Photocurable sheet sealant for fuel cell, cured product, fuel cell, and sealing method

Abstract

The present invention aims to provide a photocurable sheet sealant having adhesion to an electrolyte membrane and hydrogen barrier properties. The photocurable sheet sealant for fuel cells of the present invention comprises (A) component: urethane (meth) acrylate, (B) component: phenoxy resin, and (C) component: photopolymerization initiator.

Description

Technical Field

[0001] This invention relates to a photocurable sheet sealant for fuel cells, a cured product, a fuel cell, and a sealing method. Background Technology

[0002] In recent years, fuel cells have attracted attention as a new energy system for automobiles and homes. A fuel cell is a power generation device that generates electricity by reacting hydrogen and oxygen chemically. Furthermore, fuel cells are considered a clean next-generation power generation device due to their high energy efficiency during power generation and the production of water through the reaction of hydrogen and oxygen. There are four types of fuel cells: solid polymer fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells. Among them, solid polymer fuel cells, due to their relatively low operating temperature (around 80°C) and high power generation efficiency, are expected to be used in automotive power sources, home power generation devices, small power supplies for electronic devices such as mobile phones, and emergency power supplies.

[0003] like Figure 1 As shown, the cell 1 of the solid polymer fuel cell is configured to include an electrolyte membrane-electrode assembly (MEA) 5, a frame 6 supporting the MEA, and a separator 2 forming a gas flow path. The electrolyte membrane-electrode assembly (MEA) 5 is configured such that a polymer electrolyte membrane 4 is sandwiched between an air electrode (cathode) 3a and a fuel electrode (anode) 3b.

[0004] To start a solid polymer fuel cell, it is necessary to separate the supply of hydrogen-containing fuel gas to the fuel electrode and the supply of oxygen-containing oxidizing gas to the air electrode. Insufficient separation can lead to mixing of these gases, potentially reducing power generation efficiency. Therefore, sealants are typically used to prevent leakage of fuel gas or oxidizing gas. Specifically, sealants are used between adjacent separators, between separators and the frame, and between the frame and the electrolyte membrane or MEA.

[0005] Japanese Patent Application Publication No. 2002-042835 discloses a sealing structure for a fuel cell that prevents fluid from leaking out between the separators of a battery pack consisting of multiple layers of batteries with electrolyte held by electrodes stacked between separators. The structure is characterized by an elastic membrane integrally provided on one surface of the separator, the elastic membrane being formed by irradiating a photocurable resin printed onto the surface of the separator with light and then curing it. Summary of the Invention

[0006] However, as disclosed in Japanese Patent Application Publication No. 2002-042835, when printing photocurable resin onto the surface of components such as partitions by screen printing, air bubbles are easily mixed in. Due to the presence of these air bubbles, there is a problem of reduced adhesion between the photocurable resin and the component.

[0007] The present invention was made in view of the above-mentioned situation, and its object is to provide a photocurable sheet sealant for fuel cells that has a tight seal to the electrolyte membrane and low hydrogen permeability.

[0008] The key points of this invention are described below.

[0009] [1] A photocurable sheet sealant for fuel cells, comprising: (A) urethane (meth) acrylate, (B) phenoxy resin, and (C) photopolymerization initiator.

[0010] [2] The photocurable sheet sealant for fuel cells according to [1] is characterized in that the (A) component has a polycarbonate backbone.

[0011] [3] The photocurable sheet sealant for fuel cells according to [1] or [2] is characterized in that the glass transition temperature of component (B) is 50 to 120°C.

[0012] [4] A photocurable sheet sealant for fuel cells according to any one of [1] to [3], wherein the weight-average molecular weight of component (A) is 20,000 to 100,000.

[0013] [5] A photocurable sheet sealant for fuel cells according to any one of [1] to [4], wherein the photocurable sheet sealant for fuel cells contains 4 to 70 parts by weight of component (B) relative to 100 parts by weight of component (A).

[0014] [6] A photocurable sheet sealant for fuel cells according to any one of [1] to [5], wherein the (C) component has a photoinitiator compound having an absorption wavelength of 365 nm or higher, which decomposes upon irradiation with ultraviolet light of 365 nm or higher, generating free radicals that participate in polymerization.

[0015] [7] A photocurable sheet sealant for fuel cells according to any one of [1] to [6], wherein the photocurable sheet sealant for fuel cells further contains at least one of a monomer having a (meth)acryloyl group that is monofunctional, difunctional, trifunctional or tetrafunctional or more as a (D) component.

[0016] [8] A photocurable sheet sealant for fuel cells according to any one of [1] to [7], wherein the photocurable sheet sealant for fuel cells is a sealant between adjacent partitions in a fuel cell, or a sealant between the frame of a fuel cell and an electrolyte membrane or an electrolyte membrane-electrode junction.

[0017] [9] A cured material, which is formed by curing the photocurable sheet sealant for fuel cells according to any one of claims 1 to 8.

[0018]

[10] The cured product according to [9], wherein the hydrogen permeability of the cured product is 1.0 × 10⁻⁶. -14 mol·m / m 2 Below ·s·Pa.

[0019]

[11] A fuel cell comprising the solidified material described in [9] or

[10] .

[0020]

[12] A method for sealing at least a portion between flanges of a sealed component having at least two flanges, comprising the following steps:

[0021] The process of transferring the photocurable sheet sealant for fuel cells as described in any one of [1] to [7] onto the surface of at least one of the flanges by active energy rays;

[0022] The process of bonding one flange and the other flange, which are printed with the photocurable sheet sealant for fuel cells, together across the photocurable sheet sealant; and

[0023] The process of curing the photocurable sheet sealant for the fuel cell to seal at least a portion between the at least two flanges.

[0024]

[13] A method for sealing at least a portion between the flanges of a sealed component having at least two flanges, comprising the steps of: [1] to [7]

[0025] The process of transferring the photocurable sheet sealant for fuel cells as described in any one of [1] to [7] to at least one flange of the flange;

[0026] The process of forming a sealing gasket composed of a cured material obtained by irradiating the transferred photocurable sheet sealant for fuel cells with an activation energy ray and then curing it; and

[0027] The process of placing another flange on the sealing gasket, pressing a flange printed with a photocurable sheet sealant for fuel cells and the other flange through the sealing gasket, and sealing at least a portion between the at least two flanges.

[0028]

[14] The method according to any one of

[12] or

[13] , wherein, in the step of transferring the photocurable sheet sealant for fuel cells, the photocurable sheet sealant for fuel cells is pre-die-cut into the shape required for sealing.

[0029]

[15] A photocurable sheet sealant for fuel cells, wherein the photocurable sheet sealant for fuel cells is obtained by applying a coating containing (A) component: urethane (meth) acrylate, (B) component: phenoxy resin, (C) component: photopolymerization initiator and organic solvent to a sealing substrate and drying the organic solvent. Attached Figure Description

[0030] Figure 1 This is a schematic cross-sectional view of a single cell of a fuel cell. Figure 1 In the diagram, 1 represents the cell unit of a solid polymer fuel cell, 2 represents the separator, 3a represents the air electrode (cathode), 3b represents the fuel electrode (anode), 4 represents the polymer electrolyte membrane, 5 represents the electrolyte membrane-electrode assembly (MEA), 6 represents the frame, 7 represents the adhesive or sealant, 8a represents the oxidation gas flow path, 8b represents the fuel gas flow path, and 9 represents the cooling water flow path.

[0031] Figure 2 This is a simplified diagram representing the entire fuel cell. Figure 2 In the diagram, 10 represents the battery pack and 11 represents the solid polymer fuel cell. Detailed Implementation

[0032] The present invention will now be described in detail. Furthermore, in this specification, "X~Y" is used to mean "above X and below Y," referring to the numerical values ​​"X and Y" preceding and following it. In this specification, "(meth)acrylate" refers to both acrylate and methacrylate.

[0033] One aspect of the present invention relates to a photocurable sheet sealant for fuel cells, comprising (A) urethane (meth)acrylate, (B) phenoxy resin, and (C) a photopolymerization initiator. The photocurable sheet sealant for fuel cells of the present invention provides excellent adhesion to the electrolyte membrane and low hydrogen permeability.

[0034] <(A)Component>

[0035] The urethane (meth)acrylate used as component (A) in this invention is not particularly limited, but is preferably a urethane (meth)acrylate formed from the reaction product of a polyol compound having two or more hydroxyl groups in its molecule, a compound having two or more isocyanate groups in its molecule, and a (meth)acrylate containing at least one hydroxyl group in its molecule. From the viewpoint of obtaining a cured product with excellent low hydrogen permeability, a urethane (meth)acrylate having a polycarbonate backbone is preferred. Furthermore, the weight-average molecular weight of component (A) is preferably 20,000 to 100,000, more preferably 25,000 to 90,000, and particularly preferably 30,000 to 80,000. By adopting the above range, the interfacial affinity is further improved when bonded to adherents such as electrolyte membranes, separators, and frames, resulting in excellent adhesion to components and low hydrogen permeability. In the specification, weight-average molecular weight refers to the weight-average molecular weight converted from polystyrene by gel permeation chromatography.

[0036] Examples of polyol compounds containing two or more hydroxyl groups include polyether polyols, polyester polyols, caprolactone diol, bisphenol polyols, polyisoprene polyols, hydrogenated polyisoprene polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, castor oil polyols, and polycarbonate diols. Among these, polycarbonate diols, polybutadiene polyols, and hydrogenated polybutadiene polyols are preferred, with polycarbonate diols being particularly preferred from the viewpoint of low hydrogen permeability and excellent cured product properties. They can be used alone or in combination.

[0037] Examples of compounds having two or more isocyanate groups within their molecules include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. From the viewpoint of obtaining a flexible cured product, aliphatic polyisocyanates and alicyclic polyisocyanates are preferred. They can be used alone or in combination. Examples of aromatic polyisocyanates include 2,4-methylphenylene diisocyanate, 2,6-methylphenylene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, tetramethylxylene diisocyanate, diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, and triphenylmethane triisocyanate. Examples of alicyclic polyisocyanates include isophorone diisocyanate, bis(4-isocyanate-cyclohexyl)methane, 1,3-bis(isocyanate-methyl)cyclohexane, 1,4-bis(isocyanate-methyl)cyclohexane, norbornene diisocyanate, and norbornene triisocyanate. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, 1,3,6-hexamethylene triisocyanate, and 1,6,11-undecane triisocyanate. From the perspective of excellent adhesion to the electrolyte membrane, diisocyanates such as isophorone diisocyanate and hexamethylene diisocyanate are preferred.

[0038] Examples of (meth)acrylates containing at least one hydroxyl group in their molecule include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, mono(meth)acrylates of diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and polyethylene glycol, and mono(meth)acrylates or di(meth)acrylates of triols such as trimethylolethane, trimethylolpropane, and glycerol. From the viewpoint of obtaining a cured product with excellent flexibility, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, or hydroxybutyl (meth)acrylate are preferred. They can be used alone or in combination.

[0039] The method for synthesizing the urethane (meth)acrylate as component (A) is not particularly limited, and known methods can be used. For example, a method can be described in which a polyol compound having two or more hydroxyl groups in its molecule is reacted with an isocyanate compound having two or more isocyanate groups in its molecule at a molar ratio (polyol compound: isocyanate compound) preferably 3:1 to 1:3, more preferably 2:1 to 1:2, in a diluent (e.g., methyl ethyl ketone, methoxyphenol, etc.) to obtain a urethane prepolymer. Then, the residual isocyanate groups in the obtained polyurethane prepolymer are further reacted with a sufficient amount of (meth)acrylate containing at least one or more hydroxyl groups in its molecule to synthesize a polyurethane (meth)acrylate.

[0040] In addition, examples of catalysts used in the synthesis include triphenylaluminum, trioctylaluminum, dibutyltin dilaurate, copper naphthenate, zinc naphthenate, zinc octylate, zinc octenate, zirconium naphthenate, cobalt naphthenate, tetra-n-butyl-1,3-diacetoxydistannoxane, triethylamine, 1,4-diaza[2,2,2]bicyclooctane, and N-ethylmorpholine. From the viewpoint of high activity and the ability to obtain cured products with excellent durability, dibutyltin dilaurate, zinc naphthenate, zinc octylate, or zinc octenate are preferred. These catalysts are preferably used in quantities of 0.0001 to 10 parts by mass relative to 100 parts by mass of the total reactants. Furthermore, the reaction temperature is typically carried out at 10 to 100°C, and particularly preferably at 30 to 90°C.

[0041] <(B) Ingredients>

[0042] The phenoxy resin used as component (B) in this invention is, for example, a compound obtained by epichlorohydrin and bisphenol. Examples of components (B) include bisphenol-type phenoxy resins, phenolic varnish-type phenoxy resins, naphthyl-type phenoxy resins, and biphenyl-type phenoxy resins. The resins listed above can be used alone or in combination. From the viewpoint of good adhesion to the electrolyte membrane, bisphenol-type phenoxy resins are particularly preferred. From the viewpoint of good compatibility with component (A) of this invention and the yield of a flexible cured product, a copolymer of bisphenol A and bisphenol F is preferred. These can be used alone or in combination.

[0043] Furthermore, to improve the adhesion to electrolyte membranes and other substrates and the bonding affinity with the substrate during pressing, it is preferable that the sheet sealant softens during hot pressing. Therefore, the glass transition temperature of the phenoxy resin is preferably in the range of 50–120°C, more preferably in the range of 60–90°C. By using this range, good affinity at the interface is achieved when bonding with substrates such as electrolyte membranes, separators, and frames, resulting in excellent adhesion to the electrolyte membrane.

[0044] The phenoxy resin used as component (B) above can be a commercially available product. Examples of commercially available products include Phenoto YP-50, Phenoto YP-50S, Phenoto YP-55, Phenoto YP-70, ZX-1356-2, FX-316 (manufactured by Nippon Steel Chemical Co., Ltd.), jER1256, jER4250 or jER4275 (manufactured by Mitsubishi Chemical Co., Ltd.), PKHB, PKHC, PKHH, PKHJ, PKFE (manufactured by Inchem Co., Ltd.), etc.

[0045] The amount of component (B) in this invention (when containing two or more components, its total amount) is preferably 4 to 70 parts by mass relative to 100 parts by mass of component (A), more preferably 10 to 60 parts by mass, and particularly preferably 15 to 50 parts by mass. From the viewpoint of obtaining a cured product with better adhesion to the electrolyte membrane and lower hydrogen permeability, the above range is preferred.

[0046] <(C) Ingredients>

[0047] The photopolymerization initiator used in this invention as component (C) is a compound that generates free radicals by irradiation with active energy rays such as ultraviolet light. From the viewpoint that component (C) can be sufficiently photocured even by light irradiation beyond the frame and exhibits excellent adhesion to the electrolyte membrane, it is preferable to be a compound having an absorption wavelength of 365 nm or higher, which decomposes upon irradiation with ultraviolet light at a wavelength of 365 nm or higher and generates free radicals that participate in polymerization. Specifically, examples include thioxanthone-based photoradical polymerization initiators and acylphosphine oxide-based photoradical polymerization initiators. Furthermore, they can be used alone or in combination of two or more.

[0048] Examples of thioxanthone-based photoradical polymerization initiators include, but are not limited to, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one meso chloride, etc. Examples of acylphosphine oxide-based photoradical polymerization initiators include, for example, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, etc., but are not limited to these.

[0049] The amount of component (C) in this invention (when it contains two or more components, the total amount) is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, relative to 100 parts by mass of component (A). Within this range, the adhesion to the electrolyte membrane is excellent.

[0050] <(D) Components>

[0051] Furthermore, in this invention, as component (D), at least one of monofunctional, difunctional, trifunctional, and tetrafunctional monomers having a (meth)acryloyl group may be added. They may be used alone or as a mixture of two or more.

[0052] Examples of monofunctional monomers having a (meth)acryloyl group include lauryl methacrylate, stearyl methacrylate, tetrahydrofurfuryl methacrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, cyclohexyl methacrylate, dicyclopentenyl (meth)acrylate, isobornyl methacrylate, benzyl methacrylate, phenyl methacrylate, phenoxyethyl methacrylate, phenoxydiethylene methacrylate, phenoxytetraethylene glycol methacrylate, nonylphenoxyethyl methacrylate, butoxyethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glyceryl (meth)acrylate, modified butyl methacrylate, epichlorohydrin-modified phenoxy (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and morpholino methacrylate. Examples of difunctional monomers having a (meth)acrylyl group include neopentyl glycol di(meth)acrylate, bisphenol A di(meth)acrylate, epichlorohydrin-modified bisphenol A di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, dicyclopentenyl di(meth)acrylate, and di(meth)acrylyl isocyanurate. Examples of trifunctional monomers having a (meth)acrylyl group include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, epichlorohydrin-modified trimethylolpropane tri(meth)acrylate, epichlorohydrin-modified glycerol tri(meth)acrylate, and tri(acryloyloxyethyl)isocyanurate. In addition, examples of polyfunctional monomers having a (meth)acryloyl group include di(trimethylolpropane)tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa(meth)acrylate. These polymerizable monomers can be used alone or in mixtures of two or more.

[0053] (D) Components: From the viewpoint of excellent adhesion to various components, (meth)acrylate monomers with a repeating number of ether bond structural units of 8 to 25 are preferred; (meth)acrylate monomers with a repeating number of ether bond structural units of 9 to 20 or 14 to 23 are more preferred. Specific examples include polyethylene glycol mono(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol mono(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol mono(meth)acrylate, and polytetramethylene glycol di(meth)acrylate. In addition, commercially available products include, for example, M-90G, AM-130G, M-90G, M-230G, A-400, A-600, APG-700, A-1000, 9G, 14G, 23G, 1206PE (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), PDE-600, PDP-700, ADE-600 (manufactured by Nippon Oil Company), Light Ester 130MA, Light Ester 130MA, Light Ester 130A, 14EG, 14EG-A (manufactured by Kyoeisha Chemical Co., Ltd.), etc., but are not limited to these.

[0054] In this invention, the amount of component (D) (when containing two or more components, its total amount) is preferably 1 to 50 parts by mass relative to 100 parts by mass of component (A), more preferably 1.5 to 30 parts by mass, and particularly preferably 2 to 20 parts by mass. By adopting the above range, the sealing performance of various components is further improved.

[0055] <(E) Components>

[0056] Furthermore, in this invention, as component (E), a silane coupling agent can be incorporated to improve adhesion to electrolyte membranes, frames, etc. Examples of components (E) include, for instance, silane coupling agents containing glycidyl groups such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, and 3-epoxypropoxypropylmethyldiethoxysilane, as well as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxy... Silane coupling agents containing vinyl groups, such as silanes; silane coupling agents containing (meth)acryloyl groups, such as γ-methacryloxypropyltrimethoxysilane; silane coupling agents containing amino groups, such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; and other silanes such as γ-mercaptopropyltrimethoxysilane and γ-chloropropyltrimethoxysilane. Among these, from the viewpoint of further improving adhesion, silane coupling agents containing glycidyl groups or (meth)acryloyl groups are preferred. These can be used alone or in combination of two or more.

[0057] The amount of component (E) in this invention (when it contains two or more components, its total amount) is preferably 0.1 to 10 parts by mass relative to 100 parts by mass of component (A), more preferably 0.5 to 7 parts by mass, and particularly preferably 1 to 5 parts by mass. By adopting the above range, the sealing performance of various components is further improved.

[0058] Without prejudice to the purpose of this invention, the sheet sealant of this invention may be formulated in appropriate amounts with various elastomers such as peroxides, acrylic rubber, polyurethane rubber, and styrene copolymers, fillers, preservation stabilizers, antioxidants, light stabilizers, plasticizers, dyes, pigments, flame retardants, sensitizers, thermal free radical initiators, organic solvents, heavy metal passivators, ion traps, emulsifiers, water dispersion stabilizers, defoamers, release agents, leveling agents, waxes, rheology control agents, surfactants, and other additives (any components).

[0059] In this invention, since heat curing properties can be imparted when the adherend is opaque, peroxides can be added.

[0060] Furthermore, in order to improve the elastic modulus and flowability of the cured product, filler materials that do not hinder storage stability can be added. Specifically, examples include organic powders, inorganic powders, and metallic powders. Examples of inorganic powder filler materials include glass, calcined silica, alumina, mica, ceramics, silicone rubber powder, calcium carbonate, aluminum nitride, carbon powder, kaolin, dried clay minerals, and dried diatomaceous earth. The amount of inorganic powder is preferably about 0.1 to 100 parts by weight relative to 100 parts by weight of component (A).

[0061] To improve the mechanical strength of the cured material, fumed silica-based filler materials can be used. Preferably, substances that have undergone hydrophobic treatment, such as organochlorosilanes, polyorganosiloxanes, and hexamethyldisilazane, are used. Specific examples of fumed silica include commercially available products manufactured by Aerosil Japan under trade names such as Aerosil R974, R972, R972V, R972CF, R805, R812, R812S, R816, R8200, RY200, RX200, RY200S, and R202.

[0062] From the viewpoint of improving the storage stability and weather resistance of the photocurable sheet sealant for fuel cells, the addition of antioxidants and light stabilizers is preferred. As antioxidants, phenolic antioxidants, hindered phenolic antioxidants, organosulfur antioxidants, amine antioxidants, and benzotriazole antioxidants can be used. As light stabilizers, hindered amine light stabilizers and benzoate ester light stabilizers can be used. Furthermore, the following commercially available products can be used as both antioxidants and light stabilizers. For example, SUMILIZER BHT, SUMILIZER S, SUMILIZER BP-76, SUMILIZER MDP-S, SUMILIZER GM, SUMILIZER BBM-S, SUMILIZER WX-R, SUMILIZER NW, SUMILIZER BP-179, SUMILIZER BP-101, SUMILIZER GA-80, SUMILIZER TNP, SUMILIZERTPP-R, SUMILIZER P-16 (manufactured by Sumitomo Chemical Corporation), ADK STAB AO-20, ADK STAB AO-30, ADK STABAO-40, ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-70, ADK STAB AO-80, ADK STABAO-330, ADK STAB PEP-4C, ADK STAB PEP-8, ADK The following are listed: STAB PEP-24G, ADK STAB PEP-36, ADKSTAB HP-10, ADK STAB 2112, ADK STAB 260, ADK STAB 522A, ADK STAB 329K, ADK STAB1500, ADK STAB C, ADK STAB 135A, ADK STAB 3010 (manufactured by AREA), Tinuvin 770, Tinuvin 765, Tinuvin 144, Tinuvin 622, Tinuvin 111, Tinuvin 123, Tinuvin 292 (manufactured by Ciba Specialty Chemicals), etc. There are no particular limitations on the amount of these antioxidants and light stabilizers combined, but they are preferably 0.001 to 5 parts by weight, more preferably 0.01 to 3 parts by weight, relative to 100 parts by weight of component (A).

[0063] Examples of organic solvents that can be used in this invention include alcohols such as methanol and ethanol, chlorinated solvents such as dichloroethane and trichloroethane, fluorinated solvents such as trichlorofluoroethane, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, acetate solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate, dimethyl ether, methyl ethyl ether, diethyl ether, alkane solvents such as pentane, hexane, heptane, and cyclohexane, and aromatic hydrocarbon solvents such as benzene, toluene, and xylene. From the viewpoint of high compatibility with components (A), (B), and (C) of this invention, ketone solvents are preferred. Furthermore, the composition containing components (A) to (C) of this invention, after being diluted with an organic solvent, is called a coating solution.

[0064] The photocurable sheet sealant for fuel cells of the present invention can be manufactured by existing known methods. For example, it can be manufactured by mixing a specified amount of components (A) to (C) using a mixing machine or other mixing means, preferably at a temperature of 10 to 70°C for 0.1 to 5 hours. In addition, it is preferable to manufacture it in a light-protected environment.

[0065] There are no particular limitations on the method for processing the present invention into a sheet; for example, known techniques can be used. For instance, a liquid coating solution is prepared by diluting a composition containing components (A) to (C) of the present invention with an organic solvent. This solution is then applied to a support such as a polyethylene terephthalate film that has undergone pre-release treatment using methods such as flow coating, roller coating, gravure roller coating, wire-wound coating, or lip coating. The organic solvent is then dried, thereby obtaining a film with an arbitrary thickness. When preparing the coating solution, it can be diluted with the solvent after the components are combined, or it can be diluted with the solvent before the components are combined. Alternatively, a sheet can be obtained by applying a coating solution containing components (A) to (C) of the present invention and an organic solvent to a sealing substrate, followed by drying the organic solvent. Furthermore, the sheet after the organic solvent evaporates from the coating solution is in an uncured (unreacted) state.

[0066] The thickness of the photocurable sheet sealant for fuel cells of the present invention is preferably about 1 to 500 μm, more preferably 5 to 400 μm, and even more preferably 10 to 200 μm. By employing this range, excellent adhesion to the electrolyte membrane and low hydrogen gas permeability are achieved, therefore it is preferred.

[0067] From the viewpoints of operability and storage, the photocurable sheet sealant for fuel cells of the present invention preferably has a three-layer structure consisting of a support, a sealant layer, and a release film. When applied to a component, the support and release film can be easily peeled off for use. Examples of materials for the support or release film include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, as well as paper, cloth, and non-woven fabrics. From the viewpoint of release properties, plastic films are preferred. The thickness of the support and release film is preferably 3 to 300 μm, more preferably about 5 to 150 μm. From the viewpoint of improving peelability from the sealant layer, the release film preferably utilizes a release film treated with fluorinated compounds, silicone compounds, long-chain alkyl compounds, etc.

[0068] <Cured product>

[0069] The cured product of this invention is formed by irradiating the photocurable sheet sealant of this invention with active energy rays such as ultraviolet light. There are no limitations on the curing method as long as the cured product is formed from the photocurable sheet sealant of this invention.

[0070] <Uses>

[0071] Suitable applications for using the photocurable sheet sealant or its cured form of the present invention are fuel cells.

[0072] <Fuel Cells>

[0073] A fuel cell is a power generation device that produces electricity by chemically reacting hydrogen and oxygen. There are four main types of fuel cells: solid polymer fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells. Solid polymer fuel cells, due to their relatively low operating temperature (around 80°C) and high power generation efficiency, are used in automotive power sources, home power generation devices, small power supplies for electronic devices such as mobile phones, and emergency power supplies.

[0074] like Figure 1 As shown, a representative solid polymer fuel cell 1 comprises an electrolyte membrane-electrode assembly (MEA) 5, a frame 6 supporting the MEA, and a separator 2 forming a gas flow path. The MEA 5 is configured such that a polymer electrolyte membrane 4 is sandwiched between an air electrode (cathode) 3a and a fuel electrode (anode) 3b. Furthermore, during startup of the solid polymer fuel cell, fuel gas (hydrogen) and oxidizing gas (oxygen) are supplied through oxidizing gas flow path 8a and fuel gas flow path 8b, respectively. Additionally, to mitigate heat generation during power generation, cooling water flows in a cooling water flow path 9. Furthermore, as... Figure 2As shown, hundreds of these batteries are stacked together to form a battery pack, which is referred to as battery pack 10. A solid polymer fuel cell 11 has this battery pack 10.

[0075] When fuel gas (hydrogen) is supplied to the fuel electrode and oxidizing gas (oxygen) is supplied to the oxygen electrode (air electrode), the following reaction occurs at each electrode, resulting in the overall formation of water (H2 + 1 / 2O2 → H2O). Specifically, as described below, protons (H+) generated at the fuel electrode... + The oxygen diffuses in the solid polymer membrane (polymer electrolyte membrane) and moves toward the oxygen electrode side, while the water (H2O) produced by the reaction with oxygen is discharged from the oxygen electrode side.

[0076] Fuel electrode (anode): H2 → 2H + +2e -

[0077] Oxygen electrode (cathode): 1 / 2O2 + 2H+ + +2e - →H2O.

[0078] To start a solid polymer fuel cell, it is necessary to separate the hydrogen-containing fuel gas supplied to the anode electrode and the oxygen-containing oxidizing gas supplied to the cathode electrode. Insufficient separation can lead to mixing of these gases, potentially reducing power generation efficiency. Therefore, sealants are commonly used to prevent leakage of fuel gas or oxygen. Specifically, sealants are applied between adjacent separators, between separators and the frame, and between the frame and the electrolyte membrane or MEA.

[0079] Examples of polymeric electrolyte membranes include cation exchange membranes with ion conductivity. From the perspective of chemical stability and strong high-temperature performance, examples include fluorinated polymers with sulfonic acid groups as shown in formula (3). Commercially available examples include DuPont's Nafion (registered trademark), AGC's Flemion (registered trademark), and Asahi Kasei Corporation's Aciplex (registered trademark). Polymeric electrolyte membranes are generally difficult to bond, but bonding is possible using the photocurable sheet sealant of this invention.

[0080]

[0081] [Chemical Formula 1]

[0082] The fuel electrode, referred to as the hydrogen electrode or anode, uses a known fuel electrode. For example, a catalyst using carbon-supported platinum, nickel, ruthenium, or similar catalysts is employed. Similarly, the air electrode, referred to as the oxygen electrode or cathode, uses a known air electrode. For example, a catalyst using carbon-supported platinum, alloy, or similar catalysts is employed. A gas diffusion layer, which facilitates gas diffusion or moisturizes the electrolyte, may also be provided on the surface of each electrode. Known gas diffusion layers can be used, such as carbon paper, carbon cloth, or carbon fiber.

[0083] The partition 2 is as follows Figure 1 The diagram shows a flow path with fine irregularities through which fuel gas or oxidizing gas is supplied to the electrodes. Additionally, the separator is made of materials such as aluminum, stainless steel, titanium, graphite, and carbon.

[0084] The frame is a component designed to support and reinforce the electrolyte membrane or MEA of the thin film to prevent rupture. The frame can be made of thermoplastic resins such as polyvinyl chloride, polyethylene naphthalate (PEN), polyethylene terephthalate, polypropylene, and polycarbonate. Furthermore, for bonding the component using the light-curing sheet sealant or its cured product of the present invention, the component is preferably translucent.

[0085] The fuel cell of the present invention refers to a fuel cell characterized by sealing using the photocurable sheet sealant or its cured form of the present invention. Examples of components in a fuel cell requiring sealing include separators, frames, electrolytes, fuel electrodes, air electrodes, and MEAs. More specific sealing locations include the positions between adjacent separators, between separators and frames, and between frames and electrolyte membranes or MEAs. The primary purpose of sealing "between separators and frames" or "between polymer electrolyte membranes or MEAs and frames" is to prevent gas mixing or leakage. The purpose of sealing adjacent separators is to prevent gas leakage and to prevent cooling water leakage from the cooling water flow path to the outside. Since the acid generated by the electrolyte membrane creates a strongly acidic atmosphere, the sealant is required to be acid-resistant.

[0086] <Sealing Construction Method>

[0087] The sealing application method (sealing method) using the light-curing sheet sealant of the present invention is not particularly limited, and the following two application methods can be cited as examples.

[0088] The first sealing method is as follows.

[0089] This method seals at least a portion between the flanges of a sealed component having at least two flanges. The method comprises: a step of transferring a photocurable sheet sealant for fuel cells of the present invention onto the surface of at least one of the flanges, where at least one flange is permeable to an active energy line; a step of bonding one flange with the transferred photocurable sheet sealant and the other flange together via the photocurable sheet sealant; and a step of curing the photocurable sheet sealant to seal at least a portion between the at least two flanges.

[0090] The first sealing method is illustrated using the sealing method between the electrolyte membrane and the frame as an example. The sealing method generally consists of three steps: a transfer process, an bonding process, and a curing process. Furthermore, although the sealing method between the electrolyte membrane and the frame is illustrated, it can also be used between separators, and between the fuel cell frame and the electrolyte membrane or electrolyte electrode assembly.

[0091] [Transfer Printing Process]

[0092] As a transfer method, the release liner on the lightly peeling side of a UV-curable sheet sealant is peeled off and pressed onto an electrolyte membrane. From the viewpoint of improving the adhesion to the substrate, a roller laminator is preferred, in which the transfer is performed while heating and pressurizing.

[0093] [Lamination Process]

[0094] After the transfer, the substrate film remaining on the UV-curable sheet sealant is peeled off and bonded to the frame, then heated and pressurized during bonding. From the viewpoint of achieving bubble-free bonding, it is preferable to bond in a vacuum or low-pressure atmosphere. Examples of bonding devices include vacuum presses, vacuum laminators, and autoclaves.

[0095] [Curing Process]

[0096] In the bonded assembly, the photocurable sheet sealant can be cured by irradiating the frame side with active energy rays, thus integrating it into the structure. The photocurable sheet sealant of this invention cures rapidly even under irradiation with active energy rays, forming a strong and tough cured product, while exhibiting strong adhesion to electrolyte membranes and plastics. The irradiation with active energy rays is preferably in the wavelength range of 150–750 nm, and can be performed using low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, metal halide lamps, or LED lamps at a frequency of 1–100 kJ / m². 2 The cumulative light intensity is used for curing, preferably 5–70 kJ / m². 2 The cumulative amount of light.

[0097] The second sealing construction method is as follows.

[0098] This method seals at least a portion between the flanges of a sealed component having at least two flanges, characterized by comprising the following steps: transferring the photocurable sheet sealant for fuel cells of the present invention onto at least one flange of the flanges; irradiating the transferred photocurable sheet sealant for fuel cells with an activation energy line to form a gasket formed from a cured product obtained by curing the photocurable sheet sealant for fuel cells; and disposing the other flange on the gasket, pressing the flange on which the photocurable sheet sealant for fuel cells is transferred and the other flange together through the gasket to seal at least a portion between the at least two flanges.

[0099] Furthermore, in the process of transferring the photocurable sheet sealant for fuel cells in the first and second sealing construction methods, it is preferable to pre-die-cut the photocurable sheet sealant for fuel cells into the shape required for sealing, so that the size and shape can be optimized.

[0100] The energy storage modulus (25°C) of the cured photocurable sheet sealant for fuel cells of the present invention is 1×10⁻⁶. 4 ~1×10 9 Pa, preferably 1×10 Pa 5 ~1×10 8 Pa. Details of the energy storage modulus test are shown in the embodiments. By employing the aforementioned range, since the solidified material is soft, it can adequately buffer external stresses applied to the fuel cell, preventing a deterioration in the fuel cell's performance.

[0101] Furthermore, the elongation of the cured product of the photocurable sheet sealant for fuel cells of the present invention is preferably 50–2000%, more preferably 100–1500%, and particularly preferably 150–1200%. Elongation refers to the value measured according to JIS K 6251:2010. Details of the elongation test are shown in the examples. By employing the range described above, when the electrolyte membrane and frame are bonded together, strain occurs due to the curing shrinkage of the sealant, and the cured product can absorb this strain, thus providing a fuel cell with excellent durability in terms of resistance to thermal cycling, etc.

[0102] Furthermore, the hydrogen permeability of the cured product of the photocurable sheet sealant for fuel cells of the present invention is preferably 1.0 × 10⁻⁶. -14 The following is a description of the lower limit for the hydrogen permeability of the cured product. There is no particular limitation on this lower limit; for example, it can be 1.0 × 10⁻⁶. -15 The above describes how the hydrogen gas can be adequately sealed, thus maintaining the battery performance of the fuel cell.

[0103] Example

[0104] The following examples illustrate the invention in more detail, but the invention is not limited to these examples.

[0105] <Synthetic Example 1: Carbamate Acrylate (a1)>

[0106] 582.26 parts by mass of methyl ethyl ketone, 59.94 parts by mass of isophorone diisocyanate, 0.05 parts by mass of 4-methoxyphenol, and 0.1 parts by mass of dibutyltin dilaurate were added to a glass reaction vessel equipped with a thermometer, stirrer, and reflux tube. The mixture was heated to 60°C while stirring. 520 parts by mass of polycarbonate diol (T5651, manufactured by Asahi Kasei Chemicals Co., Ltd.) heated to 70°C was added dropwise. After the addition was complete, the mixture was stirred for 3 hours to allow the reaction to proceed. Next, 2.32 parts by mass of 2-hydroxyethyl acrylate was added dropwise. After the addition was complete, the mixture was stirred for 3 hours to allow the reaction to proceed. The molar ratio of isophorone diisocyanate to polycarbonate diol was 1:2. The reaction was considered complete when the isocyanate groups disappeared, yielding polycarbonate polyurethane acrylate. The weight-average molecular weight was 60,000.

[0107] <Synthetic Example 2: Polyorganosiloxanes Containing Terminal Acrylates (a'1)>

[0108] To 2000 parts by mass of a two-terminated silanol polydimethylsiloxane with a weight average molecular weight of 20000, 8 parts by mass of aminopropylmethyldimethoxysilane were added, and the mixture was stirred at 100°C for 2 hours under nitrogen purging to obtain a terminal amino polydimethylsiloxane. Then, to 100 parts by mass of the obtained resin, 0.8 parts by mass of ethyl 2-isocyanate acrylate were added, and the mixture was stirred at 50°C for 1 hour under nitrogen purging to obtain a polyorganosiloxane containing terminal acrylate.

[0109] <Preparation of UV-curable sheet sealant>

[0110] Example 1

[0111] 100 parts by weight of urethane acrylate, which is component (a1) of the present invention,

[0112] Component (B) consists of 33 parts by mass of a copolymer of bisphenol A and bisphenol F, namely a phenoxy resin (manufactured by Mitsubishi Chemical Corporation JER4250) with a glass transition temperature of 70°C; and component (C) consists of 2 parts by mass of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (manufactured by IGM Resins B.V. TPO).

[0113] One part by weight of polyethylene glycol dimethacrylate (23G manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) having 23 repeating ether bonds as component (d1) and one part by weight of polyethylene glycol dimethacrylate (14G manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) having 14 repeating ether bonds as component (d2).

[0114] As component (E), component (e1) contains 1 part by weight of γ-methacryloyloxypropyltrimethoxysilane (Shin-Etsu Chemical Industry Co., Ltd. KBM-503), and

[0115] Ten parts by weight of methyl ethyl ketone, used as an organic solvent, were mixed in a mixer for 60 minutes under light-shielding conditions and at room temperature (25°C) to obtain a sealant composition.

[0116] Next, the sealant composition was coated onto a 35 μm polyethylene terephthalate (PET) release film and placed at 100°C for 10 minutes to remove the solvent and allow it to dry. Then, a 25 μm PET release film was adhered to the coated surface after the solvent was removed, resulting in a light-curing sheet sealant with an adhesive layer thickness of 50 μm, i.e., Example 1.

[0117] Example 2

[0118] Except for removing components (d1) and (d2) in Example 1, Example 2 was prepared in the same manner as in Example 1 to obtain Example 2.

[0119] Comparative Example 1

[0120] Comparative Example 1 was prepared in the same manner as in Example 1, except that a terminal acrylate-containing polyorganosiloxane containing component (a'1) was used instead of component (a1) in Example 1.

[0121] Comparative Example 2

[0122] Comparative Example 2 was prepared in the same manner as in Example 1, except that component (b1) was removed in Example 1.

[0123] The test methods used in the examples and comparative examples in Table 1 are described below.

[0124] <(1) Sheet Formation Test>

[0125] The appearance of each UV-curable sheet sealant was visually observed while it was in the presence of a polyethylene terephthalate film. The observation results were evaluated according to the following criteria. The results are shown in Table 1.

[0126] Pass: Same, extremely smooth

[0127] Unqualified: It is different; the surface has many bumps and pinholes (small holes appearing on the surface of the sheet).

[0128] <(2) Hydrogen permeability test>

[0129] Each type of UV-curable sheet sealant was irradiated with ultraviolet light for 20 seconds using an ultraviolet irradiation machine, resulting in a cumulative light intensity of 45 kJ / m². 2 This process produces a 1 mm thick sheet of cured material. The cured sheet is then tested according to JIS K 7126-1:2006 (Plastics—Films and Sheets—Test Methods for Gas Transmission Rate—Part 1: Differential Pressure Method). The test method is a pressure sensor method, conducted at 23°C with the test gas (hydrogen) on the high-pressure side at 100 kPa. The results are shown in Table 1. In this invention, a thickness of 1.0 × 10⁻⁶ is preferred. -14 mol·m / m 2 Below ·s·Pa. Therefore, in Table 1, 1.0×10 -14 mol·m / m 2 The following values ​​are considered acceptable: ·s·Pa.

[0130] <(3) Test on the adhesion of the electrolyte membrane>

[0131] Using various photocurable sheet sealants, a PET film (10mm wide × 500mm long × 400μm thick) was laminated with an electrolyte membrane (Nafion, manufactured by DuPont) made of a fluorinated polymer with sulfonic acid groups at a width of 10mm × length of 500mm. A cumulative light intensity of 50kJ / m² was irradiated from the PET film side. 2 The PET film was cured by ultraviolet light to form a test piece. Then, a tensile testing machine was used to measure the peel strength of the PET film stretched 180 degrees from the electrolyte membrane at a speed of 10 mm / min. The results are shown in Table 1. In this invention, a peel strength of 1.5 N / mm or more is preferred. In addition, during the tensile test, the electrolyte membranes of Examples 1 and 2 failed midway through the test. On the other hand, the electrolyte membrane of Comparative Example 2 did not fail. It should be noted that "not measured" in Comparative Example 1 in Table 1 means that (2) the hydrogen permeability test failed, so this test was not performed.

[0132] [Table 1]

[0133]

[0134] As can be seen from Examples 1 and 2 in Table 1, the present invention can provide a photocurable sheet sealant for fuel cells that has good adhesion to the electrolyte membrane and low hydrogen permeability.

[0135] Furthermore, in Comparative Example 1 of Table 1, a photocurable sheet sealant containing terminal acrylate (a'1) was used instead of component (A) of the present invention, resulting in significantly poorer low-hydrogen gas permeability. Additionally, Comparative Example 2 was a photocurable sheet sealant without component (B) of the present invention, resulting in poor sheet formation and adhesion to the electrolyte membrane.

[0136] Further tests were conducted on (4) energy storage modulus and (5) elongation.

[0137] <(4) Energy storage modulus test>

[0138] The light-curing sheet sealant of Example 1 was cured by irradiating it with ultraviolet light to achieve a cumulative light intensity of 50 kJ / m. 2 Next, the elastic modulus of the cured material was measured. A dynamic viscoelasticity measuring apparatus (DMS6100, manufactured by Seiko Instruments Co., Ltd.) was used as the measuring device. A 0.6 mm thick sample was prepared by overlapping light-curing sheet sealant removed from a PET film, and the storage modulus of elasticity at 25°C was determined. The measurement frequency was 1 Hz. In this invention, the storage modulus of elasticity of the cured material is preferably 1 × 10⁻⁶. 4 ~1×10 9 The range of Pa. The storage elastic modulus of the cured product of the light-curing sheet sealant in Example 1 is 5 × 10⁻⁶. 6 Pa.

[0139] <(5) Determination of elongation>

[0140] The light-curing sheet sealant of Example 1 was irradiated with 50 kJ / m 2 Ultraviolet light is used to create a cured material. The cured material is then cut into test pieces with a thickness of 0.6 mm, a total length of 50 mm, and a width of 10 mm. Tensile testing is then performed using a tensile testing machine according to JIS K 6251:2010 until the test piece is cut. The tensile speed is 500 mm per minute. In this invention, the elongation of the cured material is preferably 50% to 2000%.

[0141] The cured product of the light-curing sheet sealant in Example 1 has an elongation of 870%.

[0142] Industrial applicability

[0143] This invention was made in view of the aforementioned situation, and as a light-curing sheet sealant with both sealing properties for the electrolyte membrane and hydrogen barrier properties, it can be used for various sealing applications. In particular, it is industrially useful because it is effective as a curable sealant for fuel cells.

[0144] This application is based on Japanese Patent Application No. 2020-172734, filed on October 13, 2020, the disclosure of which is incorporated herein by reference in its entirety.

[0145] Explanation of reference numerals in the attached figures

[0146] 1. Battery unit of solid polymer fuel cell

[0147] 2 partitions

[0148] 3a Air electrode (cathode)

[0149] 3b fuel electrode (anode)

[0150] 4. Polymer electrolyte membrane

[0151] 5. Electrolyte Membrane-Electrode Assembly (MEA)

[0152] 6-frame

[0153] 7 Adhesives or sealants

[0154] 8a Oxidizing Gas Flow Path

[0155] 8b fuel gas flow path

[0156] 9 cooling water path

[0157] 10 battery pack

[0158] 11 Solid Polymer Fuel Cells

Claims

1. A method for sealing at least a portion between the flanges of a sealed component having at least two flanges, comprising the following steps: The process of transferring a photocurable sheet sealant for fuel cells onto the surface of at least one of the flanges by active energy rays passing through at least one of the flanges; The process of bonding one flange and the other flange, which are printed with the photocurable sheet sealant for fuel cells, together across the photocurable sheet sealant; and The process of curing the photocurable sheet sealant for the fuel cell to seal at least a portion between at least two flanges. in, The photocurable sheet sealant for fuel cells comprises: Component A: urethane (meth)acrylate, Component B: phenoxy resin, and Component C: photopolymerization initiator. The product contains 4 to 70 parts by mass of component B relative to 100 parts by mass of component A.

2. A method for sealing at least a portion between the flanges of a sealed component having at least two flanges, comprising the following steps: The process of transferring a photocurable sheet sealant for fuel cells onto at least one flange of the flange; The process of forming a sealing gasket composed of a cured material obtained by irradiating the transferred photocurable sheet sealant for fuel cells with an activation energy ray and curing it. as well as The process involves placing another flange on the sealing gasket, pressing a flange printed with a photocurable sheet sealant for fuel cells onto the other flange through the sealing gasket, and sealing at least a portion between the at least two flanges. The photocurable sheet sealant for fuel cells comprises: Component A: urethane (meth)acrylate, Component B: phenoxy resin, and Component C: photopolymerization initiator. The product contains 4 to 70 parts by mass of component B relative to 100 parts by mass of component A.

3. The method according to claim 1 or 2, wherein, In the process of transferring the photocurable sheet sealant for fuel cells, the photocurable sheet sealant for fuel cells is pre-die-cut into the shape required for sealing.

4. The method according to claim 1 or 2, wherein, Component A has a polycarbonate backbone.

5. The method according to claim 1 or 2, wherein, The glass transition temperature of component B is 50–120°C.

6. The method according to claim 1 or 2, wherein, The weight-average molecular weight of component A is 20,000 to 100,000.

7. The method according to claim 1 or 2, wherein, The C component has an absorption wavelength above 365 nm and decomposes upon irradiation with ultraviolet light with a wavelength above 365 nm, generating a photopolymerization initiator that produces free radicals that participate in polymerization.

8. The method according to claim 1 or 2, wherein, The photocurable sheet sealant for fuel cells further comprises at least one of monofunctional, difunctional, trifunctional, and tetrafunctional monomers having (meth)acryloyl groups as component D.

9. The method according to claim 1 or 2, wherein, The method is used to seal adjacent partitions in a fuel cell, the frame and electrolyte membrane of a fuel cell, or the frame and electrolyte membrane-electrode junction of a fuel cell.

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