JPS63134502A - Sublimation purification of inorganic fluoride - Google Patents

Abstract

PURPOSE:To effect remarkable sublimation and removal of impurity metals from objective inorganic fluoride salts containing impurity metal compounds, without melting the inorganic fluoride, by carrying out sublimation purification while keeping large vapor-pressure difference between the inorganic fluoride and the impurity metal. CONSTITUTION:When the objective inorganic fluoride has high vapor pressure than the impurity metal fluoride, the fluoride is heat-treated in the presence of a metal oxide or water in the metal fluoride or in the treating atmosphere to convert the impurity metal fluoride to nonvolatile metal oxide and the objective fluoride is sublimed. When the inorganic fluoride has lower vapor pressure than the impurity metal fluoride, the amount of the metal oxide or water in the raw metal fluoride or in the treating atmosphere is reduced beforehand and the fluoride is heat-treated to effect sublimation and removal of the impurity metal while preventing the conversion of the impurity metal fluoride to nonvolatile metal oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in sublimation purification technology for efficiently separating and removing metal impurities in inorganic fluoride salts.

[Prior art and problems to be solved by the invention] With the advancement of electronics and optoelectronics, fluoride salts have become highly refined as raw materials, and as raw materials for wide light transmittance glasses, single crystals, and polycrystals. The demand for fluoride salts is increasing. Also, many possibilities regarding its uses, effects, properties, etc. have been reported.

However, on the other hand, it cannot be said that these materials are produced and supplied using economical methods that can be mass-produced to meet various uses. Although there are many examples of transition elements that are considered to be inconvenient for applications, there are few commercially available fluoride salts with an iron content of 1 ppm or less other than those produced by melt-refining.ZrPe-
BaFt-based fluoride glass is 10-" to 10-' d
A low loss of B/km is expected, but the maximum permissible iron content is reported to be 0.36 ppb.

However, in the case of fluoride salts, usually at the stage of selecting raw materials for fluoride synthesis, purified products with fewer undesirable metal components are selected, or wet purification processes such as extraction with aqueous fluoride solutions, single crystals, and ion exchange are used. In order to obtain the final purified fluoride, further steps such as synthesis or separation of undesirable components are required, and contamination with undesirable metal components is expected. At the same time, hydrolysis tends to occur and the purity of the fluoride is likely to decrease. Therefore, even if such a method is used to synthesize crude fluoride salts, it is recommended to use a dry purification process in the final stage. desirable.

Such dry refining processes include melt refining technology (Bridgeman method, Czochralski method, zone melting method), sublimation refining technology (JP-A-60-11239, JP-A-60-3636).
No. 4) etc. have been reported.

In the former case, fluoride melts are generally corrosive at high temperatures, and there are restrictions on the availability of corrosion-resistant materials; fluorides are generally difficult to apply because they have high vapor pressure near their melting point and contain many sublimable compounds; and mass production is difficult. There are also problems in that it is difficult to achieve an economical purification method due to its difficulty, and it is hardly applicable to multi-component fluoride systems containing two or more components.

On the other hand, in the latter case, for example, ZrPa+ AeFs+ H
fF*.

Impurities for fluorides such as CuFtFeF, Pe
When the product and impurities exhibit similar vapor pressure characteristics like F3, there is a problem that the degree of separation and purification also decreases.

As described above, it is clear that there is a need for an economical method that can be mass-produced in the purification of inorganic fluoride to remove impurity metals.

The purpose of the present invention is to further improve the superiority of sublimation refining technology in which the target inorganic fluoride is purified in a solid-gas system without melting by sublimating or non-volatile impurity metal components. It is.

[Means and effects for solving the problem] The present invention aims to increase the vapor pressure difference between target inorganic fluoride salts and impurity metal compounds contained in them during sublimation purification, thereby reducing impurity metals. This is an improved method of sublimation purification technology that attempts to efficiently separate and remove impurity metals. When removing the metal fluoride, the impurity metal fluoride is converted into a non-volatile metal oxide and the target fluoride is sublimated by treating the raw metal fluoride with metal oxide or water in advance or in the processing atmosphere. It has been found that impurity metals can be removed to a large extent by doing so.

In addition, when heat-treating an inorganic fluoride that has a lower vapor pressure than the impurity metal fluoride and separating and removing the impurity metal contained in the solid-gas system, it is possible to remove the metal oxide or It has been found that by reducing the amount of water and performing heat treatment without converting impurity metal fluorides into non-volatile metal oxides, impurity metals can be largely removed by sublimation.

These facts indicate that the similar ionic radii of the 08-anion and the F-anion indicate that a considerable portion of the normally solid inorganic fluoride is replaced by oxide, which is greatly affected during sublimation purification. ing.

In the present invention, metal oxides include oxygen-containing salts such as hydroxides, carbonates, sulfates, nitrates, and various hydrated salts that can decompose or react to form oxides during pretreatment or at high temperatures during sublimation purification. Contains all compounds.

It is known that the boiling points of fluorides and oxides are usually very different, as shown in the table below.

(Left below) Fluoride boiling point Oxide boiling point MgFt
2260℃ Mg0 3600'CAeF
3 129N sublimation) α-Alt': h 2980
SIF4 86 5ift 2230
FeFs >1000 (sublimation) Fe! 03 1
565FeFz ~1100 (sublimation) PeO~1
370CaFg 2500 CaO28
50CuFz ~850 (sublimation) Cu0ZrF
a ~600 (rise 11) Zr0t ~500
0BaFt 2260 Ba0 2
000Lass 2327 Lag's
4200HfF4 ~650 (sublimation) Hrot
2758WFb 19.5W
O* 18378P, 17.5
UOt 2878 Industrially produced purified inorganic fluoride salts usually contain several hundred pp- to several percent of oxides, and such mixed systems of fluorides and oxides or water require heat treatment. Solid state chemical reactions can sometimes occur between the fluoride metal and the impurity metal to combinatorially exchange metal fluorides, oxides and oxyfluorides. Further, depending on the combination, there are some in which the reaction proceeds gradually even at room temperature. For example, impurity elements that are common in crude fluoride include Fe+Si+8' and Cu, which apparently undergo chemical reactions with oxides coexisting in the product as described below.

Here, the presence of water during heating has a similar effect in that it hydrolyzes fluoride in any form such as attached water, crystal water, or water vapor in the atmosphere to spontaneously generate oxides.

(Left below) Oxide Impurity HzOln CaF, + Pea, →CaF,
+ FezO3CaOin CaF, + FeF,
−=CaFt + Fete.

BaOin CaFl + Fees -”BaF
z + FezesZrOt in ZrF4 +
FeFs −ZrtO9F+o+Fet03→ZrFt
+ Fezes 1, atOs' in LaFs + PeFs -L
a0F + Fetus→LaF3 + pe=03 AZgOs in Aj! Fs+Fees-'A
j! F! + FezO5HfO* in HfFl +
Fe)lfPh' 6JO→HfF4+FezO3N
atCO1in NaF + Na1SIFi"'=
ICO3in KF + LSiF to NaF+5i01
4 = KF + SiftMgOin Mgh+Mg
SiF4 ・6H*0”MgF1+5tO1NaBFa
in NaF + Na1COs -NaP + B
tusKBP* in KP + K wealth CO2 → to F
+ BxOiBaOin BaF, + CaFt ・
2HtO → BaF, +Cu0CaOin CaFt
+ Curt ・2H1O-*CaF, +Cu0Cu
lt ・2H*Oin Mgh = IP +
By increasing the amount of CuO oxide or coexisting water, it is possible to ensure the completion of the reaction, and by eliminating the oxide or coexisting water, the progress of the reaction can be stopped.

In carrying out claim 1(a), in the case of a homogeneous reaction, the amount of oxide to be allowed to coexist should be stoichiometrically equivalent to the impurity metal, but in the case of a sublimation system, In the case of a solid phase, an excess amount is generally required due to the heterogeneous reaction, and when added, it is preferable to use a fine powder that is easy to react.In this case, the oxide to be added is the same as the fluoride to be purified. The metal species are not particularly limited, and it may also be effective to ensure that the solid phase reaction proceeds for a long time at a temperature lower than the sublimation temperature before the sublimation purification step.

In carrying out claim 1), if the amount of oxide in the system is limited and the impurity metal is fluoride, HPSF! For more reliable fluorination, pretreatment in a reactive gas atmosphere such as
In order to achieve CIJPI> for Fs+CuF, pretreatment is performed in an oxidizing gas atmosphere such as P-rich and NF3. In addition to fluoride gas treatment, acidic ammonium fluoride NH, P
A similar effect can be obtained by heat treatment in the presence of -HP. When purifying alkali metal fluorides and Bad, these acidic fluoride salts are used from the beginning to pre-treat by creating an IF atmosphere spontaneously during heat treatment as shown in the following formula, and then the impurity metal fluoride is purified. can also be removed by sublimation.

MP-HF -MP + IF ↑ The means of claim 1.2 selects the target inorganic fluoride to be purified by sublimation depending on the combination of the impurity metal component, and replaces the impurity metal component with an oxide with a low vapor pressure during sublimation purification. Alternatively, impurity metal components can be effectively removed by using either a fluoride with a high vapor pressure. In many cases, such means are effective either as a pretreatment before sublimation or concurrently with sublimation.

The amount of oxide or water that coexists with fluoride depends on the combination of fluoride and impurity metal to be purified, quantitative ratio, target degree of purification, atmosphere (vacuum, reduced pressure, inert gas atmosphere, etc.), particle size, impurity element. It should be set individually depending on the distribution state within the crystal, etc.

(Examples) The present invention will be explained in more detail by the following Examples, but the present invention is not limited thereto.

10 g of crude HfP* (fluorine equivalent purity 99.0%) powder containing 20 ppm of Fe impurities was placed in a platinum dish in an electric furnace with a quartz core tube, and heated in a flow of humid air of 0.51/w+. After heating at 500°C for 5 hours, a vacuum pump system was connected to the quartz furnace tube, and the vacuum was raised to 0.1 Torr at 72°C.
Sublimation was carried out at 0° C. for 5 hours, and about 6 g of F9 was deposited on the inner surface of the end of the quartz tube that was exposed outside the electric furnace. The Fe content in the deposited portion was 0.5 pp- or less.

In this case, when the heat treatment in humid air was omitted and only sublimation was performed under the same conditions, the Fe content was 6 ppm.

Implementation U Using the same electric furnace equipment as in Example 1, Fe content was 20 ppm.
Crude ZrF* 55 son%, Fe content o, 5pp
- Zr0g45ao 10g of 1% powder mixture 0.
Oxyfluoride Zr? 09F+e was synthesized and then pyrolyzed and sublimated at 700° C. for 5 hours under a vacuum of 0.1 Torr to deposit about 48 ZrF. The Fe content in the deposited portion was 0.2 pp- or less.

In this case, the heat treatment to add ZrO* is omitted and the crude Zr
When sublimated from Fe alone under the same conditions, the Fe content was 4.
It was 8p9-.

1. Impurity NatCOs 0.3%, NatSiFh 2.
3% content of crude NaF (fluorine equivalent purity 97.0%)
Using the same electric furnace equipment as in Example 1, 10 g was mixed with 2 g of acidic sodium fluoride, NaF-HF, and then set.
Heat treated at 250°C for 5 hours in a nitrogen stream of 1/win.
After generating IF gas, it was further heated at 700° C. for 5 hours in a nitrogen stream of 0.51/win to release SiF# gas and obtain about 98 NaP. Heat-treated NagSiF
The a content was 0.1%.

In this case, if the NaF-HP addition heat treatment is omitted and only impurity sublimation is performed under the same conditions, the NazSiF6 content is 0.7.
%Met.

Using the same electric furnace equipment as in Example 1, the CU content was 1.1 pp.
- 1 g of fluorine equivalent purity, which has been sublimated and purified once, was mixed and set, heat treated at 700°C for 5 hours in a nitrogen stream of 0.51/@in, and then further heated at 700°C for 5 hours. Approximately 8 g of AlIF was sublimated at 1100°C for 5 hours under a vacuum of ITorr.
5 was deposited. The Cu content in the deposited portion was 0.2 ppm or less.

In this case, Aj(OH)s addition and heat treatment are omitted and the original A
When sublimated from only IFs under the same conditions, the Cu content is 1.
．． 01) It was p@.

Using the same electric furnace equipment as in Example 1, the Cυ content lppm
10 g of crude Ba1t with an Fe content of 15 pp- was heat-treated at 500°C for 5 hours in a mixed gas Q of h/Nt -0,1 mo 11 /so j, 51 /1 ein, and then simply vacuumed at 0°1 Torr. 1000
The impurities were sublimated at ℃ for 5 hours to obtain about 10 g of Bang.

The Cu content of the heat-treated product is 0.2 pp- or less, and the Fe content is 0.
．． It was 2 ppm+ or less.

In this case Ft-N! When heat treatment with a mixed gas is omitted and only impurity sublimation is performed under the same conditions, the Cu content o, sp
pm, and the Fe content was 3.8 ppm.

〔Effect of the invention〕

According to the present invention, metal impurities in inorganic fluoride salts can be efficiently removed, and in particular, this method can be mass-produced and is economical.

Patent applicant Nippon Telegraph and Telephone Corporation Morita Chemical Industry Co., Ltd. (two idiots) Procedural amendment December 26, 1985 Patent application No. 219416 of 1985 2 Title of invention Sublimation purification method of inorganic fluoride 3 Relationship with the case of the person making the amendment Patent applicant Nippon Telegraph and Telephone Corporation Morita Chemical Industry Co., Ltd. 4, agent (and 2 others)! ! 06-364-0693 (Representative) 5, Date of amendment order 7, Contents of amendment as shown in attached sheet 7, Contents of amendment +11 Amend the patent applicant column of the application as per the attached amendment request form.

(2) Amend the documents (two copies) certifying the power of attorney as shown in the attached sheet.

(3) “In the specification, page 3, line 18 (two lines from the bottom)
Add raw material 1 between the fluoride and the aqueous solution.

(4) "Single crystal" in page 3, line 19 (Suesha) of the specification is corrected to r-recrystallization.

(5) r60-3636 in page 4, line 12 of the specification
Correct 4J to '6O-36304J.

(6) In the specification, page 5, line 3 and page 8, line 3, “
^eFsJ is corrected as 'AjFsa.

that's all

Claims (1)

[Claims] 1. During sublimation purification of inorganic fluoride salts, (a) In the case of an inorganic fluoride having a higher vapor pressure than an impurity metal fluoride, metal oxidation is carried out in advance in the raw material metal fluoride or in the processing atmosphere. (b) In the case of inorganic fluoride, which has a lower vapor pressure than the impurity metal fluoride, the raw material is prepared in advance. By reducing the amount of metal oxides or water in the metal fluoride or in the processing atmosphere, we avoid converting impurity metal fluorides to non-volatile metal oxides and reduce the amount of inorganic fluoride salts and their contents, respectively. 1. A sublimation purification method for inorganic fluoride, which comprises maintaining a large vapor pressure difference between impurity metal compounds and separating the fluoride and impurity metal components by sublimation. 2. The metal oxides mentioned above include hydroxides, carbonates, sulfates, which can decompose or react to become metal oxides during heat treatment.
The sublimation purification method for inorganic fluoride according to claim 1, which contains an oxygen-containing compound such as a nitrate or a hydrated salt.