JP2002164063A - Separator for solid polymer type fuel cell and its method of manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator suitable for a fuel cell (solid polymer type fuel cell in particular) and an industrially advantageously manufacturing method of the separator. SOLUTION: The separator for a solid polymer type fuel cell is prepared by molding using a resin molding method a resin composition containing a conductive agent and a radical polymerization thermosetting resin. The conductive agent may be a carbon powder. The radical polymerization thermosetting resin may be composed of a radical polymerization resin (vinyl ester type resin in particular) and a radical polymerization diluting agent. The double bond equivalent of the radical polymerization resin is about 200 to 1,000 and the glass transition temperature of a hardened product is preferably 120 deg.C or higher. The ratio (weight ratio) of the conductive agent to the radical polymerization thermosetting resin is about 55/45 to 95/5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin composition useful as a separator for a polymer electrolyte fuel cell, a separator formed from the resin composition, and a method for producing the separator.

[0002]

2. Description of the Related Art A polymer electrolyte fuel cell is a solid polymer fuel cell comprising an ion exchange membrane (ion conductive polymer membrane) such as perfluorocarbon sulfonic acid in which a sulfonic acid group is introduced into a fluorocarbon skeleton such as a polytetrafluoroethylene skeleton. A molecular electrolyte membrane, two electrodes disposed on both sides of the electrolyte membrane, and a separator provided with a gas supply groove for supplying a gas such as hydrogen or oxygen to each electrode,
And two current collectors disposed on both sides of these separators.

[0003] Among these constituent materials, the separator is required to have properties such as gas impermeability, low electrical resistance (conductivity), sulfuric acid resistance, and high mechanical strength. Therefore, conventionally, a method of using a plate made of titanium or graphite and forming the plate by machining such as cutting has been studied. However, this method lacks mass productivity,
Industrial implementation is difficult.

Japanese Patent Application Laid-Open No. H10-334927 discloses a solid prepared by molding a resin composition containing carbon powder and a thermosetting resin (phenol resin, polyimide resin, epoxy resin, furan resin, etc.) by a resin molding method. A separator for a polymer fuel cell is disclosed. However, phenolic resins used as thermosetting resins cure slowly and have low productivity. For example, the examples in this patent document require post-curing for 10 hours or more. In addition, with the curing of the phenol resin, gas such as water vapor is generated,
The cured product is warped and the gas impermeability is reduced.

Further, Japanese Patent Application Laid-Open No. 4-267062 discloses a gas separator for a fuel cell made of stainless steel or copper. However, although these metals have high industrial productivity, when they come into contact with hydrogen gas used as fuel for a long time, the materials deteriorate, so that the battery characteristics rapidly deteriorate.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a separator suitable for a fuel cell (particularly a polymer electrolyte fuel cell) and a method for producing the separator industrially advantageously.

Another object of the present invention is to provide a polymer electrolyte fuel cell separator exhibiting gas impermeability, low electric resistance, durability (particularly acid resistance such as sulfuric acid resistance) and high mechanical strength. It is an object of the present invention to provide a method for easily and efficiently obtaining a separator.

It is still another object of the present invention to provide a separator for a polymer electrolyte fuel cell having high dimensional accuracy and a method for obtaining the separator with high molding accuracy.

Another object of the present invention is to provide a resin composition suitable for the separator.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, the use of a conductive agent and a radical polymerizable thermosetting resin in combination has led to the demand for a separator. They have found that a fuel cell separator having both material properties and industrial productivity can be obtained, and have completed the present invention.

That is, the resin composition for a fuel cell separator of the present invention contains a conductive agent and a radical polymerizable thermosetting resin. The radical polymerizable thermosetting resin system may be at least composed of a radical polymerizable resin (particularly, a radical polymerizable resin and a radical polymerizable diluent). From the viewpoints of acid resistance (sulfuric acid resistance, etc.), mechanical properties and moldability, the radical polymerizable resin is a vinyl ester resin (particularly, a vinyl ester resin obtained by adding (meth) acrylic acid to a bisphenol epoxy resin). Is preferred. From the viewpoint of crosslinkability, the double bond equivalent of the radical polymerizable resin is 200 to 1000 (preferably 200 to 80).
0), and in view of the relationship with the operating temperature of the separator, the cured product of the radical polymerizable thermosetting resin is 120 ° C.
It is preferable to have the above glass transition temperature. The radical polymerization diluent is at least an aromatic vinyl compound (particularly,
Styrene). The ratio (weight ratio) of the conductive agent to the radically polymerizable thermosetting resin system is approximately 55/45 to 95/5: conductive agent / radical polymerizable thermosetting resin system. As the conductive agent, carbon powder is preferable. In particular, the resin composition includes a carbon powder, a radically polymerizable vinyl ester resin having a plurality of α, β-ethylenically unsaturated double bonds, and a single polymer having an α, β-ethylenically unsaturated double bond. And the ratio (weight ratio) of the vinyl ester resin and the monomer is 100/0 (former / latter).
20/80, the ratio (weight ratio) of the carbon powder to the total amount of the vinyl ester resin and the monomer.
However, the former / the latter may be 55/45 to 95/5. The resin composition may further contain a low-shrinking agent (particularly, a thermoplastic resin such as a styrene-based thermoplastic elastomer, a saturated polyester-based resin, or a vinyl acetate-based polymer). The ratio of the low shrinkage agent is about 0.1 to 30 parts by weight based on 100 parts by weight of the radical polymerizable thermosetting resin system.

The present invention also includes a separator for a polymer electrolyte fuel cell (such as a carbon separator) formed of the resin composition. This separator is excellent in gas impermeability and durability. Further, the resin composition is excellent in moldability. Therefore, the present invention also includes a method for producing the separator (such as a carbon separator) by molding the resin composition by a resin molding method. In the above method, the resin composition may be kneaded with a pressure kneader and molded.

In the specification of the present application, “radical polymerizable thermosetting resin system” means a resin composition composed of at least a radical polymerizable resin, and when a radical polymerizable diluent is used together with the resin. We use both meanings. Further, “radical polymerizable resin” means a polymer or oligomer compound having a radical unsaturated bond, and “radical polymerizable diluent” means a monomer having a radical unsaturated bond. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Conductive agent] As the conductive agent, various components such as carbon powder (conventional artificial graphite powder, expanded graphite powder, natural graphite) can be used as long as they mainly contribute to lowering the electrical resistance of the separator. Powder, coke powder, conductive carbon black, etc.), carbon fiber, metal powder and the like. These conductive agents can be used alone or in combination of two or more. Usually, a powdery conductive agent such as carbon powder is used. Because these conductive agents are filled at high density,
A powder whose particle size has been adjusted or a powder whose surface has been treated in advance can also be used.

The average particle size of the conductive agent (especially carbon powder) has a close relationship with the ratio of the radical polymerizable thermosetting resin system, and cannot be specified unconditionally.
m, preferably about 20 nm to 80 μm, and more preferably about 1 to 50 μm.

[Radical Polymerizable Thermosetting Resin System] The radical polymerizable thermosetting resin system is composed of at least a radical polymerizable resin, and may be composed of a radical polymerizable resin alone. As the radical polymerizable resin, a resin or an oligomer having an α, β-ethylenically unsaturated bond (polymerizable unsaturated bond), for example, a vinyl ester resin, an unsaturated polyester resin, a urethane (meth) acrylate, a polyester ( (Meth) acrylate and the like can be used. These radically polymerizable resins can be used alone or in combination of two or more. The radical polymerizable resin usually has a plurality of α, β-ethylenically unsaturated bonds.

(1) Vinyl Ester Resin A vinyl ester resin (epoxy (meth) acrylate or the like) is a product of a ring-opening addition reaction between an epoxy group and a carboxyl group of an α, β-ethylenically unsaturated compound. ,
An oligomer having an α, β-ethylenically unsaturated bond such as a (meth) acryloyl group at a terminal, for example, a compound having one or more functional epoxy groups in a molecule and a carboxyl group containing an unsaturated monobasic acid or the like. A reaction product with an ethylenically unsaturated compound can be exemplified.

The compound having one or more functional epoxy groups in the molecule includes an epoxy resin and a compound having an epoxy group and a (meth) acryloyl group in the molecule.

Examples of the epoxy resin include a glycidyl ether type epoxy resin, a glycidyl ester type epoxy resin, an alicyclic epoxy resin in which a double bond of a cycloalkene ring such as a cyclohexene ring is epoxidized, a glycidylamine type epoxy resin, and a copolymer. An example is a type epoxy resin.

As the glycidyl ether type epoxy resin, bisphenol type epoxy resins [for example, bisphenol A type, bisphenol F type, bisphenol AD]
(Hydroxyphenyl) C _1-10 such as epoxy resin
Epoxy resin with alkane skeleton, bisphenol S
Epoxy resin, etc.], novolak epoxy resin (for example, phenol novolak type, cresol novolak type epoxy resin, etc.), aliphatic epoxy resin (for example, hydrogenated bisphenol A type epoxy resin, propylene glycol mono to diglycidyl ether, pentane Erythritol mono to tetraglycidyl ether, etc.), monocyclic epoxy resin (for example, resorcing ricidyl ether), heterocyclic epoxy resin (for example, triglycidyl isocyanurate having a triazine ring, hydantoin type epoxy resin having a hydantoin ring, etc.) And tetrakis (glycidyloxyphenyl) ethane.

Examples of the glycidyl ester type epoxy resin include glycidyl esters of carboxylic acids (particularly, polycarboxylic acids) such as diglycidyl phthalate, diglycidyl terephthalate, dimethyl glycidyl phthalate, diglycidyl tetrahydrophthalate, and diglycidyl hexahydrophthalate. Can be illustrated.

Examples of the alicyclic epoxy resin include alicyclic diepoxy acetal, alicyclic diepoxy adipate, alicyclic diepoxycarboxylate, vinylcyclopentadiene dioxide, and vinylcyclohexene mono to dioxide. .

Glycidylamine type epoxy resins include reaction products of amines (particularly polyamines) with epichlorohydrin, for example, tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol,
Examples thereof include diglycidylaniline and diglycidyltoluidine.

As the copolymerizable epoxy resin, for example,
Examples thereof include a copolymer having a bisphenol A skeleton and a bisphenol F skeleton.

These epoxy resins may be halogenated epoxy resins having a halogen atom (bromine, chlorine, etc.), if necessary. As a commercially available epoxy resin, for example, JP-A-9-110948 can be referred to.

The preferred range of the epoxy equivalent of the epoxy resin varies depending on the particle size of the conductive agent such as carbon powder, and is not particularly limited, but is 50 to 5000 g / eq, preferably 100 to 1000 g / eq, more preferably 150 to 1000 g / eq. 500 g / eq (especially 170 to 250 g / e
q).

Compounds having an epoxy group and a (meth) acryloyl group in the molecule include C _1-4 alkyl glycidyl (meth) acrylates such as glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate.
Examples thereof include (meth) acryloyloxy C _4-6 alkenylene oxide such as 4- (meth) acryloyloxymethylcyclohexene oxide.

Among these epoxy group-containing compounds, a glycidyl ether type epoxy resin, an epoxy resin having a saturated or unsaturated hydrocarbon ring or a heterocyclic ring, particularly a bisphenol type epoxy resin is preferred. Bisphenol type epoxy resin (bisphenol A type epoxy resin, etc.)
Is low in viscosity, so that the ratio of the conductive agent can be increased, and is also preferable from the viewpoint of acid resistance (sulfuric acid resistance). Also,
When a bisphenol-type epoxy resin is used, the moldability of the resin composition can be improved from the above properties, and the mechanical strength of the molded article can be improved.

Examples of the carboxyl group-containing ethylenically unsaturated compound such as an unsaturated monobasic acid include unsaturated monocarboxylic acids such as (meth) acrylic acid, crotonic acid, and cinnamic acid, and polybasic acid anhydrides. And a reaction product with a compound having a (meth) acryloyl group and an active hydrogen atom (such as a hydroxyl group).

Examples of the polybasic anhydrides include aliphatic dicarboxylic anhydrides such as maleic anhydride and succinic anhydride, and aromatic dicarboxylic anhydrides such as phthalic anhydride, tetrahydrophthalic anhydride and hexahydrophthalic anhydride. Can be Examples of the compound having a (meth) acryloyl group and an active hydrogen atom include monohydroxy compounds [for example, hydroxy C _2-6 alkyl such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and the like. Methacrylate), and a reaction product of (meth) acrylic acid and a polyhydric alcohol [trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate, glycerin di (meth) acrylate, etc.].

Of these carboxyl group-containing ethylenically unsaturated compounds, unsaturated monocarboxylic acids, particularly (meth) acrylic acid, are preferred.

The ratio (molar ratio) of the carboxyl group-containing ethylenically unsaturated compound to the epoxy compound is as follows: carboxyl group / epoxy group = 0.8 / 1 to 1.2 / 1, preferably 0.9 / 1 to 1/1. It is about 1/1.

The ring-opening addition reaction between the epoxy group and the carboxyl group can be carried out under conventional conditions. For example, tertiary amines such as trialkylamine and dimethylbenzylamine, and phosphines such as triphenylphosphine can be used. At a reaction temperature of about 80 to 150 ° C.,
The reaction may be performed for about 10 hours.

When it is necessary to increase the viscosity at the time of molding the resin, a polycarboxylic anhydride is added to the hydroxyl group generated by the reaction between the epoxy group and the carboxyl group to form a carboxyl group. A vinyl ester resin capable of thickening with alkali may be used.

(2) Unsaturated polyester resin As the unsaturated polyester resin, a reaction product of an unsaturated polybasic acid, a polyol and, if necessary, a saturated polybasic acid can be used. As the polybasic acid, a dicarboxylic acid or a reactive derivative thereof is usually used.

Examples of unsaturated polybasic acids include C _4-6 aliphatic unsaturated polybasic acids such as maleic anhydride, fumaric acid, maleic acid and itaconic acid, and anhydrides thereof.

The saturated polybasic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid,
C _2-10 aliphatic saturated polybasic acids such as sebacic acid; C _8-12 aromatic polybasic acids such as isophthalic acid, terephthalic acid, phthalic acid, phthalic anhydride, tetrachlorophthalic anhydride, trimellitic acid, and pyromellitic acid polybasic acid or its anhydride; 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, HET acid (chlorendic acid), C _8-10 alicyclic polybasic acids or anhydrides thereof such as anhydride familiar acid can be exemplified .

The proportion of the unsaturated polybasic acid in the polybasic acid is, for example, about 25 to 100 mol%, preferably about 30 to 100 mol%, and more preferably about 50 to 100 mol%.

As the polyol, C _2-12 alkylene glycol (eg, ethylene glycol, propylene glycol, butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-
Hexanediol, neopentyl glycol, etc.), polyoxy _C2-4 alkylene glycol (eg, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, etc.), aromatic diols (eg, bisphenol A, bisphenol A)
—C _2-4 alkylene oxide adduct) and the like.

The esterification reaction is carried out by a conventional method, for example,
The reaction can be carried out in an inert gas atmosphere in the presence of an esterification catalyst at normal pressure or reduced pressure at a temperature of about 70 to 120 ° C. while removing water generated from the reaction system.

Ratio (molar ratio) between polybasic acid and polyol
Is a ratio such that the carboxyl group of the polybasic acid / the hydroxyl group of the polyol = 0.7 / 1 to 1.3 / 1, preferably about 0.8 / 1 to 1.2 / 1.

(3) Urethane (meth) acrylate As the urethane (meth) acrylate, a reaction product of a polyurethane oligomer having an isocyanate group at a terminal and the above-mentioned hydroxy C _2-6 alkyl (meth) acrylate can be used.

As the polyurethane oligomer, a conventional polyurethane oligomer using an excess amount of a diisocyanate component with respect to the diol component can be used. For example, diisocyanate components (such as aromatic diisocyanates such as tolylene diisocyanate and diphenylmethane diisocyanate, xylylene diisocyanate, Aromatic diisocyanates such as tetramethylxylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate, and diol components (C _2-12 alkylene glycol, polyoxy C _2-4 alkylene glycol) Reaction products with polyether diols, polyester diols, polycarbonate diols, etc.).

The ratio (molar ratio) of hydroxyl groups to isocyanate groups in the urethane oligomer is such that hydroxyl groups / isocyanate groups = 0.7 / 1 to 1.2 / 1, preferably 0.8 / 1 to 1.1 / 1. And more preferably about 0.9 / 1 to 1/1.

The urethanization reaction is carried out by a conventional method, for example,
The reaction is performed at a temperature of about 50 to 100 ° C. in an inert gas atmosphere in the presence of a catalyst.

(4) Polyester (meth) acrylate As the polyester (meth) acrylate, a polyester oligomer having a hydroxyl group or a carboxyl group at the terminal, the (meth) acrylic acid or the hydroxy C _2-6 alkyl (meth) acrylate, Reaction products with glycidyl (meth) acrylate can be used.

The polyester oligomer may be linear or may be branched by using a polyhydric alcohol (for example, glycerin) in addition to the constituent monomers of the unsaturated polyester. The polyester oligomer can be obtained by adjusting the ratio of a polybasic acid (particularly a saturated polybasic acid) and a polyol, and performing the same esterification reaction as described above.

(Meth) acrylic acid or hydroxy C _2-6
The amount of the alkyl (meth) acrylate or glycidyl (meth) acrylate used is 0.8 to 1 mol of the hydroxyl group or carboxyl group of the polyester oligomer.
To 1.2 mol, preferably about 0.9 to 1.2 mol.

Among these radically polymerizable resins, vinyl ester resins, particularly bisphenol type epoxy resins, are preferred because they have high acid resistance (sulfuric acid resistance, etc.) and mechanical properties and are excellent in molding fluidity. The reaction product with acrylic acid is preferred.

The double bond equivalent in the radical polymerizable resin is
It is about 200 to 1000, preferably about 200 to 800, and more preferably about 200 to 650. If the double bond equivalent is too small, a cured product having a very high crosslinking density is generated,
Fragile and difficult to use industrially. Conversely, if the double bond equivalent is too large, sufficient crosslinking cannot be obtained, and it becomes difficult to obtain sufficient heat resistance, mechanical properties, and the like.

Incidentally, vinyl ester resin, unsaturated polyester resin, polyurethane (meth) acrylate,
The acid value of the radical polymerizable resin such as polyester (meth) acrylate is about 0.1 to 5 mgKOH / g, preferably about 0.5 to 3 mgKOH / g.

(Radical Polymerizable Diluent) The radical polymerizable resin has at least one double bond (particularly, α, β-ethylenically unsaturated bond) in the molecule for lowering the viscosity and adjusting the crosslink density. It is preferable to dilute with a reactive diluent having the formula (radical polymerizable diluent).

As the radical polymerizable diluent, (meth)
Unsaturated carboxylic acids such as acrylic acid, crotonic acid and cinnamic acid; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2- (meth) acrylate Ethylhexyl,
Unsaturated carboxylic acid C such as dodecyl (meth) acrylate
_1-12 alkyl ester; unsaturated carboxylic acid glycidyl ester such as glycidyl (meth) acrylate; (meth)
Unsaturated carboxylic acid hydroxy C _2-8 alkyl ester such as 2-hydroxyethyl acrylate; nitrogen-containing monomer such as (meth) acrylamide, (meth) acrylonitrile, vinylpyrrolidone; styrene, vinyltoluene, divinylbenzene, p- aromatic vinyl compounds such as t-butylstyrene; ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate,
C _2-8 alkylene glycol unsaturated carboxylate such as 1,6-hexanediol di (meth) acrylate; polyoxyalkylene glycol unsaturated carboxylate such as diethylene glycol di (meth) acrylate; trimethylolpropane tri (meth) Examples thereof include polyfunctional (meth) acrylates such as acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol tetra (meth) acrylate. Among these diluents, an aromatic vinyl compound, particularly styrene, is preferable from the viewpoint of moldability and economy. These diluents can be used alone or in combination of two or more.

The aromatic vinyl compound (especially styrene) is
Compared to (meth) acrylic monomers (diluents), it has higher copolymerizability with radically polymerizable resins (such as vinyl ester resins) and can improve the physical properties (mechanical strength, etc.) of molded products, Since the efficiency (decrease in viscosity) is high, moldability can be improved even in a small amount. Further, the aromatic vinyl compound has higher chemical resistance than other diluents (for example, an acrylic diluent). Therefore, the radical polymerizable diluent preferably contains at least an aromatic vinyl compound (particularly, styrene).

The ratio (weight ratio) of the radical polymerizable resin to the radical polymerizable diluent is usually
Radical polymerizable diluent can be selected from the range of about 100/0 to 20/80, and is 95/5 to 20/80, preferably 90/10 to 40/60, and more preferably 90/10.
About 55/45. In order to achieve higher heat resistance, it is advantageous to reduce the ratio of the diluent.

The ratio (weight ratio) of the conductive agent to the radical polymerizable thermosetting resin system is as follows: conductive agent / radical polymerizable thermosetting resin system = 55/45 to 95/5, preferably 60/40.
９５95/5, more preferably about 65/35 to 92/8. If the proportion of the conductive agent is too small, the conductivity is not improved, and if the proportion of the conductive agent is too large, the molding fluidity becomes insufficient and molding becomes difficult.

The ratio (weight ratio) of the conductive agent to the radical polymerizable resin is expressed as follows: conductive agent / radical polymerizable resin = 55 /
It is about 45-95 / 5, preferably about 60 / 40-95 / 5, and more preferably about 65 / 35-95 / 5.

[Low Shrinkage Agent] The resin composition of the present invention preferably contains a low shrinkage agent in order to reduce warpage and curing shrinkage of the molded article and improve dimensional accuracy. In general, a radical polymerizable thermosetting resin shrinks during polymerization molding, and is likely to have irregularities and warpages, often resulting in reduced dimensional accuracy. Even in such a case, the dimensional accuracy of the molded article can be improved by the low shrinkage agent.

As the low-shrinking agent, non-polymerizable resins, for example, polyester resins (for example, saturated aromatic polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyethylene adipate, polybutylene adipate, polybutylene sebacate, etc.) Saturated aliphatic polyester-based resins, copolymerized saturated polyester-based resins having polyoxyethylene units, etc.), acrylic resins [for example, (meth) such as polymethyl methacrylate and the like]
Homo- or copolymers containing acrylic acid C _1-10 alkyl ester as a monomer component], vinyl acetate polymers (eg, polyvinyl acetate, ethylene-vinyl acetate copolymer, etc.), styrene resins [eg, Homo- or copolymers of styrene monomers such as polystyrene, styrene
(Meth) acrylic acid block copolymer, styrene- (meth) acrylic acid ester block copolymer, styrene-
A copolymer of styrene and a copolymerizable monomer such as a vinyl acetate block copolymer, crosslinked polystyrene and the like], a polyolefin resin [eg, polyethylene, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic Acid ester copolymers, etc.], and thermoplastic elastomers (eg, styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and the like). it can. Among these low-shrinkage agents, styrene-based thermoplastic elastomers [for example, styrene-diene-based copolymer (for example,
Styrene-butadiene block copolymer, styrene-isoprene block copolymer or hydrogenated product thereof))],
Saturated polyester resins and vinyl acetate polymers (for example, polyvinyl acetate) are preferred.

These low-shrinking agents can be used alone or in combination of two or more. The ratio of these low-shrinkage agents is 0.1 to 30 parts by weight, preferably 0.5 to 25 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the radical polymerizable thermosetting resin system. Parts. If the proportion of the low shrinkage agent is too small, the dimensional accuracy tends to decrease, and if it is too large, physical properties such as heat resistance deteriorate.

The number-average molecular weight of the low-shrinking agent can be selected according to the type of the thermosetting resin, and is not particularly limited, but is usually 1000 to 10 × 10 ⁵ , preferably 2000 to ⁵ × 10 ⁵ .
× 10 ⁵ , more preferably about 3000 to 2 × 10 ⁵ .

When molded with a resin composition containing a low-shrinking agent, the shrinkage of the molded article can be reduced to 0.15% or less, preferably 0.1% or less, more preferably 0.05% or less. Accuracy can be improved.

A rubber component may be added to the radical polymerizable thermosetting resin system in order to improve physical properties of the separator as a cured product, for example, toughness and impact resistance. As the rubber component, a liquid rubber or a modified product thereof [for example, acrylonitrile butadiene rubber having a carboxyl group terminal (NB)
R), epoxy terminal NBR, vinyl terminal NBR
Etc.], and particulate rubber (for example, crosslinked acrylic fine particles). The amount of the rubber component is usually 1 to 100 parts by weight of the radical polymerizable thermosetting resin system.
It is about 30 parts by weight.

[Curing Agent and Curing Accelerator] To the resin composition of the present invention, a conventional curing agent used for curing a radical polymerizable thermosetting resin system and, if necessary, a conventional curing accelerator are added. By doing so, it can be easily cured.

As the curing agent, an organic peroxide, for example,
Aliphatic peroxide (methyl ethyl ketone peroxide, t
-Butyl peroxy 2-ethylhexanoate, di-t-
Butyl peroxide, lauroyl peroxide, etc.), aromatic peroxides (benzoyl peroxide, dicumyl peroxide, cumene hydroperoxide, t-butyl peroxybenzoate, etc.), alicyclic peroxides (cyclohexanone peroxide, etc.) ) Can be exemplified. The ratio of the curing agent is about 0.1 to 5 parts by weight, preferably about 0.5 to 3 parts by weight, and more preferably about 1 to 3 parts by weight, based on 100 parts by weight of the radical polymerizable thermosetting resin system. .

Examples of the curing accelerator include metal salts (such as transition metal salts such as cobalt naphthenate and cobalt octoate);
Examples include amines (tertiary amines such as dimethylaniline and diethylaniline), acetylacetone and the like.
The ratio of the curing accelerator is the radical polymerizable thermosetting resin system 1
The amount is about 0.01 to 3 parts by weight, preferably about 0.05 to 2 parts by weight, and more preferably about 0.1 to 2 parts by weight, based on 00 parts by weight.

[Other Additives] The resin composition of the present invention comprises
If necessary, filler (aluminum hydroxide, glass powder, calcium carbonate, talc, silica, clay, glass balloon, etc.), polymerization inhibitor (hydroquinone, t-butylcatechol, etc.), fiber reinforcing agent (glass fiber, carbon Fibers, etc.), release agents (metal soaps such as calcium stearate and zinc stearate, silicone or fluorine-based organic compounds, phosphoric acid compounds, etc.), thickeners (oxides or hydroxides such as magnesium, calcium, etc.) And other conventional additives.

[Glass Transition Temperature of Cured Product] A radical polymerizable thermosetting resin system composed of at least a radical polymerizable resin (that is, a radical polymerizable resin alone, a radical polymerizable resin and a radical polymerizable diluent) The glass transition temperature of the cured product of the cured resin composition) is preferably 120 ° C. or higher (particularly about 140 to 200 ° C.). The upper limit temperature of the polymer electrolyte fuel cell used may exceed 100 ° C., and it is preferable that the separator be glassy and maintain sufficient elasticity up to around this temperature.

[Molding Method and Use of Resin Composition] The resin composition of the present invention has high fluidity and moldability, and can be molded by a conventional resin molding method. Examples of the resin molding method include conventional molding methods such as casting, compression molding, and injection molding. More specifically, a molded article can be obtained by injecting the resin composition into a predetermined mold and applying heat and pressure. In particular, by utilizing the radical reaction,
The generation of warpage can be suppressed, and a uniform molded body can be obtained within a short time. Furthermore, since it can be molded by a resin molding method, a groove as a gas flow path can be formed accurately without cutting. In addition, in order to obtain a homogeneous molded body, the resin composition can be degassed or degassed.

When the resin composition is kneaded with an ordinary kneader, a powdery or coarse-grained compound may be formed. On the other hand, when the resin composition is kneaded with a pressure-type kneader, a viscous or clay-like homogeneous compound can be obtained. In particular, a compound having a uniform composition and excellent fluidity can be produced even when the conductive agent is filled at a high concentration. Therefore, when the compound is molded by using a pressurized kneader, a molded body having no irregularities on its surface, having a smooth surface, having an excellent appearance, and having no defects such as voids is obtained. The mechanical properties can also be improved.

In the pressure kneader, the pressure is not particularly limited as long as a homogeneous compound can be obtained.
10 kgf / cm ² (9.8 × 10 ^{3 to} 9.8 × 10 ⁵ P
a), preferably 0.3 to 8 kgf / cm ² , more preferably 0.5 to 8 kgf / cm ² (particularly 1 to 8 kgf / cm ² )
/ Cm ² ).

Examples of the shape of the blade of the pressurized kneader include a Banbury type, a sigma blade, a simplex (single curve) and the like. Of these shapes, Banbury-type blades are preferred. The rotation speed of the blade is not particularly limited, but is about 5 to 150 rpm, preferably about 10 to 120 rpm. The temperature for kneading is not particularly limited, but is from room temperature to 100 ° C, preferably from room temperature to
It is about 80 ° C. (for example, room temperature to 50 ° C.). The kneading can be performed in an appropriate atmosphere, and can be usually performed in the air. In addition, kneading is usually performed under light shielding.

In the present invention, a clay-like or viscous compound can be obtained by kneading the resin composition with a pressure kneader. The viscosity of this compound (according to a Helipath viscometer) is 10 ² to 10 ^{6 at} 25 ° C.
Pa · s, preferably about 10 ³ to 10 ⁶ Pa · s, and more preferably about 10 ³ to 10 ⁵ Pa · s. It should be noted that kneading with a pressure kneader can improve the mechanical strength and thermal conductivity of the resin composition. In particular, even when a non-conductive substance (for example, a low-shrinking agent, etc.) is added, the Degree can be improved, and a molded article without defects can be obtained.

The cured product of the resin composition of the present invention exhibits gas impermeability, low electric resistance, acid resistance (sulfuric acid resistance) and high mechanical strength, and can be easily molded by a resin molding method. Although it can be used for various applications such as electronic parts, it is useful as a fuel cell, particularly as a separator for a polymer electrolyte fuel cell having a polymer electrolyte membrane.

This separator is usually in the form of a flat plate, and is formed with a groove as a gas passage for supplying hydrogen gas or oxidizing gas (oxygen-containing gas such as oxygen).
The thickness of the separator is 1 to 10 mm (particularly 2 to 5 m
m), and one or more grooves may be formed in the separator.

[0076]

According to the present invention, a cured molded article formed from the resin composition of the present invention can be filled with a conductive agent at a high ratio, so that it exhibits high conductivity, high mechanical strength, low gas permeability, and durability. High resistance (especially acid resistance such as sulfuric acid resistance) and dimensional accuracy. Furthermore, since the resin composition of the present invention can be molded by a resin molding method and is a compound having excellent fluidity, it has excellent moldability. Therefore, the resin composition of the present invention is suitable as a separator material for a fuel cell, particularly for a polymer electrolyte fuel cell.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments will be described below to facilitate understanding of the present invention, but the present invention is not limited to these embodiments.

Example 1 In a four-neck flask equipped with a stirrer, a condenser, a nitrogen gas introducing device and a thermometer, 374 g of bisphenol A type epoxy resin (Epototo YD128, manufactured by Toto Kasei Co., Ltd., epoxy equivalent 187 g / eq), Methacrylic acid 172
g, triphenylphosphine 0.2 g, and hydroquinone 0.1 g as a thermal polymerization inhibitor were charged and reacted at 120 ° C. for 8 hours to obtain 546 g of a vinyl ester resin having an acid value of 1.8 mgKOH / g. This vinyl ester resin was diluted with 364 g of a styrene monomer to obtain a resin composition.

180 g of this resin composition and artificial graphite powder (SGL25, manufactured by SSC Corporation, average particle size 25 μm)
m) 450 g, artificial graphite powder (manufactured by SCE Corporation,
SGB20, average particle size 20 μm) 850 g, t-butyl peroxybenzoate (manufactured by NOF CORPORATION, TBP
B) After kneading 3.6 g well and degassing, 300 × 30
50 kg / cm ² (4.9 × 10 ^{6) in} a flat mold of 0 × 8 mm
Pa) at 150 ° C. for 2 minutes to form a flat plate.

Example 2 Using 280 g of the resin composition obtained in Example 1 and 1100 g of artificial graphite powder (SGB20), a flat plate was formed in the same manner as in Example 1.

Example 3 450 g of the resin composition obtained in Example 1, 500 g of artificial graphite powder (SGL) and 20 g of artificial graphite powder (SGB)
Using 0 g, a flat plate was formed in the same manner as in Example 1.

Incidentally, 1.5 g of t-butyl peroxybenzoate (manufactured by NOF Corporation, TBPB) was added to 100 g of the used vinyl ester resin composition, and the glass transition temperature of the cured product was 160 ° C. Was.

The following physical property evaluation was performed on the flat plates obtained in Examples 1 to 3. Table 1 shows the results.

(Electrical Resistance) The electric resistance was measured according to JIS R 7202.

(Bending strength) Three-point bending method JIS K7
203.

(Gas Permeability) The gas permeability is measured using nitrogen gas and is expressed by the following equation.

Nitrogen gas permeability = Nitrogen gas permeation rate / test specimen thickness / time / cross-sectional area / differential pressure (unit: cm ² / sec · atm).

(Sulfuric acid resistance) The appearance evaluation after immersion in 50% by weight sulfuric acid at 50 ° C. for one month was evaluated according to the following criteria.

：: No change in appearance is visually observed. ×: Change in appearance is visually observed.

[0090]

[Table 1]

From the results shown in Table 1, the flat plate molded with the resin composition of the present invention has low electric resistance, high bending strength,
Low gas permeability and excellent sulfuric acid resistance.

Example 4 280 g of the resin composition obtained in Example 1 and artificial graphite powder (SGL10, manufactured by SSC Corporation, average particle size 10 μm)
m) 330 g, artificial graphite powder (manufactured by SCE Corporation,
SGL25, average particle size 25 μm) 770 g, t-butyl peroxybenzoate (manufactured by NOF CORPORATION, TBP
B) 5.6 g was kneaded with an ordinary kneader, and a flat plate was formed in the same manner as in Example 1. The kneaded compound was coarse.

Example 5 224 g of the resin composition obtained in Example 1 and a styrene-butadiene block copolymer (D-KX410CS, Sh
el JSR Elastomer Co., Ltd.) 28
g, artificial graphite powder (manufactured by SCE Corporation, SGL1)
0, average particle diameter 10 μm) 330 g, artificial graphite powder (manufactured by SCE Corporation, SGL25, average particle diameter 25 μm) 7
70 g and 5.6 g of t-butyl peroxybenzoate (manufactured by NOF CORPORATION, TBPB) were kneaded with a usual kneader, and a flat plate was formed in the same manner as in Example 1. The kneaded compound was coarse.

Example 6 As a kneader, a pressurized kneader (manufactured by Moriyama Co., Ltd., D
0.5-3) and 3.92 × 10 ⁵ Pa (4 kg)
A flat plate was formed in the same manner as in Example 5 except that kneading was performed at 40 ° C. and 50 rpm under a pressure of f / cm ² ). The kneaded compound was clay-like.

Example 7 A flat plate was formed in the same manner as in Example 6, except that a saturated polyester resin (manufactured by Toyobo Co., Byron 330) was used instead of the styrene-butadiene copolymer. In addition,
The kneaded compound was clay-like.

The electric resistance, bending strength and sulfuric acid resistance of the flat plates obtained in Examples 4 to 7 were measured.
Thermal conductivity, shrinkage, and warpage were measured by the following methods. Table 2 shows the results.

(Thermal conductivity) 50 mm × 50 mm × 10 m
m at a temperature of 23 ° C. by a hot disk method (surface heating source method) (a method of determining the thermal conductivity by relative comparison based on the international standard substance of NIST, USA).
The measurement was performed using a thermophysical property measuring device (TPA-501 type, manufactured by Kyoto Electronics Industry Co., Ltd.) The measurement was repeated three times and indicated as an average value.

(Shrinkage ratio) 300 mm × 300 mm × 5 m
The linear shrinkage was measured for the m plate.

(Warp) 300 mm × 300 mm × 1 mm
Was kept at 23 ° C. × 50% RH for 1 day. The thickness error of each flat plate was 0.1 mm or less. Each flat plate was placed on a horizontal glass plate, and the distance (m) between the four corners (ends) and the glass plate starting from the center of a 300 mm square.
m) was measured and expressed as an average value.

[0100]

[Table 2]

As is apparent from the results shown in Table 2, shrinkage and warpage of the flat plate can be suppressed by adding a low-shrinking agent. Also, when kneaded with a pressure kneader, it is possible to obtain a molded product having high bending strength and thermal conductivity and small shrinkage and warpage.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 53/02 C08L 53/02 63/10 63/10 67/00 67/00 H01M 8/10 H01M 8 / 10 // B29K 63:00 B29K 63:00 71:00 71:00 105: 06 105: 06 307: 04 307: 04 F term (reference) 4F201 AA13E AA18 AA20E AA24 AA32 AA45 AB04 AB13 AB18 AH81 AR02 BA01 BC01 BC12 BC37 BK01 BK26 4J002 AA021 BB032 BB072 BB082 BC032 BC042 BF022 BF032 BG042 BG052 BP002 BP012 CD201 CF032 CF062 CF072 CF102 CF211 CF271 CK021 AB016 DA026 DA036 DA066 FA046 FA016 FD010 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 FD116 AB25 AE02 AE03 AE04 AE05 AG02 AG03 AG04 AG23 AG24 AG27 AJ04 BA05 BA06 BA07 BA08 BA09 BA13 BA14 BA15 BA19 BA20 BA24 BA26 BA27 CA02 CA03 CA04 CA05 CA06 CA12 CA33 CB03 CC02 CD00 5H026 AA02 AA06 BB02 BB10 EE05 EE18 HH00 HH08 HH09

Claims (19)

[Claims] 1. A resin composition for a fuel cell separator comprising a conductive agent and a radical polymerizable thermosetting resin system. 2. The resin composition according to claim 1, wherein the radical-polymerizable thermosetting resin system comprises at least a radical-polymerizable resin. 3. The resin composition according to claim 1, wherein the radical-polymerizable thermosetting resin system comprises a radical-polymerizable resin and a radical-polymerizable diluent. 4. The resin composition according to claim 2, wherein the radical polymerizable resin is a vinyl ester resin. 5. The resin composition according to claim 2, wherein the radical polymerizable resin is a vinyl ester resin obtained by adding (meth) acrylic acid to a bisphenol type epoxy resin. 6. The radical polymerizable resin having a double bond equivalent of 2
The resin composition according to claim 2, wherein the number is from 00 to 1,000. 7. The resin composition according to claim 1, wherein the cured product of the radical polymerizable thermosetting resin has a glass transition temperature of 120 ° C. or higher. 8. The resin composition according to claim 3, wherein the radical polymerizable diluent contains at least an aromatic vinyl compound. 9. The composition according to claim 1, wherein the ratio (weight ratio) of the conductive agent to the radically polymerizable thermosetting resin system is 55/45 to 95/5. Resin composition. 10. The resin composition according to claim 1, wherein the conductive agent comprises carbon powder. 11. A carbon powder, a radically polymerizable vinyl ester resin having a plurality of α, β-ethylenically unsaturated double bonds, and a monomer having an α, β-ethylenically unsaturated double bond. Wherein the ratio (weight ratio) of the vinyl ester resin and the monomer is 100/0 to former / latter.
20/80, and the ratio (weight ratio) of the carbon powder to the total amount of the vinyl ester resin and the monomer is:
The resin composition according to claim 1, wherein the former / the latter is 55/45 to 95/5. 12. A double-walled vinyl ester resin comprising carbon powder, a vinyl ester resin obtained by adding (meth) acrylic acid to a bisphenol-type epoxy resin, and a radical polymerizable diluent containing at least styrene. The resin composition according to claim 1, wherein the binding equivalent is 200 to 800. 13. The resin composition according to claim 1, further comprising a low-shrinking agent. 14. The resin composition according to claim 13, wherein the low-shrinking agent is at least one selected from the group consisting of a styrene-based thermoplastic elastomer, a saturated polyester-based resin, and a vinyl acetate-based polymer. 15. The resin composition according to claim 13, wherein the proportion of the low-shrinkage agent is 0.1 to 30 parts by weight based on 100 parts by weight of the radical polymerizable thermosetting resin. 16. A separator for a polymer electrolyte fuel cell formed from the resin composition according to claim 1. 17. A method for producing the separator according to claim 16, wherein the resin composition according to claim 1 is molded by a resin molding method. 18. The method according to claim 17, wherein the resin composition according to claim 1 is kneaded and molded by a pressure kneader. 19. The pressure in the pressurized kneader is 9.8.
The method according to claim 18, wherein the pressure is from × 10 ^{3 to} 9.8 × 10 ⁵ Pa.