JP2022176792A - Alkaline water electrolysis diaphragm, and method of producing the same - Google Patents

Abstract

To provide an alkaline water electrolysis diaphragm excellent in the stability of ion conductivity in a hot alkali.SOLUTION: The alkaline water electrolysis diaphragm comprising a porous layer including an organic polymer and an inorganic particle. The porous layer is a layer constituting at least one surface of the diaphragm, is characterized in that the content of macro-voids having a long diameter of 30 μm or larger on the cross section in the thickness direction of the porous layer is 40% or less, and X represented by the following formula (1) is 0.6 or greater. Formula (1): X=air permeability of diaphragm (second)/thickness of diaphragm (μm).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a diaphragm for alkaline water electrolysis and a method for producing the same. More specifically, the present invention relates to a diaphragm for alkaline water electrolysis, which has excellent stability of ion conductivity in hot alkali, and a method for producing the same.

Electrolysis of water (also called "electrolysis") is known as one of the industrial production methods of hydrogen gas. This is done by applying an electric current to water added as an electrolyte. For such electrolysis of water, an electrolytic cell is used which has an anode chamber and a cathode chamber in which an anode and a cathode are respectively arranged and which are separated by a diaphragm.

Electrolysis of water is performed by the transfer of electrons (or ions). Therefore, the diaphragm is required to have high ionic conductivity in order for the electrolysis reaction to take place efficiently. Furthermore, since the electrolysis of water is performed using high-concentration alkaline water of about 30% at 80 to 100 ° C. and in some cases under a high pressure of 1 MPa or more, in order to maintain high ionic conductivity are also required to have heat resistance and alkali resistance.

Various porous membranes manufactured by a non-solvent induced phase separation method (NIPS method) have been known as diaphragms used for electrolysis of water. In the production of porous membranes by the non-solvent-induced phase separation method, the porous structure such as pore size is affected by the rate of substitution between the solvent and the non-solvent. It is generally known that coarse pores such as voids are difficult to form on the surface of a porous membrane. The substitution rate of the solvent and the non-solvent depends on the addition of a hydrophilic additive such as polyvinylpyrrolidone or lithium chloride to the coating composition used to prepare the porous membrane, or the hydrophilicity of the coating composition by the hydrophilic additive. It is known that it is affected by , thickening, etc. (for example, Non-Patent Document 1, Non-Patent Document 2).

Further, in a diaphragm used for electrolysis of water, it is known to incorporate inorganic particles into a diaphragm made of a resin in order to increase the ionic conductivity of the diaphragm (for example, Patent Document 1, Patent document 2).

International Publication No. 2019/021774 JP 2020-169349 A

Desalination, 2006, Vol. 192, p. 190-197 Desalination, 1988, Vol. 68, p. 167-177

According to the studies of the present inventors, although a diaphragm having a porous layer containing inorganic particles has excellent ion conductivity, when the diaphragm having the porous layer is used as a diaphragm for alkaline water electrolysis, the ion conductivity is poor. There is a problem that it tends to fluctuate over time.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a diaphragm for alkaline water electrolysis which is excellent in the stability of ion conductivity in hot alkali.

The present inventors have investigated a diaphragm having a porous layer containing inorganic particles, and found that the size and content of macrovoids contained in the porous layer are deeply involved in the stability of ionic conductivity. Found. Furthermore, it was found that the gas permeability per unit thickness, as an index of the porous structure of the diaphragm, also affects the stability of the ionic conductivity. Then, by using a composition having specific viscosity characteristics as the composition containing inorganic particles for forming the porous layer, the generation and growth of macrovoids are suppressed, and the porous layer has a controlled porous structure. The present inventors have completed the present invention based on the finding that a diaphragm having a

That is, the diaphragm for alkaline water electrolysis of the present invention is a diaphragm for alkaline water electrolysis having a porous layer containing an organic polymer and inorganic particles,
The porous layer is a layer constituting at least one surface of the diaphragm, and the content of macrovoids having a major axis of 30 μm or more in a cross section in the thickness direction of the porous layer is 40% or less,
The diaphragm for alkaline water electrolysis is characterized in that X represented by the following formula (1) is 0.6 or more.
X = air permeability of diaphragm (seconds)/thickness of diaphragm (μm) (1)

The diaphragm for alkaline water electrolysis of the present invention is excellent in the stability of ion conductivity in hot alkali. Therefore, by using the diaphragm for alkaline water electrolysis of the present invention in an alkaline water electrolysis apparatus, high-purity hydrogen gas can be stably produced for a long period of time.

FIG. 4 is a conceptual diagram for explaining the maximum shear rate during application;

The present invention will be described in detail below.
A combination of two or more of the individual preferred embodiments of the invention described below is also a preferred embodiment of the invention.

1. Diaphragm for Alkaline Water Electrolysis A diaphragm for alkaline water electrolysis, which is Embodiment 1 of the present invention, will be described.
The diaphragm for alkaline water electrolysis of the present invention is a diaphragm for alkaline water electrolysis having a porous layer containing an organic polymer and inorganic particles,
The porous layer is a layer constituting at least one surface of the diaphragm, and the content of macrovoids having a major axis of 30 μm or more in a cross section in the thickness direction of the porous layer is 40% or less,
It is characterized in that X represented by the following formula (1) is 0.6 or more.
X = air permeability of diaphragm (seconds)/thickness of diaphragm (μm) (1)
In this specification, a porous layer containing an organic polymer and inorganic particles is also simply referred to as a porous layer.
The diaphragm for alkaline water electrolysis of the present invention includes a porous layer containing an organic polymer and inorganic particles as a layer constituting at least one surface thereof. That is, the porous layer constituting the diaphragm for alkaline water electrolysis of the present invention is a layer constituting at least one surface of the diaphragm. By having the porous layer, a large amount of electrolytic solution can be impregnated, and ion permeability is exhibited.

The diaphragm for alkaline water electrolysis of the present invention may be composed only of the porous layer, or may further include a porous support. By further including the porous support, the strength of the porous layer can be improved, the strength of the diaphragm for alkaline water electrolysis can be improved, and the breakage of the ion permeable membrane during electrolysis can be suppressed. . The porous support is preferably a sheet-like member.

When the diaphragm for alkaline water electrolysis of the present invention contains a porous support, its form is not particularly limited as long as the porous layer constitutes at least one surface of the diaphragm. For example, the structure of the diaphragm for alkaline water electrolysis includes a mode (1) in which a porous layer is laminated on one side of a porous support, and a porous layer is laminated on both sides of a porous support. Form (2) described above is a preferred embodiment.

Furthermore, in the form (1), the organic polymer and / or inorganic particles similar to the organic polymer and inorganic particles constituting the porous layer are contained in part or all of the inside of the porous support (1a ) is also a preferred embodiment.
Similarly, in form (2), the organic polymer and/or inorganic particles similar to the organic polymer and inorganic particles constituting at least one of the porous layers are contained in part or all of the interior of the porous support. Form (2a) is also a preferred embodiment.

Among the above modes (1a), one surface of the porous support has the above porous layer, and a part or all of the inside of the porous support is removed from the interface between the porous layer and the porous support. Another preferred embodiment is a form (1b) having a layer (impregnated layer) impregnated with the same component as the material constituting the porous layer.
Similarly, in the above mode (2a), the porous support has the above porous layers on both sides of the porous support, and a portion of the inside of the porous support is formed from the interface between the porous layer and the porous support. A form (2b) having a layer (impregnated layer) impregnated with a component similar to the material constituting at least one porous layer in part or all of the porous layer (2b).

Among them, the diaphragm for alkaline water electrolysis of the present invention preferably has the above-described form (1a), (1b), (2a) or (2b) in that the strength of the diaphragm is further increased. (2b) is more preferred, and form (1b) is even more preferred.

As described above, in the diaphragm for alkaline water electrolysis of the present invention, at least one porous layer constituting the surface layer has a macrovoid content of 30 μm or more in the cross section in the thickness direction of the porous layer. 40% or less. The condition that "the content of macrovoids having a major axis of 30 μm or more in the cross section in the thickness direction of the porous layer is 40% or less" is also referred to as condition (Y). Also, the content of macrovoids having a major axis of 30 μm or more is sometimes simply referred to as the macrovoid content.

When the diaphragm for alkaline water electrolysis of the present invention contains a porous support, regardless of its form, at least one of the porous layers constituting the surface of the diaphragm for alkaline water electrolysis of the present invention satisfies the condition (Y). Be satisfied. When there are porous layers forming the surface of the diaphragm for alkaline water electrolysis of the present invention on both sides, both porous layers preferably satisfy the condition (Y).

In the present invention, a macrovoid means a void having a major axis of 10 μm or more and a minor axis of 5 μm or more. The length and breadth are determined as follows.
That is, the thickness direction of the diaphragm for alkaline water electrolysis of the present invention, that is, the cross section of the diaphragm cut in the direction perpendicular to the surface of the diaphragm is observed with a field emission scanning electron microscope (FE-SEM) and used as a measurement target. A cross-sectional observation image of the porous layer is obtained. Although the imaging magnification of the field emission scanning electron microscope is not particularly limited, it is preferably 100 to 2,000 times, more preferably 200 to 1,000 times, in consideration of the size of macrovoids and the like.

The length in the thickness direction (Lt) and the length in the plane direction (Lf) are obtained from the void image observed in the obtained cross-sectional observation image, and the major axis and the minor axis are larger than (Lt) and (Lf). The longer diameter is the longer diameter, and the smaller diameter is the shorter diameter.

The thickness direction length (Lt) is the thickness direction of the diaphragm, that is, the length in the direction perpendicular to the surface of the diaphragm. Specifically, the point closest to the diaphragm (porous membrane) surface in the void, The distance in the thickness direction of the diaphragm (perpendicular to the surface of the diaphragm) from the point closest to the opposite surface is defined as the thickness direction length (Lt) of the void. A value obtained by dividing the area (S) of the void by the length (Lt) in the thickness direction is defined as the length (Lf) of the void in the plane direction. Among (Lt) and (Lf) obtained in this manner, the larger one is taken as the major axis (Lb) of the void, and the smaller one as the minor axis (Ls).

The thickness direction length (Lt) and area (S) of the voids are obtained by extracting the void portions as dark portions from the cross-sectional observation image using image analysis software (eg, Scion Image, manufactured by Scion). can be done.

A void having a major axis of 10 μm or more and a minor axis of 5 μm or more determined in this way is called a macrovoid. It is important that the content of macrovoids with a diameter of 30 μm or more is 40% or less.

The macrovoid content rate means the ratio (percentage) of the total area of macrovoids having a major axis of 30 μm or more to the area of the porous layer in the cross-sectional observation image. Usually, in the cross-sectional observation image, the area surrounded by the thickness (total thickness) of the porous layer in the thickness direction of the diaphragm (porous membrane) and the line segment with a length of 400 μm in the planar direction of the diaphragm (porous layer) is the measurement area.

Then, in the measurement region, using image analysis software (eg, Scion Image, manufactured by Scion), the total area of macrovoids having a major axis of 30 μm or more (that is, the total area of the individual macrovoids) (Sy ) and the area (St) of the measurement region, the ratio (percentage) of (Sy) to (St) is determined, and the obtained value is defined as the content of macrovoids having a major axis of 30 μm or more.

In the porous layer of the diaphragm for alkaline water electrolysis of the present invention, the content of macrovoids having a length of 30 μm or more determined as described above is 40% or less. From the viewpoint that the diaphragm for alkaline water electrolysis of the present invention is also excellent in strength properties such as tensile strength, the macrovoid content is preferably 35% or less, more preferably 30% or less, and even more preferably. 25% or less.

For the same reason, it is preferable that the content of macrovoids having a length of 20 μm or more determined in the same manner is 40% or less. It is more preferably 35% or less, still more preferably 30% or less, and most preferably 25% or less.

In the diaphragm for alkaline water electrolysis of the present invention, X represented by the following formula (1) is 0.6 or more.
X = air permeability of diaphragm (seconds)/thickness of diaphragm (μm) (1)
In the formula (1), the air permeability of the diaphragm means the air permeability of the diaphragm. The air permeability can be determined by a conventionally known measuring method, and a value measured using a commercially available measuring device can be adopted. The gas used for measurement is air. For example, the air permeability is measured using an Oken type air permeability tester (manufactured by Asahi Seiko Co., Ltd., model number: EGBO), and the measured value is used as the air permeability of the diaphragm for alkaline water electrolysis of the present invention. can. It is preferable to arbitrarily select and measure a plurality of points, for example, three points for one sample, and take the average value as the air permeability.

The film thickness of the diaphragm in the formula (1) means the thickness of the diaphragm for alkaline water electrolysis of the present invention. As for the measurement method, values measured with a micrometer are adopted. Usually, it is preferable to measure the thickness at a plurality of points, for example, 10 points, and take the average value as the film thickness of the diaphragm. As the micrometer, it is preferable to use a commercially available product such as Digimatic Micrometer (manufactured by Mitutoyo Corporation).

X can be determined using the air permeability (seconds) and film thickness (μm) of the diaphragm for alkaline water electrolysis of the present invention measured by the above-described measuring method. X is more preferably 0.65 or more, still more preferably 0.70 or more, and particularly preferably 0.75 or more. On the other hand, although the upper limit of X is not particularly limited, it is preferably 4.00 or less, more preferably 3.50 or less.

Regarding the diaphragm for alkaline water electrolysis of the present invention, any portion of the diaphragm can be used as a measurement sample in measuring the air permeability and film thickness for obtaining the above macrovoid content rate and X above. is in the form of a sheet, draw a circle with the center of the sheet as the center and 80% of the total area in the plane direction of the sheet. ) is preferred.

The selection site may be one, but preferably three or more, more preferably five. Then, it is preferable to measure the content rate of macrovoids, X, for each of the selected locations, and take a simple average value of the measured values as the content rate of macrovoids, X, in the diaphragm.

The porous layer contains an organic polymer and inorganic particles.
Examples of the organic polymer include fluorine-based resins, olefin-based resins, and aromatic hydrocarbon-based resins.

Examples of the fluorine-based resin include ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polytetra fluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer and the like.
Examples of the olefin resin include polyethylene, polypropylene, polybutene, polymethylpentene, and the like.
Examples of the aromatic hydrocarbon resin include polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylsulfone, polyarylate, polyetherimide, polyimide, and polyamideimide. etc.

Among them, the organic polymer is preferably an aromatic hydrocarbon resin in terms of excellent heat resistance, pressure resistance and alkali resistance, and is selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone. At least one is more preferable, and polysulfone is even more preferable in that the diaphragm can be easily produced. Only one kind of the organic polymer may be used, or two or more kinds thereof may be used in combination.

The content of the organic polymer is preferably 5 to 40% by mass based on 100% by mass of the diaphragm for alkaline water electrolysis. When the content of the organic polymer 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 is more preferably 7% by mass or more, still more preferably 10% by mass or more, and more preferably 35% by mass or less in 100% by mass of the diaphragm for alkaline water electrolysis, It is more preferably 30% by mass or less.

The content of the organic polymer is preferably 28 to 40% by mass based on 100% by mass of the diaphragm for alkaline water electrolysis when the diaphragm for alkaline water electrolysis does not contain a porous support, which will be described later. When the content of the organic polymer is within the above range, a void structure controlled by the organic polymer can be easily formed in the diaphragm. The content of the organic polymer is more preferably 31% by mass or more, more preferably 38% by mass or less, and even more preferably 36% by mass or less in 100% by mass of the diaphragm for alkaline water electrolysis. .

In addition, when the diaphragm for alkaline water electrolysis contains a porous support described later, the content of the organic polymer is preferably 5 to 35% by mass based on 100% by mass of the diaphragm for alkaline water electrolysis. When the content of the organic polymer is within the above range, a void structure controlled by the organic polymer can be easily formed in the diaphragm. The content of the organic polymer is more preferably 8% by mass or more, still more preferably 12% by mass or more, and even more preferably 17% by mass or more in 100% by mass of the diaphragm for alkaline water electrolysis. It is preferably 30% by mass or less, still more preferably 25% by mass or less, even more preferably 23% by mass or less, and particularly preferably 21% by mass or less.

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. material; carbides such as titanium, zirconium, hafnium, and the like. Only one kind of the inorganic particles may be contained, or two or more kinds thereof may be contained.
Among them, metal hydroxides or metal oxides are preferable, and magnesium hydroxide, zirconium hydroxide, titanium hydroxide, zirconium oxide, and titanium oxide are more preferable, and magnesium hydroxide is more preferable because it can improve ion permeability. , zirconium hydroxide, titanium hydroxide and titanium oxide are more preferable, magnesium hydroxide, zirconium hydroxide and titanium hydroxide are more preferable, and magnesium hydroxide is particularly preferable.

The inorganic particles may be surface-untreated or surface-treated. Examples of the surface treatment include known surface treatments using silane coupling agents, stearic acid, oleic acid, phosphate esters, and the like.

The shape of the inorganic particles is not particularly limited, and may be any shape such as amorphous; granular; granular; plate-like such as flaky or hexagonal plate-like; Among them, the shape of the inorganic particles is preferably granular or plate-like, more preferably plate-like, and still more preferably flaky, in terms of excellent adhesion to the resin. . The shape of the inorganic particles is preferably plate-like, and more preferably flake-like, in that the structure becomes dense and the membrane strength can be improved.

The average particle size of the inorganic particles is preferably 0.05 μm or more, and preferably 2.0 μm or less, in that the structure becomes dense and the strength of the diaphragm can be improved. The average particle size of the inorganic particles is more preferably 0.08 μm or more, still more preferably 0.1 μm or more, more preferably 1.5 μm or less, and even more preferably 1 μm or less. .

The average particle size is a volume average particle size (D50) obtained from particle size distribution measurement by laser diffraction method. Specifically, the average particle size is obtained by measuring the particle size distribution using a laser diffraction/scattering particle size distribution analyzer (for example, "model number LA-920" manufactured by Horiba Ltd.), and measuring the median diameter in the volume-based particle size distribution ( D50) is taken as the average particle size. A measurement sample is obtained by mixing particles with ethanol and irradiating ultrasonic waves to disperse the particles.

The inorganic particles preferably have an aspect ratio of 2.0 to 8.0. When the aspect ratio is within the above range, the membrane can have even better ion permeability and excellent uniformity. The aspect ratio is more preferably 2.5 to 7.0, even more preferably 3.0 to 6.0.

The aspect ratio means the ratio [(a)/(b)] of the longest diameter (a) and the shortest diameter (b), and the inorganic particles are observed with SEM, and any 10 particles of the obtained image In, using analysis software, etc., the ratio of the longest diameter (a) and the shortest diameter (b) of each particle [(a) / (b)] is measured, and the simple average value of these ratios is the particle can be obtained as the aspect ratio of Generally, it is preferable to use the shortest diameter (b) as the shortest diameter among the diameters passing through the midpoint of the longest diameter (a) and orthogonal to the longest diameter.

As the longest diameter (a), for example, when the shape of the particles is plate-like such as flaky or hexagonal plate-like, the major diameter of the plate surface of the particle is adopted, and when it is fibrous, the length of the fiber is used. adopt.
As the shortest diameter (b), for example, when the shape of the particles is plate-like such as flakes or hexagonal plates, the thickness of the particles is adopted, and when the shape is fibrous, the thickness of the fibers is adopted. . As the thickness of the particles and the thickness of the fibers, it is preferable to employ the thickness and thickness at the midpoint of the longest diameter a, respectively.

Magnesium hydroxide is particularly preferable as the inorganic particles because it is particularly excellent in alkali resistance and durability, and a diaphragm for alkaline water electrolysis can be obtained at a relatively low cost. Magnesium hydroxide that can be used in the present invention preferably has an average particle size and an aspect ratio of the above average particle size and aspect ratio, respectively.

The magnesium hydroxide preferably has a crystallite size of 35 nm or more in a direction perpendicular to the (110) plane measured by X-ray diffraction. When the crystallite size in the direction perpendicular to the (110) plane is within the above range, the ion permeability of the membrane and the uniformity of the membrane 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. Although the upper limit of the crystallite diameter in the direction perpendicular to the (110) plane is not particularly limited, it is usually, for example, 400 nm or less, preferably 350 nm or less, and more preferably 300 nm or less.

The magnesium hydroxide preferably has a crystallite diameter of 15 nm or more in a direction perpendicular to the (001) plane measured by X-ray diffraction.
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. Although the upper limit of the crystallite diameter in the direction perpendicular to the (001) plane is not particularly limited, it is usually, for example, 300 nm or less, preferably 250 nm or less, and more preferably 200 nm or less. The crystallite diameter is obtained by measuring the X-ray diffraction pattern of magnesium hydroxide particles by a powder X-ray diffraction method, and using the Scherrer formula from the spread of the diffraction line (half width) attributed to the lattice plane of interest. It can be obtained by calculating the crystallite diameter (the crystallite diameter in the direction perpendicular to the lattice plane).

Examples of methods for obtaining magnesium hydroxide having a specific crystallite size range include the following methods.
An aqueous solution of magnesium salt (magnesium chloride, magnesium nitrate, etc.) or an aqueous dispersion of magnesium oxide obtained by a conventionally known method is used as a raw material, and alkaline physical properties (lithium hydroxide, sodium hydroxide, calcium hydroxide, aqueous ammonia etc.), a hydration reaction is carried out to prepare magnesium hydroxide. At this time, by adding organic acids such as formic acid, acetic acid and propionic acid, polybasic acids such as nitric acid and sulfuric acid, or mixtures thereof, the solubility of the generated magnesium hydroxide can be adjusted and the temperature of the hydrothermal reaction can be adjusted. Particles with different crystallite sizes can be prepared by appropriately adjusting the temperature (eg, 150° C. to 270° C.) and time (eg, 30 minutes to 10 hours). The larger the amount of acid added, the more the crystal grows and the larger the crystallite size. 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 size.

In the present invention, general commercial products can also be used as the inorganic particles. For example, commercial 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 Material Co., Ltd., MAGSTAR #20 manufactured by Tateho Chemical Industry Co., Ltd., and Kajima Chemical Industry Co., Ltd. Manufacture #200 and the like.

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, still more preferably 40% by mass or more, and more preferably 85% by mass or less in 100% by mass of the diaphragm for alkaline water electrolysis, It is more preferably 80% by mass or less.

The content of the inorganic particles is preferably 50 to 90% by mass based on 100% by mass of the diaphragm for alkaline water electrolysis when the diaphragm for alkaline water electrolysis does not contain a porous support, which will be described later. When the content of the inorganic particles is within the above range, the structure can be made dense, and the strength of the diaphragm can be improved. The content of the inorganic particles is more preferably 85% by mass or less, still more preferably 80% by mass or less, and more preferably 55% by mass or more in 100% by mass of the diaphragm for alkaline water electrolysis. , more preferably 60% by mass or more.

In addition, when the diaphragm for alkaline water electrolysis contains a porous support described later, the content of the inorganic particles is preferably 30 to 50% by mass based on 100% by mass of the diaphragm for alkaline water electrolysis. When the content of the inorganic particles is within the above range, the structure can be made dense, and the strength of the diaphragm can be improved. The content of the inorganic particles is more preferably 32% by mass or more, still more preferably 34% by mass or more, and 46% by mass or less in 100% by mass of the diaphragm for alkaline water electrolysis. More preferably, it is 42% by mass or less, and even more preferably 39% by mass or less.

The porous layer preferably contains 40 to 80 parts by mass of the organic polymer, more preferably 45 to 70 parts by mass, more preferably 45 to 60 parts by mass with respect to 100 parts by mass of the inorganic particles. preferable. When the content ratio of the inorganic particles and the organic polymer is within the above range, the strength of the diaphragm can be improved, and a diaphragm having a mass reduction rate within a predetermined range can be easily obtained. Further, the diaphragm for alkaline water electrolysis preferably contains 40 to 80 parts by mass, more preferably 45 to 70 parts by mass, and 45 to 60 parts by mass of the organic polymer with respect to 100 parts by mass of the inorganic particles. More preferably, it contains

Although the thickness of the porous layer is not particularly limited, it is usually preferably from 30 to 2000 μm. When the diaphragm for alkaline water electrolysis of the present invention consists of only a porous layer, the thickness of the porous layer is preferably 30 to 2000 μm, more preferably 100 μm or more, and even more preferably 200 μm or more. The upper limit is more preferably 1000 μm or less, and even more preferably 500 μm or less. When the diaphragm for alkaline water electrolysis of the present invention contains a porous support, the thickness of the porous layer is preferably 30 to 1000 μm, more preferably 500 μm or less, even more preferably 100 μm or less, most preferably 60 μm or less.

The method for measuring the thickness of the porous layer is not particularly limited. It can be determined from a microscopic image obtained by observing with (FE-SEM). Usually, the thickness is measured at a plurality of arbitrary locations, for example, five locations, and the average value thereof can be used as the thickness of the porous layer.

When the diaphragm for alkaline water electrolysis consists of only a porous layer, the thickness can be measured with a commercially available measuring instrument in the same manner as the thickness of the diaphragm for alkaline water electrolysis of the present invention. For example, a value measured using a Digimatic Micrometer (manufactured by Mitutoyo) can be used. It is possible to measure the thickness at 5 or more arbitrary points (for example, 10 points) and take the average value as the thickness of the porous layer.

Examples of materials for the 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, it preferably contains at least one resin selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide in that it can exhibit excellent heat resistance and alkali resistance, and more than the group consisting of polypropylene and polyphenylene sulfide. More preferably, it contains at least one selected resin.

Examples of the form of the porous support include nonwoven fabric, woven fabric, mesh, porous membrane, mixed fabric of nonwoven fabric and woven fabric, and the like, preferably nonwoven fabric, woven fabric, or mesh. Nonwoven fabrics and meshes are more preferred, and nonwoven fabrics are even more preferred.

As the porous support, nonwoven fabric, woven fabric, or mesh containing at least one resin selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide is preferred. Furthermore, non-woven fabrics or meshes containing polyphenylene sulfide are preferred as porous supports.

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 diaphragm for alkaline water electrolysis of the present invention can exhibit the effects of the present invention. , more preferably 50 to 1000 μm, still more preferably 80 to 500 μm, and most preferably 80 to 250 μm.

The thickness of the porous support is determined by observing the thickness direction of the diaphragm for alkaline water electrolysis of the present invention, that is, the cross section of the diaphragm cut in the direction perpendicular to the surface of the diaphragm with a field emission scanning electron microscope (FE-SEM). It can be obtained from the obtained microscopic image. Usually, the thickness is measured at a plurality of arbitrary positions, for example, 5 positions, and the average value thereof can be used as the thickness of the porous support.

Moreover, when the porous support can be isolated, the thickness can be measured with a commercially available measuring instrument in the same manner as the thickness of the diaphragm for alkaline water electrolysis of the present invention. For example, a value measured using a Digimatic Micrometer (manufactured by Mitutoyo) can be used. The thickness can be measured at arbitrary 5 or more points (for example, 10 points) and the average value can be taken as the thickness of the porous support.

Although the air permeability of the alkaline water electrolysis cell of the present invention is not particularly limited, it is preferably 50 to 5000 seconds. When the air permeability is within the above range, the gas barrier property is good, and it is possible to satisfactorily prevent mixing of oxygen gas and hydrogen gas. The air permeability is preferably 100 to 1000 seconds, more preferably 150 to 800 seconds. The air permeability can be obtained by the above-described measuring method using air as the measuring gas.

The thickness of the diaphragm for alkaline water electrolysis of the present invention is not particularly limited, and may be appropriately selected according to the size of the equipment to be used, handleability, and the like. ~500 μm is more preferred, and 150-350 μm is most preferred. Although the method for measuring the thickness is not particularly limited, it is preferable to employ a value measured with a micrometer, for example. Usually, it is preferable to measure the thickness at a plurality of points, for example, 10 points, and take the average value as the film thickness of the diaphragm. As the micrometer, it is preferable to use a commercially available product such as Digimatic Micrometer (manufactured by Mitutoyo Corporation).

The diaphragm for alkaline water electrolysis of the present invention preferably has a porosity of 25 to 80%, more preferably 30 to 75%, even more preferably 35 to 70%. When the porosity of the membrane as a whole is within the above range, the gaps in the membrane are more continuously filled with the electrolytic solution, so that the membrane tends to exhibit higher ionic conductivity.
The above porosity is calculated from the measured density value of the diaphragm measured by the method shown below, and the calculated density value of the diaphragm calculated using the density value (true density) and composition ratio of each component constituting the diaphragm. It can be calculated from the formula.
Porosity (%) = [1 - (measured density value) / (calculated density value)] × 100
The measured density value can be calculated by measuring the mass and volume of a test piece cut from an arbitrary location of the obtained diaphragm and dividing the mass by the volume. The volume can be calculated by measuring the vertical and horizontal lengths of the test piece using calipers, and measuring the film thickness based on the film thickness measurement method described above. Also, the mass of the test piece can be measured using a precision balance with four digits below the decimal point for the test piece whose volume has been measured.

The ion conductivity of the diaphragm for alkaline water electrolysis of the present invention can be calculated by the method described in Examples. The ion conductivity of the diaphragm for alkaline water electrolysis of the present invention is preferably more than 100 mS/cm. In this case, the electrolysis efficiency in alkaline water electrolysis can be made higher.

The diaphragm for alkaline water electrolysis of the present invention preferably has a mass reduction rate of 2% or less due to detachment of diaphragm components after ultrasonic treatment in water at 30° C. for 3 minutes at a frequency of 38 kHz and an output of 100 W. By subjecting the diaphragm to ultrasonic treatment, some diaphragm components may fall off. When the strength of the diaphragm is low, the components of the diaphragm are likely to fall off due to ultrasonic treatment, and the amount that falls off increases. The mass reduction rate due to the shedding of the diaphragm component is more preferably 1.5% or less, still more preferably 1.2% or less, and particularly preferably 1% or less.

The mass reduction rate due to the shedding of diaphragm components before and after ultrasonic treatment in water at 30° C. at a frequency of 38 kHz and an output of 100 W for 3 minutes in the above diaphragm for alkaline water electrolysis can be obtained by the following formula.
Mass reduction rate (%) = 100 - (diaphragm mass after ultrasonic treatment) / (diaphragm weight before ultrasonic treatment) x 100
In the above ultrasonic treatment test, the diaphragm is placed so that the entire diaphragm is immersed in water.

The membrane for alkaline water electrolysis of the present invention preferably has a membrane resistance ratio of 0.7 or more, more preferably 0.7, calculated by the following formula when subjected to the following thermal alkali durability test. 8 or more.
Membrane resistance ratio = (Membrane resistance after 240 hours)/(Membrane resistance after 24 hours)
(Heat alkali endurance test)
The diaphragm for alkaline water electrolysis of the present invention is cut into a 3 cm square, and this is used as a test piece. The two test pieces are placed in a fluororesin container (made of PFA), immersed in 30 g of a 30% KOH aqueous solution, and held at 90°C. After 24 hours and 240 hours of immersion, the test pieces are taken out and the membrane resistance is measured at room temperature.
Membrane resistance can be measured by the method described in Examples.

Since the diaphragm for alkaline water electrolysis of the present invention has the above structure, it is excellent in the stability of ion conductivity in hot alkaline water. Therefore, by using the diaphragm for alkaline water electrolysis of the present invention as a diaphragm of a water electrolyzer using an alkaline aqueous solution as an electrolyte, high-purity hydrogen gas can be stably produced for a long period of time.

The method for producing the diaphragm for alkaline water electrolysis of the present invention is not particularly limited, but preferred production methods include, for example, production method (1) (Embodiment 3) or production method (2) (Embodiment 4) described below. is given.

2. Composition for Diaphragm for Alkaline Water Electrolysis A composition for a diaphragm for alkaline water electrolysis, which is a preferred embodiment (Embodiment 2) of the present invention, will be described. The composition according to Embodiment 2 is also referred to as composition (i) of the present invention or simply composition (i).

The composition (i) contains an organic polymer and inorganic particles, has a viscosity (25° C.) of 30000 mPa s or less at a shear rate of 10 s ⁻¹ , and has a viscosity (25° C.) at a shear rate of 0.1 s ⁻¹ A composition for a diaphragm for alkaline water electrolysis having a viscosity of 100000 mPa·s or more.

The viscosity (25°C) is the viscosity at normal temperature (25°C) and is measured by the following method.
(Method for measuring viscosity (25°C))
Using a rheometer (HAAKE Rheost 6000) and a plate PP35Ti (D=35 mm), the sample is allowed to stand in an atmosphere of 25°C for 2 hours, the sample stage is adjusted to 25°C, and an appropriate amount is introduced. After homogenizing the sample by treating it at a shear rate of 500 s ⁻¹ for 30 seconds and then holding it for 10 seconds without shearing for temperature conditioning, 1000 measurement points are obtained in 9 minutes from a shear rate of 0 to 300 s ⁻¹ . From the obtained data, find a linear approximation formula at 5 points before and after the closest measurement point for each of 0.1 s ^-1 , 10 s ^-1 and 250 s ^-1 , and each value calculated from there is .1 s ^-1 , 10 s ^-1 , 250 s ^-1 ) at 25°C.

The above composition (i) can be preferably used as a composition for producing a diaphragm for alkaline water electrolysis, particularly as a coating composition, and is used to produce the diaphragm for alkaline water electrolysis described as Embodiment 1 of the present invention. It can also be preferably used as a composition for A preferred embodiment of composition (i) described below is also a preferred embodiment when used as a coating composition.

Composition (i) has a viscosity (25° C.) of 30000 mPa·s or less at a shear rate of 10 s ⁻¹ . The viscosity (25° C.) at a shear rate of 10 s ⁻¹ is preferably 25000 mPa·s or less, more preferably 20000 mPa·s or less.

When the composition (i) is used as a composition for coating, it has a low viscosity (25° C.) at a shear rate of 10 s ⁻¹ , so that it has excellent coating performance during coating. It is also useful as a composition that exhibits effects such as easy control of the thickness) and excellent impregnation when applied to a porous support.

The above composition (i) preferably has a viscosity (25° C.) of 10000 mPa·s or more at a shear rate of 10 s ⁻¹ . If it is less than 10000 mPa·s, the fluidity is too high and the yield during coating may decrease. The viscosity (25° C.) at a shear rate of 10 s ⁻¹ is more preferably 12000 mPa·s or more, more preferably 14000 mPa·s or more.

The above composition (i) preferably has a viscosity (25° C.) at a shear rate of 250 s ⁻¹ of 15,000 mPa s or less, more preferably 12,000 mPa s or less, and preferably 10,000 mPa s or less. More preferred. The above composition (i) preferably has a viscosity (25° C.) of 5000 mPa·s or more at a shear rate of 250 s ⁻¹ . The viscosity (25° C.) at a shear rate of 250 s ⁻¹ is more preferably 6000 mPa·s or more, more preferably 7000 mPa·s or more.

The above composition (i) has a viscosity (25° C.) of 100000 mPa·s or more at a shear rate of 0.1 s ⁻¹ . The viscosity (25° C.) at a shear rate of 0.1 s ⁻¹ is preferably 200000 mPa·s or more, more preferably 300000 mPa·s or more. Since the viscosity (25° C.) at a shear rate of 0.1 s ⁻¹ is 100000 mPa·s or more, the composition (i) is useful as a composition for obtaining a film in which the formation and growth of macrovoids are suppressed. is.
The above composition (i) preferably has a viscosity (25° C.) of 600000 mPa·s or less at a shear rate of 0.1 s ⁻¹ . It is more preferably 500000 Pa·s or less, still more preferably 450000 Pa·s or less.

In the composition (i), when A is the viscosity (25 ° C.) at a shear rate of 0.1 s ^-1 and B is the viscosity (25 ° C.) at a shear rate of 10 s ^-1 , the ratio of A to B (A / B ) is preferably 5 or more. The ratio (A/B) is more preferably 8 or more, still more preferably 15 or more, and particularly preferably 20 or more. On the other hand, the upper limit is not particularly limited, but is usually 60 or less, preferably 50 or less, more preferably 40 or less.

Composition (i) above comprises an organic polymer. The same organic polymer as that contained in the porous layer constituting the diaphragm for alkaline water electrolysis of the present invention can be used as the organic polymer, and preferred embodiments thereof are also the same.
The composition (i) contains inorganic particles. The same inorganic particles as those contained in the porous layer constituting the diaphragm for alkaline water electrolysis of the present invention can be used as the inorganic particles, and preferred embodiments thereof are also the same.

The composition (i) preferably further contains a solvent. The solvent is not particularly limited, but an organic solvent is preferable, and a solvent capable of dissolving an organic polymer is preferable. Preferred organic solvents include organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethylsulfoxide. These solvents may be used singly or in combination of two or more. Among them, N-methyl-2-pyrrolidone is preferable because it has excellent solubility of organic polymers and excellent dispersibility of inorganic particles. The solvent may contain a solvent other than an organic solvent such as water.

The composition (i) may also contain a metal chloride. Examples of metal chlorides include lithium chloride, sodium chloride, potassium chloride, magnesium chloride and calcium chloride. These salts may be used singly or in combination of two or more. Among them, lithium chloride is preferable because of its excellent solubility in a solvent. By including a metal chloride, it becomes easier to control the viscosity of the composition (i) within the preferred range described above. The content of the metal chloride is preferably 0.001% by mass or more and less than 1% by mass relative to 100% by mass of the inorganic particles contained in the composition (i). The content of the metal chloride is more preferably 0.01% by mass or more, still more preferably 0.05% by mass or more, and more preferably 0.5% by mass or less, based on 100% by mass of the inorganic particles. 2 mass % or less is more preferable. A form in which the composition (i) contains a metal chloride is also one of the preferred embodiments of the present invention.
The composition (i) may contain additives other than those described above. Examples include plasticizers and surfactants. If the composition (i) does not contain a solvent, it preferably contains a plasticizer.

As long as the composition (i) has the above viscosity (25° C.) characteristics, the content of each component, the composition ratio, and the like are not particularly limited.
For example, the composition (i) contains a solvent, and the total content of the inorganic particles and the organic polymer in the composition (i) is 40% by mass or more with respect to 100% by mass of the composition (i). preferable. It is more preferably 45% by mass or more, and still more preferably 48% by mass or more. On the other hand, the upper limit is not particularly limited, but is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, and particularly preferably 55% by mass or less.

Further, the content of the inorganic particles in the composition (i) is preferably 50 to 90% by mass with respect to 100% by mass of the total content of the inorganic particles and the organic polymer. The content is more preferably 85% by mass or less, more preferably 80% by mass or less, more preferably 55% by mass or more, and even more preferably 60% by mass or more.

Moreover, the content of the metal chloride contained in the composition (i) is preferably 0.001% by mass or more and less than 1% by mass relative to 100% by mass of the inorganic particles. Furthermore, it is more preferable that the content is within the preferable range described above.

When the composition (i) does not contain a solvent, the total content of the organic polymer and the inorganic particles is preferably 80 to 100% by mass with respect to 100% by mass of the composition (i). When the content is within the above range, it becomes easier to control the viscosity of the composition (i) within the above preferable range.

As described above, the composition (i) contains an organic polymer and inorganic particles, and has a high viscosity (25° C.) of a predetermined value or more when the shear rate is low, and relatively Due to its low viscosity (25°C), it is not only advantageous for film structure control such as suppressing the formation and growth of macrovoids, but also coating performance such as controllability of coating amount (coating thickness) and impregnation. Therefore, it can be preferably used, for example, as a coating composition for producing alkaline water electrolysis with excellent stability of ion conductivity in hot alkali.

Furthermore, the effect of suppressing the formation and growth of macrovoids due to the viscosity characteristics of the composition (i) was obtained by applying a non-solvent-induced phase separation method to the coating film obtained using the composition (i). It becomes more pronounced when subjected to a reaction (coagulation reaction). Therefore, the composition (i) can be particularly preferably used as a coating composition in a method for producing a diaphragm for alkaline water electrolysis including a non-solvent-induced phase separation step.

Moreover, when the composition (i) is used as a coating composition, the composition (i) preferably contains a solvent. By containing a solvent, the composition (i) has even better coating performance, and when the coating film obtained using the composition (i) is subjected to a non-solvent-induced phase separation step, It becomes easier to control the porous structure.

The composition (i) can also be preferably used as a molding composition for producing a diaphragm for alkaline water electrolysis. In particular, it can be preferably used in a method for producing a diaphragm for alkaline water electrolysis, in which a thermally induced phase separation method is applied to a film obtained by molding.
When the composition (i) is used as a molding composition, it preferably does not contain a solvent.

A method for preparing the composition (i) is not particularly limited, and the composition (i) can be prepared by mixing an organic polymer and inorganic particles.
The mixing method is not particularly limited, and conventionally known mixing and dispersing methods can be employed. Examples thereof include known means of mixing and dispersing, such as a melt-kneading method, a method using a mixer, a ball mill, a jet mill, a disper, a sand mill, a roll mill, a pot mill, a paint shaker, and the like. Moreover, you may add a dispersing agent etc. suitably as needed.

It is preferable to use a solvent because the organic polymer and the inorganic particles are easily mixed uniformly. As a method for preparing a mixture using a solvent, for example, when an organic polymer, inorganic particles and a solvent are mixed, the three components may be mixed at the same time, or a dispersion of inorganic particles dispersed in a solvent may be prepared in advance. Then, the dispersion and the organic polymer may be mixed, or a dispersion in which inorganic particles are dispersed and a resin solution in which the organic polymer is dispersed or dissolved in a solvent are prepared in advance, and then these dispersions and You may mix a resin liquid. As the solvent, the same solvents as those described above can be used, and preferred embodiments are also the same.

Among them, a dispersion liquid in which inorganic particles are dispersed and a resin liquid in which an organic polymer is dispersed or dissolved in a solvent are used because the dispersion state of the inorganic particles can be easily controlled and the organic polymer and the inorganic particles can be uniformly mixed. are prepared in advance, and then these dispersion liquids and resin liquids are mixed. The organic polymer and inorganic particles used here are the same as the organic polymer and inorganic particles described in Embodiment 2, respectively.

The concentration of the inorganic particles in the dispersion liquid is not particularly limited, but is preferably 30 to 60% by weight with respect to 100% by weight of the dispersion liquid in terms of easy mixing. More preferably 40 to 60% by mass, still more preferably 50 to 60% by mass. Even when the dispersion further contains a metal chloride, the concentration of the inorganic particles in the dispersion is the same as above.

The concentration of the organic polymer in the resin liquid in which the organic polymer is dispersed or dissolved is not particularly limited, but is preferably 10 to 50% by mass with respect to 100% by mass of the resin liquid in terms of ease of mixing. More preferably 20 to 40% by mass, still more preferably 25 to 35% by mass. Even when the resin liquid further contains a metal chloride, the concentration of the organic polymer in the resin liquid is the same as above.

The mixing and dispersing methods are not particularly limited, and include known mixing and dispersing means such as methods using mixers, ball mills, jet mills, dispersers, sand mills, roll mills, pot mills, paint shakers, and the like. Moreover, a dispersing agent or the like may be added as appropriate.

The mixture containing the inorganic particles, the organic polymer and the solvent obtained as described above can be used as the composition (i), and the mixture containing additives such as metal chlorides can also be used as the composition ( i) can also be used. For example, the method of mixing additives is not particularly limited. When a metal chloride is mixed, for example, the metal chloride may be added to the mixture obtained by the above method, or the metal chloride may be added when preparing a dispersion liquid in which inorganic particles are dispersed in a solvent. They may be mixed, added to a dispersion liquid in which inorganic particles are dispersed in a solvent, or added to a resin liquid in which an organic polymer is dissolved or dispersed. The same is true when mixing additives other than metal chlorides.

A dispersion liquid in which inorganic particles are dispersed in a solvent is used as a method for adding a metal chloride, since thickening or the like is unlikely to occur during the preparation of the composition (i), and a uniform mixed state of each component can be easily obtained. and a method of adding a metal chloride to a mixture containing inorganic particles, an organic polymer and a solvent.

When the metal chloride is mixed with the dispersion or the like, the metal chloride may be mixed in the form of powder, or a liquid (additive liquid) in which the metal chloride is dissolved or dispersed in a solvent is prepared in advance. may be used. As the solvent, the same solvents as those mixed with the organic polymer or inorganic particles can be preferably used.

When the composition (i) contains a solvent, the preparation method using the solvent is adopted, and the type of the organic polymer (material, molecular weight), the type of inorganic particles (material, shape) of the composition (i) , particle size), the type of solvent (solvent power, polarity), the content of each of these, the combination of these, the presence or absence of additives such as metal chlorides, the amount, etc., to adjust the viscosity characteristics. Thus, the composition (i) according to Embodiment 2 of the present invention can be obtained.

3. Method for Producing Diaphragm for Alkaline Water Electrolysis A method for producing the diaphragm for alkaline water electrolysis of the present invention will be described.
The manufacturing method of the diaphragm for alkaline water electrolysis of the present invention is the following manufacturing methods (1) and (2).
The production method (1) contains an organic polymer and inorganic particles, and has a viscosity (25° C.) of 30000 mPa s or less at a shear rate of 10 s ⁻¹ and a viscosity (25° C.) of 100000 mPa at a shear rate of 0.1 s ⁻¹ .・It is characterized by using a composition that is s or more.
The production method (2) uses a composition containing an organic polymer and inorganic particles and having a viscosity (25° C.) of 100000 mPa s or more at a shear rate of 0.1 s ⁻¹ , and the viscosity of the composition is 30000 mPa s. applying the composition at a shear rate of:
By using these manufacturing methods (1) or (2), it becomes possible to efficiently manufacture the diaphragm for alkaline water electrolysis (Embodiment 1) of the present invention. Moreover, by using these production methods (1) or (2), it becomes possible to efficiently produce a diaphragm for alkaline water electrolysis which is excellent in the stability of ion conductivity in hot alkali.

<Method for producing diaphragm for alkaline water electrolysis (1)>
A method (1) for producing a diaphragm for alkaline water electrolysis, which is a preferred embodiment (Embodiment 3) of the present invention, will be described.
The composition used in the production method (1) is also referred to as composition (A).
As the composition (A), the same composition as the above composition (i) can be used, and its preferred embodiment is also the same as the above composition (i).

The production method (1) is preferably a method for producing a membrane having a porous structure by forming a membrane using the composition (A) and subjecting the obtained membrane to phase separation.
Among them, a manufacturing method including the following steps (1a) to (3a) is preferable.
(1a) Step of preparing composition (A) (2a) Step of forming a coating film using composition (A) (3a) Step of making the coating film into a porous structure by a non-solvent induced phase separation method As the method for preparing the composition (A) in (1a), the method for preparing the composition (i) described in Embodiment 2 can be adopted as it is. A preferred embodiment is also the same. Step (1a) is preferably a step of preparing a composition containing a solvent (coating composition).
Step (2a) is a step of forming a coating film using the composition (A) obtained in step (1a).

A composition containing a solvent (coating composition) is preferably used as the composition (A). When the above composition (A) is used as a coating composition, it has a low viscosity (25° C.) at a shear rate of 10 s ⁻¹ and thus exhibits excellent fluidity during coating, resulting in excellent coating performance. Therefore, the composition (A) can be used as a composition for coating, which is easy to uniformly control the coating amount (coating thickness), and has excellent impregnation properties with respect to a porous support. Preferred aspects of the composition (A) used as the coating composition in the production method (2) are the same as the preferred aspects of the composition (i) described above.

Preferred examples of the method for forming the coating film include a method of applying the composition (A) onto a substrate. The step (2a) preferably includes a step of applying the composition (A) to a porous support.
The coating method is not particularly limited, and examples thereof include known coating means such as methods using die coating, spin coating, gravure coating, curtain coating, spray, applicator, coater, and the like.

The substrate is not particularly limited as long as it can be coated with the composition (A) to form a coating film. Examples include films or sheets made of resins such as phthalate, polypropylene, polyethylene, polyvinyl chloride, polyvinyl acetal, polymethyl methacrylate, polycarbonate, and glass plates. Among them, a film or sheet of polytetraethylene terephthalate is preferable.
As the porous support, the same one as described in the description of Embodiment 1 can be used, and preferred embodiments are also the same.

When the diaphragm for alkaline water electrolysis includes a porous support, the composition (A) may be applied to the porous support. Examples of the coating method include a method of directly coating the composition (A) on the porous support and a method of immersing the porous support in the composition (A). Further, a method of applying the composition (A) onto the substrate described above, bringing the coated product into contact with the porous support, and impregnating the porous support with the composition (A). By impregnating the porous support with the composition (A), a composite in which the coating film derived from the composition (A) and the porous support are integrated can be produced.
The amount of the composition (A) to be applied is not particularly limited, and may be appropriately set so that the obtained diaphragm has a thickness capable of exhibiting the above effects.

The step (3a) is a step of forming the coating film obtained in the step (2a) into a porous structure by a non-solvent-induced phase separation method. The step (3a) can also be referred to as a step of contacting the coating film obtained in the step (2a) with a liquid containing a non-solvent for the organic polymer to form a porous structure in the coating film. A liquid containing a non-solvent for the organic polymer is also referred to as a non-solvent-containing liquid.
By bringing the coating film into contact with a liquid containing a non-solvent for the organic polymer, the non-solvent diffuses in the coating film and the organic polymer that is not dissolved in the non-solvent is solidified. On the other hand, the solvent in the coating film that is soluble in the non-solvent is eluted from the coating film. Such phase separation causes the organic polymer to solidify and form a porous structure.

When the composition (A) for forming a coating film has a viscosity (25° C.) of 100000 mPa s or more at a shear rate of 0.1 s ⁻¹ , the phase separation rate of the coating film made of the composition is suppressed to be low. Therefore, a porous structure in which the formation and growth of macrovoids is suppressed is easily obtained.

Examples of the method of bringing the coating film into contact with the non-solvent-containing liquid include a method of immersing the coating film in the non-solvent-containing liquid (coagulation bath). When the composition (A) for forming a porous layer is applied to a porous support to form a coating film, the porous support having the coating film formed thereon may be immersed in the non-solvent. .

Examples of non-solvents for the organic polymer include solvents that do not substantially dissolve the organic polymer. The organic polymer does not substantially dissolve means that the solubility of the organic polymer is 100 mg or less with respect to 100 g of the solvent at 25°C.
Examples of the non-solvent include water such as pure water, distilled water, and ion-exchanged water; lower alcohols such as methanol, ethanol, and propyl alcohol; and mixed solvents thereof. water is preferred, and ion-exchanged water is more preferred.
The non-solvent-containing liquid may contain a non-solvent for the organic polymer, and its concentration is not particularly limited. For example, the non-solvent-containing liquid has a concentration of 100% by mass or 100% is one of the preferred embodiments.

On the other hand, the form in which the non-solvent-containing liquid contains a solvent other than the non-solvent is also one of preferred embodiments. In this case, the concentration of the non-solvent in the non-solvent-containing liquid is preferably 10% by mass or more. It is more preferably 20% by mass or more, and still more preferably 40% by mass or more. On the other hand, the upper limit is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 60% by mass or less.

The non-solvent-containing liquid also preferably contains 10% by mass or more and 90% by mass or less of the non-solvent with respect to the total amount of 100% by mass of the non-solvent and the solvent other than the non-solvent contained in the non-solvent-containing liquid. . It is more preferably 20% by mass or more, still more preferably 40% by mass or more, while the upper limit is more preferably 80% by mass or less, further preferably 60% by mass or less.

In addition, the solvent other than the non-solvent is not particularly limited, but preferably contains the same solvent as the solvent contained in the coating film. When the non-solvent-containing liquid contains a solvent similar to the solvent contained in the coating film, the content of the solvent similar to the solvent contained in the coating film is 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 80% by mass or less, and still more preferably 40% by mass or more and 60% by mass or less with respect to 100% by mass of the total amount of the solvent is.

The temperature condition of the step (3a) is preferably 5 to 30°C, more preferably 10 to 30°C, more preferably 15 to 30°C, in that the coating film can be uniformly solidified. is more preferred.
Through the step (3a), the coating film formed in the step (2a) is solidified to form a porous structure. The coating film that has solidified and has a porous structure is the solvent component contained in the non-solvent-containing liquid used in the step (3a) such as the above non-solvent and / or the solvent component contained in the coating film formed in the step (2a). including.

The method (1) for producing a diaphragm for alkaline water electrolysis of the present invention preferably further includes the following step (4a).
(4) A step of drying the coating film having a porous structure obtained in step (3a) to obtain a porous layer.
In step (4a), the porous layer can be obtained by removing volatile components such as non-solvents contained in the coating film having the porous structure obtained in step (3a).

The drying temperature is preferably 60 to 100°C, more preferably 60 to 80°C. The drying time is preferably 2 to 60 minutes, more preferably 2 to 30 minutes, even more preferably 5 to 30 minutes.

The method (1) for producing a diaphragm for alkaline water electrolysis includes, in addition to the above-described steps (1a) to (4), other known steps such as a step of press treatment to make the density of the diaphragm uniform. You can
As described above, the method (1) for producing a diaphragm for alkaline water electrolysis of the present invention is preferably a production method including the above steps (1a) to (3a). It is more preferable that it is a manufacturing method including. However, the method (1) for producing a diaphragm for alkaline water electrolysis of the present invention is not limited to these preferred forms.

<Method for producing diaphragm for alkaline water electrolysis (2)>
A method (2) for producing a diaphragm for alkaline water electrolysis, which is a preferred embodiment (Embodiment 4) of the present invention, will be described.
The production method (2) uses a composition containing an organic polymer and inorganic particles and having a viscosity (25° C.) of 100000 mPa s or more at a shear rate of 0.1 s ⁻¹ , and the viscosity of the composition is 30000 mPa s. applying the composition at a shear rate of:
The composition used in the production method (2) is referred to as composition (B).

The composition (B) contains an organic polymer and inorganic particles, and has a viscosity (25° C.) of 100000 mPa·s or more at a shear rate of 0.1 ^{s −1} .
The organic polymer and the inorganic particles are the same as the organic polymer and the inorganic particles used in the production method (1), and preferred embodiments thereof are also the same.

The above composition (B) has a viscosity (25° C.) of 100000 mPa·s or more at a shear rate of 0.1 s ⁻¹ . The viscosity (25° C.) at a shear rate of 0.1 s ⁻¹ is preferably 200000 mPa·s or more, more preferably 300000 mPa·s or more.
The composition (B) preferably has a viscosity (25° C.) of 600000 mPa·s or less at a shear rate of 0.1 s ⁻¹ . It is more preferably 500000 Pa·s or less, still more preferably 450000 Pa·s or less.

The composition (B) has a viscosity (25° C.) at a shear rate of 10 s ⁻¹ of preferably 30000 mPa s or less, more preferably 25000 mPa s or less, and further preferably 20000 mPa s or less. On the other hand, the lower limit is preferably 10000 mPa·s or more, more preferably 12000 mPa·s or more.

The composition (B) preferably has a viscosity (25° C.) at a shear rate of 250 s ⁻¹ of 15,000 mPa s or less, more preferably 12,000 mPa s or less, and 10,000 mPa s or less. More preferred. The viscosity (25° C.) at a shear rate of 250 s ⁻¹ is preferably 5000 mPa·s or more, more preferably 6000 mPa·s or more, and even more preferably 7000 mPa·s or more.

The composition (B) preferably further contains a solvent. The solvent is not particularly limited, but an organic solvent is preferable, and a solvent capable of dissolving an organic polymer is preferable. Preferred organic solvents are the same as the solvents that can be used in the composition (i) above.

The composition (B) preferably contains a metal chloride, and the preferred type of metal chloride, preferred content of the metal chloride, etc. are the same as in the case of the metal chloride in the composition (i). be.
The composition (B) may contain additives other than those described above. Its preferred mode is also the same as in composition (i).
As long as the composition (B) has the above viscosity (25° C.) characteristics, the content of each component, the composition ratio and the like are not particularly limited.

For example, the composition (B) contains a solvent, and the total content of the inorganic particles and the organic polymer in the composition (B) is 40% by mass or more with respect to 100% by mass of the composition (B). preferable. It is more preferably 45% by mass or more, and still more preferably 48% by mass or more. On the other hand, the upper limit is not particularly limited, but is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, and particularly preferably 55% by mass or less.

Further, the content of the inorganic particles in the composition (B) is preferably 50 to 90% by mass with respect to 100% by mass of the total content of the inorganic particles and the organic polymer. The content is more preferably 85% by mass or less, more preferably 80% by mass or less, more preferably 55% by mass or more, and even more preferably 60% by mass or more.

Further, when the composition (B) contains the metal chloride, the content of the metal chloride contained in the composition (B) is 0.001% by mass or more and less than 1% by mass relative to 100% by mass of the inorganic particles. is preferably The content of the metal chloride is more preferably 0.01% by mass or more, still more preferably 0.05% by mass or more, and more preferably 0.5% by mass or less, based on 100% by mass of the inorganic particles. 2 mass % or less is more preferable.
The composition (B) can be prepared in the same manner as the composition (i) described in the second embodiment.

The production method (2) is not particularly limited as long as it includes the step of applying the composition (B) at a shear rate at which the viscosity of the composition is 30000 mPa s or less, but the following steps A production method including (1b) to (3b) is preferable.
(1b) Step of preparing composition (B) (2b) Step of forming a coating film using composition (B) (3b) Step of making the coating film into a porous structure by a non-solvent induced phase separation method In (1b), the method for preparing composition (i) described in Embodiment 2, that is, the method for preparing composition (A) in step (1a) is applied mutatis mutandis to prepare composition (B). be able to. The step (1b) is preferably a step of preparing a composition (coating composition) containing a solvent as the composition (B).
The step (2b) is a step of forming a coating film using the composition (B) obtained in the step (1b). A composition containing a solvent (coating composition) is preferably used as the composition (B).
In step (2b), it is necessary to apply the composition (B) at such a shear rate that the viscosity of the composition (B) becomes 30000 mPa·s or less.

The above shear rate means the maximum shear rate applied to the composition (B) during application. The maximum shear rate will be explained using FIG. 1 as an example. FIG. 1 schematically shows the configuration of the coater when viewed from the side. The shear rate is determined by V/H, where V (m/s) is the conveying speed of the substrate and H (m) is the gap. As shown in FIG. 1, the coating liquid such as composition (B) is put in the vicinity of the coater and sandwiched between the coater and the back roll. receive. The gap H gradually becomes smaller toward the tip of the coater and becomes minimum at the tip of the blade. When the velocity is constant, the shear velocity applied to the coating liquid is maximized at the position where the gap H is minimized. This shear rate is the maximum shear rate, and in the case of a coater, it is the shear rate applied to the coating solution at the tip of the blade.

In other words, in the step (2b), it is necessary to control the maximum shear rate so that the viscosity of the composition (B) when applied is 30000 mPa·s or less.
By setting the viscosity at the time of coating within the above range, coating with excellent uniformity of the coating thickness, impregnation into the porous support, etc. becomes possible.

It is preferable to adjust the maximum shear rate so that the viscosity of the composition (B) at the time of application is 30,000 mPa s or less, more preferably 25,000 mPa s or less, and 20,000 mPa. • It is more preferable to adjust the maximum shear rate to s or less. On the other hand, the upper limit of the viscosity is preferably 5000 mPa·s or more, more preferably 6000 mPa·s or more.

The temperature of the composition (B) during application is not particularly limited, but is preferably 0 to 50°C, more preferably 10 to 40°C, and even more preferably 15 to 35°C.

Preferred examples of the method for forming the coating film include a method of applying the composition (B) onto a substrate. The step (2a) preferably includes a step of applying the composition (B) to the porous support.

The coating method is not particularly limited, and examples thereof include known coating means such as methods using die coating, spin coating, gravure coating, curtain coating, spray, applicator, coater, and the like. Among them, a coating method using a die coating, a coater, or the like is preferred because it is easy to adjust the maximum shear rate so that the viscosity of the composition (B) at the time of coating is 30000 mPa s or less in the above preferred temperature range. preferable.

The substrate and the porous support are the same as in the step (2a) in the production method (1), and preferred embodiments are also the same.
When producing a diaphragm for alkaline water electrolysis containing a porous support, it is preferable to apply the composition (B) to the porous support. ), and preferred embodiments are also the same. The amount of the composition (B) to be applied is not particularly limited, and may be set as appropriate so that the obtained diaphragm has a thickness capable of exhibiting the above effects.

The step (3b) is a step of forming the coating film obtained in the step (2b) into a porous structure by a non-solvent-induced phase separation method. The step (3b) can also be said to be a step of contacting the coating film obtained in the step (2b) with a liquid containing a non-solvent for the organic polymer (non-solvent-containing liquid) to make the coating film into a porous structure.
Various conditions such as the type of non-solvent, the composition of the non-solvent-containing liquid, and the temperature in the step (3b) are the same as in the step (3a) in the production method (1), including preferred embodiments.
Through the step (3b), the coating film formed in the step (2b) is solidified to have a porous structure.

Since the coating film is a coating film obtained by applying the composition (B) having a viscosity (25 ° C.) of 100000 mPa s or more at a shear rate of 0.1 s ^-1 , the phase separation reaction in the coating film is slow. As a result, it becomes easier to obtain a porous structure in which the generation and growth of macrovoids are suppressed.
The coating film having a porous structure contains the solvent component contained in the non-solvent-containing liquid used in step (3b) and/or the solvent component contained in the coating film formed in step (2b).

Preferably, the production method (2) further includes the following step (4b).
(4b) A step of drying the coating film having a porous structure obtained in step (3b) to obtain a porous layer.
Various conditions such as drying temperature and drying time in step (4b) are the same as in step (4a) in production method (1), including preferred embodiments.
In addition to the steps (1b) to (4b) described above, the manufacturing method (2) may include other known steps such as a step of press treatment to make the density of the diaphragm uniform.

As described above, the method (2) for producing a diaphragm for alkaline water electrolysis of the present invention is preferably a production method including the above steps (1b) to (3b). It is more preferable that it is a manufacturing method including. However, the method (2) for producing a diaphragm for alkaline water electrolysis of the present invention is not limited to these preferred modes.

4. As a preferred embodiment (Embodiment 5) of the present invention, the diaphragm for alkaline water electrolysis according to Embodiment 5 contains an organic polymer and inorganic particles, and has a viscosity (25° C.) of 30000 mPa·s or less at a shear rate of 10 s ⁻¹ . and a viscosity (25° C.) of 100000 mPa·s or more at a shear rate of 0.1 s ⁻¹ .

The diaphragm for alkaline water electrolysis according to Embodiment 5 is produced using the above composition, and preferable aspects of the composition are the same as those of the composition (i) according to Embodiment 2, It is the same as the preferred aspect of the composition (A) used in the production method (1) according to the third embodiment. As for the preferred process, conditions, etc. for producing the diaphragm for alkaline water electrolysis according to Embodiment 5, the preferred process, conditions, etc. in the production method (1) according to Embodiment 3 can be applied as they are.
The diaphragm for alkaline water electrolysis according to Embodiment 5 can be preferably used, for example, as a diaphragm for alkaline water electrolysis that is excellent in the stability of ion conductivity in hot alkali.

5. As a preferred embodiment (Embodiment 6) of the present invention, the diaphragm for alkaline water electrolysis according to Embodiment 6 contains an organic polymer and inorganic particles, and has a viscosity (25° C.) of 100000 mPa·s or more at a shear rate of 0.1 s ⁻¹ . and applying the composition at a shear rate at which the composition has a viscosity of 30000 mPa·s or less.

The diaphragm for alkaline water electrolysis according to Embodiment 6 is produced using the above composition. It is the same as the aspect. As for the preferred process, conditions, etc. for producing the diaphragm for alkaline water electrolysis according to Embodiment 6, the preferred process, conditions, etc. in the production method (2) according to Embodiment 4 can be applied as they are.
The diaphragm for alkaline water electrolysis according to Embodiment 6 can be preferably used, for example, as a diaphragm for alkaline water electrolysis that is excellent in the stability of ion conductivity in hot alkali.

6. Applications All of the diaphragms for alkaline water electrolysis according to the above-described embodiments of the present invention can be suitably used as diaphragms for electrolysis of water using an alkaline aqueous solution as an electrolyte. The same applies to each diaphragm for alkaline water electrolysis manufactured by the manufacturing method (1) according to the third embodiment of the present invention and the manufacturing method (2) according to the fourth embodiment of the present invention.

An electrolysis apparatus and an electrolysis method using the diaphragm for alkaline water electrolysis of the present invention will be described below. The electrolysis apparatus and the electrolysis method described below are not limited to the case of using the diaphragm for alkaline water electrolysis according to Embodiment 1, and when the diaphragm for alkaline water electrolysis of Embodiments 5 and 6 are used, can also be applied as it is to the case of using each diaphragm for alkaline water electrolysis manufactured by the manufacturing method according to the third and fourth embodiments.

(Electrolyzer)
The diaphragm for alkaline water electrolysis of the present invention is used as a member of an alkaline water electrolysis device. Examples of the alkaline water electrolysis apparatus include those including an anode, a cathode, and the diaphragm for alkaline water electrolysis arranged between the anode and the cathode. More specifically, the alkaline water electrolysis apparatus has an electrolytic cell having an anode chamber in which an anode exists and a cathode chamber in which a cathode exists, which are separated by the diaphragm for alkaline water electrolysis.

The 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 the anode and the cathode. The smaller the distance between the electrodes, the lower the electrical resistance and the higher the electrolysis efficiency of the electrolyser. The diaphragm for alkaline water electrolysis of the present invention can also be suitably used in an electrolytic apparatus having a so-called "zero-gap structure" in which the diaphragm and each electrode are placed in contact with each other so as to minimize the distance between the electrodes. .

The anode and cathode are not particularly limited as long as they are known electrodes, and examples include copper, lead, nickel, chromium, titanium, gold, platinum, iron, metal compounds thereof, metal oxides, and metals thereof. electrodes containing known conductive substrates such as alloys containing two or more of The electrode may be formed by forming a catalyst layer on the conductive substrate. The catalyst layer is not particularly limited, and includes known ones including metal compounds containing nickel, cobalt, palladium, iridium, platinum, etc., metal oxides, alloys, and the like. The shape of the electrode is not particularly limited, and includes known shapes such as a sheet shape, a rod shape, and a prism shape. It is preferably in the form of a sheet in that it can be

The electrolytic device may also include other commonly used members. Examples of the other members include a gas-liquid separation tank for separating generated gas and electrolyte, a condenser for stably performing electrolysis, a mist separator, and the like.

(Electrolysis method)
The method of electrolyzing water using the alkaline water electrolysis apparatus provided with the diaphragm for alkaline water electrolysis of the present invention is not particularly limited, and a known method can be used. For example, it can be carried out by filling an electrolytic solution into an alkaline water electrolysis apparatus provided with the above-described diaphragm for alkaline water electrolysis of the present invention and applying an electric current in the electrolytic solution.

As the 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 electrolytic solution is not particularly limited, but it is preferably 20 to 40% by mass in order to further increase the electrolysis efficiency.

The temperature for electrolysis is preferably 50 to 120° C., more preferably 80 to 90° C., since the ion conductivity of the electrolytic solution can be further improved and the electrolysis efficiency can be further increased. The current can be applied under known conditions and methods, and is 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 that hydrogen can be produced efficiently. The electrolysis voltage is preferably adjusted to about 2V, eg, not exceeding 1.5 to 2.5V, so that the current density is high.

The pressure for electrolysis is not particularly limited. Normal pressure may be used, or pressurization may be used. The diaphragm for alkaline water electrolysis of the present invention is excellent in wear resistance of the diaphragm and maintains good gas barrier properties, and is therefore useful even when performing electrolysis under high pressure conditions of 1 MPa or higher such as 3 MPa. .

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited only to these examples. Unless otherwise specified, "part" means "mass part" and "%" means "mass %".
In the examples, each evaluation was performed by the following methods.

<Method for measuring viscosity (25°C) of coating composition>
The coating composition obtained in each example etc. was processed at a shear rate of 500 s ^-1 for 30 seconds using a rheometer (HAAKE Rheost 6000) and a plate PP35Ti (D = 35 mm) to homogenize the sample. 1000 measurement points were obtained in 9 minutes from shear rate 0 to 300 s ⁻¹ after holding for 10 seconds for temperature control without shearing. From the obtained data, a linear approximation formula is obtained at 5 points before and after the closest measurement point for each of 0.1 s ^-1 , 10 s ^-1 and 250 s ^-1 , and the values calculated therefrom are 0.1 s ^-1 and 10 s ^{-1. 1} and 250 s ^-1 respectively.

<Method for measuring film thickness>
The thickness of the diaphragm for alkaline water electrolysis obtained in each example was measured using a digimatic micrometer (manufactured by Mitutoyo Corporation). Ten arbitrary points were measured, and the average value was used as the film thickness.

<Method for measuring macrovoid content>
The diaphragm for alkaline water electrolysis obtained in each example etc. was subjected to FE-SEM (manufactured by JEOL Ltd., model number: JSM-7600F) to obtain a cross-sectional observation image (cross-sectional observation image) perpendicular to the surface of the diaphragm. rice field. The magnification was 300 times.
For the obtained cross-sectional observation image, a range of 60 μm in the depth direction from the outermost surface of the diaphragm and a range of about 400 μm in the direction perpendicular to the depth direction were set as measurement regions, and image analysis software (ScionImage) was used. , the void image was extracted as a dark area, and the others as a bright area. For each void image extracted, the major axis (Lb) and minor axis (Ls) are obtained, the area (S) of each void image having a major axis (Lb) of 30 μm or more is obtained, the sum of them is obtained, and the obtained total The area was defined as the total macrovoid area (Sy). On the other hand, the area (St) of the measurement region was determined, and the ratio (percentage) of (Sy) to (St) (Sy/St×100(%)) was determined. A similar operation was performed in five arbitrary fields of view, and the simple average value was taken as the content of macrovoids having a major axis of 30 μm or more in the measured diaphragm. The length in the thickness direction (Lt) and the length in the plane direction (Lf) are obtained in each void image, and the length in the thickness direction (Lt) and the length in the plane direction (Lf) are obtained, and the larger one of (Lt) and (Lf) is the major axis (Lb), and the smaller one is the minor axis (Ls).
Here, the thickness direction length (Lt) is the thickness direction of the diaphragm, that is, the length in the direction perpendicular to the surface of the diaphragm. The distance in the thickness direction of the diaphragm (perpendicular to the surface of the diaphragm) between the closest point and the point closest to the opposite surface was taken as the thickness direction length (Lt) of the void. A value obtained by dividing the void area (S) by the length in the thickness direction (Lt) was defined as the length in the plane direction (Lf) of the void image.

<Membrane resistance>
(Measuring method)
Two diaphragm samples for measurement are prepared for the diaphragm for alkaline water electrolysis obtained in each example. Using each diaphragm sample, a cell formed with the following cell configuration was allowed to stand in a constant temperature bath at 25° C. for 30 minutes, and then AC impedance was measured under the following measurement conditions. Membrane resistance is calculated from the intercept component (Rb) without the measurement sample and the following formula. The above measurement is performed on two membrane samples, and the average value of the obtained measured values (two points) is calculated and taken as the membrane resistance of the membrane.
[Membrane resistance (Ωcm ² )] = (Ra-Rb) x 1.77
(Measurement condition)
・Cell configuration Working electrode: Ni plate Counter electrode: Ni plate Electrolyte solution: 30 wt% potassium hydroxide aqueous solution Sample pretreatment: immersed overnight in the above electrolyte solution Effective area for measurement: 1.77 cm2
· AC impedance measurement conditions Applied voltage: 10 mV vs. Open circuit voltage frequency range: 100kHz to 100Hz
<Method for measuring air permeability>
The air permeability of the diaphragm for alkaline water electrolysis obtained in each example was measured using an Oken type air permeability tester (manufactured by Asahi Seiko Co., Ltd., model number: EGBO). Measurements were taken at three arbitrary points, and the average value was taken as the air permeability.

<Air permeability per unit film thickness>
For the diaphragm for alkaline water electrolysis obtained in each example, etc., the air permeability (X) per unit film thickness was calculated from the air permeability and film thickness obtained by the above method, using the following equation.
X = air permeability of diaphragm (seconds)/thickness of diaphragm (μm)
<Heat alkali durability test>
A diaphragm for alkaline water electrolysis obtained in each example was cut into a 3 cm square, and this was used as a test piece. Two of these test pieces were placed in a fluororesin container (made of PFA) and immersed in 30 g of a 30% KOH aqueous solution at 90°C. After 24 hours and 240 hours of immersion, the membrane resistance was measured at room temperature, and (membrane resistance after 240 hours/membrane resistance after 24 hours) was calculated as the membrane resistance ratio after the hot alkali durability test. .

<Evaluation method of ultrasonic test>
The mass reduction rate of the diaphragm for alkaline water electrolysis obtained in each example was evaluated by the following ultrasonic test.
(Ultrasonic test)
The diaphragm for alkaline water electrolysis obtained in each example etc. was cut into a size of 5×5 cm and used as a diaphragm sample. Put it in and seal it, and use an ultrasonic cleaning machine (manufactured by SND Co., Ltd., model name: US-103, high frequency output: 100 W, transmission frequency: 38 kHz) in which the temperature of the water tank is adjusted to 30 ° C., for 1 hour in the water tank. After standing still, ultrasonic waves were applied for 3 minutes.
(Mass reduction rate after ultrasonic test)
The weight of each diaphragm sample before and after the ultrasonic test was measured using a precision balance (manufactured by A&D, model number: GH-200), and the mass reduction rate was calculated according to the following formula.
Mass reduction rate (%) = 100 - (mass after ultrasonic test (g) / mass before ultrasonic test (g) x 100)
[Example 1]
(1. Preparation of inorganic particle dispersion)
Magnesium hydroxide (average particle size 0.20 μm, plate shape, aspect ratio 6.21) and N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) are mixed so that the mass ratio is 1:1, A magnesium hydroxide dispersion was prepared by carrying out dispersion treatment at room temperature for 6 hours using a pot mill containing zirconia media balls.

(2. Preparation of coating composition)
Using the magnesium hydroxide dispersion obtained above, the solid content is 51%, and 40 parts by mass of polysulfone resin (manufactured by BASF, product number Ultrason S3010) (PSU) for 100 parts by mass of magnesium hydroxide. A mixture was prepared by adding 0.1% by mass of lithium chloride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) with respect to 100% by mass of magnesium hydroxide. The resulting mixture was mixed at room temperature for about 30 minutes at 1000 rpm in a rotation-revolution mixer (manufactured by THINKY Co., Ltd., product number Awatori Mixer ARE-500) to obtain a coating mixture (1). The resulting coating composition (1) had a viscosity (25° C.) at 10 s ⁻¹ of 24000 mPa s, a viscosity (25° C.) at 250 ^s −1 of 6000 mPa s, and a viscosity at 0.1 s ⁻¹ (25° C.) was 300,000 mPa·s.

(3. Film formation)
A polyphenylene sulfide nonwoven fabric (film thickness: 130 μm, basis weight: 60 g/m 2 ) was impregnated with coating composition (1) at a shear rate of 50 s ⁻¹ (viscosity at coating: 17,000 mPa·s). After that, the nonwoven fabric impregnated with the coating composition (1) was bathed in a water bath filled with deionized water at room temperature for 5 minutes to solidify the coating liquid to form a film. After the water bath, the resulting membrane was dried in a dryer at 80°C for 10 minutes to obtain a diaphragm for alkaline water electrolysis (1) composed of a composite of a nonwoven fabric, a membrane containing magnesium hydroxide and a polysulfone resin. . The obtained diaphragm for alkaline water electrolysis (1) was evaluated by the method described above.
The film thickness was 210 μm. The content of macrovoids having a major axis of 30 μm or more was 15%, and the air permeability per unit film thickness was 1.1. The membrane resistance ratio before and after the hot alkali durability test was 0.83, and the mass reduction rate after ultrasonic irradiation was 1.1%.

[Example 2]
Coating composition (1) and coating composition (2) were prepared in the same manner as in Example 1. In (3. Film formation) of Example 1, the coating composition (2) was used instead of the coating composition (1), and the non-solvent in the water tank was replaced with ion-exchanged water by 50% ion-exchanged water. A diaphragm (2) was prepared in the same manner, except that a mixed aqueous solution of 50% N-methyl-2-pyrrolidone was used, and after coagulation it was allowed to stand in ion-exchanged water for 10 minutes. The film thickness of the obtained diaphragm (2) was 195 μm. The content of macrovoids having a major axis of 30 μm or more was 6%, and the air permeability per unit film thickness was 2.0. The film resistance ratio before and after the hot alkali durability test was 0.91, and the mass reduction rate after ultrasonic irradiation was 0.9%.

[Example 3]
Coating composition (1) and coating composition (3) were prepared in the same manner as in Example 1.
In (3. Film formation) of Example 1, the coating composition (3) was used instead of the coating composition (1), and the non-solvent in the water tank was replaced with ion-exchanged water by 20% ion-exchanged water. A diaphragm (3) was prepared in the same manner except that a mixed aqueous solution of 80% N-methyl-2-pyrrolidone was used, and after coagulation it was allowed to stand in ion-exchanged water for 10 minutes. The film thickness of the obtained diaphragm (3) was 185 μm. The content of macrovoids having a major axis of 30 μm or more was 3%, and the air permeability per unit film thickness was 2.5. The film resistance ratio before and after the hot alkali durability test was 0.89, and the mass reduction rate after ultrasonic irradiation was 1.3%.

[Example 4]
A coating composition (4) similar to the coating composition (1) was prepared in the same manner as in Example 1.
In (3. Film formation) of Example 1, the coating composition (4) was used instead of the coating composition (1), and the non-solvent in the water tank was replaced with ion-exchanged water by 70% ion-exchanged water. A 30% N-methyl-2-pyrrolidone mixed aqueous solution was used, applied at a shear rate of 50 s ⁻¹ (viscosity at application: 17000 mPa s), and after coagulation, the membrane was left to stand for 10 minutes in ion-exchanged water. (4) was produced. The film thickness of the obtained diaphragm (4) was 200 μm. The content of macrovoids having a major axis of 30 μm or more was 13%, and the air permeability per unit film thickness was 1.2. The membrane resistance ratio before and after the hot alkali durability test was 0.84, and the mass reduction rate after ultrasonic irradiation was 0.8%.

[Example 5]
In (1. Preparation of inorganic particle dispersion) of Example 1, zirconium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., product number UEP) was used instead of magnesium hydroxide, and (2. Preparation of coating composition ), except that the solid content was changed to 48%, to prepare a coating composition (5). A diaphragm (5) was prepared in the same manner as in (3. Film formation) in Example 1, except that the coating composition (5) was used instead of the coating composition (1). The resulting coating composition (5) had a viscosity (25° C.) at 10 s ⁻¹ of 19000 mPa s, a viscosity (25° C.) at 250 ^s −1 of 6300 mPa s, and a viscosity at 0.1 s ⁻¹ (25°C) was 250,000 mPa·s. The film thickness of the obtained diaphragm (5) was 205 μm. The content of macrovoids with a major axis of 30 μm or more was 38%, and the air permeability per unit film thickness was 0.6. The film resistance ratio before and after the hot alkali durability test was 0.78, and the mass reduction rate after ultrasonic irradiation was 1.4%.

[Example 6]
In (1. Preparation of inorganic particle dispersion) of Example 1, titanium oxide (average particle size 0.5 μm) was used instead of magnesium hydroxide, and in (2. Preparation of coating composition), solid content A coating composition (6) was prepared in the same manner, except that the was changed to 48%. Next, a diaphragm (6) was prepared in the same manner as in (3. Film formation) in Example 1, except that the coating composition (6) was used instead of the coating composition (1). The resulting coating composition (6) had a viscosity (25° C.) at 10 s ⁻¹ of 20000 mPa s, a viscosity (25° C.) at 250 ^s −1 of 6500 mPa s, and a viscosity at 0.1 s ⁻¹ (25° C.) was 270,000 mPa·s. The film thickness of the obtained diaphragm (6) was 225 μm. The content of macrovoids with a major axis of 30 μm or more was 26%, and the air permeability per unit film thickness was 0.9. The membrane resistance ratio before and after the hot alkali durability test was 0.81, and the mass reduction rate after ultrasonic irradiation was 1.5%.

[Example 7]
Coating composition (7) was prepared in the same manner as in (2. Preparation of coating composition) of Example 1, except that the amount of polysulfone resin was changed to 50 parts by mass. A diaphragm (7) was prepared in the same manner as in (3. Film formation) in Example 1, except that the coating composition (7) was used instead of the coating composition (1). The resulting coating composition (7) had a viscosity (25° C.) at 10 s ⁻¹ of 29000 mPa s, a viscosity (25° C.) at 250 ^s −1 of 12000 mPa s, and a viscosity at 0.1 s ⁻¹ . (25°C) was 570,000 mPa·s. The film thickness of the obtained diaphragm (7) was 220 μm. The content of macrovoids having a major axis of 30 μm or more was 3%, and the air permeability per unit film thickness was 2.4. The film resistance ratio before and after the hot alkali durability test was 0.85, and the mass reduction rate after ultrasonic irradiation was 0.7%.

[Example 8]
Coating composition (8) was prepared in the same manner as in Example 1 (2. Preparation of coating composition coating liquid), except that the solid content was changed to 46%. A film (8) was prepared in the same manner as in (3. Formation of coating film) in Example 1, except that the coating composition (8) was used instead of the coating composition (1). The resulting coating composition (8) had a viscosity (25° C.) at 10 s ⁻¹ of 15000 mPa s, a viscosity (25° C.) at 250 ^s −1 of 5300 mPa s, and a viscosity at 0.1 s ⁻¹ (25° C.) was 110,000 mPa·s. The film thickness of the obtained diaphragm (8) was 240 μm. The content of macrovoids with a major axis of 30 μm or more was 38%, and the air permeability per unit film thickness was 0.6. The membrane resistance ratio before and after the hot alkali durability test was 0.77, and the mass reduction rate after ultrasonic irradiation was 1.6%.

[Comparative Example 1]
A coating composition (c1) was prepared in the same manner as in (2. Preparation of coating composition) of Example 1, except that the solid content was changed to 39%. A diaphragm (c1) was prepared in the same manner as in (3. Formation of coating film) in Example 1, except that the coating composition (c1) was used instead of the coating composition (1). The resulting coating composition (c1) had a viscosity (25° C.) at 10 s ⁻¹ of 5500 mPa s, a viscosity (25° ^C. ) at 250 s −1 of 2800 mPa s, and a viscosity at 0.1 s ⁻¹ (25° C.) was 70,000 mPa·s. The film thickness of the obtained diaphragm (c1) was 260 μm. The content of macrovoids having a major axis of 30 μm or more was 45%, and the air permeability per unit film thickness was 0.5. The film resistance ratio before and after the hot alkali durability test was 0.61, and the mass reduction rate after ultrasonic irradiation was 2.2%.

From the above, it was confirmed that the diaphragms for alkaline water electrolysis of the examples are superior in the stability of the membrane resistance (ionic conductivity) in the hot alkaline solution as compared with the diaphragms for alkaline water electrolysis of the comparative examples. Therefore, it is considered that the diaphragms for alkaline water electrolysis of Examples can maintain good ion conductivity and can stably produce hydrogen gas of high purity for a long period of time.

Claims (6)

A diaphragm for alkaline water electrolysis having a porous layer containing an organic polymer and inorganic particles,
The porous layer is a layer constituting at least one surface of the diaphragm, and the content of macrovoids having a major axis of 30 μm or more in a cross section in the thickness direction of the porous layer is 40% or less,
A diaphragm for alkaline water electrolysis, wherein X represented by the following formula (1) is 0.6 or more.
X = air permeability of diaphragm (seconds)/thickness of diaphragm (μm) (1) A composition containing an organic polymer and inorganic particles, having a viscosity (25°C) of 30,000 mPa·s or less at a shear rate of 10 s ^-1 and a viscosity (25°C) of 100,000 mPa·s or more at a ^shear rate of 0.1 s -1 A method for producing a diaphragm for alkaline water electrolysis, characterized by using A composition containing an organic polymer and inorganic particles and having a viscosity (25° C.) of 100000 mPa s or more at a shear rate of 0.1 s ⁻¹ is used, and the composition is applied at a shear rate at which the viscosity of the composition becomes 30000 mPa s or less. A method for producing a diaphragm for alkaline water electrolysis, comprising a step of applying a substance. Alkaline water containing an organic polymer and inorganic particles, having a viscosity (25°C) of 30,000 mPa·s or less at a shear rate of 10 s ^-1 and a viscosity (25°C) of 100,000 mPa·s or more at ^a shear rate of 0.1 s -1 A composition for a membrane for electrolysis. A composition containing an organic polymer and inorganic particles, having a viscosity (25°C) of 30,000 mPa·s or less at a shear rate of 10 s ^-1 and a viscosity (25°C) of 100,000 mPa·s ^or more at a shear rate of 0.1 s -1 A diaphragm for alkaline water electrolysis produced using A composition containing an organic polymer and inorganic particles and having a viscosity (25° C.) of 100000 mPa s or more at a shear rate of 0.1 s ⁻¹ is used, and the composition is applied at a shear rate at which the viscosity of the composition becomes 30000 mPa s or less. A diaphragm for alkaline water electrolysis produced by a manufacturing method including a step of applying a substance.

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