JP2010050429A - Binder composition for electric double-layer capacitor electrode, the electric double-layer capacitor electrode, and the electric double-layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a binder composition for an electric double-layer capacitor electrode, wherein the adhesiveness with a collector is superior, and an electric double-layer capacitor can be provided that holds the high-discharging capacity, even under recycling or under an high-temperature environment due to heating, or the like, at charge/discharge time. <P>SOLUTION: The binder composition for an electric double-layer capacitor electrode contains 0.1-20 wt.% of epoxy group-containing ethylene unsaturated monomer and/or amide group-containing ethylene unsaturated monomer, 0.1-5 wt.% of alkoxysilyl group-containing ethylene unsaturated monomer and/or N-methylol group-containing ethylene unsaturated monomer, 0.1-10 wt.% of at least one kind of monomer selected from a group consisting of carboxyl group-containing ethylene unsaturated monomer; tertiary butyl group-containing ethylene unsaturated monomer; sulfonic acid group-containing ethylene unsaturated monomer and phosphorous acid group-containing ethylene unsaturated monomer; and cross-linked emulsion composed by emulsion polymerization of ethylene unsaturated monomers other than the monomers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a binder composition for an electric double layer capacitor electrode that is excellent in electrolytic solution resistance, binding property, and flexibility. Furthermore, the present invention relates to a binder composition for an electric double layer capacitor electrode capable of obtaining an electric double layer capacitor excellent in charge / discharge cycle characteristics and high capacity, and more specifically, an electric double layer capacitor electrode using the binder, and the The present invention relates to an electric double layer capacitor including electrodes.

  In recent years, due to advances in electronic technology, the performance of electronic devices has improved, and miniaturization and portability have progressed, and the demand for secondary batteries with high energy density as the power source has increased. Secondary batteries include, for example, nickel metal hydride secondary batteries, lithium ion secondary batteries, etc. These secondary batteries are also being developed for high-capacity and long-life products due to the miniaturization and weight reduction of equipment. Yes. Furthermore, in recent years, electric double layer capacitors have attracted attention because of their longer life than secondary batteries, charge / discharge characteristics due to rapid large currents, and the advantage of not using environmentally hazardous substances such as heavy metals. Due to the characteristics of the electric double layer capacitor, there are increasing demands in the field of hybrid vehicles, fuel cell vehicles, and natural energy.

  The electrode constituting the electric double layer capacitor is composed of an electrode active material such as activated carbon, a conductivity imparting agent such as conductive carbon black or acetylene black, and a binder. It is made by applying and binding to the body (Patent Document 1). Conventionally, a solvent-based binder has been used as a binder used in this electric double layer capacitor. However, in order to eliminate environmental pollution in the process, Patent Document 1 has studied using an aqueous dispersion as a binder. ing. Examples of the aqueous dispersion include natural latex, styrene-butadiene rubber latex, nitrile butadiene rubber latex, butyl rubber latex, polytetrafluoroethylene dispersion, and the like. However, these binders have a problem that the binding property with the current collector is not sufficient, and the flexibility after high-temperature drying is extremely deteriorated.

  In order to solve this problem, Patent Documents 2 and 3 use an acrylic copolymer having a specific composition. That is, in Patent Documents 2 and 3, an acrylic binder having a low glass transition temperature can be obtained by synthesizing an aqueous dispersion composed of (meth) acrylic acid esters having high carbon number- (meth) acrylonitrile. To ensure the flexibility. However, simply setting the glass transition temperature of the acrylic binder to a specific range is not sufficient for binding to the current collector, and if the amount of binder used is increased to ensure binding, the electrode There was a problem that the internal resistance of the film could not be improved.

Thus, as the performance of the binder for making the electric characteristics of the electric double layer capacitor more advanced, not only the electrolytic solution resistance and heat resistance but also the current collector, electrode active material, conductive material, etc. It is necessary that the material has a high binding property with each material and has a good binding force even with a small amount.
JP 2004-128145 A WO2004 / 084245 WO2005 / 013298

  The present invention provides an electric double layer capable of providing an electric double layer capacitor that has excellent adhesion to a current collector and retains a high discharge capacity even under repeated or high temperature environments due to heat generation during charging and discharging. It aims at providing the binder composition for capacitor electrodes. Furthermore, an electric double layer capacitor electrode that has little influence on the electrode active material, ensures current collection, improves its utilization efficiency, and achieves charge / discharge cycle characteristics of the capacitor and high capacity, and An object is to provide an electric double layer capacitor using an electrode.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the first invention is (A) epoxy group-containing ethylenically unsaturated monomer (a) and / or amide group-containing ethylenically unsaturated monomer (b) 0.1-20 wt%,
(B) alkoxysilyl group-containing ethylenically unsaturated monomer (c) and / or N-methylol group-containing ethylenically unsaturated monomer (d) 0.1 to 5% by weight,
(C) a carboxyl group-containing ethylenically unsaturated monomer (e), a tertiary butyl group-containing ethylenically unsaturated monomer (f), a sulfonic acid group-containing ethylenically unsaturated monomer (g), and phosphorus 0.1 to 10% by weight of at least one monomer selected from the group consisting of acid group-containing ethylenically unsaturated monomers (h),
The present invention also relates to a binder composition for an electric double layer capacitor electrode comprising a cross-linked emulsion obtained by emulsion polymerization of an ethylenically unsaturated monomer (i) other than the monomers (a) to (h).

  The second invention is a compound having two or more functional groups capable of reacting with at least one functional group selected from the group consisting of an epoxy group, an amide group, a carboxyl group, a sulfonic acid group, and a phosphoric acid group (j And a binder composition for an electric double layer capacitor electrode according to the first invention.

Further, in the third invention, the crosslinked emulsion contains a carbonyl group-containing ethylenically unsaturated monomer 0 as an ethylenically unsaturated monomer (i) in a total of 100% by weight of the ethylenically unsaturated monomer. Emulsion polymerization of a monomer containing 5 to 10% by weight, and
The present invention relates to the binder composition for an electric double layer capacitor electrode according to the first or second invention, comprising the cross-linked emulsion and a compound having a functional group capable of reacting with a carbonyl group.

  The fourth invention is characterized in that the ethylenically unsaturated monomer (i) contains at least one monomer selected from the group consisting of styrene, 2-ethylhexyl acrylate, and cyclohexyl methacrylate. The present invention relates to a binder composition for an electric double layer capacitor electrode according to any one of the inventions 1-3.

  Moreover, 5th invention is related with the electrical double layer capacitor electrode dispersion containing the binder composition for electrical double layer capacitor electrodes of any one of 1st-4th invention, and an electrode active material.

  The sixth invention also relates to an electric double layer capacitor electrode in which an electrode active material layer formed using the electric double layer capacitor electrode dispersion of the fifth invention is bound to a current collector.

  The seventh invention also relates to an electric double layer capacitor comprising the electric double layer capacitor electrode of the sixth invention, an electrolytic solution, and a separator.

  The binder for an electric double layer capacitor electrode of the present invention is excellent in electrolytic solution resistance, adhesion to a current collector, and flexibility. The electric double layer capacitor using the binder composition for an electric double layer capacitor electrode of the present invention can be reduced in discharge capacity reduction in a charge / discharge cycle even under repeated or high temperature environments due to heat generation during charge / discharge. A long-life electric double layer capacitor can be provided.

  The binder for an electric double layer capacitor electrode of the present invention comprises a crosslinked emulsion obtained by copolymerizing a monomer containing an ethylenically unsaturated monomer having a specific functional group. The binder composition containing the crosslinkable emulsion ensures a resistance to electrolyte by adopting a cross-linked structure with specific functional groups, and the binder composition containing the crosslinkable emulsion contributes to adhesion to the current collector. By including a specific component, a binder composition having excellent current collector adhesion can be obtained. Furthermore, the binder for electric double layer capacitor electrodes excellent in flexibility can be obtained by adjusting the composition ratio of the binder composition. Thus, an electrode capable of achieving charge / discharge cycle characteristics and high capacity of the battery can be obtained.

  The cross-linking structure of the cross-linking emulsion in the present invention may be cross-linking inside the particles or cross-linking between the particles, and may be a cross-link by adding a cross-linking agent separately. .

The crosslinked emulsion used for the binder for the electric double layer capacitor electrode of the present invention is 100% by weight of the ethylenically unsaturated monomer used,
(A) Epoxy group-containing ethylenically unsaturated monomer (a) and / or amide group-containing ethylenically unsaturated monomer (b) 0.1 to 20% by weight,
(B) alkoxysilyl group-containing ethylenically unsaturated monomer (c) and / or N-methylol group-containing ethylenically unsaturated monomer (d) 0.1 to 5% by weight,
(C) a carboxyl group-containing ethylenically unsaturated monomer (e), a tertiary butyl group-containing ethylenically unsaturated monomer (f), a sulfonic acid group-containing ethylenically unsaturated monomer (g), and phosphorus 0.1 to 10% by weight of at least one monomer selected from the group consisting of acid group-containing ethylenically unsaturated monomers (h),
And a cross-linked emulsion obtained by emulsion polymerization of an ethylenically unsaturated monomer (i) other than the monomers (a) to (h).

  By using the monomer contained in (A), an epoxy group and / or an amide group can be left in the particles or the surface of the cross-linked emulsion, and thereby physical properties such as adhesion of the current collector. Can be improved. In the epoxy group-containing ethylenically unsaturated monomer (a) and amide group-containing ethylenically unsaturated monomer (b), the functional groups are likely to remain inside or on the surface of the emulsion even after particle synthesis. Great adhesion to the body. Some of them may be used for the crosslinking reaction, and by adjusting the degree of crosslinking of these functional groups, it is possible to balance the resistance to electrolyte and adhesion.

  Examples of the epoxy group-containing ethylenically unsaturated monomer (a) include glycidyl (meth) acrylate and 3,4-epoxycyclohexyl (meth) acrylate.

Examples of the amide group-containing ethylenically unsaturated monomer (b) include first amide group-containing ethylenically unsaturated monomers such as (meth) acrylamide;
Alkylol (meth) acrylamides such as N-methylolacrylamide, N, N-di (methylol) acrylamide, N-methylol-N-methoxymethyl (meth) acrylamide;
N-methoxymethyl- (meth) acrylamide, N-ethoxymethyl- (meth) acrylamide, N-propoxymethyl- (meth) acrylamide, N-butoxymethyl- (meth) acrylamide, N-pentoxymethyl- (meth) acrylamide Monoalkoxy (meth) acrylamides such as;
N, N-di (methoxymethyl) acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N, N-di (ethoxymethyl) acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N, N- Di (propoxymethyl) acrylamide, N-butoxymethyl-N- (propoxymethyl) methacrylamide, N, N-di (butoxymethyl) acrylamide, N-butoxymethyl-N- (methoxymethyl) methacrylamide, N, N- Dialkoxy (meth) acrylamides such as di (pentoxymethyl) acrylamide, N-methoxymethyl-N- (pentoxymethyl) methacrylamide;
Dialkylamino (meth) acrylamides such as N, N-dimethylaminopropylacrylamide, N, N-diethylaminopropylacrylamide;
Dialkyl (meth) acrylamides such as N, N-dimethylacrylamide and N, N-diethylacrylamide;
Etc.

  Among the amide group-containing ethylenically unsaturated monomers described above, alkylols (meth) such as N-methylolacrylamide, N, N-di (methylol) acrylamide, N-methylol-N-methoxymethyl (meth) acrylamide, etc. Monomers having an N-methylol group such as acrylamides can also be used as the monomer (d) described later. That is, these monomers are preferably used because they have both the function of the monomer contained in (A) and the function of the monomer contained in (B).

  A part of the functional group of the monomer contained in (A) may react during particle polymerization and be used for intra-particle crosslinking. When the monomer (a) and / or the monomer (b) is less than 0.1% by weight, the amount of functional groups remaining in the interior of the particle or on the surface after polymerization is reduced, and the current collector Cannot contribute enough to improve adhesion. On the other hand, if it exceeds 20% by weight, there will be a problem in polymerization stability at the time of emulsion polymerization, or even if it can be polymerized, there will be a problem in storage stability.

  The functional group (alkoxysilyl group, N-methylol group) possessed by the monomer contained in (B) is a self-crosslinking reactive functional group, and has the effect of mainly forming internal crosslinks during particle synthesis. Electrolytic solution resistance can be improved by sufficiently carrying out particle crosslinking.

  Examples of the alkoxysilyl group-containing ethylenically unsaturated monomer (c) include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltributoxysilane, and γ-methacryloxy. Propylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxymethyltrimethoxysilane , Γ-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane and the like.

  Examples of the N-methylol group-containing ethylenically unsaturated monomer (d) include N-methylol (meth) acrylamide, N, N-di (methylol) acrylamide, and N-methylol-N-methoxymethyl (meth) acrylamide. And alkylol (meth) acrylamides.

  The alkoxysilyl group and N-methylol group in the monomer (c) and the monomer (d) can be mainly self-condensed during polymerization to introduce a crosslinked structure into the emulsion, but some of them are polymerized. It may remain inside or on the surface of the particles later. The remaining alkoxysilyl group or N-methylol group contributes to the inter-particle crosslinking of the binder composition or has the effect of contributing to the improvement in adhesion to the current collector.

  When the monomer (c) and / or the monomer (d) is less than 0.1% by weight, the emulsion is not sufficiently crosslinked and the electrolytic solution resistance is deteriorated. On the other hand, if it exceeds 5% by weight, there will be a problem in the polymerization stability at the time of emulsion polymerization, or even if it can be polymerized, there will be a problem in storage stability.

  The functional group of the monomer contained in (C) [carboxyl group, tertiary butyl group (tertiary butanol is eliminated by heat to form a carboxyl group), sulfonic acid group, phosphoric acid group] is a crosslinked emulsion. Even after the polymerization, it remains in the particles and on the surface, and has the effect of improving the physical properties such as the adhesion of the current collector, and at the same time, the effect of ensuring the stability during the particle synthesis.

  Examples of the carboxyl group-containing ethylenically unsaturated monomer (e) include maleic acid, fumaric acid, itaconic acid, citraconic acid, or alkyl or alkenyl monoesters thereof, β- (meth) acryloxyethyl phthalate. Monoester, isophthalic acid β- (meth) acryloxyethyl monoester, terephthalic acid β- (meth) acryloxyethyl monoester, succinic acid β- (meth) acryloxyethyl monoester, acrylic acid, methacrylic acid, crotonic acid And cinnamic acid.

  Examples of the tertiary butyl group-containing ethylenically unsaturated monomer (f) include tertiary butyl (meth) acrylate.

Examples of the sulfonic acid group-containing ethylenically unsaturated monomer (g) include vinyl sulfonic acid and styrene sulfonic acid.
Examples of the phosphoric acid group-containing ethylenically unsaturated monomer (h) include (2-hydroxyethyl) methacrylate acid phosphate.

  The carboxyl group, tertiary butyl group, sulfonic acid group, and phosphoric acid group in the monomer (e), monomer (f), monomer (g) and monomer (h) are a part of them. May react during polymerization and be used for intraparticle cross-linking. When the monomer (e), the monomer (f), the monomer (g) and the monomer (h) are less than 0.1% by weight, the stability of the emulsion is deteriorated. On the other hand, when it exceeds 10% by weight, the hydrophilicity of the binder composition becomes too strong and the resistance to electrolytic solution is deteriorated. Further, these functional groups may react with each other during drying to be used for crosslinking within or between particles.

  For example, the epoxy group in the epoxy group-containing ethylenically unsaturated monomer (a) reacts with the carboxyl group in the carboxyl group-containing ethylenically unsaturated monomer (e) during polymerization and drying to crosslink into the emulsion. Structure can be introduced. Similarly, the tertiary butyl group in the tertiary butyl group-containing ethylenically unsaturated monomer (f) also generates tertiary butyl alcohol and a carboxyl group when heat of a certain temperature or more is applied. It can react with epoxy groups as well.

  The crosslinked structure can also be formed by a reaction between the crosslinked emulsion constituting the binder composition and the crosslinking agent. That is, the binder composition of the present invention is a compound (j) having two or more functional groups capable of reacting with at least one functional group selected from an epoxy group, an amide group, a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Is preferably included as a crosslinking agent.

  Examples of the functional group that can react with the epoxy group include a carboxyl group, an acid anhydride group, a vinyl ether group, and an amino group. Examples of the functional group capable of reacting with an amide group include a carbonyl group. Examples of the functional group capable of reacting with a carboxyl group include an epoxy group, an aziridinyl group, a carbodiimide group, and an oxazoline group. Examples of the functional group capable of reacting with the sulfonic acid group include a hydroxyl group, an epoxy group, and an amino group. Examples of the functional group capable of reacting with a phosphate group include a hydroxyl group, an epoxy group, and an amino group.

The compound (j) that can be used in the present invention is exemplified below. Examples of the compound having two or more carboxyl groups include o-phthalic acid, isophthalic acid, terephthalic acid, 1,4-dimethylterephthalic acid, 1,3-dimethylisophthalic acid, 5-sulfo-1,3-dimethylisophthalate. Aromatic dicarboxylic acids such as acid, 4,4-biphenyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, norbornene dicarboxylic acid, diphenylmethane-4,4′-dicarboxylic acid, and phenylindanedicarboxylic acid ;
Aromatic dicarboxylic anhydrides such as phthalic anhydride, 1,8-naphthalenedicarboxylic anhydride, 2,3-naphthalenedicarboxylic anhydride;
Alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid;
Alicyclic dicarboxylic anhydrides such as hexahydrophthalic anhydride, 3-methyl-hexahydrophthalic anhydride, 4-methyl-hexahydrophthalic anhydride, 1,2-cyclohexanedicarboxylic anhydride;
Aliphatic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, suberic acid, maleic acid, chloromaleic acid, fumaric acid, dodecanedioic acid, pimelic acid, citraconic acid, glutaric acid, itaconic acid And dicarboxylic acids.

  Examples of the compound having two or more acid anhydride groups include pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, and diphenylsulfonetetracarboxylic dianhydride. , Diphenyl sulfide tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, perylene tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, "Ricacid TMTA-C", "Ricacid MTA" manufactured by Shin Nippon Rika Co., Ltd. -10 "," Licacid MTA-15 "," Licacid TMEG series "," Licacid TDA "and the like.

  Examples of the compound having two or more vinyl ether groups include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, pentaerythritol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, Tripropylene glycol divinyl ether, neopentyl glycol divinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, glycerin divinyl ether, trimethylolpropane divinyl ether, 1,4-dihydroxylcyclohexane divinyl ether, 1,4-dihydroxymethylcyclohexanedivinyl a , Hydroquinone divinyl ether, ethylene oxide modified hydroquinone divinyl ether, ethylene oxide modified resorcin divinyl ether, ethylene oxide modified bisphenol A divinyl ether, ethylene oxide modified bisphenol S divinyl ether, glycerin trivinyl ether, sorbitol tetravinyl ether, trimethylolpropane trivinyl ether, Examples include pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol hexavinyl ether, dipentaerythritol polyvinyl ether, ditrimethylolpropane tetravinyl ether, and ditrimethylolpropane polyvinyl ether.

Examples of the compound having two or more amino groups include aliphatic diamines such as ethylenediamine and hexamethylenediamine;
Alicyclic diamines such as 4,4′-diamino-3,3′-dimethyldicyclohexylmethane, 4,4′-diamino-3,3′-dimethyldicyclohexyl, diaminocyclohexane, isophoronediamine;
Araliphatic diamines such as xylylenediamine, α, α, α ′, α ′,-tetramethylxylylenediamine;
Etc.

  Examples of the compound having two or more epoxy groups include bisphenol A-epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-di) Glycidylaminomethyl) cyclohexane and the like.

  Examples of the compound having two or more aziridinyl groups include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxite), N, N′-toluene-2,4-bis (1-aziridine). Carboxite), bisisophthaloyl-1- (2-methylaziridine), tri-1-aziridinylphosphine oxide, N, N′-hexamethylene-1,6-bis (1-aziridinecarboxite), tri Methylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, tris-2,4,6- (1-aziridinyl) -1,3,5-triazine , Trimethylolpropane tris [3- (1-aziridinyl) propionate], trimethylolpropane tris [3- (1-azi Lysinyl) butyrate], trimethylolpropane tris [3- (1- (2-methyl) aziridinyl) propionate], trimethylolpropane tris [3- (1-aziridinyl) -2-methylpropionate], 2,2 ′ -Bishydroxymethylbutanol tris [3- (1-aziridinyl) propionate], pentaerythritol tetra [3- (1-aziridinyl) propionate], diphenylmethane-4,4-bis-N, N′-ethyleneurea, 1,6 -Hexamethylenebis-N, N'-ethyleneurea, 2,4,6- (triethyleneimino) -Syn-triazine, bis [1- (2-ethyl) aziridinyl] benzene-1,3-carboxylic acid amide, etc. Is mentioned.

  Examples of the compound having two or more carbodiimide groups include Nisshinbo Co., Ltd. Carbodilite series. Among them, Carbodilite V-02, 04, 06, E-01, 02, 03A is preferably an aqueous type or an aqueous emulsion type, and therefore has good compatibility with the crosslinked emulsion of the present invention. Moreover, even if it is an oily type like Carbodilite V-05, it can be used for the binder composition of this invention, for example by using surfactant and making it an aqueous dispersion.

  Examples of the compound having two or more oxazoline groups include 2'-methylenebis (2-oxazoline), 2,2'-ethylenebis (2-oxazoline), 2,2'-ethylenebis (4-methyl-2- Oxazoline), 2,2'-propylenebis (2-oxazoline), 2,2'-tetramethylenebis (2-oxazoline), 2,2'-hexamethylenebis (2-oxazoline), 2,2'-octa Methylenebis (2-oxazoline), 2,2′-p-phenylenebis (2-oxazoline), 2,2′-p-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′- p-phenylenebis (4-methyl-2-oxazoline), 2,2′-p-phenylenebis (4-phenyl-2-oxazoline), 2,2′-m-phenylenebis ( -Oxazoline), 2,2'-m-phenylenebis (4-methyl-2-oxazoline), 2,2'-m-phenylenebis (4,4'-dimethyl-2-oxazoline), 2,2'- m-phenylenebis (4-phenylenebis-2-oxazoline), 2,2′-o-phenylenebis (2-oxazoline), 2,2′-o-phenylenebis (4-methyl-2-oxazoline), 2 , 2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline), 2,2′-bis (4-ethyl-2-oxazoline), 2,2′-bis ( 4-phenyl-2-oxazoline) and the like.

Examples of the compound having two or more hydroxyl groups include linear aliphatics such as ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. Diols;
Branched chain aliphatic diols such as propylene glycol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol;
Cyclic diols such as 1,4-bis (hydroxymethyl) cyclohexane;
Etc.

  Examples of the compound having a carbonyl group include aldehyde compounds such as formalin and paraformaldehyde. The amide group contained in the crosslinked emulsion reacts to form a methylol group when formalin is added. The obtained methylol group is used for forming a crosslinked structure.

  The compound (j) used as the crosslinking agent is preferably added in an amount of 0.1 to 50 parts by weight, more preferably 5 to 40 parts by weight, based on 100 parts by weight of the solid content of the crosslinked emulsion.

  Furthermore, two or more kinds of compounds (j) in the binder composition can be used in combination. For example, an epoxy group derived from the monomer (a) reacts with a carboxyl group to generate a hydroxyl group. It is also possible to form a stronger crosslinked structure by reacting this hydroxyl group with a compound having two or more isocyanate groups.

  Examples of the compound having two or more isocyanate groups include aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, and alicyclic polyisocyanate.

  Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6 -Tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate, xylylene diisocyanate and the like can be mentioned.

  Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as HMDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, and 1,3-butylene diisocyanate. , Dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate and the like.

  Examples of the araliphatic polyisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene. 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, and the like.

  Examples of the alicyclic polyisocyanate include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1, Examples include 4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), 1,4-bis (isocyanate methyl) cyclohexane, and the like. .

  Moreover, the trimethylol propane adduct body of the said polyisocyanate, the trimer which has an isocyanurate ring, etc. can be used. Furthermore, polyphenylmethane polyisocyanate (also known as PAPI), naphthylene diisocyanate, and polyisocyanate-modified products thereof can be used. As the polyisocyanate-modified product, a carbodiimide group, a uretdione group, a uretoimine group, a burette group reacted with water, a group of isocyanurate groups, or a modified product having two or more of these groups is used. it can. A reaction product of polyol and diisocyanate can also be used as the polyfunctional isocyanate compound.

  The crosslinking reaction between at least one functional group selected from the epoxy group, amide group, carboxyl group, sulfonic acid group, and phosphoric acid group in these cross-linked emulsions and the functional group in compound (j) strengthens the cross-linking. For this purpose, heat treatment may be performed as necessary during electrode production. For example, the reaction between the carboxyl group in the crosslinked emulsion and the epoxy group in the compound having two or more epoxy groups is preferably heat-treated at 160 ° C to 250 ° C.

  Furthermore, in addition to these compounds (j), the binder composition is used for the purpose of further strengthening the crosslinked structure of the binder composition, the purpose of improving the adhesion with the current collector, and the purpose of adjusting the mechanical strength of the binder. A third component can be added to the product. As an additive for improving the adhesion with the current collector, since the current collector is mainly a metal compound, components that generally improve the metal adhesion, such as phosphoric acid, imidazole silane compounds, etc. Can be added. Further, as an additive for adjusting the mechanical strength of the binder, it is possible to blend a resin such as a polyamide resin, a polyester resin, or a polyurethane resin. These 3rd components will not be restricted to this as long as the said objective is satisfy | filled.

  In addition to the composition of the ethylenically unsaturated monomers (a) to (h) described above, the crosslinked emulsion used for the binder for the electric double layer capacitor electrode of the present invention is other than the monomers (a) to (h). The ethylenically unsaturated monomer (i) can be obtained by emulsion polymerization, but the carbonyl group-containing ethylenically unsaturated monomer (i) can be used as the monomer (i) in 100% by weight of the ethylenically unsaturated monomer. It is preferable to carry out emulsion polymerization of a monomer containing 0.5 to 10% by weight of a saturated monomer. In this case, a compound having a functional group capable of reacting with a carbonyl group is added to the obtained emulsion as a crosslinking agent, and the electrolytic solution resistance is improved by introducing a crosslinked structure when used as a binder composition and drying. Can be made.

  If the carbonyl group-containing ethylenically unsaturated monomer is less than 0.5% by weight, the emulsion may not be sufficiently crosslinked and the electrolytic solution resistance may deteriorate. On the other hand, if it exceeds 10% by weight, the stability after adding the cross-linking agent may deteriorate.

  Examples of the carbonyl group-containing ethylenically unsaturated monomer include diacetone acrylamide, diacetone methacrylamide, acrolein, N-vinylformamide, vinyl methyl ketone, vinyl ethyl ketone, acetoacetoxyethyl acrylate, acetoacetoxypropyl acrylate, and acetoacetate. Examples include acetoxybutyl acrylate, acetoacetoxyethyl methacrylate, acetoacetoxypropyl methacrylate, and acetoacetoxybutyl methacrylate.

  Examples of the compound having a functional group capable of reacting with a carbonyl group used as a crosslinking agent include hydrazine derivatives having at least two hydrazide groups in one molecule. For example, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, In addition to aliphatic dihydrazides such as glutaric dihydrazide, adipic dihydrazide and sebacic acid dihydrazide, carbonic polyhydrazide, aliphatic, alicyclic, aromatic bissemicarbazide, aromatic dicarboxylic dihydrazide, polyhydrazide of polyacrylic acid, aromatic Examples include hydrocarbon dihydrazides, hydrazine-pyridine derivatives, and dihydrazides of unsaturated dicarboxylic acids such as maleic acid dihydrazide. These compounds are preferably added in an amount of 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the solid content of the crosslinked emulsion.

The monomer (i) constituting the cross-linked emulsion is selected from ethylenically unsaturated monomers other than the monomers (a) to (h), such as methyl (meth) acrylate and ethyl (meth) acrylate. , Propyl (meth) acrylate, n-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) ) Acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate Rate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, icosyl (meth) acrylate, heicosyl (meth) acrylate, docosyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, (meth) acrylonitrile, etc. (Meth) acrylate;
2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, allyl Hydroxyl-containing ethylenically unsaturated compounds such as alcohol;
Dialkylamino group-containing ethylenically unsaturated compounds such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate methylethylaminoethyl (meth) acrylate, dimethylaminostyrene, diethylaminostyrene;
Perfluoromethylmethyl (meth) acrylate, perfluoroethylmethyl (meth) acrylate, 2-perfluorobutylethyl (meth) acrylate, 2-perfluorohexylethyl (meth) acrylate, 2-perfluorooctylethyl (meth) acrylate , 2-perfluoroisononylethyl (meth) acrylate, 2-perfluorononylethyl (meth) acrylate, 2-perfluorodecylethyl (meth) acrylate, perfluoropropylpropyl (meth) acrylate, perfluorooctylpropyl (meta ) Perfluoroalkyl having a C 1-20 perfluoroalkyl group such as acrylate, perfluorooctyl amyl (meth) acrylate, perfluorooctyl undecyl (meth) acrylate, etc. (Meth) acrylate;
Perfluoroalkyl group-containing ethylenically unsaturated compounds such as perfluoroalkylethylene, perfluoroalkyl such as perfluorobutylethylene, perfluorohexylethylene, perfluorooctylethylene, and perfluorodecylethylene;
Polyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, propoxypolyethylene glycol (meth) acrylate, n-butoxypolyethylene glycol (meth) acrylate, n-pentoxypolyethylene glycol (meth) Acrylate, phenoxypolyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, ethoxypolypropylene glycol (meth) acrylate, propoxypolypropylene glycol (meth) acrylate, n-butoxypolypropylene glycol (meth) acrylate N-Pentoxypolypropylene Recall (meth) acrylate, phenoxypolypropylene glycol (meth) acrylate, polytetramethylene glycol (meth) acrylate, methoxypolytetramethylene glycol (meth) acrylate, phenoxytetraethylene glycol (meth) acrylate, hexaethylene glycol (meth) acrylate, Ethylenically unsaturated compounds having a polyether chain such as methoxyhexaethylene glycol (meth) acrylate;
Ethylenically unsaturated compounds having a polyester chain such as lactone-modified (meth) acrylate;
(Meth) acrylic acid dimethylaminoethyl methyl chloride salt, trimethyl-3- (1- (meth) acrylamide-1,1-dimethylpropyl) ammonium chloride, trimethyl-3- (1- (meth) acrylamidopropyl) ammonium chloride, And quaternary ammonium base-containing ethylenically unsaturated compounds such as trimethyl-3- (1- (meth) acrylamide-1,1-dimethylethyl) ammonium chloride;
Fatty acid vinyl compounds such as vinyl acetate, vinyl butyrate, vinyl propionate, vinyl hexanoate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate;
Vinyl ether compounds such as butyl vinyl ether and ethyl vinyl ether;
Α-olefin compounds such as 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene;
Allyl compounds such as allyl acetate, allylbenzene, allyl cyanide;
Vinyl compounds such as vinyl cyanide, vinylcyclohexane, vinylmethylketone, styrene, α-methylstyrene, 2-methylstyrene, chlorostyrene;
Examples include ethynyl compounds such as acetylene, ethynylbenzene, and ethynyltoluene.

  Monomer (i) is used in combination of two or more of the monomers listed above in order to adjust the polymerization stability and glass transition temperature of the particles, as well as film forming properties and coating film properties. be able to. For example, styrene, which is a hydrophobic monomer, may be copolymerized to ensure polymerization stability. In addition, it is preferable to use (meth) acrylonitrile or the like for adjusting the physical properties of the coating film because rubber elasticity is exhibited.

  Further, among these monomers, it is possible to use at least one monomer selected from styrene, 2-ethylhexyl acrylate, and cyclohexyl methacrylate, in terms of resistance to electrolytic solution, adhesion to the current collector, and flexibility. It is preferable because it is excellent. When styrene is used, the amount used is preferably 5 to 65% by weight in 100% by weight of the ethylenically unsaturated monomer. Moreover, when using 2-ethylhexyl acrylate, it is preferable that the usage-amount is 20 to 75 weight% in 100 weight% of ethylenically unsaturated monomers. Moreover, when using cyclohexyl methacrylate, it is preferable that the usage-amount is 5-65 weight% in 100 weight% of ethylenically unsaturated monomers.

  The crosslinked emulsion of the present invention is synthesized by a conventionally known emulsion polymerization method.

  As the emulsifier used in the emulsion polymerization in the present invention, a conventionally known one such as a reactive emulsifier having an ethylenically unsaturated group or a non-reactive emulsifier having no ethylenically unsaturated group may be arbitrarily used. it can.

  Reactive emulsifiers having an ethylenically unsaturated group can be further roughly classified into anionic and nonionic nonionic ones. In particular, when an anionic reactive emulsifier or nonionic reactive emulsifier having an ethylenically unsaturated group is used, the dispersed particle size of the copolymer becomes fine and the particle size distribution becomes narrow. When used, the resistance to electrolytic solution can be improved, which is preferable. This anionic reactive emulsifier or nonionic reactive emulsifier having an ethylenically unsaturated group may be used singly or in combination.

Specific examples of the anionic reactive emulsifier having an ethylenically unsaturated group are illustrated below, but the emulsifiers that can be used in the present invention are not limited to those described below. Examples of the emulsifier include alkyl ethers (commercially available products include, for example, Aqualon KH-05, KH-10, KH-20, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Adeka Soap SR-10N, SR-20N manufactured by ADEKA Corporation. Latemuru PD-104 manufactured by Kao Corporation);
Sulfosuccinic acid ester-based (for example, Latmul S-120, S-120A, S-180P, S-180A, Sanyo Chemical Co., Ltd., Elemiol JS-2, etc., manufactured by Kao Corporation);
Alkyl phenyl ether type or alkyl phenyl ester type (commercially available products include, for example, Aqualon H-2855A, H-3855B, H-3855C, H-3856, HS-05, HS-10, HS, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. -20, HS-30, ADEKA Corporation ADEKA rear soap SDX-222, SDX-223, SDX-232, SDX-233, SDX-259, SE-10N, SE-20N, SE-, etc.);
(Meth) acrylate sulfate ester (commercially available products such as Antox MS-60, MS-2N, Sanyo Kasei Kogyo Co., Ltd. Elminol RS-30 manufactured by Nippon Emulsifier Co., Ltd.);
Examples of the phosphoric acid ester (commercially available products include H-3330PL manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Adeka Soap PP-70 manufactured by ADEKA Co., Ltd.), and the like.

Nonionic reactive emulsifiers that can be used in the present invention include, for example, alkyl ether-based (commercially available products such as Adeka Soap ER-10, ER-20, ER-30, ER-40, manufactured by ADEKA Corporation, Latemu PD-420, PD-430, PD-450, etc. manufactured by Kao Corporation);
Alkyl phenyl ether type or alkyl phenyl ester type (commercially available products include, for example, Aqualon RN-10, RN-20, RN-30, RN-50, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., ADEKA rear soap NE- manufactured by ADEKA Co., Ltd. 10, NE-20, NE-30, NE-40, etc.);
(Meth) acrylate sulfate-based (as commercial products, for example, RMA-564, RMA-568, RMA-1114, etc. manufactured by Nippon Emulsifier Co., Ltd.) can be mentioned.

  In obtaining the cross-linked emulsion of the present invention by emulsion polymerization, a non-reactive emulsifier having no ethylenically unsaturated group can be used in combination with the above-described reactive emulsifier having an ethylenically unsaturated group, if necessary. Non-reactive emulsifiers can be broadly classified into non-reactive anionic emulsifiers and non-reactive nonionic emulsifiers.

Examples of non-reactive nonionic emulsifiers include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether;
Polyoxyethylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether;
Sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate;
Polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate;
Polyoxyethylene higher fatty acid esters such as polyoxyethylene monolaurate and polyoxyethylene monostearate;
Glycerin higher fatty acid esters such as oleic acid monoglyceride and stearic acid monoglyceride;
Examples thereof include polyoxyethylene / polyoxypropylene / block copolymer and polyoxyethylene distyrenated phenyl ether.

Examples of non-reactive anionic emulsifiers include higher fatty acid salts such as sodium oleate;
Alkylaryl sulfonates such as sodium dodecylbenzenesulfonate;
Alkyl sulfate salts such as sodium lauryl sulfate;
Polyoxyethylene alkyl ether sulfate ester salts such as sodium polyoxyethylene lauryl ether sulfate;
Polyoxyethylene alkylaryl ether sulfate salts such as sodium polyoxyethylene nonylphenyl ether sulfate;
Alkyl sulfosuccinic acid ester salts such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, sodium polyoxyethylene lauryl sulfosuccinate and derivatives thereof;
Examples thereof include polyoxyethylene distyrenated phenyl ether sulfate salts.

  The usage-amount of the emulsifier used in this invention is not necessarily limited, According to the physical property calculated | required when a crosslinked emulsion is finally used as a binder for electric double layer capacitor electrodes, it can select suitably. For example, the amount of the emulsifier is usually preferably 0.1 to 30 parts by weight, more preferably 0.3 to 20 parts by weight, based on 100 parts by weight of the total of ethylenically unsaturated monomers. More preferably, it is in the range of 5 to 10 parts by weight.

In the emulsion polymerization of the crosslinked emulsion of the present invention, a water-soluble protective colloid can be used in combination. Examples of the water-soluble protective colloid include polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol;
Cellulose derivatives such as hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose salts;
Natural polysaccharides such as guar gum; and the like, and these can be used singly or in combination. The amount of the water-soluble protective colloid used is 0.1 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the total amount of ethylenically unsaturated monomers.

  Examples of the aqueous medium used in the emulsion polymerization of the cross-linked emulsion of the present invention include water, and a hydrophilic organic solvent can be used as long as the object of the present invention is not impaired.

  The polymerization initiator used for obtaining the crosslinked emulsion of the present invention is not particularly limited as long as it has the ability to initiate radical polymerization, and a known oil-soluble polymerization initiator or water-soluble polymerization initiator is used. be able to. The oil-soluble polymerization initiator is not particularly limited, and examples thereof include benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy (2-ethylhexanoate), and tert-butyl peroxide. Organic peroxides such as oxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4- Examples thereof include azobis compounds such as dimethylvaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobiscyclohexane-1-carbonitrile and the like. These can be used alone or in combination of two or more. These polymerization initiators are preferably used in an amount of 0.1 to 10.0 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated monomer.

  In the present invention, it is preferable to use a water-soluble polymerization initiator. For example, ammonium persulfate, potassium persulfate, hydrogen peroxide, 2,2′-azobis (2-methylpropionamidine) dihydrochloride and the like are conventionally known. A thing can be used conveniently. Moreover, when performing emulsion polymerization, a reducing agent can be used together with a polymerization initiator if desired. Thereby, it becomes easy to accelerate the emulsion polymerization rate or to perform the emulsion polymerization at a low temperature. Examples of such a reducing agent include reducing organic compounds such as metal salts such as ascorbic acid, ersorbic acid, tartaric acid, citric acid, glucose, formaldehyde sulfoxylate, sodium thiosulfate, sodium sulfite, sodium bisulfite, Examples include reducing inorganic compounds such as sodium bisulfite, ferrous chloride, Rongalite, thiourea dioxide, and the like. These reducing agents are preferably used in an amount of 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the total ethylenically unsaturated monomer. In addition, it can superpose | polymerize by a photochemical reaction, radiation irradiation, etc. irrespective of an above described polymerization initiator. The polymerization temperature is not less than the polymerization start temperature of each polymerization initiator. For example, in the case of a peroxide-based polymerization initiator, it may be usually about 70 ° C. The polymerization time is not particularly limited, but is usually 2 to 24 hours.

  Further, if necessary, sodium acetate, sodium citrate, sodium bicarbonate, etc. as a buffering agent, and octyl mercaptan, 2-ethylhexyl thioglycolate, octyl thioglycolate, stearyl mercaptan, lauryl mercaptan as chain transfer agents A suitable amount of mercaptans such as t-dodecyl mercaptan can be used.

When a monomer having an acidic functional group such as a carboxyl group-containing ethylenically unsaturated monomer is used for the polymerization of the cross-linked emulsion, it can be neutralized with a basic compound before or after the polymerization. When neutralizing, ammonia or alkylamines such as trimethylamine, triethylamine, butylamine;
Alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine, aminomethylpropanol;
It can be neutralized with a base such as morpholine. However, it is a highly volatile base that has a high effect on drying properties, and preferred bases are aminomethylpropanol and ammonia.

  The glass transition temperature (hereinafter also referred to as Tg) of the cross-linked emulsion is preferably -30 to 70 ° C, more preferably -20 to 30 ° C. When Tg is less than −30 ° C., the binder excessively covers the electrode active material, and the impedance tends to increase. On the other hand, if Tg exceeds 70 ° C., the flexibility and tackiness of the binder become poor, and the adhesion of the electrode active material to the current collector and the moldability of the electrode may be inferior. The glass transition temperature is a value obtained using a DSC (differential scanning calorimeter).

  The measurement of the glass transition temperature by DSC (differential scanning calorimeter) can be performed as follows. About 2 mg of resin obtained by drying the cross-linked emulsion is weighed on an aluminum pan, the test container is set on a DSC measurement holder, and the endothermic peak of the chart obtained under a temperature rising condition of 10 ° C./min is read. The peak temperature at this time is defined as the glass transition temperature of the present invention.

  In the present invention, the particle structure of the cross-linked emulsion may be a multilayer structure, so-called core-shell particles. For example, it is possible to localize a resin obtained by mainly polymerizing a monomer having a functional group in the core part or the shell part, or to provide a difference in Tg or composition between the core and the shell, thereby providing curability and drying properties. Further, the film forming property and the mechanical strength of the binder can be improved.

  The average particle size of the cross-linked emulsion is preferably 10 to 500 nm, more preferably 30 to 250 nm, from the viewpoint of the binding property of the electrode active material and the stability of the emulsion. Further, when a large amount of coarse particles exceeding 1 μm are contained, the stability of the emulsion is impaired, so that the coarse particles exceeding 1 μm are preferably at most 5% by weight. In addition, the average particle diameter in the present invention represents a volume average particle diameter and can be measured by a dynamic light scattering method.

  The average particle diameter can be measured by the dynamic light scattering method as follows. The cross-linked emulsion dispersion is diluted with water 200 to 1000 times depending on the solid content. About 5 ml of the diluted solution is injected into a cell of a measuring apparatus [Microtrack manufactured by Nikkiso Co., Ltd.], and the measurement is performed after inputting the solvent (water in the present invention) and the refractive index condition of the resin according to the sample. The peak of the volume particle size distribution data (histogram) obtained at this time is defined as the average particle size of the present invention.

Furthermore, the strength and elongation rate of the coating film obtained by forming a film of the cross-linked emulsion are 1.0 to 7.0 N / mm ² in strength and 300 to 2000% elongation from the viewpoint of the toughness of the resin. It is more preferable that the strength is 2.0 to 5.5 N / mm ² and the elongation is 400 to 1200%. If the strength is less than 1.0 N / mm ² , the holding force of the active material and the binding force to the current collector may be deteriorated, and if the strength exceeds 7.0 N / mm ² , the coating film becomes rigid. It becomes too much and the binding power becomes worse. When the elongation is less than 300%, the coating film is fragile and sufficient binding strength may not be obtained. Moreover, when elongation rate exceeds 2000%, the retention strength of an active material and the binding force to a collector may worsen. In addition, the intensity | strength and elongation rate of the coating film in this invention are the breaking strength and breaking elongation measured with Tensilon.

  Measurement of the strength and elongation of the coating film with Tensilon can be performed by the following method. The cross-linked emulsion is dried to prepare a sheet having a thickness of about 0.5 mm. The measurement specimen is cut out to 5 mm × 60 mm, and the film thickness is measured accurately. The measurement is performed under a constant temperature and humidity condition of a temperature of 23 ° C. and a humidity of 50% using a tensile tester [Tensilon manufactured by Orientec Co., Ltd.] with a chuck distance of 20 mm and a tensile speed of 50 mm / min. The breaking strength obtained by measurement, the breaking strength calculated from the breaking elongation in consideration of the film thickness, and the breaking elongation are defined as the strength and elongation of the present invention.

  The binder composition for an electric double layer capacitor electrode containing the cross-linked emulsion of the present invention can contain a film forming aid, an antifoaming agent, a leveling agent, a preservative, a pH adjusting agent, a viscosity adjusting agent and the like as required. .

  The film-forming aid is responsible for the temporary plasticization function that helps the formation of the coating film and evaporates relatively quickly after the coating film is formed, thereby improving the strength of the coating film. Is preferably a solvent having a temperature of 110 to 200 ° C. Specifically, propylene glycol monobutyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol monobutyl ether, diethylene glycol diethyl ether, dipropylene glycol monopropyl ether, carbitol, butyl carbitol, dibutyl carbitol, benzyl alcohol, etc. Is mentioned. Among these, ethylene glycol monobutyl ether and propylene glycol monobutyl ether are particularly preferable because they have a high film forming auxiliary effect in a small amount. These film forming aids are preferably contained in the binder composition in an amount of 0.5 to 15% by weight.

  The viscosity modifier may be used in an amount of 1 to 100 parts by weight with respect to 100 parts by weight of the crosslinked emulsion. Examples of the viscosity modifier include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, polyacrylic acid (and its salt), oxidized starch, phosphorylated starch, and casein.

  The binder composition for an electric double layer capacitor electrode of the present invention can be used for a positive electrode and a negative electrode of an electric double layer capacitor. In addition, it can also be used for energy devices, that is, secondary batteries, solar batteries, and the like.

  The electric double layer capacitor electrode binder composition of the present invention is blended with an electrode active material to form an electric double layer capacitor electrode dispersion. The electric double layer capacitor electrode dispersion is applied to a current collector and dried. Thus, an electric double layer capacitor electrode can be manufactured.

  In the present invention, the electric double layer capacitor electrode binder composition is usually used in an amount of 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, per 100 parts by weight of the electrode active material. When the amount of the binder composition is less than 0.1 parts by weight, the force for binding the electrode active material to the current collector is insufficient, and the electrode active material may fall off and the battery capacity may be reduced. On the other hand, when the amount of the binder exceeds 20 parts by weight, the resistance in the battery may increase and the capacity of the battery may decrease.

  Examples of the electrode active material include activated carbon, polyacene, carbon fiber, carbon whisker, and graphite.

  Examples of the conductivity imparting agent used in combination with the electrode active material include acetylene black, ketjen black, and carbon black. As for the usage-amount of an electroconductive material, 0.5-20 weight part is preferable with respect to 100 weight part of electrode active materials. If the amount is less than 0.5 parts by weight, the conductivity is low, and the capacity when charging / discharging at a high rate of the electric double layer capacitor may decrease. The current collector is not particularly limited as long as it is usually used for an electric double layer capacitor electrode, and examples thereof include metal materials such as aluminum, titanium, tartan, stainless steel, gold, and platinum.

  In order to form an electric double layer capacitor electrode, the electric double layer capacitor electrode dispersion is applied to a current collector in the form of a slurry, heated and dried, and the electrode active material layer is bonded to the current collector. An electrode formed by wearing can be obtained. As a coating method of the electric double layer capacitor electrode dispersion, any method such as a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, or a brush coating method can be used. As drying methods, standing drying, blower dryer, hot air dryer, vacuum dryer, infrared heater, far infrared heater and the like can be used.

  The electric double layer capacitor of the present invention includes an electric double layer capacitor electrode manufactured using the electric double layer capacitor electrode dispersion. When an electric double layer capacitor is assembled using the electric double layer capacitor electrode obtained as described above, tetraethylammonium tetrafluoroborate and triethylmonomethyl are added to an electrolyte such as propylene carbonate, ethylene carbonate, butylene carbonate, and γ-butyrolactone. An electrolyte such as ammonium tetrafluoroborate is dissolved, and a separator such as a polyethylene nonwoven fabric or a polypropylene nonwoven fabric is used.

  EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the following examples do not limit the scope of rights of the present invention. In the examples, “part” represents “part by weight” and “%” represents “% by weight”.

[Example 1]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser was charged with 40 parts of ion-exchanged water and 0.2 part of Adeka Soap SR-10 (manufactured by ADEKA) as a surfactant. 50 parts of styrene, 40 parts of 2-ethylhexyl acrylate, 7 parts of methyl methacrylate, 1 part of acrylic acid, 2 parts of acrylamide, 0.3 part of 3-methacryloxypropyltrimethoxysilane, 53 parts of ion-exchanged water, and Adekaria as a surfactant 1% of the pre-emulsion in which 1.8 parts of soap SR-10 (manufactured by ADEKA Corporation) was mixed in advance was further added. After raising the internal temperature to 70 ° C. and sufficiently substituting with nitrogen, 10% of 10 parts of a 5% aqueous solution of potassium persulfate was added to initiate polymerization. After maintaining the reaction system at 70 ° C. for 5 minutes, the remaining pre-emulsion and the remaining 5% aqueous solution of potassium persulfate were added dropwise over 3 hours while maintaining the internal temperature at 70 ° C., and stirring was further continued for 2 hours. . After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C. 25% aqueous ammonia was added to adjust the pH to 8.5, and the solid content was adjusted to 48% with ion-exchanged water to obtain a crosslinked emulsion. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

[Examples 2-5, 10, 11, 15 and Comparative Examples 1-3]
The composition shown in Table 1 was synthesized in the same manner as in Example 1, and the crosslinked emulsions of Examples 2-5, 10, 11, and 15 and the non-crosslinked emulsions of Comparative Examples 1 to 3 were obtained. .

[Examples 6-9, 12-14, and 16]
The composition shown in Table 1 was used to polymerize an ethylenically unsaturated monomer in the same manner as in Example 1 to synthesize an emulsion, and then add the compound (j) shown in Table 1 as a crosslinking agent. The crosslinked emulsions of Examples 6-9, 12-14, and 16 were obtained.

Carbodilite V-02; Carbodiimide curing agent (Nisshinbo Co., Ltd., NCN equivalent 600)
ADEKA rear soap SR-10; alkyl ether anionic surfactant (manufactured by ADEKA Corporation)
ADEKA rear soap ER-20; alkyl ether nonionic surfactant (manufactured by ADEKA Corporation)

[Binder composition for electric double layer capacitor electrode and preparation of electric double layer capacitor electrode]
To 5 parts of the obtained emulsion, 100 parts of activated carbon, 4 parts of acetylene black and 2 parts of carboxymethyl cellulose as a thickener are added, and an appropriate amount of ion-exchanged water is added so that the total solid content is 50%. Then, a dispersion for an electrode was prepared. The dispersion was applied to an aluminum substrate, dried at 80 ° C. for 30 minutes with an air dryer, and then vacuum-dried at 250 ° C. for 72 hours, followed by roll pressing to obtain an electrode. Two pieces of this electrode cut into a circle of 15 mm were prepared. The two electrodes were opposed to obtain a coin-type electric double layer capacitor through a polypropylene separator.

  About the emulsion obtained by the Example and the comparative example, the electrode and the capacitor were created by said method, and binding property, electrolyte solution resistance, and the battery characteristic were evaluated.

(Binding property)
Using a knife on the electrode surface, 6 incisions were made from the mixture layer to the depth reaching the current collector, both vertically and horizontally at intervals of 2 mm, to make a grid cut. An adhesive tape was applied to the cut and immediately peeled off, and the degree of the active material falling off was determined by visual judgment. The evaluation criteria are shown below. The evaluation results are shown in Table 2.
○: “No peeling”
○ △: “Partial separation”
△ ×: “Peeling at most parts”
×: “Completely peeled”

(Electrolytic solution resistance)
The prepared electrode was immersed in a propylene carbonate solution at 70 ° C. for 24 hours, and the swelling state of the film and the elution state of the resin before and after the immersion were calculated as follows for comparative evaluation.
Swelling rate (%) = (weight after immersion) / (weight before immersion)
Dissolution rate (%) = (weight after immersion drying) / (weight before immersion) -1
As the swelling rate is closer to 100% and the dissolution rate is closer to 0%, the resistance to electrolytic solution is higher. The evaluation results are shown in Table 2.

(Battery characteristics evaluation)
A charge / discharge cycle test of an electric double layer capacitor incorporating a propylene carbonate liquid (PC liquid) and a separator as an electrolyte and an electrolyte prepared using the binder compositions obtained in Examples 1 to 16 and Comparative Examples 1 to 3 went. The discharge capacity at the first time was set to 100%, and the discharge capacity after 100 hours at 70 ° C. was measured to obtain the rate of change (the closer to 100%, the better). The evaluation results are shown in Table 2.

As shown in Table 2, when the binder compositions of Examples 1 to 16 were used, the balance between the electrolytic solution resistance and the binding property was achieved, and the battery capacity was also reduced after 70 hours at 100C. Is suppressed. On the other hand, when the binder compositions of Comparative Examples 1 to 3 are used, the electrolytic solution resistance and the binding property are lowered, and the battery characteristics are also deteriorated.

Claims (7)

(A) Epoxy group-containing ethylenically unsaturated monomer (a) and / or amide group-containing ethylenically unsaturated monomer (b) 0.1 to 20% by weight,
(B) alkoxysilyl group-containing ethylenically unsaturated monomer (c) and / or N-methylol group-containing ethylenically unsaturated monomer (d) 0.1 to 5% by weight,
(C) a carboxyl group-containing ethylenically unsaturated monomer (e), a tertiary butyl group-containing ethylenically unsaturated monomer (f), a sulfonic acid group-containing ethylenically unsaturated monomer (g), and phosphorus 0.1 to 10% by weight of at least one monomer selected from the group consisting of acid group-containing ethylenically unsaturated monomers (h),
And the binder composition for electric double layer capacitor electrodes containing the bridge | crosslinking type emulsion formed by emulsion-polymerizing ethylenically unsaturated monomers (i) other than said monomer (a)-(h).   It includes a compound (j) having two or more functional groups capable of reacting with at least one functional group selected from the group consisting of an epoxy group, an amide group, a carboxyl group, a sulfonic acid group, and a phosphoric acid group. The binder composition for electric double layer capacitor electrodes according to claim 1. The crosslinked emulsion further contains 0.5 to 10% by weight of a carbonyl group-containing ethylenically unsaturated monomer as the ethylenically unsaturated monomer (i) in 100% by weight of the ethylenically unsaturated monomer. Formed by emulsion polymerization of monomers, and
The binder composition for an electric double layer capacitor electrode according to claim 1 or 2, comprising the cross-linked emulsion and a compound having a functional group capable of reacting with a carbonyl group.   The ethylenically unsaturated monomer (i) contains at least one monomer selected from the group consisting of styrene, 2-ethylhexyl acrylate, and cyclohexyl methacrylate. Binder composition for electric double layer capacitor electrode.   The dispersion for electric double layer capacitor electrodes containing the binder composition for electric double layer capacitor electrodes in any one of Claims 1-4, and an electrode active material.   An electric double layer capacitor electrode, wherein an electrode active material layer formed using the electric double layer capacitor electrode dispersion according to claim 5 is bound to a current collector. An electric double layer capacitor comprising the electric double layer capacitor electrode according to claim 6, an electrolytic solution, and a separator.