TWI829046B - Base material for alkaline water electrolysis separator and alkaline water electrolysis separator - Google Patents

Abstract

The present invention provides a base material for an alkaline water electrolysis separator made of a material with high mechanical strength, etc., and by using the base material for an alkaline water electrolysis separator, it provides an alkaline water electrolysis separator having both low conductive resistance, gas barrier properties, etc. Alkaline water electrolysis separator. The present invention relates to a base material for an alkaline water electrolysis separator and an alkaline water electrolysis separator containing the base material for an alkaline water electrolysis separator and a porous membrane of a polymer resin. Characteristics of the aforementioned base material for an alkaline water electrolysis separator It is composed of non-woven fabrics containing polyphenylene sulfide fibers with special-shaped cross-sections. The density is 0.30g/ ^cm3 or more and 0.80g/ ^cm3 or less. The tensile elongation in the longitudinal and transverse directions is between 10% and 35%. the following.

Description

Base material for alkaline water electrolysis separator and alkaline water electrolysis separator

The present invention relates to a base material for alkaline water electrolysis separators (hereinafter, the "base material for alkaline water electrolysis separators" may be referred to as "base material") and an alkaline water electrolysis separator (hereinafter, may be referred to as "alkali water electrolysis separators"). Water electrolytic separator" is referred to as "separator").

As one of the industrial production methods of hydrogen, there is the alkaline water electrolysis method. Generally speaking, an alkaline water electrolysis device has more than one electrolytic cell. The electrolytic cell is divided into an anode chamber and a cathode chamber through an alkaline water electrolysis diaphragm. When a direct current is applied between the two electrodes, oxygen is generated in the anode chamber. , generating hydrogen in the cathode chamber. When water is electrolyzed, generally, sodium hydroxide, potassium hydroxide, etc. are added to the water as an electrolyte in order to improve the conductivity of the electrolyte solution.

For alkaline water electrolysis separators, gas barrier properties (gas barrier properties) are required to block oxygen and hydrogen so that they do not mix. In addition, since ions transport electrons in the electrolyte of alkaline water electrolysis, in order to improve the electrolysis efficiency , and the separator also requires high ion permeability. In addition, alkali resistance to alkaline electrolytes is required; in order to exhibit ion conductivity, electrolysis is performed at about 60°C to 150°C, so heat resistance during electrolysis is required; when an alkaline water electrolysis separator is installed in an electrolytic cell, Mechanical strength that will not cause damage to the diaphragm, etc. is required.

Previously, it has been known to use "a base material for alkaline water electrolysis separators made of polyphenylene sulfide (PPS) fibers using a wet papermaking method" for alkaline water electrolysis separators.

For example, Patent Document 1 discloses an alkaline water electrolysis separator, which is a porous membrane including a porous support (substrate for alkaline water electrolysis separators) made of polyphenylene sulfide fibers and a polymer resin.

In addition, Patent Document 2 discloses a base material for an alkaline water electrolysis separator, which is composed of thermoplastic fibers containing polyphenylene sulfide fibers with a crimp number of 2 Å/25 mm to 10 Å/25 mm by plasma treatment. The wet non-woven fabric is made of hydrophilic treatment.

In addition, Patent Document 3 discloses a separator composed of a nonwoven fabric selected from polytetrafluoroethylene as a nonwoven fabric used in a hydrogen generating device separator (alkaline water electrolysis separator). , polypropylene, and poly-p-phenylene sulfide, and has the following characteristics (1) to (5). In addition, it is disclosed that the separator is made of The non-woven fabric is essentially composed of single fibers of polyarylene sulfide resin.

(1) The single filament fineness of the fibers constituting the non-woven fabric is from 2 dtex to less than 20 dtex; (2) The stiffness and softness of the non-woven fabric is from 50 mN·cm to 150 mN·cm; (3) The bulk density of the non-woven fabric is 0.2g/cm ³ Above and below 0.8g/ ^cm3 ; (4) The unit area weight of the non-woven fabric is above 50g/ ^m2 and below 200g/ ^m2 ; (5) The thickness of the non-woven fabric is above 0.1mm and below 0.5mm.

However, the nonwoven fabrics described in Patent Document 2 and Patent Document 3 have insufficient mechanical strength, and when the alkaline water electrolysis separator is installed in an electrolytic cell, the separator may be damaged or the like.

On the other hand, in Patent Document 1, strength is improved by allowing woven fabric to exist in nonwoven fabric. In addition, Patent Document 4 proposes the use of polyphenylene sulfide fabric for water electrolyzers instead of nonwoven fabrics. Patent Document 5 discloses an electrically insulating paper using a wet-laid nonwoven fabric made of polyphenylene sulfide fibers and a method for manufacturing the electrically insulating paper. The aforementioned electrically insulating paper uses a large amount of unstretched fibers as a binder component to eliminate voids as much as possible and form a dense structure, thereby exhibiting excellent insulation destructive properties. However, since it has a dense structure, its ion permeability and elongation are insufficient. As a result, it is insufficient in terms of low conductive resistance and suppression of film damage.

Therefore, base materials for alkaline water electrolysis separators and alkaline water electrolysis separators that have high uniformity, excellent processability, and high strength are required. [Prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2014-129563. [Patent Document 2] Japanese Patent Application Publication No. 2016-089197. [Patent Document 3] Japanese Patent Application Publication No. 2018-100434. [Patent Document 4] Japanese Patent Publication No. 2019-513902. [Patent Document 5] Japanese Patent Application Publication No. 2010-024574.

[Problem to be solved by the invention]

The present invention has been accomplished in view of the above background technology, and an object of the present invention is to provide a base material for an alkaline water electrolysis separator composed of a material with high mechanical strength, etc., and by using the base material for an alkaline water electrolysis separator , and provide an alkaline water electrolysis separator with low conductive resistance, gas barrier properties, etc. [Means used to solve problems]

The inventors of the present invention have repeatedly conducted diligent research to solve the above-mentioned problems, and as a result, solved the problems by the following invention.

That is, the present invention provides (1) a base material for an alkaline water electrolysis separator, characterized in that it is composed of a non-woven fabric containing polyphenylene sulfide fibers with a special-shaped cross-section, and has a density of 0.30g/cm ³ or more to 0.80g. /cm ³ or less, and the tensile elongation in the longitudinal and transverse directions is between 10% and below 35%.

In addition, the present invention provides (2) an alkaline water electrolysis separator, which is a porous membrane having the base material for an alkaline water electrolysis separator as described in the above (1) and a polymer resin. [Invention effect]

Generally speaking, nonwoven fabrics have high uniformity and excellent processability. Therefore, it is considered that if nonwoven fabrics are fully utilized as base materials for alkaline water electrolysis separators (if the unique physical properties of nonwoven fabrics are specialized and used as base materials for alkaline water electrolysis separators) ), the uniformity and mechanical strength can be maintained at a high level, and the characteristics of other base materials for alkaline water electrolysis separators can also be achieved. Furthermore, the present invention has been actually achieved and completed.

The base material for an alkaline water electrolysis separator of the present invention has particularly high mechanical strength. Therefore, when the alkaline water electrolysis separator is installed in an electrolytic cell, damage to the separator can be preferably suppressed. In addition, the alkaline water electrolytic separator using the base material of the present invention has low conductive resistance (that is, high ion permeability) and is also excellent in gas barrier properties. In addition, it has excellent alkali resistance to alkaline electrolytes and heat resistance during electrolysis.

[Substrate for alkaline water electrolysis separators] The base material for an alkaline water electrolysis separator of the present invention is composed of a nonwoven fabric containing polyphenylene sulfide fibers (hereinafter, "polyphenylene sulfide" may be abbreviated as "PPS") with a special-shaped cross-section. The nonwoven fabric is not particularly limited, but is preferably produced by a wet papermaking method. In addition, the base material for alkaline water electrolysis separators of the present invention preferably has a form including stretched PPS fibers as main fibers and unstretched PPS fibers as binder fibers. Most of the unstretched PPS fibers have an amorphous structure and are melted by heating to function as binder fibers. On the other hand, stretched PPS fiber is stretched during the fiber manufacturing step, and the fiber has strong single-filament fiber strength and excellent dimensional stability.

In the present invention, when stretched PPS fibers and unstretched PPS fibers are used, it is easy to provide a base material for an alkaline water electrolysis separator excellent in mechanical strength. In addition, an alkaline water electrolysis separator using the base material for an alkaline water electrolysis separator can have both low conductive resistance and high gas barrier properties.

[Polyphenylene sulfide fiber (PPS fiber)] The so-called polyphenylene sulfide (PPS) fiber refers to a polymer with "-(C ₆ H ₄ -S)-" as the main structural unit. Synthetic fiber composed of PPS polymer. Preferred PPS polymers include, for example, polyphenylene sulfide, polyphenylene sulfide ketone, polyphenylene sulfide ketone, and the like. Moreover, random copolymers, block copolymers, etc. of these polymers can also be mentioned. Furthermore, mixtures of the aforementioned polymers can be exemplified. Particularly preferred PPS polymers include p-phenylene units represented by -(C ₆ H ₄ -S)- as the main component of the polymer, preferably 90% by mass or more of the PPS polymer as a whole. Structural units of PPS polymer.

When the base material for alkaline water electrolysis separators has a p-phenylene unit represented by -(C ₆ H ₄ -S)-, it also exhibits excellent resistance to high-temperature and high-concentration alkaline solutions, thereby It can realize the efficiency of alkaline water electrolysis equipment and also shows chemical stability against active oxygen generated during the electrolysis of water.

[Special-shaped cross-section of PPS fiber] The PPS fiber in the present invention must have a profile. Here, the so-called "special-shaped cross-section" refers to a cross-sectional shape other than a circular cross-sectional shape when cut perpendicularly to the longitudinal direction of the fiber, and is not particularly limited. For example, it refers to a triangular shape, a Y-shaped shape, a flat shape, Sections of dog bone shape, trefoil shape, etc. For example, these PPS fibers can be obtained by direct spinning using a special-shaped mold, dissolving or splitting composite fibers, etc. In the present invention, it is particularly preferable to use direct spinning using a special-shaped mold. It is a PPS fiber with a special cross-section.

In addition, from the viewpoint of strength improvement, PPS fibers having a Y-shaped or trilobal cross-sectional shape are more preferred. Compared with the circular cross-sectional shape, the Y-shaped shape or the three-lobed shape has a larger specific surface area, an increase in the bonding points between fibers, and an increase in wet paper strength and base paper strength after the papermaking step. Not only that, it can be used to enter the hot calendering process. It deforms and adheres to the space inside the nonwoven fabric, thus helping to improve the strength of the nonwoven fabric. In addition, the PPS fiber having the above-mentioned special-shaped cross section is preferably a so-called crimp-free PPS fiber that has no crimp.

The content of "PPS fibers with special-shaped cross-sections" in the base material for alkaline water electrolysis separators of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 30% by mass relative to the entire PPS fiber. Quality% or more. If it is outside the above range, the same situation as described below may occur.

The base material for alkaline water electrolysis separator of the present invention may have a single-layer structure or a multi-layer structure. The content of "PPS fiber with a special-shaped cross-section" in each layer is preferably 10% by mass or more, more preferably 30% by mass or more based on the total amount of PPS fibers in each layer. If the content of the PPS fiber having a special-shaped cross-section is less than 10% by mass, the mechanical strength of the base material for an alkaline water electrolysis separator may be reduced. In addition, the mechanical strength (base paper strength) of the nonwoven fabric containing PPS fibers is not sufficiently improved, and the nonwoven fabric may be easily damaged when forming the nonwoven fabric (that is, paper breaks may easily occur during papermaking). Furthermore, all PPS fibers can also be PPS fibers with special-shaped cross-sections.

[Unstretched PPS fiber, stretched PPS fiber] The content of the unstretched PPS fiber in the base material for alkaline water electrolysis separator of the present invention is preferably 30 mass% or more and 90 mass% or less, and more preferably 40 mass% or more and 85 mass% or less relative to the entire PPS fiber. , preferably 50 mass% or more and 80 mass% or less. If it is outside the above range, the same situation as described below may occur.

In the base material for alkaline water electrolysis separator of the present invention, the content of unstretched PPS fibers in each layer is preferably 30 mass% or more and 90 mass% or less, more preferably 40 mass% relative to the total fiber amount of each layer. % or more and less than 80 mass%. If the content of the unstretched PPS fibers is too small, the effect of the adhesive that connects the fibers to each other may be insufficient, and sufficient mechanical strength for the nonwoven fabric may not be obtained. In addition, if the content of the unstretched PPS fiber is too high, the shrinkage in the width direction during the hot calendaring process may increase, thereby worsening the distribution.

[Crystallization enthalpy] The crystallization enthalpy of the unstretched PPS fiber used in manufacturing the base material for the alkaline water electrolysis separator of the present invention is preferably 20 J/g or more. More preferably, it is 21 J/g or more, still more preferably 22 J/g or more, and particularly preferably 24 J/g or more. If the crystallization enthalpy is too low, the effect of the adhesive bonding fibers to each other may be insufficient, and sufficient mechanical strength for the nonwoven fabric may not be obtained. In addition, the upper limit of the crystallization enthalpy is not particularly limited, but is actually 35 J/g or less.

In order to make the crystallization enthalpy of the aforementioned unstretched PPS fibers 20 J/g or more (or more than the above-mentioned lower limit), it is preferable to use at least one of the following two methods. (1) Control of crystallization enthalpy of unstretched PPS fiber during manufacturing: based on control of thermal history such as cooling method and cooling rate during spinning (2) Control of crystallization enthalpy of unstretched PPS fibers after production: Management of storage temperature and storage time of unstretched PPS fibers

Specific methods for performing the above control are described below. (1) Control of crystallization enthalpy of unstretched PPS fiber during production The ideal cooling process during spinning is to cool as quickly as possible within the range that can stabilize the melt elongation deformation. In addition, after cooling to room temperature, it is not good to increase the temperature to a temperature higher than room temperature.

Specifically, the cooling process during spinning is preferably such that the temperature of the quenching cooling air is 30° C. or lower. The temperature of the quenching cooling air is preferably below 28°C, particularly preferably below 26°C. If the temperature of the quenching cooling air is too high, cooling may become insufficient and unstretched PPS fibers having a crystallization enthalpy [J/g] of 20 J/g or more (or above the above-mentioned lower limit) may not be produced.

(2) Control of crystallization enthalpy of unstretched PPS fiber after production 1) Storage temperature It is preferable to store the unstretched PPS fiber after production in a room not exposed to direct sunlight, and it is also preferable to store it in a place where the room temperature does not rise as much as possible.

If the storage temperature becomes relatively high, the decrease in crystallization enthalpy may be accelerated. In addition, if the storage time becomes long-term, the crystallization enthalpy may decrease slowly with the passage of time. In this regard, the storage temperature is preferably 80°C or lower, more preferably 60°C or lower, and particularly preferably 50°C or lower. The lower limit of the storage temperature is not particularly limited, but is preferably -20°C or higher.

2) Storage time The storage time from the time of manufacture is preferably within 1 year, more preferably within 10 months, and even more preferably within 9 months. By using it within one year after production, the crystallization enthalpy [J/g] of the unstretched PPS fiber can be made to be 20 J/g or more (or more than the above-mentioned lower limit).

[Diameter of PPS fiber] The diameter of the PPS fiber is preferably 0.1 μm to 30 μm, more preferably 1.0 μm to 25 μm, especially 2 μm to 20 μm. When the nonwoven fabric in the present invention is produced by the wet papermaking method, if the diameter of the PPS fiber is within the above range, the production efficiency can be improved.

If the diameter of the PPS fiber is too small, it is easy to fall off the papermaking wire of the wet papermaking machine, or the quality of the nonwoven fabric is reduced due to poor dispersion of the PPS fiber. In addition, when a nonwoven fabric is produced and used as a base material for an alkaline water electrolysis separator, the density of the base material for an alkaline water electrolysis separator may become higher and the electrical resistance may become higher. Furthermore, the strength and/or elongation of the fibers may become insufficient, making it difficult to obtain the strength of the nonwoven fabric required as a base material for alkaline water electrolysis separators.

On the other hand, if the diameter of the PPS fiber is too large, the degree of entanglement between the fibers in the slurry may become insufficient, causing paper breakage in the wet papermaking step. In addition, the contact points between the fibers may become excessively deformed. Too little, making it difficult to maintain strength. In addition, when a nonwoven fabric is made and used as a base material for an alkaline water electrolysis separator, the mechanical strength is weak, so the separator may be damaged in the electrolytic tank or during installation. After the film is formed, the alkaline water electrolysis separator is formed. When used, the retention of the film-forming solution may be reduced, resulting in defects in the alkaline water electrolysis separator. Furthermore, when a porous membrane is formed on a base material as an alkaline water electrolysis separator, the retention property of the resin coating liquid for porous membrane formation may be reduced, resulting in defects in the alkaline water electrolysis separator.

Furthermore, the above "diameter of PPS fiber with a special cross-section" is used to cut the base material for alkaline water electrolysis separator with a sharp knife and observe the alkaline water electrolysis separator with a 2000x scanning electron microscope (SEM). The cross-section of the base material is used to calculate the arithmetic mean value of the diameter of each fiber by taking the diameter of a perfect circle with the same area as the cross-sectional area of 100 randomly selected fibers.

[Fiber length of PPS fiber] The fiber length of the PPS fiber used in the base material for the alkaline water electrolysis separator of the present invention is preferably 1 mm to 30 mm, more preferably 5 mm to 27 mm, particularly preferably 7 mm to 25 mm. When the fiber length of the PPS fiber is less than the above-mentioned lower limit, it may fall off from the papermaking wire during wet papermaking, and sufficient strength may not be obtained. On the other hand, when the fiber length of the PPS fiber exceeds the above upper limit, entanglement may occur when dispersed in water, and a uniform texture may not be obtained.

[Method for manufacturing base material and nonwoven fabric for alkaline water electrolysis separator] The base material for the alkaline water electrolysis separator of the present invention is preferably produced by a wet papermaking method, and particularly preferably a wet papermaking method is used to produce the base material for an alkaline water electrolysis separator with a single-layer structure. When manufacturing using a wet papermaking method, fibers are first dispersed uniformly in water, and then passed through a screen (to remove foreign matter, lumps, etc.) to prepare a slurry. The final fiber concentration of the slurry is preferably 0.01% by mass to 0.50% by mass relative to the entire slurry. This slurry is made into wet paper using a paper machine. In the process, chemicals such as dispersants, defoaming agents, hydrophilic agents, antistatic agents, polymer binders, release agents, antibacterial agents, and bactericides may also be added.

As a paper machine, for example, a paper machine using a single paper-making wire such as a fourdrinier wire, a rotary wire, a tilt wire, or a combined paper-making machine in which two or more paper-making wires of the same or different types are connected in a line can be used. In addition, when the non-woven fabric has a multi-layer structure of two or more layers, the following methods can be used to manufacture the non-woven fabric: "Laminated paper making method", which is to laminate wet papers made by each paper machine; and "Casting method" ”, after forming one of the layers, a slurry with dispersed fibers is cast on the layer to perform lamination. When the fiber-dispersed slurry is cast, the first layer formed can be in a wet paper state or a dry state. In addition, two or more dry layers can also be thermally fused to form a multi-layer nonwoven fabric.

In the wet papermaking method, Yankee dryer, air dryer, cylinder dryer, suction drum dryer, infrared dryer, etc. are used The dryer dries the wet paper produced by the papermaking wire and squeezed out of water through the wet press section, thereby obtaining the nonwoven fabric used as the base material for the alkaline water electrolysis separator. When drying the wet paper, the wet paper is closely contacted with a hot roller of a Yankee dryer or the like and is hot-pressed and dried, thereby improving the smoothness of the closely bonded surface. The so-called hot press drying refers to drying by pressing wet paper against a hot roller using a touch roller or the like. The surface temperature of the heat roller is preferably 100°C to 180°C, more preferably 120°C to 160°C. The pressure of using the contact roller to press the wet paper against the hot roller is preferably 50N/cm to 1000N/cm, more preferably 100N/cm to 800N/cm.

The base material for alkaline water electrolysis separator of the present invention may be subjected to hot rolling processing if necessary. As a calendering unit used in the hot calendering process of the base material for alkaline water electrolysis separator, a calendering unit using a combination of various rollers can be exemplified. Examples of combinations of various rollers include: metal roller-metal roller, metal roller-elastic roller, metal roller-cotton roller, metal roller-fluorinated rubber (viton) roller, metal roller-silicon roller, etc. Calendering of combinations of rollers components. These rolling components can be used alone or in combination of two or more types.

During hot rolling processing, the surface temperature of the metal roller is preferably 100°C to 260°C, more preferably 150°C to 250°C. If the temperature of the metal roller is too low, the unstretched PPS fibers may not melt and fiber-fiber bonding may not occur. In addition, if the temperature of the metal roller is too high, the fibers constituting the base material for alkaline water electrolysis separators may adhere to the metal roller, thereby impairing the uniformity of the surface of the nonwoven fabric.

The clamping pressure during hot rolling processing is preferably 190N/cm to 1800N/cm, more preferably 200N/cm to 1400N/cm, and particularly preferably 210N/cm to 600N/cm. The processing speed is preferably 5m/min to 150m/min, more preferably 10m/min to 80m/min, especially 10m/min to 40m/min.

[Layer composition of base material for alkaline water electrolysis separator] The substrate for the alkaline water electrolysis separator of the present invention can be a single layer, or a multi-layer structure in which the fibers of each layer have the same composition, or a multi-layer structure in which the fibers of each layer have different compositions. Compared with a single-layer structure, in the case of a multi-layer structure, the weight per unit area of each layer is reduced, thereby reducing the fiber concentration of the slurry, thereby improving the uniformity of the texture of the base material for alkaline water electrolysis separators. In addition, even if the texture of each layer is uneven, it can be filled by lamination. Furthermore, the papermaking speed can be increased and the workability can also be improved.

[Unit area weight of the base material for alkaline water electrolysis separator] The unit area weight of the base material for alkaline water electrolysis separator of the present invention is not particularly limited, but is preferably 20 g/m ² to 150 g/m ² , more preferably 30g/m ² to 100g/m ² . When the weight per unit area is too small, the mechanical strength of the base material for alkaline water electrolysis separators may become low. When the weight per unit area is too large, the conductive resistance may become high, and when installed in an electrolytic cell, liquid leakage may occur from the thickness direction portion of the alkaline water electrolysis separator.

The thickness of the base material for the alkaline water electrolysis separator of the present invention is not particularly limited, but is preferably 30 μm to 300 μm, more preferably 40 μm to 250 μm, and particularly preferably 60 μm to 180 μm. When the thickness is too small, the mechanical strength of the base material for alkaline water electrolysis separators may be reduced. When the thickness is too large, the conductive resistance may become high, and when it is installed in an electrolytic cell, liquid leakage may occur from the thickness direction portion of the alkaline water electrolysis separator.

[Density of the base material for alkaline water electrolysis separator] The density of the base material for alkaline water electrolysis separator of the present invention is 0.30g/cm ³ to 0.80g/cm ³ , preferably 0.35g/cm ³ to 0.70g/ cm ³ , more preferably 0.35g/cm ³ to 0.60g/cm ³ , particularly preferably 0.35g/cm ³ to 0.55g/cm ³ . "Density" is found by making the units consistent and dividing "weight per unit area" by "thickness".

If the density is less than 0.30 g/cm ³ , the mechanical strength of the alkaline water electrolysis separator base material becomes low. On the other hand, if the density exceeds 0.80 g/cm ³ , the base material for an alkaline water electrolysis separator becomes dense and the conductive resistance becomes high (ion permeability becomes low). In addition, the alkaline water electrolysis separator's ability to grip the inside of the base material is reduced. Therefore, in the alkaline water electrolysis separator, the porous membrane described below is peeled off from the alkaline water electrolysis separator base material. In addition, when the preferred (better or particularly preferred) range of the density is excessively smaller than the above range or excessively larger than the above range, the same situation as above may occur.

[Concrete method to bring density into the scope of the present invention] In order to bring the density of the base material for alkaline water electrolysis separators into the above range, it is preferable to adjust the fiber diameter during the fiber production stage (spinning stage). For example, the fiber diameter can be made thinner by reducing the molecular weight of the PPS resin, reducing the discharge volume of a single hole, reducing the nozzle hole diameter, etc. As a result, the density of the base material can be increased. On the other hand, the fiber diameter can be made thicker by increasing the molecular weight of the PPS resin, increasing the discharge volume of a single hole, increasing the nozzle hole diameter, etc. As a result, the density of the base material can be reduced.

In addition, in order to bring the density of the base material for alkaline water electrolysis separators into the above range, in the nonwoven fabric production stage (papermaking stage), the papermaking speed, contact roller pressure, clamping pressure or metal during hot calendering can be adjusted. The temperature of the roller can be achieved (can be achieved).

Specifically, for example, the density of the base material can be increased by increasing the nip pressure during hot rolling processing or increasing the temperature of the metal roller during hot rolling processing. On the contrary, the density of the base material can be reduced by lowering the nip pressure during hot rolling processing or lowering the temperature of the metal roller during hot rolling processing.

In addition, as the nonwoven fabric production device (paper machine), the nonwoven fabric production member (papermaking member), the form of the slurry, and the nonwoven fabric production method (papermaking method), for example, papermaking wires such as fourdrinier wire, cylinder wire, and inclined wire are used alone. Papermaking machines, or combined papermaking machines in which two or more papermaking wires of the same or different types are connected in line, can increase the density of the base material by slowing down the papermaking speed or increasing the pressure of the contact roller. On the contrary, by speeding up the papermaking speed or reducing the pressure of the contact roller, the density of the base material can be reduced.

[Tensile elongation of substrate for alkaline water electrolysis separator] In the base material for alkaline water electrolysis separator of the present invention, the tensile elongation in both the longitudinal and transverse directions is from 10% to 35%, preferably from 15% to 32%, and more preferably from 18% to 32%. Below 32%, preferably above 20% to below 30%.

If the tensile elongation in the longitudinal and transverse directions is less than 10%, the alkaline water electrolysis separator will be damaged when it is installed in the electrolytic cell. On the other hand, if the tensile elongation exceeds 35%, the membrane component of the alkaline water electrolytic separator will be damaged, and the gas barrier properties will decrease. In addition, when the preferred (more preferred or particularly preferred) range of the tensile elongation is excessively smaller than the above range or excessively larger than the above range, the same situation as described above may occur.

[Concrete method to bring tensile elongation into the scope of the present invention] In order to bring the tensile elongation of the base material for alkaline water electrolysis separators into the above range, it is preferable to adjust 1) the cutting length of the unstretched PPS fiber or the stretched PPS fiber, 2) the crystallization enthalpy of the unstretched PPS fiber, and 3) the stretching Elongation of PPS fiber. In order to increase the tensile elongation of the base material, the following methods are preferred: 1) Extend the cutting length of the unstretched PPS fiber or the extended PPS fiber, 2) Increase the crystallization enthalpy of the unstretched PPS fiber to improve the adhesive effect, 3) Improve the elongation of stretched PPS fibers. On the other hand, in order to reduce the tensile elongation of the base material, it is preferable to use the following methods: 1) shorten the cutting length of the unstretched PPS fiber or the extended PPS fiber, 2) reduce the melting enthalpy of the unstretched PPS fiber, 3) reduce Extend the elongation of PPS fiber.

In addition, in order to make the tensile elongation of the base material for alkaline water electrolysis separators fall into the above range, in the nonwoven fabric production stage (papermaking stage), the papermaking speed, contact roller pressure, speed during hot calendering, etc. can be adjusted. to achieve (can be achieved).

Specifically, for example, by increasing the speed during hot rolling processing, the tensile elongation of the base material can be increased. On the contrary, by reducing the speed during hot rolling processing, the tensile elongation of the base material can be reduced.

In addition, as the nonwoven fabric production device (paper machine), the nonwoven fabric production member (papermaking member), the form of the dispersion liquid, and the nonwoven fabric production method (papermaking method), papermaking wires such as fourdrinier wires, cylinder wires, and inclined wires can be used individually. A papermaking machine, or a combined papermaking machine in which two or more papermaking wires of the same or different types are connected in line, can increase the tensile elongation of the base material by slowing down the papermaking speed or increasing the pressure of the contact roller, etc., and conversely, by Speeding up the papermaking speed or reducing the pressure of the contact roller can reduce the tensile elongation of the substrate.

[Alkaline water electrolysis separator] The alkaline water electrolysis separator of the present invention includes the aforementioned base material for the alkaline water electrolysis separator and a porous membrane of polymer resin. In the alkaline water electrolysis separator of the present invention, the base material for alkaline water electrolysis separator and the porous membrane may each be laminated by one sheet, or a plurality of sheets may be laminated. Although not particularly limited, in terms of maintaining the strength of the alkaline water electrolysis separator or preventing peeling, it is preferable that a part of the alkaline water electrolysis separator penetrates into the alkaline water electrolysis separator base material and becomes integrated.

[Porous membrane] Examples of the polymer resin used to form the porous membrane include polystyrene-based resins such as polystyrene, polyetherstaining, and polystyrene; fluorine-based resins such as polyvinylidene fluoride and polytetrafluoroethylene; polyethylene, polypropylene, Vinyl-based resins such as polystyrene; thioether-based resins such as polyphenylene sulfide; polyphenylenebenzobisoxazole; ketone-based resins such as polyketone; polyimide, polyetherimide, etc. Amine resin; ester resin such as polycarbonate, etc. These resins can be used individually, or two or more types can be used together.

The thickness of the porous film is not particularly limited, but in terms of mechanical strength, gas barrier properties (gas barrier properties), conductive resistance, etc., it is preferably 30 μm to 600 μm, more preferably 50 μm to 500 μm, and particularly preferably 70 μm to 400 μm. . In addition, the size of the pores of the porous membrane is not particularly limited. In terms of mechanical strength, ion permeability, etc., the number average diameter is preferably 0.010 μm to 5 μm, more preferably 0.015 μm to 3 μm, and particularly preferably is 0.020μm to 2μm.

The manufacturing method of the porous membrane is not particularly limited, and examples thereof include: non-solvent-induced phase separation method, heat-induced phase separation method, water vapor-induced phase separation method, solvent evaporation method, etc. The aforementioned non-solvent-induced phase separation method has at least The manufacturing method includes the following steps: Dissolve "the aforementioned polymer resin and preferably a water-soluble resin" in a water-soluble organic solvent to prepare a film-forming solution, apply the film-forming solution to a substrate, and utilize the defects of the polymer resin The step of using a solvent to precipitate (phase separate) the polymer resin; and the step of using "a poor solvent of the polymer resin" such as water to dissolve, remove and clean the "water-soluble resin and/or the water-soluble organic solvent".

As the above-mentioned water-soluble resin, a resin dissolved in both “the above-mentioned water-soluble organic solvent” and “the above-mentioned poor solvent of the polymer resin” can be preferably used. Specific examples include: polyethylene glycol, polypropylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, polyethylenimine, poly(meth)acrylic acid, dextran, polymaleic acid ( anhydride), etc., or copolymers of these, etc. In the case of acids such as carboxylic acids, some or all of them may form salts. The water-soluble resin may contain (prepare): surfactant; (poly)glycerol; sugar derivatives such as sugar and sugar alcohol; and inorganic salts such as lithium salt, potassium salt, sodium salt, calcium salt, and magnesium salt. Examples of the salt include nitrate, sulfate, hydrochloride, fluoroborate, fluorophosphate, perchlorate, and the like.

As the water-soluble organic solvent, a water-soluble organic solvent that dissolves the polymer resin and the water-soluble resin can be preferably used. Specifically, for example, N-methyl-2-pyrrolidone; N,N-dimethylacetamide; N,N-dimethylformamide; dimethylstyrene; tetrahydrofuran; ( Alkylene glycol solvents such as di- or tri-propylene glycol monoalkyl ether and (di- or tri-propylene glycol monoalkyl ether acetate); carbonate-based solvents such as ethylene carbonate and propylene carbonate. These water-soluble organic solvents can be used individually or in mixture of 2 or more types.

As the "poor solvent for the polymer resin", a solvent that does not dissolve the polymer resin but causes phase separation and precipitation and dissolves the water-soluble resin can be preferably used. Specific examples thereof include water, methanol, ethanol, propanol, isopropyl alcohol, butanol, ethylene glycol, and propylene glycol. These solvents can be used individually or in mixture of 2 or more types. [Example]

Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to this Example.

(1) Fineness (dtex) Measured based on JIS L1015 (2010) 8.5.1.

(2) Crystallization enthalpy (J/g) Using a differential scanning calorimeter (Q100 manufactured by TA Instruments), the PPS fiber was weighed so that it became 2.0 mg±0.1 mg, and the measurement was performed at a temperature rise rate of 20° C./min in a nitrogen atmosphere. For the exothermic peak observed from about 110°C to 140°C based on the endothermic and exothermic curve, a reference line is drawn so as to form a straight line through the vicinity of 100°C and the vicinity of 200°C, and the area surrounded by the endothermic and exothermic curve and the reference line is calculated.

(3) Circle converted diameter (μm) As mentioned above, use a sharp knife to cut the base material, observe the cross section of the base material with a 2000x scanning electron microscope (SEM), and calculate it from the arithmetic mean of 100 randomly selected fibers. . Based on the following formula, the diameter (μm) of an imaginary perfect circle having the same area as the cross-sectional area of the fiber having a special-shaped cross-section, that is, the circle-converted diameter (μm), was calculated. Furthermore, the density of polyphenylene sulfide fiber (PPS fiber) is calculated to be 1.35g/cm ³ . Circle conversion diameter (μm) = 2×{D/(100000×ρ×π)} ^0.5 ×10 ⁴ D: Monofilament fineness (dtex) ρ: Fiber density (g/cm ³ )

[PPS fiber 1 (extended PPS fiber, special-shaped profile)] PPS polymer (manufactured by KUREHA Co., Ltd.: PHOTRON KPS) was spun from a trilobal-shaped nozzle hole at a spinning temperature of 300°C and a discharge rate per hole of 0.32 g/min. Next, cooling air at 20° C. and 100 m/min was blown to one side from the side of the spun yarn to perform asymmetric cooling. Then, it was extracted at a spinning speed of 1170 m/min to obtain unstretched PPS fibers. The obtained unstretched PPS fiber had a trilobal-shaped fiber cross section, a fineness of 2.7 dtex, and a crystallization enthalpy of 26.0 J/g.

The obtained unstretched PPS fiber was stretched to 2.1 times between stretching rollers at 90°C. Then, heat treatment is performed by passing through a 210° C. heat treatment roll at the same speed as the stretching roll. Furthermore, an oil agent was added and heat treatment was performed at 175° C., and then cut. The obtained stretched PPS fiber "PPS fiber 1" (special-shaped cross-section, no crimp) has a trilobal-shaped cross-section, a fineness of 1.3 dtex, a circular diameter of 11 μm, and a fiber length of 5 mm.

[PPS fiber 2 (extended PPS fiber, special-shaped profile)] Using the same method as PPS fiber 1, changing the cutting length after stretching, we produced stretched PPS fiber "PPS fiber 2" (special-shaped cross-section, no crimp). The obtained PPS fiber 2 had a trilobal cross section, a fineness of 1.3 dtex, a circular diameter of 11 μm, and a fiber length of 10 mm.

[PPS fiber 3 (extended PPS fiber, special-shaped profile)] Using the same method as PPS fiber 1, changing the cut length after stretching, we produced stretched PPS fiber "PPS fiber 3" (special-shaped cross-section, no crimp). The obtained PPS fiber 3 had a trilobal cross-section, a fineness of 1.3 dtex, a circular diameter of 11 μm, and a fiber length of 20 mm.

[PPS fiber 4 (extended PPS fiber, circular cross-section)] PPS polymer (manufactured by KUREHA Co., Ltd.: PHOTRON KPS) was spun from a circular nozzle hole at a spinning temperature of 305°C and a single hole discharge amount of 0.24 g/min. Next, cooling air at 20° C. and 80 m/min was blown to one side from the side of the spun yarn to perform asymmetric cooling. Then, it was extracted at a spinning speed of 1100 m/min to obtain unstretched PPS fibers. The obtained unstretched PPS fiber had a circular fiber cross-section and a fineness of 2.2 dtex.

The obtained unstretched PPS fiber was stretched to 2.0 times between stretching rollers at 90°C. Then, heat treatment is performed by passing through a 210° C. heat treatment roll at the same speed as the stretching roll. Furthermore, an oil agent was added and heat treatment was performed at 175° C., and then cut. The obtained stretched PPS fiber "PPS fiber 4" (circular cross section, no crimp) has a circular cross section, a fineness of 1.1 dtex, a diameter of 10 μm, and a fiber length of 10 mm.

[PPS fiber 5 (extended PPS fiber, circular cross-section)] Using the same method as PPS fiber 4, changing the cut length after stretching, we produced stretched PPS fiber "PPS fiber 5" (circular cross-section, no crimp). The obtained PPS fiber 5 had a circular cross-section, a fineness of 1.1 dtex, a diameter of 10 μm, and a fiber length of 20 mm.

[PPS fiber 6 (unstretched PPS fiber, special-shaped profile)] Use the same method as PPS fiber 1 to make unstretched PPS fibers and then cut them. The obtained unstretched PPS fiber "PPS fiber 6" had a trilobal cross-section, a fineness of 2.6 dtex, a circular diameter of 16 μm, and a fiber length of 5 mm.

[PPS fiber 7 (unstretched PPS fiber, special-shaped profile)] Using the same method as PPS fiber 6, changing the cutting length, we produced unstretched PPS fiber "PPS fiber 7" (special-shaped cross-section, no crimp). PPS fiber 7 has a trilobal cross-section, a fineness of 2.6 dtex, a circular diameter of 16 μm, and a fiber length of 10 mm.

[PPS fiber 8 (unstretched PPS fiber, circular cross-section)] PPS polymer (manufactured by KUREHA Co., Ltd.: PHOTRON KPS) was spun from a circular nozzle hole at a spinning temperature of 305°C and a single hole discharge amount of 0.24 g/min. Then, cooling air at 20° C. and 80 m/min was blown to one side from the side of the spun yarn to perform asymmetric cooling. Then, the fiber was extracted at a spinning speed of 1380 m/min and then cut. The obtained unstretched PPS fiber "PPS fiber 8" had a circular cross-section, a fineness of 1.7 dtex, a diameter of 13 μm, a fiber length of 10 mm, and a crystallization enthalpy of 24.4 J/g.

[Example 1 to Example 11, Comparative Example 1 to Comparative Example 8] According to the fiber composition described in Table 1, the fibers were dispersed in water at a dispersion concentration of 0.2% by mass for 1 minute. Then, in the case of a single layer, an inclined mesh papermaking machine is used to form wet paper, and in the case of two layers, an inclined mesh/cylindrical mesh hybrid papermaking machine is used to form wet paper. Then, hot-press drying was performed using a Yankee dryer with a surface temperature of 160° C. to obtain a base material for an alkaline water electrolysis separator having a weight per unit area as shown in Table 1. When using an inclined wire/cylindrical wire composite papermaking machine, the first layer of wet paper is formed on the cylinder wire side, and the second layer of wet paper is formed on the inclined wire side.

[Table 1] Fiber composition [mass %] Target unit area weight [g/m ² ] Extend PPS Unextended PPS PPS fiber 1 PPS fiber 2 PPS fiber 3 PPS fiber 4 PPS fiber 5 PPS fiber 6 PPS fiber 7 PPS fiber 8 Example 1 single layer 30 70 40 2 single layer 30 70 40 3 single layer 30 70 40 4 single layer 30 70 40 5 single layer 30 70 50 6 single layer 30 70 50 7 single layer 30 70 80 8 first floor 30 70 20 second floor 30 70 20 9 first floor 30 70 20 second floor 30 70 20 10 first floor 30 70 20 second floor 30 70 20 11 first floor 30 70 20 second floor 30 70 20 Comparative example 1 single layer 30 70 40 2 single layer 30 70 40 3 first floor 30 70 20 second floor 30 70 20 4 first floor 30 70 20 second floor 30 70 20 5 first floor 30 70 20 second floor 30 70 20 6 single layer 30 70 40 7 single layer 30 70 155 8 single layer 30 70 40

[Hot rolling treatment] In Examples 2, 4, 6, 7, 9 and 11, and Comparative Examples 1, 5, 7 and 8, the base material for alkaline water electrolysis separator was hot pressed under the hot rolling conditions described in Table 2. Delayed processing.

[Table 2]

[Film formation of alkaline water electrolysis separator] Polyethylene (polymer resin, manufactured by Solvay Specialty Polymers, Udel (registered trademark) P) 17% by mass and polyethylene glycol (weight average molecular weight Mw100,000, manufactured by Sigma-Aldrich Japan Contract Co., Ltd.) 5% by mass were added The solution was stirred and dissolved in 78% by mass of N-methyl-2-pyrrolidone (manufactured by Junsei Chemical Co., Ltd.) as a solvent at a temperature of 70° C. to obtain a film-forming solution.

The film-forming solution was applied to the substrate for the alkaline water electrolytic separator produced in the above-mentioned Examples and Comparative Examples so that the total film thickness of the alkaline water electrolytic separator before drying became 300 μm. Immediately after coating, the coated substrate is immersed in a coagulation bath (pure water) whose temperature is adjusted to 40°C in a vertical manner relative to the water surface, so that the polymer resin can be phase separated. Then, the organic solvent is removed by thoroughly washing with pure water, and an alkaline water electrolysis separator having a base material for an alkaline water electrolysis separator and a porous membrane of a polymer resin is obtained.

In the examples and comparative examples, the unit area weight, thickness, and density of the base material for alkaline water electrolysis separators were measured, the tensile elongation in the longitudinal and transverse directions was measured, and the rupture of the base material for alkaline water electrolysis separators was carried out. The results of the evaluation of strength and alkaline water electrolysis separators (conductivity resistance, gas barrier properties) are shown in Table 3 below.

[Weight per unit area] In accordance with JIS P 8124:2011, the base material for alkaline water electrolysis separators was cut into 100 mm × 100 mm test pieces, and 20 pieces were measured using an electronic analytical scale (manufactured by Shimadzu Corporation). The arithmetic mean of each value is used as the weight per unit area [g/cm ² ].

[thickness] According to JIS P 8118:2014, from the test pieces collected during the unit area weight measurement, 20 pieces were measured one by one using a micrometer (manufactured by MITUTOYO Co., Ltd.), and the arithmetic mean of the obtained values was used as the thickness [ μm].

[Density] Divide the above-mentioned "unit area weight" by the above-mentioned "thickness" and adjust the units to calculate the density [g/cm ³ ].

[Tensile elongation] As a test piece for measuring the tensile elongation in the longitudinal direction (MD), a base material for an alkaline water electrolytic separator cut into short strips of 50 mm × 200 mm with the longitudinal direction as the long side was prepared. In addition, as a test piece for measuring the tensile elongation in the transverse direction (CD), a base material for an alkaline water electrolysis separator cut into short strips of 50 mm × 200 mm with the transverse direction as the long side was prepared. In accordance with JIS P 8113:2006, a fixed-speed tensioning type tensile testing machine "single column material testing machine, model: STB-1225S" (manufactured by A&D Co., Ltd.) was used. The distance between the chucks was set to 100mm. The moving speed was set to 100 mm/min, the tensile test specimen was stretched at a constant speed, and the elongation at breakage of the tensile test specimen was measured as tensile elongation [%].

[Bursting strength] In accordance with JIS P 8112:2008, the base material for alkaline water electrolysis separators was cut into 60 mm × 60 mm test pieces, and 20 pieces were measured using a Mullen burst testing machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.). The arithmetic mean of each value is taken as the bursting strength [kPa].

[Electrolysis device] The alkaline water electrolysis device is composed of: an alkaline water electrolysis diaphragm, an anode and a cathode. The alkaline water electrolysis diaphragm is separated into an anode chamber with an anode and a cathode chamber with a cathode. Oxygen and hydrogen are generated from the two electrodes. Blocked by the alkaline water electrolytic separator without mixing.

[Performance Test of Alkaline Water Electrolysis Separator] An electrolysis unit was produced using an alkaline water electrolysis separator having the base material for the alkaline water electrolysis separator produced in the above-mentioned Examples and Comparative Examples and the porous membrane produced in the above-mentioned manner. and electrolysis equipment. The electrolyte supplied to the electrolysis device was a potassium hydroxide aqueous solution with a concentration of 25% by mass, and the liquid temperature was set to 80°C. A pure nickel mesh is used as the anode, and an active cathode for hydrogen generation is used as the cathode. The electrolysis area of the electrolysis unit is set to 1dm ² , and the electrolysis voltage required to flow a unit current of 0.4A/cm ² from the electrolysis device to the electrolysis unit, the hydrogen concentration in the generated oxygen, and the oxygen in the generated hydrogen are measured. concentration.

[Conductive resistance] Based on the measurement results of electrolysis voltage in the performance test of the above-mentioned alkaline water electrolytic separator, the alkaline water electrolytic separator to be the standard (unit area weight of the base material for alkaline water electrolytic separator) was evaluated according to the following evaluation criteria: The conductive resistance of the alkaline water electrolysis separator when the conductive resistance of 50g/m ² ) is set to 1.

Evaluation benchmark "A": Less than 0.950 "B": above 0.950 to less than 0.975 "C": 0.975 or more and less than 1.000 "D": 1.000 or more

[Gas barrier properties] In the above performance test of the alkaline water electrolysis separator, the amount of oxygen mixed [mol%] was calculated based on the oxygen concentration in the generated hydrogen. As an indicator of the gas barrier properties of the alkaline water electrolysis separator, the following evaluation criteria were used Make an evaluation.

Evaluation benchmark "A": Less than 0.3% "B": 0.3% or more to less than 0.4% "C": 0.4% or more to less than 0.5% "D": 0.5% or more

[table 3] physical properties Evaluation Weight per unit area [g/m ² ] Thickness[μm] Density [g/cm ³ ] Tensile elongation in longitudinal direction [%] Tensile elongation transverse direction [%] Bursting strength[kPa] Conductive resistance[-] Gas barrier properties[-] Example 1 41 119 0.35 25 25 210 A A 2 37 67 0.55 20 25 179 B A 3 40 124 0.32 twenty one 18 161 A A 4 41 70 0.59 12 14 158 B A 5 48 139 0.35 twenty one 18 189 B B 6 50 86 0.58 17 16 207 B A 7 80 174 0.48 32 27 380 B B 8 41 120 0.34 25 twenty four 173 A A 9 40 76 0.53 twenty three 26 176 B A 10 40 112 0.36 twenty one 18 165 A A 11 40 65 0.61 18 19 146 A B Comparative example 1 39 68 0.57 18 17 148 C B 2 41 125 0.33 twenty two 20 132 B B 3 42 125 0.34 twenty two twenty one 142 B A 4 40 118 0.34 18 16 131 B B 5 40 69 0.58 15 15 122 B D 6 39 157 0.25 twenty one 19 120 B B 7 155 303 0.51 36 31 460 D B 8 40 48 0.83 9 8 176 D B

It can be seen that there are examples of nonwoven fabrics containing PPS fibers with special-shaped cross-sections, a density of 0.30g/cm ³ or more and 0.80g/cm ³ or less, and a tensile elongation in both the longitudinal and transverse directions of 10% or more and 35% or less. The base materials for alkaline water electrolysis separators of Examples 1 to 11 have high burst strength, low conductive resistance, and excellent gas barrier properties.

In contrast, it can be seen that the base materials for alkaline water electrolysis separators of Comparative Examples 1 to 5 are composed of nonwoven fabrics that do not contain PPS fibers with a special-shaped cross section. Therefore, the base materials for alkaline water electrolysis separators of Comparative Examples 2 to 5 are The rupture strength of the base material was low, the conductive resistance of the alkaline water electrolysis separator of Comparative Example 1 was high, and the gas barrier properties of the alkaline water electrolysis separator of Comparative Example 5 were low.

In addition, it was found that the base material for alkaline water electrolysis separators of Comparative Example 6, which was composed of a nonwoven fabric containing PPS fibers with a special-shaped cross-section but had a density less than 0.30 g/cm ³ , had low rupture strength. In addition, it was found that Comparative Example 7 in which the base material for alkaline water electrolysis separators is composed of a nonwoven fabric containing PPS fibers with a special-shaped cross-section but has a tensile elongation in the longitudinal direction exceeding 35%, and a density exceeding 0.80 g/cm ³ in both the longitudinal and transverse directions The alkaline water electrolysis separator of Comparative Example 8, whose tensile elongation rate did not reach 10%, all had high conductive resistance. [Industrial Availability]

The substrate for an alkaline water electrolysis separator of the present invention can be widely used in the field of hydrogen production using alkaline water electrolysis.

Claims (5)

A base material for alkaline water electrolysis separators, which is composed of non-woven fabrics containing polyphenylene sulfide fibers with special-shaped cross-sections. The density is 0.30g/ ^cm3 or more and 0.80g/ ^cm3 or less, and the tensile elongation in the longitudinal and transverse directions is The ratio is more than 10% and less than 35%; the aforementioned special-shaped cross-section is Y-shaped or trilobal; the aforementioned non-woven fabric contains extended polyphenylene sulfide fiber and unstretched polyphenylene sulfide fiber. Compared with the overall polyphenylene sulfide fiber, The content of unstretched polyphenylene sulfide fiber is 30 mass% or more and 90 mass% or less. The base material for alkaline water electrolysis separators according to claim 1, wherein the nonwoven fabric is produced by a wet papermaking method. The base material for alkaline water electrolysis separator as described in claim 1 or 2 is composed of a single-layer non-woven fabric or a multi-layer non-woven fabric. The base material for alkaline water electrolysis separators as described in claim 1 or 2 is composed of a multi-layered nonwoven fabric, and the content of unstretched polyphenylene sulfide fiber in each layer is 30% by mass relative to the total fiber content of each layer. More than 90% by mass. An alkaline water electrolysis separator is a porous membrane having a base material for an alkaline water electrolysis separator as described in any one of claims 1 to 4 and a polymer resin.