JP2003133179A - Electrically conductive film for electric current collection and electrically conductive paint for film manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically conductive film most suitable for an electric double-layer capacitor collector in which a block copolymer, such as SEBS is used, has a superior electrolyte-resistance, its internal resistance is small, and is easily manufactured by a casting method, and to provide an electrically conductive paint in which a block copolymer, such as SEBS, used for its manufacturing is used and has a superior viscosity stability. SOLUTION: The electric-current collecting, electrically conductive film is used for the electric double-layer capacitor, which includes an elastomer, coconsisting of (1) a hydrogen additive of 10-90 wt.% of the block copolymer made of an aromatic vinyl compound whose content of bond unit of aromatic vinyl compound is 10-40 wt.% and of a conjugated dien and (2) a hydrogen additive of 90-10 wt.% of a random copolymer made of an aromatic vinyl compound, whose content of bond unit of aromatic vinyl compound is 5-30 wt.% as well as an electrically conductive filler. These components are contained in an electrically conductive paint used to manufacture the film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive film for collecting electricity, which is used in contact with a solid polarizable electrode of an electric double layer capacitor, and a conductive paint used for its production.

[0002]

2. Description of the Related Art An electric double layer capacitor is an electric element composed of a solid polarizable electrode and an electrolyte. As shown in FIG. 1, a pair of electric double layer capacitors are filled inside a sealing frame body 4 with a porous separator 3 interposed therebetween. It is basically composed of solid polarizable electrodes 2 and 2, and a metal electrode plate 6 provided in contact with the current collector 5 by sealing the solid polarizable electrode 2 with a current collector 5.

As an electrolyte for a solid polarizable electrode, an electrolytic solution in which an electrolyte salt is dissolved is generally used (JP-A-49-6).
8254 publication). This has the function of accumulating charges in the electric double layer formed between the electrolytic solution and the electrode due to the polarization of the electrode such as conductive carbon. The electric double layer capacitor is used as a small power source for semiconductor memory backup and the like, but there is a demand for miniaturization and high performance thereof. Furthermore, electric double-layer capacitors are expected to be used as auxiliary power sources for electric vehicles and fuel cell vehicles.

Conventionally used electric double layer capacitors use an aqueous electrolytic solution as an electrolytic solution, usually an aqueous sulfuric acid solution of about 25 to 50% by weight (JP-A-62-268).
119, JP-A-63-213915, JP-A-2-174210, etc. and those using an organic solvent-based electrolytic solution (JP-A-49-68254, JP-A-7-254254).
-86096 gazette).

In general, an organic solvent-based electrolyte has a high output voltage, but has a drawback that since the ionic conductivity is small, the internal resistance of the electric double layer capacitor is large and the output current is small. On the other hand, the aqueous electrolytic solution has a low output voltage, but since it has a high ionic conductivity, it has a small internal resistance and a large output current can be obtained. Further, the one using an organic solvent-based electrolytic solution is flammable, and from the viewpoint of safety, development of an electric double layer capacitor having a large output using an aqueous electrolytic solution is desired.

By the way, in an electric double layer capacitor using an aqueous electrolyte, when a metal electrode plate is provided in direct contact with a solid polarizable electrode, the electrode plate is corroded by the acid of the aqueous electrolyte, which causes deterioration of function and liquid leakage. From happening,
The metal electrode plate is provided through an acid-resistant conductive polymer film (referred to as a current collecting conductive film).

As the conductive polymer film, an elastomer film containing a conductive filler is generally used (JP-A-2-174210, JP-A-4-240708, JP-A-5-299296, etc.). ). However, these conventionally used conductive films are inferior in acid resistance, and when used for a long time, they are eroded by an acidic aqueous electrolyte and may deteriorate in function or cause liquid leakage. Further, since the volume resistivity in the direction perpendicular to the film surface was about 8 to 500 Ωcm, it was difficult to increase the output of the condenser.

In order to solve the above problems, use of various elastomers as a base polymer has been proposed. One of them is polystyrene-polybutadiene-polystyrene block copolymer (S) produced by anionic polymerization.
Hydrogenated product of BS) [usually referred to as SEBS. S
Is a polystyrene block, E is a polyethylene block,
B is a polybutylene block (E: hydrogenated product of cis and trans polybutadiene units, B: 1,2-polybutadiene unit hydrogenated product)]. SEBS
Has excellent electrolytic solution resistance and is stable even after long-term use.

In order to produce a conductive film for collecting electricity, for example, a conductive coating material prepared by dissolving a base polymer in an organic solvent and dispersing a conductive filler such as conductive carbon on a smooth surface is prepared. A method is used in which a film is obtained by casting (casting) on a suitable substrate having the above and evaporating the solvent. However, the conductive paint containing only SEBS as a base polymer causes a phenomenon in which the viscosity is increased and the fluidity is lost when the temperature is higher than 35 ° C. during the preparation of the paint. It was found that, in order to recover, it was necessary to apply strong shearing force and then stir after cooling. This phenomenon was remarkable especially in the case of a conductive paint having a solid content of 10% by weight or more. The re-fluidized paint is
It is possible to manufacture a film using this,
Not only does it require extra steps for re-fluidization,
From the viewpoint of stability of the quality of the film, it is important that the conductive paint does not thicken and maintains a constant viscosity.

In the film formation by the casting method, in order to obtain a film having a uniform film thickness, it is necessary for the conductive coating material to have a viscosity stability in which the viscosity change due to the temperature rise is small. The thickened conductive paint using SEBS caused problems such as coating failure, uneven film thickness even if coating was possible, and scratches when peeling the film. There is a problem that a quality conductive film cannot be obtained.

[0011]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a conductive material suitable for a current collector of an electric double layer capacitor, which uses a block copolymer such as SEBS and has excellent electrolytic solution resistance and a small internal resistance. The object of the present invention is to provide a conductive coating material having excellent viscosity stability, which is obtained by using a block copolymer such as SEBS and the like which is used for its production.

[0012]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that when a mixture of SEBS and hydrogenated SBR is used, the viscosity change due to temperature rise is small. The present invention has been completed based on the findings. Thus, according to the present invention, the following (i) to (iii)
Will be provided. (I) A conductive film for current collection used in an electric double layer capacitor, comprising an elastomer component and a conductive filler, wherein the elastomer component is (1) a block copolymer of an aromatic vinyl compound and a conjugated diene. Hydrogenated product 1
0 to 90 parts by weight and (2) 90 to 10 parts by weight of a hydrogenated product of a random copolymer of an aromatic vinyl compound and a conjugated diene (however, the total of (1) and (2) is 100 parts by weight). Conductive fill film for current collection consisting of. (Ii) A paint for producing a conductive film for collecting electricity for use in an electric double layer capacitor, wherein the paint comprises a solution of an elastomer component and a conductive filler dispersed in the elastomer component (1). Hydrogenated product of block copolymer of aromatic vinyl compound and conjugated diene 10-9
0 to 10 parts by weight and 90 to 10 parts by weight of the hydrogenated product of the random copolymer of (2) an aromatic vinyl compound and a conjugated diene (however, the total of (1) and (2) is 100 parts by weight). An electrically conductive coating material for producing an electrically conductive film for current collection comprising (Iii) A conductive current-collecting film formed using the conductive paint according to (ii).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. (A) Conductive film The conductive film for collecting electricity of the electric double layer capacitor of the present invention (hereinafter sometimes simply referred to as "conductive film") has (1) an aromatic vinyl compound as an elastomer component. It is characterized by comprising a hydrogenated product of a block copolymer with a conjugated diene and (2) a hydrogenated product of a random copolymer of an aromatic vinyl compound and a conjugated diene.

The conductive film of the present invention contains the above-mentioned elastomer components (1) and (2) and the conductive filler in an amount of usually 5 to 100 parts by weight, preferably 10 to 80 parts by weight, based on 100 parts by weight of the total amount thereof. , More preferably 20 to 70 parts by weight, and the volume resistivity in the direction perpendicular to the surface of the conductive film is usually 0.1 to 5 Ωcm, preferably 0.1 to 3
Ωcm, more preferably 0.1 to 1Ωcm. If the amount of the conductive filler is too small, the volume resistivity of the conductive film is too large, and if the amount of the conductive filler is too large, it becomes difficult to manufacture the conductive film. The thickness of the conductive film of the present invention is appropriately determined depending on the shape, but is preferably 10 to 100 μm, more preferably 20 to 80 μm.
μm. If it is too thin, the strength of the film will be insufficient, making it difficult to use. If it is too thick, the resistance will increase. The conductive film of the present invention is preferably a film produced by the solvent casting method described below because a conductive filler such as conductive carbon is easily dispersed uniformly throughout the film. In the film produced by the solvent casting method, since the conductive filler is not oriented in the plane direction, the volume resistivity measured in the direction perpendicular to the plane also has a low value.

(I) Elastomer Component The elastomer component used in the present invention is (1) a hydrogenated product of a block copolymer of an aromatic vinyl compound and a conjugated diene and (2) an aromatic vinyl compound and a conjugated diene. And a hydrogenated product of a random copolymer. The hydrogenated product (1) of a block copolymer of an aromatic vinyl compound and a conjugated diene comprises (a) an aromatic vinyl compound or at least two blocks A containing the aromatic vinyl compound as a main component, and (b) a conjugated diene or it. A block copolymer of at least one block B as a main component (hereinafter sometimes simply referred to as “block copolymer”) in which the carbon-carbon double bond in block B is hydrogenated is preferable. .

Specific examples of the aromatic vinyl compound include α
-Methylstyrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, p-vinyltoluene, vinylnaphthalene, vinylanthracene and the like can be mentioned. Of these, unsubstituted aromatic vinyl compounds such as styrene and α-methylstyrene are preferable. The aromatic vinyl compounds can be used alone or in combination of two or more kinds. Specific examples of the conjugated diene include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. Butadiene and isoprene are particularly preferable. Is particularly preferable.

The hydrogenated product of the block copolymer used in the present invention may be a block copolymer having either a linear structure or a branched structure, but the block A is preferably 2 or more. Particularly, a block copolymer having a polystyrene block at both ends and a polybutadiene block or a polyisoprene block in the middle is preferable from the viewpoint of elongation at break and tensile strength. The hydrogenated products of these block copolymers usually contain S
Called EBS and SEPS. The structure of a copolymer having two or more blocks A is generally AB-
A triblock, such as A-B-A-B (A-B)
a straight chain such as a multiblock represented by _m (where m is an integer of 2 or more), and [(A−B) _n ] _p M (where n is
Is an integer of 1 or more, p is an integer of 2 or more, M is a residue of a polyfunctional coupling agent), and linear and star-shaped ones are exemplified.

Content of the aromatic vinyl compound bonding unit in the hydrogenated product of the block copolymer (means the content of the aromatic vinyl compound bonded to the polymer chain by polymerization in the polymer, and simply means the aromatic The content of the vinyl compound is sometimes referred to as), usually 10 to 40% by weight, preferably 1
It is 5 to 35% by weight. If the content of the binding unit of the aromatic vinyl compound is too small, the strength of the film will be insufficient, and if it is too large, the flexibility of the film will be lost, which is not preferable. The molecular weight of the hydrogenated product of the block copolymer is not particularly limited, but it is converted to standard polystyrene measured by GPC (gel permeation chromatography) using toluene from the balance of elongation and flexibility when formed into a film. The weight average molecular weight of is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 20,000 to 800,000, and most preferably in the range of 50,000 to 500,000.

The second elastomer component used in the present invention is a hydrogenated product (2) of a random copolymer of an aromatic vinyl compound and a conjugated diene. Specific examples and preferable examples of the aromatic vinyl compound and the conjugated diene are the same as those in the case of the block copolymer. Furthermore, if necessary, a random copolymer obtained by copolymerizing another monomer copolymerizable therewith can also be used within a range not impairing the object of the present invention. Examples of such a monomer include acrylic acid alkyl esters (wherein the alkyl group has about 1 to 8 carbon atoms), methacrylic acid alkyl esters (wherein the alkyl group has about 1 to 8 carbon atoms), and the like. These monomers can be used alone or in combination of two or more kinds. However, acrylic acid,
The use of unsaturated carboxylic acids such as methacrylic acid is not preferable because it reduces the acid resistance of the hydrogenated product of the random copolymer.

The content of the aromatic vinyl compound bonding unit in the hydrogenated product of the random copolymer is usually 5 to 30% by weight, preferably 15 to 25% by weight. If the content of aromatic vinyl compound bonding units is too small, the compatibility of the block copolymer with hydrogenated products will be reduced, and the strength when formed into a film will be reduced. This is not preferable because it deteriorates the property.

The above block copolymer can be prepared by a known method, for example, in JP-B-36-19286 and JP-B-4.
In accordance with the method described in JP-A-3-17979, JP-B-45-31951, JP-B-46-32415, etc., an organolithium compound is used as an initiator in a hydrocarbon solvent to give an aromatic vinyl compound. It can be produced by polymerizing with a conjugated diene. During the polymerization, adjustment of the reactivity ratio between the aromatic vinyl compound and the conjugated diene, control of the microstructure of the polymerized conjugated diene part,
A polar compound can be used for the purpose of adjusting the polymerization rate.

Examples of the hydrocarbon solvent used here include aliphatic hydrocarbons such as butane, heptane, hexane, isopentane, heptane, octane, isooctane: cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane. Alicyclic hydrocarbons such as benzene, ethylbenzene,
Examples thereof include aromatic hydrocarbons such as xylene, and these can be used alone or in admixture of two or more. The amount of the hydrocarbon solvent used is usually such that the monomer concentration is 1 to 50% by weight.

Examples of polar compounds include ethers such as tetrahydrofuran, diethyl ether, anisole, dimethoxybenzene and ethylene glycol dimethyl ether; amines such as triethylamine, tetramethylenediamine, N-dimethylaniline and pyridine;
Examples thereof include thioethers, phosphines, phosphoramides, alkylbenzene sulfonic acids, and alkoxides such as potassium and sodium, which can be selected according to required characteristics. The amount of the polar compound used can be appropriately determined depending on the kind of the compound, etc., but usually 0.001 to 1 mol per 1 mol of the organolithium compound,
It is preferably in the range of 0.01 to 5 mol.

As the organic lithium compound, organic monolithium compounds, organic dilithium compounds, etc. are used.
Specific examples thereof include n-butyl lithium, sec-butyl lithium, tert-butyl lithium, n-hexyl lithium, isohexyl lithium, phenyl lithium, naphthyl lithium, hexamethylene dilithium, butadienyl dilithium and iso. Examples thereof include prenyldilithium. Generally, organic monolithium compounds are used, and these are used alone or in combination of two or more kinds. The amount used is appropriately selected depending on the molecular weight of the target polymer and the kind of the organolithium compound, but is usually 0.00 per 1 mol of the organolithium compound.
It is in the range of 1 to 1 mol, preferably 0.01 to 0.5 mol. The polymerization reaction may be an isothermal reaction or an adiabatic reaction, and is usually carried out at a polymerization temperature range of 0 to 150 ° C, preferably 20 to 120 ° C. A block copolymer prepared by adding a coupling agent after the above polymerization reaction can also be used.

Examples of the coupling agent include tin tetrachloride, tin dichloride, tin tetrabromide, silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, germanium tetrachloride, lead dichloride, methyltrichlorosilane, Dimethyldichlorosilane, butyltrichlorosilane, dibutyldichlorotin,
Pistrichlorosilylethane, pistrichlorostannylethane, tetramethoxysilicon, tetramethoxytin,
Metal compounds such as tetraethoxysilicon, tetraethoxytin, tetrabutoxysilicon and tetrabutoxytin;
Unsaturated nitriles such as ethyl acrylonitrile; dihalogenated hydrocarbons such as dibromobenzene, dichlorobenzene, dibromoethylene; dimethyl adipate, diethyl adipate, ethyl benzoate, dimethyl terephthalate, diethyl terephthalate, dimethyl isophthalate, etc. Carboxylic acid esters; carboxylic acid halides such as terephthalic acid dichloride, phthalic acid dichloride, isophthalic acid dichloride, adipic acid dichloride; carbon tetrachloride and the like. These coupling agents are used alone or as a mixture of two or more thereof, and the amount thereof is usually 0.25 to 2 equivalents, preferably 0.30 to 1.5, per organolithium compound. It is equivalent. The coupling reaction is usually performed at 0 to 150 ° C. for 0.1 to 20 hours. Further, as the block copolymer, one prepared by using a modifier after the above polymerization reaction can also be used. Examples of the modifier include unsaturated carboxylic acids such as maleic anhydride disclosed in JP-B-62-61615, imino compounds, cyanamide compounds, acylidinyl compounds and amide compounds disclosed in JP-B-4-387770. And so on. The amount of vinyl bond in the conjugated diene of the block copolymer obtained by the above-mentioned method or the block B mainly composed of it is not particularly limited, but is usually 90 mol% or less, preferably 1 to 60 mol%, More preferably, it is 5 to 30 mol%. If the vinyl bond amount is too large, the film loses flexibility, which is not preferable.

The random copolymer can be produced by radical polymerization and the above-mentioned anionic polymerization. In the case of anionic polymerization, the same polymerization solvent, polymerization catalyst, and polar compound as in the case of the above block copolymer are used, and a known method is used so that the aromatic vinyl compound is randomly distributed in the polymer chain. It can be obtained by polymerizing. In the case of radical polymerization, it can be obtained by a known method such as solution polymerization in which a monomer is polymerized in an organic solvent or emulsion polymerization in which a monomer is emulsified (medium is water). At that time, organic peroxides such as cumene hydroperoxide, benzoyl peroxide and isopropylbenzene peroxide, persulfates such as potassium persulfate and ammonium persulfate, known radical polymerization initiators such as redox catalysts, and n-octyl. Known mercaptans such as mercaptan and tert-dodecyl mercaptan, known molecular weight regulators such as carbon tetrachloride, fatty acid soaps having 12 to 18 carbon atoms, known anionic surfactants such as sodium dodecylbenzenesulfonate, etc. Polymerization is performed in a temperature range of about 0 to 50 ° C. using a polymerization agent such as the emulsifier. Preferred is a random copolymer obtained by anionic polymerization with less impurities such as residual surfactant.

In this case, the vinyl bond amount of the conjugated diene unit in the random copolymer is not particularly limited, but usually 90.
It is not more than mol%, preferably 1 to 60 mol%, and more preferably 5 to 30 mol%. If the vinyl bond amount is too large, the film loses flexibility, which is not preferable. The molecular weight of the hydrogenated product of the random copolymer is not particularly limited, but it is converted into standard polystyrene by GPC (gel permeation chromatography) using toluene from the balance of elongation and flexibility when formed into a film. Has a weight average molecular weight of 10,000 to 1,000,
000 is preferable and 20,000 to 800,000
0 is more preferable, and 50,000 to 500,000 is more preferable.
The range of 0 is most preferable.

The hydrogenated products of block copolymers and random copolymers can be obtained by subjecting each of the copolymers obtained as described above to conventional methods, for example, JP-A-4-96905 and JP-A-4-96904. Japanese Patent Publication, Japanese Patent Publication No. 1-53851, Japanese Patent Publication No. 63-5402, Japanese Patent Publication No. 48-355.
No. 5, Japanese Patent Publication No. 45-20504, specifically, the above-mentioned copolymer is cyclopentanone,
It can be obtained by a method of dissolving in an inert solvent such as tetrahydrofuran and adding hydrogen in the presence of a hydrogenation catalyst. As the hydrogenation catalyst, for example, nickel supported on carbon or diatomaceous earth, platinum, palladium, rhodium and other hydrogenation metal catalysts, Raney nickel, organonickel compounds, organocobalt compounds, or these compounds and other organometallic compounds An example is a composite catalyst of The hydrogenation rate of the conjugated diene unit in the block and random copolymer is preferably as high as possible from the viewpoint of strength and acid resistance, and the iodine value is preferably 30 or less, more preferably 20 or less.

Hydrogenated products of block copolymers and random copolymers are commercially available. The hydrogenated block copolymer is a hydrogenated product of a block copolymer of styrene and butadiene, such as Kraton G1657 (styrene content 13% by weight), Kraton G1650 (styrene content 29% by weight), etc. stock)
Manufactured by Asahi Kasei Kogyo Co., Ltd., Tuftec H1221 (styrene content 12% by weight), Tuftec H1062 (styrene content 18% by weight), Tuftec H1041 (styrene content 30% by weight), and the like.
The hydrogenated product of a random copolymer of styrene and butadiene is Dynaron 1320P (styrene content 10
Wt%), Dynaron 1910P (styrene content 30
% By weight, etc. (all manufactured by JSR Co., Ltd.).

Of the elastomer component in the present invention,
The ratio of the hydrogenated product of the block copolymer (1) to the hydrogenated product of the random copolymer (2) is 10 to 9 for (1).
0 parts by weight, preferably 30 to 70 parts by weight, (2) 90
-10 parts by weight, preferably 70-30 parts by weight (however,
The total of (1) and (2) is 100 parts by weight. ). If the proportion of the hydrogenated product of the random copolymer is too low, the viscosity increase due to the temperature rise of the conductive coating material containing the elastomer component and the conductive filler during the production of the conductive film of the present invention is not improved, and if it is too high. It is not preferable because the strength of the film decreases.

(Ii) Conductive Filler Examples of the conductive filler constituting the conductive film of the present invention include carbon, graphite, powdery or fibrous metal or metal oxide. The specific surface area of the conductive filler is preferably 20 m ² / g or more, more preferably 500 m ² / g or more. If the specific surface area is too small, the volume resistivity of the conductive film becomes large, which is not preferable. Specific examples of carbon include furnace blacks such as conductive furnace black, super conductive furnace black, and extra conductive furnace black, conductive channel black, and acetylene black. Examples of commercially available conductive carbons include, for example, Continex CF (Conductive Carbon Black manufactured by Continental Carbon Co., Ltd.), Ketjen Black EC (Conductive furnace black manufactured by Ketjen Black International Co., Ltd.), and Vulcan C (Conductive Carbon Black manufactured by Kyabot). Furnace black),
BLACKPEARLS 2000 (Cabot's Conductive Furnace Black), Denka Acetylene Black (Denki Kagaku Kogyo's Acetylene Black) and the like are preferably used.

Further, the primary particle diameter of scale-like natural graphite, graphite fiber, carbon whiskers, etc. is 10
It is also possible to improve the conductivity by using in combination with a conductive optional component such as conductive particles having a particle size of not less than 20 nm, preferably not less than 20 nm and not more than 100 nm, preferably not more than 80 nm. Moreover, when using a conductive arbitrary component together, preferably 0.1 to 100 parts by weight of the elastomer component.
Add 5 parts by weight. Since the conductive optional component is easily oriented in the plane direction of the film, the problem that if mixed in a large amount, the conductive film obtained by casting the conductive paint containing the elastomer component and the conductive filler becomes electrically non-uniform There is.

(B) Conductive paint The paint for producing the conductive film for current collection of the present invention (hereinafter sometimes referred to as "conductive paint") includes the above-mentioned elastomer components (1) and (2). 100 parts by weight in total, 5 to 100 parts by weight of the conductive filler, and 100 to 100 parts by weight of a solvent for dissolving the elastomer component.
1000 parts by weight. Further, various additives, cross-linking agents and the like can be contained as necessary. The elastomer component is (1) 10 to 90% by weight, preferably 30 to 90% by weight of the hydrogenated product of the block copolymer.
70 parts by weight and (2) 90 to 10 parts by weight, preferably 70 to 30 parts by weight of the hydrogenated product of the above-mentioned random copolymer (however, the total of (1) and (2) is 100 parts by weight). ) And. If the hydrogenated product of the random copolymer is too small, the viscosity increase due to the temperature rise of the conductive coating cannot be prevented, and if it is too large, the strength of the conductive film decreases, which is not preferable.

(I) Solvent The solvent used in the conductive paint of the present invention may be any solvent capable of dissolving the elastomer component, and examples thereof include aromatic solvents such as toluene, benzene and xylene, ether solvents such as tetrahydrofuran, It is a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, and an organic solvent such as a chlorine-containing solvent.

(Ii) Additives To the conductive coating material of the present invention, if necessary, a compounding agent such as an antiaging agent may be added within a range that does not impair the effects of the present invention. However, it is not preferable to use a substance having a polar group such as a softening agent or a plasticizer that easily causes bleeding, or a tackifier that lowers the electrolytic solution resistance of the conductive film. When the strength of the obtained film is insufficient, a resin (plastic) can be added to reinforce it. The resin used is preferably one that is not easily eroded by an acidic electrolyte,
For example, olefin resins such as polyethylene and polypropylene, polystyrene and polyvinyl chloride,
Particularly, polyvinyl chloride excellent in acid resistance is preferable. The blending ratio is preferably 0.1 to 50 parts by weight, and more preferably 5 to 20 parts by weight with respect to 100 parts by weight of the elastomer component. If it is too small, the reinforcing effect will not be sufficient, and conversely,
If it is too large, the flexibility of the film will be insufficient.

In order to increase the strength of the conductive film, a cross-linking agent for the elastomer component is mixed in the conductive paint,
It may be crosslinked after film formation. The elastomer component can be crosslinked with sulfur, which is a general crosslinking agent for elastomers, sulfur donors, quinone crosslinking systems, organic peroxides, resin crosslinking systems, and the like. A cross-linking agent containing no metal such as zinc oxide is preferable because it is used as a current collector of an electric double-layer capacitor using as an electrolytic solution. Examples of compounds that can be crosslinked without using a metal compound include, for example, thiurams alone such as tetramethylthiuram disulfide and tetraoctylthiuram disulfide, or sulfenamides such as N-cyclohexylbenzothiazole sulfenamide (added Sulfurization accelerator), triazine thiol and benzothiazole combination system, benzoyl peroxide, hydroperoxide, dialkyl peroxide, peroxyketals and other organic peroxides alone system and trimethylolpropane trioxide Examples thereof include combinations with polyfunctional monomers (crosslinking aids) such as acrylate and triallyl cyanurate. The amount of the cross-linking agent is not particularly limited, but is usually 0.1 to 20 parts by weight, preferably 0.1 to 100 parts by weight of the elastomer component.
10 to 10 parts by weight.

(Iii) Preparation of Conductive Paint The conductive paint of the present invention is prepared by uniformly dispersing and dissolving a conductive filler and other additives in a solution in which an elastomer component is dissolved. The method is not particularly limited. For example, a method of adding an elastomer component, a conductive filler and other additives used as necessary to a solvent and uniformly dispersing and dissolving this with a known disperser such as a ball mill, an elastomer component and a conductive filler in advance and necessary A method of kneading the other additives to be added according to the above and dissolving and dispersing the kneaded product and the solvent using a known disperser such as a ball mill.

The solid content of the conductive coating material of the present invention is not particularly limited, but it is usually adjusted to 10 to 50% by weight, preferably 20 to 40% by weight before use. If the concentration is too low, a sufficiently thick film cannot be obtained when the conductive film is produced, while if the concentration is too high, the viscosity of the solution becomes too high and the film thickness is not uniform.

(C) Method for producing conductive film The conductive film of the present invention is coated with the above-mentioned conductive coating material of the present invention on a releasable substrate and dried, and then the produced film is releasable. Manufactured by peeling from the substrate,
It can be produced by a so-called solution casting method (casting method). A specific manufacturing method will be described below. First,
If necessary, lumps and undispersed substances in the conductive paint of the present invention are removed by a filter or the like. The filter to be used includes, but is not necessarily limited to, a thread-like fiber, a material obtained by weaving a metal or the like in a mesh pattern, or a material obtained by forming fine pores into a planar material. . Further, if necessary, defoaming is performed to remove bubbles contained in the paint. Examples of the defoaming method include, but are not limited to, a vacuum method and an ultrasonic method.

The conductive coating material includes a bar coater, a T-die, and a bar on a flat surface of a smooth releasable substrate such as polyethylene terephthalate, fluororesin, paper, metal, glass plate, polyester film, and polyvinyl chloride film. It is applied using a T-die, a doctor knife, a meer bar, a roll coater, a die coater or the like, or by spraying, brush printing, roll, spin coating, dipping or the like so as to have a uniform thickness. Further, when the desired film thickness cannot be obtained by one coating, the coating can be repeated. Then, it is usually dried at about 30 to 150 ° C to remove the solvent, and if necessary, at 130 to 180 ° C for 5 minutes.
Crosslinking is performed for about 180 minutes to form a film, and the film is peeled from the releasable substrate. By removing the solvent, the residual solvent concentration is usually 5% by weight or less, preferably 2% by weight or less, more preferably 1% by weight or less, and particularly preferably 0.5% by weight or less.

If the drying temperature is at or above the boiling point of the solvent, or near the boiling point, foaming may occur and the surface may become uneven, so the drying temperature should be determined according to the characteristics of the solvent.
A temperature lower than the boiling point of the solvent by 5 ° C. or more, preferably 10 ° C. or more may be used as a guide, and the drying is usually performed in the range of 30 to 100 ° C. It is also possible to dry again after peeling the film. When a cross-linking agent is added for cross-linking, the solvent is sufficiently removed, and then the temperature is usually 5 to 180 at 130 to 180 ° C.
Minutes, preferably about 10 to 120 minutes, to crosslink. If the cross-linking temperature is too high, the cross-linking agent may decompose before being sufficiently cross-linked, so the cross-linking temperature is also determined according to the properties of the cross-linking agent. Note that the timing of crosslinking does not necessarily have to be immediately after removing the solvent.

An electric double layer capacitor using an aqueous electrolytic solution using the conductive film of the present invention as described above,
It can be manufactured by the following procedure. It should be noted that the electric double layer capacitor is not limited to the basic cell which is the minimum constitutional unit, but one in which a plurality of basic cells are connected in series to increase the output voltage, one in which they are connected in parallel to increase the output current, and It may also include a power supply that is a combination of. The basic cell of an electric double layer capacitor has a separator inside a sealing frame made of non-conductive butyl rubber in which one of the bottoms is a conductive film for collecting electricity and the above-mentioned conductive film is sealed with co-crosslinking or an insulating adhesive. The solid polarizable electrode, and the open part of the sealing frame is sealed with a conductive film so as to be in close contact with one of the solid polarizable electrodes, and the metal electrode plate is thermocompression-bonded or conductively bonded to each conductive film. It can be manufactured by fixing with an agent or the like. The separator is
This is for preventing an electrical short circuit due to the contact of both solid polarizable electrodes, and for example, a non-woven fabric such as glass fiber, polypropylene fiber, polyethylene fiber, or a porous membrane is used.

As the solid polarizable electrode, a paste-like electrode obtained by mixing a fixed activated carbon having a high conductivity and not causing an electrochemical reaction with the electrolytic solution and the electrolytic solution is usually used. As the fixed activated carbon, for example, activated carbon obtained by immobilizing powdered activated carbon with a phenol-based or fluorine-based resin or the like is used. Activated carbon is preferably immobilized by a mechanical or physical method in order to maintain its shape. In addition, since the electrolytic solution is an acidic solution and is not volatile, the concentration is usually 25-
A sulfuric acid aqueous solution of about 50% by weight is used.

[0044]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. The volume resistivity of the conductive film was measured by using a volume resistivity in a direction perpendicular to the film surface of 20 mm × 20 mm, using a 3220 low resistance meter manufactured by Hioki Electric Co., Ltd. Further, parts and% in the following text are based on weight.

Examples 1 to 4 and Comparative Example 1 80 parts of hydrogenated polystyrene-polybutadiene-polystyrene block copolymer (SEBS) (Kreton G1650 manufactured by Shell Chemical Co., Ltd .: styrene content 29%),
Hydrogenated styrene-butadiene random copolymer (H-
SBR) (JR Earl Dynaron 1320
P: styrene content 10%) 20 parts and conductive carbon (Ketjenblack International Ketjenblack EC: specific surface area of about 800 m ² / g) 50
Parts to 500 parts of toluene and add 2 parts in a ball mill.
The mixture was dispersed and mixed for 24 hours while being cooled to 0 ° C. or lower to obtain a uniform slurry.

This slurry was filtered from a ball mill while naturally falling on a 100-mesh wire net to remove lumps and undispersed substances, and then defoamed using a vacuum defoaming machine to obtain a solid content of 31.1%. A conductive paint was obtained. This conductive coating material was applied onto a polyethylene terephthalate film (thickness: 38 μm) that had been subjected to a release treatment using a doctor blade, dried at 80 ° C. for 1 hour, and then peeled off to a thickness of 50 μm
A uniform conductive film of m was obtained. Similarly, SEBS
(Part) / HSBR (part) are 70/30 and 60 respectively
A conductive paint containing the amount of conductive carbon shown in Table 1 was prepared at / 40, 100/0 and 20/80, and a conductive film was prepared using these. The volume resistivity of each of the obtained films, the elongation at break and the tensile strength were measured by the method of JIS K6301. The viscosity increase of the conductive paint was measured by a B-type viscometer (rotor No. 3, rotation speed 2 rpm, temperature 23 ° C., measured value after 30 seconds) and the viscosity (η ₀ ) of the conductive paint immediately after the preparation. After heating the prepared conductive coating material at 40 ° C. for 30 minutes and then cooling it again to 20 ° C. or less, the viscosity (η) was measured, and (η−η ₀ ) / η ₀ was obtained to increase the viscosity. (The larger the value, the greater the viscosity increase.). The results of these measurements are shown in Table 1.

[0047]

According to the results shown in Table 1, a mixture of a hydrogenated product of a styrene-butadiene block copolymer and a hydrogenated product of a styrene-butadiene random copolymer was used as an elastomer component in toluene together with a conductive black. It can be seen that the paint prepared by mixing with the above composition does not increase in viscosity due to temperature increase. In addition, the conductive film formed by using this paint has a good balance between tensile strength and elongation (Examples 1 to 4). On the other hand, it can be seen that the paint using only the hydrogenated product of the styrene-butadiene block copolymer as the elastomer component has a significantly increased viscosity due to the temperature rise, and a film having a uniform film thickness cannot be obtained (Comparative Example 1). ).

[0049]

As described above, according to the present invention, an electric electrode which can be easily formed into a film by a casting method, has a low volume resistivity, is excellent in acid resistance, and is excellent in adhesion to a solid polarizable electrode and a metal electrode plate. A conductive film for collecting current of a multilayer capacitor is provided. Further, according to the present invention, there is provided a conductive paint for producing a conductive film for collecting current of an electric double layer capacitor, which has excellent dispersibility of a conductive filler and has viscosity stability.

[Brief description of drawings]

FIG. 1 is a schematic sectional view illustrating a basic configuration of an electric double layer capacitor.

[Explanation of symbols]

1: Basic cell 2: Polarizable electrode 3: Porous separator 4: Sealing frame 5: Current collector (conductive film for current collection) 6: Metal electrode plate

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 109/06 C09D 153/02 153/02 H01B 1/20 A H01B 1/20 B H01G 9/00 301F F Term (reference) 4J002 AC08X BC05X BP01W DA016 DA026 DA066 DE046 FA046 FD016 FD116 GH01 GQ02 4J038 CA041 CA042 CA101 CA102 CQ011 CQ012 KA12 NA04 NA20 NA25 5G301 DA18 DA42 DD02 DD08

Claims (3)

[Claims] 1. A conductive film for current collection used in an electric double layer capacitor, comprising an elastomer component and a conductive filler, wherein the elastomer component comprises (1) a block copolymer of an aromatic vinyl compound and a conjugated diene. 10 to 90 parts by weight of polymer hydrogenated product, and (2) hydrogenated product 90 of random copolymer of aromatic vinyl compound and conjugated diene
A conductive film for collecting current, which comprises 10 to 10 parts by weight (however, the total of (1) and (2) is 100 parts by weight). 2. A paint for producing a conductive film for collecting electricity for use in an electric double layer capacitor, wherein the paint comprises conductive solution dispersed in a solution of an elastomer component, wherein the elastomer component is ( 1) 10 to 90 parts by weight of a hydrogenated product of a block copolymer of an aromatic vinyl compound and a conjugated diene, and (2) 90 to 10 parts by weight of a hydrogenated product of a random copolymer of an aromatic vinyl compound and a conjugated diene. An electrically conductive coating material for producing an electrically conductive film for current collection, which comprises 100 parts by weight (however, the total of (1) and (2) is 100 parts by weight). 3. A conductive film for collecting electricity, which is formed by using the conductive paint according to claim 2.