JP2638620B2 - Method for producing anhydrous neodymium fluoride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to Nd-Fe which has recently attracted attention as a high-performance magnet.
The present invention relates to a method for producing anhydrous NdF ₃ suitable for producing Nd and Nd alloy as raw materials for a B-based magnet.

[Prior art] Generally, Nd or Nd alloy is anhydrous NdF ₃ (hereinafter referred to as NdF ₃ ).
NdF ₃ is usually produced by reacting Nd compounds such as NdCl ₃ with hydrofluoric acid to produce NdF ₃ -nH ₂ O, which is then heated to produce NdF ₃ -nH ₂ O. However, there is no document describing the details.

[Problems to be solved by the invention]

However, the present inventors have found that, in any of the above methods, when commercially available anhydrous NdF ₃ is used as a raw material, not only does the yield of Nd fall far below the theoretical value, but also various troubles in the production process. I noticed that it occurred and announced it. (Japanese Unexamined Patent Publication No. Sho 60-77943 for the Ca reduction method and Japanese Patent Application No. 63-173487 for molten salt electrolysis).

The present inventors have conducted intensive studies to determine the cause, and as a result, commercially available anhydrous NdF ₃ contains ₃ to 10% by weight of NdOF, which reduces the yield or causes trouble. That was expressed. That is, (a) the reaction in the step of producing Nd or an Nd alloy by a metal reduction method of Ca or the like is performed according to the following equation (1).

In the reaction of the formula (1), CaCL ₂ is added to dissolve generated CaF ₂ and to improve the separation of the Nd compound from CaCl ₂ -CaF ₂ .

However, if NdOF is present, the reduction reaction of (1)
In addition, NdOF does not dissolve with CaCl ₂ smoothly and remains in the formed alloy, thus deteriorating the quality of the formed alloy.

(B) As a molten salt electrolysis method using NdF ₃ , LiF—NdF ₃
Nd ₂ O ₃ in the manner as LiF-NdF ₃ -Nd ₂ O ₃ based electrolyzing NdF ₃ in the system
And electrolysis.

In the electrolytic method, the NdOF there NdOF to cost only NdOF equivalent in NdF ₃ of since it is not electrolyzed.

Also, the bath in which NdOF exists has a large specific gravity and a large viscosity,
Due to its low solubility, it precipitates below the normal electrolytic bath.
Therefore, the alloy is easily suspended in the produced molten Nd alloy, and the quality of the alloy is reduced as in the case of the Ca reduction method.

Furthermore, since the molten salt electrolysis method is a continuous operation due to its characteristics, if NdF ₃ is electrolyzed and NdOF is not electrolyzed, the NdOF concentration in the electrolytic bath gradually increases. Therefore, if the operation is performed for a long time, the normal operation cannot be maintained due to the accumulation of NdOF, and the operation must be interrupted.

Therefore, to make Nd or Nd alloy efficiently, Nd
It is necessary to use anhydrous NdF ₃ with a low OF content,
F ₃ results NdOF has studied the cause of contamination during the next it was found.

The production of anhydrous NdF ₃ can be obtained by reacting an Nd compound with hydrofluoric acid (HF) as described above to produce NdF ₃ .nH ₂ O and heating it.

When NdCl ₂ is used as an example of the Nd compound, the chemical reaction formula is as follows: NdCl ₃ + 3HF + nH ₂ O → NdF ₃ · nH ₂ O + 3HCl (2) NdF ₃ .nH containing water obtained by the above reaction by the formula (2)
By heating the ₂ O (3) no problem if Tsukurere anhydrous NdF ₃ by reaction formula.

However, if the heating conditions are not appropriate, it reacts with the moisture and oxygen in the air according to the equations (4) and (5) to generate NdOF, which becomes NdF ₃ mixed with NdOF. That is, if the heating temperature is too low in the three reactions (3), moisture remains, and if the heating temperature is too high, (4)
By the reaction of (5), NdF ₃ containing NdOF is formed, and when the heating temperature is further increased, all become NdOF.

This is consistent with the fact that the amount of NdOF in commercially available NdF ₃ varies greatly from lot to lot.

The present invention has been made in view of the above circumstances, to heat the NdF ₃ · nH ₂ O,
An object of the present invention is to provide a production method capable of obtaining NdF ₃ having a small content of NdOF.

[Means for solving the problem]

In order to achieve the above object, as a result of various examinations of the heating conditions, in the method of the present invention, when heating in the air, the heating temperature is 100 to 800 ° C., and under a reduced pressure of 10 ^-1 mmHg or less. In the case of heating, it has been found that a condition in which the heating temperature is 50 to 1100 ° C. is suitable.

[Action]

Since the method of the present invention has the above configuration, (4)
Any of the reactions represented by the formula (5) is suppressed.

The method of heating NdF ₃ · nH ₂ O to obtain NdF ₃ includes: i) heating in air ii) heating under reduced pressure iii) heating in an inert gas atmosphere iv) i) to iii The method of iv) can be selected if the conditions of i) to iii) are determined. The conditions of i) to iii) will be described.

i) Method of heating in the atmosphere If the temperature is selected so that the reaction of the above formula (3) proceeds and the reactions of the formulas (4) and (5) do not occur, the reaction of the formula (3) becomes Nd
Complete by maintaining F ₃ .nH ₂ O at 100 ° C.
(4) Since the reaction of (5) is affected by moisture and O ₂ in the atmosphere, the upper part of the sample placed in the container and the lower part not in contact with the atmosphere even when heated under the same conditions. Unlike the above, NdOF formation is gradually observed at about 650 ° C in the upper part, whereas NdO is not seen until about 800 ° C in the lower part.
The formation of F is observed.

Therefore, the heating temperature range in the atmosphere is 100 to 800
° C, especially 100-650 ° C.

ii) Heating method under reduced pressure Under reduced pressure, moisture and O ₂ in the atmosphere in contact with NdF ₃ · nH ₂ O to be heated are small, and further generated H ₂ O is sequentially removed by a pressure reducing means such as a vacuum pump. Therefore, the generation of NdOF is suppressed even under severer heating conditions,
The heating conditions are determined by the balance with the degree of pressure reduction.

For example, the heating temperature at a degree of vacuum of about 10 ^-1 mmHg, which can be easily reached, is preferably 50 to 1100 ° C, particularly preferably 100 to 800 ° C.

In general, firing in the air is more economical, but firing at a reduced temperature will broaden the appropriate temperature range and can be fired in a short time.

Further, if a NdF ₃ .nH ₂ O is stirred during heating, for example, a rotary kiln or the like can be used to obtain NdF ₃ with uniformity and little variation, which is particularly effective for baking in the atmosphere.

iii) Method of heating in an inert gas atmosphere In this method, H ₂ O is generated when the reaction of (3) proceeds, and this reacts with NdF ₃ to generate NdOF, thereby causing the reaction of (4). It is not suitable as the method of the invention.

Example 1 NdF ₃ .nH ₂ O obtained by reacting NdCl ₃ and HF was put in a container and calcined by heating at various temperatures in the air for 1 hour. For NdF ₃ heated at each temperature, the amount of air loss was measured to determine the residual moisture, and the amount of NdOF in NdF ₃ N was measured for the upper and lower samples in the container, and the weight ratio of NdOF / NdF _{3 was} measured. I asked.

Air loss The sample was dried in air at 200 ° C. for 1 hour. It was determined NdF ₃ peak and NdOF peak of diffracted X-rays using the Kα line of measurement Cu of NdOF amount in NdF _3. The peak used for quantification was 2θ = 2 for NdF ₃
8.3 ° and NdOF are 2θ = 27.2 °.

The results are shown in FIG. 100 ~ 800 ℃, especially 100 ~ 650
It can be seen that when calcined at a temperature of ° C., NdF ₃ containing almost no NdOF and containing no water can be obtained.

FIG. 2 shows the diffraction X-ray pattern of NdF ₃ fired at 400 ° C., and FIG. ₃ shows the diffraction X-ray pattern of commercially available NdF ₃ as a target. In the figure, A is the peak of NdF ₃ and B is
This shows the peak of NdOF, and NdF ₃ produced by the method of the present invention has no peak of NdOF.

Example 2 Example 2 was the same as Example 1 except that it was fired at 10 ^-1 mmHg. The results are shown in FIG. As is clear from the figure, Nd with almost no NdOF content over a wide temperature range compared to firing in the atmosphere
F ₃ is obtained and it is found that the product can be obtained in a short time. The diffraction X-ray of NdF ₃ obtained by firing at 600 ° C. showed the same pattern as in FIG.

〔The invention's effect〕

As described above, since the NdF ₃ production method of the present invention is NdF ₃ of NdOF hardly contain obtained, Nd this as a raw material
Alternatively, when producing an Nd alloy, in any of the Ca reduction method and the molten electrolysis method, the yield is greatly increased and troubles are eliminated, so that operation is simplified and labor is saved, and Many effects such as easy maintenance are exhibited.

[Brief description of the drawings]

FIG. 1 is a diagram showing the dehydration rates at various temperatures and the weight ratio of NdOF / NdF ₃ of the sample in the upper and lower parts when fired in air, and FIG. 2 is a graph showing NdF fired in air at 400 ° C. Figure of diffracted X-rays _3, FIG. 3 is diagram of the diffracted X-rays of commercial NdF _3, dehydration rate in Figure 4 is the temperature of the fired samples under a reduced pressure of 10 ^-1 mmHg, and top, bottom sample NdOF / NdF
FIG. ₃ is a diagram showing a weight ratio of ₃ .

Claims (2)

(57) [Claims] 1. A method for producing anhydrous neodymium fluoride having NdOF of 2% by weight or less by heating and calcining NdF ₃ .nH ₂ O, characterized by calcining at 100 to 800 ° C. in the atmosphere. To produce anhydrous neodymium fluoride. 2. A method for producing anhydrous neodymium fluoride having NdOF of 2% by weight or less by heating and calcining NdF ₃ .nH ₂ O, comprising: 10 ^-1.
A method for producing anhydrous neodymium fluoride, comprising calcination at a temperature of 50 to 1100 ° C. under reduced pressure of not more than mmHg.