JP5719668B2 - Adhesive seal member for fuel cell - Google Patents

Description

  The present invention relates to an adhesive seal member that seals a constituent member of a fuel cell, and more particularly to an adhesive seal member that has good sealing performance even at extremely low temperatures.

  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 an automotive power source, 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, it is important to ensure the sealing performance around the MEA and the porous layer and between adjacent separators. It becomes. For example, Patent Documents 1 and 2 propose rubber materials using ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), and the like as seal members for sealing these constituent members.

JP 2009-94056 A JP 2010-146781 A JP 2004-150591 A European Patent No. 0315363

  A polymer membrane such as a perfluorinated sulfonic acid membrane is used for the electrolyte membrane of the solid polymer fuel cell. For this reason, when the rubber composition 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 cross-linking and bonding process of the seal member at a lower temperature and in a shorter time.

  In this respect, the rubber composition constituting the sealing member described in Patent Documents 1 and 2 can be crosslinked in a relatively short time at a low temperature of 130 ° C. or lower. Therefore, the seal member can also be applied in the vicinity of the electrolyte membrane. Further, the seal member includes an adhesive component. For this reason, even if it does not use another adhesive agent, it can adhere | attach with a member. However, the rubber elasticity of EPM and EPDM may be lost at an extremely low temperature of about -20 to -30 ° C. For this reason, when using a fuel cell in a cold district etc., it is difficult to ensure desired sealing performance.

  The present invention has been made in view of such a situation, and provides an adhesive seal member for a fuel cell which can be crosslinked at a low temperature in a short time and has a good sealing property even at an extremely low temperature. Let it be an issue.

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 by sealing the constituent members of the fuel cell.
(A) One or more rubber components selected from ethylene-propylene rubber and ethylene-propylene-diene rubber.
(B) Organic peroxide having a one-hour half-life temperature of 130 ° C. or lower.
(C) A crosslinking aid.
(D) One or more adhesive components selected from resorcinol compounds and melamine compounds, aluminate coupling agents, and silane coupling agents.
(E) A softener having a pour point of −40 ° C. or lower.

  When a softening agent is added to EPM or EPDM, the glass transition point (Tg) decreases. However, when the pour point of the softening agent is high, even if the softening agent is blended, the decrease in rubber elasticity at extremely low temperatures cannot be improved. For example, Patent Documents 3 and 4 disclose rubber compositions containing a softening agent such as poly-α-olefin. According to the document, the softening agent is only blended in order to improve the lubricity and flexibility of the rubber molded body. Therefore, no consideration is given to the pour point of the softener. In this regard, the adhesive seal member of the present invention includes a softener having a pour point of −40 ° C. or less (the above (E)). A softener having a pour point of −40 ° C. or lower has a low viscosity and easily flows even at an extremely low temperature of about −20 to −30 ° C. For this reason, when the said softener is mix | blended with EPM and EPDM, the fall of the rubber elasticity under cryogenic temperature can be suppressed. Therefore, the adhesive seal member of the present invention is excellent in sealability even at extremely low temperatures.

  Moreover, the adhesive sealing member of this invention contains an adhesive component (above (D)). 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, 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. That is, the operation reliability of the fuel cell can be improved.

  In the adhesive sealing member of the present invention, “sealing the constituent members of the fuel cell” means sealing around the constituent members and between the constituent members. The adhesive seal member of the present invention has rubber elasticity in a wide temperature range from the operating temperature of the fuel cell to about −30 ° C. For this reason, according to the adhesive sealing member of this invention, not only the sealing by adhesion | attachment but the sealing by stress is attained. 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 sealed between the other members by stress. Can be adopted. Of course, the adhesive sealing member of the present invention may be bonded to both members, and the members may be bonded and sealed. When rubber elasticity is lost at a very low temperature, the sealing performance is more likely to deteriorate in the stress seal than in the adhesive seal. In this regard, according to the adhesive seal member of the present invention, the rubber elasticity is maintained even at an extremely low temperature, and therefore the sealability is not easily lowered even with a stress seal.

  Further, according to the adhesive seal member of the present invention, an organic peroxide having a one-hour half-life temperature of 130 ° C. or less is used as the 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 130 ° C. or less, crosslinking can be performed at a lower temperature (specifically, 150 ° 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.

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 one or more selected from ethylene-propylene rubber (EPM) and ethylene-propylene-diene rubber (EPDM). As the rubber component, one of EPM and EPDM may be used, or a mixture of both may be used. Further, two or more of the same types of rubbers having different ethylene contents and the like, which will be described later, may be mixed and used. Considering acid resistance and water resistance in the operating environment of the fuel cell, it is desirable that the rubber component contains EPDM.

  EPM and EPDM are less likely to crystallize at extremely low temperatures as the ethylene content decreases. That is, EPM and EPDM having a low ethylene content are less likely to have a reduced rubber elasticity even at extremely low temperatures. Therefore, it is desirable to use EPM and EPDM having an ethylene content of 53% by mass or less as a rubber component from the viewpoint of suppressing a decrease in rubber elasticity at an extremely low temperature and improving a sealing property. EPM and EPDM having an ethylene content of 50% by mass or less are more preferable. On the other hand, if the ethylene content is too small, the physical properties of the rubber may be reduced. Therefore, from the viewpoint of securing the elongation and tensile strength required for the adhesive seal member, it is desirable to use EPM or EPDM having an ethylene content of 40% by mass or more as the rubber component.

  Next, the organic peroxide (B) will be described. Examples of the organic peroxide having a one-hour half-life temperature of 130 ° C. or lower 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.

  Next, the crosslinking aid (C) will be described. What is necessary is just to select a crosslinking adjuvant suitably according to the kind of said organic peroxide (B). 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 it has a great effect of improving the crosslinking density and tensile strength.

  When the rubber component is crosslinked, the molecules are constrained at the crosslinking point. For this reason, the more cross-linking points, the harder the crystallization of the rubber component. That is, by increasing the crosslinking density, crystallization of the rubber component at an extremely low temperature can be suppressed. In order to increase the crosslinking density, for example, the blending amount of the organic peroxide (B) and the crosslinking aid (C) may be increased. From such a viewpoint, it is desirable that the compounding amount of the organic peroxide is 1 part by mass or more with respect to 100 parts by mass of the rubber component. On the other hand, when the amount of the organic peroxide is too large, the crosslinking density rapidly increases during the crosslinking reaction, resulting in a decrease in adhesive strength. Therefore, the compounding amount of the organic peroxide is desirably 10 parts by mass or less with respect to 100 parts by mass of the rubber component. Similarly, the blending 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. On the other hand, when there are too many compounding quantities of a crosslinking adjuvant, a crosslinking density will become large too much and will cause the fall of adhesive force. For this reason, it is desirable that the amount of the crosslinking aid is 3 parts by mass or less.

  Next, the adhesive component (D) will be described. The adhesive component (D) 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 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. 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 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. 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. 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.

  Next, the softening agent (E) will be described. The pour point of the softener is -40 ° C or lower. Examples of such softeners include polyalphaolefin, dioctyl phthalate (DOP), dioctyl adipate (DOA), dioctyl sebacate (DOS), and dibutyl sebacate (DBS). One of these may be used alone, or two or more may be used in combination. Of these, poly-α-olefins are preferred from the viewpoint of good compatibility with the rubber component and difficulty in bleeding. The poly α olefin is obtained by polymerizing an α olefin having 6 to 16 carbon atoms. In the polyalphaolefin, the smaller the molecular weight, the lower the viscosity and the lower the pour point.

  The lower the pour point, the harder the softener becomes harder to cure at extremely low temperatures. Therefore, the lower the pour point, the greater the effect of suppressing the crystallization of the rubber component at extremely low temperatures. The pour point of a more preferable softener is −50 ° C. or lower. On the other hand, if the pour point is too low, it tends to volatilize during operation of the fuel cell. Therefore, the pour point of the softener is desirably -80 ° C or higher. The pour point may be measured according to JIS K2269 (1987).

  In order for the adhesive seal member to maintain good sealing properties without losing rubber elasticity even at extremely low temperatures, the blending amount of the softening agent may be 5 parts by mass or more with respect to 100 parts by mass of the rubber component. desirable. More preferably, it is 10 parts by mass or more, and more preferably 20 parts by mass or more. On the other hand, if the blending amount of the softening agent is too large, it will bleed and it will be difficult to obtain the blending effect of the softening agent. For this reason, it is desirable that the blending amount of the softening agent is 50 parts by mass or less with respect to 100 parts by mass of the rubber component. More preferably, it is 40 mass parts or less, Furthermore, it is good to set it as 30 mass parts 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. For this reason, it is desirable that the compounding amount of carbon black is 10 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the rubber component.

  Other additives include anti-aging agents, tackifiers, processing aids, and the like. For example, examples of the antiaging 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. Moreover, you may mix | blend the softener whose pour point is higher than -40 degreeC with the softener of said (E). Examples of softeners that can be used in combination include petroleum oils such as process oil, lubricating oil, paraffin, liquid paraffin, and petroleum jelly, fatty oil softeners such as castor oil, linseed oil, rapeseed oil, coconut oil, and tall oil. , Waxes such as sub, beeswax, carnauba wax and lanolin, linoleic acid, palmitic acid, stearic acid, lauric acid and the like.

<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 (B) an organic peroxide, (C) a crosslinking aid, and (D) an adhesive component are premixed and kneaded at 80 to 140 ° C. for several minutes. Next, the obtained kneaded material is cooled, and (B) an organic peroxide, (C) a crosslinking aid, and (D) an adhesive component 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 (D) adhesive component in the stage of preliminary mixing.

  The prepared rubber composition is crosslinked at a predetermined temperature. By crosslinking, the rubber composition becomes the adhesive seal member of the present invention. Under the present circumstances, if it bridge | crosslinks making it contact with a member, the said member and an adhesive sealing member can be adhere | attached. Here, the crosslinking temperature is desirably 150 ° 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 the member so that it can be easily crosslinked and adhered. 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.

  As described above, from the viewpoint of suppressing crystallization of the rubber component at an extremely low temperature, it is preferable that the crosslinking density is large. When determining the crosslinking density, a value of 100% modulus can be used as an index. For example, the 100% modulus of the adhesive seal member of the present invention is desirably 2 MPa or more and 4 MPa or less. In this case, since the crosslinking density is large, the rubber elasticity is not easily lowered even at an extremely low temperature. The 100% modulus is a value obtained by dividing the tensile force when the dumbbell-shaped test piece is stretched 100% by the initial cross-sectional area of the dumbbell-shaped test piece. The 100% modulus may be measured according to JIS K6251 (2010).

  The adhesive seal member of the present invention is excellent in sealability even at extremely low temperatures. This is also apparent from the fact that, as will be shown later in the examples, the Gehman twist test temperature T2 of the adhesive seal member of the present invention is −40 ° C. or lower. The Gehman torsion test may be performed according to JIS K6261 (2006). T2 is a temperature at which the specific modulus with respect to the modulus at room temperature (23 ° C. ± 2 ° C.) is doubled. If T2 is −40 ° C. or lower, rubber elasticity is maintained even at an extremely low temperature, and a desired sealing property can be ensured.

<Application to fuel cells>
The adhesive seal member of the present invention seals the constituent members of the fuel cell. The fuel cell to be applied only needs to operate at a temperature at which the rubber component 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 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 portion include a separator between the separator and the separator facing each other across the MEA, a periphery of the MEA and the porous layer, and between the separator and the separator respectively 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 an adhesive seal member 4 a.

  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 in the stacking direction (vertical 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 periphery of the MEA 2 and to the separator 3 to be laminated. The adhesive seal member 4a seals the periphery of the MEA 2 between the separators 3 facing each other.

  An adhesive seal member 4b is interposed between the separators 3 facing each other in the cell C adjacent in the stacking direction. The adhesive seal member 4b has a rectangular frame shape with a thin thickness in the stacking direction. The lower surface of the adhesive seal member 4b is bonded to the upper surface of the separator 3 disposed below. A frame-like lip portion 40b is formed on the peripheral edge of the upper surface of the adhesive seal member 4b (shown by hatching in the adhesive seal member 4b shown above the cell C in FIG. 3). The lip portion 40b is in contact with the lower surface of the separator 3 disposed above. The lip portion 40b is pressed and deformed by the fastening force in the stacking direction when the cells C are stacked and the polymer electrolyte fuel cell 1 is assembled. Thereby, a seal line is formed and leakage of the refrigerant is suppressed. The adhesive seal members 4a and 4b are included in the adhesive seal member of the present invention.

  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 periphery of the MEA 2 is 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 150 ° C. in a short time. Therefore, there is little possibility that the electrolyte membrane 20 deteriorates during the bonding process. In addition, the separators 3 facing each other in the cell C adjacent in the stacking direction are also 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, even at an extremely low temperature of about -20 to -30 ° C, the sealing performance of the adhesive seal members 4a and 4b is unlikely to deteriorate. 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.

<Preparation of rubber composition>
The rubber composition of each of the examples and comparative examples was prepared by blending the raw materials shown in Table 1 below. In Table 1, the following were used for each raw material.
(A) Rubber component EPDM (1): “JSR EP27” manufactured by JSR Corporation (ethylene content = 54 mass%).
EPDM (2): “Esprene (registered trademark) 505A” manufactured by Sumitomo Chemical Co., Ltd. (ethylene content = 50 mass%).
EPDM (3): “Mitsui EPT 4045M” manufactured by Mitsui Chemicals, Inc. (ethylene content = 45 mass%).
EPDM (4): “Keltan (registered trademark) 4903” manufactured by DSM (ethylene content = 48 mass%).
EPDM (5): “Mitsui EPT 9090M” manufactured by Mitsui Chemicals, Inc. (ethylene content = 41 mass%).
(B) Organic peroxide peroxyketal: “Perhexa (registered trademark) C-40” manufactured by NOF Corporation (1,1-di (t-butylperoxy) cyclohexane, purity 40%, 1 hour half-life Temperature = 111.1 ° C).
(C) Crosslinking assistant maleimide compound: “Barunok (registered trademark) PM” manufactured by Ouchi Shinsei Chemical Co., Ltd.
(D) 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: “KBM403” (3-glycidoxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.
(E) Softener paraffinic process oil: “Diana (registered trademark) process oil PW380” manufactured by Idemitsu Kosan Co., Ltd. (pour point = −15 ° C.).
Poly α-olefin (1): “SpectraSyn (registered trademark) 4” manufactured by ExxonMobil (pour point = −60 ° C.)
Polyalphaolefin (2): “SpectraSyn 10” manufactured by ExxonMobil (pour point = −48 ° C.)
Poly α-olefin (3): “SpectraSyn 2C” manufactured by ExxonMobil (pour point = −57 ° C.)
Polyalphaolefin (4): “Shinflude (registered trademark) 401” manufactured by Nippon Steel Chemical Co., Ltd. (pour point = −73 ° C.)
(F) Reinforcing agent carbon black (GPF grade): “Show Black (registered trademark) IP200” manufactured by Cabot Japan Co., Ltd.

  First, in Table 1, (A) rubber component, (E) softener, and (F) reinforcing agent were kneaded at 120 ° C. for 5 minutes using a Banbury mixer. After the kneaded product is cooled, (B) an organic peroxide, (C) a crosslinking aid, and (D) an adhesive component are added, and the mixture is kneaded at 50 ° C. for 10 minutes using an open roll. Obtained. The obtained rubber composition was molded into a flat plate having a predetermined thickness by pressing.

<Manufacture of seal members and evaluation of tensile properties>
The rubber compositions of Examples 1 to 12 and Comparative Example 1 were cross-linked by holding at 150 ° C. for 10 minutes to produce seal members. The seal members of Examples 1 to 12 are included in the adhesive seal member of the present invention.

  About the sealing member of an Example and a comparative example, 100% modulus was measured. The measurement of 100% modulus was performed according to JIS K6251 (2010). Dumbbell-shaped No. 5 was used for the test piece. The measurement results are summarized in Table 1 above.

  As shown in Table 1, the 100% modulus of the seal member of the example was 2 MPa or more, which was larger than the 100% modulus of the seal member of Comparative Example 1. In each of the seal members of the examples, the blending amount of the crosslinking aid is larger than that of the seal member of the comparative example. For this reason, about the sealing member of the Example, the crosslinking density became large and the 100% modulus became large.

<Evaluation of adhesiveness>
A 90 ° peel test in accordance with JIS K6256-2 (2006) was conducted 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, the test piece was prepared by holding at 150 ° C. for 10 minutes for crosslinking and bonding. 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 an index 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 (I).
Peel strength index = (Peel strength of each seal member) / (Peel strength of the seal member of Comparative Example 1) × 100 (I)
As shown in Table 1, the peel strength of the seal member of the example was the same as the peel strength of the seal member of Comparative Example 1. Thus, the adhesiveness of the sealing member of an Example is favorable.

<Evaluation of low temperature characteristics>
[Geman twist test]
For the seal members of Examples and Comparative Examples, a Gehman torsion test based on JIS K6261 (2006) was performed, and a temperature T2 at which the ratio modulus to the modulus at room temperature (23 ° C.) was doubled was measured. The measurement results are summarized in Table 1 above.

  As shown in Table 1, T2 of the sealing member of Comparative Example 1 was −31 ° C., whereas T2 of the sealing member of the example was −40 ° C. or less. From this result, it can be seen that the seal member of the example is not easily hardened even at an extremely low temperature of −20 to −30 ° C. and can maintain rubber elasticity. For example, when Example 12 using the same EPDM is compared with Comparative Example 1, the pour point is −15 ° C. in the seal member of Example 12 containing the polyα-olefin (2) having a pour point of −48 ° C. T2 was lower than that of the seal member of Comparative Example 1 containing the paraffinic process oil. From this result, it is possible to confirm the effect of suppressing the decrease in rubber elasticity by the softening agent having a pour point of −40 ° C. or lower. In addition, the sealing member of Example 2 contains both the poly alpha olefin (1) whose pour point is -60 degreeC and paraffin type process oil whose pour point is -15 degreeC as a softening agent. For this reason, in the sealing member of Example 2, T2 raised a little compared with the sealing member of Example 1 containing only the poly alpha olefin (1) whose pour point is -60 degreeC.

[Compression set test]
The compression set test based on JIS K6262 (2006) was done about the sealing member of the Example and the comparative example. Two types of compression set tests were performed: a low temperature test at −30 ° C. and a high temperature test at 100 ° C. In the low temperature test, after compression for 24 hours at −30 ° C., the sample was released and the thickness after 30 minutes had passed under the same temperature was measured to calculate the compression set. In the high temperature test, after compression for 24 hours at 100 ° C., the sample was released and the thickness after 30 minutes at room temperature was measured to calculate compression set. In any test, the compression rate was 25%. The measurement results are summarized in Table 1 above. In Table 1, the compression set at −30 ° C. and 100 ° C. is an index when the seal member of Comparative Example 1 is used as the reference (100). The compression set index was calculated by the following formula (II).
Compression set index = (compression set of each seal member) / (compression set of seal member of Comparative Example 1) × 100 (II)

  As shown in Table 1, the compression set of the seal member of the example was smaller than that of the seal member of Comparative Example 1 in both the low temperature and high temperature tests. For example, when Example 12 using the same EPDM and Comparative Example 1 are compared, the seal member of Example 12 containing polyα-olefin (2) having a pour point of −48 ° C. in both the low temperature and high temperature tests. The compression set was smaller than that of the seal member of Comparative Example 1 containing paraffinic process oil having a pour point of −15 ° C. From this result, it is possible to confirm the effect of suppressing the decrease in rubber elasticity by the softening agent having a pour point of −40 ° C. or lower. As described above, the seal member of the example is difficult to sag both at a high temperature of 100 ° C. and at an extremely low temperature of −30 ° C. Therefore, according to the adhesive seal member of the present invention, it is possible to realize an improvement in sealability at an extremely low temperature without sacrificing the sealability at a high temperature.

  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. Further, the adhesive seal member of the present invention does not lose rubber elasticity even at an extremely low temperature of about −20 to −30 ° C. For this reason, good sealing performance is exhibited even in cold regions. As described above, according to the adhesive seal member of the present invention, both the adhesive seal and the stress seal are possible in a wide temperature range in which the fuel cell is used.

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 40b: Lip part C: Cell

Claims (4)

An adhesive seal member for a fuel cell, comprising a crosslinked product of a rubber composition containing the following (A) to (E), and sealing a constituent member of a fuel cell.
(A) One or more rubber components selected from ethylene-propylene rubber and ethylene-propylene-diene rubber.
(B) An organic peroxide having a one-hour half-life temperature of 130 ° C. or less and a blending amount of 100 parts by weight of the rubber component (A) of 1 part by weight or more and 10 parts by weight or less .
(C) A crosslinking aid having a blending amount of 0.1 to 3 parts by mass with respect to 100 parts by mass of the rubber component of (A) .
(D) One or more adhesive components selected from resorcinol compounds and melamine compounds, aluminate coupling agents, and silane coupling agents.
(E) A softener having a pour point of −40 ° C. or less and a blending amount of 100 parts by mass of the rubber component (A) of 5 parts by mass or more and 50 parts by mass or less .   The adhesive seal member for a fuel cell according to claim 1, wherein the softening agent (E) is a polyα-olefin. The adhesive seal member for a fuel cell according to claim 1 or 2, wherein the 100% modulus is 2 MPa or more and 4 MPa or less. The adhesive seal member for a fuel cell according to any one of claims 1 to 3, wherein a Gehmann twist test temperature T2 is -40 ° C or lower.

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