JP5049528B2 - Method for producing high purity alkali metal hydroxide - Google Patents

Description

  The present invention relates to a method for producing a high-purity alkali metal hydroxide capable of effectively removing heavy metals in a crude alkali metal hydroxide.

  For example, in the manufacture of electronic components such as semiconductor wafers and color filters, an alkali metal hydroxide is used to planarize the wafer surface by etching, remove the resist material, or clean the surface. Alkali metal hydroxide used in the manufacture of these electronic components is a high-purity water that does not contain metal impurities such as nickel, chromium, iron, and copper in order to prevent deterioration of semiconductor wafers and deterioration of semiconductor device characteristics. It is required to use an alkali metal oxide. In addition, there is an increasing demand for drugs that do not contain such impurities in medical use and cosmetics.

  As a method for producing high-purity alkali metal hydroxide, a production method for purifying alkali hydroxide with an ion exchange membrane can be mentioned (for example, see Patent Document 1). Although this method has a sufficiently high refining accuracy, it takes a relatively long time to install equipment, and it is difficult to obtain highly purified alkali hydroxide anywhere. Also disclosed are a method for removing nickel in potassium hydroxide with activated carbon (for example, see Patent Document 2) and a method for removing iron and nickel in sodium hydroxide with activated carbon (for example, see Patent Document 3). Yes. These can be handled with relatively simple equipment and can be highly purified, but there are few metal species that can be purified. In addition, some metal species are eluted from here, and this pretreatment may take effort.

  On the other hand, it is known to supplement a metal with a chelate resin or an ion exchange resin to purify a solution to be contacted or recover a metal. As examples of the purification of alkali hydroxide by these resins, purification by a chelate resin having a specific structure is disclosed (for example, see Patent Document 4). These can be purified by removing heavy metals such as iron, but further high processing is not disclosed, and 150 to 500 g / liter of caustic soda concentration is mentioned as a preferable example in terms of handling concentration. However, even in the region of higher concentration than this, high-level purification was not satisfied. In addition, in the analysis of heavy metals in alkali hydroxide, there is a method in which a heavy metal in alkali hydroxide is adsorbed with a chelate resin (typically iminodiacetic acid) and separated from the alkali metal, and then the metal content is desorbed and measured. It is used. However, in order to increase the capture efficiency of metals, for example, in the analysis of sodium hydroxide, it is necessary to dilute to a concentration of several weight percent or less (hereinafter%) (for example, see Non-Patent Document 1). On the other hand, the alkali hydroxide on the market is around 48% for both typical sodium hydroxide and potassium hydroxide (depending on the solution temperature, both sodium hydroxide and potassium hydroxide are around 730 g / l). There are many cases, and there are many cases in the stage of use, but there are many cases where they are stored and used in a range of 20 to 60% including a temporary storage form. Therefore, the methods known so far have not been able to cover a high concentration region which is generally distributed and used and have a high degree of purification.

  Aminophosphate-type chelate resins have been reported as those capable of removing calcium, strontium, and the like in salt water (see, for example, Patent Document 5). And it describes that it has selectivity with respect to bivalent metal ions, such as calcium, magnesium, strontium, in high concentration salt solution.

Japanese Patent Application Laid-Open No. 09-078276 JP 2000-203828 A JP-A-2005-001955 JP-A-01-027648 JP 05-032714 A Journal of the Seawater Society of Japan VOL. 58, NO. 1, p. 58-92, issued February 1, 2004

  The present invention provides a method for producing a high-purity alkali metal hydroxide aqueous solution capable of removing and purifying the heavy metal content contained in the crude alkali metal hydroxide aqueous solution in a high concentration state. .

As a result of intensive investigations on the removal of heavy metal from a crude alkali metal hydroxide aqueous solution with a concentration as marketed, it is possible to remove heavy metals in the crude alkali metal hydroxide with a chelate resin capable of removing or adsorbing boron. As a result, the present invention has been completed. That is, the present invention specifically includes
(1) Ri manufacturing method der high purity alkali metal hydroxide aqueous solution, and removing the heavy metals in the crude alkali metal hydroxide solution by the chelating resin with N- methylglucamine group,
(2) The method for producing a high-purity alkaline hydroxide aqueous solution as described in 1 above, wherein the heavy metal to be removed is iron, nickel, copper, manganese, and / or chromium,
(3) concentration of the crude alkali metal hydroxide solution is a 21 to a 20 to 60 wt%
It is a manufacturing method of high purity alkali metal hydroxide aqueous solution in any one . Also,
(4) A method for removing heavy metals in a crude alkali metal hydroxide aqueous solution, wherein a chelate resin having an N-methylglucamine group is used.

  According to the production method of the present invention, heavy metals can be removed even from a high-concentration crude alkali metal hydroxide aqueous solution, so that high-purity alkali metal hydroxide can be easily provided without performing a concentration operation or the like.

Examples of the alkali metal hydroxide handled in the present invention include sodium hydroxide and potassium hydroxide, and potassium hydroxide is particularly preferable because it can efficiently remove heavy metal.
In the present invention, the concentration of the crude alkali metal hydroxide aqueous solution can be expected to have a heavy metal reduction effect at any concentration, but in the sense that it does not carry out unnecessary operations such as transportation efficiency, storage efficiency, and subsequent simmering to a high concentration by handling, It is preferably 20% or more, and preferably 60% or less, more preferably 35% or more and 55% or less, and particularly preferably 40% or more and 53% or less as a range in which solidification does not occur.

  In addition, although the crude alkali hydroxide metal used is exclusively produced by the ion exchange membrane method, the metals as impurities contained therein are calcium, magnesium, strontium, barium, iron, nickel, Examples include copper, zinc, lead, cadmium, manganese, cobalt, vanadium, molybdenum, chromium, zirconium, silver, tin, aluminum, mercury, antimony, titanium, bismuth, gallium, and thallium. It is desirable to reduce this as much as possible. . Furthermore, even if a specific metal (heavy metal) is contained in a small amount, the quality of the product is greatly affected, and iron, nickel, copper, manganese, chromium, and calcium can be further reduced to a low level.

  In the present invention, the heavy metal in the high-purity alkali metal hydroxide, that is, impurities such as iron, nickel, copper, manganese, or chromium is 500 ppb or less (hereinafter ppb), preferably 50 ppb or less, more preferably 20 ppb. Or less, more preferably 5 ppb or less, and 0.1 ppb or more.

  Note that the crude alkali metal hydroxide aqueous solution suitable for this method varies depending on the contained heavy metal. For example, when the concentration after removing impurities is 5 ppb or less, the concentration of each metal that can be mixed before removal is preferably 10 ppm by weight (hereinafter ppm), more preferably 3 ppm or less. In addition, the lower limit of each heavy metal contained in the crude alkali metal hydroxide aqueous solution is larger than the content of each heavy metal in the high purity alkali metal hydroxide.

In the production method of the present invention, for example, the chelate resin is packed in a packed tower, and a crude alkali metal hydroxide aqueous solution is passed therethrough, whereby heavy metals in the solution can be easily removed. It is also possible to reduce heavy metals by batch operation such as storing a crude alkali metal hydroxide solution in a tank or the like, adding the chelate resin, and stirring.
The chelate resin to which heavy metals are adsorbed in the present invention is regenerated by a known deuterium metal operation such as washing with ultrapure water or the like, back washing operation, further treatment with acid such as hydrochloric acid or nitric acid, and washing with water. The method is applicable. And the chelate resin reproduced | regenerated in this way can be used for the manufacturing method of this invention.

As the chelate resin used in the present invention , any chelate resin having an N-methylglucamine group can be used, and those having basicity are preferred. As the chelate resin, polystyrene, polystyrene - -CH ₂ -N (CH ₃₎ divinylbenzene copolymer or a phenol resin _{CH 2 - (CHOH) n -CH} 2 OH groups (n is about 3 to 5 integer Are more preferable. Specifically, there is one in which an N-methylglucamine group is bonded to a polystyrene-divinylbenzene copolymer. As a commercial product, Diaion CRB02 (trade name, manufactured by Mitsubishi Chemical Corporation), Amberlite IRA743 (trade name,
Rohm & Haas) and Uniselec UR-3500S (trade name, manufactured by Unitika Ltd.).

  In this invention, what is necessary is just to determine the usage-amount of this chelate resin by content of the heavy metal in a crude alkali metal hydroxide. For example, when heavy metal is removed in a packed tower, the superficial velocity (hereinafter referred to as SV) is SV = 0.1-5 [1 / h], more preferably SV = 0.2-3 [1 / h. ], Especially preferably, heavy metal can be efficiently removed by contacting at SV = 0.3-2 [1 / h].

  In the production method of the present invention, the operating temperature is about 0 ° C to 60 ° C, preferably 5 ° C to 50 ° C, more preferably 10 ° C to 45 ° C. When the contact temperature with the chelate resin is within this range, it is preferable because heavy metals in the crude alkali metal hydroxide can be efficiently removed.

  For example, a high-purity alkali metal hydroxide aqueous solution is produced by removing heavy metals by flowing in the above-mentioned SV at a temperature between 0 ° C. and 60 ° C. with the chelate resin packed in a column with a crude alkali metal hydroxide aqueous solution. Can do. Alternatively, the crude alkali metal hydroxide aqueous solution and the chelate resin may be contacted in batches at a temperature between 0 ° C. and 60 ° C., for example, for 2 hours to remove heavy metals to produce a high purity alkali metal hydroxide aqueous solution. it can.

  The high-purity alkali metal hydroxide aqueous solution produced using the production method of the present invention can be used after adjusting the concentration depending on the application.

High-purity alkali metal hydroxide manufactured using the manufacturing method of the present invention is used for manufacturing electronic parts such as semiconductor wafers and color filters, planarizing by wafer surface etching, removing resist material, or cleaning the surface. Can be used.
By using the purification method of the present invention, high-purity alkali metal hydroxide used for manufacturing electronic components such as semiconductor wafers and color filters, planarizing by wafer surface etching, removing resist material, or cleaning the surface, etc. Can be provided.

Embodiment A method for removing heavy metals in a crude aqueous alkali metal hydroxide solution using a chelate resin having an N-methylglucamine group.
A method of removing iron, nickel, copper, manganese, and / or chromium in a crude aqueous alkali metal hydroxide solution using a chelate resin having an N-methylglucamine group .
A method of removing heavy metals in a crude alkali metal hydroxide aqueous solution having a concentration of 20 to 60% by weight using a chelate resin having an N-methylglucamine group .

<Example>
EXAMPLES Hereinafter, although this invention is demonstrated using an Example, these inventions are not limited. In addition,% represents weight%, ppm represents weight ppm, and ppb represents weight ppb.

Diaion CRB-02 (Mitsubishi Chemical Corporation) is used as a chelating resin having boron adsorption performance by taking 100 g of 48% sodium hydroxide aqueous solution with an iron-containing concentration of 1.27 ppm in a polytetrafluoroethylene polytetrafluoroethylene (PTFE) container. (Product / functional group N-methylglucamine) 10 g or 20 g was added, and the mixture was stirred at room temperature for 2 hours.
Thereafter, these solutions were collected, analyzed for iron content (the following analysis method), and compared with the uncontacted stock solution of the chelate resin, the removal rate was shown in Table 1.

○ Iron ion analysis method Ultrapure water was added to the collected sample to make it acidic with hydrochloric acid. Then, 10% hydroxylammonium hydrochloride aqueous solution was added and boiled for several minutes, then the pH was adjusted to 3-5 with dilute ammonia water, and orthophenanthroline hydrochloride solution (0.3%) was added. Then, it was made up with ammonium acetate buffer (20%) and distilled water, allowed to stand for 10 minutes at room temperature to develop color, and the absorbance was determined with an absorptiometer. Separately, the same operation was performed without using the collected sample, and the absorbance of the blank was determined. The iron concentration was determined using a separately prepared calibration curve.

<Comparative Examples 1-9>
The same procedure as in Example 1 was performed except that the chelate resin was replaced with another chelate resin or an ion exchange resin. In addition, the chelate resin or ion exchange resin used in Comparative Examples 1-9 was described below.
Comparative Example 1 Diaion PK-216 (functional group —SO ₃ Na)
Comparative Example 2 Diaion PK-228 (functional group -SO ₃ Na)
Comparative Example 3 Diaion WA-30 (functional group —CH ₂ N (CH ₃ ) ₂ )
Comparative Example 4 Diaion CR-11 (functional group, iminodiacetic acid Na)
Comparative Example 5 Diaion CR-20 (functional group —CH ₂ NH (CH ₂ CH ₂ NH—) _n H)
As above, manufactured by Mitsubishi Chemical Corporation.
Comparative Example 6 Lebatit Monoplus TP-208 (functional group, iminodiacetic acid Na)
Comparative Example 7 Levacit monoplus TP-260 (functional group aminophosphoric acid)
As above, manufactured by LANXESS.
Comparative Example 8 UR-3300S (functional group aminophosphoric acid)
As above, manufactured by Unitika Ltd.
Comparative Example 9 Amberlite IRA410JCL (functional group, dimethylethanolamine chloride, manufactured by Rohm & Haas Co., Ltd.)

Take 100 g of 48% sodium hydroxide aqueous solution containing iron (shown as initial concentration, ppm) shown in Table 2 in a PTFE container, add chelate resin Diaion CRB-02 in the amount shown in Table 2, and stir at room temperature. For 2 hours.
Thereafter, these solutions were collected, and the iron content was analyzed to obtain the equilibrium concentration (ppm) and the equilibrium adsorption concentration calculated therefrom. Table 2 shows these results.

  As in Example 2, the reaction was carried out under the conditions described in Table 3 with 100 g of a 48% aqueous potassium hydroxide solution. The results are shown in Table 3.

100 g of 48% aqueous sodium hydroxide solution was placed in a PTFE container, 10 g of chelate resin Diaion CRB-02 was added, and the mixture was stirred at room temperature for 2 hours.
Thereafter, an aqueous sodium hydroxide solution was collected and analyzed for heavy metal content. Table 4 (ppb) shows the results of these analyzes and the uncontacted stock solution of the chelate resin.

○ Analytical method of nickel, copper, and manganese Ultrapure water was added to the collected samples and then neutralized with nitric acid. Then, a 100 mM ammonium acetate aqueous solution (pH 5.5) was added to make up the volume to prepare a test solution. This test solution was washed with ultrapure water after capturing the target metal with a chelate disk. Then, the target metal was eluted from the chelate disk using dilute nitric acid, measured up with ultrapure water, and each metal concentration was measured with an inductively coupled plasma mass spectrometer (ICP-MS). Created a calibration curve).

○ Analysis method of chromium After adding ultrapure water to the collected sample, it was neutralized with nitric acid. And after adding a reducing agent, it adjusted to pH 5 vicinity by aqueous ammonia solution, and made up to make a test solution. This sample solution was captured with a chelate disk to capture chromium ions and washed with ultrapure water. Chromium ions were eluted from the chelate disk using dilute nitric acid, measured up with ultrapure water and measured by ICP-MS (a calibration curve was created in advance).

  The heavy metal content was measured in the same manner as in Example 4 except that a 48% aqueous potassium hydroxide solution was used instead of the 48% aqueous sodium hydroxide solution. The results are shown in Table 4.

  Since the present invention can remove and purify heavy metals in crude alkali hydroxide metal, it can be applied to all fields such as semiconductor wafer polishing and other electronic materials, pharmaceuticals, cosmetics, etc., at the time of alkali hydroxide production, shipment, acceptance It can be easily applied in any case such as in use.

Claims (4)

A method for producing a high-purity alkali metal hydroxide aqueous solution, wherein heavy metals in a crude alkali metal hydroxide aqueous solution are removed by a chelate resin having an N-methylglucamine group . The method for producing a high-purity alkali metal hydroxide aqueous solution according to claim 1 , wherein the heavy metal to be removed is iron, nickel, copper, manganese, and / or chromium. The manufacturing method of the high purity alkali metal hydroxide aqueous solution of Claim 1 or Claim 2 whose density | concentration of the said crude alkali metal hydroxide aqueous solution is 20 to 60 weight%. A method for removing heavy metals in a crude aqueous alkali metal hydroxide solution , wherein a chelate resin having an N-methylglucamine group is used.