Adhesive composition for fuel cell and water electrolysis device, fuel cell adhesive member and water electrolysis device adhesive member using said adhesive composition, and method for producing these adhesive members

Abstract

This adhesive composition for a fuel cell is for bonding a thin plate-like base material, which is a constituent member of a fuel cell, and a sealing member produced from a rubber composition, and includes: (A) an adhesive liquid including a solvent and an adhesive component comprising a silane coupling agent as a principal component or comprising a silane coupling agent and an organic titanate compound as principal components; and (B) a dye that is compatible with the adhesive component and that dissolves in the solvent. The content of the dye is more than 25 parts by mass and 45 parts by mass or less when the non-volatile content of the adhesive composition is assumed to be 100 parts by mass. The adhesive composition is colored by the dye in a color different from the color of the base material or the sealing member.

Description

Adhesive composition for fuel cells and water electrolysis devices, adhesive member for fuel cells using the adhesive composition, adhesive member for water electrolysis devices, and method for manufacturing these adhesive members.

[0001] This disclosure relates to an adhesive composition for bonding components of fuel cells and water electrolyzers to sealing members, an adhesive member for fuel cells manufactured using the adhesive composition, an adhesive member for water electrolyzers, and a method for manufacturing these adhesive members.

[0002] Fuel cells exhibit a stacked structure in which numerous cells are stacked. The stack of cells is fastened together by end plates located on both sides in the stacking direction. For example, a cell in a polymer electrolyte fuel cell has an electrode member including a membrane electrode assembly (MEA) and separators arranged on either side of the electrode member. Rubber sealing members are placed around the electrode member and between adjacent separators to ensure sealing and insulation against reaction gases such as hydrogen and air, and refrigerants. Similarly, a device that produces hydrogen by electrolysis of water (a water electrolyzer) is also composed of a stack of cells having electrode members, separators, and sealing members, just like a fuel cell.

[0003] In order to maintain high sealing performance in the operating environment of fuel cells and water electrolyzers (hereinafter sometimes referred to as "fuel cells, etc."), a method of integrating a sealing member and a mating member using an adhesive is effective. For example, Patent Document 1 describes a method for bonding a rubber gasket (sealing member) to a separator, in which a silane coupling agent-based primer is applied to the surface of the rubber gasket, the primer-coated surface is brought into close contact with the separator, and the rubber gasket is heated while being pressed and fixed. Patent Document 2 describes an adhesive for bonding a sealing member to a separator, in which the main component is a copolymer oligomer type silane coupling agent having hydrophilic and hydrophobic functional groups in specific proportions. In Patent Document 2, the adhesive mainly composed of a silane coupling agent is applied to the surface of the separator, dried, and then a rubber composition is laminated, crosslinked, and bonded.

[0004] JP 2017-183198 A, WO 2022 / 208926 A1, JP 2018-59630 A

[0005] An adhesive mainly composed of a silane coupling agent is almost colorless and transparent, and the coating film formed on the surface of an object to be coated such as a separator is extremely thin. Therefore, it is difficult to visually determine whether the adhesive is properly applied within a predetermined range. If there are uneven coatings or uncoated areas, the seal member may peel off or the sealing performance may deteriorate.

[0006] As a method for determining the coating state of the adhesive, a method of adding a colorant to the adhesive to color the coating film can be considered. However, since the colorant does not have adhesiveness, there is a risk that the adhesiveness may decrease depending on the blending amount. Pigments are known as colorants, but since pigments do not dissolve in solvents, they tend to precipitate and it is difficult to form a uniform coating film. In addition, since pigment particles that do not have adhesiveness are dispersed in the formed adhesive layer, the seal member may be easily peeled off, or stress may concentrate in the vicinity of the pigment particles due to the compressive force in the lamination direction, and there is a risk that cracks in the seal member may occur starting from the pigment particles.

[0007] In this regard, Patent Document 3 describes coloring an adhesive for bonding a cyclic metal core material and an elastomer member with a dye. However, the adhesive described in Patent Document 3 is a general adhesive such as a phenolic resin-based or epoxy resin-based adhesive used for bearing parts of automobiles and wind turbines, and does not use a silane coupling agent. It is also described that the dye can be either water-soluble or oil-soluble. That is, in Patent Document 3, a silane coupling agent is not assumed as an adhesive component, and no consideration is given to the compatibility between the dye and the adhesive component.

[0008] For example, in adhesives, if the compatibility between the adhesive component and the dye is poor, the dye may precipitate or clump, making it difficult to form a uniform coating film. In this case, the sealing member may peel off easily, or cracking may occur due to compressive force in the lamination direction. Furthermore, in fuel cells and the like, thin components and high dimensional accuracy are required, and the thickness of the adhesive layer interposed between the sealing member and the mating component must also be extremely thin. Thus, adhesives used to bond components and sealing members in fuel cells and the like must satisfy the specific requirements of these devices (operating environment, compressive durability, thinness, dimensional accuracy, etc.), and therefore, it is difficult to achieve both adhesion and identifiability.

[0009] This disclosure has been made in view of the above circumstances, and aims to provide an adhesive composition that can be used to bond components of fuel cells and water electrolyzers to sealing members, and that can achieve both adhesiveness and identifiability. Furthermore, it aims to provide adhesive members for fuel cells and water electrolyzers manufactured using the adhesive composition, and methods for manufacturing these adhesive members.

[0010] (1) In order to solve the above problems, the adhesive composition for fuel cells of the present disclosure is an adhesive composition for fuel cells that bonds a thin plate-shaped substrate which is a component of a fuel cell to a sealing member manufactured from a rubber composition, and comprises (A) an adhesive liquid having an adhesive component whose main component is a silane coupling agent, or whose main component is a silane coupling agent and an organic titanate compound, and a solvent, and (B) a dye which is compatible with the adhesive component and is soluble in the solvent, wherein the content of the dye is greater than 25 parts by mass when the non-volatile content of the adhesive composition is 100 parts by mass, and is 45 parts by mass or less, and the adhesive composition is colored with the dye to a color different from the color of the substrate or the sealing member.

[0011] The adhesive composition for fuel cells disclosed herein (hereinafter sometimes simply referred to as "adhesive composition"; the same applies to the adhesive composition for water electrolysis equipment described later) is colored with a dye. When the object to be coated is a substrate, the adhesive composition is colored with a color different from the color of the substrate, and when the object to be coated is a sealing member, it is colored with a color different from the color of the sealing member. This makes the adhesive composition easier to identify on the surface of the object to be coated, and makes it easier to determine the quality of the coating by visual inspection or a color inspection machine. As a result, uneven coating and missed spots are less likely to occur, and peeling of the sealing member and deterioration of sealing performance can be suppressed. In this disclosure, "color" mainly refers to hue, one of the three elements of color, and refers to shades such as red, blue, green, and yellow.

[0012] In the adhesive composition of this disclosure, the dye is compatible with the adhesive component and dissolves in the solvent. This makes it less likely for the dye to precipitate and clump to form, allowing for the formation of a homogeneous coating film. As a result, peeling of the sealing member and a decrease in sealing performance can be suppressed. Furthermore, since the dye content is 45 parts by mass or less when the non-volatile content of the adhesive composition is 100 parts by mass, the adhesive performance is less likely to decrease. Thus, the adhesive composition of this disclosure makes it possible to achieve both adhesiveness and distinctiveness.

[0013] (2) In the configuration of (1) above, the fuel cell adhesive composition may be applied to the substrate or the sealing member to a thickness of 0.01 μm or more and 1 μm or less. This configuration is suitable for achieving the thinning of the components and high dimensional accuracy required for fuel cells.

[0014] (3) In any of the above configurations, the fuel cell adhesive composition may be applied to the substrate. With this configuration, a flexible rubber sealing member (which may be an uncrosslinked rubber composition) is laminated onto a thin plate-shaped substrate, so that displacement of the sealing member is suppressed, and dimensional accuracy and workability are improved.

[0015] (4) In the configuration of (3) above, the base material may be a separator. This configuration makes it possible to improve the adhesive reliability between the separator and the sealing member.

[0016] (5) In the configuration of (4) above, the separator may be silver-colored and the dye may be black or red-colored. In this configuration, a black or red-colored adhesive composition is applied to the silver-colored separator. Therefore, the presence of the adhesive composition is easily visible on the separator, and the quality of the application can be easily determined.

[0017] (6) In any of the above configurations, the dye may be a xanthene dye or an azine dye. This configuration makes it easier to select a dye that is compatible with the adhesive component, dissolves in the solvent, and can provide color in a relatively small amount.

[0018] (7) The adhesive member for fuel cells of the present disclosure comprises a thin plate-shaped base material, a sealing member manufactured from a rubber composition, and an adhesive layer for bonding the base material and the sealing member, wherein the adhesive layer is formed from an adhesive composition for fuel cells having any of the above configurations.

[0019] According to the adhesive member for fuel cells of this disclosure (hereinafter sometimes simply referred to as "adhesive member"; the same applies to the adhesive member for water electrolysis equipment described later), the adhesive composition applied to the surface of the substrate or sealing member is easily identifiable during the manufacturing process, and the quality of the application can be easily determined by visual inspection or a color inspection machine. As a result, adhesion defects are less likely to occur, and a high-quality adhesive member for fuel cells with high sealing performance is realized.

[0020] (8) In the configuration of (7) above, the thickness of the adhesive layer may be 0.01 μm or more and 1 μm or less. This configuration is suitable for achieving the thinning of components and high dimensional accuracy required for fuel cells.

[0021] (9) In the configuration of (7) or (8) above, the base material may be a stainless steel separator. This configuration improves the reliability of adhesion between the separator and the sealing member. Also, stainless steel separators usually exhibit a silvery color due to their metallic luster. Therefore, when compared with the color of the separator, various colors such as black, red, blue, and green can be distinguished, and the range of dyes that can be used for coloring is broadened.

[0022] (10) In any of the configurations described in (7) to (9) above, the rubber composition may be configured to have one or more selected from ethylene-propylene rubber, ethylene-propylene-diene rubber, and ethylene-butene-diene rubber. This configuration makes it possible to realize a sealing member with excellent sealing properties, durability, and high-temperature characteristics.

[0023] (11) A method for manufacturing an adhesive member for a fuel cell according to the present disclosure is a method for manufacturing an adhesive member for a fuel cell having any of the configurations of (7) to (10) above, characterized by comprising: a coating step of applying the adhesive composition for a fuel cell to the substrate; a determination step of determining whether the coating state is good or bad based on the color of the applied adhesive composition; and, if the coating state is determined to be good, an adhesion step of arranging the uncrosslinked rubber composition on the coated surface of the substrate to form a laminate, heating and pressurizing the laminate to crosslink the rubber composition to form the sealing member, and bonding the sealing member to the substrate.

[0024] According to the method for manufacturing adhesive members for fuel cells described herein (hereinafter sometimes simply referred to as "method for manufacturing adhesive members"; the same applies to the method for manufacturing adhesive members for water electrolysis devices described later), in the judgment step, the quality of the application is determined by the color of the applied adhesive composition. This makes it possible to avoid uneven application, missed areas, etc. As a result, peeling of the sealing member and deterioration of sealing performance can be suppressed in the manufactured adhesive members for fuel cells.

[0025] (12) In order to solve the above problems, the adhesive composition for a water electrolysis apparatus of the present disclosure is an adhesive composition for a water electrolysis apparatus that bonds a thin plate-shaped substrate which is a component of a water electrolysis apparatus and a sealing member manufactured from a rubber composition, comprising: (A) an adhesive liquid having an adhesive component whose main component is a silane coupling agent, or whose main component is a silane coupling agent and an organic titanate compound, and a solvent; and (B) a dye which is compatible with the adhesive component and is soluble in the solvent, wherein the content of the dye is 3 parts by mass or more and 45 parts by mass when the non-volatile content of the adhesive composition is 100 parts by mass, and the adhesive composition is colored with the dye to a color different from the color of the substrate or the sealing member.

[0026] The adhesive composition for water electrolysis devices disclosed herein is the same as the adhesive composition for fuel cells disclosed herein, except that the minimum dye content is 3 parts by mass or more. Reducing the dye content does not easily reduce adhesiveness. The adhesive composition for water electrolysis devices disclosed herein makes it possible to achieve both adhesiveness and identifiability.

[0027] (13) In the configuration of (12) above, the amount of the dye may be greater than 25 parts by mass when the non-volatile content of the adhesive composition is 100 parts by mass. With this configuration, the color derived from the dye in the adhesive composition becomes darker, making it easier to identify the adhesive composition on the surface of the object to be coated, and making it easier to judge whether the coating is good or bad.

[0028] (14) In the configuration of (12) or (13) above, the adhesive composition for the water electrolysis apparatus may be applied to the substrate or the sealing member to a thickness of 0.01 μm or more and 1 μm or less. This configuration is suitable for achieving the thinning of the components and high dimensional accuracy required for a water electrolysis apparatus.

[0029] (15) In any of the configurations described in (12) to (14) above, the adhesive composition for the water electrolysis device may be applied to the substrate. With this configuration, a flexible rubber sealing member (which may be an uncrosslinked rubber composition) is laminated onto a thin plate-shaped substrate, thereby suppressing misalignment of the sealing member and improving dimensional accuracy and workability.

[0030] (16) In the configuration of (15) above, the base material may be a separator. This configuration makes it possible to improve the adhesive reliability between the separator and the sealing member.

[0031] (17) In the configuration of (16) above, the separator may be silver-colored and the dye may be black or red-colored. In this configuration, a black or red-colored adhesive composition is applied to the silver-colored separator. Therefore, the presence of the adhesive composition is easily visible on the separator, and the quality of the application can be easily determined.

[0032] (18) In any of the configurations described in (12) to (17) above, the dye may be a xanthene dye or an azine dye. This configuration makes it easier to select a dye that is compatible with the adhesive component, dissolves in the solvent, and can provide color in a relatively small amount.

[0033] (19) The adhesive member for a water electrolysis apparatus according to the present disclosure comprises a thin plate-shaped base material, a sealing member manufactured from a rubber composition, and an adhesive layer for bonding the base material and the sealing member, wherein the adhesive layer is formed from an adhesive composition for a water electrolysis apparatus having any of the configurations described in (12) to (18) above.

[0034] According to the adhesive member for water electrolysis equipment disclosed herein, the adhesive composition applied to the surface of the substrate or sealing member can be easily identified during the manufacturing process, and the quality of the application can be easily determined by visual inspection or a color inspection machine. As a result, adhesion defects are less likely to occur, and a high-quality adhesive member for water electrolysis equipment with high sealing performance is realized.

[0035] (20) In the configuration of (19) above, the thickness of the adhesive layer may be 0.01 μm or more and 1 μm or less. This configuration is suitable for achieving the thinning of components and high dimensional accuracy required for water electrolysis devices.

[0036] (21) In the configuration of (19) or (20) above, the base material may be a stainless steel separator. This configuration improves the reliability of adhesion between the separator and the sealing member. Also, stainless steel separators usually exhibit a silvery color due to their metallic luster. Therefore, when compared with the color of the separator, various colors such as black, red, blue, and green can be distinguished, and the range of dyes that can be used for coloring is broadened.

[0037] (22) In any of the configurations described in (19) to (21) above, the rubber composition may be configured to have one or more selected from ethylene-propylene rubber, ethylene-propylene-diene rubber, and ethylene-butene-diene rubber. This configuration makes it possible to realize a sealing member with excellent sealing properties, durability, and high-temperature characteristics.

[0038] (23) A method for manufacturing an adhesive member for a water electrolysis apparatus according to the present disclosure is a method for manufacturing an adhesive member for a water electrolysis apparatus having any of the configurations described in (19) to (22) above, comprising: a coating step of applying the adhesive composition for a water electrolysis apparatus to the substrate; a determination step of determining whether the coating state is good or bad based on the color of the applied adhesive composition; and, if the coating state is determined to be good, an adhesion step of arranging the uncrosslinked rubber composition on the coated surface of the substrate to form a laminate, heating and pressurizing the laminate to crosslink the rubber composition to form the sealing member, and bonding the sealing member to the substrate.

[0039] In the method for manufacturing adhesive members for water electrolysis devices according to the present disclosure, the quality of the coating is determined in the judgment step by the color of the applied adhesive composition. This makes it possible to avoid uneven coating, missed spots, etc. As a result, peeling of the sealing member and deterioration of sealing performance can be suppressed in the manufactured adhesive members for water electrolysis devices.

[0040] The adhesive composition of this disclosure is easily identifiable when applied to the surface of a substrate or sealing member. Therefore, it becomes easy to determine the quality of the application by visual inspection or a color inspection machine. As a result, uneven application and missed areas are less likely to occur, and peeling of the sealing member and deterioration of sealing performance can be suppressed. Furthermore, deterioration of adhesiveness can be suppressed, and both adhesiveness and identifiability can be achieved. The adhesive member of this disclosure has fewer adhesion defects and excellent sealing performance. In the manufacturing method of the adhesive member of this disclosure, the quality of the application is determined by the color of the applied adhesive composition in the judgment step. This makes it possible to avoid uneven application and missed areas of the adhesive composition.

[0041] This is a cross-sectional view showing one embodiment of an adhesive member for fuel cells in the present disclosure.

[0042] The following describes embodiments of the adhesive composition for fuel cells, adhesive composition for water electrolysis devices, adhesive member for fuel cells, adhesive member for water electrolysis devices, method for manufacturing the adhesive member for fuel cells, and method for manufacturing the adhesive member for water electrolysis devices of the present disclosure. In the embodiments, the adhesive composition for fuel cells and the adhesive composition for water electrolysis devices are collectively described as "adhesive composition." Similarly, the adhesive member for fuel cells and the adhesive member for water electrolysis devices are collectively described as "adhesive member," and the method for manufacturing the adhesive member for fuel cells and the method for manufacturing the adhesive member for water electrolysis devices are collectively described as "method for manufacturing the adhesive member." Note that the embodiments are not limited to the following forms and can be implemented in various modified and improved forms that can be carried out by those skilled in the art. Numerical ranges using "~" in this specification indicate a range that includes the numerical values ​​written before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described stepwise in this specification, the upper and lower limits described individually can be arbitrarily combined. In addition, the upper and lower limits of the numerical ranges can be replaced with the values ​​shown in the examples.

[0043] <Adhesive Composition>The adhesive composition of the present disclosure is applied to at least one of a fuel cell and a water electrolysis device. The adhesive composition of the present disclosure adheres one or more thin plate-like base materials selected from the constituent members of a fuel cell and a water electrolysis device and a seal member manufactured from a rubber composition. Examples of the fuel cell include a solid polymer fuel cell (PEFC) (including a direct methanol fuel cell (DMFC)). Examples of the water electrolysis device include an alkaline water electrolysis device, a proton exchange membrane (PEM) type water electrolysis device, and an anion exchange membrane (AEM) type water electrolysis device. The base material varies depending on the type, configuration, etc. of the fuel cell and the water electrolysis device. For example, in a solid polymer fuel cell and a PEM type water electrolysis device, a separator, a membrane electrode assembly (MEA) of an electrode member, a gas diffusion layer (GDL), etc. can be mentioned. The base material and the seal member will be described later.

[0044] The adhesive composition of the present disclosure has an adhesive liquid having an adhesive component (A) whose main component consists of a silane coupling agent or whose main component consists of a silane coupling agent and an organic titanate compound, and a solvent, and (B) a dye that is compatible with the adhesive component of the adhesive liquid and is soluble in the solvent.

[0045] (A) Adhesive Liquid [Adhesive Component] The main component of the adhesive component is a silane coupling agent or a silane coupling agent and an organic titanate compound. In this specification, the "main component" is a component that occupies 50% by mass or more when the entire adhesive component is 100% by mass. For example, the adhesive component may be in a form consisting only of a silane coupling agent (content ratio 100% by mass), may be in a form consisting only of a silane coupling agent and an organic titanate compound (total content ratio 100% by mass), or may be in a form containing a silane coupling agent, an organic titanate compound blended as necessary, and other components (content ratio less than 50% by mass).

[0046] The silane coupling agent can be appropriately selected from a group of compounds having one or more functional groups selected from amino groups, vinyl groups, and epoxy groups, taking into consideration adhesion and other factors. The silane coupling agent can be used alone or in a mixture of two or more. Alternatively, a copolymer oligomer obtained by copolymerizing two or more silane coupling agents may be used. The copolymer oligomer is preferably one having the hydrophilic functional group of (a) and the hydrophobic functional group of (b) below. (a) One or more selected from the group consisting of silanol groups, alkoxy groups, amino groups, isocyanate groups, epoxy groups, ureido groups, carboxyl groups, and hydroxyl groups, and containing at least a silanol group or an alkoxy group. (b) One or more selected from the group consisting of vinyl groups, (meth)acryloyl groups, maleimide groups, methyl groups, ethyl groups, styryl groups, phenyl groups, and mercapto groups.

[0047] By using specific functional groups shown in (a) and (b) for the hydrophilic and hydrophobic functional groups in the silane coupling agent, the adhesion, water resistance, and acid resistance of the adhesive layer can be improved. Of these, the hydrophobic functional group prevents water from penetrating the adhesive layer by imparting hydrophobicity, thereby contributing to improved water resistance and acid resistance. The hydrophilic functional group reacts with the substrate and components in the sealing material (such as carbon black) to contribute to adhesion. For example, a copolymer oligomer can be produced by oligomerizing a silane coupling agent having the functional group of (a) and a silane coupling agent having the functional group of (b). In this specification, (meth)acryloyl group means acryloyl group or methacryloyl group, and (meth)acrylate means acrylate or methacrylate.

[0048] Among the silane coupling agents having a hydrophilic functional group in (a), the silane coupling agents having a hydrophilic functional group other than a silanol group and an alkoxy group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 3-isocyanatopropyltriethoxysilane, 3-ureidopropyltrialkoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-carboxypropyltrimethoxysilane, 3-carboxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, and the like. Among these, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane are preferred.

[0049] Examples of silane coupling agents having the hydrophobic functional group of (b) include vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, N-(trimethoxysilylpropyl)maleimide, N-(triethoxysilylpropyl)maleimide, p-styryltrimethoxysilane, p-styryltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-mercaptopropylmethyltrimethoxysilane, 3-mercaptopropylmethyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxysilane. Among these, vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, N-(trimethoxysilylpropyl)maleimide, and N-(triethoxysilylpropyl)maleimide are preferred.

[0050] The oligomerization reaction begins by charging each silane coupling agent into a reactor equipped with a distillation apparatus and a stirrer, and stirring at approximately 60°C for about 1 hour. Next, approximately 0.5 to 2.0 moles of an acid such as formic acid are added within 1 hour to a total of 1 mole of the silane coupling agent having hydrophilic functional groups as shown in (a) and the silane coupling agent having hydrophobic functional groups as shown in (b). The temperature inside the reactor is maintained at approximately 65°C while the acid is being added. The mixture is stirred for a further 1 to 5 hours to allow the reaction to proceed, and at the same time, the alcohol produced by hydrolysis is distilled under reduced pressure. Distillation is stopped when only water remains in the distillate, and then the mixture is diluted to a silane concentration of 30 to 80% by mass. The copolymer oligomer obtained in this way is an oligomer soluble in alcoholic organic solvents such as methanol and ethanol. From the viewpoint of improving film-forming properties, water resistance, and acid resistance when applying adhesive compositions, copolymer oligomers of trimers or more are desirable.

[0051] Other adhesive components besides silane coupling agents include organic titanate compounds and aluminate coupling agents. When using one or more selected from organic titanate compounds and aluminate coupling agents, the total content ratio with the silane coupling agent should be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or even 100% by mass. Furthermore, phenolic resins, bismaleimide resins, vinyl resins, etc., may be added to improve the water resistance and acid resistance of the formed adhesive layer by increasing adhesion to the substrate and imparting hydrophobicity. When adding these resins, it is preferable that their content be 20% by mass or less when the total adhesive components are considered to be 100% by mass.

[0052] When an organic titanate compound is included, acid resistance, particularly acid resistance during high-temperature and long-term use, is improved. It is desirable to use one or more organic titanate compounds selected from titanium alkoxides, titanium chelates, and titanium acylates.

[0053] Examples of titanium alkoxides include tetramethyl titanate, tetraethyl titanate, tetran-propyl titanate, tetraisopropyl titanate, tetran-butyl titanate, tetraisobutyl titanate, tetra-t-butyl titanate, tetraoctyl titanate, tetrastearyl titanate, tetra(2-ethylhexyl) titanate, and tetramethyl titanate. Among these, tetraisopropyl titanate, tetran-butyl titanate, and tetrastearyl titanate are preferred.

[0054] Examples of titanium chelates include titanium acetylacetonate, titanium octylene glycolate, titanium tetraacetylacetonate, titanium ethylacetoacetate, and titanium triethanolaluminate. Among these, titanium acetylacetonate and titanium ethylacetoacetate are preferred.

[0055] Examples of titanium acylates include titanium isostearate, tri-n-butoxytitanium monostearate, di-i-propoxytitanium distearate, titanium stearate, di-i-propoxytitanium diisostearate, and (2-n-butoxycarbonylbenzoyloxy)tributoxytitanium. Among these, titanium stearate is preferred.

[0056] When an aluminate-based coupling agent is included, the strength of the coating film is improved. Examples of aluminate-based coupling agents include aluminum alkyl acetate diisopropylate, aluminum ethyl acetate diisopropylate, aluminum trisethyl acetate, aluminum isopropylate, aluminum diisopropylate monosecondary butyrate, aluminum secondary butyrate, aluminum ethylate, aluminum bisethyl acetate monoacetylacetonate, aluminum trisacetylacetonate, and aluminum monoisopropoxymonoleoxyethyl acetate. One of these can be used alone, or two or more can be used in combination. Among these, aluminum alkyl acetate diisopropylate, aluminum ethyl acetate diisopropylate, and aluminum trisethyl acetate are preferred.

[0057] [Solvent] The solvent is not particularly limited as long as it can dissolve the adhesive component. Examples include alcohol-based organic solvents such as methanol, ethanol, isopropanol, 2-ethoxyethanol (ethylene glycol monoethyl ether), and butoxyethanol (ethylene glycol monobutyl ether), and ketone-based organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. The concentration of the adhesive component in the adhesive solution can be appropriately determined considering the adhesive properties, for example, it is preferable to set it to 0.5% by mass or more and 25% by mass or less.

[0058] As the adhesive liquid containing the copolymer oligomer of the silane coupling agent and the solvent mentioned above, commercially available products such as "CHEMLOK® 5151" from Road Corporation, "MEGUM® 3290" from Dow Chemical Company, and "X-12-1048" and "KR-513" from Shin-Etsu Chemical Co., Ltd. may be used.

[0059] (B) Dye: The dye used is compatible with the adhesive components of the adhesive solution and is soluble in the solvent of the adhesive solution. One dye or a combination of two or more dyes may be used. Here, "compatible with adhesive components" means that when 1.5 g of dye is added to 100 mL of adhesive solution with an adhesive component concentration of 5% by mass and stirred for 5 minutes, the state is observed visually and there is no turbidity or precipitate.

[0060] The adhesive composition of this disclosure is colored with a dye to a color different from the color of the substrate or sealing member. When applying the adhesive composition to a substrate, it is sufficient to color it to a color different from the color of the substrate, and when applying it to a sealing member, it is sufficient to color it to a color different from the color of the sealing member. By making the color of the coating film different from the color of the object to be coated, rather than being colorless and transparent, it becomes easier to judge whether the coating is good or bad. The color of the dye is not limited, but a color that stands out against the color of the object to be coated is desirable. For example, when the substrate is a silver-colored separator, using a black or red-colored dye is preferable because the presence of the adhesive composition applied to the substrate can be easily identified.

[0061] From the viewpoint of making the color as dark as possible to improve visibility, the dye content should be 3 parts by mass or more, based on 100 parts by mass of the non-volatile content of the adhesive composition. 5 parts by mass or more, and even 10 parts by mass or more, are preferable. Furthermore, as a result of repeated studies by the inventors, it has been found that when the pH of the dye solution obtained by dissolving the dye in a solvent is close to neutral, the curability of the adhesive component improves, and the adhesion does not easily decrease. Therefore, if the adhesion does not easily decrease even when the dye content is increased, visibility can be further improved by increasing the dye content to more than 25 parts by mass. On the other hand, from the viewpoint of ensuring the desired adhesion, the dye content should be 45 parts by mass or less, based on 100 parts by mass of the non-volatile content of the adhesive composition. The dye content may also be 40 parts by mass or less, or 35 parts by mass or less, and if the adhesion tends to decrease when the dye content increases, it is preferable to set it to 25 parts by mass or less, and even more preferably 15 parts by mass or less. In this specification, "non-volatile content" means the mass of residual components after the solvent is removed from the adhesive composition. Furthermore, it is desirable that the presence of the adhesive composition can be identified even when the coating film is thin. For example, it is preferable that the coloring power of the dye is exerted and the presence of the adhesive composition can be identified even when the thickness of the coating film of the adhesive composition is 0.01 μm or more and 1 μm or less.

[0062] Suitable dyes that have high coloring power even in relatively small amounts include xanthene dyes and azine dyes. Among xanthene dyes, rhodamine is preferable. Examples of red dyes include rhodamine B (CI Basic Violet 10), CI Solvent RED 49, CI Basic RED 1:1, and CI Basic Red 1, while examples of black dyes include CI Solvent Black 7. "CI" stands for Color Index. The Color Index is a database of colorants compiled by organizations such as the British Dye and Color Society. <Adhesive Members> The adhesive member for fuel cells of this disclosure comprises a thin plate-shaped substrate, a sealing member manufactured from a rubber composition, and an adhesive layer for bonding the substrate and the sealing member, wherein the adhesive layer is formed from the adhesive composition for fuel cells of this disclosure. The adhesive member for water electrolysis equipment of this disclosure comprises a thin plate-shaped substrate, a sealing member manufactured from a rubber composition, and an adhesive layer for bonding the substrate and the sealing member, wherein the adhesive layer is formed from the adhesive composition for water electrolysis equipment of this disclosure.

[0063] First, as an example of the adhesive member of the present disclosure, an embodiment of the adhesive member for fuel cells of the present disclosure will be described. Figure 1 shows a cross-sectional view of the adhesive member for fuel cells of this embodiment. As shown in Figure 1, the adhesive member for fuel cells 1 comprises a separator 10, a sealing member 20, and an adhesive layer 30. The separator 10 is made of stainless steel and has a silvery rectangular plate shape. In the region of the separator 10 that overlaps with the electrode member (not shown) when a fuel cell is constructed, a total of six grooves 11 extending in the longitudinal direction are recessed. The grooves 11 become flow paths for refrigerant and the like. The sealing member 20 is arranged on the upper peripheral edge of the separator 10. The sealing member 20 has a frame shape when viewed from above. The sealing member 20 is made of a crosslinked rubber composition having ethylene-butene-diene rubber. The sealing member 20 has a lip portion 21 that protrudes upward. The top of the lip portion 21 has a curved shape. The sealing member 20 elastically contacts another separator that is stacked when the fuel cell is constructed. The adhesive layer 30 has a frame shape when viewed from above and is positioned between the separator 10 and the sealing member 20. The adhesive layer 30 is formed from the adhesive composition of this disclosure and has a reddish color. The adhesive layer 30 adheres the separator 10 and the sealing member.

[0064] The fuel cell adhesive member 1 is manufactured as follows. First, a rubber composition for forming the sealing member 20 is prepared. The prepared rubber composition is molded into a predetermined shape to produce an uncrosslinked rubber member. Next, the adhesive composition is applied to a predetermined position on the upper surface of the separator 10, and the application state is checked. Here, since the adhesive composition exhibits a reddish color, it is easily identifiable on the silver-colored upper surface of the separator 10. If the application state is good, the manufactured rubber member is laminated onto the upper surface of the coating film and crosslinked and bonded under predetermined conditions. In this way, the fuel cell adhesive member 1 is manufactured in which the separator 10 and the sealing member 20 are integrated via an adhesive layer 30. Next, the individual components constituting the fuel cell adhesive member and water electrolysis device adhesive member of this disclosure will be described.

[0065] [Substrate] As mentioned above, the substrates used in fuel cells and water electrolyzers vary depending on the type and configuration of the fuel cell and water electrolyzer. For example, in polymer electrolyte fuel cells and PEM-type water electrolyzers, examples include separators, membrane electrode assemblies of electrode members, and gas diffusion layers. Among these, examples of separator materials include stainless steel, titanium, copper, magnesium, aluminum, carbon, graphite, and conductive resins (thermoplastic resins or thermosetting resins containing carbon, graphite, polyacrylonitrile-based carbon fibers, etc.). From the viewpoint of acid resistance and cost, stainless steel (especially austenitic) and titanium (especially pure titanium) are desirable. Furthermore, a carbon thin film such as a diamond-like carbon film (DLC film) or graphite film may be formed on the surface of the main body made of these materials by treatment such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). In the area of ​​the separator to which the sealing member is bonded (the area to which the adhesive composition is applied), surface treatment such as forming irregularities may be applied to increase the wettability of the adhesive composition and improve adhesion. The separator's configuration is not limited, including the formed flow paths and manifold holes; its shape and thickness can be determined as appropriate. Considering power generation performance, the separator's thickness should ideally be between 0.1 mm and 0.5 mm.

[0066] [Sealing Members] Sealing members are manufactured by injection molding, press molding, etc., of a rubber composition. The rubber components constituting the rubber composition may be liquid rubber or solid rubber. Examples of rubber components include ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), ethylene-butene-diene rubber (EBT), silicone rubber, fluororubber, butyl rubber (IIR), ethylene-propylene rubber (EPM), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). In particular, it is desirable to use one or more selected from EPM, EPDM, and EBT because of their high water resistance and acid resistance at high temperatures. In addition to rubber components, the rubber composition may also contain crosslinking agents, crosslinking aids, plasticizers, reinforcing agents, anti-aging agents, processing aids, etc.

[0067] As a crosslinking agent, it is preferable to use organic peroxides because they do not contain volatile components such as sulfur. Among these, dialkyl peroxides, peroxyketals, peroxyesters, ketone peroxides, diacyl peroxides, and peroxydicarbonates are particularly suitable because they can be crosslinked at relatively low temperatures. Examples of crosslinking aids include maleimide compounds, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPT), bifunctional (meth)acrylates, and 1,2-polybutadiene. Examples of plasticizers include petroleum-based plasticizers such as process oil, lubricating oil, paraffin, liquid paraffin, and petrolatum; fatty oil-based plasticizers such as castor oil, linseed oil, rapeseed oil, and coconut oil; waxes such as tall oil, subsulfate, beeswax, carnauba wax, and lanolin; linoleic acid, palmitic acid, stearic acid, and lauric acid. Examples of reinforcing agents include carbon black and amorphous silica (white carbon). Anti-aging agents include phenols, amines, imidazoles, phosphoric acids, and waxes.

[0068] The sealing member may be arranged in a ring along the outer edge on the surface of the substrate, or it may be arranged to surround a predetermined area. The thickness of the sealing member is preferably 0.2 mm to 5 mm, and more preferably 0.5 mm to 3 mm.

[0069] [Adhesive Layer] The adhesive layer that adheres the substrate and the sealing member is formed from the adhesive composition of the present disclosure described above. From the viewpoint of achieving a thinner component and high dimensional accuracy, the thickness of the adhesive layer is preferably 0.01 μm or more and 1 μm or less. The color of the adhesive layer is not particularly limited as long as it differs from the color of the component (substrate or sealing member) to which the adhesive composition is applied.

[0070] <Method for Manufacturing Adhesive Members> The method for manufacturing adhesive members for fuel cells and one embodiment of the method for manufacturing adhesive members for water electrolysis devices both include a coating step, a determination step, and an adhesive step. Each step will be described in order below.

[0071] [Coating Process] In this process, the adhesive composition of the present disclosure is applied to the substrate. The adhesive composition may be prepared by first preparing a dye solution by dissolving the dye in a solvent, and then mixing this dye solution with the adhesive solution and stirring. Alternatively, the dye may be added to the adhesive solution and stirred. The adhesive composition may be applied by brushing, using coating machines such as dispensers, blade coaters, bar coaters, die coaters, comma coaters (registered trademark), and roll coaters, or by spraying or dipping, and then air-drying at room temperature, or heating if necessary. The adhesive composition may be applied in two or more layers, but a single layer application is preferable from the viewpoint of shortening the coating process time.

[0072] [Determination Process] In this process, the quality of the coating is determined by the color of the applied adhesive composition (coating film). The determination may be made visually, by a color inspection machine, or by both.

[0073] [Bonding Process] In this process, if the application of the adhesive composition is deemed satisfactory, an uncrosslinked rubber composition is placed on the adhesive composition surface of the substrate to form a laminate. This laminate is then heated and pressurized to crosslink the rubber composition to form a sealing member, and the sealing member is bonded to the substrate. In or before this process, a rubber composition for forming the sealing member is first prepared. The rubber composition can be prepared by kneading the rubber components and any additional components as needed using a roll, kneader, Banbury mixer, etc. The prepared rubber composition may be molded into a predetermined shape by injection molding, press molding, etc. (preparation of an uncrosslinked rubber member). This eliminates the need for complicated alignment, facilitates continuous processing, and improves productivity. Then, the rubber composition (rubber member) is laminated onto the coating film formed on the substrate, and heated and pressurized. Heating and pressurizing can be done using a press, bonding machine, etc. The heating temperature should be between 130°C and 200°C, taking into consideration the crosslinking temperature of the rubber components. The pressure applied during pressurization should be set appropriately, taking into consideration factors such as adhesion and preventing damage to the sealing material. The heating and pressurizing time (bonding time) should be approximately 3 to 30 minutes.

[0074] Although the above describes a method of crosslinking and bonding using an uncrosslinked rubber composition in the bonding process, the adhesive member of this disclosure may also be manufactured by first crosslinking the rubber composition to produce a sealing member, placing it on the coated surface of the adhesive composition on the substrate, and heating and pressurizing it as necessary.

[0075] Next, the present disclosure will be described in more detail with reference to examples. Various adhesive compositions were manufactured and their identifiability when applied to a substrate was evaluated. Furthermore, evaluation samples were prepared by bonding sealing members to a substrate using the manufactured adhesive compositions, and the adhesiveness and compression durability of the sealing members were evaluated.

[0076] <Identifiableness of Adhesive Compositions> [Adhesive Liquid (A1)] A copolymer oligomer was produced by copolymerizing two types of silane coupling agents. First, 100 parts by mass of vinyltrimethoxysilane, 68.4 parts by mass of 3-aminopropyltrimethoxysilane, and 33.1 parts by mass of water were charged into a reactor equipped with a distillation apparatus and a stirrer, and stirred at approximately 60°C for approximately 1 hour. Next, formic acid was added within 1 hour so that the amount added was 1.0 mole per 1 mole of the total mass of silane coupling agents. The temperature inside the reactor was maintained at approximately 65°C while the formic acid was being added. The mixture was stirred for a further 3 hours to allow the reaction to proceed, and at the same time, the alcohol produced by hydrolysis was distilled under reduced pressure. Distillation was stopped when only water remained in the distillate, and then the mixture was diluted to a silane concentration of 50% by mass to obtain the copolymer oligomer. The hydrophobic functional group in the copolymer oligomer is a vinyl group, and the hydrophilic functional groups are a silanol group, an alkoxy group, and an amino group. The prepared copolymer oligomer was diluted with a mixed solvent of methanol and ethanol (mass ratio 1:1) to obtain an adhesive solution (A1) with a copolymer oligomer (silane coupling agent) concentration of 5% by mass.

[0077] [Adhesive Solution (A2)] 12.5 parts by mass of tetraisopropyl titanate, an organic titanate compound, was mixed with 100 parts by mass of the copolymer oligomer (silane coupling agent) used in adhesive solution (A1) to prepare the adhesive component. This was diluted with a mixed solvent of ethanol and 2-ethoxyethanol (mass ratio 9:1) to obtain adhesive solution (A2) with an adhesive component concentration of 5% by mass.

[0078] [Adhesive Solution (A3)] 100 parts by mass of the copolymer oligomer (silane coupling agent) used in adhesive solution (A1) was mixed with 50 parts by mass of tetraisopropyl titanate, an organic titanate compound, to form the adhesive component. This was diluted with a mixed solvent of ethanol and 2-ethoxyethanol (mass ratio 9:1) to obtain adhesive solution (A3) with an adhesive component concentration of 5% by mass.

[0079] Furthermore, commercially available adhesives containing copolymer oligomer-type silane coupling agents were prepared as adhesive liquids (A4) to (A6).

[0080] [Adhesive liquid (A4)] CHEMLOK® 5151, manufactured by Road Corporation. The hydrophilic functional groups of the copolymer oligomer are silanol groups and alkoxy groups, and the hydrophobic functional group is vinyl group. The solvent (diluent) is ethanol.

[0081] [Adhesive liquid (A5)] "MEGUM® 3290" manufactured by Dow Chemical Company. The hydrophilic functional groups of the copolymer oligomer are silanol groups, alkoxy groups, and amino groups, and the hydrophobic functional group is vinyl group. The solvent is ethanol.

[0082] [Adhesive liquid (A6)] "KR-513" manufactured by Shin-Etsu Chemical Co., Ltd. The hydrophilic functional groups of the copolymer oligomer are silanol groups and alkoxy groups, and the hydrophobic functional groups are acryloyl groups and methyl groups. The solvent is ethanol.

[0083] [Colorants] Five types of dyes and one type of pigment were prepared as colorants. Details are as follows: (i) Dyes (B1) CI Solvent RED 49, red. (B2) CI Basic RED 1:1, red. (B3) CI Basic Red 1, red. (B4) CI Solvent Black 7, black. (B5) CI Acid Red 27, red. (ii) Pigment Carbon black: "Aqua-Black (registered trademark) 001" manufactured by Tokai Carbon Co., Ltd., black.

[0084] [Manufacturing of Adhesive Compositions] A colorant solution was prepared by adding a colorant to a solvent and stirring it. Various adhesive compositions were then manufactured by combining this colorant solution with an adhesive solution and stirring it. The solvent used to add the colorant was the same as the solvent used in the adhesive solution to be combined with it. The manufactured adhesive compositions were numbered from 1 to 15. Tables 1 and 2 show the components of the adhesive compositions (combinations of adhesive components and colorants in the adhesive solution, and their respective contents). In Tables 1 and 2, the units of the components are parts by mass when the non-volatile content of the adhesive composition is set to 100 parts by mass.

[0085] [Solubility of colorants in solvents] The colorants were added to the solvent of the adhesive solution used in the manufacture of the adhesive composition, stirred, and their solubility was observed visually. As a result, all the dyes used in adhesive compositions No. 1 to 17 dissolved (indicated by ○ in Tables 1 and 2), while the pigment used in adhesive composition No. 18 did not dissolve (indicated by × in Table 2).

[0086] [Compatibility of colorants with adhesive components] 1.5 g of colorant was added to 100 mL of adhesive solution with an adhesive component concentration of 5% by mass, which is used when manufacturing adhesive compositions, and the mixture was stirred for 5 minutes. The state was then visually observed. For adhesive solutions (A4) to (A6) using commercially available adhesives, the concentration of the adhesive component was adjusted to 5% by mass using a solvent as appropriate. Compatibility was evaluated as good if there was no turbidity or precipitate, and as poor if at least one of turbidity or precipitate was observed. As a result, the compatibility of the dyes used in adhesive compositions No. 1 to 16 was good (indicated by ○ in Tables 1 and 2), but the compatibility of the dye used in adhesive composition No. 17 and the pigment used in adhesive composition No. 18 was poor (indicated by × in Table 2).

[0087] [Evaluation of Identifiableness] The manufactured adhesive composition was spray-coated to the surface of a substrate to a predetermined thickness, air-dried at room temperature (20°C ± 5°C), and then the coating was visually observed. As substrates, a silver-colored stainless steel plate made of SUS304 and a silver-colored titanium plate made of pure titanium were used. Both substrates were rectangular plates with a width of 25 mm, a length of 60 mm, and a thickness of 1.5 mm. The adhesive composition was applied to a square area on the surface of the substrate with a width of 25 mm and a length of 25 mm. The types of substrates and the thickness of the coating (adhesive layer) are summarized in Tables 1 and 2 above. In Tables 1 and 2, stainless steel plates are indicated as "SUS" and titanium plates as "Ti".

[0088] As a result, for adhesive compositions No. 1-16 and 18, regardless of the thickness of the coating film, the color of the coating film differed from the color of the substrate, and the coating film could be identified on the substrate (indicated by ○ in Tables 1 and 2). However, in sample No. 16, the dye content exceeded 45 parts by mass. Therefore, although identification was achieved, the adhesiveness decreased, as will be described later. On the other hand, for adhesive composition No. 17, even with a coating film thickness of 0.2 μm, the color development was weak, and it was difficult to identify the coating film on the substrate (indicated by × in Table 2). This is thought to be due to poor compatibility of the dye with the adhesive component. In addition, for adhesive composition No. 18, which used a black pigment, the coating film could be identified on the substrate.

[0089] <Adhesion of the adhesive composition and compression durability of the sealing member> [Preparation of evaluation samples] First, a rubber composition for forming the sealing member was prepared as follows: 100 parts by mass of ethylene-butene-diene rubber (EBT-K-9330M, manufactured by Mitsui Chemicals, Inc.), 1.0 part by mass of a phenolic antioxidant (Nocrac® NS-5, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 50 parts by mass of carbon black (Seast® SO, manufactured by Tokai Carbon Co., Ltd.) as a reinforcing agent, and 15 parts by mass of poly-α-olefin (PAO601, manufactured by Nippon Steel Chemical & Material Co., Ltd.) as a plasticizer were kneaded at 120°C for 5 minutes using a Banbury mixer. The mixture was then cooled, and 6 parts by mass of the crosslinking agent 1,1-di(t-butylperoxy)cyclohexane ("Perhexa® C-80" manufactured by NOF Corporation) was added. The mixture was then kneaded at 50°C for 10 minutes using an open roll to prepare the rubber composition.

[0090] Next, a rubber composition was placed on the surface of the substrate used for the identification evaluation, overlapping the adhesive composition coating, to form a laminate. This laminate was then placed in a mold and heated and pressurized at 170°C for 10 minutes. In this way, an evaluation sample was produced in which a sealing member (2.0 mm thick), which is a crosslinked rubber composition, and the substrate were bonded together via the adhesive layer. Hereafter, the numbers of the evaluation samples correspond to the numbers of the adhesive compositions used.

[0091] [Evaluation of Adhesion] A peel test was performed on the evaluation samples to assess the adhesion between the substrate and the sealing member. In the peel test, a gripping portion was created by making an incision in the end of the sealing member that was not adhered to the substrate, and the gripping portion was pulled perpendicular to the substrate at a speed of 10 mm / second to peel off the sealing member. The condition of the peeled surface was then visually observed, and the adhesion was evaluated as good if material failure (cutting of the sealing member) occurred, and as poor if interface failure occurred.

[0092] Peel tests were performed on two types of samples: "initial" and "after acidic water immersion." The "initial" sample was left at room temperature after sample preparation, while the "after acidic water immersion" sample was prepared by immersing the prepared sample in a 90°C sulfuric acid solution (pH 3.0) for 368 hours, then removing it and leaving it at room temperature. The test results for the samples after acidic water immersion serve as an indicator of the quality of acid-resistant adhesion at high temperatures.

[0093] As a result, samples No. 1 to 15 showed good adhesion both initially and after immersion in acidic water (indicated by circles in Tables 1 and 2). In contrast, sample No. 16, which had a high dye content, showed poor initial adhesion (indicated by an X in Table 2). For sample No. 16, acid resistance was not evaluated due to the poor initial adhesion. Furthermore, for samples No. 17 and 18, the compatibility of the colorant with the adhesive component was poor, and the colorant precipitated in the adhesive composition, so the adhesive was not evaluated.

[0094] [Evaluation of Compression Durability] The durability of the sealing material was evaluated by performing a compression test on the evaluation sample. The compression test was performed as follows: First, the evaluation sample was placed in a press machine and fixed in a state where the sealing material was compressed by 40% in the thickness direction. In this state, the temperature was raised to 100°C and held for 10 minutes. After that, it was cooled to room temperature and the evaluation sample was removed from the press machine. The removed evaluation sample's sealing material was cut in the thickness direction and the cross-section was visually observed. If there were no cracks, the compression durability was evaluated as good; if there were cracks, the compression durability was evaluated as poor.

[0095] As a result, samples No. 1 to 16 all showed no cracks and demonstrated good compressive durability (indicated by circles in Tables 1 and 2 above). On the other hand, samples No. 17 and 18, which used a coloring agent with poor compatibility with the adhesive component, developed cracks and showed poor compressive durability (indicated by crosses in Table 2 above).

[0096] Based on the above, it was confirmed that adhesive compositions No. 1 to 15 can provide identifiable features while ensuring adhesion, and that the quality of the applied state can be easily determined.

[0097] 1: Adhesive member for fuel cell, 10: Separator, 11: Groove, 20: Sealing member, 21: Lip, 30: Adhesive layer.

Claims

1. A fuel cell adhesive composition for bonding a thin plate-shaped substrate, which is a component of a fuel cell, and a sealing member manufactured from a rubber composition, comprising: (A) an adhesive liquid having an adhesive component whose main component is a silane coupling agent, or whose main component is a silane coupling agent and an organic titanate compound, and a solvent; and (B) a dye that is compatible with the adhesive component and soluble in the solvent, wherein the content of the dye is greater than 25 parts by mass when the non-volatile content of the adhesive composition is 100 parts by mass, and is 45 parts by mass or less, and the adhesive composition is colored with the dye to a color different from the color of the substrate or the sealing member.

2. The fuel cell adhesive composition according to claim 1, which is applied to the substrate or the sealing member with a thickness of 0.01 μm or more and 1 μm or less.

3. The fuel cell adhesive composition according to claim 1 or claim 2, which is applied to the substrate.

4. The fuel cell adhesive composition according to claim 3, wherein the substrate is a separator.

5. The fuel cell adhesive composition according to claim 4, wherein the separator is silver-colored and the dye is black or red-colored.

6. The fuel cell adhesive composition according to any one of claims 1 to 5, wherein the dye is a xanthene dye or an azine dye.

7. A fuel cell adhesive member comprising a thin plate-shaped base material, a sealing member manufactured from a rubber composition, and an adhesive layer for bonding the base material and the sealing member, wherein the adhesive layer is formed from the fuel cell adhesive composition described in any one of claims 1 to 6.

8. The adhesive member for a fuel cell according to claim 7, wherein the thickness of the adhesive layer is 0.01 μm or more and 1 μm or less.

9. The adhesive member for a fuel cell according to claim 7 or claim 8, wherein the base material is a separator made of stainless steel.

10. The adhesive member for a fuel cell according to any one of claims 7 to 9, wherein the rubber composition comprises one or more selected from ethylene-propylene rubber, ethylene-propylene-diene rubber, and ethylene-butene-diene rubber.

11. A method for manufacturing an adhesive member for a fuel cell according to any one of claims 7 to 10, comprising: a coating step of applying the adhesive composition for a fuel cell to a substrate; a determination step of determining whether the coating is good or bad based on the color of the applied adhesive composition; and, if the coating is determined to be good, an adhesion step of arranging the uncrosslinked rubber composition on the coated surface of the substrate to form a laminate, heating and pressurizing the laminate to crosslink the rubber composition to form the sealing member, and adhering the sealing member to the substrate.

12. An adhesive composition for a water electrolysis apparatus, for bonding a thin plate-shaped substrate, which is a component of the water electrolysis apparatus, and a sealing member manufactured from a rubber composition, comprising: (A) an adhesive liquid having an adhesive component whose main component is a silane coupling agent, or whose main component is a silane coupling agent and an organic titanate compound, and a solvent; and (B) a dye that is compatible with the adhesive component and dissolves in the solvent, wherein the content of the dye is 3 parts by mass or more and 45 parts by mass or less when the non-volatile content of the adhesive composition is 100 parts by mass, and the adhesive composition is colored with the dye to a color different from the color of the substrate or the sealing member.

13. The adhesive composition for a water electrolysis apparatus according to claim 12, wherein the content of the dye is greater than 25 parts by mass when the nonvolatile content of the adhesive composition is 100 parts by mass.

14. The adhesive composition for a water electrolysis apparatus according to claim 12 or claim 13, which is applied to the substrate or the sealing member with a thickness of 0.01 μm or more and 1 μm or less.

15. The adhesive composition for a water electrolysis apparatus according to any one of claims 12 to 14, which is applied to the substrate.

16. The adhesive composition for a water electrolysis apparatus according to claim 15, wherein the substrate is a separator.

17. The adhesive composition for a water electrolysis apparatus according to claim 16, wherein the separator is silver-colored and the dye is black or red-colored.

18. The adhesive composition for a water electrolysis apparatus according to any one of claims 12 to 17, wherein the dye is a xanthene dye or an azine dye.

19. An adhesive member for a water electrolysis apparatus, comprising a thin plate-shaped base material, a sealing member manufactured from a rubber composition, and an adhesive layer for bonding the base material and the sealing member, wherein the adhesive layer is formed from the adhesive composition for a water electrolysis apparatus described in any one of claims 12 to 18.

20. The adhesive member for a water electrolysis apparatus according to claim 19, wherein the thickness of the adhesive layer is 0.01 μm or more and 1 μm or less.

21. The adhesive member for a water electrolysis apparatus according to claim 19 or 20, wherein the base material is a separator made of stainless steel.

22. The adhesive member for a water electrolysis apparatus according to any one of claims 19 to 21, wherein the rubber composition comprises one or more selected from ethylene-propylene rubber, ethylene-propylene-diene rubber, and ethylene-butene-diene rubber.

23. A method for manufacturing an adhesive member for a water electrolysis device according to any one of claims 19 to 22, comprising: a coating step of applying the adhesive composition for a water electrolysis device to a substrate; a determination step of determining whether the coating state is good or bad based on the color of the applied adhesive composition; and, if the coating state is determined to be good, an adhesion step of arranging the uncrosslinked rubber composition on the coated surface of the substrate to form a laminate, heating and pressurizing the laminate to crosslink the rubber composition to form the sealing member, and bonding the sealing member to the substrate.

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