JPH0613406B2 - Manufacturing method of hematite particle powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a hematite particle powder, more specifically, a uniform particle size at a low temperature and a short reaction time, and The present invention relates to an industrially and economically advantageous method for producing a hematite particle powder capable of obtaining a hematite particle powder having independent particles.

The main uses of the hematite particle powder produced by the present invention are as a red pigment powder for paints, a colorant for rubber / plastics, and a starting material for magnetic particle powders.

[Conventional technology]

Since the hematite particle powder has a red color, it is widely used as a pigment powder for paints, and is also used as an adhesive for rubber / plastics.

Further, the hematite particle powder is also used as a starting material in the production of magnetic particle powder for magnetic recording or electrostatic copying. That is, magnetic particle powders such as magnetite particle powder and maghemite particle powder are produced by reducing the hematite particle powder or further oxidizing it if necessary.

As described above, the hematite particle powder is used in various fields, but the characteristic commonly required in any field is that the dispersibility is excellent. As a result, it is necessary that the particle sizes are uniform and that the individual particles are independent. That is, it is necessary to disperse the hematite particle powder uniformly and easily in the production of a paint, in the case of forming a paint, and in the case of kneading in the coloring of rubber / plastics. Further, in the manufacture of a magnetic recording medium, the magnetic particle powder is uniformly and easily dispersed at the time of manufacturing a magnetic paint to be applied on a base film, and at the time of kneading with a resin in the manufacture of a magnetic toner for electrostatic copying. Therefore, it is necessary that the starting material, hematite particle powder, be uniform and easily dispersed.

Conventionally, as a method for producing a hematite particle powder, an oxygen-containing gas is aerated in a reaction aqueous solution containing ferrous hydroxide obtained by reacting an aqueous ferrous salt solution with an alkali, so that a starting material is prepared from the aqueous solution. Is known, and then the magnetite particle powder is heated in air.

[Problems to be solved by the invention]

The particle size is uniform, and the hematite particle powder in which the individual particles are independent, in other words, the hematite particle powder having excellent dispersibility is the most demanded at present, but in the case of the known method as described above. The particle size of the magnetite particles powder generated from the aqueous solution is asymmetric, the particle size of the hematite particles obtained by heating the magnetite particles is naturally asymmetric, and is 500 ° C or more. By heating at, the sintering occurs between the particles.

Further, a method for producing a hematite particle powder in which individual particles are independent has been tried in the past, and for example, Japanese Patent Publication No.
55-8459, Method of hydrothermal treatment of ferrous chloride aqueous solution in a high-pressure vessel while adding oxygen, and Journal of Colloid and Interface Science
A method for treating an aqueous solution of ferric chloride described in Vol. 63, No. 3 (1978), pp. 509-524 is known. In all of these methods, hematite particle powder is directly produced from an aqueous solution to obtain a hematite particle powder in which individual particles are independent.

However, the former method requires a high temperature of 130 ° C or higher, and thus requires a special device called a high-pressure container,
In addition, there is a drawback in that there is a risk of adding oxygen in the reaction under high temperature and high pressure. The latter method does not require a special device such as a high-pressure container because it is a reaction at 100 ° C to 130 ° C, but hematite particles with asymmetric particle size are easily generated, and 100% hematite particle powder is generated. To do so, a long reaction time of 30 hours or more is required, which is not industrial or economical.

Therefore, 130 ℃ that does not require special equipment such as high-pressure container
At a low temperature of less than 1, and by a reaction for a short time, the particle size is uniform, and the technical means for industrially and economically obtaining a hematite particle powder in which each particle is independent is strongly established. Is requested.

[Means for solving problems]

The present inventor, at a low temperature of less than 130 ° C., and further, by a reaction of a short time, the particle size is uniform, and as a result of various studies to obtain a hematite particle powder in which individual particles are independent, The invention was reached.

That is, the present invention has a specific surface area of 150 m ² / g or more obtained by heating a ferric chloride aqueous solution having a Fe ³⁺ concentration of less than 0.1 mol / to a temperature range of 70 to 90 ° C. to cause hydrolysis. An acidic suspension containing β-FeOOH particles at a concentration of less than 0.1 mol / 100-130
It is a method for producing a hematite particle powder, which comprises producing a hematite particle having a uniform particle size by performing a hydrothermal treatment in a temperature range of ° C.

[Work]

First, the most important point in the present invention is that the specific surface area obtained by hydrolyzing an aqueous ferric chloride solution having a Fe ³⁺ concentration of less than 0.1 mol / 70 ° C. in a temperature range of 70 to 90 ° C. is 150 m 2. ² / g
When an acidic suspension containing the above β-FeOOH particles at a concentration of less than 0.1 mol / is subjected to hydrothermal treatment, the particle size becomes uniform at a low temperature of less than 130 ° C and for a short reaction time. In addition, it is the point that a hematite particle powder in which each particle is independent is obtained.

In the present invention, the reason why hematite particles having a uniform particle size are produced in a short time has not been clarified yet, but the present inventor has a reaction mechanism for producing hematite particles by hydrothermally treating an aqueous solution of ferric chloride. , Is due to the dissolution precipitation reaction of β-FeOOH particles produced by hydrolysis of ferric chloride, and when hydrothermally treating β-FeOOH particles having a specific surface area of 150 m ² / g or more, the particle size is uniform. It is presumed that the dissolution rate is uniform and the reaction occurs rapidly due to the fineness.

Next, various conditions for carrying out the present invention will be described.

The β-FeOOH particle powder in the present invention has a specific surface area of 150 m ² /
It must be g or more. If it is less than 150 m ² / g, it is difficult to obtain hematite particles having a uniform particle size, and it takes a long time for the hematite particle formation reaction. In the present invention, the β-FeOOH particle powder of 150 m ² / g or more is obtained by a method of hydrolyzing a ferric chloride aqueous solution by heating it in the temperature range of 70 to 90 ° C.

The suspension containing β-FeOOH to be hydrothermally treated in the present invention,
Must be acidic, otherwise 100-1
In the temperature range of 30 ℃, hematite particles are not formed because α-FeOOH is stably formed.

The concentration of the acidic suspension containing β-FeOOH particles in the present invention is less than 0.1 mol /. When it is 0.1 mol / or more, hematite particles are not formed.

The reaction temperature in the present invention is 100 to 130 ° C. 100 ° C
If it is less than this, hematite particles are not formed because the dissolution of β-FeOOH does not proceed sufficiently. Hematite particles are generated even when the temperature exceeds 130 ° C, but this is not industrially and economically because a special device such as a high-pressure container is required.

〔Example〕

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

The average diameter of the particles in the following examples is the average of the numerical values measured from electron micrographs, and the specific surface area is BE.
It is a value measured by the T method.

Example 1 500 ml of an FeCl ₃ aqueous solution containing Fe ³⁺ 0.05 mol / was heated at 80 ° C. for 30 minutes to produce yellowish brown precipitate particles. The pH of the suspension at this time was 1.3. Remove a part of the reaction solution, wash with water,
An electron micrograph (× 100,000) of the yellowish brown particle powder obtained by drying and drying is shown in FIG. As a result of X-ray diffraction, this yellow-brown particle powder was β-FeOOH and had a specific surface area of 190 m.
It was ² / g.

The acidic suspension having a pH of 1.3 containing 0.05 mol / β-FeOOH particles was placed in a closed container, and hydrothermally treated at 125 ° C. for 15 hours to form a reddish brown precipitate. The particle powder obtained by washing the reddish brown precipitate with water, filtering and drying was hematite as shown in the X-ray diffraction of FIG. 2, and the electron micrograph (×
As is clear from 10,000), the average particle size was 0.6 μm, the particle sizes were uniform, and the individual particles were independent particles. The particle size distribution of the obtained particle powder is shown in a histogram in FIG.

Example 2 β-Fe having a specific surface area of 240 m ² / g was prepared in the same manner as in Example 1 except that the FeCl ₃ concentration when producing β-FeOOH was 0.01 mol /.
Got OOH.

The acidic suspension of pH 1.4 containing the above 0.01 mol / β-FeOOH particles was placed in a closed container and subjected to hydrothermal treatment at 105 ° C. for 12 hours to form a reddish brown precipitate. The particle powder obtained by washing the reddish brown precipitate with water, filtering and drying was hematite as a result of X-ray diffraction, and had an average particle diameter of 0.15 μm, as is clear from the electron micrograph (× 20,000) shown in FIG. , The particle size was uniform, and the individual particles were independent particles. The particle size distribution of the obtained particle powder is shown in a histogram in FIG.

Comparative Example 1 500 ml of FeCl ₃ acidic aqueous solution containing Fe ³⁺ 0.05 mol / pH 1.8 was put in a closed container, hydrothermally treated at 125 ° C. for 15 hours, and then cooled to room temperature to form a reddish brown precipitate. The reddish yellowish brown particle powder obtained by extracting a part of the reaction solution, washing with water, filtering and drying was, as is clear from the electron micrograph (× 15,000) shown in FIG. 7, isotropic particles with needle-like particles. And are mixed, and as is clear from the X-ray diffraction shown in FIG.
-The peaks of FeOOH and hematite were confirmed. In FIG. 8, peak A is hematite and peak B is β-FeOOH.

The acidic suspension containing the reddish-brown precipitate was then washed at 125 ° C for 2
Hydrothermal treatment was performed for 0 hours to form a reddish brown precipitate. The particle powder obtained by washing the reddish brown precipitate with water, filtering and drying was a hematite particle as a result of X-ray diffraction. As is clear from the electron micrograph (× 10,000) shown in FIG. 9, the particle size was non-uniform. Met. The histogram of the particle size distribution of the obtained particle powder is shown in FIG.

Comparative Example 2 A yellowish brown precipitate was formed by hydrothermal treatment in the same manner as in Example 1 except that an acidic suspension having a pH of 1.3 containing 120 m ² / g of β-FeOOH was used. The particle powder obtained by washing the yellowish brown precipitate with water, filtering and drying, remained as β-FeOOH, as is clear from the X-ray diffraction results and the electron micrograph (× 100,000) shown in FIG.

Comparative Example 3 An acidic suspension having a pH of 1.3 containing 0.15 mol / β-FeOOH particles was hydrothermally treated in the same manner as in Example 1 to form a yellowish brown precipitate. The particle powder obtained by washing the yellowish brown precipitate with water, filtering and drying, remained as β-FeOOH as is clear from the X-ray diffraction shown in FIG. 12 and the electron micrograph (× 30,000) shown in FIG. .

Comparative Example 4 A yellow-brown precipitate was produced in the same manner as in Example 1 except that the hydrothermal treatment temperature was 95 ° C. Wash the yellowish brown precipitate with water,
The particle powder obtained by drying and drying remained β-FeOOH as is clear from the X-ray diffraction shown in FIG. 14 and the electron micrograph (× 20,000) shown in FIG.

[Effect]

According to the method for producing the hematite particle powder in the present invention,
As shown in the above Examples, the particle size is uniform, and it is possible to obtain a hematite particle powder in which individual particles are independent, and since the particle powder has excellent dispersibility, a red pigment powder for paints. Suitable as a colorant for rubber / plastics and a starting material for magnetic particle powder.

Further, in the present invention, at a low temperature of less than 130 ° C. which does not require a special device such as a high-pressure container, and moreover, due to the reaction for a short time, the particle size is uniform, and the individual particles are independent. The hematite particle powder can be obtained industrially and economically.

[Brief description of drawings]

1, FIG. 3, FIG. 5, FIG. 7, FIG. 9, FIG. 11, FIG. 13, and FIG.
Are all electron micrographs showing the particle structure of the particle powder. FIG. 1 is the starting material of Example 1, β-FeOOH particle powder, and FIGS. 3, 5 and 9 are Example 1 and Example, respectively. 2 and the hematite particle powder obtained in Comparative Example 1, FIG.
Is a mixed particle powder of β-FeOOH and hematite which is a product in the course of the reaction of Comparative Example 1, and FIGS. 11, 13 and 15 show β obtained in Comparative Example 2, Comparative Example 3 and Comparative Example 4, respectively.
-FeOOH particle powder. 4, 6 and 10 are histograms showing the particle size distributions of the hematite particles obtained in Example 1, Example 2 and Comparative Example 1, respectively. 2, FIG. 8, FIG. 12 and FIG. 14 are X-ray diffraction patterns of the particle powders obtained in Example 1, Comparative Example 1, Comparative Example 3 and Comparative Example 4, respectively.

Claims (1)

[Claims] 1. A β- having a specific surface area of 150 m ² / g or more obtained by heating an aqueous solution of ferric chloride having a Fe ³⁺ concentration of less than 0.1 mol / l to a temperature range of 70 to 90 ° C. to hydrolyze it. 0.1 mol of FeOOH particles
A method for producing a hematite particle powder, characterized in that a hematite particle having a uniform particle size is produced by hydrothermally treating an acidic suspension containing a concentration of less than / in a temperature range of 100 to 130 ° C.