Solid polymer electrolyte membrane, alkaline water electrolysis apparatus, and production method of solid polymer electrolyte membrane

Abstract

To provide: a solid polymer electrolyte membrane for alkaline water electrolysis excellent in omnidirectional large pressure resistance generated on a diaphragm partitioning an anode chamber and a cathode chamber of a water electrolysis apparatus and having a gas blocking property stably suppressing mixing of an oxygen gas and a hydrogen gas; and an alkaline water electrolysis apparatus.SOLUTION: There is provided a solid polymer electrolyte membrane which contains a nonwoven fabric comprising a fluorine-containing polymer having an ion exchange group and a polymer having a hydrogen permeability coefficient within a predetermined range, in which the weight of the fluorine-containing polymer per unit area of the solid polymer electrolyte membrane is within a predetermined range.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a solid polymer electrolyte membrane, an alkaline water electrolysis device, and a method for manufacturing a solid polymer electrolyte membrane.

Background Art

[0002] In power generation using renewable energy such as solar power generation and wind power generation, the amount of power generation varies depending on the time zone and natural conditions. Therefore, it has been proposed to convert surplus power into hydrogen. As a method for converting surplus power into hydrogen, there is electrolysis of water, which has the advantage of obtaining high-purity hydrogen compared to the method of reforming fossil fuels. When electrolyzing water, generally, in order to enhance the conductivity of the electrolyte, sodium hydroxide, potassium hydroxide, etc. are added to water as an electrolyte, and a direct current is applied between both electrodes to perform electrolysis.

[0003] An electrolytic cell for performing electrolysis is partitioned into an anode chamber and a cathode chamber via a diaphragm. In the anode chamber, oxygen is generated, and in the cathode chamber, hydrogen is generated. The diaphragm is required to have gas barrier properties so as to block and prevent mixing of this oxygen gas and hydrogen gas. Further, in the electrolysis of water, the medium that transports electricity (electrons) is ions, and in order to efficiently perform electrolysis, high ion permeability of the diaphragm is also desired.

[0004] As an alkaline water electrolysis diaphragm, in Patent Document 1, an alkaline water electrolysis diaphragm containing a polymer having a sulfonic acid type functional group is known. It is described that by thinning the thickness of an ion exchange membrane made of a polymer having a sulfonic acid type functional group to 25 to 70 μm and adjusting the ion exchange capacity, the electrolysis voltage can be kept low even at a high current density. However, in Patent Document 2, it is described that the gas permeability improves when the thickness of the ion exchange membrane is reduced, and there is a problem that the gas barrier property deteriorates when thinned.

[0005] In a water electrolysis device, a large pressure is applied in all directions to the diaphragm that separates the anode chamber and the cathode chamber. Therefore, high strength is required for the solid polymer electrolyte membrane. However, a solid polymer electrolyte membrane with high strength has a high electrical resistance, resulting in a high electrolysis voltage. Therefore, Patent Document 3 describes that by adjusting the characteristics of a fluorine-containing polymer having an ion exchange group that constitutes the solid polymer electrolyte membrane and a woven fabric, it is possible to obtain excellent strength and reduce the electrolysis voltage. However, since the woven fabric is formed of warp and weft threads, it has excellent properties in the longitudinal and transverse directions, but has the drawback that its properties in the diagonal direction are extremely poor.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described above, a large pressure is generated in all directions on the diaphragm, but in the conventionally disclosed technologies, a diaphragm for alkaline water electrolysis having strength in the machine direction (MD), width direction (TD), and diagonal direction has not been obtained. If cracks occur in the membrane due to insufficient strength, there is a problem that oxygen gas and hydrogen gas are mixed, and the hydrogen concentration in oxygen enters the explosive range.

[0008] Therefore, an object of the present invention is to provide a solid polymer electrolyte membrane for alkaline water electrolysis that has excellent resistance to large pressures in all directions generated in the diaphragm that separates the anode chamber and the cathode chamber of a water electrolysis device, and has a gas barrier property that stably suppresses the mixing of oxygen gas and hydrogen gas, and an alkaline water electrolysis device.

Means for Solving the Problems

[0009] As a result of intensive research to solve the above problems, the present inventors have found that a solid polymer electrolyte membrane (separator) containing a fluorine-containing polymer having an ion exchange group and a non-woven fabric composed of a polymer having a low hydrogen permeation coefficient can solve the above problems by controlling the weight of the fluorine-containing polymer having an ion exchange group per 1 m 2 and have completed the present invention.

[0010] That is, the present invention is as follows. [1] A solid polymer electrolyte membrane comprising a fluorine-containing polymer having an ion exchange group and a non-woven fabric containing a polymer having a hydrogen permeation coefficient of 50 Barrer or less at 90 °C, wherein the weight of the fluorine-containing polymer per 1 m of the solid polymer electrolyte membrane is 10 g or more and 130 g or less. 2 Solid polymer electrolyte membrane. [2] The solid polymer electrolyte membrane according to [1], wherein the ion exchange capacity of the fluorine-containing polymer is 0.90 meq / g dry resin or more and 1.40 meq / g dry resin or less. [3] The solid polymer electrolyte membrane according to [1] or [2], wherein the material of the non-woven fabric is a hydrocarbon-based polymer. [4] The solid polymer electrolyte membrane according to any one of [1] to [3], wherein the material of the non-woven fabric is selected from the group consisting of polyphenylene sulfide, polyether ketone, and polyethylene. [5] The solid polymer electrolyte membrane according to [4], wherein the material of the non-woven fabric is polyphenylene sulfide and the crystallinity of the non-woven fabric is 30% or more and 60% or less. [6] The solid polymer electrolyte membrane according to any one of [1] to [5], wherein the basis weight of the non-woven fabric is 5 g / m 2 or more and 100 g / m 2 or less. [7] The solid polymer electrolyte membrane according to any one of [1] to [6], wherein the fineness of the fibers constituting the nonwoven fabric is in the range of 0.5 denier or more and 10 denier or less. [8] The solid polymer electrolyte membrane according to any one of [1] to [7], wherein the volume fraction of the polymer constituting the nonwoven fabric in the mixed layer of the fluorine-containing polymer and the nonwoven fabric of the solid polymer electrolyte membrane is 20% or more and 70% or less. [9] The solid polymer electrolyte membrane according to any one of [1] to [8], wherein the ion exchange group is a sulfonic acid type functional group.

[10] The solid polymer electrolyte membrane according to any one of [1] to [9], wherein the fluorine-containing polymer having the ion exchange group contains a polymer having a unit represented by the following formula (A) or formula (B). Formula (A) -[CF2-CF(-O-CF2CF(CF3)-O-(CF2)m-SO3M)]- [In the formula, m is an integer from 1 to 6, and M is an alkali metal. ] Formula (B) -[CF2-CF(-O-(CF2)m-SO3M)]- [In the formula, m is an integer from 1 to 6, and M is an alkali metal. ]

[11] The solid polymer electrolyte membrane according to any one of [1] to

[10] , having a hydrophilic layer as the outermost layer on both sides or one side of the solid polymer electrolyte membrane.

[12] The solid polymer electrolyte membrane according to

[11] , wherein the hydrophilic layer is an inorganic particle layer containing inorganic particles.

[13] The solid polymer electrolyte membrane according to

[12] , wherein the inorganic particles are inorganic particles composed of at least one selected from the group consisting of oxides, nitrides, and carbides of Group 4 elements or Group 14 elements.

[14] The solid polymer electrolyte membrane according to

[13] , wherein the inorganic particles are inorganic particles composed of SiO2, SiC, ZrO2, or ZrC.

[15] The solid polymer electrolyte membrane for alkaline water electrolysis, the solid polymer electrolyte membrane according to any one of [1] to

[14] .

[16] An electrolytic cell equipped with a cathode and an anode, The solid polymer electrolyte membrane according to any one of [1] to

[14] , and comprising, The solid polymer electrolyte membrane is mounted in the electrolytic cell so as to partition the inside of the electrolytic cell into a cathode chamber and an anode chamber on the cathode side. Alkaline water electrolysis device.

[17] A method for producing a solid polymer electrolyte membrane according to any one of [1] to

[14] , comprising: A step of producing a fluorine-containing polymer, A step of obtaining a nonwoven fabric, A step of forming a film from the fluorine-containing polymer, A step of embedding the nonwoven fabric and the film to form a composite membrane, A step of hydrolyzing the composite membrane with an acid or an alkali, A method for producing a solid polymer electrolyte membrane, comprising.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a solid polymer electrolyte membrane for alkaline water electrolysis and an alkaline water electrolysis device that are excellent in the pressure resistance in all directions generated in the diaphragm that partitions the anode chamber and the cathode chamber of the water electrolysis device, and have a gas barrier property that stably suppresses the mixing of oxygen gas and hydrogen gas.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "the present embodiments") will be described in detail. Note that the present invention is not limited to the following present embodiments, and can be variously modified and implemented within the scope of the gist thereof.

[0014] 〔Solid polymer electrolyte membrane〕 The solid polymer electrolyte membrane of the present embodiment is a solid polymer electrolyte membrane including a fluorine-containing polymer having an ion-exchange group and a non-woven fabric including a polymer having a hydrogen permeation coefficient of 50 Barrer or less at 90 °C, wherein the weight of the fluorine-containing polymer per 1 m 2 of the solid polymer electrolyte membrane is 10 g or more and 130 g or less. According to the solid polymer electrolyte membrane of the present embodiment having the above-described configuration, it has excellent strength, and when performing alkaline water electrolysis, the electrolysis voltage can be kept low even at a high current density, and further, the mixing of oxygen gas and hydrogen gas generated even at a low current density can be suppressed. A solid polymer electrolyte membrane for alkaline water electrolysis and an alkaline water electrolysis device having gas barrier properties can be obtained.

[0015] Hereinafter, the fluorine-containing polymer having an ion-exchange group, the non-woven fabric, and the hydrophilic layer of the present embodiment will be described.

[0016] 〔Fluorine-containing polymer having an ion-exchange group〕 The fluorine-containing polymer having an ion-exchange group used in the solid polymer electrolyte membrane may be one kind, or two or more kinds may be mixed and used. The fluorine-containing polymer contains a unit based on a fluorine-containing olefin. The solid polymer electrolyte membrane may contain a polymer having an ion-exchange group other than the fluorine-containing polymer having an ion-exchange group, but the polymer having an ion-exchange group in the solid polymer electrolyte membrane preferably consists essentially of a fluorine-containing polymer having an ion-exchange group. Consisting essentially of a fluorine-containing polymer having an ion-exchange group means that the content of the fluorine-containing polymer having an ion-exchange group is 95% by mass or more based on the total mass of the polymer having an ion-exchange group in the solid polymer electrolyte membrane. The upper limit of the content of the fluorine-containing polymer having an ion-exchange group is 100% by mass based on the total mass of the polymer in the solid polymer electrolyte membrane.

[0017] Specific examples of the polymer having an ion-exchange group other than the fluorine-containing polymer having an ion-exchange group include polymers of heterocyclic compounds containing one or more nitrogen atoms in the ring, and one or more polyazole compounds selected from the group consisting of polymers of heterocyclic compounds containing one or more nitrogen atoms and oxygen atoms and / or sulfur atoms in the ring. Specific examples of the polyazole compound include polyimidazole, polybenzimidazole, polybenzobisimidazole, polybenzoxazole, polyoxazole, polythiazole, and polybenzothiazole. Also, from the viewpoint of oxidation resistance, other polymers include polyphenylene sulfide resin and polyphenylene ether resin.

[0018] Specific examples of the ion-exchange group of the fluorine-containing polymer having an ion-exchange group include sulfonic acid type functional groups and carboxylic acid type functional groups, and sulfonic acid type functional groups are preferred from the viewpoint of being able to further reduce the electrolysis voltage.

[0019] The fluorine-containing polymer having a sulfonic acid type functional group preferably contains a unit based on a fluorine-containing olefin and a unit based on a monomer having a sulfonic acid type functional group and a fluorine atom. Examples of the fluorine-containing olefin include fluoroolefins having 2 to 3 carbon atoms and having one or more fluorine atoms in the molecule. Specific examples of the fluoroolefin include tetrafluoroethylene (hereinafter also referred to as TFE), chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and hexafluoropropylene. Among them, TFE is preferred in terms of the production cost of the monomer, the reactivity with other monomers, and the excellent properties of the resulting fluorine-containing polymer(s). The fluorine-containing olefin may be used alone or in combination of two or more.

[0020] As the unit based on the monomer having a sulfonic acid type functional group and a fluorine atom, the unit represented by the formula (1) is preferred. Formula (1): -[CF2-CF(-L-(SO3M) n )]-

[0021] Examples of the unit represented by the formula (1) include the unit represented by the formula (1-1), the unit represented by the formula (1-2), and the like. Formula (1-1): -[CF2-CF(-O-R f1 -SO3M)]- Formula (1-2): -[CF2-CF(-R f1 -SO3M)]-

[0022] However, R f1 is a perfluoroalkylene group which may contain an oxygen atom between carbon atoms. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, more preferably 2 or more, preferably 20 or less, and more preferably 10 or less.

[0023] M is an alkali metal. Examples of the alkali metal include Li, Na, K, Rb, Cs, and the like.

[0024] Specific examples of the unit represented by formula (1-1) include the following units. In the formula, w is an integer from 1 to 8, and x is an integer from 1 to 5. The definition of M in the formula 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)]-

[0025] Specific examples of the unit represented by formula (1-2) include the following units. In the formula, w is an integer from 1 to 8. The definition of M in the formula is as described above. -[CF2-CF(-(CF2) w -SO3M)]- -[CF2-CF(-CF2-O-(CF2) w -SO3M)]-

[0026] The fluorine-containing polymer (S) may contain units based on monomers other than units based on fluorine-containing olefins and units based on monomers having a sulfonic acid-type functional group and a fluorine atom. Specific examples of other monomers include CF2=CFR f5 (where R f5 is a perfluoroalkyl group having 2 to 10 carbon atoms.), CF2=CF-OR f6 (where R f6 is a perfluoroalkyl group having 1 to 10 carbon atoms.), CF2=CFO(CF2) v CF=CF2 (where v is an integer from 1 to 3).

[0027] The ion exchange capacity of the fluorine-containing polymer having an ion exchange group is not particularly limited, but is preferably in the range of 0.90 meq / g dry resin or more and 1.40 meq / g dry resin or less, more preferably in the range of 1.00 meq / g dry resin or more and 1.30 meq / g dry resin or less, and even more preferably in the range of 1.05 meq / g dry resin or more and 1.17 meq / g dry resin or less. If the ion exchange capacity is 0.90 meq / g dry resin or more, the electrolysis voltage of the water electrolysis device tends to be reduced. If the ion exchange capacity is 1.40 meq / g dry resin or less, the water content of the polymer does not become excessively high, and film wrinkles are less likely to occur during film formation. If the ion exchange capacity is 1.00 meq / g dry resin or more, the film has flexibility and the handleability tends to improve. If it is 1.30 meq / g dry resin or less, the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas tends to improve. If the ion exchange capacity is 1.05 meq / g dry resin or more, the strength is sufficient and the handleability tends to be excellent. If it is 1.17 meq / g dry resin or less, a sufficient strength to withstand film breakage can be maintained.

[0028] The thickness of the fluorine-containing polymer membrane having an ion exchange group is not particularly limited, but is preferably in the range of 20 μm or more and 150 μm or less, and more preferably 20 μm or more and 100 μm or less. If the thickness is 20 μm or more, the film has flexibility and the handleability tends to improve. If it is 150 μm or less, the strength is sufficient and the handleability tends to be excellent. If the thickness is 20 μm or more, the film has flexibility and the handleability tends to improve. If it is 100 μm or less, the electrolysis voltage of the water electrolysis device tends to be reduced.

[0029] In a solid polymer electrolyte membrane composed of a fluorine-containing polymer having an ion-exchange group and a nonwoven fabric, the weight of the fluorine-containing polymer having an ion-exchange group is not particularly limited, but is preferably in the range of 10 g or more and 130 g or less, more preferably 25 g or more and 120 g or less, and even more preferably 25 g or more and 105 g or less. If the weight of the fluorine-containing polymer having an ion-exchange group is 10 g or more, the strength is sufficient and the handleability tends to be excellent. If it is 130 g or less, the strength is sufficient and the handleability tends to be excellent. If the weight of the fluorine-containing polymer having an ion-exchange group is 25 g or more, the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas tends to improve. If it is 120 g or less, the membrane has flexibility and the handleability tends to improve. If the weight of the fluorine-containing polymer having an ion-exchange group is 25 g or more, the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas tends to improve. If it is 105 g or less, the electrolysis voltage of the water electrolysis device tends to be reduced.

[0030] The solid polymer electrolyte membrane may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, for example, a mode in which a plurality of layers containing a fluorine-containing polymer having an ion-exchange group and having different ion-exchange capacities are laminated can be mentioned.

[0031] [Nonwoven fabric] The reinforcing material made of nonwoven fabric can improve the strength in the diagonal direction with respect to the machine direction (MD) and the width direction (TD) compared to other reinforcing materials (e.g., woven fabric, etc.). Since the woven fabric is formed by warp and weft, the characteristics in the longitudinal and transverse directions are excellent, but there is a drawback that the characteristics in the diagonal direction are extremely poor.

[0032] The basis weight of the nonwoven fabric is not particularly limited, but is preferably 5 g / m 2 or more and 100 g / m 2 or less, more preferably 5 g / m 2 or more and 60 g / m 2 or less. If the basis weight of the nonwoven fabric is 5 g / m 2 or more, the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas tends to improve. If it is 100 g / m2 If the following conditions are met, the membrane has flexibility and the handleability tends to improve. When the basis weight of the nonwoven fabric is 5 g / m 2 or more, the gas barrier property that suppresses the mixing of oxygen gas and hydrogen gas tends to improve. When it is 60 g / m 2 or less, the electrolysis voltage of the water electrolysis device tends to be reduced.

[0033] The fineness of the fibers constituting the nonwoven fabric is not particularly limited, but is preferably 0.5 denier or more and 10 denier or less, and more preferably 0.5 denier or more and 4 denier or less. If it is 0.5 denier or more, the gas barrier property that suppresses the mixing of oxygen gas and hydrogen gas tends to improve. If it is 10 denier or less, the membrane has flexibility and the handleability tends to improve. If it is 0.5 denier or more, the gas barrier property that suppresses the mixing of oxygen gas and hydrogen gas tends to improve. If it is 4 denier or less, the electrolysis voltage of the water electrolysis device tends to be reduced.

[0034] The thickness of the nonwoven fabric is not particularly limited, but is preferably 20 μm or more and 150 μm or less, and more preferably 30 μm or more and 130 μm or less. If it is 20 μm or more, the strength is sufficient and the handleability tends to improve. If it is 150 μm or less, the electrolysis voltage of the water electrolysis device tends to be reduced. If it is 30 μm or more, the gas barrier property that suppresses the mixing of oxygen gas and hydrogen gas tends to improve. If it is 130 μm or less, the membrane has flexibility and the handleability tends to improve.

[0035] Examples of the method for producing the nonwoven fabric include the wet method, the dry method, and the spunbond method. When producing a nonwoven fabric with a low basis weight, the wet method is preferred.

[0036] The polymer constituting the nonwoven fabric is not particularly limited, but the hydrogen permeability coefficient at 90 °C is preferably 50 Barrer or less, more preferably 20 Barrer or less, and still more preferably 15 Barrer or less. If it is 50 Barrer or less, the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas as a solid polymer electrolyte tends to improve.

[0037] Since the gas permeability of the polymer is inversely proportional to the film thickness, it is preferable to calculate and compare the gas permeability coefficient (Permeability) obtained by multiplying the measured gas permeability by the film thickness in order to compare the differences between materials. The unit of barrer (Barrer) representing the permeability coefficient [1 barrer = 1×10 -10 cm(STP)·cm / cm 2 ·sec·cmHg] is used for representation.

[0038] The fibers constituting the nonwoven fabric are preferably composed of a material selected from the group consisting of polyphenylene sulfide (hereinafter referred to as PPS), polyether ether ketone (hereinafter referred to as PEEK), and polyethylene (hereinafter referred to as PE) from the viewpoints of excellent alkali durability and gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas. Nonwoven fabrics made of perfluoropolymers such as polytetrafluoroethylene, or copolymer compositions of tetrafluoroethylene and hexafluoropropylene, or perfluorovinyl ether have a large gas diffusion coefficient and a high hydrogen permeability coefficient because the molecular packing is loose.

[0039] The crystallinity of PPS constituting the nonwoven fabric is not particularly limited, but is preferably 30% or more and 60% or less, and more preferably 35% or more and 50% or less. If it is 30% or more, the alkali durability tends to improve, and if it is 60% or less, the strength is sufficient and the handling property tends to be excellent. If it is 35% or more, the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas tends to improve, and if it is 50% or less, the film has flexibility and the handling property tends to improve.

[0040] The crystallinity was determined using the following formula with the heat of the exothermic peak and the heat of the cold crystallization peak obtained from the differential curve of the chart obtained by placing 4 mg of nonwoven fabric in an aluminum pan and heating it at a heating rate of 20 °C / min using a differential scanning calorimeter DSC3500 manufactured by NETZSCH Corporation.

[0041] In this example, the following value was used for the heat of fusion of the completely crystalline PPS. Crystallinity K = (Δhm - Δhc) / Δh Δhm: Heat of fusion Δhc: Heat of cold crystallization Δh: Heat of fusion of complete crystallization Δh of PPS: 112.3 J / g

[0042] The solid polymer electrolyte membrane of this embodiment is not particularly limited, and examples thereof include a structure in which a fluorine-containing polymer is embedded in a nonwoven fabric and a structure in which a part of the nonwoven fabric is filled with a fluorine-containing polymer. From the viewpoint of further improving the strength of the membrane and the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas, it is preferable that the nonwoven fabric is embedded in the membrane.

[0043] In the mixed layer of the fluorine-containing polymer and the nonwoven fabric, the volume fraction of the polymer constituting the nonwoven fabric is not particularly limited, but is 20% or more and 70% or less, and preferably 20% or more and 60% or less. If the volume fraction of the polymer constituting the nonwoven fabric is 20% or more, the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas tends to improve, and if it is 70% or less, the membrane has flexibility and the handling property tends to improve. If the volume fraction of the polymer constituting the nonwoven fabric is 20% or more, the gas barrier property for suppressing the mixing of oxygen gas and hydrogen gas tends to improve, and if it is 60% or less, the electrolysis voltage of the water electrolysis device tends to be reduced.

[0044] 〔Hydrophilic layer〕 The solid polymer electrolyte membrane preferably has a hydrophilic layer as at least one outermost layer, and more preferably has hydrophilic layers as the outermost layers on both sides. By providing a hydrophilic layer as the outermost layer of the solid polymer electrolyte membrane, gas adhesion to the surface of the separator is suppressed. As a result, an increase in the electrolysis voltage during alkaline water electrolysis is further suppressed. Examples of the hydrophilic layer include an inorganic particle layer containing inorganic particles.

[0045] The inorganic particles preferably have excellent corrosion resistance to acids or alkalis and have hydrophilicity. Specifically, at least one selected from the group consisting of oxides, nitrides, and carbides of Group 4 elements or Group 14 elements is preferred, more preferably SiO2, SiC, ZrO2, ZrC, and particularly preferably ZrO2.

[0046] The average particle diameter of the inorganic particles is preferably 0.5 to 1.5 μm, and more preferably 0.7 to 1.3 μm. If the average particle diameter of the inorganic particles is equal to or greater than the lower limit value, a high gas adhesion suppression effect can be obtained. If the average particle diameter of the inorganic particles is equal to or less than the upper limit value, the inorganic particles have excellent resistance to dropping off. Here, the average particle diameter of the inorganic particles means the average particle diameter of particles (secondary particles) in which primary particles are aggregated. The inorganic particles are dispersed in ethanol so that the concentration becomes 0.01% by mass or less, and a particle size distribution measuring device (MT3000II manufactured by Microtrac Bell Corporation) is used to show the particle diameter (D50) at the point where the cumulative volume in the cumulative volume normal distribution curve with the total volume of the obtained particle size distribution being 100% is 50%.

[0047] The method for forming the hydrophilic layer on the solid polymer electrolyte membrane is not particularly limited, and a known method can be used. For example, a method of applying a liquid in which fine particles of an inorganic oxide are dispersed in a binder polymer solution by spraying or the like can be mentioned.

[0048] Examples of the binder polymer include vinyl compounds having a functional group that can be converted into a sulfonic acid type ion exchange group. The coating conditions are not particularly limited, and for example, spraying can be used at 30 to 90°C. Examples of methods other than the spraying method include roll coating.

[0049] From the viewpoints of preventing gas adhesion and increasing the electrical resistance due to the thickness, the average thickness of the coating layer is preferably 1 to 10 μm. The thickness of the coating layer is determined by a scanning electron microscope.

[0050] [Method for producing a solid polymer electrolyte membrane] Next, the method for producing the solid polymer electrolyte membrane of the present embodiment will be described. The method for producing the solid polymer electrolyte membrane of the present embodiment is not particularly limited, but preferably includes the following steps 1) to 6). 1) Step of producing a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor that can become an ion exchange group by hydrolysis (polymer production step); 2) Step of obtaining a nonwoven fabric (nonwoven fabric production step); 3) Step of forming a film from a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor that can become an ion exchange group by hydrolysis (film forming step); 4) Step of embedding the nonwoven fabric and the film to form a composite membrane (embedding step); 5) Step of hydrolyzing the composite membrane with an acid or an alkali (hydrolysis step); 6) Optionally, a hydrophilic layer is formed on at least one surface of the ion exchange membrane precursor simultaneously with step 4) or between step 4) and step 5), or a hydrophilic layer is formed on at least one surface of the ion exchange membrane after step 5) (coating step).

[0051] In the solid polymer electrolyte membrane of the present embodiment, for example, the composition of the fluorine-containing polymer is controlled in the polymer production step of 1) among the above steps. Hereinafter, each step will be described in detail.

[0052] 1) Process (Polymer production process) A fluorine-containing polymer having a group convertible to a sulfonic acid-type functional group is preferred, and a copolymer (hereinafter also referred to as a fluorine-containing polymer (S)) of a fluorine-containing olefin and a monomer having a group convertible to a sulfonic acid-type functional group and a fluorine atom (hereinafter also referred to as a fluorine-containing monomer (S')) is more preferred. Hereinafter, the fluorine-containing polymer (S) will be described in detail.

[0053] As the method for copolymerizing the fluorine-containing polymer (S), known methods such as solution polymerization, suspension polymerization, and emulsion polymerization can be employed. Known methods can be adopted.

[0054] Examples of the fluorine-containing olefin include those exemplified above. From the viewpoints of the production cost of the monomer, the reactivity with other monomers, and the excellent properties of the obtained fluorine-containing polymer (S), TFE is preferred. The fluorine-containing olefin may be used alone or in combination of two or more.

[0055] Examples of the fluorine-containing monomer (S') include compounds having one or more fluorine atoms in the molecule, an ethylenic double bond, and a group convertible to a sulfonic acid-type functional group. From the viewpoints of the production cost of the monomer, the reactivity with other monomers, and the excellent properties of the obtained fluorine-containing polymer (S), the compound represented by the formula (2) is preferred. Formula (2) CF2=CF-L-(A) n The definitions of L and n in the formula (2) are as described above. A is a group convertible to a sulfonic acid-type functional group. The group convertible to a sulfonic acid-type functional group is preferably a functional group that can be converted to a sulfonic acid-type functional group by hydrolysis. Specific examples thereof include -SO2F, -SO2Cl, and -SO2Br.

[0056] As the compound represented by the formula (2), a compound represented by the formula (2-1) or a compound represented by the formula (2-2) is preferable. Formula (2-1): CF2=CF-O-R f1 -A Formula (2-2): CF2=CF-R f1 -A In the formula, the definitions of R f1 , Rf2, r and A are as described above.

[0057] Specific examples of the compound represented by the 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

[0058] Specific examples of the compound represented by the 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

[0059] As the fluorine-containing monomer (S’), the following compounds are preferable from the viewpoint of easy industrial synthesis. CF2=CF-O-CF2CF2-SO2F, CF2=CF-O-CF2CF2CF2-SO2F, CF2=CF-O-CF2CF2CF2CF2-SO2F, CF2=CF-O-CF2CF(CF3)-O-CF2CF2-SO2F, CF2=CF-O-CF2CF(CF3)-O-CF2CF2CF2-SO2F, CF2=CF-O-CF2CF(CF3)-SO2F, CF2=CF-CF2CF2-SO2F, CF2=CF-CF2CF2CF2-SO2F, CF2=CF-CF2-O-CF2CF2-SO2F. One kind may be used alone, or two or more kinds may be used in combination.

[0060] The fluorine-containing monomer (S') may be used alone or in combination of two or more kinds. In the production of the fluorine-containing polymer (S'), in addition to the fluorine-containing olefin and the fluorine-containing monomer (S'), other monomers may be further used. Examples of the other monomers include those exemplified above.

[0061] The ion exchange capacity of the fluorine-containing monomer (S') can be adjusted by changing the content of the group convertible to the ion exchange group in the fluorine-containing monomer.

[0062] 2) Process (Nonwoven fabric manufacturing process) Methods for manufacturing nonwoven fabrics include the wet method of dispersing short fibers and long fibers in water and lifting them onto a net-like net to form a fleece, the dry method of thermocompression bonding the fibers as a fusing component, and the spunbond method of directly accumulating continuous long fibers obtained by melting and spinning the raw material polymer to form a fleece. When manufacturing a nonwoven fabric with a low basis weight, the wet method is preferred. When manufacturing a PPS nonwoven fabric by the wet method, first, undrawn yarns and drawn yarns are mixed and dispersed in water to produce a slurry. Next, this slurry is supplied to a cylinder mold paper machine to create a wet nonwoven fabric, which can be manufactured by passing it through a heated calendar for hot pressing.

[0063] 3) Process (Film-forming process) The method for forming a film from the fluorine-containing polymer obtained in the above step 1) is not particularly limited, but it is preferable to use an extruder. The fluorine-containing polymer film may have a single-layer structure or a multilayer structure. In the case of a multilayer structure (layer (II)), examples of the method include separately forming a fluorine-containing polymer having an ion-exchange group constituting layer (I-1) and a fluorine-containing polymer having an ion-exchange group constituting layer (I-2) into films.

[0064] 4) Step (Embedding step) In the embedding step, although not particularly limited, a method of stacking in the order of the film obtained in the above step 3) / the nonwoven fabric obtained in the above step 2) and heat-pressing with a flat-plate hot press or a known roll-to-roll method is preferable.

[0065] 5) Step (Hydrolysis step) The composite membrane obtained in the above step 4) is hydrolyzed with an acid or an alkali. The hydrolysis is preferably carried out, for example, in an aqueous solution of 2.5 to 4.0 N potassium hydroxide (KOH) and 20 to 40% by mass of DMSO (dimethyl sulfoxide) at 40 to 90°C for 10 minutes to 24 hours. Then, it is preferable to carry out a salt exchange treatment using a 0.5 to 0.7 N sodium hydroxide (NaOH) solution under the conditions of 80 to 95°C. From the viewpoint of preventing an increase in the electrolysis voltage, the treatment time of the above salt exchange treatment is preferably less than 2 hours. A schematic diagram of a diaphragm including the fluorine-containing polymer having an ion-exchange group and the nonwoven fabric obtained in step 5) is shown in FIG. 1.

[0066] 6) Step (Coating step) When the hydrophilic layer is an inorganic particle layer, examples of the method for forming the inorganic particle layer include applying a coating liquid containing inorganic particles, a binder, and a dispersion medium onto the surface of an ion-exchange membrane precursor or an ion-exchange membrane and drying it.

[0067] As a method for preparing the coating liquid, a method in which inorganic particles, a binder, and a dispersion medium are mixed, stirred using a ball mill or the like to make it uniform, and then subjected to a dispersion treatment using a bead mill is preferable. By using this method, it is easy to control the average secondary particle diameter of the inorganic particles within the above-described range.

[0068] As the dispersion medium, when the binder is methyl cellulose, water can be mentioned, and when it is a fluorine-containing polymer having a sulfonic acid group, an alcohol-based solvent (ethanol, isopropyl alcohol, etc.) can be mentioned.

[0069] Examples of the coating method of the coating liquid include a spray method, a roll coating method, etc. Examples of the drying method include a method using a heating roll, a method using an oven, etc. Industrially, a method of continuously performing a heat treatment using a roll press machine equipped with a heating roll is preferable. The drying temperature is preferably 30°C or higher, more preferably equal to or higher than the boiling point of the dispersion medium. The drying temperature is preferably less than the melting point of the fluorine-containing polymer.

[0070] The solid polymer electrolyte membrane of the present invention can be suitably applied to various uses. Among them, it can be suitably applied for alkaline water electrolysis. In addition, the solid polymer electrolyte membrane of the present invention can also be used for, for example, a PEM type water electrolysis membrane, a solid polymer electrolyte membrane for hydrogen peroxide production, a solid polymer electrolyte membrane for ozone production, a proton selective permeation membrane used for waste acid recovery, etc., a cation exchange membrane for alkaline chloride electrolysis, a diaphragm for a redox flow battery, a cation exchange membrane for electrodialysis used for desalination or salt production, electrolysis for TMAH production, and production of persulfate.

[0071] [Alkaline water electrolysis device] An alkaline water electrolysis device is one equipped with a diaphragm for alkaline water electrolysis, an anode, and a cathode. The inside of the alkaline water electrolysis device is partitioned, via a diaphragm for alkaline water electrolysis, into an anode chamber equipped with an anode and a cathode chamber equipped with a cathode, and the oxygen gas and hydrogen gas generated at each electrode are configured not to be blocked by the diaphragm for alkaline water electrolysis and mixed.

[0072] Figure 2 is a schematic diagram showing an example of the alkaline water electrolysis apparatus of the present invention. The alkaline water electrolysis apparatus 100 includes an electrolytic cell 110 having a cathode 112 and an anode 114, and a solid polymer electrolyte membrane 1 mounted in the electrolytic cell 110 so as to partition the inside of the electrolytic cell 110 into a cathode chamber 116 on the cathode 112 side and an anode chamber 118 on the anode 114 side.

[0073] The cathode 112 may be arranged in contact with the solid polymer electrolyte membrane 1, or may be arranged at a distance from the solid polymer electrolyte membrane 1. As the material constituting the cathode chamber 116, a material resistant to alkaline water and hydrogen is preferable. Examples of such materials include stainless steel and nickel.

[0074] The anode 114 may be arranged in contact with the solid polymer electrolyte membrane 1, or may be arranged at a distance from the solid polymer electrolyte membrane 1. As the material constituting the anode chamber 118, a material resistant to alkaline water and oxygen is preferable. An example of such a material is nickel.

[0075] [Alkaline water electrolysis method] The method of alkaline water electrolysis performed using the alkaline water electrolysis apparatus is to fill the inside of the alkaline water electrolysis apparatus with an alkaline solution and apply a direct current between the anode and the cathode. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or potassium hydroxide is used, but sodium hydroxide is preferable. The concentration of the alkaline solution is not particularly limited, but is preferably 15 wt% to 40 wt%, more preferably 15 wt% to 25 wt%. If it is in the range of 15 wt% to 40 wt%, the ionic conductivity of the solution is sufficiently exhibited, and the voltage loss due to the solution can be reduced.

[0076] Also, the temperature at the time of electrolysis is not particularly limited, but is preferably 60°C to 150°C, more preferably 80°C to 100°C. If it is in the range of 60°C to 150°C, the ionic conductivity of the solution is sufficiently exhibited, and the voltage loss due to the solution can be reduced.

[0077] [Other embodiments of the alkaline water electrolysis apparatus] The alkaline water electrolyzer of the present invention only needs to be equipped with the solid polymer electrolyte membrane of the present invention as a diaphragm, and the configuration other than the solid polymer electrolyte membrane may be a known one. The electrolytic cell may be of a monopolar type in which the cathode chambers and the anode chambers are alternately arranged with a solid polymer electrolyte membrane interposed therebetween, and the cathode chambers and the anode chambers are electrically in parallel, or the back surfaces of the cathode chambers and the back surfaces of the anode chambers are electrically connected, and each chamber is electrically in series. It may be a bipolar type.

Example

[0078] Hereinafter, the present embodiment will be specifically described with reference to examples and comparative examples, but the present embodiment is not limited to only these examples. The evaluation methods and measurement methods used in the present embodiment are as follows.

[0079] (Ion exchange capacity) Using about 1 g of a fluorine-containing polymer having an ion exchange group, press molding was performed at 290 ° C. and a pressure of 15 kgf / cm 2 for 4 minutes to obtain a film corresponding to each polymer. The total ion exchange capacity was measured by neutralization titration of the obtained film, and EW was calculated by substituting it into the following formula. EW = 1 / "Total ion exchange capacity" × 1000

[0080] (Thickness of the fluorine-containing polymer membrane having an ion exchange group) The thickness of the fluorine-containing polymer membrane having an ion exchange group was determined as follows. After immersing in water at 23 ° C. for 24 hours, the cross-section of the membrane was observed with an optical microscope, and the average value measured at 10 locations was determined.

[0081] (Hydrogen permeation coefficient at 90 ° C) The gas permeability of hydrogen was measured using a gas permeability measuring device (GTR-10FC manufactured by GTR Tech Co., Ltd.). Since the gas permeability of the membrane is inversely proportional to the membrane thickness, the gas permeability coefficient (Permeability) was calculated by multiplying the measured gas permeability value by the membrane thickness in order to compare the differences between materials. The unit of the gas permeability coefficient is expressed in Barrer units (1 Barrer = 1×10 -10 cm 3 (STP)·cm / (s·cm 2 ·cmHg)). Specifically, for the polymer with non-woven fabric, a 1-μm film was prepared, and the hydrogen permeability (unit: GPU) was measured under an environment of 90°C, and the gas permeability coefficient (unit: Barrer) was obtained by multiplying the membrane thickness. Note that the GPU (Gee-Pee-You) unit [1 GPU = 1×10 -6 cm 3 (STP) / cm 2 ·sec·cmHg].[[]END]]

[0082] (Cell Voltage Evaluation) The voltage characteristics of the solid polymer electrolyte membrane were evaluated using a self-made device (see Figure 3) by the following method. Figure 3 shows a conceptual diagram of the alkaline water electrolysis device fabricated in this example. First, the electrolytic cell 10 has a cathode chamber 1 with a cathode (nickel electrode) 11 and an anode chamber 2 with an anode (nickel electrode) 21 via a solid polymer electrolyte membrane 3. And the electrolyte is supplied to the electrolytic cell 10 by a pump 40 via an electrolyte supply line 30. Then, the hydrogen gas generated at the cathode 11 is sent from the cathode chamber 1 to the cathode tank 12, and the oxygen gas generated at the anode 21 is sent from the anode chamber 3 to the anode tank 22. Although not shown in the figure, the electrolytic cell is composed of six bipolar cells connected in series, and the anode area and the cathode area of each cell are both 30 cm 2 . The cathode chamber 2 and the anode chamber 2 separated by the solid polymer electrolyte membrane were filled with a 20 wt% NaOH aqueous solution at 90°C. A current density of 0.60 A / cm was applied between the cathode 11 and the anode 21 2A direct current was applied to start the electrolysis operation. Then, the potential difference between the two electrodes was measured 24 hours after the start of electrolysis. This potential difference between the two electrodes was defined as the cell voltage. During electrolysis, since water in the NaOH aqueous solution was consumed by electrolysis, pure water was periodically added to the cathode tank 12 so that the NaOH concentration remained constant. Also, to prevent oxygen gas and hydrogen gas generated from the electrodes from accumulating in the electrolysis cell, the electrolytic solution in both electrode chambers was circulated at a flow rate of 50 L / min with a pump 40. The cell voltage of 0.60 A / cm 2 is preferably 2.17 V or less from the viewpoint of hydrogen cost.

[0083] (Gas barrier property evaluation) Using Figure 3, the evaluation was performed under the same conditions as the cell voltage evaluation except for the current density. Electrolysis was carried out continuously for 24 hours at 0.10 A / cm 2 . After 24 hours, the gas in the anode tank 22 obtained by water electrolysis was measured by gas chromatography (Agilent Technologies, 990 Micro GC). The hydrogen concentration in oxygen is preferably 15000 ppm or less from the viewpoint of the explosion range (the composition concentration range of the mixed gas in which an explosion phenomenon occurs when a fire source is brought close when hydrogen is mixed with oxygen).

[0084] (Strength evaluation) The strength evaluation of the solid polymer electrolyte membrane was performed using a tensile tester. First, the solid polymer electrolyte membrane was immersed in pure water for 24 hours. Eight strip-shaped samples with a width of 10 mm and a length of 100 mm were cut out at an angle of 45° diagonally with respect to the machine direction (MD) and the width direction (TD) using an art knife. The film thickness of the obtained strip samples was measured, and a tensile test was performed at a constant speed of 100 mm / min using an autograph (AGS-X manufactured by Shimadzu Corporation) in a state where the film was wet, and the measured load (N) when the film broke and the cross-sectional area of the sample (m 2 ) were used to calculate the breaking point stress [MPa]. Eight samples were measured, and the average value was taken as the breaking point stress.

[0085] (Production of fluorine-containing polymer having ion exchange groups) To prepare a fluoropolymer having an ion-exchange group, polymerization was carried out using the following general formula (I) and monomers represented by the following general formulas (II) and (III) as sulfonic acid group-containing monomers. CF2=CF2(I) CF2=CFO(CF2)2SO2F (II) CF2=CFOCF2CF(CF3)O(CF2)2SO2F (III)

[0086] Fluoropolymers A1 to A4 having an ion-exchange group and fluoropolymer B1 having an ion-exchange group were prepared by solution polymerization shown below. However, in the case of fluoropolymers A1 to A4, general formula (I) and general formula (III) were used, and in the case of fluoropolymer B1, general formula (I) and general formula (II) were used, respectively.

[0087] More specifically, fluoropolymers A1 to A4 having an ion-exchange group and fluoropolymer B1 having an ion-exchange group were prepared by solution polymerization shown below. First, a sulfonic acid group-containing monomer and a CF3CHFCHFCF2CF3 (HFC43 -10 mee) solution were charged into a 20 L stainless steel autoclave, and the inside of the container was sufficiently purged with nitrogen. Then, it was further replaced with TFE (trifluoroethylene, CF2=CF2), and heated until the temperature inside the container became stable at 35 °C and pressurized with TFE. Next, a 5% HFC43 -10 mee solution of (CF3CF2CF2COO)2 was added as a polymerization initiator to start the reaction. While intermittently feeding TFE with stirring at 35 °C, a 5% HFC43 -10 mee solution of (CF3CF2CF2COO)2 was added in the middle to lower the TFE pressure. When a predetermined amount of TFE was supplied, methanol was added to stop the polymerization. After discharging unreacted TFE out of the system, the obtained polymerization solution was dried under reduced pressure to distill off unreacted monomers and HFC43 -10 mee to obtain fluoropolymers A1 to A4 having an ion-exchange group and fluoropolymer B1 having an ion-exchange group. The obtained fluoropolymers having an ion-exchange group were pelletized using a twin-screw devolatilization extruder. By adjusting the conditions at this time, fluoropolymers A1 to A3 having ion exchange groups with different ion exchange capacities and fluoropolymer B1 having an ion exchange group were prepared as shown in Table 1.

[0088]

Table 1

[0089] (Non-woven fabric) [Non-woven fabric 1] A non-woven fabric with a basis weight of 19 g / m made of 4-denier yarn of PPS with a hydrogen permeation coefficient of 0.5 Barrer at 90 °C was used. 2 and a non-woven fabric with a film thickness of 53 μm was used.

[0090] [Non-woven fabric 2] A non-woven fabric with a basis weight of 40 g / m made of 4-denier yarn of PPS with a hydrogen permeation coefficient of 0.5 Barrer at 90 °C was used. 2 and a non-woven fabric with a film thickness of 81 μm was used.

[0091] [Non-woven fabric 3] A non-woven fabric with a basis weight of 40 g / m made of 4-denier yarn of PPS with a hydrogen permeation coefficient of 0.5 Barrer at 90 °C was used. 2 and a non-woven fabric with a film thickness of 51 μm was used.

[0092] [Non-woven fabric 4] A non-woven fabric with a basis weight of 12 g / m made of 1-denier yarn of PPS with a hydrogen permeation coefficient of 0.5 Barrer at 90 °C was used. 2 and a non-woven fabric with a film thickness of 30 μm was used.

[0093] [Non-woven fabric 5] A non-woven fabric with a basis weight of 40 g / m made of 10-denier yarn of PPS with a hydrogen permeation coefficient of 0.5 Barrer at 90 °C was used. 2 and a non-woven fabric with a film thickness of 80 μm was used.

[0094] [Non-woven fabric 6] A 4 - denier yarn made of PPS with a hydrogen permeability coefficient of 0.5 Barrer at 90°C was used, and the basis weight was 60 g / m 2 A non - woven fabric with a basis weight of 60 g / m and a film thickness of 126 μm was used.

[0095] [Non - woven fabric 7] A 4 - denier yarn made of PEEK with a hydrogen permeability coefficient of 1.0 Barrer at 90°C was used, and the basis weight was 20 g / m 2 A non - woven fabric with a basis weight of 20 g / m and a film thickness of 55 μm was used.

[0096] [Non - woven fabric 8] A 4 - denier yarn made of PE with a hydrogen permeability coefficient of 14.0 Barrer at 90°C was used, and the basis weight was 40 g / m 2 A non - woven fabric with a basis weight of 40 g / m and a film thickness of 55 μm was used.

[0097] (Woven fabric) [Woven fabric 1] 50 - denier yarns made of PTFE were used for the warp and weft, and plain - woven so that the density of the PTFE yarns was 80 threads per inch, and a woven fabric with a basis weight of 35 g / m 2 was used.

[0098] [Film formation] Using the fluoropolymers A1 - A3 having an ion - exchange group, fluoropolymer B1 having an ion - exchange group, non - woven fabrics 1 - 8, and woven fabrics 1 - 2 obtained above, film formation was carried out to prepare samples of Examples 1 - 12 and samples of Comparative Examples 1 - 4.

[0099] (Example 1) The fluorine - containing polymer A1 having an ion - exchange group was molded by an apparatus equipped with an extruder, a T - die, and a take - up machine to obtain a film. As a result of observing the cross - section of the film with an optical microscope, the thickness was 40 μm. Kapton (registered trademark) H type 100 μm / non - woven fabric 1 / fluorine - containing polymer A1 film / Kapton (registered trademark) H type 100 μm were overlapped in this order. The overlapped members were heated at a temperature of 250°C and a surface pressure of 5 MPa / m 2After heat-pressing for 10 minutes using a flat press machine manufactured by Tester Sangyo Co., Ltd., the polyimide films on both sides were peeled off to obtain a precursor film. This precursor was saponified by immersing it in an 80 °C aqueous solution containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Subsequently, the composite membrane was immersed in a 50 °C aqueous solution containing 0.5 N of sodium hydroxide (NaOH) for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 °C. In a mixed solution of 50 / 50 parts by mass of water and ethanol, 20% by mass of a fluorine-based polymer having a sulfonic acid group obtained by hydrolyzing a copolymer of CF2=CF2 and CF2=CFOCF2CF(CF3)O(CF2)2SO2F with a total ion exchange capacity of 1.0 meq / g was dissolved. 40% by mass of zirconium oxide with an average primary particle diameter of 1.0 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. This suspension was applied to both sides of the ion exchange membrane after the hydrolysis and salt exchange treatment by spraying and dried to form a coating layer. The crystallinity of the PPS nonwoven fabric in the solid polymer electrolyte membrane obtained as described above was 34%. For the solid polymer electrolyte membrane, alkaline water electrolysis evaluation was performed as described above, and the cell voltage at 0.60 A / cm 2 was 2.13 V, and the hydrogen concentration in oxygen at 0.10 A / cm 2 was 12537 ppm, which was good.

[0100] (Examples 2 to 12, Comparative Example 3) In Examples 2 to 12 and Comparative Example 3, composite membranes were produced and evaluated in the same manner as in Example 1 under the configurations and film-forming conditions described in Table 2.

[0101] In Comparative Example 1, a fluorine-containing polymer A1 having an ion-exchange group was molded using an apparatus equipped with an extruder, a T-die, and a take-up machine to obtain a film. As a result of observing the cross-section of the film with an optical microscope, the thickness was 50 μm. This film was saponified by immersing it in an 80°C aqueous solution containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Thereafter, the composite membrane was immersed in a 50°C aqueous solution containing 0.5 N of sodium hydroxide (NaOH) for 1 hour to substitute the counter ion of the ion-exchange group with Na, and then washed with water. It was further dried at 60°C. In a mixed solution of 50 / 50 parts by mass of water and ethanol, 20% by mass of a fluorine-based polymer having a sulfonic acid group obtained by hydrolyzing a copolymer of CF2=CF2 and CF2=CFOCF2CF(CF3)O(CF2)2SO2F with a total ion-exchange capacity of 1.0 meq / g was dissolved. 40% by mass of zirconium oxide with an average primary particle diameter of 1.0 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. This suspension was applied to both sides of the ion-exchange membrane after the hydrolysis and salt-exchange treatment by a spraying method and dried to form a coating layer. Regarding the solid polymer electrolyte membrane obtained as described above, as described above, an alkaline water electrolysis evaluation was performed, and at 0.60 A / cm 2 The cell voltage under the conditions was 2.06 V, and at 0.10 A / cm 2 The hydrogen concentration in oxygen under the conditions was 20421 ppm, and the hydrogen concentration in oxygen was high.

[0102] In Comparative Example 2, a single membrane was produced and evaluated in the same manner as in Comparative Example 1 under the same conditions except for the configuration described in Table 2.

[0103]

Table 2

[0104] As shown in Table 2, the solid polymer electrolyte membranes of Examples 1 to 12 have a strength in the diagonal direction of 70 MPa or more and can sufficiently withstand the large pressure generated in the water electrolysis device. Also, when performing alkaline water electrolysis, the cell voltage is less than 2.17 V even at a high current density, and the hydrogen cost can be reduced. Further, at a low current density, the hydrogen concentration in oxygen is 15,000 ppm or less, and it was found that the mixing of oxygen gas and hydrogen gas is suppressed and the explosion risk is low. On the other hand, in Comparative Examples 1 to 4, it was also found that the strength was insufficient and the balance between the hydrogen concentration in oxygen and the cell voltage was poor.

Industrial Applicability

[0105] The solid polymer electrolyte membrane of the present invention has a low electrolysis voltage during electrolysis and further has gas barrier properties, so it has industrial applicability as a material for water electrolysis and alkali chloride electrolysis.

Explanation of Signs

[0106] 1 Cathode chamber 2 Anode chamber 3 Diaphragm 10 Electrolytic cell 11 Cathode (nickel electrode) 12 Cathode tank 21 Anode (nickel electrode) 22 Anode tank 30 Electrolyte supply line 40 Pump 100 Alkaline water electrolysis device 110 Electrolytic cell 114 Anode 112 Cathode 116 Anode chamber 118 Cathode chamber 201 Solid polymer electrolyte 202 Electrolyte 203 Nonwoven fabric

Claims

1. A fluorine-containing polymer having an ion-exchange group, and A nonwoven fabric containing a polymer having a hydrogen permeability coefficient of 50 Barrer or less at 90 °C A solid polymer electrolyte membrane comprising: The weight of the fluorine-containing polymer per 1 m of the solid polymer electrolyte membrane ２ is 10 g or more and 130 g or less, A solid polymer electrolyte membrane.

2. The solid polymer electrolyte membrane according to claim 1, wherein the ion-exchange capacity of the fluorine-containing polymer is 0.90 meq / g dry resin or more and 1.40 meq / g dry resin or less.

3. The solid polymer electrolyte membrane according to claim 1, wherein the material of the nonwoven fabric is a hydrocarbon-based polymer.

4. The solid polymer electrolyte membrane according to claim 1, wherein the material of the nonwoven fabric is selected from the group consisting of polyphenylene sulfide, polyether ketone, and polyethylene.

5. The solid polymer electrolyte membrane according to claim 4, wherein the material of the nonwoven fabric is polyphenylene sulfide, and the crystallinity of the nonwoven fabric is 30% or more and 60% or less.

6. The basis weight of the nonwoven fabric is 5 g / m ２ or more and 100 g / m ２ or less. The solid polymer electrolyte membrane according to claim 1.

7. The solid polymer electrolyte membrane according to claim 1, wherein the fineness of the fibers constituting the nonwoven fabric is in the range of 0.5 denier or more and 10 denier or less.

8. The solid polymer electrolyte membrane according to claim 1, wherein in the mixed layer of the fluorine-containing polymer and the nonwoven fabric of the solid polymer electrolyte membrane, the volume fraction of the polymer constituting the nonwoven fabric is 20% or more and 70% or less.

9. The solid polymer electrolyte membrane according to claim 1, wherein the ion-exchange group is a sulfonic acid type functional group.

10. The solid polymer electrolyte membrane according to claim 1, wherein the fluorine-containing polymer having an ion-exchange group contains a polymer having a unit represented by the following formula (A) or formula (B). Formula (A) - [CF ２ - CF(-O-CF ２ CF(CF ３ )-O-(CF ２ )m-SO ３ M)]- [Wherein, m is an integer of 1 to 6, and M is an alkali metal.] Formula (B) - [CF ２ - CF(-O-(CF ２ )m-SO ３ M)]- [Wherein, m is an integer of 1 to 6, and M is an alkali metal.]

11. The solid polymer electrolyte membrane according to claim 1, having a hydrophilic layer as the outermost layer on both sides or one side of the solid polymer electrolyte membrane.

12. The solid polymer electrolyte membrane according to claim 11, wherein the hydrophilic layer is an inorganic particle layer containing inorganic particles.

13. The solid polymer electrolyte membrane according to claim 12, wherein the inorganic particles are inorganic particles composed of at least one selected from the group consisting of oxides, nitrides, and carbides of Group 4 elements or Group 14 elements.

14. The inorganic particles are SiO ２ , SiC, ZrO ２ or inorganic particles composed of ZrC, and the solid polymer electrolyte membrane according to claim 13.

15. The solid polymer electrolyte membrane according to any one of claims 1 to 14, wherein the solid polymer electrolyte membrane is for alkaline water electrolysis.

16. An electrolytic cell provided with a cathode and an anode, and the solid polymer electrolyte membrane according to any one of claims 1 to 14 are provided, wherein the solid polymer electrolyte membrane is mounted in the electrolytic cell so as to partition the inside of the electrolytic cell into a cathode chamber and an anode chamber on the cathode side, an alkaline water electrolysis apparatus.

17. A method for manufacturing the solid polymer electrolyte membrane according to any one of claims 1 to 14, comprising: a step of manufacturing a fluorine-containing polymer; a step of obtaining a nonwoven fabric; a step of forming the fluorine-containing polymer into a film; a step of embedding the nonwoven fabric and the film to form a composite membrane; a step of hydrolyzing the composite membrane with an acid or an alkali; A method for manufacturing a solid polymer electrolyte membrane, including the above steps.

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