WO2016204262A1

WO2016204262A1 - Ion exchange membrane for water electrolysis, and method for manufacturing said ion exchange membrane

Info

Publication number: WO2016204262A1
Application number: PCT/JP2016/068049
Authority: WO
Inventors: 健吾織田; 伸渡辺
Original assignee: 株式会社トクヤマ
Priority date: 2015-06-17
Filing date: 2016-06-17
Publication date: 2016-12-22
Also published as: TW201714743A; JP2018127506A

Abstract

[Problem] To provide a laminated ion exchange membrane for water electrolysis that has high gas barrier properties and low membrane resistance. Also to provide a method for continuously manufacturing a thick laminated ion exchange membrane with high gas barrier properties, wherein the method limits increases in membrane resistance and peeling does not occur even in cases of high water content such as in a liquid phase. [Solution] A laminated ion exchange membrane obtained by filling an ion exchange resin in the voids of a laminated porous substrate film in which multiple sheets of a porous substrate film with 30-50% porosity and mean pore diameter of 0.01 µm to less than 0.1 µm are laminated, wherein the total thickness of the porous substrate film is 50-200 µm, and the difference in porosity of adjacent porous substrate films is 10% or less.

Description

Ion exchange membrane for water electrolysis and method for producing the ion exchange membrane

The present invention relates to an ion exchange membrane for water electrolysis and a method for producing the ion exchange membrane.

Ion exchange membranes are used as membranes for electrodialysis used in salt production and desalting processes in the food sector, electrolyte membranes for fuel cells, and for acid recovery from acids containing metal ions generated in the steel industry. It is used industrially in many fields such as diffusion dialysis membranes. In such an ion exchange membrane, a base film having a function as a reinforcing material or a support for the ion exchange resin is used, and the ion exchange resin is supported by the base film. Thus, a certain film strength and film shape stability are imparted. Since ion exchange resins have many ion exchange groups, if there is no base film, if the ion exchange membrane is immersed in an aqueous electrolyte solution, it will swell easily, resulting in a decrease in strength and shape change of the ion exchange membrane. End up.

Conventionally, it is known to use a porous thermoplastic resin film as the base film, and it is actually used. The ion exchange membrane using such a porous substrate film is filled with an ion exchange resin in the voids in the porous substrate film, and as a result, the electrical resistance of the membrane (hereinafter referred to as membrane resistance) Has the advantage of low.

An ion exchange membrane has been conventionally used as an electrolyte membrane for fuel cells, but is currently attracting attention as an electrolyte membrane for water electrolysis for producing hydrogen. An electrolyte membrane for water electrolysis is required to have low membrane resistance and high gas barrier properties. Water electrolysis methods include alkaline water electrolysis, cation exchange membrane water electrolysis, and anion exchange membrane water electrolysis. Among these, cation exchange membrane type water electrolysis and anion exchange membrane type water electrolysis capable of internal compression of hydrogen are attracting attention. However, pressure is applied by internal compression, and the generated hydrogen is likely to permeate the ion exchange membrane. Therefore, a higher gas barrier property is required for the ion exchange membrane.

It is conceivable to increase the thickness of the ion exchange membrane as the most effective method for improving the gas barrier property. In order to produce a thick ion exchange membrane, it is necessary to produce an ion exchange membrane using a thicker porous substrate film. However, a thick porous substrate film generally has a high porosity and a large pore diameter. When an ion exchange membrane is produced using a thick porous substrate film, the porosity and pore diameter of the porous substrate film are large, so that the dimensional change due to swelling and shrinkage of the ion exchange resin becomes large. As a result, a gap is generated between the ion exchange resin and the porous substrate film, and the gas barrier property is lowered. Therefore, it is not preferable to use a general thick porous substrate film, and an ion exchange membrane having a high gas barrier property has not been obtained.

As an ion exchange membrane used for a liquid fuel type fuel cell membrane, Patent Document 1 discloses a liquid fuel permeability in which two cation exchange membrane layers of a low water content type and a high water content type are arranged on both side layers. Low cation exchange membranes for fuel cells have been proposed.

Further, in Patent Document 2, as a method for producing an ion exchange membrane used in a desalting step or an electrolyte of a fuel cell, polymerization that is a precursor of an ion exchange resin is performed on a plurality of porous resin sheets having different vertical and horizontal orientation strengths. A method for producing an ion exchange membrane is disclosed in which an impregnating composition is impregnated, resin sheets are superposed so that the orientation directions intersect, and a polymerizable compound is polymerized.

Japanese Patent No. 5059341 Japanese Patent No. 5436357

The ion exchange membrane for a fuel cell disclosed in Patent Document 1 has a low water content type and a high water content type by laminating two ion exchange membranes of a low water content type and a high water content type and performing hot pressing. We have succeeded in producing an ion exchange membrane having two layers of cation exchange membrane layers on both sides and having low liquid fuel permeability. However, since hot pressing is performed at the time of production, a new disadvantage arises in that the ion exchange groups in the ion exchange membrane are decomposed at a high temperature and the membrane resistance increases. For this reason, when it uses for water electrolysis, problems, such as efficiency becoming low, will arise.

Patent Document 1 also describes a method in which two porous substrate films having different porosity are laminated by hot pressing and then impregnated with a polymerizable composition to be cured by polymerization. The voids of the porous substrate film are crushed by hot pressing, and the porosity is lowered, and the membrane resistance of the ion exchange membrane is increased.

The ion exchange membrane disclosed in Patent Document 2 has a porous resin sheet that is a highly oriented resin sheet, and a laminated porous resin sheet that is laminated so that the orientation directions thereof intersect each other. Therefore, the obtained ion exchange membrane has a high tear strength. However, when this ion exchange membrane is used for water electrolysis, swelling of the ion exchange membrane is suppressed due to the anisotropy of each porous resin sheet constituting the substrate. As a result, the membrane resistance cannot be sufficiently reduced, and the efficiency of water electrolysis becomes insufficient. Further, Comparative Example 2 of Patent Document 2 describes an example using a laminated porous resin sheet having strength anisotropy integrated by pre-pressing a porous resin sheet in advance. However, it has been reported that film resistance is increased by hot pressing. This is considered to be because the voids of the porous resin sheet were crushed by the hot press, resulting in a decrease in the porosity and an increase in membrane resistance, as described in connection with Patent Document 1.

Accordingly, an object of the present invention is a laminated ion exchange membrane for water electrolysis having a high gas barrier property and low membrane resistance, and a method for continuously producing the ion exchange membrane, which suppresses an increase in membrane resistance. It is another object of the present invention to provide a method for producing a laminated ion exchange membrane that does not peel even when the water content is high, such as in a liquid phase.

The present inventors have intensively studied to solve the above problems. As a result, by increasing the porosity of the porous substrate film, the average pore diameter, and the thickness of the porous substrate film within a specific range, an increase in membrane resistance is suppressed, and high gas barrier properties are peeled off. The present inventors have found the knowledge that such a laminated ion exchange membrane is particularly useful as an ion exchange membrane for water electrolysis, and have completed the present invention.

That is, according to the present invention, an ion exchange resin is filled in the voids of a laminated porous substrate film in which a plurality of porous substrate films having a porosity of 30 to 50% and an average pore diameter of 0.01 to less than 0.1 μm are laminated. An ion exchange membrane for water electrolysis, wherein the total thickness of the porous base film is 50 to 200 μm, and the difference in porosity between adjacent porous base films is 10% or less, And a step of preparing a polymerizable composition comprising a polymerizable monomer and a polymerization initiator, laminating a plurality of porous substrate films to form a laminated porous substrate film, and polymerizing the laminated porous substrate film A step of contacting a polymerizable composition containing a polymerizable monomer and a polymerization initiator and filling the voids of the laminated porous substrate film with the polymerizable composition to obtain an ion exchange membrane precursor, in the ion exchange membrane precursor Ion exchange tree of polymerizable composition A method for producing an ion exchange membrane for water electrolysis, comprising a step of converting to fat.

The present invention also relates to the use of the above-described laminated ion exchange membrane for water electrolysis, a water electrolysis apparatus using the laminated ion exchange membrane, and electrolysis of water to obtain hydrogen by electrolyzing water using the apparatus. Regarding the method.

Since the ion exchange membrane for water electrolysis of the present invention has low membrane resistance and low hydrogen permeability, it is possible to suppress the generated hydrogen from permeating the ion exchange membrane and efficiently produce high-pressure hydrogen gas. .

According to the production method of the present invention, a thick laminated ion exchange having a high gas barrier property is suppressed by suppressing the increase in membrane resistance by laminating a porous substrate film having a specific porosity and average pore diameter. A membrane can be produced, and a laminated ion exchange membrane suitable for water electrolysis can be obtained.

In the production method of the present invention, the most important characteristics are the porosity of the porous substrate film used when forming the laminated ion exchange membrane, the average pore diameter, and the porosity of the porous substrate film to be laminated. It is in controlling the difference. That is, by immersing a laminated porous substrate film in a polymerizable composition for an ion exchange resin, polymerizing the polymerizable composition to produce a laminated ion exchange membrane, an excessive dimensional change of the ion exchange resin And the generation of a gap between the porous substrate film and the ion exchange resin is suppressed. Furthermore, the polymer of the polymerizable composition functions as a bonding agent, the porous substrate films are bonded to each other, and this ion exchange membrane is in an atmosphere where the water content of the ion exchange membrane is high, such as in a liquid phase, There is no peeling.

The figure which shows the roll feed process used when manufacturing an ion exchange membrane. It is the schematic of a water electrolysis apparatus.

(Ion exchange membrane for water electrolysis)
The ion exchange membrane for water electrolysis of the present invention has a porosity of 30 to 50% and an average pore diameter of 0.01 to less than 0.1 μm. A laminated ion exchange membrane filled with an ion exchange resin, wherein the total thickness of the porous substrate films is 50 to 200 μm, and the difference in porosity between adjacent porous substrate films is 10% or less. Hereinafter, the laminated ion exchange membrane and the ion exchange membrane for water electrolysis may be used synonymously, but the use of the laminated ion exchange membrane is not limited.

<Porous substrate film>
In the porous base film, a large number of fine pores penetrating from the front surface to the back surface are formed.

The average pore diameter can be measured by a half dry method in accordance with ASTM-F316-86, and is 0.01 to less than 0.1 μm, and preferably 0.015 to 0.09 μm. When the average pore diameter is less than 0.01 μm, the membrane resistance increases, and when it is 0.1 μm or more, the hydrogen permeability of the ion exchange membrane increases. Moreover, the porosity was calculated by the following formula, measuring the volume (Vcm ³ ) and mass (Ug) of the porous substrate film, and setting the density of the material of the porous substrate film as X (g / cm ³ ). Value.
Porosity = [(V−U / X) / V] × 100 [%]

In order to achieve the effect of the present invention, the porosity needs to be 30 to 50%, preferably 33 to 47%. When the porosity is less than 30%, the membrane resistance of the ion exchange membrane increases, and when it exceeds 50%, the hydrogen permeability of the ion exchange membrane increases. The thickness of each porous substrate film is generally 5 to 100 μm, preferably 10 to 50 μm, more preferably 10 to 40 μm. The total thickness of the porous substrate film is 50 to 200 μm. In the present invention, the total thickness of the porous substrate film is the thickness of the laminated porous substrate film in which a plurality of porous substrate films are laminated. The number of porous substrate films is not particularly limited as long as it is 2 or more, but is preferably 2 to 5, more preferably 2 to 3. The width of the porous substrate film is not particularly limited, but is 200 to 1500 mm in consideration of availability and production.

In a laminated porous substrate film in which a plurality of porous substrate films are laminated, the difference in porosity between adjacent porous substrate films is 10% or less, preferably 0 to 8%, more preferably 0 to 4%. The difference in porosity is obtained from (AB) from the porosity A of a film having a large porosity and the porosity B of a small film. When the difference in porosity between adjacent porous substrate films exceeds 10%, the swelling rate of each layer of the laminated porous substrate film filled with the ion exchange resin when the ion exchange membrane is used is different. As guessed, when the counter-ion is ion-exchanged, it peels off at the interface between the porous substrate films. In addition, when using 3 or more porous base film, the difference of the porosity of adjacent porous base films should just be 10% or less, and the difference of the porosity between films which are not adjacent is 10%. % May be exceeded. For example, when three porous substrate films are laminated, the difference in porosity between the first layer and the second layer and the difference in porosity between the second layer and the third layer should be 10% or less. The difference in porosity between the first layer and the third layer may exceed 10%. However, it is preferable that the difference in the porosity of all the porous substrate films is 10% or less.

The porous substrate film may be formed of various thermoplastic resins, but when used as a substrate film of an ion exchange membrane, a thermoplastic resin having no ion exchange group, for example, polychlorinated Vinyl chloride resins such as vinyl, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-olefin copolymer; polyamide resins such as nylon 6 and nylon 66; ethylene, propylene, 1- Preferred are olefin polymers or copolymers such as butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene, 5-methyl-1-heptene, and the porosity. An olefin polymer or copolymer that is easy to control the average pore diameter and excellent in flexibility is more preferable, and polyethylene is most preferable. That.

The porous substrate film may be stretched or unstretched, but in general, the ion exchange membrane is improved in strength and the hydrogen permeability is suppressed by increasing the crystallinity of the film. From such a viewpoint, it is preferable that the film is stretched in a uniaxial or biaxial direction. Moreover, it is preferable that the orientation direction of each porous base film in the laminated porous base film is aligned. In addition, the orientation direction being uniform means that the angle formed by the orientation direction of each porous substrate film (in the case of a biaxially stretched film, the direction in which the stretching ratio is high) is within ± 10 °. Say. When the alignment direction is aligned, the ion exchange membrane is easily swelled and the membrane resistance is lower than when the alignment direction is not aligned.

The porous substrate film as described above is described in a method known per se, for example, in JP-A-9-216964, JP-A-9-235399, JP-A 2002-338721, and the like. It can be formed by a method. That is, a film having a predetermined thickness is formed by extrusion molding or the like using a resin composition in which an additive for pore formation is blended with a thermoplastic resin for film formation (for example, polyethylene), and then stretch-molded if necessary. Thereafter, an additive added to the obtained film is removed by extraction with an organic solvent, dissolution with an acid or alkali, and the like, whereby a film having a large number of target pores can be obtained.

<Ion exchange resin>
The ion exchange resin filled in the voids of the porous substrate film may be a known one, for example, an ion exchange group that expresses ion exchange ability in a hydrocarbon-based or fluorine-based resin, specifically, A cation exchange group or an anion exchange group is introduced. Among these, an anion exchange type ion exchange resin that has an alkaline reaction field and can use relatively inexpensive iron, cobalt, nickel, or an alloy thereof as an electrode is preferable.

Examples of the hydrocarbon-based resin include styrene-based resins and acrylic resins, and examples of the fluorine-based material include perfluorocarbon-based resins. As an ion exchange resin, since hydrogen permeability is low and it can be obtained at low cost, a resin obtained by introducing an ion exchange group into a hydrocarbon resin is preferable.

The hydrocarbon-based resin is a resin that does not substantially contain a carbon-fluorine bond, and that most of the main chain and side chain bonds constituting the resin are composed of carbon-carbon bonds. To tell. That is, a small amount of other atoms such as oxygen, nitrogen, silicon, sulfur, boron, and phosphorus are interposed between the carbon-carbon bonds constituting the main chain and the side chain by ether bond, ester bond, amide bond, siloxane bond, etc. You may do it. In addition, the atoms bonded to the main chain and the side chain need not all be hydrogen atoms, and if the amount is small, other atoms such as chlorine, bromine, fluorine, iodine, etc., or substituents containing other atoms It may be replaced.

The ion exchange group described above is a functional group that can be negatively or positively charged in an aqueous solution. In the case of a cation exchange group, examples thereof include a sulfonic acid group, a carboxylic acid group, and a phosphonic acid group. In particular, sulfonic acid groups that are strongly acidic groups are preferred. In the case of a cation exchange membrane, the counter cation is preferably a hydrogen ion. Examples of anion exchange groups include primary to tertiary amino groups, quaternary ammonium groups, pyridyl groups, imidazole groups, and quaternary pyridinium groups. Generally, quaternary ammoniums that are strongly basic are used. Groups and quaternary pyridinium groups are preferred. In the case of an anion exchange membrane, the counter anion is preferably carbonate ion, bicarbonate ion, hydroxide ion or the like.

Laminated ion exchange membranes in which voids in the laminated porous substrate film are filled with ion exchange resin are used without limitation for various applications like ordinary ion exchange membranes, but have low membrane resistance and hydrogen permeability. In particular, it is preferably used as an ion exchange membrane for water electrolysis incorporated in an electrolysis apparatus for electrolyzing water to obtain hydrogen.

(Production method of laminated ion exchange membrane)
The ion exchange membrane for water electrolysis of the present invention prepares a polymerizable composition (hereinafter also simply referred to as a polymerizable composition) containing a polymerizable monomer and a polymerization initiator for forming the ion exchange resin. Step (polymerizable composition preparation step), laminating a plurality of porous substrate films to form a laminated porous substrate film, and polymerization including a polymerizable monomer and a polymerization initiator in the laminated porous substrate film The ion-exchange membrane precursor (step of preparing the ion-exchange membrane precursor), and the ion-exchange membrane precursor in the ion-exchange membrane precursor It is produced by using the polymerizable composition as an ion exchange resin (ion exchange resin forming step).

1. Polymerizable composition preparation step;
In the present invention, the polymerizable composition is a composition for forming an ion exchange resin. The polymerizable composition is a polymerizable monomer having a functional group capable of introducing an ion exchange group (functional group for introducing an exchange group) or a polymerizable monomer having an ion exchange group (hereinafter referred to as a polymerizable monomer). These monomers may be referred to as “basic polymerizable monomer components”), and may further contain a crosslinkable polymerizable monomer. The polymerizable composition is prepared by mixing these components and a polymerization initiator.

The polymerizable monomer is not particularly limited as long as it is a monomer that can produce the above-described hydrocarbon-based or fluorine-based resin. Therefore, there is no limitation as long as it is a hydrocarbon-based or fluorine-based polymerizable monomer used as a monomer for forming an ion exchange resin or its precursor resin, and a polymerizable monomer having a functional group for introducing an exchange group. In order to produce an ion exchange resin as a polymerizable monomer having a monomer and an ion exchange group, those conventionally used can be used without limitation.

For example, examples of the hydrocarbon polymerizable monomer having a functional group for introducing a cation exchange group include styrene, vinyl toluene, vinyl xylene, α-methyl styrene, vinyl naphthalene, α-halogenated styrenes, and the like. it can.

Examples of hydrocarbon polymerizable monomers having an anion exchange group-introducing functional group include styrene, bromobutyl styrene, vinyl toluene, chloromethyl styrene, vinyl pyridine, vinyl imidazole, α-methyl styrene, vinyl naphthalene, and the like. It is done. Styrene and the like can be used for introducing a cation exchange group or an anion exchange group.

The ion exchange group introduced into the hydrocarbon polymerizable monomer having a functional group for introducing a cation or anion exchange group described above is a functional group that can be negatively or positively charged in an aqueous solution. In the case of an exchange group, a sulfonic acid group, a carboxylic acid group, a phosphonic acid group and the like can be mentioned, and a sulfonic acid group which is a strongly acidic group is generally preferable. Examples of anion exchange groups include primary to tertiary amino groups, quaternary ammonium groups, pyridyl groups, imidazole groups, and quaternary pyridinium groups. Generally, quaternary ammoniums that are strongly basic are used. Groups and quaternary pyridinium groups are preferred.

Hydrocarbon polymerizable monomers having a cation exchange group include sulfonic acid polymerizable monomers such as α-halogenated vinyl sulfonic acid, styrene sulfonic acid, and vinyl sulfonic acid, methacrylic acid, acrylic acid, anhydrous Examples thereof include carboxylic acid polymerizable monomers such as maleic acid, phosphonic acid polymerizable monomers such as vinyl phosphoric acid, salts and esters thereof, and the like.

Examples of the hydrocarbon polymerizable monomer having an anion exchange group include amine polymerizable monomers such as vinylbenzyltrimethylamine, [4- (4-vinylphenyl) -methyl] -trimethylamine, and vinylbenzyltriethylamine. And nitrogen-containing heterocyclic polymerizable monomers such as vinyl pyridine and vinyl imidazole, and salts and esters thereof.

In addition, when a polymerizable monomer having an ion exchange group is used as the polymerizable monomer as described above, the target laminated ion exchange membrane becomes an ion exchange resin when the polymerization step described later is completed. However, when a polymerizable monomer having a functional group for introducing an ion exchange group is used, an ion exchange resin is obtained by carrying out an ion exchange group introduction step after the polymerization step, and the desired laminated ion exchange A membrane can be obtained.

Further, the crosslinkable polymerizable monomer is used for densifying the ion exchange resin, and is not particularly limited, for example, divinylbenzene, Examples include divinyl sulfone, butadiene, chloroprene, divinyl biphenyl, trivinylbenzenes, divinyl naphthalene, diallylamine, divinyl pyridine and the like.

Such a crosslinkable polymerizable monomer is generally preferably 0.1 to 50 parts by weight, more preferably 1 to 40 parts by weight with respect to 100 parts by weight of the basic polymerizable monomer component described above. .

Furthermore, in addition to the polymerizable monomer having a functional group for introducing an exchange group, the polymerizable monomer having an ion exchange group, and a crosslinkable polymerizable monomer, these polymerizable monomers are optionally used. Another polymerizable monomer copolymerizable with the monomer may be added. Examples of such other polymerizable monomers include styrene, acrylonitrile, methylstyrene, acrolein, methyl vinyl ketone, vinyl biphenyl, and the like. Styrene is also a polymerizable monomer having a functional group for introducing an exchange group, but a part of the functional group may remain without introducing an exchange group. Styrene and the like into which no exchange group is introduced are regarded as other polymerizable monomers.

In the present invention, the polymerizable composition contains a polymerization initiator together with the polymerizable monomer. As the polymerization initiator, conventionally known polymerization initiators are used without particular limitation. Specifically, octanoyl peroxide, lauroyl peroxide, t-butyl peroxy-2-ethylhexanoate, benzoyl peroxide, t-butyl peroxyisobutyrate, t-butyl peroxylaurate, t- Organic peroxides such as hexyl peroxybenzoate and di-t-butyl peroxide are used.

Such a polymerization initiator is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of all polymerizable monomer components to be used.

The polymerizable composition may further contain an acid trapping agent. In the reaction of introducing an exchange group into the functional group for introducing an exchange group, an acid may be generated. For example, hydrochloric acid is generated when chloromethylstyrene or the like is converted to quaternary ammonium. Since the acid may be gasified during the polymerization to generate bubbles in the polymer, it is preferably neutralized with an acid trapping agent. As the acid trapping agent, for example, epoxy compounds, (amines, ammonium salts) and the like are preferably used.

In the polymerizable composition containing the various components described above, a matrix resin can be blended as necessary in order to adjust the viscosity.

Examples of such matrix resins include ethylene-propylene copolymers, saturated aliphatic hydrocarbon polymers such as polybutylene, styrene polymers such as styrene-butadiene copolymers, and polyvinyl chloride. In addition to these polymers, various comonomers (for example, vinyl toluene, vinyl xylene, chlorostyrene, chloromethyl styrene, α-methyl styrene, α-halogenated styrene, α, β, β'-trihalogenated styrene, etc.) And monoolefins such as ethylene and butylene, and conjugated diolefins such as butadiene and isoprene) can be used.

These matrix resins are used in such an amount that the polymerizable composition has a viscosity such that the polymerizable composition can be quickly filled and held in the voids of the porous base film without causing dripping or the like.

2. Ion exchange membrane precursor production process;
In this step, after laminating a plurality of porous substrate films to form a laminated porous substrate film, the polymerizable composition is brought into contact with the laminated porous substrate film, and the polymerizable composition is introduced into the voids. An ion exchange membrane precursor is produced by filling the product. By carrying out like this, the air layer by a bubble etc. becomes difficult to produce between each porous base film which comprises a laminated porous base film.

When laminating a plurality of porous substrate films, there is no treatment to reduce the porosity of the porous substrate film, such as thermocompression bonding and welding, so the porosity of the porous substrate film can be maintained, and ion exchange Film resistance does not increase when a film is used. That is, the temperature at the time of laminating the porous base film is about 5 to 40 ° C., the pressure is about 0 to 0.05 MPa, and the films are stacked without impairing the porosity. . The pressure applied at the time of lamination is about the tension when passing through a line roll 3 described later, and the plurality of films are in a state where they can be easily peeled off. However, after the films are laminated, in the ion exchange resin forming step described later, the polymerizable composition impregnated in the laminated porous substrate film is polymerized, and the porous substrate film constituting the laminated porous substrate film Is bonded via a polymer and does not peel off.

When laminating a plurality of porous substrate films to form a laminated porous substrate film, the difference in porosity between adjacent porous substrate films is set to 10% or less. When the difference in porosity between adjacent porous substrate films exceeds 10%, the swelling rate of each layer of the laminated porous substrate film filled with the ion exchange resin when the ion exchange membrane is used is different. As guessed, when the counter-ion is ion-exchanged, it peels off at the interface between the porous substrate films. Further, as described above, when a stretched porous substrate film is used as the porous substrate film, it is preferable to align the layers in the orientation direction.

The filling of the polymerizable composition into the voids is preferably carried out by dipping, but can also be carried out by spraying or the like instead of dipping.

3. Ion exchange resin forming step;
After obtaining an ion exchange membrane precursor in which the polymerizable composition is filled in the voids of the laminated porous substrate film 4 as described above, the polymerizable composition is used as an ion exchange resin, and the present invention is intended. This is an ion exchange membrane for water electrolysis.

In the ion exchange resin formation step, first, the ion exchange membrane precursor is polymerized. The polymerization is preferably carried out under pressure. When a polymerizable monomer having an ion exchange group is used as a basic polymerizable monomer component of the polymerizable composition filled in the ion exchange membrane precursor, the intended water electrolysis is performed by polymerization. An ion exchange membrane is obtained. When a monomer having a functional group for introducing an exchange group is used as the basic polymerizable monomer component, an ion exchange group is introduced after the polymerization.

In the present invention, the laminated porous base film does not join the porous base films by heat fusion or the like, and the polymerizable composition in the ion exchange membrane precursor (fills the voids of each porous base film) The polymerized composition) is polymerized under pressure, whereby the laminated porous substrate film is joined and integrated simultaneously with the formation of the ion exchange resin (or its precursor resin), and each porous group The material films are firmly bonded to each other.

That is, in the ion exchange membrane precursor preparation step and this step, the laminated porous substrate film is not heat-sealed. However, excess polymerizable composition exudes to the interface of the porous substrate film due to pressurization during polymerization. Polymerization is carried out in a state in which the polymerizable composition leached at the base film interface and the polymerizable composition filled in the gaps of the porous base film are continuous. By the polymerization, an ion exchange resin (or a precursor resin thereof) is formed in a form continuous from the upper surface to the lower surface of the laminated porous substrate film, and the porous substrate films are bonded together via the resin. As a result, the resin obtained by polymerization of the polymerizable composition becomes a bonding agent without peeling at the interface of each porous substrate film, and the laminated porous substrate film is joined and integrated. .

The pressurization and polymerization of the ion exchange membrane precursor may be performed so that peeling at the interface of the porous substrate film does not occur. For example, the ion exchange membrane precursor (laminated porous substrate film) is released from the mold. It is good to superpose | polymerize by heating by inserting | pinching between an adhesive film and performing a pressurization in this state.

In addition, as the releasable film, a film having heat resistance that can withstand polymerization described later and that can be easily peeled off after polymerization is used. For example, low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or random α-olefins such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, or Polyolefins such as block copolymers, ethylene / vinyl acetate copolymers, ethylene / vinyl alcohol copolymers, ethylene / vinyl compound copolymers such as ethylene / vinyl chloride copolymers, polystyrene, acrylonitrile / styrene copolymers, ABS, styrene resins such as α-methylstyrene / styrene copolymer, polyvinyl chloride, polyvinylidene chloride, vinyl chloride / vinylidene chloride copolymer, polyvinyl compounds such as polymethyl acrylate and polymethyl methacrylate, nylon 6 , Nylon 6-6, nylon Polyamide such as 6-10, nylon 11, nylon 12, etc., thermoplastic polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyphenylene oxide, etc., biodegradable resin such as polylactic acid, or a mixture thereof The film which consists of one of these resin can be mentioned, The film which concerns may be biaxially stretched.

That is, an appropriate film may be selected from the above films according to the type of monomer component in the polymerizable composition and used as a releasable film. In particular, a polyester film such as polyethylene terephthalate (PET) is most preferable from the viewpoint of heat resistance and peelability.

The pressurizing pressure may generally be about 0.1 to 1.0 MPa. The pressurization may be performed by a press, but isotropic pressurization using an inert gas such as nitrogen as a pressure medium is preferable from the viewpoint of maintaining the porosity of the base film.

The polymerization temperature is a temperature lower than the melting point of the thermoplastic resin forming the laminated porous substrate film, and may be any temperature that does not impair the orientation and porosity of the porous substrate film. Generally, it is in the range of about 40 to 100 ° C. in the case of a polyolefin film. That is, by performing polymerization by heating to such a temperature range, the porous substrate films can be polymerized without causing heat fusion. At this time, the polymerization may be performed in a state where a part of the porous substrate film is dissolved in the polymerizable composition. As a result, the bonding strength of the porous substrate film can be increased, and the membrane strength can be further improved.

The polymerization time varies depending on the polymerization temperature and the like, but is generally about 3 to 20 hours.

As described above, when a monomer having an ion exchange group is used as a basic monomer component in the polymerizable composition, an ion exchange resin is formed by the above-described polymerization. An ion exchange membrane for water electrolysis is obtained. When a monomer having a functional group for introducing an exchange group is used as a basic monomer component, the resin obtained by the above polymerization does not have an ion exchange group. Introduce.

The introduction of the ion exchange group is carried out by a method known per se. For example, in the case of producing a cation exchange membrane, it is carried out by a treatment such as sulfonation, chlorosulfonation, phosphoniumation, hydrolysis, and the like. When producing an exchange membrane, it is carried out by a process such as amination or alkylation.

The introduction of the ion exchange group is performed after the polymerization of the ion exchange membrane precursor, and is performed after the release film is peeled off when it is sandwiched between the release films and polymerized under pressure.

The film thickness of the obtained laminated ion exchange membrane is preferably 50 to 220 μm, more preferably 50 to 180 μm, although it depends on the thickness of the laminated porous substrate film and the type and amount of the introduced ion exchange resin.

<Preferred manufacturing process>
The manufacturing method mentioned above can also be implemented using what was cut | judged to the moderate magnitude | size as a porous base film, and can also be implemented using the elongate sheet wound by the roll. Industrially, it is advantageous in terms of productivity to use a long sheet wound around a roll as a porous substrate film.

FIG. 1 shows an example of a process for producing an ion exchange membrane for water electrolysis in which two porous substrate films are laminated using such a long sheet.

The

porous substrate films

2a and 2b are unwound from the raw rolls 1a and 1b around which the

porous substrate films

2a and 2b are wound, and finally wound on the take-up roll 6. A porous substrate film is laminated on the roll 3 to obtain a laminated porous substrate film 4. The laminated porous substrate film 4 passes through a polymerizable composition immersion tank 9 containing a polymerizable composition provided between the line roll 3 and the take-up roll 6, and the polymerizable property in the tank 9 is reached. Immerse in the composition. By this immersion, an ion exchange membrane precursor 4 ′ in which the polymerizable composition is filled in the voids of the laminated porous substrate film 4 is obtained, and is wound around the winding roll 6 in the form of such a precursor. .

In the example of FIG. 1, filling of the polymerizable composition into the voids is performed by dipping, but it is also possible to carry out by spray coating or the like instead of dipping. By performing such an operation while laminating the porous base film and winding it on the take-up roll 6, the polymerizable composition can be sufficiently filled in the voids of the laminated porous base film 4. .

On the other hand, the releasable film 7 is wound on the take-up roll 6 from the releasable film original fabric roll 8 via a nip roll (pressure roll) 5. As a result, the ion exchange membrane precursor 4 ′ and the release film 7 are simultaneously wound on the winding roll 6.

That is, the ion exchange membrane precursor 4 ′ is held on the take-up roll 6 while being held between the release film 7 and pressed by the roll pressure. Therefore, in the polymerization described below, an excess polymerizable composition present at the interface of the porous substrate film by pressurization by the nip roll 5 (generally about 0.1 to 1.0 MPa) is placed in the voids of the film. Polymerization is carried out in the pressed state, and the occurrence of resin accumulation is effectively prevented.

The ion exchange membrane precursor 4 ′ in which the polymerizable composition is filled in the voids of the laminated porous substrate film 4 is heated under pressure in a polymerization apparatus such as a heating oven while being wound around the take-up roll 6. Used for all polymerizations. That is, when a monomer having an ion exchange group is used as the basic monomer component, the intended laminated ion exchange membrane can be obtained upon completion of this polymerization. When a monomer having a functional group for introducing an exchange group is used as a basic component, an ion exchange group is introduced after the completion of the polymerization.

The laminated ion exchange membrane thus formed is appropriately cut into an appropriate size and used or sold as an ion exchange membrane for water electrolysis.

The laminated ion exchange membrane is preferably used as an ion exchange membrane for water electrolysis that is incorporated in an electrolysis apparatus for electrolyzing water and obtaining hydrogen because it has low membrane resistance and hydrogen permeability and high bonding strength. .

Although it should not be construed as limiting in any way, the membrane resistance of the laminated ion exchange membrane is a value measured by the method of the examples described later, preferably about 10 to 30 mΩ · cm ² , more preferably about 10 to 20 mΩ · cm ^2. The hydrogen permeability is preferably 4000 to 9000 cc / m ² · 24 hr · atm, more preferably 4000 to 7000 cc / m ² · 24 hr · atm. The bonding strength is preferably 350 to 1500 gf / cm, more preferably 500 to 1500 gf / cm.

The laminated ion exchange membrane has a relatively thick film thickness, a relatively low porosity of the base film, and a small average pore diameter, so that it has excellent gas barrier properties and low hydrogen permeability. On the other hand, since the thickness is large and the average pore diameter and porosity of the base film are relatively low, the membrane resistance is expected to increase, but the membrane resistance is not as great as predicted. This cause is not theoretically constrained at all, but can be estimated as follows. The porous film is considered to have a small pore diameter and a low porosity in the surface layer (skin layer) as compared with the inside of the film. The interface between the skin layer and the electrolytic solution is a rate-determining process for conductivity when measuring the membrane resistance. That is, since ions enter the ion exchange membrane through the skin layer, they are easily affected by the pore diameter and porosity of the skin layer. Further, when laminating the porous film, since the treatment such as thermocompression bonding and welding is usually performed, the pore diameter of the skin layer becomes smaller and the porosity also decreases, resulting in an increase in membrane resistance. However, in the present invention, when the porous film is laminated, since the lamination is performed under the condition that the porosity can be maintained, an increase in the membrane resistance is suppressed. On the other hand, gas permeability is significantly affected by the size of the gap between the base film and the ion exchange resin. In the present invention, the substrate film filled with the ion exchange resin is controlled to have a specific range of porosity (average pore diameter, porosity), and further, the difference in the porosity of adjacent substrate films is reduced. And no gap between the ion exchange resin and high gas barrier properties. Furthermore, since the porous substrate film constituting the laminated porous substrate film is bonded via the ion exchange resin, high bonding strength can be obtained.

The ion exchange membrane for water electrolysis of the present invention is composed of the above laminated ion exchange membrane, and has low membrane resistance and low hydrogen permeability, so that it suppresses the generated hydrogen from passing through the ion exchange membrane, High-pressure hydrogen gas can be efficiently produced by cation exchange membrane type or anion exchange membrane type water electrolysis capable of internal compression.

(Water electrolysis apparatus and electrolysis method)
The water electrolysis apparatus of the present invention includes an anode and a cathode, and has the above-described laminated ion exchange membrane between the anode and the cathode. The water electrolysis apparatus is not particularly limited as long as it has the above basic structure, and includes various structures known as water electrolysis apparatuses. Accordingly, it may be an alkaline water electrolysis device or a solid polymer water electrolysis device. Moreover, an electric power source is provided outside the water electrolysis apparatus. The power source is preferably renewable energy or surplus power, but is not limited thereto. Further, a storage system using a hydrogen liquefaction system, a compression device, a hydrogen storage alloy, or the like may be provided.

FIG. 2 shows a simple configuration example of such a water electrolysis apparatus, but the water electrolysis apparatus of the present invention is not limited to the structure of FIG. FIG. 2 shows an example using an anion exchange membrane. As shown in FIG. 2, the water electrolysis apparatus includes a laminated ion exchange membrane (ion exchange membrane for water electrolysis) 10, a cathode 11, and an anode 12 installed in an electrolytic cell 20. The cathode 11 and the anode 12 are connected to an external power source 30 via conducting

wires

31 and 32, respectively. The electrolytic cell is provided with raw water supply pipes 13 and 14 for supplying raw water. As the raw water, a dilute alkaline aqueous solution is preferably used from the viewpoint of electrolysis efficiency, and for example, a dilute aqueous solution of KOH is used. By supplying raw water and energizing from an external power source, water electrolysis starts. The reaction on the cathode side and the anode side is as follows.

(Cathode side) 2H ₂ O + 2e ⁻ → H ₂ + 2OH ⁻
(Anode side) 2OH ⁻ → 1 / 2O ₂ + H ₂ O + 2e ⁻

On the cathode side, hydrogen and hydroxide ions are generated by electrolysis of water. The hydroxide ions reach the anode side through the laminated ion exchange membrane 10, and generate oxygen, water, and electrons. Hydrogen generated on the cathode side is recovered through the gas recovery tube 15, and oxygen is recovered through the gas recovery tube 16.

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to these examples.

In addition, the measuring method of the membrane resistance, hydrogen permeability, and joining strength used for the characteristic evaluation of the ion exchange membrane shown in an Example and a comparative example is shown below.

1) Membrane resistance First, the film thickness (Dry film thickness) of each obtained bicarbonate type anion exchange membrane when dried at room temperature overnight was measured. Next, in the case of an anion exchange membrane, it is immersed in an aqueous solution of 0.5 mol·L ⁻¹ —NaCl, and in the case of a cation exchange membrane, it is immersed in an aqueous solution of 3 mol·L ⁻¹ —H ₂ SO ₄ at 25 ° C. for 4 hours or more. The ion exchange membrane is made into a chloride ion type and proton type ion exchange membrane by placing the ion exchange membrane in the center of a two-chamber cell equipped with a platinum electrode, and anion exchange is performed on both sides of the ion exchange membrane. In the case of a membrane, a 0.5 mol·L ⁻¹ -NaCl aqueous solution is filled, and in the case of a cation exchange membrane, a 3 mol·L ⁻¹ —H ₂ SO ₄ aqueous solution is filled, and an AC bridge (frequency 1000 cycles / second) is 25 ° C. The resistance between the electrodes was measured (amΩ · cm ² ). Similarly, the resistance between the electrodes was measured without installing the ion exchange membrane (bmΩ · cm ² ), and the membrane resistance was determined from the difference in resistance between the electrodes when the ion exchange membrane was installed.
Membrane resistance = a−b [mΩ · cm ² ]

2) Hydrogen Permeability The obtained bicarbonate type anion exchange membrane was cut into 5 cm × 5 cm and attached to a gas permeability measuring device (GTR-200X FTS, manufactured by GTR Tech Co., Ltd.), and the hydrogen permeation amount was measured. . In the measurement, first, the ion exchange membrane is sandwiched between cells of the apparatus, and a carrier gas (argon gas) is flowed to one side of the ion exchange membrane at a temperature of 40 ° C., a humidity of 90% RH, and a flow rate of 30 mL / min. On the other hand, hydrogen gas is introduced as a test gas under conditions of a temperature of 40 ° C., a humidity of 90% RH, and a flow rate of 30 mL / min, and the amount of hydrogen permeated to the carrier gas side within the sampling time is detected by a gas chromatograph. The hydrogen permeability per 62 cm ² was calculated, and the hydrogen permeability of the ion exchange membrane was evaluated.
Hydrogen permeability [cc / m ² · 24 hr · atm] = (273 / T) × (1 / A) × B × (1 / t)
T: Measurement temperature (K)
A: Transmission area (cm ² )
B: Permeated gas amount (μL)
t: Sampling time (s)

3) Joining strength A sample with a part of the joining surface peeled off in advance with a width of 15 mm and a length of 150 mm at 25 ° C. and 65% relative humidity is created between chucks on a tensile tester (Autograph AGS-X manufactured by Shimadzu Corporation). The bonding force was measured at a speed of 500 mm / min after setting the T state at a distance of 75 mm. The bonding strength was determined from the measured bonding force by the following formula.
Bonding strength (gf / cm) = bonding force (gf) / sample width (cm)

<Example 1>
First, 90 parts by weight of chloromethylstyrene, 10 parts by weight of 57% -divinylbenzene, 5 parts by weight of a polymerization initiator (trade name: perbutyl O), and 5 parts by weight of an epoxy compound (trade name: Epolite 40E) are mixed for polymerization. A monomer composition was obtained. 800 g of the obtained polymerizable composition was put in a 1000 ml container, and a porous substrate film A (film thickness 25 μm, average pore diameter 0.07 μm, unwound from each of two raw rolls in this polymerizable composition, (Porosity 44%, made of polyethylene) was laminated on a roll and then immersed.

Subsequently, after taking out this laminated porous substrate film from the polymerizable composition and winding it on a take-up roll while covering both sides of the laminated porous substrate film with a 50 μm polyester film as a release film, Polymerization was carried out at 90 ° C. for 5 hours under a nitrogen pressure of 0.3 MPa to obtain an anion exchange membrane precursor.

This anion exchange membrane precursor was immersed in an aqueous solution containing 6% by weight of trimethylamine and 25% by weight of acetone at room temperature for 16 hours to introduce anion exchange groups to obtain an anion exchange membrane. Subsequently, it was suspended in a large excess of 0.5 mol·L ⁻¹ -KHCO ₃ aqueous solution, and the counter ion was ion exchanged from chloride ion to bicarbonate ion to obtain a bicarbonate type anion exchange membrane.

The membrane resistance and hydrogen permeability of the obtained anion exchange membrane were measured. The results are shown in Table 1.

<Example 2>
Bicarbonate type in the same manner as in Example 1 except that the porous base film used was changed to porous base film B (film thickness 25 μm, average pore diameter 0.07 μm, porosity 35%, made of polyethylene). An anion exchange membrane was obtained, and membrane resistance and hydrogen permeability were measured. The measurement results are shown in Table 1.

<Example 3>
A bicarbonate type anion exchange membrane was obtained in the same manner as in Example 1 except that the porous base film A and the porous base film B were laminated, and the membrane resistance and hydrogen permeability were measured. The measurement results are shown in Table 1.

<Comparative Example 1>
A bicarbonate type anion exchange membrane was obtained in the same manner as in Example 1 except that the porous substrate film A used was changed from two to one, and membrane resistance and hydrogen permeability were measured. The measurement results are shown in Table 1.

<Comparative example 2>
A bicarbonate type anion exchange membrane was obtained in the same manner as in Example 1 except that the porous base film used was changed from two to one, and the porous base film B was used. Was measured. The measurement results are shown in Table 1.

<Comparative Example 3>
Bicarbonate type in the same manner as in Example 1 except that the porous base film B and the porous base film C (thickness 25 μm, average pore diameter 0.1 μm or more, porosity 53%, made of polyethylene) were laminated. Although an anion exchange membrane was obtained, peeling of the interface was partially observed after the ion exchange of the counter ion from chloride ion to bicarbonate ion, and a perfect ion exchange membrane could not be obtained.

<Comparative example 4>
Except that the porous substrate film used was a porous substrate film D (film thickness 55 μm, average pore diameter of 0.1 μm or more, porosity 63%, made of polyethylene), and was changed from two to one. In the same manner as in Example 1, a bicarbonate type anion exchange membrane was obtained, and membrane resistance and hydrogen permeability were measured. The measurement results are shown in Table 1.

<Comparative Example 5>
Implemented except that porous substrate film A ′ (film thickness 55 μm, average pore diameter 0.07 μm, porosity 44%, made of polyethylene) was used as the substrate in a single layer instead of the laminated porous substrate film A bicarbonate type anion exchange membrane was obtained in the same manner as in Example 1, and membrane resistance and hydrogen permeability were measured. The measurement results are shown in Table 1.

As shown in Table 1, in Examples 1, 2, and 3, it was possible to obtain a laminated ion exchange membrane that was thick, had low membrane resistance, low hydrogen permeability, and high bonding strength. On the other hand, in Comparative Examples 1 and 2, since the film thickness was thin, the hydrogen permeability could not be reduced. In Comparative Example 3, the difference in porosity was so large that peeling occurred. In Comparative Example 4, a thick film having a low membrane resistance was formed, but the hydrogen permeability could not be reduced because the porosity and the average pore diameter were large. In Comparative Example 5, since a single layer porous substrate film was used, the membrane resistance was hardly increased, but the hydrogen permeability was not sufficiently reduced.

DESCRIPTION OF SYMBOLS 1a, 1b: Porous base film

original fabric roll

2a, 2b: Porous base film 3: Line roll 4: Laminated porous base film 4 ': Ion exchange membrane precursor 5: Nip roll 6: Winding roll 7 : Releasable film 8: releasable film original fabric roll 9: polymerizable composition immersion tank 10: laminated ion exchange membrane (ion exchange membrane for water electrolysis)
11: Cathode 12: Anode 13, 14: Raw water supply pipe 15, 16: Gas recovery pipe 20: Electrolyzer 30: External power supply 31, 32: Conductor

Claims

Laminated ion exchange in which a void is formed by laminating a plurality of porous substrate films having a porosity of 30 to 50% and an average pore diameter of 0.01 to less than 0.1 μm, and the voids of the laminated porous substrate film are filled with an ion exchange resin. An ion exchange membrane for water electrolysis, wherein the total thickness of the porous base film is 50 to 200 μm, and the difference in porosity between adjacent porous base films is 10% or less.
The ion exchange membrane for water electrolysis according to claim 1, wherein the ion exchange resin is a hydrocarbon ion exchange resin.
The ion exchange membrane for water electrolysis according to claim 1 or 2, wherein the porous substrate film is an olefin polymer or a copolymer.
A step of preparing a polymerizable composition containing a polymerizable monomer and a polymerization initiator, laminating a plurality of porous substrate films to form a laminated porous substrate film, and polymerizing the laminated porous substrate film A step of contacting a polymerizable composition containing a monomer and a polymerization initiator and filling the voids of the laminated porous substrate film with the polymerizable composition to obtain an ion exchange membrane precursor, in the ion exchange membrane precursor The method for producing an ion exchange membrane for water electrolysis according to claim 1, comprising a step of using the polymerizable composition as an ion exchange resin.
The method for producing an ion exchange membrane for water electrolysis according to claim 4, wherein the polymerizable monomer contained in the polymerizable composition is a hydrocarbon-based polymerizable monomer.
The method for producing an ion exchange membrane for water electrolysis according to claim 4 or 5, wherein the porous substrate film is an olefin polymer or a copolymer.
A porous porous substrate film in which a plurality of porous substrate films having a porosity of 30 to 50% and an average pore diameter of less than 0.01 to 0.1 μm are laminated is filled with an ion exchange resin, and is porous. Use of a laminated ion exchange membrane for water electrolysis in which the total thickness of the base film is 50 to 200 μm and the difference in porosity between adjacent porous base films is 10% or less.
A porous porous substrate film in which a plurality of porous substrate films having a porosity of 30 to 50% and an average pore diameter of less than 0.01 to 0.1 μm are laminated is filled with an ion exchange resin, and is porous. A water electrolysis apparatus in which an anode and a cathode are installed through a laminated ion exchange membrane in which a total thickness of base films is 50 to 200 μm and a difference in porosity between adjacent porous base films is 10% or less.
A porous porous substrate film in which a plurality of porous substrate films having a porosity of 30 to 50% and an average pore diameter of less than 0.01 to 0.1 μm are laminated is filled with an ion exchange resin, and is porous. Water is added to the water electrolysis apparatus in which the anode and the cathode are installed through a laminated ion exchange membrane in which the total thickness of the base film is 50 to 200 μm and the difference in porosity between adjacent porous base films is 10% or less. Water is electrolyzed to obtain hydrogen by conducting electricity between electrodes and electrolyzing water.