Laminate for fuel cell

Abstract

The present invention provides a laminate for a fuel cell, excellent in acid-resistant adhesiveness even under a high-temperature and long-term condition.　Provided is a laminate that is obtained by bonding a separator 5 that serves as a base material and a lip 4b that serves as a sealing member, with an adhesive layer 6 therebetween. The lip 4b is formed of a rubber composition containing a component (A) described below. The adhesive layer 6 is formed of an adhesive containing a component (α) and a component (β) described below. (A) A rubber component that is composed of at least one of an ethylene-propylene-diene rubber and an ethylene-butene-diene rubber. (α) A copolymerized oligomer type silane coupling agent that has a specific hydrophilic functional group and a specific hydrophobic functional group at a specific ratio. (β) An organic titanate compound.

Description

Laminate for fuel cells

[0001] The present invention relates to a laminate for a fuel cell in which a substrate and a sealing member are bonded via an adhesive layer, and more particularly to a laminate for sealing a fuel cell in which a substrate for a fuel cell, such as a metal separator, and a rubber sealing member are bonded via an adhesive layer.

[0002] Fuel cells, which generate electricity through the electrochemical reaction of gases, have high power generation efficiency, emit clean gases, and have very little impact on the environment. Among them, solid polymer fuel cells can be operated at relatively low temperatures and have a high output density. For this reason, solid polymer fuel cells are expected to be used in a variety of applications, including power generation and automotive power sources.

[0003] In a polymer electrolyte fuel cell, a cell is a power generation unit, with a membrane electrode assembly (MEA) sandwiched between separators (made of metal or the like). The MEA consists of a polymer membrane (electrolyte membrane) that serves as an electrolyte and a pair of electrode catalyst layers (a fuel electrode (anode) catalyst layer and an oxygen electrode (cathode) catalyst layer) arranged on both sides of the electrolyte membrane in the thickness direction. A porous layer (gas diffusion layer) for diffusing gas is further arranged on the surfaces of the pair of electrode catalyst layers. A fuel gas such as hydrogen is supplied to the fuel electrode side, and an oxidant gas such as oxygen or air is supplied to the oxygen electrode side. Power generation occurs through an electrochemical reaction at the three-phase interface between the supplied gas, the electrolyte, and the electrode catalyst layer. A polymer electrolyte fuel cell is constructed by stacking multiple cells as described above, and fastening them together with end plates or the like arranged at both ends of the cell stacking direction.

[0004] The separators are formed with flow paths for gases supplied to each electrode and for coolant to reduce heat generation during power generation. Furthermore, since the electrolyte membrane is proton conductive when it contains water, it must be kept wet during operation. Therefore, to prevent gas mixing and leakage of gas and coolant, and to maintain a wet state inside the cell, it is important to ensure sealing around the MEA and porous layer and between adjacent separators. For this purpose, sealing members (gaskets) are required to seal the above-mentioned locations.

[0005] The sealing member is also exposed to water produced during power generation, which contains sulfonic acid and other substances eluted from the electrolyte membrane, so the adhesion of the sealing member to the separator must be acid-resistant.

[0006] The present applicant has already proposed a laminate for a fuel cell in which a separator and a sealing member are bonded via an adhesive layer made of a specific adhesive, with the aim of improving acid-resistant adhesion (Patent Document 1). This laminate for a fuel cell exhibits good acid-resistant adhesion by using an adhesive containing a silane coupling agent that is a copolymer oligomer type having specific hydrophilic functional groups and specific hydrophobic functional groups, and in which the molar ratio (Ma / Mb) of the amount of hydrophilic functional groups contained in one mole of the copolymer oligomer to the amount of hydrophobic functional groups contained in one mole of the copolymer oligomer is set within a specific range.

[0007] International Publication No. 2022 / 208926

[0008] The laminate for fuel cells in Patent Document 1 exhibits good acid-resistant adhesion. However, in recent years, there has been a trend toward higher power generation temperatures to improve power generation efficiency, and new technological developments are needed to improve the acid-resistant adhesion between the substrate and the sealing member so that good adhesion can be obtained even under more severe conditions.

[0009] The present invention has been made in view of the above circumstances, and provides a laminate for a fuel cell that exhibits excellent acid-resistant adhesion.

[0010] As a result of extensive research to solve the above problems, the inventors have discovered that by using an adhesive that combines a specific silane coupling agent and an organic titanate compound as an adhesive for bonding a substrate and a sealing member made of a specific rubber composition, it is possible to improve the acid-resistant adhesion between the substrate and the sealing member, and to demonstrate excellent acid-resistant adhesion even under high-temperature and long-term conditions.

[0011] That is, the gist of the present invention is the following [1] to [4]. [1] A laminate for a fuel cell, in which a substrate and a sealing member are bonded via an adhesive layer, the sealing member being made of a rubber composition containing the following component (A), and the adhesive layer being made of an adhesive containing the following components (α) and (β): (A) at least one of ethylene-propylene-diene rubber and ethylene-butene-diene rubber; (α) a copolymer oligomer-type silane coupling agent having a hydrophilic functional group and a hydrophobic functional group, the hydrophilic functional group being the following (a) and the hydrophobic functional group being the following (b), and the molar ratio (Ma / Mb) of the amount of substance Ma (mol) of the hydrophilic functional group to the amount of substance Mb (mol) of the hydrophobic functional group contained in 1 mole of the silane coupling agent molecule being 0.33 to 3.00: (a) at least one 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 containing at least a silanol group or an alkoxy group; (b) at least one 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; (β) an organic titanate compound; [2] The laminate for a fuel cell according to [1], wherein the component (β) in the adhesive is at least one of a titanium alkoxide and a titanium chelate; [3] The laminate for a fuel cell according to [1] or [2], wherein the blending amount of the component (β) in the adhesive is 0.5 to 200 parts by mass per 100 parts by mass of the component (α); [4] The laminate for a fuel cell according to any one of [1] to [3], wherein the substrate is a substrate made of austenitic stainless steel.

[0012] According to the present invention, it is possible to provide a laminate for a fuel cell that exhibits excellent acid-resistant adhesion, particularly under high-temperature and long-term conditions.

[0013] 1 is a cross-sectional view showing an example of a laminate for a fuel cell according to the present invention, and FIG. 2 is a cross-sectional view showing an example of a fuel cell seal body using the laminate for a fuel cell according to the present invention.

[0014] Next, an embodiment of the present invention will be described in detail. However, the present invention is not limited to this embodiment. In this specification, the term "(meth)acryloyl group" means an acryloyl group or a methacryloyl group, and the term "(meth)acrylate" means an acrylate or a methacrylate.

[0015] A laminate for a fuel cell according to one embodiment of the present invention (hereinafter sometimes referred to as "the present fuel cell laminate") is a laminate for a fuel cell comprising a substrate and a sealing member bonded via an adhesive layer, characterized in that the sealing member comprises a rubber composition (hereinafter sometimes referred to as "the present rubber composition") containing the following component (A), and the adhesive layer comprises an adhesive containing the following components (α) and (β): (A) at least one of an ethylene-propylene-diene rubber and an ethylene-butene-diene rubber; (α) a copolymer oligomer-type silane coupling agent having a hydrophilic functional group and a hydrophobic functional group, wherein the hydrophilic functional group is the following (a) and the hydrophobic functional group is the following (b), and the molar ratio (Ma / Mb) of the amount of substance Ma (mol) of the hydrophilic functional group to the amount of substance Mb (mol) of the hydrophobic functional group contained in 1 mole of the silane coupling agent molecule is 0.33 to 3.00: (a) at least one 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 containing at least a silanol group or an alkoxy group; (b) at least one 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; and (β) an organic titanate compound.

[0016] The fuel cell laminate of Patent Document 1, which is the prior art described above, exhibited good acid-resistant adhesion after, for example, immersion in a sulfuric acid aqueous solution (pH = 3.0) at 90°C for 168 hours or 336 hours, but in some cases, for example, under harsher conditions such as a higher temperature environment or a longer period of time, there is room for improvement in the acid-resistant adhesion. For example, the fuel cell laminate of Patent Document 1 has room for improvement in acid-resistant adhesion after immersion in a sulfuric acid aqueous solution (pH = 3.0) at 120°C for 336 hours, which is a harsher condition.

[0017] The present fuel cell laminate can maintain good acid-resistant adhesion even under severe conditions such as higher temperature environments and long periods of time. For example, the present fuel cell laminate exhibits good acid-resistant adhesion even after immersion in a sulfuric acid aqueous solution (pH = 3.0) at a high temperature of 120°C for a long period of 336 hours, thereby further improving adhesion reliability compared to conventional techniques.

[0018] Furthermore, the present fuel cell laminate surprisingly exhibits good acid-resistant adhesion even after immersion for an even longer period of, for example, 672 hours in a sulfuric acid aqueous solution (pH = 3.0) at 120°C, thereby dramatically improving adhesion reliability compared to conventional techniques. In particular, when a titanium alkoxide, for example, is used as the organic titanate compound (β) incorporated into the adhesive layer of the present fuel cell laminate, the adhesive layer exhibits good acid-resistant adhesion even after immersion for an even longer period of, for example, 840 hours in a sulfuric acid aqueous solution (pH = 3.0) at 120°C, making it particularly useful. The sealing member, adhesive layer, and substrate that constitute the present fuel cell laminate will now be described.

[0019] <Sealing Member> First, each material of the present rubber composition for forming the sealing member will be described.

[0020] <Rubber Component (A)> As the rubber component (A), at least one of ethylene-propylene-diene rubber (EPDM) and ethylene-butene-diene rubber (EBT) is used. From the viewpoint of further improving the acid-resistant adhesion of the sealing material, particularly the acid-resistant adhesion under high-temperature and long-term conditions, and from the viewpoint of sealability, it is preferable to use EBT as the rubber component (A).

[0021] The diene amount (mass proportion of the diene component) of EPDM and EBT is, for example, preferably in the range of 3 to 15 mass %, more preferably in the range of 3.5 to 14.5 mass %.

[0022] As the diene component of EPDM and EBT, for example, a diene monomer having 5 to 20 carbon atoms is preferable, and specific examples thereof include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB), 5-vinyl-2-norbornene (VNB), 5-butylidene-2-norbornene, 2-methallyl-5-norbornene, and 2-isopropenyl-5-norbornene.

[0023] The ethylene content (mass proportion of the ethylene component) of the EPDM is, for example, preferably in the range of 35 to 50 mass%, more preferably in the range of 40 to 50 mass%, and the propylene content (mass proportion of the propylene component) is, for example, preferably in the range of 42 to 55 mass%, more preferably in the range of 44 to 50 mass%.

[0024] The ethylene content (mass proportion of the ethylene component) of EBT is, for example, preferably in the range of 35 to 55 mass%, more preferably in the range of 40 to 53 mass%, and the butene content (mass proportion of the butene component) is, for example, preferably in the range of 35 to 55 mass%, more preferably in the range of 38 to 50 mass%.

[0025] The rubber component (A) is the main component of the rubber composition and typically accounts for 40% by mass or more of the entire rubber composition. The amount of the rubber component (A) is, for example, preferably in the range of 40 to 80% by mass, more preferably in the range of 45 to 75% by mass, of the entire rubber composition.

[0026] In addition to the rubber component (A), the rubber composition may contain various additives that are used in ordinary rubber compositions, such as a plasticizer, a filler, a crosslinking agent (organic peroxide or the like), a crosslinking aid, and an antioxidant.

[0027] <<Plasticizer>> Examples of plasticizers include petroleum-based plasticizers such as process oil, lubricating oil, paraffin, liquid paraffin, and vaseline, fatty oil-based plasticizers such as castor oil, linseed oil, rapeseed oil, and coconut oil, waxes such as tall oil, sab, beeswax, carnauba wax, and lanolin, linoleic acid, palmitic acid, stearic acid, and lauric acid. These may be used alone or in combination of two or more.

[0028] The blending amount of the plasticizer is usually 60 parts by mass or less, preferably 5 to 50 parts by mass, and more preferably 8 to 40 parts by mass, per 100 parts by mass of the rubber component (A). The blending amount of the plasticizer may be in the range of 10 to 30 parts by mass, or 10 to 25 parts by mass, per 100 parts by mass of the rubber component (A).

[0029] Among plasticizers, those with a pour point of -30°C or less are preferred, and those with a pour point of -40°C or less are more preferred. Examples of such plasticizers include poly-α-olefins, dioctyl phthalate (DOP), dioctyl adipate (DOA), dioctyl sebacate (DOS), and dibutyl sebacate (DBS). These may be used alone or in combination of two or more. Among these, poly-α-olefins are preferred from the viewpoints of good compatibility with the rubber component (A) and resistance to bleeding. Poly-α-olefins are obtained by polymerizing α-olefins having 6 to 16 carbon atoms. In poly-α-olefins, the smaller the molecular weight, the lower the viscosity and the lower the pour point.

[0030] As mentioned above, the lower the pour point of a plasticizer, the less likely it is to harden at extremely low temperatures. Therefore, the lower the pour point of a plasticizer, the greater the effect of suppressing crystallization of the rubber component at extremely low temperatures. On the other hand, if the pour point is too low, it is more likely to volatilize during operation of the fuel cell, etc. Therefore, it is desirable that the pour point of the plasticizer be -80°C or higher. The pour point can be measured in accordance with JIS K 2269 (1987).

[0031] The kinematic viscosity of the plasticizer at 40°C is preferably 8 to 500 mm 2 / s, more preferably in the range of 9 to 460 mm 2 / s range. That is, when a plasticizer exhibiting such a kinematic viscosity is used, it has good compatibility with rubber and low volatility, and therefore excellent compression set (low settling). The kinematic viscosity of the plasticizer is measured in accordance with JIS K 2283.

[0032] Filler: Examples of fillers include carbon black and silica. These may be used alone or in combination of two or more. The grade of the carbon black is not particularly limited, and examples include SAF grade, ISAF grade, HAF grade, MAF grade, FEF grade, GPF grade, SRF grade, FT grade, and MT grade.

[0033] From the viewpoint of adhesion to the adhesive layer, the filler is preferably a filler containing carbon black, but the filler may consist solely of carbon black. The amount of the filler is usually in the range of 10 to 150 parts by mass, preferably 20 to 100 parts by mass, per 100 parts by mass of the rubber component (A). The amount of the filler may be in the range of 25 to 80 parts by mass, or 30 to 70 parts by mass, per 100 parts by mass of the rubber component (A).

[0034] <Crosslinking Agent> The crosslinking agent is preferably an organic peroxide, and preferably one having a one-hour half-life temperature of 160°C or less. Examples of organic peroxides include dialkyl peroxides, peroxyketals, peroxyesters, ketone peroxides, diacyl peroxides, and peroxydicarbonates. These may be used alone or in combination of two or more. Among these, it is preferable to use at least one selected from the group consisting of dialkyl peroxides, peroxyketals, and peroxyesters having a one-hour half-life temperature of 100 to 160°C, and it is particularly preferable to use at least one selected from the group consisting of dialkyl peroxides, peroxyketals, and peroxyesters having a one-hour half-life temperature of 110 to 160°C, because this provides excellent scorch resistance and reactivity with adhesives to the rubber composition kneaded with the crosslinking agent.

[0035] Here, the "half-life" refers to the time it takes for the concentration of the organic peroxide to decrease to half of its initial value. Therefore, the "half-life temperature" is an index showing the decomposition temperature of the organic peroxide. The "one-hour half-life temperature" is the temperature at which the half-life is one hour. In other words, the lower the one-hour half-life temperature, the easier it is to decompose at a low temperature and the faster the reaction rate. If the one-hour half-life temperature is too low, scorching is more likely to occur and the organic peroxide will not react well with the adhesive.

[0036] Examples of dialkyl peroxides include di(2-t-butylperoxypropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3.

[0037] Examples of peroxyketals include n-butyl-4,4-di(t-butylperoxy)valerate, 2,2-di(t-butylperoxy)butane, 2,2-di(4,4-di(t-butylperoxy)cyclohexyl)propane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-di(t-butylperoxy)-2-methylcyclohexane.

[0038] Examples of peroxyesters include t-butyl peroxybenzoate, t-butyl peroxyacetate, t-propyl peroxyacetate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxy-2-ethylhexyl monocarbonate, t-butyl peroxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxymaleic acid, and t-hexylperoxyisopropyl monocarbonate.

[0039] Among these, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, n-butyl-4,4-di(t-butylperoxy)valerate, 2,2-di(t-butylperoxy)butane, t-butylperoxybenzoate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, di(2-t-butylperoxypropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-hexyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 are preferred because of their high reactivity with the rubber component (A). Particularly preferred are 1,1-di(t-butylperoxy)cyclohexane, n-butyl-4,4-di(t-butylperoxy)valerate, 1,1-di(t-hexylperoxy)cyclohexane, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, di(2-t-butylperoxypropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and t-butylcumyl peroxide.

[0040] The amount of crosslinking agent (in the case of a 100% pure base material) is preferably in the range of 0.4 to 12 parts by mass per 100 parts by mass of the rubber component (A). If the amount of crosslinking agent is too small, it tends to be difficult to sufficiently proceed with the crosslinking reaction, while if the amount of crosslinking agent is too large, the crosslink density tends to increase rapidly during the crosslinking reaction, resulting in a decrease in adhesive strength. When a base material of 100% purity is not used as the organic peroxide, it is blended so that the ratio calculated as the base material falls within the above range.

[0041] <<Crosslinking Auxiliary Agent>> Examples of crosslinking auxiliary agents include maleimide compounds, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPT), bifunctional (meth)acrylates, and 1,2-polybutadiene. These may be used alone or in combination of two or more. Among these, it is preferable to use maleimide compounds and TAIC because they have a significant effect of improving crosslink density and strength.

[0042] The amount of the crosslinking aid is preferably 5 parts by mass or less per 100 parts by mass of the rubber component (A). If the amount of the crosslinking aid is too large, the crosslink density increases rapidly during the crosslinking reaction, and the tensile elongation and adhesive strength tend to decrease.

[0043] <<Antiaging Agent>> Examples of antiaging agents include amine-based, phenol-based, imidazole-based, phosphate-based, and wax-based agents. These may be used alone or in combination of two or more. Specific examples include amine-based antiaging agents such as N-phenyl-1-naphthylamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, di(4-octylphenyl)amine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonylamido)diphenylamine, and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine; 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butylphenol, 2,4,6-tri-t-butylphenol; and styrenated phenol. and phenol-based antioxidants such as phenol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-methylenebis(2,6-t-butylphenol), 4,4'-isopropylidenebis(2,6-di-t-butylphenol), and 2,2'-isobutylidenebis(4,6-dimethylphenol); and imidazole-based antioxidants such as 2-mercaptobenzimidazole, 2-mercaptobenzimidazole zinc salt, and 2-mercaptomethylbenzimidazole.

[0044] The blending amount of the antioxidant is usually in the range of 0.1 to 10 parts by mass per 100 parts by mass of the rubber component (A). The blending amount of the antioxidant can be appropriately set within the above range, and may be, for example, 1 to 8 parts by mass, 2 to 6 parts by mass, etc.

[0045] Although the rubber composition may contain an adhesive component (such as a silane coupling agent), it is preferable that the rubber composition does not contain an adhesive component (such as a silane coupling agent) from the viewpoint of improving releasability when molding the seal member. Therefore, the amount of the adhesive component (such as a silane coupling agent) is preferably less than 0.1% by mass, preferably less than 0.01% by mass, and more preferably 0% by mass, of the total rubber composition.

[0046] <<Preparation of Rubber Composition>> The present rubber composition for forming the above-mentioned seal member is prepared by kneading the rubber component (A) and, as necessary, various additives such as a plasticizer, a filler, an organic peroxide (crosslinking agent), a crosslinking aid, an antioxidant, a processing aid, etc., using a roll, a kneader, a Banbury mixer, etc. As described below, the present rubber composition is molded, press-molded, etc. to form a seal member of a predetermined thickness.

[0047] <Adhesive Layer> Next, the adhesive layer made of the present rubber composition that bonds the sealing member and the substrate will be described. It is important to use an adhesive containing the following components (α) and (β) as the adhesive that forms the adhesive layer. With an adhesive containing only one of the following components (α) and (β), it tends to be difficult to improve the acid-resistant adhesion between the sealing member and the substrate under high-temperature and long-term conditions.

[0048] <Silane Coupling Agent (α)> The component (α) is a copolymer oligomer-type silane coupling agent having a hydrophilic functional group and a hydrophobic functional group, wherein the hydrophilic functional group is (a) and the hydrophobic functional group is (b), and the molar ratio (Ma / Mb) of the amount of hydrophilic functional group (moles) to the amount of hydrophobic functional group (moles) contained in one mole of the silane coupling agent is 0.33 to 3.00. (a) At least one 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) At least one 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.

[0049] As described above, the silane coupling agent shown in (α) has one or more hydrophilic functional groups shown in (a) (however, a silanol group or an alkoxy group is essential, and the others are optional), and one or more hydrophobic functional groups shown in (b). Among the hydrophilic functional groups shown in (a), from the viewpoint of reactivity with the substrate and the sealing material, silanol groups (hydroxy groups constituting a silanol structure), alkoxy groups, amino groups, and isocyanate groups are preferred, and silanol groups, alkoxy groups, and amino groups are more preferred. Furthermore, from the viewpoint of reactivity with the rubber components, crosslinking agents, and crosslinking aids in the sealing material, among the hydrophobic functional groups shown in (b), vinyl groups, (meth)acryloyl groups, and maleimide groups are preferred, and vinyl groups are more preferred.

[0050] Furthermore, in order to obtain acid-resistant adhesion, particularly under high-temperature and long-term conditions, the silane coupling agent (α) must have a molar ratio (Ma / Mb) of the amount of hydrophilic functional groups (Ma) to the amount of hydrophobic functional groups (Mb) contained in one mole of the molecule, of 0.33 to 3.00. From the same viewpoint, the molar ratio (Ma / Mb) is preferably in the range of 0.40 to 2.90, and more preferably in the range of 0.45 to 2.75. Alternatively, the molar ratio (Ma / Mb) may be in the range of 0.45 to 2.00.

[0051] Furthermore, the silane coupling agent shown in (α) is a copolymer oligomer type, that is, a copolymer oligomer, from the viewpoint of film-forming properties, etc. That is, the silane coupling agent shown in (α) can be obtained by subjecting a silane coupling agent having each functional group shown in (a) or (b) to an oligomerization reaction.

[0052] Among the silane coupling agents having a hydrophilic functional group shown in (a), examples of silane coupling agents having a hydrophilic functional group other than a silanol group and an alkoxy group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, 3-isocyanatepropyltriethoxysilane, 3-ureidopropyltrialkoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-carboxypropyltrimethoxysilane, 3-carboxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, and 3-hydroxypropyltriethoxysilane. These may be used alone or in combination of two or more. Among these, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane are preferred.

[0053] Examples of silane coupling agents having a hydrophobic functional group shown in (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, n-propyltriethoxysilane, etc. These may be used alone or in combination of two or more. Of these, vinyltrimethoxysilane, vinyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, N-(trimethoxysilylpropyl)maleimide, and N-(triethoxysilylpropyl)maleimide are preferred.

[0054] In the above oligomerization reaction, for example, 0.5 to 2.0 moles of a silane coupling agent having a hydrophilic functional group as shown in (a) but not having the hydrophobic functional group are used for every 1.0 mole of a silane coupling agent having a hydrophobic functional group as shown in (b). Furthermore, 0.2 to 5.0 moles of water for hydrolysis are used for every mole of the total amount of the silane coupling agent having a hydrophilic functional group as shown in (a) and the silane coupling agent having a hydrophobic functional group as shown in (b). It should be noted that among the silane coupling agents having a hydrophilic functional group as shown in (a), silane coupling agents having hydrophilic functional groups other than silanol groups and alkoxy groups do not necessarily need to be included. In the above oligomerization reaction, the above raw materials are charged into a reactor equipped with a distillation apparatus and a stirrer, and stirred at about 60°C for about 1 hour. Then, approximately 0.5 to 2.0 moles of an acid such as formic acid are added within 1 hour per mole of the combined total of the silane coupling agent having a hydrophilic functional group shown in (a) and the silane coupling agent having a hydrophobic functional group shown in (b). The temperature during this process is maintained at approximately 65°C. The mixture is stirred for an additional 1 to 5 hours to allow the reaction to proceed, while the alcohol produced by hydrolysis is distilled under reduced pressure. The distillation is terminated when only water remains, and the silane concentration is then adjusted to a range of 30 to 80% by mass by dilution to obtain a copolymeric oligomer (silane coupling agent (α)). This copolymeric oligomer is soluble in alcoholic organic solvents such as methanol and ethanol. It should be noted that the copolymeric oligomer is preferably a trimer or higher in order to enhance film-forming properties, water resistance, and acid resistance during adhesive application.

[0055] Furthermore, commercially available adhesives containing the copolymer oligomers can also be used as they are. Specific examples include CHEMLOK5151 manufactured by Lord Far East Co., Ltd. (the molar ratio (Ma / Mb) of the amount of hydrophilic functional groups to the amount of hydrophobic functional groups contained in 1 mole of the copolymer oligomer is 1.13), MEGUM3290 manufactured by The Dow Chemical Company (the molar ratio (Ma / Mb) of the amount of hydrophilic functional groups to the amount of hydrophobic functional groups contained in 1 mole of the copolymer oligomer is 2.70), and X-12-1048 manufactured by Shin-Etsu Chemical Co., Ltd. (the molar ratio (Ma / Mb) of the amount of hydrophilic functional groups to the amount of hydrophobic functional groups contained in 1 mole of the copolymer oligomer is 2.70). Examples of suitable copolymers include X-12-1050 manufactured by Shin-Etsu Chemical Co., Ltd. (a molar ratio of the amount of substance Ma (mol) of hydrophilic functional groups to the amount of substance Mb (mol) of hydrophilic functional groups contained in 1 mole of the copolymer oligomer (Ma / Mb): 3.00), X-12-1050 manufactured by Shin-Etsu Chemical Co., Ltd. (a molar ratio of the amount of substance Ma (mol) of hydrophilic functional groups to the amount of substance Mb (mol) of hydrophobic functional groups contained in 1 mole of the copolymer oligomer (Ma / Mb): 1.67), and KR-513 manufactured by Shin-Etsu Chemical Co., Ltd. (a molar ratio of the amount of substance Ma (mol) of hydrophilic functional groups to the amount of substance Mb (mol) of hydrophobic functional groups contained in 1 mole of the copolymer oligomer (Ma / Mb): 0.49).

[0056] <Organic Titanate Compound (β)> Component (β) is a component that constitutes the adhesive together with component (α) and is used to improve acid-resistant adhesion, particularly acid-resistant adhesion between a substrate and a sealing member under high-temperature and long-term conditions. As the organic titanate compound (β), it is preferable to use at least one selected from the group consisting of titanium alkoxide, titanium chelate, and titanium acylate.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] Among these organic titanate compounds (β), titanium alkoxides and titanium chelates are preferred, and titanium alkoxides are more preferred, from the viewpoint of further improving acid-resistant adhesion, particularly acid-resistant adhesion between a substrate and a sealing member under high-temperature and long-term conditions.

[0061] Among titanium alkoxides, from the viewpoint of solubility and hydrolysis, R 1 The titanium alkoxides in which the alkyl group represented by the formula: Ti(OR 1 )4...(1) [In formula (1), R 1 each independently represents the same or different alkyl group.

[0062] R in (1) above 1 Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, a stearyl group, and an isostearyl group.

[0063] From the viewpoint of acid-resistant adhesion, particularly acid-resistant adhesion under high-temperature and long-term conditions, the blending amount of component (β) is preferably 0.5 parts by mass or more per 100 parts by mass of component (α), more preferably 1 to 200 parts by mass, even more preferably 3 to 200 parts by mass, and particularly preferably 5 to 200 parts by mass. If the blending amount of component (β) is outside the above range, acid-resistant adhesion under high-temperature and long-term conditions tends to be insufficient. The blending amount of component (β) can be set appropriately within the above range, and may be, for example, in the range of 10 to 150 parts by mass, 30 to 120 parts by mass, or 35 to 70 parts by mass per 100 parts by mass of component (α).

[0064] In addition to the (α) and (β) components, the adhesive forming the adhesive layer may contain phenolic resins, bismaleimide resins, vinyl resins, etc., to enhance adhesion to the substrate and ensure hydrophobicity, thereby preventing water penetration into the adhesive layer and improving water resistance and acid resistance. However, it is preferable that the adhesive contains the (α) and (β) components as its main components. The term "main component" refers to the main component of the adhesive, and means that the total amount of the (α) and (β) components is 50% by mass or more of the adhesive (excluding the solvent). The total amount of the (α) and (β) components can be adjusted appropriately within the above range, and may be, for example, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or even 100% by mass of the adhesive (excluding the solvent).

[0065] The adhesive that forms the adhesive layer is usually used as a solution diluted with an organic solvent so that the total amount of the silane coupling agent shown in (α) and the organic titanate compound shown in (β) is about 0.5 to 25% by mass. Examples of the organic solvent include alcohol-based organic solvents such as methanol, ethanol, butoxyethanol, isopropanol, and 2-ethoxyethanol (ethylene glycol monoethyl ether), ketone-based organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and acetylacetone, and hydrocarbon solvents such as xylene and toluene.

[0066] <Substrate> Next, the substrate will be described. Examples of the material of the substrate include stainless steel, titanium, copper, magnesium, aluminum, carbon, graphite, and conductive resin (thermoplastic resin or thermosetting resin mixed with graphite, polyacrylonitrile-based carbon fiber, etc.). Among these, from the viewpoint of acid resistance, substrates made of stainless steel, titanium (pure titanium or titanium alloy), and conductive resin are preferred. Furthermore, from the viewpoint of providing a fuel cell laminate with excellent acid-resistant adhesion, it is preferable to use a substrate made of austenitic stainless steel. Specific examples of austenitic stainless steel include SUS304, SUS301, and SUS316L.

[0067] From the viewpoint of acid resistance, it is effective to use a substrate made of stainless steel, particularly a substrate made of austenitic stainless steel, as the substrate, but there is a problem in that such substrates are difficult to adhere to. Therefore, for example, when only a silane coupling agent (α) is used as the adhesive, there is room for improvement in acid-resistant adhesion under high-temperature and long-term conditions, but when an organic titanate compound (β) is further blended as a constituent component of the adhesive as in the present invention, it can be said to be excellent in that it can satisfy acid-resistant adhesion even when a substrate made of stainless steel, particularly austenitic stainless steel, is used as the substrate.

[0068] Furthermore, from the viewpoint of electrical conduction reliability, the surface of the substrate made of the above-mentioned material may have a carbon thin film such as a DLC film (diamond-like carbon film) or a graphite film formed by a process such as a PVD method (physical vapor deposition), a CVD method (chemical vapor deposition), etc. The thickness of the carbon thin film is preferably 10 to 500 nm.

[0069] <Laminate Manufacturing Method> Next, a method for manufacturing the present fuel cell laminate will be described. First, the present rubber composition for forming a sealing member is prepared as described above. The present rubber composition is molded, press-molded, or the like to produce a flat rubber member of a predetermined thickness. The flat rubber member may be crosslinked or uncrosslinked, but uncrosslinked is preferred from the viewpoint of improving adhesion. An adhesive containing a silane coupling agent (α) and an organic titanate compound (β) is then applied to a substrate such as a stainless steel plate by any method, such as spraying, dipping, or roll coating, and optionally dried at room temperature. The flat rubber member is then laminated on the surface, and crosslinked and bonded under predetermined conditions (e.g., 130 to 200°C for 3 to 30 minutes), thereby producing a laminate in which the substrate and the crosslinked rubber member (sealing member) are bonded together. It is preferable to mold the crosslinked rubber member into a predetermined shape in advance according to the shape of the sealing portion, as this eliminates the need for complicated alignment, facilitates continuous processing, and improves productivity. The crosslinked rubber member may also be formed by crosslinking the prepared rubber composition using a predetermined mold on a substrate coated with the adhesive as described above, thereby achieving stronger crosslinked adhesion.

[0070] The thickness of each member in the present fuel cell laminate varies depending on the sealing portion where the laminate is used. For example, the thickness of the substrate is usually in the range of 0.05 to 5 mm, preferably in the range of 0.1 to 3 mm. The thickness of the sealing member is usually in the range of 0.2 to 5 mm, preferably in the range of 0.5 to 3 mm. The thickness of the adhesive layer is usually 1×10 -5 in the range of 0.025 mm, preferably 2 × 10 -5The adhesive layer may be a multi-layered layer of two or more layers, but a single layer is preferred in terms of shortening the coating process time.

[0071] <Fuel Cell Constituent Component> The present fuel cell laminate is used as a fuel cell constituent component. Examples of fuel cell constituent components include a laminate formed by bonding a fuel cell substrate and a sealing member that seals the substrate via an adhesive layer.

[0072] The substrate for a fuel cell varies depending on the type and structure of the fuel cell, but examples thereof include a separator, a gas diffusion layer (GDL), and an MEA (electrolyte membrane, electrode). Examples of separators include those made of metals such as stainless steel (e.g., SUS304) and titanium, and those made of conductive resins (thermoplastic or thermosetting resins mixed with graphite, polyacrylonitrile-based carbon fibers, etc.). Furthermore, the separator may have a thin carbon film, such as a DLC film or graphite film, formed on the surface of the separator made of the above metals by a process such as PVD or CVD. Examples of fuel cells to which the present invention is applicable include polymer electrolyte fuel cells (PEFCs) (including direct methanol fuel cells (DMFCs)).

[0073] An example of the fuel cell laminate is shown in Figure 1. Figure 1 shows a component comprising a separator 5, which is a rectangular thin plate with a cross-sectional irregularity formed by a total of six grooves extending in the longitudinal direction, and a lip 4b, which is rectangular and has a cross-sectional convexity, provided on the periphery of the separator 5 via an adhesive layer 6. The lip 4b is a sealing member made of the rubber composition containing the rubber component (A), and the adhesive layer 6 is made of an adhesive containing a silane coupling agent (α) and an organic titanate compound (β).

[0074] <Fuel Cell Seal> Next, an example of a fuel cell seal using the fuel cell laminate according to the present invention is shown in Figure 2. Figure 2 mainly shows a single cell 1 in a fuel cell formed by stacking a plurality of cells, and cell 1 includes an MEA 2, a gas diffusion layer (GDL) 3, a sealing member 4, a separator 5, and an adhesive layer 6. The sealing member 4 is made of the present rubber composition containing the rubber component (A), and the adhesive layer 6 is made of an adhesive containing a silane coupling agent (α) and an organic titanate compound (β).

[0075] 2, examples of the fuel cell seal include one in which a separator 5 and a seal member 4 are bonded via an adhesive layer 6, one in which an MEA 2 and a seal member 4 are bonded via an adhesive layer 6, and one in which a gas diffusion layer 3 and a seal member 4 are bonded via an adhesive layer 6. The adhesive layer 6′ that bonds adjacent seal members 4 together may be a layer made of an adhesive containing a silane coupling agent (α) and an organic titanate compound (β), but it may also be an adhesive layer made of, for example, rubber cement or a rubber composition that is liquid at room temperature (23°C) (liquid ethylene propylene rubber (liquid EPM), liquid EPDM, liquid acrylonitrile-butadiene rubber (liquid NBR), liquid hydrogenated acrylonitrile-butadiene rubber (liquid H-NBR), etc.).

[0076] Although not shown, the MEA 2 comprises an electrolyte membrane and a pair of electrodes arranged on either side of the electrolyte membrane in the stacking direction. The electrolyte membrane and the pair of electrodes are rectangular thin plates. Gas diffusion layers 3 are arranged on either side of the MEA 2 in the stacking direction. The gas diffusion layers 3 are porous layers each having a rectangular thin plate shape.

[0077] The separator 5 is made of titanium and has a rectangular thin plate shape, with a total of six grooves extending in the longitudinal direction, which give the separator 5 a rough cross section. The separators 5 are arranged opposite each other in the stacking direction of the gas diffusion layer 3. The rough shape is used to define gas flow paths 7 between the gas diffusion layer 3 and the separator 5 for supplying gas to the electrodes.

[0078] The sealing member 4 has a rectangular frame shape. The sealing member 4 is adhered to the peripheral edges of the MEA 2 and the gas diffusion layer 3, and to the separator 5, via an adhesive layer 6, thereby sealing the peripheral edges of the MEA 2 and the gas diffusion layer 3. In the example of Fig. 2, the sealing member 4 is made up of two separate members, an upper and a lower member, but it may also be a single sealing member combining the two.

[0079] When a fuel cell such as a polymer electrolyte fuel cell is in operation, a fuel gas and an oxidant gas are each supplied through a gas flow channel 7. The peripheral edge of the MEA 2 is sealed by a sealing member 4 via an adhesive layer 6. This prevents gas mixing and leakage.

[0080] <Fuel Cell Including Fuel Cell Laminate> One embodiment of the present invention includes a fuel cell including the present fuel cell laminate, and a fuel cell vehicle (FVC) including the fuel cell. That is, one embodiment of the present invention includes a fuel cell including a laminate for a fuel cell in which a substrate and a sealing member are bonded via an adhesive layer, wherein the sealing member is made of the present rubber composition containing component (A), and the adhesive layer is made of an adhesive containing component (α) and component (β). Another embodiment of the present invention includes a fuel cell vehicle (FVC) including a fuel cell including a laminate for a fuel cell in which a substrate and a sealing member are bonded via an adhesive layer, wherein the sealing member is made of the present rubber composition containing component (A), and the adhesive layer is made of an adhesive containing component (α) and component (β).

[0081] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0082] First, the rubber composition, adhesive, and substrate shown below were prepared.

[0083] <Rubber Composition> <Rubber Composition (R1)> 100 parts by mass of ethylene-butene-diene rubber (EBT-K-9330M, manufactured by Mitsui Chemicals, Inc.), 1 part by mass of antioxidant (Nocrac NS-5, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 50 parts by mass of carbon black (FEF-grade carbon black, Seast SO, manufactured by Tokai Carbon Co., Ltd.), and 15 parts by mass of plasticizer (poly-α-olefin, PAO601, manufactured by Nippon Steel Chemical & Material Co., Ltd.) were kneaded using a Banbury mixer at 120°C for 5 minutes. After cooling the kneaded mixture, 6 parts by mass of crosslinker (Perhexa C-80, manufactured by NOF Corporation) was added, and the mixture was further kneaded using an open roll at 50°C for 10 minutes to prepare rubber composition (R1).

[0084] Rubber Composition (R2) Rubber composition (R2) was prepared in the same manner as rubber composition (R1), except that the ethylene-butene-diene rubber (manufactured by Mitsui Chemicals, Inc., EBT-K-9330M) was replaced with an ethylene-propylene-diene rubber (manufactured by Mitsui Chemicals, Inc., EPT-9090M).

[0085] Rubber composition (R3) A rubber composition (R3) was prepared in the same manner as in the rubber composition (R1), except that the ethylene-butene-diene rubber (EBT-K-9330M, manufactured by Mitsui Chemicals, Inc.) was replaced with an ethylene-propylene-diene rubber (Esprene 5361, manufactured by Sumitomo Chemical Co., Ltd.).

[0086] <Adhesive> The adhesive materials shown below were prepared.

[0087] Silane Coupling Agent (α1) 100 parts by mass of vinyltrimethoxysilane, 68.4 parts by mass of 3-aminopropyltrimethoxysilane, and 33.1 parts by mass of water (1.74 moles per mole of the total amount of the silane coupling agents) were charged into a reactor equipped with a distillation apparatus and a stirrer, and stirred at approximately 60°C for approximately 1 hour. Thereafter, an acid such as formic acid was added within 1 hour in an amount of approximately 0.5 to 2.0 moles per mole of the total amount of the silane coupling agents. The temperature during this process was maintained at approximately 65°C. The mixture was stirred for an additional 1 to 5 hours to allow the reaction to proceed, and the alcohol produced by hydrolysis was distilled under reduced pressure. The distillation was stopped when only water remained in the distilled water, and the silane concentration was then adjusted by dilution to 30 to 80% by mass, yielding a copolymerized oligomer having a molar ratio (Ma / Mb) of 1.17, where Ma is the amount of hydrophilic functional groups contained in 1 mole of the molecule, and Mb is the amount of hydrophobic functional groups contained in 1 mole of the molecule. The hydrophobic functional groups are vinyl groups, and the hydrophilic functional groups are silanol groups, alkoxy groups, and amino groups.

[0088] <<Silane Coupling Agent (α2)>> X-12-1050 manufactured by Shin-Etsu Chemical Co., Ltd. (The molar ratio (Ma / Mb) of the amount of hydrophilic functional groups Ma (moles) to the amount of hydrophobic functional groups Mb (moles) contained in 1 mole of the copolymer oligomer is 1.67, the hydrophobic functional groups are acryloyl groups, and the hydrophilic functional groups are silanol groups and alkoxy groups.)

[0089] <<Silane Coupling Agent (α3)>> KR-513 manufactured by Shin-Etsu Chemical Co., Ltd. (The molar ratio (Ma / Mb) of the amount of hydrophilic functional groups Ma (moles) to the amount of hydrophobic functional groups Mb (moles) contained in 1 mole of the copolymer oligomer is 0.49, the hydrophobic functional groups are acryloyl groups and methyl groups, and the hydrophilic functional groups are silanol groups and alkoxy groups.)

[0090] Silane Coupling Agent (α′1): X-12-972F manufactured by Shin-Etsu Chemical Co., Ltd. (The functional groups in the copolymer oligomer are only hydrophilic functional groups. The hydrophilic functional groups are silanol groups, alkoxy groups, and amino groups.)

[0091] <<Silane Coupling Agent (α′2)>> X-24-9590 manufactured by Shin-Etsu Chemical Co., Ltd. (The functional groups in the copolymer oligomer are only hydrophilic functional groups. The hydrophilic functional groups are silanol groups, alkoxy groups, and amino groups.)

[0092] <Titanium alkoxide (β1-1)> Tetraisopropyl titanate (A-1, manufactured by Nippon Soda Co., Ltd.)

[0093] <Titanium alkoxide (β1-2)> Tetra-normal-butyl titanate (manufactured by Nippon Soda Co., Ltd., B-1)

[0094] <Titanium alkoxide (β1-3)> Tetrastearyl titanate (manufactured by Matsumoto Fine Chemical Co., Ltd., Orgatix TA-90)

[0095] Titanium acylate (β2) Titanium stearate (manufactured by Nippon Soda Co., Ltd., S-151)

[0096] Titanium chelate (β3-1) Titanium acetylacetonate (manufactured by Matsumoto Fine Chemicals Co., Ltd., Orgatix TC-100)

[0097] Titanium chelate (β3-2) Titanium ethyl acetoacetate (manufactured by Matsumoto Fine Chemicals Co., Ltd., Orgatix TC-710)

[0098] Inorganic titanate compound (β'1) Titanium oxide (SSP-M, manufactured by Sakai Chemical Industry Co., Ltd.)

[0099] Inorganic titanate compound (β'2) Titanium oxide (manufactured by Sakai Chemical Industry Co., Ltd., STR-100N)

[0100] <Substrate> The following substrates were prepared: <SUS (1)> A substrate made of stainless steel (SUS304) (width 25 mm, length 60 mm, thickness 1.5 mm).

[0101] <SUS (2)> Stainless steel (SUS316) substrate (width 25 mm, length 60 mm, thickness 1.5 mm)

[0102] Example 1: 100 parts by mass of silane coupling agent (α1) and 0.5 parts by mass of titanium alkoxide (β1-1) were mixed, and the mixture was diluted with an alcohol-based organic solvent containing ethanol and butoxyethanol to prepare an adhesive with a solids concentration of 10% by mass (an adhesive with a total blend of silane coupling agent (α1) and titanium alkoxide (β1-1) of 10% by mass, 85% by mass of ethanol, and 5% by mass of butoxyethanol). SUS (1) was prepared as a substrate, and the adhesive prepared above was spray-coated on the surface of the substrate within the range specified by JIS K 6256-2 to a thickness of approximately 0.5 μm. Thereafter, the rubber composition (R1) and the substrate were bonded to each other by crosslinking using a predetermined mold and held at 170°C for 15 minutes so as to have a shape conforming to JIS K 6256-2, and an adhesion evaluation sample (laminate) was produced in which a rubber molded body (sealing member) having a thickness of 2.0 mm and a substrate were bonded via an adhesive layer (thickness 0.5 µm).

[0103] Examples 2 to 15, Comparative Examples 1 to 7 Adhesion evaluation samples (laminates) for Examples 2 to 15 and Comparative Examples 1 to 7 were prepared in the same manner as Example 1, except that the type of rubber composition, the type and blending ratio of the silane coupling agent and titanate compound, and the type of substrate were changed as shown in Tables 1 and 2. For example, in the case of Example 2, the adhesion evaluation sample (laminate) was prepared as follows. 100 parts by mass of silane coupling agent (α1) and 5 parts by mass of titanium alkoxide (β1-1) were mixed, and the mixture was diluted with an alcohol-based organic solvent containing ethanol and butoxyethanol to prepare an adhesive with a solids concentration of 10% by mass (an adhesive with a total blending amount of silane coupling agent (α1) and titanium alkoxide (β1-1) of 10% by mass, 85% by mass of ethanol, and 5% by mass of butoxyethanol). SUS (1) was prepared as a substrate, and the adhesive prepared above was spray-coated on its surface within the range specified by JIS K 6256-2 to a thickness of approximately 0.5 μm after application. Thereafter, the rubber composition (R1) and the substrate were crosslinked and bonded by holding them at 170°C for 15 minutes using a predetermined mold to form a shape conforming to JIS K 6256-2, thereby producing an adhesion evaluation sample (laminate) in which a 2.0 mm-thick rubber molded body (sealing member) and the substrate were bonded via an adhesive layer (0.5 μm thick).

[0104] The adhesion evaluation samples (laminates) of the Examples and Comparative Examples thus obtained were evaluated for various properties according to the following criteria. The results are shown in Tables 1 to 3 below.

[0105] <Evaluation test for initial adhesion> The adhesion evaluation samples (laminates) obtained as described above were subjected to a 90° peel test specified in JIS K6256-2 (2006) in an environment at room temperature (23°C), and the adhesion between the substrate and the rubber molded body (sealing member) in each adhesion evaluation sample (laminate) was evaluated according to the following criteria. The results are shown in Tables 1 and 2. (Evaluation criteria) ◯ (very good): Material failure of the rubber molded body (sealing member) was observed. × (poor): Material failure of the rubber molded body (sealing member) was not observed.

[0106] <Evaluation Test (1) for Acid-Resistant Adhesion Under High-Temperature and Long-Term Conditions> Adhesion evaluation samples (laminates) from the Examples and Comparative Examples were placed in a sulfuric acid solution adjusted to pH 3.0 and immersed in the sulfuric acid solution at 120°C for 336 hours (or 672 hours). The adhesion evaluation samples were then removed from the sulfuric acid solution and allowed to stand for one day. A 90° peel test was then performed in accordance with JIS K 6256-2 (2006), and the samples were visually observed and evaluated according to the following criteria. The results are shown in Tables 1 and 2. Note that a "-" in the evaluation column in Table 2 indicates that the initial adhesion evaluation was "x," and therefore the acid-resistant adhesion was not evaluated. (Evaluation Criteria) ◎ (Excellent): The combined percentage of material failure of the rubber molded body and cohesive failure of the adhesive layer exceeded 80%. ○ (Very Good): The combined percentage of material failure of the rubber molded body and cohesive failure of the adhesive layer was 50-80%. Δ (good): Material failure of the rubber molding and cohesive failure of the adhesive layer are present, but the total proportion is less than 50%. × (poor): The proportion of interfacial peeling is nearly 100%.

[0107] <Evaluation Test for Acid-Resistant Adhesion Under High-Temperature and Long-Term Conditions (2)> Next, to verify the effect of the type of organic titanate compound on acid-resistant adhesion, a test was conducted with an even longer immersion time. Specifically, Examples 3, 8, and 9 differ only in the type of organic titanate compound: Example 3 uses titanium alkoxide, Example 8 uses titanium acylate, and Example 9 uses titanium chelate. The adhesion evaluation samples (laminates) of Examples 3, 8, and 9 were placed in a sulfuric acid solution adjusted to pH 3.0 and immersed in the sulfuric acid solution at 120°C for 840 hours. The adhesion evaluation samples were then removed from the sulfuric acid solution and allowed to stand for one day. A 90° peel test was then conducted in accordance with JIS K 6256-2 (2006), visually observed, and evaluated according to the criteria of the above-mentioned <Evaluation Test for Acid-Resistant Adhesion Under High-Temperature and Long-Term Conditions (1)>. The results are shown in Table 3.

[0108]

[0109]

[0110]

[0111] <Results of Evaluation Test (1) for Acid-Resistant Adhesion Under High-Temperature and Long-Term Conditions> From the results in Tables 1 and 2 above, all of the adhesion evaluation samples (laminates) of the Examples had good "initial adhesion," and further obtained excellent ratings in the evaluations of "acid-resistant adhesion at 120°C for 336 hours" and "acid-resistant adhesion at 120°C for 672 hours."

[0112] In contrast, the adhesion evaluation samples (laminates) of Comparative Examples 1 and 2 did not use the organic titanate compound (β) defined in the present invention, and therefore were inferior in the evaluation of "acid-resistant adhesion at 120°C for 336 hours," resulting in unsatisfactory acid-resistant adhesion under high-temperature and long-term conditions.

[0113] The adhesion evaluation sample (laminate) of Comparative Example 3 did not use the silane coupling agent (α) specified in the present invention, and therefore resulted in a poor result in the evaluation of "initial adhesion." Specifically, interfacial peeling was observed between the rubber molded body (sealing member) and the adhesive layer, resulting in unsatisfactory results in adhesion. Comparative Examples 4 and 5 did not use the silane coupling agent (α) specified in the present invention, but instead used other silane coupling agents (α'), and therefore resulted in poor results in the evaluation of "initial adhesion." Specifically, interfacial peeling was observed between the rubber molded body (sealing member) and the adhesive layer, resulting in unsatisfactory results in adhesion. Thus, since Comparative Examples 3 to 5 were unsatisfactory in terms of initial adhesion, it was easily predicted that they would also result in unsatisfactory results in acid-resistant adhesion under high-temperature and long-term conditions.

[0114] In addition, Comparative Examples 6 and 7 did not use the organic titanate compound (β) defined in the present invention, but used an inorganic titanate compound (β'), and therefore were inferior in the evaluation of "acid-resistant adhesion at 120°C for 336 hours," resulting in unsatisfactory acid-resistant adhesion under high-temperature and long-term conditions.

[0115] From the above, it was shown that a laminate satisfying the requirements of the present invention has excellent initial adhesiveness and acid resistance under high temperature and long-term conditions.

[0116] <Results of Evaluation Test (2) for Acid-Resistant Adhesion Under High-Temperature and Long-Term Conditions> As shown in Table 1 above, Examples 3, 8, and 9 all have excellent acid-resistant adhesion, but the results in Table 3 above show that Examples 3 and 9 are particularly excellent, with Example 3 being particularly excellent. The above shows that the use of titanium alkoxide or titanium chelate as the organic titanate compound (β) can further improve acid-resistant adhesion under high-temperature and long-term conditions, and that titanium alkoxide is more preferable when compared to the two.

[0117] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0118] The laminate of the present invention is a laminate in which a sealing member is bonded to a substrate of various kinds via an adhesive layer, and can be suitably used as a laminate for sealing a fuel cell in which a substrate for a fuel cell, such as a metal separator, and a sealing member are bonded via an adhesive layer.

[0119] 4b Lip (sealing member) 5 Separator (substrate) 6 Adhesive layer

Claims

1. A laminate for a fuel cell, comprising a substrate and a sealing member bonded via an adhesive layer, the sealing member being made of a rubber composition containing the following component (A), and the adhesive layer being made of an adhesive containing the following components (α) and (β): (A) at least one of ethylene-propylene-diene rubber and ethylene-butene-diene rubber; (α) a silane coupling agent of a copolymer oligomer type having a hydrophilic functional group and a hydrophobic functional group, the hydrophilic functional group being the following (a), the hydrophobic functional group being the following (b), and the molar ratio (Ma / Mb) of the amount of substance Ma (mol) of the hydrophilic functional group to the amount of substance Mb (mol) of the hydrophobic functional group contained in 1 mole of the molecule being 0.33 to 3.

00. (a) At least one 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 containing at least a silanol group or an alkoxy group; (b) At least one 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; (β) An organic titanate compound.

2. The laminate for a fuel cell according to claim 1, wherein the component (β) in said adhesive is at least one of a titanium alkoxide and a titanium chelate.

3. The laminate for a fuel cell according to claim 1 or 2, wherein the blending amount of the component (β) in the adhesive is 0.5 to 200 parts by mass per 100 parts by mass of the component (α).

4. The laminate for a fuel cell according to any one of claims 1 to 3, wherein the substrate is made of austenitic stainless steel.

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