Solid polymer electrolyte membrane, membrane electrode assembly, water electrolysis device, and method for producing hydrogen

Abstract

Provided are a solid polymer electrolyte membrane exhibiting high proton conductivity and low hydrogen permeability, a membrane electrode assembly, a water electrolysis apparatus, and a method for producing hydrogen.　This solid polymer electrolyte membrane contains a fluorine-containing polymer having an ion exchange group. The solid polymer electrolyte membrane has an elastic modulus in water at 80°C of 13 MPa or greater, and satisfies formula (A), where D [nm] is the distance between ion clusters measured through X-ray small angle scattering, and X [mEq / g dry resin] is the ion exchange capacity in the fluorine-containing polymer.　Formula (A): 4.55 − 0.85X ≤ D ≤ 4.16

Description

Solid polymer electrolyte membrane, membrane electrode assembly, water electrolysis apparatus, and hydrogen production method

[0001] This disclosure relates to a solid polymer electrolyte membrane, a membrane electrode assembly, a water electrolysis device, and a method for producing hydrogen.

[0002] From the perspective of power-to-gas, that is, converting surplus electricity into gas for storage and utilization, the use of polymer electrolyte water electrolyzers (PEM-type water electrolyzers) is being considered. For example, Patent Document 1 discloses a polymer electrolyte water electrolyzer having a membrane electrode assembly that includes an anode and a cathode having a catalyst layer, and a polymer electrolyte membrane disposed between the anode and the cathode.

[0003] International Publication No. 2019 / 088298

[0004] In recent years, there has been a demand for further performance improvements in water electrolysis devices, specifically for reducing hydrogen crossover. Here, hydrogen crossover refers to the movement of hydrogen gas generated at the cathode to the anode side through the solid polymer electrolyte membrane in a water electrolysis device. When hydrogen crossover occurs, there is a problem in that the hydrogen gas recovery efficiency decreases. Therefore, the solid polymer electrolyte membrane is required to be able to suppress the permeation of hydrogen gas generated in the system, that is, to have low hydrogen permeability. In addition, the solid polymer electrolyte membrane is also required to have high proton conductivity in order to improve the performance of water electrolysis devices. When the inventors evaluated the solid polymer electrolyte membrane described in the above-mentioned Patent Document 1, they found that there is room for improvement in terms of low hydrogen permeability.

[0005] This disclosure is made in view of the above-mentioned problems, and the problem that one embodiment of the present invention aims to solve is to provide a solid polymer electrolyte membrane exhibiting high proton conductivity and low hydrogen permeability, a membrane electrode assembly, a water electrolysis device, and a method for producing hydrogen.

[0006] The disclosure includes the following embodiments: [1] A solid polymer electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups, wherein the elastic modulus in water at 80°C is 13 MPa or more, and the following formula (A) is satisfied when the distance between ion clusters measured by small-angle X-ray scattering is D [nm] and the ion exchange capacity of the fluorine-containing polymer is X [milliequivalents / g dry resin]: Formula (A) 4.55 - 0.85X ≤ D ≤ 4.16 [2] The solid polymer electrolyte membrane according to [1], wherein the elastic modulus in water is 17 MPa or more. [3] The solid polymer electrolyte membrane according to [1] or [2], wherein the solid polymer electrolyte membrane has a layer comprising the fluorine-containing polymer, and the thickness of the layer is 30 μm or more. [4] The solid polymer electrolyte membrane according to any one of [1] to [3], wherein the fluorine-containing polymer comprises units having ion exchange groups. [5] The solid polymer electrolyte membrane according to [4], wherein the units having ion exchange groups are units having two or more ion exchange groups. [6] The solid polymer electrolyte membrane according to [4] or [5], wherein the unit having the ion exchange group includes a unit represented by formula (1-3). In formula (1-3), R ｆ１ R is a perfluoroalkylene group which may contain oxygen atoms between carbon atoms, ｆ２ is a perfluoroalkylene group which may contain an oxygen atom between single bonds or carbon atoms, r is 0 or 1, and M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation. [7] The solid polymer electrolyte membrane according to [6], wherein the fluorine-containing polymer contains units based on tetrafluoroethylene and units represented by the above formula (1-3), the content of the units based on tetrafluoroethylene is 88.0 to 94.0 mol% of the total units in the fluorine-containing polymer, and the content of the units represented by the above formula (1-3) is 6.0 to 12.0 mol% of the total units in the fluorine-containing polymer. [8] The solid polymer electrolyte membrane according to any one of [1] to [7], wherein the peak intensity ratio C, determined by small-angle X-ray scattering and defined by the following formula (E), is 10 or more and 90 or less. Formula (E) Peak intensity ratio C = I ｍ－ｃｒｙｓｔａｌ / I ｍ－ｃｌｕｓｔｅｒ[9] A solid polymer electrolyte membrane according to any one of [1] to [8], wherein the initial strain expressed in formula 1 below is 90.0% or less, the creep rate expressed in formula 2 below is 0.400% / h or less, and the PTL penetration rate expressed in formula 3 below is 0.70 μm / h or less, as measured by a thermomechanical analyzer (TMA). (Equation 1) Initial strain (%) = (TMA reading at load 3g - TMA reading at load 500g) / underwater cross-sectional thickness D × 100 (Equation 2) Creep rate (%) / h = [{strain (500)(24)} - initial strain] / 24 (Equation 3) PTL penetration rate (μm / h) = penetration height / 72 In the equations, underwater cross-sectional thickness D is the cross-sectional thickness obtained by observing the electrolyte membrane in water at 25°C, strain (X)(T) is the absolute value of the difference between the TMA reading after T time has elapsed since applying a constant load of Xg and the TMA reading at load 3g, divided by the cross-sectional thickness D in the underwater environment, and TMA reading is the height value calculated by performing height calibration on the measurement base.

[10] A solid polymer electrolyte membrane according to any of [1] to [9], wherein the conductivity is 0.20 S / cm or more.

[11] A method for producing a solid polymer electrolyte membrane, comprising: forming a film of a fluorine-containing polymer having a group that can be converted into an ion exchange group to produce a precursor film; and then converting the group that can be converted into an ion exchange group in the precursor film into an ion exchange group to obtain a solid polymer electrolyte membrane according to any one of [1] to

[10] , wherein the TQ value of the fluorine-containing polymer having a group that can be converted into an ion exchange group is 290°C or less, and the film formation temperature when carrying out the film formation is lower than the TQ value of the fluorine-containing polymer having a group that can be converted into an ion exchange group.

[12] A method for producing an electrolyte membrane with a catalyst layer, comprising: heating and pressurizing a laminate including a solid polymer electrolyte membrane according to any one of [1] to

[10] and a first catalyst layer arranged to be in contact with one surface of the electrolyte membrane, wherein the heating temperature is higher than 130°C and 180°C or less.

[13] A membrane electrode assembly comprising a solid polymer electrolyte membrane according to any one of [1] to

[10] , a cathode catalyst layer disposed on one side of the electrolyte membrane, and an anode catalyst layer disposed on the other side of the electrolyte membrane.

[14] A water electrolysis device comprising the membrane electrode assembly described in

[13] , a power supply unit connected to the cathode catalyst layer side and the anode catalyst layer side in the membrane electrode assembly, and a water supply unit for supplying water to the anode catalyst layer side.

[15] A method for producing hydrogen by electrolyzing water using the water electrolysis device described in

[14] .

[0007] According to one embodiment of the present invention, there are provided a solid polymer electrolyte membrane, a membrane electrode assembly, a water electrolysis device, and a method for producing hydrogen, which exhibit high proton conductivity and low hydrogen permeability.

[0008] It is a diagram for explaining the distance D between ion clusters. It is a cross-sectional view schematically showing an example of the membrane electrode assembly of the present disclosure. It is an image diagram of a PTL (Porous transport layer) in the measurement of initial strain, creep rate, and PTL intrusion rate.

[0009] The following definitions of terms apply throughout this specification and the claims, unless otherwise specified. An "ion exchange group" is a group capable of exchanging at least a part of the ions contained in this group with other ions, and examples thereof include the following sulfonic acid type functional group and carboxylic acid type functional group. A "sulfonic acid type functional group" means a sulfonic acid group (-SO ３ H), or a sulfonate group. Here, as the form of the sulfonate group, for example, (-SO ３ － )Ma ＋ (-SO ３ － [[ID=1十九]] ) ２ Mb ２＋ (-SO ３ － ) ３ Mc ３＋ are included (however, Ma ＋ is an alkali metal ion or a quaternary ammonium cation, Mb ２＋ is a divalent metal ion, and Mc ３＋( is a trivalent metal ion.) Note that when there are two ligands, the number of ion exchange groups is counted as two, and when there are three ligands, the number of ion exchange groups is counted as three. "Carboxylic acid-type functional group" means a carboxylic acid group (-COOH) or a carboxylic acid base. Here, the form of a carboxylic acid base is, for example, (-COOH － ) Ma ＋ , (-COO － ) ２ Mb ２＋ , and, (-COO － ) ３ Mc ３＋ (However, Ma ＋ is an alkali metal ion or a quaternary ammonium cation, and Mb ２＋ It is a divalent metal ion, Mc ３＋ is a trivalent metal ion. Note that if there are two ligands, the number of ion exchange groups is counted as two, and if there are three ligands, the number of ion exchange groups is counted as three. A "precursor membrane" is a membrane containing a polymer that has groups that can be converted into ion exchange groups. "Groups that can be converted into ion exchange groups" means groups that can be converted into ion exchange groups by known treatments such as hydrolysis and acidification. "Groups that can be converted into sulfonic acid-type functional groups" means groups that can be converted into sulfonic acid-type functional groups by known treatments such as hydrolysis and acidification. "Groups that can be converted into carboxylic acid-type functional groups" means groups that can be converted into carboxylic acid-type functional groups by known treatments such as hydrolysis and acidification.

[0010] In polymers, a "unit" refers to an atomic group derived from a single monomer molecule, formed by the polymerization of monomers. A unit may be an atomic group directly formed by a polymerization reaction, or it may be an atomic group in which a portion of the atomic group is converted to a different structure by processing the polymer obtained by the polymerization reaction. In the following, units derived from individual monomers will be referred to by adding "unit" to the monomer name, as appropriate.

[0011] Numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Also, in numerical ranges described in this specification, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0012] [Solid Polymer Electrolyte Membrane] The solid polymer electrolyte membrane of this disclosure (hereinafter also referred to as "electrolyte membrane") is a solid polymer electrolyte membrane containing a fluorine-containing polymer having ion exchange groups (hereinafter also referred to as "fluorine-containing polymer (I)"), wherein the elastic modulus in water at 80°C is 13 MPa or more, and when the distance between ion clusters measured by small-angle X-ray scattering is D [nm] and the ion exchange capacity of the fluorine-containing polymer is X [milliequivalents / g dry resin], the following equation (A) is satisfied: Equation (A) 4.55 - 0.85X ≤ D ≤ 4.16 A water electrolysis apparatus using the electrolyte membrane of this disclosure exhibits high proton conductivity and low hydrogen permeability. The reason for this is not entirely clear, but it is presumed to be as follows: If the elastic modulus in water at 80°C of the electrolyte membrane is 13 MPa or more, deformation of the electrolyte membrane during operation of the water electrolysis apparatus can be suppressed. This is thought to reduce the amount of hydrogen permeation during water electrolysis operation. In the electrolyte membrane of this disclosure, the hydrophobic portion, which is the main chain of the fluorine-containing polymer (I), and the ion exchange groups are separated at a microscopic level. As a result, multiple ion exchange groups gather together, and water molecules coordinated around them are collected, forming ion clusters. That is, the ion clusters of the electrolyte membrane of this disclosure are thought to consist of the hydrophobic portion that forms the main chain of the fluorine-containing polymer (I), a portion where multiple ion exchange groups are gathered, and water molecules coordinated around it. More specifically, in the electrolyte membrane of this disclosure, as shown in Figure 1, two large ion clusters 1 and a small ion channel 2 connecting them are formed. As a result, ion channels pass continuously in the thickness direction of the membrane, and this allows ions (especially protons H) to pass through. ＋It functions as a conduction channel. Ion clusters are permeable to hydrogen, while parts other than ion clusters are not. Therefore, it is thought that the larger the distance between ion clusters (distance D in Figure 1), the greater the hydrogen barrier effect. On the other hand, if the distance between ion clusters becomes too large, the proton conduction channel becomes longer and the proton conductivity decreases. Furthermore, proton conductivity is affected by the ion exchange capacity of the fluorine-containing polymer. In this disclosure, we have found that if a specific relationship is satisfied between the distance between ion clusters and the ion exchange capacity described above, both the hydrogen barrier effect and proton conductivity can be improved.

[0013] Various models have been proposed for ion conduction in electrolyte membranes containing fluorinated polymers with ion exchange groups. Among them, the ion cluster model proposed by Gierke et al. is widely known (Reference: GIERKE, TD; MUNN, GE; WILSON, FC. The morphology in nafion perfluorinated membrane products, as determined by wide‐and small‐angle x‐ray studies. Journal of Polymer Science Part B: Polymer Physics, 1981, 19.11: 1687-1704).

[0014] The electrolyte membrane of this disclosure contains a fluorine-containing polymer (I) described later, and satisfies the following equation (A) when its ion exchange capacity is X [milliequivalents / g dry resin] and the distance between ion clusters of the electrolyte membrane is D [nm]. Hereinafter, the distance between ion clusters is also referred to as distance D. Equation (A) 4.55 - 0.85X ≤ D ≤ 4.16 The distance D is preferably, for example, 4.60 - 0.85X ≤ D, more preferably 4.65 - 0.85X ≤ D, even more preferably 4.70 - 0.85X ≤ D, particularly preferably 4.80 - 0.85X ≤ D, and most preferably 4.90 - 0.85X ≤ D, from the viewpoint of further suppressing hydrogen permeation. The distance D is preferably 4.15 or less, more preferably 4.10 or less, even more preferably 4.05 or less, particularly preferably 3.95 or less, and most preferably 3.90 or less, from the viewpoint of further improving proton conductivity. For example, the distance D is more preferably 4.65 - 0.85X ≤ D ≤ 4.15, even more preferably 4.70 - 0.85X ≤ D ≤ 4.10, particularly preferably 4.80 - 0.85X ≤ D ≤ 4.05, and most preferably 4.90 - 0.85X ≤ D ≤ 3.95. The distance D is determined by the small-angle X-ray scattering method described in the Examples section below.

[0015] In the electrolyte membrane, the peak intensity ratio C, defined by the following formula (E), is preferably, for example, 5 or more, 10 or more, 15 or more, 20 or more, 30 or more, 40 or more, or 50 or more, from the viewpoint of further suppressing hydrogen permeation. The above peak intensity ratio is preferably, for example, 90 or less, more preferably 80 or less, even more preferably 70 or less, and particularly preferably 60 or less, from the viewpoint of further improving proton conductivity. As for the above peak intensity ratio C, for example, 5 to 90 is preferred, 10 to 80 is more preferred, 20 to 70 is even more preferred, 20 to 60 is particularly preferred, and 40 to 60 is most preferred. Formula (E) Peak intensity ratio C = I ｍ－ｃｒｙｓｔａｌ / I ｍ－ｃｌｕｓｔｅｒ The peak intensity ratio C is determined by the small-angle X-ray scattering method described in the Examples section below. Also, I in equation (E) ｍ－ｃｒｙｓｔａｌ and I ｍ－ｃｌｕｓｔｅｒ Further details are provided in the Examples section below.

[0016] Specific examples of methods for adjusting distance D within the above range include adjusting the hydrolysis conditions of the precursor film, which will be described later, adjusting the types of units and ion exchange capacity contained in the fluorine-containing polymer (I), and combinations of these methods. Here, the above-mentioned fluorine-containing polymer (I) is obtained by converting the groups that can be converted into ion exchange groups of the fluorine-containing polymer (F) into ion exchange groups.

[0017] The water modulus of the electrolyte membrane of this disclosure at 80°C is 13 MPa or higher, and more preferably 15 MPa or higher, more preferably 17 MPa or higher, and even more preferably 20 MPa or higher, from the viewpoint of further suppressing hydrogen permeation. The water modulus of the electrolyte membrane of this disclosure at 80°C is preferably 200 MPa or lower, and may be 150 MPa or lower, 100 MPa or lower, 80 MPa or lower, 60 MPa or lower, 50 MPa or lower, 40 MPa or lower, 35 MPa or lower, or 30 MPa or lower. As for the water modulus of the electrolyte membrane of this disclosure at 80°C, for example, from the viewpoint of further suppressing hydrogen permeation, 13 to 200 MPa is preferred, 15 to 100 MPa is more preferred, 20 to 50 MPa is particularly preferred, and 20 to 35 MPa is most preferred. The modulus of elasticity in water at 80°C of the electrolyte membrane of this disclosure is preferably 13 to 200 MPa, more preferably 15 to 100 MPa, even more preferably 15 to 50 MPa, and particularly preferably 15 to 20 MPa, in terms of conductivity. The modulus of elasticity in water at 80°C of the electrolyte membrane is determined by the method described in the Examples section below.

[0018] Specific examples of methods for adjusting the water modulus of the electrolyte membrane at 80°C to within the above range include adjusting the film formation conditions of the electrolyte membrane (e.g., film formation temperature), adjusting the type of units contained in the fluorine-containing polymer (I) and its ion exchange capacity, and combinations thereof.

[0019] From the viewpoint of hydrogen permeability, the thickness of the electrolyte membrane (thickness when dry) is preferably 30 μm or more, more preferably 40 μm or more, even more preferably 50 μm or more, and particularly preferably 60 μm or more. From the viewpoint of conductivity, the thickness is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 120 μm or less, particularly preferably 100 μm or less, and most preferably 90 μm or less. From the viewpoint of balancing hydrogen permeability and conductivity, the thickness of the electrolyte membrane (thickness when dry) is preferably 30 to 200 μm, more preferably 40 to 150 μm, even more preferably 50 to 120 μm, particularly preferably 50 to 100 μm, and most preferably 60 to 90 μm. The thickness of the electrolyte membrane (thickness when dry) is measured by the method described in the Examples section below.

[0020] The electrolyte membrane may have a single-layer structure or a multi-layer structure, provided it has a layer containing a fluorine-containing polymer (I), but a single-layer structure is preferred. When the electrolyte membrane has a single-layer structure, the electrolyte membrane is a layer containing a fluorine-containing polymer (I). When the electrolyte membrane has a multi-layer structure with multiple layers containing different fluorine-containing polymers (I), it is sufficient that the ion exchange capacity X [milliequivalents / g dry resin] of at least one fluorine-containing polymer (I) satisfies the above formula (A), and it is preferable that the ion exchange capacity X [milliequivalents / g dry resin] of all fluorine-containing polymers (I) satisfies the above formula (A). The thickness (thickness when dry) of the layer containing the fluorine-containing polymer (I) (preferably a fluorine-containing polymer (I) whose ion exchange group is a sulfonic acid type functional group) in the electrolyte membrane is preferably, for example, 15 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 50 μm or more, or 60 μm or more, from the viewpoint of hydrogen permeation. From the viewpoint of conductivity, the above thicknesses are preferably, for example, 200 μm or less, 150 μm or less, 120 μm or less, 100 μm or less, and 90 μm or less. As for the thickness of the layer containing the fluorine-containing polymer (I) in the electrolyte membrane (thickness when dry), from the viewpoint of balancing hydrogen permeability and conductivity, for example, 30 to 200 μm is preferred, 40 to 150 μm is more preferred, 50 to 120 μm is even more preferred, 50 to 100 μm is particularly preferred, and 60 to 90 μm is most preferred. The thickness of the layer containing the fluorine-containing polymer (I) (thickness when dry) is measured by the same method as described for the thickness of the electrolyte membrane. If the electrolyte membrane has a multilayer structure, the thickness of each layer can be measured by taking a cross-section of the electrolyte membrane using a laser microscope. Specifically, three different cross-sections of the electrolyte membrane are photographed, and the thickness of three different points is measured for each of the resulting magnified images (objective lens magnification 20x), and the arithmetic mean of the total of nine thicknesses is taken as the thickness of each layer. For example, the three different locations mentioned above can be any three points selected at equal intervals relative to the cut surface.

[0021] Electrolyte membranes are required to withstand high pressure at high temperatures for extended periods. Therefore, the inventors have found that the durability of an electrolyte membrane can be evaluated by measuring underwater compression creep (specifically, initial strain, creep rate, and PTL penetration rate). PTL stands for Porous transport layer. For the PTL, a small opening diameter d, defined as the diameter of the opening as shown in black in Figure 3, is preferred; for example, an opening diameter d of 50 to 300 μm is preferred. Furthermore, the initial strain, creep rate, and PTL penetration rate in underwater compression creep are determined by the method described in the Examples section below.

[0022] The initial strain of the electrolyte membrane is preferably small. Specifically, the initial strain is preferably 90.0% or less, more preferably 70.0% or less, even more preferably 60.0% or less, and particularly preferably 55.0% or less. The lower limit of the initial strain is not particularly limited, but for example, 30.0%, 40.0%, 42.0%, 44.0%, 45.0%, 50.0%, and 55.0% are preferred. In one embodiment of the present invention, the initial strain of the electrolyte membrane is preferably 30.0 to 90.0%, more preferably 40.0 to 70.0%, and even more preferably 45.0 to 60.0%. In one embodiment of the present invention, the initial strain of the electrolyte membrane is preferably 30.0 to 90.0%, more preferably 40.0 to 70.0%, even more preferably 50.0 to 70.0%, particularly preferably 55.0 to 70.0%, and most preferably 61.0 to 70.0%.

[0023] The creep rate of the electrolyte membrane is preferably low. Specifically, the creep rate is preferably 0.400% / h or less, more preferably 0.350% / h or less, even more preferably 0.315% / h or less, particularly preferably 0.310% / h or less, and most preferably 0.300% / h or less. The lower limit of the creep rate is not particularly limited, but for example, 0.100% / h, 0.200% / h, and 0.250% / h are preferred. As for the creep rate of the electrolyte membrane, for example, 0.100 to 0.400% / h is preferred, 0.200 to 0.350% / h is more preferred, 0.250 to 0.315% / h is even more preferred, and 0.250 to 0.310% / h is particularly preferred.

[0024] The PTL penetration rate of the electrolyte membrane is preferably low. Specifically, the PTL penetration rate is preferably 0.70 μm / h or less, more preferably 0.50 μm / h or less, and even more preferably 0.44 μm / h or less. The lower limit of the PTL penetration rate is not particularly limited, but for example, 0.20 μm / h and 0.25 μm / h are preferred. The PTL penetration rate of the electrolyte membrane is preferably 0.20 to 0.70 μm / h, and more preferably 0.25 to 0.50 μm / h.

[0025] The initial strain, creep rate, and PTL penetration rate of the electrolyte membrane are not particularly limited, but for example, it is preferable that they fall within the above range when the ion exchange capacity X of the fluorine-containing polymer (I), described later, is preferably 1.00 mm equivalent / g dry resin or more and 1.65 mm equivalent / g dry resin or less, more preferably 1.10 mm equivalent / g dry resin or more and 1.45 mm equivalent / g dry resin or less, even more preferably 1.15 mm equivalent / g dry resin or more and 1.45 mm equivalent / g dry resin or less, and particularly preferably 1.20 mm equivalent / g dry resin or more and 1.35 mm equivalent / g dry resin or less or 1.35 mm equivalent / g dry resin or more and 1.45 mm equivalent / g dry resin or less.

[0026] The initial strain, creep rate, and PTL penetration rate of the electrolyte membrane are not particularly limited, but are preferably within the above range when the thickness of the electrolyte membrane (thickness when dry) is preferably 40 μm to 150 μm, more preferably 90 μm to 150 μm, even more preferably 95 μm to 140 μm, and particularly preferably 100 μm to 135 μm. However, when comparing multiple electrolyte membranes using PTLs with the same aperture diameter d and with substantially the same thickness, it is considered that the durability of the electrolyte membrane can be compared without being greatly affected by the thickness itself.

[0027] In the underwater compression creep of the electrolyte membrane, it is preferable that one or more of the initial strain, creep rate, and PTL penetration rate are within the above range, more preferably two or more are within the above range, and even more preferably all are within the above range.

[0028] <Fluorine-containing polymer (I)> Fluorine-containing polymer (I) is a fluorine-containing polymer having ion exchange groups. Specific examples of ion exchange groups in fluorine-containing polymer (I) include sulfonic acid-type functional groups and carboxylic acid-type functional groups. Sulfonic acid-type functional groups are preferred because they can further reduce the electrolysis voltage when an electrolyte membrane is applied to a water electrolysis device.

[0029] The fluorine-containing polymer (I) preferably contains units having ion exchange groups, and more preferably is a copolymer polymer containing units having ion exchange groups and units based on a fluorine-containing olefin.

[0030] The unit having ion exchange groups is preferably a unit having two or more ion exchange groups, in that it can further suppress hydrogen permeation of the electrolyte membrane and adjust the elastic modulus and distance D of the electrolyte membrane in water. The unit having two or more ion exchange groups is preferably a unit based on perfluorovinyl ether or perfluoroallyl ether, and is more preferably a unit based on perfluorovinyl ether in that it exhibits superior effects in this disclosure.

[0031] The units having ion exchange groups preferably include units having sulfonic acid-type functional groups and fluorine atoms, and more preferably the units represented by formula (1). Formula (1) -[CF ２ -CF(-L-(SO ３ M) ｎ ) ] -

[0032] L is an n+1 valent perfluorohydrocarbon group which may contain an etheric oxygen atom. The etheric oxygen atom may be located at the terminal end of the perfluorohydrocarbon group or between carbon atoms. The number of carbon atoms in the n+1 valent perfluorohydrocarbon group is preferably 1 or more, more preferably 2 or more, preferably 20 or less, and more preferably 10 or less.

[0033] L is preferably an n+1 valent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom, more preferably a divalent perfluoroalkylene group which may contain an etheric oxygen atom in the n=1 embodiment, or a trivalent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom in the n=2 embodiment. The above divalent perfluoroalkylene group may be linear or branched.

[0034] M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation. n is 1 or greater, preferably 1 or 2, and more preferably 2.

[0035] Specific examples of the unit represented by formula (1) include the unit represented by formula (1-1), the unit represented by formula (1-2), the unit represented by formula (1-3), and the unit represented by formula (1-4). Among these, the unit represented by formula (1-3) or the unit represented by formula (1-4) is preferred, and the unit represented by formula (1-3) is more preferred, as it can further suppress hydrogen permeation of the electrolyte membrane. Formula (1-1) -[CF ２ -CF(-OR-R) ｆ１ -SO ３ M)] - Formula (1-2) - [CF ２ -CF(-R ｆ１ -SO ３ M) ]-

[0036]

[0037]

[0038] R ｆ１ This is a perfluoroalkylene group which may contain oxygen atoms between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, preferably 20 or less, and more preferably 10 or less.

[0039] R ｆ２ This is a perfluoroalkylene group which may contain single bonds or oxygen atoms between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, preferably 20 or less, and more preferably 10 or less.

[0040] R ｆ３ This is a perfluoroalkylene group which may contain single bonds or oxygen atoms between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, preferably 20 or less, and more preferably 10 or less.

[0041] r is 0 or 1. m is 0 or 1. M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation.

[0042] Of the units represented by formula (1-1) and formula (1-2), the unit represented by formula (1-5) is more preferable. Formula (1-5) - [CF ２ -CF (-(CF ２ ) ｘ - (OCF ２ CFY) ｙ -O-(CF ２ ) ｚ -SO ３ M) - x is 0 or 1, y is an integer from 0 to 2, z is an integer from 1 to 4, and Y is F or CF ３ Therefore, M is as described above.

[0043] The following are specific examples of units represented by equation (1-1). In the equation, w is an integer from 1 to 8, and x is an integer from 1 to 5. The definition of M in the equation is as described above. -[CF ２-CF(-O-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF(-O-CF) ２ CF (CF ３ )-O-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF(-(O-CF ２ CF (CF ３ )) ｘ -SO ３ M) ]-

[0044] Specific examples of units represented by equation (1-2) include the following units. w in the equation is an integer from 1 to 8. The definition of M in the equation is as described above. -[CF ２ -CF (-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF (-CF ２ -O-(CF ２ ) ｗ -SO ３ M) ]-

[0045] The unit represented by formula (1-3-1) is preferred over the unit represented by formula (1-3-3). The definition of M in the formula is as described above.

[0046]

[0047] R ｆ４ R is a linear perfluoroalkylene group having 1 to 6 carbon atoms. ｆ５ This is a linear perfluoroalkylene group having 1 to 6 carbon atoms, which may contain single bonds or oxygen atoms between carbon atoms. The definitions of r and M are as described above.

[0048] The following are specific examples of units represented by equation (1-3-1):

[0049]

[0050] The unit represented by formula (1-4) is preferably the unit represented by formula (1-4-1). ｆ１ , Rｆ２ The definitions of N and M are as described above.

[0051]

[0052] Specific examples of the unit represented by formula (1-4-1) include the following.

[0053]

[0054] The units having an ion-exchange group may be used alone or in combination of two or more. The content of the units having an ion-exchange group is preferably 5.0 to 15.0 mol%, more preferably 6.0 to 12.0 mol%, and still more preferably 7.0 to 10.0 mol% based on all the units in the fluorine-containing polymer (I).

[0055] Examples of the fluorine-containing olefin include fluoroolefins having 2 to 3 carbon atoms and having one or more fluorine atoms in the molecule. Specific examples of the fluoroolefin include tetrafluoroethylene (hereinafter also referred to as "TFE"), chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and hexafluoropropylene. Among them, TFE is preferred from the viewpoints of the production cost of the monomer, reactivity with other monomers, and excellent properties of the obtained fluorine-containing polymer (I). The fluorine-containing olefin may be used alone or in combination of two or more. The content of the units based on the fluorine-containing olefin is preferably 85.0 to 95.0 mol%, more preferably 88.0 to 94.0 mol%, and still more preferably 90.0 to 93.0 mol% based on all the units in the fluorine-containing polymer (I).

[0056] The fluorine-containing polymer (I) may contain units based on a fluorine-containing olefin and units based on other monomers other than the units having an ion-exchange group. Specific examples of the other monomers include CF ２ =CFR ｆ６ (where R ｆ６ is a perfluoroalkyl group having 2 to 10 carbon atoms), CF ２ =CF-OR ｆ７ (where R ｆ７(These are perfluoroalkyl groups having 1 to 10 carbon atoms.) CF ２ = CFO (CF ２ ) ｖ CF = CF ２ (wherein v is an integer between 1 and 3.) The content of units based on other monomers is preferably 10 mol% or less, more preferably 1 mol% or less, even more preferably 0.1 mol% or less, and particularly preferably 0 mol%, relative to the total units in the fluorine-containing polymer (I), from the viewpoint of maintaining ion exchange performance.

[0057] In the fluorine-containing polymer (I), the total content of units having ion exchange groups and units based on fluorine-containing olefins is preferably 90 mol% or more, more preferably 99 mol% or more, particularly preferably 99.9 mol% or more, and most preferably 100 mol% relative to the total units in the fluorine-containing polymer (I).

[0058] In the fluorine-containing polymer (I), the molar ratio of units having ion exchange groups to units based on fluorine-containing olefins (units having ion exchange groups / units based on fluorine-containing olefins) is preferably 0.06 to 0.15, and more preferably 0.09 to 0.13.

[0059] A preferred embodiment of the fluorine-containing polymer (I) includes a TFE unit and a unit represented by formula (1-3). This enhances the effects described in this disclosure. In this case, the content of TFE units is preferably 88.0 to 94.0 mol%, and more preferably 90.0 to 93.0 mol%, relative to the total units in the fluorine-containing polymer (I). The content of the unit represented by formula (1-3) is preferably 6.0 to 12.0 mol%, and more preferably 7.0 to 10.0 mol%, relative to the total units in the fluorine-containing polymer (I). The effects described in this disclosure are enhanced when the content of TFE units and the unit represented by formula (1-3) falls within the above ranges.

[0060] The fluorine-containing polymer (I) is preferably substantially free of units having only one ion-exchange group, as this provides superior effects in this disclosure. Specifically, the fluorine-containing polymer (I) is preferably substantially free of units represented by formula (1-1) and formula (1-2). The statement that the fluorine-containing polymer (I) is substantially free of units having only one ion-exchange group means that the content of units having only one ion-exchange group relative to the total units in the fluorine-containing polymer (I) is 0.1 mol% or less, preferably 0.01 mol% or less, and more preferably 0 mol%.

[0061] The fluorinated polymer (I) is preferably substantially free of units based on monomers having a cyclic ether structure, as this provides superior effects in this disclosure. "Substantially free of units based on monomers having a cyclic ether structure" means that the content of units based on monomers having a cyclic ether structure is 0.1 mol% or less relative to the total units in the fluorinated polymer (I), preferably 0.01 mol% or less, and more preferably 0 mol%. Specific examples of units based on monomers having a cyclic ether structure include the units containing a cyclic ether structure described in International Publication No. 2020 / 184681.

[0062] The electrolyte membrane of this disclosure may contain polymers other than fluorine-containing polymer (I), but it is preferable that the polymers in the solid polymer electrolyte membrane consist substantially of fluorine-containing polymer (I). "Substantially consisting of fluorine-containing polymer (I)" means that the content of fluorine-containing polymer (I) is 95% by mass or more of the total mass of polymers in the solid polymer electrolyte membrane. An upper limit for the content of fluorine-containing polymer (I) is 100% by mass of the total mass of polymers in the solid polymer electrolyte membrane. Specific examples of polymers other than fluorine-containing polymer (I) include one or more polyazole compounds selected from the group consisting of polymers of heterocyclic compounds containing one or more nitrogen atoms in the ring, and polymers of heterocyclic compounds containing one or more nitrogen atoms and oxygen and / or sulfur atoms in the ring. Specific examples of polyazole compounds include polyimidazole compounds, polybenzimidazole compounds, polybenzobisimidazole compounds, polybenzoxazole compounds, polyoxazole compounds, polythiazole compounds, and polybenzothiazole compounds. Furthermore, from the standpoint of oxidation resistance of solid polymer electrolyte membranes, other polymers that can be mentioned include polyphenylene sulfide resins and polyphenylene ether resins.

[0063] The content of fluorine-containing polymer (I) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 95 to 100% by mass, based on the total mass of the electrolyte membrane.

[0064] The ion exchange capacity X of the fluorine-containing polymer (I) is preferably 0.90 mm equivalent / g dry resin or more, more preferably 1.00 mm equivalent / g dry resin or more, even more preferably 1.05 mm equivalent / g dry resin or more, particularly preferably 1.10 mm equivalent / g dry resin or more, and most preferably 1.20 mm equivalent / g dry resin or more, from the viewpoint of further reducing the electrolytic voltage when applied to a water splitting apparatus and adjusting the water modulus and distance D of the electrolyte membrane. The ion exchange capacity X of the fluorine-containing polymer (I) is preferably 1.65 mm equivalent / g dry resin or less, more preferably 1.45 mm equivalent / g dry resin or less, even more preferably 1.40 mm equivalent / g dry resin or less, particularly preferably 1.35 mm equivalent / g dry resin or less, and most preferably 1.30 mm equivalent / g dry resin or less, from the viewpoint of the strength of the membrane electrode assembly when hydrated and adjusting the water modulus and distance D of the electrolyte membrane. As for the ion exchange capacity X of the fluorine-containing polymer (I), from the viewpoint of hydrogen permeation, for example, a dry resin with a capacity of 1.00 to 1.65 milliequivalents / g is preferred, a dry resin with a capacity of 1.15 to 1.45 milliequivalents / g is more preferred, a dry resin with a capacity of 1.15 to 1.35 milliequivalents / g is even more preferred, a dry resin with a capacity of 1.15 to 1.30 milliequivalents / g is particularly preferred, and a dry resin with a capacity of 1.20 to 1.30 milliequivalents / g is most preferred. As for the ion exchange capacity X of the fluorine-containing polymer (I), from the viewpoint of conductivity, for example, a dry resin with a capacity of 1.00 to 1.65 milliequivalents / g is preferred, a dry resin with a capacity of 1.20 to 1.60 milliequivalents / g is more preferred, a dry resin with a capacity of 1.25 to 1.55 milliequivalents / g is even more preferred, a dry resin with a capacity of 1.30 to 1.50 milliequivalents / g is particularly preferred, and a dry resin with a capacity of 1.40 to 1.50 milliequivalents / g is most preferred. The fluorine-containing polymer (I) may be used alone, or two or more types may be used in a laminated or mixed form.

[0065] <Reinforcing Material> The electrolyte membrane may contain a reinforcing material. Examples of the reinforcing material include porous bodies, fibers, woven fabrics, non-woven fabrics, etc. Examples of the material of the reinforcing material include polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, polyethylene, polypropylene, polyphenylene sulfide, polyether ether ketone, etc. It is preferable that the electrolyte membrane does not contain a reinforcing material.

[0066] <Platinum-containing Substance> The electrolyte membrane may contain a platinum-containing substance. The platinum-containing substance only needs to contain platinum atoms. Specific examples of the platinum-containing substance include platinum itself, platinum oxide, composite metal oxides containing platinum, and platinum alloys. Specific examples of the composite oxide containing platinum include M ｘ Pt ３ O ４ (M is at least one metal atom selected from the group consisting of Li, Na, Mg, Ca, Zn, Cd, Co, Ni, Mn, Cu, Ag, Bi, and Ce, and x is greater than 0 and less than or equal to 1.) are included. Specific examples of the platinum alloy include alloys containing at least one metal selected from the group consisting of transition metals and noble metals other than platinum and platinum.

[0067] Specific examples of the shape of the platinum-containing substance include particulate and sheet-like. When the platinum-containing substance is particulate, the platinum-containing substance may be core-shell type particles. An example of the core-shell type particles is a mode in which the core is carbon or a particle containing a metal other than platinum, and the shell contains platinum atoms.

[0068] The platinum-containing substance may be supported on a carrier. Specific examples of the carrier include carbon carriers such as carbon black powder, graphitized carbon, carbon fiber, and carbon nanotube.

[0069] <Cerium-containing Substance> This electrolyte membrane may contain a cerium-containing substance. The cerium-containing substance only needs to contain cerium atoms. Specific examples of the cerium-containing substance include cerium oxide, composite metal oxides containing cerium, etc. For example, cerium oxide (CeO２ (Cerium(IV) oxide), Ce ２ O ３ (Cerium(III) oxide, etc.) These cerium oxides may be doped with polyvalent metal ions such as zirconium and praseodymium. The shape of the cerium-containing material is not particularly limited, but particulate form is one example.

[0070] <Method for Manufacturing an Electrolyte Membrane> An example of a method for manufacturing the electrolyte membrane of this disclosure is as follows. First, a fluorine-containing polymer (F), described below, is formed to obtain a precursor membrane containing the fluorine-containing polymer (F) (hereinafter also referred to as "Step 1"). Next, groups in the precursor membrane that can be converted into ion exchange groups are converted into ion exchange groups by hydrolysis to obtain the electrolyte membrane of this disclosure containing the fluorine-containing polymer (I) (hereinafter also referred to as "Step 2").

[0071] (Step 1) Step 1 is a step of forming a film of a fluorine-containing polymer (F) to obtain a precursor film containing the fluorine-containing polymer (F). Methods for forming the precursor film include melt extrusion and hot press molding, with hot press molding being preferred. Known hot press equipment such as a flat plate press and a roll press can be used for hot press molding.

[0072] When hot press forming is performed using a flat plate press, the surface pressure is preferably 0.5 MPa or higher, and preferably 15 MPa or lower. When hot press forming is performed using a roll press, the linear pressure is preferably 20 kg / cm or higher, and preferably 50 kg / cm or lower. It is preferable to perform hot press forming by gradually increasing the pressure. This results in a more uniform thickness of the precursor film.

[0073] In step 1, the film formation temperature when forming the fluorine-containing polymer (F) is preferably lower than the TQ value of the fluorine-containing polymer (F). In other words, the value obtained by subtracting the film formation temperature (hereinafter also referred to as "T2") from the TQ value of the fluorine-containing polymer (F) (hereinafter also referred to as "T1") (T1-T2) is greater than 0°C. This makes it easier to adjust the water modulus of the electrolyte membrane to the above range. T1-T2 is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, from the viewpoint that the solid polymer electrolyte membrane exhibits lower hydrogen permeability. T1-T2 is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 35°C or lower, from the viewpoint that the film formation performance of the precursor membrane is better. The film formation temperature is preferably, for example, 290°C or lower, more preferably 280°C or lower, and even more preferably 270°C or lower, from the viewpoint that the film formation performance of the precursor membrane is excellent and the appearance of the precursor is improved. It is believed that a superior appearance of the precursor film tends to improve the performance of the water electrolysis device. The film deposition temperature is preferably 100 to 290°C, more preferably 150 to 290°C, and even more preferably 220 to 280°C.

[0074] The film formation temperature is the melting temperature in the case of melt extrusion, and the hot press temperature in the case of hot press molding. In particular, the hot press temperature is the temperature of the thermocouple attached to the metal plate in contact with the fluorine-containing polymer (F) in the hot press apparatus. The method for measuring the TQ value will be described later.

[0075] The heating time for heating the fluorine-containing polymer (F) at the above-mentioned film formation temperature is preferably 5 minutes or more, and preferably 10 minutes or less.

[0076] In the method for manufacturing an electrolyte membrane according to this disclosure, after obtaining a plurality of precursor films of fluorine-containing polymers (F) in step 1, each precursor film may be laminated, or the plurality of fluorine-containing polymers (F) may be co-extruded in step 1. The plurality of fluorine-containing polymers (F) may be the same or different. After lamination, it is preferable to bond them by heating press or the like.

[0077] In the method for manufacturing an electrolyte membrane according to this disclosure, a cooling process may be performed to cool the precursor membrane obtained in step 1. Cooling may be performed, for example, until the precursor membrane reaches room temperature (25°C). The cooling method is not particularly limited, and known methods can be used.

[0078] (Step 2) Step 2 is a step of converting groups in the precursor membrane that can be converted into ion exchange groups by hydrolysis to obtain an electrolyte membrane of the present disclosure containing a fluorine-containing polymer (I).

[0079] Specific examples of methods for converting groups in a precursor membrane that can be converted into ion exchange groups include methods of subjecting the precursor membrane to hydrolysis or acidification. Among these, in step 2, hydrolysis is preferable from the standpoint of adjusting the distance D of the electrolyte membrane, and a method of contacting the precursor membrane with an alkaline aqueous solution is more preferable. Furthermore, in step 2, it is also preferable to perform acidification after the hydrolysis.

[0080] Specific examples of methods for bringing a precursor film into contact with an alkaline aqueous solution include immersing the precursor film in an alkaline aqueous solution and spraying the alkaline aqueous solution onto the surface of the precursor film.

[0081] The alkaline aqueous solution preferably contains an alkali metal hydroxide, a water-soluble organic solvent, and water. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide. In this specification, a water-soluble organic solvent is an organic solvent that dissolves readily in water, and specifically, an organic solvent with a solubility of 0.1 g or more in 1,000 mL of water (20°C) is preferred, and an organic solvent with a solubility of 0.5 g or more is particularly preferred. The water-soluble organic solvent preferably contains at least one selected from the group consisting of aprotic organic solvents, alcohols, and amino alcohols, and is particularly preferred to contain an aprotic organic solvent. The water-soluble organic solvent may be used alone or in combination of two or more.

[0082] Specific examples of aprotic organic solvents include dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone, with dimethyl sulfoxide being preferred. Specific examples of alcohols include methanol, ethanol, isopropanol, butanol, methoxyethoxyethanol, butoxyethanol, butylcarbitol, hexyloxyethanol, octanol, 1-methoxy-2-propanol, and ethylene glycol. Specific examples of amino alcohols include ethanolamine, N-methylethanolamine, N-ethylethanolamine, 1-amino-2-propanol, 1-amino-3-propanol, 2-aminoethoxyethanol, 2-aminothioethoxyethanol, and 2-amino-2-methyl-1-propanol.

[0083] The concentration of alkali metal hydroxide in the alkaline aqueous solution is preferably 1% by mass or more, more preferably 3% by mass or more, preferably 60% by mass or less, and more preferably 55% by mass or less. The content of water-soluble organic solvent in the alkaline aqueous solution is preferably 1% by mass or more, more preferably 3% by mass or more, preferably 60% by mass or less, and more preferably 55% by mass or less. The concentration of water in the alkaline aqueous solution is preferably 39 to 80% by mass.

[0084] As an alkaline aqueous solution, it is preferable to include sodium hydroxide or potassium hydroxide and dimethyl sulfoxide, and more preferably potassium hydroxide and dimethyl sulfoxide, in order to adjust the electrolyte membrane distance D.

[0085] The temperature for hydrolysis (or the temperature of the alkaline aqueous solution if one is used) is preferably 0 to 120°C, more preferably 60 to 110°C, and even more preferably 90 to 100°C, from the standpoint of adjusting the electrolyte membrane distance D.

[0086] The contact time between the precursor film and the alkaline aqueous solution is preferably 3 minutes or more, more preferably 5 minutes or more, preferably 150 minutes or less, and more preferably 50 minutes or less.

[0087] After contact between the precursor film and the alkaline aqueous solution, a treatment to remove the alkaline aqueous solution may be performed. One method for removing the alkaline aqueous solution is to wash the precursor film that has been in contact with the alkaline aqueous solution with water.

[0088] The film obtained after hydrolysis treatment by contacting a precursor film with an alkaline aqueous solution may be brought into contact with an acidic aqueous solution to convert the ion exchange groups to the acidic form. Specific examples of methods for contacting the hydrolyzed film with an acidic aqueous solution include immersing the hydrolyzed film in an acidic aqueous solution and spraying the acidic aqueous solution onto the surface of the hydrolyzed film. The acidic aqueous solution preferably contains an acid component and water. Specific examples of the acid component include hydrochloric acid and sulfuric acid.

[0089] Although the above-described method for manufacturing the electrolyte membrane was explained using the example of an electrolyte membrane without reinforcing material, the method is not limited to this, and the electrolyte membrane may be manufactured using reinforcing material. When using reinforcing material, for example, a method of joining the precursor membrane or electrolyte membrane and the reinforcing material by heat pressing or melt lamination may be used. From the viewpoint of the elastic modulus in water, an embodiment without reinforcing material is also preferable.

[0090] Although a method for manufacturing an electrolyte membrane according to one embodiment of the present invention has been described above, the invention is not limited thereto, and may be manufactured by, for example, a casting method (a method of manufacturing an electrolyte membrane by applying an aqueous dispersion containing a fluorine-containing polymer (I) to a substrate, drying it, and peeling off the substrate). However, from the viewpoint of the effects of the present invention, a manufacturing method having steps 1 and 2 described above is preferred.

[0091] (Fluorine-containing polymer (F)) Fluorine-containing polymer (F) is a fluorine-containing polymer having a group that can be converted into an ion exchange group. Specific examples of the groups in fluorine-containing polymer (F) that can be converted into an ion exchange group include a group that can be converted into a sulfonic acid type functional group and a group that can be converted into a carboxylic acid type functional group. A group that can be converted into a sulfonic acid type functional group is preferred because it can further reduce the electrolysis voltage when an electrolyte membrane is applied to a water electrolysis device.

[0092] The fluorine-containing polymer (F) preferably has units based on monomers having groups that can be converted into ion exchange groups, and more preferably is a copolymer polymer containing units based on monomers having groups that can be converted into ion exchange groups and units based on fluorine-containing olefins.

[0093] Units based on monomers having groups that can be converted into ion exchange groups are preferably units based on monomers having two or more groups that can be converted into ion exchange groups, in order to further suppress hydrogen permeation of the electrolyte membrane. Monomers having two or more groups that can be converted into ion exchange groups are CF ２ = A monomer containing a group represented by CF-O- (i.e., perfluorovinyl ether), or CF ２ = CF - CF ２ A monomer containing a group represented by -O- (i.e., a perfluoroallyl ether) is preferred, as it exhibits superior effects in this disclosure. ２ A monomer containing a group represented as =CF-O- is more preferable.

[0094] The monomer having a group that can be converted into an ion exchange group is preferably a monomer having a group that can be converted into a sulfonic acid type functional group and a fluorine atom, and more preferably a monomer having one or more fluorine atoms in the molecule, having an ethylenic double bond, and having a group that can be converted into a sulfonic acid type functional group. From the viewpoint of the manufacturing cost of the monomer, reactivity with other monomers, and the properties of the resulting fluorine-containing polymer (F), the compound represented by formula (2) is preferred. Formula (2) CF ２ =CF - L - (A) ｎ The definitions of L and n in formula (2) are as described above. A is a group that can be converted to a sulfonic acid type functional group. The group that can be converted to a sulfonic acid type functional group is preferably a functional group that can be converted to a sulfonic acid type functional group by hydrolysis. A specific example of a group that can be converted to a sulfonic acid type functional group is -SO ２ F, -SO ２ Cl, -SO ２ Br is one example. Multiple A's may be the same or may be different.

[0095] Compounds represented by formula (2) include those represented by formula (2-1), formula (2-2), formula (2-3), and formula (2-4). Among these, the unit represented by formula (2-3) or formula (2-4) is preferred, and the unit represented by formula (2-3) is more preferred, as it can further suppress hydrogen permeation through the electrolyte membrane. Formula (2-1) CF ２ =CF-O-R ｆ１ -A Formula (2-2) CF ２ =CF-R ｆ１ -A

[0096]

[0097] R in the formula ｆ１ , R ｆ２ The definitions of r and A are as described above.

[0098]

[0099] R in the formula ｆ１ , R ｆ２ , R ｆ３ The definitions of r, m, and A are as described above.

[0100] Of the compounds represented by formula (2-1) and formula (2-2), the compound represented by formula (2-5) is preferred. Formula (2-5) CF ２ = CF - (CF ２ ) ｘ - (OCF ２ CFY) ｙ -O-(CF ２ ) ｚ -SO ３ The definitions of x, y, z, and Y in equation F are as described above.

[0101] Specific examples of compounds represented by formula (2-1) include the following compounds. In the formula, w is an integer from 1 to 8, and x is an integer from 1 to 5. CF ２ =CF - O - (CF ２ ) ｗ -SO ２ F CF ２ = CF - O - CF ２ CF (CF ３)-O-(CF ２ ) ｗ -SO ２ F CF ２ =CF - [O - CF ２ CF (CF ３ )] ｘ -SO ２ F

[0102] Specific examples of compounds represented by formula (2-2) include the following compounds. In the formula, w is an integer from 1 to 8. CF ２ = CF - (CF ２ ) ｗ -SO ２ F CF ２ = CF - CF ２ -O-(CF ２ ) ｗ -SO ２ F

[0103] Of the compounds represented by formula (2-3), the compound represented by formula (2-3-1) is preferred.

[0104]

[0105] R in the formula ｆ４ , R ｆ５ The definitions of r and A are as described above.

[0106] Specific examples of compounds represented by formula (2-3-1) include the following:

[0107]

[0108] Of the compounds represented by formula (2-4), the compound represented by formula (2-4-1) is preferred.

[0109]

[0110] R in the formula ｆ１ , R ｆ２ The definition of A is as stated above.

[0111] Specific examples of compounds represented by formula (2-4-1) include the following:

[0112]

[0113] A monomer having a group that can be converted into an ion exchange group may be used alone or in combination of two or more types.

[0114] Examples of fluorine-containing olefins include those exemplified above, and TFE is preferred due to its superior monomer production cost, reactivity with other monomers, and the characteristics of the resulting fluorine-containing polymer (F). Fluorine-containing olefins may be used individually or in combination of two or more.

[0115] In the production of the fluorine-containing polymer (F), in addition to fluorine-containing olefins and monomers having groups that can be converted into ion exchange groups, other monomers may also be used. Examples of other monomers are those exemplified above. From the viewpoint of maintaining ion exchange performance, the content of units based on other monomers is preferably 10 mol% or less, more preferably 1 mol% or less, even more preferably 0.1 mol% or less, and particularly preferably 0 mol% relative to the total units in the fluorine-containing polymer (F).

[0116] A preferred embodiment of the fluorine-containing polymer (F) includes a TFE unit and a unit represented by formula (2-3). This enhances the effects described in this disclosure. In this case, the content of TFE units is preferably 88.0 to 94.0 mol%, and more preferably 90.0 to 93.0 mol%, relative to the total units in the fluorine-containing polymer (F). The content of the unit represented by formula (2-3) is preferably 6.0 to 12.0 mol%, and more preferably 7.0 to 10.0 mol%, relative to the total units in the fluorine-containing polymer (F). The effects described in this disclosure are enhanced when the content of TFE units and the unit represented by formula (2-3) falls within the above ranges.

[0117] The fluorine-containing polymer (F) is preferably substantially free of units having only one group that can be converted to an ion exchange group, as this provides superior effects in this disclosure. Specifically, the fluorine-containing polymer (F) is preferably substantially free of units represented by formula (2-1) and formula (2-2). The statement that the fluorine-containing polymer (F) is substantially free of units having only one group that can be converted to an ion exchange group means that the content of units having only one group that can be converted to an ion exchange group relative to the total units in the fluorine-containing polymer (F) is 0.1 mol% or less, preferably 0.01 mol% or less, and more preferably 0 mol%.

[0118] The fluorine-containing polymer (F) is preferably substantially free of units based on monomers having a cyclic ether structure, as this provides superior effects in this disclosure. "Substantially free of units based on monomers having a cyclic ether structure" means that the content of units based on monomers having a cyclic ether structure is 0.1 mol% or less relative to the total units in the fluorine-containing polymer (F), preferably 0.01 mol% or less, and more preferably 0 mol%. Specific examples of units based on monomers having a cyclic ether structure are as described above.

[0119] The TQ value of the fluorine-containing polymer (F) is preferably 100°C or higher, more preferably 150°C or higher, and even more preferably 200°C or higher, from the viewpoint of improving the appearance of the precursor film. Furthermore, the above TQ value is preferably 350°C or lower, more preferably 290°C or lower, and even more preferably 250°C or lower. For example, the TQ value of the fluorine-containing polymer (F) is preferably 100 to 350°C, more preferably 150 to 290°C, even more preferably 200 to 280°C, and particularly preferably 200 to 250°C. The TQ value (melt flow rate value) is a value related to the molecular weight of the polymer, and the polymer is a volume flow rate of 100 mm². ３ This is the temperature when it is shown as / second, and is determined by the method described in the Examples section below.

[0120] The polymerization method for fluorine-containing polymers (F) can be any known method, such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization.

[0121] [Electrolyte membrane with catalyst layer] The membrane electrode assembly of the present disclosure includes the electrolyte membrane (the electrolyte membrane of the present disclosure) and a catalyst layer disposed on one side of the electrolyte membrane. Preferably, the catalyst layer is disposed in contact with one side of the electrolyte membrane. Examples of the catalyst layer include a first catalyst layer and a second catalyst layer.

[0122] (First catalyst layer) The first catalyst layer is arranged so as to be in contact with one surface of the electrolyte membrane. Preferably, the first catalyst layer is the catalyst layer of the cathode in the membrane electrode assembly (hereinafter also referred to as the "cathode catalyst layer").

[0123] The first catalyst layer preferably contains a catalyst and further contains a polymer having ion exchange groups. The catalyst is preferably a supported catalyst, in which a catalyst containing platinum atoms is supported on a carbon support, because the first catalyst layer can be suitably used as a cathode catalyst layer. Examples of catalysts containing platinum atoms include platinum, platinum alloys, or platinum having a core-shell structure. Examples of carbon support include carbon black powder. The polymer having ion exchange groups is not particularly limited; for example, known fluorine-containing polymers having ion exchange groups can be used.

[0124] The thickness of the first catalyst layer is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more. Furthermore, the above thickness is preferably 20 μm or less, and more preferably 15 μm or less. The thickness of the first catalyst layer can be measured in the same way as the electrolyte membrane, except that the object of measurement is the first catalyst layer.

[0125] The laminate preferably includes a second catalyst layer. The second catalyst layer is arranged in contact with the surface (the other surface) of the electrolyte membrane opposite to the surface (one surface) on which the first catalyst layer is located. The second catalyst layer is preferably the catalyst layer of the anode in the membrane electrode assembly (hereinafter also referred to as the "anode catalyst layer").

[0126] The second catalyst layer preferably contains a catalyst and further contains a polymer having ion exchange groups. Specific examples of the catalyst included in the second catalyst layer include catalysts containing iridium oxide, as these allow the second catalyst layer to be suitably used as an anode catalyst layer. Examples include iridium oxide catalysts, composite oxide catalysts containing iridium and other metal elements, alloys containing iridium oxide, or catalysts containing iridium oxide having a core-shell structure. The polymer having ion exchange groups is not particularly limited; for example, known fluorine-containing polymers having ion exchange groups can be used.

[0127] The thickness of the second catalyst layer is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more. Furthermore, the above thickness is preferably 20 μm or less, and more preferably 15 μm or less. The thickness of the second catalyst layer can be measured in the same way as the electrolyte membrane, except that the measurement target is the second catalyst layer.

[0128] (Method for manufacturing an electrolyte membrane with a catalyst layer) The method for manufacturing an electrolyte membrane with a catalyst layer (hereinafter also referred to as "the CCM") in this disclosure (hereinafter also referred to as "the method for manufacturing the CCM") is a method for obtaining a CCM by preferably heating and pressurizing a laminate (hereinafter also referred to as "the laminate") having an electrolyte membrane and a catalyst layer disposed in contact with one surface of the electrolyte membrane. Specific examples of the method for manufacturing the laminate include a method using a transfer sheet (hereinafter also referred to as "the method for manufacturing the laminate 1") and a method of directly applying a catalyst layer forming composition to the surface of the electrolyte membrane (hereinafter also referred to as "the method for manufacturing the laminate 2").

[0129] ・Method 1 for manufacturing the laminate The method 1 for manufacturing the laminate is carried out as follows, for example. First, a coating liquid for forming the first catalyst layer is applied to the surface of a release substrate, and if necessary, the coating film of the coating liquid for forming the first catalyst layer is dried (hereinafter also referred to as "drying treatment") to obtain a first transfer sheet having a release substrate and a first catalyst layer disposed on the surface of the release substrate. Next, the laminate is obtained by laminating the first transfer sheet so that the first catalyst layer on the first transfer sheet and one side of the electrolyte membrane are in contact. The release substrate may or may not be removed after the first catalyst layer has come into contact with the electrolyte membrane.

[0130] Specific examples of drying methods include hot air circulation ovens, vacuum ovens, electric furnaces, and infrared heating furnaces. The drying temperature is preferably between 1 and 130°C.

[0131] The manufacturing method 1 for this laminate may include a heat treatment in which the coating film after drying is heated. The heating temperature in the heat treatment is preferably 130 to 200°C. Specific examples of heat treatment methods include a hot air circulation oven, a vacuum oven, an electric furnace, and an infrared heating furnace.

[0132] The coating liquid for forming the first catalyst layer is a liquid obtained by dispersing a polymer having ion exchange groups and a catalyst, which may be included in the first catalyst layer described above, in a liquid medium (e.g., an organic solvent, water, etc.). Examples of release substrates include ETFE (a copolymer of TFE and ethylene) sheets.

[0133] If the laminate further includes a second catalyst layer, the method for manufacturing the laminate 1 may further include the following steps: A coating liquid for forming the second catalyst layer is applied to the surface of a release substrate and dried (heat-treated) as necessary to obtain a second transfer sheet having a release substrate and a second catalyst layer disposed on the surface of the release substrate. Next, the laminate further including the second catalyst layer is obtained by laminating the second transfer sheet so that the second catalyst layer on the second transfer sheet and the other surface of the electrolyte membrane are in contact. The release substrate may or may not be removed after the second catalyst layer and the electrolyte membrane have been brought into contact.

[0134] The details of the drying process when manufacturing the second catalyst layer are the same as those when manufacturing the first catalyst layer.

[0135] The manufacturing of the second catalyst layer may include a heat treatment in which the coating film after drying is heated. The details of the heat treatment when manufacturing the second catalyst layer are the same as those when manufacturing the first catalyst layer.

[0136] The coating liquid for forming the second catalyst layer is a liquid obtained by dispersing a polymer having ion exchange groups and a catalyst, which may be included in the second catalyst layer described above, in a liquid medium (e.g., an organic solvent, water, etc.). The release substrate is the same as the release substrate used in the method for producing the first catalyst layer described above.

[0137] If the laminate further includes a gas diffusion layer, the manufacturing method 1 for the laminate may further include the step of laminating the first catalyst layer onto one side of the electrolyte membrane and removing the release substrate, and then laminating the gas diffusion layer onto the side of the first catalyst layer opposite to the side on which the electrolyte membrane is located. If the laminate also includes a second catalyst layer, the manufacturing method may further include the step of laminating the second catalyst layer onto the other side of the electrolyte membrane and removing the release substrate, and then laminating the gas diffusion layer onto the side of the second catalyst layer opposite to the side on which the electrolyte membrane is located.

[0138] ・Method 2 for manufacturing the laminate A specific example of the second method for manufacturing the laminate is a method in which the above-mentioned coating liquid for forming the first catalyst layer is applied to one side of the electrolyte membrane, and the coating film of the coating liquid for forming the first catalyst layer is dried as necessary (hereinafter also referred to as "drying treatment") to obtain the laminate.

[0139] In the manufacturing method 2 of the laminate, the details of the drying treatment when manufacturing the first catalyst layer are the same as the drying treatment when manufacturing the first catalyst layer in the manufacturing method 1 of the laminate described above.

[0140] The second method for manufacturing the laminate may include a heat treatment in which the coating film after drying is heated. The details of the heat treatment when manufacturing the first catalyst layer in the second method for manufacturing the laminate are the same as the heat treatment when manufacturing the first catalyst layer in the first method for manufacturing the laminate described above.

[0141] If the laminate further includes a second catalyst layer, the manufacturing method 2 for the laminate may further include a step of applying the above-described coating liquid for forming the second catalyst layer to the other surface of the electrolyte membrane and performing a drying treatment as necessary. This yields the laminate further including the second catalyst layer.

[0142] In the manufacturing method 2 of this laminate, the details of the drying process when manufacturing the second catalyst layer are the same as the drying process when manufacturing the first catalyst layer in the manufacturing method 1 of this laminate described above.

[0143] The second method for manufacturing the laminate may include a heat treatment in which the coating film after drying is heated. The details of the heat treatment when manufacturing the second catalyst layer in the second method for manufacturing the laminate are the same as the heat treatment when manufacturing the first catalyst layer in the first method for manufacturing the laminate described above.

[0144] If the laminate further includes a gas diffusion layer, the manufacturing method 2 for the laminate may further include a step of laminating the gas diffusion layer on the surface of the first catalyst layer opposite to the surface on which the electrolyte membrane is located. If the laminate further includes a second catalyst layer, the manufacturing method may further include a step of laminating the gas diffusion layer on the surface of the second catalyst layer opposite to the surface on which the electrolyte membrane is located.

[0145] <Heating and Pressurizing Process> In the manufacturing method of this CCM, it is preferable to include a step of heating and pressurizing the laminate at a temperature higher than 130°C and 180°C or lower (hereinafter also referred to as the "heating and pressurizing process").

[0146] The heating temperature in the heating and pressurizing process is higher than 130°C, preferably higher than 140°C, more preferably higher than 145°C, and even more preferably higher than 150°C, from the viewpoint of superior effects in this disclosure. The heating temperature in the heating and pressurizing process is 180°C or lower, preferably lower than 178°C, more preferably 175°C or lower, and even more preferably 170°C or lower, from the viewpoint of superior effects in this disclosure. As for the heating temperature in the heating and pressurizing process, for example, it is preferably between 130°C and 180°C, more preferably between 140°C and 175°C, and particularly preferably between 150°C and 170°C.

[0147] In the heating and pressing process, the heating temperature is the hot press temperature in the case of hot press molding. Specifically, the hot press temperature is the temperature of the thermocouple attached to the metal plate in contact with the fluorine-containing polymer (F) in the hot press equipment.

[0148] The heating time in the heating and pressurizing process is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 7 minutes or more, from the viewpoint of achieving the effects described herein. The heating time in the heating and pressurizing process is preferably 60 minutes or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less, from the viewpoint of suppressing decomposition.

[0149] Specific examples of heating methods in the heating and pressing process include hot presses (flat plate presses, roll presses).

[0150] The pressurization process in the heating and pressurization step can be carried out, for example, using the hot press apparatus described above. When the pressurization is performed with a flat plate press, the surface pressure is preferably 0.2 MPa or more, more preferably 1.0 MPa or more, even more preferably 1.5 MPa or more, and particularly preferably 2.0 MPa or more. Furthermore, the surface pressure is preferably 30.0 MPa or less, more preferably 10.0 MPa or less, and even more preferably less than 3.0 MPa. When the pressurization is performed with a roll press, the linear pressure is preferably 3 kg / cm or more, and also preferably 200 kg / cm or less.

[0151] The pressurization time in the heating and pressurizing process is preferably the same as the heating time described above.

[0152] By undergoing the above heating and pressurizing process, hydrogen permeation is further suppressed when this CCM is used in a water electrolysis device. The CCM obtained by this manufacturing method can be suitably used in the manufacture of water electrolysis devices (solid polymer water electrolysis devices).

[0153] The film thickness of this CCM is preferably 40 μm or more, more preferably 50 μm or more, preferably 200 μm or less, and more preferably 120 μm or less. The film thickness of this CCM can be measured in the same manner as the film thickness of the electrolyte membrane described above, except that the object of measurement is an electrolyte membrane with a catalyst layer.

[0154] [Membrane Electrode Assembly] The membrane electrode assembly of the present disclosure includes the electrolyte membrane (the electrolyte membrane of the present disclosure), a cathode catalyst layer disposed on one side of the electrolyte membrane, and an anode catalyst layer disposed on the other side of the electrolyte membrane. The membrane electrode assembly of the present disclosure preferably includes the CCM described above. The membrane electrode assembly of the present disclosure is suitably used in a polymer electrolyte water electrolysis apparatus.

[0155] Figure 2 is a schematic cross-sectional view showing an example of a membrane electrode assembly of the present disclosure. In the example of Figure 2, the membrane electrode assembly 20 includes an anode 22 having a catalyst layer 26 and a gas diffusion layer 28, a cathode 24 having a catalyst layer 26 and a gas diffusion layer 28, and an electrolyte membrane 10 disposed between the anode 22 and the cathode 24 in contact with the catalyst layer 26.

[0156] Details of the electrolyte membrane 10 are as described above.

[0157] The anode 22 and cathode 24 each have a catalyst layer 26 and a gas diffusion layer 28, respectively.

[0158] Specific examples of the catalyst layer 26 include a layer containing a catalyst and a polymer having ion exchange groups. Specific examples of the catalyst include supported catalysts in which a catalyst containing platinum, a platinum alloy, or platinum having a core-shell structure is supported on a carbon support, iridium oxide catalysts, composite oxide catalysts containing iridium and other metal elements, alloys containing iridium oxide, and catalysts containing iridium oxide having a core-shell structure. Carbon black powder can be used as the carbon support. The polymer having ion exchange groups is not particularly limited, and for example, known fluorine-containing polymers having ion exchange groups can be used.

[0159] The gas diffusion layer 28 has the function of rapidly diffusing the gas generated from the catalyst layer to the outside of the catalyst layer and also functions as a current collector. Specific examples of the gas diffusion layer include carbon paper, carbon cloth, carbon felt, titanium oxide fiber sintered body, and titanium oxide particle sintered body. The anode side is at a high potential, and since carbon materials would be oxidized, it is preferable to use a titanium oxide fiber sintered body or a titanium oxide particle sintered body. The titanium oxide sintered body may be plated with platinum or the like as needed. The gas diffusion layer 28 on the cathode 24 may be treated to be water-repellent with PTFE or the like. In the film electrode assembly shown in Figure 2, the gas diffusion layer 28 is included, but the gas diffusion layer is an arbitrary component and does not have to be included in the film electrode assembly.

[0160] <Method for Manufacturing a Membrane Electrode Assembly> A method for manufacturing a membrane electrode assembly involves forming a cathode catalyst layer on one side of an electrolyte membrane and an anode catalyst layer on the other side of the electrolyte membrane. An example of a method for manufacturing a membrane electrode assembly is to use a laminate having an anode catalyst layer and a release substrate (e.g., an ETFE sheet) and a laminate having a cathode catalyst layer and a release substrate (e.g., an ETFE sheet) to bond catalyst layers to both sides of an electrolyte membrane, and then peel off the release substrate. The above laminate may have a gas diffusion layer between the catalyst layer and the release substrate. In this case, the gas diffusion layer can be formed on the side of the catalyst layer opposite to the electrolyte membrane. A method for manufacturing the catalyst layer is to apply a catalyst layer forming coating liquid to a predetermined position (e.g., the surface of the release substrate) and dry it as necessary. The catalyst layer forming coating liquid is a liquid in which a polymer having ion exchange groups and a catalyst are dispersed in a dispersion medium.

[0161] [Water Electrolyzer] The water electrolyzer of the present disclosure comprises the above-described membrane electrode assembly, a water supply unit that supplies water to the anode catalyst layer, and a power supply unit that is electrically connected to the anode catalyst layer and the cathode catalyst layer. In the water electrolyzer of the present disclosure, when a DC voltage is applied by the power supply unit while water is supplied to the anode catalyst layer by the water supply unit, water decomposes on the anode catalyst layer side, generating oxygen and protons. On the cathode catalyst layer side, protons that have moved to the cathode catalyst layer side via the electrolyte membrane gain electrons, generating hydrogen. The water electrolyzer of the present disclosure may have the same configuration as known water electrolyzers, except for having the above-described components (for example, an oxygen recovery member for recovering generated oxygen, and a hydrogen recovery member for recovering generated hydrogen).

[0162] [Method for producing hydrogen] The method for producing hydrogen according to this disclosure involves electrolyzing water (electrolyte) using the water electrolysis apparatus described above to produce hydrogen. With the method for producing hydrogen according to this disclosure, hydrogen can be produced efficiently because the water electrolysis apparatus of this disclosure is used.

[0163] The present invention will be described in detail below with reference to examples. Examples 1-1 to 1-3, Examples 2 to 5, and Example 11 are examples, and Examples 6 to 10 are comparative examples. However, the present invention is not limited to these examples.

[0164] [Measurement Method] <Percentage of Each Unit> The percentage of each unit in the fluorine-containing polymer was calculated from the ion exchange capacity measurement results described later, and the amount of each monomer used in the production of the polymer.

[0165] <Ion exchange capacity> After vacuum drying, the fluorine-containing polymer is weighed and placed in a polycarbonate container, and then subjected to a 0.7 mol / L NaOH solution (solvent: H ２ O / CH ３ Immerse in OH = 10 / 90 (mass ratio) at 60°C for 72 hours or more to obtain -SO in fluorine-containing polymers. ２The F group was completely converted to the Na salt form. The NaOH solution after immersion was back-titrated with 0.1 mol / L HCl using phenolphthalein as an indicator, and the amount of NaOH in the solution was determined to calculate the ion exchange capacity (milliequivalents / g dry resin). Note that "meq / g" refers to "milliequivalents / g dry resin," which is the unit of ion exchange capacity.

[0166] <TQ Value> Using a flow tester (Shimadzu Corporation, CFT-500D) equipped with a nozzle 1 mm in length and 1 mm in inner diameter, particles containing a fluorine-containing polymer after vacuum drying were melt-extruded at an extrusion pressure of 2.94 MPa (gauge pressure) while varying the temperature. The polymer extrusion volume was 100 mm. ３ The temperature at which this occurs per second is defined as the TQ value.

[0167] <Film Thickness of Electrolyte Membrane During Drying> The electrolyte membrane was placed on a dial gauge stand 7002 (manufactured by Mitutoyo Corporation), and the thickness of nine different points was measured using a digital gauge 543-250 (manufactured by Mitutoyo Corporation) with a flat terminal of 5 mm in diameter attached to its tip. The arithmetic mean was taken as the film thickness of the electrolyte membrane during drying. Specifically, the electrolyte membrane obtained by the method described in [Method of Manufacturing Electrolyte Membrane] below was cut into a 7.0 cm x 7.0 cm square, and the film thickness was measured at nine points at equal intervals on the four sides and diagonals (nine points placed at 2 cm intervals with a reference point 0.5 mm inward from each side). The arithmetic mean of these nine points was taken as the film thickness of the electrolyte membrane during drying.

[0168] <Thickness of Electrolyte Membrane in Water> The electrolyte membrane was immersed in pure water and left in an 80°C oven for 16 hours. After the immersion period, the water-containing electrolyte membrane was photographed using a laser microscope (product name "VK-X1000", manufactured by Keyence Corporation) while immersed in pure water at room temperature (25°C). The thickness in water was measured using a magnified image of the cross-section of the photographed electrolyte membrane (objective lens magnification 20x). The photograph was taken at three different locations on the cross-section of the electrolyte membrane, and the thickness was measured at three different locations for each image obtained. The arithmetic mean of the thicknesses of the total of nine points was taken as the thickness of the electrolyte membrane in water. The three different locations were the far right, far left, and center of the magnified image.

[0169] <Modulus of Elasticity in Water> The electrolyte membrane was immersed in pure water and left in an 80°C oven for 16 hours. After leaving it at room temperature (25°C) for 3 hours, the electrolyte membrane was punched out using a dumbbell-shaped tool (JIS K 6251:2017) to prepare a test specimen of the water-containing electrolyte membrane. The parallel portion of the electrolyte membrane punched out using the dumbbell-shaped tool was 15 mm. The test specimen was clamped in a chuck, placed in a bath heated to 80°C, and left to stand for 5 minutes. Then, a tensile test was performed at a speed of 50 mm / min using a TENSILON RTI-1225 (A&D Company, Limited). The elongation in the tensile test was measured by the change in the length of the parallel portion before and after the tensile test. The modulus of elasticity in water was calculated from the obtained stress-strain curve and the film thickness in water.

[0170] <Distance between clusters D> The electrolyte membrane obtained by the method described in [Electrolyte Membrane Preparation Method] below was cut into a 2.0 cm x 2.0 cm square and used as the measurement sample. Measurements were performed on the electrolyte membrane using an X-ray diffraction analyzer, and the angle showing the peak of the obtained scattered light intensity was calculated. The small-angle X-ray scattering measurement was performed with the electrolyte membrane placed on a sample stage. The measurement was performed at room temperature (25°C) and relative humidity of 30%, and the scattering profile q range was 0.1 to 5 nm. －１ The measurement was performed within the range of ). The q range was adjusted as needed by changing the wavelength or camera length. Here, q is the absolute value of the scattering vector defined as q = 4π / λ × sin(θ / 2), where λ is the wavelength of the incident X-ray and θ is the scattering angle. For the small-angle X-ray scattering measurement, the "Aichi Synchrotron Radiation Center BL8S3" was used, with an incident X-ray wavelength of 1.5 Å (8.2 keV), a beam size of approximately 660 μm × 370 μm, a camera length of 2,124 mm, a PILATUS 2M detector, and an exposure time of 120 sec. For data processing, the obtained 2D data was annularly averaged to become 1D, and then transmittance correction, air scattering correction, and sample thickness correction were performed. In addition, if reinforcing cloth or other materials are used in the electrolyte membrane, scattering other than from the electrolyte membrane is measured and corrected to obtain a scattering profile originating from the electrolyte membrane for analysis. The peaks detected in the scattering profile obtained by the above procedure indicate the existence of structural regularity in the electrolyte membrane. Generally, q = 0.8 to 4 (nm－１ The peak position (q) detected within the range of ) ｍ The peak position is a factor indicating the spacing between ion clusters. The spacing D (distance D) between ion clusters was calculated from the following equation (E): Equation (E) D = 2π / q ｍ (nm)

[0171] <Peak Intensity Ratio> The scattering profile was obtained in the same manner as the measurement of the distance D between clusters described above. Generally, q = 1.0 (nm) －１ Peak intensity detected in the range less than (I ｍ－ｃｒｙｓｔａｌ ) is a factor that reflects the size and quantity of the crystal, and q = 1.0 to 4 (nm －１ Peak intensity (I) detected within the range of ) ｍ－ｃｌｕｓｔｅｒ ) is a factor that reflects the size and amount of ion clusters. For samples where the peak position is difficult to confirm due to the crystal origin, q = 0.16 (nm) －１ The intensity of ) ｍ－ｃｒｙｓｔａｌ Let's assume that the peak intensity (I) originates from the cluster. ｍ－ｃｌｕｓｔｅｒ ) and peak intensity derived from crystals (I ｍ－ｃｒｙｓｔａｌ The ratio of ) was defined by the following equation (E), and the peak intensity ratio C was calculated. Equation (E) Peak intensity ratio C = I ｍ－ｃｒｙｓｔａｌ / I ｍ－ｃｌｕｓｔｅｒ

[0172] <Conductivity> A substrate with four-terminal electrodes arranged at 5 mm intervals was placed in close contact with a 5 mm wide electrolyte membrane. The resistance of the electrolyte membrane was measured using a known four-terminal method under constant temperature and humidity conditions of 80°C and 95% relative humidity, with AC: 10 kHz and voltage: 1 V, and the conductivity was calculated. The standard dimensions and thickness of the membrane used in the calculation were measured under conditions of 23°C and 50% RH relative humidity. Based on the calculated conductivity, evaluation was performed according to the following criteria. A higher conductivity value indicates better proton conductivity of the electrolyte membrane. In practical applications, B － A rating above this is preferable. ＋ : Conductivity of 0.36 S / cm or more A: Conductivity of 0.31 S / cm or more and less than 0.36 S / cm B: Conductivity of 0.25 S / cm or more and less than 0.31 S / cm B － : Conductivity of 0.20 S / cm or more and less than 0.25 S / cm C: Conductivity of less than 0.20 S / cm

[0173] <Low Hydrogen Permeability> The hydrogen concentration in the gas at the anode of each membrane electrode assembly was measured according to the following procedure, and the hydrogen crossover was evaluated. First, the membrane electrode assembly was sandwiched between platinum-plated titanium fiber sintered bodies (manufactured by Bekalt Co., Ltd.) with a thickness of 0.25 mm and a porosity of 60 volume%, and a platinum-plated titanium plate with a straight channel was used as a separator, resulting in an electrode area of ​​16 cm². ２ A membrane electrode assembly was incorporated into the single cell. When the membrane electrode assembly was clamped, a pressure of 1.3 MPa was applied to the electrode portion. Next, in order to sufficiently hydrate the electrolyte membrane and the fluorine-containing polymer of both electrodes, pure water with a conductivity of 1.0 μS / cm or less, a temperature of 80°C, and atmospheric pressure was supplied to the anode and cathode sides at a flow rate of 50 mL / min for 4 hours. After that, pure water with a conductivity of 1.0 μS / cm or less, a temperature of 80°C was supplied to the anode side at a flow rate of 50 mL / min, and while maintaining atmospheric pressure at both the anode and cathode, a high-current potentio / galvanostat HCP-803 (manufactured by Biologic) was used to conduct a current test of 32 A (current density 2 A / cm²). ２ While maintaining the current, a 4-hour water electrolysis was performed as a break-in period. Subsequently, 0-48A (current density 0-3A / cm²) was used. ２ IV (current-voltage) measurements were performed by gradually increasing the current within the specified range. Four IV measurements were taken. Subsequently, pure water with a conductivity of 1.0 μS / cm or less, a temperature of 80°C, and atmospheric pressure was supplied to the cell at a rate of 50 mL / min. With the back pressure at both the anode and cathode at atmospheric pressure, a high-current potentio / galvanostat HCP-803 (manufactured by Biologic) was used to measure 3.2 A (current density 0.2 A / cm²). ２ ) for 11 hours at 8A (current density 0.5A / cm²) ２ ) for 7 hours at 16A (current density 1A / cm²) ２ ) for 4 hours, and 32A (current density 2A / cm²) ２The gas was held at the specified current for 4 hours. After the holding time for each current, water was separated from the gas discharged from the anode side. The hydrogen concentration in the gas on the anode side was then measured using a micro GC (Agilent 490, manufactured by Agilent Corporation), and the hydrogen concentration in the gas at the final measurement point (volume %) was measured (hydrogen content / gas content). From the current and gas concentration at the time of measurement, the amount of hydrogen permeating from the cathode side to the anode side was calculated, and by multiplying this by the film thickness during drying, the result was obtained as 2 A / cm². ２ The hydrogen permeability coefficient of the electrolyte membrane during water electrolysis operation at the given current density was calculated. Based on the calculated hydrogen permeability coefficient, evaluation was performed according to the following criteria. A smaller hydrogen permeability coefficient indicates superior low hydrogen permeability of the electrolyte membrane. In practical terms, a rating of B or higher is preferable. A ＋ : Hydrogen permeability coefficient (cc・cm / cm ２ sec・atm) is 0.86 × 10 －６ Below, A: Hydrogen permeability coefficient (cc・cm / cm) ２ sec・atm) is 0.86 × 10 －６ Super 1.2×10 －６ Below A － : Hydrogen permeability coefficient (cc・cm / cm ２ sec・atm) is 1.2 × 10 －６ Super 2.0×10 －６ Below, B: Hydrogen permeability coefficient (cc・cm / cm) ２ sec.atm) is 2.0 × 10 －６ Super 2.8×10 －６ Below, C: Hydrogen permeability coefficient (cc・cm / cm) ２ sec・atm) is 2.8 × 10 －６ super

[0174] <Underwater Compression Creep> [Measurement Equipment] TMA4000SE (NETZSCH Japan Co., Ltd., hereinafter also referred to as "TMA") [Measurement Conditions] Measurement Mode: Penetration Method Load Mode: Constant Load Measurement Atmosphere: Underwater Environment Temperature Increase Condition: From room temperature (25°C) to 80°C at 10°C / min Evaluation Film Size: 1.0 cm × 0.5 cm PTL (Porous Transport Layer): Material: Titanium (Type 1) Thickness: 200 μm Size: 0.5 cm × 0.5 cm Aperture Ratio: 45% Aperture Diameter d: 200 μm Distance between Circles w: 100 μm Image Diagram: Figure 3 (Black area indicates the opening) Underwater cross-sectional thickness D: The cross-sectional thickness strain (X) (T) obtained by cutting the evaluation film with a sharp razor blade and observing the cross-section under 25°C underwater conditions. T: The absolute difference between the TMA reading after T time has elapsed since applying a constant load of Xg and the TMA reading at a load of 3g, divided by the cross-sectional thickness D in the underwater environment. TMA reading: The height value calculated by performing height calibration on a quartz base.

[0175] [Measurement Method] First, a titanium PTL was placed on top of the quartz glass in the sample chamber, and the pre-treated evaluation film (heat treatment in 80°C water for 16 hours) was placed on top of it. The water temperature in the measurement environment was maintained at 80°C for 30 minutes, and then a load was applied from 3g to 500g at a rate of 10g / min. The absolute difference between the TMA reading at a load of 500g and the TMA reading at a load of 3g, divided by the cross-sectional thickness D in the water environment, was defined as the initial strain (Equation 1). Next, after the initial strain was observed, a constant load of 500g was continuously applied for 72 hours. Furthermore, the difference between the strain (500)(24) after 24 hours of continuous application of a constant load of 500g and the initial strain, divided by 24 hours, was defined as the creep rate at 80°C (Equation 2). Next, after initial strain was observed, a constant load of 500g was applied for 72 hours. The height (μm) of the polymer that penetrated into the PTL from the opening was measured using an optical microscope (Keyence) and defined as the penetration height (μm). The value obtained by dividing the penetration height by 72 hours was defined as the PTL penetration velocity (Equation 3).

[0176] (Equation 1) Initial strain (%) = (TMA reading at 3g load - TMA reading at 500g load) / underwater cross-sectional thickness D × 100 (Equation 2) Creep rate (%) / h = [{strain (500) (24)} - initial strain] / 24 (Equation 3) PTL penetration speed (μm / h) = penetration height / 72

[0177] <Evaluation of Appearance Characteristics> The appearance of the precursor film in each example was visually inspected. In addition, the film thickness of the precursor film was measured when dried, in the same manner as in the measurement of the electrolyte film thickness when dried, except that the electrolyte film was replaced with the precursor film, and the standard deviation was calculated to be used as an indicator of in-plane smoothness of the film. The appearance characteristics were evaluated according to the following evaluation criteria. For practical purposes, a rating of B or higher is preferable. A: Film transparency is remarkably high and in-plane smoothness is remarkably excellent. B: Film transparency is high and in-plane smoothness is excellent. C: Film transparency is low and insufficient in-plane smoothness of the film.

[0178] [Abbreviations] <Monomers> ・TFE: Tetrafluoroethylene monomer ・m1: Monomer represented by the formula m1 below ・Monomer m2: CF ２ = CFOCF ２ CF (CF ３ ) O (CF ２ ) ２ SO ２ F. Monomer m11: A monomer represented by the following formula m11.

[0179]

[0180]

[0181] <Radical polymerization initiators> ・V-601: Dimethyl 2,2'-azobis (2-methylpropionate) ・AIBN: 2,2'-Azobis (isobutyrinitrile)

[0182] <Solvent> ・HFE-347pc-f: HCF ２ CF ２ OCH ２ CF ３ ・HFC-52-13p:CF ３ (CF ２ ) ４ CF ２ H ・HCFC-225cb: CClF２ CF ２ CHClF ・HCFC-141b:CH ３ CCl ２ F

[0183] [Production of Fluorine-Containing Polymer] <Fluorine-Containing Polymer F1> In a 21,100 mL stainless steel reactor, 6,665 g of monomer m1 and 5,406 g of HCFC-225cb were charged under reduced pressure of -0.1 MPaG while cooled, and the inside was degassed. Then, the mixture was stirred at 142 rpm, the temperature was raised to 70°C, TFE was introduced, and the total pressure was set to 0.96 MPaG. 332 g of an HCFC-225cb solution containing 3.00 mass% AIBN was injected into the reactor under pressure to start polymerization. TFE was continuously added while maintaining the starting pressure. When the amount of TFE continuously introduced reached 1,297 g, the reactor was cooled to below 20°C, unreacted TFE was released, and a liquid composition F1 was obtained, which is a solution in which fluorine-containing polymer F1 is dissolved in unreacted monomer m1 and HCFC-225cb. 10.0 kg of HCFC-225cb was added to the reactor in several batches, and 11.6 kg of liquid composition F1 was diluted and transferred to another tank. The diluted liquid composition was kept at 25°C and quantitatively added to 34.5 kg of HCFC-141b at 25°C, and stirred to agglomerate the fluorine-containing polymer F1 and form particles containing the fluorine-containing polymer F1. After stirring, the liquid containing the particles with fluorine-containing polymer F1 was filtered using a filter cloth. The separated and recovered particles containing fluorine-containing polymer F1 were washed by adding a mixed solvent of 10.0 kg of HCFC-141b at 25°C and 5.0 kg of HCFC-225cb, stirring, and then filtering. The washing was repeated a total of five times to obtain particles containing fluorine-containing polymer F1. The particles containing fluorine-containing polymer F1 were vacuum-dried at 90°C for 16 hours to obtain 2,189 g of fluorine-containing polymer F1.

[0184] <Fluorine-containing polymer F2> In a 230 mL stainless steel reactor, 50.0 g of monomer m1, 80.5 g of HFC-52-13p, and CH ３107 mg of OH was charged, and freeze-degassing was thoroughly performed using liquid nitrogen. Then, the temperature was raised to 70°C while stirring at 300 rpm, and TFE was introduced to bring the total pressure to 0.77 MPaG. V-601 was dissolved in HFC-52-13p at a concentration of 2.60 mass% to prepare an initiator solution, and 3.08 g of the initiator solution was injected under pressure into the reactor to start polymerization. TFE was continuously added while maintaining the starting pressure. When the amount of TFE continuously introduced reached 18.5 g, the reactor was cooled to 10°C, unreacted TFE was vented, and liquid composition F2, which is a solution in which the fluorine-containing polymer F2 is dissolved in unreacted monomer m1 and HFC-52-13p, was obtained. 136 g of liquid composition F2 was kept at 25°C and added to 379 g of HFE-347pc-f at -17°C. The mixture was stirred to agglomerate the fluorine-containing polymer F2 and form particles containing the fluorine-containing polymer F2. After stirring, the liquid containing the particles with fluorine-containing polymer F2 was filtered using filter paper. The separated and recovered particles containing fluorine-containing polymer F2 were washed by adding 150 g of HFE-347pc-f at -17°C, stirring, and then filtering. The washing process was repeated a total of three times to obtain particles containing fluorine-containing polymer F2. The particles containing fluorine-containing polymer F2 were vacuum-dried at 240°C for 16 hours to obtain 27.6 g of fluorine-containing polymer F2.

[0185] <Fluorine-containing polymer F3> 75.0 g of monomer m1 and 92.2 g of HFC-52-13p were charged into a 230 mL stainless steel reactor, and freeze-degassing was thoroughly carried out using liquid nitrogen. Then, the temperature was raised to 70°C while stirring at 300 rpm, and TFE was introduced to bring the total pressure to 0.71 MPaG. V-601 was dissolved in HFC-52-13p at a concentration of 1.70 mass% to prepare an initiator solution, and 3.05 g of the initiator solution was injected into the reactor under pressure to start polymerization. TFE was continuously added while maintaining the starting pressure. When the amount of TFE continuously introduced reached 13.7 g, the reactor was cooled to 10°C, unreacted TFE was vented, and liquid composition F3, which is a solution in which fluorine-containing polymer F3 is dissolved in unreacted monomer m1 and HFC-52-13p, was obtained. 177 g of liquid composition F3 was kept at 25°C and added to 288 g of HFE-347pc-f at 25°C. The mixture was stirred to agglomerate the fluorine-containing polymer F3 and form particles containing the fluorine-containing polymer F3. After stirring, the liquid containing the particles with fluorine-containing polymer F3 was filtered using filter paper. The separated and recovered particles containing fluorine-containing polymer F3 were washed by adding 150 g of HFE-347pc-f at 25°C, stirring, and then filtering. The washing process was repeated a total of three times to obtain particles containing fluorine-containing polymer F3. The particles containing fluorine-containing polymer F3 were vacuum-dried at 240°C for 16 hours to obtain 23.9 g of fluorine-containing polymer F3.

[0186] <Fluorine-containing polymer F4> In Example 3, fluorine-containing polymer F4 was obtained in the same manner except that the amount of monomer used was changed. Note that fluorine-containing polymer F4 is a copolymer of TFE and monomer m1.

[0187] <Fluorine-containing polymer F5> In Example 3, fluorine-containing polymer F5 was obtained in the same manner except that the amount of monomer used was changed. Note that fluorine-containing polymer F5 is a copolymer of TFE and monomer m1.

[0188] <Fluorine-containing polymer F6> Fluorine-containing polymer F6 was manufactured in accordance with the description in paragraph 0197 of Japanese Patent Application Publication No. 2015-099772. Fluorine-containing polymer F6 is a copolymer of TFE and monomer m2.

[0189] <Fluorine-containing polymer F7> Fluorine-containing polymer F7 was prepared in accordance with the description in paragraph 0218 of International Publication No. 2016 / 104379. Fluorine-containing polymer F7 is a copolymer of TFE and monomer m1.

[0190] <Fluorine-containing polymer F8> 100 g of monomer m2 and 52.0 g of HFC-52-13p were charged into a 230 mL stainless steel reactor, and freeze-degassing was thoroughly carried out using liquid nitrogen. Then, the temperature was raised to 70°C while stirring at 300 rpm, TFE was introduced, and the total pressure was set to 1.00 MPaG. AIBN was dissolved in HFC-52-13p at a concentration of 0.51 mass% to prepare an initiator solution, and 3.02 g of the initiator solution was injected into the reactor under pressure to start polymerization. TFE was continuously added while maintaining the starting pressure. When the amount of TFE continuously introduced reached 10.3 g, the reactor was cooled to 10°C, unreacted TFE was vented, and liquid composition F8, which is a solution in which fluorine-containing polymer F8 is dissolved in unreacted monomer m2 and HFC-52-13p, was obtained. 152 g of liquid composition F8 was diluted with 133 g of HFC-52-13p. The diluted liquid composition F8 was kept at 25°C and added to 426 g of HFE-347pc-f at 25°C. The mixture was stirred to agglomerate the fluorine-containing polymer F8 and form particles containing the fluorine-containing polymer F8. After stirring, the liquid containing the particles with fluorine-containing polymer F8 was filtered using filter paper. The separated and recovered particles containing fluorine-containing polymer F8 were washed by adding a mixed solvent of 400 g of HFE-347pc-f at 25°C and 103 g of HFC-52-13p, stirring, and then filtering. The washing process was repeated a total of three times to obtain particles containing fluorine-containing polymer F8. The particles containing fluorine-containing polymer F8 were vacuum-dried at 240°C for 16 hours to obtain 18.9 g of fluorine-containing polymer F8.

[0191] <Fluorine-containing polymer F9> In a 230 mL stainless steel reactor, 50.0 g of monomer m1 and 80.5 g of HFC-52-13p are added, along with CH ３107 mg of OH was charged, and freeze-degassing was thoroughly performed using liquid nitrogen. Then, the temperature was raised to 70°C while stirring at 300 rpm, TFE was introduced, and the total pressure was set to 0.87 MPaG. V-601 was dissolved in HFC-52-13p at a concentration of 2.60 mass% to prepare an initiator solution, and 3.08 g of the initiator solution was injected under pressure into the reactor to start polymerization. TFE was continuously added while maintaining the starting pressure. When the amount of TFE continuously introduced reached 14.6 g, the reactor was cooled to 10°C, unreacted TFE was vented, and liquid composition F9, which is a solution in which the fluorine-containing polymer F9 is dissolved in unreacted monomer m1 and HFC-52-13p, was obtained. 149 g of liquid composition F9 was kept at 25°C and added to 382 g of HFE-347pc-f at -17°C. The mixture was stirred to agglomerate the fluorine-containing polymer F9 and form particles containing it. After stirring, the liquid containing the particles with fluorine-containing polymer F9 was filtered using filter paper. The separated and recovered particles containing fluorine-containing polymer F9 were washed by adding 150 g of HFE-347pc-f at 25°C, stirring, and then filtering. The washing process was repeated a total of three times to obtain particles containing fluorine-containing polymer F9. The particles containing fluorine-containing polymer F9 were vacuum-dried at 240°C for 16 hours to obtain 22.2 g of fluorine-containing polymer F9.

[0192] Table 1 shows the ion exchange capacity (indicated as IEC in Table 1), TQ value, and TFE unit content relative to the total units contained in the fluorine-containing polymer (indicated as TFE unit content in Table 1) for each fluorine-containing polymer.

[0193] <Fluorine-containing polymer F10> Fluorine-containing polymer F10 was prepared according to the description in Example 7 of paragraphs 0144-0145 of International Publication No. 2007 / 013532. Fluorine-containing polymer F10 is a copolymer of TFE and monomer m11.

[0194] [Examples 1-1 to 1-3, Examples 2 to 11] [Manufacture of Electrolyte Membrane] Using each fluorine-containing polymer, the electrolyte membranes of each example were obtained by the following method. The fluorine-containing polymer was hot-pressed using a hot press (SA-301, manufactured by Tester Industries Co., Ltd., 50-ton single-acting hydraulic hot press) at the temperatures listed in the film formation temperature column of Table 1, with surface pressures of 0.5 MPa, 2 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa, 12 MPa, and 15 MPa for 5 minutes each, and then rapidly cooled to obtain a precursor film (film thickness 45-70 μm). The obtained precursor film was immersed in potassium hydroxide / dimethyl sulfoxide / water = 30 / 10 / 60 (mass ratio) at 95°C (temperature at hydrolysis) for 16 hours, and then immersed in ultrapure water at 95°C for 30 minutes. This process was repeated twice to obtain the -SO of the fluorine-containing polymer. ２ The F group is hydrolyzed, and -SO ３ The K group was converted. Furthermore, by repeating the process of immersing the polymer in a 3 mol / L hydrochloric acid aqueous solution at 80°C for 30 minutes, followed by immersion in ultrapure water at 80°C for 30 minutes, 10 times, the fluorine-containing polymer was converted to -SO ３ K group -SO ３ The H group was converted. The resulting membrane was then sandwiched between filter paper and dried at 25°C for 72 hours to obtain the electrolyte membrane for each example. The water modulus, distance D, and conductivity of the obtained electrolyte membranes were measured. Furthermore, it was determined whether each example satisfied equation (A): 4.55 - 0.85X ≤ D ≤ 4.16 (where D is the distance D [nm] and X is the ion exchange capacity [meq / g]). If it satisfied, it was classified as Y; otherwise, it was classified as N. The results are shown in Table 1. Additionally, the peak intensity ratio was measured using the obtained electrolyte membranes. The results are shown in Table 2.

[0195] [Manufacturing of Membrane Electrode Assembly] A polymer (ion exchange capacity: 1.10 mm equivalent / g dry resin) obtained by copolymerizing TFE and monomer m2, hydrolysis, and acid treatment was dispersed in a water / ethanol = 40 / 60 (mass%) solvent at a solid content concentration of 26.0% to obtain a dispersion (hereinafter also referred to as "dispersion Y"). Ethanol (18.06 g) and Zeolora-H (manufactured by Nippon Zeon) (10.58 g) were added to dispersion Y (33.0 g), and the mixture was mixed at 2,200 rpm for 5 minutes using a rotation-orbit mixer (manufactured by Thinky, Awatori Rentaro). Ethanol (46.44 g) and water (75.75 g) were added to the mixed composition (54.06 g), and further a specific surface area of ​​100 m² containing 74.8 mass% iridium was added. ２ 40.0 g of iridium oxide catalyst (manufactured by Tanaka Kikinzoku Co., Ltd.) was added. The resulting mixture was treated with a planetary bead mill (rotation speed 300 rpm) for 90 minutes to obtain an anode catalyst ink with a solid content concentration of 22% by mass. The anode catalyst ink was then applied to an ETFE sheet with an iridium content of 1.0 mg / cm³. ２ The material was coated using an applicator, dried at 80°C for 10 minutes, and then heat-treated at 150°C for 15 minutes to obtain an anode catalyst layer decal.

[0196] A supported catalyst (TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) (11 g), in which 46% by mass of platinum was supported on carbon powder, was mixed with water (59.4 g) and ethanol (39.6 g) and mixed and pulverized using an ultrasonic homogenizer to obtain a catalyst dispersion. To the catalyst dispersion, a mixture (29.2 g) was added, which consisted of dispersion Y (20.1 g), ethanol (11 g), and Zeolora-H (manufactured by Nippon Zeon Co., Ltd.) (6.3 g) that had been pre-mixed and kneaded. Furthermore, water (3.66 g) and ethanol (7.63 g) were added to the obtained dispersion and mixed with paint conditioner for 60 minutes to obtain a cathode catalyst ink with a solid content concentration of 10.0% by mass. The cathode catalyst ink was applied to an ETFE sheet using a die coater, dried at 80°C, and then heat-treated at 150°C for 15 minutes to obtain a platinum content of 0.4 mg / cm². ２ A cathode catalyst layer decal was obtained.

[0197] One side of a 7.0 cm x 7.0 cm electrolyte membrane was placed opposite the side of a 4.0 cm x 4.0 cm anode catalyst layer decal containing the catalyst layer, and the other side of the electrolyte membrane was placed opposite the side of a 4.0 cm x 4.0 cm cathode catalyst layer decal containing the catalyst layer. Using a hot press (SA-401-H, manufactured by Tester Industries Co., Ltd., a 20-ton high-precision hot press), the two halves were joined by flat pressing at a surface pressure of 2.6 MPa for 10 minutes at the "Heating temperature for electrolyte membrane with catalyst layer" shown in Table 1, thereby obtaining a laminate containing an electrolyte membrane with a catalyst layer. After lowering the temperature to 70°C, the pressure was released and the laminate was removed. The ETFE sheets of the anode catalyst layer decal and cathode catalyst layer decal were peeled off, resulting in an electrode area of ​​16 cm². ２ A membrane electrode assembly was obtained. The low hydrogen permeability described above was evaluated using the obtained membrane electrode assembly. The evaluation results based on the above evaluation criteria are shown in Table 1.

[0198]

[0199]

[0200] As shown in Table 1, it was confirmed that the electrolyte membrane of this disclosure exhibits high proton conductivity and low hydrogen permeability (Examples 1-1 to 1-3, 2-5, and 11).

[0201] Using the fluorine-containing polymers F1 to F5 used in Examples 1-1 and 2 to 5, electrolyte membranes were manufactured in the same manner as described above for the production of electrolyte membranes, and these were used as evaluation membranes. However, the evaluation membranes were manufactured so that the film thickness when dry was 100 to 135 μm. The values ​​of the compressed creep in water were measured for the obtained evaluation membranes. The results are shown in Table 3.

[0202]

[0203] As shown in Table 3, when using the electrolyte membrane of this disclosure, it was confirmed that the durability of the electrolyte membrane is also excellent (Examples 1-1, 2-5).

[0204] The appearance characteristics of the precursor films obtained in Examples 1-1, 2-5, and 10-11 were evaluated. The results are shown in Table 4.

[0205] As shown in Table 4, the precursor membrane used in the electrolyte membrane of this disclosure was confirmed to have excellent appearance characteristics (Examples 1-1, 2-5, and 11). The entire contents of the specifications, claims, drawings, and abstracts of Japanese Patent Application Nos. 2024-193002, 2024-192955, 2024-192998, and 2025-081814, filed on November 1, 2024, are incorporated herein by reference as the disclosure of this invention.

[0206] 1 Ion cluster 2 Ion channel 10 Electrolyte membrane 20 Membrane electrode assembly 22 Anode 24 Cathode 26 Catalyst layer 28 Gas diffusion layer

Claims

1. A solid polymer electrolyte membrane containing a fluorine-containing polymer having ion exchange groups, wherein the elastic modulus in water at 80°C is 13 MPa or higher, and the following equation (A) is satisfied when the distance between ion clusters measured by small-angle X-ray scattering is D [nm] and the ion exchange capacity of the fluorine-containing polymer is X [milliequivalents / g dry resin]: Equation (A) 4.55 - 0.85X ≤ D ≤ 4.16 2. The solid polymer electrolyte membrane according to claim 1, wherein the elastic modulus in water is 17 MPa or more.

3. The solid polymer electrolyte membrane according to claim 1, wherein the solid polymer electrolyte membrane has a layer containing the fluorine-containing polymer, and the thickness of the layer is 30 μm or more.

4. The solid polymer electrolyte membrane according to claim 1, wherein the fluorine-containing polymer includes units having ion exchange groups.

5. The solid polymer electrolyte membrane according to claim 4, wherein the unit having an ion exchange group is a unit having two or more ion exchange groups.

6. The solid polymer electrolyte membrane according to claim 4, wherein the unit having the ion exchange group includes a unit represented by formula (1-3). In formula (1-3), R ｆ１ R is a perfluoroalkylene group which may contain oxygen atoms between carbon atoms, ｆ２ is a perfluoroalkylene group which may contain oxygen atoms between single bonds or carbon atoms, r is 0 or 1, and M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation.

7. The solid polymer electrolyte membrane according to claim 6, wherein the fluorine-containing polymer comprises units based on tetrafluoroethylene and units represented by formula (1-3), the content of the units based on tetrafluoroethylene is 88.0 to 94.0 mol% of the total units in the fluorine-containing polymer, and the content of the units represented by formula (1-3) is 6.0 to 12.0 mol% of the total units in the fluorine-containing polymer.

8. The solid polymer electrolyte membrane according to claim 1, wherein the peak intensity ratio C, determined by small-angle X-ray scattering and defined by the following formula (E), is 10 or more and 90 or less. Formula (E): Peak intensity ratio C = I ｍ－ｃｒｙｓｔａｌ / I ｍ－ｃｌｕｓｔｅｒ 9. The solid polymer electrolyte membrane according to claim 1, wherein, as measured by a thermomechanical analyzer (TMA), the initial strain represented by formula 1 below is 90.0% or less, the creep rate represented by formula 2 below is 0.400% / h or less, and the PTL penetration rate represented by formula 3 below is 0.70 μm / h or less. (Equation 1) Initial strain (%) = (TMA reading at load 3g - TMA reading at load 500g) / underwater cross-sectional thickness D × 100 (Equation 2) Creep rate (%) / h = [{strain (500) (24)} - initial strain] / 24 (Equation 3) PTL penetration speed (μm / h) = penetration height / 72 In the equations, underwater cross-sectional thickness D is the cross-sectional thickness obtained by observing the electrolyte membrane in water at 25°C, strain (X) (T) is the absolute value of the difference between the TMA reading after T time has elapsed since applying a constant load of Xg and the TMA reading at load 3g, divided by the cross-sectional thickness D in the underwater environment, and TMA reading is the height value calculated by performing height calibration on the measurement base.

10. The solid polymer electrolyte membrane according to claim 1, wherein the conductivity is 0.20 S / cm or more.

11. A method for producing a solid polymer electrolyte membrane, comprising: forming a film of a fluorine-containing polymer having groups that can be converted into ion exchange groups to produce a precursor film; and then converting the groups in the precursor film that can be converted into ion exchange groups into ion exchange groups to obtain the solid polymer electrolyte membrane described in claim 1, wherein the TQ value of the fluorine-containing polymer having groups that can be converted into ion exchange groups is 290°C or less, and the film formation temperature when carrying out the film formation is lower than the TQ value of the fluorine-containing polymer having groups that can be converted into ion exchange groups.

12. A method for producing an electrolyte membrane with a catalyst layer, comprising heating and pressurizing a laminate including a solid polymer electrolyte membrane according to any one of claims 1 to 10 and a first catalyst layer disposed in contact with one surface of the electrolyte membrane, wherein the heating temperature is higher than 130°C and 180°C or lower.

13. A membrane electrode assembly comprising: a solid polymer electrolyte membrane according to any one of claims 1 to 10; a cathode catalyst layer disposed on one side of the electrolyte membrane; and an anode catalyst layer disposed on the other side of the electrolyte membrane.

14. A water electrolysis apparatus comprising: a membrane electrode assembly according to claim 13; a power supply unit connected to the cathode catalyst layer side and the anode catalyst layer side of the membrane electrode assembly; and a water supply unit for supplying water to the anode catalyst layer side.

15. A method for producing hydrogen, comprising producing hydrogen by electrolyzing water using the water electrolysis apparatus described in claim 14.

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