Method for manufacturing a sealing laminate

Abstract

A method for producing a sealing laminate that exhibits good adhesion of a primer to a substrate made of stainless steel having a relatively high chromium content is provided. [Solution] A sealing laminate is manufactured by integrating a stainless steel substrate having a chromium content of 16% by mass or more with a sealing member via a primer layer. The manufacturing method of the sealing laminate includes a primer application step of applying a primer containing a coupling agent to the substrate, a pre-baking step of heat-treating the primer-coated substrate at a temperature of 170°C to 250°C, a rubber composition application step of applying an uncrosslinked rubber composition to form the sealing member on the primer-coated surface of the substrate, and a cross-linking and bonding step of cross-linking the rubber composition to form the sealing member and adhering it to the substrate.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a sealing laminate for use in a fuel cell, a water electrolysis device, or the like. [Background technology]

[0002] Fuel cells have a stack structure in which many cells are stacked. The cell stack is fastened by end plates arranged on both sides in the stacking direction. For example, a cell of a polymer electrolyte fuel cell has electrode members including a membrane electrode assembly (MEA) and separators arranged to sandwich the electrode members. Rubber seal members are arranged around the electrode members and between adjacent separators to ensure sealing and insulation against reactant gases such as hydrogen and air and refrigerants. Similarly to fuel cells, devices that produce hydrogen by electrolysis of water (water electrolysis devices) are also composed of a stack of cells each having electrode members, separators, and seal members.

[0003] In order to maintain high sealing performance in the operating environment of fuel cells and water electrolysis systems (hereinafter sometimes referred to as "fuel cells, etc."), it is effective to use an adhesive to integrate a sealing member and a mating member. For example, as a method for bonding a substrate such as a separator to a rubber sealing member, Patent Document 1 describes a method in which a primer (adhesive) containing a copolymer oligomer-type silane coupling agent is applied to the surface of the substrate, the primer is pre-baked at 100 to 160°C, and then an uncrosslinked rubber composition is crosslinked and bonded to the surface. Patent Document 2 describes a method in which an adhesive containing a copolymer oligomer-type silane coupling agent is applied to the surface of the substrate, and after drying at room temperature as necessary, an uncrosslinked rubber composition is crosslinked and bonded to the surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-80006 [Patent Document 2] International Publication No. 2022 / 208926 Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Documents 1 and 2, titanium is preferably used for substrates such as separators from the viewpoint of acid resistance. Titanium has a relatively high reactivity with silane coupling agents used as primers. Therefore, as described in Patent Document 1, it is believed that a laminate having the desired adhesive properties can be produced by applying a primer to the surface of the substrate and then heat treating (pre-baking) it at a relatively low temperature of 100 to 160°C.

[0006] However, when stainless steel is used as the substrate, conventional methods have had the problem of insufficient primer adhesion. That is, heat treatment within the aforementioned temperature range did not adequately bond the primer to the substrate. The reason for this is thought to be that stainless steel contains a certain amount of chromium, which exists in a stable oxide state and therefore has low reactivity with coupling agents. If the primer does not adhere well to the substrate, the adhesion of the sealing material laminated via the primer will also be reduced.

[0007] Incidentally, the examples of Patent Document 2 describe a laminate sample for evaluation, which was produced by applying a primer to a SUS304 substrate and then crosslinking and adhering an uncrosslinked rubber composition to the surface using a mold. In this case, the substrate and the rubber composition were compressed in a mold and held at 170°C for 15 minutes. This is thought to have enabled the two to be bonded together without prior heat treatment of the primer. However, for example, in a method in which a rubber composition is injection-molded onto the primer-coated surface of a substrate, if the adhesion of the primer to the substrate is weak, the primer may peel off due to the injection pressure. In this respect, high adhesion between the substrate and the primer is also required.

[0008] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a method for manufacturing a sealing laminate in which a primer layer has good adhesion to a substrate made of stainless steel having a relatively high chromium content. [Means for solving the problem]

[0009] (1) In order to solve the above-mentioned problems, the manufacturing method of the sealing laminate of the present disclosure is a manufacturing method of a sealing laminate in which a substrate made of stainless steel having a chromium content of 16% by mass or more and a sealing member are integrated via a primer layer, and is characterized by having the following steps: a primer application step of applying a primer having a coupling agent to the substrate; a pre-baking step of heat-treating the substrate to which the primer has been applied at a temperature of 170°C or more and 250°C or less; a rubber composition placement step of placing an uncrosslinked rubber composition to form the sealing member on the primer-coated surface of the substrate; and a cross-linking adhesion step of cross-linking the rubber composition to form the sealing member and adhering it to the substrate.

[0010] In the method for manufacturing a sealing laminate of the present disclosure, stainless steel having a chromium content of 16% by mass or more is used as the substrate material. After applying a primer containing a coupling agent to the substrate, the substrate is heat-treated at a temperature of 170°C or higher and 250°C or lower in a pre-baking process. By performing heat treatment at a higher temperature than conventional methods and increasing the amount of heat, bonding between the coupling agent and iron, which has relatively high reactivity in stainless steel, is enhanced. This improves adhesion between the substrate and the primer, even when the chromium content is relatively high. As a result, adhesion of the sealing member laminated to the substrate via the primer is also improved, resulting in a sealing laminate with excellent adhesion reliability. Furthermore, due to the high adhesion between the substrate and the primer, the primer is less likely to peel off in the subsequent rubber composition application process, even when an uncrosslinked rubber composition is injection-molded onto the primer-coated surface of the substrate.

[0011] (2) In the above-described configuration, the rubber composition disposing step may be performed by injection molding the rubber composition. This configuration eliminates the need for a step of molding an uncrosslinked rubber composition into a predetermined shape in advance, thereby improving productivity. As described above, the high adhesion between the substrate and the primer prevents the primer from peeling off due to injection pressure.

[0012] (3) In any of the above configurations, the substrate may be made of austenitic stainless steel. Austenitic stainless steel contains nickel in addition to chromium and has excellent corrosion resistance. This configuration is suitable for manufacturing components for fuel cells and the like.

[0013] (4) In any of the above configurations, the heat treatment time in the pre-baking step may be 0.5 minutes or more and 20 minutes or less. This configuration allows the substrate and the coupling agent to bond together. On the other hand, it also prevents excessive heating from deactivating the functional groups in the coupling agent that react with the rubber component.

[0014] (5) In any of the above configurations, the cross-linking and bonding step may be performed at a temperature of 210° C. or higher and 270° C. or lower. This configuration is suitable for progressing the cross-linking reaction of the rubber component and the reaction with the coupling agent within a practical time period.

[0015] (6) In any of the above configurations, the coupling agent may be a copolymer oligomer of a hydrophilic functional group-containing silane coupling agent and a hydrophobic functional group-containing silane coupling agent. The hydrophilic functional group of the silane coupling agent forms a hydrogen bond with hydroxyl groups present on the stainless steel surface as Fe-OH, Fe-COOH, etc., and then undergoes a dehydration condensation reaction to form a strong covalent bond. The hydrophobic functional group of the silane coupling agent reacts with the rubber component. This allows for strong adhesion between the substrate and the sealing member via the primer. Furthermore, with this configuration, the siloxane bond of the silane coupling agent is oligomerized, improving the strength and water resistance of the primer layer.

[0016] (7) In any of the above configurations, the rubber composition may contain one or more rubber components selected from ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), and ethylene-butene-diene rubber (EBT). These rubber components can be crosslinked with organic peroxides and are suitable for improving the water resistance and acid resistance of the sealing member at high temperatures.

[0017] (8) In any of the above configurations, the sealing laminate may be configured as a component of a fuel cell or a water electrolysis device. That is, the sealing laminate obtained by the manufacturing method of the present disclosure can be embodied as a component of at least one of a fuel cell and a water electrolysis device. This configuration can improve the adhesive reliability between a separator or the like as a substrate and the sealing member. For example, if peeling occurs in the sealing member, compression during construction of a fuel cell or the like can cause stress to concentrate at the peeling point, which can lead to cracks in the sealing member. This configuration can suppress peeling of the sealing member, thereby suppressing the occurrence of cracks. [Effects of the Invention]

[0018] According to the manufacturing method of the sealing laminate of the present disclosure, it is possible to improve the adhesion of the primer to a substrate made of stainless steel, which has a relatively high chromium content, and thereby improve the adhesion of the sealing member laminated via the primer. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the method for producing a sealing laminate of the present disclosure will be described. Note that the embodiments are not limited to the following embodiments, and can be implemented in various modified and improved forms that are within the skill of those in the art. In this specification, numerical ranges using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper and lower limit values ​​can be arbitrarily combined. Furthermore, the upper and lower limit values ​​of a numerical range can be replaced with values ​​shown in the examples.

[0020] The method for producing a sealing laminate of the present disclosure includes a primer application step, a pre-baking step, a rubber composition placement step, and a cross-linking step. Each step will be described below in order.

[0021] <Primer application process> This process involves applying a primer containing a coupling agent to the substrate. The substrate is stainless steel with a chromium content of 16% by mass or more. Examples of suitable stainless steel include austenitic, austenitic-ferritic, and ferritic stainless steels. For example, austenitic stainless steels (SUS300 series) containing nickel and offering excellent corrosion resistance are suitable for use in components such as fuel cells. Specific examples include SUS301, SUS304, SUS310S, and SUS316. Considering adhesion to the primer, it is desirable for the chromium content of the stainless steel to be 25% by mass or less.

[0022] The primer contains a coupling agent as an adhesive component. Examples of coupling agents include silane coupling agents, organic titanate compounds, aluminate coupling agents, and zirconate coupling agents. One selected from these may be used alone, or two or more may be mixed together. Furthermore, phenolic resins, bismaleimide resins, vinyl resins, etc. may be added to enhance adhesion to the substrate and impart hydrophobicity, thereby improving the water resistance and acid resistance of the primer layer formed.

[0023] The silane coupling agent may be appropriately selected from a group of compounds having one or more functional groups selected from amino, vinyl, and epoxy groups, taking into consideration adhesive properties, etc. Silane coupling agents can be used singly or in combination, or a copolymer oligomer in which two or more silane coupling agents are copolymerized can also be used. In the copolymer oligomer, the siloxane bond of the silane coupling agent is oligomerized, improving the strength and water resistance of the primer layer. Copolymer oligomers having the following hydrophilic functional group (a) and hydrophobic functional group (b) are preferred. (a) One or more selected from the group consisting of a silanol group, an alkoxy group, an amino group, an isocyanate group, an epoxy group, a ureido group, a carboxy group, and a hydroxy group, and contains at least a silanol group or an alkoxy group. (b) One or more members selected from the group consisting of a vinyl group, a (meth)acryloyl group, a maleimide group, a methyl group, an ethyl group, a styryl group, a phenyl group, and a mercapto group.

[0024] By using specific functional groups (a) and (b) as the hydrophilic and hydrophobic functional groups in the silane coupling agent, the adhesion, water resistance, and acid resistance of the primer layer can be improved. Of these, the hydrophobic functional group imparts hydrophobic properties, preventing water penetration into the primer layer and contributing to improved water resistance and acid resistance. The hydrophilic functional group reacts with the substrate or components in the sealing material (e.g., carbon black) to contribute to 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). In this specification, the term "(meth)acryloyl group" refers to an acryloyl group or a methacryloyl group, and the term "(meth)acrylate" refers to an acrylate or a methacrylate.

[0025] Among the (a) silane coupling agents having a hydrophilic functional group, examples of silane coupling agents having a hydrophilic functional group other than a silanol group or 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-isocyanatepropyltriethoxysilane, 3-ureidopropyltrialkoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-carboxypropyltrimethoxysilane, 3-carboxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, and 3-hydroxypropyltriethoxysilane. Among these, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane are preferred.

[0026] Examples of silane coupling agents having a hydrophobic functional group (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.

[0027] The oligomerization reaction begins by placing each silane coupling agent in a reactor equipped with a distillation apparatus and a stirrer and stirring at approximately 60°C for approximately 1 hour. Next, approximately 0.5 to 2.0 moles of an acid such as formic acid are added within 1 hour for each mole of the silane coupling agent with a hydrophilic functional group (shown in (a)) and the silane coupling agent with a hydrophobic functional group (shown in (b)). During the acid addition, the temperature inside the reactor is maintained at approximately 65°C. The reaction is continued for an additional 1 to 5 hours with stirring, while the alcohol produced by hydrolysis is distilled under reduced pressure. The distillation is terminated when only water remains in the distillate, and the distillate is then diluted to a silane concentration of 30 to 80% by mass. The resulting copolymerized oligomer is soluble in alcohol-based organic solvents such as methanol and ethanol. A copolymerized oligomer of trimer or higher is desirable for improving film-forming properties, water resistance, and acid resistance when applying a primer.

[0028] When an organic titanate compound is contained, acid resistance, particularly acid resistance during long-term use at high temperatures, is improved. The organic titanate compound is preferably one or more compounds selected from titanium alkoxides, titanium chelates, and titanium acylates.

[0029] Examples of titanium alkoxides include tetramethyl titanate, tetraethyl titanate, tetra-normal propyl titanate, tetraisopropyl titanate, tetra-normal butyl titanate, tetraisobutyl titanate, tetra-t-butyl titanate, tetraoctyl titanate, tetrastearyl titanate, tetra(2-ethylhexyl) titanate, tetramethyl titanate, etc. Among these, tetraisopropyl titanate, tetra-normal butyl titanate, and tetrastearyl titanate are preferred.

[0030] Examples of titanium chelates include titanium acetylacetonate, titanium octylene glycolate, titanium tetraacetylacetonate, titanium ethylacetoacetate, titanium triethanolaluminate, etc. Among these, titanium acetylacetonate and titanium ethylacetoacetate are preferred.

[0031] Examples of titanium acylate include titanium isostearate, tri-n-butoxytitanium monostearate, di-i-propoxytitanium distearate, titanium stearate, di-i-propoxytitanium diisostearate, (2-n-butoxycarbonylbenzoyloxy)tributoxytitanium, etc. Among these, titanium stearate is preferred.

[0032] The inclusion of an aluminate-based coupling agent improves coating film strength. Examples of aluminate-based coupling agents include aluminum alkylacetoacetate diisopropylate, aluminum ethylacetoacetate diisopropylate, aluminum trisethylacetoacetate, aluminum isopropylate, aluminum diisopropylate mono-secondary butylate, aluminum secondary butylate, aluminum ethylate, aluminum bisethylacetoacetate monoacetylacetonate, aluminum trisacetylacetonate, and aluminum monoisopropoxymonoroxyethylacetoacetate. These can be used alone or in combination. Among these, aluminum alkylacetoacetate diisopropylate, aluminum ethylacetoacetate diisopropylate, and aluminum trisethylacetoacetate are preferred.

[0033] When a zirconate-based coupling agent is contained, heat resistance is improved. Examples of zirconate-based coupling agents include normal propyl zirconate, normal butyl zirconate, zirconium tetraacetylacetonate, and zirconium monoacetylacetonate. Among them, normal propyl zirconate and normal butyl zirconate are preferred.

[0034] The primer can be used by adding a solvent to the coupling agent to dilute it to a predetermined concentration. The concentration of the coupling agent can be determined appropriately taking into account factors such as adhesion and the thickness of the primer layer to be formed. For example, it can be 0.1% by mass or more and 25% by mass or less, assuming that the total amount of the primer is 100% by mass. Examples of solvents 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 solvents can be used alone or in combination.

[0035] As a primer containing a copolymer oligomer of a silane coupling agent and a solvent, for example, commercially available products such as "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. may be used.

[0036] In addition to the coupling agent and solvent, the primer may contain other components such as dyes. For example, adding a dye to the primer to a color different from that of the substrate makes the primer easier to distinguish on the substrate surface, facilitating visual or color inspection with a color inspection device. As a result, uneven coating and missed areas are less likely to occur. Here, "color" refers primarily to the hue of the three elements of color, such as red, blue, green, and yellow. A dye that is compatible with the coupling agent and soluble in the solvent is desirable. "Compatible with the coupling agent" means that when 1.5 g of dye is added to 100 mL of primer containing 5% by weight of coupling agent and stirred for 5 minutes, the solution is visually observed to be free of turbidity and precipitate.

[0037] The primer may be applied by brush coating, or by a coating machine such as a dispenser, blade coater, bar coater, die coater, Comma Coater (registered trademark), or roll coater, or by a spray method, immersion method, etc. The primer may be applied in two or more layers, but a single layer is preferable from the viewpoint of shortening the application process time, etc.

[0038] <Pre-bake process> This process involves heat-treating the primer-coated substrate at a temperature of 170°C or higher and 250°C or lower. From the viewpoint of promoting the reaction between the substrate and the coupling agent, a heat treatment temperature of 180°C or higher is more preferable. Conversely, excessive heating may deactivate and reduce the functional groups in the coupling agent that react with the rubber component. To prevent this resulting decrease in adhesion to the sealing material, a heat treatment temperature of 240°C or lower, or even 210°C or lower, is preferable. The heat treatment time is preferably 0.5 minutes (30 seconds) or longer to promote the reaction between the substrate and the coupling agent. A heat treatment time of 2 minutes or longer, or 5 minutes or longer, is more preferable. On the other hand, from the viewpoint of preventing the deactivation of the functional groups in the coupling agent that react with the rubber component due to excessive heating, a heat treatment time of 20 minutes or shorter is preferable. Furthermore, considering productivity, a heat treatment time of 10 minutes or shorter is preferable.

[0039] <Rubber composition placement step> This step is a step of placing an uncrosslinked rubber composition for forming a seal member on the primer-coated surface of the substrate. The rubber composition may be prepared by kneading the rubber component and other components blended as needed using a roll, kneader, Banbury mixer, or the like. In this step, the rubber composition may be placed on the primer-coated surface of the substrate as is or in the form of a preform molded into a predetermined shape, or the rubber composition may be injection molded onto the primer-coated surface of the substrate.

[0040] The rubber component may be liquid or solid rubber. Examples of the rubber component include ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), ethylene-butene-diene rubber (EBT), silicone rubber, fluororubber, butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). Among these, it is preferable to use one or more selected from EPM, EPDM, and EBT because of their high water resistance and acid resistance at high temperatures.

[0041] Components other than the rubber component include crosslinking agents, crosslinking aids, softeners, reinforcing agents, antioxidants, and processing aids. Organic peroxides are preferably used as crosslinking agents because they do not contain volatile components such as sulfur, which may corrode metals. Among these, dialkyl peroxides, peroxyketals, peroxyesters, ketone peroxides, diacyl peroxides, and peroxydicarbonates, which can crosslink at relatively low temperatures, are preferred. Examples of crosslinking aids include maleimide compounds, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPT), bifunctional (meth)acrylates, and 1,2-polybutadiene. Softeners 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, safflower, beeswax, carnauba wax, and lanolin; linoleic acid, palmitic acid, stearic acid, and lauric acid. Reinforcing agents include carbon black and amorphous silica (white carbon). Antiaging agents include phenols, amines, imidazoles, phosphates, and waxes.

[0042] <Crosslinking adhesion process> This step involves crosslinking the rubber composition to form a sealing member and adhering it to a substrate. This step can be carried out by heating a laminate of the substrate, primer, and uncrosslinked rubber composition. Pressure may also be applied, if necessary. The heating temperature may be determined appropriately, taking into consideration the crosslinking temperature of the rubber component and the promotion of the reaction with the coupling agent. For example, the heating temperature may be 210°C or higher and 270°C or lower. The heating time may be approximately 1 to 10 minutes. This step produces a sealing laminate in which a stainless steel substrate having a chromium content of 16% by mass or higher and a sealing member are integrated via a primer layer. Furthermore, to improve the water resistance of the sealing member, a secondary crosslinking step in which the laminate is further heated may be added after this step. The heating temperature in the secondary crosslinking step may be approximately the same as that in this step (210 to 270°C).

[0043] The sealing laminate obtained by the manufacturing method of the present disclosure can be embodied as a component of at least one of a fuel cell and a water electrolysis device. Examples of fuel cells include polymer electrolyte fuel cells (PEFCs) (including direct methanol fuel cells (DMFCs)). Examples of water electrolysis devices include alkaline water electrolysis devices, proton exchange membrane (PEM) water electrolysis devices, and anion exchange membrane (AEM) water electrolysis devices. The substrate varies depending on the type and configuration of the fuel cell or water electrolysis device, and examples of substrates include separators in polymer electrolyte fuel cells and PEM water electrolysis devices. From the perspective of achieving thin and high dimensional accuracy in the components, the thickness of the primer layer disposed between the substrate and the sealing member is preferably 0.001 μm to 3 μm, and more preferably 0.01 μm to 1 μm. The thickness of the sealing member is preferably 0.2 mm to 5 mm, and even more preferably 0.5 mm to 3 mm. [Example]

[0044] Next, the present disclosure will be described more specifically with reference to examples. Laminate samples were produced by varying the temperature and time of the pre-baking step, and the sealing member was bonded to the substrate via a primer. The adhesiveness and adhesive durability after immersion in hot water were evaluated.

[0045] <Production of laminate samples> [Preparation of Rubber Composition] A rubber composition for forming a seal member was prepared as follows: First, 100 parts by mass of ethylene-propylene-diene rubber (Esprene® 505, manufactured by Sumitomo Chemical Co., Ltd.) as a rubber component, 45 parts by mass of carbon black (SPHERON® 5200, manufactured by Cabot Japan) as a reinforcing agent, and 20 parts by mass of a poly-α-olefin compound (SpectraSyn® 4, manufactured by ExxonMobil Corp.) as a softener were kneaded using a Banbury mixer at 120°C for 5 minutes. Next, the kneaded mixture was cooled, and 5 parts by mass of a peroxyketal crosslinking agent (1,1-di(t-butylperoxy)cyclohexane, "Perhexa (registered trademark) C-40" manufactured by NOF Corporation) and 0.8 parts by mass of a maleimide compound crosslinking aid ("Valnoc (registered trademark) PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added, and the mixture was kneaded using an open roll at 50°C for 10 minutes to prepare a rubber composition.

[0046] [Primer manufacturing] A copolymerized oligomer was produced as a coupling agent for a primer by copolymerizing two silane coupling agents. First, 100 parts by weight of vinyltrimethoxysilane, 68.4 parts by weight of 3-aminopropyltrimethoxysilane, and 33.1 parts by weight 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 at a rate of 1.0 mole per mole of silane coupling agent. During the addition of formic acid, the temperature inside the reactor was maintained at approximately 65°C. The reaction was stirred for an additional 3 hours, during which the alcohol produced by hydrolysis was distilled under reduced pressure. The distillation was terminated when only water remained in the distillate, and the distillate was then diluted to a silane concentration of 50% by weight to obtain a copolymerized oligomer. The hydrophobic functional group in the copolymerized oligomer was a vinyl group, and the hydrophilic functional groups were a silanol group, an alkoxy group, and an amino group. The produced copolymerized oligomer was diluted with a solvent in which methanol and ethanol were mixed at a mass ratio of 1:1 to produce a primer with a copolymerized oligomer (silane coupling agent) concentration of 5 mass %.

[0047] [Laminate sample manufacturing] (1) Examples 1 to 7 and Comparative Examples 1 to 4 First, the prepared primer was spray-coated onto the surface of a stainless steel plate (SUS304) substrate so that the thickness after application was 80 nm (primer application step). Next, this substrate was heat-treated by maintaining it at the predetermined temperatures shown in Tables 1 and 2 below for the predetermined time (pre-baking step). Subsequently, the prepared rubber composition was injection-molded onto the primer-coated surface of the substrate at 100°C (rubber composition placement step). Then, the laminate of the substrate and the rubber composition was maintained at 250°C for 2 minutes to crosslink the rubber composition to form a crosslinked rubber (sealing member) and adhere it to the substrate (cross-linking and adhesion step). In this way, laminate samples in which the substrate and sealing member were integrated via the primer layer were produced. The produced laminate samples were of eleven types, with different pre-baking temperatures and times. Of these, samples in which the pre-baking temperature was 170°C or higher and 250°C or lower were numbered Examples 1 to 7, and the other samples were numbered Comparative Examples 1 to 4. The stainless steel substrate used had dimensions of 25 mm wide, 60 mm long, and 2 mm thick, and the chromium content was 19%. The laminate sample produced had dimensions of 25 mm wide, 60 mm long, and 7 mm thick.

[0048] (2) Example 8 A laminate sample was produced in the same manner as in Example 2, except that the type of stainless steel plate used as the substrate was changed to SUS310S with a chromium content of 25%. The produced laminate sample was numbered Example 8.

[0049] Table 1 shows the temperature, time, etc. of the pre-baking process for the samples of Examples 1 to 8. Table 2 shows the temperature, time, etc. of the pre-baking process for the samples of Comparative Examples 1 to 4. Tables 1 and 2 also show the evaluation results described below. [Table 1] [Table 2]

[0050] <Evaluation of Adhesion> The laminate samples were subjected to a peel test in accordance with JIS K6256-2:2013 to evaluate the adhesion between the substrate and the sealing material. In the peel test, the sealing material was pulled at a 90° angle to the substrate at a speed of 10 mm / s to peel the sealing material. The peel test was performed on two types of samples: "initial" and "after hot water immersion." The "initial" sample was left at room temperature after production, while the "after hot water immersion" sample was immersed in hot water at 120°C for 840 hours, then removed and left at room temperature. The test results for the samples after hot water immersion serve as an indicator of water resistance at high temperatures. The peeled condition was then visually observed. If the sealing material was observed on the peeled surface, the adhesion was evaluated as good (indicated by a circle in Table 1). If the sealing material was not observed on the peeled surface, the adhesion was evaluated as poor (indicated by an x ​​in Table 2). As shown in Table 2, in the sample of Comparative Example 1, the temperature of the pre-baking step was as low as 160°C, so the substrate and the primer could not be sufficiently bonded. Therefore, when the rubber composition was injection-molded in the subsequent rubber composition placement step, part of the primer peeled off due to the injection pressure. As a result, although a laminate sample was produced, the adhesion of the sealing member was poor and it was not in a condition to perform a peel test. Therefore, the adhesion of the sample of Comparative Example 1 was not evaluated.

[0051] As shown in Table 1, the samples of Examples 1 to 7 had good adhesion both initially and after immersion in hot water. Furthermore, the sample of Example 8, which had a higher chromium content in the substrate than these samples, also had good adhesion. In contrast, as shown in Table 2, the sample of Comparative Example 2, which had a lower pre-baking temperature, had a longer heating time, which improved the adhesion of the primer compared to the sample of Comparative Example 1, and the primer did not peel off due to the injection pressure. However, the adhesion between the substrate and the primer was insufficient, and the adhesion of the produced laminate sample was poor. Furthermore, in the samples of Comparative Examples 3 and 4, which had a higher pre-baking temperature, it is believed that some of the vinyl groups in the primer were deactivated by the heat treatment. Therefore, the adhesion between the primer and the rubber was insufficient, resulting in poor adhesion. Since the initial adhesion of the samples of Comparative Examples 2 to 4 was poor, the adhesion of the samples after immersion in hot water was not evaluated. [Industrial Applicability]

[0052] The method for producing a sealing laminate of the present disclosure is suitable for producing components for fuel cells, water electrolysis devices, and the like.

Claims

1. A method for producing a sealing laminate in which a stainless steel substrate having a chromium content of 16% by mass or more and a sealing member are integrated via a primer layer, the method comprising: a primer application step of applying a primer having a coupling agent to the substrate; a pre-baking step of heat-treating the substrate coated with the primer at a temperature of 170°C or higher and 250°C or lower; a rubber composition disposing step of disposing an uncrosslinked rubber composition for forming the seal member on the primer-coated surface of the substrate; a crosslinking and adhering step of crosslinking the rubber composition to form the sealing member and adhering the sealing member to the substrate; A method for producing a sealing laminate, comprising:

2. The method for producing a sealing laminate according to claim 1 , wherein the rubber composition disposing step is carried out by injection molding the rubber composition.

3. The method for producing a sealing laminate according to claim 1, wherein the substrate is made of austenitic stainless steel.

4. The method for producing a sealing laminate according to claim 1, wherein the time for the heat treatment in the pre-baking step is 0.5 minutes or more and 20 minutes or less.

5. The method for producing a sealing laminate according to claim 1 , wherein the cross-linking step is carried out at a temperature of 210° C. or higher and 270° C. or lower.

6. The method for producing a sealing laminate according to claim 1 , wherein the coupling agent comprises a copolymer oligomer of a silane coupling agent containing a hydrophilic functional group and a silane coupling agent containing a hydrophobic functional group.

7. 2. The method for producing a sealing laminate according to claim 1, wherein the rubber composition contains one or more rubber components selected from ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), and ethylene-butene-diene rubber (EBT).

8. 2. The method for producing a sealing laminate according to claim 1, wherein the sealing laminate is a component of a fuel cell or a water electrolysis device.

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