JP2017183162A - Seal member for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal member for fuel cell exhibiting excellent sealability even under cryogenic condition, while maintaining mechanical properties required for the seal member.SOLUTION: In a seal member consisting of a crosslinked body of rubber composition for use in a seal member 4a of a fuel cell seal body formed by bonding the constituent members 2, 3, 5 for fuel cell and the seal member 4a via an adhesive layer 6, or by bonding the seal members 4a via the adhesive layer 6, the rubber composition contains following components (A)-(C). (A) A solid rubber consisting of an ethylene-butene-diene rubber. (B) A poly α olefin compound having kinetic viscosity of 8 mm/s or less at 100°C. (C) A crosslinking agent composed of an organic peroxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell sealing member used for sealing a fuel cell constituent member.

  The fuel cell generates electricity by the electrochemical reaction of gas, has high power generation efficiency, cleans the discharged gas, and has very 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. As a sealing member for sealing these constituent members, for example, a sealing member (rubber gasket) made of ethylene-propylene-diene terpolymer rubber (EPDM), ethylene-propylene copolymer rubber (EPM) or the like has been proposed. (See Patent Documents 1 and 2).

  Further, in such a sealing member, since the rubber elasticity of the EPM and EPDM may be lost at extremely low temperatures, it is possible to ensure a desired sealing property when the fuel cell is used in a cold region. Since it becomes difficult, development of a seal member that can provide good sealing performance even at extremely low temperatures has been studied. For example, a rubber component composed of at least one of EPM and EPDM having an ethylene content of 53% by weight or less, an organic peroxide having a one-hour half-life temperature of 130 ° C. or less, a crosslinking aid, and a specific adhesive component A fuel cell adhesive seal member has been proposed (see Patent Document 3).

JP 2009-94056 A JP 2010-146781 A JP 2012-226908 A

  However, even the fuel cell adhesive seal member described in Patent Document 3 is still inadequate in terms of sealability at extremely low temperatures (low temperature settling properties), and is good even under severe low temperature conditions. Actually, there is a demand for a sealing member that can ensure sealing performance. In addition, it is required to improve the sealing performance under cryogenic conditions without impairing other mechanical properties (tensile strength, elongation at break, etc.) required for a fuel cell sealing member.

  The present invention has been made in view of such circumstances, and provides a fuel cell sealing member having excellent sealing properties even under cryogenic conditions while maintaining the mechanical properties required for the sealing member. Is the purpose.

In order to achieve the above object, the present invention is a fuel cell sealing member used for sealing a constituent member of a fuel cell, and comprises a rubber composition containing the following components (A) to (C): The gist of the sealing member for a fuel cell comprising the cross-linked product is as follows.
(A) Solid rubber made of ethylene-butene-diene rubber.
(B) A polyalphaolefin compound having a kinematic viscosity at 100 ° C. of 8 mm ² / s or less.
(C) A crosslinking agent comprising an organic peroxide.

  That is, the present inventors have intensively studied to solve the above problems. In the course of the research, solid rubber (A) made of ethylene-butene-diene rubber, which is difficult to crystallize at low temperatures, is used as a rubber component of a fuel cell seal member, and power generation of the fuel cell is hindered. In order to avoid this, it was conceived that an organic peroxide was used as a crosslinking agent for the rubber component. Since ethylene-butene-diene rubber has a long side chain in the butene portion and a large steric hindrance in the molecular structure as compared with EPDM, it is difficult to crystallize at low temperatures and can improve the sealability under low temperature conditions. However, the use of ethylene-butene-diene rubber alone did not reach the target level in sealing properties under cryogenic conditions, so it was excellent in compatibility with ethylene-butene-diene rubber, and more general When blended with a specific poly-α-olefin compound (B), which has a lower viscosity than a plasticizer for EPDM and is less likely to deteriorate the low-temperature sealability, it does not cause a bleed-out problem and is required for a seal member It has been found that excellent sealing properties can be obtained even under cryogenic conditions while maintaining mechanical properties, and the present invention has been achieved.

The fuel cell sealing member of the present invention comprises a solid rubber (A) made of ethylene-butene-diene rubber, a polyα-olefin compound (B) having a kinematic viscosity at 100 ° C. of 8 mm ² / s or less, and an organic peroxide. And a crosslinked product of a rubber composition containing the crosslinking agent (C). From this, the sealing member for fuel cells of this invention can show the outstanding sealing performance also on cryogenic conditions, maintaining the mechanical physical property requested | required of a sealing member.

  In particular, when the content of the polyalphaolefin compound (B) in the rubber composition is in the range of 0.5 to 40 parts by weight with respect to 100 parts by weight of the solid rubber (A) made of the ethylene-butene-diene rubber, It becomes more excellent at low temperature.

  In addition, when the fuel cell seal member is composed of a crosslinked rubber composition containing solid rubber comprising at least one of ethylene-propylene rubber and ethylene-propylene-diene rubber together with the components (A) to (C), the hardness And fine adjustment of the viscosity can be easily performed.

It is sectional drawing which shows an example of a fuel cell seal body. It is sectional drawing which shows an example using the sealing member for fuel cells of this invention.

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

The fuel cell sealing member of the present invention (hereinafter sometimes simply referred to as “seal member”) is used to seal the constituent members of the fuel cell, and as described above, It consists of a crosslinked product of a rubber composition containing the components (A) to (C). Here, the “solid rubber” is a rubber that is solid at room temperature (23 ° C.), and has a Mooney viscosity (ML _{1 + 4} 100 ° C.) at 5 ° C. of 5 or more in accordance with JIS K 6300-1. Refers to rubber and indicates that it is not liquid rubber.
(A) Solid rubber made of ethylene-butene-diene rubber.
(B) A polyalphaolefin compound having a kinematic viscosity at 100 ° C. of 8 mm ² / s or less.
(C) A crosslinking agent comprising an organic peroxide.

  In the ethylene-butene-diene rubber of the above (A), the ethylene content is preferably 60% by weight or less, particularly preferably 53% by weight or less, from the viewpoint of improving the sealing property at an extremely low temperature. On the other hand, if the ethylene content is too low, the physical properties of the rubber will be lowered, and it will be difficult to ensure the elongation and tensile properties necessary for the sealing member, so the ethylene content is 40% by weight or more. Is preferred.

  In the ethylene-butene-diene rubber (A), the amount of diene (mass ratio of the diene component) is preferably in the range of 1 to 20% by weight, more preferably from the viewpoint of better low-temperature sagability. A range of 3 to 15% by weight is preferred.

  As a rubber component of the seal member of the present invention, EPDM or EPM solid rubber is used in combination with a solid rubber made of ethylene-butene-diene rubber in view of enabling fine adjustment of hardness and viscosity. -It can contain in the ratio of less than 50 weight part with respect to 100 weight part of butene-diene rubbers.

Along with the solid rubber composed of the ethylene-butene-diene rubber (A), a poly α-olefin compound (B) having a kinematic viscosity at 100 ° C. of 8 mm ² / s or less is used as a material for the sealing member of the present invention. The kinematic viscosity at 100 ° C. of the polyα-olefin compound (PAO) is more preferably in the range of ^{2 to} 8 mm ² / s from the viewpoint of low temperature properties. The kinematic viscosity of the poly α-olefin compound is measured in accordance with JIS K 2283.

  The blending amount of the poly α-olefin compound (B) is 0.5 to 40 parts by weight with respect to 100 parts by weight of the solid rubber made of the ethylene-butene-diene rubber of (A). This is preferable from the viewpoint of further improving the low-temperature property while maintaining the mechanical properties required for the sealing member without causing a problem. From the same viewpoint, the amount of the poly α-olefin compound (B) is more preferably 5 to 30 parts by weight.

  The solid rubber cross-linking agent (C) made of ethylene-butene-diene rubber (A) is made of an organic peroxide. Examples of the organic peroxide include peroxyketals, peroxyesters, diacyl peroxides, peroxydicarbonates, dialkyl peroxides, hydroperoxides, and the like. These may be used alone or in combination of two or more. Among these organic peroxides, for example, those composed of organic peroxides having a one-hour half-life temperature of 160 ° C. or less are preferably used. In order to adhere to an electrolyte membrane, the one-hour half-life temperature is It is preferable to use an organic peroxide of 130 ° C. or lower. Furthermore, peroxyketals and peroxyesters having a one-hour half-life temperature of 100 ° C. or more because they are easily cross-linked at a temperature of about 130 ° C. and are excellent in handleability of a rubber composition kneaded with a cross-linking agent. At least one of these is preferable, and a one-hour half-life temperature of 110 ° C. or higher is particularly preferable. Moreover, when a peroxy ester is used, crosslinking can be performed in a shorter time.

  In the present invention, the “half-life” in an organic peroxide having a one-hour half-life temperature of 160 ° C. or lower in the crosslinking agent (C) means that the concentration of organic peroxide (active oxygen amount) is an initial value. Time to halve. 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. For example, by using an organic peroxide having a one-hour half-life temperature of 160 ° 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 fuel cell seal body of the present invention can be used also in the vicinity of the electrolyte membrane of a solid polymer fuel cell.

  Examples of the peroxyketal include n-butyl-4,4-di (t-butylperoxy) valerate, 2,2-di (t-butylperoxy) butane, and 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-hexyl) Peroxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-butylperoxy) -2-methylcyclohexane and the like.

  Examples of the peroxyester include t-butyl peroxybenzoate, t-butyl peroxyacetate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t- Butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxymalein Examples thereof include acid and t-hexylperoxyisopropyl monocarbonate.

  Among these, 1,1-di (t-butylperoxy) cyclohexane, t-butylperoxyacetate, because the reaction with the solid rubber comprising the ethylene-butene-diene rubber (A) is relatively fast. t-Butylperoxyisopropyl monocarbonate is preferred. Especially, when t-butyl peroxyisopropyl monocarbonate is used, crosslinking can be performed in a shorter time.

  The compounding amount of the specific crosslinking agent (C) (in the case of a raw material having a purity of 100%) is 0.4 to 12 parts by weight with respect to 100 parts by weight of the solid rubber comprising the ethylene-butene-diene rubber of (A). The range of is preferable. If the amount of the specific crosslinking agent (C) is too small, it tends to be difficult to sufficiently advance the crosslinking reaction. If the amount of the specific crosslinking agent (C) is too large, There is a tendency for the crosslinking density to increase during the reaction, leading to a decrease in elongation.

  In addition to the components (A) to (C), the rubber composition used for the seal member of the present invention includes a softener (plasticizer), a crosslinking aid, a reinforcing agent, an anti-aging agent, a tackifier, Various additives such as processing aids may be blended.

  Examples of the softener include petroleum oil softeners such as process oil, lubricating oil and petrolatum, fatty oil softeners such as castor oil, linseed oil, rapeseed oil and coconut oil, tall oil, sub, beeswax and carnauba wax. And waxes such as lanolin, linoleic acid, palmitic acid, stearic acid, lauric acid and the like.

  The blending amount of the softening agent is usually in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the solid rubber made of the ethylene-butene-diene rubber (A).

  Examples of the crosslinking aid include maleimide compounds, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), and trimethylolpropane trimethacrylate (TMPT). These may be used alone or in combination of two or more. Among these, it is preferable to use a maleimide compound because the effect of improving the crosslinking density and strength is great.

  The amount of the crosslinking aid is preferably in the range of 0.1 to 3 parts by weight with respect to 100 parts by weight of the solid rubber composed of the ethylene-butene-diene rubber (A). If the blending amount of the crosslinking aid is too small, there is a tendency that it is difficult to sufficiently advance the crosslinking reaction. If the blending amount of the crosslinking aid is too large, the crosslinking density becomes too large and adhesion is caused. There is a tendency for power to decline.

  Examples of the reinforcing agent include carbon black and silica. The grade of the 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.

  The compounding amount of the reinforcing agent is usually in the range of 10 to 150 parts by weight with respect to 100 parts by weight of the solid rubber made of the ethylene-butene-diene rubber (A).

  Examples of the anti-aging agent include phenol-based, imidazole-based, and wax. The blending amount of the anti-aging agent is usually in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the solid rubber made of the ethylene-butene-diene rubber (A).

<Fabrication of sealing member for fuel cell>
The fuel cell sealing member of the present invention is prepared, for example, by kneading the rubber composition containing the components (A) to (C) and, if necessary, other various additives, and then crosslinking the rubber composition. Can be produced. In addition, a roll, a kneader, a Banbury mixer, etc. are used for the said kneading | mixing. Moreover, it is preferable that the said sealing member is shape | molded by the predetermined shape according to the shape of a seal part. For example, when it is formed into a film shape, a sealing member can be attached to various constituent members of the fuel cell with an adhesive and used. Note that the sealing member of the present invention may be used in such a manner that the sealing member is disposed without being bonded between various constituent members of the fuel cell. In addition, the sealing member of the present invention is vulcanized and molded (vulcanized and bonded) to the coated surface of the adhesive in addition to pasting (post-bonding) the vulcanized molded member with an adhesive. ), The constituent members such as the MEA and separator of the fuel cell and the sealing member of the present invention can be integrally formed in the mold as will be described later.

<Fuel cell seal body>
Examples of the fuel cell seal body of the present invention include a fuel cell component and a seal member (the fuel cell seal member of the present invention) that seals the fuel cell structural member bonded via an adhesive layer. .

  The fuel cell components sealed by the seal member of the present invention vary depending on the type and structure of the fuel cell. For example, separators (metal separators, etc.), gas diffusion layers (GDL), MEAs (electrolyte membranes, Electrode) and the like.

  An example of the fuel cell seal body of the present invention is shown in FIG. FIG. 1 mainly shows a single cell 1 in a fuel cell in which a plurality of cells are stacked. The cell 1 includes an MEA 2, a gas diffusion layer (GDL) 3, a seal member 4a, A separator 5 and an adhesive layer 6 are provided.

  As the fuel cell seal body of the present invention, for example, as shown in FIG. 1, a separator 5 and a seal member 4 a are bonded via an adhesive layer 6, and an MEA 2 and a seal member 4 a have an adhesive layer 6. A gas diffusion layer 3 and a seal member 4a bonded via an adhesive layer 6, an adjacent seal member 4a bonded via an adhesive layer 6, etc. can give.

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

  The separator 5 is preferably made of a metal such as titanium, and a metal separator having a carbon thin film such as a DLC film (diamond-like carbon film) or a graphite film is particularly preferable from the viewpoint of conduction reliability. The separator 5 has a rectangular thin plate shape and is provided with a total of six grooves extending in the longitudinal direction. The cross section of the separator 5 has an uneven shape due to the grooves. The separators 5 are opposed to each other on both sides of the gas diffusion layer 3 in the stacking direction. A gas flow path 7 for supplying gas to the electrode is defined between the gas diffusion layer 3 and the separator 5 by using an uneven shape.

  The sealing member 4a has a rectangular frame shape. The sealing member 4 a is bonded to the peripheral portion of the MEA 2 and the gas diffusion layer 3 and the separator 5 through the adhesive layer 6 to seal the peripheral portion of the MEA 2 and the gas diffusion layer 3. In FIG. 1, the seal member 4 a uses two members that are divided into upper and lower parts, but may be a single seal member that combines them.

  During operation of a fuel cell such as a polymer electrolyte fuel cell, fuel gas and oxidant gas are supplied through the gas flow path 7 respectively. Here, the peripheral edge of the MEA 2 is sealed by the seal member 4 a via the adhesive layer 6. For this reason, gas mixing and leakage do not occur.

  The fuel cell seal body of the present invention can be produced, for example, as follows. First, as described above, the fuel cell sealing member of the present invention is produced.

  Next, the adhesive layer forming material (adhesive) is applied to one or both of a constituent member for a fuel cell such as a metal separator and a sealing member that seals the constituent member. It is possible to obtain the fuel cell seal body of the present invention in which the constituent member and the seal member are bonded via an adhesive layer.

  Examples of the adhesive layer forming material (adhesive) include rubber paste, a rubber composition that is liquid at room temperature, and a primer. Examples of the liquid rubber composition include a rubber composition containing a rubber component, an organic peroxide (crosslinking agent) and the like. An example of the rubber component is a liquid rubber. Specifically, liquid EPM, liquid EPDM, liquid acrylonitrile-butadiene rubber (liquid NBR), liquid hydrogenated acrylonitrile-butadiene rubber (liquid H-NBR) Etc. are used alone or in combination of two or more. Examples of the primer include a primer containing a copolymer oligomer of an amino group-containing silane coupling agent and a vinyl group-containing silane coupling agent.

  Examples of the method for applying the adhesive layer forming material include dispenser application and the like. Usually, the application may be performed under normal temperature conditions.

  When the liquid rubber composition is used, the thickness of the adhesive layer in the fuel cell seal body of the present invention is usually 0.01 to 0.5 mm, preferably 0.05 to 0.3 mm. Moreover, when using the said primer, it is 10-500 nm normally, Preferably it is 30-200 nm.

  In addition, if the fuel cell constituent member and the seal member are integrated by vulcanization adhesion of the seal member to manufacture the fuel cell seal body, it can be manufactured as follows. That is, a fuel cell component having an adhesive layer formed therein is placed in a molding die for the seal member, and the rubber composition for forming the seal member is brought into contact with the fuel cell component in the mold. This is a production method in which cross-linking molding is performed in a heated state.

  Furthermore, FIG. 2 shows another usage example using the fuel cell seal member of the present invention. FIG. 2 shows a rectangular thin plate shape with a total of six grooves extending in the longitudinal direction, and a rectangular shape with an adhesive layer 6 interposed between the peripheral portion of the separator 5 having the above-described cross-sectional uneven shape. This is a member provided with a lip 4b having a convex section. The fuel cell seal member of the present invention is used as the lip 4b. As the separator 5 forming material and the adhesive layer 6 forming material, the same materials as those described above are used.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

  First, prior to the examples and comparative examples, the following rubber composition materials were prepared.

[EPDM]
Ethylene-propylene-diene rubber (manufactured by JSR, EP342)

[EBT (component A)]
Ethylene-butene-diene rubber having an ethylene content of 50% by weight and a diene content of 7.6% by weight (manufactured by Mitsui Chemicals, K-4030M)

〔Carbon black〕
Toast Carbon Co., Ltd., Seast 116

[Paraffin oil]
Sunper 110, manufactured by Nippon Oil Corporation

[Low viscosity PAO-1 (component B)]
Polyalphaolefin compound having a kinematic viscosity at 100 ° C. of 2 mm ² / s (manufactured by Chevron Phillips, Synfluid PAO 2cSt)

[Low viscosity PAO-2 (component B)]
Polyalphaolefin compound having a kinematic viscosity at 100 ° C. of 4 mm ² / s (manufactured by Chevron Phillips, Synfluid PAO 4cSt)

[Low viscosity PAO-3 (component B)]
Polyalphaolefin compound having a kinematic viscosity at 100 ° C. of 8 mm ² / s (manufactured by Chevron Phillips, Synfluid PAO 8cSt)

[Low viscosity PAO-4]
Polyalphaolefin compound having a kinematic viscosity at 100 ° C. of 65 mm ² / s (manufactured by Chevron Phillips, Synfluid PAO 65cSt)

[Silicone oil]
KF-50, manufactured by Shin-Etsu Chemical Co., Ltd.

[Peroxide (C component)]
Perhexa C-40 manufactured by NOF Corporation

[Examples 1 to 3, Comparative Examples 1 to 5]
Each component shown in Table 1 to be described later was blended at a ratio shown in the same table, and kneaded using a Banbury mixer and an open roll to prepare a rubber composition.
The rubber composition was vulcanized by holding at 160 ° C. for 10 minutes to produce a vulcanized rubber having a predetermined thickness to be a seal member.

  With respect to the rubber composition and vulcanized rubber obtained as described above, each characteristic was evaluated according to the following criteria. The results are also shown in Table 1 below.

<Bleedability>
The vulcanized rubber (thickness 2 mm) was allowed to stand at room temperature (25 ° C.) for 1 day, and then its surface was visually observed. And the thing in which bleed was seen was evaluated as x, and the thing in which bleed was not seen was evaluated as (circle).

<Tensile strength>
Using a vulcanized rubber, the tensile strength (TS) was measured as follows. That is, the vulcanized rubber was punched out with a JIS No. 5 dumbbell, and the tensile strength (MPa) was measured according to JIS K 6251.
Table 1 below shows an index of the tensile strength of each vulcanized rubber when the tensile strength of the vulcanized rubber which is the product of Comparative Example 1 is used as a reference (100).
That is, the index of tensile strength was calculated by the following formula.
Tensile strength index = (Tensile strength (MPa) of each vulcanized rubber) / (Tensile strength (MPa) of vulcanized rubber of Comparative Example 1 as a reference) × 100
And in Table 1 of the postscript, the case where the said tensile strength index was 90 or more was evaluated as (circle), and the case where the said tensile strength index was less than 90 was evaluated as x.

<Elongation at cutting>
Using vulcanized rubber, elongation at break (elongation at break (Eb)) was measured as follows. That is, the vulcanized rubber was punched out with a JIS No. 5 dumbbell, and the elongation at break (breaking elongation) (%) was measured according to JIS K 6251.
Table 1 below shows an index of the elongation at break of each vulcanized rubber when the elongation at break of the vulcanized rubber which is the product of Comparative Example 1 is defined as a reference (100).
That is, the index of elongation at break was calculated by the following formula.
Elongation index at break = (Elongation at break of each vulcanized rubber (%)) / (Elongation at break of vulcanized rubber of Comparative Example 1 as reference) (%) × 100
In Table 1 described later, the case where the elongation index at break was 90 or more was evaluated as ◯, and the case where the elongation index at break was less than 90 was evaluated as x.

<Low temperature compression set>
The rubber composition was heated at 160 ° C. for 15 minutes, and the vulcanized rubber thus obtained was subjected to a compression set test at a low temperature in accordance with JIS K 6262. That is, the vulcanized rubber was compressed at a compression rate of 25% and left in that state at −40 ° C. for 24 hours, then the compression was released, and the thickness of the vulcanized rubber after 30 minutes at the same temperature was measured. Measured to calculate compression set (%).
Table 1 below shows an index of compression set of each vulcanized rubber when the compression set of the vulcanized rubber which is the product of Comparative Example 1 is used as a reference (100).
That is, the compression set index was calculated by the following equation.
Compression set index = (compression set (%) of each vulcanized rubber) / (compression set (%) of vulcanized rubber of Comparative Example 1 as reference) × 100
In Table 1 described later, a case where the compression set index was 90 or less was evaluated as ◯, and a case where the compression set index was greater than 90 was evaluated as x.

≪Comprehensive evaluation≫
In the evaluation of each characteristic, the case of all “◯” was regarded as the comprehensive evaluation “◯”, and the case where there was at least one “×” in the evaluation of each characteristic was regarded as the “total evaluation”.

From the result of the said table | surface, the vulcanized rubber (seal member) of an Example uses EBT (ethylene-butene-diene rubber) as a polymer, and was bridge | crosslinked by the peroxide (organic peroxide), and also 100 degreeC The material includes a polyα-olefin compound (low viscosity PAO-1 to -3) having a kinematic viscosity of 8 mm ² / s or less. Therefore, the low temperature compression set (low temperature settling property) is good while maintaining the mechanical properties (TS, Eb). Moreover, there is no bleed out.

On the other hand, the vulcanized rubber of Comparative Example 1 uses EPDM as a polymer and is crosslinked by peroxide (organic peroxide), but the material contains paraffin oil instead of low-viscosity PAO. The low temperature compression set was worsened. The vulcanized rubber of Comparative Example 2 contains low-viscosity PAO-1 in the material as in Example 1. However, since only EPDM was used as a polymer, deterioration in low-temperature compression set was observed. The vulcanized rubber of Comparative Example 3 uses EBT as a polymer and is crosslinked with peroxide, and further contains low-viscosity PAO. The low-viscosity PAO has a kinematic viscosity at 100 ° C. of 8 mm ² / s. Since it was significantly exceeded, deterioration in low temperature compression set was observed. The vulcanized rubber of Comparative Example 4 uses EBT as a polymer and is crosslinked with peroxide, but the material contains paraffin oil instead of low-viscosity PAO, and deteriorates low temperature compression set. Was seen. The vulcanized rubber of Comparative Example 5 uses EBT as a polymer and is crosslinked with peroxide, and the material contains silicone oil instead of low-viscosity PAO. Although there was no problem, problems such as a decrease in mechanical properties (TS, Eb) and occurrence of bleed out were observed.

  The fuel cell seal member of the present invention is a fuel cell seal body in which a fuel cell component member such as a metal separator and a rubber seal member for sealing the same are bonded via an adhesive layer, or the above seal member It is used for the above-mentioned sealing member of a fuel cell sealing body in which the two are bonded via an adhesive layer.

1 cell 2 MEA
3 Gas diffusion layer 4a Seal member 4b Lip 5 Separator 6 Adhesive layer 7 Gas flow path

Claims (2)

A fuel cell sealing member used for sealing a component of a fuel cell, comprising a crosslinked rubber composition containing the following components (A) to (C): Seal member.
(A) Solid rubber made of ethylene-butene-diene rubber.
(B) A polyalphaolefin compound having a kinematic viscosity at 100 ° C. of 8 mm ² / s or less.
(C) A crosslinking agent comprising an organic peroxide.   The content of the polyalphaolefin compound (B) in the rubber composition is in the range of 0.5 to 40 parts by weight with respect to 100 parts by weight of the solid rubber (A) made of the ethylene-butene-diene rubber. The sealing member for fuel cells as described.

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