JP2002119872A - Anion exchange resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anion exchange resin of a salt type which has a extremely low metal content. SOLUTION: Chloromethyl ether is reacted in the presence of Lewis acid like zinc chloride with a styrene-divinyl benzene crosslinked copolymer and is chloromethylated. Trimethylamine, etc., are reacted therewith to form the anion exchange resin. This resin is cleaned with an aqueous hydrochloric acid solution, by which the metal content thereof is lowered down to <=100 ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an anion exchange resin,
In particular, the present invention relates to an anion exchange resin in which the ion exchange group is of a salt type and the content of metal ions is extremely small.

[0002]

BACKGROUND OF THE INVENTION Anion exchange resins, along with cation exchange resins, are widely used in water treatment and other fields. Typical anion exchange resins available on the market are those having a crosslinked copolymer of a monovinyl monomer and a polyvinyl monomer as a base and having a primary to tertiary ammonium group or a quaternary ammonium group as an ion exchange group. . Among these anion exchange resins, the most widely consumed is a strongly basic anion exchange resin having a quaternary ammonium group as an ion exchange group. Since the quaternary ammonium group is more stable in the salt form than in the free form (OH form), this anion exchange resin is supplied to the market exclusively as the salt form, especially as the chloride ion form.

In the most common method for producing an anion exchange resin having a quaternary ammonium group as an ion exchange group, first, a monovinyl monomer and a polyvinyl monomer, usually styrene and divinylbenzene are copolymerized to form a crosslinked copolymer. A mother body consisting of Next, after introducing a haloalkyl group into this, a tertiary amine, usually trimethylamine or dimethylethanolamine, is reacted to give the mother a quaternary amine.
A quaternary ammonium group is introduced. When ammonia or a primary or secondary amine is reacted instead of a tertiary amine, a primary or secondary amino group can be introduced. Since the obtained anion exchange resin is a salt type having a halogen ion derived from a haloalkyl group as a counter ion, it is usually supplied to the market as a product only by washing with water to remove unreacted amine and the like.

[0004]

The most common method for introducing a haloalkyl group into a base is to prepare chloromethyl methyl ether in the presence of a Lewis acid such as zinc chloride, iron chloride, aluminum chloride or tin chloride. Let your mother react
This is a method of introducing a chloromethyl group into the parent. Therefore, these metals are contained in the formed anion exchange resin. And it is impossible to sufficiently reduce the content of these metals by ordinary water washing performed after reacting the amine, and the anion exchange resin generally removes several hundred ppm to several thousand ppm of metal. It is supplied to the market in a state where it is contained. However, depending on the use of the anion exchange resin, the metal in the resin may be eluted during use to contaminate the product. In general, an anion exchange resin is used after being converted to a free form. If a large amount of metal is contained in the resin at that time, this metal flows out and pollutes the environment. Accordingly, an object of the present invention is to provide a salt type anion exchange resin having a remarkably small metal content.

[0005]

The anion exchange resin according to the present invention is based on a crosslinked copolymer of a monovinyl monomer and a polyvinyl monomer as a base, and ion-exchanges a primary to tertiary amino group or a quaternary ammonium group. Wherein the ion-exchange group is of a salt type and has a metal content of 1
It is characterized by being at most 00 ppm.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The anion exchange resin according to the present invention is produced by producing an anion exchange resin according to a conventional method, and then eluting a contained metal from the obtained anion exchange resin. . First, a crosslinked copolymer is produced by copolymerizing a monovinyl monomer and a polyvinyl monomer, usually styrene and divinylbenzene. The ratio of the polyvinyl monomer in the monomer mixture varies depending on the use of the anion exchange resin, but is usually several% (weight). The copolymerization reaction is usually performed by a suspension polymerization method, but may be performed by another polymerization method depending on the shape required for a product.

A haloalkyl group is first introduced into the obtained crosslinked copolymer as a step prior to introducing an ion exchange group. Usually, after drying the copolymer, chloromethyl methyl ether is reacted in the presence of a catalyst in a solvent capable of swelling the cross-linked copolymer such as benzene, toluene, and ethane dichloride, and the cross-linked copolymer is reacted. To introduce a chloromethyl group. As the catalyst, a Lewis acid such as zinc chloride, iron chloride, aluminum chloride, and tin chloride is used. The haloalkyl group-introduced cross-linked copolymer is washed with water to remove residual chloromethyl methyl ether and catalyst, and then reacted with ammonia or an amine to react the halogen atom of the haloalkyl group with the nitrogen of the ammonia or amine. Replace with atom. Usually, trimethylamine or dimethylethanolamine is reacted to obtain a strongly basic anion exchange resin having a quaternary ammonium group.

[0008] The anion exchange resin contains several hundred to several thousand ppm of a metal derived from a catalyst, and its content does not decrease so much only by washing with water. Generally, a porous resin, particularly a resin having a high specific surface area of 5 m ² / g or more in a dry state, tends to have a higher metal content than a gel resin.

In the present invention, the metal content of the anion exchange resin containing a large amount of metal is reduced to 100 ppm or less by washing with an aqueous acid solution. Usually, hydrochloric acid is used as the acid aqueous solution, but sulfuric acid or the like may be used. For washing, it is only necessary to fill the column with an anion exchange resin and pass an acid aqueous solution through the column at room temperature. As the aqueous acid solution, an aqueous solution of 5 N or less, preferably 1 to 2 N is used. The liquid passing speed is preferably about 0.1 to 5 hr ^-1 . The flow rate is usually 1 BV (BED VOLUME) or more, and more specifically, may be determined depending on how much the metal content of the anion exchange resin is reduced. It is easy to reduce the metal content to 10 ppm or less by increasing the flow rate.
pm or less.
If the metal content is reduced to a desired level by passing the acid aqueous solution, the acid aqueous solution is subsequently switched to pure water and passed through, the remaining acid is removed, and the product is anion exchange resin. I do. In addition, instead of washing with an aqueous acid solution, the metal content can be reduced by washing with an alkaline aqueous solution such as an aqueous caustic soda solution, but since the resin is free, it must be converted back to a salt form. Operationally disadvantageous.

[0010]

The present invention will be described more specifically with reference to the following examples. Example 1 Styrene and industrial divinylbenzene were subjected to suspension polymerization to obtain a porous crosslinked copolymer (average particle size: 680).
μm, specific surface area 40 m ² / g, divinylbenzene content 6% by weight). 100 g of the crosslinked copolymer was placed in a glass flask, 315 mL of chloromethyl methyl ether was added, and the mixture was stirred at room temperature for 1 hour to swell. To this, 51 g of zinc chloride was added, and the mixture was stirred at room temperature for 30 minutes, heated to 50 ° C. over 2 hours, and kept at this temperature for 8 hours to perform a chloromethylation reaction. After cooling the flask to room temperature, 500 mL of pure water was added over 4 hours to deactivate the catalyst and decompose unreacted chloromethyl methyl ether. The chloromethylated copolymer was recovered by filtration and washed well with water.

The chloromethylated crosslinked copolymer 1
00 g, 230 mL of toluene and 380 mL of pure water were placed in a glass flask, stirred at 50 ° C. for 1 hour to swell, and then allowed to cool. Next, 226 mL of a 30% aqueous solution of trimethylamine was added, the temperature was raised to 50 ° C. over 2 hours, and the temperature was maintained at this temperature for 8 hours to perform an amination reaction. The toluene was distilled off by distillation to obtain an anion exchange resin in which a trimethylammonium methyl group was bonded to the crosslinked copolymer.

This resin is filled in a glass column, and 2N-
20 BV of hydrochloric acid was passed through at room temperature for 5.7 hours to elute the contained metal, followed by washing with water. About 1 g of this anion exchange resin was weighed and placed in a quartz Erlenmeyer flask, to which 9 g of concentrated sulfuric acid, about 13 mL of concentrated nitric acid and about 1.5 mL of 30% hydrogen peroxide solution were added, and the resin was wet-decomposed by heating. Then, pure water was added to the decomposed product to make 50 mL, and ICP
Was used to measure the zinc content. Resin zinc content is 1pp
m (dry basis). The zinc content in the resin before washing with 2N-hydrochloric acid was 1290 ppm.

Example 2 A cross-linked copolymer was prepared in the same manner as in Example 1 except that 60 g of ferric chloride was used instead of 51 g of zinc chloride as a catalyst for the chloromethylation reaction. An anion exchange resin with attached groups was obtained. The iron content of this resin was 964 ppm. The resin was washed with 2N hydrochloric acid in exactly the same manner as in Example 1, but the iron content was 1 ppm or less.

Continued on the front page (72) Inventor Masao Tate 1-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu-shi F-term in the Kurosaki Plant of Mitsubishi Chemical Corporation (reference) 4J100 AB02P AB16Q CA04 CA23 CA31 GC04 HA27 HA31 JA16

Claims (6)

[Claims] 1. An anion exchange resin comprising a crosslinked copolymer of a monovinyl monomer and a polyvinyl monomer as a base and a primary to tertiary amino group or a quaternary ammonium group as an ion exchange group. Is a salt type and has a metal content of 100 ppm or less. 2. The anion exchange resin according to claim 1, wherein the metal content is 10 ppm or less. 3. The anion exchange resin according to claim 1, wherein the metal content is 5 ppm or less. 4. The anion exchange resin according to claim 1, wherein a counter ion of the ion exchange group is a chloride ion. 5. An ion-exchange group represented by the formula (1): 5. A quaternary ammonium group represented by the formula: wherein R ¹ and R ² are methyl groups and R ³ is a methyl group or a 2-hydroxyethyl group. The anion exchange resin according to any one of the above. 6. A copolymerization step of copolymerizing a monovinyl monomer and a polyvinyl monomer to form a crosslinked copolymer, a haloalkylation step of introducing a haloalkyl group into the obtained crosslinked copolymer in the presence of a Lewis acid, An ion-exchange group-introducing step of reacting an amine with the cross-linked copolymer into which the haloalkyl group has been introduced to form a halide-type anion-exchange resin, and containing the resulting anion-exchange resin by washing with an aqueous acid solution. Acid washing step to remove the metal
The method for producing an anion exchange resin according to any one of claims 1 to 5, wherein