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

Abstract

Provided is a solid polymer electrolyte membrane which hardly causes surface unevenness when brought into contact with a solvent.　The solid polymer electrolyte membrane contains: a fluorine-containing polymer having an ion exchange group; and a woven fabric. The warps and wefts constituting the woven fabric contain polyether ether ketone, the diameters of the warps and wefts constituting the woven fabric are each independently 30 µm or less, the density of the warps constituting the woven fabric and the density of the wefts constituting the woven fabric are each independently 110 per inch or more.

Description

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

[0001] This disclosure relates to solid polymer electrolyte membranes. This disclosure also relates to membrane electrode assemblies including the solid polymer electrolyte membrane, water electrolysis apparatuses including the membrane electrode assemblies, electrolytic hydrogenation apparatuses, and methods for producing hydrogen.

[0002] Solid polymer electrolyte membranes can be applied to a variety of uses, and various studies have been conducted on them. For example, solid polymer electrolyte membranes are used as membrane electrode assemblies with catalyst layers and electrodes on both sides in solid polymer fuel cells and solid polymer water electrolyzers. An example of such a solid polymer electrolyte membrane is the one described in Patent Document 1.

[0003] Patent Document 1 discloses a membrane electrode assembly that includes a polymer electrolyte membrane, the solid polymer electrolyte membrane includes a fluorine-containing polymer having ion exchange groups, and a woven fabric, wherein the woven fabric satisfies predetermined parameters.

[0004] International Publication No. 2020 / 162511

[0005] Patent Document 1, mentioned above, shows the use of polyetheretherketone (PEEK) in the warp and weft threads of a woven fabric. When the present inventors investigated the use of PEEK in the warp and weft threads, they found that irregularities tend to occur on the surface of the solid polymer electrolyte membrane when it comes into contact with a solvent, and that improvement is necessary.

[0006] This disclosure has been made in view of the above-mentioned problems, and one embodiment of the present invention aims to provide a solid polymer electrolyte membrane that is less prone to surface irregularities when in contact with a solvent. Another embodiment of the present invention also aims to provide a membrane electrode assembly, a water electrolysis apparatus, and an electrolytic hydrogenation apparatus.

[0007] This disclosure includes the following embodiments: [1] A solid polymer electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups and a woven fabric, wherein the warp and weft threads constituting the woven fabric contain polyetheretherketone, the diameter of the warp and weft threads constituting the woven fabric is independently 30 μm or less, and the density of the warp threads constituting the woven fabric and the density of the weft threads constituting the woven fabric are independently 110 threads / inch or more. [2] The solid polymer electrolyte membrane according to [1], wherein the ion exchange capacity of the fluorine-containing polymer is 0.90 milliequivalents / gram dry resin or more. [3] The solid polymer electrolyte membrane according to [1] or [2], wherein the density of the warp threads constituting the woven fabric and the density of the weft threads constituting the woven fabric are independently 150 threads / inch or more. [4] The solid polymer electrolyte membrane according to any one of [1] to [3], wherein the opening ratio of the woven fabric is 50 to 90%. [5] A solid polymer electrolyte membrane according to any one of [1] to [4], wherein the denier count of the warp threads and the denier count of the weft threads constituting the above woven fabric are each independently 10.0 or less. [6] A solid polymer electrolyte membrane according to any one of [1] to [5], wherein the film thickness of the above solid polymer electrolyte membrane is 50 to 150 μm. [7] A membrane electrode assembly according to any one of [1] to [6], wherein the above ion exchange group is a sulfonic acid type functional group. [8] A membrane electrode assembly according to any one of [1] to [7], wherein the above fluorine-containing polymer includes a unit based on a fluorine-containing olefin and a unit having a sulfonic acid type functional group and a fluorine atom. [9] A membrane electrode assembly according to [8], wherein the above unit having a sulfonic acid type functional group and a 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.

[10] A solid polymer electrolyte membrane according to any one of [1] to [9] used in a water electrolysis apparatus.

[11] A membrane electrode assembly comprising an anode having a catalyst layer, a cathode having a catalyst layer, and a solid polymer electrolyte membrane according to any one of [1] to [9] disposed between the anode and the cathode.

[12] A water electrolysis apparatus comprising the membrane electrode assembly according to

[11] .

[13] An electrolytic hydrogenation apparatus comprising the membrane electrode assembly according to

[11] .

[14] A method for producing hydrogen by electrolyzing water using the water electrolysis apparatus according to

[12] .

[0008] According to one embodiment of the present invention, a solid polymer electrolyte membrane is provided that is less prone to surface irregularities when in contact with a solvent. Furthermore, according to one embodiment of the present invention, a membrane electrode assembly, a water electrolysis apparatus, an electrolytic hydrogenation apparatus, and a method for producing hydrogen are provided that are less prone to surface irregularities when in contact with a solvent.

[0009] This is a cross-sectional view showing an example of a solid polymer electrolyte membrane of this disclosure. This is a schematic plan view showing an example of a woven fabric included in a solid polymer electrolyte membrane of this disclosure, viewed in the direction of the film thickness of the solid polymer electrolyte membrane. This is a partial cross-sectional view illustrating the measurement position of the film thickness of the solid polymer electrolyte membrane of this disclosure. This is a cross-sectional view showing an example of a membrane electrode assembly of this disclosure. This is a cross-sectional view of a solid polymer electrolyte membrane with surface irregularities in some areas.

[0010] The following definitions of terms apply throughout this specification and the claims unless otherwise specified. “Ion exchange group” means a group capable of exchanging at least some of the ions it contains with other ions, such as the sulfonic acid type functional group and the carboxylic acid type functional group described below. “Sulfonic acid type functional group” means a sulfonic acid group (-SO ３ H), or sulfonic acid base (-SO ３ M ２ However, M ２is an alkali metal or a quaternary ammonium cation.). "Carboxylic acid type functional group" means a carboxylic acid group (-COOH) or a carboxylate group (-COOM １ . However, M １ is an alkali metal or a quaternary ammonium cation.). "Precursor membrane" means a membrane containing a polymer having a group that can be converted into an ion exchange group. "Group that can be converted into an ion exchange group" means a group that can be converted into an ion exchange group by treatments such as hydrolysis treatment and acidification treatment. "Group that can be converted into a sulfonic acid type functional group" means a group that can be converted into a sulfonic acid type functional group by treatments such as hydrolysis treatment and acidification treatment. "Group that can be converted into a carboxylic acid type functional group" means a group that can be converted into a carboxylic acid type functional group by known treatments such as hydrolysis treatment and acidification treatment.

[0011] "Unit" in a polymer means an atomic group derived from one molecule of the monomer formed by polymerization of the monomer. The unit may be an atomic group directly formed by a polymerization reaction, or may be an atomic group in which a part of the atomic group is converted into another structure by treating the polymer obtained by the polymerization reaction.

[0012] The numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another stepwise numerical range. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

[0013] [Solid Polymer Electrolyte Membrane] The solid polymer electrolyte membrane of this disclosure comprises a fluorine-containing polymer having ion exchange groups (hereinafter also referred to as "fluorine-containing polymer (I)") and a woven fabric. Here, the warp and weft threads constituting the woven fabric contain polyether ether ketone (PEEK). Furthermore, the diameter of the warp and weft threads constituting the woven fabric is independently 30 μm or less. Moreover, the density of the warp and weft threads constituting the woven fabric is independently 110 threads / inch or more.

[0014] Figure 1 is a cross-sectional view showing an example of a solid polymer electrolyte membrane according to the present disclosure. The solid polymer electrolyte membrane 10 includes an electrolyte 12 containing a fluorine-containing polymer (I) and a woven fabric 14 disposed within the electrolyte 12. The woven fabric 14 is composed of yarns 14a, 14b, and 14c.

[0015] In the solid polymer electrolyte membrane of this disclosure, the mechanism by which surface irregularities are less likely to occur when the warp and weft threads constituting the woven fabric meet the above requirements is not entirely clear, but the inventors speculate as follows: When the solid polymer electrolyte membrane comes into contact with a solvent, the fluorine-containing polymer (I) swells due to the solvent, and the solid polymer electrolyte membrane may deform. Here, the PEEK contained in the warp and weft threads has a high elastic modulus and is resistant to deformation. When such warp and weft threads are arranged with the above-described predetermined thread diameter and density, even if the fluorine-containing polymer (I) swells, many of the warp and weft threads restrain the fluorine-containing polymer (I). As a result, the fluorine-containing polymer (I) becomes less likely to deform locally, and as a result, surface irregularities are less likely to occur when it comes into contact with a solvent.

[0016] The structure of the solid polymer electrolyte membrane (hereinafter also simply referred to as "solid polymer electrolyte membrane") described herein will be explained below.

[0017] <Fluorine-containing polymer> The electrolyte described above contains a fluorine-containing polymer (I). That is, the solid polymer electrolyte membrane 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 more, more preferably 1.00 milliequivalents / gram dry resin or more, even more preferably 1.05 milliequivalents / gram dry resin or more, even more preferably 1.10 milliequivalents / gram dry resin or more, particularly preferably 1.20 milliequivalents / gram dry resin or more, and most preferably 1.25 milliequivalents / gram dry resin or more, from the viewpoint that it can further reduce the electrolysis voltage when applied to an electrolytic device. 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, even more preferably 1.43 milliequivalents / gram dry resin or less, and particularly preferably 1.30 milliequivalents / gram dry resin or less, as this makes it less likely for irregularities to occur on the surface of the solid polymer electrolyte membrane when in contact with the solvent. The ion exchange capacity of the fluorine-containing polymer (I) is preferably 0.90 milliequivalents / gram dry resin or more and 2.00 milliequivalents / gram dry resin or less, more preferably 1.00 milliequivalents / gram dry resin or more and 1.50 milliequivalents / gram dry resin or less, even more preferably 1.05 milliequivalents / gram dry resin or more and 1.43 milliequivalents / gram dry resin or less, even more preferably 1.05 milliequivalents / gram dry resin or more and 1.30 milliequivalents / gram dry resin or less, particularly preferably 1.10 milliequivalents / gram dry resin or more and 1.30 milliequivalents / gram dry resin or less, and most preferably 1.20 milliequivalents / gram dry resin or more and 1.30 milliequivalents / gram dry resin or less, from the viewpoint of being able to further reduce the electrolytic voltage when applied to an electrolytic device.The ion exchange capacity of the fluorinated polymer (I) is preferably 0.90 mm equivalents / gram dry resin or more and 1.50 mm equivalents / gram dry resin or less, more preferably 0.90 mm equivalents / gram dry resin or more and 1.30 mm equivalents / gram dry resin or less, even more preferably 0.90 mm equivalents / gram dry resin or more and less than 1.25 mm equivalents / gram dry resin, even more preferably 0.90 mm equivalents / gram dry resin or more and less than 1.20 mm equivalents / gram dry resin, particularly preferably 0.95 mm equivalents / gram dry resin or more and 1.10 mm equivalents / gram dry resin or less, and most preferably 0.95 mm equivalents / gram dry resin or more and 1.05 mm equivalents / gram dry resin or less, from the standpoint that irregularities are less likely to occur on the surface of the solid polymer electrolyte membrane when it comes into contact with the solvent, especially in water electrolysis under high pressure conditions.

[0018] The fluorine-containing polymer (I) used in the solid polymer electrolyte membrane may be one type, or two or more types may be used in a laminated or mixed form. The solid polymer electrolyte membrane may contain polymers other than fluorine-containing polymer (I), but it is preferable that the polymers in the solid polymer electrolyte membrane consist substantially of fluorine-containing polymer (I). "Substantially consisting of fluorine-containing polymer (I)" means that the content of fluorine-containing polymer (I) is 95% by mass or more of the total mass of polymers in the solid polymer electrolyte membrane. An upper limit for the content of fluorine-containing polymer (I) is 100% by mass of the total mass of polymers in the solid polymer electrolyte membrane. Specific examples of polymers other than fluorine-containing polymer (I) include one or more polyazole compounds selected from the group consisting of polymers of heterocyclic compounds containing one or more nitrogen atoms in the ring, and polymers of heterocyclic compounds containing one or more nitrogen atoms and oxygen and / or sulfur atoms in the ring. Specific examples of polyazole compounds include polyimidazole compounds, polybenzimidazole compounds, polybenzobisimidazole compounds, polybenzoxazole compounds, polyoxazole compounds, polythiazole compounds, and polybenzothiazole compounds. In addition, from the viewpoint of oxidation resistance of solid polymer electrolyte membranes, other polymers such as polyphenylene sulfide resins and polyphenylene ether resins can also be mentioned.

[0019] 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, with sulfonic acid-type functional groups being preferred because they can further reduce the electrolysis voltage. The fluorine-containing polymer (I) may or may not contain carboxylic acid-type functional groups. Below, we will mainly describe in detail embodiments of fluorine-containing polymers having sulfonic acid-type functional groups (hereinafter also referred to as "fluorine-containing polymer (S)").

[0020] The fluorine-containing polymer (S) preferably contains units based on fluorine-containing olefins, as well as units having sulfonic acid-type functional groups and fluorine atoms. Examples of fluorine-containing olefins include fluoroolefins having 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 in terms of monomer production cost, reactivity with other monomers, and the properties of the resulting fluorine-containing polymer (S). One type of fluorine-containing olefin may be used alone, or two or more types may be used in combination. The content of units based on fluorine-containing olefins relative to the total units contained in the fluorine-containing polymer (S) is preferably 65 to 95 mol%.

[0021] As a unit having a sulfonic acid type functional group and a fluorine atom, the unit represented by formula (1) is preferred. Formula (1) -[CF ２ -CF(-L-(SO ３ M) ｎ ) ] -

[0022] 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.

[0023] L is preferably an n+1 valent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom, and particularly preferably a divalent perfluoroalkylene group which may contain an etheric oxygen atom in the n=1 embodiment, or a trivalent perfluoroaliphatic hydrocarbon group which may contain an etheric oxygen atom in the n=2 embodiment. The above divalent perfluoroalkylene group may be linear or branched.

[0024] M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation. n is 1 or 2. If n is 2, the two M atoms may be the same or different.

[0025] The unit represented by formula (1) is preferably the unit represented by formula (1-1), the unit represented by formula (1-2), the unit represented by formula (1-3), or the unit represented by formula (1-4). Formula (1-1) - [CF ２ -CF(-OR-R) ｆ１ -SO ３ M)] - Formula (1-2) - [CF ２ -CF(-R ｆ１ -SO ３ M) ]-

[0026]

[0027]

[0028] 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.

[0029] R ｆ２ 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.

[0030] 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.

[0031] r is 0 or 1. m is 0 or 1. M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation.

[0032] Of the units represented by formula (1-1) and formula (1-2), the unit represented by formula (1-5) is more preferable. Formula (1-5) - [CF ２ -CF (-(CF ２ ) ｘ - (OCF ２ CFY) ｙ -O-(CF ２ ) ｚ -SO ３ M) - x is 0 or 1, y is an integer from 0 to 2, z is an integer from 1 to 4, and Y is F or CF ３ Therefore, M is as described above.

[0033] The following are specific examples of units represented by equation (1-1). In the equation, w is an integer from 1 to 8, and x is an integer from 1 to 5. The definition of M in the equation is as described above. -[CF ２ -CF(-O-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF(-O-CF) ２ CF (CF ３ )-O-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF(-(O-CF ２ CF (CF ３ )) ｘ -SO ３ M) ]-

[0034] Specific examples of units represented by equation (1-2) include the following units. w in the equation is an integer from 1 to 8. The definition of M in the equation is as described above. -[CF ２ -CF (-(CF ２ ) ｗ -SO ３ M) ]- -[CF ２ -CF (-CF ２ -O-(CF ２ ) ｗ -SO ３ M) ]-

[0035] 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.

[0036]

[0037] R ｆ４ R is a linear perfluoroalkylene group having 1 to 6 carbon atoms. ｆ５ This is a linear perfluoroalkylene group having 1 to 6 carbon atoms, which may contain single bonds or oxygen atoms between carbon atoms. The definitions of r and M are as described above.

[0038] The following are specific examples of units represented by equation (1-3-1):

[0039]

[0040] The unit represented by formula (1-4) is preferably the unit represented by formula (1-4-1). ｆ１ , R ｆ２ The definition of M is as described above.

[0041]

[0042] The following are specific examples of units represented by equation (1-4-1):

[0043]

[0044] The units having sulfonic acid-type functional groups and fluorine atoms may be used individually or in combination of two or more types. The content of units based on units having sulfonic acid-type functional groups and fluorine atoms relative to the total number of units in the fluorine-containing polymer (S) is preferably 5 to 35 mol%.

[0045] Fluorine-containing polymer (I) may contain units based on fluorine-containing olefins, as well as units based on other monomers other than those having sulfonic acid-type functional groups and fluorine atoms. Specific examples of other monomers include CF ２ = CFR ｆ６ (However, R ｆ６ (These are perfluoroalkyl groups having 2 to 10 carbon atoms.) CF ２ = CF - ORｆ７ (However, R ｆ７ (These are perfluoroalkyl groups having 1 to 10 carbon atoms.) CF ２ = CFO (CF ２ ) ｖ CF = CF ２ (wherein v is an integer between 1 and 3.) Examples include monomers having a cyclic ether structure, such as those described in International Publication No. 2020 / 184681. The content of units based on other monomers is preferably 30% by mass or less, may be 1% by mass or less, or 0.1% by mass or less, relative to the total units in the fluorine-containing polymer (I), in order to maintain ion exchange performance, and may not contain units based on other monomers.

[0046] The solid polymer electrolyte membrane may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, for example, one embodiment may involve stacking multiple layers containing a fluorine-containing polymer (I) with different ion exchange capacities.

[0047] <Woven Fabric> The solid polymer electrolyte membrane has a woven fabric. The warp and weft threads constituting the woven fabric satisfy the requirements described above. The woven fabric and the warp and weft threads constituting it will be described below.

[0048] The denier count of the warp threads and weft threads constituting the woven fabric is preferably 2.0 or higher, more preferably 3.0 or higher, even more preferably 4.0 or higher, and particularly preferably 5.0 or higher, in terms of superior strength and dimensional stability of the solid polymer electrolyte membrane. The denier count of the warp threads and weft threads constituting the woven fabric is preferably 60.0 or lower, more preferably 20.0 or lower, even more preferably 15.0 or lower, particularly preferably 10.0 or lower, and most preferably 9.0 or lower, in terms of further reducing the electrolysis voltage when applied to an electrolytic device. The denier count of the warp threads and weft threads constituting the woven fabric is preferably 2.0 or higher and 60.0 or lower, more preferably 2.0 or higher and 20.0 or lower, and even more preferably 2.0 or higher and 10.0 or lower. When the ion exchange capacity of the fluorine-containing polymer (I) is 1.10 milliequivalents / gram dry resin or more, more preferably 1.20 milliequivalents / gram dry resin or more, the denier count of the warp threads and weft threads constituting the woven fabric is preferably 2.0 to 60.0, more preferably 3.0 to 20.0, even more preferably 3.0 to 15.0, even more preferably 3.0 to 10.0, particularly preferably 4.0 to 10.0, and most preferably 5.0 to 9.0. The denier count of the warp threads and weft threads constituting the woven fabric is preferably 2.0 to 60.0, more preferably 2.0 to 20.0, even more preferably 2.0 to 10.0, even more preferably 2.0 to 5.0, and particularly preferably 2.0 to 4.0, respectively, when the ion exchange capacity of the fluorine-containing polymer (I) is less than 1.25 milliequivalents / gram dry resin, more preferably less than 1.20 milliequivalents / gram dry resin. Note that the denier count is the value obtained by expressing the mass of 9,000 m of yarn in grams (g / 9,000 m).

[0049] As described above, the diameter of the warp and weft threads constituting the fabric is independently 30 μm or less, preferably 28 μm or less, and more preferably 25 μm or less. The diameter of the warp and weft threads constituting the fabric is often 8 μm or more, preferably 12 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, and particularly preferably 23 μm or more. The diameter of the warp and weft threads constituting the fabric is independently 8 μm or more and 30 μm or less, more preferably 12 μm or more and 28 μm or less, and even more preferably 15 μm or more and 28 μm or less. The diameters of the warp and weft threads constituting the woven fabric are, independently of the ion exchange capacity of the fluorine-containing polymer (I) being 1.10 milliequivalents / gram dry resin or more, more preferably 1.20 milliequivalents / gram dry resin or more, respectively, preferably 8 μm to 30 μm, more preferably 12 μm to 28 μm, even more preferably 15 μm to 28 μm, particularly preferably 20 μm to 28 μm, and most preferably 23 μm to 25 μm. When the ion exchange capacity of the fluorine-containing polymer (I) is less than 1.25 milliequivalents / gram dry resin, more preferably less than 1.20 milliequivalents / gram dry resin, the diameters of the warp and weft threads constituting the woven fabric are preferably 8 μm to 30 μm, more preferably 12 μm to 28 μm, even more preferably 12 μm to 25 μm, particularly preferably 12 μm to 20 μm, and most preferably 15 μm to 20 μm, respectively. The above thread diameters may be measured from the cross-section of the solid polymer electrolyte membrane or determined by calculation. When measuring the warp thread diameter from the cross-section of the solid polymer electrolyte membrane, the thread diameter is the arithmetic mean of the diameters of 10 different warp threads arbitrarily selected based on a magnified image (e.g., 100x) of the cross-section of the solid polymer electrolyte membrane obtained using a microscope in a cross-section perpendicular to the direction in which the warp threads extend. If the cross-sectional shape of the warp thread is not circular, the area of ​​the cross-section is calculated, and the diameter of the circle that gives that area is taken as the diameter of the warp thread. The diameter of the weft thread can be measured using the same method as the diameter of the warp thread.

[0050] When calculating the yarn diameter, the value used is calculated from the denier number and the density of the materials constituting the warp and weft threads, assuming that the cross-sectional shapes of the warp and weft threads are perfect circles. Specifically, the value calculated by the following formula (D1) is used.

[0051]

[0052] In the above formula (D1), D represents the diameter of the yarn, and its unit is μm. In formula (D1), d represents the denier number. In formula (D1), π represents pi. In formula (D1), ρ represents the density of the material constituting the yarn, and its unit is g / cm³. ３ The density of PEEK is 1.30 g / cm³. ３ Use this.

[0053] The warp and weft threads that make up the woven fabric may consist of either monofilaments, which are made up of one filament, or multifilaments, which are made up of two or more filaments, with monofilaments being preferred.

[0054] As described above, the density of the warp and weft threads constituting the woven fabric is preferably 110 threads / inch or more, more preferably 130 threads / inch or more, more preferably 150 threads / inch or more, even more preferably 180 threads / inch or more, and particularly preferably 200 threads / inch or more. Furthermore, in terms of being able to further reduce the electrolytic voltage when applied to an electrolytic device, it is preferably 350 threads / inch or less, and more preferably 250 threads / inch or less. The density of the warp and weft threads constituting the woven fabric is preferably 110 threads / inch or more and 350 threads / inch or less, more preferably 150 threads / inch or more and 350 threads / inch or less, even more preferably 180 threads / inch or more and 350 threads / inch or less, and particularly preferably 200 threads / inch or more and 350 threads / inch or less. The density of the warp and weft threads constituting the woven fabric is preferably 110 threads / inch to 350 threads / inch, more preferably 130 threads / inch to 300 threads / inch, even more preferably 150 threads / inch to 250 threads / inch, particularly preferably 180 threads / inch to 250 threads / inch, and most preferably 200 threads / inch to 250 threads / inch, respectively, when the ion exchange capacity of the fluorine-containing polymer (I) is 1.10 milliequivalents / gram dry resin or more, and more preferably 1.20 milliequivalents / gram dry resin or more. The density of the warp and weft threads constituting the woven fabric is preferably 110 threads / inch to 350 threads / inch, more preferably 150 threads / inch to 350 threads / inch, even more preferably 180 threads / inch to 350 threads / inch, particularly preferably 200 threads / inch to 350 threads / inch, and most preferably 250 threads / inch to 300 threads / inch, respectively, when the ion exchange capacity of the fluorine-containing polymer (I) is less than 1.25 milliequivalents / gram dry resin, more preferably less than 1.20 milliequivalents / gram dry resin. The density of the warp and weft threads constituting the woven fabric is determined by the following method. First, for the warp threads, 100 adjacent warp threads are selected from the optical microscope image observed from the normal direction of the surface of the solid polymer electrolyte membrane, and the distance between the two outermost warp threads is measured five times at different locations to calculate the arithmetic mean of the distances. The density of the warp threads (unit: threads / inch) is calculated using the obtained arithmetic mean.For the weft threads, 100 adjacent weft threads are selected from an optical microscope image observed from the normal direction of the surface of the solid polymer electrolyte membrane. The distance between the two outermost weft threads is measured five times at different locations, and the arithmetic mean of the distances is calculated. The density of the weft threads (in units of threads / inch) is then calculated using the obtained arithmetic mean. In the case of a multifilament thread, the above measurement is performed on each spaced-out thread, not on the number of filaments that make up the thread.

[0055] As described above, the warp and weft threads constituting the fabric contain polyetheretherketone (PEEK). Polyetheretherketone is preferred because it has a high modulus of elasticity and is resistant to deformation, and because it makes it easy to reduce the diameter of the warp and weft threads constituting the fabric. Aromatic polyetheretherketone is preferred. Aromatic polyetheretherketone refers to a polyetheretherketone that contains an aromatic ring (such as a benzene ring), and two ether bonds and a carbonyl bond as a unit. As for the polyetheretherketone, it is preferable that it consists of a unit in which three benzene rings are linked by an ether bond, an ether bond, and a carbonyl bond, in that order. The warp and weft threads constituting the fabric preferably contain 90% by mass or more of polyetheretherketone, more preferably 95% by mass or more, and are also preferably composed solely of polyetheretherketone. Furthermore, it is also preferable that the fabric be composed solely of warp and weft threads composed of polyetheretherketone.

[0056] The warp and weft threads that make up the woven fabric are preferably made of slit yarn, as this offers superior durability and strength.

[0057] In the woven fabric, it is preferable that the warp and weft threads are approximately perpendicular. Approximately perpendicular means that the angle between the warp and weft threads is 90 ± 10 degrees. Furthermore, the structure of the woven fabric is not particularly limited, and examples include plain weave, twill weave, and satin weave, with plain weave being preferred.

[0058] The basis weight of the woven fabric is 6.0 g / m², which offers an excellent balance between the strength and handling properties of the solid polymer electrolyte membrane.２ The above is preferable, and 7.50 g / m ２ The above is more preferable, 8.0 g / m ２ The above is even more preferable, 10.0 g / m ２ The above is particularly preferable. The basis weight of the woven fabric is 40.0 g / m². ２ The following is preferable: 20.0 g / m ２ The following is more preferable: 15.0 g / m ２ The following is even more preferable. The basis weight of the woven fabric is determined by the method described in the later examples.

[0059] Furthermore, the opening ratio of the woven fabric is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more, in that it can further reduce the water electrolysis voltage when applied to a water electrolysis device. The opening ratio of the woven fabric is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less, in that it provides superior strength to the solid polymer electrolyte membrane. The opening ratio of the woven fabric is preferably 50% to 90%, more preferably 55% to 80%, even more preferably 60% to 80%, and particularly preferably 60% to 70%. The opening ratio of the woven fabric is calculated by 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"). In particular, when the average diameters and average spacings of the warp and weft threads are different, the opening ratio of the woven fabric is calculated by the following formula (ε1), based on the average diameter R11 of the warp threads, the average spacing P11 between adjacent warp threads (hereinafter also referred to as "pitch P11"), the average diameter R12 of the weft threads, and the average spacing P12 between adjacent weft threads (hereinafter also referred to as "pitch P12"). Here, R1, R11, and R12 are the thread diameters measured by the method described above. Pitch P1, P11, and P12 are calculated using the arithmetic mean of the spacing between 10 points at arbitrarily selected different locations based on a magnified image (e.g., 100x) of the cross-section of the solid polymer electrolyte membrane obtained using a microscope. Opening ratio of woven fabric (%) = [P1 / (P1 + R1)] ２ × 100 (ε) Open area ratio of woven fabric (%) = [P11 / (P11+R11)] [P12 / (P12+R12)] × 100 (ε1)

[0060] The following combinations are preferred for the warp and weft thread diameters, denier counts, denier counts, and aperture ratios of the woven fabric, as well as the ion exchange capacity of the fluorine-containing polymer (I), in order to minimize surface irregularities in the solid polymer electrolyte membrane: • A combination where the thread diameter is 8 μm or more and 30 μm or less, the denier count is 2.0 or more and 60.0 or less, the density is 110 threads / inch or more and 300 threads / inch or less, the aperture ratio is 50% or more and 90% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 0.90 milliequivalents / gram dry resin or more and 2.00 milliequivalents / gram dry resin or less. • A combination where the thread diameter is 12 μm or more and 28 μm or less, the denier count is 3.0 or more and 20.0 or less, the density is 130 threads / inch or more and 300 threads / inch or less, the aperture ratio is 55% or more and 80% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 1.00 milliequivalents / gram dry resin or more and 1.50 milliequivalents / gram dry resin or less. - A combination in which the thread diameter is 15 μm or more and 28 μm or less, the denier number is 3.0 or more and 15.0 or less, the density is 150 threads / inch or more and 250 threads / inch or less, the aperture ratio is 60% or more and 80% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 1.05 mm equivalents / gram dry resin or more and 1.43 mm equivalents / gram dry resin or less. - A combination in which the thread diameter is 20 μm or more and 28 μm or less, the denier number is 3.0 or more and 10.0 or less, the density is 180 threads / inch or more and 250 threads / inch or less, the aperture ratio is 60% or more and 70% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 1.05 mm equivalents / gram dry resin or more and 1.43 mm equivalents / gram dry resin or less. - A combination in which the thread diameter is 23 μm or more and 25 μm or less, the denier number is 4.0 or more and 10.0 or less, the density is 200 threads / inch or more and 250 threads / inch or less, the aperture ratio is 60% or more and 70% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 1.05 mm equivalents / gram dry resin or more and 1.30 mm equivalents / gram dry resin or less. - A combination in which the thread diameter is 23 μm or more and 25 μm or less, the denier number is 5.0 or more and 9.0 or less, the density is 200 threads / inch or more and 250 threads / inch or less, the aperture ratio is 60% or more and 70% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 1.10 mm equivalents / gram dry resin or more and 1.30 mm equivalents / gram dry resin or less.

[0061] The following combinations are preferred for the warp and weft thread diameters, denier counts, denier counts, and density of the warp and weft threads constituting the woven fabric, as well as the ion exchange capacity of the fluorine-containing polymer (I), particularly in terms of minimizing surface irregularities in the solid polymer electrolyte membrane during water electrolysis under high-pressure conditions: • A combination in which the thread diameter is 8 μm or more and 30 μm or less, the denier count is 2.0 or more and 60.0 or less, the density is 110 threads / inch or more and 350 threads / inch or less, the ion exchange capacity of the fluorine-containing polymer (I) is 0.90 milliequivalents / gram dry resin or more and 1.50 milliequivalents / gram dry resin or less. - Combinations where the thread diameter is 12 μm or more and 28 μm or less, the denier count is 2.0 or more and 20.0 or less, the density is 150 threads / inch or more and 350 threads / inch or less, the aperture ratio is 50% or more and 90% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 0.90 milliequivalents / gram dry resin or more and 1.30 milliequivalents / gram dry resin or less. - Combinations where the thread diameter is 12 μm or more and 25 μm or less, the denier count is 2.0 or more and 10.0 or less, the density is 180 threads / inch or more and 350 threads / inch or less, the aperture ratio is 50% or more and 90% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 0.90 milliequivalents / gram dry resin or more and less than 1.25 milliequivalents / gram dry resin. - A combination in which the thread diameter is 12 μm or more and 20 μm or less, the denier count is 2.0 or more and 5.0 or less, the density is 200 threads / inch or more and 350 threads / inch or less, the aperture ratio is 50% or more and 90% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 0.90 milliequivalents / gram dry resin or more and less than 1.20 milliequivalents / gram dry resin. - A combination in which the thread diameter is 15 μm or more and 20 μm or less, the denier count is 2.0 or more and 4.0 or less, the density is 250 threads / inch or more and 350 threads / inch or less, the aperture ratio is 50% or more and 90% or less, and the ion exchange capacity of the fluorine-containing polymer (I) is 0.90 milliequivalents / gram dry resin or more and less than 1.10 milliequivalents / gram dry resin. - A combination of yarns with a diameter of 15 μm or more and 20 μm or less, a denier number of 2.0 or more and 4.0 or less, a density of 250 threads / inch or more and 350 threads / inch or less, an aperture ratio of 50% or more and 90% or less, and an ion exchange capacity of fluorine-containing polymer (I) of 0.95 milliequivalents / gram dry resin or more and less than 1.05 milliequivalents / gram dry resin.

[0062] <Film Thickness> The film thickness of the solid polymer electrolyte membrane is preferably 20 μm or more, more preferably 40 μm or more, even more preferably 50 μm or more, and particularly preferably 60 μm or more. The film thickness of the solid polymer electrolyte membrane is preferably 150 μm or less, more preferably 130 μm or less, and even more preferably 90 μm or less, from the viewpoint that the electrolysis voltage can be further reduced when applied to an electrolytic device. The film thickness of the solid polymer electrolyte membrane is preferably 20 μm or more and 150 μm or less, more preferably 40 μm or more and 130 μm or less, even more preferably 50 μm or more and 130 μm or less, particularly preferably 60 μm or more and 130 μm or less, and most preferably 60 μm or more and 90 μm or less. The method for measuring the film thickness of the solid polymer electrolyte membrane of this disclosure will be described below.

[0063] First, the solid polymer electrolyte membrane is dried at 90°C for 2 hours. Then, the solid polymer electrolyte membrane is cut in a direction parallel to the film thickness direction, and a magnified image (e.g., 100x magnification) of the cross-section of the solid polymer electrolyte membrane is taken using an optical microscope (product name "BX-51", manufactured by Olympus Corporation). When cutting the solid polymer electrolyte membrane, the cut is made along a direction parallel to the direction in which either the warp or weft threads constituting the woven fabric within the solid polymer electrolyte membrane extend, and between the selected threads. Figure 2 will be used to explain the cutting position of the solid polymer electrolyte membrane in more detail. Figure 2 is a schematic plan view of the woven fabric 14 in the solid polymer electrolyte membrane 10 as seen in the film thickness direction. As shown in Figure 2, the woven fabric 14 includes warp threads 14a, 14b, and 14c, and weft threads 14A, 14B, and 14C that are perpendicular to the warp threads. In the example shown in Figure 2, the solid polymer electrolyte membrane 10 is cut along the line A-A', which is in the direction of the weft and located between threads 14A and 14B selected from the weft. This exposes the cross-section of the solid polymer electrolyte membrane 10 as shown in Figure 1.

[0064] Next, using the magnified image, any two adjacent threads present in the cross-section are selected. Then, the film thickness of the solid polymer electrolyte membrane is measured at each point, moving from the center of one thread toward the center of the other thread, in increments of 1 / 10 of the distance between them (note that the last point is the center of the other thread, and the film thickness at this point is not measured). The film thicknesses obtained at each point are then arithmetically averaged. However, if the film thickness includes the thickness of the thread, the film thickness measured at this point is not included in the calculation. The measurement locations for the film thickness of the solid polymer electrolyte membrane will be explained more specifically using the example in Figure 3. Figure 3 is a partial cross-sectional view illustrating the measurement locations for the film thickness of the solid polymer electrolyte membrane 10. In the example in Figure 3, adjacent threads 14a and 14b are selected from the threads in Figure 1. As shown in Figure 3, the film thicknesses t1 to t9 are measured at points c1 to c10, excluding the last point c10, by moving from point c0, which is the center of thread 14a, toward point c10, which is the center of thread 14b, in increments of 1 / 10 of the distance between them. From the measured film thicknesses t1 to t9, the arithmetic mean of the total seven thicknesses, from film thickness t2 to t8 (excluding film thickness t1 which includes the thickness of thread 14a) to film thickness t9 which includes the thickness of thread 14b, is calculated.

[0065] This film thickness calculation is performed at 10 different cross-sections of the solid polymer electrolyte membrane, and the arithmetic mean of the film thicknesses at these 10 locations is taken as the film thickness of the solid polymer electrolyte membrane in this disclosure.

[0066] [Method for manufacturing solid polymer electrolyte membranes] As a method for manufacturing solid polymer electrolyte membranes, for example, one can produce a membrane (hereinafter also called a "precursor membrane") containing a polymer of a fluorine-containing monomer (hereinafter also called a "fluorine-containing monomer (I')") having a group that can be converted into an ion exchange group (hereinafter also called a "fluorine-containing polymer (I')") and a woven fabric, and then produce the membrane by converting the groups in the precursor membrane that can be converted into ion exchange groups into ion exchange groups.

[0067] A preferred embodiment of the method for producing the precursor film is a method in which a laminate in which a fluorine-containing polymer (I') is arranged on both sides of a woven fabric is sandwiched between transfer substrates such as a film with a melting point of 70 to 180°C, and then heated and pressed. Specific examples of transfer substrates include polyethylene film, polypropylene film, polystyrene film, and polyethylene terephthalate film. The transfer substrate may be a single-layer transfer substrate or a multi-layer transfer substrate having two or more layers. When the transfer substrate is a multi-layer structure, each layer may be made of the same material or of different materials. Specific examples of materials constituting each layer are as described above.

[0068] The form of the woven fabric is as described above, so I will omit further explanation.

[0069] 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 fluorine-containing polymer (S') will be described in detail below.

[0070] Methods for copolymerizing fluorine-containing polymers (S') can include known methods such as solution polymerization, suspension polymerization, and emulsion polymerization.

[0071] 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. The content of units based on fluorine-containing olefins relative to the total units in the fluorine-containing polymer (S') is preferably 65 to 95 mol%.

[0072] As the fluorine-containing monomer (S'), compounds having one or more fluorine atoms in the molecule, an ethylenic double bond, and a group that can be converted into a sulfonic acid type functional group can be mentioned. As the fluorine-containing monomer (S'), a compound represented by the formula (2) is preferable from the viewpoints of the production cost of the monomer, reactivity with other monomers, and excellent properties of the obtained fluorine-containing polymer (S). Formula (2) CF ２ =CF-L-(A) ｎ The definitions of L and n in the formula (2) are as described above. When n is 2, the two A's may be the same as each other or different from each other. A is a group that can be converted into a sulfonic acid type functional group. The group that can be converted into a sulfonic acid type functional group is preferably a functional group that can be converted into a sulfonic acid type functional group by hydrolysis. Specific examples of the group that can be converted into a sulfonic acid type functional group include -SO ２ F, -SO ２ Cl, -SO ２ Br can be mentioned.

[0073] As the compound represented by the formula (2), a compound represented by the formula (2-1), a compound represented by the formula (2-2), a compound represented by the formula (2-3), and a compound represented by the formula (2-4) are preferable. Formula (2-1) CF ２ =CF-O-R ｆ１ -A Formula (2-2) CF ２ =CF-R ｆ１ -A

[0074]

[0075] The definitions of R ｆ１ , R ｆ２ , r and A in the formula are as described above.

[0076] [[ID=3故6]]

[0077] The definitions of R ｆ１ , R ｆ２ , R ｆ３ , r, m and A in the formula are as described above.

[0078] As the compound represented by the formula (2-1) and the compound represented by the formula (2-2), a compound represented by the formula (2-5) is preferable. Formula (2-5) CF２ =CF-(CF ２ ) ｘ -(OCF ２ CFY) ｙ -O-(CF ２ ) ｚ -SO ２ F. The definitions of x, y, z and Y in the formula are as described above.

[0079] 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. CF ２ =CF-O-(CF ２ ) ｗ -SO ２ F CF ２ =CF-O-CF ２ CF(CF ３ )-O-(CF ２ ) ｗ -SO ２ F CF ２ =CF-[O-CF ２ CF(CF ３ )] ｘ -SO ２ F

[0080] 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. CF ２ =CF-(CF ２ ) ｗ -SO ２ F CF ２ =CF-CF ２ -O-(CF ２ ) ｗ -SO ２ F

[0081] As the compound represented by formula (2-3), the compound represented by formula (2-3-1) is preferred.

[0082]

[0083] In the formula, the definitions of R ｆ４ , R ｆ５ , r and A are as described above.

[0084] Specific examples of the compound represented by formula (2-3-1) include the following.

[0085]

[0086] Of the compounds represented by formula (2-4), the compound represented by formula (2-4-1) is preferred.

[0087]

[0088] R in the formula ｆ１ , R ｆ２ The definition of A is as stated above.

[0089] Specific examples of compounds represented by formula (2-4-1) include the following:

[0090]

[0091] The fluorine-containing monomer (S') may be used alone or in combination of two or more types. The content of units based on the fluorine-containing monomer (S') relative to the total units of the fluorine-containing polymer (S') is preferably 5 to 35 mol%. In addition to the fluorine-containing olefin and fluorine-containing monomer (S'), other monomers may also be used in the production of the fluorine-containing polymer (S'). Examples of other monomers include those exemplified above.

[0092] 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').

[0093] Specific examples of methods for converting groups in a precursor film that can be converted into ion exchange groups include methods of subjecting the precursor film to hydrolysis or acidification. Among these, a method of contacting the precursor film with an alkaline aqueous solution is preferred.

[0094] Specific examples of methods for bringing the precursor film into contact with an alkaline aqueous solution include immersing the precursor film in the 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.

[0095] The alkaline aqueous solution preferably contains an alkali metal hydroxide, a water-soluble organic solvent, and water. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide. In this specification, a water-soluble organic solvent is an organic solvent that dissolves readily in water, and specifically, an organic solvent with a solubility of 0.1 g or more in 1,000 ml of water (20°C) is preferred, and an organic solvent with a solubility of 0.5 g or more is particularly preferred. The water-soluble organic solvent preferably contains at least one selected from the group consisting of aprotic organic solvents, alcohols, and amino alcohols, and is particularly preferred to contain an aprotic organic solvent. The water-soluble organic solvent may be used alone or in combination of two or more.

[0096] 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.

[0097] The concentration of alkali metal hydroxide is preferably 1 to 60% by mass, and particularly preferably 3 to 55% by mass, in the alkaline aqueous solution. The content of 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 concentration of water is preferably 39 to 80% by mass, in the alkaline aqueous solution.

[0098] 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.

[0099] After contacting the precursor film with an alkaline aqueous solution, the resulting film may be contacted with an acidic aqueous solution to convert the ion exchange groups to the acidic form. Specific examples of methods for contacting the precursor film with an acidic aqueous solution include immersing the precursor film in the acidic aqueous solution and spraying the acidic aqueous solution onto the surface of the precursor film. The acidic aqueous solution preferably contains an acid component and water. Specific examples of the acid component include hydrochloric acid and sulfuric acid.

[0100] [Membrane Electrode Assembly] The membrane electrode assembly of this disclosure includes an anode having a catalyst layer, a cathode having a catalyst layer, and a solid polymer electrolyte membrane disposed between the anode and the cathode. The solid polymer electrolyte membrane is as described above and therefore its description is omitted.

[0101] Figure 4 is a cross-sectional view showing an example of a membrane electrode assembly of the present disclosure. The membrane electrode assembly 20 includes an anode 22 having a catalyst layer 26 and a gas diffusion layer 28, a cathode 24 having a catalyst layer 26 and a gas diffusion layer 28, and a solid polymer electrolyte membrane 10 disposed between the anode 22 and the cathode 24 in contact with the catalyst layer 26.

[0102] <Anode and Cathode> The anode and cathode each have a catalyst layer. In the example in Figure 4, the anode 22 and cathode 24 each have a catalyst layer 26 and a gas diffusion layer 28. In at least one of the anode 22 and cathode 24, there may be a region where a portion of the gas diffusion layer 28 and the catalyst layer 26 overlap in the thickness direction. Also, in at least one of the anode 22 and cathode 24, the catalyst layer 26 may be omitted, and the gas diffusion layer 28 may perform the role of the catalyst layer 26.

[0103] Specific examples of catalyst layers include layers containing a catalyst and a polymer having ion exchange groups. Specific examples of catalysts include supported catalysts in which a catalyst containing platinum, a platinum alloy, or platinum having a core-shell structure is supported on a carbon support, ruthenium oxide catalysts, iridium oxide catalysts, ruthenium-containing composite oxides, iridium-containing composite oxides, ruthenium oxide-containing catalysts having a core-shell structure, and iridium oxide-containing catalysts having a core-shell structure. Carbon black powder is used as the carbon support. Fluorine-containing polymers having ion exchange groups are used as the polymers having ion exchange groups. The catalyst included in the anode-side catalyst layer is preferably one or more catalysts selected from the group consisting of ruthenium oxide catalysts, iridium oxide catalysts, ruthenium-containing composite oxides, iridium-containing composite oxides, ruthenium oxide-containing catalysts having a core-shell structure, and iridium oxide-containing catalysts having a core-shell structure. The supported catalyst is preferred as the catalyst included in the cathode-side catalyst layer.

[0104] The gas diffusion layer has the function of uniformly diffusing gas into the catalyst layer and also functions as a current collector. Specific examples of the gas diffusion layer include carbon paper, carbon cloth, carbon felt, and metal mesh. For the anode-side gas diffusion layer, a metal mesh is preferably used. The metal material constituting the metal mesh is preferably a metal with high corrosion resistance, such as titanium, zirconium, niobium, and tantalum, with titanium being preferred. The gas diffusion layer may be treated to be water-repellent with PTFE or the like. If the gas diffusion layer is a metal mesh, its surface may be coated with a precious metal such as platinum. In the film electrode assembly shown in Figure 3, the gas diffusion layer 28 is included, but the gas diffusion layer is an arbitrary component and does not have to be included in the film electrode assembly. Furthermore, as described above, the gas diffusion layer may contain the catalyst mentioned above.

[0105] The film thickness of the anode and cathode is preferably 5 to 100 μm, more preferably 5 to 50 μm, even more preferably 5 to 30 μm, and particularly preferably 5 to 15 μm, independently of each other. The film thickness of the anode and cathode is measured using an image obtained by measuring a cross-section of the film electrode assembly cut in a plane parallel to the film thickness direction with an optical microscope, and is the arithmetic mean value at any 20 locations.

[0106] [Method for Manufacturing a Membrane Electrode Assembly] Examples of methods for manufacturing a membrane electrode assembly include forming a catalyst layer on a solid polymer electrolyte membrane and then sandwiching the resulting assembly between gas diffusion layers, and forming a catalyst layer on a gas diffusion layer to form electrodes (anode, cathode) and sandwiching a solid polymer electrolyte membrane between these electrodes. Methods for manufacturing the catalyst layer include applying a catalyst layer forming coating solution to a predetermined position on the solid polymer electrolyte membrane and drying it as needed. Alternatively, a catalyst layer forming coating solution may be applied to a substrate and dried to form the catalyst layer on the substrate, after which the formed catalyst layer is transferred to the solid polymer electrolyte membrane. The catalyst layer forming coating solution may be a liquid in which a polymer having ion exchange groups and a catalyst are dispersed in a dispersion medium.

[0107] <Applications> The solid polymer electrolyte membrane of this disclosure can be used for water electrolysis. The membrane electrode assembly of this disclosure can be used in water electrolysis apparatuses (specifically, solid polymer type water electrolysis apparatuses). Furthermore, the membrane electrode assembly of this disclosure can be used in electrolytic hydrogenation apparatuses for aromatic compounds (e.g., toluene).

[0108] [Water Electrolyzer] The water electrolyzer of the present disclosure includes the membrane electrode assembly described above. Because the water electrolyzer of the present disclosure includes the membrane electrode assembly described above (solid polymer electrolyte membrane of the present disclosure), irregularities are less likely to occur on the surface of the solid polymer electrolyte membrane when it comes into contact with the solvent (water). When irregularities are less likely to occur on the surface of the solid polymer electrolyte membrane, it is thought that pinholes are less likely to occur in the solid polymer electrolyte membrane for reasons such as reduced stress concentration and reduced contact with other components (especially penetration into the gas diffusion layer via the catalyst layer). The water electrolyzer of the present disclosure can have the same configuration as known water electrolyzers, except that it includes the membrane electrode assembly described above.

[0109] [Electrolytic Hydrogenation Apparatus] The electrolytic hydrogenation apparatus of this disclosure includes the membrane electrode assembly described above. The electrolytic hydrogenation apparatus of this disclosure may have the same configuration as known electrolytic hydrogenation apparatuses, except for including the membrane electrode assembly described above (for example, an oxygen recovery member for recovering generated oxygen, and a hydrogen recovery member for recovering generated hydrogen). Because the electrolytic hydrogenation apparatus of this disclosure includes the membrane electrode assembly described above (the solid polymer electrolyte membrane of this disclosure), irregularities are less likely to occur on the surface of the polymer electrolyte membrane when it comes into contact with a solvent (for example, toluene). If irregularities are less likely to occur on the surface of the solid polymer electrolyte membrane, it is thought that pinholes are less likely to occur in the solid polymer electrolyte membrane for the same reasons as described in the section on water electrolysis apparatuses. The electrolytic hydrogenation apparatus of this disclosure can suitably electrolytically hydrogenate aromatic compounds such as benzene, toluene, and naphthalene.

[0110] [Method for producing hydrogen] The method for producing hydrogen according to this disclosure involves electrolyzing water (electrolyte) using the water electrolysis apparatus described above to produce hydrogen. Because the water electrolysis apparatus described herein is used in the method for producing hydrogen according to this disclosure, hydrogen can be produced efficiently.

[0111] The present invention will be described in detail below with reference to examples. Examples 1 to 5 and 11 to 13 are examples, and examples 6 to 10 are comparative examples. However, the present invention is not limited to these examples.

[0112] [Measurement Method] <Ion Exchange Capacity of Fluorine-Containing Polymer> A fluorine-containing polymer was left to stand for 24 hours in a glove box flowing dry nitrogen, and its dry mass was measured. Then, the fluorine-containing polymer was immersed in a 2 mol / L sodium chloride aqueous solution at 60°C for 1 hour. After washing the fluorine-containing polymer with ultrapure water, it was removed, and the ion exchange capacity X (milliequivalents / gram dry resin) of the fluorine-containing polymer was determined by titrating the solution in which the fluorine-containing polymer had been immersed with a 0.1 mol / L sodium hydroxide aqueous solution. Note that "meq / g" means "milliequivalents / g dry resin," which is the unit of ion exchange capacity.

[0113] <Fabric weight, yarn diameter, opening ratio, and density> The raw 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 arithmetic mean was used to determine the fabric weight (g / m²).２ The following was determined: The yarn diameter, opening ratio, warp density, and weft density were calculated using the method described above.

[0114] <Film Thickness> The film thickness of the solid polymer electrolyte membrane was determined using the method described above.

[0115] [Example 1] <Production of fluorine-containing polymer (S'-1)> CF ２ =CF ２ The monomer (X) represented by the following formula (X) was copolymerized to obtain a fluorine-containing polymer (S'-1) (ion exchange capacity: 1.25 milliequivalents / gram dry resin). The ion exchange capacity represents the ion exchange capacity of the fluorine-containing polymer obtained when hydrolyzed by the procedure described later, and the same applies to each of the following examples. CF ２ = CF - O - CF ２ CF (CF ３ )-O-CF ２ CF ２ -SO ２ F ... (X)

[0116] <Manufacturing of Film α1> A fluorine-containing polymer (S'-1) was molded by melt extrusion to obtain a film α1 (film thickness: 30 μm) made of the fluorine-containing polymer (S'-1).

[0117] <Manufacturing of Woven Fabric A1> Woven fabric A1 was obtained by plain weaving polyetheretherketone (PEEK) yarn with a diameter of 25 μm and 5.7 denier for both the warp and weft threads, so that the density of the warp and weft threads were independently 200 threads / inch. The basis weight of woven fabric A1 is 10.0 g / m ２ The opening ratio was 64.5%. The warp and weft threads were composed of slit yarn. The above PEEK had the following structure.

[0118]

[0119] <Manufacturing of Solid Polymer Electrolyte Membrane> PET film / film α1 / woven fabric A1 / film α1 / PET film were layered in this order. Each layered component was subjected to a temperature of 200°C and a surface pressure of 30 MPa / m². ２After heating and pressing the materials in a flatbed press for 10 minutes, the transfer substrates on both sides were peeled off at a temperature of 50°C to obtain a precursor film.

[0120] 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 a solid polymer electrolyte film.

[0121] [Examples 2 to 13] Solid polymer electrolyte membranes were obtained in the same manner as in Example 1, except that the film and fabric were changed as shown in Table 1. The film and fabric used in each example are described below.

[0122] <Production of Film α2> A fluorine-containing polymer (S'-2) was molded by melt extrusion to obtain film α2 (film thickness: 30 μm) made of the fluorine-containing polymer (S'-2). The fluorine-containing polymer (S'-2) was obtained in the same manner as the fluorine-containing polymer (S'-1), except that the ratio of monomers used in copolymerization was adjusted so that the ion exchange capacity was as shown in the table below.

[0123] <Production of Film α3> A fluorine-containing polymer (S'-3) was molded by melt extrusion to obtain film α3 (film thickness: 30 μm) made of the fluorine-containing polymer (S'-3). The fluorine-containing polymer (S'-3) was obtained in the same manner as the fluorine-containing polymer (S'-1), except that the ratio of monomers used in copolymerization was adjusted so that the ion exchange capacity was as shown in the table below.

[0124] <Manufacturing of Film α4> A fluorine-containing polymer (S'-1) was molded by melt extrusion to obtain Film α4 (film thickness: 45 μm) made of the fluorine-containing polymer (S'-1).

[0125] <Manufacturing of Film α5> A fluorine-containing polymer (S'-2) was molded by melt extrusion to obtain Film α5 (film thickness: 40 μm) made of the fluorine-containing polymer (S'-2).

[0126] <Production of Film α6> A fluorine-containing polymer (S'-3) was molded by melt extrusion to obtain film α6 (film thickness: 30 μm) made of the fluorine-containing polymer (S'-3). The fluorine-containing polymer (S'-3) was obtained in the same manner as the fluorine-containing polymer (S'-1), except that the ratio of monomers used in copolymerization was adjusted so that the ion exchange capacity was as shown in the table below.

[0127] <Manufacturing of Woven Fabric A2> Woven fabric A2 was obtained in the same manner as woven fabric A1, except that the warp density and weft density were adjusted to the values ​​shown in the table below.

[0128] <Manufacturing of Woven Fabric A3> Woven fabric A3 was obtained in the same manner as woven fabric A1, except that the yarns used for the warp and weft had diameters shown in the table below, and the density of the warp and weft were adjusted to the values ​​shown in the table below.

[0129] <Manufacturing of Woven Fabric A4> PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, density 2.14 g / cm³) ３ Using yarn with a diameter of 35 μm, consisting of the above, as both warp and weft threads, a plain weave was obtained to obtain woven fabric A4, with a warp and weft density of 100 threads / inch. The basis weight of woven fabric A4 was 16.2 g / m². ２ The opening ratio was 74.3%. The warp and weft threads were composed of slit yarn.

[0130] <Manufacturing of Woven Fabric A5> Woven fabric A5 was obtained in the same manner as woven fabric A1, except that the yarns used for the warp and weft had diameters shown in the table below, and the density of the warp and weft yarns was adjusted to the values ​​shown in the table below.

[0131] <Manufacturing of Woven Fabric A6> Woven fabric A6 was obtained in the same manner as woven fabric A1, except that the yarns used for the warp and weft had diameters shown in the table below, and the density of the warp and weft yarns was adjusted to the values ​​shown in the table below.

[0132] <Manufacturing of Woven Fabric A7> Woven fabric A7 was obtained in the same manner as woven fabric A1, except that the yarns used for the warp and weft had diameters shown in the table below, and the density of the warp and weft yarns was adjusted to the values ​​shown in the table below.

[0133] <Manufacturing of Woven Fabric A8> Woven fabric A8 was obtained in the same manner as woven fabric A1, except that the warp and weft threads used were made of the material shown in the table below and had a thread diameter of the value shown in the table below, and the density of the warp and weft threads was adjusted to the values ​​shown in the table below.

[0134] <Manufacturing of Woven Fabric A9> Woven fabric A9 was obtained in the same manner as woven fabric A1, except that the warp and weft threads used were of the material shown in the table below, with thread diameters shown in the table below, and the density of the warp and weft threads was adjusted to the values ​​shown in the table below.

[0135] <Manufacturing of Woven Fabric A10> Woven fabric A10 was obtained in the same manner as woven fabric A1, except that the warp and weft threads used were made of the material shown in the table below and had a thread diameter of the value shown in the table below, and the density of the warp and weft threads was adjusted to the values ​​shown in the table below.

[0136] [Evaluation Method] <Evaluation of Surface Irregularities> First, each example of the solid polymer electrolyte membrane was immersed in 95°C water for 60 minutes. The cross-section of each immersed solid polymer electrolyte membrane was observed at 200x magnification using an optical microscope (Olympus BX-51) to obtain an image and evaluate the frequency of surface irregularities in the solid polymer electrolyte membrane. The evaluation method will be explained in detail with reference to Figure 5. Figure 5 is a cross-sectional view of a solid polymer electrolyte membrane in which surface irregularities have occurred in some areas. The solid polymer electrolyte membrane 10a shown in Figure 5 includes an electrolyte 12 and a woven fabric 14 placed in the electrolyte 12. The woven fabric 14 is composed of threads 14a, 14b, and 14c. In Figure 5, points pa, pb, and pc are the center positions in the cross-sectional views of threads 14a, 14b, and 14c, respectively. Also in Figure 5, the dashed lines in the left-right direction of the paper are imaginary lines passing through points pa, pb, and pc. In Figure 5, the electrolyte 12 between threads 14a and 14b is deformed into a convex shape upwards on the paper, resulting in surface irregularities.

[0137] Here, in a direction perpendicular to the above-mentioned imaginary line, the distance from point pa to the upper surface of the electrolyte 12 on the paper is defined as distance da1. Similarly, in a direction perpendicular to the above-mentioned imaginary line, the distance from point pb to the upper surface of the electrolyte 12 on the paper is defined as distance db1, and in a direction perpendicular to the above-mentioned imaginary line, the distance from point pc to the upper surface of the electrolyte 12 on the paper is defined as distance dc1. Similarly, in a direction perpendicular to the above-mentioned imaginary line, the distance from point pa to the lower surface of the electrolyte 12 on the paper is defined as distance da2. Furthermore, in a direction perpendicular to the above-mentioned imaginary line, the distance from point pb to the lower surface of the electrolyte 12 on the paper is defined as distance db2, and in a direction perpendicular to the above-mentioned imaginary line, the distance from point pc to the lower surface of the electrolyte 12 on the paper is defined as distance dc2. As described above, in the solid polymer electrolyte membrane 10a, the distances from the center of 10 adjacent threads to the surface of the electrolyte 12 (Figure 5 intermediate distances da1, db1, dc1, da2, db2, and dc2) are measured on the observation image, and the arithmetic mean of these distances (hereinafter referred to as "distance d") is calculated. ａｖｅ It is also called "calculating ).

[0138] Furthermore, in Figure 5, the maximum distance from the electrolyte 12 to the top of the paper in a direction perpendicular to the virtual line between threads 14a and 14b is defined as distance d11. Similarly, the minimum distance from the electrolyte 12 to the bottom of the paper in a direction perpendicular to the virtual line between threads 14a and 14b is defined as distance d12. Also, in Figure 5, the maximum distance from the electrolyte 12 to the top of the paper in a direction perpendicular to the virtual line between threads 14b and 14c is defined as distance d21. Similarly, the minimum distance from the electrolyte 12 to the bottom of the paper in a direction perpendicular to the virtual line between threads 14b and 14c is defined as distance d22. That is, on the surface of the solid polymer electrolyte membrane 10a side where the electrolyte 12 is deformed into a convex shape (top of the paper in Figure 5), the maximum distance from the electrolyte 12 in a direction perpendicular to the virtual line between the two threads is measured on the observation image. Furthermore, on the surface of the solid polymer electrolyte membrane 10a where the electrolyte 12 is deformed into a concave shape (the lower part of the paper in Figure 5), the minimum distance to the electrolyte 12 between the two threads in a direction perpendicular to the dashed line is measured on the observation image.

[0139] The maximum distance between the two threads and the distance d ａｖｅ The absolute value of the difference between the two threads, and the minimum distance between the two threads and the distance d. ａｖｅ The absolute value of the difference between the two is the distance d. ａｖｅ If the ratio is 50% or more, it is assumed that surface irregularities have occurred between the two threads. For example, in Figure 5, the distance d12 and d ａｖｅ The absolute value of the difference between is d ａｖｅSince the ratio is 50% or more, it is determined that surface irregularities occur between thread 14a and thread 14b. (A) The above determination is made between each of 10 adjacent threads, and the number of locations that satisfy the above criteria is counted. Based on the number of counted surface irregularities, the surface irregularities were evaluated according to the following criteria. In practical terms, an A, B, or C rating is preferable, an A or B rating is more preferable, and an A rating is even more preferable. A: The number of surface irregularities is 0. B: The number of surface irregularities is 1. C: The number of surface irregularities is 2. D: The number of surface irregularities is 3 or more. (B) For the example that received an A rating in (A) above, the same determination is made between each of 100 adjacent threads, and the number of locations that satisfy the above criteria is counted. Based on the number of counted surface irregularities, the surface irregularities were evaluated according to the following criteria. S: The number of surface irregularities is 0. A: The number of surface irregularities is 1 to 3. B: The number of surface irregularities is between 4 and 9.

[0140] [Results] The conditions for fabricating the solid polymer electrolyte membrane, and the results of various measurements and evaluations of the obtained solid polymer electrolyte membrane are shown in Table 1.

[0141]

[0142] From the results shown in Table 1, it was confirmed that the solid polymer electrolyte membranes of Examples 1-5 and 11-13, in which the warp and weft threads constituting the fabric contain polyetheretherketone, the thread diameters of the warp and weft threads constituting the fabric are independently 30 μm or less, and the density of the warp threads constituting the fabric and the density of the weft threads constituting the fabric are independently 110 threads / inch or more, are less prone to surface irregularities when in contact with a solvent compared to the solid polymer electrolyte membranes of Examples 6-10, which do not satisfy one or more of the above requirements. Furthermore, from a comparison between Examples 1, 2, 4, and 5 and Example 3, it was confirmed that when the density of the warp and weft threads constituting the fabric is independently 180 threads / inch or more, surface irregularities are even less likely to occur. From a comparison between Example 1 and Example 5, it was confirmed that when the ion exchange capacity is 1.20 milliequivalents / g dry resin or more, and the thread diameters of the warp and weft threads constituting the fabric are independently 23 μm or more, surface irregularities are even less likely to occur. From a comparison of Example 1 and Example 4, it was confirmed that when the ion exchange capacity of the fluorine-containing polymer is 1.30 milliequivalents / gram dry resin or less, surface irregularities are less likely to occur.

[0143] 10 Solid polymer electrolyte membrane 12 Electrolyte 14 Woven fabric 14a, 14b, 14c Yarn 20 Membrane electrode assembly 22 Anode 24 Cathode 26 Catalyst layer 28 Gas diffusion layer

[0144] Furthermore, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-197476, filed on November 12, 2024, are incorporated herein by reference as disclosure of the present invention.

Claims

1. A solid polymer electrolyte membrane comprising a fluorine-containing polymer having ion exchange groups and a woven fabric, wherein the warp and weft threads constituting the woven fabric contain polyether ether ketone, the diameter of the warp and weft threads constituting the woven fabric are independently 30 μm or less, and the density of the warp threads constituting the woven fabric and the density of the weft threads constituting the woven fabric are independently 110 threads / inch or more.

2. The solid polymer electrolyte membrane according to claim 1, wherein the ion exchange capacity of the fluorine-containing polymer is 0.90 milliequivalents / gram of dry resin or more.

3. The solid polymer electrolyte membrane according to claim 1 or 2, wherein the density of the warp threads constituting the woven fabric and the density of the weft threads constituting the woven fabric are each independently 150 threads / inch or more.

4. The solid polymer electrolyte membrane according to claim 1 or 2, wherein the opening ratio of the woven fabric is 50 to 90%.

5. The solid polymer electrolyte membrane according to claim 1 or 2, wherein the denier count of the warp threads and the denier count of the weft threads constituting the woven fabric are each independently 10.0 or less.

6. The solid polymer electrolyte membrane according to claim 1 or 2, wherein the thickness of the solid polymer electrolyte membrane is 50 to 150 μm.

7. The membrane electrode assembly according to claim 1 or 2, wherein the ion exchange group is a sulfonic acid type functional group.

8. The membrane electrode assembly according to claim 1 or 2, wherein the fluorine-containing polymer comprises units based on fluorine-containing olefins and units having sulfonic acid-type functional groups and fluorine atoms.

9. The membrane electrode assembly according to claim 8, 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.

10. A solid polymer electrolyte membrane used in a water electrolysis apparatus, according to claim 1 or 2.

11. A membrane electrode assembly comprising an anode having a catalyst layer, a cathode having a catalyst layer, and a solid polymer electrolyte membrane according to claim 1 or 2 disposed between the anode and the cathode.

12. A water electrolysis apparatus comprising the membrane electrode assembly described in claim 11.

13. An electrolytic hydrogenation apparatus comprising the membrane electrode assembly described in claim 11.

14. A method for producing hydrogen, comprising producing hydrogen by electrolyzing water using the water electrolysis apparatus described in claim 12.

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