Film and reinforcing member for electrolyte membrane of polymer electrolyte fuel cell using same

Abstract

To provide a film that is superior in not only high-temperature mechanical characteristics and high-temperature hydrolysis resistance, but also thickness uniformity and punching workability, and a reinforcement member for electrolyte membrane of a solid-state polymer fuel cell using the same.SOLUTION: The present invention relates to a film that has at least one A layer including 90 mass% or more in total of a polymer A1 of 240°C or higher in fusion point and a resin A2 of 170°C or higher in glass transition temperature, the polymer A including 90 mol% or more of a constitutional unit derived from 4-methyl-1-pentene, wherein the mass ratio A1 / A2 of the resin A2 to the polymer A1 is 95 / 5 to 50 / 50.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film containing a blend of polymethylpentene resins, and to a reinforcing member for an electrolyte membrane of a polymer electrolyte fuel cell using the film. [Background technology]

[0002] Fuel cells are cells that have electrodes placed on both sides of an electrolyte membrane and generate electricity through an electrochemical reaction between hydrogen and oxygen. Because only water is produced during power generation, they are attracting attention as a clean energy system. Among them, polymer electrolyte fuel cells have the advantages of a relatively low operating temperature and a short start-up time, and are therefore expected to become widespread as batteries for mobile vehicles such as automobiles and ships. However, they are still expensive, partly because they require expensive platinum-based catalysts for the electrodes, and there is a demand for lower manufacturing costs.

[0003] Increasing the operating temperature of fuel cells increases their power density and enables them to be made smaller, so increasing their maximum operating temperature is being considered as one way to reduce prices. The typical maximum operating temperature for polymer electrolyte fuel cells is 90-95°C, but in the future this will be around 120°C, meaning that the resin components used in fuel cells will need to have improved high-temperature, long-term durability in the presence of water (high-temperature hydrolysis resistance) (see NEDO Technology Development Roadmap (Fuel Cells for HDEVs) published in 2022: https: / / www.nedo.go.jp / library / battery_hydrogen.html).

[0004] A polymer electrolyte fuel cell is a power generating unit that consists of a cell consisting of an assembly of a solid polymer electrolyte membrane and electrodes, reinforced by a resin reinforcing frame, and a gas diffusion layer sandwiched between two metal separators. The reinforcing frame and separator are typically bonded together 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, the adhesive may melt during operation, resulting in leakage of hydrogen and oxygen. Therefore, for an operating temperature of around 120°C, the melting point of the hot-melt adhesive must be at least 150°C or higher, and the adhesive processing temperature must be even higher, at 170-180°C, to fully melt the adhesive. For this reason, the reinforcing frame must also have improved high-temperature mechanical properties around 170-180°C.

[0005] As a film to be used for such a reinforcing frame, for example, Patent Document 1 discloses providing a reinforcing frame that mechanically reinforces the electrolyte membrane around the periphery of the fuel cell, and using a biaxially stretched film of polyethylene naphthalenedicarboxylate (PEN) as the reinforcing frame. However, the long-term high-temperature durability at 121°C and 100% RH was only about 200 hours at most, which was not sufficient to meet the above-mentioned requirements.

[0006] On the other hand, polymethylpentene resins are substances that are excellent in long-term durability at high temperatures, and have good heat resistance among polyolefin resins, and therefore are used in various applications where relatively high temperatures are expected.

[0007] For example, Patent Document 2 proposes the use of a polymethylpentene resin as a release layer of a release film. This document also discloses that the storage modulus E' of the release layer at 175°C is 30 MPa or more and 80 MPa or less. However, if the storage modulus is within this range, it cannot be said that the high-temperature mechanical properties are sufficient for applications in which adhesive processing is performed at high temperatures as described above.

[0008] Patent Document 3 proposes a release layer for a release sheet for producing synthetic leather, the release layer comprising as its main component a cyclic olefin resin composition containing a cyclic olefin resin and a polymethylpentene resin, the cyclic olefin resin having a glass transition temperature of 150° C. or higher. This document also discloses that the storage modulus E' of the cyclic olefin resin composition at 150° C. is 100 MPa or higher.

[0009] Furthermore, Patent Document 4 discloses that it is preferable to use one or more materials selected from the group consisting of polyethylene naphthalate, cycloolefin polymer, cycloolefin copolymer, and methylpentene polymer as the base layer of a laminate consisting of a first surface layer / a first intermediate layer / a base layer / a second intermediate layer / a second surface layer. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 4944419 [Patent Document 2] Patent Publication No. 2021-194871 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-279838 [Patent Document 4] Japanese Patent Application Laid-Open No. 2018-135467 Summary of the Invention [Problem to be solved by the invention]

[0011] However, according to the investigations of the present inventors, when a film is formed by blending a polymethylpentene resin having an insufficiently high melting point (for example, a melting point below 240°C) with a cyclic olefin resin having a glass transition temperature of 150°C or higher, as in the invention of Patent Document 3, it has been found that unevenness in the film thickness is likely to occur due to reasons such as miscibility and compatibility during melting. Such unevenness in the film thickness poses a problem in that it is likely to cause poor adhesion, particularly when the film is used as a reinforcing member for an electrolyte membrane of a polymer electrolyte fuel cell in which many power generation units are stacked.

[0012] Furthermore, the inventors' investigations have revealed that when a film is formed using only a cycloolefin copolymer having a glass transition temperature of 150°C or higher, the punching processability of the film (particularly the generation of burrs) is likely to deteriorate, as described in the examples of Patent Document 4. Such deterioration in the punching processability of the film is likely to cause problems such as reduced productivity, particularly when processing a reinforcing member for an electrolyte membrane into a frame shape.

[0013] Therefore, an object of the present invention is to provide a film that not only has excellent high-temperature mechanical properties and high-temperature hydrolysis resistance, but also has good thickness uniformity and punching processability, and a reinforcing member for an electrolyte membrane of a solid polymer fuel cell using the same. [Means for solving the problem]

[0014] As a result of intensive research to solve the above problems, the inventors have found that the above object can be achieved by forming a film using a blend containing a specific polymethylpentene resin and a resin having a glass transition temperature of 170°C or higher in a specific mass ratio, and have thus completed the present invention.

[0015] That is, the present invention includes the following:

[0016] [1] A film having at least one layer A containing a polymer A1 containing 90 mol % or more of structural units derived from 4-methyl-1-pentene based on all units and having a melting point of 240°C or higher, and a resin A2 having a glass transition temperature of 170°C or higher, in a total amount of 90 mass % or more, A film in which the mass ratio A1 / A2 of the polymer A1 to the resin A2 is in the range of 95 / 5 to 50 / 50.

[0017] [2] The film according to [1], wherein the time during which the retention rate of the maximum stress measured by a tensile test of the layer A becomes 60% of the initial value before and after being kept at 120°C and 100% RH is 2000 hours or more in at least one in-plane direction of the film.

[0018] [3] The film according to [1] or [2], wherein the resin A2 is a cyclic olefin resin.

[0019] [4] The film according to any one of [1] to [3], wherein the mass ratio A1 / A2 is in the range of 95 / 5 to 87 / 13.

[0020] [5] The film according to any one of [1] to [4], further comprising at least one heat-sealable layer.

[0021] [6] The film according to any one of [1] to [5], which is used as a reinforcing member for an electrolyte membrane of a solid polymer fuel cell for reinforcing the outer peripheral edge of the electrolyte membrane of the solid polymer fuel cell.

[0022] [7] A reinforcing member for an electrolyte membrane of a solid polymer fuel cell for reinforcing the outer peripheral edge of the electrolyte membrane of a solid polymer fuel cell, the reinforcing member for an electrolyte membrane of a solid polymer fuel cell comprising the film according to any one of [1] to [6]. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a film that not only has excellent high-temperature mechanical properties and high-temperature hydrolysis resistance but also has good thickness uniformity and punching processability, and a reinforcing member for an electrolyte membrane of a polymer electrolyte fuel cell using the same.

[0024] The reason why the inclusion of a specific polymethylpentene resin and a resin with a glass transition temperature of 170°C or higher in a specific mass ratio results in particularly good thickness uniformity and punching processability is unclear, but is thought to be as follows.

[0025] That is, by using polymer A1 containing 90 mol% or more of structural units derived from 4-methyl-1-pentene and having a melting point of 240°C or higher, dispersibility and the like are improved in resin A2 having a glass transition temperature of 170°C or higher compared to when a larger amount of copolymerization component is used, and it is thought that this makes it easier to achieve good thickness uniformity. Furthermore, polymer A1 also has excellent mold releasability, and using it in a certain mass ratio or higher is thought to improve punching processability. [Brief explanation of the drawings]

[0026] [Figure 1A] FIG. 1 is a schematic diagram showing the vicinity of a die to a cooling roll of an example of a vertical drop type film forming machine that can be used in the present invention. [Figure 1B] FIG. 1 is a schematic diagram showing the vicinity of a die to a cooling roll of an example of an oblique drop type film forming machine that can be used in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be described in detail below. For convenience of explanation, the film formation direction of a film 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 thickness direction may be referred to as the width direction, transverse direction, or TD direction. Furthermore, various physical property values ​​described in this specification are specifically measured by the methods described in the Examples.

[0028] [film] The film of the present invention has at least one layer A containing polymer A1 and resin A2 in a total amount of 90 mass % or more, and may have two or more layers A. The film may also have a layer B, a layer A, and a layer B in this order, with layer A serving as a base layer and layer B serving as a heat-sealable layer. Furthermore, the film may have a layer C as an intermediate layer (such as an easy-adhesion layer), and may have a layer B, a layer C, a layer A, a layer C, and a layer B in this order.

[0029] At least two of the A layer, B layer and C layer may be laminated by coextrusion, or all of the layers may be laminated by coextrusion.

[0030] 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 viewpoints of ease of production and low cost of production equipment, etc. Here, "unstretched" refers to a state in which the film has not been stretched 1.2 times or more in any direction by a stretching process such as inter-roll stretching or tenter stretching, and preferably refers to a state in which the film has not been stretched 1.1 times or more in any direction.

[0031] In the case of a stretched film, the storage modulus measured in a tensile mode at 175°C can be made higher than that of an unstretched film, at least in the stretching direction. The stretching ratio in the case of uniaxial stretching is 1.2 to 5.0 times, and the stretching ratio in the case of biaxial stretching is 1.2 to 5.0 times in the MD direction and 1.2 to 5.0 times in the TD direction.

[0032] Furthermore, the film of the present invention may contain other layers. For example, a protective film, a release film, a cover film, etc. may be provided on the surface side of the B layer. Furthermore, an intermediate layer, an easy-adhesion layer, etc., having a composition different from that of the C layer may be included between the B layer and the C layer. Also, a layer structure in which the C layer and the A layer are repeatedly included is possible, such as a laminated film including the B layer, the C layer, the A layer, the C layer, the A layer, the C layer, and the B layer. The structure of each layer will be described below.

[0033] [A layer] In order to provide durability in a harsh humid and hot environment, the resin contained in the resin composition constituting Layer A preferably does not have functional groups that can become reaction sites for water molecules, and preferably has a high melting point or a high glass transition temperature to withstand the heat generated during lamination and the heat generated by the environment.

[0034] From this perspective, in the present invention, polymer A1 containing 90 mol% or more of structural units derived from 4-methyl-1-pentene and having a melting point of 240°C or higher is used as the main component of the resin composition constituting layer A, and resin A2 having a glass transition temperature of 170°C or higher is used in combination to improve high-temperature mechanical properties at 170 to 180°C.

[0035] The total content of polymer A1 and resin A2 in layer A may be 90% by mass or more, but from the viewpoint of improving high-temperature hydrolysis resistance and high-temperature mechanical properties at 170 to 180° C., the content is preferably 95% by mass or more, more preferably 98% by mass or more, and most preferably 100% by mass in layer A. When the content is within this range, the effect of improving heat resistance due to the 4-methyl-1-pentene polymer is easily obtained, and further, a film with improved high-temperature mechanical properties at 170 to 180° C. is easily obtained.

[0036] The mass ratio A1 / A2 of polymer A1 to resin A2 may be in the range of 95 / 5 to 50 / 50, preferably in the range of 95 / 5 to 80 / 20, and most preferably in the range of 95 / 5 to 87 / 13.Within this content range, the 4-methyl-1-pentene polymer is likely to have an improved effect on heat resistance, and a film with good punching processability is likely to be obtained.

[0037] Layer A may contain less than 10% by mass of other resin A3, but for the same reasons, it is preferable that Layer A contains 0% to less than 5% by mass of resin A3, more preferably 0% to less than 2% by mass, and most preferably does not contain other resin A3.

[0038] [Polymer A1] Polymer A1 contains 90 mol% or more and 100 mol% or less of structural units derived from 4-methyl-1-pentene relative to all structural units, preferably 92 mol% or more and 100 mol% or less, more preferably 95 mol% or more and 100 mol% or less, and most preferably 100 mol%.

[0039] Polymer A1 may further contain structural units derived from an α-olefin other than 4-methyl-1-pentene in an amount of 0 mol% or more and less than 10 mol%, preferably 0 mol% or more and less than 8 mol%, and more preferably 0 mol% or more and less than 5 mol%, based on all structural units.

[0040] That is, examples of polymer A1 include homopolymers polymerized using 4-methyl-1-pentene as a monomer, as well as copolymers copolymerized with 90 mol % or more of 4-methyl-1-pentene as a monomer and less than 10 mol % of an α-olefin other than 4-methyl-1-pentene as a monomer.

[0041] When polymer A1 is a copolymer, the copolymerized monomer is preferably an α-olefin having a carbon number of 2 to 20. Examples of the α-olefin to be copolymerized include one or more of ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-tetradecene, and 1-octadecene.

[0042] Melting point T of polymer A1 mA1 The melting point T of the polymer A1 is 240°C or higher, preferably 241°C or higher and 250°C or lower, and more preferably 242°C or higher and 245°C or lower. mA1 can be controlled by controlling the stereoregularity and the type and content of the monomer to be copolymerized.

[0043] [Resin A2] Resin A2 is not particularly limited as long as it has suitable compatibility and dispersibility with polymer A1 and has a glass transition temperature of 170° C. or higher. Examples include cyclic olefin resins, polyphenylene ether resins (PPE), polyphenylsulfone resins (PPSU), polysulfone resins (PSU), polyethersulfone resins (PESU), and polyetherimide resins (PEI).

[0044] Among these, cyclic olefin resins and polyphenylene ether resins are preferred, and cyclic olefin resins are most preferred, from the viewpoint of stability when blended with polymer A1 and melt-kneaded and extruded at the same temperature. If the stability during melt-kneading and extrusion is insufficient, the thickness unevenness of the film tends to worsen, and black, deteriorated resin foreign matter tends to be generated and mixed into the film.

[0045] Examples of cyclic olefin resins having a glass transition temperature of 170° C. or higher include cycloolefin copolymers (COC) obtained by copolymerizing norbornenes with α-olefins such as ethylene, and homoaddition polymers of norbornenes.

[0046] Commercially available cycloolefin copolymers (COC) include TOPAS6017S (glass transition temperature 178°C) manufactured by Polyplastics Co., Ltd., and commercially available norbornene homopolymers include polynorbornene (glass transition temperature ≧250°C) manufactured by Sumitomo Bakelite Co., Ltd., both of which can be used as Resin A2.

[0047] As polyphenylene ether resins (PPE), PX100F (glass transition temperature 204° C.) manufactured by Mitsubishi Engineering Plastics Corporation and the like are commercially available and can be used as resin A2.

[0048] Commercially available polyphenylsulfone resins (PPSU) include Ultrason P (glass transition temperature 220°C) manufactured by BASF Japan, commercially available polysulfone resins (PSU) include Ultrason S (glass transition temperature 187°C) manufactured by BASF Japan, and commercially available polyethersulfone resins (PESU) include Ultrason E (glass transition temperature 225°C) manufactured by BASF Japan, and all of these can be used as Resin A2.

[0049] As a polyetherimide resin (PEI), ULTEM (glass transition temperature 215°C) manufactured by Kureha Extron Corporation and the like are commercially available and can be used as Resin A2.

[0050] [Other Resins A3] Layer A may contain another resin A3 other than polymer A1 and resin A2. The other resin A3 may have a suitable compatibility and dispersibility with polymer A1 and resin A2, and examples thereof include 4-methyl-1-pentene copolymers such as copolymers of 4-methyl-1-pentene and α-olefins, and polyolefins (including modified polyolefins), with copolymers of 4-methyl-1-pentene and α-olefins being preferred. Copolymers of 4-methyl-1-pentene and α-olefins are advantageous in that they do not have functional groups that act as reaction sites for water molecules, and the use of copolymers of 4-methyl-1-pentene and α-olefins improves dispersibility in polymer A1. The copolymers of 4-methyl-1-pentene and α-olefins should have the same copolymerization composition as polymer A1 and a melting point T mA3 The temperature is less than 240°C.

[0051] Examples of polyolefin resins include the following polyolefin resins and modified polyolefin resins: In this specification, the term "modified" refers to a resin containing a structural unit different from the structural unit of polyolefin or the like in the same molecule.

[0052] Examples of polyolefin resins include polyolefin resins such as high-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, linear low-density polyethylene, polypropylene, and poly(1-butene). Blends of these polyolefin resins and copolymers containing these as constituent components are also included. Among these polyolefin resins, polypropylene is particularly preferred.

[0053] In particular, when mixing with a 4-methyl-1-pentene polymer (polymer A1) by melt kneading, a similar polyolefin resin or a modified polyolefin resin can be used, but from the viewpoint of compatibility, it is preferable to use a polypropylene resin copolymerized with 4-methyl-1-pentene or a maleic acid-modified polypropylene resin. The modification method can be graft modification or copolymerization.

[0054] Specific modified polyolefin resins include, for example, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, and copolymers in which a part or all of the carboxylic acid moieties in these copolymers have been converted into salts with sodium, lithium, potassium, zinc, or calcium, ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / ethyl methacrylate copolymer, and ethylene / ethyl acrylate-g-maleic anhydride copolymer (where "-g-" represents graft (hereinafter referred to as "ethyl acrylate-g-maleic anhydride copolymer"). (same), ethylene / methyl methacrylate-g-maleic anhydride copolymer, ethylene / propylene-g-maleic anhydride copolymer, ethylene / butene-1-g-maleic anhydride copolymer, ethylene / propylene / 1,4-hexadiene-g-maleic anhydride copolymer, ethylene / propylene / dicyclopentadiene-g-maleic anhydride copolymer, ethylene / propylene / 2,5-norbornadiene-g-maleic anhydride copolymer, hydrogenated styrene / butadiene / styrene-g-maleic anhydride copolymer, hydrogenated styrene / isoprene / styrene-g-maleic anhydride copolymer, etc. Among these, maleic acid-modified polypropylene or ethylene-propylene copolymer, etc. are particularly preferred.

[0055] [Other optional ingredients in Layer A] Layer A may contain a crystal nucleating agent that promotes crystallization in order to achieve excellent high-temperature mechanical properties.

[0056] In order to obtain a suitable crystallization-promoting effect, the nucleating agent is preferably contained in Layer A in an amount of 0.001% by mass to 0.8% by mass, more preferably 0.002% by mass to 0.5% by mass, and even more preferably 0.05% by mass to 0.3% by mass.

[0057] Furthermore, Layer A may contain an appropriate filler as needed to improve slippage, as long as it does not impair the objectives of the present invention. Examples of fillers that can be used include those conventionally known as slippage-imparting agents for films and sheets, such as 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, and crosslinked silicone resin particles. Furthermore, Layer A may also contain, as appropriate, colorants, antistatic agents, antioxidants, organic lubricants, catalysts, and the like. In particular, when considering use in a humid and hot environment, additives with low elution are preferably used.

[0058] Other optional components include various additives that have conventionally been used in 4-methyl-1-pentene polymers, etc. Examples of such additives include stabilizers, impact modifiers, flame retardants, mold release agents, sliding modifiers, colorants, and plasticizers.

[0059] [Characteristics of Layer A] The storage modulus of Layer A measured in a tensile mode at 175°C using a dynamic viscoelasticity measuring device is preferably greater than 80 MPa in at least one in-plane direction of the film. The storage modulus should be greater than 80 MPa in at least one direction, but it is also preferable that the storage modulus be within this range in the direction perpendicular to the direction in which the storage modulus is maximum.

[0060] From the viewpoint of improving high-temperature mechanical properties and high-temperature hydrolysis resistance, the storage modulus in at least one direction is preferably 90 MPa or more, more preferably 100 MPa or more, even more preferably 120 MPa or more, and particularly preferably 140 MPa or more. The higher the storage modulus at 175°C, the more preferable it is, but an example of an industrially feasible maximum value is about 500 MPa.

[0061] The storage modulus can be adjusted by changing the type of resin A2, changing the content of resin A2, or, in the manufacturing method described below, changing the air gap distance or the time required to pass through the air gap. In particular, selecting the type of resin A2 and increasing the content of resin A2 are effective.

[0062] Furthermore, the time (durability time) during which the retention rate of the maximum stress measured by a tensile test becomes 60% of the initial value before and after holding Layer A at 120°C and 100% RH is preferably 2000 hours or more in at least one in-plane direction of the film. The durability time of Layer A may be 2000 hours or more in at least one in-plane direction of the film, but it is also preferable that this range is satisfied in the direction perpendicular to the direction for which the durability time is maximum.

[0063] In other words, this range of durability time of Layer A corresponds to the retention rate of the maximum stress measured by a tensile test relative to the initial value in at least one in-plane direction of the film before and after holding Layer A at 120°C and 100% RH for 2000 hours.

[0064] From the viewpoint of further improving high-temperature hydrolysis resistance, the retention rate of such layer A is preferably 80% or more, more preferably 90% or more, and even more preferably 93% or more. The retention rate of layer A is usually 100% or less, and preferably 99% or less. The retention rate of layer A and the time (durability time) until the retention rate reaches 60% can be adjusted by the molecular structure (copolymerization ratio), stereoregularity, melting point, and molecular weight of polymer A1, and the type and content of resin A2, etc.

[0065] From the viewpoint of obtaining the necessary high-temperature mechanical properties, the thickness of Layer A may be 20 μm or more, preferably 25 μm or more, more preferably 35 μm or more, and even more preferably 45 μm or more, and from the viewpoint of suppressing the thickness of the fuel cell, the thickness is preferably 300 μm or less, more preferably 270 μm or less, and even more preferably 250 μm or less, and may alternatively be 150 μm or less or 130 μm or less.

[0066] [B layer (thermal adhesive layer)] The film may have a layer B which is a heat-sealable layer or the like. Layer B as a heat-sealable layer contains 100 to 70 mass % of heat-sealable polyolefin B1, and from the viewpoints of wet heat durability and adhesive strength to an adherend, it preferably contains 100 to 75 mass %, more preferably 100 to 80 mass %, even more preferably 100 to 90 mass %, and most preferably 100 mass % of heat-sealable polyolefin B1. In this specification, "heat-sealable" refers to the property of being able to be fused to an adherend by heating, and preferably refers to the property of being able to be fused to a metal such as SUS316 by heating.

[0067] When Layer B is provided on both sides of Layer A, the Layers B may have the same or different compositions, but when, for example, adherends made of the same material are to be thermally bonded, it is preferable to provide heat-sealable layers of the same composition on both sides. The thicknesses of the heat-sealable layers may be the same or different, but in such cases, it is preferable to provide heat-sealable layers of the same thickness on both outermost surfaces.

[0068] From the viewpoint of high-temperature hydrolysis resistance as a reinforcing member, 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. Moreover, if the thickness is too thin, the mechanical relaxation function in the thickness direction as a heat-fusible layer is weakened, so the thickness is preferably 10 μm or more, more preferably 15 μm or more, and particularly preferably 20 μm or more.

[0069] [Heat-bondable polyolefin B1] As the heat-fusible polyolefin B1, an unmodified polyolefin resin can be used, but modified polyolefins are preferred, and modified polyolefins containing polypropylene are particularly preferred.

[0070] 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. Specific examples include polyethylenes such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene resins, polypropylene, polyisobutylene, poly(1-butene), polyvinylcyclohexane, polystyrene, poly(p-methylstyrene), poly(α-methylstyrene), α-olefin copolymers such as ethylene-propylene block copolymers, ethylene-propylene random copolymers, ethylene-butene-1 copolymers, ethylene-4-methyl-1-pentene copolymers, ethylene-butene-propylene terpolymers, ethylene-propylene diene rubbers, and ethylene-hexene copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-methyl methacrylate copolymers, ethylene-vinyl acetate-methyl methacrylate copolymers, polybutadiene-styrene copolymers, polybutadiene-maleic anhydride copolymers, and ionomer resins. Furthermore, chlorinated polyolefins obtained by chlorinating these polyolefins can also be used.

[0071] As described above, various types of heat-fusible polyolefin B1 can be used, but it is particularly preferable to use modified polyolefin resins in which various functional groups (e.g., carboxyl groups, hydroxyl groups, etc.) have been introduced into polyolefin resins.

[0072] Furthermore, among these modified polyolefin resins, modified polyolefin resins having an acid value of 1 to 200 mgKOH / g (also referred to as acid-modified polyolefin resins) and / or modified polyolefin resins having a hydroxyl value of 1 to 200 mgKOH / g (also referred to as hydroxyl-modified polyolefin resins) can be used because they have improved adhesion to the metal layer and excellent electrolyte resistance.

[0073] Acid-modified polyolefin resins are polyolefin resins that contain carboxyl groups or carboxylic anhydride groups in the molecule, and are synthesized by modifying polyolefins with unsaturated carboxylic acids or their derivatives. The modification methods that can be used include graft modification and copolymerization.

[0074] The acid-modified polyolefin resin is a graft-modified polyolefin obtained by graft-modifying or copolymerizing at least one polymerizable ethylenically unsaturated carboxylic acid or its derivative onto a polyolefin resin before modification.

[0075] Examples of the polyolefin resin before modification include the above-mentioned polyolefin resins, and among them, preferred are propylene homopolymers, copolymers of propylene and α-olefins, ethylene homopolymers, and copolymers of ethylene and α-olefins, etc. These may be used alone or in combination of two or more.

[0076] Examples of acid-modified polyolefin resins include maleic anhydride-modified polypropylene, ethylene-(meth)acrylic acid copolymer, ethylene-acrylic acid ester-maleic anhydride terpolymer, and ethylene-methacrylic acid ester-maleic anhydride terpolymer. Specific examples include "MODIC" manufactured by Mitsubishi Chemical Corporation, "ADMER" and "UNISTOLL" manufactured by Mitsui Chemicals, Inc., "HARDLEN" manufactured by Toyobo Co., Ltd., "UMEX" manufactured by Sanyo Chemical Industry Co., Ltd., "REXPERL EAA" and "REXPERL ET" manufactured by Japan Polyethylene Corporation, "PRIMACOL" manufactured by Dow Chemical Co., Ltd., "NUCREL" manufactured by DuPont-Mitsui Polychemicals, and "BONDINE" manufactured by Arkema.

[0077] Hydroxyl-modified polyolefin resins are polyolefin resins having hydroxyl groups in the molecule, and are synthesized by graft-modifying or copolymerizing polyolefins with hydroxyl-containing (meth)acrylic esters or hydroxyl-containing vinyl ethers, as described below. Examples of the hydroxyl-containing (meth)acrylic 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-containing vinyl ethers include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether.

[0078] A particularly preferred heat-fusible polyolefin resin is a polyolefin in which the heat-fusible polyolefin B1 contains a modified product modified with an acid anhydride, the acid anhydride content is 0.1 to 3 mass %, and the amount of low-molecular-weight components with a number average molecular weight of 1000 or less extracted with acetone is less than 1 mass %.

[0079] If the anhydride 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 extracted low molecular weight components is less than 1% by mass, the low molecular weight components are less likely to bleed out onto the surface of the heat-sealable layer, and adhesion is less likely to be impaired.

[0080] [Other Resins B2] Layer B may contain 0 to 30 mass % of another resin B2 other than the heat-fusible polyolefin B1. In other words, the heat-fusible layer can contain another resin B2 that has appropriate compatibility or dispersibility with the heat-fusible polyolefin B1, as long as the object of the present invention is not impaired.

[0081] However, if the amount of other resin B2 is too large, it may reduce the inherent adhesive strength when bonding metals together, and providing Layer C, which is an easy-adhesion layer, has the effect of reducing the amount of other resin components added to Layer B. From this perspective, the upper limit of the amount of resin B2 contained in the heat-sealable layer is 30% by mass, preferably 25% by mass, more preferably 20% by mass, and particularly preferably 10% by mass. There is no particular lower limit, but as long as the adhesive strength appropriate for the intended use can be ensured, it may be 0% by mass.

[0082] Examples of resin B2 include polyamide, polyester, polyurethane, 4-methyl-1-pentene polymer (polymer A1), copolymer C1 (a copolymer of 4-methyl-1-pentene and an α-olefin) described below, polyolefins other than polymer A1 and copolymer C1, ethylene propylene diene rubber, fluororubber, and silicone rubber.

[0083] Layer B may be composed of resin alone, but may also contain 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 materials, pigments, dyes, and flame retardants, within the range that does not impair the effects of the present invention.

[0084] [C layer (easy adhesion layer)] The film may have a C layer which is an easy-adhesion layer, etc. The C layer as an easy-adhesion layer contains, for example, a copolymer C1 having 60 mol % to 99 mol % of structural units derived from 4-methyl-1-pentene and 1 mol % to 40 mol % of structural units derived from an α-olefin having 2 to 20 carbon atoms other than 4-methyl-1-pentene.

[0085] The copolymer C1 may be contained in the C layer in an amount of 100 to 50% by mass, but from the viewpoint of increasing the adhesion to the A layer and the B layer, the copolymer C1 is preferably contained in the C layer in an amount of 100 to 80% by mass, more preferably 100 to 90% by mass, and most preferably 100% by mass.

[0086] Layer C may contain 0 to 50% by mass of other resin C2, but from the viewpoint of increasing adhesion to layers A and B, layer C preferably contains 0 to 20% by mass of resin C2, more preferably 0 to 10% by mass, and most preferably does not contain other resin C2.

[0087] It is preferable that Layer C does not contain any components other than the resin component, but it may contain antioxidants, stabilizers, crosslinking agents, lubricants, metal deactivators, nucleating agents, etc., as long as the effects of Layer C are not impaired.

[0088] When layers C are provided on both sides of layer A, the layers C may have the same or different compositions, but for example, when thermally adhesive layers of the same material and thickness are provided on both surfaces, it is preferable to provide layers C of the same composition on both sides. Also, the thicknesses of the layers C may be the same or different, but in such cases, it is preferable to provide layers C of the same thickness on both sides.

[0089] In order to obtain an appropriate thickness ratio relative to layer B, the thickness of layer C is preferably 0.01 μm or more, more preferably 0.02 μm or more, and even more preferably 0.03 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less.

[0090] [Copolymer C1] Copolymer C1 may be the same as or different from polymer A1, but from the viewpoint of improving adhesion to layers A and B, copolymer C1 preferably has a lower mol% of structural units derived from 4-methyl-1-pentene than polymer A1, more preferably 10 mol% or more lower, and even more preferably 20 mol% or more lower.

[0091] Examples of the α-olefins having 2 to 20 carbon atoms, which are constituent components of copolymer C1, include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-tetradecene, and 1-octadecene. The α-olefins are preferably ethylene, propylene, 1-butene, 1-hexene, 1-octene, and 1-decene, more preferably ethylene, propylene, 1-butene, 1-hexene, and 1-octene, and even more preferably ethylene, propylene, 1-butene, and 1-hexene. The α-olefins may be used alone or in combination of two or more thereof.

[0092] In Copolymer C1, the content of structural units derived from 4-methyl-1-pentene is 60 mol% to 99 mol%, preferably 63 mol% to 98 mol%, more preferably 65 mol% to 95 mol%, even more preferably 65 mol% to 90 mol%, and particularly preferably 65 mol% to 87 mol%. The content of structural units derived from α-olefins having 2 to 20 carbon atoms other than 4-methyl-1-pentene is 1 mol% to 40 mol%, preferably 2 mol% to 37 mol%, more preferably 5 mol% to 35 mol%, even more preferably 10 mol% to 35 mol%, and particularly preferably 13 mol% to 35 mol%. When the amount of these structural units is within the above range, Layer C exhibits superior adhesion to Layers A and B.

[0093] The copolymer C1 may be an amorphous copolymer having no melting point, but may have a melting point T mC1 However, the temperature is preferably 199°C or lower, more preferably 100 to 160°C, and even more preferably 110 to 150°C.

[0094] As the copolymer C1, it is particularly preferable to use Absortomer EP1013, EP1001, etc. manufactured by Mitsui Chemicals, Inc.

[0095] [Other Resins C2] Examples of other resins C2 in copolymer C1 include polymer A1, heat-fusible polyolefin B1, 4-methyl-1-pentene resins, polyolefin resins, polyethylene resins, and the like.

[0096] [Film characteristics] Even when formed as a laminated film, the film of the present invention preferably has the same properties as when it is formed of only layer A.

[0097] For example, it is preferable that the time period during which the maximum stress measured by a tensile test remains at 60% of its initial value before and after storage at 120°C and 100% RH is 2000 hours or longer in at least one in-plane direction of the film. In other words, the maximum stress measured by a tensile test remains at 60% of its initial value before and after storage at 120°C and 100% RH in at least one in-plane direction of the film. From the viewpoint of further improving high-temperature hydrolysis resistance, the retention is preferably 80% or higher, more preferably 90% or higher, and even more preferably 93% or higher. The retention of the laminate film is typically 100% or lower, preferably 99% or lower. The retention and durability of such a laminate film depend primarily on the properties of Layer A and can be adjusted by, for example, adjusting the properties of Layer A.

[0098] Furthermore, when the film of the present invention comprises a B layer, a C layer, an A layer, a C layer, and a B layer in this order, when the thickness of the A layer is tA, the thickness of the B layer is tB, and the thickness of the C layer is tC, it is preferable that the thickness ratio of each layer satisfies the following formula (1) and the following formula (2): 2≦tA / tB≦5 (1) 10≦tB / tC≦5000 (2) When tA / tB is 5 or less, the total thickness is not too large, and the sheet is easily cooled during the co-extrusion film formation described below, making it easy to wind up into a roll. Furthermore, when tA / tB is 2 or more, when the heat-sealable layer is melted and bonded to another member, heat is less likely to reach the base layer, making it less susceptible to influences during bonding. From this viewpoint, the upper limit of tA / tB is preferably 4.5 or less, more preferably 4.0 or less, and particularly preferably 3.5 or less. Furthermore, the lower limit of tA / tB is preferably 2.2 or more, more preferably 2.4 or more, and particularly preferably 2.5 or more.

[0099] Furthermore, when tB / tC is 5000 or less, that is, the thickness of the easy-adhesion layer is not extremely thin compared to the heat-fusible layer, and the continuity of the film as the easy-adhesion layer is easily ensured. Furthermore, when tB / tC is 10 or more, there is no need to make the easy-adhesion layer unnecessarily thick. From this viewpoint, the upper limit of tB / tC is preferably 4000 or less, more preferably 3000 or less, and particularly preferably 2000 or less. The lower limit of tB / tC is preferably 15 or more, more preferably 20 or more, and particularly preferably 25 or more.

[0100] [Film manufacturing method] The film of the present invention can be produced, for example, by kneading the materials constituting Layer A, extruding the kneaded mixture, forming the film, and, if necessary, heat-treating the resulting mixture. In the case of a laminated film, it can be produced by kneading the materials constituting each layer, co-extruding the kneaded mixture, forming the laminated film, and, if necessary, heat-treating the resulting mixture. Hereinafter, a case where the film is composed of only Layer A will be described.

[0101] The method for mixing and kneading the 4-methyl-1-pentene polymer (polymer A1), resin A2, other polyolefin resin (other resin A3), and other optional components is not particularly limited, and for example, a single-screw extruder, twin-screw extruder, pressure kneader, Banbury mixer, etc. can be used. Among these, twin-screw extruders are particularly preferred. The operating conditions of the twin-screw extruder vary depending on various factors such as the type of resin and the type and amount of each component contained, and cannot be uniquely determined; however, for example, the operating temperature may be set at approximately +40°C above the melting point. The screw configuration of the extruder preferably incorporates kneading discs, which provide excellent kneading properties, at several locations.

[0102] The resin composition constituting Layer A can be melt-extruded from a die into a sheet and cooled and solidified using a cooling roll (casting drum) or the like to obtain a film. During melt-extrusion, either a vertical drop type in which a sheet-like molten material falls vertically from a die, or an oblique drop type in which a sheet-like molten material falls obliquely from a die can be used, but from the viewpoint of being able to increase the air gap distance, it is preferable to use a vertical drop type film-forming machine.

[0103] The air gap distance is preferably 50 mm or more, more preferably 60 mm or more, and even more preferably 70 mm or more, from the viewpoint of efficiently generating crystal nuclei even when polymer A1 is in a molten state and exhibiting sufficient high-temperature mechanical properties. Moreover, from the viewpoint of suppressing thickness unevenness due to shaking of the molten resin composition before contact with the chill roll, the air gap distance is preferably 200 mm or less, more preferably 150 mm or less.

[0104] The cooling temperature may be a temperature at which the resin is sufficiently solidified, but if the resin is cooled too much, the sheet-like resin may float, making efficient cooling difficult. From this viewpoint, the cooling temperature is preferably 20 to 120°C, and more preferably 30 to 100°C.

[0105] If necessary, after cooling and solidifying, the melting point T mA1 In contrast, T mA1 -100℃~TmA1 The in-plane deformation rate of the film can be easily controlled within a predetermined range by performing heat treatment at −5° C. for 1 to 60 seconds. The heat treatment method may be a roll conveying type or a floating type, but the floating type is preferred from the viewpoint of being able to relax the in-plane direction and preventing the heat-sealable layers on both sides from sticking together.

[0106] When the film is a laminated film, it is preferable that at least the easy-adhesion layer is formed by co-extrusion together with the base layer, and more preferably the easy-adhesion layer and the heat-fusible layer are formed by co-extrusion together with the base layer.

[0107] When an adhesive layer is subsequently laminated, examples of laminating methods include dry laminating and wet laminating, and examples of coating methods include extrusion resin coating, molten resin coating, and coating liquid coating.

[0108] In the present invention, when resins are co-extruded to provide a heat-sealable layer, it is preferable to melt-extrude the resins by adjusting the melt temperature appropriately according to the viscosity of the base layer. It is also preferable to select the type and molecular weight of the heat-sealable polyolefin B1 and the other resin B2 so that the melt viscosity of the heat-sealable layer is appropriate.

[0109] Furthermore, when extruding resins by coextrusion to provide an easy-adhesion layer, it is preferable to melt-extrude the resins by adjusting the melt temperature appropriately according to the viscosity of the base layer. It is also preferable to select the type and molecular weight of copolymer C1 and other resin C2 so that the melt viscosity of the easy-adhesion layer is appropriate.

[0110] The operating temperature (melting temperature) of the extruder for the heat-sealable layer is the melting point T mB1 In contrast, T mB1 +20℃~T mB1 +120℃ is preferred, T mB1 +50℃~T mB1 +100°C is more preferable.

[0111] The operating temperature (melting temperature) of the extruder for the adhesive layer is the melting point T mC1 In contrast, T mC1 +20℃~T mC1 +120℃ is preferred, T mC1 +50℃~T mC1 +100°C is more preferable.

[0112] The amount of the melted heat-fusible layer and the easily adhesive layer extruded from the extruder is determined appropriately depending on the thickness ratio relative to the base layer, the thickness of the laminate, the line speed, and the like. The above-mentioned film can be produced as a roll wound in the longitudinal direction, and can be cut or punched into an appropriate shape for use in various applications.

[0113] The film of the present invention not only has excellent high-temperature mechanical properties and high-temperature hydrolysis resistance, but also has good thickness uniformity and punching processability, and therefore can be suitably used for various applications, and can be particularly suitably used as a reinforcing member for the electrolyte membrane of a solid polymer fuel cell.

[0114] The film of the present invention is effective for applications other than as a reinforcing member for an electrolyte membrane, where heat resistance, wet heat durability, etc. are required, and examples of such applications include carrier films for various processes, release films for various processes, heat-resistant packaging films, heat-resistant container films, etc. Of course, it can also be used as other general-purpose films.

[0115] [Reinforcing material for electrolyte membrane of polymer electrolyte fuel cell] The reinforcing member for an electrolyte membrane of a solid polymer fuel cell of the present invention is a reinforcing member for an electrolyte membrane of a solid polymer fuel cell for reinforcing the outer peripheral edge portion of the solid polymer electrolyte membrane, and is characterized by including the film of the present invention described above.

[0116] The reinforcing member for the electrolyte membrane of a polymer electrolyte fuel cell may be any member that reinforces at least the electrolyte membrane of the polymer electrolyte fuel cell, and may be a reinforcing member used to reinforce only the electrolyte membrane of the polymer electrolyte fuel cell, or may be a reinforcing member used to reinforce a membrane electrode assembly, a laminate including a gas diffusion layer, etc. Such reinforcing members may be called support members, gasket members, etc., and any member that has the effect of supporting at least the electrolyte membrane of the polymer electrolyte fuel cell and increasing its strength is included in the term "reinforcing member."

[0117] The shape of the reinforcing member may be any shape that reinforces at least one side of the electrolyte membrane of the polymer electrolyte fuel cell, and examples of such shapes include a frame shape, an L-shape, a U-shape, an I-shape, etc. However, from the viewpoint of improving airtightness and reinforcing effect, the shape of the reinforcing member is preferably a frame shape having one or more openings.

[0118] The reinforcing member for the electrolyte membrane of a polymer electrolyte fuel cell can be fixed to the outer peripheral edge of the electrolyte membrane of the polymer electrolyte fuel cell using an adhesive, a hot melt adhesive, or the like. In this case, when the film of the present invention has a heat-sealable layer (layer B), it can be fixed to the outer peripheral edge of the electrolyte membrane of the polymer electrolyte fuel cell by heat fusion (hot melt). Since the film of the present invention has excellent high-temperature mechanical properties at 170 to 180°C, the heat fusion temperature can be 150°C or higher. [Example]

[0119] The present invention will be described in more detail below with reference to examples and comparative examples. In the present invention, physical properties were measured or evaluated by the following methods. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0120] (1) Average thickness, thickness variation A sample measuring 2 cm wide and 10 m long in the machine direction was cut from the center of the width of the rolled film. The thickness of the sample was measured using a micrometer at 10 cm intervals in the machine direction, a total of 100 points. The average thickness and thickness unevenness were calculated using the following formula.

[0121] Average thickness = average thickness of 100 points (μm) Thickness unevenness = (maximum thickness of 100 points - minimum thickness of 100 points) ÷ average thickness × 100 (%) If this thickness unevenness exceeds 5%, it is likely to cause problems in various applications, and in particular when used as a reinforcing member for an electrolyte membrane, it is preferable that it be 3% or less.

[0122] (2) Melting point, glass transition temperature An aluminum pan containing approximately 10 mg of resin sample was placed in a DSC device (NETZSCH, DSC214Polymer) and heated to 300°C at a rate of 5°C / min to measure the heat flow. From the obtained chart, the inflection point of the baseline shift was read as the glass transition temperature, and the peak top of the endothermic peak was read as the melting point.

[0123] (3) Storage modulus at 175°C Samples were cut into strips 4 mm wide and 50 mm long so that the longitudinal directions were MD and TD, respectively, and measured using a dynamic viscoelasticity measuring device (Rheogel-E4000, manufactured by UBM Co., Ltd.) under the following conditions: The larger of the storage moduli at 175°C in MD and TD was taken as the storage modulus at 175°C.

[0124] Measurement mode: Tensile Sample width: 4mm Chuck distance: 20mm Measurement temperature range: Room temperature to 200°C Heating rate: 2°C / min Frequency: 1Hz Amplitude 10μm Static load 100g If the storage modulus is 80 MPa or less, the high-temperature mechanical properties tend to be insufficient, particularly when used as a reinforcing member for an electrolyte membrane, and it is more preferable that the storage modulus is 90 MPa or more.

[0125] (4) 120℃ 100% RH endurance time, maximum stress retention rate after 2000 hours The samples were cut into strips 15 mm wide and 120 mm long with the longitudinal direction being the MD, and hung in a PCT tester (Pressure Cooker Test) capable of pressurizing the inside of a tank, and held at a temperature of 120°C and a relative humidity of 100% RH for 150, 200, 300, 500, 1000, 1500, and 2000 hours.

[0126] Tensile tests were performed on the initial (untreated PCT) and held samples using a tensile testing machine (Shimadzu Corporation, Autograph AGS-X) under the following conditions to determine the maximum stress obtained until fracture. The maximum stress and maximum stress retention were calculated using the following formula. The time at which the maximum stress retention rate relative to the initial value reached 60% was determined by fitting a graph plot of holding time on the horizontal axis and maximum stress retention rate on the vertical axis with a cubic polynomial, and finding the intersection of the fitting curve with the maximum stress retention rate of 60%.

[0127] Sample width: 15mm Chuck distance: 20mm Tensile speed: 200 mm / min Maximum stress = Maximum load ÷ Sample width before tensile test ÷ Sample thickness before tensile test Maximum stress retention rate (%) = Maximum tensile stress after PCT test ÷ Initial (untreated) maximum tensile stress × 100 If this maximum stress retention is less than 60%, the high-temperature hydrolysis resistance is likely to be insufficient, particularly when used as a reinforcing member for an electrolyte membrane, and it is more preferable that the maximum stress retention is 80% or more.

[0128] (5) Punching processability (burr height) Using a drilling jig (CARL, CP-5), ten holes of 6.0 mm diameter were punched in the film, and the edges of the holes were observed using an optical microscope (Hirox, RH-2000) at 35x magnification to measure the height of burrs generated during punching. The maximum height of the ten points was taken as the punching burr height (μm). If the burr height exceeds 300 μm, it is likely to cause problems in applications involving punching, and it is particularly preferable for the height to be 150 μm or less.

[0129] (6) Frequency of black foreign bodies The entire width of the film roll was visually observed over a length of 10 m in the machine direction. The observation was carried out under transmitted light, and the number of black foreign particles with a long side of 100 μm or more that could be visually identified was counted. The number of black foreign particles counted was converted into the number per unit area, and the frequency of black foreign particles (pieces / m 2 ) The frequency of these black foreign matters was 20 / m 2 If it exceeds 5 particles / m, it can easily become a problem in various applications. 2 It is particularly preferred that:

[0130] [Manufacturing example 1] (PMP1) According to Production Example 1 and Example 4 of JP-A-2022-171595, a resin (PMP1) having 100 mol% of structural units derived from 4-methyl-1-pentene and a melting point of 243 ° C. was produced as follows.

[0131] <Catalyst Preparation> (Production of Transition Metal Compound (A)) According to Synthesis Example 4 of WO 2014 / 050817, (8-octamethylfluoren-12′-yl-(2-(adamantan-1-yl)-8-methyl-3,3b,4,5,6,7,7a,8-octahydrocyclopenta[a]indene))zirconium dichloride (transition metal compound (A)) was synthesized.

[0132] (Preparation of solid catalyst component) At 30°C, 32 mL of purified decane and 14.65 mmol of solid polymethylaluminoxane (Tosoh Finechem Co., Ltd.) (calculated as 14.65 mmol of aluminum atoms) were added to a 100 mL three-neck flask equipped with a stirrer and thoroughly purged with nitrogen under a nitrogen stream to form a suspension. To this suspension, 12.75 mL of a 4.6 mmol / L toluene solution of 50 mg of the previously synthesized transition metal compound (A) (calculated as 0.059 mmol of zirconium atoms) was added with stirring. After 1.5 hours, stirring was stopped, and the resulting catalyst component was washed three times with 50 mL of decane by decantation and suspended in decane to obtain 50 mL of slurry (B). The Zr loading in this catalyst component was 100%.

[0133] (Preparation of Prepolymerized Catalyst Component) To the slurry (B) prepared above, 2.0 mL of a decane solution of diisobutylaluminum hydride (2.0 mmol / mL in terms of aluminum atom) and 7.5 mL (5.0 g) of 4-methyl-1-pentene were added under a nitrogen stream. After 1.5 hours, stirring was stopped, and the resulting prepolymerized catalyst component was washed three times with 50 mL of decane by decantation. This prepolymerized catalyst component was suspended in decane to obtain 50 mL of decane slurry (C). The concentration of the prepolymerized catalyst component in decane slurry (C) was 20 g / L, 1.05 mmol-Zr / L, and the Zr recovery rate was 90%.

[0134] (Production of polymer PMP1) At room temperature under a nitrogen stream, 425 mL of purified decane and 0.5 mL (1 mol) of a decane solution of diisobutylaluminum hydride (2.0 mmol / mL in terms of aluminum atom) were charged into a 1 L stainless steel polymerization vessel equipped with a stirrer. Next, 0.0005 mmol of the previously prepared prepolymerized catalyst component slurry solution (C) in terms of zirconium atom was added, and 48 NmL of hydrogen was charged. Next, 250 mL of 4-methyl-1-pentene was continuously charged into the polymerization vessel at a constant rate over 2 hours. The start of this charging marked the start of polymerization. The temperature was raised to 45°C over 30 minutes after the start of polymerization and then maintained at 45°C for 4 hours. 48 NmL of hydrogen was charged 1 hour and 2 hours after the start of polymerization. After 4.5 hours from the start of polymerization, the temperature was lowered to room temperature, the pressure was released, and the polymerization solution containing a white solid was immediately filtered to obtain a solid material. This solid substance was dried under reduced pressure at 80°C for 8 hours to obtain polymer PMP1. The yield was 131 g.

[0135] [Example 1] The raw materials were a blend of 95% by mass of PMP1 and 5% by mass of cyclic olefin resin COC1 (manufactured by Polyplastics Co., Ltd., TOPAS6017S, glass transition temperature 178°C), and then fed into an extruder and melt-kneaded at a melt temperature of 280°C. Using a vertical-drop film-making machine with the die-to-chill roll arrangement shown in Figure 1A, the molten resin was extruded in a slit shape from the die lip and cooled and solidified on the chill roll, which was set to a surface temperature of 60°C, to produce an unstretched film. The die lip opening was 1.0 mm, the air gap distance shown in Figure 1A was 80 mm, and the chill roll rotation speed was 5.6 m / min. This film was wound into a roll to obtain a film roll. The properties of the resulting film are summarized in Table 1.

[0136] [Examples 2 to 9] A film was obtained in the same manner as in Example 1, except that the raw material blending ratio and film-forming conditions were changed as shown in Table 1. The properties of the obtained film are summarized in Table 1. In Table 1, the polyphenylene ether resin PPE was PX100F (glass transition temperature 204°C) manufactured by Mitsubishi Engineering-Plastics Corporation.

[0137] [Comparative Examples 1 to 10] A film was obtained in the same manner as in Example 1, except that the raw material blending ratio in Example 1 was changed as shown in Table 1. The properties of the obtained film are summarized in Table 2. In Table 2, the polymethylpentene resin PMP2 is DX820 (97 mol% structural units derived from 4-methyl-1-pentene, 3 mol% α-olefin having 10 carbon atoms, melting point 232°C) manufactured by Mitsui Chemicals, Inc., and the cyclic olefin resin COC2 is TOPAS6015S (glass transition temperature 158°C) manufactured by Polyplastics Co., Ltd.

[0138] [Comparative Example 11] As in Example 1 of Patent Document 1, a biaxially stretched film (Toyobo Co., Ltd., Q5100, thickness 75 μm) was used, using polyethylene-2,6-naphthalenedicarboxylate homopolymer (PEN, melting point 271°C) as the raw material. The arrangement of the die and cooling roll of the film forming machine was an oblique drop type as shown in Figure 1B, and the die lip opening, air gap distance, cooling roll rotation speed, and cooling roll temperature were as shown in Table 1. In the biaxial stretching process, the first-stage stretching ratio in the film flow direction was 3.7 times, and the second-stage stretching ratio in the film width direction was 3.8 times. The heat setting temperature after the biaxial stretching process was 230°C. The properties of the obtained film are summarized in Table 2.

[0139] [Table 1]

[0140] [Table 2]

[0141] As is clear from Table 1, in Examples 1 to 9, a specific polymethylpentene resin and a resin with a glass transition temperature of 170°C or higher were used in a specific mass ratio, resulting in films that not only had excellent high-temperature mechanical properties and high-temperature hydrolysis resistance, but also had good thickness uniformity and punching processability. Furthermore, the frequency of black foreign matter was significantly improved compared to when polyphenylene ether resin PPE was used alone.

[0142] In contrast, as shown in Table 2, Comparative Examples 1 and 2, in which the content of polymethylpentene resin was too high, had insufficient storage modulus at 175° C. Comparative Example 3, in which the content of polymethylpentene resin was too low, had insufficient high-temperature hydrolysis resistance.

[0143] Furthermore, thickness unevenness was a problem in Comparative Examples 4 to 6, which blended a polymethylpentene resin having a melting point of less than 240°C with a cyclic olefin resin having a glass transition temperature of 170°C or higher. Comparative Example 7, which blended a cyclic olefin resin having a glass transition temperature of less than 170°C, also had large thickness unevenness, and furthermore, the storage modulus at 175°C was insufficient.

[0144] In Comparative Example 8, in which a cyclic olefin resin having a glass transition temperature of 170°C or higher was used alone, the high-temperature hydrolysis resistance was insufficient and the punching processability was also deteriorated. In Comparative Example 9, in which a polyphenylene ether resin having a glass transition temperature of 170°C or higher was used alone, the frequency of black foreign matter significantly increased.

[0145] On the other hand, in Comparative Example 10, which blended a polymethylpentene resin having a melting point of 240° C. or higher with a cyclic olefin resin having a glass transition temperature of less than 170° C., the storage modulus at 175° C. was insufficient. In Comparative Example 11, which used a biaxially stretched PEN film, the time required for the maximum stress retention to reach 60% after holding at 120° C. and 100% RH was short, and the film cracked after holding for 2000 hours, making a tensile test impossible. [Industrial Applicability]

[0146] The film of the present invention not only has excellent high-temperature mechanical properties and high-temperature hydrolysis resistance, but also has good thickness uniformity and punching processability. Therefore, it can be suitably used for various applications, particularly as a reinforcing member for the electrolyte membrane of a polymer electrolyte fuel cell. Therefore, it has high industrial applicability. [Explanation of symbols]

[0147] 1: Die 2: Resin 3: Cooling roll D: Air gap distance

Claims

1. A film having at least one layer A containing a polymer A1 containing 90 mol % or more of structural units derived from 4-methyl-1-pentene based on all units and having a melting point of 240°C or higher, and a resin A2 having a glass transition temperature of 170°C or higher, in a total amount of 90 mass % or more, A film in which the mass ratio A1 / A2 of the polymer A1 to the resin A2 is in the range of 95 / 5 to 50 / 50.

2. 2. The film according to claim 1, wherein the time during which the retention rate of the maximum stress measured by a tensile test becomes 60% of the initial value before and after the layer A is maintained at 120°C and 100% RH is 2000 hours or more in at least one in-plane direction of the film.

3. The film according to claim 1 , wherein the resin A2 is a cyclic olefin resin.

4. 2. The film according to claim 1, wherein the mass ratio A1 / A2 is in the range of 95 / 5 to 87 / 13.

5. The film of claim 1 further comprising at least one heat-sealable layer.

6. 2. The film according to claim 1, which is used as a reinforcing member for an electrolyte membrane of a polymer electrolyte fuel cell for reinforcing the outer peripheral edge of the electrolyte membrane of the polymer electrolyte fuel cell.

7. A reinforcing member for an electrolyte membrane of a solid polymer fuel cell for reinforcing the outer peripheral edge of the electrolyte membrane of a solid polymer fuel cell, the reinforcing member for an electrolyte membrane of a solid polymer fuel cell comprising the film according to any one of claims 1 to 6.

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