Biaxially oriented polyarylene sulfide membrane, method for producing biaxially oriented polyarylene sulfide membrane, electrolyte membrane reinforcing member, fuel cell, and water electrolysis device

Abstract

The present invention addresses the problem of providing a polyarylene sulfide film that is not susceptible to breakage in a temperature region exceeding 100 DEG C and that is not susceptible to wrinkling or skewing, and provides a biaxially oriented polyarylene sulfide film which contains a polyarylene sulfide (PAS) resin as a main constituent component, the ratio YA130 / YA25 of the elastic modulus (YA130) measured at 130 DEG C in the direction orthogonal to the main orientation axis and the elastic modulus (YA25) measured at 25 DEG C in the direction orthogonal to the main orientation axis is 0.25-0.80, and the thermal shrinkage rate at 130 DEG C in the direction is-1.2%-1.2%.

Description

Technical Field

[0001] The present invention relates to a biaxially oriented polyarylene sulfide film, a method for producing the biaxially oriented polyarylene sulfide film, an electrolyte membrane reinforcement member, a fuel cell, and a water electrolysis device. Background Art

[0002] In recent years, driven by the trend toward carbon neutrality, the development of fuel cells using hydrogen as an energy source, as well as water electrolysis systems for generating hydrogen, has advanced. Polymer electrolyte fuel cells, in particular, are expected to be widely used as power generation systems for smaller-scale distributed power generation facilities and mobile vehicles such as automobiles and ships due to their low reaction temperatures and high energy density.

[0003] The solid polymer membranes currently being studied in solid polymer fuel cells are proton-conducting ion exchange membranes with a thickness of about 50 to 100 μm. In particular, cation exchange membranes formed from perfluorosulfonic acid containing sulfonic acid groups, such as "Nafion" (registered trademark), have been widely studied.

[0004] Recently, there has been a demand for thinner solid polymer membranes. However, the low mechanical strength of solid polymer membranes has become a problem in terms of productivity in fuel cells and water electrolysis devices.

[0005] Patent Document 1 describes the use of a reinforcing member using polyethylene naphthalate in the peripheral portion of a fuel cell unit. Furthermore, a reinforcing member for a solid electrolyte membrane is disclosed that reduces the amount of metal elements in a polyphenylene sulfide (hereinafter sometimes referred to as PPS) resin (Patent Document 2). Furthermore, a reinforcing member for an electrolyte membrane formed from a laminate with a fluororesin is disclosed (Patent Document 3). Furthermore, a technology for reducing the thermal shrinkage of a PPS membrane is disclosed (Patent Document 4).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-103170

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-219136

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 2013-110048

[0011] Patent Document 4: International Publication No. 2021 / 045076 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] In recent years, with the development of fuel cells into large-scale mobile vehicles, the fuel cells themselves have been developed to achieve higher output and longer life. This has led to the development of fuel cells operating at temperatures exceeding 100°C, compared to the conventional operating temperature of 50-100°C. This material, in particular, is also required to exhibit long-term durability at these higher temperatures in reinforcement components.

[0014] However, even the technology described in the above patent document has problems such as being easily broken when used as an electrolyte membrane reinforcement member in an operating temperature range exceeding 100° C., or being wrinkled or warped due to shrinkage deformation caused by thermal motion.

[0015] An object of the present invention is to solve the above-mentioned problems and to provide a polyarylene sulfide film that is less likely to break in a temperature range exceeding 100° C. and is less likely to wrinkle or warp.

[0016] Means for solving problems

[0017] A preferred embodiment of the present invention is as follows.

[0018] (1) A biaxially oriented polyarylene sulfide film having a polyarylene sulfide (PAS) resin as a main component and an elastic modulus (Y) measured at 130°C in a direction perpendicular to the main orientation axis. A130 ) and the elastic modulus at 25°C in the direction perpendicular to the main orientation axis (Y A25 ) ratio Y A130 / Y A25 The value is 0.25 or more and 0.80 or less, and the heat shrinkage rate at 130° C. in this direction is −1.2% or more and 1.2% or less.

[0019] (2) A biaxially oriented polyarylene sulfide film having a glass transition temperature (Tg) of 110° C. or higher and 140° C. or lower as determined by temperature-modulated differential scanning calorimetry (temperature-modulated DSC), and a movable amorphous content of 5% or higher and 25% or lower relative to the entire film.

[0020] (3) The biaxially oriented polyarylene sulfide film according to (1) or (2), wherein the elastic modulus (Y B130 ) and the elastic modulus at 25°C in the main orientation axis direction (Y B25 ) ratio Y B130 / Y B25 The value is 0.25 or more and 0.80 or less, and the heat shrinkage rate at 130° C. in this direction is −1.2% or more and 1.2% or less.

[0021] (4) The biaxially oriented polyarylene sulfide film according to any one of (1) to (3), wherein the elastic modulus measured at 130° C. is 1.0 GPa or more in both the main orientation axis direction and the direction perpendicular to the main orientation axis.

[0022] (5) The biaxially oriented polyarylene sulfide film according to any one of (1) to (4), wherein a resonance parameter (Q value) obtained by microwave orientation measurement is 4600 or more and 5000 or less.

[0023] (6) The biaxially oriented polyarylene sulfide film according to any one of (1) to (5), wherein the weight average molecular weight (Mw) is 60,000 to 150,000.

[0024] (7) The biaxially oriented polyarylene sulfide film according to any one of (1) to (6), wherein the density is 1.3450 g / cm 3 Above and 1.3550g / cm 3 the following.

[0025] (8) The biaxially oriented polyarylene sulfide film according to any one of (1) to (7), wherein the micro endothermic peak temperature (Tmeta) (°C) determined by differential scanning calorimetry (DSC) is greater than or equal to (melting point (Tm) of the film - 100)°C and less than or equal to (Tm - 20)°C.

[0026] (9) A method for producing a biaxially oriented polyarylene sulfide film according to any one of (1) to (8), wherein after the polyarylene sulfide resin composition is melt-extruded and cooled and solidified, the film is stretched in the moving direction (MD stretching), and then the film is held with a clamp and stretched in the film width direction (TD stretching) to produce a biaxially stretched film, and then a step of heat-setting treatment is performed on the basis of setting the heat setting temperature (Ths1) of the first stage to 150°C or higher and the step of heat-setting treatment is performed on the basis of setting the heat setting temperature (Ths2) of the final stage to Ths1 or higher and 265°C or lower is continuously performed.

[0027] (10) An electrolyte membrane reinforcement member using the biaxially oriented polyarylene sulfide film according to any one of (1) to (8).

[0028] (11) The electrolyte membrane reinforcement member according to (10), comprising a component including at least a biaxially oriented polyarylene sulfide film, an organic resin layer, and a biaxially oriented polyarylene sulfide film in this order.

[0029] (12) The electrolyte membrane reinforcement member according to (10) or (11), wherein the thermal expansion coefficient measured in the temperature range of 100°C to 130°C in the direction of the highest thermal expansion coefficient is greater than 40 ppm / °C and less than 65 ppm / °C.

[0030] Measurement method: With the long side and / or short side of a rectangle set at 0°, change the direction by 10° at intervals and measure the thermal expansion coefficient in the temperature range of 100°C to 130°C. Calculate the value in the direction with the highest thermal expansion coefficient.

[0031] (13) A fuel cell comprising the electrolyte membrane reinforcement member according to any one of (10) to (12).

[0032] (14) A water electrolysis device comprising the electrolyte membrane reinforcement member according to any one of (10) to (12).

[0033] Effects of the Invention

[0034] The present invention provides a polyarylene sulfide film having excellent durability and dimensional stability. The biaxially oriented polyarylene sulfide film of the present invention is suitable for use as various components for automobiles and electrical / electronic materials, circuit substrates, heat-resistant belt substrates, films for toner stirrers for printing, mold release films, electrolyte membrane reinforcement members for fuel cells and water electrolysis devices, which require particularly high durability and dimensional stability, and current collector foil substrates for membrane capacitors and lithium-ion secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic oblique plan view showing a configuration example of an electrolyte membrane reinforced by a polyarylene sulfide membrane and an organic resin layer. DETAILED DESCRIPTION

[0036] Hereinafter, the present invention will be described.

[0037] A preferred embodiment of the present invention is a biaxially oriented polyarylene sulfide film, which has polyarylene sulfide (PAS) resin as a main component and an elastic modulus (Y) measured at 130°C in a direction perpendicular to the main orientation axis. A130 ) and the elastic modulus at 25°C in the direction perpendicular to the main orientation axis (Y A25 ) ratio Y A130 / Y A25 The ratio is 0.25 to 0.80, and the thermal shrinkage in this direction at 130° C. is −1.2% to 1.2%. This embodiment provides a polyarylene sulfide film having excellent durability and dimensional stability.

[0038] In the present invention, the biaxially oriented polyarylene sulfide film is preferably a film having a polyarylene sulfide (hereinafter, PAS) resin as a main component and being biaxially oriented. This film can be obtained by melt-molding a resin composition having a PAS resin as a main component into a sheet, biaxially stretching it, and then heat-treating it.

[0039] In the present invention, the so-called PAS resin as the main constituent refers to the content of 80% by mass or more of PAS resin. In addition, it is preferably 90% by mass or more, more preferably 95% by mass or more. If the content of PAS resin is less than 80% by mass, the heat resistance, dimensional stability, electrical properties, and mechanical properties that are characteristic of the PAS film are sometimes impaired. In addition, if a large amount of components other than PAS resin are contained, peeling, cracks, voids, etc. are sometimes generated at the interface portion with the PAS resin, thereby promoting degradation, and durability and barrier properties are poor. In addition, in the present invention, recycled raw materials of PAS resin can also be used within the scope of not impairing the effects of the invention.

[0040] The PAS resin used in the present invention is a copolymer having a repeating unit of -(Ar-S)-. Examples of Ar include units represented by the following formulas (A) to (K).

[0041]

[0042] (R1 and R2 are substituents selected from hydrogen, alkyl, alkoxy, and halogen, and R1 and R2 may be the same or different)

[0043] The repeating unit is preferably a p-arylene sulfide unit represented by the above formula (A). Representative examples thereof include polyphenylene sulfide, polysulfone, polyethersulfone, polyphenylene sulfide sulfone, and polyphenylene sulfide ketone. Particularly preferred p-arylene sulfide units are preferably p-phenylene sulfide units from the viewpoint of film properties and economic efficiency.

[0044] The PAS resin used in the present invention preferably comprises p-phenylene sulfide units represented by the following structural formula as the main constituent units, comprising from 80 mol% to 99.9 mol% of all repeating units. More preferably, it is from 90 mol% to 99.9 mol%, and most preferably, from 95 mol% to 99.9 mol%. This composition allows for excellent heat resistance and chemical resistance. However, if the p-phenylene sulfide units comprise less than 80 mol% of all repeating units, durability may be poor due to reduced crystallinity and orientation.

[0045]

[0046] Furthermore, it may be copolymerized with the copolymerization unit in a range of 0.01 mol % to 20 mol % of the repeating unit.

[0047] Preferred copolymerization units include:

[0048]

[0049]

[0050]

[0051] (Here, X represents an alkylene group, CO, or SO2 unit.)

[0052]

[0053]

[0054] (Here, R represents an alkyl group, a nitro group, a phenylene group, or an alkoxy group.)

[0055] The copolymerization method is not particularly limited, but a random copolymer is preferred.

[0056] The weight average molecular weight of the biaxially oriented polyarylene sulfide film of the present invention is preferably 60,000 or more, more preferably 65,000 or more, and further preferably 70,000 or more. By having a weight average molecular weight of 60,000 or more, the biaxially oriented film tends to have sufficient mechanical strength and thickness unevenness can be reduced. In addition, the weight average molecular weight can be exemplified as a preferred range of 150,000 or less, more preferably 120,000 or less, and further preferably 100,000 or less. By being within this range, the tensile elongation and durability of the biaxially oriented film can be improved. In addition, the weight average molecular weight is a value measured using a gel permeation chromatography (hereinafter sometimes abbreviated as GPC) equipped with a differential refractive index detector. More specifically, the value is calculated using GPC at a column temperature of 210°C and a detector temperature of 210°C, with 1-chloronaphthalene as the eluent, a flow rate of 1.0 mL / min, and a 1-chloronaphthalene solution having a PAS concentration of 0.1 mass %, and polystyrene as the standard substance.

[0057] The biaxially oriented polyarylene sulfide film of the present invention preferably has an elastic modulus (Y A130 ) and the elastic modulus at 25°C in the direction perpendicular to the main orientation axis (Y A25 ) ratio Y A130 / Y A25It is 0.25 or more and 0.80 or less. The elastic modulus ratio represents the ratio of the elastic modulus at 130°C to the elastic modulus at 25°C. A larger elastic modulus ratio indicates that a strong thermally stable structure has been formed that can suppress relaxation up to 130°C. By having this strong thermally stable structure, when used as an electrolyte membrane reinforcement member for a fuel cell, the rigidity as a reinforcement member can be maintained under a usage environment such as a temperature environment exceeding 100°C repeatedly, and deformation of the electrolyte membrane under the usage environment can be suppressed. If the elastic modulus ratio in the direction perpendicular to the main orientation axis is less than 0.25, a strong thermally stable structure may not be formed and the durability may be poor. If the elastic modulus ratio in the direction perpendicular to the main orientation axis exceeds 0.80, the high orientation is excessively developed, and the tensile elongation of the film may decrease, and the film may break due to the tension during processing during the coating process or punching process, thereby deteriorating the yield rate. The elastic modulus ratio in the direction perpendicular to the main orientation axis is more preferably 0.27 or more, further preferably 0.30 or more, and particularly preferably 0.33 or more. Furthermore, the elastic modulus ratio in the direction perpendicular to the main orientation axis is more preferably 0.75 or less, and further preferably 0.70 or less.

[0058] In the present invention, the main orientation axis direction is defined as any direction being 0°, and the elastic modulus at 25° is measured by changing the direction by 10° from -90° to 90° within the film plane. The direction with the highest elastic modulus is defined as the main orientation axis direction of the film.

[0059] In the present invention, the direction perpendicular to the main orientation axis is the point in the film surface where orientation is least likely to form and the strength is weakest. Therefore, when the elastic modulus in the perpendicular direction satisfies the above elastic modulus ratio, the film surface has a stable structure.

[0060] Regarding the ratio of elastic moduli in a direction perpendicular to the principal orientation axis of the present invention, increasing the longitudinal stretch ratio under the film forming conditions described below tends to increase the elastic modulus ratio. Furthermore, increasing the heat setting temperature tends to decrease the elastic modulus ratio. The elastic modulus is determined using the tensile testing machine described in the Examples.

[0061] The biaxially oriented polyarylene sulfide film of the present invention preferably has an elastic modulus (Y B130 ) and the elastic modulus in the main orientation axis direction measured at 25°C (Y B25 ) ratio Y B130 / Y B25It is greater than 0.25 and less than 0.80. The ratio of the elastic modulus in the main orientation axis direction within the above range indicates that a strong thermally stable structure is formed in the membrane surface, indicating that it is a stable structure even at an operating temperature exceeding 100°C when used as a reinforcing member of the electrolyte membrane. If the elastic modulus in the main orientation axis direction is less than 0.25, a strong thermally stable structure may not be formed and the durability may be poor. Since the high orientation is excessively developed if the elastic modulus ratio exceeds 0.80, the tensile elongation of the film may decrease and breakage may occur during the coating process and the punching process due to the tension during processing, thereby deteriorating the yield rate. The elastic modulus ratio in the main orientation axis direction is more preferably greater than 0.27, further preferably greater than 0.30, and particularly preferably greater than 0.33. In addition, the elastic modulus ratio in the main orientation axis direction is more preferably less than 0.75, further preferably less than 0.70. The elastic modulus ratio in the main orientation axis direction can be controlled by the film forming conditions described later.

[0062] The biaxially oriented polyarylene sulfide film of the present invention preferably has an elastic modulus measured at 130°C in the main orientation axis direction (Y B130 ) and the direction orthogonal to the main orientation axis (Y A130 ) are all above 1.0GPa. If the elastic modulus measured at 130°C is within the above range, it means that a large amount of a strong thermally stable structure is formed even at an operating temperature exceeding 130°C. When used as a reinforcing member of the electrolyte membrane, deformation under the working environment pressure can be suppressed and thermal stability can be maintained at the working environment temperature, thereby improving durability. Therefore, it is preferred. If the elastic modulus measured at 130°C is less than 1.0GPa, sometimes the rigidity is low and deformation occurs including the electrolyte membrane in an environment with an operating temperature exceeding 100°C, the thermal stability becomes low, and the durability deteriorates. The elastic modulus Y measured at 130°C is B130 and Y A130 The elastic modulus measured at 130°C is preferably 1.2 GPa or higher, and even more preferably 1.4 GPa or higher. Furthermore, the elastic modulus measured at 130°C can be 4.0 GPa or lower, and more preferably 3.5 GPa or lower. Within this range, orientation does not become excessively high, and the film's thermal shrinkage can be within the preferred range. In the film formation conditions described below, increasing the stretch ratio tends to increase the elastic modulus measured at 130°C. Furthermore, increasing the heat setting temperature tends to decrease the elastic modulus measured at 130°C.

[0063] The biaxially oriented polyarylene sulfide film of the present invention preferably has an elastic modulus measured at 25°C in the main orientation axis direction (Y B25 ) and the direction orthogonal to the main orientation axis (Y A25) are both 3.0 GPa or higher. If the elastic modulus measured at 25°C is within this range, it indicates that the molecular chains are aligned, resulting in sufficient membrane strength. This is preferable because deformation under operating environmental pressure can be suppressed when used as a reinforcing member for an electrolyte membrane, improving durability. If the elastic modulus measured at 25°C is less than 3.0 GPa, the molecular chains may not be aligned sufficiently, resulting in reduced membrane durability.

[0064] Elastic modulus Y measured at 25°C B25 and Y A25 The elastic modulus measured at 25°C is preferably 3.3 GPa or higher, and even more preferably 3.5 GPa or higher. Furthermore, the elastic modulus measured at 25°C can be 5.0 GPa or lower as an example. Within this range, orientation does not become excessively high, and the thermal shrinkage of the film can be within the preferred range. Increasing the stretch ratio under the film formation conditions described below tends to increase the elastic modulus measured at 25°C.

[0065] The biaxially oriented polyarylene sulfide film of the present invention preferably has a 130°C thermal shrinkage, measured in a direction perpendicular to the principal orientation axis, of -1.2% to 1.2%. If the thermal shrinkage in the direction perpendicular to the principal orientation axis falls within this range, dimensional change during processing and in operating temperatures exceeding 100°C is minimized, residual stress is less likely to form within the film, and dimensional stability and durability are improved. In roll-to-roll processing, where the film's width is perpendicular to the principal orientation axis, no tension is applied in the width direction. Therefore, dimensional change due to thermal shrinkage at processing temperatures may dominate. Therefore, the 130°C thermal shrinkage in the direction perpendicular to the principal orientation axis is preferably within the above range. A 130°C thermal shrinkage in the direction perpendicular to the principal orientation axis of less than -1.2% indicates expansion exceeding 1.2%, which may degrade dimensional stability and generate residual stress under operating conditions, causing membrane deformation and reduced durability. A 130°C thermal shrinkage in the direction perpendicular to the principal orientation axis of more than 1.2% may result in significant deformation during processing and degraded dimensional stability. The 130°C thermal shrinkage in the direction perpendicular to the main orientation axis is more preferably -1.0% or greater, and even more preferably -0.8% or greater. Furthermore, the 130°C thermal shrinkage in the direction perpendicular to the main orientation axis is more preferably 1.0% or less, and even more preferably 0.8% or less. In the film formation conditions described below, if the relaxation rate in the relaxation treatment after heat setting is increased, the 130°C thermal shrinkage in that direction tends to decrease. The thermal shrinkage is determined by the method described in the Examples.

[0066] The biaxially oriented polyarylene sulfide film of the present invention preferably has a 130°C thermal shrinkage rate in the main orientation axis direction of not less than -1.2% and not more than 1.2%. If the 130°C thermal shrinkage rate is within the above range, the dimensional change during processing is small, and the dimensional stability can be improved. If the 130°C thermal shrinkage rate in the main orientation axis direction is less than -1.2%, it means that the expansion exceeds 1.2%, sometimes the dimensional stability is deteriorated, and sometimes residual stress is generated in the use environment, causing the electrolyte membrane to deform and the durability to decrease. If the 130°C thermal shrinkage rate in the main orientation axis direction exceeds 1.2%, sometimes the deformation becomes larger during processing and the dimensional stability is deteriorated. The 130°C thermal shrinkage rate in the main orientation axis direction is more preferably not less than -1.0%, and further preferably not less than -0.8%. In addition, the 130°C thermal shrinkage rate in the main orientation axis direction is more preferably not more than 1.0%, and further preferably not more than 0.8%. When the longitudinal stretch ratio is increased under the film forming conditions described below, the 130°C heat shrinkage in that direction tends to increase, and when the heat setting temperature is increased, the 130°C heat shrinkage in that direction tends to decrease.

[0067] The biaxially oriented polyarylene sulfide film of the present invention preferably has a glass transition temperature (Tg) of 110°C or higher and 140°C or lower as determined by temperature-modulated differential scanning calorimetry (temperature-modulated DSC). Temperature-modulated DSC is a method for measuring the glass transition temperature of a biaxially stretched film, which is difficult to determine by DSC (see SENI GAKKAISHI (Fibers and Industries) Vol. 65, No. 11 (2009)). In addition, the specific measurement method is the method described in the examples. If the Tg determined by temperature-modulated DSC is within the above range, the rigidity can be maintained even at an operating temperature exceeding 100°C, which is preferred. If the Tg determined by temperature-modulated DSC is less than 110°C, the orientation of the molecular chains is insufficient, and therefore the durability in an environment with an operating temperature exceeding 100°C is sometimes deteriorated. If the Tg determined by temperature-modulated DSC exceeds 140°C, molecular chain orientation is extremely enhanced, which may result in a decrease in the tensile elongation of the film, leading to breakage due to tension during processing during the coating and punching steps, and thus a decrease in yield. The Tg determined by temperature-modulated DSC is more preferably 115°C or higher, and even more preferably 118°C or higher. Furthermore, the Tg determined by temperature-modulated DSC is more preferably 135°C or lower. Regarding the Tg determined by temperature-modulated DSC, increasing the stretch ratio under the film formation conditions described below tends to increase the Tg. Furthermore, increasing the heat setting temperature tends to decrease the Tg.

[0068] The biaxially oriented polyarylene sulfide film of the present invention preferably has a movable amorphous content of 5% or more and 25% or less relative to the total film content. The film mainly contains movable amorphous, rigid amorphous with its ends fixed to the crystals, and crystals. If the movable amorphous content relative to the total film content is within the above range, it means that the amount of molecular chain movement at temperatures above 100°C is reduced, which can improve durability and is therefore preferred. If the movable amorphous content relative to the total film content is less than 5%, there may be a large amount of crystals and rigid amorphous, resulting in loss of toughness and film degradation and cracking caused by temperature cycling and vibration under the use environment, thereby affecting durability. If the movable amorphous content relative to the total film content exceeds 25%, it means that there is a large amount of amorphous content moving at temperatures above 100°C, and sometimes degradation of the amorphous portion progresses under the use environment, thereby worsening durability. The movable amorphous content relative to the total film content is more preferably 12% or more. In addition, the movable amorphous content relative to the total film content is more preferably 23% or less, and further preferably 20% or less. In addition, the specific method for measuring the amount of movable amorphous particles relative to the entire film is the method described in the Examples. Among the film forming conditions described later, if the heat setting temperature is low, the amount of movable amorphous particles relative to the entire film tends to decrease, but if it is lower than a specific heat setting temperature, the amount of movable amorphous particles relative to the entire film tends to increase. If the stretch ratio is increased, the amount of movable amorphous particles relative to the entire film tends to decrease. If the temperature of the relaxation treatment is high, the amount of movable amorphous particles relative to the entire film tends to increase. In addition, if the relaxation rate of the relaxation treatment is high, the amount of movable amorphous particles relative to the entire film tends to decrease. In addition, by implementing the relaxation treatment in stages, the amount of movable amorphous particles relative to the entire film tends to decrease.

[0069] The biaxially oriented polyarylene sulfide film of the present invention preferably has a resonance parameter (Q value) of 4600 or more and 5200 or less as determined by microwave orientation measurement. In the present invention, the Q value is the average value of 10 measurements of the parameter (Q value) indicating the sharpness of the resonance of the biaxially oriented polyarylene sulfide film, measured using a molecular orientation meter (manufactured by Oji Instruments, MOA-6015). The detailed measurement method is as described in the examples. The higher the orientation of the molecular chains in the film, the greater the Q value. If the resonance parameter (Q value) is within the above range, it means that the molecular chains are fully oriented, the molecular motion is suppressed, and the durability is improved, so it is preferred. If the resonance parameter (Q value) is less than 4600, it is sometimes not fully oriented, and the mobility of the amorphous part remains in the use environment of a fuel cell or a water electrolysis device, resulting in poor durability. The resonant parameter (Q value) is more preferably 4700 or more, more preferably 4800 or more, and particularly preferably 4850 or more. The resonant parameter (Q value) is more preferably 5000 or less. In the film making conditions described later, if the stretching ratio is improved, the resonant parameter (Q value) has a tendency to increase, and if the stretching temperature is improved, the resonant parameter (Q value) has a tendency to decrease.

[0070] From the perspective of further improving thermal stability, the biaxially oriented polyarylene sulfide film of the present invention preferably has a minimal endothermic peak temperature (T-meta) (°C) determined by differential scanning calorimetry (DSC) of at least (film melting point (Tm) - 100)°C and no more than (Tm - 20)°C. The minimal endothermic peak temperature (T-meta) in the present invention refers to the thermal history of the film. If T-meta is within the above range, orientation relaxation during the film formation process is suppressed, and the thermally stable structure required for operating temperatures exceeding 100°C is easily formed, resulting in a film with excellent durability. On the other hand, if T-meta is less than (film melting point (Tm) - 100)°C, the thermal history may be slow, resulting in significant thermal dimensional change and poor dimensional stability. If T-meta exceeds (Tm - 20), orientation relaxation may progress, and durability at operating temperatures exceeding 100°C may be poor. T-meta is more preferably 200°C or higher and less than 240°C, and even more preferably 210°C or higher and less than 235°C. T-meta can be controlled at the heat setting temperature. T-meta varies depending on the film forming machine and film forming speed, but generally, the higher the heat setting temperature, the higher the T-meta.

[0071] From the viewpoint of further improving durability, the biaxially oriented polyarylene sulfide film of the present invention preferably has a film density of 1.3450 g / cm 3 Above and 1.3550g / cm3 If the density is within the above range, the crystallinity is improved while maintaining the oriented structure, and it is easy to form a thermally stable structure required for an operating temperature exceeding 100°C, and a film with excellent durability can be obtained. If the density is less than 1.3450 g / cm 3 If the density exceeds 1.3550 g / cm, crystallization may not develop, resulting in poor durability and dimensional stability. 3 , sometimes the crystallinity is excessively increased, so the orientation is reduced and the durability is poor. The density is more preferably 1.3480 g / cm 3 More preferably, the film density is 1.3520 g / cm 3 The density can be evaluated by the method described below. Among the film forming conditions described below, if the heat setting temperature is increased, the density tends to increase.

[0072] The biaxially oriented polyarylene sulfide film of the present invention can be obtained by biaxial stretching. Biaxial stretching methods include simultaneous inflation biaxial stretching, simultaneous tenter biaxial stretching, and sequential tenter biaxial stretching. Among these, sequential tenter biaxial stretching is preferred in terms of controlling film formation stability, film durability, and dimensional stability.

[0073] The thickness of the biaxially oriented polyarylene sulfide film of the present invention is not particularly limited, but from the perspective of film formability, the film thickness is preferably 0.5 μm to 300 μm. For electrolyte membrane reinforcement members, from the perspective of handleability, the thickness is more preferably 10 to 150 μm, further preferably 20 to 125 μm, and particularly preferably 35 to 100 μm. Furthermore, for battery collector foil substrates such as membrane capacitors and lithium-ion secondary batteries, the thickness is preferably 0.5 μm to 15 μm, from the perspective of balancing durability and thin film thickness. The thickness is more preferably 9.0 μm or less, further preferably 6.0 μm or less, and most preferably 4.0 μm or less. Film thickness can be measured using a micrometer, as described in detail below.

[0074] The method for producing the biaxially oriented polyarylene sulfide film of the present invention will be described using a method for producing a film using polyphenylene sulfide resin (hereinafter sometimes abbreviated as PPS resin) as the polyarylene sulfide resin as an example, but the present invention is not limited to this example.

[0075] Sodium sulfide and p-dichlorobenzene are mixed and reacted in an amide-based polar solvent such as N-methyl-2-pyrrolidone (NMP) under high temperature and high pressure. Copolymer components such as m-dichlorobenzene and trihalogenated benzenes may also be included as needed. Potassium hydroxide or an alkali metal carboxylate is added as a polymerization degree modifier, and the polymerization reaction is carried out at 230-290°C. After polymerization, the polymer is cooled and filtered as a slurry through a filter to obtain a wet granular polymer. An amide-based polar solvent is added to the granular polymer, stirred at 30-100°C, washed several times with ion-exchanged water at 30-80°C, and washed several times with an aqueous metal salt solution such as calcium acetate aqueous solution, before drying to obtain a granular polymer of polyphenylene sulfide. The granular polymer is fed into an extruder equipped with a vent and melt-extruded into strands. After cooling with water at 25°C, the granular polymer is cut into crumbs to produce PPS crumbs.

[0076] Furthermore, the obtained PPS granular polymer was preliminarily melt-kneaded (pelletized) with a polyphenylsulfone resin under the above-mentioned conditions to prepare a master batch.

[0077] In the present invention, it is preferred that PPS crumbs, which have been dried under reduced pressure at 180°C for 3 hours as needed, are first mixed with a masterbatch in a prescribed ratio, supplied to a fully threaded single-screw extruder with a melting zone set at 300-350°C, passed through a filter, and then discharged from a T-shaped die. The extruder is then rapidly quenched and solidified on a cooling drum having a surface temperature of 20-70°C while being electrostatically charged, thereby obtaining a substantially non-oriented unstretched film.

[0078] Next, the unstretched film obtained above is biaxially stretched in a temperature range above the glass transition temperature (Tg) of the polyarylene sulfide resin using a sequential biaxial stretching machine or a simultaneous biaxial stretching machine, and then subjected to one or more heat treatments at a temperature range of 150 to 280°C to obtain a biaxially oriented film. As the stretching method, a sequential biaxial stretching method (a stretching method combining stretching in one direction, such as stretching in the longitudinal direction followed by stretching in the width direction), a simultaneous biaxial stretching method (a method of simultaneously stretching in the longitudinal and width directions), or a combination thereof can be used. Here, a sequential biaxial stretching method is exemplified, in which stretching in the longitudinal direction is performed first, followed by stretching in the width direction.

[0079] The unstretched film is heated with a heating roller group and stretched (MD stretching) in one or more stages in the longitudinal (MD) direction to 2.5 or more times, more preferably 3.0 or more times, further preferably 3.3 or more times, particularly preferably 3.5 or more times, and most preferably 3.8 or more times. By setting the MD stretching to the above range, the molecular chains are arranged in the longitudinal direction, so that when stretching in the width (TD) direction described later, stress can be uniformly transmitted, the amorphous orientation in the width direction is improved, and durability and dimensional stability can be improved. In addition, the MD stretching ratio can be exemplified as 5.0 times or less as a preferred range, more preferably 4.8 times or less, further preferably 4.5 times or less, and particularly preferably 4.3 times or less. If this range is exceeded, excessive orientation in one direction during MD stretching occurs, and thus the film forming properties during transverse stretching may sometimes deteriorate. The stretching temperature is Tg to Tcc (crystallization peak temperature), preferably in the range of (Tg+5) to (Tcc-5)°C. Then, cooling is performed with a cooling roller group at 20 to 50°C.

[0080] As a stretching method in the width direction (TD direction) after MD stretching, for example, a method using a tenter is generally used. The two ends of the film are clamped with clamps, guided to the tenter, and TD stretching in the width direction is performed. The stretching temperature for TD stretching is preferably 90°C or more and 200°C or less, and the TD stretching temperature is more preferably 90°C or more, and further preferably 95°C or more. The TD stretching temperature is more preferably 180°C or less, and further preferably in the range of 160°C or less. From the viewpoint of the planarity of the film, the stretching ratio for TD stretching is preferably 1.2 times or more and 4.0 times or less. The TD stretching ratio is more preferably 3.0 times or more, and further preferably 3.3 times or more. In addition, the TD stretching ratio is more preferably 3.8 times or less, and further preferably 3.6 or less.

[0081] In this case, regarding the stretch ratio of the film, the ratio of the MD ratio to the TD ratio (stretch ratio ratio = MD ratio / TD ratio) is preferably greater than 1.0, more preferably greater than 1.1, and even more preferably greater than 1.2. By falling within this range, the structure formed in MD stretching can effectively form an oriented structure in TD stretching.

[0082] Next, in the present invention, heat setting after stretching is preferably performed in two or more stages at different temperatures. Heat setting is preferably performed continuously. "Continuously" in the present invention means performing heat setting in stages without intervening cooling steps. This heat setting treatment is preferred because it suppresses the rapid orientation relaxation caused by heat setting, forming a strong, heat-stable structure and improving durability. The heat setting temperatures are preferably a heat setting temperature Ths1 (°C) in the first stage of 150°C to 230°C, and a heat setting temperature Ths2 (°C) in the final stage of Ths1 to 265°C. The term "first stage" in the present invention refers to the heat setting treatment performed in two or more stages, excluding the final stage. For example, in a heat setting treatment process consisting of three stages, the first and second stages constitute the first stage, and the third stage constitutes the final stage. If the heat setting temperature in the first stage (hereinafter sometimes abbreviated as Ths1) is within the above range, crystallization is promoted and the structure can be fixed at a temperature where orientation relaxation is unlikely to develop. This is a preferred solution because orientation relaxation can be suppressed during the subsequent heat setting treatment. Specifically, as mentioned above, Ths1 is preferably 150°C or higher and 230°C or lower, more preferably 150°C or higher, and even more preferably 160°C or higher. Furthermore, Ths1 is more preferably 200°C or lower, and even more preferably 190°C or lower. By setting the heat setting temperature in the final stage (hereinafter sometimes abbreviated as Ths2) to Ths1 or higher and 265°C or lower, the crystallization and orientation structure formed in the first stage are not relaxed, and the strain caused by stretching can be removed, thereby improving durability and dimensional stability. Therefore, Ths2 is more preferably 200°C or higher, and even more preferably 215°C or higher. Furthermore, Ths2 is more preferably 245°C or lower, even more preferably less than 240°C, and most preferably 235°C or lower. When the heat setting treatment of the present invention is performed in three or more stages, the heat setting temperature is preferably gradually increased in the first, second, and third stages within the preferred temperature ranges of Ths1 and Ths2 described above. The heat setting time for each of the first heat setting stages is preferably 1 to 1000 seconds, more preferably 1 to 60 seconds, and even more preferably 1 to 30 seconds. Furthermore, the heat setting time for the final stage is preferably 1 to 1000 seconds, more preferably 1 to 60 seconds, and even more preferably 1 to 10 seconds. Furthermore, the total heat setting time is preferably no more than 2000 seconds, more preferably no more than 120 seconds, even more preferably no more than 30 seconds, and particularly preferably no more than 20 seconds. In the present invention, the heat setting process is preferably a process of two or more stages, but considering the total heat setting time, it is more preferably two or more stages and no more than three stages.

[0083] Next, the biaxially oriented film that has been heat-set is preferably subjected to a relaxation treatment in the width direction while being held by a clamp. In the present invention, the relaxation treatment is preferably carried out in two or more stages at different temperatures. By performing the relaxation treatment in two or more stages at different temperatures, the molecular chains that have been stretched by drawing are not relaxed sharply, but the stretched chains that cause the thermal shrinkage can be relaxed while the amorphous oriented structure remains, which can improve durability and dimensional stability. Therefore, it is a preferred solution. In the present invention, the so-called relaxation rate is a value that is a ratio of the width between the clamps before treatment to the difference between the width after treatment, for example, a relaxation rate of 2% means that when the width is 100 mm before treatment, the width is relaxed by 2%, which is 2 mm, and becomes 98 mm after treatment. The relaxation rate of the relaxation treatment in the front stage (hereinafter sometimes abbreviated as Rx1) is preferably 1.0 to 10.0%, and more preferably 3.0 to 7.0%. Furthermore, the temperature Trx1 during the relaxation treatment (Rx1) is preferably (Ths2-50)°C or higher and (Ths2)°C or lower, more preferably (Ths2-40)°C or higher and (Ths2-20)°C or lower. The relaxation rate of the subsequent relaxation treatment (hereinafter sometimes abbreviated as Rx2) is preferably 0.1 to 10%, more preferably 1.5 to 5%. The temperature Trx2 during the subsequent relaxation treatment (Rx2) is preferably (Trx1-40°C or higher and (Trx1-10)°C or lower.

[0084] Then, after cooling at a temperature preferably below 35°C, more preferably below 25°C, the film edge is removed and wound on a core. Furthermore, from the viewpoint of improving thermal dimensional stability, the wound PPS film can be conveyed under tension under certain temperature conditions for annealing. Regarding the annealing temperature, 130°C or higher and 200°C or lower is a more preferred option. If it exceeds 200°C, the planarity may be deteriorated due to shrinkage deformation during the annealing. If it is less than 130°C, the strain removal of the molecular structure brought about by the annealing may become incomplete, and the durability and dimensional stability may be deteriorated. The annealing temperature is preferably above 150°C and below 180°C. The annealing time is preferably 1 to 200 seconds, more preferably 10 to 100 seconds, and the PAS film of the present invention can be obtained by annealing while conveying at a speed of 1 to 100 m / min.

[0085] In the present invention, the polyarylene sulfide film or its roll can be subjected to any processing as needed, such as molding, surface treatment, lamination, coating, printing, embossing, and etching. In particular, corona treatment is a preferred surface treatment from the perspective of improving adhesion with the organic resin layer.

[0086] The biaxially oriented polyarylene sulfide film of the present invention may contain inactive particles within a range that does not impair the effects of the invention. Examples of inactive particles include inorganic fillers such as silica, alumina, calcium carbonate, barium carbonate, barium titanate, barium sulfate, calcium silicate, magnesium oxide, titanium oxide, and zinc oxide, and particles of organic polymer compounds that do not melt at 300°C (e.g., cross-linked polystyrene). The addition of inactive particles improves the film's slippage during the film stretching process, suppresses wrinkles when the film moves between rollers, and maintains surface irregularities even at elevated heat setting temperatures after transverse stretching, thereby suppressing surface damage and improving fluidity.

[0087] The biaxially oriented polyarylene sulfide film of the present invention has excellent durability and can therefore be suitably used as various parts for automobiles and electrical / electronic materials, circuit substrates, heat-resistant belt substrates, films for toner stirrers for printing, mold release films, electrolyte membrane reinforcement members for fuel cells and water electrolysis devices, which particularly require durability and dimensional stability, and battery collector foil substrates for membrane capacitors and lithium-ion secondary batteries.

[0088] In the present invention, the so-called electrolyte membrane reinforcement member is punched into a frame or frame shape and is used in conjunction with the peripheral portion of the electrolyte membrane. Regarding the frame-shaped electrolyte membrane reinforcement member, the center portion of the laminated electrode is cut into the shape of the electrode, and the electrolyte membrane reinforcement member is present only in the peripheral portion. Regarding the electrolyte membrane reinforcement member, at least one electrolyte membrane reinforcement member can be used by being adhered to the peripheral portion of the electrolyte membrane. In addition, it is also a preferred solution to overlap two electrolyte membrane reinforcement members. Specifically, there can be mentioned a solution in which one electrolyte membrane reinforcement member is used on each side of the electrolyte membrane, sandwiching the peripheral portion of the electrolyte membrane. Furthermore, two or more electrolyte membrane reinforcement members can be overlapped on each side of the electrolyte membrane, sandwiching the peripheral portion.

[0089] The electrolyte membrane reinforcing member may be bonded to the electrolyte membrane via an organic resin layer, and a known method (for example, Japanese Patent Application Laid-Open Nos. 2015-2029 and 2022-69952) can be applied to the biaxially oriented polyarylene sulfide film of the present invention.

[0090] The electrolyte membrane reinforcement member of the present invention preferably comprises at least a biaxially oriented polyarylene sulfide film of the present invention, an organic resin layer, and a component comprising the biaxially oriented polyarylene sulfide film of the present invention in this order. In the present invention, the organic resin layer serves as an adhesive layer, used to bond the biaxially oriented polyarylene sulfide, the organic resin layers to each other, and the electrolyte membrane. The organic resin layer may be thermosetting, thermoplastic (hot melt), or UV curable. For example, binders and / or adhesives such as polyester resins, modified olefin resins, epoxy resins, acrylic resins, silicone resins, urethane resins, and ethylene vinyl resins may be used as the organic resin layer, and these can be applied using various coating methods (e.g., gravure coating, metal rod coating, reverse roll coating, etc.). As the organic resin layer, from the viewpoint of film handling, a hot melt adhesive is preferably used, and examples thereof include "AronMelt" (registered trademark) PES-120L, PES-140H, PES-111EE, PES310S30, PES375S40, PPET1008, PPET1025, PPET2102, PPET1303S (all manufactured by Toagosei Co., Ltd.), Y-167, H-930-S, H-180S (all manufactured by Tanaka Chemical Co., Ltd.), "Nichigo "Polyester" (registered trademark) SP-154, SP-165, SP-170, SP-176 (all manufactured by Nippon Synthetic Chemical Co., Ltd.), "Byron" (registered trademark) 200, 240, 300, 550, BX1001 (all manufactured by Toyobo Co., Ltd.), "Polysol" (registered trademark) SE-1720, SE-4210E, SE-6210, SE-6210L (all manufactured by Showa Denko K.K.), etc. The film thickness of the organic resin layer is preferably in the range of 1 to 50 μm. By bonding the electrolyte membrane reinforcement member through the organic resin layer, the organic resin layer and the electrolyte membrane can be bonded, the adhesion is improved, and the durability can be further improved when used as an electrolyte membrane reinforcement member.

[0091] The electrolyte membrane reinforcement member of the present invention preferably has a thermal expansion coefficient of 40 ppm / °C to 65 ppm / °C in the direction of maximum thermal expansion coefficient measured in the temperature range of 100°C to 130°C.

[0092] In the present invention, the direction with the highest thermal expansion coefficient refers to the direction with the highest thermal expansion coefficient within the temperature range of 100°C to 130°C, measured by cutting a rectangular shape, with the long side and / or the short side of the rectangle set at 0°, and then changing the direction by 10°. A thermal expansion coefficient within this range is preferred because it reduces internal stress in the fastened electrolyte membrane reinforcement member when subjected to operating temperatures above 100°C, thereby improving durability. A thermal expansion coefficient of less than 40 ppm / °C indicates extremely high orientation, which may result in poor film forming properties of the membrane used to form the electrolyte membrane reinforcement member.

[0093] If the thermal expansion coefficient exceeds 65 ppm / °C, repeated application of operating temperatures above 100°C may cause deformation, cracking, and other deterioration due to internal stress, resulting in reduced durability. The thermal expansion coefficient is more preferably 60 ppm / °C or less. The detailed method for measuring the thermal expansion coefficient is described in the Examples. Increasing the stretch ratio in the above-mentioned film production conditions tends to reduce the thermal expansion coefficient, while increasing the heat setting temperature tends to increase the thermal expansion coefficient. Furthermore, in the manufacturing conditions for the electrolyte membrane reinforcement member described later, increasing the processing temperature tends to increase the thermal expansion coefficient.

[0094] The cell used in fuel cells and water electrolysis devices has a structure in which a catalyst layer, an electrode substrate, and a separator are sequentially laminated on both sides of an electrolyte membrane reinforced with the biaxially oriented polyarylene sulfide membrane of the present invention. A structure in which the catalyst layer is laminated on both sides of the electrolyte membrane (i.e., a structure with a layer structure of catalyst layer / electrolyte membrane / catalyst layer) is called a catalyst-coated electrolyte membrane (CCM), while a structure in which the catalyst layer and a gas diffusion substrate are sequentially laminated on both sides of the electrolyte membrane (i.e., a structure with a layer structure of gas diffusion substrate / catalyst layer / electrolyte membrane / catalyst layer / gas diffusion substrate) is called a membrane electrode assembly (MEA).

[0095] The CCM manufacturing method generally involves applying a catalyst layer paste composition for forming a catalyst layer to the surface of the electrolyte membrane and drying it, or by forming only the catalyst layer on a substrate and transferring the catalyst layer to laminate the catalyst layer onto the electrolyte membrane (transfer method). The end of the electrolyte membrane in the CCM is overlapped with the peripheral edge of the opening of the present invention membrane, which has been cut into a frame-shaped organic resin layer, and the CCM and electrolyte membrane reinforcement member are attached by hot pressing.

[0096] When MEA is produced by pressing, a known method (for example, (Electrochemistry), 1985, 53, p.269. Chemical plating method, edited by the Society of Electrochemists (J. Electrochem. Soc.), (Electrochemical Science and Technology, 1988, 135, 9, p. 2209.) The temperature and pressure during pressing can be appropriately selected depending on the thickness and moisture content of the electrolyte membrane, the catalyst layer, and the electrode substrate. Specific pressing methods include roller pressing with a specified pressure and gap, and flat plate pressing with a specified pressure.

[0097] The temperature during pressing of the film of the present application is preferably 50°C or higher and 140°C or lower. If it is within the above range, the durability of the electrolyte membrane reinforcement member can be improved without damaging the characteristics of the biaxially oriented film. If the temperature during pressing is less than 50°C, it may sometimes become adhesion from around room temperature. Since it has adhesiveness even at room temperature, the operability during manufacturing is deteriorated. If the temperature during pressing exceeds 140°C, excessive heat may be applied to the biaxially oriented film, resulting in structural changes and poor dimensional stability and durability. The temperature during pressing is more preferably 130°C or lower, and further preferably 120°C or lower. The pressing pressure is preferably 0.1MPa or higher and 10MPa or lower. If it is less than 0.1MPa, there may be no pressure applied and the appearance such as wrinkles may be deteriorated. If it exceeds 10MPa, the organic resin layer may be deformed and the appearance may be deteriorated. The pressing time is preferably 0.5 seconds or higher and 300 seconds or lower.

[0098] Hereinafter, the fuel cell and water electrolysis device of the present invention will be described.

[0099] The fuel cell of the present invention comprises an MEA using the biaxially oriented polyarylene sulfide membrane for electrolyte membrane reinforcement of the present invention. By using the biaxially oriented polyarylene sulfide membrane for electrolyte membrane reinforcement of the present invention in a fuel cell, the reinforcing effect can be enhanced even in temperature ranges exceeding 100°C, leading to a longer lifespan, for example.

[0100] The water electrolysis device of the present invention comprises an MEA using the biaxially oriented polyarylene sulfide membrane for electrolyte membrane reinforcement of the present invention. The use of the biaxially oriented polyarylene sulfide membrane for electrolyte membrane reinforcement of the present invention in the water electrolysis device provides a stable reinforcement effect in environments where output fluctuates, leading to a longer lifespan.

[0101] Example

[0102] [Methods for measuring properties]

[0103] (1) Content of polyarylene sulfide resin

[0104] The infrared absorption spectrum of the film was measured by the ATR method using an infrared spectrophotometer (PerkinElmer, Spectrorum 100 / Universal ATR (single reflection, crystal used: diamond / ZnSe). Based on the obtained infrared absorption spectrum, the polyarylene sulfide resin content was determined from the ratio of the peak attributed to the φ-S stretching vibration group of the sulfide bond based on the polyarylene sulfide to the peak attributed to other substances. In addition, in order to convert the peak height ratio into a mass ratio, a calibration curve was prepared in advance using a sample with a known mass ratio (for example, an olefin used as an incompatible resin), and the polyarylene sulfide resin content was calculated from the ratio relative to the total amount of the polyarylene sulfide and other substances.

[0105] (2) Elastic modulus at 25°C and 130°C

[0106] First, the main orientation axis direction is determined. Any direction is set as 0°, and the elastic modulus at 25°C is measured by the following method while changing the direction from -90° to 90° at 10° intervals within the film plane. The direction with the highest elastic modulus is defined as the main orientation axis direction of the film.

[0107] According to JIS K7127 (1999), a tensile test was performed using a tensile tester (RTG-1210 manufactured by A&D Company, Limited) at a temperature of 25°C or 130°C at a tensile speed of 300 mm / min. A sample film having a width of 10 mm was placed so that the length between chucks was 50 mm.

[0108] For the elastic modulus, the displacement start point is set at 0 mm and the end point is set at 10 mm. Within the measurement range of 0 to 10 mm displacement, the load difference is calculated at a calculation interval of 0.2 mm. The coordinates of the second, third, and fourth positions from the maximum value are used as raw data, and linearization is performed using the least squares method. The resulting slope is defined as the elastic modulus. Five specimens are cut so that the test length direction corresponds to the desired direction. The average of the results is then calculated.

[0109] Measuring device: A&D Company, Limited / RTG-1210

[0110] Sample size: test length 150mm × width 10mm

[0111] Length between chucks: 50mm

[0112] Tensile speed: 300mm / min

[0113] Measurement environment: 25℃ 55% RH, or 130℃

[0114] Analysis conditions: Displacement mode start point: 0mm, end point: 10mm, spacing: 0.2mm.

[0115] (3) Thermal shrinkage at 130°C

[0116] The film was cut into strips of 10 mm × 150 mm in such a way that the direction of the test length was the main orientation axis direction and the direction perpendicular to the main orientation axis. Marking lines were attached to the central 100 mm portion, and the distance between the marking lines (the distance between the marking lines before heat treatment) was measured using the following device. Next, a 3 g weight was hung on the film and heat treated for 30 minutes in a hot air furnace heated to 130 ° C. The distance between the marking lines (the distance between the marking lines after heat treatment) was measured in the same manner as above. The 130 ° C heat shrinkage rate was calculated from the following formula based on the obtained distance between the marking lines. In addition, 5 samples were measured in the main orientation axis direction and the direction perpendicular to the main orientation axis, and the average was calculated.

[0117] Length measuring device: universal projector

[0118] Sample size: test length 150mm × width 10mm

[0119] Heat treatment device: Gill aging constant temperature box

[0120] Heat treatment conditions: 130°C, 30 minutes

[0121] Load: 3g

[0122] Calculation method:

[0123] 130℃ heat shrinkage rate (%) = {(distance between markings before heat treatment) - (distance between markings after heat treatment)} / distance between markings before heat treatment × 100

[0124] (4) Glass transition temperature (°C), movable amorphous content (%)

[0125] Using a temperature-modulated DSC (Q1000) manufactured by TA Instruments, a 5 mg sample was measured under a nitrogen atmosphere at a heating rate of 2°C / min from 0°C to 200°C, a temperature modulation amplitude of ±1°C, and a temperature modulation period of 60 seconds. Based on the curve obtained from the measurement, the intersection of a straight line extending from the high-temperature side baseline to the low-temperature side and a tangent line drawn at the point where the slope of the step-like change portion of the curve reaches its maximum was defined as the glass transition temperature (Tg). The specific heat difference (ΔCp) determined from the baseline on the high-temperature side relative to Tg and the baseline on the low-temperature side relative to Tg according to JIS was determined, and the movable amorphous content (Xma) was calculated using the following formula.

[0126] Movable amorphous amount: Xma (%) = ΔCp / ΔCp0 × 100

[0127] Here, ΔCp0 represents the specific heat difference before and after Tg of completely amorphous PPS, and ΔCp0=0.2699 J / g° C. This value is based on (Wunderlich B., Thermal Analysis of Polymeric Materials, Appendix 1 (The ATHAS Data Bank), Springer (2005).)

[0128] (5) Weight average molecular weight

[0129] The molecular weight of the PAS resin and the membrane was calculated in terms of polystyrene using GPC. The GPC measurement conditions are shown below.

[0130] Apparatus: SSC-7110 manufactured by Senshu Scientific

[0131] Column: Showa Denko Shodex UT-G + Shodex UT-806M × 2

[0132] Eluent: 1-chloronaphthalene

[0133] Detector: Differential refractive index detector

[0134] Column temperature: 210°C

[0135] Pre-thermostatic bath temperature: 250°C

[0136] Pump thermostat temperature: 50°C

[0137] Detector temperature: 210°C

[0138] Flow rate: 1.0 mL / min

[0139] Sample injection volume: 300 μL (concentration: 0.1% by mass)

[0140] Standard sample: polystyrene.

[0141] (6) Resonance parameter (Q value)

[0142] The film was cut into 5 cm x 5 cm squares and evaluated using a microwave molecular orientation analyzer (MOA-6015, manufactured by Oji Instruments Co., Ltd.) at a frequency of 15 GHz. The film was rotated 30° at a time, and measurements were taken at six points up to 150°, with the average value calculated. For each sample, the average of the minimum and maximum orientation values ​​(Q) was used as the value. The measurement was performed 10 times for each sample, and the average of the obtained values ​​was used as the Q value for that sample.

[0143] (7) Melting point (Tm), micro-endothermic peak temperature (T-meta)

[0144] According to JIS K7121 (1999), a DSC (Thermo plus EVO2 DSCvesta-SL) manufactured by Rigaku Corporation was used as a differential scanning calorimeter. 5 mg of the sample was sealed in an aluminum pan and the temperature was raised from 25°C to 350°C at a heating rate of 20°C / min. At this time, the peak temperature of the observed melting endothermic peak was set as the melting point (Tm), and the temperature of the small endothermic peak that appeared in the temperature range of 150°C to below Tm°C was set as T-meta. The so-called melting point here is the point where the difference from the baseline of the DSC graph becomes the largest. Since the small endothermic peak is observed in the first run of the DSC, it is not observed in the second run where the thermal history is eliminated once the temperature is raised to above Tm. Therefore, it can be confirmed by comparing the DSC graphs of the two. The measurement was carried out 3 times for each sample, and the average value of the obtained values ​​was set as the melting point (°C) and small endothermic peak (T-meta) of the sample.

[0145] (8) Film thickness

[0146] The thickness of the biaxially oriented polyarylene sulfide film was measured at 10 random locations using a contact-type electronic micrometer (K-312A) manufactured by Anritsu Corporation in an atmosphere of 23° C. and 65% RH. The arithmetic mean of the thicknesses at these 10 locations was defined as the film thickness (unit: μm) of the biaxially oriented polyarylene sulfide film.

[0147] (9) Film density

[0148] According to JIS K7112, a sample cut into a roughly square (approximately 5 mm x 5 mm) was placed in a density gradient tube (NaBr aqueous solution, 25°C). The tube's scale was read after one night to perform the measurement. Four floating objects of known density were placed in the density gradient tube. A calibration curve was pre-created based on the position and density of these floating objects. The density of each sample was calculated based on this calibration curve. Three samples were placed in each tube, and the average of these values ​​was used as the membrane density for that sample.

[0149] (10) Thermal expansion coefficient of 100℃~130℃

[0150] In the case of a biaxially oriented polyarylene sulfide film, a hot melt adhesive ("AronMelt" (registered trademark) PPET1303S, manufactured by Toagosei Co., Ltd.) was applied to the polyarylene sulfide film using a bar coater. The film was then dried in an oven heated to 100°C for 60 seconds to obtain a biaxially oriented polyarylene sulfide / organic resin layer polyarylene sulfide film laminate having an organic resin layer thickness of 10 μm. Next, two polyarylene sulfide laminates were stacked with the organic resin layers in contact with each other and joined under the conditions shown in the table to produce a biaxially oriented polyarylene sulfide / organic resin layer / biaxially oriented polyarylene sulfide laminate, which was then used for thermal expansion coefficient evaluation.

[0151] In addition, when the biaxially oriented polyarylene sulfide film was coated with a substance other than the above-mentioned organic resin layer, the organic resin layers were overlapped so as to contact each other and joined under the conditions shown in the table to produce a biaxially oriented polyarylene sulfide film / organic resin layer / biaxially oriented polyarylene sulfide film laminate, which was then used for thermal expansion coefficient evaluation.

[0152] Regarding the thermal expansion coefficient, the above-mentioned sample is cut into a rectangular shape, the long side direction and / or the short side direction of the rectangle is set to 0°, and the thermal expansion coefficient is measured in the temperature range of 100°C to 130°C when the direction is changed every 10°. The highest direction is set as the thermal expansion coefficient of the electrolyte membrane reinforcement component.

[0153] The thermal expansion coefficient was measured during cooling after heating to 200°C in accordance with JIS K7197-1991. Assuming the initial sample length at 25°C and 65% RH is L0, the sample length at temperature T1 is L1 (mm), and the sample length at temperature T2 is L2 (mm), the average thermal expansion coefficient from T1 to T2 was calculated using the following equation.

[0154] In addition, T2=100(°C), T1=130(°C), L0=20mm.

[0155] Thermal expansion coefficient (ppm / °C) = (((L2-L1) / L0) / (T2-T1)) × 1,000,000

[0156] Heating and cooling speed: 5℃ / min

[0157] Sample width: 4mm

[0158] Load: 29.4mN

[0159] (11) Durability

[0160] The sample film was cut into a long strip of test specimens with a test length of 150 mm and a width of 10 mm and placed in an environmental testing machine set to 125°C / 2 atm / wet saturation mode / 100% RH (Highly Accelerated Life Tester PC-R8D manufactured by Hirayama Manufacturing Co., Ltd.) for 500 hours of treatment. The specimen was taken out and the breaking strength was measured. Five samples were taken in such a way that the direction of the test length was parallel to the main orientation axis and the direction orthogonal to the main orientation axis, and the measurement was carried out, and the average value of each was used for evaluation. The elongation at break retention rate shown in the following formula (1) was calculated from the average value of each direction. The durability was evaluated by the following benchmarks.

[0161] A: Elongation at break retention rate is above 85%

[0162] B: Elongation at break retention rate is above 80%

[0163] C: Elongation at break retention rate is above 75%

[0164] D: Elongation at break retention rate is less than 75%

[0165] Measuring device: A&D Company, Limited / RTG-1210

[0166] Tensile speed: 300mm / min

[0167] Measurement environment: 25°C 55% RH

[0168] Retention rate of elongation at break (%) = (elongation at break X / initial elongation at break X 0) × 100 ... (1)

[0169] (wherein, elongation at break X represents the elongation at break (unit: %) after treatment at 125°C, 2 atm, and 100% RH for 500 hours, and elongation at break X0 represents the initial elongation at break (unit: %) before treatment).

[0170] (12) Dimensional stability

[0171] A film (100 mm x 100 mm outer circumference, 80 mm x 80 mm inner circumference) cut into a rectangular frame with the main orientation axis and the direction perpendicular to the main orientation axis parallel to the frame side was placed on a press heated to 80°C and pressurized to 10 MPa. The temperature was raised to 130°C under pressure, and after 1 hour of treatment, the temperature was lowered to 80°C under pressure. The pressure was released at 80°C, and the film was removed. Dimensional stability was evaluated using the following criteria, in comparison with the film before treatment, along with the 130°C heat shrinkage rate described in (2).

[0172] A: No changes such as wrinkles and distortion are observed in the film, and the 130° C. heat shrinkage of the film in both the main orientation axis direction and the direction perpendicular to the main orientation axis is −1.0% or more and 1.0% or less.

[0173] B: Slight changes such as wrinkles and distortion are observed in the film, and the 130°C thermal shrinkage of the film in either the main orientation axis direction or the direction perpendicular to the main orientation axis is -1.2% or more and less than -1.0%, and / or exceeds 1.0% and is 1.2% or less.

[0174] C: Wrinkles and distortion are observed in the film, and the thermal shrinkage at 130°C in both the main orientation axis direction and the direction perpendicular to the main orientation axis direction is greater than -1.2% and less than -1.0%, greater than 1.0% and less than 1.2%, and / or the thermal shrinkage at 130°C in any direction is less than -1.2% or greater than 1.2%.

[0175] D: Wrinkles and distortion are observed in the film, and the 130° C. thermal shrinkage of the film in both the main orientation axis direction and the direction perpendicular to the main orientation axis direction is less than −1.2% or exceeds 1.2%.

[0176] (13) Appearance of the electrolyte membrane reinforcement member

[0177] A hot melt adhesive (manufactured by Toagosei Co., Ltd.: "AronMelt" (registered trademark) PPET1303S) as an organic resin layer was applied to the polyarylene sulfide film using a rod coater and dried in an oven heated to 100°C for 60 seconds to obtain a polyarylene sulfide film laminate of a biaxially oriented polyarylene sulfide / organic resin layer having an organic resin layer thickness of 10 μm.

[0178] Next, a perfluorosulfonic acid resin (Dupont: "Nafion" (registered trademark) 117) of 85 mm × 85 mm was used as an electrolyte membrane, and a polyarylene sulfide membrane laminate (outer circumference 100 mm × 100 mm, inner circumference 80 mm × 80 mm) was placed on both sides of the membrane. Figure 1 The electrolyte membrane reinforcement members were placed around the electrolyte membrane in the manner shown, overlapped so that the organic resin layers were in contact with each other, and bonded under the conditions shown in the table. After removal, the locations of deformation such as wrinkles and distortion in the electrolyte membrane reinforcement members were visually inspected, and the appearance of the electrolyte membrane reinforcement members was evaluated according to the following criteria.

[0179] AA: Almost no deformation of the film was observed.

[0180] A: Although some distortion was observed in the film, there was no practical problem.

[0181] B: Skewing was observed in the film, but the film was practically usable.

[0182] C: The film is distorted as a whole and is practically usable.

[0183] D: The entire film is greatly distorted and cannot be used practically.

[0184] (14) Unit durability (I)

[0185] A hot melt adhesive (manufactured by Toagosei Co., Ltd.: "AronMelt" (registered trademark) PPET1303S) as an organic resin layer was applied to the polyarylene sulfide film using a rod coater and dried in an oven heated to 100°C for 60 seconds to obtain a polyarylene sulfide film laminate of a biaxially oriented polyarylene sulfide / organic resin layer having an organic resin layer thickness of 10 μm.

[0186] Next, a 50 mm x 50 mm perfluorosulfonic acid resin (Dupont: "Nafion" (registered trademark) 117) was used as an electrolyte membrane. A polyarylene sulfide membrane laminate (outer circumference 80 mm x 80 mm, inner circumference 48 mm x 48 mm) was placed on both sides of the membrane. The membranes were placed around the electrolyte membrane and overlapped so that the organic resin layers were in contact with each other. The membranes were then joined under the conditions shown in the table to produce an electrolyte membrane with a subgasket. A pair of commercially available electrodes, BASF's fuel cell gas diffusion electrode "ELAT (registered trademark) LT120ENSI" with a 5 g / m 2 The Pt material was cut into 5 cm × 5 cm pieces, stacked opposite each other with the electrolyte membrane sandwiched between them, and incorporated into the JARI standard cell (electrode area 25 cm 2 ), tightened to a predetermined surface pressure and used as an evaluation unit.

[0187] The evaluation unit was placed in an environmental testing chamber (Highly Accelerated Life Tester PC-R8D, manufactured by Hirayama Seisakusho Co., Ltd.) set to 125°C / 2 atm / wet saturation mode / 100% RH) for 500 hours. Nitrogen gas was then introduced through the gas flow path of the JARI standard unit to a pressure of 300 kPa. The unit was then allowed to stand for one hour. The pressure change at this time was used to evaluate the presence or absence of gas leakage. The durability of the unit was evaluated using the following criteria.

[0188] A: The pressure of the sealed gas does not change, so there is no practical problem.

[0189] B: Although the pressure of the sealed gas is slightly reduced, it is still practical.

[0190] C: The pressure of the sealed gas decreases, causing gas leakage, making it impractical.

[0191] (15) Unit durability (II)

[0192] An evaluation cell was prepared in the same manner as for cell durability (I). The evaluation cell was subjected to a thermal cycle tester (Espec Corporation, TSE-11 thermal shock tester) for 500 hours, with 2000 cycles consisting of 30 minutes at -40°C and 30 minutes at 125°C. Nitrogen gas was introduced through the gas flow path of the JARI standard cell to a pressure of 300 kPa, and the cell was allowed to stand for 1 hour. The pressure change during this period was used to evaluate the presence or absence of gas leakage. The cell durability was evaluated using the following criteria.

[0193] A: The pressure of the sealed gas does not change, so there is no practical problem.

[0194] B: Although the pressure of the sealed gas is slightly reduced, it is still practical.

[0195] C: The pressure of the sealed gas decreases, causing gas leakage, making it impractical.

[0196] (Reference Example 1) Preparation of polyphenylene sulfide resin pellets (PPS pellets 1)

[0197] In a 1,000-liter SUS container equipped with a stirrer, 1 kilogram of 47% sodium hydrosulfide, 1.02 kilograms of 47% sodium hydroxide, 1.6 kilograms of N-methyl-2-pyrrolidone (NMP), 0.3 kilograms of sodium acetate, and 100 kilograms of ion-exchanged water were added. While stirring at 240 rpm and purging with nitrogen at normal pressure, the mixture was gradually heated to 235°C over approximately 180 minutes. After distilling off 209 kilograms of water and 0.4 kilograms of NMP, the reaction vessel was cooled to 160°C. The amount of hydrogen sulfide emitted was 0.02 kilograms. To the remaining mixture were added 1.02 kilograms of p-dichlorobenzene (p-DCB) and 2.40 kilograms of NMP. The reaction vessel was then sealed under nitrogen. While stirring at 400 rpm, the temperature was raised from 160°C to 220°C over 100 minutes, and the reaction was continued at 220°C for 300 minutes. Then, the temperature was raised from 220°C to 255°C over 60 minutes, and 0.8 kmol of water was injected into the system over 10 minutes, and the reaction was continued for 440 minutes. Then, the temperature was cooled from 255°C to 200°C over 100 minutes. After reaching 150°C, it was rapidly cooled to near room temperature using a blower. The contents were taken out, 1 kilogram of NMP was added, and the mixture was stirred at 85°C for 30 minutes. The solvent and the solid matter were then filtered and separated using a sieve (80 mesh). 1 kilogram of NMP was added to the resulting solid matter, stirred at 85°C for 30 minutes, and filtered. 1 kilogram of warm water was added to the resulting solid matter, stirred at 70°C for 30 minutes, and filtered. This operation was repeated three times. 0.3 kg of calcium acetate monohydrate and 1 kilogram of warm water as an aqueous solution were added to the resulting solid matter, stirred at 70°C for 30 minutes, and filtered. 1 kiloliter of warm water was added to the obtained solid material, and the mixture was stirred at 70°C for 30 minutes and separated by filtration. This operation was repeated three times and then dried under reduced pressure at 120°C for 5 hours to obtain PPS pellets 1.

[0198] (Reference Example 2) Preparation of polyphenylene sulfide resin pellets (PPS pellets 2)

[0199] PPS pellets 2 were obtained by performing the same operations as in Reference Example 1 except that the reaction temperature and time were increased from 160°C to 270°C over 180 minutes, reacted at 270°C for 135 minutes, and cooled from 270°C to 200°C over 100 minutes.

[0200] (Reference Example 3) Method for producing PPS pellets (PPS1)

[0201] The PPS pellets 1 prepared in Reference Example 1 were fed into a co-rotating twin-screw kneading extruder (manufactured by Nippon Steel Works, Ltd., screw diameter 30 mm, screw length / screw diameter = 45.5) heated to 315°C and equipped with a vent. The extruder was melt-extruded at a residence time of 90 seconds and a screw speed of 150 rpm to discharge the pellets in the form of strips. After cooling with water at 25°C, the pellets were immediately cut into crumbs to obtain PPS pellets (PPS1) having a weight-average molecular weight of 75,000 and a melting point of 280°C.

[0202] (Reference Example 4) Method for producing PPS pellets (PPS2)

[0203] The PPS pellets 2 prepared in Reference Example 2 were fed into a co-rotating twin-screw compounding extruder with a vent (manufactured by Nippon Steel Works, Ltd., screw diameter 30 mm, screw length / screw diameter = 45.5) heated to 315°C, melt-extruded at a residence time of 90 seconds and a screw speed of 150 rpm, and discharged in the form of strips. After cooling with water at a temperature of 25°C, the strips were immediately cut into crumbs, thereby obtaining PPS pellets (PPS2) having a weight-average molecular weight of 55,000 and a melting point of 280°C.

[0204] (Example 1)

[0205] The PPS pellets (PPS1) prepared in Reference Example 3 were dried under reduced pressure at 180°C for 3 hours. Subsequently, they were supplied to an extruder, melted at a temperature of 310°C under a nitrogen atmosphere, and introduced into a T-die. Subsequently, a molten monolayer sheet was extruded from the T-die in a sheet-like shape, and the molten monolayer sheet was cast while being tightly adhered to and cooled on a casting drum rotating at 3.5 m / min and maintained at a surface temperature of 25°C by an electrostatic application method to obtain an unstretched film. The obtained unstretched film was stretched (MD stretching) at a stretching temperature of 100°C along the longitudinal direction of the film at a ratio of 3.9 times by utilizing the circumferential speed difference of the rollers. The film was then clamped at both ends and guided to a tenter, where it was stretched at a ratio of 3.5 times in the width direction at a stretching temperature of 105°C (TD stretching). A first heat treatment (Ths1) was performed for 10 seconds using a tenter heated to 180°C, followed by a second heat treatment (Ths2) for 10 seconds using a tenter heated to 228°C. The film was then subjected to a first relaxation treatment (Rx1) at a relaxation rate of 5% using a tenter at 199°C, followed by a second relaxation treatment (Rx2) at a relaxation rate of 3% using a tenter at 178°C. After cooling to room temperature, the film edges were trimmed to obtain a 50μm thick biaxially oriented polyarylene sulfide film. The physical properties and characteristics of the resulting membrane and electrolyte membrane reinforcement member are shown in the table.

[0206] (Examples 2 to 14, Comparative Examples 1 to 6)

[0207] A biaxially oriented polyarylene sulfide film was obtained by the same method as in Example 1 except that the extrusion rate was adjusted and the raw materials and film-forming conditions were changed to the conditions shown in the table.

[0208] (Comparative Example 7)

[0209] A biaxially oriented polyarylene sulfide film was produced in the same manner as in Example 1 except that the extrusion rate was adjusted and the raw materials and film forming conditions were changed to those shown in the table. Many films broke during stretching, and very few samples were collected and their properties evaluated.

[0210] (Examples 15 to 17, Comparative Example 8)

[0211] The membrane obtained in Example 1 was used, and the bonding conditions with the electrolyte membrane were changed to the conditions shown in the table. The physical properties and characteristics of the electrolyte membrane reinforcement member obtained are shown in the table.

[0212] [Table 1]

[0213]

[0214] [Table 2]

[0215]

[0216] [Table 3]

[0217]

[0218] [Table 4]

[0219]

[0220] [Table 5]

[0221]

[0222] [Table 6]

[0223]

[0224] [Table 7]

[0225]

[0226] [Table 8]

[0227]

[0228] [Table 9]

[0229]

[0230] [Table 10]

[0231]

[0232] Explanation of symbols

[0233] 1: Polyarylene sulfide membrane

[0234] 2: Organic resin layer

[0235] 3: Electrolyte membrane.

Claims

1. A biaxially oriented polyarylene sulfide film, comprising polyarylene sulfide PAS resin as a main component, wherein the elastic modulus Y measured at 130°C in a direction perpendicular to the main orientation axis is A130 Elastic modulus Y at 25°C in a direction perpendicular to the main orientation axis A25 Ratio Y A130 / Y A25 The θ is 0.25 or more and 0.80 or less, and the 130° C. heat shrinkage rate in this direction is -1.2% or more and 1.2% or less.

2. A biaxially oriented polyarylene sulfide film having a glass transition temperature (Tg) of 110° C. to 140° C. as determined by temperature-modulated differential scanning calorimetry (DSC), and a movable amorphous content of 5% to 25% based on the entire film.

3. The biaxially oriented polyarylene sulfide film according to claim 1 or 2, wherein the elastic modulus Y measured at 130°C in the main orientation axis direction is B130 Elastic modulus Y at 25°C in the direction of the main orientation axis B25 Ratio Y B130 / Y B25 The θ is 0.25 or more and 0.80 or less, and the 130° C. heat shrinkage rate in this direction is −1.2% or more and 1.2% or less. The biaxially oriented polyarylene sulfide film according to claim 1 or 2, wherein the elastic modulus measured at 130°C is 1.0 GPa or more in both the main orientation axis direction and the direction perpendicular to the main orientation axis. The biaxially oriented polyarylene sulfide film according to claim 1 or 2, wherein the Q value, which is a resonance parameter determined by microwave orientation measurement, is 4600 or more and 5200 or less. The biaxially oriented polyarylene sulfide film according to claim 1 or 2, wherein the weight average molecular weight Mw is 60,000 to 150,000.

7. The biaxially oriented polyarylene sulfide film according to claim 1 or 2, wherein the density is 1.3450 g / cm 3 Above and 1.3550g / cm 3 the following.

8. The biaxially oriented polyarylene sulfide film according to claim 1 or 2, wherein the micro endothermic peak temperature Tmeta determined by differential scanning calorimetry (DSC) is (melting point (Tm) of the film - 100) ° C. to (Tm - 20) ° C., wherein the unit of Tmeta is ° C.

9. The method for producing a biaxially oriented polyarylene sulfide film according to claim 1 or 2, wherein: After the polyarylene sulfide resin composition is melt-extruded and cooled to solidify, the film is stretched in the moving direction, i.e., MD stretching. Subsequently, the film is held with a clamp and stretched in the width direction, i.e., TD stretching, to produce a biaxially stretched film. Then, a heat setting step is performed while setting the heat setting temperature Ths1 in the first stage to 150° C. or higher and the heat setting temperature Ths2 in the final stage to Ths1 or higher and 265° C. or lower is continuously performed. 10 . An electrolyte membrane reinforcement member using the biaxially oriented polyarylene sulfide film according to claim 1 . 11 . The electrolyte membrane reinforcement member according to claim 10 , comprising a component comprising at least a biaxially oriented polyarylene sulfide film, an organic resin layer, and a biaxially oriented polyarylene sulfide film in this order.

12. The electrolyte membrane reinforcement member according to claim 10, wherein the thermal expansion coefficient measured in the temperature range of 100°C to 130°C in the direction of the highest thermal expansion coefficient is 40 ppm / °C or more and 65 ppm / °C or less. Measurement method: With the long side and / or short side of a rectangle set at 0°, change the direction by 10° at intervals and measure the thermal expansion coefficient in the temperature range of 100°C to 130°C. Calculate the value in the direction with the highest thermal expansion coefficient. 13 . A fuel cell comprising the electrolyte membrane reinforcing member according to claim 10 . 14 . A water electrolysis device comprising the electrolyte membrane reinforcement member according to claim 10 .

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