JPH0261404B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a completely new method for removing arsenic compounds present as impurities in hydrofluoric acid to obtain purified hydrofluoric acid.

The hydrofluoric acid purified by the method of the present invention is widely used in the electronic material industry and the metal industry, especially as a cleaning agent and engraving agent for silicone.

Among the impurities contained in conventional hydrofluoric acid, it has become clear that arsenic and arsenic compounds, in particular, have a serious negative impact on the production of high-performance semiconductor devices. The demand for hot hydrofluoric acid is increasing.

Well-known methods for purifying hydrofluoric acid include (a) distillation of hydrofluoric acid;
(b) A method of generating hydrogen fluoride gas using specially purified raw materials, (c) A method of removing impurities as an alkali metal salt or alkaline earth metal salt, (d) A method of generating hydrogen fluoride gas in the presence of alkali ions. It depends on the method of adding an oxidizing agent to acid and causing a reaction.
(Refer to Japanese Patent Publication No. 39-5606 and Japanese Patent Publication No. 16407-1983).

Among these methods, method (d) is said to be particularly suitable for obtaining high purity hydrofluoric acid.

However, method (d) usually uses expensive oxidizing agents such as potassium permanganate and potassium dichromate, making it a very uneconomical method when the content of impurities is high. This method is unsuitable as an industrial purification method because it has the fatal disadvantage of contaminating the purified hydrofluoric acid by mixing the drug with it.

The present inventors have conducted numerous studies on methods for removing arsenic compounds from hydrofluoric acid, and as a result,
They have discovered a new method for removing arsenic compounds that is completely different from the known methods mentioned above.

That is, the present inventors added a fluorinated halogen to hydrofluoric acid containing an arsenic compound and reacted with the arsenic compound, and then distilled the raw material hydrofluoric acid to remove the arsenic contained in the raw material. They discovered that the compound changes into an easily removable type of arsenic compound, and that the arsenic content can be completely separated and removed simply by distilling hydrofluoric acid.

Halogen fluoride is represented by the general formula XF _2o+1 .
In the formula, X represents either chlorine, bromine, or iodine, and F
represents fluorine, and n takes a value of 0, 1, 2, or 3.

A specific compound is represented by the following molecular formula.

Fluorinated chlorine compounds: ClF, ClF ₃ , ClF ₅ Fluorinated bromine compounds: BrF, BrF ₃ , BrF ₅ BrF ₇ Fluorinated iodine compounds: IF, IF ₃ , IF ₅ , IF ₇ These compounds can be used alone or in mixtures. actually used in the form of

The removal effect of arsenic compounds by fluorinated halogens is thought to be due to F in fluorinated halogens converting arsenic compounds in hydrofluoric acid into arsenic pentafluoride or high boiling point refractory arsenic compounds such as polyfluoroarzenic acid. However, it is currently difficult to provide a detailed theoretical explanation of the reaction mechanism.

Due to the strong oxidizing action of halogen fluoride, arsenic is first oxidized to arsenic pentafluoride. Since this compound has a lower boiling point than hydrofluoric acid, under appropriate conditions it can be distilled together with hydrogen halides other than hydrogen fluoride or halogen gas to a lower boiling point than hydrofluoric acid. What is more important is that when arsenic compounds migrate to high-boiling compounds, they will definitely remain as residue in the pot as polyfluoroarzenic acid, and the hydrogen fluoride that will be distilled will be distilled. The fact is that the acid fraction contains almost no arsenic.

Based on analytical experiments, the present inventor has found that a hitherto unknown high boiling point compound (e.g. polyfluoroarzenic acid) is smoothly produced by the reaction of a fluorinated halogen and an arsenic compound, and also They discovered that halogen compounds can be effectively separated from hydrofluoric acid and completed the present invention.

The action of removing arsenic compounds by the halogen fluoride is much more effective than originally anticipated by the inventors due to the strong oxidizing action of the halogen fluoride.

In conventional methods, the amount of processing agent used is the raw material.
100ppm for potassium permanganate to HF
~10,000ppm, and in the case of hydrogen peroxide, a very large amount of 9,000ppm is required.

In the case of using halogen fluoride according to the method of the present invention, the effect is sufficiently exhibited at a concentration of 100 ppm or less, preferably 10 ppm to 100 ppm, based on the raw material HF.

The amount of fluorinated halogen to be added in the method of the present invention is approximately 50 ppm to 100 ppm to achieve a sufficient effect when the arsenic concentration in the raw material hydrofluoric acid is several ppm to several tens of ppm. In addition to arsenic compounds, hydrohydric acid generally contains oxidizable sulfur compounds, phosphorus compounds, and antimony compounds as impurities, and since these impurities also consume halogen fluoride, the amount of these present must be measured. Naturally, the amount of fluorinated halogen must be adjusted accordingly.

The method of the present invention can be applied to a wide range of hydrofluoric acids ranging from aqueous solutions of hydrofluoric acid to anhydrous hydrofluoric acid; however, the halogen fluoride reacts with moisture and is partially consumed. It is preferable that the amount of water is as low as possible, and the amount added must be increased depending on the amount of water.

Many experimental results show that the method of the present invention can be achieved very rationally and economically when applied to hydrofluoric anhydride with a water content of 3% or less, and has excellent industrial value.

The form of the fluorinated halogen used in the method of the present invention may be gaseous, liquid, or solid depending on the physical properties of the compound, and may be in the form of a hydrofluoric acid solution, a chlorine solution, or a bromine solution. It may also be used in this form.

Of course, the fluorinated halogen used in the present invention may be used alone or in a mixture of two or more, or may be in the form of a mixture with halogen (F ₂ , Cl ₂ , Br ₂ , I ₂ ).

Generally, among the fluorinated halogens, ClF ₃ , BrF ₃ , BrF ₅ , and IF ₅ , which are liquid at around room temperature, are stored.
It is particularly easy to handle for measuring, preparing, etc., and gaseous forms are also easy to use.

In the method of the present invention, the reaction between the halogen fluoride and the arsenic compound is not limited to temperature or pressure, but since it proceeds rapidly even at room temperature and pressure, no special conditions or equipment are required. Preferably, the reaction is carried out at the following temperatures: 10-20°C.

The method for distilling hydrofluoric acid of the present invention can achieve more satisfactory results if a batch distillation purification method or a continuous distillation purification method is employed and an efficient fractionation column is attached.

The present inventors conducted a large number of experiments regarding the method of the present invention and confirmed the superiority of the present invention, but it would be too complicated to list all of the experimental examples, so we will select only a few from among the numerous experimental examples. will be extracted and shown below as Example 1.

Therefore, the method of the present invention should not be construed as being limited to the examples shown below, but may be carried out by arbitrarily changing the embodiments without departing from the spirit and spirit of the present invention. Of course it can be done.

Example 1 In a poly(trifluorochloroethylene) container (capacity 1) equipped with a reflux condenser and a distillation tube,
Add 800g of hydrofluoric acid (HF99.9% AS 10ppm) and add chlorine trifluoride (ClF ₃ ) to the raw HF.
Add so that F in _ClF3 becomes 80ppm and
After reacting by boiling for 6 hours, the container was further heated to fractionally distill the hydrofluoric acid to obtain purified hydrofluoric acid.

When the arsenic content of this purified hydrofluoric acid was measured, it was 0.001 ppm or less, and it was found to be useful as hydrofluoric acid for electronic materials.

Example 2 Using the same equipment as in Example 1, put 800 g of hydrofluoric acid (HF99.9% As14 ppm) into a container, and add bromine trifluoride (BrF ₃ ) to the raw material HF so that the F in BrF ₃ was 100 ppm. Add it and pressurize it slightly.
After reacting at 30°C for 2 hours, the hydrofluoric acid was distilled to obtain purified hydrofluoric acid. When the arsenic content of this purified hydrofluoric acid was measured, it was less than 0.001 ppm, and it was found to be useful as hydrofluoric acid for electronic materials.

Example 3 Using the same equipment as in Example 1, 800 g of hydrofluoric acid (HF99.8% As8ppm) was placed in a container, and iodine pentafluoride (IF ₅ ) was added to the raw material HF to increase the amount of F in IF ₅ .
After adding the solution to a concentration of 75 ppm and allowing it to react overnight at 15°C, the hydrofluoric acid was distilled to obtain purified hydrofluoric acid. When the arsenic content of this purified hydrofluoric acid was measured, it was less than 0.001 ppm, and it was found to be useful as hydrofluoric acid for electronic materials.

Example 4 Using the same equipment as in Example 1, put 800 g of hydrofluoric acid (HF99.9% As10ppm) into a container, and react equimolar amounts of chlorine gas and fluorine gas to obtain gaseous fluorine monochloride. (ClF) was blown into the raw material HF so that the F content in ClF was 80 ppm, and the mixture was left to react overnight. Hydrofluoric acid was then distilled to obtain purified hydrofluoric acid.

When the arsenic content of this purified hydrofluoric acid was measured, it was less than 0.001 ppm, and it was found to be useful as hydrofluoric acid for electronic materials.

Example 5 Using the same equipment as in Example 1, 800 g of hydrofluoric acid (HF99.8% As9ppm) was placed in a container, and liquid bromine trifluoride was cooled to obtain solid bromine trifluoride ( BrF ₃ ) to the raw material HF, F in BrF ₃ is
After adding the mixture to a concentration of 70 to 80 ppm and reacting by boiling for 3 hours, the hydrofluoric acid was distilled to obtain purified hydrofluoric acid. The arsenic content of this purified hydrofluoric acid was measured to be less than 0.001 ppm, and it was found to be useful as hydrofluoric acid for electronic materials.

Example 6 Using the same equipment as in Example 1, 800 g of hydrofluoric acid (HF97.5% As7ppm, _H2O2.45 %) was placed in a container, and chlorine trifluoride ( _ClF3 ) was added to the raw material HF.
After adding F in _ClF3 to 100 to 150 ppm and allowing it to react overnight, hydrofluoric acid was distilled to obtain purified hydrofluoric acid. The arsenic content of this purified hydrofluoric acid was measured.
It was 0.001 ppm or less, and was useful as hydrofluoric acid for electronic materials.

Example 7 Poly(trifluorochloroethylene) container (capacity 1) equipped with a condensing reflux device and a distillation tube
In addition, liquid bromine trifluoride (BrF ₃ ) is the raw material for HF.
Hydrofluoric acid (HF99.8%) added to 75-100 ppm as F in _BrF3
As8ppm) was continuously charged at a feed rate of 200g/hour, heated and rectified.

The arsenic content of purified hydrofluoric acid obtained by continuous operation for 8 hours using this method was measured to be 0.001 ppm.
It was found to be useful as hydrofluoric acid for electronic materials.

Example 8 800 g of anhydrous hydrofluoric acid (HF 99.9%, As 10 ppm) was placed in a stainless steel container (1), and 10 g of chlorine pentafluoride (ClF ₅ , bp-13.1°C) was blown into it. Next, this solution was transferred to the distillation apparatus used in Example 1, and rectified under the same conditions as in Example 1 to obtain purified hydrofluoric acid.

When the arsenic content of this purified hydrofluoric acid was measured, it was less than 0.001 ppm.

Example 9 Put 800g of anhydrous hydrofluoric acid (HF99.8%, As10ppm) into a stainless steel container (1), add 1g of bromine fluoride (BrF, bp20℃), and heat at 10℃.
I left it for 2 hours. This solution was then used in Example 1.
The mixture was transferred to the distillation apparatus used in Example 1 and rectified under the same conditions as in Example 1 to obtain 700 g of purified hydrofluoric acid.

When the arsenic content of this purified hydrofluoric acid was measured, it was 0.001 ppm or less.

Example 10 Using the same equipment as in Example 1, 800 g of anhydrous hydrofluoric acid (HF99.9%, As8ppm) was placed in a container, and 0.5 g of bromine pentafluoride (BrF ₅ , bp40.5°C) was added to this. After total reflux for 3 hours, purified hydrofluoric acid was taken out.

When the arsenic content of this purified hydrofluoric acid was measured, it was 0.001 ppm or less.

Example 11 Put 800g of anhydrous hydrofluoric acid (HF99.8%, As10ppm) into a stainless steel container (1), add 1g of iodine heptafluoride ( _IF7 , bp55℃),
It was left at 0°C overnight. Next, this solution was transferred to the distillation apparatus used in Example 1, and rectified under the same conditions as in Example 1 to obtain purified hydrofluoric acid.

When the arsenic content of this purified hydrofluoric acid was measured, it was 0.001 ppm or less.

Claims (1)

[Claims] 1 General formula XF _2o+1 (wherein, X represents chlorine, bromine, or iodine;
n indicates a value of 0, 1, 2 or 3)
At least one fluorinated halogen selected from the group of compounds represented by is added to hydrofluoric acid containing an arsenic compound to react with the arsenic compound, and then the hydrofluoric acid is distilled. Method for purifying hydrofluoric acid.