JPH1087854A - Bipolar film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain bipolar film having a high mechanical strength and exhibiting a low water dissociation voltage and a high current efficiency at a high current density by using a specific intermediate layer in forming a bipolar film having an intermediate layer sandwiched between an anion-exchange layer and a cation-exchange layer. SOLUTION: This bipolar film has an anion-exchange layer, an intermediate layer, and a cation-exchange layer formed in this order, and the intermediate layer contains fine metal oxide particles, fine anion-exchange resin particles, and a resin having no ion-exchange group. An oxide of group IVA metal (e.g. titanium oxide or zirconium oxide) is suitably used as a typical example of the metal oxide. A sintered oxide is pref. This film is obtd. by dispersing the fine metal oxide particles, the fine anion-exchange resin particles, and the resin having no ion-exchange group in a solvent, applying the resultant dispersion to an anion-exchange film, drying the applied dispersion to form an intermediate layer, and forming a cation-exchange layer on the intermediate layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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. Further, 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 Publication No. 1-50267)
No. 3 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). Membranes using these inorganic substances have a junction structure of an anion exchange membrane and a cation exchange membrane, do not have an intermediate layer structure, and have the effect of introducing inorganic substances, but the water dissociation voltage of the bipolar membrane is sufficiently low. However, if the acid / alkali is not sufficiently washed with water at the time of the dialysis stop, the voltage increases at the time of restart. In addition, there is a closely opposed water splitter system (JP-A-2-131125) in which a metal hydroxide or a poorly water-soluble oxide is interposed between an anion exchange membrane and a cation exchange membrane. The water dissociation voltage is high only when they are closely placed, and a thick layer of water is easily formed at the interface, and the water dissociation voltage is extremely high.

Further, an inorganic ion exchanger which is present at the interface between an anion exchange membrane and a cation exchange membrane (Japanese Patent Laid-Open No.
172557, JP-A-6-172558,
JP-A-6-263896, European Patent EP0600
470, 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 drawback, see (
No. 258878, JP-A-7-222915)
As disclosed in, in order to exhibit stable performance over a long period of time, or to exhibit stable performance even after suspension of operation, a process of reforming these inorganic ion exchangers during operation or at rest is necessary. However, there are many industrial restrictions such as mixing of processing agents into products.

[0007]

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

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above-mentioned problem has occurred in a bipolar membrane having an intermediate layer between an anion exchange layer and a cation exchange layer. It has been found that the problem can be solved by a bipolar membrane characterized by having a structure containing fine particles of the above and fine particles of a resin containing an anion exchange group and a resin having no ion exchange group. Although the reason is not clear, it is considered that the presence of the intermediate layer containing the fine particles of the metal oxide and the fine particles of the resin containing the anion exchange group causes a water dissociation field to be formed in this layer. .

That is, the present invention is as follows. (1) A bipolar membrane having an anion exchange layer, an intermediate layer, and a cation exchange layer in order, wherein the intermediate layer is made of a metal oxide fine particle, a resin fine particle containing an anion exchange group, and a resin having no ion exchange group. Having a bipolar membrane. (2) The bipolar film according to the above (1), wherein the metal oxide fine particles are fine particles containing an oxide of at least one metal selected from Group IVA.

[0010] The intermediate layer referred to in the present invention is defined as 2 in FIG.
As shown in the figure, it is a layer located between the anion exchange layer 1 and the cation exchange layer 3, and another layer or the like is additionally provided as long as the potential of the membrane is not extremely impaired. Multiple layers may be used. The thickness of this intermediate layer is
It is several μm to several hundred μm. The thickness of the bipolar film as shown in FIG. 1 is about several tens μm to several mm.

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 known hydrated oxides and acidic salt type inorganic ion exchangers are not stable under the conditions of strong acids and strong alkalis 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,
As a typical example, Group IVA metal oxides such as titanium oxide and zirconium oxide are preferably used. Sintered oxides etc. are also advantageous in terms of strength and chemical resistance,
preferable. 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. When the average particle size is too large, when forming the intermediate layer, uniform ones are difficult to obtain, and the voltage of water dissociation tends to be high, and when too small, handling becomes very complicated,
Problems may arise with application on an industrial scale.

The surface area per unit weight (specific surface area) of the metal oxide fine particles is preferably as large as possible because the voltage of water dissociation can be reduced. Preferably 3 m ² / g
It is more preferably at least 5 m ² / g. But,
Since the specific surface area is determined due to strength and structural restrictions, the specific surface area is limited, and the maximum value of the specific surface area is 25%.
It is about 0 m ² / g. Such metal oxide fine particles are commercially available and can be easily obtained.

As described above, the metal oxide fine particles preferably have a specific specific surface area and an average particle diameter, whereby the acid and the base can be separated with a low water dissociation voltage. The fine particles of a resin containing an anion exchange group referred to in the present invention are not particles having a large particle size such as commercially available ion exchange resins, but have a large specific surface area having a small particle size obtained by emulsion polymerization or the like. Resin fine particles containing As the shape of the fine particles of the resin containing an anion exchange group, those having a small primary particle diameter and a large specific surface area are effective. Primary particle size is 0.01 μm to 0.3 μm
These fine particles are usually aggregated into aggregated particles having a larger average particle size than the primary particle size. Fine particles having an average particle diameter of 0.5 μm to 10 μm at the time of handling are preferable. If the average particle size is too large, it is difficult to obtain a uniform layer when forming the intermediate layer, and the voltage of water dissociation tends to be high.If the average particle size is too small, handling becomes very complicated, and industrial Problems can arise with application on a scale.

Examples of fine particles of a resin containing an anion exchange group include quaternized polyvinyl pyridine, quaternized polyvinyl imidazole, quaternized polyvinyl benzyl chloride, copolymers of these with divinyl benzene, and fluorine-containing anion exchange resins. And the like. The surface area (specific surface area) per unit weight of the fine particles of the resin containing an anion exchange group is preferably as large as possible, preferably 1 m ² /
It is preferable that the amount is equal to or more than g, since the voltage of water dissociation can be lowered. However, the specific surface area is determined due to structural restrictions, so there is a restriction from this aspect. The maximum value of the specific surface area is about 250 m ² / g. Such fine particles of a resin containing an anion exchange group can be easily produced by emulsion polymerization or the like.

The ion exchange capacity of the fine resin particles containing anion exchange groups is 2.0 me per unit weight of the resin.
q / g to 5.5 meq / g is preferred. If the exchange capacity is too low, the water splitting voltage becomes high, so the exchange capacity is preferably high, but the upper limit is restricted by the additives and the monomer composition to be copolymerized. The fine particles of the resin containing an anion exchange group preferably have a crosslinked structure in view of the electric resistance, stability and mechanical strength of the intermediate layer. This cross-linked structure is preferably three-dimensional cross-linked, and a cross-linking agent having two or more vinyl groups is preferably used as a monomer for forming the fine particles.

Examples of the crosslinking agent include m-, p-, o-, divinylbenzene, divinylsulfone, butadiene, chloroprene, trivinylbenzenes, divinylnaphthalene,
Examples include polyvinyl compounds such as trivinylnaphthalene. Further, as another crosslinking agent, polyamine crosslinking can also be used. As the polyamine crosslinking agent, known diamines and polyamines, for example, N, N-dimethylpropanediamine, N, N, N ′, N′-tetramethylhexanediamine and the like can be used.

The resin fine particles containing an anion exchange group may contain additional substances such as a plasticizer and a linear polymer. As the degree of crosslinking of the fine particles,
It is preferable that about 1 part to 50 parts, preferably about 5 parts to 40 parts, of a crosslinking agent such as divinylbenzene is contained with respect to other monomers. To increase the mechanical strength, it is preferable to add a cross-linking agent.
Problems such as an increased water dissociation voltage may occur.

The weight composition ratio of the fine particles of the metal oxide to the fine particles of the resin containing an anion exchange group is preferably such that the contact interface between the fine particles is large, and the weight ratio is 1: 9. ~ 9: 1 is preferred. More preferably, the ratio is 4: 6 to 8: 2. When the composition is out of the above-mentioned composition range, a disadvantage 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 fine particles of the metal oxide and the fine particles of the resin containing an anion exchange group, but generally the above range is preferable.

The resin having no ion-exchange group means that the above-mentioned metal oxide fine particles and resin fine particles containing an anion-exchange group are dispersed in an intermediate layer. As for those having excellent chemical resistance, polystyrene, polysulfone, styrene butadiene rubber, hydrogenated styrene butadiene rubber,
Known chemical resistant resins and elastomers such as nitrile butadiene rubber and chlorinated polyethylene resin can be used. Of these resins, although the reason is not clear, polystyrene, polysulfone, chlorinated polyethylene and the like are particularly preferable.

The resin having no ion-exchange group can sufficiently disperse the fine particles of the metal oxide and the fine particles of the resin containing the anion-exchange group, and can strengthen the structure of the intermediate layer. It is considered necessary to prevent penetration by an electric field of 1% to 45% per unit weight of the intermediate layer. If the amount of the resin having no ion-exchange group is too small, the layer of the metal oxide fine particles or the fine particles containing an anion exchange group may be easily peeled off, which may cause a problem in the stability of the membrane performance. If the amount is too large, the fine particles are scattered in the resin, which tends to increase the potential of the membrane. It is considered that this is because the contact area between the fine particles is reduced, and it becomes difficult to function as a water dissociation field and a generated proton and hydroxyl ion transfer field.

According to the present invention, there is provided an intermediate layer comprising a metal oxide fine particle, a resin fine particle containing an anion exchange group, and a resin having no ion exchange group between the anion exchange layer and the cation exchange layer. An object of the present invention is to provide a bipolar membrane having a novel structure based on efficient water dissociation. In the present invention, the dissociation of water in the intermediate layer of the bipolar membrane is caused by the surface of the metal oxide fine particles inside the intermediate layer, the surface of the resin fine particles containing an anion exchange group, their interface, or the anion exchange layer or the cation exchange layer. It is not clear whether it is a bonding interface between the layer and the intermediate layer. However, the distance, positional relationship, exchange group density, water molecules that hydrate to fixed charges, etc., between the surface of the metal oxide fine particles and the anion exchange group of the resin fine particles containing an anion exchange group in contact with it, Performance is believed to be affected and the design of the internal structure of the middle layer is very important.

According to the results of the study by the present inventors, although the reason is not clear, it has been found that the intermediate layer having the structure described below exhibits particularly excellent performance. That is, (1) the metal oxide fine particles have an appropriate specific surface area and the contact area with the resin fine particles containing an anion exchange group is large, and (2) the metal oxide fine particles and the anion exchange group The resin particles containing no ion-exchange groups and the resin containing no ion-exchange group form a mosaic structure, and dissociated hydrogen ions and hydroxyl ions can reach the cation layer and the anion layer without recombination, respectively. And so on.

The water dissociation voltage of a bipolar membrane having such a structure is mainly determined by the structure of the intermediate layer, which is a site of water dissociation, and depends on the type of metal oxide fine particles and resin fine particles containing anion exchange groups. It is considered to be influenced by the shape, form, and dispersion structure of the metal oxide fine particles and the resin fine particles containing an anion exchange group in the intermediate layer. What is particularly important here is that even if one of the three elements constituting the intermediate layer, metal oxide fine particles, resin fine particles containing anion exchange groups, or resin not containing ion exchange groups is missing, water dissociation occurs. That is, a bipolar film having a low voltage and exhibiting a low voltage for a long period of time cannot be obtained. For example, a low water dissociation voltage cannot be obtained only by the resin containing no metal oxide fine particles and an ion exchange group as the intermediate layer, and similarly, a resin fine particle containing an anion exchange group and a resin not containing an ion exchange group Alone does not provide a low water dissociation voltage. Although the cause is not clear, it is considered that the surface area of the water dissociation field is insufficient.

If there is no resin containing no ion exchange group, the voltage performance will not be stabilized. Although the cause is not clear, the above-mentioned fine particles alone cause the intermediate layer to be brittle and insufficient in strength, causing separation of the intermediate layer and increasing the voltage, and the exchange groups of the anion exchange layer and the cation exchange layer are not affected by the electric field. It is considered that this is because it becomes easier to enter the building, and the performance does not stabilize due to interpenetration.

Therefore, in the present invention, it is particularly preferable that the structure of the intermediate layer is strictly designed and controlled as described above. The above description relates to an intermediate layer formed between the anion exchange layer and the cation exchange layer, which is a component of the bipolar membrane, and mainly serves as a water dissociation field. The greatest advantage of the present invention is that the water dissociation field can be designed independently of the anion exchange layer and the cation exchange layer, and a bipolar membrane exhibiting high current efficiency performance at a low water dissociation voltage can be provided.

Next, the anion exchange layer and the cation exchange layer will be described, but this does not limit the present invention. Examples of the anion exchange layer include quaternized polyvinyl pyridine, quaternized polyvinyl imidazole, quaternized polyvinyl benzyl chloride, a copolymer of these with divinylbenzene, and a fluorine-containing anion exchange resin. It may include three-dimensional crosslinking by benzene or the like, and a known anion exchange membrane can be used. This is because the anion exchange layer can be designed separately from the intermediate layer that mainly controls the water dissociation voltage of the bipolar membrane, so that the membrane can be designed according to the process, and there is an advantage that the membrane can be produced according to the needs.

The cation exchange layer is made of a known cation exchange resin containing polystyrene sulfonic acid or a cation exchange resin containing perfluorosulfonic acid resin.
If necessary, three-dimensional crosslinking with divinylbenzene or the like may be included. Further, if necessary, an additional substance such as 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, as a reinforcing material,
A net, cloth, microporous membrane, or the like may be used.

As a method for producing the bipolar membrane of the present invention, fine particles of a metal oxide, fine particles of a resin containing an anion exchange group and a resin having no ion exchange group are dispersed in a solvent on an anion exchange membrane. Mixed and dried,
An intermediate layer is formed. Further, a cation exchange layer is formed. That is, the cation exchange membrane may be bonded with a cation exchange adhesive or may be heated and pressed. Alternatively, a bipolar membrane can be obtained by dissolving a resin containing a cation exchange group in a solvent, applying the resin on the surface of the intermediate layer, and drying it. The method for synthesizing the cation exchange resin that can be used as the cation exchange layer is not particularly limited.

In particular, when the cation exchange layer is coated with a solvent and dried, in order to prevent the resin from excessively entering the intermediate layer, a resin containing polysulfone, etc., having a thickness of 0.5 μm is used as long as the membrane potential does not rise. It may be applied between the intermediate layer and the cation exchange layer with a thickness of about less than. Further, on the cation exchange membrane, fine particles of a metal oxide, fine particles of a resin containing an anion exchange group, and a resin having no ion exchange group are dispersed in a solvent, mixed, coated and dried to form an intermediate layer. Further, an anion exchange layer is formed. That is, the anion exchange membrane may be adhered with an anion exchange adhesive or may be heated and pressed and fused. Alternatively, a bipolar membrane can be obtained by dissolving a resin containing an anion exchange group in a solvent, applying the resin on the surface of the intermediate layer, and then drying. The method for synthesizing the anion exchange resin that can be used as the anion exchange layer is not particularly limited.

In particular, when the anion exchange layer is coated and dried with a solvent, in order to prevent the resin from excessively entering the intermediate layer, a resin containing polysulfone is used in an amount of 0.1 as long as the membrane potential does not rise. It may be applied to a thickness of about 5 μm or less between the intermediate layer and the anion exchange layer. In the present invention, additional layers can be formed as necessary to improve current efficiency and chemical durability. In this case, the anion exchange layer is formed on the surface of the anion exchange layer opposite to the side in contact with the intermediate layer. The method for forming this layer may be any of a casting method and an adhesion method as in the case of forming the anion exchange layer.

Similarly, a cation exchange layer is formed on the surface of the cation exchange layer opposite to the side in contact with the intermediate layer. The method for forming this layer may be any of a casting method and an adhesion method as in the case of forming the anion exchange layer. The bipolar film of the present invention as described above has the following two advantages. The first feature is that the metal oxide fine particles and the resin fine particles containing an anion exchange group have a specific surface area and an average particle diameter in a certain range, and the metal oxide fine particles and the resin fine particles containing an anion exchange group are mixed. By providing an intermediate layer dispersed in a resin having no ion exchange group,
It is to show low water dissociation voltage at high current density.

The second feature is that the intermediate layer for water dissociation effective for a low water dissociation voltage can be designed and manufactured separately from the anion exchange layer and the cation exchange layer, so that it is easy to provide other functions. is there. In order to achieve high current efficiency, the cation exchange layer may have a three-dimensional cross-linking structure or an ion cluster structure, if necessary. Further, it is easy to put a reinforcing cloth into each layer constituting the bipolar film of the present invention in order to improve the mechanical strength.

As described above, according to the present invention, since the anion exchange layer, the cation exchange layer, and the intermediate layer can be individually designed and manufactured, it is easy to manufacture a large-sized bipolar membrane used on an industrial scale. It is a high-performance bipolar membrane that is easy to manufacture a bipolar membrane adapted to individual dialysis conditions.

[0035]

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. In addition, a part represents a weight part 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. [Dialysis Performance of Bipolar Membrane] A platinum plate-coated 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. Place 50 ml of 10% NaOH and 3.5% HCl in each room and perform electrodialysis for 1 hour. At this time, the current density was 100 mA / c.
The water dissociation voltage of the membrane at m ² is read on a voltmeter connected to a reference electrode using a Luggin tube. The generation efficiency of hydrogen ions and hydroxyl ions of the bipolar membrane was determined by acid-base titration. 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.

[0037]

Examples 1 to 3 Three kinds of commercially available zirconium oxide fine particles were used as metal oxide fine particles. The fine particles of this metal oxide are as shown in Table 1, and the specific surface area is
They are ¹⁰ , 17, and 107 m2 / g, respectively. Fine resin particles containing an anion exchange group were obtained by the following procedure.

6 parts of sodium lauryl sulfate are added to 400 parts of water, and the mixture is stirred while maintaining the temperature at 60 ° C. Add 2.55 parts of potassium persulfate and stir further. Next, 22.7 parts of a styrene monomer and 55.7 parts of vinylbenzyl chloride were used.
And a monomer obtained by mixing 21.7 parts (purity 55%) of divinylbenzene is added, and emulsion polymerization is performed at 60 ° C. for 24 hours. The fine particles after polymerization are filtered, washed, and quaternized with trimethylamine. After quaternization, neutralize with HCl, wash, filter and dry. When the anion exchange capacity of the fine particles was measured, it was 3 meq / g · resin. Also,
The aggregate particle diameter of these fine particles is about 1 μm, and the specific surface area is
It was 9.4 m ² / g · resin.

The thus obtained 6 parts of fine particles of a resin containing an anion exchange group, 4 parts of the fine particles of zirconium oxide and 1.11 parts of styrene polymer were subjected to 211.09.
The resulting mixture was dispersed and dissolved in a portion of the DMF solution to prepare a cast liquid for the intermediate layer. On the anion exchange membrane reinforced with a PP core material, the above intermediate layer casting liquid was cast-dried to a thickness of 100 μm and dried.
Twice to form an intermediate layer of about 10 μm.

Further, a cation exchange layer was formed by the following procedure. Styrene was polymerized to obtain a non-crosslinked polymer. This polymer was sulfonated with concentrated sulfuric acid, and the exchange capacity was 1.6.
A meq / g ion exchange resin was obtained. Further, 90 parts of this ion exchange resin and 10 parts of nitrile butadiene rubber were dissolved in dimethylformamide to prepare a solution containing about 20 wt% of the ion exchange resin, and cast on a dried intermediate layer. After casting, the film was dried at 105 ° C. for 10 minutes to form a cation exchange layer to form a bipolar membrane. At this time, the thickness of the cation exchange layer was about 40 μm.

By the above method, three types of bipolar films having an intermediate layer were obtained by using the three types of zirconium oxide fine particles having different specific surface areas. After equilibration of these bipolar membranes with 1.5N saline overnight, 100 mA /
Dialysis was performed at a current density of cm ² , and the voltage of the bipolar membrane was measured. The results are shown in Table 1 and FIG. All of these current efficiencies exceeded 97%.

Further, as a result of continuous dialysis evaluation of the membrane of Example 2, the dialysis performance of the bipolar membrane with respect to water dissociation voltage and current efficiency remained stable for almost five months without any change.

[0043]

Comparative Example 1 As shown in Table 3, fine particles of zirconium oxide (specific surface area: 3 m ² / g) having a specific surface area different from those of Examples 1 to 3 were used in the same manner as in Example 1. Then, an intermediate layer was formed on the anion exchange membrane, and further, a cation exchange layer was formed to obtain a bipolar membrane. After the bipolar membrane was equilibrated overnight with 1.5 N saline solution, 100 m
Dialysis was performed at a current density of A / cm ² , and the voltage of the bipolar membrane was measured. The results are shown in Table 3 and FIG.

[0044]

Examples 4 to 11 As shown in Tables 1 and 2, fine particles of a commercially available metal oxide (titanium oxide: specific surface area 46 m ² / g)
And the weight ratio of the resin fine particles containing an anion exchange group to 1: 9
The casting liquid for the intermediate layer was adjusted so that the content of the styrene resin, which is a resin containing no ion exchange group, was 20% per unit weight of the intermediate layer.

In the same manner as in Example 1, after forming an intermediate layer on the anion exchange membrane by casting, a cation exchange layer was formed to obtain a bipolar membrane. The thickness of the intermediate layer of each of these films was about 10 μm. By the above method, a bipolar membrane having an intermediate layer in which the weight ratio of the metal oxide fine particles to the resin fine particles containing an anion exchange group is different was obtained. After equilibrating these bipolar membranes with 1.5 N saline overnight, dialysis was performed at a current density of 100 mA / cm ² to measure the voltage of the bipolar membranes. The results of the dialysis performance are shown in Tables 1, 2 and FIG. All of these current efficiencies exceeded 97%.

[0046]

Comparative Example 2 Resin fine particles containing an anion exchange group were obtained by the following suspension polymerization. 6 parts of sodium lauryl sulfate is added to 400 parts of water, and the mixture is stirred while maintaining the temperature at 60 ° C. Next, a monomer obtained by mixing 22.7 parts of a styrene monomer, 55.7 parts of vinylbenzyl chloride, 21.7 parts of divinylbenzene (purity 55%) and 2 parts of benzoyl peroxide was further added, and the mixture was added at 60 ° C. for 24 hours. Perform suspension polymerization. The fine particles after polymerization are filtered, washed, and quaternized with trimethylamine. After quaternization, neutralize with HCl, wash, filter and dry. The anion exchange capacity of the fine particles is 3 meq /
g · resin, specific surface area was 0.5 m ² / g.

As shown in Table 3, the weight ratio of the fine particles of the metal oxide (titanium oxide: specific surface area 46 m ² / g) to the fine particles of the resin containing the anion exchange group was 6: 4.
The casting liquid for the intermediate layer was adjusted so that the content of the styrene resin, which is a resin containing no ion exchange group, was 20% per unit weight of the intermediate layer. In the same manner as in Example 1, after forming an intermediate layer on the anion exchange membrane by casting, a cation exchange layer was formed to obtain a bipolar membrane. The thickness of the intermediate layer of these films was about 10 μm.

After the bipolar membrane was equilibrated overnight with 1.5 N saline, dialysis was performed at a current density of 100 mA / cm ² to measure the voltage of the bipolar membrane. Table 3 shows the results of the dialysis performance.

[0049]

Comparative Example 3 As shown in Table 3, the intermediate layer contained only metal oxide fine particles (titanium oxide: specific surface area 46 m ² / g) and a styrene resin, and the weight of the styrene resin in the intermediate layer was The casting liquid of the intermediate layer was adjusted so as to be 20% per unit weight. In the same manner as in Example 1, after forming an intermediate layer on the anion exchange membrane by casting, a cation exchange layer was formed to obtain a bipolar membrane. The thickness of the intermediate layer of this film was about 10 μm.

After the bipolar membrane was equilibrated overnight with 1.5 N saline, dialysis was performed at a current density of 100 mA / cm ² to measure the voltage of the bipolar membrane. The results of the dialysis performance are shown in Table 3 and FIG.

[0051]

Comparative Example 4 As shown in Table 3, the intermediate layer contained only fine particles (resin surface area of 9.4 m ² / g) of a resin containing an anion exchange group and a styrene resin, and the weight of the styrene resin in the intermediate layer was intermediate. The casting liquid of the intermediate layer was adjusted so as to be 20% per unit weight of the layer. In the same manner as in Example 1, after forming an intermediate layer on the anion exchange membrane by casting, a cation exchange layer was formed to obtain a bipolar membrane. The thickness of the intermediate layer of this film was about 10 μm.

After the bipolar membrane was equilibrated overnight with a 1.5N saline solution, dialysis was performed at a current density of 100 mA / cm ² , and the voltage of the bipolar membrane was measured. The results of the dialysis performance are shown in Table 3 and FIG.

[0053]

Examples 12 to 15 As shown in Table 2, commercially available metal acids
Fine particles (titanium oxide: specific surface area 46m) ^Two/ G) and
When the weight ratio of the resin fine particles containing an anion exchange group is 6: 4
Yes, the content of styrene resin in the intermediate layer
Cast the middle layer to be 10-40% by weight
The liquid was adjusted. Anion exchange in the same manner as in Example 1
After casting the intermediate layer four times on the membrane, the cation exchange layer
It was formed into a bipolar film. The thickness of the interlayer of these membranes
The size was about 20 μm. By the above method, ion
Difference in content of styrene resin, which is a resin that does not contain exchange groups
Thus, a bipolar film having an intermediate layer was obtained.

After these bipolar membranes were equilibrated overnight with 1.5 N saline, dialysis was performed at a current density of 100 mA / cm ² to measure the voltage of the bipolar membranes. The results of the dialysis performance are shown in Table 2 and FIG. All of these current efficiencies exceeded 97%.

[0055]

Comparative Example 5 As shown in Table 3, the weight ratio of metal oxide fine particles (titanium oxide: specific surface area 46 m ² / g) to resin fine particles containing an anion exchange group was 6: 4. An intermediate layer casting solution containing no styrene resin was prepared. In the same manner as in Example 1, an intermediate layer was cast on an anion exchange membrane four times, and then a cation exchange layer was formed to form a bipolar membrane. The thickness of the intermediate layer of this film was about 20 μm.

After the bipolar membrane was equilibrated overnight with 1.5 N saline, dialysis was performed at a current density of 100 mA / cm ² , and the voltage of the bipolar membrane was measured. The results of the dialysis performance are shown in Table 3 and FIG. The current efficiency of this film was over 97%.

[0057]

Comparative Example 6 As shown in Table 3, the weight ratio of metal oxide fine particles (titanium oxide: specific surface area 46 m ² / g) to resin fine particles containing anion exchange groups was 6: 4, Styrene resin content of 5 per unit weight of the intermediate layer
The casting liquid of the intermediate layer was adjusted to be 0%. In the same manner as in Example 1, an intermediate layer was cast on an anion exchange membrane four times, and then a cation exchange layer was formed to form a bipolar membrane. The thickness of the intermediate layer of this film was about 20 μm.

After the bipolar membrane was equilibrated overnight with 1.5 N saline, dialysis was performed at a current density of 100 mA / cm ² to measure the voltage of the bipolar membrane. The results of the dialysis performance are shown in Table 3 and FIG.

[0059]

Examples 16 and 17 The ion exchange capacity of fine particles of a resin containing an anion exchange group was 2 meq / g and 3.9 in Cl type.
Fine particles of meq / g were prepared by emulsion polymerization in the same manner as in Example 1. As shown in Table 2, the weight ratio of the fine particles of the metal oxide (titanium oxide: specific surface area 46 m ² / g) to the fine particles of the resin containing an anion exchange group was 6: 4, and the styrene resin in the intermediate layer was Of the intermediate layer was adjusted to 20% per unit weight of the intermediate layer. In the same manner as in Example 1, two intermediate layers were formed on the anion exchange membrane.
After the formation of a single cast, a cation exchange layer was formed to obtain a bipolar membrane. Each of the intermediate layers of these films has a thickness of about 1
It was 0 μm.

After these bipolar membranes were equilibrated overnight with 1.5 N saline, dialysis was performed at a current density of 100 mA / cm ² , and the voltage of the bipolar membrane was measured. Table 2 shows the results of the dialysis performance. All of these current efficiencies exceeded 97%.

[0061]

Comparative Example 7 In the same manner as in Example 16, the ion exchange capacity of the fine particles of a resin containing an anion exchange group was 1 me in Cl type.
Fine particles of q / g were prepared. As shown in Table 3, fine particles of metal oxide (titanium oxide: specific surface area 46 m ² /
g) and the weight ratio of the fine particles of the resin containing the anion exchange group is 6: 4, and the content of the styrene resin in the intermediate layer is 20% per unit weight of the intermediate layer. Was adjusted. In the same manner as in Example 1, an intermediate layer was cast twice on the anion exchange membrane, and then a cation exchange layer was formed to obtain a bipolar membrane. The thickness of the intermediate layer of this film was about 10 μm.

After the bipolar membrane was equilibrated overnight with 1.5 N saline, dialysis was performed at a current density of 100 mA / cm ² to measure the voltage of the bipolar membrane. Table 3 shows the results of the dialysis performance.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

[0066]

The bipolar membrane of the present invention has a novel structure comprising fine particles of a metal oxide, fine particles of a resin containing an anion exchange group, and a resin having no ion exchange group between an anion exchange layer and a cation exchange layer. Having an intermediate layer of Since this intermediate layer can be individually designed with the anion layer and the cation exchange layer, it can exhibit a low water dissociation voltage at a high current density and at the same time obtain a high current efficiency.

Further, it is easy to introduce a reinforcing cloth into the anion exchange layer or the cation exchange layer for increasing the mechanical strength of the membrane, and it is possible to easily realize the addition of other functions such as selection of an optimum resin. 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 of the present invention.

FIG. 2 is a diagram showing the relationship between the specific surface area of the metal oxide fine particles used in the bipolar membranes shown in the examples and comparative examples and the water dissociation voltage.

FIG. 3 is a graph showing the relationship between the weight ratio of the fine particles of the metal oxide and the fine particles of the resin containing an anion exchange group used in the bipolar membranes shown in Examples and Comparative Examples and the water dissociation voltage.

FIG. 4 has intermediate layers shown in Examples and Comparative Examples.
It is a figure which shows the relationship between content of styrene resin which is a resin which does not contain an ion exchange group, and water dissociation voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anion exchange layer 2 Intermediate layer 3 Cation exchange layer 4 Fine particles of metal oxide 5 Fine particles of resin containing anion exchange group 6 Resin having no ion exchange group

Claims (2)

[Claims] 1. A bipolar membrane having an anion exchange layer, an intermediate layer, and a cation exchange layer sequentially, wherein the intermediate layer has no metal oxide fine particles and no resin fine particles containing an anion exchange group and no ion exchange groups. Bipolar film with resin. 2. The bipolar film according to claim 1, wherein the metal oxide fine particles contain at least one metal oxide selected from the group IVA.