Cell seal material of fuel cell for automobile

Abstract

To provide a cell seal material of a novel fuel cell for an automobile indicating a good adhesion (seal property) while having a low-surface pressure.SOLUTION: A cell seal material of a fuel cell for an automobile, includes: an elastic layer containing a foam rubber layer; and an adhesive agent layer to be laminated and arranged onto both main front surfaces of the elastic layer. The foam rubber layer is formed by a foam material of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a subber component, a phenol resin, a cross-linking agent, and a foam agent. A content ratio of a phenol resin cross-linking agent in the unfoamed rubber layer is 2.0 to 20.0 mass% in terms of a solid content.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sealing material for cells of automotive fuel cells.

Background Art

[0002] In recent years, polymer electrolyte fuel cells have been developed as fuel cells and are becoming more widespread in automotive applications and the like. In a polymer electrolyte fuel cell, a basic component called a membrane electrode assembly (MEA) in which a fuel electrode (negative electrode), a polymer membrane (electrolyte membrane), and an oxygen electrode (positive electrode) are laminated in this order and integrated is sandwiched from above and below by a separator (bipolar plate) in which a supply flow path for reaction gas is engraved to form one basic unit (single cell). By stacking and connecting these single cells in series to form a cell stack, a high voltage is obtained (see, for example, Patent Document 1).

[0003] In the cell stack of the above fuel cell, a sealing material such as a gasket is provided between the cells to prevent leakage of the cooling water supplied between the cells. As the above sealing material, for example, an annular member such as a fluororubber ring having elasticity has been proposed. By disposing the fluororubber ring between the cells to be sealed and pressing them against each other, sealing performance is exhibited.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The cell stack of the fuel cell is assembled with a predetermined fastening load applied from both ends of the cell laminate. However, if the fastening load acts over a long period of time, sagging is likely to occur in the polymer membrane (electrolyte membrane), fuel electrode (negative electrode), oxygen electrode (positive electrode), etc. that make up the membrane electrode assembly within the cell stack, and it becomes difficult to maintain a predetermined surface pressure between the cells.

[0006] On the other hand, when the fastening load of the cell stack of the fuel cell is set high in advance and an attempt is made to impart a certain degree of rigidity even when the above sagging occurs, the constituent members of the cell are likely to be damaged during fastening or during use after fastening. Particularly in the case of a cell stack for an automotive fuel cell, when the fastening load of the cell stack is set high, the constituent members of the cell are likely to be damaged by vibrations and impacts during operation.

[0007] For this reason, as a sealing material for cells of an automotive fuel cell, a material that has excellent sealing performance even at low surface pressure has been required between the cells of an automotive fuel cell.

[0008] Under such circumstances, an object of the present invention is to provide a novel sealing material for cells of an automotive fuel cell that exhibits high adhesion (sealing performance) at low surface pressure.

Means for Solving the Problems

[0009] As a result of intensive studies by the present inventors to achieve the above object, it has been found that the above technical problems can be solved by a sealing material for cells of a specific automotive fuel cell having an elastic layer made of a foamed rubber layer and adhesive layers laminated and disposed on both main surfaces of the elastic layer, and the present invention has been completed based on this finding.

[0010] That is, the present invention (1) has an elastic layer including a foamed rubber layer and adhesive layers laminated and disposed on both main surfaces of the elastic layer, The foamed rubber layer is composed of a foam of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent. The content ratio of the phenolic resin crosslinking agent in the unfoamed rubber layer is 2.0 to 20.0% by mass in terms of solid content. A sealing material for a cell of a fuel cell for a vehicle, characterized in that: (2) The elastic layer is composed of only the foamed rubber layer or a laminated integrated product in which the foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a resin plate. The sealing material for a cell of a fuel cell for a vehicle according to (1) above. (3) The amount of diene constituting the ethylene-propylene-diene terpolymer (EPDM) is 1 to 20% by mass. The sealing material for a cell of a fuel cell for a vehicle according to (1) or (2) above. (4) The foamed rubber layer is a foam having a foaming ratio of 1.5 times or more of the unfoamed rubber layer. The sealing material for a cell of a fuel cell for a vehicle according to any one of (1) to (3) above. (5) The adhesive layer contains, as an adhesive, at least one selected from urethane resin, natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene, nitrile rubber, ethylene-propylene-diene terpolymer, butyl rubber, chloroprene rubber, thermoplastic elastomer, and water addition products of any of these. The sealing material for a cell of a fuel cell for a vehicle according to any one of (1) to (4) above. (6) The thermoplastic elastomer is at least one selected from styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers. The sealing material for a cell of a fuel cell for a vehicle according to (5) above. It is to provide the above.

Effects of the Invention

[0011] According to the present invention, it is possible to provide a novel sealing material for a cell of a fuel cell for a vehicle that exhibits high adhesion (sealing property) at a low surface pressure.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0013] The sealing material for a cell of a fuel cell for a vehicle according to the present invention has an elastic layer including a foamed rubber layer and adhesive layers laminated on both main surfaces of the elastic layer, respectively, wherein the foamed rubber layer is composed of a foam of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent, and is characterized in that the content ratio of the phenolic resin crosslinking agent in the unfoamed rubber layer is 2.0 to 20.0% by mass in terms of solid content.

[0014] The sealing material for a cell of a fuel cell for a vehicle according to the present invention has a laminated structure including an elastic layer and adhesive layers laminated on both main surfaces of the elastic layer, respectively.

[0015] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the elastic layer includes a foamed rubber layer.

[0016] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, as the form of the elastic layer, in addition to the form consisting only of a foamed rubber layer (hereinafter referred to as the first form), there can be mentioned a form consisting of a laminated integrated product in which foamed rubber layers are laminated on both main surfaces of a base material layer made of a resin plate (hereinafter referred to as the second form).

[0017] FIG. 1 is a schematic cross-sectional view of a vertical section in an exemplary form of a sealing material for a cell of a fuel cell for a vehicle according to the present invention, and shows an exemplary form when the elastic layer adopts a first form. In the exemplary form shown in FIG. 1, the sealing material 1 for a cell of a fuel cell for a vehicle includes an elastic layer i composed only of a foamed rubber layer r, and adhesive layers s, s laminated and disposed on both main surfaces of the elastic layer i, respectively.

[0018] Further, FIG. 2 is a schematic cross-sectional view of a vertical section in another exemplary form of the sealing material for a cell of a fuel cell for a vehicle according to the present invention, and shows an exemplary form when the elastic layer adopts a second form. In FIG. 2, the sealing material 1 for a cell of a fuel cell for a vehicle includes an elastic layer i composed of a laminated integrated body of a base material layer b made of a resin plate and foamed rubber layers r, r laminated and disposed on both main surfaces of the base material layer, and adhesive layers s, s laminated and disposed on both main surfaces of the elastic layer i, respectively.

[0019] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the elastic layer preferably has a thickness of 300 to 800 μm, and more preferably 400 to 700 μm.

[0020] The thickness of the elastic layer means the arithmetic average value when the thicknesses at 10 locations are measured using a dial gauge.

[0021] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, when the elastic layer adopts a first form, that is, a form composed only of a foamed rubber layer, the thickness of the elastic layer corresponds to the thickness of the foamed rubber layer.

[0022] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, when the elastic layer adopts a first form, that is, a form composed only of a foamed rubber layer (only), the thickness of the elastic layer corresponds to the thickness of the foamed rubber layer. In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, when the elastic layer adopts the second form, that is, a form composed of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a resin plate, the thickness of the elastic layer corresponds to the total thickness of the base material layer made of a resin plate and the thickness of the foamed rubber layer.

[0023] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the foamed rubber layer constituting the elastic layer is composed of a foamed product of an unfoamed rubber layer.

[0024] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the foamed rubber layer is preferably a foamed product having a foaming ratio of 1.5 times or more of the unfoamed rubber layer, more preferably a foamed product having a foaming ratio of 2.0 times or more of the unfoamed rubber layer, and even more preferably a foamed product having a foaming ratio of 2.5 times or more of the unfoamed rubber layer. The upper limit of the foaming ratio of the unfoamed rubber layer is not particularly limited, but the foaming ratio of the unfoamed rubber is usually 6.0 times or less.

[0025] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, when the foaming ratio of the unfoamed rubber layer is 1.5 times or more, excellent adhesion (sealing property) can be easily exhibited even when the surface pressure is low.

[0026] In the present application documents, the above foaming ratio means a value calculated by the following formula. Foaming ratio = Thickness of foamed rubber layer / Thickness of unfoamed rubber layer (However, the thickness of the foamed rubber layer means the arithmetic mean value when the thicknesses at 10 locations are measured using a dial gauge, and the thickness of the unfoamed rubber layer also means the arithmetic mean value when the thicknesses at 10 locations are measured using a dial gauge.)

[0027] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the foamed rubber layer is composed of a foamed product of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent.

[0028] As for the above ethylene-propylene-diene terpolymer (EPDM), it is preferable that the amount of diene constituting the EPDM is 1 to 20% by mass, and more preferably 5 to 15% by mass.

[0029] By the amount of diene constituting the EPDM being within the above range, it is possible to easily impart the desired resistance to sagging to the foamed rubber layer.

[0030] By the unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a foamed rubber layer having desired properties can be easily obtained.

[0031] The unfoamed rubber layer preferably contains 10 to 90% by mass, and more preferably 30 to 70% by mass, of an ethylene-propylene-diene terpolymer (EPDM) in terms of solid content.

[0032] By the unfoamed rubber layer containing the above ethylene-propylene-diene terpolymer (EPDM) in the above ratio, it is possible to easily provide a sealing material excellent in adhesion (sealing property) and resilience.

[0033] Further, in the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the above unfoamed rubber layer contains a phenolic resin crosslinking agent as a crosslinking agent.

[0034] The unfoamed rubber layer contains 2.0 to 20.0% by mass, and preferably 2.6 to 17.5% by mass, of a phenolic resin crosslinking agent in terms of solid content.

[0035] By the unfoamed rubber layer containing the above phenolic resin crosslinking agent in the above ratio, it is possible to easily control the flexibility of the foamed rubber layer and easily provide a sealing material for a cell of a fuel cell for a vehicle excellent in adhesion (sealing property) and resilience.

[0036] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the above unfoamed rubber layer contains a crosslinking accelerator. Examples of the crosslinking accelerator include one or more selected from halogen compounds such as tin chloride, and acid compounds such as phosphoric acid, nitric acid, citric acid, and salicylic acid.

[0037] The foaming agent constituting the unfoamed rubber layer is not particularly limited, but is preferably a microcapsule in which a volatile liquid foaming agent is encapsulated with a thermoplastic shell polymer having gas barrier properties. When the microcapsule is heated, the outer shell of the capsule softens, and the liquid foaming agent encapsulated in the capsule vaporizes, increasing the internal pressure. Due to such an action, the capsule expands to form hollow spherical particles, and pores are formed in the foamed rubber layer by the hollow spherical particles.

[0038] Examples of the volatile liquid foaming agent constituting the microcapsule include low-boiling hydrocarbons such as isopentane, isobutane, and isopropane.

[0039] Examples of the thermoplastic shell polymer constituting the microcapsule include one or more selected from polyacrylonitrile, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-methyl methacrylate copolymer, vinylidene chloride-ethyl methacrylate, acrylonitrile-methyl methacrylate copolymer, acrylonitrile-ethyl methacrylate, and the like.

[0040] By containing the microcapsule as a foaming agent in the unfoamed rubber layer, the foamability of the unfoamed rubber layer can be easily controlled, a foamed rubber layer having suitable flexibility can be easily formed, and a sealing material for a fuel cell for an automobile that exhibits excellent adhesion (sealing property) even when the surface pressure is low can be easily provided.

[0041] The unfoamed rubber layer preferably contains the foaming agent in an amount of 1.0 to 10.0% by mass in terms of solid content, and more preferably 2.0 to 8.0% by mass.

[0042] By containing the foaming agent in the unfoamed rubber layer at the above ratio, it is possible to easily control the flexibility of the foamed rubber layer and easily provide a sealing material excellent in adhesion (sealing property).

[0043] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, when the elastic layer takes the second form, the elastic layer is composed of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a resin plate, respectively.

[0044] In these application documents, the laminated integrated body means a state in which adjacent layers are chemically or physically fixed.

[0045] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the resin plate constituting the base material layer is not particularly limited. Examples of the resin plate constituting the base material layer include plate-like materials made of one or more resins selected from polyethylene (PE)-based resins, polypropylene (PP)-based resins, polyethylene terephthalate (PET)-based resins, polyethylene naphthalate (PEN)-based resins, polyvinyl chloride (PVC)-based resins, polystyrene (PS)-based resins, acrylic resins (PMMA), polycarbonate (PC)-based resins, polyphenylene sulfide (PPS)-based resins, polytetrafluoroethylene (PTFE)-based resins, polyether ether ketone (PEEK)-based resins, polyether sulfone (PES)-based resins, polyamide (PA)-based resins, polyimide (PI)-based resins, and the like. As the resin plate constituting the base material layer, among the above-described plate-like materials, plate-like materials made of one or more resins selected from polyethylene terephthalate (PET)-based resins, polyethylene naphthalate (PEN)-based resins, polystyrene (PS)-based resins, polyphenylene sulfide (PPS)-based resins, polyether sulfone (PES)-based resins, and the like are preferable.

[0046] In the sealing material for a cell of a fuel cell for a vehicle according to the present invention, the thickness of the resin plate constituting the base material layer is not particularly limited, but is usually 1 to 500 μm.

[0047] The thickness of the resin plate means the arithmetic mean value when measuring the thickness at 10 locations using a dial gauge.

[0048] In the sealing material for the cell of the fuel cell for automobiles according to the present invention, when the elastic layer adopts the second form, since the elastic layer has a base material layer made of a resin plate, the handleability (handling property) of the sealing material can be easily improved.

[0049] In the sealing material for the cell of the fuel cell for automobiles according to the present invention, the elastic layer made of a foamed rubber layer is formed by dissolving a rubber compound containing a desired amount of ethylene-propylene-diene terpolymer (EPDM), a phenol resin crosslinking agent, a crosslinking accelerator, a foaming agent, etc. in an organic solvent to form a coating solution, applying the coating solution onto the main surface of a suitable base material, fixing it to form an unfoamed rubber layer, and then heating this at a predetermined temperature for a predetermined time to cause foaming.

[0050] The foaming ratio can be easily controlled by adjusting the types and blending ratios of the rubber component constituting the rubber compound, the phenol resin crosslinking agent, the crosslinking accelerator, and the foaming agent. In particular, it can be easily controlled by adjusting the crosslinking speed of EPDM which is the rubber component.

[0051] When increasing the crosslinking speed, since crosslinking proceeds before the rubber component is expanded and deformed by the foaming gas, it becomes easier to suppress the foaming ratio. Conversely, when decreasing the crosslinking speed, since the deformation of the rubber component by the foaming gas takes precedence over the curing speed of the rubber by crosslinking, the foaming ratio tends to increase.

[0052] In the sealing material for the cell of the fuel cell for automobiles according to the present invention, when the elastic layer made of a foamed rubber layer adopts the first form, that is, the form consisting only of the foamed rubber layer, the above coating solution is applied onto the main surface of a suitable base material such as a metal plate, fixed to form an unfoamed rubber layer, then this is foamed to form a foamed rubber layer, and then this is peeled off from the base material layer to obtain the target elastic layer (the elastic layer consisting only of the foamed rubber layer).

[0053] In the sealant for a cell of an automotive fuel cell according to the present invention, when the elastic layer made of a foamed rubber layer takes the second form, that is, a form composed of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a resin plate, the coating liquid is applied and fixed on both main surfaces of the base material layer made of a resin plate to form an unfoamed rubber layer, and then this is foamed to form a foamed rubber layer, whereby the target elastic layer (an elastic layer composed of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a resin plate) can be obtained.

[0054] The sealant for a cell of an automotive fuel cell according to the present invention is one in which adhesive layers are further laminated and arranged on both main surfaces of the elastic layer. In the sealant for a cell of an automotive fuel cell according to the present invention, the adhesive layer is formed by the adhesive constituting the adhesive layer adhering to the main surface of the elastic layer by its adhesive force.

[0055] The thickness of each of the adhesive layers is preferably 1 to 100 μm, more preferably 5 to 70 μm, and even more preferably 10 to 60 μm. The thicknesses of the adhesive layers formed on both main surfaces of the elastic layer may be the same or different.

[0056] In the sealant for a cell of an automotive fuel cell according to the present invention, when the thickness of the adhesive layer is within the above range, the desired adhesion (sealability) can be easily exhibited.

[0057] The thickness of the adhesive layer means the arithmetic mean value when the thicknesses at 10 locations are measured using a dial gauge. In the sealant for a cell of an automotive fuel cell according to the present invention, when the thickness of the adhesive layer is within the above range, the desired adhesion (sealability) can be easily imparted to the sealant.

[0058] In the sealant material for a cell of a fuel cell for a vehicle according to the present invention, the adhesive layer preferably contains at least one selected from urethane resin, natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene (SBR), nitrile rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), butyl rubber (IIR), chloroprene rubber (CR), thermoplastic elastomer, and any of the above hydrates.

[0059] In the sealant material for a cell of a fuel cell for a vehicle according to the present invention, the thermoplastic elastomer is preferably at least one selected from styrenic thermoplastic elastomers, olefinic thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers.

[0060] In the sealant material for a cell of a fuel cell for a vehicle according to the present invention, examples of the styrenic thermoplastic elastomer include copolymers of α-methylstyrene-ethylene-butylene-α-methylstyrene, triblock copolymers of styrene-butadiene-styrene, random copolymers of styrene-butadiene, block copolymers of styrene-isobutylene-styrene, hydrogenated products in which part or all of the carbon-carbon double bond portions of these copolymers such as styrene-butadiene-styrene (SBS) are hydrogenated, maleic anhydride-modified styrene-isoprene-styrene block copolymers, maleic anhydride-modified styrene-butadiene-styrene block copolymers (MAH-SBS), and the like. Examples of the hydrogenated product in which part or all of the carbon-carbon double bond moieties of a copolymer such as the above styrene-butadiene-styrene (SBS) are hydrogenated include styrene-(ethylene / propylene)-styrene block copolymer (SEPS; hydrogenated product of SIS), styrene-(ethylene / butylene)-styrene block copolymer (SEBS; hydrogenated product of SBS), styrene-ethylene-(ethylene / propylene)-styrene block copolymer (SEEPS; hydrogenated product of styrene-butadiene / isoprene-styrene block copolymer), styrene-isobutylene-styrene block copolymer (SIBS), hydrogenated styrene butadiene (hydrogenated SBR), maleic anhydride-modified styrene-(ethylene / butylene)-styrene block copolymer (MAH-SEBS), maleic anhydride-modified styrene-(ethylene / propylene)-styrene block copolymer (MAH-SEPS), and the like. One or more selected therefrom may be mentioned.

[0061] In the sealant material for a fuel cell of an automobile according to the present invention, since the adhesive layer contains a thermoplastic elastomer as an adhesive, good sealing performance can be easily exhibited as compared with the case where there is no adhesive layer.

[0062] In the sealant material for a fuel cell of an automobile according to the present invention, the adhesive layer preferably contains 50 to 100% by mass, more preferably 60 to 90% by mass of the thermoplastic elastomer in terms of solid content.

[0063] In the sealant material for a fuel cell of an automobile according to the present invention, the adhesive layer can easily exhibit good sealing performance by containing the thermoplastic elastomer in the above ratio.

[0064] In the sealant material for a fuel cell of an automobile according to the present invention, the adhesive layer can be formed, for example, by applying an adhesive-containing liquid containing a thermoplastic elastomer onto the main surface of the elastic layer obtained by the method described above.

[0065] According to the present invention, it is possible to provide a sealing material for a cell of a fuel cell for a vehicle that exhibits high adhesion (sealing property) at low surface pressure.

[0066] Next, the present invention will be described more specifically with reference to examples, but these are merely illustrative and do not limit the present invention.

[0067] (Example 1) (1) Preparation of elastic material As shown in Table 1, a hydrocarbon solvent was dissolved in a rubber compound obtained by kneading an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a filler, a phenolic resin crosslinking agent, a foaming agent, and a crosslinking accelerator so that the content ratio of the phenolic resin crosslinking agent was 2.6% by mass in terms of solid content to obtain a liquid of an unfoamed rubber composition. The obtained liquid of the unfoamed rubber composition was coated with a coater to a predetermined thickness and then dried at 60°C in a drying furnace to obtain an unfoamed rubber molded body having a thickness of 0.3 mm. The unfoamed rubber molded body obtained by the above drying treatment was heat-treated in an oven at 180°C to be crosslinked and foamed, thereby producing an elastic material foamed to a foaming ratio of 2.7 times. The manufacturing conditions are shown in Table 1. In addition, a rubber compound not containing a foaming agent was prepared in the above rubber compound, and the torque change of an uncrosslinked rubber molded body having a thickness of 3 mm molded using the obtained rubber compound was measured by a moving die rheometer (MDR) in the following manner. The results are shown in Table 1.

[0068] <Measurement of torque change by moving die rheometer (MDR)> In the above uncrosslinked rubber molded body, based on the provisions of JIS K6300-2, the torque change over time was measured using a moving die rheometer (MDR). The results are shown in Table 1. The MH shown in Table 1 is the maximum value of the torque measured by the above method. Since the torque increases as the crosslinking of the above uncrosslinked rubber molded body progresses, the value of MH serves as an indicator of the degree of crosslinking. The higher the MH, the higher the crosslink density of the crosslinked rubber molded body obtained, which means that a crosslinked rubber molded body with a higher crosslink density is obtained. Therefore, even in the case of an elastic material obtained by crosslinking and foaming an unfoamed rubber molded body having the same composition as the uncrosslinked rubber molded body except for containing a foaming agent, the crosslink density of the foamed rubber constituting the elastic material increases, and when used as a sealing material, it is easier to reduce stress relaxation and exhibits excellent sealing performance.

[0069] (2) Application of Adhesive A thermoplastic elastomer adhesive liquid, which is an adhesive, was applied in a predetermined amount to both main surfaces of the elastic material made of the foamed rubber obtained in (1) using a coater, and dried in a drying furnace, thereby forming adhesive layers on both main surfaces of the elastic material, respectively, to obtain the target sealing material. The stress relaxation rate and gas leakage property of the obtained sealing material were measured by the following methods. The results are shown in Table 1.

[0070] <Measurement of Stress Relaxation Rate> Samples obtained by punching out the obtained sealing material into a donut shape with an inner diameter of 10 mm and an outer diameter of 20 mm were sandwiched between the upper and lower flanges by a commercially available compression-tension testing machine (Autograph AG50kGN, manufactured by Shimadzu Corporation), compressed at an initial surface pressure of 1.0 MPa, and maintained at 25°C for 3.5 hours. Then, the surface pressure at the time when 3.5 hours had elapsed since the start of compression was measured. Then, the stress relaxation rate was determined by the following formula. Stress relaxation rate = (Initial surface pressure - Surface pressure at the time of 3.5 hours after the start of compression) ÷ Initial surface pressure × 100 (%) The stress relaxation rate is an indicator of the sealing performance of the sealing material. When the sealing material is tightened at a predetermined tightening surface pressure, it indicates the ratio at which the tightening surface pressure has decreased at the time when a predetermined time has elapsed since the start of tightening. The smaller the stress relaxation rate of the sealing material, the less the sealing performance of the sealing material deteriorates over time, which means that the sealing performance is excellent.

[0071] <Evaluation of gas leakage> Next, air gas was injected into the doughnut-shaped sample sandwiched and crimped between the upper and lower flanges described above so that a predetermined gas pressure (0.3 to 0.5 MPa) was applied, and a seal test was performed. The sealing performance was evaluated by confirming the pressure (MPa) applied to the sealing material with a pressure meter and checking for the presence or absence of gas leakage. The results are shown in Table 1.

[0072] (Examples 2 to 4, Comparative Examples 1 to 2) (1) Preparation of elastic material In the “(1) Preparation of elastic material” of Example 1, except that the compounding ratio in terms of solid content of the phenolic resin crosslinking agent in the rubber compound was changed as shown in Table 1, after obtaining an unfoamed rubber molded body in the same manner as in Example 1, crosslinking and foaming were performed to obtain the foaming ratio shown in Table 1 to produce an elastic material. The manufacturing conditions are shown in Table 1. Also, the torque value (dN·m) of the uncrosslinked rubber molded body prepared in the same manner as in Example 1 was measured by a moving die rheometer (MDR) in the same manner as in Example 1. The results are shown in Table 1.

[0073] (2) Application of adhesive On both main surfaces of each elastic material made of foamed rubber obtained in Examples 2 to 4 and Comparative Example 1, a thermoplastic elastomer adhesive liquid, which is an adhesive, was applied in a predetermined amount using a coater in the same manner as in Example 1(2), and dried in a drying furnace to form an adhesive layer on both main surfaces of the elastic material, respectively, to obtain the target sealing material. In Comparative Example 2, the elastic material prepared in (1) above was used as the sealing material without applying an adhesive layer. The stress relaxation rate and gas leakage of the obtained sealing material were measured in the same manner as in Example 1. The results are shown in Table 1.

[0074]

Table 1

[0075] The sealing materials according to the present invention obtained in Examples 1 to 4 each have an elastic material made of a foamed rubber and adhesive layers laminated on both main surfaces of the elastic material. The foamed rubber is composed of a crosslinked and foamed body of an unfoamed rubber molded body containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a predetermined amount of a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent. Therefore, as shown in Table 1, since the uncrosslinked rubber molded bodies prepared in Examples 1 to 4 have a high maximum torque value MH and a high crosslinking density when measuring the torque change by MDR, it is considered that they exhibit excellent sealing properties capable of reducing stress relaxation when the obtained elastic material is used as a sealing material. Actually, as shown in Table 1, the sealing materials according to the present invention obtained in Examples 1 to 4 have a low stress relaxation rate even when the surface pressure is low, and it can be seen that they can exhibit excellent adhesion (sealing properties) without gas leakage when evaluating gas leakage.

[0076] On the other hand, the uncrosslinked rubber molded body prepared in Comparative Example 1 does not contain a predetermined amount of a phenolic resin crosslinking agent. Therefore, as shown in Table 1, since the uncrosslinked rubber molded body prepared in Comparative Example 1 has a low maximum torque value MH and a low crosslinking density when measuring the torque change by MDR, it can be seen that when the elastic material obtained in Comparative Example 1 is used as a sealing material, it is considered to be inferior in sealing properties and unable to reduce stress relaxation. Actually, as shown in Table 1, it can be seen that the sealing material obtained in Comparative Example 1 has a high stress relaxation rate and is inferior in adhesion (sealing properties) with gas leakage occurring when evaluating gas leakage.

[0077] Also, the sealing material obtained in Comparative Example 2 does not contain an adhesive layer (consists only of an elastic material). Therefore, as shown in Table 1, it can be seen that the sealing material obtained in Comparative Example 2 has a higher stress relaxation rate compared to the sealing material having the adhesive layer obtained in Example 1, and it can be seen that it is inferior in adhesion (sealing properties) with gas leakage occurring when evaluating gas leakage.

Industrial Applicability

[0078] According to the present invention, it is possible to provide a novel sealing material for a cell of an automotive fuel cell that exhibits high adhesion (sealing property) at a low surface pressure.

Explanation of Symbols

[0079] 1 Sealing material for a cell of an automotive fuel cell i Elastic layer r Foamed rubber layer s Adhesive layer b Base material layer

Claims

1. An elastic layer including a foamed rubber layer, and adhesive layers laminated and disposed on both main surfaces of the elastic layer respectively, wherein the foamed rubber layer is composed of a foam of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) which is a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent, and the content ratio of the phenolic resin crosslinking agent in the unfoamed rubber layer is 2.0 to 20.0% by mass in terms of solid content. A sealing material for a cell of a fuel cell for a vehicle, characterized by the above.

2. The sealing material for a cell of a fuel cell for a vehicle according to Claim 1, wherein the elastic layer consists only of the foamed rubber layer or is a laminated integrated product in which the foamed rubber layer is laminated and disposed on both main surfaces of a base material layer made of a resin plate.

3. The sealing material for a cell of a fuel cell for a vehicle according to Claim 1, wherein the diene amount constituting the ethylene-propylene-diene terpolymer (EPDM) is 1 to 20% by mass.

4. The sealing material for a cell of a fuel cell for a vehicle according to Claim 1, wherein the foamed rubber layer is a foam having a foaming ratio of 1.5 times or more of the unfoamed rubber layer.

5. The sealing material for a cell of a fuel cell for a vehicle according to Claim 1, wherein the adhesive layer contains at least one selected from urethane resin, natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene, nitrile rubber, ethylene-propylene-diene terpolymer, butyl rubber, chloroprene rubber, thermoplastic elastomer, and any water addition product thereof as an adhesive.

6. The sealing material for a cell of a fuel cell for a vehicle according to Claim 5, wherein the thermoplastic elastomer is at least one selected from styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers.

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