JPH0324412B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides particles having a spherical shape and a bulk density of 0.40 to 1.30 g/cm ³ and containing Si.
Spinel-type M ²⁺ _x Fe ²⁺ _1-x Fe ³⁺ ₂ O ₄ particles with uniform particle size containing 0.1 to 5.0 atom% of Fe (however,
0<x≦1, M ²⁺ is Mn, Zn, Cu, Ni, Co, Mg
The present invention relates to spinel-type ferrite particles having a spherical shape made of one or more divalent metals, and a method for producing the same.

The spherical spinel-type ferrite particles produced by the present invention are mainly used as material powders for magnetic developing materials for copying, electromagnetic wave absorbing materials, and the like.

[Prior art]

In recent years, spinel-type ferrite particle powder has been widely used as a material powder for molded magnetic bodies such as magnetic developing materials for copying and electromagnetic wave absorbing materials.

Spinel-type ferrite molded magnetic material is manufactured by molding spinel-type ferrite particle powder into a certain shape and then firing it, kneading it into resin or oil, or microcapsulating it. In order to obtain a ferrite-molded magnetic material, it is necessary that the spinel-type ferrite particles, which are magnetic material powders, have high filling properties, and for this purpose, the particle shape must be as isotropic as possible. In particular, it is required to be a powder that is spherical, uniform in particle size, and has little cohesiveness between particles, and as a result, has a high bulk density. If it is possible to obtain spinel-type ferrite particles with a spherical shape with high filling properties, the powder can be packed in the closest density, which not only improves the performance of the molded magnetic material but also improves the quality of the molded magnetic material after molding and firing. Shrinkage rate is reduced and highly accurate dimensional control is possible.

Traditionally, spinel-type ferrite particles have been produced using iron oxide and Mn, Zn, Cu, Ni, Co, Mg.
A manufacturing method in which ferrite auxiliary raw materials such as compounds are mixed, heated, fired, and crushed, the so-called dry method, and an aqueous solution of Fe ²⁺ salt and M ²⁺ salt of divalent metals such as Mn, Zn, Cu, Ni, Co, Mg, etc. The so-called wet method is a method of manufacturing by blowing an oxygen-containing gas such as air into a suspension containing Fe ²⁺ and M ²⁺ hydroxides obtained by the reaction of an aqueous solution and an aqueous alkaline solution. be.

[Problem that the invention seeks to solve]

Spinel-type ferrite particles with high filling properties are currently most in demand, but the particles obtained by the above-mentioned known methods are still
It is difficult to say that the particles exhibit a spherical shape with high filling properties.

That is, the spinel-type ferrite particles obtained by the dry process are obtained by pulverizing a calcined ferrite lump with a powerful pulverizer, and therefore, the particles are irregularly shaped particles with asymmetric particle sizes. Moreover, sintering occurs between particles.

Further, the spinel-type ferrite particles obtained by the wet method are generally granular or cubic particles, and the dry granules have strong cohesiveness among the particles.

As an attempt to obtain spherical ferrite particles by a wet method, for example, there is a method for producing cobalt ferrite particles described in JP-A-49-35900.

However, as shown in Comparative Example 2 below, the cobalt ferrite particles obtained by the method described in JP-A-49-35900 have insufficient sphericity and asymmetric particle sizes. Moreover, the cohesion between the particles is strong. This is produced by the hydrolysis reaction of iron carbonate obtained from ferrous sulfate and cobalt sulfate and an alkali metal carbonate, so cobalt ferrite core particles are rapidly precipitated and formed, resulting in a change in shape. It is thought that sufficient control was not possible.

As mentioned above, there is a strong demand for the establishment of a method for producing spinel-type ferrite particle powder which has an isotropic particle shape, particularly a spherical shape, a uniform particle size, and low agglomeration between particles.

[Means for solving problems]

The present inventor has conducted various studies on a method for producing spinel-type ferrite particle powder that has an isotropic particle shape, particularly a spherical shape, a uniform particle size, and low cohesion between particles. The present invention has been achieved.

That is, the present invention has particles having a spherical shape and a bulk density of 0.40 to 1.30 g/cm ³ ,
Spinel-type M ²⁺ _x Fe ²⁺ _1-x Fe ³⁺ ₂ O ₄ particles containing 0.1 to 0.5 at% of Si relative to Fe (however, 0<x≦
1. M ²⁺ represents one or more divalent metals such as Mn, Zn, Cu, Ni, Co, Mg, etc.) and a spinel-type ferrite particle powder exhibiting a spherical shape, and an aqueous Fe ²⁺ salt solution; 50 mol of M ²⁺ (where M ²⁺ represents one or more divalent metals such as Mn, Zn, Cu, Ni, Co, Mg, etc.) relative to Fe ²⁺ in the Fe ²⁺ salt aqueous solution. Fe ²⁺ and M ²⁺ hydroxide obtained by reacting an aqueous M ²⁺ salt solution containing a proportion of 0.80 to 0.99 equivalents of alkali hydroxide with respect to the total amount of Fe ²⁺ and M ²⁺ Fe ²⁺ containing
In oxidizing the Fe ²⁺ and M ²⁺ hydroxides by passing an oxygen-containing gas through the reaction aqueous solution of salt and M ²⁺ salt while heating, the alkali hydroxide or the
Water-soluble silicate is added in advance to either the reaction aqueous solution of Fe ²⁺ salt or M ²⁺ salt containing hydroxides of Fe ²⁺ and M ²⁺ in an amount of 0.1 to 5.0 atomic % based on Fe ²⁺ in terms of Si. After that, while heating at a temperature of 70 to 100°C, oxygen-containing gas is passed through the air, and then under the same conditions as the heating oxidation conditions, the hydroxides of Fe ²⁺ and M ²⁺ are subjected to a post-oxidation reaction. Spinel-type M ²⁺ _x Fe ²⁺ _1-x that takes on a spherical shape by adding 1.00 equivalents or more of alkali hydroxide to the total amount of Fe ²⁺ and M ²⁺ remaining in the mother liquor
This is a method for producing spinel-type ferrite particle powder exhibiting a spherical shape by producing Fe ³⁺ ₂ O ₄ particles (0<x≦1).

[Effect]

First, the most important point in the present invention is that the mixing ratio of the divalent metal salt to ferrous iron is within a specific range, and the type of alkali is alkali hydroxide, and the amount added is within a specific range. By doing this, it is possible to obtain spinel-type ferrite particles exhibiting a spherical shape. Moreover, the sphericity of the produced particles is improved by the addition of water-soluble silicate, and the particle size is uniform. Because of this, the points of contact between the particles become small, so the agglomeration is extremely weak and individual particles can be obtained.

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

As the Fe ²⁺ salt aqueous solution in the present invention, ferrous sulfate, ferrous chloride, etc. are used.

As the divalent metal M ²⁺ salt aqueous solution in the present invention, sulfates, chlorides, nitrates, etc. of Mn, Zn, Cu, Ni, Co, Mg, etc. are used.

The ratio of M ²⁺ salt aqueous solution to Fe ²⁺ salt aqueous solution is
It is 50 mol% or less in terms of M ²⁺ based on Fe ²⁺ .

If it is less than 50 mol%, spinel-type ferrite particles with a desired composition and a spherical shape can be produced, but if it exceeds 50 mol%, M ²⁺ oxidation occurs in addition to spinel-type ferrite particles. Things get mixed in.

As the alkali hydroxide in the present invention, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal oxides and hydroxides such as magnesium hydroxide and calcium hydroxide can be used. .

The amount of alkali hydroxide used to precipitate Fe ²⁺ and M ²⁺ hydroxides in the present invention is as follows:
It is 0.80 to 0.99 equivalent based on the total amount of Fe ²⁺ and M ²⁺ in the Fe ²⁺ salt and M ²⁺ salt aqueous solutions.

When the amount is less than 0.80 equivalent or more than 0.99 equivalent, it is difficult to produce spinel-type ferrite particles exhibiting a spherical shape.

Contains hydroxides of Fe ²⁺ and M ²⁺ in the present invention
The reaction temperature when oxygen-containing gas is passed through the reaction aqueous solution of Fe ²⁺ salt and M ²⁺ salt is 70°C to 100°C.

If the temperature is less than 70°C, acicular goethite particles are mixed, and even if it exceeds 100°C, spherical spinel-type ferrite particles are produced, but this is not suitable for industrial use.

The oxidation means is carried out by passing an oxygen-containing gas (for example, air) into the liquid.

Water-soluble silicates used in the present invention include sodium and potassium silicates.

The amount of water-soluble silicate added is
It is 0.1 to 5.0 atomic% in terms of Si.

If it is less than 0.1 atomic %, it will not be possible to obtain spinel-type ferrite particles having excellent sphericity and a spherical shape with uniform particle size, which is the objective of the present invention.

When the amount exceeds 5.0 atomic %, the added water-soluble silicate precipitates alone and is mixed in the spinel-shaped ferrite particles having a spherical shape.

The water-soluble silicate in the present invention is involved in the ^shape of the spherical spinel-type ferrite particles that are produced ^. Contains hydroxide of
It is necessary to pass oxygen-containing gas into the reaction aqueous solution of Fe ²⁺ salt and M ²⁺ before generating spinel-type ferrite particles, and alkali hydroxide or
It can be added to any reaction aqueous solution of Fe ²⁺ salt and M ²⁺ salt containing hydroxides of Fe ²⁺ and M ²⁺ .

When a water-soluble silicate is added to an aqueous ferrous salt solution, the object of the present invention cannot be achieved because the water-soluble silicate is precipitated as SiO ₂ at the same time as it is added.

Almost the entire amount of the added water-soluble silicate was contained in the produced spinel-type ferrite particle powder, and as shown in the examples below, the obtained spinel-type ferrite particle powder contained almost the same amount as the added amount. are doing.

In the present invention, the amount of alkali hydroxide added to Fe ²⁺ and M ²⁺ remaining in the reaction mother liquor after oxidizing the hydroxides of Fe ²⁺ and M ²⁺ is 1.00 equivalent or more.

If the amount is less than 1.00 equivalent, all Fe ²⁺ and M ²⁺ will not precipitate. A preferable amount is 1.00 equivalent or more in consideration of industrial efficiency.

In the present invention, the reaction temperature and oxidation means when adding alkali hydroxide to Fe ²⁺ and M ²⁺ remaining in the reaction mother liquor after oxidizing the hydroxides of Fe ²⁺ and M ²⁺ are as described above. Contains hydroxides of Fe ²⁺ and M ²⁺
The conditions may be the same as those used when oxygen-containing gas is bubbled through the reaction aqueous solution of Fe ²⁺ salt and M ²⁺ salt.

〔Example〕

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

In addition, the average particle diameter in the following examples and comparative examples is determined by the BET method, and the bulk density is determined by JIS K 5101.
It was measured by the method described in .

The amount of Si and M ²⁺ in the particles was measured using a “fluorescent X-ray analyzer model 3063M” (manufactured by Rigaku Denki Kogyo) and
The measurement was performed by performing fluorescent X-ray analysis in accordance with the "General Rules for Fluorescent X-ray Analysis" of K 0119.

Example 1 Fe ²⁺ 1.68mol/ferrous sulfate aqueous solution 1050ml
Manganese sulfate aqueous solution with Mn2.10mol/M2 ⁺
250ml and Zn0.94mol/Zinc sulfate aqueous solution 250ml
The mixed aqueous solution obtained by adding each of these was added to sodium silicate (3
In addition to 1690 ^ml of a 2.54 ^- N NaOH aqueous solution containing ^2.0 g (corresponding to 0.57 atomic % of Si to Fe ²⁺ ), ), add another 760ml of water to make a total volume of 4000ml,
At PH6.4 and temperature 92℃, Fe(OH) ₂ , Mn
A mixed colloid aqueous solution of (OH) ₂ and Zn(OH) ₂ was produced, and the above mixed colloid was oxidized by bubbling 15 air per minute for 200 minutes, and then oxidized with 2.54-N.
Add 307 ml of NaOH aqueous solution (Fe ²⁺ , Mn ²⁺ and
This corresponds to 1.05 equivalent to the total amount of Zn ²⁺ . ), PH
11.0 and a temperature of 92° C. with 15 air per minute for 30 minutes to produce Mn-Zn ferrite particles.

The generated particles are washed with water, separated, dried, and
Shattered.

The obtained Mn-Zn ferrite particle powder is shown in Figure 1.
As is clear from the electron micrograph (×30,000) shown in Figure 2 and the electron micrograph (×100,000) shown in Figure 2, there is no aggregation between particles, and the average particle diameter is
Mn− exhibits a spherical shape with improved sphericity of 0.21 μm.
It was Zn ferrite.

In addition, as a result of fluorescent X-ray analysis, this spherical Mn-Zn ferrite particle powder has a composition of Mn0:
32.1mol%, ZnO: 14.2mol%, Fe ₂ O ₃ : 53.7mol
%, the Si content was 0.60 atomic %, and the particles were spinel-type ferrite particles with a bulk density of 0.63 g/cm ³ .

Example 2 Add 1050 ml of ferrous sulfate aqueous solution containing 1.68 mol of Fe ²⁺
A mixed aqueous solution obtained by adding 500 ml of a nickel sulfate aqueous solution containing 2.04 mol of Ni as Mn ²⁺ was added to sodium silicate (3
In addition to 1750 ml of a 3.46-N NaOH aqueous solution containing 5.0 g (corresponding to 1.36 atomic % of Si to Fe ²⁺ ), (corresponding to 0.90 equivalent to Fe ²⁺ and Ni ²⁺ ),
Add another 360ml of water to make a total volume of 4000ml, pH 6.8,
A mixed colloid aqueous solution of Fe(OH) ₂ and Ni(OH) ₂ was generated at a temperature of 90°C, and the mixed colloid was oxidized by blowing air at a rate of 15 per minute for 180 minutes.
Next, 217 ml of a 3.46-N NaOH aqueous solution was added (corresponding to 1.12 equivalents to the total amount of Fe ²⁺ and Ni ²⁺ ), and air was aerated at a rate of 15 per minute for 30 minutes at a pH of 12.0 and a temperature of 90°C. Ni ferrite particles were produced.

The generated particles are washed with water, separated, dried, and
Shattered.

As is clear from the electron micrograph (×50000) shown in Fig. 3, the obtained Ni ferrite particles have the following properties:
There is no aggregation between particles, and the average particle size is
It was Ni ferrite with a spherical shape of 0.22 μm.

In addition, as a result of fluorescent X-ray analysis, this spherical Ni ferrite particle powder has a composition of Ni0:
46.0 mol%, Fe ₂ O ₃ : 54.0 mol%, Si content was 1.40 atomic %, and they were spinel-type ferrite particles with a bulk density of 0.58 g/cm ³ .

Comparative Example 1 1050 ml of ferrous sulfate aqueous solution containing 1.68 mol of Fe ²⁺
Manganese sulfate aqueous solution with Mn2.10mol/M2 ⁺
250ml and Zn0.94mol/Zinc sulfate aqueous solution 250ml
The mixed aqueous solution obtained by adding each was added to 2390 ml of a 2.54-N NaOH aqueous solution prepared in advance in the reactor (for Fe ²⁺ , Mn ²⁺ and Zn ²⁺
This corresponds to 1.20 equivalents. ) Add another 60ml of water to make a total volume of 4000ml, and at pH 13.2 and temperature 90℃, Fe
A mixed colloid aqueous solution of (OH) ₂ , Mn(OH) ₂ and Zn(OH) ₂ is generated, and the above mixed colloid is added every minute.
Mn-Zn ferrite particles were produced by aerating 15 air for 240 minutes.

The generated particles are washed with water, separated, dried, and
Shattered.

The obtained Mn-Zn ferrite particle powder is shown in Figure 4.
As is clear from the electron micrograph (×20,000) shown in Figure 2, the particles were cubic in shape.

This Mn-Zn ferrite particle powder exhibiting a cubic shape has an average particle diameter of 0.20 μm, and as a result of fluorescent X-ray analysis, the composition is MnO: 32.5 mol%, ZnO:
The bulk density was 13.9mol%, Fe ₂ O ₃ : 53.6mol%.
They were spinel-type ferrite particles of 0.23 g/ml.

Comparative Example 2 1050 ml of ferrous sulfate aqueous solution containing 1.68 mol of Fe ²⁺
A mixed aqueous solution obtained by adding 500 ml of a cobalt sulfate aqueous solution containing 2.01 mol of Co ²⁺ as M ²⁺ was added to 2.36-N Na ₂ CO ₃ prepared in advance in a reactor.
In addition to 1275 ml of aqueous solution (corresponding to 0.90 equivalent for Fe ²⁺ and Co ²⁺ ), add 835 ml of water to make a total volume of 4000 ml.
ml, and generate a mixed colloidal aqueous solution of Fe(OH) ₂ and Co(OH) ₂ at pH 6.5 and temperature 88°C.
The above mixed colloid was oxidized by bubbling 15 air per minute for 230 minutes, and then a 2.54-N NaOH aqueous solution was added.
Add 285 ml (corresponding to 1.08 equivalents to the total amount of Fe ²⁺ and Co ²⁺ ), and add 285 ml per minute at pH 11.0 and temperature 88°C.
15 air was bubbled through for 30 minutes to produce Co ferrite particles.

The generated particles are washed with water, separated, dried, and
Shattered.

As shown in the electron micrograph (×20,000) shown in FIG. 5, the obtained Co ferrite particles had an irregular shape and could hardly be called spherical.

The average particle size of the particles was 0.15 μm and the bulk density was 0.25 g/cm ³ .

〔effect〕

As shown in the above example, the spinel-type ferrite particles according to the present invention are particles exhibiting a spherical shape with improved sphericity and having a uniform particle size. Since the particles have little agglomeration and, as a result, have a large bulk density, they are suitable as material powders for molded magnetic bodies such as magnetic developing materials for copying and radio wave absorbing materials, which are currently most in demand.

When manufacturing molded magnetic materials such as magnetic developing materials for copying and radio wave absorbing materials, close packing is possible when spinel-type ferrite particles exhibiting a spherical shape with improved sphericity obtained by the present invention are used. This makes it possible to improve the performance of molded magnetic materials, and
Dimensions can be controlled with high precision by reducing the shrinkage rate due to firing.

[Brief explanation of drawings]

1 to 5 are electron micrographs showing the particle morphology (structure) of spinel-type ferrite particles, and FIGS. 1 and 2 show the spherical Mn-Zn ferrite obtained in Example 1. Electron micrographs showing different magnifications of particle powder (Figure 1 is ×30000;
Figure 2 is an electron micrograph (×100,000) of the Ni ferrite particles obtained in Example 2 and exhibiting a spherical shape, and Figure 4 is an electron micrograph (×50,000) of the Ni ferrite particles obtained in Comparative Example 1 which exhibited a cubic shape. An electron micrograph (×20,000) of the Mn-Zn ferrite particles and FIG. 5 are an electron micrograph (×20,000) of the amorphous Co ferrite particles obtained in Comparative Example 2.

Claims (1)

[Claims] 1. The particle shape is spherical, the bulk density is 0.40 to 1.30 g/cm ³ , and Si is less than Fe.
Spinel type M ²⁺ _x containing 0.1 to 5.0 at%
Fe ²⁺ _1-x Fe ³⁺ ₂ O ₄ particles (0<x≦1, M ²⁺
A spherical spinel-type ferrite particle powder consisting of one or more divalent metals such as Mn, Zn, Cu, Ni, Co, and Mg. 2 Fe ²⁺ salt aqueous solution and Fe ²⁺ in the Fe ²⁺ salt aqueous solution
M ²⁺ (However, M ²⁺ is Mn, Zn, Cu, Ni,
Indicates one or more divalent metals such as Co and Mg)
An aqueous M ²⁺ salt solution containing 50 mol% or less of
Fe ²⁺ and M ²⁺ obtained by reacting 0.80 to 0.99 equivalents of alkali hydroxide with the total amount of Fe ²⁺ and M ²⁺
The reaction solution of Fe ²⁺ salt and M ²⁺ salt containing hydroxides was heated while bubbling oxygen-containing gas through the above.
In oxidizing Fe ²⁺ and M ²⁺ hydroxides, either the alkali hydroxide or the reaction aqueous solution of Fe ²⁺ salt and M ²⁺ salt containing the Fe ²⁺ and M ²⁺ hydroxides. Si for Fe ²⁺ with water-soluble silicate in advance
Add 0.1 to 5.0 atomic% in terms of conversion, and then add 70 to 5.0 atomic%.
Oxygen-containing gas is bubbled through while heating in a temperature range of 100°C, and then under the same conditions as the heating oxidation conditions, Fe ²⁺ and M ²⁺ hydroxides are oxidized to remove Fe remaining in the reaction mother liquor. By adding 1.00 equivalents _or more of alkali hydroxide to the total amount of ²⁺ _and ^{M 2+} , spinel _- ^shaped _M ²⁺ <x≦1) A method for producing spinel-type ferrite particles having a spherical shape.