JP2002201305A - Polyimide porous film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aromatic polyimide porous film consisting essentially of a poly(p-phenylenepyromellitimide)-based polyimide porous film, etc., having open pores on the surface and to provide a method for producing the same. SOLUTION: A solution of a polyamic acid derived from an amic acid-forming compound of an aromatic diamine component consisting essentially of p- phenylenediamine and an aromatic tetracarboxylic acid consisting essentially of pyromellitic dianhydride is cast on a smooth substrate, immersed in a solution composed of a good solvent of the polyamic acid/a 1-6C alcohol and coagulated. The obtained polyamic acid porous film is imidated. Especially, the porous film is isoimidated and then imidated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a porous film (porous film) made of polyimide and a method for producing the same. More specifically, the present invention relates to a novel polyimide porous film having excellent heat resistance, surface properties, homogeneity, and impregnation as a heat-resistant base material for use in an electronic laminated substrate, and a method for producing the same.

[0002]

2. Description of the Related Art A base material used for an electronic laminated substrate is required to have various properties such as heat resistance, thermal dimensional stability, moisture dimensional stability, electrical insulation, and light weight. Aromatic polyimides have excellent heat resistance and are used industrially in a wide range including the electronic field. However, aromatic polyimides generally have low adhesiveness to copper foil or glass fiber, and attempts have been made to improve the adhesiveness of polyimides in electronic substrate applications in order to maintain long-term reliability.

The use of a porous thin film can be considered as one of the means for solving such problems as miniaturization of the electronic substrate and improvement of the adhesiveness.

Conventionally, a porous polyimide membrane has been used as a membrane for separating gas or liquid. For example, Japanese Unexamined Patent Publication No.
-170934, JP-A-57-170935, JP-A-57-170936, JP-B-61-53
Japanese Patent Publication No. 086 or Japanese Patent Publication No. 58-25690 proposes a porous polyimide membrane used as a gas separation membrane by using a phase inversion method or a wet film formation. On the other hand, JP-A-6-293834 discloses that a polyimide precursor 3
It is described that a polyimide precursor porous film is formed by using a mixed solution composed of at least one kind of poor solvent, and a polyimide porous film having high hydrogen gas permeability can be obtained by performing a ring closing treatment.

[0005] However, these polyimide porous membranes all have a small pore diameter, and the pore diameter of the porous membrane is at most about several μm, and a porous membrane having sufficient impregnating performance has not been obtained.

On the other hand, JP-A-11-310658 discloses that a porous film is laminated on a cast film of a polyamic acid solution, immersed in a poor solvent to produce a polyamic acid porous film, and then heated and imidized. As a result, a semi-rigid aromatic polyimide porous membrane useful for a separator having a through hole has been successfully obtained.

[0007] Among aromatic polyimides, a polyimide comprising an amide acid-forming compound of paraphenylenediamine and pyromellitic acid having a completely rigid structure is expected to have high heat resistance, thermal dimensional stability and moisture dimensional stability. . However, in terms of moldability, the polyimide is infusible and insoluble, and it is difficult to mold in the state of polyimide. Therefore, a molding process is performed before the polyimide is formed. Polyamic acid is mentioned as one of the precursors, and polyamic acid is extremely susceptible to hydrolysis and is composed of paraphenylenediamine and pyromellitic dianhydride, which are starting materials of a highly rigid fully rigid polyimide. Polyimide acid is particularly susceptible to hydrolysis. The resulting polyimide is extremely brittle and a film that can withstand practical use has not been obtained. In particular, it was particularly difficult to mold a rigid polyimide having paraphenylenediamine as a diamine component.

Further, Polymer Vol. 36 N
o. 14, 2685-2697, (1995) disclose semi-rigid polyimides such as poly (4,4'-oxydiphenylene-pyromellitimide) and rigid polyimides such as polyparaphenylenepyromellitimide and poly (paraphenylene-imide). A method for producing a nano-sized porous film of (3,3 ′, 4,4′-biphenyltetracarboximide) is described. As a method, there is disclosed a method in which a microphase-separated polyimide precursor film copolymerized with a thermally decomposable component is produced, and then heated to decompose and remove the thermally decomposed component and imidized. However, when the porous membrane obtained by this method is heated to remove the thermal decomposition component and imidize, the polymer rearrangement occurs.
The microphase-separated structure formed during the preparation of the polyimide precursor film cannot be retained, and the porous structure is broken. Also,
These porous membrane surfaces do not have openings.

As described above, a polyparaphenylenepyromellitimide-based polyimide porous film having continuous pores has not been hitherto known, and a high impregnating heat dimension suitable as a heat-resistant base material for use in electronic substrate laminate substrates. It is expected to appear as a polyimide porous film having excellent stability.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rigid polyimide porous membrane having excellent heat resistance, impregnation property and thermal dimensional stability. Another object of the present invention is to provide a method for industrially producing such a rigid polyimide porous membrane.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found a rigid polyimide porous film having continuous holes as a heat-resistant base material for use in an electronic laminated substrate and a method for producing the same. Completed and arrived at the present invention.

That is, the present invention is as follows. 1. A polyimide porous membrane having polyparaphenylenepyromellitimide as a main repeating unit having pores of about 0.1 to 20 μm in diameter on the surface and having air permeability of more than 0 seconds and not more than 1000 seconds / 100 ml. 2. The polyamic acid solution obtained from the reaction of the amide acid-forming compound of the tetracarboxylic acid with the diamine component is prepared by mixing the polyamic acid with a good solvent / alcohol having 1 to 6 carbon atoms in a volume ratio of 50/50 to 0/100 by volume. A method for producing a polyimide porous membrane, comprising imidizing a polyamic acid porous membrane obtained by coagulating a coagulating liquid. 3. A polyimide characterized by being coagulated in a coagulation bath in which the composition ratio of the alcohol having 1 to 6 carbon atoms in the coagulation liquid is increased stepwise using a multistage coagulation bath when coagulating the polyamic acid solution. A method for producing a porous membrane. 4. After isoimidating the polyamic acid porous membrane,
A method for producing a polyimide porous membrane, comprising heating to imidize. 5. A method for producing a polyimide porous membrane, comprising introducing a polyamic acid porous membrane into a poor solvent for a polyamic acid containing dicyclohexylcarbodiimide (DCC) to cause imidization.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, regarding the present invention, the characteristics of the porous membrane, the preparation of the polyamic acid solution, the production of the polyamic acid porous membrane, and the imidization of the polyamic acid porous membrane are sequentially described.
This will be described in detail.

<Characteristics of porous membrane> The polyimide porous membrane of the present invention has an air permeability of more than 0 seconds and not more than 1000 seconds / 10
It is preferably in the range of 0 ml, and preferably in the range of 1 to 500 seconds / 100 ml. Breathability is 1000 seconds / 100m
If it exceeds 1, the desired impregnation property of the present invention cannot be sufficiently obtained, which is not preferable. Further, it is considered that the breathability of 0 second cannot actually occur.

The polyimide porous membrane of the present invention has pores of 0.1 to 20 μm on the membrane surface. 0.
An opening of 1 to 20 μm has a diameter when the diameter is constant, and a long axis diameter of 0.1 to 20 μm when a long axis diameter and a short axis diameter exist.
Shall be referred to as the opening. Such a rigid polyimide porous membrane is a novel one that has never been known before and is excellent in impregnation and substance permeability. Therefore, when this is used as a prepreg base material, impregnation with a thermosetting resin can be performed quickly, and when this is used as a heat-resistant base material of a laminate, it is preferable because an anchor effect on an adhesive surface is exhibited. In addition, the measurement method of the air permeability mentioned here is based on the method mentioned later.

<Preparation of Polyamic Acid> Generally, the polymerization of polyamic acid is obtained by a reaction between a diamine component in a solution and an amic acid-forming compound of tetracarboxylic acid. In the present invention, the amide acid-forming compound of tetracarboxylic acid includes tetracarboxylic acid, tetracarboxylic dianhydride, tetracarboxylic acid halide, lower esters of tetracarboxylic acid and the like, and preferably tetracarboxylic dianhydride. Can be Specifically, in the present invention, an amide acid-forming compound of pyromellitic acid is used as a main component of the amide acid-forming compound of tetracarboxylic acid. More specifically, pyromellitic dianhydride is used. In addition to pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, , 3,4,5-thiophenetetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic dianhydride, 2,3 ′,
3,4′-benzophenonetetracarboxylic dianhydride,
3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic acid Dianhydride, 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-p
-Terphenyltetracarboxylic dianhydride, 2,2 ',
3,3′-p-terphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-p-terphenyltetracarboxylic dianhydride, 1,2,4,5-naphthalenetetracarboxylic dianhydride Anhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,5,6-anthracenetetracarboxylic dianhydride, 1 , 2,6,7-
Phenanthrenetetracarboxylic dianhydride, 1,2,2
7,8-phenanthrenetetracarboxylic dianhydride,
1,2,9,10-phenanthrenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5
8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride,
2,3,6,7-tetrachloronaphthalene 1,4,5
8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride , Bis (3,4-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2 3-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride,
1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxy) Phenyl) propane dianhydride, 2,6-bis (3,4-dicarboxyphenoxy) pyridine dianhydride, 1,1,1,3,3,3-hexafluoro-2,2
Preferred are bis- (3,4-dicarboxyphenyl) propane dianhydride and bis (3,4-dicarboxyphenyl) dimethylsilane dianhydride. Also preferred are tetracarboxylic acids, tetracarboxylic halides, methyl esters of tetracarboxylic acids, ethyl esters of tetracarboxylic acids, butyl esters of tetracarboxylic acids, and phenyl esters of tetracarboxylic acids corresponding to the above compounds. These compounds may be used alone or in combination. These compounds may be contained in an amount of 10 mol% or less, preferably 5% or less, based on the amide acid-forming compound of all tetracarboxylic acids.

In the present invention, paraphenylenediamine is used as the main component of the diamine component. Further, in addition to paraphenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-
Diaminonaphthalene, 1,8-diaminonaphthalene,
2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 2,6-diaminoanthracene, 2,7-diaminoanthracene, 1,8-diaminoanthracene, 2,
4-diaminotoluene, 2,5-diamino-m-xylene, 2,5-diaminopyridine, 2,6-diaminopyridine, 3,5-diaminopyridine, 2,4-diaminotoluenebenzidine, 3,3′-diamino Biphenyl,
3,3′-dichlorobenzidine, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 2,2 ′
-Diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenyl ether,
4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane,
3,3-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfide, 4,4′-diaminodiphenylsulfide, 4,4′-diaminodiphenylthioether, 4,
4′-diamino-3,3 ′, 5,5′-tetramethyldiphenyl ether, 4,4′-diamino-3,3 ′,
5,5'-tetraethyldiphenyl ether, 4,4 '
-Diamino-3,3 ', 5,5'-tetramethyldiphenylmethane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3 -Aminophenoxy) benzene,
1,4-bis (4-aminophenoxy) benzene, 2,
6-bis (3-aminophenoxy) pyridine, 1,4-
Bis (3-aminophenylsulfonyl) benzene, 1,4
-Bis (4-aminophenylsulfonyl) benzene,
1,4-bis (3-aminophenylthioether) benzene, 1,4-bis (4-aminophenylthioether) benzene, 4,4′-bis (3-aminophenoxy) diphenylsulfone, 4,4′-bis ( 4-aminophenoxy) diphenylsulfone, bis (4-aminophenyl) aminebis (4-aminophenyl) -N-methylaminebis (4-aminophenyl) -N-phenylaminebis (4-aminophenyl) phosphonoxide,
1,1-bis (3-aminophenyl) ethane, 1,1-
Bis (4-aminophenyl) ethane, 2,2-bis (3
-Aminophenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4-amino-
3,5-dimethylphenyl) propane, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3
-Aminophenoxy) phenyl] sulfone, bis [4-
(4-aminophenoxy) phenyl] sulfone, bis [4
-(4-aminophenoxy) phenyl] ether, bis
[4- (4-aminophenoxy) phenyl] methane, bis
[3-methyl 4- (4-aminophenoxy) phenyl] methane, bis [3,5-dimethyl-4- (3-aminophenoxy) phenyl] methane, 1,1-bis [4- (4-aminophenoxy) Phenyl] ethane, 1,1-bis [3-
Methyl-4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [3-chloro-4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [3,5-dimethyl-4- (4-aminophenoxy) phenyl] ethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3-methyl-4- (4-
Aminophenoxy) phenyl] propane, 2,2-bis
[3-Chloro-4- (4-aminophenoxy) phenyl]
Propane, 2,2-bis [3,5-dimethyl-4- (4
-Aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane,
2,2-bis [3-methyl-4- (4-aminophenoxy) phenyl] butane, 2,2-bis [3,5-dimethyl-4- (4-aminophenoxy) phenyl] butane,
2,2-bis [3,5-dibromo-4- (4-aminophenoxy) phenyl] butane, 1,1,1,3,3,3
-Hexafluoro-2,2-bis (4-aminophenyl) propane, 1,1,1,3,3,3-hexafluoro-2,2-bis [3-methyl-4- (4-aminophenoxy) [Phenyl] propane and the like are preferred.
These compounds may be used alone or in combination. In addition, these compounds are used in an amount of 10 to the total diamine component.
It may be contained at a ratio of not more than mol%, preferably not more than 5%.

The solvent for the polymerization of the polyamic acid may be any solvent that dissolves the amide acid-forming compound of the tetracarboxylic acid, the diamine, and the polyamic acid and does not react with DCC. Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide,
Examples thereof include 1,3-dimethylimidazolidinone, tetramethylurea, 1,3-dipyropylimidazolidinone, N-methylcaprolactam, and dimethylsulfoxide. Since polyamic acid is hydrolyzed by moisture,
The solvent is preferably dehydrated.

The polymer concentration of the polyamic acid solution in the present invention is preferably 1 to 15% by weight, more preferably 3 to 10% by weight.

In order to obtain the polyamic acid in the present invention, the amount of the diamine used in the above organic solvent is preferably 0.90 to 1.10, more preferably 0.95 to 1.10, as a ratio to the number of moles of the amic acid-forming compound. It is preferable to make the polyamic acid by reacting with 1.05.

In order to block the terminal of the polymer, phthalic anhydride and its substituted product, hexahydrophthalic anhydride and its substituted product, succinic anhydride and its substituted product, and / or aniline and its substituted product can be used. It is not limited to this.

The reaction temperature is -10 to 100 ° C.
And more preferably -10 to 80 ° C.
The resulting polyamic acid solution was filtered under a nitrogen atmosphere,
It is more preferable to remove solid matter for forming a film.

<Manufacture of Polyamic Acid Porous Membrane> The polyamic acid solution prepared by the above-mentioned method was cast on a substrate surface having a smooth surface, and was mixed with a good solvent of polyamic acid / alcohol having 1 to 6 carbon atoms. Capacity ratio is 50 / 50-0 / 1
A polyamic acid porous membrane can be produced by coagulation into a coagulation liquid of No. 00. More preferably, a polyamic acid porous membrane having continuous pores can be produced by using a multi-stage coagulation bath and coagulating the coagulation liquid stepwise in a direction in which the composition ratio of the lower alcohol increases. A preferred embodiment is to coagulate a polyamic acid solution cast with a coagulation liquid having a volume ratio of a good solvent of polyamic acid / an alcohol having 1 to 6 carbon atoms to the coagulation liquid of the first stage at a volume ratio of 50/50 to 31/69. Then, in the second and subsequent stages, the composition ratio of the lower alcohol is higher than that of the coagulation solution in the first stage, and the volume ratio of the good solvent of polyamic acid to the alcohol having 1 to 6 carbon atoms is 30/70 to 10/90. Coagulation with a coagulation liquid. More preferably, in the third and subsequent stages, the mixture is coagulated with a coagulating liquid having a higher composition ratio of the alcohol having 1 to 6 carbon atoms. The coagulation time of each stage in the multi-stage coagulation bath varies depending on the concentration of the polyamic acid polymer, the chemical structure of the polyamic acid polymer, the type of solvent, and the composition ratio of the coagulation solution, and may be appropriately determined.

The alcohol having 1 to 6 carbon atoms includes
Examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol. Also, since polyamic acid is hydrolyzed by moisture,
The alcohol is preferably dehydrated.

Examples of the good solvent for the polyamic acid include N, N-dimethylformamide, N, N-dimethylacetamide, used as a solvent for polymerizing the polyamic acid.
N-methyl-2-pyrrolidone, hexamethylphosphoramide, 1,3-dimethylimidazolidinone, tetramethylurea, 1,3-dipyropylimidazolidinone, N-
Examples thereof include methylcaprolactam and dimethylsulfoxide, and are preferably the same as the solvent used for the polymerization.
Preferably, the good solvent is also dehydrated.

The temperature at which the polyamic acid solution is cast is:
100 ° C. or lower is preferable, and 50 ° C. or lower is more preferable. When cast at a temperature of 100 ° C. or higher, the polyamic acid is imide-cyclized, and water as a by-product is generated, which causes a reduction in molecular weight due to hydrolysis, which is not preferable.

The temperature at which the thin film obtained by casting the above-mentioned polyamic acid is solidified into a coagulating liquid is 10 times, similarly to the casting temperature.
0 ° C. or lower is preferable, and 50 ° C. or lower is more preferable. 1
When cast at a temperature of 00 ° C. or higher, the polyamic acid is imide-cyclized and water is generated as a by-product, which is not preferable because the hydrolysis causes a decrease in molecular weight.

<Imidization of Polyamic Acid Porous Membrane> A polyimide porous membrane can be produced by imidizing the polyamic acid porous membrane produced by the above method. Examples of the imidation method include a method of heat-cyclizing a polyamic acid; a method of chemically ring-closing an acid anhydride and a chemical ring-closing agent such as pyridine and triphenyl phosphite; And then heating. Among them, a method of performing imidization by heating after isoimidation is preferable because the influence of hydrolysis is small and a porous structure can be maintained during the heat imidization.

In the present invention, the term "isoimide" means an isoimide or a partially isoimidized one, which is ring-closed by heating or chemical action to form an imide, having an isoimide component of 5% or more, preferably 50% or more. Things.

In the present invention, as a method for producing a polyisoimide porous membrane by isoimidizing a polyamic acid porous membrane, a part or part of the method is directly introduced into a solution of a polyamic acid poor solvent containing DCC as a condensing agent. The reaction is completely reacted with DCC to produce an imidized polyimide precursor porous film, and the generated dicyclohexylcarbodiurea (hereinafter, referred to as DCU) is immediately eluted into the solvent.

At this time, the poor solvent for the polyamic acid is D
The alcohol having 1 to 6 carbon atoms used for producing the polyamic acid porous membrane, which dissolves CC, does not react with DCC, and does not dissolve polyamic acid, can be used. Examples of such alcohol include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and the like. Further, since the obtained polyisoimide component reacts with moisture and returns to polyamic acid, the alcohol is preferably dehydrated.

The DCC concentration in the DCC solution is not particularly limited as long as the reaction proceeds sufficiently, but is not particularly limited.
It is more preferably at least 1% by weight.

When the polyamic acid porous membrane is introduced into the DCC solution, the temperature of the DCC solution is preferably 10 ° C. or higher, more preferably 20 to 80 ° C. Thereby, the reactivity can be increased, and the solubility of the generated DCU can be improved. Further, it is preferable that the obtained polyisoimide porous membrane is further washed with a solvent in which DCU and DCC are dissolved.

In order to enhance the activity of DCC,
A reagent such as 4-dimethylaminopyridine or 4-pyrrolidylpyridine may be used together with C.

The polyisoimide porous membrane produced by the above method is imidized by heating. This method may use any method. Examples of the heating method include, but are not limited to, hot air drying, vacuum drying, infrared drying, and microwave heating. A polyimide porous film can be obtained by performing a heat treatment at 50 to 500 ° C. using these methods. At this time, it is preferable that the imidization be completely advanced by increasing the temperature stepwise.

[0036]

According to the present invention, it is possible to provide a novel polyimide porous membrane having continuous pores which cannot be obtained by the conventional method and which is excellent in heat resistance, thermal dimensional stability, moisture dimensional stability and impregnation. . The polyimide porous film of the present invention can be used as a heat-resistant base material of a prepreg for a printed wiring board and a laminated board for a printed circuit by utilizing the excellent characteristics as described above. When producing a polyamic acid porous membrane, it is possible to design the porous structure of the polyimide porous membrane by adjusting the coagulation time, the polyamic acid polymer concentration, the type of the coagulation liquid solvent, and the composition ratio of the coagulation liquid. .

[0037]

EXAMPLES Hereinafter, preferred embodiments of the present invention will be described with reference to examples, but the present invention is not limited to the examples. 1) Logarithmic viscosity of polyamic acid It was dissolved in NMP (N-methyl-2-pyrrolidone) and measured with an Ubbelohde viscosity tube at 35 ° C at a polymer concentration of 0.5 g / 100 mL. 2) Air permeability The air permeation time was determined by the method of "JISL1096-1990 6.27 air permeability", and the air permeability was evaluated.
The shorter this time, the better the air permeability.

Example 1 Paraphenylenediamine in a separable flask equipped with a stirrer and a nitrogen inlet tube
9 parts by weight were dissolved in 400 parts by weight of NMP. After the solution was cooled to 0 ° C. using an ice bath, 18.0 parts by weight of pyromellitic dianhydride was added and stirred. When the heat generation stopped, the cooling was stopped, and the mixture was stirred at room temperature for 3 hours to complete the reaction. After completion of the reaction, the mixture was filtered under a nitrogen atmosphere and then defoamed to obtain a polyamic acid solution. The polymer concentration of this polyamic acid solution was 6% by weight, and the logarithmic viscosity was 12 dL / g.
Met.

The above polyamic acid solution was cast on a glass plate using a doctor knife (clearance: 600 μm), and then NMP / isopropyl alcohol =
After being immersed in a coagulation liquid of 50/50 for 20 minutes, in a coagulation liquid of NMP / isopropyl alcohol = 30/70 for 20 minutes, and in isopropyl alcohol for 20 minutes, a polyamic acid porous membrane was obtained by peeling off from the glass plate.

Next, the polyamic acid porous membrane obtained by the above operation was immersed in an isopropyl alcohol solution having a DCC concentration of 30% by weight for 20 minutes, and then washed with NMP for 10 minutes and isopropyl alcohol for 20 minutes to obtain a polyisoimide porous film. A membrane was obtained.

After fixing the obtained polyisoimide porous membrane in a frame, the temperature was 80 ° C. × 5 minutes, 200 ° C. × 10 minutes, 250 ° C. × 10 minutes.
The temperature was increased stepwise in steps of 8 minutes, 350 ° C. × 5 minutes, and 380 ° C. × 5 minutes to effect imidization, thereby obtaining a polyimide porous film. I
As a result of R measurement, a peak characteristic of isoimide (920c
m ^-1 ) was not observed. The obtained polyimide porous membrane had openings of 0.1 to 20 μm in diameter on the surface, and the air permeability was 120 seconds / 100 ml.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (× 2000) showing the surface structure (air contact surface) of a polyimide porous film of Example 1.

FIG. 2 is an electron micrograph (× 5000) showing the surface structure (glass surface) of the polyimide porous film of Example 1.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Jiro Sakanobu 2-1 Hinode-cho, Iwakuni-shi, Yamaguchi Pref.

Claims (5)

[Claims] 1. An opening having a diameter of about 0.1 to 20 μm on the surface and a gas permeability of more than 0 second and not more than 1000 seconds / 10
A polyimide porous membrane containing 0 ml of polyparaphenylenepyromellitimide as a main repeating unit. 2. A solution of a polyamic acid obtained from the reaction of a diamine component with an amide acid-forming compound of a tetracarboxylic acid, wherein the volume ratio of the polyamic acid to a good solvent / alcohol having 1 to 6 carbon atoms is 50/50 to 0. The method for producing a polyimide porous membrane according to claim 1, wherein the polyamic acid porous membrane obtained by coagulating a coagulating liquid of / 100 is imidized. 3. When coagulating the polyamic acid solution,
Using a multi-stage coagulation bath, the number of carbon atoms in the coagulation liquid is 1
3. The method for producing a polyimide porous membrane according to claim 2, wherein the coagulation is performed in a coagulation bath in which the volume ratio of the alcohol of No. 6 increases. 4. The method for producing a polyimide porous membrane according to claim 2, wherein the polyamic acid porous membrane is isoimidized and then heated to imidize. 5. The method for producing a porous polyimide membrane according to claim 4, wherein the polyamic acid porous membrane is isoimidized by introducing the polyamic acid porous membrane into a poor solvent of polyamic acid containing dicyclohexylcarbodiimide (DCC). .