Rubber composition for fuel cell sealing, sealing member for fuel cell, and fuel cell using them

Abstract

The sealing member 4 formed of a rubber composition is used as a fuel cell sealing member. The rubber composition contains the following components (A) to (C) in specific proportions and includes at least one selected from the group consisting of (meth)acrylic monomers having any one of a carboxyl group, a hydroxyl group, and an amide group and a silane coupling agent. The sealing member 4 has excellent flexibility, elongation rate in a wide temperature range from low temperature to high temperature, excellent sealing performance, and can reduce damage to the electrolyte membrane. (A) At least one polymer selected from the group consisting of poly(meth)acrylate, polyisoprene, polybutadiene, polyurethane, and polyester having a (meth)acryloyl group; (B) a monofunctional (meth)acrylic monomer having a glass transition temperature of 0°C or lower; (C) a monofunctional (meth)acrylic monomer having a glass transition temperature of 50°C or higher.

Description

Technical Field

[0001] The present invention relates to a rubber composition for fuel cell sealing for sealing constituent members of a fuel cell, a sealing member for a fuel cell, and a fuel cell using them. Background Art

[0002] A fuel cell generates electricity through an electrochemical reaction of gases, has a relatively high power generation efficiency, emits clean gases, and has a minimal impact on the environment. Among them, a polymer electrolyte fuel cell can operate at a relatively low temperature and has a large output density. Therefore, the above polymer electrolyte fuel cell is expected to be used for various purposes such as power generation and automotive power sources.

[0003] In a polymer electrolyte fuel cell, a cell unit formed by sandwiching a membrane electrode assembly (MEA) with separators serves as a power generation unit. The MEA is composed of a polymer membrane (electrolyte membrane) as an electrolyte and a pair of electrode catalyst layers (fuel electrode (anode) catalyst layer, oxygen electrode (cathode) catalyst layer) disposed on both sides of the electrolyte membrane. A porous layer for gas diffusion is also disposed 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 is performed through an electrochemical reaction at the three-phase interface of the supplied gas, electrolyte, and electrode catalyst layer. A polymer electrolyte fuel cell is configured by fastening a cell stack body in which a plurality of the above cell units are stacked using end plates or the like disposed at both ends in the cell unit stacking direction.

[0004] Flow paths for gases supplied to each electrode and flow paths for a refrigerant for alleviating heat generation during power generation are formed in the separators. For example, if the gases supplied to each electrode are mixed, problems such as a decrease in power generation efficiency occur. In addition, the electrolyte membrane has proton conductivity in a state containing water. Therefore, during operation, it is necessary to keep the electrolyte membrane in a moist state. Thus, in order to prevent gas mixing, leakage of gas and refrigerant, and keep the inside of the cell unit moist, it is important to ensure the sealing performance around the MEA and the porous layer and between adjacent separators. As a sealing member for sealing the above constituent members, for example, a sealing member (rubber gasket) made of ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), etc. has been proposed (for example, refer to Patent Documents 1 and 2).

[0005] In addition, in order to further improve the sealing performance between the MEA, separator, etc., the above-mentioned sealing member is adhesively bonded to target members such as the MEA and separator as needed for use. As the bonding method at this time, for example, a method of performing cross-linking while bonding by heating in a state where a rubber composition as a forming material of the sealing member is in contact with the target member (thermal cross-linking bonding method), a method of post-bonding a sealing member manufactured by performing thermal cross-linking and a target member using an adhesive, etc. are known (for example, refer to Patent Documents 3 and 4).

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-94056

[0009] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2010-146781

[0010] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2017-65042

[0011] Patent Document 4: International Publication No. 2013 / 147020 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] However, the electrolyte membrane constituting the MEA is a polymer membrane and is easily damaged by heat. Therefore, if the above-mentioned thermal cross-linking bonding method is adopted, there is a risk of deterioration of the electrolyte membrane.

[0014] In addition, the MEA usually uses a fluorine-based polymer with poor adhesiveness, so there is also a problem that it is difficult to bond with a general adhesive.

[0015] Furthermore, the electrolyte membrane constituting the MEA is very thin and is easily damaged by changes in air pressure, vibrations from the outside, etc. Therefore, it is necessary to use a soft sealing member and adhesive. In addition, if the curing of the above-mentioned sealing member and adhesive is insufficient in order to ensure flexibility, there is a risk that the eluate will have an adverse effect on power generation. Therefore, such a situation also needs to be avoided.

[0016] In addition, it is predicted that fuel cells will expand worldwide to commercial vehicles such as buses and trucks that travel long distances. Among the above-mentioned sealing members and adhesives, in order to prevent seal leakage in cold regions and hot regions, elongation in a relatively wide temperature range from low temperature to high temperature is further required.

[0017] The present invention has been completed in view of such circumstances, and provides a rubber composition for fuel cell seals, a sealing member for fuel cells, and a fuel cell using them, which have excellent flexibility, elongation in a wide temperature range from low temperature to high temperature, excellent sealing performance, and can reduce damage to the electrolyte membrane.

[0018] Means for Solving the Problem

[0019] The inventors of the present invention have repeatedly conducted in-depth research to solve the above problems. During the process of this research, it was mainly studied to crosslink the sealing member for fuel cells by using free radical crosslinking such as ultraviolet crosslinking and electron beam crosslinking instead of thermal crosslinking, so as to suppress damage to the electrolyte membrane during crosslinking adhesion, etc. As a result, it was conceived to form a sealing member formed of a free radical crosslinkable composition using a specific polymer (A) having a (meth)acryloyl group as the polymer of the above sealing member. In addition, as the material of the above sealing member, by blending an adhesive component, a monofunctional (meth)acrylic acid monomer, etc. and adjusting its blending ratio, etc., various experiments were carried out to make the flexibility, elongation at low and high temperatures, and sealing performance excellent. As a result, it was found that as the monofunctional (meth)acrylic acid monomer in the material of the above sealing member, two monofunctional (meth)acrylic acid monomers (B) and (C) with different glass transition temperatures (Tg) are used in a specific blending ratio, and further, as the adhesive component, it contains at least one selected from the group consisting of (meth)acrylic acid monomers having any one of a carboxyl group, a hydroxyl group, and an amide group and a silane coupling agent, and the desired object can be achieved.

[0020] However, the gist of the present invention lies in the following [1] to

[10] .

[0021] [1] A rubber composition for fuel cell seals, which is a fuel cell seal rubber composition showing free radical crosslinkability and containing the following components (B) and (C) with the following component (A) as the main component, and is characterized in that

[0022] The total content of components (B) and (C) relative to 100 parts by weight of component (A) is 10 to 100 parts by weight, the weight ratio of component (B) to component (C) [(B) / (C)] is 0.1 to 20, and the fuel cell seal rubber composition contains at least one selected from the group consisting of (meth)acrylic acid monomers having any one of a carboxyl group, a hydroxyl group, and an amide group and a silane coupling agent,

[0023] (A) At least one polymer having a (meth)acryloyl group and selected from the group consisting of poly(meth)acrylate, polyisoprene, polybutadiene, polyurethane, and polyester,

[0024] (B) A monofunctional (meth)acrylic monomer having a glass transition temperature below 0 °C

[0025] (C) A monofunctional (meth)acrylic monomer having a glass transition temperature above 50 °C.

[0026] [2] The rubber composition for fuel cell sealing according to [1], wherein the number average molecular weight of the component (A) is 3,000 to 100,000.

[0027] [3] The rubber composition for fuel cell sealing according to [1] or [2], wherein the glass transition temperature of the component (A) is -40 °C or lower.

[0028] [4] The rubber composition for fuel cell sealing according to any one of [1] to [3], wherein the component (A) is at least one selected from the group consisting of poly(meth)acrylate, polyisoprene, and polybutadiene, which has a (meth)acryloyl group.

[0029] [5] The rubber composition for fuel cell sealing according to any one of [1] to [4], wherein the component (A) is a polymer having a (meth)acryloyl group at the molecular chain end.

[0030] [6] The rubber composition for fuel cell sealing according to any one of [1] to [3], wherein the component (A) is a poly(meth)acrylate having a (meth)acryloyl group at the molecular chain end.

[0031] [7] The rubber composition for fuel cell sealing according to any one of [1] to [6], wherein the rubber composition for fuel cell sealing further contains a photo radical polymerization initiator.

[0032] [8] The rubber composition for fuel cell sealing according to any one of [1] to [7], wherein the rubber composition for fuel cell sealing further contains a polyfunctional (meth)acrylic monomer.

[0033] [9] A sealing member for a fuel cell, characterized in that the sealing member for a fuel cell is formed from a crosslinked body of the rubber composition for fuel cell sealing according to any one of [1] to [8].

[0034]

[10] A fuel cell, which is a fuel cell formed by stacking a plurality of single cells, wherein the single cell has a separator and a membrane electrode assembly as constituent members, and the end portions between the separator and the membrane electrode assembly are sealed. It is characterized in that the end portions between the separator and the membrane electrode assembly constituting the single cell are sealed by at least one of a crosslinked body of the fuel cell sealing rubber composition described in any one of [1] to [8] and the fuel cell sealing member described in [9].

[0035] Advantages of the Invention

[0036] As can be seen from the above, according to the present invention, the flexibility of the crosslinked body of the fuel cell sealing rubber composition and the elongation rate in a wide temperature range from low temperature to high temperature become excellent. In addition, the fuel cell sealing rubber composition of the present invention has a high adhesiveness to MEA, separators, etc., and further exhibits free radical crosslinkability. Therefore, according to the present invention, excellent sealing performance can be obtained, and damage to the electrolyte membrane can be reduced. In addition, no eluate that adversely affects power generation appears in the crosslinked body of the fuel cell sealing rubber composition of the present invention, so it can exhibit excellent performance in fuel cell applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a cross-sectional view showing an example in which the fuel cell sealing member of the present invention is used as a sealing body. DETAILED DESCRIPTION OF THE INVENTION

[0038] Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to this embodiment.

[0039] In addition, in this specification, the term “(meth)acrylic acid” is used as a concept including both acrylic acid and methacrylic acid, the term “(meth)acrylate” is used as a concept including both acrylate and methacrylate, and the term “(meth)acryloyl” is used as a concept including both acryloyl and methacryloyl. In addition, the term “polymer” is used as a concept including both copolymer and oligomer.

[0040] As described above, the rubber composition for fuel cell sealing of the present invention (hereinafter sometimes simply referred to as "rubber composition") is a rubber composition for fuel cell sealing showing free radical crosslinkability, which has the following component (A) as the main component and contains the following components (B) and (C). The total content of components (B) and (C) relative to 100 parts by weight of component (A) is 10 to 100 parts by weight, and the weight ratio of component (B) to component (C) [(B) / (C)] is 0.1 to 20. Moreover, the fuel cell sealing member of the present invention (hereinafter sometimes simply referred to as "sealing member") is formed of a crosslinked product of the above rubber composition.

[0041] (A) At least one polymer having a (meth)acryloyl group and selected from the group consisting of poly(meth)acrylate, polyisoprene, polybutadiene, polyurethane, and polyester.

[0042] (B) A monofunctional (meth)acrylic acid monomer having a glass transition temperature (Tg) of 0 °C or lower.

[0043] (C) A monofunctional (meth)acrylic acid monomer having a glass transition temperature (Tg) of 50 °C or higher.

[0044] Herein, the above "main component" generally refers to a component accounting for 45% by weight or more of the entire rubber composition, and preferably refers to a component accounting for 50% by weight or more of the entire rubber composition. In addition, from the viewpoint of the effects of the present invention, it is preferred that the polymer used in the above rubber composition consists only of the above component (A).

[0045] In addition, when the above "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" corresponds to the above components (B) and (C), the above "total content of components (B) and (C) relative to 100 parts by weight of component (A)" and the "weight ratio of component (B) to component (C)" represent the ratio including the "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group".

[0046] Furthermore, the "(meth)acrylic acid monomer having an amide group" in the present invention not only includes a monomer having an amide group (-CO-NH 2 ) but also means a "(meth)acrylic acid monomer having an amide bond in the molecular chain".

[0047] In addition, among the "(meth)acrylic acid monomers having any one of a carboxyl group, a hydroxyl group, and an amide group" described above, from the aspect of obtaining higher adhesiveness, it is preferable to use a (meth)acrylic acid monomer having a carboxyl group.

[0048] Hereinafter, each material used in the rubber composition of the present invention will be described in detail.

[0049] <Component (A)>

[0050] (Component (A) is a specific polymer having a (meth)acryloyl group. The above (meth)acryloyl group may be present as a side chain with respect to the molecular chain (main chain) of Component (A), or may be present at the end of the above molecular chain. From the viewpoint of more effectively exerting the effects of the present invention, it is preferable to have a (meth)acryloyl group at the molecular chain end.

[0051] Examples of the above Component (A) include poly(meth)acrylate, polyisoprene, polybutadiene, polyurethane, polyester, and polymers having a (meth)acryloyl group as described above. They can be used alone or in combination of two or more. Among them, poly(meth)acrylate, polyisoprene, and polybutadiene are preferable, and poly(meth)acrylate is more preferable.

[0052] Moreover, poly(meth)acrylate having a (meth)acryloyl group at the molecular chain end is particularly preferable.

[0053] The number average molecular weight (Mn) of the above Component (A) is preferably in the range of 3000 to 100000, more preferably in the range of 4500 to 95000, and still more preferably in the range of 6000 to 50000. That is, because if the above number average molecular weight (Mn) is too small, a tendency for poor high-temperature elongation and low-temperature elongation can be observed, and if the above number average molecular weight (Mn) is too large, a tendency for poor high-temperature elongation can be observed, and a tendency for high viscosity and reduced operability can be observed.

[0054] From the viewpoint of more effectively exerting the effects of the present invention, the molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the above Component (A) is preferably 1.1 to 1.6, more preferably 1.1 to 1.4. In addition, the above number average molecular weight (Mn) and weight average molecular weight (Mw) are measured by gel permeation chromatography (GPC). Specifically, chloroform is used as the mobile phase, the measurement is carried out using a polystyrene gel column, and the number average molecular weight and the like can be obtained by conversion to polystyrene.

[0055] In addition, the glass transition temperature (Tg) of the above component (A) is preferably -40°C or lower, more preferably -50°C or lower. That is, this is because if the glass transition temperature (Tg) of the above component (A) is too high, a tendency for poor compression set at low temperatures and low-temperature elongation can be observed. In addition, the lower limit is not particularly limited and is, for example, -100°C.

[0056] The glass transition temperature (Tg) of the component (A) is measured by a differential scanning calorimeter (DSC). Specifically, using a differential scanning calorimetry device (DSC) SSC-5200 manufactured by Seiko Instruments Inc., the sample is temporarily heated to 200°C at a rate of 25°C / minute and held for 10 minutes. After a preliminary adjustment of cooling the temperature to 50°C at a rate of 25°C / minute, the measurement is carried out during the period of heating to 200°C at a heating rate of 10°C / minute. The integral value is obtained from the resulting DSC curve, and the glass transition temperature is obtained from its maximum point.

[0057] From the viewpoint of more effectively exerting the effects of the present invention, the viscosity of the above component (A) at 23°C (viscosity obtained by a B-type viscometer) is preferably 2 to 4000 Pa·s, more preferably 100 to 2000 Pa·s.

[0058] In addition, when the above component (A) is a poly(meth)acrylate having a (meth)acryloyl group at the molecular chain end, its molecular chain (main chain) is composed of a homopolymer, copolymer of one or more (meth)acrylic acid monomers, or a copolymer of one or more (meth)acrylic acid monomers and a vinyl-based monomer copolymerizable therewith.

[0059] As the above-mentioned (meth)acrylic acid monomers, for example, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, octadecene (meth)acrylate, docosyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, phenyl (meth)acrylate, tolylcarbonyl (meth)acrylate, tolyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl oxyethyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentyl oxyethyl (meth)acrylate, isobornyl (meth)acrylate, etc. can be mentioned. They can be used alone or in copolymerization of multiple kinds.

[0060] In addition, the above-mentioned (meth)acrylic acid monomers can be copolymerized with other monomers and further block copolymerized. As the monomers for copolymerization, for example, styrene-based monomers such as styrene, fluorine-containing vinyl monomers such as perfluoroethylene, silicon-containing vinyl-based monomers such as vinyltrimethoxysilane, nitrile group-containing vinyl-based monomers such as acrylonitrile and methacrylonitrile, amide group-containing vinyl-based monomers such as acrylamide and methacrylamide, etc. can be mentioned.

[0061] Among the above, (meth)acrylate monomers such as ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, etc. are preferred, and acrylate monomers with 2 to 14 carbon atoms in the ester group and methacrylate monomers with 8 to 14 carbon atoms in the ester group are more preferred. If the number of carbon atoms in the ester group is outside the above range, a tendency of poor compression set at low temperature can be observed. In addition, especially if the number of carbon atoms is greater than the above range, a tendency of poor reactivity during polymerization and difficulty in synthesis can be observed.

[0062] In the case where the above component (A) is a poly(meth)acrylate having a (meth)acryloyl group at the molecular chain end, it is preferably a copolymer of (meth)acrylate monomers having a (meth)acryloyl group at the molecular chain end, and more preferably a copolymer obtained by radical polymerization of (meth)acrylate monomers such as ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, etc. Among them, a copolymer obtained by polymerizing n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate is particularly preferred.

[0063] As the copolymerization ratio (weight ratio) of the above (meth)acrylate monomers, for example, in the case of a copolymer obtained by polymerizing n-butyl acrylate and 2-ethylhexyl acrylate (n-butyl acrylate∶2-ethylhexyl acrylate), from the viewpoint of more effectively exerting the effects of the present invention, it is preferably 40 to 60∶60 to 40.

[0064] In the case where the above component (A) is a poly(meth)acrylate having a (meth)acryloyl group at the molecular chain end, as long as it is a (meth)acrylic acid polymer having a (meth)acryloyl group at at least one molecular chain end, from the viewpoint of more effectively exerting the effects of the present invention, a (meth)acrylic acid polymer having (meth)acryloyl groups at both ends of the molecular chain is preferred.

[0065] From the viewpoint of more effectively exerting the effects of the present invention, the above component (A) is preferably a compound represented by the following general formula (1).

[0066] [Chemical formula 1]

[0067]

[0068] (In the general formula (1), R 1 is a hydrogen atom or an ester residue having 1 to 20 carbon atoms, R 2 and R 3 are hydrogen atoms or organic groups having 1 to 20 carbon atoms, and n is an integer of 20 to 800.)

[0069] In the above general formula (1), the ester residue having 1 to 20 carbon atoms can be any of linear, branched, and cyclic forms. For example, methyl ester residue, ethyl ester residue, n-propyl ester residue, isopropyl ester residue, n-butyl ester residue, isobutyl ester residue, tert-butyl ester residue, pentyl ester residue, hexyl ester residue, heptyl ester residue, octyl ester residue, cyclopentyl ester residue, cyclohexyl ester residue, etc. can be cited. Among them, as the above ester residue, an ester residue having 2 to 14 carbon atoms is preferred. In addition, in general formula (1), as the organic group, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 20 carbon atoms such as alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms, and aralkyl group having 7 to 20 carbon atoms can be cited. As the above organic group, from the viewpoint of improving reactivity, a hydrogen atom or an alkyl group is preferred, and among them, a hydrogen atom or a methyl group is more preferred. In addition, in general formula (1), n is 20 to 800, and among them, 50 to 400 is preferred.

[0070] When the above component (A) is a poly(meth)acrylate having a (meth)acryloyl group at the molecular chain end, as a method for its synthesis, a known synthesis method can be used. For example, it can be synthesized by radical polymerization of a (meth)acrylic acid monomer. Among them, living radical polymerization and atom transfer radical polymerization are preferred.

[0071] In addition, the poly(meth)acrylate having a (meth)acryloyl group at the molecular chain end as described above can also be obtained as a commercial product. For example, RC-100C, RC-200C (manufactured by Kaneka Corporation, etc.) can be cited.

[0072] <Component (B)>

[0073] The monofunctional (meth)acrylic acid monomer as the above component (B) is a (meth)acrylate compound having one (meth)acryloyl group in the molecular structure. Moreover, component (B) is a monofunctional (meth)acrylic acid monomer having a glass transition temperature (Tg) of 0 °C or lower.

[0074] The glass transition temperature (Tg) of the above component (B) is preferably -40 °C or lower, more preferably -50 °C or lower. In addition, the lower limit value of the glass transition temperature (Tg) of the above component (B) is not particularly limited, for example, it is -100 °C.

[0075] Regarding the glass transition temperature (Tg) of this component (B), for the homopolymer of this monofunctional (meth)acrylic acid monomer, it is measured by a differential scanning calorimeter (DSC) by the same method as the method described above.

[0076] As the component (B) described above, specifically, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, mono(2-acryloyloxyethyl) succinate, mono(2-acryloyloxyethyl) phthalate, 2-acryloyloxyethyl hexahydrophthalate, 2-acryloyloxyethyl-2-hydroxyethyl-phthalate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate, etc. can be used alone or in combination of two or more. Among them, from the viewpoints of low-temperature elongation rate and the like, n-butyl acrylate and 2-ethylhexyl acrylate are more preferable.

[0077] In addition, in the materials of the rubber composition of the present invention, when "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" is used as the adhesive component, this substance can be a substance equivalent to the above-mentioned component (B). For example, the above-mentioned mono(2-acryloyloxyethyl) succinate, mono(2-acryloyloxyethyl) phthalate, 2-acryloyloxyethyl hexahydrophthalate, 2-acryloyloxyethyl-2-hydroxyethyl-phthalate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate, etc. are equivalent to the above-mentioned adhesive component. Among them, from the viewpoints of adhesiveness and the like, mono(2-acryloyloxyethyl) succinate, mono(2-acryloyloxyethyl) phthalate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxybutyl acrylate are more preferable.

[0078] In addition, when "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" is equivalent to the above-mentioned component (B), the proportion of "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" relative to the whole of the above-mentioned component (B) is preferably in the range of 1 to 100% by weight, more preferably in the range of 20 to 80% by weight.

[0079] From the viewpoint of further improving the effects of the present invention, the content of the above-mentioned component (B) is preferably in the range of 1 to 90 parts by weight, more preferably in the range of 5 to 50 parts by weight, relative to 100 parts by weight of the component (A).

[0080] In addition, as described above, when the "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" corresponds to the above component (B), the above ratio is the ratio of the component (B) containing the "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group)".

[0081] <Component (C)>

[0082] The monofunctional (meth)acrylic monomer as the above component (C) is a (meth)acrylate compound having one (meth)acryloyl group in the molecular structure. Moreover, the component (C) is a monofunctional (meth)acrylic monomer having a glass transition temperature (Tg) of 50 °C or higher.

[0083] The glass transition temperature (Tg) of the above component (C) is preferably 70 °C or higher, more preferably 90 °C or higher. In addition, the upper limit value of the glass transition temperature (Tg) of the above component (C) is not particularly limited, for example, it is 250 °C.

[0084] Regarding the glass transition temperature (Tg) of this component (C), for the homopolymer of this monofunctional (meth)acrylic monomer, it is measured by a differential scanning calorimeter (DSC) by the same method as the method described above.

[0085] As the above component (C), specifically, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, (meth)acrylic acid, dicyclopentenyl (meth)acrylate, (meth)acryloylmorpholine, dimethyl (meth)acrylamide, 2-hydroxyethyl (meth)acrylamide, isopropyl (meth)acrylamide, diethyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, 2-hydroxyethyl methacrylate, etc. can be used alone or in combination of two or more. Among them, from the viewpoints of tensile strength, high-temperature elongation rate, etc., isobornyl (meth)acrylate and dicyclopentyl (meth)acrylate are more preferred.

[0086] In addition, among the materials of the rubber composition of the present invention, when a "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" is used as an adhesive component, this substance may be a substance corresponding to the above component (C). For example, the aforementioned 2-hydroxyethyl (meth)acrylamide, isopropyl (meth)acrylamide, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, (meth)acryloylmorpholine, (meth)acrylic acid, 2-hydroxyethyl methacrylate, etc. correspond to the above adhesive component. Among them, from the viewpoints of adhesiveness and the like, 2-hydroxyethyl (meth)acrylamide, isopropyl (meth)acrylamide, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, and dimethylaminopropyl (meth)acrylamide are more preferred.

[0087] In addition, when a "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" corresponds to the above component (C), the proportion of the "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" relative to the entire above component (C) is preferably in the range of 1 to 100% by weight, and more preferably in the range of 20 to 80% by weight.

[0088] From the viewpoint of further improving the effects of the present invention, the content of the above component (C) is preferably in the range of 1 to 90 parts by weight, and more preferably in the range of 5 to 50 parts by weight, relative to 100 parts by weight of the component (A).

[0089] In addition, as described above, when a "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" corresponds to the above component (C), the above proportion is the proportion of the component (C) that is a "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group".

[0090] In addition, in the present invention, the total content of the components (B) and (C) relative to 100 parts by weight of the above component (A) is 10 to 100 parts by weight. From the viewpoint of further improving the effects of the present invention, it is preferably 15 to 90 parts by weight, and more preferably 20 to 80 parts by weight.

[0091] Furthermore, in the present invention, the weight ratio of the component (B) to the above component (C) [(B) / (C)] is 0.1 to 20. From the viewpoint of further improving the effects of the present invention, it is preferably 0.15 to 15, and more preferably 0.2 to 10.

[0092] In addition, as described above, when the "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" corresponds to the above component (B) or (C), each of the above ratios is the ratio of the component (B) or (C) containing the "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group".

[0093] <(D) (Adhesive component)>

[0094] When a (meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group is used as the above-mentioned components (B) and (C), it is not necessary to contain other (meth)acrylic acid monomers having any one of a carboxyl group, a hydroxyl group, and an amide group, or a silane coupling agent in the rubber composition of the present invention. However, in other cases, it is necessary to separately contain a (meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group, and a silane coupling agent as the component (D) (adhesive component) in the rubber composition of the present invention. As the above-mentioned adhesive component (D), a (meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group and a silane coupling agent can be used in combination, or any one of them can be used.

[0095] In addition, examples of the (meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group that does not correspond to the above-mentioned components (B) and (C) but corresponds to the above-mentioned adhesive component (D) include 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxypropyl methacrylate, and mono(2-methacryloyloxyethyl) succinate.

[0096] In addition, in the materials of the rubber composition of the present invention, when a silane coupling agent is used as the adhesive component (D), examples of the silane coupling agent include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris(2-methoxyethoxy)silane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-2(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. They can be used alone or in combination of two or more.

[0097] From the viewpoint of further improving the effects of the present invention, the content of the above-mentioned adhesive component (D) is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 7.5 parts by weight, relative to 100 parts by weight of the component (A).

[0098] <Various additives>

[0099] In the materials of the rubber composition of the present invention, in addition to the above-mentioned components (A) to (C) and component (D) which are essential components thereof, the following components (E) to (G) can be appropriately blended.

[0100] <Component (E)>

[0101] In the materials of the rubber composition of the present invention, a polyfunctional (meth)acrylic monomer (E) can be blended. The above-mentioned polyfunctional (meth)acrylic monomer (E) is a (meth)acrylate compound having two or more (meth)acryloyl groups in its molecular structure. Specifically, known ethylenically unsaturated polyfunctional monomers can be cited. As the (meth)acrylic monomer having two (meth)acryloyl groups in its molecular structure, for example, 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2,4-diethyl-1,5-pentanediol di(meth)acrylate, butylethylpropanediol di(meth)acrylate, 3-methyl-1,7-octanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate and other alkanediol di(meth)acrylates, ethoxylated cyclohexanedimethanol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, propoxylated ethoxylated bisphenol A di(meth)acrylate, 1,1,1-trimethylol ethane di(meth)acrylate and the like can be cited.

[0102] As the (meth)acrylic monomer having three or more methacryloyl groups, for example, trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxytri(meth)acrylate, trimethylolpropane propoxytri(meth)acrylate, glycerol propoxytri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, bis(trimethylolpropane) tetra(meth)acrylate, monopentaerythritol (meth)acrylate, dipentaerythritol (meth)acrylate, tripentaerythritol (meth)acrylate, pentaerythritol acrylate compounds such as poly(pentaerythritol) (meth)acrylate having a pentaerythritol structure and a (meth)acrylate structure, etc. can be cited.

[0103] The above-mentioned component (E) can be used alone or in combination of two or more. In addition, among the above-mentioned component (E), from the viewpoint of further improving the effects of the present invention, 1,9-nonanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2,4-diethyl-1,5-pentanediol di(meth)acrylate, butylethylpropanediol di(meth)acrylate, 3-methyl-1,7-octanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate and other alkanediol di(meth)acrylates, and pentaerythritol acrylate-based compounds are preferred. Among them, 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate are more preferred.

[0104] The number of carbon atoms in the molecular chain (main chain) of the polyfunctional (meth)acrylic monomer of the above-mentioned component (E) is preferably 6 or more. If the number of carbon atoms is less than the above value, a tendency of poor high-temperature elongation and low-temperature elongation can be observed.

[0105] In addition, in the materials of the rubber composition of the present invention, when "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" is used as an adhesive component, this substance may be a substance equivalent to the above-mentioned component (E). Specifically, substances in which any one of a carboxyl group, a hydroxyl group, and an amide group is bonded to the molecular chain of the above-listed compounds can be cited. In addition, when "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" is equivalent to the above-mentioned component (E), the proportion of "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" relative to the total amount of the above-mentioned component (E) is preferably in the range of 1 to 100% by weight, and more preferably in the range of 20 to 80% by weight.

[0106] From the viewpoint of further improving the effects of the present invention, the content of the above-mentioned component (E) is preferably in the range of 0.1 to 10 parts by weight, and more preferably in the range of 0.2 to 7.5 parts by weight, relative to 100 parts by weight of the component (A).

[0107] In addition, when the "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" described above corresponds to the above component (E), the content of the component (E) represents the proportion including the "(meth)acrylic acid monomer having any one of a carboxyl group, a hydroxyl group, and an amide group)".

[0108] <Component (F)>

[0109] In the material of the rubber composition of the present invention, a photo radical polymerization initiator (F) can be blended. As the photo radical polymerization initiator of the above component (F), a compound that generates radicals by irradiating energy rays is preferred. For example, benzophenone type compounds such as benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, anthraquinone type compounds such as tert-butyl anthraquinone, 2-ethyl anthraquinone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, oligomer {2-hydroxy-2-methyl-1-[4-(1-methylethenyl)phenyl]propanone}, benzyldimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoin methyl ether, 2-methyl-[4-(methylthio)phenyl]-2-morpholin-1-propanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropanoyl)benzyl]phenyl}-2-methylpropan-1-one and other alkylbenzophenone type compounds, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, diethyl thioxanthone, isopropyl thioxanthone and other thioxanthone type compounds, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and other acylphosphine oxide type compounds, methyl phenylglyoxylate and other phenylglyoxylate type compounds, etc. They can be used alone or in combination of two or more. Among them, from the viewpoint of excellent reactivity, alkylbenzophenone type compounds are preferred, and specifically, 2-hydroxy-2-methyl-1-phenylpropan-1-one and the like are preferred.

[0110] When the above component (F) is contained, its content is preferably in the range of 0.01 to 10 parts by weight, more preferably 0.1 to 10 parts by weight, relative to 100 parts by weight of the component (A).

[0111] <Component (G)>

[0112] An anti-aging agent (G) can be incorporated into the materials of the rubber composition of the present invention. The anti-aging agent as the above-mentioned component (G) is not particularly limited. For example, amine-based anti-aging 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, bis(4-octylphenyl)amine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonamide)diphenylamine, N-phenyl-N'-(1,3-dimethylbutyl)p-phenylenediamine, etc.; phenolic anti-aging agents such as 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butylphenol, 2,4,6-tri-tert-butylphenol, styrenated phenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-methylenebis(2,6-tert-butylphenol), 4,4'-isopropylidenebis(2,6-di-tert-butylphenol), 2,2'-isobutylidenebis(4,6-dimethylphenol), etc.; imidazole-based anti-aging agents such as 2-mercaptobenzimidazole, zinc salt of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, etc.; sulfur-based anti-aging agents such as dilauryl thiodipropionate, distearyl thiodipropionate, etc. They can be used alone or in combination of two or more. Among them, amine-based anti-aging agents and phenolic anti-aging agents are preferred, and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine is more preferred.

[0113] When the above-mentioned component (G) is contained, its content is preferably in the range of 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the component (A).

[0114] <Other additives>

[0115] In the materials of the rubber composition of the present invention, in addition to the above-mentioned components (A) to (G), various additives such as fillers (silica, carbon black, calcium carbonate, titanium oxide, talc, clay, glass beads, etc.), compatibilizers, curing property regulators, lubricants, pigments, defoaming agents, foaming agents, light stabilizers, surface modifiers, etc. can be incorporated within the range that does not impair the effects of the present invention.

[0116] <Manufacturing method of the sealing member>

[0117] The above-mentioned rubber composition as the forming material of the sealing member of the present invention is prepared, for example, by manually stirring each material other than the component (A) using a warm water bath and then adding the component (A) and mixing using a mixer.

[0118] From the viewpoint of formability, the viscosity of the above rubber composition at 23°C (viscosity obtained by a B-type viscometer) is preferably 0.1 to 1000 Pa·s, more preferably 0.5 to 500 Pa·s.

[0119] Then, the above rubber composition is coated on various constituent members such as separators of fuel cells by various methods such as dispenser, spraying, inkjet, screen printing, etc., and irradiated with active energy rays to crosslink it, whereby a sealing member can be produced.

[0120] Alternatively, it can also be produced by coating the above rubber composition on the surface of various constituent members of a fuel cell coated with an adhesive and irradiating it with active energy rays to cure it.

[0121] Furthermore, methods such as FIPG (Form-in-Place Gasket), CIPG (Cure-in-Place Gasket), MIPG (Mold-in-Place Gasket), etc. can also be used to produce the above sealing member.

[0122] Alternatively, the above rubber composition can also be preformed into a predetermined shape according to the shape of the sealed object part of various constituent members of a fuel cell using a mold or the like. Even if formed as described above, since it exhibits viscosity, it can also exhibit sealing performance. Additionally, for example, the material obtained by forming as described above can be pasted using an adhesive as needed for use.

[0123] <Sealing method>

[0124] The constituent members of a fuel cell are sealed using the above rubber composition or sealing member, and the above rubber composition or sealing member is irradiated with active energy rays to crosslink it, whereby sealing can be performed in a short time (for example, about several tens of seconds). In addition, the rubber composition of the present invention can be easily formed into a film-like sealing member, and by thinning the sealing member, miniaturization of the fuel cell can be achieved. Specifically, for example, it is easy to make the thickness of the film-like sealing member 50 to 1000 μm, and miniaturization of the fuel cell can be achieved. Furthermore, the sealing member of the present invention has excellent flexibility, elongation rate in a wide temperature range from low temperature to high temperature, excellent sealing performance, and can reduce damage to the electrolyte membrane.

[0125] In addition, the rubber composition and even the sealing member of the present invention are crosslinked by active energy rays such as electron rays and ultraviolet rays, but if necessary, heating can also be assisted to crosslink it. Additionally, since the damage to MEA etc. is small, crosslinking using ultraviolet rays is preferred. As the active energy source, there is no particular limitation, and known active energy sources can be used, for example, high-pressure mercury lamps, black lights, LEDs, fluorescent lamps, etc.

[0126] The sealing member of the present invention is used for the constituent members of a fuel cell. Moreover, as described above, in the sealing member of the present invention, since the damage to the MEA or the like is small, it is preferably an ultraviolet crosslinked body. In addition, since crosslinking can be carried out even without incorporating a photo radical polymerization initiator (F), it can also be an electron beam crosslinked body.

[0127] <Fuel cell>

[0128] The constituent members for a fuel cell sealed by the rubber composition or the sealing member of the present invention vary depending on the type, structure, etc. of the fuel cell. For example, there can be cited separators (metal separators, carbon separators, etc.), gas diffusion layers, MEA (electrolyte membrane, electrodes), etc.

[0129] An example of the sealing member of the present invention is as Figure 1 shown. Figure 1 Mainly shown is a single cell unit 1 in a fuel cell formed by stacking a plurality of cell units. The cell unit 1 includes an MEA 2, a gas diffusion layer 3, a sealing member 4, and a separator 5. Moreover, between the separator 5 constituting the above cell unit 1 and the end of the MEA 2, it is sealed by the sealing member 4 (the sealing member of the present invention).

[0130] The above sealing member 4 is manufactured by the manufacturing method described above and is sealed according to the sealing method described above. In addition, since the adhesiveness of the above sealing member 4 is excellent, the adhesion reliability to the separator 5, MEA 2, etc. is very high even without passing through an adhesive layer. Since it is not necessary to separately provide such an adhesive layer, the above sealing member 4 can contribute to the simplification of the manufacturing process of the fuel cell.

[0131] Although not shown, the MEA 2 is composed of an electrolyte membrane and a pair of electrodes disposed on both sides in the stacking direction with the electrolyte membrane interposed therebetween. The electrolyte membrane and the pair of electrodes are in the shape of a rectangular thin plate. The gas diffusion layers 3 are disposed on both sides in the stacking direction with the MEA 2 interposed therebetween. The gas diffusion layer 3 is a porous layer and is in the shape of a rectangular thin plate.

[0132] The separator 5 is preferably a separator made of carbon or metal, and from the viewpoint of conduction reliability, a metal separator having a carbon thin film such as a DLC film (diamond-like carbon film) or a graphite film is particularly preferred. The separator 5 is in the shape of a rectangular thin plate and is recessed in total with six grooves extending in the length direction. Through these grooves, the cross section of the separator 5 has a concavo-convex shape. The separator 5 is arranged to face both sides in the stacking direction of the gas diffusion layer 3. Between the gas diffusion layer 3 and the separator 5, a gas flow path 6 for supplying gas to the electrode is defined by the concavo-convex shape.

[0133] During the operation of a fuel cell such as a solid polymer fuel cell, a fuel gas and an oxidant gas are respectively supplied through a gas flow path 6. Here, the peripheral portion of the MEA2 is sealed by a sealing member 4. Therefore, gas mixing and leakage do not occur.

[0134] Example

[0135] Hereinafter, examples will be described together with comparative examples. However, the present invention is not limited to these examples as long as it does not exceed its gist.

[0136] First, before the examples and comparative examples, the following materials are prepared.

[0137] <(Component (A) (specific polymer having a (meth)acryloyl group))>

[0138] [Polymer A1 (synthesis example)]

[0139] According to a known method (for example, described in Japanese Patent Application Laid-Open No. 2012-211216), cuprous bromide is used as a catalyst, pentamethyldiethylenetriamine is used as a ligand, and diethyl 2,5-dibromohexanedioate is used as a radical polymerization initiator. As the acrylic acid monomers, 50 parts by weight / 50 parts by weight of 2-ethylhexyl acrylate / n-butyl acrylate are used, and the acrylic acid monomer / radical polymerization initiator ratio (molar ratio) is set to 180 for polymerization to obtain a copolymer of 2-ethylhexyl acrylate / n-butyl acrylate with a terminal bromo group. This copolymer is dissolved in N,N-dimethylacetamide, potassium acrylate is added, and heating and stirring are carried out at 70 °C under a nitrogen atmosphere. After removing N,N-dimethylacetamide from this mixed solution by vacuum distillation, butyl acetate is added to the residue, and insoluble components are removed by filtration. Butyl acetate in the filtrate is removed by vacuum distillation to obtain a copolymer of 2-ethylhexyl acrylate / n-butyl acrylate having an acryloyl group at the terminal [Polymer A1]. The number average molecular weight is 23000, the molecular weight distribution is 1.1, and the average number of acryloyl groups introduced per molecule of the polymer is obtained by 1 1H-NMR analysis, and the result is about 1.9. In addition, the glass transition temperature (Tg) is -50 °C.

[0140] [Polymer A2 (synthesis example)]

[0141] The acrylic acid monomer / radical polymerization initiator ratio is set to 60, and otherwise, a copolymer of 2-ethylhexyl acrylate / n-butyl acrylate having an acryloyl group at the terminal [Polymer A2] is obtained in the same manner as the acryloyl-terminated polyacrylate [Polymer A1]. The number average molecular weight is 3000, the molecular weight distribution is 1.2, and by 1The average number of acryloyl groups introduced per molecule of the polymer was determined by 1H-NMR analysis to be about 1.8. In addition, the glass transition temperature (Tg) was -50°C.

[0142] [Polymer A3 (Synthesis Example)]

[0143] The ratio of acrylic acid monomer to free radical polymerization initiator was set to 120, and otherwise, by the same method as acryloyl-terminated polyacrylate [Polymer A1], a 2-ethylhexyl acrylate / n-butyl acrylate copolymer [Polymer A3] having an acryloyl group at the terminal was obtained. The number average molecular weight was 12,000, and the molecular weight distribution was 1.1. By 1 1H-NMR analysis was used to determine the average number of acryloyl groups introduced per molecule of the polymer, and the result was about 1.9. In addition, the glass transition temperature (Tg) was -50°C.

[0144] [Polymer A4 (Synthesis Example)]

[0145] The ratio of acrylic acid monomer to free radical polymerization initiator was set to 550, and otherwise, by the same method as acryloyl-terminated polyacrylate [Polymer A1], a 2-ethylhexyl acrylate / n-butyl acrylate copolymer [Polymer A4] having an acryloyl group at the terminal was obtained. The number average molecular weight was 95,000, and the molecular weight distribution was 1.4. By 1 1H-NMR analysis was used to determine the average number of acryloyl groups introduced per molecule of the polymer, and the result was about 2.0. In addition, the glass transition temperature (Tg) was -51°C.

[0146] [Polymer A5]

[0147] BAC-45, acryloyl-terminated polybutadiene, manufactured by Osaka Organic Chemical Industry Co., Ltd., glass transition temperature (Tg): -64°C, number average molecular weight: 3000

[0148] [Polymer A6]

[0149] UC-203M, acryloyl-modified polyisoprene, manufactured by KURARAY Co., Ltd., glass transition temperature (Tg): -60°C, number average molecular weight: 35,000

[0150] <Component (B) (monofunctional (meth)acrylic acid monomer having a glass transition temperature (Tg) of 0°C or lower)>

[0151] HA (2-ethylhexyl acrylate, Tg: -70°C, manufactured by Mitsubishi Chemical Corporation)

[0152] BA (n-butyl acrylate, Tg: -55°C, manufactured by Mitsubishi Chemical Corporation)

[0153] HOA-MS(N) (Light Acrylate HOA-MS(N), mono(2-acryloyloxyethyl) succinate, Tg: -40 °C, manufactured by Kyoeisha Chemical Co., Ltd.)

[0154] HOP-A(N) (Light Ester HOP-A(N), 2-hydroxypropyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd., Tg: -7 °C)

[0155] ※ In addition, the above HOA-MS(N) and HOP-A(N) also function as adhesive components.

[0156] <(C) component (monofunctional (meth)acrylic monomer with a glass transition temperature (Tg) of 50 °C or higher)>

[0157] IB-X (Light Ester IB-X, isobornyl methacrylate, Tg: 180 °C, manufactured by Kyoeisha Chemical Co., Ltd.)

[0158] FA-513M (dicyclopentanyl methacrylate, Tg: 175 °C, manufactured by Hitachi Chemical Co., Ltd.)

[0159] IBXA (isobornyl acrylate, Tg: 97 °C, manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0160] NIPAM (N-isopropylacrylamide, Tg: 134 °C, manufactured by KJ Chemicals Co., Ltd.)

[0161] ※ In addition, the above NIPAM also functions as an adhesive component.

[0162] <(D) component (adhesive component)>

[0163] KBM-503 (3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0164] KBM-5103 (3-acryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0165] HO-MS(N) (Light Ester HO-MS(N), mono(2-methacryloyloxyethyl) succinate, Tg: 20 °C, manufactured by Kyoeisha Chemical Co., Ltd.)

[0166] <(E) component (polyfunctional monomer)>

[0167] Blemmer NDMA (1,9-nonanediol dimethacrylate, manufactured by NOF Corporation)

[0168] <(F) Component (Photoinitiator for Free Radical Polymerization)>

[0169] Omnirad1173 (2-Hydroxy-2-methyl-1-phenylpropan-1-one, manufactured by iGM RESINS Co., Ltd.)

[0170] <(G) Component (Antioxidant)>

[0171] NONFLEX DCD (4,4'-Bis(α,α-dimethylbenzyl)diphenylamine, manufactured by Seiko Chemical Co., Ltd.)

[0172] [Examples 1 to 28, Comparative Examples 1 to 7]

[0173] (Preparation of Rubber Composition for Fuel Cell Sealing)

[0174] The respective components shown in Tables 1 to 3 described later were blended in the proportions shown in the tables to prepare a rubber composition. At this time, after manually stirring the materials other than the (A) component using a warm water bath, the (A) component was added, and the mixture was mixed using a planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) to prepare the above rubber composition.

[0175] Then, using the above rubber composition, the evaluation of each characteristic was carried out according to the following criteria. The results are shown together in Tables 1 to 3 described later.

[0176] In addition, for the above rubber compositions other than the rubber composition of Example 20, ultraviolet rays (UV) were irradiated (irradiation intensity: 250 mW / cm 2 , cumulative light amount: 3000 mJ / cm 2 ) using a high-pressure mercury UV irradiator (manufactured by Heraeus Co., Ltd., F600V-10) for crosslinking, and the evaluation of each of the following characteristics was carried out.

[0177] For the rubber composition of Example 20, electron beam (EB) was irradiated (acceleration voltage: 250 kV, irradiation dose: 400 kGy) using a standard EB testing machine (EC250) manufactured by Iwasaki Electric Co., Ltd. for crosslinking, and the evaluation of each of the following characteristics was carried out.

[0178] <Adhesion to Electrolyte Membrane>

[0179] An electrolyte membrane with a thickness of 0.1 mm (manufactured by Chemours Company, Nafion NR212) was cut into a length of 50 mm × a width of 10 mm. After setting it at a predetermined position of a frame jig having a hole of 50 mm × 10 mm × a depth of 1 mm, the above rubber composition was poured into the hole of the frame jig to crosslink the rubber composition. Then, the crosslinked body (rubber layer) of the rubber composition was blanked into strips with a width of 10 mm from the frame jig, and an adhesion evaluation sample was obtained by bonding an electrolyte membrane with a length of 50 mm × a width of 10 mm and a rubber layer with a length of 50 mm × a width of 10 mm in an overlapping manner of 10 mm in the length direction. Then, the two ends in the length direction of the above adhesion evaluation sample were clamped with a chuck, and after performing a tensile test at a tensile speed of 10 mm / min with respect to the length direction of the adhesion evaluation sample, the adhesion surface between the electrolyte membrane and the rubber layer was visually evaluated according to the following criteria.

[0180] ○: Material rupture of the rubber occurred on the entire bonding surface.

[0181] ×: Interface peeling.

[0182] <Adhesion to SUS304>

[0183] A plate made of SUS304 (SUS304 plate) with a thickness of 0.1 mm was cut into a length of 50 mm × a width of 10 mm. After setting it at a predetermined position of a frame jig having a hole of 50 mm × 10 mm × a depth of 1 mm, the above rubber composition was poured into the hole of the frame jig to crosslink the rubber composition. Then, the crosslinked body (rubber layer) of the rubber composition was blanked into strips with a width of 10 mm from the frame jig, and an adhesion evaluation sample was obtained by bonding a SUS304 plate with a length of 50 mm × a width of 10 mm and a rubber layer with a length of 50 mm × a width of 10 mm in an overlapping manner of 10 mm in the length direction. Then, the two ends in the length direction of the above adhesion evaluation sample were clamped with a chuck, and after performing a tensile test at a tensile speed of 10 mm / min with respect to the length direction of the adhesion evaluation sample, the adhesion surface between the SUS304 plate and the rubber was visually evaluated according to the following criteria.

[0184] ○: Material rupture of the rubber occurred on the entire bonding surface.

[0185] ×: Interface peeling.

[0186] <100% modulus, high temperature elongation, low temperature elongation>

[0187] JIS No. 3 dumbbells were blanked from a sheet obtained by crosslinking a material coated with the above rubber composition using a rod coater, and a tensile test was performed in accordance with JIS K 6250 and JIS K 6251.

[0188] Then, the stress at 100% elongation at 23°C (100% modulus (MPa)), the elongation at break at high temperature (80°C) and low temperature (-30°C) (high temperature elongation (%), low temperature elongation (%)) are measured.

[0189] Based on the above measurement results, the 100% modulus is evaluated according to the following criteria.

[0190] ◎: Less than 1.0 Mpa

[0191] ○: 1.0 Mpa or more and less than 3.0 Mpa

[0192] ×: 3.0 Mpa or more

[0193] In addition, based on the above measurement results, the high temperature elongation and low temperature elongation are evaluated according to the following criteria.

[0194] ◎: Exceeding 150%

[0195] ○: 100 - 150%

[0196] ×: Less than 100%

[0197] "Comprehensive Evaluation"

[0198] When all characteristics are evaluated as "○" or "◎", and the number of "◎" is two or more, the comprehensive evaluation is "◎". In addition, when all characteristics are evaluated as "○" or "◎", and the number of "◎" is less than two, the comprehensive evaluation is "○". In addition, when there is even one "×" in the evaluation of each characteristic, the comprehensive evaluation is "×".

[0199] Table 1 (parts by weight)

[0200]

[0201] ※: Indicates a substance that also corresponds to the adhesive component.

[0202] Table 2 (parts by weight)

[0203]

[0204] ※: Indicates a substance that also corresponds to the adhesive component.

[0205] Table 3 (parts by weight)

[0206]

[0207] ※: Indicates a substance that also corresponds to the adhesive component.

[0208] As can be seen from the results of Tables 1 to 3 above, in Examples 1 to 28 that satisfy the requirements of the present invention, the adhesiveness to the electrolyte membrane and SUS304 is excellent, and thus the sealing performance is excellent. In addition, it can be seen that in Examples 1 to 28, the 100% modulus is small, so the flexibility is excellent, and the low-temperature elongation rate and high-temperature elongation rate are also excellent. Furthermore, in Examples 1 to 28, since it is formed by UV crosslinking or EB crosslinking, damage to the electrolyte membrane can be reduced.

[0209] In contrast, in Comparative Example 1, the (C) component is not included, resulting in a poor evaluation of the high-temperature elongation rate. In Comparative Example 2, the (B) component is not included, resulting in poor evaluations of the 100% modulus and low-temperature elongation rate. In Comparative Example 3, the value of [(B) / (C)] (weight ratio) is greater than the specified range of the present invention, resulting in a poor evaluation of the high-temperature elongation rate. In Comparative Example 4, the value of [(B) / (C)] (weight ratio) is less than the specified range of the present invention, resulting in poor evaluations of the 100% modulus and low-temperature elongation rate. In Comparative Example 5, substances that can be adhesive components such as the (D) component are not included (at least one selected from the group consisting of (meth)acrylic acid monomers having any one of a carboxyl group, a hydroxyl group, and an amide group and a silane coupling agent), resulting in poor adhesiveness to the electrolyte membrane and SUS304. In Comparative Example 6, the proportion of [(B)+(C)] is greater than the specified range of the present invention, resulting in a poor evaluation of the low-temperature elongation rate. In Comparative Example 7, the proportion of [(B)+(C)] is less than the specified range of the present invention, resulting in poor evaluations of the high-temperature elongation rate and low-temperature elongation rate.

[0210] Furthermore, in the above examples, specific embodiments of the present invention are shown, but the above examples are merely examples and should not be construed in a limiting manner. It is intended to include various modifications apparent to those skilled in the art within the scope of the present invention.

[0211] Industrial Applicability

[0212] The rubber composition and the sealing member of the present invention are used for constituting members of a fuel cell. Moreover, in addition to the members treated as the sealing member alone and the members treated in the form of being assembled in a fuel cell, for example, it can also be used for a fuel cell sealing body formed by bonding a fuel cell constituent member such as a metal separator to the above sealing member.

[0213] Explanation of Reference Numerals

[0214] 1: Cell unit;

[0215] 2: MEA;

[0216] 3: Gas diffusion layer;

[0217] 4: Sealing member;

[0218] 5: Partition board;

[0219] 6: Gas flow path.

Claims

1. A rubber composition for fuel cell sealing, which is a rubber composition for fuel cell sealing showing free radical crosslinkability and having the following component (A) as the main component and containing the following components (B) and (C), characterized in that, the total content of components (B) and (C) relative to 100 parts by weight of component (A) is 10 to 100 parts by weight, the weight ratio of component (B) to component (C) [(B) / (C)] is 0.1 to 20, and the rubber composition for fuel cell sealing contains at least one selected from the group consisting of (meth)acrylic monomers having any one of a carboxyl group, a hydroxyl group, and an amide group and a silane coupling agent as an adhesive component, (A) At least one polymer having a (meth)acryloyl group and selected from the group consisting of poly(meth)acrylate, polyisoprene, polybutadiene, polyurethane, and polyester, (B) A monofunctional (meth)acrylic monomer having a glass transition temperature of 0 °C or lower, (C) A monofunctional (meth)acrylic monomer having a glass transition temperature of 50 °C or higher, the number average molecular weight of the component (A) is 3000 to 100000, as the adhesive component, when containing "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" corresponding to component (B), the proportion of "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" relative to the whole of component (B) is 1 to 100% by weight; as the adhesive component, when containing "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" corresponding to component (C), the proportion of "(meth)acrylic monomer having any one of a carboxyl group, a hydroxyl group, and an amide group" relative to the whole of component (C) is 1 to 100% by weight; as the adhesive component, when additionally containing a (D) adhesive component of "at least one selected from the group consisting of (meth)acrylic monomers having any one of a carboxyl group, a hydroxyl group, and an amide group and a silane coupling agent", the content of the adhesive component (D) is 0.1 to 10 parts by weight relative to 100 parts by weight of component (A).

2. The rubber composition for fuel cell sealing according to claim 1, wherein, the glass transition temperature of the component (A) is -40 °C or lower.

3. The rubber composition for fuel cell sealing according to claim 1 or 2, wherein, the component (A) is at least one selected from the group consisting of poly(meth)acrylate, polyisoprene, and polybutadiene having a (meth)acryloyl group.

4. The rubber composition for fuel cell sealing according to claim 1 or 2, wherein, the component (A) is a polymer having a (meth)acryloyl group at the molecular chain end.

5. The rubber composition for fuel cell sealing according to claim 1 or 2, wherein, the component (A) is a poly(meth)acrylate having a (meth)acryloyl group at the molecular chain end.

6. The rubber composition for fuel cell sealing according to claim 1 or 2, wherein, The rubber composition for fuel cell sealing further contains a photo radical polymerization initiator.

7. The rubber composition for fuel cell sealing according to claim 1 or 2, wherein, the rubber composition for fuel cell sealing further contains a polyfunctional (meth)acrylic monomer.

8. A sealing member for fuel cell, characterized in that, the sealing member for fuel cell is formed of a crosslinked product of the rubber composition for fuel cell sealing according to any one of claims 1 to 7.

9. A fuel cell, which is a fuel cell formed by stacking a plurality of cell units, the cell unit having a separator and a membrane electrode assembly as constituent members, and the end portion between the separator and the membrane electrode assembly being sealed, characterized in that, the end portion between the separator and the membrane electrode assembly constituting the cell unit is sealed by at least one of a crosslinked product of the rubber composition for fuel cell sealing according to any one of claims 1 to 7 and the sealing member for fuel cell according to claim 8.

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