JPS5925813B2 - anion exchange membrane - Google Patents

Description

[Detailed description of the invention] The present invention relates to improved anion exchange membranes.

That is, the present invention provides an anion exchange membrane using a thermally conductive base material as a core material. Conventionally, various anions have been proposed for use in electrodialysis.

However, their common drawback is low current efficiency or otherwise poor membrane durability. In some cases, the current efficiency may be low to begin with, but in other cases, even if the film exhibits good performance at the beginning of current application, deterioration may gradually be observed in terms of performance such as electrical resistance and current efficiency, and physical properties such as mechanical strength. Become. Although various causes of such deterioration can be considered, since the deterioration progresses significantly when the current density is increased, it is inferred that one major cause is probably heat generation inside the membrane during energization.

In other words, such heat generation is associated with current distribution, non-uniformity of film composition, etc., and causes a considerable local temperature rise inside the film, which causes the film to deteriorate. Keeping the above points in mind, the present inventors have conducted various studies, and as a result of using a thermally conductive base material, i.e., a thermally conductive material, as the core material, i.e., backing, of the anion exchange membrane. We found that it is possible to solve this problem.

Here, the advantage of using a core material made of a thermally conductive material can be interpreted as follows.

In other words, the core material serves as a good thermal conductor and helps disperse the heat generated inside the membrane. Since the membrane itself has electrical resistance, it is inevitable that heat will be generated when electricity is applied, although there may be differences in degree. The core material made of thermally conductive material carries away the generated heat and prevents localized abnormal temperature rises.
Overall, it works to suppress the rise in temperature. In this way, deterioration of the film due to temperature rise will be suppressed. The base material used for the core material in the present invention is not particularly limited as long as it is thermally conductive, but in general, it has a thermal conductivity of O. -IrL・℃
Those having the above-mentioned properties are preferably used.

Specifically, metal or carbonaceous nets are particularly preferably used. Hereinafter, a net-like material will be explained as a representative core material. There are no particular limitations on the metal network as long as the constituent metals are not severely eroded under electrolytic conditions.

For example, Ti, Zr, Nb, Ta, Mo, W, Fe
, Co, Ni, Cu, Ag, Au, , Ru, Rh, , P
d, Co, Ir-, pt-ri-Cr-Mno metals or alloys thereof can be suitably used. Further, as the carbonaceous net-like material, in addition to woven fabrics and mats made of various carbon fibers, materials such as graphite film can also be used. There are no particular restrictions on the shape of these membranes, but extremely thick membranes are undesirable because they not only make the battery case unnecessarily large but also increase the electrical resistance of the membrane itself.

Generally less than 5mm thick, preferably 2mW! Below is 0.
A diameter of 0.05 mm or more is preferably used. Furthermore, there is no restriction on the shape of the mesh, and in addition to various weaving methods, perforated plates, sponge-like materials, and non-woven fabrics may also be used without any inferiority. That is, the net-like material referred to herein is a general term for perforated plates including perforated plates and sponge-like materials in addition to nets. Furthermore, the size of the openings (voids) in the mesh is generally not limited as long as it does not impede the passage of ions, but if the openings are extremely large, the effect will be diminished, so a diameter of 5 mm is usually used. or below the corner, preferably 1m
A diameter or angle of less than m is preferably used. Also,
Since the above net-like material is used as the core material of the ion exchange membrane, the surface of the net-like material may be appropriately processed by etching etc. in order to improve the affinity with the ion exchange resin. effective.

Furthermore, what is interesting is that the core material of the anion exchange membrane as described above is charged with a potential of the same sign as the charge possessed by the ion exchange groups of the ion exchange membrane from outside the ion exchange membrane, for example, to cause electrolysis. Obtained by doing.

That is, since all thermally conductive base materials are generally electrically conductive at the same time, by applying a potential to the core material, the entire core material is maintained at approximately the same potential. By appropriately adjusting the magnitude of this potential, if a positive potential is applied to the core material of the anion exchange membrane, it will prevent the passage of cations and reduce the selective passage of the ion exchange membrane. It acts to further improve the results. It goes without saying that when a potential is applied to the core material, the potential must be kept to such an extent that the core material itself does not function as an electrode.

In addition, when a polymeric substance having ion exchange properties or which can be converted into ion exchange properties is attached to a thermally conductive and electrically conductive base material used as a core material, the base material that will become the core material and the An insulating material may be interposed between the polymer materials.

For example, after coating the base material that will become the core material in advance with a substance that does not have electrical conductivity or ion conductivity, and then attaching a substance that has ion exchange properties or that can easily impart ion exchange properties, if necessary, An ion exchange group may be introduced.
In such a case, the potential applied to the thermally conductive and electrically conductive core material is not particularly limited. That is, a potential of several volts to several hundred volts may be applied. Incidentally, as described above, the potential applied to the core material of the anion exchange membrane may be applied continuously at a constant potential, or may be applied intermittently.

Alternatively, it may be a pulsating wave obtained by rectifying alternating current. At this time, the period of the pulsating flow is not particularly limited. Alternatively, a sawtooth potential commonly used in the electronics industry may be applied. In addition, many of the core materials having thermal conductivity and electrical conductivity have excellent mechanical strength, so that they are comparable to others in terms of reinforcing function as a so-called core material.

Furthermore, by maintaining the shape of the core material appropriately, it is also possible to create membranes with complex shapes. In other words, the shape of the core material may be appropriately selected and the ion exchange resin may be coated on it. For example, a mold that fits the required curved surface is made, a core material is sandwiched between the molds, and the upper monomer mixture is poured into the mold for polymerization, or a thermoplastic resin is heated and pressure molded together with the core material. An ion exchange membrane in a desired shape can be produced by various methods such as a method in which a flat plate is formed and then transformed into an arbitrary shape after film formation. The type of anion exchange resin membrane used in the present invention is not particularly limited and can be appropriately selected depending on the case.

Further, the method of manufacturing a membrane using a metal or carbonaceous mesh material as a core material is not limited in any way, and any method that can be conceived by a normal engineer may be adopted. Some examples of methods for producing anion exchange membranes using a thermally conductive base material as a core material will be shown below. (1) In the case of a heterogeneous anion exchange membrane, a fine powder of a polymerized or condensed anion exchange resin or an inorganic ion exchanger is uniformly mixed with an appropriate thermoplastic polymer, and then What is necessary is to embed a mesh material and heat mold it into a film shape. In addition, the above-mentioned fine powder ion exchange resin is uniformly dispersed in a viscous polymer solution in which a linear polymer is dissolved, and the net is coated with this by coating, dipping, spraying, etc., and the solvent is scattered to form a film. You can also use it as Alternatively, a membrane may be formed by embedding a mesh in a mixture of an inorganic ion exchanger or the like and cement. In this way, a network-containing ion exchange membrane can be manufactured by applying conventionally known techniques for manufacturing heterogeneous ion exchange membranes. (2) Similarly, for a homogeneous anion exchange membrane, a network-containing ion exchange membrane can be manufactured by applying various techniques conventionally proposed for manufacturing a homogeneous ion exchange membrane.

More specifically, for example, there is an embodiment in which a monomer having a polymerizable functional group such as vinyl or allyl is used to directly coat the net-like material by means such as coating, dipping, or spraying, and then heat-polymerize it. It will be done.

In this case, if it is necessary to prevent the polymerization raw material solution from dripping,
The viscosity of the polymerization raw material may be adjusted depending on the shape of the net-like material, or it may be coated with a suitable film-like material such as cellophane. The liquid viscous coating solution used here uses one or more types of fluorine-containing vinyl and aryl monomers, and in order to increase the viscosity, it is appropriately coated with a soluble oxidation-resistant polymer finely dispersed oxidation-resistant polymer. A polymer may also be present. Using this appropriately mixed viscous material, directly coat the net-like material by means such as coating, dipping, or spraying, and polymerize this by heating under pressure or normal pressure, or use other known methods as necessary. Introduction of an anion exchange group and conversion to an anion exchange group may be carried out by using the method.

As long as an insoluble polymer structure is formed, the polymerization may be carried out by radical or ionic polymerization, and radiation, X-rays, light energy, etc. may be used. There is also a method using an inert polymer compound.

That is, a thermoplastic polymer is attached onto a net-like material by thermoforming to form a thin film-like material, and ion exchange groups are introduced into this by some method. The method for attaching the polymer is not particularly limited, and for example, a method in which one or more of the above-mentioned polymer compounds is dissolved or dispersed in a suitable solvent, the above-mentioned net-like material is immersed in the solvent, and the solvent is scattered; A method in which the solution or dispersion is applied or sprayed to scatter the solvent, or a fine powder of the above-mentioned polymer is electrostatically charged, and the net-like material is also charged with an opposite charge. A method of electrostatically adhering the polymer and heating it to fuse the fine powder polymer to form a film-like material.A method of melting the above polymer at a high temperature that does not cause thermal decomposition and then applying a net-like material to the polymer. Effective methods include a method of immersion attachment and a method of molding the above-mentioned polymer using a net-like material as a core. The most suitable method may be selected depending on the type of polymer compound used, the range of the polymer such as molecular weight, the material and shape of the mesh, and the purpose of use of the ion exchange membrane containing the mesh. Ion exchange groups must be introduced into the attached polymer compound. As a method for introducing ion exchange groups, if the attached polymer is a polymer into which ion exchange groups can be introduced, it is necessary to directly treat it with an ion exchange group introduction reagent that does not significantly corrode the mesh material. Bye. In addition, the adhered polymer compound is impregnated with a polymerizable vinyl or aryl compound at room temperature or under heating, and at the same time, a radical polymerization initiator is coexisted so that the impregnated compound is not scattered under conditions such as heating under pressure. All you have to do is polymerize. In this case, a crosslinkable polyvinyl compound may be present to form a three-dimensional structure, or a linear structure may be formed. Further, the polymerization means is not limited to radical polymerization, and may be cationic polymerization, anionic polymerization, or redox polymerization. Furthermore, if the adhered polymer is impregnated with too much vinyl or aryl compound, resulting in significant dimensional changes and weak mechanical strength, add an appropriate solvent to the impregnation bath to dilute it and impregnate it. The amount may be decreased. If the amount of impregnation is small, the pre-adhered polymer may be swollen with a solvent and then immersed in the monomer. Of course, the amount of impregnation can also be increased by heating. In addition to the above-mentioned impregnation method, a vinyl or aryl monomer may be graft-polymerized onto a polymer attached by radiation or the like.

In this case, the pre-adhered polymer may be irradiated with radiation to form radicals and then immersed in the monomer or monomer mixture, or the polymer may be irradiated with radiation while being immersed. may be impregnated and then irradiated with radiation to polymerize. Among these various methods, the most suitable method should be adopted depending on the purpose of use of the ion exchange membrane containing the mesh, the type of polymer attached, the shape of the mesh, the material, etc.
o or above, the thermally conductive and electrically conductive base material of the present invention is used as a core material,
Although several examples for producing an anion exchange membrane generally used as a core material of a mesh have been shown, the present invention is not limited to the above examples in any way.

Basically, any material may be used as long as the thermally conductive and electrically conductive network material and the anion exchange membrane are integrated in some way. The present invention is that a polymer having an anion exchange group is in the form of a membrane and contains a network within the membrane.

Also, the presence of minute cracks and pinholes is not allowed.
That is, it is preferable that the permeation of water under pressure be as low as that of a normal ion exchange resin membrane. That is, it is desirable that the amount of water permeation is 10-5 cc/Cd-Atm-Sec or less. Further, as the ion exchange group bonded to the anion exchange resin portion of the present invention, any conventionally known functional group capable of becoming positively charged in an aqueous solution of Gζ can be used without any restriction. Namely, primary, secondary, tertiary amines, quaternary ammonium, tertiary sulfonium, quaternary phosphonium,
Onium bases such as arsonium stibonium and goharticinium. The embodiment using the ion exchange membrane of the present invention is not particularly limited, and can be used for electrodialysis and electrolysis in systems where mixing of the anolyte and catholyte does not occur and selective permeation of anions is required. Some examples will be given below, but the present invention is not limited to these examples in any way.

Example 1 100 parts of polyvinyl chloride fine powder, 1 part of 4-vinylpyridine
A paste mixture consisting of 60 parts of styrene, 10 parts of styrene, 15 parts of divinylbenzene, 25 parts of dioctyl phthalate, and 3 parts of benzoyl peroxide was uniformly applied to a 100-mesh nickel wire mesh with a thickness of 0.3 mm while degassing. completely covered the nickel wire mesh.

Next, both sides of this were covered with cellophane and polymerized by heating at 90'C for 8 hours to obtain a film-like polymer. The membrane was reacted with a mixed solution of methanol and methyl iodide in a ratio of 1:1 at 25° C. for 10 hours to obtain an anion exchange membrane having a quaternary ammonium base as an exchange group. After fully equilibrating the anion exchange membrane obtained here with 0.5N NaCl and 1.0NHC1, the membrane properties were measured and found that the electrical resistance was 6.5Ω-Cd.The 0.5N NaCl solution was electrodialyzed. The current effect on chlorine ion permeation was determined to be 98%. Note that the current density at this time was 2 A/Dm2. Example 2 250 parts of 2-methyl-5-vinylpyridine, purity approximately 50
To 80 parts of divinylbenzene, 30 parts of polyisobrene was added to form a polymer solution, and then 3 parts of benzoyl peroxide was added and dissolved to prepare a paste mixture. 10 parts of carbon fiber chips were added and uniformly dispersed by stirring with a homogenizer.

Next, this was applied with a 120 denier thread to a carbon fiber cloth with 36 threads in both length and width, while degassing it evenly, and both sides were covered with a polypynyl alcohol sheet and heated at 90°C for 8 hours. Polymerization was carried out by heating to obtain a polymer membrane. Carbon fiber chips were evenly distributed between the meshes of the carbon fiber woven fabric, and it had electrical conductivity. Next, the film-like polymer was placed in a 1:1 solution of methyl iodide and methanol at 25°C.
A strongly basic anion exchange membrane was obtained by immersing the membrane in water for 16 hours.

The electrical resistance of this film was 3.8Ω-Cd. Also 0.
The ring ratio determined from the membrane potential generated between 5NNaC1 and 2.5NNaC1 was 0.94. On the other hand, the above paste-like mixture was directly transferred to a polyvinyl chloride woven fabric (120
(denier, number of shots, 35 pieces both vertically and horizontally), covered both sides with a polyvinyl alcohol sheet, heated and polymerized at 90°C for 8 hours, and then soaked in a 1:1 solution of methyl iodide and methanol. The membrane was immersed at 25° C. for 16 hours to obtain a strongly basic anion exchange membrane.

The electrical resistance of this film is 3.9Ω-Cd and 0.5NNaC
The ring ratio determined from the membrane potential generated between 1 and 2.5N NaC1 was 0.94. The following experiment was conducted using two anion exchange membranes with different reinforcing materials.

That is, the membrane was sandwiched between a two-chamber acrylic cell equipped with silver/silver chloride electrodes, both chambers were filled with 0.1 N NaCl solution, and electrodialysis was performed for 3 hours at a current density of 5 A/Dm2.
The liquid on both sides of the membrane was vigorously stirred, and the effective current-carrying area of the membrane was 20 cd. At the beginning of electrodialysis, the temperature of the solution was 2
Although the temperature was 8°C, when electrodialysis was performed for 3 hours, the liquid reservoir was 75°C in both chambers when using the carbon fiber reinforced membrane of the present invention.
It was getting to ℃. Further, when a polyvinyl chloride woven fabric reinforced material was used, the temperature of the liquid reservoir was 76°C. The current efficiency was 99% and 97%, respectively. Next, electrodialysis was repeated for 6 hours using the same membrane under the same conditions to determine the current efficiency.The current efficiency remained unchanged at 99% for the membrane reinforced with carbon fiber, but 94% for the membrane reinforced with polyvinyl chloride woven fabric.
It was down to Furthermore, the quaternization rate of each membrane used by electrodialysis was determined.

Before being used for electrodialysis, the quaternization rate is 95% for those reinforced with carbon fiber and 9% for those reinforced with polyvinyl chloride woven fabric.
As a result of electrodialysis twice for 1 hour each, which was 6%, the carbon fiber-reinforced product remained unchanged at 95%, but the polyvinyl chloride woven fabric reinforced product had decreased to 85%. This is because quaternary ammonium bases generally have low resistance to temperature, and heat is generated by the anion exchange membrane during electrodialysis.
It is thought that the temperature inside the membrane rose in the membrane based on polyvinyl chloride woven fabric, and the quaternary ammonium base decomposed. Example 3 300 parts of chloromethylstyrene, 20 parts of divinylbenzene with a purity of 55%, 20 parts of styrene, 30 parts of styrene-ptadiene copolymer rubber, and 4 parts of benzoyl peroxide
The paste-like mixture consisting of 100% of the total weight was uniformly applied onto a nickel 100 mesh wire mesh having a thickness of 0.3 mm so that the wire mesh was completely covered, and while deaerating the wire.

Cover both sides of this with polyvinyl alcohol sheets.
・The polymer film was polymerized by heating at 80'C for 24 hours. This was immersed in a 30% trimethylamine aqueous solution to prepare an anion exchange membrane having a quaternary ammonium base as an ion exchange group. The electrical resistance of this film is 0.5NNa
In C1, 3.2Ω-Cri! L, 2.0NNaC1
When electrodialyzed at a current density of 2.0 A/Drrl, the current efficiency was 92%. Now, a three-chamber electrodialysis device was made by combining this anion exchange membrane with a sulfonic acid type cation exchange membrane using a titanium wire mesh as a reinforcing material manufactured by the method described below.

That is, a silver plate is used as the anode, then a cation exchange membrane,
A concentration chamber, an anion exchange membrane, and a cathode made of silver chloride are arranged in this order, and the anode and cathode chambers are filled with 2.5N NaCl and electrodialyzed at 5A/DTrI to determine the current efficiency from the concentration increase in the concentration chamber. Ta. As a result, the current efficiency was 88%.
Note that the leakage current was 0.5% or less. Next, a potential of -2.3V was applied to the base material of the cation exchange membrane of this electrodialysis device, and a potential of +1.2V was applied to the base material of the anion exchange membrane from another external DC power supply. Electrodialysis was performed under the same conditions as above.

As a result, the current efficiency was 92%. The cation exchange membrane used in the above electrodialysis was obtained by the following method.

Claims (1)

[Claims] 1 Anion exchange membrane using a thermally conductive base material as the core material.