JPH0635516B2 - Method for producing amphoteric ion exchanger - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel method for producing a zwitterion exchanger,
In particular, it relates to a good method for producing an amphoteric ion exchanger whose substrate is a perfluorocarbon type.

[Prior Art and Problems] Zwitterion exchangers are generally used as a membrane substance for the purpose of concentrating salts or separating salts and sugars, salts and amino acids, etc. Charge mosaic membranes have been developed for the purpose of concentration and desalination. These charge mosaic membranes are membranes in which a portion having an anion exchange group and a portion having a cation exchange group are arranged in a mosaic pattern. Both of the anion and cation exchange group portions are strong electrolytes and have a transport number of 1 It is required to be close to and close enough.

Such amphoteric ion exchange membranes are very difficult to manufacture and have not yet been used industrially. As a conventionally known method for producing an amphoteric ion exchange membrane, there are mainly the following two methods.

1) A method in which a neutral base polymer substance is formed into a film and then two kinds of ion exchange groups are sequentially introduced.

2) A method in which a polymer substance having one of the ion exchange groups is formed into a film and then another ion exchange group is introduced.

That is, in the method of 1), for example, polystyrene partially chloromethylated is selected as the polymer, and this is dissolved in cyclohexane and coated on a polyvinyl chloride support,
After forming the thin film, crosslinking and sulfonation are performed in concentrated sulfuric acid, and then chloromethyl group is reacted with trimethylamine. Further, in the method 2), for example, a polyamine obtained by adding an appropriate amount of trimethylamine to chloromethylated polystyrene is dissolved in a mixed solution of ethanol / chloroform, coated on a polyvinyl chloride support to form a thin film. After formation, it is crosslinked and sulfonated in concentrated sulfuric acid.

However, these production methods require many steps and are quite troublesome, and a high technique is required to obtain a good amphoteric ion exchange membrane.

[Means for Solving Problems] In view of the above, the present inventors have earnestly studied on a simple method for producing an amphoteric ion exchange membrane, and as a result, a vinyl monomer having an onium base in a cation exchanger is ion-exchanged. Utilizing the fact that it can be bonded to the cation-exchange group in a one-to-one relationship with
Further, the present invention has been provided based on the finding that a good amphoteric ion exchanger can be easily obtained by polymerizing a vinyl monomer bound to the cation exchanger. That is, in the present invention, a cation exchanger is contacted with a vinyl monomer having an onium base so that substantially all the cation exchange groups of the cation exchanger are ion-exchanged with the onium base of the vinyl monomer. After that, the vinyl monomer is polymerized, and the amphoteric ion exchanger is produced.

Although the description and examples have been mainly given to the membrane-shaped zwitterion exchanger in the present specification, the present invention can be equally implemented regardless of such a shape. In general, in addition to a membrane, a known cation exchanger such as a granular, tubular, or fibrous form is used as a raw material, and a desired amphoteric ion exchanger can be produced depending on the shape. The cation exchanger substrate used in the present invention generally has a hydrocarbon-based or fluorocarbon-based main chain, but a fluorocarbon-based one is particularly preferable, and a perfluorocarbon-based one is useful. That is, a fluorocarbon-based cation exchanger can achieve an ion exchange reaction very quickly by contact with a vinyl monomer having an anion exchange group, which will be described later, as compared with a hydrocarbon-based cation exchanger, and thus, can be easily and conveniently used. A very good zwitterion exchanger can be obtained. As the cation exchange group of the cation exchanger, a known sulfonic acid group, carboxylic acid group,
Examples thereof include a phenolic hydroxyl group, a phosphoric acid group and a thiol group, with a sulfonic acid group being particularly preferred. Examples of the above-mentioned fluorocarbon-based cation exchanger include perfluoroalkyl vinyl ether sulfonyl halide containing perfluoro (3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) as a main component, and tetrafluoroethylene. A typical example thereof is a copolymer of

Next, the vinyl monomer having an onium base used in the present invention is a polymerizable monomer having a so-called onium base such as a quaternary ammonium base or a quaternary phosphonium base known as an onium base. In particular, when a vinyl monomer having a quaternary ammonium salt group is used to bring it into contact with the above-mentioned cation exchanger, an ion exchange reaction is rapidly achieved, and a good amphoteric ion exchanger can be easily obtained. You can Examples of vinyl monomers having such an onium base include general formulas such as N-vinylbenzyl-trimethylammonium chloride and N-vinylbenzyl-triethylammonium chloride. A vinylbenzyltrialkylammonium halide represented by (R is an alkyl group) is preferable, and it is easily bonded to a cation exchanger by ion exchange.

Further, by using a crosslinking agent together with the vinyl monomer having an onium base as the anion exchange group, a stable amphoteric ion exchanger having excellent mechanical strength can be obtained. Known divinyl compounds such as divinylbenzene are used as the cross-linking agent, and especially N, N'-di (vinylbenzyl) -N, N, N ', N'-tetramethyl-α, ω
-General formula such as alkylene diammonium dichloride The cross-linking agent represented by (n: integer of 2 to 20) is preferably used in view of its chemical and physical stability. The amount of the cross-linking agent used is determined according to the target amphoteric ion exchanger. For example, in the case of obtaining a zwitterion exchange membrane, in consideration of electric resistance, it is generally 2 to 100%, preferably 5 to 5% of the vinyl monomer. It can be arbitrarily changed at a rate of 95%.

In the present invention, the method of contacting a cation exchanger with a vinyl monomer having an onium base and ion-exchanging the cation exchange group of the cation exchanger with the onium base of the vinyl monomer is not particularly limited. Instead, known means can be directly adopted. The following treatment method can be given as an example of a typical method that is generally adopted industrially. For example, a method in which a vinyl monomer having an onium base is applied to the cation exchanger as it is, or dissolved or dispersed in a suitable solvent and then sprayed, or a method in which the cation exchanger is immersed in a solution of the monomer. Is. By such a method, the cation exchange group of the cation exchanger and the onium base of the vinyl monomer are easily ion-exchanged and bonded at a substantially 1: 1 ratio. Since the rate of the above-mentioned ion exchange is extremely different depending on the kind of the cation exchanger, the kind of the vinyl monomer having the onium base to be used and the treatment concentration of the vinyl monomer are used depending on the predetermined cation exchanger. It is necessary to select the processing temperature, processing time, etc. As described above, in particular, the cation exchanger having a sulfonic acid group is suitable for the production of the amphoteric ion exchanger of the present invention because the ion exchange with the vinyl monomer having an onium base is achieved and bonded very quickly. Is. Generally, the treatment temperature for contacting the vinyl monomer having an onium base with the cation exchanger is in the range of 10 to 100 ° C. and the treatment time is in the range of 1 to 30 hours, and the cation exchange group of the cation exchanger is substantially Are all ion-exchanged at a ratio of 1: 1. The degree of ion exchange of the cation exchange group of the cation exchanger with the onium base of the vinyl monomer depends on, for example, a decrease in the concentration of the monomer when the onium base-containing monomer is subjected to contact treatment in a solution. It can be easily confirmed by measuring the amount or the amount of cations that emerge after ion exchange. Therefore, depending on the kind of the cation exchanger and the vinyl monomer having an onium base, by conducting a trial in advance, substantially all the cation exchanger of the cation exchanger (at a ratio of 1: 1) is obtained. The conditions for ion exchange with the onium base of the vinyl monomer may be determined.

Next, the present invention obtains an amphoteric ion exchanger by polymerizing a vinyl monomer having an onium base bound to the above cation exchanger by ion exchange. The method of polymerizing a vinyl monomer is easily achieved by bringing the cation exchange membrane into contact with a solution containing a polymerization initiator. A radical polymerization initiator or a cationic polymerization initiator is preferably used as the polymerization initiator. As the radical polymerization initiator, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, potassium peroxodisulfate, ammonium peroxodisulfate, t-butyl hydroperoxide,
Peroxides such as hydrogen peroxide; azo compounds such as azobisisobutyronitrile, azobis-2-amidinopropane hydrochloride; hydrogen peroxide-ammonia, ethylamine, Fe
(II) Salts and the like; redox initiators such as peroxodisulfate-sodium sulfite-sodium sulfite triethanolamine; sodium perchlorate-sodium sulfite are also suitably used and may be irradiated with ionizing radiation. Further, as the initiator of the cationic polymerization, aluminum chloride,
Metal halides such as zinc chloride, stannic chloride, titanium chloride, boron trifluoride, antimony pentachloride; phosphoric acid,
Protic acids such as sulfuric acid and chlorosulfonic acid are used.

Any polymerization conditions may be used, but generally, the polymerization may be carried out at a temperature not higher than the decomposition temperature of the vinyl monomer having an onium base or not higher than the boiling point of the solvent used. The polymerization time varies depending on the type of catalyst used and the polymerization temperature and cannot be specified unconditionally, but it is about 3 hours to 3 days for a general radical polymerization initiator and 5 for a redox system.
Minutes to 10 hours. In the case of cationic polymerization, 1
It is about a day from time.

[Effect] According to the present invention, the vinyl monomer having an onium base in the cation exchanger has substantially 1% of the onium base of the vinyl monomer via the cation exchange group of the cation exchange group. Since they are bound by ion exchange at a ratio of 1: 1, the vinyl monomer can then be polymerized to obtain a good amphoteric ion exchanger. That is, the amphoteric ion exchanger obtained in the present invention has a cation exchange capacity of 0.1 to 3 meq / g and an anion exchange capacity of 0.1 to 3 meq / g, and the ratios thereof are 1: 0.97. Homogeneity is substantially 1: 1 which is ˜1.0.

[Examples] Examples of the present invention will be given below, but the present invention is not limited to these examples.

Example 1 95 parts of N-vinylbenzyl-trimethylammonium chloride on Nafion 117 (trade name; manufactured by DuPont), which is a perfluorocarbon-based cation exchange membrane,
N, N'-di (vinylbenzyl) -N, N, N ', N'
-It was immersed in an aqueous solution of 5 parts of tetramethyl 1,6 hexenediammonium dichloride at 60 ° C for 24 hours to ion exchange the vinyl monomer having an anion exchange group. By measuring the decrease amount of vinyl monomer in the solution by ultraviolet absorption,
It was confirmed that the bonds were one-to-one. Then, the above cation exchange membrane was immersed in an aqueous solution of 5% ammonium persulfate and treated at 70 ° C. for 24 hours.

The electric resistance of the obtained treated film was 10 Ω · cm ² in 0.5N-NaCl. In addition, 0.5N-KC of this film
and the cation exchange capacity was 0.50.
It was 91 meq / g and the anion exchange capacity was 0.91 meq / g, and it was a complete amphoteric membrane.

For the above-mentioned Nafion 117 and the amphoteric ion exchange membrane of this treatment, 0.5 N-NaCl / 0.5 M-
The results obtained by calculating the diffusion constant [mol / hr · m ² (mol / liter)] of sodium chloride and glycol using a dialysate consisting of glucose are shown below.

The treated membrane has a larger diffusion constant of sodium chloride than that of Nafion 117, making it difficult for glucose to permeate.

Example 2 2 g of Nafion 117 was immersed in 100 ml of a 1% aqueous solution of diallylamine hydrochloride at 70 ° C. for 20 hours to cause ion exchange of vinyl monomers having anion exchange groups.

Then, 2 g of potassium persulfate and 1 g of sodium sulfite were dissolved in the above solution to start the polymerization of the vinyl monomer. After 5 hours, the membrane was taken out and washed with saline. The electric resistance of this treated film was 8.0 Ω · cm ² in 0.5N-NaCl at 25 ° C. Cation exchange capacity is 0.91 meq
/ g, the anion exchange capacity was 0.91 meq / g, and the membrane was completely an amphoteric ion exchange membrane.

Claims (7)

[Claims] 1. A cation exchanger is contacted with a vinyl monomer having an onium base to cause ion exchange of substantially all the cation exchange groups of the cation exchanger with the onium base of the vinyl monomer. And then polymerizing the vinyl monomer, the method for producing an amphoteric ion exchanger. 2. The production method according to claim 1, wherein the cation exchanger is a polymer having a perfluorocarbon as a main chain. 3. The method according to claim 1, wherein the cation exchange group of the cation exchanger is a sulfonic acid group. 4. The production method according to claim 1, wherein the cation exchanger is in the form of a film. 5. The production method according to claim 1, wherein the onium base is a quaternary ammonium group. 6. The production method according to claim 1, wherein the vinyl monomer having an onium base is a vinylbenzyltrialkylammonium salt. 7. The method according to claim 1 or 4, wherein the amphoteric ion exchanger is in the form of a film.