JP5396337B2 - Adhesive seal member for fuel cell - Google Patents

Description

  The present invention relates to an adhesive seal member that seals between members constituting a fuel cell, and more particularly to an adhesive seal member capable of both an adhesive seal and a stress seal.

  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 a membrane electrode assembly (MEA) or the like is sandwiched between separators is a power generation unit. The MEA includes a polymer membrane (electrolyte membrane) serving as an electrolyte, a pair of electrode catalyst layers (a fuel electrode (anode) catalyst layer, an oxygen electrode (cathode) catalyst layer) disposed on both sides in the thickness direction of the electrolyte membrane, Consists of. On the surface of the pair of electrode catalyst layers, a porous layer for further diffusing gas is disposed. 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 by an electrochemical reaction at the three-phase interface between the supplied gas, the electrolyte, and the electrode catalyst layer. The polymer electrolyte fuel cell is configured by fastening a cell laminate in which a large number of the cells are laminated with end plates or the like arranged at both ends in the cell lamination 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. As a sealing member for sealing between these constituent members, for example, a rubber material using ethylene-propylene-diene rubber (EPDM) has been proposed (for example, see Patent Documents 1 and 2).

JP 2002-371161 A JP 2009-94056 A

The rubber material described in Patent Document 1 is produced by crosslinking EPDM having a number average molecular weight of 10 ⁴ to 10 ⁶ order and ethylene / α-olefin copolymer rubber having a number average molecular weight of 10 ³ to 10 ⁵ order. Is done. The rubber material does not have adhesiveness. For this reason, a separate adhesive is required for bonding to the member.

  A polymer membrane such as a perfluorinated sulfonic acid membrane is used for the electrolyte membrane of the solid polymer fuel cell. Therefore, when the material for the seal member is disposed near the electrolyte membrane for crosslinking and bonding, it is necessary to consider that the electrolyte membrane does not deteriorate due to heating during crosslinking. That is, it is desirable to perform the bonding process of the seal member at a lower temperature and in a shorter time.

  In this regard, according to the adhesive seal member described in Patent Document 2, crosslinking can be performed at a low temperature. That is, adhesion to the member can be performed at a low temperature. However, if the crosslinking is attempted in a shorter time, there is a problem that the strength and elongation of the adhesive seal member are lowered.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide an adhesive seal member for a fuel cell that can be crosslinked at a low temperature in a short time and has desired strength and elongation.

In order to solve the above-mentioned problems, an adhesive seal member for a fuel cell of the present invention (hereinafter referred to as “adhesive seal member of the present invention” as appropriate) is a rubber composition containing the following (A) to (E): It consists of a cross-linked product and is characterized in that it seals between the components 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) Ethylene / α-olefin copolymer (C) A crosslinking agent selected from organic peroxides having a one-hour half-life temperature of 130 ° C. or lower.
(D) A crosslinking aid.
(E) One or more adhesive components selected from resorcinol compounds and melamine compounds, aluminate coupling agents, and silane coupling agents.

  According to the adhesive seal member of the present invention, an organic peroxide having a one-hour half-life temperature of 130 ° C. or lower is used as a crosslinking agent (above (C)). 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 130 ° C. or lower, crosslinking can be performed at a lower temperature (specifically, 130 ° C. or lower) 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.

  For example, when the rubber component (A) is to be crosslinked in a short time using the crosslinking agent (C), the crosslinking density rapidly increases. For this reason, it is thought that the tensile strength and elongation of the obtained rubber material become small. In this regard, the adhesive seal member of the present invention includes an ethylene / α-olefin copolymer in addition to the rubber component (A) (above (B)). It is considered that the crosslinking sites of the rubber component are dispersed by blending the ethylene / α-olefin copolymer. This suppresses a rapid increase in crosslink density. Therefore, in the obtained adhesive seal member, the tensile strength and elongation are not easily lowered. The ethylene / α-olefin copolymer is a resin component. By adding a resin component to the rubber component, the strength of the adhesive seal member can be improved as compared with the case of using only the rubber component. Furthermore, the insulating property of the adhesive seal member can be improved. In addition, when a resin component is added, there exists a possibility that an adhesive sealing member may become easy to sag. However, the adhesive seal member of the present invention has an appropriate crosslinking density. For this reason, compared with the case of only a rubber component, sagability is hard to fall.

  Moreover, the adhesive sealing member of this invention contains an adhesive component (above (E)). Therefore, the adhesive seal member of the present invention can be bonded to the member without using another adhesive. For example, when a resorcinol compound and a melamine compound are included as an adhesive component, the melamine compound becomes a methylene donor and the resorcinol compound becomes a methylene donor. At the time of cross-linking, a chemical bond is formed between the resorcinol compound and the rubber component, and between the resorcinol compound and the member to be bonded by donating a methylene group. Thereby, a rubber component (adhesive sealing member) and a member are adhere | attached. When an aluminate coupling agent is included as an adhesive component, the adhesive seal member and the member are bonded via the aluminate coupling agent. Similarly, when a silane coupling agent is included as an adhesive component, the adhesive seal member and the member are bonded via the silane coupling agent.

  The adhesive strength of these adhesive components is great. In addition, even in the operating environment of the fuel cell, the adhesive force is unlikely to decrease. Therefore, when the adhesive seal member of the present invention is used for a fuel cell, good sealing performance is ensured even when the fuel cell is operated for a long period of time. That is, the operation reliability of the fuel cell can be improved.

  The adhesive seal member of the present invention has rubber elasticity. For this reason, according to the adhesive sealing member of this invention, the sealing by stress is attained. Therefore, for example, when the adhesive seal member of the present invention is disposed between opposing members, the adhesive seal member of the present invention is bonded to only one member, and the other member is stressed. A mode of sealing can be employed. Of course, the adhesive sealing member of the present invention may be bonded to both members, and the members may be bonded and sealed.

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.

  Below, embodiment of the adhesive seal member for fuel cells of this invention is described. The adhesive seal member for a fuel cell according to the present invention is not limited to the following embodiment, 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>
As described above, the adhesive seal member of the present invention comprises a crosslinked product of the rubber composition containing the above (A) to (E). First, the rubber component (A) will be described. The rubber component is at least one selected from ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), and hydrogenated acrylonitrile-butadiene rubber (H-NBR). One of these may be used alone, or two or more may be mixed and used. Further, two or more kinds of rubbers having different Mooney viscosities described later may be mixed and used.

  The Mooney viscosity of the rubber component is desirably 90 [ML (1 + 4) 100 ° C.] or less. When the Mooney viscosity is 90 [ML (1 + 4) 100 ° C.] or less, the fluidity of the rubber composition before crosslinking increases. For this reason, the moldability at the time of injection molding and transfer molding suitable for the production of a sealing member for a fuel cell is improved. A more preferable Mooney viscosity is 60 [ML (1 + 4) 100 ° C.] or less. In this specification, the Mooney viscosity adopts a value measured according to JIS K6300-1 (2001).

  From the viewpoint of acid resistance and water resistance in the operating environment of the fuel cell, the rubber component desirably contains EPDM. In this case, the diene content of EPDM is desirably 4% by mass or more and 9% by mass or less. Here, the amount of diene is the mass ratio of the diene component in EPDM. When the amount of diene is less than 4% by mass, the crosslink density becomes small, so that there is a possibility that desired tensile strength cannot be obtained in the cross-linked product (adhesive seal member). On the other hand, when the amount of diene exceeds 9% by mass, the crosslinking density increases, and thus there is a possibility that desired elongation cannot be obtained in the crosslinked product.

  Although the diene component of EPDM is not particularly limited, for example, a diene monomer having 5 to 20 carbon atoms is desirable. Specifically, 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cycloocta Examples include diene, dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB), 5-butylidene-2-norbornene, 2-methallyl-5-norbornene, 2-isopropenyl-5-norbornene, and the like.

  Next, the ethylene / α-olefin copolymer (B) will be described. The kind of ethylene / α-olefin copolymer is not particularly limited. For example, a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms is suitable. Examples of the α-olefin having 3 to 10 carbon atoms include propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, nonene-1, and decene-1. Etc. One of these may be used alone, or two or more may be used in combination.

  The blending amount of the ethylene / α-olefin copolymer is desirably 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component (A). When the ethylene / α-olefin copolymer is less than 5 parts by mass, the influence on crosslinking is small, and the reinforcing effect cannot be sufficiently obtained. Therefore, in the cross-linked product (adhesive seal member), there is a possibility that desired tensile strength and elongation cannot be obtained. On the other hand, if the ethylene / α-olefin copolymer exceeds 30 parts by mass, the cross-linked product becomes hard and the rubber elasticity decreases. For this reason, there exists a possibility that desired tensile strength and elongation may not be obtained in a crosslinked product.

  Next, the crosslinking agent (C) will be described. The crosslinking agent is selected from organic peroxides having a one-hour half-life temperature of 130 ° C. or lower. Examples of such organic peroxides include peroxyketals, peroxyesters, diacyl peroxides, peroxydicarbonates, and the like. Among them, peroxyketals and peroxyesters having a one-hour half-life temperature of 100 ° C. or more are easy to crosslink at a temperature of about 130 ° C. and are excellent in the handleability of a rubber composition kneaded by adding a crosslinking agent. It is desirable to employ at least one of the above. In particular, a one-hour half-life temperature of 110 ° C. or higher is preferable. Moreover, when a peroxy ester is used, crosslinking can be performed in a shorter time.

  Examples of the peroxyketal include n-butyl 4,4-di (t-butylperoxy) valerate, 2,2-di (t-butylperoxy) butane, 2,2-di (4,4-di). (T-butylperoxy) cyclohexyl) propane, 1,1-di (t-butylperoxy) cyclohexane, 1,1-di (t-hexylperoxy) cyclohexane, 1,1-di (t-hexylperoxy) ) -3,3,5-trimethylcyclohexane, 1,1-di (t-butylperoxy) -2-methylcyclohexane and the like.

  Examples of peroxyesters include t-butyl peroxybenzoate, t-butyl peroxyacetate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t -Butylperoxy 2-ethylhexyl monocarbonate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxymalein An acid, t-hexyl peroxy isopropyl monocarbonate, etc. are mentioned.

  Of these, 1,1-di (t-butylperoxy) cyclohexane, t-butylperoxyacetate, and t-butylperoxyisopropyl monocarbonate are preferred because of their relatively fast reaction with the rubber component. . Especially, when t-butyl peroxyisopropyl monocarbonate is used, crosslinking can be performed in a shorter time.

  In order to sufficiently advance the crosslinking reaction, the amount of the crosslinking agent is desirably 1 part by mass or more with respect to 100 parts by mass of the rubber component (A). On the other hand, when there are many compounding quantities of a crosslinking agent, a crosslinking density will rise rapidly at the time of a crosslinking reaction, and the fall of adhesive force will be caused. From such a viewpoint, the amount of the crosslinking agent is desirably 10 parts by mass or less with respect to 100 parts by mass of the rubber component (A).

  Next, the crosslinking aid (D) will be described. What is necessary is just to select a crosslinking adjuvant suitably according to the kind of said crosslinking agent (C). Examples of the crosslinking aid include maleimide compounds, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), and trimethylolpropane trimethacrylate (TMPT). Among these, it is desirable to use a maleimide compound because the effect of improving the crosslinking density and strength is great. In this case, in order to allow the crosslinking reaction to proceed sufficiently, the amount of the crosslinking aid is desirably 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component (A). On the other hand, when there are many compounding quantities of a crosslinking adjuvant, a crosslinking density will become large too much and will cause the adhesive force fall. For this reason, it is desirable that the amount of the crosslinking aid is 3 parts by mass or less.

  Next, the adhesive component (E) will be described. The adhesive component (E) is at least one selected from resorcinol compounds and melamine compounds, aluminate coupling agents, and silane coupling agents. That is, a resorcinol compound, a melamine compound, an aluminate coupling agent, and a silane coupling agent may be used alone. In addition, resorcinol compounds and melamine compounds and aluminate coupling agents, resorcinol compounds and melamine compounds and silane coupling agents, aluminate coupling agents and silane coupling agents may be used in combination. Good. Furthermore, you may use all the resorcinol type compound and melamine type compound, an aluminate type coupling agent, and a silane coupling agent.

Examples of the resorcinol compound include resorcin, modified resorcin / formaldehyde resin, resorcin / formaldehyde (RF) resin, and the like. One of these may be used alone, or two or more may be mixed and used. Among these, a modified resorcin / formaldehyde resin is preferable in that it has low volatility, low hygroscopicity, and excellent compatibility with rubber. Examples of the modified resorcin / formaldehyde resin include those represented by the following general formulas (1) to (3). In particular, those represented by the general formula (1) are suitable.

  In order to obtain a desired adhesive force, the compounding amount of the resorcinol compound is desirably 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component (A). It is more preferable that it is 0.5 parts by mass or more. Further, since excessive blending causes a decrease in the physical properties of the rubber, the blending amount of the resorcinol compound is desirably 10 parts by mass or less. It is more preferable that it is 5 parts by mass or less.

Examples of the melamine compound include methylated formaldehyde / melamine polymer, hexamethylenetetramine, and the like. One of these may be used alone, or two or more may be mixed and used. These decompose under heating during crosslinking and supply formaldehyde to the system. Of these, a methylated product of formaldehyde / melamine polymer is preferred because it has low volatility, low hygroscopicity, and excellent compatibility with rubber. As the methylated formaldehyde / melamine polymer, for example, those represented by the following general formula (4) are suitable. In particular, in the general formula (4), a mixture in which n = 1 compound is 43 to 44% by mass, n = 2 compound is 27 to 30% by mass, and n = 3 compound is 26 to 30% by mass is preferable. .

  The compounding ratio of the resorcinol compound and the melamine compound is preferably in the range of 1: 0.5 to 1: 2 in terms of mass ratio. A range of 1: 0.77 to 1: 1.5 is more preferred. When the compounding ratio of the melamine compound to the resorcinol compound is less than 0.5, there is a tendency that the tensile strength, elongation and the like of the rubber are slightly reduced. On the other hand, when the blending ratio of the melamine compound exceeds 2, the adhesive force is saturated. For this reason, the compounding beyond it leads to a cost increase.

  The aluminate coupling agent may be appropriately selected from an aluminum organic compound having a hydrolyzable alkoxy group and a portion having an affinity for the rubber component in consideration of adhesiveness and the like. For example, aluminum alkyl acetoacetate diisopropylate, aluminum ethyl acetoacetate diisopropylate, aluminum trisethyl acetoacetate, aluminum isopropylate, aluminum diisopropylate monosecondary butyrate, aluminum secondary butyrate, aluminum ethylate, aluminum bis Examples include ethyl acetoacetate monoacetylacetonate, aluminum trisacetylacetonate, aluminum monoisopropoxymonooroxyethyl acetoacetate, and the like. One of these may be used alone, or two or more may be mixed and used. Of these, aluminum alkyl acetoacetate / diisopropylate, aluminum ethylacetoacetate / diisopropylate, and aluminum trisethylacetoacetate are preferable.

  In order to obtain a desired adhesive strength, the blending amount of the aluminate coupling agent is desirably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component (A). It is more preferable that it is 2 parts by mass 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, it is desirable that the compounding amount of the aluminate coupling agent is 10 parts by mass or less. It is more preferable that it is 6 parts by mass or less.

  The silane coupling agent may be appropriately selected from a group of compounds having an epoxy group, an amino group, a vinyl group or the like as a functional group in consideration of adhesiveness. 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 force, the amount of the silane coupling agent is desirably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component (A). It is more preferable that it is 2 parts by mass 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, it is preferable that the compounding quantity of a silane coupling agent is 10 mass parts or less. It is more preferable that it is 6 parts by mass 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 (E). For example, it is desirable to include carbon black as a reinforcing agent. The grade of carbon black is not particularly limited, and may be appropriately selected from SAF class, ISAF class, HAF class, MAF class, FEF class, GPF class, SRF class, FT class, MT class, and the like. When the blending amount of carbon black is increased, the adhesive seal member becomes hard. Thereby, there exists a possibility that tensile strength and elongation may fall. Therefore, the blending amount of carbon black may be appropriately determined in consideration of the blending amount of the ethylene / α-olefin copolymer (B). For example, the compounding amount of carbon black is desirably 10 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the rubber component (A).

  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 may be up to about 40 parts by mass with respect to 100 parts by mass of the rubber component (A). Examples of the plasticizer include organic acid derivatives such as dioctyl phthalate (DOP) and phosphoric acid derivatives such as tricresyl phosphate. The blending amount of the plasticizer is preferably up to about 40 parts by mass with respect to 100 parts by mass of the rubber component (A), like the softener. Examples of the anti-aging agent include phenolic, imidazole, and wax. The anti-aging agent may be blended in an amount of about 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component (A).

<Method for Producing Adhesive Seal Member for Fuel Cell>
The adhesive seal member of the present invention is produced by crosslinking the rubber composition containing the above (A) to (E) and various additives as required. What is necessary is just to prepare a rubber composition as follows, for example. First, materials other than the crosslinking agent (C), the crosslinking assistant (D), and the adhesive component (E) are premixed and kneaded at 80 to 140 ° C. for several minutes. Next, the obtained kneaded product is cooled, and a crosslinking agent (C), a crosslinking aid (D), and an adhesive component (E) are added. And using rolls, such as an open roll, it kneads for 5 to 30 minutes at roll temperature 40-70 degreeC. In addition, you may mix | blend an adhesive component (E) in the stage of preliminary mixing.

  The prepared rubber composition is crosslinked while being brought into contact with a member to be bonded. By crosslinking, the rubber composition becomes the adhesive seal member of the present invention. Here, the crosslinking temperature is desirably 130 ° C. or lower. 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, when it is formed into a film shape, an adhesive seal member can be attached to a member to be bonded and can be easily bonded. In this case, since complicated alignment between the constituent members of the fuel cell is not required, continuous processing is facilitated. Further, if an adhesive seal member is laminated on the member in advance, the bonding operation is further facilitated. Thus, by making the adhesive seal member of the present invention into a film shape, for example, the productivity of the fuel cell can be further improved. Moreover, it is also possible to integrally mold the structural members such as the MEA and separator of the fuel cell and the adhesive seal member of the present invention by placing them in a mold and heating them.

<Application to fuel cells>
The adhesive seal member of the present invention is suitable for sealing between constituent members of a fuel cell. The fuel cell to be applied only needs to operate at a temperature at which the organic component (rubber component, ethylene / α-olefin copolymer) 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 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 seal member has been conventionally disposed. In addition, the adhesive seal member of the present invention may be used for all parts that require sealing in a fuel cell, or may be used for a part of parts that require sealing. Examples of the sealing part 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.

  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 adhesive seal members 4 a and 4 b.

  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 disposed on both sides in the stacking direction with the electrolyte membrane 20 interposed therebetween.

  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 separators 3 are arranged to face each other on both sides of the MEA 2 in the stacking direction. 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 4a has a rectangular frame shape with a large thickness in the stacking direction. The adhesive seal member 4a is bonded to the peripheral edge of the MEA 2 and the separator 3. The adhesive seal member 4a seals the peripheral edge of the MEA 2.

  The adhesive seal member 4b has a rectangular frame shape with a thin thickness in the stacking direction. The adhesive seal member 4b is bonded to the separator 3 facing away from the cell C adjacent in the stacking direction. The refrigerant flow path 31 is sealed between the separators 3 facing away by the adhesive seal member 4b.

  During operation of the polymer electrolyte fuel cell 1, fuel gas and oxidant gas are supplied through the gas flow paths 30. Further, the refrigerant flows through the refrigerant flow path 31 in order to relieve the heat generated during power generation. Here, the peripheral edge of the MEA 2 is adhesively sealed by the adhesive seal member 4a. For this reason, gas mixing and leakage do not occur. Further, the wet state of the electrolyte membrane 20 is also maintained. Furthermore, the adhesive seal member 4a can be bonded at a low temperature of about 130 ° C. in a short time. Therefore, there is little possibility that the electrolyte membrane 20 deteriorates during the bonding process. Further, the separators 3 facing each other in the cell C adjacent in the stacking direction are also adhesively sealed by the adhesive seal member 4b. For this reason, it is difficult for the refrigerant to leak from the refrigerant flow path 31 to the outside. Further, the tensile strength and elongation of the adhesive seal members 4a and 4b are large. Furthermore, the adhesiveness of the adhesive seal members 4 a and 4 b is not easily lowered even in the operating environment of the polymer electrolyte fuel cell 1. Therefore, the polymer electrolyte fuel cell 1 is excellent in durability. That is, the polymer electrolyte fuel cell 1 can be stably operated over a long period of time.

  Next, an Example is given and this invention is demonstrated in detail.

(1) Preparation of rubber composition The raw materials shown in Table 1 below were blended to prepare each rubber composition of Examples and Comparative Examples. In Table 1, the following were used for each raw material.
(A) Rubber component EPDM (1): “JSR EP27” manufactured by JSR Corporation (Mooney viscosity = 105 [ML (1 + 4) 100 ° C.), diene amount = 4.5 mass%).
EPDM (2): “JSR EP51” manufactured by JSR Corporation (Mooney viscosity = 38 [ML (1 + 4) 100 ° C.), diene amount = 5.8 mass%).
EPDM (3): “Esplen (registered trademark) 501A” manufactured by Sumitomo Chemical Co., Ltd. (Mooney viscosity = 44 [ML (1 + 4) 100 ° C.], diene amount = 4.0% by mass).
EPDM (4): “JSR EP33” manufactured by JSR Corporation (Mooney viscosity = 45 [ML (1 + 4) 100 ° C.], diene amount = 8.1 mass%).
(B) Ethylene / α-olefin copolymer Ethylene / α-octene copolymer: “EXACT (registered trademark) 0210” manufactured by DEX PLASTOMERS
(C) Crosslinking agent peroxyester: “Perbutyl (registered trademark) I” manufactured by NOF Corporation (t-butylperoxyisopropyl monocarbonate, 1 hour half-life temperature = 118 ° C.). The blending amount of the crosslinking agent is not a value in a diluted state, but a value when the organic peroxide is 100%.
(D) Crosslinking aid maleimide compound: “Barnock (registered trademark) PM” manufactured by Ouchi Shinsei Chemical Co., Ltd.
(E) Adhesive component resorcinol-based compound: “Tacchiol (registered trademark) 620” manufactured by Taoka Chemical Industry Co., Ltd. Melamine-based compound: “SUMIKANOL (registered trademark) 507AP” manufactured by Sumitomo Chemical Co., Ltd.
Silane coupling agent: “KBM303” (2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.
Aluminate-based coupling agent: “Plenact (registered trademark) AL-M” (aluminum alkyl acetoacetate diisopropylate) manufactured by Ajinomoto Fine Techno Co., Ltd.
(F) Additive carbon black (GPF grade): “Show Black (registered trademark) IP200” manufactured by Cabot Japan Co., Ltd.
Paraffinic process oil: “Diana (registered trademark) process oil PW380” manufactured by Idemitsu Kosan Co., Ltd.

  First, in Table 1, the rubber component (A), the ethylene / α-olefin copolymer (B), carbon black, and paraffinic process oil were kneaded at 120 ° C. for 5 minutes using a Banbury mixer. After cooling the kneaded product, a cross-linking agent (C), a cross-linking aid (D), and an adhesive component (E) are appropriately added, and kneaded at 50 ° C. for 10 minutes using an open roll to obtain a rubber composition. It was. The obtained rubber composition was molded into a flat plate having a predetermined thickness by pressing.

(2) Evaluation of fluidity In the process of preparing the rubber composition, the Mooney viscosity of the kneaded product obtained by kneading the rubber component (A), the ethylene / α-olefin copolymer (B), carbon black, and paraffinic process oil. Was measured. The Mooney viscosity was measured at a test temperature of 80 ° C. according to JIS K6300-1 (2001). The measurement results are summarized in Table 1 above. Table 1 shows the Mooney viscosity index as a measurement result when the Mooney viscosity of the kneaded product of Comparative Example 1 is used as a reference (100). The Mooney viscosity index was calculated by the following formula (I). A larger Mooney viscosity index indicates higher fluidity.
Mooney viscosity index = (Mooney viscosity of the kneaded product of Comparative Example 1) / (Mooney viscosity of each kneaded product) × 100 (I)
For the kneaded material other than Comparative Example 1, EPDM (2) to (4) having a small Mooney viscosity was used. Therefore, as shown in Table 1, the Mooney viscosity index of the kneaded material other than Comparative Example 1 was larger than that of Comparative Example 1. In other words, the liquidity became high. Therefore, according to the rubber composition other than Comparative Example 1, the moldability at the time of injection molding and transfer molding is improved.

(3) Manufacture of seal member and evaluation of mechanical strength The rubber compositions of Examples 1 to 10 and Comparative Examples 2 and 3 were cross-linked by holding at 130 ° C. for 10 minutes to manufacture seal members. Moreover, the rubber composition of Comparative Example 1 was crosslinked by holding at 130 ° C. for 20 minutes to produce a seal member. The seal members of Examples 1 to 10 are included in the adhesive seal member of the present invention (the same applies hereinafter).

About the sealing member of an Example and a comparative example, tensile strength and elongation at the time of cutting were measured. The tensile strength and elongation at break were measured according to JIS K6251 (2004). Dumbbell-shaped No. 5 was used for the test piece. The measurement results are summarized in Table 1 above. Table 1 shows the ratio of the tensile strength and the elongation at break of each seal member as an index when the tensile strength and the elongation at break of the seal member of Comparative Example 1 are each set as a reference (100). The tensile strength and elongation index at break were calculated by the following formulas (II) and (III), respectively.
Tensile strength index = (Tensile strength of each seal member) / (Tensile strength of seal member of Comparative Example 1) × 100 (II)
Elongation index at cutting = (Elongation at cutting of each sealing member) / (Elongation at cutting of the sealing member of Comparative Example 1) × 100 (III)
As shown in Table 1, the tensile strength of the seal member of the example was larger than the tensile strength of the seal member of Comparative Example 1. Similarly, the elongation at the time of cutting of the seal member of the example was larger than the elongation at the time of cutting of the sealing member of Comparative Example 1. On the other hand, the ethylene / α-olefin copolymer (B) is not blended in the sealing members of Comparative Examples 2 and 3. For this reason, when it bridge | crosslinked on the same conditions as an Example, both tensile strength and elongation at the time of cutting became small. From the above, it was confirmed that the adhesive strength member of the present invention is less likely to decrease in tensile strength and elongation even when crosslinked at a low temperature for a short time.

  Here, the compounding quantity of the ethylene-alpha-olefin copolymer (B) of the sealing member of Example 7 is 5 mass parts. That is, in the seal member of Example 7, the blending amount of the ethylene / α-olefin copolymer (B) is smaller than that of the seal member of Example 1 ((B) = 10 parts by mass). For this reason, the tensile strength and elongation at break were slightly reduced. On the contrary, the blending amount of the ethylene / α-olefin copolymer (B) in the seal member of Example 8 is 30 parts by mass. Since the blending amount of the ethylene / α-olefin copolymer (B) is large, the elongation at break was large. The tensile strength was slightly reduced.

(4) Evaluation of insulation The volume resistivity of the sealing members of Examples and Comparative Examples was measured according to JIS K6271 (2008). The measurement was performed by applying a DC voltage of 100V. The measurement results are summarized in Table 1 above. As shown in Table 1, the volume resistivity of the seal member of the example was 1 × 10 ¹³ Ωcm. On the other hand, the volume resistivity of the sealing member of the comparative example was 1 × 10 ¹² Ωcm. That is, the sealing member of the example has higher insulation. This is considered to be a blending effect of the ethylene / α-olefin copolymer which is a resin component.

(5) Manufacture of seal member and evaluation of adhesiveness A 90 ° peel test based on JIS K6256-2 (2006) was performed to evaluate the adhesiveness of the seal members of Examples and Comparative Examples. First, a flat rubber composition having a width of 25 mm, a length of 60 mm, and a thickness of 5 mm was placed on the surface of a stainless steel plate having a width of 25 mm, a length of 60 mm, and a thickness of 2 mm. Subsequently, while pressing from the rubber composition side, it was held at 130 ° C. for 10 minutes to crosslink and bond, thereby preparing a test piece. Next, the produced test piece was attached to a predetermined test jig, and a 90 ° peel test was performed. Table 1 collectively shows the peel strength of each test piece in the 90 ° peel test. Table 1 shows, as an index, the ratio of the peel strength of each seal member when the peel strength of the seal member of Comparative Example 1 is used as a reference (100). The peel strength index was calculated by the following formula (IV).
Peel strength index = (Peel strength of each seal member) / (Peel strength of the seal member of Comparative Example 1) × 100 (IV)
As shown in Table 1, the peel strength of the seal member of the example was equal to or greater than the peel strength of the seal member of Comparative Example 1. Thus, according to the sealing member of the example, it can be seen that the crosslinking reaction proceeds sufficiently even under the crosslinking conditions of a low temperature and for a short time, and a large adhesive force is expressed. On the other hand, the peel strength of the seal members of Comparative Examples 2 and 3 was smaller than that of the seal member of Comparative Example 1. For the sealing members of Comparative Examples 2 and 3, the ethylene / α-olefin copolymer (B) is not blended. For this reason, when it bridge | crosslinks at low temperature and for a short time, it is thought that tensile strength and elongation become small and desired adhesive force is not expressed.

  According to the adhesive seal member of the present invention, it is possible to bond to the member at a low temperature and in a short time without using another adhesive. In addition, the adhesive seal member of the present invention contains an ethylene / α-olefin copolymer, so that even if it is crosslinked at a low temperature for a short time, the tensile strength and elongation are not easily lowered. The adhesive seal member of the present invention has rubber elasticity. For this reason, according to the adhesive seal member of the present invention, both an adhesive seal and a stress seal are possible. Therefore, the adhesive seal member of the present invention is suitable for sealing between the constituent members of the fuel cell.

1: Solid polymer fuel cell 2: MEA 20: Electrolyte membrane 21a, 21b: Electrode 3: Separator 30: Gas flow path 31: Refrigerant flow path 4a, 4b: Adhesive seal member C: Cell

Claims (9)

An adhesive seal member for a fuel cell, comprising a crosslinked product of a rubber composition containing the following (A) to (E), and 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) Ethylene / α-olefin copolymer (C) A crosslinking agent selected from organic peroxides having a one-hour half-life temperature of 130 ° C. or lower.
(D) A crosslinking aid.
(E) One or more adhesive components selected from resorcinol compounds and melamine compounds, aluminate coupling agents, and silane coupling agents.   2. The fuel cell adhesive seal member according to claim 1, wherein the rubber component (A) has a Mooney viscosity of 90 [ML (1 + 4) 100 ° C.] or less. The rubber component (A) includes ethylene-propylene-diene rubber,
The adhesive seal member for a fuel cell according to claim 1 or 2, wherein the ethylene-propylene-diene rubber has a diene content of 4% by mass or more and 9% by mass or less.   The blending amount of the ethylene / α-olefin copolymer (B) is 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component (A). An adhesive seal member for a fuel cell according to claim 1.   The adhesive seal member for a fuel cell according to any one of claims 1 to 4, wherein the organic peroxide (C) includes peroxyketal and peroxyester.   The fuel cell according to any one of claims 1 to 5, wherein a blending amount of the crosslinking agent (C) is 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the rubber component (A). Adhesive seal member. The crosslinking aid (D) includes a maleimide compound,
The amount of the crosslinking aid is 0.1 to 3 parts by mass with respect to 100 parts by mass of the rubber component (A). Adhesive seal member.   The adhesive seal member for a fuel cell according to any one of claims 1 to 7, wherein the rubber composition further contains carbon black.   The adhesive seal member for a fuel cell according to any one of claims 1 to 8, wherein the rubber composition further contains a softening agent.

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