JPH06327919A - Filter material having resistance to chemical and its production - Google Patents

Abstract

PURPOSE:To impart resistance to chemicals to a polymide fiber made filter material and to remarkably expand the field of application of the filter material by applying the condensed polycyclic polynuclear arom. hydrocarbon on the permeable formed body consisting of high heat resistant polyimide fiber having a repeating unit expressed by a specified formula. CONSTITUTION:The heat polycondensation reaction of the condensed polycyclic polynuclear arom. resin obtained by heat condensation polymerization of the condensed polycyclic arom. hydrocarbon such as naphthalene, anthracene, phenantheren, pyrene and pitch with the permeable formed body consisting of high heat resistant polyimide fiber having the repeating unit expressed by formula I (in the formula, (n) is an integer of <=1, (x) is the arom. group selected from formulae II, III and IV, and R is at least one kind bivalent arom. group selected from formulae V, VI, VII, VIII and IX) in the presence of the cross- linking agent such as 1,4-benzene dimethanol an acid catalyst. In this way, the filter material improved in resistance to chemicals is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a polyimide fiber which is heat-resistant and less likely to be clogged, has a long service life, is large in size, has a self-supporting rigidity, and can be applied as a filter material having excellent chemical resistance. TECHNICAL FIELD The present invention relates to a breathable molded body and a method for producing the molded body.

[0002]

2. Description of the Related Art Conventionally, many breathable materials made of plastic materials such as cellulose, acetyl cellulose, Teflon, polycarbonate and nylon are commercially available, and various pore diameters can be obtained. However, none have high heat resistance. As a highly heat resistant material, there is a breathable molded product using glass fiber, but the molded product is very bulky and it is difficult to mold it into a thin and compact molded product.
As the glass-made air-permeable material, many sintered glass-made air-permeable materials are commercially available, but a thin and large-sized air-permeable molded body is liable to break and cannot be obtained. Further, glass filters generally have a drawback that they are easily clogged.

An aromatic polyimide is mentioned as a polymer material that can be used for molding a highly heat-resistant molded body. Conventionally, it is difficult to make a woven fabric of aromatic polyimide even if it is made into a filter cloth by making a breathable filter using this polymer material, and much less a molded body that can be used as a filter has not been obtained. . Also, molding a molded body using a polyimide powder material is described by BH Lee in Modern Plastics Encyclopedia (M
odernPlastic Encyclopedi
a) 1988, p. 62. However, this is not a simple molding method because it may be necessary to process it into a preformed body. When using this method, spreading the polyimide powder material evenly over a large area
This is not possible if the powder layer is thin. As described above, it is extremely difficult to mold a thin and large-sized air-permeable molded product using the aromatic polyimide powder material.
Furthermore, since aromatic polyimide is a highly heat resistant and sparingly soluble material, it is difficult to obtain a powder having a uniform particle size distribution from this material.

[0004]

DISCLOSURE OF THE INVENTION As a result of earnest research to obtain an air-permeable molded article having various porosity, which has a high heat resistance and can be obtained in a desired shape even in a large size, the present inventors have found that Using polyimide fiber, preform this aromatic polyimide fiber into a nonwoven fabric or felt, and subject the aromatic polyimide fiber nonwoven fabric or felt to heat / pressure treatment for a suitable time at a temperature exceeding the glass transition point of polyimide. It succeeded in obtaining a filter medium by shrinking by the above method and molding it into a desired shape having rigidity so that it could be self-supporting, and applied for a patent.
(Japanese Patent Application No. 5-62534)

However, since the polyimide fiber has poor hydrochloric acid resistance, when hydrogen chloride is contained in the filter gas of incinerators for industrial and municipal waste, the performance as a filter medium deteriorates in a short period of time. Further, since the alkali resistance is also poor, if the powder is alkaline in the steps of recovering the powder raw material and collecting the powder product in the chemical industry, the performance similarly deteriorates in a short period of time. There is a method of dipping the fluororesin for the purpose of improving the chemical resistance, but the melt viscosity of the fluororesin is 340
Since it is as high as 10 ¹¹ to 10 ¹³ poise even at a temperature of up to 380 ° C., it is difficult to completely cover the fiber surface of the polyimide fibers in the air-permeable molded article with the fluororesin. It cannot exhibit chemical resistance.

The object of the present invention is to obtain a large-sized object in a desired shape, to have a large surface area, to make it as thin and compact as possible, to obtain air permeability of various porosities, and to prevent clogging for a long time. It has a long life, high heat resistance, and excellent chemical resistance, especially acid and alkali resistance. An object of the present invention is to provide a breathable molded product (filter material) having the above-mentioned various properties and a manufacturing method capable of manufacturing the same. In particular, the object of the present invention is to provide acid resistance even at a normal use temperature of 260 ° C.
It is an object of the present invention to provide a filter medium formed from a polyimide fiber non-woven fabric or felt having excellent alkali resistance and a production method capable of producing the same.

[0007]

The above object can be achieved by the high heat resistant and chemically resistant filter material of the present invention and the method for producing the same. That is, 1) A filtering material characterized by coating a condensed polycyclic polynuclear aromatic resin on a breathable molded product made of a highly heat-resistant polyimide fiber having a repeating unit represented by the following general formula (1).

[0008]

[Chemical 4]

2) A breathable molded product made of highly heat-resistant polyimide fiber having a repeating unit represented by the following general formula (1) is added with naphthalene, anthracene, phenanthrene,
Coated with condensed polycyclic polynuclear aromatic resin obtained by heating polycondensation of condensed polycyclic aromatic hydrocarbons such as pyrene and pitch with a crosslinking agent such as 1,4-benzenedimethanol in the presence of an acid catalyst. A filter material characterized by being.

[0010]

[Chemical 5]

3) An air-permeable molded body made of highly heat-resistant polyimide fiber having a repeating unit represented by the following general formula (1), and an intermediate condensate of a condensed polycyclic polynuclear aromatic resin in an organic solvent in an amount of 20 to 60. %), Which is impregnated with a solution dissolved at a concentration of 10%, dried, and thermoset to coat the condensed polycyclic polynuclear aromatic resin according to the above 1) on the air-permeable molded article.
A method for producing the above-described filter material.

[0012]

[Chemical 6]

An object of the present invention is to impart chemical resistance to a breathable molded article made of highly heat-resistant polyimide fiber, and particularly to provide a breathable molded article having resistance to acids and alkalis. For this purpose, the skeleton of the present invention,
It is to protect with a chemical resistant film without impairing breathability. As a result of earnest research, the present inventors have found that the above object can be achieved by coating the surface of a breathable molded product made of highly heat-resistant polyimide fiber with a thermosetting resin. In particular, it is preferable to coat the condensed polycyclic polynuclear aromatic resin as the thermosetting resin because it is possible to impart the chemical resistance while maintaining the heat resistance and the adhesiveness of the coating film to the air-permeable molding.

In the present invention, as a method for coating the surface of the air-permeable molded article made of highly heat-resistant polyimide fiber with a thermosetting resin, the above-mentioned air-permeable molded article is placed in a low molecular weight compound of a resin component or a solvent thereof. It was achieved by immersing the molded body in a solution diluted with, or by coating on the surface of the molded body, coating on the surface of the polyimide fiber constituting the breathable molded body, and condensing in the presence of a condensation catalyst. It Of course, instead of the low molecular weight compound of the resin component, an intermediate condensate is condensed, and then this intermediate condensate is diluted with a solvent, if necessary, and the molded body is immersed therein, or the surface of the molded body is immersed. It may be applied to cover the surface of the polyimide fiber to form a protective film.

In the present invention, coating the gas-permeable molded article with a condensed polycyclic polynuclear aromatic resin means the following states, as is apparent from the above description. That is, in the present invention, a method for forming a breathable molded product from high heat-resistant polyimide fibers is, for example, preforming a nonwoven fabric or felt from high heat-resistant polyimide fibers, and heating and pressurizing this molded product to form polyimide fibers. The air-permeable molded article is formed by fusing each other to such an extent that the desired air-permeability is maintained. Therefore, this breathable molded product leaves the surface of the raw material polyimide fiber on the surface and inside of the molded product. In such a breathable molded product, a low molecular weight compound as a constituent component of a condensed polycyclic polynuclear aromatic resin (may be an intermediate condensate obtained by condensing a low molecular weight compound of a resin component to an intermediate condensate) or a solution obtained by diluting them with a solvent By coating the surface of the breathable molded article and the surface of the polyimide fibers inside the breathable molded article with the low molecular weight compound of the resin component by immersing the solution in the surface of the breathable molded article or by infiltrating the solution into the surface of the breathable molded article. You can

As a method for coating the surface of the highly heat-resistant polyimide fiber of the air-permeable molded article with a condensed polycyclic polynuclear aromatic resin as a thermosetting resin, condensed polycyclic aromatics such as naphthalene, anthracene, phenanthrene, pyrene and pitch can be used. A group hydrocarbon together with an acid catalyst and a crosslinking agent such as 1,4-benzenedimethanol, or if necessary diluted with a solvent, or the above condensed polycyclic aromatic hydrocarbon in the presence of an acid catalyst,
An intermediate condensate that has been condensed by heat reaction with a cross-linking agent such as 1,4-benzenedimethanol to form an intermediate condensate, or if necessary diluted with a solvent and coated on the surface of a molded body, and then heat polycondensed. By reacting, a heat-resistant and chemical-resistant protective film can be provided on the surface of the molded body. A solvent-soluble intermediate condensate of the above condensed polycyclic polynuclear aromatic resin 1
An example is SK resin developed by Sumikin Kako Co., Ltd. The chemical structural formula (1) is shown below. Here, the expression “dissolving in a solvent” does not mean that the resin or the like is completely dissolved in the molecular dispersion. In some cases, it may be in a colloidal dispersed state, but in short, it is sufficient that the resin or the like penetrates into the air-permeable molded article to make it chemically resistant.

[0017]

[Chemical 7]

The more preferable embodiment of the present invention will be specifically described below. However, the present invention is not limited to the following description. That is, a solvent-soluble intermediate condensate of the condensed polycyclic polynuclear aromatic resin described above is used as an organic solvent solution having a concentration of 10 to 60%, and a high heat-resistant polyimide molding is dipped in this solution, and the solvent is dried. By coating the surface of the polyimide molded body with an intermediate condensate of a condensed polycyclic polynuclear aromatic resin, and then maintaining the temperature at a thermosetting temperature for a predetermined time, and by thermosetting, a protective film having excellent chemical resistance can be provided. it can.

(Function) In the present invention, by coating a condensed polycyclic polynuclear aromatic resin, a filter material made of a highly heat-resistant polyimide molding having air permeability is provided with excellent chemical resistance, particularly acid resistance and alkali resistance. It is a thing. Further, by performing the coating of the condensed polycyclic polynuclear aromatic resin of the present invention, the condensed polycyclic polynuclear aromatic resin firmly binds and fixes the contact points between the polyimide fibers of the high heat-resistant polyimide molded body, so that ventilation is achieved. The strength of the filter material made of a highly heat-resistant polyimide molded article can be significantly increased.

[0020]

EXAMPLES An example of the above-described filter material made of the air-permeable, highly heat-resistant polyimide molding of the present invention and a method for producing the same will be described below with reference to examples. However, the present invention is not limited to the examples below.

Example 1 80 g of benzophenone-3,3'4,4 'was previously added to a container.
-A unit weight of 475 g / prefabricated by a needle punch method from a polyimide fiber having a draw ratio of 1: 5 and a thickness of 30 μm, which was produced from tetracarboxylic dianhydride and 4,4′-methylene-bis- (tolylene isocyanate). m ^2, the felt thickness 2 mm, by keeping the temperature 340 ° C. for 30 minutes was formed into 1mm thick sheets, width 45 mm,
A test piece having a length of 120 mm was cut out. The chemical structural formula (2) of polyimide constituting the above polyimide fiber is shown below.

[0022]

[Chemical 8]

The test piece was immersed in the above-mentioned SK resin solution.
After soaking for 1 minute, the SK resin was heat-cured on the polyimide fiber of the test piece by leaving it to stand at room temperature for 24 hours to dry, and then leaving it in an electric furnace at 150 ° C. for 24 hours. The thickness of the test piece coated with SK resin and heat-cured was measured to calculate the density. This test piece was sandwiched between pipes having a diameter of 20 mm, and the air passage amount was measured under a pressure of 0.1 kg / cm ² . Further, this test piece was immersed in a 10% hydrochloric acid solution at 23 ° C. for 200 hours and a 5% sodium hydroxide solution for 120 hours, washed with water and dried, and then the tensile strength was measured to calculate the retention rate. The results are shown in Table 1.

[0024]

[Table 1]

Example 2 The polyimide fiber test piece used in Example 1 was added to a solution of SK resin having a concentration of 40% prepared in the same manner as in Example 1.
After soaking for 1 minute, the SK resin was heat-cured on the polyimide fiber of the test piece by leaving it to stand at room temperature for 24 hours to dry, and then leaving it in an electric furnace at 150 ° C. for 24 hours. In the same manner as in Example 1, the density and air permeability were measured,
Further, the sample was immersed in a 10% hydrochloric acid solution at 23 ° C. for 200 hours and a 5% sodium hydroxide solution for 120 hours, washed with water and dried, and then the tensile strength was measured to calculate the retention rate. First result
Shown in the table.

Example 3 The polyimide fiber test piece used in Example 1 was immersed in a solution of 60% SK resin prepared in the same manner as in Example 1 for 5 minutes, and then left at room temperature for 24 hours. Dried
Subsequently, the SK resin was thermally cured on the polyimide fiber of the test piece by leaving it in an electric furnace at 150 ° C. for 24 hours. In the same manner as in Example 1, the density and air permeability were measured,
Further, the sample was immersed in a 10% hydrochloric acid solution at 23 ° C. for 200 hours and a 5% sodium hydroxide solution for 120 hours, washed with water and dried, and then the tensile strength was measured to calculate the retention rate. First result
Shown in the table.

Comparative Example 1 The polyimide fiber test piece used in Example 1 was treated in the same manner as in Example 1 without being coated with SK resin.
The air permeability was measured, and it was immersed in a 10% hydrochloric acid solution at 23 ° C for 200 hours and a 5% sodium hydroxide solution for 120 hours, washed with water, dried, and then measured for tensile strength to calculate the retention rate. did. The results are shown in Table 2.

[0028]

[Table 2]

Comparative Example 2 The polyimide fiber test piece used in Example 1 was added to a 5% strength SK resin solution prepared in the same manner as in Example 1
After soaking for 1 minute, the SK resin was heat-cured on the polyimide fiber of the test piece by leaving it to stand at room temperature for 24 hours to dry, and then leaving it in an electric furnace at 150 ° C. for 24 hours. In the same manner as in Example 1, the density and air permeability were measured,
Further, the sample was immersed in a 10% hydrochloric acid solution at 23 ° C. for 200 hours and a 5% sodium hydroxide solution for 120 hours, washed with water and dried, and then the tensile strength was measured to calculate the retention rate. Second result
Shown in the table.

Comparative Example 3 The polyimide fiber test piece used in Example 1 was immersed in a solution of SK resin having a concentration of 80% prepared in the same manner as in Example 1 for 5 minutes and then left at room temperature for 24 hours. Dried
Subsequently, the SK resin was thermally cured on the polyimide fiber of the test piece by leaving it in an electric furnace at 150 ° C. for 24 hours. In the same manner as in Example 1, the density and air permeability were measured,
Further, the sample was immersed in a 10% hydrochloric acid solution at 23 ° C. for 200 hours and a 5% sodium hydroxide solution for 120 hours, washed with water and dried, and then the tensile strength was measured to calculate the retention rate. Second result
Shown in the table.

Comparative Example 4 60 g of distilled water was weighed in advance in a container, and 40 g of polytetrafluoroethylene having a particle diameter of 3 μm was added little by little while stirring to prepare a polytetrafluoroethylene suspension.
The polyimide fiber test piece used in Example 1 was immersed in the above polytetrafluoroethylene suspension for 5 minutes, then left to stand at room temperature for 24 hours to be dried, and subsequently placed in an electric furnace for 340 minutes.
The surface of the polyimide fiber of the test piece was covered with polytetrafluoroethylene by leaving it at 5 ° C. for 5 hours. The density and the air permeability were measured in the same manner as in Example 1, and 23
It was immersed in a 10% hydrochloric acid solution at 200C for 200 hours and a 5% sodium hydroxide solution for 120 hours, washed with water and dried, and then the tensile strength was measured to calculate the retention rate. The results are shown in Table 2.

[0032]

EFFECTS OF THE INVENTION The condensed polycyclic polynuclear aromatic resin of the present invention can improve the chemical resistance which is a weak point of polyimide by coating it on a polyimide fiber. When applied, it imparts chemical resistance to the filter medium, thereby making it possible to remarkably expand the field of application of the filter medium. Further, by the coating treatment of the condensed polycyclic polynuclear aromatic resin of the present invention, the condensed polycyclic polynuclear aromatic resin firmly bonds and fixes the contact points between the polyimide fibers of the high heat-resistant polyimide molded body, and thus the air permeability The effect of remarkably increasing the strength of the filtering material made of the high heat resistant polyimide molded body is exhibited.

Claims (3)

[Claims] 1. A filter material comprising a breathable molded product made of highly heat-resistant polyimide fibers having a repeating unit represented by the following general formula (1) and a condensed polycyclic polynuclear aromatic resin coated thereon. [Chemical 1] 2. A gas-permeable molded article made of highly heat-resistant polyimide fiber having a repeating unit represented by the following general formula (1), and condensed polycyclic aromatic hydrocarbons such as naphthalene, anthracene, phenanthrene, pyrene and pitch. A filtration material, which comprises coating a condensed polycyclic polynuclear aromatic resin obtained by heating polycondensation with a crosslinking agent such as 1,4-benzenedimethanol in the presence of an acid catalyst. [Chemical 2] 3. A breathable molding comprising a highly heat-resistant polyimide fiber having a repeating unit represented by the following general formula (1), and an intermediate condensation product of a condensed polycyclic polynuclear aromatic resin in an organic solvent in an amount of 20 to 60. % Of said solution is impregnated with a solution dissolved therein, dried, and heat-cured to coat said gas-permeable molded article with the condensed polycyclic polynuclear aromatic resin according to claim 1.
A method for producing the above-described filter material. [Chemical 3]