JP2021025076A - Electrolytic diaphragm for alkaline solution and manufacturing method for the same - Google Patents

Abstract

To provide a diaphragm having higher membrane strength, higher ion conductivity and more excellent yield for alkaline solution electrolysis, and to provide a manufacturing method for the diaphragm.SOLUTION: An electrolytic diaphragm for alkaline solution includes an organic polymer 22 and inorganic particles 21. In a cross section perpendicular to the surface of the membrane, a ratio SMACRO/SA of the sum SMACRO of areas of macro-voids having a pore diameter of 10 μm or more to the total area SA from one surface to the other surface of the membrane is 25% or less in a range of 0.4 a or more away from width a of the cross section from both ends in the longitudinal direction toward the center. In a range between a position 10 μm away from the surface of the membrane in the depth direction and a position 20 μm away from the surface of the membrane, a ratio of the sum of the areas of resin internal pores 23, which are closed only by the contour line of the organic polymer and have a pore diameter of 0.08-1.20 μm, to the sum of the total area SR of the organic polymer and the areas of the resin internal pores is 5% or more.SELECTED DRAWING: Figure 3

Description

The present invention relates to a diaphragm for alkaline water electrolysis and a method for producing the diaphragm.

Electrolysis of water is known as one of the industrial production methods of hydrogen gas, which has been attracting attention as an energy source in recent years. The electrolysis of water is generally carried out by applying a direct current to water to which sodium hydroxide, potassium hydroxide or the like is added as an electrolyte in order to enhance conductivity. For the electrolysis of such water, an electrolytic cell having an anode chamber and a cathode chamber, which are separated by a diaphragm, is used.

The electrolysis of water is carried out by the movement of electrons (or ions). Therefore, in order to efficiently perform electrolysis, the diaphragm is required to have high ion permeability. Further, a gas barrier property capable of blocking oxygen generated in the anode chamber and hydrogen generated in the cathode chamber is required. In the electrolysis of water, a high concentration alkaline aqueous solution of about 30% is used, and it is carried out at about 80 to 90 ° C. Therefore, the diaphragm for electrolysis of alkaline water used for electrolysis of water is also required to have high temperature resistance and alkali resistance. Further, as a diaphragm for alkaline water electrolysis, a diaphragm having both higher membrane strength, higher ionic conductivity, less defects due to macrovoids, and better yield has been required.

As the diaphragm for alkaline water electrolysis, various porous membranes produced by the non-solvent-induced phase separation method (NIPS) have been proposed so far.
Regarding film formation by the non-solvent-induced phase separation method, Non-Patent Document 1 describes a coating liquid as an effect of adding an additive such as lithium chloride to a cast solution in the production of a polyvinylidene fluoride film by the non-solvent-induced phase separation method. It is described that the solvent / non-solvent exchange during NIPS is controlled by suppressing the thermodynamic miscibility of.
However, there is not much knowledge about the above additives in the diaphragm for alkaline water electrolysis in which a resin having alkali resistance and heat resistance and inorganic particles are used in combination.

Desalination 192 (2006) 190-197

An object of the present invention is to provide a diaphragm for alkaline water electrolysis and a method for producing the diaphragm, which have both higher membrane strength, higher ionic conductivity, and better yield.

The present inventors suppressed the formation of macrovoids inside the membrane by adding lithium chloride to the diaphragm for alkaline water electrolysis containing an organic polymer and inorganic particles, and excellent in membrane strength and ionic conductivity. We have found that it is possible to provide a diaphragm for alkaline water electrolysis which has a membrane structure and has both higher membrane strength, higher ionic conductivity and better yield, and has completed the present invention.

That is, the alkaline water electrolysis diaphragm of the present invention is an alkaline water electrolysis diaphragm containing an organic polymer and inorganic particles; in a cross section perpendicular to the surface of the membrane, from both ends in the longitudinal direction toward the center. in an area away to the width a of the cross section or 0.4a; to the total area S _a from one surface of the membrane to the other surface, the ratio of the sum S _mACRO area macrovoids pore diameter is 10μm or more S _{MACRO /} S _a There are more than 25%; in a range between a position away membrane location and 20μm apart 10μm from the surface in the depth direction of the contour lines of the total area S _R and organic polymer in an organic polymer only the closed pore size a vacancy for the sum _S R _{+ S MICRO} the sum _{S MICRO} the area of the resin pores are 0.08Myuemu～1.20Myuemu, the sum _{S MICRO} area of the resin within the pores ratio is _{S MICRO / (S R + S} MICRO) is more than 5%. It is preferable that the inorganic particles are contained in an amount of 150% by volume or more based on the organic polymer.

The method for producing a diaphragm for alkaline water electrolysis of the present invention includes a resin mixed solution preparation step of mixing an organic polymer resin (R), inorganic particles, and lithium chloride with a solvent to prepare a resin mixed solution, and a resin mixed solution preparation step. It includes a film forming step of forming a film using a resin mixed solution.

According to the present invention, it is possible to provide a diaphragm for alkaline water electrolysis and a method for producing the diaphragm, which have both higher membrane strength, higher ionic conductivity, and better yield.

It is sectional drawing which shows typically one form of the cross section of the diaphragm for alkaline water electrolysis of this invention. In the cross section perpendicular to the surface of the alkaline water electrolysis diaphragm of the present invention, from both ends in the longitudinal direction toward the center, in a range separated from the surface of the film by 0.4 a or more with respect to the width a of the cross section, in the depth direction. It is a figure which shows typically the range between the position which is separated by 10 μm, and the position which is separated by 20 μm. It is a figure which shows typically the pores of the diaphragm for electrolysis of alkaline water of this invention closed only by the contour line of an organic polymer.

The present invention will be described in detail below. It should be noted that a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention. Further, in the present specification, the description of "A to B" means "A or more and B or less".

1. 1. Alkaline water electrolysis diaphragm The alkaline water electrolysis diaphragm of the present invention is an alkaline water electrolysis diaphragm containing an organic polymer and inorganic particles; in a cross section perpendicular to the surface of the membrane, from both ends in the longitudinal direction toward the center. Te, in an area away to the width a of the cross section or 0.4a; to the total area S _a from one surface of the membrane to the other surface, the sum of the areas of macro voids is pore diameter 10μm or more S _mACRO ratio _{S MACRO} / _{S a} There are more than 25% of the; in a range between a position away 10μm from the surface of the film in the depth direction and 20μm away, of the total area _{S R} and organic polymer in an organic polymer pore size a vacancy closed only by contour with respect to the sum _S R _{+ S MICRO} the sum _{S MICRO} the area of the resin pores are 0.08Myuemu～1.20Myuemu, the sum of the areas of the resin within the pores S ratio of _{MICRO S MICRO / (S R +} S MICRO) is 5% or more.

1-1 Organic polymer The diaphragm for alkaline water electrolysis of the present invention contains an organic polymer. Organic polymers retain inorganic particles. The organic polymer functions as a partition wall for holding the inorganic particles, and can prevent the inorganic particles from falling off from the diaphragm in an alkaline solution while minimizing the decrease in the hydrophilic surface of the inorganic particles described later.

The organic polymer is an organic polymer resin (R) that retains inorganic particles and can preferably exert the effects of the present invention without swelling in an alkaline solution [hereinafter, may be simply referred to as a resin (R)]. If so, it is not particularly limited. Examples of the resin (R) include fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene; olefin resins such as polypropylene; and aromatic hydrocarbon resins such as polysulfone and polystyrene. These may be used individually by 1 type, and may be used in combination of 2 or more type. Among them, an aromatic hydrocarbon-based resin is preferable because it can be used as a diaphragm for alkaline water electrolysis, which is further excellent in heat resistance and alkali resistance.

More specifically, the aromatic hydrocarbon-based resin includes polyarylene sulfide resins such as polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, and polyphenylene sulfide, and polyphenylsulfone. , Polyarylate, polyetherimide, polyimide, polyamideimide and the like. Among them, at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone is preferable in that it can impart even more excellent alkali resistance, and from the viewpoint of production, polysulfone and polysulfone are preferable. Ethersulfone is more preferred.

By using at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone, for example, when producing a diaphragm using a non-solvent-induced phase separation method or a steam-induced phase separation method, When the sulfonyl group has an appropriate affinity with the inorganic particles described later, the phase separation conditions can be easily adjusted. Further, by further increasing the alkali resistance, the stability of the dimensions, mass, resistance value and the effect of suppressing the generation of new pores when used in an alkaline solution for a long time become excellent.

The content of the resin (R) is preferably 3 to 40% by mass in 100% by mass of the diaphragm for alkaline water electrolysis. When the content of the resin (R) is within the above range, the inorganic components are eluted from the alkaline water electrolyzing diaphragm in an alkaline solution while the ion permeability and toughness of the alkaline water electrolyzing diaphragm are good. It is further suppressed. In addition, it can be a diaphragm for alkaline water electrolysis that exhibits high ionic conductivity and is also excellent in ion permeability, gas barrier property, heat resistance and alkali resistance. The content of the resin (R) is more preferably 5 to 35% by mass, still more preferably 7 to 30% by mass, based on 100% by mass of the diaphragm for alkaline water electrolysis.

The content of the resin (R) is preferably 5 to 40% by mass in 100% by mass of the alkaline water electrolyzing diaphragm when the alkaline water electrolyzing diaphragm of the present invention does not contain the porous support described later. , More preferably 10 to 35% by mass, still more preferably 10 to 25% by mass. When the alkaline water electrolysis diaphragm of the present invention contains a porous support described later as an organic polymer, the content of the resin (R) is preferably 3 to 20% by mass in 100% by mass of the alkaline water electrolysis diaphragm. It is more preferably 5 to 18% by mass, still more preferably 7 to 15% by mass.

The diaphragm for alkaline water electrolysis of the present invention preferably contains 10 to 40 parts by mass of the resin (R), more preferably 12 to 35 parts by mass, and 15 to 33 parts by mass with respect to 100 parts by mass of the inorganic particles described later. It is more preferable to include parts by mass. When the content ratio of the inorganic particles and the resin (R) is within the above range, the elution of the inorganic component from the alkaline water electrolysis diaphragm in the alkaline solution is further suppressed. Further, it can be a diaphragm for alkaline water electrolysis which exhibits high ionic conductivity and is also excellent in ion permeability, gas barrier property, flexibility, heat resistance and alkali resistance.

1-1-1 Porous support The diaphragm for alkaline water electrolysis of the present invention is composed of the above-mentioned organic polymer and a film containing inorganic particles described later, and the above-mentioned organic polymer contains a porous support. May be good. The porous support is a porous organic polymer, which does not inhibit ion permeability and can be a support for a diaphragm for alkaline water electrolysis. The porous support is preferably a sheet-like member.

Examples of the material of the porous support include polyarylene sulfide resin such as polyethylene, polypropylene, polysulfone, polyethersulfone, polyphenylsulfone, and polyphenylene sulfide, and resin materials such as polyketone, polyimide, polyetherimide, and fluororesin. Can be mentioned. These may be used individually by 1 type, or may be used in combination of 2 or more type. Among them, it is preferable to contain at least one resin material selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide in that it can exhibit excellent heat resistance and alkali resistance, and the group consisting of polypropylene and polyphenylene sulfide. It is more preferable to contain at least one more selected resin material.

Examples of the form of the porous support include non-woven fabrics, woven fabrics (woven fabrics), knitted fabrics, meshes, porous films, felts, and mixed fabrics of non-woven fabrics and woven fabrics, but non-woven fabrics and woven fabrics are preferable. Cloth, mesh, or felt can be mentioned, and more preferably, non-woven fabric, woven cloth, or mesh can be mentioned.

As the porous support, a non-woven fabric, a woven fabric, a mesh, or a felt containing at least one resin selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide is preferable. Further, as the porous support, a non-woven fabric, mesh, or felt containing polyphenylene sulfide is preferable. The total content of polypropylene, polyethylene, and polyphenylene sulfide in the porous support is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more.

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 exert the effect of the present invention, but is preferably 30 to 2000 μm, for example. , More preferably 50 to 1000 μm, still more preferably 80 to 500 μm, and most preferably 80 to 250 μm.

1-2 Inorganic particles The diaphragm for alkaline water electrolysis of the present invention contains inorganic particles. The alkaline water electrolysis diaphragm of the present invention can exhibit ion permeability by filling the space between the inorganic particles or the gap between the particles and the organic polymer with the electrolytic solution. Further, by containing the inorganic particles, it is possible to prevent the alkaline water electrolysis diaphragm from becoming hydrophilic and the oxygen gas and hydrogen gas generated in the electrolysis of water from adhering to the diaphragm and hindering the electrolysis.

Examples of the inorganic particles used in the present invention include hydroxides or oxides such as magnesium, zirconium, titanium, zinc, aluminum and tantalum, and sulfates such as calcium, barium, lead and strontium. Of these, magnesium hydroxide, zirconium hydroxide, titanium hydroxide, zirconium oxide, titanium oxide, calcium sulfate, and barium sulfate are preferable because the dispersibility of the inorganic particles and the stability in an alkaline solution are further excellent. Magnesium oxide, zirconium oxide, titanium oxide and barium sulfate are more preferable. The inorganic particles may be used alone or in combination of two or more.

The inorganic particles may be natural products or synthetic products. Further, the surface may be untreated, and the surface may be treated with a silane coupling agent, stearic acid, oleic acid, fatty acid, higher fatty acid, carboxylic acid ester, phosphoric acid ester or the like in order to improve dispersion in a solvent. It may be processed. The shape of the inorganic particles is not particularly limited as long as it is in the form of particles, and may be any of irregular shapes; spherical shapes such as true spheres and oblong spheres; plate shapes such as flakes and hexagonal plates; and fibrous shapes. However, it is preferable that it is spherical, plate-shaped, or fibrous because it is easily dispersed in a solvent and it is easy to prepare a resin composition, and it is preferable in terms of ion permeability and particle retention of an alkaline water electrolytic diaphragm. It is more preferably plate-shaped.

The inorganic particles preferably have an aspect ratio of 1.0 to 8.0. When the aspect ratio is in the above range, the diaphragm having further excellent ion permeability and excellent uniformity can be obtained. The aspect ratio is more preferably 1.5 to 7.0, and even more preferably 2.0 to 6.0.
In the present specification, the aspect ratio means the ratio (a / b) of the longest diameter a to the shortest diameter b, and any 10 particles of the obtained image obtained by observing powdery inorganic particles with SEM. In, the ratio (a / b) of the longest diameter a and the shortest diameter b of each particle can be measured by using analysis software or the like, and the simple average value of those ratios can be obtained as the aspect ratio of the particles. ..

As the longest diameter a, for example, when the shape of the particles is plate-shaped, the major axis of the plate surface of the particles is adopted, and when the particles are fibrous, the length of the fibers is adopted. Further, the shortest diameter among the diameters orthogonal to the longest diameter through the midpoint of the longest diameter a is defined as the shortest diameter b. As the shortest diameter b, for example, when the shape of the particles is plate-shaped, the thickness of the particles is adopted, and when the shape of the particles is fibrous, the thickness of the fibers is adopted. As the thickness of the particles and the thickness of the fibers, the thickness and the thickness at the midpoint of the longest diameter a are adopted, respectively.

The average particle size of the inorganic particles is preferably 0.01 to 2.0 μm, more preferably 0.05 to 1.0 μm, and 0, in that the dispersibility of the inorganic particles is further excellent. It is more preferably .08 to 0.7 μm. The average particle size is a volume obtained from particle size distribution measurement by a laser diffraction / scattering method using an inorganic particle dispersion that has been dispersed using inorganic particles and a 0.2 mass% sodium hexametaphosphate aqueous solution. The average particle size (d50). When the average particle size of the inorganic particles is in the above range, a diaphragm having high ionic conductivity and excellent ion permeability and gas barrier properties can be obtained.

The specific surface area of the inorganic particles, in that the ion-permeable diaphragm is excellent even more preferably 5~35m ² / g, more preferably ^{5.5~25m 2 / g, 6~20m 2 /} g Is more preferable. The specific surface area is the specific surface area measured by the BET method using liquid nitrogen for powdery inorganic particles. Since the ion path in the diaphragm for alkaline water electrolysis is formed by the highly hydrophilic surface of the inorganic particles, if the specific surface area of the inorganic particles is within the above range, the diaphragm can be made more excellent in ion permeability.

The content of the inorganic particles is preferably 30 to 95% by mass in 100% by mass of the diaphragm for alkaline water electrolysis. When the content of the inorganic particles is in the above range, elution of the inorganic component in the alkaline solution is further suppressed, high ionic conductivity is exhibited, and ion permeability, gas barrier property, heat resistance and alkali resistance are improved. It can be an excellent diaphragm. The content of the inorganic particles is more preferably 32 to 92% by mass, still more preferably 35 to 90% by mass, based on 100% by mass of the diaphragm for alkaline water electrolysis.

When the alkaline water electrolysis diaphragm of the present invention does not contain the porous support, the content of the inorganic particles is preferably 60 to 95% by mass, more preferably 60% by mass, based on 100% by mass of the alkaline water electrolysis diaphragm. Is 65 to 92% by mass, more preferably 75 to 90% by mass.
When the alkaline water electrolysis diaphragm of the present invention contains the porous support, the content of the inorganic particles is preferably 30 to 50% by mass, more preferably 32 to 48% by mass in 100% by mass of the alkaline water electrolysis diaphragm. It is by mass, more preferably 35 to 45% by mass.
Further, it is preferable that the inorganic particles are contained in an amount of 150% by volume or more (that is, 1.5 times the volume of the organic polymer or more) with respect to the organic polymer.

FIG. 1 schematically shows one form of the diaphragm for alkaline water electrolysis of the present invention. The alkaline water electrolysis diaphragm 1 includes a monomembrane layer 2 and a support layer 3. The single film layer 2 is a layer containing the resin (R) and the inorganic particles, and the support layer 3 is a layer containing the resin (R), the inorganic particles and the porous support.

In the diaphragm for alkaline water electrolysis of the present invention, the above-mentioned single film layer 2 may be formed on one surface of the support layer 3 or may be formed on both surfaces.
Further, the diaphragm for alkaline water electrolysis of the present invention does not have to have the single film layer 2 described above, and is a composite as a support layer 3 in which inorganic particles, the resin (R) and the porous support are integrated. It may be a body. By forming the above composite, the strength and toughness of the diaphragm for alkaline water electrolysis can be improved.

1-3 Membrane internal structure The alkaline water electrolysis diaphragm of the present invention is an alkaline water electrolysis diaphragm containing an organic polymer and inorganic particles; in a cross section perpendicular to the surface of the membrane, from both ends in the longitudinal direction to the center. headed, in an area away to the width a of the cross section or 0.4a; to the total area S _a from one surface of the membrane to the other surface, the sum of the areas of macro voids is pore diameter 10μm or more S ratio _{S MACRO} / _{S a} of the _MACRO There are more than 25%; in the range between the position away membrane location and 20μm apart 10μm from the surface in the depth direction of, the total area _{S R} and organic polymer in an organic polymer the pore size a vacancy closed only by contour with respect to the sum _S R _{+ S MICRO} the sum _{S MICRO} the area of the resin pores are 0.08Myuemu～1.20Myuemu, the area of the resin within the pores the proportion of the sum _{S MICRO S MICRO / (S R} + S MICRO) is 5% or more.

In the following, "to the total area _{S A} to one of the surfaces other surface of the membrane, the ratio _{S MACRO} / _{S A} of the sum _{S MACRO} area macrovoids pore diameter is 10μm or more" described above, and macrovoids prevalence In some cases. Also, the "to the sum _S R _{+ S MICRO} the sum _{S MICRO} area of the total area _{S R} and the resin within the pores of an organic polymer, the ratio of the sum _{S MICRO} area of the resin within the pores _{S MICRO} / (S _"R + S _MICRO )" may be referred to as the resin internal pore ratio.

1-3-1 Macrovoid abundance As described above, the macrovoid abundance is 0.4a or more away from the width a of the cross section from both ends in the longitudinal direction toward the center in the cross section perpendicular to the surface of the film. in ranges, to the total area _{S a} from one surface of the film to the other surface, pore size is the ratio _{S mACRO} / _{S a} of the sum _{S mACRO} area of macrovoids is 10μm or more. The macrovoid abundance is 25% or less, preferably 10% or less, more preferably 5% or less, and further preferably no macrovoid.

Specifically, as a method for determining the macrovoid abundance, "in a cross section perpendicular to the surface of the film, a range separated from both ends in the longitudinal direction toward the center by 0.4 a or more with respect to the width a of the cross section. , Select the measurement area. The measurement region is all (from one surface to the other surface) in the thickness direction of the film, and at least 300 μm, preferably 300 to 500 μm in the width direction. Then, the ratio of the total area of macrovoids to the area of the measurement area is obtained. The above measurement is preferably carried out by observing the entire cross section of the film at a magnification of 100 to 500 times, particularly preferably 300 times. If it does not fit in one field of view in the thickness direction, it may have multiple fields of view.

FIG. 2 schematically shows a cross section 10 of the alkaline water electrolysis diaphragm 1 in a cross section 10 perpendicular to the surface 11 of the alkaline water electrolysis diaphragm 1 from both ends in the longitudinal direction toward the center. Within a range of 0.4a or more away from a, the measurement region is all (from one surface to the other surface) in the thickness direction of the film, and at least 300 μm, preferably 300 to 500 μm in the width direction. For example, a cross-sectional observation image at a magnification of 100 to 300 (preferably, the entire film occupies 80% or more of the viewing area) is obtained. The range shown by 12 in FIG. 2 is used for measuring the resin internal pore ratio described later. As for the macrovoid abundance, as described above, in the thickness direction of the film, the measurement region is all from one surface to the other surface.

This cross-section observation image is divided into a bright part, a quasi-bright part, and a dark part by using analysis software. Here, the bright part is an inorganic particle, the quasi-bright part is an organic polymer, and the dark part is a pore and a void. When a closed outer circumference is extracted from the void, the average value of the diameters connecting the two points on the outer circumference of the void and passing through the center of gravity is calculated and used as the pore diameter. Subsequently, macrovoids having a pore diameter of 10 μm or more are extracted, and the sum S _MACRO of these areas is obtained. Then, a macro void existence ratio _{S MACRO} / _{S A} to the total area _{S A} from one surface of the film to the other surface.

1-3-2 Resin internal pore ratio As described above, the resin internal pore ratio is 0.4a with respect to the width a of the cross section from both ends in the longitudinal direction toward the center in the cross section perpendicular to the surface of the film. _{The sum of the total area S R} of the organic polymer and the area of the internal pores of the resin S in the range above and between the position 10 μm away from the surface of the film and the position 20 μm away from the surface of the film. with respect to the sum _S R _{+ S MICRO} with _MICRO, a said percentage of the sum _{S MICRO} the area of the resin within the pores _{S MICRO / (S R + S} MICRO). The resin internal pore ratio is 5% or more, more preferably 10% or more. The upper limit of the resin internal pore ratio is 20%. When the pore ratio inside the resin is within the above range, the diaphragm for alkaline water electrolysis has both higher membrane strength, higher ionic conductivity, and better yield.

To specifically explain the method for determining the resin internal pore ratio, in the cross section 10 perpendicular to the surface 11 of the alkaline water electrolysis diaphragm 1 shown in FIG. 2, the width of the cross section 10 from both ends in the longitudinal direction toward the center. A cross-sectional observation image by FE-SEM measurement is obtained in a range 12 that is 0.4 a or more away from a and between a position 10 μm away from the surface 11 in the depth direction S and a position 20 μm away. The cross-section observation image is divided into a bright part, a quasi-bright part, and a dark part using analysis software. Here, the bright part is an inorganic particle, the quasi-bright part is an organic polymer, and the dark part is a pore and a void.

When the obtained cross-sectional observation image is schematically shown in FIG. 3, 21 is an inorganic particle and 22 is an organic polymer. The organic polymer 22 may form a resin partition wall. Reference numeral 23 denotes pores closed only by the contour line of the organic polymer, and resin internal pores having a pore diameter of 0.08 μm to 1.20 μm, and 24 are voids.

For the vacancies extracted in the cross-sectional observation image, the average value of the diameters that connect the two points on the outer circumference of the vacancies and pass through the center of gravity is calculated and used as the pore diameter of each vacancies. Subsequently, the resin internal pores having pores having a pore diameter of 0.08 μm to 1.20 μm, which are closed only by the contour line of the organic polymer, are extracted, and the sum of these areas is obtained. On the other hand, the sum of the areas of the organic polymer is obtained from the sum of the areas of the semi-bright areas, and the resin internal pore ratio is obtained from these values.

The measurement region for determining the resin internal pore ratio is "a range of a cross section perpendicular to the surface of the film, 0.4a or more away from the width a of the cross section from both ends in the longitudinal direction toward the center". , Select from the range between the position 10 μm away from the surface of the film and the position 20 μm away in the depth direction. Preferably, in the image observed by FE-SEM at a magnification of 20,000, 10 rectangular measurement regions having a thickness direction of 4.4 μm and a width direction of 6.2 μm are selected. In each measurement region, with respect to the sum _S R _{+ S MICRO} the sum _{S MICRO} area of the total area _{S R} and the resin within the pores of an organic polymer, the ratio of the sum _{S MICRO} the area of said resin within the pores _{S MICRO} / ( S _R + S _MICRO ) is calculated for 10 places, and the average value is calculated.

The surface of the alkaline water electrolysis diaphragm is not particularly limited, and may be, for example, the surface of the alkaline water electrolysis diaphragm 1 on the single film layer 2 side or the surface on the support layer 3 side in FIG. Further, as a method for determining the resin internal pore ratio, it is preferable to evaluate and determine the image observed by FE-SEM in the above range 12. The observation magnification is not particularly limited, but it is usually evaluated at a magnification of 20,000 or more, preferably at a magnification of 20,000, and if necessary, at a higher magnification. For example, an image observed at a magnification of 30,000 is evaluated. It is also preferable to determine.

In the alkaline water electrolysis diaphragm of the present invention, when the macrovoid abundance determined in this way is 25% or less and the resin internal pore ratio is 5% or more, higher film strength, higher ionic conductivity and higher ionic conductivity are obtained. It is possible to obtain a diaphragm that has both better yield and can be suitably used for electrolysis of alkaline water. The macrovoid abundance rate and the resin internal pore rate are included in the scope of the present invention as long as the above-mentioned predetermined values are obtained in at least one field of view arbitrarily selected. The minimum size of the region for obtaining the macrovoid abundance and the resin internal pore ratio is a region of 2.8 μm × 4.2 μm.

1-4 Porosity In the diaphragm for alkaline water electrolysis of the present invention, the porosity of the entire membrane is preferably 25 to 80%, more preferably 30 to 75%, still more preferably 35 to 70%. When the porosity of the entire membrane is within the above range, the voids in the diaphragm are more continuously filled with the electrolytic solution, so that higher ionic conductivity is exhibited, ion permeability is superior, and gas barrier property is excellent. It can be a diaphragm.

The porosity of the entire membrane is the calculated density of the diaphragm calculated using the measured density value of the diaphragm measured by the method shown below, the density value (true density) of each component constituting the diaphragm, and the composition ratio. From the value, it can be calculated from the following formula.
Porosity (%) = [1- (measured density value) / (calculated density value)] x 100
The measured density value can be calculated by measuring the mass and volume of a test piece cut out from an arbitrary location on the obtained diaphragm and dividing the mass by the volume. The volume can be calculated by measuring the length in the vertical direction and the length in the horizontal direction of the test piece using a caliper, and measuring the film thickness based on the above-mentioned film thickness measuring method. Further, the mass of the test piece can be measured by using a precision balance having four digits after the decimal point for the test piece whose volume has been measured.

1-5 Ion conductivity The ionic conductivity of the diaphragm for alkaline water electrolysis of the present invention can be calculated by the method described in Examples. The ionic conductivity of the diaphragm for electrolysis of alkaline water of the present invention is preferably more than 100 mS / cm. In this case, the electrolysis efficiency in alkaline water electrolysis can be further increased.

1-6 Thickness The thickness of the diaphragm for alkaline water electrolysis of the present invention is not particularly limited and may be appropriately selected depending on the size of the equipment to be used, handleability, etc., but the film has high ionic conductivity and gas barrier properties. From the viewpoint of ion permeability and strength, 50 to 2000 μm is preferable, 100 to 1000 μm is more preferable, 100 to 500 μm is further preferable, and 150 to 350 μm is most preferable.
When the above-mentioned porous support is included, the thickness of the diaphragm for alkaline water electrolysis of the present invention is preferably 50 to 2000 μm, more preferably 100 to 1000 μm, still more preferably 100 to 500 μm, and most preferably 150 to 300 μm. Is.

2. 2. Method for producing alkaline water electrolytic diaphragm The method for producing an alkaline water electrolytic diaphragm of the present invention is a resin mixed solution preparation in which an organic polymer resin (R), inorganic particles, and lithium chloride are mixed with a solvent to prepare a resin mixed solution. It includes a step and a film forming step of forming a film using the resin mixed solution. It is preferable to include a dispersion liquid preparation step before the resin mixed liquid preparation step.
Each step will be described below.

2-1 Dispersion liquid preparation step In the above production method, when inorganic particles are mixed with the above resin (R), a dispersion liquid in which the inorganic particles are dispersed in a solvent is prepared in advance and then mixed with the above resin (R). Is preferable. A dispersant may be added to the dispersion.

Examples of the dispersant include cationic surfactants; anionic surfactants; conventionally known pigment dispersants having hydrophilic functional groups such as carboxy group, phosphoric acid group and sulfonic acid group.
As the cationic surfactant, a cationic surfactant having a hydrocarbon chain having 5 or more carbon atoms in the molecule is more preferable.
As the anionic surfactant, an anionic surfactant having a hydrocarbon chain having 5 or more carbon atoms in the molecule is more preferable.
The polymer pigment dispersant is not particularly limited as long as it is a polymer having a hydrophilic functional group, but is preferably a polymer having a hydrocarbon chain having 5 or more carbon atoms in the main chain or side chain, and further, a constituent unit (a constituent unit ( The repeating unit) is more preferably a polymer containing a hydrocarbon chain having 5 or more carbon atoms, and the constituent unit is further preferably a polymer containing a polyester or polyether having 5 or more carbon atoms.

As such a polymer, even if the polymer contains only a structural unit containing a hydrocarbon chain having 5 or more carbon atoms as a repeating unit, a structural unit other than the structural unit containing a hydrocarbon chain having 5 or more carbon atoms can be used. It may be further included as a repeating unit.
Further, in the latter case, even if the polymer is composed of a block containing only a structural unit containing a hydrocarbon chain having 5 or more carbon atoms as a repeating unit and a block composed of other structural units, carbon is contained in the molecule. It may be a polymer having a structure in which a structural unit containing a hydrocarbon chain having a number of 5 or more and another structural unit are randomly connected.
The amount of the dispersant used is preferably 1 to 10 parts by mass, more preferably 1.2 to 8.0 parts by mass, and further preferably 1.5 to 5.0 parts by mass or less with respect to 100 parts by mass of the solvent. .. By doing so, the dispersion stability of the inorganic particles can be improved more effectively.

The content of the inorganic particles in the dispersion is preferably 20 to 70% by mass, more preferably 30 to 65% by mass, and further preferably 50 to 65% by mass.

The solvent for dispersing the inorganic particles is not particularly limited as long as it has the property of dissolving the resin (R) to be mixed later, and is, for example, N-methyl-2-pyrrolidone, N, N-dimethyl. Examples thereof include acetamide, N, N-dimethylformamide, dimethyl sulfoxide, methyl ethyl ketone, toluene and the like. These solvents may be used alone or in combination of two or more. Of these, N-methyl-2-pyrrolidone is preferable because it improves the dispersibility of the inorganic particles. The amount of the solvent used with respect to the inorganic particles in the dispersion is preferably 50 to 100 parts by mass, more preferably 50 to 90 parts by mass, still more preferably 50 to 80 parts by mass with respect to 100 parts by mass of the inorganic particles.

The method for dispersing the inorganic particles in the solvent is not particularly limited, and known mixing and dispersing means such as a method using a mixer, a ball mill, a jet mill, a disper, a sand mill, a roll mill, a pot mill, a bead mill, a paint shaker, etc. are applied. be able to.

The average particle size of the inorganic particles in the dispersion is preferably 0.1 to 1.0 μm, more preferably 0.15 to 0.8 μm, and even more preferably 0.15 to 0.5 μm. The average particle size of the inorganic particles in the dispersion is obtained from the particle size distribution measurement by the dynamic light scattering method, and can be specifically measured by the method described in Examples.

2-2 Resin mixed liquid preparation step In the resin mixed liquid preparation step, preferably, the organic polymer resin (R) and lithium chloride are mixed with the dispersion liquid prepared in the dispersion liquid preparation step to prepare a resin mixed liquid. .. By adding lithium chloride, a macrovoid-free film in which pores are preferably formed inside the resin (R) as an organic polymer constituting a partition wall and preferably exhibit flexibility can be produced. The amount of lithium chloride added is preferably 1.0% by mass or more with respect to 100% by mass of the inorganic particles. The upper limit is, for example, 10% by mass.

An organic hydrophilic additive may be added to the resin mixture. Examples of the organic hydrophilic additive include water-soluble polymers such as polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyethyleneimine, polyacrylic acid and dextran; surfactants; glycerin; sugars and the like. The amount of the hydrophilic additive used is preferably 0.1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the inorganic particles in the dispersion liquid.

The method of mixing the resin (R) with the dispersion prepared in the dispersion preparation step is not particularly limited as long as the method can sufficiently mix the dispersion and the resin (R). The resin (R) may be mixed with the dispersion as it is, or a resin solution in which the resin (R) is dissolved in a solvent may be prepared in advance and the resin solution and the dispersion may be mixed. Good. Among them, a method of preparing the resin solution and mixing the resin solution and the dispersion to obtain a resin mixture is a method in which the inorganic particles and the resin (R) can be more uniformly dispersed and mixed. preferable.

The solvent used when preparing the resin mixture is not particularly limited as long as it has the property of dissolving the resin (R), and is, for example, N-methyl-2-pyrrolidone, N, N-dimethyl. Examples thereof include acetamide, N, N-dimethylformamide, dimethyl sulfoxide, methyl ethyl ketone, toluene and the like. Among them, the same solvent as the solvent used for preparing the dispersion is preferable in that the inorganic particles and the resin (R) can be more uniformly dispersed and mixed.

The content of the resin (R) in the resin solution is preferably 5 to 50% by mass, more preferably 10 to 45% by mass, and further preferably 15 to 40% by mass.
Examples of the mixing method include the same means as the mixing and dispersing means described in the dispersion liquid preparation step.

The dispersion liquid and the resin (R) are preferably 10 to 40 parts by mass, more preferably 12 to 35 parts by mass, still more preferably 15 to 33 parts by mass of the resin (R) with respect to 100 parts by mass of the inorganic particles. It is preferable to mix them so as to be parts by mass. Further, it is preferable that the inorganic particles are contained in an amount of 150% by volume or more based on the resin (R) as the organic polymer. When the content ratio of the inorganic particles and the resin (R) is in the above range, the elution of the inorganic component in the alkaline solution of the obtained alkaline water electrolysis diaphragm is further suppressed, and higher ionic conductivity is exhibited. At the same time, it is possible to produce a diaphragm for alkaline water electrolysis, which is more excellent in ion permeability, gas barrier property, heat resistance and alkali resistance.

When the dispersion liquid of the inorganic particles and the solution of the resin (R) are mixed, the total content of the solvent in the dispersion liquid of the inorganic particles and the solvent in the solution of the resin (R) is the dispersion of the inorganic particles. It is preferably 30 to 75% by mass with respect to 100% by mass of the total mass of the liquid and the solution of the resin (R). It is more preferably 35 to 70% by mass, and even more preferably 40 to 65% by mass. In order to adjust the porosity of the diaphragm for alkaline water electrolysis to a preferable range, it is preferable to use a solvent in such a ratio.

2-3 Film forming step In the film forming step, a film is formed using the resin mixed solution obtained in the resin mixed solution preparing step.
As a method for forming the film, the following steps (a) and (b) can be easily produced in that a diaphragm for alkaline water electrolysis in which the elution of inorganic components in an alkaline solution is further suppressed can be easily produced. Is preferably included.
(A) A step of forming a coating film of the above resin mixture, and
(B) A step of coagulating the coating film by contacting the coating film with a non-solvent to obtain a porous film.

(A) Step of forming a coating film of the resin mixed solution As a method of forming a coating film of the resin mixed solution, for example, a method of applying the resin mixed solution obtained above on a base material or the above resin mixing solution Examples thereof include a method of immersing a base material in a liquid to obtain a base material impregnated with the above resin mixed liquid. Among them, the method of applying the above resin mixed solution on the substrate is preferable because the coating film can be easily formed.

The method of applying the resin mixture onto the substrate is not particularly limited, and known coating means such as a method using die coating, spin coating, gravure coating, curtain coating, spray, applicator, bar coater, etc. is applied. can do.

The base material is not particularly limited as long as it can be applied with the resin mixed solution to form a coating film, and is, for example, polyethylene terephthalate, polyethylene naphthalate, polypropylene, polyethylene, polyvinyl chloride, polyvinyl chloride. Examples thereof include films or sheets made of resins such as acetal, polymethyl methacrylate, and polycarbonate, and glass plates. Of these, polyethylene terephthalate is preferable because it is easy to handle and the cost of raw materials can be reduced.
Further, when producing a diaphragm for alkaline water electrolysis containing the above-mentioned porous support, the above-mentioned porous support may be used as the above-mentioned base material.

Further, in the case of producing a diaphragm for alkaline water electrolysis, which is a composite in which a film containing inorganic particles, the resin (R) and a porous support are integrated, the resin mixture is applied onto the substrate. Then, the porous support may be placed on the coating liquid to impregnate the porous support with the coating liquid.

The amount of the resin mixture applied is not particularly limited, and may be appropriately set so that the diaphragm has a thickness capable of exerting the above-mentioned effects.

(B) Step of solidifying the coating film by contacting the coating film with a non-solvent By contacting the coating film with a non-solvent, the non-solvent diffuses into the coating film and does not dissolve in the non-solvent. The resin (R) solidifies. On the other hand, the solvent in the coating film that can be dissolved in the non-solvent elutes from the coating film. By the phase separation occurring in this way, the resin (R) (and the inorganic particles) solidifies to form a porous film.

Examples of the method of bringing the coating film into contact with the non-solvent include a method of immersing the coating film in the non-solvent (coagulation bath), a method of exposing the coating film to the non-solvent vapor atmosphere, and the like. Further, the coating film may be exposed to the non-solvent vapor atmosphere and then subsequently immersed in the non-solvent. In this case, the time of exposure to the non-solvent vapor atmosphere can be about 3 to 60 seconds, and the time of immersion in the non-solvent can be about 1 to 15 minutes.

The temperature of the non-solvent in which the coating film is immersed is preferably 10 ° C. or higher, more preferably 15 ° C. or higher, and even more preferably 20 ° C. or higher. Further, 55 ° C. or lower is preferable, 50 ° C. or lower is more preferable, and 45 ° C. or lower is more preferable. By setting such a temperature, more ion paths can be formed in the manufactured diaphragm, and it is easier to manufacture a diaphragm for alkaline water electrolysis that exhibits high ionic conductivity and has both higher gas barrier properties and higher durability. it can.

The non-solvent is not particularly limited as long as it has a property of substantially not dissolving the resin (R), but for example, ion-exchanged water; lower alcohols such as methanol, ethanol and isopropyl alcohol; or these. A mixed solvent or the like can be preferably used. Ion-exchanged water is preferable from the viewpoint of economy and waste liquid treatment. In addition to the above-mentioned components, the non-solvent may contain a small amount of the same solvent as the solvent contained in the coating film.

The amount of the non-solvent used is preferably 50 to 10000 parts by mass with respect to 100 parts by mass of the coating film, that is, 100 parts by mass of the solid content of the resin mixture used for forming the coating film. It is more preferably 100 to 5000 parts by mass, and even more preferably 200 to 1000 parts by mass. It is preferable to use the non-solvent in such a ratio in terms of adjusting the porosity of the obtained diaphragm to a preferable range and extracting the solvent in the coating film completely into the non-solvent.

Further, in order to remove the non-solvent, the coating film solidified in the above step may be dried to obtain a diaphragm.
The drying temperature of the coating film is preferably 60 to 120 ° C.
The drying time is preferably 0.5 to 120 minutes, more preferably 1 to 60 minutes, and even more preferably 1 to 30 minutes.

In the method for producing a diaphragm for alkaline water electrolysis of the present invention, it is considered that the addition of lithium chloride increases the hydrophilicity of the resin mixture and facilitates the aggregation of the resin (R). Therefore, it is considered that a film having a film internal structure in which pores are formed in the agglomerated resin (R) is produced, and a film capable of achieving both higher film strength, higher ionic conductivity, and better yield is produced. As described above, the diaphragm for alkaline water electrolysis of the present invention can be easily produced by the above-mentioned steps.

3. 3. Applications The diaphragm for alkaline water electrolysis of the present invention can achieve both higher film strength, higher ionic conductivity, and better yield. Therefore, the diaphragm for electrolysis of alkaline water of the present invention can be suitably used as a diaphragm for electrolysis of water using an alkaline aqueous solution as an electrolytic solution. Further, in addition to the above-mentioned alkaline water electrolysis diaphragm, it can be used for applications such as an alkaline fuel cell separator, a primary battery separator, a battery separator such as a secondary battery separator, and a salt electrolysis separator.

4. Alkaline water electrolyzer The diaphragm for alkaline water electrolysis of the present invention is used as a member of the alkaline water electrolyzer. Examples of the alkaline water electrolyzer include an anode, a cathode, and a diaphragm for alkaline water electrolysis arranged between the anode and the cathode. More specifically, the alkaline water electrolyzer has an anode chamber in which an anode exists and a cathode chamber in which a cathode exists, which are separated by the alkaline water electrolysis diaphragm.
Examples of the anode and the cathode include known electrodes such as a conductive substrate containing nickel or a nickel alloy or the like.

5. Electrolysis method The method of electrolyzing water using the alkaline water electrolysis apparatus provided with the alkaline water electrolysis diaphragm of the present invention is not particularly limited and can be performed by a known method. For example, it can be carried out by filling the alkaline water electrolyzer equipped with the alkaline water electrolysis diaphragm of the present invention described above with an electrolytic solution 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 used. The concentration of the electrolyte in the electrolytic solution is not particularly limited, but is preferably 20 to 40% by mass in that the electrolytic efficiency can be further improved.
The temperature at the time of electrolysis is preferably 50 to 120 ° C., more preferably 80 to 90 ° C., in that the ionic conductivity of the electrolytic solution can be further improved and the electrolytic efficiency can be further improved. The current application conditions can be performed by known conditions and methods.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "part" means "part by mass" and "%" means "% by mass".

<Example 1>
(1. Preparation of magnesium hydroxide dispersion)
Magnesium hydroxide (average particle size 0.20 μm) and N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) are mixed so that the mass ratio is 1: 1 and a pot mill containing zirconia media balls is used. , Magnesium hydroxide dispersion was prepared by carrying out dispersion treatment at room temperature for 6 hours.

(2. Preparation of polysulfone resin solution)
A polysulfone resin (manufactured by BASF, product number Ultrazone S3010) was thermally dissolved in N-methyl-2-pyrrolidone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at a concentration of 30% by mass at 80 to 100 ° C.

(3. Preparation of coating liquid)
The magnesium hydroxide dispersion and the polysulfone resin solution obtained above were weighed so that the solid content was 40% by mass and the polysulfone resin (PSU) was 33 parts by mass with respect to 100 parts by mass of magnesium hydroxide. Furthermore, 5% by mass of lithium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is added to 100% by mass of magnesium hydroxide, and the rotation / revolution mixer (manufactured by Shinky Co., Ltd., product number Awatori Rentaro ARE-500) is used at room temperature for 1000 rpm. Was mixed for about 10 minutes. The obtained mixed solution was filtered through a 200 mesh of SUS to obtain a coating solution.

(4. Formation of coating film)
A polyphenylene sulfide non-woven fabric (Toray Industries, Inc., torque converter paper # 100) was applied so that the thickness of the diaphragm after drying was 250 μm in total, and the non-woven fabric was completely impregnated with the coating liquid. Then, the non-woven fabric impregnated with the coating liquid was bathed in water at room temperature for 10 minutes to solidify the coating liquid to form a film. After bathing in water, the obtained membrane was dried in a dryer at 80 ° C. for 30 minutes to obtain a diaphragm for alkaline water electrolysis composed of a composite of a non-woven fabric and a membrane containing magnesium hydroxide and polysulfone resin.

(5. Film thickness measurement method)
The thickness of the obtained diaphragm for electrolysis of alkaline water was measured using a digital micrometer (manufactured by Mitutoyo Co., Ltd.). Arbitrary 10 points were measured, and the average value was taken as the film thickness. The film thickness was 250 μm.

(6. Measurement and calculation method of macrovoid abundance inside the membrane and pore ratio inside the resin)
The cross section perpendicular to the surface of the obtained alkaline water electrolysis diaphragm was separated from the surface of the film by 0.4 a or more with respect to the width a of the cross section from both ends in the longitudinal direction toward the center. A cross-sectional observation image (magnification: 30,000 times) was obtained by FE-SEM (manufactured by JEOL Ltd., model number: JSM-7600F) measurement in the range between the position and the position separated by 20 μm.
With respect to the obtained cross-sectional observation image, the image is divided into a bright part, a quasi-bright part and a dark part by median processing using analysis software (Image-Pro Polymer), and the area of the quasi-bright part corresponding to the polysulfone resin is determined. The total value, the total value of the area of the pores having a pore diameter of 10 μm or more, and the dark part of the area of the pores having a pore diameter of 0.08 μm to 1.20 μm that are closed only by the contour line of the organic polymer. The total value of the area of was calculated. Then, from these values, the macrovoid abundance and the resin internal pore ratio were determined. As a result, the macrovoid abundance was 0%, and the resin internal pore ratio was 12.6%.

(7. Measurement of bubble point value)
The bubble point value of the obtained diaphragm for electrolysis of alkaline water was measured using a liquid porosimeter (manufactured by Porous Materials). Specifically, a 2.5 cmφ diaphragm was immersed in ion-exchanged water at room temperature for 1 hour to be sufficiently moistened, and then a fluorine-based solvent, Galwick (manufactured by Porous Materials), was filled on the diaphragm. The gas pressure on the diaphragm was increased, the liquid film of water was destroyed, and the gas pressure at the time when Galwick permeated the membrane and observed its weight with a balance was used as the bubble point value. The bubble point value of the diaphragm was 1000 kPa or more, which is the upper limit of measurement.

(8. Method of measuring ionic conductivity)
The ionic conductivity of the obtained diaphragm for electrolysis of alkaline water was measured by the following measuring method. As a result, it was 225 mS / cm.
(Measuring method)
Prepare two diaphragm samples for measurement.
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 measurement was performed under the following measurement conditions to obtain the section component (Ra). The ionic conductivity is measured by the following formula using the section component (Rb) when no measurement sample is inserted and the value of the film thickness obtained by the above film thickness measuring method.
The above measurement is performed on two diaphragm samples, the average value of the obtained measured values (2 points) is calculated, and this is used as the ionic conductivity of the diaphragm.
[Ion conductivity (mS / cm)] = [Film thickness (cm)] ÷ [(Ra-Rb) x 1000 x 1.77]
(Measurement condition)
・ Cell composition Working electrode: Ni plate Counter electrode: Ni plate Electrolyte: 30% by mass potassium hydroxide aqueous solution Sample pretreatment: Immerse in the above electrolyte overnight Measurement effective area: 1.77 cm ²
・ AC impedance measurement conditions Applied voltage: 10 mV vs. Open circuit voltage Frequency range: 100kHz to 100Hz

(9. Evaluation method of film strength)
The obtained diaphragm for alkaline water electrolysis was evaluated for film strength by the following bending test and tensile strength test.

(Bending test)
Using a bending tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd., model number No. 514), between the test receiving plate and the mandrel so that the support of the test piece of the separator for electrochemical elements cut out to 2 x 5 cm is on the inside. It was sandwiched, bent at 180 ° C. for 2 seconds, and then the presence or absence of cracks on the coating film surface was confirmed using a 10 magnification of a laser microscope (manufactured by KEYENCE, model number VK-9700). As a result, no cracks were generated.

(Tensile strength test)
A test piece of a separator for an electrochemical element cut out to a size of 3 x 10 cm was allowed to stand for 1 hour in a constant temperature and humidity environment of 23 ° C. and 50%, and then a tensile tester (manufactured by Shimadzu Corporation, model number Autograph AG-1kN XPlus). ) Was pulled in the MD direction (longitudinal direction of the non-woven fabric and the coating direction of the coating liquid) at a distance of 5 cm between the jigs and a speed of 10 cm / min, and the strength at break was measured and found to be 330 N / 30 mm.

<Example 2>
A diaphragm for alkaline water electrolysis was obtained in the same manner as in Example 1 except that the amount of lithium chloride used was changed to 2% by mass with respect to 100% by mass of magnesium hydroxide. The film thickness was 270 μm, the macrovoid abundance was 23%, the resin internal pore ratio was 5.7%, and the bubble point value was 455 kPa.
As a result of measuring the ionic conductivity of the obtained diaphragm for electrolysis of alkaline water in the same manner as in Example 1, it was 198 mS / cm. No cracks were generated in the flexibility test, and the tensile strength was 310 N / 30 mm.

<Comparative example 1>
A diaphragm for alkaline water electrolysis was obtained in the same manner as in Example 1 except that lithium chloride was not used. The film thickness was 261 μm, the macrovoid abundance was 28%, the resin internal pore ratio was 0%, and the bubble point value was 1000 kPa or more, which is the upper limit of measurement.
The ionic conductivity of the obtained diaphragm for electrolysis of alkaline water was measured in the same manner as in Example 1 and found to be 149 mS / cm. No cracks were generated in the flexibility test, but the tensile strength was 260 N / 30 mm.

<Comparative example 2>
Alkaline as in Example 1 except that lithium chloride was not used and isopropyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of water as a non-solvent in (4. Formation of coating film). A diaphragm for water electrolysis was obtained. The film thickness was 243 μm, the macrovoid abundance was 0%, the resin internal pore ratio was 0%, and the bubble point value was 1000 kPa or more, which is the upper limit of measurement.
The ionic conductivity of the obtained diaphragm for electrolysis of alkaline water was measured in the same manner as in Example 1 and found to be 149 mS / cm. Cracks were observed in the flexibility test, and the tensile strength was 340 N / 30 mm.

1 Alkaline water electrolysis diaphragm 2 Single film layer 3 Support layer 10 Alkaline water electrolysis diaphragm cross section 11 Alkaline water electrolysis diaphragm surface 12 Measurement range a Width of cross section perpendicular to the surface of alkaline water electrolysis diaphragm S Alkaline water Depth direction from the surface of the electrolysis diaphragm 21 Inorganic particles 22 Organic polymer 23 Pore closed by only the contour line of the organic polymer, and the pore diameter is 0.08 μm to 1.20 μm Resin internal pores 24 Voids

Claims (3)

A diaphragm for alkaline water electrolysis containing an organic polymer and inorganic particles.
In a cross section perpendicular to the surface of the film, in a range separated from both ends in the longitudinal direction toward the center by 0.4 a or more with respect to the width a of the cross section.
To the total area _{S A} from one surface of the membrane to the other surface, the ratio _{S MACRO} / _{S A} of the sum _{S MACRO} area macrovoids pore diameter is 10μm or more is 25% or less,
In the range between the position apart positions and 20μm apart 10μm in depth from the surface of the film, a hole diameter a pore closed by only the contour lines of the total area S _R and organic polymer in an organic polymer 0 with respect to the sum _S R _{+ S MICRO} the sum _{S MICRO} the area of the resin pores are .08Myuemu～1.20Myuemu, the ratio of the sum _{S MICRO} area of the resin within the pores _{S MICRO / (S R + S} MICRO) is 5% or more,
Septum for alkaline water electrolysis. The diaphragm for alkaline water electrolysis according to claim 1, which contains 150% by volume or more of the inorganic particles with respect to the organic polymer. A resin mixed solution preparation step of mixing an organic polymer resin (R), inorganic particles, and lithium chloride with a solvent to prepare a resin mixed solution, and
A method for producing a diaphragm for alkaline water electrolysis, which comprises a film forming step of forming a film using the resin mixed solution.

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