JPH05214124A - Production of cation exchange membrane - Google Patents

Abstract

PURPOSE:To obtain the subject exchange membrane excellent in mechanical strength, ion selectivity and exchange volume and useful for separation membrane of ultrafiltration, etc., by using a styrenesulfonic acid derivative suitable for introduction of an exchange group as an ion-introducing monomer. CONSTITUTION:A monomer mixture liquid containing styrene, a styrenesulfonic acid derivative such as styrenesulfonic acid amine salt having a functional group suitable for introduction of exchange group, divinylbenzene, a radical polymerization initiator is polymerized to provide the objective exchange membrane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a cation exchange membrane used for various separation membranes such as ultrafiltration, dialysis, electrodialysis, reverse dialysis and gas separation.

More specifically, the present invention provides a method for producing a cation exchange membrane which can eliminate the step of introducing a sulfonic group by using a styrene sulfonic acid derivative as a monomer.

[0003]

Cation exchange membranes are used in a wide range of fields such as electrodialysis, membranes for electrode reaction, and diffusion dialysis, and many membranes have been proposed. Most of these membranes are made by introducing a sulfone group into a membrane having a styrene-divinylbenzene copolymer as a skeleton by various sulfonating agents (Japanese Patent Publication No. 39/39).
-19542, Japanese Patent Publication No. 40-28951, Japanese Patent Publication No. 4
9-16553). The cation exchange membrane produced by these conventional production methods has a three-dimensional crosslinked structure and is widely used in the field of electrodialysis and the like due to its excellent ion selectivity and electrochemical properties.

[0004]

The steps of the above-mentioned conventional production method are roughly divided into two steps, a polymerization step for forming a film of a styrene-divinylbenzene skeleton and a sulfonation step for introducing a sulfone group. Is divided into

However, the sulfonation process has the following problems. 1. All of the various sulfonating agents used in the sulfonation step are highly dangerous chemicals, and even if special consideration is given to their handling and equipment, they are still dangerous steps.

2. In order to introduce a sulfone group into a three-dimensionally crosslinked film of a styrene-divinylbenzene skeleton, the introduction of a sulfone group has to be carried out for a long time or under conditions of intense sulfonation. Therefore, the occurrence of side reactions other than the desired sulfonation is unavoidable, and the performance of the resin part and the reinforcing material is deteriorated, especially the mechanical strength is lowered, and the denseness of the resin part is impaired and the electrical characteristics are deteriorated.

3. The purpose is achieved by adjusting the sulfonation conditions in order to obtain membranes with different exchange capacities, but it is extremely difficult to control with good reproducibility and strictness at this time, and there is a problem in terms of quality control. As described above, the conventional sulfonation process has many problems, and a manufacturing method capable of omitting the sulfonation process is desired.

Therefore, in order to omit the sulfonation step,
It is conceivable to use monomers having sulphonic groups. However, for example, in the case of sodium styrenesulfonate in which a styrene group is introduced into a styrene monomer, sodium styrenesulfonate is hydrophilic,
In order to carry out a uniform polymerization system, an aqueous solution system is adopted, and if the polymerization is carried out as it is, a film-like product cannot be obtained.

When polymerization is carried out without using a solvent system, styrene monomer and divinylbenzene monomer are hydrophobic, whereas sodium styrenesulfonate is hydrophilic, so that it does not dissolve in the monomer and is non-uniform. It will be a polymerization. As described above, the conventional polymerization using sodium styrenesulfonate was not a method for producing an ion exchange resin, and a film-like product could not be obtained. Therefore, a manufacturing method capable of omitting the sulfonation step has been desired, but it has not yet been realized in the manufacturing method of the ion exchange membrane.

[0010]

Means for Solving the Problems In order to solve the above problems, the inventors of the present invention have made extensive studies by focusing on the difference in hydrophobicity and hydrophilicity depending on the monomer derivative having a sulfone group. The inventors have found that the above object can be achieved by using a styrene sulfonic acid derivative, and completed the present invention.

That is, according to the present invention, in the method for producing a cation exchange membrane, a monomer having a functional group suitable for introducing an exchange group is used as a derivative of a styrenesulfonic acid amine salt or an amide, so that the sulfo group introduction step can be performed. An unnecessary manufacturing method is provided. The cation exchange membrane produced by the present invention may or may not include a base material (reinforcing material).

The styrene sulfonic acid derivative used in the present invention has the following characteristics. 1. Since it has a vinyl group capable of polymerizing, it polymerizes with a crosslinking agent such as divinylbenzene to form a three-dimensional crosslinked structure. 2. It exhibits hydrophobicity due to the amine salt or amide bonded to the sulfone group, and this monomer becomes a uniform polymer when dissolved in other styrene, divinylbenzene, plasticizer, or the like. 3. It is easily deamined by hydrolysis with an alkali to form a sulfone group.

From the above characteristics, by using a styrene sulfonic acid derivative as a monomer for introducing an exchange group, the performance of the membrane can be improved rather, and the cation exchange membrane can be easily produced by omitting the sulfonation step. be able to.

The styrene sulfonic acid derivative used in the present invention, such as the amine salt of styrene sulfonic acid and the derivative of styrene sulfonic acid amide, can be uniformly dissolved in styrene, divinylbenzene, a plasticizer, etc. It is important to have hydrophobicity to
It may be aliphatic or aromatic, and may be linear or branched.

However, it is necessary to consider the following in selecting the amine or amide. The larger the molecular weight of the amine or amide of the styrene sulfonic acid amine salt or styrene sulfonic acid amide, the stronger the hydrophobicity and the more easily it dissolves in other coexisting monomers. Therefore, the larger the molecular weight of the amine or amide, the better. If it becomes too large, it becomes difficult to deamine during hydrolysis. Since the molecular weight of styrene sulfonic acid amine salt and styrene sulfonic acid amide also becomes large, there is a limit in obtaining a membrane having a high exchange capacity.

Further, in the form of amine or amide, when compared with the same carbon number, styrene is more aliphatic than aromatic,
High solubility in divinylbenzene. Further, among the aliphatic amines, it is more preferable that the branched one has a higher straight chain than the one having the same carbon number, because the branched one has a higher solubility in the monomer. For example, styrenesulfonic acid n-laurylamine, which is a straight-chain amine salt, has almost no solubility in styrene when compared with 12 carbon atoms, but styrenesulfonic acid tri-n-butylamine, which is a branched amine salt, is paired with styrene. 1
But it dissolves well.

In the present invention, in addition to the styrene sulfonic acid amine salt and the styrene sulfonic acid amide, a commonly used copolymerizable monomer, a crosslinking agent, a radical polymerization catalyst, a plasticizer, etc. A linear polymer having plasticity can be used in the mixed liquid. Also, it can be combined with a base material if necessary.

Examples of the copolymerizable monomer include styrene, acrylonitrile, ethylstyrene, vinyl chloride, acrolein, methyl vinyl ketone, maleic anhydride, maleic acid and its salts or esters, itaconic acid and its salts or esters. Can be selected as appropriate.
As the cross-linking agent, m-, p-, o-divinylbenzene,
Polyvinyl compounds such as divinyl sulfone, butadiene, chloroprene, trivinylbenzenes, divinylnaphthalene and trivinylnaphthalene are used.

As the radical polymerization agent, known radical polymerization initiators such as benzoyl peroxide, azoisobutyronitrile and dicumyl peroxide are used.
As a linear polymer substance soluble in the monomer mixture,
Polystyrenes, polybutadienes, polyisobutylenes, styrene-butadiene copolymers, ethylene-propylene copolymers, polyhalogenated olefins, polyhalosulfonated olefins, polyvinyl chloride powder, polyethylene fine powder, polypropylene fine powder Used.

As the plasticizer, phthalic acid esters such as dimethyl phthalate and dioctyl phthalate, aliphatic acids and aromatic alcohol esters are used. The base can be appropriately selected from polyolefins such as polyethylene and polypropylene, polyhalogenated olefins such as polyvinyl chloride and polyvinylidene chloride, nylon and the like, and these polymers can be used alone or in combination with other substances. Polymers are also preferable, and woven fabrics, non-woven fabrics, nets, sheets or their porous materials made from them are not particularly limited.

The cation exchange membrane of the present invention can be manufactured by the following manufacturing method. A monomer mixture solution containing each of the above components is polymerized or, if necessary, adhered to a substrate and then polymerized to obtain a film polymer. A cation exchange membrane can be formed by hydrolyzing the obtained membrane polymer.

[0022]

EFFECTS OF THE INVENTION The method for producing a cation exchange membrane of the present invention eliminates the need for the sulfonation step, which has heretofore been various problems, and enables the rationalization of the membrane forming process. Further, it has become possible to provide a cation exchange membrane excellent in mechanical strength and performance.

[0023]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. Example 1 10 parts of divinylbenzene (purity 55%), 192 parts of tri-n-butylamine styrenesulfonate, 35 parts of styrene
Part, and a monomer mixture liquid containing 2 parts of benzoyl peroxide is prepared. After dipping the above monomer mixture in a polyvinyl chloride base material of 50 denier [trade name Tevilon: Teijin Limited], a polyester film [trade name of Lumirror: Toray Industries Ltd.] was coated on both sides to 90 ° C. Polymerization was carried out by heating for 6 hours to obtain a linear polymer.

Next, the obtained membrane polymer was hydrolyzed in a 1N sodium hydroxide aqueous solution at 40 ° C. for 2 hours, and then removed with an 80% aqueous methanol solution at 40 ° C. for 2 hours to remove an amine salt. Was carried out and equilibrated with a 0.5N-NaCl aqueous solution to obtain a cation exchange membrane. This film has a thickness of 96
μ, resistance at 25 ℃ in 0.5N-NaCl 2.0Ω · c
The film had m ² , a breaking strength of 4.5 kg / cm, a breaking elongation of 20%, and an exchange capacity of 1.4 meq / q-dry, which was a predetermined value.

This film had a low electric resistance and a practically sufficient strength. Further, in an electrodialysis tank in which this cation exchange membrane and an anion exchange membrane [Asaplex Chemical Industry Co., Ltd., Aciplex A-172] were combined, at a temperature of 25 ° C. and a current density of 4 A / dm ² , ．
The chloride ion concentration in the concentrated water obtained by concentrating 5N-NaCl was 3.8 N.

Example 2 18 parts of divinylbenzene (purity 55%), 124 parts of tri-n-octylamine styrenesulfonate, 58 parts of styrene
Part, and a monomer mixture liquid containing 2 parts of benzoyl peroxide is prepared. A plain weave fabric made of polypropylene, which had been previously irradiated with electron beams, was dipped in the monomer mixture, covered on both sides with a polyester film, and polymerized by heating at 90 ° C. for 6 hours to obtain a film-like polymer.

Then, this membrane polymer was hydrolyzed and equilibrated in the same manner as in Example 1 to obtain a cation exchange membrane. This film had a film thickness of 95 μ, a resistance of 1.7 Ω · cm ² at 25 ° C. in 0.5N-NaCl, a breaking strength of 4.4 kg / cm and a breaking elongation of 19%, and an exchange capacity of 1. 5 meq
/ G-dry film. In this way, the electrical resistance is low,
Moreover, a film having practically sufficient strength was obtained. or,
Using this cation exchange membrane, electrodialysis was carried out in the same manner as in Example 1, and the concentration of chlorine ion in the concentrated water obtained as a result of concentrating 0.5N-NaCl was 3.6 N.

Example 3 10 parts of divinylbenzene (purity 55%), 237 parts of tri-n-pentylamine styrenesulfonate, styrene 29
Part and benzoyl peroxide 2 parts were mixed in the same manner as in Example 1 to obtain a cation exchange membrane. This film has a film thickness of 98 μ and a resistance of 1.9 at 25 ° C. in 0.5 N NaCl.
Ω · cm ² Breaking strength 4.6kg / cm, Breaking elongation 19%
And the exchange capacity was 1.5 meq / g-dry membrane. The concentration of chlorine ions in the concentrated water obtained by electrodialysis in the same manner as in Example 1 was 3.8N.

Comparative Example 1 Styrene sulfonic acid tri-n-butylamine 1 of Example 1
A monomer mixture liquid having the same composition as in Example 1 was heated and polymerized under heating under the same conditions as in Example 1 except that 92 parts was changed to 55 parts by weight of styrene to obtain a membranous polymer. The obtained membrane polymer was sulfonated with 99.5 WT% sulfuric acid at 40 ° C. to introduce an exchange group to obtain a cation exchange membrane.

This film has a film thickness of 98 μ and 0.5 N-NaC.
resistance at 25 ° C. in 2.0 l, Ω · cm ² , breaking strength of 3.6
kg / cm, breaking elongation 12%, exchange capacity 1.
It was a 4 meq / g-dry film. When electrodialysis was performed in the same manner as in Example 1, the chloride ion concentration in the obtained concentrated water was 3.7 N. As described above, the cation exchange membrane of the example according to the present invention is equal to or higher than the cation exchange membrane subjected to the conventional sulfonation process in mechanical strength of elongation, mechanical property of elongation and concentration performance in electrodialysis. Shows the performance of.

Claims (1)

[Claims] 1. A method for producing a cation exchange membrane, wherein the monomer having a functional group suitable for introducing an exchange group is a styrene sulfonic acid derivative.