JP3137226B2 - Production method of high purity strontium chloride - Google Patents

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 strontium chloride, and more particularly to a method for producing extremely high-purity strontium chloride excluding impurities.

[0002]

2. Description of the Related Art Strontium chloride is used in semiconductors, phosphors,
It has been conventionally used as an intermediate material for optical lenses and the like. Strontium chloride used in these fields requires high purity. In recent years, in particular, 256M
High-dielectric strontium titanate has attracted attention as a capacitor for memory cells of more than one byte, and when used as a raw material, particularly high purity is required.

In the case of semiconductors, not only transition metals such as Fe, Ni, and Cu, which have a significant effect on device reliability, but also alkali metals such as Na and K are required to have a content of 100 ppb or less. It is necessary to remove the impurities of the raw material to the utmost.

Conventionally, strontium chloride has been purified by dissolving strontium hydroxide or strontium carbonate in hydrochloric acid and concentrating it for crystallization, or by melting strontium carbonate and calcium chloride and extracting and condensing a molten mass with water. Can be When further purification is required, various precipitants, for example, heavy metal is purified by adding hydrogen sulfide and iron to remove bromine by adding bromine, and then repeating concentration crystallization and cooling crystallization. Is still not enough
Further, there is a problem that the process becomes complicated and the cost increases.

On the other hand, as a method for producing strontium titanate, strontium carbonate and titanium oxide are mixed,
After firing at a temperature of 1100 ° C. or higher, a solid phase method of mechanically pulverizing is used. In the solid-phase method, since impurities in the raw materials remain in the product as they are, it is necessary to use high-purity raw materials.In addition, strontium titanate produced in this way cannot avoid the contamination of impurities, and high purity titanic acid cannot be avoided. It is difficult to get strontium. In order to solve this problem, a liquid phase method for producing strontium titanate by solid-liquid separation of a precipitate formed by adding a precipitant to a water-soluble strontium salt and a water-soluble titanium salt, washing and drying, and then firing, Alternatively, a method of producing strontium titanate by firing a crystal obtained by reacting a mixed solution of an oxalic acid solution with a water-soluble strontium salt and a water-soluble titanium salt has been adopted. However, even in these methods, contamination of impurities from the raw material is inevitable, so that it is not always sufficient. Therefore, high purity of the raw material is indispensable, and here, an important method for producing high purity strontium chloride is provided as a raw material for producing the strontium titanate and the like.

[0006]

[Specific means for solving the problem]
As a result of earnestly studying means for solving the above problems,
When the strontium chloride solution is used to precipitate strontium chloride crystals by a recrystallization method using hydrochloric acid, the concentration of hydrochloric acid in the slurry is precipitated in the range of 10 to 25%, and the slurry is further washed with a high-purity liquid 1 to 5 times the weight of the crystals. Thereby, the transition metals Fe, Ni, and Cu are 0.02 ppm or less, the alkali metals Na and K are 0.05 ppm or less, and the alkaline earth metals Ba and Ca are 10 ppm or less. The present inventors have found that strontium chloride crystals of the formula (1) can be obtained, and have reached the present invention.

Hereinafter, this method will be described. As the strontium salt, strontium chloride is used,
Strontium carbonate or strontium hydroxide as an intermediate raw material may be used by dissolving it in hydrochloric acid, and may be in the form of strontium chloride finally.

When the obtained strontium chloride solution and hydrochloric acid solution are mixed, strontium chloride crystals are precipitated by the common ion effect. At this time, the higher the hydrochloric acid concentration of the precipitated slurry, the higher the yield of strontium chloride crystals, but the alkaline earth metal Ba contained in the raw strontium chloride is included in the precipitated crystals and becomes higher than the raw strontium chloride. . However, it has been found that this Ba also decreases when the concentration of hydrochloric acid is reduced to a certain level or less. That is,
When the concentration of hydrochloric acid in the precipitation slurry at the end of the purification is 10 to
Ba can be removed by extracting crystals in the range of 25%.

On the other hand, the purity of the obtained strontium chloride crystal cannot be said to be sufficient as it is, and the high purity strontium chloride can be obtained by washing the crystal with a high purity liquid in an amount of 1 to 5 times the weight of the crystal. Can be

As the high purity liquid, pure water, hydrochloric acid, purified strontium chloride saturated solution, alcohols and the like are used. The type of washing water may be appropriately selected from the viewpoint of yield, price and purity. Further, it is necessary to wash the washing water in an amount of 1 to 5 times by weight of the obtained strontium chloride crystal.
If the amount of washing water is small, sufficiently purified strontium chloride cannot be obtained. On the other hand, if the amount of washing water is further increased, the degree of purification will not be improved, and the yield will decrease and the price will increase due to the use of washing water, which is not economical.

The temperature at the time of precipitation and solid-liquid separation is not particularly limited, but the lower the temperature, the lower the solubility is. As a purification method, a method of adding strontium salt to hydrochloric acid, a method of adding hydrochloric acid to strontium salt, a method of simultaneously adding hydrochloric acid and strontium salt, and the like, can provide high-purity strontium chloride crystals and are limited. Not something.

[0012]

The present invention will be described below in detail with reference to examples. Examples 1-4, Comparative Examples 1 and 2 150 kg of industrial 35% hydrochloric acid solution in a 300 L Teflon tank
After charging, a predetermined amount of a 30% strontium chloride solution was added while stirring to obtain the hydrochloric acid concentration shown in Table 1. Next, after cooling the slurry to 25 ° C., solid-liquid separation was performed using a resin filter, and the crystals were washed with ethanol having the same weight as the obtained crystals. Analysis of this crystal,
The results are shown in Table 1. The analytical values are values converted to 100% strontium chloride.

[0013]

[Table 1]

Examples 5-7, Comparative Examples 3, 4 150 kg of a 35% hydrochloric acid solution for industrial use in a 300 L Teflon tank
After the addition, 90 kg of a 30% strontium chloride solution was added with stirring. Next, the slurry was cooled to 25 ° C.
After cooling, a solid-liquid separation was performed with a resin filter, and a washing test of the obtained crystals was performed using ethanol. The crystals were analyzed, and the results are shown in Table 2. The analytical values are values converted to 100% strontium chloride.

[0015]

[Table 2]

Examples 8 to 10 and Comparative Examples 5 and 6 30% strontium chloride solution 1 in a 300 L Teflon tank
After charging 50 kg, 150 kg of an industrial 35% hydrochloric acid solution was added with stirring. Next, this slurry was added to 25
After cooling to ° C., solid-liquid separation was performed using a resin filter, and a washing test of the obtained crystals was performed using a special grade 35% hydrochloric acid solution of a reagent. The crystals were analyzed, and the results are shown in Table 3. The analytical values are values converted to 100% strontium chloride.

[0017]

[Table 3]

Example 11 After charging 40 kg of pure water and 40 kg of strontium carbonate into a 300 L Teflon tank, 225 kg of industrial 35% hydrochloric acid was added with stirring. Next, the slurry was cooled to 25 ° C.
After that, solid-liquid separation was carried out using a resin filter, and the obtained crystals were washed with a saturated solution of strontium chloride obtained in Example 9 at 1.5 times the weight of the crystals. As a result of analyzing this crystal, Fe, Ni, and Cu were found to be 0.02 pp each.
m, Na and K are each 0.05 ppm or less, Ba, C
a was 7 ppm and 6 ppm, respectively. The analytical values are values converted to 100% strontium chloride.

[0019]

According to the method of the present invention, it has become possible to obtain high-purity strontium chloride having extremely few impurities required in the field of semiconductors and the like.

Continuation of front page (56) References JP-A-61-270215 (JP, A) JP-A-6-343978 (JP, A) JP-A-2-233520 (JP, A) JP-B-46-23491 (JP, A) , B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C01F 11/32 CA (STN)

Claims (2)

(57) [Claims] 1. A method for producing high-purity strontium chloride, comprising purifying strontium chloride with hydrochloric acid by crystallizing the crystallization slurry at a hydrochloric acid concentration of 10 to 25%. 2. A method for producing high-purity strontium chloride, comprising washing the strontium chloride crystal obtained by the method according to claim 1 with a high-purity liquid at least 1 to 5 times the weight of the deposited amount.