Hot melt adhesive sheet

Abstract

To provide a hot-melt adhesive sheet which exhibits good adhesiveness to a hardly adhesive article even when an aging treatment by heating is omitted.SOLUTION: A hot-melt adhesive sheet in which an adhesive layer formed of a hot-melt adhesive is laminated on at least one surface of a sheet-like base material, wherein the hot-melt adhesive contains a moisture-curable polyurethane resin and an epoxy resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, polyurethane adhesives have been widely used as adhesives for various plastics due to their adhesive stability in low temperature ranges (e.g., -10°C to 15°C), as well as their adhesiveness, flexibility, processability, and ease of various molecular designs in room temperature ranges (25±10°C). The polyurethane-based adhesives include those that contain a polyester polyol, an acrylic polyol, or the like as a main component and a polyisocyanate as a crosslinking agent, and are used by generating urethane bonds by causing a crosslinking reaction between the main component and the crosslinking agent; and those that contain a polyurethane having a certain chain length (a so-called polyurethane prepolymer) as a main component and an isocyanate-based crosslinking agent as a crosslinking agent, and are used by causing a crosslinking reaction between the main component and the crosslinking agent to proceed and harden.

[0003] Also known is a two-component adhesive that contains a polyurethane resin as a base agent, an epoxy resin, and an isocyanate-based crosslinking agent (see Patent Document 1). In recent years, hot melt adhesives have been increasingly used to bond members because they are easier to handle than liquid adhesives such as those described in Patent Document 1 below. The hot melt adhesive is often used in the form of a hot melt adhesive sheet, particularly from the viewpoint of ease of handling. The hot melt adhesive sheet generally comprises a sheet-like substrate formed of a polymer sheet, and an adhesive layer formed of the hot melt adhesive and laminated on the sheet-like substrate.

[0004] The hot melt adhesive sheet is produced by coating one or both sides of a sheet substrate with a coating liquid in which a hot melt adhesive is dissolved in an organic solvent, drying the coating in a heating oven, and then coating one or both sides of the sheet substrate with a solventless coating liquid that becomes a hot melt adhesive by a thermosetting reaction, and then thermosetting the coating in a heating oven (aging treatment). However, if the aging treatment is insufficient, it is difficult to obtain a hot melt adhesive sheet with sufficient adhesive strength. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2013 / 157604 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the hot melt adhesive sheet is produced by aging treatment using heat, there is a problem that the heating increases carbon dioxide emissions. From the viewpoint of reducing such environmental load, it is desired that the hot melt adhesive sheet be produced by aging treatment at room temperature without using heat.

[0007] However, conventional hot melt adhesive sheets cannot be subjected to sufficient aging treatment at room temperature, and it is therefore difficult to obtain good adhesion to difficult-to-adhere articles such as solid electrolyte membranes while producing them by aging treatment at room temperature.

[0008] Therefore, an object of the present invention is to provide a hot melt adhesive sheet that exhibits good adhesion to difficult-to-adhere articles even without aging treatment by heating. [Means for solving the problem]

[0009] The hot melt adhesive sheet according to the present invention comprises: A hot melt adhesive sheet in which an adhesive layer formed of a hot melt adhesive is laminated on at least one surface of a sheet-like substrate, The hot melt adhesive contains a moisture-curing polyurethane resin and an epoxy resin. [Effects of the Invention]

[0010] According to the present invention, there is provided a hot melt adhesive sheet that exhibits good adhesion to difficult-to-adhere articles even without heat aging treatment. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of a hot melt adhesive sheet according to one embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view showing a state in which a hot melt adhesive sheet according to one embodiment of the present invention is attached to a solid electrolyte membrane of a polymer electrolyte fuel cell and used; DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a hot melt adhesive sheet according to one embodiment of the present invention will be described with reference to the drawings. Hereinafter, one embodiment of the present invention may be simply referred to as the present embodiment.

[0013] As shown in FIG. 1, the hot melt adhesive sheet 10 according to this embodiment is a hot melt adhesive sheet in which an adhesive layer 10b formed of a hot melt adhesive is laminated on one surface of a sheet-like substrate 10a. In the hot melt adhesive sheet 10 shown in FIG. 1, the adhesive layer 10b is laminated on only one side of the sheet-like substrate 10a, but the adhesive layer 10b may also be laminated on the other side of the sheet-like substrate 10a. That is, 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 sheet-like substrate 10a.

[0014] The hot melt adhesive sheet 10 of this embodiment is a hot melt adhesive sheet in which an adhesive layer formed of a hot melt adhesive is laminated on at least one surface of a sheet-like substrate, and the hot melt adhesive contains a moisture-curing polyurethane resin and an epoxy resin.

[0015] (Moisture-curing polyurethane resin (A)) The moisture-curable polyurethane resin (A) is obtained by urethane bonding reaction components including a polyol (a) having two or more hydroxyl groups per molecule and a polyisocyanate (b) having two or more isocyanate groups per molecule.

[0016] The moisture-curable polyurethane resin (A) is usually linear or branched and has two or more molecular ends. In one embodiment, the moisture-curable polyurethane resin (A) has an unreacted isocyanate group at one or two or more molecular ends. In another embodiment, the moisture-curable polyurethane resin (A) has an unreacted isocyanate group at an end of the main chain. In yet another embodiment, the moisture-curable polyurethane resin (A) has an unreacted isocyanate group at one end or both ends of the main chain.

[0017] The isocyanate group reacts with moisture in the air to convert it into an amino group and carbon dioxide. The amino group further reacts with other unreacted isocyanate groups in the moisture-curable polyurethane resin to form a urea bond, allowing the moisture-curable polyurethane resin (A) to cure even at room temperature (e.g., 23°C).

[0018] In the hot melt adhesive sheet 10 according to this embodiment, the moisture-curable polyurethane resin (A) has a structural unit derived from a polyol (a) having an ester bond, a carbonate bond, or an ether bond. That is, the polyol (a) can be an ester bond-containing polyol (a1), a carbonate bond-containing polyol (a2), or an ether bond-containing polyol (a3).

[0019] As the ester bond-containing polyol (a1), a polyester obtained by a condensation reaction between a polycarboxylic acid and a polyhydric alcohol can be used.

[0020] Examples of the polycarboxylic acid 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, methylcyclohexene tricarboxylic acid, pyromellitic acid, dimer acids derived from unsaturated fatty acids, and acid anhydrides thereof.

[0021] Examples of the polyhydric alcohol 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.

[0022] The polyhydric alcohol may be a polyhydric alcohol having a carboxyl group (hereinafter also referred to as a carboxyl group-containing polyhydric alcohol). Examples of the carboxyl group-containing polyhydric alcohol include dimethylolpropionic acid, dimethylolbutanoic acid, and diphenolic acid. Furthermore, the polyhydric alcohol may be modified with a caprolactone compound such as ε-caprolactam.

[0023] Examples of the carbonate bond-containing polyol (a2) include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, and random / block copolymers thereof.

[0024] The carbonate bond-containing polyol (a2) has excellent hydrolysis resistance and heat resistance, and therefore, when the moisture-curable polyurethane resin (A) contains structural units derived from the carbonate bond-containing polyol (a2), an adhesive layer 10b having excellent hot water resistance can be obtained.

[0025] Examples of the ether bond-containing polyol (a3) ​​include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and random / block copolymers thereof.

[0026] The ether bond-containing polyol (a3) ​​has better hydrolysis resistance than the ester bond-containing polyol (a1), and therefore, when the moisture-curable polyurethane resin (A) contains structural units derived from the ether bond-containing polyol (a3), an adhesive layer 10b with excellent hot water resistance can be obtained.

[0027] Examples of the polyisocyanate (b) include aliphatic isocyanate compounds, alicyclic isocyanate compounds, and aromatic isocyanate compounds.

[0028] Examples of the aliphatic isocyanate compound include hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, trimethylhexamethylene diisocyanate, and xylylene diisocyanate.

[0029] Examples of the alicyclic isocyanate compound include isophorone diisocyanate, methylcyclohexane diisocyanate, lysine diisocyanate, and cyclohexane-1,4-diisocyanate.

[0030] Examples of the aromatic isocyanate compound include tolylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, tetraalkyldiphenylmethane isocyanate, dialkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate.

[0031] The molar ratio of the polyisocyanate (b) to the polyol (a) is preferably 1.3 or more and 5.0 or less, more preferably 1.5 or more and 4.5 or less, and even more preferably 1.8 or more and 4.0 or less.

[0032] In the hot melt adhesive sheet 10 according to this embodiment, the molar ratio of polyisocyanate (b) to polyol (a) is within the above range, ensuring a sufficient amount of isocyanate groups for moisture curing. This allows the moisture-curable polyurethane resin to cure sufficiently even at room temperature, improving the hydrolysis resistance of the moisture-curable polyurethane resin (A) after curing and providing better adhesion under hot water conditions.

[0033] The content of the moisture-curable polyurethane resin (A) in the hot melt adhesive may be 20% by mass or more, 45% by mass or more, 70% by mass or more, or 90% by mass or more. In one aspect of the hot melt adhesive sheet 10 according to the present embodiment, the hot melt adhesive may be composed solely of the moisture-curable polyurethane resin (A).

[0034] (Epoxy resin (B)) The epoxy groups of the epoxy resin (B) react with amino groups derived from isocyanate groups generated when the moisture-curable polyurethane resin (A) cures, thereby increasing the crosslink density of the hot melt adhesive sheet 10 according to this embodiment and providing superior adhesiveness under hot water conditions.

[0035] The epoxy resin (B) may be, for example, a triphenylmethane-type epoxy resin, a bisphenol-type epoxy resin, a novolac-type epoxy resin, or an alicyclic epoxy resin. Examples of the bisphenol-type epoxy resin include bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol S-type epoxy resin. The bisphenol-type epoxy resin may be a long-chain epoxy resin, such as a phenoxy resin. The bisphenol-type epoxy resin may be a modified product, such as one modified with CTBN or ATBN. Examples of the novolac-type epoxy resin include phenol novolac-type epoxy resin and cresol novolac-type epoxy resin. The novolac-type epoxy resin may contain a naphthalene skeleton or may be a naphthalene-skeleton-containing novolac-type epoxy resin. The alicyclic epoxy resin may be, for example, a dicyclopentadiene-type epoxy resin. These various epoxy resins may be used alone or in combination of two or more.

[0036] The epoxy resin (B) is preferably one or more epoxy resins selected from the group consisting of triphenylmethane-type epoxy resins, bisphenol A-type epoxy resins, and naphthalene skeleton-containing novolac-type epoxy resins, and more preferably a bisphenol A-type epoxy resin.

[0037] In the hot melt adhesive sheet 10 according to this embodiment, the epoxy equivalent of the epoxy resin (B) may be 100 g / eq or more and 1500 g / eq or less, preferably 100 g / eq or more and 1100 g / eq or less, more preferably 400 g / eq or more and 1100 g / eq or less, and even more preferably 800 g / eq or more and 1100 g / eq or less. The epoxy equivalent is determined by the method specified in JIS K7236.

[0038] The hot melt adhesive sheet 10 according to this embodiment has an epoxy equivalent of the epoxy resin (B) within the above range, and therefore exhibits even better adhesiveness under hot water conditions.

[0039] In one aspect of the hot melt adhesive sheet 10 according to this embodiment, the content of the epoxy resin is 5 parts by mass or more and 150 parts by mass or less, preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 20 parts by mass or more and 80 parts by mass or less, and even more preferably 20 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the moisture-curing polyurethane resin.

[0040] The sheet-like substrate 10a used in the hot melt adhesive sheet 10 according to this embodiment is not particularly limited, but examples thereof include PEN (polyethylene naphthalate) film, perfluorocarbon sulfonic acid resin sheet (film), and PPS (polyphenylene sulfide) film.

[0041] Next, referring 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 of this embodiment is adhered is a membrane electrode assembly (MEA) 20 of a solid polymer fuel cell.

[0042] The membrane electrode assembly (MEA) 20, which is the substrate, is configured to allow hydrogen gas to pass from the negative electrode side to the positive electrode side and to react the hydrogen with oxygen supplied to the positive electrode side to generate electricity.

[0043] As shown in FIG. 2, in a membrane electrode assembly (MEA) 20, a positive electrode 202 and a negative electrode 203 are laminated on opposite sides of a solid electrolyte membrane 201, respectively. The positive electrode 202 includes a positive electrode catalyst layer 202 a and a positive electrode gas diffusion layer 202 b laminated on the positive electrode catalyst layer 202 a , and the positive electrode catalyst layer 202 a is laminated on one side of the solid electrolyte membrane 201 . The negative electrode 203 includes a negative electrode catalyst layer 203 a and a negative electrode gas diffusion layer 203 b laminated on the negative electrode catalyst layer 203 a, and the negative electrode catalyst layer 203 a is laminated on the other side of the solid electrolyte membrane 201 .

[0044] As shown in FIG. 2, the positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a are formed so as 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 also formed so as to have smaller planar dimensions than the positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a. That is, in the membrane electrode assembly (MEA) 20, 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, the planar dimensions of the positive electrode 202 are smaller than the planar dimensions of the solid electrolyte membrane 201, and therefore, on the positive electrode side (one side) of the membrane electrode assembly (MEA) 20, a positive electrode-side electrolyte membrane exposed region 201a is formed on the outer periphery, where the solid electrolyte membrane 201 extends outward beyond the positive electrode catalyst layer 202a and the surface of the solid electrolyte membrane 201 is exposed. Furthermore, since the planar dimensions of the negative electrode 203 are smaller than the planar dimensions of the solid electrolyte membrane 201, an negative electrode-side electrolyte membrane exposed region 201b is formed on the outer periphery of the negative electrode side (other surface 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 surface of the solid electrolyte membrane 201 is exposed.

[0045] Furthermore, on the positive electrode side of the membrane electrode assembly (MEA) 20, a positive electrode side catalyst layer exposed region 202a1 is formed in which the positive electrode catalyst layer 202a extends outward beyond the positive electrode gas diffusion layer 202b, exposing the surface of the positive electrode catalyst layer 202a. The positive electrode catalyst layer exposed region 202a1 is formed inside the positive electrode 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 surround 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. That is, on the positive electrode side of the membrane electrode assembly (MEA), a second boundary line L2, which is the boundary line between the positive electrode side electrolyte membrane exposed region 201a and the positive electrode side catalyst layer exposed region 202a1, is formed inside a first boundary line L1, which is the boundary line between the positive electrode side electrolyte membrane exposed region 201a and the positive electrode side catalyst layer exposed region 202a1.

[0046] On the negative electrode side of the membrane electrode assembly (MEA) 20, an 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, exposing the surface of the negative electrode catalyst layer 203a. The negative electrode catalyst layer exposed region 203a1 is formed inside the negative electrode 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 surround the outer periphery of the membrane electrode assembly (MEA) 20. The negative electrode catalyst layer exposed region 203a1 is formed in a ring shape that is smaller than the negative electrode electrolyte membrane exposed region 201b. That is, on the negative electrode side of the membrane electrode assembly (MEA) 20, a fourth boundary line L4, which is the boundary line between the negative electrode side electrolyte membrane exposed region 201b and the negative electrode side catalyst layer exposed region 203a1, is formed inside a third boundary line L3, which is the boundary line between the negative electrode side electrolyte membrane exposed region 201b and the negative electrode side catalyst layer exposed region 203a1.

[0047] In the state of use shown in Figure 2, two hot melt adhesive sheets 10, namely, a first hot melt adhesive sheet 10 adhered to the positive electrode side of the membrane electrode assembly (MEA) 20 and a second hot melt adhesive sheet 10 adhered to the negative electrode side of the membrane electrode assembly (MEA) 20, are used as subgasket materials for a solid polymer fuel cell.

[0048] The first hot melt adhesive sheet 10 is annular and has a shape such that when it is placed on the membrane electrode assembly (MEA) 20, its outer peripheral edge is outside the membrane electrode assembly (MEA) 20, and its inner peripheral edge fits within the positive electrode side catalyst layer exposed region 202a1 and the negative electrode side catalyst layer exposed region 203a1. That is, the hollow portion of the first hot melt adhesive sheet 10 has a shape that is slightly larger than the positive electrode gas diffusion layer 202b.

[0049] The second hot melt adhesive sheet 10 also has a shape similar to that of the first hot melt adhesive sheet 10 .

[0050] In this embodiment, the first hot melt adhesive sheet 10 and the second hot melt adhesive sheet 10 are used as the subgasket material by directly bonding the outer periphery of the adhesive layer 10b outside the membrane electrode assembly (MEA) 20.

[0051] The first hot melt adhesive sheet 10 has its inner periphery adhered to the outer periphery of the membrane electrode assembly (MEA) 20, except for its outer periphery adhered to the second hot melt adhesive sheet 10, and is adhered in the range 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. Specifically, the surface of the adhesive layer 10b of the first hot melt adhesive sheet 10 used as the subgasket material has an adhesive surface that is bonded to the membrane electrode assembly (MEA) 20, which is the adherend. The first hot melt adhesive sheet 10 in this embodiment is annular as described above, and the adhesive surface of the adhesive layer 10b is also annular. The first hot melt adhesive sheet 10 in this embodiment has a first annular adhesive region, the radially outermost region of the annular adhesive surface, that is bonded to a second hot melt adhesive sheet 10 having the same shape. The adhesive surface of the hot melt adhesive sheet 10 in this embodiment further has a second annular adhesive region that is bonded to the positive electrode-side electrolyte membrane exposed region 201a and a third annular adhesive region that is bonded to the positive electrode-side catalyst layer exposed region 202a1. On the adhesive surface, the third annular adhesive region, the second annular adhesive region, and the first annular adhesive region are arranged in this order from the radially outside, so that the first annular adhesive region surrounds the second annular adhesive region, and the second annular adhesive region surrounds the third annular adhesive region. The second hot melt adhesive sheet 10 is adhered in the same manner as the first hot melt adhesive sheet 10.

[0052] By adhering (coating) 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 preventing a decrease in performance as a solid polymer fuel cell.

[0053] As explained above, in a polymer electrolyte fuel cell, hydrogen and oxygen react with each other in a membrane electrode assembly (MEA) 20 to generate electricity. When hydrogen and oxygen react as described above, the membrane electrode assembly (MEA) 20 reaches a relatively high temperature (for example, 95° C.). When the solid polymer fuel cell is installed as a power source in an automobile, the central portion of the membrane / electrode assembly (MEA) 20 is sufficiently cooled by circulating antifreeze contained in a radiator through a pipe. However, since the pipe is not usually extended to the edge portion of the membrane / electrode assembly (MEA) 20, the edge portion of the membrane / electrode assembly (MEA) 20 continues to maintain a high temperature.

[0054] Here, in the hot melt adhesive sheet 10 according to this embodiment, the adhesive layer 10b is configured as described above, and therefore the adhesive layer 10b has excellent long-term resistance to hot water. Therefore, when the hot melt adhesive sheet of this embodiment is used as a subgasket material in a polymer electrolyte fuel cell installed in an automobile, as described above, even if the adhesive layer 10b comes into contact with water at a high temperature such as 95°C, the adhesiveness with the solid electrolyte membrane 201 can be maintained for a long period of time. As will be described later, the solid electrolyte membrane 201 is usually made of a fluororesin such as perfluorocarbon sulfonic acid.

[0055] In the membrane electrode assembly (MEA) 20, the positive electrode catalyst layer 202 a and the negative electrode catalyst layer 203 a are generally formed using a catalyst ink composition containing a catalyst support material such as a carbon material supporting a catalyst, a proton-conductive polymer, and a solvent.

[0056] 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 perfluorocarbon sulfonic acid resin include "Nafion" (trade name) manufactured by DuPont, "Flemion" (trade name) manufactured by Asahi Kasei Corporation, and "Aciplex" (trade name) manufactured by Asahi Glass Co., Ltd.

[0057] When the solid electrolyte membrane 201 of the membrane electrode assembly (MEA) 20 is formed of a perfluorocarbon sulfonic acid resin, the adhesive layer 10b exhibits excellent adhesion to the solid electrolyte membrane 201. This makes it difficult for water molecules to enter between the adhesive layer 10b and the solid electrolyte membrane 201, and the moisture-curable polyurethane resin (A) in the adhesive layer 10b is less likely to be hydrolyzed, so the hot melt adhesive sheet 10 according to this embodiment exhibits excellent hot water resistance.

[0058] When the hot melt adhesive contains the epoxy resin (B), the hot melt adhesive is thermally cured by thermocompression bonding the hot melt adhesive sheet 10 and the solid electrolyte membrane 201, and the adhesive layer 10b exhibits excellent adhesion to the solid electrolyte membrane 201. This makes it difficult for water molecules to enter between the adhesive layer 10b and the solid electrolyte membrane 201, and the moisture-curable polyurethane resin (A) in the adhesive layer 10b is less likely to be hydrolyzed, so the hot melt adhesive sheet 10 according to this embodiment exhibits excellent hot water resistance.

[0059] The positive electrode catalyst layer 202a and the negative electrode catalyst layer 203a are layers containing catalyst particles. The catalyst particles contained in the positive electrode catalyst layer 202a include platinum. The catalyst particles contained in the negative electrode catalyst layer 203a include platinum compounds. The platinum compound may be an alloy of platinum and at least one metal selected from the group consisting of ruthenium, palladium, nickel, molybdenum, iridium, and iron.

[0060] Positive electrode gas diffusion layer 202b and negative electrode gas diffusion layer 203b are made of a porous conductive substrate. Examples of the porous conductive substrate include carbon paper and carbon cloth.

[0061] The hot melt adhesive sheet 10 according to this embodiment can also be used in redox flow batteries, water electrolysis devices, and the like. Hot melt adhesive sheets used in redox flow batteries are used to prevent electrolyte permeation.

[0062] The hot melt adhesive sheet according to the present invention is not limited to the above-described embodiment, nor is it limited by the above-described effects. The hot melt adhesive sheet according to the present invention can be modified in various ways without departing from the gist of the present invention.

[0063] The matters disclosed by this specification include the following.

[0064] (1) A hot melt adhesive sheet in which an adhesive layer formed of a hot melt adhesive is laminated on at least one surface of a sheet-like substrate, The hot melt adhesive contains a moisture-curing polyurethane resin and an epoxy resin. Hot melt adhesive sheet. (2) The content of the epoxy resin is 5 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the moisture-curable polyurethane resin. The hot melt adhesive sheet according to (1). (3) The epoxy equivalent of the epoxy resin is 100 g / eq or more and 1500 g / eq or less. A hot melt adhesive sheet according to (1) or (2). (4) The hot melt adhesive sheet according to any one of (1) to (3), wherein the epoxy resin is one or more epoxy resins selected from the group consisting of triphenylmethane-type epoxy resins, bisphenol A-type epoxy resins, and naphthalene skeleton-containing novolac-type epoxy resins. [Example]

[0065] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0066] The moisture-curable polyurethane resin (A) and epoxy resin (B) used in the examples and comparative examples are as follows. (Polyurethane resin (A)) PU1: Moisture-curing ester-based polyurethane resin, manufactured by Toyochem Co., Ltd., model number "RH-3143B4" PU2: Moisture-curing carbonate-based polyurethane resin, manufactured by Toyochem Co., Ltd., model number "RH-3143B4C" PU3: Polycarbonate-type polyurethane resin, manufactured by DIC, model number "TA-205FT" PU4: Ester-type polyurethane resin, manufactured by Toyobo MC Co., Ltd., model number "UR-3210" (Epoxy resin (B)) EP1: Bisphenol A epoxy resin, manufactured by Nanya Plastics Co., Ltd., model number "NPES-304", epoxy equivalent weight 900-1000g / eq EP2: Bisphenol A epoxy resin, manufactured by Mitsubishi Chemical Corporation, model number "jER1001", epoxy equivalent weight 450-500g / eq EP3: Rubber-modified epoxy resin, manufactured by ADEKA Corporation, model number "EPR-1415-1", epoxy equivalent weight 400g / eq EP4: Bisphenol A epoxy resin, manufactured by Nanya Plastics Co., Ltd., model number "NPES-301", epoxy equivalent weight 450-550g / eq EP5: Triphenylmethane epoxy resin, manufactured by Nippon Kayaku Co., Ltd., model number "EPPN-501HY", epoxy equivalent weight 167g / eq EP6: Naphthalene-containing novolac epoxy resin, manufactured by Nippon Kayaku Co., Ltd., model number "NC-7000L", epoxy equivalent weight 232g / eq (Isocyanate crosslinker (C)) IC1: Isocyanate crosslinking agent, manufactured by Mitsui Chemicals, Inc., model number "D-110N"

[0067] Example 1 The polyurethane resin (A) in Table 1 was dissolved in methyl ethyl ketone (MEK), and then the epoxy resin (B) in Table 1 was further added to obtain a resin composition solution. The resin composition solution was applied to the entire surface of one side of a PPS film (length: 300 mm, width: 200 mm, thickness: 25 μm, Torelina: manufactured by Toray Industries, Inc.) so that the adhesive layer would have a thickness of 20 μm after drying, and then dried at 100°C for 1 minute. Thereafter, the sheet was left to stand for 72 hours under conditions of room temperature and a relative humidity of 50%, to obtain a hot melt adhesive sheet.

[0068] The obtained hot melt adhesive sheet and a perfluorocarbon sulfonic acid resin sheet were superimposed so that the exposed surface of the adhesive layer of the hot melt adhesive sheet was in contact with one side of a perfluorocarbon sulfonic acid resin sheet (tetrafluoroethylene / perfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether] copolymer membrane (manufactured by DuPont, product name "NAFIONN-115")) (same shape as the film with the hot melt adhesive layer). Using a laminator adjusted to 140°C, the hot melt adhesive sheet and the perfluorocarbon sulfonic acid resin sheet were bonded together by thermocompression bonding to prepare an adhesive sheet.

[0069] (Comparative Example 1) The polyurethane resin (A) in Table 1 was dissolved in methyl ethyl ketone (MEK), and then the epoxy resin (B) and isocyanate crosslinking agent (C) in Table 1 were further added to obtain a resin composition solution. The resin composition solution was applied to the entire surface of one side of a PPS film (length: 300 mm, width: 200 mm, thickness: 25 μm, Torelina: manufactured by Toray Industries, Inc.) so that the adhesive layer would have a thickness of 20 μm after drying, and then dried at 100°C for 1 minute. Thereafter, the sheet was left in an oven at 40°C for 48 hours to obtain a hot melt adhesive sheet. An adhesive sheet was produced in the same manner as in Example 1 using a hot melt adhesive sheet.

[0070] Table 1 shows the compositions of the adhesive sheets in Example 1 and Comparative Example 1, and the temperatures at which the aging treatment was carried out in producing the adhesive sheets.

[0071] [Table 1]

[0072] In Example 1, which satisfied all of the constituent requirements of the present invention, an adhesive sheet having adhesiveness equivalent to that of the adhesive sheet of Comparative Example 1 was obtained without carrying out the aging treatment by heating as in Comparative Example 1.

[0073] (Examples 2 to 18, Comparative Examples 2 to 9) An adhesive sheet was prepared in the same manner as in Example 1, except that the types and amounts of polyurethane resin (A) and epoxy resin (B) were as shown in Table 2.

[0074] <Hot water resistance test 1> Test specimens measuring 10 mm wide x 80 mm long were cut out from the adhesive sheets of Examples 1 to 18 and Comparative Examples 2 to 9, and the test specimens were immersed in hot water at 95°C for 72 hours. After cooling to room temperature, the hot water resistance of each test specimen was evaluated according to the following criteria. ·Good: No peeling observed after immersion. ·△: After immersion, no peeling was observed, but some lifting was observed. ·×: Peeling was observed after immersion.

[0075] Table 2 shows the evaluation results of the hot water resistance test 1 for Examples 1 to 18 and Comparative Examples 2 to 9.

[0076] [Table 2]

[0077] As can be seen from the results in Table 2, most of the examples showed better results in terms of hot water resistance than the comparative examples.

[0078] Furthermore, in Table 2, good hot water resistance was also obtained for the adhesive sheets of Examples 9 and 10, which used epoxy resins (B) other than bisphenol A-type epoxy resins, namely triphenylmethane-type epoxy resins and naphthalene-skeleton-containing novolac-type epoxy resins.

[0079] (Reference examples 1~4) An adhesive sheet was prepared in the same manner as in Example 1, except that the moisture-curable polyurethane resin (A) and epoxy resin (B) in Table 3 were used.

[0080] <Hot water resistance test 2> Test specimens measuring 10 mm wide x 80 mm long were cut out from the adhesive sheet of each Reference Example, and the test specimens were immersed in hot water at 120°C for 24 hours. After cooling to room temperature, the hot water resistance of each test specimen was evaluated according to the following criteria. ·Good: No peeling observed after immersion. ·△: After immersion, no peeling was observed, but some lifting was observed. ·×: Peeling was observed after immersion.

[0081] The evaluation results of the hot water resistance test 2 are shown in Table 3.

[0082] [Table 3]

[0083] The results in Table 3 show that by using bisphenol A type epoxy resin as the epoxy resin in a hot melt adhesive sheet, an adhesive sheet with excellent hot water resistance can be obtained even under harsh conditions such as hot water at 120°C.

[0084] From the above, it can be seen that the present invention can provide a hot melt adhesive sheet that exhibits good adhesion to difficult-to-adhere articles even without aging treatment by heating. [Explanation of symbols]

[0085] 10 hot melt adhesive sheet, 20 membrane / electrode assembly (MEA), 201 solid electrolyte membrane, 202 positive electrode, 203 negative electrode, 10a sheet-like 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 of a hot melt adhesive is laminated on at least one surface of a sheet-like substrate, The hot melt adhesive contains a moisture-curing polyurethane resin and an epoxy resin. Hot melt adhesive sheet.

2. The content of the epoxy resin is 5 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the moisture-curable polyurethane resin, The hot melt adhesive sheet according to claim 1 .

3. The epoxy equivalent of the epoxy resin is 100 g / eq or more and 1500 g / eq or less. The hot melt adhesive sheet according to claim 1 .

4. the epoxy resin is one or more epoxy resins selected from the group consisting of triphenylmethane-type epoxy resins, bisphenol A-type epoxy resins, and naphthalene skeleton-containing novolac-type epoxy resins; The hot melt adhesive sheet according to any one of claims 1 to 3.

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