resin composition

Abstract

The present invention provides a resin composition which exhibits excellent coatability and adhesive properties, can achieve a balance between high electron conductivity and dispersibility and dispersion stability of a fibrous carbon material, and can yield a lithium secondary battery having a high capacity retention rate. The present invention is a resin composition which contains a fibrous carbon material, a non-aqueous solvent and a poly(vinyl acetal) resin. The poly(vinyl acetal) resin has constituent units having an acidic functional group, has an average degree of polymerization of 150-1500, and has a hydroxyl group content of 40.0-80.0 mol%.

Description

[Technical Field]

[0001] The present invention relates to a resin composition that has excellent coatability and adhesiveness, and is capable of achieving both high electronic conductivity and the dispersibility and dispersion stability of a fibrous carbon material, and that can provide a lithium secondary battery with a high capacity retention rate. [Background technology]

[0002] In recent years, fibrous carbon materials such as carbon nanotubes and VGCF have shown excellent electrical properties, and are expected to be put to practical use in a wide range of fields, including electronics. For example, research is being conducted into adding them as conductive additives to electrodes for secondary batteries and transparent electrodes.

[0003] The fibrous carbon material is generally used in the form of a composition dispersed in water or an organic solvent. For example, Patent Document 1 discloses a conductive resin composition having a resin component including polyvinyl acetal (A) and a curable resin (B), and a carbon component including carbon nanotubes (C) having an aspect ratio and an average fiber diameter within a predetermined range. Furthermore, Patent Document 2 discloses a fine carbon fiber dispersion liquid comprising fine carbon fibers, a dispersion medium, a polymer-based dispersant, and a basic compound having a pKa of 7.5 or more. Furthermore, Patent Document 3 discloses a composition containing fine particles made of polyvinyl acetal resin, a fibrous conductive material, and a liquid dispersion medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-28900 A [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-181140 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-209435 Summary of the Invention [Problem to be solved by the invention]

[0005] However, fibrous carbon materials have the problem of low solubility and dispersibility, and are unable to maintain a stable dispersion state in solvents. It is known that they are particularly unable to maintain a dispersion state in non-aqueous solvents. Furthermore, while fibrous carbon materials have excellent electrical, thermal, and mechanical properties, they have a very large aspect ratio, which makes them prone to entanglement, making it difficult to obtain high-performance composite materials that fully utilize their properties. To solve the above problem, it is necessary to add a large amount of a resin component as a dispersant, but this has the problem of impairing the properties of the fibrous carbon material. Even the compositions disclosed in Patent Documents 1 to 3 are insufficient to exhibit high dispersibility while maintaining high electronic conductivity of the fibrous carbon material.

[0006] The present invention aims to provide a resin composition that has excellent coatability and adhesiveness, and can simultaneously achieve high electronic conductivity and the dispersibility and dispersion stability of a fibrous carbon material, and that can provide a lithium secondary battery with a high capacity retention rate. [Means for solving the problem]

[0007] The present invention provides a method for producing a carbon fiber composite material, comprising: The polyvinyl acetal resin is a resin composition having a structural unit having an acidic functional group, an average degree of polymerization of 150 or more and 1500 or less, and a hydroxyl group content of 40.0 mol % or more and 80.0 mol % or less. The present invention will be described in detail below.

[0008] As a result of intensive research, the present inventors have found that by using a combination of a fibrous carbon material, a non-aqueous solvent, and a polyvinyl acetal resin having a specific structure, it is possible to achieve excellent coatability and adhesiveness, as well as high electronic conductivity and dispersibility of the fibrous carbon material. Furthermore, it has been found that by using the above resin composition, a lithium secondary battery having a high capacity retention rate can be obtained, and this has led to the completion of the present invention.

[0009] The resin composition of the present invention contains a fibrous carbon material. By including the fibrous carbon material, the conductive properties can be improved.

[0010] The fibrous carbon material means a carbon material having an aspect ratio (average fiber length / average fiber diameter) of 30 or more. From the viewpoint of efficiently forming an electron conduction path, the aspect ratio (average fiber length / average fiber diameter) of the above-mentioned fibrous carbon material is preferably 50 or more, more preferably 100 or more, even more preferably 200 or more, even more preferably 400 or more, and is preferably 500,000 or less, more preferably 300,000 or less, even more preferably 100,000 or less, even more preferably 50,000 or less, and particularly preferably 20,000 or less.

[0011] Examples of the fibrous carbon material include carbon fibers and carbon nanotubes. Examples of the carbon fiber include PAN-based carbon fiber, pitch-based carbon fiber, cellulose-based carbon fiber, and vapor grown carbon fiber (VGCF). The carbon nanotubes are cylindrical carbon materials, and examples thereof include single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0012] From the viewpoint of efficiently forming an electron conduction path, the average fiber diameter of the above-mentioned fibrous carbon material is preferably 0.40 nm or more, more preferably 0.50 nm or more, even more preferably 1.0 nm or more, even more preferably 5.0 nm or more, and is preferably 200.0 nm or less, more preferably 150.0 nm or less, even more preferably 100.0 nm or less. The average fiber diameter can be measured, for example, by Raman spectroscopy (Raman).

[0013] From the viewpoint of efficiently forming an electron conduction path, the average fiber length of the above-mentioned fibrous carbon material is preferably 0.10 μm or more, more preferably 0.50 μm or more, even more preferably 1.0 μm or more, even more preferably 5.0 μm or more, and is preferably 500.0 μm or less, more preferably 250.0 μm or less, even more preferably 200.0 μm or less, even more preferably 100.0 μm or less. The average fiber length can be measured, for example, by Raman spectroscopy (Raman).

[0014] From the viewpoint of maintaining a stable dispersion state, the specific gravity of the above-mentioned fibrous carbon material is preferably 1.0 or more, more preferably 1.3 or more, even more preferably 1.5 or more, even more preferably 1.8 or more, and is preferably 2.5 or less, more preferably 2.3 or less, even more preferably 2.1 or less. The specific gravity can be measured by a method in accordance with JIS Z8807.

[0015] The specific surface area of ​​the above fibrous carbon material is set to 8m from the viewpoint of increasing conductivity while maintaining dispersibility. 2 / g or more, and 2 / g or more is more preferable, and 100m 2 / g or more is more preferable, and 2 / g or more is even more preferable, and2 / g or less, and 1500m 2 / g or less is more preferable, and 1200m 2 / g or less is more preferable, and 2 It is even more preferable that the saturation coefficient is 1 / g or less. The specific surface area can be measured, for example, by using a specific surface area measuring device ("ASAP-2000" manufactured by Shimadzu Corporation).

[0016] From the viewpoint of enhancing electronic conductivity, the peak intensity ratio of the G band to the D band (G / D ratio) in the above-mentioned fibrous carbon material is preferably 0.1 or more, more preferably 5 or more, and even more preferably 10 or more, and is preferably 100 or less, more preferably 85 or less, and even more preferably 70 or less. The G / D ratio can be determined, for example, by measuring the Raman spectrum by Raman spectroscopy. When the above fibrous carbon material was measured by Raman spectroscopy, the G band (1580 cm ) corresponding to the sp2 bond was observed. -1 around 1360cm ) and the D band corresponding to sp3 bonds ( -1 Two peaks are clearly observed. When the carbon material is crystalline, one of the two bands mentioned above becomes minimal. For example, in the case of single-crystal diamond, the peak at 1580 cm -1 On the other hand, in the case of high-purity graphite structure, the G band around 1360 cm is hardly observed. -1 The nearby D band is barely visible.

[0017] The fibrous carbon material may be a discontinuous fiber in which the fibers are intermittently divided, or may be a continuous fiber in which the fibers are not divided. 。

[0018] The content of the above-mentioned fibrous carbon material in the resin composition of the present invention is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, even more preferably 0.5% by weight or more, even more preferably 1.5% by weight or more, and is preferably 15.0% by weight or less, more preferably 10.0% by weight or less.

[0019] The resin composition of the present invention contains a non-aqueous solvent. The non-aqueous solvent means a solvent in which the water content is 100 ppm or less by weight. Examples of the non-aqueous solvent include organic solvents such as ketones, alcohols, aromatic hydrocarbons, esters, and amides. Examples of the ketones include acetone, methyl ethyl ketone, dipropyl ketone, and diisobutyl ketone. Examples of the alcohols include methanol, ethanol, isopropanol, and butanol. Examples of the aromatic hydrocarbons include toluene and xylene. Examples of the esters include methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate, methyl pentanoate, ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, butyl hexanoate, 2-ethylhexyl acetate, and 2-ethylhexyl butyrate. Also usable are methyl cellosolve, ethyl cellosolve, butyl cellosolve, terpineol, dihydroterpineol, butyl cellosolve acetate, butyl carbitol acetate, terpineol acetate, dihydroterpineol acetate, and the like. Examples of the carbonates include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate. The amides preferably contain a lactam structure, more preferably a 3- to 6-membered ring lactam structure, and even more preferably a 5-membered ring lactam structure. Specific examples of the amides include dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, and diethylformamide.

[0020] The content of the non-aqueous solvent in the resin composition of the present invention is preferably 60.0% by weight or more, more preferably 70.0% by weight or more, and is preferably 99.9% by weight or less.

[0021] The resin composition of the present invention contains a polyvinyl acetal resin. The polyvinyl acetal resin has a structural unit having an acidic functional group, an average degree of polymerization of 150 or more and 1500 or less, and a hydroxyl group content of 40.0 mol % or more and 80.0 mol % or less. By containing the above-mentioned polyvinyl acetal resin, the dispersibility of the fibrous carbon material can be sufficiently improved even if the amount of polyvinyl acetal resin added as a dispersant is reduced, and high electronic conductivity and dispersibility of the fibrous carbon material can be achieved at the same time.

[0022] The polyvinyl acetal resin has a structural unit having an acidic functional group. The acidic functional group is preferably a Bronsted acidic group. Examples of the Bronsted acidic group include a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a sulfinic acid group, a sulfenic acid group, a phosphonic acid group, and salts thereof. Among these, at least one selected from the group consisting of a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group is preferred. When the modified polyvinyl acetal resin has the structural unit having the acidic functional group, the dispersibility of the fibrous carbon material can be improved even when added in a small amount.

[0023] The structural unit having an acidic functional group may have a structure in which the acidic functional group is bonded directly to a carbon atom constituting the main chain as a side chain, or may have a structure in which the acidic functional group is bonded to a carbon atom constituting the main chain via an alkylene group.Furthermore, the structural unit having an acidic functional group may have a structure in which the acidic functional group is bonded to a carbon atom constituting the main chain via an acetal bond.

[0024] The structural unit having an acidic functional group may have a three-dimensional structure in which two acidic functional groups are bonded to the same carbon constituting the main chain, or a three-dimensional structure in which one acidic functional group is bonded to a carbon constituting the main chain. It may also have a three-dimensional structure in which one acidic functional group is bonded to each adjacent carbon constituting the main chain, or a three-dimensional structure in which an acidic functional group is bonded to only one of the adjacent carbons constituting the main chain. Of these, a three-dimensional structure in which two acidic functional groups are bonded to the same carbon constituting the main chain, or a three-dimensional structure in which one acidic functional group is bonded to each adjacent carbon constituting the main chain, is preferred. Furthermore, a three-dimensional structure in which two acidic functional groups are bonded to the same carbon constituting the main chain is preferred because it increases steric hindrance and can widen the network structure of the cured product obtained by combining with an epoxy resin, thereby improving the flexibility of the resulting cured product.

[0025] The structural unit having the acidic functional group may have a stereostructure in which the acidic functional groups are bonded in the same direction to the carbon atoms constituting the main chain, that is, an isotactic configuration, or in which the acidic functional groups are bonded alternately on opposite sides to the carbon atoms constituting the main chain, that is, a syndiotactic configuration, or in which the acidic functional groups are bonded randomly, that is, an atactic configuration.

[0026] When the structural unit having the acidic functional group has a structure in which the acidic functional group is bonded to a carbon atom constituting the main chain via an alkylene group, the alkylene group is preferably an alkylene group having 1 to 10 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms, and even more preferably an alkylene group having 1 to 3 carbon atoms.

[0027] The alkylene group having 1 to 10 carbon atoms includes a linear alkylene group, a branched alkylene group, and a cyclic alkylene group. Examples of the linear alkylene group include a methylene group, a vinylene group, an n-propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, and a decamethylene group. Examples of the branched alkylene group include a methylmethylene group, a methylethylene group, a 1-methylpentylene group, and a 1,4-dimethylbutylene group. Examples of the cyclic alkylene group include a cyclopropylene group, a cyclobutylene group, and a cyclohexylene group. Of these, a linear alkylene group is preferred, a methylene group, a vinylene group, and an n-propylene group are more preferred, and a methylene group and a vinylene group are even more preferred.

[0028] Examples of the structural unit having an acidic functional group include structural units represented by the following formulas (1-1) to (1-5).

[0029] [ka]

[0030] In the above formulas (1-1) to (1-5), R 1 , R 3 , R 5 , R 7 , R 9 , R 11 , R 13 , R 15 each independently represents a single bond or an alkylene group having 1 to 10 carbon atoms; R 2 , R 4 , R 6 , R 8 , R 10 , R 12 , R 14 , R 16 represents an acidic functional group. Above R 1 , R 3 , R 5 , R7 , R 9 , R 11 , R 13 , R 15 is preferably a single bond or an alkylene group having 1 to 5 carbon atoms, and more preferably a single bond or an alkylene group having 1 to 3 carbon atoms.

[0031] The alkylene group having 1 to 10 carbon atoms includes a linear alkylene group, a branched alkylene group, and a cyclic alkylene group. Examples of the linear alkylene group include a methylene group, a vinylene group, an n-propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, and a decamethylene group. Examples of the branched alkylene group include a methylmethylene group, a methylethylene group, a 1-methylpentylene group, and a 1,4-dimethylbutylene group. Examples of the cyclic alkylene group include a cyclopropylene group, a cyclobutylene group, and a cyclohexylene group. Of these, a linear alkylene group is preferred, a methylene group, a vinylene group, and an n-propylene group are more preferred, and a methylene group and a vinylene group are even more preferred.

[0032] When the acidic functional group is a carboxylic acid group, examples of the structural unit having a carboxyl group include a structural unit represented by the following formula (2-1), a structural unit represented by the following formula (2-2), a structural unit represented by the following formula (2-3), and a structural unit represented by the following formula (2-4).

[0033] [ka]

[0034] In the above formulas (2-1) to (2-4), R 17 ~R 23 are each independently a single bond or an alkylene group having 1 to 10 carbon atoms; X 17 ~X 23 each independently represents a hydrogen atom, a metal atom, or a methyl group. The alkylene group having 1 to 10 carbon atoms includes, in the formula (1-1), R 1 The same can be mentioned. Examples of the metal atom include a sodium atom, a lithium atom, and a potassium atom, with a sodium atom being preferred.

[0035] Examples of the constitutional unit having a sulfonic acid group include constitutional units represented by the following formula (3).

[0036] [ka]

[0037] In the above formula (3), R 24 represents a single bond or an alkylene group having 1 to 10 carbon atoms; X 24 represents a hydrogen atom, a metal atom or a methyl group. The alkylene group having 1 to 10 carbon atoms includes, in the formula (1-1), R 1 The same can be mentioned. The metal atom is, for example, X in the formula (2-1). 17 The same can be mentioned.

[0038] The constitutional unit having a phosphate group includes a constitutional unit represented by the following formula (4).

[0039] [ka]

[0040] In the above formula (4), R 25 represents a single bond or an alkylene group having 1 to 10 carbon atoms; X 25 and X 26 each independently represents a hydrogen atom, a metal atom, or a methyl group. The alkylene group having 1 to 10 carbon atoms includes, in the formula (1-1), R 1 The same can be mentioned. The metal atom is, for example, X in the formula (2-1). 17The same can be mentioned.

[0041] The content of the structural unit having an acidic functional group relative to all structural units of the polyvinyl acetal resin is preferably 0.01 mol % or more and 20.0 mol % or less. Within the above range, the dispersibility of the fibrous carbon material can be further improved. The content of the structural unit having the acidic functional group is more preferably 0.1 mol% or more, even more preferably 0.5 mol% or more, even more preferably 1.0 mol% or more, more preferably 15.0 mol% or less, even more preferably 12.0 mol% or less, even more preferably 10.0 mol% or less. The content of the structural unit having the acidic functional group can be measured, for example, by NMR.

[0042] The Bronsted acid amount in the polyvinyl acetal resin is preferably 0.1 mg / g or more and 200 mg / g or less. Within the above range, the dispersibility of the fibrous carbon material can be further improved. The Bronsted acid amount is more preferably 0.2 mg / g or more and more preferably 175 mg / g or less. The Bronsted acid amount means the amount of potassium hydroxide required to neutralize the Bronsted acid contained in the polyvinyl acetal resin. The Bronsted acid amount can be measured, for example, by acid-base titration according to JIS K0070-1992.

[0043] The polyvinyl acetal resin preferably has a structural unit having an acetal group represented by the following formula (5-1), a structural unit having a hydroxyl group represented by the following formula (5-2), and a structural unit having an acetyl group represented by the following formula (5-3).

[0044] [ka]

[0045] In the above formula (5-1), R 26 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. The alkyl group preferably has 1 or more carbon atoms, preferably 10 or less carbon atoms, and more preferably 5 or less carbon atoms.

[0046] In the above formula (5-1), R 26 When is an alkyl group having 1 to 20 carbon atoms, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, an octadecyl group, etc. Of these, a methyl group and an n-propyl group are preferred.

[0047] In the polyvinyl acetal resin, the content of the structural unit having the acetal group represented by the formula (5-1) (hereinafter also referred to as "acetal group amount") is preferably 5.0 mol % or more and 60.0 mol % or less. Within the above range, the dispersibility of the fibrous carbon material can be further improved. The amount of acetal groups is more preferably 7.0 mol% or more, even more preferably 10.0 mol% or more, even more preferably 15.0 mol% or more, more preferably 50.0 mol% or less, even more preferably 40.0 mol% or less, even more preferably 35.0 mol% or less. In this specification, the amount of acetal groups is calculated by counting the two acetalized hydroxyl groups, since the acetal groups of the polyvinyl acetal resin are obtained by acetalizing two hydroxyl groups. The amount of acetal groups can be measured, for example, by NMR.

[0048] Furthermore, when the polyvinyl acetal resin has an acetal group having an acidic modifying group represented by formula (1-5) as a structural unit having an acidic modifying group, the sum of the content of the structural unit having an acidic modifying group represented by formula (1-5) and the content of the structural unit having an acetal group represented by formula (5-1) in the polyvinyl acetal resin (hereinafter also referred to as the "total acetal group content") is preferably 15.0 mol% or more, more preferably 20.0 mol% or more, and is preferably 60.0 mol% or less, more preferably 50.0 mol% or less.

[0049] In the polyvinyl acetal resin, the content of the structural unit having a hydroxyl group represented by the formula (5-2) (hereinafter also referred to as "hydroxyl group amount") is 40.0 mol % or more and 80.0 mol % or less. By setting the content within the above range, the dispersibility and dispersion stability of the fibrous carbon material can be sufficiently improved, and high electronic conductivity can be exhibited. The amount of hydroxyl groups is preferably 45.0 mol% or more, more preferably 50.0 mol% or more, and even more preferably 55.0 mol% or more, and is preferably 75.0 mol% or less, more preferably 70.0 mol% or less, and even more preferably 65.0 mol% or less. The amount of hydroxyl groups can be measured by, for example, NMR.

[0050] In the polyvinyl acetal resin, the content of the structural unit having an acetyl group represented by the above formula (5-3) (hereinafter also referred to as "acetyl group amount") is preferably 0.1 mol% or more, more preferably 1.0 mol% or more, even more preferably 2.0 mol% or more, even more preferably 5.0 mol% or more, and is preferably 20.0 mol% or less, more preferably 15.0 mol% or less, even more preferably 12.0 mol% or less, and even more preferably 8.0 mol% or less. When the amount of acetyl groups is within the above range, thickening can be suppressed and coatability can be further improved. The amount of acetyl groups can be measured by, for example, NMR.

[0051] The polyvinyl acetal resin has an average degree of polymerization of 150 or more and 1,500 or less. Within the above range, the dispersibility of the fibrous carbon material can be sufficiently improved, and high electronic conductivity can be exhibited. The average degree of polymerization is preferably 200 or more and 1,000 or less. The average degree of polymerization can be measured, for example, by gel permeation chromatography (GPC).

[0052] From the viewpoint of achieving both dispersibility and adhesiveness, the glass transition temperature of the polyvinyl acetal resin is preferably 60°C or higher, more preferably 65°C or higher, and is preferably 115°C or lower, more preferably 100°C or lower. The glass transition temperature can be measured, for example, by differential scanning calorimetry.

[0053] The content of the polyvinyl acetal resin in the resin composition of the present invention is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and is preferably 30.0% by weight or less, more preferably 15.0% by weight or less.

[0054] The ratio of the content of the polyvinyl acetal resin to the content of the fibrous carbon material in the resin composition of the present invention (polyvinyl acetal resin content / fibrous carbon material content) is preferably 0.1 or more and 2.0 or less. When the content is within the above range, the dispersibility of the fibrous carbon material is good, and conductive paths are easily formed, resulting in even better electronic conductivity. The ratio of the above contents is more preferably 0.2 or more and more preferably 1.5 or less.

[0055] Examples of methods for producing the polyvinyl acetal resin include a method in which a polyvinyl acetate resin obtained by polymerizing a monomer such as vinyl acetate is saponified by adding an acid or alkali, and then purified to adjust the Na ion content of the polyvinyl alcohol resin, and then acetalized.

[0056] As the polyvinyl alcohol resin, for example, a conventionally known polyvinyl alcohol resin such as a resin produced by saponifying a polyvinyl acetate resin with an alkali, an acid, aqueous ammonia, or the like can be used. The polyvinyl alcohol resin may be fully saponified, but does not need to be fully saponified as long as it has at least one unit having two consecutive hydroxyl groups at the meso and racemo positions at at least one location on the main chain, and may be a partially saponified polyvinyl alcohol resin. Furthermore, as the polyvinyl alcohol resin, a copolymer of vinyl alcohol and a monomer copolymerizable with vinyl alcohol, such as an ethylene-vinyl alcohol copolymer resin or a partially saponified ethylene-vinyl alcohol copolymer resin, may also be used. The polyvinyl acetate resin may be, for example, an ethylene-vinyl acetate copolymer.

[0057]

[0033] Examples of methods for preparing the polyvinyl acetal resin having a structural unit having an acidic functional group include a method in which polyvinyl acetate obtained by copolymerizing a monomer having an acidic functional group with vinyl acetate is saponified to obtain polyvinyl acetate, and the resulting polyvinyl alcohol is acetalized by a conventionally known method. Alternatively, the polyvinyl acetal resin may be one in which an acidic functional group is introduced by post-modification of the polyvinyl acetal resin obtained by acetalizing unmodified polyvinyl alcohol by a conventionally known method. Examples of the monomer having an acidic functional group include monocarboxylic acids such as acrylic acid, crotonic acid, methacrylic acid, and oleic acid; dicarboxylic acids such as methylenemalonic acid, itaconic acid, 2-methyleneglutaric acid, 2-methyleneadipic acid, and 2-methylenesebacic acid; and maleic anhydride and metal salts thereof.

[0058] The polyvinyl alcohol resin preferably has a degree of saponification of 80.0 mol % or more and 99.9 mol % or less, and more preferably 85.0 mol % or more and 95.0 mol % or less. By using the polyvinyl alcohol resin, the dispersibility of the fibrous carbon material can be further improved.

[0059] The acetalization can be carried out by a known method, and is preferably carried out in an aqueous solvent, a mixed solvent of water and an organic solvent compatible with water, or an organic solvent. As the organic solvent compatible with water, for example, an alcohol-based organic solvent can be used. Examples of the organic solvent include alcohol-based organic solvents, aromatic organic solvents, aliphatic ester-based solvents, ketone-based solvents, lower paraffin-based solvents, ether-based solvents, amide-based solvents, and amine-based solvents. Examples of the alcohol-based organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol. Examples of the aromatic organic solvent include xylene, toluene, ethylbenzene, and methyl benzoate. Examples of the aliphatic ester solvent include methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, and ethyl acetoacetate. Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone, and acetophenone. Examples of the lower paraffin solvent include hexane, pentane, octane, cyclohexane, and decane. Examples of the ether solvent include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol diethyl ether. Examples of the amide solvent include N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetanilide. Examples of the amine solvent include ammonia, trimethylamine, triethylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, aniline, N-methylaniline, N,N-dimethylaniline, and pyridine. These solvents can be used alone or in combination of two or more. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferred from the viewpoints of solubility in the resin and ease of purification.

[0060] The acetalization is preferably carried out in the presence of an acid catalyst. The acid catalyst is not particularly limited, and examples thereof include mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; carboxylic acids such as formic acid, acetic acid, and propionic acid; and sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, and paratoluenesulfonic acid. These acid catalysts may be used alone or in combination of two or more compounds. Among these, hydrochloric acid, nitric acid, and sulfuric acid are preferred, and hydrochloric acid is particularly preferred.

[0061] The aldehyde used in the acetalization reaction includes aldehydes having a chain aliphatic group, a cyclic aliphatic group, or an aromatic group having 1 to 10 carbon atoms. Any known aldehyde can be used as this aldehyde. The aldehyde used in the acetalization reaction is not particularly limited, and examples thereof include aliphatic aldehydes and aromatic aldehydes. Examples of the aliphatic aldehyde include formaldehyde, acetaldehyde, propionaldehyde, n-butylaldehyde, isobutyraldehyde, n-valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, n-heptylaldehyde, n-octylaldehyde, octylaldehyde, n-nonylaldehyde, n-decylaldehyde, and amylaldehyde. Examples of the aromatic aldehyde include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. Also usable are cyclic polymers such as paraldehyde and metaldehyde. These aldehydes may be used alone or in combination of two or more. Among them, formaldehyde, acetaldehyde, butylaldehyde, 2-ethylhexylaldehyde, n-nonylaldehyde, and paraldehyde are preferred as aldehydes, as they have excellent acetalization reactivity, bring about a sufficient internal plasticizing effect in the resulting resin, and as a result, can impart good flexibility. Furthermore, formaldehyde, acetaldehyde, butylaldehyde, and paraldehyde are more preferred, as they can provide an adhesive composition that is particularly excellent in impact resistance and adhesion to metals.

[0062] The amount of the aldehyde to be added can be appropriately set depending on the amount of acetal groups in the target polyvinyl acetal resin. In particular, an amount of 10 to 65 mol %, preferably 15 to 60 mol %, based on 100 mol % of polyvinyl alcohol is preferred because this allows the acetalization reaction to proceed efficiently and makes it easy to remove unreacted aldehyde.

[0063] The resin composition of the present invention may further contain additives such as other binders such as polyvinylidene fluoride, conductive aids, flame retardant aids, antifoaming agents, leveling agents, and adhesion promoters, as long as the effects of the present invention are not impaired. Furthermore, the resin composition of the present invention preferably does not contain a curable resin.

[0064] The method for producing the resin composition of the present invention is not particularly limited, and examples thereof include a method in which a polyvinyl acetal resin obtained by acetalizing raw material polyvinyl alcohol and a fibrous carbon material are added to a non-aqueous solvent and mixed. Examples of the mixing method include methods using various mixers such as a ball mill, a blender mill, and a three-roll mill.

[0065] By adding an active material to the resin composition of the present invention, a composition for a lithium secondary battery electrode can be obtained. The active material includes a positive electrode active material and a negative electrode active material. Examples of the positive electrode active material include lithium nickel oxide (e.g., LiNiO2), lithium cobalt oxide (e.g., LiCoO2), lithium manganese oxide (e.g., LiMn2O4), and composites thereof (e.g., LiNi 0.5 Mn 1.5 O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Examples of suitable oxides include particles of oxides (lithium transition metal oxides) containing lithium and transition metal elements as constituent metal elements, such as lithium manganese phosphate (LiMnPO4) and lithium iron phosphate (LiFePO4). These may be used alone or in combination of two or more. As the negative electrode active material, for example, a material that has conventionally been used as a negative electrode active material for lithium secondary batteries can be used, and examples thereof include carbon-based materials such as graphite, natural graphite, graphite carbon, and amorphous carbon, lithium transition metal oxides, lithium transition metal nitrides, silicon, and silicon compounds such as silicon oxide.

[0066] The method for producing the lithium secondary battery electrode composition is not particularly limited, and examples thereof include a method in which the active material, the resin composition of the present invention, and various additives added as needed are mixed using various mixers such as a ball mill, a blender mill, and a three-roll mill.

[0067] The lithium secondary battery electrode composition is, for example, applied to a conductive substrate and dried to form a lithium secondary battery electrode. As the coating method, various coating methods can be used, including, for example, an extrusion coater, a reverse roller, a doctor blade, an applicator, and the like. [Effects of the Invention]

[0068] According to the present invention, it is possible to provide a resin composition that has excellent coatability and adhesiveness, and can simultaneously achieve high electronic conductivity and dispersibility and dispersion stability of a fibrous carbon material, thereby enabling the production of a lithium secondary battery with a high capacity retention rate. DETAILED DESCRIPTION OF THE INVENTION

[0069] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0070] (Production Example 1) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 150, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17500 g of the solution (0.01 mol%) containing 1,2,500 mol of acetaldehyde (wherein 1 is a hydrogen atom) was added to 2,500 g of pure water and stirred at 90°C for 2 hours to dissolve the solution. The solution was cooled to 40°C, and 10 g of 35 wt% hydrochloric acid was added. The liquid temperature was then lowered to 5°C, and 62.99 g of acetaldehyde was added. This temperature was maintained to carry out an acetalization reaction, resulting in the precipitation of the reaction product. The liquid temperature was then raised to 65°C and maintained for 5 hours to complete the reaction, and 40 g of aqueous sodium hydroxide solution was added to carry out a neutralization reaction. 5,000 g of pure water was then added, the mixture was stirred, and 5,000 g of water was removed by decantation. This process of adding 5,000 g of pure water, stirring, and then removing the water by decantation was repeated three times. The solid content of the resin was then adjusted to 20 wt% using ion-exchanged water to obtain polyvinyl acetal resin A1. The obtained polyvinyl acetal resin was 1 The amounts of acetal groups, hydroxyl groups, and acetyl groups were measured using H-NMR (nuclear magnetic resonance spectroscopy), and the results are shown in Table 1. 1 H-NMR measurements were performed using deuterated DMSO as a solvent. The Bronsted acid content was also measured by acid-base titration in accordance with JIS K0070-1992. Specifically, it was measured by the following method. First, for this test, approximately 1 g of the obtained polyvinyl acetal resin was used as a sample. Approximately 40 ml of an ethanol / water (volume ratio 9:1) mixed solvent was added and the sample was dissolved by shaking. After dissolution, a 1 wt% solution of phenolphthalein was titrated with a microburette using a 0.02 mol / L ethanolic potassium hydroxide solution as an indicator until a slight red color was maintained for 30 seconds or more. A blank test was separately conducted, and the Bronsted acid content was measured using the following formula. The result was 0.2 mg / g. Bronsted acidity = [(AB) × f × (1 / 50) × (C / 1000)] × 100 / D A: Amount of ethanolic potassium hydroxide solution dropped in this test (mL) B: Amount of ethanolic potassium hydroxide solution dropped in the blank test (mL) C: Molecular weight of the structural unit having an acidic functional group D: Amount of sample (g) f: Potency of 0.02 mol / L ethanolic potassium hydroxide solution Furthermore, the glass transition temperature (Tg) of the obtained polyvinyl acetal resin was measured using a differential scanning calorimeter (DSC) at a temperature rise rate of 10°C / min, and the result was 93°C.

[0071] (Production Example 2) Sulfonic acid-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (3) (R 24 is a methylene group, X 24 Polyvinyl acetal resin A2 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer having a vinyl ether content of 1.0 mol% (wherein each represents a hydrogen atom) was used and the amount of acetaldehyde added was 32.99 g.

[0072] (Production Example 3) Phosphate group-modified polyvinyl alcohol resin (average polymerization degree 1000, saponification degree 92 mol%, structural unit represented by formula (4) (R 25 is a methylene group, X 25 , X 26 Polyvinyl acetal resin A3 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer having a vinyl ether content of 10.0 mol% (wherein each represents a hydrogen atom) was used and the amount of acetaldehyde added was 46.99 g.

[0073] (Production Example 4) Phosphate group-modified polyvinyl alcohol resin (average polymerization degree 1250, saponification degree 98 mol%, structural unit represented by formula (4) (R 25 is a vinylene group, X 25 , X 26 Polyvinyl acetal resin A4 was obtained in the same manner as in Production Example 1, except that the content of 0.1 mol% of acetaldehyde (wherein acetaldehyde is a hydrogen atom) was used and the amount of acetaldehyde added was 22.9 g.

[0074] (Production Example 5) Sulfonic acid-modified polyvinyl alcohol resin (average polymerization degree 1500, saponification degree 98 mol%, structural unit represented by formula (3) (R 24 is a methylene group, X 24Polyvinyl acetal resin A5 was obtained in the same manner as in Production Example 1, except that a vinyl acrylate copolymer having a sodium content of 10.0 mol% was used and the amount of acetaldehyde added was 53 g.

[0075] (Production Example 6) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 250 g of a polyvinyl acetal resin (content of 1.0 mol%) (wherein each represents a hydrogen atom) and 250 g of an unmodified polyvinyl alcohol resin (average degree of polymerization 500, degree of saponification 98 mol%) were used. The amount of acetaldehyde added was 52 g. Polyvinyl acetal resin A6 was obtained in the same manner as in Production Example 1, except for the above.

[0076] (Production Example 7) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 1000, saponification degree 92 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 is a hydrogen atom) (content 0.1 mol%), and 250 g of sulfonic acid-modified polyvinyl alcohol resin (average polymerization degree 1000, saponification degree 92 mol%, structural unit represented by formula (3) (R 24 is a vinylene group, X 24 250 g of a polyvinyl acetal resin having a content of 0.1 mol% (wherein each of the carbon atoms is a hydrogen atom) was used. The amount of acetaldehyde added was 26.9 g. Polyvinyl acetal resin A7 was obtained in the same manner as in Production Example 1, except for the above.

[0077] (Production Example 8) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 1250, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 is a hydrogen atom) (content 0.01 mol%), and 250 g of a phosphate group-modified polyvinyl alcohol resin (average polymerization degree 1250, saponification degree 98 mol%, containing a constitutional unit represented by formula (4) (R 25 is a methylene group, X 25 , X 26250 g of a polyvinyl acetal resin having a content of 0.1 mol% (wherein sodium atoms are present) was used. The amount of acetaldehyde added was 42.89 g. Polyvinyl acetal resin A8 was obtained in the same manner as in Production Example 1, except for the above.

[0078] (Production Example 9) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 1250, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin A9 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer containing 15.0 mol% of acetaldehyde (wherein acetaldehyde is a hydrogen atom) was used and the amount of acetaldehyde added was 38 g.

[0079] (Production Example 10) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 100, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin B1 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer having a content of 0.1 mol% (represented by hydrogen atom) was used and the amount of acetaldehyde added was 57.9 g.

[0080] (Production Example 11) Sulfonic acid-modified polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 98 mol%, structural unit represented by formula (3) (R 24 is a methylene group, X 24 Polyvinyl acetal resin B2 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer having a vinyl ether content of 10.0 mol% (wherein each represents a hydrogen atom) was used and the amount of acetaldehyde added was 53 g.

[0081] (Manufacturing Example 12) Phosphate group-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (4) (R 25 is a vinylene group, X 25 , X 26 Polyvinyl acetal resin B3 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer having a vinyl ether content of 1.0 mol% (wherein each represents a hydrogen atom) was used and the amount of acetaldehyde added was 67 g.

[0082] (Manufacturing Example 13) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 1250, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin B4 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer having a vinyl ether content of 0.01 mol% (represented by hydrogen atom) was used and the amount of acetaldehyde added was 17.99 g.

[0083] (Manufacturing Example 14) Polyvinyl acetal resin B5 was obtained in the same manner as in Production Example 1, except that an unmodified polyvinyl alcohol resin (average degree of polymerization 500, degree of saponification 92 mol%) was used and the amount of acetaldehyde added was 37 g.

[0084] (Manufacturing Example 15) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin B6 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer having a (is a hydrogen atom) content of 0.01 mol % was used.

[0085] (Manufacturing Example 16) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 150, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin B7 was obtained in the same manner as in Production Example 1, except that a vinyl ether copolymer having a vinyl ether content of 0.01 mol% (represented by hydrogen atom) was used and the amount of acetaldehyde added was 73.0 g.

[0086] (Manufacturing Example 17) Sulfonic acid-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (3) (R 24 is a methylene group, X 24Polyvinyl acetal resin A10 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a vinyl aldehyde content of 1.0 mol% (wherein each is a hydrogen atom) was used and 62 g of butyraldehyde was added instead of acetaldehyde.

[0087] (Manufacturing Example 18) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 150, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin A11 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a content of 0.1 mol% (wherein represents a hydrogen atom) was used and 62 g of butyraldehyde was added instead of acetaldehyde.

[0088] (Manufacturing Example 19) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin A12 was obtained in the same manner as in Production Example 1, except that a vinyl acrylate copolymer having a vinyl acrylate content of 0.1 mol% (represented by hydrogen atom) was used and 52.9 g of hexylaldehyde was added instead of acetaldehyde.

[0089] (Manufacturing Example 20) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin A13 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a vinyl aldehyde content of 0.005 mol% (wherein represents a hydrogen atom) was used and 63.0 g of butyraldehyde was added instead of acetaldehyde.

[0090] (Manufacturing Example 21) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17Polyvinyl acetal resin A14 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a vinyl aldehyde content of 0.001 mol% (represented by hydrogen atom) was used and 63.0 g of butyraldehyde was added instead of acetaldehyde.

[0091] (Manufacturing Example 22) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin A15 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a vinyl aldehyde content of 14.5 mol% (wherein is a hydrogen atom) was used and 48.5 g of butyraldehyde was added instead of acetaldehyde.

[0092] (Manufacturing Example 23) Phosphate group-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (4) (R 25 is a methylene group, X 25 , X 26 Polyvinyl acetal resin A16 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a vinyl aldehyde content of 1.0 mol% (wherein each hydrogen atom is a hydrogen atom) was used and 62.0 g of butyraldehyde was added instead of acetaldehyde.

[0093] (Manufacturing Example 24) Polyvinyl acetal resin B8 was obtained in the same manner as in Production Example 1, except that an unmodified polyvinyl alcohol resin (average degree of polymerization 150, degree of saponification 98 mol%) was used and 63.0 g of butyraldehyde was added instead of acetaldehyde.

[0094] (Manufacturing Example 25) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 150, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin B9 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a content of 0.01 mol% (wherein represents a hydrogen atom) was used and 17.99 g of butyraldehyde was added instead of acetaldehyde.

[0095] (Manufacturing Example 26) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 100, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin B10 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a content of 0.01 mol% (wherein represents a hydrogen atom) was used and 62.99 g of butyraldehyde was added instead of acetaldehyde.

[0096] (Manufacturing Example 27) Carboxylic acid-modified polyvinyl alcohol resin (average polymerization degree 500, saponification degree 98 mol%, structural unit represented by formula (2-1) (R 17 is a methylene group, X 17 Polyvinyl acetal resin B11 was obtained in the same manner as in Production Example 1, except that a vinyl aldehyde copolymer having a content of 0.01 mol% (wherein represents a hydrogen atom) was used and 82.99 g of butyraldehyde was added instead of acetaldehyde.

[0097] [Table 1]

[0098] (Examples 1 to 23, Comparative Examples 1 to 15) A polyvinyl acetal resin, a fibrous carbon material, and a non-aqueous solvent were mixed according to the formulation shown in Table 2 to obtain a resin composition. The non-aqueous solvent, carbon material, and resin used were as follows: <Non-aqueous solvent> N-Methylpyrrolidone <Carbon materials> MW-1: Multi-walled carbon nanotubes (Sigma-Aldrich, average fiber diameter 9 nm, average fiber length 13 μm, specific gravity 1.8, specific surface area 200 m 2 / g, G / D ratio 8.0) MW-2: Multi-walled carbon nanotubes (manufactured by Cnano, average fiber diameter 10 nm, average fiber length 150 μm, specific gravity 1.9, specific surface area 3000 m) 2 / g, G / D ratio 20) MW-3: Multi-walled carbon nanotubes (manufactured by Cnano, average fiber diameter 10 nm, average fiber length 15 μm, specific gravity 1.8, specific surface area 250 m 2 / g, G / D ratio 20) VGCF: Vapor grown carbon fiber (Showa Denko K.K., average fiber diameter 150 nm, average fiber length 15 μm, specific gravity 2.1, specific surface area 13 m) 2 / g, G / D ratio 5.5) SW-1: Single-walled carbon nanotubes (manufactured by OCSIAL, average fiber diameter 1.2±0.5 nm, average fiber length 4 μm or more, specific gravity 1.3, G / D ratio 80) AB: Granular acetylene black (manufactured by Denka Co., Ltd., average particle diameter 35 nm, specific surface area 68 m 2 / g, G / D ratio 1.27) <Resin> PVDF: Polyvinylidene fluoride (Kureha Corporation, weight-average molecular weight 630,000) PVP: Polyvinylpyrrolidone (Tokyo Chemical Industry Co., Ltd., weight-average molecular weight 40,000)

[0099] <Evaluation> The resin compositions obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Table 2.

[0100] (1) Average surface roughness (dispersibility) The obtained resin composition was applied onto a release-treated polyethylene terephthalate (PET) film so that the film thickness after drying would be 20 μm, and the coating was dried and peeled off from the PET film to prepare a sheet. The average surface roughness Ra of the obtained sheet was measured in accordance with JIS B 0601 (1994) and evaluated according to the following criteria. ◯: Ra was less than 5 μm. △: Ra was 5 μm or more and less than 8 μm. ×: Ra was 8 or more. A low average surface roughness Ra can be said to be excellent in smoothness and dispersibility.

[0101] (2) Adhesiveness The obtained resin composition was applied onto aluminum foil (thickness: 20 μm) so that the film thickness after drying would be 20 μm, and then dried to obtain a test piece in which a sheet of the resin composition was formed on the aluminum foil. This test piece was cut into a size of 1 cm in length and 2 cm in width, and using an AUTOGRAPH (Shimadzu Corporation, "AGS-J"), the sheet was pulled up while the test piece was fixed, and the peel force (N) required for the sheet to be completely peeled off from the aluminum foil was measured, and then the peel force was evaluated according to the following criteria. ◯: Peel force was 8.0 N or more. △: The peeling force was 5.0 N or more and less than 8.0 N. ×: The peeling force was less than 5.0 N.

[0102] (3) Coatability The obtained resin composition was coated on a glass plate using a doctor blade and dried in an air circulating oven at 150°C for 5 minutes to obtain a coating film. The obtained coating film was visually observed and evaluated according to the following criteria. ◯: There were no cracks or fissures on the coating surface, and the coating thickness was uniform. △: Slight cracks or fissures were observed on the coating surface. ×: Cracking or fissures were observed on the coating surface, and the coating thickness was uneven.

[0103] (4) Viscosity (dispersion stability) Ten parts by weight of the obtained resin composition was subjected to shear rate measurements of 0.1 to 1000 s using a rheometer (manufactured by Rheologica Instruments, Inc., using parallel plates with a diameter of 10 mm). -1 The viscosity was measured at a shear rate of 1 s -1 The viscosity at this temperature was taken as the paste viscosity of the sample. The measurement temperature was 20°C. The viscosity was also measured after leaving the product for one week at 20° C. The viscosity increase rate was calculated from the viscosity immediately after production and one week later using the following formula, and evaluated according to the following criteria. Viscosity increase rate (%) = (viscosity after 1 week / viscosity immediately after production) x 100 Good: Viscosity increase rate was 150% or less. △: Viscosity increase rate was more than 150% and 300% or less. ×: The viscosity increase rate was more than 300%. A small viscosity increase rate indicates excellent dispersion stability.

[0104] (5) Conductivity The obtained resin composition was applied onto a release-treated polyethylene terephthalate (PET) film so that the film thickness after drying would be 20 μm, and the coating was dried and peeled off from the PET film to prepare a sheet. The electrode resistance value of the obtained sheet was measured using an electrode resistance measuring instrument (manufactured by Hioki E.E. Corporation) and evaluated according to the following criteria. ◯: The electrode resistance value was less than 100 Ω / sq. △: The electrode resistance value was 100Ω / sq or more and less than 200Ω / sq. ×: The electrode resistance value was more than 200 Ω / sq. A low surface resistance value can be said to be excellent in electronic conductivity.

[0105] (6) DC resistance The resulting resin composition was mixed with NCM622 (LiNi 0.6 Co 0.2 Mn 0.2 A positive electrode composition was obtained by adding 10 g of 02 and 0.2 g of PVDF#7200 (polyvinylidene fluoride, manufactured by Kureha Corporation). The resulting positive electrode composition was coated on aluminum foil (20 μm thick) and dried to obtain a positive electrode sheet with a thickness of 80 μm after drying. This was then punched out to a diameter of 11 mm to obtain a positive electrode layer. A 100 μm thick lithium metal foil was punched out to a diameter of 11 mm to obtain a negative electrode layer. A 3:4:3 EC:DEC:EMC mixed solvent containing 1 mol / L LiPF6 was used as the electrolyte. The positive electrode current collector, positive electrode layer, porous PP membrane separator (25 μm thick), and lithium metal foil (negative electrode layer) were stacked in this order, and pressure was applied using a crimping machine to obtain a sealed coin-type battery. DC resistance measurements were performed on the resulting coin batteries using a charge / discharge tester (manufactured by Hokuto Denko Corporation). The voltage was measured when currents of 0.2C, 1.0C, 8.0C, and 16.0C were applied, and the DC resistance was calculated using Ohm's law and evaluated according to the following criteria. 〇: DC resistance is 8Ω or less △: DC resistance is over 8Ω and 15Ω or less ×: DC resistance exceeds 15Ω

[0106] (7) Capacity maintenance rate The capacity retention rate of the obtained coin-type battery was measured using a charge / discharge measuring device (manufactured by Hosen Co., Ltd.) The capacity retention rate was measured in the voltage range of 0.1 to 1.5 V and at an evaluation temperature of 25°C. The capacity at the 100th cycle relative to the discharge capacity at the 5th cycle was calculated as the capacity retention rate (%) and evaluated according to the following criteria. 〇: Capacity retention rate is 90% or more △: Capacity retention rate is 70% or more but less than 90% ×: Capacity retention rate is less than 70%

[0107] [Table 2] [Industrial Applicability]

[0108] According to the present invention, it is possible to provide a resin composition that has excellent coatability and adhesiveness, and can simultaneously achieve high electronic conductivity and dispersibility and dispersion stability of a fibrous carbon material, thereby enabling the production of a lithium secondary battery with a high capacity retention rate.

Claims

1. A composition comprising a fibrous carbon material, a non-aqueous solvent, and a polyvinyl acetal resin, the polyvinyl acetal resin has a structural unit having an acidic functional group, an average degree of polymerization of 150 or more and 1,500 or less, and a hydroxyl group content of 40.0 mol % or more and 80.0 mol % or less, a resin composition having a content of the fibrous carbon material of 0.05% by weight or more and 15.0% by weight or less, a content of the non-aqueous solvent of 60.0% by weight or more, and a content of the polyvinyl acetal resin of 0.1% by weight or more and 30.0% by weight or less.

2. 2. The resin composition according to claim 1, wherein the acidic functional group is at least one selected from the group consisting of a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group.

3. 3. The resin composition according to claim 1, wherein the content of the structural unit having an acidic functional group relative to all structural units of the polyvinyl acetal resin is 0.01 mol% or more and 20.0 mol% or less.

4. 4. The resin composition according to claim 1, wherein the acidic functional group is a Bronsted acidic group, and the Bronsted acid amount in the polyvinyl acetal resin is 0.1 mg / g or more and 200 mg / g or less.

5. The resin composition according to any one of claims 1 to 4, wherein the fibrous carbon material is a carbon nanotube.

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