Film and use thereof

Abstract

The present invention provides a film having good slipperiness, sufficiently maintained durability under high temperature and high humidity, and improved mechanical characteristics as compared with a film of PPSU alone, and provides a reinforcing member that is for electrolyte membranes for solid polymer electrolyte fuel cells or solid polymer electrolyte water electrolysis and that uses said film. The present invention relates to a film containing 6-94 mass parts of polyphenylsulfone and 94-6 mass parts of polysulfone, the arithmetic average height (Sa) of at least one surface being 6.0-17.5 nm.

Description

Film and Its Use

[0001] The present invention relates to a film containing a polysulfone resin and a reinforcing member for an electrolyte membrane of a solid polymer fuel cell or a solid polymer water electrolyzer using the same.

[0002] A fuel cell is a cell in which electrodes are arranged on both sides of an electrolyte membrane and electricity is generated by an electrochemical reaction between hydrogen and oxygen. Since only water is generated during power generation, it is attracting attention as a clean energy system. Among them, the solid polymer fuel cell has the advantages of a relatively low operating temperature and a short startup time, and is expected to spread as a battery for mobile bodies such as automobiles and ships. However, since an expensive platinum-based catalyst is sometimes required for the electrodes, it is still expensive, and a reduction in manufacturing cost is desired.

[0003] By increasing the operating temperature of a fuel cell, the output density becomes higher and it can be miniaturized. Therefore, as one of the measures to reduce the price, increasing the maximum operating temperature is being considered. The general maximum operating temperature of a solid polymer fuel cell is 90 to 95°C, but in the future it will be about 120°C. For the resin members used in fuel cells, an improvement in high-temperature long-term durability (high-temperature hydrolysis resistance) in the presence of water is required (refer to the NEDO Technology Development Roadmap (Fuel Cell for HDEV) published in 2022 https: / / www.nedo.go.jp / library / battery_hydrogen.html).

[0004] A solid polymer fuel cell has a cell in which a joined body of an electrolyte membrane and an electrode made of a solid polymer reinforced by a resin reinforcing frame and a gas diffusion layer are sandwiched between two separators made of metal or the like as a power generation unit. It is common for the reinforcing frame and the separator to be adhered with a hot melt adhesive. If the melting point of the hot melt adhesive is not sufficiently higher than the operating temperature of the fuel cell, there is a possibility that the adhesive will melt during operation and hydrogen and oxygen will leak. Therefore, when the operating temperature is about 120°C, the melting point of the hot melt adhesive should be at least 150°C or higher, and its adhesion processing temperature should be even higher, 170 to 180°C, in order to melt the adhesive sufficiently.

[0005] Also, using a solid polymer electrolyte membrane, water (H２ By electrolyzing O), hydrogen (H) ２ Another known technology for producing ) is called solid polymer water electrolysis. In solid polymer water electrolysis, a membrane-electrode assembly in which a catalyst layer is formed on the surface of the electrolyte membrane is used, and the reinforcing frame is required to have the same performance as in solid polymer fuel cells.

[0006] As for films used in such reinforcing frames, for example, Patent Document 1 discloses a reinforcing frame that mechanically reinforces the electrolyte membrane at the periphery of a fuel cell cell, and that a biaxially oriented film of polyethylene naphthalene dicarboxylate (PEN) is used as the reinforcing frame. However, the high-temperature long-term durability time at 121°C and 100% RH is at most about 200 hours, which was insufficient to meet the above requirements.

[0007] On the other hand, polysulfone resins, particularly polyphenylsulfone (PPSU), offer excellent heat resistance and long-term durability under high temperature and high humidity conditions, and are used in applications where these properties are required.

[0008] An example of using polyphenylsulfone films in polymer electrolyte fuel cells is the technology described in Patent Document 2, in which a polyphenylsulfone film is used as the base layer of a gasket component for a polymer electrolyte fuel cell. Furthermore, Patent Document 2 discloses that a gasket component containing polyphenylsulfone exhibits excellent hydrolysis resistance in high-temperature environments.

[0009] Patent No. 4944419 Patent No. 7151951

[0010] Our research has shown that PPSU-only films have poor lubricity (sliding properties), making it desirable to add a lubricant during film formation. However, heat-resistant films used in applications such as fuel cells may cause catalyst poisoning if the lubricant contains silica or other substances, so it is desirable to have no lubricant or only a small amount of lubricant.

[0011] Furthermore, our studies have revealed that in films in which PPSU is blended with polysulfone (PSU) or the like, the mechanical properties and durability under high temperature and high humidity conditions may decrease depending on the dispersion state of the resin.

[0012] Therefore, the object of the present invention is to provide a film that has better slipperiness, maintains sufficient durability under high temperature and high humidity conditions, and has improved mechanical properties compared to a film made of PPSU alone, and a reinforcing member for the electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis using the same.

[0013] As a result of diligent research to solve the above problems, the inventors of the present invention have found that by blending PPSU and PSU in a specific ratio and performing melt extrusion processing under specific temperature conditions, a film with better slipperiness and improved rigidity can be obtained compared to PPSU alone, thus completing the present invention.

[0014] In other words, the present invention includes the following:

[0015] [1] A film containing polyphenylsulfone and polysulfone, wherein the mass ratio of polysulfone to polyphenylsulfone is 6 / 94 or more and 94 / 6 or less, and the arithmetic mean height (Sa) of at least one surface is 6.0 nm or more and 17.5 nm or less.

[0016] [2] The film according to [1], wherein the coefficient of dynamic friction measured by bringing one surface into contact with the other surface is 1.0 or less.

[0017] [3] The film according to [1] or [2], wherein the retention rate of tensile break elongation before and after treatment when treated in hot water at a temperature of 120°C for 1600 hours is 60% or more.

[0018] [4] A film according to any one of [1] to [3], having a thickness of 20 μm or more and 300 μm or less.

[0019] [5] A film according to any one of [1] to [4], used as a reinforcing member for electrolyte membranes to reinforce the outer edge of the electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis.

[0020] [6] A reinforcing member for an electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis, comprising a film according to any one of [1] to [4], for reinforcing the outer edge of the electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis.

[0021] According to the present invention, it is possible to provide a film that has better slipperiness, maintains sufficient durability under high temperature and high humidity conditions, and has improved mechanical properties compared to a film made of PPSU alone, as well as a reinforcing member for the electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis using the same.

[0022] The exact reason why blending PPSU and PSU in a specific ratio and performing melt extrusion under specific temperature conditions yields a film with better slipperiness and improved rigidity compared to PPSU alone is unclear, but it is thought to be as follows.

[0023] In other words, in a blend of PPSU and PSU in a specific ratio, as shown in Figure 1, the dispersion state of the resin tends to form a sea-island structure, with relatively large domains forming in the center (central part) in the thickness direction, while relatively small domains are formed near the surface. In this case, the dispersion state near the surface of the film is thought to particularly affect the arithmetic mean height (Sa), and it is believed that by controlling the dispersion state by the temperature conditions of the melt extrusion process, an appropriate Sa can be obtained, resulting in good slipperiness. Furthermore, if Sa is excessively large, larger domains tend to form even in the center of the film, but by suppressing this, it is believed that a film can be obtained that maintains sufficient durability under high temperature and high humidity conditions while also improving rigidity.

[0024] The images shown are transmission electron microscope (TEM) images of various parts of the film obtained in Example 3.

[0025] The present invention will be described in detail below. For convenience of explanation, the film formation direction may be referred to as the machine axis direction, longitudinal direction, longitudinal direction, or MD direction, and the direction perpendicular to the film formation direction and the thickness direction may be referred to as the width direction, transverse direction, or TD direction. Furthermore, the various physical properties described herein are specifically measured by the methods described in the examples.

[0026] [Film Material] The film of the present invention contains polyphenylsulfone (PPSU) and polysulfone (PSU), and includes a blend containing PPSU and PSU as a polysulfone-based resin component.

[0027] Polysulfone resins are resins containing sulfonyl groups (-SO ２ These are resins that have repeating units of -) in their structure, and polyphenylsulfone, polysulfone, and polyethersulfone are typical examples.

[0028] Polyphenylsulfone is a polymer represented by the following chemical formula (1), and is known to have particularly excellent durability under high temperature and high humidity conditions among polysulfone resins.

[0029]

[0030] (In the formula, n represents the degree of polymerization.)

[0031] Furthermore, polysulfone is a polymer represented by the following chemical formula (2).

[0032]

[0033] (In the formula, n represents the degree of polymerization.)

[0034] In the present invention, the mass ratio of polysulfone to polyphenylsulfone (PSU / PPSU) is preferably 6 / 94 or more and 94 / 6 or less. From the viewpoint of further improving the tensile modulus, the mass ratio (PSU / PPSU) is more preferably 20 / 80 or more, even more preferably 40 / 60 or more, and particularly preferably 60 / 40 or more. Furthermore, from the viewpoint of further improving durability under high temperature and high humidity, the mass ratio (PSU / PPSU) is more preferably 90 / 10 or less, even more preferably 85 / 15 or less, and particularly preferably 80 / 20 or less.

[0035] In addition to polyphenylsulfone and polysulfone, other polysulfone-based resins may also be included. Examples of such other polysulfone-based resins include polyethersulfone.

[0036] From the viewpoints of durability and heat resistance under high temperature and high humidity, the content of the polysulfone resin component is preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 100% by mass in the resin component.

[0037] As the resin component other than the polysulfone resin, a resin having appropriate compatibility and dispersibility with the polysulfone resin and a glass transition point of 170°C or higher is preferred. Examples of such resins include polyetherimide and polyaryl ether ketone.

[0038] From the viewpoint of the heat resistance of the film, the glass transition temperature Tg of the resin component is preferably 170°C or higher, and more preferably 200°C or higher.

[0039] From the viewpoints of film-forming property, smoothness, transparency, etc. of the film, the content of the resin component is preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 100% by mass in the film.

[0040] It is possible to contain components other than the resin component in the film. As other components, an appropriate filler can be contained for the purpose of improving slipperiness, etc. However, in the present invention, sufficient slipperiness can be obtained without containing a filler. Also, depending on the use of the film and the type of filler, it may be more preferable not to contain a filler or to have a lower filler content. In such a case, the filler content is preferably 0.3% by mass or less, and more preferably 0.1% by mass or less.

[0041] Examples of the filler include calcium carbonate, calcium oxide, aluminum oxide, kaolin, silicon oxide, zinc oxide, carbon black, silicon carbide, tin oxide, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, crosslinked silicon resin particles, etc. Further, a colorant, an antistatic agent, an antioxidant, an organic lubricant, a catalyst, etc. can be appropriately added to the film.

[0042] [Film Properties] The film of the present invention is characterized in that the arithmetic mean height (Sa) of at least one surface is 6.0 nm or more and 17.5 nm or less. The arithmetic mean height (Sa) is a surface roughness parameter, which is the value obtained by summing up and averaging the absolute values of the deviations from the average plane to the image surface within the evaluation area. In particular, it is preferable that the Sa of the surface with a smaller Sa is 6.0 nm or more and 17.5 nm or less. Also, it is preferable that the Sa of both surfaces is 6.0 nm or more and 17.5 nm or less.

[0043] In any case, from the viewpoint of further improving the slipperiness, the arithmetic mean height (Sa) is preferably 7 nm or more, more preferably 8 nm or more, and still more preferably 12 nm or more. Also, from the viewpoint of further improving the tensile elongation retention rate and the tensile modulus, the arithmetic mean height (Sa) is preferably 16.5 nm or less, more preferably 15 nm or less.

[0044] The film of the present invention preferably has a coefficient of kinetic friction measured by bringing one surface into contact with the other surface of 1.0 or less. From the viewpoint of slipperiness, the coefficient of kinetic friction is more preferably 0.8 or less, and still more preferably 0.6 or less. Although the coefficient of kinetic friction is preferably smaller from the viewpoint of slipperiness, it may be 0.1 or more, or 0.2 or more.

[0045] From the viewpoint of durability under high temperature and high humidity, the film of the present invention preferably has a retention rate of tensile elongation of 60% or more, more preferably 70% or more, and still more preferably 80% or more before and after treatment when treated in hot water at a temperature of 120 °C for 1600 hours.

[0046] The film of the present invention has an improved tensile modulus compared to a film of pure PPSU. The tensile modulus of such a film is preferably 1400 MPa or more, more preferably 1500 MPa or more, and still more preferably 1550 MPa or more for MD or TD.

[0047] The thickness of the film of the present invention is preferably 20 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more, from the viewpoint of uniformity of film thickness and shape, mechanical properties in various applications, and handling. Furthermore, the thickness of the film is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less, from the viewpoint of thickness uniformity.

[0048] [Method for manufacturing the film] A preferred method for manufacturing the film of the present invention includes the steps of: extruding a resin composition containing PSU and PPSU in a specific mass ratio from a die as a sheet while melting and kneading it so that the melting resin temperature is 330°C or higher and 390°C or lower; and cooling and solidifying the sheet using a cast roll at a temperature of 100°C or higher and 210°C or lower.

[0049] Thus, by maintaining a specific range of molten resin temperatures during the production of films containing PSU and PPSU, the dispersion state near the surface of the film becomes appropriate, and the desired arithmetic mean height (Sa) can be obtained.

[0050] The method for melt-mixing the resin composition is not particularly limited, but for example, a single-screw extruder, a twin-screw extruder, a pressure kneader, a Banbury mixer, etc., can be used. Among these, a twin-screw extruder is particularly preferred. The screw configuration of the extruder preferably incorporates several kneading discs that provide excellent mixing performance.

[0051] When melting and kneading the resin, the molten resin temperature is preferably 330°C or higher, and more preferably 340°C or higher, from the viewpoint of suppressing excessive dispersion of the resin. Furthermore, the molten resin temperature is preferably 390°C or lower, and more preferably 380°C or lower, from the viewpoint of suppressing excessive dispersion of the resin.

[0052] The melt-kneaded resin composition is extruded from a die as a sheet, cooled and solidified on a cast roll to obtain a molded film. During cooling and solidification, it is preferable to smooth the surface using pressure rolls such as a metal elastic touch roll having a metallic elastic surface, or a touch roll having a metallic surface and capable of controlling the pressure. Furthermore, it is preferable from the viewpoint of suppressing internal stress in the resulting film that the sheet extruded from the die contacts both the cast roll and the pressure roll simultaneously or almost simultaneously. For this reason, it is preferable to use a vertical drop type in which the sheet extruded from the die is dropped vertically.

[0053] From the viewpoint of suppressing warping of the resulting film, the surface temperature of the cast roll is preferably 120°C or higher, and more preferably 130°C or higher. Furthermore, from the viewpoint of suppressing adhesion to the cast roll, the surface temperature of the cast roll is preferably 200°C or lower, and more preferably 180°C or lower.

[0054] If necessary, after cooling and solidification, heat treatment at a temperature above the glass transition temperature (Tg) of the resin component, preferably Tg+10 to Tg+30 (°C), may reduce warping and waviness of the resulting film. The heat treatment method may be either a roll conveying type or a floating type.

[0055] Furthermore, the film of the present invention may be either an unstretched film or a uniaxially or biaxially stretched film, but an unstretched film is preferred from the viewpoint of ease of manufacture and low cost of manufacturing equipment. Here, "unstretched" refers to a state in which the film has not been stretched to 1.2 times or more in any direction by a stretching process such as roll stretching or tenter stretching, and preferably to a state in which the film has not been stretched to 1.1 times or more in any direction. It is also possible to perform the above-mentioned heat treatment after stretching.

[0056] [Laminated Film] The film of the present invention can be used as a base film (hereinafter referred to as "Layer A") of a laminated film. In the case of a laminated film, it may have at least one Layer A, and may also have two or more Layer A layers. Furthermore, the laminated film may include Layer B, Layer A, and Layer B in that order, with Layer A as the base layer and Layer B as the heat-sealable layer. In addition, it may include an intermediate layer (such as an easy-adhesion layer) Layer C, and may include Layer B, Layer C, Layer A, Layer C, and Layer B in that order. Such a laminated film can be used as a heat-sealable film for reinforcing members of electrolyte membranes in polymer electrolyte fuel cells and polymer electrolyte water electrolysis.

[0057] [Layer B (Heat-Fusible Layer)] Layer B, as a heat-fusible layer, contains 100 to 70% by mass of heat-fusible polyolefin B1. From the viewpoint of moist heat durability and adhesion to the adherend, it is preferable to contain 100 to 75% by mass of heat-fusible polyolefin B1, more preferably 100 to 80% by mass, even more preferably 100 to 90% by mass, and most preferably 100% by mass. In this specification, "heat-fusible" refers to the property of being able to fuse to an adherend by heating, and preferably to the property of being able to fuse to a metal such as SUS316 by heating.

[0058] When layer B is provided on both sides of layer A, layer B may have the same composition or different compositions. However, for example, when heat-bonding adherends made of the same material, it is preferable to provide heat-fusible layers with the same composition on both sides. Furthermore, the thickness of the heat-fusible layers may be the same or different. However, in the above case, it is preferable to provide heat-fusible layers of the same thickness on both outermost surfaces.

[0059] The thickness of layer B is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less, from the viewpoint of high-temperature hydrolysis resistance as a reinforcing member. However, if it is too thin, the mechanical relaxation function in the thickness direction as a heat-sealable layer will be weakened, so it is preferably 10 μm or more, more preferably 15 μm or more, and particularly preferably 20 μm or more.

[0060] [Heat-fusible polyolefin B1] As heat-fusible polyolefin B1, it is possible to use an unmodified polyolefin resin, but a modified polyolefin is preferred, and a modified polyolefin containing polypropylene is particularly preferred.

[0061] Examples of unmodified polyolefin resins include homopolymers and copolymers of olefins having 2 to 8 carbon atoms, and copolymers of olefins having 2 to 8 carbon atoms with other monomers. Specifically, examples include polyethylene such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene resin, polypropylene, polyisobutylene, poly(1-butene), polyvinylcyclohexane, polystyrene, poly(p-methylstyrene), poly(α-methylstyrene), ethylene-propylene block copolymer, ethylene-propylene random copolymer, ethylene-butene-1 copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-butene-propylene ternary copolymer, ethylene-propylene diene rubber, ethylene-hexene copolymer and other α-olefin copolymers, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate-methyl methacrylate copolymer, polybutadiene-styrene copolymer, polybutadiene-maleic anhydride copolymer, and ionomer resins. Furthermore, chlorinated polyolefins, which are obtained by chlorinating these polyolefins, can also be used.

[0062] As described above, various types of heat-fusible polyolefin B1 can be used, but it is particularly preferable to use a modified polyolefin resin in which various functional groups (e.g., carboxyl groups, hydroxyl groups, etc.) have been introduced into the polyolefin resin.

[0063] Furthermore, among these modified polyolefin resins, modified polyolefin resins having an acid value of 1 to 200 mg KOH / g (also called acid-modified polyolefin resins) and / or modified polyolefin resins having a hydroxyl value of 1 to 200 mg KOH / g (also called hydroxyl-modified polyolefin resins) can be used because they exhibit improved adhesion to the metal layer and excellent adhesion to the electrolyte membrane.

[0064] Acid-modified polyolefin resins are polyolefin resins that have carboxyl groups or carboxylic anhydride groups in their molecules, and are synthesized by modifying polyolefins with unsaturated carboxylic acids or their derivatives. Graft modification and copolymerization can be used as modification methods.

[0065] Acid-modified polyolefin resin is a graft-modified polyolefin obtained by graft-modifying or copolymerizing a polyolefin resin before modification with at least one polymerizable ethylenically unsaturated carboxylic acid or its derivative.

[0066] Examples of polyolefin resins before modification include the polyolefin resins mentioned above, among which propylene homopolymers, copolymers of propylene and α-olefins, ethylene homopolymers, and copolymers of ethylene and α-olefins are preferred. These can be used individually or in combination of two or more.

[0067] Examples of acid-modified polyolefin resins include maleic anhydride-modified polypropylene, ethylene-(meth)acrylic acid copolymer, ethylene-acrylic acid ester-maleic anhydride terpolymer, or ethylene-methacrylic acid ester-maleic anhydride terpolymer. Specifically, these are commercially available as "Modic" from Mitsubishi Chemical Corporation, "Admer" and "Unistol" from Mitsui Chemicals, Inc., "Hardren" from Toyobo Co., Ltd., "Yumex" from Sanyo Chemical Industries, Ltd., "Rexpearl EAA" and "Rexpearl ET" from Nippon Polyethylene Co., Ltd., "Primacol" from Dow Chemical Ltd., "Nucrel" from Mitsui DuPont Polychemicals, and "Bondine" from Arkema.

[0068] Hydroxyl group-modified polyolefin resins are polyolefin resins having hydroxyl groups in their molecules, and are synthesized by graft modification or copolymerization of polyolefins with hydroxyl group-containing (meth)acrylic acid esters or hydroxyl group-containing vinyl ethers, as described later. Examples of the hydroxyl group-containing (meth)acrylic acid esters include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycerol (meth)acrylate, lactone-modified hydroxyethyl (meth)acrylate, polyethylene glycol (meth)acrylate, and polypropylene glycol (meth)acrylate. Examples of the hydroxyl group-containing vinyl ethers include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether.

[0069] Particularly preferred heat-fusible polyolefin resins include a modified product obtained by modifying the heat-fusible polyolefin B1 with an acid anhydride, wherein the acid anhydride content is 0.1 to 3% by mass, and the amount of low molecular weight components extracted with acetone, which have a number average molecular weight of 1000 or less, is less than 1% by mass.

[0070] If the anhydrous content is 0.1% by mass or more, sufficient adhesion to metals is easily obtained, and if it is 3% by mass or less, sufficient mechanical properties such as rigidity and strength are easily obtained. If the amount of low molecular weight components extracted is less than 1% by mass, the low molecular weight components are less likely to bleed out to the surface of the heat-fusible layer, and adhesion is less likely to be inhibited.

[0071] [Other Resins B2] Layer B may contain 0 to 30% by mass of other resins B2 other than the heat-fusible polyolefin B1. In other words, the heat-fusible layer can contain other resins B2 that have appropriate compatibility or dispersibility with the heat-fusible polyolefin B1, as long as it does not impair the objectives of the present invention.

[0072] However, if there is too much of the other resin B2, it may reduce the adhesion force during the original metal bonding process. By providing the easy-adhesion layer C, it is possible to increase the amount of other resin components added to the B layer. From this viewpoint, the upper limit of the resin B2 contained in the heat-fusible layer is 30% by mass, preferably 25% by mass, more preferably 20% by mass, and particularly preferably 10% by mass. There is no specific lower limit, but it may be 0% by mass as long as sufficient adhesion force according to the intended use can be ensured.

[0073] Examples of resin B2 include polyamides, polyesters, polyurethanes, 4-methyl-1-pentene polymers, copolymers of 4-methyl-1-pentene and α-olefins, polyolefins other than these (co)polymers, ethylene propylene diene rubber, fluororubber, silicone rubber, and the like.

[0074] While layer B may consist solely of resin, stabilizers such as tackifiers, antistatic agents, antioxidants, metal deactivators, dehydrating agents, and antacid adsorbents, or additives such as crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing agents, pigments, dyes, and flame retardants may be added within limits that do not impair the effects of the present invention.

[0075] Methods for laminating layer B include lamination methods such as dry lamination and wet lamination, or coating methods such as extrusion resin coating, molten resin coating, and liquid coating.

[0076] [Layer C (Easy-Adhesion Layer)] Layer C, as an easy-adhesion layer, can be provided to improve the adhesion between Layer A, which is a base film containing polyphenylsulfone, etc., and Layer B, which is a heat-fusible layer. Alternatively, instead of providing Layer C, or before forming Layer C, the surface of Layer A can be treated with corona treatment, plasma treatment, etc., to improve adhesion to the surface.

[0077] When layers C are provided on both sides of layer A, the layers C may have the same composition or different compositions. However, if, for example, heat-fusible layers of the same material and thickness are provided on both surfaces, it is preferable to provide layers C with the same composition on both sides. Furthermore, the thickness of the layers C may be the same or different, but in the above case, it is preferable to provide layers C with the same thickness on both sides.

[0078] The material constituting layer C can be any material that can improve the adhesion between layer A and layer B, and examples include coupling agents, isocyanate compounds, or materials mainly composed of resin.

[0079] Silane coupling agents are typical coupling agents, with the general formula YRSiX ３ This is a compound represented by the formula shown. Here, Y is an organic functional group such as an epoxy group, amino group, vinyl group, or mercapto group; R is an alkylene group such as a methylene group, ethylene group, or propylene group; and X is an alkoxy group such as a methoxy group or ethoxy group.

[0080] The Y portion is preferably an epoxy group, an amino group, or a vinyl group, and more preferably an epoxy group. Specifically, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane can be preferably used as silane coupling agents.

[0081] Silane coupling agents can be used together with surfactants such as silicone-based surfactants. Polyether-modified silicone-based surfactants are preferred as the silicone-based surfactant.

[0082] As the isocyanate compound, polyfunctional isocyanate compounds are preferred. Specific examples of polyfunctional isocyanate curing agents include pentane diisocyanate (PDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), m-xylylene diisocyanate (XDI), polymerized or nurated versions thereof, mixtures thereof, and copolymers with other polymers. Adducts, burettes, and isocyanurates are also examples.

[0083] Examples of resins include polyethyleneimine-based, polyester-based, polyurethane-based, polyvinyl butyral-based, acrylic-based, aminoethylated acrylic polymer-based, styrene / maleic acid copolymer-based, rubber-based, and epoxy-based resins.

[0084] These resins can also be used with crosslinking agents. For example, in addition to isocyanate compounds, crosslinking agents include oxazoline-based crosslinking agents and glycidylamine-based crosslinking agents.

[0085] The thickness of the easy-adhesion layer is, for example, 0.001 μm or more, but from the viewpoint of preventing adhesive coating from failing, it is preferably 0.010 μm or more, and more preferably 0.020 μm or more. Also, the thickness of the easy-adhesion layer is, for example, 1 μm or less, but from the viewpoint of exhibiting high adhesive strength, it is preferably 0.2 μm or less, and more preferably 0.1 μm or less.

[0086] It is preferable that the C layer does not contain any components other than those mentioned above, but it may contain antioxidants, stabilizers, lubricants, metal deactivators, nucleating agents, etc., to the extent that it does not impair the effect of the C layer.

[0087] A method for producing a laminated film having layers A, C, and B in this order includes forming layer C on layer A and / or layer B, and then laminating the remaining layers. However, the method of forming layer C on layer A, and then laminating layer B is preferred. More specifically, it is preferable to form layer C on the surface of layer A, which is a base film, by coating or the like, and then laminate molten layer B by extrusion lamination.

[0088] [Applications] The film described above can be manufactured as a roll wound in the longitudinal direction. The film can be cut, punched, etc. into appropriate shapes and used for various purposes.

[0089] The film of the present invention exhibits excellent durability under high temperature and high humidity conditions, and has good uniformity in thickness and shape, making it suitable for various applications. In particular, it is more suitable for use as a reinforcing member for electrolyte membranes in polymer electrolyte fuel cells and polymer electrolyte water electrolysis.

[0090] The film of the present invention is effective for applications other than as a reinforcing member for electrolyte membranes, such as applications requiring heat resistance and moisture heat durability. Examples of such applications include carrier films for various processes, release films for various processes, heat-resistant packaging films, and heat-resistant container films. Of course, it can also be used as other general-purpose films.

[0091] [Reinforcement Member for Electrolyte Membrane] The reinforcement member for the electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis of the present invention is a reinforcement member for the electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis for reinforcing the outer edge of the polymer electrolyte membrane, and is characterized by including the film of the present invention as described above.

[0092] A reinforcing member for the electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis system only needs to reinforce the electrolyte membrane of the polymer electrolyte fuel cell or polymer electrolyte water electrolysis system. This includes not only cases where only the electrolyte membrane of a polymer electrolyte fuel cell is reinforced, but also cases where the reinforcing member is used to reinforce an electrolyte membrane electrode assembly, or a laminate including a gas diffusion layer. Such reinforcing members may be referred to as support members, gasket members, etc., and any member that has the effect of supporting the electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis system and increasing its strength is included in the definition of "reinforcing member".

[0093] The shape of the reinforcing member can be any shape that reinforces at least one side of the electrolyte membrane of a polymer electrolyte fuel cell or the like, and examples include frame-shaped, L-shaped, U-shaped, and I-shaped. However, from the viewpoint of improving airtightness and reinforcing effect, the shape of the reinforcing member is preferably frame-shaped with one or more openings.

[0094] Reinforcement members for electrolyte membranes in polymer electrolyte fuel cells or polymer electrolyte water electrolysis can be fixed to the outer edge of the electrolyte membrane of the polymer electrolyte fuel cell or polymer electrolyte water electrolysis using adhesives, hot melt adhesives, etc. In this case, if the film of the present invention has a heat-sealable layer (layer B), it can be fixed to the outer edge of the electrolyte membrane of the polymer electrolyte fuel cell or polymer electrolyte water electrolysis by heat fusion (hot melt). Alternatively, it can be interposed between metal separators such as titanium, and the separators can be fixed to each other by heat fusion (hot melt).

[0095] The present invention will be described in more detail below with reference to examples and comparative examples. In this invention, physical properties, etc., were measured or evaluated by the following methods. Hereinafter, unless otherwise specified, "parts" means "parts by mass" and "%" means "percent mass".

[0096] (1) Film Thickness: A 50mm x 50mm section of film was cut from the center of the film roll in the width direction, and the thickness was measured at 10 random points. The thickness was measured using a Mitutoyo digital thickness gauge. The arithmetic mean of each measurement was calculated to determine the film thickness.

[0097] (2) Sensory evaluation of slipperiness A 50 mm x 50 mm section of film was cut from the center of the film roll in the width direction. The film surface 1 (the CR (cast roll) side during film formation) and the film surface 2 (the opposite side of surface 1) were placed on top of each other, and the slipperiness was evaluated by sensory evaluation by rubbing them together with fingers. The evaluation criteria were as follows: ○: The overlapping films slide against each other. ×: The overlapping films stick together and cannot slide against each other.

[0098] (3) Coefficient of Dynamic Friction (μK) A 70 mm x 200 mm section of film was cut from the center of the film roll in the width direction and used for measurement. The coefficient of dynamic friction (μK) was evaluated by performing a sliding test using a Tensilon universal material tester (RTG-1210, A&D Corporation). Film surface 1 (CR side during film formation) was fixed to the bottom surface (50 mm x 100 mm) of a 1400 g metal rectangular parallelepiped with the surface facing outwards. Next, film surface 2 (opposite side of surface 1) was fixed to a flat metal plate with adhesive tape. The metal rectangular parallelepiped was placed so that film surface 1 and film surface 2 were in contact, and the coefficient of dynamic friction was measured at a tensile speed of 200 mm / min and a measurement displacement of 100 mm under 23°C and 65% RH conditions. The evaluation criteria were as follows: ○: 0.1 < μK ≤ 1.0 ×: Greater than 1.0 or the coefficient of friction was too high to measure

[0099] (4) Arithmetic mean height (Sa) A 50 mm x 100 mm section of film was cut from the center of the film roll in the width direction and used for measurement. The arithmetic mean height (Sa) was measured on the film surface 1 (CR side during film formation) using a non-contact surface shape measurement system (VertScan VS1000 manufactured by Hitachi High-Tech Science Corporation) under the following conditions. (Measurement conditions) ・Measurement mode: WAVE mode ・Objective lens: 10x ・0.5x Tube lens ・Average value of N3 measurements was used. The evaluation criteria were as follows: ○: 7 nm ≤ Sa ×: Sa is less than 7 nm

[0100] (5) Tensile modulus of elasticity The following sample pieces were cut from the center of the film roll in the width direction, so that the length direction was MD and TD, and used for measurement. The tensile modulus of elasticity was evaluated by performing a static tensile test using an Autograph precision universal tester (AGS-X, Shimadzu Corporation). (Measurement conditions) ・Temperature and humidity environment: 23°C, 65% RH ・Tensile speed: 200 mm / min ・Test piece: Strip shape with width 10 mm x length 100 mm ・Film direction: MD, TD ・Average value of N5 measurements was used

[0101] (6) Evaluation of tensile strength retention and durability under high temperature and high humidity conditions (Preparation of durability evaluation samples) A ​​10 mm x 120 mm piece of film was cut from the center of the film roll in the width direction. This film was completely submerged in a stainless steel container filled with deionized water, and the stainless steel container was placed in an accelerated life test apparatus (EHS-412H manufactured by ESPEC Corporation) set to a temperature of 120°C for 1600 hours to obtain a film after durability treatment. (Evaluation of tensile strength) Test pieces were cut from the film before and after this treatment and used for measurement. Tensile strength was evaluated by performing a static tensile test using an Autograph precision universal tester (AGS-X manufactured by Shimadzu Corporation) under the following conditions. • Temperature and humidity environment: 23°C, 65% RH • Tensile speed: 200 mm / min • Test specimen: Strip shape, 10 mm wide x 100 mm long • Film orientation: MD • Average value of 5 measurements was used (Evaluation of tensile strength retention rate) The tensile strength retention rate was evaluated using the following formula: Tensile strength retention rate (%) = (Tensile strength after durability treatment ÷ Tensile strength before durability treatment) × 100% The evaluation criteria were as follows: ○: Tensile strength retention rate before and after durability treatment is 60% or higher ×: Tensile strength retention rate before and after durability treatment is less than 60%

[0102] [Example 1] 10% by mass of polyphenylsulfone (BASF, Ultrazone® P2010, indicated as PPSU in the table) and 90% by mass of polysulfone (BASF, Ultrazone® S3010, indicated as PSU in the table) were used as resin raw materials and dry blended in a tumbler. Next, after vacuum drying at 160°C for 24 hours, the mixture was fed into a twin-screw extruder and melt-kneaded to a molten resin temperature of 360°C. After extrusion through a 600 mm wide T-die, a film with a thickness of 25 μm was produced by pressing with a cast roll set to a surface temperature of 140°C and a nip roll set to a surface temperature of 90°C, and then cooling and solidifying. Here, the molten resin temperature was measured with a thermocouple installed near the tip of the extruder's screw. The properties and evaluation results of the obtained film are summarized in Table 1.

[0103] [Examples 2-7] Films were obtained in the same manner as in Example 1, except that the film formation conditions were changed as shown in Table 1. The characteristics and evaluation results of the obtained films are summarized in Table 1. Figure 1 shows transmission electron microscope (TEM) images of various parts of the film obtained in Example 3.

[0104] [Comparative Example 1] A film was obtained in the same manner as in Example 1, except that only polyphenylsulfone was used as the resin and the thickness of the resulting film was changed to 162 μm. The properties and evaluation results of the obtained film are summarized in Table 1.

[0105] [Comparative Example 2] A film was obtained in the same manner as in Example 1, except that 95% by mass of polyphenylsulfone and 5% by mass of polysulfone were used as the resin, and the thickness of the resulting film was changed to 162 μm. The properties and evaluation results of the obtained film are summarized in Table 1.

[0106] [Comparative Example 3] A film was obtained in the same manner as in Example 1, except that only polysulfone was used as the resin and the thickness of the resulting film was changed to 162 μm. The properties and evaluation results of the obtained film are summarized in Table 1.

[0107] [Comparative Example 4] A film was obtained in the same manner as in Example 1, except that 5% by mass of polyphenylsulfone and 95% by mass of polysulfone were used as the resin, and the thickness of the resulting film was changed to 162 μm. The properties and evaluation results of the obtained film are summarized in Table 1.

[0108] [Comparative Examples 5-6] Films were obtained in the same manner as in Example 1, except that the molten resin temperature was changed as shown in Table 1 in Example 2. The properties and evaluation results of the obtained films are summarized in Table 1.

[0109]

[0110] As is clear from Table 1, in Examples 1 to 7, by blending PPSU and PSU in a specific ratio and performing melt extrusion processing under specific temperature conditions, films were obtained that had better slipperiness, sufficient durability under high temperature and high humidity conditions, and improved mechanical properties compared to films made of PPSU alone.

[0111] Furthermore, as shown in Figure 1, in the film of Example 3, the resin dispersion state is a sea-island structure, with relatively large domains formed in the center (central part) in the thickness direction, while relatively small domains are formed near the surface. In particular, the dispersion state near the surface of the film affects Sa, so by keeping Sa within a specific range, the slipperiness is improved, and the formation of excessively large domains is suppressed, resulting in a film with improved durability under high temperature and high humidity conditions and enhanced rigidity.

[0112] In contrast, Comparative Example 1, in which a film was made using PPSU alone, and Comparative Example 2, in which the PPSU blending ratio was too high, had a small arithmetic mean height Sa, poor slipperiness, and a low tensile modulus.

[0113] Furthermore, in Comparative Example 3, where the film was made using PSU alone, and in Comparative Example 4, where the PSU blending ratio was too high, the arithmetic mean height Sa was small, the slipperiness was poor, and the durability under high temperature and high humidity conditions was inferior compared to the case of PPSU alone.

[0114] Furthermore, in Comparative Example 5, where the melt extrusion temperature was too low, the resin dispersion was insufficient, as can be seen from the large arithmetic mean height Sa, resulting in poor tensile modulus and durability under high temperature and high humidity conditions. Conversely, in Comparative Example 6, where the melt extrusion temperature was too high, the resin dispersion became too fine, resulting in a small arithmetic mean height Sa and poor lubricity.

[0115] [Example 8] (Production of laminated film) An easy-to-adhere adhesive composition (solid content concentration 2% by mass) with the following composition using ion-exchanged water as a solvent was applied to one side of the film obtained in Example 3 by a roll coater method so that the thickness of the easy-to-adhere layer in the final obtained film was 20 nm, and the film was heated and dried at a temperature of 175°C for 60 seconds to cure it.

[0116] <Easy-to-use adhesive composition> The above easy-to-use adhesive composition is aqueous, and its solid component is prepared such that 84% by mass is derived from an epoxy silane coupling agent (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) and 16% by mass is derived from a silicone surfactant (L77, manufactured by Momentive Performance Materials Inc.).

[0117] Next, a heat-sealable layer was formed on the easily adhesive layer of the obtained film. Admer QE840 (Mitsui Chemicals, Inc., acid-modified polypropylene) was used as the heat sealant for forming the heat-sealable layer, and it was formed by extrusion lamination. The thickness of the heat-sealable layer was 50 μm. Using the obtained laminated film, the heat-sealable layers were bonded together by heating and pressurizing (180°C, 10 seconds, 1 MPa) to create T-shaped peel test specimens, and peel evaluation was performed. When the cross-section of the test specimen after evaluation was examined with a microscope, no interfacial delamination occurred on the surface of the base film, and sufficient peel strength accompanied by cohesive failure of the heat-sealable layer was confirmed.

[0118] The film of the present invention exhibits superior slipperiness, maintains sufficient durability under high temperature and high humidity conditions, and has improved mechanical properties compared to a film made solely of PPSU. Therefore, it can be suitably used in a variety of applications, and is particularly suitable for use as a reinforcing member for electrolyte membranes in polymer electrolyte fuel cells or polymer electrolyte water electrolysis systems. Consequently, its industrial applicability is high.

Claims

1. A film containing polyphenylsulfone and polysulfone, wherein the mass ratio of polysulfone to polyphenylsulfone is 6 / 94 or more and 94 / 6 or less, and the arithmetic mean height (Sa) of at least one surface is 6.0 nm or more and 17.5 nm or less.

2. The film according to claim 1, wherein the coefficient of dynamic friction measured by bringing one surface into contact with the other surface is 1.0 or less.

3. The film according to claim 1, wherein the retention rate of tensile break elongation before and after treatment in hot water at a temperature of 120°C for 1600 hours is 60% or more.

4. The film according to claim 1, wherein the thickness is 20 μm or more and 300 μm or less.

5. The film according to any one of claims 1 to 4, used as a reinforcing member for an electrolyte membrane to reinforce the outer edge of an electrolyte membrane in a polymer electrolyte fuel cell or polymer electrolyte water electrolysis.

6. A reinforcing member for an electrolyte membrane of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis, comprising the film described in any one of claims 1 to 4, for reinforcing the outer edge of the electrolyte membrane of the polymer electrolyte fuel cell or polymer electrolyte water electrolysis.

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