WO2014196435A1

WO2014196435A1 - Varnish, porous polyimide film produced using said varnish, and method for producing said film

Info

Publication number: WO2014196435A1
Application number: PCT/JP2014/064164
Authority: WO
Inventors: 司菅原
Original assignee: 東京応化工業株式会社
Priority date: 2013-06-07
Filing date: 2014-05-28
Publication date: 2014-12-11
Also published as: TWI636076B; JPWO2014196435A1; JP6342891B2; TW201509999A

Abstract

The purpose of the present invention is to provide a production method which enables the production of a homogeneous and highly dense porous polyimide film and a separator equipped with the porous polyimide film by removing resin microparticles from a polyimide film containing the resin microparticles by thermal decomposition. A method for producing a porous polyimide film according to the present invention comprises: a baking step of baking an unbaked composite film comprising a polyamic acid or polyimide, resin microparticles and a condensing agent at a temperature that is lower than the decomposition temperature of the resin microparticles to produce a polyimide-(resin microparticle) composite film; and a microparticle removal step of removing the resin microparticles from the polyimide-(resin microparticle) composite film.

Description

Varnish, porous polyimide film produced using the same, and method for producing the same

The present invention relates to a varnish, a porous polyimide film produced using the varnish, and a production method thereof.

Recently, research has been conducted on porous polyimide as a separator for a lithium ion battery, a fuel cell electrolyte membrane, a gas or liquid separation membrane, and a low dielectric constant material.

For example, from a method of making a porous material using a specific mixed solvent in a polyamic acid solution, a method of heat imidizing a polyamic acid containing a hydrophilic polymer and then removing the hydrophilic polymer to make it porous, and from a polyimide containing silica particles A method of removing silica to make it porous is known (see Patent Documents 1 to 3).

Among them, the method of removing the silica from the polyimide containing the silica particles and making it porous is an effective means for forming a homogeneous and dense porous polyimide film, but in order to make it porous, the polyimide film after baking is used. It was necessary to remove silica particles by treating with hydrofluoric acid.

JP 2007-2111136 A JP 2000-044719 A JP 2012-107144 A

However, since hydrofluoric acid (HF) used in the method for producing a porous polyimide film using silica particles is highly dangerous, it needs to be handled with care and requires managed equipment. Therefore, a method for producing a porous polyimide film that does not use hydrofluoric acid has been desired.

The present invention has been made in view of the above circumstances, and by removing resin fine particles by thermal decomposition from a polyimide film containing resin fine particles, a homogeneous and high-density porous polyimide film and a separator using the same are manufactured. It aims at providing the manufacturing method which can be performed.

The present inventors have produced a polyimide-resin fine particle composite film at a temperature lower than the decomposition temperature of the resin fine particles contained therein, and then removed the resin fine particles by thermal decomposition, so that even if hydrofluoric acid is not used, it is homogeneous and has a high density. The inventors have found that a porous polyimide film can be produced, and have completed the present invention.

In the first aspect of the present invention, an unfired composite film containing polyamic acid or polyimide, resin fine particles, and a condensing agent is fired at a temperature lower than the decomposition temperature of the resin fine particles to obtain a polyimide-resin fine particle composite film. A method for producing a porous polyimide film, comprising a firing step and a fine particle removal step of removing the resin fine particles from the polyimide-resin fine particle composite film.

The second aspect of the present invention is a porous polyimide film produced by the method of the first aspect.

The third aspect of the present invention is a separator comprising the porous polyimide film of the second aspect.

According to a fourth aspect of the present invention, there is provided a polyimide-resin fine particle composite comprising a firing step of firing an unfired composite film containing polyamic acid or polyimide, resin fine particles, and a condensing agent at a temperature lower than a decomposition temperature of the resin fine particles. It is a manufacturing method of a film | membrane.

A fifth aspect of the present invention is a varnish containing polyamic acid or polyimide, resin fine particles, a condensing agent, and an organic solvent.

According to the present invention, by removing resin fine particles from a polyimide film containing resin fine particles by thermal decomposition, a homogeneous and high-density porous polyimide film and a separator using the same can be produced without using hydrofluoric acid. Can do.

It is a figure which shows the intensity | strength of the polyimide-resin fine particle composite film formed into a film using the varnish of this invention. It is a figure which shows the porous polyimide membrane of this invention. 6 is an enlarged view of the back surface of a porous polyimide film of Comparative Example 1. FIG. 1 is an enlarged view of a back surface of a porous polyimide film of Example 1. FIG. 6 is an enlarged view of the back surface of a porous polyimide film of Example 2. FIG. 6 is an enlarged view of the back surface of the porous polyimide film of Example 3. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. .

The method for producing a porous polyimide film of the present invention comprises calcining an unfired composite film containing polyamic acid or polyimide, resin fine particles, and a condensing agent at a temperature lower than the decomposition temperature of the resin fine particles. A baking step for forming a film, and a fine particle removing step for removing the resin fine particles from the polyimide-resin fine particle composite film.

[Manufacture of varnish]
In the method for producing a porous polyimide film of the present invention, first, a varnish containing polyamic acid or polyimide, resin fine particles, a condensing agent, and an organic solvent is prepared. The varnish is prepared by producing a polyamic acid or polyimide solution in which the following predetermined resin fine particles are dispersed.

In the varnish, an organic solvent in which fine particles are dispersed in advance and polyamic acid or polyimide are mixed at an arbitrary ratio, or tetracarboxylic dianhydride and diamine are polymerized in an organic solvent in which fine particles are dispersed in advance to form a polyamic acid. Further, it can be produced by further imidizing into a polyimide, and finally the viscosity is preferably 300 to 1500 cP, more preferably 400 to 700 cP. If the viscosity of the varnish is within this range, it is possible to form a film uniformly.

In the varnish, resin fine particles and polyamic acid or polyimide are mixed so that the fine particle / polyimide ratio is 1 to 3.5 (mass ratio) when the fine particles are baked into a polyimide-resin fine particle composite film. It is preferably 1.2 to 3 (mass ratio). Fine particles and polyamic acid or polyimide may be mixed so that the volume ratio of fine particles / polyimide is 1.5 to 4.5 when a polyimide-fine particle composite film is formed. More preferably, it is 1.8 to 3 (volume ratio). If the fine particle / polyimide mass ratio or volume ratio is equal to or higher than the lower limit value, pores having an appropriate density as a separator can be obtained. If the fine particle / polyimide mass ratio or volume ratio is equal to or lower than the upper limit value, problems such as increase in viscosity and cracks in the film occur It is possible to form a film stably without any problems.

<Resin fine particles>
The resin fine particles used in the present invention can be used without particular limitation as long as they are insoluble in the organic solvent used for the varnish and can be selectively removed after film formation. Further, those having a high sphericity and a small particle size distribution index are preferred. The fine particles having these conditions are excellent in dispersibility in the varnish and can be used in a state where they are not aggregated with each other. As the particle diameter (average diameter) of the fine particles used, for example, those having a particle diameter of 100 to 2000 nm can be used. By satisfying these conditions, the pore diameter of the porous film obtained by removing the fine particles can be made uniform, so that the applied electric field can be made uniform, particularly when used as a separator.

As a material of the resin fine particles, for example, an ordinary linear polymer or a known depolymerizable polymer can be used without limitation depending on the purpose. A normal linear polymer is a polymer in which polymer molecular chains are randomly cut during thermal decomposition, and a depolymerizable polymer is a polymer in which the polymer is decomposed into monomers during thermal decomposition. All of them disappear from the polyimide film by decomposition to monomers, low molecular weight substances, or CO ₂ during heating. The decomposition temperature of the resin fine particles used is preferably 200 to 320 ° C., more preferably 230 to 260 ° C. When the decomposition temperature is 200 ° C. or higher, film formation can be performed even when a high-boiling solvent is used for the varnish, and the range of selection of the baking conditions for polyimide is widened. If the decomposition temperature is less than 320 ° C., only the resin fine particles can be lost without causing thermal damage to the polyimide.

As the linear polymer, for example, low density or amorphous polyethylene, amorphous polypropylene, ethylene vinyl acetate copolymer resin, polyamide or the like can be used. Examples of the depolymerizable polymer include (meth) acrylic resins, α-methylstyrene resins, polyacetal homopolymers and copolymers.

The (meth) acrylic resin is obtained from alkyl (meth) acrylates such as methyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. And a copolymer obtained by copolymerizing two or more kinds of homopolymers. Furthermore, you may use what copolymerized with the other monomer (For example, glycidyl methacrylate, styrene, etc.) which has the said (meth) acrylic-acid alkylester as a main component and can copolymerize with this.

Examples of the α-methylstyrene resin include a homopolymer of α-methylstyrene and a copolymer of α-methylstyrene as a main component and other monomers copolymerizable therewith. The above depolymerizable polymers may be used alone or in combination.

Among these depolymerizable polymers, methyl methacrylate or isobutyl methacrylate alone (polymethyl methacrylate or polyisobutyl methacrylate) having a low thermal decomposition temperature, or a copolymer having a main component thereof is preferable for handling during pore formation. .

<Polyamide acid>
As the polyamic acid used in the present invention, those obtained by polymerizing an arbitrary tetracarboxylic dianhydride and a diamine can be used without any particular limitation. The amount of tetracarboxylic dianhydride and diamine used is not particularly limited, but 0.50 to 1.50 mol of diamine is preferably used relative to 1 mol of tetracarboxylic dianhydride, and 0.60 to 1. It is more preferable to use 30 mol, and it is particularly preferable to use 0.70 to 1.20 mol.

The tetracarboxylic dianhydride can be appropriately selected from tetracarboxylic dianhydrides conventionally used as raw materials for polyamic acid synthesis. The tetracarboxylic dianhydride may be an aromatic tetracarboxylic dianhydride or an aliphatic tetracarboxylic dianhydride. From the viewpoint of the heat resistance of the resulting polyimide resin, the aromatic tetracarboxylic dianhydride may be used. Preference is given to using carboxylic dianhydrides. Tetracarboxylic dianhydride may be used in combination of two or more.

Preferable specific examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxy Phenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′- Biphenyltetracarboxylic dianhydride, 2,2,6,6-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2 , 3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2 -Bis (2,3-dicarbox Phenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) Ether dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic dianhydride, 4,4- (p-phenylenedioxy) diphthal Acid dianhydride, 4,4- (m-phenylenedioxy) diphthalic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic acid Anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride , 2, , 6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bisphthalic anhydride fluorene, 3,3 ′, 4,4′-diphenyl Examples include sulfonetetracarboxylic dianhydride. Examples of the aliphatic tetracarboxylic dianhydride include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, cyclohexane tetracarboxylic dianhydride, 1, Examples include 2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, and the like. Among these, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride are preferable from the viewpoints of price and availability. These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

The diamine can be appropriately selected from diamines conventionally used as a raw material for synthesizing polyamic acid. This diamine may be an aromatic diamine or an aliphatic diamine, but an aromatic diamine is preferred from the viewpoint of the heat resistance of the resulting polyimide resin. These diamines may be used in combination of two or more.

Examples of aromatic diamines include diamino compounds in which one or about 2 to 10 phenyl groups are bonded. Specifically, phenylenediamine and derivatives thereof, diaminobiphenyl compounds and derivatives thereof, diaminodiphenyl compounds and derivatives thereof, diaminotriphenyl compounds and derivatives thereof, diaminonaphthalene and derivatives thereof, aminophenylaminoindane and derivatives thereof, diaminotetraphenyl Compounds and derivatives thereof, diaminohexaphenyl compounds and derivatives thereof, and cardo-type fluorenediamine derivatives.

Phenylenediamine is m-phenylenediamine, p-phenylenediamine, etc., and phenylenediamine derivatives include diamines to which alkyl groups such as methyl group and ethyl group are bonded, such as 2,4-diaminotoluene, 2,4-triphenylene. Diamines and the like.

The diaminobiphenyl compound is a compound in which two aminophenyl groups are bonded to each other. For example, 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, and the like.

The diaminodiphenyl compound is a compound in which two aminophenyl groups are bonded to each other via other groups. The bond is an ether bond, a sulfonyl bond, a thioether bond, a bond by alkylene or a derivative group thereof, an imino bond, an azo bond, a phosphine oxide bond, an amide bond, a ureylene bond, or the like. The alkylene bond has about 1 to 6 carbon atoms, and the derivative group has one or more hydrogen atoms in the alkylene group substituted with halogen atoms or the like.

Examples of diaminodiphenyl compounds include 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ketone 3,4′-diaminodiphenyl ketone, 2,2-bis (p-aminophenyl) propane, 2,2′-bis (p-aminophenyl) hexafluoropropane, 4-methyl-2,4-bis ( p-aminophenyl) -1-pentene, 4-methyl- , 4-bis (p-aminophenyl) -2-pentene, iminodianiline, 4-methyl-2,4-bis (p-aminophenyl) pentane, bis (p-aminophenyl) phosphine oxide, 4,4 '-Diaminoazobenzene, 4,4'-diaminodiphenylurea, 4,4'-diaminodiphenylamide, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1 , 3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) Phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenyl) Phenoxy) phenyl] hexafluoropropane, and the like.

Of these, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, and 4,4'-diaminodiphenyl ether are preferable from the viewpoint of price and availability.

The diaminotriphenyl compound is one in which two aminophenyl groups and one phenylene group are bonded via another group, and the other groups are the same as those of the diaminodiphenyl compound. Examples of diaminotriphenyl compounds include 1,3-bis (m-aminophenoxy) benzene, 1,3-bis (p-aminophenoxy) benzene, 1,4-bis (p-aminophenoxy) benzene, and the like. be able to.

Examples of diaminonaphthalene include 1,5-diaminonaphthalene and 2,6-diaminonaphthalene.

Examples of aminophenylaminoindane include 5 or 6-amino-1- (p-aminophenyl) -1,3,3-trimethylindane.

Examples of diaminotetraphenyl compounds include 4,4′-bis (p-aminophenoxy) biphenyl, 2,2′-bis [p- (p′-aminophenoxy) phenyl] propane, 2,2′-bis [ and p- (p′-aminophenoxy) biphenyl] propane, 2,2′-bis [p- (m-aminophenoxy) phenyl] benzophenone, and the like.

Examples of cardo-type fluorenediamine derivatives include 9,9-bisaniline fluorene.

The aliphatic diamine preferably has about 2 to 15 carbon atoms, and specific examples include pentamethylene diamine, hexamethylene diamine, and heptamethylene diamine.

In addition, a compound in which the hydrogen atom of these diamines is substituted with at least one substituent selected from the group such as a halogen atom, a methyl group, a methoxy group, a cyano group, and a phenyl group may be used.

The means for producing the polyamic acid used in the present invention is not particularly limited, and for example, a known method such as a method of reacting an acid and a diamine component in an organic solvent can be used.

The reaction between tetracarboxylic dianhydride and diamine is usually carried out in an organic solvent. The organic solvent used for the reaction of the tetracarboxylic dianhydride and the diamine is particularly capable of dissolving the tetracarboxylic dianhydride and the diamine and not reacting with the tetracarboxylic dianhydride and the diamine. It is not limited. An organic solvent can be used individually or in mixture of 2 or more types.

Examples of organic solvents used in the reaction of tetracarboxylic dianhydride with diamine include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N Nitrogen-containing polar solvents such as N, diethylformamide, N-methylcaprolactam, N, N, N ′, N′-tetramethylurea; β-propiolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone Lactone polar solvents such as γ-caprolactone and ε-caprolactone; dimethyl sulfoxide; acetonitrile; fatty acid esters such as ethyl lactate and butyl lactate; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dioxane, tetrahydrofuran, methyl cellosolve acetate, e Ethers such as Roussel cellosolve acetate; include phenolic solvents cresols, and the like. These organic solvents can be used alone or in admixture of two or more. The amount of the organic solvent used is not particularly limited, but it is desirable that the content of the polyamic acid to be produced is 5 to 50% by mass.

Among these organic solvents, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N, N- Nitrogen-containing polar solvents such as diethylformamide, N-methylcaprolactam, N, N, N ′, N′-tetramethylurea are preferred.

The polymerization temperature is generally −10 to 120 ° C., preferably 5 to 30 ° C. The polymerization time varies depending on the raw material composition used, but is usually 3 to 24 Hr (hour). Further, the intrinsic viscosity of the polyamic acid solution obtained under such conditions is preferably in the range of 1000 to 100,000 cP (centipoise), and more preferably in the range of 5,000 to 70,000 cP.

<Polyimide>
The polyimide used in the present invention is not limited to its structure and molecular weight as long as it is a soluble polyimide that can be dissolved in the organic solvent used in the varnish of the present invention. About a polyimide, you may have a functional group which accelerates | stimulates a crosslinking reaction etc. at the time of baking, or a functional group which can be condensed, such as a carboxy group.

Use of a monomer to introduce a flexible bending structure into the main chain in order to obtain a polyimide soluble in an organic solvent, for example, ethylenediamine, hexamethylenediamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, Aliphatic diamines such as 4,4′-diaminodicyclohexylmethane; 2-methyl-1,4-phenylenediamine, o-tolidine, m-tolidine, 3,3′-dimethoxybenzidine, 4,4′-diaminobenzanilide, etc. Aromatic diamines; polyoxyalkylene diamines such as polyoxyethylene diamine, polyoxypropylene diamine and polyoxybutylene diamine; polysiloxane diamines; 2,3,3 ′, 4′-oxydiphthalic anhydride, 3,4,3 ′, 4′-oxydiphthalic anhydride, 2,2-bis (4- Hydroxyphenyl) propane dibenzoate-3,3 ', use of such 4,4'-tetracarboxylic dianhydride is valid. In addition, the use of a monomer having a functional group that improves the solubility in an organic solvent, for example, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 2-trifluoromethyl-1,4 It is also effective to use a fluorinated diamine such as phenylenediamine. Furthermore, in addition to the monomer for improving the solubility of the polyimide, the same monomers as those described in the column for the polyamic acid can be used in combination as long as the solubility is not inhibited.

There is no restriction | limiting in particular in the means to manufacture the polyimide which can be melt | dissolved in the organic solvent used by this invention, For example, well-known methods, such as the method of making a polyamic acid chemically imidize or heat-imidize and dissolve in an organic solvent, are used. be able to. Examples of such polyimide include aliphatic polyimide (total aliphatic polyimide), aromatic polyimide and the like, and aromatic polyimide is preferable. The aromatic polyimide is obtained by thermally or chemically obtaining a polyamic acid having a repeating unit represented by the formula (1) by a ring-closing reaction or by dissolving a polyimide having a repeating unit represented by the formula (2) in a solvent. Good. In the formula, Ar represents an aryl group.

<Condensation agent>
In the method for producing a porous polyimide film of the present invention, a condensing agent is further contained in the varnish for the purpose of firing the unfired composite film below the thermal decomposition temperature of the resin fine particles.

The condensing agent has an imidization promoting effect at the time of heating imidization, and any known one can be used without particular limitation as long as the unfired composite film can be fired below the thermal decomposition temperature of the resin fine particles. it can.

Examples of the condensing agent include amine compounds such as aniline, diethyl-t-butylamine, diisopropylethylamine, phenethylamine, dodecylamine, triethylamine, tributylamine, and triethanolamine; nitrogen-containing heterocyclic compounds such as imidazole and pyridine; 4 Examples thereof include a thermal base generator that decomposes with heat such as a quaternary ammonium salt or a carbamate compound to generate a base.

As the thermal base generator, a compound (A-1) that decomposes by heat to generate an imidazole compound can be further preferred. Hereinafter, the compound (A-1) will be described in detail.

The imidazole compound generated from the compound (A-1) promotes ring closure of the polyamic acid as a basic imidization catalyst. The imidazole compound generated from the compound (A-1) may be an imidazole or a compound in which part or all of the hydrogen atoms bonded to the carbon atoms in the imidazole are substituted with a substituent. It is preferable that it is an imidazole compound represented by (3).

(Wherein R ¹ , R ² , and R ³ are each independently a hydrogen atom, halogen atom, hydroxyl group, mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfonate group, phosphino group, (A phosphinyl group, a phosphonate group, or an organic group is shown.)

Examples of the organic group represented by R ¹ , R ² , or R ³ include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, and an aralkyl group. This organic group may contain a hetero atom. The organic group may be linear, branched or cyclic. This organic group is usually monovalent, but may be divalent or higher when forming a cyclic structure.

R ¹ and R ² may be bonded to each other to form a cyclic structure, and may include a hetero atom bond. Examples of the cyclic structure include a heterocycloalkyl group and a heteroaryl group, and may be a condensed ring.

When the organic group represented by R ¹ , R ² , or R ³ contains a hetero atom, examples of the hetero atom include an oxygen atom, a nitrogen atom, and a silicon atom. Specific examples of the bond containing a hetero atom include an ether bond, a thioether bond, a carbonyl bond, a thiocarbonyl bond, an ester bond, an amide bond, a urethane bond, an imino bond (—N═C (—R) — or —C (= NR)-(wherein R represents a hydrogen atom or an organic group, hereinafter the same), carbonate bond, sulfonyl bond, sulfinyl bond, azo bond and the like. Among these, from the viewpoint of heat resistance of the imidazole compound, an ether bond, a thioether bond, a carbonyl bond, a thiocarbonyl bond, an ester bond, an amide bond, a urethane bond, an imino bond, a carbonate bond, a sulfonyl bond, and a sulfinyl bond are preferable.

A hydrogen atom contained in a group other than an organic group represented by R ¹ , R ² , or R ³ may be substituted with a hydrocarbon group. The hydrocarbon group may be linear, branched or cyclic.

R ¹ , R ² , and R ³ are each independently preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and a halogen atom. A hydrogen atom is more preferable. Since imidazole in which R ¹ , R ² , and R ³ are all hydrogen atoms has a simple structure with little steric hindrance, it can easily act on polyamic acid as an imidation catalyst.

Compound (A-1) is not particularly limited as long as it can decompose by heat to generate an imidazole compound, preferably an imidazole compound represented by the above formula (3). Regarding compounds that have been conventionally blended in photosensitive compositions and generate amines by the action of light, the skeleton derived from amines generated during exposure is an imidazole compound, preferably an imidazole compound represented by the above formula (3) The compound used as compound (A-1) is obtained by substituting the skeleton derived from

Suitable compound (A-1) includes a compound represented by the following formula (4).

(Wherein R ¹ , R ² , and R ³ are each independently a hydrogen atom, halogen atom, hydroxyl group, mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, phosphino group, sulfonate group, R ⁴ and R ⁵ each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, or a sulfino group. , Sulfo group, sulfonate group, phosphino group, phosphinyl group, phosphono group, phosphonate group, or organic group R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are each independently a hydrogen atom or a halogen atom. , Hydroxyl group, mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfino group, sulfo group , Sulfonate group, phosphino group, phosphinyl group, phosphono group, phosphonato group, amino group, ammonio group, or organic group, R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are two or more of them. May be bonded to form a cyclic structure and may contain a bond of a hetero atom.)

In the formula (4), R ¹ , R ² , and R ³ are the same as those described for the formula (3).

In the formula (4), examples of the organic group represented by R ⁴ or R ⁵ include those exemplified for R ¹ , R ² , and R ³ . This organic group may contain a hetero atom as in the case of R ¹ , R ² and R ³ . The organic group may be linear, branched or cyclic.

R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 4 to 13 carbon atoms, a cycloalkenyl group having 4 to 13 carbon atoms, or an aryl having 7 to 16 carbon atoms. An oxyalkyl group, an aralkyl group having 7 to 20 carbon atoms, an alkyl group having 2 to 11 carbon atoms having a cyano group, an alkyl group having 1 to 10 carbon atoms having a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, 2 carbon atoms An amide group having ˜11, an alkylthio group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms, and an ester group having 2 to 11 carbon atoms (—COOR or —OCOR (where R represents a hydrocarbon group)) ), Aryl groups having 6 to 20 carbon atoms, electron donating groups and / or electron withdrawing groups substituted aryl groups having 6 to 20 carbon atoms, electron donating groups and / or electron withdrawing groups substituted benzyl groups , Amino group is preferably a methylthio group. More preferably, both R ⁴ and R ⁵ are hydrogen atoms, or R ⁴ is a methyl group and R ⁵ is a hydrogen atom.

In the formula (4), examples of the organic group represented by R ⁶ , R ⁷ , R ⁸ , R ⁹ , or R ¹⁰ include those exemplified for R ¹ , R ² , and R ³ . This organic group may contain a hetero atom as in the case of R ¹ and R ² . The organic group may be linear, branched or cyclic.

Two or more of R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ may be bonded to form a cyclic structure, and may include a hetero atom bond. Examples of the cyclic structure include a heterocycloalkyl group and a heteroaryl group, and may be a condensed ring. For example, R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are two or more of them bonded to each other, and R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are bonded to each other. A ring atom may be shared to form a condensed ring such as naphthalene, anthracene, phenanthrene, and indene.

R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 4 to 13 carbon atoms, or a cyclohexane having 4 to 13 carbon atoms. Alkenyl group, aryloxyalkyl group having 7 to 16 carbon atoms, aralkyl group having 7 to 20 carbon atoms, alkyl group having 2 to 11 carbon atoms having a cyano group, alkyl group having 1 to 10 carbon atoms having a hydroxyl group, carbon number An alkoxy group having 1 to 10 carbon atoms, an amide group having 2 to 11 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms, an ester group having 2 to 11 carbon atoms, and an aryl having 6 to 20 carbon atoms Group, electron donating group and / or electron withdrawing group substituted aryl group having 6 to 20 carbon atoms, electron donating group and / or electron withdrawing group substituted benzyl group, cyano group, methylthio group, nitro group Is Door is preferable.

In addition, as R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ , two or more of them are bonded, and R ⁶ , R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are bonded. It is also preferred if a benzene ring atom is shared to form a condensed ring such as naphthalene, anthracene, phenanthrene or indene.

Among the compounds represented by the above formula (4), a compound represented by the following formula (5) is preferable.

(Wherein R ¹ , R ² , and R ³ have the same meanings as in formulas (3) and (4). R ⁴ to R ⁹ have the same meanings as in formula (4). R ¹¹ is a hydrogen atom or Represents an organic group, and R ⁶ and R ⁷ do not become a hydroxyl group, and R ⁶ , R ⁷ , R ⁸ , and R ⁹ may combine with each other to form a cyclic structure. And may contain a heteroatom bond.)

Since the compound represented by the formula (5) has a substituent —O—R ¹¹ , it has excellent solubility in an organic solvent.

In the formula (5), when R ¹¹ is an organic group, examples of the organic group include those exemplified for R ¹ , R ² , and R ³ . This organic group may contain a hetero atom. The organic group may be linear, branched or cyclic. R ¹¹ is preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and more preferably a methyl group.

Suitable compounds (A-1) also include compounds represented by the following formula (6).

(Wherein R ¹ , R ² , and R ³ are each independently a hydrogen atom, halogen atom, hydroxyl group, mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, phosphino group, sulfonate group, (A phosphinyl group, a phosphonato group, or an organic group. R ¹² represents an optionally substituted hydrocarbon group.)

In Formula (6), R ¹ , R ² , and R ³ are the same as those described for Formula (3).

In the formula (6), R ¹² is an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or an optionally substituted 6 to 20 carbon atoms. Examples thereof include an aryl group and an optionally substituted aralkyl group having 7 to 20 carbon atoms, and an optionally substituted aralkyl group having 7 to 20 carbon atoms is preferable. When the aryl group or aralkyl group is substituted, examples of the substituent include a halogen atom, a nitro group, an alkyl group having 1 to 4 carbon atoms, and an alkoxy group having 1 to 4 carbon atoms.

The compound represented by the formula (6) is a reaction between an imidazole compound represented by the formula (3) and a chloroformate represented by the following formula (7), an imidazole compound represented by the formula (3) and the following: It can synthesize | combine by reaction with the dicarbonate represented by Formula (8), or the reaction of the carbonyldiimidazole compound represented by following formula (9), and the alcohol represented by following formula (10).

(In formulas (7) to (10), R ¹ , R ² , and R ³ have the same meaning as in formula (3). R ¹² has the same meaning as in formula (6).)

Specific examples of the compound particularly suitable as the compound (A-1) are shown below.

The content of the condensing agent in the varnish is not particularly limited as long as the object of the present invention is not impaired. The content is preferably 1 to 300 parts by mass, more preferably 1 to 50 parts by mass, and more preferably 1 to 25 parts by mass with respect to 100 parts by mass of the polyamic acid or polyimide.

In the present invention, for the purpose of uniformly dispersing the fine particles in the varnish, a dispersant may be further added together with the fine particles. By adding the dispersant, the polyamic acid or polyimide and the fine particles can be mixed more uniformly, and furthermore, the fine particles in the molded precursor film can be uniformly distributed. As a result, it is possible to provide a dense opening on the surface of the finally obtained porous polyimide and to allow the front and back surfaces to communicate efficiently, thereby improving the air permeability of the film.

[Production of unfired composite film]
Film formation of an unfired composite film containing the polyamic acid or polyimide of the present invention, resin fine particles, and a condensing agent is performed by applying the varnish on a substrate or a substrate provided with a release layer, and under normal pressure or vacuum. The drying is carried out at 0 to 50 ° C., preferably at a normal pressure of 10 to 30 ° C.

The production of the substrate provided with the release layer is performed by applying a release agent on the substrate and drying or baking. As the mold release agent used here, a known mold release agent such as an ammonium alkylphosphate salt, fluorine-based or silicone can be used without any particular limitation. The dried polyamic acid film or polyimide is peeled from the substrate to form an unfired composite film. At that time, a slight release agent remains on the peeled surface of the unfired composite film. The remaining release agent is discolored at the time of firing, and greatly affects the wettability and electrical characteristics of the film surface. Therefore, it is preferable to remove the release agent particularly when the unfired composite film is peeled from the substrate and moved to the firing step.

Therefore, in the present invention, the unfired composite film peeled off from the substrate may be provided with a cleaning process using an organic solvent. In that case, the organic solvent to be used can be used without particular limitation as long as it dissolves the release agent and does not dissolve or swell the unfired composite film. For example, alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol can be preferably used. As a cleaning method, a known method such as a method of immersing a film in a cleaning solution and taking it out or a method of shower cleaning can be selected.

Subsequently, for the purpose of removing the cleaning liquid, the unfired composite film after the cleaning step may be dried as it is, but the cleaning may be repeated a plurality of times using a mixed solvent of water and a water-soluble organic solvent. Good.

[Production of polyimide-resin fine particle composite film (firing process)]
The polyimide-resin fine particle composite film composed of polyimide and fine particles can be obtained by peeling the substrate from or without peeling, and subjecting the unfired composite film to post-treatment (baking) by heating. In the firing step, it is preferable to complete imidization.

Here, the firing temperature of the polyimide film varies depending on the structure of the polyamic acid and the selected condensing agent, but is set to be lower than the decomposition temperature of the applied resin fine particles within the range in which the condensing agent promotes imidization. . In particular, the temperature is preferably 180 to 320 ° C., more preferably 180 to 250 ° C.

When firing is performed, for example, when the firing temperature is set to 230 ° C., the temperature is raised from room temperature to 230 ° C. in 3 hours and then maintained at 230 ° C. for 20 minutes, or stepwise from room temperature in increments of 50 ° C. It is also possible to use a stepwise drying-thermal imidation method such as raising the temperature to 20 ° C. (holding for 20 minutes at each step) and finally holding at 230 ° C. for 20 minutes. Moreover, when peeling and baking from a board | substrate, the method of fixing the edge part of a non-baking composite film to the formwork made from SUS, etc. can also be taken.

The film thickness of the completed polyimide-resin fine particle composite film can be obtained by measuring and averaging the thicknesses of a plurality of locations with a micrometer, for example. The average film thickness is preferably different depending on the use of the polyimide-resin fine particle composite film or the porous polyimide film. For example, when used for a separator or the like, it is preferably 5 to 500 μm. More preferably.

[Porosification of polyimide-resin particle composite membrane (particle removal process)]
A porous polyimide film can be produced with good reproducibility by thermally decomposing and removing resin fine particles from the polyimide-resin fine particle composite film.

Fine particle removal is performed by maintaining at a temperature of 230 to 350 ° C. at a thermal decomposition temperature of the selected resin fine particle or a temperature equal to or higher than the thermal decomposition temperature for a certain time. If the temperature to hold is less than 350 degreeC, since a thermal deterioration is not seen in a polyimide film, it is preferable. The fine particle removal is preferably performed in an atmosphere in which oxygen or water vapor is added to an inert gas.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to these examples.

<Examples 1 to 3, Comparative Examples 1 and 2>
In Examples and Comparative Examples, the following tetracarboxylic dianhydrides, diamines, organic solvents, fine particles, and condensing agents were used.
Tetracarboxylic dianhydride (A), (A1): pyromellitic dianhydride, diamine (B), (B1): 4,4′-diaminodiphenyl ether, organic solvent (C), (C1): N , N-dimethylacetamide fine particles Silica: 700 nm silica (density: 2.2)
PMMA: polymethyl methacrylate (density: 1.17)
・ Condensation agent (E)
(E1): Imidazole (E2):

[Preparation of varnish]
Tetracarboxylic dianhydride, diamine, and organic solvent were put into a separable flask equipped with a stirrer, a stirring blade, a reflux condenser, and a nitrogen gas introduction tube. Nitrogen was introduced into the flask through a nitrogen gas introduction tube, and the atmosphere in the flask was changed to a nitrogen atmosphere. Next, while stirring the contents of the flask, tetracarboxylic dianhydride and diamine were reacted at 50 ° C. for 20 hours to obtain a polyamic acid solution. A condensing agent and fine particles were added to the obtained polyamic acid solution in the amounts shown in Table 1 and stirred to prepare a varnish. In Example 3, the blending amount was adjusted in advance so that the volume in the film was equivalent to that in the case of silica fine particles (the volume ratio of fine particles / polyimide was about 2.6 when a polyimide-fine particle composite film was used). .

[Formation of polyimide-resin fine particle composite film]
The varnish was formed into a film using an applicator on a glass plate coated with a release agent. Prebaking was performed at 70 ° C. for 5 minutes to form an unfired composite film having a thickness of 25 μm. After peeling off the unfired composite film from the substrate, the release agent was removed with ethanol. In Comparative Example 1, the firing process was performed at 320 ° C. for 15 minutes, and in Comparative Examples 2 and Examples 1 to 3, the firing process was performed at 230 ° C. for 15 minutes. To complete imidization. The film strength and elongation measurement results of the polyimide-resin fine particle composite films formed in Comparative Examples 1 and 2 and Examples 1 and 2 are shown in FIGS. 1 (a) and 1 (b), respectively. The film strength and elongation measurement results of Example 3 were the same as those of Example 1.

[Porous polyimide film formation (particulate removal process)]
The polyimide-resin fine particle composite film was heat treated at 270 ° C. for 30 minutes in the example, and immersed in a 10% HF solution for 10 minutes in the comparative example, thereby removing the fine particles contained in the film. SEM images of the surface of the obtained porous polyimide film are shown in FIGS.

According to the comparison between Examples 1 and 2 and Comparative Examples 1 and 2 shown in FIG. 1, the heat treatment was performed at a low temperature of 230 ° C. by adding (E1) or (E2) as a condensing agent. However, it turns out that the polyimide film | membrane with favorable film | membrane intensity | strength is obtained equivalent to the comparative example 1 which carried out the thermal imidation in high temperature. On the other hand, in Comparative Example 2 containing no condensing agent, the film strength was greatly reduced.

FIG. 2 shows SEM images of the front surface, back surface, and cross section of the porous polyimide films prepared in Comparative Example 1 and Examples 1 to 3. Furthermore, enlarged SEM images of the back surfaces of Comparative Example 1 and Examples 1 to 3 are shown in FIGS. From these figures, it was confirmed that PMMA was decomposed and disappeared at 270 ° C., and that the polyimide film could be made porous in the same manner as that obtained by subjecting conventional silica to HF treatment.

Claims

A firing step in which an unfired composite film containing polyamic acid or polyimide, resin fine particles, and a condensing agent is fired at a temperature lower than the decomposition temperature of the resin fine particles to form a polyimide-resin fine particle composite film;
A fine particle removal step of removing the resin fine particles from the polyimide-resin fine particle composite film;
The manufacturing method of the porous polyimide membrane which has this.
A porous polyimide film produced by the method according to claim 1.
A separator comprising the porous polyimide film according to claim 2.
A method for producing a polyimide-resin fine particle composite film comprising a baking step of baking an unfired composite film containing polyamic acid or polyimide, resin fine particles, and a condensing agent at a temperature lower than the decomposition temperature of the resin fine particles.
Varnish containing polyamide acid or polyimide, resin fine particles, condensing agent, and organic solvent.