Hot melt adhesive sheet

Abstract

To provide a hot melt adhesive sheet capable of simultaneously realizing: an adhesive layer sufficiently embedding an outer edge of a solid electrolyte membrane of a polymer electrolyte fuel cell, after adhering the adhesive layer onto the solid electrolyte membrane; and a prevention of uneven thickness of the adhesive layer.SOLUTION: A hot melt adhesive sheet 10 includes an adhesive layer 10b formed with a hot melt adhesive, laminated at least on one side of a base material 10a. The hot melt adhesive includes a cross-linked product of an adhesive composition including a cross-linking agent. The adhesive composition includes a polyester resin, an epoxy resin and an isocyanate-based cross-linking agent. The epoxy resin includes a bisphenol type epoxy resin and a rubber-modified epoxy resin. The bisphenol type epoxy resin has an epoxy equivalent of 450 to 1000 g / eq, inclusive.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hot melt adhesive sheet.

Background Art

[0002] Conventionally, a hot melt adhesive sheet having an adhesive layer formed by a hot melt adhesive has been known. It is also known to use such a hot melt adhesive sheet by adhering it to a solid electrolyte membrane of a solid polymer fuel cell (for example, Patent Document 1 below).

[0003] As shown in Patent Document 1 below, the solid polymer fuel cell usually includes a membrane / electrode assembly (MEA), and the membrane / electrode assembly (MEA) is configured such that a positive electrode and a negative electrode are respectively disposed on both surfaces of a solid electrolyte membrane facing each other. Here, in the solid polymer fuel cell, the positive electrode is usually configured such that a positive electrode gas diffusion layer is disposed on a positive electrode catalyst layer, and the negative electrode is configured such that a negative electrode gas diffusion layer is disposed on a negative electrode catalyst layer. And in the membrane / electrode assembly (MEA), the positive electrode catalyst layer of the positive electrode is disposed on one surface of the solid electrolyte membrane, and the negative electrode catalyst layer of the negative electrode is disposed on the other surface of the solid electrolyte membrane.

[0004] Further, the positive electrode catalyst layer and the negative electrode catalyst layer are configured to have a planar dimension smaller than that of the solid electrolyte membrane, the positive electrode gas diffusion layer is configured to have a planar dimension smaller than that of the positive electrode catalyst layer, and the negative electrode gas diffusion layer is configured to have a planar dimension smaller than that of the negative electrode catalyst layer.

[0005] Therefore, when the membrane / electrode assembly (MEA) is viewed from one side in plan view, the outer edge of the solid electrolyte membrane on one side extends outward beyond the outer edge of the positive electrode catalyst layer in the positive electrode, and when the membrane / electrode assembly (MEA) is viewed from the other side in plan view, the outer edge of the solid electrolyte membrane on the other side extends outward beyond the outer edge of the negative electrode catalyst layer in the negative electrode. In other words, when the membrane / electrode assembly (MEA) is viewed in plan view from one side, one exposed surface is formed on the outer edge side of one side of the solid electrolyte membrane between the outer edge of that side of the solid electrolyte membrane and the outer edge of the positive electrode catalyst layer. When the membrane / electrode assembly (MEA) is viewed in plan view from the other side, another exposed surface is formed on the outer edge side of the other side of the solid electrolyte membrane between the outer edge of that side of the solid electrolyte membrane and the outer edge of the negative electrode catalyst layer.

[0006] Furthermore, as described in Patent Document 1 below, the hot-melt adhesive sheet is bonded to the solid electrolyte membrane by sandwiching one exposed surface of the solid electrolyte membrane and the other exposed surface of the solid electrolyte membrane between two hot-melt adhesive sheets. More specifically, the adhesive layer of one of the hot-melt adhesive sheets is bonded to one exposed surface of the solid electrolyte membrane, and the adhesive layer of the other hot-melt adhesive sheet is bonded to the other exposed surface of the fixed electrolyte membrane. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2019 / 216402 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, as described above, after bonding the adhesive layer of one of the hot-melt adhesive sheets to one exposed surface of the solid electrolyte membrane and bonding the adhesive layer of the other hot-melt adhesive sheet to the other exposed surface of the solid electrolyte membrane, the gap between the outer edge of the solid electrolyte membrane and the adhesive layer may become large. In other words, the adhesive layer of the hot-melt adhesive sheet may not adequately embed the outer edge of the solid electrolyte membrane.

[0009] Furthermore, after bonding the adhesive layer of one of the hot-melt adhesive sheets to one exposed surface of the solid electrolyte membrane and the adhesive layer of the other hot-melt adhesive sheet to the other exposed surface of the solid electrolyte membrane, the thickness of the adhesive layers may become uneven.

[0010] As described above, the inability of the adhesive layer of the hot-melt adhesive sheet to adequately embed the outer edge of the solid electrolyte membrane, and the uneven thickness of the adhesive layer of the hot-melt adhesive sheet, are undesirable because they lead to a decrease in the power generation efficiency of the polymer electrolyte fuel cell. However, it is still difficult to say that sufficient consideration has been given to both adequately embedding the outer edge of the solid electrolyte membrane with the adhesive layer of the hot melt adhesive sheet and suppressing the unevenness of the thickness of the adhesive layer of the hot melt adhesive sheet.

[0011] The present invention has been made to solve the above problems, and aims to provide a hot-melt adhesive sheet that can solve both the problem of sufficiently embedding the outer edge of the solid electrolyte membrane of a polymer electrolyte fuel cell with the adhesive layer after the adhesive layer has been bonded to the solid electrolyte membrane, and the problem of uneven thickness of the adhesive layer. [Means for solving the problem]

[0012] The hot melt adhesive sheet according to the present invention is A hot-melt adhesive sheet in which an adhesive layer formed with a hot-melt adhesive is laminated on at least one surface of a substrate, The hot melt adhesive comprises a crosslinked product of an adhesive composition containing a crosslinking agent, and the adhesive composition contains a polyester resin, an epoxy resin, and an isocyanate-based crosslinking agent. The epoxy resin includes a bisphenol-type epoxy resin and a rubber-modified epoxy resin. The bisphenol-type epoxy resin has an epoxy equivalent of 450 g / eq or more and 1000 g / eq or less. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a hot-melt adhesive sheet that can solve both the problem of sufficiently embedding the outer edge of the solid electrolyte membrane of a polymer electrolyte fuel cell with the adhesive layer after the adhesive layer has been bonded to the solid electrolyte membrane, and the problem of uneven thickness of the adhesive layer. [Brief explanation of the drawing]

[0014] [Figure 1] A schematic cross-sectional view showing the structure of a hot-melt adhesive sheet according to one embodiment of the present invention. [Figure 2] A schematic cross-sectional view showing a hot-melt adhesive sheet according to one embodiment of the present invention attached to the solid electrolyte membrane of a polymer electrolyte fuel cell and used in that state. [Modes for carrying out the invention]

[0015] A hot-melt adhesive sheet according to one embodiment of the present invention will be described below with reference to the drawings. Hereinafter, one embodiment of the present invention may be simply referred to as "this embodiment."

[0016] As shown in Figure 1, the hot melt adhesive sheet 10 according to this embodiment is a hot melt adhesive sheet in which an adhesive layer 10b formed with a hot melt adhesive is laminated on one side of a base material 10a. In the hot melt adhesive sheet 10 shown in FIG. 1, the adhesive layer 10b is laminated only on one surface of the base material 10a, but the adhesive layer 10b may be laminated on the other surface of the base material 10a. That is, the hot melt adhesive sheet 10 may be a hot melt adhesive sheet in which the adhesive layer 10b is laminated on both surfaces of the base material 10a.

[0017] In the hot melt adhesive sheet 10 according to the present embodiment, the hot melt adhesive includes a crosslinked product of an adhesive composition containing a crosslinking agent. In the hot melt adhesive sheet 10 according to the present embodiment, the adhesive composition contains a polyester resin, an epoxy resin, and an isocyanate-based crosslinking agent. In the hot melt adhesive sheet 10 according to the present embodiment, the epoxy resin includes a bisphenol type epoxy resin and a rubber-modified epoxy resin. In the hot melt adhesive sheet 10 according to the present embodiment, the bisphenol type epoxy resin has an epoxy equivalent of 450 g / eq or more and 1000 g / eq or less. <00><000097> Hereinafter, the polyester resin is referred to as polyester resin (A), the epoxy resin is referred to as epoxy resin (B), and the isocyanate-based crosslinking agent is referred to as isocyanate-based crosslinking agent (C). Among the polyester resins (A), the crystalline polyester resin is referred to as crystalline polyester resin (a1), and the non-crystalline polyester resin is referred to as non-crystalline polyester resin (a2). Furthermore, among the epoxy resins (B), the bisphenol type epoxy resin is referred to as bisphenol type epoxy resin (b1), and the rubber-modified epoxy resin is referred to as rubber-modified epoxy resin (b2).

[0019] The hot melt adhesive sheet 10 according to the present embodiment is used, for example, by adhering it to the solid electrolyte membrane 201 of a solid polymer fuel cell as described later. A polymer electrolyte fuel cell typically includes a membrane / electrode assembly (MEA) 20, which is configured such that a positive electrode 202 and a negative electrode 203 are arranged on opposite sides of a solid electrolyte membrane 201. In the film / electrode assembly (MEA) 20, the positive electrode 202 is configured such that a positive electrode gas diffusion layer 202b is placed on a positive electrode catalyst layer 202a, and the negative electrode 203 is configured such that a negative electrode gas diffusion layer 203b is placed on a negative electrode catalyst layer 203a. In other words, in the membrane / electrode assembly (MEA) 20, on one side of the solid electrolyte membrane 201, the positive electrode 202 is formed by arranging the positive electrode catalyst layer 202a and the positive electrode gas diffusion layer 202b in that order, and on the other side of the solid electrolyte membrane 201, the negative electrode 203 is formed by arranging the negative electrode catalyst layer 203a and the negative electrode gas diffusion layer 203b in that order.

[0020] Furthermore, when the membrane / electrode assembly (MEA) 20 is viewed from one side in plan view, the outer edge of the solid electrolyte membrane 201 on one side extends outward beyond the outer edge of the positive electrode catalyst layer 202a, and the outer edge of the positive electrode catalyst layer 202a extends outward beyond the outer edge of the positive electrode gas diffusion layer 202b. Furthermore, when the membrane / electrode assembly (MEA) 20 is viewed from the other side in a plan view, the outer edge of the solid electrolyte membrane 201 on the other side extends outward beyond the outer edge of the negative electrode catalyst layer 203a, and the outer edge of the negative electrode catalyst layer 203a extends outward beyond the outer edge of the negative electrode gas diffusion layer 203b. Specifically, on the outer edge side of one side of the solid electrolyte membrane 201, a first exposed surface (positive electrode side electrolyte membrane exposed region 201a, described later) is formed between the outer edge of the solid electrolyte membrane 201 and the outer edge of the positive electrode catalyst layer 202a, and on the outer edge side of the positive electrode catalyst layer 202a, a second exposed surface (positive electrode side catalyst layer exposed region 202a1, described later) is formed between the outer edge of the positive electrode catalyst layer 202a and the positive electrode gas diffusion layer 202b. Furthermore, on the outer edge side of the other side of the solid electrolyte membrane 201, a third exposed surface (negative electrode side electrolyte membrane exposed region 201b, described later) is formed between the outer edge of the other side of the solid electrolyte membrane 201 and the outer edge of the negative electrode catalyst layer 203a, and a fourth exposed surface (negative electrode side catalyst layer exposed region 203a1, described later) is formed between the outer edge of the negative electrode catalyst layer 203a and the negative electrode gas diffusion layer 203b.

[0021] In the membrane / electrode assembly (MEA) 20 configured as described above, the hot-melt adhesive sheet 10 is bonded to the solid electrolyte membrane 201 by sandwiching the solid electrolyte membrane 201 from both sides (i.e., one side and the other side) using two hot-melt adhesive sheets 10. The sandwiching of the solid electrolyte membrane 201 from both sides using two hot-melt adhesive sheets 10 is carried out by bonding the adhesive layer 10b of one hot-melt adhesive sheet 10 to the first exposed surface formed on one side of the solid electrolyte membrane 201 and the second exposed surface formed on the positive electrode catalyst layer 202a, and bonding the adhesive layer 10b of the other hot-melt adhesive sheet 10 to the third exposed surface formed on the other side of the solid electrolyte membrane 201 and the fourth exposed surface formed on the negative electrode catalyst layer 203a.

[0022] Here, epoxy equivalent (unit: g / eq) refers to the molecular weight of epoxy resin per functional group (glycidyl group). Therefore, it can be said that the smaller the epoxy equivalent value, the greater the number of epoxy groups per structural unit in the epoxy resin, and the larger the epoxy equivalent value, the smaller the number of epoxy groups per structural unit in the epoxy resin. Therefore, the smaller the epoxy equivalent value of the epoxy resin used, the higher the crosslinking density with which the epoxy resin will harden. In other words, an epoxy resin with a small epoxy equivalent value becomes a cured body with a high crosslinking density through crosslinking. On the other hand, the larger the epoxy equivalent value of the epoxy resin used, the lower the crosslinking density at which the epoxy resin will harden. In other words, epoxy resins with a large epoxy equivalent value become cured bodies with a low crosslinking density when crosslinked. Furthermore, while a hardened material with a high crosslink density exhibits high mechanical strength, it suffers from poor ductility due to its high mechanical strength. Conversely, a hardened material with a low crosslink density exhibits high ductility, but suffers from poor mechanical strength due to its high ductility.

[0023] In the hot-melt adhesive sheet 10 according to this embodiment, the hot-melt adhesive for forming the adhesive layer 10b contains a bisphenol-type epoxy resin having an appropriate epoxy equivalent of 450 g / eq to 1000 g / eq. Therefore, when the adhesive layer 10b is heated and used, the bisphenol-type epoxy resin can be crosslinked in the adhesive layer 10b with an appropriate crosslinking density. Therefore, the adhesive layer 10b of the hot-melt adhesive sheet 10 according to this embodiment can exhibit a good balance of appropriate mechanical strength and appropriate ductility when heated for use. In other words, the adhesive layer 10b of the hot melt adhesive sheet 10 according to this embodiment can exhibit suitable toughness when heated and used. Furthermore, the hot-melt adhesive contains the polyester resin in addition to the bisphenol-type epoxy resin described above. Furthermore, the polyester resin has the characteristic of having a high elastic modulus, and as a result of having a high elastic modulus, it also has the characteristic of having excellent resilience. Therefore, when the adhesive layer 10b formed by the hot-melt adhesive is heated and used, it can exhibit not only the toughness caused by the bisphenol-type epoxy resin, but also the resilience caused by the polyester resin. Furthermore, because the hot-melt adhesive contains a rubber-modified epoxy resin as the epoxy resin, the adhesive layer 10b formed by the hot-melt adhesive can exhibit appropriate rubber elasticity when heated and used. As described above, the adhesive layer 10b of the hot melt adhesive sheet 10 exhibits various characteristics, and when the adhesive layer 10b of one hot melt adhesive sheet 10 is used to adhere to the first exposed surface of the solid electrolyte membrane 201 and the adhesive layer 10b of the other hot melt adhesive sheet 10 is used to adhere to the third exposed surface of the solid electrolyte membrane 201, it is possible to sufficiently suppress the occurrence of gaps between the adhesive layer 10b of one hot melt adhesive sheet 10 and the outer edge of the solid electrolyte membrane 201, and between the adhesive layer 10b of the other hot melt adhesive sheet 10 and the outer edge of the solid electrolyte membrane 201. In other words, the adhesive layer 10b of one hot melt adhesive sheet 10 and the adhesive layer 10b of the other hot melt adhesive sheet 10 can sufficiently embed the outer edge of the solid electrolyte membrane 201. Furthermore, because the adhesive layer 10b of the hot melt adhesive sheet 10 has the above-mentioned properties, in particular, resilience and rubber elasticity, when the adhesive layer 10b of one hot melt adhesive sheet 10 is bonded to the first exposed surface of the solid electrolyte membrane 201 and the adhesive layer 10b of the other hot melt adhesive sheet 10 is bonded to the third exposed surface of the solid electrolyte membrane 201, it is possible to suppress the non-uniformity of the thickness of the adhesive layer 10b of one hot melt adhesive sheet 10 and the adhesive layer 10b of the other hot melt adhesive sheet 10.

[0024] (Polyester resin (A)) As the polyester resin (A), one obtained by dehydrating and condensing a polycarboxylic acid and a polyol can be used. Various known polyester resins (A) can be used. The polyester resin (A) may be an unmodified polyester resin or a modified polyester resin. The term "unmodified polyester resin" refers to a polyester resin whose structure has not been partially modified by a modifying component, while the term "modified polyester resin" refers to a polyurethane resin whose structure has been partially modified by a modifying component.

[0025] The modified polyester resin may be a urethane-modified polyester resin in which part of its structure is modified by an isocyanate component, which is a modifying component, or a silicone-modified polyester resin in which part of its structure is modified by a silicone component, which is a modifying component.

[0026] The urethane-modified polyester resin can be obtained, for example, by dehydrating and condensing the polycarboxylic acid and the polyol to obtain a polyester resin, and then reacting the terminal hydroxyl groups of the polyester resin with an isocyanate component. Furthermore, the urethane-modified polyester resin can also be obtained by simultaneously reacting the polycarboxylic acid, the polyol, and the isocyanate component. Examples of commercially available urethane-modified polyester resins include TOYOBO's product names "Byron® UR-3210" and "Byron® UR-4410".

[0027] The silicone-modified polyester resin can be obtained, for example, by reacting the polycarboxylic acid, the polyol, and a modified silicone component having a reactive functional group at one or both ends. Examples of the reactive functional groups that the modified silicone component possesses include hydroxyl groups, carboxyl groups, and epoxy groups.

[0028] The polyester resin (A) may be a crystalline polyester resin (a1) or an amorphous polyester resin (a2). In other words, the unmodified polyester resin and the modified polyester resin may be a crystalline polyester resin (a1) or an amorphous polyester resin (a2).

[0029] Furthermore, crystalline polyester resin (a1) refers to a polyester resin from among the unmodified polyester resin and the modified polyester resin that exhibits at least one of a peak originating from crystallization and a peak originating from crystal melting in measurements using a differential scanning calorimeter (DSC). Furthermore, the amorphous polyester resin (a2) refers to the polyester resin among the unmodified polyester resin and the modified polyurethane resin in which neither peaks originating from crystallization nor peaks originating from crystal melting are shown in measurements using the differential scanning calorimeter (DSC).

[0030] Therefore, if it is necessary to determine whether the polyester resin (A) is a crystalline polyester resin (a1) or an amorphous polyester resin (a2), this can be determined by measuring with DSC, based on whether or not at least one of the peaks originating from crystallization and the peak originating from crystal melting is confirmed.

[0031] Examples of commercially available crystalline polyester resins (a1) include "GM920" (manufactured by TOYOBO), "GM913" (manufactured by TOYOBO), "GM-350" (manufactured by TOYOBO), "GM-900" (manufactured by TOYOBO), "UE-9400" (manufactured by Unitika), "UE-3400" (manufactured by Unitika), and "UE-3410" (manufactured by Unitika).

[0032] Furthermore, in the adhesive layer 10b of the hot melt adhesive sheet 10, if a portion of the epoxy resin (B) is in an unreacted state (unopened ring state), when the polyester resin (A) is hydrolyzed and becomes a short chain having hydroxyl groups or carboxyl groups at the molecular ends, the unreacted epoxy groups can be reacted with these to make the polyester resin (A) long chain again.

[0033] Examples of the polycarboxylic acids constituting the polyester resin (A) include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and biphenyldicarboxylic acid; aromatic oxycarboxylic acids such as p-oxybenzoic acid and p-(hydroxyethoxy)benzoic acid; saturated aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid; unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid; unsaturated alicyclic dicarboxylic acids such as tetrahydrophthalic acid; alicyclic dicarboxylic acids such as hexahydrophthalic acid and 1,2-cyclohexanedicarboxylic acid; and tricarboxylic acids and tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid.

[0034] Examples of polyols constituting the polyester resin (A) include aliphatic glycols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 2-butyl-2-ethyl-1,3-propanediol; and oligoalkylene glycols such as diethylene glycol, triethylene glycol, and dipropylene glycol. Examples include: alicyclic glycols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; polyalkylene ether glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; triols such as trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol; and ethylene oxide adducts and propylene oxide adducts of bisphenol A, and ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A.

[0035] The polyester resin (A) preferably contains a crystalline polyester resin (a1) that exhibits a softening point of 120°C or higher. The softening point of crystalline polyester resin (a1) is the softening point determined by the ring-and-sphere method of JIS K 7234. In the hot-melt adhesive sheet 10 according to this embodiment, the adhesive layer 10b contains a crystalline polyester resin (a1) having the softening point described above, which further suppresses the softening of the adhesive layer 10b in a high-temperature environment (for example, 95°C). As a result, after the adhesive layer 10b is bonded to the first and third exposed surfaces of the solid electrolyte membrane 201, it can sufficiently embed the outer edge of the solid electrolyte membrane 201, thereby suppressing uneven thickness, and also providing excellent resistance to hot water, acids, and alcohols. For example, when the adhesive layer 10b of the hot melt adhesive sheet 10 according to this embodiment is used by adhering it to the solid electrolyte membrane of a polymer electrolyte fuel cell, the adhesive layer 10b can maintain sufficient adhesion to the solid electrolyte membrane 201 even if it comes into contact with water and alcohol such as polyethylene glycol contained in the antifreeze, or is exposed to highly acidic conditions at high temperatures such as 95°C. For example, a commercially available crystalline polyester resin (a1) having a softening point of 120°C or higher is "GM-913" manufactured by TOYOBO Corporation.

[0036] The softening point of the crystalline polyester resin (a1) may be 140°C or lower, 135°C or lower, or 130°C or lower.

[0037] Furthermore, it is preferable that the crystalline polyester resin (a1) has a glass transition temperature Tg of -65°C or lower. Having the above-described glass transition temperature Tg allows the crystalline polyester resin (a1) to exhibit a sufficient rubbery state even in high-temperature environments (e.g., 95°C). Therefore, in the hot-melt adhesive sheet 10 according to this embodiment, since the adhesive layer 10b contains a crystalline polyester resin (a1) having the above-mentioned glass transition temperature Tg, the adhesive layer 10b can also exhibit a sufficiently rubbery state in a high-temperature environment. As a result, after the adhesive layer 10b is bonded to the first and third exposed surfaces of the solid electrolyte membrane 201, it can sufficiently embed the outer edge of the solid electrolyte membrane 201, thereby suppressing uneven thickness, and also providing excellent resistance to hot water, acids, and alcohols. As an example of a commercially available crystalline polyester resin (a1) having a glass transition temperature Tg of -65°C or lower, the above-mentioned product name "GM-913" (manufactured by TOYOBO Corporation) can be cited.

[0038] The glass transition temperature Tg of a crystalline polyester resin (a1) can be measured, for example, using a differential scanning calorimeter (DSC). More specifically, the glass transition temperature for a sample can be determined from the DSC curve obtained when a sample (crystalline polyester resin (a1)) is heated from a temperature at least 30K lower than the predicted glass transition temperature Tg to a temperature at least 30K higher than the predicted glass transition temperature at a heating rate of 5°C / min while flowing nitrogen gas through it. The glass transition temperature (Tg) can be determined by determining the midpoint glass transition temperature based on the method described in JIS K7121:1987 "Method for Measuring Transition Temperatures of Plastics".

[0039] The glass transition temperature Tg of the crystalline polyester resin (a1) may be -90°C or higher, -80°C or higher, or -75°C or higher.

[0040] In order to achieve the effect of excellent resistance to hot water, acid, and alcohol, the polyester resin (A) preferably contains 50% by mass or more of crystalline polyester resin (a1), more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more. Furthermore, in order to particularly favorably achieve the effects of excellent resistance to hot water, acid, and alcohol, it is especially preferable that the polyester resin (A) is entirely composed of crystalline polyester resin (a1). That is, it is especially preferable that the polyester resin (A) contains 100% by mass of crystalline polyester resin (a1).

[0041] The crystalline polyester resin (a1) preferably has a number average molecular weight Mn of more than 30,000, more preferably 31,000 or more, more preferably 32,000 or more, more preferably 33,000 or more, and more preferably 34,000 or more. The crystalline polyester resin (a1) preferably has a number average molecular weight Mn of 40,000 or less, more preferably 39,000 or less, more preferably 38,000 or less, more preferably 37,000 or less, and more preferably 36,000 or less. In the hot-melt adhesive sheet 10 according to this embodiment, the adhesive layer 10b contains a crystalline polyester resin (a1) having the number average molecular weight Mn as described above. As a result, after the adhesive layer 10b is bonded to the first exposed surface and the third exposed surface of the solid electrolyte membrane 201, it is possible to sufficiently embed the outer edge of the solid electrolyte membrane 201, thereby suppressing uneven thickness. In addition, it exhibits excellent resistance to hot water, acid, and alcohol.

[0042] The number-average molecular weight Mn of crystalline polyester resin (a1) can be measured by gel permeation chromatography (GPC). The number-average molecular weight Mn of crystalline polyester resin (a1) can be measured, for example, using the following apparatus and conditions. Measuring device and measurement conditions ·Equipment: Product name “HLC-8020” (manufactured by Tosoh Corporation) • Column: Product names "TSKgel G2000HXL", "TSKgel G3000HXL", "TSKgel G4000HXL" (all manufactured by Tosoh Corporation) • Solvent: THF ·Flow rate: 1.0mL / min • Sample concentration: 2g / L ·Injection volume: 100μL ·Temperature: 40℃ • Detector: Model number "RI-8020" (manufactured by Tosoh Corporation) • Standard material: TSK standard polystyrene (manufactured by Tosoh Corporation)

[0043] The crystalline polyester resin (a1) preferably has a melt viscosity of 2,000 dPa·s or more at 200°C, more preferably 3,000 dPa·s or more, more preferably 4,000 dPa·s or more, more preferably 5,000 dPa·s or more, and more preferably 6,000 dPa·s or more. The crystalline polyester resin (a1) preferably has a melt viscosity of 10,000 dPa·s or less at 200°C, more preferably 9,000 dPa·s or less, more preferably 8,000 dPa·s or less, and more preferably 7,000 dPa·s or less. In the hot-melt adhesive sheet 10 according to this embodiment, the adhesive layer 10b contains a crystalline polyester resin (a1) having the melt viscosity described above. As a result, after the adhesive layer 10b is bonded to the first exposed surface and the third exposed surface of the solid electrolyte membrane 201, it is possible to sufficiently embed the outer edge of the solid electrolyte membrane 201, thereby suppressing uneven thickness. In addition, it exhibits excellent resistance to hot water, acid, and alcohol.

[0044] The melt viscosity of crystalline polyester resin (a1) was determined using a micro-compounder (Thermo Corporation, product name "HAAKE MiniLabII") at 200°C for 100 minutes. -1 Measurement can be performed under the condition of ×1min.

[0045] (Epoxy resin (B)) As described above, epoxy resin (B) contains bisphenol-type epoxy resin (b1) and rubber-modified epoxy resin (b2).

[0046] Examples of bisphenol-type epoxy resins (b1) include bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol AD-type epoxy resin. The bisphenol-type epoxy resin (b1) may be a modified resin. In other words, the bisphenol-type epoxy resin (b1) may be a modified bisphenol A-type epoxy resin, a modified bisphenol F-type epoxy resin, or a modified bisphenol AD-type epoxy resin. As explained above, the epoxy equivalent of the bisphenol-type epoxy resin (b1) is 450 g / eq or more and 1000 g / eq or less. The epoxy equivalent can be determined according to JIS K 7236.

[0047] It is preferable to use the bisphenol A type epoxy resin as the bisphenol type epoxy resin (b1). Examples of commercially available bisphenol A type epoxy resins include the product names "jER 1001," "jER 1002," "jER 1003," "jER 1055," "jER 1004," and "jER 1004AF," all manufactured by Mitsubishi Chemical Corporation.

[0048] The bisphenol-type epoxy resin (b1) may be present in an amount of 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more, per 100 parts by mass of the polyester resin (A). The bisphenol-type epoxy resin (b1) may be present in amounts of 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less, per 100 parts by mass of the polyester resin (A).

[0049] The rubber-modified epoxy resin (b2) is not particularly limited as long as it is a compound having at least one epoxy group in its molecule and a structure derived from rubber; various known compounds can be used. The rubber-modified epoxy resin (b2) may be used alone or in combination of two or more types. Examples of the rubber-modified epoxy resin (b2) include a reaction product of epoxy resin and rubber. As the epoxy resin, for example, a bisphenol-type epoxy resin (b1) as described above can be used.

[0050] Examples of the aforementioned rubbers include natural rubber, acrylonitrile butadiene rubber (NBR), carboxyl-terminated acrylonitrile butadiene rubber (CTBN), amino-terminated acrylonitrile butadiene rubber (ATBN), styrene butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber (EPDM), acrylic rubber (ACM), butyl rubber (IIR), and butadiene rubber. From the viewpoint of reactivity with epoxy groups, the aforementioned rubber is preferably one that has a functional group at its end that can react with epoxy groups, such as an amino group, a hydroxyl group, or a carboxyl group.

[0051] The rubber-modified epoxy resin (b2) is preferably a reaction product of epoxy resin and acrylonitrile butadiene rubber (NBR) (NBR-modified epoxy resin), a reaction product of epoxy resin and carboxyl-terminated acrylonitrile butadiene rubber (CTBN-modified epoxy resin), or a reaction product of epoxy resin and amino-terminated acrylonitrile butadiene rubber (ATBN-modified epoxy resin), due to its easy availability and reactivity with epoxy groups. Among these, NBR-modified epoxy resin is particularly preferred. A commercially available example of the aforementioned NBR-modified epoxy resin is "ADEKA Resin EPR-1415-1," manufactured by ADEKA Corporation. Furthermore, the method for producing the rubber-modified epoxy resin (b2) is not particularly limited as long as it is a method that can react the epoxy resin with the rubber, and various known production methods can be used.

[0052] The physical properties of the rubber-modified epoxy resin (b2) are not particularly limited, but it is preferable that the epoxy equivalent is 150 g / eq or more and 1000 g / eq, in terms of handling ease and adhesive properties. In the rubber-modified epoxy resin (b2), the epoxy equivalent can be determined in accordance with JIS K 7236.

[0053] The rubber-modified epoxy resin (b2) may be present in an amount of 3 parts by mass or more, 5 parts by mass or more, or 7 parts by mass or more, per 100 parts by mass of the polyester resin (A). The rubber-modified epoxy resin (b2) may be present in amounts of 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less, per 100 parts by mass of the polyester resin (A).

[0054] The mass ratio of rubber-modified epoxy resin (b2) to bisphenol-type epoxy resin (b1) may be 20% or more, 25% or more, or 30% or more. Furthermore, the mass ratio of the rubber-modified epoxy resin (b2) to the bisphenol-type epoxy resin (b1) may be 50% or less, 45% or less, or 40% or less.

[0055] (Isocyanate-based crosslinking agent (C)) The isocyanate-based crosslinking agent (C) is not particularly limited, but conventionally used known agents such as isocyanurate, biuret, adduct, and polymeric agents having polyfunctional isocyanate groups can be used. Examples include 2,4-toluylene diisocyanate dimers, triphenylmethane triisocyanate, tris-(p-isocyanatephenyl)thiophosphite, polyfunctional aromatic isocyanates, polyfunctional aromatic aliphatic isocyanates, polyfunctional aliphatic isocyanates, fatty acid-modified polyfunctional aliphatic isocyanates, blocked polyisocyanates, and polyisocyanate prepolymers.

[0056] Among these isocyanate-based crosslinking agents (C), if they are aromatic, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate are preferred. If it is an aliphatic compound, modified forms such as hexamethylene diisocyanate and isophorone diisocyanate are preferred. Furthermore, as the isocyanate-based crosslinking agent (C), it is preferable that one molecule contains three or more isocyanate groups. Furthermore, as the isocyanate-based crosslinking agent (C), polymers of the polyisocyanate, adducts with other compounds, and urethane prepolymers obtained by reacting a low molecular weight polyol with a polyamine such that the molecular ends are isocyanates are also preferably used. Among the various isocyanate-based crosslinking agents (C) listed above, xylylene diisocyanate is preferred. An example of a commercially available xylylene diisocyanate is "Takenate D-110N," manufactured by Mitsui Takeda Chemical Co., Ltd.

[0057] As described above, in the adhesive layer 10b of the hot melt adhesive sheet 10 of this embodiment, the isocyanate-based crosslinking agent (C) may be contained in an amount of 3 parts by mass or more, 5 parts by mass or more, or 7 parts by mass or more, per 100 parts by mass of the polyester resin (A). The isocyanate-based crosslinking agent (C) may be present in amounts of 20 parts by mass or less, 15 parts by mass or less, or 12 parts by mass or less, per 100 parts by mass of the polyester resin (A).

[0058] Next, with reference to Figure 2, we will further explain the case where the adherend to which the adhesive layer 10b of the hot melt adhesive sheet 10 according to this embodiment is bonded is the membrane / electrode assembly (MEA) 20 of a polymer electrolyte fuel cell, as an example.

[0059] The film / electrode assembly (MEA) 20, which is the adherend, is configured to allow hydrogen gas to permeate from the negative electrode side to the positive electrode side and to generate electricity by reacting the hydrogen with the oxygen supplied to the positive electrode side.

[0060] As shown in Figure 2, in the membrane / electrode assembly (MEA) 20, the positive electrode 202 and the negative electrode 203 are stacked on opposite sides of the solid electrolyte membrane 201, respectively. The positive electrode 202 comprises a positive electrode catalyst layer 202a and a positive electrode gas diffusion layer 202b laminated on the positive electrode catalyst layer 202a, with the positive electrode catalyst layer 202a being laminated on one side of the solid electrolyte membrane 201. The negative electrode 203 comprises a negative electrode catalyst layer 203a and a negative electrode gas diffusion layer 203b laminated on the negative electrode catalyst layer 203a, with the negative electrode catalyst layer 203a being laminated on the other side of the solid electrolyte membrane 201.

[0061] As shown in Figure 2, the positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a are formed to have smaller planar dimensions than the solid electrolyte membrane 201, and the positive electrode gas diffusion layer 202b and the negative electrode gas diffusion layer 203b are formed to have smaller planar dimensions than both the positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a. In other words, in the membrane / electrode assembly (MEA), the planar dimensions of the positive electrode 202 and the negative electrode 203 are smaller than the planar dimensions of the solid electrolyte membrane 201. As described above, because the planar dimensions of the positive electrode 202 are smaller than the planar dimensions of the solid electrolyte membrane 201, a positive electrode side electrolyte membrane exposed region 201a is formed on the outer periphery of the positive electrode side (one side) of the membrane / electrode assembly (MEA) 20, where the solid electrolyte membrane 201 extends outward beyond the positive electrode catalyst layer 202a and the solid electrolyte membrane 201 is exposed on the surface. Furthermore, because the planar dimensions of the negative electrode 203 are smaller than those of the solid electrolyte membrane 201, a negative electrode side electrolyte membrane exposed region 201b is formed on the outer periphery of the negative electrode side (other side) of the membrane / electrode assembly (MEA) 20, where the solid electrolyte membrane 201 extends outward beyond the negative electrode catalyst layer 203a and the solid electrolyte membrane 201 is exposed. The positive electrode side electrolyte membrane exposed region 201a is the first exposed surface described above, and the negative electrode side electrolyte membrane exposed region 201b is the third exposed surface described above.

[0062] Furthermore, on the positive electrode side of the film / electrode assembly (MEA) 20, a positive electrode side catalyst layer exposed region 202a1 is formed where the positive electrode catalyst layer 202a extends outward beyond the positive electrode gas diffusion layer 202b, and the positive electrode catalyst layer 202a is exposed on the surface. The positive electrode side catalyst layer exposed region 202a1 is formed inside the positive electrode side electrolyte membrane exposed region 201a and outside the positive electrode gas diffusion layer 202b. In this embodiment, the positive electrode side electrolyte membrane exposed region 201a is formed in an annular shape so as to encircle the outer periphery of the membrane / electrode assembly (MEA) 20. The positive electrode side catalyst layer exposed region 202a1 is formed in a ring shape that is smaller than the positive electrode side electrolyte membrane exposed region 201a. In other words, on the positive electrode side of the membrane / electrode assembly (MEA), a second boundary line L2 is formed inside the first boundary line L1, which is the boundary line between the positive electrode side catalyst layer exposed region 202a1 and the positive electrode gas diffusion layer 202b. The positive electrode side catalyst layer exposed region 202a1 is the second exposed surface described above.

[0063] On the negative electrode side of the film / electrode assembly (MEA) 20, a negative electrode side catalyst layer exposed region 203a1 is formed where the negative electrode catalyst layer 203a extends outward beyond the negative electrode gas diffusion layer 203b, and the negative electrode catalyst layer 203a is exposed on the surface. The negative electrode side catalyst layer exposed region 203a1 is formed inside the negative electrode side electrolyte membrane exposed region 201b and outside the negative electrode gas diffusion layer 203b. In this embodiment, the negative electrode side electrolyte membrane exposed region 201b is formed in an annular shape so as to encircle the outer periphery of the membrane / electrode assembly (MEA) 20. The negative electrode side catalyst layer exposed region 203a1 is formed in a ring shape that is smaller than the negative electrode side electrolyte membrane exposed region 201b. In other words, on the negative electrode side of the membrane / electrode assembly (MEA) 20, a fourth boundary line L4 is formed inside the third boundary line L3, which is the boundary line between the negative electrode side catalyst layer exposed region 203a1 and the negative electrode gas diffusion layer 203b. The negative electrode side catalyst layer exposed region 203a1 is the fourth exposed surface described above.

[0064] In the usage configuration shown in Figure 2, two hot-melt adhesive sheets 10 are used as sub-gasket materials for a polymer electrolyte fuel cell: a first hot-melt adhesive sheet 10 bonded to the positive electrode side of the membrane / electrode assembly (MEA) 20, and a second hot-melt adhesive sheet 10 bonded to the negative electrode side of the membrane / electrode assembly (MEA) 20.

[0065] The first hot-melt adhesive sheet 10 is annular in shape, and when superimposed on the film / electrode assembly (MEA) 20, its outer edge is located outside the film / electrode assembly (MEA) 20, while its inner edge is located within the positive electrode side catalyst layer exposure region 202a1 and the negative electrode side catalyst layer exposure region 203a1. In other words, the hollowed-out portion of the first hot-melt adhesive sheet 10 has a shape that is slightly larger than the positive electrode gas diffusion layer 202b.

[0066] The second hot melt adhesive sheet 10 has the same shape as the first hot melt adhesive sheet 10.

[0067] In this embodiment, the first hot-melt adhesive sheet 10 and the second hot-melt adhesive sheet 10 are directly bonded to the outer periphery of the adhesive layer 10b outside the film / electrode assembly (MEA) 20 and used as the sub-gasket material.

[0068] The first hot-melt adhesive sheet 10 has its inner circumference, excluding the outer circumference that is bonded to the second hot-melt adhesive sheet 10, bonded to the outer circumference of the film / electrode assembly (MEA) 20, and is bonded to the area from the positive electrode side electrolyte membrane exposed region 201a (first exposed surface) beyond the first boundary line L1 to the positive electrode side catalyst layer exposed region 202a1 (second exposed surface). The second hot melt adhesive sheet 10 is bonded in the same way as the first hot melt adhesive sheet 10.

[0069] By adhering (attaching) the hot-melt adhesive sheet 10 to the membrane / electrode assembly (MEA) 20 as described above, a portion of the positive electrode gas can permeate through the positive electrode side electrolyte membrane exposed region 201a, and a portion of the negative electrode gas can permeate through the negative electrode side electrolyte membrane exposed region 201b, thereby suppressing a decrease in the performance of the polymer electrolyte fuel cell.

[0070] Here, the hot melt adhesive sheet 10 according to this embodiment is configured as described above. Therefore, as described above, by adhering the first hot-melt adhesive sheet 10 from the positive electrode side electrolyte membrane exposed region 201a (first exposed surface) to the positive electrode side catalyst layer exposed region 202a1 (second exposed surface) beyond the first boundary line L1, and adhering the second hot-melt adhesive sheet 10 from the negative electrode side electrolyte membrane exposed region 201b (third exposed surface) to the negative electrode side catalyst layer exposed region 203a1 (fourth exposed surface) beyond the third boundary line L3, it is possible to sufficiently embed the outer edge of the solid electrolyte membrane 201 with the adhesive layer 10b and to suppress unevenness in the thickness of the adhesive layer 10b. Specifically, even if the first hot-melt adhesive sheet 10 and the second hot-melt adhesive sheet 10 are held for 500 hours in a 95°C atmosphere while a load of 7.5 MPa is applied to the outside of each of the first and second hot-melt adhesive sheets 10 (the substrate 10a side) via a metal gasket, the adhesive layer 10b can sufficiently embed the outer edge of the solid electrolyte membrane 201, and unevenness in the thickness of the adhesive layer 10b can be suppressed.

[0071] As explained earlier, in a polymer electrolyte fuel cell, electricity is generated when hydrogen and oxygen react in the membrane / electrode assembly (MEA) 20. As described above, when hydrogen and oxygen react, the membrane / electrode assembly (MEA) 20 reaches a relatively high temperature (for example, 95°C). When the aforementioned polymer electrolyte fuel cell is installed as a power source for an automobile, the central portion of the membrane / electrode assembly (MEA) 20 is sufficiently cooled by circulating antifreeze contained in a radiator through a pipeline. However, since the pipeline is not usually provided to the edges of the membrane / electrode assembly (MEA) 20, the edges of the membrane / electrode assembly (MEA) 20 continue to maintain a high temperature.

[0072] Furthermore, when the antifreeze is circulating, some of the antifreeze may leak out of the pipeline, and the leaked antifreeze may come into contact with the adhesive layer 10b attached to the edge of the solid electrolyte membrane 201. Since the aforementioned antifreeze typically contains polyethylene glycol and water as its liquid components, in such cases, the adhesive layer 10b is in contact with polyethylene glycol and water at high temperatures.

[0073] Furthermore, in the reaction that generates electricity as explained earlier, hydrogen ions (H) are released into the membrane / electrode assembly (MEA) 20. + As a result of mass transfer, the membrane / electrode assembly (MEA) 20 becomes strongly acidic, equivalent to dilute sulfuric acid of about 0.1 to 0.5 M. In such cases, the adhesive layer 10b attached to the edge of the solid electrolyte membrane 201 is exposed to a strongly acidic environment at high temperatures.

[0074] In this embodiment, the hot-melt adhesive sheet 10 contains a crystalline polyester resin (a1) having the above-described physical properties in the adhesive layer 10b, thereby providing the adhesive layer 10b with excellent resistance to hot water, acid, and alcohol. Therefore, when a hot-melt adhesive sheet 10 configured in this manner is used as a sub-gasket material in a polymer electrolyte fuel cell mounted on an automobile, as described above, even if the adhesive layer 10b comes into contact with water or alcohol at high temperatures such as 95°C, or is exposed to strong acid at high temperatures such as 95°C, the adhesion to the solid electrolyte membrane 201 can be maintained for a long period of time (1000 hours). As will be described later, the solid electrolyte membrane 201 is usually formed from a fluororesin such as perfluorocarbon sulfonic acid.

[0075] In the film / electrode assembly (MEA) 20, the positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a are generally formed using a catalyst-supporting material such as a carbon material on which the catalyst is supported, a proton-conducting polymer, and a catalyst ink composition containing a solvent.

[0076] The solid electrolyte membrane 201 of the membrane / electrode assembly (MEA) 20 is formed of a fluororesin, such as perfluorocarbon sulfonic acid resin. Examples of the aforementioned perfluorocarbon sulfonic acid resins include "Nafion" manufactured by DuPont, "Flemion" manufactured by Asahi Kasei Corporation, and "Aciplex" manufactured by Asahi Glass Co., Ltd. Perfluorocarbon sulfonic acid resin is, for example, a resin having the polymer structure shown in formula (1) below. For example, in formula (1) below, m, n, and x are as follows: in "Nafion", m≧1, n=2, and x=5~13.5; in "Asiplex", m=0,1, n=2~5, and x=1.5~14; and in "Flemion", m=0,1, and n=1~5.

[0077] [ka]

[0078] The positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a are layers containing catalyst particles. Platinum is an example of a catalyst particle contained in the positive electrode catalyst layer 202a. Examples of catalyst particles contained in the negative electrode catalyst layer 203a include platinum compounds. Examples of the platinum compound include an alloy of platinum with at least one metal selected from the group consisting of ruthenium, palladium, nickel, molybdenum, iridium, and iron.

[0079] The positive electrode gas diffusion layer 202b and the negative electrode gas diffusion layer 203b are composed of a porous conductive substrate. Examples of the porous conductive substrate include carbon paper and carbon cloth.

[0080] Furthermore, the hot melt adhesive sheet 10 according to this embodiment can also be used in redox flow batteries. Hot-melt adhesive sheets used in redox flow batteries are used to suppress the permeation of the electrolyte.

[0081] The matters disclosed herein include the following:

[0082] (1) A hot-melt adhesive sheet in which an adhesive layer formed with a hot-melt adhesive is laminated on at least one surface of a substrate, The hot melt adhesive comprises a crosslinked product of an adhesive composition containing a crosslinking agent, and the adhesive composition comprises a polyester resin, an epoxy resin, and an isocyanate-based crosslinking agent. The epoxy resin includes a bisphenol-type epoxy resin and a rubber-modified epoxy resin. The bisphenol-type epoxy resin has an epoxy equivalent of 450 g / eq or more and 1000 g / eq or less. Hot melt adhesive sheet.

[0083] (2) The polyester resin includes a crystalline polyester resin having a softening point of 120°C or higher. The hot melt adhesive sheet described in (1) above.

[0084] (3) The bisphenol-type epoxy resin includes a bisphenol A-type epoxy resin. The hot melt adhesive sheet described in (1) or (2) above.

[0085] (4) The rubber-modified epoxy resin is an NBR-modified epoxy resin. A hot melt adhesive sheet as described in any of (1) to (3) above.

[0086] (5) Used by adhering it to the solid electrolyte membrane of a polymer electrolyte fuel cell. A hot melt adhesive sheet as described in any of (1) to (4) above.

[0087] The hot-melt adhesive sheet according to the present invention is not limited to the embodiments described above. Furthermore, the hot-melt adhesive sheet according to the present invention is not limited by the effects described above. The hot-melt adhesive sheet according to the present invention can be modified in various ways without departing from the spirit of the present invention. [Examples]

[0088] [Example of dissolution of bisphenol-type epoxy resin (b1)] <Example of dissolution of bisphenol-type epoxy resin (b1): B1> A reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen injection pipe, and manhole was prepared. While purging the inside of the reaction vessel with nitrogen, 400.0 g of bisphenol A type epoxy resin (epoxy equivalent: 450-500 g / eq, jER1001: manufactured by Mitsubishi Chemical Corporation; hereinafter referred to as epoxy resin B1) was charged, and while stirring, 600.0 g of methyl ethyl ketone (MEK) was charged as a solvent, and the temperature of the system was raised to 60°C to completely dissolve epoxy resin B1 in the methyl ethyl ketone. This yielded a dissolved product of epoxy resin B1, BB1 (hereinafter referred to as epoxy resin solution BB1). The solid content of the obtained epoxy resin solution BB1 was 40% by mass.

[0089] <Example of dissolution of bisphenol-type epoxy resin (b1): B2> Except for using bisphenol A type epoxy resin (epoxy equivalent: 670-770 g / eq, jER1003: manufactured by Mitsubishi Chemical Corporation; hereinafter referred to as epoxy resin B2) instead of epoxy resin B1, a solution of epoxy resin B2, BB2 (hereinafter referred to as epoxy resin solution BB2), was obtained in the same manner as in the above solution example B1. The solid content of the obtained epoxy resin solution BB2 was 40% by mass.

[0090] <Example of dissolution of bisphenol-type epoxy resin (b1): B3> Except for using bisphenol A type epoxy resin (epoxy equivalent: 875-975 g / eq, jER1004: manufactured by Mitsubishi Chemical Corporation; hereinafter referred to as epoxy resin B3) instead of epoxy resin B1, a solution of epoxy resin B3, BB3 (hereinafter referred to as epoxy resin solution BB3), was obtained in the same manner as in the above solution example B1. The solid content of the obtained epoxy resin solution BB3 was 40% by mass.

[0091] <Example of dissolution of bisphenol-type epoxy resin (b1): B4> Except for using bisphenol A type epoxy resin (epoxy equivalent: 1,750-2,200 g / eq, jER1007: manufactured by Mitsubishi Chemical Corporation; hereinafter referred to as epoxy resin B4) instead of epoxy resin B1, a solution of epoxy resin B4 (hereinafter referred to as epoxy resin solution B4) was obtained in the same manner as in the above solution example B1.

[0092] <Example of dissolution of bisphenol-type epoxy resin (b1): B5> Except for using bisphenol A type phenoxy resin (epoxy equivalent: 7,500-8,500 g / eq, jER1256: manufactured by Mitsubishi Chemical Corporation; hereinafter referred to as epoxy resin B5) instead of epoxy resin B1, a solution of epoxy resin B5, BB5 (hereinafter referred to as epoxy resin solution B5), was obtained in the same manner as in the above solution example B1.

[0093] <Example of dissolution of bisphenol-type epoxy resin (b1): B6> Except for using a bisphenol A novolac type epoxy resin (epoxy equivalent: 200-220 g / eq, jER157S70: manufactured by Mitsubishi Chemical Corporation; referred to as epoxy resin B6) instead of epoxy resin B1, a solution of epoxy resin B6, BB6 (hereinafter referred to as epoxy resin solution BB6), was obtained in the same manner as in the above solution example B1.

[0094] (Example 1) To the epoxy resin solution BB1, a first urethane-modified polyester resin (product name "Byron® UR-3210" manufactured by TOYOBO Corporation), a rubber-modified epoxy resin (b2) (product name "Adeka Resin EPR-1415-1" manufactured by Adeka Corporation), and an isocyanate-based crosslinking agent (C) (product name "Takenate D-110N" manufactured by Mitsui Takeda Chemical Co., Ltd.) were added in the proportions shown in Table 1A below to obtain the hot-melt adhesive layer composition according to Example 1. The urethane-modified polyester resin ("UR-3210") was added to the epoxy resin solution BB1 as follows. Specifically, the process was carried out by preparing a solution (hereinafter referred to as the first urethane-modified polyester resin solution) in which the first urethane-modified polyester resin was dissolved in a mixed solvent obtained by mixing toluene and methyl ethyl ketone in a mass ratio of toluene:methyl ethyl ketone = 8:2, so that the solution was at a concentration of 25% by mass, and then adding the first urethane-modified polyester resin solution to the epoxy resin solution BB1.

[0095] (Example 2) A hot-melt adhesive layer composition according to Example 2 was obtained in the same manner as in Example 1, except that epoxy resin solution BB2 was used instead of epoxy resin solution BB1.

[0096] (Example 3) A hot-melt adhesive layer composition according to Example 3 was obtained in the same manner as in Example 1, except that epoxy resin solution BB3 was used instead of epoxy resin solution BB1.

[0097] (Example 4) A hot-melt adhesive layer composition according to Example 4 was obtained in the same manner as in Example 1, except that a second urethane-modified polyester resin (product name "Byron® UR-4410" manufactured by TOYOBO Corporation) was used as the polyester resin (A) instead of the first urethane-modified polyester resin. The second urethane-modified polyester resin was added to the epoxy resin solution BB1 in the same manner as in Example 1, in the form of a second urethane-modified polyester resin solution.

[0098] (Example 5) A hot-melt adhesive layer composition according to Example 5 was obtained in the same manner as in Example 1, except that epoxy resin solution BB2 was used instead of epoxy resin solution BB1, and the second urethane-modified polyester resin was used instead of the first urethane-modified polyester resin. The second urethane-modified polyester resin was added to the epoxy resin solution BB2 in the same manner as in Example 4.

[0099] (Example 6) A hot-melt adhesive layer composition according to Example 6 was obtained in the same manner as in Example 1, except that epoxy resin solution BB3 was used instead of epoxy resin solution BB1, and the second urethane-modified polyester resin was used instead of the first urethane-modified polyester resin. The second urethane-modified polyester resin was added to the epoxy resin solution BB3 in the same manner as in Example 4.

[0100] (Example 7) A hot-melt adhesive layer composition according to Example 7 was obtained in the same manner as in Example 1, except that a first crystalline polyester resin (product name "GM-920" manufactured by TOYOBO Corporation) was used instead of the first urethane-modified polyester resin. The first crystalline polyester resin was added to the epoxy resin solution BB1 in the same manner as in Example 1, in the form of a first crystalline polyester resin solution.

[0101] (Example 8) A hot-melt adhesive layer composition according to Example 8 was obtained in the same manner as in Example 1, except that epoxy resin solution BB2 was used instead of epoxy resin solution BB1, and the first crystalline polyester resin was used instead of the first urethane-modified polyester resin. The first crystalline polyester resin was added to the epoxy resin solution BB2 in the same manner as in Example 7.

[0102] (Example 9) A hot-melt adhesive layer composition according to Example 9 was obtained in the same manner as in Example 1, except that epoxy resin solution BB3 was used instead of epoxy resin solution BB1, and the first crystalline polyester resin was used instead of the first urethane-modified polyester resin. The first crystalline polyester resin was added to the epoxy resin solution BB3 in the same manner as in Example 7.

[0103] (Example 10) A hot-melt adhesive layer composition according to Example 10 was obtained in the same manner as in Example 1, except that a second crystalline polyester resin (product name "GM-913" manufactured by TOYOBO Corporation) was used instead of the first urethane-modified polyester resin. The second crystalline polyester resin was added to the epoxy resin solution BB1 in the same manner as in Example 1, in the form of a second crystalline polyester resin solution.

[0104] (Example 11) A hot-melt adhesive layer composition according to Example 11 was obtained in the same manner as in Example 1, except that epoxy resin solution BB2 was used instead of epoxy resin solution BB1, and the second crystalline polyester resin was used instead of the first urethane-modified polyester resin. The second crystalline polyester resin was added to the epoxy resin solution BB2 in the same manner as in Example 10.

[0105] (Example 12) A hot-melt adhesive layer composition according to Example 12 was obtained in the same manner as in Example 1, except that epoxy resin solution BB3 was used instead of epoxy resin solution BB1, and the second crystalline polyester resin was used instead of the first urethane-modified polyester resin. The second crystalline polyester resin was added to the epoxy resin solution BB3 in the same manner as in Example 10.

[0106] (Example 13) A hot-melt adhesive layer composition according to Example 13 was obtained in the same manner as in Example 1, except that a third-crystalline polyester resin (product name "UE-9400" manufactured by Unitika Corporation) was used instead of the first urethane-modified polyester resin. The third crystalline polyester resin was added to the epoxy resin solution BB1 in the same manner as in Example 1, in the form of a third crystalline polyester resin solution.

[0107] (Example 14) A hot-melt adhesive layer composition according to Example 14 was obtained in the same manner as in Example 1, except that epoxy resin solution BB2 was used instead of epoxy resin solution BB1, and the third crystalline polyester resin was used instead of the first urethane-modified polyester resin. The third crystalline polyester resin was added to the epoxy resin solution BB2 in the same manner as in Example 13.

[0108] (Example 15) A hot-melt adhesive layer composition according to Example 15 was obtained in the same manner as in Example 1, except that epoxy resin solution BB3 was used instead of epoxy resin solution BB1, and the third crystalline polyester resin was used instead of the first urethane-modified polyester resin. The third crystalline polyester resin was added to the epoxy resin solution BB3 in the same manner as in Example 13.

[0109] (Example 16) A hot-melt adhesive layer composition according to Example 16 was obtained in the same manner as in Example 1, except that a fourth crystalline polyester resin (product name "UE-3400" manufactured by Unitika Corporation) was used instead of the first urethane-modified polyester resin. The fourth crystalline polyester resin was added to the epoxy resin solution BB1 in the same manner as in Example 1, in the form of a fourth crystalline polyester resin solution.

[0110] (Example 17) A hot-melt adhesive layer composition according to Example 17 was obtained in the same manner as in Example 1, except that epoxy resin solution BB2 was used instead of epoxy resin solution BB1, and the fourth crystalline polyester resin was used instead of the first urethane-modified polyester resin. The fourth crystalline polyester resin was added to the epoxy resin solution BB2 in the same manner as in Example 16.

[0111] (Example 18) A hot-melt adhesive layer composition according to Example 18 was obtained in the same manner as in Example 1, except that epoxy resin solution BB3 was used instead of epoxy resin solution BB1, and the fourth crystalline polyester resin was used instead of the first urethane-modified polyester resin. The fourth crystalline polyester resin was added to the epoxy resin solution BB3 in the same manner as in Example 16.

[0112] (Example 19) A hot-melt adhesive layer composition according to Example 19 was obtained in the same manner as in Example 1, except that a fifth crystalline polyester resin (product name "UE-3410" manufactured by Unitika Corporation) was used instead of the first urethane-modified polyester resin. The fifth crystalline polyester resin was added to the epoxy resin solution BB1 in the same manner as in Example 1, in the form of a fifth crystalline polyester resin solution.

[0113] (Example 20) A hot-melt adhesive layer composition according to Example 20 was obtained in the same manner as in Example 1, except that epoxy resin solution BB2 was used instead of epoxy resin solution BB1, and the fifth crystalline polyester resin was used instead of the first urethane-modified polyester resin. The fifth crystalline polyester resin was added to the epoxy resin solution BB2 in the same manner as in Example 19.

[0114] (Example 21) A hot-melt adhesive composition according to Example 21 was obtained in the same manner as in Example 1, except that epoxy resin solution BB3 was used instead of epoxy resin solution BB1, and the fifth crystalline polyester resin was used instead of the first urethane-modified polyester resin. The fifth crystalline polyester resin was added to the epoxy resin solution BB3 in the same manner as in Example 19.

[0115] [Table 1A]

[0116] (Comparative Example 1) A hot-melt adhesive layer composition according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the rubber-modified epoxy resin (b2) was not added.

[0117] (Comparative Example 2) A hot-melt adhesive layer composition according to Comparative Example 2 was obtained in the same manner as in Example 2, except that the rubber-modified epoxy resin (b2) was not added.

[0118] (Comparative Example 3) A hot-melt adhesive layer composition according to Comparative Example 3 was obtained in the same manner as in Example 3, except that the rubber-modified epoxy resin (b2) was not added.

[0119] (Comparative Example 4) A hot-melt adhesive layer composition according to Comparative Example 4 was obtained in the same manner as in Example 4, except that the rubber-modified epoxy resin (b2) was not added.

[0120] (Comparative Example 5) A hot-melt adhesive layer composition according to Comparative Example 5 was obtained in the same manner as in Example 5, except that the rubber-modified epoxy resin (b2) was not added.

[0121] (Comparative Example 6) A hot-melt adhesive layer composition according to Comparative Example 6 was obtained in the same manner as in Example 6, except that the rubber-modified epoxy resin (b2) was not added.

[0122] (Comparative Example 7) A hot-melt adhesive layer composition according to Comparative Example 7 was obtained in the same manner as in Example 7, except that the rubber-modified epoxy resin (b2) was not added.

[0123] (Comparative Example 8) A hot-melt adhesive layer composition according to Comparative Example 8 was obtained in the same manner as in Example 8, except that the rubber-modified epoxy resin (b2) was not added.

[0124] (Comparative Example 9) A hot-melt adhesive layer composition according to Comparative Example 9 was obtained in the same manner as in Example 9, except that the rubber-modified epoxy resin (b2) was not added.

[0125] (Comparative Example 10) A hot-melt adhesive layer composition according to Comparative Example 10 was obtained in the same manner as in Example 10, except that the rubber-modified epoxy resin (b2) was not added.

[0126] (Comparative Example 11) A hot-melt adhesive layer composition according to Comparative Example 11 was obtained in the same manner as in Example 11, except that the rubber-modified epoxy resin (b2) was not added.

[0127] (Comparative Example 12) A hot-melt adhesive layer composition according to Comparative Example 12 was obtained in the same manner as in Example 12, except that the rubber-modified epoxy resin (b2) was not added.

[0128] (Comparative Example 13) A hot-melt adhesive layer composition according to Comparative Example 13 was obtained in the same manner as in Example 13, except that the rubber-modified epoxy resin (b2) was not added.

[0129] (Comparative Example 14) A hot-melt adhesive layer composition according to Comparative Example 14 was obtained in the same manner as in Example 14, except that the rubber-modified epoxy resin (b2) was not added.

[0130] (Comparative Example 15) A hot-melt adhesive layer composition according to Comparative Example 15 was obtained in the same manner as in Example 15, except that the rubber-modified epoxy resin (b2) was not added.

[0131] (Comparative Example 16) A hot-melt adhesive layer composition according to Comparative Example 16 was obtained in the same manner as in Example 16, except that the rubber-modified epoxy resin (b2) was not added.

[0132] (Comparative Example 17) A hot-melt adhesive layer composition according to Comparative Example 17 was obtained in the same manner as in Example 17, except that the rubber-modified epoxy resin (b2) was not added.

[0133] (Comparative Example 18) A hot-melt adhesive layer composition according to Comparative Example 18 was obtained in the same manner as in Example 18, except that the rubber-modified epoxy resin (b2) was not added.

[0134] (Comparative Example 19) A hot-melt adhesive layer composition according to Comparative Example 19 was obtained in the same manner as in Example 19, except that the rubber-modified epoxy resin (b2) was not added.

[0135] (Comparative Example 20) A hot-melt adhesive layer composition according to Comparative Example 20 was obtained in the same manner as in Example 20, except that the rubber-modified epoxy resin (b2) was not added.

[0136] (Comparative Example 21) A hot-melt adhesive layer composition according to Comparative Example 21 was obtained in the same manner as in Example 21, except that the rubber-modified epoxy resin (b2) was not added.

[0137] The formulations of the hot-melt adhesive layer compositions for Comparative Examples 1 to 21 are shown in Table 1B below.

[0138] [Table 1B]

[0139] (Comparative Example 22) A hot-melt adhesive layer composition according to Comparative Example 22 was obtained in the same manner as in Example 1, except that epoxy resin solution BB4 was used instead of epoxy resin solution BB1.

[0140] (Comparative Example 23) A hot-melt adhesive layer composition according to Comparative Example 23 was obtained in the same manner as in Example 1, except that epoxy resin solution BB5 was used instead of epoxy resin solution BB1.

[0141] (Comparative Example 24) A hot-melt adhesive layer composition according to Comparative Example 24 was obtained in the same manner as in Example 1, except that epoxy resin solution BB6 was used instead of epoxy resin solution BB1.

[0142] (Comparative Example 25) A hot-melt adhesive layer composition according to Comparative Example 25 was obtained in the same manner as in Example 1, except that epoxy resin solution BB4 was used instead of epoxy resin solution BB1, and the second urethane-modified polyester resin was used instead of the first urethane-modified polyester resin.

[0143] (Comparative Example 26) A hot-melt adhesive layer composition according to Comparative Example 26 was obtained in the same manner as in Example 1, except that epoxy resin solution BB5 was used instead of epoxy resin solution BB1, and the second urethane-modified polyester resin was used instead of the first urethane-modified polyester resin.

[0144] (Comparative Example 27) A hot-melt adhesive layer composition according to Comparative Example 27 was obtained in the same manner as in Example 1, except that epoxy resin solution BB6 was used instead of epoxy resin solution BB1, and the second urethane-modified polyester resin was used instead of the first urethane-modified polyester resin.

[0145] (Comparative Example 28) A hot-melt adhesive layer composition according to Comparative Example 28 was obtained in the same manner as in Example 1, except that epoxy resin solution BB4 was used instead of epoxy resin solution BB1, and the first crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0146] (Comparative Example 29) A hot-melt adhesive layer composition according to Comparative Example 29 was obtained in the same manner as in Example 1, except that epoxy resin solution BB5 was used instead of epoxy resin solution BB1, and the first crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0147] (Comparative Example 30) A hot-melt adhesive layer composition for Comparative Example 30 was obtained in the same manner as in Example 1, except that epoxy resin solution BB6 was used instead of epoxy resin solution BB1, and the first crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0148] (Comparative Example 31) A hot-melt adhesive layer composition according to Comparative Example 31 was obtained in the same manner as in Example 1, except that epoxy resin solution BB4 was used instead of epoxy resin solution BB1, and the second crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0149] (Comparative Example 32) A hot-melt adhesive layer composition according to Comparative Example 32 was obtained in the same manner as in Example 1, except that epoxy resin solution BB5 was used instead of epoxy resin solution BB1, and the second crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0150] (Comparative Example 33) A hot-melt adhesive layer composition according to Comparative Example 33 was obtained in the same manner as in Example 1, except that epoxy resin solution BB6 was used instead of epoxy resin solution BB1, and the second crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0151] (Comparative Example 34) A hot-melt adhesive layer composition according to Comparative Example 34 was obtained in the same manner as in Example 1, except that epoxy resin solution BB4 was used instead of epoxy resin solution BB1, and the third crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0152] (Comparative Example 35) A hot-melt adhesive layer composition according to Comparative Example 35 was obtained in the same manner as in Example 1, except that epoxy resin solution BB5 was used instead of epoxy resin solution BB1, and the third crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0153] (Comparative Example 36) A hot-melt adhesive layer composition according to Comparative Example 36 was obtained in the same manner as in Example 1, except that epoxy resin solution BB6 was used instead of epoxy resin solution BB1, and the third crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0154] (Comparative Example 37) A hot-melt adhesive layer composition according to Comparative Example 37 was obtained in the same manner as in Example 1, except that epoxy resin solution BB4 was used instead of epoxy resin solution BB1, and the fourth crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0155] (Comparative Example 38) A hot-melt adhesive layer composition according to Comparative Example 38 was obtained in the same manner as in Example 1, except that epoxy resin solution BB5 was used instead of epoxy resin solution BB1, and the fourth crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0156] (Comparative Example 39) A hot-melt adhesive layer composition according to Comparative Example 39 was obtained in the same manner as in Example 1, except that epoxy resin solution BB6 was used instead of epoxy resin solution BB1, and the fourth crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0157] (Comparative Example 40) A hot-melt adhesive layer composition for Comparative Example 40 was obtained in the same manner as in Example 1, except that epoxy resin solution BB4 was used instead of epoxy resin solution BB1, and the fifth crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0158] (Comparative Example 41) A hot-melt adhesive layer composition for Comparative Example 41 was obtained in the same manner as in Example 1, except that epoxy resin solution BB5 was used instead of epoxy resin solution BB1, and the fifth crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0159] (Comparative Example 42) A hot-melt adhesive layer composition according to Comparative Example 42 was obtained in the same manner as in Example 1, except that the epoxy resin solution BB6 was used instead of the epoxy resin solution BB1, and the sixth crystalline polyester resin was used instead of the first urethane-modified polyester resin.

[0160] The formulations of the hot-melt adhesive layer compositions according to Comparative Examples 22 to 42 are shown in Table 1C below.

[0161]

Table 1C

[0162] Also, various physical properties of the various polyester resins (A) (the first urethane-modified polyester resin (UR-3210), the second urethane-modified polyester resin (UR-4410), the first crystalline polyester resin (GM-920), the second crystalline polyester resin (GM-913), the third crystalline polyester resin (UE-9400), the fourth crystalline polyester resin (UE-3400), and the fifth crystalline polyester resin (UE-3410)) incorporated in the hot-melt adhesive layer compositions according to each example are shown in Table 2 below.

[0163]

Table 2

[0164] [Coating of the hot-melt adhesive layer composition] The hot-melt adhesive layer compositions according to each example and each comparative example were diluted with methyl ethyl ketone (MEK) so that the solid content became 30% by mass. Next, a PEN film with a hot-melt adhesive layer was obtained for each example and each comparative example according to the following procedure. (1) Apply the diluted hot melt adhesive layer composition to the entire surface of one side of the PEN film (length: 210 mm, width: 150 mm, thickness: 100 μm, Teonex: manufactured by Toyobo Film Solutions Co., Ltd.). The coating is carried out so that the thickness of the dried hot-melt adhesive layer composition is 20 μm. (2) The PEN film coated with the diluted hot melt adhesive layer composition is dried at 100°C for 1 minute to obtain a PEN film having a dried hot melt adhesive layer composition. (3) The PEN film having the dried hot melt adhesive layer composition is left in an oven at 40°C for 48 hours to allow the curing reaction (crosslinking reaction) to proceed. This gives rise to a PEN film with a hot melt adhesive layer.

[0165] (Retention rate of the thickness of the hot melt adhesive layer) For each example of a PEN film with a hot-melt adhesive layer, and for each comparative example of a PEN film with a hot-melt adhesive layer, the retention rate of the thickness of the hot-melt adhesive layer after adhesion to the solid electrolyte membrane of a polymer electrolyte fuel cell was evaluated. In this evaluation, the substrate used was a membrane / electrode assembly (MEA) 20 of a polymer electrolyte fuel cell, as shown in Figure 2. The adhesion of the PEN film with the hot-melt adhesive layer according to each example and comparative example to the film / electrode assembly (MEA) 20, which is the adherend, was carried out according to the following procedure. The explanation of the composition of the membrane / electrode assembly (MEA) 20 will be omitted. Bonding procedure (1) For each example and each comparative example, prepare two PEN films with a hot melt adhesive layer. In each example and comparative example, the PEN film with the hot-melt adhesive layer is annular in shape, and when superimposed on the film / electrode assembly (MEA) 20, its outer edge is outside the film / electrode assembly (MEA) 20, while its inner edge is contained within the positive electrode side catalyst layer exposure region 202a1 and the negative electrode side catalyst layer exposure region 203a1. In other words, in each example and each comparative example, the hollow portion of the PEN film with the hot melt adhesive layer has a shape that is slightly larger than the positive electrode gas diffusion layer 202b and the negative electrode gas diffusion layer 203b. (2) The PEN film with one hot melt adhesive layer is brought into contact with the entire area of ​​the positive electrode side electrolyte membrane exposed region 201a and a part of the positive electrode side catalyst layer exposed region 202a1. Furthermore, another PEN film with a hot melt adhesive layer is brought into contact with the entire negative electrode side electrolyte membrane exposed region 201b and a portion of the negative electrode side catalyst layer exposed region 203a1. This results in a test specimen in which two PEN films with hot-melt adhesive layers are bonded to a membrane / electrode assembly (MEA) 20. (3) After exposing the specimens to a 95°C atmosphere, a pair of metal gaskets are brought into contact with the central portion of the exposed surface of one PEN film with a hot melt adhesive layer and the other PEN film with a hot melt adhesive layer. Subsequently, the specimen is held for 500 hours under a 95°C atmosphere while a load of 7.5 MPa is applied to it via the pair of metal gaskets. This allows one PEN film with a hot-melt adhesive layer and another PEN film with a hot-melt adhesive layer to be hot-melt bonded to the film / electrode assembly (MEA) 20. The retention rate of the hot melt adhesive layer thickness was evaluated according to the following criteria. standard Excellent: The thickness of the hot melt adhesive layer after bonding (center portion) is 80% or more of the thickness of the hot melt adhesive layer before bonding (center portion). Unacceptable: The thickness of the hot melt adhesive layer after bonding (center portion) is less than 80% of the thickness of the hot melt adhesive layer before bonding (center portion). The results of investigating the thickness retention rate of the hot melt adhesive layer are shown in Table 3 below.

[0166] (Embedding properties due to hot melt adhesive layer) The embedding properties of the PEN film with a hot-melt adhesive layer according to each example, and the PEN film with a hot-melt adhesive layer according to each comparative example, after being bonded to the solid electrolyte membrane of a polymer electrolyte fuel cell were investigated. The embedding properties of the hot-melt adhesive layer were evaluated by adhering two PEN films with hot-melt adhesive layers from each example and comparative example to a film / electrode assembly (MEA) 20 according to the procedure described above, and then observing the adhesion state of the two PEN films with hot-melt adhesive layers using a laser microscope. The observation magnification of the laser microscope was set to 400x. Furthermore, the embedding properties of the hot-melt adhesive layer were evaluated according to the following criteria. standard Excellent: The distance from the outer edge of the solid electrolyte membrane to the hot melt adhesive layer is 200 μm or less. Unacceptable: The distance from the outer edge of the solid electrolyte membrane to the hot melt adhesive layer exceeds 200 μm. The results of the investigation into embedding properties using a hot-melt adhesive layer are shown in Table 3 below.

[0167] [Table 3]

[0168] Table 3 shows that in each example, the PEN film with a hot-melt adhesive layer received an "excellent" rating for both thickness retention and embedding ability. In contrast, the PEN films with hot-melt adhesive layers in each comparative example were evaluated as "unacceptable" in terms of both thickness retention and embedding ability.

[0169] Next, hot-melt adhesive layer compositions for Test Examples 1 to 20 were prepared as shown below.

[0170] [Test Example 1] Using the same formulation as in Example 10, a hot-melt adhesive layer composition according to Test Example 1 was obtained.

[0171] [Test Example 2] A hot-melt adhesive layer composition for Test Example 2 was obtained in the same manner as in Test Example 1, except that the amount of epoxy resin B1 was changed from 25 parts by mass to 30 parts by mass.

[0172] [Test Example 3] A hot-melt adhesive layer composition for Test Example 3 was obtained in the same manner as in Test Example 1, except that the amount of epoxy resin B1 was changed from 25 parts by mass to 35 parts by mass.

[0173] [Test Example 4] Using the same formulation as in Example 11, a hot-melt adhesive layer composition according to Test Example 4 was obtained.

[0174] [Test Example 5] A hot-melt adhesive layer composition for Test Example 5 was obtained in the same manner as in Test Example 4, except that the amount of epoxy resin B2 was changed from 25 parts by mass to 30 parts by mass.

[0175] [Test Example 6] A hot-melt adhesive layer composition for Test Example 6 was obtained in the same manner as in Test Example 4, except that the amount of epoxy resin B2 was changed from 25 parts by mass to 35 parts by mass.

[0176] [Test Example 7] A hot-melt adhesive layer composition for Test Example 7 was obtained in the same manner as in Comparative Example 10, except that the amount of epoxy resin B1 was changed from 25 parts by mass to 20 parts by mass.

[0177] [Test Example 8] A composition for a hot-melt adhesive layer according to Test Example 8 was obtained in the same manner as in Comparative Example 11, except that the compounding amount of epoxy resin B2 was changed from 25 parts by mass to 20 parts by mass.

[0178] [Test Example 9] A composition for a hot-melt adhesive layer according to Test Example 9 was obtained with the same formulation as in Comparative Example 10.

[0179] [Test Example 10] A composition for a hot-melt adhesive layer according to Test Example 10 was obtained with the same formulation as in Comparative Example 11.

[0180] [Test Example 11] A composition for a hot-melt adhesive layer according to Test Example 11 was obtained with the same formulation as in Test Example 1, except that epoxy resin B1 was not added.

[0181] [Test Example 12] As shown in Table 4.

[0182] [Test Example 13] A composition for a hot-melt adhesive layer according to Test Example 13 was obtained with the same formulation as in Test Example 1, except that the second crystalline polyester resin was replaced with the sixth crystalline polyester resin (trade name "GM-350" manufactured by TOYOBO Co., Ltd.).

[0183] [Test Example 14] A composition for a hot-melt adhesive layer according to Test Example 14 was obtained with the same formulation as in Test Example 4, except that the second crystalline polyester resin was replaced with the sixth crystalline polyester resin.

[0184] [Test Example 15] A composition for a hot-melt adhesive layer according to Test Example 15 was obtained with the same formulation as in Test Example 1, except that the second crystalline polyester resin was replaced with the seventh crystalline polyester resin (trade name "GM-900" manufactured by TOYOBO Co., Ltd.).

[0185] [Test Example 16] A hot-melt adhesive layer composition according to Test Example 16 was obtained using the same formulation as in Test Example 4, except that the seventh crystalline polyester resin was used instead of the second crystalline polyester resin.

[0186] [Test Example 17] A hot-melt adhesive layer composition for Test Example 17 was obtained using the same formulation as in Test Example 1, except that the amount of isocyanate-based crosslinking agent (C) (Takenate D-110N) was changed from 10 parts by mass to 15 parts by mass.

[0187] [Test Example 18] A hot-melt adhesive layer composition for Test Example 18 was obtained using the same formulation as in Test Example 4, except that the amount of isocyanate-based crosslinking agent (C) (Takenate D-110N) was changed from 10 parts by mass to 15 parts by mass.

[0188] [Test Example 19] A hot-melt adhesive layer composition for Test Example 19 was obtained using the same formulation as in Test Example 1, except that the amount of isocyanate-based crosslinking agent (C) (Takenate D-110N) was changed from 10 parts by mass to 5 parts by mass.

[0189] [Test Example 20] A hot-melt adhesive layer composition for Test Example 20 was obtained using the same formulation as in Test Example 4, except that the amount of isocyanate-based crosslinking agent (C) (Takenate D-110N) was changed from 10 parts by mass to 5 parts by mass.

[0190] The formulations of the hot-melt adhesive layer compositions for Test Examples 1 to 20 are shown in Table 4 below.

[0191] [Table 4]

[0192] Furthermore, the various physical properties of the sixth crystalline polyester (GM-350) and the seventh crystalline polyester resin (GM-900) are shown in Table 5 below.

[0193] [Table 5]

[0194] [Coating of hot melt adhesive layer compositions] Except for using the hot-melt adhesive layer composition for each test example, a PEN film with a hot-melt adhesive layer for each example was obtained in the same manner as for the PEN film with a hot-melt adhesive layer for each example and each comparative example.

[0195] [Preparation of the first adhesive sheet] Two PEN films with a hot-melt adhesive layer were prepared for each test example, and the two PEN films with hot-melt adhesive layers were placed on top of each other so that the hot-melt adhesive layers were in contact with each other. Using a laminator adjusted to 140°C, two PEN films with hot-melt adhesive layers for each test example were heat-pressed together to create the first adhesive sheet for each test example.

[0196] [Preparation of the second adhesive sheet] The PEN film with the hot-melt adhesive layer and the perfluorocarbon sulfonic acid resin sheet were superimposed on each test example so that the exposed surface of the hot-melt adhesive layer of the PEN film with the hot-melt adhesive layer of each test example was in contact with one side of the perfluorocarbon sulfonic acid resin sheet (tetrafluoroethylene / perfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether] copolymer film (manufactured by DuPont, trade name "NAFIONN-115")) (same shape as the film with the hot-melt adhesive layer). Using a laminator adjusted to 140°C, the PEN film with the hot-melt adhesive layer for each test example and the perfluorocarbon sulfonic acid resin sheet were heat-pressed together to create a second adhesive sheet for each test example.

[0197] [Hot water resistance 1] For the first adhesive sheet of each test example, a test piece with a size of 10 mm in width × 80 mm in length was cut out from the first adhesive sheet of each test example, and the test piece was immersed in hot water at 95°C for 1000 hours. After cooling to room temperature, the heat resistance of each test piece was evaluated according to the following criteria. · Excellent: No peeling is observed after immersion. · Poor: Peeling is observed after immersion.

[0198] [Acid resistance 1] For the first adhesive sheet of each test example, a test piece with a size of 10 mm in width × 80 mm in length was cut out from the first adhesive sheet of each test example, and the test piece was immersed in dilute sulfuric acid with a pH of 2 at 95°C for 1000 hours. After cooling to room temperature, the acid resistance of each test piece was evaluated according to the following criteria. · Excellent: No peeling is observed after immersion. · Poor: Peeling is observed after immersion.

[0199] [Alcohol resistance 1] For the first adhesive sheet of each test example, a test piece with a size of 10 mm in width × 80 mm in length was cut out from the first adhesive sheet of each test example, and the test piece was immersed in a water-ethylene glycol mixed solution (the mixing ratio of ethylene glycol is 50% by volume) at 95°C for 1000 hours. After cooling to room temperature, the alcohol resistance of each test piece was evaluated according to the following criteria. · Excellent: No peeling is observed after immersion. · Poor: Peeling is observed after immersion.

[0200] [Heat resistance 2] For the second adhesive sheet of each test example, a test piece with a size of 10 mm in width × 80 mm in length was cut out from the second adhesive sheet of each test example, and the test piece was immersed in hot water at 95°C for 1000 hours. After cooling to room temperature, the heat resistance of each test piece was evaluated according to the following criteria. · Excellent: No peeling is observed after immersion. · Poor: Peeling is observed after immersion.

[0201] [Acid resistance 2] For each test example's second adhesive sheet, a test specimen measuring 10 mm wide x 80 mm long was cut from the second adhesive sheet of each test example. This test specimen was immersed in dilute sulfuric acid at 95°C and pH 2 for 1000 hours. After cooling to room temperature, the acid resistance of each test specimen was evaluated according to the following criteria. • Excellent: No peeling was observed after immersion. • Not suitable: Peeling is observed after immersion.

[0202] [Alcohol resistance 2] For each test example's second adhesive sheet, a test specimen measuring 10 mm wide x 80 mm long was cut from the second adhesive sheet of each test example. This test specimen was immersed in a water-ethylene glycol mixed solution (ethylene glycol ratio: 50% by volume) at 95°C for 1000 hours. After cooling to room temperature, the alcohol resistance of each test specimen was evaluated according to the following criteria. • Excellent: No peeling was observed after immersion. • Not suitable: Peeling is observed after immersion.

[0203] Table 5 below shows the results of evaluating the first adhesive sheet for each test example for hot water resistance 1, acid resistance 1, and alcohol resistance 1. Table 6 below shows the results of evaluating the second adhesive sheet for each test example for hot water resistance 2, acid resistance 2, and alcohol resistance 2.

[0204] [Table 6]

[0205] Table 6 above shows that in Test Examples 1-6, all evaluation items for both the first and second adhesive sheets were rated "Excellent," meaning that no peeling was observed. In contrast, in test examples 7-20, all evaluation items for both the first and second adhesive sheets were "unacceptable," meaning that peeling was observed. [Explanation of Symbols]

[0206] 10 Hot melt adhesive sheet, 20 Membrane / electrode assembly (MEA), 201 Solid electrolyte membrane, 202 Positive electrode, 203 Negative electrode, 10a Substrate, 10b Adhesive layer, 201a Positive electrode side electrolyte membrane exposed region, 201b Negative electrode side electrolyte membrane exposed region, 202a Positive electrode catalyst layer, 202b Positive electrode gas diffusion layer, 203a Negative electrode catalyst layer, 203b Negative electrode gas diffusion layer, 202a1 Positive electrode side catalyst layer exposed region, 203a1 Negative electrode side catalyst layer exposed region, L1 1st boundary line, L2 2nd boundary line, L3 3rd boundary line, L4 4th boundary line.

Claims

1. A hot-melt adhesive sheet in which an adhesive layer formed with a hot-melt adhesive is laminated on at least one surface of a substrate, The hot melt adhesive comprises a crosslinked product of an adhesive composition containing a crosslinking agent, and the adhesive composition contains a polyester resin, an epoxy resin, and an isocyanate-based crosslinking agent. The epoxy resin includes a bisphenol-type epoxy resin and a rubber-modified epoxy resin. The polyester resin includes a urethane-modified polyester resin or a crystalline polyester resin. The bisphenol-type epoxy resin has an epoxy equivalent of 450 g / eq or more and 1000 g / eq or less. The material contains 10 to 50 parts by mass of the bisphenol-type epoxy resin and 3 to 20 parts by mass of the rubber-modified epoxy resin per 100 parts by mass of the polyester resin. The polyester resin is contained in an amount of 3 to 20 parts by mass of the isocyanate-based crosslinking agent per 100 parts by mass of the polyester resin. Hot melt adhesive sheet.

2. The polyester resin includes the crystalline polyester resin having a softening point of 120°C or higher. The hot melt adhesive sheet according to claim 1.

3. The bisphenol-type epoxy resin includes a bisphenol A-type epoxy resin. The hot melt adhesive sheet according to claim 1 or 2.

4. The rubber-modified epoxy resin is an NBR-modified epoxy resin. The hot melt adhesive sheet according to claim 1 or 2.

5. Used by adhering it to the solid electrolyte membrane of a polymer electrolyte fuel cell. The hot melt adhesive sheet according to claim 1 or 2.

Images