Photocurable adhesive composition for polymer electrolyte, and layered product

Abstract

Provided are: a photocurable adhesive composition for a polymer electrolyte, which contains components (A) to (D) at specified proportions; and a layered product. Component (A) is a urethane (meth)acrylate obtained by reacting component (a1), component (a2) and component (a3) (component (a1) is a hydrogenated polybutadiene or hydrogenated polyisoprene having a hydroxyl group at a terminal, component (a2) is an aromatic diisocyanate, and component (a3) is a (meth)acrylate having one hydroxyl group per molecule. Component (B) is an alkyl (meth)acrylate having an alkyl group with 4-20 carbon atoms. Component (C) is an epoxidized polybutadiene or an epoxidized polyisoprene. Component (D) is a radical photopolymerization initiator.

Description

Photocurable adhesive composition and laminate for polymer electrolytes

[0001] The present disclosure relates to a photocurable adhesive composition for polymer electrolytes and a laminate.

[0002] A solid polymer fuel cell generally comprises a membrane electrode assembly in which an electrode catalyst layer is formed on each side of an electrolyte membrane, a pair of gas diffusion layers bonded to each side of the membrane electrode assembly, a pair of fuel cell separators, and a resin sheet, and the membrane electrode assembly and the resin sheet are bonded together with an adhesive.

[0003] In a polymer electrolyte fuel cell, water is produced by a reaction between protons and oxygen on the cathode side. The heat of the reaction produced when water is produced causes the membrane electrode assembly to reach a high temperature close to the boiling point of water. Polymer electrolyte membranes swell significantly in water, especially hot water, making adhesives prone to peeling. Therefore, adhesives for polymer electrolyte membranes must be durable enough to withstand immersion in hot water without easily peeling off from the electrolyte membrane.

[0004] On the other hand, when water and electricity are supplied to a structure similar to a fuel cell, hydrogen can be generated. By using such a water electrolysis device, it is possible to convert highly fluctuating electrical energy from natural energy sources such as solar cells and wind power into chemical energy called hydrogen and store it in a space-saving and highly efficient manner. Such a water electrolysis device can also generate CO ２ It has been attracting attention in recent years as there has been a demand to reduce emissions.

[0005] However, in the case of a water electrolysis device, the adhesive that bonds the membrane electrode assembly and the resin sheet is exposed not only to water but also to high-concentration oxygen, and therefore, this adhesive is required to be durable against high-temperature water under high-oxygen concentration conditions.

[0006] As an adhesive for the above-described polymer electrolyte membrane, Japanese Patent Application Laid-Open No. 2021-190293 discloses a fuel cell in which a membrane electrode assembly and a resin sheet are bonded with a photocurable adhesive or a thermosetting adhesive.

[0007] Furthermore, WO 2019 / 172347 discloses a curable composition for polymer electrolytes, comprising: component (A): a radically polymerizable compound having a (meth)acryloyl group; component (B): a compound having, in the molecule, at least one skeleton selected from the group consisting of polybutadiene, polyisoprene, hydrogenated polybutadiene, and hydrogenated polyisoprene, and an epoxy group; and component (C): a radical polymerization initiator, in specific proportions.

[0008] However, the photocurable adhesive or thermosetting adhesive described in JP 2021-190293 A and the curable composition for polymer electrolytes described in WO 2019 / 172347 A had insufficient durability when immersed in hotter water for a longer period of time.

[0009] Furthermore, it was unclear whether the photocurable adhesive or thermosetting adhesive described in JP 2021-190293 A and the curable composition for polymer electrolytes described in WO 2019 / 172347 A had durability against high-temperature water under high-oxygen concentration conditions.

[0010] An object of one embodiment of the present disclosure is to provide a photocurable adhesive composition for polymer electrolytes and a laminate having such adhesion durability that the bonded joint between a polymer electrolyte membrane and a substrate (preferably a resin sheet) does not easily peel off when the bonded joint is immersed in high-temperature water (particularly high-temperature water under high-oxygen concentration conditions) for a long period of time.

[0011] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the problems can be solved by a photocurable adhesive composition for polymer electrolytes and a laminate containing a urethane (meth)acrylate having a specific structure, an alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms, an epoxidized polybutadiene or an epoxidized polyisoprene, and a photoradical polymerization initiator in specific proportions, and have completed the present disclosure.

[0012] The present disclosure includes the following aspects. [1] A photocurable adhesive composition for polymer electrolytes, comprising: component (A): a urethane (meth)acrylate obtained by reacting the following components (a1), (a2), and (a3): component (a1): a hydrogenated polybutadiene or hydrogenated polyisoprene having a terminal hydroxyl group; component (a2): an aromatic diisocyanate; component (a3): a (meth)acrylate having one hydroxyl group per molecule; component (B): an alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms; component (C): an epoxidized polybutadiene or epoxidized polyisoprene; and component (D): a photoradical polymerization initiator, wherein the content ratios of components (A) to (D) are, based on the total composition, as follows: component (A): 1% by mass to 70% by mass component (B): 10% by mass to 70% by mass component (C): 1% by mass to 20% by mass component (D): 0.1% by mass to 10% by mass. [2] The photocurable adhesive composition for polymer electrolytes according to [1], wherein the content of component (A) is 10% by mass or more, based on the entire composition. [3] The photocurable adhesive composition for polymer electrolytes according to [1] or [2], further comprising the following component (F1) in a proportion of 1% by mass to 70% by mass, based on the entire composition: Component (F1): a urethane (meth)acrylate obtained by reacting component (a1), and the following components (f2) and (a3): Component (f2): an aliphatic diisocyanate [4] The photocurable adhesive composition for polymer electrolytes according to any one of [1] to [3], further comprising, as component (E), polymer fine particles having a volume average primary particle diameter of 0.5 μm to 50 μm, measured by a wet method, in an amount of 1% by mass to 50% by mass, based on the entire composition. [5] The photocurable adhesive composition for polymer electrolytes according to any one of [1] to [4], wherein the total amount of the component (A) and the component (B) is 80 parts by mass or more when the total amount of the compounds having a (meth)acryloyl group is 100 parts by mass. [6] The photocurable adhesive composition for polymer electrolytes according to any one of [1] to [5], which is used as an adhesive or sealant for fuel cells. [7] The photocurable adhesive composition for polymer electrolytes according to any one of [1] to [5], which is used as an adhesive or sealant for water electrolysis systems.[8] A laminate comprising a first substrate, a cured product formed from the photocurable adhesive composition for polymer electrolytes according to any one of [1] to [7], and a second substrate, wherein both or one of the first substrate and the second substrate is a polymer electrolyte.

[0013] According to one aspect of the present disclosure, it is possible to provide a photocurable adhesive composition for polymer electrolytes and a laminate having adhesion durability (hereinafter also referred to as "hot water immersion durability") such that a bonded portion between a polymer electrolyte membrane and a substrate (preferably a resin sheet) does not easily peel off when the bonded portion is immersed in high-temperature water (particularly high-temperature water under high-oxygen concentration conditions) for a long period of time.

[0014] FIG. 1A is an explanatory diagram illustrating the configuration of an MEGA film printed with a photocurable adhesive. FIG. 1B is a schematic cross-sectional view taken along line II in FIG. 1A. FIG. 2A is an explanatory diagram illustrating the configuration of an adhesion sample. FIG. 2B is a schematic cross-sectional view taken along line II-II in FIG. 2A. FIG. 3A is an explanatory diagram illustrating the configuration of a cut sample. FIG. 3B is a schematic cross-sectional view taken along line III-III in FIG. 3A. FIG. 4 is an explanatory diagram illustrating the configuration of an evaluation sample.

[0015] Various embodiments of the technology disclosed in this specification will be described in detail below. In this specification, acrylate and / or methacrylate will be referred to as (meth)acrylate, acryloyl group and / or methacryloyl group will be referred to as (meth)acryloyl group, and acrylic acid and / or methacrylic acid will be referred to as (meth)acrylic acid.

[0016] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical value before "to" as the lower limit and the numerical value after "to" as the upper limit. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0017] In this specification, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the intended purpose is achieved.

[0018] In this specification, the amount of each component in a composition means the total amount of the corresponding substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition.

[0019] A photocurable adhesive composition for polymer electrolytes according to one embodiment of the present disclosure is a composition containing component (A), component (B), component (C), and component (D), wherein the content ratios of components (A) to (D) are, based on the total composition, as follows: component (A): 1% by mass to 70% by mass component (B): 10% by mass to 70% by mass component (C): 1% by mass to 20% by mass component (D): 0.1% by mass to 10% by mass component. Preferably, component (E) is contained in an amount of 1% by mass to 50% by mass based on the total composition.

[0020] Components (A) to (E), other components, the photocurable adhesive composition for polymer electrolytes, the method of use, and the laminate and method of producing the same will be described in detail below.

[0021] 1. Component (A) Component (A) is a urethane (meth)acrylate obtained by reacting the following components (a1), (a2), and (a3): Component (a1): Hydrogenated polybutadiene or hydrogenated polyisoprene having a terminal hydroxyl group Component (a2): Aromatic diisocyanate Component (a3): (meth)acrylate having one hydroxyl group per molecule Below, components (a1), (a2), and (a3) ​​will be explained, followed by their reaction ratios and reaction conditions, and then the molecular weight and content of component (A).

[0022] 1-1. Component (a1) Component (a1) is a hydrogenated polybutadiene having terminal hydroxyl groups or a hydrogenated polyisoprene having terminal hydroxyl groups. By virtue of having these skeletons, component (a1) exhibits excellent durability (hot water immersion durability) when immersed in high-temperature water for extended periods of time. The polybutadiene having terminal hydroxyl groups or the polyisoprene having terminal hydroxyl groups before hydrogenation may be obtained by radical polymerization or anionic polymerization. The iodine value (the number of grams of iodine added per 100 g of resin), which is an indicator of the degree of hydrogenation of component (a1), is preferably 0 g to 50 g or less, more preferably 0 g to 20 g or less. The molecular weight of component (a1) is preferably 500 to 10,000, more preferably 1,000 to 5,000, in terms of number average molecular weight (hereinafter referred to as "Mn"). The average number of hydroxyl groups contained in one molecule of component (a1) is preferably 1.5 to 2.5, and more preferably 1.7 to 2.3.

[0023] In the present disclosure, Mn refers to the average molecular weight measured by GPC (gel permeation chromatography) converted into polystyrene. A specific method for measuring Mn will be described in the Examples below.

[0024] Specific examples of the component (a1) include NISSO-PB GI-1000, GI-2000, and GI-3000 manufactured by Nippon Soda Co., Ltd.; Krasol H-LBH P2000 and P3000 manufactured by Cray Valley Corporation; Polytail H manufactured by Mitsubishi Chemical Corporation; and Epol manufactured by Idemitsu Kosan Co., Ltd.

[0025] 1-2. Component (a2) The component (a2) is an aromatic diisocyanate, which means a compound having two isocyanate groups bonded to an aromatic ring.

[0026] Specific examples of the component (a2) include tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate.

[0027] The use of component (a2) results in excellent hot water immersion durability. Furthermore, the hot water immersion durability under high oxygen concentration conditions is also excellent. A diisocyanate other than component (a2) that does not have an aromatic skeleton may be included within a range that does not significantly impair the effects of one embodiment of the present disclosure. Examples of diisocyanates include isophorone diisocyanate, hexamethylene diisocyanate, norbornane diisocyanate, and hydrogenated diphenylmethane diisocyanate.

[0028] 1-3. Component (a3) ​​Component (a3) ​​is a (meth)acrylate having one hydroxyl group per molecule. As component (a3), a compound having one hydroxyl group and one (meth)acryloyl group per molecule is preferred from the viewpoint of the quality stability of component (A). Furthermore, as the (meth)acrylate, acrylate is preferred from the viewpoint of excellent photocurability.

[0029] Specific examples of compounds having one hydroxyl group and one (meth)acryloyl group in one molecule include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; hydroxy group-containing aromatic mono(meth)acrylates such as 2-hydroxy-3-phenoxypropyl (meth)acrylate; hydroxy group-containing alicyclic mono(meth)acrylates such as 1,4-cyclohexanedimethanol mono(meth)acrylate; and polyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and polytetramethylene glycol mono(meth)acrylate.

[0030] Specific examples of the compound having one hydroxyl group and two or more (meth)acryloyl groups in one molecule include trimethylolpropane di(meth)acrylate, di(meth)acrylate of an ethylene oxide adduct of trimethylolpropane, di(meth)acrylate of a propylene oxide adduct of trimethylolpropane, di(meth)acrylate of an ethylene oxide adduct of isocyanuric acid, di(meth)acrylate of a propylene oxide adduct of isocyanuric acid, pentaerythritol tri(meth)acrylate, and 2-hydroxy-3-acryloyloxypropyl methacrylate.

[0031] 1-4. Reaction ratio The reaction ratio of component (a1) to component (a2) affects the molecular weight of component (A) and the number of urethane bonds contained in one molecule. The reaction ratio of component (a1) to component (a2) is preferably 1.05 to 2.0 moles, and more preferably 1.1 to 1.5 moles, of component (a2) per mole of component (a1).

[0032] The reaction ratio of component (a3) ​​relative to the number of moles of isocyanate remaining after components (a1) and (a2) have almost completely reacted is preferably 0.95 to 1.1 moles, and more preferably 0.98 to 1.05 moles, which allows for sufficient introduction of (meth)acryloyl groups at the terminals of component (A) while preventing the composition from containing an excessive amount of component (a3).

[0033] 1-5. Reaction Conditions General conditions for urethanization reactions may be applied as reaction conditions for components (a1), (a2), and (a3). For example, a preferred reaction temperature is 40°C to 100°C, more preferably 50°C to 90°C. A catalyst for the urethanization reaction may also be selected as desired. Examples include tin-based catalysts such as dibutyltin dilaurate and dioctyltin dilaurate; transition metal complexes such as zinc(II) acetylacetonate, iron(III) acetylacetonate, and zirconium(IV) acetylacetonate; and amine-based catalysts such as triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7. Alternatively, the reaction may be carried out at a relatively high temperature for a long period of time without using a catalyst for the urethanization reaction.

[0034] Since component (A) has a very high viscosity or becomes semi-solid, it is preferable to use a (meth)acrylate that will ultimately be contained in the adhesive instead of a solvent when synthesizing component (A). This (meth)acrylate is preferably component (B) described below.

[0035] The order of adding the components (a1), (a2), and (a3) ​​can be selected arbitrarily. For example, there is a method in which the components (a1), (a3), and catalyst are dissolved in the component (B), and then the component (a2) is added, and the urethanization reaction is completed all at once. Another example is a method in which the component (a1) is dissolved in the component (B), the component (a2) is dissolved, the catalyst is added, and the mixture is heated to carry out the urethanization reaction, and then the component (a3) ​​is added, and the urethanization reaction is completed. Another example is a method in which the component (a2) and the catalyst are dissolved in the component (B), and then the urethanization reaction is carried out while continuously adding the component (a1), and then the component (a3) ​​is added, and the urethanization reaction is completed. As described above, there are various orders for adding the raw materials and catalysts, and the order can be determined by comprehensively considering the product quality, ease of production, ease of management, etc.

[0036] 1-6. Molecular Weight and Content of Component (A) The molecular weight of component (A) is preferably Mn from 1,000 to 100,000, more preferably from 3,000 to 50,000, and even more preferably from 5,000 to 30,000. When component (A) has an Mn of 1,000 to 100,000, the adhesive strength with the polymer electrolyte and the hot water immersion durability are improved.

[0037] The content of component (A) is 1% by mass to 70% by mass, preferably 5% by mass to 70% by mass, more preferably 10% by mass to 70% by mass, even more preferably 20% by mass to 60% by mass, and particularly preferably 25% by mass to 55% by mass, based on the entire composition. When the content of component (A) is 1% by mass or more, the viscosity does not become too low, allowing coating to be performed to an appropriate thickness, and furthermore, hot water immersion durability is improved. On the other hand, when the content is 70% by mass or less, the viscosity does not become too high, resulting in excellent high-speed coating properties. Furthermore, when screen printing is performed, bubbles and defects are less likely to occur.

[0038] When component (F1), which will be described later, is not used, the content of component (A) is preferably 10% by mass to 70% by mass, more preferably 20% by mass to 60% by mass, and even more preferably 25% by mass to 55% by mass, based on the entire composition. When component (F1) is not used, if the content of component (A) is 10% by mass or more, the viscosity does not become too low, allowing coating to an appropriate thickness, and further, hot water immersion durability is particularly good. On the other hand, if the content is 70% by mass or less, the viscosity does not become too high, resulting in excellent high-speed coating properties. Furthermore, when screen printing is performed, bubbles and defects are less likely to occur.

[0039] When using the component (F1) of the component (F) described below, the content of the component (A) is preferably 1% by mass to 60% by mass, more preferably 5% by mass to 50% by mass, and even more preferably 10% by mass to 40% by mass, based on the entire composition. When the component (F1) is used, a content of the component (A) of 1% by mass or more improves hot water immersion durability, and the initial elongation at break of the bonded joint between the polymer electrolyte membrane and the substrate (preferably a resin sheet) is stably maintained even after immersion in high-temperature water (particularly high-temperature water under high-oxygen concentration conditions) for a long period of time (hereinafter also referred to as "long-term stability"). On the other hand, when the content is 60% by mass or less, the viscosity is not too high, resulting in excellent high-speed coating properties. Furthermore, bubbles and defects are less likely to occur when screen printing is performed.

[0040] 2. Component (B) Component (B) is an alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms. Component (B) has the effect of reducing the viscosity of the adhesive composition of one embodiment of the present disclosure, thereby improving the coatability, and the effect of improving the hot water immersion durability. As the (meth)acrylate of component (B), an acrylate is preferred from the viewpoint of photocurability.

[0041] Specific examples of the component (B) include n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate.

[0042] The content of component (B) is 10% by mass to 70% by mass, preferably 15% by mass to 60% by mass, and more preferably 20% by mass to 50% by mass, based on the total composition. When the content of component (B) is 10% by mass or more, the viscosity does not become too high, and the composition exhibits excellent high-speed coatability. On the other hand, when the content of component (B) is 70% by mass or less, the viscosity does not become too low, and the composition can be coated to an appropriate film thickness.

[0043] 3. Component (C) Component (C) is epoxidized polybutadiene or epoxidized polyisoprene. Preferred examples of component (C) include polybutadiene or polyisoprene in which the double bond has been epoxidized; polybutadiene or polyisoprene having hydroxyl groups at its terminals in which the hydroxyl groups have been epoxidized with epichlorohydrin or the like; and polybutadiene or polyisoprene in which a compound having two or more epoxy groups per molecule has been added to the carboxyl groups at its terminals. Of these, compounds in which the double bond of polybutadiene has been epoxidized are particularly preferred because they have excellent hot water immersion durability.

[0044] The molecular weight Mn of component (C) is preferably 500 to 5,000, and more preferably 1,000 to 2,000. When the Mn of component (C) is within this range, the hot water immersion durability is improved and compatibility with the composition is also improved.

[0045] Specific examples of the component (C) product include NISSO-PB JP-100 and JP-200 manufactured by Nippon Soda Co., Ltd.; and Epolead PB-3600 and PB-4700 manufactured by Daicel Corporation.

[0046] The content of component (C) is 1 to 20% by mass, preferably 2 to 15% by mass, based on the total mass of the composition. By setting the content of component (C) to 1 to 20% by mass, good hot water immersion durability is achieved.

[0047] 4. Component (D) Component (D) is a photoradical polymerization initiator. The inclusion of component (D) imparts photocurability. The content of component (D) is 0.1% by mass to 10% by mass, preferably 0.2% by mass to 5% by mass, and more preferably 0.3% by mass to 3% by mass, based on the total composition. A content of component (D) of 0.1% by mass or more prevents insufficient photocurability, while a content of 10% by mass or less prevents the photoinitiator itself and its decomposition products from becoming contaminants, which is preferable. In particular, when the polymer electrolyte is used in a fuel cell or water electrolysis device, these contaminants can poison the catalyst and reduce product performance, but this can be prevented.

[0048] Specific examples of component (D) include benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, oligo[2-hydroxy-2-methyl-1-[4-1-(methylvinyl)phenyl]propanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)benzyl]phenyl]propanone, and the like. acetophenone compounds such as {phenyl}-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)]phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)butan-1-one and 3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-octylcarbazole; Benzoin compounds such as benzoin, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenone compounds such as benzophenone, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, methyl-2-benzophenone, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, and 4-methoxy-4'-dimethylaminobenzophenone; acylphosphine oxide compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide;and thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propylthioxanthone, 3-[3,4-dimethyl-9-oxo-9H-thioxanthone-2-yl-oxy]-2-hydroxypropyl-N,N,N-trimethylammonium chloride, and fluorothioxanthone. Other compounds include benzyl, ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate, methyl phenylglyoxylate, ethyl anthraquinone, phenanthrenequinone, and camphorquinone.

[0049] Of these compounds, it is preferable that the component (D) contains an acylphosphine oxide compound from the viewpoint of the curability of the composition.

[0050] 5. Other Components In addition to components (A) to (D), the photocurable adhesive composition for polymer electrolytes according to one embodiment of the present disclosure can contain other components depending on the purpose, application, etc. Preferred examples of other components include polymer microparticles having a volume average primary particle diameter of 0.5 μm to 50 μm as measured by a wet method (hereinafter referred to as "component (E)"), and a compound having a (meth)acryloyl group other than components (A) and (B) (hereinafter referred to as "component (F)"). Component (F) includes a urethane (meth)acrylate obtained by reacting an aliphatic diisocyanate (hereinafter referred to as "component (F1)"), and a component (F) other than component (F1) (hereinafter referred to as "component (F2)"). Component (E) and component (F) are described below.

[0051] 5-1. Component (E) Component (E) is a polymer fine particle having a volume average primary particle diameter of 0.5 μm to 50 μm as measured by a wet method. By including an appropriate amount of component (E), it is possible to improve screen printing properties and reduce variations in thickness when the polymer electrolyte and a resin sheet are laminated together.

[0052] When the fine particles are inorganic fine particles such as silica or alumina, there is a risk of trace metal ions eluting when exposed to high-temperature water for a long period of time. Because typical polymer electrolytes contain sulfonic acid, the water produced by fuel cells becomes weakly acidic, which may result in trace metal ions eluting. Trace amounts of metal ions are undesirable because they can poison the fuel cell catalyst or embrittle the polymer electrolyte. On the other hand, component (E) is preferable because it does not have the above problems.

[0053] The component (E) is preferably a chemically crosslinked polymer particle or a polyolefin-based particle. Specific examples of the chemically crosslinked polymer particle include a copolymer of methyl methacrylate and ethylene glycol dimethacrylate, a copolymer of styrene and divinylbenzene, and polyurethane. Examples of the polyolefin-based particle include polyethylene and polypropylene.

[0054] From the viewpoint of screen printability, the volume average primary particle diameter of component (E) is preferably in the range of 0.5 μm to 50 μm, more preferably in the range of 1 μm to 40 μm, and even more preferably in the range of 2 μm to 30 μm. If the volume average primary particle diameter is 0.5 μm or more, the thixotropy is not too strong, and minute air bubbles after printing are less likely to disappear. Conversely, if the volume average primary particle diameter is 50 μm or less, the probability of large particles that clog the screen mesh being mixed in can be reduced. In the present disclosure, the volume average primary particle diameter refers to a value measured using a laser diffraction / scattering particle size distribution analyzer (wet method; for example, LA-920 manufactured by Horiba, Ltd.).

[0055] 5-2. Component (F) The composition of one embodiment of the present disclosure may contain component (F) for the purpose of adjusting physical properties other than adhesiveness, such as the glass transition temperature and elastic modulus of the cured product. Component (F) includes component (F1), a urethane (meth)acrylate obtained by reacting with an aliphatic diisocyanate, and component (F2), a component other than component (F1). Component (F1) is a urethane (meth)acrylate obtained by reacting with an aliphatic diisocyanate, and is a urethane (meth)acrylate different from component (A).

[0056] 5-3. Component (F1) Component (F1) is a urethane (meth)acrylate obtained by reacting the following components (a1), (f2), and (a3): Component (a1): hydrogenated polybutadiene or hydrogenated polyisoprene having a hydroxyl group at the end Component (f2): aliphatic diisocyanate Component (a3): (meth)acrylate having one hydroxyl group per molecule

[0057] 5-3-1. Component (a1), Component (f2), and Component (a3) ​​The components (a1) and (a3) ​​used to obtain component (F1) are the same as the components used to obtain component (A), and are as described above. The component (f2) used to obtain component (F1) is an aliphatic diisocyanate. In this specification, an aliphatic diisocyanate refers to a diisocyanate having a saturated aliphatic group in the molecule. The component (f2) is a non-aromatic diisocyanate different from component (a2), and is an aliphatic diisocyanate. The component (f2) is a compound that can be reacted with components (a1) and (a3) ​​to obtain an aliphatic urethane (meth)acrylate.

[0058] Specific examples of the component (f2) include alicyclic diisocyanates such as isophorone diisocyanate, norbornane diisocyanate, and hydrogenated diphenylmethane diisocyanate, as well as linear diisocyanates such as hexamethylene diisocyanate.

[0059] 5-3-2. Reaction conditions The reaction conditions for the components (a1), (f2), and (a3) ​​are the same as those for producing the component (A) described above. That is, when producing the component (A) described above in "1-5. Reaction conditions," the component (f2) may be used in place of the component (a2).

[0060] That is, typical conditions for a urethanization reaction may be applied as the reaction conditions for component (a1), component (f2), and component (a3). For example, a preferred reaction temperature is 40°C to 100°C, more preferably 50°C to 90°C. A catalyst for the urethanization reaction may also be selected as desired. Examples include tin-based catalysts such as dibutyltin dilaurate and dioctyltin dilaurate; transition metal complexes such as zinc(II) acetylacetonate, iron(III) acetylacetonate, and zirconium(IV) acetylacetonate; and amine-based catalysts such as triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7. Alternatively, the reaction may be carried out at a relatively high temperature for a long period of time without using a urethanization reaction catalyst.

[0061] Since component (F1) has a very high viscosity or becomes semi-solid, it is preferable to use a (meth)acrylate that will ultimately be contained in the adhesive instead of a solvent when synthesizing component (F1), and this (meth)acrylate is preferably the above-mentioned component (B).

[0062] The order of adding the components (a1), (f2), and (a3) ​​can be selected arbitrarily. For example, there is a method in which the components (a1), (a3), and catalyst are dissolved in the component (B), and then the component (f2) is added, and the urethanization reaction is completed all at once. Another example is a method in which the component (a1) is dissolved in the component (B), the component (f2) is dissolved, the catalyst is added, and the mixture is heated to perform the urethanization reaction, and then the component (a3) ​​is added, and the urethanization reaction is completed. Another example is a method in which the component (f2) and the catalyst are dissolved in the component (B), and then the urethanization reaction is performed while continuously adding the component (a1), and then the component (a3) ​​is added, and the urethanization reaction is completed. As described above, there are various orders for adding the raw materials and catalysts, and the order can be determined by comprehensively considering the product quality, ease of production, ease of management, etc.

[0063] 5-3-3. Molecular Weight and Content of Component (F1) The molecular weight of component (F1) is preferably Mn from 1,000 to 100,000, more preferably from 3,000 to 50,000, and even more preferably from 5,000 to 30,000. When component (F1) has an Mn of 1,000 to 100,000, the adhesive strength to the polymer electrolyte and the hot water immersion durability are improved.

[0064] When component (F1) is contained, its content is 1% by mass to 60% by mass, preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 40% by mass, based on the entire composition. When the content of component (F1) is 1% by mass or more, the combination with component (A) provides good hot water immersion durability and good long-term stability. When the content is 60% by mass or less, the viscosity does not become too high, providing excellent high-speed coating properties. Furthermore, when screen printing is performed, bubbles and defects are less likely to occur. When long-term stability of elongation at break is not particularly important and adhesion durability is particularly important, it is preferable not to contain component (F1).

[0065] The total content of components (A) and (F1), based on the entire composition, can be 10% by mass to 70% by mass, preferably 20% by mass to 60% by mass, and more preferably 25% by mass to 55% by mass. When the total content of components (A) and (F1) is 10% by mass or more, both hot water immersion durability and long-term stability are excellent. On the other hand, when the content is 70% by mass or less, the viscosity is not too high, resulting in excellent high-speed coating properties. Furthermore, bubbles and defects are less likely to occur when screen printing is performed.

[0066] The content ratio of component (A) to component (F1) can be adjusted depending on the intended use of the composition. As described above, when component (F1) is added in combination with component (A), the composition exhibits both excellent hot water immersion durability and long-term stability. However, even when component (F1) is mixed with component (A), it improves long-term stability without significantly impairing the adhesive durability inherent in component (A). Therefore, for example, to improve both adhesive durability and long-term stability, components (A) and (F1) are used in approximately equal amounts by mass. Similarly, to improve adhesive durability, component (A) can be used in greater amounts than component (F1), while to improve long-term stability, component (F1) can be used in greater amounts than component (A). For example, when component (A) is used in greater amounts than component (F1), the mass ratio of component (A):component (F1) can be 7:1 to 1.1:1, specifically, the mass ratio of component (A):component (F1) can be 3:1. On the other hand, when component (F1) is used in greater amounts than component (A), the mass ratio of component (F1):component (A) can be 7:1 to 1.1:1, specifically, the mass ratio of component (F1):component (A) can be 3:1.

[0067] 5-3-4. Specific Examples of Component (F1) Specific examples of the component (F1) include a urethanization reaction product of isophorone diisocyanate, hydrogenated polybutadiene diol, and 2-hydroxyethyl (meth)acrylate, a urethanization reaction product of isophorone diisocyanate, hydrogenated polybutadiene diol, and 4-hydroxybutyl (meth)acrylate, and a urethanization reaction product of hexamethylene diisocyanate, hydrogenated polybutadiene diol, and 2-hydroxyethyl (meth)acrylate.

[0068] Component (F2) Component (F2) is a component other than component (F1). The content of component (F2) is preferably less than 20 parts by mass, relative to 100 parts by mass of the total amount of compounds having a (meth)acryloyl group, in order to improve adhesion durability with the polymer electrolyte. In the composition of one embodiment of the present disclosure, the content of component (F2) may be 0 parts by mass, or, when component (F2) is included, the lower limit can be greater than 0 parts by mass.

[0069] A specific example of the component (F2) is a monomer other than the component (B) that has one (meth)acryloyl group per molecule. Specific examples of monomers having one (meth)acryloyl group per molecule other than component (B) include (meth)acrylic acid, acrylic acid dimer, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, (meth)acrylate of an ethylene oxide adduct of phenol, (meth)acrylate of an ethylene oxide adduct of nonylphenol, (meth)acrylate of an ethylene oxide adduct of phenoxyphenol, (meth)acrylate of an ethylene oxide adduct of p-cumylphenol, and ethylene oxide of o-phenylphenol. Adducts of (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, 3-ethyl-3-oxetanyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, 1-adamantyl (meth)acrylate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl hexyl acrylate ... hexahydrophthalic acid, N-(meth)acryloyloxyethylhexahydrophthalimide, N-(meth)acryloyloxyethyltetrahydrophthalimide, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 1,Examples include 4-cyclohexanedimethanol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polytetramethylene glycol mono(meth)acrylate, 2,2,3,3-tetrafluoropropyl(meth)acrylate, and 1H,1H,5H-octafluoropentyl(meth)acrylate.

[0070] Other specific examples of component (F2) include compounds other than component (A) that have two (meth)acryloyl groups per molecule, such as di(meth)acrylates of aliphatic diols such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate; di(meth)acrylates of alicyclic diols such as cyclohexanedimethylol di(meth)acrylate and tricyclodecanedimethylol di(meth)acrylate; Polyalkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate; esterification reaction products of neopentyl glycol, hydroxypivalic acid, and (meth)acrylic acid; fluorene-based di(meth)acrylates such as 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene; di(meth)acrylates of alkylene oxide adducts of bisphenol-based compounds such as di(meth)acrylates of alkylene oxide adducts of bisphenol A; di(meth)acrylates of hydrogenated bisphenol-based compounds such as di(meth)acrylate of hydrogenated bisphenol A; Epoxy (meth)acrylates having two (meth)acryloyl groups in one molecule, such as an adduct of bisphenol A epoxy resin and (meth)acrylic acid, or an adduct of 1,9-nonanediol diglycidyl ether and (meth)acrylic acid; polyester (meth)acrylates having two (meth)acryloyl groups in one molecule, such as an ester of phthalic acid, ethylene glycol, and (meth)acrylic acid;Examples of such compounds include compounds having one hydroxyl group and two (meth)acryloyl groups in one molecule, such as trimethylolpropane di(meth)acrylate, di(meth)acrylate of an alkylene oxide adduct of trimethylolpropane, di(meth)acrylate of an alkylene oxide adduct of isocyanuric acid, and 2-hydroxy-3-acryloyloxypropyl methacrylate; and urethane (meth)acrylates other than components (A) and (F1).

[0071] Specific examples of urethane (meth)acrylates other than component (A) and component (F1) include a urethanization reaction product of tolylene diisocyanate, a polyether diol, and 2-hydroxypropyl (meth)acrylate, a urethanization reaction product of isophorone diisocyanate, a polyether diol, and 2-hydroxyethyl (meth)acrylate, a urethanization reaction product of isophorone diisocyanate, a polyester diol, and 2-hydroxyethyl (meth)acrylate, a urethanization reaction product of isophorone diisocyanate, a polycarbonate diol, and 2-hydroxyethyl (meth)acrylate, etc. In the alkylene oxide adducts, examples of the alkylene oxide include ethylene oxide and propylene oxide.

[0072] Other specific examples of the component (F2) include compounds other than the component (A) that have three or more (meth)acryloyl groups in one molecule.For example, polyol poly(meth)acrylates such as trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol di-, tri-, or tetra(meth)acrylate, dipentaerythritol penta-, or hexa(meth)acrylate, tri(meth)acrylate of an isocyanuric acid ethylene oxide 3-mol adduct, glycerin tri(meth)acrylate, and polyglycerin poly(meth)acrylate; Poly(meth)acrylates of polyol alkylene oxide adducts such as tri(meth)acrylate of trimethylolpropane alkylene oxide adduct, tetra(meth)acrylate of ditrimethylolpropane alkylene oxide adduct, tri- or tetra(meth)acrylate of pentaerythritol alkylene oxide adduct, penta- or hexa(meth)acrylate of dipentaerythritol alkylene oxide adduct, tri(meth)acrylate of glycerin alkylene oxide adduct, and poly(meth)acrylate of polyglycerin alkylene oxide adduct; epoxy(meth)acrylates having three or more (meth)acryloyl groups in one molecule, such as adducts of phenol novolac epoxy resin and (meth)acrylic acid, and adducts of cresol novolac epoxy resin and (meth)acrylic acid; Examples of the urethane (meth)acrylate include a urethane reaction product of isophorone diisocyanate and pentaerythritol tri(meth)acrylate, and a urethane reaction product of an isocyanurate trimer of hexamethylene diisocyanate and 4-hydroxybutyl acrylate, each having three or more (meth)acryloyl groups in one molecule; a polyester (meth)acrylate including an ester of phthalic acid, trimethylolpropane, and (meth)acrylic acid, and a dendrimer-type poly(meth)acrylate, each having three or more (meth)acryloyl groups in one molecule; and a polymer having a (meth)acryloyl group, such as a polymer in which glycidyl (meth)acrylate is added to a carboxylic acid of a (meth)acrylic polymer containing (meth)acrylic acid as a structural unit, or a polymer in which (meth)acrylic acid is added to an epoxy group of a (meth)acrylic polymer containing glycidyl (meth)acrylate as a structural unit.In the alkylene oxide adduct, examples of the alkylene oxide include ethylene oxide and propylene oxide.

[0073] The composition of one embodiment of the present disclosure may contain a radical polymerizable monomer other than components (A), (B), and (F). Specific examples of such a monomer include styrene, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, (meth)acryloylmorpholine, N,N-dimethylaminopropyl(meth)acrylamide, N-vinylpyrrolidone, and N-vinylcaprolactam.

[0074] 5-5. Other Components In addition to the components (E) and (F), the composition of one embodiment of the present disclosure may contain, as necessary, a thermal radical polymerization initiator, a polymer, a tackifier, a plasticizer, an antifoaming agent, a leveling agent, a polymerization inhibitor, a stabilizer, an organic solvent, and the like.

[0075] If necessary, a thermal radical polymerization initiator such as an organic peroxide or an azo compound may be added to the composition of one embodiment of the present disclosure.

[0076] Specific examples of organic peroxides include 1,1-bis(t-butylperoxy)2-methylcyclohexane, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(4,4-dibutylperoxycyclohexyl)propane, 1,1 -bis(t-butylperoxy)cyclododecane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di(m-toluoylperoxy)hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate peroxyacetic acid, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxyacetate, 2,2-bis(t-butylperoxy)butane, t-butyl peroxybenzoate, n-butyl-4,4-bis(t-butylperoxy)valerate, di-t-butylperoxyisophthalate, α,α'-bis(t-butylperoxy)diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, Examples of the azo compound include t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, diisopropylbenzene hydroperoxide, t-butyltrimethylsilyl peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, and t-butyl hydroperoxide. Specific examples of the azo compound include 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, azodi-t-octane, and azodi-t-butane.

[0077] Specific examples of polymers include uncrosslinked, soluble (meth)acrylic resins, polystyrene, styrene-acrylonitrile copolymers, polybutadiene, polyisoprene, polyisobutylene, hydrogenated polybutadiene, hydrogenated polyisoprene, maleated polybutadiene, maleated polyisoprene, maleated polypropylene, chlorinated polypropylene, petroleum resins, hydrogenated petroleum resins, xylene resins, polytetramethylene glycol, polyvinyl acetate, ethylene-vinyl acetate copolymers, ethylene-acrylic copolymers, polyesters, polyamides, polyurethanes, and polycarbonates. These may act as adhesion-imparting components, or may act as tackifiers or plasticizers, as described below.

[0078] Specific examples of tackifiers include rosin esters. Specific examples of plasticizers include dioctyl phthalate. Examples of defoaming agents include hydrocarbon-based, silicone-based, fluorosilicone-based, fluorine-based, and mineral spirit-based agents, and known defoaming agents can be used. Examples of leveling agents include hydrocarbon-based, silicone-based, and fluorine-based agents, and known defoaming agents can be used.

[0079] Examples of polymerization inhibitors that can be used include hydroquinone, methoxyhydroquinone, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, and aluminum salt of N-nitrosophenylhydroxylamine, and known ones can be used. Examples of stabilizers that can be used include hindered phenol-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, hindered amine-based antioxidants, and ultraviolet absorbers, and known ones can be used.

[0080] Any known organic solvent can be used as long as it dissolves the components (A) to (D). However, considering that the solvent drying step reduces production efficiency and there are concerns about residual solvent, it is preferable not to use a solvent.

[0081] 6. Photocurable Adhesive Composition for Polymer Electrolytes A photocurable adhesive composition for polymer electrolytes according to one embodiment of the present disclosure contains components (A) to (D) in specific proportions. In the present disclosure, the term "polymer electrolyte" may refer to a polymer electrolyte membrane formed into a film or sheet, or may contain a polymer electrolyte as a binder. Examples of materials containing a polymer electrolyte as a binder include catalyst layers in fuel cells and Pt-based catalyst-supported carbon fixed with an ionomer polymer electrolyte. The composition according to one embodiment of the present disclosure can be preferably applied to polymer electrolyte membranes.

[0082] The composition of one embodiment of the present disclosure can be produced by a conventional method, such as by mixing components (A) to (D), optionally adding other components, and stirring according to a conventional method. The mixture may be heated if necessary, but from the viewpoint of stability, it is preferable to keep the temperature at 100°C or lower. Furthermore, when polymer fine particles, which are component (E), are added, the composition is preferably produced by a method and under conditions that ensure sufficient dispersibility of the fine particles.

[0083] The viscosity of the composition according to one embodiment of the present disclosure can be appropriately determined by a person skilled in the art depending on the application method. For example, in the case of screen printing, the viscosity is determined at 25°C and a shear rate of 10 sec. －１ The viscosity is preferably 1 Pa·s to 50 Pa·s, and more preferably 5 Pa·s to 30 Pa·s.

[0084] 7. Method of Use The photocurable adhesive composition for polymer electrolytes according to one embodiment of the present disclosure can be used according to conventional methods, such as by applying the composition to a first substrate, then laminating the first substrate with a second substrate, and irradiating the first substrate with light. At least one of the first substrate and the second substrate is preferably a polymer electrolyte, and the other is preferably a resin sheet, as this has a significant effect in improving adhesion durability. The composition according to one embodiment of the present disclosure can be preferably used as an adhesive to bond a polymer electrolyte to a resin sheet, and more preferably to bond a polymer electrolyte membrane to a resin sheet. Note that the term "substrate" simply refers to a general term for polymer electrolytes and other substrates.

[0085] The composition of the present disclosure may be applied to the substrate by a known method such as screen printing, a dispenser, a jet dispenser, gravure printing, inkjet printing, or dipping, and may be applied to the substrate by screen printing. The composition of the present disclosure may be applied to the end face on the side where the polymer electrolyte membrane and the resin sheet are laminated.

[0086] When applying the composition of one embodiment of the present disclosure, the application thickness may be selected depending on the substrate to be used and the intended use, and is preferably 1 μm to 500 μm, more preferably 5 μm to 100 μm.

[0087] Specific examples of polymer electrolyte membranes include perfluorocarbon materials having sulfonic acid groups. Commercially available polymer electrolytes include Nafion (registered trademark) manufactured by DuPont, FLEMION (registered trademark) manufactured by Asahi Glass Co., Ltd., Aciplex (registered trademark) manufactured by Asahi Kasei Corporation, and GORE-SELECT (registered trademark) membrane manufactured by Gore Japan Ltd.

[0088] The substrate may be a polymer electrolyte membrane in which a catalyst, carbon, or the like is fixed by a polymer electrolyte, such as a membrane electrode assembly (MEA) of a fuel cell.

[0089] Specific examples of resin sheets include polyolefin, polyethylene naphthalate, nylon, polystyrene, polycarbonate, polyimide, polyetherimide, polyphenylene ether, polyether ether ketone, polysulfone, polyphenyl sulfone, polyether sulfone, and polyphenylene sulfide.

[0090] Examples of polyolefin resin sheets include polyethylene, polypropylene, cycloolefin polymer, and acid-modified versions of these. Furthermore, the resin sheet may contain a mixture of rubber particles, liquid rubber, tackifier, plasticizer, etc., or may have heat-fusible properties.

[0091] The resin sheet may have a multilayer structure. For example, a three-layer sheet using a heat-resistant polymer for the core and a heat-sealable polyolefin resin for the surface layer is preferably used in the production of a fuel cell. The composition of one embodiment of the present disclosure can be particularly preferably used to bond such a three-layer sheet to a polymer electrolyte membrane.

[0092] When the resin sheet is made of a material that is difficult to adhere to, the surface may be activated by plasma treatment, corona discharge treatment, chemical treatment, surface roughening treatment, etching treatment, flame treatment, or the like.

[0093] The curing of the composition according to one embodiment of the present disclosure can be achieved by laminating two substrates together and then irradiating the substrate with light from the side of the substrate that transmits light. Therefore, it is preferable that one of the substrates is light-transmitting. In the case of a polymer electrolyte membrane that does not transmit light because it fixes carbon, such as in a membrane electrode assembly (MEA) of a fuel cell, it is preferable that the resin sheet is light-transmitting.

[0094] Examples of light used to cure the composition of one embodiment of the present disclosure include ultraviolet light, visible light, far infrared light, incandescent lamps, fluorescent lamps, and sunlight. Of these, ultraviolet light or visible light is preferred, and ultraviolet light is particularly preferred. In addition, if the resin sheet does not transmit ultraviolet light, visible light may be used. As for visible light, it is preferable that the visible light has a short wavelength within the wavelength range transmitted by the resin sheet.

[0095] Examples of light sources that can irradiate light include high-pressure mercury lamps, metal halide lamps, and LEDs that emit ultraviolet and short-wavelength visible light. Examples of LED wavelengths include 365 nm, 385 nm, 405 nm, and 435 nm.

[0096] The amount of ultraviolet light irradiation may be appropriately set depending on the light source. For example, in the UV-A region (near 365 nm) or UV-V region (near 405 nm), it is 50 mJ / cm ２ ~5,000mJ / cm ２ and preferably 100 mJ / cm ２ ~3,000mJ / cm ２ is more preferred.

[0097] In addition, when the resin sheet has low light transmittance, a thermal radical polymerization initiator may be blended into the composition of one embodiment of the present disclosure, and the composition may be semi-cured by light irradiation to temporarily fix the resin sheet, and then the polymerization reaction may be completed by heating or by the passage of time.

[0098] 8. Laminate A laminate according to one embodiment of the present disclosure includes a first substrate, a cured product formed from the photocurable adhesive composition for polymer electrolytes according to one embodiment of the present disclosure, and a second substrate, wherein one or both of the first substrate and the second substrate are polymer electrolytes. At least one of the first substrate and the second substrate is preferably a polymer electrolyte, and the other is preferably a resin sheet, as this provides a significant improvement in adhesion durability. Because the laminate according to one embodiment of the present disclosure uses the photocurable adhesive composition for polymer electrolytes according to one embodiment of the present disclosure, the laminate has excellent adhesion at the bonded portion between the polymer electrolyte and the substrate (preferably a resin sheet) and excellent adhesion durability when immersed in high-temperature water (particularly high-temperature water under high-oxygen concentration conditions) for a long period of time.

[0099] The present disclosure will be described in more detail below with reference to examples and comparative examples. However, the present disclosure is not limited to these examples. In the following, "parts" means parts by mass, and the numerical values ​​indicating the blending ratios in the tables mean mass%.

[0100] 1. Production Examples 1) Production Example 1 [Production of Component (A)] A 2-L four-neck separable flask was charged with 808 g (1.0 mol of hydroxyl groups) of hydrogenated polybutadiene (GI-1000 manufactured by Nippon Soda Co., Ltd., hydroxyl value 69.4 mg KOH / g; hereinafter referred to as "GI-1000") as component (a1), 0.68 g of 2,6-di-t-butyl-p-cresol (hereinafter referred to as "DBC"), and 405 g of lauryl acrylate (hereinafter referred to as "LA"), and the mixture was dissolved by stirring using a stirrer. A thermometer, gas inlet tube, dropping funnel, and reflux condenser were attached to the flask, and the contents were stirred while a mixed gas of oxygen and nitrogen (5 vol% oxygen) was circulated through the flask. To this solution, 109 g (1.25 mol as isocyanate groups) of 2,4-tolylene diisocyanate was added as component (a2) via a dropping funnel and dissolved with stirring. Next, 0.54 g of dibutyltin dilaurate (hereinafter referred to as "DBTL") was added as a catalyst, and after stirring and dissolving, the mixture was heated to 80 °C and reacted for 2 hours. Thereafter, 29.0 g (0.25 mol as hydroxyl groups) of 2-hydroxyethyl acrylate (hereinafter referred to as "HEA") was added, and the reaction was carried out at 80 °C for 5 hours with stirring. The disappearance of the isocyanate groups was confirmed using an IR spectrum (Spectrum Two, manufactured by PerkinElmer Co., Ltd.), and the synthesis was terminated. The resulting product was a mixture containing 70 mass% of polyurethane acrylate (hereinafter referred to as "PUA-1") corresponding to component (A) and 30 mass% of LA, a diluent monomer that also corresponds to component (B). The Mn and Mw of PUA-1 were measured according to the following method, and were found to be 9,800 and 25,600.

[0101] [Molecular Weight Measurement] Using a gel permeation chromatograph (HLC-8320 manufactured by Tosoh Corporation), Mn (number average molecular weight) and Mw (weight average molecular weight) in terms of polystyrene were obtained under the following measurement conditions: Measurement conditions: Column: TSKgel-SuperMultipore HZ-M (4.6 mm ID x 15 cm) x 3 (for low molecular weight, exclusion limit molecular weight 2,000,000) manufactured by Tosoh Corporation; Column temperature: 40°C; Eluent: tetrahydrofuran (0.35 ml / min); Detector: RI; Sample concentration: 0.1%

[0102] 2) Production Example 2 [Production of Component (A)] A 2-L four-neck separable flask was charged with 808 g (1.0 mol as hydroxyl groups) of GI-1000, 0.71 g of DBC, and 426 g of LA as component (a1), and the mixture was stirred and dissolved using a stirrer. A thermometer, a gas inlet tube, a dropping funnel, and a reflux condenser were attached to the flask, and the mixture was stirred while a mixed gas of oxygen and nitrogen (5 vol% oxygen) was circulated through the flask. 156 g (1.25 mol as isocyanate groups) of 4,4'-diphenylmethane diisocyanate as component (a2) was added to the solution via the dropping funnel and dissolved with stirring. Next, 0.57 g of DBTL was added as a catalyst, dissolved with stirring, and then the mixture was heated to 80°C and reacted for 2 hours. Thereafter, 29.0 g of HEA (0.25 mol as hydroxyl groups) was charged and reacted at 80 °C for 5 hours with stirring. The disappearance of the isocyanate groups was confirmed using IR spectroscopy, and the synthesis was terminated. The resulting product was a mixture containing 70 mass% of polyurethane acrylate (hereinafter referred to as "PUA-2") corresponding to component (A) and 30 mass% of LA, which is a diluent monomer and also corresponds to component (B). The Mn and Mw of PUA-2 were measured in the same manner as above, and were found to be 12,100 and 35,500, respectively.

[0103] 3) Production Example 3 [Production of Component (F1)] A 2 L four-neck separable flask was charged with 808 g (1.0 mol as hydroxyl groups) of GI-1000 as component (a1), 0.67 g of DBC, and 404 g of LA as component (a1), and the mixture was stirred and dissolved with a stirrer attached. This flask was equipped with a thermometer, a gas inlet tube, a dropping funnel, and a reflux condenser, and the mixture was stirred while circulating a mixed gas of oxygen and nitrogen (oxygen 5 vol%) through the flask. To this solution, 105 g (1.25 mol as isocyanate groups) of hexamethylene diisocyanate was charged from the dropping funnel as an isocyanate compound that is not component (a2) and corresponds to component (f2), and the mixture was stirred and dissolved. Next, 0.54 g of DBTL was charged as a catalyst, and after stirring and dissolving, the mixture was heated to 80°C and reacted for 2 hours. Thereafter, 29.0 g of HEA (0.25 mol as hydroxyl groups) was charged and the mixture was allowed to react at 80 °C for 5 hours while stirring. The disappearance of the isocyanate groups was confirmed using IR spectroscopy, and the synthesis was terminated. The resulting product was a mixture containing 70 mass% of polyurethane acrylate (hereinafter referred to as "PUA'-1"), which does not correspond to component (A) but corresponds to component (F1), and 30 mass% of LA, which is a diluent monomer and also corresponds to component (B). The Mn and Mw of PUA'-1 were measured in the same manner as above, and the results were Mn of 11,800 and Mw of 30,400.

[0104] 4) Production Example 4 [Production of Component (F1)] A 2 L four-neck separable flask was charged with 808 g (1.0 mol as hydroxyl groups) of GI-1000 as component (a1), 0.70 g of DBC, and 418 g of LA as component (a1), and the mixture was stirred and dissolved with a stirrer attached. This flask was equipped with a thermometer, a gas inlet tube, a dropping funnel, and a reflux condenser, and the mixture was stirred while circulating a mixed gas of oxygen and nitrogen (oxygen 5 vol%) through the flask. To this solution, 139 g (1.25 mol as isocyanate groups) of isophorone diisocyanate was charged from the dropping funnel as an isocyanate compound that is not component (a2) and corresponds to component (f2), and the mixture was stirred and dissolved. Next, 0.56 g of DBTL was charged as a catalyst, and after stirring and dissolving, the mixture was heated to 80°C and reacted for 2 hours. Thereafter, 29.0 g of HEA (0.25 mol as hydroxyl groups) was charged and the mixture was allowed to react at 80 °C for 5 hours while stirring. The disappearance of the isocyanate groups was confirmed using IR spectroscopy, and the synthesis was terminated. The resulting product was a mixture containing 70 mass% of polyurethane acrylate (hereinafter referred to as "PUA'-2"), which does not correspond to component (A) but corresponds to component (F1), and 30 mass% of LA, which is a diluent monomer and also corresponds to component (B). The Mn and Mw of PUA'-2 were measured in the same manner as above, and the results were Mn of 11,500 and Mw of 31,000.

[0105] 2. Examples 1-2, Comparative Examples 1-4 1) Preparation of Photocurable Adhesive Compositions The components shown in Table 1 were blended so that the mass percentages of each component were as shown in Table 1, and the blended components were stirred and mixed in a conventional manner to prepare photocurable adhesive compositions. When dissolving, the components were heated to approximately 80°C as necessary. Component (E) was blended in the final step of the composition preparation. The abbreviations in Table 1 have the following meanings.

[0106] Component (A) PUA-1: polyurethane acrylate contained in the product of Production Example 1 PUA-2: polyurethane acrylate contained in the product of Production Example 2 Component (B) LA: LA (lauryl acrylate) manufactured by Osaka Organic Chemical Industry, Ltd. Component (C) JP-100: NISSO-PB JP-100 (epoxidized polybutadiene, oxirane oxygen concentration 7.8%, Mn approximately 1,200) manufactured by Nippon Soda Co., Ltd. Component (D) TPO: Omnirad TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide) manufactured by IGM Resins Component (E) MX-500L: crosslinked acrylic monodisperse particles MX-500L (volume average primary particle diameter 5 μm) manufactured by Soken Chemical & Engineering Co., Ltd. Component (F) (Component (F1)) PUA'-1: polyurethane acrylate contained in the product of Production Example 3 PUA'-2: polyurethane acrylate contained in the product of Production Example 4

[0107] 2) Evaluation of Hot Water Immersion Durability A 7 μm-thick membrane of a fluorine-containing polymer having sulfonic acid groups was used as the polymer electrolyte membrane for fuel cells. A polyester sheet was attached to one side of this membrane as a support. The other substrate (preferably a resin sheet) was a three-layer sheet consisting of a 160 μm-thick polyethylene naphthalate sheet with 55 μm-thick acid-modified polyolefin hot-melt sheets attached to both sides. These two substrates were cut into a rectangle measuring 50 mm wide and 80 mm long. The composition listed in Table 1 was screen-printed to a width of 12.5 mm, a length of 70 mm, and a thickness of 0.04 mm on the edge of the polymer electrolyte membrane (the side without the support). The three-layer sheet was then laminated on top of this so that the two substrates overlapped, and the adhesive was photocured by irradiating it with 405 nm LED light from the three-layer sheet side. The LED irradiation conditions were 850 mW / cm. ２The time was 4 seconds. After photocuring, six 10 mm-wide test pieces were cut from the adhesive sample. The electrolyte membrane support was peeled off from the resulting adhesive test piece, and the piece was immersed in ion-exchanged water placed in a pressure vessel. The vessel was then closed and held at 120°C for 500 hours. After the holding time, the sample was removed from the pressure vessel, quickly wiped clean, and the three-layer sheet surface was attached to a metal plate with double-sided tape. Then, ion-exchanged water was immediately dripped onto the sample so that the adhesive bonded area was immersed in the ion-exchanged water. While still immersed in water, a 1 m-long thread was attached to the edge of the electrolyte membrane, and a 90° peel test was performed using a tensile tester at a tensile speed of 10 mm / min. Measurements were performed three times for each sample at each time point, and the average values ​​are shown in Table 1. If the electrolyte membrane completely peeled off in water, the table indicated "peeled off." Furthermore, the IR spectrum of the surfaces of both substrates exposed after peeling was measured using the μ-ATR method to identify the location of failure, and the results are listed in Table 1. Here, "membrane structure" indicates that both exposed surfaces were polymer electrolyte membranes, and that the weakest point was not the adhesive interface but the polymer electrolyte membrane itself. Also, "membrane interface" indicates that peeling occurred at the interface between the polymer electrolyte membrane and the photocurable adhesive.

[0108] 3) Evaluation of hot water immersion durability under high oxygen concentration conditions The composition of Example 1 or Comparative Example 2 was screen-printed to a width of 12.5 mm, a length of 70 mm, and a thickness of 0.04 mm on the edge of the above polymer electrolyte membrane (the side without the support). The above three-layer sheet was laminated on top of this, shifted in the width direction so that the shear adhesive strength could be measured later. Next, 405 nm LED light was irradiated from the three-layer sheet side to photocure the adhesive. The LED irradiation conditions were 850 mW / cm ２The adhesive strength was evaluated after 4 seconds. After photocuring, six 10 mm-wide test pieces were cut from the adhesive sample, and the electrolyte membrane support was peeled off. A pressure-resistant container capable of sealing gas and measuring internal pressure was prepared and filled with ion-exchanged water. The adhesive test piece was immersed in the ion-exchanged water, and oxygen was sealed in the pressure-resistant container to set the oxygen pressure to 0.3 MPa. The container was then held at 95°C for 1,000 hours, after which the adhesive strength was evaluated. Prior to evaluating the adhesive strength, the occurrence of water blisters was visually evaluated. To evaluate the adhesive strength, the test piece was removed from the ion-exchanged water immediately before measurement, the ion-exchanged water was quickly wiped off, and the electrolyte membrane was reinforced by attaching it to a metal plate with double-sided tape. The shear adhesive strength was measured at a tensile speed of 10 mm / min before the electrolyte membrane dried. Measurements were performed three times for each sample at each time point, and the average values ​​are shown in Evaluation Results 2 in Table 1. Furthermore, the IR spectrum of the surfaces of both substrates exposed after peeling was measured using the μ-ATR method to identify the location of the breakdown, and the results are shown in Evaluation Result 2 in Table 1. Here, "sheet interface" indicates that peeling occurred at the interface between the three-layer sheet and the photocurable adhesive. Furthermore, "membrane interface" indicates that peeling occurred at the interface between the polymer electrolyte membrane and the photocurable adhesive.

[0109]

[0110] 4) Evaluation Results As is clear from Evaluation Result 1 in Table 1, Example 1 containing the (A) component PUA-1 and Example 2 containing PUA-2 exhibited excellent hot water immersion durability under the severe accelerated test conditions of 120°C water immersion. In contrast, Comparative Example 1 containing PUA'-1 produced from a non-aromatic diisocyanate different from the (a2) component and Comparative Example 2 containing PUA'-2 exhibited adhesive strength reduced to one-fifth of that of Examples 1 and 2, and even suffered from interfacial failure. Furthermore, Comparative Examples 3 and 4, which did not contain the (C) component, exhibited even poorer hot water immersion durability than Comparative Examples 1 and 2. These results demonstrate that the composition according to the present disclosure is suitable as an adhesive between a polymer electrolyte membrane and a resin sheet used in a fuel cell. Meanwhile, as is clear from Evaluation Result 2 in Table 1, Example 1 also exhibited significantly superior hot water immersion durability under high-oxygen conditions compared to Comparative Example 2. These results demonstrate that the composition according to the present disclosure is suitable as an adhesive between a polymer electrolyte membrane and a resin sheet used in a water electrolysis system.

[0111] 3. Examples 3 to 5, Comparative Example 5 1) Preparation of Photocurable Adhesive Composition In each of Examples 3 to 5 and Comparative Example 5, the components shown in Table 2 were blended so that the content (mass %) of each component was as shown in the "Blending Composition" column of Table 2, and the blend was stirred and mixed in a conventional manner to prepare a photocurable adhesive composition. When dissolving, the mixture was heated to approximately 80°C as necessary. Component (E) was blended in the final step of the composition preparation. In Table 2, the same abbreviations as in Table 1 refer to the same substances as in Table 1. Details of abbreviations not listed in Table 1 are as follows. In Table 2, compounds that do not apply or were not blended are indicated with a "-" sign. Component (D) O-380: Omnirad 380 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) manufactured by IGM Resins

[0112] 2) Evaluation of Hot Water Immersion Durability - Substrate Used - A substrate (hereinafter also referred to as "MEGA") in which a membrane electrode assembly (MEA) and a gas diffusion layer (GDL) were integrated was used as the polymer electrolyte membrane for the fuel cell. The portion where the MEGA and the resin frame were bonded with a photocurable adhesive was the end of the electrolyte membrane (the portion where the electrolyte membrane was exposed) where the cathode catalyst was not applied. Therefore, a MEGA without a cathode catalyst was used as a substrate having the entire surface corresponding to this end. Hereinafter, this will be referred to as the "MEGA membrane." The layer structure of the MEGA membrane was, from the bonding surface, a polymer electrolyte membrane, an anode catalyst layer, a water-repellent layer, and an anode-side GDL. The polymer electrolyte membrane was approximately 7 μm thick and was a fluorine-containing polymer having sulfonic acid groups. The base material for the resin frame was a three-type, five-layer sheet consisting of a 140 μm-thick polyphenylene ether (PPE) sheet with an acid-modified polyolefin hot-melt resin layer formed on both sides via an adhesive layer primarily composed of PPE and polyolefin. Hereinafter, this will be referred to as the "frame resin sheet." The surface of this frame resin sheet (the acid-modified polyolefin hot-melt sheet) was the same as the surface of the "three-layer sheet (resin sheet)" in Examples 1 and 2 and Comparative Examples 1 to 4.

[0113] -Preparation of Evaluation Samples- Evaluation samples were prepared as follows. As shown in FIG. 1A or FIG. 1B, a MEGA membrane 10 was cut to a size of 90 mm x 30 mm, and a photocurable adhesive 11 of each of the photocurable adhesive compositions shown in Table 2 was screen-printed on the edge of the surface of the polymer electrolyte membrane 10a of the MEGA membrane 10 to a width of 12.5 mm, a length of 70 mm, and a thickness of 0.04 mm. The MEGA membrane 10 had a configuration in which the polymer electrolyte membrane 10a, an anode catalyst layer 10b, a water-repellent layer 10c, and a gas diffusion layer (GDL) 10d were laminated in this order. As shown in FIG. 2A or FIG. 2B, a frame resin sheet 12 cut to a size of 90 mm x 30 mm was laminated on top of the photocurable adhesive 11 so that the length of the overlap 13 was 5 mm. In this case, in order to be able to evaluate the shear adhesive strength later, the frame resin sheet 12 was arranged so that the long side 15 opposite the long side 14 having the portion to be bonded to the photo-curable adhesive 11 and the long side 17 opposite the long side 16 having the photo-curable adhesive 11 were positioned in opposite directions. Next, 405 nm LED light was irradiated from the frame resin sheet 12 side to photo-cure the photo-curable adhesive 11, and an adhesion sample 18 was produced. The LED irradiation conditions were 850 mW / cm ２ So it was set to 4 seconds.

[0114] -Hot Water Immersion Test (Hot Water Immersion Durability)- 0.3 L of ion-exchanged water was placed in a 0.9 L Teflon-coated pressure vessel, and the above-mentioned adhesive sample 18 was placed therein with a Teflon plate weight placed on top to allow immersion. Note that "Teflon" is a registered trademark. The lid of the pressure vessel was then closed, and the vessel was maintained at 110°C for 2,500 hours. During this time, the vessel was opened every week, and the water and adhesive sample 18 were removed and observed. 0.3 L of fresh ion-exchanged water was added, and the immersion test was continued again. This procedure was repeated up to 2,500 hours. However, for adhesive sample 18 whose adhesive portion peeled off during this procedure, the time at which the peeling occurred was recorded. Peeling of the adhesive portion is shown in the "Peeling during peeling" column of Table 2, and the adhesive sample 18 after peeling of the adhesive portion was air-dried at 23°C and 50% RH for at least one day, and then the IR spectrum was measured using the μ-ATR method to identify the location of failure (peeling surface). These results are shown in the "Evaluation result 3" column of Table 2. "Membrane interface" in Table 2 means that the photocurable adhesive 11 peeled off at the interface of the polymer electrolyte membrane 10a.

[0115] -Adhesion Strength Evaluation After Durability Test- After immersion at 110°C for 2,500 hours, the adhesion strength between the polymer electrolyte membrane 10a and the anode catalyst layer 10b in the bonded sample 18 was weakened, so the bonded sample was peeled at the interface in water. The peeled product consisting of the polymer electrolyte membrane 10a, the photocurable adhesive 11, and the frame resin sheet 12, which was peeled from the bonded sample 18, was used as a peel adhesion sample. Thereafter, as shown in Figure 3A or 3B, the water adhering to the peel adhesion sample was wiped off with paper, and the peel adhesion sample was air-dried in a room at 23°C and 50% RH for at least one day. Six cut samples 20 were then cut into 1 cm widths to obtain six pieces. As shown in Figure 4, because the polymer electrolyte membrane 10a was thin and weak, the cut sample 20 was attached to an aluminum plate 22 using double-sided tape 21 to prepare an evaluation sample 30. The shear adhesion strength of the evaluation sample 30 was measured using a tensile tester at a pulling rate of 10 mm / min in an environment of 23°C and 50% RH. The shear adhesive strength was measured in accordance with JIS K 6850 1999, "Test Method for Tensile Shear Adhesion Strength of Rigid Adherends," using a tensile shear load parallel to the adhesive surface, and the unit was "MPa." If the evaluation sample 30 broke during the measurement, the location of the breakage was identified by measuring the IR spectrum of the peeled surface using the μ-ATR method. These measurement results are listed in the "Evaluation Results 3" column of Table 2. The shear adhesive strength is the average value for six evaluation samples 30 and is listed in the "Adhesion Strength" column of Table 2. Regarding the location of breakage, "membrane rupture" listed in Table 2 means that the polymer electrolyte membrane 10a itself stretched and broke. That is, in the case of Example 3, which is listed as "membrane rupture" in Table 2, the polymer electrolyte membrane 10a did not peel off from the photocurable adhesive 11. "Sheet interface" means that peeling occurred at the interface with the frame resin sheet 12. That is, in the cases of Examples 4 and 5, the photocurable adhesive 11 and the frame resin sheet 12 were peeled off, but the polymer electrolyte membrane 10 a was not peeled off from the photocurable adhesive 11 .

[0116] 3) Evaluation of long-term stability (evaluation of durability of cured adhesive) Each of the photocurable adhesive compositions shown in Table 2 was applied as a photocurable adhesive to a thickness of 100 μm on a 50 μm thick fluororesin sheet using an applicator. LED light of 405 nm was irradiated from this surface at 850 mW / cm. ２ The photocurable adhesive was cured by irradiating the adhesive with light for 4 seconds. Next, a dumbbell-shaped No. 3 punching blade according to JIS K6251 (2017) was used to obtain dumbbell-shaped cured adhesive products. Twelve dumbbell-shaped cured adhesive products were produced for each of the cured adhesive products. Six of the dumbbell-shaped cured adhesive products were conditioned for at least one day in a room at 23°C and 50% RH. After that, the cured adhesive products were peeled from the fluororesin sheet in a 23°C and 50% RH environment. A tensile test was then performed on the cured adhesive products using a tensile tester at a tensile speed of 50 mm / min. The remaining six were immersed in ion-exchanged water at 120°C for 1,000 hours. After immersion, the adhering water was wiped off with paper and air-dried for at least one day in a room at 23°C and 50% RH. The cured adhesive products were then peeled from the fluororesin sheet in a 23°C and 50% RH environment. A tensile test was then performed on the cured adhesive products using a tensile tester at a tensile speed of 50 mm / min. The breaking strength and breaking elongation values ​​obtained in the tensile test were averaged over six samples and are shown in the "Evaluation Results 4" column of Table 2. The breaking strength is shown in units of "MPa" and the breaking elongation is shown in units of "%". The breaking elongation value after immersion in hot water was divided by the initial value, and the resulting value (%) was shown as the "breaking elongation retention rate" in the "Evaluation Results 4" column of Table 2.

[0117]

[0118] 4) Evaluation Results As is clear from Table 2, Examples 3 to 5 containing PUA-1 as component (A) exhibited excellent durability under severe long-term hot water immersion conditions, including 2,500 hours of immersion in 110°C water. In particular, Example 3, which contained 40% by mass of component (A), showed excellent adhesion durability, with no peeling at the adhesive interface (Table 2, "Deep Peel": "None," and "Shear Adhesion": "Membrane Rupture"). Examples 4 and 5 also exhibited adhesive strength with the polymer electrolyte membrane 10a of 0.5 MPa or greater (Table 2, "Adhesion (MPa)" under "Shear Adhesion"), demonstrating excellent adhesion durability. On the other hand, Comparative Example 5, which did not contain component (A), exhibited peeling of the polymer electrolyte membrane in water after 840 hours of immersion in 110°C water, demonstrating the importance of component (a2), a raw material for component (A). Furthermore, when focusing on the elongation at break as a measure of the durability (long-term stability) of the cured product, the lower the content of component (A), the better the results. When a high breaking elongation retention rate is required in addition to adhesive durability, it has been found effective to use a urethane acrylate containing (a1) and (f2) as constituent components (i.e., a urethane acrylate not containing (a2)) in combination with component (A).

[0119] The photocurable adhesive composition for polymer electrolytes and the laminate according to one embodiment of the present disclosure have such adhesion durability that the bonded portion between a polymer electrolyte membrane and a substrate (preferably a resin sheet) does not easily peel even when the bonded portion is immersed in high-temperature water for a long period of time, and are therefore suitable as a photocurable adhesive or a photocurable sealant for fuel cells.Furthermore, the photocurable adhesive composition for polymer electrolytes and the laminate according to one embodiment of the present disclosure have such adhesion durability that the bonded portion between a polymer electrolyte membrane and a substrate (preferably a resin sheet) does not easily peel even when the bonded portion is immersed in high-temperature water under high-oxygen conditions for a long period of time, and are therefore suitable as a photocurable adhesive or a photocurable sealant for water electrolysis devices.

[0120] REFERENCE SIGNS LIST 10 MEGA membrane 10a Polymer electrolyte membrane 10b Anode catalyst layer 10c Water-repellent layer 10d Gas diffusion layer 11 Photocurable adhesive 12 Frame resin sheet 13 Overlap 14, 15 Long sides of frame resin sheet 16, 17 Long sides of MEGA membrane 18 Adhesion sample 20 Cut sample 21 Double-sided tape 22 Aluminum plate 30 Evaluation sample

[0121] The disclosures of Japanese Patent Application No. 2023-099597, filed June 16, 2023, and Japanese Patent Application No. 2024-017531, filed February 7, 2024, are incorporated herein by reference in their entirety. All publications, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A photocurable adhesive composition for polymer electrolytes comprising: component (A): a urethane (meth)acrylate obtained by reacting the following components (a1), (a2), and (a3); component (a1): a hydrogenated polybutadiene or hydrogenated polyisoprene having a hydroxyl group at its terminal; component (a2): an aromatic diisocyanate; component (a3): a (meth)acrylate having one hydroxyl group per molecule; component (B): an alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms; component (C): an epoxidized polybutadiene or epoxidized polyisoprene; and component (D): a photoradical polymerization initiator, wherein the content of components (A) to (D) is, based on the total content of the composition, as follows: component (A): 1% by mass to 70% by mass component (B): 10% by mass to 70% by mass component (C): 1% by mass to 20% by mass component (D): 0.1% by mass to 10% by mass.

2. A photocurable adhesive composition for polymer electrolytes according to claim 1, wherein the content of said component (A) is 10 mass % or more based on the total composition.

3. The photocurable adhesive composition for polymer electrolytes according to claim 1, further comprising the following component (F1) in an amount of 1% by mass to 70% by mass based on the total amount of the composition: Component (F1): a urethane (meth)acrylate obtained by reacting the component (a1), the following component (f2), and the component (a3); Component (f2): an aliphatic diisocyanate.

4. The photocurable adhesive composition for polymer electrolytes according to claim 1, further comprising, as component (E), polymer fine particles having a volume average primary particle diameter of 0.5 μm to 50 μm as measured by a wet method in an amount of 1% by mass to 50% by mass based on the total mass of the composition.

5. A photocurable adhesive composition for polymer electrolytes as described in claim 1, in which the total amount of components (A) and (B) is 80 parts by mass or more when the total amount of compounds having a (meth)acryloyl group is 100 parts by mass.

6. The photocurable adhesive composition for polymer electrolytes according to claim 1, which is used as an adhesive or sealant for fuel cells.

7. The photocurable adhesive composition for polymer electrolytes according to claim 1, which is used as an adhesive or sealant for a water electrolysis device.

8. A laminate comprising a first substrate, a cured product formed from the photocurable adhesive composition for polymer electrolytes according to any one of claims 1 to 7, and a second substrate, wherein either or both of the first substrate and the second substrate are polymer electrolytes.

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