JP5268313B2 - Adhesive seal member for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive sealing member for a fuel cell capable of crosslinking at low temperatures and having high sealing performance and adhesive reliability. <P>SOLUTION: The adhesive sealing member 5 for the fuel cell adhesively-sealing between constitution members of the fuel cell is constituted with a crosslinking material of a rubber composition containing following (A) to (C). (A) is at least one or more rubber components selected from ethylene-propylene rubber, ethylene-propylene-diene rubber, acrylonitrile-butadiene rubber, and hydrogenated acrylonitrile-butadiene rubber; (B) is a crosslinker selected from organic peroxides having a one-hour half-life temperature of 120&deg;C or lower; and (C) is a silane coupling agent. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an adhesive seal member that adhesively seals members constituting a fuel cell.

  A fuel cell that generates electricity by an electrochemical reaction of gas has high power generation efficiency, clean gas discharged, and extremely little influence on the environment. Among these, the polymer electrolyte fuel cell can be operated at a relatively low temperature and has a large power density. For this reason, various uses, such as a power generation and a power supply for automobiles, are expected.

  In a polymer electrolyte fuel cell, a cell in which an electrolyte membrane electrode assembly (MEA) is sandwiched between separators serves as a power generation unit. The MEA includes a polymer membrane (electrolyte membrane) serving as an electrolyte and a pair of electrodes (fuel electrode and oxygen electrode) disposed on both sides of the electrolyte membrane. Each of the pair of electrodes includes a catalyst layer and a gas diffusion layer. A fuel gas such as hydrogen or hydrocarbon is supplied to the fuel electrode, and an oxidant gas such as oxygen or air is supplied to the oxygen electrode. Power generation is performed by an electrochemical reaction at the three-phase interface between the supplied gas, electrolyte, and electrode. The polymer electrolyte fuel cell is configured by fastening a cell stack in which a plurality of the cells are stacked with end plates or the like disposed at both ends in the cell stacking direction.

The separator is formed with a flow path of gas supplied to each electrode and a flow path of refrigerant for relaxing heat generation during power generation. For example, when the gas supplied to each electrode is mixed, problems such as a decrease in power generation efficiency occur. The electrolyte membrane has proton conductivity in a state containing water. For this reason, it is necessary to keep the electrolyte membrane in a wet state during operation. Therefore, in order to prevent gas mixing, gas and refrigerant leakage, and to keep the inside of the cell moist, a sealing property such as between the electrolyte membrane and the separator or between adjacent separators is secured. It becomes important. An epoxy resin, silicone rubber, or the like is used as a seal member for sealing between the constituent members of these fuel cells (see, for example, Patent Documents 1 and 2).
JP 2006-252858 A JP 2006-244765 A

  Silicone rubber can be crosslinked at a relatively low temperature and has excellent heat resistance and cold resistance. However, when silicone rubber is used as a sealing member, there are the following problems. That is, silicone rubber has low mechanical strength and high gas permeability. In addition, polymer membranes such as perfluorinated sulfonic acid membranes are used as electrolyte membranes for solid polymer fuel cells. For this reason, during operation, an acid such as hydrofluoric acid may be generated from the electrolyte membrane. However, the acid resistance of silicone rubber is not sufficient. In addition, an adhesive is separately required to bond the silicone rubber and a mating member such as a separator. Further, when the silicone rubber is crosslinked, a platinum catalyst is used. For this reason, from the viewpoint of preventing catalyst poisoning or the like, strict management of the working environment is required at the time of crosslinking. Accordingly, there is a need for a new seal member that replaces silicone rubber.

  On the other hand, as a sealing member for a fuel cell, one that can be crosslinked at a lower temperature and in a shorter time is desirable. As described above, the electrolyte membrane of the solid polymer fuel cell is a polymer membrane such as a perfluorinated sulfonic acid membrane. Here, in the case where the sealing member is disposed near the electrolyte membrane for crosslinking, it is necessary to consider that the electrolyte membrane is not deteriorated by heating at the time of crosslinking. That is, it is desirable to perform the crosslinking step at a lower temperature and in a shorter time.

  This invention is made | formed in view of such an actual condition, and makes it a subject to provide the adhesive sealing member for fuel cells which can be bridge | crosslinked at low temperature and has high sealing performance and adhesive reliability.

The adhesive seal member for a fuel cell of the present invention (hereinafter referred to as “adhesive seal member of the present invention” as appropriate) comprises a crosslinked product of a rubber composition containing the following (A) to (C): The structural members are bonded and sealed.
(A) One or more rubber components selected from ethylene-propylene rubber, ethylene-propylene-diene rubber, acrylonitrile-butadiene rubber, and hydrogenated acrylonitrile-butadiene rubber.
(B) A crosslinking agent selected from organic peroxides having a one-hour half-life temperature of 120 ° C. or lower.
(C) Silane coupling agent.

  In the adhesive seal member of the present invention, the rubbers listed in (A) above are used instead of silicone rubber. Since these rubbers have low gas permeability, sealing properties are improved. Here, the crosslinking of the rubbers listed in the above (A) is usually performed at a temperature of 150 ° C. or higher. However, in the adhesive seal member of the present invention, an organic peroxide having a one-hour half-life temperature of 120 ° C. or less is used as a crosslinking agent (above (B)). Here, the “half-life” is the time until the concentration of the organic peroxide becomes half of the initial value. Therefore, the “half-life temperature” is an index indicating the decomposition temperature of the organic peroxide. The “1 hour half-life temperature” is a temperature at which the half-life is 1 hour. In other words, the lower the one-hour half-life temperature, the easier it is to decompose at low temperatures. By using an organic peroxide having a one-hour half-life temperature of 120 ° C. or less, crosslinking can be performed at a lower temperature (specifically, 120 ° C. or less) and in a short time. Therefore, for example, the adhesive seal member of the present invention can be used also in the vicinity of the electrolyte membrane of the solid polymer fuel cell. Further, according to the crosslinking agent (B), a platinum catalyst used for crosslinking of the silicone rubber is not necessary at the time of crosslinking. In addition, it is difficult to cause poor curing due to impurities, dirt, and the like. For this reason, the adhesive seal member of the present invention is not easily affected by the working environment and is easy to handle.

  Moreover, the adhesive sealing member of this invention contains a silane coupling agent as an adhesive component (above (C)). For this reason, it is not necessary to separately use an adhesive in bonding with the constituent members of the fuel cell. According to the adhesive seal member of the present invention, a strong chemical bond is formed between the rubber component (adhesive seal member) and the constituent member via the silane coupling agent, and the two are bonded. The adhesive strength between the two is high, and the adhesive strength is unlikely to decrease even in the operating environment of the fuel cell. Therefore, according to the adhesive seal member of the present invention, good sealability is ensured even when the fuel cell is operated for a long time. Thereby, the operation reliability of the fuel cell can be improved.

  Below, embodiment of the adhesive seal member for fuel cells of this invention is described. The adhesive seal member for a fuel cell of the present invention is not limited to the following embodiments, and various modifications and improvements that can be made by those skilled in the art without departing from the gist of the present invention. It can be implemented in the form.

<Adhesive seal member for fuel cell>
The adhesive sealing member of this invention consists of a crosslinked material of the rubber composition containing said (A)-(C). First, the rubber component (A) is one or more selected from ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), and hydrogenated acrylonitrile-butadiene rubber (H-NBR). It is. One of these may be used alone, or two or more may be mixed and used.

  Next, the crosslinking agent (B) is selected from organic peroxides having a one-hour half-life temperature of 120 ° C. or less. Examples of such organic peroxides include diacyl peroxide, peroxy ester, and peroxydicarbonate. Among these, it is desirable to employ a diacyl peroxide having a one-hour half-life temperature of 90 ° C. or more because it is easily crosslinked at about 120 ° C. In particular, the one-hour half-life temperature is preferably less than 110 ° C, and more preferably less than 100 ° C.

  Examples of the diacyl peroxide include dibenzoyl peroxide, a mixture of di (3-methylbenzoyl) peroxide, benzoyl (3-methylbenzoyl) peroxide, and dibenzoyl peroxide. Examples of peroxyesters include t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, and the like. Of these, dibenzoyl peroxide is preferred because it is easy to store the crosslinking agent.

  In order to sufficiently advance the crosslinking reaction, the amount of the crosslinking agent is desirably 0.5 parts by weight or more with respect to 100 parts by weight of the rubber component (A). Further, considering the storage stability of the rubber composition prepared by adding a cross-linking agent, the content is preferably 5 parts by weight or less.

  Next, the silane coupling agent (C) may be appropriately selected from the group of compounds having an epoxy group, amino group, vinyl group or the like as a functional group in consideration of adhesiveness and the like. For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris (2-methoxyethoxy) silane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxy Examples thereof include silane, 3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. One of these may be used alone, or two or more may be mixed and used. In particular, when one or more selected from the group of compounds having an epoxy group is used, the adhesive force is improved and the adhesive force is hardly reduced even in the operating environment of the fuel cell. Specifically, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Etc. are suitable.

  In order to obtain a desired adhesive strength, the amount of the silane coupling agent is desirably 0.5 parts by weight or more with respect to 100 parts by weight of the rubber component (A). More preferably, it is 2 parts by weight or more. Excessive blending also causes a decrease in the physical properties of the rubber and there is a risk that the processability will also decrease. For this reason, the amount of the silane coupling agent is desirably 10 parts by weight or less. It is more preferable if it is 6 parts by weight or less.

  The rubber composition constituting the adhesive seal member of the present invention may contain various additives usually used as additives for rubber in addition to the above (A) to (C). For example, carbon black is widely used as a reinforcing agent. However, when carbon black is blended in a large amount, it may react with radicals generated from the crosslinking agent (B) at the time of crosslinking, thereby inhibiting the crosslinking reaction. Therefore, when carbon black is blended, the blending amount is desirably 10 parts by weight or less with respect to 100 parts by weight of the rubber component (A). 5 parts by weight or less, more preferably 1 part by weight or less is more preferable.

  For example, white carbon is suitable as a reinforcing agent used in place of or together with carbon black. White carbon is known as amorphous silica, and specifically includes dry method silica, wet method silica, and synthetic silicate-based silica. The amount of white carbon is desirably 30 parts by weight or more with respect to 100 parts by weight of the rubber component (A). In consideration of ease of kneading, molding processability, etc., the amount of white carbon is desirably 80 parts by weight or less.

  Other additives include softeners, plasticizers, anti-aging agents, tackifiers, processing aids, and the like. Softeners include petroleum oils such as process oil, lubricating oil, paraffin, liquid paraffin and petrolatum, fatty oil softeners such as castor oil, linseed oil, rapeseed oil and coconut oil, tall oil, sub, beeswax , Waxes such as carnauba wax and lanolin, linoleic acid, palmitic acid, stearic acid, lauric acid and the like. The blending amount of the softening agent is preferably up to about 10 parts by weight with respect to 100 parts by weight of the rubber component (A) in consideration of the strength of the produced adhesive seal member. Examples of the plasticizer include organic acid derivatives such as dioctyl phthalate (DOP) and phosphoric acid derivatives such as tricresyl phosphate. The amount of the plasticizer is preferably up to about 10 parts by weight with respect to 100 parts by weight of the rubber component (A) in consideration of the strength of the adhesive seal member to be produced, like the softener. Moreover, as an anti-aging agent, a phenol type, an imidazole type, a wax, etc. are mentioned, It is good to mix | blend about 0.5-10 weight part with respect to 100 weight part of the said rubber component (A).

  The rubber composition can be prepared by mixing the above (A) to (C) and various additives as required. For example, each material other than the crosslinking agent (B) and the silane coupling agent (C) is premixed and then kneaded at 80 to 140 ° C. for several minutes. After cooling the kneaded product, the crosslinking agent (B) and the silane coupling agent (C) are added, and the mixture is prepared by kneading at a roll temperature of 40 to 60 ° C. for 5 to 30 minutes using rolls such as an open roll. be able to. In addition, you may mix | blend a silane coupling agent (C) in the stage of preliminary mixing.

  The prepared rubber composition is placed between components to be adhesively sealed and crosslinked. By crosslinking, the rubber composition becomes the adhesive seal member of the present invention. Here, the crosslinking temperature is desirably 120 ° C. or lower. The crosslinking time is desirably 20 minutes or less. By performing crosslinking at a low temperature for a short time, for example, the adhesive seal member of the present invention can be used also in the vicinity of the electrolyte membrane of a polymer electrolyte fuel cell.

  The prepared rubber composition is desirably molded into a predetermined shape. For example, if it is formed into a film shape, the constituent members can be easily bonded to each other by affixing and crosslinking the film-like rubber composition on the constituent members of the fuel cell. Moreover, the complicated alignment conventionally performed becomes unnecessary and it becomes easy to perform continuous processing. Furthermore, if a film-like rubber composition is laminated on the constituent members in advance, adhesion processing becomes easier. Moreover, it is also possible to integrally mold the structural member such as the MEA or the frame of the fuel cell and the molded body of the rubber composition by placing them in a mold and heating them.

<Application to fuel cells>
The adhesive seal member of the present invention provides an adhesive seal between the constituent members of the fuel cell. The fuel cell to be applied may be any one that operates at a temperature at which the rubber component that serves as the skeleton of the adhesive seal member of the present invention can be used. For example, a polymer electrolyte fuel cell (PEFC) (including a direct methanol fuel cell (DMFC)) is suitable.

  The part to be bonded and sealed (between constituent members) varies depending on the type and structure of the fuel cell. That is, the adhesive seal member of the present invention is required to be airtight and liquid-tight, and can be used for any part where the adhesive seal member has been used conventionally. Examples of the adhesive seal portion include a separator between the separators facing each other across the MEA, a frame supporting the MEA and the separator, and between the separators and separators constituting adjacent cells. In addition, the adhesive seal member of the present invention may be used for all parts that require an adhesive seal in a fuel cell, or may be used for a part of a part that requires an adhesive seal. The material of the constituent member may be an inorganic material such as a metal or a carbon material, or an organic material such as a resin.

  An embodiment of a polymer electrolyte fuel cell using the adhesive seal member of the present invention will be shown below. FIG. 1 is a perspective view of a polymer electrolyte fuel cell using the adhesive seal member of the present invention. As shown in FIG. 1, the polymer electrolyte fuel cell 1 is configured by stacking a number of cells C. FIG. 2 shows a perspective view of the stacked cells C (for only three cells). FIG. 3 shows an exploded perspective view of a single cell C. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. As shown in FIGS. 2 to 4, the cell C includes an MEA 2, a separator 3, and a frame 4.

  The MEA 2 includes an electrolyte membrane 20 and a pair of electrodes 21a and 21b. The electrolyte membrane 20 has a rectangular thin plate shape. The pair of electrodes 21a and 21b has a rectangular thin plate shape. The pair of electrodes 21a and 21b are arranged on both sides with the electrolyte membrane 20 in between. The frame 4 is made of metal and has a rectangular frame shape. The frame 4 holds the periphery of the electrolyte membrane 20.

  The separator 3 is made of metal and has a rectangular thin plate shape. The separator 3 has a total of six grooves extending in the longitudinal direction. Due to the groove, the cross section of the separator 3 has an uneven shape (see FIG. 4). The separator 3 is disposed opposite to both sides of the MEA 2 (also both sides of the frame 4). A gas flow path 30 for supplying gas to the electrodes 21a and 21b is defined between the MEA 2 and the separator 3 by using an uneven shape. Further, between the separators 3 facing each other in the cell C adjacent to each other in the stacking direction, a refrigerant flow path 31 for flowing a refrigerant is defined using an uneven shape.

  The adhesive seal member 5 (adhesive seal member of the present invention) is disposed between the electrolyte membrane 20 and the frame 4. Further, a conventional silicone rubber seal member 7 is disposed between the frame 4 and the separator 3 and between the separators 3 facing each other in the cell C adjacent in the stacking direction.

  During operation of the polymer electrolyte fuel cell 1, fuel gas and oxidant gas are supplied through the gas flow paths 30. Here, the electrolyte membrane 20 and the frame 4 are adhesively sealed by the adhesive seal member 5. Since the gas permeability of the adhesive seal member 5 is small, gas mixing and leakage do not occur. Further, the wet state of the electrolyte membrane 20 is also maintained. In addition, in the case of the adhesive seal member 5, crosslinking can be performed at a low temperature of about 120 ° C. and in a short time. Therefore, there is little possibility that the electrolyte membrane 20 will deteriorate at the time of crosslinking. Further, the adhesiveness of the adhesive seal member 5 is not easily lowered even in the operating environment of the polymer electrolyte fuel cell 1. For this reason, at the time of an operation | movement, the favorable sealing performance by the adhesive seal member 5 is ensured. Therefore, the polymer electrolyte fuel cell 1 can be stably operated over a long period of time.

  In the present embodiment, the conventional silicone rubber seal member 7 is disposed between the frame 4 and the separator 3 and between the separators 3 facing each other in the cell C adjacent in the stacking direction. However, the adhesive seal member of the present invention may be applied to these parts. That is, in addition to the gap between the electrolyte membrane 20 and the frame 4, the adhesive seal member 5 is interposed between the frame 4 and the separator 3 or between the separators 3 facing each other in the cell C adjacent in the stacking direction. You may arrange. If it carries out like this, the gas permeability of a seal part will become small and seal nature will improve more. In addition, since it is difficult to be affected by the working environment at the time of cross-linking, the occurrence of poor curing and the like is reduced. Further, it is not necessary to use a separate adhesive to bond the adhesive seal member 5 and the constituent members such as the separator 3.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(1) Preparation of rubber composition The raw materials shown in the following Table 1 were blended to prepare each rubber composition of Examples and Comparative Examples. In Table 1, the following were used for each raw material. The seal member of Comparative Example 1 is a conventional silicone rubber (“LSR2650” manufactured by Momentive Performance Materials Japan GK).
(A) Rubber component EPDM: “JSR EP27” manufactured by JSR Corporation, NBR: “Nipol (registered trademark) DN101” manufactured by Zeon Corporation.
(B) Crosslinker dialkyl peroxide: “Perhexa (registered trademark) 25B-40” (2,5-dimethyl-2,5-di (t-butylperoxy) hexane, manufactured by Nippon Oil & Fats Co., Ltd., 1 hour half-life Temperature = 138 ° C.), diacyl peroxide: “Nyper (registered trademark) FF” (dibenzoyl peroxide, 1 hour half-life temperature = 92 ° C.) manufactured by the same company. In addition, these compounding amounts are not values in a diluted state but values when each organic peroxide is 100%.
(C) Adhesive component silane coupling agent: “KBM403” (3-glycidoxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., resorcinol compound: “Tactrol (registered trademark) 620 manufactured by Taoka Chemical Co., Ltd. "Melamine compound:" Sumikanol (registered trademark) 507A "manufactured by Sumitomo Chemical Co., Ltd.
(D) Other additive carbon black (MAF grade): “Show Black (registered trademark) IP200” manufactured by Cabot Japan Co., Ltd., White carbon: “Nipsil ER” manufactured by Tosoh Silica Co., Ltd., paraffinic process oil: “Diana (registered trademark) process oil PW380” manufactured by Idemitsu Kosan Co., Ltd., acrylic auxiliary agent: “Hicross ED-P” manufactured by Seiko Chemical Co., Ltd.

  First, in Table 1, the rubber component (A), carbon black, white carbon, softener, and plasticizer were appropriately kneaded at 120 ° C. for 5 minutes using a Banbury mixer. After cooling the kneaded material as necessary, a cross-linking agent (B), a cross-linking aid, and an adhesive component (C) are appropriately added, and kneaded at 40 ° C. for 10 minutes using an open roll to obtain a rubber composition. It was. The obtained rubber composition was molded into a 2 mm thick film by pressing.

(2) Manufacture of seal member and evaluation of mechanical strength The rubber compositions of Examples 1 to 3 were crosslinked by holding at 120 ° C. for 10 minutes to obtain a seal member. The seal members of Examples 1 to 3 are included in the adhesive seal member of the present invention (the same applies hereinafter). Further, the rubber compositions of Comparative Examples 2 and 3 were crosslinked at 130 ° C. for 10 minutes, and the rubber compositions of Comparative Examples 4 and 5 were crosslinked at 120 ° C. for 10 minutes to crosslink each. did. Moreover, in the case of the silicone rubber of the comparative example 1, it crosslinked at 130 degreeC using the catalyst which consists of a platinum compound. About each sealing member of an Example and a comparative example, tensile strength was measured. The tensile strength was measured in accordance with JIS K6251 (test piece: No. 5 type dumbbell). The results are summarized in Table 1 above. In Table 1, the ratio of the tensile strength of each seal member when the tensile strength of the silicone rubber of Comparative Example 1 is defined as a standard (100) is shown as a strength index.

  As shown in Table 1, the sealing members of Examples 1 to 3 all had a higher tensile strength than the silicone rubber of Comparative Example 1. That is, it was confirmed that the adhesive seal member of the present invention has higher mechanical strength than conventional silicone rubber. On the other hand, the sealing members of Comparative Examples 2 and 3 had lower tensile strength than the silicone rubber of Comparative Example 1 even though the same EPDM as in Examples 1 to 3 was used as the rubber component. In the sealing members of Comparative Examples 2 and 3, dialkyl peroxide having a 1-hour half-life temperature exceeding 130 ° C. was used as a crosslinking agent. For this reason, it is considered that under the above-mentioned crosslinking conditions (130 ° C. × 10 minutes), the crosslinking reaction hardly proceeds and sufficient strength cannot be obtained. Incidentally, when the rubber composition of Comparative Examples 2 and 3 was crosslinked at 180 ° C. to produce a seal member, the tensile strength was larger than that of the silicone rubber of Comparative Example 1. Further, in the seal member of Comparative Example 5, as in Examples 1 and 2, diacyl peroxide was used as a crosslinking agent. Nevertheless, the reason why the tensile strength was reduced is thought to be that the crosslinking reaction was inhibited by a large amount of carbon black.

(3) Manufacture of seal member and evaluation of adhesiveness (a) 90 ° peel test A 90 ° peel test in accordance with JIS K6256-2 was conducted to evaluate the adhesiveness of each seal member in Examples and Comparative Examples. First, the rubber compositions of Examples and Comparative Examples are arranged on the surface of a stainless steel plate. The rubber compositions of Examples 1 to 3 and Comparative Examples 4 and 5 are at a temperature of 120 ° C., and the rubber compositions of Comparative Examples 2 and 3 are used. A test piece was prepared by holding the object at a temperature of 130 ° C. for 20 minutes to crosslink and bond the material. In addition, in the case of the silicone rubber of the comparative example 1, it crosslinked at 130 degreeC using the catalyst which consists of a platinum compound. Adhesion to the stainless steel plate was performed by applying an adhesive. Next, the produced test piece was attached to a predetermined test jig, and a 90 ° peel test was performed. The results are summarized in Table 1 above. Table 1 shows the ratio of the peel strength of each seal member as a strength index when the peel strength of the silicone rubber of Comparative Example 1 is used as a reference (100).

  As shown in Table 1, in each of the sealing members of Examples 1 to 3, the peel strength was higher than that of the silicone rubber of Comparative Example 1. In particular, the peel strength of the seal member of Example 3 using NBR as the rubber component was increased. When the peel strengths of the seal members of Examples 1 and 2 were compared, the seal member of Example 2 having a larger amount of carbon black was slightly smaller. As described above, in the seal members of Examples 1 to 3, since the diacyl peroxide having a low one-hour half-life temperature of 92 ° C. was used as the cross-linking agent, the cross-linking reaction sufficiently progressed even at a low temperature of 120 ° C. However, a high adhesive force was expressed.

  On the other hand, the peel strength of the sealing members of Comparative Examples 2 to 5 was smaller than that of the silicone rubber of Comparative Example 1. Among these, the sealing members of Comparative Examples 4 and 5 do not contain a silane coupling agent (adhesive component (C)). Therefore, it turns out that adhesive force is scarce. Moreover, although the sealing members of Comparative Examples 2 and 3 contained the adhesive component (C), the peel strength was small. As described above, since the dialkyl peroxide was used as the cross-linking agent in the sealing members of Comparative Examples 2 and 3, the cross-linking reaction hardly progressed under the above cross-linking conditions (130 ° C. × 20 minutes), and sufficient adhesive strength was obtained. It is thought that it was not possible.

(B) T-shaped peeling test The following T-shaped peeling test was performed, and the adhesiveness of each sealing member of an Example and a comparative example was evaluated. First, a test piece was prepared. A required number of strip-shaped stainless steel plates having a width of 1 cm and a thickness of 0.1 mm were prepared, and the surface was degreased. Two stainless steel plates were placed facing each other, and the rubber compositions of Examples and Comparative Examples were interposed in the gaps between the stainless steel plates. The rubber compositions of Examples 1 to 3 and Comparative Examples 4 and 5 were held at a temperature of 120 ° C., and the rubber compositions of Comparative Examples 2 and 3 were held at a temperature of 130 ° C. for 10 minutes while being compressed by 10 to 30 μm in the thickness direction. The rubber composition was cross-linked to bond the stainless steel plates together. In addition, in the case of the silicone rubber of the comparative example 1, it crosslinked at 130 degreeC using the catalyst which consists of a platinum compound. Adhesion between the stainless steel plates was performed by applying an adhesive.

  Next, each produced test piece was attached to the tensile test apparatus, and the T-shaped peeling test was done. FIG. 5 schematically shows the state of the T-peel test. As shown in FIG. 5, the test piece 60 includes a pair of stainless steel plates 61 a and 61 b and a seal member 62 that adheres between them. The end of the stainless steel plate 61a that is not bonded is sandwiched by the gripping tool 63a and is bent in the peeling direction (indicated by an upward white arrow in the figure) at an angle of about 90 ° with respect to the bonding surface. . Similarly, the end of the stainless steel plate 61b that is not bonded is sandwiched by the gripping tool 63b and bent in the peeling direction (indicated by a downward white arrow in the figure) at an angle of about 90 ° with respect to the bonding surface. It has been. That is, the sealing members 62 between the stainless steel plates 61a and 61b were peeled by pulling the free ends of the stainless steel plates 61a and 61b in the opposite directions of about 180 ° with the gripping tools 63a and 63b. In addition, this test was performed under 23 degreeC (room temperature), and the moving speed of the holding tools 63a and 63b was 10 mm / min. The T-shaped peel strength of each test piece in the T-shaped peel test was determined according to JIS K6854-3. Moreover, the T-shaped peel strength of the test piece using the silicone rubber of Comparative Example 1 was used as a reference (100), and the ratio of the T-shaped peel strength of each test piece to the test piece was calculated.

  In addition, in order to evaluate the adhesion reliability of each seal member, after performing an environmental resistance test on each test piece, a T-shaped peel test was performed in the same manner as described above. The environmental resistance test was performed by immersing each test piece in warm water at 90 ° C. for 100 hours, and further for 1000 hours. Also in this case, the ratio of the T-shaped peel strength of each test piece was calculated in the same manner as described above. Table 1 summarizes the strength index of the T-peel strength of each test piece in each T-peel test.

  As shown in Table 1, in each of the sealing members of Examples 1 to 3, the T-shaped peel strength was higher than that of the silicone rubber of Comparative Example 1. That is, it was confirmed that the adhesive seal member of the present invention has an excellent adhesive force. Further, even after the environmental resistance test, the T-shaped peel strength of the sealing members of Examples 1 to 3 is larger than that of the silicone rubber of Comparative Example 1. From this result, it can be seen that the adhesive seal member of the present invention is less likely to decrease the adhesive force even when used for a long time in the operating environment of the fuel cell in contact with hot water or steam. That is, the adhesive seal member of the present invention has high adhesion reliability. On the other hand, the sealing members of Comparative Examples 2 to 5 had a T-peeling strength lower than that of the silicone rubber of Comparative Example 1, as in the case of the 90 ° peel test, before and after the environmental resistance test.

(4) Application to solid polymer fuel cells Using the rubber compositions of Examples 1 to 3, solid polymer fuel cells were produced. That is, the rubber compositions of Examples 1 to 3 were placed between the electrolyte membrane 20 and the frame 4 as shown in FIG. 4 and held at 120 ° C. for 10 minutes to crosslink and adhere. It was. That is, the electrolyte membrane 20 and the frame 4 were bonded and sealed with the seal members of Examples 1 to 3. The polymer electrolyte fuel cell was operated for 24 hours, and the sealing performance of each sealing member was confirmed. As a result, neither gas mixing nor leakage occurred, and it was confirmed that good adhesion was ensured.

1 is a perspective view of a polymer electrolyte fuel cell using an adhesive seal member of the present invention. It is a perspective view of the laminated | stacked cell. It is a disassembled perspective view of a single cell. It is IV-IV sectional drawing of FIG. It is a schematic diagram which shows the mode of the T-shaped peeling test in an Example.

Explanation of symbols

1: Solid polymer fuel cell 2: MEA 20: Electrolyte membrane 21a, 21b: Electrode 3: Separator 30: Gas flow path 31: Refrigerant flow path 4: Frame 5: Adhesive seal member 7: Seal member 60: Test piece 61a, 61b: stainless steel plate 62: seal members 63a, 63b: gripping tool C: cell

Claims (5)

An adhesive seal member for a fuel cell, comprising a cross-linked product of a rubber composition containing the following (A) to (C) , carbon black, and white carbon, and adhesively sealing between constituent members of the fuel cell.
(A) One or more rubber components selected from ethylene-propylene rubber, ethylene-propylene-diene rubber, acrylonitrile-butadiene rubber, and hydrogenated acrylonitrile-butadiene rubber.
(B) A crosslinking agent selected from organic peroxides having a one-hour half-life temperature of 120 ° C. or lower.
(C) Silane coupling agent.   The adhesive seal member for a fuel cell according to claim 1, wherein the organic peroxide (B) is diacyl peroxide.   The amount of the crosslinking agent (B) is 0.5 to 5 parts by weight with respect to 100 parts by weight of the rubber component (A). Adhesive seal member.   The fuel cell according to any one of claims 1 to 3, wherein the amount of the silane coupling agent is 0.5 to 10 parts by weight with respect to 100 parts by weight of the rubber component (A). Adhesive seal member. 5. The adhesive seal member for a fuel cell according to claim 1, wherein an amount of the carbon black is 10 parts by weight or less based on 100 parts by weight of the rubber component (A).

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