JPH07126410A - Bipolar membrane - Google Patents

Abstract

PURPOSE:To provide a bipolar membrane exhibiting a good mechanical strength, a high electric current efficiency and a low water dissociation voltage at a high electric current density. CONSTITUTION:A bipolar membrane comprises at least two layers. Therein, the first layer 1 comprises composite particles 3 comprising a porous material having an average particle diameter of 0.5-50mum, a pore volume of 0.5-1.4cm<3>/g and an average fine pore diameter of 20-100nm, and an ion exchange group- containing polymer contained in the porous material, and a matrix polymer 4 having ion exchange groups having an electric charge opposite to that of the ion exchange groups of the composite particles 3. The ion exchange capacity of the ion exchange group-containing polymer in the porous material is 0.01-1.3meq/g per unit weight of the first layer, and the ion exchange capacity of the matrix polymer is 0.7-3.0meq/g per unit weight of the first layer. The second layer comprises a polymer having ion exchange groups having an electric charge opposite to that of the ion exchange groups of the matrix polymer 4.

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 decomposing water to produce hydrogen ions and hydroxide ions and producing an acid or a base from a neutral salt.

[0002]

2. Description of the Related Art Proposals concerning bipolar films are described in V. J.
Frilete [J. Phys. Chem. 60,4
35 (1956)], a lot has been done over the past 30 years. For example, one in which an anion exchange membrane and a cation exchange membrane are joined with an ion exchange adhesive (Japanese Patent Publication No. 34-3961), an anion exchange membrane and a cation exchange membrane are fine powder of a strongly basic anion exchange resin, or a strong acidity. Of the paste-type mixture of the cation exchange resin and the thermoplastic resin, and press-bonded (Japanese Patent Publication No. 35-14).
No. 531), a mixture of a partially polymerized vinyl pyridine and an epoxy resin was applied to a cation exchange membrane, and radiation was applied during curing (Japanese Patent Publication No. 38-16638).
Issue gazette) etc. However, these bipolar films
Although the current density is low, the water dissociation voltage of the membrane is high,
It was industrially unattractive. Further, a bipolar membrane in which anion permeability or cation permeability is imparted from one side of a single sheet, and ion permeability of the opposite charge is imparted from the other side (Japanese Patent Publication No. Sho 60-31860),
A bipolar film in which a polymeric film having a functional group suitable for introducing an ion-exchange group is covered with a coating film, the monolith is subjected to a sulfonation treatment, and then the coating film is peeled off, and then an anion-exchange group is introduced on the peeled surface. There is a proposal such as a method for manufacturing a film (Japanese Patent Publication No. 14251/1991). However, these are not industrially useful because it is difficult to control the reaction at the time of introducing an exchange group, it may be difficult to produce a membrane having a large industrial scale, and high current efficiency may not be obtained.

On the other hand, a laminated structure useful for the production of a bipolar film, in which a matrix polymer and an ion exchange resin dispersed therein are composed of an interface layer (intermediate layer) having opposite charges (Japanese Patent Laid-Open No. 60-210638). However, the voltage of water dissociation of the membrane is relatively low, but it is still not sufficient. Furthermore, a bipolar membrane 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. 1-502673).
No. 4,766,161) and the like, which show low water dissociation voltage, but use a very fine ion exchange resin, and gelation and drying process during anion layer formation. Control is difficult and not easy to manufacture. Further, since the polymer is dissolved in a solvent, cast and dried to obtain a film, it has drawbacks such as difficulty in production and poor mechanical strength as compared with the one obtained by bulk polymerization. Further, there is one using an inorganic material for the purpose of lowering the high electric resistance of the bipolar film. A bipolar membrane in which an anion exchange membrane or a cation exchange membrane is immersed in a cation aqueous solution in an oxidized state, treated with an alkaline aqueous solution, and heated and pressurized to join the two membranes (Japanese Patent Publication No. 3-505894). A bipolar membrane (Japanese Patent Application Laid-Open No. 4-63292) in which a polymer film of a cation exchange group is formed on the surface of an anion exchange membrane in which heavy metal ions are present in the membrane, and an anion exchange resin is impregnated after impregnating the cation exchange membrane with iron. There is a bipolar film coated on the surface (Japanese Patent Laid-Open No. 4-228591). Membranes using these inorganic substances have a structure of an anion exchange membrane and a cation exchange membrane that does 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. There was a drawback that you could not get.

[0004]

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

[0005]

Means for Solving the Problems The above-mentioned problems are, in a bipolar membrane having at least two layers, a composite particle in which a first layer therein has a polymer containing an ion exchange group in a porous body and the ion exchange. Consisting of a matrix polymer containing an ion-exchange group having an opposite charge to the group,
This can be solved by a bipolar membrane characterized in that the second layer is made of a polymer having ion-exchange groups having a charge opposite to that of the matrix polymer.
Here, the first layer is a layer in which the composite particles 3 containing an ion exchange resin are present in a dispersed state in the matrix polymer 4, as indicated by 1 in FIG.
It is arranged in close contact with the anion exchange resin layer or the cation exchange resin layer. Further, as shown in FIG. 2, it may be between both the anion exchange resin layer and the cation exchange resin layer and may be in contact with both of them. The second layer is shown in FIG.
2 is an ion exchange resin layer having a charge opposite to that of the matrix polymer of the first layer. The third layer is the layer shown by 5 in FIG. 2, which is an ion exchange resin layer having the opposite charge to the second layer and the same charge as the matrix polymer of the first layer. The thickness of the bipolar film as shown in FIGS. 1 and 2 is several μm.
The range is about several mm.

The term "composite particles" as used herein means particles having a structure in which a polymer having an ion exchange group is coated on the inner surface of the pores of the porous body or partially filled in the pores. It may be a quality ion exchange resin particle. The matrix polymer referred to here is a polymer containing an ion-exchange resin forming the first layer, and has a continuous and uniform structure. The present invention provides efficient water dissociation due to the structure of the first layer composed of the above composite particles dispersed in a matrix polymer, and an ion-exchange group contained in the matrix polymer even if the first layer itself is present. It is based on the fact that it also functions as a single-layer ion exchange membrane having the same charge, and provides a bipolar membrane having a novel structure.

It is not clear whether the dissociation of water in the first layer of the bipolar membrane referred to in the present invention occurs in the cation exchange resin portion, or in the anion exchange resin portion or at their bonding interface. However, the distance between the ion-exchange group in the porous particle containing the ion-exchange group and the ion-exchange group of the matrix polymer surrounding it, the positional relationship, the density of the exchange group, the water molecules hydrated to a fixed charge, and the like It is believed that performance is affected and the design of the internal structure of the first layer is extremely important. As a result of intensive investigations, the present inventors have found that the first layer of the structure described below provides performance that meets the purpose, although the reason is not clear, and completed the present invention. That is, (1) since the composite is composed of a porous body having an appropriate particle size, pore size, and pore volume,
The contact area between the ion-exchange resin and the matrix polymer in the porous body is large, and (2) the porous body particles containing ion-exchange groups are dispersed in the matrix polymer to form a kind of mosaic structure. The dissociated hydrogen ions and hydroxide ions do not recombine,
That is, the cation exchange resin layer and the anion exchange resin layer can be reached.

The dialysis voltage of the bipolar membrane having such a structure is mainly determined by the structure of the first layer, which is the field of water dissociation, and it depends on the kind of complex particles, the internal structure, the kind of ion exchange resin contained, It is considered to be influenced by the morphology, the exchange capacity, and the dispersion structure of the porous particles in the matrix polymer. Further, in the present invention, the first layer alone exhibits the same ion selective permeability as the monolayer membrane of the ion exchange group possessed by the matrix polymer. For example, if the matrix polymer exhibits anion exchange resin-like properties, the anion alone It has been found that it can also serve as an ion exchange resin layer. Therefore, the bipolar film can be formed only by joining the second layer having an opposite charge to the ion exchange group contained in the matrix polymer of the first layer. The reason for this is not clear, but for example, when forming the first layer, the raw material monomer of the matrix polymer and the porous body particles containing an ion exchange group are mixed and cast, and after the polymerization, the surfaces on both sides thereof are polymerized. It is considered that the porous particles containing the ion-exchange group are not exposed and are covered with the matrix polymer.

The porous body used in the present invention may be either an inorganic porous body or an organic porous body impregnated with an ion exchange group, or an ion exchange resin porous body. Examples of the inorganic porous material here include silicon, boron,
It is a porous oxide obtained by sintering aluminum, titanium and the like. Sintered oxides and the like are advantageous in strength and are preferably used. In addition, two or more kinds of these oxides may be contained, and further, other component elements may be contained. Among the inorganic porous materials, the silicon oxide porous material is most preferable because the particle diameter, the pore diameter, the pore volume and the specific surface area can be arbitrarily selected. Examples of the organic porous body here include well-known polyolefin-based porous bodies such as polyethylene and polypropylene, polyvinyl alcohol-based, polysulfone, vinylidene fluoride-based, polyacrylonitrile-based, cellulose-based, polyurethane-based, polystyrene-based and the like. It may be a porous body containing no ion exchange group, or an ion exchange group such as a sulfonic acid group or a quaternary ammonium group.

When the porous body is impregnated with an ion exchange resin, a porous body having a structure in which the impregnated ion exchange resin is likely to be thinly coated on the inner surfaces of the pores is effective. Is an index of average pore diameter, pore volume, particle diameter, and surface area. For example, the average pore diameter is 20 n.
m to 1000 nm is effective, and preferably 50 nm to
It is 700 nm. If the pore size of the porous body is too small, the impregnation of the ion exchange resin will be insufficient, and if it is too large, the coating area of the impregnated ion exchange resin will be insufficient and the voltage for dissociating water will be high. Furthermore, when the composite is formed and dispersed in the matrix polymer, pores remain in the composite, and the matrix polymer penetrates into the pores, resulting in a large interfacial area between the matrix polymer and the composite. It is also necessary to obtain it, and for this reason, the average pore diameter as described above is preferable. The pore volume of the porous body is preferably sufficiently large so that a sufficient amount can be impregnated when the ion exchange resin is impregnated, and a sufficient and sufficient exchange capacity can be obtained when the composite is formed. the porous body, there is a limit in terms of strength and manufacturing, the range is preferably 0.5cm ³ /g~1.4cm ³ / g. If it is less than 0.5 cm ³ / g, the voltage of water dissociation becomes high, which is not preferable.

The ion exchange resin with which the porous material is impregnated may be either a non-crosslinked type or a crosslinked type. Specifically, it is a polystyrene sulfonic acid resin, a perfluorosulfonic acid resin, or a quaternized resin. Examples thereof include polyvinyl pyridine resins, quaternized polyvinyl benzyl chloride resins, quaternized polyvinyl imidazole resins, copolymers of these with divinylbenzene, and precursors thereof into which an ion exchange group is introduced after impregnation. The molecular weight of the impregnated resin is
If it is a non-crosslinked polymer, it is 10,000 or more, preferably 70,000 or more. If the molecular weight of the resin is too low, the electric resistance of the film becomes high, and in the washing step or chemical reaction step during the production, It falls off and does not become enough. The larger the molecular weight, the more preferable. However, if the molecular weight is too large, it becomes difficult for the polymer to be dissolved in the solvent when impregnating the polymer, and it becomes impossible to impregnate a desired amount. Further, a structure in which the surface of the pores inside the porous body is thinly coated with an ion exchange resin is preferable, and an impregnation amount of the resin is selected so as to coat the entire surface of the pores but not to fill the pores. The amount of ion exchange resin with which the porous body is impregnated is preferably 10 to 80% of the pore volume, and more preferably 20 to 60%. This impregnation amount is preferably as large as possible, but if it is too large, the pores of the porous body are filled with the ion exchange resin and the voltage of water dissociation becomes high, which is not preferable. The ion exchange capacity of this resin is 1.0 meq / g to 5.4 meq / g as the ion exchange resin to be impregnated, and preferably 3.0 to 5.4 meq / g. As a whole of the first layer, 0.02 meq / g to 1.3 meq
/ G, preferably 0.06 meq / g to 1.3
It is meq / g. If the exchange capacity is too low, the voltage of water dissociation becomes high, which is not preferable. On the contrary, the exchange capacity is preferably high, but the upper limit is restricted by the monomers and additives to be copolymerized.

As a method for forming the composite particles used here, a resin containing an ion exchange group may be dissolved in a suitable solvent in a porous body, and then impregnated and dried, or a chemistry capable of converting into an ion exchange group. The ion exchange group may be introduced after impregnation with a solution of a resin having a chemically active site. Further, composite particles may be obtained by impregnating the porous body with a monomer mixture containing a monomer having an ion exchange group and then polymerizing or copolymerizing the same. Alternatively, the composite particles may be obtained by impregnating the porous body with a monomer having a chemically active site that can be converted into an ion-exchange group, polymerizing or copolymerizing the monomer, and then introducing the ion-exchange group. The particle size of the porous particles is preferably 0.5 μm to 50 μm. Further, the range of 1 μm to 10 μm is most preferable in order to lower the voltage of water dissociation. If the particle size is too large, it is difficult to obtain a uniform one when forming a layer, and the voltage of water dissociation tends to increase, and if it is too small, a porous body with an appropriate pore volume and pore size cannot be obtained. Not only that, when trying to form a complex, they often aggregate with each other or fail to be uniformly impregnated with the ion exchange resin, resulting in a high voltage of water dissociation.

The surface area (specific surface area) per unit weight of the porous body is preferably as large as possible as long as the resin to be impregnated can coat the inside of the porous body as uniformly as possible. It is preferable that it is 1 m ² / g or more because the voltage of water dissociation can be lowered. However, since the surface area is determined by the pore diameter and the pore volume, there are restrictions from this aspect. Such porous particles are manufactured by a known method, for example, a method of granulating and firing silica sol such as the method described in JP-A-61-122173.

As described above, the composite particles have a porous body which is the base of the composite and have an average particle diameter, an average pore diameter and a pore volume within a preferable range, whereby an acid and a base can be generated at a low water dissociation voltage. And can be separated. Even if the composite particles are replaced with ion exchange resins having the same particle size but different pore volumes and average pore sizes, the low water dissociation voltage as in the present invention cannot be achieved at all. However, it is considered that the same effect as that of the present invention can be obtained if the ion exchange resin having the same shape as the composite particles of the present invention is obtained. Therefore, even if such an ion exchange resin is used instead of the composite particles. Good. As the matrix polymer, when the ion exchange resin impregnated in the porous body is a cation exchange group, quaternized polyvinyl pyridine, quaternized polyvinyl imidazole, quaternized polyvinyl benzyl chloride, and a copolymer of these with divinyl benzene And a fluorine-containing anion exchange resin and the like. Conversely, in the case of an anion exchange group, it is a cation exchange resin containing polystyrene sulfonic acid or a cation exchange resin containing perfluorosulfonic acid resin.

The ion exchange capacity of the matrix polymer is 1.0 meq / g to 4.5 meq / g, preferably 2.0 meq / g to 4.5 meq / g. 0.7 meq / g to 3.0 meq / g as a whole of the first layer
If the exchange capacity is too low, the electric resistance becomes high, which is not preferable. On the contrary, the exchange capacity is preferably high, but the upper limit is restricted by the monomers and additives to be copolymerized. The matrix polymer of the first layer is preferably a cross-linked structure from the viewpoint of electric resistance, dimensional stability and mechanical strength of the film. This cross-linked structure is preferably three-dimensional cross-linked and used as a monomer for forming the matrix polymer. A crosslinking agent having two or more vinyl groups is preferably used.
Examples of the crosslinking agent include polyvinyl compounds such as m-, p-, o-, divinylbenzene, divinylsulfone, butadiene, chloroprene, trivinylbenzenes, divinylnaphthalene, and trivinylnaphthalene.
Further, polyamine cross-linking can be used as the other cross-linking agent, and as the polyamine cross-linking agent, for example, known diamines such as N, N-dimethylpropanediamine, N, N, N ′, N′-tetramethylhexanediamine, or , Polyamines can be used. In addition, these matrix polymers may contain additional substances such as plasticizers and linear polymers as needed for the purpose of increasing elasticity, improving adhesion, and increasing viscosity.

The degree of crosslinking of the matrix polymer is such that divinylbenzene is 1 part to 1 with respect to other monomers.
It is preferably contained in an amount of about 3 parts, more preferably 5 to 13 parts. Outside this range, when it is used as a bipolar membrane, disadvantages such as a gradual increase in water dissociation voltage may occur. Further, the weight composition ratio of the composite particles, which is a porous material impregnated with the ion exchange resin, and the matrix polymer does not deteriorate mechanical strength or electrical resistance such that the composition ratio of the matrix polymer becomes too small and becomes brittle. The composition range is good, and the range is 1: 2
The ratio of 1: 4 is desirable, and when the amount of the composite particles is too large, cracks and reduction in strength may occur when forming the first layer, and when the amount is too small, disadvantages such as an increase in water dissociation voltage may occur. Further, the composite particles may be crushed for the purpose of uniformly dispersing the composite particles in which the porous material is impregnated with the ion exchange resin in the matrix polymer.

When the matrix polymer of the first layer contains a cation exchange group, an anion exchange resin layer is formed as the second layer of the bipolar membrane of the present invention. The anion exchange resin layer includes a quaternized polyvinyl pyridine, a quaternized polyvinyl benzyl chloride, a quaternized polyvinyl imidazole, a fluorine-containing anion exchange resin, and the like, and if necessary, three-dimensional crosslinking with divinylbenzene or a halomethyl group. It may also include polyamine crosslinking by amination of. If the matrix polymer of the first layer contains an anion exchange group, a cation exchange resin layer is formed as the second layer of the bipolar membrane of the present invention. The cation exchange resin layer is a cation exchange resin containing polystyrene sulfonic acid or a cation exchange resin containing perfluorosulfonic acid resin, and may contain three-dimensional crosslinking with divinylbenzene or the like, if necessary. Accordingly, an additional substance such as a plasticizer or a linear polymer may be contained. A woven fabric of polyvinyl chloride or polypropylene may be used as the reinforcing fabric for increasing the mechanical strength. In addition, a mesh, cloth, microporous film, or the like may be used as the reinforcing material.

As a method for producing the bipolar membrane of the present invention, an anion exchange resin layer or a cation exchange resin layer is formed as a second layer on the first layer formed by introducing an exchange group into the composite particles and the matrix polymer. Form. That is, when the anion exchange resin layer is formed as the second layer on one surface of the first layer, the anion exchange membrane is formed with an anion exchange adhesive material, and when the cation exchange resin layer is formed, the cation exchange adhesive layer is formed. The cation exchange membrane is adhered or heat-pressed and fused with a material. Further, a resin containing an anion exchange group or a cation exchange group can be dissolved in a solvent, a first layer surface can be applied and dried to obtain a bipolar film, and a three-dimensionally crosslinked one can be used as the second layer. You can also The method for synthesizing the ion exchange resin that can be used in the present invention is not particularly limited. For example, in the case of an anion exchange resin, a mixed monomer of vinylbenzyl chloride having a halomethyl group and divinylbenzene is polymerized to form an exchange group with trimethylamine or the like. In the case of a cation exchange resin, a method of polymerizing a mixed monomer of styrene and dibenenylbenzene to introduce an exchange group with sulfuric acid or a sulfo group hydrophobized with amine hydrochloride or the like is used. A method of polymerizing a mixed monomer of a styrene sulfonic acid monomer and divinylbenzene is used.

In the present invention, the third layer may be formed if necessary in order to improve the current efficiency and the chemical durability. In this case, an ion exchange resin layer having the same charge as that of the matrix polymer of the first layer is formed in close contact with the surface of the first layer opposite to the side in contact with the second layer. Therefore, the polymer of the third layer is basically an ion exchange resin layer having a charge on the side opposite to the second layer, and the method of forming the third layer is the same as that of forming the second layer described above. Either a casting method or an adhesion method may be used.
As described above, the present inventors have earnestly studied and, as a result, have obtained a bipolar film having the following three advantages. That is,
The first feature of the present invention is that a composite containing an ion exchange resin in a porous body having a certain range of average particle diameter, pore volume, and average pore diameter is dispersed in the first layer, so that high current That is, the density shows a low water dissociation voltage.

The second feature of the present invention is that if the matrix polymer of the first layer has an anion exchange group, it can be used as an anion layer, and if it has a cation exchange group, it can be used as a cation layer. Is possible,
Therefore, high performance as a bipolar film can be achieved even with only the first layer and the second layer, which is very advantageous in manufacturing. The third feature of the present invention is that the first layer for water dissociation effective for low water dissociation voltage can be designed and manufactured separately from the anion exchange resin layer and the cation exchange resin layer as the second layer, and therefore other It is easy to add the functionality of. That is, in order to realize high current efficiency, the anion exchange resin layer and the cation exchange resin layer may have a three-dimensional cross-linking structure or an ion cluster structure, if necessary. Moreover, it is easy to put a reinforcing cloth in 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 first layer, the second layer, and the third layer can be individually designed and manufactured, it is easy to manufacture a large-sized bipolar film used on an industrial scale. Rather, it is a high-performance bipolar membrane that makes it easy to fabricate bipolar membranes that meet individual dialysis conditions.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The performance of the bipolar film of the example was measured as follows. That is, a platinum plate plated with platinum black is used as an anode and a cathode, and is partitioned into four chambers by a cation exchange membrane, a bipolar membrane and an anion exchange membrane. 5 1N saline
0 ml is placed in each of 1 to 4 chambers and electrodialysis is performed for 1 hour. At this time, the water dissociation voltage of the membrane at a current density of 100 mA / cm ² is read by a voltmeter connected to the reference electrode using a Luggin tube. The transport numbers of hydrogen ions and hydroxide ions in the bipolar membrane were determined by acid-base titration. The dialysis area is 8 cm ² .

(Examples 1 to 4) JP-A-61-2217
According to the method described in Japanese Patent Publication No. ^3, a silica porous body having an average particle diameter of 5 μm and a pore volume of 1.1 cm ³ / g has an average pore diameter of 20.
Four types, namely, nm, 60 nm, 150 nm, and 700 nm were manufactured. The method of forming a composite from these silica porous bodies was performed by the following procedure. 59.6 parts of one kind of porous silica material was taken in a rotary evaporator, and 5.1 parts of styrene monomer, 2.9 parts of divinylbenzene (purity 56%), 32.3 parts of n-hexane, and azobisisobutyrate. A mixed solution of 0.1 part of ronitrile is added little by little to the internal silica porous body while rotating the rotary evaporator under the condition of 0.1 atm at room temperature. After the addition is completed, transfer to another container and 60 under a nitrogen atmosphere.
Polymerization was carried out at ℃ for 24 hours. After the polymerization, the polymer was washed with methanol and sufficiently dried, and then the polymer impregnated in the silica porous body was sulfonated with concentrated sulfuric acid to form a composite. The exchange capacity of the entire composite was about 1.0 meq / g, and the volume of the resin part was about 30% of the pore volume of the porous silica material.

When the first layer was formed using this composite, the following procedure was performed. 50 parts of composite powder, 3.63 parts of styrene, divinylbenzene (purity 56%) 1
7.86 parts, vinylbenzyl chloride 45.78 parts,
Polyvinyl chloride resin 10 parts, nitrile butadiene rubber 5
Parts, 10 parts of dimethyl phthalate, and 0.2 parts of a polymerization initiator, azobisisobutyronitrile, were mixed and deaerated under reduced pressure to remove air from the complex. A polyvinyl chloride woven fabric was impregnated with the mixed liquid of the monomer and the composite, covered with a polyester film, and subjected to bulk polymerization at 60 ° C. for 24 hours to obtain a film. The obtained film-like material was quaternized with an aqueous trimethylamine solution containing acetone to obtain a first layer, and the thickness of the first layer obtained at this time was 90 μm. Next, the surface on which the second layer was formed on the first layer was previously polished with sandpaper to partially expose the dispersed composite particles.

The second layer was formed on the first layer thus obtained by the following procedure. Styrene was polymerized to obtain a non-crosslinked polymer. This polymer was sulfonated with concentrated sulfuric acid to obtain an ion exchange resin having an exchange capacity of 1.5 meq / g. Further, 90 parts of this ion exchange resin and 10 parts of polyvinyl chloride were dissolved in dimethylformamide to prepare a solution containing about 15% by weight of the ion exchange resin, which was cast on the dried first layer. 110 ℃ ~ 120 after casting
It was dried at 0 ° C. for 10 minutes to form a second layer, which was a bipolar film. At this time, the thickness of the second layer was 35 μm. Four kinds of bipolar membranes were obtained by using the four kinds of porous silica materials by the same method as the above. After equilibrating these bipolar membranes with 1N saline solution overnight, 100 mA / cm ²
The dialysis was performed at the current densities shown in Table 1 and the voltage of the bipolar membrane and the efficiency of the caustic soda generation current were measured.
Shown in.

Comparative Example 1 A silica porous material having an average particle diameter of 5 μm and a pore volume of 1.1 cm ³ / g has an average pore diameter of 60 n.
I prepared m items. A bipolar film was formed in the same manner as in Examples 1 to 4 except that this porous body was used instead of the composite, and the performance thereof was measured. The obtained results are shown in Table 1 and FIG. (Comparative Example 2) The average pore diameter of the silica porous body is 1300 n.
A bipolar film was formed by the same method as in Examples 1 to 4 except that m was used, and its performance was measured by the same method. The obtained results are shown in Table 1 and FIG. (Example 5) Average pore size 60 nm, pore volume 0.6 cm ³ /
g, a bipolar membrane was formed by the same method as in Examples 1 to 4 except that a silica porous body having an average particle diameter of 5 μm was used, the performance was measured by the same method, and the obtained results are shown in Table 1. And shown in FIG.

(Comparative Example 3) A bipolar membrane was formed in the same manner as in Example 5 except that the porous silica had a pore volume of 0.2 cm ³ / g. The measurement results are shown in Table 1 and FIG. Example 6 A silica porous material having an average particle diameter of 50 μm, a pore volume of 1.1 cm ³ and an average pore diameter of 60 nm was prepared. A bipolar film was formed on this porous body in the same manner as in Examples 1 to 4, the performance was measured, and the obtained results are shown in Table 1.
And shown in FIG. (Comparative Example 4) A crosslinked styrenesulfonic acid cation exchange resin having an average particle size of 5 μm was prepared instead of the composite. Pore volume of cation exchange resin is 0.04cm
^{It was 3} / g and the pore diameter was 40 nm. Using this cation exchange resin, a bipolar membrane was formed in the same manner as in Examples 1 to 4, the performance was measured, and the obtained results are shown in Table 1 and FIG.
Shown in. (Example 7) A first layer and a second layer were formed in the same manner as in Example 1, the side opposite to the first layer was polished with sandpaper to partially expose the composite, and then the third layer was formed as follows. Formed by the method.

A copolymer of styrene and chloromethylstyrene containing 30% by weight of chloromethylstyrene was dissolved in dimethylformamide, N, N, N ', N'-tetramethylhexamethylenediamine was added, and styrene-chloromethyl was added. Styrene copolymer 15% and N, N, N ', N'-
A solution containing 1% of tetramethylhexamethylenediamine was obtained. Before gelation occurred, this solution was cast on the other surface of the first layer, allowed to stand at room temperature for 5 minutes, and then dried in a hot air dryer at 120 ° C. for 15 minutes to form a third layer. The bipolar membrane was equilibrated overnight with 1N saline and then 100 mA.
The performance was measured by performing dialysis at a current density of / cm ² , and the obtained results are shown in Table 1 and FIG. (Example 8) A silica porous material having an average particle diameter of 10 µm, a pore volume of 1.1 cm ³ , and an average pore diameter of 60 nm was prepared. A bipolar film was formed on this porous body in the same manner as in Examples 1 to 4, the performance was measured, and the obtained results are shown in Table 1.
And shown in FIG.

[0028]

[Table 1]

[0029]

The bipolar of the present invention is characterized by a first layer having a novel structure, and since this first layer can be individually designed as an anion exchange resin layer or a cation exchange resin layer,
It is possible to obtain high current efficiency while exhibiting low water dissociation voltage at high current density. Next, in order to increase the mechanical strength of the membrane, it is easy to introduce a reinforcing cloth into the anion-exchange resin layer or the cation-exchange resin layer, which is the first layer, and to add other functionality such as selection of the optimum resin. Can be realized with almost no effect on the dialysis performance of the membrane.
There are a number of excellent advantages in that industrial scale membranes can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a schematic view of the structure of a bipolar film composed of first and two layers according to the present invention.

FIG. 2 is a schematic view of the structure of a bipolar film including the first to third layers of the present invention.

FIG. 3 is a diagram showing the relationship between the average pore diameter of the porous bodies used in the bipolar membranes shown in Examples and Comparative Examples and the water dissociation voltage.

[Explanation of symbols]

 1 1st layer 2 2nd layer 3 composite particle 4 matrix polymer 5 3rd layer

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[Submission date] October 21, 1994

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On the other hand, a laminated structure useful for the production of a bipolar film, in which a matrix polymer and an ion exchange resin dispersed therein are composed of an interface layer (intermediate layer) having opposite charges (Japanese Patent Laid-Open No. 60-210638). However, the voltage of water dissociation of the membrane is relatively low, but it is still not sufficient. Furthermore, a bipolar membrane 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. 1-502673).
JP, US Pat. No. 4766161) and Oh
However , although it shows low water dissociation voltage, it is not easy to manufacture because it is difficult to use a very fine ion exchange resin and it is difficult to control the gelation and the drying process during the formation of the anion layer. Further, since the polymer is dissolved in a solvent, cast and dried to obtain a film, it has drawbacks such as difficulty in production and poor mechanical strength as compared with the one obtained by bulk polymerization. Further, there is one using an inorganic material for the purpose of lowering the high electric resistance of the bipolar film. A bipolar membrane in which an anion exchange membrane or a cation exchange membrane is immersed in a cation aqueous solution in an oxidized state, treated with an alkaline aqueous solution, and heated and pressurized to join the two membranes (Japanese Patent Publication No. 3-505894). A bipolar membrane (Japanese Patent Application Laid-Open No. 4-63292) in which a polymer film of a cation exchange group is formed on the surface of an anion exchange membrane in which heavy metal ions are present in the membrane, and an anion exchange resin is impregnated after impregnating the cation exchange membrane with iron. There is a bipolar film coated on the surface (Japanese Patent Laid-Open No. 4-228591). Membranes using these inorganic substances have a structure of an anion exchange membrane and a cation exchange membrane that does 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. There was a drawback that you could not get.

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(Examples 1 to 4) JP-A-61-2217
According to the method described in Japanese Patent Publication No. ^3, a silica porous body having an average particle size of 5 μm and a pore volume of 1.1 cm ³ / g has an average pore size of 20.
Four types, namely, nm, 60 nm, 150 nm, and 700 nm were manufactured. The method of forming a composite from these silica porous bodies was performed by the following procedure. 59.6 parts of one kind of porous silica material was taken in a rotary evaporator, and 5.1 parts of styrene monomer, 2.9 parts of divinylbenzene (purity 56%), 32.3 parts of n-hexane and azobisiso a mixture of butyronitrile 0.1 parts little added Dzudzu into the interior of the porous silica while rotating the rotary evaporator over the conditions of 0.1atm at room temperature.
After the addition is complete, transfer to another container, under a nitrogen atmosphere at 60 ° C,
It was polymerized for 24 hours. After the polymerization, the polymer was washed with methanol and sufficiently dried, and then the polymer impregnated in the silica porous body was sulfonated with concentrated sulfuric acid to form a composite. The exchange capacity of the entire composite was about 1.0 meq / g, and the volume of the resin part was about 30% of the pore volume of the porous silica material.

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Comparative Example 3 A bipolar membrane was formed in the same manner as in Example 5 except that the silica porous material had a pore volume of 0.2 cm ³ / g. The measurement results are shown in Table 1 and FIG. Example 6 A silica porous material having an average particle diameter of 50 μm, a pore volume of 1.1 cm ³ / g and an average pore diameter of 60 nm was prepared. A bipolar film was formed from this porous body in the same manner as in Examples 1 to 4, the performance thereof was measured, and the obtained results are shown in Table 1 and FIG. (Comparative Example 4) A crosslinked styrenesulfonic acid cation exchange resin having an average particle size of 5 μm was prepared instead of the composite. Pore volume of cation exchange resin is 0.04cm
^{It was 3} / g and the pore diameter was 40 nm. Using this cation exchange resin, a bipolar membrane was formed in the same manner as in Examples 1 to 4, the performance was measured, and the obtained results are shown in Table 1 and FIG.
Shown in. (Example 7) A first layer and a second layer were formed in the same manner as in Example 1, the side opposite to the first layer was polished with sandpaper to partially expose the composite, and then the third layer was formed as follows. Formed by the method.

Claims (1)

[Claims] 1. In a bipolar film comprising at least two layers, the first layer has (1) an average particle size of 0.5 μm to 5 μm.
0 μm range, (2) Pore volume 0.5 cm ³ / g ~
Range of 1.4 cm ³ / g, (3) average pore diameter is 20 nm
In the range of up to 1000 nm, comprising composite particles having a polymer containing an ion exchange resin in a porous body and a matrix polymer containing an ion exchange group having a charge opposite to that of the ion exchange group. The exchange capacity of the polymer containing the ion exchange group is in the range of 0.02 meq / g to 1.3 meq / g per unit weight of the first layer, and the exchange capacity of the matrix polymer is per unit weight of the first layer, The second layer is composed of a polymer having an ion exchange group having a charge opposite to that of the ion exchange group contained in the matrix polymer, in the range of 0.7 eq / g to 3.0 meq / g. Bipolar membrane.