JPS6364924A - Production of beta-hydrous ferric oxide particle powder showing bar shape - Google Patents

Abstract

PURPOSE:To produce the titled particles containing neither twin nor branch- shaped particles, by subjecting an acidic suspension containing >= a specific concentration of amorphous beta-hydrous ferric oxide particles having a specific surface area of >= specific volume to hydrothermal treatment. CONSTITUTION:An acidic suspension containing >=0.1mol/l amorphous beta-hydrous ferric oxide particles having >=150m<2>/g specific surface area is subjected to hydrothermal treatment at 100-130 deg.C to produce beta-hydrous ferric oxide particle powder showing a bar shape. By this method, beta-hydrous ferric oxide particle powder containing neither twin nor branch-shaped particle, showing a bar shape, is obtained. Since the particle powder has improved dispersibility, the powder is suitable as yellowish brown pigment powder for coating compound, colorant for rubber and plastics, starting raw material for magnetic particle powder, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing rod-shaped β-hydrated ferric oxide particles, which do not contain mixed twins or dendritic particles. First, it is an object of the present invention to provide a β-hydrated ferric oxide particle powder having a rod shape in which needle-like particles are aggregated and not formed into tactoids.

The main uses of the rod-shaped β-hydrated ferric oxide particles according to the present invention include yellowish brown pigment powder for paints, colorants for rubber and plastics, and starting materials for magnetic particle powders.

[Conventional technology]

Hydrous ferric oxide particles have a yellowish-brown color and are widely used as pigment powders for paints.
It is also used as a coloring agent for plastics.

Furthermore, hydrated ferric oxide particles are also used as a starting material for producing magnetic particles for magnetic recording.

That is, magnetic particles such as magnetite particles and maghemite particles are produced by reducing hydrous ferric oxide particles or further oxidizing them if necessary.

As mentioned above, hydrous ferric oxide particles are used in various fields, and the characteristic commonly required in all fields is excellent dispersibility.

That is, in the production of paints, it is necessary to uniformly and easily disperse the hydrous ferric oxide particles during kneading in the coloring of rubber and plastics. In addition, in the field of magnetic recording, the demand for higher recording densities is increasing, and in the production of magnetic recording media, it is necessary to uniformly and easily disperse magnetic particle powder when producing magnetic paint to be coated on a base film. It is required to improve the orientation and packing density by dispersion, and for this purpose, it is necessary that the starting material, hydrated ferric oxide particle powder, be uniform and easily dispersed. .

In order to be a hydrous ferric oxide particle powder with excellent dispersibility, it must not contain twins or dendritic particles, and must have a rod-like shape.

This fact is clear from the descriptions in, for example, Japanese Patent Laid-Open Nos. 51-86795 and 50415698. That is, Japanese Patent Application Laid-Open No. 51-86795 states, ``The present invention...
The purpose is to produce γ-FeJsa particles with good dispersibility and high coercive force. It is written as...j. Furthermore, JP-A-50-115698 states, ``The present invention improves the particle morphology of yellow iron oxide pigments that have been used in large amounts...'' and ``...・The specific surface area of the products treated according to the present invention is reduced to 172 to 1/3. This can be clearly seen from the electron micrograph in Figure 1. The width of the shape increases,
The length is smaller. Therefore, it can be seen that the needle-like tactoid particles are transformed into rod-like particles.

” and “...The specific surface area is approximately 1/3, and the oil absorption is significantly reduced, so when used in paints, the characteristics are improved.... Magnetic powder has a small specific surface area, so
When used as a magnetic paint, it has excellent magnetic field orientation and can increase the packing density of the magnetic powder in the coating layer.・・・・・・
As described in ``Acicular tactoid particles are transformed into rod-shaped particles, and as a result, when the specific surface area becomes smaller, the oil absorption decreases, the magnetic field orientation is excellent, and the packing density is improved.

In other words, it has been shown that the dispersibility is improved.

As hydrated ferric oxide, α-hydrated ferric oxide, β-hydrated ferric oxide, T-hydrated ferric oxide, etc., which have different crystal structures, are known.

Compared to α-hydrated ferric oxide particle powder and T-hydrated ferric oxide particle powder, β-hydrated ferric oxide particle powder provides particles that do not contain twins or dendritic particles. Cheap.

Conventionally, as a method for producing β-hydrated ferric oxide particles, there are roughly two known methods, as disclosed in Japanese Patent Publication No. 47-25959.

The first method is to hydrolyze ferric chloride particles, and the second method is to perform an oxidation reaction by passing an oxygen-containing gas through an aqueous ferrous chloride solution.

[Problem that the invention seeks to solve]

Hydrous ferric oxide particles that are not mixed with twins or dendritic particles and have a rod shape, in other words, hydrous ferric oxide particles with excellent dispersibility, are currently in demand. be.

As mentioned above, in the case of β-hydrated ferric oxide particle powder,
It is relatively easy to obtain particles that do not contain twins or dendritic particles, but when using the first method described above, it is easy to obtain particles that are spindle-shaped rather than rod-shaped, and when using the second method, particles that are spindle-shaped rather than rod-shaped are easily obtained. In this case, tactoid particles, which are aggregates of needle-like particles, are easily obtained.

This fact is based on, for example, the above-mentioned Japanese Patent Publication No. 41-25959, which states that ``...β-FeOO1L precipitated particles are produced by a hydrolysis reaction of an aqueous ferric salt solution containing ions such as fluorine and chlorine. However, according to this method, the shape of the β-FeOOH precipitated particles obtained is spindle-shaped...'' and chlorine ions are present at a ratio of at least 3 or more to iron ion atoms. The short axis is 220 to 250, and the long axis is 0.5 to 0.5, which is produced by oxidizing an aqueous solution of ferrous salt containing
Electron X! It is clear from the microphotograph and the large specific surface area of the particles of 34rd/g.

Therefore, there is a strong demand for the establishment of a technical means for obtaining a β-hydrated ferric oxide particle powder that is free from twins and dendritic particles and has a rod shape.

[Means for solving problems]

The present inventor has arrived at the present invention as a result of various studies in order to obtain β-hydrated ferric oxide particle powder that is free from twins and dendritic particles and has a rod shape. .

That is, in the present invention, 0.1 μol of β-hydrated ferric oxide particles exhibiting an amorphous shape with a specific surface area of 150 m2/g or more
β-hydrous ferric oxide particles having a rod-like shape are produced by hydrothermally treating an acidic suspension containing a concentration of /1 or more at a temperature range of 100 to 130°C. This is a method for producing ferric oxide particles.

[For production]

First, the most important point in the present invention is that the specific surface area is 15
β-Fe008 exhibiting an amorphous shape with 0rrf/g or more
When an acidic suspension containing particles at a concentration of 0.1 ol/1 or more is hydrothermally treated in a temperature range of 100 to 130°C, rod-shaped β-hydrated ferric oxide particles can be obtained. It is.

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

The starting material particles in the present invention have a specific surface area of 15011
? The particles are β-hydrated ferric oxide particles having an amorphous shape with a particle size of 1/g or more. If the specific surface area is 150 m2/g or less, tactoid particles, which are aggregates of needle-like particles, are generated, and the rod-shaped β-hydrated ferric oxide particles that are the object of the present invention cannot be generated. The amorphous β-FeOOH particles having a weight of 150 dnog or more can be obtained by a method of hydrolyzing a ferric chloride aqueous solution by heating it in a temperature range of 70 to 90°C.

The suspension containing β-hydrous ferric oxide particles exhibiting an amorphous shape in the present invention needs to be acidic; if it is not acidic, tactoid particles in which needle-shaped particles are aggregated are obtained, and the present invention It is not possible to obtain the desired rod-shaped β-hydrated ferric oxide particles.

In the present invention, the concentration of the acidic suspension containing the amorphous β-hydrated ferric oxide particles is 0.1 ol/11 or more. If it is less than O.1 ol/l, hematite particles will be produced, making it impossible to obtain the rod-shaped β-hydrated ferric oxide particles that are the object of the present invention.

The reaction temperature in the present invention is 100 to 130°C.

When the temperature is 100° C. or lower, the amorphous β-hydrated ferric oxide particles, which are the starting materials, remain as they are, and no particle growth reaction occurs.

Although β-hydrous ferric oxide particles are generated when the temperature is 130° C. or higher, this is not industrially or economically viable because it requires special equipment such as a high-pressure container.

〔Example〕

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

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

Example 1 FeC1z aqueous solution 5 containing Fe”0.2 mol/1
00 ml was heated at 80° C. for 30 minutes to form tan precipitated particles. At this time, the pH of the suspension was 1.3. A part of the reaction solution was taken out, washed with water, subjected to PiIA, and dried to obtain a yellowish brown particle powder. x30,000), the particles were amorphous, and as a result of X-ray diffraction, they were β-Fe00H, and the specific surface area was 160rrr/g.

The above acidic suspension of 0.2 ol/1 β-Fe00H (pifl containing particles, 3) was placed in a sealed container,
Hydrothermal treatment at ℃ for 15 hours produced a yellow brown precipitate. The yellowish brown precipitate was washed with water, filtered and dried, and the resulting powder was
As shown in the X-ray diffraction shown in Figure 2, it is β-Fe00H, and as is clear from the electron micrograph (X30.000) shown in Figure 3, the long axis is 0.7 μm and the axial ratio (long axis/short axis ) were rod-shaped particles with a ratio of 8:l. Moreover, the specific surface area of this particle powder was 14.5rd/g.

Example 2 Fe when obtaining amorphous β-FeOOII as a starting material
Amorphous β-Fe00H particles with a specific surface area of 180 rrr/g were produced in the same manner as in Example 1 except that the C15 concentration was 0.15 mol/1.

The above acidic suspension of pH 1.3 containing 0.15 mol/1 of amorphous β-Fe008 particles was placed in a closed container, and 1.
Hydrothermal treatment at 05° C. for 20 hours produced a yellow brown precipitate. The particles obtained by washing the yellow brown precipitate with water, filtering and drying were found to be β-FeOOH as a result of X-ray diffraction, and as is clear from the electron micrograph (X40,000) shown in Figure 4, the long axis 0.3 μ-, and the axial ratio (major axis/minor axis) is 7:
The particles were rod-shaped. Further, the specific surface area of this particle powder was 1B, OITr/g.

Comparative Example 1 Using the amorphous β-Fe008 particles used in Example 1,
, O5mol/1 β-Fe00H suspension was hydrothermally treated in the same manner as in Example 1 to produce a reddish brown precipitate. The particles obtained by washing the reddish-brown precipitate with water, filtering, and drying are hematite particles, as is clear from the X-ray diffraction shown in FIG. As expected, the particles were isotropically shaped.

Comparative Example 2 A yellow brown precipitate was produced by hydrothermal treatment in the same manner as in Example 1, except that an acidic suspension of pH 1.3 containing 130 rrf/g of β-FeOOH was used. The particles obtained by washing the yellowish brown precipitate with water, filtering and drying were found to be tactoid particles in which needle-shaped particles were aggregated as a result of X-ray diffraction and electron U microscopic observation. Moreover, the specific surface area of this particle powder is 35. O
n? /g.

Comparative Example 3 A yellow brown precipitate was produced in the same manner as in Example 1, except that the temperature of the hydrothermal treatment was 95°C. As is clear from the X-ray diffraction results and the electron micrograph (X30,000) shown in FIG. 7, the particles obtained by washing the yellow brown precipitate with water, filtering, and drying exhibited the amorphous shape of the starting material. β-Fe00
They remained H particles.

〔effect〕

According to the method for producing β-hydrated ferric oxide particles of the present invention, as shown in the previous example, β-hydrated particles are not mixed with twins or dendritic particles and have a rod-like shape. Ferric oxide particles can be obtained, and the particles have excellent dispersibility, so they are suitable as yellow-brown pigment powders for paints, colorants for rubber and plastics, and starting materials for magnetic particles. be.

[Brief explanation of drawings]

1, 3, 4, 6, and 7 are all electron 11J microphotographs showing the particle structure of the particle powder, and FIG. 1 shows the β-FeOOH particle powder, which is the starting material particle of Example 1. ,
3, FIG. 4, and FIG. 7 show the β-FeOOH particles obtained in Example 1, Example 2, and Comparative Example 3, respectively, and FIG. 6 shows the hematite particles obtained in Comparative Example 1. Both FIGS. 2 and 5 are X-ray diffraction diagrams, and FIG.
The β-FeOOH particle powder obtained in Example 1, FIG.
This is hematite particle powder obtained in Comparative Example 1.

Claims (1)

[Claims] (1) An acidic suspension containing amorphous β-hydrated ferric oxide particles with a specific surface area of 150 m^2/g or more at a concentration of 0.1 mol/l or more at a temperature range of 100 to 130°C β-hydrous ferric oxide particles having a rod shape are produced by hydrothermal treatment with a rod shape.
- A method for producing a hydrous ferric oxide particle powder.