JPH06310318A - Granular magnetite particle powder and its manufacture - Google Patents

Abstract

PURPOSE:To provide a granular magnetite particle powder which is provided with a coercive force of 30 to 150Oe, whose heat-resisting property is excellent and whose coloring power is high and to provide a manufacturing method in which the granular magnetite particle powder can be obtained industrially. CONSTITUTION:A ferrous salt aqueous solution at 1.0 to 2.6mol% in terms of Fe<2+> with reference to the total of Fe in a granular magnetite particle as well as a zinc salt aqueous solution and a hydroxide alkali aqueous solution at 0.5 to 4.0mol% in terms of Zn are added to, and mixed with, a water dispersed liquid containing a granular magnetite particle powder in a nonoxidizing atmosphere, and this mixture is adjusted in such a way that an OH-group concentration in the dispersed liquid becomes 0.3 to 1.0mol%. After that, a gas containing oxygen is aerated at a temperature of 50 deg.C or higher, the particle surface of the granular magnetite particle is covered with ZnxFe2+yOz (where 0.4<=x<=1.0, x+y=1, 4.0<=z<=4.3).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a coercive force of 30 to 150O.
The present invention relates to a granular magnetite particle powder having e and having excellent heat resistance and high coloring power, and a method for producing the same.

The main uses of the granular magnetite particles according to the present invention are as coloring pigment powders for paints, printing inks, resins, magnetic toners and magnetic carrier material powders.

[0003]

2. Description of the Related Art Granular magnetite powder particles, which have a black color, are widely used as a black color pigment to be dispersed in a vehicle or kneaded with a resin.

Since the granular magnetite particle powder is a ferromagnetic particle exhibiting a black color, it is mixed and dispersed in a resin to form a composite particle, so that a magnetic toner material particle powder for electrostatic copying and a magnetic carrier material. It is also widely used as a particle powder.

When the granular magnetite particle powder is used as a black coloring pigment, if the coercive force is too high, magnetic reaggregation occurs between the particles and it becomes difficult to disperse it in a vehicle or a resin. Then, the coercive force is required to be as low as possible and 150 Oe or less.

When the granular magnetite particle powder is used as the material particle powder for magnetic toner, the coercive force is as low as possible, particularly 150 Oe or less, in consideration of the reduction of image density in continuous copying and the improvement of image loss phenomenon. Is required. This fact indicates that the toner using the magnetic powder having a coercive force of 170 Oersted in JP-A-57-46254 has a remarkable image defect phenomenon and the continuous copy stability is poor. Further, in the case of a coercive force of 300 Oersted. , It was magnetically magnetized on the non-magnetic cylindrical body and agglomerated to impair the fluidity, and the spikes did not occur, and the image could not be displayed. ”,“ ... Coercive force of 150 Oersted or more. If so, the image loss phenomenon becomes remarkable and the continuous copy stability becomes poor.

As described above, the granular magnetite particle powder is generally used as a black color pigment, but when it is used, it is often exposed to a high temperature of 150 ° C. or higher, especially 200 ° C. or higher. It is required that the color tone is stable (hereinafter referred to as heat resistance) even at a temperature of 200 ° C or higher.

This fact is due to the fact that when the pigment is used as a coloring agent for thermoplastic resins such as polyethylene, polypropylene, styrene, ABS, etc., in Japanese Patent Publication No. 54-7292, these pigments are used especially in yellow iron oxide pigments. Since the thermoplastic resin is molded at a high temperature of almost 200 ° C. or more, the fading and discoloration of the pigment is decisive at that time, and the range of use is remarkably limited. 5
5-65406, "Generally, the following characteristics are required for the magnetic powder for magnetic toner in such a one-component system ... iv) It has blackness that can be practically used. Magnetic toner Although it is possible to include a colorant therein, it is preferable that the powder itself has a black color and no colorant is used.v) High heat resistance, color tone, especially blackness and electromagnetic characteristics It is necessary to be sufficiently stable in the temperature range of about 0 to 150 ° C ..

The phenomenon that the color tone changes from black to dark brown is
As is well known, but blackness of the granular magnetite particles tends to blackness superior higher the Fe ²⁺ content depends on the content of Fe ^2+, 0.99 ° C. or higher, preferably 200 ° C. of about hot This is because Fe ²⁺ in the magnetite particles is oxidized to become Fe ³⁺ and transformed into maghemite when exposed to.

Further, if the granular magnetite particle powder can be colored with the smallest possible amount, it is advantageous not only in terms of workability such as handling but also in terms of resource saving and energy saving. The coloring power is required to be as high as possible by maintaining it as much as possible.

Conventionally, granular magnetite particle powder is a suspension containing Fe (OH) ₂ colloid and Fe-containing precipitate obtained by reacting an aqueous ferrous salt solution with an aqueous alkali solution such as alkali hydroxide or alkali carbonate. It is obtained by a so-called wet method in which an oxygen-containing gas is aerated.

Various attempts have been made to improve various properties of the granular magnetite particles, and the granular magnetite particles are made of soluble inorganic compounds such as zinc hydroxide, zinc phosphate, zinc phosphite, aluminum phosphate and silica. A method of coating (US Pat. No. 4,082,905), a method of coating granular magnetite particles with ferrite having 1.5 to 13 mol% of a divalent metal other than Fe (JP-A-3-37265).
Gazette), during the formation reaction of granular magnetite particles powder,
A method of coprecipitating an oxide of Zn, Mn, Ni, Co, Mg, Cu or Cd (Japanese Patent Publication No. 59-43408).
Japanese Patent Publication No. 3-48505).

By the way, in the field of magnetic recording as a method for improving various properties of magnetic particle powder such as magnetite particle powder, for example, particles of needle-like magnetic particle powder as disclosed in JP-A-60-165703. Although coating the surface with zinc ferrite or the like has been carried out, it has not yet been proposed to carry out this technique in the pigment field.

[0014]

A granular magnetite particle powder having a coercive force as low as possible, particularly 150 Oe or less, and excellent heat resistance and high coloring power is the most demanded at present. However, although the granular magnetite particle powder obtained by the above-mentioned known wet method has a low coercive force of about 40 to 130 Oe, it has poor heat resistance and coloring power.

That is, as shown in Comparative Examples below, these granular magnetite particle powders start to undergo transformation to maghemite at a temperature of about 130 ° C., so that the color changes from black to brown, and as a result, the coloring power is low. Met.

The particles described in the above-mentioned US Pat. No. 4,082,905 improve the heat resistance, but are still not sufficient.

The particles described in Japanese Patent Laid-Open No. 3-67265 mentioned above control the amount of charge and do not improve the heat resistance, and in fact, as shown in Comparative Example 4 mentioned later, 14
At a temperature near 0 ° C., transformation into maghemite begins to occur and heat resistance is poor.

The granular magnetite particles described in JP-B-59-43408 and JP-B-3-48505 do not improve heat resistance and coloring power.

The coating of acicular magnetic particle powder with zinc ferrite, which is carried out in the above-mentioned magnetic recording field, increases the saturation magnetization value of the magnetic particle powder and improves the change over time in response to the demand for high density recording. However, the heat resistance and the coloring power are not intended at all, and in fact, as shown in Comparative Examples below, the heat resistance is poor as the transformation to maghemite begins to occur at a temperature of about 120 to 145 ° C. there were.

Therefore, the present invention has a technical problem to obtain a granular magnetite particle powder having a coercive force as low as possible, particularly 150 Oe or less, and having excellent heat resistance and high coloring power. To do.

[0021]

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

That is, according to the present invention, the surface of the particles is Zn _x Fe.
_{2 + y} O _z (However, 0.4 ≦ x ≦ 1.0, x + y = 1,
4.0 ≦ z ≦ 4.3), wherein the amount of Zn in the Zn _x Fe _{2 + y} O _z is 0.5 to 0.5 based on the total Fe in the granular magnetite particles.
The content of the granular magnetite particles is 4.0 mol%, and the total amount of Fe in the granular magnetite particles is 1 in terms of Fe ²⁺ in an aqueous dispersion containing the granular magnetite particles in a non-oxidizing atmosphere. .0-26mo
0.5% to 4.0mo in terms of 1% ferrous salt solution and Zn
Add 1% zinc salt aqueous solution and alkaline hydroxide aqueous solution.
When mixed, the OH group concentration in the dispersion is 0.3 to 1.0 mol
/ L, and then oxygen-containing gas was ventilated at a temperature of 50 ° C. or more to make Zn _x Fe _{2 + y} O _z (where 0.4 ≦ x ≦
1.0, x + y = 1, 4.0 ≦ z ≦ 4.3) for producing a granular magnetite particle powder.

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

The granular magnetite particle powder as the particles to be treated in the present invention contains 1% of Fe ²⁺ obtained by the wet method.
The particles are black particles containing 2 to 24 wt% and may be spherical, cubic, octahedral, or any other shape. In addition, the particle size is BE in consideration of dispersibility.
The T specific surface area is preferably in the range of ³ to 15 m ² / g.

The granular magnetite particles containing 12 to 24 wt% of Fe ²⁺ usually have a black color,
In order to obtain target particles having a higher degree of blackness and a higher coloring power, Fe ²⁺ is contained in a large amount as the particles to be treated, and in particular, Fe ²⁺ is 14 wt% or more, more preferably , 17 wt% or more may be used.

The type of coating used in the present invention is Zn _x F
e _{2 + y} O _z (However, 0.4 ≦ x ≦ 1.0, x + y = 1,
4.0 ≦ z ≦ 4.3). When x is less than 0.4, the heat resistance is not sufficiently improved and the heat generation starting temperature is lowered. When x exceeds 1.0, Zn ions that do not contribute to the formation of the coating are individually separated and deposited as Zn (OH) ₂ fine particles.

Z in Zn _x Fe _{2 + y} O _z in the present invention
The amount of n was 0. 0 based on the total Fe in the granular magnetite particles.
It is 5 to 4.0 mol%. If it is less than 0.5 mol%, the heat resistance is not sufficiently improved and the heat generation start temperature is lowered. Even if it exceeds 4.0 mol%, the heat resistance can be improved, but it is meaningless to add more than necessary.

As the amount of Zn in Zn _x Fe _{2 + y} O _z increases and the x value approaches 1, the heat resistance of the obtained granular magnetite particles tends to improve.

F in Zn _x Fe _{2 + y} O _z in the present invention
e ²⁺ may be an amount necessary for producing Zn _x Fe _{2 + y} O _z .

The granular magnetite particles according to the present invention are contained in an aqueous dispersion containing the granular magnetite particles in a non-oxidizing atmosphere in an amount of 1.0 to 2 in terms of Fe ²⁺ with respect to all Fe in the granular magnetite particles. 26 mol% ferrous salt aqueous solution, 0.5-4.0 mol% zinc salt aqueous solution in terms of Zn, and alkali hydroxide aqueous solution were added and mixed, and the OH group concentration in the dispersion was 0.3-1. After adjusting to 0 mol / l, an oxygen-containing gas was aerated at a temperature of 50 ° C. or higher, and the particle surface of the granular magnetite particles was treated with Zn _x Fe _{2 + y} O _z (where 0.4 ≦ x ≦ 1.0, x
+ Y = 1, 4.0 ≦ z ≦ 4.3).

The atmosphere during addition and mixing in the present invention is as follows:
It is a non-oxidizing atmosphere. To create a non-oxidizing atmosphere,
Nitrogen gas or the like may be passed through the reaction vessel. When not in a non-oxidizing atmosphere, Zn is formed on the surface of granular magnetite particles.
_x Fe _{2 + y} O _z does not grow sufficiently, and Zn _x Fe _{2 + y} O _z fine particles are separately deposited.

The ferrous salt aqueous solution in the present invention includes:
Ferrous sulfate, ferrous chloride and the like can be used.

The amount of the ferrous salt aqueous solution is Zn _x Fe _{2 + y} O
It may be an amount necessary for generating _z, and is 1.0 to 26 m in terms of Fe ²⁺ with respect to all Fe in the granular magnetite particles.
ol% is preferred.

As the zinc salt aqueous solution in the present invention, zinc sulfate, zinc chloride, zinc nitrate, zinc phosphate or the like can be used.

The amount of Zn in the aqueous zinc salt solution is 0.5 to 4.0 mol% with respect to the total Fe in the granular magnetite particles. If it is less than 0.5 mol%, the heat resistance is not sufficiently improved and the heat generation start temperature is lowered. 4.0 mol%
If it exceeds the limit, the heat resistance can be improved, but it is meaningless to add more than necessary.

The alkali hydroxide aqueous solution in the present invention is
Sodium hydroxide, potassium hydroxide and the like can be used.

The amount of the alkali hydroxide aqueous solution may be adjusted so that the OH group concentration in the dispersion becomes 0.3 to 1.0 mol / l. If it is less than 0.3 mol / l, Zn _x Fe _{2 + y} O _z will not grow sufficiently on the surface of the granular magnetite particles, and Zn _x Fe _{2 + y} O _z fine particles will be separated and deposited alone. 1.0 mol / l is sufficient to grow Zn _x Fe _{2 + y} O _z on the surface of the granular magnetite particles.

Air is most suitable as the oxygen-containing gas used in the present invention.

The temperature during the oxidation reaction in the present invention is 50 ° C.
That is all. When the temperature is lower than 50 ° C., acicular goethite particles and acicular lepidcrosite particles are generated together with the generation of granular magnetite particles, and are mixed.

[0040]

First, the most important point in the present invention is 1.0 in terms of Fe ^{2+ in} terms of Fe ²⁺ in all the Fe in the granular magnetite particles in an aqueous dispersion containing the granular magnetite particles in a non-oxidizing atmosphere. ˜26 mol% ferrous salt aqueous solution, 0.5 to 4.0 mol% in terms of Zn cobalt aqueous solution and alkaline hydroxide aqueous solution are added and mixed to obtain an OH group concentration of 0.3 to 1 in the dispersion. When the oxygen-containing gas was aerated at a temperature of 50 ° C. or higher after adjusting so as to be 0.0 mol / l, the particle surface was Zn _x Fe _{2 + y} O _z (however, 0.4 ≦ x ≦ 1. 0, x + y = 1, 4.0 ≦ z ≦
4.3) granular magnetite particles coated with Zn in the Zn _x Fe _{2 + y} O _z in an amount of 0.5 to 4.0 mol% based on the total Fe in the granular magnetite particles.
It is possible to obtain a granular magnetite particle powder having a coercive force of 30 to 150 O.
The fact is that it has e and is excellent in heat resistance and coloring power.

Although the theoretical elucidation of the mechanism for improving the above-mentioned various properties of the granular magnetite particle powder according to the present invention has not been carried out yet, the present inventor has determined the atmosphere during addition / mixing as shown in Comparative Examples below. Since it is not possible to obtain a granular magnetite particle powder having various characteristics aimed at by the present invention when an oxidizing atmosphere is used or when the OH group concentration is outside the range of 0.3 to 1.0 mol / l, Addition
By making the atmosphere during mixing non-oxidizing, the occurrence of the oxidation reaction is controlled to uniformly carry out the oxidation reaction in the system, and by adjusting the OH group concentration to a specific range, the solubility of the hydroxide can be improved. It is considered that a uniform and dense film is formed on the particle surface of the granular magnetite particles due to the synergistic effect of lowering and controlling the precipitation and separation of new nuclei alone.

The granular magnetite particle powder according to the present invention had an exothermic onset temperature of 150 ° C. or higher, preferably 200 ° C. or higher, as shown in Examples below, and was extremely excellent in heat resistance. Even at a high temperature of 200 ° C., the rate of change of Fe ²⁺ before and after heating was 8% or less, especially 6% or less, and the amount of Fe ²⁺ before heating was substantially maintained. And as a result, ΔE is 0.8 or less,
In particular, it was 0.6 or less, and it was confirmed that the blackness was sufficiently maintained and the heat resistance was extremely excellent.

[0043]

The present invention will be described below with reference to examples and comparative examples. The particle diameters of the particles in the following Examples and Comparative Examples are shown by the values measured by the BET method.

The amount of Zn and the amount of Fe in the particle powder are IPC-
It is shown by the value measured by AES.

The magnetic measurement of particles is carried out by "vibrating sample magnetometer".
VSM-3S-15 "(manufactured by Toei Industry Co., Ltd.) under a magnetic field of 10 kOe.

The heat resistance of the particles is measured by the "differential scanning calorimeter DSC".
-200 "(manufactured by Seiko Denshi Kogyo Co., Ltd.) was used to indicate the exothermic onset temperature (° C) by differential thermal analysis.

Then, 20 particles of granular magnetite particles were added.
^Shows the change rate (%) of Fe ²⁺ before and after heating at 0 ° C. for 1 hour and shows L before heating.
₁ ^*, a ₁ ^* and b ₁ ^* and after heat treatment of the L ₂ ^*, a ₂ ^*
And b ₂ ^* were measured respectively, and the change in hue before and after the heat treatment was shown by Equation 1.

[0048]

[Equation 1]

The hue is represented by L ^* value (brightness), a ^* value and b ^* value, and these are used for measuring a colorimetric test piece as a light source spectrocolorimeter MSC-IS-2D (Suga Tester ( L ^* value, a ^* value, b by Hunter's Lab space
^* Each value is color-measured and the International Certification Committee (Commis
sion International de l '
Eclairage, CIE) 1976 (L ^* , a ^* ,
b ^* ) The values are shown according to the uniform perceptual color space.

A sample piece for hue measurement was prepared by kneading 0.5 g of granular magnetite particle powder and 0.5 cc of castor oil with a Hoover type Mahler to form a paste, 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.

Example 1 Octahedral magnetite produced from an aqueous solution (average particle size 0.26 μm, coercive force 120 Oe, BET specific surface area 5.5 m ² / g, Fe ²⁺ content 20.1 wt%) 185
A 0.24 mol ZnSO ₄ solution and a 0.50 mol FeSO ₄ solution were mixed with 3 g of a dispersion of 6 g in water at a temperature of 90 ° C. while aeration of N ₂ gas at a rate of 20 l / min.
7.0 mol of NaOH aqueous solution was added to bring the total volume to 3
It was 9.5 l. The amount of Zn ^{2+ and the} amount of Fe ^{2+ in} this dispersion were respectively 1. to the total Fe in the granular magnetite particles.
The concentration was 00 mol% and 2.09 mol%, and the OH group concentration was 0.94 mol / l.

After that, the N ₂ gas was switched to air and 10
A coating reaction with zinc ferrite was performed by stirring the solution for 20 minutes at a temperature of 90 ° C. while aerating at a rate of 0 l / min.
The black precipitate obtained was filtered, washed with water and dried at 60 ° C. to obtain black particle powder.

The obtained black particle powder was subjected to composition analysis of Zn and Fe measured by the following method. As a result, the composition of the particle surface was x = 0.97 in the general formula Zn _x Fe _{2 + y} O _z ,
2 + y = 2.03 (however, the amount of Zn in the coating is 1.0 mol% with respect to the total Fe in the particles to be treated, the total Fe in the coating is
The amount was 2.1 mol% based on the total Fe in the particles to be treated. This black particle powder has a BET specific surface area of 4.9 m.
² / g, the Fe ²⁺ content was 20.5 wt%, and the magnetic characteristics were that the coercive force Hc was 124 Oe and the residual magnetization σ was
r is 12.8 emu / g and saturation magnetization σs is 85.4 em.
It was u / g.

The exothermic onset temperature by differential thermal analysis is 219 ° C.
And was excellent in heat resistance. And 200
Fe ²⁺ content after heating for 60 minutes at ℃ 19.6wt
%, The rate of change with respect to the amount of Fe ²⁺ before heating of 20.5 wt% was 4.4%, showing no significant change compared with the content of Fe ²⁺ before heating, and a bluish black color was obtained. I was presenting. As a result, it was confirmed that the coloring power was also excellent.
Further, ΔE was 0.42.

Composition analysis was carried out by using 10 g of the above black particle powder.
Was suspended in 100 ml of water, the suspension was placed in a reaction vessel and heated to 60 ° C., 200 ml of 1-N HCl solution was added with stirring, and the amount of Zn dissolved in the solution and Fe
This was done by measuring the amount. That is, 6 points of measurement samples are prepared, and the moment when HCl is added is set to t = 0, 1, 5, 1
Samples were taken out one by one after each time of 0, 30, 60, and 120 minutes, and the amounts of Zn and Fe in the filtrate obtained by filtering black particles were analyzed.

Examples 2 to 10, Comparative Examples 1 to 4 Type of granular magnetite particles powder to be treated, type and amount of zinc salt aqueous solution in mixing step, amount of ferrous salt aqueous solution, amount of NaOH aqueous solution, Also, a coated magnetite particle powder was obtained in the same manner as in Example 1 except that the temperature in the oxidation reaction step was variously changed.

Tables 1 to 3 show the main production conditions and various characteristics of the coated magnetite particle powder at this time.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

All the coated granular magnetite particles obtained in Examples 2 to 10 had excellent heat resistance.

Comparative Example 2 was carried out in the same manner as in Example 1 except that the atmosphere during addition and mixing was not air bubbling with N ₂ gas, and the particles obtained after the coating treatment were the same. As a result of electron microscope observation, it was confirmed that zinc ferrite fine particles were separately precipitated in addition to the octahedral magnetite particles. Also in Comparative Example 3, similarly, in the particles obtained after the coating treatment, as a result of electron microscope observation, it was confirmed that zinc ferrite fine particles were separately precipitated in addition to the octahedral magnetite particles.

[0063]

The granular magnetite particle powder according to the present invention has a coercive force of 30 to 150 Oe, as shown in the above embodiment.
Moreover, since it has excellent heat resistance and high coloring power, it is suitable as a coloring pigment powder for paints / printing inks / resins, magnetic toners / magnetic carriers.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isao Aoki 4-1-2, Funairinami, Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creative Center (72) Inventor Hiromitsu Misawa Naka-ku, Hiroshima City, Hiroshima Prefecture Funabiri South 4-1-2 Toda Kogyo Co., Ltd. Creation Center (72) Inventor Minoru Yoshizawa 4-1-2 Funariri Minami Toda Kogyo Co., Ltd. Creation Center

Claims (2)

[Claims] 1. The particle surface is Zn _x Fe _{2 + y} O _z (however,
0.4 ≦ x ≦ 1.0, x + y = 1, 4.0 ≦ z ≦ 4.
3) Granular magnetite particles coated with 3),
Granular magnetite particle powder, wherein the amount of Zn in the Zn _x Fe _{2 + y} O _z is 0.5 to 4.0 mol% with respect to the total Fe in the granular magnetite particles. 2. In an aqueous dispersion containing granular magnetite particles, 1.0 to 36 mo in terms of Fe ²⁺ with respect to all Fe in the granular magnetite particles in a non-oxidizing atmosphere.
0.5% to 4.0mo in terms of 1% ferrous salt solution and Zn
Add 1% zinc salt aqueous solution and alkaline hydroxide aqueous solution.
When mixed, the OH group concentration in the dispersion is 0.3 to 1.0 mol
/ L, and then oxygen-containing gas was ventilated at a temperature of 50 ° C. or more to make Zn _x Fe _{2 + y} O _z (where 0.4 ≦ x ≦
1.0, x + y = 1, 4.0 ≦ z ≦ 4.3), a method for producing granular magnetite particles.