Resin composition for sealing material, sealing material using said resin composition, and solid polymer fuel cell and water electrolysis device using said sealing material

Abstract

A resin composition includes (A) an acrylic resin, (B) an epoxy resin, and (C) an epoxy resin curing agent, wherein the (A) acrylic resin has a glass transition temperature of 5-35°C, the (A) acrylic resin is a copolymer of source material monomers including (a1) methyl methacrylate, (a2) styrene, and (a3) glycidyl (meth)acrylate, the percentage of the (a3) glycidyl (meth)acrylate relative to the total quantity of the source material monomers is less than 3.0 mass%, and the total included quantity of the (B) epoxy resin and the (C) epoxy resin curing agent is 1-30 parts by mass per 100 parts by mass of the (A) acrylic resin. This resin composition can improve reworkability and adhesion between sealing material layers.

Description

Resin composition for sealing material, sealing material using said resin composition, and solid polymer fuel cell and water electrolysis device using said sealing material

[0001] The present invention relates to a resin composition for a sealing material for a polymer electrolyte fuel cell, a sealing material using the resin composition, and a polymer electrolyte fuel cell and a water electrolysis device using the sealing material.

[0002] A polymer electrolyte fuel cell (hereinafter sometimes referred to as a "fuel cell") generates electricity and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen with an oxidant gas containing oxygen. FIG. 1 shows a cross-sectional view of a cell 10, which is a constituent unit of a typical fuel cell. A typical fuel cell is constructed by stacking tens to hundreds of cells 10. The cell 10 has a sealant 16 for the purpose of fixing the electrolyte membrane 11.

[0003] For example, Patent Documents 1 and 2 propose techniques for fuel cell sealing materials.

[0004] JP 2016-94581 A JP 2015-2029 A

[0005] In recent years, there has been a demand for increasing the yield of each product in order to reduce the burden on the environment. Therefore, fuel cell sealants are required to have the ability to be repositioned after application. In this specification, this ability is sometimes referred to as "reworkability." Patent Documents 1 and 2 do not consider reworkability at all.

[0006] It is believed that the reworkability of fuel cell sealants can be improved by reducing the tackiness of the sealant layers. However, in recent years, cells have been used that have regions where the sealant layers are bonded to each other in an opposing manner, as shown in Figure 2. In such cells, reducing the tackiness of the sealant layers has led to the problem of insufficient adhesion between the sealant layers.

[0007] An object of the present invention is to provide a resin composition for a sealing material that can improve reworkability and adhesion between sealing material layers, a sealing material using the resin composition, and a solid polymer fuel cell and a water electrolysis device using the sealing material.

[0008] In order to solve the above problems, the present invention provides the following [1] to

[11] : [1] A resin composition for a sealing material, the resin composition comprising (A) an acrylic resin, (B) an epoxy resin, and (C) an epoxy resin curing agent, the (A) acrylic resin having a glass transition temperature of 5°C or more and 35°C or less, the (A) acrylic resin being a copolymer of raw material monomers including (a1) methyl methacrylate, (a2) styrene, and (a3) ​​glycidyl (meth)acrylate, the proportion of the (a3) ​​glycidyl (meth)acrylate relative to the total amount of the raw material monomers being less than 3.0 mass%, and the total content of the (B) epoxy resin and the (C) epoxy resin curing agent being 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the (A) acrylic resin. [2] The resin composition according to [1], wherein the (B) epoxy resin is at least one selected from the group consisting of a phenol novolac epoxy resin, a bisphenol A epoxy resin, and a bisphenol F epoxy resin. [3] The resin composition according to [1] or [2], wherein the (B) epoxy resin has an epoxy equivalent of 150 g / eq or more and 1500 g / eq or less. [4] The resin composition according to any one of [1] to [3], wherein the (C) epoxy resin curing agent is a polyamine-based curing agent. [5] A sealing material formed from the resin composition according to [1]. [6] A sealing material having, in this order, a first substrate, a sealing material layer, and a second substrate, wherein the sealing material layer is formed from the resin composition according to any one of [1] to [4], and at least one of the first substrate and the second substrate is peelable. [7] The sealing material according to [5] or [6], which is a sealing material for a polymer electrolyte fuel cell. [8] The sealing material according to [5] or [6], which is a sealing material for a water electrolysis device. [9] A polymer electrolyte fuel cell having a sealed portion made of the sealing material according to [7].

[10] The polymer electrolyte fuel cell according to [9], wherein the sealing material has sealing material layers formed from the resin composition according to [1], and has regions where the sealing material layers face each other and are bonded together.

[11] A water electrolysis device having a sealed portion formed by the sealing material according to [8].

[0009] The resin composition for a sealing material of the present invention, the sealing material using the resin composition, and the solid polymer fuel cell and water electrolysis device using the sealing material can have good reworkability and good adhesion between sealing material layers.

[0010] 1 is a cross-sectional view showing an example of a cell constituting a fuel cell, FIG. 2 is a cross-sectional view showing another example of a cell constituting a fuel cell, showing a part of the cell, and FIG. 3 is a cross-sectional view showing an example of a sealing material.

[0011] [Resin composition for sealing material] The resin composition for sealing material of the present invention comprises (A) an acrylic resin, (B) an epoxy resin, and (C) an epoxy resin curing agent, wherein the (A) acrylic resin has a glass transition temperature of 5°C or more and 35°C or less, the (A) acrylic resin is a copolymer of raw material monomers including (a1) methyl methacrylate, (a2) styrene, and (a3) ​​glycidyl (meth)acrylate, and the proportion of the (a3) ​​glycidyl (meth)acrylate to the total amount of the raw material monomers is less than 3.0 mol%, and the total content of the (B) epoxy resin and the (C) epoxy resin curing agent is 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the (A) acrylic resin.

[0012] <(A) Acrylic Resin> (A) Acrylic resin is a copolymer of raw material monomers including (a1) methyl methacrylate, (a2) styrene, and (a3) ​​glycidyl (meth)acrylate.

[0013] The acrylic resin (A) is a main component of the resin composition. The content of the acrylic resin (A) relative to the total amount of the resin composition is preferably 77% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less, and even more preferably 85% by mass or more and 99% by mass or less.

[0014] The (A) acrylic resin must have a glass transition temperature of 5°C or higher and 35°C or lower. If the glass transition temperature is lower than 5°C, good reworkability cannot be achieved. If the glass transition temperature is higher than 35°C, good adhesion between sealing material layers cannot be achieved. The (A) acrylic resin preferably has a glass transition temperature of 5°C or higher and 27°C or lower, and more preferably has a glass transition temperature of 5°C or higher and 20°C or lower.

[0015] The glass transition temperature of the (A) acrylic resin can be adjusted, for example, by the weight-average molecular weight of the (A) acrylic resin. Increasing the weight-average molecular weight tends to increase the glass transition temperature, while decreasing the weight-average molecular weight tends to decrease the glass transition temperature. The glass transition temperature of the (A) acrylic resin can also be adjusted by (a4) ethyl (meth)acrylate, which will be described later. Increasing the ratio of (a4) ethyl (meth)acrylate to the total amount of raw material monomers tends to decrease the glass transition temperature, while decreasing the ratio of (a4) ethyl (meth)acrylate to the total amount of raw material monomers tends to increase the glass transition temperature. In this specification, the weight-average molecular weight is a value measured by gel permeation chromatography (GPC) and converted into polystyrene equivalent.

[0016] (a1) Methyl Methacrylate: By including (a1) methyl methacrylate as a raw material monomer for the (A) acrylic resin, for example, the following effects i) to iii) can be expected. On the other hand, if the content of (a1) methyl methacrylate is too high, the hardness of the sealing material layer may increase, making it difficult for the sealing material layer to conform to the shape of the adherend. For this reason, it is preferable to adjust the content of (a1) methyl methacrylate while considering the balance between the effects i) to iii) below and the hardness of the sealing material layer. i) The glass transition temperature of the (A) acrylic resin can be finely adjusted, making it easier to control the adhesion and bonding conditions between materials with different polarities. Increasing the content of (a1) methyl methacrylate tends to increase the glass transition temperature of the (A) acrylic resin. Polar materials include electrolyte membranes for fuel cells, and non-polar materials include components other than the electrolyte of the fuel cell. ii) Since the (A) acrylic resin can be prevented from decomposing due to moisture and acid and causing a weight loss, it is possible to easily prevent a decrease in the cohesive strength and adhesive strength of the sealing material under high temperature and high humidity conditions. iii) Since the (A) acrylic resin can have a high softening point, it is possible to improve the handleability when used as a sealing material.

[0017] The content of (a1) methyl methacrylate relative to the total amount of raw material monomers is preferably 10% by mass or more and 45% by mass or less, more preferably 15% by mass or more and 40% by mass or less, and even more preferably 20% by mass or more and 35% by mass or less.

[0018] (a2) Styrene: Styrene is a non-polar component composed of CH as a constituent element, and therefore can easily improve the adhesion between materials with different polarities. Furthermore, styrene has a relatively high glass transition temperature, which can improve the cohesive strength of the resin composition, thereby making it easier to improve the heat-resistant adhesion of the resin composition. Furthermore, the inclusion of styrene can easily reduce the tackiness of the sealing material layer. On the other hand, if the content of (a2) styrene is too high, the hardness of the sealing material layer increases, which may make it difficult for the sealing material layer to conform to the shape of the adherend. Therefore, it is preferable to adjust the content of (a2) styrene in consideration of the balance between the above-mentioned effect and the hardness of the sealing material layer.

[0019] A common method for imparting heat-resistant adhesive properties to a resin composition is to blend additives such as a silane coupling agent and a tackifier into the resin. However, blending additives can cause the additives to bleed out from the sealant layer. On the other hand, the method of using (a2) styrene as a raw material monomer for (A) acrylic resin is preferred because it does not cause the bleed-out problem.

[0020] The content of (a2) styrene relative to the total amount of raw material monomers is preferably 1% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less.

[0021] (a3) Glycidyl (meth)acrylate: The (A) acrylic resin must contain less than 3.0 mol% of (a3) ​​glycidyl (meth)acrylate relative to the total amount of raw material monomers. If the content of (a3) ​​glycidyl (meth)acrylate is 3.0 mol% or more, the adhesion between the sealing material layers cannot be improved. On the other hand, if the raw material monomers of the (A) acrylic resin do not contain (a3) ​​glycidyl (meth)acrylate, the reworkability cannot be improved.

[0022] The content of (a3) ​​glycidyl (meth)acrylate relative to the total amount of raw material monomers is preferably 0.1% by mass or more and less than 3.0% by mass, and more preferably 0.5% by mass or more and 2.0% by mass or less.

[0023] As the glycidyl (meth)acrylate, either glycidyl acrylate or glycidyl methacrylate can be suitably used, but from the viewpoint of versatility in polymerization, it is more preferable to use glycidyl methacrylate.

[0024] (a4) Ethyl (meth)acrylate: The acrylic resin (A) preferably further contains ethyl (meth)acrylate (a4) as a raw material monomer. By including ethyl (meth)acrylate (a4), the glass transition temperature of the acrylic resin (A) can be easily set to 35° C. or lower.

[0025] The content of (a4) ethyl (meth)acrylate relative to the total amount of raw material monomers is preferably 30% by mass or more and 95% by mass or less, more preferably 40% by mass or more and 85% by mass or less, and even more preferably 50% by mass or more and 75% by mass or less, in order to easily adjust the glass transition temperature of (A) acrylic resin to 5°C or more and 35°C or less.

[0026] As the ethyl (meth)acrylate, either ethyl acrylate or ethyl methacrylate can be suitably used, but it is more preferable to use ethyl acrylate from the viewpoints that it is easily copolymerizable, has industrial versatility, and its softening point can be easily adjusted.

[0027] Other Monomers The raw material monomers for the acrylic resin (A) may further contain other monomers, such as acrylic acid, methacrylic acid, 2-hydroxymethacrylate, acrylamide, and methacrylamide.

[0028] (A) The acrylic resin is a copolymer obtained by copolymerizing raw material monomers. Examples of copolymerization methods include suspension polymerization, emulsion polymerization, and solution polymerization. Among these copolymerization methods, suspension polymerization is preferred because it can produce polymers with narrow molecular weight distributions and low residual monomer content, high molecular weight polymers, no emulsifier is required, resulting in low impurities, and copolymer resins with excellent water resistance and heat resistance can be easily obtained. For example, in the case of suspension polymerization, polymerization conditions are preferably 50 to 80°C and 2 to 24 hours. The copolymer may be in any form, such as alternating, random, block, or graft.

[0029] In the aqueous suspension polymerization, one or more suspension stabilizers can be used, examples of which include water-soluble polymers such as polyvinyl alcohol, partially saponified polyvinyl alcohol, polyvinylpyrrolidone, (meth)acrylates, polyacrylamide, partially saponified polyacrylamide, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose, and inorganic salt powders such as calcium phosphates and calcium carbonate.

[0030] It is preferable that the polymerization initiator generates an oil-soluble polymerization initiation radical species after decomposition. Typical examples of the radical polymerization initiator include azo radical polymerization initiators and peroxide radical polymerization initiators. Examples of the azo radical polymerization initiator include 2,2'-azobispropane, 2,2'-dichloro-2,2'-azobispropane, 1,1'-azo(methylethyl)diacetate, 2,2'-azobis(2-amidinopropane) hydrochloride, 2,2'-azobis(2-aminopropane) nitrate, 2,2'-azobisisobutane, 2,2'-azobisisobutylamide, 2,2'-azobisisobutyronitrile, methyl 2,2'-azobis-2-methylpropionate, 2,2' -Dichloro-2,2'-azobisbutane, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobisisobutyric acid dimethyl, 1,1'-azobis(1-methylbutyronitrile-3-sodium sulfonate), 2-(4-methylphenylazo)-2-methylmalonodinitrile, 4,4'-azobis-4-cyanovaleric acid, 3,5-dihydroxymethylphenylazo-2-allylmalonodinitrile, 2,2'-azobis-2-methylvaleronitrile, 4,4'-azobis Dimethyl 2,2'-azobis-4-cyanovalerate, 2,2'-azobis-2,4-dimethylvaleronitrile, 1,1'-azobiscyclohexanenitrile, 2,2'-azobis-2-propylbutyronitrile, 1,1'-azobiscyclohexanenitrile, 2,2'-azobis-2-propylbutyronitrile, 1,1'-azobis-1-chlorophenylethane, 1,1'-azobis-1-cyclohexanecarbonitrile, 1,1'-azobis-1-cycloheptanenitrile, 1 , 1'-azobis-1-phenylethane, 1,1'-azobiscumene, 4-nitrophenylazobenzyl ethyl cyanoacetate, phenylazodiphenylmethane, phenylazotriphenylmethane, 4-nitrophenylazotriphenylmethane, 1,1'-azobis-1,2-diphenylethane, poly(bisphenol A-4,4'-azobis-4-cyanopentanoate), poly(tetraethylene glycol-2,2'-azobisisobutyrate), and the like.Examples of the peroxide radical polymerization initiator include acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, 2-chlorobenzoyl peroxide, 3-chlorobenzoyl peroxide, 4-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, 4-bromomethylbenzoyl peroxide, lauroyl peroxide, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, tert-butyl triphenylperacetate, tert-butyl hydroperoxide, tert-butyl performate, tert-butyl peracetate, tert-butyl benzoate, tert-butyl perphenylacetate, tert-butyl 4-methoxyacetate, and tert-butyl per-N-(3-toluyl)carbamate. Examples of the polymerization initiator include peroxides such as benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, and methyl ethyl ketone peroxide.

[0031] Furthermore, a mercapto compound can be added as a chain transfer agent, examples of which include chain transfer agents having a hydroxyl group, such as mercaptoethanol, mercaptopropanol, mercaptobutanol, mercaptopropanediol, mercaptobutanediol, hydroxybenzenethiol and derivatives thereof; 1-butanethiol, butyl-3-mercaptopropionate, methyl-3-mercaptopropionate, 2,2-(ethylenedioxy)diethanethiol, ethanethiol, 4-methylbenzenethiol, dodecyl mercaptan, propanethiol, butanethiol, pentanethiol, 1-octanethiol, cyclopentanethiol, cyclohexanethiol, thioglycerol, and 4,4-thiobisbenzenethiol.

[0032] The weight-average molecular weight of the (A) acrylic resin is preferably 100,000 or more and 1,000,000 or less, more preferably 150,000 or more and 800,000 or less, and even more preferably 200,000 or more and 600,000 or less. By setting the weight-average molecular weight to 100,000 or more, it is possible to easily improve adhesive strength in high-temperature environments. By setting the weight-average molecular weight to 1,000,000 or less, it is possible to easily suppress gelation during polymerization.

[0033] The (A) acrylic resin preferably has an epoxy equivalent of 2000 g / eq or more and 30,000 g / eq or less, and more preferably 4000 g / eq or more and 20,000 g / eq or less. By making the (A) acrylic resin have an epoxy equivalent of 2000 g / eq or more, it is possible to easily improve the adhesion between the sealing material layers. By making the (A) acrylic resin have an epoxy equivalent of 30,000 g / eq or less, it is possible to easily increase the cohesive strength of the sealing material layer. By increasing the cohesive strength of the sealing material layer, it is possible to easily suppress foaming of the sealing material layer when moisture contained in the electrolyte membrane is gasified and released during heat pressing.

[0034] The resin composition of the present invention must contain, in addition to the above-mentioned (A) acrylic resin, a (B) epoxy resin and a (C) epoxy resin curing agent. Furthermore, the resin composition of the present invention must have a total content of the (B) epoxy resin and the (C) epoxy resin curing agent of 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the (A) acrylic resin. By making the total content of the (B) epoxy resin and the (C) epoxy resin curing agent 1 part by mass or more, it is possible to easily improve reworkability. By making the total content of the (B) epoxy resin and the (C) epoxy resin curing agent 30 parts by mass or less, it is possible to easily improve adhesion between sealing material layers. The total content of the (B) epoxy resin and the (C) epoxy resin curing agent is preferably 1 part by mass or more and 25 parts by mass or less, more preferably 1 part by mass or more and 20 parts by mass or less, per 100 parts by mass of the (A) acrylic resin.

[0035] The ratio of the active hydrogen equivalent (g / eq) of the epoxy resin curing agent (C) to the epoxy equivalent (g / eq) of the epoxy resin (B) is preferably 0.8 or more and 1.2 or less.

[0036] <(B) Epoxy Resin> The (B) epoxy resin may be at least one selected from phenol novolac epoxy resins, bisphenol A epoxy resins, and bisphenol F epoxy resins. Among these, phenol novolac epoxy resins are preferred because they have low water absorption and therefore excellent stability over time of the adhesiveness of the sealing material layer.

[0037] The epoxy equivalent of the (B) epoxy resin is preferably 150 g / eq or more and 1500 g / eq or less, and more preferably 150 g / eq or more and 1000 g / eq or less. By setting the epoxy equivalent of the (B) epoxy resin to 1500 g / eq or less, it becomes easier to uniformly disperse the (B) epoxy resin in the (A) acrylic resin.

[0038] The weight-average molecular weight of the (B) epoxy resin is preferably 250 or more and 5000 or less, and more preferably 300 or more and 3000 or less. By setting the weight-average molecular weight to 5000 or less, it becomes easier to uniformly disperse the (B) epoxy resin in the (A) acrylic resin.

[0039] <(C) Epoxy Resin Curing Agent> Examples of the (C) epoxy resin curing agent include polyamine-based curing agents, acid anhydride-based curing agents, thiol-based curing agents, and latent curing agents such as imidazole compounds, ketimine compounds, and dicyandiamide. Among these, polyamine-based curing agents are preferred because they can easily lower the reaction temperature.

[0040] Examples of polyamine-based curing agents include aliphatic polyamines, aromatic polyamines, polyamidoamines, etc. Among these, aliphatic polyamines are preferred because they can easily lower the reaction temperature.

[0041] The polyamine curing agent preferably has an active hydrogen equivalent of 50 g / eq or more and 700 g / eq or less, and more preferably 75 g / eq or more and 500 g / eq or less. By setting the active hydrogen equivalent of the polyamine curing agent to 50 g / eq or more, the pot life of the resin composition can be easily extended. By setting the active hydrogen equivalent of the polyamine curing agent to 700 g / eq or less, the reaction with the (B) epoxy resin can easily proceed, and a resin composition with better durability can be obtained.

[0042] (Other Additives) The resin composition may contain additives such as pigments, flame retardants, ultraviolet absorbers, antioxidants, antistatic agents, and silane coupling agents, as long as the effects of the present invention are not impaired.

[0043] [Sealing material] The sealing material of the present invention is formed from the resin composition of the present invention described above. The form of the sealing material is preferably a solid such as a particle or sheet, and from the viewpoint of handling, a sheet form is more preferable. When forming the sealing material of the present invention into a sheet form, from the viewpoint of handling, it is preferable to form a sealing material layer by coating a sealing material layer-forming composition obtained by dissolving the resin composition of the present invention described above in a solvent on a substrate and drying it.

[0044] The following embodiments can be mentioned as embodiments of the sealing material of the present invention. Fig. 3 is a cross-sectional view showing the following embodiment. The sealing material of the following embodiment is preferably in the form of a sheet. <Embodiment of sealing material> A sealing material having a first substrate, a sealing material layer, and a second substrate in this order, wherein the sealing material layer is formed from the resin composition of the present invention described above, and at least one of the first substrate and the second substrate is peelable.

[0045] Examples of the first substrate and the second substrate include plastic films such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polystyrene, triacetyl cellulose, poly(meth)acrylate, polyvinyl chloride, and polyphenylene sulfide; paper; and the like. Among these, plastic films are preferred, and polyethylene naphthalate films are more preferred. The thickness of the first substrate and the second substrate is preferably 10 μm or more and 100 μm or less, more preferably 25 μm or more and 75 μm or less.

[0046] At least one of the first substrate and the second substrate is preferably subjected to a release treatment on its surface to facilitate peeling from the sealing material layer. The release agent for the release treatment is preferably a non-silicone release agent such as polyolefin, in order to suppress adverse effects caused by migration of the release component to the electrolyte membrane and the sealing material layer.

[0047] The thickness of the sealing material layer is preferably 10 μm or more and 500 μm or less, and more preferably 20 μm or more and 200 μm or less.

[0048] The sealing material of the present invention can be used in sealing portions of fuel cells, more specifically, in sealing portions of cells that constitute a fuel cell. During use, for example, the sealing material is heated to seal the sealing portions of the cells. The sealing material of the present invention can also be used in sealing portions of water electrolysis devices, more specifically, in sealing portions of cells that constitute a water electrolysis device.

[0049] [Solid Polymer Electrolyte Fuel Cell] The solid polymer electrolyte fuel cell of the present invention has a sealed portion formed by the sealing material of the present invention. FIG. 1 is a cross-sectional view showing an example of a cell constituting a typical fuel cell. The cell 10 is composed of a composite (MEA: Membrane and Electrode Assembly) consisting of a solid polymer electrolyte membrane 11 and a pair of electrodes (anode and cathode) 12, 13 arranged on both sides of the membrane. Separators (14, 15) are arranged on both sides of the composite and have gas flow channels (14a, 15a) for supplying fuel gas and oxidant gas, respectively. A typical fuel cell is constructed by stacking tens to hundreds of cells 10, sandwiching the stack between end plates via current collector plates and insulating plates, and fastening them from both ends with fastening bolts. The cell 10 in FIG. 1 does not have an area where the sealing material layers face each other and are bonded to each other. However, in recent years, a cell 10 has also been used that has regions where the sealing material layers are bonded to each other in a facing relationship, as shown in FIG.

[0050] The sealing material of the present invention can be suitably used as a sealing material in the above-mentioned general-purpose fuel cell, and in particular, as a sealing material in a fuel cell having an area where sealing material layers are bonded to each other in an opposing manner.

[0051] [Water Electrolysis Apparatus] The water electrolysis apparatus of the present invention comprises a sealed portion formed by the sealing material of the present invention. The sealed portion is preferably a sealed portion of a cell constituting the water electrolysis apparatus.

[0052] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0053] 1. Measurement and Evaluation The sealing materials of the examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Table 2.

[0054] 1-1. Reworkability The sealing materials of the Examples and Comparative Examples were cut to a width of 2.5 cm and a length of 12.5 cm to prepare samples. A PET film (thickness 25 μm, width 2.5 cm, length 12.5 cm) was superimposed on the sealing material layer of the cut sample and laminated under room temperature to prepare Evaluation Sample 1. Evaluation Sample 1 was left in a room temperature atmosphere for 1 minute, and then the PET film was pulled at an angle of 90°, at a speed of 100 mm / min under room temperature conditions using a Tensilon tensile tester to measure the peel strength between the sealing material layer and the PET film. The smaller the peel strength, the better the reworkability. A peel strength of 0.050 N / mm or less is considered to be good reworkability.

[0055] 1-2. Adhesion Strength 1 (Adhesion Strength Between Sealing Material Layers) Two samples of each sealing material from the Examples and Comparative Examples were cut to a width of 5 cm and a length of 10 cm. The two cut samples were overlapped with the sealing materials facing each other and temporarily laminated with a heated roller at 100°C. Then, they were permanently bonded by heat pressing at 140°C, 0.2 MPa, and 30 seconds. After this bonding, the samples were cut into strips with a width of 1 cm and a length of 10 cm to prepare Evaluation Sample 2. One of the cut samples from Evaluation Sample 2 was pulled at an angle of 180°, a speed of 10 mm / min, and in a room temperature atmosphere using a Tensilon tensile tester to measure the peel strength between the sealing material layers. A peel strength of 0.20 N / mm or more indicates good adhesion between the sealing material layers.

[0056] 1-3. Adhesion Strength 2 (Adhesion Strength Between Sealing Material Layer and Electrolyte Membrane) Two samples were prepared by cutting the sealing materials of the Examples and Comparative Examples to a width of 5 cm and a length of 10 cm. The two cut samples and the electrolyte membrane were overlapped in the following order, laminated temporarily with a heated roller at 100°C, and then permanently bonded by heat pressing at 140°C, 0.2 MPa, and 30 seconds. After this bonding, the sample was cut into a strip of 1 cm width and 10 cm length to prepare Evaluation Sample 3. The electrolyte membrane used was "Nafion NRE-212 (trade name), 50 μm thick" manufactured by DuPont. One cut sample of Evaluation Sample 3 was pulled at an angle of 180°, a speed of 10 mm / min, and in a room temperature atmosphere using a Tensilon tensile tester, and the peel strength between the sealing material layer and the electrolyte membrane of one cut sample was measured. A peel strength of 0.20 N / mm or more can be said to indicate good adhesion between the sealing material layer and the electrolyte membrane. In Comparative Example 7, the sealing material layer of the sample was foamed when the evaluation sample was produced, so the peel strength could not be measured. <Lamination order> First substrate of the first cut sample, sealing material layer of the first cut sample, electrolyte membrane, sealing material layer of the second cut sample, first substrate of the second cut sample

[0057] 1-4. Adhesion Strength 3 (Hot Water Durability Adhesion Strength Between Sealing Material Layer and Electrolyte Membrane) Evaluation Sample 3 was immersed in a heat-resistant bottle containing ion-exchanged water, and then the heat-resistant bottle containing the sample was placed in a 95°C oven for 500 hours. After 500 hours, Evaluation Sample 3 was removed from the 95°C hot water and left in a room temperature atmosphere for 24 hours. One of the cut samples was then pulled at an angle of 180°, at a speed of 10 mm / min, and in a room temperature atmosphere using a Tensilon tensile tester, and the peel strength between the sealing material layer and the electrolyte membrane of one of the cut samples was measured. However, peel strength could not be measured for Comparative Examples 2 and 3, where the electrolyte membrane peeled off after the evaluation sample was removed from the hot water. A peel strength of 0.50 N / mm or more indicates good adhesion between the sealing material layer and the electrolyte membrane. Peel strength could not be measured for Comparative Example 7 because the sealing material layer of the sample foamed during the preparation of the evaluation sample.

[0058] Theoretical Tg The theoretical Tg of the acrylic resin (A) obtained in the examples and comparative examples was calculated using the following FOX formula. The FOX formula calculates the glass transition temperature of the homopolymer of each monomer constituting a polymer consisting of n kinds of monomers as Tg ｉ (K), and the mass fraction of each monomer is W ｉ Let (W １ +W ２ +...+W ｉ +…W ｎ = 1. (FOX formula) 1 / Tg = W １ / Tg １ +W ２ / Tg ２ +...+W ｉ / Tg ｉ +...+W ｎ / Tg ｎ

[0059] 2. Preparation of Sealing Material Example 1 [Preparation of (A) Acrylic Resin] A 1-liter separable flask was charged with a homogeneous mixture containing 200 parts by weight of water containing 0.2% by weight of polyvinyl alcohol, 10 parts by weight of styrene monomer (ST), 25 parts by weight of methyl methacrylate monomer (MMA), 1 part by weight of glycidyl methacrylate monomer (GMA), 64 parts by weight of ethyl acrylate monomer (EA), 0.1 parts by weight of benzoyl peroxide as a polymerization initiator, and a chain transfer agent for molecular weight adjustment. The mixture was heated to 70°C while stirring under a nitrogen atmosphere and subjected to suspension polymerization for 4 hours. Water was then removed from the suspension by decantation. The solid matter was washed with water while suction filtering, and the water was removed. The mixture was then vacuum dried at 60°C to obtain Acrylic Resin C, the acrylic resin (A) used in Example 1. The weight-average molecular weight of Acrylic Resin C was 31 x 10 ４ The monomer composition and molecular weight are shown in Table 1.

[0060] ​[Preparation of Resin Composition] (A) Acrylic resin, (B) Epoxy resin, and (C) Epoxy resin curing agent were mixed in the proportions shown in Table 2 to obtain the resin composition of Example 1. In Table 2, the "Type" of (B) Epoxy resin "1" is a bisphenol A type epoxy resin (weight average molecular weight 370, manufactured by Mitsubishi Chemical Corporation, trade name jER828, epoxy equivalent 185), and the "Type" of epoxy resin "2" is a phenol novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name NC-3000, epoxy equivalent 270). In Table 1, the (C) Epoxy resin curing agent is a polyamine type curing agent (manufactured by Huntsman, trade name JEFFAMINE D-400, active hydrogen equivalent 100).

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[0062] Examples 2 to 13, Comparative Examples 1 to 8 Resin compositions and sealing materials of Examples 2 to 13 and Comparative Examples 1 to 8 were obtained in the same manner as in Example 1, except that the compounding ratio and weight average molecular weight of the raw material monomers of (A) acrylic resin were set to the values ​​in Table 1, and the compounding ratio of (A) acrylic resin, (B) epoxy resin, and (C) epoxy resin curing agent in the resin composition was set to the values ​​in Table 2. The weight average molecular weight of each Example and Comparative Example was adjusted by the amount of chain transfer agent.

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[0065] From the results in Tables 1 and 2, it can be confirmed that the resin compositions for the sealing materials of the examples can improve reworkability and also improve adhesion between the sealing material layers (adhesion strength 1). Furthermore, it can be confirmed that the resin compositions for the sealing materials of the examples can improve adhesion between the sealing material layer and the electrolyte membrane (adhesion strengths 2 and 3).

[0066] 10: Cell 11: Electrolyte membrane 12, 13: Electrodes 14, 15: Separators 14a, 15a: Gas flow passages 16: Sealing material 16a: First substrate 16b: Sealing material layer 16c: Second substrate

Claims

1. A resin composition for a sealing material, comprising: (A) an acrylic resin, (B) an epoxy resin, and (C) an epoxy resin curing agent; the (A) acrylic resin has a glass transition temperature of 5°C or higher and 35°C or lower; the (A) acrylic resin is a copolymer of raw material monomers including (a1) methyl methacrylate, (a2) styrene, and (a3) ​​glycidyl (meth)acrylate; a ratio of the (a3) ​​glycidyl (meth)acrylate to a total amount of the raw material monomers is less than 3.0 mass%; and the combined content of the (B) epoxy resin and the (C) epoxy resin curing agent is 1 part by mass or higher and 30 parts by mass or lower per 100 parts by mass of the (A) acrylic resin.

2. The resin composition according to claim 1, wherein the epoxy resin (B) is at least one selected from the group consisting of phenol novolac type epoxy resins, bisphenol A type epoxy resins and bisphenol F type epoxy resins.

3. The resin composition according to claim 1, wherein the epoxy equivalent of the epoxy resin (B) is 150 g / eq or more and 1500 g / eq or less.

4. The resin composition according to claim 1, wherein the epoxy resin curing agent (C) is a polyamine-based curing agent.

5. A sealing material formed from the resin composition according to claim 1.

6. A sealing material having a first substrate, a sealing material layer, and a second substrate in this order, the sealing material layer being formed from the resin composition described in claim 1, and at least one of the first substrate and the second substrate being peelable.

7. The sealing material according to claim 5 or 6, which is a sealing material for a polymer electrolyte fuel cell.

8. The sealing material according to claim 5 or 6, which is a sealing material for a water electrolysis device.

9. A polymer electrolyte fuel cell having a sealing portion formed by the sealing material according to claim 7.

10. A solid polymer fuel cell as described in claim 9, wherein the sealing material within the solid polymer fuel cell has a sealing material layer formed from the resin composition described in claim 1, and has an area in which the sealing material layers are bonded to each other facing each other.

11. A water electrolysis device having a sealing portion formed by the sealing material according to claim 8.

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