JPS58135136A - Preparation of powder of needle-like crystal of iron beta-oxyhydroxide particle - Google Patents

Abstract

PURPOSE:To prepare powder of high-purity iron beta-oxyhydroxide particle showing a lamellar state, easily washable with water, by introducing an oxygen-containing gas into an aqueous solution of ferrous chloride to which a strong acid is added so that the solution is oxidized. CONSTITUTION:0.3-6.0mol% strong acid (e.g., hydrochloric acid) based on a ferrous salt is added to an aqueous solution of ferrous chloride, and an oxygen- containing gas is introduced to the solution under heating, to give powder of iron beta-oxyhydroxide particle in a lamellar state, having promoted growth in the direction of the minor aixs. When the powder of the particle is used as a raw material for ferrite, it is easily arranged in a fixed direction in case of blending it with a raw material composition for ferrite. Consequently, it is calcined under heating to give powder of ferrite particle having uniform particle diameter of crystal, improved orientation properties, and uniform composition. When it is used as pigment, it shows low oil absorption, increased hiding power and tinting strength, and preferable pigment characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing β-iron oxyhydroxide particles.

Specifically, in a method for producing β-iron oxyhydroxide particle powder by passing an oxygen-containing gas through a ferrous chloride aqueous solution to oxidize it, a strong acid is added to the ferrous chloride aqueous solution to oxidize the ferrous chloride solution. It is characterized in that β-iron oxyhydroxide particles having a plate-like shape are obtained by adding ~6.0 mol % and then oxidizing.

The thus obtained β-iron oxyhydroxide particle powder exhibiting a plate-like shape is particularly preferable as a raw material for pigments and ferrites.

Generally, iron oxyhydroxide particles are widely used as raw materials for pigments and ferrites.

That is, Special Publication No. 45-1 f 705 and Special Publication No. 4
According to the method for producing barium or strontium 7-elite particles described in Publication No. 6-11706, a mixture of a-iron oxyhydroxide particles having a plate shape and a barium or strontium raw material is added. Hexagonal plate-shaped barium or strontium 7-elite particles are obtained by heating and firing a mixture arranged in a certain direction by pressure, liquid phase precipitation, or a combination of both.

This hexagonal plate-shaped barium or quartzium 7-elite particle powder has good orientation, so it is very preferable as a magnet material for sintering magnets, rubber, and plastics.

Also, regarding iron oxyhydroxide particle powder for pigments,
Pigment properties of a plate-shaped pigment are more preferable than those of a needle-shaped pigment.

This fact is confirmed, for example, in Japanese Patent Application Laid-Open No. 50-115698 [... Thin acicular aggregates (particle size ratio 1:8.
The tactoid particles of 5) are transformed into rod-shaped particles by a dissolution precipitation reaction. Accordingly, the particle size ratio is 1:3.4.
At the same time, the specific surface area changes from 40.7'/g to 13.31
It decreased significantly to 1/g. The thus altered pigment had a low absorption capacity as a pigment, increased shading power and coloring power, and changed its color from dark yellow to bright yellow, making it suitable for use as a coloring material. It is clear from the statement ``.

Conventionally, the method for producing β-iron oxyhydroxide particles is as follows:
There are two known methods.

One of them is a method of hydrolyzing a ferric chloride aqueous solution, and the other is a method of performing an oxidation reaction by passing an oxygen-containing gas through the ferrous chloride aqueous solution.

The β-iron oxyhydroxide particles obtained by the first method have a spindle shape.

The present invention belongs to the second method.

Conventionally, the most typical method for producing β-iron oxyhydroxide by passing an oxygen-containing gas through an aqueous solution of mineral chloride to perform an oxidation reaction is disclosed in Japanese Patent Publication No. 47-25959.
This is the method described in the publication, and the PH
The β-iron oxyhydroxide particles are produced in a reaction solution of 2 or less. The β-iron oxyhydroxide particles powder obtained by the above method has a long axis of 0.5 to 0.0 as shown in Example 1. 0.8μm, minor axis 220~250X (0,022~0.025 fi
xs>rD It has a needle-like shape.

In view of the above, the present inventor aimed to obtain β-iron oxyhydroxide particle powder exhibiting a plate-like form.
The present invention was arrived at as a result of various studies on methods for promoting the growth of β-iron oxyhydroxide particles exhibiting an acicular shape in the minor axis direction.

That is, the present invention provides a method for producing β-iron oxyhydroxide particle powder by passing an oxygen-containing gas through a ferrous chloride aqueous solution to oxidize the ferrous chloride aqueous solution.
β-iron oxyhydroxide obtained by adding 0.5 to 6.0 mol% of strong acid to ferrous iron and then oxidizing to obtain β-iron oxyhydroxide particles having a plate-like shape. This is a method for producing particulate powder.

Next, the technical background that led to the completion of the present invention and the structure of the present invention will be described.

The present inventor has conducted various studies on the type and amount of additives at l/1 in order to promote the growth of β-iron oxyhydroxide particles exhibiting an acicular shape in the minor axis direction. In a method for producing β-iron oxyhydroxide particle powder by passing an acid-containing gas through a ferrous chloride aqueous solution to oxidize it, a strong acid is added to the ferrous chloride aqueous solution at a ratio of 0.3 to ferrous iron.
When ~6.0 mol% is added and then oxidized,
A new finding was obtained that growth in the minor axis direction can be promoted and β-iron oxyhydroxide particles having a plate-like shape can be obtained.

In a method for producing β-iron oxyhydroxide particles by passing an oxygen-containing gas through an aqueous ferrous chloride solution to oxidize it, a strong acid is added to the aqueous ferrous chloride solution at a rate of 0.3 to 6. β obtained by adding 0 mol% and then oxidizing
- Theoretical elucidation of the phenomenon in which the growth of iron oxyhydroxide particles in the minor axis direction is promoted is not yet clear.

The above-mentioned phenomenon will be explained as follows by extracting some of them from the numerous experimental examples conducted by the present inventor.

FIG. 1 is a diagram showing the relationship between the amount of HC/ added and the short axis of the produced β-iron oxyhydroxide particles.

That is, a ferrous chloride aqueous solution (2"n) with a total volume of 51 obtained by adding 0 to 7.0 mol% of HQI to the total iron was heated at a temperature of 7.
This figure shows the relationship between the short axis length of β-iron oxyhydroxide particles obtained by performing an oxidation reaction by passing air at 10 7 per minute at 0° C. and the amount of Hot added.

As shown in FIG. 1, the short axis of the β-iron oxyhydroxide particles tends to become longer as the HOZ increases.

Incidentally, there is a conventional method described in JP-A-52-100400 in which a strong acid is added during the production of β-iron oxyhydroxide particles.

The method described in JP-A No. 52-100400 involves adding strong acids such as hydrochloric acid, sulfuric acid, and nitric acid to an aqueous solution containing ferric chloride, ammonium chloride, and urea and heating the mixture. β- exhibiting a needle-like shape suitable as a raw material
The purpose is to obtain iron oxyhydroxide particles.

In the above method, the purpose of adding ammonium chloride and urea is that when obtaining β-iron oxyhydroxide particles from an aqueous ferric chloride solution, spindle-shaped particles are likely to be obtained as described above, but ammonium chloride and by adding urea, it is made into needle-like crystals.

The addition of strong acid aims to improve the axial ratio of the acicular β-iron oxyhydroxide particles. It can be seen that this is also achieved by decreasing the amount in the short axis direction...
As is clear from the description, it has the action and effect of suppressing growth in the minor axis direction, and is completely different from the present invention, which promotes growth in the minor axis direction.

Next, various conditions for implementing the method of the present invention will be described.

Strong acids used in the present invention include hydrochloric acid, sulfuric acid,
Nitric acid etc. can be used.

In the present invention, the amount of strong acid added is 0.3 to 60
It is mole%.

In this case, the effect of promoting the growth of the β-iron oxyhydroxide particles in the minor axis direction is not sufficient.

If the content is 60 mol % or more, it is possible to obtain β-iron oxyhydroxide particles having a plate-like shape in which growth in the minor axis direction is promoted, but the effect is not significant.

In addition, when adding 03 to 60 mol % of a strong acid, as described above, the growth of the β-iron oxyhydroxide particles obtained in the minor axis direction tends to be promoted as the amount added increases.

Therefore, by adjusting the above addition amount, it is possible to obtain β-iron oxyhydroxide particles exhibiting a plate-like shape having a desired short axis.

The present invention configured as described above has the following effects.

That is, according to the present invention, it is possible to obtain β-iron oxyhydroxide particles having a plate-like shape in which growth in the minor axis direction is promoted.

When the thus obtained β-iron oxyhydroxide particles having a plate-like shape are used as a raw material for ferrite, the β-iron oxyhydroxide particles can be easily mixed with a ferrite raw material composition. The grains are aligned in a certain direction, so if you heat and sinter it, the crystal grain size will be uniform and the orientation will be excellent.
In addition, preferred ferrite particles having a uniform composition can be obtained.

When used as a pigment, the amount of oil is low, the shade power and coloring power are increased, and the pigment properties are favorable.

Further, since the β-iron oxyhydroxide particles obtained according to the present invention have a plate-like shape, they have a better cleaning effect than those that have an acicular shape.
By washing with water, highly pure β-iron oxyhydroxide particles can be easily obtained. Highly purified β-iron oxyhydroxide particles are particularly preferred as raw materials for ferrite and pigments.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

In addition, the long axis and short axis of the particles in the above experimental examples, the following examples, and comparative examples are shown as average values of numerical values measured from electron micrographs.

Moreover, the β-iron oxyhydroxide particle powder exhibiting a plate-like shape is X! [Identified by diffraction method.]

Example 1 3 moi of ferrous chloride aqueous solution 364 and 1 mol/l)
Salt 1! 0.41 (equivalent to 4.0 mol% based on ferrous iron) and water were further added to adjust the total volume to 51. Air was bubbled through the mixture at a temperature of 50°C for 27 hours at a rate of 101 per minute to form particulate powder. generated.

The produced particles were washed with water, separated from P, dried, and crushed by a conventional method.

As a result of identifying the generated particles by X@ diffraction method, the particles were 100% β-
It was iron oxyhydroxide particle powder.

As a result of electron microscopic observation, the obtained β-iron oxyhydroxide particles had a plate-like shape with an average short axis of 1200× and a long axis of 0.4 μm.

Examples 2 to 8 Particle powders were produced in the same manner as in Example 1, except that the amount of ferrous chloride aqueous solution used, the type and amount of strong acid used, and the reaction temperature were varied.

All produced particles were identified by XM diffraction method, and as a result, 10
It was a 0% β-iron oxyhydroxide particle powder. The main manufacturing conditions and characteristics at this time are shown in Table 1.

As a result of electron microscopic observation, the β-iron oxyhydroxide particles obtained in Examples 2 to 8 all had a plate-like shape.

Comparative Example 1 β-Iron oxyhydroxide particles were produced in the same manner as in Example 7 except that hydrochloric acid was not added.

As a result of electron microscopy, the obtained β-iron oxyhydroxide particles had a needle-like shape with an average short axis of 250× and a long axis of 06μ.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the amount of Hot added and the short axis of the produced β-iron oxyhydroxide particles. Patent applicant Toda Kogyo Co., Ltd. Matsui Gobezu 1 Short 0/234! ;67 Hd7. ♂↑(Moloshi%)

Claims (1)

[Claims] In a method for producing β-iron oxyhydroxide particle powder by passing an oxygen-containing gas through a ferrous chloride aqueous solution to oxidize it, a strong acid is added to the ferrous chloride aqueous solution to give an α6 to 6 A method for producing I-iron oxyhydroxide particles, which comprises adding .0 mol % and then oxidizing to obtain β-iron oxyhydroxide particles having a plate-like shape.