JP3350332B2 - Method for producing aggregated rare earth hydroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flocculant having a narrow particle size distribution and good fluidity useful as a raw material for a rare earth oxide sintered body and as a sintering aid for ceramics such as silicon nitride and aluminum nitride. it relates manufacturing <br/> method for producing bulk rare earth hydroxide compound.

[0002]

2. Description of the Related Art Heretofore, rare earth hydroxides have generally been produced by adding a base to a rare earth salt aqueous solution, but the hydroxide formed by this method is difficult to filter by very fine particles. It is an acidic gel-like substance. Therefore, in the prior art,
There are problems that it takes time for filtration, that it is difficult to remove by-products by washing with water, that the dried product is solidified, and that pulverization is required, which is troublesome, and that the cost is high and that impurities are mixed.

[0003]

The present invention is to challenge it to solve] In view of the above problems, good filterability, easy removal of the by-product by washing with water, do not require grinding after drying of the agglomerated mass rare earth hydroxide compound It is intended to provide a manufacturing method.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and studied the precipitation conditions of rare earth hydroxides. As a result, the present invention has been completed. That is,
Method for producing a cohesive mass rare earth hydroxide of the present invention, Oh Raka <br/> in dimethyl aqueous solution of nitric acid and consist of base salts, characterized by the dropwise addition of a rare earth salt solution and a base solution at the same time The gist of the present invention is a method for producing an aggregated rare earth hydroxide, and more specifically, a method in which a base is ammonia.

Hereinafter, the present invention will be described in detail. The greatest feature of the present invention is to obtain an aggregated rare earth hydroxide by simultaneously dropping an aqueous solution of a rare earth salt and an aqueous solution of a base into an aqueous solution in which a salt composed of nitric acid and a base is dissolved in advance.
Preliminarily dissolving the salt is particularly effective for agglomerating the fine rare earth element hydroxide by the salting out effect.

The salt concentration of the salt aqueous solution prepared in advance is preferably in the range of 0.2 to 1.0 mol / L. When the salt concentration is less than 0.2 mol / L, the produced hydroxide becomes a gel, and when it exceeds 1.0 mol / L, The effect of the rare earth hydroxide on the agglomeration is saturated, so that only the chemical is wasted. The liquid volume of the salt solution is preferably 30% to 70% of the final liquid volume. If it is less than 30%, the generated hydroxide will be gelled, and if it exceeds 70%, the amount of rare earth hydroxide generated will be small. It impairs productivity.

The pre-dissolved salt consists of nitric acid and a base.
In order to simplify the reaction system, the components of the rare earth salt aqueous solution and the base aqueous solution to be added later are nitric acid.
It is preferable to use a material consisting of the same base as the component of the salt which is dissolved in advance . Also, the ultimate purpose is
When in that by sintering a rare earth hydroxide to obtain a rare earth oxide, acid and base to decompose volatilized during firing, for example, ammonium nitrate Salts pre-dissolved, nitric acid to rare earth salt rare earth, the salt groups It is preferred to use ammonia.

Next, an aqueous solution of a rare earth salt and an aqueous solution of a base are simultaneously dropped into the aqueous solution in which the salt is dissolved in advance. At this time, when these are separately added, the agglomeration of the rare earth hydroxide does not occur. The concentration of the aqueous solution of the rare earth salt is not particularly limited, but is 0.
The amount is preferably 1 to 1.0 mol / L , and if it is less than 0.1 mol / L , the productivity is deteriorated. The concentration of the aqueous solution of the base is not particularly limited, but the number of moles to be introduced is preferably 1.0 to 1.2 times the stoichiometric amount necessary to completely convert the rare earth element in the rare earth salt aqueous solution to hydroxide, and more than this. Is just a waste of medicine.

The total amount of the aqueous solution of the rare earth salt and the aqueous solution of the base is preferably added over 2 to 10 hours. If it is less than 2 hours, the state of aggregation is not sufficient, and if it exceeds 10 hours, no particular effect can be expected. The reaction temperature is not particularly limited,
As a general reaction condition, for example, a temperature of about room temperature to about 80 ° C. is preferable.

The product obtained by the method of the present invention is an agglomerate having an average particle diameter of 5 μm or more and 100 μm or less.
It is quickly filtered off by a conventional method. Also, by-products are easily removed by washing with water. Thereafter, drying is performed at a temperature of 30 ° C. or more and 200 ° C. or less according to a conventional method for a time necessary to remove adhering water, and a smooth, fluid, powdery, aggregated rare earth hydroxide having an average particle size of 5 μm to 100 μm is obtained. Obtained and does not require a grinding step. This is extremely useful in handling as a raw material for rare earth oxide sintered bodies and as a sintering aid for ceramics such as silicon nitride and aluminum nitride.

When the aggregated rare earth hydroxide is fired at a temperature of 600 ° C. to 1700 ° C. for about 1 to 4 hours as needed, a smooth and fluid powdery aggregated rare earth oxide is obtained. And does not require a grinding step. This is useful as a raw material for rare earth oxide spraying or as a lint during sintering of a reactive metal.

The rare earth elements applied to the present invention include La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Y containing Y.
One or more members are selected from the group consisting of Dy, Ho, Er, Tm, Yb and Lu.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The function of the present invention is based on the fact that a salt aqueous solution composed of nitric acid and a base dissolved in advance agglomerates fine rare earth hydroxide particles formed later due to the salting out effect.

[0014]

EXAMPLES Hereinafter, embodiments of the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these. (Example 1) 5 L of 0.5 mol / L ammonium nitrate aqueous solution in advance
Into a 10 L beaker and stir at room temperature (21 ° C.), and add 2.5 L of 3.0 mol / L yttrium nitrate aqueous solution and 3.0 L
2.5 L of an aqueous ammonia solution of mol / L was simultaneously added dropwise over 4 hours. The product was filtered through Nutsche and washed with 5 L of deionized water. The aqueous wash was to obtain a dried 16 hours at 50 ° C. powdered agglomerated mass yttrium hydroxide 610g (Y ₂ 0 ₃ content of 45.7 wt%). The angle of repose of the powder is 43 °, and the particle diameter is 0.1 μm or more and 1 μm by observation with a scanning electron microscope.
The following fine particles were observed to be agglomerated in a lump, and the average particle diameter by laser diffraction was 37 μm, which was smooth and had good fluidity. The average particle size is measured by Microtrac's laser diffraction method.
(SPA).

Example 2 The agglomerated yttrium hydroxide obtained in Example 1 was calcined at 800 ° C. for 2 hours to obtain a powdery agglomerated yttrium oxide 27.
9 g were obtained. The angle of repose of the powder was 42 °, and it was observed by scanning electron microscopy that fine particles having a particle diameter of 0.1 μm or more and 1 μm or less were aggregated in a lump, and the average particle diameter determined by laser diffraction was 35 μm and smooth. It had good fluidity.

[0016] (Example 3) the erbium nitrate reacted in the same manner as in Example 1, powdery aggregate bulk erbium hydroxide 812 g (Er ₂ 0 ₃ content
58.6% by weight). The angle of repose of the powder was 41 °, and it was observed by scanning electron microscopy that fine particles having a particle size of 0.1 μm or more and 1 μm or less were aggregated in a lump. It had good fluidity.

Example 4 Gadolinium nitrate was reacted in the same manner as in Example 1,
Powdered agglomerated mass hydroxide gadolinium 780g (Gd ₂ 0 ₃ content of 57.3 wt%) was obtained. The angle of repose of the powder is 41 °, and the particle size is 0.1 μm or more and 1 μm by scanning electron microscope observation.
The following fine particles could be observed to be aggregated in a lump, and the average particle diameter determined by a laser diffraction method was 39 μm, which was smooth and had good fluidity.

Comparative Example 1 2.5 L of a 1.0 mol / L yttrium nitrate aqueous solution and 2.5 L of deionized water were placed in a 10 L beaker, and 2.5 L of a 3.0 mol / L aqueous ammonia solution was added thereto while stirring at room temperature (21 ° C.). It was added dropwise over 4 hours. The produced yttrium hydroxide was filtered with Nutsche and washed with 5 L of deionized water. Solids 623g with a water washing was dried for 16 hours at 50 ℃ (Y ₂ 0 ₃ content of 44.8
% By weight). The solid content was firmly agglomerated and the angle of repose and the average particle size could not be measured.

Comparative Example 2 5 L of 0.5 mol / L ammonium nitrate aqueous solution
And 2.5 L of 1.0 mol / L yttrium nitrate aqueous solution in a 10 L beaker, and stir at room temperature (21 ° C.).
2.5 L of a molar / L aqueous ammonia solution was added dropwise over 4 hours. The produced yttrium hydroxide was filtered with Nutsche and washed with 5 L of deionized water. 50 washes
℃ in dried 16 hours to obtain a solid 617g (Y ₂ 0 ₃ content of 45.2 wt%). The solid content was firmly agglomerated and the angle of repose and the average particle size could not be measured.

[0020] was obtained (Comparative Example 3) yttrium nitrate aqueous solution and aqueous ammonia in the same manner as in Example 1 except that the simultaneous dropwise in 1 hour yttrium hydroxide 620 g (Y ₂ 0 ₃ content of 45.0 wt%) .
The solid content was firmly agglomerated and the angle of repose and the average particle size could not be measured.

[0021]

According to the present invention, an agglomerated rare earth hydroxide having a narrow particle size distribution and a good flowability, which is useful as a raw material for a rare earth oxide sintered body and as a sintering aid for a ceramic raw material, etc. It can be manufactured in a simple process and at low cost, and its industrial value is extremely high.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C01F 17/00

Claims (2)

(57) [Claims] 1. A salt composed of nitric acid and a base is dissolved in advance.
A rare earth salt aqueous solution and a base aqueous solution
Of agglomerate rare earth hydroxide, characterized by being dropped on
Manufacturing method . 2. The method according to claim 1, wherein the base is ammonia.
For producing an aggregated rare earth hydroxide .