JP7319899B2 - Fuel cell sealing material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel cell sealing member used for sealing a fuel cell component.

A fuel cell generates electricity through an electrochemical reaction of gas, has high power generation efficiency, emits clean gas, and has very little impact on the environment. Among them, polymer electrolyte fuel cells can be operated at relatively low temperatures and have high power densities. Therefore, polymer electrolyte fuel cells are expected to be used in various applications such as power generation and power sources for automobiles.

In a polymer electrolyte fuel cell, a cell in which a membrane electrode assembly (MEA) or the like is sandwiched between separators serves as a power generation unit. The MEA consists of a polymer membrane (electrolyte membrane) serving as an electrolyte, a pair of electrode catalyst layers (fuel electrode (anode) catalyst layer, oxygen electrode (cathode) catalyst layer) arranged on both sides in the thickness direction of the electrolyte membrane, consists of A porous layer for diffusing gas is further disposed on the surfaces of the pair of electrode catalyst layers. 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. Electricity is generated by an electrochemical reaction at the three-phase interface between the supplied gas, the electrolyte, and the electrode catalyst layer. A polymer electrolyte fuel cell is constructed by clamping a cell stack, in which a large number of the above cells are stacked, with end plates or the like arranged at both ends in the cell stacking direction.

The separators are provided with flow paths for gas supplied to each electrode and flow paths for coolant for alleviating heat generation during power generation. For example, if the gases supplied to each electrode are mixed, problems such as a decrease in power generation efficiency will occur. In addition, the electrolyte membrane has proton conductivity when it contains water. Therefore, the electrolyte membrane must be kept wet during operation. Therefore, in order to prevent gas mixing, leakage of gas and refrigerant, and keep the inside of the cell in a moist state, it is important to ensure sealing performance around the MEA and the porous layer and between adjacent separators. becomes. As sealing members for sealing these constituent members, for example, sealing members (rubber gaskets) made of ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), etc. have been proposed (Patent Documents 1 and 2). reference).

JP 2009-94056 A JP 2010-146781 A

By the way, since the fuel cell is constructed by stacking 200 to 300 cells and fastening the sealing member (rubber gasket) as described above while compressing it, the sealing member has a high Elongation (compression cracking resistance) is required. In addition, fuel cells are expected to expand worldwide for use in commercial vehicles such as buses and trucks that run long distances. Low settling property is further required.
In other words, in the sealing member, it is a problem to satisfy all of compression cracking resistance, low settling property, and resistance in a wide temperature range from low temperature to high temperature.

Conventionally, as a method for eliminating low temperature resistance and resistance to compression cracking, a method of adding a large amount of a softening agent (plasticizer) having a low pour point to the material of the sealing member has been adopted.
However, since the thickness of the sealing member for a fuel cell is usually as thin as about 1 mm, the above method is greatly affected by volumetric shrinkage due to volatilization of the softening agent, etc., and settling is likely to occur.
On the other hand, when the amount of the softening agent added is reduced, the seal member becomes difficult to stretch, resulting in a problem of reduced resistance to compression cracking.
Further, in order to improve the low temperature resistance of the sealing member, it is known to use ethylene-butene-diene rubber as the rubber component and polyαolefin as a softening agent. However, there is still room for improvement.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sealing member for a fuel cell which is excellent in resistance to compression cracking and low settling in a wide temperature range from low to high.

That is, the present inventors have made earnest studies to solve the above problems. In the course of this research, we discovered that rubber components such as ethylene-propylene rubber, ethylene-propylene-diene rubber, and ethylene-butene-diene rubber, which have excellent properties as rubber components for fuel cell sealing members, were used, and that fuel cell power generation was inhibited. The use of an organic peroxide as a cross-linking agent was investigated in order to prevent this from occurring. Then, in order to satisfy all of the requirements for compression cracking resistance, low settling, and resistance in a wide temperature range from low to high temperatures, we repeatedly mixed and experimented with various additives to determine the pour point and kinematic viscosity. When a hydrocarbon-based softening agent (B) having a straight chain structure within the range of and a bifunctional (meth)acrylate monomer (C) are added in combination, it was found that the desired object can be achieved. arrived at the invention.

However, the gist of the present invention is the following [1] to [5].
[1] A sealing member for a fuel cell, which is used to seal the constituent members of a fuel cell, characterized by comprising a crosslinked rubber composition containing the following components (A) to (D): A sealing member for a fuel cell.
(A) at least one rubber component selected from the group consisting of ethylene-propylene rubber, ethylene-propylene-diene rubber and ethylene-butene-diene rubber;
(B) A linear hydrocarbon-based softening agent having a pour point of -30°C or lower and a kinematic viscosity at 40°C of 8 to 500 mm ² /s.
(C) a bifunctional (meth)acrylate monomer;
(D) a cross-linking agent comprising an organic peroxide;
[2] The fuel cell sealing member according to [1], wherein the hydrocarbon-based softening agent (B) is a polyαolefin.
[3] The fuel cell sealing member according to [1] or [2], wherein the main chain of the bifunctional (meth)acrylate monomer (C) is an aliphatic hydrocarbon.
[4] of [1] to [3], wherein the content of the hydrocarbon-based softening agent (B) in the rubber composition is in the range of 5 to 60 parts by weight per 100 parts by weight of the rubber component (A); Any one of the fuel cell sealing members.
[5] The content of the bifunctional (meth)acrylate monomer (C) in the rubber composition is in the range of 0.1 to 10 parts by weight per 100 parts by weight of the rubber component (A) [1] The sealing member for a fuel cell according to any one of [4].

The sealing member for a fuel cell of the present invention comprises at least one rubber component (A) selected from the group consisting of ethylene-propylene rubber, ethylene-propylene-diene rubber and ethylene-butene-diene rubber, and having a pour point of −30° C. or lower. and a kinematic viscosity at 40° C. of 8 to 500 mm ² /s, a linear hydrocarbon-based softening agent (B), a bifunctional (meth)acrylate monomer (C), and an organic peroxide and a cross-linked rubber composition containing a cross-linking agent (D) consisting of Therefore, the sealing member for a fuel cell of the present invention can exhibit excellent performance in resistance to compression cracking and low settling in a wide temperature range from low to high.

1 is a cross-sectional view showing an example of a fuel cell sealing body of the present invention; FIG. 1 is a cross-sectional view showing an example using the fuel cell sealing member of the present invention; FIG.

Next, an embodiment 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 "sealing member") is used for sealing the constituent members of a fuel cell. It consists of a crosslinked rubber composition containing components (A) to (D). The "pour point" of component (B) below refers to the minimum temperature at which component (B) flows when cooled by a method specified in JIS K 2269. In addition, the "kinematic viscosity" in component (B) below is measured according to JIS K 2283.
(A) at least one rubber component selected from the group consisting of ethylene-propylene rubber, ethylene-propylene-diene rubber and ethylene-butene-diene rubber;
(B) A linear hydrocarbon-based softening agent having a pour point of -30°C or lower and a kinematic viscosity at 40°C of 8 to 500 mm ² /s.
(C) a bifunctional (meth)acrylate monomer;
(D) a cross-linking agent comprising an organic peroxide;

The constituent materials of the sealing member of the present invention will be described in detail below.

[Rubber component (A)]
The rubber component (A) is the main component of the rubber composition and usually accounts for the majority of the entire rubber composition. As described above, as the rubber component (A), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), and ethylene-butene-diene rubber (EBT) are used alone or in combination of two or more. used for

The ethylene content in the rubber component (A) is preferably 60% by weight or less, more preferably 53% by weight or less, from the viewpoint of improving sealability at extremely low temperatures. On the other hand, if the ethylene content is too low, the physical properties of the rubber deteriorate and it becomes difficult to ensure the elongation and tensile properties necessary for the seal member. is preferred.

From the viewpoint of acid resistance and water resistance in the operating environment of the fuel cell, it is preferable to use EPDM as the rubber component (A). It is preferable to use EBT as.
As the diene content in EPDM or EBT increases, the crosslink density of the sealing member, which is a crosslinked body, increases in proportion to the increase, and the low-temperature sealability is further improved. For this reason, the diene content (mass ratio of the diene component) is preferably in the range of 1 to 20% by weight, more preferably in the range of 3 to 15% by weight.

As the diene component, for example, diene-based monomers having 5 to 20 carbon atoms are preferable. ,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB), 5-butylidene-2-norbornene, 2- methallyl-5-norbornene, 2-isopropenyl-5-norbornene and the like.

[Hydrocarbon Softener (B)]
As the hydrocarbon-based softening agent (B), a straight-chain hydrocarbon-based softening agent having a pour point of −30° C. or lower and a kinematic viscosity at 40° C. of 8 to 500 mm ² /s is used. . The pour point of the hydrocarbon-based softening agent (B) is preferably -35 to -80°C, more preferably -40 to -80°C, from the viewpoint of low temperature property and volatility. The kinetic viscosity at 40° C. of the hydrocarbon-based softening agent (B) is preferably 9 to 460 mm ² /s, more preferably 10, from the viewpoint of volatility and compatibility with the rubber component (A). ˜420 mm ² /s. As the hydrocarbon-based softening agent (B), a hydrocarbon-based softening agent having a straight chain structure is used as described above from the viewpoint of compatibility with the rubber component (A).

Further, it is preferable that the amount of the hydrocarbon-based softening agent (B) volatilized when heated at 250° C. for 1 hour is less than 80% by weight. More preferably less than 60% by weight, still more preferably less than 40% by weight. That is, with such a softening agent that is difficult to volatilize, the seal member of the present invention is more excellent in resistance to settling.

Examples of the hydrocarbon-based softening agent (B) include paraffin, liquid paraffin, ethylene-propylene copolymer, polyisoprene, polybutadiene, and polyαolefin. And these are used individually or in combination of 2 or more types.

The hydrocarbon-based softening agent (B) is preferably a straight-chain olefin, more preferably a poly-α-olefin or an ethylene-propylene copolymer, from the viewpoint of low squat.

The content of the hydrocarbon-based softening agent (B) in the rubber composition satisfactorily obtains kneading processability, suppression of bleed-out, resistance to compression cracking in a wide temperature range from low to high temperatures, and low settling. from the viewpoint of , it is preferably 5 to 60 parts by weight, more preferably 5 to 55 parts by weight, and still more preferably 5 to 50 parts by weight, based on 100 parts by weight of the rubber component (A).

[Bifunctional (meth)acrylate monomer (C)]
The bifunctional (meth)acrylate monomer (C) is a (meth)acrylate monomer having two (meth)acrylic groups. In the present invention, a (meth)acryloyl group means an acryloyl group or a methacryloyl group, and a (meth)acrylate monomer means an acrylate monomer or a methacrylate monomer.
Among the bifunctional (meth)acrylate monomers (C), from the viewpoint of compatibility with the rubber component (A), heat resistance, etc., the main chain of the bifunctional (meth)acrylate monomer (C) is carbonized. Hydrogen-based ones are preferred.
Further, the main chain of the bifunctional (meth)acrylate monomer (C) is preferably an aliphatic hydrocarbon, and the number of carbon atoms thereof is preferably in the range of 2 to 14, more preferably 2 to 10. .
Examples of the bifunctional (meth)acrylate monomer (C) include ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate. , 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1 , 5-pentadiol di(meth)acrylate and the like. These are used alone or in combination of two or more. Among them, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 1,9-nonanediol di(meth)acrylate are preferable. In addition, "(meth)acrylate" in the above compound names means acrylate or methacrylate.

The content of the bifunctional (meth)acrylate monomer (C) in the rubber composition makes the cross-linking reaction appropriate, and good resistance to compression cracking, low settling, and resistance in a wide temperature range from low to high temperatures. From the viewpoint, it is preferably 0.1 to 10 parts by weight, more preferably 0.15 to 7.5 parts by weight, still more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the rubber component (A). part range.

[Crosslinking agent (D)]
The cross-linking agent (D) of the rubber component (A) is composed of an organic peroxide. Examples of the organic peroxides include peroxyketals, peroxyesters, diacyl peroxides, peroxydicarbonates, dialkyl peroxides and hydroperoxides. These may be used alone or in combination of two or more. Among such organic peroxides, for example, organic peroxides having a one-hour half-life temperature of 160° C. or less are preferably used. It is preferable to use an organic peroxide having a half-life temperature of 130° C. or less. Further, peroxyketals and peroxyesters having a 1-hour half-life temperature of 100°C or higher because they are easily crosslinked at a temperature of about 130°C and the rubber composition kneaded with a crosslinking agent is excellent in handleability. At least one of the above is preferable, and those having a one-hour half-life temperature of 110° C. or higher are particularly preferable. Crosslinking can be performed in a shorter time by using a peroxyester.

In the present invention, the “half-life” of the organic peroxide having a 1-hour half-life temperature of 160° C. or less in the cross-linking agent (D) means that the concentration of the organic peroxide (the amount of active oxygen) is the initial value. It's 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 the temperature at which the half-life is 1 hour. That is, the lower the 1-hour half-life temperature, the easier it is for the organic peroxide to decompose at a low temperature. 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) in a short time. Therefore, for example, the fuel cell sealing member of the present invention can be used in the vicinity of the electrolyte membrane of a polymer electrolyte fuel cell.

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-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 peroxy isopropyl monocarbonate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxymalein acid, t-hexylperoxyisopropyl monocarbonate and the like.

Among these, 1,1-di(t-butylperoxy)cyclohexane, t-butylperoxyacetate, and t-butylperoxyisopropyl monocarbonate are preferred because they react relatively quickly with the rubber component (A). is preferred. Among them, t-butylperoxyisopropyl monocarbonate can be used for crosslinking in a shorter time.

The amount of the cross-linking agent (D) (in the case of a raw material with a purity of 100%) is preferably in the range of 0.4 to 12 parts by weight per 100 parts by weight of the rubber component (A). If the amount of the specific cross-linking agent (D) is too small, it tends to be difficult to allow the cross-linking reaction to proceed sufficiently. There is a tendency that the crosslink density increases during the reaction, leading to a decrease in elongation.

In addition to the above components (A) to (D), the rubber composition used for the sealing member of the present invention contains various additives such as reinforcing agents, anti-aging agents, adhesive components, tackifiers, and processing aids. There is no problem even if it mix|blends an agent.

Examples of the reinforcing agent include carbon black and silica. Among them, carbon black is preferably used from the viewpoint of settling property and the like.
The grade of the carbon black is not particularly limited, and may be appropriately selected from SAF grade, ISAF grade, HAF grade, MAF grade, FEF grade, GPF grade, SRF grade, FT grade, MT grade, and the like.

The amount of the reinforcing agent compounded is preferably 5 to 150 parts by weight, more preferably 10 to 120 parts by weight, per 100 parts by weight of the rubber component (A).

Examples of the anti-aging agent include amine-based anti-aging agents, phenol-based anti-aging agents, imidazole-based anti-aging agents, and waxes. Among them, amine anti-aging agents are preferably used from the viewpoint of anti-oxidation efficacy and the like.
The amount of the antioxidant compounded is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the rubber component (A).

Examples of the adhesive components include resorcinol-based compounds, melamine-based compounds, aluminate-based coupling agents, silane coupling agents, and the like. Among them, a silane coupling agent is preferably used from the viewpoint of adhesiveness and the like.
The amount of the adhesive component compounded is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, per 100 parts by weight of the rubber component (A).

The rubber composition used for the sealing member of the present invention may optionally contain a petroleum softener such as process oil, lubricating oil, petrolatum, castor oil, etc., in combination with the hydrocarbon softener (B). , linseed oil, rapeseed oil, coconut oil and other fatty oil softeners, tall oil, waxes such as beeswax, carnauba wax and lanolin, linoleic acid, palmitic acid, stearic acid, lauric acid and other softeners. It is also possible to use in However, in this case, the amount of the optional softening agent used must be less than 50 parts by weight, preferably less than 40 parts by weight, with respect to 100 parts by weight of the hydrocarbon-based softening agent (B). More preferably less than 30 parts by weight.

Further, the rubber composition used for the sealing member of the present invention may optionally contain a monofunctional (meta ) acrylate monomers and trifunctional (meth)acrylate monomers may optionally be used. However, in this case, the amount of the above optional (meth)acrylate monomer used should be less than 100 parts by weight with respect to 100 parts by weight of the bifunctional (meth)acrylate monomer (C), preferably Less than 75 parts by weight, more preferably less than 50 parts by weight.

<Production of sealing member for fuel cell>
For the sealing member for a fuel cell of the present invention, for example, the components (A) to (D) and, if necessary, various other additives are blended to prepare a rubber composition, which is then crosslinked. It can be produced by The cross-linking molding of the sealing member is usually performed by thermal cross-linking in a mold (thermal cross-linking at 130 to 190° C. for 1 to 30 minutes). Since the sealing member for a fuel cell of the present invention contains the component (C), electron beam crosslinking can be performed in combination with the thermal crosslinking.
It is preferable that the seal member is formed into a predetermined shape in accordance with the shape of the seal portion. For example, when formed into a film, the sealing member can be used by attaching it to various constituent members of the fuel cell with an adhesive. In addition, the sealing member of the present invention may be used in such a manner that it is arranged without adhering between various constituent members of the fuel cell. In addition, the sealing member of the present invention may be pasted (post-adhered) with an adhesive after cross-linking, or may be cross-linked (cross-linked) to the surface to which the adhesive is applied. Therefore, as will be described later, it is also possible to integrally mold the constituent members such as the MEA and the separator of the fuel cell and the sealing member of the present invention in a mold.

<Fuel cell seal body>
Examples of the fuel cell sealing member of the present invention include those in which a fuel cell constituent member and a sealing member for sealing it (the fuel cell sealing member of the present invention) are adhered via an adhesive layer. .

The fuel cell components to be sealed by the sealing member of the present invention vary depending on the type, structure, etc. of the fuel cell. electrodes).

An example of the fuel cell sealing 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, and the cell 1 includes an MEA 2, a gas diffusion layer (GDL) 3, a sealing member 4a, A separator 5 and an adhesive layer 6 are provided.

As the fuel cell sealing body of the present invention, for example, as shown in FIG. one in which the gas diffusion layer 3 and the sealing member 4a are bonded via the adhesive layer 6; and one in which the adjacent sealing members 4a are bonded via the adhesive layer 6. can give.

Although not shown, the MEA 2 is composed of an electrolyte membrane and a pair of electrodes arranged on both sides in the stacking direction with the electrolyte membrane interposed therebetween. The electrolyte membrane and the pair of electrodes are rectangular thin plates. Gas diffusion layers 3 are arranged on both sides of the MEA 2 in the stacking direction. 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 from the viewpoint of conduction reliability, a metal separator having a carbon thin film such as a DLC film (diamond-like carbon film) or graphite film is particularly preferable. The separator 5 has a rectangular thin plate shape, and is provided with a total of six grooves extending in the longitudinal direction. The separators 5 are arranged on both sides of the gas diffusion layer 3 in the stacking direction so as to face each other. Between the gas diffusion layer 3 and the separator 5, a gas flow path 7 for supplying gas to the electrodes is defined by utilizing the uneven shape.

The sealing member 4a has a rectangular frame shape. The sealing member 4a is adhered to the periphery of the MEA 2 and the gas diffusion layer 3 and the separator 5 via the adhesive layer 6 to seal the periphery of the MEA 2 and the gas diffusion layer 3. FIG. In the example of FIG. 1, the sealing member 4a uses two members divided into upper and lower parts, but a single sealing member combining the two may also be used.

During operation of a fuel cell such as a polymer electrolyte fuel cell, a fuel gas and an oxidant gas are each supplied through the gas channel 7 . Here, the periphery of the MEA 2 is sealed by a sealing member 4a with an adhesive layer 6 interposed therebetween. Therefore, no gas mixture or leakage occurs.

The fuel cell sealing 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, by applying the adhesive layer forming material (adhesive) to one or both of the fuel cell component such as the metal separator and the sealing member for sealing it, the fuel cell component such as the metal separator is coated. It is possible to obtain the fuel cell sealing body of the present invention, in which the constituent member and the sealing member are adhered via the adhesive layer.

As the adhesive layer-forming material (adhesive), for example, a rubber paste, a rubber composition that is liquid at room temperature (23° C.), a primer, or the like is used. Examples of the liquid rubber composition include a rubber composition containing a rubber component, an organic peroxide (crosslinking agent), and the like. Examples of the rubber component include liquid rubbers, and specific examples include liquid EPM, liquid EPDM, liquid acrylonitrile-butadiene rubber (liquid NBR), and liquid hydrogenated acrylonitrile-butadiene rubber (liquid H-NBR). etc. are used singly 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 application is usually performed at room temperature.

The thickness of the adhesive layer in the fuel cell sealing member of the present invention is usually 0.01 to 0.5 mm, preferably 0.05 to 0.3 mm, when the liquid rubber composition is used. When the above primer is used, the thickness of the adhesive layer is usually 10-500 nm, preferably 30-200 nm.

Further, if the fuel cell component and the sealing member are integrated by cross-linking adhesion of the sealing member to manufacture the fuel cell sealing body, the fuel cell sealing body can be manufactured as follows. That is, the fuel cell constituent member having the adhesive layer formed thereon is placed in a mold for molding the seal member, and the rubber composition for forming the seal member is brought into contact with the fuel cell constituent member in the mold. It is a manufacturing method in which cross-linking molding is performed in a state where it is held.

Further, another usage example using the fuel cell sealing member of the present invention is shown in FIG. FIG. 2 shows a rectangular sheet-shaped separator 5 having a total of six grooves extending in the longitudinal direction and having the uneven cross-sectional shape described above. It is a member provided with a lip 4b having a convex section shape. The fuel cell sealing member of the present invention is used as the lip 4b. As the material for forming the separator 5 and the material for forming the adhesive layer 6, 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 Examples and Comparative Examples, the following rubber composition materials were prepared. The "pour point" of the softener below indicates the lowest temperature at which the softener flows when cooled by the method specified in JIS K 2269. In addition, the "kinematic viscosity" in the following softening agent is a value measured according to JIS K 2283.

[Rubber (i) (A component)]
Ethylene-propylene-diene rubber (manufactured by Mitsui Chemicals, EPT-9090M) with an ethylene content of 41% by weight and a diene content of 14% by weight

[Rubber (ii) (Component A)]
Ethylene-butene-diene rubber (manufactured by Mitsui Chemicals, EBT-K-9330M) with an ethylene content of 50% by weight and a diene content of 7.1% by weight

[Rubber (iii) (A component)]
Ethylene-propylene-diene rubber (manufactured by Sumitomo Chemical Co., Ltd., Esprene 5365) with an ethylene content of 46% by weight and a diene content of 8.5% by weight

[Rubber (iv) (Component A)]
Ethylene-propylene rubber (manufactured by Mitsui Chemicals, EPT 0045) with an ethylene content of 51% by weight

[Softening agent (i) (B component)]
^A poly-α-olefin softener (Nippon Steel Chemical & Material Co., PAO401)

[Softening agent (ii) (B component)]
^A poly-α-olefin softener (Nippon Steel Chemical & Material Co., PAO10)

[Softening agent (iii) (B component)]
A poly- ^α -olefin softener (manufactured by Exxon Corporation, Spectrashin +6)

[Softening agent (iv) (B component)]
A poly-αolefin-based softening agent (SpectraSyn 40, manufactured by Exxon) having a pour point of −36° C. and a kinematic viscosity of 396 mm ² /s at 40° C.

[Softening agent (v) (B component)]
Ethylene-propylene copolymer softener (Lucant LX004, manufactured by Mitsui Chemicals, Inc.) having a pour point of −40° C. and a kinematic viscosity of 400 mm ² /s at 40° C.

[Softener (vi)]
A poly- ^α -olefin softener (Nippon Steel Chemical & Material Co., PAO210)

[Softener (vii)]
A poly-α-olefin-based softener (SpectraSyn Elite 65, manufactured by Exxon) having a pour point of −42° C. and a kinematic viscosity of 614 mm ² /s at 40° C.

[Softener (viii)]
A naphthenic softener having a pour point of −42.5° C. and a kinematic viscosity at 40° C. of 20.1 mm ² /s (Sansen 410, manufactured by Nippon Sun Oil Co., Ltd.)

[Softener (ix)]
A paraffin-based softening agent having a pour point of −17.5° C. and a kinematic viscosity at 40° C. of 30.6 mm ² /s (manufactured by Idemitsu Kosan Co., Ltd., Diana Process PW-32).

[Crosslinking aid (i) (component C)]
1,6-hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat #230) represented by the following chemical formula

[Crosslinking aid (ii) (component C)]
1,9-nonanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat #260) represented by the following chemical formula

[Crosslinking aid (iii)]
Pentaerythritol tetraacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., A-TMMT) represented by the following chemical formula

〔Carbon black〕
SPHERON5200 (GPF grade) manufactured by Cabot Japan

[Organic Peroxide (Component D)]
Made by NOF Corporation, Perhexa C

[Anti-aging agent]
Amine anti-aging agent (manufactured by Seiko Chemical Co., Ltd., Nonflex RD)

[Examples 1 to 13, Comparative Examples 1 to 5]
(Preparation of crosslinked rubber for sealing member)
A rubber composition was prepared by blending each component shown in Tables 1 and 2 below in the ratio shown in the table and kneading the mixture using a Banbury mixer and an open roll. Then, the obtained rubber composition was crosslinked by holding it at 160° C. for 10 minutes using a predetermined mold to prepare a disk-shaped crosslinked rubber (sample) with a diameter of 15 mm and a thickness of 1 mm.

The properties of the crosslinked rubber (sample) obtained as described above were evaluated according to the following criteria. The results are also shown in Tables 1 and 2 below.

<High temperature settling resistance>
The above crosslinked rubber (sample) was subjected to a compression set test at high temperature in accordance with JIS K 6262. That is, the crosslinked rubber is compressed at a compression rate of 25%, heated at 120 ° C. for 24 hours in that state, released, and the thickness of the crosslinked rubber after 30 minutes at room temperature (25 ° C.) was measured to calculate the compression set (%). Then, high-temperature settling resistance was evaluated according to the following criteria.
A: Permanent compression strain is 10% or less.
◯: Permanent compression strain is 15% or less.
Δ: Compression set is 20% or less.
x: Compression set exceeds 20%.

<Low temperature settling resistance>
A low-temperature compression set test was performed on the crosslinked rubber (sample) according to JIS K 6262. That is, the crosslinked rubber was compressed at a compression rate of 25%, left at −30° C. for 24 hours in that state, released, and left at room temperature (25° C.) for 30 minutes. The thickness was measured to calculate the compression set (%). Then, low-temperature settling resistance was evaluated according to the following criteria.
A: Permanent compression strain is 40% or less.
◯: Permanent compression set is 50% or less.
Δ: Compression set is 60% or less.
x: Compression set exceeds 60%.

<High temperature compression crack resistance>
For the above crosslinked rubber (sample), using a jig similar to that used in the compression set test specified in JIS K 6262, in a state of compression at a predetermined compression rate (50%, 55%, or 60%) After heating at 120° C. for 24 hours, it was released, and the crosslinked rubber was visually checked for cracks in appearance. Then, hot compression crack resistance was evaluated according to the following criteria.
⊚: No appearance cracks were observed even at a compressibility of 60%.
◯: No appearance cracks were observed at compression ratios of 55% and 50%.
Δ: No appearance cracks were observed at a compressibility of 50%.
x: Appearance cracks are observed even at a compressibility of 50%.

<Low temperature compression crack resistance>
For the above crosslinked rubber (sample), using a jig similar to that used in the compression set test specified in JIS K 6262, in a state of compression at a predetermined compression ratio (50%, 55%, or 60%) After being left at −30° C. for 24 hours, it was released and the crosslinked rubber was visually checked for external cracks. Then, low-temperature compression cracking resistance was evaluated according to the following criteria.
⊚: No appearance cracks were observed even at a compressibility of 60%.
◯: No appearance cracks were observed at compression ratios of 55% and 50%.
Δ: No appearance cracks were observed at a compressibility of 50%.
x: Appearance cracks are observed even at a compressibility of 50%.

≪Comprehensive evaluation≫
Comprehensive evaluation was performed according to the following criteria.
⊚: Each of the above characteristics was evaluated as either ∘ or ⊚, and three or more evaluations were ⊚.
◯: Each of the above characteristics was evaluated as either ◯ or ⊚.
Δ: The evaluation of each of the above characteristics was any of Δ, ◯, and ⊚, including one or more Δ.
x: Any of the above characteristics was evaluated as x.

From the results in Tables 1 and 2, it can be seen that the crosslinked rubbers (sealing members) of Examples are excellent in resistance to compression cracking and low settling in a wide temperature range from low temperature to high temperature.
On the other hand, the crosslinked rubber of Comparative Example 1 uses a softener with a low kinematic viscosity that is different from the softener (component B) specified in the present invention. The result was that the sagging property was not obtained. The crosslinked rubber of Comparative Example 2 uses a softening agent with a high kinematic viscosity different from the softening agent (component B) specified in the present invention. It was an unsatisfactory result. The crosslinked rubber of Comparative Example 3 uses a softening agent having a cyclic structure different from the softening agent (component B) specified in the present invention. It was a result that could not be done. Since the crosslinked rubber of Comparative Example 4 uses a tetrafunctional (meth)acrylate monomer as a crosslinking aid instead of a bifunctional (meth)acrylate monomer (component C), it can be used particularly under high and low temperature conditions. The result was inferior in compression cracking resistance. Since the crosslinked rubber of Comparative Example 5 uses a softener with a high pour point different from the softener (component B) specified in the present invention, it exhibits resistance to compression cracking and low settling, especially under low temperature conditions. It was an unsatisfactory result.

The fuel cell sealing member of the present invention is a fuel cell sealing body in which a fuel cell component such as a metal separator and a rubber sealing member that seals it are adhered via an adhesive layer, or the above sealing member. It is used for the sealing member of the fuel cell sealing body which is adhered to each other via an adhesive layer.

1 cell 2 MEAs
3 gas diffusion layer 4a sealing member 4b lip 5 separator 6 adhesive layer 7 gas channel

Claims (5)

A sealing member for a fuel cell, which is used to seal components of a fuel cell, and contains the following components (A) to (D ), and the content of component (B) is 100 parts by weight of component (A). The content of component (C) is in the range of 0.1 to 10 parts by weight per 100 parts by weight of component (A), and component (D) (purity of 100% A fuel cell sealing member comprising a crosslinked rubber composition having a content of 0.4 to 12 parts by weight per 100 parts by weight of component (A).
(A) at least one rubber component selected from the group consisting of ethylene-propylene rubber, ethylene-propylene-diene rubber and ethylene-butene-diene rubber;
(B) A linear hydrocarbon-based softening agent having a pour point of -30°C or lower and a kinematic viscosity at 40°C of 8 to 500 mm ² /s.
(C) a bifunctional (meth)acrylate monomer;
(D) a cross-linking agent comprising an organic peroxide; 2. The fuel cell sealing member according to claim 1, wherein said hydrocarbon-based softening agent (B) is a poly-α-olefin. 3. The fuel cell sealing member according to claim 1, wherein the main chain of said bifunctional (meth)acrylate monomer (C) is an aliphatic hydrocarbon. The content of the hydrocarbon-based softening agent (B) in the rubber composition is in the range of 5 to 55 parts by weight per 100 parts by weight of the rubber component (A), according to any one of claims 1 to 3. A sealing member for a fuel cell as described above. Claim 1, wherein the content of the bifunctional (meth)acrylate monomer (C) in the rubber composition is in the range of 0.15 to 7.5 parts by weight per 100 parts by weight of the rubber component (A). 5. The sealing member for a fuel cell according to any one of -4.

Images