JPS62128927A - Production of hematite grain powder - Google Patents

Abstract

PURPOSE:To produce raw material powder for ferrite, pigment powder for paint and starting raw material powder for a magnetic recording magnetic material by allowing alkali carbonate to react with a ferrous salt aq. soln. contg. soluble Mg salt of specified amount and sulfonic acid compd. and tartaric acid (tartrate) and blowing O2 into the obtained FeCO3-contg. soln. to oxidize it. CONSTITUTION:An aq. soln. of 1.1-1.7 equivalent alkali carbonate impressed in terms of CO3 for Fe contained in a ferrous salt aq. soln. such as Na2CO3, K2CO3 and (NH4)2CO3 is allowed to react with the ferrous salt aq. soln. such as FeCl2 and FeSO4 to produce an FeCO3-contg. aq. soln. and O2-contg. gas such as air is blown therein to oxidize it. In this case, 0.1-5.0atom% soluble Mg salt such as MgSO4 impressed in terms of Mg for contained Fe and sulfonic acid compd. or tartaric acid (tartrate) are added to the above-mentioned ferrous salt aq. soln., an alkali carbonate aq. soln. or an FeCO3-contg. aq. soln.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing hematite particles, in which only hematite particles are produced from an aqueous solution under normal pressure without using special equipment such as an autoclave. The purpose is to obtain industrially and economically advantageous results.

The main uses of the hematite particles according to the present invention are raw material powder for ferrite, pigment powder for paints, coloring agents for rubber and plastics, and magnetic recording materials! 3 Starting material powder for magnetic materials, etc.

(Prior Art) Hematite particles are currently widely used as raw material powder for ferrite.

That is, ferrite is made of main raw materials such as hematite particles and r3a, Sr or pb compounds, or Zn,
It is manufactured by mixing auxiliary raw materials such as Mn, old, Mg, or Cu compounds, heating, firing, and pulverizing the mixture.

In addition, since hematite particle powder has a red color, it is widely used as a pigment powder for paints when mixing pigments and vehicles to produce paints. It is also used as a coloring agent.

Furthermore, hematite particle powder is currently widely used as a starting material for magnetic recording magnetic materials.

That is, magnetic recording magnetic materials such as magnetite particle powder and maghemite particle powder are mixed and dispersed in a vehicle to form a magnetic paint, and the magnetic paint is applied to a film or the like to be used as a magnetic recording medium. The magnetic recording magnetic material is produced by heating and reducing hematite particles in a reducing gas to produce magnetite particles, or by
It is manufactured by oxidizing it in air to form maghemite particles.

As mentioned above, hematite particles are used in various fields, but the characteristic commonly required for hematite particles in all fields is excellent dispersibility. It is necessary that the particle size is uniform and that the particles are individually dispersed.

In other words, when manufacturing ferrite, the better the dispersibility of hemaquite particles, which are the main raw material, the more uniform the raw materials can be mixed, and as a result, the progress of the ferrite reaction is easier, and the performance of the final product, ferrite, is improved. will improve.

Next, it is necessary to uniformly and easily disperse hematite particles in the production of paints and during kneading in the production of rubber and plastics. Hematite particle powder is required.

Furthermore, magnetic recording magnetic materials such as magnetite particle powder and maghemite particle powder are uniformly and
In addition, it is necessary to easily disperse the hematite particles, and for this purpose, the hematite particles as a starting material are required to have excellent dispersibility.

Conventionally, the manufacturing method for hematite particles starts from an aqueous solution by bubbling an oxygen-containing gas into a reaction aqueous solution containing ferrous hydroxide obtained by reacting a ferrous salt aqueous solution and an alkaline aqueous solution. A method is known in which magnetite particles as a raw material are generated and then the magnetite particle powder is heated in air at about 500° C. or higher. However, in this method, since the heat treatment is carried out in air at a high temperature, sintering occurs between the particles and between the particles, making it difficult to obtain hematite powder in which the particles are separated one by one. Furthermore, in terms of particle size, it is difficult to say that the particles have a uniform particle size.

In addition, conventionally, in order to obtain hematite particle powder in which the particles are separated one by one and the particle size is uniform, there have been methods for producing magite particle powder directly from an aqueous solution, for example, as described in Japanese Patent Publication No. 55-4694, There are methods described in Publication No. 60-29646 and Japanese Unexamined Patent Publication No. 51-8193.

In the method described in Japanese Patent Publication No. 55-4694, an aqueous suspension of precipitated ferric hydroxide is prepared in an alkaline PL+ region at a temperature of at least 100°C in the presence of a small amount of a nucleating phosphonic acid compound. It is heat-treated, and was designated as
In the method described in Publication No. 29646, an aqueous suspension of ferric hydroxide is mixed with one or more crystallization control agents selected from water-soluble compounds having coordination ability for iron such as tartaric acid. It is heated at a temperature of at least 100° C. in the presence of an alkaline solution.

In addition, the method described in JP-A No. 51-8193 involves adding an alkali hydrogen carbonate alone to a ferrous salt solution, or adding both an alkali hydrogen carbonate, an alkali carbonate, and an alkali hydroxide, pH 7-11, temperature 65℃-100℃
The oxidation reaction is carried out at a temperature of .

[Problem that the invention seeks to solve]

Hematite particle powder, which has excellent dispersibility due to its uniform particle size and individual particles, is currently in demand, but the above-mentioned Japanese Patent Publication No. 5
The methods described in Japanese Patent Publication No. 5-4694 and Japanese Patent Publication No. 60-29646 both require high temperatures of 100°C or higher and require a special device called an "autoclave", so they are not industrially or economically viable. do not have.

Furthermore, although the method described in JP-A-51-8193 generates hemacite particles from an aqueous solution under normal pressure, other types of particles other than hematite are mixed in the hematite particles that are generated. .

Therefore, there is a strong demand for the establishment of a technical means for industrially and economically mass producing only hematite particles whose particle size is uniform and each particle is discrete.

[Means for solving problems]

The present inventor has conducted various studies in order to industrially and economically obtain only hematite particles with uniform particle size and individual particles without using special equipment such as an autoclave. The invention has been achieved.

That is, the present invention provides FeC0f obtained by reacting a ferrous salt aqueous solution with an alkali carbonate aqueous solution at a ratio of 1.1 to 1.7 equivalents in terms of CO3 to Fe in the ferrous salt aqueous solution.
When oxidizing the aqueous solution containing FeCO by passing an oxygen-containing gas through the aqueous solution containing FeCO3, any one of the ferrous salt aqueous solution, the alkaline carbonate aqueous solution, and the aqueous solution containing FeCO3 before being oxidized by passing the oxygen-containing gas through the aqueous solution. Adding 0.1 to 5.0 atomic % of a water-soluble magnesium salt based on Fe in terms of Mg and 0.1 to 1.5 mol % of a phosphonic acid compound or tartaric acid or its salt based on Fe, This is a method for producing hematite particle powder, which comprises producing hematite particles from an aqueous solution by then oxidizing the solution by passing an oxygen-containing gas through the solution.

[For production]

First, the most important point in the present invention is that the ferrous salt aqueous solution and the Fe in the ferrous salt aqueous solution are 1.1 in terms of COs.
When oxidizing an aqueous solution containing FeCO5 obtained by reacting an aqueous alkali carbonate solution at a ratio of ~1.7 equivalents with an oxygen-containing gas, a water-soluble magnesium salt and a phosphonic acid compound or a tartaric acid or its salt are mixed in advance. When adding , it is possible to generate only hematite particles directly from an aqueous solution under normal pressure, so it is possible to produce hematite particle powder with uniform particle size and individual particles. The point is that it can be mass-produced industrially and economically.

In the present invention, the particle morphology of the obtained hematite particles has an axial ratio (long axis: short axis) of 3.0:1 to i, when a water-soluble magnesium salt and a phosphonic acid compound are added.
It has a spindle shape of about s:i, and when a water-soluble magnesium salt and tartaric acid or its salt are added, it has a spherical shape.

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

Examples of the ferrous salt aqueous solution used in the present invention include a ferrous sulfate aqueous solution and a ferrous chloride aqueous solution.

As the alkali carbonate used in the present invention, sodium carbonate, potassium carbonate, ammonium carbonate, etc. can be used alone or in combination.

The ferrous salt aqueous solution and the alkali carbonate may be added either first or simultaneously.

The reaction temperature in the present invention is 70 to 100°C.

If the temperature is 70° C. or lower, goethite particles will be mixed in the hematite particles. Although the object of the present invention can be achieved even when the temperature is 100° C. or higher, it requires special equipment such as an autoclave, which is not industrially or economically viable.

The amount of alkali carbonate in the present invention is C03 relative to Fe.
It can be used in an amount of 1.1 to 1.7 equivalents. If the amount is less than 1.1 equivalent, granular magnetite particles will be mixed in the hematite particles. Although the object of the present invention can be achieved when the amount is 1.7 equivalents or more, there is no point in adding more than necessary and it is not economical.

As the water-soluble magnesium salt in the present invention, magnesium sulfate and magnesium chloride can be used.

The amount of water-soluble magnesium salt in the present invention is 0.1 to 5.0 atomic % based on Fe in terms of Mg. 0.1(
If it is less than atomic %, granular magnetite particles will be mixed in the hematite particles. Although the object of the present invention can be achieved even when the content is 5.0 at % or more, there is no point in adding more than necessary.

The water-soluble magnesium salt in the present invention affects the type of particles produced through a synergistic effect with a phosphonic acid compound or tartaric acid or its salt, and therefore,
It must be added before the hematite particle production reaction starts, and it is added to either the ferrous salt aqueous solution, the aqueous alkali carbonate solution, or the aqueous solution containing FeCO3 before being oxidized by aerating the oxygen-containing gas. be able to.

In the present invention, a phosphonic acid compound or tartaric acid or a salt thereof can be used.

Examples of the phosphonic acid compound include hydroxyethane diphosphonic acid and tetrasodium hydroxyethane diphosphonate.

Salts of tartaric acid include sodium tartrate, potassium tartrate, and the like.

The amount of the phosphonic acid compound or tartaric acid or its salt added in the present invention is 0.1 to 1.5 mol % based on Fe. When the content is 0.1 mol% or less, spindle-shaped goethite particles and granular hematite particles coexist. 1.
When the amount is 5 mol% or more, fine irregularly shaped particles are produced.

The phosphonic acid compound or tartaric acid or its salt in the present invention affects the type of particles produced through a synergistic effect with the water-soluble magnesium salt, and therefore,
It must be added before the hematite particle production reaction starts, and it is added to either the ferrous salt aqueous solution, the aqueous alkali carbonate solution, or the aqueous solution containing FeC0z before being oxidized by aerating oxygen-containing gas. be able to.

In the present invention, the water-soluble magnesium salt and the phosphonic acid compound or tartaric acid or its salt may be added in any order or at the same time.

〔Example〕

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

In addition, the average particle diameter and axial ratio (long axis: short axis) of particles in the following examples and comparative examples are all shown as average values of numerical values measured from electron micrographs.

Example I 1.5 mol/j of ferrous sulfate obtained by adding 5.6 g of magnesium sulfate (MgSOa.7H) so as to contain 1.0 atomic % in terms of Mg based on Fe! Aqueous solution 1.
A 1,12 mol 1/1 Na, CO3 aqueous solution 3.51 was obtained by adding 4.1 g of tetrasodium hydroxyethane diphosphonate to contain 0.6 mol% based on Fe.
In addition to 01 (Coff/Fe=1.4/1), temperature 8
Generation of pecks was performed at 0°C.

Particles were generated by blowing 201 air per minute into the aqueous solution containing FeC0* at a temperature of 80° C. for 3.3 hours.

The end point of the oxidation reaction was determined by extracting a portion of the reaction solution, adjusting it to acidity with hydrochloric acid, and then using a red blood salt solution to determine the presence or absence of a blue coloring reaction of Fe''.

The generated particles were separated in a furnace, washed with water, dried, and pulverized using a conventional method.

This particle powder is shown in the electron W4 micrograph (X20
, 000), the particle size is uniform, each particle is different, and the average value of the long axis is 0.6 μm.
The particles were spindle-shaped with a uniaxial ratio (long axis: short axis) of 2.5:1.

The X-ray diffraction pattern of this particle is shown in FIG. As is clear from FIG. 2, peak A is a peak indicating hematite, and it can be seen that it consists only of hematite.

Examples 2 to 20 Types of ferrous salts, types, concentrations and equivalent ratios of alkali carbonates, type I of water-soluble magnesium salts, amount and timing of addition, types, amounts and timing of addition of phosphonic acid compounds, tartaric acid Particles were produced in the same manner as in Example 1, except that the type, amount, timing, and temperature of the salt and its salt were varied.

As a result of X-ray diffraction, it was confirmed that all the particles obtained in Examples 2 to 20 were only hematite particles.

An electron micrograph (x 20,000) of the hematite particles obtained in Example 11 is shown in Figure 3, and an X-ray diffraction diagram is shown in Figure 4.
Shown in t. In FIG. 4, peak A is a peak indicating hematite.

Table 1 shows the main manufacturing conditions and characteristics of the maquito particles produced.

Comparative Example 1 Particles were produced in the same manner as in Example 1 except that magnesium sulfate was not added.

The generated particles were separated in a furnace, washed with water, dried, and pulverized using a conventional method.

This particle powder is shown in the electron micrograph (x20,
000), granular particles were mixed in the spindle-shaped particles. Moreover, the results of X-ray diffraction showed peaks of hematite and magnetite.

Comparative Example 2 Particles were produced in the same manner as in Example except that tetrasodium hydroxyethane diphosphonate was not added.

The generated particles were separated in a furnace, washed with water, dried, and pulverized using a conventional method.

This particle powder is shown in the electron micrograph (x 20
．． 000), spherical particles were mixed in the spindle-shaped particles. Moreover, the results of X-ray diffraction showed peaks of goethite and hematite.

Comparative Example 3 Particles were produced in the same manner as in Example 11 except that magnesium sulfate was not added.

The generated particles were washed, dried, and pulverized door-to-door using conventional methods.

The electron micrograph of Figure 7 (X20.0
00). Moreover, this particle powder showed peaks of hematite and magnetite as a result of X-ray diffraction.

Comparative Example 4 Tetrasodium hydroxyethane diphosphonate 13.7g
Particles were produced in the same manner as in Example 1, except that 2.0 mol % of Fe was added.

The generated particles were washed, dried, and pulverized door-to-door using conventional methods.

This particle powder is shown in the electron micrograph (x 20
．． 000), they were fine amorphous particles.

Comparative Example 5 Particles were produced in the same manner as in Example 11, except that 8.8 g of sodium tartrate (corresponding to 2.0 mol % based on Fe) was added.

The generated particles were separated in a furnace, washed with water, dried, and pulverized using a conventional method.

This particle powder is shown in the electron micrograph (x 20
．． 000), they were fine amorphous particles.

Comparative Example 6 Particles were produced in the same manner as in Example 1 except that the temperature was 65°C.

The generated particles were washed, dried, and pulverized door-to-door using conventional methods.

As is clear from the X-ray diffraction diagram shown in FIG. 10, this particle powder was a mixture of hematite particles and goethite particles. In FIG. 10, peak A is a peak indicating hematite, and peak B is a peak indicating goethite.

Comparative Example 7 Particles were produced in the same manner as in Example 4 except that the temperature was 65°C.

The generated particles were washed, dried, and pulverized door-to-door using conventional methods.

As is clear from the X-ray diffraction diagram shown in FIG. 11, this particle powder was a mixture of hematite particles and goethite particles. In FIG. 11, peak A is a peak indicating hematite, and peak B is a peak indicating goethite.

〔effect〕

According to the method for producing hematite particles according to the present invention, only hematite particles can be directly produced from an aqueous solution under normal pressure, as shown in the above-mentioned example.
It is economically very advantageous.

The hematite particles obtained by the present invention have a uniform particle size and each particle is dispersed, so it has excellent dispersibility and can be used as raw material powder for ferrite, pigment powder for paints, rubber, etc. It is suitable as a coloring agent for plastic dyeing and a starting material powder for magnetic recording materials.

[Brief explanation of drawings]

1 and 2 are electron micrographs (x 2
0.000) and an X-ray diffraction diagram. In Figure 2, peak A
This is a peak indicating hematite. 3 and 4 are an electron micrograph (X 20,000) and an X-ray diffraction diagram showing the particle structure of spindle-shaped hematite particles containing Co obtained in Example 11, respectively. In FIG. 4, peak A is a peak indicating hematite. Figures 5 to 9 are all electron micrographs (×20.0
00) and show the particle structures of the powder particles obtained in Comparative Examples 1 to 5, respectively. FIGS. 1O and 11 are X-ray diffraction patterns of the particles obtained in Comparative Example 6 and Comparative Example 7, respectively.

Claims (1)

[Claims] (1) An aqueous solution containing FeCO_3 obtained by reacting a ferrous salt aqueous solution with an alkali carbonate aqueous solution at a ratio of 1.1 to 1.7 equivalents in terms of CO_3 to Fe in the ferrous salt aqueous solution. When oxidizing by aerating an oxygen-containing gas, the FeCO before oxidizing by aerating the ferrous salt aqueous solution, the alkali carbonate aqueous solution, and the oxygen-containing gas in advance.
Mg relative to Fe in any of the aqueous solutions containing _3
0.1 to 5.0 atomic % of a water-soluble magnesium salt and 0.1 to 1.5 mol % of a phosphonic acid compound or tartaric acid or its salt based on Fe are added, and then oxygen-containing gas is bubbled through. 1. A method for producing hematite particles, the method comprising producing hematite particles from an aqueous solution by oxidizing the hematite particles.