WO2015030025A1

WO2015030025A1 - Method for manufacturing diaphragm for alkaline water electrolysis, and diaphragm for alkaline water electrolysis

Info

Publication number: WO2015030025A1
Application number: PCT/JP2014/072357
Authority: WO
Inventors: 勇三村木; 健郎井上; 樋口　浩之; 川口　佳秀; 原田　憲章
Original assignee: 日東電工株式会社
Priority date: 2013-08-30
Filing date: 2014-08-27
Publication date: 2015-03-05
Also published as: JP2015048504A

Abstract

Provided is a method for manufacturing a diaphragm for alkaline water electrolysis, which has excellent ion permeability and chemical resistance and hardly undergoes the adhesion of a gas, which is generated at an electrode upon the electrolysis, onto the surface thereof. The method for manufacturing a diaphragm for alkaline water electrolysis according to the present invention comprises: a step of preparing a resin composition comprising an epoxy resin, a curing agent and a porogen; and a step of producing a resin sheet using the resin composition. In one embodiment, the method for manufacturing a diaphragm for alkaline water electrolysis according to the present invention additionally involves a step of removing the porogen from the resin sheet.

Description

Process for producing diaphragm for alkaline water electrolysis and diaphragm for alkaline water electrolysis

The present invention relates to a method for producing a diaphragm for alkaline water electrolysis and a diaphragm for alkaline water 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, a water electrolysis method using a polymer electrolyte can be mentioned. However, the technique uses an expensive noble metal such as platinum as a catalyst. 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 membranes for alkaline water electrolysis, asbestos cloth and ceramic porous membranes are known. However, asbestos cloth has a problem in durability at 100 ° C. or more, and there is also a problem of health damage. The ceramic porous membrane has a problem that it requires a very high-temperature treatment process at the time of processing, and also has a problem that the thickness is high and the resistance becomes high. In addition, an ion-permeable diaphragm containing a hydrophilic inorganic material has been proposed as a diaphragm used in the alkaline water electrolysis method (Patent Document 1). This ion-permeable diaphragm exhibits wettability to water based on the wettability of a hydrophilic inorganic material added in a large amount, and has ion permeability because it is porous. However, this ion-permeable diaphragm has a problem that the gas generated by the electrode during electrolysis tends to adhere to the surface of the diaphragm because the polymer material as a matrix is essentially hydrophobic. As a result, in electrolysis using alkaline water as the electrolytic solution, the electrical resistance characteristics are insufficient and a voltage rise occurs.

JP 2008-144262 A

The present invention has been made in order to solve the above-described conventional problems. The object of the present invention is excellent ion permeability and chemical resistance, and gas generated at the electrode during electrolysis adheres to the diaphragm surface. An object of the present invention is to provide a method for producing a diaphragm for alkaline water electrolysis that is difficult to perform.

The manufacturing method of the diaphragm for alkaline water electrolysis of this invention includes the process of preparing the resin composition containing an epoxy resin, a hardening | curing agent, and a porogen, and the process of obtaining a resin sheet using this resin composition.
In one embodiment, the manufacturing method of the diaphragm for alkaline water electrolysis of this invention further includes the process of removing the said porogen from the said resin sheet.
In one embodiment, in the method for producing a diaphragm for alkaline water electrolysis according to the present invention, in the step of obtaining a resin sheet using the resin composition, the resin composition is molded to obtain a cured body, and the cured body Cutting the surface layer portion with a predetermined thickness to obtain the resin sheet.
In one embodiment, in the method for producing a diaphragm for alkaline water electrolysis according to the present invention, the cured body is cylindrical, and the surface layer portion of the cured body is rotated while rotating the cured body about a cylindrical axis. Including cutting.
In one embodiment, the porogen is polyethylene glycol or polypropylene glycol.
According to another aspect of the present invention, a diaphragm for alkaline water electrolysis is provided. This diaphragm for alkaline water electrolysis is obtained by the above production method.
According to still another aspect of the present invention, a composite membrane for alkaline water electrolysis is provided. The composite membrane for alkaline water electrolysis includes the above diaphragm for alkaline water electrolysis and a porous reinforcing body disposed on one or both surfaces of the diaphragm for alkaline water electrolysis.
In one embodiment, the said porous reinforcement body is comprised from the polymer which has a hydrophilic functional group.
In one embodiment, the porous reinforcing body is a woven fabric, a nonwoven fabric, a net, a mesh, or a sintered porous membrane.

According to the present invention, a diaphragm having a porous structure suitable for alkaline water electrolysis can be obtained by using a resin composition containing an epoxy resin and a porogen. The alkaline water electrolysis diaphragm is excellent in ion permeability and chemical resistance, and the gas generated at the electrode during electrolysis hardly adheres to the diaphragm surface.

It is the schematic which shows an example of the method of cutting the surface layer part of a cylindrical hardening body. It is a SEM photograph which shows the mode of the bubble adhering to the diaphragm for electrolysis in an Example and a comparative example.

Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.
A. Method for producing diaphragm for alkaline water electrolysis The method for producing a diaphragm for alkaline water electrolysis according to the present invention comprises a step of preparing a resin composition containing an epoxy resin, a curing agent and a porogen (step 1), and the resin composition. A step of obtaining a resin sheet (step 2). The membrane for alkaline water electrolysis thus obtained is made porous by removing the porogen in the resin sheet in an aqueous solvent such as alkaline water, and is excellent in ion permeability. That is, in one embodiment, the diaphragm for alkaline water electrolysis obtained by the production method of the present invention is a precursor of a porous body, and becomes porous when used, specifically, when immersed in alkaline water. obtain. In another embodiment, the production method of the present invention further includes a step of removing the porogen from the resin sheet. In this embodiment, the diaphragm for alkaline water electrolysis is provided as a porous body excellent in ion permeability.

Since the diaphragm for alkaline water electrolysis obtained by the production method of the present invention is composed of an epoxy resin, it is excellent in chemical resistance, and the gas generated at the electrode during electrolysis hardly adheres to the surface of the diaphragm.

A-1. Process 1
The resin composition can be prepared by mixing an epoxy resin, a curing agent, and a porogen at room temperature. In one embodiment, the said resin composition is obtained by dissolving an epoxy resin and a hardening | curing agent in a porogen.

Any appropriate epoxy resin can be used as the epoxy resin. An aromatic epoxy resin may be used, and a non-aromatic epoxy resin may be used. Examples of the aromatic epoxy resin include a polyphenyl-based epoxy resin, an epoxy resin containing a fluorene ring, an epoxy resin containing triglycidyl isocyanurate, and an epoxy resin containing a heteroaromatic ring (for example, a triazine ring). Examples of polyphenyl-based epoxy resins include bisphenol A type epoxy resins, brominated bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, stilbene type epoxy resins, biphenyl type epoxy resins, and bisphenol A novolac types. Examples thereof include an epoxy resin, a cresol novolac type epoxy resin, a diaminodiphenylmethane type epoxy resin, and a tetrakis (hydroxyphenyl) ethane-based epoxy resin. Examples of non-aromatic epoxy resins include aliphatic glycidyl ether type epoxy resins, aliphatic glycidyl ester type epoxy resins, alicyclic glycidyl ether type epoxy resins, alicyclic glycidyl amine type epoxy resins, and alicyclic glycidyl ester types. An epoxy resin etc. are mentioned. These may be used alone or in combination of two or more.

The epoxy resin is preferably a bisphenol A type epoxy resin, a brominated bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol AD type epoxy resin, an epoxy resin containing a fluorene ring, an epoxy resin containing triglycidyl isocyanurate, An alicyclic glycidyl ether type epoxy resin, an alicyclic glycidyl amine type epoxy resin or an alicyclic glycidyl ester type epoxy resin is used. If these epoxy resins are used, a three-dimensional network skeleton having an excellent porous structure as a diaphragm for electrolysis can be formed, and uniform pores can be formed. Moreover, the diaphragm for alkaline water electrolysis excellent in chemical resistance and intensity | strength can be obtained.

The epoxy equivalent of the epoxy resin is preferably 6000 or less, more preferably 2000 or less. Within such a range, a three-dimensional network skeleton having an appropriate porosity and pore diameter (average pore diameter) as an electrolysis diaphragm and an excellent porous structure is formed, and uniform pores are formed. obtain. Moreover, the diaphragm for alkaline water electrolysis which is excellent in chemical-resistance and intensity | strength, and the gas produced | generated with the electrode at the time of electrolysis cannot adhere easily can be obtained.

In one embodiment, two or more epoxy resins having different epoxy equivalents are used. By using a plurality of epoxy resins having different epoxy equivalents, gas adhesion, mechanical properties such as strength, chemical resistance, etc. of the diaphragm for alkaline water electrolysis can be adjusted. Preferably, epoxy resins having epoxy equivalents different by 100 or more are used. For example, a combination of an epoxy resin having a high epoxy equivalent (for example, epoxy equivalent: 2000 to 4000) and an epoxy resin having a low epoxy equivalent (for example, epoxy equivalent: 150 to 200) is used in combination. By increasing the ratio, a diaphragm for alkaline water electrolysis excellent in flexibility and / or strength can be obtained.

The weight average molecular weight of the epoxy resin is preferably 370 to 12000, more preferably 370 to 4000. If it is such a range, the diaphragm for alkaline water electrolysis which is excellent in ion permeability, chemical-resistance, and intensity | strength, and the gas produced | generated by the electrode at the time of electrolysis cannot adhere easily can be obtained. In addition, the weight average molecular weight in this specification can be calculated | required by a gel permeation chromatography (GPC) measurement (solvent tetrahydrofuran).

The molecular weight distribution (weight average molecular weight / number average molecular weight) of the epoxy resin is preferably 1.0 to 10, more preferably 1.0 to 5.0. If it is such a range, the diaphragm for alkaline water electrolysis which is excellent in ion permeability, chemical-resistance, and intensity | strength, and the gas produced | generated by the electrode at the time of electrolysis cannot adhere easily can be obtained. In addition, the number average molecular weight in this specification can be calculated | required by a gel permeation chromatography (GPC) measurement (solvent tetrahydrofuran).

The melting point of the epoxy resin is preferably 170 ° C. or lower, more preferably 120 ° C. or lower, and further preferably 20 ° C. to 50 ° C. Within such a range, a three-dimensional network skeleton having an excellent porous structure as a diaphragm for electrolysis can be formed, and uniform pores can be formed. Moreover, the diaphragm for alkaline water electrolysis excellent in chemical resistance and intensity | strength can be obtained.

Any appropriate curing agent may be used as the curing agent. An aromatic curing agent may be used, and a non-aromatic curing agent may be used. Examples of aromatic curing agents include aromatic amines such as metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, benzyldimethylamine, and dimethylaminomethylbenzene; aromatics such as phthalic anhydride, trimellitic anhydride, and pyromellitic anhydride An aromatic acid anhydride; a phenol resin; a phenol novolak resin; an amine containing a heteroaromatic ring (for example, an amine containing a triazine ring) and the like. Non-aromatic curing agents include, for example, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, bis (hexamethylene) triamine, 1,3,6-trisaminomethylhexane, polymethylenediamine, Aliphatic amines such as trimethylhexamethylene diamine and polyether diamine; isophorone diamine, menthane diamine, N-aminoethylpiperazine, 3,9-bis (3-aminopropyl) 2,4,8,10-tetraoxaspiro ( 5,5) Fats containing alicyclic amines such as undecane adduct, bis (4-amino-3-methylcyclohexyl) methane, bis (4-aminocyclohexyl) methane, modified products thereof, polyamines and dimer acid Polyamidoamine etc. And the like. These may be used alone or in combination of two or more.

As the curing agent, a curing agent having two or more primary amines in the molecule is preferably used. Specific examples of the curing agent having two or more primary amines in the molecule include metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, polymethylenediamine, bis (4-amino-3-methylcyclohexyl) methane and bis (4- Aminocyclohexyl) methane and the like. If these curing agents are used, a three-dimensional network skeleton having an excellent porous structure as a diaphragm for electrolysis can be formed, and uniform pores can be formed. Moreover, the diaphragm for alkaline water electrolysis which is excellent in intensity | strength and has an appropriate elasticity modulus can be obtained.

When an aromatic epoxy resin is used as the epoxy resin, aliphatic amines or alicyclic amines can be preferably used as the curing agent. When a non-aromatic epoxy resin (for example, alicyclic epoxy resin) is used as the epoxy resin, aromatic amines can be preferably used as the curing agent. If an epoxy resin and a hardening | curing agent are used in these combinations, the diaphragm for alkaline water electrolysis excellent in heat resistance can be obtained.

The content of the curing agent in the resin composition is preferably such that the curing agent equivalent is 0.6 to 1.5 with respect to 1 equivalent of epoxy group of the epoxy resin. If it is such a range, the diaphragm for alkaline water electrolysis which is excellent in heat resistance, chemical durability, a mechanical characteristic, etc. can be obtained.

The above curing agent and curing accelerator may be used in combination. By using a curing accelerator, the porous structure can be controlled. Specifically, unreacted functional groups can be reduced by using a curing accelerator. As a result, it is possible to obtain a diaphragm for alkaline water electrolysis that is excellent in thermal properties and mechanical properties and is chemically stable. Examples of the curing accelerator include tertiary amines such as triethylamine and tributylamine; imidazoles such as 2-phenol-4-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenol-4,5-dihydroxyimidazole. Etc. The content of the curing accelerator is preferably 1 to 5 parts by weight with respect to 100 parts by weight of the curing agent.

The porogen is preferably a solvent capable of dissolving the epoxy resin and the curing agent. In addition, when the resin composition is cured, that is, when the epoxy resin and the curing agent are polymerized, it is used as a solvent that can cause reaction-induced phase separation. The porogen may be a solvent that can dissolve a polymer of an epoxy resin and a curing agent.

Specific examples of the porogen include cellosolves such as methyl cellosolve and ethyl cellosolve; esters such as ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate; glycols such as polyethylene glycol and polypropylene glycol; polyoxyethylene monomethyl ether; Ethers such as polyoxyethylene dimethyl ether can be used as the porogen. These may be used alone or in combination of two or more.

As the porogen, methyl cellosolve, ethyl cellosolve, polyethylene glycol, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, polypropylene glycol, polyoxyethylene monomethyl ether or polyoxyethylene dimethyl ether can be preferably used. Among these, polyethylene glycol, polypropylene glycol, polyoxyethylene monomethyl ether or propylene glycol monomethyl ether acetate is preferable, and polyethylene glycol or polypropylene glycol is more preferable. If these porogens are used, a three-dimensional network skeleton having an excellent porous structure as a diaphragm for electrolysis can be formed, and uniform pores can be formed.

The content of the porogen is preferably 40% by weight to 80% by weight, more preferably 60% by weight to 70% by weight, and still more preferably 60% by weight with respect to the total amount of the epoxy resin, the curing agent and the porogen. % To 65% by weight. If it is such a range, the diaphragm for alkaline water electrolysis which has a porosity, a hole diameter (average hole diameter), and air permeability suitable as a diaphragm for electrolysis can be obtained.

A-2. Process 2
Examples of a method for obtaining a resin sheet from the resin composition include the following methods.
(Method i) A method in which the resin composition is applied onto any appropriate substrate, and then the coating layer is cured to obtain a resin sheet.
(Method ii) A method in which the resin composition is molded to obtain a cured product, and a surface layer portion of the cured product is cut at a predetermined thickness to obtain a resin sheet.

A-2-1. Method i
In method i, the resin composition is applied onto any appropriate substrate, and then the coating layer is heated, whereby the epoxy resin and the curing agent react to form a three-dimensional crosslinked structure. At this time, a co-continuous structure is formed by phase separation of the crosslinked epoxy resin and the porogen.

Examples of the coating layer forming method include a coating method, a relief printing method, a direct gravure printing method, an intaglio printing method, a lithographic printing method, and a stencil printing method.

The thickness of the coating layer is preferably 55 μm to 500 μm, more preferably 60 μm to 250 μm.

Any appropriate curing method may be employed as the method for curing the coating layer. For example, curing by heating can be employed, in which case the heating temperature is typically 40 ° C. to 200 ° C. and the heating time is typically 10 minutes to 100 hours.

In one embodiment, the resin sheet manufactured in this way can be provided as a diaphragm for alkaline water electrolysis. In this case, the diaphragm for alkaline water electrolysis of the present invention can become porous when it is used, specifically, when immersed in alkaline water which is electrolytic water. More specifically, in the alkaline water, the porogen is removed from the alkaline water electrolysis diaphragm to form a three-dimensional network skeleton and to form communicating pores.

In another embodiment, the method further includes a step of removing the porogen from the resin sheet after the coating layer is heated. Examples of the method for removing the porogen include the method described in the section A-2-2 below.

Note that another substrate may be placed on the coating layer formed on the base material, and the coating layer may be heated while being sandwiched between the pair of substrates.

A-2-2. Method ii

In method ii, the epoxy resin and the curing agent in the resin composition are polymerized, and the resin composition is cured to form a cured body having a three-dimensional crosslinked structure. When the cured body is formed, a co-continuous structure is formed by phase separation between the epoxy resin crosslinked body and the porogen.

The cured body is formed in a columnar shape, for example. If a column-shaped hardening body is formed, it will be excellent in the efficiency at the time of cutting.

The cured body can be obtained by curing the resin composition. The cylindrical cured body is obtained, for example, by charging the resin composition into a cylindrical mold and then curing the resin composition. The curing temperature and time for curing can be set to any appropriate conditions depending on the composition of the resin composition and the like.

The curing temperature at the time of the curing is, for example, 20 ° C. to 120 ° C. When cured at such a temperature, a three-dimensional network skeleton having an excellent porous structure as a diaphragm for electrolysis is formed, and a diaphragm for alkaline water electrolysis in which uniform pores are formed can be obtained. In addition, the diaphragm for alkaline water electrolysis with a small average hole diameter can be obtained, so that hardening temperature is high. In one embodiment, the curing process may be performed with the curing temperature set at 20 ° C. to 40 ° C. and the curing time set preferably at 3 hours to 100 hours, more preferably 20 hours to 50 hours. . In another embodiment, the curing temperature is preferably set to 40 ° C. to 120 ° C., more preferably 60 ° C. to 100 ° C., and the curing time is preferably 10 minutes to 300 minutes, more preferably 30 minutes to 180 minutes. And the curing process is performed. After the curing treatment, post-cure may be performed as necessary. By performing post-cure, the degree of crosslinking of the cured product can be increased. The temperature of the post cure is, for example, 50 ° C. to 160 ° C., and the time is, for example, 2 hours to 48 hours.

The dimension of the cured body can be any appropriate dimension. When the cured body is cylindrical, the diameter of the cured body is typically 20 cm or more, and preferably 30 cm to 150 cm. The length (axial direction) of the cured body is typically 20 cm to 200 cm, preferably 20 cm to 150 cm, more preferably 20 cm to 120 cm. If it is such a dimension, it is excellent in manufacturing efficiency.

After forming the cured body as described above, a resin sheet can be obtained by cutting the surface layer portion of the cured body. FIG. 1 is a schematic diagram illustrating an example of a method of cutting the cured body when the cured body is cylindrical. When the cured body is cylindrical, the cured body 100 is attached to the shaft 10, and the surface layer portion of the cured body 100 is attached to the cured body 100 using any appropriate blade 20 while rotating the cured body 100 around the cylindrical axis. Cutting (slicing) at a predetermined thickness. According to such a method, the resin sheet 110 can be obtained efficiently.

The rotational speed of the cured body 100 is, for example, 2 m / min to 70 m / min.

Cutting thickness (thickness of resin sheet 110), preferably 55 μm to 500 μm, more preferably 60 μm to 250 μm. Although the length of the resin sheet 110 is not specifically limited, From the viewpoint of the manufacturing efficiency of the resin sheet 110, it is 100 m or more, for example, Preferably it is 1000 m or more.

In another embodiment, the method further includes a step of removing porogen from the resin sheet. By removing the porogen, a diaphragm for alkaline water electrolysis having a porous structure can be obtained.

Examples of the method for removing porogen from the resin sheet include a method of immersing the resin sheet in a solvent capable of extracting the porogen. Ultrasonic waves may be applied while dipping. Further, it may be immersed in a heated solvent (for example, 40 ° C. to 100 ° C.).

As the solvent used for removing the porogen, it is preferable to use a halogen-free solvent. Specific examples of the solvent include water, DMF (N, N-dimethylformamide), DMSO (dimethyl sulfoxide), THF (tetrahydrofuran) and the like.

The step of removing porogen from the resin sheet may be performed in multiple stages. The step of removing the porogen from the resin sheet can be performed, for example, in three or more stages. At each stage, the porogen may be removed by changing the type and / or temperature of the solvent.

Preferably, after the step of removing the porogen from the resin sheet, the membrane for alkaline water electrolysis is dried. The drying conditions are not particularly limited, and the temperature is, for example, 40 ° C. to 120 ° C., preferably 50 ° C. to 100 ° C. The drying time is, for example, about 10 seconds to 5 minutes. For the drying treatment, a drying apparatus employing a known sheet drying method such as a tenter method, a floating method, a roll method, or a belt method can be used. A plurality of drying methods may be combined.

B. Diaphragm for alkaline water electrolysis The diaphragm for alkaline water electrolysis of the present invention has a three-dimensional network skeleton composed of a crosslinked epoxy resin and has pores communicating so that ions can permeate. The diaphragm for alkaline water electrolysis of this invention can be manufactured with said manufacturing method, for example.

The diaphragm for alkaline water electrolysis preferably has an electrical resistance value of 0.5 Ω · cm ² or less, more preferably 0.5 Ω · cm ² or less, when a potassium hydroxide aqueous solution having a temperature of 25 ° C./concentration of 25.5 wt% is used as the electrolyte. It is 0.1 Ω · cm ² or less, more preferably 0.01 Ω · cm ² to 0.08 Ω · cm ² , and particularly preferably 0.01 Ω · cm ² to 0.06 Ω · cm ² . According to the present invention, having a three-dimensional network skeleton composed of a crosslinked epoxy resin and having pores communicating so that ions can permeate, it has excellent ion permeability, as described above. In addition, a diaphragm for alkaline water electrolysis having a small electric resistance value can be obtained. In addition, in this specification, the electrical resistance value of the diaphragm for alkaline water electrolysis means the electrical resistance value after porogen is removed when the diaphragm for alkaline water electrolysis is obtained by the said manufacturing method.

The thickness of the membrane for alkaline water electrolysis is preferably 55 μm to 500 μm, more preferably 60 μm to 250 μm, and still more preferably 70 μm to 150 μm. If it is such a range, the diaphragm for alkaline water electrolysis will be excellent in ion permeability, and has a practically acceptable strength. In the present specification, the “thickness of the diaphragm for alkaline water electrolysis” refers to the thickness after the porogen is removed when the diaphragm for alkaline water electrolysis is obtained by the above production method.

The average pore size of the membrane for alkaline water electrolysis is preferably 0.02 μm to 3.5 μm. If it is such a range, the diaphragm for alkaline water electrolysis which is very excellent in ion permeability can be obtained. In the present specification, the “average pore diameter of the diaphragm for alkaline water electrolysis” refers to the average pore diameter after the porogen is removed when the diaphragm for alkaline water electrolysis is obtained by the above production method. The average pore diameter is a median diameter measured and calculated by a mercury intrusion method.

The porosity of the membrane for alkaline water electrolysis is preferably 20% to 80%, more preferably 30% to 80%, and further preferably 40% to 70%. Note that the porosity of the diaphragm for alkaline water electrolysis is a value calculated by the formula {1- (apparent density of the diaphragm for alkaline water electrolysis / true density of the material constituting the diaphragm for alkaline water electrolysis)} × 100. Say. In the present specification, the “porosity of the diaphragm for alkaline water electrolysis” refers to the porosity after the porogen is removed when the diaphragm for alkaline water electrolysis is obtained by the above production method.

In one embodiment, a composite membrane for alkaline water electrolysis comprising the above diaphragm for alkaline water electrolysis and a porous reinforcing body disposed on one or both surfaces of the diaphragm for alkaline water electrolysis can be provided. By providing the porous reinforcing body, it is possible to obtain a composite membrane that has sufficient strength as a diaphragm for electrolysis and is excellent in short-circuit prevention between electrodes.

Examples of the form of the upper porous reinforcing body include woven fabric, non-woven fabric, net, mesh, and 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 porosity of the porous reinforcing body is preferably 10% to 90%, more preferably 10% to 55%, and further preferably 10% to 50%. The porosity of the porous reinforcing body means a value calculated by the formula {1- (apparent density of porous reinforcing body / true density of material constituting porous reinforcing body)} × 100.

The thickness of the porous 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 porous 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. Examples of the polymer having a hydrophilic functional group include a polymer in which a hydrophilic functional group is introduced into a resin having a skeleton such as a fluorine resin, an olefin resin, and an aromatic hydrocarbon resin. Among these, a polymer using ultrahigh molecular weight polyethylene as a resin serving as a skeleton can be preferably used. In the porous reinforcing body, the polymer preferably has a hydroxyl group, a carboxylic acid group, an amino group, an amide group, or a cyano group as the hydrophilic functional group. By using such a polymer having a functional group, it is possible to obtain a composite film that is excellent in hydrophilicity and hardly adheres to the gas generated at the electrode during electrolysis.

Any appropriate method can be adopted as a method for introducing the hydrophilic 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 resin serving as the skeleton, a monomer having a hydrophilic functional group, and a crosslinking as necessary. And a method of copolymerizing the agent. A graft polymerization method is preferably employed, and a radiation graft polymerization method is more preferably employed.

As the radiation graft polymerization method, for example, after making the resin that becomes a skeleton porous, the resin that becomes the skeleton is irradiated with radiation to generate free radicals, and then the resin irradiated with the radiation and the hydrophilic And a method in which a monomer composition containing a monomer having a functional functional group is brought into contact with each other and graft polymerization is carried out starting from the free radical (pre-irradiation method). Moreover, you may use the method (simultaneous irradiation method) of irradiating with radiation in the state which coexisted resin used as frame | skeleton, and a monomer, and graft-polymerizing. In this specification, a film-like resin (resin that becomes a skeleton) subjected to graft polymerization is referred to as a base material.

Examples of the monomer having a hydrophilic functional group include acrylic acid, methacrylic acid, 2-hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 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-dimethylamino Ethyl acrylate 2- (dimethylamino) ethyl acrylate, N- (2-hydroxyethyl) acrylamide, acryloylmorpholine, N-isopropylacrylamido , 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.

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.

Examples of the base material include woven fabric, non-woven fabric, net, mesh, and sintered porous membrane.

The porosity of the base material (porous reinforcing body before graft polymerization) is preferably 10% to 95%, more preferably 15% to 90%, and further preferably 15% to 75%. Particularly preferred is 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 density of material constituting base material)} × 100. Value.

The weight graft ratio of the porous reinforcing body having a hydrophilic functional group obtained by graft polymerization is preferably 1% to 80%, more preferably 3% to 50%.

The diaphragm for alkaline water electrolysis and the porous reinforcing body can be laminated by heating and pressurizing with a hot press machine or a heating roll, for example. Preferably, the diaphragm for alkaline water electrolysis and the porous reinforcing body are laminated, and only the end of the laminated body is heated. Moreover, when using the composite membrane for alkaline water electrolysis as a diaphragm for electrolysis, pressure may be applied from both sides with an electrode or the like to fix the diaphragm for alkaline water electrolysis and the porous reinforcing body.

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) Contact angle of air in water After immersing the diaphragm for electrolysis obtained in Examples and Comparative Examples in pure water at 25 ° C. for 10 minutes, an automatic contact angle measuring device (trade name “OCA30” manufactured by dataphysics instruments, Inc.) ) Was used to measure the contact angle of air (bubbles) adhering to the diaphragm for electrolysis. In addition, the mode (SEM photograph) of the bubble adhering to the diaphragm for electrolysis in an Example and a comparative example is shown in FIG.
(3) Electric resistance The film resistance of the samples obtained in the examples and comparative examples was measured by an AC voltage drop method. The sample was immersed in an electrolytic solution at 25 ° C. (potassium hydroxide aqueous solution having a concentration of 25.5% by weight) for 10 minutes, set in a measurement cell (platinum electrode), and measured at an alternating current of 1 kHz.
(4) 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 25.5 wt% 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.
(5) Gas barrier property The gas generated on the cathode side after 1 hour from the start of alkaline water electrolysis in (4) above is recovered, and the cathode is obtained by gas chromatography (trade name “GC-8A” manufactured by Shimadzu Corporation). The gas barrier properties were evaluated by measuring the hydrogen purity of the gas generated on the side.

[Example 1]
70 parts by weight of bisphenol A type epoxy resin (Mitsubishi Chemical Co., Ltd., jER (registered trademark) 827, epoxy equivalent: 180-190), bisphenol A type epoxy resin (Mitsubishi Chemical Co., Ltd., jER (registered trademark) 1009, epoxy equivalent) : 2400-3300) and 30 parts by weight of polyethylene glycol (PEG 200, manufactured by Sanyo Chemical Co., Ltd.) were mixed to prepare a polyethylene glycol solution of an epoxy resin.
A mold release agent (manufactured by Nagase ChemteX, QZ-13) is thinly applied to the inner surface of a cylindrical mold (stainless steel, inner diameter 20 cm, height 30 cm), and the mold is dried at 70 ° C. ± 30 ° C. Dry in the machine. This mold was filled with a polyethylene glycol solution of the epoxy resin prepared as described above, and 22.3 parts by weight of bis (4-aminocyclohexyl) methane was added as a curing agent. Thus, the epoxy resin composition containing an epoxy resin, a hardening | curing agent, and a porogen was prepared.
Next, the epoxy resin composition was stirred with an anchor blade at 300 rpm for 30 minutes. Next, vacuum degassing was performed at about 0.1 MPa until the bubbles disappeared using a vacuum disk (manufactured by ASONE, VZ type). After standing for about 2 hours, the mixture was again stirred for about 30 minutes and vacuum degassed again. Next, the epoxy resin composition was cured by leaving at 27 ° C. for 72 hours. Thereby, the hardening body of the epoxy resin composition was obtained.
Next, using a cutting lathe device (manufactured by Toshiba Machine Co., Ltd.), the surface layer portion of the cured body was continuously sliced with a thickness of 100 μm to obtain an epoxy resin sheet. The epoxy resin sheet was immersed in pure water at 60 ° C. to remove polyethylene glycol, and then dried at 70 ° C. for 2 minutes, 80 ° C. for 1 minute, and 90 ° C. for 1 minute to obtain a diaphragm for alkaline water electrolysis. The thickness of the diaphragm for alkaline water electrolysis was 88 μm.
The obtained diaphragm for alkaline water electrolysis was subjected to the above evaluations (2) to (5). The evaluation results are shown in Table 1.
In the evaluation, in order to allow water to permeate into the membrane of the obtained alkaline water electrolysis diaphragm, it was immersed in a 10 wt% aqueous isopropyl alcohol solution for 10 minutes, and then the isopropyl alcohol was sufficiently replaced with pure water.

[Comparative Example 1]
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 was peeled off, further washed in pure water at 25 ° C. for 30 minutes, air dried at 25 ° C., and then dried in an 80 ° C. dryer for 30 minutes to obtain a sheet-like diaphragm for electrolysis. .
The obtained diaphragm for electrolysis was subjected to the evaluations (2) to (5). The evaluation results are shown in Table 1.
In the evaluation, in order to allow water to penetrate into the membrane of the obtained diaphragm for electrolysis, the membrane was immersed in a 10 wt% isopropyl alcohol aqueous solution for 10 minutes, and then the isopropyl alcohol was sufficiently replaced with pure water.

As is apparent from Table 1, the alkaline water electrolysis diaphragm of the present invention has low electrical resistance and excellent ion permeability. In addition, according to the present invention, it is possible to obtain an alkaline water electrolysis diaphragm in which the contact angle of air in water is large, that is, the gas generated during electrolysis hardly adheres to the surface.

100 Cured body 110 Resin sheet

Claims

Preparing a resin composition comprising an epoxy resin, a curing agent and a porogen;
A step of obtaining a resin sheet using the resin composition,
A method for producing a diaphragm for alkaline water electrolysis.
The method for producing a diaphragm for alkaline water electrolysis according to claim 1, further comprising a step of removing the porogen from the resin sheet.
In the step of obtaining a resin sheet using the resin composition, the method includes molding the resin composition to obtain a cured body, and cutting the cured body surface layer portion with a predetermined thickness to obtain the resin sheet. Item 2. A method for producing a diaphragm for alkaline water electrolysis according to Item 1.
The manufacturing method of the diaphragm for alkaline water electrolysis of Claim 3 including cutting the surface layer part of this hardening body while the said hardening body is cylindrical shape, rotating this hardening body centering on a cylinder axis | shaft. .
The method for producing a diaphragm for alkaline water electrolysis according to claim 1, wherein the porogen is polyethylene glycol or polypropylene glycol.
A diaphragm for alkaline water electrolysis obtained by the production method according to any one of claims 1 to 5.
A composite membrane for alkaline water electrolysis comprising the diaphragm for alkaline water electrolysis according to claim 6 and a porous reinforcing body disposed on one or both surfaces of the diaphragm for alkaline water electrolysis.
The composite membrane for alkaline water electrolysis according to claim 7, wherein the porous reinforcing body is composed of a polymer having a hydrophilic functional group.
The composite membrane for alkaline water electrolysis according to claim 7, wherein the porous reinforcing body is a woven fabric, a nonwoven fabric, a net, a mesh, or a sintered porous membrane.
The composite membrane for alkaline water electrolysis according to claim 8, wherein the porous reinforcing body is a woven fabric, a nonwoven fabric, a net, a mesh, or a sintered porous membrane.