JP3173099B2 - Method for producing cation exchange membrane - Google Patents

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 a sulfone group introduction step by using a styrene sulfonic acid derivative as a monomer.

[0003]

2. Description of the Related Art Cation exchange membranes have been used in a wide range of fields such as electrodialysis, electrode reaction diaphragms, and diffusion dialysis, and many membranes have been proposed. Most of these films are made by introducing sulfone groups with various sulfonating agents into a film having a styrene-divinylbenzene copolymer as a skeleton (Japanese Patent Publication No. Sho 39).
-19542, JP-B-40-28951, JP-B-4
No. 9-16553). Cation exchange membranes manufactured by these conventional methods have a three-dimensional cross-linked structure and are widely used in the field of electrodialysis and the like because of their excellent ion selectivity and electrochemical properties.

[0004]

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

[0005] However, the sulfonation step has the following problems. 1. The various sulfonating agents used in the sulfonation process are all highly dangerous chemicals, and even if special consideration is given to their handling and equipment, these processes are still dangerous.

[0006] 2. In order to introduce a sulfone group into a three-dimensionally crosslinked film having a styrene-divinylbenzene skeleton, the sulfone group had to be introduced for a long time or under severe sulfonation conditions. For this reason, the occurrence of a side reaction other than the intended sulfonation is inevitable, and the performance of the resin portion and the reinforcing material is deteriorated, particularly the mechanical strength is reduced, and the denseness of the resin portion is impaired to deteriorate the electrical characteristics.

[0007] 3. In order to obtain membranes having different exchange capacities, the objective is achieved by adjusting the sulfonation conditions. However, in this case, it is extremely difficult to control strictly with good reproducibility, and there is a problem in terms of quality control. As described above, the conventional sulfonation step has many problems, and a production method which can omit the sulfonation step is desired.

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

In the case of polymerizing without using a solvent system, styrene monomer and divinylbenzene monomer are hydrophobic, whereas sodium styrenesulfonate is hydrophilic. Will result in excessive polymerization. As described above, conventionally, polymerization using sodium styrenesulfonate is a method for producing an ion exchange resin, and a film cannot be obtained. For this reason, a production method that can omit the sulfonation step has been desired, but it has not been realized yet in the production method of the ion exchange membrane.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies by focusing on the fact that monomer derivatives having a sulfone group have different hydrophobicity and hydrophilicity. The present inventors have found that the above object can be achieved by using a styrenesulfonic acid derivative, and have accomplished the present invention.

That is, the present invention provides a method for producing a cation exchange membrane, in which a monomer having a functional group suitable for introducing an exchange group is converted into a styrene sulfonate amine salt or an amide derivative. It provides a manufacturing method that is unnecessary. The cation exchange membrane manufactured in 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 polymerizable vinyl group, it polymerizes with a crosslinking agent such as divinylbenzene to form a three-dimensional crosslinked structure. 2. The monomer exhibits hydrophobicity due to the amine salt or amide bonded to the sulfone group, and this monomer becomes a uniform polymer when dissolved in another styrene, divinylbenzene, a plasticizer, or the like. 3. It is easily deamined by hydrolysis treatment with an alkali or the like to form a sulfone group.

From the above-mentioned characteristics, by using a styrene sulfonic acid derivative as a monomer for introducing an exchange group, a cation exchange membrane can be easily produced without deteriorating the performance of the membrane and rather by improving the membrane performance and omitting the sulfonation step. be able to.

The amines and amides of the styrene sulfonic acid derivatives used in the present invention, such as styrene sulfonic acid amine salts and styrene sulfonic acid amides, are uniformly dissolved in styrene, divinylbenzene, plasticizers and the like. It is important to have a hydrophobic property,
It may be aliphatic or aromatic, and may be linear or branched.

However, it is necessary to consider the following in selecting an amine or amide. The higher the molecular weight of the amine or amide of the styrene sulfonic acid amine salt or styrene sulfonic acid amide, the higher the molecular weight of the amine or amide is preferable because the hydrophobicity becomes stronger and the compound easily dissolves in other coexisting monomers. If it is too large, it becomes difficult to remove amine during hydrolysis. In addition, since the molecular weight of the styrene sulfonic acid amine salt or styrene sulfonic acid amide also increases, there is a limitation in obtaining a membrane having a high exchange capacity.

In the form of amines or amides, when compared with the same number of carbon atoms, aliphatic is styrene or aromatic than aromatic.
High solubility in divinylbenzene. Among aliphatic amines, those branched from straight chains are more preferred because of their higher solubility in monomers when compared at the same carbon number. For example, n-laurylamine styrenesulfonate, which is a straight-chain amine salt, has almost no solubility in styrene, but tri-n-butylamine styrenesulfonate, which is a branched amine salt, has a one-to-one ratio with styrene. 1
But it dissolves well.

In the present invention, in addition to styrene sulfonic acid amine salt and styrene sulfonic acid amide, a commonly used copolymerizable monomer, a crosslinking agent, a radical polymerization catalyst, a plasticizer, and the like. A plastic linear polymer can be used in the mixture. Moreover, it can also be combined with a base material as needed.

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 crosslinking agent, m-, p-, o-divinylbenzene,
Polyvinyl compounds such as divinyl sulfone, butadiene, chloroprene, trivinylbenzenes, divinylnaphthalene, and trivinylnaphthalene are used.

[0019] as a radical polymerization agent, benzoyl peroxide, azobisisobutyronitrile, known radical polymerization initiator such as dicumyl peroxide is used. Linear polymer substances soluble in the monomer mixture include polystyrenes, polybutadienes, polyisobutylenes, styrene-butadiene copolymers, ethylene-propylene copolymers, polyhalogenated olefins, polyhalogenated olefins , Polyvinyl chloride powder, polyethylene fine powder, and polypropylene fine powder.

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.These polymers may be used alone or in combination with other polymers. Polymers are also preferred, and there is no particular limitation on woven fabrics, nonwoven fabrics, nets, sheets or their porous materials made therefrom.

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

[0022]

According to the method for producing a cation exchange membrane of the present invention, a sulfonation step, which has conventionally had various problems, is not required, and a large rationalization of the membrane production process has become possible. In addition, a cation exchange membrane excellent in mechanical strength and performance can be provided.

[0023]

The present invention will now be described by way of examples, which should not be construed as limiting the invention. Example 1 10 parts of divinylbenzene (purity 55%), 192 parts of tri-n-butylamine styrenesulfonate, 35 parts of styrene
And a monomer mixture consisting of 2 parts of benzoyl peroxide. The monomer mixture was immersed in a 50-denier polyvinyl chloride substrate (trade name: Tavilon: manufactured by Teijin Limited), and then covered with a polyester film (trade name: Lumirror: manufactured by Toray Industries, Inc.). For 6 hours to obtain a film- like polymer.

Next, the obtained polymer film is hydrolyzed in a 1N aqueous solution of sodium hydroxide at 40 ° C. for 2 hours, and then removed with an 80% aqueous methanol solution at 40 ° C. for 2 hours to remove amine salts. 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 ° C. in 0.5 N NaCl 2.0 Ω · c
m ² , the breaking strength was 4.5 kg / cm, the breaking elongation was 20%, and the exchange capacity was 1.4 meq / g- dry as specified.

This film was a film having low electric resistance and sufficient strength for practical use. In an electrodialysis tank combining this cation exchange membrane and an anion exchange membrane (Aciplex A-172, manufactured by Asahi Kasei Kogyo Co., Ltd.), the temperature was 25 ° C. and the current density was 4 A / dm ² . .
The concentration of chloride ions 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
And a monomer mixture consisting of 2 parts of benzoyl peroxide. A plain woven cloth made of polypropylene, which had been previously irradiated with an electron beam, was immersed in the monomer mixture, and then both sides were covered with a polyester film, followed by heat polymerization at 90 ° C. for 6 hours to obtain a film-like polymer.

Next, the membrane polymer was hydrolyzed and equilibrated in the same manner as in Example 1 to obtain a cation exchange membrane. This film had a thickness of 95 μm, a resistance of 1.7 Ω · cm ² at 25 ° C. in 0.5 N NaCl, a breaking strength of 4.4 kg / cm, and a breaking elongation of 19%. 5 meq
/ G-dry film. In this way, the electric resistance is low,
Moreover, a film having practically sufficient strength was obtained. or,
Electrodialysis was performed using this cation exchange membrane 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, 29 parts of styrene
And a cation exchange membrane in the same manner as in Example 1 except that the monomer mixture consisting of 2 parts by weight and 2 parts of benzoyl peroxide was mixed. This film has a thickness of 98 μm and a resistance of 1.9 in 0.5 N NaCl at 25 ° C.
Ω · cm ² breaking strength 4.6 kg / cm, breaking elongation 19%
And the exchange capacity was 1.5 meq / g-dry membrane. In addition, the chloride ion concentration in the concentrated water obtained by performing electrodialysis in the same manner as in Example 1 was 3.8 N.

Comparative Example 1 Tri-n-butylamine styrenesulfonate 1 of Example 1
Except that 92 parts were changed to 55 parts of styrene, a monomer mixture having the same composition as in Example 1 was heated and polymerized by heating under the same conditions as in Example 1 to obtain a film-like 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 thickness of 98 μm, 0.5N NaC
resistance at 25 ° C. in 2.0 Ω · cm ² , breaking strength 3.6
kg / cm, elongation at break 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 has mechanical strength and elongation as compared with the cation exchange membrane subjected to the conventional sulfonation step.
It shows equal or better performance in characteristics and concentration performance in electrodialysis.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI // C08L 25:18 (56) References JP-A-58-92409 (JP, A) JP-A-56-50905 (JP, A JP-A-2-277555 (JP, A) JP-B-45-9980 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/22 B01J 39/20 B01J 47 / 12 C08F 12/30 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A monomer having a sulfone group, the monomer
Monomer, crosslinker, and radical polymerization
Polymerizing a monomer mixture containing a catalyst, or
-After adhering the mixed solution to the substrate, polymerized
To produce cation exchange membranes by hydrolyzing
The monomer having the sulfone group has hydrophobicity
Amine styrene sulfonate or styrene sulfonate
A method for producing a cation exchange membrane, characterized by being a mid .