JPH0759643B2 - Method for producing modified cation exchange membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to the production of a cation exchange membrane which has a low electric resistance and is capable of obtaining a high concentration of brackish water particularly in the concentration of seawater by an ion exchange membrane electrodialysis method. Regarding the method.

[Prior art and its problems]

Conventionally, in Japan, various modified ion-exchange membranes suitable for obtaining high-concentration brackish water have been researched and developed with the establishment of seawater-concentrating salt-making technology by ion-exchange membrane electrodialysis. For example, Japanese Examined Patent Publication No. 60-59921 discloses a cation-exchange membrane having excellent electrochemical properties by mixing acrylonitrile or methacrylonitrile with a styrene-chloromethylstyrene-based monomer and copolymerizing the mixture, followed by crosslinking treatment. Has been proposed. That is, Japanese Patent Publication 60-59
The cation exchange membrane manufactured by No. 921 has a considerably low electric resistance and a high concentration of brine is obtained. However, as a cation exchange membrane that is industrially put to practical use, it is required to have the ability to obtain as high a concentration of brackish water as possible, even if the electric resistance is as low as possible, or even if the electric resistance is the same. Particularly in recent years, in the salt-making technology using the ion-exchange membrane electrodialysis method, the electric resistance is lower in order to reduce the electric power consumption and to pursue a low price that can compete with imported raw material salts.
Further, an ion exchange membrane capable of obtaining high-concentration brackish water is desired.

[Means for Solving Problems] As a result of intensive research in view of the problems and desires described above, the present inventors have treated the surface of a cation exchange membrane matrix having a haloalkyl group with ionizing radiation, The inventors have found that a desired cation exchange membrane can be easily obtained, and have proposed the present invention. That is, the present invention is characterized in that the surface of a cation exchange membrane having a haloalkyl group or a cation exchange membrane matrix is irradiated with ionizing radiation, and a cation exchange group is introduced into the cation exchange membrane matrix. A method for producing a cation exchange membrane.

The cation exchange membrane having a haloalkyl group or the cation exchange membrane matrix of the present invention generally has an aromatic compound having a haloalkyl group and an unsaturated bond and a cation exchange group or a functional group suitable for introducing a cation exchange group. Obtained by polymerizing with monomers. Examples of the aromatic compound having a haloalkyl group and an unsaturated bond include chloromethylstyrene, chloromethylvinylnaphthalene, bromomethylstyrene and bromomethylvinylnaphthalene, with chloromethylstyrene being particularly preferred. In addition, examples of the monomer having a cation exchange group or a functional group suitable for introducing a cation exchange group include styrene, a styrenesulfonic acid derivative, a vinylsulfonic acid derivative, an acrylic acid ester, and maleic anhydride. The proportion of the aromatic compound having such a haloalkyl group is generally 0.5 to 40 parts by weight, preferably 1 to 20 parts by weight, relative to 100 parts by weight of the cation exchange group or a monomer suitable for introducing the cation exchange group. is there. If necessary, a divinyl compound such as divinylbenzene can be used as a crosslinking agent.

The cation exchange membrane matrix having a haloalkyl group of the present invention can also be obtained by a method of introducing a haloalkyl group by post-treatment into a polymer or copolymer of a monomer suitable for introducing a haloalkyl group. For example, a method of haloalkylating a polymer such as styrene or vinyltoluene or a copolymer thereof with divinylbenzene or divinylsulfone with a haloalkyl ether solution in the presence of a Lewis acid, a method of haloalkylating with hydrogen chloride or an aldehyde, etc. Is obtained by haloalkylation of, particularly halomethylated.

The specific cation exchange membrane or the cation exchange membrane matrix of the present invention may be produced according to a known method for producing an ion exchange membrane using the above-mentioned monomer mixture. Therefore, in addition to the above-mentioned respective monomers, a finely divided thermoplastic polymer substance as a polymerization catalyst, a plasticizer, a thickener or a reinforcing material, a film-shaped substrate, etc. are appropriately used. Examples of the polymerization catalyst include benzoyl peroxide, azobisisobutyronitrile, dicumyl peroxide and the like. Examples of the plasticizer include dioctyl phthalate and dibutyl phthalate. Examples of the fine powdery thermoplastic material include polyethylene, polyvinyl chloride, acrylonitrile-vinyl chloride copolymer, vinyl chloride-vinylidene chloride copolymer, NBR, SBR, and polybutadiene. Examples of the film substrate include glass fiber, hair, vinylon,
Kanekalon, Teviron, Tetoron, Saran, Nylon,
Bonnell (above, trade name), cloth such as polyethylene and polypropylene, and mesh are used.

In the present invention, by irradiating the surface of the cation exchange membrane having a haloalkyl group or the matrix of the cation exchange membrane with ionizing radiation, high concentration brackish water can be obtained with almost no increase in electric resistance. A cation exchange membrane that can be manufactured can be easily manufactured. Examples of the ionizing radiation used in the present invention include radiation sources such as plasma, ultraviolet rays, x-rays, gamma rays, and electron beams. Among them, plasma, ultraviolet rays from a mercury lamp, and electron beams are simple and convenient. Such an ionizing radiation irradiation method may be carried out in vacuum, in air, or an inert gas such as nitrogen, argon, or helium as an atmosphere, or may be carried out continuously or intermittently. In the present invention, when the dose of ionizing radiation is too large, the electric resistance of the obtained cation exchange membrane increases. Therefore, the dose of ionizing radiation in the present invention may be determined according to the radiation source, its intensity, the irradiation time, etc., in consideration of the electrical resistance of the cation exchange membrane obtained by experiments in advance, but it is generally several. The intended purpose can be achieved by the irradiation time of minutes to several tens of minutes.

In the present invention, a desired cation exchange membrane can be obtained by introducing a cation exchange group into the cation exchange membrane matrix which has been irradiated with ionizing radiation according to a conventional method. For example, when introducing a sulfonic acid group as a cation exchange group, it is generally achieved by using concentrated sulfuric acid, chlorosulfonic acid or a mixture thereof. Also,
The cation exchange group can be introduced by a known method such as a sulfone group, a carboxyl group or a phosphon group.

[Action and effect]

Although the mechanism of action of the present invention has not been fully clarified yet, irradiation with ionizing radiation causes the existing haloalkyl group to decompose in an extremely thin surface layer of the cation exchange membrane or the cation exchange membrane matrix, and It is presumed that some of them crosslink to form an extremely dense structure in the surface layer portion. As a result, it is considered that the obtained cation exchange membrane exhibits the ability to obtain high-concentration brackish water with almost no increase in electric resistance.

Therefore, in the salt-making technology of seawater concentration by electrodialysis using the modified cation exchange membrane of the present invention, the electric power consumption rate can be greatly reduced with current efficiency, which is extremely effective industrially.

〔Example〕

Examples are given below for illustrating the present invention further in detail, but the present invention is not limited to the description of the examples below.

The electric resistance of the film in the examples is 0.5N-NaCl.
The measurement was performed at 25 ° C for 1000 cycles.

Examples 1 to 3, Comparative Example 1 10 parts by weight of styrene, 2 parts by weight of chloromethylstyrene, 2 parts by weight of acrylonitrile, 1 part by weight of dioctyl phthalate and 1 part by weight of finely powdered polyvinyl chloride were heated and mixed, and benzoyl was added thereto. After 0.2 part by weight of peroxide was added and applied to a polyvinyl chloride cloth, it was polymerized by heating to obtain a polymer film matrix (raw film). This polymer membrane matrix was irradiated with the prescribed radiation shown in Table 1, and then treated with a solution of sulfuric acid-chlorosulfonic acid (1: 1) at 40 ° C. for 1 hour. For each cation exchange membrane obtained,
Anion Exchange Membrane (Neoceptor AC manufactured by Tokuyama Soda Co., Ltd.)
S) was combined with electrodialysis to concentrate seawater. The conditions for electrodialysis are temperature 30 ℃, current density 3A / d.
m ² and seawater velocity 6 cm / sec.

The results are shown in Table 1 as the chlorine ion concentration (normal) in the obtained brine.

Claims (1)

[Claims] 1. A cation-exchange membrane having a haloalkyl group or the surface of a cation-exchange membrane matrix is irradiated with ionizing radiation to introduce a cation-exchange group into the cation-exchange membrane matrix. For producing high quality cation exchange membrane