JPS62128930A - Production of hematite grain powder - Google Patents

Abstract

PURPOSE:To industrially and economically produce hematite grain powder suitable for the various applications by adding previously sulfonic acid compd. or tartaric acid (tartrate) to either of a ferrous salt aq. soln. and an alkali carbonate aq. soln. in case of allowing the ferrous salt aq. soln. to react with the alkali carbonate aq. soln. to form FeCO3 and blowing oxygen or the like therein to oxidize it. CONSTITUTION:An aq. soln. contg. FeCO3 is formed by adding 1.8 equivalent alkali carbonate aq. soln. such as Na2CO3 and (NH4)2CO3 impressed in terms of CO3 for Fe content contained in an aq. soln. of ferrous salt such as FeCl2 and FeSO4 thereto. It is oxidized by blowing oxygen-contg. gas such as air into this aq. soln. In this case, hematite grain powder suitable as a raw material of ferrite, pigment for paint, rubber and a magnetic recording magnetic material can be inexpensively produced without using an autoclave or the like by adding 0.1-1.5mol% sulfonic acid compd. or tartaric acid (tartrate) for contained Fe to some sq. soln. of the ferrous salt aq. soln., the alkali carbonate aq. soln. or the FeCO3-contg. aq. soln. before the blowing of oxidizing gas.

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 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.

That is, ferrite is made of main raw materials such as hematite particles and Ba, Sr or 1 is a pb compound, or Zn, M
It is manufactured by mixing n5Nt, Mg, or auxiliary raw materials such as C, u compounds, heating, firing, and pulverizing.

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 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 hematite 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, a method of producing magite particle powder directly from an aqueous solution has been proposed, for example, in Japanese Patent Publication No. 55-4694, Special Public Service 1986-2964
There are methods described in Japanese Patent Publication No. 6 and Japanese Unexamined Patent Publication 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. It is a special public service in the 1980s.
The method described in Japanese Patent Publication No. 29646 discloses that an aqueous suspension of ferric hydroxide is mixed with one or more crystallization control agents selected from water-soluble compounds having a coordinating ability for iron, such as tartaric acid. It is heated at a temperature of at least 100° C. in the presence of alkalinity.

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 also require a special device called an "autoclave", which makes them difficult to achieve industrially and economically. isn't it.

Furthermore, the method described in JP-A-51-8193 uses water under normal pressure. Although hematite particles are generated from the liquid 8, 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 uneven.

(Means for Solving the Problems) The present inventor has developed an industrial and economical method for producing only hematite particles, which have uniform particle size and are individually dispersed, without using special equipment such as an autoclave. As a result of various studies to achieve this goal, we have arrived at the present invention.

That is, the present invention provides Fe(:Os) obtained by reacting an aqueous ferrous salt solution with an aqueous alkali carbonate solution having a ratio of 1.8 equivalents or more in terms of GO3 to Fe in the aqueous ferrous salt solution. When oxidizing the aqueous solution containing oxygen by passing an oxygen-containing gas through the aqueous solution containing the iron,
0.0 for Fe in any of the aqueous solutions containing CO5.
A method for producing hematite particle powder, which comprises adding 1-1.5 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. It is.

[For production]

First of all, 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 1.8 in terms of CO.
When a phosphonic acid compound or tartaric acid or its salt is added in advance to the aqueous solution containing FeCO5 obtained by reacting it with an aqueous alkali carbonate solution in an equivalent or more proportion, by passing an oxygen-containing gas through the aqueous solution, Due to the fact that only hematite particles can be directly generated from an aqueous solution under normal pressure, the particle size is uniform, and
The advantage is that it is possible to industrially and economically mass-produce hematite particle powder in which the particles are separated one by one.

In the present invention, when a phosphonic acid compound is added, the particle morphology of the obtained hematite particles changes depending on the axial ratio (long axis;
short axis) is 2. It becomes a spindle shape with a ratio of s:i to about 1.5:1, and when tartaric acid or a salt thereof is added, it becomes 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 CO1 relative to Fe.
It can be used in a ratio of 8 equivalents or more in terms of O1.

If the amount is 1.8 equivalents or less, granular magnetite particles will be mixed in the hematite particles.7 In the present invention, a phosphonic acid compound, tartaric acid, or a salt thereof can be used.

Examples of phosphonic acid compounds include hydroxyethane diphosphonic acid and hydroxyethane diphosphonic i! 24 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. 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, and therefore needs to be added before the hematite particle production reaction starts, and the ferrous salt Peck before oxidizing aqueous solution, aqueous alkali carbonate solution, and oxygen stand by passing gas
It can be added to any aqueous solution containing s.

〔Example〕

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

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

Example 1 Ferrous sulfate contains 1.5+wol/j! Aqueous solution 1.5 f
1.54 mol/41 NatCOs aqueous solution obtained by adding 4.1 g of tetrasodium hydroxyethane diphosphonate to 0.6 mol% of fi to Pe. In addition to Ol (COs/Pe=2.0 equivalent), temperature 8
FeCO5 production was performed at 0°C.

Particles were generated by blowing 202 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 micrograph (X 20
, 000), the particle size is uniform,
Each particle is different, and the average value of the long axis is 0.6μ
The particles were spindle-shaped with an axis ratio (long axis: short axis) of 2.2:1.

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 21 The type of ferrous salt, the type, concentration and equivalent ratio of alkali carbonate, the type, amount and timing of addition of phosphonic acid compound, the type, amount and timing of addition of tartaric acid and its salts, and the temperature Particles were produced in the same manner as in Example 1, except for making various changes.

As a result of xNIA diffraction, it was confirmed that all the particles obtained in Examples 2 to 21 were only hematite particles.

An electron micrograph (x 20,000) of the hematite particles obtained in Example 12 is shown in Figure 3, and an X-ray diffraction diagram is shown in Figure 4.
Shown below. Peak A in FIG. 4 indicates hematite.

The properties of the powder are shown in Table 1.

Comparative Example 1 1.12 mol/1 NazCOs aqueous solution 3.011
Particles were produced in the same manner as in Example 1, except that (corresponding to CO*/Fe-1,4 equivalent) was used.

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), 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 1.12 mol/It NazCOs aqueous solution 3.01
Particles were produced in the same manner as in Example 12, except for using COi/Fe (corresponding to 1.4 equivalents).

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

This particle powder was transferred to the electron rIr4 micrograph (X20
,000). Moreover, this particle powder showed peaks of hematite and magnetite as a result of X-ray diffraction.

Comparative Example 3 Tetrasodium hydroxyethane diphosphonate 13.7 g
Particles were produced in the same manner as in Example 1, except that 2.0 mol % of 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 4 Particles were produced in the same manner as in Example 12, except that 8.8 g of sodium tartrate (corresponding to 2.0 mol % based on Fe) was added.

The produced particles were separated in a furnace, washed with water, dried, and crushed in a conventional manner.

This particle powder is shown in the electron micrograph (X20,
000>, it was a fine amorphous particle.

Comparative Example 5 Particles were produced in the same manner as in Example 1 except that the temperature was 65°C.

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

As is clear from the X-ray diffraction diagram shown in Figure 9, this particle powder was a mixture of hematite particles and goethite particles. In Figure 9, peak A indicates hematite, and peak B indicates goethite. This is the peak shown.

Comparative Example 6 Particles were produced in the same manner as in Example 12, 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. 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.

〔effect〕

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

The hematite particles obtained by the present invention have uniform particle size and each particle is disjointed, 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 plastics and a starting material powder for magnetic recording materials.

[Brief explanation of drawings]

1 and 2 are electron micrographs (X20
．． 000) and an X-ray diffraction diagram. In FIG. 2, peak A is a peak indicating hemaquite. 3 and 4 are an electron micrograph (X20,000) and an X-ray diffraction diagram showing the particle structure of spindle-shaped hematite particles containing Co obtained in Example 12, respectively. In FIG. 4, peak A is a peak indicating hemaquite. 5 to 9 are electron micrographs (X20.0
00) and show the particle structures of the powder particles obtained in Comparative Examples 1 to 5, respectively. FIG. 10 is an X-ray diffraction diagram obtained in Comparative Example 6, respectively.

Claims (1)

[Claims] (1) Oxygen-containing gas is added to the FeCO_3-containing aqueous solution obtained by reacting a ferrous salt aqueous solution with an alkali carbonate aqueous solution having a ratio of 1.8 equivalents or more in terms of CO_3 to Fe in the ferrous salt aqueous solution. When aerating and oxidizing, the FeCO_3 before being oxidized by aerating the ferrous salt aqueous solution, the alkali carbonate aqueous solution, and the oxygen-containing gas in advance.
0.1 to 1 for Fe in any aqueous solution containing
．． A method for producing hematite particle powder, which comprises adding 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.