Electrolyte membranes, electrolytic devices, and redox flow batteries

Abstract

The present invention provides: an electrolyte membrane which is not susceptible to the generation of a pinhole if used in a cell that has an anode and a cathode, while being applied with a voltage for a long period of time; and an electrolysis device and a redox flow battery, each of which comprises this electrolyte membrane.　An electrolyte membrane which comprises a woven fabric and a fluorine-containing polymer that has an ion exchange group, wherein: the woven fabric is composed of a yarn A that extends in one direction and a yarn B that extends in a direction which is generally perpendicular to the yarn A; the aspect ratio YACA2 / YACA1 is more than 1, while being higher than the aspect ratio YAA2 / YAA1; and the aspect ratio YACB2 / YACB1 is more than 1, while being higher than the aspect ratio YAB2 / YAB1. (Meanwhile, YACA2, YACA1, YAA2, YAA1, YACB2, YACB1, YAB2 and YAB1 are as defined in the description.)

Description

[Technical Field]

[0001] The present invention relates to an electrolyte membrane, an electrolytic device, and a redox flow battery. [Background technology]

[0002] Electrolyte membranes can be applied to a variety of uses, and various studies have been conducted on them. For example, Patent Document 1 discloses an electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups and a woven fabric, and it has been shown that by specifying the aperture ratio of the woven fabric, the denier number of the woven fabric, and the relationship between the film thickness of the electrolyte membrane and the ion exchange capacity of the fluorine-containing polymer, the electrolysis voltage can be reduced when applied to a water electrolysis device. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2020 / 162511 [Overview of the project] [Problems that the invention aims to solve]

[0004] When manufacturing electrolyte membranes containing electrolytes and woven fabrics, cleaning treatments such as brushing the surface of the woven fabric may be performed to remove foreign matter adhering to the fabric. The inventors have found that when an electrolyte membrane containing the woven fabric that has undergone the above-described cleaning treatment is used for a long period of time under voltage in a cell having an anode and a cathode, pinholes may occur in the electrolyte membrane. A pinhole is a defect where a hole penetrates the material. When a pinhole occurs, problems arise, such as an increase in the amount of material movement between the anode / cathode or positive / negative electrode, which were separated by an electrolyte membrane in electrolysis or battery applications, or damage or a short circuit starting from that point.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide an electrolyte membrane in which pinholes are less likely to occur when a voltage is applied for a long time in a cell having an anode and a cathode, and an electrolytic device and a redox flow battery including the same.

Means for Solving the Problems

[0006] As a result of intensive studies on the above problems, the present inventors have found that in an electrolyte membrane including a fluorine-containing polymer having an ion exchange group and a woven fabric composed of yarn A and yarn B substantially orthogonal thereto, the aspect ratio YA of yarn A at the intersection of yarn A and yarn B CA2 / YA CA1 is greater than 1, and the aspect ratio YA of yarn A at the midpoint between yarns B A2 / YA A1 is greater than that, and further, the aspect ratio YA of yarn B at the intersection of yarn A and yarn B CB2 / YA CB1 is greater than 1, and the aspect ratio YA of yarn B at the midpoint between yarns A B2 / YA B1 is greater than that, and the inventors have found that the desired effect can be obtained, leading to the present invention.

[0007] That is, the inventors have found that the above problems can be solved by the following configuration. [1] An electrolyte membrane including a fluorine-containing polymer having an ion exchange group and a woven fabric, wherein the woven fabric is composed of yarn A extending in one direction and yarn B extending in a direction substantially orthogonal to yarn A, both the yarn A and the yarn B are made of a material that does not elute in an alkaline aqueous solution, For each of 10 different cross-sections when the electrolyte membrane is cut along the thickness direction of the electrolyte membrane so as to pass through the central position of the yarn B in the electrolyte membrane, the maximum length Y of the yarn A in the thickness direction of the electrolyte membrane CA1 and the maximum length Y of the yarn A in the direction orthogonal to the thickness direction of the electrolyte membrane measured for the maximum length Y CA1 are measured, and the 10 obtained maximum lengths Y CA2 are measured, and the 10 obtained maximum lengths YCA1 The arithmetic mean of the average maximum length YA CA1 The obtained 10 locations with the maximum length Y CA2 The arithmetic mean of the average maximum length YA CA2 Aspect ratio YA CA2 / YA CA1 Calculate, The maximum length Y of thread A in the thickness direction of the electrolyte membrane is determined for each of the 10 different cross-sections obtained when the electrolyte membrane is cut at an intermediate point between the threads B in a direction parallel to the direction in which the thread B extends within the electrolyte membrane. A1 And the aforementioned maximum length Y A1 The maximum length Y of thread A measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. A2 The maximum length Y of the 10 locations obtained was measured. A1 The arithmetic mean of the average maximum length YA A1 The obtained 10 locations with the maximum length Y A2 The arithmetic mean of the average maximum length YA A2 Aspect ratio YA A2 / YA A1 When calculated, The aspect ratio YA CA2 / YA CA1 However, it is greater than 1, and the aspect ratio YA A2 / YA A1 Larger than, Furthermore, for each of the 10 different cross-sections obtained by cutting the electrolyte membrane along the thickness direction so as to pass through the center of the thread A within the electrolyte membrane, the maximum length Y of the thread B in the thickness direction of the electrolyte membrane is determined. CB1 And the aforementioned maximum length Y CB1 The maximum length Y of the thread B measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. CB2 The maximum length Y of the 10 locations obtained was measured. CB1 The arithmetic mean of the average maximum length YA CB1 The obtained 10 locations with the maximum length Y CB2 The arithmetic mean of the average maximum length YA CB2 Aspect ratio YA CB2 / YA CB1 Calculate, The maximum length Y of thread B in the thickness direction of the electrolyte membrane is determined for each of the 10 different cross-sections obtained when the electrolyte membrane is cut at an intermediate point between threads A in the electrolyte membrane, in a direction parallel to the direction in which thread A extends within the electrolyte membrane. B1 And the aforementioned maximum length Y B1 The maximum length Y of the thread B measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. B2 The maximum length Y of the 10 locations obtained was measured. B1 The arithmetic mean of the average maximum length YA B1 The obtained 10 locations with the maximum length Y B2 The arithmetic mean of the average maximum length YA B2 Aspect ratio YA B2 / YA B1 When calculated, The aspect ratio YA CB2 / YA CB1 However, it is greater than 1, and the aspect ratio YA B2 / YA B1 A larger electrolyte membrane. [2] The aspect ratio YA CA2 / YA CA1 and the aspect ratio YA CB2 / YA CB1 The electrolyte membrane described in [1], wherein all of the values ​​are 1.2 or higher. [3] The aspect ratio YA A2 / YA A1 and the aspect ratio YA B2 / YA B1 The electrolyte membrane described in [1] or [2], wherein the values ​​are all between 0.8 and 3.5. [4] The aspect ratio YA A2 / YA A1 The aspect ratio YA CA2 / YA CA1 The ratio of and the aspect ratio YA B2 / YA B1 The aspect ratio YA CB2 / YA CB1 An electrolyte membrane according to any one of items [1] to [3], wherein the ratio of each is 1.2 or greater. [5] The electrolyte membrane according to any one of [1] to [4], wherein both the denier count of yarn A and the denier count of yarn B are 15 to 50. [6] The electrolyte membrane according to any one of [1] to [5], wherein yarn A and yarn B are each independently composed of a material selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyether ether ketone, and polyphenylene sulfide. [7] The electrolyte membrane according to any one of [1] to [6], wherein the density of both thread A and thread B is 70 to 150 threads / inch. [8] The electrolyte membrane according to any one of [1] to [7], wherein the ion exchange group is a sulfonic acid type functional group. [9] The electrolyte membrane according to any one of [1] to [8], wherein the fluorine-containing polymer comprises a unit based on a fluorine-containing olefin and a unit having a sulfonic acid-type functional group and a fluorine atom.

[10] The electrolyte membrane according to [9], wherein the fluorine-containing olefin is a fluoroolefin having 2 to 3 carbon atoms and having one or more fluorine atoms in the molecule.

[11] The electrolyte membrane according to [9] or

[10] , wherein the unit having the sulfonic acid type functional group and the fluorine atom is a unit represented by formula (1). Formula (1) -[CF2-CF(-L-(SO3M) n )]- L is an n+1 valent perfluorohydrocarbon group which may contain an etheric oxygen atom, M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation, and n is 1 or 2.

[12] The electrolyte membrane according to any one of [1] to

[11] , wherein the woven fabric is a heat-pressed woven fabric.

[13] The electrolyte membrane according to any one of [1] to

[12] , wherein the ion exchange capacity of the fluorine-containing polymer is 0.90 milliequivalents / gram dry resin or more.

[14] An electrolytic device comprising an electrolyte membrane as described in any one of items [1] to

[13] .

[15] A redox flow battery comprising an electrolyte membrane as described in any one of items [1] to

[13] . [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an electrolyte membrane that is less prone to pinhole formation when used with a voltage applied for a long period of time in a cell having an anode and a cathode, as well as an electrolytic device and a redox flow battery containing the same. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic partial plan view showing an example of the electrolyte membrane of the present invention. [Figure 2] This is a partial cross-sectional view of the electrolyte membrane in Figure 1, when it is cut along the CA-CA' line. [Figure 3] This is a partial cross-sectional view of the electrolyte membrane in Figure 1, taken along the line A-A'. [Figure 4] Figure 1 is a partial cross-sectional view of the electrolyte membrane when cut along the CB-CB' line. [Figure 5] This is a partial cross-sectional view of the electrolyte membrane in Figure 1, when it is cut along the line B-B'. [Figure 6] This is a magnified partial plan view of a portion of the electrolyte membrane shown in Figure 1. [Figure 7] Figure 6 is a partial cross-sectional view of the electrolyte membrane when it is cut along the line A1-A1'. [Figure 8] Figure 6 is a partial cross-sectional view of the electrolyte membrane when it is cut along the line A2-A2'. [Figure 9] Figure 6 is a partial cross-sectional view of the electrolyte membrane when it is cut along the line B1-B1'. [Figure 10] Figure 6 is a partial cross-sectional view of the electrolyte membrane when it is cut along the line B2-B2'. [Modes for carrying out the invention]

[0010] The following definitions of terms apply throughout this specification and the claims unless otherwise specified. An "ion exchange group" is a group that can exchange at least some of the ions it contains with other ions. Examples include the sulfonic acid type functional group and the carboxylic acid type functional group described below. A "sulfonic acid type functional group" refers to a sulfonic acid group (-SO3H) or a sulfonic acid base (-SO3M). 2 However, M 2 It means an alkali metal or quaternary ammonium cation. A "carboxylic acid-type functional group" refers to a carboxylic acid group (-COOH) or a carboxylic acid base (-COOH). 1 However, M 1 It means an alkali metal or quaternary ammonium cation. 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" refers to groups that can be converted into ion exchange groups through treatments such as hydrolysis or acidification. "A group that can be converted to a sulfonic acid type functional group" refers to a group that can be converted to a sulfonic acid type functional group through treatments such as hydrolysis or acidification. "Groups that can be converted to carboxylic acid-type functional groups" refers to groups that can be converted to carboxylic acid-type functional groups by known treatments such as hydrolysis or acidification.

[0011] In polymers, a "unit" refers to an atomic group derived from one 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.

[0012] A numerical range represented using "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively.

[0013] [Electrolyte membrane] The electrolyte membrane of the present invention comprises a fluorine-containing polymer having ion exchange groups and a woven fabric. The woven fabric is composed of yarn A extending in one direction and yarn B extending in a direction substantially perpendicular to yarn A. Both yarn A and yarn B are made of materials that do not dissolve in an alkaline aqueous solution. Furthermore, the aspect ratio YA is calculated by the method described later. CA2 / YA CA1 The aspect ratio YA is greater than 1 and calculated by the method described below. A2 / YA A1 It is larger than that. Also, the aspect ratio YA calculated by the method described later. CB2 / YA CB1 The aspect ratio YA is greater than 1 and calculated by the method described below. B2 / YA B1 It is larger than that. The electrolyte membrane of the present invention is less prone to pinhole formation when used under prolonged voltage in a cell having an anode and a cathode. Although the detailed reasons for this are not clear, it is presumed to be due to the following reasons. When manufacturing electrolyte membranes containing electrolytes and woven fabric, cleaning treatments such as brushing the surface of the woven fabric may be performed to remove foreign matter adhering to the fabric. When the woven fabric is cleaned in this way, misalignment of the threads constituting the fabric may occur. It is presumed that this causes the electrolyte to swell in areas where the density of the threads has decreased, and that this swelling comes into contact with other components within the cell, resulting in the occurrence of pinholes (holes in the membrane). Here, in the woven fabric contained in the electrolyte of the present invention, aspect ratio YA CA2 / YA CA1 It is greater than 1. Aspect ratio YA CA2 / YA CA1 As explained in the diagram below, this represents the aspect ratio of the cross-section of thread A at the intersection of thread A and thread B, and the aspect ratio YA CA2 / YA CA1 The larger the value, the more the thread A is compressed in the thickness direction at the intersection. Also, aspect ratio YA A2 / YA A1represents the aspect ratio of the cross-section of yarn A at the midpoint between yarns B. In the woven fabric contained in the electrolyte of the present invention, the aspect ratio YA CA2 / YA CA1 is the aspect ratio YA A2 / YA A1 is larger than. As a result, it is considered that yarn A becomes difficult to move by the cleaning treatment, and the occurrence of yarn displacement can be suppressed. As a result, when the electrolyte membrane of the present invention is used by applying a voltage for a long time in a cell having an anode and a cathode, it is presumed that the electrolyte membrane is less likely to swell and the generation of pinholes can be suppressed.

[0014] FIG. 1 is a partial plan view schematically showing an example of the electrolyte membrane of the present invention. The electrolyte membrane 10 has an electrolyte 12 and a woven fabric 14 disposed in the electrolyte 12. The woven fabric 14 includes yarns 14A1, 14A2, 14A3, and 14A4, and yarns 14B1, 14B2, 14B3, and 14B4. The yarns 14A1, 14A2, 14A3, and 14A4 correspond to yarn A constituting the woven fabric 14, and the yarns 14B1, 14B2, 14B3, and 14B4 correspond to yarn B constituting the woven fabric 14.

[0015] FIG. 2 is a partial cross-sectional view showing an example when the electrolyte membrane is cut along the thickness direction so as to pass through the center position of yarn B in the electrolyte membrane in FIG. 1. Specifically, it is a cross-section exposed when the electrolyte membrane 10 is cut along the line CA-CA' in FIG. 1. In the cross-section of the electrolyte membrane 10 in FIG. 2, the electrolyte 12 containing the fluorine-containing polymer (I) and the yarns 14A1, 14A2, 14A3, 14A4, and 14B2 disposed in the electrolyte 12 are exposed.

[0016] The method for calculating the aspect ratio YA CA2 / YA CA1 in the present invention will be described. For each of 10 different cross-sections when the electrolyte membrane is cut along the thickness direction so as to pass through the center position of yarn B in the electrolyte membrane, the maximum length Y of yarn A in the thickness direction of the electrolyte membrane CA1 and the maximum length YCA1 The maximum length Y in the direction orthogonal to the thickness direction of the electrolyte membrane of yarn A that was measured CA2 and are measured. Specifically, in the example of FIG. 2, the electrolyte membrane 10 is cut along the line CA-CA' passing through the center position of the yarn 14B2 in the electrolyte membrane 10. Thereby, a cross-section of the electrolyte membrane 10 as shown in FIG. 2 is exposed. Similarly, the electrolyte membrane 10 is cut at the center position of a yarn B other than the yarn 14B2 (for example, the yarn 14B3) to expose the cross-section of the electrolyte membrane 10. After obtaining cross-sections at 10 different locations in this way, an arbitrary yarn A (the yarn 14A1 in FIG. 2) in each cross-section is selected, and the maximum length Y CA2 and the maximum length Y CA1 and are measured. The 10 maximum lengths Y obtained in this way CA1 are averaged to obtain the average maximum length YA<00001​​​​​​​​​​​​​​​​​​​​​​​​​​The maximum length Y of thread A measured in the direction perpendicular to the thickness direction of the electrolyte membrane. A2 To measure and Specifically, in the example shown in Figure 3, the electrolyte membrane 10 is cut along the line A-A', which is located midway between threads 14B2 and 14B3. This exposes the cross-section of the electrolyte membrane 10 as shown in Figure 3. Similarly, the electrolyte membrane 10 is cut at a location other than the midpoint between threads 14B2 and 14B3 (for example, midway between threads 14B3 and 14B4) to expose the cross-section of the electrolyte membrane 10. After obtaining 10 different cross-sections in this manner, an arbitrary thread A (thread 14A1 in Figure 2) is selected at each cross-section, and the maximum length Y of the selected thread A is determined. A2 and maximum length Y A1 To measure and The maximum length Y of the 10 locations obtained in this way A1 The arithmetic mean of the average maximum length YA A1 The maximum length Y of the 10 locations obtained for this purpose. A2 The arithmetic mean of the average maximum length YA A2 The ratio of the aspect ratio YA A2 / YA A1 Let's assume that.

[0019] Aspect Ratio YA CA2 / YA CA1 The lower limit is greater than 1, and from the viewpoint of superior effects of the present invention, 1.2 or higher is preferred, 1.5 or higher is more preferred, 2.0 or higher is even more preferred, 2.5 or higher is particularly preferred, and 4.0 or higher is most preferred. Aspect Ratio YA CA2 / YA CA1 The upper limit is preferably 7.0 or less, more preferably 6.0 or less, and particularly preferably 5.0 or less, in order to suppress the voltage increase caused by a decrease in the opening ratio of the woven fabric.

[0020] Aspect Ratio YA A2 / YA A1 From the viewpoint of achieving superior effects of the present invention, a value of 0.5 to 3.5 is preferred, 0.8 to 3.5 is more preferred, and 0.8 to 2.0 is particularly preferred.

[0021] Aspect Ratio YAA2 / YA A1 Aspect ratio YA CA2 / YA CA1 The ratio ((YA CA2 / YA CA1 ) / (YA A2 / YA A1 )) is greater than 1 (i.e., aspect ratio YA CA2 / YA CA1 The aspect ratio is YA A2 / YA A1 (greater than) , from the viewpoint of superior effects of the present invention, 1.2 or higher is preferred, 1.4 or higher is more preferred, 1.6 or higher is even more preferred, 2.2 or higher is particularly preferred, and 2.4 or higher is most preferred. The above ratio ((YA CA2 / YA CA1 ) / (YA A2 / YA A1 The upper limit of )) is preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0 or less, in order to suppress the occurrence of current shielding due to excessive flattening of the intersection.

[0022] Average maximum length YA CA2 From the viewpoint of achieving superior effects of the present invention, a particle size of 20 to 160 μm is preferred, 20 to 90 μm is more preferred, and 20 to 80 μm is particularly preferred. Average maximum length YA CA1 From the viewpoint of achieving superior effects of the present invention, a thickness of 10 to 80 μm is preferred, 10 to 60 μm is more preferred, and 10 to 40 μm is particularly preferred. Average maximum length YA A2 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 140 μm is preferred, 20 to 80 μm is more preferred, and 20 to 60 μm is particularly preferred. Average maximum length YA A1 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 80 μm is preferred, 20 to 60 μm is more preferred, and 20 to 40 μm is particularly preferred.

[0023] Figure 4 is a partial cross-sectional view showing an example of what happens when the electrolyte membrane is cut along the thickness direction so as to pass through the center of thread A in Figure 1. Specifically, it is the cross-section exposed when the electrolyte membrane 10 is cut along the CB-CB' line in Figure 1. In the cross-section of the electrolyte membrane 10 in Figure 4, the electrolyte 12 containing the fluorine-containing polymer (I) and the threads 14B1, 14B2, 14B3, 14B4, and 14A1 arranged in the electrolyte 12 are exposed.

[0024] Aspect ratio YA in the present invention CB2 / YA CB1 The calculation method will be explained. For each of the 10 different cross-sections obtained by cutting the electrolyte membrane along the thickness direction of the electrolyte membrane, passing through the center of thread B, the maximum length Y of thread B in the thickness direction of the electrolyte membrane is determined. CB1 And, maximum length Y CB1 The maximum length Y of thread B measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. CB2 To measure and Specifically, in the example in Figure 4, the electrolyte membrane 10 is cut along the CB-CB' line passing through the center of thread 14A1 in the electrolyte membrane. This exposes the cross-section of the electrolyte membrane 10 as shown in Figure 4. Similarly, the electrolyte membrane 10 is cut at the center of thread A other than thread 14A1 (for example, thread 14A2) to expose the cross-section of the electrolyte membrane 10. After obtaining 10 different cross-sections in this way, an arbitrary thread B (thread 14B1 in Figure 4) is selected at each cross-section, and the maximum length Y of the selected thread B is determined. CB2 and maximum length Y CB1 To measure and The maximum length Y of the 10 locations obtained in this way CB1 The arithmetic mean of the average maximum length YA CB1 The maximum length Y of the 10 locations obtained for this purpose. CB2 The arithmetic mean of the average maximum length YA CB2 The ratio of the aspect ratio YA CB2 / YA CB1 Let's assume that.

[0025] Figure 5 is a partial cross-sectional view showing an example of what happens when the electrolyte membrane is cut in the direction parallel to the direction in which the threads A in the electrolyte membrane extend, and at an intermediate point between the threads A, along the thickness direction of the electrolyte membrane. Specifically, it is the cross-section exposed when the electrolyte membrane 10 is cut along the line B-B' in Figure 1. In the cross-section of the electrolyte membrane 10 in Figure 5, the electrolyte 12 containing the fluorine-containing polymer (I) and the threads 14B1, 14B2, 14B3, and 14B4 arranged in the electrolyte 12 are exposed.

[0026] Aspect ratio YA in the present invention B2 / YA B1 The calculation method will be explained. For each of the 10 different cross-sections obtained by cutting the electrolyte membrane along the thickness direction at an intermediate point between threads A in the electrolyte membrane, in a direction parallel to the direction in which thread A extends within the electrolyte membrane, the maximum length Y of thread B in the thickness direction of the electrolyte membrane is determined. B1 And, maximum length Y B1 The maximum length Y of thread B measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. B2 To measure and Specifically, in the example shown in Figure 5, the electrolyte membrane 10 is cut along the line B-B', which is located midway between threads 14A1 and 14A2. This exposes the cross-section of the electrolyte membrane 10 as shown in Figure 5. Similarly, the electrolyte membrane 10 is cut at a location other than the midpoint between threads 14A1 and 14A2 (for example, midway between threads 14A2 and 14A3) to expose the cross-section of the electrolyte membrane 10. After obtaining 10 different cross-sections in this manner, an arbitrary thread B (thread 14B1 in Figure 5) is selected at each cross-section, and the maximum length Y of the selected thread B is determined. B2 and maximum length Y B1 To measure and The maximum length Y of the 10 locations obtained in this way B1 The arithmetic mean of the average maximum length YA B1 The maximum length Y of the 10 locations obtained for this purpose. B2 The arithmetic mean of the average maximum length YA B2 The ratio of the aspect ratio YA B2 / YA B1 Let's assume that.

[0027] Aspect Ratio YA CB2 / YA CB1 The lower limit is greater than 1, and from the viewpoint of superior effects of the present invention, 1.2 or higher is preferred, 1.5 or higher is more preferred, 2.0 or higher is even more preferred, 2.5 or higher is particularly preferred, and 4.0 or higher is most preferred. Aspect Ratio YA CB2 / YA CB1 The upper limit is preferably 7.0 or less, more preferably 6.0 or less, and particularly preferably 5.0 or less, in order to suppress the voltage increase caused by a decrease in the opening ratio of the woven fabric.

[0028] Aspect Ratio YA B2 / YA B1 From the viewpoint of achieving superior effects of the present invention, a value of 0.5 to 3.5 is preferred, 0.8 to 3.5 is more preferred, and 0.8 to 2.0 is particularly preferred.

[0029] Aspect Ratio YA B2 / YA B1 Aspect ratio YA CB2 / YA CB1 The ratio ((YA CB2 / YA CB1 ) / (YA B2 / YA B1 )) is greater than 1 (i.e., aspect ratio YA CB2 / YA CB1 The aspect ratio is YA B2 / YA B1 (greater than) , from the viewpoint of superior effects of the present invention, 1.2 or higher is preferred, 1.4 or higher is more preferred, 1.6 or higher is even more preferred, 2.2 or higher is particularly preferred, and 2.4 or higher is most preferred. The above ratio ((YA CB2 / YA CB1 ) / (YA B2 / YA B1 The upper limit of )) is preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0 or less, in order to suppress the occurrence of current shielding due to excessive flattening of the intersection.

[0030] Average maximum length YA CB2From the viewpoint of achieving superior effects of the present invention, a particle size of 20 to 160 μm is preferred, 20 to 90 μm is more preferred, and 20 to 80 μm is particularly preferred. Average maximum length YA CB1 From the viewpoint of achieving superior effects of the present invention, a thickness of 10 to 80 μm is preferred, 10 to 60 μm is more preferred, and 10 to 40 μm is particularly preferred. Average maximum length Y B2 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 140 μm is preferred, 20 to 80 μm is more preferred, and 20 to 60 μm is particularly preferred. Average maximum length Y B1 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 80 μm is preferred, 20 to 60 μm is more preferred, and 20 to 40 μm is particularly preferred.

[0031] Figure 6 is a magnified partial plan view of a portion of the electrolyte membrane shown in Figure 1. The reference numerals for each component in Figure 6 are the same as those for each component in Figure 1.

[0032] Figure 7 is a partial cross-sectional view showing an example of a cut made along the thickness direction of the electrolyte membrane in Figure 6, parallel to the direction in which the thread B in the electrolyte membrane extends, and at a point where the distance from the end X1 of one thread B closer to the other thread B toward the end Y1 of the other thread B closer to the first thread B is 1 / 4 of the distance between end X1 and end Y1. Specifically, Figure 7 is the cross-section exposed when the electrolyte membrane 10 is cut along the line A1-A1' in Figure 6. In the cross-section of the electrolyte membrane 10 in Figure 7, the electrolyte 12 containing the fluorine-containing polymer (I) and the threads 14A1 and 14A2 arranged in the electrolyte 12 are exposed.

[0033] Next, aspect ratio YA A12 / YA A11 The calculation method will be explained. The maximum length Y of thread A in the thickness direction of the electrolyte membrane is determined for each of 10 different cross-sections obtained by cutting along the thickness direction of the electrolyte membrane at a point where, in a direction parallel to the direction in which thread B extends, and moving from the end X1 of one thread B closer to the other thread B toward the end Y1 of the other thread B closer to the first thread B, the distance is 1 / 4 of the distance between end X1 and end Y1. A11 And, maximum length Y A11 The maximum length Y of thread A measured in the direction perpendicular to the thickness direction of the electrolyte membrane. A12 To measure and Specifically, in the example shown in Figure 7, the electrolyte membrane 10 is cut along the line A1-A1', which is located at a point where a distance equal to 1 / 4 of the distance between ends X1 and Y1 is traveled from end X1 toward end Y1. This exposes the cross-section of the electrolyte membrane 10 as shown in Figure 7. Similarly, the electrolyte membrane 10 is cut at a position other than between threads 14B1 and 14B2 to expose the cross-section of the electrolyte membrane 10. After obtaining 10 different cross-sections in this manner, an arbitrary thread A (thread 14A1 in Figure 7) is selected at each cross-section, and the maximum length Y of the selected thread A is determined. A12 and maximum length Y A11 To measure and The maximum length Y of the 10 locations obtained in this way A11 The arithmetic mean of the average maximum length YA A11 The maximum length Y of the 10 locations obtained for this purpose. A12 The arithmetic mean of the average maximum length YA A12 The ratio of the aspect ratio YA A12 / YA A11 Let's assume that.

[0034] Aspect Ratio YA A12 / YA A11 From the viewpoint of achieving superior effects of the present invention, a value of 0.5 to 3.5 is preferred, and 0.8 to 2.0 is particularly preferred.

[0035] Aspect Ratio YA A12 / YA A11 Aspect ratio YA CA2 / YA CA1 The ratio ((YACA2 / YA CA1 ) / (YA A12 / YA A11 )) is preferably greater than 1, more preferably 1.2 or greater, even more preferably 1.4 or greater, still more preferably 1.6 or greater, particularly preferably 2.2 or greater, and most preferably 2.4 or greater, from the viewpoint of achieving superior effects of the present invention. The above ratio ((YA CA2 / YA CA1 ) / (YA A12 / YA A11 The upper limit of )) is preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0 or less, in order to suppress the occurrence of current shielding due to excessive flattening of the intersection. Average maximum length YA A12 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 140 μm is preferred, 20 to 80 μm is more preferred, and 20 to 60 μm is particularly preferred. Average maximum length YA A11 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 80 μm is preferred, 20 to 60 μm is more preferred, and 20 to 40 μm is particularly preferred.

[0036] Figure 8 is a partial cross-sectional view showing an example of a cut made along the thickness direction of the electrolyte membrane in Figure 6, in a direction parallel to the direction in which the thread B in the electrolyte membrane extends, and at a point where the distance from the end X1 of one thread B closer to the other thread B toward the end Y1 of the other thread B closer to the first thread B is 3 / 4 of the distance between end X1 and end Y1. Specifically, Figure 8 is the cross-section exposed when the electrolyte membrane 10 is cut along the line A2-A2' in Figure 6. In the cross-section of the electrolyte membrane 10 in Figure 8, the electrolyte 12 containing the fluorine-containing polymer (I) and the threads 14A1 and 14A2 arranged in the electrolyte 12 are exposed.

[0037] Next, aspect ratio YA A22 / YA A21 The calculation method will be explained. The maximum length Y of thread A in the thickness direction of the electrolyte membrane is determined for each of 10 different cross-sections obtained by cutting along the thickness direction of the electrolyte membrane at a point where, in a direction parallel to the direction in which thread B extends within the electrolyte membrane, and moving from the end X1 of one thread B closer to the other thread B toward the end Y1 of the other thread B closer to the first thread B, the distance is 3 / 4 of the distance between end X1 and end Y1. A21 And, maximum length Y A21 The maximum length Y of thread A measured in the direction perpendicular to the thickness direction of the electrolyte membrane. A22 To measure and Specifically, in the example shown in Figure 8, the electrolyte membrane 10 is cut along the line A2-A2', which is located at a point where a distance equal to 3 / 4 of the distance between ends X1 and Y1 is traveled from end X1 toward end Y1. This exposes the cross-section of the electrolyte membrane 10 as shown in Figure 8. Similarly, the electrolyte membrane 10 is cut at a position other than between threads 14B1 and 14B2 to expose the cross-section of the electrolyte membrane 10. After obtaining 10 different cross-sections in this manner, an arbitrary thread A (thread 14A1 in Figure 8) is selected at each cross-section, and the maximum length Y of the selected thread A is determined. A22 and maximum length Y A21 To measure and The maximum length Y of the 10 locations obtained in this way A21 The arithmetic mean of the average maximum length YA A21 The maximum length Y of the 10 locations obtained for this purpose. A22 The arithmetic mean of the average maximum length YA A22 The ratio of the aspect ratio YA A22 / YA A21 Let's assume that.

[0038] Aspect Ratio YA A22 / YA A21 From the viewpoint of achieving superior effects of the present invention, a value of 0.5 to 3.5 is preferred, and 0.8 to 2.0 is particularly preferred.

[0039] Aspect Ratio YA A22 / YA A21 Aspect ratio YA CA2 / YA CA1 The ratio ((YACA2 / YA CA1 ) / (YA A22 / YA A21 )) is preferably greater than 1, more preferably 1.2 or greater, even more preferably 1.4 or greater, still more preferably 1.6 or greater, particularly preferably 2.2 or greater, and most preferably 2.4 or greater, from the viewpoint of achieving superior effects of the present invention. The above ratio ((YA CA2 / YA CA1 ) / (YA A22 / YA A21 The upper limit of )) is preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0 or less, in order to suppress the occurrence of current shielding due to excessive flattening of the intersection. Average maximum length YA A22 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 140 μm is preferred, 20 to 80 μm is more preferred, and 20 to 60 μm is particularly preferred. Average maximum length YA A21 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 80 μm is preferred, 20 to 60 μm is more preferred, and 20 to 40 μm is particularly preferred.

[0040] Figure 9 is a partial cross-sectional view showing an example of a cut made along the thickness direction of the electrolyte membrane in Figure 6, in a direction parallel to the direction in which the thread A in the electrolyte membrane extends, and at a point where the distance from the end X2 of one thread A closer to the other thread A toward the end Y2 of the other thread A closer to the first thread A is 1 / 4 of the distance between end X2 and end Y2. Specifically, Figure 9 is the cross-section exposed when the electrolyte membrane 10 is cut along the line B1-B1' in Figure 6. In the cross-section of the electrolyte membrane 10 in Figure 9, the electrolyte 12 containing the fluorine-containing polymer (I) and the threads 14B1 and 14B2 arranged in the electrolyte 12 are exposed.

[0041] Next, aspect ratio YA B12 / YA B11 The calculation method will be explained. The maximum length Y of thread B in the thickness direction of the electrolyte membrane is determined for each of 10 different cross-sections obtained by cutting along the thickness direction of the electrolyte membrane at a point where, in a direction parallel to the direction in which thread A extends within the electrolyte membrane, and at a point where, for two adjacent threads A, the distance traveled from the end X2 of one thread A closer to the other thread A toward the end Y2 of the other thread A is 1 / 4 of the distance between end X2 and end Y2. B11 And, maximum length Y B11 The maximum length Y of thread B measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. B12 To measure and Specifically, in the example in Figure 9, the electrolyte membrane 10 is cut along the line B1-B1', which is located at a point where a distance equal to 1 / 4 of the distance between ends X2 and Y2 is traveled from end X2 toward end Y2. This exposes the cross-section of the electrolyte membrane 10 as shown in Figure 9. Similarly, the electrolyte membrane 10 is cut at a position other than between threads 14A1 and 14A2 to expose the cross-section of the electrolyte membrane 10. After obtaining 10 different cross-sections in this manner, an arbitrary thread B (thread 14B1 in Figure 9) is selected at each cross-section, and the maximum length Y of the selected thread B is determined. B12 and maximum length Y B11 To measure and The maximum length Y of the 10 locations obtained in this way B11 The arithmetic mean of the average maximum length YA B11 The maximum length Y of the 10 locations obtained for this purpose. B12 The arithmetic mean of the average maximum length YA B12 The ratio of the aspect ratio YA B12 / YA B11 Let's assume that.

[0042] Aspect Ratio YA B12 / YA B11 From the viewpoint of achieving superior effects of the present invention, a value of 0.5 to 3.5 is preferred, and 0.8 to 2.0 is particularly preferred.

[0043] Aspect Ratio YA B12 / YA B11 Aspect ratio YA CB2 / YA CB1 The ratio ((YACB2 / YA CB1 ) / (YA B12 / YA B11 )) is preferably greater than 1, more preferably 1.2 or greater, even more preferably 1.4 or greater, still more preferably 1.6 or greater, particularly preferably 2.2 or greater, and most preferably 2.4 or greater, from the viewpoint of achieving superior effects of the present invention. The above ratio ((YA CB2 / YA CB1 ) / (YA B12 / YA B11 The upper limit of )) is preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0 or less, in order to suppress the occurrence of current shielding due to excessive flattening of the intersection. Average maximum length YA B12 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 140 μm is preferred, 20 to 80 μm is more preferred, and 20 to 60 μm is particularly preferred. Average maximum length YA B11 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 80 μm is preferred, 20 to 60 μm is more preferred, and 20 to 40 μm is particularly preferred.

[0044] Figure 10 is a partial cross-sectional view showing an example of a cut made along the thickness direction of the electrolyte membrane in Figure 6, parallel to the direction in which the thread A in the electrolyte membrane extends, and at a point where a distance equal to 3 / 4 of the distance between ends X2 and Y2 is traveled from the end X2 of one thread A closer to the other thread A toward the end Y2 of the other thread A closer to the first thread A. Specifically, Figure 10 is the cross-section exposed when the electrolyte membrane 10 is cut along the line B2-B2' in Figure 6. In the cross-section of the electrolyte membrane 10 in Figure 10, the electrolyte 12 containing the fluorine-containing polymer (I) and the threads 14B1 and 14B2 arranged in the electrolyte 12 are exposed.

[0045] Next, aspect ratio YA B22 / YA B21 The calculation method will be explained. The maximum length Y of thread B in the thickness direction of the electrolyte membrane is determined for each of 10 different cross-sections obtained when cutting along the thickness direction of the electrolyte membrane at a point where, in a direction parallel to the direction in which thread A extends within the electrolyte membrane, and at a point where, for two adjacent threads A, the distance traveled from the end X2 of one thread A closer to the other thread A toward the end Y2 of the other thread A is 3 / 4 of the distance between end X2 and end Y2. B21 And, maximum length Y B21 The maximum length Y of thread B measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. B22 To measure and Specifically, in the example shown in Figure 10, the electrolyte membrane 10 is cut along the line B2-B2', which is located at a point where a distance equal to 3 / 4 of the distance between ends X2 and Y2 is traveled from end X2 toward end Y2. This exposes the cross-section of the electrolyte membrane 10 as shown in Figure 10. Similarly, the electrolyte membrane 10 is cut at a position other than between threads 14A1 and 14A2 to expose the cross-section of the electrolyte membrane 10. After obtaining 10 different cross-sections in this manner, an arbitrary thread B (thread 14B1 in Figure 10) is selected at each cross-section, and the maximum length Y is determined for each cross-section of the selected thread B. B22 and maximum length Y B21 To measure and The maximum length Y of the 10 locations obtained in this way B21 The arithmetic mean of the average maximum length YA B21 The maximum length Y of the 10 locations obtained for this purpose. B22 The arithmetic mean of the average maximum length YA B22 The ratio of the aspect ratio YA B22 / YA B21 Let's assume that.

[0046] Aspect Ratio YA B22 / YA B21 From the viewpoint of achieving superior effects of the present invention, a value of 0.5 to 3.5 is preferred, and 0.8 to 2.0 is particularly preferred.

[0047] Aspect Ratio YA B22 / YA B21 Aspect ratio YA CB2 / YA CB1 The ratio ((YACB2 / YA CB1 ) / (YA B22 / YA B21 )) is preferably greater than 1, more preferably 1.2 or greater, even more preferably 1.4 or greater, still more preferably 1.6 or greater, particularly preferably 2.2 or greater, and most preferably 2.4 or greater, from the viewpoint of achieving superior effects of the present invention. The above ratio ((YA CB2 / YA CB1 ) / (YA B22 / YA B21 The upper limit of )) is preferably 4.0 or less, more preferably 3.5 or less, and particularly preferably 3.0 or less, in order to suppress the occurrence of current shielding due to excessive flattening of the intersection. Average maximum length YA B22 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 140 μm is preferred, 20 to 80 μm is more preferred, and 20 to 60 μm is particularly preferred. Average maximum length YA B21 From the viewpoint of achieving superior effects of the present invention, a thickness of 20 to 80 μm is preferred, 20 to 60 μm is more preferred, and 20 to 40 μm is particularly preferred.

[0048] The maximum lengths of threads A and B described above are measured using magnified images (e.g., 100x magnification) of the cross-section of the electrolyte membrane taken with an optical microscope (product name "BX-51", manufactured by Olympus Corporation).

[0049] One method, though not limited to the above, for achieving the aforementioned aspect ratios is to heat-press the woven fabric. This makes the intersection of thread A and thread B more easily compressed in the thickness direction compared to the rest of the fabric. Therefore, the aspect ratios can be adjusted to the aforementioned values.

[0050] The thickness of the electrolyte membrane is preferably 30 to 400 μm, more preferably 30 to 300 μm, even more preferably 30 to 200 μm, particularly preferably 30 to 90 μm, and most preferably 30 to 60 μm. The thickness of the electrolyte membrane is measured using a magnified image (e.g., 100x magnification) of the cross-section of the electrolyte membrane taken with an optical microscope (product name "BX-51", manufactured by Olympus Corporation). If the surface of the electrolyte membrane has irregularities, the thickness of 10 recessed points and the thickness of 10 raised points on the electrolyte membrane are measured, and the arithmetic mean of the total thickness of 20 points is taken as the thickness of the electrolyte membrane. However, if the raised portion contains thread A or thread B as described above, the thickness of the raised portion is the value obtained by subtracting the thickness of the thread present in the raised portion.

[0051] <Woven fabric> The opening ratio of the woven fabric is preferably 50% or more, more preferably 55% or more, even more preferably 60% or more, and particularly preferably 70% or more, as this allows for a further reduction in the electrolytic voltage when the electrolyte membrane is applied to various devices. The upper limit of the opening ratio of the woven fabric is preferably 90% or less, and particularly preferably 80% or less, in that it provides superior strength to the electrolyte membrane. The opening ratio of a woven fabric is calculated using the following formula (ε), based on the average diameter R1 of the yarn and the average spacing P1 between adjacent yarns (hereinafter also referred to as "pitch P1"). Here, the average thread diameter R1 refers to the arithmetic mean of the diameters of 10 different threads arbitrarily selected based on a magnified image (e.g., 100x) of the woven fabric surface obtained using a microscope. The pitch P1 refers to the arithmetic mean of the intervals between 10 different points arbitrarily selected based on a magnified image (e.g., 100x) of the woven fabric surface obtained using a microscope. Opening ratio of woven fabric (%) = [P1 / (P1+R1)] 2 ×100 (ε)

[0052] The denier counts of yarn A and yarn B constituting the woven fabric are preferably 2 or higher, more preferably 10 or higher, even more preferably 15 or higher, and particularly preferably 20 or higher, in terms of superior strength and dimensional stability of the electrolyte membrane. The denier counts of yarn A and yarn B may be the same or different. The upper limits for the denier count of yarn A and yarn B constituting the woven fabric are preferably 150 or less, more preferably 120 or less, even more preferably 90 or less, particularly preferably 60 or less, and most preferably 50 or less, in order to further reduce the electrolytic voltage when the electrolyte membrane is applied to various devices. The denier count is the mass of 9000 meters of yarn expressed in grams (g / 9000m).

[0053] The density of both thread A and thread B is preferably 50 threads / inch or more, more preferably 70 threads / inch or more, and particularly preferably 90 threads / inch or more, in terms of excellent strength and dimensional stability of the membrane electrode assembly. In terms of further reducing the electrolytic voltage when the electrolyte membrane is applied to various devices, it is preferably 200 threads / inch or less, more preferably 150 threads / inch or less, and particularly preferably 100 threads / inch or less. Note that the densities of thread A and thread B may be the same or different.

[0054] Threads A and B may consist of either a monofilament made of one filament or a multifilament made of two or more filaments, with monofilaments being preferred.

[0055] Both thread A and thread B are made of materials that do not dissolve in alkaline aqueous solutions; specifically, they are threads made of materials that do not dissolve even when immersed in a 32% by mass sodium hydroxide aqueous solution. Yarn A and yarn B are preferably each independently composed of a material selected from the group consisting of polytetrafluoroethylene (hereinafter also referred to as "PTFE"), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter also referred to as "PFA"), polyether ether ketone (hereinafter also referred to as "PEEK"), and polyphenylene sulfide (hereinafter also referred to as "PPS"), in order to have superior yarn durability. Slit yarns may be used for yarns A and B, but if slit yarns are used, it is preferable to use twisted yarns.

[0056] In the woven fabric, threads A and B are approximately perpendicular. "Approximately perpendicular" means that the angle between threads A and B is 90 ± 10 degrees. Thread A may be either a warp thread or a weft thread in a woven fabric, but if thread A is a weft thread, then thread B is a warp thread, and if thread A is a warp thread, then thread B is a weft thread.

[0057] When the material constituting the woven fabric is PTFE, the basis weight of the fabric should be 20-40 g / m², as this strikes an excellent balance between the strength of the electrolyte membrane and its ease of handling. 2 Preferably, 30-40 g / m 2 That is particularly preferable. When the material constituting the woven fabric is PFA, the basis weight of the fabric should be 10-30 g / m², as this offers an excellent balance between the strength and handling properties of the electrolyte membrane. 2 Preferably, 15-25 g / m 2 That is particularly preferable. When the material constituting the woven fabric is PEEK, the basis weight of the fabric should be 5-40 g / m², as this offers an excellent balance between the strength and handling properties of the electrolyte membrane. 2 Preferably, 5-30 g / m 2 That is particularly preferable. When the material constituting the woven fabric is PPS, the basis weight of the woven fabric should be between 5 and 40 g / m², as this provides an excellent balance between the strength and handling properties of the electrolyte membrane. 2 Preferably, 5-30 g / m 2 That is particularly preferable.

[0058] <Electrolyte> The electrolyte contains a fluorine-containing polymer (I). The ion exchange capacity of the fluorine-containing polymer (I) is preferably 0.90 milliequivalents / gram dry resin or higher, more preferably greater than 1.10 milliequivalents / gram dry resin, even more preferably 1.15 milliequivalents / gram dry resin or higher, particularly preferably 1.20 milliequivalents / gram dry resin or higher, and most preferably 1.25 milliequivalents / gram dry resin or higher, as this allows for a greater reduction in the electrolytic voltage when an electrolyte membrane is applied to various devices. The upper limit of the ion exchange capacity of the fluorine-containing polymer (I) is preferably 2.00 milliequivalents / gram dry resin or less, more preferably 1.50 milliequivalents / gram dry resin or less, and particularly preferably 1.43 milliequivalents / gram dry resin or less, in order to minimize the swelling of the electrolyte in areas where the density of the thread is low.

[0059] The fluorine-containing polymer (I) used in the electrolyte membrane may be a single type, or two or more types may be used in a laminated or mixed form. The electrolyte membrane may contain polymers other than fluorine-containing polymer (I), but it is preferable that the polymers in the 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 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 electrolyte membrane. Specific examples of polymers other than fluorine-containing polymers (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 the electrolyte membrane, other polymers that can be mentioned include polyphenylene sulfide resin and polyphenylene ether resin.

[0060] The fluorine-containing polymer (I) has ion exchange groups. Specific examples of ion exchange groups 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 electrolytic voltage when an electrolyte membrane is applied to various devices. The following will mainly describe in detail the embodiments of fluorine-containing polymers having sulfonic acid-type functional groups (hereinafter also referred to as "fluorine-containing polymers (S)").

[0061] The fluorine-containing polymer (S) preferably contains units based on fluorine-containing olefins and units having sulfonic acid-type functional groups and fluorine atoms. Examples of fluorine-containing olefins include fluoroolefins with 2 to 3 carbon atoms and one or more fluorine atoms in the molecule. Specific examples of fluoroolefins include tetrafluoroethylene (hereinafter also referred to as "TFE"), chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and hexafluoropropylene. Among these, TFE is preferred due to its superior monomer production cost, reactivity with other monomers, and the characteristics of the resulting fluorine-containing polymer (S). Fluorine-containing olefins may be used individually or in combination of two or more types.

[0062] As a unit having a sulfonic acid-type functional group and a fluorine atom, the unit represented by formula (1) is preferred. Formula (1) -[CF2-CF(-L-(SO3M) n )]-

[0063] 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, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.

[0064] As L, an n+1 valent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom is preferred, and in the n=1 embodiment, a divalent perfluoroalkylene group which may contain an etheric oxygen atom, or in the n=2 embodiment, a trivalent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom, is particularly preferred. The above-mentioned divalent perfluoroalkylene group may be in either a linear or branched chain configuration.

[0065] M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation. n is either 1 or 2.

[0066] The units represented by formula (1) are preferably those represented by formula (1-1), formula (1-2), formula (1-3), or formula (1-4). Equation (1-1) -[CF2-CF(-OR f1 -SO3M)]- Equation (1-2) -[CF2-CF(-R f1 -SO3M)]-

[0067] [ka]

[0068] [ka]

[0069] R f1 This is a perfluoroalkylene group which may contain an oxygen atom between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.

[0070] R f2This is a perfluoroalkylene group which may contain a single bond or an oxygen atom between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.

[0071] R f3 This is a perfluoroalkylene group which may contain a single bond or an oxygen atom between carbon atoms. The number of carbon atoms in the above perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, preferably 20 or less, and particularly preferably 10 or less.

[0072] r is either 0 or 1. m is either 0 or 1. M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation.

[0073] The units represented by formula (1-1) and formula (1-2) are more preferably those represented by formula (1-5). Equation (1-5) -[CF2-CF(-(CF2) x -(OCF2CFY) y -O-(CF2) z -SO3M)]- x is 0 or 1, y is an integer between 0 and 2, z is an integer between 1 and 4, and Y is either F or CF3. M is as described above.

[0074] 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. -[CF2-CF(-O-(CF2) w -SO3M)]- -[CF2-CF(-O-CF2CF(CF3)-O-(CF2) w -SO3M)]- -[CF2-CF(-(O-CF2CF(CF3)) x -SO3M)]-

[0075] The following are specific examples of units represented by equation (1-2). w in the equation is an integer between 1 and 8. The definition of M in the equation is as described above. -[CF2-CF(-(CF2) w -SO3M)]- -[CF2-CF(-CF2-O-(CF2) w -SO3M)]-

[0076] 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.

[0077] [ka]

[0078] R f4 R is a linear perfluoroalkylene group having 1 to 6 carbon atoms, f5 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.

[0079] The following are specific examples of units represented by equation (1-3-1):

[0080] [ka]

[0081] The unit represented by formula (1-4) is preferably the unit represented by formula (1-4-1). f1 , R f2 The definitions of M and other factors are as described above.

[0082] [ka]

[0083] The following are specific examples of units represented by equation (1-4-1):

[0084] [Chemical]

[0085] The units having a sulfonic acid type functional group and a fluorine atom may be used alone or in combination of two or more.

[0086] 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 a sulfonic acid type functional group and a fluorine atom. Specific examples of other monomers include CF2=CFR f6 (where R f6 is a perfluoroalkyl group having 2 to 10 carbon atoms.), CF2=CF-OR f7 (where R f7 is a perfluoroalkyl group having 1 to 10 carbon atoms.), CF2=CFO(CF2) v CF=CF2 (where v is an integer of 1 to 3). From the viewpoint of maintaining ion exchange performance, the content of the units based on other monomers is preferably 30% by mass or less based on all the units in the fluorine-containing polymer (I).

[0087] The electrolyte membrane may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, for example, there is a mode in which a plurality of layers containing the fluorine-containing polymer (I) and having different ion exchange capacities are laminated.

[0088] <Method for producing electrolyte membrane> As a method for producing an electrolyte membrane, a film containing a fluorine-containing monomer having a group that can be converted into an ion exchange group (hereinafter also referred to as a fluorine-containing monomer (I')) (hereinafter also referred to as a "fluorine-containing polymer (I')") and a woven fabric (hereinafter also referred to as a "precursor membrane") is produced, and then a group that can be converted into an ion exchange group in the precursor membrane is converted into an ion exchange group for production.

[0089] The form of the woven fabric is as described above. It is preferable to use a heat-pressed woven fabric. This makes it easier to adjust each aspect ratio to the values ​​described above.

[0090] As the fluorine-containing polymer (I'), a polymer of a fluorine-containing monomer having a group that can be converted to a sulfonic acid-type functional group (hereinafter also referred to as "fluorine-containing polymer (S')") is preferred, and a copolymer polymer of a fluorine-containing olefin and a monomer having a group that can be converted to a sulfonic acid-type functional group and a fluorine atom is particularly preferred. The following provides a detailed explanation of fluorine-containing polymers (S').

[0091] Methods for copolymerizing fluorine-containing polymers (S') can include known methods such as solution polymerization, suspension polymerization, and emulsion polymerization.

[0092] 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 (S). Fluorine-containing olefins may be used individually or in combination of two or more types.

[0093] Examples of fluorine-containing monomers (S') include compounds that have one or more fluorine atoms in the molecule, have an ethylenically active double bond, and have a group that can be converted to a sulfonic acid-type functional group. As the fluorine-containing monomer (S'), the compound represented by formula (2) is preferred due to its superior manufacturing cost, reactivity with other monomers, and the characteristics of the resulting fluorine-containing polymer (S). Equation (2) CF2 = CF - L - (A) n The definitions of L and n in equation (2) are as described above. A is a group that can be converted to a sulfonic acid type functional group. Preferably, the group can be converted to a sulfonic acid type functional group by hydrolysis. Specific examples of groups that can be converted to a sulfonic acid type functional group include -SO2F, -SO2Cl, and -SO2Br.

[0094] The compounds represented by formula (2) are preferably those represented by formula (2-1), formula (2-2), formula (2-3), and formula (2-4). Equation (2-1) CF2 = CF - OR f1 -A Equation (2-2) CF2 = CF - R f1 -A

[0095] [ka]

[0096] R in the formula f1 , R f2 The definitions of r and A are as described above.

[0097] [ka]

[0098] R in the formula f1 , R f2 , R f3 The definitions of r, m, and A are as described above.

[0099] The compound represented by formula (2-1) and, more preferably, the compound represented by formula (2-5). Equation (2-5) CF2 = CF - (CF2) x -(OCF2CFY) y -O-(CF2) z -SO3 M The definitions of M, x, y, z, and Y in the formula are as described above.

[0100] Specific examples of the compound 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. CF2=CF-O-(CF2) w -SO2F CF2=CF-O-CF2CF(CF3)-O-(CF2) w -SO2F CF2=CF-[O-CF2CF(CF3)] x -SO2F

[0101] Specific examples of the compound represented by formula (2-2) include the following compounds. In the formula, w is an integer from 1 to 8. CF2=CF-(CF2) w -SO2F CF2=CF-CF2-O-(CF2) w -SO2F

[0102] As the compound represented by formula (2-3), the compound represented by formula (2-3-1) is preferred.

[0103]

Chemical formula

[0104] ]>R in the formula f4 、R f5 、r and the definition of A are as described above.

[0105] Specific examples of the compound represented by formula (2-3-1) include the following.

[0106]

Chemical formula

[0107] As the compound represented by formula (2-4), the compound represented by formula (2-4-1) is preferred.

[0108]

Chemical formula

[0109] R in the formula f1 , R f2 The definition of A is as described above.

[0110] Specific examples of compounds represented by formula (2-4-1) include the following:

[0111] [ka]

[0112] Fluorine-containing monomers (S') may be used individually or in combination of two or more. In addition to fluorine-containing olefins and fluorine-containing monomers (S'), other monomers may also be used in the production of fluorine-containing polymers (S'). Examples of other monomers include those exemplified above.

[0113] The ion exchange capacity of the fluorine-containing polymer (I') can be adjusted by changing the content of groups that can be converted into ion exchange groups in the fluorine-containing polymer (I').

[0114] A specific example of a method for manufacturing a precursor film is the extrusion method. More specifically, a film (I') made of a fluorine-containing polymer (I') is formed, and then the film (I'), woven fabric, and film (I') are arranged in that order and stacked using a lamination roll or a vacuum lamination apparatus.

[0115] 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 treatment or acidification treatment. Among these methods, the method of contacting the precursor film with an alkaline aqueous solution is preferred.

[0116] 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. The temperature of the alkaline aqueous solution is preferably 30 to 100°C, and particularly preferably 40 to 100°C. The contact time between the precursor film and the alkaline aqueous solution is preferably 3 to 150 minutes, and particularly preferably 5 to 50 minutes.

[0117] 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. Specifically, an organic solvent with a solubility of 0.1 g or more in 1000 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. Water-soluble organic solvents may be used individually or in combination of two or more types.

[0118] 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.

[0119] The concentration of alkali metal hydroxide in the alkaline aqueous solution is preferably 1 to 60% by mass, and particularly preferably 3 to 55% by mass. The content of the water-soluble organic solvent is preferably 1 to 60% by mass, and particularly preferably 3 to 55% by mass, in the alkaline aqueous solution. The water concentration is preferably 39-80% by mass in the alkaline aqueous solution.

[0120] 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.

[0121] After contacting the precursor film with an alkaline aqueous solution, the resulting film 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 bringing a precursor film into contact with an acidic aqueous solution include immersing the precursor film in an acidic aqueous solution and spraying the acidic aqueous solution onto the surface of the precursor film. An acidic aqueous solution preferably contains an acidic component and water. Specific examples of acidic components include hydrochloric acid and sulfuric acid.

[0122] <Application> The electrolyte membrane of the present invention can be used as an electrolyte membrane in water electrolysis devices (for example, a diaphragm in an alkali chloride electrolysis device, or a solid polymer electrolyte membrane in a solid polymer water electrolysis device), or as a cation exchange membrane in a redox flow battery.

[0123] [Electrolyzer] The electrolytic apparatus of the present invention includes the electrolyte membrane described above. Because the electrolytic apparatus of the present invention includes the electrolyte membrane described above, the occurrence of pinholes in the electrolyte membrane can be suppressed. This makes it possible to reduce the electrolysis voltage. Specific examples of electrolytic devices include alkali chloride electrolytic devices and polymer electrolyte water electrolytic devices. The electrolytic device of the present invention can have the same configuration as known electrolytic devices, except that it has the electrolyte membrane described above.

[0124] [Redox flow battery] The redox flow battery of the present invention includes the electrolyte membrane described above. Because the redox flow battery of the present invention includes the electrolyte membrane described above, the occurrence of pinholes in the electrolyte membrane can be suppressed. This makes it possible to reduce the movement of the positive and negative electrode liquids and prevent a decrease in the capacity retention rate. The redox flow battery of the present invention may have the same configuration as known redox flow batteries, except that it has the electrolyte membrane described above. [Examples]

[0125] The present invention will be described in detail below with reference to examples. Examples 1 to 4 are examples, and Examples 5 to 6 are comparative examples. However, the present invention is not limited to these examples.

[0126] [Aspect Ratio] Aspect ratio YA of woven fabric in electrolyte membrane CA2 / YA CA1 Aspect ratio YA A2 / YA A1 , (YA CA2 / YA CA1 ) / (YA A2 / YA A1 ), aspect ratio YA CB2 / YA CB1 Aspect ratio YA B2 / YA B1 , (YA CB2 / YA CB1 ) / (YA B2 / YA B1 The value was calculated according to the method described in the section on the electrolyte membrane above.

[0127] [Fabric weight] The woven fabric roll used was cut into 20 x 20 cm pieces, and its mass was measured. The above measurement was performed five times, and the basis weight (g / m²) of the woven fabric was determined based on the average value. 2 ) was sought.

[0128] [Density of warp and weft threads that make up the fabric] The density of the warp and weft threads constituting the woven fabric was calculated according to the following method: For both the warp and weft threads, the average value of the length of 10 threads measured five times from observations using an optical microscope was converted to density (threads / inch).

[0129] [Number of pinholes after electrolytic evaluation] A polymer (ion exchange capacity: 1.10 milliequivalents / gram dry resin) was obtained by copolymerizing TFE with monomer (X) described later, and then hydrolyzing and acid treatment to obtain an acidic polymer. This polymer was dispersed in a water / ethanol = 40 / 60 (mass%) solvent at a solid content concentration of 25.8% to obtain a dispersion (hereinafter also referred to as "dispersion X"). To the obtained dispersion X (19.0 g), ethanol (0.52 g) and water (3.34 g) were added, and then iridium oxide catalyst (manufactured by Tanaka Kikinzoku Co., Ltd.) containing 76 mass% iridium in the dispersion (13.0 g) was added. The resulting mixture was treated with a planetary bead mill (rotation speed 300 rpm) for 30 minutes, then water (4.49 g) and ethanol (4.53 g) were added, and the mixture was further treated with a planetary bead mill (rotation speed 200 rpm) for 60 minutes to obtain an anode catalyst ink with a solid content concentration of 40 mass%. On one surface of the solid polymer electrolyte membrane obtained by the procedure described later, an anode catalyst ink containing iridium at a concentration of 2.0 mg / cm³ is applied. 2 The film was coated using a bar coater, dried at 80°C for 10 minutes, and then heat-treated at 150°C for 15 minutes to obtain an electrolyte film with an anode catalyst layer.

[0130] 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 (29.2g) was added, which consisted of dispersion X (20.1g), ethanol (11g), and Zeolora-H (manufactured by Zeon Corporation) (6.3g), all of which had been pre-mixed and kneaded. Furthermore, water (3.66g) and ethanol (7.63g) were added to the resulting dispersion, and the mixture was mixed for 60 minutes using paint conditioner to obtain a cathode catalyst ink with a solid content concentration of 10.0% by mass. A 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, resulting in a platinum content of 0.4 mg / cm³. 2 A cathode catalyst layer decal was obtained.

[0131] The electrolyte membrane with the anode catalyst layer is placed with the side without the anode catalyst layer facing the side of the cathode catalyst layer decal that has the catalyst layer. The membrane is heated and pressed at a press temperature of 150°C for 2 minutes at a pressure of 3 MPa to bond the electrolyte membrane with the anode catalyst layer and the cathode catalyst layer. After the temperature is lowered to 70°C, the pressure is released and the membrane is removed. The ETFE sheet of the cathode catalyst layer decal is peeled off, resulting in an electrode area of ​​25 cm². 2 A film electrode assembly was obtained.

[0132] The membrane electrode assembly obtained using the above procedure was heat-treated at 150°C for 15 minutes, and then set in the water electrolysis evaluation jig EH50-25 (manufactured by Greenlight Innovation). Next, to ensure the solid polymer electrolyte membrane and both electrode ionomers were sufficiently hydrated, pure water with a conductivity of 1.0 μS / cm or less, at a temperature of 80°C and atmospheric pressure, was supplied to both the anode and cathode sides at a flow rate of 50 mL / min for 12 hours. After that, the cathode side was purged with nitrogen. After nitrogen purging, pure water with a conductivity of 1.0 μS / cm or less, at a temperature of 80°C and atmospheric pressure, is supplied to the anode side at a flow rate of 50 mL / min. The generated gas pressure on the cathode side is maintained at atmospheric pressure, and a current density of 2 A / cm² is supplied by a Kikusui Electronics PWR1600L DC power supply. 2 It ran for 300 hours. After operation, the number of pinholes (holes) in the solid polymer electrolyte membrane of the membrane electrode assembly was measured using a pinhole inspection device (product name "TRS-70", manufactured by Sanko Electronics Laboratory Co., Ltd.). ◎: There were no pinholes. ○: There were 1-2 pinholes. ×: There were three or more pinholes.

[0133] [Production of fluorine-containing polymer (S'-1)] CF2=CF2 was copolymerized with a monomer (X) represented by the following formula (X) to obtain a fluorine-containing polymer (S'-1) (ion exchange capacity: 1.25 milliequivalents / gram dry resin). CF2=CF-O-CF2CF(CF3)-O-CF2CF2-SO2F ···(X)

[0134] The ion exchange capacity described in the above section [Production of Fluorine-containing Polymer (S'-1)] represents the ion exchange capacity of the fluorine-containing polymer obtained when fluorine-containing polymer (S'-1) is hydrolyzed according to the procedure described later.

[0135] [Manufacturing of film-coated substrate Y1] A film-coated substrate Y1 was obtained by attaching a fluorine-containing polymer (S'-1) to a substrate made of polyethylene terephthalate film (melting point: 250-260°C) using a melt extrusion method, thereby forming a film α1 (film thickness: 45 μm) made of the fluorine-containing polymer (S'-1) on the substrate.

[0136] [Manufacturing of film-coated substrate Y2] A film-coated substrate Y2 was obtained in which a fluorine-containing polymer (S'-1) was attached to a substrate made of polyethylene terephthalate film (melting point: 250-260°C) by melt extrusion, thereby forming a film α2 (film thickness: 30 μm) made of fluorine-containing polymer (S'-1) on the substrate.

[0137] [Manufacturing of woven fabric A1-1] Fabric A1 was obtained by plain weaving 24.2 denier PFA yarn for both the warp and weft, with a PFA yarn density of 100 threads / inch. The basis weight of fabric A1 was 21.2 g / m². 2 Furthermore, the warp and weft threads were composed of monofilaments. Woven fabric A1, temperature: 160℃, surface pressure: 30MPa / m 2 Woven fabric A1-1 was obtained by heating and pressing it for 10 minutes in a flat plate press.

[0138] [Manufacturing of woven fabric A1-2] The woven fabric A1 described above was subjected to the following conditions: temperature: 160°C, surface pressure: 40 MPa / m² 2 Woven fabric A1-2 was obtained by heating and pressing it for 10 minutes in a flat plate press.

[0139] [Manufacturing of woven fabric A1-3] The woven fabric A1 described above was subjected to the following conditions: temperature: 200°C, surface pressure: 40 MPa / m² 2 Woven fabric A1-3 was obtained by heating and pressing it for 10 minutes in a flat plate press.

[0140] [Manufacturing of Woven Fabric A2] Fabric A2 was obtained by plain weaving 23.6 denier PTFE yarn for both the warp and weft, with a PTFE yarn density of 27 threads / inch. The basis weight of fabric A2 was 23.6 g / m². 2 Furthermore, the warp and weft threads were composed of slit yarn.

[0141] [Example 1] The film-coated substrate Y1, woven fabric A1-1, and film-coated substrate Y1 were layered in this order. The film-coated substrate Y1 was positioned so that film α1 on it was in contact with woven fabric A1-1. Furthermore, woven fabric A1-1 was used after its surface was brushed with a brush having polypropylene bristles. Each overlapping component is subjected to a temperature of 200°C and a surface pressure of 30 MPa / m. 2 After heating and pressing the substrates for 10 minutes using a flat plate press, the substrates on both sides were peeled off at a temperature of 50°C to obtain a precursor film.

[0142] The precursor film was immersed in a solution of dimethyl sulfoxide / potassium hydroxide / water = 30 / 5.5 / 64.5 (mass ratio) at 95°C for 30 minutes to hydrolyze the groups in the precursor film that can be converted to sulfonic acid functional groups, converting them to K-type sulfonic acid functional groups, and then washed with water. After that, the obtained film was immersed in 1M sulfuric acid to convert the terminal groups from K-type to H-type, and then dried to obtain an electrolyte film (solid polymer electrolyte film). Using the obtained electrolyte membrane, the aspect ratio of the woven fabric within the electrolyte membrane and the number of pinholes after electrolytic evaluation were measured. The results are shown in Table 1.

[0143] [Examples 2-6] Except for changing the type of film-coated substrate and woven fabric as shown in Table 1, the electrolyte membrane was prepared using the same method as in Example 1, and the aspect ratio of the woven fabric in the electrolyte membrane and the number of pinholes after electrolytic evaluation were measured. In addition, the woven fabrics used in each example were brushed on the surface using a brush with polypropylene bristles, as in Example 1. The results are shown in Table 1. In Table 1, "unprocessed" in Examples 5 and 6 means that woven fabric A1 or woven fabric A2 was not heat-pressed.

[0144] In Table 1, "Denier (g / 9000m)" represents the denier count of the warp threads (thread A) and weft threads (thread B) that make up the fabric. In all of Examples 1 to 6, the denier counts of the warp and weft threads that make up the fabric were the same. Furthermore, in all of Examples 1 to 6, the density of the warp and weft threads constituting the fabric was the same. Furthermore, as shown in Table 1, in all of the examples 1 to 6, the aspect ratio YA A2 / YA A1 and aspect ratio YA B2 / YA B1 The values ​​were the same. Furthermore, as shown in Table 1, in all of the examples 1 to 6, the aspect ratio YA CA2 / YA CA1 and aspect ratio YA CB2 / YA CB1 The values ​​were the same. Furthermore, as shown in Table 1, in all of the examples 1 to 6, (YA CA2 / YA CA1 ) / (YA A2 / YA A1 ), and (YA CB2 / YA CB1 ) / (YA B2 / YA B1 The values ​​were the same.

[0145] [Table 1]

[0146] As shown in Table 1, aspect ratio YA CA2 / YA CA1 and aspect ratio YA CB2 / YA CB1 Both are greater than 1, (YA CA2 / YA CA1 ) / (YA A2 / YA A1 ) and (YA CB2 / YA CB1 ) / (YA B2 / YA B1 It was confirmed that if a woven fabric in which all of the following are greater than 1 is included in the electrolyte membrane, the occurrence of pinholes in the electrolyte membrane can be suppressed when the electrolyte membrane is used with a voltage applied for a long time in a cell having an anode and a cathode (Examples 1 to 4).

[0147] For the woven fabric in the electrolyte membrane in each example, the aspect ratio YA A12 / YA A11 Aspect ratio YA A22 / YA A21 Aspect ratio YA B12 / YA B11 , and aspect ratio YA B22 / YA B21 The aspect ratio YA in each example was calculated according to the method described in the section on the electrolyte membrane above. A12 / YA A11 Aspect ratio YA A22 / YA A21 Aspect ratio YA B12 / YAB11 , and aspect ratio YA B22 / YA B21 In each case, the aspect ratio YA A2 / YA A1 and aspect ratio YA B2 / YA B1 It was the same. [Explanation of symbols]

[0148] 10 Electrolyte membrane 12 Electrolytes 14 Woven fabric 14A1, 14A2, 14A3, 14A4 thread 14B1, 14B2, 14B3, 14B4 thread Y CA1 ,Y CA2 ,Y A1 ,Y A2 ,Y A11 ,Y A12 ,Y A21 ,Y A22 Maximum length Y CB1 ,Y CB2 ,Y B1 ,Y B2 ,Y B11 ,Y B12 ,Y B21 ,Y B22 Maximum length X1,X2,Y1,Y2 End

[0149] Furthermore, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2020-177531, filed on October 22, 2020, are incorporated herein by reference as the disclosure of the specification of this invention.

Claims

1. An electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups, and a woven fabric, The woven fabric is composed of yarn A extending in one direction and yarn B extending in a direction substantially perpendicular to yarn A. Both thread A and thread B are made of materials that do not dissolve in alkaline aqueous solutions. For each of 10 different cross-sections when cutting along the thickness direction of the electrolyte membrane so as to pass through the center position of the yarn B in the electrolyte membrane, the maximum length Y of the yarn A in the thickness direction of the electrolyte membrane ＣＡ１ and the maximum length Y ＣＡ１ of the yarn A in the direction orthogonal to the thickness direction of the electrolyte membrane, which was measured ＣＡ２ were measured, and the average maximum length YA ＣＡ１ obtained by arithmetic-averaging the 10 measured maximum lengths Y ＣＡ１ and the average maximum length YA ＣＡ２ obtained by arithmetic-averaging the 10 measured maximum lengths Y ＣＡ２ were calculated, and the aspect ratio YA ＣＡ２ / YA ＣＡ１ was calculated. The maximum length Y of thread A in the thickness direction of the electrolyte membrane is determined for each of the 10 different cross-sections obtained when the electrolyte membrane is cut at an intermediate point between the threads B in a direction parallel to the direction in which the thread B extends within the electrolyte membrane. Ａ１ And the aforementioned maximum length Y Ａ１ The maximum length Y of the thread A measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. Ａ２ The maximum length Y of the 10 locations obtained was measured. Ａ１ The arithmetic mean of the average maximum length YA Ａ１ The obtained 10 locations with the maximum length Y Ａ２ The arithmetic mean of the average maximum length YA Ａ２ Aspect ratio YA Ａ２ / YA Ａ１ When calculated, The aspect ratio YA ＣＡ２ / YA ＣＡ１ However, it is greater than 1, and the aspect ratio YA Ａ２ / YA Ａ１ Larger than, Furthermore, for each of the 10 different cross-sections obtained by cutting the electrolyte membrane along the thickness direction so as to pass through the center position of the thread A within the electrolyte membrane, the maximum length Y of the thread B in the thickness direction of the electrolyte membrane is determined. ＣＢ１ And the aforementioned maximum length Y ＣＢ１ The maximum length Y of the thread B measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. ＣＢ２ The maximum length Y of the 10 locations obtained was measured. ＣＢ１ The arithmetic mean of the average maximum length YA ＣＢ１ The obtained 10 locations with the maximum length Y ＣＢ２ The arithmetic mean of the average maximum length YA ＣＢ２ Aspect ratio YA ＣＢ２ / YA ＣＢ１ Calculate, The maximum length Y of thread B in the thickness direction of the electrolyte membrane is determined for each of the 10 different cross-sections obtained when the electrolyte membrane is cut at an intermediate point between threads A in a direction parallel to the direction in which the thread A extends within the electrolyte membrane. Ｂ１ And the aforementioned maximum length Y Ｂ１ The maximum length Y of the thread B measured in the direction perpendicular to the thickness direction of the electrolyte membrane is measured. Ｂ２ The maximum length Y of the 10 locations obtained was measured. Ｂ１ The arithmetic mean of the average maximum length YA Ｂ１ The obtained 10 locations with the maximum length Y Ｂ２ The arithmetic mean of the average maximum length YA Ｂ２ Aspect ratio YA Ｂ２ / YA Ｂ１ When calculated, The aspect ratio YA ＣＢ２ / YA ＣＢ１ However, it is greater than 1, and the aspect ratio YA Ｂ２ / YA Ｂ１ A larger electrolyte membrane.

2. The aspect ratio YA ＣＡ２ / YA ＣＡ１ and the aspect ratio YA ＣＢ２ / YA ＣＢ１ The electrolyte membrane according to claim 1, wherein all of the values ​​are 1.2 or greater.

3. The aspect ratio YA Ａ２ / YA Ａ１ and the aspect ratio YA Ｂ２ / YA Ｂ１ The electrolyte membrane according to claim 1 or 2, wherein all of these values ​​are between 0.8 and 3.

5.

4. The aspect ratio YA Ａ２ / YA Ａ１ The aspect ratio YA ＣＡ２ / YA ＣＡ１ The ratio of and the aspect ratio YA Ｂ２ / YA Ｂ１ The aspect ratio YA ＣＢ２ / YA ＣＢ１ The electrolyte membrane according to any one of claims 1 to 3, wherein the ratio of each is 1.2 or greater.

5. The electrolyte membrane according to any one of claims 1 to 4, wherein both the denier count of yarn A and the denier count of yarn B are 15 to 50.

6. The electrolyte membrane according to any one of claims 1 to 5, wherein each of the yarns A and B is independently composed of a material selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyether ether ketone, and polyphenylene sulfide.

7. The electrolyte membrane according to any one of claims 1 to 6, wherein the density of both thread A and thread B is 70 to 150 threads / 25.4 mm (70 to 150 threads / inch).

8. The electrolyte membrane according to any one of claims 1 to 7, wherein the ion exchange group is a sulfonic acid type functional group.

9. The electrolyte membrane according to any one of claims 1 to 8, wherein the fluorine-containing polymer comprises a unit based on a fluorine-containing olefin and a unit having a sulfonic acid-type functional group and a fluorine atom.

10. The electrolyte membrane according to claim 9, wherein the fluorine-containing olefin is a fluoroolefin having 2 to 3 carbon atoms and having one or more fluorine atoms in the molecule.

11. The electrolyte membrane according to claim 9 or 10, wherein the unit having the sulfonic acid type functional group and the fluorine atom is a unit represented by formula (1). Formula (1) -[CF ２ -CF(-L-(SO ３ M) ｎ )- L is an n+1 valent perfluorohydrocarbon group which may contain an etheric oxygen atom, M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation, and n is 1 or 2.

12. The electrolyte membrane according to any one of claims 1 to 11, wherein the woven fabric is a heat-pressed woven fabric.

13. The electrolyte membrane according to any one of claims 1 to 12, wherein the ion exchange capacity of the fluorine-containing polymer is 0.90 milliequivalents / gram dry resin or more.

14. An electrolytic apparatus comprising an electrolyte membrane according to any one of claims 1 to 13.

15. A redox flow battery comprising an electrolyte membrane according to any one of claims 1 to 13.

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