Polymer electrolyte fuel cell sealing material

Abstract

The present invention addresses the problem of providing a polymer electrolyte fuel cell sealing material in which sealing performance is hardly reduced even after long-term operation of a polymer electrolyte fuel cell. In a polymer electrolyte fuel cell sealing material according to the present invention, a sheet-type adhesive member (1) contains an acrylic rubber (a), an epoxy resin (b), and an epoxy hardener (c), and the initial adhesive strength obtained by the following measurement method is 1.5 N / cm or higher. [(i) Prepare two sheets of the sealing material cut to be 25 mm wide by 100 mm long. (ii) Paste the two sheets together by bringing 80 mm lengths of the sheet-type adhesive members in contact with one other using a roll laminator under conditions with a temperature of 100 °C, a pressure of 4 N / cm, and a press-bonding speed of 1 m / min, thereby obtaining a test piece. (iii) Respectively paste two polyimide films for fixing to two portions of the sheet-type adhesive members at the non-contact portions of the test piece, fix one end of one film to a lower chuck, and fix one end of the other film to an upper chuck. (iv) Use a universal tensile testing machine to measure the T-peel strength at a tensile speed of 50 mm / min.]

Description

Solid polymer fuel cell sealing material

[0001] The present invention relates to a sealing material for a polymer electrolyte fuel cell.

[0002] The solid polymer electrolyte membrane to which the sealing material for polymer electrolyte fuel cells is adhered is typically made of a fluororesin with a perfluoroalkyl group as its main chain, which has led to the problem that conventional sealing materials have insufficient adhesion.

[0003] Patent Document 1 discloses a method of bonding a solid polymer electrolyte membrane by thermocompression bonding to achieve good sealing properties. Patent Document 2 discloses a method of improving adhesion by subjecting the surface of a solid polymer electrolyte membrane to ion exchange treatment. Patent Document 3 discloses a method of improving adhesion by blending a fluorine atom-containing acrylic monomer into an adhesive.

[0004] JP-A-6-119928 JP-A-9-199145 JP-A-2004-269782

[0005] With conventional sealing methods, it has been difficult to reliably seal the periphery of the solid polymer electrolyte membrane. In particular, when a solid polymer fuel cell is operated for a long period of time, the solid polymer fuel cell sealing material is exposed to acidic hot water at approximately 95°C. It has been difficult to maintain high sealing performance to prevent hydrogen leakage in such an acidic hot water environment. For these reasons, there has been a demand for a solid polymer fuel cell sealing material whose sealing performance does not deteriorate even when the solid polymer fuel cell is operated for a long period of time.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sealing material for a polymer electrolyte fuel cell whose sealing properties are not likely to deteriorate even when the polymer electrolyte fuel cell is operated for a long period of time.

[0007] A polymer electrolyte fuel cell sealing material according to a first embodiment has a sheet-like adhesive member, the sheet-like adhesive member containing an acrylic rubber (a), an epoxy resin (b), and an epoxy curing agent (c), and has an initial adhesive strength of 1.5 N / cm or more, as measured by the following initial adhesive strength measurement methods (1) to (4). (1) Two sheets of the polymer electrolyte fuel cell sealing material are prepared by cutting them into a width of 25 mm and a length of 100 mm. (2) Next, the two sheets are bonded together using a roll laminator with the sheet-like adhesive member at a temperature of 100°C, a pressure of 4 N / cm, and a compression speed of 1 m / min, with a length of 80 mm being brought into contact with each other, to form a test specimen. (3) Two polyimide films for fixing to a universal tensile tester are attached to two non-contacting portions of the sheet-like adhesive member of the test specimen, and then one end of one of the attached polyimide films is fixed to the lower chuck of the tensioning device of the universal tensile tester, and one end of the other attached polyimide film is fixed to the upper chuck of the tensioning device of the universal tensile tester. (4) The initial adhesive strength, which is the T-peel strength, of the fixed test specimen is measured using the universal tensile tester at a tension speed of 50 mm / min.

[0008] In a second aspect, in the first aspect, the acrylic rubber (a) has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, and an epoxy group.

[0009] A third aspect is the first or second aspect, wherein the epoxy resin (b) has a number average molecular weight of 300 to 5,500.

[0010] A fourth aspect is any one of the first to third aspects, wherein the epoxy curing agent (c) is an acid anhydride, a phenol compound, or a diamine compound.

[0011] In a fifth aspect, in any one of the first to fourth aspects, the sheet-like adhesive member further contains a curing accelerator (d).

[0012] A sixth aspect is the fifth aspect, wherein the curing accelerator (d) is dicyandiamide, a hydrazide compound, or an imidazole compound.

[0013] In a seventh aspect, in any one of the first to sixth aspects, the acrylic rubber (a) includes a copolymer of at least one of an acrylic acid ester and a derivative thereof, and at least one of acrylonitrile and a derivative thereof.

[0014] In an eighth aspect, in the seventh aspect, the acrylic rubber (a) is a Fourier transform infrared spectrophotometer, and the wave number (1740 cm) attributed to a carbonyl group of at least one of the acrylic acid ester and its derivative measured by an ATR method. －１ ) and the wave number (2240 ​​cm) attributable to at least one nitrile group of the acrylonitrile and its derivatives. －１ The ratio of the absorbance peak areas (nitrile group / carbonyl group) in the absorbance of the compound (C10) is 0.001 to 0.05.

[0015] In a ninth aspect, in any one of the first to eighth aspects, the epoxy resin (b) is 1 to 150 parts by mass per 100 parts by mass of the acrylic rubber (a).

[0016] A tenth aspect is any one of the first to ninth aspects, wherein the functional group equivalent ratio of the epoxy curing agent (c) to the epoxy resin (b) is 0.1 to 0.9.

[0017] According to the present invention, it is possible to provide a sealing material for a polymer electrolyte fuel cell whose sealing performance is not likely to deteriorate even when the polymer electrolyte fuel cell is operated for a long period of time.

[0018] FIG. 1 is a perspective view showing an example of a sealing material; FIG. 2 is a perspective view showing an example of a sealing material; FIG. 3 is a perspective view showing an example of a sealing material; FIG. 4 is an exploded perspective view showing an example of a sealing material used in a unit cell; FIG. 5 is an explanatory diagram of a method for measuring the adhesive strength between a solid polymer electrolyte membrane and a sealing material; and FIG. 6 is an explanatory diagram of a method for measuring the adhesive strength between two sealing materials.

[0019] The present invention will be described below based on preferred embodiments.

[0020] The sealing material of this embodiment is a sealing material for a polymer electrolyte fuel cell, and has a sheet-shaped adhesive member, which contains an acrylic rubber (a), an epoxy resin (b), and an epoxy curing agent (c).

[0021] The acrylic rubber (a) plays a role in maintaining an appropriate melt viscosity of the sheet-shaped adhesive member at the initial stage of heating, and also imparts good flexibility and adhesiveness to the cured sheet-shaped adhesive member, thereby forming a sealing material that has good adhesion to the solid polymer electrolyte membrane, electrodes, and separators and is free of cracks.

[0022] The acrylic rubber (a) is an acrylic rubber having at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, and an epoxy group. Generally, acrylic rubber (ACM) is composed of a polymer containing an acrylic ester as a main component. The acrylic rubber (a) preferably contains a copolymer of at least one of an acrylic ester and its derivatives and at least one of acrylonitrile and its derivatives.

[0023] The acrylic acid ester is not particularly limited as long as two or more types are copolymerizable with each other or with acrylonitrile, and examples thereof include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-dimethylaminoethyl acrylate, 2-hydroxyethyl acrylate, etc., and derivatives thereof. Examples of acrylic acid ester derivatives include unsaturated carboxylic acid esters such as methacrylic acid esters.

[0024] Examples of acrylonitrile and its derivatives include unsaturated carboxylic acid nitriles such as acrylonitrile and methacrylonitrile.

[0025] The functional group of the acrylic rubber (a) is preferably derived from at least one functional group-containing monomer selected from the group consisting of carboxyl group-containing monomers, hydroxyl group-containing monomers, and epoxy group-containing monomers. At least a portion of the functional group-containing monomers may also serve as acrylic acid esters and their derivatives. The carboxyl group-containing monomer is not particularly limited, but examples include unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Anhydrides of these carboxyl group-containing monomers can also be used as carboxyl group-containing monomers. (Meth)acrylic acid refers to acrylic acid and / or methacrylic acid. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-chloropropyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate. Examples of epoxy group-containing monomers include glycidyl (meth)acrylate and 2-ethyl (meth)acrylate glycidyl ether.

[0026] The acrylic rubber (a) may be a copolymer containing other monomers in addition to the above-mentioned monomers, as long as the properties of the copolymer are not affected. Examples of the other monomers include amino group-containing monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate, and amide group-containing monomers such as (meth)acrylamide and N-methylol (meth)acrylamide.

[0027] As a method for producing a copolymer of an acrylic acid ester or the like or a copolymer containing an acrylic acid ester or the like and acrylonitrile or the like, a general copolymerization method such as suspension polymerization or emulsion polymerization is used.

[0028] The weight average molecular weight (Mw) of the acrylic rubber (a) is not particularly limited, but is preferably 100,000 or more and 2,000,000 or less. If the Mw is below the above range, the flexibility of the cured product tends to deteriorate, resulting in reduced sealing properties. On the other hand, if the Mw exceeds the above range, the paint tends to become significantly thickened when made into a paint, resulting in the paint losing its fluidity (gelling), making the paint difficult to handle. The Mw is measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0029] The acrylic rubber (a) has a wave number (1740 cm) attributable to the carbonyl group of at least one of the acrylic ester and its derivative, measured by an attenuated total reflection method (ATR method) using a Fourier transform infrared spectrophotometer. －１ ) and the wave number (2240 ​​cm) attributable to at least one nitrile group (or, synonymously, cyano group) of the acrylonitrile and its derivatives. －１ ) is preferably 0.001 to 0.05.

[0030] If the "nitrile group / carbonyl group" ratio is less than the above range, the adhesiveness will be poor, and bonding will not be possible, or even if bonding is possible, there will be a tendency for the sealant to easily peel when subjected to stress or load, or for the sealant to be easily destroyed or peeled when heated. On the other hand, if the "nitrile group / carbonyl group" ratio exceeds the above range, there will be a tendency for compatibility with solvents and other resins to be poor, making it difficult to form into a coating material.

[0031] The epoxy resin (b) can impart acid and hot water resistance to the sealing material by reacting with the acrylic rubber (a) and / or the epoxy curing agent (c).

[0032] Examples of the epoxy resin (b) include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD ​​type epoxy resins, bisphenol S type epoxy resins, alicyclic epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, and glycidyl ether type epoxy resins, and these can be used alone or in combination of two or more.

[0033] The number-average molecular weight of the epoxy resin (b) is preferably 300 to 5500, more preferably 300 to 2000. If the number-average molecular weight is less than 300, the reactivity with other components tends to be too high, and the storage stability of the resulting sealant tends to decrease. On the other hand, if the number-average molecular weight exceeds 5500, the compatibility with other components, particularly the acrylic rubber (a), tends to decrease, and the uniformity of the resulting sealant tends to decrease.

[0034] The epoxy resin (b) preferably has an epoxy equivalent of 150 to 2500, more preferably 300 to 1000. If the epoxy equivalent is less than 150, the reactivity with other components becomes too high, and the storage stability of the resulting sealant tends to decrease. On the other hand, if the epoxy equivalent is more than 2500, the reactivity with other components becomes insufficient, and the resulting sealant tends to become less viscous and more fluid when heated. As a result, when the sealant is heated, the viscosity of the sealant decreases, and the sealant tends to foam or flow, and its thermal stability tends to decrease.

[0035] It is preferable that the epoxy resin (b) is 1 to 150 parts by mass per 100 parts by mass of the acrylic rubber (a). If the ratio of the epoxy resin (b) is less than this range, the reactivity of the sealing material decreases, and it becomes difficult for the material to become insoluble or infusible even when heated, which tends to reduce thermal stability. On the other hand, if the ratio of the epoxy resin (b) exceeds this range, the flexibility of the resulting sealing material decreases, and the sealing performance tends to deteriorate.

[0036] Examples of the epoxy curing agent (c) include acid anhydrides, phenolic compounds, and diamine compounds. Among these, aromatic diamine compounds are preferred from the viewpoints of reactivity and storage stability. The epoxy curing agent (c) can be used alone or in combination of two or more.

[0037] Examples of the diamine compound include 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 3,3'-dimethyl-4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,3'-dimethoxy-4,4'-diaminodiphenylmethane, 2,2'-bis(3-aminophenyl)propane, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 3,3'-diaminobiphenyl, 1,3-bis(3-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane ... bis[3-methyl-4-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-chloro-4-(4-aminophenoxy)phenyl]propane, 2,2-bis[3,5-dimethyl-4-(4-aminophenoxy)phenyl]propane, 1,1'-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1'-bis[3-chloro-4-(4-aminophenoxy)phenyl]ethane, bis[4- (4-aminophenoxy)phenyl]methane, bis[3-methyl-4-(4-aminophenoxy)phenyl]methane, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bis(2,6-dimethylbisaniline), and the like.

[0038] The functional group equivalent ratio of the epoxy curing agent (c) to the epoxy resin (b), expressed as the ratio (c) / (b), is preferably 0.1 to 0.9, and more preferably 0.2 to 0.6. If the functional group equivalent ratio is less than 0.1, the crosslink density of the epoxy resin in the sheet-like adhesive member composition becomes sparse, tending to reduce acidic hot water resistance. On the other hand, if the functional group equivalent ratio exceeds 0.9, crosslinking of the epoxy resin in the sheet-like adhesive member composition progresses, tending to reduce adhesiveness during the B-stage.

[0039] Furthermore, the content of the epoxy curing agent (c) is preferably 0.01 to 50 parts by mass per 100 parts by mass of the acrylic rubber (a). If the content of the epoxy curing agent (c) is less than 0.01 parts by mass, the crosslinking density of the epoxy resin in the sheet-like adhesive member composition becomes sparse, which tends to reduce acidic hot water resistance. On the other hand, if the content of the epoxy curing agent (c) exceeds 50 parts by mass, the crosslinking of the epoxy resin in the sheet-like adhesive member composition progresses, which tends to reduce adhesiveness in the B-stage. By partially crosslinking the epoxy resin (b) and the epoxy curing agent (c), a sheet-like adhesive member in a stable B-stage state can be produced.

[0040] The sheet-like adhesive member may further contain a curing accelerator (d). Examples of the curing accelerator (d) include dicyandiamide, a hydrazide compound, and an imidazole compound. The curing accelerator (d) may be used alone or in combination of two or more. The curing accelerator (d) may be in a microencapsulated form.

[0041] The sheet-like adhesive member may further contain a filler with an average particle size of 1 μm or less for purposes such as controlling melt viscosity, improving thermal conductivity, and imparting flame retardancy. Examples of fillers include inorganic fillers such as silica, alumina, magnesia, aluminum nitride, boron nitride, titanium oxide, calcium carbonate, and aluminum hydroxide, as well as organic fillers such as silicone resins and fluororesins. When a filler is used, its content in the sheet-like adhesive member is preferably 1 to 40% by mass. A filler content of less than 1% by mass tends to fail to achieve the intended effect. On the other hand, a filler content of more than 40% by mass causes excessive viscosity increase in the coating material, making it difficult to form a sheet-like film. Even if a film can be formed, the high filler content in the sheet-like adhesive member tends to impair flexibility and adhesion, resulting in poor sealing properties.

[0042] The sheet-like adhesive member may contain other components in addition to (a) to (d) as long as the components do not affect the properties.

[0043] The method for producing the sealing material is not particularly limited. For example, first, a coating material containing a mixture of the acrylic rubber (a), the epoxy resin (b), and the epoxy curing agent (c) is prepared. Subsequently, the coating material is applied to one side of the substrate (or the release side if a peelable protective film is used) so that the thickness of the sheet-like adhesive member after drying is preferably 1 to 50 μm, more preferably 3 to 20 μm. The coating material is then dried and desolvated to form a sheet-like adhesive member, which can then be cut into a frame. The substrate used for coating may be peeled off from the sheet-like adhesive member after formation. Here, to protect the sealing material, a peelable protective film is preferably provided on the exposed surface of the sheet-like adhesive member of the sealing material. The protective film is peeled off when the sealing material is used. The coating material for the sheet-like adhesive member can be prepared by dissolving the components kneaded using a roll mill or the like in a liquid medium, or by mixing or dispersing solutions in which the components are previously dissolved in a liquid medium.

[0044] The thickness of the sheet-like adhesive member after drying is preferably 1 to 50 μm, more preferably 3 to 20 μm. If the thickness of the sheet-like adhesive member is less than 1 μm, the sealing performance tends to decrease due to the thin thickness. On the other hand, if the thickness of the sheet-like adhesive member exceeds 50 μm, drying failure is likely to occur during application and drying, and if the adhesive is used in a state containing residual solvent, air bubbles are likely to occur inside the sheet-like adhesive part, which not only reduces sealing performance but also tends to increase costs due to reduced productivity.

[0045] The shape of the sealing material is not limited to a rectangular frame, but can be selected appropriately according to the shape of the fuel cell, such as a circular frame. Furthermore, when processing the sealing material, a tape-like sealing material with through holes at predetermined intervals along the length may be used. A frame-shaped sealing material can be obtained by cutting the sealing material so that the through holes are included in the center.

[0046] The sealing material has an initial adhesive strength of 1.5 N / cm or more, preferably 1.5 to less than 2.5 N / cm, and more preferably 2.5 N / cm or more, as measured by the following initial adhesive strength measurement methods (1) to (4). An initial adhesive strength of 1.5 N / cm or more improves the adhesion between the sheet-like adhesive member of the sealing material and the adherend (including the substrate), as well as the adhesion between the adherends of the sheet-like adhesive members. This not only results in excellent sealing properties for a polymer electrolyte fuel cell sealing material, but also tends to improve adhesion when exposed to an acidic hot water environment. Furthermore, an initial adhesive strength of 0.8 to less than 1.5 N / cm tends to result in inferior adhesion and sealing properties compared to a strength of 1.5 N / cm or more, but still provides sealing properties sufficient for use as a polymer electrolyte fuel cell sealing material. An initial adhesive strength of less than 0.8 N / cm tends to result in poor adhesion and insufficient sealing properties for a polymer electrolyte fuel cell sealing material. (Method for Measuring Initial Adhesion Strength) (1) Two sheets of sealing material cut to a width of 25 mm and a length of 100 mm were prepared. (2) Next, the two sheets were bonded together using a roll laminator at a temperature of 100°C, a pressure of 4 N / cm, and a compression speed of 1 m / min, with a length of 80 mm in contact with each other, to prepare a test specimen. (3) Two polyimide films were attached to the two non-contacting portions of the sheet adhesive member of the test specimen for fixing to a universal tensile tester, and one end of one of the attached polyimide films was fixed to the lower chuck of the tensioning device of the universal tensile tester, and one end of the other attached polyimide film was fixed to the upper chuck of the tensioning device of the universal tensile tester. (4) The initial adhesive strength, which is the T-peel strength, of the fixed test specimen was measured using a universal tensile tester at a tension speed of 50 mm / min.

[0047] Furthermore, the sealing material preferably has a mass change rate of 5 to 10%, more preferably less than 5%, as measured by the following measurement method. When the mass change rate is less than 5%, the sealant undergoes little change in its physical properties in an acidic hot water environment, and therefore tends to have sufficient acidic hot water resistance as a sealing material for a polymer electrolyte fuel cell. When the mass change rate is 5 to 10%, the sealant undergoes some slight change in its physical properties in an acidic hot water environment compared to when the mass change rate is less than 5%, but tends to have acidic hot water resistance sufficient for use as a sealing material for a polymer electrolyte fuel cell. When the mass change rate is more than 10%, the sealant undergoes significant change in its physical properties in an acidic hot water environment, and therefore tends to not have sufficient acidic hot water resistance as a sealing material for a polymer electrolyte fuel cell. (Method for Measuring Mass Change Rate) (1) Two sheets of sealing material are prepared, and the adhesive members of the two sealing materials are brought into contact with each other using a roll laminator under conditions of a temperature of 100°C, a pressure of 4 N / cm, and a pressure bonding speed of 1 m / min. This is then cut into a 50 mm x 50 mm piece to serve as a test specimen. (2) The mass of the test specimen is measured before and after immersion in a sulfuric acid aqueous solution (pH 2) at 95°C for 250 hours, 500 hours, 750 hours, or 1000 hours, and the mass change rate is calculated based on the following formula. After immersion, the test specimen is wiped clean of moisture from the surface and left to stand for 1 hour in an environment of 25°C / 50% RH. Mass change rate = [mass of test specimen before immersion / mass of test specimen after immersion] x 100 (%)

[0048] An example of a sealing material is shown in Fig. 1. The sealing material 10 shown in the figure is made up of only a sheet-like adhesive member 1 having a rectangular frame shape.

[0049] The sheet-like adhesive member 1 can be used not only as a single layer sealing material 10, but also to manufacture a sealing material 10 having the sheet-like adhesive member 1 on at least one side of a substrate 2, as shown in FIG. 2. Alternatively, the sealing material 10 may have a three-layer structure in which the sheet-like adhesive member 1, substrate 2, and adhesive layer 3 are laminated, as shown in FIG. 3. The processing of the sheet-like adhesive member 1 can be carried out in parallel with the processing of the sealing material 10. For example, the sealing material 10 may be processed into a frame shape after the tape-like sheet-like adhesive member 1 and substrate 2 are bonded together and through-holes are formed in the longitudinal direction of the resulting laminate, or after further bonding to an electrode 20, which will be described later.

[0050] Examples of the substrate 2 include heat-resistant plastic films made of polyimide, polyphenylene sulfide, polyether sulfone, polyether ether ketone, liquid crystal polymer, polyethylene terephthalate, polyethylene naphthalate, etc., and composite heat-resistant films such as epoxy resin-glass cloth, among which polyethylene naphthalate is particularly preferred from the viewpoints of acid and hot water resistance and cost.

[0051] The thickness of the substrate 2 is preferably 12 to 125 μm, and more preferably 12 to 50 μm. If the thickness is less than 12 μm, handling during processing tends to be poor. On the other hand, if the thickness exceeds 125 μm, the flexibility of the sealing material is impaired, which reduces its ability to conform to the adherend, and in turn tends to lead to a decrease in sealing performance.

[0052] The sealing material of the embodiment can be used in a unit cell in a stack of polymer electrolyte fuel cells. FIG. 4 is an exploded view of a unit cell 100, showing a sealing material 10, an electrode 20, and a separator 30. In the unit cell 100, the sealing material 10 is in contact with both sides of the electrode 20, and a separator 30 is in contact with the surface of the sealing material 10 that is not in contact with the electrode 20. Examples of the electrode 20 include a membrane electrode assembly (MEA) for a fuel cell, a catalyst coated membrane (CCM) for a fuel cell, and a gas diffusion electrode (GDE). Examples of the separator 30 include a fluorine-based resin having a perfluoroalkyl group as its main chain.

[0053] The present invention will be specifically described below with reference to examples.

[0054] Sheet-like adhesive member compositions were obtained by mixing the components according to the formulations shown in Tables 1, 2, and 3. The sheet-like adhesive member compositions were prepared as coatings using methyl ethyl ketone (MEK) as a liquid medium, and were applied to one side of a 16 μm-thick polyethylene naphthalate (PEN) film, followed by drying in a hot air circulating oven set at 100° C. to obtain sealing materials consisting of a laminate in which a 20 μm-thick sheet-like adhesive member was laminated on one side of the PEN film.

[0055] Details of each component used in the sheet-like adhesive member are as follows. The epoxy group-containing acrylic rubber (nitrile group / carbonyl group ratio 0.08, Mw = 900,000) had poor solubility in methyl ethyl ketone and could not be used as a coating material. Furthermore, the bisphenol F epoxy resin (number average molecular weight 8,600, epoxy equivalent weight 4,300 g / eq) had poor compatibility with the acrylic rubber and separated, making it impossible to form a film.

[0056] (a-1) Carboxyl group-containing acrylic rubber: "nitrile group / carbonyl group" 0.0036, Mw = 900,000 (a-2) Hydroxyl group-containing acrylic rubber: "nitrile group / carbonyl group" 0.0064, Mw = 900,000 (a-3) Epoxy group-containing acrylic rubber: "nitrile group / carbonyl group" 0.029, Mw = 900,000 (a-4) Epoxy group-containing acrylic rubber: "nitrile group / carbonyl group" 0, Mw = 900,000

[0057] (b-1) Bisphenol A type epoxy resin: number average molecular weight 390, epoxy equivalent 180 g / eq (b-2) Bisphenol A type epoxy resin: number average molecular weight 4000, epoxy equivalent 2000 g / eq (b-3) Trifunctional epoxy resin: number average molecular weight 630, epoxy equivalent 210 g / eq (b-4) Bisphenol A type epoxy resin: number average molecular weight 5500, epoxy equivalent 4000 g / eq

[0058] (c-1) Acid anhydride: pyromellitic anhydride, functional group equivalent: 109 g / eq (c-2) Phenol compound: phenol novolak (TD-2091 manufactured by DIC Corporation), functional group equivalent: 140 g / eq (c-3) Diamine compound: diaminodiphenylmethane, functional group equivalent: 50 g / eq

[0059] (d-1) Dicyandiamide (d-2) Imidazole compound: 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine-isocyanuric acid adduct (d-3) Hydrazide compound: Adipic acid dihydrazide (d-4) Microcapsule-type curing agent: Novacure (registered trademark) HX3941HP, manufactured by Asahi Kasei Corporation

[0060]

[0061]

[0062]

[0063] [Evaluation] The evaluation method for the sealing material obtained in each example will be described.

[0064] (1) Adhesion Evaluation (I) (1-1) Preparation of Test Specimens Two sealing materials were prepared by cutting the sealing material with the sheet-like adhesive member obtained in each example to a width of 25 mm and a length of 100 mm. Separately, a solid polymer electrolyte membrane (manufactured by DuPont, product name: Nafion membrane) was prepared and cut to a width of 25 mm and a length of 80 mm. These members were then bonded together as shown in Figure 5. Specifically, a sealing material 10 with sheet-like adhesive members 1 abutting on both sides of the solid polymer electrolyte membrane 11 was bonded using a roll laminator to prepare a test specimen. The lamination conditions were a temperature of 50°C, a pressure of 4 N / cm, and a compression speed of 1 m / min. The length α of the contact between the solid polymer electrolyte membrane 11 and the sheet-like adhesive member 1 was 80 mm. In addition, the portion β (a portion not in contact with the test piece, length 20 mm) of the sheet-like adhesive member 1 in FIG. 5 that is not attached to the solid polymer electrolyte membrane 11 is an attachment portion when fixed to a universal tensile testing machine described next.

[0065] (1-2) Measurement of Initial Adhesion Strength The T-peel strength of the test specimen in (1-1) above was measured using a universal tensile tester without immersion in a 95°C aqueous sulfuric acid solution (pH 2). That is, the upper β in FIG. 5 was pulled upward in the figure, while the lower β was simultaneously pulled downward in the figure. Specifically, two polyimide films for fixing to the universal tensile tester were attached to two locations on the sheet-like adhesive member 1 at the non-contact portion (portion β) of the test specimen that was not immersed in a 95°C aqueous sulfuric acid solution (pH 2). One end of one of the attached polyimide films was then fixed to the lower chuck of the tensioning device of the universal tensile tester, and one end of the other attached polyimide film was fixed to the upper chuck of the tensioning device of the universal tensile tester. The initial adhesive strength, which is the T-peel strength, of this fixed test specimen was measured using a universal tensile tester at a tension rate of 50 mm / min.

[0066] (1-3) Measurement of 250-Hour Acid Hot Water Resistance Test The acid hot water resistance test using T-peel strength measurement was conducted in the same manner as in (1-2) above, except that the test specimen in (1-1) above was immersed in a 95°C aqueous sulfuric acid solution (pH 2) for 250 hours, instead of not being immersed, and then the moisture on the test specimen surface was wiped off and the specimen was left to stand for 1 hour in an environment of 25°C / 50% RH. The test results were evaluated as follows. Good (A): After immersion, the test specimen did not exhibit interfacial delamination between the solid polymer electrolyte membrane and the sheet-like adhesive member. Furthermore, the failure morphology in the T-peel strength measurement showed that failure occurred within the solid polymer electrolyte membrane layer, but no interfacial delamination occurred between the solid polymer electrolyte membrane and the sheet-like adhesive member. Poor (X): After immersion, the test specimen exhibited interfacial delamination between the solid polymer electrolyte membrane and the sheet-like adhesive member, or the failure morphology in the T-peel strength measurement showed interfacial delamination between the solid polymer electrolyte membrane and the sheet-like adhesive member.

[0067] (1-4) Measurement of Acid Hot Water Resistance Test at 500 H, 750 H, and 1000 H Measurements and evaluations were carried out in the same manner as above (1-3), except that the immersion time of 250 hours was changed to 500 hours, 750 hours, and 1000 hours, respectively.

[0068] (2) Adhesion Evaluation (II) (2-1) Preparation of Test Specimen Two sheets of sealing material were prepared by cutting the sealing material with the sheet-like adhesive member obtained in each example to a width of 25 mm and a length of 100 mm. Next, these two sealing materials were bonded together as shown in Figure 6. Specifically, the sheet-like adhesive members 1 of two sealing materials 10 were abutted against each other and bonded using a roll laminator to prepare a test specimen. The lamination conditions were a temperature of 100°C, a pressure of 4 N / cm, and a pressure bonding speed of 1 m / min. The length α of the sheet-like adhesive members 1 abutting against each other was 80 mm. Note that the portion β of the sealing material 10 in Figure 6 where the sheet-like adhesive member 1 is not attached (the non-abutting portion of the test specimen, length 20 mm) is the attachment portion when fixed to the universal tensile tester described below.

[0069] (2-2) Measurement of Initial Adhesion Strength The T-peel strength of the test specimen in (2-1) above was measured using a universal tensile tester without immersion in a 95°C aqueous sulfuric acid solution (pH 2). That is, the upper β in FIG. 6 was pulled upward in the figure, while the lower β was simultaneously pulled downward in the figure. Specifically, two polyimide films for fixing to the universal tensile tester were attached to two locations on the sheet-like adhesive member 1 at the non-contact portion (portion β) of the test specimen that was not immersed in a 95°C aqueous sulfuric acid solution (pH 2). One end of one of the attached polyimide films was then fixed to the lower chuck of the tensioning device of the universal tensile tester, and one end of the other attached polyimide film was fixed to the upper chuck of the tensioning device of the universal tensile tester. The initial adhesive strength, which is the T-peel strength, of this fixed test specimen was measured using a universal tensile tester at a tension rate of 50 mm / min.

[0070] (2-3) Measurement of Acid Hot Water Resistance Test 250 Hours The acid hot water resistance test using T-peel strength measurement was carried out in the same manner as in (2-2) above, except that the test specimens in (2-1) above were immersed in a 95°C aqueous sulfuric acid solution (pH 2) for 250 hours, instead of not being immersed, and then the moisture on the surface of the test specimen was wiped off and left to stand for 1 hour in an environment of 25°C / 50% RH. The test results were evaluated as follows: A (Excellent): 2.5 N / cm or more B (Good): 1.5 to less than 2.5 N / cm C (Fair): 0.8 to less than 1.5 N / cm X (Poor): Less than 0.8 N / cm

[0071] (2-4) Measurement of Acid Hot Water Resistance Test at 500 H, 750 H, and 1000 H Measurement and evaluation were carried out in the same manner as above (2-3), except that the immersion time was changed from 250 hours to 500 hours, 750 hours, and 1000 hours, respectively.

[0072] (3) Mass change rate (3-1) Preparation of test specimen Two sheets of sealing material with the sheet-like adhesive member obtained in each example were prepared and laminated using a roll laminator so that the sheet-like adhesive members of the two sealing materials overlapped each other. The lamination conditions were a temperature of 100 ° C, a pressure of 4 N / cm, and a pressure bonding speed of 1 m / min. Then, the above sample was cut into a size of 50 mm x 50 mm, which was used as a test specimen.

[0073] (3-2) Measurement of Acid Hot Water Resistance Test 250 Hours The masses of the test specimens in (3-1) above were measured before and after immersion in a 95°C aqueous sulfuric acid solution (pH 2) for 250 hours, and the mass change rate was calculated based on the following formula: Mass change rate = [Test specimen mass before immersion / Test specimen mass after immersion] x 100 (%). Test specimens after immersion were immersed in a 95°C aqueous sulfuric acid solution (pH 2) for 250 hours, then the moisture on the test specimen surface was wiped off and the specimen was left to stand for 1 hour in an environment of 25°C / 50% RH. The test results were evaluated as follows: if the mass change rate was less than 5%, it was considered good (A); if the mass change rate was 5% to 10%, it was considered fair (B); and if the mass change rate was more than 10%, it was considered poor (X).

[0074] (3-3) Measurement of Acid Hot Water Resistance Test at 500 H, 750 H, and 1000 H Measurement and evaluation were carried out in the same manner as above (3-2), except that the immersion time was changed from 250 hours to 500 hours, 750 hours, and 1000 hours, respectively.

[0075] The results of the measurements and evaluations are shown in Tables 4, 5 and 6.

[0076]

[0077]

[0078]

[0079] It was confirmed that the sealing materials of Examples 1 to 23 had good adhesion between the solid polymer electrolyte membrane and the sealing material, and were excellent in acid and hot water resistance.

[0080] The polymer electrolyte fuel cell sealing material of the present invention has excellent resistance to acidic hot water and maintains high sealing properties, and therefore can be operated for a long period of time in an acidic hot water environment.

[0081] REFERENCE SIGNS LIST 1...sheet-shaped adhesive member, 2...substrate, 3...adhesive layer, 10...sealing material, 20...electrode, 30...separator, 100...single cell

Claims

1. A test specimen having a sheet-like adhesive member, the sheet-like adhesive member containing acrylic rubber (a), epoxy resin (b), and epoxy curing agent (c), and the following initial adhesive strength measurement methods (1) to (4): (1) Prepare two sheets of a polymer electrolyte fuel cell sealing material cut to a width of 25 mm and a length of 100 mm. (2) Next, use a roll laminator to attach the two sheets of sheet-like adhesive member to each other at a temperature of 100°C, a pressure of 4 N / cm, and a pressure bonding speed of 1 m / min, with a length of 80 mm in contact with each other. (3) Two polyimide films for fixing to a universal tensile tester are attached to two sheet-like adhesive members at the non-contacting portions of the test specimen, and then one end of one of the attached polyimide films is fixed to the lower chuck of the tension device of the universal tensile tester, and one end of the other attached polyimide film is fixed to the upper chuck of the tension device of the universal tensile tester. (4) The fixed test specimen is measured for initial adhesive strength, which is T-peel strength, at a pulling speed of 50 mm / min using a universal tensile tester. A polymer electrolyte fuel cell sealing material characterized in that the initial adhesive strength according to the method is 1.5 N / cm or more.

2. The polymer electrolyte fuel cell sealing material according to claim 1, characterized in that the acrylic rubber (a) has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group and an epoxy group.

3. The solid polymer electrolyte fuel cell sealing material according to claim 1, wherein the epoxy resin (b) has a number average molecular weight of 300 to 5,500.

4. The polymer electrolyte fuel cell sealing material according to claim 1, wherein the epoxy curing agent (c) is an acid anhydride, a phenol compound or a diamine compound.

5. The polymer electrolyte fuel cell sealing material according to claim 1, wherein the sheet-like adhesive member further contains a curing accelerator (d).

6. The polymer electrolyte fuel cell sealing material according to claim 5, wherein the curing accelerator (d) is dicyandiamide, a hydrazide compound or an imidazole compound.

7. The solid polymer electrolyte fuel cell sealing material according to claim 2, characterized in that the acrylic rubber (a) contains a copolymer of at least one of an acrylic acid ester and a derivative thereof, and at least one of acrylonitrile and a derivative thereof.

8. The acrylic rubber (a) has a wave number (1740 cm) attributable to at least one carbonyl group of the acrylic ester and / or its derivative, measured by an ATR method using a Fourier transform infrared spectrophotometer. －１ ) and the wave number (2240 ​​cm) due to at least one nitrile group of the acrylonitrile and its derivative. －１ 8. The polymer electrolyte fuel cell sealing material according to claim 7, wherein the ratio of peak areas of absorbance in the measurement of the absorption peak (nitrile group / carbonyl group) is 0.001 to 0.

05.

9. The polymer electrolyte fuel cell sealing material according to claim 3, characterized in that the epoxy resin (b) is 1 to 150 parts by mass per 100 parts by mass of the acrylic rubber (a).

10. The polymer electrolyte fuel cell sealing material according to claim 1, characterized in that the functional group equivalent ratio of said epoxy curing agent (c) to said epoxy resin (b) is 0.1 to 0.9.

Images