JPH07277738A - Granular magnetite powder and production thereof - Google Patents

Abstract

PURPOSE:To obtain granular magnetite particle powder which is black, has a small magnetization value and is made hydrophobic on their particle surfaces. CONSTITUTION:The granular magnetite particle powder contains 3 to 6wt.% of aluminum atoms in the spinel type crystal lattice with 8.340-8.375Angstrom lattice constant, is made hydrophobic on the particle surface, and has 28.5-50emu/g magnetization value in the magnetic field of 1kOe. These granular magnetite particle powder is obtained by adding an aluminum compound to a ferrous compound in an alkali aqueous solution in an amount of 15 to 70mol%, calculated as Al based on the ferrous ion, then adding a ferrous salt aqueous solution to form an alkaline suspension containing precipitates of aluminum and iron and having over 10pH and passing an oxygen-containing gas through the suspension to form granular magnetite particles, then making the magnetite particles hydrophobic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a granular magnetite particle powder having a black color, a small magnetization value and a hydrophobic particle surface, and a method for producing the same.

The main uses of the granular magnetite particle powder according to the present invention are color pigment powders for paints, printing inks, rubber / plastics, magnetic toners, magnetic carrier material particle powders and the like.

[0003]

2. Description of the Related Art Magnetite particles have a black color and are widely used as black color pigment powders for paints, printing inks, rubbers and plastics.

Since the magnetite particle powder is a ferromagnetic particle, it is mixed and dispersed in a resin to form a composite particle, so that a magnetic toner material particle powder and a magnetic carrier material particle for electrostatic copying are obtained. Used as a powder.

In any of the above fields, there is no end to the demands for higher performance and higher quality, and the improvement of the characteristics of the magnetite particle powder, which is the material particle powder, in particular, the good dispersibility in vehicles and resins. There is a strong demand.

[0006] This fact is true when it comes to color pigments for paints, printing inks, and rubber / plastics, "... coating film," on page 8 of the Journal of Coloring Materials Vol. 49, No. 1 (1976). It seems to be no exaggeration to say that most of the characteristics to be possessed are largely determined by the dispersibility of the pigment in the coating film if they are the same pigment. The theory teaches that if the dispersibility of the pigment is good, the color tone becomes clear, and the basic basic properties of the pigment, such as coloring power and swelling power, are improved. In addition, the air resistance of the coating film is improved, which results in improving the durability of the coating film.In this way, the dispersibility of the pigment in the coating film is an extremely important factor that determines various characteristics of the coating film. It can be understood that it is. "

Regarding magnetite particle powder as a material particle powder for magnetic toner, JP-A-55-6540 is known.
Good compatibility with resin of "6 ... VII)"
Usually, the particle size of the toner is several tens of μm or less, and the degree of microscopic mixing in the toner is important for the characteristics of the toner. ...
... "is as described.

Further, regarding the magnetite particle powder as the material particle powder for magnetic carrier, JP-A-61-161
No. 53660, "In accordance with the present invention, the dispersibility of primary particles is improved, the magnetic powder is uniformly dispersed, and the difference in charging property and magnetic property between magnetic developer particles is reduced." Is the street.

Conventionally, magnetite particle powder is produced by a so-called wet method in which it is directly produced from an aqueous solution.

That is, in the wet method, Fe (OH) ₂ or F obtained by mixing an aqueous ferrous salt solution such as ferrous sulfate with an alkaline aqueous solution such as sodium hydroxide or sodium carbonate.
60 to 10 in an aqueous solution containing Fe-containing precipitates such as eCO ₃
This is a method of ventilating an oxidizing gas in a temperature range of 0 ° C. (Japanese Patent Publication No. 44-668).

However, the magnetite particles obtained by the above-mentioned wet method have a magnetization value of 55 to 70 emu.
/ G is large and magnetic aggregation is likely to occur,
It was an obstacle to improving dispersibility.

Moreover, the granular magnetite particle powder obtained by the wet method is not well compatible with the resin because the particle surface is hydrophilic in addition to the above magnetic agglomeration, resulting in an impediment to the improvement of dispersibility. I was supposed to call. This fact is described in Japanese Unexamined Patent Publication No. 58-68754, "Particularly, the magnetic fine particles used in the one-component magnetic toner are generally hydrophilic, so that the dispersibility in the binder resin is poor and the image quality is poor. It is as follows. ”

Therefore, in various fields, in order to further improve the dispersibility in vehicles and resins, granular magnetite particle powder having a small magnetization value and a hydrophobic particle surface is strongly demanded. This requirement is particularly strong in the field of magnetic toner.

That is, when the granular magnetite particle powder is used as the material particle powder for magnetic toner, a magnetite particle powder having a small magnetization value and a hydrophobic particle surface is strongly required in order to realize high image quality. There is. This fact will be explained below.

As the electrostatic copying machine becomes smaller and faster and has higher performance, there is a strong demand for magnetic toner which is a developer and has improved characteristics, that is, high density development and high resolution.

The characteristics of the magnetic toner are closely related to the characteristics of the magnetic particle powder contained in the resin. In order to enable high density development, the content of the magnetic particle powder contained in the resin is required. However, if the content of the magnetic particle powder is increased, magnetic toner remains as agglomerates on the latent image after development due to magnetic agglomeration of the magnetic particle powder, and a fine latent image is faithfully reproduced. It is difficult to reproduce, and high resolution cannot be obtained.

This fact is described in Japanese Unexamined Patent Publication No. 4-184354, "Toner faithful to signals and originals, that is, faithful to latent images and developing at high density is required. There is.

However, it is difficult to satisfy the above high requirements by using a toner containing a magnetic material.

For example, if the content of the magnetic material is simply increased in order to increase the coloring power of the magnetic toner to obtain a high density, the image quality deteriorates and it becomes impossible to satisfy the high resolution. Because the size of the ears is related to the magnetic force of the toner. As the amount of magnetic material increases, the ears grow larger. Such ears tend to remain as agglomerates due to the aggregating force even on the latent image after the toner is developed, and it becomes difficult to faithfully reproduce a fine latent image.

On the contrary, in order to satisfy the high resolution, it is considered that the content of the magnetic material is reduced to reduce the magnetic cohesive force, but in addition to the reduction of the coloring power, the developability is lowered due to the increase of the charge amount, and the toner is reduced. The production efficiency will be reduced. In that case, it may be improved by using a colorant such as carbon black in combination, but it may be difficult to put it into practical use because it may cause deterioration of environmental dependency. ‥‥‥

Therefore, it has been proposed to adjust the magnetic force to obtain a high-performance toner. ‥‥"as well as"‥
By containing an appropriate amount of a magnetic material having an appropriately small magnetic force, fine line reproducibility is improved, and an image quality can be obtained by developing with high fidelity to a latent image or a signal. "..." is as described.

In addition, since the surface of the magnetic particle powder is hydrophilic, it is difficult to disperse it in the resin, and the content of the magnetic particles becomes nonuniform among the magnetic toner particles. Magnetic agglomeration tends to occur mainly in the magnetic toner particles having a large content of.

Therefore, in order to obtain a magnetic toner capable of high-concentration development and high resolution, even if the content of the magnetic particle powder contained in the resin is increased, a magnetic cohesive force is not generated, so that the magnetic property is improved. There is a strong demand for the particle surface to be hydrophobic in order to minimize the magnetization value of the particle powder and to improve the dispersibility in the resin.

Conventionally, as a magnetic particle powder having a small magnetization value, there is a method (JP-A-4-184354) in which zinc ferrite particles or zinc-manganese ferrite particles having the same spinel type crystal structure as magnetite particle powder are used.

Various attempts have been made to improve various properties of the magnetite particle powder. For example, a method of adding an aluminum compound in the reaction for producing the magnetite particle powder (Japanese Patent Publication No. 1-38684, JP-A-4-3684).
No. 190242) is known.

[0026]

Granular magnetite particles having a black color, a small magnetization value and a hydrophobic particle surface are currently most demanded. The powder is
Not yet obtained.

That is, the zinc ferrite particles and the zinc-manganese ferrite particles described in the above-mentioned Japanese Patent Laid-Open No. 4-184354 have a small magnetization value, but since the hue is not brown but brown, it is a black magnetic toner. Inadequate as a material for

The granular magnetite particle powder obtained by the method described in Japanese Patent Publication No. 1-36864 and Japanese Patent Application Laid-Open No. 4-190242 has a black color peculiar to magnetite particles, but is shown in Comparative Example 1 below. As described above, the magnetization value is large, and magnetic agglomeration easily occurs.

Therefore, it is a technical object of the present invention to obtain a granular magnetite particle powder which is black and has a small magnetization value and whose surface is made hydrophobic.

[0030]

The above technical problems can be achieved by the present invention as follows.

That is, in the present invention, the particle surface of granular magnetite particles containing 3 to 6 wt% of aluminum element in the spinel type crystal lattice and having a lattice constant of 8.340 to 8.375Å is made hydrophobic. Granular magnetite particles having a magnetization value of 2 in a magnetic field of 1 kOe.
Granular magnetite particles powder of 8.5 to 50 emu / g, aluminum element in the spinel type crystal lattice 3 to 6
wt% and the lattice constant is 8.340
Granular magnetite particles having a particle size of 8.375Å, the surface of which is coated with aluminum hydroxide, and the surface of which hydroxide of aluminum is hydrophobized, having a magnetization value in a magnetic field of 1 kOe. Is 19
It is obtained by adding 15 to 70 mol% of an aluminum compound in terms of Al to ferrous iron in the granular magnetite particle powder of ~ 45 emu / g and an alkaline aqueous solution, and then adding a ferrous salt aqueous solution. Oxygen-containing gas is passed through an alkaline suspension containing aluminum- and iron-containing precipitates to a pH of 10 or more to generate granular magnetite particles, which are then filtered and washed with water, and then the granular magnetite particles are hydrophobized. Treatment or, if necessary, adjusting the pH of the alkaline suspension containing the generated granular magnetite powder to a range of 5 to 9 to deposit residual aluminum as hydroxide on the particle surface of the granular magnetite particles. After that, it is filtered, washed with water, and then the hydroxide surface of the aluminum is subjected to a hydrophobic treatment to give granular magnetite particles. A method of producing a powder.

The structure of the present invention will be described in more detail as follows.

First, the granular magnetite particle powder according to the present invention will be described.

The granular magnetite particle powder according to the present invention requires that the aluminum element is contained in the spinel type crystal lattice, and whether or not the aluminum element is contained in the spinel type crystal lattice is the lattice constant. It can be confirmed by measuring.

When the spinel type crystal lattice does not contain aluminum element, it is not possible to obtain granular magnetite particles having a small magnetization value.

The content of aluminum element in the granular magnetite particles according to the present invention is 3 to 6 wt%. 3 wt
When it is less than%, it is not possible to obtain granular magnetite particles having a small magnetization value, so that the magnetic cohesive force is large and the dispersibility in the vehicle or the resin is poor. Even if a magnetic toner is manufactured using such granular magnetite particles, high density and high resolution cannot be satisfied.

In the present invention, the upper limit of the amount of elemental aluminium that can be contained in the spinel type crystal lattice is 6
wt%. The larger the amount of aluminum element contained in the spinel type crystal lattice, the smaller the magnetization value of the obtained granular magnetite particles.

The granular magnetite particles according to the present invention have a lattice constant of 8.340 to 8.375Å. The larger the amount of aluminum element contained in the spinel type crystal lattice, the smaller the lattice constant tends to be. When the content of aluminum element is 3 wt%, the lattice constant is 8.375.
Granular magnetite particles of about Å are obtained, and when the content of aluminum element is 6 wt%, the lattice constant is 8.340 Å
Some granular magnetite particles are obtained.

The granular magnetite particles according to the present invention have a magnetization value of 28.5 to 50 emu / g. The magnetization value tends to decrease as the amount of aluminum element contained in the spinel type crystal lattice increases, and when the content of aluminum element is 6 wt%, granular magnetite particles having a magnetization value of about 28.5 emu / g are generated. can get. If it exceeds 50 emu / g, the magnetic cohesive force is large and the dispersibility in the vehicle or the resin is poor. Even if a magnetic toner is manufactured using such granular magnetite particles, high density and high resolution cannot be satisfied.

Granular magnetite particles according to the present invention are coated with a known hydrophobizing agent such as a coupling agent, silicone and higher fatty acid. The deposition amount of the hydrophobic treatment agent is
Granular magnetite particles are converted into carbon elements and converted to 0.
It is 01 to 4.0 wt%. If it is less than 0.01 wt%, the hydrophobicity is insufficient and the dispersibility is insufficiently improved.
If it exceeds 4.0 wt%, the entire amount of the hydrophobizing agent is not deposited on the surface of the magnetite particles, and the hydrophobizing agent is present alone, which is not preferable.

Examples of coupling agents include silane coupling agents, titanate coupling agents, aluminate coupling agents and the like.

The silicone may be silicone oil or the like.

The higher fatty acids include stearic acid, isostearic acid, palmitic acid, isopalmitic acid, oleic acid and the like.

In the granular magnetite particle powder according to the present invention, the surface of the particle may be coated with aluminum hydroxide, if necessary. The upper limit of the amount of aluminum hydroxide deposited is 9 wt% or less with respect to the magnetite particles, and since the aluminum hydroxide is non-magnetic, the granular magnetite has a smaller magnetization value of 19 to 45 emu / g. Particles can be obtained. The lower limit of the amount of residual aluminum that can be deposited as hydroxides on the surfaces of the granular magnetite particles is 1 wt% with respect to the magnetite particles.

In the granular magnetite particles according to the present invention, the surface of the particles is hydrophobized with, if necessary, a hydroxide of aluminum deposited thereon. The deposition amount of the hydrophobic treatment agent is
It is 0.01 to 4.0 wt% in terms of carbon element as in the case of magnetite particles in which aluminum hydroxide is not deposited on the particle surface. Magnetite particles with aluminum hydroxide deposited on the particle surface are more hydrophilic than magnetite particles without aluminum hydroxide deposited on the particle surface, so make the particle surface hydrophobic. Is particularly effective.

With the granular magnetite particle powder according to the present invention, particles having a BET specific surface area of 1 to 15 m ² / g can be obtained. If the BET specific surface area is less than 1 m ² / g or more than 15 m ² / g, the dispersibility in resin deteriorates.

Next, a method for producing the granular magnetite particle powder according to the present invention as described above will be described.

The granular magnetite particles according to the present invention are obtained by adding 15 to 70 mol% of an aluminum compound in terms of Al to ferrous iron in an alkaline aqueous solution, and then adding a ferrous salt aqueous solution. Oxygen-containing gas is passed through an alkaline suspension containing aluminum- and iron-containing precipitates to a pH of 10 or more to generate granular magnetite particles, which are then filtered and washed with water, and then the granular magnetite particles are hydrophobized. Treatment or, if necessary, adjusting the pH of the produced alkaline suspension containing the granular magnetite particles to a range of 5 to 9, and depositing residual aluminum as hydroxide on the particle surface of the granular magnetite particles. After that, it is obtained by filtering, washing with water, and then hydrophobizing the surface of the aluminum hydroxide.

As the alkaline aqueous solution in the present invention,
Sodium hydroxide, potassium hydroxide and the like can be used.

As the aluminum compound in the present invention, aluminum sulfate, sodium aluminate, aluminum chloride, aluminum nitrate and the like can be used.

The amount of aluminum compound added is 15 to 70 mol% in terms of Al based on ferrous iron. 15mo
If it is less than 1%, 3 wt% or more of the aluminum element in the spinel type crystal lattice cannot be contained, so that magnetite particle powder having a small magnetization value cannot be obtained. Even when it exceeds 70 mol%, the aluminum element in the spinel type crystal lattice can be contained, but since it cannot contain the aluminum element exceeding 6 wt%, it is meaningless to add more than necessary.

The ferrous salt aqueous solution in the present invention includes
A ferrous sulfate aqueous solution, a ferrous chloride aqueous solution or the like can be used.

In the present invention, it is essential to add the aluminum compound to the alkaline aqueous solution and then the ferrous salt aqueous solution. If the order of addition is reversed or if the addition is carried out simultaneously, the spinel type is added. The elemental aluminum cannot be contained in the crystal lattice, and as a result, the granular magnetite particle powder having a small magnetization value, which is the object of the present invention, cannot be obtained. Moreover, the above-mentioned publicly known special fair 1
In the inventions described in JP-A-36864 and JP-A-4-190242, acicular goethite particles are easily generated and mixed with granular magnetite particles, but in the present invention, generation of acicular goethite particles is suppressed and granular. Magnetite particles can be easily generated.

The pH value of the oxidation reaction is 10 or more. If the pH value is less than 10, acicular goethite particles are likely to be generated and aluminum element is preferentially contained in acicular goethite particles, so that it is difficult to include granular magnetite particles in the spinel type crystal lattice. Becomes

The oxidizing means in the present invention is carried out by passing an oxygen-containing gas (for example, air) through the liquid.

The temperature during the oxidation reaction in the present invention is 70
Is in the range of -100 ° C. If the temperature is lower than 70 ° C, acicular goethite particles are likely to be mixed. Even when the temperature exceeds 100 ° C., the elemental aluminum can be contained in the spinel type crystal lattice, but it is not industrial because it requires a special device such as an autoclave.

The hydrophobic treatment in the present invention may be carried out by either a dry treatment or a wet treatment, but it is preferably carried out by a dry treatment. In this case, a wheel type kneader, a raider, a Henschel mixer or the like is used. be able to.
The addition amount is 0.1 to 5.0 with respect to the granular magnetite particles.
If it is less than 0.1 wt%, the hydrophobic treatment is insufficient, and if it exceeds 5.0 wt%, the entire amount of the hydrophobic treatment agent is not adsorbed on the surface of the particles, and the hydrophobic property is not adsorbed. The chemical treating agent is present alone.

In the present invention, in order to deposit the residual aluminum as hydroxide on the surface of the granular magnetite particles, the alkaline suspension having a pH of 10 or more may be adjusted to a pH range of 5 to 9. If the pH is lower than 5 or higher than 9, it is difficult to form aluminum hydroxide, and the aluminum hydroxide is not deposited on the surface of the granular magnetite particles, and the aluminum hydroxide is suspended in the suspension as aluminum ions. Remain.

Further, the hydrophobizing treatment after the aluminum hydroxide is adhered to the surface of the granular magnetite particles is carried out in the same manner as the granular magnetite particles in which the aluminum hydroxide is not adhered to the surface of the particles. be able to.

[0060]

First, the most important point in the present invention is to add an aluminum compound and a ferrous iron aqueous solution to an alkaline aqueous solution in this order, and to set a specific amount of the aluminum compound to be added. It is a fact that when the range is set to a specific range, aluminum element can be contained in the spinel type crystal lattice of the granular magnetite particles, and as a result, granular magnetite particle powder having a small magnetization value can be obtained.

Although the reason why the aluminum element can be contained in the spinel type crystal lattice of the granular magnetite particles has not been clarified yet, the present inventor has confirmed that the alkaline aqueous solution, the aluminum compound and the When the order of addition of the aqueous ferrous salt solution was changed, the amount of the aluminum compound added was 15 mol% with respect to the ferrous iron.
In the case where the pH is less than 10 and the pH during the oxidation reaction is less than 10, granular magnetite particles having a small magnetization value cannot be obtained. Therefore, the order of addition of the alkaline aqueous solution, the aluminum compound and the ferrous salt aqueous solution, It is considered to be due to the synergistic effect of the addition amount and pH during the oxidation reaction.

With respect to the reason why granular magnetite particles having a small magnetization value can be obtained, the present inventor has found that the granular magnetite particle powder according to the present invention contains an aluminum element in the spinel type crystal lattice, as will be shown in the examples. The lattice constant of magnetite particles that are not formed is about 8.4 Å, whereas the lattice constant is small as 8.349-8.367 Å, and as shown in FIG. Since the lattice constant tends to be small and it is recognized that the aluminum element strongly influences the formation of the spinel type crystal lattice, the magnetic moment in which the aluminum element having no magnetic moment is contained in the spinel type crystal lattice. It is believed that this is due to the fact that it is contained by substituting the iron element with.

The following is a partial description of a large number of experimental examples conducted by the present inventor.

FIG. 1 shows the relationship between the amount of aluminum element contained in the spinel type crystal lattice and the lattice constant of the granular magnetite particle powder. That is, A to be added
except that the amount of the l ₂ (SO ₄ ) ₃ aqueous solution was variously changed.
2 is a graph in which the content of aluminum element and the lattice constant of the granular magnetite particle powder obtained in the same manner as in Example 1 below are measured and plotted. As shown in FIG. 1, the lattice constant of the granular magnetite particles tends to decrease as the content of aluminum element increases.

The hydrophobic magnetized granular magnetite particle powder according to the present invention has its property changed from hydrophilic to hydrophobic, and its dispersibility in resin is improved. This is because, as shown in Example 7 below, the granular magnetite particle powder before the hydrophobizing treatment has a water vapor monomolecular adsorption amount of 1.41 mg / g, which indicates the ease of adsorbing water. It can be confirmed from the fact that the water vapor monomolecular adsorption amount after the hydrophobic treatment is reduced to 1.20 mg / g.

The granular magnetite particles according to the present invention in which the hydroxide of aluminum is adhered to the surface of the particle and the surface of which is hydrophobized, the aluminum hydroxide is non-magnetic. It can have a smaller magnetization value. In addition, the amount of water vapor monomolecular adsorption is smaller than the value before the hydrophobization treatment, as shown in Example 6 below, and the hydrophilicity is changed to the hydrophobicity.

The granular magnetite particles according to the present invention have a hue of 13 ≦ L ^* ≦ 20, a ^* > 0.7, -3 ≦ of the known zinc ferrite particles and zinc manganese ferrite particles described above.
As shown by b ^* ≦ 0, a ^* is larger than 0.7 and is dark brown, compared with 13 ≦ L ^* ≦ 20, −1 ≦
a ^* ≦ 0.7, indicates the hue of ^{-3 ≦ b * ≦ 0, a} * is enough to hold black inherent small magnetite particles less than 0.7.

[0068]

The present invention will be described below with reference to examples and comparative examples.

The shapes of the particles in the following Examples and Comparative Examples were observed with a transmission electron microscope and a scanning electron microscope.

The magnetic property of the magnetic particle powder is a value measured under a magnetic field of 1 kOe using a "vibrating sample magnetometer VSM-3S-15" (manufactured by Toei Industry Co., Ltd.).

The amount of Al contained in the granular magnetite particles was determined by "high-frequency plasma emission spectroscopic analyzer ICAP-57".
5 ”(manufactured by Nippon Jarrell Ash Co., Ltd.).

The lattice constant of the granular magnetite particles is "X
It is a value measured using a line diffraction device RAD-2A "(manufactured by Rigaku Denki Co., Ltd.).

The deposition amount of the hydrophobizing agent is "Horiba
The amount of carbon was measured by using a sulfur analyzer EMIA-2200 "(manufactured by Horiba, Ltd.).

The degree of hydrophobization depends on the "water vapor adsorption device BEL".
"SORP18" (manufactured by Nippon Bell Co., Ltd.) was used to show the amount of adsorbed water vapor single molecule as a value. That is, the granular magnetite particles were degassed at 120 ° C. for 2 hours,
Measure the water vapor adsorption isotherm at the adsorption temperature of ° C and
This is the value obtained from the formula.

The hue is represented by L ^* (brightness), a ^* value and b ^* value, which are obtained by measuring a colorimetric test piece with a light source spectrocolorimeter M.
Hu using SC-IS-2D (manufactured by Suga Test Instruments Co., Ltd.)
The L ^* value, the a ^* value, and the b ^* value are measured by the Lab space of the interferometer, and the international certification committee (Commission
n International de 1'Ecl
image, CIE) 1976 (L ^* , a ^* , b ^* )
The values are shown according to the uniform perceptual color space.

A sample piece for measuring hue was formed into a paste by kneading 0.5 g of granular magnetite particle powder and 0.5 cc of castor oil with a Hoover type Mahler, and adding 4.5 g of clear lacquer to this paste and kneading to form a paint. , Cast coated paper using a 6 mil applicator.

<Production of Granular Magnetite Particle Powder> Examples 1 to 6 and Comparative Examples 1 to 4;

Example 1 In 22.07 l of a 4.3N aqueous NaOH solution, 0.672
5 l of a mol / l Al ₂ (SO ₄ ) ₃ aqueous solution was added,
Then, 1.8 mol / l ferrous sulfate aqueous solution 14.9
3 l were added to give a total of 42 l of an alkaline suspension containing the aluminum and iron containing precipitate. The pH of this alkaline suspension was 10.6. Then, the temperature of the alkaline suspension is raised to 100 l / mi at a temperature of 90 ° C.
Air was bubbled through at a flow rate of n for 110 minutes to form a black precipitate. The black precipitate was separated by filtration, washed with water, and dried at 60 ° C. to obtain black particle powder.

As a result of electron microscopic observation, the obtained black particle powder was a granular particle, and as a result of X-ray diffraction, it was confirmed that only a peak of spinel type crystals was shown and it was a magnetite particle. Also, the BET specific surface area is 8.5 m ² / g
Met.

This granular magnetite particle powder had an aluminum content of 3.54 wt%, a lattice constant of 8.367Å, and a magnetic characteristic of a magnetization value of 43.9 em.
It was u / g.

Examples 2 to 3 and Comparative Examples 1 to 4 The order of addition of the aqueous alkali solution, the aluminum compound and the aqueous ferrous salt solution, the type and amount of the aluminum compound, and the pH and temperature of the alkaline suspension were variously changed. Particles were generated in the same manner as in Example 1 except for the above.

Table 1 shows the main manufacturing conditions and various characteristics at this time.

The black particle powders obtained in Examples 2 and 3 all show only the peak of spinel type crystals,
It was confirmed to be granular magnetite particles.

The particle powders produced in Comparative Examples 2 and 4 were found to have a spinel-type crystal peak and a goethite peak as a result of X-ray diffraction. Since it is recognized as acicular particles,
It is a mixed powder of granular magnetite particles and a large amount of non-magnetic acicular goethite particles, and as a result, it is recognized that the magnetization value is small.

Example 4 A part of the reaction mother liquor containing the black precipitate obtained in Example 1 was sampled, and sulfuric acid was added to the sampled solution with stirring to add p.
By adjusting H to 7, aluminum hydroxide is deposited on the surface of the granular magnetite particles, which is then filtered, washed with water, and dried at 60 ° C. A granular magnetite particle powder that had been deposited was obtained.

The granular magnetite particle powder whose surface is coated with aluminum hydroxide has a total aluminum content of 6.74 wt%, and the amount of aluminum contained in the spinel type crystal lattice is as described above. As I did, 3.
Since it was 54 wt%, the deposited amount of aluminum was 3.20 wt% (6.74-3.54 = 3.20).

Table 1 shows the main manufacturing conditions and various characteristics at this time.

Examples 5 to 6 The same procedure as in Example 4 was carried out except that the type of reaction mother liquor containing granular magnetite particles and the pH at the time of deposition with aluminum hydroxide were changed. Aluminum hydroxide was deposited.

Table 1 shows the main manufacturing conditions and various characteristics at this time.

<Hydrophobic treatment of granular magnetite particle powder> Examples 7 to 23;

Example 7 10 kg of granular magnetite particles powder obtained in Example 2
And 15 g of the silane coupling agent A-143 (manufactured by Nippon Yunika Co., Ltd.) were put into a wheel-type kneader (trade name: Sand Mill Co., Ltd., Matsumoto Foundry Co., Ltd.), and operated for 1 hour to obtain the above black color. The particle powder was hydrophobized with a silane coupling agent.

The granular magnetite particle powder having the silane coupling agent deposited on the surface of the obtained particle has a carbon deposition amount of 0.03 wt% and a magnetization value of 40.3 emu / g.
The BET surface area was 5.7 m ² / g, and the water vapor monomolecular adsorption amount was 1.20 mg / g.

Examples 8 to 23 Granular magnetite particle powder was subjected to a hydrophobic treatment in the same manner as in Example 7 except that the type of particles to be treated and the type and amount of the hydrophobizing agent were variously changed.

Table 2 shows the main manufacturing conditions and various characteristics at this time.

[0095]

[Table 1]

[0096]

[Table 2]

[0097]

The granular magnetite particle powder according to the present invention is black, has a small magnetization value, and has a good dispersibility in vehicles and resins due to the particle surface being hydrophobized. It is suitable for use as a color pigment powder for paints, printing inks, rubber / plastics, magnetic toners, and magnetic carriers.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of aluminum element contained in the spinel crystal lattice of the granular magnetite particles according to the present invention and the lattice constant.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Minoru Yoshizawa 4-1-2, Funairi Minami, Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creative Center (72) Inventor Naoki Uchida Naka-ku, Hiroshima City, Hiroshima Prefecture Funadari Minami 4-1-2 Toda Kogyo Co., Ltd. Creation Center (72) Inventor Kazuo Fujioka 4-1-2 Funarimi Minami-ku, Hiroshima-ku, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creation Center

Claims (4)

[Claims] 1. A spinel type crystal lattice containing 3 to 6 wt% of aluminum element and having a lattice constant of 8.
Granular magnetite particles having a particle size of 340 to 8.375Å whose surface is hydrophobized, and having a magnetization value of 28.5 to 50e in a magnetic field of 1 kOe.
A granular magnetite particle powder characterized by having a content of mu / g. 2. A spinel type crystal lattice containing 3 to 6 wt% of aluminum element and having a lattice constant of 8.
Granular magnetite particles having a particle size of 340 to 8.375Å, the surface of which is coated with aluminum hydroxide, and the surface of aluminum hydroxide is further hydrophobized, and a magnetic field of 1 kOe. 2. The granular magnetite particles having a magnetization value of 19 to 45 emu / g. 3. An aluminum- and iron-containing precipitate obtained by adding 15 to 70 mol% of an aluminum compound in terms of Al to ferrous iron in an alkaline aqueous solution, and then adding a ferrous salt aqueous solution. A method for producing granular magnetite particles by aerating an oxygen-containing gas in an alkaline suspension having a pH of 10 or more containing, filtering, washing with water, and then subjecting the granular magnetite particles to a hydrophobic treatment. Item 2. A method for producing a granular magnetite particle powder according to Item 1. 4. An aluminum- and iron-containing precipitate obtained by adding an aluminum compound in an alkaline aqueous solution in an amount of 15 to 70 mol% in terms of Al with respect to ferrous iron, and then adding a ferrous salt aqueous solution. Granules of magnetite are produced by aerating an oxygen-containing gas in an alkaline suspension having a pH of 10 or more containing, and then the pH of the alkaline suspension is adjusted to a range of 5 to 9 to obtain the above-mentioned granular magnetite. The granular magnetite according to claim 2, wherein the residual aluminum is deposited on the surface of the particles as a hydroxide, filtered, washed with water, and then the surface of the hydroxide of the aluminum is hydrophobized. A method for producing particle powder.