WO2014119208A1 - Electrolytic membrane - Google Patents

Abstract

Provided is an electrolytic membrane, the percentage change in the surface area of which during use is low. Said electrolytic membrane exhibits excellent ion permeability and makes it possible to prevent voltage increases due to gases generated at electrodes during electrolysis becoming attached to the surface of the membrane. This electrolytic membrane comprises an ion-permeable membrane and can be wetted by an aqueous solution of potassium hydroxide having a concentration of 30 wt.%. The mean pore diameter of said ion-permeable membrane is between 0.01 and 20 µm, inclusive, and when the ion-permeable membrane is immersed in purified water, the surface area thereof changes by no more than 20%. In a preferred embodiment, the electrical resistivity of the ion-permeable membrane when an aqueous solution of potassium hydroxide at a temperature of 25°C and a concentration of 40 wt.% is used as the electrolyte is no more than 0.5 Ω∙cm².

Description

Electrolysis diaphragm

The present invention relates to a diaphragm for electrolysis.

Conventionally, an energy composition centered on oil has been established, but in addition to being a limited resource, oil is limited in the areas where it can be produced. A supply method is required. Reflecting this energy situation, hydrogen is attracting attention as a new energy source to replace oil. As an industrial method for producing hydrogen, there is a water electrolysis method using a polymer electrolyte. However, since an expensive noble metal such as platinum is used as a catalyst, there is a problem that costs increase. On the other hand, the alkaline water electrolysis method is expected as a method for stably obtaining hydrogen at low cost by electrolyzing alkaline water without using an expensive noble metal catalyst.

As a diaphragm used in the alkaline water electrolysis method, for example, a diaphragm composed of a fluorinated hydrocarbon polymer having a sulfonic acid group has been proposed (Patent Document 1). However, such a diaphragm has a large area change due to swelling of the polymer when it is incorporated into an electrolytic cell and becomes wet, and the occurrence of wrinkles, tearing, deformation, etc. becomes a problem.

Also, a diaphragm containing a hydrophilic inorganic material has been proposed as a diaphragm used in the alkaline water electrolysis method (Patent Document 2). This diaphragm exhibits wettability to water and has ion permeability because it is porous. However, there is a problem that the wettability to alkaline water is insufficient in an electrolysis environment. The increase in voltage due to the generated gas adhering to the diaphragm surface becomes a problem. Moreover, the diaphragm of patent document 1 also has the problem that ion permeability is inadequate.

JP 59-182984 A JP 2008-144262 A

The present invention has been made in order to solve the above-described conventional problems. The purpose of the present invention is to provide a gas that is excellent in ion permeability, has a small area change rate during use, and is generated at an electrode during electrolysis. An object of the present invention is to provide a diaphragm for electrolysis that can suppress an increase in voltage due to the adhesion of sapphire to the diaphragm surface.

The electrolysis membrane of the present invention is an electrolysis membrane comprising an ion permeable membrane and exhibiting wettability with respect to an aqueous potassium hydroxide solution having a concentration of 30% by weight. The average pore size of the ion permeable membrane is 0.01 μm to The area change rate when the ion permeable membrane is immersed in pure water is 20% or less.
In a preferred embodiment, the electric resistance value of the ion permeable membrane is 0.5 Ω · cm ² or less when a potassium hydroxide aqueous solution having a temperature of 25 ° C./concentration of 30% by weight is used as an electrolyte.
In a preferred embodiment, the ion permeable membrane is composed of a polymer having a medium acid ion exchange group, a weak acid ion exchange group, a strongly basic ion exchange group, a medium basic ion exchange group, or a weak basic ion exchange group. The
In a preferred embodiment, in the ion permeable membrane, the medium acid ion exchange group, weak acid ion exchange group, strong basic ion exchange group, medium basic ion exchange group, or weak basic ion exchange group is formed by graft polymerization. Has been introduced.
In a preferred embodiment, the diaphragm for electrolysis of the present invention further comprises a porous reinforcing body disposed on one side or both sides of the ion permeable membrane.
In a preferred embodiment, the reinforcing body is disposed on both sides of the ion permeable membrane.
In a preferred embodiment, the reinforcing body is composed of a polymer having a medium acid ion exchange group, a weak acid ion exchange group, a strongly basic ion exchange group, a medium basic ion exchange group, or a weak basic ion exchange group. Yes.
In a preferred embodiment, the medium acidic ion exchange group, weak acid ion exchange group, strong basic ion exchange group, medium basic ion exchange group or weak basic ion exchange group is introduced into the reinforcing body by graft polymerization. Has been.
According to another aspect of the present invention, an electrochemical cell for producing hydrogen is provided. The membrane for electrolysis is used in this electrochemical cell for hydrogen production.

According to the present invention, by providing a microporous ion permeable membrane, it is possible to obtain a diaphragm for electrolysis that is excellent in ion permeability and has a small area change rate during use. Moreover, the diaphragm for electrolysis of this invention has high wettability with respect to alkaline aqueous solution, and the gas produced | generated at the time of electrolysis cannot adhere to the surface easily, As a result, a voltage rise can be suppressed.

It is a schematic sectional drawing of the diaphragm for electrolysis by preferable embodiment of this invention. It is a schematic sectional drawing of the diaphragm for electrolysis by preferable embodiment of this invention.

Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.
A. Overall Structure of Electrolysis Membrane The electrolysis membrane of the present invention includes a microporous ion permeable membrane.

The diaphragm for electrolysis of the present invention may have a single membrane configuration having one ion permeable membrane or a laminated configuration including an ion permeable membrane. With a single membrane configuration, a diaphragm for electrolysis with higher ion permeability can be obtained, which is useful in applications where the demand for strength is relatively low. On the other hand, if it is a laminated structure, the diaphragm for electrolysis which is high intensity | strength and cannot be short-circuited more can be obtained. As a specific example of the diaphragm for electrolysis of a laminated structure, the diaphragm for electrolysis provided with a reinforcement body at least on one side of the ion permeable membrane can be mentioned.

FIG. 1 is a schematic cross-sectional view of a diaphragm for electrolysis according to a preferred embodiment of the present invention. An electrolysis diaphragm 100 shown in FIG. 1 includes an ion permeable membrane 10 and a porous reinforcing body 20. FIG. 2 is a schematic cross-sectional view of a diaphragm for electrolysis according to another preferred embodiment of the present invention. An electrolysis diaphragm 100 ′ shown in FIG. 2 includes porous reinforcing bodies 20 on both sides of the ion permeable membrane 10. In the case of the laminated configuration, the reinforcing body 20 may be arranged on one side of the ion permeable membrane 10 as shown in FIG. 1 or may be arranged on both sides of the ion permeable membrane 10 as shown in FIG. . Preferably, the reinforcing body 20 is disposed on both sides of the ion permeable membrane 10. With such a configuration, it is possible to obtain a diaphragm for electrolysis that is less warped and excellent in properties such as resistance value. When the reinforcing body 20 is disposed on one side of the ion permeable membrane 10, the diaphragm for electrolysis 100 of the present invention may be used with the ion permeable membrane 10 disposed on the anode electrode side or disposed on the cathode electrode side. May be used. The ion permeable membrane 10 and the reinforcing body 20 can be laminated by heating and pressurizing using a hot press machine or a heating roll, for example. Preferably, the ion permeable membrane 10 and the reinforcing body 20 are laminated, and only the end of the laminated body is heated. By heating in this way, it is possible to prevent the reinforcing body 20 from being heated excessively and reducing wettability. Moreover, when using the diaphragm for electrolysis of this invention as a diaphragm, it may apply pressure from both sides with an electrode etc., and may fix the ion permeable film 10 and the reinforcement body 20. FIG. Further, as described later, when the ion permeable membrane and / or the reinforcing body is formed by graft polymerization, the ion permeable membrane and the reinforcing body before grafting may be laminated by the above method, and then the grafting may be performed. .

1 or 2, the ion permeable membrane 10 is reinforced by the reinforcing body 20, has a sufficient strength as a diaphragm for electrolysis, and is excellent in short circuit prevention between electrodes. Moreover, since the reinforcement body 20 is porous as above-mentioned, it can express the said effect, without inhibiting ion permeability. Furthermore, since the ion permeable membrane 10 is reinforced as described above, the ion permeable membrane 10 can be thinned, and as a result, an electrolysis diaphragm having excellent ion permeability can be obtained.

The thickness of the diaphragm for electrolysis of the present invention is preferably 15 μm to 1500 μm, more preferably 35 μm to 1000 μm, and further preferably 50 μm to 500 μm.

The electrolysis membrane of the present invention exhibits wettability with respect to a 30% by weight potassium hydroxide aqueous solution. More specifically, in the present invention, in the case of a single membrane configuration having one ion permeable membrane, the ion permeable membrane exhibits wettability as described above, and in the case of a laminated configuration having an ion permeable membrane and a reinforcing body. The ion permeable membrane and the reinforcing body exhibit wettability as described above. Since the electrocoating membrane of the present invention exhibits wettability as described above, it is difficult for gases (hydrogen gas and oxygen gas) generated by alkaline water electrolysis to adhere, and voltage increase due to the gas can be suppressed. In the present specification, “showing wettability with respect to an aqueous potassium hydroxide solution” means that the electrocoating membrane is immersed in an aqueous potassium hydroxide solution at a temperature of 80 ° C./concentration of 30% by weight for 100 hours. Also means that wettability is not lost. Specifically, when the potassium hydroxide aqueous solution having a concentration of 30% by weight is dropped on the surface of the electrolysis capsule after being immersed in the potassium hydroxide aqueous solution as described above, the dropped potassium hydroxide aqueous solution is In this case, the electrolysis film is referred to as an electrolysis film “showing wettability to an aqueous potassium hydroxide solution”.

In the diaphragm for electrolysis of the present invention, the area change rate when immersed in pure water is preferably 20% or less, more preferably 10% or less. In the diaphragm for electrolysis of the present invention, the area change rate when immersed in an aqueous potassium hydroxide solution having a concentration of 30% by weight is preferably 20% or less, more preferably 10% or less. The diaphragm for electrolysis having an area change rate in such a range is less likely to be wrinkled, broken, deformed, folded, etc., and exhibits a long life and stable performance. As described above, the diaphragm for electrolysis having a small area change rate can be obtained by providing a microporous ion permeable membrane having a small area change rate as described later. A method for measuring the area change rate will be described later.

B. Ion permeable membrane The ion permeable membrane can transmit ions generated at the cathode electrode (for example, anions such as hydroxide ions) to the anode electrode. The ion permeable membrane preferably exhibits ion permeability (anion permeability) in a potassium hydroxide aqueous solution having a concentration of 30% by weight. Specifically, the ion permeable membrane has an electrical resistance value of preferably 0.5 Ω · cm ² or less, more preferably 0.5 Ω · cm ² or less when an aqueous solution of potassium hydroxide having a temperature of 25 ° C./concentration of 30% by weight is used as an electrolyte. is a 0.1 [Omega · cm ² or less, still more preferably ^{0.01Ω · cm 2 ~ 0.05Ω · cm} 2. When the electrolysis membrane of the present invention has a laminated structure (that is, provided with a reinforcing body), the thickness of the ion permeable membrane is preferably 5 μm to 300 μm, more preferably 5 μm to 200 μm, and still more preferably. 5 μm to 100 μm. If it is such a range, the ion permeable film excellent in ion permeability can be obtained. When the electrolysis membrane of the present invention has a single membrane structure having one ion permeable membrane, the thickness of the ion permeable membrane (that is, the thickness of the electrolysis membrane) is preferably 15 μm to 300 μm, more preferably 15 μm to It is 200 μm, more preferably 15 μm to 100 μm. If it is such a range, the membrane for electrolysis which is excellent in ion permeability and has the intensity | strength which is practically acceptable can be obtained.

The ion permeable membrane is microporous. The microporous ion permeable membrane means an ion permeable membrane having pores with a pore diameter of 20 μm or less over the entire surface. Since the diaphragm for electrolysis of the present invention includes a microporous ion permeable membrane, it has very good ion permeability. In addition, since the ion permeable membrane shows wettability to alkaline water, when using the diaphragm for electrolysis, the polymer constituting the ion permeable membrane is swollen by the electrolytic solution so as to block the pores, and the membrane is passed through the diaphragm. Gas can be prevented from passing through. The ion permeable membrane can be obtained by making the material constituting the ion permeable membrane microporous by any appropriate method such as a stretching method or a phase separation method.

The area change rate of the ion permeable membrane when immersed in pure water is 20% or less. When such an ion permeable membrane is used, wrinkles, tears, deformations, folds, etc. occur even when the dry / wet state of the ion permeable membrane is repeated by replacing the electrolyte during operation, shutdown and maintenance. It is difficult to obtain a diaphragm for electrolysis that exhibits a long life and stable performance. The area change rate of the ion permeable membrane when immersed in pure water is preferably 15% or less, more preferably 10% or less, and further preferably 5% or less. The smaller the area change rate when immersed in pure water, the better. The lower limit value of the area change rate is, for example, 1%. In the present specification, the area of the microporous ion permeable membrane and the diaphragm for electrolysis means an apparent area. For example, when the ion-permeable membrane has a rectangular shape in plan view, the area of the surface defined by the four sides of the rectangle is the area of the ion-permeable membrane.

As described above, a small area change rate when immersed in pure water means a small area change rate when immersed in alkaline water. When the ion permeable membrane is immersed in an aqueous potassium hydroxide solution having a concentration of 30% by weight, the area change rate is preferably 20% or less, more preferably 15% or less, and even more preferably 5% or less. Particularly preferably, it is 3% or less. The smaller the area change rate when immersed in an aqueous potassium hydroxide solution having a concentration of 30% by weight, the better. The lower limit value of the area change rate is, for example, 0.5%. In alkaline water electrolysis, since the electrolytic solution is strongly basic, it is dangerous to incorporate the electrolytic diaphragm in a wet state, but if the electrolytic diaphragm of the present invention provided with the ion permeable membrane is used, it is in a dry state. Even if it is assembled as it is, the area change rate in the electrolytic solution is small, so that it is possible to perform stable alkaline water electrolysis while ensuring the safety at the time of incorporation.

As described above, an ion permeable membrane having a small area change rate can be obtained by forming a hole having a predetermined diameter as described above. More details are as follows. Since the ion permeable membrane is composed of a polymer, it swells in the electrolyte solution. However, in the conventional ion permeable membrane, the swelling of the polymer directly affects the macroscopic shape of the ion permeable membrane, and the area changes. On the other hand, in the present invention, the polymer swells and deforms, but in the in-plane direction, it deforms so as to close the hole. As a result, the area change of the ion permeable membrane itself can be suppressed. In other words, when the deformation of the polymer acts on the shape of the ion permeable membrane, the holes in the ion permeable membrane used in the present invention have a buffering effect, and as a result, the area change of the ion permeable membrane can be suppressed. In the present invention, since the pores of the ion permeable membrane are closed as described above, it is possible to obtain a diaphragm for electrolysis excellent in gas barrier properties.

The average pore diameter of the ion permeable membrane upon drying is 0.01 μm to 20 μm, preferably 0.03 μm to 10 μm, more preferably 0.05 μm to 1 μm, and still more preferably 0.05 μm to 0.00 μm. 5 μm. If it is such a range, the ion permeable film which is very excellent in ion permeability can be obtained. Further, if the average pore diameter of the ion permeable membrane is within the above range, the ion permeable membrane can be used when the electrolysis membrane of the present invention is used, that is, when the electrolysis membrane is immersed in alkaline water as an electrolytic solution. Since the constituent material (polymer) swells and the pores are blocked, it is possible to provide an electrolysis capsule excellent in gas barrier properties. Furthermore, as described above, the area change of the ion permeable membrane itself can be suppressed. In the present specification, the average pore diameter means a dried sample, that is, left in a temperature: 25 ° C., humidity: 60% environment until the weight does not change over time (for example, 12 hours or more). The diameter measured and calculated by the mercury intrusion method.

Examples of the material constituting the ion permeable membrane include a polymer having an anion exchangeable functional group. By having an anion exchangeable functional group, ion permeability and wettability with respect to alkaline water are imparted. As the polymer having an anion-exchangeable functional group, a polymer having mechanical durability and chemical durability with respect to alkaline water and appropriately swelled in alkaline water is preferably used.

The upper limit of the degree of swelling with respect to an aqueous potassium hydroxide solution having a concentration of 30% by weight of the material (polymer) constituting the ion permeable membrane is preferably 250% or less, more preferably 150% or less, and still more preferably 100%. It is as follows. Within such a range, an ion permeable membrane having a small area change rate can be obtained. The lower limit of the degree of swelling is preferably 1% or more. Within such a range, an ion permeable membrane having excellent gas barrier properties can be obtained. The material (polymer) can be selected according to the degree of swelling depending on the use of the diaphragm for electrolysis. For example, a material (polymer) having a relatively low degree of swelling can be selected for applications where a lower area change rate is required, and a degree of swelling is relatively high for applications where higher gas barrier properties are required. A high material (polymer) can be selected. In the present specification, the degree of swelling means the degree of weight swelling at a liquid temperature of 25 ° C. and an immersion time of 12 hours.

Examples of the polymer having an anion-exchange functional group include a polymer in which an anion-exchange functional group is introduced into a skeleton resin such as a fluorine resin, an olefin resin, or an aromatic hydrocarbon resin. . Among these, from the viewpoint of chemical stability against alkaline water, a polymer in which an anion exchangeable functional group is introduced into a fluororesin or an olefin resin is preferably used. From the viewpoint of easy introduction of an anion-exchangeable functional group, an olefin resin is preferably used.

Examples of the fluororesin include, for example, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene. Examples include fluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, and the like. Among them, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, vinylidene fluoride-hexafluoropropylene copolymer or tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer is preferable.

Examples of the olefin resin include low density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, polypropylene, polybutene, polymethylpentene, and copolymers having a repeating unit constituting these compounds. Among these, polypropylene, ultra high molecular weight polyethylene, low density polyethylene or high density polyethylene is preferable. The viscosity average molecular weight of the ultrahigh molecular weight polyethylene used as the material constituting the ion permeable membrane is preferably 500,000 to 10,000,000, more preferably 1,000,000 to 10,000,000. In addition, the said viscosity average molecular weight can be measured by the viscosity method prescribed | regulated to ASTMD4020.

Examples of the aromatic hydrocarbon resins include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyether ether ketone, polyether ketone, polysulfone, polystyrene, polyether sulfone, Examples include polyphenylene sulfide, polyarylate, polyetherimide, polyimide, polyamideimide, thermoplastic polyimide, and a copolymer having a repeating unit constituting these compounds.

The anion exchange functional group is a neutral acid ion exchange group, a weak acid ion exchange group, a strongly basic ion exchange group, a medium basic ion exchange group, or a weak basic ion exchange group. If a polymer having such a functional group is used, an ion permeable membrane having excellent wettability to alkaline water and excellent ion permeability can be obtained.

In the present specification, the medium acidic ion exchange group means a functional group having an acid dissociation constant pKa in water of 1 or more and less than 2. Examples of the intermediate acidic ion exchange group include a phosphomethyl group and a phosphate group. In the present specification, the weakly acidic ion exchange group means a functional group having an acid dissociation constant pKa in water of 2 or more, preferably 2 to 10. Examples of the weakly acidic ion exchange group include a carboxylic acid group, a phenolic hydroxyl group, and a carboxymethyl group. An ion permeable membrane composed of a polymer having a medium acidic group and a weakly acidic group has a wettability to alkaline water by neutralizing the intermediate acidic group and the weak acidic group with an alkali metal ion (for example, potassium). Can be improved. Note that the membrane composed of a polymer having a strongly acidic group is easily exchanged by alkali metal ions in alkaline water and the wettability with respect to alkaline water is reduced. It is not preferable.

In the present specification, the strongly basic ion exchange group means a functional group having a base dissociation constant pKb in water of less than 2. Examples of the strongly basic ion exchange group include a quaternary ammonium base, a sulfonium base, a phosphonium base, a pyridinium base, and the like. In the present specification, the medium basic ion exchange group refers to a functional group having a base dissociation constant pKb in water of 2 or more and less than 4. Examples of the medium basic ion exchange group include an epichlorohydrin triethanolamine group. In the present specification, the weakly basic ion exchange group means a functional group having a base dissociation constant pKb in water of 4 or more, preferably 4 to 10. Examples of the weakly basic ion exchange group include a primary amino group, a secondary amino group, a tertiary amino group, an imidazole group, an amide group, a cyano group, and a pyridyl group.

Any appropriate method can be adopted as a method for introducing the anion-exchangeable functional group. Examples of the method include a graft polymerization method such as a radiation graft polymerization method and a chemical initiator graft polymerization method; a monomer constituting the skeleton resin, a monomer having an anion-exchangeable functional group, and as necessary. And a method of copolymerizing with a crosslinking agent. A graft polymerization method is preferably employed, and a radiation graft polymerization method is more preferably employed. By using the radiation graft polymerization method, hydrophilicity (more specifically, wettability to alkaline water) can be obtained for a long time without impairing the properties (for example, mechanical durability, chemical durability) of the resin as the skeleton. ) Can be obtained. Furthermore, an ion permeable membrane composed of a polymer into which an anion-exchange functional group has been introduced by radiation graft polymerization loses hydrophilicity even in high-temperature alkaline water (for example, a 30 wt% potassium hydroxide aqueous solution at 80 ° C.). Absent. Hereinafter, as a typical example of a method for introducing an anion-exchangeable functional group, a preferred embodiment in which the functional group is introduced by a radiation graft polymerization method will be described.

In the radiation graft polymerization method, the resin as a skeleton is made microporous, then radiation is applied to the resin as a skeleton to generate free radicals, and then anion exchange is performed with the resin irradiated with the radiation. A method (pre-irradiation method) in which a monomer having a functional group and / or a monomer composition containing a monomer capable of introducing an anion-exchangeable functional group is brought into contact and graft polymerization is performed using the free radical as a starting point. preferable. Compared with the method of graft polymerization by irradiating radiation in the coexistence of the resin and the monomer that forms the skeleton (simultaneous irradiation method), the polymerization of the monomers is suppressed and the amount of the monomer contributing to the graft polymerization is large. This is because the utilization rate of the monomer is excellent. Preferably, the resin serving as the skeleton is used in a film form. In this specification, a film-like resin (resin that becomes a skeleton) subjected to graft polymerization is referred to as a base material.

As the pre-irradiation method, a polymer radical method in which irradiation is performed in an inert gas for polymerization may be used, or a peroxide method in which irradiation is performed in the presence of oxygen for polymerization may be used. The polymer radical method is preferred. If a polymer radical method is used, it can suppress that a monomer polymerizes without being graft-polymerized. Examples of the radiation include α rays, β rays, γ rays, electron beams, ultraviolet rays, and the like. Preferably, it is a gamma ray or an electron beam.

The substrate used for producing the ion permeable membrane is preferably microporous. The average pore diameter of the substrate is preferably 0.01 μm to 20 μm, more preferably 0.03 μm to 10 μm, still more preferably 0.05 μm to 1 μm, and particularly preferably 0.05 μm to 0.5 μm. It is.

Any appropriate method can be adopted as a method for making the substrate microporous. For example, a stretching method, a phase separation method, an extraction method, a melt quenching method, a chemical treatment method, a fusion method, a foaming method, a method in which these methods are appropriately combined, and the like can be adopted. Among them, the stretching method or the phase separation method is preferable. The stretching method is a method of making a porous film by stretching a nonporous film in a uniaxial direction or a biaxial direction at a predetermined magnification. According to the method, a uniform and excellent pore shape is obtained. Can do. Moreover, according to the phase separation method, it can be easily made microporous.

The radiation irradiation dose in the radiation graft polymerization method is usually 1 kGy to 500 kGy (kilo gray: 1 gray corresponds to 1 J / kg energy absorption), and preferably 5 kGy to 300 kGy. If the irradiation dose is less than 1 kGy, a sufficient number of free radicals for graft polymerization may not be generated. On the other hand, if the irradiation dose is more than 500 kGy, there is a possibility that excessive crosslinking reaction or deterioration of the resin constituting the substrate proceeds. The temperature during irradiation is not particularly limited, but is, for example, −200 ° C. to 60 ° C., preferably about −200 ° C. to 25 ° C. If the environmental temperature at the time of irradiation and after irradiation is too higher than the glass transition temperature of the resin constituting the substrate, the generated free radicals may be deactivated. The resin after irradiation is preferably placed at a low temperature of room temperature or lower, more preferably −60 ° C. or lower.

A method in which a resin (base material) irradiated with radiation is brought into contact with a monomer composition containing a monomer having an anion-exchange functional group and / or a monomer capable of introducing an anion-exchange functional group, and graft polymerization is performed. Examples of the method include a method of immersing a resin (base material) irradiated with radiation in a monomer composition. In the monomer composition, monomers having an anion exchange functional group or monomers capable of introducing an anion exchange functional group may be used alone or in combination of two or more.

The monomer composition may be a homogeneous solution containing an organic solvent or an emulsion solution containing a water-soluble solvent (for example, water). As the organic solvent, any appropriate solvent can be used as long as it can dissolve the monomer and can penetrate the base material. The organic solvent is preferably a lower alcohol having 1 to 6 carbon atoms, more preferably a lower alcohol having 1 to 4 carbon atoms, still more preferably ethanol or methanol. Further, acetone, methyl acetate, ethyl acetate, hexane, or toluene may be used as the organic solvent. Preferably, the monomer composition is deoxygenated by performing vacuum degassing and bubbling with an inert gas such as nitrogen.

Examples of the monomer having an anion-exchange functional group include vinyl compounds having an anion-exchange functional group, and a vinyl compound represented by the following general formula (1) can be preferably used.
H ₂ C═C (X) R ¹ (1)
X represents a hydrogen atom or a linear or branched alkyl group. When X is an alkyl group, the carbon number is preferably 1 to 10, more preferably 1 to 5. R ¹ is a linear or branched alkyl group having the above anion-exchange functional group, preferably a hydroxyl group, a carboxylic acid group, a primary amino group, a secondary amino group, a tertiary amino group, or an amide group. , A cyano group, a quaternary ammonium base, an imidazole group, a pyridyl group and / or a linear or branched alkyl group having a quaternary pyridinium base. R ¹ preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and still more preferably 1 to 6 carbon atoms. With such a carbon number, an ion permeable membrane having excellent hydrophilicity can be obtained.

Specific examples of the monomer having an anion-exchangeable functional group include acrylic acid, methacrylic acid, 2-hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, and 4-hydroxybutyl. Acrylate, 2-hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, vinyl acetate, allylamine, acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dimethylaminopropylacrylamide, N, N -Dimethylaminoethyl acrylate 2- (dimethylamino) ethyl acrylate, N- (2-hydroxyethyl) acrylamide, acryloylmorpholine, N-isopropyla Kurylamide, acrylonitrile, methacrylonitrile, 1-vinylimidazole, 2-vinylpyridine, 4-vinylpyridine, methylvinylpyridine, ethylvinylpyridine, vinylpyrrolidone, vinylcarbazole, aminostyrene, alkylaminostyrene, dialkylaminostyrene, trialkyl Aminostyrene, vinylbenzyltrimethylammonium chloride, etc. are mentioned. Of these, acrylic acid, methacrylic acid, 2-hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, acrylamide or methacrylamide are preferable. These monomers may be used alone or in combination of two or more. Further, after the graft polymerization, for example, a hydrophilic effect can be further enhanced by performing a neutralization treatment using an about 1 N aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, or the like.

Examples of the monomer capable of introducing the anion-exchange functional group include alkyl esters of styrene sulfonic acid; alkyl esters of vinyl sulfonic acid; alkyl esters of acrylic phosphonic acid; lithium salts, sodium salts, and potassium of styrene sulfonic acid. Examples thereof include lithium salt, ammonium salt, lithium salt, sodium salt, potassium salt or ammonium salt of vinyl sulfonic acid; lithium salt, sodium salt, potassium salt or ammonium salt of acrylic phosphonic acid. When an alkyl ester of styrene sulfonic acid, vinyl sulfonic acid, or acrylic phosphonic acid is used, ion permeability and hydrophilicity can be imparted by hydrolyzing the ester into an acid form after graft polymerization. In the case of using a salt of styrene sulfonic acid, vinyl sulfonic acid or acrylic phosphonic acid, after the graft polymerization, for example, by performing acid treatment with about 1 N nitric acid, hydrochloric acid or sulfuric acid, the above anion-exchangeable one can be obtained. An ion permeable membrane having a functional group and exhibiting ion permeability and hydrophilicity can be obtained.

Specific examples of the alkyl ester of styrene sulfonic acid include styrene sulfonic acid ethyl ester, styrene sulfonic acid propyl ester, styrene sulfonic acid isopropyl ester, styrene sulfonic acid n-butyl ester, styrene sulfonic acid tert butyl ester, and styrene sulfonic acid isobutyl. Examples thereof include styrene sulfonic acid pentyl ester, styrene sulfonic acid neopentyl ester, styrene sulfonic acid isopentyl ester, and styrene sulfonic acid tert pentyl ester. Specific examples of the alkyl ester of vinyl sulfonic acid include vinyl sulfonic acid ethyl ester and vinyl sulfonic acid methyl ester.

Halogenated alkylstyrene may be used as a monomer capable of introducing the anion-exchangeable functional group. Specific examples of the halogenated alkyl styrene include chloromethyl styrene, bromomethyl styrene, iodomethyl styrene, chloroethyl styrene, bromoethyl styrene, iodoethyl styrene, chloropentyl styrene, bromopentyl styrene, iodopentyl styrene, chlorohexyl styrene, Examples include bromohexyl styrene, iodohexyl styrene, chloropropyl styrene, bromopropyl styrene, iodopropyl styrene, chlorobutyl styrene, bromobutyl styrene, and iodobutyl styrene. When halogenated alkylstyrene is used, after graft polymerization, for example, aqueous ammonia or alkylamine (eg, diamine, triamine, tetraamine, trimethylamine, triethylamine, tributylamine, dimethylethylamine) is dissolved in alcohol, acetone and / or water. Ion permeability and hydrophilicity can be imparted by subjecting the halogenated alkyl group to quaternary ammoniumation with the solution or the like. For example, an ion permeable membrane having ion permeability and hydrophilicity can be obtained by performing phosphoniumation treatment with a solution in which tributylphosphine is dissolved in alcohol and / or acetone.

The concentration of the monomer having an anion exchangeable functional group and the monomer capable of introducing the anion exchangeable functional group in the monomer composition is preferably 0.1% by weight to 70% by weight, more preferably 5% by weight. ~ 60% by weight. When the concentration of the monomer is less than 0.1% by weight, the graft polymerization reaction may not proceed sufficiently. On the other hand, when the concentration of the monomer is higher than 70% by weight, unreacted monomers may remain, leading to a decrease in yield.

Other monomer may be contained in the monomer composition. As the other monomer, any appropriate monomer can be used as long as it is a monomer copolymerizable with the monomer having an anion exchange functional group or a monomer capable of introducing an anion exchange functional group. The content of other monomers is preferably 0.5% by weight to 100% by weight with respect to the total amount of the monomer having an anion exchange functional group and the monomer capable of introducing an anion exchange functional group. More preferably, it is 1 to 50% by weight.

The other monomer in the monomer composition may be a crosslinking agent. By using a monomer composition containing a crosslinking agent, an ion permeable membrane having a crosslinked structure and excellent durability (for example, water resistance, alkali resistance, heat resistance, oxidation resistance) can be obtained. Examples of the crosslinking agent include vinyl compounds having two or more vinyl groups. Specific examples of the crosslinking agent include divinylbenzene.

The temperature at which the substrate irradiated with radiation and the monomer composition are brought into contact (reaction temperature in the graft polymerization reaction) is preferably 0 ° C. to 100 ° C., more preferably 30 ° C. to 80 ° C. The time for contacting the substrate irradiated with radiation and the monomer composition (reaction time in the graft polymerization reaction) is preferably 3 minutes to 48 hours.

After the graft polymerization reaction, the polymer having an anion-exchange functional group is preferably washed with an organic solvent such as toluene, methanol, isopropyl alcohol, acetone, or water, and then dried.

The weight graft ratio of the ion-permeable membrane having an anion-exchange functional group obtained by graft polymerization is preferably 5% to 150%, more preferably 10% to 100%. In this specification, the weight graft ratio is a value calculated by (weight of base material after graft polymerization−weight of base material before graft polymerization) / (weight of base material before graft polymerization) × 100. Say.

When the diaphragm for electrolysis of the present invention includes an ion permeable membrane and a reinforcing body, the grafting process for the base material constituting the ion permeable membrane constitutes the base material and the reinforcing body (or the reinforcing body constituting the ion permeable membrane). May be performed after the substrate is laminated, or may be performed before the ion permeable membrane and the reinforcing body are laminated. Preferably, the graft treatment is performed after laminating the base material constituting the ion permeable membrane and the reinforcing body (or the base material constituting the reinforcing body). When the grafting process is performed after laminating the base material constituting the ion permeable membrane and the base material constituting the reinforcing body, the grafting process can be simultaneously performed on both base materials. Thus, if the graft | grafting process is simultaneously performed with respect to both base materials, the diaphragm for electrolysis which is excellent in ion permeability and shows the high wettability with respect to alkaline water can be obtained. When grafting is performed on both substrates simultaneously, the weight graft ratio of the diaphragm for electrolysis is preferably 5% to 150%, more preferably 10% to 100%.

C. Reinforcing body The reinforcing body is porous. Examples of the form of the porous reinforcing body include a woven fabric, a nonwoven fabric, a net, a mesh, and a sintered porous membrane. A sintered porous membrane is preferable. If it is a sintered porous membrane, strength and ion permeability are remarkably excellent. Examples of a method for obtaining a sintered porous film include a sintering method described in JP-A-2-214647.

The hole diameter of the reinforcing body is larger than the hole diameter of the ion permeable membrane. The size of the holes in the reinforcement can be indirectly evaluated by the air permeability (more specifically, the size and thickness of the holes affect the air permeability). The air permeability of the reinforcing body is preferably 1 cm ³ / cm ² · second or more, more preferably 3 cm ³ / cm ² · second or more, and further preferably 5 cm ³ / cm ² · second or more. If it is such a range, the electrocoating membrane excellent in ion permeability can be obtained. The upper limit of the air permeability of the reinforcing body is, for example, 500 cm ³ / cm ² · sec. If the air permeability exceeds 500 cm ³ / cm ² · sec or more, the strength of the reinforcing body may be reduced. In the present specification, the air permeability can be measured by Frazier method evaluation based on JIS L 1096 8.26 IA.

The porosity of the reinforcing body is preferably 10% to 90%, more preferably 10% to 55%, and further preferably 10% to 50%. The porosity of the reinforcing body refers to a value calculated by the formula {1- (apparent density of reinforcing body / true specific gravity of material constituting the reinforcing body)} × 100.

The thickness of the reinforcing body is preferably 10 μm to 1000 μm, more preferably 30 μm to 500 μm, and further preferably 50 μm to 200 μm. If it is such a range, it has sufficient intensity | strength as a reinforcement body and can prevent the short circuit of an electrode.

As the material constituting the reinforcing body, any appropriate material can be used as long as the effects of the present invention can be obtained. As a material which comprises the said porous reinforcement body, the polymer which has a hydrophilic functional group is mentioned, for example, Preferably the polymer which has an anion exchange functional group is mentioned. Examples of the polymer having an anion-exchangeable functional group include the polymers described in the above section B. Among these, a polymer using ultrahigh molecular weight polyethylene as a resin serving as a skeleton can be preferably used. In the reinforcing body, the polymer preferably has a hydroxyl group, a carboxylic acid group, an amino group, an amide group, or a cyano group as an anion-exchangeable functional group.

The introduction of an anion-exchangeable functional group in the reinforcing body can be performed by the method described in the above section B. That is, also in the reinforcing body, the anion-exchangeable functional group is preferably introduced by a graft polymerization method, and preferably by a radiation graft polymerization method. The grafting process for the base material constituting the reinforcing body may be performed after the ion permeable membrane (or the base material constituting the ion permeable membrane) and the base material constituting the reinforcing body are laminated. You may carry out before laminating | stacking. Preferably, the graft treatment is performed after laminating the ion permeable membrane (or the base material constituting the ion permeable membrane) and the base material constituting the reinforcing body. When the grafting process is performed after laminating the base material constituting the ion permeable membrane and the base material constituting the reinforcing body, the grafting process can be simultaneously performed on both base materials.

The air permeability of the base material used for producing the reinforcing body is preferably 1 cm ³ / cm ² · sec or more, more preferably 3 cm ³ / cm ² · sec or more, and further preferably 5 cm ³ / cm ^2. -More than a second. If it is such a range, the electrocoating membrane excellent in ion permeability can be obtained. The upper limit of the air permeability of the reinforcing body is, for example, 500 cm ³ / cm ² · sec.

Examples of the form of the substrate used for producing the reinforcing body include woven fabric, non-woven fabric, net, mesh, sintered porous membrane, and the like.

In the reinforcing body, the porosity of the base material (reinforcing body before graft polymerization) is preferably 10% to 95%, more preferably 15% to 90%, and further preferably 15% to 75%. It is particularly preferably 15% to 70%. If it is such a range, the reinforcement which is excellent in ion permeability and excellent in the short circuit prevention performance of an electrode can be obtained. In this specification, the porosity of the base material (reinforcing body before graft polymerization) is calculated by the formula {1- (apparent density of base material / true specific gravity of the material constituting the base material)} × 100. Value.

The weight graft ratio of the reinforcing body having an anion-exchangeable functional group obtained by graft polymerization is preferably 5% to 150%, more preferably 10% to 100%.

As described above, the diaphragm for electrolysis of the present invention is excellent in ion permeability, has a small area change rate at the time of use, has high wettability with respect to an alkaline aqueous solution, and can suppress an increase in voltage. Such a diaphragm for electrolysis can be suitably used for an electrochemical cell for hydrogen production. According to another aspect of the present invention, an electrochemical cell for hydrogen production using the electrolysis membrane can be provided.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The evaluation methods in the examples are as follows. In Examples, unless otherwise specified, “parts” and “%” are based on weight.

(1) Measurement of thickness Digital upright gauge R1-205 (manufactured by Ozaki Seisakusho; measuring element: Φ5 mm, measuring force: 1.1 N or less) was used for the thickness. Unless otherwise specified, the measured values are at 25 ° C. ± 2 ° C. and 65 ± 20% RH.
(2) Measurement of average pore diameter The average pore diameter of the base materials used in Examples and Comparative Examples was determined by a mercury intrusion method using a mercury intrusion apparatus.
(3) Air permeability The air permeability of the substrates used in Examples and Comparative Examples was measured according to the Frazier method based on JIS L 1096 8.26 IA method.
(4) Wettability with respect to aqueous potassium hydroxide solution The diaphragm for electrolysis was immersed in an aqueous potassium hydroxide solution having a concentration of 30% by weight maintained at 80 ° C. for 100 hours. Thereafter, the diaphragm for electrolysis was pulled up, and the remaining potassium hydroxide aqueous solution was sufficiently washed and removed, and then dried. Next, a pH test paper (product number “1-1745-01” manufactured by ASONE Co., Ltd.) is applied to one side (back side) of the diaphragm for electrolysis, and potassium hydroxide having a concentration of 30% by weight from the other side (front side). One drop (about 50 mg) of the aqueous solution was added dropwise. One minute after dropping, when the potassium hydroxide aqueous solution reached the back surface and the pH test paper was discolored, it was judged that there was wettability.
(5) Rate of area change The diaphragm for electrolysis cut into a predetermined area is placed in an environment at a temperature of 25 ° C./humidity of 60%, and the area of the diaphragm for electrolysis after 12 hours is designated as S _0. Was immersed in pure water at 60 ° C., and the area of the diaphragm for electrolysis after 3 hours was set as S ₁ , and the area change rate was calculated by the following formula.
Area change rate (%) = ((S ₁ −S ₀ ) / S ₀ ) × 100
In addition, the area change when immersed in pure water correlates with the area change when immersed in alkaline water. Moreover, the area change when immersed in pure water is more conspicuous than the area change when immersed in alkaline water. Therefore, the area change rate measured using pure water as described above is a preferable index of the area change when immersed in alkaline water.
(6) Electrical resistance The electrical resistance of the diaphragms for electrolysis obtained in the examples and comparative examples was measured according to JIS C 2313. As the electrolytic solution, an aqueous potassium hydroxide solution having a concentration of 40% by weight was used. A platinum plate was used as the electrode. The liquid temperature at the time of measurement was set to 25 ° C. The measurement was performed after the diaphragm for electrolysis was immersed in the electrolyte for 10 minutes.
(7) Alkaline water electrolysis evaluation Alkaline water electrolysis evaluation of the diaphragm for electrolysis obtained by the Example and the comparative example was performed using the H-type cell made from an acrylic resin. As the electrolytic solution, an aqueous potassium hydroxide solution having a concentration of 30% by weight was used, and a Ni electrode was used as the electrode. The liquid temperature at the time of measurement was set to 25 ° C. The current density was 0.2 A / cm ² , the voltage when a constant current was applied continuously for 1 hour was measured, and alkaline water electrolysis was evaluated based on the average value of the measured values 50 minutes to 1 hour after the start of measurement. Went. The measurement was performed after the diaphragm for electrolysis was immersed in the electrolyte for 10 minutes.
(8) Gas barrier property The gas generated on the cathode side after 1 hour from the start of alkaline water electrolysis in (7) above is recovered, and the cathode is obtained by gas chromatography (manufactured by Shimadzu Corporation, trade name “GC-8A”). The gas barrier properties were evaluated by measuring the hydrogen purity of the gas generated on the side. In Table 1, the case where the hydrogen purity is 99.9% or more is marked with ◯, and the case where it is less than 99.9% is marked with x.
(9) Smoothness The thickness of 9 points randomly selected in the diaphragms for electrolysis obtained in Examples and Comparative Examples was measured, and the thickness of the thickest part and the thickness of the thinnest part with respect to the average value of the thicknesses. The smoothness was evaluated by the ratio of the difference. In Table 1, the case where the difference between the thickness of the thickest part and the thickness of the thinnest part was (thickness average value × 30%) or less was marked as “◯”, and the case where it was larger than (thickness average value × 30%).

[Example 1] Production of diaphragm A for electrolysis (one ion permeable membrane) A biaxially stretched microporous base material 1 made of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 1,200,000 (TODENTSU NITTO ( Free radicals were generated by irradiating a 45 kGy electron beam to a Shanghai Power Co., Ltd. product name: FIBR0SS, thickness: 16 μm, average pore size: 0.08 μm. After electron beam irradiation, it was stored at -70 ° C.
Next, 250 g of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) and 250 g of methanol (manufactured by Wako Pure Chemical Industries, Ltd.) were added to the separable flask to prepare a mixed solution, and nitrogen gas was maintained while maintaining the temperature at 25 ° C. Oxygen remaining in the mixed solution was removed by performing bubbling for 1 hour.
The base material 1 irradiated with the electron beam is put into the mixed liquid, the liquid temperature is raised to 55 ° C., and the polymerization temperature is kept at 55 ° C. for 4 minutes to perform the polymerization treatment. Methacrylic acid was graft polymerized (weight graft ratio: 32%).
Next, the graft-polymerized base material 1 was immersed in an aqueous solution of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) having a concentration of 10% by weight with the liquid temperature maintained at 60 ° C. for 1 hour, and the graft chain portion was replaced with a potassium salt. did. Thereafter, the base material 1 is pulled up, washed with water to wash away excess potassium hydroxide, and then water on the surface portion is removed to obtain a diaphragm A for electrolysis comprising a microporous ion permeable membrane 1a having ion permeability. It was.
The obtained diaphragm A for electrolysis was subjected to the above evaluations (4) to (9). The evaluation results are shown in Table 1.

[Example 2] Preparation of diaphragm B for electrolysis (one ion permeable membrane structure) Except that the polymerization time in the graft polymerization was changed from 4 minutes to 5 minutes, the ion permeable membrane 1b ( A diaphragm B for electrolysis having a weight graft ratio of 42% was obtained. The obtained diaphragm B for electrolysis was subjected to the above evaluations (4) to (9). The evaluation results are shown in Table 1.

[Example 3] Production of diaphragm C for electrolysis (one ion permeable membrane structure) Using acrylamide (manufactured by Wako Pure Chemical Industries, Ltd.) instead of methacrylic acid, the polymerization temperature in the graft polymerization (temperature of the polymerization solution) was 55 ° C. The membrane C for electrolysis which consists of the ion permeable film 2a (weight graft ratio: 51%) was obtained like Example 1 except having changed into 60 degreeC and having changed the polymerization processing time in graft polymerization into 4 minutes for 5 minutes. . The obtained diaphragm C for electrolysis was subjected to the above evaluations (4) to (9). The evaluation results are shown in Table 1.

[Example 4] Production of diaphragm D for electrolysis (one ion permeable membrane configuration) Instead of methacrylic acid, acrylamide (manufactured by Wako Pure Chemical Industries, Ltd.) was used, and the polymerization temperature in the graft polymerization (temperature of the polymerization solution) was 55 ° C. Except that the temperature was changed to 60 ° C. and the polymerization time in the graft polymerization was changed from 4 minutes to 8 minutes, the membrane D for electrolysis composed of the ion permeable membrane 2b (weight graft ratio: 79%) was obtained in the same manner as in Example 1. . The obtained diaphragm D for electrolysis was subjected to the above evaluations (4) to (9). The evaluation results are shown in Table 1.

[Example 5] Production of diaphragm E for electrolysis (reinforcing body 1 / ion permeable membrane 1c / reinforcing body 1) Base material 1 used in Example 1 and wet nonwoven fabric 1 for constituting the reinforcing body (Hirose Paper Co., Ltd.) Product name: HOP-15H, polyethylene / polypropylene core-sheath structure, thickness: 84 μm, air flow rate: 345 cm ³ / cm ² · second) to be wet nonwoven fabric 1 / substrate 1 / wet nonwoven fabric 1 And three-layer laminated substrate I was obtained by heat welding using a hot roll machine heated to 150 ° C.
Next, free radicals were generated by irradiating the substrate I with an electron beam of 45 kGy. After irradiation, it was stored at -70 ° C.
Next, 250 g of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) and 250 g of methanol are added to a separable flask to prepare a mixed solution, and bubbling with nitrogen gas is performed for 1 hour while keeping the temperature at 25 ° C. Then, oxygen remaining in the mixed solution was removed.
The base material I irradiated with the electron beam was put into the mixed liquid, the liquid temperature was raised to 55 ° C., and the polymerization temperature was maintained for 7 minutes while maintaining the liquid temperature at 55 ° C. Methacrylic acid was graft polymerized (weight graft ratio: 72%).
Next, the graft-polymerized substrate I was immersed in an aqueous solution of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) having a concentration of 10% by weight with the liquid temperature maintained at 60 ° C. for 1 hour, and the graft chain portion was converted to potassium salt. did. Thereafter, the substrate I is pulled up, washed with water to wash away excess potassium hydroxide, and then water on the surface portion is removed to remove the ion-permeable microporous ion-permeable membrane 1c and the porous reinforcing body 1 An electrolysis diaphragm E was obtained.
The obtained diaphragm E for electrolysis was subjected to the evaluations (4) to (9). The evaluation results are shown in Table 1.

[Example 6] Preparation of diaphragm F for electrolysis (reinforcing body 2 / ion permeable membrane 1d / reinforcing body 2) In place of wet nonwoven fabric 1, sintered porous membrane 1 made of ultrahigh molecular weight polyethylene (manufactured by Nitto Denko Corporation, product) Name: sunmap, thickness: 100 μm, air flow rate: 16 cm ³ / cm ² · second), and using a heat roll machine heated to 160 ° C., in the same manner as in Example 5, a diaphragm for electrolysis F was obtained (reinforcing body 2 / ion permeable membrane 1d / reinforcing body 2, weight graft ratio: 54%). The obtained diaphragm F for electrolysis was subjected to the above evaluations (4) to (9). The evaluation results are shown in Table 1.

[Comparative Example 1]
As the ion permeable membrane, a nonporous ion permeable membrane C1 (made by DuPont, trade name: Nafion 212CS, thickness: 50 μm) composed of a perfluorocarbon polymer having a sulfonic acid group is used. The diaphragm for electrolysis comprised from (one ion permeable membrane 1 structure) was obtained. This diaphragm for electrolysis was subjected to the evaluations (4) to (9). The evaluation results are shown in Table 1.

[Comparative Example 2]
A cross-linked polyethylene film (thickness 30 μm) obtained by subjecting a non-porous polyethylene film to a cross-linking treatment by 100 kGy electron beam irradiation was irradiated with a 75 kGy electron beam to generate free radicals. Next, the crosslinked polyethylene film produced by free radicals was immersed in a methanol solution (concentration: 60% by weight) of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) whose liquid temperature was maintained at 70 ° C. for 2 hours, and the crosslinked polyethylene film Then, methacrylic acid was graft polymerized (weight graft ratio: 41%). Subsequently, the graft-polymerized crosslinked polyethylene film was immersed in an aqueous solution of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) having a concentration of 10% by weight maintained at 60 ° C. for 1 hour to make the graft chain portion a potassium salt. Thereafter, the film was pulled up, washed with water to wash away excess potassium hydroxide, and then water on the surface portion was removed to obtain a diaphragm for electrolysis comprising an ion permeable membrane C2. This diaphragm for electrolysis was subjected to the evaluations (4) to (9). The evaluation results are shown in Table 1.

[Comparative Example 3]
The microporous substrate 1 used in Example 1 (manufactured by Nitto (Shanghai) Power Source Co., Ltd., trade name: FIBR0SS, thickness: 16 μm, average pore size: 0.08 μm) was directly used as a diaphragm for electrolysis. . This diaphragm for electrolysis was subjected to the evaluations (4) to (9). The evaluation results are shown in Table 1.

[Comparative Example 4]
First, 30 g of 1-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) and 12 g of calcium fluoride (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed and sufficiently stirred with a homomixer. 4 g of polysulfone (trade name “ULTRASON S6010” manufactured by BASF Corporation) was added thereto, heated to 60 ° C., sufficiently stirred and dissolved again, and then defoamed to prepare a suspension.
A 200 mesh, 190 μm thick polyethylene net (nip (polyethylene) strong net, manufactured by NBC Co., Ltd.) was stretched, and 10 ml of the suspension was poured onto a 10 cm × 10 cm glass frame placed on the bottom. . Thereafter, the frame into which the suspension was poured was immersed in pure water at 25 ° C. and left at room temperature for 10 minutes to extract 1-methyl-2-pyrrolidone. Thereafter, the solidified sheet-like material is peeled off from the frame, further washed in pure water at 25 ° C. for 30 minutes, air-dried at 25 ° C., and then dried in a dryer at 80 ° C. for 30 minutes to obtain a sheet-like ion permeable membrane. C3 was obtained. The obtained ion permeable membrane C3 was subjected to the evaluations (4) and (9). The results are shown in Table 1. The ion permeable membrane C3 had many irregularities on the surface and the film thickness varied from 300 μm to 1500 μm, and the area change rate, electrical resistance, alkaline water electrolysis evaluation and gas barrier property evaluation could not be performed.

[Comparative Example 5]
First, 30 g of 1-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) and 24 g of calcium fluoride (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed and sufficiently stirred with a homomixer. 8 g of polysulfone (manufactured by BASF, trade name “ULTRASON S6010”) was added thereto, heated to 60 ° C., sufficiently stirred and dissolved again, and defoamed to prepare a suspension.
Next, the suspension was applied to a glass plate with a gap of 300 μm using a Baker type applicator. A 200 mesh, 190 μm thick polyethylene net (nip (polyethylene) strong net, manufactured by NBC)) was placed on this, and surface pressure was applied by a hand roller to sufficiently immerse the suspension in the mesh. Thereafter, the suspension was applied again at a gap of 400 μm using a Baker type applicator in the same manner. Thereafter, the glass plate was immersed in pure water at 25 ° C. and left at room temperature for 10 minutes to extract 1-methyl-2-pyrrolidone. The solidified sheet is peeled off, further washed in pure water at 25 ° C. for 30 minutes, air-dried at 25 ° C., and then dried in a dryer at 80 ° C. for 30 minutes to obtain a sheet-like ion permeable membrane C4. It was. The obtained ion permeable membrane C4 had a smooth surface and a uniform thickness of around 380 μm. The obtained ion permeable membrane C4 was subjected to the evaluations (4) to (9). The evaluation results are shown in Table 1.

As is apparent from Table 1, the diaphragm for electrolysis of the present invention has a small area change rate when immersed in pure water, a small electrical resistance, and can suppress an increase in voltage. Moreover, the diaphragm for electrolysis of this invention is excellent also in gas barrier property. In addition, the diaphragm for electrolysis which consists of a nonporous ion permeable film had a large area change rate (Comparative Examples 1 and 2), and the diaphragm for electrolysis which was inferior in wettability became high in the electrolysis voltage (Comparative Example 3). Moreover, when the microporous base material comprised from the polymer which does not have an anion exchange functional group is used as an ion permeable film, it is inferior to gas barrier property (comparative example 3).

Further, in the diaphragm for electrolysis of the present invention, the ion permeable membrane (in the case of having a reinforcing body, the ion permeable membrane and the reinforcing body) is formed by introducing an anion-exchangeable functional group by radiation graft polymerization so Even when immersed in water for a long time, wettability to alkaline water is maintained.

The diaphragm for electrolysis of the present invention can be suitably used as a diaphragm used in alkaline water electrolysis.

DESCRIPTION OF SYMBOLS 10 Ion permeable membrane 20 Reinforcement body 100, 100 'Electrolyte diaphragm

Claims (9)

1. A diaphragm for electrolysis comprising an ion permeable membrane and exhibiting wettability with respect to an aqueous potassium hydroxide solution having a concentration of 30% by weight,
   The average pore diameter of the ion permeable membrane is 0.01 μm to 20 μm, and the area change rate when the ion permeable membrane is immersed in pure water is 20% or less.
   Diaphragm for electrolysis.
2. The diaphragm for electrolysis of Claim 1 whose electrical resistance value is 0.5 ohm * cm < ² > or less when using the potassium hydroxide aqueous solution whose temperature of the said ion permeable film is 25 degreeC / concentration 30 weight% as electrolyte solution.
3. The ion permeable membrane is composed of a polymer having a medium acidic ion exchange group, a weak acid ion exchange group, a strong basic ion exchange group, a medium basic ion exchange group, or a weak basic ion exchange group. The diaphragm for electrolysis of 2.
4. In the ion permeable membrane, the medium acid ion exchange group, weak acid ion exchange group, strong basic ion exchange group, medium basic ion exchange group or weak basic ion exchange group is introduced by graft polymerization. Item 4. The diaphragm for electrolysis according to item 3.
5. The membrane for electrolysis according to any one of claims 1 to 4, further comprising a porous reinforcing body disposed on one side or both sides of the ion permeable membrane.
6. The membrane for alkaline water electrolysis according to claim 5, wherein the reinforcing body is disposed on both sides of the ion permeable membrane.
7. The said reinforcement body is comprised from the polymer which has a moderately acidic ion exchange group, a weakly acidic ion exchange group, a strongly basic ion exchange group, a medium basic ion exchange group, or a weakly basic ion exchange group. The diaphragm for electrolysis of 6.
8. In the reinforcing body, the medium acid ion exchange group, weak acid ion exchange group, strong basic ion exchange group, medium basic ion exchange group or weak basic ion exchange group is introduced by graft polymerization. The diaphragm for electrolysis of 7.
9. An electrochemical cell for hydrogen production using the electrolyzing membrane according to claim 1.
   

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