Hot melt adhesive sheet

Abstract

To provide a hot melt adhesive sheet having an adhesive layer which is excellent in adhesion to an adherend, and is excellent in hot water resistance, acid resistance and alcohol resistance.SOLUTION: There is provided a hot melt adhesive sheet in which an adhesive layer formed of a hot melt adhesive is stacked on at least one surface of a base material, wherein the hot melt adhesive contains a crosslinked product of an adhesive composition containing a crosslinking agent and contains a polyurethane resin, an epoxy resin and an isocyanate-based crosslinking agent, the polyurethane resin contains a polyester urethane resin having an aromatic polyester skeleton, and the epoxy resin contains a non-modified epoxy resin having an epoxy equivalent of 300 g / eq or more and 1,500 g / eq or less.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, as adhesives for various plastics, polyurethane-based adhesives have been widely used because of their adhesive stability in a low temperature range (for example, -10°C to 15°C), and their adhesiveness, flexibility, processability, and ease of various molecular designs in a normal temperature range (25 ± 10°C). As the polyurethane-based adhesive, there are those containing polyester polyol or acrylic polyol as the main agent and polyisocyanate as the crosslinking agent, and generating urethane bonds by allowing a crosslinking reaction to proceed between the main agent and the crosslinking agent for use; and those containing a polyurethane (so-called polyurethane prepolymer) having a certain chain length as the main agent and an isocyanate-based crosslinking agent as the crosslinking agent, and being used by allowing a crosslinking reaction to proceed between the main agent and the crosslinking agent for curing.

[0003] In addition, as a two-component adhesive containing a polyurethane resin as the main agent, an epoxy resin, and an isocyanate-based crosslinking agent, Patent Document 1 below describes an adhesive having excellent moisture and heat resistance. In recent years, from the viewpoint of excellent handling properties compared to the liquid adhesives described in Patent Document 1 below, the opportunity to use hot melt adhesives for bonding members has been increasing. The hot melt adhesive is often used in the form of a hot melt adhesive sheet particularly from the viewpoint of excellent handling properties. The hot melt adhesive sheet usually includes a base material layer formed of a polymer sheet and an adhesive layer laminated on the base material layer and formed of the hot melt adhesive.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] International Publication No. 2013 / 157604 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Improving moisture and heat resistance (resistance to hot water) is required not only for two-part adhesives like those described in Reference 1, but also for the adhesive layer of hot-melt adhesive sheets.

[0006] Furthermore, while there is a need to improve the acid resistance and alcohol resistance of the adhesive layer in hot melt adhesive sheets, such requirements are not being met. Furthermore, the adhesive layer of the hot-melt adhesive sheet is required to ensure sufficient adhesion to the substrate through heat-press bonding.

[0007] This invention has been made in view of the problems of the prior art, and its objective is to provide a hot-melt adhesive sheet having an adhesive layer that exhibits excellent adhesion to the adherend, as well as excellent resistance to hot water, acid, and alcohol. [Means for solving the problem]

[0008] 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 also contains a polyurethane resin, an epoxy resin, and an isocyanate-based crosslinking agent. The polyurethane resin contains a polyester urethane resin having an aromatic polyester skeleton. The epoxy resin contains an unmodified epoxy resin with an epoxy equivalent weight of 300 g / eq or more and 1500 g / eq or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a hot-melt adhesive sheet having an adhesive layer that exhibits excellent adhesion to the adherend and excellent resistance to hot water, acid, and alcohol. [Brief explanation of the drawing]

[0010] [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]

[0011] 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."

[0012] 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 Figure 1, the adhesive layer 10b is laminated only on one side of the substrate 10a, but the adhesive layer 10b may also be laminated on the other side of the substrate 10a. In other words, the hot melt adhesive sheet 10 may be a hot melt adhesive sheet in which adhesive layers 10b are laminated on both sides of a base material 10a.

[0013] In the hot melt adhesive sheet 10 according to this embodiment, the hot melt adhesive includes a crosslinked product of an adhesive composition containing a crosslinking agent, and also contains a polyurethane resin, an epoxy resin, and an isocyanate-based crosslinking agent. In the hot-melt adhesive sheet 10 according to this embodiment, the polyurethane resin contains a polyester urethane resin having an aromatic polyester skeleton. In the hot-melt adhesive sheet 10 according to this embodiment, the epoxy resin contains a non-modified epoxy resin having an epoxy equivalent of 300 g / eq or more and 1500 g / eq or less. Hereinafter, the polyurethane resin is referred to as polyurethane 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).

[0014] (Polyurethane resin (A)) The polyurethane resin (A) is obtained by urethane-bonding a reaction component containing a polyol component (a) having two or more hydroxyl groups in one molecule and a polyisocyanate component (b) having two or more isocyanate groups in one molecule.

[0015] As described above, in the hot-melt adhesive sheet 10 according to this embodiment, the polyurethane resin (A) contains a polyester polyurethane resin having an aromatic polyester skeleton.

[0016] In this specification, the polyester polyurethane resin means a product obtained by reacting a hydroxyl group-containing polyester having a hydroxyl group (corresponding to the above polyol component (a)) with a polyisocyanate component (b). That is, in this specification, the polyester urethane resin is a urethane bond product of a hydroxyl group-containing polyester having a hydroxyl group and a polyisocyanate component (b).

[0017] As the hydroxyl group-containing polyester, a polyester obtained by a condensation reaction of a polyvalent carboxylic acid and a polyvalent alcohol can be used.

[0018] Examples of the aforementioned polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, itaconic acid, fumaric acid, tetrahydrophthalic acid, hexahydrophthalic acid, adipic acid, sebacic acid, azelaic acid, trimellitic acid, methylcyclohexentricarboxylic acid, or pyromellitic acid, dimer acids derived from unsaturated fatty acids, and their acid anhydrides.

[0019] Examples of the aforementioned polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, pentamethylene glycol, hexamethylene glycol, heptamethylene glycol, and octamethylene glycol. Furthermore, the polyhydric alcohol may also be a polyhydric alcohol having a carboxyl group (hereinafter also referred to as a carboxyl group-containing polyhydric alcohol). Examples of polyhydric alcohols containing carboxyl groups include dimethylolpropionic acid, dimethylolbutanoic acid, and diphenolic acid. Furthermore, the polyhydric alcohol may be modified with a caprolactone compound such as ε-caprolactam.

[0020] Examples of the polyisocyanate component (b) to be reacted with the hydroxyl group-containing polyester include aliphatic isocyanate compounds, alicyclic isocyanate compounds, and aromatic isocyanate compounds. Examples of the aliphatic isocyanate compounds include hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, trimethylhexamethylene diisocyanate, and xylylene diisocyanate. Examples of the aforementioned alicyclic isocyanate compounds include isophorone diisocyanate, methylcyclohexane diisocyanate, lysine diisocyanate, and cyclohexane-1,4-diisocyanate. Examples of the aforementioned aromatic isocyanate compounds include tolylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyle diisocyanate, tetraalkyldiphenylmethane isocyanate, dialkyldiphenylmethane diisocyanate, 1,3'-phenylenediisocyanate, and 1,4'-phenylenediisocyanate.

[0021] In this embodiment, the hot-melt adhesive sheet 10 is a polyester urethane resin having an aromatic polyester skeleton. The aromatic polyester skeleton can be provided in the polyester urethane resin by using phthalic acid, isophthalic acid, terephthalic acid, or the like as the polycarboxylic acid when obtaining the hydroxyl group-containing polyester. As described above, if the polyester urethane resin has an aromatic polyester skeleton, the polyester urethane resin will exhibit high hydrophobicity, and the adhesive layer 10b containing such a polyester urethane resin will have improved hydrophobicity. As a result, the adhesive layer 10b has excellent resistance to hot water, acid, and alcohol.

[0022] Examples of commercially available polyester polyurethane resins include the Byron® UR series manufactured by Toyobo Co., Ltd. Among the Byron® UR series manufactured by Toyobo Co., Ltd., it is preferable to use Byron® UR-3200 and UR-3210 as commercially available products. Byron® UR-3210 is a toluene-free version of Byron® UR-3200. Therefore, considering the need to minimize the amount of volatile organic compounds (VOCs) generated, it is preferable to use Byron® UR-3210 as a commercially available product.

[0023] The polyester urethane resin having an aromatic polyester skeleton is more preferably characterized by a glass transition temperature Tg of 10°C or less. Because the polyester urethane resin having an aromatic polyester skeleton has the above-described structure, when it is incorporated into the adhesive layer 10b, the adhesive layer 10b can exhibit good adhesion to an adherend such as a substrate 10a. Examples of the base material 10a include PEN (polyethylene naphthalate) film, perfluorocarbon sulfonic acid resin sheet (film), and PPS (polyphenylene sulfide) film. Furthermore, because the polyester urethane resin has the above-described structure, the adhesive layer 10b has excellent toughness. As a result, even when an external force is applied to the adhesive layer 10b, the adhesive layer 10b becomes less likely to break.

[0024] The glass transition temperature Tg is more preferably 5°C or lower, even more preferably 0°C or lower, and even more preferably -2°C or lower. Furthermore, the glass transition temperature is preferably -30°C or higher, more preferably -20°C or higher, even more preferably -10°C or higher, and even more preferably -5°C or higher. Furthermore, Byron® UR-3200 and UR-3210 have an aromatic polyester skeleton and a glass transition temperature (Tg) of 10°C or lower.

[0025] The glass transition temperature (Tg) can be measured, for example, using a DSC instrument. More specifically, the glass transition temperature Tg can be determined from the DSC curve obtained when the sample (polyester urethane resin) is heated at a rate of 5°C / min while flowing nitrogen gas from a temperature 30K or more lower than the expected glass transition temperature Tg to a temperature 30K or more higher than the expected glass transition temperature Tg. The glass transition temperature (Tg) can be determined based on the method described in JIS K7121:1987, "Method for Measuring the Transition Temperature of Plastics."

[0026] The polyurethane resin (A) may also contain polyurethane resins other than the polyester urethane resin. As the polyurethane resin other than the polyester urethane resin mentioned above, various known types can be used, but it is preferable that the polyol component (a) contains a constituent unit derived from a polyol (a1) with a skeleton having 8 or more carbon atoms.

[0027] In addition to the polyester urethane resin mentioned above, it is preferable that the polyurethane resin contains a hydroxyl group-containing polyurethane resin, which has hydroxyl groups, in order to react with the isocyanate-based crosslinking agent (C). Furthermore, it is preferable that the hydroxyl group-containing polyurethane resin has hydroxyl groups at its terminal ends. The hydroxyl value of the hydroxyl group-containing polyurethane resin is preferably 0.1 mg KOH / g or more and 20 mg KOH / g or less, and more preferably 1 mg KOH / g or more and 15 mg KOH / g or less.

[0028] In polyurethane resins other than the polyester urethane resin described above, it is more preferable that the polyol component (a) contains a general polyol (a2) together with a polyol (a1) having 8 or more carbon atoms in its skeleton. In the following, a general polyol (a2) may simply be referred to as polyol (a2). In this specification, a polyol (a1) having eight or more carbon atoms in its skeleton means a polyol in which eight or more carbon atoms are bonded between hydroxyl groups, and the eight or more carbon atoms between hydroxyl groups may be bonded via heteroatoms, and adjacent carbon atoms may be bonded together in a saturated or unsaturated bond. The polyol (a1) having 8 or more carbon atoms in its skeleton is preferably a polycarbonate polyol. Furthermore, in polyols (a1) having 8 or more carbon atoms in the skeleton, it is preferable that the number of heteroatoms in the portion containing 8 or more carbon atoms is 2 or less. Furthermore, for polyols (a1) having 8 or more carbon atoms in their skeleton, it is preferable that the molecule contains residues obtained by removing multiple hydrogen atoms from saturated or unsaturated hydrocarbons having 8 or more carbon atoms. Furthermore, it is preferable that the polyol (a1) having 8 or more carbon atoms in its skeleton has an alkylene group having 6 or more carbon atoms.

[0029] Examples of polyols (a1) having 8 or more carbon atoms in the skeleton include polyester polyols obtained by condensation polymerization of monomers containing dicarboxylic acids (such as sebaciic acid (10 carbon atoms), azelaic acid (9 carbon atoms), isophthalic acid (8 carbon atoms), and terephthalic acid (8 carbon atoms)) and glycols (such as 1,9-nonanediol (9 carbon atoms) and 1,4-bishydroxymethylcyclohexane (8 carbon atoms)).

[0030] Furthermore, examples of polyols (a1) having 8 or more carbon atoms in the skeleton include polycarbonate polyols such as poly(1,4-cyclohexanedimethylene carbonate)diol (8 carbon atoms), polyoctamethylene carbonatediol (8 carbon atoms), polynonameethylene carbonatediol (9 carbon atoms), and polydecamethylene carbonatediol (10 carbon atoms), as well as random / block copolymers of monomers containing these.

[0031] Furthermore, polyols (a1) having eight or more carbon atoms in their skeleton can also be found in polyols derived from dimer acids. The aforementioned dimer acid is a 36-carbon dicarboxylic acid obtained by dimerizing an 18-carbon unsaturated fatty acid such as oleic acid or linoleic acid, and is a plant-derived fatty acid. A typical structure of the aforementioned dimer acid is represented by the following formula (1). The dimer acid may also contain a trimer acid. Trimer acid is a tricarboxylic acid with 54 carbon atoms obtained by trimerizing the above-mentioned unsaturated fatty acid with 18 carbon atoms. It is also produced as a by-product during the manufacture of dimer acid, and commercially available dimer acid usually contains trimer acid.

[0032] [ka]

[0033] Dimer ols, which are polyols derived from dimer acids, are 36-carbon polyols obtained by reducing the carboxyl group of the above-mentioned dimer acid to a hydroxyl group. The polyol may or may not have unsaturated bonds in its molecule. Specific examples of such dimer polyols include dimer ols. Similarly, trimer triols are polyols obtained by reducing the carboxyl group of a trimer acid to a hydroxyl group. Commercially available dimer triols typically contain trimer triol. Therefore, polyols derived from dimer acids, dimer polyols, and dimer diols may contain trimer triols.

[0034] Furthermore, polyolefin polyols can also be cited as polyols (a1) having 8 or more carbon atoms in their skeleton. Polyolefin polyols are polymers formed by the polymerization of one or more polyolefins, each having multiple hydroxyl groups. Specific examples of such polyolefin polyols include polyethylene butylenediol, polybutadienediol, and hydrogenated polybutadienediol. These are polyols with extremely long carbon chains because the carbon chains polymerize with each other.

[0035] By including a polyurethane resin (A) in the adhesive layer 10b of the hot melt adhesive sheet 10 that has a polyurethane resin (A) having structural units derived from a polyol (a1) with 8 or more carbon atoms in its skeleton (more specifically, a polyurethane resin other than the polyester urethane resin), the hydrophobicity of the adhesive layer 10b can be improved compared to one that includes a polyurethane resin that does not have structural units derived from a polyol (a1) with 8 or more carbon atoms in its skeleton. As a result, such an adhesive layer 10b will have excellent resistance to hot water, acid, and alcohol.

[0036] As the polyol (a2), conventionally known polyols used in the synthesis of polyurethane resins can be used. Specific examples of the polyol (a2) include polyester polyols, polyether polyols, polycarbonate polyols, and other polyols.

[0037] Examples of polyester polyols include those obtained by condensation polymerization of aliphatic dicarboxylic acids (e.g., succinic acid, adipic acid, glutaric acid, etc.) and low molecular weight glycols (e.g., ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentyl glycol, etc.). The polyester polyol described above may be copolymerized with a dicarboxylic acid or glycol having 8 or more carbon atoms.

[0038] Specific examples of such polyester polyols include polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene / butylene adipate diol, polyneopentyl / hexyl adipate diol, poly-3-methylpentane adipate diol, polybutylene isophthalate diol, polycaprolactone diol, and poly-3-methylvalerolactone diol. Polyester polyols have superior heat resistance compared to polyether polyols. Therefore, polyester polyols are more advantageous than polyether polyols in that they provide the resulting adhesive layer 10b with excellent heat resistance.

[0039] Specific examples of polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and random / block copolymers thereof. Polyether polyols have superior hydrolysis resistance compared to polyester polyols. Therefore, polyether polyols are more advantageous than polyester polyols in that the resulting adhesive layer 10b has excellent hydrolysis resistance.

[0040] Specific examples of polycarbonate polyols include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, and random / block copolymers thereof. The polycarbonate polyol described above may also be copolymerized with a diol having 8 or more carbon atoms. By using various polycarbonate diols as described above as polycarbonate polyols, it is possible to provide polyurethane resins other than the polyester urethane resin with the constituent units of polycarbonate diols. Here, polycarbonate polyol exhibits excellent hydrolysis resistance and heat resistance. Therefore, it is advantageous in that the resulting adhesive layer 10b has excellent hydrolysis resistance and heat resistance. Among polycarbonate polyols, polyhexamethylene carbonate is preferred from the standpoint of cost and ease of obtaining the material.

[0041] Other specific examples of polyols include acrylic polyols, epoxy polyols, polyether ester polyols, siloxane-modified polyols, α,ω-polymethyl methacrylate diols, α,ω-polybutyl methacrylate diols, and siloxane-modified polyols.

[0042] To summarize the above explanation regarding the polyol (a2), it is preferable to use a polycarbonate polyol with excellent hydrolysis resistance and heat resistance, from the viewpoint of ensuring that the adhesive layer 10b of the resulting hot melt adhesive sheet 10 has excellent heat and water resistance. Furthermore, from the viewpoint of cost and ease of obtaining materials, it is particularly preferable to use polyhexamethylene carbonate among the polycarbonate polyols mentioned above.

[0043] The number-average molecular weight Mn of the polyol (a1) and polyol (a2) (determined by the terminal functional group determination method) is not particularly limited, but is preferably 500 or more and 6000 or less. Because the number-average molecular weight Mn of the polyol (a1) and the polyol (a2) are within the above-mentioned numerical range, cohesive force due to urethane bonding is more easily expressed in the adhesive layer 10b of the hot-melt adhesive sheet 10 of this embodiment. As a result, the adhesive of this embodiment has high mechanical properties. Furthermore, if the number-average molecular weight Mn of a crystalline polyol is too large, a whitening phenomenon may occur in the adhesive layer 10b when it is formed into a film-like structure. Therefore, when using crystalline polyols individually as polyol (a1) and polyol (a2), it is preferable to use polyols with a number average molecular weight Mn of 3,000 or less. Furthermore, the polyol (a1) and the polyol (a2) may each be used individually or in combination of two or more types.

[0044] Preferably, the polyol (a1) is blended in a proportion of 10% by mass or more and 60% by mass or less when the polyol component (a) is considered to be 100% by mass. By incorporating the polyol (a1) in a proportion of 10% by mass or more, the hot melt adhesive according to this embodiment can be made to have sufficient resistance to hot water, acid, and alcohol. Furthermore, by incorporating the polyol (a1) in a proportion of 60% by mass or less, the compatibility between the urethane resin (A) and the epoxy resin (B) is improved, and the resulting hot-melt adhesive can be made to have excellent adhesion to resin films formed from polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, and perfluorocarbon sulfonic acid resin. Furthermore, if the polyol component (a) is a copolymer of a monomer having 8 or more carbon atoms in its skeleton and a monomer having 7 or fewer carbon atoms in its skeleton, the parts by mass of the monomer having 8 or more carbon atoms in its skeleton are calculated as parts by mass of polyol (a1), and the parts by mass of the monomer having 7 or fewer carbon atoms in its skeleton are calculated as parts by mass of polyol (a2).

[0045] In addition to the polyol (a1) and polyol (a2), a short-chain diol (a3) ​​may be used as the polyol component (a) if necessary. Specific examples of the short-chain diol (a3) ​​include aliphatic glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, and neopentyl glycol, and their low-molar alkylene oxide adducts (number-average molecular weight Mn less than 500 by terminal functional group determination method); alicyclic glycols such as 1,4-bishydroxymethylcyclohexane and 2-methyl-1,1-cyclohexanedimethanol, and their low-molar alkylene oxide adducts (number-average molecular weight Mn less than 500, same as above); aromatic glycols such as xylylene glycol, and their low-molar alkylene oxide adducts (number-average molecular weight Mn less than 500, same as above); bisphenols such as bisphenol A, thiobisphenol, and sulfonbisphenol, and their low-molar alkylene oxide adducts (number-average molecular weight Mn less than 500, same as above). Among the short-chain diols (a3) ​​described above, it is preferable to use ethylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentyl glycol, etc., and it is particularly preferable to use ethylene glycol, 1,3-butylene glycol, and 1,4-butylene glycol. These short-chain diols (a3) ​​may be used individually or in combination of two or more.

[0046] Furthermore, when producing polyurethane resins other than the polyester urethane resin, polyhydric alcohol compounds can also be used as materials for the polyurethane resins other than the polyester urethane resin, similar to the short-chain diol (a3) ​​mentioned above. Specific examples of the aforementioned polyhydric alcohol compounds include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, tris-(2-hydroxyethyl)isocyanurate, 1,1,1-trimethylolethane, and 1,1,1-trimethylolpropane.

[0047] If necessary, a hydroxyl group-containing compound (a4) having a carboxyl group may be used. The hydroxyl group-containing compound (a4) having a carboxyl group typically has two or more hydroxyl groups in one molecule. Furthermore, the hydroxyl group-containing compound (a4) having a carboxyl group typically has two or more hydroxyl groups per molecule, and therefore reacts with a polyisocyanate component (b) having two or more isocyanate groups per molecule to obtain a polyurethane resin.

[0048] Examples of the hydroxyl group-containing compounds (a4) having a carboxyl group include dimethylolpropanoic acid, dimethylolbutanoic acid, their alkylene oxide low molar adducts (number average molecular weight Mn less than 500), γ-caprolactone low molar adducts (number average molecular weight Mn less than 500), half-esters derived from acid anhydrides and glycerol, and compounds derived by free radical reactions of monomers containing a hydroxyl group and an unsaturated group with monomers containing a carboxyl group and an unsaturated group. Among these various compounds, it is preferable to use dimethylolpropanoic acid or dimethylolbutanoic acid, and it is particularly preferable to use dimethylolpropanoic acid. These compounds may be used individually or in combination of two or more. Here, the number-average molecular weight Mn refers to the value measured by the terminal functional group determination method. The various compounds described above are examples of preferred compounds in the present invention. Therefore, the hydroxyl group-containing compound (a4) having a carboxyl group used in the present invention is not limited to the various compounds described above. Therefore, in addition to the various compounds mentioned above, any hydroxyl group-containing compound (a4) having a carboxyl group that is currently commercially available and easily obtainable on the market can be used in the present invention.

[0049] As the polyisocyanate component (b), conventionally known polyisocyanate components used in the production of polyurethane resins can be used. Specific examples of the polyisocyanate component (b) include toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, mixtures thereof, 4-methoxy-1,3-phenylenediisocyanate, 4-isopropyl-1,3-phenylenediisocyanate, 4-chlor-1,3-phenylenediisocyanate, 4-butoxy-1,3-phenylenediisocyanate, 2,4-diisocyanate diphenyl ether, 4,4'-methylenebis(phenylene isocyanate) (MDI), and crude or polymeric MDI, juliene diisocyanate, xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine Examples include aromatic diisocyanates such as diisocyanate and 4,4-diisocyanate dibenzyl; aliphatic diisocyanates such as methylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 1,10-decamethylene diisocyanate; alicyclic diisocyanates such as 1,4-cyclohexylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate, and hydrogenated XDI; and polyurethane prepolymers obtained by reacting these diisocyanates with low molecular weight polyols such that the terminal ends are isocyanates.

[0050] Among these polyisocyanate components (b), from the viewpoint of obtaining an industrially stable, inexpensive, and heat-resistant adhesive layer 10b for a hot-melt adhesive sheet 10, it is preferable to use aromatic isocyanates, and it is particularly preferable to use toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, mixtures thereof, 4,4'-methylenebis(phenylene isocyanate) (MDI), and crude or polymeric MDI. By using an aromatic isocyanate as the polyisocyanate component (b), the polyurethane resin other than the polyester urethane resin can be provided with aromatic diisocyanate constituent units. These polyisocyanate components (b) may be used individually or in combination of two or more.

[0051] (Method of manufacturing polyurethane resin (A)) Regarding the manufacturing method of polyurethane resin (A), the following will first explain the manufacturing method of polyester urethane resin, and then explain the manufacturing method of polyurethane resins other than polyester urethane resin.

[0052] Polyester urethane resin can be produced by reacting a hydroxyl group-containing polyester with a polyisocyanate component (b). The reaction between the hydroxyl group-containing polyester and the polyisocyanate component (b) can be carried out by conventionally known methods. As explained above, in the hot-melt adhesive sheet 10 according to this embodiment, the polyester urethane resin has an aromatic polyester skeleton. The aforementioned polyester urethane resin having an aromatic polyester skeleton can be achieved by using phthalic acid, isophthalic acid, terephthalic acid, or the like as the polycarboxylic acid when obtaining the hydroxyl group-containing polyester.

[0053] Polyurethane resins other than polyester urethane resin can be manufactured by conventionally known methods for producing polyurethane. The following describes a method for producing urethane resins other than polyester urethane resins using a polyol (a1) having 8 or more carbon atoms in its skeleton. Furthermore, even if a polyol (a1) having 8 or more carbon atoms in its skeleton is not used, polyurethane resins other than polyester urethane resins can be manufactured in the same manner as described below. First, a reaction composition containing a polyol (a1) having 8 or more carbon atoms in its skeleton, the polyol (a2), the polyisocyanate component (b), and a short-chain diol (a3) ​​used as a chain extender as needed is reacted in the presence or absence of an organic solvent that does not contain active hydrogen in its molecule to obtain a polyurethane resin other than a polyester urethane resin. Furthermore, when obtaining polyurethane resins other than polyester urethane resins, the hydroxyl group-containing compound (a4) having a carboxyl group may be used as needed. The reaction composition described above should generally have a composition in which the equivalent ratio of isocyanate groups to hydroxyl groups is 0.8 to 1.25. Furthermore, the reaction can be carried out by a one-shot method or a multi-stage method, usually at 20 to 150°C, preferably 60 to 110°C.

[0054] The mass-average molecular weight Mw of polyurethane resins other than the polyester polyurethane resin obtained as described above is preferably 1,000 or more and 100,000 or less. By having a mass-average molecular weight Mw within the above numerical range, the hot-melt adhesive containing the polyurethane resin (A) exhibits properties such as adhesion to the substrate, resistance to hot water, resistance to acid, and resistance to alcohol more effectively. Note that the mass-average molecular weight Mw of polyurethane resins other than the polyester urethane resin mentioned above refers to the value measured by gel permeation chromatography (GPC). The mass-average molecular weight Mw of polyurethane resins other than the aforementioned polyester urethane resin 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) • Columns: Product names "TSKgel G2000HXL", "G3000HXL", "G4000GXL" (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)

[0055] In this embodiment, a catalyst can be used as needed in the synthesis of the polyester urethane resin and polyurethane resins other than the polyester urethane resin. Examples of the catalysts include salts of metals with organic or inorganic acids, such as dibutyltin laurate, dioctyltin laurate, stanus octoate, zinc octoate, and tetra-n-butyl titanate, organometallic derivatives, organic amines such as triethylamine, and diazabicycloundecene catalysts. The catalyst promotes the synthesis reaction of the polyester urethane resin and polyurethane resins other than polyester urethane. On the other hand, excessive use of the catalyst may induce a decomposition reaction that breaks down substances other than the polyester urethane resin and the polyurethane resin other than polyester, and as a result, the resulting hot melt adhesive may have poor heat resistance over long periods of time. Therefore, when using the catalyst, it is preferable to use an appropriate amount of the catalyst.

[0056] The polyester urethane resin and the polyurethane resin other than the polyester urethane resin may be synthesized without using an organic solvent, or they may be synthesized using an organic solvent. As the organic solvent, an organic solvent that is inert to the isocyanate group, or an organic solvent that is less reactive to the isocyanate group than the reactive component, can be used. Specific examples of the aforementioned organic solvents include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbon solvents such as toluene, xylene, Swazole (trade name, manufactured by Cosmo Oil Co., Ltd.), and Solvesso (trade name, manufactured by Exxon Chemical Corporation); aliphatic hydrocarbon solvents such as n-hexane; alcohol solvents such as methanol, ethanol, and isopropyl alcohol; ether solvents such as dioxane and tetrahydrofuran; ester solvents such as ethyl acetate, butyl acetate, and isobutyl acetate; carbonate ester solvents such as dimethyl carbonate, diethyl carbonate, and ethylene carbonate; glycol ether ester solvents such as ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybutyl acetate, and ethyl-3-ethoxypropionate; amide solvents such as dimethylformamide and dimethylacetamide; and lactam solvents such as N-methyl-2-pyrrolidone. Toluene, methyl ethyl ketone, and ethyl acetate are particularly preferred from the viewpoint of increasing the solubility of polyurethane resins and from the viewpoint of being easily volatilized when obtaining hot-melt adhesives.

[0057] (Epoxy resin (B)) As described above, epoxy resin (B) contains an unmodified epoxy resin with an epoxy equivalent weight of 300 g / eq or more and 1500 g / eq or less. The epoxy equivalent may be 350 g / eq or more, or 400 g / eq or more. Furthermore, the epoxy equivalent may be 1000 g / eq or less. Furthermore, unmodified epoxy resin refers to epoxy resin that has not been modified with rubber or other materials. Furthermore, the epoxy equivalent mentioned above refers to the value determined according to JIS K 7236.

[0058] Examples of the unmodified epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol AD ​​type epoxy resin. Among these unmodified epoxy resins, it is preferable to use bisphenol A type epoxy resin. Examples of commercially available bisphenol A type epoxy resins with an epoxy equivalent weight of 300 g / eq to 1500 g / eq include Mitsubishi Chemical Corporation's product names "JER 1001" (epoxy equivalent weight 450-500 g / eq), "JER 1002" (epoxy equivalent weight 600-700 g / eq), "JER 1003" (epoxy equivalent weight 670-770 g / eq), "JER 1055" (epoxy equivalent weight 800-900 g / eq), "JER 1004" (epoxy equivalent weight 875-975 g / eq), and "JER 1004AF" (epoxy equivalent weight 875-975 g / eq). The aforementioned unmodified epoxy resin may be used alone or in combination of two or more types.

[0059] The epoxy resin (B) may contain a rubber-modified epoxy resin in addition to the unmodified epoxy resin. In this embodiment, the adhesive layer 10b of the hot melt adhesive sheet 10 contains, in addition to the unmodified epoxy resin, the rubber-modified epoxy resin, as the epoxy resin (B), makes it easier to suppress the peeling of the adhesive layer 10b from the adherend even after immersion for a long period of time, such as 1000 hours, in hot water at 95°C, dilute sulfuric acid (pH2) at 95°C, or in a water-ethylene glycol mixed solution at 95°C (ethylene glycol mixing ratio is 50% by volume) while the adhesive layer 10b is attached to the adherend (e.g., PEN film, perfluorocarbon sulfonic acid resin sheet, PPS film, etc.). The rubber-modified epoxy resin refers to a compound having at least one epoxy group in its molecule and possessing a structure derived from rubber. The aforementioned rubber-modified epoxy resin may be used alone or in combination of two or more types. Examples of the rubber-modified epoxy resin include a reaction product of an unmodified epoxy resin and rubber. As the unmodified epoxy resin, for example, the bisphenol A type epoxy resin, the bisphenol F type epoxy resin, the bisphenol AD ​​type epoxy resin, and the like can be used.

[0060] By having an epoxy equivalent of 300 g / eq or more and 1500 g / eq or less of the aforementioned unmodified epoxy resin, the unmodified epoxy resin can be crosslinked with an appropriate crosslinking density in the crosslinking reaction using the isocyanate-based crosslinking agent (C). As a result, the adhesive layer 10b containing the unmodified epoxy resin with an epoxy equivalent of 300 g / eq to 1500 g / eq can exhibit sufficient adhesion to the adherend. Furthermore, if the epoxy equivalent of the unmodified epoxy resin exceeds 1500 g / eq, the amount of epoxy groups per unit mass becomes insufficient, making it impossible to crosslink the unmodified epoxy resin with a sufficient crosslinking density in the crosslinking reaction using the isocyanate-based crosslinking agent (C). Therefore, if the adhesive layer 10b contains an unmodified epoxy resin with an epoxy equivalent of more than 1500 g / eq, the adhesive layer 10b will not be able to obtain sufficient strength, which is undesirable. Furthermore, if the epoxy equivalent of the unmodified epoxy resin is less than 300 g / eq, the amount of epoxy groups per unit mass becomes too high, resulting in an excessively high crosslink density of the unmodified epoxy resin in the crosslinking reaction using the isocyanate-based crosslinking agent (C). Therefore, when the adhesive layer 10b contains the unmodified epoxy resin with an epoxy equivalent of less than 300 g / eq, the crosslinking density of the adhesive layer 10b becomes too high due to the unmodified epoxy resin, making it hard and brittle, and as a result, sufficient adhesion to the adherend cannot be ensured, which is undesirable.

[0061] 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.

[0062] The rubber-modified epoxy resin 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 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 employed.

[0063] The physical properties of the rubber-modified epoxy resin 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.

[0064] The epoxy resin (B) may be present in amounts of 10 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more, per 100 parts by mass of the polyurethane resin (A). Furthermore, the epoxy resin (B) may be present in amounts of 60 parts by mass or less, or 50 parts by mass or less, per 100 parts by mass of polyurethane resin (A). Furthermore, among the epoxy resins (B), the unmodified epoxy resin is preferably present in an amount of 10 parts by mass or more, and more preferably in an amount of 20 parts by mass or more, per 100 parts by mass of polyurethane resin (A). Furthermore, the unmodified epoxy resin is preferably present in an amount of 40 parts by mass or less, and more preferably in an amount of 30 parts by mass or less, per 100 parts by mass of polyurethane resin (A). Furthermore, among the epoxy resins (B), the rubber-modified epoxy resin is preferably present in an amount of 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of polyurethane resin (A). Furthermore, the rubber-modified epoxy resin is preferably present in an amount of 30 parts by mass or less, and more preferably in an amount of 20 parts by mass or less, per 100 parts by mass of polyurethane resin (A). Furthermore, if the epoxy resin (B) contains both the unmodified epoxy resin and the rubber-modified epoxy resin, the ratio of the mass ratio of the unmodified epoxy resin to the mass ratio of the rubber-modified epoxy may be 1.1 or greater, 1.2 or greater, or 1.3 or greater. Furthermore, the ratio of the mass ratio of the unmodified epoxy to the mass ratio of the rubber-modified epoxy may be 3.0 or less, 2.0 or less, or 1.5 or less.

[0065] (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.

[0066] 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 aforementioned 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.

[0067] In the adhesive layer 10b of the hot melt adhesive sheet 10 of this embodiment, the isocyanate-based crosslinking agent (C) is preferably contained in an amount of 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass, per 100 parts by mass of the polyurethane resin (A). The isocyanate-based crosslinking agent (C) is preferably contained in an amount of 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the polyurethane resin (A). In the adhesive layer 10b of the hot melt adhesive sheet 10 according to this embodiment, the isocyanate-based crosslinking agent (C) is contained in the above-mentioned mass ratio, so that even after the adhesive layer 10b is attached to an adherend (e.g., PEN film, perfluorocarbon sulfonic acid resin sheet, PPS film, etc.) and immersed for a long period of time of 1000 hours in hot water at 95°C, dilute sulfuric acid (pH2) at 95°C, or a water-ethylene glycol mixed solution at 95°C (ethylene glycol mixing ratio is 50 vol%), the peeling of the adhesive layer 10b from the adherend is suppressed. In other words, the adhesive layer 10b of the hot melt adhesive sheet 10 has excellent long-term resistance to hot water, long-term resistance to acid, and long-term resistance to alcohol.

[0068] The inventors speculate that the adhesive layer 10b of the hot melt adhesive sheet 10 according to this embodiment exhibits excellent adhesion to the adherend, as well as excellent resistance to hot water, acid, and alcohol, as follows.

[0069] As described above, the adhesive layer 10b of the hot melt adhesive sheet 10 according to this embodiment is formed of a hot melt adhesive, which includes a polyurethane resin (A) containing a polyester urethane resin having an aromatic polyester skeleton, and an epoxy resin (B) containing an epoxy equivalent of 300 g / eq to 1500 g / eq (such as a bisphenol A type epoxy resin), as well as an isocyanate crosslinking agent (C). Furthermore, in the adhesive layer 10b, the polyester urethane resin having an aromatic polyester skeleton and the unmodified epoxy resin having an epoxy equivalent of 300 g / eq to 1500 g / eq are crosslinked with an isocyanate-based crosslinking agent (C). In other words, in the adhesive layer 10b of the hot melt adhesive sheet 10 according to this embodiment, the polyester urethane resin having an aromatic polyester skeleton and the unmodified epoxy resin having an epoxy equivalent of 300 g / eq to 1500 g / eq are included in a state that is crosslinked by an isocyanate-based crosslinking agent (C). As explained above, the polyester urethane resin having an aromatic polyester skeleton exhibits high hydrophobicity. Therefore, by including the polyester urethane resin having an aromatic polyester skeleton in the adhesive layer 10b, the hydrophobicity of the adhesive layer 10b is improved. As a result, the adhesive layer 10b is expected to have excellent resistance to hot water, acid, and alcohol. Furthermore, if the epoxy equivalent of the unmodified epoxy resin contained in the adhesive layer 10b is 300 g / eq or more and 1500 g / eq or less, the unmodified epoxy resin will be crosslinked in the adhesive layer 10b by the isocyanate-based crosslinking agent (C) with an appropriate crosslinking density. As a result, the adhesive layer 10b is expected to exhibit good adhesion to the adherend. Based on the above, it is considered that the adhesive layer 10b of the hot melt adhesive sheet 10 according to this embodiment has excellent adhesion to the adherend, as well as excellent resistance to hot water, acid, and alcohol.

[0070] 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 sheet 10 according to this embodiment is bonded is the membrane / electrode assembly (MEA) 20 of a polymer electrolyte fuel cell, as an example.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] The second hot melt adhesive sheet 10 has the same shape as the first hot melt adhesive sheet 10.

[0079] 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.

[0080] 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, across the first boundary line L1, to the positive electrode side catalyst layer exposed region 202a1. The second hot melt adhesive sheet 10 is bonded in the same way as the first hot melt adhesive sheet 10.

[0081] 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.

[0082] As explained earlier, in polymer electrolyte fuel cells, electricity is generated by the reaction of hydrogen and oxygen 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.

[0083] 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.

[0084] 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.

[0085] In this embodiment, the hot melt adhesive sheet 10 has the adhesive layer 10b configured as described above, and the adhesive layer 10b has excellent long-term resistance to hot water, long-term resistance to acid, and long-term resistance to alcohol. Therefore, when the hot-melt adhesive sheet according to this embodiment is used as a sub-gasket material in a solid polymer 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 a 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.

[0086] 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.

[0087] 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.

[0088] [ka]

[0089] 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.

[0090] 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.

[0091] 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.

[0092] The matters disclosed herein include the following:

[0093] (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 also contains a polyurethane resin, an epoxy resin, and an isocyanate-based crosslinking agent. The polyurethane resin contains a polyester urethane resin having an aromatic polyester skeleton. The epoxy resin contains an unmodified epoxy resin with an epoxy equivalent weight of 300 g / eq to 1500 g / eq. Hot melt adhesive sheet.

[0094] With this configuration, the adhesive layer of the hot melt adhesive sheet exhibits excellent adhesion to the adherend, as well as excellent resistance to hot water, acid, and alcohol.

[0095] (2) The polyurethane resin further comprises a polyurethane resin having structural units derived from a polyol with 8 or more carbon atoms in its skeleton. The hot melt adhesive sheet described in (1) above.

[0096] With this configuration, the adhesive layer of the hot melt adhesive sheet exhibits superior adhesion to the adherend, as well as superior resistance to hot water, acid, and alcohol.

[0097] (3) The polyurethane resin having structural units derived from a polyol with 8 or more carbon atoms in its skeleton contains a hydroxyl group-containing polyurethane resin having a hydroxyl group, The hydroxyl value of the hydroxyl group-containing polyurethane resin is 0.1 mg KOH / g or more and 20 mg KOH / g or less. The hot melt adhesive sheet described in (1) or (2) above.

[0098] With this configuration, the adhesive layer of the hot melt adhesive sheet exhibits superior adhesion to the adherend, as well as superior resistance to hot water, acid, and alcohol.

[0099] (4) The polyurethane resin having structural units derived from a polyol with 8 or more carbon atoms in its skeleton has aromatic diisocyanate as a structural unit. A hot melt adhesive sheet as described in any of (1) to (3) above.

[0100] With this configuration, the adhesive layer of the hot melt adhesive sheet exhibits superior adhesion to the adherend, as well as superior resistance to hot water, acid, and alcohol.

[0101] (5) The mass-average molecular weight Mw of the polyurethane resin having structural units derived from polyols with 8 or more carbon atoms in their skeleton is 1,000 or more and 100,000 or less. A hot melt adhesive sheet as described in any of (1) to (4) above.

[0102] With this configuration, the adhesive layer of the hot melt adhesive sheet exhibits superior adhesion to the adherend, as well as superior resistance to hot water, acid, and alcohol.

[0103] (6) The aforementioned polyester urethane resin has a glass transition temperature (Tg) of 10°C or less. A hot melt adhesive sheet as described in any of (1) through (5) above.

[0104] With this configuration, the adhesive layer of the hot melt adhesive sheet exhibits superior adhesion to the adherend, as well as superior resistance to hot water, acid, and alcohol.

[0105] (7) The aforementioned unmodified epoxy resin is a bisphenol A type epoxy resin. A hot melt adhesive sheet as described in any of (1) through (6) above.

[0106] With this configuration, the adhesive layer of the hot melt adhesive sheet exhibits superior adhesion to the adherend, as well as superior resistance to hot water, acid, and alcohol.

[0107] (8) 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) through (7) above.

[0108] 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]

[0109] (Example 1) The following components were mixed in the proportions shown in Table 1 below to obtain the hot melt adhesive layer composition according to Example 1. • A polyurethane resin having structural units derived from a polyol (a1) having 8 or more carbon atoms in its skeleton (hereinafter also referred to as polyurethane resin A1). • Polyester urethane resin (product name "Byron® UR-3210" manufactured by Toyobo Co., Ltd.; hereinafter also referred to as polyurethane resin A2) • A bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation, product name "JER1001" (epoxy equivalent weight 450-500 g / eq; hereinafter also referred to as epoxy resin B1). • Rubber-modified epoxy resin (product name "Adeka Resin EPR-1415-1" manufactured by Adeka Corporation; hereinafter also referred to as epoxy resin B2) • Isocyanate-based crosslinking agent (C) (product name "Takenate D-110N" manufactured by Mitsui Takeda Chemical Co., Ltd.) Polyurethane resin A1 was synthesized as follows, and epoxy resin B1 was dissolved as follows.

[0110] [Synthesis of polyurethane resin A1] 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, 300.0 g of polyhexamethylene carbonate diol with hydroxyl groups at both ends (Duranol: T6002, manufactured by Asahi Kasei Chemicals Corporation), 200.0 g of polycyclohexanedimethanol / hexanediol copolymer carbonate diol (product name "ETERNACOLLUM-90 (3 / 1)", manufactured by Ube Industries, Ltd., hydroxyl value = 112.2 mg KOH / g, cyclohexanedimethanol / hexanediol = 3 / 1 molar ratio), and 10.0 g of 1,3-butylene glycol were charged. Next, 207.3g of methyl ethyl ketone (MEK) was added as a solvent, and the system was stirred. After the system became homogenized, 111.8 g of 4,4'-diphenylmethane diisocyanate (MDI) was added at 50°C and the reaction was carried out at 80°C to obtain the reaction solution. The viscosity of the reaction solution is adjusted by diluting it with methyl ethyl ketone (MEK) as a solvent, and the free isocyanate group is measured by infrared absorption spectroscopy to obtain a value of 2,270 cm⁻¹. -1 The reaction was allowed to proceed until the absorption of was eliminated, yielding a resin solution AA1 containing polyurethane resin A1. The obtained resin solution AA1 had a solid content of 30% by mass, and the polyurethane resin A1 had a hydroxyl value of 2.5 mgKOH / g and contained 29.7% by mass of polyol (a1) having 8 or more carbon atoms in its skeleton. Furthermore, the mass-average molecular weight of polyurethane resin A1, as measured by GPC, was 72,000.

[0111] [Dissolution of epoxy resin B1] A reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen injection pipe, and manhole was prepared. While replacing the inside of the reaction vessel with nitrogen, 400.0 g of epoxy resin B1 (JER1001) was charged, and 600.0 g of methyl ethyl ketone (MEK) was charged as a solvent while stirring. Subsequently, the temperature inside the system was raised to 60°C to completely dissolve epoxy resin B1, thereby obtaining the dissolved epoxy resin B1 product BB1 (hereinafter referred to as epoxy resin solution BB1). The solid content of the obtained epoxy resin solution BB1 was 40% by mass.

[0112] The hot-melt adhesive layer composition according to Example 1 was obtained in more detail as follows. (1) Mix resin solution AA1 and epoxy resin solution BB1 so that polyurethane resin A1 and epoxy resin B1 are in the proportions shown in Table 1 below to obtain a mixed solution. (2) Add polyurethane resin A2 (polyester urethane resin), epoxy resin B2 (rubber-modified epoxy resin), and isocyanate-based crosslinking agent (C) to the mixed solution in the proportions shown in Table 1 below. (3) Completely dissolve the polyurethane resin A2, the epoxy resin B2, and the isocyanate-based crosslinking agent (C) in the mixed solution.

[0113] [Table 1]

[0114] (Example 2) A hot-melt adhesive layer composition according to Example 2 was obtained in the same manner as in Example 1, except that the epoxy resin B2 was not added.

[0115] (Example 3) A hot-melt adhesive layer composition according to Example 3 was obtained in the same manner as in Example 1, except that "JER1003" (epoxy equivalent of 670-770 g / eq), manufactured by Mitsubishi Chemical Corporation, was used as the bisphenol A type epoxy resin instead of "JER1001," manufactured by Mitsubishi Chemical Corporation.

[0116] (Example 4) A hot-melt adhesive layer composition according to Example 4 was obtained in the same manner as in Example 3, except that the epoxy resin B2 was not added.

[0117] (Example 5) A hot-melt adhesive layer composition according to Example 5 was obtained in the same manner as in Example 1, except that "JER1004" (epoxy equivalent of 875-975 g / eq), manufactured by Mitsubishi Chemical Corporation, was used as the bisphenol A type epoxy resin instead of "JER1001," manufactured by Mitsubishi Chemical Corporation.

[0118] (Example 6) A hot-melt adhesive layer composition according to Example 6 was obtained in the same manner as in Example 5, except that the epoxy resin B2 was not added.

[0119] (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 "JER1007" (epoxy equivalent of 1750-2200 g / eq), manufactured by Mitsubishi Chemical Corporation, was used as the bisphenol A type epoxy resin instead of "JER1001," also manufactured by Mitsubishi Chemical Corporation.

[0120] (Comparative Example 2) A hot-melt adhesive layer composition according to Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that the epoxy resin B2 was not added.

[0121] (Comparative Example 3) A hot-melt adhesive layer composition according to Comparative Example 3 was obtained in the same manner as in Example 1, except that "JER1256" (epoxy equivalent of 7500-8500 g / eq), manufactured by Mitsubishi Chemical Corporation, was used as the bisphenol A type epoxy resin instead of "JER1001".

[0122] (Comparative Example 4) A hot-melt adhesive layer composition according to Comparative Example 4 was obtained in the same manner as in Comparative Example 3, except that the epoxy resin B2 was not added.

[0123] (Comparative Example 5) A hot-melt adhesive layer composition for Comparative Example 5 was obtained in the same manner as in Example 1, except that "JER157S70" (epoxy equivalent 200-220 g / eq), a novolac-type epoxy resin manufactured by Mitsubishi Chemical Corporation, was used instead of "JER1001" (a bisphenol A-type epoxy resin).

[0124] (Comparative Example 6) A hot-melt adhesive layer composition according to Comparative Example 6 was obtained in the same manner as in Comparative Example 5, except that the epoxy resin B2 was not added.

[0125] (Comparative Example 7) A hot-melt adhesive layer composition according to Comparative Example 7 was obtained in the same manner as in Example 1, except that no epoxy resin was added.

[0126] (Comparative Example 8) A hot-melt adhesive layer composition according to Comparative Example 8 was obtained in the same manner as in Comparative Example 7, except that the epoxy resin B2 was not added.

[0127] [Coating of hot melt adhesive layer compositions] Each example of the hot-melt adhesive layer composition was diluted with methyl ethyl ketone (MEK) to a solid content of 30% by mass. In each example, a diluted hot-melt adhesive layer composition was applied to the entire surface of one side of a PEN film (length: 210 mm, width: 150 mm, thickness: 100 μm, Theonex: manufactured by Toyobo Film Solutions Co., Ltd.). After application, it was dried at 100°C for 1 minute, and then left in a 40°C oven for 48 hours to allow the curing reaction (crosslinking reaction) to proceed, resulting in a PEN film with a hot-melt adhesive layer. The coating was applied so that the thickness of the hot-melt adhesive layer after drying was 20 μm.

[0128] [Preparation of the first adhesive sheet] Two PEN films with a hot-melt adhesive layer were prepared for each 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 example were heat-pressed together to create the first adhesive sheet for each example.

[0129] [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 example so that the exposed surface of the hot-melt adhesive layer of the PEN film with the hot-melt adhesive layer of each 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 example and the perfluorocarbon sulfonic acid resin sheet were heat-pressed together to produce a second adhesive sheet for each example.

[0130] [Hot water resistance 1] For each example's first adhesive sheet, a test specimen measuring 10 mm in width and 80 mm in length was cut from the first adhesive sheet of each example, and the test specimen was immersed in 95°C hot water for 1000 hours. After cooling to room temperature, the hot water resistance of each test specimen was evaluated according to the following criteria. • ○: No peeling was observed after immersion. •△: No peeling was observed after immersion, but some lifting was seen. • ×: Peeling was observed after immersion.

[0131] [Acid resistance 1] For each example's first adhesive sheet, a test specimen measuring 10 mm wide x 80 mm long was cut from the first adhesive sheet of each 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. • ○: No peeling was observed after immersion. •△: No peeling was observed after immersion, but some lifting was seen. • ×: Peeling was observed after immersion.

[0132] [Alcohol resistance 1] For each example's first adhesive sheet, a test specimen measuring 10 mm wide x 80 mm long was cut from the first adhesive sheet of each 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. • ○: No peeling was observed after immersion. •△: No peeling was observed after immersion, but some lifting was seen. • ×: Peeling was observed after immersion.

[0133] [Hot water resistance 2] For each 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 example, and the test specimen was immersed in 95°C hot water for 1000 hours. After cooling to room temperature, the hot water resistance of each test specimen was evaluated according to the following criteria. • ○: No peeling was observed after immersion. •△: No peeling was observed after immersion, but some lifting was seen. • ×: Peeling was observed after immersion.

[0134] For each 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 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. • ○: No peeling was observed after immersion. •△: No peeling was observed after immersion, but some lifting was seen. • ×: Peeling was observed after immersion.

[0135] [Alcohol resistance 2] For each 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 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. • ○: No peeling was observed after immersion. •△: No peeling was observed after immersion, but some lifting was seen. • ×: Peeling was observed after immersion.

[0136] [Initial adhesion] For each example, the initial adhesion strength of the first adhesive sheet (an adhesive sheet consisting of a hot-melt adhesive layer sandwiched between two PEN films) was evaluated using an autograph. A test specimen measuring 10 mm wide x 80 mm long was cut from the first adhesive sheet of each example, and the adhesive strength of this test specimen was measured using an autograph. Then, samples with an adhesive strength of 3N / 10mm or higher were evaluated as ○, and those with an adhesive strength of less than 3N / 10mm were evaluated as ×.

[0137] The results of each of the above evaluations are shown in Table 2 below.

[0138] [Table 2]

[0139] From Table 2 above, it can be seen that in each example, both the first adhesive sheet and the second adhesive sheet received a "○" rating for all evaluation items. Furthermore, it can be seen that the evaluation result for initial adhesion in each example was also positive (〇). In contrast, in each comparative example, it can be seen that at least one evaluation item is marked with a triangle (△) or a cross (×). Furthermore, looking at the entries for hot water resistance (hot water resistance 1 and hot water resistance 2), acid resistance (acid resistance 1 and 2), and alcohol resistance (alcohol resistance 1 and alcohol resistance 2) for each comparative example in Table 2, it can be seen that the evaluation results for Comparative Examples 1, 3, 5, and 7 are "△", while the evaluation results for Comparative Examples 2, 4, 6, and 8 are "×". Comparative Examples 1, 3, 5, and 7 all contain epoxy resin B2 (rubber-modified epoxy resin), while Comparative Examples 2, 4, 6, and 8 do not contain epoxy resin B2 (rubber-modified epoxy resin). From this, it can be inferred that Comparative Examples 1, 3, 5, and 7 exhibit improved resistance to hot water, acid, and alcohol due to the inclusion of epoxy resin B2 (rubber-modified epoxy resin). [Explanation of symbols]

[0140] 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 used by adhering it to a solid electrolyte membrane of a polymer electrolyte fuel cell, wherein an adhesive layer formed of a hot-melt adhesive is laminated on at least one side of the substrate, The hot melt adhesive comprises a crosslinked product of an adhesive composition containing a crosslinking agent, and also contains a polyurethane resin, an epoxy resin, and an isocyanate-based crosslinking agent. The polyurethane resin is composed of a polyester urethane resin having an aromatic polyester skeleton and a polyurethane resin other than the polyester urethane resin. Polyurethane resins other than the aforementioned polyester urethane resin are polyurethane resins having structural units derived from polyols with 8 or more carbon atoms in their skeletons. The epoxy resin contains an unmodified epoxy resin with an epoxy equivalent weight of 300 g / eq or more and 1500 g / eq or less. Hot melt adhesive sheet.

2. The polyurethane resin having structural units derived from a polyol with eight or more carbon atoms in its skeleton contains a hydroxyl group-containing polyurethane resin having a hydroxyl group, The hydroxyl value of the hydroxyl group-containing polyurethane resin is 0.1 mg KOH / g or more and 20 mg KOH / g or less. The hot melt adhesive sheet according to claim 1.

3. The polyurethane resin having structural units derived from a polyol with eight or more carbon atoms in its skeleton has aromatic diisocyanate as a structural unit. The hot melt adhesive sheet according to claim 1 or 2.

4. The mass-average molecular weight Mw of the polyurethane resin having structural units derived from a polyol with eight or more carbon atoms in its skeleton is 1,000 or more and 100,000 or less. The hot melt adhesive sheet according to claim 1 or 2.

5. The polyester urethane resin having an aromatic polyester skeleton has a glass transition temperature Tg of 10°C or less. The hot melt adhesive sheet according to claim 1 or 2.

6. The aforementioned unmodified epoxy resin is a bisphenol A type epoxy resin. The hot melt adhesive sheet according to claim 1 or 2.

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