JPH0557214B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing hematite particles, and it is possible to industrially and economically produce only hematite particles from an aqueous solution under normal pressure without using special equipment such as an autoclave. The purpose is to gain an advantage. The main uses of the hematite particles according to the present invention include raw material powder for ferrite, pigment powder for paints, coloring agents for rubber and plastics, and starting raw material powder for magnetic recording magnetic materials. [Prior Art] Hematite particles are currently widely used as raw material powder for ferrite. In other words, ferrite is made of main raw materials such as hematite particles and Ba, Sr or Pb compounds, or Zn,
It is manufactured by mixing auxiliary raw materials such as Mn, Ni, 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 powder 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 used as a magnetic recording medium by applying the magnetic paint to a film or the like. Magnetic recording magnetic materials are produced by heating and reducing hematite particles in a reducing gas to form magnetite particles, or by oxidizing the same 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 producing ferrite, the better the dispersibility of hematite particles, which are the main raw material, the better.
It becomes possible to uniformly mix the raw materials, and as a result, the ferrite-forming reaction progresses easily, and the performance of the final product, ferrite, is improved. Next, it is necessary to uniformly and easily disperse hematite particle powder 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 need to be uniformly and easily dispersed when manufacturing magnetic paints, and for this purpose, hematite particle powder, which is a starting material, is an excellent material. It is required to have dispersibility. Conventionally, the manufacturing method of hematite particle powder is as follows:
By passing an oxygen-containing gas through a reaction aqueous solution containing ferrous hydroxide obtained by reacting a ferrous salt aqueous solution and an alkaline aqueous solution, magnetite particles are generated as a starting material from the aqueous solution, and then,
A method is known in which the magnetite particles are heated in air at a temperature of about 500°C or higher. however,
In this method, since the heat treatment is performed in air at high temperatures, sintering occurs between particles and between particles.
It is difficult to obtain hematite particles in which the particles are individually dispersed, and in terms of particle size, it is difficult to say that the particles have a uniform particle size. In addition, conventionally, particles were separated one by one,
In order to obtain hematite particle powder with uniform particle size,
Examples of methods for producing hematite particles directly from an aqueous solution include methods described in Japanese Patent Publications No. 55-4694, Japanese Patent Publication No. 60-29646, and Japanese Patent Application Laid-Open No. 51-8193. The method described in Japanese Patent Publication No. 55-4694 involves heating an aqueous suspension of precipitated ferric hydroxide at a temperature of at least 100°C in an alkaline pH range in the presence of at least one organic phosphonic acid compound. The method described in Japanese Patent Publication No. 60-29646 involves crystallization control of an aqueous suspension of ferric hydroxide with a water-soluble compound selected from water-soluble compounds having coordinating ability for iron such as tartaric acid. It is heated at a temperature of at least 100°C in an alkaline environment in the presence of one or more types of agents. In addition, the method described in Japanese Patent Application Laid-open No. 51-8193 is
Add alkali hydrogen carbonate alone to the ferrous salt solution, or add both alkali hydrogen carbonate, alkali carbonate, and alkali hydroxide, and adjust the pH to 7 to 11 and the temperature
The oxidation reaction is carried out at a temperature of 65°C to 100°C. [Problems to be Solved by the Invention] Hematite particle powder, which has uniform particle size and excellent dispersibility due to the fact that the particles are individually dispersed, is currently most in demand. The above-mentioned Special Publication No. 55-4694 and Special Publication No. 1983
The methods described in Publication No. -29646 all require high temperatures of 100° C. or higher, and also require a special device called an "autoclave", so they are not industrially or economically viable. In addition, the method described in Japanese Patent Application Laid-open No. 51-8193 is
Although hematite particles are generated from an aqueous solution under normal pressure, other types of particles other than hematite are mixed in the generated hematite particles. 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 the problem] The present inventor has realized that the particle size is uniform without using special equipment such as an autoclave.
Only individual hematite particles are used industrially.
As a result of various studies aimed at achieving economical results, the present invention was arrived at. That is, the present invention provides an aqueous solution of an alkali carbonate obtained by reacting an aqueous ferrous salt solution with an aqueous alkali carbonate solution at a ratio of 1.1 to 1.7 equivalents in terms of CO ₃ to Fe in the aqueous ferrous salt solution.
When the aqueous solution containing FeCO ₃ is oxidized by passing an oxygen-containing gas through the aqueous solution, either the ferrous salt aqueous solution, the alkali carbonate aqueous solution, or the aqueous solution containing FeCO ₃ before being oxidized by passing the oxygen-containing gas through the aqueous solution. 0.1 to 5.0 as Mg equivalent to Fe in the liquid
0.1 for atomic% water-soluble magnesium salt and Fe
This is a method for producing hematite particle powder, which comprises adding ~1.5 mol% of a phosphonic acid compound or tartaric acid or a salt thereof, and then generating hematite particles from an aqueous solution by oxidizing the mixture by passing an oxygen-containing gas through the solution. [Function] First, the most important point in the present invention is that the ferrous salt aqueous solution is obtained by reacting an aqueous alkali carbonate solution at a ratio of 1.1 to 1.7 equivalents in terms of CO ₃ to Fe in the ferrous aqueous solution. When a water-soluble magnesium salt and a phosphonic acid compound or tartaric acid or a salt thereof are added in advance to oxidize the aqueous solution containing FeCO ₃ by passing an oxygen-containing gas through the aqueous solution containing FeCO 3 , hematite particles can be directly extracted from the aqueous solution under normal pressure. Due to the fact that only hematite particles can be produced, it is possible to industrially and economically mass-produce hematite particle powder with uniform particle size and individual particles. In the present invention, when a water-soluble magnesium salt and a phosphonic acid compound are added, the particle morphology of the hematite particles obtained in the present invention is spindle-shaped with an axial ratio (long axis: short axis) of about 3.0:1 to 1.5:1. When water-soluble magnesium salt and tartaric acid or its salt are added, it becomes spherical. 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 lower than 70°C, goethite particles will be mixed in the hematite particles. Although the purpose of the present invention can be achieved even when the temperature exceeds 100°C,
It requires special equipment such as an autoclave, and is not industrially or economically viable. The amount of alkali carbonate in the present invention can be used in a ratio of 1.1 to 1.7 equivalents based on Co ₃ based on Fe. 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 exceeds 1.7 equivalents, 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.
If it is less than 0.1 atomic %, granular magnetite particles will be mixed in the hematite particles. Although the purpose of the present invention can be achieved even when the content exceeds 5.0 at %, there is no point in adding more than necessary. The water-soluble magnesium salt in the present invention has a synergistic effect with the phosphonic acid compound or tartaric acid or its salt, which affects the type of particles produced, and therefore, before the hematite particle production reaction starts. It can be added to either a ferrous salt aqueous solution, an alkali carbonate aqueous solution, or an aqueous solution containing FeCO ₃ before being oxidized by aeration with an oxygen-containing gas. In the present invention, a phosphonic acid compound or tartaric acid or a salt thereof can be used. As the phosphonic acid compound, hydroxyethane diphosphonic acid, hydroxyethane diphosphonic acid 4
There are sodium, etc. 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. If it is less than 0.1 mol%, spindle-shaped goethite particles and granular hematite particles will coexist. If it exceeds 1.5 mol%, fine amorphous particles will be produced. The phosphonic acid compound or tartaric acid or its salt in the present invention affects the type of particles produced through a synergistic action with the water-soluble magnesium salt, and therefore, before the hematite particle production reaction starts. It can be added to either a ferrous salt aqueous solution, an alkali carbonate aqueous solution, or an aqueous solution containing FeCO ₃ before being oxidized by aeration with an oxygen-containing gas. 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 1 1.5 mol of ferrous sulfate/1.5 aqueous solution obtained by adding 5.6 g of magnesium sulfate (MgSO ₄ 7H ₂ O) to contain 1.0 atomic % in terms of Mg based on Fe,
It was added to 3.0 of a 1.12 mol/Na ₂ CO ₃ aqueous solution obtained by adding 4.1 g of tetrasodium hydroxyethane diphosphonate so as to contain 0.6 mol% based on Fe (CO ₃ /Fe = 1.4 equivalent), and the temperature was 80°C. _FeCO3 at °C
was generated. Particles were generated by blowing 20 air per minute into the aqueous solution containing FeCO ₂ at a temperature of 80° C. for 3.3 hours. At the end point of the oxidation reaction, a part of the reaction solution is extracted and adjusted to acidity with hydrochloric acid, and then Fe ²⁺ is added using red blood salt solution.
Judgment was made based on the presence or absence of a blue color reaction. The produced particles were separated, washed with water, dried, and crushed by a conventional method. As is clear from the electron micrograph (×20,000) shown in Figure 1, this particle powder has a uniform particle size, each particle is irregular, and the average value of the long axis is 0.6 μm, and the axial ratio (length The particles were spindle-shaped with a ratio of 2.5:1 (axis: short axis). Moreover, the X-ray diffraction diagram 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, types, amounts and times of addition of water-soluble magnesium salts, types, amounts and times of addition of phosphonic acid compounds, tartaric acid and its types of salt,
Particles were produced in the same manner as in Example 1, except that the amount added, timing of addition, and temperature were varied. As a result of X-ray diffraction, it was confirmed that any of the particles obtained in Examples 2 to 20 were only hematite particles. An electron micrograph (×20000) of the hematite particles obtained in Example 11 is shown in FIG. 3, and an X-ray diffraction diagram is shown in FIG. In FIG. 4, peak A is a peak indicating hematite. Table 1 shows the main manufacturing conditions and characteristics of the produced hematite particles. Comparative Example 1 Particles were produced in the same manner as in Example 1, except that magnesium sulfate was not added. The produced particles were separated, washed with water, dried, and crushed by a conventional method. As is clear from the electron micrograph (×20,000) shown in FIG. 5, this particulate powder was a mixture of granular particles in spindle-shaped particles. Also,
The X-ray diffraction results showed hematite and magnetite peaks. Comparative Example 2 Particles were produced in the same manner as in Example 1, except that tetrasodium hydroxyethane diphosphonate was not added. The produced particles were separated, washed with water, dried, and crushed by a conventional method. As is clear from the electron micrograph (×20,000) shown in FIG. 6, this particle powder had spindle-shaped particles mixed with spherical particles. Also,
The results of X-ray diffraction showed goethite and hematite peaks. Comparative Example 3 Particles were produced in the same manner as in Example 11 except that magnesium sulfate was not added. The produced particles were separated, washed with water, dried, and crushed by a conventional method. This particle powder is shown in the electron micrograph of Fig. 7 (×
20000). Moreover, this particle powder showed peaks of hematite and magnetite as a result of X-ray diffraction. Comparative Example 4 Tetrasodium hydroxyethane diphosphonate
Particles were produced in the same manner as in Example 1, except that 13.7 g (corresponding to 2.0 mol% of Fe) was added. The resulting particles were separated, washed with water, dried, and pulverized using a conventional method. As is clear from the electron micrograph (×20,000) shown in FIG. 8, the powder particles 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 produced particles were separated, washed with water, dried, and crushed by a conventional method. As is clear from the electron micrograph (×20,000) shown in FIG. 9, the particles were fine particles with irregular shapes. Comparative Example 6 Particles were produced in the same manner as in Example 1 except that the temperature was 65°C. The produced particles were separated, washed with water, dried, and crushed by a conventional method. 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 11 except that the temperature was 65°C. The resulting particles were separated, washed with water, dried, and pulverized using a conventional method. 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 Figure 11, peak A
is a peak indicating hematite, and peak B is a peak indicating goethite.

【table】

〔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 previous example, which is very advantageous industrially and economically. It is. The hematite particle powder obtained by the present invention is
Since the particle size is uniform and the particles are individually dispersed, it has excellent dispersibility, and is a starting material for ferrite raw material powder, pigment powder for paints, coloring agents for rubber and plastics, and magnetic recording materials. It is suitable as a raw material powder.

[Brief explanation of the drawing]

1 and 2 are an electron micrograph (×20,000) and an X-ray diffraction diagram showing the particle structure of the hematite particles obtained in Example 1, respectively. Figure 2
Among them, peak A is a peak indicating hematite.
3 and 4 are an electron micrograph (×20,000) and an X-ray diffraction diagram showing the particle structure of the spherical hematite particles obtained in Example 11, respectively.
In FIG. 4, peak A is a peak indicating hematite. 5 to 9 are electron micrographs (×20,000) showing the particle structures of the powder particles obtained in Comparative Examples 1 to 5, respectively. FIGS. 10 and 11 are X-ray diffraction patterns of the particles obtained in Comparative Example 6 and Comparative Example 7, respectively.

Claims (1)

[Claims] 1 Ferrous salt aqueous solution and Fe in the ferrous salt aqueous solution
When oxygen-containing gas is passed through an aqueous solution containing FeCO _{3 obtained by reacting FeCO 3} with an aqueous alkali carbonate solution at a ratio of 1.1 to 1.7 equivalents in terms of CO ₃ , the ferrous salt aqueous solution, the A water-soluble magnesium salt of 0.1 to 5.0 atomic % (calculated as Mg with respect to Fe) and 0.1 atomic % with respect to Fe in any of the aqueous solutions containing FeCO ₃ before oxidation by passing through an aqueous alkali carbonate solution and an oxygen-containing gas. A method for producing hematite particle powder, which comprises adding ~1.5 mol% of a phosphonic acid compound or tartaric acid or a salt thereof, and then generating hematite particles from an aqueous solution by oxidizing the mixture by passing an oxygen-containing gas through the solution.