JPS5940849B2 - Cation exchange membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an ion exchange membrane using a thermally conductive base material coated with an insulating material as a core material.

Conventionally, several methods have already been proposed for ion exchange membrane salt electrolysis. For example, the two-chamber electrolysis method using a fluorine-based ion exchange membrane and the three-chamber electrolysis method using a protective diaphragm in addition to the ion exchange membrane are both basic aspects, but various modifications can be made to each. has been submitted. 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. There are various possible causes of such deterioration, but since the deterioration progresses markedly when the current density is increased, it is inferred that one major cause is probably heat generation within the membrane during energization.

That is, such heat generation, in conjunction with the current distribution, non-uniformity of the film composition, etc., causes a considerable local temperature rise inside the film, which causes the film to deteriorate. With the above points in mind, the inventors of the present invention have conducted various studies, and as a result, the core material, or packing, of an ion exchange membrane has been made of a thermally conductive base material, that is, a thermally conductive material, coated with an insulating material. We have found that the above problem can be solved by using this method. That is, the present invention is a cation exchange membrane using a thermally conductive base material coated with an insulating material as a core material. The base material used for the core material in the present invention is not particularly limited as long as it is thermally conductive, but generally, the base material has a thermal conductivity of O
, 0 Olcal/se (...--℃ or higher, preferably O
, 005 calsec-CffL·°C or more is preferably used. Specifically, a metal or carbonaceous mesh material is particularly preferably used. Hereinafter, a core material and a net-like material will be representatively explained. 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, C
o, Ni, Cu, Ag, Au, Ru, Rh, Pd, Co
, Ir, P, V, and C, metals such as Mn 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 nets, but extremely thick ones are not preferred because they not only make the battery case unnecessarily large but also increase the electrical resistance of the membrane itself.

Generally, the thickness is 5 mm or less, preferably 2 mm or less and 0.05
A person higher than me is preferably used. Further, 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 mesh (voids) is generally not limited as long as it does not impede the passage of ions, but
If the opening is extremely large, the effect will be diminished, so the diameter or angle is usually less than 5mm, preferably 1m7! A diameter or angle smaller than L is preferably used.

Furthermore, what is interesting is that the core material of the ion exchange membrane of the present invention is charged with a potential having the same sign as the charge possessed by the ion exchange groups of the ion exchange membrane from outside the ion exchange membrane to perform electrolysis. It can be obtained by

That is, in the case of a cation exchange membrane, since the ion exchange group generally has a negative charge, a negative potential of the same sign as the ion exchange group is applied to the core material of the cation exchange membrane from outside the cation exchange membrane. For example, electrolysis is performed. A polymeric substance that has ion exchange properties or can be converted to ion exchange properties is attached to a thermally conductive and electrically conductive base material used as a core material when producing the cation exchange membrane of the present invention. When this is done, it is necessary to interpose an insulating material between the base material serving as the core material and the polymer material. 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 can easily impart ion exchange properties, the necessary An ion exchange group may be introduced by. 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 100 volts may be applied. At this time, for example, the cation exchange membrane has a negative electrostatic potential, that is,
The interface within the pores of the cation exchange membrane is charged with a negative potential, promoting the function of selectively permeating cations and blocking the permeation of anions. Incidentally, the potential applied to the core material of the ion exchange membrane in this manner may be applied continuously at a constant level, 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 type 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 they are not compatible with other materials 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. That is, 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, and a monomer mixture with a core material sandwiched between them is poured into the mold for polymerization, or a thermoplastic resin is molded under heat and pressure together with the core material. An ion exchange membrane of a desired shape can be produced by various methods such as a method of making a flat plate and transforming it into an arbitrary shape after film formation. The type of ion exchange resin membrane used in the present invention is not particularly limited and can be appropriately selected according to the situation. 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 cation exchange membranes using a thermally conductive base material as a core material will be shown below. 2) In the case of a heterogeneous cation exchange membrane, a fine powder of a polymerized or condensed cation exchange resin or an inorganic ion exchanger is uniformly mixed with an appropriate thermoplastic polymer, and then What is necessary is to embed a net-like material coated with an insulating 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 this is coated on the network by coating, dipping, spraying, etc., and the solvent is scattered to form a film. It may also be in the form of Alternatively, the mesh may be embedded in a mixture of an inorganic ion exchanger or the like and cement to form a membrane. In this way, the network-containing ion exchange membrane can be manufactured by applying conventionally known techniques for manufacturing heterogeneous ion exchange membranes. 2) Similarly, for homogeneous cation exchange membranes, various techniques conventionally proposed for the production of homogeneous ion exchange membranes are applied to create ion exchange membranes containing a mesh coated with an insulating material. be able to.

Next, to list some embodiments, (a) First, a monomer having a polymerizable functional group such as vinyl or allyl is used to directly coat with an insulating material by means such as coating, dipping, or spraying. An example is an embodiment in which the net-like material is coated and then heated and polymerized.

In this case, if it is necessary to prevent the polymerization raw material from dripping,
The viscosity of the polymerization raw material may be adjusted depending on the shape of the net, or it may be coated with a suitable film 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. This properly mixed viscous material is directly coated on the network by coating, dipping, spraying, etc., and this is heated and polymerized under pressure or normal pressure, and if necessary, sulfonation, Introduction of a cation exchange group and conversion into a cation exchange group may be carried out by hydrolysis or other known means.

Polymerization results in the formation of an insoluble polymer structure.
It can be polymerized both radically and ionicly,
Radiation, X-rays, optical energy, etc. may also be used.

(b) Next, there is a method using a linear polymer electrolyte.

That is, a fluorine-containing anionic polymer electrolyte is dissolved in a suitable solvent, and a net-like material coated with an insulating material is coated with the solution by means such as coating, dipping, or spraying, and then If the solvent is scattered and the remaining film is used, if it is insoluble, it can be left as it is; if it is soluble, it can be made insolubilized by appropriate means such as radiation irradiation, X-ray irradiation, ultraviolet rays, etc. can. These are just a few examples, and salts, acids, and bases used in water or with linear polyelectrolytes or compounds that can be converted into linear polyelectrolytes by simple means such as hydrolysis. It is also effective to heat a thermoplastic, water-insoluble polymer electrolyte to coat the network and, if necessary, introduce ion exchange groups.

As this type of linear polymer, those represented by the following are particularly effective. (However, m is a positive integer, 1 and n are O or a positive integer, and X represents a halogen or -OH group) (c) There is also a method using an inert polymer compound.

That is, a thermoplastic polymer such as polyvinyl fluoride, polyfluorinated vinyl, polytrifluoromonochloroethylene, polytetrafluoroethylene, etc. is coated with an insulating material by thermoforming. It is applied to a material to form a thin film-like material, and ion exchange groups are introduced into this film by some method. The method of attaching the polymer is not particularly limited, and for example, a method of dissolving or dispersing one or more of the above-mentioned polymer compounds in a suitable solvent, immersing the above-mentioned net-like material in the solvent, and scattering the solvent; A method in which the solvent is scattered by coating or spraying a φ solution/dispersion, or by electrostatically charging the fine powder of the above-mentioned polymer and also charging the net-like material with the opposite charge. A method of electrostatically adhering a substance and heating it to fuse a finely powdered polymer to form a film-like substance, and a method of melting the above-mentioned polymer at a high temperature that does not cause thermal decomposition to form a film-like substance, for example, Effective methods include a method of attaching a material by dipping, a method of molding the polymer using the network material as a core, and the like. The most suitable method may be selected depending on the type of polymer compound used, the physical properties of the polymer such as molecular weight, the material and shape of the mesh, and the purpose of use of the mesh-containing ion exchange membrane. . 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 may be directly treated with an ion exchange group introduction reagent. Also,
This 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, and the impregnated compound is heated and polymerized under conditions such that the impregnated compound does not scatter, for example, under pressure. Just let it happen. In this case, a crosslinkable polyvinyl compound may be present to form a three-dimensional structure, or a linear structure may be formed. In addition, the polymerization method is not limited to radical polymerization, but also cationic polymerization,
Anionic polymerization or redox polymerization may be used. Furthermore, if the adhered polymer is impregnated with an excessively large amount of vinyl or aryl compound, resulting in significant dimensional changes and weak mechanical strength, add an appropriate solvent to the impregnating bath to dilute it and impregnate it to reduce the impregnated 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 to 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. Furthermore, after being impregnated, radiation may be irradiated to polymerize. Among these various methods, the most suitable one may 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.
For example, a sheet of vinylidene fluoride is heat-fused onto a mesh material, immersed in acrylic acid or a mixture of acrylic acid and styrene, divinylbenzene, etc., and irradiated with radiation to cause graft polymerization. Alternatively, polyethylene is heated to fuse it onto the net-like material, and this is immersed in a heated mixed solution of methacrylic acid, divinylbenzene, and benzoyl peroxide to fully impregnate the attached polyethylene. Then, the cation exchange membrane of the present invention can be obtained by carrying out heating polymerization under high pressure in an autoclave, followed by fluorination treatment. (d) There is also a method based on mold polymerization.

That is, a crosslinking agent such as vinylbenzene is added to acrylic acid, methacrylic acid, styrene sulfonate esters, vinyl sulfonate esters, etc., a radical polymerization initiator is further added, and other additives such as dilution are added as necessary. A solvent, a linear polymer, a fine powder crosslinkable polymer, etc. are added and mixed uniformly, and this is placed as a core in a mold corresponding to the shape of the net covered with an insulating material. This is a method in which the above-mentioned monomer mixture is poured and polymerized by heating. In this case, if there is no oxidation resistance, fluorination treatment is sufficient to impart oxidation resistance. Some examples for making the ion exchange membrane of the present invention have been shown, but the above examples are not sufficient. Therefore, the present invention is not limited in any way.

Further, in the present invention, the polymer having a cation exchange group is in the form of a membrane, and the inside thereof contains a network coated with an insulating substance.

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, the water permeability is 10-5
It is desirable that it is cc/Dm2·Atm-Sec or less. When the ion exchange membrane of the present invention is used for alkali metal salt electrolysis, an anion exchange thin layer is applied on one membrane surface as previously proposed in order to improve the current efficiency of the generated alkali hydroxide. may be present, or a neutral thin layer may be present.

In this case, it is particularly preferred if the thin layer is crosslinked and becomes dense. In addition, the presence of this anion exchange or neutral thin layer is determined by physical or chemical adhesion.
In the case of adsorption, the cation exchange resin part and the thin layer may be attached to each other by entanglement of polymer chains at the interface, or by ionic bonds, covalent bonds, coordinate bonds, etc. May exist. The thin layer may then be present in a layered manner on top of the cationic resin part, or may be present by a suitable chemical reaction towards the interior of the molded cation exchange resin part. In addition, the method of impregnating and polymerizing cation-exchanging, neutral, and anion-exchanging monomers that we proposed earlier is also effective. In this case, fluorination may be performed afterwards. The above treatment provides advantages such as improving the current efficiency of the cation exchange membrane itself and improving the purity of the alkali metal hydroxide produced. However, if the post-treatment material does not have oxidation resistance, it may be necessary to fluorinate it. Alternatively, the oxidizing agent may be present on the cathode side or inside the membrane where no oxidizing agent is present. Further, as the ion exchange group bonded to the cation exchange resin portion of the present invention, any conventionally known functional group that can become negatively charged in aqueous solution can be used without any restriction.

Namely, sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphorous acid group, sulfuric acid ester group, phosphoric acid ester group, phosphorous acid ester group, phenol group, thiol group, boric acid group, silicate group, stannic acid group, etc. It is. It is sufficient that these ion exchange groups are present to the extent that it functions as an ion exchange membrane. In addition, the anion exchange thin layer present in the surface layer has functional groups that can be negatively charged in an aqueous solution, such as primary, secondary, tertiary amines, quaternary ammonium, Tertiary sulfonium, quaternary phosphonium,
Onium bases such as arsonium, stibonium, and cobalticinium. As a neutral thin layer, it is effective both when there is no functional group that can dissociate in an aqueous solution and when the above-mentioned anion exchange group and cation exchange group are present in approximately equal amounts. . In addition, when a thin layer exists on the surface layer, a cation exchange resin component exists on top of this anion exchange thin layer and neutral thin layer, forming a sandwich-like anion exchange and cation exchange resin component. Exchangeable thin layers may also be present. The embodiment using the ion exchange membrane of the present invention is not particularly limited, and can be used for electrolysis in a system where mixing of the anode and catholyte does not occur and selective permeation of cations is required.

For example, it is effective for use in organic electrolytic reactions and electrolytic dimerization reactions of acrylonitrile. Moreover, it can be used not only for alkali metal salt electrolysis but also for a wide range of electrolysis reactions of inorganic electrolyte solutions. It is particularly effective for the electrolysis of alkali metal salts, i.e., halides, sulfates, nitrates, phosphates, etc. of lithium, sodium, potassium, rubidium, cesium, etc. It is also effective for the electrolysis of acids, i.e., hydrochloric acid, sulfuric acid, nitric acid, Can be used for electrolysis of phosphoric acid, etc.

As the ion exchange resin part of the present invention, it is generally preferable to use a fluorine-based resin having oxidation resistance. In the present invention, if the cation exchange resin part is made of a material that is resistant to oxidizing agents such as fluorine-based or inorganic substances, it may be used as it is by placing it between the anode and the cathode, or it may be used as is. When the cation exchange resin part is made of a material that does not have oxidation resistance in the system, and if oxidizing substances are generated from the anode during electrolysis, to prevent oxidative deterioration of the resin part due to this. As mentioned above,
The cation exchange membrane portion may be treated to impart acid resistance, such as fluorination or chlorination. Examples will be given below, but the present invention is not limited to the actual examples in any way.

EXAMPLE A film-like material was molded using a polymer obtained from a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether sulfonyl fluoride and resulting in a dry resin with an exchange capacity of 0.91 meq/9.

That is, 100 mesh nickel wire mesh is immersed in a 2% dimethylformamide solution of polyvinylidene fluoride, pulled out, air-dried, and then heated in an air dryer at 180°C to form a nickel wire mesh. A thin film of polyvinylidene fluoride was formed on top of it for insulation.

Claims (1)

[Claims] 1. A cation exchange membrane that uses a thermally conductive base material coated with an insulating material as a core material.