JP4518112B2 - Purification method of basic anion exchange resin - Google Patents

Description

  The present invention relates to a method for purifying a basic anion exchange resin. Specifically, it is a method for purifying a basic anion exchange resin used for the production of pure water used for semiconductor production, etc., particularly a boron-selective anion exchange resin, and elution of total organic carbon (TOC). The present invention relates to a reducing purification method.

In order to improve the water quality to the utmost as an ultrapure water production application, the ion exchange resin performance is also focused on components eluted from the resin, especially total organic carbon (TOC), and various purified ion exchanges. Resin has been developed.
As a method for reducing TOC eluted from ion exchange resins generally used in aqueous systems, a method of washing with highly treated clean water such as ultrapure water and a method of washing with a water-soluble organic solvent are known. ing. However, these methods cannot effectively reduce TOC elution.

As a method for reducing TOC elution from a boron-selective ion exchange resin, a method in which a glucamine exchange group which is a weakly basic exchange group is prepared in a free base form and a strong base exchange group is prepared in a salt form and used. Is known (Patent Document 1). However, in this method, it is necessary to prepare the ion exchange resin in a salt form in two steps, and the processing becomes complicated.
For the same purpose, a method of bringing a boron selective adsorption resin into contact with a heated alkali metal hydroxide aqueous solution is also known (Patent Document 2). However, even in this method, a strong base component that causes TOC elution remains in the ion exchange resin after adjustment, and reduction of TOC elution cannot be sufficiently achieved. Further, in this method, cleaning is performed with ultrapure water that has been heated after being brought into contact with the alkali metal hydroxide aqueous solution. However, in the case of cleaning only with warmed ultrapure water, the desorbed TOC component is washed out from the resin. Therefore, a considerable amount of ultrapure water is required.
JP-A-8-238478 Japanese Patent Laid-Open No. 2001-27877

  The object of the present invention is to provide basic anion exchange mainly used for removing boron in treated water in the production of ultrapure water used for applications such as semiconductor production, pharmaceuticals, and pure water in the food field. It is to reduce the total organic carbon (TOC) eluted from the resin, especially the boron selective ion exchange resin.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention combined total heat treatment with an alkaline solution and washing with a water-soluble organic solvent to obtain total organic carbon (TOC) from a basic anion exchange resin. ) Was found to be able to be effectively and unexpectedly reduced, and the present invention was reached.
That is, the gist of the present invention, I boron-selective ion exchange resins der having an amino polyol group as a functional group, total organic carbon (TOC) basic ion exchange resins containing quaternary ammonium groups cause elution in the alkali concentration 2 wt% alkali solution, after heat treatment under the following conditions 60 ° C. or higher 120 ° C., basic and wherein the washing with water-soluble organic solvent or aqueous solution on the 50 wt% or more anionic Purification method of ion exchange resin.

Another gist of the present invention resides in the method for purifying the basic anion exchange resin, wherein the basic anion exchange resin is a boron selective ion exchange resin.
Another gist of the present invention resides in the method for purifying the basic anion exchange resin, wherein the boron selective ion exchange resin has an amino polyol group as a functional group.
Another gist of the present invention is the method for purifying the basic anion exchange resin, wherein the alkaline solution is an aqueous alkali metal hydroxide solution.

Another gist of the present invention resides in the method for purifying the basic anion exchange resin, wherein the water-soluble organic solvent is an alcohol having 1 to 6 carbon atoms or acetone.
Another subject of the present invention, the heating temperature in an alkaline solution is, consists in the purification method of the basic anion exchange resin, characterized in that at 80 ° C. or higher.
Another gist of the present invention resides in a basic anion exchange resin obtained by the purification method. Another gist of the present invention resides in a basic anion exchange resin obtained by the above purification method having an acid adsorption capacity of 2 meq / g or more and a neutral salt decomposition capacity of 0.2 meq / g or less.

  According to the purification method of the present invention, TOC elution can be effectively reduced.

The purification method of the present invention is characterized in that the basic anion exchange resin is heated in an alkaline solution and then washed with a water-soluble organic solvent.
[Basic anion exchange resin]
The basic anion exchange resin in the present invention usually has a quaternary ammonium group such as a trimethylammonium group, a dimethylethanolammonium group, or a dimethylammonium group as a functional group. The present invention is particularly suitable for purification of boron-selective ion exchange resins among basic ion exchange resins. Examples of the ion exchange resin for removing boron include those having a trimethylammonium group and the like, but those having an aminopolyol group shown in Japanese Patent Publication No. 4-68980 are preferred, and more preferably a reaction with glucamine. Having a glucamine structure (having a glucamine exchange group). Those having an amino polyol group are usually classified as boron-selective ion exchange resins.

  The basic anion exchange resin is usually produced by producing a crosslinked copolymer having a haloalkyl group and introducing an ion exchange group into this. A crosslinked copolymer having a haloalkyl group as a precursor of a basic ion exchange resin can be obtained by copolymerizing a monovinyl aromatic monomer and a polyvinyl aromatic monomer, such as styrene and divinylbenzene, by a known method. There is a method obtained by reacting a crosslinked copolymer with chloromethyl methyl ether. Alternatively, it can be obtained by copolymerizing a haloalkylstyrene such as chloromethylstyrene or bromobutylstyrene with a polyvinyl aromatic monomer. By reacting these with an amine (amination reaction) by a known method, a basic ion exchange resin can be obtained.

[Heat treatment in alkaline solution]
(1) Alkaline solution The alkali solution used for this invention should just have the capability to reduce the strong base component of basic ion exchange resin, and the solution which exhibits a strong alkali is preferable. The alkali is preferably an alkali metal hydroxide. For example, sodium hydroxide, lithium hydroxide, potassium hydroxide, etc. are mentioned. From an economical viewpoint, sodium hydroxide is preferably used.

  The solvent of the alkaline solution is usually water, but may be a mixed solution of water and alcohol, or may be alcohol. As the alcohol, an alcohol having 1 to 3 carbon atoms such as methanol, ethanol, isopropyl alcohol and the like can be used, but methanol is preferable. In the case of a mixed solution of water and alcohol, the content of water is usually 70% by weight or more, preferably 90% by weight or more.

The alkali concentration in the alkali solution is usually 2% by weight or more and preferably 4% by weight or more and 15% by weight or less, but considering the specific gravity difference of the basic anion exchange resin to be provided in the alkali solution. Then, 4 weight% or more and 12 weight% or less are suitable. (2) Heat treatment The heat treatment conditions vary depending on the concentration of the alkali solution, the amount of the alkali solution relative to the resin amount, etc., but the heating temperature usually needs to be 60 ° C or higher, and is higher for shortening the treatment time. The temperature is 80 ° C. or higher, more preferably 90 ° C. or higher. Usually, it is 120 ° C. or lower.

About processing time, if it is high temperature and high concentration, it can be performed in a comparatively short time. For example, the treatment may be performed at 90 to 110 ° C. for 4 to 18 hours.
Examples of the method for heat treatment with an alkaline solution include a column method in which a column is filled with a resin and the alkaline solution is passed, and a batch method in which a resin and an alkaline solution are put in a container and stirred. Considering the contact at high temperature, in the column method, in order to suppress the generation of bubbles, liquid passage under pressure is preferable.
In this case, the required amount of the alkaline solution is usually equal to or more than the amount of the resin to be provided (1 time) and there is no restriction on the upper limit. Less than 3 times the amount.

[Washing with water-soluble organic solvent or aqueous solution of 50% by weight or more]
The basic anion exchange resin that has been heat-treated with the alkali solution needs to be washed with a water-soluble organic solvent or an aqueous solution of 50% by weight or more in order to remove the TOC component that is desorbed when heat-treated with the alkali solution. is there.

Although only a heat treatment with an alkaline solution reduces the strong base component that causes TOC elution, the desorbed TOC component has a strong affinity with the resin. For example, cleaning with ultrapure water alone is effective. It does not lead to removal. Moreover, it is possible to effectively remove the TOC component derived from the styrene skeleton present in the resin only by contacting with a water-soluble solvent such as methanol. However, since the strong base component is preserved, there are not a few TOC components. Elution from the resin occurs over time.
(1) Pretreatment After the heat treatment with an alkali solution, it is desirable to remove the alkali solution from the resin in advance before washing with a water-soluble organic solvent or the like. As the method, it is desirable from the viewpoint of efficiency that the resin and the solution heat-treated with the alkaline solution are packed in a column and washed with water. It is desirable that the water quality usually required for washing with water is at least demineralized water. The washing amount is usually 2 BV or more, preferably 4 BV or more. The flow rate is usually SV 0.5 to 2.0.
(2) Water-soluble organic solvent The water-soluble organic solvent means an organic solvent that can be mixed at an arbitrary ratio of water. For example, alcohols having 1 to 6 carbon atoms such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, and hexyl alcohol, acetone and the like can be exemplified, but methanol is preferred. Two or more water-soluble organic solvents can be used in combination.
(3) An aqueous solution of 50% by weight or more of a water-soluble organic solvent An aqueous solution of the above-mentioned water-soluble organic solvent can also be used, but in order to efficiently remove the TOC component, the concentration of the water-soluble organic solvent should be higher Preferably, it is usually 50% by weight or more in the aqueous solution, preferably 70% by weight or more. More preferably, 90% by weight or more is used.
(4) Cleaning method Examples of a cleaning method using a water-soluble organic solvent include a column method in which a column is filled with a resin and a batch method in which a resin and a water-soluble organic solvent are placed in a container and stirred. The column method is more suitable for the efficiency of washing.

  When the column method is used, the washing amount is 1 BV or more with respect to the filled resin amount. The filling of the resin is usually carried out using water, but at least 2 BV or more is suitable because the amount of the resin is required to replace the inside of the column system with a water-soluble organic solvent or the like. Although there is no upper limit, usually 10 BV or less is used. The flow rate is usually SV 0.5 to 2.0. After washing with a water-soluble organic solvent or the like, a water flow rate of 10 to 50 BV is appropriate within a flow rate range of SV1 to 10 using ultrapure water in a state where the column is packed in order to replace the resin with water.

When the batch method is used, it is preferable to increase the replacement efficiency by performing the treatment with the attached water removed (drained state), and replacing the water-soluble organic solvent in the same amount as the resin amount twice or more.
When the column is packed in order to replace the resin with water after washing with a water-soluble organic solvent or the like, a water flow rate of 10 to 50 BV is appropriate in the range of flow rates SV1 to 10 using ultrapure water. Moreover, when this is performed by a batch method, it is appropriate to replace 20 to 100 times with ultrapure water having the same volume as the resin amount in a state where the attached water-soluble organic solvent is removed.

[Basic anion exchange resin after purification]
The neutral salt decomposition capacity of the basic anion exchange resin obtained by the purification method of the present invention is preferably as small as possible, usually 0.3 meq / g or less, preferably 0.2 meq / g or less, more preferably. Is 0.1 meq / g or less. The method for measuring the neutral salt decomposition capacity is described in “Diaion Ion Exchange Resin / Synthetic Adsorbent Manual (I) Basics Issued by Mitsubishi Chemical Corporation (Revised Edition, Issued on January 10, 1995, 144p)”. Depending on the method.
The neutral salt decomposition capacity is derived from the quaternary ammonium group in the ion exchange resin, and the small amount means that the strong base component is small. As described in JP-A-8-238478, when the counter ion of the strongly basic exchange group is in the hydroxide ion form, it causes TOC elution, thereby reducing the strong base component, TOC elution can be reduced.

  The effect of TOC reduction is exhibited by heat treatment in an alkaline solution and washing with a water-soluble organic solvent alone, but by treating in the order of the present invention, a quaternary ammonium group that causes TOC elution ( It is considered that the TOC component generated at this time and the component derived from the styrene skeleton are simultaneously and efficiently washed with a water-soluble organic solvent at the same time, thereby exhibiting a single or more reduction effect.

  Further, it is presumed that the strong base component is mainly composed of a tertiary ammonium group of the produced glucamine exchange group further quaternized by overreaction in the amination reaction during the production of the anion exchange resin. In the heat treatment in the alkaline solution, a reaction for tertiaryizing the quaternized ammonium group occurs, which has an effect of increasing the stability against elution. At the same time, an effect of removing a part of the exchange group that is easily decomposed and desorbed, that is, likely to cause TOC, and removed first is expected.

  The acid adsorption capacity of the ion exchange resin obtained by the purification method of the present invention is preferably larger, usually 1 meq / g or more, preferably 2 meq / g or more, and usually 5 meq / g or less. The acid adsorption capacity (= total exchange capacity) can be found in “Diaion Ion Exchange Resin / Synthetic Adsorbent Manual (I) Basics Issued by Mitsubishi Chemical Co., Ltd.” It can be measured by the method described.

Example 1
1) 1 liter of boron-selective ion exchange resin resin (Diaion (registered trademark) CRB0, manufactured by Mitsubishi Chemical Corporation) is packed into a cylindrical glass column having an inner diameter of 65 mm and a length of 500 mm, and the flow rate is SV2 for 1 hour. Then, it was washed with demineralized water.
2) The resin that had been washed with water was taken out from the column, and drained by a centle filtration method to remove adhering water.
3) A drained resin was added to a 3 liter glass round bottom flask with a side tube equipped with a Dimroth reflux tube, and 1.1 liter of a 4% aqueous sodium hydroxide solution was further added. The flask was placed in an oil bath, and the temperature of the oil was raised from room temperature to about 105 ° C. over 1 hour so that the temperature inside the flask became 100 ° C. while gently stirring the resin, and this state was maintained for 8 hours. .
4) The flask was allowed to cool and the resin was taken out, and then filled in the glass column, followed by washing with demineralized water at a flow rate of SV2 for 2 hours.
5) Further, 2 liters of reagent-grade methanol was passed over 2 hours at a flow rate SV1.
6) Subsequently, ultrapure water was passed for 4 hours at a flow rate of SV5.

The performance of the obtained ion exchange resin was measured using the method described in the Diaion Ion Exchange Resin / Synthetic Adsorbent Manual (I) Basic Edition (revised on January 10, 1995, 135p) issued by Mitsubishi Chemical Corporation. And measured. As a result, the water content was 53.2%, the acid adsorption capacity was 2.66 meq / g (0.8 meq / mL), and the neutral salt decomposition capacity was 0.14 meq / g.
Moreover, TOC elution evaluation of the obtained ion exchange resin was performed by the following method.

<TOC elution evaluation method>
Charge 0.4 liters of ion exchange resin into an acrylic column (inner diameter 25 mm, 1000 mm length), pass ultrapure water (18.2 MΩ · cm, 1 ppb) at SV10, The TOC and the column outlet TOC at the time of resin filling were measured with a TOC meter (A-1000) manufactured by Anatelle and expressed as TOC increment (ΔTOC) (Table 1).
Comparative Example 1: Only methanol washing The same operation as in Example 1 was carried out except that the preparation was carried out except for steps 2), 3) and 4).

The acid adsorption capacity and neutral salt decomposition capacity of Comparative Example 1 are estimated to be the same as those of Comparative Example 3.
Comparative Example 2: Thermal alkali treatment only The same operation as in Example 1 was performed except that adjustment was made except for step 5).
Comparative Example 3: No washing treatment General performance of Diaion (registered trademark) CRB02 manufactured by Mitsubishi Chemical Corporation used in Example 1, Comparative Examples 1 and 2 was measured in the same manner as in Example 1. As a result, the water content was 53.7%, the acid adsorption capacity was 2.61 meq / g (0.8 meq / mL), and the neutral salt decomposition capacity was 0.57 meq / g. The elution evaluation was performed in the same manner as in Example 1.
The elution evaluation results of Comparative Examples 1 to 3 are shown in Table 1.

Claims (7)

What boron selective ion exchange resins der having an amino polyol group as a functional group, total organic carbon (TOC) eluting causative quaternary ammonium groups basic ion exchange resin containing an alkali concentration of 2 wt% or more of A method for purifying a basic anion exchange resin , comprising heat-treating in an alkaline solution under conditions of 60 ° C. or higher and 120 ° C. or lower and then washing with a water-soluble organic solvent or an aqueous solution of 50% by weight or more thereof.   2. The method for purifying a basic anion exchange resin according to claim 1, wherein the alkali solution is an aqueous alkali metal hydroxide solution.   The method for purifying a basic anion exchange resin according to claim 1 or 2, wherein the water-soluble organic solvent is an alcohol or acetone having 1 to 6 carbon atoms. The heating temperature in an alkaline solution is a purification method of a basic anion exchange resin according to any one of claims 1 to 3, characterized in that a 80 ° C. or higher.   A basic anion exchange resin, which is a boron-selective ion exchange resin having an aminopolyol group as a functional group, obtained by the purification method according to claim 1.   The basic anion exchange resin according to claim 5, wherein the acid adsorption capacity is 2 meq / g or more and the neutral salt decomposition capacity is 0.2 meq / g or less. A method for producing ultrapure water, wherein the basic anion exchange resin according to claim 5 or 6 is used.