JP2000239008A - Production of highly pure phosphoric acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a highly pure phosphoric acid having a low content of impurity metals by hydrating purified phosphorus oxychloride by adding pure water thereto, and concentrating the obtained hydrated product. SOLUTION: Phosphorus oxychloride is purified by distillation to provide a phosphorus oxychloride having <=10 ppb impurity metal content. The obtained phosphorus oxychloride is fed to a reactor vessel made of a fluororesin, and heated to 10-110 deg.C. Pure water is added to the heated phosphorus oxychloride in the mixing ratio regulated so that the concentration of the reactant may be 5-74 wt.%, and the obtained mixture is hydrated at a temp. of 10-110 deg.C for 30-180 min to provide the hydrated product. The hydrated product is concentrated under a reduced pressure of 5-50 mmHg at a temp. of 60-110 deg.C to remove hydrogen chloride generated by the hydration together with the water to provide the objective phosphoric acid having <=10 ppb content of the impurity metals. Preferably, the reactor vessel made of the fluororesin can be the one in which at least a surface contacting with the aqueous solution of the phosphorus oxychloride to be hydrated is made of the fluororesin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-purity phosphoric acid which can be used as a raw material of a detergent in a semiconductor device manufacturing process, a liquid crystal device manufacturing process, and the like.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process and a liquid crystal device manufacturing process, a cleaning agent is used to remove impurities on the surface of a semiconductor, metal, or glass. I have. As such a cleaning agent, a strong acid such as hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid, a strong alkali such as caustic soda, ammonia, hydrazine, and hydroxylamine, ammonium fluoride, an alkanolamine, and an organic solvent are used. However, the use of these has problems such as work safety and environmental pollution, and a new cleaning agent which is safe and free from environmental pollution is required.

As such a detergent, a detergent using phosphoric acid and urea has been studied. For example, a polyphosphoric acid-urea condensate or a phosphoric acid-urea polymer which is a reaction product of orthophosphoric acid and urea has been studied. A cleaning agent containing as an active ingredient has been studied. Naturally, such a cleaning agent is required to have a high purity. For example, when used for cleaning semiconductors, the impurity metal is required to be 10 ppb or less.

As high-purity phosphoric acid, so-called EE phosphoric acid, which is obtained by purifying a raw material yellow phosphorus and hydrolyzing the purified yellow phosphorus, is known. Content of impurity metal is 100
It was at a level of ppb or less, and could be used only as a cleaning agent for semiconductors for quite limited applications.

[0005] JP-A-55-47212 and JP-A-55-167113 disclose a method for producing high-purity phosphoric acid as a glass raw material for optical fibers. In the methods disclosed in these publications, high-purity phosphoric acid is produced by introducing gaseous phosphorus oxychloride together with a carrier gas into pure water and hydrolyzing the phosphorus oxychloride. However, even with such a method, it has been difficult to obtain phosphoric acid having a high purity, for example, having an impurity metal of 10 ppb or less.

An object of the present invention is to provide a production method capable of producing high-purity phosphoric acid having, for example, an impurity metal content of 10 ppb or less.

[0007]

According to the present invention, there is provided a method for purifying phosphorus oxychloride by distillation, adding the purified water to pure water, hydrolyzing the purified water in a resin reaction vessel, and concentrating the hydrolysis product. A method for producing high-purity phosphoric acid, characterized in that:

In the present invention, as the resin used in the resin-made reaction vessel, a resin which does not react upon contact with phosphorus oxychloride, hydrochloric acid, phosphoric acid or water can be used, and a fluorine resin is preferably used. Therefore, as the resin-made reaction vessel in the present invention, a fluororesin-made reaction vessel is preferably used.

Examples of the fluorine resin include tetrafluoroethylene resin (PTFE), ethylene tetrafluoride-propylene hexafluoride copolymer resin (FEP), ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer resin (PFA), Examples thereof include a fluorinated ethylene-ethylene copolymer resin (ETFE), an ethylene trifluoride chloride resin (PCTFE), and a vinylidene fluoride resin (PVDF). The used tetrafluoroethylene resin (PTFE) is preferably used.

In the present invention, the hydrolysis product is preferably concentrated under reduced pressure. By concentrating under reduced pressure, the residual amount of hydrogen chloride (HCl) generated by hydrolysis can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, phosphorus oxychloride is first purified by distillation. The boiling point of phosphorus oxychloride is 10
Since it is 7.2 ° C, it can be distilled at normal pressure,
Vacuum distillation may be performed if necessary. In the case of producing phosphoric acid having a content of an impurity metal of 10 ppb or less as high-purity phosphoric acid, the content of the impurity metal of the purified phosphorus oxychloride after distillation is preferably 10 ppb or less.

Next, in the present invention, phosphorus oxychloride purified by distillation is added to pure water and hydrolyzed in a resin-made reaction vessel. Pure water is preferably high-purity water. When producing high-purity phosphoric acid having an impurity metal of 10 ppb or less, it is necessary that the impurity metal be pure water of 10 ppb or less. The mixing ratio of pure water and phosphorus oxychloride is preferably such that the concentration of the reaction substrate is about 5 to 74% by weight. Also, put pure water in the reaction vessel,
The temperature for introducing phosphorus oxychloride into pure water in a reaction vessel is preferably about 10 to 110 ° C. The introduction time is preferably from 10 to 360 minutes.

The reaction temperature during the hydrolysis in the reaction vessel is preferably about 10 to 110 ° C., and the reaction time is preferably about 30 to 180 minutes. In general, when the concentration of the reaction substrate, that is, the concentration of phosphorus oxychloride is low, hydrolysis proceeds rapidly at a low temperature, and when the concentration of phosphorus oxychloride is high, a high temperature is required. For example, when the concentration of phosphorus oxychloride is 20% by weight, a reaction at 20 ° C. for about 2 hours is required. In the case of 50% by weight, the reaction is performed at 90 ° C. for about 2 hours, and in the case of 74% by weight, the reaction is required at 110 ° C. for about 1 hour.

In the present invention, phosphorus oxychloride is hydrolyzed in a reaction vessel made of resin. By hydrolyzing in a resin-made reaction vessel, high-purity phosphoric acid can be obtained. The resin-made reaction vessel used in the present invention may be any as long as the surface in contact with the aqueous solution of phosphorus oxychloride to be hydrolyzed is formed at least from a resin. For example, when a surface in contact with an aqueous solution of phosphorus oxychloride is hydrolyzed in a reaction vessel formed of glass lining, impurity metals are eluted from the glass lining, and high-purity phosphoric acid as in the present invention cannot be obtained.

In the present invention, after the hydrolysis, the hydrolysis product is concentrated to remove hydrogen chloride and water generated by the hydrolysis. When concentrating at 150 ° C. under normal pressure, for example, about 0.2% of hydrochloric acid may remain. Therefore,
In the present invention, concentration is preferably performed under reduced pressure. The conditions for the concentration under reduced pressure are not particularly limited.
A temperature range of about 60 to 110 ° C. under a reduced pressure of about 50 mmHg can be exemplified. For example, 20 mmHg
At 90 ° C. under reduced pressure, 94% by weight of phosphoric acid is obtained, and the concentration of residual hydrochloric acid is 2.5 ppm or less.

[0016]

The present invention will be described below in more detail with reference to examples. The metal analysis was performed using an ICP (inductively coupled high frequency plasma) mass spectrometer [SPQ9000 (manufactured by Seiko Instruments Inc.)].

[Purification of phosphorus oxychloride] A commercially available phosphorus oxychloride was charged into a distillation apparatus manufactured by Pyrex and distilled under normal pressure, and a fraction having a boiling point of 107.2 ° C was collected. The analysis results of typical metals of the obtained purified phosphorus oxychloride are as follows. Al: 0 ppb Na: 1 ppb Fe: 3 ppb Ca: 1 ppb Ni: 1 ppb

[Hydrolysis of Phosphorus Oxychloride] (Example 1) 150 g of pure water was placed in a reaction vessel made of PTFE, and 150 g of the above-mentioned phosphorus oxychloride purified by distillation was cooled to 20 to 20 in an ice bath. It was introduced into pure water at 90 ° C. for 1 hour. After the introduction, the temperature was raised to 90 ° C., and the temperature was maintained at the same temperature for 2 hours to carry out hydrolysis to complete the reaction. 20mm after reaction
The pressure was reduced to Hg, and the mixture was concentrated under reduced pressure at a temperature of 90 ° C. to remove hydrogen chloride and water generated in the hydrolysis reaction, thereby obtaining 101.9 g of 94% by weight phosphoric acid (100% yield).

Example 2 150 g of pure water was placed in a PTFE reaction vessel, and the phosphorus oxychloride 3 purified by distillation was used.
While cooling in an ice bath, 7.5 g was added at 20 to 70 ° C. for 1 hour.
It was introduced into pure water over time. After the introduction, the mixture was kept at 20 to 30 ° C. for 2 hours to complete the hydrolysis reaction. It was concentrated under reduced pressure in the same manner as in Example 1 to obtain 25.5 g (yield 100%) of 94% by weight phosphoric acid.

Example 3 100 g of pure water was placed in a PTFE reaction vessel, and the phosphorus oxychloride 28 purified by distillation was used.
While cooling in an ice bath, 0 g was introduced into pure water at 20 to 80 ° C. over 3 hours. After the introduction, the temperature was raised to 110 ° C,
The hydrolysis was completed by maintaining the same temperature for 1 hour. The mixture was concentrated under reduced pressure in the same manner as in Example 1 to obtain 94% by weight phosphoric acid 19
0.2 g (100% yield) was obtained.

Comparative Example A hydrolysis reaction and concentration under reduced pressure were carried out in the same manner as in Example 1 by using a Pyrex reaction vessel instead of a PTFE reaction vessel, and 101.9 g of 94% by weight phosphoric acid was obtained (yield: 100). %).

Table 1 shows the results of analysis of representative metals in phosphoric acid obtained in Examples 1 to 3 and Comparative Example. Also,
Table 1 also shows the results of metal analysis of EE phosphoric acid, which is a commercially available high-purity phosphoric acid.

[0023]

[Table 1]

As is evident from the results in Table 1, the high-purity phosphoric acid produced according to the present invention has a very high purity, with the content of each impurity metal being 10 ppb or less. .

Although the high-purity phosphoric acid obtained in Examples 1 to 3 has a high concentration of 94% by weight, it can be used after being diluted to an appropriate concentration with pure water, if necessary. .

[0026]

According to the present invention, for example, phosphoric acid having a very high purity such that the content of an impurity metal is 10 ppb or less can be produced by a simple process.

Accordingly, it is possible to produce high-purity phosphoric acid useful as a raw material of a cleaning agent used in a semiconductor device manufacturing process, a liquid crystal device manufacturing process, and the like.

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[Procedure amendment]

[Submission date] February 4, 2000 (200.2.4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

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[Claims]

2. The method for producing high-purity phosphoric acid according to claim 1, wherein the hydrolysis product is concentrated under reduced pressure.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

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[0007]

According to the present invention, phosphorus oxychloride is purified by distillation, added to pure water, hydrolyzed in a fluorine resin reaction vessel, and then the hydrolysis product is concentrated. This is a method for producing high-purity phosphoric acid.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

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[0008] In the present invention, the resin used in the anti-reaction container unit, full fluororesin is used.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

Next, in the present invention, phosphorus oxychloride purified by distillation is added to pure water and hydrolyzed in a fluorine resin reaction vessel. Pure water is preferably high-purity water. When producing high-purity phosphoric acid having an impurity metal of 10 ppb or less, it is necessary that the impurity metal be pure water of 10 ppb or less. The mixing ratio of pure water and phosphorus oxychloride is preferably such that the concentration of the reaction substrate is about 5 to 74% by weight. Further, pure water is put in the reaction vessel, and the introduction temperature when introducing phosphorus oxychloride into the pure water in the reaction vessel is preferably about 10 to 110 ° C. The introduction time is preferably from 10 to 360 minutes.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

In the present invention, phosphorus oxychloride is hydrolyzed in a reaction vessel made of a fluororesin . High-purity phosphoric acid can be obtained by hydrolysis in a reaction vessel made of a fluororesin . The fluorine resin reaction vessel used in the present invention may be any one provided that the surface in contact with the aqueous solution of phosphorous oxychloride to be hydrolyzed is formed at least from a fluorine resin. For example, when the surface in contact with the aqueous solution of phosphorus oxychloride is hydrolyzed in a reaction vessel formed of glass lining, impurity metals are eluted from the glass lining, and high-purity phosphoric acid as in the present invention cannot be obtained.

Claims (3)

[Claims] 1. A high-purity phosphoric acid comprising purifying phosphorus oxychloride by distillation, adding the purified water to pure water, hydrolyzing it in a resin-made reaction vessel, and concentrating the hydrolysis product. Manufacturing method. 2. The method for producing high-purity phosphoric acid according to claim 1, wherein the reaction vessel made of a resin is a reaction vessel made of a fluororesin. 3. The method for producing high-purity phosphoric acid according to claim 1, wherein the hydrolysis product is concentrated under reduced pressure.