JPH03137003A - Production of high-purity metal fluoride - Google Patents

Abstract

PURPOSE:To improve purity by calcining the metal fluoride of alkaline and alkaline earth metals, lanthanide metals and >= 1 kinds selected from Zr, Hf, Y, In, and Al in the presence of a gaseous mixture composed of a fluorinating agent and O2. CONSTITUTION:The soluble salts, such as sulfates of the alkaline and alkaline earth metals, the lanthanide metals and >=1 kinds of the metals selected from Zr, Hf, Y, In, and Al are dissolved in water and are adjusted to 1 to 11 pH. The fluorinating agent, such as HF, is then added to the refined liquid prepd. by adding a chelate agent, such as diethyl dithiocarbamate, to this aq. soln. and filtering away the formed insoluble matter. This liquid is concentrated by heating to form the metal fluoride. After the metal fluoride is sufficiently dried, the metal fluoride is calcined at 300 to 700 deg.C while the gaseous mixture composed of the fluorinating agent of 1 to 50% concn. in the gas and the O2 of 1 to 50% similar concn. is passed therethrough. The high-purity metal fluoride is thus obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing high-purity metal fluoride useful as a raw material for fluoride optical fibers, etc., and in particular to a method for producing a high-purity metal fluoride that is useful as a raw material for fluoride optical fibers. The present invention relates to a method for producing a chemical compound.

[Prior art] Iron, copper, nickel,
Included are transition metals such as cobalt and oxygen. Conventionally, in order to obtain metal fluorides with less transition metal impurities, they are generally purified by solvent extraction or ion exchange methods and then fluorinated, but in order to reduce the oxygen content, metal fluorides The dehydration and calcination are carried out in an inert gas atmosphere such as nitrogen or argon by introducing hydrogen fluoride gas. These metal fluorides are contaminated with organic substances originating from raw materials or from reagents, solvents, ion exchange resins, etc. during the purification process, but in such an inert atmosphere carbon desorption does not occur sufficiently and the fired metal The fluoride will contain carbon. When fiberization is performed using carbon-containing metal fluoride,
This is not desirable as it causes scattering.

[Means for Solving the Problems] In view of the current situation, the present inventors have conducted intensive studies and have unexpectedly discovered that metal fluorides of extremely high purity can be obtained by treatment in a system in the presence of oxygen. We have arrived at the present invention. That is, the present invention provides a fluoride of at least one metal selected from alkali metals, alkaline earth metals, lanthanide metals, zirconium, hafnium, yttrium, indium, and aluminum while flowing a mixed gas of a fluorinating agent and oxygen to This is a method for producing high-purity metal fluoride, characterized by processing at 700°C. “The method for producing metal fluoride, which is the raw material of the present invention, is not particularly limited, but
The method of No. 5715 is preferred. That is, the pH of the soluble salt aqueous solution of the metal is maintained at 1.0 to 11, and diethyldithiocarbamate (DDTC) or ammonium pyrrolidine dithiocarbamate (APDC) is added in an amount of 0.005% or more by weight based on the raw material compound. In this method, the precipitate formed is removed by filtration. Here, as the raw metal soluble salt, sulfate, hydroxide, carbonate, bicarbonate, chloride, nitrate, acid chloride, etc. are used. Alkali metals include Li, Na, and K, alkaline earth metals include Ca5Ba, Mg, and Be, and lanthanide metals include La and Nb.

As the diethyldithiocarbamate of Gd, Tb, Yb, sodium salt, potassium salt, ammonium salt, etc. are used, respectively.

As the aqueous solution of the above metal to which DDTC or APDC is added as a chelating agent, not only a soluble aqueous solution but also a solution in which an insoluble compound such as an oxide is dissolved with an acid to form a soluble salt and then the pH is adjusted can be used. can do.

The pH range at which the chelating agent is added is preferably maintained at 1.0 to 11. Outside this range, transition metal precipitation will not be sufficiently generated, resulting in insufficient purification. The high-purity solution obtained in this way is used for fluorination, and the fluorination agents used include hydrofluoric acid, hydrogen fluoride gas, ammonium fluoride, acidic ammonium fluoride, fluorine gas, and halogenated fluorine. , nitrogen trifluoride, and the like.

The soluble salts of metals used in the present invention often produce water-insoluble fluorides, but after the addition of a soluble fluorinating agent, the liquid is concentrated to precipitate the fluorides. However, it is also possible to add a fluorinating agent during the concentration process and perform the reaction and concentration at the same time. Alternatively, fluoride can be produced by first concentrating to precipitate soluble salts, separating and drying, and then reacting with a gaseous fluorinating agent. The metal fluoride thus obtained may be subjected to other purification methods.

In the present invention, the metal fluoride produced in this way is further processed to extremely reduce the amount of oxygen and carbon, and after being thoroughly dried, the metal fluoride is treated while flowing a mixed gas of a fluorinating agent and oxygen. Fire in the range of 300-700"C.

Examples of the fluorinating agent include hydrogen fluoride, fluorine, nitrogen trifluoride, and halogenated fluorine gas. Among these, hydrogen fluoride is most preferred from the viewpoint of ease of handling, material quality, etc. The concentration of this fluorinating agent is preferably in the range of 1 to 50% in terms of concentration in the gas, and if it is less than this range, oxygen cannot be removed sufficiently.

Moreover, if it exceeds this range, carbon cannot be sufficiently scattered. The concentration of oxygen is preferably in the range of 1 to 50%,
If it is less than this range, carbon cannot be sufficiently scattered, and if it exceeds this range, the oxygen content will increase. The firing temperature is preferably in the range of 300 to 700°C; below this range, oxygen removal will not be sufficient, and above this range, the oxygen content will be high.

The present invention will be specifically explained below using examples.

Example 1 100g of commercially available reagent aluminum chloride, anhydrous salt was added to 2! Pour into a beaker, add 11% of ultrapure water to dissolve and adjust the pH, and then add 0% of ammonium pyrrolidine dithiocarbamate.
5 g was added, and the liquid was transferred to a separating funnel and extracted with chloroform. Hydrofluoric acid was added to this purified II, and the mixture was heated and concentrated to obtain crystals of aluminum fluoride trihydrate. After filtering the crystals, dry them in a drying oven made of tetrafluoroethylene resin, place the dried product in a platinum dish, and use a platinum furnace tube to flow high-purity air and hydrogen fluoride gas at 0.542/min each. The aluminum fluoride was then calcined at 600'C for 2 hours to obtain high purity aluminum fluoride. The results of this analysis are shown in Table 1.

Fruit Example 2 500 g of commercially available reagent zirconium acid chloride was placed in a 51 beaker, and ultrapure water was added to dissolve it to bring the total amount to 51. This 1 g liquid was passed through a membrane filter (pore size: 0.2 μm) to remove insoluble impurities.

Next, an O column with an inner diameter of 26 mm and a length of 500 mm was filled with a cation exchange resin to a height of 300 mm, and the mouth filtrate was passed through the column at a rate of 11 ml/cm/min. Aqueous ammonia was added to the ion-exchange purified liquid to form a hydroxide, which was passed through the mouth, hydrofluoric acid was added, and the mixture was concentrated by heating to obtain trihydrate crystals of zirconium fluoride. This crystal was placed in a platinum dish and fired at 500°C for 2 hours using a platinum furnace tube while flowing high-purity air at 11/min and hydrofluoric acid gas at 0.5β/min to obtain high-purity zirconium fluoride. . The results of this analysis are shown in Table 1.

Comparative Examples 1 to 4 Comparative Example 1) was conducted in the same manner as Example 1 except that hydrofluoric acid gas was not passed during firing. The same procedure as in Example 1 was carried out except that high-purity air was not circulated during firing (Comparative Example 2). The same procedure as Example 2 was carried out except that hydrofluoric acid gas was not passed during firing (Comparative Example 3).

The same procedure as Example 2 was carried out except that high-purity air was not circulated during firing (Comparative Example 4). The results of these analyzes are shown in Table 1.

[Effects of the Invention] According to the method of the present invention, it is possible to efficiently obtain a high-purity metal fluoride that is a raw material for optical fibers, etc., and in particular, it is possible to obtain a metal fluoride that is extremely low in oxygen and carbon. .

Claims (1)

[Claims] Alkali metals, alkaline earth metals, lanthanide metals, zirconium, hafnium, yttrium, indium,
A method for producing a high-purity metal fluoride, which comprises treating a fluoride of at least one metal selected from aluminum at 300 to 700°C while flowing a mixed gas of a fluorinating agent and oxygen.