) Aromatic diamine

Examples of the aromatic diamine include compounds having 2 amino groups on one aromatic ring (benzene ring, etc.), and compounds having 2 or more aromatic rings (benzene ring, etc.) and containing-O-, -S-, -CO-, -CH₂-、-SO-、-SO₂Compounds with 2 amino groups, crosslinked by an iso-or single bond. Specifically, for example, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, 4 '-diaminodiphenyl ether, 4' -diaminodiphenyl sulfide, 4 '-diaminodiphenylcarbonyl, 4' -diaminodiphenylmethane, 1, 4-bis (4-aminophenoxy) benzene, and the like. Among them, 4' -diaminodiphenyl ether is particularly preferable. This is because the use of these aromatic diamine components allows the reaction to proceed more smoothly and a film which is stronger and has higher heat resistance to be produced.

(3) Organic polar solvent

The organic polar solvent to be used is preferably an aprotic organic polar solvent, and examples thereof include N-methyl-2-pyrrolidone (hereinafter referred to as "NMP"), N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, and 1, 3-dimethyl-2-imidazolidinone. One or more of these mixed solvents may be used. NMP is particularly preferred. The amount of the organic polar solvent to be used may be about 100 to 300 parts by weight (preferably about 150 to 250 parts by weight) based on 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the aromatic diamine component as raw materials. Since the aromatic amic acid oligomer produced is readily soluble in the above-mentioned organic polar solvent, there is an advantage in that the amount of solvent used can be minimized.

(4) Preparation of aromatic amic acid oligomer solution

The following is an example of a method for preparing an aromatic amic acid oligomer (having a number average molecular weight of about 1000 to 7000) by partially polycondensing the above 2 or more mixed aromatic tetracarboxylic acid components and organic diamine components in an organic polar solvent.

As the method for preparing the 1 st aromatic amic acid oligomer, 2 or more aromatic tetracarboxylic dianhydrides and aromatic diamines are subjected to a polycondensation reaction in an organic polar solvent in approximately equimolar amounts at a temperature of about 80 ℃ or lower to produce an aromatic amic acid oligomer (having a number average molecular weight of about 1000 to 7000).

Specifically, a mixture of about 15 to 55 mol% (preferably 20 to 50 mol%) of an asymmetric aromatic tetracarboxylic dianhydride and about 85 to 45 mol% (preferably 80 to 50 mol%) of a symmetric aromatic tetracarboxylic dianhydride is supplied to the polycondensation reaction. As the organic polar solvent, NMP is particularly preferred, as mentioned above.

The reason why the reaction temperature is set to about 80 ℃ or lower is to suppress the occurrence of imidization reaction in the formation of the aromatic amic acid oligomer. More preferably, the reaction temperature is 30 to 70 ℃. When the reaction temperature exceeds 80 ℃, polyimide is likely to be formed by the imidization reaction, which is not preferable. The reaction time varies depending on the reaction temperature, and is usually about several hours to 72 hours.

The molecular weight of the aromatic amic acid oligomer may be adjusted by any known method. For example, it can be suitably carried out by the following method: an aromatic tetracarboxylic acid component/an aromatic diamine component are polymerized at a molar ratio of 0.5 to 0.95 to form an aromatic amic acid oligomer having a predetermined molecular weight, and then an aromatic tetracarboxylic acid component is added as needed so that the aromatic tetracarboxylic acid component/the aromatic diamine component are substantially equimolar (see Japanese examined patent publication (Kokoku) No. 1-22290); and a method in which a compound for inhibiting the polymerization of water or the like is caused to coexist in a predetermined amount when the aromatic tetracarboxylic acid component and the aromatic diamine component react in a substantially equimolar amount (see Japanese patent publication No. Hei 2-3820).

As a 2 nd type of preparation method of the aromatic amic acid oligomer, 2 or more kinds of aromatic tetracarboxylic acid diesters and aromatic diamines are subjected to a polycondensation reaction in an organic polar solvent at approximately equimolar amounts at a temperature of about 90 to 120 ℃ to produce an aromatic amic acid oligomer (number average molecular weight of about 1000 to 7000).

Specifically, a mixture of about 15 to 55 mol% (preferably 20 to 50 mol%) of the asymmetric aromatic tetracarboxylic acid diester and about 85 to 45 mol% (preferably 80 to 50 mol%) of the symmetric aromatic tetracarboxylic acid diester is supplied to the polycondensation reaction. As the organic polar solvent, NMP is particularly preferred, as mentioned above.

The reaction temperature and reaction time are closely related to each other in order to adjust the aromatic amic acid oligomer having the desired molecular weight. The heating temperature may be usually 90 to 120 ℃, but when the reaction temperature is in a high temperature range, it is preferable to shorten the reaction time in order to suppress the amount of imide product produced (imide formation rate) and increase the molecular weight. The heating treatment may be carried out by gradually raising the temperature to a predetermined temperature, reacting at the predetermined temperature for about 1 to 3 hours, and then cooling. For example, the temperature is raised to 90 to 120 ℃ for about 1 to 4 hours, the reaction is carried out for about 30 minutes to 2 hours at the temperature, and then the reaction product is cooled.

In the above-mentioned preparation methods of the 1 st and 2 nd, the substantially equimolar amounts mean the reaction ratios at which the desired semiconductive tubular PI film can be obtained by preparing the aromatic amic acid in a predetermined oligomer degree. When both components are uniformly dissolved in the organic polar solvent, the mixture may be heated as necessary (e.g., about 40 to 70 ℃).

The aromatic amic acid oligomer solution can be prepared by the above-described preparation methods 1 and 2 so that the number average molecular weight (Mn) is about 1000 to 7000 (preferably about 3000 to 7000). The meaning of specifying this range is that if the number average molecular weight is 1000 or less (i.e., about monomer or dimer), the effect of the conductive property cannot be obtained, and if the number average molecular weight is 7000 or more, the solubility of the oligomer is extremely lowered, and the solution is gelled and the like, and thus cannot be used (for example, see comparative example B-1). The number average molecular weight can be measured, for example, by the method described in examples.

The aromatic amic acid oligomer of the present invention is prepared so that the number average molecular weight (Mn) is about 1000 to 7000, and the ratio (Mw/Mn) of the number average molecular weight (Mn) to the weight average molecular weight (Mw) is usually 2 or less.

The aromatic amic acid oligomer solution produced by this heat treatment may contain aromatic amic acid oligomers as the main component, but may also contain products in which some of them are further reacted to cause imidization. However, the formation rate (imidization rate) of imide compounds in the aromatic amic acid oligomer is 30% or less, preferably 25% or less, and more preferably 20% or less. The amount of by-produced imide compounds (imidization ratio) can be measured, for example, by the method described in examples.

Further, the concentration of non-volatile matter in the aromatic amic acid oligomer solution can be adjusted to a high concentration of about 30 to 45% by weight. The reason why such a high nonvolatile concentration can be prepared is that the oligomer is not polymerized and is therefore easily dissolved in a solvent. Therefore, a film having a thick film can be easily produced, and the amount of solvent used is small, so that the cost can be reduced and the solvent can be easily evaporated and removed. The "nonvolatile concentration" used herein means the concentration measured by the method described in example B-1.

(5) Preparation of semiconductive aromatic amic acid composition

The aromatic amic acid oligomer solution thus obtained was uniformly mixed with conductive CB powder to prepare a semiconductive aromatic amide composition.

The reason why the CB powder is used for imparting resistance characteristics is that the CB powder is superior in mixing dispersibility and stability (change with time after mixing and dispersion) when mixed with a prepared monomer mixed solution as compared with other generally known conductive materials such as metals and metal oxides, and does not adversely affect the polycondensation reaction.

The CB powder has various physical properties (resistance, volatile matter, specific surface area, particle diameter, pH, DBP oil absorption, etc.) depending on the production raw material (natural gas, acetylene, tar, etc.) and the production conditions (combustion conditions). It is preferable to select a stable and easily available CB powder that does not cause variation in desired resistance even when the amount of the CB powder is mixed and dispersed in a minimum amount.

The conductive CB powder has an average particle diameter of usually about 15 to 65nm, and particularly preferably about 20 to 40nm when used for an intermediate transfer belt of an electrophotographic system used for a color printer, a color copier and the like.

Examples thereof include channel black and furnace black subjected to oxidation treatment. Specific examples thereof include Special Black 4(pH3, volatile matter content 14%, particle size 25nm) and Special Black 5(pH3, volatile matter content 15%, particle size 20nm) manufactured by Degusa corporation.

The method of mixing the CB powder in the aromatic amic acid oligomer solution is not particularly limited as long as the CB powder is uniformly mixed and dispersed in the aromatic amic acid oligomer solution. For example, a ball mill, a roller mill, an ultrasonic mill, or the like can be used.

The amount of the CB powder to be added is preferably about 3 to 30 parts by weight (more preferably about 10 to 25 parts by weight) based on 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the organic diamine as the raw material of the aromatic amic acid oligomer.

Here, the CB powder is used in the above range in order to impart Volume Resistivity (VR) and Surface Resistivity (SR) in the semiconductive region to the film. The lower limit of 3 parts by weight or more is because an amount of such an extent is necessary in order to obtain sufficient conductivity; the upper limit of about 30 parts by weight is because the film exhibits a lower electrical resistance and maintains moldability, thereby preventing a decrease in the physical properties of the film itself.

The semiconductive aromatic amic acid composition has a nonvolatile content of about 30 to 45 wt.%, the CB powder in the nonvolatile content has a concentration of about 3 to 25 wt.% (preferably about 10 to 20 wt.%), and the aromatic amic acid oligomer has a nonvolatile content of about 75 to 97 wt.% (preferably about 80 to 90 wt.%).

In addition, additives such as imidazole compounds (2-methylimidazole, 1, 2-dimethylimidazole, 2-methyl-4-methylimidazole, 2-ethyl-4-ethylimidazole, 2-phenylimidazole), surfactants (fluorine-based surfactants, etc.) may be added to the above composition within a range not adversely affecting the effect of the present invention.

Thus, a semiconductive aromatic amic acid composition for molding in which CB powder is uniformly dispersed can be produced.

B-2 semi-conductive endless tubular polyimide film

Next, a method for molding a semiconductive endless tubular polyimide film using the semiconductive aromatic amic acid composition prepared as described above will be described.

The molding method employs a rotary molding method using a rotary cylinder. First, a semiconductive aromatic amic acid composition was poured onto the inner surface of a rotating cylinder and uniformly cast on the entire inner surface.

The injection-casting method is, for example, a method in which a semiconductive aromatic amic acid composition is injected into a rotating cylinder while the cylinder is stopped, and the rotating speed is gradually increased to a speed at which centrifugal force acts, and the composition is uniformly cast on the entire inner surface by centrifugal force. Alternatively, injection-casting may be performed without using a centrifugal force. For example, a horizontally long slit-shaped nozzle is disposed on the inner surface of a cylinder, and the cylinder is rotated slowly and continuously, and the nozzle is also rotated (at a speed higher than the rotation speed). Then, the semiconductive aromatic amic acid composition for molding is uniformly sprayed from the nozzle onto the entire inner surface of the cylinder.

In either method, the inner surface of the rotating cylinder is made into a mirror surface, and barriers for preventing liquid leakage are provided along the circumference at both end edges. The cylinder is mounted on a rotating roller and can be indirectly rotated by the rotation of the roller.

The heating is performed indirectly from the outside by disposing a heat source such as a far infrared heater around the cylinder. The size of the cylinder depends on the size of the semiconducting tubular PI film desired.

The inner surface of the cylinder is heated to a temperature of about 100 to 190 ℃ and preferably about 110 to 130 ℃ at first (heating stage 1). The temperature rise rate is, for example, about 1 to 2 ℃/min. Maintaining the temperature for 1 to 2 hours to evaporate more than half of the solvent, thereby forming a self-supporting tubular film. However, when the polyimide is initially heated at such a high temperature, the polyimide is highly crystallized, which affects the dispersion state of CB, and a strong film cannot be formed. Therefore, in the 1 st heating stage, the upper limit temperature is controlled to about 190 ℃ at the maximum, and the polycondensation reaction is terminated at this temperature, whereby a strong tubular PI film is obtained.

After this stage, the second heating stage 2 is performed at a temperature of about 280 to 400 ℃ (preferably about 300 to 380 ℃) for completing the imidization. In this case, it is also preferable that the temperature is gradually increased to the temperature, rather than being suddenly increased from the temperature in the 1 st heating stage.

The 2 nd heating stage may be performed in a state where the endless tubular film is attached to the inner surface of the rotating cylinder as it is, or may be performed by heating the endless tubular film to 280 to 400 ℃ by providing another heating means for imidization after the 1 st heating stage by peeling the endless tubular film off the rotating cylinder and taking it out. The time for the imidization is usually about 2 to 3 hours. Therefore, the time required for the entire steps of the 1 st and 2 nd heating stages is usually about 4 to 7 hours.

Thus, the semiconductive endless tubular PI film of the present invention was produced. The thickness of the film is not particularly limited, but is usually about 50 to 150 μm, preferably about 60 to 120 μm. Particularly, when the intermediate transfer belt is used for an electrophotographic intermediate transfer belt, it is preferably about 75 to 100 μm.

The semiconductivity of the film is a resistance characteristic determined by both volume resistivity (Ω · cm) (hereinafter referred to as "VR") and surface resistivity (Ω/□) (hereinafter referred to as "SR"), which is imparted by the mixed dispersion of CB powder. The range of the resistivity can be changed by the amount of the CB powder to be mixed. As the resistivity range of the film of the present invention, VR: 10²～10¹⁴，SR：10³～10¹⁵As a preferable range, VR: 10⁶～10¹³，SR：10⁷～10¹⁴. These resistivity ranges can be easily achieved by using the above-mentioned CB powder blending amount. The content of CB in the film of the present invention is usually about 3 to 25 wt%, preferably about 10 to 20 wt%.

The semiconductive PI film of the present invention has a very homogeneous resistivity. That is, the semiconductive PI film of the present invention is characterized in that the variability of logarithmic conversion values of the surface resistivity SR and the volume resistivity VR is small, and the standard deviation of the respective logarithmic conversion values at all measurement points in the film is within 0.2, preferably within 0.15. Further, the difference between the surface resistivities (logarithmic conversion values) of the front surface and the back surface of the film is small, and the difference is preferably 0.4 or less, more preferably 0.2 or less. Further, the present invention has the following features: the log conversion value LogSR of the surface resistivity minus the log conversion value LogVR of the volume resistivity can be maintained at a high value of 1.0 to 3.0, preferably 1.3 to 3.0.

The PI film of the present invention has the above excellent electrical characteristics, and it is considered that a semiconductive aromatic amic acid composition obtained by mixing an "aromatic amic acid oligomer" with CB powder is used in the film production process. That is, in this composition, CB powder is uniformly dispersed in the aromatic amic acid oligomer, and the uniform dispersibility and high molecular weight can be maintained in the film production process, and therefore, it is considered that excellent properties can be imparted to the PI film of the present invention.

The PI film of the present invention has various uses because of its excellent functions such as resistance characteristics. For example, an important application requiring charging characteristics includes an electrophotographic intermediate transfer belt used in a color printer, a color copier, and the like. The tape has a required semiconductivity (resistivity), for example, VR10⁹～10¹²、SR10¹⁰～10¹³The semiconductive endless tubular PI film of the present invention can be suitably applied.

The non-conductive or semiconductive PI film of the present invention has excellent performance as a tape and has a high yield strength (σ)_Y) And breaking strength (. sigma.)_cr). Yield strength (sigma)_Y) At 120MPa or more, particularly 120 to 160MPa, the ratio (σ) of the breaking strength and the yield strength_cr/σ_Y) Is 1.10 or more, particularly about 1.10 to 1.35.

C. Third invention

The semiconductive endless tubular polyimide-based film (hereinafter also referred to as a "semiconductive tubular PI-based film") of the present invention is produced by rotational molding and heat treatment (imidization) using a semiconductive polyimide-based precursor composition (hereinafter also referred to as a "semiconductive PI precursor composition").

C-1 semiconductive polyimide precursor composition

The semiconductive polyimide precursor composition of the present invention is produced by mixing a high molecular weight polyimide precursor solution or a high molecular weight polyamideimide solution with a nylon salt type monomer solution in which 2 or more kinds of aromatic tetracarboxylic acid diesters and aromatic diamines are dissolved in an organic polar solvent in approximately equimolar amounts to prepare a mixed solution, and uniformly dispersing carbon black (hereinafter also referred to as "CB") in the mixed solution.

(1) Aromatic tetracarboxylic acid diesters (half esters)

As the 2 or more kinds of aromatic tetracarboxylic acid diesters as the molding raw materials, a mixture of at least one asymmetric aromatic tetracarboxylic acid diester and at least one symmetric aromatic tetracarboxylic acid diester is used.

The asymmetric aromatic tetracarboxylic acid diester used in the present invention will be described below.

Here, examples of the asymmetric aromatic tetracarboxylic acid include compounds in which 4 carboxyl groups are bonded to non-point-symmetric positions on a monocyclic or polycyclic aromatic ring (benzene ring, naphthalene ring, biphenyl ring, anthracene ring), or compounds in which 2 monocyclic aromatic rings (benzene ring, etc.) are bonded to-CO-, -CH-₂-、 -SO₂Compounds in which 4 carboxyl groups are bonded in non-point-symmetrical positions, in compounds crosslinked by an iso-or single bond.

Specific examples of the asymmetric aromatic tetracarboxylic acid include 1, 2, 3, 4-benzenetetracarboxylic acid, 1, 2, 6, 7-naphthalenetetracarboxylic acid, 2, 3, 3 ', 4' -biphenyltetracarboxylic acid, 2, 3, 3 ', 4' -benzophenonetetracarboxylic acid, 2, 3, 3 ', 4' -diphenylethertetracarboxylic acid, 2, 3, 3 ', 4' -diphenylmethane tetracarboxylic acid, and 2, 3, 3 ', 4' -diphenylsulfonetetracarboxylic acid.

The asymmetric aromatic tetracarboxylic acid diester (half ester) used in the present invention includes diesters of the asymmetric aromatic tetracarboxylic acids, and specifically includes compounds in which 2 carboxyl groups are esterified in 4 carboxylic acids of the asymmetric tetracarboxylic acids and one of 2 carboxyl groups adjacent to each other on the aromatic ring is esterified.

Examples of the 2-ester in the asymmetric aromatic tetracarboxylic acid diester include a di-lower alkyl ester, preferably a di-C ester such as dimethyl ester, diethyl ester or dipropyl ester_1-3Alkyl esters (in particular dimethyl esters).

Among the asymmetric aromatic carboxylic acid diesters, dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid and diethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid are preferably used, and dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid is particularly preferably used.

The asymmetric aromatic tetracarboxylic acid diester can be produced by a commercially available method or a known method. For example, by mixing 1 part of the corresponding asymmetric aromatic tetracarboxylic dianhydride and 2 parts (molar ratio) of the corresponding alcohol (lower alcohol, preferably C)_1-3Alcohol, etc.) can be easily produced by a known method. By such a method, the acid anhydride as the raw material reacts with the alcohol to open the ring, and a diester (half-ester) having an ester group and a carboxyl group on the adjacent carbons of the aromatic ring can be produced.

Next, the symmetric aromatic tetracarboxylic acid diester used in the present invention will be described below.

Here, the symmetric aromatic tetracarboxylic acid includes compounds in which 4 carboxyl groups are bonded to point-symmetric positions on monocyclic or polycyclic aromatic rings (benzene ring, naphthalene ring, biphenyl ring, anthracene ring), or compounds in which 2 monocyclic aromatic rings (benzene ring, etc.) are bonded to a point-symmetric position with-CO-, -O-, -CH-, - -CO-, -O-, -CH-O-or-O-groups₂-、-SO₂Compounds in which 4 carboxyl groups are bonded in point-symmetrical positions on compounds crosslinked by an iso-or single bond.

Specific examples of the symmetrical aromatic tetracarboxylic acid include 1, 2, 4, 5-benzenetetracarboxylic acid, 2, 3, 6, 7-naphthalenetetracarboxylic acid, 3 ', 4, 4' -biphenyltetracarboxylic acid, 3 ', 4, 4' -benzophenonetetracarboxylic acid, 3 ', 4, 4' -diphenylethertetracarboxylic acid, 3 ', 4, 4' -diphenylmethane tetracarboxylic acid, 3 ', 4, 4' -diphenylsulfonetetracarboxylic acid, and the like.

The diester (half-ester) of a symmetric tetracarboxylic acid used in the present invention includes a diester (half-ester) of the symmetric aromatic tetracarboxylic acid, and specifically includes a compound in which 2 carboxyl groups are esterified among 4 carboxyl groups of the symmetric tetracarboxylic acid and one of 2 carboxyl groups adjacent to each other on an aromatic ring is esterified.

Examples of the 2 esters of the symmetric aromatic tetracarboxylic acid diester includeDi-lower alkyl ester, preferably C such as dimethyl ester, diethyl ester, dipropyl ester_1-3Alkyl esters (in particular dimethyl esters).

Among the above symmetrical aromatic carboxylic acid diesters, dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, diethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, dimethyl 1, 2, 4, 5-benzenetetracarboxylic acid, and diethyl 1, 2, 4, 5-benzenetetracarboxylic acid are preferably used, and dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid is particularly preferably used.

The symmetric aromatic tetracarboxylic acid diester can be produced by a commercially available method or a known method. For example, by reacting 1 part of the corresponding symmetric aromatic tetracarboxylic dianhydride with 2 parts (molar ratio) of the corresponding alcohol (lower alcohol, preferably C)_1-3Alcohol, etc.) can be easily produced by a known method. By such a method, the acid anhydride as the raw material reacts with the alcohol to open the ring, and a diester (half-ester) having an ester group and a carboxyl group on the adjacent carbons of the aromatic ring can be produced.

The mixing ratio of the asymmetric and symmetric aromatic tetracarboxylic acid diester is particularly specified to be about 10 to 50 mol% (preferably 20 to 40 mol%) of the asymmetric aromatic tetracarboxylic acid diester and about 90 to 50 mol% (preferably 80 to 60 mol%) of the symmetric aromatic tetracarboxylic acid diester. Particularly, it is preferable that the asymmetric aromatic tetracarboxylic acid diester is about 20 to 30 mol% and the symmetric aromatic tetracarboxylic acid diester is about 70 to 80 mol%.

The reason why the above-mentioned asymmetric and symmetric aromatic tetracarboxylic acid component must be blended is as follows. When only the symmetric aromatic tetracarboxylic acid diester is used, the polyimide film exhibits crystallinity, and therefore the film is pulverized during the heat treatment and cannot be formed into a film. On the other hand, when only the asymmetric aromatic tetracarboxylic acid diester is used, although the film can be formed into an endless tubular PI film, the yield strength and elastic modulus of the obtained film are weak, and when the film is used as a rotating belt, problems such as poor responsiveness during driving and elongation of the rotating belt occur in an initial stage.

On the other hand, when the aromatic tetracarboxylic acid diester is used, a semiconductive endless tubular PI film having a high yield strength and a high elastic modulus can be obtained while having an extremely high film-forming property (moldability).

Further, the applicant considered that addition of an asymmetric aromatic tetracarboxylic acid diester could bend the polyamic acid molecule to impart flexibility.

Therefore, the coexistence effect of the symmetric and asymmetric aromatic tetracarboxylic acid derivatives can be most effectively exhibited at the mixing ratio of the two compounds as described above.

(2) Aromatic diamine

Examples of the aromatic diamine include compounds having 2 amino groups on one aromatic ring (benzene ring, etc.), and compounds having 2 or more aromatic rings (benzene ring, etc.) and containing-O-, -S-, -CO-, -CH₂-、-SO-、-SO₂Compounds with 2 amino groups, crosslinked by an iso-or single bond. Specifically, for example, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, 4 '-diaminodiphenyl ether, 4' -diaminodiphenyl sulfide, 4 '-diaminodiphenylcarbonyl, 4' -diaminodiphenylmethane, 1, 4-bis (4-aminophenoxy) benzene, and the like. Among them, 4' -diaminodiphenyl ether is particularly preferable. This is because the use of these aromatic diamines allows the reaction to proceed more smoothly and a film having higher toughness and higher heat resistance to be produced.

(3) Nylon salt type monomer solution

The 2 or more aromatic tetracarboxylic acid diesters and the aromatic diamine are uniformly dissolved in an organic polar solvent in approximately equimolar amounts to prepare a nylon salt type monomer solution. When both components are uniformly dissolved in an organic polar solvent, they may be heated (for example, about 40 to 70 ℃) as necessary. The two components may be dissolved in the organic polar solvent by a known mixing method such as stirring.

The organic polar solvent to be used is preferably an aprotic organic polar solvent, and examples thereof include N-methyl-2-pyrrolidone (hereinafter referred to as "NMP"), N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, and 1, 3-dimethyl-2-imidazolidinone. One or a mixture of two or more of them may be used. NMP is particularly preferred. The amount of the organic polar solvent to be used may be about 100 to 300 parts by weight (preferably about 120 to 200 parts by weight) based on 100 parts by weight of the total amount of the 2 or more kinds of aromatic tetracarboxylic acid diesters and aromatic diamines as raw materials.

The applicant believes that the nylon salt type monomer solution substantially maintains a monomer state of an ion pair of a carboxylic acid ion of an aromatic tetracarboxylic acid diester and an ammonium ion of an aromatic diamine in an organic polar solvent (for example, see the following formula). Further, since the organic polar solvent is substantially in a monomer state, it is easily dissolved in the organic polar solvent, and there is an advantage that the amount of the solvent to be used can be reduced as much as possible.

(wherein Ar represents a 4-valent group obtained by removing 2 carboxyl groups and 2 ester groups from an aromatic tetracarboxylic acid, Ar' represents a 2-valent group obtained by removing 2 amino groups from an aromatic diamine, and R represents an alkyl group.)

(4) High molecular weight polyimide precursor solution or high molecular weight polyamideimide solution

As the high molecular weight polyimide precursor solution, a polyamic acid solution having a number average molecular weight of 10000 or more is used; the high molecular weight polyamideimide solution used is a polyamideimide solution having a number average molecular weight of 10000 or more. The number average molecular weight in the present specification is a value measured by GPC method (in terms of solvent: NMP, polyethylene oxide).

Polyamic acid solution

The polyamic acid solution having a number average molecular weight of 10000 or more can be produced by a known method using, for example, biphenyltetracarboxylic dianhydride and diaminodiphenyl ether as starting materials in an organic polar solvent. The organic polar solvent used in the nylon salt type monomer solution can be used.

Examples of the biphenyltetracarboxylic dianhydride include 2, 3, 3 ', 4' -biphenyltetracarboxylic dianhydride (a-BPDA), 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride (s-BPDA), and 2, 2 ', 3, 3' -biphenyltetracarboxylic dianhydride.

Examples of the diaminodiphenyl ether component include 4, 4 ' -diaminodiphenyl ether, 3 ' -diaminodiphenyl ether, and 3, 4 ' -diaminodiphenyl ether.

The amount of the biphenyltetracarboxylic dianhydride and the diaminodiphenyl ether component may be substantially equimolar. The polycondensation reaction between the two can be carried out by a known method, and for example, a method in which a biphenyltetracarboxylic acid component is added to a solution containing a diaminodiphenyl ether component at room temperature (about 15 to 30 ℃) to cause amidation to prepare a polyamic acid solution can be mentioned. The obtained polyamic acid has a number average molecular weight of 10000 or more, preferably 12000 to 20000.

Polyamide-imide solution

The polyamideimide solution having a number average molecular weight of 10000 or more is produced by a known reaction such as a polycondensation reaction of an acid anhydride comprising trimellitic anhydride and benzophenone tetracarboxylic anhydride with an aromatic isocyanate in an organic polar solvent. As the organic polar solvent, the organic polar solvent used for the nylon salt type monomer solution can be used.

The acid anhydride may contain trimellitic anhydride in an amount of about 70 to 95 mol% and benzophenone tetracarboxylic anhydride in an amount of about 5 to 30 mol%.

Examples of the aromatic isocyanate include tolyiene diisocyanate, 3 '-diphenylsulfone diisocyanate, isophorone diisocyanate, 1, 4-diisocyanate, 4' -dicyclohexylmethane diisocyanate, m-xylene diisocyanate, p-xylene diisocyanate, and 1, 4-cyclohexylene diisocyanate.

The total number of carboxyl groups and acid anhydride groups in the acid component is preferably substantially equal to the total number of aromatic isocyanate groups.

The number average molecular weight of the polyamideimide is 10000 or more, preferably about 15000 to 20000.

(5) Mixed solution

The nylon salt type monomer solution is mixed with a high molecular weight polyimide precursor solution or a high molecular weight polyamideimide solution to prepare a mixed solution. The mixing may be carried out by a known method such as a screw mixer, a magnetic mixer, or a ball mill.

The amount (ratio) of the both is preferably in the range of about 10 to 50 parts by weight (preferably about 20 to 30 parts by weight) of the nonvolatile component of the high molecular weight polyimide precursor solution (particularly, a polyamic acid solution having a number average molecular weight of 10000 or more) or the high molecular weight polyamideimide solution (a polyamideimide solution having a number average molecular weight of 10000 or more) per 100 parts by weight of the nonvolatile component in the nylon salt type monomer solution. The term "nonvolatile weight" as used herein means the amount measured by the method described in example C-1.

Further, when the nonvolatile weight of the high molecular weight polyimide precursor solution or the high molecular weight polyamide imide solution is less than 10 parts by weight based on the nonvolatile weight of the nylon salt type monomer, the effect of the present invention is difficult to be obtained, and when carbon black is added to a solution of more than 50 parts by weight, the rate of increase in viscosity is remarkably increased, and pulverization of the carbon black becomes difficult, and as a result, it is necessary to add a large amount of organic polar solvent, and the production efficiency is lowered.

(6) Semiconductive PI precursor composition

Next, CB powder was uniformly dispersed in the mixed solution to prepare a semiconductive PI precursor composition.

The reason why the CB powder is used for imparting the electrical resistance characteristics is that the mixing dispersibility and stability (change with time after mixing and dispersion) between the CB powder and the prepared monomer mixed solution are excellent (compared with other generally known metal and metal oxide conductive materials), and the CB powder does not have an adverse effect on the polycondensation reaction.

The CB powder has various physical properties (resistance, volatile matter, specific surface area, particle diameter, pH, DBP oil absorption, etc.) depending on the production raw material (natural gas, acetylene gas, tar, etc.) and the production conditions (combustion conditions). It is preferable to select a stable and easily available CB powder that does not cause variation in desired resistance even when the amount of the CB powder is mixed and dispersed in a minimum amount.

The conductive CB powder has an average particle diameter of usually about 15 to 65nm, and when it is used particularly for an intermediate transfer belt of an electrophotographic system used for a color printer, a color copier and the like, it is preferably about 20 to 40 nm.

Carbon black having a high conductivity index, such as ketjen black (ketjen black) and acetylene black, is likely to cause 2-time aggregation, is likely to cause linkage of conductivity, and is difficult to control in a semiconductive region. Therefore, it is effective to use an acidic carbon black in which the structure formation is difficult.

Examples thereof include channel black and furnace black subjected to oxidation treatment. Specific examples thereof include Special Black 4(pH3, volatile matter content 14%, particle size 25nm) and Special Black 5(pH3, volatile matter content 15%, particle size 20nm) manufactured by Degusa corporation.

The method for mixing the CB powder is not particularly limited as long as the CB powder is uniformly mixed and dispersed in the mixed solution C. For example, a ball mill, a roller mill, an ultrasonic mill, or the like is used.

The amount of the CB powder to be added is preferably about 5 to 40 parts by weight (preferably about 10 to 30 parts by weight) based on 100 parts by weight of the total amount of (1) the aromatic tetracarboxylic acid component and the organic diamine as the raw materials of the nylon salt type monomer, and (2) the acid anhydride and the diamine as the raw materials of the high molecular weight polyimide, or the acid anhydride and the aromatic isocyanate as the raw materials of the high molecular weight polyamideimide. Here, the CB powder is used in the above range in order to impart Volume Resistivity (VR) and Surface Resistivity (SR) in the semiconductive region to the film. The lower limit of about 5 parts or more is because an amount of such an extent is necessary for obtaining sufficient conductivity; the upper limit of about 40 parts by weight is because the film exhibits a lower electric resistance and maintains moldability, thereby preventing a decrease in the physical properties of the film itself.

The concentration of non-volatile matter in the semiconductive PI precursor composition is about 20 to 60 wt%, and the concentration of CB powder in the non-volatile matter is about 5 to 30 wt% (preferably about 9 to 23 wt%). The "nonvolatile concentration" used herein means the concentration measured by the method described in example C-1.

In addition, additives such as imidazole compounds (2-methylimidazole, 1, 2-dimethylimidazole, 2-methyl-4-methylimidazole, 2-ethyl-4-ethylimidazole, 2-phenylimidazole), surfactants (fluorine-based surfactants, etc.) may be added to the composition within a range not adversely affecting the effect of the present invention.

Thus, a semiconductive PI precursor composition for molding in which CB powder was uniformly dispersed was produced.

In the semiconductive PI precursor composition of the present invention, by mixing a high molecular weight polyimide precursor solution or a high molecular weight polyamideimide solution in a nylon salt type monomer, the storage stability of a state in which carbon black is uniformly dispersed is significantly improved. The conductive tubular polyimide film obtained by rotational molding of the semiconductive PI precursor composition using the same is imparted with conductivity having extremely stable and uniform resistivity in the thickness direction. Although the reason for this is not yet determined, the applicant is: in the polyimide-based precursor composition, a polymer having a relatively high number average molecular weight is present, and the polymer component and the carbon black are physically linked or bonded to each other to inhibit aggregation of the carbon black. The applicant also considered that the influence of the centrifugal force on the carbon black particles during the spin molding is alleviated by the viscosity of the polymer, and that the influence of the temperature convection and the evaporation convection when the solvent is volatilized can also be alleviated. Further, the imidization reaction rate due to heating is also reduced.

Conductive endless tubular polyimide-based film

Next, a method for forming a conductive tubular PI film using the semiconductive PI precursor composition prepared as described above will be described.

The molding method employs a rotary molding method using a rotary cylinder. First, a semiconductive PI precursor composition was poured onto the inner surface of a rotating cylinder and uniformly cast on the entire inner surface.

The injection-casting method is, for example, a method in which a semiconductive PI precursor composition is injected into a rotating cylinder which is stopped in an amount corresponding to the final film thickness, and then the rotating speed is gradually increased to a speed at which a centrifugal force acts, and the composition is uniformly cast on the entire inner surface by the centrifugal force. Alternatively, injection-casting may be performed without using a centrifugal force. For example, a horizontally long slit-shaped nozzle is disposed on the inner surface of a rotating cylinder, and the cylinder is rotated slowly and continuously, and the nozzle is also rotated (at a speed higher than the rotating speed). Then, the semiconductive PI precursor composition for molding is uniformly sprayed from the nozzle over the entire inner surface of the cylinder.

In either method, the inner surface of the rotating cylinder is made into a mirror surface, and barriers for preventing liquid leakage are provided along the circumference at both end edges. The cylinder is mounted on a rotating roller and can be indirectly rotated by the rotation of the roller.

The heating is performed indirectly from the outside by disposing a heat source such as a far infrared heater around the cylinder. The size of the cylinder depends on the size of the semiconducting tubular PI film desired.

The inner surface of the cylinder is heated to a temperature of about 100 to 190 ℃ and preferably about 110 to 130 ℃ at first (heating stage 1). The temperature rise rate is, for example, about 1 to 2 ℃/min. Maintaining the temperature for 1 to 3 hours to evaporate more than half of the solvent, thereby forming a self-supporting tubular film. However, when the polyimide is initially heated at such a high temperature, the polyimide is highly crystallized, which affects the dispersion state of CB, and a strong coating cannot be formed. Therefore, in the 1 st heating stage, the upper limit temperature is controlled to about 190 ℃ at the maximum, and the polycondensation reaction is terminated at this temperature, whereby a strong tubular PI film is obtained.

After this stage, the second heating stage 2 is performed at a temperature of about 280 to 400 ℃ (preferably about 300 to 380 ℃) for completing the imidization. In this case, it is also preferable that the temperature is gradually increased to the temperature, rather than being suddenly increased from the temperature in the 1 st heating stage.

The 2 nd heating stage may be performed in a state where the endless tubular film is attached to the inner surface of the rotating cylinder as it is, or may be performed by heating the endless tubular film to 280 to 400 ℃ by providing another heating means for imidization after the 1 st heating stage by peeling the endless tubular film off the rotating cylinder and taking it out. The time for the imidization is usually about 2 to 3 hours. Therefore, the time required for the entire steps of the 1 st and 2 nd heating stages is usually about 4 to 7 hours.

Thus, the conductive endless tubular polyimide-based film of the present invention was produced. The thickness of the film is not particularly limited, but is usually about 30 to 200 μm, preferably about 50 to 120 μm. Particularly, when the intermediate transfer belt is used for an electrophotographic intermediate transfer belt, it is preferably about 70 to 100 μm.

The semiconductivity of the film is a resistance characteristic determined by both volume resistivity (Ω · cm) (hereinafter referred to as "VR") and surface resistivity (Ω/□) (hereinafter referred to as "SR"), which is imparted by the mixed dispersion of CB powder. The range of the resistivity can be changed by the amount of the CB powder to be mixed. As the resistivity range of the film of the present invention, VR: 10²～10¹⁴，SR：10³～10¹⁵As a preferable range, VR: 10⁶～10¹³，SR：10⁷～10¹⁴. These resistivity ranges can be easily achieved by using the above-mentioned CB powder blending amount. The content of CB in the film of the present invention is usually about 5 to 30 wt%, preferably about 9 to 23 wt%.

The semiconductive PI film of the present invention has a very homogeneous resistivity. That is, the semiconductive PI film of the present invention is characterized in that the variability of logarithmic conversion values of the surface resistivity SR and the volume resistivity VR is small, and the standard deviation of the respective logarithmic conversion values at all measurement points in the film is within 0.2, preferably within 0.15. Further, the difference between the surface resistivities (logarithmic conversion values) of the front surface and the back surface of the film is small, and the difference is preferably 0.4 or less, more preferably 0.2 or less. Further, the present invention has the following features: the log conversion value LogSR of the surface resistivity minus the log conversion value LogVR of the volume resistivity can be maintained at a high value of 1.0 to 3.0, preferably 1.5 to 3.0.

Since the PI film of the present invention has the above excellent electrical characteristics, it is considered that CB is physically and uniformly incorporated into the entangled structure of the polymer chains by mixing a high molecular weight polyimide precursor or a high molecular weight polyamideimide precursor solution, and therefore, CB is hardly affected by evaporation of a solvent in a film production process, a high molecular weight of a nylon salt type monomer, and the like, and a conductive endless tubular polyimide-based film can be obtained in a homogeneous CB-dispersed state in a precursor composition solution.

The PI film of the present invention has various uses because of its excellent functions such as resistance characteristics. For example, an important application requiring charging characteristics includes an electrophotographic intermediate transfer belt used in a color printer, a color copier, and the like. The tape has a required semiconductivity (resistivity), for example, VR10⁹～10¹²、SR10¹⁰～10¹³The semiconductive endless tubular PI-based film of the present invention can be suitably used.

The semiconductive PI film of the present invention has excellent performance as a belt and has high yield strength (σ)_Y) And breaking strength (. sigma.)_cr). Yield strength (sigma)_Y) At 120MPa or more, particularly 120 to 160MPa, the ratio (σ) of the breaking strength and the yield strength_cr/σ_Y) Is 1.10 or more, particularly about 1.10 to 1.35.

D. Fourth invention

The semiconductive endless tubular polyimide film (hereinafter also referred to as a "semiconductive tubular PI film") of the present invention is produced by rotational molding and heat treatment (imidization) using a semiconductive high-concentration polyimide precursor composition (hereinafter also referred to as a "semiconductive high-concentration PI precursor composition").

D-1 semiconductive high-concentration polyimide precursor composition

The semiconductive high-concentration polyimide precursor composition of the present invention is produced by dissolving an aromatic tetracarboxylic acid diester and an aromatic diamine in approximately equimolar amounts in a carbon black dispersion liquid in which carbon black (hereinafter also referred to as "CB") is uniformly dispersed in an organic polar solvent. Namely, it has the following features: the molding material is produced by adding equimolar amounts of monomers (equimolar amounts of the aromatic tetracarboxylic acid diester and the aromatic diamine) as the molding raw materials to a uniform dispersion of previously prepared CB.

(1) Carbon black dispersion

In the present invention, conductive CB powder is used in the PI precursor composition in order to impart semiconductivity. The reason why the CB powder is used is that the semiconductive high-concentration polyimide precursor composition prepared has excellent mixing dispersibility and dispersion stability (change with time after mixing and dispersion) of CB and does not adversely affect the polycondensation reaction (compared with other generally known metal or metal oxide conductive materials).

The CB powder has various physical properties (resistance, volatile matter, specific surface area, particle diameter, pH, DBP oil absorption, etc.) depending on the production raw material (natural gas, acetylene gas, tar, etc.) and the production conditions (combustion conditions). It is preferable to select a stable and easily available CB powder that does not cause variation in desired resistance even when the amount of the CB powder is mixed and dispersed in a minimum amount.

The conductive CB powder has an average particle diameter of usually about 15 to 65nm, and when it is used particularly for an intermediate transfer belt of an electrophotographic system used for a color printer, a color copier and the like, it is preferably about 20 to 40 nm.

Carbon black having a high conductivity index, such as ketjen black and acetylene black, is likely to cause 2-time aggregation (structure), and is likely to cause linkage of conductivity, and is difficult to control in a semiconductive region. Therefore, it is effective to use an acidic carbon black in which the structure formation is difficult.

Examples thereof include channel black and furnace black subjected to oxidation treatment. Specific examples thereof include Special Black 4(pH3, volatile matter content 14%, particle size 25nm) and Special Black 5(pH3, volatile matter content 15%, particle size 20nm) manufactured by Degusa corporation.

The organic polar solvent used for the carbon black dispersion is preferably an aprotic organic polar solvent, and examples thereof include N-methyl-2-pyrrolidone (hereinafter referred to as "NMP"), N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, and 1, 3-dimethyl-2-imidazolidinone. One or a mixed solution of two or more of them may be used. NMP is particularly preferred.

The carbon black dispersion is produced by uniformly dispersing CB powder in the organic polar solvent. The method for mixing the CB powder is not particularly limited as long as the CB powder is uniformly mixed and dispersed in the organic polar solvent. For example, a ball mill, a roller mill, an ultrasonic mill, or the like is used.

The amount of the CB powder is about 3 to 25 parts by weight, preferably about 5 to 15 parts by weight, based on 100 parts by weight of the organic polar solvent. The amount of the complex is in a range in which the viscosity of the organic polar solvent is not increased or CB is not aggregated 2 times by van der waals force. The lower limit of 3 parts by weight or more based on 100 parts by weight of the organic polar solvent is an amount necessary for not reducing the nonvolatile concentration of the semiconductive high-concentration polyimide precursor composition to be produced. The upper limit is 25 parts by weight or less in order to provide sufficient distance between the uniformly dispersed CB particles and prevent 2 times of aggregation due to van der waals force.

(2) Aromatic tetracarboxylic acid diesters (half esters)

As the 2 or more kinds of aromatic tetracarboxylic acid diesters as the molding raw materials, a mixture of at least one asymmetric aromatic tetracarboxylic acid diester and at least one symmetric aromatic tetracarboxylic acid diester is used.

The asymmetric aromatic tetracarboxylic acid diester used in the present invention will be described below.

Here, the asymmetric aromatic tetracarboxylic acid includes compounds in which 4 carboxyl groups are bonded to non-point-symmetric positions on monocyclic or polycyclic aromatic rings (benzene ring, naphthalene ring, biphenyl ring, anthracene ring, etc.), or compounds in which 2 monocyclic aromatic rings (benzene ring, etc.) are bonded to non-point-symmetric positions with-CO-, -CH-, - -O-groups₂-、-SO₂4 carboxyl groups bound to non-points on compounds crosslinked by an iso-or single bondSymmetrically positioned compounds.

Specific examples of the asymmetric aromatic tetracarboxylic acid include 1, 2, 3, 4-benzenetetracarboxylic acid, 1, 2, 6, 7-naphthalenetetracarboxylic acid, 2, 3, 3 ', 4' -biphenyltetracarboxylic acid, 2, 3, 3 ', 4' -benzophenonetetracarboxylic acid, 2, 3, 3 ', 4' -diphenylethertetracarboxylic acid, 2, 3, 3 ', 4' -diphenylmethane tetracarboxylic acid, and 2, 3, 3 ', 4' -diphenylsulfonetetracarboxylic acid.

The asymmetric aromatic tetracarboxylic acid diester (half ester) used in the present invention includes diesters of the asymmetric aromatic tetracarboxylic acids, and specifically includes compounds in which 2 carboxyl groups are esterified in 4 carboxylic acids of the asymmetric aromatic tetracarboxylic acids and one of 2 carboxyl groups adjacent to each other on the aromatic ring is esterified.

Examples of the 2-ester in the asymmetric aromatic tetracarboxylic acid diester include a di-lower alkyl ester, preferably C such as dimethyl ester, diethyl ester, dipropyl ester and the like_1-3Alkyl esters (especially the dimethyl esters).

Among the diesters of the asymmetric aromatic carboxylic acids, dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid and diethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid are preferably used, and dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid is particularly preferably used.

The asymmetric aromatic tetracarboxylic acid diester can be produced by a commercially available method or a known method. For example, by mixing 1 part of the corresponding asymmetric aromatic tetracarboxylic dianhydride and 2 parts (molar ratio) of the corresponding alcohol (lower alcohol, preferably C)_1-3Alcohol, etc.) can be easily produced. By such a method, the acid anhydride as the raw material reacts with the alcohol to open the ring, and a diester (half-ester) having an ester group and a carboxyl group on the adjacent carbons of the aromatic ring can be produced.

Next, diesters of symmetric aromatic tetracarboxylic acids used in the present invention will be described below.

Here, the aromatic compound is a symmetric aromatic compoundExamples of the tetracarboxylic acid include compounds in which 4 carboxyl groups are bonded to a point-symmetrical position on a monocyclic or polycyclic aromatic ring (e.g., benzene ring, naphthalene ring, biphenyl ring, and anthracene ring), and compounds in which 2 monocyclic aromatic rings (e.g., benzene ring) are bonded to a point-symmetrical position with-CO-, -O-, -CH-, -C-₂-、-SO₂Compounds in which 4 carboxyl groups are bonded in point-symmetrical positions on compounds crosslinked by an iso-or single bond.

Specific examples of the symmetrical aromatic tetracarboxylic acid include 1, 2, 4, 5-benzenetetracarboxylic acid, 2, 3, 6, 7-naphthalenetetracarboxylic acid, 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, 3, 3 ', 4, 4' -benzophenonetetracarboxylic acid, 3, 3 ', 4, 4' -diphenylethertetracarboxylic acid, 3, 3 ', 4, 4' -diphenylmethane tetracarboxylic acid, 3, 3 ', 4, 4' -diphenylsulfonetetracarboxylic acid, and the like.

The diester (half-ester) of a symmetric aromatic tetracarboxylic acid used in the present invention includes a diester (half-ester) of the symmetric aromatic tetracarboxylic acid, and specifically includes a compound in which 2 carboxyl groups are esterified among 4 carboxylic acids of the symmetric aromatic tetracarboxylic acid and one of 2 carboxyl groups adjacent to each other on an aromatic ring is esterified.

Examples of the 2-membered ester of the symmetric aromatic tetracarboxylic acid diester include a di-lower alkyl ester, preferably C such as dimethyl ester, diethyl ester and dipropyl ester_1-3Alkyl esters (in particular dimethyl esters).

Among the above symmetrical aromatic carboxylic acid diesters, dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, diethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid, dimethyl 1, 2, 4, 5-benzenetetracarboxylic acid, and diethyl 1, 2, 4, 5-benzenetetracarboxylic acid are preferably used, and dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid is particularly preferably used.

The symmetric aromatic tetracarboxylic acid diester can be produced by a commercially available method or a known method. For example, by reacting 1 part of the corresponding symmetric aromatic tetracarboxylic dianhydride with 2 parts (molar ratio) of the corresponding alcohol (lower alcohol, preferably C)_1-3Alcohol, etc.) can be easily produced by a known method. By such a methodIn the method, an acid anhydride as a raw material is reacted with an alcohol to open a ring, thereby producing a diester (half-ester) having an ester group and a carboxyl group on adjacent carbons of an aromatic ring.

The mixing ratio of the asymmetric and symmetric aromatic tetracarboxylic diesters is particularly specified to be about 10 to 50 mol% (preferably 20 to 40 mol%) of the asymmetric aromatic tetracarboxylic diester and about 90 to 50 mol% (preferably 80 to 60 mol%) of the symmetric aromatic tetracarboxylic diester. In particular, it is preferable that the asymmetric aromatic tetracarboxylic acid diester is about 20 to 30 mol% and the symmetric aromatic tetracarboxylic acid diester is about 70 to 80 mol%.

The reason why the above-mentioned symmetric and asymmetric aromatic tetracarboxylic diesters must be blended is as follows. When only the symmetric aromatic tetracarboxylic acid diester is used, the polyimide film exhibits crystallinity, and therefore the film is pulverized during the heat treatment and cannot be formed into a film. On the other hand, when only the asymmetric aromatic tetracarboxylic acid derivative is used, although the film can be formed into an endless tubular PI film, the obtained film has a low yield strength and a low elastic modulus, and when the film is used as a rotating belt, the film is not only poor in response during driving but also has problems such as elongation of the rotating belt at an initial stage.

On the other hand, when the aromatic tetracarboxylic acid diester is used, a semiconductive endless tubular PI film having a high yield strength and a high elastic modulus can be obtained while having an extremely high film-forming property (moldability).

Further, the applicant considered that addition of an asymmetric aromatic tetracarboxylic acid diester could bend the polyamic acid molecule to impart flexibility.

The coexistence effect of the symmetric and asymmetric aromatic tetracarboxylic acid derivatives can be most effectively exhibited at the mixing ratio of the two compounds as described above.

(3) Aromatic diamine

As the aromatic diamine, there may be mentionedA compound having 2 amino groups on one aromatic ring (benzene ring, etc.), or 2 or more aromatic rings (benzene ring, etc.) — O-, -S-, -CO-, -CH₂-、-SO-、-SO₂Compounds with 2 amino groups, crosslinked by an iso-or single bond. Specifically, for example, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, 4 '-diaminodiphenyl ether, 4' -diaminodiphenyl sulfide, 4 '-diaminodiphenylcarbonyl, 4' -diaminodiphenylmethane, 1, 4-bis (4-aminophenoxy) benzene, and the like. Among them, 4' -diaminodiphenyl ether is particularly preferable. This is because the use of these aromatic diamines allows the reaction to proceed more smoothly and a film which is stronger and has higher heat resistance to be produced.

(4) Semiconductive high-concentration polyimide precursor composition

Next, the aromatic tetracarboxylic acid diester and the aromatic diamine are added in approximately equimolar amounts and dissolved in the obtained carbon black dispersion.

The semiconductive high-concentration polyimide precursor composition is produced by adding the aromatic tetracarboxylic acid component and the organic diamine in approximately equimolar amounts to a carbon black dispersion and uniformly dissolving the components by stirring. When both components are uniformly dissolved in the carbon black dispersion, heating (for example, about 40 to 70 ℃) may be performed as necessary. The two components may be dissolved in the organic polar solvent by a known mixing method such as stirring.

The blending amount of the aromatic tetracarboxylic acid diester and the aromatic diamine may be adjusted so that the carbon black in the carbon black dispersion is about 5 to 35 parts by weight (preferably about 8 to 30 parts by weight) with respect to 100 parts by weight of the total amount of the aromatic tetracarboxylic acid diester and the aromatic diamine. The blending amount is within the above range in order to impart Volume Resistivity (VR) and Surface Resistivity (SR) in the semiconductive region to the film.

The applicant believes that the semiconductive high-concentration polyimide precursor composition substantially remains in a monomer state (for example, see the following formula) as an ion pair of a carboxylic acid ion of an aromatic tetracarboxylic acid diester and an ammonium ion of an aromatic diamine in an organic polar solvent.

(wherein Ar represents a 4-valent group obtained by removing 2 carboxyl groups and 2 ester groups from an aromatic tetracarboxylic acid, Ar' represents a 2-valent group obtained by removing 2 amino groups from an aromatic diamine, and R represents an alkyl group.)

Further, since the organic polar solvent is substantially in a monomer state, it is easily dissolved in the organic polar solvent, and there is an advantage that the amount of the solvent to be used can be reduced as much as possible. In addition, the nonvolatile concentration in the composition can be set as follows: for example, the concentration is about 35 to 60 wt%, preferably about 40 to 60 wt%. The concentration of CB in the nonvolatile fraction can be set to: for example, about 4 to 30 wt%, preferably about 10 to 25 wt%. The "nonvolatile concentration" used herein means the concentration measured by the method described in example D-1.

In addition, additives such as imidazole compounds (2-methylimidazole, 1, 2-dimethylimidazole, 2-methyl-4-methylimidazole, 2-ethyl-4-ethylimidazole, 2-phenylimidazole), surfactants (fluorine-based surfactants, etc.) may be added to the composition within a range not adversely affecting the effect of the present invention.

Thus, a semiconductive PI precursor composition in which CB powder is uniformly dispersed and nonvolatile matter is dissolved or dispersed at a high concentration is produced.

In the semiconductive high-concentration PI precursor composition of the present invention, a carbon black dispersion in which CB powder is uniformly dispersed is prepared, and the CB powder is uniformly dispersed by dissolving the aromatic tetracarboxylic acid diester and the aromatic diamine component in the carbon black dispersion, and the storage stability of the uniformly dispersed state of the CB powder is significantly improved. Further, a conductive polyimide tube obtained by rotational molding of a semiconductive PI precursor composition using the same is imparted with conductivity having extremely stable and uniform resistivity in the thickness direction thereof.

In the semiconductive high-concentration PI precursor composition of the present invention, since a monomer as a molding material is dissolved in the carbon black dispersion, the nonvolatile concentration can be significantly increased to about 35 to 60% by weight. Therefore, a film having a thick film can be easily produced by using the semiconductive high-concentration PI precursor composition of the present invention, and the amount of solvent used is small, so that the cost can be reduced and the solvent can be easily evaporated and removed.

Further, the semiconductive high-concentration PI precursor composition of the present invention can have a viscosity as high as about 10 to 60 poise, and therefore, the PI film is less likely to be affected by the centrifugal force of spin molding.

D-2 semi-conductive endless tubular polyimide film

Next, a method for forming a semiconductive endless tubular PI film using the semiconductive PI precursor composition prepared as described above will be described.

The molding method employs a rotary molding method using a rotary cylinder. First, a semiconductive PI precursor composition was poured onto the inner surface of a rotating cylinder and uniformly cast on the entire inner surface.

The injection-casting method is, for example, a method in which a semiconductive PI precursor composition is injected into a rotating cylinder which is stopped in an amount corresponding to the final film thickness, and then the rotating speed is gradually increased to a speed at which a centrifugal force acts, and the composition is uniformly cast on the entire inner surface by the centrifugal force. Alternatively, injection-casting may be performed without using a centrifugal force. For example, a horizontally long slit-shaped nozzle is disposed on the inner surface of a rotating cylinder, and the cylinder is rotated slowly and continuously, and the nozzle is also rotated (at a speed higher than the rotating speed). Then, the semiconductive PI precursor composition for molding is uniformly sprayed from the nozzle over the entire inner surface of the cylinder. The cylinder is mounted on a rotating roller and can be indirectly rotated by the rotation of the roller.

The heating is performed indirectly from the outside by disposing a heat source such as a far infrared heater around the cylinder. The size of the cylinder depends on the size of the semiconducting tubular PI film desired.

The inner surface of the cylinder is heated to a temperature of about 100 to 190 ℃ and preferably about 110 to 130 ℃ at first (heating stage 1). The temperature rise rate is, for example, about 1 to 2 ℃/min. Maintaining the temperature for 1 to 3 hours to evaporate more than half of the solvent, thereby forming a self-supporting tubular film. However, when the polyimide is initially heated at such a high temperature, the polyimide is highly crystallized, which affects the dispersion state of CB, and a strong film cannot be formed. Therefore, in the 1 st heating stage, the upper limit temperature is controlled to about 190 ℃ at the maximum, and the polycondensation reaction is terminated at this temperature, whereby a strong tubular PI film is obtained.

After this stage, the second heating stage 2 is performed at a temperature of about 280 to 400 ℃ (preferably about 300 to 380 ℃) for completing the imidization. In this case, it is also preferable that the temperature is gradually increased to the temperature rather than being suddenly increased from the stage 1 heating temperature.

The heating in the 2 nd stage may be performed in a state where the endless tubular film is attached to the inner surface of the rotating cylinder as it is, or the endless tubular film may be peeled off from the rotating cylinder and taken out after the 1 st heating stage is completed, and other heating means for imidization may be provided to heat the endless tubular film to 280 to 400 ℃. The time for the imidization is usually about 2 to 3 hours. Therefore, the time required for the entire steps of the 1 st and 2 nd heating stages is usually about 4 to 7 hours.

Thus, the semiconductive tubular PI film of the present invention was produced. The thickness of the film is not particularly limited, but is usually about 30 to 200 μm, preferably about 60 to 120 μm. Particularly, when the intermediate transfer belt is used for an electrophotographic intermediate transfer belt, it is preferably about 75 to 100 μm.

The semiconductivity of the film is a resistance characteristic determined by both volume resistivity (Ω · cm) (hereinafter referred to as "VR") and surface resistivity (Ω/□) (hereinafter referred to as "SR"), which is imparted by the mixed dispersion of CB powder. The range of the resistance can be changed by the amount of the CB powder to be mixed. As the resistivity range of the film of the present invention, VR: 10²～10¹⁴，SR：10³～10¹⁵As a preferable range, VR: 10⁶～10¹³，SR：10⁷～10¹⁴. These resistivity ranges can be easily achieved by using the above-mentioned CB powder blending amount. The content of CB in the film of the present invention is usually about 5 to 25 wt%, and preferably about 8 to 20 wt%.

The semiconductive tubular PI film of the invention has a very homogeneous resistivity. That is, the semiconductive tubular PI film of the present invention is characterized in that the variability of logarithmic conversion values of the surface resistivity SR and the volume resistivity VR is small, and the standard deviation of the respective logarithmic conversion values at all measurement points in the film is within 0.2, preferably 0.15 or less. Further, the difference between the surface resistivities (logarithmic conversion values) of the front surface and the back surface of the film is small, and the difference is preferably 0.4 or less, more preferably 0.2 or less. Further, the present invention has the following features: the log conversion value LogSR of the surface resistivity minus the log conversion value LogVR of the volume resistivity can be maintained at a high value of 1.0 to 3.0, preferably 1.5 to 3.0.

The PI film of the present invention has various uses because of its excellent functions such as resistance characteristics. For example, an important application requiring charging characteristics includes an electrophotographic intermediate transfer belt used in a color printer, a color copier, and the like. The tape has a required semiconductivity (resistivity), for example, VR10⁹～10¹²、SR10¹⁰～10¹³The semiconductivity of the invention can be suitably appliedAn endless tubular PI film.

The semiconductive PI film of the present invention has excellent performance as a belt and has high yield strength (σ)_Y) And breaking strength (. sigma.)_cr). Yield strength (sigma)_Y) At 120MPa or more, particularly 120 to 160MPa, the ratio (σ) of the breaking strength and the yield strength_cr/σ_Y) Is 1.10 or more, particularly about 1.10 to 1.35.

Examples

The present invention will be described in more detail below with reference to comparative examples and examples, but the present invention is not limited to these examples.

A. First invention

The first invention will be described in more detail with reference to comparative examples and examples.

The yield strength (yield stress), breaking strength, Volume Resistivity (VR), Surface Resistivity (SR), and nonvolatile concentration in this example were values measured as follows.

[ yield Strength (MPa) (simply. sigma.) ]_Y) And breaking Strength (MPa) (simply. sigma.)_cr)]

The film obtained in each example was cut into a width of 5mm and a length of 100mm, and the cut film was measured as a test piece by a uniaxial tensile tester (odograph) at a tensile distance of 40mm and a deformation speed of 200 mm/min. Reading σ from the recorded S-S curve_YAnd σ_cr。

The yield strength and the breaking strength are strength factors important in designing a material for a belt, and at least the yield strength needs to be 120 MPa. This is because plastic deformation (dimensional change due to extension) due to stress when a load is applied cannot be generated in the assembly.

Further, it is necessary that the fracture strength is higher than the yield strength, and the durability (toughness) against rotation of the belt is imparted. As its object, it is necessary to at leastσ_cr/σ_Y1.10 or more.

[ VR and SR ]

The obtained tubular film was cut into a length of 400mm as a sample, and measured at 5 places at equal intervals in the width direction and at 8 places at equal intervals in the longitudinal (circumferential) direction, respectively, using a resistance measuring instrument "Hiresta IP-HR probe" manufactured by Mitsubishi chemical corporation, and the total of the measured values was 40 places, and the average value of the whole was expressed.

VR is measured after 10 seconds with 100V applied, and SR is measured after 10 seconds with 500V applied.

[ non-volatile concentration ]

The sample (monomer mixture solution, etc.) is placed in a heat-resistant container such as a metal cup, and the weight of the sample is determined to be Ag. The heat-resistant container containing the sample was placed in an electric oven, and heated and dried at 120 ℃x12 minutes, 180 ℃x12 minutes, 260 ℃x30 minutes, and 300 ℃x30 minutes in this order, and the weight (nonvolatile weight) of the obtained solid content was assumed to be Bg. For the same sample, the values of a and B (n is 5) were measured for 5 samples, and substituted into the following formula (I) to determine the nonvolatile concentration. The average value of the 5 samples was used as the nonvolatile concentration in the present invention.

Nonvolatile concentration ═ B/A X100 (%) (I)

Example A-1

716.0g (2.0 moles) of dimethyl 2, 3, 3 ', 4 ' -biphenyltetracarboxylic acid (1 mole of a reaction product of 2, 3, 3 ', 4 ' -biphenyltetracarboxylic dianhydride and 2 moles of methanol, half ester) and 400.0g (2.0 moles) of 4, 4 ' -diaminodiphenyl ether were mixed at ordinary temperature and uniformly dissolved in 1540g of NMP solvent. The solution had a nonvolatile concentration of 34.6% by weight, a solution viscosity of about 250 mPas, and was stable in a monomer state without substantially undergoing a polycondensation reaction. Hereinafter, the asymmetric monomer solution A will be referred to as an asymmetric monomer solution A.

On the other hand, 716.0g (2.0 moles) of dimethyl 3, 3 ', 4, 4 ' -biphenyltetracarboxylic acid (1 mole of a reaction product of 3, 3 ', 4, 4 ' -biphenyltetracarboxylic dianhydride and 2 moles of methanol, half ester) and 400.0g (2.0 moles) of 4, 4 ' -diaminodiphenyl ether were mixed at room temperature and uniformly dissolved in 1540g of an NMP solvent. The solution had a nonvolatile concentration of 34.6% by weight, a solution viscosity of about 250 mPas, and was stable in a monomer state without substantially undergoing a polycondensation reaction. Hereinafter, the term "symmetrical monomer solution B" will be used.

Then, the asymmetric monomer solution A and the symmetric monomer solution B were thoroughly mixed with 0.037 wt% (based on nonvolatile matter) of a fluorine-based surfactant (EF-351, manufactured by Tohkem Products, Co., Ltd.) in the respective quantitative ratios described in EX.1 and EX.2 shown in Table A-1, and defoamed. A predetermined amount of each of the monomer solutions C for molding was collected from the respective solutions, and the collected solution was poured into a rotating cylinder and molded under the following conditions.

Rotating the cylinder: a metal cylinder having a mirror surface on the inner surface with an inner diameter of 100mm and a width of 530mm was placed on two rotating rollers and was arranged so as to rotate together with the rotation of the rollers.

Injection amount of the molding monomer solution C: 45.9g

Heating temperature: a far infrared heater is disposed on the outer surface of the cylinder, and the temperature of the inner surface of the cylinder is controlled to 170 ℃.

First, 45.9g of each of the monomer solutions was uniformly poured into the bottom surface of the cylinder with the rotation of the cylinder stopped. Then, the rotation was started immediately, the speed was increased slowly to 24rad/s, and the mixture was uniformly cast on the entire inner surface and heated. The heating was carried out at a temperature of 170 ℃ while maintaining the rotation and for 90 minutes.

After completion of the 90-minute rotation-heating, the reaction mixture was cooled to room temperature, the rotary cylinder was detached as it was, and the reaction mixture was left to stand in a hot-air retention type oven (hot-air furnace) to start heating for imidization. The heating was also carried out slowly to a temperature of 350 ℃. Then, the film was heated at this temperature for 30 minutes, cooled to room temperature, and the tubular PI film formed on the inner surface of the cylinder was peeled off and taken out. The results of the examples are set forth in Table A-2.

TABLE A-1

TABLE A-2

Comparative example A-1

The asymmetric monomer solution A and the symmetric monomer solution B of example A-1 were mixed at the quantitative ratios of EX.3 to 6 shown in Table A-1, and molding, imidation, peeling from a rotating cylinder, and taking out were carried out under the same conditions as in this example to measure. The respective results are set forth in Table A-2.

Example A-2

Using the asymmetric monomer solution A and the symmetric monomer solution B in example A-1, in the same manner as in this example at the quantitative ratio described in EX.7 shown in Table A-1, first, they were uniformly mixed, and then, 14.0g (8.33 parts by weight based on 100 parts by weight of the total monomers) of CB powder (pH3, particle diameter 23nm) was added thereto, followed by thorough mixing and dispersion in a ball mill, and finally, deaeration was carried out. The resulting solution was used as a semiconductive monomer solution for molding. The concentration of non-volatile components in the semiconductive monomer solution was 36.8% by weight, and the concentration of CB in the non-volatile components was 9.19% by weight.

Then, 45.9g of the solution was collected, poured into a rotating cylinder in the same manner as in example A-1, molded under the same conditions, and imidized. The obtained imidized film was peeled off from the rotating cylinder and taken out for measurement. The results are set forth in Table A-2.

Comparative example A-2

First, the asymmetric monomer solution A and the symmetric monomer solution B of example A-1 were uniformly mixed in the same manner as in this example at the quantitative ratios of EX.8 and EX.9 shown in Table A-1, and then, CB powder was added thereto in an amount of 8.33 parts by weight based on 100 parts by weight of the total amount of all monomers in the same manner as in example A-2, and the mixture was sufficiently mixed and dispersed in a ball mill and then defoamed. The resulting solution was used as a semiconductive monomer solution for molding. The concentration of non-volatile components in the semiconductive monomer solution was 36.8% by weight, and the concentration of CB in the non-volatile components was 9.19% by weight.

Then, 45.9g of each of the solutions A and B was collected, poured into a rotary cylinder in the same manner as in example A-1, and molded under the same conditions. After the imidization, the film was peeled off from the rotating cylinder and taken out for measurement. The results are set forth in Table A-2.

B. Second invention

Next, the second invention will be described in more detail with reference to comparative examples and examples.

Example B-1

358.0g (1.0 mole) of dimethyl 2, 3, 3 ', 4 ' -biphenyltetracarboxylic acid (a reactant of 1 mole of 2, 3, 3 ', 4 ' -biphenyltetracarboxylic dianhydride and 2 moles of methanol, diester) and dimethyl 3, 3 ', 4, 4 ' -biphenyltetracarboxylic acid (a reactant of 1 mole of 3, 3 ', 4, 4 ' -biphenyltetracarboxylic dianhydride and 2 moles of methanol, diester) 358.0g (1.0 mole) and 400.0g (2.0 moles) of 4, 4 ' -diaminodiphenyl ether were mixed and uniformly dissolved in 1674g of NMP solvent at 60 ℃ and then heated to 100 ℃ for 1hr at 1hr, heated at 100 ℃ and then cooled. This solution was an oligomer-like solution having a nonvolatile concentration of 32.9% by weight and a number average molecular weight of 2000. Hereinafter, the "oligomer mixed solution A" will be referred to.

To 1000g of the oligomer mixed solution A, 71.7g of Carbon Black (CB) powder (pH3, particle diameter 23nm) and NMP142.5g were added, and the mixture was thoroughly mixed and dispersed in a ball mill, followed by deaeration. This was used as a semiconductive oligomer solution for molding. The semiconductive oligomer solution had a nonvolatile content concentration of 33.0% by weight, and a CB concentration in the nonvolatile content of 17.89% by weight.

Then, 109g of the solution was collected and poured into a rotating cylinder, and the mixture was molded under the following conditions.

Rotating the cylinder: a metal cylinder having an inner diameter of 175mm and a width of 540mm and a mirror surface on the inner surface thereof was placed on two rotating rollers and was disposed so as to rotate together with the rotation of the rollers.

Heating temperature: a far infrared heater is disposed on the outer surface of the cylinder, and the temperature of the inner surface of the cylinder is controlled to 120 ℃.

First, 109g of the solution was uniformly applied to the inner surface of the cylinder while the rotating cylinder was rotating, and heating was started. The heating was carried out at a temperature of 120 ℃ at 2 ℃/min while maintaining the rotation, and the temperature was maintained for 90 minutes.

After completion of the rotation and heating, the rotating cylinder was directly detached without cooling, and the heated cylinder was left in a hot air retention type oven to start heating for imidization. The heating was also carried out slowly to a temperature of 320 ℃. Then, the film was heated at this temperature for 30 minutes, cooled to room temperature, and peeled off to take out the semiconductive tubular PI film formed on the inner surface of the cylinder. Further, the thickness of the film was 90 μm.

The "nonvolatile concentration" in the present specification is a value calculated as follows. The sample (semiconductive oligomer solution or the like) is placed in a heat-resistant container such as a metal cup and accurately weighed, and the weight of the sample at this time is Ag. The heat-resistant container containing the sample was placed in an electric oven, and heated and dried at 120 ℃x12 minutes, 180 ℃x12 minutes, 260 ℃x30 minutes, and 300 ℃x30 minutes in this order, and the weight (nonvolatile weight) of the obtained solid content was assumed to be Bg. For the same sample, the values of a and B (n is 5) were measured for 5 samples, and substituted into the following formula (I) to determine the nonvolatile concentration. The average value of the 5 samples was used as the nonvolatile concentration in the present invention.

Nonvolatile concentration ═ B/A X100 (%) (I)

Reference example B-1

Dimethyl carboxylate and diaminodiphenyl ether were mixed in the same quantitative ratio as in example B-1, and the solution dissolved at 60 ℃ was directly cooled. This solution was a substantially monomer solution having a nonvolatile concentration of 32.9 wt%. Hereinafter referred to as "monomer solution A".

To 1000g of the monomer solution A, 31.0g of CB powder (pH3, particle diameter 23nm) and 60.0g of NMP were added, and the mixture was thoroughly mixed and dispersed in a ball mill, followed by degassing. The resulting solution was used as a semiconductive monomer solution for molding. The concentration of non-volatile matter in the semiconductive monomer solution was 33.0% by weight, and the concentration of CB in the non-volatile matter was 8.61% by weight.

Then, 109g of the solution was collected and subjected to thermoforming in the same manner as in example B-1, followed by peeling and taking out the semiconductive tubular PI film. Further, the thickness of the film was 92 μm.

Example B-2

143.2g (0.4 mol) of dimethyl 2, 3, 3 ', 4 ' -biphenyltetracarboxylic acid (1 mol of a reactant, diester, of 2, 3, 3 ', 4 ' -biphenyltetracarboxylic dianhydride and 2 mol of methanol) and dimethyl 3, 3 ', 4, 4 ' -biphenyltetracarboxylic acid (1 mol of a reactant, diester, of 3, 3 ', 4, 4 ' -biphenyltetracarboxylic dianhydride and 2 mol of methanol) are mixed and uniformly dissolved in 1674g of NMP solvent at 60 ℃ together with 572.8g (1.6 mol) of 4, 4 ' -diaminodiphenyl ether (2 mol), and then the mixture is heated to 110 ℃ for 1hr at 1hr, and then cooled after heating at 110 ℃ for 1 hr. This solution was an oligomer-like solution having a nonvolatile concentration of 32.9% by weight and a number average molecular weight of 4000. Hereinafter, the "oligomer mixed solution B" will be referred to as "oligomer mixed solution B".

To 1000g of this oligomer mixed solution B, 78.9g of CB powder (pH3, particle diameter 23nm) and 157.1g of NMP were added, and the mixture was thoroughly mixed and dispersed in a ball mill, followed by degassing. This was used as a semiconductive oligomer solution for molding. The semiconductive oligomer solution had a nonvolatile content concentration of 33.0% by weight, and a CB concentration of 19.34% by weight in the nonvolatile content.

Then, 109g of the solution was collected and poured into a rotating cylinder, followed by thermoforming in the same manner as in example B-1, and the semiconductive tubular PI film was peeled off and taken out. Further, the thickness of the film was 89 μm.

Comparative example B-1

Dimethyl carboxylate and diaminodiphenyl ether were mixed in the same amount ratio as in example B-1, dissolved at 60 ℃, then heated to 130 ℃ over 1hr, heated at 130 ℃ for 1hr, and then cooled. However, the cooled solution was a gel-like solid which became cloudy and could not be used for molding.

The gel is not re-dissolvable even when diluted with a solvent. The imidization ratio of the obtained gel was measured, and it was confirmed that imidization reaction was performed by about 35%. That is, the applicant considered that the solubility decreased and the resin component precipitated due to the excessive imidization reaction caused by the high heating temperature.

Test example B-1

The film production conditions of the above examples B-1 to B-2, reference example B-1 and comparative example B-1 and the measurement results of the resistance values of the obtained films are shown in Table B-1. The surface resistivity, the average volume resistivity and the standard deviation in Table B-1 are all expressed in logarithmic scale values.

[ number average molecular weight ]

The number average molecular weight was measured by GPC method (in terms of solvent: NMP, polyethylene oxide).

[ imidization ratio ]

By absorption from the imide group in an infrared spectrophotometer (1780 cm)^-1) And absorption from benzene ring (1510 cm)^-1) Is calculated from the ratio of the intensities of (a). The absorption of the benzene ring did not change either in the precursor or after imidization, and therefore this was used as a control.

[ measurement of Surface Resistivity (SR) and Volume Resistivity (VR) ]

The obtained tubular film was cut into a length of 400mm as a sample, and 3 places were measured at equal intervals in the width direction and 4 places were measured at equal intervals in the longitudinal (circumferential) direction using a resistance measuring instrument "Hiresta IP-HR probe" manufactured by Mitsubishi chemical corporation, and the total of 12 places was expressed as an average value of the whole.

The Volume Resistivity (VR) was measured after 10 seconds with 100V applied voltage, and the Surface Resistivity (SR) was measured after 10 seconds with 500V applied voltage.

As can be seen from table B-1, the standard deviation of the surface resistivity and the volume resistivity of the films of examples was very small, i.e., the variability was small, compared to the reference examples and comparative examples.

In addition, the films of the examples had very small differences in surface resistivity (logarithmic conversion value) between the front and back sides of the films, and had good characteristics as intermediate transfer belts for color copiers, compared with the reference examples and comparative examples.

In general, when the heating temperature rise rate in the molding is accelerated, the Log (SR/VR)) obtained by subtracting the Log converted value LogSR of the surface resistivity from the Log converted value LogVR of the volume resistivity is lowered, and therefore, when the transfer tape is used, there is a problem that the charge cannot be removed and charged accurately, which causes an image failure. However, it is found that the use of the oligomer mixture solution can maintain this value at a high value (1.0 to 3.0), and thus the productivity of the film can be further improved.

C. Third invention

Next, a third invention will be described in more detail with reference to comparative examples and examples. Hereinafter, the term "a-BPDA" denotes 2, 3, 3 ', 4' -biphenyltetracarboxylic dianhydride, and the term "s-BPDA" denotes 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride. The number average molecular weight was measured by GPC method (solvent: NMP).

Example C-1

22.8g of methanol and 160g of N-methyl-2-pyrrolidone were put into 14g of a-BPDA and 56g of s-BPDA (20 mol%: 80 mol%) and reacted at a water bath temperature of 70 ℃ under a nitrogen flow. Subsequently, the mixture was cooled to a bath temperature of 65 ℃ and then 47.6g of 4, 4' -diaminodiphenyl ether (ODA) was added thereto, followed by slow stirring to obtain 300.4g of a nylon salt type monomer solution. The viscosity of the solution was 1.8 poise, and the nonvolatile concentration was 36.3% by weight.

Next, 47.6g of ODA was added to 448g of N-methyl-2-pyrrolidone being flowed under nitrogen, and the mixture was kept at 50 ℃ and stirred to be completely dissolved. To this solution was slowly added a-BPDA: 35g and s-BPDA: 35g of the powder, to obtain 605.6g of a polyamic acid solution. The polyamic acid solution had a number-average molecular weight of 16000, a viscosity of 30 poise and a nonvolatile concentration of 18.0% by weight.

180g of a polyimide precursor solution was prepared by mixing 100g of the nylon salt monomer solution and 80g of the polyamic acid solution. The viscosity was 13 poise and the nonvolatile concentration was 28.2% by weight.

To 150g of this precursor solution, 7.5g of acidic carbon (pH3.0) and 16.7g of N-methyl-2-pyrrolidone were added, and uniform dispersion of carbon black was carried out in a ball mill. The master batch solution had a nonvolatile content of 28.6% by weight, a CB concentration in the nonvolatile content of 15.1% by weight, an average particle diameter of carbon black of 0.28 μm and a maximum particle diameter of 0.58 μm. The average particle diameter of the carbon black after 10 days was 0.28. mu.m, and the maximum particle diameter was 0.76. mu.m, which was hardly changed.

The "nonvolatile concentration" in the present specification is a value calculated as follows. The sample (nylon salt type monomer solution, etc.) is placed in a heat-resistant container such as a metal cup and accurately weighed, and the weight of the sample at this time is taken as Ag. The heat-resistant container containing the sample was placed in an electric oven, and heated and dried at 120 ℃. times.12 minutes, 180 ℃. times.12 minutes, 260 ℃. times.30 minutes, and 300 ℃. times.30 minutes in this order, and the weight (nonvolatile weight) of the obtained solid content was defined as Bg. For the same sample, the values of a and B (n is 5) were measured for 5 samples, and substituted into the following formula (I) to determine the nonvolatile concentration. The average value of the 5 samples was used as the nonvolatile concentration in the present invention.

Nonvolatile concentration ═ B/A X100 (%) (I)

Example C-2

22.8g of methanol and 160g of N-methyl-2-pyrrolidone were put into 35g of a-BPDA and 35g of s-BPDA (50 mol%: 50 mol%) and reacted at a water bath temperature of 80 ℃ under a nitrogen flow. Subsequently, the mixture was cooled to a bath temperature of 65 ℃ and then 47.6g of 4, 4' -diaminodiphenyl ether (ODA) was added thereto, followed by slow stirring to obtain 300.4g of a nylon salt type monomer solution. The viscosity of the solution was 1.8 poise, and the nonvolatile concentration was 36.3% by weight.

Next, 47.6g of ODA was added to 448g of N-methyl-2-pyrrolidone being flowed under nitrogen, and the mixture was kept at 50 ℃ and stirred to be completely dissolved. To this solution was slowly added s-BPDA: 70g, to obtain a polyamic acid solution 605.6 g. The polyamic acid solution had a number average molecular weight of 12000, a viscosity of 12 poise, and a nonvolatile concentration of 18.0% by weight.

180g of a polyimide precursor solution was prepared by mixing 100g of the nylon salt monomer solution and 80g of the polyamic acid solution. The viscosity was 5.2 poise and the nonvolatile concentration was 28.2% by weight.

To 150g of this precursor solution were added 7.5g of acidic carbon (pH3.0) and 16.7g of N-methyl-2-pyrrolidone, and the carbon black was uniformly dispersed in a ball mill. The master batch solution had a nonvolatile content of 28.6% by weight, a CB concentration in the nonvolatile content of 15.1% by weight, an average particle diameter of carbon black of 0.31 μm and a maximum particle diameter of 0.77 μm. The average particle diameter of the carbon black after 10 days was 0.31 μm, and the maximum particle diameter was 0.88. mu.m, showing almost no change.

Example C-3

22.8g of methanol and 250g of N-methyl-2-pyrrolidone were put into 21g of a-BPDA and 49g of s-BPDA (30 mol%: 70 mol%) and reacted at a water bath temperature of 80 ℃ under a nitrogen flow. Then, the mixture was cooled to a bath temperature of 65 ℃ and 47.6g of 4, 4' -diaminodiphenyl ether (ODA) was added thereto and the mixture was stirred slowly to obtain 390.4g of a nylon salt monomer solution. The viscosity of the solution was 0.7 poise, and the nonvolatile concentration was 27.9% by weight.

To 200g of the nylon salt type monomer solution, 110g of a polyamideimide solution (available from VYLOMAX HR-16NN Toyobo Co., Ltd.) (number average molecular weight: 21000, solid content: 14% by weight, viscosity: 500 poise) was mixed to prepare 310g of a polyimide precursor solution. The viscosity was 18 poise and the nonvolatile concentration was 23.0% by weight.

To 260g of this precursor solution, 10.9g of acidic carbon (pH3.0) and 25.2g of N-methyl-2-pyrrolidone were added, and uniform dispersion of carbon black was carried out in a ball mill. The master batch solution had a nonvolatile content of 23.9% by weight, a carbon black concentration in the nonvolatile content of 15.4% by weight, an average particle diameter of the carbon black of 0.215 μm, and a maximum particle diameter of 0.51. mu.m. The average particle diameter of the carbon black after 10 days was 0.218. mu.m, and the maximum particle diameter was 0.58. mu.m, which was almost unchanged.

Reference example C-1

To 200g of the nylon salt type monomer prepared in example C-1, 13.5g of acidic carbon (pH3.0) and 120g of an organic solvent (NMP) were added, and the mixture was subjected to main dispersion in a ball mill. The solution had a viscosity of 5 poise, a nonvolatile matter concentration of 25.8% by weight, a CB concentration in the nonvolatile matter of 15.7% by weight, an average particle diameter of carbon black of 0.39 μm, and a maximum particle diameter of 2.26 μm. The average particle diameter of the carbon black after 10 days was 0.79 μm, and the maximum particle diameter was 7.70 μm, and aggregation of the carbon black was confirmed.

Reference example C-2

47.6g of ODA was added to 450g of N-methyl-2-pyrrolidone under a nitrogen flow, and the mixture was kept at 50 ℃ and stirred to be completely dissolved. To this solution was slowly added s-BPDA: 70g, to obtain 567.6g of a polyamic acid solution. The polyamic acid solution had a weight-average molecular weight of 5000, a viscosity of 6.6 poise, and a nonvolatile concentration of 19.2% by weight. A polyimide precursor solution (180 g) was prepared by mixing 80g of the solution with 100g of the nylon salt type monomer prepared in example C-2, and 9.5g of acidic carbon (pH3.0) and 120g of an organic solvent (NMP) were added thereto to perform primary dispersion in a ball mill. The solution had a viscosity of 6 poise, a nonvolatile matter concentration of 19.8% by weight, a CB concentration in the nonvolatile matter of 15.5% by weight, an average particle diameter of carbon black of 0.26 μm and a maximum particle diameter of 0.87. mu.m. The average particle diameter of the carbon black after 10 days was 0.77 μm, and the maximum particle diameter was 5.10 μm, and aggregation of the carbon black was confirmed.

Example C-4 (production of tubular polyimide film by rotational Molding)

While rotating a cylindrical mold having an outer diameter of 300mm, an inner diameter of 270mm and a length of 500mm at a rotational speed of 100rpm (10.5rad/s), 480mm wide solutions of examples C-1, C-2, C-3 and reference examples C-1 and C-2 were uniformly applied to the inner surface of the cylindrical mold. The coating thickness was calculated from the nonvolatile concentration so that the thickness of the polyimide tape was 100 μm. The solvent evaporation was carried out by raising the temperature to 110 ℃ over 60 minutes and then maintaining the temperature at 110 ℃ for 120 minutes, thereby producing a tube having self-supporting properties.

Then, the tube was put into a high-temperature heating furnace in a state where the tube was adhered to the inner surface of the cylindrical mold, and the temperature was raised to 320 ℃ over 120 minutes, and the tube was heated at 320 ℃ for 60 minutes to convert polyimide. Then, the tube-shaped polyimide film was cooled to room temperature, and taken out from the mold. The surface state thereof was judged by naked eyes.

The Surface Resistivity (SR) and the Volume Resistivity (VR) were measured by cutting the obtained polyimide-based tube into a length of 400mm as a sample, measuring 3 places at equal intervals in the width direction and 4 places at equal intervals in the longitudinal (circumferential) direction using a resistance measuring instrument "Hiresta IP-HR probe" manufactured by Mitsubishi chemical corporation, and the total of the measured 12 places was expressed as an average value of the whole.

The Volume Resistivity (VR) was measured after 10 seconds with 100V applied voltage, and the Surface Resistivity (SR) was measured after 10 seconds with 500V applied voltage.

The measurement results are summarized in Table C-1. The surface resistivity, the average volume resistivity, and the standard deviation in Table C-1 are all expressed in logarithmic conversion values. In addition, the CB content in the tube and the thickness of the tube are also shown in Table C-1.

TABLE C-1

As can be seen from table C-1, the standard deviation of the surface resistivity and the volume resistivity of the tubular articles of the examples was very small, i.e., the variability was small, compared to the reference examples.

In addition, the tubular articles of the examples had very small differences in surface resistivity (logarithmic conversion value) between the front and back sides of the tubular articles, and had good characteristics as electrophotographic transfer belts, compared to the reference examples.

In addition, since a value (Log (SR/VR)) obtained by subtracting a Log-converted value LogVR of the volume resistivity from a Log-converted value LogSR of the surface resistivity is generally decreased when the heating temperature rise rate in molding is accelerated, there is a problem that the charge cannot be removed and charged accurately when the transfer tape is used, which causes an image failure. However, it is found that the use of the semiconductive PI precursor composition of the present invention can maintain the value at a high value (1.0 to 2.0).

In contrast, in the reference example, the surface resistivity of the tubular article is smaller than the back surface resistivity, and the applicant believes that a concentration gradient of carbon black is generated in the thickness direction of the tubular article. The volume resistivity value was found to be high, and the variability was found to be high.

D. Fourth invention

Next, a fourth invention will be described in more detail with reference to comparative examples and examples. Hereinafter, the term "a-BPDA" means 2, 3, 3 ', 4' -biphenyltetracarboxylic dianhydride, and the term "s-BPDA" means 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride.

Example D-1

27g of acidic carbon (pH3.0, volatile 14.5%) was added to 153g of N-methyl-2-pyrrolidone, which was an organic polar solvent, and after preliminary dispersion, the mixture was subjected to main dispersion in a ball mill. The average particle diameter of the carbon black was 0.29. mu.m, and the maximum particle diameter was 0.55. mu.m. Next, 14g of a-BPDA, 56g of s-BPDA and 22.8g of methanol were put into 120g of this solution, and the mixture was reacted at a bath temperature of 60 ℃ under a nitrogen stream.

Then, after cooling to a water bath temperature of 50 ℃, 47.6g of 4, 4' -diaminodiphenyl ether (ODA) was charged and slowly stirred to obtain 260g of a carbon black-dispersed high-concentration polyimide precursor composition composed of monomers. The solution had a viscosity of 32 poise, a nonvolatile matter concentration of 48.9% by weight, a CB concentration in the nonvolatile matter of 14.2% by weight, an average particle diameter of carbon black of 0.29 μm and a maximum particle diameter of 0.58 μm. The average particle diameter of the carbon black after 10 days was 0.31 μm, and the maximum particle diameter was 0.67 μm, which was almost unchanged.

The "nonvolatile concentration" in the present specification is a value calculated as follows. The sample (carbon black-dispersed high-concentration polyimide precursor composition, etc.) is placed in a heat-resistant container such as a metal cup and accurately weighed, and the weight of the sample at this time is taken as Ag. The heat-resistant container containing the sample was placed in an electric oven, and heated and dried at 120 ℃. times.12 minutes, 180 ℃. times.12 minutes, 260 ℃. times.30 minutes, and 300 ℃. times.30 minutes in this order, and the weight (nonvolatile weight) of the obtained solid content was defined as Bg. For the same sample, the values of a and B (n is 5) were measured for 5 samples, and substituted into the following formula (I) to determine the nonvolatile concentration. The average value of the 5 samples was used as the nonvolatile concentration in the present invention.

Nonvolatile concentration ═ B/A X100 (%) (I)

Example D-2

10g of furnace black (pH9.0, volatile 1.5%) was added to 120g of N-methyl-2-pyrrolidone as an organic polar solvent, and after preliminary dispersion, main dispersion was carried out in a ball mill. The average particle diameter of the carbon black was 0.67 μm, and the maximum particle diameter was 3.92. mu.m. Then, to 125g of this solution were charged 35g of a-BPDA, 35g of s-BPDA and 22.8g of methanol, and the mixture was reacted at a water bath temperature of 70 ℃ under a nitrogen stream. Then, after cooling to a water bath temperature of 50 ℃, 47.6g of 4, 4' -diaminodiphenyl ether (ODA) was charged and slowly stirred to obtain 265g of a carbon black-dispersed high-concentration polyimide precursor composition consisting of a monomer. The solution had a viscosity of 12 poise, a nonvolatile matter concentration of 44.7% by weight, a CB concentration in nonvolatile matter of 8.2% by weight, an average particle diameter of carbon black of 0.77 μm, and a maximum particle diameter of 3.92. mu.m. The average particle diameter of the carbon black after 10 days was 0.77 μm, and the maximum particle diameter was 4.47. mu.m, which was almost unchanged.

Comparative example D-1

20g of an acidic carbon (pH3.0, volatile matter content 14.5%) was added to 600g of a high molecular weight polyamic acid solution (viscosity 50 poise, nonvolatile matter concentration 18.0 wt%) synthesized from s-BPDA and ODA, and the mixture was subjected to primary dispersion in a ball mill, whereby the thickening efficiency of the solution was high and the solution was gelled. Then, 300g of an organic solution (NMP) was added to the solution, and redispersed. The solution had a viscosity of 8 poise, a nonvolatile matter concentration of 13.9% by weight, a CB concentration in nonvolatile matter of 15.6% by weight, an average particle diameter of carbon black of 0.32 μm, and a maximum particle diameter of 0.77 μm. The average particle diameter of the carbon black after 10 days was 0.32. mu.m, and the maximum particle diameter was 0.77. mu.m, which was almost unchanged.

Reference example D-1

22.8g of methanol and 160g of N-methyl-2-pyrrolidone were put into 35g of a-BPDA and 35g of s-BPDA (50 mol%: 50 mol%) and reacted at a water bath temperature of 70 ℃ under a nitrogen flow. Then, after cooling to a water bath temperature of 60 ℃, 47.6g of 4, 4' -diaminodiphenyl ether (ODA) was added thereto and slowly stirred to obtain 300.4g of a nylon salt type monomer solution. The viscosity of the solution was 1.8 poise, and the nonvolatile concentration was 36.3% by weight. To this solution were added 16.5g of acidic carbon (ph3.0, volatile 14.5%) and 140g of organic solvent (NMP), and the main dispersion was carried out in a ball mill. The solution had a viscosity of 5 poise, a nonvolatile matter concentration of 27.5% by weight, a CB concentration in the nonvolatile matter of 12.3% by weight, an average particle diameter of carbon black of 0.47 μm, and a maximum particle diameter of 1.73 μm. The average particle diameter of the carbon black after 10 days was 0.78 μm, and the maximum particle diameter was 5.12 μm, and aggregation of the carbon black was confirmed.

Example D-3 (production of tubular polyimide film by rotational Molding)

While rotating a cylindrical mold having an outer diameter of 300mm, an inner diameter of 270mm and a length of 500mm at a rotational speed of 100rpm (10.5rad/s), 480mm wide solutions of examples D-1 and D-2 and comparative examples D-1 and D-1 were uniformly applied to the inner surface of the cylindrical mold. The coating thickness was calculated from the nonvolatile concentration so that the thickness of the polyimide tape was 100 μm. The solvent was heated to 100 ℃ for 60 minutes, and then the solvent evaporation at 100 ℃ was visually observed, and the time required for completion of the solvent evaporation was measured.

Then, the tube was put into a high temperature furnace in a state where the tube was adhered to the inner surface of the cylindrical mold, and the temperature was raised to 320 ℃ over 120 minutes, and the tube was heated at 320 ℃ for 60 minutes to convert polyimide. Then, the tube-shaped polyimide film was cooled to normal temperature, and taken out of the mold. The results are shown in Table D-1. The CB content in the tube and the thickness of the tube film are also shown in Table D-1.

The Surface Resistivity (SR) was measured by cutting the obtained tubular polyimide film into a length of 400mm as a sample, measuring 3 places at equal intervals in the width direction and 4 places at equal intervals in the longitudinal (circumferential) direction using a resistance measuring instrument "Hiresta IP-HR probe" manufactured by Mitsubishi chemical corporation, and measuring 12 places in total as an average value. The Surface Resistivity (SR) was measured after 10 seconds under the application of 500V.

TABLE D-1

Forming solution	Time required for solvent evaporation	Surface state	Surface resistivity (omega/□)	CB content in tubes (% by weight)	Thickness of tube (μm)
						Example D-1	45 minutes	Good effect	2.5×1010	14.2	94～102
Example D-2	60 minutes	Good effect	5.0×107	8.1	96～103
						Comparative example D-1	170 minutes	Good effect	2.0×1010	15.6	88～102
Reference example D-1	110 minutes	Having carbon agglomerates	2.0×106	12.3	95～104

In the conventional method (comparative example), the nonvolatile concentration of the molding material is low, and much time is required for volatilizing a large amount of the organic polar solvent, and the production efficiency is very poor. In addition, in the method of adding and dispersing CB to a monomer solution or the like, the reaction of the monomer solution proceeds due to heat generation during dispersion, and the solution state becomes unstable.

ADVANTAGEOUS EFFECTS OF INVENTION

The tubular PI film of the invention can be used for simply, efficiently and economically manufacturing a high-quality non-conductive or semiconductive endless (seamless) tubular polyimide film.

Specifically, according to the first invention, a direct endless tubular PI film can be obtained by a combination of a polyimide monomer raw material composed of a specific composition and a rotational molding method. In addition, the time is greatly shortened compared with the current manufacturing method of the endless tubular PI film through the polyamic acid. In addition, the process management is greatly rationalized, so that the productivity is improved, and a more stable high-quality tubular PI film can be obtained. The obtained endless tubular PI film can be used for various purposes, and in particular, a semiconductive endless tubular PI film can be more suitably used as an intermediate transfer belt of an electrophotographic system used in, for example, a color printer, a color copier, or the like.

The semiconductive tubular PI film according to the second aspect of the present invention has a uniform resistivity because it uses, as a molding material, an aromatic amic acid oligomer obtained by polycondensation of a predetermined aromatic tetracarboxylic acid component and an aromatic diamine component. That is, the semiconductive tubular PI film of the present invention has the following excellent characteristics: the variability of the surface resistivity and the volume resistivity is small, the difference between the surface resistivities (logarithmic conversion values) of the front surface and the back surface of the film is small, and the value obtained by subtracting the logarithmic conversion value LogVR of the volume resistivity from the logarithmic conversion value LogSR of the surface resistivity can be maintained at a high value (1.0 to 3.0). Therefore, the semiconductive tubular PI film of the present invention can be suitably used as, for example, an intermediate transfer belt used in a color copying machine or the like, and can appropriately remove and charge electric charges, thereby enabling excellent image processing.

The semiconductive tubular PI film according to the third aspect of the present invention has a uniform resistivity because a semiconductive polyimide precursor composition obtained by uniformly dispersing carbon black in a mixed solution of a nylon salt type monomer solution and a high molecular weight polyimide precursor solution or a high molecular weight polyamide imide solution is used as a molding material. That is, the semiconductive tubular PI film of the present invention has the following excellent characteristics: the variability of the surface resistivity and the volume resistivity is small, and the difference between the surface resistivities (logarithmic conversion values) of the surface and the back of the film is small. Therefore, the semiconductive tubular PI film of the present invention can be suitably used as an intermediate transfer belt in, for example, a color electrophotographic system, and can appropriately remove and charge electric charges, thereby enabling excellent image processing.

In the semiconductive high-concentration PI precursor composition of the fourth aspect of the invention, the CB powder is uniformly dispersed, and the storage stability of the uniformly dispersed state of the CB powder is very high. Further, a conductive tubular PI film obtained by rotational molding of a semiconductive PI precursor composition using the same is imparted with conductivity having very stable and uniform resistivity in the thickness direction thereof. That is, when the transfer sheet is used as an electrophotographic intermediate transfer belt used in, for example, a color printer or a color copier, it is possible to appropriately remove or charge charges from or to perform excellent image processing. In addition, the semiconductive high-concentration PI precursor composition of the present invention can increase the nonvolatile concentration to about 35 to 60% by weight because the monomer as a molding material is dissolved in the carbon black dispersion. Therefore, a film with a thick film can be easily produced by using the semiconductive high-concentration PI precursor composition of the present invention, and the amount of solvent used is small, so that the cost can be reduced and the solvent can be evaporated and removed more easily.

Claims (20)

1. A semiconductive aromatic amic acid composition characterized by,

comprising an aromatic amic acid oligomer obtained by polycondensation of 2 or more aromatic tetracarboxylic acid components and an aromatic diamine in equimolar amounts, carbon black and an organic polar solvent,

wherein the monomer components forming the aromatic amic acid oligomer are only an aromatic tetracarboxylic acid component and an aromatic diamine,

the 2 or more aromatic tetracarboxylic acid components are composed of at least one asymmetric aromatic tetracarboxylic acid component and at least one symmetric aromatic tetracarboxylic acid component.

2. The semiconductive aromatic amic acid composition according to claim 1 wherein said aromatic amic acid oligomer is an aromatic amic acid oligomer obtained by polycondensation reaction of 2 or more aromatic tetracarboxylic dianhydrides and aromatic diamines in equimolar amounts in an organic polar solvent at a temperature of 80 ℃ or less,

the 2 or more than 2 kinds of aromatic tetracarboxylic dianhydride are composed of at least one asymmetric aromatic tetracarboxylic dianhydride and at least one symmetric aromatic tetracarboxylic dianhydride.

3. The semiconductive aromatic amic acid composition according to claim 2, wherein the 2 or more aromatic tetracarboxylic dianhydrides are a mixture of 15 to 55 mol% of an asymmetric aromatic tetracarboxylic dianhydride and 85 to 45 mol% of a symmetric aromatic tetracarboxylic dianhydride.

4. The semiconductive aromatic amic acid composition according to claim 1, wherein said aromatic amic acid oligomer is an aromatic amic acid oligomer obtained by polycondensation of at least 2 aromatic tetracarboxylic acid diesters and an aromatic diamine in equimolar amounts in an organic polar solvent at a temperature of 90 to 120 ℃,

the 2 or more aromatic tetracarboxylic diesters are composed of at least one asymmetric aromatic tetracarboxylic diester and at least one symmetric aromatic tetracarboxylic diester.

5. The semiconductive aromatic amic acid composition according to claim 4, wherein the 2 or more aromatic tetracarboxylic acid diesters are a mixture of 15 to 55 mol% of an asymmetric aromatic tetracarboxylic acid diester and 85 to 45 mol% of a symmetric aromatic tetracarboxylic acid diester.

6. The semiconductive aromatic amic acid composition according to claim 1, wherein said aromatic amic acid oligomer has a number average molecular weight of 1000 to 7000.

7. The semiconductive aromatic amic acid composition according to claim 1, wherein the amount of carbon black blended is 3 to 30 parts by weight per 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the aromatic diamine,

the aromatic tetracarboxylic acid component is composed of an asymmetric aromatic tetracarboxylic acid component and a symmetric aromatic tetracarboxylic acid component.

8. A process for producing a semiconductive endless tubular polyimide film, which comprises subjecting the semiconductive aromatic amic acid composition according to claim 1 to rotational molding and heat treatment.

9. A semiconductive endless tubular polyimide film for an electrophotographic intermediate transfer belt manufactured by the manufacturing method according to claim 8.

10. A process for producing a semiconductive aromatic amic acid composition,

in an organic polar solvent, 2 or more kinds of aromatic tetracarboxylic acid components and aromatic diamine are subjected to partial polycondensation reaction in equimolar amounts to obtain an aromatic amic acid oligomer solution, the aromatic amic acid oligomer solution is uniformly mixed with conductive carbon black powder,

the 2 or more aromatic tetracarboxylic acid components are composed of at least one asymmetric aromatic tetracarboxylic acid component and at least one symmetric aromatic tetracarboxylic acid component.

11. The semiconductive aromatic amic acid composition of claim 1 wherein the aromatic diamine is 4, 4' -diaminodiphenyl ether.

12. The semiconductive aromatic amic acid composition of claim 3 wherein the asymmetric aromatic tetracarboxylic dianhydride is 2, 3, 3 ', 4' -biphenyltetracarboxylic dianhydride and the symmetric aromatic tetracarboxylic dianhydride is 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride.

13. The semiconductive aromatic amic acid composition of claim 5 wherein the asymmetric aromatic tetracarboxylic acid diester is dimethyl 2, 3, 3 ', 4' -biphenyltetracarboxylic acid and the symmetric aromatic carboxylic acid diester is dimethyl 3, 3 ', 4, 4' -biphenyltetracarboxylic acid.

14. The semiconductive aromatic amic acid composition according to claim 2, wherein the 2 or more kinds of aromatic tetracarboxylic dianhydrides are a mixture of 20 to 50 mol% of asymmetric aromatic tetracarboxylic dianhydrides and 80 to 50 mol% of symmetric aromatic tetracarboxylic dianhydrides.

15. The semiconductive aromatic amic acid composition according to claim 4, wherein the 2 or more aromatic tetracarboxylic acid diesters are a mixture of 20 to 50 mol% of an asymmetric aromatic tetracarboxylic acid diester and 80 to 50 mol% of a symmetric aromatic tetracarboxylic acid diester.

16. The semiconductive aromatic amic acid composition according to claim 1, wherein the concentration of CB powder in the nonvolatile portion of the semiconductive aromatic amic acid composition is from 3 to 25% by weight.

17. The semiconductive aromatic amic acid composition according to claim 1, wherein the concentration of CB powder in the nonvolatile portion of the semiconductive aromatic amic acid composition is 10 to 20% by weight.

18. The semiconductive aromatic amic acid composition according to claim 1, wherein said aromatic amic acid oligomer has an imidization degree of 30% or less.

19. The semiconductive aromatic amic acid composition according to claim 1, wherein said aromatic amic acid oligomer has an imidization degree of 25% or less.

20. The semiconductive aromatic amic acid composition according to claim 1, wherein said aromatic amic acid oligomer has an imidization degree of 20% or less.