Aqueous composition containing polyimide precursor, method for producing polyimide film, and method for producing porous polyimide film

Abstract

The present invention relates to an aqueous composition containing a polyimide precursor, a method for producing a polyimide film, and a method for producing a porous polyimide film. The aqueous composition containing a polyimide precursor comprises at least one polymer material selected from the group consisting of a water-insoluble fibrous organic substance and a polyalkylene oxide having a viscosity-average molecular weight of 5,000,000 or greater, a polyimide precursor, particles, and water.

Description

Technical Field

[0001] The present invention relates to an aqueous composition containing a polyimide precursor, a method for producing a polyimide film, and a method for producing a porous polyimide film. Background Art

[0002] Polyimide resin is a material having excellent mechanical strength, chemical stability, and heat resistance, and polyimide films having these characteristics have attracted attention.

[0003] Polyimide membranes are sometimes suitably used in filters (eg, filters, oil filters, fuel filters, etc.) and secondary batteries (eg, separators for lithium secondary batteries, solid electrolyte holders in all-solid-state batteries, etc.).

[0004] For example, Patent Document 1 describes a varnish for producing a porous membrane, which contains at least one resin (A) selected from the group consisting of polyamic acid, polyimide, a polyamideimide precursor and polyamideimide, fine particles (B), and a surfactant (C) containing silicon atoms and / or fluorine atoms and having an alkylene oxide chain.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-056225

[0006] When a polyimide film is produced using an aqueous polyimide precursor-containing composition comprising a polyimide precursor, particles, and water, if particles settle or float during the production process, the amount of particles varies in the thickness direction of the polyimide film.

[0007] If the amount of particles varies in the thickness direction of the polyimide film, physical properties may vary in the thickness direction of the polyimide film (for example, in the case of a porous polyimide film, the porosity may vary in the thickness direction), which is sometimes not preferable. Summary of the Invention

[0008] The present invention aims to provide an aqueous composition containing a polyimide precursor that can suppress particle precipitation during the production of a polyimide film, compared to a composition containing a polyimide precursor, a polyalkylene oxide having a viscosity-average molecular weight of less than 5,000,000 or a water-insoluble fibrous organic substance, namely carboxymethyl cellulose, particles, and water.

[0009] The above issues can be solved by the following mechanisms.

[0010] <1>

[0011] A polyimide precursor-containing aqueous composition comprises at least one polymer material selected from the group consisting of a water-insoluble fibrous organic substance and a polyalkylene oxide having a viscosity-average molecular weight of 5,000,000 or more, a polyimide precursor, particles, and water.

[0012] <2>

[0013] according to <1> The aqueous composition containing a polyimide precursor, wherein

[0014] The content of the polymer material is 0.5% by mass or more and 8.0% by mass or less relative to the polyimide precursor.

[0015] <3>

[0016] according to <2> The aqueous composition containing a polyimide precursor, wherein

[0017] The content of the polymer material is 1.0% by mass or more and 3.0% by mass or less relative to the polyimide precursor.

[0018] <4>

[0019] according to <1> to <3> The aqueous composition containing a polyimide precursor according to any one of the preceding claims, wherein

[0020] The content of the polymer material is 0.05% by mass or more and 15% by mass or less relative to the particles.

[0021] <5>

[0022] according to <4> The aqueous composition containing a polyimide precursor, wherein

[0023] The content of the polymer material is 0.1% by mass or more and 2.0% by mass or less relative to the particles.

[0024] <6>

[0025] according to <1> to <5> The aqueous composition containing a polyimide precursor according to any one of the preceding claims, wherein

[0026] The polyalkylene oxide is polyethylene oxide.

[0027] <7>

[0028] according to <1> to <6> The aqueous composition containing a polyimide precursor according to any one of the preceding claims, wherein

[0029] The viscosity average molecular weight of the polyalkylene oxide is 6,000,000 to 11,000,000.

[0030] <8>

[0031] according to <1> to <7> The aqueous composition containing a polyimide precursor according to any one of the preceding claims, wherein

[0032] The fiber diameter of the water-insoluble fibrous organic matter is 1 nm or more and 500 nm or less.

[0033] <9>

[0034] according to <1> to <8> The aqueous composition containing a polyimide precursor according to any one of the preceding claims, wherein

[0035] The water-insoluble fibrous organic matter has a fiber length of 10 nm to 10,000 nm.

[0036] <10>

[0037] according to <1> to <9> The aqueous composition containing a polyimide precursor according to any one of the preceding claims, wherein

[0038] The particles are resin particles.

[0039] <11>

[0040] according to <10> The aqueous composition containing a polyimide precursor, wherein

[0041] The resin particles are particles containing a resin containing a structural unit derived from styrene.

[0042] <12>

[0043] according to <1> to <11> The aqueous composition containing a polyimide precursor according to any one of the preceding claims, wherein

[0044] The content of the water is 70% by mass or more relative to the total mass of the aqueous composition containing the polyimide precursor.

[0045] <13>

[0046] according to <1> to <12> The aqueous composition containing a polyimide precursor according to any one of the preceding claims, wherein

[0047] The viscosity at 25° C. is 1 Pa·s or more and 200 Pa·s or less.

[0048] <14>

[0049] A method for producing a polyimide film comprises the following steps:

[0050] Will <1> to <13> A step of applying the aqueous composition containing a polyimide precursor described in any one of the preceding claims on a substrate to form a coating film;

[0051] a step of drying the coating to form a film comprising at least one polymer material selected from the group consisting of the water-insoluble fibrous organic matter and polyalkylene oxide having a viscosity-average molecular weight of 5,000,000 or more, the polyimide precursor, and the particles; and

[0052] a step of imidizing the polyimide precursor contained in the film to form a polyimide film.

[0053] <15>

[0054] A method for manufacturing a porous polyimide membrane comprises the following steps:

[0055] Will <1> to <13> A step of applying the aqueous composition containing a polyimide precursor described in any one of the preceding claims on a substrate to form a coating film;

[0056] The step of drying the coating to form a film comprising at least one polymer material selected from the group consisting of the water-insoluble fibrous organic matter and polyalkylene oxide having a viscosity-average molecular weight of 5,000,000 or more, the polyimide precursor, and the particles;

[0057] a step of imidizing the polyimide precursor contained in the film to form a polyimide film; and

[0058] a step of removing the particles from the film or the polyimide film.

[0059] Effects of the Invention

[0060] according to <1> The present invention provides an aqueous composition containing a polyimide precursor that can suppress particle precipitation or floating during the production of a polyimide film, compared to a composition containing polyalkylene oxide having a viscosity-average molecular weight of less than 5,000,000 or carboxymethyl cellulose, a water-insoluble fibrous organic substance, a polyimide precursor, particles, and water.

[0061] according to <2> or <3> The present invention can provide an aqueous composition containing a polyimide precursor, which can suppress particle precipitation or floating during the production of a polyimide film, compared to a case where the content of the polymer material relative to the polyimide precursor is less than 0.5% by mass or greater than 8.0% by mass.

[0062] according to <4> or <5> The present invention can provide an aqueous composition containing a polyimide precursor, which can suppress particle precipitation or floating during the production of a polyimide film, compared to when the content of the polymer material relative to the particles is less than 0.05% by mass or greater than 15% by mass.

[0063] according to <6> The present invention can provide an aqueous composition containing a polyimide precursor, which can suppress the precipitation or floating of particles during the production of a polyimide film, compared to a case where the polyalkylene oxide is polypropylene oxide.

[0064] according to <7> The present invention provides an aqueous composition containing a polyimide precursor, which can suppress particle precipitation or floating during the production of a polyimide film, compared to a case where the viscosity average molecular weight of the polyalkylene oxide is less than 6,000,000 or greater than 11,000,000.

[0065] according to <8> The present invention can provide an aqueous composition containing a polyimide precursor, which can suppress particle precipitation or floating during the production of a polyimide film, compared to when the fiber diameter of the water-insoluble fibrous organic material is larger than 500 nm.

[0066] according to <9> The present invention can provide an aqueous composition containing a polyimide precursor, which can suppress particle precipitation or floating during the production of a polyimide film, compared to when the fiber length of the water-insoluble fibrous organic material is less than 10 nm or greater than 10,000 nm.

[0067] according to <10> The present invention can provide an aqueous composition containing a polyimide precursor, in which the specific gravity of the resin particles and the solution is close to that of the inorganic particles, and thus the movement of the particles can be easily suppressed.

[0068] according to <11> The present invention can provide an aqueous composition containing a polyimide precursor, wherein the particle specific gravity is closer to the solution specific gravity than when the particles are made of polymethyl methacrylate, and thus the movement of the particles can be easily suppressed.

[0069] according to <12> The present invention can provide an aqueous composition containing a polyimide precursor that can suppress particle precipitation or floating during the production of a polyimide film, compared to a case where the water content relative to the total mass of the aqueous composition containing a polyimide precursor is less than 70% by mass.

[0070] according to <13> The present invention provides an aqueous composition containing a polyimide precursor, which can suppress particle precipitation or floating during the production of a polyimide film, compared to a composition having a viscosity of more than 100 Pa·s at 25° C.

[0071] according to <14> The invention involved can provide a method for producing a polyimide film, which can produce a polyimide film with less variation in the amount of particles in the thickness direction than when using an aqueous composition containing a polyimide precursor comprising polyalkylene oxide having a viscosity-average molecular weight of less than 5,000,000 or carboxymethyl cellulose, a water-insoluble fibrous organic substance, a polyimide precursor, particles, and water.

[0072] according to <15> The invention involved can provide a method for producing a polyimide film, which can obtain a porous polyimide film with less variation in porosity in the thickness direction compared to the case of using an aqueous composition containing a polyimide precursor comprising polyalkylene oxide having a viscosity-average molecular weight of less than 5 million or a water-insoluble fibrous organic substance, namely carboxymethyl cellulose, a polyimide precursor, particles and water. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0074] Figure 1 Schematic diagram showing a porous polyimide membrane produced using an aqueous composition containing a polyimide precursor according to the present embodiment;

[0075] Figure 2 A schematic partial cross-sectional view showing an example of a lithium ion secondary battery including a porous polyimide membrane produced using the aqueous composition containing a polyimide precursor according to the present embodiment as a separator for the lithium ion secondary battery;

[0076] Figure 3 It is a partial cross-sectional schematic diagram showing an example of an all-solid-state battery including a porous polyimide membrane produced using the aqueous composition containing a polyimide precursor according to the present embodiment.

[0077] Explanation of symbols

[0078] 10-Porous polyimide membrane

[0079] 10A-Empty hole

[0080] 31-Substrate

[0081] 51-peeling layer

[0082] 100-Lithium-ion secondary battery

[0083] 200-All-solid-state battery DETAILED DESCRIPTION

[0084] Hereinafter, embodiments of the present invention will be described in detail.

[0085] In the present embodiment, the concept of "film" includes not only what is generally called "film" but also what is generally called "thin film" and "sheet".

[0086] Furthermore, in the present embodiment, the "solid content" refers to components other than water and a water-soluble organic solvent (ie, an aqueous solvent).

[0087] <Aqueous composition containing polyimide precursor>

[0088] The aqueous composition containing a polyimide precursor according to this embodiment (hereinafter also referred to as "the aqueous composition according to this embodiment") comprises at least one polymer material selected from the group consisting of a water-insoluble fibrous organic substance and a polyalkylene oxide having a viscosity-average molecular weight of 5 million or more, a polyimide precursor, particles, and water.

[0089] Here, the “aqueous composition” refers to a composition containing water, wherein the total content of water and a water-soluble organic solvent (ie, an aqueous solvent) is 50% by mass or more relative to the total mass of the aqueous composition according to the present embodiment.

[0090] The aqueous composition according to the present embodiment having the above-described structure can suppress the precipitation or floating of particles during the process of producing a polyimide film.

[0091] The reason is not clear yet, but is speculated as follows.

[0092] It is considered that the polyalkylene oxide having a viscosity average molecular weight of 5,000,000 or more contained in the aqueous composition according to the present embodiment has a high molecular weight and contains a large amount of alkylene oxide (i.e., -(C m H 2m O) a structural unit represented by -, m represents an integer of 2 or greater), and thus adjacent molecules in the aqueous composition containing water interact with each other to form a network structure.

[0093] Furthermore, in the aqueous composition containing water, the fibers are entangled with each other and connected at intersections, thereby maintaining the network structure of the water-insoluble fibrous organic matter.

[0094] Therefore, it is presumed that the particles in the aqueous composition according to the present embodiment are captured by the mesh structure and are suppressed from settling or floating.

[0095] In particular, even a small amount of water-insoluble fibrous organic matter and / or polyalkylene oxide having a viscosity-average molecular weight of 5 million or more can inhibit the precipitation or floating of particles, so it is presumed that it is difficult to increase the viscosity of the aqueous composition involved in this embodiment, and it is difficult to affect the physical properties of the manufactured polyimide film (including porous polyimide film).

[0096] 〔Polyimide precursor〕

[0097] The aqueous composition according to this embodiment contains a polyimide precursor.

[0098] The polyimide precursor is a resin (polyimide precursor) having a repeating unit represented by the general formula (I).

[0099] [Chemical Formula 1]

[0100]

[0101] (In general formula (I), A represents a tetravalent organic group, and B represents a divalent organic group.)

[0102] Here, in the general formula (I), the tetravalent organic group represented by A is a residue obtained by removing four carboxyl groups from tetracarboxylic dianhydride serving as a raw material.

[0103] On the other hand, the divalent organic group represented by B is a residue obtained by removing two amino groups from a diamine serving as a raw material.

[0104] That is, the polyimide precursor having a repeating unit represented by the general formula (I) is a polymer of tetracarboxylic dianhydride and diamine.

[0105] Examples of tetracarboxylic dianhydrides include aromatic and aliphatic compounds, and aromatic compounds are preferred. That is, in general formula (I), the tetravalent organic group represented by A is preferably an aromatic organic group.

[0106] Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenylsulfone tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3',4,4'-biphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-dimethyldiphenylsilane tetracarboxylic dianhydride, 3,3',4,4'-tetraphenylsilane tetracarboxylic dianhydride, 1,2,3,4-furan tetracarboxylic dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, 4,4'-bis( 3,4-dicarboxyphenoxy)diphenylsulfone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylpropane dianhydride, 3,3',4,4'-perfluoroisopropyldiphthalic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic 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, and bis(triphenylphthalic acid)-4,4'-diphenylmethane dianhydride.

[0107] 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-tricarboxynorbornane-2-acetic dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 5-(2,5-dioxytetrahydrofuranyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, and bicyclo[2,2,2]-oct-7-ene-2,3,5,6-tetracarboxylic acid. aliphatic or alicyclic tetracarboxylic dianhydrides such as dianhydride; aliphatic tetracarboxylic dianhydrides having an aromatic ring such as 1,3,3a,4,5,9b-hexahydro-2,5-dioxy-3-furyl)-naphthalene[1,2-c]furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-5-methyl-5-(tetrahydro-2,5-dioxy-3-furyl)-naphthalene[1,2-c]furan-1,3-dione, and 1,3,3a,4,5,9b-hexahydro-8-methyl-5-(tetrahydro-2,5-dioxy-3-furyl)-naphthalene[1,2-c]furan-1,3-dione.

[0108] Among them, as the tetracarboxylic dianhydride, for example, aromatic tetracarboxylic dianhydrides are preferred, and specifically, for example, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyl ether tetracarboxylic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride are preferred. Pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride are more preferred, and 3,3',4,4'-biphenyltetracarboxylic dianhydride is particularly preferred.

[0109] Moreover, the tetracarboxylic dianhydride may be used individually by 1 type, and may use 2 or more types simultaneously in combination.

[0110] When two or more kinds are used simultaneously, they may be used simultaneously with aromatic tetracarboxylic dianhydride or aliphatic tetracarboxylic acid, or aromatic tetracarboxylic dianhydride and aliphatic tetracarboxylic dianhydride may be used in combination.

[0111] On the other hand, a diamine compound is a diamine compound having two amino groups in its molecular structure. Examples of diamine compounds include aromatic and aliphatic compounds, with aromatic compounds being preferred. Specifically, in general formula (I), the divalent organic group represented by B is preferably an aromatic organic group.

[0112] Examples of the diamine compound include p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, 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-trimethylindane, 6-amino-1-(4'-aminophenyl)-1,3,3-trimethylindane, 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-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)-biphenyl, 1,3'-bis(4-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 4,4'-(p-phenyleneisopropylidene)dianiline, 4,4'-(m-phenyleneisopropylidene)dianiline, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[4- Aromatic diamines such as (4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl; aromatic diamines having two amino groups bonded to an aromatic ring and heteroatoms other than the nitrogen atom of the amino groups such as diaminotetraphenylthiophene; 1,1-m-xylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, nonamethylenediamine, 4,4-diaminoheptamethylenediamine, 1,4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadienediamine, hexahydro-4,7-methyleneindanyl dimethylenediamine, tricyclo[6,2,1,0 2.7 ]-undecenedimethyldiamine, 4,4'-methylenebis(cyclohexylamine) and other aliphatic diamines and alicyclic diamines.

[0113] Among them, the diamine compound is preferably an aromatic diamine compound, specifically, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenyl sulfone, and particularly preferably 4,4'-diaminodiphenyl ether and p-phenylenediamine.

[0114] The diamine compound may be used alone or in combination of two or more. When two or more are used in combination, either an aromatic diamine compound or an aliphatic diamine compound may be used simultaneously, or both aromatic diamine compounds and aliphatic diamine compounds may be used in combination.

[0115] The weight average molecular weight of the polyimide precursor used in the present embodiment is, for example, preferably 5,000 or more and 300,000 or less, and more preferably 10,000 or more and 150,000 or less.

[0116] The weight average molecular weight of the polyimide precursor is measured by gel permeation chromatography (GPC) under the following measurement conditions.

[0117] ·Color column: TOSOH CORPORATION TSKgelα-M (7.8mm ID×30cm)

[0118] Eluent: DMF (dimethylformamide) / 30mM LiBr / 60mM phosphoric acid

[0119] Flow rate: 0.6 mL / min

[0120] Injection volume: 60uL

[0121] Detector: RI (differential refractive index detector)

[0122] The content of the polyimide precursor is, for example, preferably 0.1 mass % or more and 10 mass % or less, and more preferably 0.5 mass % or more and 8 mass % or less, relative to the total mass of the aqueous composition according to the present embodiment.

[0123] 〔particle〕

[0124] The aqueous composition according to this embodiment contains particles.

[0125] The particles contained in the aqueous composition according to the present embodiment are in a dispersed state without being dissolved.

[0126] The material of the particles is not particularly limited as long as the particles are insoluble in the aqueous composition according to the present embodiment, and are broadly classified into resin particles and inorganic particles as described below.

[0127] Here, in this embodiment, “the particles do not dissolve” means that the particles do not dissolve in the target solution (specifically, the aqueous solvent contained in the aqueous composition containing the polyimide precursor) at 25° C., and also includes dissolving in the range of 3% by mass or less relative to the target solution.

[0128] Furthermore, the particles may be contained in the polyimide film produced using the aqueous composition according to the present embodiment, or may be removed from the produced polyimide film.

[0129] The volume average particle size D50v of the particles is not particularly limited. The volume average particle size D50v of the particles is preferably, for example, 0.1 μm or more and 10 μm or less. The lower limit of the volume average particle size D50v of the particles may be 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, or 0.5 μm or more. Furthermore, the upper limit of the volume average particle size D50v of the particles may be 7 μm or less, 5 μm or less, 3 μm or less, or 2 μm or less.

[0130] Furthermore, the volume size distribution index (GSDv) of the particles is, for example, preferably 1.30 or less, more preferably 1.25 or less, and most preferably 1.20 or less.

[0131] The particle size distribution of the particles in the aqueous composition according to the present embodiment is measured by the following method.

[0132] The composition to be measured was diluted and the particle size distribution of the particles in the solution was measured using a Coulter counter LS13 (manufactured by Beckman Coulter, Inc.) Based on the measured particle size distribution, the volume cumulative distribution was plotted from the smaller diameter side for each divided particle size range (channel).

[0133] Furthermore, in the volume cumulative distribution drawn from the smaller diameter side, the particle size at 16% cumulatively is defined as volume particle size D16v, the particle size at 50% cumulatively is defined as volume average particle size D50v, and the particle size at 84% cumulatively is defined as volume particle size D84v.

[0134] The volume size distribution index (GSDv) of the particles is calculated from the particle size distribution obtained by the above method as (D84v / D16v). 1 / 2 .

[0135] When measurement by the above-mentioned method is difficult, the particle size distribution of the particles in the aqueous composition according to the present embodiment can be measured by a method such as a dynamic light scattering method.

[0136] The shape of the particles is preferably, for example, spherical.

[0137] When a porous polyimide membrane is produced by removing particles from a polyimide membrane using spherical particles, a porous polyimide membrane having spherical pores can be obtained.

[0138] In addition, in the present embodiment, the "spherical shape" in the particles includes both spherical shapes and substantially spherical shapes (shapes close to spherical shapes).

[0139] Specifically, it means that the ratio of the major diameter to the minor diameter (major diameter / minor diameter) is greater than 1 and less than 1.5, and the proportion of particles is greater than 80%. The ratio of particles of the major diameter to the minor diameter (major diameter / minor diameter) is greater than 1 and less than 1.5, for example, is preferably greater than 90%. The closer the ratio of the major diameter to the minor diameter is to 1, the more spherical the shape.

[0140] As the particles, either resin particles or inorganic particles can be used. However, resin particles are preferably used for the following reasons, for example.

[0141] Since both the resin particles and the polyimide precursor are organic materials, compared to the use of inorganic particles, the particle dispersibility in the aqueous composition containing the polyimide precursor or in a coating film based on the aqueous composition containing the polyimide precursor, the surface adhesion to the polyimide precursor, etc. are easily improved. Furthermore, during the imidization step when manufacturing the polyimide film, the resin particles easily absorb volume shrinkage, thereby easily preventing cracks from occurring in the polyimide film due to this volume shrinkage.

[0142] Hereinafter, specific materials of the resin particles and the inorganic particles will be described.

[0143] (resin particles)

[0144] The resin particles are not particularly limited as long as they are insoluble in the aqueous composition containing the polyimide precursor (specifically, the aqueous solvent contained in the polyimide precursor solution). For example, preferably, the resin particles are composed of a resin other than polyimide.

[0145] Specific examples of the resin particles include ethylene resins represented by polystyrenes, poly(meth)acrylic acids, polyvinyl acetates, polyvinyl alcohols, polyvinyl butyrals, and polyvinyl ethers; condensation resins represented by polyesters, polyurethanes, and polyamides; hydrocarbon resins represented by polyethylene, polypropylene, and polybutadiene; and fluorine resins represented by polytetrafluoroethylene and polyvinyl fluoride.

[0146] Here, "(meth)acrylic acid" includes both "acrylic acid" and "methacrylic acid." Furthermore, (meth)acrylic acid includes (meth)acrylic acid, (meth)acrylate, and (meth)acrylamide.

[0147] Furthermore, the resin particles may or may not be cross-linked.

[0148] When the resin particles are vinyl-based resin particles, they can be obtained by addition polymerization of monomers.

[0149] Examples of monomers for obtaining vinyl resins include styrenes having a styrene skeleton, such as styrene, alkyl-substituted styrenes (e.g., α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, etc.), halogen-substituted styrenes (e.g., 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, etc.), and vinylnaphthalene; (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, lauryl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and vinyl isopropenyl ketone; acids such as (meth)acrylic acid, maleic acid, cinnamic acid, fumaric acid, and vinyl sulfonic acid; and bases such as ethyleneimine, vinylpyridine, and vinylamine.

[0150] The vinyl resin may be a resin obtained by using any of these monomers alone, or a resin obtained by using a copolymer of two or more monomers.

[0151] As other monomers, monofunctional monomers such as vinyl acetate, difunctional monomers such as divinylbenzene, ethylene glycol dimethacrylate, nonane diacrylate, and decanediol diacrylate, and polyfunctional monomers such as trimethylolpropane triacrylate and trimethylolpropane trimethacrylate may be used together.

[0152] By using a bifunctional monomer and a polyfunctional monomer simultaneously, crosslinked resin particles can be obtained.

[0153] From the viewpoint of productivity and adaptability to the particle removal step described later, the resin particles are preferably, for example, polystyrene-based, poly(meth)acrylic acid-based, or polyester-based resin particles, and more preferably polystyrene-based, styrene-(meth)acrylic acid-based copolymers, or poly(meth)acrylic acid-based resin particles.

[0154] Here, polystyrenes refer to resins containing constituent units derived from styrene-based monomers (monomers having a styrene skeleton). More specifically, for example, when the total amount of constituent units constituting the resin is 100 mol%, the polystyrenes preferably contain 30 mol% or more of the constituent units, and more preferably contain 50 mol% or more of the constituent units.

[0155] Furthermore, poly(meth)acrylic acid refers to methacrylic resins and acrylic resins, and is a resin containing constituent units derived from (meth)acrylic acid-based monomers (monomers having a (meth)acryloyl backbone). More specifically, for example, when the total proportion of constituent units derived from (meth)acrylic acid and / or constituent units derived from (meth)acrylate esters (the total of the components in the polymer) is 100 mol%, the poly(meth)acrylic acid preferably contains 30 mol% or more of these constituent units, and more preferably 50 mol% or more of these constituent units.

[0156] Furthermore, polyesters are resins obtained by polycondensation of polycarboxylic acids and polyols and having ester bonds in the main chain.

[0157] From the viewpoint of easily suppressing the movement of particles due to a small difference in specific gravity with the solution, the resin particles are preferably resin particles based on a resin containing constituent units derived from styrene. For example, when the total of the constituent units constituting the resin is set to 100 mol%, it is preferred that the constituent units derived from styrene are contained at 30 mol% or more, more preferably at 50 mol% or more, further preferably at 80 mol% or more, and particularly preferably at 100 mol%.

[0158] These resin particles may be used alone or in combination of two or more.

[0159] The resin particles preferably maintain their particle shape during, for example, the process of producing the aqueous composition according to the present embodiment and the process of applying the aqueous composition according to the present embodiment and drying the coating film (before removing the resin particles) when producing a polyimide film. From these viewpoints, the glass transition temperature of the resin particles is preferably, for example, 60°C or higher, preferably 70°C or higher, and more preferably 80°C or higher.

[0160] The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, by the "extrapolated glass transition onset temperature" method described in JIS K 7121:1987 "Plastics - Determination of Transition Temperatures".

[0161] (Inorganic particles)

[0162] Specific examples of the inorganic particles include silicon dioxide particles, magnesium oxide particles, aluminum oxide particles, zirconium oxide particles, calcium carbonate particles, calcium oxide particles, titanium dioxide particles, zinc oxide particles, and cerium oxide particles.

[0163] As described above, the shape of the particles is preferably spherical, for example. From this viewpoint, inorganic particles are preferably silica particles, magnesium oxide particles, calcium carbonate particles, and alumina particles, more preferably silica particles, titanium oxide particles, and alumina particles, and even more preferably silica particles.

[0164] These inorganic particles may be used alone or in combination of two or more.

[0165] Furthermore, when the wettability and dispersibility of the inorganic particles with respect to the solvent of the aqueous composition according to the present embodiment are insufficient, the surface of the inorganic particles may be modified as needed.

[0166] Examples of methods for modifying the surface of inorganic particles include treatment with an alkoxysilane having an organic group such as a silane coupling agent, and coating with an organic acid such as oxalic acid, citric acid, and lactic acid.

[0167] The content of the particles can be determined according to the purpose of the polyimide film. For example, relative to the total mass of the aqueous composition involved in this embodiment, it is preferably 0.1 mass % or more and 20 mass % or less, more preferably 0.5 mass % or more and 20 mass % or less, and further preferably 1 mass % or more and 20 mass % or less.

[0168] In the aqueous composition according to the present embodiment, the content of the particles is, for example, preferably 10% by mass to 120% by mass, more preferably 25% by mass to 110% by mass, and even more preferably 30% by mass to 100% by mass relative to the polyimide precursor.

[0169] By setting the particle content to this level, a porous polyimide membrane with high porosity can be easily obtained while maintaining mechanical strength. A porous polyimide membrane with such mechanical strength and high porosity is effective as a separator for secondary batteries.

[0170] [Water-insoluble fibrous organic matter and polyalkylene oxide with a viscosity-average molecular weight of 5 million or more]

[0171] The aqueous composition according to the present embodiment contains at least one polymer material selected from the group consisting of a water-insoluble fibrous organic substance and a polyalkylene oxide having a viscosity-average molecular weight of 5,000,000 or more (hereinafter simply referred to as high-molecular-weight polyalkylene oxide).

[0172] Hereinafter, the water-insoluble fibrous organic matter and the high-molecular-weight polyalkylene oxide are collectively referred to as a specific polymer material.

[0173] [Water-insoluble fibrous organic matter]

[0174] The water-insoluble fibrous organic matter refers to a water-insoluble organic matter that is a thin, long, linear solid with a linear diameter of 1 nm or more.

[0175] The type of the fibrous organic material is not particularly limited, but resin fibers, plant fibers, and the like are preferred.

[0176] Furthermore, the water-insoluble fibrous organic matter means that the amount of the fibrous organic matter dissolved in 100 parts by mass of water at 25°C is less than 1 part by mass.

[0177] Examples of materials constituting the water-insoluble fibrous organic matter include plant fibers (specifically, cellulose fibers) and aramid fibers.

[0178] From the viewpoint of suppressing the precipitation or floating of particles, the fiber diameter of the water-insoluble fibrous organic matter is preferably, for example, 1 nm or more and 500 nm or less.

[0179] From the viewpoint of suppressing the precipitation or floating of particles, the fiber length of the water-insoluble fibrous organic matter is preferably, for example, 10 nm or more and 10,000 nm or less.

[0180] The fiber diameter and fiber length of the water-insoluble fibrous organic matter can be measured by the following method.

[0181] The fiber length was measured using a scanning electron microscope (SEM) for 20 fibers and the average value was obtained. The fiber diameter was measured using one end of each fiber as a unit for the maximum diameter of 20 fibers and the average value was obtained.

[0182] The water-insoluble fibrous organic material is obtained by fibrillating water-insoluble fibers as a raw material.

[0183] Here, microfibrillation refers to a state in which a raw material fiber is broken into its constituent microfibrils (fine fibers) or a state in which microfibrils in the raw material fiber appear on the fiber surface and become fluffy.

[0184] Microfibrillation uses an external force such as a mechanical shear force (for example, a high-pressure homogenizer), and the raw material fibers are finely divided to the above-mentioned fiber diameter by this external force.

[0185] That is, the water-insoluble fibrous organic matter used in the present embodiment can also be called microfibrillated fibers.

[0186] As the water-insoluble fibrous organic substance, a commercially available product can be used.

[0187] Examples of commercially available water-insoluble fibrous organic substances include Serish (microfibrous cellulose) and Tiara (microfibrous aramid) manufactured by Daicel Miraizu Ltd. and BiNFi-s (binfis, microfibrous cellulose) manufactured by Sugino Machine Limited.

[0188] [Polyalkylene oxide having a viscosity average molecular weight of 5,000,000 or more]

[0189] Polyalkylene oxide refers to a m H 2m O) n Here, m and n each independently represent an integer greater than 2.

[0190] As m, for example, it is preferably 2 or more and 6 or less, and from the viewpoint of availability, for example, it is more preferably 2 or more and 3 or less. From the viewpoint of the formability of the network structure and from the viewpoint of high affinity with the particle surface and easy obstruction of the movement of the particles, for example, it is particularly preferably 2. That is, from the viewpoint of high affinity with the particle surface and easy obstruction of the movement of the particles compared to polypropylene oxide, polyalkylene oxide, for example, polyethylene oxide is preferable.

[0191] Furthermore, n may be any integer that satisfies the viscosity average molecular weight of 5,000,000 or more.

[0192] High molecular weight polyalkylene oxides can be obtained by ring-opening polymerization of cyclic ethers such as ethylene oxide, propylene oxide, and oxetane.

[0193] Furthermore, the terminal of the high molecular weight polyalkylene oxide may be modified within a range that does not impair the effect of suppressing the precipitation or floating of particles.

[0194] The viscosity average molecular weight of the high molecular weight polyalkylene oxide is preferably 6 million to 11 million, more preferably 7 million to 11 million, and even more preferably 8 million to 10 million, from the viewpoint of suppressing particle sedimentation or floating and from the viewpoint of availability.

[0195] The viscosity average molecular weight of the high molecular weight polyalkylene oxide can be measured by the following method.

[0196] 1 g of the sample was uniformly dissolved in 100 cm2 of dichloromethane. 3 , the specific viscosity ηsp was measured by Ubbelohde viscometer at 25℃, and ηsp / c=〔η〕+0.45〔η〕 2 c (where c is the concentration [g / cm 3 ]) Determine the limiting viscosity [η] (cm3 / g), and the viscosity average molecular weight was determined by the following formula (I) given by H. Schnell.

[0197] Formula (I): [η]=1.23×10 -4 Mv 0.83

[0198] As the high molecular weight polyalkylene oxide, a commercially available product can be used.

[0199] Examples of commercially available high-molecular-weight polyalkylene oxides include PEO (registered trademark) series manufactured by SUMITOMO SEIKA CHEMICALS CO., LTD. (specifically, PEO-29, PEO-27, etc.), and Alcox series manufactured by Meisei Chemical Works, Ltd. (specifically, E-300, etc.).

[0200] In the aqueous composition of this embodiment, the specific polymer material may be used alone or in combination of two or more. Specifically, the specific polymer material may be used alone or in combination of two or more fibrous organic substances, may be used alone or in combination of two or more high molecular weight polyalkylene oxides, or may be used in combination of one or more fibrous organic substances and one or more high molecular weight polyalkylene oxides.

[0201] The content of the specific polymer material is, for example, preferably 0.5 mass % to 8.0 mass %, more preferably 1.0 mass % to 3.0 mass %, and further preferably 1.5 mass % to 2.0 mass % relative to the polyimide precursor.

[0202] The specific polymer material is a component that is difficult to remove during the coating and drying steps in the production process of the polyimide film, and therefore, for example, is preferably used in a small amount.

[0203] Furthermore, in the aqueous composition involved in this embodiment, from the viewpoint of suppressing the precipitation or floating of particles, the content of the specific polymer material is, for example, preferably from 0.05 mass % to 15.0 mass % relative to the particles, more preferably from 0.1 mass % to 2.0 mass %, and even more preferably from 0.2 mass % to 1.5 mass %.

[0204] 〔water〕

[0205] The aqueous composition according to this embodiment contains water.

[0206] Examples of water include distilled water, ion-exchanged water, deionized water, ultrafiltered water, and pure water.

[0207] The water content is, for example, preferably 70% by mass or more, more preferably 75% by mass or more, further preferably 80% by mass or more, and particularly preferably 85% by mass or more, relative to the total mass of the aqueous composition according to this embodiment.

[0208] The upper limit of the water content may be determined according to the application of the polyimide film, and is, for example, 90% by mass.

[0209] In the aqueous composition according to the present embodiment, the content of water relative to the aqueous solvent containing water is, for example, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more.

[0210] Here, the term "aqueous solvent" refers to a general term for water and a water-soluble organic solvent. Water-soluble means that the target substance dissolves in water at 1% by mass or more at 25°C.

[0211] [Other ingredients]

[0212] In addition to the above-mentioned polyimide precursor, particles, specific polymer material, and water, the aqueous composition according to the present embodiment may further contain other components as needed.

[0213] (Water-soluble organic solvent)

[0214] -Organic amine compounds-

[0215] The aqueous composition according to the present embodiment preferably contains, as one of the water-soluble organic solvents, for example, an organic amine compound.

[0216] The organic amine compound is a compound that converts the polyimide precursor (its carboxyl group) into an amine salt to improve its solubility in the aqueous solvent and also acts as an imidization accelerator. Specifically, the organic amine compound is preferably an amine compound with a molecular weight of 170 or less. The organic amine compound is a compound other than the diamine compound that serves as the raw material of the polyimide precursor.

[0217] The organic amine compound is preferably a water-soluble compound, for example. Water-soluble means that the target substance dissolves in water at 1% by mass or more at 25°C.

[0218] Examples of the organic amine compound include primary amine compounds, secondary amine compounds, and tertiary amine compounds.

[0219] Among them, the organic amine compound is preferably at least one selected from the group consisting of secondary amine compounds and tertiary amine compounds (particularly, a tertiary amine compound). If a tertiary amine compound or a secondary amine compound (particularly, a tertiary amine compound) is used as the organic amine compound, the solubility of the polyimide precursor in the solvent is more easily improved, the film forming properties are easily improved, and the storage stability of the aqueous composition involved in this embodiment is easily improved.

[0220] Furthermore, as organic amine compounds, in addition to monoamine compounds, divalent or higher polyamine compounds can also be mentioned. If a divalent or higher polyamine compound is used, a pseudo crosslinked structure is easily formed between molecules of the polyimide precursor, and the storage stability of the aqueous composition involved in this embodiment is easily improved.

[0221] Examples of the primary amine compound include methylamine, ethylamine, n-propylamine, isopropylamine, 2-ethanolamine, and 2-amino-2-methyl-1-propanol.

[0222] Examples of the secondary amine compound include dimethylamine, 2-(methylamino)ethanol, 2-(ethylamino)ethanol, and morpholino.

[0223] Examples of the tertiary amine compound include 2-dimethylaminoethanol, 2-diethylaminoethanol, 2-dimethylaminopropanol, pyridine, triethylamine, picolinate, N-methylmorpholine (e.g., N-methylmorpholine, N-ethylmorpholine), 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, and N-alkylpiperidines (e.g., N-methylpiperidine, N-ethylpiperidine).

[0224] Among them, for example, tertiary amine compounds are preferred, N-alkylmorpholines are more preferred, and N-methylmorpholine is particularly preferred.

[0225] The organic amine compounds may be used alone or in combination of two or more.

[0226] The content of the organic amine compound is, for example, preferably 40% by mass or more and 100% by mass or less, more preferably 45% by mass or more and 90% by mass or less, and further preferably 50% by mass or more and 80% by mass or less, relative to the polyimide precursor.

[0227] -Other water-soluble organic solvents-

[0228] The aqueous composition according to the present embodiment may contain other water-soluble organic solvents (excluding the above-mentioned organic amine compounds) as needed.

[0229] Other water-soluble organic solvents include aprotic polar solvents, water-soluble ether solvents, water-soluble ketone solvents, water-soluble alcohol solvents, and the like.

[0230] Examples of aprotic polar solvents include N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), 1,3-dimethyl-2-imidazolidinone (DMI), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide (DEAc), dimethyl sulfoxide (DMSO), hexamethylenephosphonamide (HMPA), N-methylcaprolactam, N-acetyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone.

[0231] The water-soluble ether solvent is a water-soluble solvent having an ether bond in one molecule.

[0232] Examples of the water-soluble ether solvent include tetrahydrofuran (THF), dioxane, trioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether. Among them, tetrahydrofuran and dioxane are preferred as water-soluble ether solvents.

[0233] The water-soluble ketone solvent is a water-soluble solvent having a ketone group in one molecule.

[0234] Examples of the water-soluble ketone solvent include acetone, methyl ethyl ketone, and cyclohexanone. Among these, acetone is preferred as the water-soluble ketone solvent.

[0235] The water-soluble alcohol solvent is a water-soluble solvent having an alcoholic hydroxyl group in one molecule.

[0236] Examples of the water-soluble alcohol solvent include methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, monoalkyl ethers of ethylene glycol, propylene glycol, monoalkyl ethers of propylene glycol, diethylene glycol, monoalkyl ethers of diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, glycerol, 2-ethyl-2-hydroxymethyl-1,3-propanediol, and 1,2,6-hexanetriol. Among these, methanol, ethanol, 2-propanol, ethylene glycol, monoalkyl ethers of ethylene glycol, propylene glycol, monoalkyl ethers of propylene glycol, diethylene glycol, and monoalkyl ethers of diethylene glycol are preferred as the water-soluble alcohol solvent.

[0237] The other water-soluble organic solvents may be used alone or in combination of two or more.

[0238] The boiling point of the other water-soluble organic solvent is preferably, for example, 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. When the boiling point of the water-soluble organic solvent is within the above range, the water-soluble organic solvent is less likely to remain in the polyimide film, and a polyimide film with high mechanical strength is easily obtained.

[0239] The content of the aqueous solvent containing water is, for example, preferably 75% by mass or more, and more preferably 80% by mass or more, relative to the total mass of the aqueous composition according to the present embodiment.

[0240] (Other additives)

[0241] The aqueous composition according to this embodiment may contain a catalyst for promoting the imidization reaction, a leveling material for improving the film forming quality, and the like.

[0242] As the catalyst for accelerating the imidization reaction, a dehydrating agent such as acid anhydride, an acid catalyst such as a phenol derivative, a sulfonic acid derivative, or a benzoic acid derivative can be used.

[0243] Furthermore, the aqueous composition according to the present embodiment may contain a conductive material (conductive material (e.g., a volume resistivity of less than 10) as a conductive agent added to impart conductivity) depending on the intended use of the polyimide film. 7 Ω·cm) or semi-conductive materials (e.g., volume resistivity 10 7 Ω·cm or more and 10 13 Ω·cm or less)).

[0244] Examples of the conductive agent include carbon black (eg, acidic carbon black at pH 5.0 or less); metals (eg, aluminum or nickel); metal oxides (eg, yttrium oxide, tin oxide); and ion conductive substances (eg, potassium titanate, LiCl).

[0245] These conductive materials may be used alone or in combination of two or more.

[0246] Furthermore, the aqueous composition according to this embodiment may contain LiCoO 2 , LiMn 2 O, or the like used as an electrode of a lithium ion battery.

[0247] 〔Physical properties〕

[0248] The viscosity of the aqueous composition according to the present embodiment at 25° C. is, for example, preferably from 1 Pa·s to 200 Pa·s, and more preferably from 5 Pa·s to 180 Pa·s.

[0249] The aqueous composition according to the present embodiment can suppress the precipitation or floating of particles even if it has the above-mentioned viscosity.

[0250] The viscosity of the aqueous composition according to the present embodiment at 25° C. is measured using an E-type viscometer (for example, TVE-22H, TOKI SANGYO CO., LTD).

[0251] Regarding the aqueous composition involved in this embodiment, from the viewpoint of achieving the above-mentioned viscosity at 25°C, for example, the total content of solid components is preferably 1 mass % or more and 35 mass % or less, more preferably 3 mass % or more and 30 mass % or less, and even more preferably 5 mass % or more and 25 mass % or less, relative to the total mass of the aqueous composition involved in this embodiment.

[0252] <Method for Producing Polyimide Membrane and Method for Producing Porous Polyimide Membrane>

[0253] The method for manufacturing the polyimide film involved in the present embodiment has the following steps: a step of applying the aqueous composition involved in the present embodiment described above on a substrate to form a coating film (also referred to as the first step); a step of drying the coating film to form a coating film containing a specific polymer material, a polyimide precursor and particles (also referred to as the second step); and a step of imidizing the polyimide precursor contained in the coating film to form a polyimide film (also referred to as the third step).

[0254] The method for manufacturing the porous polyimide film involved in the present embodiment has the following steps: a step of applying the aqueous composition involved in the present embodiment described above on a substrate to form a coating film (the first step); a step of drying the coating film to form a coating film containing a specific polymer material, a polyimide precursor and particles (the second step); a step of imidizing the polyimide precursor contained in the coating film to form a polyimide film (the third step); and a step of removing particles from the coating film or the polyimide film (also referred to as the fourth step).

[0255] The first step, the second step, and the third step are common steps and are therefore described together below.

[0256] Hereinafter, an example of a method for producing a porous polyimide membrane according to the present embodiment will be described with reference to the drawings.

[0257] Figure 1 Schematic diagram showing the structure of a porous polyimide membrane obtained by the method for producing a porous polyimide membrane according to the present embodiment.

[0258] Figure 1 In the figure, 31 denotes a substrate, 51 denotes a peeling layer, 10A denotes a hole, and 10 denotes a porous polyimide film.

[0259] [Step 1]

[0260] In the first step, the aqueous composition according to the present embodiment described above (ie, the aqueous composition containing the specific polymer material, the polyimide precursor, the particles, and water) is applied onto the substrate to form a coating film.

[0261] [Method for preparing aqueous composition]

[0262] In the first step, first, the aqueous composition according to the present embodiment is prepared.

[0263] In the following, in the first step, a case where a high molecular weight polyalkylene oxide is used as the specific polymer material will be described as an example, but the same method can be used also when a water-insoluble fibrous organic substance is used as the specific polymer material.

[0264] There are no particular limitations on the method for preparing the aqueous composition used in the first step (ie, the aqueous composition according to the present embodiment).

[0265] First, a high molecular weight polyalkylene oxide is dispersed or dissolved in an aqueous solvent to prepare a solution containing the high molecular weight polyalkylene oxide.

[0266] In a dispersion of particles, tetracarboxylic dianhydride and a diamine compound are polymerized to produce a resin (polyimide precursor), and then the above-mentioned solution containing a high molecular weight polyalkylene oxide is added thereto to prepare an aqueous composition.

[0267] Furthermore, when the particles are resin particles, the resin particles can be produced in an aqueous solvent to obtain the above-mentioned dispersion.

[0268] Specific examples of the method for preparing the aqueous composition include the following method.

[0269] First, a high molecular weight polyalkylene oxide is dispersed or dissolved in an aqueous solvent to obtain a solution containing the high molecular weight polyalkylene oxide. Separately, resin particles are produced in the aqueous solvent to obtain a resin particle dispersion. Next, tetracarboxylic dianhydride and a diamine compound are polymerized in the resin particle dispersion in the presence of an organic amine compound to produce a resin (polyimide precursor), to which the solution containing the high molecular weight polyalkylene oxide is added to obtain a mixed solution. The solution containing the high molecular weight polyalkylene oxide is then added to the resulting mixed solution to form an aqueous composition.

[0270] Another example of a method for preparing an aqueous composition includes a method in which a solution containing a high molecular weight polyalkylene oxide is added to a dispersion in which particles are dispersed to prepare a mixed solution, and a polyimide precursor is synthesized in the mixed solution to prepare the aqueous composition; a method in which a solution obtained by dissolving a polyimide precursor in an aqueous solvent, dried resin particles, and the solution containing the high molecular weight polyalkylene oxide are mixed; a method in which a solution obtained by dissolving a polyimide precursor in an aqueous solvent, a dispersion in which resin particles are preliminarily dispersed in an aqueous solvent, and the solution containing the high molecular weight polyalkylene oxide are mixed.

[0271] When preparing an aqueous composition, a solution containing a polyimide precursor can be used, in which a resin (polyimide precursor) is produced by polymerizing tetracarboxylic dianhydride and a diamine compound in an organic solvent such as an aprotic polar solvent (for example, N-methylpyrrolidone (NMP)), and then adding the resulting mixture to an aqueous solvent to precipitate the resin (polyimide precursor).

[0272] [Coating of polyimide precursor solution]

[0273] In the first step, the aqueous composition obtained by the above-described method is applied to a substrate to form a coating film. The resulting coating film comprises a specific polymer material, a polyimide precursor, particles, and an aqueous solvent. Furthermore, the particles in the coating film are distributed in a state where aggregation is suppressed.

[0274] As a substrate for coating an aqueous composition ( Figure 1 The substrate 31 in the figure is not particularly limited.

[0275] Examples of the substrate include substrates made of resins such as polystyrene and polyethylene terephthalate; substrates made of glass; substrates made of ceramics; metal substrates such as iron and stainless steel (SUS); and composite material substrates obtained by combining these materials.

[0276] Furthermore, as needed, a release layer ( Figure 1 Furthermore, it is also effective to roughen the surface of the substrate to the size of the particle size and promote exposure of the particles on the substrate contact surface.

[0277] The method for applying the aqueous composition to the substrate is not particularly limited, and examples thereof include various methods such as spray coating, spin coating, roll coating, bar coating, slot die coating, and inkjet coating.

[0278] [Second step]

[0279] In the second step, the coating film obtained in the first step is dried to form a coating film containing the specific polymer material, the polyimide precursor, and the particles.

[0280] The method for drying the coating film formed on the substrate is not particularly limited, and various methods such as heat drying, natural drying, and vacuum drying may be mentioned.

[0281] More specifically, for example, the coating is preferably dried to form the coating so that the solvent remaining in the coating becomes 50% or less (for example, preferably 30% or less) relative to the solid content of the coating.

[0282] In the second step, during the process of drying to form the film, a treatment for exposing the particles may be performed. By performing the treatment for exposing the particles, the porosity of the porous polyimide film can be increased.

[0283] Specific examples of the treatment for exposing particles include the following methods.

[0284] In the process of drying the coating to form a film comprising a specific polymer material, a polyimide precursor, and particles, as described above, the polyimide precursor in the formed film is in a water-soluble state. Therefore, the film can be exposed from the film by, for example, wiping it with water or immersing it in water. Specifically, for example, a process is performed to expose the particles by wiping the film surface with water, thereby removing the polyimide precursor (and solvent) covering the particles. As a result, the particles are exposed on the treated film surface.

[0285] In particular, when a film in which no particles are buried is formed, it is preferable to employ, for example, the above-mentioned treatment as a treatment for exposing the particles buried in the film.

[0286] [Step 3]

[0287] In the third step, the polyimide precursor contained in the film obtained in the second step is imidized to form a polyimide film.

[0288] In the third step, specifically, the film obtained in the second step is heated and imidized to form a polyimide film.

[0289] Furthermore, as the imidization proceeds, the imidization rate increases, and the polyimide film becomes less soluble in an organic solvent.

[0290] [Imidization]

[0291] In the third step, heating for imidating the polyimide precursor in the film is performed by, for example, multi-stage heating in two or more stages.

[0292] For example, when the particles are resin particles and heating is performed in two stages, specifically, the following heating conditions are employed:

[0293] The heating conditions for the first stage are preferably a temperature that maintains the shape of the resin particles. Specifically, a temperature range of 50°C to 150°C is preferred, and a range of 60°C to 140°C is more preferred. Furthermore, the heating time is preferably in the range of 10 minutes to 60 minutes, for example. For example, the higher the heating temperature, the shorter the heating time.

[0294] The heating conditions for the second stage include, for example, heating at 150°C to 450°C (preferably 200°C to 400°C) for 20 minutes to 120 minutes. By setting the heating conditions within this range, the imidization reaction proceeds further. During the heating reaction, the temperature is preferably increased in stages or at a constant rate until the final heating temperature is reached.

[0295] In addition, the heating conditions are not limited to the above-mentioned two-stage heating method, and for example, a method of heating in one stage can be adopted. When the method of heating in one stage is adopted, for example, imidization can be completed only under the heating conditions shown in the above-mentioned second stage.

[0296] [Step 4]

[0297] In the fourth step, particles are removed from the film obtained in the second step or the polyimide film obtained in the third step. After the fourth step, the particle portion becomes a void ( Figure 1 The porous polyimide membrane ( Figure 1 The porous polyimide membrane 10).

[0298] Specifically, in the fourth step, the particles can be removed while the film is heated and the polyimide precursor is imidized in the film obtained in the second step, or they can be removed from the polyimide film after imidization in the third step.

[0299] Examples of methods for removing particles from the film include a method of removing particles (preferably resin particles) by decomposing them by heating, a method of removing the particles by dissolving them in an organic solvent, and a method of removing resin particles by decomposition using laser light or the like.

[0300] When a method of decomposing and removing particles by heating is used, the third step described above can be combined. That is, the particles can be removed by heating in the third step.

[0301] These methods may be performed by only one method or by using two or more methods simultaneously.

[0302] In the fourth step, when the resin particles are decomposed and removed by heating, heating is preferably performed at a temperature equal to or higher than the melting temperature of the resin particles, for example.

[0303] The resin particles can be removed under the heating conditions for imidization in the third step.

[0304] When a method of removing the resin particles by dissolving them in an organic solvent is used, specifically, a method of bringing the film or polyimide film into contact with an organic solvent to dissolve and remove the resin particles in the organic solvent is exemplified.

[0305] Examples of methods for bringing a film or polyimide film into contact with an organic solvent include immersing the film or polyimide film in an organic solvent, applying an organic solvent on the film or polyimide film, and bringing the film or polyimide film into contact with organic solvent vapor.

[0306] The organic solvent for dissolving the resin particles is not particularly limited as long as it does not dissolve the polyimide precursor and the polyimide but can dissolve the resin particles.

[0307] When the particles are resin particles, the organic solvent that can be used includes, for example, ethers such as tetrahydrofuran and 1,4-dioxane; aromatics such as benzene and toluene; ketones such as acetone; and esters such as ethyl acetate.

[0308] Among these, ethers such as tetrahydrofuran and 1,4-dioxane and aromatics such as benzene and toluene are preferred, and tetrahydrofuran and toluene are more preferably used.

[0309] When removing particles by dissolving them in an organic solvent, the removal is preferably performed when the imidization ratio of the polyimide precursor in the film is 10% or higher, for example, from the viewpoint of particle removal and suppression of dissolution of the film itself in the organic solvent.

[0310] As a method for making the imidization ratio 10% or more, the heating conditions in the first stage in the third step can be mentioned, for example.

[0311] That is, for example, it is preferred that after the first stage heating in the third step, the particles in the coating be dissolved in an organic solvent and removed.

[0312] Here, the imidization ratio of the polyimide precursor will be described.

[0313] Examples of the polyimide precursor that is partially imidized include precursors having a structure of a repeating unit represented by the following general formula (I-1), the following general formula (I-2), and the following general formula (I-3).

[0314] [Chemical Formula 2]

[0315]

[0316] In general formulae (I-1), (I-2), and (I-3), A represents a tetravalent organic group, and B represents a divalent organic group. l represents an integer greater than or equal to 1, and m and n each independently represent an integer greater than or equal to 0.

[0317] In addition, the definitions of A and B are the same as those of A and B in the general formula (I) described later.

[0318] The imidization rate of a polyimide precursor is expressed as the ratio of the number of imide ring-closed bonding sites (2n + m) to the total number of bonding sites (2l + 2m + 2n) in the bonding sites of the polyimide precursor (the reaction sites between tetracarboxylic dianhydride and diamine compound). Specifically, the imidization rate of a polyimide precursor is expressed as "(2n + m) / (2l + 2m + 2n)."

[0319] In addition, the imidization ratio (the value of "(2n+m) / (2l+2m+2n)") of the polyimide precursor was measured by the following method.

[0320] -Measurement of the Imidization Ratio of Polyimide Precursor-

[0321] Preparation of polyimide precursor samples

[0322] (i) A polyimide precursor solution to be measured is applied to a silicone wafer in a film thickness ranging from 1 μm to 10 μm to prepare a coating film sample.

[0323] (ii) The coating sample is immersed in tetrahydrofuran (THF) for 20 minutes to replace the solvent in the coating sample with tetrahydrofuran (THF). The immersion solvent is not limited to THF and can be selected from solvents that do not dissolve the polyimide precursor and are miscible with the solvent components contained in the polyimide precursor solution. Specifically, alcohol solvents such as methanol and ethanol, and ether compounds such as dioxane can be used.

[0324] (iii) The coating sample was removed from the THF, and THF adhering to the surface of the coating sample was removed by blowing N2 gas. The coating sample was dried under reduced pressure of 10 mmHg or less at a temperature within a range of 5°C to 25°C for 12 hours or more to prepare a polyimide precursor sample.

[0325] Preparation of 100% imidization standard sample

[0326] (iv) In the same manner as in the above-mentioned (i), the polyimide precursor solution to be measured is applied onto a silicone wafer to prepare a coating film sample.

[0327] (v) The coating film sample was heated at 380° C. for 60 minutes to carry out an imidization reaction, thereby preparing a 100% imidization standard sample.

[0328] Measurement and analysis

[0329] (vi) The infrared absorption spectra of the 100% imidization standard sample and the polyimide precursor sample were measured using a Fourier transform infrared spectrophotometer (FT-730 manufactured by HORIBA, Ltd.). The 1500 cm-1 wavelength of the 100% imidization standard sample was determined. -1 The absorption peaks (Ab'(1500cm) derived from aromatic rings are nearby. -1 )) and 1780cm -1 The absorption peak (Ab'(1780cm) derived from the imide bond is near -1 ) ratio I'(100).

[0330] (vii) Similarly, the polyimide precursor sample was measured to obtain the 1500 cm -1 The absorption peaks (Ab(1500cm) derived from aromatic rings are nearby. -1 )) and 1780cm -1 The absorption peak (Ab(1780cm) derived from the imide bond is near -1 )) of the ratio I(x).

[0331] Then, the imidization ratio of the polyimide precursor was calculated based on the following formula using the measured absorption peaks I'(100) and I(x).

[0332] Formula: Imidization ratio of polyimide precursor = I(x) / I'(100)

[0333] Formula: I'(100)=(Ab'(1780cm -1 )) / (Ab'(1500cm -1 ))

[0334] Formula: I(x)=(Ab(1780cm -1 )) / (Ab(1500cm -1 ))

[0335] The imidization rate of the polyimide precursor is also applicable to the imidization rate of aromatic polyimide precursors. When measuring the imidization rate of aliphatic polyimide precursors, the peak derived from the structure that does not change before and after the imidization reaction is used as the internal standard peak instead of the absorption peak of the aromatic ring.

[0336] The substrate used in the first step may be peeled from the film after the second step, may be peeled from the polyimide film after the third step, or may be peeled from the obtained porous polyimide film after the fourth step.

[0337] A polyimide membrane or a porous polyimide membrane is produced as described above.

[0338] [Average film thickness of polyimide film or porous polyimide film]

[0339] The average film thickness of the polyimide film or porous polyimide film produced using the aqueous composition according to the present embodiment is not particularly limited and can be selected according to the intended use.

[0340] For example, the average thickness of the porous polyimide membrane may be 10 μm or more and 1000 μm or less. The average thickness of the polyimide membrane or porous polyimide membrane may be 20 μm or more, or 30 μm or more, and the average thickness of the polyimide membrane or porous polyimide membrane may be 500 μm or less, or 400 μm or less.

[0341] When the film thickness is as described above, for example, a separator for a secondary battery described later is preferable.

[0342] The average film thickness of the polyimide film or porous polyimide film in the present embodiment is calculated by measuring the film thickness of the polyimide film at five locations using an eddy current film thickness meter CTR-1500E manufactured by Sanko Electronics Co., Ltd. and calculating the arithmetic average thereof.

[0343] [Applications of porous polyimide membranes]

[0344] The porous polyimide membrane produced using the aqueous composition according to the present embodiment may be suitably used in, for example, filters or secondary batteries.

[0345] In particular, the porous polyimide film is preferably used as a separator for lithium ion secondary batteries, for example.

[0346] <Lithium-ion secondary battery>

[0347] Regarding a lithium ion secondary battery having a porous polyimide membrane produced using the aqueous composition according to this embodiment as a separator for a lithium ion secondary battery, refer to Figure 2 Provide explanation.

[0348] Figure 2 It is a partial cross-sectional schematic diagram showing an example of a lithium ion secondary battery to which the separator for lithium ion secondary batteries is applied.

[0349] like Figure 2As shown, the lithium-ion secondary battery 100 includes a positive electrode active material layer 110, a separator layer 510, and a negative electrode active material layer 310 housed within an exterior member (not shown). The positive electrode active material layer 110 is provided on a positive electrode current collector 130, and the negative electrode active material layer 310 is provided on a negative electrode current collector 330. The separator layer 510 is provided to separate the positive electrode active material layer 110 from the negative electrode active material layer 310 and is arranged between the positive electrode active material layer 110 and the negative electrode active material layer 310 so that the positive electrode active material layer 110 and the negative electrode active material layer 310 face each other. The separator layer 510 includes a separator 511 and an electrolyte 513 filled within the pores of the separator 511. A porous polyimide film manufactured using the aqueous composition according to this embodiment is applied to the separator 511. The positive electrode current collector 130 and the negative electrode current collector 330 are components provided as needed.

[0350] (Positive Electrode Current Collector 130 and Negative Electrode Current Collector 330)

[0351] The materials used for the positive electrode current collector 130 and the negative electrode current collector 330 are not particularly limited as long as they are known conductive materials. For example, metals such as aluminum, copper, nickel, and titanium can be used.

[0352] (Positive Electrode Active Material Layer 110)

[0353] The positive electrode active material layer 110 is a layer containing a positive electrode active material. As needed, it may contain known additives such as a conductive additive and a binder resin. There is no particular limitation on the positive electrode active material, and known positive electrode active materials can be used. For example, lithium-containing composite oxides (LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiFeMnO4, LiV2O5, etc.), lithium-containing phosphates (LiFePO4, LiCoPO4, LiMnPO4 and LiNiPO4, etc.), conductive polymers (polyacetylene, polyaniline, polypyrrole, polythiophene, etc.), etc. can be mentioned. The positive electrode active material can be used alone or in combination of two or more.

[0354] (Negative Electrode Active Material Layer 310)

[0355] The negative electrode active material layer 310 is a layer containing a negative electrode active material. If necessary, it may contain well-known additives such as a binder resin. There is no particular limitation on the negative electrode active material, and well-known positive electrode active materials can be used. For example, carbon materials (graphite (natural graphite, artificial graphite), carbon nanotubes, graphitized carbon, low-temperature sintered carbon, etc.), metals (aluminum, silicon, zirconium, titanium, etc.), metal oxides (tin dioxide, lithium titanate, etc.), etc. can be mentioned. One type of negative electrode active material can be used alone, or two or more types can be used at the same time.

[0356] (Electrolyte 513)

[0357] The electrolyte solution 513 may be, for example, a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent.

[0358] Examples of the electrolyte include lithium salt electrolytes (LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiN(FSO2)2, LiN(CF3SO2)2, LiN(C2F5SO2), LiC(CF3SO2)3, etc.) One electrolyte may be used alone, or two or more electrolytes may be used simultaneously.

[0359] Examples of the non-aqueous solvent include cyclic carbonates (ethylene carbonate, propylene carbonate, butylene carbonate, etc.), chain carbonates (diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, etc.), etc. The non-aqueous solvent may be used alone or in combination of two or more.

[0360] (Method for Manufacturing Lithium-Ion Secondary Battery 100)

[0361] An example of a method for manufacturing the lithium-ion secondary battery 100 will be described.

[0362] A coating liquid for forming the positive electrode active material layer 110 containing a positive electrode active material is applied to the positive electrode current collector 130 and dried to obtain a positive electrode including the positive electrode active material layer 110 provided on the positive electrode current collector 130 .

[0363] Similarly, a coating solution for forming the negative active material layer 310 containing the negative active material is applied to the negative current collector 330 and dried to obtain a negative electrode having the negative active material layer 310 provided on the negative current collector 330. The positive electrode and the negative electrode can be compressed as needed.

[0364] Next, a separator 511 is placed between the positive electrode active material layer 110 and the negative electrode active material layer 310 so that they face each other, thereby forming a laminated structure. The laminated structure comprises the positive electrode (positive electrode current collector 130, positive electrode active material layer 110), separator layer 510, and negative electrode (negative electrode active material layer 310, negative electrode current collector 330) stacked in this order. Compression processing can be performed as needed.

[0365] Next, after the stacked structure is housed in an exterior member, the electrolyte 513 is injected into the stacked structure. The injected electrolyte 513 also permeates the pores of the separator 511.

[0366] In this manner, the lithium ion secondary battery 100 is obtained.

[0367] <All-solid-state battery>

[0368] Next, an all-solid-state battery to which a porous polyimide membrane produced using the aqueous composition according to this embodiment is applied will be described. Figure 3 Provide explanation.

[0369] Figure 3 FIG. 1 is a partial cross-sectional schematic diagram showing an example of an all-solid-state battery according to this embodiment. Figure 3 As shown, the all-solid-state battery 200 includes a positive electrode active material layer 220, a solid electrolyte layer 620, and a negative electrode active material layer 420 housed within an exterior member (not shown). The positive electrode active material layer 220 is disposed on a positive electrode current collector 240, and the negative electrode active material layer 420 is disposed on a negative electrode current collector 440. The solid electrolyte layer 620 is disposed between the positive electrode active material layer 220 and the negative electrode active material layer 420, with the positive electrode active material layer 220 and the negative electrode active material layer 420 facing each other. The solid electrolyte layer 620 includes a solid electrolyte 624 and a retainer 622 that retains the solid electrolyte 624. The pores of the retainer 622 are filled with the solid electrolyte 624. The retainer 622 that retains the solid electrolyte 624 is preferably a porous polyimide membrane manufactured using the aqueous composition according to this embodiment. The positive electrode current collector 240 and the negative electrode current collector 440 are components provided as needed.

[0370] (Positive Electrode Current Collector 240 and Negative Electrode Current Collector 440)

[0371] Examples of materials used for the positive electrode current collector 240 and the negative electrode current collector 440 include the same materials as those described in the above-mentioned lithium ion secondary battery.

[0372] (Positive Electrode Active Material Layer 220 and Negative Electrode Active Material Layer 420)

[0373] Examples of materials used for the positive electrode active material layer 220 and the negative electrode active material layer 420 include the same materials as those described in the above-mentioned lithium ion secondary battery.

[0374] (Solid Electrolyte 624)

[0375] The solid electrolyte 624 is not particularly limited, and a known solid electrolyte may be used, for example, a polymer solid electrolyte, an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte, a nitride solid electrolyte, and the like.

[0376] Examples of polymer solid electrolytes include fluororesins (such as single polymers of polyvinylidene fluoride, polyhexafluoropropylene, and polytetrafluoroethylene, and copolymers containing these as constituent units), polyethylene oxide resins, polyacrylonitrile resins, and polyacrylate resins. For example, sulfide solid electrolytes are preferred due to their excellent lithium ion conductivity. From a similar perspective, sulfide solid electrolytes containing at least one of sulfur, lithium, and phosphorus as constituent elements are preferred.

[0377] Examples of the oxide solid electrolyte include oxide solid electrolyte particles containing lithium, such as Li2O-B2O3-P2O5 and Li2O-SiO2.

[0378] Examples of sulfide solid electrolytes include those containing at least one of sulfur, lithium, and phosphorus as a constituent element. Examples include 8Li2O·67Li2S·25P2S5, Li2S, P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li3PO4-P2S5, LiI-Li2S-P2O5, and LiI-Li2S-B2S3.

[0379] Examples of the halide solid electrolyte include LiI and the like.

[0380] Examples of nitride solid electrolytes include Li 3 N and the like.

[0381] (Method for Manufacturing All-Solid-State Battery 200)

[0382] An example of a method for manufacturing the all-solid-state battery 200 will be described.

[0383] A coating liquid for forming the positive electrode active material layer 220 containing a positive electrode active material is applied to the positive electrode current collector 240 and dried to obtain a positive electrode including the positive electrode active material layer 220 provided on the positive electrode current collector 240 .

[0384] Similarly, a coating liquid for forming the negative electrode active material layer 420 containing the negative electrode active material is applied to the negative electrode current collector 440 and dried to obtain a negative electrode including the negative electrode active material layer 420 provided on the negative electrode current collector 440 .

[0385] The positive electrode and the negative electrode can be compressed as needed.

[0386] Next, a coating liquid containing the solid electrolyte 624 for forming the solid electrolyte layer 620 is applied onto the substrate and dried to form a layered solid electrolyte.

[0387] Next, a polyimide film (a porous polyimide film produced using the aqueous composition of this embodiment) serving as a retainer 622 and a layered solid electrolyte 624 are stacked on the positive electrode active material layer 220 of the positive electrode, as a material for forming the solid electrolyte layer 620. Furthermore, the negative electrode is stacked on the material for forming the solid electrolyte layer 620, with the negative electrode active material layer 420 facing the positive electrode active material layer 220, to form a laminated structure. The laminated structure comprises a positive electrode (positive electrode current collector 240, positive electrode active material layer 220), a solid electrolyte layer 620, and a negative electrode (negative electrode active material layer 420, negative electrode current collector 440) stacked in this order.

[0388] Next, the stacked structure is subjected to compression processing, and the pores of the polyimide film serving as the support 622 are impregnated with the solid electrolyte 624 to support the solid electrolyte 624 .

[0389] Next, the stacked structure is housed in an exterior member.

[0390] In this way, the all-solid-state battery 200 is obtained.

[0391] Example

[0392] Hereinafter, examples will be described, but the present invention is not limited to these examples. In the following description, "parts" and "%" are based on mass unless otherwise specified.

[0393] [Preparation of resin particle dispersion]

[0394] -Resin particle dispersion (B1)-

[0395] 180 parts by mass of styrene, 1 part by mass of surfactant Dowfax 2A1 (47% solution, The Dow Chemical Company), and 120 parts by mass of deionized water were mixed and stirred in a dissolver at 1,500 rpm for 30 minutes to emulsify to produce a monomer emulsion. Subsequently, 0.2 parts by mass of Dowfax 2A1 (47% solution, The Dow Chemical Company) and 300 parts by mass of deionized water were added to a reaction vessel. Under a nitrogen atmosphere, the mixture was heated to 75°C, and then 10 parts by mass of the monomer emulsion was added. Subsequently, a polymerization initiator solution prepared by dissolving 2.0 parts by mass of ammonium persulfate in 12 parts by mass of deionized water was added dropwise over 10 minutes. After the addition, the mixture was reacted for 50 minutes, and then the remaining monomer emulsion was added dropwise over 180 minutes to react for a further 180 minutes. The mixture was then cooled to produce a resin particle dispersion (B1). The solid content concentration of the resin particle dispersion (B1) was 30.0% by mass. Furthermore, the average particle size of the resin particles was 0.38 μm.

[0396] -Resin particle dispersion (B2)-

[0397] Resin particle dispersion (B2) was obtained by the same method as for resin particle dispersion (B1), except that styrene was replaced with methyl methacrylate. The solid content concentration of resin particle dispersion (B2) was 36.0% by mass. The average particle size of the resin was 0.37 μm.

[0398] [Preparation of a solution containing polyalkylene oxide]

[0399] -Polyalkylene oxide-containing solution (C1)-

[0400] A high molecular weight polyalkylene oxide solution (C1) having a solid content concentration of 0.5% by mass was obtained by adding a high molecular weight polyalkylene oxide (grade: PEO-29, polyethylene oxide with a viscosity average molecular weight of 8 to 10 million, manufactured by SUMITOMO SEIKA CHEMICALS CO., LTD.) to deionized water.

[0401] -Polyalkylene oxide-containing solution (C2)-

[0402] A high molecular weight polyalkylene oxide (grade: PEO-27, polyethylene oxide with a viscosity average molecular weight of 6 to 8 million, manufactured by SUMITOMO SEIKA CHEMICALS CO., LTD.) was added to deionized water to obtain a high molecular weight polyalkylene oxide-containing solution (C2) having a solid content concentration of 0.5% by mass.

[0403] -Polyalkylene oxide-containing solution (C3)-

[0404] A high molecular weight polyalkylene oxide (grade: PEO-18, polyethylene oxide with a viscosity average molecular weight of 4.3 to 4.8 million, manufactured by SUMITOMO SEIKA CHEMICALS CO., LTD.) was added to deionized water to obtain a high molecular weight polyalkylene oxide-containing solution (C3) having a solid content concentration of 0.5% by mass.

[0405] [Preparation of a solution containing carboxymethyl cellulose]

[0406] -Solution containing carboxymethyl cellulose (C4)-

[0407] Carboxymethyl cellulose (Product No. 1160, Daicel Miraizu Ltd., also referred to as "CMC") was added to deionized water to obtain a carboxymethyl cellulose-containing solution (C4) having a solid content concentration of 0.5% by mass.

[0408] [Preparation of a solution containing water-insoluble fibrous organic matter]

[0409] -Solution containing water-insoluble fibrous organic matter (C5)-

[0410] Microfibrous aramid (trade name: Tiara, product number: KY400S, Daicel Miraizu Ltd., fiber diameter 30 nm, fiber length 3,000 nm) was added to deionized water to obtain a solution (C5) containing water-insoluble fibrous organic matter with a solid content concentration of 0.5% by mass.

[0411] -Solution containing water-insoluble fibrous organic matter (C6)-

[0412] Microfibrous cellulose (trade name: Serish, product number: KY100G, Daicel Miraizu Ltd., fiber diameter 20 nm, fiber length 3,000 nm) was added to deionized water to obtain a solution (C6) containing water-insoluble fibrous organic matter having a solid content concentration of 0.5% by mass.

[0413] <Example A1>

[0414] [Preparation of aqueous composition containing polyimide precursor (PAA-1)]

[0415] To 170 g of the resin particle dispersion (B1), 28 g (96 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 10 g (96 mmol) of p-phenylenediamine (PDA), and 360 g of ion-exchanged water were added, and the mixture was stirred at 20°C for 10 minutes.

[0416] Next, 20 g (211 mmol) of N-methylmorpholine (organic amine compound) was slowly added, and the mixture was dissolved and reacted with stirring for 24 hours while maintaining the reaction temperature at 60° C. to produce a polyimide precursor (A1) based on BPDA and PDA. 150 g of a polyalkylene oxide-containing solution (C1) was slowly added thereto to obtain an aqueous composition (PAA-1) containing a polyimide precursor.

[0417] The obtained polyimide precursor-containing aqueous composition (PAA-1) had a polyimide precursor content of 5.1% by mass, a resin particle content of 6.8% by mass, a high-molecular-weight polyalkylene oxide content of 0.1% by mass, and a water content of 85.1% by mass relative to the total mass.

[0418] Furthermore, as a result of measurement by the above-described method, the viscosity of the polyimide precursor-containing aqueous composition (PAA-1) at 25° C. was 150 Pa·s.

[0419] <Examples A2 to A9, Comparative Examples 1 and 2>

[0420] Aqueous polyimide precursor-containing compositions (PAA-2) to (PAA-11) were obtained in the same manner as in Example A1, except that the types and amounts of the resin particle dispersion and the polyalkylene oxide-containing solution were appropriately changed to adjust the contents of the components to those shown in Table 1.

[0421] In Comparative Example 2, a solution containing carboxymethyl cellulose was used instead of a solution containing polyalkylene oxide.

[0422] <Example B1 to Example B9>

[0423] Aqueous polyimide precursor-containing compositions (PAA-12) to (PAA-20) were obtained in the same manner as in Example A1, except that the type and amount of the resin particle dispersion were appropriately changed, a solution containing a water-insoluble fibrous organic substance was used instead of the solution containing polyalkylene oxide, and the contents of the components were as shown in Table 1.

[0424] <Evaluation>

[0425] A porous polyimide membrane was produced using the aqueous composition containing the polyimide precursor obtained in each example.

[0426] (Method for producing porous polyimide membrane)

[0427] First, an aluminum plate was prepared as a substrate. A release layer was provided on the aluminum plate. A solution of release agent KS-700 (manufactured by Shin-Etsu Chemical Co., Ltd.) dissolved in toluene was applied to the release layer to a thickness of approximately 0.05 μm after drying, and then heated at 400°C.

[0428] Next, the aqueous composition containing a polyimide precursor obtained in each example was applied to the release layer of the aluminum substrate so that the film thickness after drying was 30 μm to form a coating film, and then dried at 90°C for 1 hour. Then, the temperature was raised from room temperature (25°C, the same applies hereinafter) to 390°C at a rate of 10°C / min, maintained at 390°C for 1 hour, and then cooled to room temperature to obtain a porous polyimide film with a film thickness of approximately 30 μm.

[0429] Furthermore, the aqueous polyimide precursor-containing composition (PAA-11) containing carboxymethyl cellulose in Comparative Example 2 had high viscosity, and therefore poor coating properties during coating as described above. As a result, a coating film with large variations in film thickness was formed.

[0430] (Confirmation of particle sedimentation or floating)

[0431] The obtained porous polyimide membrane was cut in the thickness direction, and the cut surface was observed using a scanning electron microscope (SEM, Hitachi High-Technologies Corporation, FE-SEM S4700).

[0432] The cut surface was divided into two equal parts in the thickness direction, and the porosity on the upper and lower cut surfaces was measured by image analysis. The obtained measured values ​​were substituted into the following formula (A) to determine S.

[0433] Formula (A): S = 1 - (porosity with a "small" value) / (porosity with a "large" value)

[0434] Among them, the porosity with a "small" value indicates that the measured porosity value above and below the cut surface divided into two equal parts along the thickness direction is smaller, and the porosity with a "large" value indicates that the measured porosity value above and below the cut surface divided into two equal parts along the thickness direction is larger.

[0435] The degree of particle sedimentation or floating is evaluated based on the value of S obtained by the above formula (A). The smaller the value of S, the less the particle sedimentation or floating. For example, S is preferably less than 0.1.

[0436] The evaluation indicators are as follows.

[0437] -Evaluation indicators-

[0438] G5: S less than 0.03

[0439] G4: S is 0.03 or more and less than 0.05

[0440] G3: S is 0.05 or more and less than 0.1

[0441] G2: S is 0.1 or more and less than 0.2

[0442] G1: S is 0.2 or more

[0443]

[0444]

[0445] From the results shown in Table 1 and Table 2, it can be seen that by using the aqueous composition containing a polyimide precursor of this example, it is possible to suppress the precipitation or floating of particles during the process of producing a polyimide film.

[0446] The above-described embodiments of the present invention are provided for the purpose of illustration and explanation. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed embodiments. It is obvious that various modifications and variations are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily explain the principles of the present invention and its application. Thus, other persons skilled in the art will be able to understand the present invention through various modifications optimized for specific uses of the assumed various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. An aqueous composition containing a polyimide precursor, comprising a polymer material, a polyimide precursor, particles, and water, wherein the polymer material comprises a water-insoluble fibrous organic substance, The fiber diameter of the water-insoluble fibrous organic matter is greater than or equal to 1 nm and less than or equal to 500 nm. The fiber length of the water-insoluble fibrous organic matter is 10 nm or more and 10,000 nm or less, The content of the polymer material is 0.5% by mass or more and 8.0% by mass or less relative to the polyimide precursor, and The content of the polymer material is 0.05% by mass or more and 15% by mass or less relative to the particles.

2. An aqueous composition containing a polyimide precursor, comprising a polymer material, a polyimide precursor, particles, and water, wherein the polymer material comprises a polyalkylene oxide having a viscosity-average molecular weight of 6 million to 11 million. The content of the polymer material is 0.5% by mass or more and 8.0% by mass or less relative to the polyimide precursor, and The content of the polymer material is 0.05% by mass or more and 15% by mass or less relative to the particles.

3. The aqueous composition containing a polyimide precursor according to claim 1 or 2, wherein The content of the polymer material is 1.0% by mass or more and 3.0% by mass or less relative to the polyimide precursor.

4. The aqueous composition containing a polyimide precursor according to claim 1 or 2, wherein The content of the polymer material is 0.1% by mass or more and 2.0% by mass or less relative to the particles.

5. The aqueous composition containing a polyimide precursor according to claim 2, wherein The polyalkylene oxide is polyethylene oxide.

6. The aqueous composition containing a polyimide precursor according to claim 1 or 2, wherein The particles are resin particles.

7. The aqueous composition containing a polyimide precursor according to claim 6, wherein The resin particles are particles containing a resin containing a structural unit derived from styrene.

8. The aqueous composition containing a polyimide precursor according to claim 1 or 2, wherein The content of the water is 70% by mass or more relative to the total mass of the aqueous composition containing the polyimide precursor.

9. The aqueous composition containing a polyimide precursor according to claim 1 or 2, wherein The viscosity at 25° C. is 1 Pa·s or more and 200 Pa·s or less.

10. A method for producing a polyimide film, comprising the following steps: A step of applying the aqueous composition containing a polyimide precursor according to any one of claims 1 to 9 onto a substrate to form a coating film; a step of drying the coating to form a coating comprising at least one of the polymer material selected from the group consisting of the water-insoluble fibrous organic matter and the polyalkylene oxide having a viscosity-average molecular weight of 6,000,000 to 11,000,000, the polyimide precursor, and the particles; and a step of imidizing the polyimide precursor contained in the film to form a polyimide film.

11. A method for producing a porous polyimide membrane, comprising the following steps: A step of applying the aqueous composition containing a polyimide precursor according to any one of claims 1 to 9 onto a substrate to form a coating film; The step of drying the coating to form a coating comprising at least one of the polymer material selected from the group consisting of the water-insoluble fibrous organic matter and the polyalkylene oxide having a viscosity-average molecular weight of 6,000,000 to 11,000,000, the polyimide precursor, and the particles; a step of imidizing the polyimide precursor contained in the coating to form a polyimide film; and a step of removing the particles from the coating or the polyimide film.

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