Sealing agent for fuel cell and fuel cell using the same

Abstract

To provide a sealing agent for a fuel cell excellent in low contamination property, and a fuel cell having the sealing agent.SOLUTION: The sealing agent for the fuel cell contains (A) a photopolymerization initiator having at least one ethylenic unsaturated group in a molecule and (B) a curable compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sealing agent for a fuel cell and a fuel cell using the same. [Background technology]

[0002] Fuel cells are power generation systems that use hydrogen obtained by reforming gasoline or natural gas as fuel, and extract the energy generated when the hydrogen reacts with oxygen as electricity. Polymer electrolyte fuel cells, a type of fuel cell, use an ion exchange membrane as the electrolyte, and because the electrolyte is thin and has a high current density, they can be made small and lightweight, and development is underway for use as a power source for homes and automobiles.

[0003] In fuel cells, sealants with high barrier properties and high adhesiveness are required to prevent leakage of reaction gases and coolant and to hold the power generation section, and have been developed (Patent Document 1).

[0004] Furthermore, in solid polymer fuel cells, in order to improve productivity, it is required to bond the polymer electrolyte membrane (a perfluorocarbon material having sulfonic acid groups, such as Nafion manufactured by Chemours) to other substrates (heat-resistant polymers, metals, etc.) in a short time, and development of photocurable sealants is underway (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7318366 [Patent Document 2] Patent No. 7235037 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been a strong demand for sealing agents for polymer electrolyte membranes to suppress the so-called contamination caused by the elution of sealing agent components into the catalyst layer, in order to prevent a decrease in fuel cell performance caused by the elution of sealing agent components into the catalyst layer.

[0007] In view of the above problems, an object of the present invention is to provide a sealant for a fuel cell that is excellent in low contamination properties and a fuel cell that includes the sealant. [Means for solving the problem]

[0008] That is, the present invention relates to the following [1] to [7]. In this application, "(numerical value 1) to (numerical value 2)" indicates that the upper and lower limits are included. Also, the (meth)acryloyl group means a methacryloyl group and / or an acryloyl group, and the (meth)acrylate means a methacrylate and / or an acrylate. [1] A sealing agent for a fuel cell, comprising: (A) a photopolymerization initiator having at least one ethylenically unsaturated group in the molecule; and (B) a curable compound. [2] The sealing agent for a fuel cell according to the above item [1], further comprising (C) a filler. [3] The sealing agent for fuel cells according to the above item [1] or [2], wherein the (A) photopolymerization initiator having at least one ethylenically unsaturated group in the molecule contains a photopolymerization initiator having a (meth)acryloyl group. [4] The sealing agent for a fuel cell according to any one of the above items [1] to [3], wherein the curable compound (B) is a polybutadiene compound having a reactive group in the molecule. [5] The sealing agent for a fuel cell according to any one of the above items [1] to [4], wherein the curable compound (B) contains a urethane (meth)acrylate compound. [6] The fuel cell sealant according to any one of the above items [1] to [5], which is used as a sealant for a polymer electrolyte membrane. [7] A fuel cell comprising the sealing agent for a fuel cell according to any one of the above items [1] to [6]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a sealant for a fuel cell that is excellent in low contamination properties and a fuel cell that includes the sealant. DETAILED DESCRIPTION OF THE INVENTION

[0010] The fuel cell sealant of the present invention (also simply referred to as "sealant") contains (A) a photopolymerization initiator having at least one ethylenically unsaturated group in the molecule and (B) a curable compound, and is particularly suitable as a sealant for polymer electrolyte membranes in solid polymer fuel cells. The sealant for polymer electrolyte membranes is mainly used to hold a membrane electrode assembly (MEA) to a gasket.

[0011] The sealing agent of the present invention has excellent low-staining properties. Low-staining properties can be evaluated by weight change rate and electrical conductivity. The weight change rate is an indicator of the amount of eluted components, and is preferably 2% or less, more preferably 1.5% or less, after 240 hours at 95°C. Electrical conductivity is an indicator of the degree of electrical influence of eluted components, and the initial value is preferably 2 μS / cm or less, more preferably 1.5 μS / cm or less, and after 240 hours at 95°C, it is preferably 15 μS / cm or less, more preferably 12 μS / cm or less, and particularly preferably 10 μS / cm or less. Specific measurement methods are described in the Examples below.

[0012] [(A) Photopolymerization initiator having at least one ethylenically unsaturated group in the molecule] The sealing agent of the present invention contains, as component (A), a photopolymerization initiator having at least one ethylenically unsaturated group in the molecule (also simply referred to as "component (A)"). The ethylenically unsaturated group in the present invention is a curable substituent, such as a styryl group, a vinyl group, an allyl group, a maleimide group, a (meth)acryloyl group, or a (meth)acrylamide group, and the presence of such a substituent contributes to low contamination.

[0013] Component (A) may be, for example, KAYAKURE RTM Examples include RPI-4 (manufactured by Nippon Kayaku Co., Ltd.: reaction product of 2-isocyanatoethyl methacrylate and 2-hydroxy-1-[4-(2-hydroxyethoxyphenyl]-2-methylpropan-1-one) and MBP (manufactured by Shinryo Corporation: 4-methacryloyloxybenzophenone).

[0014] Component (A) may be used alone or in combination of two or more. In the sealing agent of the present invention, component (A) is preferably contained in an amount of 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the total amount of component (A) and component (B) described below.

[0015] [(B) Curable compound] The sealing agent of the present invention contains a curable compound (also simply referred to as "component (B)") as component (B). Component (B) is not particularly limited as long as it is a compound that is cured by light, but is preferably a compound having a (meth)acryloyl group or a vinyl group, and examples thereof include (meth)acrylate, urethane (meth)acrylate, polybutadiene compound having a reactive group in the molecule, and epoxy (meth)acrylate. Note that in this application, component (A) is not included in component (B).

[0016] [(Meth)acrylate] Specific examples of (meth)acrylates include tricyclodecane acrylate, bicyclopentenyl acrylate, bicyclopentenyloxyethyl acrylate, tricyclodecanyl acrylate, tricyclodecanyl methacrylate, lauryl (meth)acrylate, N-acryloyloxyethyl hexahydrophthalimide, acryloylmorpholine, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, cyclohexane-1,4-dimethanol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenylpolyethene. Oxy(meth)acrylate, 2-hydroxy-3-phenyloxypropyl(meth)acrylate, o-phenylphenol monoethoxy(meth)acrylate, o-phenylphenol polyethoxy(meth)acrylate, p-cumylphenoxyethyl(meth)acrylate, isobornyl(meth)acrylate, tribromophenyloxyethyl(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate, dicyclopentenyloxyethyl(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-Nonanediol di(meth)acrylate, tricyclodecane dimethanol (meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxydi(meth)acrylate, bisphenol A polypropoxydi(meth)acrylate, bisphenol F polyethoxydi(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tris(acryloxyethyl)isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate Examples of suitable monomers include acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, diacrylate of an ester of neopentyl glycol and hydroxypivalic acid, and diacrylate of an ε-caprolactone adduct of an ester of neopentyl glycol and hydroxypivalic acid. Preferred examples include isobornyl(meth)acrylate and tricyclodecane dimethanol di(meth)acrylate.

[0017] [Urethane (meth)acrylate] Urethane (meth)acrylates have a flexible skeleton specific to the urethane structure, and therefore the cured product has excellent adhesiveness, so they are preferably used as curable compounds. From the viewpoint of hot water immersion resistance and low moisture permeability, it is even more preferable to use compounds having a polybutadiene, hydrogenated polybutadiene, polyisoprene, or hydrogenated polyisoprene structure. The urethane (meth)acrylate can be obtained by reacting (a) a polyol, (b) an organic polyisocyanate, and (c) a hydroxyl group-containing (meth)acrylate to synthesize it in a conventional manner, and a catalyst such as a tin compound may be used as needed. In the synthesis of urethane (meth)acrylate, 1 equivalent of the hydroxyl group of the component (a) is preferably reacted with 1.1 to 2.0 equivalents, and particularly preferably 1.3 to 2.0 equivalents, of the isocyanate group of the component (b). The reaction temperature is preferably room temperature (25°C) to 100°C. It is preferable to react 0.95 to 1.1 equivalents of hydroxyl groups in component (c) with 1 equivalent of isocyanate groups in the reaction product of component (a) and component (b). The reaction temperature is preferably room temperature (25°C) to 100°C.

[0018] Specific examples of (a) polyols include hydroxyl-terminated polybutadiene, hydroxyl-terminated hydrogenated polybutadiene, hydroxyl-terminated polyisoprene, hydroxyl-terminated hydrogenated polyisoprene, tricyclodecane dimethanol, dimer diol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,18-octadecanediol, 1,2 Examples of suitable diols include 0-icosanediol, 1-methyl-1,8-octanediol, 2-methyl-1,8-octanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, cyclohexane-1,4-dimethanol, polyethylene glycol, polypropylene glycol, bisphenol A poly(n≒2-20)ethoxydiol, and bisphenol A poly(n≒2-20)propoxydiol, as well as polyester polyols that are reaction products of these diols with dibasic acids or their anhydrides (e.g., succinic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, isophthalic acid, terephthalic acid, phthalic acid, or anhydrides thereof). Preferred are polyester polyols and polyols having aromatic rings, with polyester polyols having aromatic rings being particularly preferred. Examples of the aromatic ring include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthroline ring; and aromatic heterocycles such as a furan ring, a pyrrole ring, a thiophene ring, a pyridine ring, a thiazole ring, and a benzothiazole ring; and preferably a benzene ring or a naphthalene ring. The component (a) may be used alone or in combination of two or more.

[0019] Specific examples of (b) organic polyisocyanates include tolylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-cyclohexylmethane diisocyanate, xylylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, trimethylhexamethylene diisocyanate, dimeryl diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-diphenylene diisocyanate, etc. Preferred examples include tolylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0020] Specific examples of (c) hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 1,4-butanediol (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, an ε-caprolactone adduct of 2-hydroxyethyl (meth)acrylate, and 2-hydroxy-3-phenyloxypropyl (meth)acrylate. Preferred examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and polyethylene glycol mono(meth)acrylate.

[0021] The weight average molecular weight of the urethane (meth)acrylate in terms of polystyrene measured by GPC is preferably 1,000 to 100,000, more preferably 3,000 to 80,000, and particularly preferably 5,000 to 60,000. By having it within the above range, it is possible to obtain excellent solubility in the composition while maintaining good adhesion and hot water immersion resistance.

[0022] [Polybutadiene compounds with reactive groups in the molecule] Polybutadiene compounds having a reactive group in the molecule are commercially available, for example, as NISSO-PB JP-100, JP-200, TEAI-1000, and TE-2000 (manufactured by Nippon Soda Co., Ltd.), Epolead PB3600 and 4700 (manufactured by Daicel Corporation), Adeka Cizer BF-1000 (manufactured by ADEKA Corporation), and Ricon 657 (manufactured by Cray Valley Chemical Industries, Ltd.). From the viewpoint of low contamination, the number average molecular weight of these polybutadiene compounds having a reactive group in the molecule has a lower limit of preferably 500, more preferably 750, and particularly preferably 1000. From the viewpoint of handleability, the upper limit of the number average molecular weight is preferably 10,000, more preferably 8,000, and particularly preferably 6,000.

[0023] [Epoxy (meth)acrylate] Epoxy (meth)acrylates are obtained by a known method by reacting an epoxy resin with (meth)acrylic acid. The epoxy resins used as raw materials are not particularly limited, but examples include epoxidized polybutadiene, resorcinol diglycidyl ether, bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenol novolac epoxy resin, cresol novolac epoxy resin, bisphenol A novolac epoxy resin, bisphenol F novolac epoxy resin, alicyclic epoxy resin, aliphatic linear epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, hydantoin epoxy resin, isocyanurate epoxy resin, phenol novolac epoxy resin having a triphenolmethane skeleton, and diglycidyl ethers of bifunctional phenols such as catechol and resorcinol, diglycidyl ethers of bifunctional alcohols, and their halides and hydrogenated derivatives. The ratio of epoxy groups to (meth)acryloyl groups is not limited and is appropriately selected from the viewpoint of process suitability. Partial epoxy (meth)acrylates in which some of the epoxy groups are acrylic esters are preferably used, with the acrylic ester content preferably being about 30 to 70%.

[0024] [(Meth)acrylate having a phosphate group] The sealing agent of the present invention may contain a (meth)acrylate having a phosphate group. The (meth)acrylate having a phosphate group is a compound containing one or more, preferably 1 to 5, phosphate groups and one or more, preferably 1 to 3, (meth)acryloyl groups in the molecule. The (meth)acrylate having a phosphate group is not particularly limited, but examples thereof include 2-(meth)acryloyloxyethyl acid phosphate (e.g., "Light Ester P-1M" and "Light Acrylate P-1A" manufactured by Kyoeisha Chemical Co., Ltd.), alkylene (meth)acrylate phosphates such as methylene (meth)acrylate phosphate, ethylene (meth)acrylate phosphate, propylene (meth)acrylate phosphate, and tetramethylene (meth)acrylate phosphate, and phosphate esters of polyethylene glycol monoacrylate. Examples of such an acid ester include phosphate esters of polypropylene glycol monomethacrylate, bis(2-(meth)acryloyloxyethyl) acid phosphate (for example, "Light Ester P-2M" and "Light Acrylate P-2A" manufactured by Kyoeisha Chemical Co., Ltd.), ethylene oxide-modified di(meth)acrylate phosphate, tris(2-acryloyloxyethyl)phosphate, and a mixture of caprolactone-modified mono(meth)acrylate phosphate and caprolactone-modified di(meth)acrylate phosphate (for example, "KAYAMER PM-21" manufactured by Nippon Kayaku Co., Ltd.).

[0025] Component (B) may be used alone or in combination of two or more. In the sealant of the present invention, component (B) is preferably contained in an amount of 20 to 90 parts by mass, more preferably 30 to 80 parts by mass, per 100 parts by mass of the total amount of the sealant.

[0026] [(C) Filler] The sealing agent of the present invention may contain a filler (also simply referred to as "component (C)") as component (C). Either an inorganic filler or an organic filler may be used as component (C).

[0027] Examples of inorganic fillers include silica, silicon carbide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, magnesium oxide, zirconium oxide, aluminum hydroxide, magnesium hydroxide, calcium silicate, aluminum silicate, lithium aluminum silicate, zirconium silicate, barium titanate, glass fiber, carbon fiber, molybdenum disulfide, and asbestos, and preferred are fused silica, crystalline silica, silicon nitride, boron nitride, calcium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, aluminum hydroxide, calcium silicate, and aluminum silicate, with silica, alumina, and talc being preferred. Two or more of these inorganic fillers may be mixed and used.

[0028] [Organic filler] The sealing agent of the present invention may contain an organic filler, such as urethane fine particles, acrylic fine particles, styrene fine particles, styrene olefin fine particles, and silicone fine particles. Preferred examples of urethane microparticles include Art Pearl JB-800T and HB-800BK (manufactured by Negami Chemical Industrial Co., Ltd.); preferred examples of acrylic microparticles include Chemisnow MX-500 (manufactured by Soken Chemical & Engineering Co., Ltd.); preferred examples of styrene microparticles include Tefablock T320C, T331C, SJ4400, SJ5400, SJ6400, SJ4300C, SJ5300C, and SJ6300C (manufactured by Mitsubishi Chemical Corporation); preferred examples of styrene olefin microparticles include Septon SEPS2004 and SEPS2063 (manufactured by Kuraray Co., Ltd.); and preferred examples of silicone microparticles include KMP-594, KMP-597, and KMP-598 (manufactured by Shin-Etsu Chemical Co., Ltd.), and DOWSIL EP-5500 and EP-2601 (manufactured by Dow-Toray Industries, Inc.). These organic fillers may be used alone or in combination of two or more. Furthermore, two or more types may be used to form a core-shell structure. Of these, acrylic fine particles and silicone fine particles are preferred.

[0029] When component (C) is used in the sealing agent of the present invention, it is preferably contained in an amount of 3 to 30 parts by mass, more preferably 5 to 20 parts by mass, per 100 parts by mass of the total amount of the sealing agent. If the filler content is less than 3 parts by mass, the adhesive strength decreases and moisture resistance reliability also deteriorates, which may result in a significant decrease in adhesive strength after moisture absorption. If the filler content is more than 30 parts by mass, handling may be impaired. Furthermore, the average particle size of the filler is preferably 0.1 to 20 μm, more preferably 1 to 10 μm. The average particle size can be measured using a laser diffraction / scattering particle size distribution analyzer (dry type) (manufactured by Seishin Enterprise Co., Ltd.: LMS-30). The filler is preferably spherical in shape.

[0030] The sealing agent of the present invention may contain, in addition to component (A), other photoradical polymerization initiators. The photoradical polymerization initiator is not particularly limited as long as it is a compound that generates radicals or acids and initiates a chain polymerization reaction when irradiated with ultraviolet or visible light. Examples of the photoradical polymerization initiator include benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone, benzophenone, 2-ethylanthraquinone, 2-hydroxy-2-methylpropiophenone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, camphorquinone, 9-fluorenone, and diphenyl disulfide. Specific examples include Omnirad RTM 651, 184, 2959, 127D, 907, 369, 379EG, 819, 784, 754, 500, TPO, IRGACURE RTM OXE01, OXE02, OXE03, OXE04, DAROCURE RTM 1173, LUCIRIN RTM TPO (manufactured by BASF), Seikuol RTM Z, BZ, BEE, BIP, BBI (Seiko Chemical Co., Ltd.), KAYACURE RTMDETX-S (manufactured by Nippon Kayaku Co., Ltd.) and the like. Among these, initiators having any of a phenyl sulfide structure, an oxime ester structure, a thioxanthone structure, and a phosphine oxide structure in the molecule are preferred. Commercially available products include Omnirad RTM 819, TPO, IRGACURE RTM OXE01, OXE02, OXE03, OXE04, LUCIRIN RTM TPO, CAYACURE RTM Examples include DETX-S. By using two or more photopolymerization initiators with different absorption wavelengths, the irradiated light can be efficiently absorbed, reducing unreacted materials in the sealant. This reduces the elution of sealant components into the catalyst layer.

[0031] The sealing agent of the present invention may contain a silane coupling agent. Examples of silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, N-(2-(vinylbenzylamino)ethyl)3-aminopropyltrimethoxysilane hydrochloride, 3-methacryloxypropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, and 3-chloropropyltrimethoxysilane. These silane coupling agents are sold by Shin-Etsu Chemical Co., Ltd. and other companies under the names KBM series and KBE series, and are therefore readily available on the market. When a silane coupling agent is used in the sealing agent of the present invention, it is preferably contained in an amount of 0.05 to 3 parts by mass per 100 parts by mass of the total amount of the sealing agent.

[0032] [Compounds containing thiol groups] The sealing agent of the present invention may contain a compound having a thiol group, such as methanedithiol, 1,2-dimercaptoethane, 1,2-dimercaptopropane, 2,2-dimercaptopropane, 1,3-dimercaptopropane, 1,2,3-trimercaptopropane, 1,4-dimercaptobutane, 1,6-dimercaptohexane, bis(2-mercaptoethyl)sulfide, 1,2-bis(2-mercaptoethylthio)ethane, 1,5-dimercapto-3-oxapentane, and 1,8-dimercapto-3,6-dioxapentane. saoctane, 2,2-dimethylpropane-1,3-dithiol, 3,4-dimethoxybutane-1,2-dithiol, 2-mercaptomethyl-1,3-dimercaptopropane, 2-mercaptomethyl-1,4-dimercaptobutane, 2-(2-mercaptoethylthio)-1,3-dimercaptopropane, 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane, 1,1,1-tris(mercaptomethyl)propane, tetrakis(mercaptomethyl)methane, ethylene glycol Lithium bis(2-mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), 1,4-butanediol bis(2-mercaptoacetate), 1,4-butanediol bis(3-mercaptopropionate), trimethylolpropane tris(2-mercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate) Dipentaerythritol hexakis(3-mercaptopropionate), dipentaerythritol hexakis(2-mercaptoacetate), 1,2-dimercaptobenzene, 1,3-dimercapto-2-propanol, 2,3-dimercapto-1-propanol, 1,2-dimercapto-1,3-butanediol, hydroxyethyl-tris(mercaptoethylthiomethyl)methane, hydroxyethylthiomethyl-tris(mercaptoethylthio)methane, ethylene glycol bis(3-mercaptopropionate), propylene glycol bis(3-mercaptopropionate), butanediol bis(3-mercaptopropionate), octanediol bis(3-mercaptopropionate), tetraethylene glycol bis(3-mercaptopropionate), Ethylene glycol bis(4-mercaptobutyrate), propylene glycol bis(4-mercaptobutyrate), butanediol bis(4-mercaptobutyrate), octanediol bis(4-mercaptobutyrate), trimethylolpropane tris(4-mercaptobutyrate), pentaerythritol tetrakis(4-mercaptobutyrate), ethylene glycol bis(6-mercaptovalerate), propylene glycol bis(6-mercaptovalerate) , butanediol bis(6-mercaptovalerate), octanediol bis(6-mercaptovalerate), trimethylolpropane tris(6-mercaptovalerate), pentaerythritol tetrakis(6-mercaptovalerate), 1,6-hexanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 4,4'-bis(mercaptomethyl)phenyl sulfide, 2,4'-bis(mercaptomethyl)phenyl sulfide, 2,4,4'-tri( mercaptomethyl)phenyl sulfide, 2,2',4,4'-tetra(mercaptomethyl)phenyl sulfide, 1,3,5-tris[2-(3-mercaptopropionyloxy)ethyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, polysulfide polymers, etc., which may be used alone or in combination of two or more. Among these, preferred are trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), 1,3,5-tris[2-(3-mercaptopropionyloxy)ethyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3-mercapto Preferred are 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and pentaerythritol tetrakis(3-mercaptobutyrate), and more preferred are 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and pentaerythritol tetrakis(3-mercaptobutyrate), which have a secondary thiol structure.

[0033] The compound having a thiol group may be produced by a known method, or a commercially available compound may be used. RTM PE1, BD1, NR1, trimethylolpropane tris(3-mercaptobutyrate), trimethylolethane tris(3-mercaptobutyrate) (manufactured by Resonac Co., Ltd.), polythiol RTM 340M (manufactured by Toray Fine Chemicals Co., Ltd.), pentaerythritol tetrakis(3-mercaptopropionate) (manufactured by SC Organic Chemicals Co., Ltd.), and the like.

[0034] Also preferred are compounds having three or more functional thiol groups in the molecule. Examples include 2,4,4'-tri(mercaptomethyl)phenyl sulfide, 2,2',4,4'-tetra(mercaptomethyl)phenyl sulfide, 1,3,5-tris[2-(3-mercaptopropionyloxy)ethyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3-mercaptobutyloxyethyl)1,3,5-triazine-2,4,6(1H,3H,5H)-trione, pentaerythritol tetrakis(3-mercaptobutyrate), and 1,4-bis(3-mercaptobutyryloxy)butane. This is because the increased crosslink density can improve heat resistance and other properties.

[0035] When a compound having a thiol group is used in the sealing agent of the present invention, it is preferable that the compound be contained in an amount of 1 to 10 parts by mass relative to 100 parts by mass of the total amount of the sealing agent.

[0036] The sealing agent of the present invention may contain a thermosetting component in addition to a photocurable component. Examples of the thermosetting component include, but are not limited to, a thermosetting resin, a thermosetting agent, and a thermal radical polymerization agent. The thermosetting resin is preferably an epoxy resin. Examples of the thermosetting agent include, but are not limited to, a phenol-based curing agent, an amine-based curing agent, and the like. Those having a hydrazide structure are particularly preferred.

[0037] The epoxy resin is preferably a bifunctional or higher functional epoxy resin, such as epoxidized polybutadiene, resorcinol diglycidyl ether, bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenol novolac epoxy resin, cresol novolac epoxy resin, bisphenol A novolac epoxy resin, bisphenol F novolac epoxy resin, alicyclic epoxy resin, aliphatic linear epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, hydantoin epoxy resin, isocyanurate epoxy resin, phenol novolac epoxy resin having a triphenolmethane skeleton, diglycidyl ethers of bifunctional phenols such as catechol and resorcinol, diglycidyl ethers of bifunctional alcohols, and their halides and hydrogenated derivatives. Epoxidized polybutadiene is preferred.

[0038] The thermal radical polymerization initiator is not particularly limited as long as it is a compound that generates radicals by heating and initiates a chain polymerization reaction, and examples thereof include organic peroxides, azo compounds, benzoin compounds, benzoin ether compounds, acetophenone compounds, and benzopinacol, with benzopinacol being preferred. For example, an organic peroxide is Kayamec RTM A, M, R, L, LH, SP-30C, Perkadox CH-50L, BC-FF, Kadox B-40ES, Perkadox 14, Trigonox RTM 22-70E, 23-C70, 121, 121-50E, 121-LS50E, 21-LS50E, 42, 42LS, Kayaester RTM P-70, TMPO-70, CND-C70, OO-50E, AN, Kayabutyl RTM B, Percadox 16, Kayacarvone RTM BIC-75, AIC-75 (manufactured by Kayaku Akzo Co., Ltd.), Permec RTM N, H, S, F, D, G, Perhexa RTM H,HC,TMH,C,V,22,MC,Percure RTM AH, AL, HB, PerbutylRTM H, C, ND, L, Park Mill RTM H., D., Parloyle RTM IB, IPP, Perocta RTM ND (manufactured by NOF Corporation) and other products are available commercially.

[0039] Furthermore, commercially available azo compounds include VA-044, 086, V-070, VPE-0201, and VSP-1001 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0040] The content of the thermal radical polymerization initiator is preferably 0.0001 to 10 parts by mass, more preferably 0.0005 to 5 parts by mass, and particularly preferably 0.001 to 3 parts by mass, per 100 parts by mass of the total amount of the sealing agent.

[0041] The sealing agent of the present invention may further contain additives such as antioxidants, radical polymerization inhibitors, pigments, leveling agents, antifoaming agents, solvents, etc. These additives are preferably those that have little tendency to contaminate the catalyst layer.

[0042] [Antioxidants] Commercially available antioxidants include Irganox 1010, 1035, 1076, and 1222 (manufactured by BASF), and commercially available ultraviolet absorbers include Tinuvin P, 234, 320, 326, 327, 328, and 213 (manufactured by BASF), and Sumisorb 110, 130, 140, 220, 250, 300, 320, 340, 350, and 400 (manufactured by Sumika Chemtex Corporation).

[0043] [Radical polymerization inhibitor] The radical polymerization inhibitor is not particularly limited as long as it is a compound that reacts with radicals generated from a photoradical polymerization initiator, a thermal radical polymerization initiator, or the like to prevent polymerization, and can be a quinone-based, piperidine-based, hindered phenol-based, nitroso-based, etc. Specifically, naphthoquinone, 2-hydroxynaphthoquinone, 2-methylnaphthoquinone, 2-methoxynaphthoquinone, 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-methoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-phenoxypiperidine-1-oxyl, hydroquinone, Quinone, 2-methylhydroquinone, 2-methoxyhydroquinone, parabenzoquinone, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butylcresol, stearyl β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butyl tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl], 2,4,8,10-tetraoxaspiro[5,5]undecane, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenylpropionate)methane], 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-sec-triazine-2,4,6-(1H,3H,5H)trione, paramethoxyphenol, 4-methoxy-1-naphthol, thiodiphenylamine, aluminum salt of N-nitrosophenylhydroxyamine, Adeka STAB LA-81, LA-82 (manufactured by ADEKA Corporation), and the like, but are not limited thereto.Of these, naphthoquinone-based, hydroquinone-based, nitroso-based, and piperazine-based radical polymerization inhibitors are preferred, naphthoquinone, 2-hydroxynaphthoquinone, hydroquinone, 2,6-di-tert-butyl-p-cresol, and Polystop 7300P (manufactured by Hakuto Co., Ltd.) are more preferred, and Polystop 7300P (manufactured by Hakuto Co., Ltd.) is most preferred.

[0044] The content of the radical polymerization inhibitor is preferably 0.0001 to 1 part by mass, more preferably 0.001 to 0.5 parts by mass, and particularly preferably 0.01 to 0.2 parts by mass, per 100 parts by mass of the total amount of the sealing agent.

[0045] The following method is one example of a method for obtaining the sealing agent of the present invention. First, components (A) and (B) are heated and dissolved. Next, after cooling to room temperature, component (C), a silane coupling agent, a compound having a thiol group, an antifoaming agent, a leveling agent, a solvent, etc. are added as needed, and the mixture is mixed uniformly using a known mixing device such as a three-roll mill, a sand mill, a ball mill, a planetary mixer, etc., to produce the sealing agent. If necessary, filtration may be performed after mixing to remove impurities.

[0046] The sealing agent of the present invention is applied to a substrate, and then laminated to another member, and cured by irradiating with ultraviolet light. However, it may also be cured by electron beams, or may additionally be thermally cured.

[0047] When the sealant of the present invention is used as a sealant for a polymer electrolyte membrane, the process includes the steps of applying the sealant of the present invention to a membrane electrode assembly (MEA) sheet, laminating the applied sealant to a support frame, and irradiating the support frame with ultraviolet light. The application method is not particularly limited, and examples include screen printing and methods using a dispenser. The material of the support frame is not particularly limited, and examples include engineering plastics such as polyethylene naphthalate resin (PEN), polyethylene terephthalate resin (PET), polyphenylene sulfide resin (PPS), and syndiotactic polystyrene resin (SPS), general-purpose plastics such as polypropylene resin (PP), and combinations thereof. [Example]

[0048] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0049] [Synthesis Example 1] A flask equipped with a thermometer, condenser, and stirrer was charged with 780.89 g of hydroxyl-terminated liquid polybutadiene (LBH-P2000 manufactured by Cray Valley, hydroxyl value 49.2 mg KOH / g) and 144.60 g of isophorone diisocyanate (Wanka Chemical's WANNATE IPDI, molecular weight 222.3), and the mixture was allowed to react at 80° C. The isocyanate content at this stage was determined by adding excess di-n-butylamine to react with the isocyanate, and then neutralizing titrating the remaining di-n-butylamine with a standard hydrochloric acid solution. It was confirmed that the value was within a range of plus or minus 2% of the residual isocyanate amount calculated from the calculated value. Next, 0.5 g of methoquinone (polymerization inhibitor), 73.71 g of 2-hydroxyethyl acrylate (molecular weight 116.1), and 0.3 g of tin octylate (catalyst) were added, and the mixture was stirred at 80°C. The absorption spectrum of the isocyanate group (at 2280 cm) was measured by infrared absorption spectroscopy. -1 The reaction was continued until the methyl group disappeared, yielding a urethane acrylate oligomer having a weight-average molecular weight of 9,700.

[0050] [Synthesis Example 2] A flask equipped with a thermometer, condenser, and stirrer was charged with 895.04 g of polypropylene glycol (AGC Corporation EXCENOL 3020, hydroxyl value 36.2 mg KOH / g) and 83.44 g of isophorone diisocyanate (Wanka Chemical Co., Ltd. WANNATE IPDI, molecular weight 222.3) and allowed to react at 80 °C. The isocyanate content was determined by adding excess di-n-butylamine to react with the isocyanate, and then neutralizing the remaining di-n-butylamine with a standard hydrochloric acid solution. The resulting value was confirmed to be within ±2% of the calculated residual isocyanate content. Next, 0.5 g of methoquinone (polymerization inhibitor), 20.72 g of 2-hydroxyethyl acrylate (molecular weight 116.1), and 0.3 g of tin octoate (catalyst) were added and stirred at 80 °C. The isocyanate group absorption spectrum (at 2280 cm) was measured by infrared absorption spectroscopy. -1 The reaction was continued until the methyl group disappeared, yielding a urethane acrylate oligomer having a weight-average molecular weight of 22,850.

[0051] [Examples 1 to 4, Comparative Examples 1 to 4] Component (A), component (B), photopolymerization initiator, and antioxidant were mixed at 90°C in the proportions shown in Table 1 below, and then cooled to room temperature. Component (C) was added and stirred, and then dispersed in a disperser to prepare a sealing agent, which was then evaluated as follows.

[0052] [Weight change rate] The sealant was sandwiched between a PET film (Toyo Cross: SP1030, 100 μm thick) and a PET film (Lintec: LT-H, 50 μm thick), stretched using a roll press until the sealant was 250 μm thick, and then irradiated with a high-pressure mercury lamp (Ushio Inc.: UVX-02516S1AFL01, with a filter that cuts off 320 nm or less) at 75 mW / cm. 2 , 3000mJ / cm 2The cured product was irradiated with light and then cured. The initial weight of the cured product was measured, then immersed in hot water at 95°C for 240 hours, air-dried in an environment of 25°C and 50% RH for at least 48 hours, and then the weight after the test was measured. The weight change rate between the initial and post-test values ​​was calculated, and the results are shown in Tables 1 and 2.

[0053] [Electrical conductivity] 0.15 g of the cured product obtained using the same method as in the evaluation of weight change rate was placed in 25 g of ultrapure water and shaken at room temperature for 60 seconds in a shaker (AS ONE Corporation: Double One Lab Shaker SPR-2) to obtain extracted water. The initial electrical conductivity of the extracted water was measured using a conductivity meter (METTLER TOREDO: SevenMulti), and then the extracted water and the cured product were placed in a constant temperature bath at 95°C for 240 hours of hot water extraction, and the electrical conductivity after the test was measured.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Table 3]

[0057] From the results in Tables 1 and 2, it was confirmed that the sealing agent of the present invention has a small weight change rate after immersion in hot water and low electrical conductivity before and after hot water extraction, resulting in little elution and excellent low contamination.

Claims

1. A sealing agent for a fuel cell, comprising: (A) a photopolymerization initiator having at least one ethylenically unsaturated group in the molecule; and (B) a curable compound.

2. The sealing agent for a fuel cell according to claim 1 , further comprising (C) a filler.

3. 2. The sealing agent for a fuel cell according to claim 1, wherein the photopolymerization initiator (A) having at least one ethylenically unsaturated group in the molecule contains a photopolymerization initiator having a (meth)acryloyl group.

4. 2. The sealing agent for a fuel cell according to claim 1, wherein the curable compound (B) comprises a polybutadiene compound having a reactive group in the molecule.

5. The sealing agent for a fuel cell according to claim 1 , wherein the curable compound (B) contains a urethane (meth)acrylate compound.

6. The fuel cell sealant according to claim 1, which is used as a sealant for a polymer electrolyte membrane.

7. A fuel cell comprising the sealing agent for a fuel cell according to any one of claims 1 to 6.

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