JP7129903B2 - Diaphragm for alkaline water electrolysis - Google Patents

Description

The present invention relates to a diaphragm for alkaline water electrolysis. More particularly, it relates to a diaphragm for alkaline water electrolysis and an alkaline water electrolysis apparatus including the same.

Water electrolysis is known as one of the industrial production methods of hydrogen, and in recent years, water electrolysis is used to convert surplus electricity into gaseous fuels such as hydrogen and methane, which are then stored and used. A technology called Power to Gas has attracted attention. Under these circumstances, various researches and developments have been carried out on the electrolysis of water. Various manufacturing methods have been proposed so far.

For example, a method for producing a diaphragm for alkaline water electrolysis has been proposed, which comprises depositing at least one metal oxide selected from titanium oxide and zirconium oxide on the surface of a microporous membrane by an aerosol deposition method ( For example, see Patent Document 1). A method for producing a diaphragm for alkaline water electrolysis, which includes the steps of preparing a resin composition containing an epoxy resin, a curing agent, and a porogen, and obtaining a resin sheet using the resin composition, has also been proposed ( For example, see Patent Document 2).

JP 2015-101775 A JP 2015-48504 A

When a direct current is applied to the electrolyte during electrolysis of water, cations in the electrolyte usually gather at the cathode and anions gather at the anode, causing ions to move between the anode chamber and the cathode chamber. In order to perform electrolysis efficiently, it is desirable that the diaphragm has high ionic conductivity. On the other hand, if gas such as oxygen generated in the anode chamber or hydrogen generated in the cathode chamber adheres to the surface of the diaphragm or permeates into the diaphragm, the ionic conductivity of the diaphragm decreases. Therefore, it is desired that the diaphragm itself has high ionic conductivity, low adhesion of gas, and gas barrier properties capable of blocking gas.

In the inventions described in Patent Documents 1 and 2, gas adhesion (low adhesion) and gas barrier properties of diaphragms are measured and evaluated. There is room for improvement in order to lower the adhesion of gas and improve the gas barrier properties while ensuring sufficient ionic conductivity.

The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a method that achieves both ionic conductivity, low gas adhesion, and gas barrier properties.

The present inventors have studied various methods for achieving both ion conductivity, low gas adhesion, and gas barrier properties in a diaphragm for alkaline water electrolysis. Focusing on a diaphragm having a resin composition layer obtained by impregnating a resin composition containing inorganic particles, one surface and the other surface of the diaphragm, respectively, the resin composition based on the surface of the porous support A diaphragm was prepared by adjusting the position of the layer surface within a predetermined range. The present inventors have found that this diaphragm has lower gas adhesion, remarkably excellent gas barrier properties, and sufficiently maintains its performance even after use, while sufficiently maintaining the ionic conductivity of the diaphragm for alkaline water electrolysis. The present inventors have found that it is possible to solve the above-mentioned problems, and arrived at the present invention.

That is, the present invention provides a diaphragm for use in alkaline water electrolysis, comprising a porous support and a resin obtained by impregnating the porous support with a resin composition containing an organic polymer and inorganic particles. Having a composition layer, on one surface of the diaphragm, the average position of the resin composition layer surface relative to the surface of the porous support measured by the following method is +20 μm or more and +100 μm or less, and the other side of the diaphragm The diaphragm for alkaline water electrolysis is characterized in that the average position on the surface of is -10 μm or more and +10 μm or less.
Method for measuring the average position of the surface of the resin composition layer relative to the surface of the porous support:
(1) A cross section obtained by cutting perpendicularly to one surface of the diaphragm and ion milling the cut surface is examined using a scanning electron microscope, and the length in the width direction is 160 μm. Select five regions of
(2) The porous support in the region on the left side of the midpoint in the width direction on the one surface side of the diaphragm on the enlarged photograph of the one surface portion of the diaphragm taken using a scanning electron microscope for each region and the edge of the porous support in the region on the right side of the midpoint in the width direction, and a straight line having a length of 120 μm or more in the width direction between both ends is defined as a reference line A.
(3) On the enlarged photograph of (2), when a line parallel to the reference line A is scanned from the side opposite to the one surface side of the diaphragm to the one surface side of the diaphragm, the length of the parallel line A filling line B is defined as a boundary line at which a filling portion where the ratio of the total length of the space portion on the parallel line to the length of the parallel line is 10% or less.
(4) A distance X between the reference line A and the filling line B is calculated. The position of the resin composition layer surface relative to the surface of the porous support is -X when the filling line B is in front of the reference line A in the scanning direction of the parallel lines, and +X when it exceeds the reference line A. and
(5) For each region, select any five regions in the same manner as in (1) in the enlarged photograph of the surface portion on the opposite side of the one surface of the diaphragm taken using a scanning electron microscope. , in each region, the reference line A' and the filling line B' are obtained in the same manner as in (2) to (4), the distance X' between the reference line A' and the filling line B' is calculated, and the porous support surface Determine the position +X' or -X' on the surface of the resin composition layer based on .
(6) the average value of the position +X or -X on the surface of the resin composition layer based on the surface of the porous support for each region, and the resin composition layer based on the surface of the porous support for each region The average value of the surface position +X' or -X' is defined as the average position of the resin composition layer surface relative to the surface of the porous support on each surface.
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.

The diaphragm for alkaline water electrolysis of the present invention has the structure described above, and the diaphragm for alkaline water electrolysis has both ion conductivity, low gas adhesion, and gas barrier properties.

FIG. 4 is a reference diagram for explaining a method for measuring the average position of the surface of the resin composition layer with reference to the surface of the porous support according to the present invention. FIG. 4 is a reference diagram for explaining a method for measuring the average position of the surface of the resin composition layer with reference to the surface of the porous support according to the present invention.

<Diaphragm for alkaline water electrolysis>
A diaphragm for alkaline water electrolysis of the present invention has a porous support and a resin composition layer obtained by impregnating the porous support with a resin composition containing an organic polymer and inorganic particles. On the surface of the membrane, the average position of the resin composition layer surface relative to the surface of the porous support measured by the above method is +20 μm or more and +100 μm or less, and on the other surface of the diaphragm, the average position is −10 μm. It is more than +10 micrometers or less.
Thus, on one side, a resin composition layer substantially having a thickness of 20 μm or more and 100 μm or less (a resin composition layer having such a thickness basically includes the porous support) is formed on the surface of the porous support. It is also called a single layer because there is no layer), and on the other side, the resin composition layer is moderately filled to the vicinity of the interface of the porous support, so that both sides are roughly equivalent. In addition, since the single film layer is provided only on one surface, both ion conductivity and gas barrier properties can be achieved in a well-balanced manner.

Regarding (1) above, selecting arbitrary five regions using a scanning electron microscope in a cross section obtained by cutting perpendicularly to one surface of the diaphragm and ion milling the cut surface, Five different regions with a width of 160 μm may be selected from one section, or a total of five regions with a width of 160 μm may be selected from two to five sections. For example, at the center of the coating width when forming a coating film by coating the resin composition, any three regions of the cross section of the resin composition in the flow direction, any two of the cross sections in the direction perpendicular to the flow direction A region of locations can be selected. The conditions for the ion milling process may be appropriately set so as to be suitable for obtaining a cross section for observation.

Regarding (2) above, the magnified photograph may be an enlarged photograph of one surface portion of the diaphragm having a width of 160 μm, and both ends of the diaphragm in the thickness direction can be observed in one field of view. It doesn't matter if it's not something. An arbitrary end of the porous support in the region on the left side of the midpoint in the width direction and an arbitrary end of the porous support in the region on the right side of the midpoint in the width direction are connected, and the width direction between both ends is A straight line having a length of 120 μm or more can be used as the reference line A. Among them, among the ends of the porous support in the region on the left side of the midpoint in the width direction, the point closest to the surface of the membrane It is preferable that the reference line A is a straight line connecting a point closest to the surface of the diaphragm among the ends of the porous support in the region on the right side of the midpoint. The point closest to the surface of the diaphragm means, when the surface of the diaphragm is composed of a resin composition, the point at the end of the porous support portion that is closest to the surface, and the surface of the diaphragm is the porous support. When it is composed of body parts, the end of the porous support part constituting the surface of the diaphragm is the closest point to the surface of the diaphragm (the distance from the surface of the diaphragm is 0), so the surface of the diaphragm It can be any point at the end of the constituent porous support portion.

Regarding (3) above, the space portion on the parallel lines means that there is no material constituting the diaphragm for alkaline water electrolysis of the present invention, such as a porous support or a resin composition, on the parallel lines at a point in time during the parallel line scanning. It means a space part (void part). The space portion is the black portion in FIGS. 1 and 2, which are conceptual diagrams of enlarged photographs of the cross section of the diaphragm for alkaline water electrolysis taken using a scanning electron microscope (SEM). 1 and 2, the portions where the materials constituting the diaphragm for alkaline water electrolysis of the present invention, such as the porous support and the resin composition, are present. The length of the space portion on the parallel lines can be measured by observing the cross section of the diaphragm for alkaline water electrolysis of the present invention using SEM according to the method described in the Examples.
Further, the total length of the space portions on the parallel lines means summing up the lengths of the space portions when there are two or more intermittent space portions on the parallel lines. Note that the length of parallel lines is the total length of parallel lines within the range shown in the captured image.
Only one filling portion may be present in the enlarged photograph, or two or more filling portions may be present. If there are two or more filling sections, there will also be two or more boundary lines where the filling sections end. In this case, the filling line B is , the line closest to the reference line A.

Regarding (4) above, the distance X between the reference line A and the filling line B is the distance between two straight lines parallel to each other, and is also referred to as the X value in this specification. The reference line A corresponds to the surface of the porous support, and the filling line B corresponds to the position of the surface of the resin composition layer. In this specification, the position of the surface of the resin composition layer is defined as a relative position with respect to the surface of the porous support, and when the filling line B is in front of the reference line A in the scanning direction of the parallel lines is set to -X, and when exceeding the reference line A, it is set to +X.
The magnification of the magnified photograph when determining the reference line A and the filling line B and measuring the X value can be appropriately selected, but is preferably 300 times or more, more preferably 500 times or more. Also, the magnification is preferably 1200 times or less, more preferably 1000 times or less.

In the above (5), the surface opposite to the surface of the porous support/resin composition layer measured in the above (2) to (4) is determined in the same manner as the reference line A in the above (2). A reference line A' is obtained, a filling line B' is obtained in the same manner as the method for obtaining the filling line B in (3) above, a distance X' between the reference line A' and the filling line B' is calculated, and the porous support is obtained. The position +X' or -X' of the resin composition layer surface relative to the surface is determined.

Regarding (6) above, the average value of the position +X or −X on the surface of the resin composition layer based on the surface of the porous support for each region, and the resin composition based on the surface of the porous support for each region When the average value of the position +X' or -X' on the layer surface is within the range according to the present invention, the single layer is formed on the surface of the porous support on one side of the diaphragm as described above. On the other side, the resin composition layer is appropriately filled up to the vicinity of the interface of the porous support, and the effect of the present invention can be exhibited. When the average value of the position +X or −X is +20 μm or more and +100 μm or less, the average value of the position +X′ or −X′ should be −10 μm or more and +10 μm or less, and the position +X or − When the average value of X is −10 μm or more and +10 μm or less, the average value of the position +X′ or −X′ should be +20 μm or more and +100 μm or less.

In the diaphragm for alkaline water electrolysis of the present invention, on one surface of the diaphragm (surface having a single membrane layer ), the average position of the surface of the resin composition layer relative to the surface of the porous support measured by the above method is +25 μm or more is preferable, +30 μm or more is more preferable, and +35 μm or more is even more preferable. Thereby, gas barrier property can be made more excellent. Also, the average position is preferably +80 μm or less, more preferably +70 μm or less, and even more preferably +60 μm or less. Thereby, ionic conductivity can be made more excellent.

In the diaphragm for alkaline water electrolysis of the present invention, on the other surface of the diaphragm (the surface without the single membrane layer ), the average position of the resin composition layer surface relative to the surface of the porous support measured by the above method is It is preferably −8 μm or more, more preferably −5 μm or more. Also, the average position is preferably +8 μm or less, more preferably +5 μm or less.

The diaphragm for alkaline water electrolysis of the present invention, which will be described in detail later, includes, for example, a step of forming a coating film from the resin composition according to the present invention, a step of impregnating a porous support with the resin composition, and a step of impregnating the resin composition. It can be obtained by a method including a step of solidifying the resin composition by contacting the porous support impregnated with the substance with a non-solvent. Usually, the single film layer is formed on the surface of the porous support on which the coating film is formed. Here, the average position of the surface of the resin composition layer with respect to the surface of the porous support on the surface having the single layer can be adjusted by adjusting the amount of the resin composition applied, the viscosity, the temperature of the non-solvent, and the like. can be adjusted as appropriate. In addition, the average position of the surface of the resin composition layer relative to the surface of the porous support on the surface without the single layer is determined by the amount and viscosity of the coated resin composition, and the hydrophilicity of the material of the porous support. After impregnating the porous support with the resin composition, it can be appropriately adjusted by adjusting the time until it is brought into contact with the non-solvent.

The constituent materials of the diaphragm for alkaline water electrolysis of the present invention will be described below, and then the method for producing the same will be described.

[Resin composition]
(organic polymer)
The resin composition according to the invention contains an organic polymer. The organic polymer usually retains the inorganic particles described later in the resin composition.
The organic polymer is not particularly limited as long as the effect of the present invention can be exhibited, but a polymer that does not substantially swell in an alkaline solution is more preferable.
From such a viewpoint, examples of the organic polymer include fluorine-based resins such as polyvinylidene fluoride and polytetrafluoroethylene; olefin-based resins such as polypropylene; aromatic hydrocarbon-based 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, aromatic hydrocarbon-based resins are preferable in that they can be used as a diaphragm for alkaline water electrolysis with further excellent heat resistance and alkali resistance.

More specifically, the aromatic hydrocarbon resins include, for example, polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylsulfone, polyarylate, polyether Examples include imides, polyimides, polyamideimides, and the like. Among them, at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone is preferable in terms of being able to impart even better alkali resistance. Ethersulfone is more preferred.
By using at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone, the obtained diaphragm for alkaline water electrolysis has higher ionic conductivity and higher alkali resistance. Therefore, the stability of dimensions and the like is excellent when used in an alkaline solution for a long period of time.

From the viewpoint of suitably adjusting the ionic conductivity and durability of the diaphragm, the mass ratio of the organic polymer is preferably 1% by mass or more, preferably 2% by mass, based on 100% by mass of the diaphragm for alkaline water electrolysis of the present invention. It is more preferably 3% by mass or more, still more preferably 5% by mass or more, and particularly preferably 7% by mass or more. In addition, the mass ratio is preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, and even more preferably 20% by mass or less, 15% by mass or less is particularly preferable.

(Inorganic particles)
The resin composition according to the present invention contains inorganic particles. By containing inorganic particles, the diaphragm for alkaline water electrolysis of the present invention can exhibit high ionic conductivity by filling the gaps between the inorganic particles and the organic polymer with the electrolytic solution. In addition, the diaphragm for alkaline water electrolysis of the present invention is made hydrophilic by containing inorganic particles, and it is possible to suppress a decrease in ionic conductivity due to adhesion of oxygen gas and hydrogen gas generated in the electrolysis of water to the diaphragm. can.

Examples of the inorganic particles include, but are not limited to, hydroxides or oxides of magnesium, zirconium, titanium, zinc, aluminum, tantalum, and sulfates of calcium, barium, lead, strontium, and the like. Among them, magnesium hydroxide, zirconium hydroxide, titanium hydroxide, zirconium oxide, titanium oxide, calcium sulfate, and barium sulfate are preferable in terms of dispersibility of inorganic particles and stability in an alkaline solution. Magnesium, zirconium oxide, titanium oxide and barium sulfate are more preferred.
The inorganic particles may be used singly or in combination of two or more.
The inorganic particles may be either natural or synthetic. Moreover, the surface may be untreated, or the surface may be treated with a silane coupling agent, stearic acid, oleic acid, phosphate ester, or the like.

The shape of the inorganic particles is not particularly limited as long as it is particulate, and can be classified into a spherical shape such as a perfect sphere and an oblong sphere; a plate shape such as a flaky shape and a hexagonal plate shape; a fibrous shape; , It may be in any shape such as an irregular shape having a complicated shape, but it is preferably spherical, plate-like, or fibrous because it is easy to disperse in a solvent and easy to prepare a resin composition. A plate-like shape is more preferable from the viewpoint of the ionic conductivity of the water electrolysis membrane and the retention of inorganic particles.

The inorganic particles preferably have an aspect ratio of 1.0 or more and 8.0 or less. The aspect ratio is more preferably 1.5 or more, still more preferably 2.0 or more. Also, the aspect ratio is more preferably 7.0 or less, still more preferably 6.0 or less. When the aspect ratio is within the above range, the diaphragm for alkaline water electrolysis has even more excellent ionic conductivity and excellent uniformity.
In this specification, the aspect ratio means the ratio (a/b) between the longest diameter a and the shortest diameter b, and the inorganic particles are observed with SEM, and in any 10 particles of the obtained image, analysis software etc., the ratio (a/b) between the longest diameter a and the shortest diameter b of each particle can be measured, and the simple average value of these ratios can be obtained as the aspect ratio of the particle.
As the longest diameter a, for example, when the shape of the particle is plate-like, the length of the plate surface of the particle is used, and when the particle is fibrous, the length of the fiber is used. The shortest diameter among the diameters passing through the midpoint of the longest diameter a and perpendicular to the longest diameter is defined as the shortest diameter b. As the shortest diameter b, for example, when the shape of the particles is plate-like, the thickness of the particles is used, and when the shape is fibrous, the thickness of the fibers is used. As the thickness of the particles and the thickness of the fibers, the thickness and thickness at the midpoint of the longest diameter a are employed, respectively.

The average particle size of the inorganic particles is preferably 0.01 μm or more and 2.0 μm or less in order to further improve the dispersibility of the inorganic particles. The average particle size is more preferably 0.05 μm or more, and still more preferably 0.08 μm or more. Also, the average particle size is more preferably 1.0 μm or less, and still more preferably 0.7 μm or less.
In the present specification, the average particle size is obtained from particle size distribution measurement by a laser diffraction/scattering method using an inorganic particle dispersion liquid that has been subjected to dispersion treatment using inorganic particles and a 0.2% by mass sodium hexametaphosphate aqueous solution. is the volume average particle size (d50). When the average particle size of the inorganic particles is within the above range, the diaphragm for alkaline water electrolysis can be made more excellent in ion conductivity and gas barrier properties.

The specific surface area of the inorganic particles is preferably 5 m ² /g or more and 35 m ² /g or less in order to further improve the ion conductivity of the diaphragm for alkaline water electrolysis. The specific surface area is more preferably 5.5 m ² /g or more, still more preferably 6 m ² /g or more. Also, the specific surface area is more preferably 25 m ² /g or less, still more preferably 20 m ² /g or less.
In this specification, the specific surface area is 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 mainly by the highly hydrophilic surfaces of the inorganic particles, when the specific surface area of the inorganic particles is within the above range, the ion conductivity for alkaline water electrolysis is even more excellent. It can be a diaphragm.

Particles having an average particle size and specific surface area in the above ranges are, for example, pulverized using a ball mill or the like, and the resulting coarse particles are dispersed in a dispersant to obtain a desired particle size, and then dried and solidified. In addition to the method of screening the coarse particles by sieving, etc., the preparation conditions are optimized at the stage of producing particles, and (nano)particles with the desired particle size can be obtained. is.

The mass ratio of the inorganic particles is preferably 30% by mass or more in 100% by mass of the diaphragm for alkaline water electrolysis of the present invention, from the viewpoint of improving the durability and ionic conductivity of the diaphragm. The mass ratio is more preferably 32% by mass or more, and still more preferably 35% by mass or more. Moreover, the mass ratio is preferably 95% by mass or less. The mass ratio is more preferably 90% by mass or less, still more preferably 80% by mass or less, and particularly preferably 65% by mass or less.

[Porous support]
The diaphragm for alkaline water electrolysis of the present invention further has a porous support. The porous support is a member that is porous, has ion permeability, and can serve as a support for a diaphragm for alkaline water electrolysis. The porous support is preferably a sheet-like member.

Examples of materials for the porous support include polyarylene sulfide resins such as polyethylene, polypropylene, polysulfone, polyethersulfone, polyphenylsulfone, and polyphenylene sulfide, and resins such as polyketone, polyimide, polyetherimide, and fluorine-based resins. mentioned. These may be used individually by 1 type, and may be used in combination of 2 or more type. 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 is selected from the group consisting of polypropylene and polyphenylene sulfide. It is more preferred to include at least one resin that

Examples of the form of the porous support include nonwoven fabric, woven fabric (fabric), knitted fabric, mesh, porous membrane, felt, and mixed fabric of nonwoven fabric and woven fabric. Nonwoven fabric is preferred. , woven fabric, mesh or felt, more preferably non-woven fabric or mesh.

The porous support used in the present invention preferably contains at least one resin selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide. Among these, polypropylene, polyethylene, and polyphenylene sulfide. Non-woven fabric, woven fabric, mesh or felt containing at least one resin selected from the group consisting of is more preferred, and non-woven fabric, mesh or felt containing polyphenylene sulfide is even more preferred. 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, and even more preferably 90% by mass or more. In addition, the upper limit of the content is not particularly limited, and may be 100% by mass.

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. preferable. The thickness is more preferably 50 µm or more, still more preferably 80 µm or more, and particularly preferably 100 µm or more. Moreover, the thickness is more preferably 280 μm or less, still more preferably 260 μm or less, and particularly preferably 250 μm or less.
The thickness of the porous support is measured using the method of Examples.

The mass ratio of the porous support is preferably 20% by mass or more, more preferably 25% by mass or more, and 30% by mass or more in 100% by mass of the diaphragm for alkaline water electrolysis of the present invention. is more preferable, and 35% by mass or more is particularly preferable. The mass ratio is preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% by mass or less.

(other ingredients)
The diaphragm for alkaline water electrolysis of the present invention further contains, as additive components, water-soluble polymers such as polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyethyleneimine, polyacrylic acid and dextran; surfactants; glycerin; organic compounds such as saccharides. , calcium chloride, magnesium chloride, lithium chloride, and other inorganic compounds.
From the viewpoint of durability of the diaphragm, the content of other components in the diaphragm for alkaline water electrolysis of the present invention is preferably 5% by mass or less in 100% by mass of the diaphragm. It is more preferably 2% by mass or less, still more preferably 1% by mass or less, and particularly preferably 0.1% by mass or less.

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. It is preferably 50 μm or more and 1 mm or less. The thickness is more preferably 75 μm or more, still more preferably 100 μm or more, and particularly preferably 150 μm or more. Further, the thickness is more preferably 800 μm or less, still more preferably 600 μm or less, and particularly preferably 400 μm or less.
The thickness of the diaphragm for alkaline water electrolysis is measured using the method of the examples.

The diaphragm for alkaline water electrolysis of the present invention preferably has a porosity of 25% or more and 80% or less. The porosity is more preferably 30% or more, still more preferably 35% or more, and particularly preferably 38% or more, from the viewpoint of improving the ionic conductivity. Moreover, the porosity is more preferably 75% or less, still more preferably 70% or less, and particularly preferably 65% or less, from the viewpoint of improving gas barrier properties.
The porosity can be measured according to the method described in Examples.

The diaphragm for alkaline water electrolysis of the present invention preferably has an air contact angle in water of 140° or more on each of one surface and the other surface. The contact angle of air in water is more preferably 143° or more, still more preferably 145° or more, and particularly preferably 148° or more. Although the upper limit of the contact angle of air in water is not particularly limited, it is usually 175° or less. When the contact angle of air in water is within the above range, a diaphragm can be obtained in which adhesion of bubbles of oxygen gas or hydrogen gas to the surface of the diaphragm is extremely suppressed.
In the diaphragm for alkaline water electrolysis of the present invention, the difference in contact angle of air in water between one surface and the other surface is preferably 10° or less, more preferably 4° or less.
The contact angle of air in water can be measured according to the method described in Examples.

The diaphragm for alkaline water electrolysis of the present invention preferably has an ionic conductivity of 100 mS/cm or more and 300 mS/cm or less. The ionic conductivity is more preferably 110 mS/cm or more, even more preferably 120 mS/cm or more. Further, the ionic conductivity is more preferably 270 mS/cm or less, even more preferably 250 mS/cm or less. When the ionic conductivity is within the above range, the electrolysis efficiency in water electrolysis is high, and gas cross-leakage can be suppressed to a low level.
The ionic conductivity can be measured according to the method described in Examples.

The diaphragm for alkaline water electrolysis of the present invention preferably has a bubble point value of 300 kPa or more from the viewpoint of enhancing gas barrier properties. The bubble point value is more preferably 400 kPa or more, even more preferably 500 kPa or more. The upper limit of the bubble point value is not particularly limited, but it is usually 3000 kPa or less.
The bubble point value can be measured according to the method described in Examples.

The diaphragm for alkaline water electrolysis of the present invention is intended for use as a diaphragm for use in an alkaline water electrolysis apparatus containing an aqueous electrolytic solution.

(Manufacturing method of the diaphragm for alkaline water electrolysis of the present invention)
The method for producing the diaphragm for alkaline water electrolysis of the present invention is not particularly limited, and known methods can be applied. A non-solvent induced phase separation method and a vapor induced phase separation method are preferred in that they can efficiently produce a diaphragm for alkaline water electrolysis with excellent properties.
Specifically, the method for producing the alkaline water electrolysis membrane preferably includes the following steps (1) to (3).
(1) preparing a dispersion containing inorganic particles and a solvent;
(2) mixing the dispersion and the organic polymer to prepare a resin mixture;
(3) Steps of forming a film using the resin mixed solution Each step will be explained below.

(1) Step of preparing a dispersion containing inorganic particles and a solvent In the above production method, when the inorganic particles are mixed with the organic polymer, the inorganic particles may be mixed in solid form, or the inorganic particles may be dispersed in the solvent. Although a dispersion (slurry) may be prepared and then mixed, it is preferable to prepare a dispersion in which inorganic particles are dispersed in a solvent and then mix. By mixing the inorganic particles with the organic polymer after preparing the dispersion of the inorganic particles, the inorganic particles and the organic polymer can be mixed more uniformly, thereby forming partition walls in which the inorganic particles are formed by the organic polymer. It is possible to obtain a diaphragm for alkaline water electrolysis in which the inorganic components are uniformly distributed and immobilized inside and the elution of inorganic components is more sufficiently suppressed. A dispersant may be added to the dispersion liquid.
The content of the inorganic particles in the dispersion liquid is preferably 20% by mass or more and 70% by mass or less. The content of the inorganic particles is more preferably 30% by mass or more, still more preferably 45% by mass or more. Moreover, the content of the inorganic particles is more preferably 65% by mass or less. By doing so, the diameter of the micropores in the finally obtained membrane can be controlled, and a diaphragm for alkaline water electrolysis having both ion conductivity and gas barrier properties can be obtained.

The solvent for dispersing the inorganic particles is not particularly limited as long as it has the property of dissolving the above organic polymer to be mixed later. Examples include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, methyl ethyl ketone, toluene and the like. These solvents may be used singly or in combination of two or more. Among them, N-methyl-2-pyrrolidone and N,N-dimethylformamide are preferable from the viewpoint of good dispersibility of the inorganic particles. The amount of the solvent used for the inorganic particles in the dispersion is preferably 50 parts by mass or more and less than 100 parts by mass, more preferably 50 parts by mass or more and 90 parts by mass or less, and 50 parts by mass or more and 80 parts by mass with respect to 100 parts by mass of the inorganic particles. More preferably less than parts by mass. By doing so, the diameter of the micropores of the finally obtained membrane can be controlled, and a diaphragm for alkaline water electrolysis having both ion conductivity and gas barrier properties can be obtained.

Dispersants include water-soluble polymers such as polyvinylpyrrolidone, polyethylene glycol, polyethyleneimine, polyacrylic acid, dextran; ethylene glycol: cationic surfactant; anionic surfactant; carboxy group, phosphoric acid group, sulfonic acid group conventionally known pigment dispersants having functional groups such as The amount of the dispersant used in the solvent in the dispersion is preferably more than 1 part by mass and 10 parts by mass or less, more preferably 1.2 parts by mass or more and 8 parts by mass or less, with respect to 100 parts by mass of the solvent, and 1.5 parts by mass. Part or more and less than 5 parts by mass is more preferable. By doing so, it becomes possible to control and improve the particle size of the inorganic particles in the dispersion liquid and the dispersion stability of the inorganic particles in the diaphragm forming step, and the fine pore size of the finally obtained membrane can be improved. can be controlled, and a diaphragm for alkaline water electrolysis having both ion conductivity and gas barrier properties can be obtained.

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, ball mill, jet mill, disper, sand mill, roll mill, pot mill, bead mill, paint shaker, etc. are applied. be able to.

The average particle size of the inorganic particles in the dispersion is more preferably 0.1 μm or more and 1.0 μm or less, still more preferably 0.15 μm or more and 0.8 μm or less, and particularly preferably 0.15 μm or more and 0.5 μm or less. . The average particle size of the inorganic particles in the dispersion can be determined by particle size distribution measurement using a dynamic light scattering method, and can be specifically measured by the method described in Examples.

(2) Step of mixing the dispersion and the organic polymer to prepare a resin mixture As a method of mixing the organic polymer with the dispersion prepared in step (1), the dispersion and the organic polymer are mixed sufficiently. It is not particularly limited as long as it can be mixed into the dispersion liquid, and the organic polymer may be mixed as it is in the dispersion liquid, or a resin solution in which the organic polymer is dissolved in a solvent is prepared in advance, and the resin solution and the dispersion liquid are prepared. may be mixed with. Among them, the method of preparing a resin solution and mixing the resin solution and the dispersion liquid is preferable because the inorganic particles and the organic polymer can be dispersed and mixed more uniformly.
The solvent used for preparing the resin solution is not particularly limited as long as it has the property of dissolving the organic polymer. Examples include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, 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 liquid is preferable in that the inorganic particles and the organic polymer can be more uniformly dispersed and mixed.

The content of the organic polymer in the resin solution is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 45% by mass or less, and 15% by mass or more and 40% by mass or less. is more preferable.
Examples of the mixing method include the same means as the mixing and dispersing means described in step (1).

The dispersion liquid and the organic polymer are preferably mixed so that the amount of the organic polymer is 10 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the inorganic particles. The amount of the organic polymer to be mixed is more preferably 12 parts by mass or more, and still more preferably 15 parts by mass or more. Further, the amount of the organic polymer mixed is more preferably 35 parts by mass or less, and still more preferably 33 parts by mass or less. When the content ratio of the inorganic particles and the organic polymer is within the range described above, the elution of the inorganic component in the obtained diaphragm for alkaline water electrolysis in the alkaline solution is further suppressed. In addition, it is possible to produce a diaphragm for alkaline water electrolysis that is more excellent in ion conductivity, gas barrier properties, heat resistance and alkali resistance.

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

A compound soluble in both the solvent of the resin mixture and the non-solvent of the organic polymer may be added to the resin mixture as an additive for the purpose of adjusting the average pore size of the diaphragm. Examples of the additives include water-soluble polymers such as polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyethyleneimine, polyacrylic acid, and dextran; surfactants; glycerin; organic compounds such as sugars; calcium chloride, magnesium chloride, and chloride; inorganic compounds such as lithium.

(3) Step of Forming a Film Using the Resin Mixture A film is formed using the resin mixture obtained in step (2).
As the method for forming the membrane, the following steps (3-a), ( 3-b) is preferably included.
(3-a) forming a coating film of the resin mixture, and
(3-b) Step of Contacting the Coating Film with a Non-Solvent to Solidify the Coating Film to Obtain a Porous Film Each step will be described below.

(3-a) Step of forming a coating film of the resin mixed solution Examples of the method of forming the coated film of the resin mixed solution include a method of applying the resin mixed solution obtained above on a substrate, and a method of applying the resin mixed solution obtained above on a substrate. A method of obtaining a substrate impregnated with the resin mixture by immersing the substrate in the resin mixture can be used. Among them, the method of applying the above-mentioned resin mixed solution onto a base material is preferable in that a 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 methods using die coating, spin coating, gravure coating, curtain coating, spray, applicator, bar coater, etc. are applied. can do.

The substrate is not particularly limited as long as it can be coated with the resin mixture to form a coating film. Examples include polyethylene terephthalate, polyethylene naphthalate, polypropylene, polyethylene, polyvinyl chloride, and polyvinyl. A film or sheet made of a resin such as acetal, polymethyl methacrylate, polycarbonate, or the like, a glass plate, or the like can be used. Among them, polyethylene terephthalate is preferable because it is easy to handle and the material cost can be reduced. In the production of the diaphragm for alkaline water electrolysis, which is a composite in which the coating film and the porous support are integrated, the resin mixed solution is applied onto the base material, and the porous support is applied onto the coating solution. A method of impregnating the porous support with the coating liquid by placing the body on the support may be used.
Alternatively, the porous support may be used as the substrate, a coating film may be formed on the porous support, and the porous support may be impregnated with the resin mixture.
The amount of the resin mixed solution to be applied is not particularly limited, and may be appropriately set so that the diaphragm has a thickness capable of exhibiting the above-described effects.

(3-b) A step of contacting the coating film with a non-solvent to solidify the coating film By contacting the coating film with the non-solvent, the non-solvent diffuses in the coating film and dissolves in the non-solvent. Do not allow the organic polymer to solidify. On the other hand, the solvent in the coating film that is soluble in the non-solvent is eluted from the coating film. When the phase separation occurs in this way, the organic polymer (and inorganic particles) is solidified to form the diaphragm for alkaline water electrolysis of the present invention.
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), and a method of exposing the coating film to the non-solvent vapor atmosphere.
The non-solvent is not particularly limited as long as it does not substantially dissolve the organic polymer. Examples include water such as ion-exchanged water; lower alcohols such as methanol, ethanol, and isopropyl alcohol; Among them, ion-exchanged water is preferable from the viewpoint of economy and waste liquid treatment. In addition to the components described above, 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 parts by mass or more and 10000 parts by mass or less 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 parts by mass or more and 5000 parts by mass or less, and still more preferably 200 parts by mass or more and 1000 parts by mass or less. It is preferable to use the non-solvent in such a ratio in order to adjust the porosity of the membrane to be obtained within a preferable range and to completely extract the solvent in the coating film into the non-solvent.
Furthermore, in order to remove the non-solvent, the coating film solidified in the above step may be dried to obtain the diaphragm.
The drying temperature for 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, even more preferably 1 to 30 minutes.
As described above, the diaphragm for alkaline water electrolysis of the present invention can be easily produced by the steps (1) to (3) described above.

<Alkaline water electrolysis device>
An alkaline water electrolysis device comprising the diaphragm for alkaline water electrolysis of the present invention is also one aspect of the present invention.
The diaphragm for alkaline water electrolysis of the present invention is one in which inorganic components are less likely to elute in an alkaline solution, and is excellent in alkali resistance. In addition, both higher ion conductivity and higher gas barrier properties are achieved. Therefore, the diaphragm for alkaline water electrolysis of the present invention can be suitably used as a diaphragm for water electrolysis using an alkaline aqueous solution as an electrolyte. An alkaline water electrolysis apparatus including such a diaphragm for alkaline water electrolysis of the present invention can exhibit effects based on the diaphragm for alkaline water electrolysis.

The diaphragm for alkaline water electrolysis of the present invention is suitably 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 of the present invention arranged between the anode and the cathode. More specifically, the alkaline water electrolysis apparatus of the present invention has an anode chamber having an anode and a cathode chamber having a cathode separated by the diaphragm for alkaline water electrolysis of the present invention.
The anode and the cathode are not particularly limited, and known electrodes can be used. For example, those containing a conductive substrate containing nickel or a nickel alloy can be used.

[Electrolysis method of water electrolysis device]
The method of electrolyzing water using the alkaline water electrolysis apparatus including 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 including 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 used. Although the concentration of the electrolyte in the electrolytic solution is not particularly limited, it is preferably 20 to 40% by mass from the viewpoint of further improving the electrolysis efficiency.
The temperature for electrolysis is preferably 50 to 120° C., more preferably 70 to 90° C., since the ion conductivity of the electrolytic solution can be further improved and the electrolysis efficiency can be further improved. Current application conditions can be performed by known conditions and methods.

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 "part by weight" and "%" means "% by mass".

<Average particle size of raw material inorganic particles (powder)>
A laser diffraction/scattering particle size distribution analyzer (product Name: LA-920, manufactured by Horiba Ltd.) was used to measure the particle size distribution, and the median diameter (d50) in the obtained volume-based particle size distribution was defined as the average particle size (μm) of the inorganic particles.

<Specific surface area of inorganic particles>
The specific surface area of the inorganic particles was measured using a BET specific surface area meter (trade name: Macsorb HM model-1210, manufactured by Mountec). Specifically, inorganic particles (powder) as a measurement sample were placed in a cell, and deaeration treatment was performed at 200° C. while nitrogen gas was circulated in the cell. After the degassing treatment, the cell was immersed in liquid nitrogen while nitrogen gas was circulated in the cell to adsorb nitrogen onto the measurement sample at a temperature of -196°C. Next, the specific surface area was measured by the BET method by keeping the cell at room temperature and measuring the amount of desorbed nitrogen. The measurement was performed three times for each sample, and the average value was taken as the specific surface area (m ² /g) of the inorganic particles.

<Aspect ratio of inorganic particles>
An observation image of the inorganic particles (powder) was obtained with a scanning electron microscope (FE-SEM, trade name: JSM-7600F, manufactured by JEOL Ltd.) at a magnification of 20,000. Using analysis software (Image-Pro Premier), the ratio (a/b) between the longest diameter a and the shortest diameter b of each particle was measured for any 10 particles in the obtained image, and the ratio of these ratios was calculated. An addition average was calculated and taken as the aspect ratio of the inorganic particles.
As the longest diameter a, for example, when the shape of the particle is plate-like, the length of the plate surface of the particle is used, and when the particle is fibrous, the length of the fiber is used. The shortest diameter among the diameters passing through the midpoint of the longest diameter a and perpendicular to the longest diameter is defined as the shortest diameter b. 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 used, and when the particles are fibrous, the thickness of the fibers is used. As the thickness of the particles and the thickness of the fibers, the thickness and thickness at the midpoint of the longest diameter a were used, respectively.

<Average particle size of inorganic particles in inorganic particle dispersion>
0.1 part by mass of the obtained inorganic particle dispersion was diluted with 2 parts by mass of a dispersion medium, and the diluted solution of the inorganic particle dispersion was measured with a particle size distribution analyzer (trade name: FPAR-1000, Otsuka Electronics) using a dynamic light scattering method. Co., Ltd.), the particle size of the inorganic particles dispersed in the inorganic particle dispersion is measured, and the average particle size obtained by the cumulant method analysis is the average particle size of the inorganic particles dispersed in the inorganic particle dispersion. did.

<Thickness of porous support>
The porous support was measured at arbitrary 10 points using a digimatic micrometer (manufactured by Mitutoyo), and the average value was calculated as the thickness of the porous support.

<Average Position on Resin Composition Layer Surface and Separator Thickness Based on Porous Support Surface>
For five measurement points, the following method was used to determine the reference line A, the filling line B, the X value that is the distance between the reference line A and the filling line B, and the resin composition layer surface based on the surface of the porous support. position +X or -X, reference line A', filling line B', X' value which is the distance between reference line A' and filling line B', resin composition layer surface based on porous support surface position +X' or -X' was obtained. Also, the thickness T of the diaphragm was obtained from the distance between the filling line B and the filling line B'. The average value of the positions +X or -X and the average value of the positions +X' or -X' are the average values of five measurement points.

<Reference line A>
One surface of the obtained diaphragm for alkaline water electrolysis is cut perpendicularly, and the cross section obtained by ion milling the cut surface is examined with a scanning electron microscope for a region having a width of 160 μm. An 800-fold magnified photograph was taken using the camera. The field of view was set to be 20% or more of the total thickness of the diaphragm from the surface of one side of the diaphragm.
Of the porous support portion in the obtained enlarged photograph, the point closest to the surface of the diaphragm in the region on the left side of the midpoint in the width direction and the point closest to the surface of the diaphragm in the region on the right side of the midpoint A straight line having a length of 120 μm or more in the width direction between both ends was defined as a reference line A. The point closest to the surface of the diaphragm is the point at the end of the porous support portion closest to the surface when the surface of the diaphragm is composed of a resin composition, and the surface of the diaphragm is porous. When it is composed of the ends of the support portion, the end portion of the porous support portion constituting the surface of the diaphragm is the closest point to the surface of the diaphragm (the distance from the surface of the diaphragm is 0), so the diaphragm is any point at the end of the porous support portion that constitutes the surface of the

<Filling line B>
When a line parallel to the reference line A is scanned sequentially from the side opposite to the surface side of the reference line A to the surface side of the reference line A, the space portion (nonwoven fabric fiber A filling line B was defined as a boundary line where the filling portion where the ratio of the total length of the porous substrate and the composition (such as a portion without the porous substrate and the composition) is 10% or less. When there are two or more filling portions, the filling line B is the line closest to the reference line A among the boundary lines where the filling portions end.

<X value and position of the surface of the resin composition layer relative to the surface of the porous support>
The distance between the reference line A and the filling line B was calculated from the photographed image as the X value. The position of the resin composition layer surface with respect to the surface of the porous support is -X when the filling line B is in front of the reference line A (inside the membrane) in the scanning direction of the parallel lines, and the reference +X was given when exceeding line A (outside the membrane).
Next, after moving the field of view in the thickness direction toward the other surface, the reference line A' and the filling line B' are obtained in the same manner for the other surface. The position +X' or -X' of the surface of the resin composition layer based on the surface was determined.

<Thickness of Diaphragm>
The reference line A, the fill line B, the distance X between them, the positional relationship between the reference line A and the fill line B on one surface, and the reference line A', the fill line B', and the distance between them on the other surface After obtaining the distance X' and the positional relationship between the reference line A' and the filling line B', the magnification is lowered in the thickness direction until the entire diaphragm can be confirmed, and the reference lines B and B' are determined. was calculated from the photographed image as the thickness T of the diaphragm.

<Porosity>
The porosity of the obtained diaphragm for alkaline water electrolysis was calculated from the calculated density value calculated from the composition ratio using the measured density value of the diaphragm measured by the method shown below and the density value of each composition component, as shown below. Calculated from the formula.
Porosity (%) = [1 - (measured density value) / (calculated density value)] × 100
The measured density value was calculated by measuring the mass and volume of a test piece cut out from an arbitrary location of the obtained diaphragm and dividing the mass by the volume. The volume was calculated by measuring the vertical and horizontal lengths of the test piece using vernier calipers, and measuring the film thickness based on the film thickness measurement method described above. In addition, the mass of the test piece was measured using a precision balance with 4 decimal places for the test piece whose volume was measured.

<Contact angle of air in water>
The contact angle of air in water on the surface of the obtained diaphragm for alkaline water electrolysis was measured by immersing the diaphragm in pure water at 23° C. and then using a three-phase kit (manufactured by Kyowa Interface Science Co., Ltd.). About 2 μl of air bubbles (air) are attached to the surface of the diaphragm, and the contact angle is measured 30 seconds after the air bubbles are attached using a contact angle meter (solid-liquid interface analyzer DropMaster 700, manufactured by Kyowa Interface Science Co., Ltd.). was measured using Here, CA (X) is the contact angle of air in water on the surface for which the X value was obtained in the measurement of the average position of the resin composition layer surface with respect to the porous support surface, and the surface for which the X' value was obtained. The contact angle of air in water was defined as CA(X'), and each contact angle was obtained.

<Ionic conductivity>
After leaving the cell formed with the following cell configuration in a constant temperature bath at 25° C. for 30 minutes, AC impedance measurement was performed under the following measurement conditions. Using the intercept component (Rb) and the film thickness obtained by the above film thickness measurement method, the ion conductivity was calculated as the average value of two measurement points according to the following formula.
[Ionic conductivity (mS / cm)] = [film thickness (cm)] ÷ [(Ra-Rb) × 1000 × 1.77]
(Measurement condition)
・Cell configuration Working electrode: Ni plate Counter electrode: Ni plate Electrolyte solution: 30% by mass potassium hydroxide aqueous solution Sample pretreatment: immersed overnight in the above electrolyte solution Effective area for measurement: 1.77 cm ²
- AC impedance measurement conditions Applied voltage: 10 mV vs. Open circuit voltage Frequency range: 100kHz to 100Hz

<bubble point value>
The bubble point value of the obtained diaphragm for alkaline water electrolysis was measured using a liquid porosimeter (manufactured by Porous Materials). Specifically, a diaphragm of 2.5 cmφ was immersed in deionized water at room temperature for 1 hour to be sufficiently wet, and then the diaphragm was filled with Galwick (manufactured by Porous Materials), which is a fluorine-based solvent. The gas pressure against the diaphragm was increased, and the gas pressure at the time when the liquid film of water was broken, Galwick permeated the film, and the weight was observed with a balance was taken as the bubble point value.
A larger bubble point value indicates a higher effect of suppressing gas permeation.

[Preparation Example 1]
200 parts by mass of magnesium hydroxide particles (plate-like, average particle size 0.36 μm, specific surface area: 10 m ² /g, aspect ratio 4.7), N-methyl-2-pyrrolidone (manufactured by Mitsubishi Chemical Corporation) 150 parts by mass, 5 parts by mass of polyvinylpyrrolidone was mixed as a dispersant, and zirconia beads were used to perform dispersion treatment in a bead mill for 30 minutes, after which the zirconia beads were removed to obtain a magnesium hydroxide particle dispersion. The average particle size of the magnesium hydroxide particles in the resulting magnesium hydroxide particle dispersion was 280 nm.
200 parts by mass of the obtained magnesium hydroxide particle dispersion, polysulfone resin (trade name: Ultrason S3010, manufactured by BASF) at a concentration of 35% by mass at 80 to 100 ° C. N-methyl-2-pyrrolidone (Mitsubishi Chemical 100 parts by mass of the polysulfone resin solution obtained by thermally dissolving it in (manufactured by Thinky Corporation) is weighed and rotated at room temperature using a rotation and revolution mixer (trade name: Awatori Mixer ARE-500, manufactured by Thinky Corporation). After mixing for about 10 minutes at several thousand min ⁻¹ , filtration was performed to obtain a film-forming composition.

[Preparation Example 2]
200 parts by mass of magnesium hydroxide particles (plate-like, average particle size 0.36 μm, specific surface area: 10 m ² /g, aspect ratio 4.7), N-methyl-2-pyrrolidone (manufactured by Mitsubishi Chemical Corporation) 150 parts by mass, 5 parts by mass of polyvinylpyrrolidone was mixed as a dispersant, and zirconia beads were used to perform dispersion treatment in a bead mill for 30 minutes, after which the zirconia beads were removed to obtain a magnesium hydroxide particle dispersion. The average particle size of the magnesium hydroxide particles in the resulting magnesium hydroxide particle dispersion was 280 nm.
200 parts by mass of the obtained magnesium hydroxide particle dispersion, polysulfone resin (trade name: Ultrason S3010, manufactured by BASF) at a concentration of 35% by mass at 80 to 100 ° C. N-methyl-2-pyrrolidone (Mitsubishi Chemical 100 parts by mass of polysulfone resin solution and 45 parts by mass of N-methyl-2-pyrrolidone (manufactured by Mitsubishi Chemical Co., Ltd.) obtained by thermally dissolving them in (manufactured by Mitsubishi Chemical Corporation) were weighed and ARE-500 (manufactured by Thinky Corporation), the mixture was mixed at room temperature at a rotational speed of 1000 min ⁻¹ for about 10 minutes, and then filtered to obtain a film-forming composition.

[Example 1]
The film-forming composition obtained in Preparation Example 1 was applied to a polyethylene terephthalate (PET) film with an applicator so that the basis weight was 22 mg/cm ² , and a nonwoven fabric made of polyphenylene sulfide fibers (basis weight: 100 g/m ² , thickness: 205 μm), the nonwoven fabric was completely impregnated with the film-forming composition. Thereafter, the nonwoven fabric impregnated with the film-forming composition is subjected to a water bath at room temperature for 10 minutes to solidify the coating film, and then the coating film is peeled off from the PET film together with the nonwoven fabric in water to obtain magnesium hydroxide particles. , polysulfone resin and a non-woven fabric were obtained. The obtained membrane was dried at 80° C. for 30 minutes in a dryer to obtain a diaphragm for alkaline water electrolysis.

The obtained diaphragm for alkaline water electrolysis had a thickness (T) of 245 μm, an average value of position X on the surface of the resin composition layer based on the surface of the porous support was −5 μm, an average value of X′ was +41 μm, and porosity. was 51%, the air contact angle CA(X) in water was 157°, CA(X') was 160°, the ionic conductivity was 150 mS/cm, and the bubble point value was 620 kPa.

[Example 2]
The film-forming composition obtained in Preparation Example 2 was applied to a polyethylene terephthalate (PET) film with an applicator so that the basis weight was 28 mg/cm ² . /m ² , thickness: 205 μm), the nonwoven fabric was completely impregnated with the film-forming composition. Thereafter, the nonwoven fabric impregnated with the film-forming composition is subjected to a water bath at room temperature for 10 minutes to solidify the coating film, and then the coating film is peeled off from the PET film together with the nonwoven fabric in water to obtain magnesium hydroxide particles. , polysulfone resin and a non-woven fabric were obtained. The obtained membrane was dried at 80° C. for 30 minutes in a dryer to obtain a diaphragm for alkaline water electrolysis.
The obtained diaphragm for alkaline water electrolysis had a thickness T of 249 μm, an average value of position X on the surface of the resin composition layer based on the surface of the porous support of +3 μm, an average value of X′ of +38 μm, and a porosity of 49%. , the air contact angle CA(X) in water was 158°, CA(X') was 162°, the ionic conductivity was 145 mS/cm, and the bubble point value was 650 kPa.

[Comparative Example 1]
The film-forming composition obtained in Preparation Example 1 was applied to a polyethylene terephthalate (PET) film with an applicator so that the basis weight was 24 mg/cm ² , and a nonwoven fabric made of polyphenylene sulfide fibers (basis weight: 100 g/m ² , thickness: 205 μm), and immediately after that, the coating film was solidified by water bathing at room temperature for 10 minutes. Thereafter, the coated film was peeled off from the PET film together with the nonwoven fabric in water to obtain a water-containing film composed of magnesium hydroxide particles, polysulfone resin and nonwoven fabric. The obtained membrane was dried at 80° C. for 30 minutes in a dryer to obtain a diaphragm for alkaline water electrolysis.
The obtained diaphragm for alkaline water electrolysis had a thickness T of 256 μm, an average value of position X on the surface of the resin composition layer relative to the surface of the porous support was −18 μm, an average value of X′ was +52 μm, and the porosity was 55. %, the air contact angle CA(X) in water was 140°, CA(X') was 159°, the ionic conductivity was 120 mS/cm, and the bubble point value was 270 kPa.

[Comparative Example 2]
The film-forming composition obtained in Preparation Example 2 was applied onto a polyethylene terephthalate (PET) film with an applicator so that the weighing value was 26 mg/cm ² , and the resin composition layer was placed on top for comparison. The diaphragm for alkaline water electrolysis obtained in Example 1 was brought into contact and impregnated with the film-forming composition. After that, the membrane impregnated with the film-forming composition is subjected to a water bath at room temperature for 10 minutes to solidify the coating film, and then the coating film is peeled off from the PET film together with the nonwoven fabric in water. Magnesium hydroxide obtained. A diaphragm for alkaline water electrolysis having layers of magnesium hydroxide particles and polysulfone resin on both sides was obtained by drying the water-containing membrane composed of the particles, polysulfone resin and non-woven fabric in a dryer at 80° C. for 30 minutes.
The obtained diaphragm for alkaline water electrolysis had a thickness T of 264 µm, an average position X of the resin composition layer surface relative to the surface of the porous support of +25 µm, an average X' of +45 µm, and a porosity of 53%. , the air contact angle CA(X) in water was 152°, CA(X') was 156°, the ionic conductivity was 56 mS/cm, and the bubble point value was 460 kPa.

From the above results, on one surface, the average position of the resin composition layer surface relative to the surface of the porous support is +20 μm or more and +100 μm or less, and on the other surface, the average position is −10 μm or more and +10 μm. In the diaphragms for alkaline water electrolysis of Examples 1 and 2 prepared as follows, on the other surface, the position of the resin composition layer surface relative to the surface of the porous support was -10 μm from the inside of the membrane. Compared with the diaphragm for alkaline water electrolysis of Comparative Example 1, which was prepared to be One thing was recognized. Furthermore, it was confirmed that the bubble point value is high, gas permeation is suppressed, and high ionic conductivity is exhibited.
In addition, in the diaphragms for alkaline water electrolysis of Examples 1 and 2, on the other surface, the position of the resin composition layer surface relative to the surface of the porous support was prepared so that it was outside the membrane beyond +10 μm. In comparison with the diaphragm for alkaline water electrolysis of Example 2, the contact angle and bubble point values on both surfaces of the diaphragm show that the gas adhesion on both sides of the diaphragm is equivalent, but the effect of suppressing gas permeation and ionic conductivity are higher. A high diaphragm was observed.
The reason why the diaphragm for alkaline water electrolysis of Comparative Example 2 has a lower gas barrier property than those of Examples 1 and 2, although the diaphragm for alkaline water electrolysis is substantially formed with single membrane layers on both sides, is as follows. The following reasons are conceivable. That is, since the diaphragm of Comparative Example 2 uses the diaphragm for alkaline water electrolysis obtained in Comparative Example 1 as a base material, the polysulfone once solidified is partially redissolved by contact with the paint. Therefore, in Comparative Example 2, solidification of the polysulfone of the original paint and solidification of the redissolved polysulfone occurred, but in the portion where the polysulfone was redissolved, the originally formed microstructure was once destroyed and formed by the microstructure. This is considered to be due to the change in the diameter of the pores that had been formed (increased, as can be inferred from the results).

Claims (2)

A diaphragm used for alkaline water electrolysis,
The diaphragm has a porous support and a resin composition layer obtained by impregnating the porous support with a resin composition containing an organic polymer and inorganic particles. The average position of the resin composition layer surface relative to the surface of the porous support is +20 μm or more and +100 μm or less, and the average position of the other surface of the diaphragm is −10 μm or more and +10 μm or less. A diaphragm for alkaline water electrolysis, characterized by:
Method for measuring the average position of the surface of the resin composition layer relative to the surface of the porous support:
(1) A cross section obtained by cutting perpendicularly to one surface of the diaphragm and ion milling the cut surface is examined using a scanning electron microscope, and the length in the width direction is 160 μm. Select five regions of
(2) The porous support in the region on the left side of the midpoint in the width direction on the one surface side of the diaphragm on the enlarged photograph of the one surface portion of the diaphragm taken using a scanning electron microscope for each region and the edge of the porous support in the region on the right side of the midpoint in the width direction, and a straight line having a length of 120 μm or more in the width direction between both ends is defined as a reference line A.
(3) On the enlarged photograph of (2), when the parallel line of the reference line A is scanned from the side opposite to the one surface side of the diaphragm to the one surface side of the diaphragm, the length of the parallel line A filling line B is defined as a boundary line where a filling portion having a ratio of the total length of the space portion on the parallel line of 10% or less ends.
(4) A distance X between the reference line A and the filling line B is calculated. The position of the resin composition layer surface relative to the surface of the porous support is -X when the filling line B is in front of the reference line A in the scanning direction of the parallel lines, and +X when it exceeds the reference line A. and
(5) For each region, select any five regions in the same manner as in (1) in the enlarged photograph of the surface portion on the opposite side of the one surface of the diaphragm taken using a scanning electron microscope. , in each region, the reference line A' and the filling line B' are obtained in the same manner as in (2) to (4), the distance X' between the reference line A' and the filling line B' is calculated, and the porous support surface Determine the position +X' or -X' on the surface of the resin composition layer based on .
(6) the average value of the position +X or -X on the surface of the resin composition layer based on the surface of the porous support for each region, and the resin composition layer based on the surface of the porous support for each region The average value of the surface position +X' or -X' is defined as the average position of the resin composition layer surface relative to the surface of the porous support on each surface. An alkaline water electrolysis apparatus comprising the diaphragm for alkaline water electrolysis according to claim 1 .

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