Alkaline water electrolysis diaphragm and method for producing the same

Abstract

To provide an alkaline water electrolysis diaphragm that can well suppress the residence of bubbles and can achieve a high electrolytic efficiency even when used for an electrolytic apparatus of zero-gap structure.SOLUTION: An alkaline water electrolysis diaphragm is provided, in which an average area of depressed portion is 7 μm2 or smaller on at least one diaphragm surface, and the area ratio of the depressed portion on the diaphragm surface is 20% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a diaphragm for alkaline water electrolysis. More specifically, the present invention relates to a diaphragm for alkaline water electrolysis in which the retention of generated gas is favorably suppressed, and a method for manufacturing the same.

Background Art

[0002] The electrolysis of water (also referred to as "electrolysis") is known as one of the industrial production methods of hydrogen. Generally, it is performed by applying an electric current to water added with an electrolyte such as sodium hydroxide or potassium hydroxide in order to enhance conductivity. For such electrolysis of water, an electrolytic cell having an anode chamber and a cathode chamber in which an anode (anode) and a cathode (cathode) are respectively arranged, and these are partitioned by a diaphragm is used.

[0003] The electrolysis of water is performed by the movement of electrons (or ions). Therefore, the above diaphragm is required to have high ion permeability in order for the electrolysis reaction to be efficiently performed. Further, a gas barrier property capable of blocking oxygen molecules generated in the anode chamber and hydrogen molecules generated in the cathode chamber is required. Furthermore, since the electrolysis of water is performed using a high-concentration alkaline water of about 30% at 80 to 100 ° C. and in some cases under a pressure of 1 MPa, high heat resistance, alkali resistance, and mechanical strength are also required.

[0004] As diaphragms used for the electrolysis of water, various ones have been known so far. For example, Patent Document 1 discloses an alkaline water electrolysis diaphragm having a polymer porous membrane containing a polymer resin and inorganic particles, and controlling the porosity of the polymer porous membrane, the average pore diameter of the surface, and the ratio of the mode particle diameter of the inorganic particles to this average pore diameter within a specific range.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in the electrolysis of water, when gas bubbles generated at each electrode stay on the electrode surface, there is a problem that the active area of the electrode decreases, the cell voltage increases, and the electrolysis efficiency decreases. Therefore, in the design of the electrode, various types that are less likely to have gas bubbles stay on the electrode surface have been studied. In recent years, in a water electrolysis device, as a structure with good electrolysis efficiency, a zero-gap structure, which is a cell structure in which a diaphragm and an electrode are in contact to reduce the distance between the electrodes, is known. In the zero-gap structure, bubbles are even more likely to stay on the surfaces of the electrode and the diaphragm, and the decrease in electrolysis efficiency due to the diaphragm becomes more significant.

[0007] The present invention has been made in view of the above situation, and an object thereof is to provide a diaphragm for alkaline water electrolysis that can favorably suppress the retention of bubbles and achieve high electrolysis efficiency even when used in an electrolysis device having a zero-gap structure.

Means for Solving the Problems

[0008] The present inventor has variously studied the cause of gas bubbles staying on the surface of the diaphragm for alkaline water electrolysis, and found that the unevenness on the diaphragm surface causes gas bubbles to easily stay on the diaphragm surface. Then, the present inventor has found that by setting the average area of the recessed portions on one or both surfaces of the diaphragm and the area ratio of the recessed portions within a predetermined range, the retention of bubbles is significantly suppressed, and it becomes a diaphragm for alkaline water electrolysis that can achieve high electrolysis efficiency even when used in a water electrolysis device having a zero-gap structure, and thus has completed the present invention.

[0009] That is, the present invention is a diaphragm for alkaline water electrolysis, characterized in that on at least one diaphragm surface, the average area of the recessed portions is 7 μm 2 or less, and the area ratio of the recessed portions on the diaphragm surface is 20% or less.

[0010] The diaphragm for alkaline water electrolysis preferably has an arithmetic mean roughness Ra of the diaphragm surface of 0.8 μm or less.

[0011] The diaphragm for alkaline water electrolysis preferably contains an organic polymer resin and inorganic particles.

[0012] The inorganic particles are preferably metal hydroxide particles and / or metal oxide particles.

[0013] The organic polymer resin is preferably at least one resin selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone.

[0014] The present invention also provides a method for manufacturing the above-described diaphragm for alkaline water electrolysis. The manufacturing method includes: step (1) of preparing a dispersion solution containing an organic polymer resin, inorganic particles, and a solvent; step (2) of forming a coating film using the dispersion solution; step (3) of contacting the coating film with a non-solvent for the organic polymer resin to solidify the coating film; and step (4) of drying the solidified coating film to obtain a porous film. In step (3), the contact rate of the coating film with the non-solvent is 0.3 m / min or more.

[0015] In the method for manufacturing the diaphragm for alkaline water electrolysis, step (3) is preferably carried out under the condition of an absolute humidity of 20 g / m 3 or less.

[0016] In the method for manufacturing the diaphragm for alkaline water electrolysis, step (2) is preferably carried out under the condition of an absolute humidity of 20 g / m 3 or less.

Advantages of the Invention

[0017] The diaphragm for alkaline water electrolysis of the present invention effectively suppresses retention of bubbles of oxygen gas and hydrogen gas generated during water electrolysis. Use of the diaphragm for alkaline water electrolysis of the present invention enables extremely efficient water electrolysis and provides a highly efficient water electrolysis apparatus. [Brief description of the drawings]

[0018]

Figure 1

[0019] The present invention will be described in detail below. In addition, a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

[0020] 1. Diaphragms for alkaline water electrolysis The diaphragm for alkaline water electrolysis of the present invention has a mean area of ​​depressed portions of 7 µm or less on at least one of the diaphragm surfaces. 2 or less, and the area ratio of the depressed portions on the diaphragm surface is 20% or less. By setting the state of at least one of the diaphragm surfaces within a specific range, the diaphragm for alkaline water electrolysis of the present invention can effectively suppress retention of oxygen gas and hydrogen gas bubbles generated during electrolysis in the diaphragm, thereby improving the electrolysis efficiency of an electrolysis device using the diaphragm. It is believed that the reason the diaphragm for alkaline water electrolysis of the present invention is excellent in suppressing retention of bubbles is that by setting the surface state of the diaphragm for alkaline water electrolysis of the present invention within the above specific range, the diaphragm surface becomes relatively smooth and there is less space for the retention of bubbles generated during alkaline water electrolysis, thereby effectively suppressing retention of oxygen gas and hydrogen gas bubbles.

[0021] In the present invention, the "depressed portion" on the diaphragm surface refers to the following portion. That is, when one surface (the first surface) or both surfaces (the first surface and the second surface) of the diaphragm for alkaline water electrolysis of the present invention are observed using a laser microscope such as VK9700 (manufactured by Keyence Corporation), with the diaphragm surface as the XY plane, the plane obtained by the least squares method of the Z-direction height data is used as the reference plane, and the portion where the Z-direction height is -1.5 μm or less with respect to the reference plane is defined as the "depressed portion A". Further, when there is a raised portion with respect to the reference plane, the hollow portion formed surrounded by the raised portion with a Z-direction height of +1.5 μm or more, when in contact with the electrode, has a space with the reference plane. Therefore, this hollow portion can also be regarded as a depressed portion, and this is defined as the "depressed portion B". The "depressed portion" in the present invention includes both the above-mentioned "depressed portion A" and "depressed portion B". The reference plane can be determined from the measurement analysis in the observation field of the laser microscope. Specifically, for the observation image obtained at 150 times magnification of the objective lens of the laser microscope VK9700 (manufactured by Keyence Corporation), using the analysis software VK Analyzer VK-H1A1 (manufactured by Keyence Corporation), 15000 μm 2 is specified as the measurement area, and it is obtained by performing the least squares method analysis.

[0022] The shape of the above-mentioned depressed portion is not particularly limited and may be any concave shape. For example, (substantially) hemispherical, (substantially) polygonal pyramid, (substantially) cone, (substantially) elliptical cone, or a shape formed by combining them, or an irregular shape, etc. can be mentioned. Also, the shape of the opening portion of the above-mentioned depressed portion is not particularly limited and may be polygonal, circular, elliptical, and their deformations, or irregular. Also, the bottom surface of the above-mentioned depressed portion may be curved.

[0023] The average area of the above-mentioned depressed portion is 7 μm 2 or less. The above-mentioned depressed portion includes the above-mentioned "depressed portion A" and "depressed portion B". Therefore, "the average area of the above-mentioned depressed portion is 7 μm 2 or less." means that the average areas of both the "depressed portion A" and the "depressed portion B" are 7 μm 2 or less. The average area of the above-mentioned recessed part is 5 μm in that it can further suppress the retention of bubbles. 2 It is preferably below, and more preferably 4 μm 2 It is even more preferably below. The average area of the above-mentioned recessed part can be obtained by performing image analysis on an observation image (150 times magnification of the objective lens) obtained by a laser microscope (for example, VK9700, manufactured by Keyence Corporation) using analysis software (for example, VK Analyzer VK-H1A1, manufactured by Keyence Corporation), and specifically, it can be measured and obtained by the method described in the examples.

[0024] In the diaphragm for alkaline water electrolysis of the present invention, further, the area ratio of the recessed parts on the surface of the diaphragm is 20% or less. On the surface of the diaphragm for alkaline water electrolysis of the present invention, when the average area of the above-mentioned recessed parts is within the above-mentioned range and the area ratio of the above-mentioned recessed parts is within the above-mentioned range, the surface of the diaphragm becomes smooth, and the retention of bubbles generated during electrolysis can be remarkably suppressed. As described above, the above-mentioned recessed parts include "recessed part A" and "recessed part B". Therefore, the area ratio of the above-mentioned recessed parts is the sum of the area ratio of recessed part A and the area ratio of recessed part B. The area ratio of the above-mentioned recessed parts is preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less. The area ratio of the above-mentioned recessed parts can be obtained by performing image analysis on an observation image (150 times magnification of the objective lens) obtained by a laser microscope (for example, VK9700, manufactured by Keyence Corporation) using analysis software (for example, VK Analyzer VK-H1A1, manufactured by Keyence Corporation), and calculating the ratio (%) of the total area of the recessed parts (A and B) existing in the above-mentioned observation field of view to the area of the entire observation field of view of the diaphragm surface, and specifically, it can be measured and obtained by the method described in the examples.

[0025] The diaphragm for alkaline water electrolysis preferably has an arithmetic mean roughness Ra of the diaphragm surface of 0.8 μm or less. When the arithmetic mean roughness Ra is 0.8 μm or less, the retention of bubbles can be further suppressed. The arithmetic mean roughness Ra is more preferably 0.6 μm or less, and even more preferably 0.5 μm or less, in terms of further suppressing the retention of bubbles. The lower limit of the arithmetic mean roughness Ra of the diaphragm surface is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.08 μm or more. The arithmetic mean roughness Ra of the diaphragm surface is a value that can be obtained by measuring using a laser microscope or the like in accordance with the method conforming to JIS B0601:2001, and specifically, it can be obtained by measuring in the method described in the examples below.

[0026] The diaphragm for alkaline water electrolysis contains an organic polymer resin and inorganic particles. The diaphragm for alkaline water electrolysis preferably has a porous membrane containing an organic polymer resin and inorganic particles. By having a porous membrane, ion permeability is exhibited.

[0027] (Organic polymer resin) The organic polymer resin is not particularly limited as long as it is an organic polymer resin usually used for diaphragms for alkaline water electrolysis, and examples thereof include fluorine-based resins, olefin-based resins, and aromatic hydrocarbon-based resins. The organic polymer resin may be only one type, or may be a combination of two or more types. Among them, the organic polymer resin preferably contains an aromatic hydrocarbon-based resin in terms of excellent heat resistance and alkali resistance.

[0028] Examples of the fluororesin include ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, and the like.

[0029] Examples of the olefin resin include polyethylene, polypropylene, polybutene, polymethylpentene, and the like.

[0030] Examples of the aromatic hydrocarbon resin include polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylsulfone, polyarylate, polyetherimide, polyimide, polyamideimide, and the like. Among them, at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone is preferable in terms of excellent alkali resistance, and polysulfone is more preferable in terms of easy production of the diaphragm.

[0031] The content of the organic polymer resin is preferably 5 to 40% by mass in 100% by mass of the diaphragm for alkaline electrolysis. When the content of the organic polymer resin is within the above range, elution of inorganic components from the diaphragm in an alkaline solution can be suppressed. The content of the organic polymer resin is more preferably 7% by mass or more, still more preferably 10% by mass or more, more preferably 35% by mass or less, and still more preferably 30% by mass or less in 100% by mass of the diaphragm for alkaline electrolysis.

[0032] (Inorganic particles) When the diaphragm for alkaline electrolysis contains inorganic particles, the diaphragm is hydrophilized, and adhesion of oxygen gas and hydrogen gas bubbles to the diaphragm surface can be suppressed. Examples of the inorganic particles include metal hydroxides or metal oxides such as magnesium, zirconium, titanium, zinc, aluminum, and tantalum; sulfates such as calcium, barium, lead, and strontium; nitrides such as titanium, zirconium, and hafnium; carbides such as titanium, zirconium, and hafnium, etc. The inorganic particles may contain only one kind or two or more kinds. Among them, metal hydroxides or metal oxides are preferable in that they can make the separator hydrophilic, have excellent ion permeability, and can suppress gas adhesion. Magnesium hydroxide, zirconium hydroxide, titanium hydroxide, zirconium oxide, and titanium oxide are more preferable. Magnesium hydroxide, zirconium hydroxide, titanium hydroxide, and titanium oxide are still more preferable. Magnesium hydroxide, zirconium hydroxide, and titanium hydroxide are even more preferable. Magnesium hydroxide is particularly preferable.

[0033] The inorganic particles may have an untreated surface or a surface-treated surface. Examples of the surface treatment include known surface treatments using silane coupling agents, stearic acid, oleic acid, phosphate esters, etc.

[0034] The shape of the inorganic particles is not particularly limited and may be any shape such as irregular shape, granular shape, particulate shape, flaky shape, hexagonal plate shape, plate shape, fibrous shape, etc. Among them, in terms of excellent adhesion to the resin, the shape of the inorganic particles is preferably granular, flaky, or plate-shaped, more preferably plate-shaped or flaky, and still more preferably flaky.

[0035] In terms of increasing the hydrophilic surface area and efficiently forming the penetration path of the electrolyte in the separator, the average particle diameter of the inorganic particles is preferably 0.05 μm or more and preferably 2.0 μm or less. The average particle diameter of the inorganic particles is more preferably 0.1 μm or more, still more preferably 0.2 μm or more, more preferably 1.5 μm or less, and still more preferably 1.0 μm or less. The above average particle diameter is the volume average particle diameter (D50) obtained from the measurement of the particle size distribution by the laser diffraction method. Specifically, the average particle diameter is measured by using a laser diffraction / scattering type particle size distribution measuring device (model number "LA-920" manufactured by Horiba, Ltd.) to measure the particle size distribution, and the median diameter (D50) in the particle size distribution based on volume is taken as the average particle diameter. Note that a measurement sample is a mixture of particles in ethanol with ultrasonic irradiation for dispersion.

[0036] Among the above inorganic particles, magnesium hydroxide is preferable in that it is particularly excellent in alkali resistance and durability, relatively inexpensive, and a separator for alkaline water electrolysis can be obtained. Hereinafter, the preferred form of magnesium hydroxide in the present invention will be described.

[0037] The magnesium hydroxide used in the present invention preferably has an aspect ratio of 2.0 to 8.0. When the aspect ratio is within the above range, the ion permeability is further excellent, and a separator excellent in uniformity can be obtained. The above aspect ratio is more preferably 2.5 to 7.0, and still more preferably 3.0 to 6.0. The above aspect ratio means the ratio [(a) / (b)] of the longest diameter (a) to the shortest diameter (b). Observe the particles of magnesium hydroxide by SEM, and in any 10 particles of the obtained image, use analysis software or the like to measure the ratio [(a) / (b)] of the longest diameter (a) to the shortest diameter (b) of each particle, and the simple average value of these ratios can be obtained as the aspect ratio of the particle. Usually, it is preferable to take the shortest diameter among the diameters orthogonal to the longest diameter passing through the midpoint of the longest diameter (a) as the shortest diameter (b). As the above longest diameter (a), for example, when the particle shape is plate-like such as flaky or hexagonal plate-like, the major axis of the particle plate surface is adopted, and when it is fibrous, the fiber length is adopted. As the above shortest diameter (b), for example, when the particle shape is plate-like such as flaky or hexagonal plate-like, the particle thickness is adopted, and when it is fibrous, the fiber thickness is adopted. As the particle thickness and the fiber thickness, it is preferable to adopt the thickness and the thickness at the midpoint of the longest diameter a, respectively.

[0038] The magnesium hydroxide preferably has a crystallite diameter in the direction perpendicular to the (110) plane measured by X-ray diffraction of 35 nm or more. When the crystallite diameter in the direction perpendicular to the (110) plane is within the above range, the ion permeability of the separator and the uniformity of the separator are further improved. The crystallite diameter in the direction perpendicular to the (110) plane is preferably 40 nm or more, more preferably 50 nm or more, still more preferably 60 nm or more, and particularly preferably 65 nm or more. The upper limit of the crystallite diameter in the direction perpendicular to the (110) plane is not particularly limited, but is usually, for example, 400 nm or less, preferably 350 nm or less, and more preferably 300 nm or less.

[0039] The magnesium hydroxide preferably has a crystallite diameter in the direction perpendicular to the (001) plane measured by X-ray diffraction of 15 nm or more. The crystallite diameter in the direction perpendicular to the (001) plane is more preferably 18 nm or more, still more preferably 21 nm or more, and particularly preferably 24 nm or more. The upper limit of the crystallite diameter in the direction perpendicular to the (001) plane is not particularly limited, but is usually, for example, 300 nm or less, preferably 250 nm or less, and more preferably 200 nm or less.

[0040] The crystallite diameter can be obtained by measuring the X-ray diffraction pattern of magnesium hydroxide particles by the powder X-ray diffraction method and calculating the crystallite diameter (the crystallite diameter in the direction perpendicular to the above lattice plane) using the Scherrer equation from the broadening (half-width) of the diffraction line attributed to the target lattice plane.

[0041] Examples of the method for obtaining magnesium hydroxide within the above-specified crystallite diameter range include the following methods. An aqueous solution of a magnesium salt (such as magnesium chloride, magnesium nitrate, etc.) or a water dispersion of magnesium oxide obtained by a conventionally known method is used as a raw material, and a hydration reaction is carried out by adding an alkaline substance (such as lithium hydroxide, sodium hydroxide, calcium hydroxide, aqueous ammonia, etc.) to prepare magnesium hydroxide. At this time, by adding an organic acid such as formic acid, acetic acid, propionic acid, a polybasic acid such as nitric acid, sulfuric acid, or a mixture thereof, the solubility of the generated magnesium hydroxide can be adjusted, or the temperature (for example, 150 ° C to 270 ° C) and time (for example, 30 minutes to 10 hours) of the hydrothermal reaction can be appropriately adjusted to prepare particles with different crystallite diameters. The more the amount of acid added, the more the crystal growth progresses and the larger the crystallite diameter. Also, the higher the temperature of the hydrothermal reaction and the longer the time, the more the crystal growth progresses and the larger the crystallite diameter.

[0042] In the present invention, a general commercially available product can also be used as magnesium hydroxide. Examples of commercially available products of magnesium hydroxide that can be used in the present invention include 200-06H manufactured by Kyowa Chemical Industry Co., Ltd., UP650-1 manufactured by Ube Materials Co., Ltd., MAGSTAR #20 manufactured by Tateho Chemical Industry Co., Ltd., #200 manufactured by Kojima Chemical Industry Co., Ltd., and the like.

[0043] The content of the inorganic particles is preferably 30 to 90% by mass in 100% by mass of the diaphragm for alkaline water electrolysis. When the content of the inorganic particles is within the above range, the diaphragm for alkaline water electrolysis has excellent ion permeability. The content of the inorganic particles is more preferably 35% by mass or more in 100% by mass of the diaphragm for alkaline water electrolysis, still more preferably 40% by mass or more, more preferably 85% by mass or less, and still more preferably 80% by mass or less.

[0044] The above-mentioned diaphragm for alkaline water electrolysis preferably contains 20 to 60 parts by mass of the above-mentioned organic polymer resin with respect to 100 parts by mass of the above-mentioned inorganic particles. When the content ratio of the above-mentioned inorganic particles and the organic polymer resin is within the above-mentioned range, the diaphragm for alkaline water electrolysis has excellent ion permeability, gas barrier property, heat resistance, and alkali resistance. The above-mentioned diaphragm for alkaline water electrolysis more preferably contains 22 to 55 parts by mass of the above-mentioned organic polymer resin with respect to 100 parts by mass of the above-mentioned inorganic particles, and still more preferably contains 25 to 50 parts by mass.

[0045] (Porous support) The above-mentioned diaphragm for alkaline water electrolysis may further contain a porous support. The above-mentioned porous support is porous, has ion permeability, and can serve as a support for the diaphragm for alkaline water electrolysis. By further including the above-mentioned porous support, the strength of the above-mentioned porous membrane can be improved, the strength of the diaphragm for alkaline water electrolysis can be improved, and damage to the ion permeable membrane during electrolysis can be suppressed. The above-mentioned porous support is preferably a sheet-like member.

[0046] Examples of the material of the above-mentioned porous support include resins such as polyethylene, polypropylene, polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyketone, polyimide, polyetherimide, and fluorine-based resins. These may be used alone or in combination of two or more. Among them, in terms of being able to exhibit excellent heat resistance and alkali resistance, it is preferable to contain at least one resin selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide, and more preferably to contain at least one resin selected from the group consisting of polypropylene and polyphenylene sulfide.

[0047] Examples of the form of the above-mentioned porous support include non-woven fabric, woven fabric, mesh, porous membrane, or a mixed fabric of non-woven fabric and woven fabric, etc. Preferably, non-woven fabric, woven fabric, or mesh is mentioned, more preferably non-woven fabric and mesh are mentioned, and still more preferably non-woven fabric is mentioned.

[0048] As the porous support, in particular, a non-woven fabric, a woven fabric, or a mesh containing at least one resin selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide is preferable. Further, as the porous support, a non-woven fabric or a mesh containing polyphenylene sulfide is preferable. The porous support is preferably one that has been hydrophilized by gas treatment, fiber lubricant, etc. in terms of improving the adhesion to the coating film.

[0049] When the porous support is in the form of a sheet, the thickness of the porous support is not particularly limited as long as the alkali water electrolysis diaphragm can exhibit the effects of the present invention. For example, it is preferably 30 to 300 μm, more preferably 50 to 250 μm, and still more preferably 100 to 200 μm.

[0050] In the alkali water electrolysis diaphragm, the porous film may be laminated on one or both sides of the porous support, or the porous support and the porous film may be integrated. The integration means a state in which the porous film is present in part or all of the porous support. In terms of enhancing the strength and toughness of the alkali water electrolysis diaphragm, it is preferable that the alkali water electrolysis diaphragm is a composite in which the porous support and the porous film are integrated.

[0051] The porosity of the alkali water electrolysis diaphragm is preferably 20 to 80% by volume, more preferably 25 to 75% by volume, and still more preferably 30 to 70% by volume. When the porosity is within the above range, the pores in the diaphragm can be continuously filled with the electrolyte, resulting in excellent ion permeability and a layer with excellent gas barrier properties. The porosity can be determined by immersing the alkali water electrolysis diaphragm in the electrolyte overnight and measuring the mass of the diaphragm before and after liquid absorption. Specifically, it can be determined by the following formula. Porosity (% by volume) = (mass of the diaphragm after immersion - mass of the diaphragm before immersion) / density of the electrolyte / volume of the diaphragm × 100

[0052] The pore size of the above-mentioned diaphragm for alkaline water electrolysis is preferably 0.01 to 1 μm, more preferably 0.05 to 0.9 μm, and even more preferably 0.1 to 0.8 μm. When the pore size is within the above range, the ion permeability is further improved. The above-mentioned pore size can be determined by measuring from the surface observation image (magnification ×25000) by FE-SEM measurement of the diaphragm for alkaline water electrolysis. Specifically, for any 10 voids in the FE-SEM image of the above-mentioned diaphragm for alkaline water electrolysis, using analysis software (Image-Pro Premier, manufactured by Nippon Roper Co., Ltd.), the diameter passing through the centroid of each selected void is measured as the pore size, and the average value is calculated and obtained.

[0053] The thickness of the above-mentioned diaphragm for alkaline water electrolysis is preferably 50 to 1000 μm in terms of excellent electrolysis efficiency and durability. The thickness of the above-mentioned diaphragm for alkaline water electrolysis is more preferably 100 μm or more, even more preferably 200 μm or more, more preferably 500 μm or less, and even more preferably 400 μm or less.

[0054] 2. Method for manufacturing a diaphragm for alkaline water electrolysis A method for manufacturing the diaphragm for alkaline water electrolysis of the present invention will be described. The method for manufacturing the diaphragm for alkaline water electrolysis of the present invention is not particularly limited, and known methods can be applied. However, in terms of efficiently manufacturing a diaphragm having the above-described surface state, the non-solvent induced phase separation method is preferable. Specifically, a manufacturing method including the following steps (1) to (4) is preferable. (1) Step of preparing a dispersion solution containing an organic polymer resin, inorganic particles, and a solvent (2) Step of forming a coating film using the above dispersion solution (3) Step of bringing the above coating film into contact with a non-solvent for the above organic polymer resin to solidify the above coating film (4) Step of drying the above solidified coating film to obtain a porous film

[0055] In step (3) of the above manufacturing method, it is preferable that the contact rate between the coating film and the non-solvent is 0.3 m / min or more. When the contact rate between the coating film and the non-solvent is within the above range, a separator having the above-described surface state can be easily manufactured. A method for manufacturing a separator for alkaline water electrolysis, which includes the above steps (1) to (4) and in which the contact rate between the coating film and the non-solvent in step (3) is 0.3 m / min or more, is also one aspect of the present invention. Each step of the method for manufacturing a separator for alkaline water electrolysis of the present invention will be described below.

[0056] Step (1) The method for manufacturing a separator for alkaline water electrolysis of the present invention includes a step (1) of preparing a dispersion solution containing an organic polymer resin, inorganic particles, and a solvent. The dispersion solution is a solution for forming a porous membrane containing the above-described organic polymer resin and inorganic particles. The organic polymer resin and the inorganic particles are the same as the organic polymer resin and the inorganic particles described in "1. Separator for Alkaline Water Electrolysis", respectively.

[0057] The preparation of the dispersion solution is not particularly limited and can be carried out by mixing the organic polymer resin, the inorganic particles, and the solvent. When mixing the organic polymer resin, the inorganic particles, and the solvent, the three components may be mixed simultaneously, or a dispersion (slurry) in which the inorganic particles are dispersed in the solvent may be prepared in advance, and then the dispersion and the organic polymer resin may be mixed, or a dispersion (slurry) or a solution in which the inorganic particles and the organic polymer resin are respectively dispersed or dissolved in the solvent may be prepared in advance, and then the dispersion and the solution may be mixed. Among these, a method of preparing a dispersion (slurry) or a solution in which the inorganic particles and the organic polymer resin are respectively dispersed or dissolved in the solvent, and then mixing the dispersion and the solution to prepare a dispersion solution is preferable in that the organic polymer resin and the inorganic particles can be uniformly mixed and a separator with a smooth surface can be easily manufactured.

[0058] As the solvent to be mixed with the above-mentioned organic polymer resin and inorganic particles, those having the property of being able to dissolve the organic polymer resin are preferred. For example, organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide can be mentioned. These solvents may be used alone or in combination of two or more. Among them, N-methyl-2-pyrrolidone is preferred in terms of easy dissolution of the organic polymer resin. The above solvent may contain other solvents in addition to the above-mentioned organic solvents.

[0059] The method of the above mixing and dispersion is not particularly limited, and known mixing and dispersion means such as methods using a mixer, ball mill, jet mill, disper, sand mill, roll mill, pot mill, paint shaker, etc. can be mentioned.

[0060] The concentration of the organic polymer resin in the solution in which the above-mentioned organic polymer resin is dissolved is preferably 10 to 50% by mass, more preferably 15 to 40% by mass, and still more preferably 20 to 30% by mass in terms of easy mixing.

[0061] The solution containing the above-mentioned organic polymer resin and the dispersion liquid containing inorganic particles are preferably mixed so that the organic polymer resin is 20 to 60 parts by mass, more preferably 22 to 55 parts by mass, and still more preferably 25 to 50 parts by mass with respect to 100 parts by mass of the inorganic particles.

[0062] Step (2) The method for producing the diaphragm for alkaline water electrolysis of the present invention then includes a step (2) of forming a coating film using the dispersion solution obtained in the above step (1). Examples of the method for forming the above coating film include a method of applying the above dispersion solution onto a substrate. The method of the above coating is not particularly limited, and known coating means such as methods using die coating, spin coating, gravure coating, curtain coating, spraying, applicator, coater, etc. can be mentioned.

[0063] The base material is not particularly limited as long as it can form a coating film by applying the above dispersion solution. For example, films or sheets made of resins such as polyethylene terephthalate, polyethylene naphthalate, polypropylene, polyethylene, polyvinyl chloride, polyvinyl acetal, polymethyl methacrylate, and polycarbonate, and glass plates can be mentioned. Among them, films or sheets of polyethylene terephthalate are preferred.

[0064] When the alkaline water electrolysis diaphragm includes a porous support, it is preferable to apply the above dispersion solution to the porous support. Examples of the coating method include a method of directly applying the above dispersion solution to the porous support, a method of immersing the porous support in the above dispersion solution, a method of applying the above dispersion solution on the base material and bringing the porous support into contact with the coated object to impregnate the porous support with the above dispersion solution. By impregnating the porous support with the above dispersion solution, a composite in which the porous membrane and the porous support are integrated can be produced.

[0065] The coating amount of the above dispersion solution is not particularly limited and may be appropriately set so that the obtained diaphragm has a desired thickness capable of exhibiting the above-described effects.

[0066] The step (2) of forming the above coating film is preferably carried out under the following conditions of an absolute humidity of 20 g / m 3 By carrying out the above step (2) under the above-described conditions, a diaphragm having the above-described surface state can be manufactured more efficiently. The above step (2) is more preferably carried out under the following conditions of an absolute humidity of 20 g / m 3 and even more preferably carried out under the following conditions of an absolute humidity of 10 g / m 3 The lower limit value of the above absolute humidity is not particularly limited and may be 0 g / m However, from the viewpoint of excellent economic efficiency, it is usually preferably 0.5 g / m 3 or more, and more preferably 1.0 g / m 3 or more. 3 The upper limit value of the absolute humidity is not particularly limited, and may be, for example, 30 g / m The absolute humidity can be obtained by multiplying the relative humidity and the saturated water vapor amount at the working atmosphere temperature for forming the coating film.

[0067] Step (3) The method for manufacturing the diaphragm for alkaline water electrolysis of the present invention includes a step (3) of bringing the coating film formed in the above step (2) into contact with a non-solvent for the above organic polymer resin to solidify the coating film. By bringing the above coating film into contact with a non-solvent for the above organic polymer resin, the non-solvent diffuses into the above coating film, and the organic polymer resin that does not dissolve in the non-solvent solidifies. On the other hand, the solvent in the coating film that can dissolve in the non-solvent elutes from the coating film. Due to such phase separation, the organic polymer resin solidifies, and a film having pores (porous film) is formed.

[0068] Examples of the method of bringing the above coating film into contact with the above non-solvent include a method of immersing the above coating film in the above non-solvent (coagulation bath).

[0069] Examples of the non-solvent for the above organic polymer resin include solvents having a property of not substantially dissolving the above organic polymer resin. Not substantially dissolving the above organic polymer resin means a case where the solubility of the organic polymer resin is 100 mg or less with respect to 100 g of the solvent. Examples of the above non-solvent include water such as pure water, distilled water, and ion-exchanged water; lower alcohols such as methanol, ethanol, and propyl alcohol; or a mixed solvent thereof. Among them, water is preferable from the viewpoints of economy and waste liquid treatment, and ion-exchanged water is more preferable. In addition, a small amount of a solvent similar to the solvent contained in the coating film may be contained in the non-solvent for immersing the above coating film in addition to the above-described components.

[0070] In the manufacturing method of the present invention, when the coating film is brought into contact with the non-solvent, the contact speed between the coating film and the non-solvent is preferably 0.3 m / min or more. When the contact speed is within the above range, a separator having a surface with the above-described recessed portion within a predetermined range can be obtained. The contact speed is more preferably 0.5 m / min or more, and even more preferably 0.7 m / min or more. The upper limit of the contact speed is not particularly limited, but is preferably 20 m / min or less, and more preferably 10 m / min or less. The contact speed can be set by the peripheral speed of the roller that conveys the coating film or the like.

[0071] Among the steps (3) of bringing the coating film into contact with the non-solvent to solidify the coating film, regarding the atmosphere until the coating film is brought into contact with the non-solvent, the absolute humidity is 20 g / m 3 It is preferably carried out under the following conditions. By carrying out the step (3) under the above-described conditions, a separator having the above-described surface state can be manufactured more easily. The step (3) is carried out under 15 g / m 3 It is more preferably carried out under the following conditions, and more preferably carried out under 10 g / m 3 It is even more preferably carried out under the following conditions. The absolute humidity can be obtained by multiplying the relative humidity and the saturated water vapor amount at the working atmosphere temperature for forming the coating film. The lower limit value of the absolute humidity is not particularly limited and may be 0 g / m 3 However, from the viewpoint of excellent economy, it is usually preferably 0.5 g / m 3 or more, and more preferably 1.0 g / m 3 or more.

[0072] The temperature condition of the step (3) is preferably 10 to 30 °C, more preferably 15 to 25 °C, and even more preferably 20 to 25 °C in terms of being easy to control the absolute humidity constantly.

[0073] Step (4) The method for manufacturing the diaphragm for alkaline water electrolysis of the present invention further includes a step (4) of drying the coating film solidified in the above step (3) to obtain a porous film. By drying the coating film solidified in step (3) to remove the above non-solvent, a porous film can be obtained. The drying temperature is preferably 60 to 120 °C, more preferably 70 to 100 °C. The drying time is preferably 2 to 120 minutes, more preferably 5 to 60 minutes, and even more preferably 10 to 30 minutes.

[0074] By the above-described steps (1) to (4), the diaphragm for alkaline water electrolysis of the present invention can be easily manufactured. The method for manufacturing the diaphragm for alkaline water electrolysis may include other known steps in addition to the above-described steps (1) to (4).

[0075] 3. Use The diaphragm for alkaline water electrolysis of the present invention preferably suppresses the retention of bubbles generated during electrolysis. Further, the diaphragm for alkaline water electrolysis of the present invention is also excellent in ion permeability, gas barrier property, and alkali resistance. The diaphragm for alkaline water electrolysis of the present invention can be suitably used as a diaphragm for electrolysis of water using an alkaline aqueous solution as an electrolyte. Hereinafter, an electrolysis apparatus and an electrolysis method using the diaphragm for alkaline water electrolysis of the present invention will be described.

[0076] (Electrolysis Apparatus) The diaphragm for alkaline water electrolysis of the present invention is used as a member of an alkaline water electrolysis apparatus. Examples of the alkaline water electrolysis apparatus include those including an anode, a cathode, and the above-described diaphragm for alkaline water electrolysis disposed between the anode and the cathode. More specifically, the alkaline water electrolysis apparatus has an electrolytic cell including an anode chamber where an anode exists and a cathode chamber where a cathode exists, separated by the above-described diaphragm for alkaline water electrolysis.

[0077] The above-mentioned diaphragm for alkaline water electrolysis is preferably installed so as to be in contact with the anode or the cathode, and more preferably installed so as to be in contact with both the anode and the cathode. When the distance between the electrodes becomes smaller, the electrical resistance becomes smaller, and the electrolysis efficiency of the electrolyzer can be made higher. When using the diaphragm for alkaline water electrolysis of the present invention, even in an electrolytic cell with a so-called "zero-gap structure" in which the diaphragm is installed in contact with each electrode so that the distance between the electrodes is minimized, the retention of generated bubbles can be suppressed, and high electrolysis efficiency can be achieved. Therefore, the diaphragm for alkaline water electrolysis of the present invention can be suitably used in an electrolytic device with a zero-gap structure.

[0078] The above-mentioned anode and cathode are not particularly limited as long as they are known electrodes. For example, electrodes including known conductive substrates such as copper, lead, nickel, chromium, titanium, gold, platinum, iron, metal compounds of these metals, metal oxides, and alloys containing two or more of these metals can be mentioned.

[0079] The above-mentioned electrode may be one in which a catalyst layer is formed on the above-mentioned conductive substrate. The above-mentioned catalyst layer is not particularly limited, and examples include known ones containing metal compounds, metal oxides, or alloys containing nickel, cobalt, palladium, iridium, platinum, or the like.

[0080] The shape of the above-mentioned electrode is not particularly limited, and known shapes such as sheet shape, rod shape, and prismatic shape can be mentioned. In terms of having a large contact area with the above-mentioned diaphragm for alkaline water electrolysis and being able to further improve the electrolysis efficiency of the electrolytic device, a sheet shape is preferred.

[0081] In addition, the above-mentioned electrolytic device may be provided with other members that are usually used. Examples of the above-mentioned other members include a gas-liquid separation tank for separating the generated gas and the electrolytic solution, a capacitor for stably performing electrolysis, a mist separator, and the like. Since the retention of bubbles is well suppressed in the diaphragm for alkaline water electrolysis of the present invention, it can be suitably used even in a high-pressure system where the bubble size becomes small.

[0082] (Electrolysis method) The method for electrolyzing water using the alkaline water electrolysis device equipped with the diaphragm for alkaline water electrolysis of the present invention is not particularly limited and can be carried out by known methods. For example, it can be carried out by filling the alkaline water electrolysis device equipped with the diaphragm for alkaline water electrolysis of the present invention described above with an electrolytic solution and applying an electric current in the electrolytic solution.

[0083] As the above electrolytic solution, an alkaline aqueous solution in which an electrolyte such as potassium hydroxide or sodium hydroxide is dissolved is preferably used. The concentration of the electrolyte in the above electrolytic solution is not particularly limited, but is preferably 20 to 40% by mass in terms of further improving the electrolysis efficiency.

[0084] As the temperature for performing electrolysis, 50 to 120°C is preferable, and 80 to 90°C is more preferable in terms of further improving the ionic conductivity of the electrolytic solution and further increasing the electrolysis efficiency. The conditions for applying the current can be carried out by known conditions and methods, usually 0.2 A / cm 2 or more, preferably 0.3 A / cm 2 or more. The higher the current density to be applied, the more hydrogen gas and oxygen gas can be obtained in a short time, so hydrogen can be produced efficiently. The electrolysis voltage is preferably adjusted so as not to exceed, for example, 1.5 to 2.5 V so that it becomes about 2 V and the current density increases.

[0085] As described above, the diaphragm for alkaline water electrolysis of the present invention can preferably suppress the retention of bubbles generated by electrolysis of water. Further, it is excellent in ion permeability, gas barrier property, and alkali resistance. By using the diaphragm for alkaline water electrolysis of the present invention, even in an electrolysis device having a zero-gap structure, the retention of bubbles can be suppressed and electrolysis can be carried out with high electrolysis efficiency.

Examples

[0086] Examples are given below to explain the present invention in more detail, but the present invention is not limited to these examples only. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0087] In the examples, various evaluations were carried out by the following methods. (Method for measuring film thickness) The thickness of the obtained diaphragm for alkaline electrolysis was measured using a digital micrometer (manufactured by Mitutoyo Corporation). Ten arbitrary points of a 5 cm□ diaphragm sample were measured, and the average value was taken as the film thickness.

[0088] (Method for measuring the average area and area ratio of the depressed part) Using a laser microscope VK9700 (manufactured by Keyence Corporation), observation images of the diaphragm surface were obtained at a magnification of 150 times for ten arbitrary fields of a 5 cm□ diaphragm sample. For each obtained image, height analysis of line thickness measurement was performed with respect to the diagonal line of the observation field using analysis software VK Analyzer VK-H1A1 (manufactured by Keyence Corporation). A point at -1.5 μm in the Z direction (height direction) from the reference plane was defined as the reference point A from the obtained cross-sectional profile. It is preferably analytically favorable that there are three or more of these reference points A. Then, using image analysis software (Image-Pro Premier, manufactured by Nippon Roper Co., Ltd.) for the obtained image, points farther from the reference point A than the above reference plane (points where Z direction ≤ -1.5 μm) were shown in dark color, and binarization was automatically performed for the portions darker than the reference point A defined above. The area of each depressed part of the dark part was obtained, and the "average area of the depressed part A in one field" was calculated from the simple average (number average) thereof. Also, the ratio of the total area of each depressed part A to the area of the entire observation field, that is, the "area ratio of the depressed part A in one field" was calculated. The same image analysis was performed for a total of ten fields, and the simple average values (number average) of the average area and area ratio of the depressed part A in each field were obtained, and these were taken as the "average area of the depressed part A" and the "area ratio of the depressed part A" of the diaphragm sample.

[0089] Similarly, a reference point B was defined as the point at +1.5 μm in the Z direction (height direction) from the reference plane on the cross-sectional profile obtained in the same manner. It is preferably analytically favorable that there are three or more such reference points B. Subsequently, for the acquired image, using image analysis software, points farther from the reference plane than the reference point B (points at ≧1.5 μm in the Z direction) were shown in light color, and those lighter than the reference point B defined above were automatically extracted and binarized. Then, the areas of the regions surrounded by light color (depression site B) were specified respectively, and the "average area of depression site B in one field of view" was calculated from the simple average (number average) thereof. Also, the ratio of the total area of each depression site B to the area of the entire observation field of view, that is, the "area ratio of depression site B in one field of view" was calculated. The same image analysis was performed for a total of 10 fields of view, and the simple average values (number average) of the average area and area ratio of depression site B in each field of view were obtained, and these were taken as the "average area of depression site B" and the "area ratio of depression site B" of the diaphragm sample.

[0090] (Method for Measuring Surface Roughness) Using VK9700 (manufactured by Keyence Corporation), observation images of the diaphragm surface were acquired at a magnification of 150 times for an object in any 10 fields of view of a 5 cm□ diaphragm sample. For each acquired image, using analysis software VK Analyzer VK-H1A1 (manufactured by Keyence Corporation), the entire observation field of view was specified, and measurement was performed in a method compliant with JIS B0601:2001. A total of 10 fields of view were measured, and the simple average value was taken as the representative value of the surface roughness of the diaphragm.

[0091] (Evaluation of Electrical Characteristics) The alkaline water electrolysis evaluation of the obtained diaphragm for alkaline water electrolysis was conducted as follows. A platinum mesh (manufactured by Nilaco Corporation, product number PT-358056 / 55 mesh) cut into 3 cm × 3 cm was used as the anode electrode. A nickel mesh (manufactured by Nilaco Corporation, product number NI-318040 / 40 mesh) cut into 3 cm × 3 cm was used as the cathode electrode. The platinum mesh was applied so as to be in contact with the obtained diaphragm for alkaline water electrolysis (zero-gap structure) and fixed so as not to shift when assembling the electrolytic cell. The electrolytic cell was assembled so that the cathode electrode chamber and the anode electrode chamber were partitioned by the diaphragm. An aqueous potassium hydroxide solution with a concentration of 30% by weight was used as the electrolyte. First, after filling the electrolytic cell with the electrolyte, circulation and heating were performed, and adjustment was made so that the liquid temperature measured by the thermometer installed immediately before flowing into the electrolytic cell reached 40°C. After the electrolyte reached 40°C and 30 minutes or more had elapsed, a current density of 0.3 A / cm 2 was continuously applied for 10 minutes at a constant current density. Then, the current density was increased to 0.5 A / cm 2 , the voltage every 1 minute was recorded, and the continuous 5-point voltage collected was held until it stabilized within ±3% of the average value of the 5 points. After the stability of the voltage was confirmed, 10-point voltage measurements were performed every 1 minute, and the average value of the 10 measured values was calculated.

[0092] <Example 1> (1. Preparation of magnesium hydroxide dispersion) Magnesium hydroxide (average particle diameter 0.20 μm, plate-like, aspect ratio 6.21) and N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed so that the mass ratio was 1:1, and a magnesium hydroxide dispersion was prepared by performing a dispersion treatment at room temperature for 6 hours in a pot mill containing zirconia media balls.

[0093] (2. Preparation of polysulfone resin solution) A polysulfone resin (manufactured by BASF, product number Ultrason S3010) was dissolved in N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at a concentration of 30% by mass.

[0094] (3. Preparation of coating solution) The magnesium hydroxide dispersion liquid obtained above and the polysulfone resin solution were weighed so that the solid content was 48% by mass and the polysulfone resin (PSU) was 25 parts by mass with respect to 100 parts by mass of magnesium hydroxide, and were mixed at room temperature for about 10 minutes at 1000 rpm using a planetary mixer (manufactured by Shin-Kee Co., Ltd., product number Awatori Rentaro ARE-500). The obtained mixed liquid was filtered through a 200-mesh SUS to obtain a coating liquid.

[0095] (4. Formation of coating film) In an atmosphere with an absolute humidity of 12.7 g / m 3 The polyphenylene sulfide nonwoven fabric (manufactured by Toray Industries, Inc., TORCON PAPER #100) was set so that the peripheral speed of the automatic conveying roller was 3.0 m / min, and the obtained coating liquid was directly applied onto the running sheet so that the thickness of the diaphragm after drying was 250 μm in total, impregnating the nonwoven fabric with the coating liquid. The nonwoven fabric impregnated with the coating liquid was vertically inserted into the water surface of the water tank, and then immersed in water for 5 minutes to solidify the coating liquid to form a film. After the water bath, the obtained film was dried at 80 °C for 10 minutes using a dryer to obtain a diaphragm for alkaline water electrolysis composed of a composite of the nonwoven fabric and a film containing magnesium hydroxide and polysulfone resin. The average area of the depression site A of the obtained diaphragm was 3.3 μm 2 and the area ratio of the depression site A was 9.0%, the average area of the depression site B was 0.8 μm 2 and the area ratio of the depression site B was 0.7%, and the arithmetic mean roughness Ra was 0.47 μm. Electrical property evaluation was performed, and the cell voltage at 0.5 A / cm 2 was 1.81 V. Also, Fig. 1 shows an observation image of the surface of the obtained diaphragm for alkaline water electrolysis by a laser microscope (150 times magnification of the objective lens).

[0096] <Example 2> An alkaline water electrolysis diaphragm was produced in the same manner as in Example 1, except that in Example 1 (3. Preparation of coating liquid), the PSU was changed to 50 parts by mass with respect to 100 parts by mass of magnesium hydroxide. The average area of the depression site A of the obtained diaphragm was 2.1 μm 2and the area ratio of the depression site A is 12.4%, and the average area of the depression site B is 0.9 μm 2 and the area ratio of the depression site B is 0.5%, and the arithmetic mean roughness Ra was 0.39 μm. Electrical property evaluation was performed, and the cell voltage at 0.5 A / cm 2 was 1.88 V.

[0097] <Example 3> In Example 1 (4. Formation of the coating film), an alkali water electrolysis diaphragm was produced in the same manner as in Example 1 except that the absolute humidity was changed to 3.5 g / m 3 The average area of the depression site A of the obtained diaphragm was 0.9 μm 2 and the area ratio of the depression site A was 8.5%, there was no depression site B, and the arithmetic mean roughness Ra was 0.34 μm. Electrical property evaluation was performed, and the cell voltage at 0.5 A / cm 2 was 1.80 V.

[0098] <Example 4> In Example 1 (4. Formation of the coating film), an alkali water electrolysis diaphragm was produced in the same manner as in Example 1 except that the line speed was changed to 0.3 m / min and the absolute humidity was changed to 19.5 g / m 3 The average area of the depression site A of the obtained diaphragm was 5.9 μm 2 and the area ratio of the depression site A was 12.7%, and the average area of the depression site B was 0.9 μm 2 and the area ratio of the depression site B was 6.8%, and the arithmetic mean roughness Ra was 0.77 μm. Electrical property evaluation was performed, and the cell voltage at 0.5 A / cm 2 was 1.89 V.

[0099] <Comparative Example 1> In Example 1 (4. Formation of the coating film), an alkali water electrolysis diaphragm was produced in the same manner as in Example 1 except that the absolute humidity was changed to 20.9 g / m 3 The average area of the depression site A of the obtained diaphragm was 10.1 μm 2 and the area ratio of the depression site A was 23.8%, and the average area of the depression site B was 3.1 μm 2and the area ratio of the depression site B was 1.2%, and the arithmetic mean roughness Ra was 0.82 μm. Electrical property evaluation was performed, and the cell voltage at 0.5 A / cm 2 was 2.03 V.

[0100] <Comparative Example 2> In Example 1 (4. Formation of the coating film), an alkali water electrolysis diaphragm was produced in the same manner as in Example 1 except that the line speed was changed to 0.2 m / min. The average area of the depression site A of the obtained diaphragm was 8.2 μm 2 and the area ratio of the depression site A was 21.4%, and the average area of the depression site B was 2.7 μm 2 and the area ratio of the depression site B was 2.8%, and the arithmetic mean roughness Ra was 0.96 μm. Electrical property evaluation was performed, and the cell voltage at 0.5 A / cm 2 was 2.08 V.

[0101] <Comparative Example 3> In Comparative Example 1, an alkali water electrolysis diaphragm was produced in the same manner as in Comparative Example 1 except that the line speed was changed to 0.2 m / min. The average area of the depression site A of the obtained diaphragm was 8.6 μm 2 and the area ratio of the depression site A was 21.4%, and the average area of the depression site B was 5.0 μm 2 and the area ratio of the depression site B was 3.7%, and the arithmetic mean roughness Ra was 1.25 μm. Electrical property evaluation was performed, and the cell voltage at 0.5 A / cm 2 was 2.08 V.

Claims

1. On at least one diaphragm surface, the average area of the depressed portion is 7 μm ２ The following, and a method of using a diaphragm for alkaline water electrolysis, in which the area ratio of the depressed portion on the diaphragm surface is 20% or less, is installed in an electrolysis apparatus having an anode and a cathode, The diaphragm for alkaline water electrolysis has a porous membrane containing an organic polymer resin and inorganic particles, and a porous support, and the porous membrane is laminated only on one side of the porous support, A method of using a diaphragm for alkaline water electrolysis, characterized in that it is installed so as to be in contact with the anode and the cathode.

2. The method of using a diaphragm for alkaline water electrolysis according to claim 1, wherein the arithmetic mean roughness Ra of the diaphragm surface is 0.8 μm or less.

3. The method of using a diaphragm for alkaline water electrolysis according to claim 1 or 2, wherein the diaphragm for alkaline water electrolysis contains an organic polymer resin and inorganic particles.

4. The method of using a diaphragm for alkaline water electrolysis according to claim 3, wherein the inorganic particles are metal hydroxide particles and / or metal oxide particles.

5. The method of using a diaphragm for alkaline water electrolysis according to claim 3 or 4, wherein the organic polymer resin is at least one resin selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone.

6. An alkaline water electrolysis apparatus including an anode, a cathode, and a diaphragm for alkaline water electrolysis disposed between the anode and the cathode, The diaphragm for alkaline water electrolysis has a porous membrane containing an organic polymer resin and inorganic particles, and a porous support, and the porous membrane is laminated only on one side of the porous support. At least on one diaphragm surface, the average area of the depression sites is 7 μm ２ or less, and the area ratio of the depression sites on the diaphragm surface is 20% or less, and it is characterized in that it is installed so as to be in contact with the anode and the cathode.

Images