JPH1087853A - Production of bipolar membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a bipolar membrane having a good mechanical strength, low water dissociation voltage at a high current density and a high current efficiency. SOLUTION: A bipolar membrane having an anion exchange layer, an intermediate layer and a cation exchange layer in the given order is produced by using an anion exchange membrane or a membranous material which is convertible into an anion exchange membrane when reacted with a chemical as the anion exchange layer, forming an intermediate layer on the membranous material by applying a solution of metal oxide microparticles and an organic substance having a group convertible into an anion exchange group and/or an anion exchange group to the material and polymerizing the solution thereon, and then forming the cation exchange layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a bipolar membrane which is used for producing an acid or a base from a neutral salt by decomposing water to produce hydrogen ions and hydroxyl ions.

[0002]

2. Description of the Related Art A proposal for a bipolar film is disclosed in V.S. J.
Frillet (J. Phys. Chem. 60, 4)
35 (1956)), many have been made over the past 30 years. For example, an anion exchange membrane and a cation exchange membrane bonded with an ion exchange adhesive (Japanese Patent Publication No. 34-3961), an anion exchange membrane and a cation exchange membrane are formed of a finely powdered strong basic anion exchange resin, or a strongly acidic A paste-like mixture of a cation exchange resin and a thermoplastic resin is coated and pressed (Japanese Patent Publication No. 35-14 / 1978).
No. 531), a mixture obtained by applying a mixture of partially polymerized vinyl pyridine and an epoxy resin to a cation exchange membrane and irradiating the mixture during curing (Japanese Patent Publication No. 38-166).
No. 38). However, these bipolar membranes, although having a low current density, have a high water dissociation voltage and are not industrially attractive.

Further, an anion permeability or a cation permeability is provided from one side of a single sheet, and from the other side,
A bipolar membrane having the opposite charge of ion permeability (Japanese Patent Publication No. 60-31860), a polymer film having a functional group suitable for introducing an ion-exchange group is covered with a coating film, and the monolith is subjected to a sulfonation treatment. Then, after the coating film was peeled off, a method for producing a bipolar membrane having an anion exchange group introduced into the peeled surface (Japanese Patent Publication No. 14251/1991)
Publication). However, these are
It is difficult to control the reaction at the time of introducing the exchange group, it is difficult to produce a large-scale membrane on an industrial scale, or high current efficiency cannot be obtained.

On the other hand, a laminate structure useful for the production of a bipolar membrane is a bipolar membrane comprising an interface layer (intermediate layer) having a matrix polymer and an ion-exchange resin dispersed therein having opposite charges (JP-A-60-210638). Although the voltage of water dissociation of the membrane is relatively low,
Not enough yet. Furthermore, a bipolar membrane (intermediate layer) comprising an interface layer (intermediate layer) containing fine cation exchange resin particles dispersed in a matrix polymer containing a quaternary amine group and a non-quaternary amine group (Japanese Patent Laid-Open No. 1-502673).
And U.S. Pat. No. 4,766,161). Although this shows a low water dissociation voltage, it is difficult to use a very fine ion-exchange resin, and it is difficult to control the gelling and drying steps when forming the anion layer, and it is not easy to manufacture. Furthermore, since a polymer is dissolved in a solvent, cast and dried to obtain a film, it has a drawback that it is difficult to manufacture and has poor mechanical strength as compared with a product obtained by bulk polymerization.

Further, there is a device using an inorganic material for the purpose of lowering the high electric resistance of the bipolar film. An anion exchange membrane or a cation exchange membrane is immersed in an aqueous cation solution in an oxidized state, treated with an alkaline aqueous solution, and then heated and pressurized to join the two membranes.
No. 5894), a bipolar membrane having a polymer film of a cation exchange group formed on the surface of an anion exchange membrane in which heavy metal ions are present in the membrane (JP-A-4-63292), and a cation exchange membrane impregnated with iron. After coating the surface with an anion exchange resin (JP-A-4-2285)
No. 91). The membranes using these inorganic substances have a structure in which an anion exchange membrane and a cation exchange membrane are joined together and do not have an intermediate layer structure, and although there is an effect of introducing the inorganic substances, the water dissociation voltage of the bipolar membrane is an industrial scale production. However, it is difficult to control the performance, and there is a drawback that a water dissociation voltage is not always low.

A closely opposed water splitter system in which a metal hydroxide or a poorly water-soluble oxide is interposed between an anion exchange membrane and a cation exchange membrane (Japanese Unexamined Patent Publication No.
However, there is a drawback that water dissociation voltage is high and water dissociation voltage is extremely high when a water dissociation voltage is high and a thick layer of water is easily formed at an interface.

Further, an inorganic ion exchanger is present at the interface between an anion exchange membrane and a cation exchange membrane (Japanese Patent Laid-Open No. Hei 6-1994).
172557, JP-A-6-172558,
JP-A-6-263896, European Patent EP0600
470, U.S. Pat. No. 5,401,408, and JP-A-7-11021). Those using such an inorganic ion exchanger are more stable than those immersed in the cation aqueous solution in the above-mentioned oxidation state and treated with an alkaline aqueous solution, but the known inorganic ion exchanger itself used is a strong acid or strong acid. There is a problem that the dialysis performance of the bipolar membrane is lacking because it is easily dissolved under alkaline conditions. Regarding this disadvantage, see (JP-A-7-25878,
As disclosed in JP-A-7-222915),
In order to exhibit stable performance over a long period of time or to exhibit stable performance even after suspension of operation, it is necessary to re-form these inorganic ion exchangers during operation or at rest, and it is necessary to use a treatment agent for the product. There were many industrial restrictions such as contamination.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a bipolar membrane exhibiting good mechanical strength, low water dissociation voltage at high current density, and high current efficiency.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have accomplished the present invention. That is, the present invention is as follows. (1) A method for producing a bipolar membrane having an anion exchange layer, an intermediate layer and a cation exchange layer in this order, wherein the anion exchange layer is an anion exchange membrane or a membrane which can be an anion exchange membrane, A method for producing a bipolar membrane, in which a solution of a metal oxide fine particle and an organic substance having an anion exchange group or an organic substance having an anion exchange group is applied and polymerized to form the intermediate layer, and then the cation exchange layer is formed. (2) The method for producing a bipolar film according to claim 1, wherein the fine particles of metal oxide are fine particles containing an oxide of at least one metal selected from Group IVA of the periodic table.

In the present invention, the term "anion exchange layer" refers to the layer 1 in FIG. 1 and is a normal anion exchange membrane or a layer which reacts with a drug to form an anion exchange membrane. It is possible to use a membrane-like material before the introduction of an exchange group, which reacts with a membrane or a chemical to form an anion exchange membrane.
The term “drug” used herein means a known amine or polyamine when the anion exchange group of the anion exchange membrane is a quaternized polyvinylbenzyl halide. For example, trimethylamine, triethylamine, N, N, N ′, N'-
Tetramethyl 1,6-diaminohexane and the like,
These mixtures may be used. When the anion exchange group is a quaternized pyridium group or a quaternized imidazole group, it is a known alkyl halide, such as methyl iodide or 1,6-dibromohexane. The anion exchange layer may be three-dimensionally crosslinked with divinylbenzene, or may include a woven or nonwoven fabric for reinforcement, if necessary.

The present invention provides a method for producing a bipolar membrane having a novel structure which realizes efficient water dissociation by having an intermediate layer having a specific structure. As shown in 2 in FIG. 1, the intermediate layer is composed of metal oxide fine particles 4 containing an anion exchange resin 5.
Layer that is dispersed in the

The metal oxide referred to in the present invention is not an inorganic ion exchanger such as a hydrated oxide or an acidic salt type which is known to have ion exchange properties. This is because these known hydrated oxides or acidic salt type inorganic ion exchangers are not stable under the conditions of strong acid and strong alkali, and lack the stability of the dialysis performance of the bipolar membrane. The metal oxide referred to in the present invention is, for example, a known oxide having improved acid resistance and alkali resistance by heat treatment such as baking of a metal salt or a metal hydroxide, and typical examples include titanium oxide and zirconium oxide. Group IVA metal oxides are preferably used. Sintered oxides and the like are advantageous in both strength and chemical resistance, and are more preferably used. Note that two or more of these oxides may be contained, and further, other component elements may be contained.

As the shape of the metal oxide fine particles, those having a small primary particle diameter and a large specific surface area are effective. The primary particle diameter is about 0.02 μm to 0.5 μm, and these fine particles usually aggregate to form aggregated particles having a larger average particle diameter than the primary particle diameter.
The average particle diameter of the aggregated particles when handling is 0.5μ
Fine particles of m to 10 μm are preferred. If the average particle size is too large, when forming the intermediate layer, it is difficult to obtain a uniform one, and the water dissociation voltage tends to be high. If it is too small, handling becomes very complicated, and there is a problem in application on an industrial scale. Further, in the range the average particle diameter of the aggregated particles, specific surface area of 5m ² / g~250m ² /
The range of g is preferable for producing a bipolar membrane having good dialysis performance.

The surface area (specific surface area) per unit weight of the metal oxide fine particles is preferably as large as possible, and more preferably 5 m ² / g or more, since the voltage of water dissociation can be lowered. However, the specific surface area is determined due to strength and structural restrictions, so there is a limitation from this aspect. Further, those having a pore structure can be used, but it is necessary to ensure a sufficient contact interface between the metal oxide surface and the anion exchange resin in the intermediate layer. A size that allows the resin to enter the pores is preferred. Usually, those having an average pore diameter of 5 nm or more are preferably used. For these reasons, the maximum value of the specific surface area is about 250 m ² / g.

Such metal oxide fine particles are commercially available and can be easily obtained. As described above, the metal oxide fine particles are particularly preferable because they have a specific range of specific surface area and average particle diameter so that an acid and a base can be separated at a low water dissociation voltage. When forming the intermediate layer on the anion exchange layer, when the anion exchange layer is an anion exchange membrane, it is necessary to sufficiently remove moisture and dry. Further, when the anion exchange layer is a film-like substance that reacts with a drug to form an anion exchange membrane, it basically does not contain water, but in any case, prevents polymerization of the organic solution forming the intermediate layer. It is desirable to dry it.

The surface of the anion exchange layer forming the intermediate layer is roughened, for example, by sandblasting, or is roughened in advance using an irregular release paper when forming the anion exchange membrane, so that the intermediate layer is solidified. It is desirable to join them.
The formation of the intermediate layer is performed by drying a dried anion-exchange membrane or an organic substance solution containing a metal oxide fine particle and a group that can be an anion-exchange group or an anion-exchange group on a film-like substance that becomes an anion-exchange membrane by reacting with a drug. Casting with a doctor blade etc., superimposing release paper and polymerizing,
Alternatively, the organic material solution is cast on release paper such as a polyester film, and is superposed on the anion exchange layer and then polymerized.

An organic solution containing a group that can be an anion exchange group is a polymer which forms an intermediate layer by polymerization, and when the anion exchange group is introduced, the anion exchange resin becomes quaternized polyvinyl pyridine, quaternized polyvinyl imidazole, Any solution may be used as long as it contains a quaternized polyvinyl benzyl chloride, a copolymer of these with divinylbenzene, and a known anion exchange resin that contains a known anion exchange resin including a fluorine-containing anion exchange resin.

The organic solution containing an anion exchange group may be a solution obtained by dissolving the above-described anion exchange resin forming an intermediate layer in an organic solution containing a polymerizable organic solution, or a solution having an anion exchange group. It contains a polymerizable organic solution. At this time, the ion exchange capacity of the anion exchange resin in the intermediate layer was 2.0 per unit weight of the resin.
Meq / g to 5.5 meq / g is preferred. If the exchange capacity is too low, the water splitting voltage increases, so that the exchange capacity is preferably high, but the upper limit is restricted by additives, monomers to be copolymerized, and the like.

The anion exchange resin of the intermediate layer preferably has a crosslinked structure from the viewpoint of electrical resistance, dimensional stability and mechanical strength of the membrane. This crosslinked structure is preferably a three-dimensional crosslinked, and a crosslinking agent having two or more vinyl groups is preferably used as a monomer for forming the intermediate layer. Examples of the crosslinking agent include m-, p-, o-, divinylbenzene,
Examples include polyvinyl compounds such as divinyl sulfone, butadiene, chloroprene, trivinylbenzenes, divinylnaphthalene, and trivinylnaphthalene. Further, as another crosslinking agent, polyamine crosslinking can also be used. Known diamines or polyamines can be used as the polyamine crosslinking agent. As the polyamine crosslinking agent, known N, N-dimethylpropanediamine, N, N, N ′,
N'-tetramethyl 1,6-hexanediamine and the like.

The anion exchange resin of the intermediate layer may contain an additional substance such as a plasticizer or a linear polymer, if necessary, for the purpose of increasing elasticity, increasing adhesion or increasing viscosity. I do not care. The degree of crosslinking of the anion exchange resin in the intermediate layer is such that a crosslinking agent such as divinylbenzene is used in an amount of about 0.5 to 40 parts, preferably about 1 to 20 parts, more preferably about 5 parts to another monomer. About 15 to 15 parts by weight. To increase the mechanical strength, it is preferable to add a cross-linking agent.
On the contrary, inconveniences such as brittleness and high water dissociation voltage may occur.

The weight composition ratio of the metal oxide fine particles to the anion exchange resin is preferably such that the composition ratio of the anion exchange resin becomes too small to be brittle and the mechanical strength does not deteriorate and the electric resistance does not deteriorate. . This includes 1: 1
1: 7 is preferred. If the amount of the metal oxide fine particles is too large, a crack or a decrease in strength may be caused when the intermediate layer is formed. If the amount is too small, inconveniences such as an increase in the voltage of water dissociation may occur. This composition ratio has an optimum range depending on the form of the metal oxide, and the above range is usually preferable.

As described below, the intermediate layer includes
The water dissociation field is considered to be the layer formed in this layer. It is preferable that the metal oxide fine particles are densely dispersed while being in contact with each other in the intermediate layer having an anion exchange group, so that a bipolar film having low voltage performance can be formed. The dissociation of water in the intermediate layer of the bipolar membrane is
It is not clear whether it is the surface of the metal oxide fine particles inside the intermediate layer, the surface of the anion exchange resin, or their interface, or the bonding interface between the cation exchange layer of the cation exchange layer and the anion exchange resin of the intermediate layer. However, it is thought that the water dissociation performance is affected by the distance between the surface of the metal oxide fine particles and the anion exchange groups surrounding the particles, the positional relationship, the exchange group density, and the water molecules that hydrate to fixed charges. The design of the internal structure of the intermediate layer is very important.

The dialysis voltage of the bipolar membrane is determined mainly by the structure of the intermediate layer, which is the site of water dissociation, and depends on the type and form of the metal oxide fine particles and the anion exchange resin of the metal oxide fine particles. Although it is considered that the structure of the present invention is affected by the dispersion structure, the structure of the present invention can effectively and easily form the structure of such an intermediate layer, so that a membrane having extremely good dialysis performance can be produced on an industrial scale. It is a suitable method.

When a chemical treatment is carried out to introduce the anion exchange group, only the intermediate layer is introduced when the anion exchange layer is introduced into the anion exchange layer, and when the anion exchange group is introduced into the anion exchange layer. In the case of a film-like material that reacts with a drug to form an anion exchange membrane, it is possible to introduce an anion exchange group by treating the anion exchange layer and the intermediate layer with a drug at the same time.

The most important feature of the present invention is that the anion layer and the intermediate layer can be bonded more firmly, the performance of the bipolar membrane can be prevented from deteriorating due to the separation of the layers, and the long-term dialysis performance is stabilized. Since the intermediate layer, which is considered as a water dissociation site, can be designed and manufactured independently of the anion layer and the cation layer, a commercially available anion exchange membrane or a raw membrane of an anion exchange membrane before introduction of an exchange group can be used. Is very advantageous, and there is a very great merit.

After forming the anion exchange layer and the intermediate layer as described above, a cation exchange layer is formed to produce a bipolar membrane. The cation exchange layer is a cation exchange layer as shown in FIG. Before forming the cation exchange layer, the surface of the intermediate layer on the cation exchange layer side is adjusted so that the anion exchange resin does not cover the entire surface and the metal oxide is exposed. This may be carried out by sandblasting or by appropriately controlling the polymerization conditions of the intermediate layer.

One example of the formation of the cation exchange layer is to dissolve a polymer containing a cation exchange resin in a solvent soluble in the polymer, cast it on the intermediate layer, and dry it with hot air or the like. The cation layer serving as a cation exchange layer is a cation exchange resin containing polystyrenesulfonic acid or a cation exchange resin containing perfluorosulfonic acid resin, and may be crosslinked after cast formation, if necessary. Further, if necessary, an additional substance such as an elastomer, a plasticizer, or a linear polymer may be contained. As a reinforcing cloth for increasing mechanical strength, a woven cloth of polyvinyl chloride or polypropylene may be used. In addition, a net, cloth, a microporous membrane, or the like may be used as a reinforcing material.

As another example, an ordinary cation exchange membrane may be bonded with an ion-exchange resin, or the cation exchange membrane may be formed by applying pressure and thermally fusing.
The thickness of the bipolar film as shown in FIG.
It is about several μm to several mm, preferably 20 μm to 1 μm.
mm, more preferably 50 μm to 600 μm
It is. In the anion layer and the cation layer of the bipolar membrane, the water ion dissociated hydroxyl ions and protons move, so that the electromigration resistance is relatively low and the thickness of the layer can be increased. It becomes possible.

Further, in the present invention, a fourth layer and a fifth layer can be additionally formed as necessary to improve current efficiency and chemical durability. In this case, a new anion exchange layer may be formed on the side of the anion exchange layer opposite to the side in contact with the intermediate layer, or a new cation exchange layer may be formed on the side of the cation exchange layer opposite to the side in contact with the intermediate layer. An exchange layer may be formed. This additional fourth layer may be cast or adhered as in forming the cation exchange layer described above. Similarly, a fifth layer may be additionally formed.

The method for producing a bipolar film of the present invention as described above is industrially extremely useful and has the following three advantages. The first feature is that the anion exchange membrane or
Adhesion to the anion layer by coating and polymerizing metal oxide fine particles and an organic solution containing a group that can be an anion exchange group and / or an anion exchange group on a film-like substance that becomes an anion exchange membrane by reacting with a drug Since an intermediate layer having excellent properties can be formed, it is very advantageous for long-term industrial use.

The second feature is that the metal oxide fine particles have a specific surface area and an average particle diameter in a certain range, and the metal oxide fine particles are dispersed in the anion exchange layer.
It is to show low water dissociation voltage at high current density. The third feature is that the intermediate layer necessary for obtaining a low water dissociation voltage can be designed and manufactured separately from the anion exchange layer and the cation exchange layer, so that other functions can be easily provided. In order to realize a high current efficiency, a cation exchange resin layer may be post-crosslinked to form a three-dimensional crosslinked structure, or an ion cluster structure may be used, if necessary. Also,
In each layer constituting the bipolar film of the present invention, it is easy to put a reinforcing cloth in order to improve the mechanical strength.

As described above, according to the present invention, the intermediate layer can be firmly fixed on the anion exchange layer, and if necessary, the anion layer and the cation exchange layer can be individually designed and manufactured. This is a method for producing a high-performance bipolar membrane which is not only easy to produce a large-sized bipolar membrane used on an industrial scale but also easy to produce a bipolar membrane adapted to individual dialysis conditions.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically by way of examples, but the present invention is not limited to these examples. Parts are parts by weight, and the measuring method is as follows. [Specific surface area] It was measured by the BET adsorption method. (Primary particle diameter and average particle diameter of metal oxide fine particles)
It was measured by an electron microscope. [Performance of Bipolar Membrane] A platinum-plated nickel plate is used as an anode and a cathode, and the compartment is divided into two chambers with the anion exchange layer of the bipolar membrane facing the anode side. 10% NaOH and 3.5
% HCl was added to each room, and room temperature (2 mL) was added.
(5 ° C.) for 1 hour. At this time, the current density is 10
The water dissociation voltage of the membrane at 0 mA / cm ² is read on a voltmeter connected to a reference electrode using a Luggin tube. Also,
The generation efficiency of hydrogen ions and hydroxyl ions in the bipolar membrane was determined by acid-base titration, and was defined as the current efficiency of the bipolar membrane. The dialysis area is 8 cm ² .

Further, in the same measuring cell, 11% NaOH was continuously added to the anode compartment, 3.7% HCl was added to the cathode compartment, and the solution temperature was controlled at 40 ° C. to evaluate long-term dialysis performance. did.

[0035]

Examples 1 and 2 Aciplex A201 (manufactured by Asahi Kasei Kogyo Co., Ltd.), a commercially available anion exchange membrane, was sufficiently washed with pure water and dried to form an anion exchange layer. After drying, one side is roughened with sandpaper. An organic solution of the following viscous intermediate layer is applied to the film surface with a doctor blade to a thickness of about 50 μm and covered with a polyester film.
After polymerization at 24 ° C for 24 hours, quaternized with trimethylamine,
An intermediate layer into which an anion exchange group was introduced was formed on the anion exchange layer.

The organic solution for forming the intermediate layer is made of commercially available zirconium oxide and titanium oxide as metal oxides.
50 when the metal oxide fine particles are zirconium oxide
Parts (Example 1), 33.3 parts (Example 2) in the case of titanium oxide, 15.6 parts of styrene, 20.4 parts of divinylbenzene (purity 56%), 5 parts of vinylbenzyl chloride
2.5 parts, 5.7 parts of nitrile-butadiene rubber, 5.7 parts of dimethyl phthalate, and 6 parts of a polymerization initiator benzoyl peroxide (containing 50%) were sufficiently mixed until the mixture became viscous.

The specific surface area of the fine particles of the metal oxide, zirconium oxide 17m ² / g, titanium oxide is 46m ² /
g. The film formed with the intermediate layer on the anion exchange layer is further dried until the metal oxide of the intermediate layer is exposed.
The surface was lightly polished with sandpaper. Next, a cation exchange layer was formed on the obtained intermediate layer by the following procedure.

Styrene is polymerized to obtain a non-crosslinked polymer,
The polymer was sulfonated with concentrated sulfuric acid to give an exchange capacity of 1.
An ion exchange resin of 5 meq / g was obtained. Further, 90 parts of the ion-exchange resin and 10 parts of nitrile-butadiene rubber were dissolved in a dimethylformamide solution having a concentration of about 20% by weight, and cast on an intermediate layer. After casting, the film was dried at 105 ° C. to 110 ° C. for 10 minutes to form a cation layer to form a bipolar membrane. At this time, the thickness of the intermediate layer was about 35 μm.

The two types of bipolar films, each having an intermediate layer formed by using two types of different metal oxide fine particles by the above-described method, were equilibrated overnight with 1.5N saline solution, and then 100 mA / cm ² The dialysis was carried out at a current density of, and the water dissociation voltage of the bipolar membrane was measured. 1.05 V when the metal oxide is zirconium oxide (Example 1), and 1.02 V when the metal oxide is titanium oxide (Example 2).
V. The current efficiency of each of them is 98%
Was over.

Furthermore, as a result of continuous dialysis evaluation, the dialysis performance of the water dissociation voltage and the current efficiency of the bipolar membrane remained stable with little change for 5 months.

[0041]

Example 3 A film-like substance which reacts with a chemical to form an anion exchange membrane was obtained as follows. Styrene, divinylbenzene, vinylbenzyl chloride, nitrile butadiene rubber, a monomer solution consisting of dimethyl phthalate is applied to a polypropylene woven fabric irradiated with an electron beam, and polymerized by using a polyester film having irregularities on one side as a release paper, A film material to be an anion exchange layer was obtained.

On the film surface, a viscous monomer to be an intermediate layer as described below is applied by a doctor blade to about 50 μm,
It was covered with a polyester film and polymerized at 70 ° C. for 24 hours. An organic solution for forming the intermediate layer was prepared by adding 33.3 parts of commercially available titanium oxide as a metal oxide, 15.6 parts of styrene, and 20.5 parts of divinylbenzene (purity: 56%).
Parts, 52.5 parts of vinylbenzyl chloride, 5.7 parts of nitrile butadiene rubber, 5.7 parts of dimethyl phthalate, and 6 parts of a polymerization initiator benzoyl peroxide-based (containing 50%) organic solution, and mixed with an organic solution. To obtain a well-mixed mixture. The specific surface area of the metal oxide fine particles is 46 m ² / g.
Met.

Next, the surface was lightly sanded with sandpaper until the metal oxide of the intermediate layer was exposed. Furthermore, the anion exchange layer and the intermediate layer were simultaneously quaternized with trimethylamine to introduce anion exchange groups into the anion exchange layer and the intermediate layer, and the film having the anion layer and the intermediate layer was dried in a hot air drier. On the intermediate layer thus obtained,
A cation exchange layer was formed by the following procedure.

The non-crosslinked polymer is obtained by polymerizing styrene,
The polymer was sulfonated with concentrated sulfuric acid to give an exchange capacity of 1.
An ion exchange resin of 5 meq / g was obtained. Further, 90 parts of the ion-exchange resin and 10 parts of nitrile-butadiene rubber were dissolved in a dimethylformamide solution having a concentration of about 20% by weight, and cast on an intermediate layer. After casting, the solvent was dried at 105 ° C. to 110 ° C. for 10 minutes to form a cation layer, thereby obtaining a bipolar membrane. At this time, the thickness of the intermediate layer was about 35 μm.

The bipolar membrane was washed overnight with 1.5N saline.
After equilibration with water, 100 mA / cm ^TwoDialysis at current density of
And the water dissociation voltage of the bipolar membrane was measured.
01V. The current efficiency is over 98%
Was. Furthermore, as a result of continuous dialysis evaluation,
Dialysis performance of dissociation voltage and current efficiency is almost 5 months
It was stable without any change.

[0046]

The method of manufacturing a bipolar membrane according to the present invention is characterized by a method of forming an intermediate layer having a novel structure. In addition, since an anion exchange layer, an intermediate layer and a cation exchange layer can be individually designed, a high current density is obtained. Thus, a low water dissociation voltage can be exhibited and high current efficiency can be obtained at the same time.

Further, it is easy to introduce a reinforcing cloth into the anion exchange layer or the cation exchange resin layer for increasing the mechanical strength of the membrane, and other functions such as selection of an optimum resin can be achieved by dialysis of the membrane. It can be realized with little effect on performance. In addition, there are many excellent advantages that industrial scale membranes can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of a configuration of a bipolar film according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anion exchange layer 2 Intermediate layer 3 Cation exchange layer 4 Fine particles of metal oxide 5 Anion exchange resin

Claims (2)

[Claims] 1. A method for producing a bipolar membrane having an anion exchange layer, an intermediate layer and a cation exchange layer in this order, wherein said anion exchange layer is an anion exchange membrane or a film which can be an anion exchange membrane. Production of a bipolar membrane in which a solution of an organic substance having fine particles of a metal oxide and a group that can be an anion exchange group or an anion exchange group is applied and polymerized to form the intermediate layer, and then the cation exchange layer is formed Method. 2. The method according to claim 1, wherein the fine particles of the metal oxide are selected from the group consisting of:
The method for producing a bipolar film according to claim 1, wherein the particles are fine particles containing an oxide of at least one metal selected from the group consisting of metals.