JP2003277965A - Method for making quaternary ammonium hydroxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for making high-purity quaternary ammonium hydroxide containing anionic impurities to a lesser extent. <P>SOLUTION: The method of making the quaternary ammonium hydroxide by electrolyzing the quaternary ammonium salt by using an electrolytic cell compartmentalized by a cation exchange membrane to an anode chamber and a cathode chamber, in which a weakly acidic salt of quaternary ammonium is added to the anode and the electrolysis is performed by maintaining the pH of an anolyte at 6 to 8. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a quaternary ammonium hydroxide, and more particularly to a method for producing a high-purity quaternary ammonium hydroxide which reduces running costs and has less anionic impurities.

[0002]

2. Description of the Related Art Quaternary ammonium hydroxide is used as a phase transfer catalyst, or as a metal-free strong alkaline substance as a developing solution or a cleaning solution in the manufacture of LSI devices.

As a method for producing a quaternary ammonium hydroxide, a trialkylazine is reacted with an organic acid or an inorganic acid ester to synthesize a quaternary ammonium salt, and the hydroxide is synthesized by electrolysis using this as a raw material. The method is generally used. For the ester as a raw material, formic acid ester or the like is used because it can be obtained relatively easily and inexpensively. There is also a method using alkyl chloride.

When a salt synthesized from these alkyl chlorides and formate esters is electrolyzed, a strong acid is produced in the anolyte. For this reason, the current efficiency is lowered, and the acid component permeates the electrolytic membrane and reaches the cathode to become an anionic impurity, which causes the product purity to be lowered. In order to avoid this, various methods have been proposed. For example, a multi-chamber type electrolytic cell having two or more cation exchange membranes installed between the anode and the cathode is used to supplement the acid content that permeates the intermediate cell. Method (JP-A-60-131986)
Japanese Patent Laid-Open No. 63-2113686) and the like are proposed. However, in this method, there are problems that the number of components such as electrodes and electrolytic membranes constituting the electrolysis apparatus increases, the apparatus becomes expensive, the cell voltage rises, and the power cost increases. Further, a method of preventing acid permeation from the anode to the cathode by adding an alkali to the anolyte to control the pH to 8 or more (JP-A-1-87792, JP-A-1-87792).
No. 87797) has also been proposed. However, in this method, the pH of the anolyte increases, and depending on the type of the anode electrode used, the electrode material may elute and the life of the electrode may be significantly shortened.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a high-purity quaternary ammonium hydroxide containing a low amount of anionic impurities derived from an acid by using an inexpensive quaternary ammonium salt as a raw material, By keeping the pH in the anolyte near neutral without using expensive equipment such as a type electrolyzer, it is possible to suppress corrosion of the anode electrode and reduce running costs, and nickel-based electrodes that are vulnerable to acidic atmospheres, etc. It is intended to provide a method that can be used for an anode electrode, such as an iridium-based electrode which is weak in a basic atmosphere.

[0006]

In order to achieve the above object, the present invention provides a quaternary ammonium salt represented by the following general formula (1):

[Chemical 2] (R _{1 to} R ₄ represent an alkyl group having 1 to 8 carbon atoms. R ₁ to
R ₄ may be the same or different. X represents an organic acid or an inorganic acid. ) In a method for producing a quaternary ammonium hydroxide by electrolyzing using an electrolytic cell divided into an anode chamber and a cathode chamber by a cation exchange membrane, a quaternary ammonium weak acid salt is added to the anode, The pH is kept at 6 to 8 and electrolysis is performed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The weak quaternary ammonium salt added to the anolyte in the present invention functions as a base in the anolyte. As a result, hydrogen ions produced in the anolyte by electrolysis of water or salt are neutralized, and the current efficiency is lowered and the acid component is prevented from permeating into the cathode chamber. When the acidity of the weak acid is strong, the ability of the salt as a base is weakened, so that the pKa is preferably 5 or more.

Examples of weak quaternary ammonium salts added to the anolyte used in the present invention are that the weak acid generated in the anode is unstable and easily decomposes into water and carbon dioxide and does not accumulate in the system. Therefore, quaternary ammonium hydrogen carbonate and quaternary ammonium carbonate are preferred. Examples of these compounds include tetramethylammonium hydrogen carbonate (TM)
BC), trimethylethylammonium hydrogen carbonate, triethylmethylammonium hydrogencarbonate, tetraethylammonium hydrogencarbonate, tetrap-pyruammonium hydrogencarbonate, trimethyl (2-hydroxyethyl) ammonium hydrogencarbonate, triethyl (2-hydroxyethyl) Ammonium hydrogen carbonate, hydrogen carbonate such as triprovir (2-hydroxyethyl) ammonium hydrogen carbonate, and tetramethyl ammonium carbonate (TMA
C), trimethylethylammonium carbonate, triethylmethylammonium carbonate, tetraethylammonium carbonate, tetrap-pyruammonium carbonate, trimethyl (2-hydroxyethyl) ammonium carbonate, triethyl (2-hydroxyethyl) ammonium carbonate, triprovir Carbonates such as (2-hydroxyethyl) ammonium carbonate are mentioned. These compounds may be used alone or in combination of two or more kinds. More preferably, since the effect on the purity of the product is small, the general formula (1)

[Chemical 3] One or more compounds selected from quaternary ammonium hydrogen carbonate and quaternary ammonium carbonate, which are composed of the same quaternary ammonium ion as the quaternary ammonium hydroxide to be produced, are particularly preferable. These are usually added as an aqueous solution.

The weak quaternary ammonium salt used according to the present invention is added to neutralize a strong acid generated by electrolysis of a quaternary ammonium organic acid salt or an inorganic acid salt, and the addition amount thereof is quaternary ammonium and a weak acid. An appropriate amount is selected depending on the kind of salt, but generally 0.1 to 100% by weight, preferably 1 to 80% by weight, more preferably 10% by weight based on the quaternary ammonium organic acid salt or inorganic acid salt. Is about 70% by weight. When the amount of the weak quaternary ammonium salt is less than 0.1% by weight, the strong acid generated by the electrolysis of the quaternary ammonium organic acid salt or the inorganic acid salt is not sufficiently neutralized and remains in the anolyte, and the pH of the anolyte is decreased. If it is reduced to 6 or less, the current efficiency is lowered, and the acid component permeates the electrolytic membrane and reaches the cathode to become an anionic impurity, which lowers the product purity. 100
If it is more than 10% by weight, the pH of the anolyte becomes higher than 8 and depending on the type of the anode electrode used, the electrode material may elute and the life of the electrode may be significantly shortened, which is not preferable. For example, if the pH of the electrolyte is 6 or less, the Ni electrode, etc.
When the value is 8 or more, corrosion occurs on the iridium oxide (IrO ₂ ) electrode and the like.

In the present invention, as the cation exchange membrane for partitioning the electrolytic cell into the anode chamber and the cathode chamber, a commonly used electrolytic membrane such as a fluororesin membrane or a hydrocarbon membrane can be used. A resin film is particularly preferable. Nafion-324, Nafion-96 as the fluororesin film
6 (manufactured by DuPont) can be used, and any of them can be preferably used.

As the electrodes used in this electrolytic cell, metal electrodes and non-metal electrodes usually used in electrolysis can be used, but platinum electrodes (Pt), platinum, platinum An electrode obtained by coating titanium with iridium oxide (IrO ₂ ) or the like, a nickel (Ni) electrode, or the like, and a nickel electrode, a stainless steel electrode, or the like can be suitably used as the cathode electrode. Note that these anode and cathode electrodes can be used in any shape such as a plate shape, a rod shape, a net shape, and a perforated plate shape.

The temperature conditions during electrolysis in the present invention are 10 to 60 ° C. for both anolyte and catholyte, and a particularly preferred range is 40 to 50 ° C. Current density condition is 0.1
60 A / dm ² , particularly preferred range is 10-30 A / dm ^2.
Is. The concentration of the electrolytic solution is 1 to 60% by weight for the quaternary ammonium organic acid salt and the inorganic acid salt solution of the anolyte, and a particularly preferable range is 40 to 50% by weight. 0.1-40%, especially preferred range is 10-30%. The electrolysis device of the present invention includes two
Chambers and multi-chamber electrolysis devices with three or more chambers can also be used. An electrolysis device having three or more chambers is advantageous for reducing impurities, but the device becomes expensive. This technology is effective in reducing impurities even in two rooms,
A two-chamber electrolyzer, which is advantageous in terms of equipment cost, is suitable. The method of the present invention can be carried out in any of batch, semi-batch and continuous methods.

According to the method of the present invention, an expensive apparatus such as a multi-chamber type electrolysis apparatus is not particularly required, and corrosion of the anode electrode is suppressed to reduce the running cost. It becomes possible to produce a quaternary ammonium hydroxide.

[0014]

EXAMPLES In order to specifically describe the present invention, examples and comparative examples will be described below. The present invention is not limited to these examples.

Examples 1 to 18 Na as a cation exchange membrane
The electrolytic cell was divided into an anode chamber and a cathode chamber using fion-966 (a fluorine-based cation exchange membrane manufactured by DuPont). Examples 1 to 6 are Pt, and Examples 7 to 12 are I as an anode electrode.
rO ₂ , Ni was used in Examples 13 to 18, and Ni was used for all the cathode electrodes. In the anode chamber, 20% by weight of tetramethylammonium formate and weak quaternary ammonium salt shown in Tables 1, 2 and 3 were added and circulated (about 2400 g in total of the charged solution). The values of the added weak quaternary ammonium salt shown in Table 1, Table 2 and Table 3 are the ratio with respect to the total amount of the charged aqueous solution in% by weight. 19% by weight in the cathode chamber
Was circulated (about 2400 g in total of the charged solution), a direct current of 20 A / dm ² was applied, and electrolysis was performed at a temperature of 40 ° C. for 16 hours.
After electrolysis, the permeation amount of catholyte formic acid and the elution amount of the anode electrode were measured. As shown in Table 1, Table 2 and Table 3, by adding a weak quaternary ammonium salt to tetramethylammonium formate and electrolyzing, the permeation amount of formic acid into the catholyte and the elution of the anode Pt, the anode Ir and the anode Ni. The amount became extremely small.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

Examples 19 to 36 The same electrolytic cell as in Examples 1 to 18 was used, and the anode electrodes were Pt in Examples 19 to 24 and Ir in Examples 25 to 30.
0 _2, Example 31 to 36 using the NI, all cathode electrodes with Ni. 20 wt% of triethylmethylammonium formate salt and weak quaternary ammonium salt shown in Table 4, Table 5 and Table 6 were added to the anode chamber and circulated (about 2400 g as a whole of the charged solution). The values of the weakly added quaternary ammonium salt shown in Tables 4, 5, and 6 are the percentages by weight% with respect to the total amount of the charged aqueous solution. In the cathode chamber, a 19 wt% triethylmethylammonium hydroxide aqueous solution was circulated (about 2400 g in total of the charged liquid), and Examples 1 to 18 were used.
Electrolysis was performed under the same conditions as in. After electrolysis, the permeation amount of catholyte formic acid and the elution amount of the anode electrode were measured. As shown in Table 4, Table 5 and Table 6, by adding a quaternary ammonium weak acid salt to triethylmethylammonium formate and electrolyzing, the permeation amount of formic acid into the catholyte and the elution amount of the anode Pt, the anode Ir, and the anode Ni. Became extremely small.

[0020]

[Table 4]

[0021]

[Table 5]

[0022]

[Table 6]

Comparative Examples 1 to 3 Electrolysis was carried out in the same apparatus and conditions as in Examples 1 to 18 except that the weak quaternary ammonium salt was not added during the electrolysis of the tetramethylammonium formate of Examples 1 to 18. After electrolysis, the permeation amount of catholyte formic acid and the elution amount of the anode electrode were measured, and the results are shown in Table 7. An increase in the permeation amount of formic acid into the catholyte and an elution amount of the nickel electrode was observed.

[0024]

[Table 7]

Comparative Examples 4 to 6 Electrolysis was carried out in the same apparatus and conditions as in Examples 19 to 36 except that the weak quaternary ammonium salt was not added during the electrolysis of triethylmethylammonium formate in Examples 19 to 36. After electrolysis, the permeation amount of catholyte formic acid and the elution amount of the anode electrode were measured. The results are shown in Table 8. An increase in the permeation amount of formic acid into the catholyte and an elution amount of the nickel electrode was observed.

[0026]

[Table 8]

[0027]

According to the method of the present invention, a quaternary ammonium hydroxide is produced by electrolyzing a quaternary ammonium salt using an electrolytic cell divided into an anode chamber and a cathode chamber by a cation exchange membrane. In the method described above, a quaternary ammonium weak acid salt is added to the anode and electrolysis is performed while maintaining the pH of the anolyte at 6 to 8, whereby a high-purity quaternary ammonium hydroxide can be produced.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kuniaki Soyasu             3500 Matsuhama-cho, Niigata City, Niigata Prefecture Mitsubishi Gas             Gaku Co., Ltd., Niigata Industrial Co., Ltd. F-term (reference) 4D006 GA17 JA41Z KA33 KD14                       KE15Q KE15R KE16Q KE18Q                       MA13 MC21 MC28 PA10 PB12                 4K021 AC11 BA04 BA06 BB02 BC01                       BC03 DB05 DB06 DB12 DB13                       DB18 DB19 DB21 DB31

Claims (4)

[Claims] 1. A quaternary ammonium salt represented by the following general formula (1): (R _{1 to} R ₄ represent an alkyl group having 1 to 8 carbon atoms. R ₁ to
R ₄ may be the same or different. X represents an organic acid or an inorganic acid. ) In a method for producing a quaternary ammonium hydroxide by electrolyzing using an electrolytic cell divided into an anode chamber and a cathode chamber by a cation exchange membrane, a quaternary ammonium weak acid salt is added to the anode, A method for producing a quaternary ammonium hydroxide, which comprises electrolyzing while maintaining the pH at 6 to 8. 2. A pK of an organic acid or an inorganic acid represented by X.
The method for producing a quaternary ammonium hydroxide according to claim 1, wherein a is smaller than 5, and the pKa of the acid which is a constituent of the weak quaternary ammonium salt is 5 or more. 3. The method for producing a quaternary ammonium hydroxide according to claim 1, wherein the weak quaternary ammonium salt is hydrogen carbonate or carbonate. 4. The method for producing a quaternary ammonium hydroxide according to claim 1, wherein the electrolytic cell comprises two chambers or three or more chambers.