TW202600700A - Polyimide resin powder and polyimide molded body - Google Patents

Abstract

This invention provides a polyimide resin powder comprising a tetracarboxylic acid component and a diamine component. The tetracarboxylic acid component comprises 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2,3,3',4'-biphenyltetracarboxylic dianhydride, and the diamine component comprises p-phenylenediamine, m-phenylenediamine, and/or 4,4'-diaminodiphenyl ether. Based on the total molar amount of the diamine component, the p-phenylenediamine content is 70-98 molars, and based on the total molar amount of the diamine component, the combined content of m-phenylenediamine and 4,4'-diaminodiphenyl ether is 2-30 molars.

Description

Polyimide resin powder and polyimide molded body

This invention relates to a polyimide resin powder and a polyimide molded body obtained therefrom.

Polyimide, obtained primarily from tetracarboxylic acid and diamine, possesses excellent properties such as heat resistance, mechanical strength, electrical properties, and solvent resistance, and is widely used as a material for electrical/electronic components. Polyimide resin powder, processed into powder form, can be filled into molds and pressurized to obtain the desired molded body, thus it is widely used as a material for parts in manufacturing equipment.

As a polyimide molded article using such a polyimide resin powder, for example, Patent 1 discloses a polyimide molded article using a polyimide resin powder comprising at least one aromatic tetracarboxylic dianhydride component (A) and at least one diamine component (B). 60-100 mole percent of the at least one aromatic tetracarboxylic dianhydride component (A) comprises 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), and 40-0 mole percent comprises pyromellitic dianhydride (PMDA). The at least one diamine component (B) is a mixture of p-phenylenediamine (PPD), m-phenylenediamine (MPD), and 4,4'-diaminodiphenyl ether (ODA). [Prior Art Documents][Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2015-129277

[Problem Solved by the Invention] However, previous polyimide resin powders have resulted in more cracking or chipping during the forming process (e.g., by machining). This invention addresses these problems by providing a polyimide resin powder that can supply polyimide molded articles with higher mechanical properties and effectively suppress cracking and chipping during forming. [Technical Means for Solving the Problem]

The inventors conducted intensive research to achieve the above-mentioned objectives and discovered that by combining 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) as tetracarboxylic acid components, and containing p-phenylenediamine (PPD), m-phenylenediamine (MPD), and/or 4,4'-diaminodiphenyl ether (ODA) as diamine components in a specific ratio, the above-mentioned objectives can be achieved, thus completing the present invention.

That is, the present invention provides the following [1] to [5]. [1] A polyimide resin powder comprising units derived from a tetracarboxylic acid component (A) and units derived from a diamine component (B), wherein the units derived from the tetracarboxylic acid component (A) comprise units derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride and units derived from 2,3,3',4'-biphenyltetracarboxylic dianhydride, and the units derived from the diamine component (B) comprise units derived from p-phenylenediamine and units derived from m-phenylenediamine and/or units derived from 4,4'-diaminodiphenyl ether. Based on the total mole content of the units derived from diamine component (B), the content of the units derived from p-phenylenediamine is 70-98 moles. Based on the total mole content of the units derived from diamine component (B), the combined content of the units derived from m-phenylenediamine and the units derived from 4,4'-diaminodiphenyl ether is 2-30 moles. Based on the total mole content of the units derived from diamine component (B), the content of the units derived from 4,4'-diaminodiphenyl ether is less than 18 moles. [2] The polyimide resin powder described in [1] is wherein, based on the total molar amount of the units derived from the tetracarboxylic acid component (A), the content of the units derived from 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is 80 to 95 molars, and the content of the units derived from 2,3,3',4'-biphenyltetracarboxylic acid is 2 to 20 molars. [3] The polyimide resin powder described in [1] or [2] has a crystallinity of 25 to 36% as measured by wide-angle X-ray diffraction. [4] A polyimide molded body is formed by molding the polyimide resin powder described in any one of [1] to [3]. [5] A method for manufacturing a polyimide molded article, which is a method for manufacturing a molded article as described in [4], and includes the steps of: compressing the above-mentioned polyimide resin powder under a pressure of 50 to 500 MPa and firing it at 300 to 550°C. [Effects of the Invention]

According to the present invention, a polyimide resin powder can be provided that can supply polyimide molded articles with higher mechanical properties and can effectively suppress the generation of cracks and gaps during the processing of the molded articles (e.g., during processing by cutting).

<Polyimide Resin Powder> The polyimide resin powder of the present invention comprises units derived from tetracarboxylic acid component (A) and units derived from diamine component (B). The units derived from tetracarboxylic acid component (A) include units derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and units derived from 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA). The units derived from diamine component (B) include units derived from p-phenylenediamine (PPD), units derived from m-phenylenediamine (MPD), and/or units derived from 4,4'-diaminodiphenyl ether (ODA).

Regarding the tetracarboxylic acid component (A) that constitutes the unit derived from the tetracarboxylic acid component (A), examples include tetracarboxylic acids and their derivatives, as well as tetracarboxylic anhydrides. The polyimide resin powder system of the present invention includes 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) as tetracarboxylic acid component (A).

In the polyimide resin powder of the present invention, based on the total molar amount of units derived from tetracarboxylic acid component (A), the content of units derived from 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA) is preferably 80-98 molar%, more preferably 82-98 molar%, further preferably 85-98 molar%, especially preferably 85-95 molar%, and can be set to 91 molar% or more, and can be set to 94 molar% or less, and can also be set to 93 molar% or less. Furthermore, in the polyimide resin powder of this invention, based on the total molar amount of units derived from tetracarboxylic acid component (A), the content of units derived from 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) is preferably 2-20 molar%, more preferably 2-18 molar%, further preferably 2-15 molar%, more preferably 3-15 molar%, particularly preferably 6-15 molar%, especially preferably 7-15 molar%, and can be set to 9 molar% or less. By setting the content of units derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and units derived from 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) within the above ranges, the mechanical strength of the obtained polyimide molded article can be further improved.

Furthermore, in the polyimide resin powder of the present invention, the tetracarboxylic acid component (A), which constitutes the unit derived from the tetracarboxylic acid component (A), may also contain other tetracarboxylic acid components besides the aforementioned 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA).

There are no particular limitations on other tetracarboxylic acid components, such as aromatic tetracarboxylic acid dianhydrides (tetracarboxylic acid dianhydrides with aromatic groups) or alicyclic tetracarboxylic acid dianhydrides (tetracarboxylic acid dianhydrides with alicyclic structure).

Examples of aromatic tetracarboxylic acid dianhydrides include: 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, pyromellitic dianhydride (1,2,4,5-benzenetetracarboxylic acid dianhydride), benzophenonetetracarboxylic acid dianhydride, 4,4'-oxophthalic acid dianhydride, diphenyl sulfidetetracarboxylic acid dianhydride, p-triphenyltetracarboxylic acid dianhydride, meta-triphenyltetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, oxophthalic acid dianhydride, and 4,4'-(2,2-hexafluoroisopropyl)phthalic acid dianhydride.

Examples of alicyclic tetracarboxylic dianhydrides include: 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, [1,1'-bis(cyclohexane)]-3,3',4,4'-tetracarboxylic dianhydride, [1,1'-bis(cyclohexane)]-2,3,3',4'-tetracarboxylic dianhydride, [1,1'-bis... [(cyclohexane)]-2,2',3,3'-tetracarboxylic dianhydride, 4,4'-methylenebis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-(propane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-oxybis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-thiobis(cyclohexane-1,2- Dicarboxylic anhydride), 4,4'-sulfonylureabis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-(dimethylsilyl)bis(cyclohexane-1,2-dicarboxylic anhydride), 4,4'-(tetrafluoropropane-2,2-diyl)bis(cyclohexane-1,2-dicarboxylic anhydride), octahydrocyclopentadiene-1,3,4,6-tetracarboxylic anhydride, bicyclic [ 2.2.1] Heptane-2,3,5,6-tetracarboxylic dianhydride, 6-(carboxymethyl)bicyclo[2.2.1]Heptane-2,3,5-tricarboxylic dianhydride, bicyclo[2.2.2]Octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2]Oct-5-ene-2,3,7,8-tetracarboxylic dianhydride, tricyclo[4.2.2.0 ^2,5 ]Decane-3,4,7,8-tetracarboxylic dianhydride, tricyclo[4.2.2.0 ^2,5 ]Decan-7-ene-3,4,9,10-tetracarboxylic dianhydride, 9-oxotricyclo[4.2.1.0 ^2,5] Nonane-3,4,7,8-tetracarboxylic acid dianhydride, norane-2-spiro-α-cyclopentanone-α'-spiro-2''-norane-5,5'',6,6''-tetracarboxylic acid dianhydride, (4arH,8acH)-decanoyl-1t,4t:5c,8c-dimethylnaphthalene-2c,3c,6c,7c-tetracarboxylic acid dianhydride, (4a rH,8acH)-decanohydro-1t,4t:5c,8c-dimethylbridgenaphthalene-2t,3t,6c,7c-tetracarboxylic acid dianhydride, decahydro-1,4-ethiono-5,8-methylbridgenaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, tetradecanohydro-1,4:5,8:9,10-trimethylbridgeanthracene-2,3,6,7-tetracarboxylic acid dianhydride, etc.

In the polyimide resin powder of the present invention, based on the total molar amount of units from tetracarboxylic acid component (A), when units from other tetracarboxylic acid components are included, the content of units from other tetracarboxylic acid components is preferably 3 to 30 molars, more preferably 5 to 20 molars.

The diamine component (B) that constitutes the unit derived from the diamine component (B) is a compound having two amine structures. The polyimide resin powder of the present invention contains p-phenylenediamine (PPD), m-phenylenediamine (MPD) and/or 4,4'-diaminodiphenyl ether (ODA) as the diamine component (B).

In the polyimide resin powder of the present invention, based on the total molar amount of units derived from diamine component (B), the content of units derived from p-phenylenediamine (PPD) is 70-98 molars. Furthermore, based on the total molar amount of units derived from diamine component (B), the combined content of units derived from m-phenylenediamine (MPD) and units derived from 4,4'-diaminodiphenyl ether (ODA) is 2-30 molars. And based on the total molar amount of units derived from diamine component (B), the content of units derived from 4,4'-diaminodiphenyl ether (ODA) is 18 molars or less.

In this invention, the polyimide resin powder is formed as follows: a tetracarboxylic acid component (A) comprising units derived from 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA) and units derived from 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA) as units constituting a tetracarboxylic acid component (A), and comprising units derived from p-phenylenediamine (PPD) and m-phenylenediamine (MPD) and/or units derived from 4,4'-diamino groups. The diphenyl ether (ODA) unit is used as a unit derived from diamine component (B). Furthermore, the total content of units derived from p-phenylenediamine (PPD), m-phenylenediamine (MPD), and 4,4'-diaminodiphenyl ether (ODA) is set within the aforementioned range. This allows the polyimide resin powder to be formed into a polyimide molded body with higher mechanical properties, and effectively suppresses cracking and notching during processing. Moreover, when the total molar content of units derived from diamine component (B) is used as a benchmark, if the content of units derived from 4,4'-diaminodiphenyl ether (ODA) exceeds 18 molar%, the flexural strength and flexural modulus decrease.

When the content of p-phenylenediamine (PPD) units in the diamine component (B) is too low, the bending strength or flexural modulus of the obtained molded article decreases, resulting in poorer mechanical strength. On the other hand, when the content of p-phenylenediamine (PPD) units is too high, the suppression effect on cracking and notching during the processing of the molded article becomes insufficient.

Furthermore, when the total content of units derived from m-phenylenediamine (MPD) and 4,4'-diaminodiphenyl ether (ODA) in the diamine component (B) is too low, the suppression effect on cracking and notching during the processing of the molded article becomes insufficient. On the other hand, when the total content of units derived from m-phenylenediamine (MPD) and 4,4'-diaminodiphenyl ether (ODA) is too high, the bending strength or bending modulus of the obtained molded article decreases, resulting in poorer mechanical strength.

In the polyimide resin powder of the present invention, based on the total molar amount of units derived from diamine component (B), the content of units derived from p-phenylenediamine (PPD) is 70-98 molar%, preferably 75-95 molar%, more preferably 80-93 molar%, further preferably 82-93 molar%, further preferably 83-93 molar%, and even more preferably 85-93 molar.

Furthermore, in the polyimide resin powder of the present invention, based on the total molar content of units derived from diamine component (B), the combined content of units derived from m-phenylenediamine (MPD) and units derived from 4,4'-diaminodiphenyl ether (ODA) is 2-30 molar%, preferably 5-25 molar%, and more preferably 7-20 molar%. Moreover, when only one of the units derived from m-phenylenediamine (MPD) and units derived from 4,4'-diaminodiphenyl ether (ODA) is contained, it is sufficient that the content of only one is within the above-mentioned range; when both are contained, it is sufficient that the combined content of both is within the above-mentioned range.

Furthermore, in the polyimide resin powder of the present invention, when it contains units derived from m-phenylenediamine (MPD), the content of units derived from m-phenylenediamine (MPD) is preferably 2 to 30 mol%, more preferably 5 to 25 mol%, and even more preferably 7 to 20 mol%, based on the total molar amount of units derived from diamine component (B). It can be set to 8 mol% or more, or 12 mol% or more, or 17 mol% or less, or 13 mol% or less. Based on the total mole content of units derived from diamine component (B), when including units derived from m-phenylenediamine (MPD), the content of units derived from p-phenylenediamine (PPD) is preferably 70-98 moles, more preferably 75-95 moles, and even more preferably 80-93 moles. It can be set to 83 moles or more, or 87 moles or more, or 92 moles or less, or 88 moles or less.

Furthermore, in the polyimide resin powder of the present invention, based on the total molar amount of units derived from diamine component (B), when units derived from 4,4'-diaminodiphenyl ether (ODA) are included, the content of units derived from 4,4'-diaminodiphenyl ether (ODA) is preferably 2 to 18 molars, more preferably 5 to 17 molars, and even more preferably 7 to 15 molars, and can be set to 12 molars or more, and can be set to 9 molars or less. Based on the total mole content of units derived from diamine component (B), when including units derived from 4,4'-diaminodiphenyl ether (ODA), the content of units derived from p-phenylenediamine (PPD) is preferably 82-98 moles, more preferably 83-95 moles, and even more preferably 85-93 moles. It can be set to 91 moles or more, and can be set to 88 moles or less.

Furthermore, the polyimide resin powder of the present invention may contain other diamine components besides the above-mentioned p-phenylenediamine (PPD), m-phenylenediamine (MPD) and 4,4'-diaminodiphenyl ether (ODA) as diamine components (B) constituting the unit derived from diamine component (B).

Examples of such diamine components include aromatic diamines (diamine compounds with aromatic groups) and alicyclic diamines (diamine compounds with alicyclic structures).

Examples of aromatic diamines include: 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4''-diaminotriphenyl, 5(6)-amino-2-(4-aminophenyl)-benzimidazole, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,4-toluenediamine, 3,3'-dihydroxy-4,4'-diaminobiphenyl, and bis(4-amino-3-carboxyphenyl)methyl Alkane, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,3,5,6-tetrafluoro-1,4-diaminobenzene, 2,4,5,6-tetrafluoro-1,3-diaminobenzene, 2,3,5,6-tetrafluoro-1,4-benzene (dimethylamino), 2,2'-difluoro(1,1'-biphenyl)-4,4'-diamine, 4,4'-diaminooctafluorobiphenyl, 4,4'-oxybis(2,3,5,6-tetrafluoroaniline), etc.

Examples of alicyclic diamines include: 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-dibutylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 1,2-diaminocyclohexane, 1,3-diaminocyclobutane, and 1,4-bis(amino)cyclohexane. 1,3-Bis(aminomethyl)cyclohexane, diaminobiscycloheptane, diaminomethylbiscycloheptane, diaminooxybiscycloheptane, diaminomethyloxybiscycloheptane, isoflavone diamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirodiindane, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirodiindane.

In the polyimide resin powder of the present invention, based on the total molar amount of units from diamine component (B), when units from other diamine components are contained, the content of units from other diamine components is preferably 3 to 28 molars, more preferably 5 to 20 molars.

The polyimide resin powder of this invention has a crystallinity of preferably 25-36%, more preferably 25-30%, and even more preferably 25-28%, as measured by wide-angle X-ray diffraction. By maintaining a crystallinity within this range, the toughness of the molded article can be improved without significantly reducing its heat resistance. This, in turn, can more effectively enhance the suppression of cracking and notching during the processing of the molded article.

Furthermore, the average primary particle size of the polyimide resin powder of the present invention is preferably 3–15 μm, more preferably 4–13 μm, and even more preferably 5–12 μm. By keeping the average primary particle size within the above range, the mechanical strength of the obtained polyimide molded article can be further improved. In the present invention, the average primary particle size can be observed by scanning electron microscopy (SEM), and the obtained SEM image can be used for measurement. Specifically, the particle size of each polyimide resin particle (primary particle) constituting the polyimide resin powder can be identified using the obtained SEM image. The particle size of each polyimide resin particle can then be measured, and the measured particle size (primary particle size) can be averaged to obtain the final particle size. In this case, it is sufficient to measure the particle size of any 50 or more polyimide resin particles and calculate the average value based on the measured results.

Furthermore, the volume average particle size of the polyimide resin powder of this invention, measured by laser diffraction/scattering, is preferably 5–100 μm, more preferably 6–80 μm, and even more preferably 7–70 μm. By ensuring the volume average particle size falls within the above range, the mechanical strength of the obtained polyimide molded article can be further improved. The volume average particle size can be determined using a laser diffraction/scattering particle size distribution measuring device. According to laser diffraction/scattering, in the case of primary particle agglomeration, the agglomerated particle size (secondary particle size) is typically measured.

There are no particular limitations on the manufacturing method of the polyimide resin powder of this invention. For example, the following method can be used: polymerizing the above-mentioned tetracarboxylic acid component (A) and the above-mentioned diamine component (B) in a solvent to obtain a polyamide solution, and then performing a amide reaction on the obtained polyamide solution.

First, polyamide is obtained by polymerizing the tetracarboxylic acid component (A) with the aforementioned diamine component (B). Polyamide is preferably composed of repeating units represented by the following general formula (1). [Chemistry 1] In the above general formula (1), A is selected from two or more tetravalent groups obtained by removing the carboxyl group from the tetracarboxylic acid component (A), and B is selected from two or more divalent groups obtained by removing the amino group from the diamine component (B).

Polyamide can be obtained by using approximately equal molar amounts of tetracarboxylic acid component (A) and diamine component (B) in a solvent, and heating them as needed until the desired viscosity (or molecular weight) is achieved. Furthermore, in this invention, "approximately equal molar" means that the molar ratio of tetracarboxylic acid component (A) to diamine component (B) is approximately 0.90 or higher and 1.10 or lower, preferably approximately 0.95 or higher and 1.05 or lower.

There are no particular limitations on the solvent used in the synthesis of polyamides, and any known solvent used in the synthesis of polyamides may be used. For example, from the viewpoint of the solubility of the tetracarboxylic acid component (A) and the diamine component (B), as well as the polyamide, it is preferable to use a nitrogen-containing solvent containing at least one of these components. Furthermore, from the viewpoint of the thermal amide imidization reaction temperature, it is preferable to use a solvent with a boiling point of 100°C or higher. Examples of such solvents include: N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, 1,1,3,3-tetramethylurea, 1,3-dimethyl-2-imidazolidineone, N,N-dimethylisobutylamide, N,N-dimethylpropionic acid, etc.

Polyamide can be formed by stirring a tetracarboxylic acid component (A), a diamine component (B), and a solvent in a reaction vessel equipped with a stirring device. There are no particular restrictions on the order of addition of these raw materials; for example, a specified amount of diamine component (B) can be dissolved in the solvent before adding the tetracarboxylic acid component (A), or the tetracarboxylic acid component (A) can be dissolved in the solvent before adding the diamine component (B), or the tetracarboxylic acid component (A) and the diamine component (B) can be added to the solvent alternately. Furthermore, known reaction catalysts or other additives can be added at any time as needed.

There are no particular limitations on the reaction temperature, but it is preferably carried out at a temperature above 0°C and below 100°C, more preferably above 10°C, and even more preferably above 20°C. Furthermore, it is more preferably below 90°C, and even more preferably below 70°C. By adjusting the reaction temperature to the above range, polyimide resin powders with less deviation in coloring or mechanical properties can be produced. This temperature can be fixed, or it can be appropriately increased or decreased.

Subsequently, polyimide resin powder is obtained by using the following known reactions: a method of thermally amided a obtained polyamide solution by heating it; or a method of chemically amided using an amide agent. These amided reactions are preferably carried out in an inert atmosphere, with the inlet gas such as nitrogen or argon flowing through them.

Preferably, a polyimide resin powder comprising a polyimide (50 mol% or more) as the main component, consisting of repeating units represented by the following general formula (2), is obtained by performing a amide reaction. The ratio of repeating units represented by the following general formula (2) in the polyimide resin powder is preferably 75 mol% or more, more preferably 90 mol% or more. [Chemical 2] In the above general formula (2), _X1 is selected from two or more tetravalent groups obtained by removing the carboxyl group from the tetracarboxylic acid component (A), _{and Y1} is selected from two or more divalent groups obtained by removing the amino group from the diamine component (B).

Thermoimidinization reaction can be carried out by setting the reaction temperature appropriately according to the solvent used. Generally, it is preferred to carry out the reaction in the range of 130 to 230°C, and even more preferably in the range of 140 to 190°C.

As the amide imidizing agent used in the chemical amide imidization reaction, carboxylic anhydrides such as acetic anhydride, propionic anhydride, succinic anhydride, phthalic anhydride, and benzoic anhydride can be used. From the perspective of cost or ease of removal after the reaction, acetic anhydride is preferred. Alternatively, the catalyst added during polyamide formation can be used directly, or it can be added newly or subsequently after polyamide formation. The equivalent amount of the amide imidizing agent used is greater than or equal to the equivalent amount of the amide bonds in the polyamide undergoing the chemical amide imidization reaction, preferably 1.1 to 5 times the equivalent amount of the amide bonds, and more preferably 1.5 to 4 times. By using a slightly excess of amide-iminizing agent relative to the amide bond, amide-iminization reactions can be carried out efficiently even at relatively low temperatures.

From the perspective of reducing deviations in the physical properties of the obtained polyimide molded articles, the amide content of the polyimide resin powder should be 95% or higher, preferably 98% or higher. Here, the amide content can be determined by infrared spectroscopy using conventional methods.

<Polyimide Molded Body> The polyimide molded body of this invention is obtained by molding the aforementioned polyimide resin powder of this invention. The polyimide molded body of this invention can be obtained by molding and sintering the polyimide resin powder of this invention. That is, in this invention, the term "polyimide molded body" is defined as follows: in addition to the molded body obtained by molding polyimide powder into a specified shape, it also includes sintered or sintered bodies obtained by sintering or sintering such molded bodies. The term "polyimide molded body" also includes the concept of polyimide sintered bodies or polyimide sintered bodies.

There are no particular limitations on the method of forming polyimide resin powder. For example, a method can be used to fill polyimide resin powder into a mold and simultaneously or separately apply pressure and heat to perform compression molding and firing. From the perspective of improving the mechanical properties and productivity of polyimide molded articles, the following method is preferred: polyimide resin powder is filled into a powder forming machine and uniaxially formed at room temperature to form a specified shape, followed by pressureless sintering of the formed article (so-called direct forming). As described above, the polyimide resin powder of this invention can effectively suppress the generation of cracks and gaps during the processing of molded articles. Therefore, even when uniaxially formed at room temperature followed by pressureless sintering, the generation of cracks and gaps can be suppressed. In particular, even when heated and compressed forming is performed, the generation of cracks and gaps can be effectively suppressed, thus significantly improving productivity.

Alternatively, as a method for forming polyimide resin powder, the following method can be adopted: for polyimide resin powder, compression molding and firing can be performed simultaneously by applying pressure and heat.

Apparatus used for manufacturing polyimide molded bodies during heat compression molding includes, for example, a four-column hydraulic press, a high-pressure hot press, and a WIP (Waste-In-Place) device. Alternatively, preforms can be formed using methods such as wet CIP, dry CIP, high-pressure press, hydraulic press, rotary press, and tablet press, followed by heat compression molding.

There are no particular limitations on the conditions for compression molding and firing. The pressure is preferably 50–600 MPa, more preferably 50–500 MPa, further preferably 60–450 MPa, and even more preferably 70–400 MPa. The heating temperature is preferably 300–550°C, more preferably 350–530°C, and even more preferably 400–510°C. By setting the pressure and heating temperature within the above ranges, the generation of cracks and notches can be further suppressed, and productivity can be further improved.

Furthermore, in manufacturing the polyimide molded body of this invention, any filler can be mixed with the polyimide resin powder. There are no particular limitations on the filler used; for example, inorganic fillers such as glass fiber, ceramic fiber, boron fiber, glass beads, whiskers, diamond powder, alumina, silicon dioxide, natural mica, synthetic mica, carbon black, silver powder, copper powder, aluminum powder, nickel powder, metal fiber, ceramic fiber, whiskers, silicon carbide, silicon oxide, alumina, magnesium powder, titanium powder, carbon fiber, and graphite, or organic fillers such as fluorinated resins and aromatic polyimide fibers, can be used. These fillers may be used alone or in combination of two or more fillers.

The amount of filler used can be selected according to the application. For example, it can be used in the range of 1 to 50% by weight, based on the weight of polyimide resin powder.

The polyimide molded body of this invention possesses superior mechanical properties, thus allowing for full utilization of these properties. It is ideally suited for use as pins, guides, evaluation sockets, vacuum gaskets, and other parts in semiconductor manufacturing devices; or as bushings, seals, thrust washers, bearing retainers, piston rings, locking nut inserts, and other automotive or aerospace parts; or as bearing sleeves, roller bushings, piston rings, etc., in industrial machinery devices. [Example]

The invention will now be described in more detail by way of embodiments and comparative examples, but the invention is not limited to these examples. The measurement methods used in the following examples are shown.

<Average Primary Particle Size of Polyimide Resin Powder> The polyimide resin powder was observed using scanning electron microscopy (SEM). Using the obtained SEM images, the particle size of 50 particles in the polyimide resin powder was measured, and the measured particle sizes were averaged to determine the average primary particle size of the polyimide resin powder.

<Volume Average Particle Size of Polyimide Resin Powder> Using polyimide resin powder as the test sample, the volume average particle size was measured using a laser diffraction/scattering particle size distribution measuring device (product name "LA-920", manufactured by HORIBA).

<Crystallinity of Polyimide Resin Powder> The crystallinity of polyimide resin powder was measured using an X-ray diffraction apparatus (product name: SmartLab Fully Automated Sample Horizontal Multifunctional X-ray Diffraction Apparatus, manufactured by Rigaku Corporation). The crystallinity was determined by analyzing the X-ray diffraction spectrum obtained from the measurement using the wide-angle X-ray diffraction (WAXS) method using the area intensity ratio method. In this embodiment, the crystallinity was evaluated according to the following criteria: ◎: Crystallinity is 25% or higher and 28% or lower. ○: Crystallinity exceeds 28% but is 36% or lower. ×: Crystallinity exceeds 36% or cannot be measured.

<Flexural Strength and Flexural Modulus of Polyimide Moldeds> For polyimide molded bodies, the flexural strength and flexural modulus of elasticity were determined using a flexural strength tester at room temperature and a test speed of 0.5 mm/min. The tests were performed n=6 times, and the average values were set as the values of flexural strength and flexural modulus of elasticity. In this embodiment, the flexural strength and flexural modulus of elasticity were evaluated according to the following criteria: (Flexural Strength) ◎: 70 MPa or more ○: 28 MPa or more but less than 70 MPa ×: less than 28 MPa (Flexural Modulus of Elasticity) ◎: 1.5 GPa or more ○: 0.9 GPa or more but less than 1.5 GPa ×: less than 0.9 GPa

<Cutting Resistance Value of Polyimide Molded Body> For polyimide molded bodies, a cutting machine (DMG Mori Seiki, NV5000α) was used to perform hole machining on each polyimide molded body at two locations (designated as hole A and hole B) each time using a drill bit (drill bit diameter: 2 mm, speed: approximately 6000 rpm). During the above hole machining, a rotary dynamometer (Kistler, 9170A) was used to measure the cutting resistance. The average cutting resistance was calculated by taking the average value of the cutting resistance for hole A and hole B of each polyimide molded body, excluding the first 10% after cutting and the last 10% before cutting, and then averaging the average cutting resistance of hole A and hole B. In this embodiment, the average cutting resistance was evaluated according to the following criteria. It can be determined that the lower the average cutting resistance, the more effectively cracking and notching can be suppressed during machining of the formed body. ◎: Below 15 N ○: Above 15 N but below 20 N ×: Above 20 N

[Example 1] 3825.00 g of N-methyl-2-pyrrolidone (NMP), 456.17 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA), 34.34 g of 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA), 167.70 g of p-phenylenediamine (PPD), and 12.62 g of m-phenylenediamine (MPD) were added to a stirring tank equipped with a stirring device and a nitrogen inlet pipe. The mixture was stirred at 70°C for 30 minutes under a nitrogen atmosphere to allow it to react and obtain a polyimide precursor solution (polyamide solution). At this time, the molar ratio of s-BPDA:a-BPDA:PPD:MPD was 93:7:93:7.

Next, the obtained polyimide precursor solution was heated to 190°C and stirred for 120 minutes to initiate a thermal acetylation reaction, causing polyimide resin powder to precipitate. The precipitated powder was filtered and separated, washed once with IPA, and filtered again. It was then dried in a vacuum oven at 50°C for 3 hours, followed by drying at 150°C for 2 hours. Subsequently, it was dried in an atmospheric oven at 260°C for 2 hours to obtain aromatic polyimide powder A. The crystallinity of the obtained aromatic polyimide resin powder A was determined according to the above method. The results are shown in Table 1. Furthermore, the ratio of the tetracarboxylic acid component (A) to the diamine component (B) that constitutes the polyimide resin powder is substantially the same as the ratio of the tetracarboxylic acid component (A) and the diamine component (B) used (this is also true in Examples 2-9 and Comparative Examples 1-6 below).

Aromatic polyimide powder A was uniaxially formed for 1 minute at room temperature and a pressure of 293 MPa using a powder forming machine to obtain an aromatic polyimide molded body with a width of 5 mm × length of 40 mm × thickness of 4 mm. The obtained aromatic polyimide molded body was then pressurelessly sintered in air under the following temperature conditions: Heating rate: 10℃/min; First holding temperature: 50℃; First holding time: 30 minutes; Firing temperature: 500℃; Firing time: 15 minutes. Subsequently, the obtained polyimide molded body was used to measure its flexural strength, flexural modulus of elasticity, and cutting resistance values according to the above method. The results are shown in Table 1.

[Examples 2, 3, and 4] Except for changing the amounts of p-phenylenediamine (PPD) and m-phenylenediamine (MPD) to achieve the values shown in Table 1 in the ratio (molar ratio) of each compound, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 1.

[Examples 5 and 6] Except for using 4,4'-diaminodiphenyl ether (ODA) instead of m-phenylenediamine (MPD) and changing the ratio (molar ratio) of each compound, including p-phenylenediamine (PPD) and 4,4'-diaminodiphenyl ether (ODA), to achieve the values shown in Table 1, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 1.

[Example 7] Except for changing the amounts of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), replacing m-phenylenediamine (MPD) with 4,4'-diaminodiphenyl ether (ODA), and changing the ratio (molar ratio) of each compound to the values shown in Table 1, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 1.

[Example 8] Except for changing the amounts of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) to achieve the values shown in Table 1 in the ratio (molar ratio) of each compound, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 1.

[Example 9] Except for changing the amounts of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), as well as p-phenylenediamine (PPD) and m-phenylenediamine (MPD), and changing the ratio (molar ratio) of each compound to the values shown in Table 1, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 1.

[Comparative Examples 1 and 2] Except for changing the amount of p-phenylenediamine (PPD) and m-phenylenediamine (MPD) used, and changing the ratio (molar ratio) of each compound to the values shown in Table 2, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 2.

[Comparative Examples 3 and 4] Except for replacing m-phenylenediamine (MPD) with 4,4'-diaminodiphenyl ether (ODA) and changing the amounts of p-phenylenediamine (PPD) and 4,4'-diaminodiphenyl ether (ODA) to achieve the values shown in Table 2 in the ratio (molar ratio) of each compound, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 2.

[Comparative Example 5] Except for changing the amounts of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), as well as p-phenylenediamine (PPD) and m-phenylenediamine (MPD), and changing the ratio (molar ratio) of each compound to the values shown in Table 2, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 2.

[Comparative Example 6] Except for changing the amounts of 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), replacing m-phenylenediamine (MPD) with 4,4'-diaminodiphenyl ether (ODA), and changing the amounts of p-phenylenediamine (PPD) and 4,4'-diaminodiphenyl ether (ODA), and ensuring that the ratio (molar ratio) of each compound reached the values shown in Table 2, polyimide resin powder and polyimide molded articles were obtained in the same manner as in Example 1, and were evaluated in the same way. The results are shown in Table 2.

[Table 1] Table 1 Implementation Example 1 Implementation Example 2 Implementation Example 3 Implementation Example 4 Implementation Example 5 Implementation Example 6 Implementation Example 7 Implementation Example 8 Implementation Example 9 Tetracarboxylic acid component (A) s-BPDA (mol%) 93 93 93 93 93 93 85 98 98 a-BPDA (mol%) 7 7 7 7 7 7 15 2 2 Diamine component (B) PPD (mol%) 93 90 85 80 93 85 93 93 85 MPD (mol%) 7 10 15 20 - - - 7 15 ODA (mol%) - - - - 7 15 7 - - Average primary particle size (μm) 8.6 8.8 7.1 8.1 7.8 9.6 7.9 5.3 Uncertain Volume average particle size (μm) 29.3 31.0 34.1 36.4 50.9 41.2 69.9 13.4 15.5 Crystallinity(%) 35 35 30 27 34 34 26 30 33 evaluate ○ ○ ○ ◎ ○ ○ ◎ ○ ○ Bending strength (MPa) 52 54 54 50 89 30 31 47 35 evaluate ○ ○ ○ ○ ◎ ○ ○ ○ ○ Flexural modulus (GPa) 1.6 1.4 1.5 1.3 2.1 1.1 1.1 1.6 1.4 evaluate ◎ ○ ◎ ○ ◎ ○ ○ ◎ ◎ Average cutting resistance (N) 20 18 18 18 20 15 15 - - evaluate ○ ○ ○ ○ ○ ◎ ◎ - - *In Table 1, "-" indicates that it was not measured.

[Table 2] Table 2 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Tetracarboxylic acid component (A) s-BPDA (mol%) 93 93 93 93 98 98 a-BPDA (mol%) 7 7 7 7 2 2 Diamine component (B) PPD (mol%) 99 50 99 80 15 20 MPD (mol%) 1 50 - - 85 - ODA (mol%) - - 1 20 - 80 Average primary particle size (μm) 8.8 Uncertain 8.1 8.3 Uncertain Uncertain Volume average particle size (μm) 31.2 113 32.9 49.3 39.4 65.0 Crystallinity (%) 40 Unable to measure 38 27 - - evaluate × × × ◎ - - Bending strength (MPa) 65 33 62 26 26 Unable to measure evaluate ○ ○ ○ × × × Flexural modulus (GPa) 1.9 0.8 1.8 0.8 0.8 Unable to measure evaluate ◎ × ◎ × × × Average cutting resistance (N) twenty one 15 twenty one 10 - - evaluate × ◎ × ◎ - - *In Table 2, "-" indicates that it was not measured.

As shown in Table 1, regarding polyimide resin powder, the units derived from tetracarboxylic acid (A) include units derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and units derived from 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA). The units derived from diamine (B) include 70–98 mol% of units derived from p-phenylenediamine (PPD) and 2–30 mol% of other components. The polyimide resin powder contains 18 moles or less of units derived from m-phenylenediamine (MPD) and/or units derived from 4,4'-diaminodiphenyl ether (ODA), with the content of units derived from 4,4'-diaminodiphenyl ether (ODA) being less than 18 moles. Based on the above-mentioned polyimide resin powder, the crystallinity measured by wide-angle X-ray diffraction is in the range of 25% or more and 36% or less. The average cutting resistance of the obtained polyimide molded body is as low as 20 N or less. This results in good mechanical strength and can effectively suppress the generation of cracks and notches during the processing of the molded body (e.g., during processing by cutting). Furthermore, the obtained polyimide molded body has a large flexural strength and flexural modulus, and excellent mechanical properties. Furthermore, in Examples 9, 2, 5, and 6, the boundaries of the average first-order particles on the SEM images were unclear, making it impossible to determine the average first-order particle size.

Furthermore, in Examples 8 and 9, the crystallinity of the polyimide resin powder was in the range of 25% to 36%. Therefore, the obtained polyimide molded articles, like those in Examples 1-7, achieved an average cutting resistance of less than 20 N, exhibited good mechanical strength, and effectively suppressed cracking and chipping during the forming process (e.g., during machining). [Industrial Applicability]

The polyimide resin powder of this invention is preferably used to manufacture polyimide molded articles for various applications.

Claims (5)

A polyimide resin powder comprising units derived from a tetracarboxylic acid component (A) and units derived from a diamine component (B), wherein the units derived from the tetracarboxylic acid component (A) include units derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride and units derived from 2,3,3',4'-biphenyltetracarboxylic dianhydride, and the units derived from the diamine component (B) include units derived from p-phenylenediamine, units derived from m-phenylenediamine, and/or units derived from 4,4'-diaminodiphenyl ether. Based on the total mole content of the units derived from diamine component (B), the content of the units derived from p-phenylenediamine is 70-98 moles. Based on the total mole content of the units derived from diamine component (B), the combined content of the units derived from m-phenylenediamine and the units derived from 4,4'-diaminodiphenyl ether is 2-30 moles. Based on the total mole content of the units derived from diamine component (B), the content of the units derived from 4,4'-diaminodiphenyl ether is less than 18 moles. For example, in the polyimide resin powder of claim 1, the total molar amount of the units derived from the tetracarboxylic acid component (A) is used as a basis, the content of the units derived from 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is 80-98 molars, and the content of the units derived from 2,3,3',4'-biphenyltetracarboxylic acid is 2-20 molars. For example, the polyimide resin powder of claim 1 or 2 has a crystallinity of 25-36% as measured by wide-angle X-ray diffraction. A polyimide molded body formed from polyimide resin powder as claimed in claim 1 or 2. A method for manufacturing a polyimide molded body, which is a method for manufacturing a molded body as claimed in claim 4, and includes the steps of: compressing the above-mentioned polyimide resin powder under a pressure of 50 to 500 MPa and firing it at 300 to 550°C.