Sealant for fuel cells and fuel cells using the same

Abstract

The present invention provides a sealant for fuel cells that exhibits excellent low-contamination properties, and a fuel cell having said sealant. [Solution] A sealant for fuel cells containing (A) a photopolymerization initiator with a weight-average molecular weight of 400 or more determined by gel permeation chromatography (GPC), and (B) a curable compound.

Description

[Technical Field]

[0001] This invention relates to a sealant for fuel cells and a fuel cell using the same. [Background technology]

[0002] A fuel cell is a power generation system that uses hydrogen, obtained by reforming gasoline or natural gas, as fuel, and extracts electricity from the energy released when hydrogen chemically reacts with oxygen. A type of fuel cell, the polymer electrolyte fuel cell, uses an ion exchange membrane as its electrolyte. Because the electrolyte is thin and has a high current density, it can be made smaller and lighter, and development is progressing for use as a power source for homes and automobiles.

[0003] In fuel cells, high-barrier and high-adhesion sealants are required and are being developed to prevent leakage of reaction gases and coolant, and to maintain the power generation unit (Patent Document 1).

[0004] Furthermore, in polymer electrolyte fuel cells, there is a need to bond polymer electrolyte membranes (perfluorocarbon materials having sulfonic acid groups, such as Nafion manufactured by Chemours) to other substrates (heat-resistant polymers, metals, etc.) in a short time to improve productivity, and the 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 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, there has been a strong demand for suppressing so-called contamination, where the sealant leaches into the catalyst layer, in sealants used for polymer electrolyte membranes. This is to prevent the degradation of fuel cell performance caused by the leaching of sealant components into the catalyst layer.

[0007] In view of the above problems, the present invention aims to provide a sealant for fuel cells that exhibits excellent low-contamination properties and a fuel cell having said sealant. [Means for solving the problem]

[0008] In other words, the present invention relates to the following [1] to [8]. In this application, "(numerical value 1) to (numerical value 2)" indicates that upper and lower limits are included. Also, (meth)acryloyl group means methacryloyl group and / or acryloyl group, and (meth)acrylate means methacrylate and / or acrylate. [1] A sealant for fuel cells containing (A) a photopolymerization initiator with a weight-average molecular weight of 400 or more determined by gel permeation chromatography (GPC), and (B) a curable compound. [2] Furthermore, the fuel cell sealant described in the preceding paragraph [1] contains (C) filler. [3] The fuel cell sealant according to the preceding paragraph [1] or [2], wherein the (A) photopolymerization initiator has two or more sites in one molecule that generate radicals upon irradiation with ultraviolet light or visible light or heat. [4] A fuel cell sealant according to any one of the preceding paragraphs [1] to [3], wherein the (A) photopolymerization initiator is a polymer of 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone. [5] The fuel cell sealant according to any one of the preceding paragraphs [1] to [4], comprising a polybutadiene compound having a reactive group in its molecule as the curable compound (B). [6] The sealant for a fuel cell according to any one of the preceding items [1] to [5], containing a urethane (meth) acrylate compound as the (B) curable compound. [7] The sealant for a fuel cell according to any one of the preceding items [1] to [6], which is used as a sealant for a polymer electrolyte membrane. [8] A fuel cell comprising the sealant for a fuel cell according to any one of the preceding items [1] to [7]. [Advantages of the Invention]

[0009] According to the present invention, it is possible to provide a sealant for a fuel cell having excellent low pollution property and a fuel cell comprising the sealant. [Embodiments for Carrying Out the Invention]

[0010] The sealant for a fuel cell of the present invention (also simply referred to as "sealant") contains (A) a photoinitiator having a weight average molecular weight of 400 or more by gel permeation chromatography (GPC) and (B) a curable compound, and is particularly suitable as a sealant for a polymer electrolyte membrane of a solid polymer fuel cell. The sealant for a polymer electrolyte membrane is mainly used to hold a membrane electrode assembly (MEA: Membrane Electrode Assembly) in a gasket.

[0011] The sealant of the present invention is excellent in low pollution property. The low pollution property can be evaluated by the weight change rate and the electric conductivity. The weight change rate is an index of the amount of eluted components, and it is preferably 3% or less, more preferably 2% or less, and particularly preferably 1% or less after 240 hours at 95°C. The electric conductivity is an index of the degree of electrical influence of the 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 20 μS / cm or less, more preferably 15 μS / cm or less, and particularly preferably 10 μS / cm or less. The specific measurement method is described in the examples below.

[0012] [(A) Photopolymerization initiators with a weight-average molecular weight of 400 or more as determined by gel permeation chromatography (GPC)] The sealant of the present invention contains (A) a photopolymerization initiator (also simply referred to as "component (A)") having a weight-average molecular weight of 400 or more as determined by gel permeation chromatography (GPC). By using a photopolymerizable initiator with a weight-average molecular weight of 400 or more, elution into hot water is suppressed, resulting in good low-contamination properties. From the viewpoint of low-contamination properties, curability, and solubility in the composition, the weight-average molecular weight of component (A) is preferably 400 at the lower limit and 1500 at the upper limit.

[0013] In this invention, gel permeation chromatography (GPC) is measured under the following conditions. Measuring device: HLC-8320GPC (Tosoh Corporation) Analysis column: Three TSKgel SuperMultiporeHZ-M columns were used. Eluent: THF (tetrahydrofuran) Flow rate: 0.35ml / min Measurement temperature: 40℃ Detector: Differential refractometer Molecular weight standard: Polystyrene

[0014] (A) Examples of photopolymerization initiators with a weight-average molecular weight of 400 or more as determined by gel permeation chromatography (GPC) include Esacure ONE (manufactured by IGM RESINS, a high molecular weight α-hydroxyketone-based photopolymerization initiator: oligo(2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone), Omnipol TP (manufactured by IGM RESINS, a high molecular weight phosphorus-based photopolymerization initiator: polymer of ethyl(2,4,6-trimethylbenzoyl)-phenylphosphorinate), Omnipol 910 (manufactured by IGM RESINS, a high molecular weight aminoalkylphenone-based photopolymerization initiator: polyethylene glycol di(β-4[4-(2-dimethylamino-2-benzyl)butanoylphenyl]piperazine)propionate), and Irgacure OXE04 (manufactured by BASF, an oxime ester-based photopolymerization initiator).

[0015] Furthermore, from the viewpoint of curability and low contamination, component (A) preferably has two or more sites in one molecule that generate radicals upon irradiation with ultraviolet or visible light or heat. Compounds in which the radical generation site (2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone) is repeated within the molecule, such as polymers of 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone, are particularly preferred because they have high radical generation efficiency, i.e., reactivity, even at high molecular weights, and exhibit good curability and low contamination. Examples of polymers of 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone include Esacure ONE (manufactured by IGM RESINS) and Esacure KIP 150 (manufactured by IGM RESINS).

[0016] Component (A) may be used alone or mixed with two or more other components. In the sealant of the present invention, component (A) is preferably contained in an amount of 0.1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the total amount of component (A) and component (B) described later.

[0017] [(B) Curable compound] The sealant 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 hardens with light, but it is preferably a compound having a (meth)acryloyl group or a vinyl group, and examples include (meth)acrylate, urethane (meth)acrylate, polybutadiene compounds having a reactive group in the molecule, epoxy (meth)acrylate, and the like.

[0018] [(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 phenylpolyethyl Xy(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, Tricyclodecanedimethanol(meth)acrylate, Tricyclodecanedimethanol 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 monomers include methylates, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ester diacrylates of neopentyl glycol and hydroxypivalic acid, and diacrylates of ε-caprolactone adducts of esters of neopentyl glycol and hydroxypivalic acid. Preferably, examples include isobornyl(meth)acrylate and tricyclodecanedimethanol di(meth)acrylate.

[0019] [Urethane (meth)acrylate] Urethane (meth)acrylate is preferred as a curable compound because it has a flexible skeleton unique to urethane structures, resulting in cured products with excellent adhesion. From the viewpoint of resistance to hot water immersion, low gas permeability, and low moisture permeability, it is even more preferable to use those having polybutadiene, hydrogenated polybutadiene, polyisoprene, or hydrogenated polyisoprene structures. Urethane (meth)acrylate can be obtained by conventional methods by reacting (a) a polyol, (b) an organic polyisocyanate, and (c) a hydroxyl group-containing (meth)acrylate, with the use of a catalyst such as a tin compound as needed. In the synthesis of urethane (meth)acrylate, it is preferable to react 1.1 to 2.0 equivalents of isocyanate groups of component (b) with 1 equivalent of hydroxyl groups of component (a), and particularly preferable to react 1.3 to 2.0 equivalents. 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) for every 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.

[0020] (a)Specific examples of polyols include hydroxyl-terminated polybutadiene, hydroxyl-terminated hydrogenated polybutadiene, hydroxyl-terminated polyisoprene, hydroxyl-terminated hydrogenated polyisoprene, tricyclodecanedimethanol, dimergol, 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 include diols such as 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 which 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 their anhydrides). Preferably, the product is a polyester polyol or a polyol having an aromatic ring, and particularly preferably, a polyester polyol having an aromatic ring. Examples of aromatic rings include aromatic hydrocarbon rings such as benzene rings, naphthalene rings, anthracene rings, and phenanthroline rings; and aromatic heterocycles such as furan rings, pyrrole rings, thiophene rings, pyridine rings, thiazole rings, and benzothiazole rings; with benzene rings or naphthalene rings being preferred. Component (a) may be used alone or mixed with two or more other components.

[0021] (b) Specific examples of 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, dimethyl diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-diphenylene diisocyanate, etc. Preferably, tolylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate can be cited.

[0022] (c)Specific examples of 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, ε-caprolactone adduct of 2-hydroxyethyl (meth)acrylate, and 2-hydroxy-3-phenyloxypropyl (meth)acrylate. Preferably, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and polyethylene glycol mono(meth)acrylate can be cited.

[0023] The weight-average molecular weight of urethane (meth)acrylate in GPC (Gross Producing) on ​​a polystyrene basis is preferably 1,000 to 100,000, more preferably 3,000 to 80,000, and particularly preferably 5,000 to 60,000. Being within this range allows for excellent solubility in the composition while maintaining good adhesion and resistance to hot water immersion.

[0024] [Polybutadiene compounds containing reactive groups within the molecule] Examples of polybutadiene compounds having reactive groups in their molecules can be obtained from the market as NISSO-PB JP-100, JP-200, TEAI-1000, TE-2000 (manufactured by Nippon Soda Co., Ltd.), Epolid PB3600, 4700 (manufactured by Daicel Corporation), Adekasizer BF-1000 (manufactured by ADEKA Corporation), Ricon657 (manufactured by Clay Valley Corporation), etc. From the viewpoint of low contamination, the lower limit of the number-average molecular weight of these polybutadiene compounds having reactive groups in their molecules is preferably 500, more preferably 750, and particularly preferably 1000. From the viewpoint of handling, the upper limit of the number-average molecular weight is preferably 10000, more preferably 8000, and particularly preferably 6000.

[0025] [Epoxy (meth)acrylate] Epoxy (meth)acrylates can be obtained by known methods through the reaction of epoxy resin with (meth)acrylic acid. The epoxy resin used as a raw material is not particularly limited, but examples include epoxidized polybutadiene, resorcinol diglycidyl ether, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, phenol novolac type epoxy resin having a triphenolmethane skeleton, and others such as diglycidyl ethers of difunctional phenols such as catechol and resorcinol, diglycidyl ethers of difunctional alcohols, and their halogens and hydrogenated products. The ratio of epoxy groups to (meth)acryloyl groups is not limited and should be appropriately selected from the standpoint of process compatibility. Furthermore, partially epoxy (meth)acrylates in which a portion of the epoxy groups are acrylic esterified are preferably used. In this case, the acrylication rate is preferably around 30-70%.

[0026] [(meth)acrylate containing a phosphate group] The sealant of the present invention may contain a (meth)acrylate having a phosphate group. The (meth)acrylate having a phosphate group is a compound that contains one or more phosphate groups, preferably 1 to 5, and one or more (meth)acryloyl groups, preferably 1 to 3, within its molecule. The (meth)acrylate having a phosphate group is not particularly limited, but examples 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)acrylates 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 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 phosphate di(meth)acrylate, tris(2-acryloyloxyethyl) phosphate, and mixtures of caprolactone-modified phosphate mono(meth)acrylate and caprolactone-modified phosphate di(meth)acrylate (for example, "KAYAMER PM-21" manufactured by Nippon Kayaku Co., Ltd.).

[0027] Component (B) may be used alone or mixed with two or more other components. In the sealant of the present invention, component (B) is preferably contained in an amount of 20 to 90 parts by mass, and more preferably 30 to 80 parts by mass, per 100 parts by mass of the total amount of sealant.

[0028] [(C) Filler] The sealant of the present invention may contain a filler (also simply referred to as "component (C)") as component (C). Component (C) may be either an organic filler or an inorganic filler.

[0029] [Organic filler] Examples of organic fillers include urethane microparticles, acrylic microparticles, styrene microparticles, styrene olefin microparticles, and silicone microparticles. Preferred urethane microparticles include Artpearl P-800T, JB-800T, and JC-800TR (manufactured by Negami Kogyo Co., Ltd.). Preferred acrylic microparticles include Chemisnow MX-500L, MX-300, and KMR-3TA (manufactured by Soken Chemical Co., Ltd.), and Artpearl J-4PY (manufactured by Negami Kogyo Co., Ltd.). Preferred styrene microparticles include Tefablock T320C, T331C, SJ4400, SJ5400, SJ6400, SJ4300C, SJ5300C, and SJ6300C (manufactured by Mitsubishi Chemical Corporation). Preferred styrene olefin microparticles include Septon SEPS2004 and SEPS2063 (manufactured by Kuraray Co., Ltd.). Preferred 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.) are preferred. These organic fillers may be used individually or in combination of two or more types. They may also be used in combination to form a core-shell structure. Of these, acrylic fine particles and urethane fine particles are preferred.

[0030] The sealant of the present invention may contain an inorganic filler. Examples of the inorganic filler 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, asbestos, etc. Preferably, 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 are used, but silica, alumina, and talc are preferred. Two or more of these inorganic fillers may be used in mixture form.

[0031] In the sealant of the present invention, when component (C) is used, it is preferably contained in amounts of 3 to 30 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of the total amount of sealant. If the filler content is less than 3 parts by mass, the adhesive strength will decrease, and the moisture resistance reliability will also be poor, which may result in a greater decrease in adhesive strength after moisture absorption. If the filler content is more than 30 parts by mass, it may impair handling properties. Furthermore, the average particle size of the filler is preferably 0.1 to 20 μm, and 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 Corporation: LMS-30). The shape of the filler is preferably spherical.

[0032] The sealant of the present invention may contain other photoradical polymerization initiators in addition to component (A). 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 upon irradiation with ultraviolet or visible light. Examples include benzyldimethyl ketal, 1-hydroxycyclohexylphenyl 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-trimethylbenzoyldiphenylphosphate, camphorquinone, 9-fluorenone, and diphenyl disulfide. Specifically, 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), Sacred All RTM Z, BZ, BEE, BIP, BBI (manufactured by Seiko Chemical Co., Ltd.), KAYACURE RTMExamples include DETX-S (manufactured by Nippon Kayaku Co., Ltd.). Among these, preferably, an initiator having any of a phenyl sulfide structure, an oxime ester structure, a thioxanthone structure, or a phosphine oxide structure in the molecule. As commercially available products, Omnirad RTM 819, TPO, IRGACURE RTM OXE01, OXE02, OXE03, OXE04, LUCIRIN RTM TPO, CAYACURE RTM DETX-S and the like can be mentioned. By having two or more kinds of photoinitiators with different absorption wavelengths, the irradiated light can be efficiently absorbed, and the unreacted substances in the sealant can be reduced. Thereby, the elution of the sealant components into the catalyst layer can be reduced.

[0033] The sealant of the present invention may contain a silane coupling agent. Examples of the silane coupling agent 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, 3-chloropropyltrimethoxysilane and the like. Since these silane coupling agents are sold by Shin-Etsu Chemical Co., Ltd. and others under the KBM series, KBE series, etc., they are easily available on the market. In the sealant of the present invention, when a silane coupling agent is used, 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 sealant.

[0034] [Compound having a thiol group] The sealant of the present invention may contain a compound having a thiol group. Examples of compounds having a thiol group include 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-dioxy Octane, 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 Recallbis(2-mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), 1,4-butanediol bis(2-mercaptoacetate), 1,4-butanediol bis(3-mercaptopropionate), trimethylolpropanetris(2-mercaptoacetate), trimethylolpropanetris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptocete), pentaerythritol tetrakis(3-mercaptopropionate) Captopropionate), 1,1-dimercaptocyclohexane, 1,4-dimercaptocyclohexane, 1,3-dimercaptocyclohexane, 1,2-dimercaptocyclohexane, 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, Hydroxytyl-Tris(mercaptoethylthiomethyl)methane, Hydroxyethylthiomethyl-Tris(mercaptoethylthio)methane, Ethylene glycol bis(3-mercaptoproonate), 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,Examples include 4-bis(3-mercaptobutyryloxy)butane and polysulfide polymers, which may be used individually 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, and 1,3,5-tris(3-mercapto (Butyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and pentaerythritol tetrakis(3-mercaptobutyrate) are preferred, and more preferably, 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione having a secondary thiol structure and pentaerythritol tetrakis(3-mercaptobutyrate) are particularly preferred.

[0035] The above-mentioned compound having a thiol group may be produced by known methods, or a commercially available compound may be used. A commercially available example is Karenz MT. RTM PE1, BD1, NR1, Trimethylolpropanetris (3-mercaptobutyrate), Trimethylolethanetris (3-mercaptobutyrate) (manufactured by Resonaq Corporation), Polythiol RTM Examples include 340M (manufactured by Toray Fine Chemicals Co., Ltd.) and pentaerythritol tetrakis(3-mercaptopropionate) (manufactured by SC Organic Chemicals Co., Ltd.).

[0036] Furthermore, it is also preferable that the compound has three or more thiol groups in its 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 heat resistance and other properties can be improved by increasing the crosslinking density.

[0037] In the sealant of the present invention, when a compound having a thiol group is used, it is preferable that it be contained in an amount of 1 to 10 parts by mass per 100 parts by mass of the total amount of sealant.

[0038] The sealant of the present invention may contain a thermosetting component in addition to a photocuring component. The thermosetting component is not particularly limited, but examples include thermosetting resins, thermosetting agents, and thermal radical polymerizers, and epoxy resins are preferred as thermosetting resins. Furthermore, the thermosetting agent is not particularly limited, but examples include phenolic curing agents and amine curing agents, but those having a hydrazide structure are particularly preferred.

[0039] As the epoxy resin, a bifunctional or more epoxy resin is preferred, for example, epoxidized polybutadiene, resorcinol diglycidyl ether, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, phenol novolac type epoxy resin having a triphenolmethane skeleton, and others such as diglycidyl ethers of difunctional phenols such as catechol and resorcinol, diglycidyl ethers of difunctional alcohols, and their halogens and hydrogenated products. Epoxidized polybutadiene is a particularly preferred example.

[0040] The thermal radical polymerization initiator is not particularly limited as long as it is a compound that generates radicals upon heating and initiates a chain polymerization reaction, but examples include organic peroxides, azo compounds, benzoin compounds, benzoin ether compounds, acetophenone compounds, benzopinacol, etc., with benzopinacol being preferably used. For example, as an organic peroxide, Kayamec is used. RTM A, M, R, L, LH, SP-30C, Percadox CH-50L, BC-FF, Cadox B-40ES, Percadox 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, Percadocs 16, Kaya Carbon 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, ParRTM H, C, ND, L, Parkmill RTM H, D, Parroil RTM IB, IPP, Perocta RTM Products such as ND (manufactured by NOF Corporation) are available commercially.

[0041] In addition, azo compounds such as VA-044, 086, V-070, VPE-0201, and VSP-1001 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) are available commercially.

[0042] The thermal radical polymerization initiator is preferably contained in an amount of 0.0001 to 10 parts by mass per 100 parts by mass of the total amount of sealant, more preferably 0.0005 to 5 parts by mass, and particularly preferably 0.001 to 3 parts by mass.

[0043] The sealant of the present invention may further contain additives such as antioxidants, radical polymerization inhibitors, pigments, leveling agents, defoamers, and solvents, as needed. These additives are preferably those that have low contamination of the catalyst layer.

[0044] [Antioxidant] Commercially available antioxidants include Irganox 1010, 1035, 1076, and 1222 (manufactured by BASF), while commercially available UV 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 Co., Ltd.).

[0045] [Radical polymerization inhibitor] The radical polymerization inhibitors mentioned above are not particularly limited as long as they are compounds that react with radicals generated from photoradical polymerization initiators, thermal radical polymerization initiators, etc., to prevent polymerization, and quinone-based, piperidine-based, hindered phenol-based, nitroso-based compounds can be used. 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, hydro 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-butylphenol) Examples include, but are not limited to, thiodiphenylamine, 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 salts of N-nitrosophenylhydroxyamine, ADEKA STABE LA-81, LA-82 (manufactured by ADEKA Corporation), etc.Of these, naphthoquinone-based, hydroquinone-based, nitroso-based, and piperazine-based radical polymerization inhibitors are preferred, with naphthoquinone, 2-hydroxynaphthoquinone, hydroquinone, 2,6-di-tert-butyl-P-cresol, and Polystop 7300P (manufactured by Hakuto Co., Ltd.) being more preferred, and Polystop 7300P (manufactured by Hakuto Co., Ltd.) being the most preferred.

[0046] The radical polymerization inhibitor is preferably contained in an amount of 0.0001 to 1 part by mass per 100 parts by mass of the total amount of sealant, more preferably 0.001 to 0.5 parts by mass, and particularly preferably 0.01 to 0.2 parts by mass.

[0047] One example of a method for obtaining the sealant of the present invention is as follows: First, components (A) and (B) are heated and dissolved. Then, 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 uniformly mixed using a known mixing apparatus, such as a three-roll mill, a sand mill, a ball mill, a planetary mixer, etc. If necessary, after mixing, filtration may be performed to remove impurities.

[0048] The sealant of the present invention is applied to a substrate, bonded to other components, and cured by irradiation with ultraviolet light. However, it may also be cured by electron beam, or thermal curing may be added.

[0049] 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, bonding the applied sealant to a support frame, and irradiating with ultraviolet light from the support frame side. The application method is not particularly limited and includes methods such as screen printing and using a dispenser. The material of the support frame is not particularly limited and includes 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. [Examples]

[0050] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0051] [Synthesis Example 1] In a flask equipped with a thermometer, condenser, and stirrer, 780.89 g of hydroxyl-terminated liquid polybutadiene (HLBH-P2000, Clay Valley, hydroxyl value 49.2 mg KOH / g) and 144.60 g of isophorone diisocyanate (WANNATE IPDI, Manka Chemical, molecular weight 222.3) were charged and reacted at 80°C. The isocyanate content at this time was determined by adding an excess of di-n-butylamine to react with the isocyanate, and then titrating the remaining di-n-butylamine with hydrochloric acid standard solution. It was confirmed that this value was within plus or minus 2% of the residual isocyanate amount calculated from the original 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 octoate (catalyst) were added, and the mixture was stirred at 80°C. The absorption spectrum of the isocyanate group (2280 cm²) was then measured using infrared absorption spectroscopy. -1 The reaction was carried out until the ) disappeared, yielding a urethane acrylate oligomer with a weight-average molecular weight of 9,700.

[0052] [Synthesis Example 2] In a flask equipped with a thermometer, condenser, and stirrer, 895.04 g of polypropylene glycol (AGC Inc. EXCENOL 3020, hydroxyl value 36.2 mg KOH / g) and 83.44 g of isophorone diisocyanate (WANNATE IPDI, manufactured by Wanhua Chemical Co., Ltd., molecular weight 222.3) were charged and reacted at 80°C. The isocyanate content at this time was determined by adding an excess of di-n-butylamine to react with the isocyanate, and then titrating the remaining di-n-butylamine with hydrochloric acid standard solution to neutralize it. It was confirmed that this value was within plus or minus 2% of the residual isocyanate amount calculated. 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 the mixture was stirred at 80°C. The absorption spectrum of the isocyanate group (2280 cm²) was measured using infrared absorption spectroscopy. -1 The reaction was carried out until the ) disappeared, yielding a urethane acrylate oligomer with a weight-average molecular weight of 22,850.

[0053] [Examples 1-4, Comparative Examples 1-4] The components (A), (B), photopolymerization initiator, and antioxidant were heated and mixed at 90°C in the proportions shown in Table 1 below. After cooling to room temperature, component (C) was added and stirred, and then dispersed in a disperser to prepare a sealant, which was then evaluated as follows.

[0054] [Weight change rate] A sealant was sandwiched between two PET films (Toyo Cloth Co., Ltd.: SP1030, 100 μm thickness) and one PET film (Lintec Corporation: LT-H, 50 μm thickness). The sealant was then stretched using a roll-type press until its thickness reached 250 μm, and then heated with a high-pressure mercury lamp (Ushio Inc.: UVX-02516S1AFL01) at 75 mW / cm². 2 3000 mJ / cm² 2 Cured material was obtained by irradiation. After measuring the initial weight of the obtained cured material, it was immersed in 95°C hot water for 240 hours, air-dried in an environment of 25°C and 50% RH for more than 48 hours, and then the weight after the test was measured. The percentage change in weight between the initial and post-test was calculated, and the results are shown in Tables 1 and 2.

[0055] [Electrical conductivity] 0.15 g of the cured material, obtained by the same method as for evaluating the weight change rate, was placed in 25 g of ultrapure water and shaken for 60 seconds at room temperature using a shaker (AS ONE Corporation: Double One Lab Shaker SPR-2) to obtain extract water. The initial conductivity of the obtained extract water was measured using a conductivity meter (METTLER TOREDO: SevenMulti), and then the extract water and the cured material were placed in a constant temperature bath at 95°C and subjected to hot water extraction for 240 hours. The electrical conductivity after the test was then measured.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] The results in Tables 1 and 2 show that the sealant of the present invention exhibits a low weight change rate after immersion in hot water and low electrical conductivity before and after hot water extraction, resulting in fewer leached substances and excellent low-contamination properties.

Claims

1. A sealant for fuel cells containing (A) a photopolymerization initiator with a weight-average molecular weight of 400 or more determined by gel permeation chromatography (GPC), and (B) a curable compound.

2. Furthermore, the sealant for fuel cells according to claim 1, further comprising (C) filler.

3. The fuel cell sealant according to claim 1, wherein the (A) photopolymerization initiator has two or more sites in one molecule that generate radicals upon irradiation with ultraviolet light or visible light or heat.

4. The fuel cell sealant according to claim 1, wherein the (A) photopolymerization initiator is a polymer of 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone.

5. The fuel cell sealant according to claim 1, wherein the (B) curable compound contains a polybutadiene compound having a reactive group in its molecule.

6. The fuel cell sealant according to claim 1, comprising a urethane (meth)acrylate compound as the curable compound (B).

7. The fuel cell sealant according to claim 1, used as a sealant for polymer electrolyte membranes.

8. A fuel cell comprising a sealant for fuel cells according to any one of claims 1 to 7.

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