JP6881644B2 - Method for producing resin particle-dispersed polyimide precursor solution, resin particle-dispersed polyimide precursor solution, resin particle-containing polyimide film, method for producing porous polyimide film, and porous polyimide film. - Google Patents

Description

The present invention relates to a method for producing a resin particle-dispersed polyimide precursor solution, a resin particle-dispersed polyimide precursor solution, a resin particle-containing polyimide film, a method for producing a porous polyimide film, and a porous polyimide film.

The polyimide resin is a material having excellent mechanical strength, chemical stability, and heat resistance, and a porous polyimide film having these characteristics is attracting attention.

For example, in Patent Document 1, a densely packed deposit of monodisperse spherical inorganic fine particles is fired to form a sintered body of inorganic fine particles, and the gaps between the inorganic fine particles of the sintered body are filled with polyamic acid and then fired. A method for producing a separator for a lithium secondary battery, which dissolves and removes the inorganic fine particles by immersing it in a solution in which the inorganic fine particles are dissolved but the resin is not dissolved, is described.
Patent Document 2 describes an organic porous body having pores made of polyimide and an ionic conductor holding an electrolyte material containing a cation component and an anion component in the pores.
Patent Document 3 describes a varnish manufacturing process for producing a varnish by mixing polyamic acid or polyimide, silica particles and a solvent, or polymerizing a polyamic acid or polyimide in a solvent in which silica particles are dispersed to produce a varnish. After forming a film of the varnish produced in the manufacturing process on a substrate, imidization is completed to produce a polyimide-silica composite film, and a polyimide-silica composite film produced in the composite film manufacturing process. A method for producing a porous polyimide film having a silica removing step for removing silica is described.
Patent Document 4 describes a porous silica mold obtained in a process of manufacturing a porous silica mold obtained by filling silica particles and then sintering them to obtain a porous silica mold, and a porous silica mold obtained in a step of manufacturing a porous silica mold. Describes a method for producing a porous polyimide, which comprises a polyimide filling step of filling the voids of the above with polyimide and a silica removing step of removing silica from a porous silica mold filled with the polyimide to obtain a porous silica.

Further, Patent Document 5 describes a positive electrode, a negative electrode, and a separator layer containing a porous polyimide film having an average pore diameter of 5 μm or less and having a porous polyimide film formed by phase separation after applying a solution of polyimide or a polyimide precursor. A non-aqueous electrolyte secondary battery having, is described.
Patent Document 6 describes a step of preparing a resin composition for a film by mixing a heat-resistant resin such as polyimide, heat-extinguishing resin particles containing a polyoxyalkylene resin, and a solvent, and producing a resin composition for a film. A method for producing a porous resin film, which comprises a step of forming a film and a step of heating the formed resin composition for a film, is described.

Japanese Patent No. 5331627 Japanese Unexamined Patent Publication No. 2008-034212 Japanese Unexamined Patent Publication No. 2012-107144 Japanese Unexamined Patent Publication No. 2011-11470 Japanese Unexamined Patent Publication No. 10-302479 Japanese Unexamined Patent Publication No. 2010-024385

An object of the present invention is to provide a method for producing a resin particle-dispersed polyimide precursor solution in which the dispersibility of the resin particles is improved as compared with the case where the resin particle dispersion liquid and the polyimide precursor solution are mixed.

The following inventions are provided in order to achieve the above object.

<1>
The aqueous solvent is composed of polyester resin particles, urethane resin particles, vinyl resin particles, (meth) acrylic resin particles, (meth) acrylic acid ester resin particles, styrene / (meth) acrylic resin particles, polystyrene resin particles, and polyethylene resin particles. A polyimide precursor is formed by polymerizing a tetracarboxylic acid dianhydride and a diamine compound in the presence of an organic amine compound in a resin particle dispersion in which at least one resin particle selected from the group is dispersed. A method for producing a resin particle-dispersed polyimide precursor solution.

<2>
The method for producing a resin particle-dispersed polyimide precursor solution according to <1>, wherein the resin particle dispersion is a resin particle dispersion in which resin particles are granulated in the aqueous solvent.

<3>
The method for producing a resin particle-dispersed polyimide precursor solution according to <1> or <2>, wherein the organic amine compound is a tertiary amine compound.

<4>
The method for producing a resin particle-dispersed polyimide precursor solution according to <1> or <2>, wherein the organic amine compound is an amine compound having a heterocyclic structure containing nitrogen.

<5>
A resin particle-dispersed polyimide precursor solution obtained by the production method according to any one of <1> to <4>.

<6>
After applying the resin particle-dispersed polyimide precursor solution according to <5> to form a coating film,
A polyimide film containing resin particles obtained by heating a coating film.

<7>
A first step of applying the resin particle-dispersed polyimide precursor solution according to <5> to form a coating film, and then drying the coating film to form a film containing the polyimide precursor and the resin particles. When,
A second step of heating the film to imidize the polyimide precursor to form a polyimide film, the second step including a process of removing the resin particles.
A method for producing a porous polyimide film having.

<8>
The process of exposing the resin particles in the second step, after the process of imidizing the polyimide precursor or after the imidization and before the process of removing the resin particles, according to <7>. Method for producing a porous polyimide film.

<9>
The method for producing a porous polyimide film according to <7> or <8>, wherein the treatment for removing the resin particles is a treatment for removing the resin particles with an organic solvent that dissolves the resin particles.

<10>
The method for producing a porous polyimide film according to <7> or <8>, wherein the treatment for removing the resin particles is a treatment for removing the resin particles by heating.

<11>
A porous polyimide film produced by the method for producing a porous polyimide film according to any one of <7> to <10>.

According to the invention according to <1> or <2>, a method for producing a resin particle-dispersed polyimide precursor solution in which the dispersibility of the resin particles is improved as compared with the case where the resin particle dispersion liquid and the polyimide precursor solution are mixed. Is provided.

According to the invention according to <3> or <4>, a method for producing a porous polyimide film having excellent film forming property is provided as compared with the case where the organic amine compound is a primary amine compound.

According to the invention according to <5>, the dispersibility of the resin particles is improved as compared with the case of the resin particle-dispersed polyimide precursor solution obtained by mixing the resin particle dispersion solution and the polyimide precursor solution. A dispersed polyimide precursor solution is provided.

According to the invention according to <6>, as compared with the case of the resin particle-containing polyimide film obtained by the resin particle dispersion polyimide precursor solution obtained by mixing the resin particle dispersion liquid and the polyimide precursor solution, the resin Provided is a polyimide film containing resin particles in which variation in particle distribution is suppressed.

According to the invention according to <7>, as compared with the case of the method for producing a porous polyimide film obtained by the resin particle dispersion polyimide precursor solution obtained by mixing the resin particle dispersion liquid and the polyimide precursor solution. Provided is a method for producing a porous polyimide film in which variation in the distribution of pore diameters is suppressed.

According to the invention according to <8>, when the process of imidizing the polyimide precursor or after the imidization and before the process of removing the resin particles is not performed, the process of exposing the resin particles is not performed. A method for producing a porous polyimide film, which can obtain a porous polyimide film having a higher aperture ratio, is provided.

According to the invention according to <9> or <10>, it is a method for producing a porous polyimide film obtained by a resin particle-dispersed polyimide precursor solution obtained by mixing a resin particle dispersion liquid and a polyimide precursor solution. Compared with the case, the porous polyimide film in which the variation in the distribution of the pore diameter is suppressed even if the treatment for removing the resin particles is a treatment for removing the resin particles with an organic solvent or a treatment for removing the resin particles by heating. Manufacturing method is provided.

According to the invention according to <11>, it is empty as compared with the case of the porous polyimide film obtained by the resin particle dispersion polyimide precursor solution obtained by mixing the resin particle dispersion liquid and the polyimide precursor solution. Provided is a porous polyimide film in which variation in pore size distribution is suppressed.

It is a process drawing which shows an example of the manufacturing method of the porous polyimide film of this embodiment. It is an electron micrograph of the surface of the porous polyimide film (PIF-11) obtained in Example 11A.

Hereinafter, embodiments that are an example of the present invention will be described.

<Resin particle-dispersed polyimide precursor solution and its manufacturing method>
In the method for producing a resin particle-dispersed polyimide precursor solution according to the present embodiment, a tetracarboxylic acid dianhydride and a diamine compound are polymerized in a resin particle dispersion liquid dispersed in an aqueous solvent in the presence of an organic amine compound. This is a method for forming a polyimide precursor.

In addition, in this embodiment, "insoluble" also includes that the target substance dissolves in the range of 3% by mass or less with respect to the target liquid at 25 ° C.

The method for producing the resin particle-dispersed polyimide precursor solution according to the present embodiment is different from the case where the resin particle-dispersed polyimide precursor solution is formed by mixing the resin particle dispersion liquid and the polyimide precursor solution according to the above configuration. Therefore, the dispersibility of the resin particles is improved. The reason is not clear, but it is presumed to be due to the following reasons.

The polyimide film is, for example, a polyimide precursor solution dissolved in an organic solvent (for example, N-methylpyrrolidone (hereinafter, may be referred to as “NMP”) or N, N-dimethylacetamide (hereinafter, referred to as “DMAc”). It is obtained by applying a polyimide precursor solution in a state of being dissolved in a highly polar organic solvent such as (may be) and then heat-molding.

The polyimide film may contain particles such as inorganic particles and resin particles depending on the purpose. In this case, a polyimide precursor solution in which the particles are mixed is used. For example, when inorganic particles are mixed with a polyimide precursor solution dissolved in a highly polar organic solvent to prepare a particle-dispersed polyimide precursor solution, the dispersibility of the inorganic particles in the polyimide precursor solution is low.
On the other hand, when resin particles are mixed with a polyimide precursor solution dissolved in a highly polar organic solvent, the resin particles may be dissolved by the highly polar organic solvent in general resin particles (for example, polystyrene resin particles). , The dispersibility of the resin particles is low in this polyimide precursor solution. Further, for example, when resin particles that are difficult to dissolve in a highly polar organic solvent are produced by emulsion polymerization or the like, they are replaced with a highly polar organic solvent in order to be mixed with a polyimide precursor solution dissolved in the highly polar organic solvent. There is. In this case, the resin particles may be taken out from the dispersion liquid of the resin particles in order to replace with a highly polar organic solvent, and the taken out resin particles may agglomerate and may have low dispersibility.

On the other hand, in the method for producing the resin particle-dispersed polyimide precursor solution according to the present embodiment, the dispersibility of the resin particles is improved by the above configuration. This is because the polyimide precursor is formed in the presence of the organic amine compound in the resin particle dispersion liquid in which the resin particles are dispersed in advance, and the polyimide precursor is formed in the state where the resin particles are dispersed. Is considered to be. Further, the presence of the organic amine compound in the aqueous solvent causes the formed polyimide precursor (the carboxyl group thereof) to be in a state of being amine-chlorinated by the organic amine compound. Therefore, it is considered that a part of the organic amine salt of the polyimide precursor functions as a dispersant for the resin particles and the dispersibility of the resin particles is improved.

From the above, in the method for producing the resin particle-dispersed polyimide precursor solution according to the present embodiment, the resin particle-dispersed polyimide precursor solution is formed by mixing the resin particle dispersion liquid and the polyimide precursor solution according to the above configuration. It is presumed that the dispersibility of the resin particles is improved as compared with the case.

Further, in the method for producing a resin particle-dispersed polyimide precursor solution according to the present embodiment, a polyimide precursor is formed in a resin particle dispersion liquid in which resin particles are dispersed in advance. Therefore, the resin particle-dispersed polyimide precursor solution of the present embodiment can be obtained in one system (for example, in one container) from the preparation of the resin particle dispersion liquid to the preparation of the resin particle-dispersed polyimide precursor solution. The process of producing the resin particle-dispersed polyimide precursor solution is simplified.

The resin particle-dispersed polyimide precursor solution obtained by the method for producing the resin particle-dispersed polyimide precursor solution according to the present embodiment has improved dispersibility of resin particles. Therefore, the resin particle-containing polyimide film obtained from this polyimide precursor solution tends to suppress the variation in the distribution of the resin particles.

Further, the first step of forming a coating film using the resin particle-dispersed polyimide precursor solution according to the present embodiment and drying the coating film to form a film, and the first step of heating the film to imidize it. The porous polyimide film of the present embodiment is obtained by the treatment of removing the resin particles in the second step. The porous polyimide film obtained by this production method tends to suppress variations in the distribution of pores. In addition, variations in the shape of the pores, the diameter of the pores, etc. are likely to be suppressed. The reason for this is presumed as follows.

Since the resin particle-dispersed polyimide precursor solution of the present embodiment has improved dispersibility, it is considered that the porous polyimide film after removing the resin particles tends to suppress the variation in the distribution of pores.
Further, it is considered that the use of the resin particles makes it easy to suppress variations in the shape of the pores, the diameter of the pores, and the like. It is considered that this is because it effectively contributes to the relaxation of the residual stress in the imidization step of the polyimide precursor.
Further, since the polyimide precursor is dissolved in an aqueous solvent, the boiling point of the polyimide precursor solution is about 100 ° C. Therefore, as the film containing the polyimide precursor and the resin particles is heated, the solvent rapidly volatilizes and then the imidization reaction proceeds. Then, the resin particles in the film lose their fluidity and become insoluble in the organic solvent before being deformed by heat. Therefore, it is considered that the shape of the pores is easily maintained.

Further, the porous polyimide film of the present embodiment obtained by forming a resin particle-containing polyimide film using the resin particle-dispersed polyimide precursor solution according to the present embodiment and removing the resin particles has cracks. Easy to be suppressed. It is presumed that this is because the use of the resin particles in the method for producing the porous polyimide film of the present embodiment effectively contributes to the relaxation of the residual stress in the imidization step of the polyimide precursor.

Examples of the porous polyimide film include a method of preparing a film using a polyimide precursor solution in which silica particles are dispersed, firing the film, and then removing the silica particles. However, according to this method, it is necessary to use a chemical such as hydrofluoric acid in the treatment for removing silica particles. Therefore, these manufacturing methods have low productivity and high cost.

When silica particles are used, it is difficult to absorb volume shrinkage in the imidization step, so that it is considered that cracks are likely to occur in the polyimide film after imidization. Further, when silica particles are used, it is considered that ions are likely to remain as impurities because a chemical such as hydrofluoric acid is used.

On the other hand, since the porous polyimide film obtained by the above-mentioned production method of the present embodiment does not use silica particles, the step of obtaining the porous polyimide film is simplified. Moreover, since hydrofluoric acid is not used for removing the resin particles, it is possible to prevent ions from remaining as impurities.

Hereinafter, a method for producing the resin particle-dispersed polyimide precursor solution according to the present embodiment and the resin particle-dispersed polyimide precursor solution obtained thereby will be described.

[Manufacturing method of resin particle-dispersed polyimide precursor solution]
In the method for producing the resin particle-dispersed polyimide precursor solution of the present embodiment, first, a resin particle dispersion liquid in which resin particles are dispersed in an aqueous solvent is prepared. Then, in the resin particle dispersion liquid, the tetracarboxylic dianhydride and the diamine compound are polymerized in the presence of the organic amine compound to form a polyimide precursor.

Specifically, a step of preparing a resin particle dispersion liquid in which resin particles are dispersed in an aqueous solvent (hereinafter, also referred to as a “resin particle dispersion liquid preparation step”), and an organic amine compound and tetracarboxylic dianoxide with respect to the resin particle dispersion liquid. A step of mixing an acid dianhydride and a diamine compound and polymerizing the tetracarboxylic dianhydride and the diamine compound to form a polyimide precursor (hereinafter, also referred to as a "polyimide precursor forming step"). Have.

(Resin particle dispersion liquid preparation process)
The method of the resin particle dispersion liquid preparation step is not particularly limited as long as the resin particle dispersion liquid in which the resin particles are dispersed can be obtained in the aqueous solvent.
For example, a method of measuring resin particles insoluble in a polyimide precursor solution and an aqueous solvent for a resin particle dispersion liquid, mixing them, and stirring them to obtain them can be mentioned. The method of mixing and stirring the resin particles and the aqueous solvent is not particularly limited. For example, a method of mixing the resin particles while stirring the aqueous solvent can be mentioned. Further, in order to improve the dispersibility of the resin particles, for example, at least one of an ionic surfactant and a nonionic surfactant may be mixed.

Further, the resin particle dispersion liquid may be a resin particle dispersion liquid in which resin particles are granulated in the aqueous solvent. When the resin particles are granulated in an aqueous solvent, a resin particle dispersion liquid formed by polymerizing the monomer components in the aqueous solvent may be prepared. In this case, it may be a dispersion liquid obtained by a known polymerization method. For example, when the resin particles are vinyl resin particles, a known polymerization method (radical polymerization method such as emulsion polymerization, soap-free emulsion polymerization, suspension polymerization, mini-emulsion polymerization, microemulsion polymerization, etc.) can be applied.

For example, when an emulsion polymerization method is applied to the production of vinyl resin particles, monomers such as styrenes and (meth) acrylic acids are mixed in water in which a water-soluble polymerization initiator such as potassium persulfate or ammonium persulfate is dissolved. In addition, if necessary, a surfactant such as sodium dodecyl sulfate or diphenyloxide disulfonate is added, and the polymerization is carried out by heating with stirring to obtain vinyl resin particles.

The resin particle dispersion liquid forming step is not limited to the above method, and a commercially available resin particle dispersion liquid dispersed in an aqueous solvent may be prepared. Further, when a commercially available resin particle dispersion liquid is used, an operation such as dilution with an aqueous solvent may be performed depending on the purpose. Further, the resin particle dispersion liquid dispersed in the organic solvent may be replaced with an aqueous solvent as long as the dispersibility is not affected.

(Polyimide precursor forming step)
Next, in the resin particle dispersion, in the presence of an organic amine compound, the tetracarboxylic acid dianhydride and the diamine compound are polymerized to form a resin (polyimide precursor) to obtain a polyimide precursor solution.
According to this method, since an aqueous solvent is applied, the productivity is high, and the polyimide precursor solution is produced in one step, which is advantageous in terms of simplification of the process.

Specifically, the organic amine compound, the tetracarboxylic dianhydride, and the diamine compound are mixed with the resin particle dispersion prepared in the resin particle dispersion preparation step. Then, in the presence of the organic amine compound, the tetracarboxylic dianhydride and the diamine compound are polymerized to form a polyimide precursor in the resin particle dispersion. The order in which the organic amine compound, the tetracarboxylic dianhydride, and the diamine compound are mixed with the resin particle dispersion is not particularly limited.

When polymerizing the tetracarboxylic dianhydride and the diamine compound in the resin particle dispersion, the aqueous solvent in the resin particle dispersion may be used as it is to form a polyimide precursor. Further, if necessary, an aqueous solvent may be newly mixed. When the aqueous solvent is newly mixed, the aqueous solvent may be an aqueous solvent containing a small amount of an aproton-based polar solvent. In addition, other additives may be mixed depending on the purpose.

By the above steps, a resin particle-dispersed polyimide precursor solution is obtained.

Next, the materials constituting the resin particle-dispersed polyimide precursor solution will be described.

(Aqueous solvent)
As the aqueous solvent, when the tetracarboxylic dianhydride and the diamine compound are polymerized in the resin particle dispersion, the aqueous solvent in the resin particle dispersion used for producing the resin particle dispersion can be used as it is. Good. Further, when polymerizing the tetracarboxylic dianhydride and the diamine compound, an aqueous solvent may be prepared so as to be suitable for the polymerization.

The aqueous solvent is an aqueous solvent containing water. Specifically, the aqueous solvent is preferably a solvent containing 50% by mass or more of water with respect to the total aqueous solvent. Examples of water include distilled water, ion-exchanged water, ultra-filtered water, pure water, and the like.

The content of water is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, and further preferably 80% by mass or more and 100% by mass or less with respect to the total aqueous solvent.

The aqueous solvent used when producing the resin particle dispersion is an aqueous solvent containing water. Specifically, the aqueous solvent for the resin particle dispersion liquid is preferably an aqueous solvent containing 50% by mass or more of water with respect to the total aqueous solvent. Examples of water include distilled water, ion-exchanged water, ultra-filtered water, pure water, and the like. When a soluble organic solvent other than water is contained, for example, a water-soluble alcohol solvent may be used. In addition, water-soluble means that the target substance dissolves in water in an amount of 1% by mass or more at 25 ° C.

When the aqueous solvent contains a solvent other than water, examples of the solvent other than water include a water-soluble organic solvent and an aproton-based polar solvent. As the solvent other than water, a water-soluble organic solvent is preferable from the viewpoint of transparency, mechanical strength and the like of the polyimide molded product. In particular, the aqueous solvent does not contain an aproton polar solvent, or even if it contains a small amount, from the viewpoint of improving various properties of the polyimide molded body such as heat resistance, electrical properties, and solvent resistance in addition to transparency and mechanical strength. (For example, it is preferably 40% by mass or less, preferably 30% by mass or less with respect to the total aqueous solvent). Here, water-soluble means that the target substance dissolves in water in an amount of 1% by mass or more at 25 ° C.

The water-soluble organic solvent may be used alone or in combination of two or more.
The water-soluble organic solvent is preferably one in which the resin particles described below do not dissolve. The reason for this is that, for example, when an aqueous solvent containing water and a water-soluble organic solvent is used, the resin particles are dissolved in the process of film formation even if the resin particles are not dissolved in the resin particle dispersion liquid. This is because there is a concern that it will end up.

The water-soluble ether solvent is a water-soluble solvent having an ether bond in one molecule. Examples of the water-soluble ether solvent include tetrahydrofuran (THF), dioxane, trioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether and the like. Among these, tetrahydrofuran and dioxane are preferable as the water-soluble ether solvent.

The water-soluble ketone solvent is a water-soluble solvent having a ketone group in one molecule. Examples of the water-soluble ketone solvent include acetone, methyl ethyl ketone, cyclohexanone and the like. Among these, acetone is preferable as the water-soluble ketone solvent.

The water-soluble alcohol-based solvent is a water-soluble solvent having an alcoholic hydroxyl group in one molecule. Water-soluble alcohol solvents include, for example, methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, ethylene glycol monoalkyl ether, propylene glycol, propylene glycol monoalkyl ether, diethylene glycol, and diethylene glycol. Monoalkyl ether, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butene- Examples thereof include 1,4-diol, 2-methyl-2,4-pentanediol, glycerin, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol and the like. Among these, as the water-soluble alcohol solvent, methanol, ethanol, 2-propanol, ethylene glycol, ethylene glycol monoalkyl ether, propylene glycol, propylene glycol monoalkyl ether, diethylene glycol, and diethylene glycol monoalkyl ether are preferable.

When an aproton-based polar solvent other than water is contained as the aqueous solvent, the aproton-based polar solvent used in combination is a solvent having a boiling point of 150 ° C. or higher and 300 ° C. or lower and a dipole moment of 3.0D or higher and 5.0D or lower. is there. Specific examples of the aproton polar solvent include N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and the like. Hexamethylphosphoramide (HMPA), N-methylcaprolactam, N-acetyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone (DMI), N, N'-dimethylpropyleneurea, tetramethylurea, Examples thereof include trimethyl phosphate and triethyl phosphate.

When a solvent other than water is contained as the aqueous solvent, the solvent used in combination often has a boiling point of 270 ° C. or lower, preferably 60 ° C. or higher and 250 ° C. or lower, and more preferably 80 ° C. or higher and 230 ° C. or lower. is there. When the boiling point of the solvent used in combination is within the above range, it becomes difficult for a solvent other than water to remain in the polyimide molded product, and it becomes easy to obtain a polyimide molded product having high mechanical strength.

Here, the range in which the polyimide precursor is dissolved in the solvent is controlled by the content of water, the type and amount of the organic amine compound. In the range where the water content is low, the polyimide precursor is easily dissolved in the region where the content of the organic amine compound is low. On the contrary, in the range where the water content is high, the polyimide precursor is easily dissolved in the region where the content of the organic amine compound is high. Further, when the organic amine compound has high hydrophilicity such as having a hydroxyl group, the polyimide precursor is easily dissolved in the region where the water content is high.

(Resin particles)
The resin particles are composed of polyester resin particles, urethane resin particles, vinyl resin particles, (meth) acrylic resin particles, (meth) acrylic acid ester resin particles, styrene / (meth) acrylic resin particles, polystyrene resin particles, and polyethylene resin particles. It is at least one resin particle selected from the group.
Among these, the resin particles are preferably at least one selected from the group consisting of (meth) acrylic resin, (meth) acrylic acid ester resin, styrene / (meth) acrylic resin, and polystyrene resin.
Further, the resin particles may or may not be crosslinked. Non-crosslinked resin particles are preferable because they effectively contribute to the relaxation of residual stress in the imidization step of the polyimide precursor. Further, the resin particle dispersion is more preferably a vinyl resin particle dispersion obtained by emulsion polymerization in terms of simplifying the step of producing the resin particle-dispersed polyimide precursor solution.

In addition, in this embodiment, "(meth) acrylic" means that both "acrylic" and "methacryl" are included.

When the resin particles are vinyl resin particles, it is obtained by polymerizing a monomer. Examples of the vinyl resin monomer include the following monomers. For example, styrene, alkyl-substituted styrene (eg, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, etc.), halogen-substituted styrene. (For example, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, etc.), styrenes having a styrene skeleton such as vinylnaphthalene; methyl (meth) acrylate, ethyl (meth) acrylate, n (meth) acrylate. Esters having a vinyl group such as -propyl, n-butyl (meth) acrylate, lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, trimethylolpropane trimethacrylate (TMPTMA); acrylonitrile, methacrylonitrile Vinyl nitriles such as vinyl methyl ether, vinyl ethers such as vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone; (meth) acrylic acid, maleic acid, silicic acid, fumaric acid. , Acids such as vinyl styrene; bases such as ethyleneimine, vinylpyridine, vinylamine; and vinyl resin units obtained by polymerizing monomers such as.
Other monomers include monofunctional monomers such as vinyl acetate, bifunctional monomers such as ethylene glycol dimethacrylate, nonandiacrylate and decanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate and the like. Polyfunctional monomer of the above may be used in combination.
Further, the vinyl resin may be a resin using these monomers alone, or a resin which is a copolymer using two or more kinds of monomers.

As described above, it is preferable that the resin particles are not crosslinked, but when the resin particles are crosslinked, when a crosslinking agent is used as at least a part of the monomer component, the crosslinking agent occupies all the monomer components. The ratio is preferably 0% by mass or more and 20% by mass or less, more preferably 0% by mass or more and 5% by mass or less, and particularly preferably 0% by mass.

When the monomer used in the resin constituting the vinyl resin particles contains styrene, the ratio of styrene to all the monomer components is preferably 20% by mass or more and 100% by mass or less, and 40% by mass or more and 100% by mass or less. The following is more preferable.

(Average particle size of resin particles)
The average particle size of the resin particles is not particularly limited. For example, it is often 2.5 μm or less, preferably 2.0 μm or less, and more preferably 1.0 μm or less. The lower limit is not particularly limited, but is preferably 0.001 μm or more, preferably 0.005 μm or more, and more preferably 0.01 μm or more.
The average particle size of the resin particles is determined by using the particle size distribution obtained by the measurement of a laser diffraction type particle size distribution measuring device (for example, manufactured by Horiba Seisakusho, LA-700) with respect to the divided particle size range (channel). The cumulative distribution is subtracted from the small particle size side for the volume, and the particle size that is cumulatively 50% of all particles is measured as the volume average particle size D50v.

The resin particles may be commercially available products. Specifically, examples of the crosslinked resin particles include crosslinked polymethyl methacrylate (MBX-series, manufactured by Sekisui Kasei Kogyo Co., Ltd.), crosslinked polystyrene (SBX-series, manufactured by Sekisui Kasei Kogyo Co., Ltd.), and methacrylic acid. Examples thereof include copolymerized crosslinked resin particles of methyl and styrene (MSX-series, manufactured by Sekisui Kasei Kogyo Co., Ltd.).
Examples of non-crosslinked resin particles include polymethyl methacrylate (MB-series, manufactured by Sekisui Plastics Co., Ltd.), (meth) acrylic acid ester / styrene copolymer (FS-series: manufactured by Nippon Paint Co., Ltd.), etc. Can be mentioned.

(Polyimide precursor)
The polyimide precursor is obtained by polymerizing a tetracarboxylic dianhydride and a diamine compound. Specifically, it is a resin (polyamic acid) having a repeating unit represented by the general formula (I) of a polyimide precursor.

(In the general formula (I), A represents a tetravalent organic group and B represents a divalent organic group.)

Here, in the general formula (I), the tetravalent organic group represented by A is a residue obtained by removing four carboxyl groups from the raw material tetracarboxylic dianhydride.
On the other hand, the divalent organic group represented by B is the residue obtained by removing two amino groups from the diamine compound as a raw material.

That is, the polyimide precursor having a repeating unit represented by the general formula (I) is a polymer of a tetracarboxylic dianhydride and a diamine compound.

Examples of the tetracarboxylic dianhydride include both aromatic and aliphatic compounds, but aromatic compounds are preferable. That is, in the general formula (I), the tetravalent organic group represented by A is preferably an aromatic organic group.

Examples of the aromatic tetracarboxylic acid dianhydride include pyromellitic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyl. Sulfontetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 3,3', 4,4'- Biphenyl ether tetracarboxylic acid dianhydride, 3,3', 4,4'-dimethyldiphenylsilane tetracarboxylic acid dianhydride, 3,3', 4,4'-tetraphenylsilanetetracarboxylic acid dianhydride, 1 , 2,3,4-Frantetracarboxylic acid dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylsulfide dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) ) Diphenylsulfone dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 3,3', 4,4'-perfluoroisopropyridene diphthalic acid dianhydride, 3 , 3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3', 4'-biphenyltetracarboxylic acid dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene -Bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (triphenylphthalic acid) dianhydride, bis (triphenylphthalic acid) -4,4'-diphenyl ether dianhydride, bis (triphenylphthalic acid) Acid) -4,4'-diphenylmethane dianhydride and the like.

Examples of the aliphatic tetracarboxylic dianhydride include butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4. -Cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 3,5,6-tricarboxynorbonane -2-Acidylene dianhydride, 2,3,4,5-tetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic An aliphatic or alicyclic tetracarboxylic dianhydride such as an acid dianhydride, bicyclo [2,2,2] -oct-7-ene-2,3,5,6-tetracarboxylic dianhydride; 1 , 3,3a, 4,5,9b-hexahydro-2,5-dioxo-3-franyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a,4,5, 9b-Hexahydro-5-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a,4,5, 9b-Hexahydro-8-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione or other aliphatic tetracarboxylic acid having an aromatic ring Examples include dianhydride and the like.

Among these, as the tetracarboxylic dianhydride, an aromatic tetracarboxylic dianhydride is preferable, and specifically, for example, pyromellitic dianhydride, 3,3', 4,4'-biphenyl. Tetetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-biphenyl ether tetracarboxylic dianhydride, 3,3', 4 , 4'-benzophenonetetracarboxylic dianhydride is preferable, and further, pyromellitic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4' -Benzophenonetetracarboxylic dianhydride is preferable, and 3,3', 4,4'-biphenyltetracarboxylic dianhydride is particularly preferable.

The tetracarboxylic dianhydride may be used alone or in combination of two or more.
In addition, when two or more kinds are used in combination, even if aromatic tetracarboxylic dianhydride or aliphatic tetracarboxylic acid is used in combination, aromatic tetracarboxylic dianhydride and aliphatic tetracarboxylic dianhydride are used in combination. It may be combined with an object.

On the other hand, the diamine compound is a diamine compound having two amino groups in its molecular structure. Examples of the diamine compound include both aromatic and aliphatic compounds, but aromatic compounds are preferable. That is, in the general formula (I), the divalent organic group represented by B is preferably an aromatic organic group.

Examples of the diamine compound include p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, and 4,4'-diaminodiphenyl sulfide. , 4,4'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, 3,3-dimethyl-4,4'-diaminobiphenyl, 5-amino-1- (4'-aminophenyl) -1,3,3 -Trimethylindan, 6-amino-1- (4'-aminophenyl) -1,3,3-trimethylindan, 4,4'-diaminobenzanilide, 3,5-diamino-3'-trifluoromethylbenzanilide , 3,5-Diamino-4'-trifluoromethylbenzanilide, 3,4'-diaminodiphenyl ether, 2,7-diaminofluorene, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4' -Methylene-bis (2-chloroaniline), 2,2', 5,5'-tetrachloro-4,4'-diaminobiphenyl, 2,2'-dichloro-4,4'-diamino-5,5' -Dimethoxybiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, 2,2-bis [4- (4- (4- (4- (4- (4-) 4-) Aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-amino) Phenoxy) -biphenyl, 1,3'-bis (4-aminophenoxy) benzene, 9,9-bis (4-aminophenyl) fluorene, 4,4'-(p-phenylene isopropylidene) bisaniline, 4,4' -(M-Phenylisopropyridene) bisaniline, 2,2'-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane, 4,4'-bis [4- (4-amino) -2-Trifluoromethyl) phenoxy] -aromatic diamines such as octafluorobiphenyl; aromatics having two amino groups bonded to an aromatic ring such as diaminotetraphenylthiophene and heteroatoms other than the nitrogen atom of the amino group. Group diamines; 1,1-methaxylylene diamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, no. Namethylenediamine, 4,4-diaminoheptamethylenediamine, 1,4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadiene diamine, hexahydro-4,7-methanoin danirangemethylenediamine, tricyclo [6, 2,1,0 ^2.7 ] -Undecylenedimethyldiamine, aliphatic diamines such as 4,4'-methylenebis (cyclohexylamine), alicyclic diamines and the like can be mentioned.

Among these, the diamine compound is preferably an aromatic diamine compound, and specifically, for example, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, and the like. 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenyl sulfone are preferable, and 4,4'-diaminodiphenyl ether and p-phenylenediamine are particularly preferable.

The diamine compound may be used alone or in combination of two or more. When two or more kinds are used in combination, an aromatic diamine compound or an aliphatic diamine compound may be used in combination, or an aromatic diamine compound and an aliphatic diamine compound may be combined.

The number average molecular weight of the polyimide precursor is preferably 1000 or more and 150,000 or less, more preferably 5000 or more and 130,000 or less, and further preferably 10,000 or more and 100,000 or less.
When the number average molecular weight of the polyimide precursor is within the above range, the decrease in the solubility of the polyimide precursor in the solvent is suppressed, and the film-forming property is easily ensured.

The number average molecular weight of the polyimide precursor is measured by a gel permeation chromatography (GPC) method under the following measurement conditions.
-Column: Tosoh TSKgelα-M (7.8 mm ID x 30 cm)
-Eluent: DMF (dimethylformamide) / 30 mM LiBr / 60 mM phosphoric acid-Flow velocity: 0.6 mL / min
・ Injection amount: 60 μL
・ Detector: RI (Differential Refractometer)

The content (concentration) of the polyimide precursor is preferably 0.1% by mass or more and 40% by mass or less, preferably 0.5% by mass or more and 25% by mass or less, based on the total polyimide precursor solution. It is preferably 1% by mass or more and 20% by mass or less.

(Organic amine compound)
The organic amine compound is a compound that amine-chlorides a polyimide precursor (its carboxyl group) to increase its solubility in an aqueous solvent and also functions as an imidization accelerator. Specifically, the organic amine compound is preferably an amine compound having a molecular weight of 170 or less. The organic amine compound is preferably a compound excluding the diamine compound which is a raw material of the polyimide precursor.
The organic amine compound is preferably a water-soluble compound. Water-soluble means that the target substance dissolves in water in an amount of 1% by mass or more at 25 ° C.

Examples of the organic amine compound include a primary amine compound, a secondary amine compound, and a tertiary amine compound.
Among these, as the organic amine compound, at least one selected from a secondary amine compound and a tertiary amine compound (particularly, a tertiary amine compound) is preferable. When a tertiary amine compound or a secondary amine compound is applied as the organic amine compound (particularly, the tertiary amine compound), the solubility of the polyimide precursor in the solvent is likely to be increased, the film-forming property is easily improved, and the film-forming property is easily improved. The storage stability of the polyimide precursor solution is likely to be improved.

Moreover, as an organic amine compound, in addition to a monovalent amine compound, a divalent or higher polyvalent amine compound can also be mentioned. When a polyvalent amine compound having a divalent value or higher is applied, a pseudo-crosslinked structure is easily formed between the molecules of the polyimide precursor, and the storage stability of the polyimide precursor solution is easily improved.

Examples of the primary amine compound include methylamine, ethylamine, n-propylamine, isopropylamine, 2-ethanolamine, 2-amino-2-methyl-1-propanol and the like.
Examples of the secondary amine compound include dimethylamine, 2- (methylamino) ethanol, 2- (ethylamino) ethanol, morpholine and the like.
Examples of the tertiary amine compound include 2-dimethylaminoethanol, 2-diethylaminoethanol, 2-dimethylaminopropanol, pyridine, triethylamine, picoline, methylmorpholine, ethylmorpholine, 1,2-dimethylimidazole, and 2-ethyl-4. -Methylimidazole and the like.

Here, as the organic amine compound, an amine compound having a heterocyclic structure containing nitrogen (particularly, a tertiary amine compound) is also preferable from the viewpoint of film forming property. Examples of the amine compound having a heterocyclic structure containing nitrogen (hereinafter referred to as "nitrogen-containing heterocyclic amine compound") include isoquinolins (amine compounds having an isoquinolin skeleton) and pyridines (amine compounds having a pyridine skeleton). ), Pyrimidines (amine compounds with pyrimidine skeleton), pyrazines (amine compounds with pyrazine skeleton), piperazins (amine compounds with piperazin skeleton), triazines (amine compounds with triazine skeleton), imidazoles (imidazole) Examples thereof include amine compounds having a skeleton), morpholins (amine compounds having a morpholin skeleton), polyaniline, polypyridine, and polyamine.

The nitrogen-containing heterocyclic amine compound is preferably at least one selected from the group consisting of morpholines, pyridines, and imidazoles from the viewpoint of film-forming property, and is more than N-methylmorpholine, pyridine, and picoline. More preferably, it is at least one selected from the group.

Among these, the organic amine compound is preferably a compound having a boiling point of 60 ° C. or higher (preferably 60 ° C. or higher and 200 ° C. or lower, more preferably 70 ° C. or higher and 150 ° C. or lower). When the boiling point of the organic amine compound is 60 ° C. or higher, the organic amine compound is suppressed from volatilizing from the polyimide precursor solution during storage, and the decrease in solubility of the polyimide precursor in the solvent is easily suppressed.

The organic amine compound is preferably contained in an amount of 50 mol% or more and 500 mol% or less, preferably 80 mol% or more and 250 mol% or less, based on the carboxyl group (-COOH) of the polyimide precursor in the polyimide precursor solution. , More preferably, it is contained in an amount of 90 mol% or more and 200 mol% or less.
When the content of the organic amine compound is within the above range, the solubility of the polyimide precursor in the solvent tends to increase, and the film-forming property tends to improve. In addition, the storage stability of the polyimide precursor solution is likely to be improved.

The above-mentioned organic amine compounds may be used alone or in combination of two or more.

(Ratio of resin particles and polyimide precursor)
In the resin particle polyimide precursor solution, the ratio of the resin particles to the polyimide precursor is the mass ratio when the solid content of the polyimide precursor solution is 100, and the solid content of the polyimide precursor solution: resin particles = 100: 20. The range is preferably 100: 600 or less. The range is preferably 100: 25 or more and 100: 550 or less, and more preferably 100: 30 or more and 100: 500 or less.

(Other additives)
In the method for producing the resin particle-dispersed polyimide precursor solution of the present embodiment according to the present embodiment, the polyimide precursor solution contains a catalyst for promoting the imidization reaction, a leveling material for improving the film forming quality, and the like. It may be.
As the catalyst for promoting the imidization reaction, a dehydrating agent such as an acid anhydride, an acid catalyst such as a phenol derivative, a sulfonic acid derivative, or a benzoic acid derivative may be used.

Further, the polyimide precursor solution, depending on the intended use, for example, conductive materials added to imparting conductivity (conductivity (e.g., a volume resistivity of less than 10 ⁷ Ω · cm) or semiconducting (e.g. the following volume resistivity of 10 ⁷ Ω · cm or more ^{10 13 Ω} · cm)) may contain.
Examples of the conductive agent include carbon black (for example, acidic carbon black having a pH of 5.0 or less); metal (for example, aluminum, nickel, etc.); metal oxide (for example, yttrium oxide, tin oxide, etc.); ionic conductive substance (for example, titanium). Potassium acid acid, LiCl, etc.); etc. These conductive materials may be used alone or in combination of two or more.

Further, the polyimide precursor solution may contain inorganic particles added for improving mechanical strength depending on the purpose of use. Examples of the inorganic particles include particulate materials such as silica powder, alumina powder, barium sulfate powder, titanium oxide powder, mica, and talc.

<Polyimide film containing resin particles>
The resin particle-containing polyimide film according to the present embodiment can be obtained by applying the resin particle-dispersed polyimide precursor solution according to the present embodiment to form a coating film, and then heating the coating film.
The resin particle-containing polyimide film includes not only the resin particle-containing polyimide film that has been imidized, but also the resin particle-containing polyimide film that has been partially imidized before the imidization is completed.

Specifically, the resin particle-containing polyimide film according to the present embodiment is, for example, a step of applying a resin particle-dispersed polyimide precursor solution according to the present embodiment to form a coating film (hereinafter referred to as a “coating film forming step”). ), And a step of heating the coating film to form a polyimide film (hereinafter referred to as "heating step").

(Coating film forming process)
First, the above-mentioned resin particle-dispersed polyimide precursor solution is prepared. Next, a resin particle-dispersed polyimide precursor solution is applied onto the substrate to form a coating film.
Examples of the substrate include a resin substrate; a glass substrate; a ceramic substrate; a metal substrate; and a composite material substrate in which these materials are combined. The substrate may include a peeling layer that has been peeled.
The method of applying the resin particle-dispersed polyimide precursor solution to the substrate is not particularly limited, and examples thereof include a spray coating method, a rotary coating method, a roll coating method, a bar coating method, a slit die coating method, and an inkjet coating method. Various methods can be mentioned.

As the substrate, various substrates can be used depending on the intended use. Examples thereof include various substrates applied to liquid crystal elements; semiconductor substrates on which integrated circuits are formed, wiring boards on which wiring is formed, printed circuit boards on which electronic components and wiring are provided; substrates for wire coating materials; and the like. ..

(Heating process)
Next, the coating film obtained in the above coating film forming step is subjected to a drying treatment. By this drying treatment, a film (a dry film before imidization) is formed.
The heating conditions for the drying treatment are, for example, preferably 10 minutes or more and 60 minutes or less at a temperature of 80 ° C. or higher and 200 ° C. or lower, and the higher the temperature, the shorter the heating time. It is also effective to apply hot air during heating. At the time of heating, the temperature may be raised stepwise or the speed may be raised without changing the speed.

Next, the dried film before imidization is heated to perform imidization treatment. As a result, the polyimide resin layer is formed.
As the heating conditions for the imidization treatment, for example, by heating at 150 ° C. or higher and 400 ° C. or lower (preferably 200 ° C. or higher and 300 ° C. or lower) for 20 minutes or longer and 60 minutes or lower, an imidization reaction occurs and a polyimide film is formed. To. During the heating reaction, the temperature may be gradually increased gradually or at a constant rate before the final temperature of heating is reached.

Through the above steps, a resin particle-containing polyimide film is formed. Then, if necessary, the resin particle-containing polyimide film is taken out from the substrate to obtain the resin particle-containing polyimide film. Further, the resin particle-containing polyimide film may be post-processed depending on the intended use.

<Manufacturing method of porous polyimide film>
In the method for producing a porous polyimide film according to the present embodiment, the resin particle-dispersed polyimide precursor solution according to the present embodiment is applied to form a coating film, and then the coating film is dried to form the polyimide precursor and the polyimide precursor. A first step of forming a film containing the resin particles and a second step of heating the film to imidize the polyimide precursor to form a polyimide film, wherein the resin particles are removed. It has a second step including.

Hereinafter, a method for producing the porous polyimide film according to the present embodiment will be described.
In the description of the manufacturing method, the same components are designated by the same reference numerals in FIG. 1 to be referred to. In the reference numerals in FIG. 1, 1 is a resin particle, 3 is a substrate, 4 is a release layer, 5 is a polyimide precursor solution, 7 is a pore, and 61 is a film (polyimide film) in the process of imidizing the polyimide precursor. , And 62 represent a porous polyimide film.

Hereinafter, the manufacturing method shown in FIG. 1 (an example of the manufacturing method according to the present embodiment) will be described, but the present invention is not limited thereto.

(First step)
In the first step, first, the above-mentioned resin particle-dispersed polyimide precursor solution is prepared. Next, a resin particle-dispersed polyimide precursor solution is applied onto the substrate to form a coating film containing the polyimide precursor solution and the resin particles. Then, the coating film formed on the substrate is dried to form a film containing the polyimide precursor and the resin particles.

Among the first steps, as a method for forming a coating film containing a polyimide precursor solution and resin particles on a substrate, for example, the following method can be mentioned, but the method is not limited to this method.

Specifically, first, resin particle dispersion in which resin particles are dispersed in an aqueous solvent is prepared. Then, an organic amine compound, a tetracarboxylic dianhydride, and a diamine compound are mixed in this resin particle dispersion, and the tetracarboxylic dianhydride and the diamine compound are polymerized to form a polyimide precursor. Prepare the body solution. Next, this resin particle-dispersed polyimide precursor solution is applied onto the substrate to form a coating film containing the polyimide precursor solution and the resin particles. The resin particles in the coating film are distributed in a state where aggregation is suppressed (see FIG. 1 (A)).

The substrate on which the resin particle-dispersed polyimide precursor is applied is not particularly limited. Examples thereof include resin substrates such as polystyrene and polyethylene terephthalate; glass substrates; ceramic substrates; metal substrates such as iron and stainless steel (SUS); composite material substrates in which these materials are combined. Further, if necessary, the substrate may be provided with a release layer by performing a release treatment with, for example, a silicone-based or fluorine-based release agent.

The method of applying the resin particle-dispersed polyimide precursor solution on the substrate is not particularly limited. For example, various methods such as a spray coating method, a rotary coating method, a roll coating method, a bar coating method, a slit die coating method, and an inkjet coating method can be mentioned.

The amount of the polyimide precursor solution applied to obtain the polyimide precursor solution and the coating film containing the resin particles is the amount of the resin particles exposed from the surface of the coating film in that the pore size of the porous polyimide film is increased. It should be. For example, it is preferable to form a thickness in which the resin particles are exposed from the surface of the coating film (for example, a coating film in which the thickness of the coating film is thinner than the particle size of the resin particles).

After forming a coating film containing the polyimide precursor solution and the resin particles, it is dried to form a film containing the polyimide precursor and the resin particles. Specifically, a coating film containing a polyimide precursor solution and resin particles is dried by a method such as heat drying, natural drying, or vacuum drying to form a film. More specifically, the coating film is formed by drying the coating film so that the solvent remaining in the coating film is 50% or less, preferably 30% or less with respect to the solid content of the coating film. This film is in a state where the polyimide precursor can be dissolved in water.

Further, the coating film may be formed in an amount in which the resin particles are embedded in the coating film. In this case, a process for exposing the resin particles may be performed in the second step described later. The treatment of exposing the resin particles increases the aperture ratio of the porous polyimide film.

(Second step)
The second step is a step of heating the film containing the polyimide precursor and the resin particles obtained in the first step to imidize the polyimide precursor to form a polyimide film. The second step includes a process of removing the resin particles. A porous polyimide film is obtained through a treatment for removing resin particles.

In the second step, in the step of forming the polyimide film, specifically, the film containing the polyimide precursor and the resin particles obtained in the first step is heated to proceed with imidization, and further heated. , A polyimide film is formed. As the imidization progresses and the imidization rate increases, it becomes difficult to dissolve in an organic solvent.

Then, in the second step, a process for removing the resin particles is performed. The resin particles may be removed in the process of heating the coating film to imidize the polyimide precursor, or may be removed from the polyimide film after the imidization is completed (after imidization).
In the present embodiment, the process of imidizing the polyimide precursor is to heat the film containing the polyimide precursor and the resin particles obtained in the first step to proceed with the imidization, and the imidization is completed. The process of becoming a state before becoming a polyimide film after being formed is shown.

The treatment for removing the resin particles may be performed when the imidization rate of the polyimide precursor in the polyimide film is 10% or more in the process of imidizing the polyimide precursor in terms of the removability of the resin particles and the like. preferable. When the imidization ratio is 10% or more, it tends to be difficult to dissolve in an organic solvent and the morphology is easily maintained.

Examples of the treatment for removing the resin particles include a method of removing the resin particles by heating, a method of removing the resin particles with an organic solvent that dissolves the resin particles, a method of removing the resin particles by decomposition with a laser or the like, and the like. Of these, a method of removing the resin particles by heating and a method of removing the resin particles with an organic solvent that dissolves the resin particles are preferable.

As a method of removing by heating, for example, in the process of imidizing the polyimide precursor, the resin particles may be removed by decomposing the resin particles by heating for advancing the imidization. In this case, there is no operation of removing the resin particles with a solvent, which is advantageous for reducing the number of steps. On the other hand, depending on the type of resin particles, decomposition gas may be generated by heating. Then, due to this decomposition gas, the porous polyimide film may be broken or cracked. Therefore, in this case, it is desirable to adopt a method of removing the resin particles with an organic solvent that dissolves them.

Examples of the method of removing the resin particles with an organic solvent that dissolves the resin particles include a method of contacting (for example, immersing in a solvent) the organic solvent in which the resin particles are dissolved to dissolve and remove the resin particles. Immersion in a solvent in this state is preferable in that the dissolution efficiency of the resin particles is increased.

The organic solvent that dissolves the resin particles for removing the resin particles is particularly limited as long as it does not dissolve the polyimide film and the polyimide film that has been imidized and the resin particles are soluble. is not it. For example, ethers such as tetrahydrofuran; aromatics such as toluene; ketones such as acetone; esters such as ethyl acetate; can be mentioned.

In the second step, the heating method for heating the film obtained in the first step to promote imidization to obtain a polyimide film is not particularly limited. For example, a method of heating in two steps can be mentioned. When heating in two stages, specific heating conditions include the following.

The heating condition of the first stage is preferably a temperature at which the shape of the resin particles is maintained. Specifically, for example, the range of 50 ° C. or higher and 150 ° C. or lower is preferable, and the range of 60 ° C. or higher and 140 ° C. or lower is preferable. The heating time is preferably in the range of 10 minutes or more and 60 minutes or less. The higher the heating temperature, the shorter the heating time may be.

Examples of the heating conditions in the second stage include heating at 150 ° C. or higher and 400 ° C. or lower (preferably 200 ° C. or higher and 390 ° C. or lower) for 20 minutes or longer and 120 minutes or lower. By setting the heating conditions in this range, the imidization reaction can proceed further and a polyimide film can be formed. During the heating reaction, the temperature may be gradually increased gradually or at a constant rate before the final temperature of heating is reached.

The heating conditions are not limited to the above two-step heating method, and for example, a one-step heating method may be adopted. In the case of the one-step heating method, for example, the imidization may be completed only by the heating conditions shown in the second step above.

In the second step, from the viewpoint of increasing the aperture ratio, it is preferable to perform a treatment for exposing the resin particles so that the resin particles are exposed. In the second step, the treatment for exposing the resin particles is preferably performed in the process of imidizing the polyimide precursor, or after the imidization and before the treatment of removing the resin particles.

In this case, for example, when a film is formed on the substrate using the resin particle-dispersed polyimide precursor solution, the resin particle-dispersed polyimide precursor solution is applied onto the substrate to form a coating film in which the resin particles are embedded (FIG. 1 (A)). Next, the coating film is dried to form a film containing the polyimide precursor and the resin particles. The film formed by this method is in a state in which resin particles are buried. Before the film is heated to remove the resin particles, the resin particles are exposed from the polyimide film in the process of imidizing the polyimide precursor or after the imidization is completed (after imidization). Treatment may be applied.

In the second step, the treatment for exposing the resin particles may be performed, for example, when the polyimide film is in the following state.
When the process of exposing the resin particles is performed when the imidization rate of the polyimide precursor in the polyimide film is less than 10% (that is, the polyimide film can be dissolved in water), it is buried in the above-mentioned polyimide film. Examples of the treatment for exposing the resin particles include a treatment of wiping and a treatment of immersing the resin particles in water.

Further, when the imidization rate of the polyimide precursor in the polyimide film is 10% or more (that is, in a state where it is difficult to dissolve in an organic solvent), and when the polyimide film is in a state where imidization is completed, the resin particles. Examples of the process of exposing the resin particles include a method of mechanically cutting with a tool such as a paper scraper to expose the resin particles, and a method of decomposing the resin particles with a laser or the like to expose the resin particles.
For example, in the case of mechanical cutting, a part of the resin particles existing in the upper region of the resin particles embedded in the polyimide film (that is, the region on the side of the resin particles away from the substrate) is the resin particles. It is cut together with the polyimide film existing on the upper part, and the cut resin particles are exposed from the surface of the polyimide film (see FIG. 1 (B)).

Then, the resin particles are removed from the polyimide film on which the resin particles are exposed by the above-mentioned removal treatment of the resin particles. Then, a porous polyimide film from which the resin particles have been removed can be obtained (see FIG. 1 (C)).

In the above, the manufacturing process of the porous polyimide film subjected to the treatment for exposing the resin particles in the second step has been described, but the resin particles are exposed in the first step in terms of increasing the aperture ratio. Treatment may be applied. In this case, in the first step, the resin particles may be exposed by performing a treatment for exposing the resin particles in the process of forming the coating film by drying after obtaining the coating film. By performing the treatment of exposing the resin particles, the aperture ratio of the porous polyimide film is increased.

For example, in the process of obtaining a coating film containing a polyimide precursor solution and resin particles and then drying the coating film to form a film containing the polyimide precursor and resin particles, as described above, the film film is a polyimide precursor. The body is in a state where it can be dissolved in water. When the coating film is in this state, the resin particles can be exposed by, for example, a treatment of wiping or a treatment of immersing the film in water. Specifically, the polyimide precursor solution existing in the region equal to or larger than the thickness of the resin particle layer is present in the region equal to or larger than the thickness of the resin particle layer by performing a treatment for exposing the resin particle layer by, for example, wiping with water. The polyimide precursor solution that had been used is removed. Then, the resin particles existing in the upper region of the resin particle layer (that is, the region on the side of the resin particle layer away from the substrate) are exposed from the surface of the coating film.

In the second step, the substrate for forming the above-mentioned film used in the first step may be peeled off when it becomes a dry film, and the polyimide precursor in the polyimide film is organic. It may be peeled off when it becomes difficult to dissolve in a solvent, or it may be peeled off when it becomes a film in which imidization is completed.

Through the above steps, a porous polyimide film can be obtained. Then, the porous polyimide film may be post-processed depending on the purpose of use.

Here, the imidization ratio of the polyimide precursor will be described.
The partially imidized polyimide precursor has, for example, a structure having a repeating unit represented by the following general formula (I-1), the following general formula (I-2), and the following general formula (I-3). Precursors can be mentioned.

In the general formula (I-1), the general formula (I-2), and the general formula (I-3), A represents a tetravalent organic group and B represents a divalent organic group. l represents an integer of 1 or more, and m and n independently represent an integer of 0 or 1 or more, respectively.

In addition, A and B are synonymous with A and B in the above-mentioned general formula (I).

The imidization rate of the polyimide precursor is the total number of imide-closed bonding portions (2n + m) (2l + 2m + 2n) at the bonding portion of the polyimide precursor (reaction portion between the tetracarboxylic dianhydride and the diamine compound). ) To the ratio. That is, the imidization rate of the polyimide precursor is indicated by "(2n + m) / (2l + 2m + 2n)".

The imidization rate of the polyimide precursor (value of "(2n + m) / (2l + 2m + 2n)") is measured by the following method.

-Measurement of imidization rate of polyimide precursor-
-Preparation of polyimide precursor sample (i) The polyimide precursor composition to be measured is applied onto a silicon wafer in a film thickness range of 1 μm or more and 10 μm or less to prepare a coating film sample.
(Ii) The coating film sample is immersed in tetrahydrofuran (THF) for 20 minutes to replace the solvent in the coating film sample with tetrahydrofuran (THF). The solvent to be immersed is not limited to THF, and can be selected from a solvent that does not dissolve the polyimide precursor and can be miscible with the solvent component contained in the polyimide precursor composition. Specifically, alcohol solvents such as methanol and ethanol, and ether compounds such as dioxane can be used.
The (iii) coating samples, taken out from in THF, blowing _{N 2} gas into THF adhering to the coating surface of the sample, removed. A polyimide precursor sample is prepared by treating the coating film sample for 12 hours or more in a range of 5 ° C. or higher and 25 ° C. or lower under a reduced pressure of 10 mmHg or less to dry the coating film sample.

-Preparation of 100% imidized standard sample (iv) In the same manner as in (i) above, the polyimide precursor composition to be measured is applied onto a silicon wafer to prepare a coating film sample.
(V) The coating film sample is heated at 380 ° C. for 60 minutes to carry out an imidization reaction to prepare a 100% imidized standard sample.

-Measurement and analysis (vi) Infrared absorption spectra of 100% imidized standard sample and polyimide precursor sample are measured using a Fourier transform infrared spectrophotometer (FT-730 manufactured by Horiba Seisakusho). Aromatic ring-derived absorption peak near 1500 cm ^-1 and 100% imidization standard sample (Ab ratio 'for (1500cm ^-1)), absorption peaks derived from an imide bond in the vicinity of ^{1780cm -1 (Ab' (1780cm -1} )) Find I'(100).
(Vii) In the same manner, was measured on the polyimide precursor sample, relative to the aromatic ring derived absorption peak near ^{1500cm -1 (Ab (1500cm -1)} ), absorption peaks derived from imide bond near 1780 cm ^-1 (Ab ( The ratio I (x) of 1780 cm ^{-1)) is obtained.}

Then, using the measured absorption peaks I'(100) and I (x), the imidization rate of the polyimide precursor is calculated based on the following formula.
Formula: Imidization rate of polyimide precursor = I (x) / I'(100)
-Formula: I'(100) = (Ab'(1780 cm ^-1 )) / (Ab'(1500 cm ^-1 ))
-Formula: I (x) = (Ab (1780 cm ^-1 )) / (Ab (1500 cm ^-1 ))

The measurement of the imidization rate of the polyimide precursor is applied to the measurement of the imidization rate of the aromatic polyimide precursor. When measuring the imidization rate of the aliphatic polyimide precursor, a peak derived from a structure that does not change before and after the imidization reaction is used as an internal standard peak instead of the absorption peak of the aromatic ring.

<Porous polyimide film>
Hereinafter, the porous polyimide film of the present embodiment will be described.

The porous polyimide film obtained by the method for producing a porous polyimide film according to the present embodiment suppresses the occurrence of cracks.

(Characteristics of porous polyimide film)
The porous polyimide film of the present invention is not particularly limited, but has a porosity of 30% or more. Further, the porosity is preferably 40% or more, and more preferably 50% or more. The upper limit of the porosity is not particularly limited, but is preferably in the range of 90% or less.

The shape of the pores is preferably spherical or close to spherical. Further, the vacancies preferably have a shape in which the vacancies are connected to each other and connected to each other (see FIGS. 1 (D), 2 (D), and 3 (C)). The pore diameter of the portion where the pores are connected to each other is often, for example, 1/100 or more and 1/2 or less of the maximum diameter of the pores, and preferably 1/50 or more and 1/3 or less. , 1/20 or more and 1/4 or less is more preferable. Specifically, the average value of the pore diameters of the portions where the pores are connected to each other and connected to each other is preferably 5 nm or more and 1500 nm or less.

The average value of the pore diameter is not particularly limited, but is preferably in the range of 0.01 μm or more and 2.5 μm or less, more preferably in the range of 0.05 μm or more and 2.0 μm or less, and 0.1 μm or more and 1.5 μm. The range is preferably as follows, and more preferably 0.15 μm or more and 1.0 μm or less.

In the porous polyimide film of the present embodiment, the ratio of the maximum diameter to the minimum diameter of the pores (the ratio of the maximum value to the minimum value of the pore diameter) is 1 or more and 2 or less. It is preferably 1 or more and 1.9 or less, and more preferably 1 or more and 1.8 or less. Within this range, it is more preferable that it is close to 1. Within this range, variation in pore diameter is suppressed. Further, when the porous polyimide film of the present embodiment is applied to, for example, a battery separator of a lithium ion battery, it is possible to suppress the occurrence of turbulence in the ion flow, so that the formation of lithium dendrite is likely to be suppressed. The "ratio of the maximum diameter and the minimum diameter of the pores" is a ratio represented by a value obtained by dividing the maximum diameter of the holes by the minimum diameter (that is, the maximum value / the minimum value of the pore diameter).

The average value of the pore diameters and the average value of the pore diameters of the portions where the pores are connected to each other are values observed and measured by a scanning electron microscope (SEM). Specifically, first, a porous polyimide film is cut out and a sample for measurement is prepared. Then, this measurement sample is observed and measured by the VE SEM manufactured by KEYENCE Co., Ltd. with the image processing software provided as standard equipment. Observation and measurement are performed on 100 pieces of each of the pores in the cross section of the sample for measurement, and the average value, the minimum diameter, the maximum diameter, and the arithmetic mean diameter of each are obtained. If the shape of the hole is not circular, the longest part is the diameter.

The film thickness of the porous polyimide film is not particularly limited, but is preferably 15 μm or more and 500 μm or less.

(Use of porous polyimide film)
Applications to which the porous polyimide film according to the present embodiment is applied include, for example, a battery separator such as a lithium battery; a separator for an electrolytic capacitor; an electrolyte film such as a fuel cell; a battery electrode material; a gas or liquid separation film; Low dielectric constant materials; etc.

When the porous polyimide film according to the present embodiment is applied to a battery separator, for example, it is considered that the formation of lithium dendrite is suppressed by the action of suppressing the variation in the ion flow distribution of lithium ions. .. It is presumed that this is because the shape of the pores and the variation in the pore diameter of the porous polyimide film of the present embodiment are suppressed.
Further, for example, when applied to a battery electrode material, it is considered that the capacity of the battery increases because the chance of contact with the electrolytic solution increases. It is presumed that this is because the amount of the material such as carbon black for the electrode contained in the porous polyimide film exposed on the surface of the pore size of the porous polyimide film and the surface of the film increases.
Further, for example, it is also possible to fill the pores of the porous polyimide film with, for example, an ionic gel obtained by gelling a so-called ionic liquid and apply it as an electrolyte membrane. Since the process is simplified by the production method of the present embodiment, it is considered that a lower cost electrolyte membrane can be obtained.

Examples will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are all based on mass.

[Preparation of resin particle dispersion]
-Preparation of resin particle dispersion liquid (1)-
770 parts by mass of styrene, 230 parts by mass of butyl acrylate, 15.7 parts by mass of dodecanethiol, 19.8 parts by mass of surfactant Doufax2A1 (47% solution, manufactured by Dow Chemical), and 576 parts by mass of ion-exchanged water are mixed. , Stirred and emulsified at 1,500 rpm for 30 minutes with a dissolver to prepare a monomeric emulsion. Subsequently, 1.49 parts by mass of Dowfax2A1 (47% solution, manufactured by Dow Chemical Co., Ltd.) and 1270 parts by mass of ion-exchanged water were charged into the reaction vessel. After heating to 75 ° C. under a nitrogen stream, 75 parts by mass of the monomer emulsion was added, and then a polymerization initiator solution in which 15 parts by mass of ammonium persulfate was dissolved in 98 parts by mass of ion-exchanged water was added dropwise over 10 minutes. did. After the reaction was carried out for 50 minutes after the dropping, the remaining monomer emulsion was added dropwise over 220 minutes, and the reaction was further carried out for 180 minutes. A resin particle dispersion (1) was obtained as a styrene / acrylic resin particle dispersion whose solid content concentration was adjusted to 30% by mass after cooling. The average particle size of these resin particles was 0.18 μm.

-Preparation of resin particle dispersion liquid (2)-
An aqueous dispersion of a non-crosslinked styrene / acrylic copolymer having an average particle size of 0.1 μm (FS-102E: manufactured by Nippon Paint Co., Ltd., solid content concentration: 21% by mass) was used as the resin particle dispersion (2).

-Preparation of resin particle dispersion liquid (3)-
Mix 1000 parts by mass of styrene, 15.7 parts by mass of dodecanethiol, 15.8 parts by mass of surfactant Dowfax2A1 (47% solution, manufactured by Dow Chemical Co., Ltd.), and 576 parts by mass of ion-exchanged water, and use a dissolver to add 1,500 parts. The mixture was stirred and emulsified for 30 minutes by rotation to prepare a monomer emulsified solution. Subsequently, 1.49 parts by mass of Dowfax2A1 (47% solution, manufactured by Dow Chemical Co., Ltd.) and 1270 parts by mass of ion-exchanged water were charged into the reaction vessel. After heating to 75 ° C. under a nitrogen stream, 75 parts by mass of the monomer emulsion was added, and then a polymerization initiator solution in which 15 parts by mass of ammonium persulfate was dissolved in 98 parts by mass of ion-exchanged water was added dropwise over 10 minutes. did. After the reaction was carried out for 50 minutes after the dropping, the remaining monomer emulsion was added dropwise over 220 minutes, and the reaction was further carried out for 180 minutes. A resin particle dispersion (3) was obtained as a polystyrene resin particle dispersion whose solid content concentration was adjusted to 30% by mass after cooling. The average particle size of these resin particles was 0.21 μm.

-Preparation of resin particle dispersion liquid (4)-
A resin particle dispersion (4) was obtained as a polymethylmethacrylate resin particle dispersion in the same manner as in the resin particle dispersion (3) except that methyl methacrylate was used instead of styrene. The average particle size of these resin particles was 0.23 μm.

<Example 1>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-1)]
Resin particle dispersion liquid (1): Ion-exchanged water: 350 g was added to 100 g in terms of solid content. Add p-phenylenediamine (molecular weight 108.14): 27.28 g (252.27 mmol) and methylmorpholine (organic amine compound): 50.00 g (494.32 mmol) and stir at 20 ° C. for 10 minutes. And dispersed. Further, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22): 72.72 g (247.16 mmol) was added to this solution, and the reaction temperature was maintained at 40 ° C. , Stirred for 24 hours to dissolve and react to obtain a resin particle-dispersed polyimide precursor solution (PAA-1). (Resin particles / polyimide precursor = 100/100 (mass ratio), polyimide precursor concentration: 12% by mass)

<Example 2>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-2)]
A resin particle-dispersed polyimide precursor solution (PAA-2) was obtained in the same manner as in Example 1 except that the resin particle dispersion (1) was changed to the resin particle dispersion (2). (Resin particles / polyimide precursor = 100/100 (mass ratio), polyimide precursor concentration: 10% by mass)

<Comparative example 1>
[Preparation of Resin Particle Dispersion Polyimide Precursor Organic Solvent Solution (PAA-C1)]
NMP (N-methylpyrrolidone): 450 g was added to 100 g of a non-crosslinked styrene / acrylic copolymer powder (FS-102E: manufactured by Nippon Paint Co., Ltd.) having an average particle size of 0.1 μm in terms of solid content. p-Phenylenediamine (molecular weight 108.14): 27.28 g (252.27 mmol) was added and stirred at 20 ° C. for 10 minutes to disperse. Further, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22): 72.72 g (247.16 mmol) was added to this solution, and the reaction temperature was maintained at 40 ° C. , Stirred for 24 hours to dissolve and react, and attempted to prepare a resin particle-dispersed polyimide precursor organic solvent solution (PAA-C1). (Resin particles / polyimide precursor = 100/100 (mass ratio), polyimide precursor concentration: 15% by mass) By the time the polyimide precursor was obtained, all the resin particles had dissolved.

<Comparative example 2>
[Preparation of Silica Particle Dispersion Polyimide Precursor Aqueous Solvent Solution (PAA-C2)]
Snowtex (registered trademark) ZL (water dispersion of silica particles, particle size 70 nm or more and 100 nm or less, manufactured by Nissan Chemical Industries, Ltd.): Ion-exchanged water: 350 g was added to 100 g in terms of solid content. Add p-phenylenediamine (molecular weight 108.14): 27.28 g (252.27 mmol) and methylmorpholine (organic amine compound): 50.00 g (494.32 mmol) and stir at 20 ° C. for 10 minutes. And dispersed. Further, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22): 72.72 g (247.16 mmol) was added to this solution, and the reaction temperature was maintained at 40 ° C. , Stirred for 24 hours to dissolve and react to obtain a particle-dispersed polyimide precursor solution (PAA-C2) in which silica particles were dispersed. (Silica particles / polyimide precursor = 100/100 (mass ratio), polyimide precursor concentration: 12% by mass)

<Comparative example 3>
[Preparation of Silica Particle Dispersion Polyimide Precursor Organic Solvent Solution (PAA-C3)]
30 parts by mass of monodisperse spherical silica particles having an average diameter of 550 nm (spherical ratio: 1.0, particle size distribution index: 1.20) manufactured by Nippon Catalyst Co., Ltd. were dispersed in NMP: 30 parts by mass.
NMP (N-methylpyrrolidone): 350 g was added to 100 g of this silica dispersion liquid in terms of solid content. p-Phenylenediamine (molecular weight 108.14): 27.28 g (252.27 mmol) was added and stirred at 20 ° C. for 10 minutes to disperse. Further, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22): 72.72 g (247.16 mmol) was added to this solution, and the reaction temperature was maintained at 40 ° C. , Stirred for 24 hours to dissolve and react to obtain a particle-dispersed polyimide precursor solution (PAA-C3) in which silica particles were dispersed. (Silica particles / polyimide precursor = 100/100 (mass ratio), polyimide precursor concentration: 15% by mass)

<Example 3>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-3)]
In Example 1, instead of adding 350 g of ion-exchanged water, the resin particle-dispersed polyimide precursor solution (PAA-3) was prepared in the same manner as in Example 1 except that the ion-exchanged water was changed to 290 g and isopropanol: 60 g. Obtained. (Resin particles / polyimide precursor = 100/100 (mass ratio), polyimide precursor concentration: 12% by mass)

<Example 4>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-4)]
In Example 3, a resin particle-dispersed polyimide precursor solution (PAA-4) was obtained in the same manner as in Example 3 except that 1,2-dimethylimidazole: 47.52 g was added instead of 50 g of methylmorpholine. (Resin particles / polyimide precursor = 100/100 (mass ratio), polyimide precursor concentration: 12% by mass)

<Example 5>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-5)]
In Example 2, the resin particles were added in the same manner as in Example 2 except that the amount of the resin particle dispersion liquid (2) added (in terms of solid content) was changed from 100 g to 140 g and the ion-exchanged water to be added was changed from 350 g to 160 g. A dispersed polyimide precursor solution (PAA-5) was obtained. (Resin particles / polyimide precursor = 140/100 (mass ratio), polyimide precursor concentration: 10% by mass)

<Example 6>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-6)]
In Example 1, instead of adding 350 g of ion-exchanged water, the resin particle-dispersed polyimide precursor solution (PAA-) was changed to 290 g of ion-exchanged water and 60 g of N-methylpyrrolidone in the same manner as in Example 1. 6) was obtained. (Resin particles / polyimide precursor = 100/100 (mass ratio), polyimide precursor concentration: 12% by mass)

<Example 7>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-7)]
Resin particle dispersion liquid (3): Deionized water: 350 g and t-butanol: 200 g were added to 100 g in terms of solid content. 4,4'-Diaminodiphenyl ether (molecular weight 200.24): 13.66 g (68.2 mmol) and methylmorpholine (organic amine compound): 16.23 g (160.41 mmol) were added and at 20 ° C. Stirred for 10 minutes to disperse. Further, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22): 19.66 g (66.84 mmol) was added to this solution, and the reaction temperature was maintained at 40 ° C. , Stirred for 24 hours to dissolve and react to obtain a resin particle-dispersed polyimide precursor solution (PAA-7). (Resin particles / polyimide precursor = 300/100 (mass ratio), polyimide precursor concentration: 3.6% by mass)

<Example 8>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-8)]
Resin particle dispersion liquid (1): Deionized water: 200 g and 1-propanol: 150 g were added to 100 g in terms of solid content. 4,4'-Diaminodiphenyl ether (molecular weight 200.24): 8.21 g (41.0 mmol) and methylmorpholine (organic amine compound): 9.75 g (96.43 mmol) were added and at 20 ° C. Stirred for 10 minutes to disperse. Further, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22): 11.82 g (40.17 mmol) was added to this solution, and the reaction temperature was maintained at 40 ° C. , Stirred for 24 hours to dissolve and react to obtain a resin particle-dispersed polyimide precursor solution (PAA-8). (Resin particles / polyimide precursor = 500/100 (mass ratio), polyimide precursor concentration: 2.8% by mass)

<Example 9>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-9)]
Same as in Example 7 except that the resin particle dispersion (3) is changed to the resin particle dispersion (4), t-butanol is changed to 1-methoxy-2-propanol, and methylmorpholin is changed to dimethylaminoethanol. A resin particle-dispersed polyimide precursor solution (PAA-9) was obtained. (Resin particles / polyimide precursor = 300/100 (mass ratio), polyimide precursor concentration: 3.6% by mass)

<Example 10>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-10)]
Resin particle dispersion polyimide in the same manner as in Example 7 except that the resin particle dispersion (3) was changed to the resin particle dispersion (2), 1-propanol was changed to isopropanol, and methylmorpholin was changed to diethylaminoethanol. A precursor solution (PAA-10) was obtained. (Resin particles / polyimide precursor = 300/100 (mass ratio), polyimide precursor concentration: 3.1% by mass)

<Reference example 1>
[Preparation of resin particle dispersed polyimide precursor solution (PAA-S1)]
A flask equipped with a stirring rod, a thermometer, and a dropping funnel was filled with 900 g of ion-exchanged water. To this, p-phenylenediamine (molecular weight 108.14): 27.28 g (252.27 mmol) and methylmorpholine (organic amine compound): 50.00 g (494.32 mmol) were added, and at 20 ° C. Stirred for 10 minutes to disperse. Further, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (molecular weight 294.22): 72.72 g (247.16 mmol) was added to this solution, and the reaction temperature was maintained at 40 ° C. , Stirred for 24 hours to dissolve and react to obtain a polyimide precursor "water" solution. This polyimide precursor "water" solution is diluted 10 times, resin particle dispersion liquid (1) is added to 10 parts of the polyimide precursor at a ratio of 10 parts of solid content, and the mixture is stirred on a web blower to obtain a resin. A particle-dispersed polyimide precursor solution (PAA-S1) was obtained.

<Evaluation 1>
[Evaluation of dispersibility]
The dispersibility of the resin particle-dispersed polyimide precursor solutions obtained in Examples 1 to 10, Comparative Examples 1 to 3, and Reference Example 1 was evaluated. The specific method is as follows.
The obtained resin particle-dispersed polyimide precursor solution was stored standing at room temperature (25 ° C.) and refrigerated (3 ° C.), respectively, and the dispersed state of the resin particles was visually evaluated (the dispersion of the resin particles was evaluated. When it gets worse, layer separation of the solution and sedimentation of particles can be observed.)

-Evaluation criteria-
A: No change in the solution even after 2 months from the start of storage B: Layer separation or particle settling is observed within 1 month to 2 months after the start of storage C: Layer separation or particle settling within 1 month after the start of storage Can be seen

<Evaluation 2>
[Preparation of Porous Polyimide Film (PIF-1)]
A resin particle-dispersed polyimide precursor solution (PAA-1) is formed on a glass substrate so that the film thickness after drying is about 30 μm, dried at 90 ° C. for 1 hour, and then from 90 ° C. to 380 ° C. The temperature was raised at a rate of 10 ° C./min, held at 380 ° C. for 1 hour, and then cooled to room temperature (25 ° C., the same applies hereinafter) to obtain a porous polyimide film (PIF-1).

[Preparation of Porous Polyimide Film (PIF-2)]
A resin particle-dispersed polyimide precursor solution (PAA-1) was formed on a glass substrate so that the film thickness after drying was about 30 μm, and dried at 90 ° C. for 1 hour. Then, it was peeled off from the glass substrate and immersed in tetrahydrofuran for 1 hour. Then, the temperature was raised from 90 ° C. to 380 ° C. at a rate of 10 ° C./min, kept at 380 ° C. for 1 hour, and then cooled to room temperature to obtain a porous polyimide film (PIF-2).

[Preparation of Porous Polyimide Films (PIF-3) to (PIF-7), (PIF-9) to (PIF-10)]
Porous polyimide film (PIF-3) in the same manner as porous polyimide film (PIF-2), except that the type of resin particle-dispersed polyimide precursor solution used and the solvent used for immersion were changed to those shown in Table 2. )-(PIF-7) and (PIF-9)-(PIF-10) were obtained. However, in the case of "exposed" in Table 2, a step of exposing the resin particles with sandpaper was added after peeling from the glass substrate.

[Preparation of Porous Polyimide Film (PIF-8)]
Similar to the porous polyimide film (PIF-1), except that the resin particle-dispersed polyimide precursor solution used is changed to (PAA-2) and a step of exposing the resin particles with sandpaper after drying is added. A porous polyimide film (PIF-8) was obtained.

[Preparation of Porous Polyimide Film (PIF-11)]
A resin particle-dispersed polyimide precursor solution (PAA-7) was formed on a glass substrate so that the film thickness after drying was about 30 μm, and dried at 80 ° C. for 1 hour. Then, the whole glass substrate was immersed in tetrahydrofuran for 20 hours. After air-drying, the temperature is raised from 80 ° C. to 250 ° C. at a rate of 1 ° C./min, held at 250 ° C. for 1 hour, cooled to room temperature, peeled off from the glass substrate, and made into a porous polyimide film (PIF-). 11) was obtained.
FIG. 2 shows a photograph of the surface of the obtained porous polyimide film (PIF-11) observed with a scanning electron microscope (manufactured by Keyence Corporation: VE-8800).

[Preparation of Porous Polyimide Films (PIF-12) to (PIF-14)]
Porous polyimide films (PIF-12) to (PIF-14) in the same manner as the porous polyimide film (PIF-11), except that the type of resin particle-dispersed polyimide precursor solution used was changed to that shown in Table 2. ) Was obtained.

[Preparation of Porous Polyimide Film (PIF-C1)]
A porous polyimide film (PIF-C1) was obtained in the same manner as in the preparation of (PIF-2) except that the liquid used was changed to (PAA-C1).

[Preparation of Porous Polyimide Film (PIF-C2)]
(PAA-C2) was formed on a glass substrate so that the film thickness after drying was about 30 μm, heated at 120 ° C. for 1 hour, peeled off from the glass substrate, and from room temperature to 380 ° C. The temperature was raised at a speed of 10 ° C./min, held at 380 ° C. for 1 hour, and then cooled to room temperature to obtain a silica-polyimide composite film. The silica-polyimide composite film was immersed in 10% by mass hydrogen fluoride water to dissolve and remove silica over 6 hours, washed thoroughly with water, and dried to obtain a porous polyimide film (PIF-C2).

[Preparation of Porous Polyimide Film (PIF-C3)]
A porous polyimide film (PIF-C3) was obtained in the same manner as in the preparation of (PIF-C2) except that the liquid used was changed to (PAA-C3).

[Evaluation of cracks]
Cracks were evaluated in the porous polyimide films prepared using the resin particle-dispersed polyimide precursor solutions obtained in Examples 1A to 14A and Comparative Examples 1A to 3A. The specific method is as follows. The above 0.1mm area of the polyimide film 1 cm ² square by microscope magnification 500 and cracking were visually observed whether.

-Evaluation criteria-
A: No cracks B: 1 or more and 3 or less C: 4 or more

[Evaluation of pore size distribution]
Regarding the distribution of pore diameters (maximum diameter, minimum diameter, and average diameter) of the porous polyimide films prepared using the resin particle-dispersed polyimide precursor solutions obtained in Examples 1A to 14A and Comparative Examples 1A to 3A. Evaluation was performed. Specifically, the evaluation was performed by the method described above.

In addition, in Comparative Example 1A, the difference between the maximum diameter and the minimum diameter (and the ratio of the maximum diameter and the minimum diameter) is larger than that in the Example. It is presumed that this is because the resin particles were dissolved in N-methylpyrrolidone.

The particles of the particle dispersion liquid in Tables 1 and 2 are shown below.
(1): Resin particle dispersion liquid described above (1) Average particle size 0.18 μm
(2): Resin particle dispersion liquid described above (2) Average particle size 0.1 μm
(3): Resin particle dispersion liquid described above (3) Average particle size 0.21 μm
(4): Resin particle dispersion liquid described above (4) Average particle size 0.23 μm
-Silica (1): Snowtex (registered trademark) ZL
(Diameter 70-100nm, manufactured by Nissan Chemical Industries, Ltd.)
Silica (2): Monodisperse spherical silica particles with an average diameter of 550 nm
(Manufactured by Nippon Shokubai Co., Ltd., sphericity: 1.0, particle size distribution index: 1.20)

The details of the abbreviations in Tables 1 and 2 are shown below.
・ "PDA": p-phenylenediamine ・ "ODA": 4,4'-diaminodiphenyl ether ・ "BPDA": 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride ・ "MMO": methylmorpholin・ "DMAEt": dimethylaminoethanol ・ "DEAet": diethylaminoethanol ・ "DMIz": 1,2-dimethylimidazole ・ "IPA": isopropanol ・ "NMP": N-methylpyrrolidone ・ "THF": tetrahydrofuran ・ "Tol"":Toluene," NPA ": 1-propanol," TBA ": t-butanol," 1M2PA ": 1-methoxy-2-propanol, silica (1): dispersion of silica particles used in Comparative Example 2, silica (2): Dispersion liquid of silica particles used in Comparative Example 3 In the particle dispersion liquid number column of Comparative Examples 1 and 1A in Tables 1 and 2, the notation (2) indicates that Comparative Examples 1 and 1A are resins. The resin particle powder of the particle dispersion liquid (2) is used, and is described as described above for convenience.

1 Resin particles, 3 Substrate, 4 Peeling layer, 5 Polyimide precursor solution, 7 Pore, 61 Polyimide film, 62 Porous polyimide film

Claims (6)

Aqueous solvent from polyester resin particles, urethane resin particles, vinyl resin particles, (meth) acrylic resin particles, (meth) acrylic acid ester resin particles, styrene / (meth) acrylic resin particles, polystyrene resin particles, and polyethylene resin particles. In the resin particle dispersion liquid in which at least one resin particle selected from the above group is dispersed, a polyimide precursor is formed by polymerizing a tetracarboxylic acid dianhydride and a diamine compound in the presence of an organic amine compound. After applying the resin particle-dispersed polyimide precursor solution obtained by the method for producing the resin particle-dispersed polyimide precursor solution to form a coating film, the coating film is dried to obtain the polyimide precursor and the resin particles. The first step of forming the containing film and
A second step of heating the film to imidize the polyimide precursor to form a polyimide film, the second step including a process of removing the resin particles.
Have,
In the second step, the porous polyimide film is subjected to a treatment for exposing the resin particles after the process of imidizing the polyimide precursor or after the imidization and before the treatment for removing the resin particles. Manufacturing method. Aqueous solvent from polyester resin particles, urethane resin particles, vinyl resin particles, (meth) acrylic resin particles, (meth) acrylic acid ester resin particles, styrene / (meth) acrylic resin particles, polystyrene resin particles, and polyethylene resin particles. In the resin particle dispersion liquid in which at least one resin particle selected from the above group is dispersed, a polyimide precursor is formed by polymerizing a tetracarboxylic acid dianhydride and a diamine compound in the presence of an organic amine compound. After applying the resin particle-dispersed polyimide precursor solution obtained by the method for producing the resin particle-dispersed polyimide precursor solution to form a coating film, the coating film is dried to obtain the polyimide precursor and the resin particles. The first step of forming the containing film and
A second step of heating the film to imidize the polyimide precursor to form a polyimide film, the second step including a process of removing the resin particles.
Have,
A method for producing a porous polyimide film, wherein the treatment for removing the resin particles is a treatment for removing the resin particles with an organic solvent that dissolves the resin particles. The method for producing a porous polyimide film according to claim 1 or 2 , wherein the resin particle dispersion is a dispersion in which resin particles are granulated in the aqueous solvent. The method for producing a porous polyimide film according to any one of claims 1 to 3, wherein the organic amine compound is a tertiary amine compound. The organic amine compound, method for producing a porous polyimide film of any one of claims 1 to 4 is an amine compound having a heterocyclic structure containing nitrogen. The method for producing a porous polyimide film according to any one of claims 1 and 3 to 5, wherein the treatment for removing the resin particles is a treatment for removing by heating.

Images