WO2022131239A1 - Secondary battery electrode binder and method for producing same, secondary battery electrode mixture layer composition, secondary battery electrode, and secondary battery - Google Patents

Secondary battery electrode binder and method for producing same, secondary battery electrode mixture layer composition, secondary battery electrode, and secondary battery Download PDF

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WO2022131239A1
WO2022131239A1 PCT/JP2021/045978 JP2021045978W WO2022131239A1 WO 2022131239 A1 WO2022131239 A1 WO 2022131239A1 JP 2021045978 W JP2021045978 W JP 2021045978W WO 2022131239 A1 WO2022131239 A1 WO 2022131239A1
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polymer
secondary battery
mass
less
crosslinked polymer
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PCT/JP2021/045978
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French (fr)
Japanese (ja)
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健一 吉森
朋子 仲野
晃嗣 柴田
直彦 斎藤
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東亞合成株式会社
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/04—Acids; Metal salts or ammonium salts thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

Definitions

  • the present invention relates to a binder for a secondary battery electrode, a composition for a secondary battery electrode mixture layer, a secondary battery electrode, and a secondary battery.
  • a secondary battery various power storage devices such as a nickel hydrogen secondary battery, a lithium ion secondary battery, and an electric double layer capacitor have been put into practical use.
  • the electrodes used in these secondary batteries are produced by applying, drying, or the like on a current collector a composition for forming an electrode mixture layer containing an active material, a binder, and the like.
  • a composition for forming an electrode mixture layer containing an active material, a binder, and the like for example, in a lithium ion secondary battery, an aqueous binder containing styrene butadiene rubber (SBR) latex and carboxymethyl cellulose (CMC) is used as the binder used in the composition for the negative electrode mixture layer.
  • SBR styrene butadiene rubber
  • CMC carboxymethyl cellulose
  • a binder used for the positive electrode mixture layer a solution of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP) is widely used
  • a binder is used to firmly bind the active substances together (bonding property), the size of the active material is reduced to alleviate the stress associated with swelling and shrinkage, or the electrolyte solution is used. Studies are being conducted to improve durability by devising additives.
  • Patent Document 1 discloses a binder containing a crosslinked acrylic acid-based polymer obtained by cross-linking polyacrylic acid with a specific cross-linking agent, and even when an active material containing silicon is used, an electrode is used. It is disclosed to exhibit good cycle characteristics without disrupting the structure. Although the binder disclosed in Patent Document 1 can impart good binding property, a binder having higher binding property is required as the performance of the secondary battery is improved.
  • Patent Document 2 describes structural units derived from an ethylenically unsaturated carboxylic acid compound in an amount of 20.0% by mass or more and 79.5% by mass or less, and 100 g of water at 20 ° C.
  • Cross-linked acrylic having a water swelling degree in a specific range, containing 20.0% by mass or more and 79.5% by mass or less of structural units derived from a copolymerizable compound having an ethylenically unsaturated bond having a solubility in water of 7 g or more.
  • a binder containing an acid polymer is disclosed.
  • the binder for a secondary battery electrode disclosed in Patent Document 2 exhibits even higher binding properties.
  • the active material tends to settle when the composition for the electrode mixture layer containing the binder, the active material and water (hereinafter, also referred to as “electrode slurry”) is stored for a long period of time.
  • the settling stability of the electrode slurry may be a problem.
  • the present invention has been made in view of such circumstances, and an object thereof is to ensure the sedimentation stability of the electrode slurry and to exhibit excellent binding properties to improve the cycle characteristics of the secondary battery. It is to provide a binder for a secondary battery electrode which can be improved. Further, the present invention also provides a composition for a secondary battery electrode mixture layer containing the above binder, a secondary battery electrode obtained by using the composition, and a secondary battery.
  • the binder for the secondary battery electrode which contains the metal salt of the crosslinked polymer in which the abundance ratio of the carboxyl group metal salt of the crosslinked polymer based on X-ray photoelectron spectroscopic analysis (XPS) is 85 mol% or less, is The present invention has been completed by finding that it is possible to improve the cycle characteristics of a secondary battery by exhibiting excellent binding properties while ensuring the sedimentation stability of the electrode slurry.
  • the abundance ratio is a value based on XPS, it means the abundance ratio of the carboxyl group metal salt present in the surface layer from the surface of the crosslinked polymer to a depth of about 20 nm.
  • the unit includes 80% by mass or more and 99.9% by mass or less.
  • the carboxyl-based metal of the crosslinked polymer based on XPS which is calculated by the following formula (1) by X-ray photoelectron spectroscopic analysis (XPS) of the metal salt (neutralization degree N mol%) [hereinafter, polymer salt S].
  • the salt abundance ratio (X) is 85 mol% or less.
  • the type of the metal salt is the same for the crosslinked polymer salt R and the polymer salt S.
  • the exchange chain transfer mechanism is a reversible addition-cleavage chain transfer mechanism.
  • the crosslinked polymer contains 0.5% by mass or more and 20% by mass or less of structural units derived from the hydroxyl group-containing ethylenically unsaturated monomer with respect to all the structural units [1] to [4].
  • the binder for a secondary battery electrode according to any one of the above.
  • the crosslinked polymer is crosslinked with a crosslinkable monomer, and the amount of the crosslinkable monomer used is 0.001 mol% or more with respect to the total amount of the non-crosslinkable monomer 2 5.
  • the metal salt of the crosslinked polymer is neutralized to a neutralization degree of 80 to 100 mol%, and then the particle size measured in an aqueous medium is 0.1 ⁇ m or more and 10.0 ⁇ m or less in terms of volume-based median diameter.
  • the binder for a secondary battery electrode according to any one of [1] to [6].
  • a step of polymerizing a monomer component containing an ethylenically unsaturated carboxylic acid monomer by precipitation polymerization or dispersion polymerization and During the step, an exchange chain transfer mechanism type control agent is added in an amount of 0.0001 mol% or more and 0.50 mol% or less with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer.
  • the exchange chain transfer mechanism type control agent is a polymer (A) having a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by the exchange chain transfer mechanism.
  • a composition for a secondary battery electrode mixture layer which comprises the binder for a secondary battery electrode according to any one of [1] to [7], an active material, and water.
  • a secondary battery electrode comprising a mixture layer formed from the composition for the secondary battery electrode mixture layer according to [12] on the surface of a current collector.
  • a secondary battery comprising the secondary battery electrode according to [13].
  • the binder for a secondary battery electrode of the present invention it is possible to improve the cycle characteristics of the secondary battery by exhibiting excellent binding property while ensuring the sedimentation stability of the electrode slurry.
  • the binder for a secondary battery electrode of the present invention (hereinafter, also referred to as “the binder”) is a metal salt of a carboxyl group-containing crosslinked polymer (hereinafter, also referred to as “the present crosslinked polymer”) (hereinafter, “the present crossbridge”). It also contains “polymer salt”), and can be mixed with an active material and water to obtain a composition for a secondary battery electrode binder layer (hereinafter, also referred to as "this composition”). .. It is preferable that the above composition is an electrode slurry in a slurry state that can be applied to the current collector from the viewpoint of achieving the effect of the present invention, but it is prepared in a wet powder state and applied to the surface of the current collector.
  • the secondary battery electrode of the present invention can be obtained by forming a mixture layer formed from the above composition on the surface of a current collector such as a copper foil or an aluminum foil.
  • a current collector such as a copper foil or an aluminum foil.
  • the present binder is used in a composition for a secondary battery electrode mixture layer containing a silicon-based active material described later as an active material, the effect of the present invention is particularly large, which is preferable.
  • (meth) acrylic means acrylic and / or methacrylic
  • (meth) acrylate means acrylate and / or methacrylate
  • (meth) acryloyl group means an acryloyl group and / or a methacryloyl group.
  • This crosslinked polymer has a structural unit derived from an ethylenically unsaturated carboxylic acid monomer (hereinafter, also referred to as “component (a)”), and is a single amount containing an ethylenically unsaturated carboxylic acid monomer.
  • component (a) ethylenically unsaturated carboxylic acid monomer
  • the body component can be introduced into the polymer by precipitation polymerization or dispersion polymerization.
  • the crosslinked polymer has a carboxyl group due to having such a structural unit, the adhesiveness to the current collector is improved, and the lithium ion desolvation effect and the ionic conductivity are excellent, so that the resistance is small. , An electrode having excellent high rate characteristics can be obtained. Further, since water swelling property is imparted, the dispersion stability of the active substance or the like in the present composition can be enhanced.
  • Examples of the ethylenically unsaturated carboxylic acid monomer include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid; and (meth) acrylamide hexane acid and (meth) acrylamide dodecanoic acid.
  • (Partial) Examples thereof include alkali neutralized products, and one of these may be used alone, or two or more thereof may be used in combination.
  • a compound having an acryloyl group as a polymerizable functional group is preferable, and acrylic acid is particularly preferable in that a polymer having a long primary chain length can be obtained due to a high polymerization rate and the binder has a good binding force. be.
  • acrylic acid is used as the ethylenically unsaturated carboxylic acid monomer, a polymer having a high carboxyl group content can be obtained.
  • the content of the component (a) in the crosslinked polymer is 80% by mass or more and 99.9% by mass or less with respect to all the structural units of the crosslinked polymer.
  • the component (a) in such a range excellent adhesiveness to the current collector can be easily ensured.
  • the lower limit is 80% by mass or more, the sedimentation stability of the present composition becomes good and a higher binding force can be obtained, which is preferable.
  • it may be 82.5% by mass or more, and for example, 85% by mass or more. It may be present, and may be, for example, 87.5% by mass or more.
  • the upper limit is, for example, 97.5% by mass or less, for example 95% by mass or less, for example 92.5% by mass or less, and for example 90% by mass or less.
  • the range of the content of the component (a) may be a range in which such a lower limit and an upper limit are appropriately combined.
  • the crosslinked polymer may contain, in addition to the component (a), structural units derived from other ethylenically unsaturated monomers copolymerizable with the component (hereinafter, also referred to as “component (b)”).
  • component (b) examples include a hydroxyl group-containing ethylenically unsaturated monomer (a monomer represented by the following formula (1), a monomer represented by the formula (2)), a sulfonic acid group and a sulfonic acid group.
  • Examples thereof include a structural unit derived from an ethylenically unsaturated monomer compound having an anionic group other than a carboxyl group such as a phosphoric acid group, or a nonionic ethylenically unsaturated monomer.
  • These structural units are an ethylenically unsaturated monomer compound having an anionic group other than a carboxyl group such as a sulfonic acid group and a phosphoric acid group, or a monomer containing a nonionic ethylenically unsaturated monomer. Can be introduced by copolymerizing.
  • R 1 represents a hydrogen atom or a methyl group
  • R 2 is a monovalent organic group having a hydroxyl group and having 1 to 8 carbon atoms
  • (R 3 O) m H or R 4 O [CO (CH 2 ). ) 5 O] represents n H.
  • R 3 represents an alkylene group having 2 to 4 carbon atoms
  • R 4 represents an alkylene group having 1 to 8 carbon atoms
  • m represents an integer of 2 to 15
  • n represents an integer of 1 to 15. show.
  • the ratio of the component (b) can be 0.1% by mass or more and 20% by mass or less with respect to all the structural units of the present crosslinked polymer.
  • the ratio of the component (b) may be 0.5% by mass or more and 17.5% by mass or less, 1.0% by mass or more and 15% by mass or less, or 2% by mass or more and 12.5% by mass. % Or less, and may be 3% by mass or more and 10% by mass or less.
  • a hydroxyl group-containing ethylenically unsaturated monomer is preferable because it is excellent in binding property of the binder containing the present crosslinked polymer salt.
  • a structural unit derived from a nonionic ethylenically unsaturated monomer is preferable from the viewpoint of obtaining an electrode having good bending resistance, and the nonionic ethylenically unsaturated monomer is (meth). Examples thereof include acrylamide and its derivatives, nitrile group-containing ethylenically unsaturated monomers, and alicyclic structure-containing ethylenically unsaturated monomers.
  • the monomer represented by the above formula (1) is a (meth) acrylate compound having a hydroxyl group.
  • R 2 is a monovalent organic group having 1 to 8 carbon atoms having a hydroxyl group, the number of the hydroxyl groups may be only one or two or more.
  • the monovalent organic group is not particularly limited, and examples thereof include an alkyl group which may have a linear, branched or cyclic structure, an aryl group, an alkoxyalkyl group and the like. Be done.
  • R 2 is (R 3 O) m H or R 4 O [CO (CH 2 ) 5 O] n H
  • the alkylene group represented by R 3 or R 4 may be linear. It may be branched.
  • Examples of the monomer represented by the above formula (1) include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and hydroxyhexyl (meth) acrylate.
  • hydroxyalkyl (meth) acrylates having hydroxyalkyl groups with 1 to 8 carbon atoms such as hydroxyoctyl (meth) acrylates; polyethylene glycol mono (meth) acrylates, polypropylene glycol mono (meth) acrylates, polybutylene glycol mono (meth).
  • Acrylate and Polyalkylene Glycol Mono (meth) Acrylate such as Polypropylene Glycol Mono (Meta) Acrylate; Dihydroxyalkyl (Meta) Acrylate such as Glycerin Mono (Meta) Acrylate; Examples thereof include “Plaxel FM1", “Plaxel FM5", etc.), caprolactone-modified hydroxyacrylate (manufactured by Daicel Co., Ltd., trade names "Plaxel FA1", “Plaxel FA10L”, etc.) and the like. As the monomer represented by the above formula (1), one of these may be used alone, or two or more thereof may be used in combination.
  • the monomer represented by the above formula (2) is a (meth) acrylamide derivative having a hydroxyl group or a hydroxyalkyl group having 1 to 8 carbon atoms.
  • R 7 represents a hydrogen atom or a monovalent organic group.
  • the monovalent organic group is not particularly limited, and examples thereof include an alkyl group which may have a linear, branched or cyclic structure, an aryl group, an alkoxyalkyl group and the like. Therefore, it is preferably an organic group having 1 to 8 carbon atoms.
  • R 7 may be a hydroxyl group or a hydroxyalkyl group having 1 to 8 carbon atoms.
  • Examples of the monomer represented by the above formula (2) include hydroxy (meth) acrylamide; N-hydroxyethyl (meth) acrylamide, N-hydroxypropyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide, and the like. N-hydroxyhexyl (meth) acrylamide, N-hydroxyoctyl (meth) acrylamide, N-methylhydroxyethyl (meth) acrylamide, N-ethylhydroxyethyl (meth) acrylamide, and other hydroxyalkyl groups with 1 to 8 carbon atoms.
  • (Meta) acrylamide derivative N, N-di-hydroxyalkyl (meth) acrylamide such as N, N-dihydroxyethyl (meth) acrylamide and N, N-dihydroxyethyl (meth) acrylamide and the like can be mentioned.
  • N, N-di-hydroxyalkyl (meth) acrylamide such as N, N-dihydroxyethyl (meth) acrylamide and N, N-dihydroxyethyl (meth) acrylamide and the like can be mentioned.
  • the monomer represented by the above formula (2) one of these may be used alone, or two or more of them may be used in combination.
  • Examples of the (meth) acrylamide derivative include N-alkyl (meth) acrylamide compounds such as N-isopropyl (meth) acrylamide and Nt-butyl (meth) acrylamide; Nn-butoxymethyl (meth) acrylamide, N. -N-alkoxyalkyl (meth) acrylamide compounds such as isobutoxymethyl (meth) acrylamide; N, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide. Examples thereof include compounds, and one of these may be used alone, or two or more thereof may be used in combination.
  • nitrile group-containing ethylenically unsaturated monomer examples include (meth) achlorinitrile; (meth) acrylate cyanoalkyl ester compounds such as (meth) cyanomethyl acrylate and (meth) cyanoethyl acrylate; 4-cyanostyrene. , 4-Cyano- ⁇ -methylstyrene and other cyano group-containing unsaturated aromatic compounds; examples thereof include vinylidene cyanide, and one of these may be used alone or in combination of two or more. You may use it.
  • acrylonitrile is preferable because it has a high nitrile group content.
  • Examples of the alicyclic structure-containing ethylenically unsaturated monomer include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclodecyl (meth) acrylate and the like.
  • aliphatic substituent such as cyclododecyl (meth) acrylate (meth) acrylic acid cycloalkyl ester; isobornyl (meth) acrylate, adamantyl (meth) acrylate, cyclopentenyl (meth) acrylate, dicyclopentenyl.
  • examples thereof include oxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and cycloalkylpolyalcohol mono (meth) acrylate such as cyclohexanedimethanol mono (meth) acrylate and
  • the crosslinked polymer salt has an excellent binding property of the binder, and is a monomer represented by the above formula (1), a monomer represented by the above formula (2), (meth) acrylamide and the like. It is preferable to contain a derivative and a structural unit derived from a nitrile group-containing ethylenically unsaturated monomer, an alicyclic structure-containing ethylenically unsaturated monomer, or the like.
  • hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 1 to 8 carbon atoms is more preferable, and 2-hydroxyethyl (meth) acrylate is more preferable because it is excellent in the effect of improving the binding property of the binder.
  • 3-Hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are more preferred.
  • the component (b) when a structural unit derived from a hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less is introduced, a strong interaction with the electrode material can be exhibited. It can exhibit good binding properties to active materials. As a result, a solid and well-integrated electrode mixture layer can be obtained. Therefore, the above-mentioned "hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less" is particularly selected. An alicyclic structure-containing ethylenically unsaturated monomer is preferable.
  • (meth) acrylic acid ester examples include (meth) acrylics such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.
  • Acrylic acid ester compound Aromatic (meth) acrylic acid ester compounds such as phenyl (meth) acrylate, phenylmethyl (meth) acrylate, phenylethyl (meth) acrylate, and phenoxyethyl (meth) acrylate; Examples thereof include (meth) acrylic acid alkoxyalkyl ester compounds such as 2-methoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate, and one of these may be used alone or 2 You may use a combination of seeds or more.
  • an aromatic (meth) acrylic acid ester compound can be preferably used.
  • compounds having an ether bond such as (meth) acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate are preferable.
  • 2-Methoxyethyl (meth) acrylate is more preferred.
  • nonionic ethylenically unsaturated monomers a compound having an acryloyl group is preferable in that a polymer having a long primary chain length can be obtained due to its high polymerization rate and the binder has a good binding force.
  • a compound having a glass transition temperature (Tg) of a homopolymer of 0 ° C. or lower is preferable in terms of improving the bending resistance of the obtained electrode.
  • the metal salt of the crosslinked polymer is in the form of a salt in which a part or all of the carboxyl groups contained in the polymer is neutralized.
  • the type of metal salt is not particularly limited, but alkali metal salts such as lithium salt, sodium salt and potassium salt; alkaline earth metal salts such as magnesium salt, calcium salt and barium salt; other metal salts such as aluminum salt; Examples thereof include ammonium salts and organic amine salts.
  • alkali metal salts and alkaline earth metal salts are preferable, and alkali metal salts are more preferable, from the viewpoint that adverse effects on battery characteristics are unlikely to occur.
  • the present crosslinked polymer is a polymer having a crosslinked structure.
  • the cross-linking method in the present cross-linked polymer is not particularly limited, and examples thereof include the following methods. 1) Crosslinking of crosslinkable monomers 2) Utilizing the chain transfer to the polymer chain during radical polymerization 3) After synthesizing a polymer having a reactive functional group, if necessary, a crosslinking agent is added for post-crosslinking. Since the crosslinked polymer has a crosslinked structure, the binder containing the crosslinked polymer salt can have an excellent binding force.
  • the method by copolymerizing the crosslinkable monomer is preferable because the operation is simple and the degree of crosslinking can be easily controlled.
  • crosslinkable monomer examples include a polyfunctional polymerizable monomer having two or more polymerizable unsaturated groups, a monomer having a self-crosslinkable crosslinkable functional group such as a hydrolyzable silyl group, and the like. Can be mentioned.
  • the polyfunctional polymerizable monomer is a compound having two or more polymerizable functional groups such as a (meth) acryloyl group and an alkenyl group in the molecule, and is a polyfunctional (meth) acryloyl compound, a polyfunctional alkenyl compound, ( Meta) Examples thereof include compounds having both an acryloyl group and an alkenyl group. These compounds may be used alone or in combination of two or more. Among these, a polyfunctional alkenyl compound is preferable because a uniform crosslinked structure can be easily obtained, and a polyfunctional allyl ether compound having two or more allyl ether groups in the molecule is particularly preferable.
  • Examples of the polyfunctional (meth) acryloyl compound include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and polypropylene glycol.
  • Di (meth) acrylates of dihydric alcohols such as di (meth) acrylates; trimethylol propantri (meth) acrylates, tri (meth) acrylates of trimethylol propaneethylene oxide modified products, glycerin tri (meth) acrylates, pentaerythritols.
  • Tri (meth) acrylates of trivalent or higher polyhydric alcohols such as tri (meth) acrylates and pentaerythritol tetra (meth) acrylates, poly (meth) acrylates such as tetra (meth) acrylates; methylenebisacrylamide, hydroxyethylenebisacrylamide. And the like, bisamides and the like can be mentioned.
  • polyfunctional alkenyl compound examples include polyfunctional allyl ether compounds such as trimethylolpropanediallyl ether, trimethylolpropanetriallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, tetraallyloxyetane, and polyallyl saccharose; Polyfunctional allyl compounds such as phthalate; polyfunctional vinyl compounds such as divinylbenzene and the like can be mentioned.
  • polyfunctional allyl ether compounds such as trimethylolpropanediallyl ether, trimethylolpropanetriallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, tetraallyloxyetane, and polyallyl saccharose
  • Polyfunctional allyl compounds such as phthalate
  • polyfunctional vinyl compounds such as divinylbenzene and the like can be mentioned.
  • Examples of compounds having both (meth) acryloyl group and alkenyl group include (meth) allyl acrylate, (meth) isopropenyl acrylate, (meth) butenyl acrylate, (meth) pentenyl acrylate, (meth). 2- (2-Vinyloxyethoxy) ethyl acrylate and the like can be mentioned.
  • the above-mentioned monomer having a crosslinkable functional group include a hydrolyzable silyl group-containing vinyl monomer, N-methoxyalkyl (meth) acrylamide and the like. These compounds can be used alone or in combination of two or more.
  • the hydrolyzable silyl group-containing vinyl monomer is not particularly limited as long as it is a vinyl monomer having at least one hydrolyzable silyl group.
  • vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilanen; silyls such as trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, methyldimethoxysilylpropyl acrylate and the like.
  • Group-containing acrylic acid esters silyl group-containing methacrylic acid esters such as trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, methyldimethoxysilylpropyl methacrylate, dimethylmethoxysilylpropyl methacrylate; trimethoxysilylpropyl vinyl ether and the like.
  • Cyril group-containing vinyl ethers examples thereof include silyl group-containing vinyl esters such as trimethoxysilyl undecanoate vinyl.
  • the amount of the crosslinkable monomer used is the total amount of the monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, more preferably 0.05 parts by mass or more and 3.0 parts by mass or less, and further preferably 0.1 parts by mass or more with respect to 100 parts by mass. It is 2.0 parts by mass or less, more preferably 0.1 parts by mass or more and 1.7 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1.5 parts by mass or less.
  • the range of the amount of the crosslinkable monomer used may be a range in which such a lower limit and an upper limit are appropriately combined.
  • the amount of the crosslinkable monomer used is 0.01 parts by mass or more, it is preferable in that the binding property and the sedimentation stability of the electrode slurry are better. If it is 5.0 parts by mass or less, the stability of precipitation polymerization or dispersion polymerization tends to be high.
  • the amount of the crosslinkable monomer used is 0.001 mol% or more and 2.5 mol% with respect to the total amount of the monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.01 mol% or more and 2.0 mol% or less, more preferably 0.05 mol% or more and 1.75 mol% or less, and further preferably 0.05 mol%. It is more preferably 1.5 mol% or more, and further preferably 0.1 mol% or more and 1.0 mol% or less.
  • the range of the amount of the crosslinkable monomer used may be a range in which such a lower limit and an upper limit are appropriately combined.
  • the crosslinked polymer polymerizes a monomer component containing an ethylenically unsaturated carboxylic acid monomer (hereinafter, also referred to as “the present monomer”) by precipitation polymerization or dispersion polymerization.
  • the polymer (A) described later is 0.0001 as an exchange chain transfer mechanism type control agent with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer. It is obtained by a method comprising a step of adding mol% or more and 0.50 mol% or less.
  • the above-mentioned “intermediate” means "0.3T to 0.8T" when the time from the start of the step of polymerizing the present monomer to the end of the step is T.
  • the crosslinked polymer salt is preferably 0.4T to 0.8T, preferably 0.5T to 0.8T, in that it can achieve both excellent binding properties and sedimentation stability. More preferably, it is more preferably 0.5T to 0.7T.
  • the above lower limit and upper limit can be set in combination as appropriate.
  • Precipitation polymerization is a method for producing a polymer by carrying out a polymerization reaction in a solvent that dissolves a monomer as a raw material but does not substantially dissolve the polymer to be produced.
  • dispersion liquid of the polymer particles in which the primary particles of several tens of nm to several hundred nm are secondarily aggregated to several ⁇ m to several tens of ⁇ m can be obtained.
  • Dispersion stabilizers can also be used to control the particle size of the polymer.
  • the secondary aggregation can also be suppressed by selecting a dispersion stabilizer, a polymerization solvent, or the like. In general, precipitation polymerization that suppresses secondary aggregation is also called dispersion polymerization.
  • the exchange chain transfer mechanism type control agent includes a control agent (hereinafter, also referred to as “RAFT agent”) in the reversible addition-cleaving chain transfer polymerization method (RAFT method).
  • RAFT agent a control agent in the iodine transfer polymerization method
  • the control agent in the polymerization method using an organic tellurium compound (TERP method) the control agent in the polymerization method using an organic antimony compound (SBRP method), and the polymerization method using an organic bismuth compound (BIRP method).
  • a polymer having a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by an exchange chain transfer mechanism includes a control agent and the like. .) Is preferably used. Only one type of the polymer (A) may be used, or two or more types may be used in combination.
  • ethylenic property is formed on the polar surface of the particles. It is possible to surface-modify other than the unsaturated carboxylic acid monomer. Along with this, it is presumed that both excellent binding properties and sedimentation stability can be achieved at the same time.
  • the RAFT agent and the control agent in the iodine transfer polymerization method are preferable, and the RAFT agent is more preferable, in that the crosslinked structure of the present crosslinked polymer can be made more uniform.
  • RAFT agent a polymer (A) having a living radical polymerization active unit by a reversible addition-cleaving chain transfer method can be used.
  • RAFT agents those having a trithiocarbonate in the molecule are particularly preferable in that the crosslinked structure of the present crosslinked polymer can be made more uniform.
  • the polymer (A) having a living radical active unit by the iodine transfer polymerization method can be used as the control agent in the iodine transfer polymerization method.
  • the polymer (A) may be a monofunctional polymer having one active site, or a polymer (A) having two or more active sites and having two or more functional sites.
  • a bifunctional or higher exchange chain transfer mechanism type control agent is one in which the polymerized chain is extended in a bidirectional or higher direction. From the viewpoint of producing the crosslinked polymer, it may be preferable to use a bifunctional or trifunctional or higher exchange chain transfer mechanism type control agent.
  • the amount of the polymer (A) used is 0.0001 mol% or more and 0.50 mol% or less with respect to the total amount of the present monomer in that the crosslinked structure of the crosslinked polymer can be made more uniform. It is preferably 0.0001 mol% or more and 0.40 mol% or less, further preferably 0.0001 mol% or more and 0.30 mol% or less, and 0.0002 mol% or more and 0. It is even more preferable that it is .30 mol% or less.
  • polymerization initiator used together with the polymer (A) known polymerization initiators such as azo compounds, organic peroxides, and inorganic peroxides can be used, but are not particularly limited.
  • the conditions of use can be adjusted by known methods such as heat initiation, redox initiation with a reducing agent, and UV initiation so that the amount of radicals generated is appropriate.
  • azo compounds are preferable because they are easy to handle for safety and side reactions during radical polymerization are unlikely to occur.
  • azo compound examples include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (4-methoxy-). 2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-) 1-Carbonitrile), 2,2'-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2'-azobis (N-butyl-2-methylpropionamide) and the like. Only one kind of the radical polymerization initiator may be used, or two or more kinds thereof may be used in combination.
  • the preferable amount of the polymerization initiator to be used is, for example, 0.001 part by mass or more and 2 parts by mass or less, and for example, 0.005 part by mass or more and 1 by mass, when the total amount of the monomer components to be used is 100 parts by mass. It is not less than a part by mass, and is, for example, 0.01 part by mass or more and 0.1 part by mass or less.
  • the amount of the polymerization initiator used is 0.001 part by mass or more, the polymerization reaction can be stably carried out, and when it is 2 parts by mass or less, a polymer having a long primary chain length can be easily obtained.
  • the proportion of the polymerization initiator used is not particularly limited, but the amount of the polymerization initiator used per 1 mol of the exchange chain transfer mechanism type control agent is 0.5 mol from the viewpoint that the crosslinked structure of the present crosslinked polymer can be made uniform.
  • the value is preferably 0.2 mol or less, and more preferably 0.2 mol or less.
  • the lower limit of the amount of the polymerization initiator used with respect to 1 mol of the exchange chain transfer mechanism type control agent is 0.001 mol.
  • the amount of the polymerization initiator used with respect to 1 mol of the exchange chain transfer mechanism type control agent is preferably in the range of 0.001 mol or more and 0.5 mol or less, and more preferably in the range of 0.005 mol or more and 0.2 mol or less.
  • the polymerization solvent a solvent selected from water, various organic solvents and the like can be used in consideration of the type of the monomer used and the like. In order to obtain a polymer having a longer primary chain length, it is preferable to use a solvent having a small chain transfer constant.
  • the polymerization solvent include water-soluble solvents such as methanol, t-butyl alcohol, acetone, methyl ethyl ketone, acetonitrile and tetrahydrofuran, as well as benzene, ethyl acetate, dichloroethane, n-hexane, cyclohexane and n-heptane. One of these can be used alone or in combination of two or more.
  • the water-soluble solvent refers to a solvent having a solubility in water at 20 ° C. of more than 10 g / 100 ml.
  • Methylethylketone and acetonitrile are used in terms of being easy to unravel), obtaining a polymer with a small chain transfer constant and a large degree of polymerization (primary chain length), and being easy to operate during the process neutralization described later. preferable.
  • a highly polar solvent preferably include water and methanol.
  • the amount of the highly polar solvent used is preferably 0.05% by mass or more and 20.0% by mass or less, more preferably 0.1% by mass or more and 10.0% by mass or less, based on the total mass of the medium. It is more preferably 0.1% by mass or more and 5.0% by mass or less, and further preferably 0.1% by mass or more and 1.0% by mass or less.
  • the proportion of the highly polar solvent is 0.05% by mass or more, the effect on the neutralization reaction is recognized, and when it is 20.0% by mass or less, no adverse effect on the polymerization reaction is observed. Further, in the polymerization of a highly hydrophilic ethylenically unsaturated carboxylic acid monomer such as acrylic acid, the polymerization rate is improved when a highly polar solvent is added, and it becomes easy to obtain a polymer having a long primary chain length.
  • the highly polar solvents water is particularly preferable because it has a large effect of improving the polymerization rate.
  • the reaction temperature during the polymerization reaction in the presence of the polymer (A) is preferably 30 ° C. or higher and 120 ° C. or lower, more preferably 40 ° C. or higher and 110 ° C. or lower, and further preferably 50 ° C. or higher and 100 ° C. or lower. Is.
  • the reaction temperature is 30 ° C. or higher, the polymerization reaction can proceed smoothly.
  • the reaction temperature is 120 ° C. or lower, side reactions can be suppressed and restrictions on the initiators and solvents that can be used are relaxed.
  • first monomer a polymer chain (hereinafter, simply referred to as “first monomer”) of one kind or two or more kinds of vinyl-based monomers (hereinafter, also simply referred to as “first monomer”).
  • first monomer a polymer chain having a living radical polymerization active unit by an exchange chain transfer mechanism and a "first polymer chain”
  • the polymer (A) is used as a starting point for the polymerization of the present monomer, and the cross-linked polymer is polymerized.
  • the present cross-linked polymer which can be used as a dispersion stabilizer in a solvent and has a polymer chain having a structural unit derived from the present monomer bonded to the polymer chain of the polymer (A) is obtained as dispersed fine particles. Can be done.
  • the polymerization stability that is, the aggregation of the main crosslinked polymer during the polymerization step is suppressed, the generation of coarse aggregated particles is suppressed, and the main crosslinked weight having a small particle size and a narrow particle size distribution is suppressed. You can get coalescence.
  • the polymer (A) In order to make the polymer (A) function as a dispersion stabilizer in producing the crosslinked polymer by polymerizing the present monomer in the presence of the polymer (A), for example, the polymer (A) may be used. , 0.3 parts by mass or more and 50 parts by mass or less can be used with respect to 100 parts by mass of the total mass of this monomer. By using the polymer (A) in such a range, it is possible to produce the present crosslinked polymer mainly containing the present monomer while allowing the polymer (A) to function as a dispersion stabilizer.
  • the polymer (A) when the polymer (A) is less than 0.3 parts by mass, it is difficult to obtain a sufficient dispersion stabilizing effect, and the particle size of the crosslinked polymer tends to exceed 0.3 ⁇ m, even if it exceeds 50 parts by mass. This is because it is difficult to improve the functionality as a dispersion stabilizer, and the effect of reducing the particle size of the crosslinked polymer is also reduced.
  • the polymer (A) can be used with respect to 100 parts by mass of the total mass of this monomer, for example, 0.5 parts by mass or more, and for example, 1 part by mass or more. Further, the polymer (A) can be used, for example, 40 parts by mass or less, for example, 30 parts by mass or less, and for example, 20 parts by mass or less.
  • the range of the amount of the polymer (A) used with respect to 100 parts by mass of the total mass of this monomer can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • Method for Producing Polymer (A) A structural unit derived from the first monomer by polymerizing a monomer composition containing the first monomer in the presence of a known exchange chain transfer mechanism type control agent. It is possible to obtain a polymer (A) having a first polymerized chain having the above and a living polymerization active unit by an exchange chain transfer mechanism.
  • the polymerization conditions for producing the polymer (A) are well known to those skilled in the art, and examples of the polymerization process include various processes such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. Considering that it is a polymerization starting point in the production of coalescence and that it functions as a dispersion stabilizer, solution polymerization can be used, for example. Further, the polymerization conditions such as the type of the exchange chain transfer mechanism control agent, the type and amount of the polymerization initiator, the polymerization solvent, and the reaction temperature are appropriately selected according to the above paragraphs [0045] and [0051] to [0055].
  • the amount of the exchange chain transfer mechanism control agent used is appropriately adjusted according to the number average molecular weight (Mn) of the target polymer (A).
  • Mn number average molecular weight
  • a RAFT agent and a control agent in the iodine transfer polymerization method are preferable in that the molecular weight distribution of the polymer (A) can be narrowed.
  • the concentration at the time of producing the polymer (A) is not particularly limited with respect to the total mass of the amount charged such as the polymerization solvent and the first monomer, but is, for example, 10% by mass or more and 80% by mass. % Or less, for example, 15% by mass or more and 70% by mass or less, and for example, 20% by mass or more and 70% by mass or less.
  • a living polymerization active unit is provided at the end of the first polymerization chain, and the exchange chain transfer mechanism type having two or more functionalities is provided.
  • the mode is such that the living polymerization active unit is used as a base point to branch in two or more directions, and each of them is provided with a first polymerization chain.
  • the other polymerized chain is directly bonded to the living polymerization active unit, and the first polymerization is carried out more distally to the living polymerization active unit.
  • the first polymerized chain is bonded to the distal end of the other polymerized chain so that the chain is provided.
  • the polymer (A) can also include two or more kinds of first polymerized chains. For example, after performing living radical polymerization or the like using one or more first monomers of a certain composition, one or more first monomers of another composition are used. By carrying out living radical polymerization or the like, a polymer (A) having a first polymerized chain (block) having a structural unit derived from the first monomer having a different composition can be obtained.
  • the number average molecular weight (Mn) of the polymer (A) is not particularly limited, but is, for example, 3,000 or more, for example, 5,000 or more, and for example, 7,000 or more. Also, for example, 8,000 or more, and for example, 10,000 or more. Further, the Mn is, for example, 150,000 or less, for example, 100,000 or less, for example, 80,000 or less, and for example, 50,000 or less, and for example, 25, It is 000 or less, and is, for example, 15,000 or less, and is, for example, 12,000 or less.
  • Mn is less than 3,000, the binding property of the present crosslinked polymer salt is insufficient, and if it is more than 150,000, it becomes difficult to dissolve in the polymerization solvent of the dispersion polymerization to obtain the present crosslinked polymer. Will be difficult.
  • the range of Mn can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the weight average molecular weight (Mw) of the polymer (A) is not particularly limited, but is, for example, 5,000 or more, for example, 7,000 or more, and for example, 9,000 or more. Also, for example, 10,000 or more, for example, 13,000 or more, and for example, 15,000 or more. Further, the Mw is, for example, 200,000 or less, for example, 150,000 or less, for example, 100,000 or less, and for example, 80,000 or less, and 60,000 or less. Yes, for example 55,000 or less, and for example 50,000 or less, and for example 45,000 or less, and for example 40,000 or less, and for example 36,000 or less. Yes, for example, 35,000 or less, for example, 30,000 or less, and for example, 25,000 or less.
  • Mw is less than 5,000, the binding property of the present crosslinked polymer salt is insufficient, and if it is more than 200,000, it becomes difficult to dissolve in the polymerization solvent of the dispersion polymerization, and the present crosslinked polymer is obtained. Will be difficult.
  • the range of Mw can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • Both Mw and Mn of the polymer (A) can be measured by gel permeation chromatography using polystyrene as a standard substance. As for the details of the chromatography conditions, the conditions disclosed in the subsequent examples can be adopted.
  • the molecular weight distribution (Mw / Mn) of the polymer (A) is not particularly limited, but is, for example, 2.5 or less, for example, 2.4 or less, and for example, 2.3 or less. Yes, for example 2.0 or less, and for example 1.6 or less, and for example 1.5 or less, and for example 1.4 or less, and for example 1.3 or less. be. Further, the molecular weight distribution is, for example, 1.1 or more, for example, 1.2 or more, and for example, 1.3 or more, and for example, 1.4 or more, and for example, 1.5 or more. Is. The range of the molecular weight distribution can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the molecular weight distribution is preferably 2.4 or less, and in order to obtain the present crosslinked polymer having a smaller particle size, it is preferably 1.7 or less, and more preferably 1. It is 6 or less, and more preferably 1.4 or less.
  • the SP value of the polymer (A) is not particularly limited, but is, for example, 17 to 27 ((MPa) 1/2 ) in that the present crosslinked polymer having excellent sedimentation stability and binding property can be produced. Is preferable.
  • the SP value of the polymer (A) is, for example, 27 ((MPa) 1/2 ) or less, for example, 26 ((MPa) 1/2 ) or less, and for example, 25 ((MPa) 1 ). / 2 ) It is as follows.
  • the SP value of the polymer (A) is, for example, 17 ((MPa) 1/2 ) or more, for example, 18 ((MPa) 1/2 ) or more, and for example, 19 ((MPa) 1/2) or more. ) 1/2 ) or more.
  • the range of the SP value can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • first monomer examples include styrenes, (meth) acrylonitrile compounds, maleimide compounds, unsaturated acid anhydrides, unsaturated carboxylic acid compounds and the like. One of these or two or more of them can be used in combination.
  • Styrenes include styrene and its derivatives.
  • the styrene derivative include ⁇ -methylstyrene, ⁇ -methylstyrene, vinylxylene, vinylnaphthalene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene and p-.
  • Ethylstyrene, pn-butylstyrene, p-isobutylstyrene, pt-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chloromethylstyrene, p-chloromethylstyrene, o -Chlorostyrene, p-chlorostyrene, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, divinylbenzene and the like are exemplified, and one or more of these can be used.
  • styrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-hydroxystyrene, m-hydroxystyrene, and p-hydroxystyrene are preferable from the viewpoint of polymerizable property.
  • Examples of the (meth) acrylonitrile compound include (meth) acrylonitrile and ⁇ -methylacrylonitrile.
  • acrylonitrile is used.
  • the maleimide compound includes a maleimide and an N-substituted maleimide compound.
  • the N-substituted maleimide compound include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, and N-tert-butylmaleimide.
  • N-alkyl-substituted maleimide compounds such as N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide; N-Cycloalkyl-substituted maleimide compound; N-phenylmaleimide, N- (4-hydroxyphenyl) maleimide, N- (4-acetylphenyl) maleimide, N- (4-methoxyphenyl) maleimide, N- (4-ethoxyphenyl) ) N-aryl substituted maleimide compounds such as maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) maleimide, N-benzylmaleimide, etc., and one or more of these may be mentioned.
  • N-phenylmaleimide is used.
  • examples of the unsaturated acid anhydride include maleic anhydride, itaconic anhydride, citraconic anhydride and the like, and one or more of these can be used.
  • unsaturated carboxylic acid compound examples include (meth) acrylic acid, silicic acid, crotonic acid, and monoalkyl of unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid, and unsaturated dicarboxylic acids. Esters and the like can be mentioned, and one or more of them can be used.
  • the first monomer includes, for example, at least styrenes or a hydroxyl group-containing ethylenically unsaturated monomer (a monomer represented by the above formula (1), represented by the formula (2)). It is preferable to contain the monomer), and it is more preferable to contain the hydroxyl group-containing ethylenically unsaturated monomer. This is because styrenes are easy to polymerize in the living room and can impart appropriate hydrophobicity and affinity to organic solvents. It is possible to impart hydrophobicity or affinity to an organic solvent to the first polymerized chain.
  • the polymer (A) tends to be present on the surface layer of the present crosslinked polymer.
  • the dispersion stability of the crosslinked polymer is improved. This is because the hydroxyl group-containing ethylenically unsaturated monomer can impart the water dispersibility of the binder containing the crosslinked polymer salt and the affinity for the active material. By doing so, the binding property can be improved.
  • Styrene is, for example, 20% by mass or more of the total mass of the first monomer. This is because when the content is 20% by mass or more, the living polymerization is facilitated, and an appropriate hydrophobicity and an affinity for an organic solvent can be appropriately imparted. Further, for example, it is 30% by mass or more, and for example, 35% by mass or more, for example, 40% by mass or more, and for example, 50% by mass or more, and for example, 60% by mass or more. Further, for example, it is 65% by mass or more, for example, 70% by mass or more, and for example, 75% by mass or more.
  • the styrenes are 100% by mass or less of the total mass, for example, 95% by mass or less, for example, 90% by mass or less, and for example, 85% by mass or less, and for example, for example. It is 80% by mass or less, and for example, 75% by mass or less.
  • the range of the styrenes with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the (meth) acrylonitrile compound, maleimide compound, acid anhydride and unsaturated carboxylic acid compound can be used alone, and it is preferable to use one or more of these four types in combination with styrenes. This is because all of these four types can maintain, regulate or impart the hydrophobicity or organic solvent affinity of the first polymerized chain.
  • one or more of (meth) acrylonitrile compounds such as acrylonitrile, maleimide compounds such as N-phenylmaleimide, and acid anhydrides.
  • a combination of styrene and acrylonitrile, styrene and N-phenylmaleimide and the like is preferable.
  • the unsaturated carboxylic acid compound is preferable in that the polarity of the polymer (A) can be easily changed.
  • the total amount of these one or more first monomers other than styrenes is the first monomer for polymerizing the first polymerized chain (first). It is, for example, 20% by mass or more of the total mass of the first monomer unit of the polymerized chain). Further, for example, it is 25% by mass or more, and is, for example, 30% by mass or more, and is, for example, 35% by mass or more, and is, for example, 40% by mass or more, and is, for example, 50% by mass or more. Further, for example, it is 60% by mass or more.
  • the (meth) acrylonitrile compound is 80% by mass or less, for example, 75% by mass or less, and is, for example, 70% by mass or less, and is, for example, 65% by mass or less, based on the total mass. Further, for example, it is 60% by mass or less, for example, 55% by mass or less, and for example, 50% by mass or less.
  • the range of the styrenes with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the hydroxyl group-containing ethylenically unsaturated monomer is, for example, 50% by mass or more and 90% by mass or less of the total mass of the first monomer. This is because when it is 50% by mass or more, the precipitation stability of the electrode slurry containing the present crosslinked polymer salt can be imparted. Further, for example, 52.5% by mass or more, for example, 55% by mass or more, and for example, 57.5% by mass or more, and for example, 60% by mass or more, and for example, 62.5. It is 5% by mass or more, and is, for example, 65% by mass or more, and is, for example, 67.5% by mass or more, and is, for example, 70% by mass or more.
  • the hydroxyl group-containing ethylenically unsaturated monomer is, for example, 87.5% by mass or less, for example, 85% by mass or less, and for example, 82.5% by mass or less, based on the total mass. Further, for example, it is 80% by mass or less, for example, 77.5% by mass or less, and for example, 75% by mass or less.
  • the range of the hydroxyl group-containing ethylenically unsaturated monomer with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the first polymerized chain may be a polymerized chain containing only the first monomer described above, but if necessary, other vinyl-based monomers other than the above may be used as the first monomer. be able to.
  • known vinyl-based monomers such as (meth) acrylic acid esters such as (meth) acrylic acid and alkyl (meth) acrylic acid can be used.
  • these other monomers are, for example, 10% by mass or less, for example, 5% by mass or less, for example, 3% by mass or less, or, for example, the total mass of the monomers constituting the first polymerized chain. 1, 1% by mass or less, and for example, 0.5% by mass or less.
  • the polymer (A) may be provided with a block (another polymer chain) different from that of the first polymer chain.
  • Such other polymerized chains may be added, for example, in another synthetic step after the formation of the first polymerized chain.
  • the polymer (A) having the first polymerized chain is continuously or newly supplied with a radical polymerization initiator and another vinyl-based monomer to have a composition different from that of the first polymerized chain.
  • a polymer (A) having another polymer chain (block) consisting of units derived from a monomer other than the first monomer can be obtained.
  • a part of the monomer common to the present monomer used in the present crosslinked polymer can be partially linked in advance. It can be provided in the polymer (A).
  • the polymer (A) has a living radical polymerization active unit by an exchange chain transfer mechanism, it can be used as a solubility or dispersion stabilizer for the polymer (A) in the polymerization solvent in the precipitation polymerization or dispersion polymerization of this monomer.
  • Various monomers can be selected for the function of.
  • the exchange chain transfer mechanism of the living radical polymerization active unit in the polymer (A) includes a reversible addition-cleavage chain transfer polymerization method (RAFT method), an iodine transfer polymerization method, and a polymerization method using an organic tellurium compound (TERP method).
  • RAFT method reversible addition-cleavage chain transfer polymerization method
  • TERP method a polymerization method using an organic tellurium compound
  • Examples thereof include a polymerization method using an organic antimony compound (SBRP method), a polymerization method using an organic bismuth compound (BIRP method), and the like.
  • SBRP method organic antimony compound
  • BIRP method organic bismuth compound
  • the RAFT method and the iodine transfer polymerization method are preferable, and the RAFT method is more preferable, because the particle size of the crosslinked polymer can be reduced.
  • the abundance ratio (X) of the carboxyl group metal salt is 85 mol% or less (however, N is a value of 20 or more and 100 or less, and is the same for the crosslinked polymer salt R and the polymer salt S. Also, the type of metal salt. Is the same for the crosslinked polymer salt R and the polymer salt S).
  • X is 85 mol% or less, the sedimentation stability and binding property of the electrode slurry are excellent, more preferably 82.5 mol% or less, further preferably 80 mol% or less, and 75 mol%. The following is even more preferable.
  • X is obtained by a method according to the method described in the examples.
  • the crosslinked polymer salt preferably has a viscosity of 100 mPa ⁇ s or more in a 2% by mass aqueous solution thereof.
  • the viscosity of the 2 mass% concentration aqueous solution may be 1,000 mPa ⁇ s or more, 10,000 mPa ⁇ s or more, or 50,000 mPa ⁇ s or more.
  • the viscosity of the aqueous solution is predetermined. It is obtained by uniformly dissolving or dispersing the present cross-linked polymer salt in an amount to be a concentration in water, and then measuring the B-type viscosity (25 ° C.) at 12 rpm according to the method described in Examples.
  • This crosslinked polymer salt absorbs water and becomes swollen in water.
  • the crosslinked polymer has an appropriate degree of crosslinking
  • the larger the amount of hydrophilic groups of the crosslinked polymer the easier it is for the crosslinked polymer to absorb water and swell.
  • the degree of cross-linking the lower the degree of cross-linking, the easier it is for the cross-linked polymer to swell.
  • the number of cross-linking points is the same, the larger the molecular weight (primary chain length), the more cross-linking points that contribute to the formation of the three-dimensional network, so that the cross-linked polymer is less likely to swell.
  • the viscosity of the crosslinked polymer aqueous solution can be adjusted by adjusting the amount of hydrophilic groups of the crosslinked polymer, the number of crosslinking points, the primary chain length, and the like.
  • the number of the cross-linking points can be adjusted by, for example, the amount of the cross-linking monomer used, the chain transfer reaction to the polymer chain, the post-cross-linking reaction, and the like.
  • the primary chain length of the polymer can be adjusted by setting conditions related to the amount of radical generation such as the initiator and the polymerization temperature, and selecting the polymerization solvent in consideration of chain transfer and the like.
  • the crosslinked polymer salt does not exist as a mass (secondary agglomerate) having a large particle size, but is well dispersed as water-swelling particles having an appropriate particle size.
  • a binder containing a coalesced salt is preferable because it can exhibit good binding performance.
  • the particle size (water-swelling particle size) when a crosslinked polymer having a degree of neutralization based on a carboxyl group of 80 to 100 mol% is dispersed in water is a volume-based median diameter. It is preferably in the range of 0.1 ⁇ m or more and 10.0 ⁇ m or less. A more preferable range of the particle size is 0.15 ⁇ m or more and 8.0 ⁇ m or less, a further preferable range is 0.20 ⁇ m or more and 6.0 ⁇ m or less, and a further preferable range is 0.25 ⁇ m or more and 4.0 ⁇ m or less. A more preferable range is 0.30 ⁇ m or more and 2.0 ⁇ m or less.
  • the composition When the particle size is in the range of 0.30 ⁇ m or more and 2.0 ⁇ m or less, the composition is uniformly present in a suitable size in the present composition, so that the present composition is highly stable and exhibits excellent binding properties. It becomes possible. If the particle size exceeds 10.0 ⁇ m, the binding property may be insufficient as described above. In addition, there is a risk that the coatability will be insufficient because it is difficult to obtain a smooth coated surface. On the other hand, when the particle size is less than 0.1 ⁇ m, there is concern from the viewpoint of stable manufacturability.
  • the water-swelling particle size can be measured by the method described in the examples of the present specification.
  • the crosslinked polymer is unneutralized or has a neutralization degree of less than 80 mol%, it is neutralized to a neutralization degree of 80 to 100 mol% with an alkali metal hydroxide or the like, and the particle size when dispersed in water is measured. do it.
  • the crosslinked polymer or a salt thereof often exists as agglomerated particles in which primary particles are associated and aggregated in the state of powder or solution (dispersion liquid).
  • the particle size when dispersed in water is in the above range, the crosslinked polymer or a salt thereof has extremely excellent dispersibility, and is neutralized to a neutralization degree of 80 to 100 mol% to be water.
  • the agglomerated particles are disintegrated, and even if it is a dispersion of almost primary particles or a secondary agglomerate, a stable dispersed state is formed in which the particle size is in the range of 0.1 to 10.0 ⁇ m. It is a thing.
  • acid groups such as a carboxyl group derived from an ethylenically unsaturated carboxylic acid monomer are neutralized so that the degree of neutralization is 20 mol% or more in the present composition, and the mode of the salt is It is preferable to use as.
  • the degree of neutralization is more preferably 50 mol% or more, further preferably 70 mol% or more, still more preferably 75 mol% or more, still more preferably 80 mol% or more, and particularly preferably. It is 85 mol% or more.
  • the upper limit of the degree of neutralization is 100 mol%, and may be 98 mol% or 95 mol%.
  • the range of the degree of neutralization may be appropriately combined with the above lower limit value and upper limit value, and may be, for example, 50 mol% or more and 100 mol% or less, or 75 mol% or more and 100 mol% or less. , 80 mol% or more and 100 mol% or less.
  • the crosslinked polymer salt preferably has a water swelling degree of 20 or more and 80 or less at pH 8.
  • the degree of water swelling may be, for example, 21 or more, 23 or more, 25 or more, 27 or more, or 30 or more.
  • the degree of water swelling is 20 or more, the crosslinked polymer salt spreads on the surface of the active material or the current collector, and a sufficient adhesive area can be secured, so that good binding property can be obtained.
  • the upper limit of the degree of water swelling at pH 8 may be 75 or less, 70 or less, 65 or less, 60 or less, or 55 or less.
  • the range of the degree of water swelling at pH 8 can be set by appropriately combining the above upper limit value and lower limit value.
  • the degree of water swelling at pH 8 can be obtained by measuring the degree of swelling of the crosslinked polymer salt in water at pH 8.
  • the water having a pH of 8 for example, ion-exchanged water can be used, and the pH value may be adjusted by using an appropriate acid or alkali, a buffer solution or the like, if necessary.
  • the pH at the time of measurement is, for example, in the range of 8.0 ⁇ 0.5, preferably in the range of 8.0 ⁇ 0.3, more preferably in the range of 8.0 ⁇ 0.2, and further. It is preferably in the range of 8.0 ⁇ 0.1.
  • the measurement is performed at 25 ⁇ 5 ° C.
  • a person skilled in the art can adjust the degree of water swelling by controlling the composition and structure of the crosslinked polymer salt.
  • the degree of water swelling can be increased by introducing an acidic functional group or a highly hydrophilic structural unit into the crosslinked polymer. Further, by lowering the degree of cross-linking of the cross-linked polymer, the degree of water swelling is usually increased.
  • composition for a secondary battery electrode mixture layer of the present invention contains the present binder, an active material and water.
  • the amount of the binder used in the composition is, for example, 0.1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total amount of the active material.
  • the amount used is, for example, 0.2 parts by mass or more and 10 parts by mass or less, for example, 0.3 parts by mass or more and 8 parts by mass or less, and for example, 0.4 parts by mass or more and 5 parts by mass or less. ..
  • the amount of the binder used is 0.1 part by mass or more, sufficient binding property can be obtained.
  • the dispersion stability of the active material or the like can be ensured, and a uniform mixture layer can be formed.
  • the amount of the binder used is 20 parts by mass or less, the present composition does not have a high viscosity, and the coatability to the current collector can be ensured. As a result, a mixture layer having a uniform and smooth surface can be formed.
  • the lithium salt of the transition metal oxide can be used as the positive electrode active material, and for example, layered rock salt type and spinel type lithium-containing metal oxides can be used.
  • ⁇ Li (Ni 1-ab Co a Al b ) ⁇ and the like can be mentioned.
  • a spinel type positive electrode active material lithium manganate and the like can be mentioned.
  • Phosphate, silicate, sulfur and the like are used in addition to the oxide, and examples of the phosphate include olivine-type lithium iron phosphate and the like.
  • the positive electrode active material one of the above may be used alone, or two or more thereof may be combined and used as a mixture or a composite.
  • the amount of the unneutralized or partially neutralized present crosslinked polymer used is such that the amount of the unneutralized carboxyl group of the present crosslinked polymer is equal to or more than the amount of alkali eluted from the active material. It is preferable to use it.
  • the conductive auxiliary agent include carbon-based materials such as carbon black, carbon nanotubes, carbon fibers, graphite fine powder, and carbon fibers. Among these, carbon black, carbon nanotubes, and carbon fibers are easy to obtain excellent conductivity. Is preferable. Further, as the carbon black, Ketjen black and acetylene black are preferable. As the conductive auxiliary agent, one of the above may be used alone, or two or more thereof may be used in combination.
  • the amount of the conductive auxiliary agent used can be, for example, 0.2 to 20 parts by mass with respect to 100 parts by mass of the total amount of the active material from the viewpoint of achieving both conductivity and energy density, and for example, 0. It can be 2 to 10 parts by mass.
  • the positive electrode active material a material having a surface coating with a conductive carbon-based material may be used.
  • examples of the negative electrode active material include carbon-based materials, lithium metals, lithium alloys, metal oxides, and the like, and one or more of these can be used in combination.
  • active materials made of carbon-based materials such as natural graphite, artificial graphite, hard carbon and soft carbon (hereinafter, also referred to as “carbon-based active material”) are preferable, and graphite such as natural graphite and artificial graphite, Also, hard carbon is more preferred.
  • graphite spherical graphite is preferably used from the viewpoint of battery performance, and the preferable range of the particle size thereof is, for example, 1 to 20 ⁇ m, and for example, 5 to 15 ⁇ m.
  • a metal or a metal oxide capable of storing lithium such as silicon or tin can also be used as the negative electrode active material.
  • silicon has a higher capacity than graphite, and is an active material made of a silicon-based material such as silicon, a silicon alloy, and a silicon oxide such as silicon monoxide (SiO) (hereinafter, also referred to as "silicon-based active material").
  • silicon-based active material has a high capacity, the volume change due to charge / discharge is large. Therefore, it is preferable to use it in combination with the above carbon-based active material.
  • the amount of the silicon-based active material is large, the electrode material may be disintegrated and the cycle characteristics (durability) may be significantly deteriorated.
  • the amount used is, for example, 60% by mass or less, and for example, 30% by mass or less, based on the carbon-based active material.
  • the carbon-based active material itself has good electrical conductivity, it is not always necessary to add a conductive additive.
  • a conductive auxiliary agent is added for the purpose of further reducing resistance, the amount used is, for example, 10 parts by mass or less with respect to 100 parts by mass of the total amount of the active material, and for example, 5 from the viewpoint of energy density. It is less than the mass part.
  • the amount of the active material used is, for example, in the range of 10 to 75% by mass, and for example, in the range of 30 to 65% by mass, based on the total amount of the composition. If the amount of the active material used is 10% by mass or more, migration of the binder or the like can be suppressed, and it is also advantageous in terms of the drying cost of the medium. On the other hand, if it is 75% by mass or less, the fluidity and coatability of the present composition can be ensured, and a uniform mixture layer can be formed.
  • This composition uses water as a medium. Further, for the purpose of adjusting the properties and dryness of the composition, lower alcohols such as methanol and ethanol, carbonates such as ethylene carbonate, ketones such as acetone, tetrahydrofuran, N-methyl-2-pyrrolidone and the like. It may be a mixed solvent with a water-soluble organic solvent.
  • the proportion of water in the mixing medium is, for example, 50% by mass or more, and for example, 70% by mass or more.
  • the content of the medium containing water in the entire composition is, for example, from the viewpoint of the coatability of the slurry, the energy cost required for drying, and the productivity. , 25-60% by mass, and can be, for example, 35-60% by mass.
  • the present composition may further contain other binder components such as styrene-butadiene rubber (SBR) -based latex, carboxymethyl cellulose (CMC), acrylic-based latex and polyvinylidene fluoride-based latex.
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • acrylic-based latex acrylic-based latex
  • polyvinylidene fluoride-based latex polyvinylidene fluoride-based latex.
  • the amount used may be, for example, 0.1 to 5 parts by mass or less, and for example, 0.1 to 2 parts by mass, based on 100 parts by mass of the total amount of the active material. It can be less than or equal to parts, and can be, for example, 0.1 to 1 part by mass or less. If the amount of the other binder component used exceeds 5 parts by mass, the resistance increases and the high rate characteristics may be insufficient.
  • SBR-based latex and CMC are preferable, and SBR-
  • the SBR-based latex is an aqueous dispersion of a copolymer having a structural unit derived from an aromatic vinyl monomer such as styrene and a structural unit derived from an aliphatic conjugated diene-based monomer such as 1,3-butadiene. Show the body.
  • aromatic vinyl monomer include ⁇ -methylstyrene, vinyltoluene, divinylbenzene and the like in addition to styrene, and one or more of these can be used.
  • the structural unit derived from the aromatic vinyl monomer in the copolymer can be, for example, in the range of 20 to 70% by mass, and for example, 30 to 60, mainly from the viewpoint of binding property.
  • the structural unit derived from the aliphatic conjugated diene-based monomer in the copolymer is, for example, 30 to 70% by mass in that the binding property of the binder and the flexibility of the obtained electrode are good. It can be in the range of 40 to 60% by mass, for example.
  • the styrene / butadiene-based latex includes nitrile group-containing monomers such as (meth) acrylonitrile and (meth) as other monomers in order to further improve the performance such as binding property.
  • nitrile group-containing monomers such as (meth) acrylonitrile and (meth) as other monomers in order to further improve the performance such as binding property.
  • a carboxyl group-containing monomer such as acrylic acid, itaconic acid, and maleic acid
  • an ester group-containing monomer such as methyl (meth) acrylate
  • the structural unit derived from the other monomer in the copolymer can be, for example, in the range of 0 to 30% by mass, or can be, for example, in the range of 0 to 20% by mass.
  • the above-mentioned CMC refers to a substituent obtained by substituting a nonionic cellulose-based semisynthetic polymer compound with a carboxymethyl group and a salt thereof.
  • the nonionic cellulose-based semi-synthetic polymer compound include alkyl celluloses such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose, and microcrystallin cellulose; Examples thereof include hydroxyethyl cellulose, hydroxybutylmethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, hydroxyethylmethyl cellulose, hydroxypropylmethyl cellulose stearoxy ether, carboxymethyl hydroxyethyl cellulose, alkyl hydroxyethyl cellulose, hydroxyalkyl cellulose such as nonoxynyl hydroxyethyl cellulose and the like.
  • the composition for the secondary battery electrode mixture layer of the present invention contains the above-mentioned active material, water and a binder as essential constituents, and can be obtained by mixing each component by a known means.
  • the mixing method of each component is not particularly limited, and a known method can be adopted.
  • powder components such as an active substance, a conductive auxiliary agent and a binder are dry-blended and then mixed with a dispersion medium such as water. The method of dispersion and kneading is preferable.
  • a known mixer such as a planetary mixer, a thin film swirl mixer, or a self-revolving mixer can be used, but a thin film swirl mixer is used because a good dispersion state can be obtained in a short time. It is preferable to do this.
  • a thin film swirl mixer it is preferable to pre-disperse in advance with a stirrer such as a disper.
  • the pH of the slurry is not particularly limited as long as the effect of the present invention is exhibited, but it is preferably less than 12.5. It is more preferably less than 10.5 and even more preferably less than 10.5.
  • the viscosity of the slurry is not particularly limited as long as the effect of the present invention is exhibited, but the B-type viscosity (25 ° C.) at 20 rpm can be, for example, in the range of 100 to 6,000 mPa ⁇ s, and for example. , 500 to 5,000 mPa ⁇ s, or, for example, 1,000 to 4,000 mPa ⁇ s.
  • the viscosity of the slurry is within the above range, good coatability can be ensured.
  • the secondary battery electrode of the present invention comprises a mixture layer formed from the composition for the mixture layer of the secondary battery electrode of the present invention on the surface of a current collector such as copper or aluminum. ..
  • the mixture layer is formed by applying the present composition to the surface of the current collector and then drying and removing a medium such as water.
  • the method for applying the present composition is not particularly limited, and known methods such as a doctor blade method, a dip method, a roll coating method, a comma coating method, a curtain coating method, a gravure coating method and an extrusion method may be adopted. can. Further, the drying can be performed by a known method such as blowing warm air, reducing the pressure, (far) infrared rays, and irradiating microwaves.
  • the mixture layer obtained after drying is subjected to a compression treatment by a die press, a roll press or the like.
  • a compression treatment by a die press, a roll press or the like.
  • the thickness of the mixture layer can be adjusted to, for example, about 30 to 80% before compression, and the thickness of the mixture layer after compression is generally about 4 to 200 ⁇ m.
  • Secondary battery A secondary battery can be manufactured by providing a separator and an electrolytic solution on the secondary battery electrode of the present invention.
  • the electrolytic solution may be in the form of a liquid or in the form of a gel.
  • the separator is arranged between the positive electrode and the negative electrode of the battery, and plays a role of preventing a short circuit due to contact between the two electrodes and holding an electrolytic solution to ensure ionic conductivity.
  • the separator is preferably a film-like insulating microporous film having good ion permeability and mechanical strength.
  • polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene and the like can be used.
  • the electrolytic solution a known one that is generally used depending on the type of the active material can be used.
  • specific solvents include cyclic carbonates having a high dielectric constant and a high dissolving ability of an electrolyte such as propylene carbonate and ethylene carbonate, and low-viscosity chains such as ethylmethyl carbonate, dimethyl carbonate and diethyl carbonate. Examples thereof include state carbonate and the like, and these can be used alone or as a mixed solvent.
  • the electrolytic solution is used by dissolving lithium salts such as LiPF 6 , LiSbF 6 , LiBF 4 , LiClO 4 , and LiAlO 4 in these solvents.
  • an aqueous potassium hydroxide solution can be used as the electrolytic solution.
  • the secondary battery is obtained by forming a positive electrode plate and a negative electrode plate partitioned by a separator into a spiral or laminated structure and storing them in a case or the like.
  • the electrode slurry containing the binder for the secondary battery electrode disclosed in the present specification has excellent settling stability, it has excellent adhesion to the electrode material and excellent adhesion to the current collector in the mixture layer. Is expected to indicate. Therefore, the secondary battery provided with the electrodes obtained by using the above binder is expected to ensure good integrity and to show good durability (cycle characteristics) even after repeated charging and discharging, and is in-vehicle. Suitable for secondary batteries and the like.
  • EA ethyl acrylate
  • HOA 2-hydroxyethyl acrylate
  • the reaction of the obtained polymer 1 was obtained.
  • the calculated SP value based on the composition ratio was 26.5 ((MPa) 1/2 ).
  • the molecular weight of the polymer 1 was 82,100 for Mn, 118,300 for Mw, and 1 for Mw / Mn. It was .44.
  • EA and HEA correspond to the first vinyl-based monomer.
  • EA ethyl acrylate
  • BA n-butyl acrylate
  • HEA 2-hydroxyethyl acrylate
  • St styrene
  • AN acrylonitrile
  • DBTTC dibenzyltrithiocarbonate
  • V-65 2,2'-azobis (2, 4-Dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-65”)
  • -ABN-E 2,2'-azobis (2-methylbutyronitrile) (manufactured by Japan Finechem Company, Inc., trade name "ABN-E”)
  • the above measurement sample is measured by an X-ray photoelectron spectroscopic analyzer, and the abundance ratio (X) of the carboxyl group metal salt of each crosslinked polymer based on the X-ray photoelectron spectroscopic analysis (XPS) is calculated by the following formula (1).
  • N is a value of 20 or more and 100 or less, and is the same for the crosslinked polymer salt R and the polymer salt S.
  • the type of the metal salt is the same for the crosslinked polymer salt R and the polymer salt S.) ..
  • I 1 is a value calculated by the following formula (2) for the crosslinked polymer salt R based on XPS
  • I 2 is a value calculated by the following formula (3) for the polymer salt S based on XPS. It is a calculated value.
  • I 2 (atom%) AM2 / ( AM2 + AC2 + AO2 ) (3)
  • the XPS measurement was performed under the following conditions.
  • the particle size distribution of the hydrogel was measured with a laser diffraction / scattering particle size distribution meter (Microtrac MT-3300EXII, manufactured by Microtrac Bell) using ion-exchanged water as a dispersion medium.
  • a laser diffraction / scattering particle size distribution meter Microtrac MT-3300EXII, manufactured by Microtrac Bell
  • the particle size distribution shape measured after a few minutes became stable.
  • the particle size distribution was measured to obtain a volume-based median diameter (D50) as a representative value of the particle size.
  • LiOH ⁇ H2O lithium hydroxide monohydrate
  • the obtained polymerization reaction solution was centrifuged to settle the polymer particles, and then the supernatant was removed. Then, after redispersing the precipitate in acetonitrile having the same weight as the polymerization reaction solution, the washing operation of precipitating the polymer particles by centrifugation and removing the supernatant was repeated twice.
  • the precipitate was recovered and dried at 80 ° C. for 3 hours under reduced pressure to remove volatile components to obtain a powder of the metal salt R-1 of the carboxyl group-containing polymer. Since the metal salt R-1 of the carboxyl group-containing polymer has hygroscopicity, it was stored in a sealed container having a water vapor barrier property.
  • the particle size in the aqueous medium was 1.52 ⁇ m.
  • the XPS measurement result of the metal salt R-1 of the carboxyl group-containing crosslinked polymer is shown.
  • I 1 of the lithium salt R-1 neutralization degree 90 mol% of the carboxyl group-containing crosslinked polymer
  • I 2 using a lithium salt of 000) neutralization degree 90 mol%
  • I 2 using a lithium salt of 000 neutralization degree 90 mol%
  • Example 1 (Preparation of composition for electrode mixture layer) Prepare a SiOx (0.8 ⁇ x ⁇ 1.2) surface coated with carbon by the CVD method (hereinafter, also referred to as "Si-based active material"), and graphite (manufactured by Nippon Graphite Co., Ltd., trade name ". A mixture of CGB-10 ") and a Si-based active material was used as the active material.
  • Si-based active material SiOx (0.8 ⁇ x ⁇ 1.2) surface coated with carbon by the CVD method
  • graphite manufactured by Nippon Graphite Co., Ltd., trade name ". A mixture of CGB-10 ”
  • a metal salt of a crosslinked polymer containing graphite: Si-based active material: carboxyl group R-1 90: using water as a diluting solvent so that the solid content concentration of the composition for the electrode mixture layer is 40.0% by mass.
  • the electrode slurry was applied onto a current collector (copper foil) having a thickness of 20 ⁇ m, and dried in a ventilation dryer at 100 ° C. for 15 minutes to form a mixture layer. .. Then, the mixture layer was rolled so that the thickness was 50 ⁇ 5 ⁇ m and the packing density was 1.60 ⁇ 0.10 g / cm 3 , to obtain a negative electrode plate.
  • the 90 ° peel strength that is, the binder binding property
  • the rate of change in the solid content of the supernatant was determined by the following formula, and the sedimentation stability was evaluated by the following criteria (pass level: B evaluation or higher).
  • the change rate (%) of the supernatant solid content was 0.3%, which was an A rating.
  • Change rate of supernatant solid content (%) 100- (concentration of supernatant solid content after standing for 1 week) / (concentration of supernatant solid content immediately after preparation) x 100
  • a sample for a peeling test was prepared by pasting the mixture layer surface of the negative electrode electrode plate having a size of 100 mm ⁇ 25 mm on a 120 mm ⁇ 30 mm acrylic plate via a double-sided tape (Nichiban Co., Ltd. Nystack NW-20). After drying under reduced pressure conditions at 60 ° C. overnight, 90 ° peeling was performed at a measurement temperature of 25 ° C. and a tensile speed of 50 mm / min using a tensile tester (TENSILON universal test material machine RTE-1210 manufactured by ORIENTEC). The binding property was evaluated by measuring the peel strength between the mixture layer and the copper foil. The peel strength was as high as 15.3 N / m, which was good.
  • Examples 2 to 13 and Comparative Examples 1 to 4 An electrode slurry was prepared by performing the same operation as in Example 1 except that the metal salt of the carboxyl group-containing crosslinked polymer used as the binder was used as shown in Table 3. The 90 ° peel strength was evaluated for each electrode slurry. The results are shown in Table 3.
  • the composition for the secondary battery electrode mixture layer (electrode slurry) containing the binder for the secondary battery electrode of the present invention is excellent in sedimentation stability and binding property.
  • Met focusing on the structural units of the crosslinked polymer, when all the structural units include structural units derived from the hydroxyl group-containing ethylenically unsaturated monomer (Examples 1 and 7), the monomer is concerned. The result was that the binding property was further excellent as compared with the case where the structural unit derived from (Example 9) was not contained.
  • the composition for the secondary battery electrode mixture layer (electrode slurry) containing the binder for the secondary battery electrode of the present invention is excellent in sedimentation stability, and also has excellent adhesion and collection with the electrode material in the electrode mixture layer. Since it shows excellent adhesion to the electric body, it is expected to show good durability (cycle characteristics). Therefore, the secondary battery provided with the electrodes obtained by using the above binder is expected to ensure good integrity and to show good durability (cycle characteristics) even after repeated charging and discharging, and is in-vehicle. It is expected to contribute to increasing the capacity of secondary batteries for use.
  • the binder for a secondary battery electrode of the present invention can be particularly preferably used for a non-aqueous electrolyte secondary battery electrode, and is particularly useful for a non-aqueous electrolyte lithium ion secondary battery having a high energy density.

Abstract

The present invention provides a secondary battery electrode binder that maintains the sedimentation stability of an electrode slurry while exhibiting excellent binding properties and making it possible to improve the cycle characteristics of a secondary battery.　The present invention is a secondary battery electrode binder including a metal salt of a carboxyl group-containing crosslinked polymer, wherein the crosslinked polymer includes, relative to all the structural units thereof, 80-99.9 mass% of a structural unit derived from an ethylenically unsaturated carboxylic acid monomer, and the presence ratio of the carboxyl group metal salt of the crosslinked polymer according to X-ray photoelectron spectroscopy (XPS) is 85 mol% or less.

Description

二次電池電極用バインダー及びその利用Binder for secondary battery electrodes and their use
　本発明は、二次電池電極用バインダー、二次電池電極合剤層用組成物、二次電池電極及び二次電池に関する。 The present invention relates to a binder for a secondary battery electrode, a composition for a secondary battery electrode mixture layer, a secondary battery electrode, and a secondary battery.
　二次電池として、ニッケル水素二次電池、リチウムイオン二次電池、電気二重層キャパシタ等の様々な蓄電デバイスが実用化されている。これらの二次電池に使用される電極は、活物質及びバインダー等を含む電極合剤層を形成するための組成物を集電体上に塗布・乾燥等することにより作製される。例えばリチウムイオン二次電池では、負極合剤層用組成物に用いられるバインダーとして、スチレンブタジエンゴム（ＳＢＲ）ラテックス及びカルボキシメチルセルロース（ＣＭＣ）を含む水系のバインダーが使用されている。一方、正極合剤層に用いられるバインダーとしては、ポリフッ化ビニリデン（ＰＶＤＦ）のＮ－メチル－２－ピロリドン（ＮＭＰ）溶液が広く使用されている。 As a secondary battery, various power storage devices such as a nickel hydrogen secondary battery, a lithium ion secondary battery, and an electric double layer capacitor have been put into practical use. The electrodes used in these secondary batteries are produced by applying, drying, or the like on a current collector a composition for forming an electrode mixture layer containing an active material, a binder, and the like. For example, in a lithium ion secondary battery, an aqueous binder containing styrene butadiene rubber (SBR) latex and carboxymethyl cellulose (CMC) is used as the binder used in the composition for the negative electrode mixture layer. On the other hand, as a binder used for the positive electrode mixture layer, a solution of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP) is widely used.
　近年、各種二次電池の用途が拡大するにつれて、エネルギー密度、信頼性及び耐久性向上への要求が強まる傾向にある。例えば、リチウムイオン二次電池の電気容量を高める目的で、負極用活物質としてシリコン系の活物質を用いる仕様が増えてきている。しかしながら、シリコン系活物質は充放電時の体積変化が大きいことが知られており、繰り返し使用するにつれて電極合剤層の剥離又は脱落等が生じ、その結果、電池の容量が低下し、サイクル特性（耐久性）が悪化するという問題があった。
　このような不具合を抑制するために、バインダーによって活物質間を強固に結着させること（結着性）、活物質のサイズを小さくして膨潤収縮に伴う応力を緩和すること、あるいは電解液の添加剤を工夫することで、耐久性を改善する検討が行われている。 In recent years, as the applications of various secondary batteries have expanded, the demand for improved energy density, reliability and durability has tended to increase. For example, for the purpose of increasing the electric capacity of a lithium ion secondary battery, specifications for using a silicon-based active material as a negative electrode active material are increasing. However, it is known that the volume of silicon-based active materials changes significantly during charging and discharging, and the electrode mixture layer peels off or falls off as it is used repeatedly, resulting in a decrease in battery capacity and cycle characteristics. There was a problem that (durability) deteriorated.
In order to suppress such problems, a binder is used to firmly bind the active substances together (bonding property), the size of the active material is reduced to alleviate the stress associated with swelling and shrinkage, or the electrolyte solution is used. Studies are being conducted to improve durability by devising additives.
　そのような中、良好なサイクル特性を有しシリコン系活物質を用いた負極合剤層の耐久性向上に効果を奏するバインダーとして、アクリル酸系重合体が有効であることが報告されている。
　特許文献１には、特定の架橋剤によりポリアクリル酸を架橋した、架橋型アクリル酸系重合体を含有するバインダーが開示されており、シリコンを含む活物質を用いた場合であっても、電極構造が破壊されることなく良好なサイクル特性を示すことが開示されている。特許文献１に開示されるバインダーは、良好な結着性を付与し得るものの、二次電池の性能向上に伴い、より結着性の高いバインダーが求められている。 Under such circumstances, it has been reported that an acrylic acid-based polymer is effective as a binder having good cycle characteristics and effective in improving the durability of a negative electrode mixture layer using a silicon-based active material.
Patent Document 1 discloses a binder containing a crosslinked acrylic acid-based polymer obtained by cross-linking polyacrylic acid with a specific cross-linking agent, and even when an active material containing silicon is used, an electrode is used. It is disclosed to exhibit good cycle characteristics without disrupting the structure. Although the binder disclosed in Patent Document 1 can impart good binding property, a binder having higher binding property is required as the performance of the secondary battery is improved.
　結着性の高いバインダーとしては、例えば、特許文献２には、エチレン性不飽和カルボン酸化合物に由来する構造単位を２０．０質量％以上７９．５質量％以下、及び、２０℃における水１００ｇに対する溶解度が７ｇ以上であるエチレン性不飽和結合を有する共重合可能な化合物に由来する構造単位を２０．０質量％以上７９．５質量％以下含む、特定範囲の水膨潤度を有する架橋型アクリル酸系重合体を含有するバインダーが開示されている。 As a binder having high binding property, for example, Patent Document 2 describes structural units derived from an ethylenically unsaturated carboxylic acid compound in an amount of 20.0% by mass or more and 79.5% by mass or less, and 100 g of water at 20 ° C. Cross-linked acrylic having a water swelling degree in a specific range, containing 20.0% by mass or more and 79.5% by mass or less of structural units derived from a copolymerizable compound having an ethylenically unsaturated bond having a solubility in water of 7 g or more. A binder containing an acid polymer is disclosed.
国際公開第２０１４／０６５４０７号International Publication No. 2014/060407 国際公開第２０１６／０６７６３３号International Publication No. 2016/067633
　特許文献２に開示される二次電池電極用バインダーは、より一層高い結着性を示すものである。しかしながら、本発明者らの検討によれば、バインダー、活物質及び水を含む電極合剤層用組成物（以下、「電極スラリー」ともいう。）を長期保管した際に活物質が沈降しやすく、電極スラリーの沈降安定性が問題となることがあった。 The binder for a secondary battery electrode disclosed in Patent Document 2 exhibits even higher binding properties. However, according to the studies by the present inventors, the active material tends to settle when the composition for the electrode mixture layer containing the binder, the active material and water (hereinafter, also referred to as “electrode slurry”) is stored for a long period of time. , The settling stability of the electrode slurry may be a problem.
　本発明は、このような事情に鑑みてなされたものであり、その目的は、電極スラリーの沈降安定性を確保しつつ、かつ、優れた結着性を発揮して二次電池のサイクル特性を向上させ得る、二次電池電極用バインダーを提供することである。また、併せて、上記バインダーを含む二次電池電極合剤層用組成物、当該組成物を用いて得られる二次電池電極及び二次電池を提供することである。 The present invention has been made in view of such circumstances, and an object thereof is to ensure the sedimentation stability of the electrode slurry and to exhibit excellent binding properties to improve the cycle characteristics of the secondary battery. It is to provide a binder for a secondary battery electrode which can be improved. Further, the present invention also provides a composition for a secondary battery electrode mixture layer containing the above binder, a secondary battery electrode obtained by using the composition, and a secondary battery.
　本発明者らは、上記課題を解決するために鋭意検討した結果、エチレン性不飽和カルボン酸単量体に由来する構造単位を８０質量％以上９９．９質量％以下含む架橋重合体の金属塩であって、Ｘ線光電子分光分析（ＸＰＳ）に基づく当該架橋重合体のカルボキシル基金属塩の存在割合が８５モル％以下である架橋重合体の金属塩を含有する、二次電池電極用バインダーが、電極スラリーの沈降安定性を確保しつつ、優れた結着性を発揮して二次電池のサイクル特性を向上させ得ることを見出し、本発明を完成した。
　ここで、上記の存在割合は、ＸＰＳに基づく値であるため、上記架橋重合体の表面から２０ｎｍ程度の深さまでの表層に存在する、カルボキシル基金属塩の存在割合を意味する。 As a result of diligent studies to solve the above problems, the present inventors have made a metal salt of a crosslinked polymer containing 80% by mass or more and 99.9% by mass or less of structural units derived from an ethylenically unsaturated carboxylic acid monomer. The binder for the secondary battery electrode, which contains the metal salt of the crosslinked polymer in which the abundance ratio of the carboxyl group metal salt of the crosslinked polymer based on X-ray photoelectron spectroscopic analysis (XPS) is 85 mol% or less, is The present invention has been completed by finding that it is possible to improve the cycle characteristics of a secondary battery by exhibiting excellent binding properties while ensuring the sedimentation stability of the electrode slurry.
Here, since the abundance ratio is a value based on XPS, it means the abundance ratio of the carboxyl group metal salt present in the surface layer from the surface of the crosslinked polymer to a depth of about 20 nm.
　本発明は以下の通りである。
〔１〕カルボキシル基含有架橋重合体の金属塩を含む二次電池電極用バインダーであって、前記架橋重合体が、その全構造単位に対し、エチレン性不飽和カルボン酸単量体に由来する構造単位を８０質量％以上９９．９質量％以下含み、
　前記金属塩（中和度Ｎモル％）[以下、架橋重合体塩Ｒ]、及び、架橋重合体塩Ｒにおけるエチレン性不飽和カルボン酸単量体に由来する構造単位を１００質量％含む重合体の金属塩（中和度Ｎモル％）[以下、重合体塩Ｓ]のＸ線光電子分光分析（ＸＰＳ）により下記式（１）により算出される、ＸＰＳに基づく前記架橋重合体のカルボキシル基金属塩の存在割合（Ｘ）が８５モル％以下である、
　二次電池電極用バインダー。
（但し、Ｎは２０以上１００以下の値であり、架橋重合体塩Ｒ及び重合体塩Ｓについて同一。また、金属塩の種類は、架橋重合体塩Ｒ及び重合体塩Ｓについて同一。）
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000006
 〔２〕前記架橋重合体は、交換連鎖移動機構によるリビングラジカル重合活性単位を有する重合体である、〔１〕に記載の二次電池電極用バインダー。
〔３〕前記交換連鎖移動機構は、可逆的付加－開裂連鎖移動機構である〔２〕に記載の二次電池電極用バインダー。
〔４〕前記リビングラジカル重合活性単位は、トリチオカーボネート基である、〔２〕又は〔３〕に記載の二次電池電極用バインダー。
〔５〕前記架橋重合体は、その全構造単位に対し、水酸基含有エチレン性不飽和単量体に由来する構造単位を０．５質量％以上２０質量％以下含む、〔１〕～〔４〕のいずれか一に記載の二次電池電極用バインダー。
〔６〕前記架橋重合体は、架橋性単量体により架橋されたものであり、当該架橋性単量体の使用量が非架橋性単量体の総量に対して０．００１モル％以上２．５モル％以下である、〔１〕～〔５〕のいずれか一に記載の二次電池電極用バインダー。
〔７〕前記架橋重合体の金属塩は、中和度８０～１００モル％に中和された後、水媒体中で測定した粒子径が、体積基準メジアン径で０．１μｍ以上１０．０μｍ以下である、〔１〕～〔６〕のいずれか一に記載の二次電池電極用バインダー。
〔８〕カルボキシル基含有架橋重合体の金属塩を含む二次電池電極用バインダーの製造方法であって、
　沈殿重合若しくは分散重合により、エチレン性不飽和カルボン酸単量体を含む単量体成分を重合する工程と、
　前記工程の途中に、前記エチレン性不飽和カルボン酸単量体を含む単量体成分の総量に対して、交換連鎖移動機構型制御剤を０．０００１モル％以上０．５０モル％以下添加する工程とを、備え、
　前記交換連鎖移動機構型制御剤が、１種又は２種以上のビニル系単量体の重合鎖と交換連鎖移動機構によるリビングラジカル重合活性単位を有する重合体（Ａ）である、製造方法。
〔９〕前記重合体（Ａ）のＳＰ値が１７～２７（（ＭＰａ）1/2）である、〔８〕に記載の製造方法。
〔１０〕前記重合体（Ａ）は、水酸基含有エチレン性不飽和単量体に由来する構造単位を含む、〔８〕又は〔９〕に記載の製造方法。
〔１１〕前記水酸基含有エチレン性不飽和単量体に由来する構造単位の含有量は、前記重合体（Ａ）の全構造単位に対し、５０質量％以上９０質量％以下である、〔８〕～〔１０〕のいずれか一に記載の製造方法。
〔１２〕〔１〕～〔７〕のいずれか一に記載の二次電池電極用バインダー、活物質及び水を含む、二次電池電極合剤層用組成物。
〔１３〕集電体表面に、〔１２〕に記載の二次電池電極合剤層用組成物から形成される合剤層を備える、二次電池電極。
〔１４〕〔１３〕に記載の二次電池電極を備える、二次電池。 The present invention is as follows.
[1] A binder for a secondary battery electrode containing a metal salt of a crosslinked polymer containing a carboxyl group, wherein the crosslinked polymer is derived from an ethylenically unsaturated carboxylic acid monomer with respect to all structural units thereof. The unit includes 80% by mass or more and 99.9% by mass or less.
A polymer containing 100% by mass of structural units derived from the metal salt (neutralization degree N mol%) [hereinafter, crosslinked polymer salt R] and the ethylenically unsaturated carboxylic acid monomer in the crosslinked polymer salt R. The carboxyl-based metal of the crosslinked polymer based on XPS, which is calculated by the following formula (1) by X-ray photoelectron spectroscopic analysis (XPS) of the metal salt (neutralization degree N mol%) [hereinafter, polymer salt S]. The salt abundance ratio (X) is 85 mol% or less.
Binder for secondary battery electrodes.
(However, N is a value of 20 or more and 100 or less, and is the same for the crosslinked polymer salt R and the polymer salt S. The type of the metal salt is the same for the crosslinked polymer salt R and the polymer salt S.)
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000006
 [2] The binder for a secondary battery electrode according to [1], wherein the crosslinked polymer is a polymer having a living radical polymerization active unit by an exchange chain transfer mechanism.
[3] The binder for a secondary battery electrode according to [2], wherein the exchange chain transfer mechanism is a reversible addition-cleavage chain transfer mechanism.
[4] The binder for a secondary battery electrode according to [2] or [3], wherein the living radical polymerization active unit is a trithiocarbonate group.
[5] The crosslinked polymer contains 0.5% by mass or more and 20% by mass or less of structural units derived from the hydroxyl group-containing ethylenically unsaturated monomer with respect to all the structural units [1] to [4]. The binder for a secondary battery electrode according to any one of the above.
[6] The crosslinked polymer is crosslinked with a crosslinkable monomer, and the amount of the crosslinkable monomer used is 0.001 mol% or more with respect to the total amount of the non-crosslinkable monomer 2 5. The binder for a secondary battery electrode according to any one of [1] to [5], which is 5 mol% or less.
[7] The metal salt of the crosslinked polymer is neutralized to a neutralization degree of 80 to 100 mol%, and then the particle size measured in an aqueous medium is 0.1 μm or more and 10.0 μm or less in terms of volume-based median diameter. The binder for a secondary battery electrode according to any one of [1] to [6].
[8] A method for producing a binder for a secondary battery electrode containing a metal salt of a crosslinked polymer containing a carboxyl group.
A step of polymerizing a monomer component containing an ethylenically unsaturated carboxylic acid monomer by precipitation polymerization or dispersion polymerization, and
During the step, an exchange chain transfer mechanism type control agent is added in an amount of 0.0001 mol% or more and 0.50 mol% or less with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer. Prepare for the process,
The production method, wherein the exchange chain transfer mechanism type control agent is a polymer (A) having a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by the exchange chain transfer mechanism.
[9] The production method according to [8], wherein the SP value of the polymer (A) is 17 to 27 ((MPa) 1/2 ).
[10] The production method according to [8] or [9], wherein the polymer (A) contains a structural unit derived from a hydroxyl group-containing ethylenically unsaturated monomer.
[11] The content of the structural unit derived from the hydroxyl group-containing ethylenically unsaturated monomer is 50% by mass or more and 90% by mass or less with respect to the total structural unit of the polymer (A). [8] The manufacturing method according to any one of [10].
[12] A composition for a secondary battery electrode mixture layer, which comprises the binder for a secondary battery electrode according to any one of [1] to [7], an active material, and water.
[13] A secondary battery electrode comprising a mixture layer formed from the composition for the secondary battery electrode mixture layer according to [12] on the surface of a current collector.
[14] A secondary battery comprising the secondary battery electrode according to [13].
　本発明の二次電池電極用バインダーによれば、電極スラリーの沈降安定性を確保しつつ、優れた結着性を発揮して、二次電池のサイクル特性を向上させ得る。 According to the binder for a secondary battery electrode of the present invention, it is possible to improve the cycle characteristics of the secondary battery by exhibiting excellent binding property while ensuring the sedimentation stability of the electrode slurry.
ＸＰＳによる、カルボキシル基含有架橋重合体のリチウム塩Ｒ－１（中和度９０モル％)のI1の測定結果を示す図である。It is a figure which shows the measurement result of I 1 of the lithium salt R-1 (neutralization degree 90 mol%) of the carboxyl group-containing crosslinked polymer by XPS. ＸＰＳによる、ポリアクリル酸のリチウム塩（中和度９０モル％）のI2の測定結果を示す図である。It is a figure which shows the measurement result of I 2 of the lithium salt of polyacrylic acid (neutralization degree 90 mol%) by XPS.
　本発明の二次電池電極用バインダー（以下、「本バインダー」ともいう。）は、カルボキシル基含有架橋重合体（以下、「本架橋重合体」ともいう。）の金属塩（以下、「本架橋重合体塩」ともいう。）を含むものであり、活物質及び水と混合することにより二次電池電極合剤層用組成物（以下、「本組成物」ともいう。）とすることができる。上記の組成物は、集電体への塗工が可能なスラリー状態の電極スラリーであることが、本発明の効果を奏する点で好ましいが、湿粉状態として調製し、集電体表面へのプレス加工に対応できるようにしてもよい。銅箔又はアルミニウム箔等の集電体表面に上記組成物から形成される合剤層を形成することにより、本発明の二次電池電極が得られる。
　ここで、本バインダーは、活物質として後述のケイ素系活物質を含む二次電池電極合剤層用組成物に用いる場合、本発明の奏する効果が特に大きい点で好ましい。 The binder for a secondary battery electrode of the present invention (hereinafter, also referred to as “the binder”) is a metal salt of a carboxyl group-containing crosslinked polymer (hereinafter, also referred to as “the present crosslinked polymer”) (hereinafter, “the present crossbridge”). It also contains "polymer salt"), and can be mixed with an active material and water to obtain a composition for a secondary battery electrode binder layer (hereinafter, also referred to as "this composition"). .. It is preferable that the above composition is an electrode slurry in a slurry state that can be applied to the current collector from the viewpoint of achieving the effect of the present invention, but it is prepared in a wet powder state and applied to the surface of the current collector. It may be possible to cope with press working. The secondary battery electrode of the present invention can be obtained by forming a mixture layer formed from the above composition on the surface of a current collector such as a copper foil or an aluminum foil.
Here, when the present binder is used in a composition for a secondary battery electrode mixture layer containing a silicon-based active material described later as an active material, the effect of the present invention is particularly large, which is preferable.
　以下に、本バインダー、本バインダーを用いて得られる二次電池電極合剤層用組成物、二次電池電極及び二次電池の各々について、詳細に説明する。
　なお、本明細書において、「（メタ）アクリル」とは、アクリル及び／又はメタクリルを意味し、「（メタ）アクリレート」とは、アクリレート及び／又はメタクリレートを意味する。また、「（メタ）アクリロイル基」とは、アクリロイル基及び／又はメタクリロイル基を意味する。 Hereinafter, each of the present binder, the composition for the secondary battery electrode mixture layer obtained by using the present binder, the secondary battery electrode, and the secondary battery will be described in detail.
In addition, in this specification, "(meth) acrylic" means acrylic and / or methacrylic, and "(meth) acrylate" means acrylate and / or methacrylate. Further, the “(meth) acryloyl group” means an acryloyl group and / or a methacryloyl group.
１．本架橋重合体の構造単位
＜エチレン性不飽和カルボン酸単量体に由来する構造単位＞
　本架橋重合体は、エチレン性不飽和カルボン酸単量体に由来する構造単位（以下、「（ａ）成分」ともいう。）を有し、エチレン性不飽和カルボン酸単量体を含む単量体成分を沈殿重合若しくは分散重合することにより重合体に導入することができる。本架橋重合体が、係る構造単位を有することによりカルボキシル基を有することで、集電体への接着性が向上するとともに、リチウムイオンの脱溶媒和効果及びイオン伝導性に優れるため、抵抗が小さく、ハイレート特性に優れた電極が得られる。また、水膨潤性が付与されるため、本組成物中における活物質等の分散安定性を高めることができる。 1. 1. Structural unit of this crosslinked polymer <Structural unit derived from ethylenically unsaturated carboxylic acid monomer>
This crosslinked polymer has a structural unit derived from an ethylenically unsaturated carboxylic acid monomer (hereinafter, also referred to as “component (a)”), and is a single amount containing an ethylenically unsaturated carboxylic acid monomer. The body component can be introduced into the polymer by precipitation polymerization or dispersion polymerization. Since the crosslinked polymer has a carboxyl group due to having such a structural unit, the adhesiveness to the current collector is improved, and the lithium ion desolvation effect and the ionic conductivity are excellent, so that the resistance is small. , An electrode having excellent high rate characteristics can be obtained. Further, since water swelling property is imparted, the dispersion stability of the active substance or the like in the present composition can be enhanced.
　エチレン性不飽和カルボン酸単量体としては、例えば、（メタ）アクリル酸、イタコン酸、クロトン酸、マレイン酸、フマル酸；（メタ）アクリルアミドヘキサン酸及び（メタ）アクリルアミドドデカン酸等の（メタ）アクリルアミドアルキルカルボン酸；コハク酸モノヒドロキシエチル（メタ）アクリレート、ω－カルボキシ－カプロラクトンモノ（メタ）アクリレート、β－カルボキシエチル（メタ）アクリレート等のカルボキシル基を有するエチレン性不飽和単量体又はそれらの（部分）アルカリ中和物が挙げられ、これらの内の１種を単独で使用してもよいし、２種以上を組み合わせて使用してもよい。上記の中でも、重合速度が大きいために一次鎖長の長い重合体が得られ、バインダーの結着力が良好となる点で重合性官能基としてアクリロイル基を有する化合物が好ましく、特に好ましくはアクリル酸である。エチレン性不飽和カルボン酸単量体としてアクリル酸を用いた場合、カルボキシル基含有量の高い重合体を得ることができる。 Examples of the ethylenically unsaturated carboxylic acid monomer include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid; and (meth) acrylamide hexane acid and (meth) acrylamide dodecanoic acid. Acrylamide alkylcarboxylic acid; ethylenically unsaturated monomers having carboxyl groups such as monohydroxyethyl succinate (meth) acrylate, ω-carboxy-caprolactone mono (meth) acrylate, β-carboxyethyl (meth) acrylate, or theirs. (Partial) Examples thereof include alkali neutralized products, and one of these may be used alone, or two or more thereof may be used in combination. Among the above, a compound having an acryloyl group as a polymerizable functional group is preferable, and acrylic acid is particularly preferable in that a polymer having a long primary chain length can be obtained due to a high polymerization rate and the binder has a good binding force. be. When acrylic acid is used as the ethylenically unsaturated carboxylic acid monomer, a polymer having a high carboxyl group content can be obtained.
　本架橋重合体における（ａ）成分の含有量は、本架橋重合体の全構造単位に対して８０質量％以上、９９．９質量％以下含む。かかる範囲で（ａ）成分を含有することで、集電体に対する優れた接着性を容易に確保することができる。下限が８０質量％以上の場合、本組成物の沈降安定性が良好となり、より高い結着力が得られるため好ましく、例えば８２．５質量％以上であってもよく、また例えば８５質量％以上であってもよく、また例えば８７．５質量％以上であってもよい。また、上限は、例えば、９７．５質量％以下であり、また例えば９５質量％以下であり、また例えば９２．５質量％以下であり、また例えば９０質量％以下である。上記（ａ）成分の含有量の範囲としては、こうした下限及び上限を適宜組み合わせた範囲とすることができる。 The content of the component (a) in the crosslinked polymer is 80% by mass or more and 99.9% by mass or less with respect to all the structural units of the crosslinked polymer. By containing the component (a) in such a range, excellent adhesiveness to the current collector can be easily ensured. When the lower limit is 80% by mass or more, the sedimentation stability of the present composition becomes good and a higher binding force can be obtained, which is preferable. For example, it may be 82.5% by mass or more, and for example, 85% by mass or more. It may be present, and may be, for example, 87.5% by mass or more. The upper limit is, for example, 97.5% by mass or less, for example 95% by mass or less, for example 92.5% by mass or less, and for example 90% by mass or less. The range of the content of the component (a) may be a range in which such a lower limit and an upper limit are appropriately combined.
＜その他の構造単位＞
　本架橋重合体は、（ａ）成分以外に、これらと共重合可能な他のエチレン性不飽和単量体に由来する構造単位（以下、「（ｂ）成分」ともいう。）を含むことができる。（ｂ）成分としては、例えば、水酸基含有エチレン性不飽和単量体（以下の式（１）で表される単量体、式（２）で表される単量体）、スルホン酸基及びリン酸基等のカルボキシル基以外のアニオン性基を有するエチレン性不飽和単量体化合物、又は非イオン性のエチレン性不飽和単量体等に由来する構造単位が挙げられる。これらの構造単位は、スルホン酸基及びリン酸基等のカルボキシル基以外のアニオン性基を有するエチレン性不飽和単量体化合物、又は非イオン性のエチレン性不飽和単量体を含む単量体を共重合することにより導入することができる。
　ＣＨ２＝Ｃ（Ｒ１）ＣＯＯＲ２　　　（１）
［式中、Ｒ１は水素原子又はメチル基を表し、Ｒ２は水酸基を有する炭素原子数１～８の一価の有機基、（Ｒ３Ｏ）ｍＨ又はＲ４Ｏ［ＣＯ（ＣＨ２）５Ｏ］ｎＨを表す。なお、Ｒ３は炭素原子数２～４のアルキレン基を表し、Ｒ４は炭素原子数１～８のアルキレン基を表し、ｍは２～１５の整数を表し、ｎは１～１５の整数を表す。］
　ＣＨ２＝Ｃ（Ｒ５）ＣＯＮＲ６Ｒ７　　　（２）
［式中、Ｒ５は水素原子又はメチル基を表し、Ｒ６は水酸基又は炭素原子数１～８のヒドロキシアルキル基を表し、Ｒ７は水素原子又は１価の有機基を表す。］ <Other structural units>
The crosslinked polymer may contain, in addition to the component (a), structural units derived from other ethylenically unsaturated monomers copolymerizable with the component (hereinafter, also referred to as “component (b)”). can. Examples of the component (b) include a hydroxyl group-containing ethylenically unsaturated monomer (a monomer represented by the following formula (1), a monomer represented by the formula (2)), a sulfonic acid group and a sulfonic acid group. Examples thereof include a structural unit derived from an ethylenically unsaturated monomer compound having an anionic group other than a carboxyl group such as a phosphoric acid group, or a nonionic ethylenically unsaturated monomer. These structural units are an ethylenically unsaturated monomer compound having an anionic group other than a carboxyl group such as a sulfonic acid group and a phosphoric acid group, or a monomer containing a nonionic ethylenically unsaturated monomer. Can be introduced by copolymerizing.
CH 2 = C (R 1 ) COOR 2 (1)
[In the formula, R 1 represents a hydrogen atom or a methyl group, R 2 is a monovalent organic group having a hydroxyl group and having 1 to 8 carbon atoms, (R 3 O) m H or R 4 O [CO (CH 2 ). ) 5 O] represents n H. Note that R 3 represents an alkylene group having 2 to 4 carbon atoms, R 4 represents an alkylene group having 1 to 8 carbon atoms, m represents an integer of 2 to 15, and n represents an integer of 1 to 15. show. ]
CH 2 = C (R 5 ) CONR 6 R 7 (2)
[In the formula, R 5 represents a hydrogen atom or a methyl group, R 6 represents a hydroxyl group or a hydroxyalkyl group having 1 to 8 carbon atoms, and R 7 represents a hydrogen atom or a monovalent organic group. ]
　（ｂ）成分の割合は、本架橋重合体の全構造単位に対し、０．１質量％以上２０質量％以下とすることができる。（ｂ）成分の割合は、０．５質量％以上１７．５質量％以下であってもよく、１．０質量％以上１５質量％以下であってもよく、２質量％以上１２．５質量％以下であってもよく、３質量％以上１０質量％以下であってもよい。また、本架橋重合体の全構造単位に対して（ｂ）成分を０．１質量％以上含む場合、電解液への親和性が向上するため、リチウムイオン伝導性が向上する効果も期待できる。 The ratio of the component (b) can be 0.1% by mass or more and 20% by mass or less with respect to all the structural units of the present crosslinked polymer. The ratio of the component (b) may be 0.5% by mass or more and 17.5% by mass or less, 1.0% by mass or more and 15% by mass or less, or 2% by mass or more and 12.5% by mass. % Or less, and may be 3% by mass or more and 10% by mass or less. Further, when the component (b) is contained in an amount of 0.1% by mass or more with respect to all the structural units of the crosslinked polymer, the affinity for the electrolytic solution is improved, so that the effect of improving the lithium ion conductivity can be expected.
　（ｂ）成分としては、前記した中でも、本架橋重合体塩を含むバインダーの結着性に優れる点で、水酸基含有エチレン性不飽和単量体が好ましい。また、耐屈曲性が良好な電極が得られる観点から非イオン性のエチレン性不飽和単量体に由来する構造単位が好ましく、非イオン性のエチレン性不飽和単量体としては、（メタ）アクリルアミド及びその誘導体、ニトリル基含有エチレン性不飽和単量体、脂環構造含有エチレン性不飽和単量体等が挙げられる。 As the component (b), among the above-mentioned components, a hydroxyl group-containing ethylenically unsaturated monomer is preferable because it is excellent in binding property of the binder containing the present crosslinked polymer salt. Further, a structural unit derived from a nonionic ethylenically unsaturated monomer is preferable from the viewpoint of obtaining an electrode having good bending resistance, and the nonionic ethylenically unsaturated monomer is (meth). Examples thereof include acrylamide and its derivatives, nitrile group-containing ethylenically unsaturated monomers, and alicyclic structure-containing ethylenically unsaturated monomers.
　上記式（１）で表される単量体は、水酸基を有する（メタ）アクリレート化合物である。Ｒ２が水酸基を有する炭素原子数１～８の一価の有機基である場合、当該水酸基の数は、１個のみでもよいし、２個以上であってもよい。上記一価の有機基としては、特段制限されるものではないが、例えば、直鎖状、分岐状または環状構造を有していてもよいアルキル基、並びに、アリール基及びアルコキシアルキル基等が挙げられる。また、Ｒ２が（Ｒ３Ｏ）ｍＨ又はＲ４Ｏ［ＣＯ（ＣＨ２）５Ｏ］ｎＨである場合、Ｒ３又はＲ４が表すアルキレン基は、直鎖状であってもよいし分岐状であってもよい。 The monomer represented by the above formula (1) is a (meth) acrylate compound having a hydroxyl group. When R 2 is a monovalent organic group having 1 to 8 carbon atoms having a hydroxyl group, the number of the hydroxyl groups may be only one or two or more. The monovalent organic group is not particularly limited, and examples thereof include an alkyl group which may have a linear, branched or cyclic structure, an aryl group, an alkoxyalkyl group and the like. Be done. Further, when R 2 is (R 3 O) m H or R 4 O [CO (CH 2 ) 5 O] n H, the alkylene group represented by R 3 or R 4 may be linear. It may be branched.
　上記式（１）で表される単量体としては、例えば、２－ヒドロキシエチル（メタ）アクリレート、３－ヒドロキシプロピル（メタ）アクリレート、４－ヒドロキシブチル（メタ）アクリレート、ヒドロキシヘキシル（メタ）アクリレート及びヒドロキシオクチル（メタ）アクリレート等の炭素原子数１～８のヒドロキシアルキル基を有するヒドロキシアルキル（メタ）アクリレート；ポリエチレングリコールモノ（メタ）アクリレート、ポリプロピレングリコールモノ（メタ）アクリレート、ポリブチレングリコールモノ（メタ）アクリレート及びポリエチレングリコール－ポリプロピレングリコールモノ（メタ）アクリレート等のポリアルキレングリコールモノ（メタ）アクリレート；グリセリンモノ（メタ）アクリレート等のジヒドロキシアルキル（メタ）アクリレート；カプロラクトン変性ヒドロキシメタクリレート（ダイセル社製、商品名「プラクセルＦＭ１」、「プラクセルＦＭ５」等）、カプロラクトン変性ヒドロキシアクリレート（ダイセル社製、商品名「プラクセルＦＡ１」、「プラクセルＦＡ１０Ｌ」等）等が挙げられる。上記式（１）で表される単量体は、これらの内の１種を単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 Examples of the monomer represented by the above formula (1) include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and hydroxyhexyl (meth) acrylate. And hydroxyalkyl (meth) acrylates having hydroxyalkyl groups with 1 to 8 carbon atoms such as hydroxyoctyl (meth) acrylates; polyethylene glycol mono (meth) acrylates, polypropylene glycol mono (meth) acrylates, polybutylene glycol mono (meth). ) Acrylate and Polyalkylene Glycol Mono (meth) Acrylate such as Polypropylene Glycol Mono (Meta) Acrylate; Dihydroxyalkyl (Meta) Acrylate such as Glycerin Mono (Meta) Acrylate; Examples thereof include "Plaxel FM1", "Plaxel FM5", etc.), caprolactone-modified hydroxyacrylate (manufactured by Daicel Co., Ltd., trade names "Plaxel FA1", "Plaxel FA10L", etc.) and the like. As the monomer represented by the above formula (1), one of these may be used alone, or two or more thereof may be used in combination.
　上記式（２）で表される単量体は、水酸基又は炭素原子数１～８のヒドロキシアルキル基を有する（メタ）アクリルアミド誘導体である。式（２）において、Ｒ７は水素原子又は１価の有機基を表す。上記１価の有機基としては、特段制限されるものではないが、例えば、直鎖状、分岐状または環状構造を有していてもよいアルキル基、並びに、アリール基及びアルコキシアルキル基等が挙げられ、炭素原子数１～８の有機基であることが好ましい。その他に、Ｒ７は、水酸基又は炭素原子数１～８のヒドロキシアルキル基であってもよい。 The monomer represented by the above formula (2) is a (meth) acrylamide derivative having a hydroxyl group or a hydroxyalkyl group having 1 to 8 carbon atoms. In formula (2), R 7 represents a hydrogen atom or a monovalent organic group. The monovalent organic group is not particularly limited, and examples thereof include an alkyl group which may have a linear, branched or cyclic structure, an aryl group, an alkoxyalkyl group and the like. Therefore, it is preferably an organic group having 1 to 8 carbon atoms. In addition, R 7 may be a hydroxyl group or a hydroxyalkyl group having 1 to 8 carbon atoms.
　上記式（２）で表される単量体としては、例えば、ヒドロキシ（メタ）アクリルアミド；Ｎ－ヒドロキシエチル（メタ）アクリルアミド、Ｎ－ヒドロキシプロピル（メタ）アクリルアミド、Ｎ－ヒドロキシブチル（メタ）アクリルアミド、Ｎ－ヒドロキシへキシル（メタ）アクリルアミド及びＮ－ヒドロキシオクチル（メタ）アクリルアミド、Ｎ－メチルヒドロキシエチル（メタ）アクリルアミド及びＮ－エチルヒドロキシエチル（メタ）アクリルアミド等の炭素原子数１～８のヒドロキシアルキル基を有する（メタ）アクリルアミド誘導体；Ｎ，Ｎ－ジヒドロキシエチル（メタ）アクリルアミド及びＮ，Ｎ－ジヒドロキシエチル（メタ）アクリルアミド等のＮ，Ｎ－ジ－ヒドロキシアルキル（メタ）アクリルアミド等が挙げられる。上記式（２）で表される単量体は、これらの内の１種を単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 Examples of the monomer represented by the above formula (2) include hydroxy (meth) acrylamide; N-hydroxyethyl (meth) acrylamide, N-hydroxypropyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide, and the like. N-hydroxyhexyl (meth) acrylamide, N-hydroxyoctyl (meth) acrylamide, N-methylhydroxyethyl (meth) acrylamide, N-ethylhydroxyethyl (meth) acrylamide, and other hydroxyalkyl groups with 1 to 8 carbon atoms. (Meta) acrylamide derivative; N, N-di-hydroxyalkyl (meth) acrylamide such as N, N-dihydroxyethyl (meth) acrylamide and N, N-dihydroxyethyl (meth) acrylamide and the like can be mentioned. As the monomer represented by the above formula (2), one of these may be used alone, or two or more of them may be used in combination.
　（メタ）アクリルアミド誘導体としては、例えば、Ｎ－イソプロピル（メタ）アクリルアミド、Ｎ－ｔ－ブチル（メタ）アクリルアミド等のＮ－アルキル（メタ）アクリルアミド化合物；Ｎ－ｎ－ブトキシメチル（メタ）アクリルアミド、Ｎ－イソブトキシメチル（メタ）アクリルアミド等のＮ－アルコキシアルキル（メタ）アクリルアミド化合物；Ｎ，Ｎ－ジメチル（メタ）アクリルアミド、Ｎ，Ｎ－ジエチル（メタ）アクリルアミド等のＮ，Ｎ－ジアルキル（メタ）アクリルアミド化合物が挙げられ、これらの内の１種を単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 Examples of the (meth) acrylamide derivative include N-alkyl (meth) acrylamide compounds such as N-isopropyl (meth) acrylamide and Nt-butyl (meth) acrylamide; Nn-butoxymethyl (meth) acrylamide, N. -N-alkoxyalkyl (meth) acrylamide compounds such as isobutoxymethyl (meth) acrylamide; N, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide. Examples thereof include compounds, and one of these may be used alone, or two or more thereof may be used in combination.
　ニトリル基含有エチレン性不飽和単量体としては、例えば、（メタ）アクロリニトリル；（メタ）アクリル酸シアノメチル、（メタ）アクリル酸シアノエチル等の（メタ）アクリル酸シアノアルキルエステル化合物；４－シアノスチレン、４－シアノ－α－メチルスチレン等のシアノ基含有不飽和芳香族化合物；シアン化ビニリデン等が挙げられ、これらの内の１種を単独で使用してもよいし、２種以上を組み合わせて使用してもよい。上記の中でも、ニトリル基含有量が多い点でアクリロニトリルが好ましい。 Examples of the nitrile group-containing ethylenically unsaturated monomer include (meth) achlorinitrile; (meth) acrylate cyanoalkyl ester compounds such as (meth) cyanomethyl acrylate and (meth) cyanoethyl acrylate; 4-cyanostyrene. , 4-Cyano-α-methylstyrene and other cyano group-containing unsaturated aromatic compounds; examples thereof include vinylidene cyanide, and one of these may be used alone or in combination of two or more. You may use it. Among the above, acrylonitrile is preferable because it has a high nitrile group content.
　脂環構造含有エチレン性不飽和単量体としては、例えば、シクロペンチル（メタ）アクリレート、シクロヘキシル（メタ）アクリレート、メチルシクロヘキシル（メタ）アクリレート、ｔ－ブチルシクロヘキシル（メタ）アクリレート、シクロデシル（メタ）アクリレート及びシクロドデシル（メタ）アクリレート等の脂肪族置換基を有していてもよい（メタ）アクリル酸シクロアルキルエステル；イソボルニル（メタ）アクリレート、アダマンチル（メタ）アクリレート、シクロペンテニル（メタ）アクリレート、ジシクロペンテニルオキシエチル（メタ）アクリレート、ジシクロペンタニル（メタ）アクリレート、並びに、シクロヘキサンジメタノールモノ（メタ）アクリレート及びシクロデカンジメタノールモノ（メタ）アクリレート等のシクロアルキルポリアルコールモノ（メタ）アクリレート等が挙げられ、これらの内の１種を単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 Examples of the alicyclic structure-containing ethylenically unsaturated monomer include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclodecyl (meth) acrylate and the like. It may have an aliphatic substituent such as cyclododecyl (meth) acrylate (meth) acrylic acid cycloalkyl ester; isobornyl (meth) acrylate, adamantyl (meth) acrylate, cyclopentenyl (meth) acrylate, dicyclopentenyl. Examples thereof include oxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and cycloalkylpolyalcohol mono (meth) acrylate such as cyclohexanedimethanol mono (meth) acrylate and cyclodecanedimethanol mono (meth) acrylate. Therefore, one of these may be used alone, or two or more thereof may be used in combination.
　本架橋重合体塩は、本バインダーの結着性が優れる点で、上記式（１）で表される単量体、上記式（２）で表される単量体、（メタ）アクリルアミド及びその誘導体、並びに、ニトリル基含有エチレン性不飽和単量体、脂環構造含有エチレン性不飽和単量体等に由来する構造単位を含むことが好ましい。
　（ｂ）成分としては、本バインダーの結着性向上効果に優れる点で、炭素原子数１～８のヒドロキシアルキル基を有するヒドロキシアルキル（メタ）アクリレートがより好ましく、２－ヒドロキシエチル（メタ）アクリレート、３－ヒドロキシプロピル（メタ）アクリレート及び４－ヒドロキシブチル（メタ）アクリレートがさらに好ましい。 The crosslinked polymer salt has an excellent binding property of the binder, and is a monomer represented by the above formula (1), a monomer represented by the above formula (2), (meth) acrylamide and the like. It is preferable to contain a derivative and a structural unit derived from a nitrile group-containing ethylenically unsaturated monomer, an alicyclic structure-containing ethylenically unsaturated monomer, or the like.
As the component (b), hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 1 to 8 carbon atoms is more preferable, and 2-hydroxyethyl (meth) acrylate is more preferable because it is excellent in the effect of improving the binding property of the binder. , 3-Hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are more preferred.
　また、（ｂ）成分としては、水中への溶解性が１ｇ／１００ｍｌ以下の疎水性のエチレン性不飽和単量体に由来する構造単位を導入した場合、電極材料と強い相互作用を奏することができ、活物質に対して良好な結着性を発揮することができる。これにより、堅固で一体性の良好な電極合剤層を得ることができるため、前記した「水中への溶解性が１ｇ／１００ｍｌ以下の疎水性のエチレン性不飽和単量体」としては、特に脂環構造含有エチレン性不飽和単量体が好ましい。 Further, as the component (b), when a structural unit derived from a hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less is introduced, a strong interaction with the electrode material can be exhibited. It can exhibit good binding properties to active materials. As a result, a solid and well-integrated electrode mixture layer can be obtained. Therefore, the above-mentioned "hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less" is particularly selected. An alicyclic structure-containing ethylenically unsaturated monomer is preferable.
　また、その他の非イオン性のエチレン性不飽和単量体としては、例えば（メタ）アクリル酸エステルを用いてもよい。（メタ）アクリル酸エステルとしては、例えば、メチル（メタ）アクリレート、エチル（メタ）アクリレート、ｎ－ブチル（メタ）アクリレート、イソブチル（メタ）アクリレート、２－エチルヘキシル（メタ）アクリレート等の（メタ）アクリル酸アルキルエステル化合物；
フェニル（メタ）アクリレート、フェニルメチル（メタ）アクリレート、フェニルエチル（メタ）アクリレート、フェノキシエチル（メタ）アクリレート等の芳香族（メタ）アクリル酸エステル化合物；
２－メトキシエチル（メタ）アクリレート、２－エトキシエチル（メタ）アクリレート等の（メタ）アクリル酸アルコキシアルキルエステル化合物等が挙げられ、これらの内の１種を単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 Further, as the other nonionic ethylenically unsaturated monomer, for example, (meth) acrylic acid ester may be used. Examples of the (meth) acrylic acid ester include (meth) acrylics such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Acrylic acid ester compound;
Aromatic (meth) acrylic acid ester compounds such as phenyl (meth) acrylate, phenylmethyl (meth) acrylate, phenylethyl (meth) acrylate, and phenoxyethyl (meth) acrylate;
Examples thereof include (meth) acrylic acid alkoxyalkyl ester compounds such as 2-methoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate, and one of these may be used alone or 2 You may use a combination of seeds or more.
　活物質との結着性及びサイクル特性の観点からは、芳香族（メタ）アクリル酸エステル化合物を好ましく用いることができる。リチウムイオン伝導性及びハイレート特性がより向上する観点から、２－メトキシエチル（メタ）アクリレート及び２－エトキシエチル（メタ）アクリレートなどの（メタ）アクリル酸アルコキシアルキルエステル等、エーテル結合を有する化合物が好ましく、２－メトキシエチル（メタ）アクリレートがより好ましい。 From the viewpoint of binding property to the active material and cycle characteristics, an aromatic (meth) acrylic acid ester compound can be preferably used. From the viewpoint of further improving lithium ion conductivity and high rate characteristics, compounds having an ether bond such as (meth) acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate are preferable. , 2-Methoxyethyl (meth) acrylate is more preferred.
　非イオン性のエチレン性不飽和単量体の中でも、重合速度が速いために一次鎖長の長い重合体が得られ、バインダーの結着力が良好となる点でアクリロイル基を有する化合物が好ましい。また、非イオン性のエチレン性不飽和単量体としては、得られる電極の耐屈曲性が良好となる点でホモポリマーのガラス転移温度（Ｔｇ）が０℃以下の化合物が好ましい。 Among the nonionic ethylenically unsaturated monomers, a compound having an acryloyl group is preferable in that a polymer having a long primary chain length can be obtained due to its high polymerization rate and the binder has a good binding force. Further, as the nonionic ethylenically unsaturated monomer, a compound having a glass transition temperature (Tg) of a homopolymer of 0 ° C. or lower is preferable in terms of improving the bending resistance of the obtained electrode.
　本架橋重合体の金属塩は、当該重合体中に含まれるカルボキシル基の一部又は全部が中和された塩の形態である。金属塩の種類としては特に限定しないが、リチウム塩、ナトリウム塩、カリウム塩等のアルカリ金属塩；マグネシウム塩、カルシウム塩及びバリウム塩等のアルカリ土類金属塩；アルミニウム塩等のその他の金属塩；アンモニウム塩及び有機アミン塩等が挙げられる。これらの中でも電池特性への悪影響が生じにくい点からアルカリ金属塩及びアルカリ土類金属塩が好ましく、アルカリ金属塩がより好ましい。 The metal salt of the crosslinked polymer is in the form of a salt in which a part or all of the carboxyl groups contained in the polymer is neutralized. The type of metal salt is not particularly limited, but alkali metal salts such as lithium salt, sodium salt and potassium salt; alkaline earth metal salts such as magnesium salt, calcium salt and barium salt; other metal salts such as aluminum salt; Examples thereof include ammonium salts and organic amine salts. Among these, alkali metal salts and alkaline earth metal salts are preferable, and alkali metal salts are more preferable, from the viewpoint that adverse effects on battery characteristics are unlikely to occur.
　本架橋重合体は、架橋構造を有する重合体である。本架橋重合体における架橋方法は特に制限されるものではなく、例えば以下の方法による態様が例示される。
１）架橋性単量体の共重合
２）ラジカル重合時のポリマー鎖への連鎖移動を利用
３）反応性官能基を有する重合体を合成後、必要に応じて架橋剤を添加して後架橋
　本架橋重合体が架橋構造を有することにより、本架橋重合体塩を含むバインダーは、優れた結着力を有することができる。上記の内でも、操作が簡便であり、架橋の程度を制御し易い点から架橋性単量体の共重合による方法が好ましい。 The present crosslinked polymer is a polymer having a crosslinked structure. The cross-linking method in the present cross-linked polymer is not particularly limited, and examples thereof include the following methods.
1) Crosslinking of crosslinkable monomers 2) Utilizing the chain transfer to the polymer chain during radical polymerization 3) After synthesizing a polymer having a reactive functional group, if necessary, a crosslinking agent is added for post-crosslinking. Since the crosslinked polymer has a crosslinked structure, the binder containing the crosslinked polymer salt can have an excellent binding force. Among the above, the method by copolymerizing the crosslinkable monomer is preferable because the operation is simple and the degree of crosslinking can be easily controlled.
＜架橋性単量体＞
　架橋性単量体としては、２個以上の重合性不飽和基を有する多官能重合性単量体、及び加水分解性シリル基等の自己架橋可能な架橋性官能基を有する単量体等が挙げられる。 <Crosslinkable monomer>
Examples of the crosslinkable monomer include a polyfunctional polymerizable monomer having two or more polymerizable unsaturated groups, a monomer having a self-crosslinkable crosslinkable functional group such as a hydrolyzable silyl group, and the like. Can be mentioned.
　上記多官能重合性単量体は、（メタ）アクリロイル基、アルケニル基等の重合性官能基を分子内に２つ以上有する化合物であり、多官能（メタ）アクリロイル化合物、多官能アルケニル化合物、（メタ）アクリロイル基及びアルケニル基の両方を有する化合物等が挙げられる。これらの化合物は、１種のみを単独で用いてもよいし、２種以上を組み合わせて用いてもよい。これらの内でも、均一な架橋構造を得やすい点で多官能アルケニル化合物が好ましく、分子内に２個以上のアリルエーテル基を有する多官能アリルエーテル化合物が特に好ましい。 The polyfunctional polymerizable monomer is a compound having two or more polymerizable functional groups such as a (meth) acryloyl group and an alkenyl group in the molecule, and is a polyfunctional (meth) acryloyl compound, a polyfunctional alkenyl compound, ( Meta) Examples thereof include compounds having both an acryloyl group and an alkenyl group. These compounds may be used alone or in combination of two or more. Among these, a polyfunctional alkenyl compound is preferable because a uniform crosslinked structure can be easily obtained, and a polyfunctional allyl ether compound having two or more allyl ether groups in the molecule is particularly preferable.
　多官能（メタ）アクリロイル化合物としては、例えば、エチレングリコールジ（メタ）アクリレート、プロピレングリコールジ（メタ）アクリレート、１，６－ヘキサンジオールジ（メタ）アクリレート、ポリエチレングリコールジ（メタ）アクリレート、ポリプロピレングリコールジ（メタ）アクリレート等の２価アルコールのジ（メタ）アクリレート類；トリメチロールプロパントリ（メタ）アクリレート、トリメチロールプロパンエチレンオキサイド変性体のトリ（メタ）アクリレート、グリセリントリ（メタ）アクリレート、ペンタエリスリトールトリ（メタ）アクリレート、ペンタエリスリトールテトラ（メタ）アクリレート等の３価以上の多価アルコールのトリ（メタ）アクリレート、テトラ（メタ）アクリレート等のポリ（メタ）アクリレート；メチレンビスアクリルアミド、ヒドロキシエチレンビスアクリルアミド等のビスアミド類等を挙げることができる。 Examples of the polyfunctional (meth) acryloyl compound include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and polypropylene glycol. Di (meth) acrylates of dihydric alcohols such as di (meth) acrylates; trimethylol propantri (meth) acrylates, tri (meth) acrylates of trimethylol propaneethylene oxide modified products, glycerin tri (meth) acrylates, pentaerythritols. Tri (meth) acrylates of trivalent or higher polyhydric alcohols such as tri (meth) acrylates and pentaerythritol tetra (meth) acrylates, poly (meth) acrylates such as tetra (meth) acrylates; methylenebisacrylamide, hydroxyethylenebisacrylamide. And the like, bisamides and the like can be mentioned.
　多官能アルケニル化合物としては、例えば、トリメチロールプロパンジアリルエーテル、トリメチロールプロパントリアリルエーテル、ペンタエリスリトールジアリルエーテル、ペンタエリスリトールトリアリルエーテル、テトラアリルオキシエタン、ポリアリルサッカロース等の多官能アリルエーテル化合物；ジアリルフタレート等の多官能アリル化合物；ジビニルベンゼン等の多官能ビニル化合物等を挙げることができる。 Examples of the polyfunctional alkenyl compound include polyfunctional allyl ether compounds such as trimethylolpropanediallyl ether, trimethylolpropanetriallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, tetraallyloxyetane, and polyallyl saccharose; Polyfunctional allyl compounds such as phthalate; polyfunctional vinyl compounds such as divinylbenzene and the like can be mentioned.
　（メタ）アクリロイル基及びアルケニル基の両方を有する化合物としては、例えば、（メタ）アクリル酸アリル、（メタ）アクリル酸イソプロペニル、（メタ）アクリル酸ブテニル、（メタ）アクリル酸ペンテニル、（メタ）アクリル酸２－（２－ビニロキシエトキシ）エチル等を挙げることができる。 Examples of compounds having both (meth) acryloyl group and alkenyl group include (meth) allyl acrylate, (meth) isopropenyl acrylate, (meth) butenyl acrylate, (meth) pentenyl acrylate, (meth). 2- (2-Vinyloxyethoxy) ethyl acrylate and the like can be mentioned.
　上記自己架橋可能な架橋性官能基を有する単量体の具体的な例としては、加水分解性シリル基含有ビニル単量体、Ｎ－メトキシアルキル（メタ）アクリルアミド等が挙げられる。これらの化合物は、１種単独であるいは２種以上を組み合わせて用いることができる。 Specific examples of the above-mentioned monomer having a crosslinkable functional group include a hydrolyzable silyl group-containing vinyl monomer, N-methoxyalkyl (meth) acrylamide and the like. These compounds can be used alone or in combination of two or more.
　加水分解性シリル基含有ビニル単量体としては、加水分解性シリル基を少なくとも１個有するビニル単量体であれば、特に限定されない。例えば、ビニルトリメトキシシラン、ビニルトリエトキシシラン、ビニルメチルジメトキシシラン、ビニルジメチルメトキシシランン等のビニルシラン類；アクリル酸トリメトキシシリルプロピル、アクリル酸トリエトキシシリルプロピル、アクリル酸メチルジメトキシシリルプロピル等のシリル基含有アクリル酸エステル類；メタクリル酸トリメトキシシリルプロピル、メタクリル酸トリエトキシシリルプロピル、メタクリル酸メチルジメトキシシリルプロピル、メタクリル酸ジメチルメトキシシリルプロピル等のシリル基含有メタクリル酸エステル類；トリメトキシシリルプロピルビニルエーテル等のシリル基含有ビニルエーテル類；トリメトキシシリルウンデカン酸ビニル等のシリル基含有ビニルエステル類等を挙げることができる。 The hydrolyzable silyl group-containing vinyl monomer is not particularly limited as long as it is a vinyl monomer having at least one hydrolyzable silyl group. For example, vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilanen; silyls such as trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, methyldimethoxysilylpropyl acrylate and the like. Group-containing acrylic acid esters; silyl group-containing methacrylic acid esters such as trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, methyldimethoxysilylpropyl methacrylate, dimethylmethoxysilylpropyl methacrylate; trimethoxysilylpropyl vinyl ether and the like. Cyril group-containing vinyl ethers; Examples thereof include silyl group-containing vinyl esters such as trimethoxysilyl undecanoate vinyl.
　本架橋重合体が架橋性単量体により架橋されたものである場合、当該架橋性単量体の使用量は、架橋性単量体以外の単量体（非架橋性単量体）の総量１００質量部に対して好ましくは０．０１質量部以上５．０質量部以下であり、より好ましくは０．０５質量部以上３．０質量部以下であり、さらに好ましくは０．１質量部以上２．０質量部以下であり、一層好ましくは０．１質量部以上１．７質量部以下であり、より一層好ましくは０．５質量部以上１．５質量部以下である。上記の架橋性単量体の使用量の範囲としては、こうした下限及び上限を適宜組み合わせた範囲とすることができる。架橋性単量体の使用量が０．０１質量部以上であれば、結着性及び電極スラリーの沈降安定性がより良好となる点で好ましい。５．０質量部以下であれば、沈殿重合若しくは分散重合の安定性が高くなる傾向がある。 When the crosslinked polymer is crosslinked with a crosslinkable monomer, the amount of the crosslinkable monomer used is the total amount of the monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, more preferably 0.05 parts by mass or more and 3.0 parts by mass or less, and further preferably 0.1 parts by mass or more with respect to 100 parts by mass. It is 2.0 parts by mass or less, more preferably 0.1 parts by mass or more and 1.7 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1.5 parts by mass or less. The range of the amount of the crosslinkable monomer used may be a range in which such a lower limit and an upper limit are appropriately combined. When the amount of the crosslinkable monomer used is 0.01 parts by mass or more, it is preferable in that the binding property and the sedimentation stability of the electrode slurry are better. If it is 5.0 parts by mass or less, the stability of precipitation polymerization or dispersion polymerization tends to be high.
　同様の理由から、上記架橋性単量体の使用量は、架橋性単量体以外の単量体（非架橋性単量体）の総量に対して０．００１モル％以上２．５モル％以下であることが好ましく、０．０１モル％以上２．０モル％以下であることがより好ましく、０．０５モル％以上１．７５モル％以下であることがさらに好ましく、０．０５モル％以上１．５モル％以下であることが一層好ましく、０．１モル％以上１．０モル％以下であることがより一層好ましい。上記の架橋性単量体の使用量の範囲としては、こうした下限及び上限を適宜組み合わせた範囲とすることができる。 For the same reason, the amount of the crosslinkable monomer used is 0.001 mol% or more and 2.5 mol% with respect to the total amount of the monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.01 mol% or more and 2.0 mol% or less, more preferably 0.05 mol% or more and 1.75 mol% or less, and further preferably 0.05 mol%. It is more preferably 1.5 mol% or more, and further preferably 0.1 mol% or more and 1.0 mol% or less. The range of the amount of the crosslinkable monomer used may be a range in which such a lower limit and an upper limit are appropriately combined.
２．本架橋重合体の製造方法
　本架橋重合体は、沈殿重合若しくは分散重合により、エチレン性不飽和カルボン酸単量体を含む単量体成分（以下、「本単量体」ともいう。）を重合する工程と、前記工程の途中に、前記エチレン性不飽和カルボン酸単量体を含む単量体成分の総量に対して、交換連鎖移動機構型制御剤として後記重合体（Ａ）を０．０００１モル％以上０．５０モル％以下添加する工程とを、備える方法により得られる。
　ここで、本発明において、上記の「途中」とは、本単量体を重合する工程を開始した後から当該工程が終了するまでの時間をＴとした場合の「０．３Ｔ～０．８Ｔ」の時点を意味し、本架橋重合体塩が優れた結着性と沈降安定性を両立できる点で、０．４Ｔ～０．８Ｔであることが好ましく、０．５Ｔ～０．８Ｔであることがより好ましく、０．５Ｔ～０．７Ｔであることがさらに好ましい。上記した下限と上限を適宜組み合わせて設定できる。
　また、沈殿重合は、原料である単量体を溶解するが、生成する重合体を実質溶解しない溶媒中で重合反応を行うことにより重合体を製造する方法である。重合の進行とともにポリマー粒子は凝集及び成長により大きくなり、数十ｎｍ～数百ｎｍの一次粒子が数μｍ～数十μｍに二次凝集したポリマー粒子の分散液が得られる。ポリマーの粒子サイズを制御するために分散安定剤を使用することもできる。
　なお、分散安定剤や重合溶剤等を選定することにより上記二次凝集を抑制することもできる。一般に、二次凝集を抑制した沈殿重合は、分散重合とも呼ばれる。 2. 2. Method for Producing the Crosslinked Polymer The crosslinked polymer polymerizes a monomer component containing an ethylenically unsaturated carboxylic acid monomer (hereinafter, also referred to as “the present monomer”) by precipitation polymerization or dispersion polymerization. In the middle of the step, the polymer (A) described later is 0.0001 as an exchange chain transfer mechanism type control agent with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer. It is obtained by a method comprising a step of adding mol% or more and 0.50 mol% or less.
Here, in the present invention, the above-mentioned "intermediate" means "0.3T to 0.8T" when the time from the start of the step of polymerizing the present monomer to the end of the step is T. , And the crosslinked polymer salt is preferably 0.4T to 0.8T, preferably 0.5T to 0.8T, in that it can achieve both excellent binding properties and sedimentation stability. More preferably, it is more preferably 0.5T to 0.7T. The above lower limit and upper limit can be set in combination as appropriate.
Precipitation polymerization is a method for producing a polymer by carrying out a polymerization reaction in a solvent that dissolves a monomer as a raw material but does not substantially dissolve the polymer to be produced. As the polymerization progresses, the polymer particles become larger due to aggregation and growth, and a dispersion liquid of the polymer particles in which the primary particles of several tens of nm to several hundred nm are secondarily aggregated to several μm to several tens of μm can be obtained. Dispersion stabilizers can also be used to control the particle size of the polymer.
The secondary aggregation can also be suppressed by selecting a dispersion stabilizer, a polymerization solvent, or the like. In general, precipitation polymerization that suppresses secondary aggregation is also called dispersion polymerization.
交換連鎖移動機構型制御剤について
　本発明に係る交換連鎖移動機構型制御剤としては、可逆的付加－開裂連鎖移動重合法（ＲＡＦＴ法）における制御剤（以下、「ＲＡＦＴ剤」ともいう。）、ヨウ素移動重合法における制御剤、有機テルル化合物を用いる重合法（ＴＥＲＰ法）における制御剤、有機アンチモン化合物を用いる重合法（ＳＢＲＰ法）における制御剤、有機ビスマス化合物を用いる重合法（ＢＩＲＰ法）における制御剤等が挙げられ、１種又は２種以上のビニル系単量体の重合鎖と交換連鎖移動機構によるリビングラジカル重合活性単位を有する重合体（以下、単に「重合体（Ａ）」ともいう。）を用いることが好ましい。重合体（Ａ）は１種類のみ使用しても又は２種以上を併用してもよい。 Regarding the exchange chain transfer mechanism type control agent The exchange chain transfer mechanism type control agent according to the present invention includes a control agent (hereinafter, also referred to as “RAFT agent”) in the reversible addition-cleaving chain transfer polymerization method (RAFT method). In the control agent in the iodine transfer polymerization method, the control agent in the polymerization method using an organic tellurium compound (TERP method), the control agent in the polymerization method using an organic antimony compound (SBRP method), and the polymerization method using an organic bismuth compound (BIRP method). A polymer having a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by an exchange chain transfer mechanism (hereinafter, also simply referred to as “polymer (A)”) includes a control agent and the like. .) Is preferably used. Only one type of the polymer (A) may be used, or two or more types may be used in combination.
　沈殿重合若しくは分散重合により、エチレン性不飽和カルボン酸単量体を含む単量体成分を重合する工程の途中に、交換連鎖移動機構型制御剤を添加することで、粒子の極表面にエチレン性不飽和カルボン酸単量体以外を表面修飾させることが可能となる。これに伴い、優れた結着性と沈降安定性を両立させることができると推定される。
　これらの中でも、本架橋重合体の架橋構造をより均一にすることができる点で、ＲＡＦＴ剤及びヨウ素移動重合法における制御剤が好ましく、ＲＡＦＴ剤がより好ましい。 By adding an exchange chain transfer mechanism type control agent in the middle of the step of polymerizing a monomer component containing an ethylenically unsaturated carboxylic acid monomer by precipitation polymerization or dispersion polymerization, ethylenic property is formed on the polar surface of the particles. It is possible to surface-modify other than the unsaturated carboxylic acid monomer. Along with this, it is presumed that both excellent binding properties and sedimentation stability can be achieved at the same time.
Among these, the RAFT agent and the control agent in the iodine transfer polymerization method are preferable, and the RAFT agent is more preferable, in that the crosslinked structure of the present crosslinked polymer can be made more uniform.
　ＲＡＦＴ剤としては、可逆的付加－開裂連鎖移動法によるリビングラジカル重合活性単位を有する重合体（Ａ）を使用することができる。
　ＲＡＦＴ剤の中では、本架橋重合体の架橋構造をより一層均一にすることができる点で、分子内にトリチオカーボネートを有するものが特に好ましい。 As the RAFT agent, a polymer (A) having a living radical polymerization active unit by a reversible addition-cleaving chain transfer method can be used.
Among the RAFT agents, those having a trithiocarbonate in the molecule are particularly preferable in that the crosslinked structure of the present crosslinked polymer can be made more uniform.
　ヨウ素移動重合法における制御剤は、ヨウ素移動重合法によるリビングラジカル活性単位を有する重合体（Ａ）を使用することができる。 As the control agent in the iodine transfer polymerization method, the polymer (A) having a living radical active unit by the iodine transfer polymerization method can be used.
　重合体（Ａ）は、活性点を１個所備える１官能性のものであってもよいし、２個所以上備える２官能性以上のものを用いることもできる。２官能性以上の交換連鎖移動機構型制御剤は、２方向性以上に重合鎖が伸長するものである。本架橋重合体の製造の観点からは、２官能性又は３官能性以上の交換連鎖移動機構型制御剤を用いることが好適な場合がある。 The polymer (A) may be a monofunctional polymer having one active site, or a polymer (A) having two or more active sites and having two or more functional sites. A bifunctional or higher exchange chain transfer mechanism type control agent is one in which the polymerized chain is extended in a bidirectional or higher direction. From the viewpoint of producing the crosslinked polymer, it may be preferable to use a bifunctional or trifunctional or higher exchange chain transfer mechanism type control agent.
　重合体（Ａ）の使用量としては、架橋重合体の架橋構造をより均一にすることができる点で、本単量体の総量に対して０．０００１モル％以上０．５０モル％以下であることが好ましく、０．０００１モル％以上０．４０モル％以下であることがより好ましく、０．０００１モル％以上０．３０モル％以下であることがさらに好ましく、０．０００２モル％以上０．３０モル％以下であることがより一層好ましい。 The amount of the polymer (A) used is 0.0001 mol% or more and 0.50 mol% or less with respect to the total amount of the present monomer in that the crosslinked structure of the crosslinked polymer can be made more uniform. It is preferably 0.0001 mol% or more and 0.40 mol% or less, further preferably 0.0001 mol% or more and 0.30 mol% or less, and 0.0002 mol% or more and 0. It is even more preferable that it is .30 mol% or less.
　重合体（Ａ）とともに用いる重合開始剤としては、アゾ系化合物、有機過酸化物、無機過酸化物等の公知の重合開始剤を用いることができるが、特に限定されるものではない。熱開始、還元剤を併用したレドックス開始、ＵＶ開始等、公知の方法で適切なラジカル発生量となるように使用条件を調整することができる。一次鎖長の長い本架橋重合体を得るためには、製造時間が許容される範囲内で、ラジカル発生量がより少なくなるように条件を設定することが好ましい。
　前記の重合開始剤の中でも、安全上取り扱い易く、ラジカル重合時の副反応が起こりにくい点からは、アゾ化合物が好ましい。上記アゾ化合物の具体例としては、例えば、２，２’－アゾビスイソブチロニトリル、２，２’－アゾビス（２，４－ジメチルバレロニトリル）、２，２’－アゾビス（４－メトキシ－２，４－ジメチルバレロニトリル）、ジメチル－２，２’－アゾビス（２－メチルプロピオネート）、２，２’－アゾビス（２－メチルブチロニトリル）、１，１’－アゾビス（シクロヘキサン－１－カルボニトリル）、２，２’－アゾビス［Ｎ－（２－プロペニル）－２－メチルプロピオンアミド］、２，２’－アゾビス（Ｎ－ブチル－２－メチルプロピオンアミド）等が挙げられる。上記ラジカル重合開始剤は１種類のみ使用しても又は２種以上を併用してもよい。 As the polymerization initiator used together with the polymer (A), known polymerization initiators such as azo compounds, organic peroxides, and inorganic peroxides can be used, but are not particularly limited. The conditions of use can be adjusted by known methods such as heat initiation, redox initiation with a reducing agent, and UV initiation so that the amount of radicals generated is appropriate. In order to obtain the present crosslinked polymer having a long primary chain length, it is preferable to set the conditions so that the amount of radicals generated is smaller within the allowable range of the production time.
Among the above-mentioned polymerization initiators, azo compounds are preferable because they are easy to handle for safety and side reactions during radical polymerization are unlikely to occur. Specific examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (4-methoxy-). 2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-) 1-Carbonitrile), 2,2'-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2'-azobis (N-butyl-2-methylpropionamide) and the like. Only one kind of the radical polymerization initiator may be used, or two or more kinds thereof may be used in combination.
　重合開始剤の好ましい使用量は、用いる単量体成分の総量を１００質量部としたときに、例えば、０．００１質量部以上２質量部以下であり、また例えば、０．００５質量部以上１質量部以下であり、また例えば、０．０１質量部以上０．１質量部以下である。重合開始剤の使用量が０．００１質量部以上であれば重合反応を安定的に行うことができ、２質量部以下であれば一次鎖長の長い重合体を得やすい。
　重合開始剤の使用割合は特に制限されないが、本架橋重合体の架橋構造を均一にすることができる点から、上記交換連鎖移動機構型制御剤１ｍｏｌに対する上記重合開始剤の使用量を０．５ｍｏｌ以下とすることが好ましく、０．２ｍｏｌ以下とするのがより好ましい。また、重合反応を安定的に行う観点から、交換連鎖移動機構型制御剤１ｍｏｌに対する重合開始剤の使用量の下限は、０．００１ｍｏｌである。よって、交換連鎖移動機構型制御剤１ｍｏｌに対する重合開始剤の使用量は、０．００１ｍｏｌ以上０．５ｍｏｌ以下の範囲が好ましく、０．００５ｍｏｌ以上０．２ｍｏｌ以下の範囲がより好ましい。 The preferable amount of the polymerization initiator to be used is, for example, 0.001 part by mass or more and 2 parts by mass or less, and for example, 0.005 part by mass or more and 1 by mass, when the total amount of the monomer components to be used is 100 parts by mass. It is not less than a part by mass, and is, for example, 0.01 part by mass or more and 0.1 part by mass or less. When the amount of the polymerization initiator used is 0.001 part by mass or more, the polymerization reaction can be stably carried out, and when it is 2 parts by mass or less, a polymer having a long primary chain length can be easily obtained.
The proportion of the polymerization initiator used is not particularly limited, but the amount of the polymerization initiator used per 1 mol of the exchange chain transfer mechanism type control agent is 0.5 mol from the viewpoint that the crosslinked structure of the present crosslinked polymer can be made uniform. The value is preferably 0.2 mol or less, and more preferably 0.2 mol or less. Further, from the viewpoint of stably performing the polymerization reaction, the lower limit of the amount of the polymerization initiator used with respect to 1 mol of the exchange chain transfer mechanism type control agent is 0.001 mol. Therefore, the amount of the polymerization initiator used with respect to 1 mol of the exchange chain transfer mechanism type control agent is preferably in the range of 0.001 mol or more and 0.5 mol or less, and more preferably in the range of 0.005 mol or more and 0.2 mol or less.
　重合溶媒は、使用する単量体の種類等を考慮して水及び各種有機溶剤等から選択される溶媒を使用することができる。より一次鎖長の長い重合体を得るためには、連鎖移動定数の小さい溶媒を使用することが好ましい。
　重合溶媒としては、例えば、メタノール、ｔ－ブチルアルコール、アセトン、メチルエチルケトン、アセトニトリル及びテトラヒドロフラン等の水溶性溶剤の他、ベンゼン、酢酸エチル、ジクロロエタン、ｎ－ヘキサン、シクロヘキサン及びｎ－ヘプタン等が挙げられ、これらの１種を単独であるいは２種以上を組み合わせて用いることができる。又は、これらと水との混合溶媒として用いてもよい。本発明において水溶性溶剤とは、２０℃における水への溶解度が１０ｇ／１００ｍｌより大きいものを指す。
　上記の内、粗大粒子の生成や反応器への付着が小さく重合安定性が良好であること、析出した本架橋重合体が二次凝集しにくい（若しくは二次凝集が生じても水媒体中で解れやすい）こと、連鎖移動定数が小さく重合度（一次鎖長）の大きい重合体が得られること、及び後述する工程中和の際に操作が容易であること等の点で、メチルエチルケトン及びアセトニトリルが好ましい。 As the polymerization solvent, a solvent selected from water, various organic solvents and the like can be used in consideration of the type of the monomer used and the like. In order to obtain a polymer having a longer primary chain length, it is preferable to use a solvent having a small chain transfer constant.
Examples of the polymerization solvent include water-soluble solvents such as methanol, t-butyl alcohol, acetone, methyl ethyl ketone, acetonitrile and tetrahydrofuran, as well as benzene, ethyl acetate, dichloroethane, n-hexane, cyclohexane and n-heptane. One of these can be used alone or in combination of two or more. Alternatively, it may be used as a mixed solvent of these and water. In the present invention, the water-soluble solvent refers to a solvent having a solubility in water at 20 ° C. of more than 10 g / 100 ml.
Of the above, the formation of coarse particles and adhesion to the reactor are small and the polymerization stability is good, and the precipitated crosslinked polymer is difficult to secondary agglomerate (or even if secondary agglomeration occurs, it is in an aqueous medium. Methylethylketone and acetonitrile are used in terms of being easy to unravel), obtaining a polymer with a small chain transfer constant and a large degree of polymerization (primary chain length), and being easy to operate during the process neutralization described later. preferable.
　また、同じく工程中和において中和反応を安定かつ速やかに進行させるため、重合溶媒中に高極性溶媒を少量加えておくことが好ましい。係る高極性溶媒としては、好ましくは水及びメタノールが挙げられる。高極性溶媒の使用量は、媒体の全質量に基づいて好ましくは０．０５質量％以上２０．０質量％以下であり、より好ましくは０．１質量％以上１０．０質量％以下であり、さらに好ましくは０．１質量％以上５．０質量％以下であり、一層好ましくは０．１質量％以上１．０質量％以下である。高極性溶媒の割合が０．０５質量％以上であれば、上記中和反応への効果が認められ、２０．０質量％以下であれば重合反応への悪影響も見られない。また、アクリル酸等の親水性の高いエチレン性不飽和カルボン酸単量体の重合では、高極性溶媒を加えた場合には重合速度が向上し、一次鎖長の長い重合体を得やすくなる。高極性溶媒の中でも特に水は上記重合速度を向上させる効果が大きく好ましい。 Similarly, in order to allow the neutralization reaction to proceed stably and rapidly in the process neutralization, it is preferable to add a small amount of a highly polar solvent to the polymerization solvent. Such highly polar solvents preferably include water and methanol. The amount of the highly polar solvent used is preferably 0.05% by mass or more and 20.0% by mass or less, more preferably 0.1% by mass or more and 10.0% by mass or less, based on the total mass of the medium. It is more preferably 0.1% by mass or more and 5.0% by mass or less, and further preferably 0.1% by mass or more and 1.0% by mass or less. When the proportion of the highly polar solvent is 0.05% by mass or more, the effect on the neutralization reaction is recognized, and when it is 20.0% by mass or less, no adverse effect on the polymerization reaction is observed. Further, in the polymerization of a highly hydrophilic ethylenically unsaturated carboxylic acid monomer such as acrylic acid, the polymerization rate is improved when a highly polar solvent is added, and it becomes easy to obtain a polymer having a long primary chain length. Among the highly polar solvents, water is particularly preferable because it has a large effect of improving the polymerization rate.
　重合体（Ａ）の存在下における重合反応の際の反応温度は、好ましくは３０℃以上１２０℃以下であり、より好ましくは４０℃以上１１０℃以下であり、さらに好ましくは５０℃以上１００℃以下である。反応温度が３０℃以上であれば、重合反応を円滑に進めることができる。一方、反応温度が１２０℃以下であれば、副反応が抑制できるとともに、使用できる開始剤や溶剤に関する制限が緩和される。 The reaction temperature during the polymerization reaction in the presence of the polymer (A) is preferably 30 ° C. or higher and 120 ° C. or lower, more preferably 40 ° C. or higher and 110 ° C. or lower, and further preferably 50 ° C. or higher and 100 ° C. or lower. Is. When the reaction temperature is 30 ° C. or higher, the polymerization reaction can proceed smoothly. On the other hand, if the reaction temperature is 120 ° C. or lower, side reactions can be suppressed and restrictions on the initiators and solvents that can be used are relaxed.
　ここで、重合体（Ａ）としては、前記の通り、１種又は２種以上のビニル系単量体（以下、単に、「第１の単量体」ともいう。）の重合鎖（以下、単に、「第１の重合鎖」ともいう。）と交換連鎖移動機構によるリビングラジカル重合活性単位を有する重合体（重合体（Ａ））を用いることができる。 Here, as the polymer (A), as described above, a polymer chain (hereinafter, simply referred to as “first monomer”) of one kind or two or more kinds of vinyl-based monomers (hereinafter, also simply referred to as “first monomer”). A polymer (polymer (A)) having a living radical polymerization active unit by an exchange chain transfer mechanism and a "first polymer chain") can be simply used.
　重合体（Ａ）の存在下、本単量体を重合して本架橋重合体を製造するにあたって、重合体（Ａ）を本単量体の重合の基点として用いるとともに、当該架橋重合体の重合溶媒中における分散安定剤として用いることができ、重合体（Ａ）の重合鎖に対して、本単量体由来の構造単位を有する重合鎖を結合させた本架橋重合体を分散微粒子として得ることができる。こうすることで、重合安定性、すなわち、重合工程中の本架橋重合体の凝集を抑制して、粗大な凝集粒子の発生を抑制し、粒子径が小さく、かつ粒子径分布の狭い本架橋重合体を得ることができる。 When the present monomer is polymerized in the presence of the polymer (A) to produce the present cross-linked polymer, the polymer (A) is used as a starting point for the polymerization of the present monomer, and the cross-linked polymer is polymerized. The present cross-linked polymer which can be used as a dispersion stabilizer in a solvent and has a polymer chain having a structural unit derived from the present monomer bonded to the polymer chain of the polymer (A) is obtained as dispersed fine particles. Can be done. By doing so, the polymerization stability, that is, the aggregation of the main crosslinked polymer during the polymerization step is suppressed, the generation of coarse aggregated particles is suppressed, and the main crosslinked weight having a small particle size and a narrow particle size distribution is suppressed. You can get coalescence.
　重合体（Ａ）の存在下、本単量体を重合して本架橋重合体を製造するにあたって、重合体（Ａ）を分散安定剤として機能させるためには、例えば、重合体（Ａ）を、本単量体の総質量１００質量部に対して、０．３質量部以上５０質量部以下用いることができる。かかる範囲で用いることで、重合体（Ａ）を分散安定剤として機能させつつ、本単量体を主として含有する本架橋重合体を製造することができる。また、重合体（Ａ）が０．３質量部未満であると、十分な分散安定効果が出にくく、本架橋重合体の粒子径が０．３μｍを超えやすくなり、５０質量部を超えても、分散安定剤としての機能性も向上しにくく、かつ本架橋重合体の小粒子径化の効果も小さくなってしまうからである。 In order to make the polymer (A) function as a dispersion stabilizer in producing the crosslinked polymer by polymerizing the present monomer in the presence of the polymer (A), for example, the polymer (A) may be used. , 0.3 parts by mass or more and 50 parts by mass or less can be used with respect to 100 parts by mass of the total mass of this monomer. By using the polymer (A) in such a range, it is possible to produce the present crosslinked polymer mainly containing the present monomer while allowing the polymer (A) to function as a dispersion stabilizer. Further, when the polymer (A) is less than 0.3 parts by mass, it is difficult to obtain a sufficient dispersion stabilizing effect, and the particle size of the crosslinked polymer tends to exceed 0.3 μm, even if it exceeds 50 parts by mass. This is because it is difficult to improve the functionality as a dispersion stabilizer, and the effect of reducing the particle size of the crosslinked polymer is also reduced.
　重合体（Ａ）は、本単量体の総質量１００質量部に対して、また例えば、０．５質量部以上、また例えば、１質量部以上用いることができる。また、重合体（Ａ）は、また例えば、４０質量部以下、また例えば、３０質量部以下、また例えば、２０質量部以下用いることができる。重合体（Ａ）の本単量体の総質量１００質量部に対する使用量の範囲は、上記した下限と上限を適宜組み合わせて設定できる。 The polymer (A) can be used with respect to 100 parts by mass of the total mass of this monomer, for example, 0.5 parts by mass or more, and for example, 1 part by mass or more. Further, the polymer (A) can be used, for example, 40 parts by mass or less, for example, 30 parts by mass or less, and for example, 20 parts by mass or less. The range of the amount of the polymer (A) used with respect to 100 parts by mass of the total mass of this monomer can be set by appropriately combining the above-mentioned lower limit and upper limit.
重合体（Ａ）の製造方法
　公知の交換連鎖移動機構型制御剤の存在下、第１の単量体を含む単量体組成物を重合することで、第１の単量体由来の構造単位を有する第１の重合鎖と交換連鎖移動機構によるリビング重合活性単位を備える重合体（Ａ）を得ることができる。 Method for Producing Polymer (A) A structural unit derived from the first monomer by polymerizing a monomer composition containing the first monomer in the presence of a known exchange chain transfer mechanism type control agent. It is possible to obtain a polymer (A) having a first polymerized chain having the above and a living polymerization active unit by an exchange chain transfer mechanism.
　重合体（Ａ）を製造する際の重合条件は、当業者において周知であり、重合プロセスとしては、塊状重合、溶液重合、懸濁重合及び乳化重合等の各種プロセスが挙げられるが、本架橋重合体の製造における重合基点であることや分散安定剤的に機能することを考慮すると、例えば、溶液重合を用いることができる。また、交換連鎖移動機構制御剤の種類、重合開始剤の種類及び使用量、重合溶媒、反応温度等の重合条件は、前記の段落［００４５］及び［００５１］～［００５５］に準じて適宜選択され、交換連鎖移動機構制御剤の使用量は、目標とする重合体（Ａ）の数平均分子量（Ｍｎ）に応じて適宜調整される。
　交換連鎖移動機構制御剤としては、ＲＡＦＴ剤及びヨウ素移動重合法における制御剤が重合体（Ａ）の分子量分布を狭くできる点で好ましい。
　さらに、重合体（Ａ）を製造する際の濃度は、重合溶媒と第１の単量体など仕込み量の総質量に対して、特に限定するものではないが、例えば、１０質量％以上８０質量％以下、また例えば、１５質量％以上７０質量％以下、また例えば、２０質量％以上７０質量％以下などとすることができる。 The polymerization conditions for producing the polymer (A) are well known to those skilled in the art, and examples of the polymerization process include various processes such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. Considering that it is a polymerization starting point in the production of coalescence and that it functions as a dispersion stabilizer, solution polymerization can be used, for example. Further, the polymerization conditions such as the type of the exchange chain transfer mechanism control agent, the type and amount of the polymerization initiator, the polymerization solvent, and the reaction temperature are appropriately selected according to the above paragraphs [0045] and [0051] to [0055]. The amount of the exchange chain transfer mechanism control agent used is appropriately adjusted according to the number average molecular weight (Mn) of the target polymer (A).
As the exchange chain transfer mechanism control agent, a RAFT agent and a control agent in the iodine transfer polymerization method are preferable in that the molecular weight distribution of the polymer (A) can be narrowed.
Further, the concentration at the time of producing the polymer (A) is not particularly limited with respect to the total mass of the amount charged such as the polymerization solvent and the first monomer, but is, for example, 10% by mass or more and 80% by mass. % Or less, for example, 15% by mass or more and 70% by mass or less, and for example, 20% by mass or more and 70% by mass or less.
　典型的には、１官能性の交換連鎖移動機構型制御剤を用いた場合には、リビング重合活性単位を第１の重合鎖の末端に備える態様となり、２官能性以上の交換連鎖移機構型制御剤を用いた場合には、リビング重合活性単位を基点として２方向以上に分岐してそれぞれに第１の重合鎖を備える態様となる。なお、いずれの態様においても、別の重合鎖を備える場合には、この別の重合鎖が、リビング重合活性単位に直接結合され、リビング重合活性単位に対してより遠位側に第１の重合鎖が備えられるように、当該別の重合鎖の遠位末端に第１の重合鎖が結合された態様となっている。 Typically, when a monofunctional exchange chain transfer mechanism type control agent is used, a living polymerization active unit is provided at the end of the first polymerization chain, and the exchange chain transfer mechanism type having two or more functionalities is provided. When a control agent is used, the mode is such that the living polymerization active unit is used as a base point to branch in two or more directions, and each of them is provided with a first polymerization chain. In any of the embodiments, when another polymerized chain is provided, the other polymerized chain is directly bonded to the living polymerization active unit, and the first polymerization is carried out more distally to the living polymerization active unit. The first polymerized chain is bonded to the distal end of the other polymerized chain so that the chain is provided.
　重合体（Ａ）は、２種以上の第１の重合鎖を備えることもできる。例えば、ある種の組成の１種又は２種以上の第１の単量体を用いてリビングラジカル重合等を実施後に、他の組成で１種又は２種以上の第１の単量体を用いてリビングラジカル重合等を実施することで、異なる組成の第１の単量体由来の構造単位を有する第１の重合鎖（ブロック）を備える重合体（Ａ）を得ることができる。 The polymer (A) can also include two or more kinds of first polymerized chains. For example, after performing living radical polymerization or the like using one or more first monomers of a certain composition, one or more first monomers of another composition are used. By carrying out living radical polymerization or the like, a polymer (A) having a first polymerized chain (block) having a structural unit derived from the first monomer having a different composition can be obtained.
　重合体（Ａ）の数平均分子量（Ｍｎ）は、特に限定するものではないが、例えば、３，０００以上であり、また例えば、５，０００以上であり、また例えば、７，０００以上であり、また例えば、８，０００以上であり、また例えば、１０，０００以上である。また、同Ｍｎは、例えば、１５０,０００以下であり、また例えば、１００，０００以下であり、また例えば、８０，０００以下であり、また例えば、５０，０００以下であり、また例えば、２５，０００以下であり、また例えば、１５，０００以下であり、また例えば、１２，０００以下である。Ｍｎが３，０００未満であると、本架橋重合体塩の結着性が不十分であり、１５０,０００超であると、分散重合の重合溶媒に溶解し難くなり、本架橋重合体を得ることが困難となる。Ｍｎの範囲としては、上記した下限及び上限を適宜組み合わせて設定することができる。 The number average molecular weight (Mn) of the polymer (A) is not particularly limited, but is, for example, 3,000 or more, for example, 5,000 or more, and for example, 7,000 or more. Also, for example, 8,000 or more, and for example, 10,000 or more. Further, the Mn is, for example, 150,000 or less, for example, 100,000 or less, for example, 80,000 or less, and for example, 50,000 or less, and for example, 25, It is 000 or less, and is, for example, 15,000 or less, and is, for example, 12,000 or less. If Mn is less than 3,000, the binding property of the present crosslinked polymer salt is insufficient, and if it is more than 150,000, it becomes difficult to dissolve in the polymerization solvent of the dispersion polymerization to obtain the present crosslinked polymer. Will be difficult. The range of Mn can be set by appropriately combining the above-mentioned lower limit and upper limit.
　重合体（Ａ）の重量平均分子量（Ｍｗ）は、特に限定するものではないが、例えば、５，０００以上であり、また例えば、７，０００以上であり、また例えば、９，０００以上であり、また例えば、１０，０００以上であり、また例えば、１３，０００以上であり、また例えば、１５，０００以上である。また、同Ｍｗは、例えば、２００,０００以下であり、また例えば、１５０，０００以下であり、また例えば、１００，０００以下であり、また例えば、８０，０００以下であり、６０，０００以下であり、また例えば、５５，０００以下であり、また例えば、５０，０００以下であり、また例えば、４５，０００以下であり、また例えば、４０，０００以下であり、また例えば、３６，０００以下であり、また例えば、３５，０００以下であり、また例えば、３０，０００以下であり、また例えば、２５、０００以下である。Ｍｗが５，０００未満であると、本架橋重合体塩の結着性が不十分であり、２００,０００超であると、分散重合の重合溶媒に溶解し難くなり、本架橋重合体を得ることが困難となる。Ｍｗの範囲としては、上記した下限及び上限を適宜組み合わせて設定することができる。 The weight average molecular weight (Mw) of the polymer (A) is not particularly limited, but is, for example, 5,000 or more, for example, 7,000 or more, and for example, 9,000 or more. Also, for example, 10,000 or more, for example, 13,000 or more, and for example, 15,000 or more. Further, the Mw is, for example, 200,000 or less, for example, 150,000 or less, for example, 100,000 or less, and for example, 80,000 or less, and 60,000 or less. Yes, for example 55,000 or less, and for example 50,000 or less, and for example 45,000 or less, and for example 40,000 or less, and for example 36,000 or less. Yes, for example, 35,000 or less, for example, 30,000 or less, and for example, 25,000 or less. If Mw is less than 5,000, the binding property of the present crosslinked polymer salt is insufficient, and if it is more than 200,000, it becomes difficult to dissolve in the polymerization solvent of the dispersion polymerization, and the present crosslinked polymer is obtained. Will be difficult. The range of Mw can be set by appropriately combining the above-mentioned lower limit and upper limit.
　なお、重合体（Ａ）のＭｗ及びＭｎは、いずれも、ポリスチレンを標準物質として用いたゲルパーミエーションクロマトグラフィーにて測定することができる。クロマトグラフィー条件の詳細は、後段の実施例に開示する条件を採用することができる。 Both Mw and Mn of the polymer (A) can be measured by gel permeation chromatography using polystyrene as a standard substance. As for the details of the chromatography conditions, the conditions disclosed in the subsequent examples can be adopted.
　重合体（Ａ）の分子量分布（Ｍｗ／Ｍｎ）は、特に限定するものではないが、例えば、２．５以下であり、また例えば、２．４以下であり、また例えば、２．３以下であり、また例えば、２．０以下であり、また例えば、１．６以下であり、また例えば、１．５以下であり、また例えば、１．４以下であり、また例えば、１．３以下である。また、分子量分布は、例えば、１．１以上であり、また例えば、１．２以上であり、また例えば、１．３以上であり、また例えば、１．４以上、また例えば、１．５以上である。分子量分布の範囲としては、上記した下限及び上限を適宜組み合わせて設定することができる。 The molecular weight distribution (Mw / Mn) of the polymer (A) is not particularly limited, but is, for example, 2.5 or less, for example, 2.4 or less, and for example, 2.3 or less. Yes, for example 2.0 or less, and for example 1.6 or less, and for example 1.5 or less, and for example 1.4 or less, and for example 1.3 or less. be. Further, the molecular weight distribution is, for example, 1.1 or more, for example, 1.2 or more, and for example, 1.3 or more, and for example, 1.4 or more, and for example, 1.5 or more. Is. The range of the molecular weight distribution can be set by appropriately combining the above-mentioned lower limit and upper limit.
　重合体（Ａ）の分子量分布は狭いほど、得られる本架橋重合体の粒子径が小さくなる傾向がある。分子量分布が２．４以下であることが好適であり、より小さい粒子径の本架橋重合体を得るには、同１．７以下であることが好適であり、さらに好適には、同１．６以下であり、一層好適には、１．４以下である。 The narrower the molecular weight distribution of the polymer (A), the smaller the particle size of the obtained crosslinked polymer tends to be. The molecular weight distribution is preferably 2.4 or less, and in order to obtain the present crosslinked polymer having a smaller particle size, it is preferably 1.7 or less, and more preferably 1. It is 6 or less, and more preferably 1.4 or less.
　重合体（Ａ）のＳＰ値は、特に限定するものではないが、沈降安定性及び結着性に優れる本架橋重合体を製造できる点で、例えば、１７～２７（（ＭＰａ）1/2）であることが好ましい。重合体（Ａ）のＳＰ値は、例えば、２７（（ＭＰａ）1/2）以下であり、また例えば、２６（（ＭＰａ）1/2）以下であり、また例えば、２５（（ＭＰａ）1/2）以下である。また、重合体（Ａ）のＳＰ値は、例えば、１７（（ＭＰａ）1/2）以上であり、また例えば、１８（（ＭＰａ）1/2）以上であり、また例えば、１９（（ＭＰａ）1/2）以上である。ＳＰ値の範囲としては、上記した下限及び上限を適宜組み合わせて設定することができる。 The SP value of the polymer (A) is not particularly limited, but is, for example, 17 to 27 ((MPa) 1/2 ) in that the present crosslinked polymer having excellent sedimentation stability and binding property can be produced. Is preferable. The SP value of the polymer (A) is, for example, 27 ((MPa) 1/2 ) or less, for example, 26 ((MPa) 1/2 ) or less, and for example, 25 ((MPa) 1 ). / 2 ) It is as follows. The SP value of the polymer (A) is, for example, 17 ((MPa) 1/2 ) or more, for example, 18 ((MPa) 1/2 ) or more, and for example, 19 ((MPa) 1/2) or more. ) 1/2 ) or more. The range of the SP value can be set by appropriately combining the above-mentioned lower limit and upper limit.
　上記のＳＰ値については、Ｒ．Ｆ．Ｆｅｄｏｒｓにより著された「Ｐｏｌｙｍｅｒ Ｅｎｇｉｎｅｅｒｉｎｇ ａｎｄ Ｓｃｉｅｎｃｅ」１４（２），１４７（１９７４）に記載の計算方法によって、算出することができる。具体的には、式（４）に示す計算方法による。
Figure JPOXMLDOC01-appb-M000007
 For the above SP value, refer to R.I. F. It can be calculated by the calculation method described in "Polymer Engineering and Science" 14 (2), 147 (1974) written by Fedors. Specifically, the calculation method shown in the equation (4) is used.
Figure JPOXMLDOC01-appb-M000007
＜第１の単量体＞
　第１の単量体としては、スチレン類、（メタ）アクリロニトリル化合物、マレイミド化合物、不飽和酸無水物及び不飽和カルボン酸化合物等が挙げられる。これらのうち１種又は２種以上を組み合わせて用いることができる。 <First monomer>
Examples of the first monomer include styrenes, (meth) acrylonitrile compounds, maleimide compounds, unsaturated acid anhydrides, unsaturated carboxylic acid compounds and the like. One of these or two or more of them can be used in combination.
　スチレン類としては、スチレン及びその誘導体が含まれる。スチレン誘導体としては、例えば、α－メチルスチレン、β－メチルスチレン、ビニルキシレン、ビニルナフタレン、ｏ－メチルスチレン、ｍ－メチルスチレン、ｐ－メチルスチレン、ｏ－エチルスチレン、ｍ－エチルスチレン、ｐ－エチルスチレン、ｐ－ｎ－ブチルスチレン、ｐ－イソブチルスチレン、ｐ－ｔ－ブチルスチレン、ｏ－メトキシスチレン、ｍ－メトキシスチレン、ｐ－メトキシスチレン、ｏ－クロロメチルスチレン、ｐ－クロロメチルスチレン、ｏ－クロロスチレン、ｐ－クロロスチレン、ｏ－ヒドロキシスチレン、ｍ－ヒドロキシスチレン、ｐ－ヒドロキシスチレン、ジビニルベンゼン等が例示され、これらの内の１種又は２種以上を用いることができる。これらの中でも、重合性の観点から、スチレン、ｏ－メトキシスチレン、ｍ－メトキシスチレン、ｐ－メトキシスチレン、ｏ－ヒドロキシスチレン、ｍ－ヒドロキシスチレン、ｐ－ヒドロキシスチレンが好ましい。 Styrenes include styrene and its derivatives. Examples of the styrene derivative include α-methylstyrene, β-methylstyrene, vinylxylene, vinylnaphthalene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene and p-. Ethylstyrene, pn-butylstyrene, p-isobutylstyrene, pt-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chloromethylstyrene, p-chloromethylstyrene, o -Chlorostyrene, p-chlorostyrene, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, divinylbenzene and the like are exemplified, and one or more of these can be used. Among these, styrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-hydroxystyrene, m-hydroxystyrene, and p-hydroxystyrene are preferable from the viewpoint of polymerizable property.
　（メタ）アクリロニトリル化合物としては、例えば、（メタ）アクリロニトリル、α－メチルアクリロニトリル等が挙げられる。例えば、アクリロニトリルが用いられる。 Examples of the (meth) acrylonitrile compound include (meth) acrylonitrile and α-methylacrylonitrile. For example, acrylonitrile is used.
　マレイミド化合物としては、マレイミド化合物には、マレイミド及びＮ－置換マレイミド化合物が含まれる。Ｎ－置換マレイミド化合物としては、例えば、Ｎ－メチルマレイミド、Ｎ－エチルマレイミド、Ｎ－ｎ－プロピルマレイミド、Ｎ－イソプロピルマレイミド、Ｎ－ｎ－ブチルマレイミド、Ｎ－イソブチルマレイミド、Ｎ－ｔｅｒｔ－ブチルマレイミド、Ｎ－ペンチルマレイミド、Ｎ－ヘキシルマレイミド、Ｎ－ヘプチルマレイミド、Ｎ－オクチルマレイミド、Ｎ－ラウリルマレイミド、Ｎ－ステアリルマレイミド等のＮ－アルキル置換マレイミド化合物；Ｎ－シクロペンチルマレイミド、Ｎ－シクロヘキシルマレイミド等のＮ－シクロアルキル置換マレイミド化合物；Ｎ－フェニルマレイミド、Ｎ－（４－ヒドロキシフェニル）マレイミド、Ｎ－（４－アセチルフェニル）マレイミド、Ｎ－（４－メトキシフェニル）マレイミド、Ｎ－（４－エトキシフェニル）マレイミド、Ｎ－（４－クロロフェニル）マレイミド、Ｎ－（４－ブロモフェニル）マレイミド、Ｎ－ベンジルマレイミド等のＮ－アリール置換マレイミド化合物などが挙げられ、これらの内の１種又は２種以上を用いることができる。例えば、Ｎ－フェニルマレイミドが用いられる。 As the maleimide compound, the maleimide compound includes a maleimide and an N-substituted maleimide compound. Examples of the N-substituted maleimide compound include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, and N-tert-butylmaleimide. , N-alkyl-substituted maleimide compounds such as N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide; N-Cycloalkyl-substituted maleimide compound; N-phenylmaleimide, N- (4-hydroxyphenyl) maleimide, N- (4-acetylphenyl) maleimide, N- (4-methoxyphenyl) maleimide, N- (4-ethoxyphenyl) ) N-aryl substituted maleimide compounds such as maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) maleimide, N-benzylmaleimide, etc., and one or more of these may be mentioned. Can be used. For example, N-phenylmaleimide is used.
　また、不飽和酸無水物としては、例えば、無水マレイン酸、無水イタコン酸、無水シトラコン酸等が挙げられ、これらのうち１種又は２種以上を用いることができる。 Further, examples of the unsaturated acid anhydride include maleic anhydride, itaconic anhydride, citraconic anhydride and the like, and one or more of these can be used.

　不飽和カルボン酸化合物としては、例えば、（メタ）アクリル酸、ケイ皮酸、クロトン酸、並びに、マレイン酸、フマル酸、イタコン酸、シトラコン酸等の不飽和ジカルボン酸及び不飽和ジカルボン酸のモノアルキルエステル等が挙げられ、これのうち、１種又は２種以上を用いることができる。
Examples of the unsaturated carboxylic acid compound include (meth) acrylic acid, silicic acid, crotonic acid, and monoalkyl of unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid, and unsaturated dicarboxylic acids. Esters and the like can be mentioned, and one or more of them can be used.
　第１の単量体としては、これらの中でも、例えば、少なくともスチレン類又は水酸基含有エチレン性不飽和単量体（上記式（１）で表される単量体、式（２）で表される単量体）を含むことが好ましく、当該水酸基含有エチレン性不飽和単量体を含むことがより好ましい。
　スチレン類は、リビング重合が容易で、適度な疎水性と有機溶媒に対する親和性を付与できるからである。第１の重合鎖に疎水性ないし有機溶媒に対する親和性を付与することができる。こうすることで、例えば、極性有機溶媒中での分散重合法により本架橋重合体を製造する場合には、重合体（Ａ）が、本架橋重合体の表層に存在する傾向が生じて、本架橋重合体の分散安定性が向上される。
　水酸基含有エチレン性不飽和単量体は、本架橋重合体塩を含むバインダーの水分散性及び活物質への親和性を付与することができるからである。こうすることで、結着性を向上できる。 The first monomer includes, for example, at least styrenes or a hydroxyl group-containing ethylenically unsaturated monomer (a monomer represented by the above formula (1), represented by the formula (2)). It is preferable to contain the monomer), and it is more preferable to contain the hydroxyl group-containing ethylenically unsaturated monomer.
This is because styrenes are easy to polymerize in the living room and can impart appropriate hydrophobicity and affinity to organic solvents. It is possible to impart hydrophobicity or affinity to an organic solvent to the first polymerized chain. By doing so, for example, when the present crosslinked polymer is produced by the dispersion polymerization method in a polar organic solvent, the polymer (A) tends to be present on the surface layer of the present crosslinked polymer. The dispersion stability of the crosslinked polymer is improved.
This is because the hydroxyl group-containing ethylenically unsaturated monomer can impart the water dispersibility of the binder containing the crosslinked polymer salt and the affinity for the active material. By doing so, the binding property can be improved.
　スチレン類は、第１の単量体の総質量のうち、例えば、２０質量％以上である。２０質量％以上であるとリビング重合が容易となり、適度な疎水性と有機溶媒に対する親和性を適切に付与できるからである。また例えば、３０質量％以上であり、また例えば、３５質量％以上であり、また例えば、４０質量％以上であり、また例えば、５０質量％以上であり、また例えば、６０質量％以上であり、また例えば、６５質量％以上であり、また例えば、７０質量％以上であり、また例えば、７５質量％以上である。また、スチレン類は、前記総質量の１００質量％以下であり、また例えば、９５質量％以下であり、また例えば、９０質量％以下であり、また例えば、８５質量％以下であり、また例えば、８０質量％以下であり、また例えば、７５質量％以下である。スチレン類の前記総質量に対する範囲としては、上記した下限及び上限を適宜組み合わせて設定することができる。 Styrene is, for example, 20% by mass or more of the total mass of the first monomer. This is because when the content is 20% by mass or more, the living polymerization is facilitated, and an appropriate hydrophobicity and an affinity for an organic solvent can be appropriately imparted. Further, for example, it is 30% by mass or more, and for example, 35% by mass or more, for example, 40% by mass or more, and for example, 50% by mass or more, and for example, 60% by mass or more. Further, for example, it is 65% by mass or more, for example, 70% by mass or more, and for example, 75% by mass or more. Further, the styrenes are 100% by mass or less of the total mass, for example, 95% by mass or less, for example, 90% by mass or less, and for example, 85% by mass or less, and for example, for example. It is 80% by mass or less, and for example, 75% by mass or less. The range of the styrenes with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
　（メタ）アクリロニトリル化合物、マレイミド化合物、酸無水物及び不飽和カルボン酸化合物は、それぞれ、単独でも使用できるほか、これら４種のうち１種又は２種以上をスチレン類と組み合わせて用いることが好ましい。これら４種は、いずれも、第１の重合鎖の疎水性又は有機溶媒親和性を維持、調節又は付与することができるからである。中でも、アクリロニトリルなどの（メタ）アクリロニトリル化合物、Ｎ－フェニルマレイミドなどのマレイミド化合物及び酸無水物のうちの１種又は２種以上である。中でも、スチレンとアクリロニトリル、スチレンとＮ－フェニルマレイミドなどの組み合わせが好適である。なお、不飽和カルボン酸化合物は、重合体（Ａ）の極性を容易に変化させることができる点等において好ましい。 The (meth) acrylonitrile compound, maleimide compound, acid anhydride and unsaturated carboxylic acid compound can be used alone, and it is preferable to use one or more of these four types in combination with styrenes. This is because all of these four types can maintain, regulate or impart the hydrophobicity or organic solvent affinity of the first polymerized chain. Among them, one or more of (meth) acrylonitrile compounds such as acrylonitrile, maleimide compounds such as N-phenylmaleimide, and acid anhydrides. Of these, a combination of styrene and acrylonitrile, styrene and N-phenylmaleimide and the like is preferable. The unsaturated carboxylic acid compound is preferable in that the polarity of the polymer (A) can be easily changed.
　スチレン類と組み合わせて用いる場合、スチレン類以外のこれら１種又は２種以上の第１の単量体の総量は、第１の重合鎖を重合するための第１の単量体（第１の重合鎖の第１の単量体単位）の総質量のうち、例えば、２０質量％以上である。また例えば、２５質量％以上であり、また例えば、３０質量％以上であり、また例えば、３５質量％以上であり、また例えば、４０質量％以上であり、また例えば、５０質量％以上であり、また例えば、６０質量％以上である。また、（メタ）アクリロニトリル化合物は、前記総質量の８０質量％以下であり、また例えば、７５質量％以下であり、また例えば、７０質量％以下であり、また例えば、６５質量％以下であり、また例えば、６０質量％以下であり、また例えば、５５質量％以下であり、また例えば、５０質量％以下である。スチレン類の前記総質量に対する範囲としては、上記した下限及び上限を適宜組み合わせて設定することができる。 When used in combination with styrenes, the total amount of these one or more first monomers other than styrenes is the first monomer for polymerizing the first polymerized chain (first). It is, for example, 20% by mass or more of the total mass of the first monomer unit of the polymerized chain). Further, for example, it is 25% by mass or more, and is, for example, 30% by mass or more, and is, for example, 35% by mass or more, and is, for example, 40% by mass or more, and is, for example, 50% by mass or more. Further, for example, it is 60% by mass or more. The (meth) acrylonitrile compound is 80% by mass or less, for example, 75% by mass or less, and is, for example, 70% by mass or less, and is, for example, 65% by mass or less, based on the total mass. Further, for example, it is 60% by mass or less, for example, 55% by mass or less, and for example, 50% by mass or less. The range of the styrenes with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
　水酸基含有エチレン性不飽和単量体は、第１の単量体の総質量のうち、例えば、５０質量％以上９０質量％以下である。５０質量％以上であると、本架橋重合体塩を含む電極スラリーの沈降安定性を付与することができるからである。また例えば、５２．５質量％以上であり、また例えば、５５質量％以上であり、また例えば、５７．５質量％以上であり、また例えば、６０質量％以上であり、また例えば、６２．５質量％以上であり、また例えば、６５質量％以上であり、また例えば、６７．５質量％以上であり、また例えば、７０質量％以上である。また、水酸基含有エチレン性不飽和単量体は、例えば、前記総質量の８７．５質量％以下であり、また例えば、８５質量％以下であり、また例えば、８２．５質量％以下であり、また例えば、８０質量％以下であり、また例えば、７７．５質量％以下であり、また例えば、７５質量％以下である。水酸基含有エチレン性不飽和単量体の前記総質量に対する範囲としては、上記した下限及び上限を適宜組み合わせて設定することができる。 The hydroxyl group-containing ethylenically unsaturated monomer is, for example, 50% by mass or more and 90% by mass or less of the total mass of the first monomer. This is because when it is 50% by mass or more, the precipitation stability of the electrode slurry containing the present crosslinked polymer salt can be imparted. Further, for example, 52.5% by mass or more, for example, 55% by mass or more, and for example, 57.5% by mass or more, and for example, 60% by mass or more, and for example, 62.5. It is 5% by mass or more, and is, for example, 65% by mass or more, and is, for example, 67.5% by mass or more, and is, for example, 70% by mass or more. The hydroxyl group-containing ethylenically unsaturated monomer is, for example, 87.5% by mass or less, for example, 85% by mass or less, and for example, 82.5% by mass or less, based on the total mass. Further, for example, it is 80% by mass or less, for example, 77.5% by mass or less, and for example, 75% by mass or less. The range of the hydroxyl group-containing ethylenically unsaturated monomer with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
＜第１の重合鎖＞
　第１の重合鎖は、上記した第１の単量体のみの重合鎖であってもよいが、必要に応じて、上記以外の他のビニル系単量体を第１の単量体として用いることができる。例えば、（メタ）アクリル酸、（メタ）アクリル酸アルキルなどの（メタ）アクリル酸エステル等の公知のビニル系単量体を用いることができる。
なお、こうした他の単量体は、第１の重合鎖を構成する単量体の総質量の、例えば１０質量％以下、また例えば、５質量％以下、また例えば、３質量％以下、また例えば、１質量％以下であり、また例えば、０．５質量％以下である。 <First polymerized chain>
The first polymerized chain may be a polymerized chain containing only the first monomer described above, but if necessary, other vinyl-based monomers other than the above may be used as the first monomer. be able to. For example, known vinyl-based monomers such as (meth) acrylic acid esters such as (meth) acrylic acid and alkyl (meth) acrylic acid can be used.
It should be noted that these other monomers are, for example, 10% by mass or less, for example, 5% by mass or less, for example, 3% by mass or less, or, for example, the total mass of the monomers constituting the first polymerized chain. 1, 1% by mass or less, and for example, 0.5% by mass or less.
　また、重合体（Ａ）は、第１の重合鎖とは異なるブロック（他の重合鎖）を備えることもできる。かかる他の重合鎖は、例えば、第１の重合鎖の形成後に、別の合成工程で付加されてもよい。この場合には、第１の重合鎖を備える重合体（Ａ）に、引き続きあるいは新たにラジカル重合開始剤と他のビニル系単量体を供給して、第１の重合鎖とは異なる組成の第１の単量体以外の単量体に由来する単位からなる他の重合鎖（ブロック）を備える重合体（Ａ）を得ることができる。後述するリビングラジカル活性単位に直接連結され、かつ第１の重合鎖に連結されるように備えられることで、本架橋重合体に用いる本単量体と共通する単量体の一部を予め、重合体（Ａ）中に備えることができる。 Further, the polymer (A) may be provided with a block (another polymer chain) different from that of the first polymer chain. Such other polymerized chains may be added, for example, in another synthetic step after the formation of the first polymerized chain. In this case, the polymer (A) having the first polymerized chain is continuously or newly supplied with a radical polymerization initiator and another vinyl-based monomer to have a composition different from that of the first polymerized chain. A polymer (A) having another polymer chain (block) consisting of units derived from a monomer other than the first monomer can be obtained. By being provided so as to be directly linked to the living radical active unit described later and to be linked to the first polymerized chain, a part of the monomer common to the present monomer used in the present crosslinked polymer can be partially linked in advance. It can be provided in the polymer (A).
＜リビングラジカル重合活性単位＞
　重合体（Ａ）は、交換連鎖移動機構によるリビングラジカル重合活性単位を備えるため、本単量体の沈殿重合又は分散重合にあたって、重合体（Ａ）の重合溶媒への溶解性や分散安定剤としての機能のために、種々のモノマーを選択することができる。 <Living radical polymerization active unit>
Since the polymer (A) has a living radical polymerization active unit by an exchange chain transfer mechanism, it can be used as a solubility or dispersion stabilizer for the polymer (A) in the polymerization solvent in the precipitation polymerization or dispersion polymerization of this monomer. Various monomers can be selected for the function of.
　重合体（Ａ）におけるリビングラジカル重合活性単位の交換連鎖移動機構としては、可逆的付加－開裂連鎖移動重合法（ＲＡＦＴ法）、ヨウ素移動重合法、有機テルル化合物を用いる重合法（ＴＥＲＰ法）、有機アンチモン化合物を用いる重合法（ＳＢＲＰ法）、有機ビスマス化合物を用いる重合法（ＢＩＲＰ法）等が挙げられる。これらの中でも、本架橋重合体の粒子径を小さくできる点で、ＲＡＦＴ法及びヨウ素移動重合法が好ましく、ＲＡＦＴ法がより好ましい。 The exchange chain transfer mechanism of the living radical polymerization active unit in the polymer (A) includes a reversible addition-cleavage chain transfer polymerization method (RAFT method), an iodine transfer polymerization method, and a polymerization method using an organic tellurium compound (TERP method). Examples thereof include a polymerization method using an organic antimony compound (SBRP method), a polymerization method using an organic bismuth compound (BIRP method), and the like. Among these, the RAFT method and the iodine transfer polymerization method are preferable, and the RAFT method is more preferable, because the particle size of the crosslinked polymer can be reduced.
３．本架橋重合体塩の特性
（本架橋重合体塩のカルボキシル基金属塩の存在割合（Ｘ））
　本架橋重合体の金属塩（中和度Ｎモル％）[以下、架橋重合体塩Ｒ]、及び、架橋重合体塩Ｒにおけるエチレン性不飽和カルボン酸単量体に由来する構造単位を１００質量％含む重合体の金属塩（中和度Ｎモル％）[以下、重合体塩Ｓ]のＸ線光電子分光分析（ＸＰＳ）により下記式（１）により算出される、ＸＰＳに基づく前記架橋重合体のカルボキシル基金属塩の存在割合（Ｘ）は、８５モル％以下（但し、Ｎは２０以上１００以下の値であり、架橋重合体塩Ｒ及び重合体塩Ｓについて同一。また、金属塩の種類は、架橋重合体塩Ｒ及び重合体塩Ｓについて同一。）である。
　Ｘが８５モル％以下であると、電極スラリーの沈降安定性及び結着性に優れ、８２．５モル％以下であることがより好ましく、８０モル％以下であることがさらに好ましく、７５モル％以下であることがより一層好ましい。
　ここで、Ｘは、実施例に記載の方法に従う方法により得られる。 3. 3. Characteristics of this crosslinked polymer salt
(Abundance ratio (X) of carboxyl group metal salt of this crosslinked polymer salt)
100 mass of structural units derived from the metal salt of the present cross-linked polymer (neutralization degree N mol%) [hereinafter, cross-linked polymer salt R] and the ethylenically unsaturated carboxylic acid monomer in the cross-linked polymer salt R. % The crosslinked polymer based on XPS calculated by the following formula (1) by X-ray photoelectron spectroscopic analysis (XPS) of the metal salt of the polymer (neutralization degree N mol%) [hereinafter, polymer salt S]. The abundance ratio (X) of the carboxyl group metal salt is 85 mol% or less (however, N is a value of 20 or more and 100 or less, and is the same for the crosslinked polymer salt R and the polymer salt S. Also, the type of metal salt. Is the same for the crosslinked polymer salt R and the polymer salt S).
When X is 85 mol% or less, the sedimentation stability and binding property of the electrode slurry are excellent, more preferably 82.5 mol% or less, further preferably 80 mol% or less, and 75 mol%. The following is even more preferable.
Here, X is obtained by a method according to the method described in the examples.
＜本架橋重合体塩の水溶液粘度＞
　本架橋重合体塩は、その２質量％濃度水溶液の粘度が１００ｍＰａ・ｓ以上であることが好ましい。２質量％濃度水溶液の粘度が１００ｍＰａ・ｓ以上の場合、架橋重合体を含む組成物の保存安定性が高く、優れた結着性を発揮することが可能となる。２質量％濃度水溶液の粘度は、１，０００ｍＰａ・ｓ以上であってもよく、１０，０００ｍＰａ・ｓ以上であってもよく、５０，０００ｍＰａ・ｓ以上であってもよい
　水溶液粘度は、所定の濃度となる量の本架橋重合体塩を水中に均一に溶解又は分散した後、実施例に記載の方法に従い、１２ｒｐｍにおけるＢ型粘度（２５℃）を測定することにより得られる。 <Aqueous viscosity of this crosslinked polymer salt>
The crosslinked polymer salt preferably has a viscosity of 100 mPa · s or more in a 2% by mass aqueous solution thereof. When the viscosity of the 2% by mass concentration aqueous solution is 100 mPa · s or more, the storage stability of the composition containing the crosslinked polymer is high, and it is possible to exhibit excellent binding properties. The viscosity of the 2 mass% concentration aqueous solution may be 1,000 mPa · s or more, 10,000 mPa · s or more, or 50,000 mPa · s or more. The viscosity of the aqueous solution is predetermined. It is obtained by uniformly dissolving or dispersing the present cross-linked polymer salt in an amount to be a concentration in water, and then measuring the B-type viscosity (25 ° C.) at 12 rpm according to the method described in Examples.
　本架橋重合体塩は、水中では水を吸収して膨潤した状態となる。一般に、架橋重合体が適度な架橋度を有する場合、当該架橋重合体が有する親水性基の量が多いほど、架橋重合体は水を吸収して膨潤し易くなる。また、架橋度についていえば、架橋度が低いほど、架橋重合体は膨潤し易くなる。但し、架橋点の数が同じであっても、分子量（一次鎖長）が大きいほど三次元ネットワークの形成に寄与する架橋点が増えるため、架橋重合体は膨潤し難くなる。よって、架橋重合体の親水性基の量、架橋点の数及び一次鎖長等を調整することにより、架橋重合体水溶液の粘度を調節することができる。この際、上記架橋点の数は、例えば、架橋性単量体の使用量、ポリマー鎖への連鎖移動反応及び後架橋反応等により調整が可能である。また、重合体の一次鎖長は、開始剤及び重合温度等のラジカル発生量に関連する条件の設定、並びに、連鎖移動等を考慮した重合溶媒の選択等により調整することができる。 This crosslinked polymer salt absorbs water and becomes swollen in water. In general, when the crosslinked polymer has an appropriate degree of crosslinking, the larger the amount of hydrophilic groups of the crosslinked polymer, the easier it is for the crosslinked polymer to absorb water and swell. Regarding the degree of cross-linking, the lower the degree of cross-linking, the easier it is for the cross-linked polymer to swell. However, even if the number of cross-linking points is the same, the larger the molecular weight (primary chain length), the more cross-linking points that contribute to the formation of the three-dimensional network, so that the cross-linked polymer is less likely to swell. Therefore, the viscosity of the crosslinked polymer aqueous solution can be adjusted by adjusting the amount of hydrophilic groups of the crosslinked polymer, the number of crosslinking points, the primary chain length, and the like. At this time, the number of the cross-linking points can be adjusted by, for example, the amount of the cross-linking monomer used, the chain transfer reaction to the polymer chain, the post-cross-linking reaction, and the like. Further, the primary chain length of the polymer can be adjusted by setting conditions related to the amount of radical generation such as the initiator and the polymerization temperature, and selecting the polymerization solvent in consideration of chain transfer and the like.
＜本架橋重合体塩の粒子径＞
　本組成物において、本架橋重合体塩は大粒径の塊（二次凝集体）として存在することなく、適度な粒子径を有する水膨潤粒子として良好に分散していることが、当該架橋重合体塩を含むバインダーが良好な結着性能を発揮し得るため好ましい。 <Particle size of this crosslinked polymer salt>
In the present composition, the crosslinked polymer salt does not exist as a mass (secondary agglomerate) having a large particle size, but is well dispersed as water-swelling particles having an appropriate particle size. A binder containing a coalesced salt is preferable because it can exhibit good binding performance.
　本架橋重合体は、当該架橋重合体が有するカルボキシル基に基づく中和度が８０～１００モル％であるものを水中に分散させた際の粒子径（水膨潤粒子径）が、体積基準メジアン径で０．１μｍ以上１０．０μｍ以下の範囲にあることが好ましい。上記粒子径のより好ましい範囲は０．１５μｍ以上８．０μｍ以下であり、さらに好ましい範囲は０．２０μｍ以上６．０μｍ以下であり、一層好ましい範囲は０．２５μｍ以上４．０μｍ以下であり、より一層好ましい範囲は０．３０μｍ以上２．０μｍ以下である。粒子径が０．３０μｍ以上２．０μｍ以下の範囲であれば、本組成物中において好適な大きさで均一に存在するため、本組成物の安定性が高く、優れた結着性を発揮することが可能となる。粒子径が１０．０μｍを超えると、上記の通り結着性が不十分となる虞がある。また、平滑性な塗面が得られにくい点で、塗工性が不十分となる虞がある。一方、粒子径が０．１μｍ未満の場合には、安定製造性の観点において懸念される。
　なお、上記水膨潤粒子径は、本明細書実施例に記載の方法により測定することができる。 In this crosslinked polymer, the particle size (water-swelling particle size) when a crosslinked polymer having a degree of neutralization based on a carboxyl group of 80 to 100 mol% is dispersed in water is a volume-based median diameter. It is preferably in the range of 0.1 μm or more and 10.0 μm or less. A more preferable range of the particle size is 0.15 μm or more and 8.0 μm or less, a further preferable range is 0.20 μm or more and 6.0 μm or less, and a further preferable range is 0.25 μm or more and 4.0 μm or less. A more preferable range is 0.30 μm or more and 2.0 μm or less. When the particle size is in the range of 0.30 μm or more and 2.0 μm or less, the composition is uniformly present in a suitable size in the present composition, so that the present composition is highly stable and exhibits excellent binding properties. It becomes possible. If the particle size exceeds 10.0 μm, the binding property may be insufficient as described above. In addition, there is a risk that the coatability will be insufficient because it is difficult to obtain a smooth coated surface. On the other hand, when the particle size is less than 0.1 μm, there is concern from the viewpoint of stable manufacturability.
The water-swelling particle size can be measured by the method described in the examples of the present specification.
　架橋重合体が未中和若しくは中和度８０モル％未満の場合は、アルカリ金属水酸化物等により中和度８０～１００モル％に中和し、水中に分散させた際の粒子径を測定すればよい。一般に、架橋重合体又はその塩は、粉末又は溶液（分散液）の状態では一次粒子が会合、凝集した塊状粒子として存在する場合が多い。上記の水分散させた際の粒子径が上記範囲である場合、当該架橋重合体又はその塩は極めて優れた分散性を有するものであり、中和度８０～１００モル％に中和して水分散することにより塊状粒子が解れ、ほぼ一次粒子の分散体、若しくは２次凝集体であっても、その粒子径が０．１～１０．０μｍの範囲内にある、安定な分散状態を形成するものである。 If the crosslinked polymer is unneutralized or has a neutralization degree of less than 80 mol%, it is neutralized to a neutralization degree of 80 to 100 mol% with an alkali metal hydroxide or the like, and the particle size when dispersed in water is measured. do it. In general, the crosslinked polymer or a salt thereof often exists as agglomerated particles in which primary particles are associated and aggregated in the state of powder or solution (dispersion liquid). When the particle size when dispersed in water is in the above range, the crosslinked polymer or a salt thereof has extremely excellent dispersibility, and is neutralized to a neutralization degree of 80 to 100 mol% to be water. By dispersing, the agglomerated particles are disintegrated, and even if it is a dispersion of almost primary particles or a secondary agglomerate, a stable dispersed state is formed in which the particle size is in the range of 0.1 to 10.0 μm. It is a thing.
　本架橋重合体は、本組成物中において、中和度が２０モル％以上となるように、エチレン性不飽和カルボン酸単量体由来のカルボキシル基等の酸基が中和され、塩の態様として用いることが好ましい。上記中和度は、より好ましくは５０モル％以上であり、さらに好ましくは７０モル％以上であり、一層好ましくは７５モル％以上であり、より一層好ましくは８０モル％以上であり、特に好ましくは８５モル％以上である。中和度の上限値は１００モル％であり、９８モル％であってもよく９５モル％であってもよい。中和度の範囲は、上記下限値及び上限値を適宜組合せることができ、例えば、５０モル％以上１００モル％以下であってもよく、７５モル％以上１００モル％以下であってもよく、８０モル％以上１００モル％以下であってもよい。中和度が２０モル％以上の場合、水膨潤性が良好となり分散安定化効果が得やすいという点で好ましい。本明細書では、上記中和度は、カルボキシル基等の酸基を有する単量体及び中和に用いる中和剤の仕込み値から計算により算出することができる。なお、中和度は架橋重合体塩を、減圧条件下、８０℃で３時間乾燥処理後の粉末をＩＲ測定し、カルボン酸のＣ＝Ｏ基由来のピークとカルボン酸塩のＣ＝Ｏ基由来のピークの強度比より確認することができる。 In the present cross-linked polymer, acid groups such as a carboxyl group derived from an ethylenically unsaturated carboxylic acid monomer are neutralized so that the degree of neutralization is 20 mol% or more in the present composition, and the mode of the salt is It is preferable to use as. The degree of neutralization is more preferably 50 mol% or more, further preferably 70 mol% or more, still more preferably 75 mol% or more, still more preferably 80 mol% or more, and particularly preferably. It is 85 mol% or more. The upper limit of the degree of neutralization is 100 mol%, and may be 98 mol% or 95 mol%. The range of the degree of neutralization may be appropriately combined with the above lower limit value and upper limit value, and may be, for example, 50 mol% or more and 100 mol% or less, or 75 mol% or more and 100 mol% or less. , 80 mol% or more and 100 mol% or less. When the degree of neutralization is 20 mol% or more, the water swelling property is good and the dispersion stabilizing effect is easily obtained, which is preferable. In the present specification, the degree of neutralization can be calculated by calculation from the charged values of a monomer having an acid group such as a carboxyl group and a neutralizing agent used for neutralization. The degree of neutralization was measured by IR measurement of the crosslinked polymer salt and the powder after drying at 80 ° C. for 3 hours under reduced pressure conditions, and the peak derived from the C = O group of the carboxylic acid and the C = O group of the carboxylic acid salt were measured. It can be confirmed from the intensity ratio of the peak of origin.
＜本架橋重合体塩の水膨潤度＞
　本明細書では、水膨潤度は架橋重合体塩の乾燥時の重量「（ＷＡ）ｇ」、及び当該架橋重合体塩を水で飽和膨潤させた際に吸収される水の量「（ＷＢ）ｇ」とから、以下の式に基づいて算出される。
（水膨潤度）＝｛（ＷＡ）＋（ＷＢ）｝／（ＷＡ） <Water swelling degree of this crosslinked polymer salt>
In the present specification, the degree of water swelling is the weight "( WA ) g" of the crosslinked polymer salt when dried, and the amount of water absorbed when the crosslinked polymer salt is saturated and swelled with water "(W). B ) g ”is calculated based on the following formula.
(Water swelling degree) = {( WA ) + ( WB )} / ( WA )
　架橋重合体塩は、ｐＨ８における水膨潤度が２０以上、８０以下であることが好ましい。水膨潤度が上記範囲であれば、架橋重合体塩が水媒体中で適度に膨潤するため、電極合剤層を形成する際に、活物質及び集電体への十分な接着面積を確保することが可能となり、結着性が良好となる傾向がある。上記水膨潤度は、例えば２１以上であってもよく、２３以上であってもよく、２５以上であってもよく、２７以上であってもよく、３０以上であってもよい。水膨潤度が２０以上の場合、架橋重合体塩が活物質や集電体の表面において広がり、十分な接着面積を確保することができるため、良好な結着性が得られる。ｐＨ８における水膨潤度の上限値は、７５以下であってもよく、７０以下であってもよく、６５以下であってもよく、６０以下であってもよく、５５以下であってもよい。水膨潤度が６０を超えると、架橋重合体塩を含む電極合剤層用組成物（電極スラリー）の粘度が高くなる傾向が有り、合剤層の均一性が不足する結果、十分な結着力が得られないことがある。また、電極スラリーの塗工性が低下する虞がある。ｐＨ８における水膨潤度の範囲は、上記上限値及び下限値を適宜組合せることにより設定できる。
　ｐＨ８における水膨潤度は、ｐＨ８の水中における架橋重合体塩の膨潤度を測定することにより得ることができる。上記ｐＨ８の水としては、例えばイオン交換水を使用することができ、必要に応じて適当な酸若しくはアルカリ、又は緩衝液等を用いてｐＨの値を調整してもよい。測定時のｐＨは、例えば、８．０±０．５の範囲であり、好ましくは８．０±０．３の範囲であり、より好ましくは８．０±０．２の範囲であり、さらに好ましくは８．０±０．１の範囲である。また、測定は、２５±５℃で行う。 The crosslinked polymer salt preferably has a water swelling degree of 20 or more and 80 or less at pH 8. When the degree of water swelling is within the above range, the crosslinked polymer salt swells moderately in the aqueous medium, so that a sufficient adhesive area to the active material and the current collector is secured when forming the electrode mixture layer. It becomes possible and the binding property tends to be good. The degree of water swelling may be, for example, 21 or more, 23 or more, 25 or more, 27 or more, or 30 or more. When the degree of water swelling is 20 or more, the crosslinked polymer salt spreads on the surface of the active material or the current collector, and a sufficient adhesive area can be secured, so that good binding property can be obtained. The upper limit of the degree of water swelling at pH 8 may be 75 or less, 70 or less, 65 or less, 60 or less, or 55 or less. When the degree of water swelling exceeds 60, the viscosity of the composition for the electrode mixture layer (electrode slurry) containing the crosslinked polymer salt tends to increase, and as a result of insufficient uniformity of the mixture layer, sufficient binding force is obtained. May not be obtained. In addition, the coatability of the electrode slurry may decrease. The range of the degree of water swelling at pH 8 can be set by appropriately combining the above upper limit value and lower limit value.
The degree of water swelling at pH 8 can be obtained by measuring the degree of swelling of the crosslinked polymer salt in water at pH 8. As the water having a pH of 8, for example, ion-exchanged water can be used, and the pH value may be adjusted by using an appropriate acid or alkali, a buffer solution or the like, if necessary. The pH at the time of measurement is, for example, in the range of 8.0 ± 0.5, preferably in the range of 8.0 ± 0.3, more preferably in the range of 8.0 ± 0.2, and further. It is preferably in the range of 8.0 ± 0.1. The measurement is performed at 25 ± 5 ° C.
　なお、当業者であれば、架橋重合体塩の組成及び構造等を制御することにより、その水膨潤度の調整を行うことができる。例えば、架橋重合体に酸性官能基、又は親水性の高い構造単位を導入することにより、水膨潤度を高くすることができる。また、架橋重合体の架橋度を低くすることによっても、通常その水膨潤度は高くなる。 A person skilled in the art can adjust the degree of water swelling by controlling the composition and structure of the crosslinked polymer salt. For example, the degree of water swelling can be increased by introducing an acidic functional group or a highly hydrophilic structural unit into the crosslinked polymer. Further, by lowering the degree of cross-linking of the cross-linked polymer, the degree of water swelling is usually increased.
４．二次電池電極合剤層用組成物
　本発明の二次電池電極合剤層用組成物は、本バインダー、活物質及び水を含む。
　本組成物における本バインダーの使用量は、活物質の全量１００質量部に対して、例えば、０．１質量部以上２０質量部以下である。上記使用量は、また例えば、０．２質量部以上１０質量部以下であり、また例えば０．３質量部以上８質量部以下であり、また例えば０．４質量部以上５質量部以下である。バインダーの使用量が０．１質量部以上であれば、十分な結着性を得ることができる。また、活物質等の分散安定性を確保することができ、均一な合剤層を形成することができる。バインダーの使用量が２０質量部以下であれば、本組成物が高粘度となることはなく、集電体への塗工性を確保することができる。その結果、均一で平滑な表面を有する合剤層を形成することができる。 4. Composition for secondary battery electrode mixture layer The composition for a secondary battery electrode mixture layer of the present invention contains the present binder, an active material and water.
The amount of the binder used in the composition is, for example, 0.1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total amount of the active material. The amount used is, for example, 0.2 parts by mass or more and 10 parts by mass or less, for example, 0.3 parts by mass or more and 8 parts by mass or less, and for example, 0.4 parts by mass or more and 5 parts by mass or less. .. When the amount of the binder used is 0.1 part by mass or more, sufficient binding property can be obtained. In addition, the dispersion stability of the active material or the like can be ensured, and a uniform mixture layer can be formed. When the amount of the binder used is 20 parts by mass or less, the present composition does not have a high viscosity, and the coatability to the current collector can be ensured. As a result, a mixture layer having a uniform and smooth surface can be formed.
　上記活物質の内、正極活物質としては、遷移金属酸化物のリチウム塩を用いることができ、例えば、層状岩塩型及びスピネル型のリチウム含有金属酸化物を使用することができる。層状岩塩型の正極活物質の具体的な化合物としては、コバルト酸リチウム、ニッケル酸リチウム、並びに、三元系と呼ばれるＮＣＭ｛Ｌｉ（Ｎｉｘ，Ｃｏｙ，Ｍｎｚ）、ｘ＋ｙ＋ｚ＝１｝及びＮＣＡ｛Ｌｉ（Ｎｉ１－ａ－ｂＣｏａＡｌb）｝等が挙げられる。また、スピネル型の正極活物質としては、マンガン酸リチウム等が挙げられる。酸化物以外にもリン酸塩、ケイ酸塩及び硫黄等が使用され、リン酸塩としては、オリビン型のリン酸鉄リチウム等が挙げられる。正極活物質としては、上記のうちの１種を単独で使用してもよく、２種以上を組み合わせて混合物又は複合物として使用してもよい。 Among the above active materials, the lithium salt of the transition metal oxide can be used as the positive electrode active material, and for example, layered rock salt type and spinel type lithium-containing metal oxides can be used. Specific compounds of the layered rock salt type positive electrode active material include lithium cobalt oxide, lithium nickel oxide, and NCM {Li (Ni x , Coy, Mn z ), x + y + z = 1} and NCA, which are called ternary systems. {Li (Ni 1-ab Co a Al b )} and the like can be mentioned. Moreover, as a spinel type positive electrode active material, lithium manganate and the like can be mentioned. Phosphate, silicate, sulfur and the like are used in addition to the oxide, and examples of the phosphate include olivine-type lithium iron phosphate and the like. As the positive electrode active material, one of the above may be used alone, or two or more thereof may be combined and used as a mixture or a composite.
　なお、層状岩塩型のリチウム含有金属酸化物を含む正極活物質を水に分散させた場合、活物質表面のリチウムイオンと水中の水素イオンとが交換されることにより、分散液がアルカリ性を示す。このため、一般的な正極用集電体材料であるアルミ箔（Ａｌ）等が腐食される虞がある。このような場合には、バインダーとして未中和又は部分中和された本架橋重合体を用いることにより、活物質から溶出するアルカリ分を中和することが好ましい。また、未中和又は部分中和された本架橋重合体の使用量は、本架橋重合体の中和されていないカルボキシル基量が活物質から溶出するアルカリ量に対して当量以上となるように用いることが好ましい。 When a positive electrode active material containing a layered rock salt type lithium-containing metal oxide is dispersed in water, the dispersion liquid becomes alkaline due to the exchange of lithium ions on the surface of the active material and hydrogen ions in water. Therefore, there is a risk that aluminum foil (Al), which is a general current collector material for positive electrodes, will be corroded. In such a case, it is preferable to neutralize the alkali content eluted from the active material by using the present crosslinked polymer which has not been neutralized or partially neutralized as the binder. Further, the amount of the unneutralized or partially neutralized present crosslinked polymer used is such that the amount of the unneutralized carboxyl group of the present crosslinked polymer is equal to or more than the amount of alkali eluted from the active material. It is preferable to use it.
　正極活物質はいずれも電気伝導性が低いため、導電助剤を添加して使用されるのが一般的である。導電助剤としては、カーボンブラック、カーボンナノチューブ、カーボンファイバー、黒鉛微粉、炭素繊維等の炭素系材料が挙げられ、これらの内、優れた導電性を得やすい点からカーボンブラック、カーボンナノチューブ及びカーボンファイバーが好ましい。また、カーボンブラックとしては、ケッチェンブラック及びアセチレンブラックが好ましい。導電助剤は、上記の１種を単独で使用してもよく、２種以上を組み合わせて使用してもよい。導電助剤の使用量は、導電性とエネルギー密度を両立するという観点から、活物質の全量１００質量部に対して、例えば、０．２～２０質量部とすることができ、また例えば、０．２～１０質量部とすることができる。また、正極活物質は導電性を有する炭素系材料で表面コーティングしたものを使用してもよい。 Since all positive electrode active materials have low electrical conductivity, they are generally used by adding a conductive additive. Examples of the conductive auxiliary agent include carbon-based materials such as carbon black, carbon nanotubes, carbon fibers, graphite fine powder, and carbon fibers. Among these, carbon black, carbon nanotubes, and carbon fibers are easy to obtain excellent conductivity. Is preferable. Further, as the carbon black, Ketjen black and acetylene black are preferable. As the conductive auxiliary agent, one of the above may be used alone, or two or more thereof may be used in combination. The amount of the conductive auxiliary agent used can be, for example, 0.2 to 20 parts by mass with respect to 100 parts by mass of the total amount of the active material from the viewpoint of achieving both conductivity and energy density, and for example, 0. It can be 2 to 10 parts by mass. Further, as the positive electrode active material, a material having a surface coating with a conductive carbon-based material may be used.
　一方、負極活物質としては、例えば炭素系材料、リチウム金属、リチウム合金及び金属酸化物等が挙げられ、これらの内の１種又は２種以上を組み合わせて用いることができる。これらの内でも、天然黒鉛、人造黒鉛、ハードカーボン及びソフトカーボン等の炭素系材料からなる活物質（以下、「炭素系活物質」ともいう。）が好ましく、天然黒鉛及び人造黒鉛等の黒鉛、並びにハードカーボンがより好ましい。また、黒鉛の場合、電池性能の面から球形化黒鉛が好適に用いられ、その粒子サイズの好ましい範囲は、例えば、１～２０μｍであり、また例えば、５～１５μｍである。また、エネルギー密度を高くするために、ケイ素やスズなどのリチウムを吸蔵できる金属又は金属酸化物等を負極活物質として使用することもできる。その中でも、ケイ素は黒鉛に比べて高容量であり、ケイ素、ケイ素合金及び一酸化ケイ素（ＳｉＯ）等のケイ素酸化物のようなケイ素系材料からなる活物質（以下、「ケイ素系活物質」ともいう。）を用いることができる。しかし、上記ケイ素系活物質は高容量である反面充放電に伴う体積変化が大きい。このため、上記炭素系活物質と併用するのが好ましい。この場合、ケイ素系活物質の配合量が多いと電極材料の崩壊を招き、サイクル特性（耐久性）が大きく低下する場合がある。このような観点から、ケイ素系活物質を併用する場合、その使用量は炭素系活物質に対して、例えば、６０質量％以下であり、また例えば、３０質量％以下である。 On the other hand, examples of the negative electrode active material include carbon-based materials, lithium metals, lithium alloys, metal oxides, and the like, and one or more of these can be used in combination. Among these, active materials made of carbon-based materials such as natural graphite, artificial graphite, hard carbon and soft carbon (hereinafter, also referred to as “carbon-based active material”) are preferable, and graphite such as natural graphite and artificial graphite, Also, hard carbon is more preferred. Further, in the case of graphite, spherical graphite is preferably used from the viewpoint of battery performance, and the preferable range of the particle size thereof is, for example, 1 to 20 μm, and for example, 5 to 15 μm. Further, in order to increase the energy density, a metal or a metal oxide capable of storing lithium such as silicon or tin can also be used as the negative electrode active material. Among them, silicon has a higher capacity than graphite, and is an active material made of a silicon-based material such as silicon, a silicon alloy, and a silicon oxide such as silicon monoxide (SiO) (hereinafter, also referred to as "silicon-based active material"). ) Can be used. However, while the silicon-based active material has a high capacity, the volume change due to charge / discharge is large. Therefore, it is preferable to use it in combination with the above carbon-based active material. In this case, if the amount of the silicon-based active material is large, the electrode material may be disintegrated and the cycle characteristics (durability) may be significantly deteriorated. From such a viewpoint, when a silicon-based active material is used in combination, the amount used is, for example, 60% by mass or less, and for example, 30% by mass or less, based on the carbon-based active material.
　炭素系活物質は、それ自身が良好な電気伝導性を有するため、必ずしも導電助剤を添加する必要はない。抵抗をより低減する等の目的で導電助剤を添加する場合、エネルギー密度の観点からその使用量は活物質の全量１００質量部に対して、例えば、１０質量部以下であり、また例えば、５質量部以下である。 Since the carbon-based active material itself has good electrical conductivity, it is not always necessary to add a conductive additive. When a conductive auxiliary agent is added for the purpose of further reducing resistance, the amount used is, for example, 10 parts by mass or less with respect to 100 parts by mass of the total amount of the active material, and for example, 5 from the viewpoint of energy density. It is less than the mass part.
　本組成物がスラリー状態の場合、活物質の使用量は、本組成物全量に対して、例えば、１０～７５質量％の範囲であり、また例えば、３０～６５質量％の範囲である。活物質の使用量が１０質量％以上であればバインダー等のマイグレーションが抑えられるとともに、媒体の乾燥コストの面でも有利となる。一方、７５質量％以下であれば、本組成物の流動性及び塗工性を確保することができ、均一な合剤層を形成することができる。 When the composition is in a slurry state, the amount of the active material used is, for example, in the range of 10 to 75% by mass, and for example, in the range of 30 to 65% by mass, based on the total amount of the composition. If the amount of the active material used is 10% by mass or more, migration of the binder or the like can be suppressed, and it is also advantageous in terms of the drying cost of the medium. On the other hand, if it is 75% by mass or less, the fluidity and coatability of the present composition can be ensured, and a uniform mixture layer can be formed.
　本組成物は、媒体として水を使用する。また、本組成物の性状及び乾燥性等を調整する目的で、メタノール及びエタノール等の低級アルコール類、エチレンカーボネート等のカーボネート類、アセトン等のケトン類、テトラヒドロフラン、Ｎ－メチル－２－ピロリドン等の水溶性有機溶剤との混合溶媒としてもよい。混合媒体中の水の割合は、例えば、５０質量％以上であり、また例えば、７０質量％以上である。 This composition uses water as a medium. Further, for the purpose of adjusting the properties and dryness of the composition, lower alcohols such as methanol and ethanol, carbonates such as ethylene carbonate, ketones such as acetone, tetrahydrofuran, N-methyl-2-pyrrolidone and the like. It may be a mixed solvent with a water-soluble organic solvent. The proportion of water in the mixing medium is, for example, 50% by mass or more, and for example, 70% by mass or more.
　本組成物を塗工可能なスラリー状態とする場合、本組成物全体に占める水を含む媒体の含有量は、スラリーの塗工性、及び乾燥に必要なエネルギーコスト、生産性の観点から、例えば、２５～６０質量％の範囲とすることができ、また例えば、３５～６０質量％とすることができる。 When the present composition is in a coatable slurry state, the content of the medium containing water in the entire composition is, for example, from the viewpoint of the coatability of the slurry, the energy cost required for drying, and the productivity. , 25-60% by mass, and can be, for example, 35-60% by mass.
　本組成物は、さらに、スチレンブタジエンゴム（ＳＢＲ）系ラテックス、カルボキシメチルセルロース(ＣＭＣ)、アクリル系ラテックス及びポリフッ化ビニリデン系ラテックス等の他のバインダー成分を併用してもよい。他のバインダー成分を併用する場合、その使用量は、活物質の全量１００質量部に対して、例えば、０．１～５質量部以下とすることができ、また例えば、０．１～２質量部以下とすることができ、また例えば、０．１～１質量部以下とすることができる。他のバインダー成分の使用量が５質量部を超えると抵抗が増大し、ハイレート特性が不十分なものとなる場合がある。上記の中でも、結着性及び耐屈曲性のバランスに優れる点で、ＳＢＲ系ラテックス、ＣＭＣが好ましく、ＳＢＲ系ラテックス及びＣＭＣを併用する事がより好ましい。 The present composition may further contain other binder components such as styrene-butadiene rubber (SBR) -based latex, carboxymethyl cellulose (CMC), acrylic-based latex and polyvinylidene fluoride-based latex. When other binder components are used in combination, the amount used may be, for example, 0.1 to 5 parts by mass or less, and for example, 0.1 to 2 parts by mass, based on 100 parts by mass of the total amount of the active material. It can be less than or equal to parts, and can be, for example, 0.1 to 1 part by mass or less. If the amount of the other binder component used exceeds 5 parts by mass, the resistance increases and the high rate characteristics may be insufficient. Among the above, SBR-based latex and CMC are preferable, and SBR-based latex and CMC are more preferable in combination because they are excellent in the balance between binding property and bending resistance.
　上記ＳＢＲ系ラテックスとは、スチレン等の芳香族ビニル単量体に由来する構造単位及び１，３－ブタジエン等の脂肪族共役ジエン系単量体に由来する構造単位を有する共重合体の水系分散体を示す。上記芳香族ビニル単量体としては、スチレンの他にα－メチルスチレン、ビニルトルエン、ジビニルベンゼン等が挙げられ、これらの内の１種又は２種以上を用いることができる。上記共重合体中における上記芳香族ビニル単量体に由来する構造単位は、主に結着性の観点から、例えば、２０～７０質量％の範囲とすることができ、また例えば、３０～６０質量％の範囲とすることができる。
　上記脂肪族共役ジエン系単量体としては、例えば、１，３－ブタジエンの他に２－メチル－１，３－ブタジエン、２，３－ジメチル－１，３－ブタジエン、２－クロロ－１，３－ブタジエン等が挙げられ、これらの内の１種又は２種以上を用いることができる。上記共重合体中における上記脂肪族共役ジエン系単量体に由来する構造単位は、バインダーの結着性及び得られる電極の柔軟性が良好なものとなる点で、例えば、３０～７０質量％の範囲とすることができ、また例えば、４０～６０質量％の範囲とすることができる。
　スチレン／ブタジエン系ラテックスは、上記の単量体以外にも、結着性等の性能をさらに向上させるために、その他の単量体として（メタ）アクリロニトリル等のニトリル基含有単量体、（メタ）アクリル酸、イタコン酸、マレイン酸等のカルボキシル基含有単量体、（メタ）アクリル酸メチル等のエステル基含有単量体を共重合単量体として用いてもよい。
　上記共重合体中における上記その他の単量体に由来する構造単位は、例えば、０～３０質量％の範囲とすることができ、また例えば、０～２０質量％の範囲とすることができる。 The SBR-based latex is an aqueous dispersion of a copolymer having a structural unit derived from an aromatic vinyl monomer such as styrene and a structural unit derived from an aliphatic conjugated diene-based monomer such as 1,3-butadiene. Show the body. Examples of the aromatic vinyl monomer include α-methylstyrene, vinyltoluene, divinylbenzene and the like in addition to styrene, and one or more of these can be used. The structural unit derived from the aromatic vinyl monomer in the copolymer can be, for example, in the range of 20 to 70% by mass, and for example, 30 to 60, mainly from the viewpoint of binding property. It can be in the range of% by mass.
Examples of the aliphatic conjugated diene-based monomer include 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1, in addition to 1,3-butadiene. Examples thereof include 3-butadiene, and one or more of these can be used. The structural unit derived from the aliphatic conjugated diene-based monomer in the copolymer is, for example, 30 to 70% by mass in that the binding property of the binder and the flexibility of the obtained electrode are good. It can be in the range of 40 to 60% by mass, for example.
In addition to the above-mentioned monomers, the styrene / butadiene-based latex includes nitrile group-containing monomers such as (meth) acrylonitrile and (meth) as other monomers in order to further improve the performance such as binding property. ) A carboxyl group-containing monomer such as acrylic acid, itaconic acid, and maleic acid, and an ester group-containing monomer such as methyl (meth) acrylate may be used as the copolymerization monomer.
The structural unit derived from the other monomer in the copolymer can be, for example, in the range of 0 to 30% by mass, or can be, for example, in the range of 0 to 20% by mass.
　上記ＣＭＣとは、ノニオン性セルロース系半合成高分子化合物をカルボキシメチル基により置換した置換体及びその塩を示す。上記ノニオン性セルロース系半合成高分子化合物としては、例えば、メチルセルロース、メチルエチルセルロース、エチルセルロース、マイクロクリスタリンセルロース等のアルキルセルロース；
ヒドロキシエチルセルロース、ヒドロキシブチルメチルセルロース、ヒドロキシプロピルセルロース、ヒドロキシプロピルメチルセルロース、ヒドロキシエチルメチルセルロース、ヒドロキシプロピルメチルセルロースステアロキシエーテル、カルボキシメチルヒドロキシエチルセルロース、アルキルヒドロキシエチルセルロース、ノノキシニルヒドロキシエチルセルロース等のヒドロキシアルキルセルロースなどが挙げられる。 The above-mentioned CMC refers to a substituent obtained by substituting a nonionic cellulose-based semisynthetic polymer compound with a carboxymethyl group and a salt thereof. Examples of the nonionic cellulose-based semi-synthetic polymer compound include alkyl celluloses such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose, and microcrystallin cellulose;
Examples thereof include hydroxyethyl cellulose, hydroxybutylmethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, hydroxyethylmethyl cellulose, hydroxypropylmethyl cellulose stearoxy ether, carboxymethyl hydroxyethyl cellulose, alkyl hydroxyethyl cellulose, hydroxyalkyl cellulose such as nonoxynyl hydroxyethyl cellulose and the like.
　本発明の二次電池電極合剤層用組成物は、上記の活物質、水及びバインダーを必須の構成成分とするものであり、公知の手段を用いて各成分を混合することにより得られる。各成分の混合方法は特段制限されるものではなく、公知の方法を採用することができるが、活物質、導電助剤及びバインダー等の粉末成分をドライブレンドした後、水等の分散媒と混合し、分散混練する方法が好ましい。本組成物をスラリー状態で得る場合、分散不良や凝集のないスラリーに仕上げることが好ましい。混合手段としては、プラネタリーミキサー、薄膜旋回式ミキサー及び自公転式ミキサー等の公知のミキサーを使用することができるが、短時間で良好な分散状態が得られる点で薄膜旋回式ミキサーを使用して行うことが好ましい。また、薄膜旋回式ミキサーを用いる場合は、予めディスパー等の攪拌機で予備分散を行うことが好ましい。上記スラリーのｐＨは、本発明の効果を奏する限り特に制限されないが、１２．５未満であることが好ましく、例えば、ＣＭＣを配合する場合にはその加水分解の懸念が小さい点で、１１．５未満であることがより好ましく、１０．５未満であることがさらに好ましい。また、上記スラリーの粘度は、本発明の効果を奏する限り特に制限されないが、２０ｒｐｍにおけるＢ型粘度（２５℃）として、例えば、１００～６，０００ｍＰａ・ｓの範囲とすることができ、また例えば、５００～５，０００ｍＰａ・ｓ、また例えば、１，０００～４，０００ｍＰａ・ｓの範囲とすることができる。スラリーの粘度が上記の範囲内であれば、良好な塗工性を確保することができる。 The composition for the secondary battery electrode mixture layer of the present invention contains the above-mentioned active material, water and a binder as essential constituents, and can be obtained by mixing each component by a known means. The mixing method of each component is not particularly limited, and a known method can be adopted. However, powder components such as an active substance, a conductive auxiliary agent and a binder are dry-blended and then mixed with a dispersion medium such as water. The method of dispersion and kneading is preferable. When the present composition is obtained in a slurry state, it is preferable to finish the composition into a slurry having no poor dispersion or aggregation. As the mixing means, a known mixer such as a planetary mixer, a thin film swirl mixer, or a self-revolving mixer can be used, but a thin film swirl mixer is used because a good dispersion state can be obtained in a short time. It is preferable to do this. When using a thin film swirl mixer, it is preferable to pre-disperse in advance with a stirrer such as a disper. The pH of the slurry is not particularly limited as long as the effect of the present invention is exhibited, but it is preferably less than 12.5. It is more preferably less than 10.5 and even more preferably less than 10.5. The viscosity of the slurry is not particularly limited as long as the effect of the present invention is exhibited, but the B-type viscosity (25 ° C.) at 20 rpm can be, for example, in the range of 100 to 6,000 mPa · s, and for example. , 500 to 5,000 mPa · s, or, for example, 1,000 to 4,000 mPa · s. When the viscosity of the slurry is within the above range, good coatability can be ensured.
５．二次電池電極
　本発明の二次電池電極は、銅又はアルミニウム等の集電体表面に本発明の二次電池電極合剤層用組成物から形成される合剤層を備えてなるものである。合剤層は、集電体の表面に本組成物を塗工した後、水等の媒体を乾燥除去することにより形成される。本組成物を塗工する方法は特に限定されず、ドクターブレード法、ディップ法、ロールコート法、コンマコート法、カーテンコート法、グラビアコート法及びエクストルージョン法などの公知の方法を採用することができる。また、上記乾燥は、温風吹付け、減圧、（遠）赤外線、マイクロ波照射等の公知の方法により行うことができる。
　通常、乾燥後に得られた合剤層には、金型プレス及びロールプレス等による圧縮処理が施される。圧縮することにより活物質及びバインダーを密着させ、合剤層の強度及び集電体への密着性を向上させることができる。圧縮により合剤層の厚みを、例えば、圧縮前の３０～８０％程度に調整することができ、圧縮後の合剤層の厚みは４～２００μｍ程度が一般的である。 5. Secondary battery electrode The secondary battery electrode of the present invention comprises a mixture layer formed from the composition for the mixture layer of the secondary battery electrode of the present invention on the surface of a current collector such as copper or aluminum. .. The mixture layer is formed by applying the present composition to the surface of the current collector and then drying and removing a medium such as water. The method for applying the present composition is not particularly limited, and known methods such as a doctor blade method, a dip method, a roll coating method, a comma coating method, a curtain coating method, a gravure coating method and an extrusion method may be adopted. can. Further, the drying can be performed by a known method such as blowing warm air, reducing the pressure, (far) infrared rays, and irradiating microwaves.
Usually, the mixture layer obtained after drying is subjected to a compression treatment by a die press, a roll press or the like. By compressing, the active material and the binder are brought into close contact with each other, and the strength of the mixture layer and the adhesion to the current collector can be improved. The thickness of the mixture layer can be adjusted to, for example, about 30 to 80% before compression, and the thickness of the mixture layer after compression is generally about 4 to 200 μm.
６．二次電池
　本発明の二次電池電極にセパレータ及び電解液を備えることにより、二次電池を作製することができる。電解液は液状であってもよく、ゲル状であってもよい。
　セパレータは電池の正極及び負極間に配され、両極の接触による短絡の防止や電解液を保持してイオン導電性を確保する役割を担う。セパレータにはフィルム状の絶縁性微多孔膜であって、良好なイオン透過性及び機械的強度を有するものが好ましい。具体的な素材としては、ポリエチレン及びポリプロピレン等のポリオレフィン、ポリテトラフルオロエチレン等を使用することができる。 6. Secondary battery A secondary battery can be manufactured by providing a separator and an electrolytic solution on the secondary battery electrode of the present invention. The electrolytic solution may be in the form of a liquid or in the form of a gel.
The separator is arranged between the positive electrode and the negative electrode of the battery, and plays a role of preventing a short circuit due to contact between the two electrodes and holding an electrolytic solution to ensure ionic conductivity. The separator is preferably a film-like insulating microporous film having good ion permeability and mechanical strength. As a specific material, polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene and the like can be used.
　電解液は、活物質の種類に応じて一般的に使用される公知のものを用いることができる。リチウムイオン二次電池では、具体的な溶媒として、プロピレンカーボネート及びエチレンカーボネート等の高誘電率で電解質の溶解能力の高い環状カーボネート、並びに、エチルメチルカーボネート、ジメチルカーボネート及びジエチルカーボネート等の粘性の低い鎖状カーボネート等が挙げられ、これらを単独で又は混合溶媒として使用することができる。電解液は、これらの溶媒にＬｉＰＦ６、ＬｉＳｂＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＡｌＯ４等のリチウム塩を溶解して使用される。ニッケル水素二次電池では、電解液として水酸化カリウム水溶液を使用することができる。二次電池は、セパレータで仕切られた正極板及び負極板を渦巻き状又は積層構造にしてケース等に収納することにより得られる。 As the electrolytic solution, a known one that is generally used depending on the type of the active material can be used. In the lithium ion secondary battery, specific solvents include cyclic carbonates having a high dielectric constant and a high dissolving ability of an electrolyte such as propylene carbonate and ethylene carbonate, and low-viscosity chains such as ethylmethyl carbonate, dimethyl carbonate and diethyl carbonate. Examples thereof include state carbonate and the like, and these can be used alone or as a mixed solvent. The electrolytic solution is used by dissolving lithium salts such as LiPF 6 , LiSbF 6 , LiBF 4 , LiClO 4 , and LiAlO 4 in these solvents. In the nickel-metal hydride secondary battery, an aqueous potassium hydroxide solution can be used as the electrolytic solution. The secondary battery is obtained by forming a positive electrode plate and a negative electrode plate partitioned by a separator into a spiral or laminated structure and storing them in a case or the like.
　本明細書に開示される二次電池電極用バインダーを含む電極スラリーは、沈降安定性に優れる事から、合剤層において電極材料との優れた結着性と集電体との優れた接着性とを示すと予想される。このため、上記バインダーを使用して得られた電極を備えた二次電池は、良好な一体性を確保でき、充放電を繰り返しても良好な耐久性（サイクル特性）を示すと予想され、車載用二次電池等に好適である。 Since the electrode slurry containing the binder for the secondary battery electrode disclosed in the present specification has excellent settling stability, it has excellent adhesion to the electrode material and excellent adhesion to the current collector in the mixture layer. Is expected to indicate. Therefore, the secondary battery provided with the electrodes obtained by using the above binder is expected to ensure good integrity and to show good durability (cycle characteristics) even after repeated charging and discharging, and is in-vehicle. Suitable for secondary batteries and the like.
　以下、実施例に基づいて本発明を具体的に説明する。なお、本発明は、これらの実施例により限定されるものではない。以下において、「部」及び「％」は、特に断らない限り質量部及び質量％を意味する。
　以下の例において、カルボキシル基含有架橋重合体の金属塩についての評価は、以下の方法により実施した。 Hereinafter, the present invention will be specifically described based on Examples. The present invention is not limited to these examples. In the following, "parts" and "%" mean parts by mass and% by mass unless otherwise specified.
In the following example, the evaluation of the metal salt of the carboxyl group-containing crosslinked polymer was carried out by the following method.
≪重合体（Ａ）の合成≫
（重合体（Ａ）の分子量の測定方法）
　後記で得られた重合体（Ａ）について、以下に記載の条件にてゲルパーミエーションクロマトグラフィー（ＧＰＣ）測定を行い、ポリスチレン換算による数平均分子量（Ｍｎ）及び重量平均分子量（Ｍｗ）を得た。また、得られた値から分子量分布（Ｍｗ／Ｍｎ）を算出した。 << Synthesis of polymer (A) >>
(Method for measuring the molecular weight of the polymer (A))
The polymer (A) obtained later was subjected to gel permeation chromatography (GPC) measurement under the conditions described below to obtain a number average molecular weight (Mn) and a weight average molecular weight (Mw) in terms of polystyrene. .. Moreover, the molecular weight distribution (Mw / Mn) was calculated from the obtained values.
　なお、ＧＰＣは以下の条件で行った。
　カラム：東ソー製ＴＳＫｇｅｌ ＳｕｐｅｒＭｕｌｔｉｐｏｒｅＨＺ－Ｍ×４本
　溶媒：テトラヒドロフラン
　温度：４０℃
　検出器：ＲＩ
　流速：６００μＬ／ｍｉｎ The GPC was performed under the following conditions.
Column: Tosoh TSKgel SuperMultipore HZ-M x 4 Solvent: Tetrahydrofuran Temperature: 40 ° C
Detector: RI
Flow velocity: 600 μL / min
（合成例１：重合体１の合成）
　攪拌機、温度計を装着した１ＬフラスコにＲＡＦＴ剤（ジベンジルトリチオカーボネー
ト：以下、「ＤＢＴＴＣ」ともいう。）０．２部、２，２’－アゾビス（２，４－ジメチルバレロニトリル（富士フイルム和光純薬社製、商品名「Ｖ－６５」：以下、「Ｖ－６５」ともいう。）０．０４１部、エチルアクリレート（以下、「ＥＡ」ともいう。）３０部、２－ヒドロキシエチルアクリレート（以下、「ＨＥＡ」ともいう。）７０部、及びアセトニトリル８３部を仕込み、窒素バブリングで十分脱気し、５５℃の恒温槽で重合を開始した。５時間後、室温まで冷却し反応を停止した。上記重合溶液を、メタノール／水＝９０／１０（ｖоｌ％）から再沈殿精製、真空乾燥することで重合体１を得た。ガスクロマトグラフィー測定の結果、得られた重合体１の反応率はＥＡ：８２％、ＨＥＡ：８７％であり、当該反応率に基づき算出される重合体１の組成比は、ＥＡ／ＨＥＡ＝２８．８／７１．２質量％であった。重合体１の前記組成比に基づく計算ＳＰ値は、２６．５（（ＭＰａ）1/2）であった。重合体１の分子量は、Ｍｎは８２，１００、Ｍｗは１１８，３００、Ｍｗ／Ｍｎは１．４４であった。なお、ＥＡ及びＨＥＡが、第１のビニル系単量体に対応している。 (Synthesis Example 1: Synthesis of Polymer 1)
RAFT agent (dibenzyltrithiocarbonate: hereinafter also referred to as "DBTTC") 0.2 part, 2,2'-azobis (2,4-dimethylvaleronitrile (Fujifilm)) in a 1 L flask equipped with a stirrer and a thermometer. Wako Pure Chemical Industries, Ltd., trade name "V-65": hereinafter also referred to as "V-65") 0.041 parts, ethyl acrylate (hereinafter also referred to as "EA") 30 parts, 2-hydroxyethyl acrylate (Hereinafter, also referred to as "HEA") 70 parts and 83 parts of acetonitrile were charged, sufficiently degassed by nitrogen bubbling, and polymerization was started in a constant temperature bath at 55 ° C. After 5 hours, the reaction was stopped by cooling to room temperature. The above polymerization solution was reprecipitated from methanol / water = 90/10 (vоl%), purified and vacuum dried to obtain a polymer 1. As a result of gas chromatography measurement, the reaction of the obtained polymer 1 was obtained. The ratio was EA: 82%, HEA: 87%, and the composition ratio of the polymer 1 calculated based on the reaction rate was EA / HEA = 28.8 / 71.2% by mass. The calculated SP value based on the composition ratio was 26.5 ((MPa) 1/2 ). The molecular weight of the polymer 1 was 82,100 for Mn, 118,300 for Mw, and 1 for Mw / Mn. It was .44. EA and HEA correspond to the first vinyl-based monomer.
（合成例２～５：重合体２～５の合成）
　各原料の仕込み量を表１に記載の通りとした以外は重合体１の合成と同様の操作を行い、重合体２～５を得た。得られた各重合体について、重合体１と同様に物性値を測定し、結果を表１に示す。 (Synthesis Examples 2 to 5: Synthesis of Polymers 2 to 5)
The same operation as in the synthesis of the polymer 1 was carried out except that the amount of each raw material charged was as shown in Table 1, to obtain polymers 2 to 5. The physical property values of each of the obtained polymers were measured in the same manner as in the polymer 1, and the results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
　表１において用いた化合物の詳細を以下に示す。
・ＥＡ：エチルアクリレート
・ＢＡ：ｎ－ブチルアクリレート
・ＨＥＡ：２－ヒドロキシエチルアクリレート
・Ｓｔ：スチレン
・ＡＮ：アクリロニトリル
・ＤＢＴＴＣ：ジベンジルトリチオカーボネート
・Ｖ－６５：２，２’－アゾビス（２，４－ジメチルバレロニトリル）（富士フイルム和光純薬社製、商品名「Ｖ－６５」）
・ＡＢＮ－Ｅ：２，２’－アゾビス（２－メチルブチロニトリル）（日本ファインケム社製、商品名「ＡＢＮ－Ｅ」） Details of the compounds used in Table 1 are shown below.
EA: ethyl acrylate, BA: n-butyl acrylate, HEA: 2-hydroxyethyl acrylate, St: styrene, AN: acrylonitrile, DBTTC: dibenzyltrithiocarbonate, V-65: 2,2'-azobis (2, 4-Dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-65")
-ABN-E: 2,2'-azobis (2-methylbutyronitrile) (manufactured by Japan Finechem Company, Inc., trade name "ABN-E")
≪カルボキシル基含有架橋重合体の金属塩の製造≫
（架橋重合体の金属塩のカルボキシル基金属塩の存在割合（Ｘ）の測定）
　カルボキシル基含有架橋重合体の金属塩（中和度Ｎモル％）[以下、架橋重合体塩Ｒ]の粉末、及び、架橋重合体塩Ｒにおけるエチレン性不飽和カルボン酸単量体に由来する構造単位を１００質量％含む重合体の金属塩（中和度Ｎモル％）[以下、重合体塩Ｓ]の粉末を粉体試料ホルダーにそれぞれ充填して、測定サンプルを作製した。
　上記測定サンプルについて、Ｘ線光電子分光分析装置による測定を行い、下記式（１）により、Ｘ線光電子分光分析（ＸＰＳ）に基づく各架橋重合体のカルボキシル基金属塩の存在割合（Ｘ）を算出した（但し、Ｎは２０以上１００以下の値であり、架橋重合体塩Ｒ及び重合体塩Ｓについて同一。また、金属塩の種類は、架橋重合体塩Ｒ及び重合体塩Ｓについて同一。）。 ≪Manufacturing of metal salt of crosslinked polymer containing carboxyl group≫
(Measurement of abundance ratio (X) of carboxyl group metal salt of metal salt of crosslinked polymer)
Structure derived from the powder of the metal salt of the carboxyl group-containing crosslinked polymer (neutralization degree N mol%) [hereinafter, the crosslinked polymer salt R] and the ethylenically unsaturated carboxylic acid monomer in the crosslinked polymer salt R. A powder sample holder was filled with a powder of a polymer metal salt containing 100% by mass (neutralization degree N mol%) [hereinafter, polymer salt S] to prepare a measurement sample.
The above measurement sample is measured by an X-ray photoelectron spectroscopic analyzer, and the abundance ratio (X) of the carboxyl group metal salt of each crosslinked polymer based on the X-ray photoelectron spectroscopic analysis (XPS) is calculated by the following formula (1). (However, N is a value of 20 or more and 100 or less, and is the same for the crosslinked polymer salt R and the polymer salt S. The type of the metal salt is the same for the crosslinked polymer salt R and the polymer salt S.) ..
　Ｘ（モル％)＝I１/I２×１００　（１）
　ここで、I１は、架橋重合体塩Ｒについて、ＸＰＳに基づき、下記式（２）により算出される値であり、I２は、重合体塩Ｓについて、ＸＰＳに基づき下記式（３）により算出される値である。
　I１（ａｔｏｍ％）＝ＡＭ１／（ＡＭ１＋ＡＣ１＋ＡＯ１）　（２）
　　ＡＭ１：金属塩由来の金属の１ｓ軌道のピーク面積（％）
　　ＡＣ１：炭素の１ｓ軌道のピーク面積（％） 
　　ＡＯ１：酸素の１ｓ軌道のピーク面積（％）
　　（但し、ＡＭ１＋ＡＣ１＋ＡＯ１＝１００。）
　I２（ａｔｏｍ％）＝ＡＭ２／（ＡＭ２＋ＡＣ２＋ＡＯ２）　（３）
　　ＡＭ２：金属塩由来の金属の１ｓ軌道のピーク面積（％）
　　ＡＣ２：炭素の１ｓ軌道のピーク面積（％）
　　ＡＯ２：酸素の１ｓ軌道のピーク面積（％）
　　（但し、ＡＭ2＋ＡＣ2＋ＡＯ2＝１００。） X (mol%) = I 1 / I 2 x 100 (1)
Here, I 1 is a value calculated by the following formula (2) for the crosslinked polymer salt R based on XPS, and I 2 is a value calculated by the following formula (3) for the polymer salt S based on XPS. It is a calculated value.
I 1 (atom%) = AM1 / ( AM1 + AC1 + AO1 ) (2)
AM1 : Peak area (%) of 1s orbital of metal derived from metal salt
AC1 : Peak area (%) of carbon 1s orbital
A O1 : Peak area (%) of 1s orbit of oxygen
(However, AM1 + AC1 + AO1 = 100.)
I 2 (atom%) = AM2 / ( AM2 + AC2 + AO2 ) (3)
AM2 : Peak area (%) of 1s orbital of metal derived from metal salt
AC2 : Peak area (%) of carbon 1s orbital
A O2 : Peak area (%) of 1s orbit of oxygen
(However, AM2 + AC2 + AO2 = 100.)
　なお、ＸＰＳ測定は、以下の条件で行った。
　装置：　アルバック・ファイ社製　ＰＨＩ５０００　ＶｅｒｓａＰｒｏｂｅIII
　Ｘ線：　Ａｌ－Ｋα　（１４８６．６ｅＶ）
　試料へのＸ線入射角：　０°　（試料測定面の法線に対する角度）
　光電子検出角：　４５°　（試料測定面の法線に対する角度） The XPS measurement was performed under the following conditions.
Equipment: ULVAC-PHI PHI5000 VersaProbeIII
X-ray: Al-Kα (1486.6eV)
X-ray incident angle on the sample: 0 ° (angle of the sample measurement surface with respect to the normal)
Photoelectron detection angle: 45 ° (angle of sample measurement surface with respect to normal)
（水媒体中での粒子径（水膨潤粒子径）の測定）
　架橋重合体の金属塩の粉末０．２５ｇ、及びイオン交換水４９．７５ｇを１００ｃｃの容器に量りとり、自転／公転式攪拌機（シンキー社製、あわとり錬太郎ＡＲ－２５０）にセットした。次いで、撹拌（自転速度２，０００ｒｐｍ／公転速度８００ｒｐｍ、７分）、さらに脱泡（自転速度２，２００ｒｐｍ／公転速度６０ｒｐｍ、１分）処理を行い架橋重合体の金属塩が水に膨潤した状態のハイドロゲルを作製した。
　次に、イオン交換水を分散媒とするレーザー回折/散乱式粒度分布計（マイクロトラックベル社製、マイクロトラックＭＴ－３３００ＥＸII）にて上記ハイドロゲルの粒度分布測定を行った。ハイドロゲルに対し、過剰量の分散媒を循環しているところに、適切な散乱光強度が得られる量のハイドロゲルを投入したところ、数分後に測定される粒度分布形状が安定した。安定を確認次第、粒度分布測定を行い、粒子径の代表値としての体積基準メジアン径（Ｄ５０）を得た。 (Measurement of particle size (water-swelling particle size) in water medium)
0.25 g of the crosslinked polymer metal salt powder and 49.75 g of ion-exchanged water were weighed in a 100 cc container and set in a rotating / revolving / revolving stirrer (Awatori Rentaro AR-250, manufactured by Shinky). Next, stirring (rotation speed 2,000 rpm / revolution speed 800 rpm, 7 minutes) and defoaming (rotation speed 2,200 rpm / revolution speed 60 rpm, 1 minute) were performed to swell the metal salt of the crosslinked polymer in water. Hydrogel was prepared.
Next, the particle size distribution of the hydrogel was measured with a laser diffraction / scattering particle size distribution meter (Microtrac MT-3300EXII, manufactured by Microtrac Bell) using ion-exchanged water as a dispersion medium. When an amount of hydrogel capable of obtaining an appropriate scattered light intensity was added to the hydrogel in a place where an excessive amount of dispersion medium was circulated, the particle size distribution shape measured after a few minutes became stable. As soon as the stability was confirmed, the particle size distribution was measured to obtain a volume-based median diameter (D50) as a representative value of the particle size.
（製造例１：カルボキシル基含有重合体の金属塩Ｒ－１の製造）
　重合には、攪拌翼、温度計、還流冷却器及び窒素導入管を備えた反応器を用いた。
　反応器内にアセトニトリル５６７部、イオン交換水２．２部、アクリル酸（以下、「
ＡＡ」ともいう。）１００部、トリメチロールプロパンジアリルエーテル（大阪ソーダ社製、商品名「ネオアリルＴ－２０」）０．９部及び上記ＡＡに対して１．０モル％に相当するトリエチルアミンを仕込んだ。反応器内を十分に窒素置換した後、加温して内温を５５℃まで昇温した。内温が５５℃で安定したことを確認した後、重合開始剤として２，２’－アゾビス（２，４－ジメチルバレロニトリル）（富士フイルム和光純薬社製、商品名「Ｖ－６５」）０．０４０部を添加したところ、反応液に白濁が認められたため、この点を重合開始点とした。重合開始から７時間後（０．５８Ｔの時点に相当する重合工程の途中）、重合体１を２部、一括して添加した。なお、単量体濃度は１５％と算出された。重合開始点から１２時間経過した時点で重合反応液の冷却を開始し、内温が２５℃まで低下した後、水酸化リチウム・一水和物（以下、「ＬｉＯＨ・Ｈ２Ｏ」ともいう）の粉末５２．４部を添加した。添加後室温下１２時間撹拌を継続して、カルボキシル基含有重合体の金属塩Ｒ－１（リチウム塩、中和度９０モル％）の粒子が媒体に分散したスラリー状の重合反応液を得た。 (Production Example 1: Production of Metal Salt R-1 of Carboxyl Group-Containing Polymer)
A reactor equipped with a stirring blade, a thermometer, a reflux condenser and a nitrogen introduction tube was used for the polymerization.
In the reactor, 567 parts of acetonitrile, 2.2 parts of ion-exchanged water, acrylic acid (hereinafter, ""
Also called "AA". ) 100 parts, 0.9 part of trimethylolpropane diallyl ether (manufactured by Osaka Soda Co., Ltd., trade name "Neoallyl T-20") and triethylamine corresponding to 1.0 mol% with respect to the above AA were charged. After sufficiently replacing the inside of the reactor with nitrogen, the inside temperature was raised to 55 ° C. by heating. After confirming that the internal temperature was stable at 55 ° C, 2,2'-azobis (2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-65") was used as a polymerization initiator. When 0.040 part was added, cloudiness was observed in the reaction solution, and this point was set as the polymerization initiation point. Seven hours after the start of the polymerization (during the polymerization step corresponding to the time point of 0.58 T), two parts of the polymer 1 were added all at once. The monomer concentration was calculated to be 15%. Cooling of the polymerization reaction solution is started 12 hours after the polymerization initiation point, and after the internal temperature is lowered to 25 ° C., lithium hydroxide monohydrate (hereinafter, also referred to as “LiOH ・H2O ”). 52.4 parts of the powder of the above was added. After the addition, stirring was continued at room temperature for 12 hours to obtain a slurry-like polymerization reaction solution in which particles of the metal salt R-1 (lithium salt, neutralization degree 90 mol%) of the carboxyl group-containing polymer were dispersed in the medium. ..
　得られた重合反応液を遠心分離して重合体粒子を沈降させた後、上澄みを除去した。その後、重合反応液と同重量のアセトニトリルに沈降物を再分散させた後、遠心分離により重合体粒子を沈降させて上澄みを除去する洗浄操作を２回繰り返した。沈降物を回収し、減圧条件下、８０℃で３時間乾燥処理を行い、揮発分を除去することにより、カルボキシル基含有重合体の金属塩Ｒ－１の粉末を得た。カルボキシル基含有重合体の金属塩Ｒ－１は吸湿性を有するため、水蒸気バリア性を有する容器に密封保管した。なお、カルボキシル基含有重合体の金属塩Ｒ－１の粉末をＩＲ測定し、カルボン酸のＣ＝Ｏ基由来のピークとカルボン酸リチウムのＣ＝Ｏ由来のピークの強度比より中和度を求めたところ、仕込みからの計算値に等しく９０モル％であった。また、水媒体中での粒子径は１．５２μｍであった。 The obtained polymerization reaction solution was centrifuged to settle the polymer particles, and then the supernatant was removed. Then, after redispersing the precipitate in acetonitrile having the same weight as the polymerization reaction solution, the washing operation of precipitating the polymer particles by centrifugation and removing the supernatant was repeated twice. The precipitate was recovered and dried at 80 ° C. for 3 hours under reduced pressure to remove volatile components to obtain a powder of the metal salt R-1 of the carboxyl group-containing polymer. Since the metal salt R-1 of the carboxyl group-containing polymer has hygroscopicity, it was stored in a sealed container having a water vapor barrier property. The powder of the metal salt R-1 of the carboxyl group-containing polymer was measured by IR, and the degree of neutralization was determined from the intensity ratio of the peak derived from the C = O group of the carboxylic acid and the peak derived from the C = O of the lithium carboxylate. As a result, it was 90 mol%, which was equal to the calculated value from the preparation. The particle size in the aqueous medium was 1.52 μm.
　カルボキシル基含有架橋重合体の金属塩Ｒ－１のＸＰＳ測定結果を示す。
　まず、カルボキシル基含有架橋重合体のリチウム塩Ｒ－１（中和度９０モル％）について、Ｉ１を測定した結果、図１に示す通り、８．２ａｔｏｍ％であった。
　次に、Ｒ－１におけるエチレン性不飽和カルボン酸単量体はアクリル酸のみであるため、アクリル酸に由来する構造単位を１００質量％含む重合体（アルドリッチ社製ポリアクリル酸ａｖｅｒａｇｅＭｖ～４，０００，０００）のリチウム塩（中和度９０モル％）を用いて、Ｉ2を測定した結果、図２に示す通り、１０．６ａｔｏｍ％であった。
　上記測定により得られたＩ１及びＩ2を用いて、式（１）に基づき（Ｘ）を算出した結果、７７％であった。 The XPS measurement result of the metal salt R-1 of the carboxyl group-containing crosslinked polymer is shown.
First, as a result of measuring I 1 of the lithium salt R-1 (neutralization degree 90 mol%) of the carboxyl group-containing crosslinked polymer, it was 8.2 atom% as shown in FIG.
Next, since the ethylenically unsaturated carboxylic acid monomer in R-1 is only acrylic acid, a polymer containing 100% by mass of a structural unit derived from acrylic acid (polyacrylic acid averageMv to 4,000 manufactured by Aldrich Co., Ltd.). As a result of measuring I 2 using a lithium salt of 000) (neutralization degree 90 mol%), it was 10.6 atom% as shown in FIG.
As a result of calculating (X) based on the formula (1) using I 1 and I 2 obtained by the above measurement, it was 77%.
（製造例２～１３及び比較製造例１～４：カルボキシル基含有重合体の金属塩Ｒ－２～Ｒ－１７の製造）
　各原料の仕込み量を表２に記載の通りとした以外は製造例１と同様の操作を行い、カルボキシル基含有重合体の金属塩Ｒ－２～Ｒ－１７を含む重合反応液を得た。
　次いで、各重合反応液について製造例１と同様の操作を行い、粉末状のカルボキシル基含有重合体の金属塩Ｒ－２～Ｒ－１７を得た。各カルボキシル基含有重合体の金属塩は、水蒸気バリア性を有する容器に密封保管した。
　得られた各重合体塩について、製造例１と同様に物性値を測定し、結果を表２に示す。
　なお、カルボキシル基含有重合体の金属塩Ｒ－２～Ｒ－１７においても、Ｒ－１と同様のＸＰＳ測定を行い、Ｉ1を測定した。前記で得られたＲ－２～Ｒ－１７のＩ1、及び、Ｉ2＝１０．６ａｔｏｍ％を用いて、式（１）に基づき、（Ｘ）をそれぞれ算出した。 (Production Examples 2 to 13 and Comparative Production Examples 1 to 4: Production of metal salts R-2 to R-17 of a carboxyl group-containing polymer)
The same operation as in Production Example 1 was carried out except that the amount of each raw material charged was as shown in Table 2, to obtain a polymerization reaction solution containing the metal salts R-2 to R-17 of the carboxyl group-containing polymer.
Next, the same operation as in Production Example 1 was carried out for each polymerization reaction solution to obtain powdery metal salts R-2 to R-17 of the carboxyl group-containing polymer. The metal salt of each carboxyl group-containing polymer was sealed and stored in a container having a water vapor barrier property.
Physical property values of each of the obtained polymer salts were measured in the same manner as in Production Example 1, and the results are shown in Table 2.
The metal salts R-2 to R-17 of the carboxyl group-containing polymer were also subjected to XPS measurement in the same manner as R-1, and I 1 was measured. Using I 1 and I 2 = 10.6 atom% of R-2 to R-17 obtained above, (X) was calculated based on the formula (1), respectively.
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
　表２において用いた化合物の詳細を以下に示す。
・ＡＡ：アクリル酸
・ＨＥＡ：２－ヒドロキシエチルアクリレート
・Ｔ－２０：トリメチロールプロパンジアリルエーテル（大阪ソーダ社製、商品名「ネオアリルＴ－２０」）
・ＴＥＡ：トリエチルアミン
・Ｖ－６５：２，２’－アゾビス（２，４－ジメチルバレロニトリル）（富士フイルム和光純薬社製）
・ＬｉＯＨ・Ｈ２Ｏ：水酸化リチウム・一水和物
・Ｎａ２ＣＯ３：炭酸ナトリウム
・Ｋ２ＣＯ３：炭酸カリウム Details of the compounds used in Table 2 are shown below.
-AA: Acrylic acid-HEA: 2-Hydroxyethyl acrylate-T-20: Trimethylolpropane diallyl ether (manufactured by Osaka Soda Co., Ltd., trade name "Neoallyl T-20")
-TEA: Triethylamine-V-65: 2,2'-azobis (2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)
・ LiOH ・ H 2 O: Lithium hydroxide ・ Monohydrate ・ Na 2 CO 3 : Sodium carbonate ・ K 2 CO 3 : Potassium carbonate
実施例１
（電極合剤層用組成物の調製）
　ＳｉＯｘ（０．８＜ｘ＜１．２）の表面にＣＶＤ法で炭素をコートしたものを準備し（以下、「Ｓｉ系活物質」ともいう。）、黒鉛（日本黒鉛社製、商品名「ＣＧＢ－１０」）とＳｉ系活物質とを混合したものを活物質として用いた。電極合剤層用組成物の固形分濃度が４０．０質量％となるように、水を希釈溶媒として、黒鉛：Ｓｉ系活物質：カルボキシル基含有架橋重合体の金属塩Ｒ－１＝９０：１０：３．２（固形分）の質量比で予めよく混合した後、イオン交換水を加えてディスパーで予備分散を行った後、薄膜旋回式ミキサー（プライミクス社製、ＦＭ－５６－３０）を用いて周速度２０ｍ／秒の条件で本分散を１５秒間行うことにより、スラリー状の電極合剤層用組成物を得た。
　上記電極合剤層用組成物（電極スラリー）について、その沈降安定性を測定した。 Example 1
(Preparation of composition for electrode mixture layer)
Prepare a SiOx (0.8 <x <1.2) surface coated with carbon by the CVD method (hereinafter, also referred to as "Si-based active material"), and graphite (manufactured by Nippon Graphite Co., Ltd., trade name ". A mixture of CGB-10 ") and a Si-based active material was used as the active material. A metal salt of a crosslinked polymer containing graphite: Si-based active material: carboxyl group R-1 = 90: using water as a diluting solvent so that the solid content concentration of the composition for the electrode mixture layer is 40.0% by mass. After mixing well in advance with a mass ratio of 10: 3.2 (solid content), add ion-exchanged water and perform preliminary dispersion with a disper, and then use a thin film swirl mixer (FM-56-30, manufactured by Primix). By performing this dispersion for 15 seconds under the condition of a peripheral speed of 20 m / sec, a slurry-like composition for an electrode mixture layer was obtained.
The sedimentation stability of the composition for the electrode mixture layer (electrode slurry) was measured.
（負極極板の作製）
　次いで、可変式アプリケーターを用いて、厚さ２０μｍの集電体（銅箔）上に上記電極スラリーを塗布し、通風乾燥機内で１００℃×１５分間の乾燥を行うことにより合剤層を形成した。その後、合剤層の厚みが５０±５μｍ、充填密度が１．６０±０．１０ｇ／ｃｍ３になるよう圧延し、負極極板を得た。
　上記負極極板について、合剤層／集電体間の９０°剥離強度（すなわちバインダーの結着性）を測定した。 (Manufacturing of negative electrode plate)
Next, using a variable applicator, the electrode slurry was applied onto a current collector (copper foil) having a thickness of 20 μm, and dried in a ventilation dryer at 100 ° C. for 15 minutes to form a mixture layer. .. Then, the mixture layer was rolled so that the thickness was 50 ± 5 μm and the packing density was 1.60 ± 0.10 g / cm 3 , to obtain a negative electrode plate.
For the negative electrode plate, the 90 ° peel strength (that is, the binder binding property) between the mixture layer / the current collector was measured.
＜電極スラリーの沈降安定性＞
　上記で得られた電極スラリーの作製直後の上澄み固形分濃度、及び、当該電極スラリーを２５℃で１週間静置した後の上澄み固形分濃度を測定した。 <Settling stability of electrode slurry>
The concentration of the supernatant solid content immediately after the preparation of the electrode slurry obtained above and the concentration of the supernatant solid content after allowing the electrode slurry to stand at 25 ° C. for 1 week were measured.
　ここで、固形分濃度の測定方法について以下に記載する。
　電極スラリーの作製直後の上澄み液、及び、当該電極スラリーを２５℃で１週間静置した後の上澄み液約０．５ｇを、それぞれ予め重さを測定しておいた秤量瓶[秤量瓶の重さ＝Ｂ(ｇ)]に採取して、秤量瓶ごと正確に秤量した後[Ｗ０(ｇ)]、その試料を秤量瓶ごと無風乾燥機内に収容して１５５℃で４５分間乾燥してその時の重さを秤量瓶ごと測定し[Ｗ１(ｇ)]、以下の式により固形分濃度を求めた。
　固形分濃度（質量％）＝（Ｗ１－Ｂ）／（Ｗ０－Ｂ）×１００ Here, the method for measuring the solid content concentration will be described below.
The weight of the supernatant immediately after the preparation of the electrode slurry and about 0.5 g of the supernatant after allowing the electrode slurry to stand at 25 ° C. for 1 week are weighed in advance. After collecting at [S = B (g)] and accurately weighing the entire weighing bottle [W 0 (g)], the sample is placed in a windless dryer together with the weighing bottle and dried at 155 ° C. for 45 minutes at that time. Weighed together with the weighing bottle [W 1 (g)], the solid content concentration was determined by the following formula.
Solid content concentration (mass%) = (W 1 -B) / (W 0 -B) x 100
　以下の式により上澄み固形分変化率を求め、以下の判定基準（合格レベル：Ｂ評価以上）により沈降安定性を評価した。上澄み固形分変化率（％）は０．３％であり、Ａ評価であった。
　上澄み固形分変化率（％）＝１００－（１週間静置後の上澄み固形分濃度）／（作製直後の上澄み固形分濃度）×１００ The rate of change in the solid content of the supernatant was determined by the following formula, and the sedimentation stability was evaluated by the following criteria (pass level: B evaluation or higher). The change rate (%) of the supernatant solid content was 0.3%, which was an A rating.
Change rate of supernatant solid content (%) = 100- (concentration of supernatant solid content after standing for 1 week) / (concentration of supernatant solid content immediately after preparation) x 100
（沈降安定性の判定基準）
　Ａ：上澄み固形分濃度の変化率が１０％未満
　Ｂ：上澄み固形分濃度の変化率が１０％以上２０％未満
　Ｃ：上澄み固形分濃度の変化率が２０％以上
　なお、電極スラリー中の活物質が沈降すると、上澄み固形分の活物質濃度の低下するため、上記の上澄み固形分濃度の変化率が大きくなる。 (Criteria for sedimentation stability)
A: The rate of change in the supernatant solid content concentration is less than 10% B: The rate of change in the supernatant solid content concentration is 10% or more and less than 20% C: The rate of change in the supernatant solid content concentration is 20% or more. When the precipitate solids, the concentration of the active substance in the supernatant solids decreases, so that the rate of change in the supernatant solids concentration increases.
＜９０°剥離強度（結着性）＞
　１２０ｍｍ×３０ｍｍのアクリル板上に両面テープ（ニチバン株式会社製ナイスタックＮＷ－２０）を介して１００ｍｍ×２５ｍｍサイズの上記負極極板の合剤層面を貼り付け、剥離試験用試料を作製した。６０℃、１晩減圧条件下で乾燥させた後、引張試験機（ＯＲＩＥＮＴＥＣ社製テンシロン万能試験材料機ＲＴＥ－１２１０）を用いて、測定温度２５℃、引張速度５０ｍｍ／分における９０°剥離を行い、合剤層と銅箔間の剥離強度を測定することにより結着性を評価した。剥離強度は１５．３Ｎ／ｍと高く、良好であった。 <90 ° peel strength (bonding property)>
A sample for a peeling test was prepared by pasting the mixture layer surface of the negative electrode electrode plate having a size of 100 mm × 25 mm on a 120 mm × 30 mm acrylic plate via a double-sided tape (Nichiban Co., Ltd. Nystack NW-20). After drying under reduced pressure conditions at 60 ° C. overnight, 90 ° peeling was performed at a measurement temperature of 25 ° C. and a tensile speed of 50 mm / min using a tensile tester (TENSILON universal test material machine RTE-1210 manufactured by ORIENTEC). The binding property was evaluated by measuring the peel strength between the mixture layer and the copper foil. The peel strength was as high as 15.3 N / m, which was good.
実施例２～１３、及び比較例１～４
　バインダーとして使用するカルボキシル基含有架橋重合体の金属塩を表３の通り用いた以外は実施例１と同様の操作を行うことにより電極スラリーを調製した。各電極スラリーについて、９０°剥離強度を評価した。結果を表３に示す。 Examples 2 to 13 and Comparative Examples 1 to 4
An electrode slurry was prepared by performing the same operation as in Example 1 except that the metal salt of the carboxyl group-containing crosslinked polymer used as the binder was used as shown in Table 3. The 90 ° peel strength was evaluated for each electrode slurry. The results are shown in Table 3.
Figure JPOXMLDOC01-appb-T000010
Figure JPOXMLDOC01-appb-T000010
≪評価結果≫
　実施例１～１３の結果から明らかなように、本発明の二次電池電極用バインダーを含む二次電池電極合剤層用組成物(電極スラリー)は、沈降安定性及び結着性に優れるものであった。これらの中でも、架橋重合体の構造単位に着目すると、その全構造単位に対し、水酸基含有エチレン性不飽和単量体に由来する構造単位を含む場合（実施例１、７）、当該単量体に由来する構造単位を含まない場合（実施例９）よりも結着性に一層優れる結果であった。また、重合体（Ａ）の構造単位に着目すると、水酸基含有エチレン性不飽和単量体に由来する構造単位を含む場合（実施例１、７）、当該単量体に由来する構造単位を含まない場合（実施例９）よりも結着性に一層優れる結果であった。
　これらに対して、ＸＰＳに基づく架橋重合体のカルボキシル基金属塩の存在割合（Ｘ）が８５モル％超である、架橋重合体の金属塩を用いた場合、結着性が著しく劣ったり（比較例１及び３）、沈降安定性が著しく劣った（比較例２）。また、（Ｘ）が８５モル％以下であっても、架橋重合体の全構造単位に対しエチレン性不飽和カルボン酸単量体に由来する構造単位が８０質量％未満である、架橋重合体の金属塩を用いた場合、沈降安定性が著しく劣った（比較例４）。 ≪Evaluation result≫
As is clear from the results of Examples 1 to 13, the composition for the secondary battery electrode mixture layer (electrode slurry) containing the binder for the secondary battery electrode of the present invention is excellent in sedimentation stability and binding property. Met. Among these, focusing on the structural units of the crosslinked polymer, when all the structural units include structural units derived from the hydroxyl group-containing ethylenically unsaturated monomer (Examples 1 and 7), the monomer is concerned. The result was that the binding property was further excellent as compared with the case where the structural unit derived from (Example 9) was not contained. Focusing on the structural unit of the polymer (A), when the structural unit derived from the hydroxyl group-containing ethylenically unsaturated monomer is contained (Examples 1 and 7), the structural unit derived from the monomer is included. The result was that the binding property was further excellent as compared with the case without (Example 9).
On the other hand, when the metal salt of the crosslinked polymer in which the abundance ratio (X) of the carboxyl group metal salt of the crosslinked polymer based on XPS is more than 85 mol% is used, the binding property is significantly inferior (comparison). Examples 1 and 3), the sedimentation stability was significantly inferior (Comparative Example 2). Further, even if (X) is 85 mol% or less, the structural unit derived from the ethylenically unsaturated carboxylic acid monomer is less than 80% by mass with respect to the total structural unit of the crosslinked polymer. When a metal salt was used, the sedimentation stability was significantly inferior (Comparative Example 4).
　本発明の二次電池電極用バインダーを含む二次電池電極合剤層用組成物（電極スラリー）は、沈降安定性に優れるとともに、電極合剤層において電極材料との優れた結着性と集電体との優れた接着性を示すことから、良好な耐久性（サイクル特性）を示すと予想される。このため、上記バインダーを使用して得られた電極を備えた二次電池は、良好な一体性を確保でき、充放電を繰り返しても良好な耐久性（サイクル特性）を示すと予想され、車載用二次電池等の高容量化への寄与が期待される。
　本発明の二次電池電極用バインダーは、特に非水電解質二次電池電極に好適に用いることができ、中でも、エネルギー密度が高い非水電解質リチウムイオン二次電池に有用である。 The composition for the secondary battery electrode mixture layer (electrode slurry) containing the binder for the secondary battery electrode of the present invention is excellent in sedimentation stability, and also has excellent adhesion and collection with the electrode material in the electrode mixture layer. Since it shows excellent adhesion to the electric body, it is expected to show good durability (cycle characteristics). Therefore, the secondary battery provided with the electrodes obtained by using the above binder is expected to ensure good integrity and to show good durability (cycle characteristics) even after repeated charging and discharging, and is in-vehicle. It is expected to contribute to increasing the capacity of secondary batteries for use.
The binder for a secondary battery electrode of the present invention can be particularly preferably used for a non-aqueous electrolyte secondary battery electrode, and is particularly useful for a non-aqueous electrolyte lithium ion secondary battery having a high energy density.

Claims (14)

  1. 　カルボキシル基含有架橋重合体の金属塩を含む二次電池電極用バインダーであって、
    　前記架橋重合体が、その全構造単位に対し、エチレン性不飽和カルボン酸単量体に由来する構造単位を８０質量％以上９９．９質量％以下含み、
    　前記金属塩（中和度Ｎモル％）[以下、架橋重合体塩Ｒ]、及び、架橋重合体塩Ｒにおけるエチレン性不飽和カルボン酸単量体に由来する構造単位を１００質量％含む重合体の金属塩（中和度Ｎモル％）[以下、重合体塩Ｓ]のＸ線光電子分光分析（ＸＰＳ）により下記式（１）により算出される、ＸＰＳに基づく前記架橋重合体のカルボキシル基金属塩の存在割合（Ｘ）が８５モル％以下である、
    　二次電池電極用バインダー。
    （但し、Ｎは２０以上１００以下の値であり、架橋重合体塩Ｒ及び重合体塩Ｓについて同一。また、金属塩の種類は、架橋重合体塩Ｒ及び重合体塩Ｓについて同一。）
    Figure JPOXMLDOC01-appb-M000001
    Figure JPOXMLDOC01-appb-M000002
    Figure JPOXMLDOC01-appb-M000003
         A binder for a secondary battery electrode containing a metal salt of a crosslinked polymer containing a carboxyl group.
    The crosslinked polymer contains 80% by mass or more and 99.9% by mass or less of structural units derived from the ethylenically unsaturated carboxylic acid monomer with respect to all the structural units thereof.
    A polymer containing 100% by mass of structural units derived from the metal salt (neutralization degree N mol%) [hereinafter, crosslinked polymer salt R] and the ethylenically unsaturated carboxylic acid monomer in the crosslinked polymer salt R. The carboxyl-based metal of the crosslinked polymer based on XPS, which is calculated by the following formula (1) by X-ray photoelectron spectroscopic analysis (XPS) of the metal salt (neutralization degree N mol%) [hereinafter, polymer salt S]. The salt abundance ratio (X) is 85 mol% or less.
    Binder for secondary battery electrodes.
    (However, N is a value of 20 or more and 100 or less, and is the same for the crosslinked polymer salt R and the polymer salt S. The type of the metal salt is the same for the crosslinked polymer salt R and the polymer salt S.)
    Figure JPOXMLDOC01-appb-M000001
    Figure JPOXMLDOC01-appb-M000002
    Figure JPOXMLDOC01-appb-M000003
  2. 　前記架橋重合体は、交換連鎖移動機構によるリビングラジカル重合活性単位を有する重
    合体である、請求項１に記載の二次電池電極用バインダー。     The binder for a secondary battery electrode according to claim 1, wherein the crosslinked polymer is a polymer having a living radical polymerization active unit by an exchange chain transfer mechanism.
  3. 　前記交換連鎖移動機構は、可逆的付加－開裂連鎖移動機構である、請求項２に記載の二次電池電極用バインダー。 The binder for a secondary battery electrode according to claim 2, wherein the exchange chain transfer mechanism is a reversible addition-cleavage chain transfer mechanism.
  4. 　前記リビングラジカル重合活性単位は、トリチオカーボネート基である、請求項２又は３に記載の二次電池電極用バインダー。 The binder for a secondary battery electrode according to claim 2 or 3, wherein the living radical polymerization active unit is a trithiocarbonate group.
  5. 　前記架橋重合体は、その全構造単位に対し、水酸基含有エチレン性不飽和単量体に由来する構造単位を０．５質量％以上２０質量％以下含む、請求項１～４のいずれか１項に記載の二次電池電極用バインダー。 The crosslinked polymer is any one of claims 1 to 4, wherein the crosslinked polymer contains 0.5% by mass or more and 20% by mass or less of the structural units derived from the hydroxyl group-containing ethylenically unsaturated monomer with respect to all the structural units. The binder for the secondary battery electrode described in 1.
  6. 　前記架橋重合体は、架橋性単量体により架橋されたものであり、当該架橋性単量体の使用量が非架橋性単量体の総量に対して０．００１モル％以上２．５モル％以下である、請求項１～５のいずれか１項に記載の二次電池電極用バインダー。 The crosslinked polymer is crosslinked with a crosslinkable monomer, and the amount of the crosslinkable monomer used is 0.001 mol% or more and 2.5 mol with respect to the total amount of the non-crosslinkable monomer. % Or less, according to any one of claims 1 to 5, the binder for a secondary battery electrode.
  7. 　前記架橋重合体の金属塩は、中和度８０～１００モル％に中和された後、水媒体中で測定した粒子径が、体積基準メジアン径で０．１μｍ以上１０．０μｍ以下である、請求項１～６のいずれか１項に記載の二次電池電極用バインダー。 The metal salt of the crosslinked polymer is neutralized to a degree of neutralization of 80 to 100 mol%, and then the particle size measured in an aqueous medium is 0.1 μm or more and 10.0 μm or less in terms of volume-based median diameter. The binder for a secondary battery electrode according to any one of claims 1 to 6.
  8. 　カルボキシル基含有架橋重合体の金属塩を含む二次電池電極用バインダーの製造方法であって、
    　沈殿重合若しくは分散重合により、エチレン性不飽和カルボン酸単量体を含む単量体成分を重合する工程と、
    　前記工程の途中に、前記エチレン性不飽和カルボン酸単量体を含む単量体成分の総量に対して、交換連鎖移動機構型制御剤を０．０００１モル％以上０．５０モル％以下添加する工程とを、備え、
    　前記交換連鎖移動機構型制御剤が、１種又は２種以上のビニル系単量体の重合鎖と交換連鎖移動機構によるリビングラジカル重合活性単位を有する重合体（Ａ）である、製造方法。     A method for producing a binder for a secondary battery electrode containing a metal salt of a crosslinked polymer containing a carboxyl group.
    A step of polymerizing a monomer component containing an ethylenically unsaturated carboxylic acid monomer by precipitation polymerization or dispersion polymerization, and
    During the step, an exchange chain transfer mechanism type control agent is added in an amount of 0.0001 mol% or more and 0.50 mol% or less with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer. Prepare for the process,
    The production method, wherein the exchange chain transfer mechanism type control agent is a polymer (A) having a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by the exchange chain transfer mechanism.
  9. 　前記重合体（Ａ）のＳＰ値が１７～２７（（ＭＰａ）1/2）である、請求項８に記載の製造方法。 The production method according to claim 8, wherein the SP value of the polymer (A) is 17 to 27 ((MPa) 1/2 ).
  10. 　前記重合体（Ａ）は、水酸基含有エチレン性不飽和単量体に由来する構造単位を含む、請求項８又は９に記載の製造方法。 The production method according to claim 8 or 9, wherein the polymer (A) contains a structural unit derived from a hydroxyl group-containing ethylenically unsaturated monomer.
  11. 　前記水酸基含有エチレン性不飽和単量体に由来する構造単位の含有量は、前記重合体（Ａ）の全構造単位に対し、５０質量％以上９０質量％以下である、請求項８～１０のいずれか１項に記載の製造方法。 The content of the structural unit derived from the hydroxyl group-containing ethylenically unsaturated monomer is 50% by mass or more and 90% by mass or less with respect to the total structural unit of the polymer (A), according to claims 8 to 10. The manufacturing method according to any one.
  12. 　請求項１～７のいずれか１項に記載の二次電池電極用バインダー、活物質及び水を含む、二次電池電極合剤層用組成物。 A composition for a secondary battery electrode mixture layer containing the binder for the secondary battery electrode, the active material, and water according to any one of claims 1 to 7.
  13. 　集電体表面に、請求項１２に記載の二次電池電極合剤層用組成物から形成される合剤層を備える、二次電池電極。 A secondary battery electrode comprising a mixture layer formed from the composition for the secondary battery electrode mixture layer according to claim 12 on the surface of a current collector.
  14. 　請求項１３に記載の二次電池電極を備える、二次電池。 A secondary battery comprising the secondary battery electrode according to claim 13.
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