JP3440586B2 - Granular magnetite particle powder and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a coercive force of 2.39-1.
The present invention relates to a granular magnetite particle powder which has 1.94 kA / m , has excellent heat resistance and high coloring power, and has a controlled charge and charge amount, 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 particles have a black color and are widely used as black color pigments by dispersing them in a vehicle or kneading 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 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 resin. Considering this, the coercive force is required to be as low as possible.

When the granular magnetite particle powder is used as the material particle powder for the magnetic toner, the coercive force is as low as possible in view of the reduction of the image density in continuous copying and the improvement of the image loss phenomenon, in particular, 11.94 kA / m or less is required. This fact is based on Japanese Patent Laid-Open No. 57-4.
No. 6254, "... Coercive force 170 Oersted magnetic powder toner has a remarkable image loss phenomenon and poor continuous copy stability.
In the case of Oersted, it is magnetically magnetized on the non-magnetic cylindrical body and aggregates to impair the fluidity. The spikes did not occur and the images could not be displayed. When the coercive force is 150 oersteds or more, the image loss phenomenon is remarkable and the continuous copy stability is deteriorated.
... "is as described.

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 tend to more blackness often Fe ²⁺ content depends on the content is excellent in Fe ^2+, 0.99 ° C., the high temperature of the particular order of 200 ° C. This is because when exposed, Fe ²⁺ in the magnetite particles is oxidized to become Fe ³⁺ and transformed into maghemite.

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.

Further, regarding the charging property of the granular magnetite particles, when it is used for a magnetic toner, it is disclosed in JP-A-60-
On the other hand, it is necessary to adjust the toner to be positively or negatively charged depending on the type of the photoconductor, and from this point of view, when considering magnetic particles such as magnetite, the toner has a characteristic of being negatively charged. The characteristic of such magnetic particles is that when used in a magnetic toner having a positive charging property, a positively charged portion and a negatively charged portion coexist on one toner particle surface due to the presence of the magnetic particles exposed on the toner surface. It is presumed that a phenomenon such as different charging characteristics for each toner particle is caused, and in the one-component developing method using magnetic toner, it is assumed to be one of the causes that the copy image characteristics abnormally change due to environmental conditions, It is desirable to make the magnetic particles in the toner positively charged .... ”As described above, in the case of a positively charged toner, the magnetic particles are positively charged, and in the case of a negatively charged toner, It is preferred that the magnetic particles are negatively charged.

Then, it is preferable to adjust the charge amount of the toner to an appropriate range so as to be suitable for the developing device. For that purpose, not only the positive and negative chargeability of the magnetite particles used for the magnetic toner, It is strongly required that the charge amount can also be adjusted.

Regarding the charging property of the granular magnetite particles,
When used as a colored pigment powder for paints, printing inks, and resins, published by The Powder Engineering Society, Volume 24 of the Powder Engineering Society (1
987) pp. 816, "... Recently, the acidity or basicity is adjusted by the kind and amount of polar groups introduced into the resin to improve the dispersibility by stabilizing the adsorption on the pigment surface. Attempts have been made to do so.
However, since pigments and resins are increasingly having complex chemical structures, it is difficult to estimate their acidity and basicity and predict their adsorption properties. The contact charge amount between the resin powder and the pigment is considered to be effective in that it gives a more direct measure of the strength of adsorption. As described above, the charge characteristics of the color pigment powder affect the dispersion in the vehicle and the kneading in the resin, so that the charge and charge amount of the color pigment powder must be controlled.

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 an alkali hydroxide or an 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 (U.S. Pat. No. 4,082,905) and a method of coating granular magnetite particles with ferrite having 1.5 to 13 mol% of a divalent metal other than Fe (JP-A-3-67265).
Gazette), during the formation reaction of granular magnetite particles powder,
There is a method of coprecipitating an oxide of Zn, Mn, Ni, Co, Mg, Cu or Cd (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, the surface of acicular magnetic particle powder is coated with zinc ferrite or the like. It has not yet been proposed to carry out this technique in the pigment field.

[0017]

The coercive force is as low as possible, particularly, it has 11.94 kA / m or less, and it has excellent heat resistance and high coloring power, and the charge and charge amount are controlled. The granular magnetite particle powder thus produced is currently most demanded, but the granular magnetite particle powder obtained by the above-mentioned known wet method has a coercive force of 3.
Although it is as low as about 18 to 10.35 kA / m , as shown in the comparative example below, since the transformation to maghemite begins to occur at a temperature of about 130 ° C., the color changes from black to dark brown, resulting in coloring. The force was also low, and it was difficult to control the charge and the amount of charge.

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 the above-mentioned JP-A-3-67265 control the amount of electrification, but do not improve the heat resistance. In fact, as shown in Comparative Example 4 below,
At a temperature around 140 ° C., transformation to maghemite begins to occur and heat resistance is poor.

The granular magnetite particles described in the above Japanese Patent Publication No. 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 field of magnetic recording described above, 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 at the temperature of about 120 to 145 ° C. and the transformation to maghemite begins to occur. there were.

Therefore, the present invention has a coercive force as low as possible, particularly 11.94 kA / m or less, and has excellent heat resistance and high coloring power, and the charge and charge amount are controlled. A technical problem is to obtain the powdered granular magnetite particles.

[0023]

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

That is, in the present invention, the lower layer is Zn on the particle surface.
_x Fe _{2+ y} O _z layer (provided that 0.4 ≦ x ≦ 1.0, x +
y = 1, 4.0 ≦ z ≦ 4.3), the upper layer is Si,
Granular black magnetite particles having a coating layer which is a hydroxide, an oxide hydroxide or a coprecipitate of at least one element selected from Al and Ti, wherein the amount of Zn in the lower layer is 0.5 to 4.0 mol% with respect to the total Fe in the granular magnetite particles that are the core particles, and the amount of each element of Si, Al and Ti in the upper layer is 0.1 to the granular magnetite particles that are the core particles. a 5wt%, originating
A granular black magnetite particle powder having a heat onset temperature of 170 ° C. or higher .

Further, the present invention is the aqueous dispersion comprising a particulate magnetite particles relative to the total Fe in the granular magnetite particles in a non-oxidizing atmosphere at a Fe ²⁺ terms 1.
0-26 mol% ferrous salt aqueous solution and 0.5 in terms of Zn
˜4.0 mol% zinc salt aqueous solution and alkali hydroxide aqueous solution are added and mixed so that the OH group concentration in the dispersion is 0.3˜.
After adjusting to 1.0 mol / l, an oxygen-containing gas was aerated at a temperature of 50 ° C. or higher to make the particle surface Z
n _x Fe _{2 + y} O _z (however, 0.4 ≦ x ≦ 1.0, x +
y = 1, 4.0 ≦ z ≦ 4.3) to obtain a suspension in which the granular magnetite particles coated are obtained, then
After adding at least one compound selected from Si compound, Al compound and Ti compound to the suspension, pH
Is adjusted to 5 to 9 to coat the Zn _x Fe _{2 + y} O _z layer with a hydroxide, an oxide hydroxide or a coprecipitate of at least one element selected from Si, Al and Ti. This is a method for producing granular black magnetite particles.

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.

In the granular magnetite particle powder having a coating layer on the particle surface according to the present invention, the core particles contain Fe ²⁺ of 12 to 2.
It is a granular magnetite particle exhibiting a black content of 4 wt% and may have any shape such as a spherical shape, a cubic shape and an octahedron shape.

The granular magnetite particle powder containing 12 to 24 wt% of Fe ²⁺ usually has a black color,
In order to obtain target particles having higher blackness and higher coloring power, Fe ²⁺ is contained in a large amount, especially F ^2+.
It is preferable that the content of e ²⁺ is 14 wt% or more, more preferably 17 wt% or more.

The particle size of the granular magnetite particles having a coating layer on the surface of the particles according to the present invention is, in consideration of dispersibility, a BET specific surface area in the range of 3 to 15 m ² / g and an average particle diameter of 0.05 to. The range is preferably 0.35 μm.

The lower layer of the granular magnetite particles having a coating layer on the surface of the particles according to the present invention has a composition of Zn _x Fe _{2 + y} O _2.
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. x
When the value 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.

The Zn content in Zn _x Fe _{2 + y} O _z is 0.5 with respect to the total Fe in the core magnetite particles.
Is about 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 any amount necessary for producing Zn _x Fe _{2 + y} O _z , and is 1.0 to 26 mol% in terms of Fe ²⁺ with respect to all Fe in the core magnetite particles. Is preferred. If it is less than 1.0 mol% or exceeds 26 mol%, it becomes difficult to form a lower layer having a composition of Zn _x Fe _{2 + y} O _z . In the case of Zn _x Fe _{2 + y} O _z , when z is less than 4.0 and z is more than 4.3, Zn
It becomes difficult to form a lower layer having a composition of _x Fe _{2+ y} O _z .

The upper layer of the granular magnetite particles having a coating layer on the surface of the particles according to the present invention is a hydroxide of at least one element selected from Si, Al and Ti, an oxide hydroxide or a coprecipitate thereof. is there.

The amount of each element of Si, Al and Ti in the upper layer is
Si, A for the granular magnetite particles that are the core particles
It is 0.1 to 5 wt%, preferably 0.1 to 4 wt% in terms of 1 and Ti elements. If it is less than 0.1 wt%, it is not possible to obtain the granular magnetite particles having the controlled charge and charge amount, which is the object of the present invention. If it exceeds 5 wt%, hydroxides of Si, Al and Ti, co-precipitates of these, which do not precipitate on the surface of the granular magnetite particles, are independently formed, and the charge and charge aimed at by the present invention are obtained. It is not possible to obtain granular magnetite particles with a controlled amount.

Next, a method for producing granular magnetite particle powder having a coating layer on the surface of the particles according to the present invention as described above will be described.

The granular magnetite particles having a coating layer on the surface of the particles according to the present invention are Fe ^{2 with} respect to all Fe contained in the granular magnetite particles in an aqueous dispersion containing the particles of granular magnetite in a non-oxidizing atmosphere. ⁺ Conversion 1.
0-26 mol% ferrous salt aqueous solution and 0.5 in terms of Zn
˜4.0 mol% zinc salt aqueous solution and alkali hydroxide aqueous solution are added and mixed so that the OH group concentration in the dispersion is 0.3˜.
After adjusting to 1.0 mol / l, an oxygen-containing gas is aerated at a temperature of 50 ° C. or higher to make the surface of the particles Z
n _x Fe _{2 + y} O _z (however, 0.4 ≦ x ≦ 1.0, x + y
= 1, 4.0 ≦ z ≦ 4.3), and then, at least one compound selected from a Si compound, an Al compound and a Ti compound is added, and then the pH is adjusted to 5 to 9, It can be obtained by coating with a hydroxide of at least one element selected from Si, Al and Ti, an oxide hydroxide or a coprecipitate thereof.

The concentration of the particulate magnetite particle powder in the present invention after dispersion in water is preferably 50 to 500 g / l, more preferably 50 to 200 g / l in view of uniform coating. is there.

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 the 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 is
Ferrous sulfate, ferrous chloride and the like can be used.

The amount of the ferrous iron salt aqueous solution is Zn _x Fe _{2 + y} O
It may be an amount necessary to generate _z, and is preferably 1.0 to 26 mol% in terms of Fe ²⁺ with respect to all Fe in the granular magnetite particles that are core particles. If less than 1.0 mol% or more than 26 mol%, Zn _x Fe
It becomes difficult to form an underlayer having a composition of _{2 + y} O _z .

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

The amount of Zn in the aqueous zinc salt solution is 0.5 to 4.0 with respect to the total Fe in the granular magnetite particles as the core particles.
It is mol%. If it is less than 0.5 mol%, the heat resistance is not sufficiently improved and the heat generation start temperature is lowered.
If it exceeds 4.0 mol%, 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.

The addition of at least one compound selected from the Si compound, the Al compound and the Ti compound in the present invention is carried out after the formation of the Zn _x Fe _{2 + y} O _z layer, that is, at a temperature of 50 ° C. or higher, with an oxygen-containing gas. Granulated magnetite particles coated with Zn _x Fe _{2+ y} O _z are added to the suspension after aeration to form granular magnetite particles, then the pH is adjusted to 5-9, preferably 6-
It is formed by adjusting to 8.

As the Si compound used in the present invention,
No. 3 water glass, sodium silicate, potassium silicate and the like can be mentioned.

As the Al compound used in the present invention,
Examples thereof include aluminum sulfate, aluminum chloride, aluminum nitrate, sodium aluminate and the like.

As the Ti compound used in the present invention,
Examples include titanyl sulfate and titanium chloride.

Si compound, Al compound and Ti to be added
The solution concentration of at least one compound selected from the compounds may be such that it is used in a solution state, as long as it does not exceed the solubility.

In the present invention, the amount of at least one compound selected from the Si compound, the Al compound and the Ti compound added to the suspension is selected from Si, Al and Ti with respect to the granular magnetite particles as the core particles. 0.1 to 5.0 wt% in terms of element of at least one element
The amount is preferably 0.1 to 4.0 wt%. If the amount is less than 0.1 wt%, it is impossible to obtain the granular magnetite particles having the controlled charge and charge amount, which is the object of the present invention. If it exceeds 5.0 wt%, Si, Al, Ti that does not precipitate on the surface of the granular magnetite particles
Hydroxide, oxidic hydroxide, and coprecipitates thereof are independently formed.

In order to adjust the pH of the suspension after addition of at least one compound selected from Si compound, Al compound and Ti compound to 5 to 9, an acid (sulfuric acid, hydrochloric acid, Nitric acid) or base (sodium hydroxide,
Potassium hydroxide).

[0056]

First, the most important point in the present invention is that, in an aqueous dispersion containing granular magnetite particles, the total amount of Fe in the granular magnetite particles is 1.0 to 1.0 in terms of Fe ²⁺ in a non-oxidizing atmosphere. 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 is bubbled at a temperature of 50 ° C. or higher, and then at least one compound selected from a Si compound, an Al compound and a Ti compound is added, and then p
When H is adjusted to 5 to 9, the lower layer is Z on the particle surface.
n _x Fe _{2 + y} O _z layer (provided that 0.4 ≦ x ≦ 1.0, x
+ Y = 1, 4.0 ≦ z ≦ 4.3), and the upper layer is S
Granular magnetite particles coated with a coating layer which is a hydroxide, an oxide hydroxide or a coprecipitate of at least one element selected from i, Al and Ti, wherein the amount of Zn in the lower layer is Is 0.5 to 4.0 mol% based on the total Fe in the granular magnetite particles that are the core particles, and the amount of each element of Si, Al and Ti in the upper layer is 0.1 to the magnetite particles that are the core particles. A granular magnetite particle powder of 5 wt% can be obtained, and the granular magnetite particle powder having a coating layer formed on the surface of the particle has a coercive force of 2.39 to 11.94 kA / m , and It is a fact that the heat resistance and the coloring power are excellent and the charge and the charge amount are controlled.

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 that the atmosphere at the time of addition / mixing is controlled as shown in Comparative Examples below. When the oxidizing atmosphere is used or the OH group concentration is out of the range of 0.3 to 1.0 mol / l, it is not possible to obtain granular magnetite particle powder having excellent heat resistance and coloring power, By making the atmosphere during addition / mixing non-oxidizing, the occurrence of oxidation reaction is controlled so that the oxidation reaction in the system is carried out uniformly, and by adjusting the OH group concentration to a specific range, hydroxide is added. It has a uniform and dense Z surface on the particle surface of the granular magnetite particles due to the synergistic effect of decreasing the solubility of the particles and controlling the precipitation and separation of new nuclei alone.
It is considered that this is due to the formation of the n _x Fe _{2 + y} O _z film.

The granular magnetite particles having a coating layer formed on the surface of the particles according to the present invention have an exothermic onset temperature of 150 ° C. or higher, preferably 170, as will be shown in Examples below.
The temperature was not lower than 0 ° C, more preferably not lower than 200 ° C, and the heat resistance was extremely excellent. And, even at a high temperature of 200 ° C., F before heating and after heating for 1 hour
The rate of change of e ²⁺ is 8% or less, particularly 6.0% or less,
The amount of Fe ²⁺ before heating was almost maintained. As a result, ΔE is also 0.8 or less, particularly 0.6 or less,
It was black and it was confirmed that the heat resistance was extremely excellent.

The granular magnetite particle powder according to the present invention, in which the coating layer is formed on the surface of the particle, controls the charge and the amount of charge while maintaining excellent heat resistance and high coloring power, as shown in Examples below. can do. That is, as shown in “FIG. 4” on page 817 and “FIG. 8” on page 818 of the above-mentioned Journal of Powder Engineering, Si hydroxide, oxide hydroxide or a coprecipitate thereof is used. Since the isoelectric point is about 2 to 3, it is likely to be negatively charged, and since the isoelectric point of Al hydroxide, oxide hydroxide or coprecipitate thereof is about 9, it is likely to be positively charged. . Since the hydroxide of Ti, the hydroxide of Ti, or a coprecipitate of these is about 4 to 6, the isoelectric point tends to be negatively charged. Therefore, by combining various hydroxides, oxide hydroxides or coprecipitates of Si, Al and Ti, the charge and the charge amount can be controlled.

Since the granular magnetite particles on which the coating layer according to the present invention is formed have a controlled charge and charge amount, the magnetic toner produced using these particles is also a granular toner exposed on the surface of the magnetic toner. The charge and the amount of charge can be controlled by the magnetite particles.

The granular magnetite particles having the coating layer according to the present invention have a charge amount of -50 to +15 μC / g.
The range of is obtained.

[0062]

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 average value of the numerical values measured from electron micrographs and the value measured by the BET method.

The amount of Zn and the amount of Fe in the particle powder are shown by the values measured using "high-frequency plasma emission spectroscopic analyzer ICAP-575" (manufactured by Jarrel Ash Co., Ltd.).

The magnetic characteristics of the particles are as follows:
VSM-3S-15 "(manufactured by Toei Industry Co., Ltd.) under a magnetic field of 795.77 kA / m .

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.

[0068]

[Equation 1]

The hue is represented by L ^* value (brightness), a ^* value and b ^* value, and these are used 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 (Znmmis
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.

The charge amount is TEFV-200 manufactured by Nippon Iron Powder Co., Ltd.
After friction-charging with a / 300 iron powder carrier for 30 minutes,
It was measured using a blow-off charge amount measuring device manufactured by Toshiba Chemical Corporation.

<Generation of Zn _x Fe _{2 + y} O _z Layer> Examples 1 to 10 and Comparative Examples 1 to 4;

Example 1 Octahedral magnetite produced from an aqueous solution (average particle size 0.26 μm, BET specific surface area 5.5 m ² / g, Fe
²⁺ content 20.1 wt%, coercive force 9.55 kA / m 2 )
In a dispersion liquid of 1856 g dispersed in water at a temperature of 90 ° C, N
0.24 m while aerating ₂ gases at a rate of 20 l / min
sol ZnSO ₄ solution, 0.50 mol FeSO ₄ solution and 37.0 mol NaOH aqueous solution were added to make the total volume 39.5 l. The amount of Zn ^{2+ and the} amount of Fe ^{2+ in} this dispersion liquid are 1.00 mol% and 2.09 mol, respectively, with respect to the total Fe in the granular magnetite particles that are the core particles.
It was 1%, 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 a composition analysis of Zn and Fe measured by the following method, and as a result, the composition of the particle surface was x = 0.9 in the general formula Zn _x Fe _{2 + y} O _z .
7, 2 + y = 2.03 (however, the amount of Zn in the coating is 1.0 mol% with respect to the total Fe in the core particles, the total Fe in the coating is
The amount was 2.1 mol% based on the total Fe in the core particles). This black particle powder has a BET specific surface area of 4.9 m ^2.
/ G, the Fe ²⁺ content is 20.5 wt%, and the magnetic characteristics are as follows: coercive force Hc is 9.87 kA / m 2 , residual magnetization σr is 12.8 Am ² / kg , and saturation magnetization σs is 8
It was 5.4 Am ² / kg.

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 particle powder as core particles, type and amount of aqueous cobalt salt solution, amount of aqueous ferrous salt solution and amount of aqueous NaOH solution and oxidation in the mixing step. A coated magnetite particle powder was obtained in the same manner as in Example 1 except that the temperature in the reaction step was variously changed.

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

[0080]

[Table 1]

[0081]

[Table 2]

[0082]

[Table 3]

The coated magnetite granular magnetite powders obtained in Examples 2 to 10 were all excellent in heat resistance.

Comparative Example 2 was carried out in the same manner as in Example 1 except that the atmosphere at the time of 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. Further, as a result of electron microscopic observation, it was confirmed that the particles obtained in Comparative Example 3 had zinc ferrite fine particles separately separated and precipitated in addition to the octahedral magnetite particles.

<Formation of Si, Al and Ti Hydroxides, Oxidation Hydroxides or Coprecipitates thereof> Examples 11 to 24 and Comparative Examples 5 to 6;

Example 11 1 kg of the zinc ferrite-coated magnetite particles obtained in Example 1 was dispersed in water at 75 ° C., and an aqueous NaOH solution was added dropwise with stirring to adjust the pH to 11. Next, an aqueous solution containing 0.2 wt% of No. 3 water glass (14.8 g) in terms of Si was added dropwise to the particles and stirred for 10 minutes. Then, add sulfuric acid dropwise to adjust the pH to 5.5 and
Stir for 5 minutes. The black precipitate obtained was filtered, washed with water, and dried at 60 ° C. to obtain black particles.

The obtained black particles contained 0.19 wt% of Si.
%, And the charge amount was -21 μC / g.

Examples 12 and 13 and Comparative Example 5 Si-coated magnetite particles were obtained in the same manner as in Example 11 except that the addition amount of the Si compound and the pH were changed.

Tables 4 and 5 show the manufacturing conditions and various properties of the Si-coated magnetite particles at this time.

Example 14 1 kg of the zinc ferrite-coated magnetite particles obtained in Example 2 was dispersed in water at 70 ° C., and an aqueous NaOH solution was added dropwise with stirring to adjust the pH to 11. Next, 0.40 wt% of TiO in terms of Ti with respect to the particles
An aqueous solution containing 16.4 g of SO ₄ .2H ₂ O and an aqueous solution of NaOH were simultaneously added dropwise while maintaining the pH at 7.0. 1
After stirring for 5 minutes, the obtained black precipitate was filtered, washed with water, and dried at 60 ° C. to obtain black particles.

The black particles obtained contained 0.37 wt% of Ti.
%, And the charge amount was −16 μC / g.

[0092] type of Example 16, 17 and 18 Ti compound and addition amount, except for changing the pH may give a Ti coating treated magnetite particles in the same manner as in system 14.

Table 4 shows the production conditions and various characteristics of the Ti-coated magnetite particles at this time.

Example 15 1 kg of the zinc ferrite-coated magnetite particles obtained in Example 3 was dispersed in water at 75 ° C., and an aqueous NaOH solution was added dropwise with stirring to adjust the pH to 11. Next, 0.25 wt% of Al ₂ converted to Al based on the particles
(SO ₄ ) ₃ 15.85 g and Ti conversion 0.45 wt%
An aqueous solution containing 17.81 g of titanium chloride TiCl _{4 of was} added dropwise and stirred for 10 minutes. After that, add sulfuric acid dropwise and p
The H was adjusted to 8.5 and stirred for 15 minutes. The black precipitate obtained was filtered, washed with water, and dried at 60 ° C. to obtain black particles.

The obtained black particles contain 2.31 wt% of Al.
%, Ti 2.07 wt%, the charge amount is -1
It was 4 μC / g.

Examples 19, 20 and 24 Types and addition amounts of Si compounds, Al compounds and Ti compounds,
Si in the same manner as in Example 15 except that the pH was changed,
The Al-coated magnetite particles were obtained.

Tables 4 and 5 show the manufacturing conditions and various characteristics of the magnetite particles coated with Si and Al at this time.

Example 21 1 kg of the zinc ferrite-coated magnetite particles obtained in Example 9 was dispersed in water at 75 ° C., and an aqueous NaOH solution was added dropwise with stirring to adjust the pH to 11. Next, 0.2 wt% Al in terms of Al with respect to the particles
_An aqueous solution containing 12.6 g of ₂ (SO ₄ ) _{3 was} added dropwise to 10
Stir for minutes. Then, sulfuric acid was added dropwise to adjust the pH to 7.0 and stirred for 15 minutes. The black precipitate obtained was filtered, washed with water, and dried at 60 ° C. to obtain black particles.

The obtained black particles contained 0.19 wt% of Al.
%, And the charge amount was −5 μC / g.

Examples 22 and 23 and Comparative Example 6 Example 2 except that the amount of Al compound added and the pH were changed.
In the same manner as in 1, Al-coated magnetite particles were obtained.

Tables 4 and 5 show the production conditions and various characteristics of the Al-coated magnetite particles at this time.

[0102]

[Table 4]

[0103]

[Table 5]

[0104]

The granular magnetite particle powder according to the present invention has a coercive force of 2.39 to 11.
It has 94 kA / m, and has excellent heat resistance and high coloring power, and its charge and charge amount are controlled. Therefore, it is a colored pigment powder for paints, printing inks, and resins,
It is suitable as a material for magnetic toner and magnetic carrier.

Front page continuation (72) Inventor Hiromitsu Misawa 4-1-2, Funarinami, Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creation Center (72) Inventor Minoru Yoshizawa 4-Funeirinami, Naka-ku, Hiroshima-shi, Hiroshima No. 1-2 No. 2 in Creation Center, Toda Kogyo Co., Ltd. (56) Reference JP-A-3-67265 (JP, A) JP-A-5-286723 (JP, A) JP-A-6-151139 (JP, A) Special Kaihei 8-48524 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C01G 49/00-49/08 H01F 1/00-1/375 C09C 1/00-3/12 G03G 9/00-9 / 10,9 / 16

Claims (2)

(57) [Claims] 1. A lower layer of Zn _x Fe _{2 + y 2} O on a particle surface
_z layer (however, 0.4 ≦ x ≦ 1.0, x + y = 1, 4.0
≦ z ≦ 4.3), and a coating layer in which the upper layer is a hydroxide of at least one element selected from Si, Al and Ti, an oxide hydroxide or a coprecipitate thereof is formed. Granular black magnetite particles, the Zn in the lower layer
The amount is 0.5 to 4.0 mol% based on the total Fe in the granular magnetite particles as core particles, and the amount of each element of Si, Al and Ti in the upper layer is 0. 1 to 5 wt% and the heat generation start temperature is 1
Granular black magnetite particle powder having a temperature of 70 ° C. or higher . 2. In an aqueous dispersion containing granular magnetite particles, 1.0 to 26 mol in terms of Fe ²⁺ with respect to all Fe in the granular magnetite particles in a non-oxidizing atmosphere.
% Ferrous salt aqueous solution and 0.5 to 4.0 mol in terms of Zn
% Zinc salt aqueous solution and an alkali hydroxide aqueous solution are added and mixed so that the OH group concentration in the dispersion is 0.3 to 1.0 mol /
After adjusting so as to be 1, the oxygen-containing gas is aerated at a temperature of 50 ° C. or higher, and 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) to obtain a suspension in which granular magnetite particles coated are obtained, and then S in the suspension is obtained.
After adding at least one compound selected from the i compound, the Al compound and the Ti compound, the pH is adjusted to 5 to 9, and the hydroxide and the oxidation of at least one element selected from Si, Al and Ti are added. A method for producing a granular black magnetite particle powder, which comprises coating a hydroxide or a coprecipitate thereof on the Zn _x Fe _{2 + y} O _z layer.