JP2690827B2 - Method for producing powder of polyhedral magnetite particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of manufacturing a powder polyhedral magnetite particles powder, particularly, excellent in particle size finely and dispersibility, electrophotographic magnetic toner, electromagnetic wave absorbing material, anticorrosive coating material Useful polyhedral magnetite particles
It relates to a manufacturing method of powder .

[0002]

2. Description of the Related Art Magnetite particle powders have hitherto been widely used as electrophotographic toners, magnetic toners, black pigments, electromagnetic wave absorbers, rust preventive paints and the like. . In these applications, a material having excellent dispersibility is required for the purpose of increasing the efficiency of kneading with a resin or the like and improving the blackness.

For example, in the field of electrophotographic developers, developers can be roughly classified into two-component developers and one-component developers. The toner particle size as a one-component developer has a resolution. In order to improve, it is necessary to reduce the particle size. Therefore, the magnetite used in the one-component toner is required to have a uniform shape, a narrow particle size distribution, and good dispersibility.

However, many conventional magnetite particles are cubic particles or amorphous particles, and the particle powder is not a uniform particle group powder having a uniform shape. Irregular or cubic magnetite particles are likely to cause secondary agglomeration, and the particles are often not even with each other, resulting in poor dispersibility of the particle powder. When the dispersibility of the magnetite particle powder is deteriorated in this way, when the magnetic toner is manufactured, the content ratio of the magnetic material of each toner is different and the image density and the resolution are deteriorated.

It is therefore an object of the present invention is that the narrow particle size distribution, provides a certain shape, manufacturing method of powder dispersibility superior magnetite particles powder having a particularly polyhedral shape.

[0006]

The present invention relates to a ferrous salt aqueous solution.
Liquid with alkali metal hydroxide and alkali metal carbonate
Oxygen is added to the suspension obtained by mixing with an aqueous solution containing
Magnetite particles by blowing gas and oxidizing
In producing powder, ferrous salt, alkali metal water
The molar ratio of oxide and alkali metal carbonate is 1: 0.4-
1.2: 0.8-1.6 and the oxidation reaction temperature is 75-
By setting the temperature to 100 ° C, the average particle diameter is 0.1 to 1.5.
μm, the number of surfaces is at least 10, and
Polyhedral magnetite with a specific surface area of 3-40 m ² / g
Polyhedral magnets characterized by producing powder particles
The above object has been achieved by providing a method for producing a tight particle powder .

The average particle size of the polyhedral magnetite particles of the present invention is 0.1 when measured with a Coulter counter.
˜1.5 μm. Further, the number of surfaces of the polyhedral magnet particles is at least 10 or more, which is measured by enlarging the particles with an SEM photograph. In the production method of the present invention, examples of the ferrous salt, alkali metal hydroxide, and alkali metal carbonate include ferrous chloride, caustic soda, sodium carbonate, and the like, which will be described later. Further, the gas containing oxygen may be air.

[0008]

The present inventors have conducted intensive studies and found out a method for producing the magnetite particle powder, and the magnetite particle powder of the present invention has a polyhedral shape and a nearly spherical shape. There is. Therefore, although the average particle size of the magnetite particles is relatively small, the particle powder has dispersibility. Such dispersibility is expected to be sufficiently exhibited even when kneading with a resin, and the particle powder may be added to a composition such as a magnetic toner for electrophotography, an electromagnetic wave absorber and an anticorrosive coating material. it can. (Exemplary embodiments) will be described below in further detail a method for manufacturing the powder polyhedral magnetite particles powder of the present invention.

The polyhedral magnetite particle powder of the present invention is close to spherical and has a relatively uniform particle size, so that it has good dispersibility when kneaded with various resins. There is an advantage that it can be uniformly mixed in the toner particles. That is, the average particle size of the magnetite particles of the present invention is in the range of 0.1 to 1.5 μm, which is sufficiently fine. Therefore, it can be suitably used as a magnetic material such as a one-component toner for the purpose of improving resolution.

On the other hand, the magnetite particles of the present invention have a specific surface area in the range of 3 to 40 m ² / g, and the number of surfaces is at least 10, and the particles are nearly spherical. Secondary aggregation hardly occurs and the dispersibility is excellent. Next, in the method for producing a polyhedral magnetite particle powder of the present invention, examples of the ferrous salt include ferrous sulfate, ferrous chloride, and other ferrous salts. Iron is preferred.

Alkali metal hydroxides and alkali metal carbonates include Group Ia alkali metals and Group IIa
Alkaline hydroxides and alkali carbonates of the group Alkaline earth metals are mentioned, but caustic soda and sodium carbonate are preferred and preferred. The mixing ratio of the aqueous ferrous salt solution and the aqueous solution containing the alkali metal hydroxide and the alkali metal carbonate is determined by the molar ratio of the ferrous salt to the alkali metal hydroxide and the alkali metal carbonate in these aqueous solutions. To be done. Depending on the type of iron salt used, the combination of types of alkali, the molar ratio, and the reaction conditions, the resulting magnetite particles have a morphology of needle-like, plate-like, cubic, etc. The decision is accurate. That is, in the present invention, the molar ratio of ferrous salt, alkali metal hydroxide, and alkali metal carbonate is 1: 0.4 to 1.2: 0.8 to 1.6, and the oxidation reaction temperature is 75. It is important to set the temperature to -100 ° C.

If the above conditions are not satisfied, the polyhedral magnetite particle powder of the present invention cannot be sufficiently obtained. It is also important to use an aqueous solution containing an alkali metal hydroxide and an alkali metal carbonate. When an aqueous solution of alkali hydroxide is used in place of this aqueous solution, needle-like particles are likely to be formed, and when an aqueous solution of alkali metal carbonate is used, spindle-shaped or plate-like particles are more likely to be formed.

The inventors of the present invention have ascertained these phenomena and, as a result of diligent studies, found the above conditions, and further found the following operation procedure for producing polyhedral magnetite particles. That is, by appropriately controlling the amounts of the alkali metal hydroxide and the alkali metal carbonate, a fine hexagonal plate-like morphology is created, and thereafter 75 to 10
Oxidation for producing magnetite can be performed under the temperature condition of 0 ° C. to grow polyhedral magnetite particles.

Further, as a procedure of the above production, it is desirable to add an aqueous solution of an alkali metal carbonate to the aqueous solution of a ferrous salt, and then add an aqueous solution of alkali hydroxide. Furthermore, air is preferable as the gas containing oxygen, and the reaction time is preferably 6 to 9 hours, although it depends on the blowing rate of air, in order to obtain magnetite with a uniform particle size.

[0015]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples. Example 1 4 l of pure water was passed through a container having a volume of 15 l while aerating nitrogen gas.
1.15 l of 3.33 mol / l ferrous chloride aqueous solution was added thereto, then 2.85 l of 2.0 mol / l sodium carbonate aqueous solution was added, and the mixture was stirred and mixed for 30 minutes, and then 2. After adding 2 liters of 0 mol / l caustic soda aqueous solution to make 10 liters in total, the temperature was raised to 90 ° C. with stirring,
The product was filtered, separated and dried by bubbling 1 l / min of air for 8 hours. The obtained product is as shown in FIG. FIG. 1 is an electron micrograph showing the particle structure of the product. As shown in FIG. 1, the product obtained has an average particle size of 0.2 μm as measured by a Coulter counter and a surface number of 10 It was the above polyhedral magnetite particles.
The number of surfaces was measured by the following method. That is, as shown in FIG. 2, magnifying the magnetite particles in the SEM photograph,
The number of faces of each of the 20 particles was measured (the number of surfaces visible at this time was counted, and the back side thereof was also considered the same). The specific surface area of the obtained magnetite particles was 30 m ² / g.

Example 2 6 l of pure water was passed through a container having a capacity of 15 l while aeration of nitrogen gas.
Then, 1.0 l of a 4.0 mol / l ferrous chloride aqueous solution was added thereto, and then 2.0 l of a 2.0 mol / l sodium carbonate aqueous solution was added thereto, and the mixture was stirred and mixed for 30 minutes.
After adding 2 liters of 2.0 mol / l caustic soda aqueous solution to make 11 liters in total, the temperature was raised to 90 ° C. with stirring and 1 liter was added.
/ Min air for 8 hours to filter and separate the product,
Dried. An electron micrograph of the obtained product is shown in FIG. As shown in FIG. 3, the obtained product was polyhedral magnetite particles having an average particle size of 0.3 μm and a surface number of 10 or more. The number of surfaces was measured by the same method as in Example 1. The specific surface area of the obtained magnetite particles was 30 m ² / g.

Example 3 Purified water (5 l) while nitrogen gas was passed through a container having a capacity of 15 l
1.15 l of 3.33 mol / l ferrous chloride aqueous solution was added thereto, then 2.85 l of 2.0 mol / l sodium carbonate aqueous solution was added, and the mixture was stirred and mixed for 30 minutes, and then 2. After adding 1 liter of 0 mol / l caustic soda aqueous solution to make 10 liters in total, the temperature was raised to 90 ° C. with stirring,
The product was filtered, separated and dried by bubbling 1 l / min of air for 8 hours. The electron micrograph of the obtained product is shown in FIG.
Shown in As shown in FIG. 4, the obtained product was polyhedral magnetite particles having an average particle size of 0.25 μm and a surface number of 10 or more. The number of surfaces was measured by the same method as in Example 1. The specific surface area of the obtained magnetite particles was 35 m ² / g.

Comparative Example 1 Magnetite was produced in the same manner as in Example 1 except that the addition of the caustic soda aqueous solution was omitted. The obtained magnetite was a mixture of cubic, plate-like and polyhedral crystals as shown in FIG. Comparative Example 2 Magnetite was produced in the same manner as in Example 1 except that a 3.0 mol / l caustic soda aqueous solution was used. The obtained magnetite was an amorphous magnetite as shown in FIG.

[0019]

INDUSTRIAL APPLICABILITY The magnetite particle powder of the present invention has a narrow particle size distribution and a uniform shape, especially a polyhedron shape, and is excellent in dispersibility.
It is useful as an anticorrosion paint material. Further, according to the method for producing magnetite particle powder of the present invention, the above polyhedral magnetite particle powder of the present invention can be obtained.

[Brief description of the drawings]

FIG. 1 is an electron micrograph showing the particle structure of polyhedral magnetite particles obtained in Example 1.

FIG. 2 is an SEM photograph showing an enlarged particle structure of the polyhedral magnetite particles obtained in Example 1.

FIG. 3 is an electron micrograph showing a particle structure of polyhedral magnetite particles obtained in Example 2.

FIG. 4 is an electron micrograph showing a particle structure of polyhedral magnetite particles obtained in Example 3.

5 is an electron micrograph showing the particle structure of magnetite particles obtained in Comparative Example 1. FIG.

6 is an electron micrograph showing the particle structure of magnetite particles obtained in Comparative Example 2. FIG.

Claims (1)

(57) [Claims] 1. An oxygen-containing gas is blown into a suspension obtained by mixing an aqueous solution of a ferrous salt and an aqueous solution containing an alkali metal hydroxide and an alkali metal carbonate to oxidize the suspension.
In producing the magnetite particle powder, the molar ratio of ferrous salt, alkali metal hydroxide and alkali metal carbonate is set to 1: 0.4 to 1.2: 0.8 to 1.6, and the oxidation reaction By setting the temperature to 75 to 100 ° C. , the average particle diameter is 0.1 to 1.5 μm, and the number of surfaces is small.
At least 10 and specific surface area 3-40 m ² / g
A method for producing a polyhedral magnetite particle powder, which comprises producing a polyhedral magnetite particle powder.