Method for manufacturing multilayer structure, and multilayer structure

Abstract

The present invention provides a novel method for manufacturing a multilayer structure that can be used for a member of an electrochemical device such as a fuel cell or a water electrolysis apparatus. The method for manufacturing a multilayer structure according to the present invention comprises: disposing, on a first laminate that is provided with a release liner and a first electrolyte film that contains a hydroxyl group-containing polymer, a second electrolyte film that has an acid content of 0.8 meq / g or more; and forming a second laminate that includes the release liner, the first electrolyte membrane, and the second electrolyte membrane in the given order. As an example, the second laminate is formed by a thermocompression bonding process in which the first laminate and the second electrolyte membrane are heated and compressed.

Description

Manufacturing method of a multilayer structure and multilayer structure

[0001] This invention relates to a method for manufacturing a multilayer structure and to a multilayer structure.

[0002] In recent years, hydrogen has attracted attention as a CO2-free energy source. Methods for producing hydrogen include alkaline water electrolysis and polymer electrolyte membrane (PEM) water electrolysis.

[0003] Polymer electrolyte fuel cells (PEFCs) have advantages such as being able to operate at lower temperatures than other fuel cells and having a high power density, and are expected to become widespread in the future.

[0004] Fuel cells and water electrolysis devices, which are the reverse process of fuel cells, share many commonalities in their basic cell structure and elemental technologies. For example, various electrochemical devices such as polymer fuel cells and water electrolysis devices have a diaphragm between the anode and cathode, and ion-conductive polymer electrolyte membranes tend to be used as this diaphragm.

[0005] Furthermore, in recent years, there has been research into using multilayer structures having an electrolyte membrane containing a hydroxyl group-containing polymer such as polyvinyl alcohol laminated on top of other electrolyte membranes as components for fuel cells (for example, Patent Document 1).

[0006] Japanese Patent Publication No. 2023-106794

[0007] There is a need for new manufacturing methods for multilayer structures that can be used as components for electrochemical devices such as fuel cells and water electrolyzers.

[0008] The present invention provides a method for manufacturing a multilayer structure, comprising arranging a second electrolyte membrane having an acid content of 0.8 meq / g or more on a first laminate comprising a peel-off liner and a first electrolyte membrane containing a hydroxyl group polymer, thereby forming a second laminate comprising the peel-off liner, the first electrolyte membrane, and the second electrolyte membrane in this order.

[0009] Furthermore, the present invention provides a multilayer structure comprising, in this order, a peelable liner, a first electrolyte membrane containing a hydroxyl group-containing polymer, and a second electrolyte membrane having an acid content of 0.8 meq / g or more.

[0010] According to the present invention, a novel method for manufacturing multilayer structures that can be used as components for electrochemical devices such as fuel cells and water electrolyzers can be provided.

[0011] This is a schematic cross-sectional view showing the multilayer structure of Embodiment 1. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 1. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 1. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 1. This is a diagram illustrating an alternative manufacturing method for the multilayer structure of Embodiment 1. This is a schematic cross-sectional view showing the multilayer structure of Embodiment 2. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 2. This is a diagram illustrating an alternative manufacturing method for the multilayer structure of Embodiment 2. This is a schematic cross-sectional view showing the multilayer structure of Embodiment 3. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 3. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 3. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 3. This is a schematic cross-sectional view showing the multilayer structure of Embodiment 4. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 4. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 4. This is a diagram illustrating the manufacturing method of the multilayer structure of Embodiment 4. This is a schematic cross-sectional view showing the multilayer structure of Embodiment 5.

[0012] A method for manufacturing a multilayer structure according to a first aspect of the present invention includes arranging a second electrolyte membrane having an acid content of 0.8 meq / g or more on a first laminate comprising a peel liner and a first electrolyte membrane containing a hydroxyl group polymer, thereby forming a second laminate comprising the peel liner, the first electrolyte membrane and the second electrolyte membrane in this order.

[0013] In a second aspect of the present invention, for example, in the manufacturing method according to the first aspect, the second laminate is formed by a heat-pressing process in which the first laminate and the second electrolyte membrane are heat-pressed together.

[0014] In a third embodiment of the present invention, for example, in the manufacturing method according to the second embodiment, the temperature of the heat-pressing treatment is 60°C to 150°C.

[0015] In a fourth embodiment of the present invention, for example, in the manufacturing method according to the second or third embodiment, the peel liner has a softening point higher than the temperature of the heat-sealing treatment.

[0016] In a fifth embodiment of the present invention, for example, in a manufacturing method according to any one of the first to fourth embodiments, the hydroxyl group-containing polymer includes polyvinyl alcohol.

[0017] In a sixth aspect of the present invention, for example, in a manufacturing method according to any one of the first to fifth aspects, the first electrolyte membrane further comprises a proton-conducting polymer.

[0018] In a seventh aspect of the present invention, for example, a manufacturing method according to any one of the first to sixth aspects further includes arranging the first electrolyte membrane on the peel liner to form the first laminate.

[0019] In the eighth aspect of the present invention, for example, in the manufacturing method according to the seventh aspect, the first electrolyte membrane is placed on the peeling liner by applying a solution containing the hydroxyl group-containing polymer and water onto the peeling liner and drying the resulting coating film.

[0020] In the ninth aspect of the present invention, for example, in the manufacturing method according to the eighth aspect, the content of the hydroxyl group-containing polymer in the solution is 0.10 wt% to 80.0 wt%.

[0021] In the tenth embodiment of the present invention, for example, in the manufacturing method according to any one of the first to ninth embodiments, the contact angle of water with the surface of the peel liner is 100° or less.

[0022] In the eleventh aspect of the present invention, for example, in a manufacturing method according to any one of the first to tenth aspects, in the second laminate, the peeling force P1 between the peeling liner and the first electrolyte membrane is lower than the peeling force P2 between the first electrolyte membrane and the second electrolyte membrane.

[0023] In a twelfth aspect of the present invention, for example, a manufacturing method according to any one of the first to eleventh aspects further includes peeling the release liner from the second laminate to form a third laminate comprising the first electrolyte membrane and the second electrolyte membrane.

[0024] In a thirteenth aspect of the present invention, for example, a manufacturing method according to the twelfth aspect further includes arranging a third electrolyte membrane having an acid content of 0.8 meq / g or more on the third laminate, thereby forming a fourth laminate comprising the third electrolyte membrane, the first electrolyte membrane, and the second electrolyte membrane in that order.

[0025] In a fourteenth aspect of the present invention, for example, a manufacturing method according to any one of the first to thirteenth aspects further includes forming a catalyst layer on the second electrolyte membrane.

[0026] A multilayer structure according to a 15th aspect of the present invention comprises, in this order: a peelable liner; a first electrolyte membrane containing a hydroxyl group-containing polymer; and a second electrolyte membrane having an acid content of 0.8 meq / g or more.

[0027] The details of the present invention will be described below, but the following description is not intended to limit the present invention to any particular embodiment.

[0028] <Embodiment of Method for Manufacturing a Multilayer Structure> The method for manufacturing a multilayer structure according to this embodiment includes forming a second laminate comprising a peel liner and a first electrolyte membrane containing a hydroxyl group-containing polymer, on which a second electrolyte membrane having an acid content of 0.8 meq / g or more is placed, thereby forming a second laminate comprising the peel liner, the first electrolyte membrane, and the second electrolyte membrane in this order (forming step A1). In this specification, "multilayer structure" means a laminate comprising at least the first electrolyte membrane and the second electrolyte membrane.

[0029] In this specification, the acid content refers to the value for the electrolyte membrane in a dry state. "Dry state" means that the solvent content, such as water, in the electrolyte membrane is 0.1 wt% or less (preferably 0.01 wt% or less). The acid content of the electrolyte membrane can be considered as the ion exchange capacity. A detailed method for measuring the acid content will be described later in the Examples section.

[0030] Hereinafter, multilayer structures of Embodiments 1 to 5, which are preferred examples of this embodiment, and their manufacturing methods will be described with reference to Figures 1 to 11. Elements common to Embodiments 1 to 5 are given the same reference numerals, and their descriptions may be omitted. The descriptions of Embodiments 1 to 5 can be applied to each other as long as they do not conflict with the technical standards. Furthermore, Embodiments 1 to 5 may be combined with each other as long as they do not conflict with the technical standards.

[0031] [Embodiment 1] As shown in Figure 1, the multilayer structure 10A of Embodiment 1 comprises, in this order, a peel liner 5, a first electrolyte membrane 1 containing a hydroxyl group-containing polymer, and a second electrolyte membrane 2 having an acid content of 0.8 meq / g or more. It is preferable that the first electrolyte membrane 1 is in direct contact with the peel liner 5 and the second electrolyte membrane 2, respectively. The multilayer structure 10A has the same structure as the second laminate 21A formed by the formation step A1 described above. The multilayer structure 10A can be used as a component for producing the multilayer structure 10B of Embodiment 2, which will be described later.

[0032] The multilayer structure 10A may further include other members besides those described above. Examples of other members include a protective film that protects the second electrolyte membrane 2 and a catalyst layer, which will be described later in Embodiment 4.

[0033] As described above, the multilayer structure 10A can be manufactured by performing the forming process A1. More specifically, the multilayer structure 10A can be manufactured by the following method. First, a peel liner 5 is prepared as shown in Figure 2A. The peel liner 5 is not particularly limited as long as it can be peeled off from the multilayer structure 10A after the multilayer structure 10A has been manufactured. The peel liner 5 is preferably a membrane that does not function as an electrolyte membrane (non-electrolyte membrane), and more preferably a membrane that does not have ion exchange properties (non-ion exchange membrane). In particular, it is preferable that the peel liner 5 substantially does not contain resin having ion exchange groups such as sulfonic acid groups.

[0034] Examples of the release liner 5 include a resin-containing film (resin film); paper; and a sheet containing a metal material such as aluminum or stainless steel, with resin film being preferred. The resin film preferably contains resin as its main component and may be composed substantially of resin alone. In this specification, "main component" means the component that is present in the largest amount by weight in the release liner 5. The resin film may further contain other components besides resin.

[0035] In particular, it is preferable that the peel liner 5 has a softening point higher than the temperature of the heat-sealing treatment described later. In this case, it is possible to suppress an excessive increase in the peeling force between the peel liner 5 and the first electrolyte membrane 1 after the heat-sealing treatment. The softening point of the peel liner 5 is, for example, 70°C or higher, and may be 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, and even 150°C or higher. The upper limit of the softening point of the peel liner 5 is not particularly limited, and may be, for example, 200°C or lower, and may be 180°C or lower. In some cases, the softening point of the peel liner 5 may be less than 70°C.

[0036] In this specification, the softening point of the peel liner 5 is defined as the value measured in accordance with JIS K7196:2012 "Test method for softening temperature of thermoplastic plastic films and sheets by thermomechanical analysis". Specifically, the measurement is performed using a thermomechanical analyzer (TMA) (indenter tip diameter 1.0 mm) with a load of 50 g and a heating rate of 5 °C / min in needle penetration mode. In the TMA curve obtained therefrom, the point of intersection of a straight line obtained by extending the straight portion observed on the temperature side below the point where the indenter begins to penetrate towards the temperature side and a straight line obtained by extending the tangent of the portion where the penetration speed is maximum towards the temperature side is defined as the needle penetration temperature, and this needle penetration temperature is defined as the softening temperature.

[0037] Examples of the resin contained in the release liner 5 include polyolefin resins such as polyethylene, polypropylene, polybutene, polybutadiene, and polymethylpentene; and polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. The release liner 5 preferably contains at least one selected from the group consisting of polyethylene terephthalate and polypropylene, and particularly preferably contains polyethylene terephthalate.

[0038] The surface 5a of the release liner 5 preferably has a small water contact angle. A surface 5a with a small water contact angle tends to allow easy formation of the first electrolyte membrane 1 on said surface 5a. Specifically, as described later, when the first electrolyte membrane 1 is formed using a solution containing a hydroxyl group-containing polymer and water, the surface 5a with a small water contact angle is less likely to repel the solution. The water contact angle on the surface 5a of the release liner 5 is preferably 100° or less, and may be 90° or less, 80° or less, or even 70° or less. The lower limit of the water contact angle on the surface 5a is not particularly limited, and is, for example, 1° or more, and may be 5° or more, 10° or more, 30° or more, 50° or more, or even 60° or more. The water contact angle can be evaluated by the sessile drop method specified in Japanese Industrial Standards (JIS) R3257:1999.

[0039] The surface 5a of the release liner 5 may be subjected to a release treatment, but it is preferable that no release treatment is performed.

[0040] The thickness of the release liner 5 is not particularly limited, and is, for example, 5 μm to 100 μm, preferably 10 μm to 50 μm.

[0041] Next, the first electrolyte membrane 1 is placed on the release liner 5. Thereby, a first laminate 20 (FIG. 2C) including the release liner 5 and the first electrolyte membrane 1 can be formed. In other words, the manufacturing method of the present embodiment may further include arranging the first electrolyte membrane 1 on the release liner 5 to form the first laminate 20 (formation step A0).

[0042] The forming step A0 can be performed by, for example, the following method. First, a solution S containing the material of the first electrolyte membrane 1 is prepared. This solution S preferably contains a hydroxyl group-containing polymer and water. The hydroxyl group-containing polymer is a polymer containing at least one hydroxyl group. It is preferable that the hydroxyl group-containing polymer imparts gas barrier properties to a film formed only of the polymer.

[0043] The weight-average molecular weight of the hydroxyl group-containing polymer is not particularly limited, for example, it is 300 or more, may be 500 or more, 1000 or more, 5000 or more, 10000 or more, or even 50000 or more. The upper limit of the weight-average molecular weight of the hydroxyl group-containing polymer is, for example, 1,000,000 or less, and may be 500,000 or less. Furthermore, the weight-average molecular weight per hydroxyl group contained in the hydroxyl group-containing polymer (hydroxyl group equivalent) is, for example, 30 g / eq. to 100 g / eq.

[0044] In a preferred embodiment, the hydroxyl group-containing polymer comprises polyvinyl alcohol (PVA). In this case, the saponification degree of PVA is, for example, 90 mol% or more, may be 95 mol% or more, or even 99 mol% or more. PVA may be a completely saponified product with a saponification degree of 100 mol%.

[0045] The hydroxyl group-containing polymer is not limited to PVA. The hydroxyl group-containing polymer may comprise a polysaccharide such as pullulan.

[0046] The content of the hydroxyl group-containing polymer in the solution S is, for example, 0.10 wt% to 80.0 wt%. When the content of the hydroxyl group-containing polymer is 0.10 wt% or more, the first electrolyte membrane 1 tends to exhibit gas barrier properties. When the content of the hydroxyl group-containing polymer is 80.0 wt% or less, it is easy to adjust the thickness of the first electrolyte membrane 1 to a small value. The content of the hydroxyl group-containing polymer may be 70 wt% or less, 60 wt% or less, 50 wt% or less, 40 wt% or less, 30 wt% or less, 20 wt% or less, or even 10 wt% or less. The content of the hydroxyl group-containing polymer may be 0.5 wt% or more, or 1 wt% or more.

[0047] The first electrolyte membrane 1 preferably further contains a proton-conducting polymer. Therefore, the solution S also preferably further contains a proton-conducting polymer. The proton-conducting polymer is a polymer containing at least one proton-conducting group. Examples of proton-conducting groups include sulfonic acid groups and phosphonic acid groups, with sulfonic acid groups being preferred.

[0048] The weight-average molecular weight of the proton-conducting polymer is not particularly limited and may be, for example, 300 or more, 500 or more, 1000 or more, 5000 or more, 10000 or more, or even 50000 or more. The upper limit of the weight-average molecular weight of the proton-conducting polymer is, for example, 1 million or less, and may be 500,000 or less. Furthermore, the weight-average molecular weight of the proton-conducting polymer per proton-conducting group contained in the proton-conducting polymer (proton-conducting group equivalent) may be, for example, 50 g / eq. to 1000 g / eq., and may be 100 g / eq. to 800 g / eq.

[0049] Examples of proton-conducting polymers include hydrocarbon polymers having proton-conducting groups and fluorine-based polymers having proton-conducting groups. It is preferable that the solution S and the first electrolyte membrane 1 contain a hydrocarbon polymer having proton-conducting groups.

[0050] Examples of the hydrocarbon polymers mentioned above include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyaryl ether ketone sulfonic acid, polyphenyl sulfonic acid, polybenzimidazole sulfonic acid, polyimide sulfonic acid, and polysulfonic acids in which side chains such as alkyl groups have been introduced therein; polyvinyl phosphonic acid, polybenzimidazole phosphonic acid, and polyphosphonic acids in which side chains such as alkyl groups have been introduced therein, with polyvinyl sulfonic acid (PVS) being preferred.

[0051] The above-mentioned fluorine-based polymer preferably contains structural units derived from perfluorosulfonic acids such as perfluorovinyl ethersulfonic acid, and more preferably further contains structural units derived from perfluorovinyl compounds such as tetrafluoroethylene, together with the said structural units. The fluorine-based polymer may also be a tetrafluoroethylene-perfluorovinyl ethersulfonic acid copolymer represented by the following formula. In the following formula, n and m are integers of 1 or more.

[0052] Commercially available fluorine-based polymers include Nafion®, Aciplex®, Flemion®, and Aquivion®.

[0053] The content of the proton-conducting polymer in solution S is, for example, 0.01 wt% to 50.0 wt%. The content of the proton-conducting polymer may be 40 wt% or less, 30 wt% or less, 20 wt% or less, 10 wt% or less, 5 wt% or less, or even 1 wt% or less. The content of the proton-conducting polymer may be 0.05 wt% or more, or 0.1 wt% or more. Furthermore, in solution S, the amount of hydroxyl group-containing polymer per mole of proton-conducting polymer is, for example, 0.5 moles to 500 moles. In addition, in solution S, the amount of monomer units contained in the hydroxyl group-containing polymer per mole of monomer units (constituent units) contained in the proton-conducting polymer may be 0.5 moles to 500 moles.

[0054] Solution S preferably contains water as a solvent. Solution S may or may not contain other solvents besides water. Examples of other solvents include alcohols. The solvent content in solution S is, for example, 20.0 wt% to 99.99 wt%. The solvent content may be 30 wt% or more, 40 wt% or more, 50 wt% or more, 60 wt% or more, 70 wt% or more, and even 80 wt% or more. The solvent content may be 99.9 wt% or less, 99 wt% or less, 95 wt% or less, and even 90 wt% or less.

[0055] Solution S can be prepared, for example, by the following method. First, a first solution S1 containing a hydroxyl group-containing polymer and a second solution S2 containing a proton-conducting polymer are prepared. The first solution S1 may be prepared by mixing the hydroxyl group-containing polymer with water and heating the resulting mixture. The heating temperature of the mixture is not particularly limited, but is, for example, 50°C to 95°C. Next, solution S can be prepared by mixing the first solution S1 and the second solution S2.

[0056] Next, as shown in Figure 2B, the prepared solution S is applied to the peeling liner 5 (specifically, the surface 5a of the peeling liner 5) to obtain a coating film 4. The method of applying the solution S is not particularly limited and includes methods such as roll coating, kiss roll coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater. The solution S may be applied by printing methods such as gravure printing, offset printing, screen printing, and inkjet printing, or by using a quantitative coating device such as a dispenser.

[0057] Next, the obtained coating film 4 is dried. This forms the first electrolyte film 1 from the coating film 4, and the first laminate 20 is formed with the first electrolyte film 1 placed on the peel liner 5 (Figure 2C). The drying of the coating film 4 can be carried out, for example, under heating conditions. The heating temperature of the coating film 4 is, for example, 50°C to 100°C. The heating time of the coating film 4 is, for example, 1 minute to 30 minutes.

[0058] The first electrolyte membrane 1 is typically a proton-conducting membrane, and preferably further possesses gas barrier properties. The first electrolyte membrane 1 has the same composition as the solution S, except for the solvent content. More specifically, the first electrolyte membrane 1 contains a hydroxyl group-containing polymer, and preferably further contains a proton-conducting polymer. The first electrolyte membrane 1 preferably has gas barrier properties due to the hydroxyl group-containing polymer and proton conductivity due to the proton-conducting polymer.

[0059] In the first electrolyte membrane 1, the content of the hydroxyl group-containing polymer is, for example, 80.0 wt% to 99.99 wt%, and the content of the proton-conducting polymer is, for example, 0.01 wt% to 20.0 wt%. In the first electrolyte membrane 1, the amount of hydroxyl group-containing polymer per mole of proton-conducting polymer is, for example, 0.5 moles to 500 moles. In addition, in the first electrolyte membrane 1, the amount of monomer units contained in the hydroxyl group-containing polymer per mole of monomer units (constituent units) contained in the proton-conducting polymer may be 0.5 moles to 500 moles.

[0060] The first electrolyte membrane 1 may or may not contain a small amount of solvent such as water. The solvent content in the first electrolyte membrane 1 is, for example, 0.01 wt% to 10.0 wt%.

[0061] The acid content of the first electrolyte membrane 1 is preferably smaller than the acid content of the second electrolyte membrane 2, for example, less than 0.8 meq / g, and may be 0.5 meq / g or less, 0.3 meq / g or less, or even 0.2 meq / g or less. The lower limit of the acid content of the first electrolyte membrane 1 is not particularly limited, and may be, for example, 0.01 meq / g or more, 0.05 meq / g or more, or even 0.1 meq / g or more.

[0062] The thickness of the first electrolyte membrane 1 is, for example, 10 μm or less, and may be 5 μm or less, 2.5 μm or less, 2 μm or less, or even 1 μm or less. The lower limit of the thickness of the first electrolyte membrane 1 is, for example, 0.1 μm or more, from the viewpoint of suppressing the occurrence of defects. Since the first laminate 20 is equipped with a release liner 5, the first laminate 20 tends to have excellent handling properties even when the thickness of the first electrolyte membrane 1 is small.

[0063] Next, a forming step A1 is performed in which a second electrolyte membrane 2 is placed on the first electrolyte membrane 1 of the first laminate 20 to form a second laminate 21A. This makes possible a multilayer structure 10A corresponding to the second laminate 21A (Figure 1).

[0064] Forming step A1 is preferably carried out by a heat-pressing treatment in which the first laminate 20 and the second electrolyte membrane 2 are heat-pressed together. With the heat-pressing treatment, the first electrolyte membrane 1 of the first laminate 20 and the second electrolyte membrane 2 tend to adhere to each other with practically sufficient strength. The heat-pressing treatment may be carried out, for example, using a hot press or using a heated roll.

[0065] The temperature of the heat-sealing treatment is, for example, 50°C or higher, and may be 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, and even 110°C or higher. The higher the temperature of the heat-sealing treatment, the stronger the adhesion between the first electrolyte membrane 1 and the second electrolyte membrane 2 tends to be. The upper limit of the heat-sealing treatment temperature is, for example, 170°C or lower, and may be 160°C or lower, 150°C or lower, 140°C or lower, and even 130°C or lower. When the temperature of the heat-sealing treatment is low, the deterioration of the first electrolyte membrane 1 (especially the hydroxyl group-containing polymer contained in the first electrolyte membrane 1) tends to be suppressed by the heat-sealing treatment. Also, if the release liner 5 contains resin, it is preferable that the temperature of the heat-sealing treatment be lower than the softening point of the release liner 5. In this case, the adhesion between the release liner 5 and the first electrolyte membrane 1 tends to be suppressed by the heat-sealing treatment. The temperature for the heat-sealing process is preferably 60°C to 150°C, more preferably 70°C to 150°C, and particularly preferably 80°C to 140°C. In this case, even if the multilayer structure 10A swells upon contact with water, the multilayer structure 10A tends to be less prone to deformation. Such a multilayer structure 10A is suitable for use as a component in a fuel cell that generates water during operation.

[0066] The time for the heat sealing process is, for example, 0.1 seconds or more, and may be 1 second or more, 10 seconds or more, 1 minute or more, 3 minutes or more, 5 minutes or more, 10 minutes or more, or even 15 minutes or more. There is no particular upper limit to the time for the heat sealing process, for example, 60 minutes or less.

[0067] In the heat-sealing process, the pressure applied to the first electrolyte membrane 1 and the second electrolyte membrane 2 is, for example, 0.01 kN or more, and may be 0.1 kN or more, 0.2 kN or more, or even 0.3 kN or more. The upper limit of this pressure is not particularly limited and may be, for example, 1.0 kN or less, and may be 0.5 kN or less.

[0068] The second electrolyte membrane 2 is typically a proton-conducting membrane. The composition of the second electrolyte membrane 2 is preferably different from that of the first electrolyte membrane 1, and is particularly preferably substantially free of hydroxyl group-containing polymers. The second electrolyte membrane 2 may contain polymers (especially fluorinated polymers). In the second electrolyte membrane 2, the polymer preferably has proton-conducting groups, and is particularly preferably functional as a proton-conducting polymer. Examples of fluorinated polymers include those mentioned above for the first electrolyte membrane 1 (especially tetrafluoroethylene-perfluorovinyl ethersulfonic acid copolymers). Commercially available fluorinated polymers include Nafion®, Aciplex®, Flemion®, and Aquivion®. In this specification, fluorinated polymers refer to polymers containing fluorine atoms. The second electrolyte membrane 2 may also contain polymers other than fluorinated polymers (non-fluorinated polymers), and an example of such a non-fluorinated polymer is Pemion (manufactured by Ionomr Innovations).

[0069] The second electrolyte membrane 2 may contain a polymer (particularly a fluorine-based polymer) as its main component, or it may be composed substantially of a polymer alone. The second electrolyte membrane 2 may also be a porous filling membrane in which polymer is filled into the pores of a porous substrate. Examples of porous substrates include polyimide porous membranes and polyolefin crosslinked membranes.

[0070] The second electrolyte membrane 2 may or may not contain a small amount of solvent such as water. The solvent content in the second electrolyte membrane 2 is, for example, 0.01 wt% to 10.0 wt%.

[0071] As described above, the second electrolyte membrane 2 has an acid content of 0.8 meq / g or more. The acid content of the second electrolyte membrane 2 may be 0.85 meq / g or more, or 0.9 meq / g or more. The upper limit of the acid content of the second electrolyte membrane 2 is not particularly limited, and may be, for example, 5.0 meq / g or less, 3.0 meq / g or less, 2.0 meq / g or less, or even 1.0 meq / g or less. The acid content of the second electrolyte membrane 2 is preferably greater than the acid content of the first electrolyte membrane 1, and the difference may be, for example, 0.1 meq / g to 1.5 meq / g, or 0.5 meq / g to 1.0 meq / g.

[0072] The thickness of the second electrolyte membrane 2 is, for example, 500 μm or less, but may also be 300 μm or less, 200 μm or less, 100 μm or less, 80 μm or less, 50 μm or less, or even 30 μm or less, from the viewpoint of suppressing an increase in membrane resistance. The lower limit of the thickness of the second electrolyte membrane 2 is, for example, 2 μm or more, but may also be 10 μm or more, from the viewpoint of ensuring sufficient strength and suppressing the occurrence of defects.

[0073] In the second laminate 21A (multilayer structure 10A), it is preferable that the peeling force P1 between the peeling liner 5 and the first electrolyte membrane 1 is lower than the peeling force P2 between the first electrolyte membrane 1 and the second electrolyte membrane 2. In this case, the peeling liner 5 can be easily peeled off the second laminate 21A, thereby making it easy to fabricate the multilayer structure 10B of Embodiment 2, which will be described later.

[0074] In addition, in forming step A1, only the second electrolyte membrane 2 may be placed on the first electrolyte membrane 1 of the first laminate 20, or a laminate including the second electrolyte membrane 2 and other components may be placed. When the above laminate is placed, it is preferable to perform forming step A1 so that the second electrolyte membrane 2 included in the laminate is in contact with the first electrolyte membrane 1.

[0075] Other components include a protective film to protect the second electrolyte membrane 2 and a catalyst layer, which will be described later in Embodiment 4. The protective film is preferably one that can function as a peel-off liner that can be peeled off from the multilayer structure 10A after the multilayer structure 10A is fabricated, and the peel-off liner 5 is as described above. Details of the catalyst layer will be described later in Embodiment 4.

[0076] The manufacturing method for the multilayer structure 10A in Embodiment 1 may be a roll-to-roll method. The roll-to-roll method offers excellent productivity and is suitable for mass production of the multilayer structure 10A. Below, a method for manufacturing the multilayer structure 10A using the roll-to-roll method will be described in detail.

[0077] First, as shown in Figure 3, a long peel liner 5 is unwound from the winding body 30 and transported along the transport direction. While the peel liner 5 is being transported, a solution S containing the material for the first electrolyte membrane is applied to the surface 5a of the peel liner 5 by the coating device 40 to form a coated film 4. Next, the coated film 4 is passed through the dryer 42 to dry it. As a result, the first electrolyte membrane 1 is formed from the coated film 4, and a long first laminate 20 is formed (formation step A0).

[0078] Next, a long second electrolyte membrane 2 unwound from the winding body 32 is placed on the first electrolyte membrane 1 of the first laminate 20 to form a long second laminate 21A (multilayer structure 10A) (forming step A1). At this time, the first laminate 20 and the second electrolyte membrane 2 can be superimposed and passed between a pair of heating rolls 35 to perform a heat compression process. The resulting long second laminate 21A can be wound up by the winding body 34.

[0079] [Embodiment 2] As shown in Figure 4, the multilayer structure 10B of Embodiment 2 comprises a third electrolyte membrane 3, a first electrolyte membrane 1, and a second electrolyte membrane 2 in this order. Preferably, the first electrolyte membrane 1 is in direct contact with the third electrolyte membrane 3 and the second electrolyte membrane 2, respectively. The multilayer structure 10B has the same structure as the fourth laminate 23A formed by the formation process A3 described later. The multilayer structure 10B can be used as a diaphragm for a fuel cell. Furthermore, the multilayer structure 10B can also be used as a diaphragm for a water electrolysis device.

[0080] The multilayer structure 10B may further include other members besides those described above. Examples of other members include a protective film for protecting the second electrolyte membrane 2, a protective film for protecting the third electrolyte membrane 3, and a catalyst layer, which will be described later in Embodiment 4.

[0081] As described above, the multilayer structure 10B can be used as a diaphragm for a fuel cell. In particular, when the first electrolyte membrane 1 of the multilayer structure 10B exhibits gas barrier properties, the multilayer structure 10B tends to sufficiently suppress the movement of oxygen supplied to the cathode of the fuel cell to the anode. By suppressing the movement of oxygen, the generation of hydrogen peroxide due to the reaction of oxygen and hydrogen on the anode side and the generation of radicals caused by this hydrogen peroxide tend to be suppressed. When the generation of radicals is suppressed, the multilayer structure 10B tends to deteriorate less in the fuel cell, and thus it can function as a highly durable diaphragm for a fuel cell.

[0082] The multilayer structure 10B can be manufactured by the following method. First, a second laminate 21A (multilayer structure 10A) is manufactured by the method described above in Embodiment 1. Next, the release liner 5 is peeled off the second laminate 21A to form a third laminate 22A comprising the first electrolyte membrane 1 and the second electrolyte membrane 2 (Figure 5). In other words, the manufacturing method of this embodiment may further include peeling off the release liner 5 from the second laminate 21A to form the third laminate 22A (forming step A2).

[0083] Next, a third electrolyte membrane 3 having an acid content of 0.8 meq / g or more is placed on the first electrolyte membrane 1 of the third laminate 22A to form a fourth laminate 23A comprising the third electrolyte membrane 3, the first electrolyte membrane 1, and the second electrolyte membrane 2 in this order. In other words, the manufacturing method of this embodiment may further include placing the third electrolyte membrane 3 on the third laminate 22A to form the fourth laminate 23A (forming step A3). By forming step A3, a multilayer structure 10B corresponding to the fourth laminate 23A can be obtained (Figure 4).

[0084] Forming step A3 is preferably carried out by a heat-pressing treatment in which the third laminate 22A and the third electrolyte membrane 3 are heat-pressed together. With the heat-pressing treatment, the first electrolyte membrane 1 of the third laminate 22A and the third electrolyte membrane 3 tend to adhere with practically sufficient strength. The method and conditions for the heat-pressing treatment are those described above in Embodiment 1.

[0085] The third electrolyte membrane 3 is typically a proton-conducting membrane. The composition of the third electrolyte membrane 3 is preferably different from that of the first electrolyte membrane 1, and is particularly preferably substantially free of hydroxyl group-containing polymers. The third electrolyte membrane 3 preferably contains a polymer (particularly a fluorinated polymer). In the third electrolyte membrane 3, the polymer preferably has proton-conducting groups, and is particularly preferably functional as a proton-conducting polymer. Examples of fluorinated polymers include those mentioned above for the first electrolyte membrane 1 (particularly tetrafluoroethylene-perfluorovinyl ethersulfonic acid copolymer). Commercially available fluorinated polymers include Nafion®, Aciplex®, Flemion®, and Aquivion®. The third electrolyte membrane 3 may also contain polymers other than fluorinated polymers (non-fluorinated polymers), and an example of such a non-fluorinated polymer is Pemion (manufactured by Ionomr Innovations).

[0086] The third electrolyte membrane 3 may contain a polymer (particularly a fluorine-based polymer) as its main component, or it may be composed substantially of a polymer alone. The third electrolyte membrane 3 may also be a porous filling membrane in which polymer is filled into the pores of a porous substrate. Examples of porous substrates include polyimide porous membranes and polyolefin crosslinked membranes.

[0087] The third electrolyte membrane 3 may or may not contain a small amount of solvent such as water. The solvent content in the third electrolyte membrane 3 is, for example, 0.01 wt% to 10.0 wt%.

[0088] As described above, the third electrolyte membrane 3 has an acid content of 0.8 meq / g or more. The acid content of the third electrolyte membrane 3 may be 0.85 meq / g or more, or 0.9 meq / g or more. The upper limit of the acid content of the third electrolyte membrane 3 is not particularly limited, and may be, for example, 5.0 meq / g or less, 3.0 meq / g or less, 2.0 meq / g or less, or even 1.0 meq / g or less. The acid content of the third electrolyte membrane 3 is preferably greater than the acid content of the first electrolyte membrane 1, and the difference may be, for example, 0.1 meq / g to 1.5 meq / g, or 0.5 meq / g to 1.0 meq / g.

[0089] The thickness of the third electrolyte membrane 3 is, for example, 500 μm or less, and may also be 300 μm or less, 200 μm or less, 100 μm or less, 80 μm or less, 50 μm or less, or even 30 μm or less, from the viewpoint of suppressing an increase in membrane resistance. The lower limit of the thickness of the third electrolyte membrane 3 is, for example, 2 μm or more, and may also be 10 μm or more, from the viewpoint of ensuring sufficient strength and suppressing the occurrence of defects. The composition and thickness of the third electrolyte membrane 3 may be the same as or different from those of the second electrolyte membrane 2.

[0090] In the multilayer structure 10B, the peeling force P3 between the first electrolyte membrane 1 and the third electrolyte membrane 3 is, for example, 0.1 N / 15 mm or more, and may be 0.5 N / 15 mm or more, 0.8 N / 15 mm or more, 1.0 N / 15 mm or more, 3.0 N / 15 mm or more, 5.0 N / 15 mm or more, 8.0 N / 15 mm or more, and even 10.0 N / 15 mm or more. The upper limit of the peeling force P3 is not particularly limited, and is, for example, 30 N / 15 mm or less.

[0091] The peel force P3 can be measured by the following method. First, the multilayer structure 10B is cut to a width of 15 mm. Next, the second electrolyte membrane 2 of the multilayer structure 10B is fixed to a stainless steel plate via double-sided tape (for example, Nitto Denko No. 5000NS). Next, a test specimen is obtained by attaching single-sided tape (for example, Nitto Denko No. 31B#25) to the third electrolyte membrane 3 of the multilayer structure 10B and using it as a backing. Next, the test specimen is set in a tensile testing apparatus. Specifically, the stainless steel plate is fixed with one chuck of the tensile testing apparatus. The third electrolyte membrane 3 and the single-sided tape are fixed with the other chuck. Under an atmosphere of 23°C and 50% RH, the chuck of the tensile testing apparatus is moved at a speed of 300 mm / min, and the third electrolyte membrane 3 is peeled from the first electrolyte membrane 1 at a peeling angle of 180°. After the start of measurement, the peel strength measurement for the first 20 mm length is ignored, and the peel strength measurements for the subsequent 40 mm length are averaged. The resulting average value is identified as the peel force P3.

[0092] In addition, in forming step A3, only the third electrolyte membrane 3 may be placed on the first electrolyte membrane 1 of the third laminate 22A, or a laminate including the third electrolyte membrane 3 and other components may be placed. When the above laminate is placed, it is preferable to perform forming step A3 so that the third electrolyte membrane 3 included in the laminate is in contact with the first electrolyte membrane 1.

[0093] Other components include a protective film to protect the third electrolyte membrane 3 and a catalyst layer, which will be described later in Embodiment 4. The protective film is preferably one that can function as a peel-off liner that can be peeled off from the multilayer structure 10B after the multilayer structure 10B has been fabricated, and the peel-off liner 5 is as described above. Details of the catalyst layer will be described later in Embodiment 4.

[0094] The manufacturing method for the multilayer structure 10B in Embodiment 2 may be a roll-to-roll method. The roll-to-roll method offers excellent productivity and is suitable for mass production of the multilayer structure 10B. Below, a method for manufacturing the multilayer structure 10B using the roll-to-roll method will be described in detail.

[0095] First, as shown in Figure 6, a long peel liner 5 is unwound from the winding body 30 and transported along the transport direction. While the peel liner 5 is being transported, a solution S containing the material for the first electrolyte membrane is applied to the surface 5a of the peel liner 5 by the coating device 40 to form a coated film 4. Next, the coated film 4 is passed through the dryer 42 to dry it. As a result, the first electrolyte membrane 1 is formed from the coated film 4, and a long first laminate 20 is formed (formation step A0).

[0096] Next, a long second electrolyte membrane 2 unwound from the winding body 32 is placed on the first electrolyte membrane 1 of the first laminate 20 to form a long second laminate 21A (forming step A1). At this time, the first laminate 20 and the second electrolyte membrane 2 can be superimposed and passed between a pair of heating rolls 35 to perform the heat compression process.

[0097] Next, the release liner 5 is peeled off from the second laminate 21A and wound onto the winding body 36. This forms a long third laminate 22A (forming step A2). Next, the long third electrolyte membrane 3 unwound from the winding body 37 is placed on the first electrolyte membrane 1 of the third laminate 22A to form a long fourth laminate 23A (multilayer structure 10B) (forming step A3). At this time, the third laminate 22A and the third electrolyte membrane 3 can be passed between a pair of heating rolls 38 while they are overlapping, allowing for heat bonding. The resulting long fourth laminate 23A can be wound onto the winding body 39.

[0098] Conventionally, multilayer structures in which multiple electrolyte membranes are stacked are fabricated, for example, by the following method. First, a mask is placed on the third electrolyte membrane, and an aqueous solution containing the material for the first electrolyte membrane is sprayed into the opening of the mask. The resulting coated film is dried to form the first electrolyte membrane. Next, the mask is removed, and the second electrolyte membrane is placed on the first electrolyte membrane, thereby forming a multilayer structure comprising the third electrolyte membrane, the first electrolyte membrane, and the second electrolyte membrane in this order. However, the above method requires operations such as attaching and detaching the mask, which is time-consuming and laborious, and it is also difficult to apply a roll-to-roll method, making it difficult to improve productivity. Furthermore, with the spray method of applying the aqueous solution, it tends to be difficult to uniformly produce a thin first electrolyte membrane with a thickness of about 1 μm or less.

[0099] In contrast, according to the manufacturing method of this embodiment, as described above, the roll-to-roll method can be easily applied, and productivity can be easily improved. Furthermore, by appropriately setting the method of applying the solution S, etc., it tends to be easier to uniformly form a thin first electrolyte membrane 1.

[0100] [Embodiment 3] In the multilayer structure 10B of Embodiment 2, the end face of the first electrolyte membrane 1 is exposed to the external atmosphere. In other words, in a plan view, the first electrolyte membrane 1, the second electrolyte membrane 2, and the third electrolyte membrane 3 have the same shape and dimensions as each other. However, the multilayer structure 10B is not limited to this structure, and the end face of the first electrolyte membrane 1 may be covered by the second electrolyte membrane 2 or the third electrolyte membrane 3. In the multilayer structure 10C of Figure 7, the surface of the second electrolyte membrane 2 and the surface of the third electrolyte membrane 3 are joined around the first electrolyte membrane 1, so that the first electrolyte membrane 1 is surrounded by the second electrolyte membrane 2 and the third electrolyte membrane 3. Except as described above, the structure of the multilayer structure 10C of Embodiment 3 is the same as the structure of the multilayer structure 10B of Embodiment 2.

[0101] In the multilayer structure 10C, the first electrolyte membrane 1 is not in contact with the external atmosphere, and the material of the first electrolyte membrane 1 (hydroxyl group-containing polymer or proton-conducting polymer) is less likely to fall out to the outside. As a result, the multilayer structure 10C tends to be able to be used stably for a long period of time as a diaphragm in a fuel cell.

[0102] The multilayer structure 10C can be manufactured by the following method. First, a first laminate 20 is manufactured by the method described above in Embodiment 1. Next, a forming step A1 is performed in which a second electrolyte membrane 2 is placed on the first electrolyte membrane 1 of the first laminate 20 to form a second laminate 21B (Figure 8A). As shown in Figure 8A, in forming step A1, a second electrolyte membrane 2 that is larger than the first electrolyte membrane 1 in plan view is placed on the first electrolyte membrane 1. A detailed method of forming step A1 is the one described above in Embodiment 1.

[0103] Next, as shown in Figure 8B, the release liner 5 is peeled off from the second laminate 21B, and forming step A2 is performed to form a third laminate 22B comprising the first electrolyte membrane 1 and the second electrolyte membrane 2. Next, the third electrolyte membrane 3 is placed on top of the first electrolyte membrane 1 of the third laminate 22B (Figure 8C). As shown in Figure 8C, the third electrolyte membrane 3, which is larger than the first electrolyte membrane 1 in a plan view, is placed on top of the first electrolyte membrane 1.

[0104] Next, the laminate shown in Figure 8C is subjected to a heat-sealing treatment. Through the heat-sealing treatment, the surface of the second electrolyte membrane 2 and the surface of the third electrolyte membrane 3 are joined around the first electrolyte membrane 1, and a multilayer structure 10C (fourth laminate 23B) is obtained (Figure 7). The method and conditions for the heat-sealing treatment are those described above in Embodiment 1.

[0105] [Embodiment 4] As shown in Figure 9, the multilayer structure 10D of Embodiment 4 comprises two catalyst layers 6 and 7, with a third electrolyte membrane 3, a first electrolyte membrane 1, and a second electrolyte membrane 2 arranged between these catalyst layers 6 and 7. In the multilayer structure 10D, the catalyst layer 7, the third electrolyte membrane 3, the first electrolyte membrane 1, the second electrolyte membrane 2, and the catalyst layer 6 are arranged in this order in the stacking direction. The multilayer structure 10D has the same structure as the fourth laminate 23C formed by the formation process A3 described later. The multilayer structure 10D can be used as a component for manufacturing the multilayer structure 10E of Embodiment 5 described later.

[0106] In the multilayer structure 10D, the catalyst layer 6 may be in direct contact with the second electrolyte membrane 2. The catalyst layer 6 may cover the entire main surface of the second electrolyte membrane 2, or it may partially cover the main surface of the second electrolyte membrane 2. Similarly, the catalyst layer 7 may be in direct contact with the third electrolyte membrane 3. The catalyst layer 7 may cover the entire main surface of the third electrolyte membrane 3, or it may partially cover the main surface of the third electrolyte membrane 3.

[0107] The multilayer structure 10D can be manufactured, for example, by the following method. First, as shown in Figure 10A, a catalyst layer 6 is formed on the second electrolyte membrane 2. In other words, the manufacturing method of this embodiment may further include forming a catalyst layer 6 on the second electrolyte membrane 2 (forming step B1).

[0108] Formation step B1 can be carried out, for example, by the following method. First, a coating solution containing the material for the catalyst layer 6 is prepared. Examples of materials for the catalyst layer 6 include metal catalysts and supports on which the metal catalyst is supported. Examples of metals contained in the metal catalyst include platinum, palladium, ruthenium, rhodium, nickel, cobalt, iron, silver, and alloys thereof. Examples of materials for the support include carbon materials such as carbon, activated carbon, fullerene, carbon nanohorns, and carbon nanotubes. Examples of solvents contained in the coating solution include water and organic solvents.

[0109] Next, the prepared coating solution is applied onto the second electrolyte membrane 2 to obtain a coating film. The method of applying the coating solution is not particularly limited, and the above-described method of applying the solution S is an example. The coating solution is preferably applied by spray coating.

[0110] Next, the obtained coating film is dried. This forms a catalyst layer 6 from the coating film, and a laminate 25 is obtained in which the catalyst layer 6 is placed on the second electrolyte film 2 (Figure 10A). The drying of the coating film can be carried out, for example, under heating conditions. The heating temperature of the coating film is, for example, 80°C or higher, and may be 100°C or higher, or even 130°C or higher. The upper limit of the heating temperature of the coating film is not particularly limited, and is, for example, 200°C. The heating time of the coating film is, for example, 1 minute to 30 minutes. When drying the coating film, a heat pressing treatment may be performed to heat and press the coating film and the second electrolyte film 2 together using a hot press or the like.

[0111] The catalyst layer 6 typically functions as a catalyst for the electrochemical reaction in a fuel cell. The catalyst layer 6 may also function as a catalyst for the electrolysis reaction of water in a solid polymer water electrolysis device. The catalyst layer 6 preferably contains the above-mentioned metal catalyst and support. The thickness of the catalyst layer 6 is not particularly limited, and is, for example, 1 nm to 2000 nm.

[0112] Next, as shown in Figure 10B, a catalyst layer 7 is formed on the third electrolyte membrane 3. In other words, the manufacturing method of this embodiment may further include forming a catalyst layer 7 on the third electrolyte membrane 3 (formation step B2).

[0113] Formation step B2 can be carried out, for example, by the following method. First, a coating film containing the material for the catalyst layer 7 is prepared. Examples of the material for the catalyst layer 7 and the solvent contained in the coating solution include those described above for the catalyst layer 6. Next, the prepared coating solution is applied onto the third electrolyte membrane 3 to obtain a coating film. The method of applying the coating solution is not particularly limited, and examples of the method of applying the solution S include those described above. The coating solution is preferably applied by spray coating.

[0114] Next, the obtained coating film is dried. This forms a catalyst layer 7 from the coating film, and a laminate 26 is obtained in which the catalyst layer 7 is placed on the third electrolyte film 3 (Figure 10B). The drying of the coating film can be carried out, for example, under heating conditions. The heating temperature and heating time for the coating film are as described above for the catalyst layer 6. When drying the coating film, a heat pressing treatment may be performed to heat and press the coating film and the third electrolyte film 3 together using a hot press or the like.

[0115] The catalyst layer 7 typically functions as a catalyst for the electrochemical reaction of the fuel cell. Preferably, the catalyst layer 7 contains the aforementioned metal catalyst and support. The thickness of the catalyst layer 7 is not particularly limited, and is, for example, 1 nm to 2000 nm. The composition and thickness of the catalyst layer 7 may be the same as or different from those of the catalyst layer 6.

[0116] Next, the first laminate 20 is fabricated by the method described above in Embodiment 1. Then, a laminate 25, which includes a second electrolyte membrane 2 and a catalyst layer 6, is placed on the first electrolyte membrane 1 of the first laminate 20, and a forming step A1 is performed to form the second laminate 21C (Figure 10C). As shown in Figure 10C, in forming step A1, the first electrolyte membrane 1 of the first laminate 20 and the second electrolyte membrane 2 of the laminate 25 are brought into contact. A detailed method of forming step A1 is the one described above in Embodiment 1.

[0117] Next, as shown in Figure 10D, the peeling liner 5 is peeled off from the second laminate 21C, and a forming step A2 is performed to form a third laminate 22C comprising a first electrolyte membrane 1, a second electrolyte membrane 2, and a catalyst layer 6. Next, a forming step A3 is performed to form a fourth laminate 23C by placing a laminate 26 comprising a third electrolyte membrane 3 and a catalyst layer 7 on the first electrolyte membrane 1 of the third laminate 22C. A detailed method of forming step A3 is as described above in Embodiment 2. By forming step A3, a multilayer structure 10D corresponding to the fourth laminate 23C can be obtained (Figure 9).

[0118] In the method described above, the formation step B1, in which the catalyst layer 6 is formed on the second electrolyte membrane 2, is performed before the formation step A1, in which the second electrolyte membrane 2 is placed on the first electrolyte membrane 1 of the first laminate 20 to form the second laminate 21C. Similarly, the formation step B2, in which the catalyst layer 7 is formed on the third electrolyte membrane 3, is performed before the formation step A3, in which the third electrolyte membrane 3 is placed on the first electrolyte membrane 1 of the third laminate 22C to form the fourth laminate 23C.

[0119] However, the timing of the formation steps B1 and B2 is not limited to those described above. For example, a fourth laminate 23A (multilayer structure 10B) comprising the third electrolyte membrane 3, the first electrolyte membrane 1, and the second electrolyte membrane 2 in that order may be fabricated by the method described in Embodiment 2, and then the multilayer structure 10D may be fabricated by performing the formation steps B1 and B2. In this method, the first electrolyte membrane 1 will also be heated when the heat bonding treatment described above is performed in the formation steps B1 and B2. Excessive heat treatment may cause the first electrolyte membrane 1 (especially the hydroxyl group-containing polymer contained in the first electrolyte membrane 1) to deteriorate. When the first electrolyte membrane 1 deteriorates, the gas barrier properties of the first electrolyte membrane 1 tend to decrease, and the first electrolyte membrane 1 tends to become more easily deformed.

[0120] In contrast, if forming step B1 is performed before forming step A1, and forming step B2 is performed before forming step A3, it is possible to avoid performing unnecessary heat treatment on the first electrolyte membrane 1. In this case, the temperature of the heat-sealing treatment in forming steps B1 and B2 may be set to a relatively high value (for example, a higher value than the temperature of the heat-sealing treatment in forming steps A1 and A3).

[0121] [Embodiment 5] As shown in Figure 11, the multilayer structure 10E of Embodiment 5 comprises two electrodes 50 and 51, with a third electrolyte membrane 3, a first electrolyte membrane 1, and a second electrolyte membrane 2 arranged between these electrodes 50 and 51. In the multilayer structure 10E, the electrode 51, the third electrolyte membrane 3, the first electrolyte membrane 1, the second electrolyte membrane 2, and the electrode 50 are arranged in this order in the stacking direction. The multilayer structure 10E can be used as a membrane electrode assembly (MEA) for a fuel cell.

[0122] The electrode 50 may include a catalyst layer 6 and a diffusion layer 8, and the catalyst layer 6 may be in direct contact with the diffusion layer 8 and the second electrolyte membrane 2, respectively. The electrode 50 may cover the entire main surface of the second electrolyte membrane 2, or it may partially cover the main surface of the second electrolyte membrane 2.

[0123] The electrode 51 may include a catalyst layer 7 and a diffusion layer 9, and the catalyst layer 7 may be in direct contact with the diffusion layer 9 and the third electrolyte membrane 3, respectively. The electrode 51 may cover the entire main surface of the third electrolyte membrane 3, or it may partially cover the main surface of the third electrolyte membrane 3.

[0124] In the multilayer structure 10E, electrode 50 may function as an anode and electrode 51 may function as a cathode. Alternatively, electrode 50 may function as a cathode and electrode 51 may function as an anode.

[0125] The multilayer structure 10E can be manufactured, for example, by the following method. First, a fourth laminate 23C (multilayer structure 10D) is manufactured by the method described above in Embodiment 4. Next, a diffusion layer 8 is placed on the catalyst layer 6 to form an electrode 50 (forming step C1).

[0126] The diffusion layer 8 functions, for example, as a layer that diffuses oxygen and hydrogen supplied to the fuel cell. The diffusion layer 8 is preferably conductive, and can be made of carbon cloth, carbon paper, or the like.

[0127] Next, a diffusion layer 9 is placed on the catalyst layer 7 to form the electrode 51 (forming step C2). The diffusion layer 9 functions, for example, as a layer that diffuses oxygen and hydrogen supplied to the fuel cell. The diffusion layer 9 is preferably conductive, and carbon cloth, carbon paper, etc., can be used.

[0128] In the method described above, the formation step C1, in which the diffusion layer 8 is placed on the catalyst layer 6 to form the electrode 50, is performed after the formation step A1, in which the second electrolyte membrane 2 is placed on the first electrolyte membrane 1 of the first laminate 20 to form the second laminate 21C. Similarly, the formation step C2, in which the diffusion layer 9 is placed on the catalyst layer 7 to form the electrode 51, is performed after the formation step A3, in which the third electrolyte membrane 3 is placed on the first electrolyte membrane 1 of the third laminate 22C to form the fourth laminate 23C.

[0129] However, the timing of the formation steps C1 and C2 is not limited to those described above. For example, formation steps B1 and C1 may be performed to form the electrode 50 on the second electrolyte membrane 2, and then formation step A1 may be performed. Similarly, formation steps B2 and C2 may be performed to form the electrode 51 on the third electrolyte membrane 3, and then formation step A3 may be performed.

[0130] <Embodiment of a Fuel Cell> The fuel cell of this embodiment preferably includes components utilizing the multilayer structures 10A to 10E described above, and is particularly preferably equipped with diaphragms such as multilayer structures 10B and 10C, and membrane electrode assemblies such as multilayer structure 10E. The fuel cell may further include other components besides the multilayer structures described above. Other components include current collectors, gaskets, oxygen and hydrogen flow paths, external circuits, and various sensors for detecting power generation status.

[0131] In a fuel cell, electricity is generated by supplying hydrogen to the anode and oxygen to the cathode, and allowing electrochemical reactions to proceed in both the anode and cathode. The anode reaction in the anode, the cathode reaction in the cathode, and the overall reaction are represented by the following reaction equations: • Anode reaction: 2H₂ → 4H₂ + + 4e - • Cathode reaction: O2 + 4H + + 4e - → 2H₂O • Overall reaction: 2H₂ + O₂ → 2H₂O

[0132] As described above in Embodiment 2, when a multilayer structure equipped with a first electrolyte membrane 1 having gas barrier properties is used as a diaphragm for a fuel cell, the multilayer structure tends to sufficiently suppress, for example, the movement of oxygen supplied to the cathode of the fuel cell to the anode. By suppressing the movement of oxygen, the generation of hydrogen peroxide due to the reaction of oxygen and hydrogen on the anode side and the generation of radicals caused by the hydrogen peroxide tend to be suppressed. When the generation of radicals is suppressed, the multilayer structure tends to be less prone to degradation in the fuel cell, and thus can function as a highly durable diaphragm for the fuel cell.

[0133] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0134] (Example A1) First, polyvinyl alcohol (Millipore, PVA complete saponified (for synthesis), weight-average molecular weight: approximately 60,000) was prepared as a hydroxyl group-containing polymer. Next, the polyvinyl alcohol and distilled water were mixed and heated in a water bath at 90°C to prepare a first solution S1 containing polyvinyl alcohol at a concentration of 10 wt%. Next, an aqueous solution (Aldrich) containing poly(vinyl sulfonic acid) sodium salt at a concentration of 25 wt% was mixed with 1 mol / L hydrochloric acid (Aldrich) in equimolar amounts relative to the sodium salt to protonate the salt, and a second solution S2 containing polyvinyl sulfonic acid (PVS) at a concentration of 1 wt% was prepared as a proton-conducting polymer.

[0135] Next, the prepared first solution S1 and second solution S2 were placed in 50 mL screw-cap bottles and stirred and defoamed using a stirrer (Thinky Co., Ltd., Awatori Rentaro) at a rotation speed of 2000 rpm for 5 minutes and then at a rotation speed of 2200 rpm for 2 minutes. This prepared solution S containing the material for the first electrolyte membrane. Solution S had a solid content concentration of 8.2 wt%, and the ratio of the amount of monomer units of polyvinyl alcohol to the amount of monomer units of polyvinyl sulfonic acid was 100:1.

[0136] Next, a polyethylene terephthalate (PET) film (Toray Industries, Ltd., Lumirror S10 #25) was prepared as a release liner. Then, solution S was applied to the release liner using a stainless steel (SUS) applicator to create a coating film. The coating film was placed in a dryer and dried at 80°C for 10 minutes. This resulted in obtaining a first laminate with a first electrolyte film (thickness 5 μm) placed on top of the release liner (forming step A0). The first laminate was cut to a size of 3 cm x 3 cm.

[0137] Next, a membrane containing a tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Nafion 211, manufactured by Chemours, 25 μm thick) was prepared as the second electrolyte membrane. This second electrolyte membrane was sandwiched between two protective films (polyester film, approximately 25 μm thick). The second electrolyte membrane was cut to a size of 3 cm x 3 cm.

[0138] Next, one protective film was peeled off from the second electrolyte membrane, and the second electrolyte membrane was placed on top of the first electrolyte membrane so that the exposed surface of the second electrolyte membrane was in contact with the first electrolyte membrane of the first laminate. Then, a heat-pressing process was performed to heat-press the first laminate and the second electrolyte membrane using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). The heat-pressing process was performed for 15 minutes at a temperature of 80°C and a pressure of 0.32 kN. As a result, the second electrolyte membrane was placed on the first laminate (forming step A1), and a multilayer structure of Example A1 was obtained, comprising a release liner, the first electrolyte membrane, the second electrolyte membrane, and a protective film in this order.

[0139] (Examples A2 to A6) The multilayer structures of Examples A2 to A6 were obtained by the same method as in Example A1, except that the conditions for the heat-pressing treatment in forming step A1 were changed as shown in Table 1.

[0140] [Acid Content] For Examples A1 to A6, the acid content (ion exchange capacity) of each electrolyte membrane was measured by the following neutralization titration method. Measurements were performed five times, and the average value was taken. Specifically, a test piece was cut from the electrolyte membrane and vacuum-dried at 50°C for more than 12 hours. At this time, the weight of the dried test piece was adjusted to approximately 0.05 g. The weight of the test piece was accurately weighed. Next, 100 mL of a 0.1 mol / L sodium chloride aqueous solution was added to the test piece to dissolve it in the aqueous solution. Next, a neutralization titration was performed by slowly adding a 0.05 mol / L sodium hydroxide aqueous solution dropwise to the aqueous solution of the test piece. As an indicator, a commercially available titration phenolphthalein solution of 0.1 w / v% was added, and the endpoint was reached when it turned a light reddish-purple color. This allowed the amount of sodium hydroxide aqueous solution needed to neutralize the aqueous solution of the test piece to be calculated. The acid content (meq / g) of the electrolyte membrane was determined by the following formula. Acid content of electrolyte membrane (meq / g) = {Concentration of sodium hydroxide solution (moles / mL) × Droplet volume (mL)} / Weight of test specimen (g)

[0141] [Color Evaluation] The multilayer structures of Examples A1 to A6 were visually observed, and the degree of coloration of the multilayer structures was evaluated according to the following evaluation criteria. <Evaluation Criteria> ○: Visually colorless and transparent. △: Visually a very slight brown color can be observed. ×: Visually a dark brown color can be observed.

[0142] [Swelling Test] The multilayer structures of Examples A1 to A6 were subjected to swelling tests using the following method. First, the release liner and protective film were peeled off from the multilayer structure to prepare a laminate of the first electrolyte membrane and the second electrolyte membrane. This laminate was subjected to a swelling test by immersing it in water at room temperature (25°C) for one hour. The laminate was visually observed after the swelling test, and the deformation of the laminate was evaluated according to the following evaluation criteria. <Evaluation Criteria> ・Deformation ◎: Almost no warping or curling is observed in the laminate. 〇: Slight warping or curling is observed in the laminate. △: Warping or curling is observed in the laminate. ×: Severe warping or curling is observed in the laminate.

[0143]

[0144] The details of the materials listed in Table 1 are as follows: Nafion 211: A membrane containing tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Chemours, Nafion 211, 25 μm thick) PVA: Polyvinyl alcohol (Millipore, PVA complete saponified (for synthesis), weight-average molecular weight: approximately 60,000) PVS: Polyvinyl sulfonic acid

[0145] As described above, in Examples A1 to A6, a multilayer structure comprising a first electrolyte membrane and a second electrolyte membrane was successfully fabricated using a peelable liner. This method has the advantage of being easily applicable to the roll-to-roll method, which offers excellent productivity. Furthermore, as can be seen from Table 1, in Examples A1 to A5, where the temperature of the heat-sealing treatment was set to 70°C to 150°C, the swelling test results were better than in Example A6. From these results, it can be said that the multilayer structures of Examples A1 to A5 are particularly suitable for components such as fuel cells that generate water during operation.

[0146] In Examples A4 to A6, deformation of the laminate was observed after drying the laminate following the swelling test.

[0147] Furthermore, coloration of the multilayer structure was observed in Examples A4 and A5. It is presumed that this coloration of the multilayer structure is due to the conversion of some of the polyvinyl alcohol contained in the first electrolyte membrane into polyene during the heat-sealing process.

[0148] (Example B1) A first laminate was prepared in the same manner as in Example A1, except that the thickness of the coating film formed from solution S was changed, with a first electrolyte film (20 μm thick) placed on a peel-off liner. The first laminate was cut to a size of 6 cm x 1.5 cm.

[0149] Next, membranes containing a tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Nafion 211, manufactured by Chemours, 25 μm thick) were prepared as the second and third electrolyte membranes. These electrolyte membranes were sandwiched between two protective films (polyester film, approximately 25 μm thick). These electrolyte membranes were cut to a size of 6 cm x 1.5 cm.

[0150] Next, one protective film was peeled off from the second electrolyte membrane, and the second electrolyte membrane was placed on top of the first electrolyte membrane so that the exposed surface of the second electrolyte membrane was in contact with the first electrolyte membrane of the first laminate. Then, a heat-pressing process (first heat-pressing process) was performed to heat-press the first laminate and the second electrolyte membrane using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). The first heat-pressing process was performed for 15 minutes under conditions of a temperature of 60°C and a pressure of 0.32 kN. As a result, the second electrolyte membrane was placed on the first laminate (forming process A1), and a second laminate was obtained comprising a release liner, the first electrolyte membrane, the second electrolyte membrane, and a protective film in this order.

[0151] Next, the release liner was peeled off the second laminate to form a third laminate comprising the first electrolyte membrane and the second electrolyte membrane (forming step A2). In the third laminate, a polyimide (PI) tape was attached to an area of ​​approximately 3 mm around the edge of the first electrolyte membrane. The PI tape serves as the starting point for peeling, determining the peeling interface in a peel test that measures the peeling force between the first electrolyte membrane and the third electrolyte membrane located on the surface of the first electrolyte membrane.

[0152] Next, one protective film was peeled off from the third electrolyte membrane, and the third electrolyte membrane was placed on top of the first electrolyte membrane so that the exposed surface of the third electrolyte membrane was in contact with the first electrolyte membrane of the third laminate. Then, a heat-pressing process (second heat-pressing process) was performed to heat-press the third laminate and the third electrolyte membrane using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). In the second heat-pressing process, a spacer was used to prevent a step from occurring at the position of the PI tape. The second heat-pressing process was performed at a temperature of 60°C, a pressure of 0.32 kN, and a press area of ​​6 cm². 2 The process was carried out for 15 minutes under the conditions of (4 cm vertical x 1.5 cm horizontal). As a result, the third electrolyte membrane was placed on the third laminate (forming step A3), and a multilayer structure of Example B1 was obtained, comprising a protective film, a third electrolyte membrane, a first electrolyte membrane, a second electrolyte membrane, and a protective film in this order.

[0153] (Examples B2 to B4) The multilayer structures of Examples B2 to B4 were obtained by the same method as in Example B1, except that the conditions for the first and second heat-sealing processes were changed as shown in Table 2.

[0154] (Comparative Example B1) First, two electrolyte membranes (second electrolyte membrane and third electrolyte membrane) containing a tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Nafion 211, manufactured by Chemours, Inc., 25 μm thick) were prepared. These electrolyte membranes were sandwiched between two protective films (polyester film, approximately 25 μm thick). These electrolyte membranes were cut to a size of 6 cm x 1.5 cm.

[0155] Next, the protective film was peeled off one electrolyte membrane, and a polyimide (PI) tape was attached to the edge of this electrolyte membrane, extending approximately 3 mm. Then, the protective film was peeled off the other electrolyte membrane, and the two electrolyte membranes were overlapped so that the PI tape was placed between them. Next, a heat-pressing process was performed to heat-press these electrolyte membranes using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). The heat-pressing process was carried out for 15 minutes at a temperature of 132°C and a pressure of 0.32 kN. This resulted in obtaining a structure of Comparative Example B1, which comprises a protective film, a third electrolyte membrane, a second electrolyte membrane, and a protective film in this order.

[0156] (Comparative Example B2) The structure of Comparative Example B2 was obtained by the same method as in Comparative Example B1, except that the conditions for the heat-sealing treatment were changed as shown in Table 2.

[0157] (Comparative Example B3) Except for changing the thickness of the coating film formed from solution S, two first laminates were prepared in the same manner as in Example A1, with a first electrolyte membrane (thickness 20 μm) placed on a peel liner. These first laminates were cut to a size of 6 cm in length and 1.5 cm in width. In Comparative Example B3, one of the first electrolyte membranes is referred to as the third electrolyte membrane for convenience.

[0158] Next, a polyimide (PI) tape was attached to the edge of the first electrolyte membrane, extending approximately 3 mm. Then, the first and third electrolyte membranes were overlapped so that the PI tape was placed between them. Next, a heat-pressing process was performed to heat-press these electrolyte membranes using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). The heat-pressing process was carried out for 15 minutes at a temperature of 60°C and a pressure of 0.32 kN. This resulted in obtaining a comparative example B3 structure comprising a release liner, the first electrolyte membrane, the third electrolyte membrane, and the release liner in this order.

[0159] [Acid Content] For Examples B1 to B4 and Comparative Examples B1 to B3, the acid content (ion exchange capacity) of each electrolyte membrane was measured by the neutralization titration method described above.

[0160] [Peel Test] For the multilayer structures of Examples B1 to B4, the peel force P3 between the first electrolyte membrane and the third electrolyte membrane was measured by the following method. First, the protective film on the second electrolyte membrane side was peeled off the multilayer structure, and the second electrolyte membrane of the multilayer structure was fixed to a stainless steel plate via double-sided tape (Nitto Denko Corporation, No. 5000NS). Next, the protective film on the third electrolyte membrane side was peeled off, and single-sided tape (Nitto Denko Corporation, No. 31B#25, 25 μm thick) was attached to the third electrolyte membrane of the multilayer structure as a backing to obtain a test specimen. This test specimen was set in a tensile testing apparatus (Shimadzu Corporation, AUTOGRAPH AGX-V2 50N). Specifically, the stainless steel plate was fixed with one chuck of the tensile testing apparatus, and the third electrolyte membrane and the single-sided tape were fixed with the other chuck. Under conditions of 23°C and 50% RH, the chuck of the tensile testing apparatus was moved at a speed of 300 mm / min, and the third electrolyte membrane was peeled from the first electrolyte membrane at a peeling angle of 180°. After the start of measurement, the peel strength measurement for the first 20 mm length was ignored, and the peel strength measurements for the subsequent 40 mm length were averaged, and the resulting average value was identified as the peel force P3.

[0161] The peeling force between the second electrolyte membrane and the third electrolyte membrane was measured for the structures of Comparative Examples B1 and B2 using the same method as in Examples B1 to B4. Furthermore, the peeling force between the first electrolyte membrane and the third electrolyte membrane was measured for the structure of Comparative Example B3 using the same method as in Examples B1 to B4.

[0162]

[0163] The details of the materials listed in Table 2 are as follows: Nafion 211: A membrane containing tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Chemours, Nafion 211, 25 μm thick) PVA: Polyvinyl alcohol (Millipore, PVA complete saponified (for synthesis), weight-average molecular weight: approximately 60,000) PVS: Polyvinyl sulfonic acid

[0164] As can be seen from Table 2, the peeling force P3 between the first electrolyte membrane and the third electrolyte membrane in the multilayer structures of Examples B1 to B4 was a practically sufficient value.

[0165] (Example C1) A first laminate was prepared in the same manner as in Example A1, except that the thickness of the coating film formed from solution S was changed, with a first electrolyte film (thickness 1 μm) placed on a peel liner. The first laminate was cut to a size of 2 cm x 2 cm.

[0166] Next, membranes containing a tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Nafion 211, manufactured by Chemours, 25 μm thick) were prepared as the second and third electrolyte membranes. These electrolyte membranes were sandwiched between two protective films (polyester film, approximately 25 μm thick). These electrolyte membranes were cut to a size of 3 cm x 3 cm.

[0167] Next, a coating solution containing the catalyst layer material was prepared. Specifically, a platinum catalyst Pt / C (Pt: 46.8 wt%) used as an electrode catalyst was mixed with a 5 wt% Nafion aqueous solution (manufactured by Alfa Aesar) and an ethanol / water = 10 / 1 mixed solvent. This mixture was then dispersed in a homogenizer for approximately 30 minutes to prepare a coating solution containing the catalyst layer material (solid content 28 wt%). Next, one protective film was peeled off from the second electrolyte membrane, and this coating solution was applied to the exposed surface of the second electrolyte membrane to create a coated film. The coating solution was applied using a spray coat (manufactured by Nordson). Next, a heat-pressing treatment (first heat-pressing treatment) was performed to heat-press the coated film and the second electrolyte membrane using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). The first heat-pressing treatment was performed at a temperature of 80°C and a pressure of 0.32 kN for 5 minutes. As a result, a catalyst layer measuring 1 cm vertically and 1 cm horizontally (1 μm thick) was formed on the second electrolyte membrane.

[0168] Next, one protective film was peeled off from the third electrolyte membrane, and the above-mentioned coating solution containing the catalyst layer material was applied to the exposed surface of the third electrolyte membrane to create a coated film. The coating solution was applied by spray coating. Next, a heat-pressing treatment was performed to heat-press the coated film and the second electrolyte membrane under the same conditions as the first heat-pressing treatment described above. As a result, a catalyst layer was formed on the third electrolyte membrane.

[0169] Next, the protective film on the second electrolyte membrane was peeled off, and the second electrolyte membrane was placed on top of the first electrolyte membrane so that the surface of the exposed second electrolyte membrane was in contact with the first electrolyte membrane of the first laminate. Then, a heat-pressing treatment (second heat-pressing treatment) was performed to heat-press the first laminate and the second electrolyte membrane using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). The second heat-pressing treatment was performed for 5 minutes under the conditions of a temperature of 80°C and a pressure of 0.32 kN. As a result, the second electrolyte membrane was placed on the first laminate (forming step A1), and a second laminate was obtained comprising a release liner, a first electrolyte membrane, a second electrolyte membrane, and a catalyst layer in this order.

[0170] Next, the release liner was peeled off the second laminate to form a third laminate comprising the first and second electrolyte membranes (forming step A2). Next, the protective film on the other side was peeled off the third electrolyte membrane, and the third electrolyte membrane was placed on top of the first electrolyte membrane so that the surface of the exposed third electrolyte membrane was in contact with the first electrolyte membrane of the third laminate. Next, a heat-pressing treatment (third heat-pressing treatment) was performed to heat-press the third laminate and the third electrolyte membrane using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). The third heat-pressing treatment was performed at a temperature of 80°C, a pressure of 0.32 kN, and a press area of ​​9 cm². 2 The process was carried out for 5 minutes under the conditions of (3 cm x 3 cm). As a result, the third electrolyte membrane was placed on the third laminate (forming step A3), and a multilayer structure of Example C1 was obtained, comprising a catalyst layer, a third electrolyte membrane, a first electrolyte membrane, a second electrolyte membrane, and a catalyst layer in this order. In the multilayer structure of Example C1, the surface of the second electrolyte membrane and the surface of the third electrolyte membrane were joined around the first electrolyte membrane, so that the first electrolyte membrane was surrounded by the second and third electrolyte membranes.

[0171] (Example C2) The multilayer structure of Example C2 was obtained by the same method as in Example C1, except that the conditions for the first heat-sealing treatment were changed as shown in Table 3.

[0172] (Comparative Example C1) First, two electrolyte membranes (second electrolyte membrane and third electrolyte membrane) containing a tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Nafion 211, manufactured by Chemours, Inc., 25 μm thick) were prepared. These electrolyte membranes were sandwiched between two protective films (polyester film, approximately 25 μm thick). These electrolyte membranes were cut to a size of 3 cm x 3 cm.

[0173] Next, for each of the two electrolyte membranes, the protective film on one side was peeled off, and the above-mentioned coating solution containing the catalyst layer material was applied to the surface of the exposed electrolyte membrane to create a coated film. The coating solution was applied by spray coating. Next, a heat-pressing treatment (first heat-pressing treatment) was performed using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.) to heat-press the coated film and the electrolyte membrane. The first heat-pressing treatment was performed for 5 minutes under conditions of a temperature of 80°C and a pressure of 0.32 kN. As a result, a catalyst layer was formed on each electrolyte membrane.

[0174] Next, the protective film of one electrolyte membrane was peeled off the other, and the two were stacked together. Then, a heat-pressing treatment (second heat-pressing treatment) was performed to heat-press these electrolyte membranes using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.). The second heat-pressing treatment was performed for 5 minutes at a temperature of 80°C and a pressure of 0.32 kN. This resulted in obtaining a comparative example C1 structure comprising a catalyst layer, a third electrolyte membrane, a second electrolyte membrane, and a catalyst layer in that order.

[0175] (Comparative Example C2) First, a membrane containing a tetrafluoroethylene-perfluorovinyl ethersulfonic acid copolymer (Nafion 212, manufactured by Chemours, Inc., 50 μm thick) was prepared as the electrolyte membrane (second electrolyte membrane). The electrolyte membrane was sandwiched between two protective films (polyester film, approximately 25 μm thick). The electrolyte membrane was cut to a size of 3 cm x 3 cm.

[0176] Next, one protective film was peeled off from the electrolyte membrane, and the above-mentioned coating solution containing the catalyst layer material was applied to the surface of the exposed electrolyte membrane to create a coated film. Similarly, the other protective film was peeled off from the electrolyte membrane, and the above-mentioned coating solution containing the catalyst layer material was applied to the surface of the exposed electrolyte membrane to create a coated film. The coating solution was applied by spray coating. Next, a heat-pressing treatment (first heat-pressing treatment) was performed using a hot press (Digital Press, manufactured by Shinto Kogyo Co., Ltd.) to heat-press the two coated films and the electrolyte membrane. The first heat-pressing treatment was performed for 3 minutes under conditions of a temperature of 132°C and a pressure of 0.30 kN. This obtained a comparative example C2 structure having a catalyst layer, an electrolyte membrane, and a catalyst layer in that order.

[0177] [Acid Content] For Examples C1-C2 and Comparative Examples C1-C2, the acid content (ion exchange capacity) of each electrolyte membrane was measured by the neutralization titration method described above.

[0178] [Color Evaluation] For Examples C1-C2 and Comparative Examples C1-C2, after each heat-sealing treatment, the electrolyte membranes that underwent the heat-sealing treatment were visually observed, and the degree of coloration of the electrolyte membranes was evaluated according to the following evaluation criteria. <Evaluation Criteria> ○: Visually colorless and transparent. △: Visually a very slight brown color can be observed. ×: Visually a dark brown color can be observed.

[0179] [Fuel Cell Evaluation] Fuel cells were fabricated and their characteristics evaluated using the following method for the multilayer structures of Examples C1-C2 and the structures of Comparative Examples C1-C2. Specifically, first, a water-repellent carbon paper (Toray Industries, Ltd., model number: EC-TP1-060T) was placed as a gas diffusion layer on the fabricated structure to create a MEA. The fuel cell was fabricated by sandwiching the MEA in a single-cell power generation evaluation jig (JARI). This fuel cell was placed in a constant temperature bath set to 80°C and electrochemical evaluation was performed under the following conditions. The evaluation equipment used was a fuel cell evaluation device (Toyo Technica Co., Ltd., model number: PE-8900K) and a potentiometer / galvanostat (Solatron, Inc., model number: SI1287).

[0180] (Anode conditions) Electrode area: 1.0 cm² 2Supply gas type: 100% H₂ Gas supply rate: 139 mL / min (relative humidity: 95%) (Cathode conditions) Electrode area: 1.0 cm 2 Supply gas type: Air Gas supply rate: 332 mL / min (relative humidity: 95%)

[0181] <Evaluation of Hydrogen Crossover Current Density> In order to evaluate the degradation of an electrolyte membrane using a single cell, the permeation of the electrolyte membrane by hydrogen (hydrogen crossover) was electrochemically evaluated instead of oxygen, which is difficult to evaluate. Specifically, the hydrogen supply rate at the anode was set to 70 mL / min (relative humidity: 95%), the nitrogen supply rate at the cathode was set to 166 mL / min (relative humidity: 95%), and the potential was swept from 0.2 V to 0.6 V at 5 mV / s. The obtained current density between 0.4 V and 0.5 V was assumed to be linear and extrapolated to 0 V. The current density at 0 V obtained by extrapolation was defined as the hydrogen crossover current density (mA / cm 2 ) for evaluation. A lower value of the hydrogen crossover current density (mA / cm 2 ) indicates a lower hydrogen permeation amount. Since the material does not have selectivity for gas permeation, when hydrogen crossover is low, oxygen crossover is also reduced, and it can be considered that degradation of the electrolyte membrane is suppressed.

[0182] <Evaluation of OCV (Open Circuit Voltage)> Under the above conditions, OCV (at a current density of 0 A / cm 2 ) was evaluated. OCV is the potential when no voltage or current is applied to the single cell.

[0183] <PDat 0.6 V (Maximum Power Density)> Power generation evaluation (current-voltage curve) was performed under the above conditions, and the maximum power density at a cell voltage of 0.6 V (W / cm 2 ) was calculated.

[0184]

[0185] The details of the materials listed in Table 3 are as follows: Nafion 211: A membrane containing tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Chemours, Nafion 211, thickness 25 μm) Nafion 212: A membrane containing tetrafluoroethylene-perfluorovinyl ether sulfonic acid copolymer (Chemours, Nafion 212, thickness 50 μm) PVA: Polyvinyl alcohol (Millipore, PVA complete saponified (for synthesis), weight-average molecular weight: approximately 60,000) PVS: Polyvinyl sulfonic acid

[0186] As can be seen from Table 3, the fuel cells using the multilayer structures of Examples C1 and C2 had smaller hydrogen crossover values ​​and higher OCV values ​​compared to Comparative Examples C1 and C2. In Examples C1 and C2, the first electrolyte membrane containing a hydroxyl group-containing polymer had gas barrier properties, and it is presumed that this improved the characteristics of the fuel cells.

[0187] The multilayer structure manufactured by the manufacturing method of this embodiment can be used as a component of a fuel cell.

Claims

1. A method for manufacturing a multilayer structure, comprising 1. Placing a second electrolyte membrane having an acid content of 0.8 meq / g or more on a first laminate comprising a peel-off liner and a first electrolyte membrane containing a hydroxyl group polymer, thereby forming a second laminate comprising the peel-off liner, the first electrolyte membrane, and the second electrolyte membrane in this order.

2. The manufacturing method according to claim 1, wherein the second laminate is formed by a heat-pressing process in which the first laminate and the second electrolyte membrane are heat-pressed together.

3. The manufacturing method according to claim 2, wherein the temperature of the heat-pressing treatment is 60°C to 150°C.

4. The manufacturing method according to claim 2, wherein the peelable liner has a softening point higher than the temperature of the heat-sealing treatment.

5. The method for producing the polymer according to claim 1, wherein the hydroxyl group-containing polymer includes polyvinyl alcohol.

6. The manufacturing method according to claim 1, wherein the first electrolyte membrane further comprises a proton-conducting polymer.

7. The manufacturing method according to claim 1, further comprising arranging the first electrolyte membrane on the peel liner to form the first laminate.

8. The manufacturing method according to claim 7, wherein the first electrolyte membrane is placed on the peel liner by applying a solution containing the hydroxyl group-containing polymer and water onto the peel liner and drying the resulting coating film.

9. The manufacturing method according to claim 8, wherein the content of the hydroxyl group-containing polymer in the solution is 0.10 wt% to 80.0 wt%.

10. The manufacturing method according to claim 1, wherein the contact angle of water with respect to the surface of the peeling liner is 100° or less.

11. The manufacturing method according to claim 1, wherein in the second laminate, the peeling force P1 between the peeling liner and the first electrolyte membrane is lower than the peeling force P2 between the first electrolyte membrane and the second electrolyte membrane.

12. The manufacturing method according to claim 1, further comprising peeling the release liner from the second laminate to form a third laminate comprising the first electrolyte membrane and the second electrolyte membrane.

13. The manufacturing method according to claim 12, further comprising arranging a third electrolyte membrane having an acid content of 0.8 meq / g or more on the third laminate, thereby forming a fourth laminate comprising the third electrolyte membrane, the first electrolyte membrane, and the second electrolyte membrane in that order.

14. The manufacturing method according to claim 1, further comprising forming a catalyst layer on the second electrolyte membrane.

15. A multilayer structure comprising, in this order, a peelable liner, a first electrolyte membrane containing a hydroxyl group-containing polymer, and a second electrolyte membrane having an acid content of 0.8 meq / g or more.

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