Adhesive composition for fuel cell sealing member, member for fuel cell, and method for producing member for fuel cell

Abstract

Disclosed is an adhesive composition for a fuel cell sealing member, which is obtained by bonding a thin-plate-shaped base material (10), which is a constituent member of a fuel cell, and a sealing member (20) that is produced from a rubber composition, the adhesive composition comprises: (A) an adhesive liquid having a solvent and an adhesive component mainly composed of a silane coupling agent or mainly composed of a silane coupling agent and an organic titanate compound; and (B) a dye which is compatible with the adhesive component and is dissolved in the solvent. The content of the dye in the adhesive composition is 3 parts by mass or more and 25 parts by mass or less when the non-volatile component of the adhesive composition is 100 parts by mass, and the adhesive composition is colored in a color different from the color of the base material (10) or the sealing member (20) by means of the dye.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an adhesive composition for bonding a constituent member of a fuel cell and a sealing member, a fuel cell member manufactured using the adhesive composition, and a manufacturing method of a fuel cell member. BACKGROUND

[0002] A fuel cell has a stacked structure in which a plurality of cells are stacked. The stack of cells is fastened by end plates disposed on both sides in the stacking direction. For example, a cell of a solid polymer fuel cell has an electrode member including a membrane electrode assembly (MEA) and a separator disposed sandwiching the electrode member. Between the electrode member and the adjacent separator around the electrode member, a sealing member made of rubber is disposed in order to ensure sealing and insulation properties against a reaction gas and a refrigerant. In order to maintain high sealing properties in the working environment of the fuel cell, a method of integrating the sealing member and the object member using an adhesive is effective. For example, in Patent Literature 1, as a method of bonding a rubber gasket (sealing member) and a separator, a method in which a silane coupling agent-based primer is applied to the surface of the rubber gasket, the primer-applied surface is brought into close contact with the separator, and heating is performed in a state in which the rubber gasket is press-fitted and fixed is described. In Patent Literature 2, as an adhesive for bonding a sealing member and a separator, an adhesive in which a co-oligomer type silane coupling agent having a hydrophilic functional group and a hydrophobic functional group in a specific ratio is used as a main component is described. In Patent Literature 2, the adhesive in which the silane coupling agent is used as the main component is applied to the surface of the separator, and after drying, a rubber composition is stacked and cross-linked and bonded.

[0003] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent Application Publication No. 2017-183198; Patent Literature 2: International Publication No. 2022 / 208926; Patent Literature 3: Japanese Patent Application Publication No. 2018-59630. SUMMARY

[0004] PROBLEMS TO BE SOLVED BY THE INVENTION The adhesive in which the silane coupling agent is used as the main component is almost colorless and transparent, and the coating film formed on the surface of the coated object such as a separator is extremely thin. Therefore, it is difficult to know whether the adhesive is appropriately applied to the predetermined range only by visual inspection. If there are unevenly applied or non-applied portions, there is a risk that the sealing member will peel off or the sealing properties will decrease.

[0005] As a method for determining the coating state of the adhesive, a method of coloring the coating film by adding a colorant to the adhesive can be considered. However, since the colorant does not have adhesive properties, there is a risk that the adhesive properties may decrease depending on the amount added. Pigments are known as colorants, but since pigments are insoluble in solvents, they tend to precipitate, making it difficult to form a homogeneous coating film. In addition, since the non-adhesive pigment particles are dispersed in the formed adhesive layer, the sealing component is prone to peeling, or stress may concentrate near the pigment particles due to compressive forces in the lamination direction, potentially causing the sealing component to crack starting from the pigment particles.

[0006] Regarding this point, Patent Document 3 describes the use of dyes to color an adhesive for bonding a ring-shaped metal core material to an elastomer component. However, the adhesive described in Patent Document 3 is a general adhesive such as a phenolic resin-based or epoxy resin-based adhesive used in bearings of motor vehicles, wind turbines, etc., rather than an adhesive using a silane coupling agent. As for the dye, it is stated that water solubility and oil solubility are irrelevant. That is, in Patent Document 3, no silane coupling agent is envisioned as an adhesive component, and no research is conducted on the compatibility between the dye and the adhesive component.

[0007] For example, in adhesives, if the adhesive component has poor compatibility with the dye, the dye may precipitate or agglomerate, making it difficult to form a homogeneous coating. In this case, the sealing component may easily peel off or crack due to compressive forces in the lamination direction. Furthermore, in fuel cells, the constituent components are required to be thin and have high dimensional accuracy, resulting in an extremely thin adhesive layer sandwiched between the sealing component and the target component. Thus, the adhesive used to bond the constituent components and sealing components of the fuel cell must meet the unique requirements of the fuel cell, making it difficult to simultaneously possess both adhesiveness and identifiability.

[0008] This disclosure was made in view of the following situation, and the problem is to provide an adhesive composition for a fuel cell sealing component that can combine adhesiveness and identifiability, a fuel cell component manufactured using the adhesive composition, and a method for manufacturing the fuel cell component.

[0009] means for solving problems (1) In order to solve the above problems, the adhesive composition for fuel cell sealing components disclosed herein is an adhesive composition for fuel cell sealing components that bonds a thin plate-shaped substrate, which is a constituent component of a fuel cell, and a sealing component made of a rubber composition. The adhesive composition for fuel cell sealing components is characterized by having: (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 organotitanate 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 3 parts by mass or more and 25 parts by mass or less when the non-volatile component of the adhesive composition is 100 parts by mass, and the adhesive composition is colored by the dye to a color different from the color of the substrate or the sealing component.

[0010] The adhesive composition (hereinafter, sometimes simply referred to as "adhesive composition") for fuel cell sealing components disclosed herein is colored by dye. When the object to be coated is a substrate, the adhesive composition is colored to a color different from the substrate color; when the object to be coated is a sealing component, it is colored to a color different from the sealing component color. Therefore, the adhesive composition is easily identifiable on the surface of the object to be coated, and the quality of the coating can be easily determined by visual inspection, color inspection machines, etc. As a result, uneven coating and missed coating are less likely to occur, and peeling of the sealing component and reduction of sealing performance can be suppressed. In this disclosure, "color" primarily refers to hue among the three elements of color, specifically hues such as red, blue, green, and yellow.

[0011] In the adhesive composition disclosed herein, the dye is miscible with the adhesive component and dissolves in the solvent. Therefore, the dye is unlikely to precipitate or form agglomerates, resulting in a homogeneous coating film. Consequently, peeling of the sealing component and reduction in sealing performance can be suppressed. Furthermore, the dye content is 3 parts by mass or more and 25 parts by mass or less when the non-volatile component of the adhesive composition is 100 parts by mass. Since the coloring power is exerted by a relatively small amount of dye, the adhesive performance is not easily reduced even if the dye lacks adhesive properties. Thus, the adhesive composition according to this disclosure combines both adhesiveness and recognizability.

[0012] (2) In the configuration described in (1) above, it can also be configured as follows: the adhesive composition for the fuel cell sealing component is coated on the substrate or the sealing component with a thickness of 0.01 μm or more and 1 μm or less. This configuration is suitable for achieving thinner components and higher dimensional accuracy required for fuel cells.

[0013] (3) In any of the above configurations, the configuration may also be as follows: the fuel cell sealing member is coated with an adhesive composition onto the substrate. According to this configuration, since the soft rubber sealing member (which may also be an uncrosslinked rubber composition) is laminated onto the sheet-like substrate, positional displacement of the sealing member is suppressed, and dimensional accuracy and workability are improved.

[0014] (4) In the configuration described in (3) above, the substrate can also be a partition. According to this configuration, the bonding reliability between the partition and the sealing member can be improved.

[0015] (5) In the configuration described in (4) above, the configuration may also be as follows: the partition is silver-based, and the dye is black-based or red-based. According to this configuration, a black-based or red-based adhesive composition is coated onto the silver-based partition. Therefore, the presence of the adhesive composition is easily noticeable relative to the partition, and the quality of the coating state can be easily determined.

[0016] (6) In any of the above configurations, the dye may also be a xanthine dye or an azine dye. According to this configuration, it is easy to select a dye that is compatible with the adhesive component, soluble in a solvent, and further capable of coloring in a relatively small amount.

[0017] (7) The fuel cell component of the present disclosure is characterized by comprising: a thin plate-shaped substrate, a sealing member made of a rubber composition, and an adhesive layer for bonding the substrate to the sealing member, the adhesive layer being formed of the fuel cell sealing member adhesive composition constituted above (1).

[0018] According to the fuel cell component disclosed herein, the adhesive composition, whose state of application on the surface of the substrate or sealing component is easily identifiable during the manufacturing process, allows for easy judgment of the quality of the coating state through visual inspection, color inspection machines, or similar means. This reduces the likelihood of poor adhesion, resulting in a high-quality fuel cell component with excellent sealing performance.

[0019] (8) In the configuration described in (7) above, the adhesive layer may also be configured such that its thickness is 0.01 μm or more and 1 μm or less. This configuration is suitable for achieving the thinning of the components required for fuel cells and the realization of high dimensional accuracy.

[0020] (9) In the configuration of (7) or (8) above, it can also be configured as follows: the substrate is a stainless steel partition. According to this configuration, the adhesion reliability between the partition and the sealing member can be improved. In addition, stainless steel partitions usually have a silvery color due to their metallic luster. Therefore, when compared with the color of the partition, various colors such as black, red, blue, and green can be identified, and the selection range of dyes used for coloring is wide.

[0021] (10) In any of the configurations in (7) to (9) above, the rubber composition may also be configured such that it has one or more of the following: ethylene-propylene rubber, ethylene-propylene-diene rubber, and ethylene-butene-diene rubber. According to this configuration, a sealing component with excellent sealing performance, durability, and high-temperature properties can be achieved.

[0022] (11) The method for manufacturing a fuel cell component disclosed herein is a method for manufacturing a fuel cell component with the configuration described in (7) above, characterized in that the method for manufacturing a fuel cell component comprises: a coating step in which an adhesive composition for a fuel cell sealing component is coated onto a substrate; a judging step in which the quality of the coating state is judged by the color of the coated adhesive composition; and a bonding step in which, if the coating state is judged to be good, an uncrosslinked rubber composition is disposed on the coating surface of the adhesive composition on the substrate to form a laminate, the laminate is heated and pressurized to crosslink the rubber composition to form the sealing component, and the sealing component is bonded to the substrate.

[0023] According to the method for manufacturing fuel cell components disclosed herein, the quality of the coating state is determined based on the color of the applied adhesive composition during the judgment process. This avoids uneven coating, missed areas, and other defects. As a result, in the manufactured fuel cell components, issues such as peeling of sealing components and reduction in sealing performance can be suppressed.

[0024] Invention Effects According to the adhesive composition for fuel cell sealing components disclosed herein, the adhesive composition is easily identifiable when it is coated on the surface of a substrate or sealing component. Therefore, the quality of the coating state can be easily determined by visual inspection, color inspection machines, etc. As a result, uneven coating and missed coating are less likely to occur, and peeling of the sealing component and reduction of sealing performance can be suppressed. Furthermore, by using a relatively small amount of a specific dye, both adhesion and identifiability can be achieved. The fuel cell component of this disclosure exhibits fewer adhesion defects and excellent sealing performance. In the manufacturing method of the fuel cell component of this disclosure, the quality of the coating state is determined based on the color of the applied adhesive composition during the judgment step. This avoids uneven coating and missed coating of the adhesive composition. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view showing one embodiment of the fuel cell component of this disclosure. Detailed Implementation

[0026] Hereinafter, embodiments of the adhesive composition for fuel cell sealing components, fuel cell components, and methods for manufacturing fuel cell components disclosed herein will be described. Furthermore, the embodiments are not limited to the following manner and can be implemented through various modifications and improvements that can be made by those skilled in the art.

[0027] <Adhesive Composition for Fuel Cell Sealing Components> The adhesive composition disclosed herein bonds a sheet-like substrate, which serves as a component of a fuel cell, to a sealing member made of a rubber composition. Examples of fuel cells include solid polymer fuel cells (PEFCs) (including direct methanol fuel cells (DMFCs)). The substrate varies depending on the type and structure of the fuel cell; examples of solid polymer fuel cells include separators, membrane electrode assemblies (MEAs) of electrode components, and gas diffusion layers (GDLs). The substrate and sealing member will be described later.

[0028] The adhesive composition disclosed herein 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 organotitanate compound, and a solvent; and (B) a dye that is compatible with the adhesive component of the adhesive liquid and soluble in the solvent.

[0029] (A) Adhesive liquid [Adhesive components] The main components of the adhesive are silane coupling agents or silane coupling agents and organotitanate compounds. In this specification, "main component" refers to a component that accounts for 50% or more by mass when the adhesive as a whole is 100% by mass. For example, the adhesive may consist solely of a silane coupling agent (containing 100% by mass), may consist solely of a silane coupling agent and an organotitanate compound (both together accounting for 100% by mass), or may contain a silane coupling agent, and, if necessary, an organotitanate compound, and other components (containing less than 50% by mass).

[0030] The silane coupling agent can be appropriately selected from the group of compounds having one or more functional groups selected from amino, vinyl, and epoxy groups, taking into account properties such as adhesion. As a silane coupling agent, one can be used alone or in combination of two or more. Alternatively, a copolymer oligomer formed by copolymerizing two or more silane coupling agents can also be used. As a copolymer oligomer, a copolymer oligomer having a hydrophilic functional group (a) and a hydrophobic functional group (b) is preferred.

[0031] (a) It is selected from one or more of the group consisting of silanol, alkoxy, amino, isocyanate, epoxy, urea, carboxyl and hydroxyl, and contains at least silanol or alkoxy.

[0032] (b) Selected from one or more of the group consisting of vinyl, (meth)acryloyl, maleimide, methyl, ethyl, styryl, phenyl, and mercapto.

[0033] By making the hydrophilic and hydrophobic functional groups in the silane coupling agent the specific functional groups shown in (a) and (b), the adhesion, water resistance, and acid resistance of the adhesive layer can be improved. The hydrophobic functional groups, by imparting hydrophobicity, prevent water from penetrating the adhesive layer, thus contributing to improved water resistance and acid resistance. The hydrophilic functional groups react with components (such as carbon black) in the substrate and sealing components, thereby improving adhesion. For example, a copolymer oligomer can be produced by oligomerizing a silane coupling agent having the functional group (a) with a silane coupling agent having the functional group (b). Furthermore, in this specification, (meth)acryloyl group refers to acryloyl or methacryloyl, and (meth)acrylate refers to acrylate or methacrylate.

[0034] Among silane coupling agents having the hydrophilic functional group (a), examples of silane coupling agents having hydrophilic functional groups other than silanol and alkoxy groups include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-triethoxysilyl-N-(1,3-dimethyl- The silane composition includes butylene(2-ethylhexyl)-propylamine, 3-isocyanate-propyltriethoxysilane, 3-ureidopropyltrialkoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-carboxypropyltrimethoxysilane, 3-carboxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, and 3-hydroxypropyltriethoxysilane. Preferably, the silane composition includes 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-isocyanate-propyltriethoxysilane.

[0035] Examples of silane coupling agents having the hydrophobic functional group (b) include vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, N-(trimethoxysilylpropyl)maleimide, N-(triethoxysilylpropyl)maleimide, p-styryltrimethoxysilane, p-styryltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-mercaptopropylmethyltrimethoxysilane, 3-mercaptopropylmethyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, etc. Preferably, the following are vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, N-(trimethoxysilylpropyl)maleimide, and N-(triethoxysilylpropyl)maleimide.

[0036] The oligomerization reaction begins by placing 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, relative to a total of 1 mole of the silane coupling agent having the hydrophilic functional group shown in (a) and the silane coupling agent having the hydrophobic functional group shown in (b). During the acid addition, the temperature inside the reactor is maintained at approximately 65°C. The reaction is further stirred for 1 to 5 hours, while the alcohol generated by hydrolysis is distilled under reduced pressure. Distillation is stopped when only water remains in the distillate, and then diluted to achieve a silane concentration of 30 to 80% by mass. The resulting co-oligomer is an oligomer soluble in alcohol-based organic solvents such as methanol and ethanol. From the viewpoint of improving the film-forming properties, water resistance, and acid resistance of the coating adhesive composition, the co-oligomer is preferably a trimer or higher.

[0037] In the adhesive component, components other than silane coupling agents include organotitanate compounds and aluminate coupling agents. When using one or more selected from organotitanate compounds and aluminate coupling agents, the total content ratio with the silane coupling agent is preferably 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, and more preferably 100% by mass. Additionally, phenolic resins, bismaleimide resins, vinyl resins, etc., may be added to improve the adhesion to the substrate and impart hydrophobicity, thereby improving the water resistance and acid resistance of the formed adhesive layer. Furthermore, when these resins are added, it is preferable that the content is 20% by mass or less when the total adhesive component is 100% by mass.

[0038] When an organotitanate compound is included, acid-resistant adhesion, especially at high temperatures and during prolonged use, is improved. Preferably, one or more organotitanate compounds are selected from titanium alkoxides, titanium chelates, and titanium acylates.

[0039] Examples of titanium alkoxides include tetramethyl titanate, tetraethyl titanate, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisobutyl titanate, tetra-tert-butyl titanate, tetraoctyl titanate, tetrastearate, tetra(2-ethylhexyl) titanate, and tetramethyl titanate. Among these, tetraisopropyl titanate, tetra-n-butyl titanate, and tetrastearate are preferred.

[0040] Examples of titanium chelates include titanium acetylacetonate, titanium octanediol, titanium tetraacetylacetonate, titanium ethyl acetoacetate, and titanium triethanolate. Among these, titanium acetylacetonate and titanium ethyl acetoacetate are preferred.

[0041] Examples of titanium acylates include titanium isostearate, titanium tri-n-butoxy monostearate, titanium diisopropoxy distearate, titanium stearate, titanium diisopropoxy diisostearate, and (2-n-butoxycarbonylbenzoyloxy)tributoxy titanium. Among these, titanium stearate is preferred.

[0042] When an aluminate-based coupling agent is included, the coating strength is improved. Examples of aluminate-based coupling agents include, for instance, aluminum alkyl acetoacetate diisopropionate, aluminum ethyl acetoacetate diisopropionate, aluminum triacetoacetate, aluminum isopropoxide, aluminum diisopropoxide mono-sec-butoxide, aluminum sec-butoxide, aluminum ethoxide, aluminum bis(ethyl acetoacetate) monoacetoacetate, aluminum triacetylacetone, and aluminum monoisopropoxy monooleoyl ethyl acetoacetate. One of these agents can be used alone, or two or more can be mixed. Among these, aluminum alkyl acetoacetate diisopropionate, aluminum ethyl acetoacetate diisopropionate, and aluminum triacetoacetate are preferred.

[0043] [Solvent] There are no particular limitations on the solvent, 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), as well as 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 factors such as adhesive properties; for example, it is preferably 0.5% by mass or more and 25% by mass or less.

[0044] As adhesive liquids containing the aforementioned silane coupling agent, such as commercially available products like "CHEMLOK (registered trademark) 5151" manufactured by LORD Corporation, "MEGUM (registered trademark) 3290" manufactured by Dow Chemical Company, and "X-12-1048" and "KR-513" manufactured by Shin-Etsu Chemical Co., Ltd.

[0045] (B) Dyes As the dye, a dye that is compatible with the adhesive component of the adhesive solution and soluble in the solvent of the adhesive solution is used. Here, "compatible with the adhesive component" means that, upon visual observation, after adding 1.5 g of dye to 100 mL of adhesive solution with an adhesive component concentration of 5% by mass and stirring for 5 minutes, there is no turbidity or precipitation.

[0046] The adhesive composition disclosed herein is colored with a dye to a color different from the substrate or sealing member. When the adhesive composition is applied to a substrate, it is sufficient to use a color different from the substrate color; when applied to a sealing member, it is sufficient to use a color different from the sealing member color. By ensuring that the coating film is not colorless and transparent but a color different from the object being coated, the quality of the coating application is easily determined. The color of the dye is not limited, but a color that is conspicuous relative to the object being coated is preferred. For example, in the case of a silver-toned partition, using a black or red dye makes it easy to identify the presence of the adhesive composition applied to the substrate, which is therefore preferable.

[0047] From the viewpoint of maximizing color depth and improving recognizability, the dye content is 3 parts by mass or more when the non-volatile component of the adhesive composition is 100 parts by mass. Preferably, it is 5 parts by mass or more, and more preferably, it is 10 parts by mass or more. On the other hand, from the viewpoint of ensuring desired adhesion, the dye content is 25 parts by mass or less when the non-volatile component of the adhesive composition is 100 parts by mass. Preferably, it is 20 parts by mass or less, and more preferably, it is 15 parts by mass or less. In this invention, "non-volatile component" refers to the mass of the residual component after removing the solvent from the adhesive composition. Furthermore, it is preferable that the presence of the adhesive composition can be recognized even when the coating film is thin. For example, it is preferable that the dye's coloring power is exerted even when the thickness of the adhesive composition coating film is 0.01 μm or more and 1 μm or less, enabling the recognition of the presence of the adhesive composition.

[0048] Dyes with high tinting strength even in small quantities are preferably xaton-based or azine-based dyes. Among xaton-based dyes, rhodamine-based dyes are preferred. Examples of red dyes include Rhodamine B (CI Basic Violet 10), CI Solvent RED 49, and CI Basic RED 1:1; examples of black dyes include CI Solvent Black 7, etc. "CI" refers to the color index. The color index is a database of color materials constructed by the British Institute of Dyes and Coloring, etc.

[0049] <Components for fuel cells> The fuel cell component disclosed herein comprises a sheet-like substrate, a sealing member made of a rubber composition, and an adhesive layer for bonding the substrate to the sealing member, the adhesive layer being formed from the adhesive composition for the fuel cell sealing member disclosed herein.

[0050] First, one embodiment of the fuel cell component of this disclosure will be described. Figure 1 This is a cross-sectional view showing a component for a fuel cell according to this embodiment. (e.g.) Figure 1 As shown, the fuel cell component 1 includes a separator 10, a sealing member 20, and an adhesive layer 30. The separator 10 is made of stainless steel and is a rectangular thin plate in a silver color. In the area of ​​the separator 10 that overlaps with the electrode component (not shown) when constituting the fuel cell, a total of six grooves 11 extending along the length direction are recessed. The grooves 11 serve as flow paths for refrigerant, etc. The sealing member 20 is disposed on the periphery of the upper surface of the separator 10. The sealing member 20 appears frame-shaped 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 an upwardly protruding lip 21. The top of the lip 21 is curved. The sealing member 20 is in elastic contact with another separator stacked on top when constituting the fuel cell. The adhesive layer 30 appears frame-shaped when viewed from above and is disposed between the separator 10 and the sealing member 20. The adhesive layer 30 is formed of the adhesive composition disclosed herein and is red in color. The adhesive layer 30 bonds the partition 10 to the sealing member.

[0051] The fuel cell component 1 is manufactured as follows. First, a rubber composition for forming the sealing component 20 is prepared. The prepared rubber composition is shaped into a predetermined shape to produce an uncrosslinked rubber component. Next, an adhesive composition is applied to a predetermined position on the upper surface of the separator 10 to confirm the coating condition. Here, since the adhesive composition is reddish, it is easily identifiable on the silvery upper surface of the separator 10. Then, if the coating condition is good, the prepared rubber component is laminated onto the upper surface of the coating film and crosslinked and bonded under predetermined conditions. In this way, the fuel cell component 1, in which the separator 10 and the sealing component 20 are integrally formed via the adhesive layer 30, is manufactured. Next, the individual components constituting the fuel cell component of this disclosure will be described.

[0052] [Substrate] As mentioned earlier, the substrate used in fuel cells varies depending on the type and structure of the fuel cell. In solid polymer fuel cells, examples include separators, membrane electrode assemblies (MEAs) for electrode components, and gas diffusion layers. Materials used for separators include stainless steel, titanium, copper, magnesium, aluminum, carbon, graphite, and conductive resins (thermoplastic or thermosetting resins containing carbon, graphite, polyacrylonitrile-based carbon fibers, etc.). From the perspectives of acid resistance and cost, stainless steel (especially austenitic resins) and titanium (especially pure titanium) are preferred. Furthermore, carbon films such as diamond-like carbon (DLC) films and graphite films can be formed on the surface of the main body made of these materials through physical vapor deposition (PVD), chemical vapor deposition (CVD), or other treatments. In the areas of the separator where sealing components are bonded (areas where the adhesive composition is applied), surface treatments such as creating irregularities can be performed to improve adhesion by increasing the wettability of the adhesive composition. The structure of the separator, including the formed flow paths and manifold holes, is not limited; its shape and thickness can be appropriately determined. If power generation performance is taken into consideration, the thickness of the partition is preferably 0.1 mm or more and 0.5 mm or less.

[0053] [Sealing components] Sealing components are manufactured by injection molding, stamping, or other methods using rubber compositions. The rubber components constituting the rubber composition can be liquid 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). Among these, one or more selected from EPM, EPDM, and EBT are preferred due to their high water resistance and acid resistance at high temperatures. The rubber composition may also contain crosslinking agents, crosslinking aids, plasticizers, reinforcing agents, anti-aging agents, processing aids, etc., in addition to the rubber components.

[0054] As a crosslinking agent, organic peroxides are preferred because they do not contain volatile components such as sulfur. Among these, dialkyl peroxides, peroxyketals, peroxide esters, peroxide ketones, diacyl peroxides, and peroxydicarbonates, which can be crosslinked at relatively low temperatures, are preferred. Examples of crosslinking aids include maleimide compounds, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPT), difunctional (meth)acrylates, and 1,2-polybutadiene. Examples of plasticizers include petroleum-based plasticizers such as processing oils, lubricating oils, paraffin wax, liquid paraffin, and petroleum jelly; fatty oil-based plasticizers such as castor oil, linseed oil, rapeseed oil, and coconut oil; tall oil; base wax; beeswax; carnauba wax; lanolin and other waxes; linoleic acid; palmitic acid; stearic acid; and lauric acid. Examples of reinforcing agents include carbon black and amorphous silica (white carbon). As anti-aging agents, examples include phenolic, amine, imidazole, phosphate, and wax-based agents.

[0055] The sealing member can be arranged in a ring around the outer periphery on the surface of the substrate, or it can be arranged to surround a predetermined area. The thickness of the sealing member is preferably 0.2 mm or more and 5 mm or less, and more preferably 0.5 mm or more and 3 mm or less.

[0056] [Adhesive layer] The adhesive layer that bonds the substrate to the sealing member is formed from the aforementioned adhesive composition for fuel cell sealing members disclosed herein. From the viewpoint of achieving thinness and high dimensional accuracy of the constituent member, 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 member (substrate or sealing member) on which the adhesive composition is coated.

[0057] <Manufacturing Method of Components for Fuel Cells> One method for manufacturing components for fuel cells disclosed herein includes a coating process, a judgment process, and a bonding process. Each process will be described in turn below.

[0058] [Coating process] In this process, the adhesive composition for fuel cell sealing components disclosed herein is applied to a substrate. The adhesive composition is prepared by first preparing a dye solution in which the dye is dissolved in a solvent, and then stirring the dye solution together with the adhesive solution. Alternatively, the dye can be added to the adhesive solution and stirred. The adhesive composition can be applied by spraying, dipping, or other methods using coating machines such as dispensing machines, doctor blade coaters, bar coaters, die coaters, comma coaters (registered trademark), and roller coaters, and then dried naturally at room temperature or by heating as needed. Furthermore, the adhesive composition can be applied in multiple layers (two or more), but from the viewpoint of minimizing the coating process time, single-layer coating is preferred.

[0059] [Judgment Process] In this process, the quality of the coating is determined based on the color of the applied adhesive composition (film). This determination can be made visually, using a colorimeter, or a combination of both.

[0060] [Adhesion process] In this process, if the adhesive composition is deemed to be in good coating condition, an uncrosslinked rubber composition is deposited on the coated surface of the adhesive composition on the substrate to form a laminate. This laminate is then heated and pressurized to crosslink the rubber composition, forming a sealing member, which is then bonded to the substrate. Before or during this process, a rubber composition for forming the sealing member is first prepared. The rubber composition is prepared by mixing the rubber components and other required components using a roller, kneader, or Banbury mixer. The prepared rubber composition is preferably pre-formed into a predetermined shape (for the production of the uncrosslinked rubber member) using injection molding, stamping, or similar methods. This eliminates the need for cumbersome alignment, facilitates continuous processing, and improves productivity. Then, the coated laminated rubber composition (rubber member) formed on the substrate is heated and pressurized. Heating and pressurization can be performed using a stamping press, welding equipment, or similar methods. The heating temperature is set to 130°C or higher and 200°C or lower, taking into account the crosslinking temperature of the rubber components. The pressure applied during pressurization should be set appropriately, taking into account factors such as adhesion and the inhibition of damage to the sealing components. The heating and pressurization time (bonding time) should be set to approximately 3 to 30 minutes.

[0061] The above describes a method of crosslinking and bonding using an uncrosslinked rubber composition in the bonding process. However, the fuel cell component of this disclosure can also be manufactured by pre-crosslinking the rubber composition to pre-manufacture a sealing component, placing the sealing component on the coating surface of the adhesive composition of the substrate, and heating and pressurizing it as needed.

[0062] Example The present disclosure will now be described in more detail by way of examples. Various adhesive compositions were manufactured, and their identifiability when coated on a substrate was evaluated. In addition, evaluation samples were manufactured by bonding sealing members to a substrate using the manufactured adhesive compositions, and their adhesion and compression durability of the sealing members were evaluated.

[0063] <Identification of Adhesive Compositions> [Adhesive liquid (A1)] Copolymer oligomers were prepared by copolymerizing two 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 placed in a reactor equipped with a distillation apparatus and a stirrer, and stirred at approximately 60°C for about 1 hour. Next, formic acid was added within 1 hour relative to 1 mol of the total mass of the silane coupling agent, so that the added amount was 1.0 mol. During the addition of formic acid, the temperature inside the reactor was maintained at approximately 65°C. The reaction was further stirred for 3 hours, while the alcohol generated by hydrolysis was distilled under reduced pressure. Distillation was stopped when only water remained in the distillate, and then diluted to a silane concentration of 50% by mass to obtain the copolymer oligomer. The hydrophobic functional group in the copolymer oligomer is vinyl, and the hydrophilic functional groups are silanol, alkoxy, and amino groups. The prepared co-oligomer was diluted with a mixed solvent of methanol and ethanol (mass ratio 1:1) to obtain an adhesive solution (A1) with a concentration of 5% by mass of the co-oligomer (silane coupling agent) as the adhesive component.

[0064] [Adhesive liquid (A2)] A bonding component was formed by mixing 12.5 parts by mass of tetraisopropyl titanate, an organotitanate compound, with 100 parts by mass of the co-oligomer (silane coupling agent) used in the adhesive liquid (A1). This was then diluted with a mixed solvent of ethanol and 2-ethoxyethanol (mass ratio 9:1) to obtain an adhesive liquid (A2) with a bonding component concentration of 5% by mass.

[0065] [Adhesive liquid (A3)] An adhesive component was formed by mixing 50 parts by mass of tetraisopropyl titanate, an organotitanate compound, with 100 parts by mass of the co-oligomer (silane coupling agent) used in the adhesive liquid (A1). This was then diluted with a mixed solvent of ethanol and 2-ethoxyethanol (mass ratio 9:1) to obtain an adhesive liquid (A3) with a concentration of 5% by mass of the adhesive component.

[0066] Furthermore, commercially available adhesives containing silane coupling agents of the copolymer oligomer type were prepared as adhesive liquids (A4) to (A6).

[0067] [Adhesive liquid (A4)] "CHEMLOK (registered trademark) 5151" is manufactured by LORD Corporation. The hydrophilic functional groups of the copolymer are silanol and alkoxy groups, and the hydrophobic functional group is vinyl. The solvent (diluent) is ethanol.

[0068] [Adhesive liquid (A5)] MEGUM 3290 (registered trademark) is manufactured by Dow Chemical Company. The hydrophilic functional groups of the copolymer oligomer are silanol, alkoxy, and amino groups, while the hydrophobic functional group is vinyl. The solvent is ethanol.

[0069] [Adhesive liquid (A6)] "KR-513" is manufactured by Shin-Etsu Chemical Co., Ltd. The hydrophilic functional groups of the copolymer oligomer are silanol and alkoxy groups, and the hydrophobic functional groups are acryloyl and methyl groups. The solvent is ethanol.

[0070] [Coloring agent] Five dyes and one pigment were prepared as coloring agents. Details are as follows.

[0071] (i) dyes (B1) Rhodamine B (CI Basic Violet 10), red.

[0072] (B2) CI Solvent RED 49, red.

[0073] (B3) CI Basic RED 1:1, red.

[0074] (B4) CI Solvent Black 7, black.

[0075] (B5) CI Acid Red 27, red.

[0076] (ii) Pigments Carbon black: "Aqua-Black (registered trademark) 001" manufactured by Tokai Carbon Co., Ltd., black.

[0077] [Preparation of adhesive composition] A colorant liquid is prepared by pre-adding a colorant to a solvent and stirring. This colorant liquid is then stirred together with an adhesive liquid to produce various adhesive compositions. The solvent added to the colorant is the same solvent used in the combined adhesive liquid. The prepared adhesive compositions are numbered 1 to 15. Tables 1 and 2 show the components of the adhesive compositions (the combination of the adhesive components and colorant in the adhesive liquid, and their respective contents). In Tables 1 and 2, the units of components are parts by mass based on 100 parts by mass of the non-volatile components of the adhesive composition.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Solubility of colorant relative to solvent] The colorant was added to the solvent of the adhesive liquid used in the manufacture of the adhesive composition, stirred, and visually observed for dissolution. The results showed that the dyes used in adhesive compositions No. 1 to 14 dissolved completely (marked with ○ in Tables 1 and 2), while the pigment used in adhesive composition No. 15 did not dissolve (marked with × in Table 2).

[0081] [Compatibility of colorant with adhesive components] 1.5 g of colorant was added to 100 mL of an adhesive solution containing 5% by mass of the adhesive component, which was used in the manufacture of the adhesive composition, and the state was visually observed after stirring for 5 minutes. For adhesive solutions (A4) to (A6) using commercially available adhesives, the concentration of the adhesive component was adjusted to 5% by mass using appropriate solvents. The absence of turbidity and precipitation was evaluated as good compatibility, while the presence of at least one of turbidity or precipitation was evaluated as poor compatibility. As a result, the dyes used in adhesive compositions No. 1 to 13 showed good compatibility (marked with ○ in Tables 1 and 2), while the dye used in adhesive composition No. 14 and the pigment used in adhesive composition No. 15 showed poor compatibility (marked with × in Table 2).

[0082] [Evaluation of recognizability] The prepared adhesive composition was sprayed onto the surface of the substrate to a predetermined thickness and allowed to dry naturally at room temperature (20℃±5℃). The coating was then visually inspected. The substrates used were silver-toned SUS304 stainless steel and silver-toned pure titanium. Each substrate was a rectangular plate 25mm wide, 60mm long, and 1.5mm thick. The adhesive composition was applied to a square area 25mm wide and 25mm long on the surface of the substrate. The type of substrate and the thickness of the coating (adhesive layer) are detailed in Tables 1 and 2. In Tables 1 and 2, stainless steel is designated as "SUS" and titanium as "Ti".

[0083] As a result, for adhesive compositions No. 1 to 13 and 15, regardless of the coating thickness, the color of the coating differs from the color of the substrate, making the coating identifiable on the substrate (marked with ○ in Tables 1 and 2). However, in sample No. 13, the dye content exceeds 25 parts by mass. Therefore, although identifiability is achieved, adhesion is reduced, as will be described later. On the other hand, for adhesive composition No. 14, even with a coating thickness of 0.2 μm, the color is light, making it difficult to identify the coating on the substrate (marked with × in Table 2). This can be attributed to the poor compatibility of the dye with the adhesive component. Furthermore, for adhesive composition No. 15, which uses a black pigment, the coating is identifiable on the substrate.

[0084] <Adhesive properties of adhesive compositions and compression durability of sealing components> [Evaluation of sample manufacturing] First, a rubber composition for forming sealing components was prepared as follows. Using a Banbury internal mixer, 100 parts by weight of ethylene-butene-diene rubber (Mitsui Chemicals Co., Ltd.'s "EBT-K-9330M"), 1.0 part by weight of a phenolic anti-aging agent (Ouchi Shinsei Chemical Co., Ltd.'s "NOCRAC (registered trademark) NS-5"), 50 parts by weight of carbon black (Tokai Carbon Co., Ltd.'s "Seast (registered trademark) SO"), and 15 parts by weight of polyalphaolefin (Nippon Steel Chemical & Material Co., Ltd.'s "PAO601") were mixed at 120°C for 5 minutes. Then, these mixtures were cooled, and 6 parts by weight of a crosslinking agent, 1,1-di(tert-butylperoxy)cyclohexane (Nippon Oil Co., Ltd.'s "Perhexa (registered trademark) C-80"), were added, and the mixture was mixed using open rollers at 50°C for 10 minutes to prepare the rubber composition.

[0085] Next, a rubber composition was deposited on the surface of the substrate used in the identification evaluation to form a laminate, in which the adhesive composition coating was overlapped. This laminate was placed in a mold and heated and pressurized at 170°C for 10 minutes. In this way, an evaluation sample was manufactured, in which a sealing member (2.0 mm thick) serving as a crosslinked rubber composition was bonded to the substrate via an adhesive layer. Hereinafter, the numbers of the evaluation samples correspond to the numbers of the adhesive compositions used.

[0086] [Evaluation of Adhesion] Peel tests were conducted on the evaluation samples to assess the adhesion between the substrate and the sealing member. In the peel test, a notch was made at the end of the sealing member not bonded to the substrate to create a clamping portion. The clamping portion was pulled at a speed of 10 mm / s in a direction perpendicular to the substrate, causing the sealing member to peel off. The condition of the peeled surface was then visually observed. Material damage (cutting off the sealing member) was evaluated as good adhesion, while interface damage was evaluated as poor adhesion.

[0087] Peel tests were conducted on two types of samples: "initial" and "after acid water immersion." "Initial" samples were those left at room temperature after manufacturing, while "after acid water immersion" samples were those that had been immersed in a sulfuric acid aqueous solution (pH 3.0) at 90°C for 368 hours and then left at room temperature. The test results for the "after acid water immersion" samples served as an indicator of their acid resistance and adhesion at high temperatures.

[0088] As a result, samples No. 1 through 12 exhibited good adhesion both initially and after immersion in acidic water (marked with ○ in Table 1). In contrast, sample No. 13, with a higher dye content, showed poor initial adhesion (marked with × in Table 2). Due to the poor initial adhesion of sample No. 13, acid-resistant adhesion was not evaluated. Furthermore, for samples No. 14 and 15, the adhesive was not evaluated because the colorant had poor compatibility with the adhesive component, resulting in colorant precipitation in the adhesive composition.

[0089] [Evaluation of Compression Durability] Compression tests were conducted on the evaluation samples to assess the durability of the sealing components. The compression tests were performed as follows: First, the evaluation samples were placed in a press and fixed in a state where the sealing components were compressed by 40% along the thickness direction. The temperature was then raised to 100°C and maintained for 10 minutes. After cooling to room temperature, the evaluation samples were removed from the press. The sealing components of the removed evaluation samples were cut along the thickness direction, and the cross-section was visually observed. If no cracks were found, the compression durability was assessed as good; if cracks were found, the compression durability was assessed as poor.

[0090] As a result, samples No. 1 through 13 showed no cracks and exhibited good compression durability (marked with ○ in Tables 1 and 2). On the other hand, samples No. 14 and 15, which used colorants with poor compatibility with the adhesive components, developed cracks and exhibited poor compression durability (marked with × in Table 2).

[0091] From the above, the following can be confirmed: According to the adhesive compositions No.1 to 12, adhesion can be ensured and identification can be given, and the quality of the coating state can be easily judged.

[0092] Explanation of reference numerals in the attached figures: 1: Fuel cell component; 10: Separator; 11: Tank; 20: Sealing component; 21: Lip; 30: Adhesive layer.

Claims

1. An adhesive composition for a fuel cell sealing component, comprising bonding a sheet-like substrate, which is a component of a fuel cell, and a sealing component made of a rubber composition, wherein the adhesive composition for a fuel cell sealing component is characterized in that, The adhesive composition for the fuel cell sealing component has the following characteristics: (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 organotitanate compound, and a solvent; and (B) A dye that is compatible with the adhesive component and soluble in the solvent. The dye content is 3 parts by weight or more and 25 parts by weight when the non-volatile component of the adhesive composition is 100 parts by weight. The adhesive composition is colored by the dye to a color different from that of the substrate or the sealing member.

2. The adhesive composition for fuel cell sealing components according to claim 1, characterized in that, The adhesive composition for the fuel cell sealing component is applied to the substrate or the sealing component with a thickness of 0.01 μm or more and 1 μm or less.

3. The adhesive composition for fuel cell sealing components according to claim 1, characterized in that, The fuel cell sealing component is coated onto the substrate with an adhesive composition.

4. The adhesive composition for fuel cell sealing components according to claim 3, characterized in that, The substrate is a partition.

5. The adhesive composition for fuel cell sealing components according to claim 4, characterized in that, The partition is silver in color. The dye is either black or red.

6. The adhesive composition for fuel cell sealing components according to claim 1, characterized in that, The dye is a xanthan dye or an azine dye.

7. A component for a fuel cell, characterized in that, The fuel cell component comprises a thin plate-shaped substrate, a sealing member made of a rubber composition, and an adhesive layer for bonding the substrate to the sealing member. The adhesive layer is formed from the adhesive composition for fuel cell sealing components as described in claim 1.

8. The fuel cell component according to claim 7, characterized in that, The thickness of the adhesive layer is greater than 0.01 μm and less than 1 μm.

9. The fuel cell component according to claim 7, characterized in that, The substrate is a stainless steel partition.

10. The fuel cell component according to claim 7, characterized in that, The rubber composition has one or more selected from ethylene-propylene rubber, ethylene-propylene-diene rubber, and ethylene-butene-diene rubber.

11. A method for manufacturing a component for a fuel cell, comprising the method for manufacturing a component for a fuel cell as described in claim 7, characterized in that, The method for manufacturing the fuel cell component includes: In the coating process, the adhesive composition for the fuel cell sealing component is coated onto the substrate; The evaluation process involves determining the quality of the coating state based on the color of the applied adhesive composition. as well as In the bonding process, if the coating condition is determined to be good, an uncrosslinked rubber composition is applied to the coating surface of the adhesive composition on the substrate to form a laminate. The laminate is heated and pressurized to crosslink the rubber composition to form the sealing member, and the sealing member is bonded to the substrate.

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