JP3460779B2 - Magnetic iron oxide particle powder for magnetic toner having a spherical shape and magnetic toner using the magnetic iron oxide particle powder - Google Patents

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is a fine particle having a spherical shape and a particle size of 0.05 to 0.30 .mu.m, and has a high coercive force. In this case, the present invention relates to a magnetic particle powder for magnetic toner, which has high fluidity, high resolution due to suppression of fogging, and excellent blackness, and a magnetic toner using the magnetic iron oxide particle powder.

[0002]

2. Description of the Related Art Conventionally, as one of electrostatic latent image developing methods, a so-called "composite particle" in which a magnetic particle powder such as magnetite particle powder is mixed and dispersed in a resin without using a carrier is used as a developer. The developing method using "one-component magnetic toner" is widely known and widely used.

In recent years, as the performance of electrostatic copying machines has become smaller and faster, the characteristics of magnetic toner, which is a developer, have been improved.
That is, there is a strong demand for a magnetic toner having a small particle size, in which fogging is suppressed and high resolution is obtained. Conventionally used spherical magnetite particles have a low coercive force, so that when they are used as a magnetic toner having a small particle size, the magnetic stress is reduced,
The toner is less likely to be agitated on the sleeve, and it is difficult to uniformly charge the toner. As a result, insufficiently charged toner is generated, which causes fog. In order to solve the above problems, there is a strong demand for magnetic particles having high coercive force and excellent fluidity.

Since the fluidity of the magnetic toner largely depends on the surface condition of the magnetic particles exposed on the surface of the magnetic toner, it is necessary that the magnetic particle powder itself has excellent fluidity, and the octahedron or When the particles are angular particles such as hexahedron, the fluidity as magnetic particles is poor, and when the toner is magnetic toner, the fluidity is poor. On the other hand, when the particles are rounded particles such as spheres, the fluidity as magnetic particles is good, and also when the particles are magnetic toners, the fluidity is good. Therefore, rounded magnetic particles such as spheres are strongly required.

The blackness of the magnetic particle powder is described in "Powder and Powder Metallurgy" Vol. 26, No. 7, pp. 239-240, "The blackness of the sample depends on the Fe (II) content and the average particle size," A powder having an average particle size of 0.2 μm is a bluish black powder, and is most suitable as a black pigment ....
When the Fe (II) content is 10% or more, there is a slight difference in blackness, but all the samples are black. Fe
(II) When the content is reduced to 10% or less, each sample changes from black to reddish brown. It is known that, in the case of magnetite particle powder of about 0.1 to 0.5 μm used for magnetic toner, it is mainly influenced by the Fe ²⁺ content. Therefore, a magnetite particle powder having a high Fe ²⁺ content and a high blackness is required.

Regarding the dispersibility of the magnetic particle powder in the resin, "Generally, the following various characteristics are required for the magnetic powder for the magnetic toner in such a one-component system" in JP-A-55-65406. VII) Good mixability with resin. Normally, the toner particle size is several tens of μm or less, and the degree of microscopic mixing in the toner is important for the toner characteristics. As described in the following, it is required that the magnetic particle powder has a good mixing property with the resin, and as is well known, such a magnetic particle powder is required to have an oil absorption amount as small as possible.

Further, since the surface of the magnetic particle powder is hydrophilic, it becomes difficult to disperse it in the resin, and the content of the magnetic particles becomes non-uniform 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, the particle surface is made hydrophobic in order to improve the dispersibility in the resin so that the content of the magnetic particle powder contained in the resin is made uniform. Required to be sex.

The magnetite particle powder used as the magnetic particle powder for the magnetic toner is an octahedron magnetite particle powder (Japanese Patent Publication No. 44-668) or a spherical magnetite particle (Japanese Patent Publication No. 62-51208). Japanese Patent Laid-Open No. 3-201509.
In the "... octahedral magnetite particle powder described in Japanese Patent Publication No. 2003-242242, the Fe ²⁺ content is 0.3 in terms of molar ratio with ^respect to Fe ^3+.
Approximately 0.45, which is excellent in blackness, but has large remanence and is likely to cause magnetic aggregation, resulting in poor dispersibility and poor mixability with the resin. ...
Spherical magnetite particle powder has a small residual magnetization and is less likely to cause magnetic agglomeration, and thus has excellent dispersibility and good mixing with a resin, but the Fe ²⁺ content is a molar ratio to Fe ^3+. Since it is about 0.28 at most, it becomes a slightly brownish black color, and the blackness is inferior. As described above, the conventional spherical or octahedral magnetite particles are
It does not have sufficient characteristics.

[0009] Conventionally, in order to improve the characteristics of magnetite particles, a manufacturing method in which Si is added during a magnetite-forming reaction has been studied. For example, a silicon component is added to a ferrous salt solution to add iron to iron. After mixing with 1.0 to 1.1 equivalents of alkali, the pH is maintained at 7 to 10 to carry out the oxidation reaction, and 0.9 to 1.2 relative to the initial alkali during the reaction.
A method for obtaining magnetite particles by adding an equivalent amount of insufficient iron and performing an oxidation reaction while maintaining the pH at 6 to 10 (Japanese Patent Publication No. 25747/1993).
No. 0))), an oxygen-containing gas is passed through a ferrous salt reaction aqueous solution containing a ferrous hydroxide colloid obtained by reacting 0.80 to 0.99 equivalents of alkali hydroxide with Fe ^2+. When generating magnetite particles by doing,
The water-soluble silicate is 0.1 to 5 in terms of Si with respect to Fe.
Spheroidal magnetite particles by two-step reaction by adding 0 atomic% to generate magnetite nucleus crystal particles and then adding 1.00 equivalent or more of alkali hydroxide to the remaining Fe ^2+. Method for obtaining powder (Japanese Patent Publication No. 3-9045), 0.90 to Fe ²⁺
In producing magnetite particles by passing an oxygen-containing gas through a ferrous salt reaction aqueous solution containing a ferrous hydroxide colloid obtained by reacting 0.99 equivalents of alkali hydroxide, a water-soluble silicate By adding 0.4 to 4.0 atom% in terms of Si in terms of Si to generate magnetite nuclear crystal particles, and then adding 1.00 equivalent or more of alkali hydroxide to the remaining Fe ^2+. A two-step reaction is performed to generate spherical magnetite particles containing elemental silicon, and then a water-soluble aluminum salt in an alkaline suspension containing residual Si is converted to 0.0 in terms of Al.
After adding 1 to 2.0% by weight, the pH was adjusted to 5 to 9 and the spherical shape was formed by depositing as a co-precipitate of silica and alumina on the surface of the spherical magnetite particles containing the silicon element. And the like (Japanese Patent Laid-Open No. 7-110598).

[0010]

In view of the above problems,
Fine particles having a spherical shape and a particle size of 0.05 to 0.30 μm and having a high coercive force make the magnetic toner having a small particle diameter have high fluidity and fogging to suppress the resolution. The magnetic iron oxide particle powder for magnetic toner, which is high and has excellent blackness, is currently most demanded, but such magnetic iron oxide particle powder for magnetic toner has not been provided yet.

That is, the magnetite particles described in JP-B-8-25747 (JP-A-5-213620) have a ratio of 1.0 to ferrous iron in the primary reaction.
Since ~ 1.1 equivalent of alkali is added, the obtained magnetite particles have a large particle size distribution and cannot have a uniform particle size.

The magnetite particles described in JP-B-3-9045 and JP-A-7-110598 are:
Since there is no pH adjustment during the primary reaction and the pH is as low as below 8.0, a large amount of elemental sulfur is taken in,
It has a low crystal magnetic anisotropy and a low coercive force.

Therefore, the present invention is a fine particle having a spherical shape and a particle size of 0.05 to 0.30 μm, and has a high coercive force, so that when it is used as a magnetic toner particle having a small particle diameter, it is fluidized. It is a technical object to provide a magnetic iron oxide particle powder for a magnetic toner, which has high properties and has a high resolution due to suppression of fogging and is excellent in blackness.

[0014]

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

That is, in the present invention, the average particle size is 0.05 to
0.30 μm and sphericity Φ is 0.95 to 1.0
And contains 1.7 to 4.5 atomic% of silicon in terms of Si, and Mn, Zn, Ti, Zr, S on the particle surface.
i, magnetite particles having an adherend layer made of any one of oxides, hydroxides, hydrous oxides of one or more elements selected from Al, or a mixture thereof,
The coercive force Hc (O
e) is the following relational expression with the average particle diameter d (μm): 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207
-322.7 × d, and the amount of the elemental sulfur contained in the magnetic powder is 0.35% by weight or less. Powder.

[0016] The average particle size was in 0.05~0.30μm
And the sphericity Φ is 0.95 to 1.0, and it is Fe in terms of Si.
Is 1.7 to 4.5 atomic% of silicon, and the surface of the particles is coated with a hydrophobizing agent. The magnetite particles have a coercive force H in an external magnetic field of 10 kOe.
c (Oe) is the following relational expression with the average particle diameter d (μm): 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207
-322.7 × d, and the amount of the elemental sulfur contained in the magnetic powder is 0.35% by weight or less. Powder.

[0017] The average particle size was in 0.05~0.30μm
And the sphericity Φ is 0.95 to 1.0, and it is Fe in terms of Si.
And 1.7 to 4.5 atomic% of silicon, and non-magnetic oxide fine particles of one or more elements selected from Fe, Mn, Zn, Ti, Zr, Si, and Al on the particle surface. Alternatively, it is a magnetite particle to which non-magnetic hydrated oxide particles are fixed, and the coercive force Hc (Oe) of the particle in an external magnetic field of 10 kOe is the following relational expression with the average particle diameter d (μm): 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207
-322.7 × d, and the amount of the elemental sulfur contained in the magnetic powder is 0.35% by weight or less. Powder.

[0018] The average particle size was in 0.05~0.30μm
And the sphericity Φ is 0.95 to 1.0, and it is Fe in terms of Si.
And 1.7 to 4.5 atomic% of silicon, and an oxide or hydroxide of one or more elements selected from Mn, Zn, Ti, Zr, Si and Al as a lower layer on the surface of the particle. Particles, a hydrous oxide or a mixture thereof, and a coercive force of the particles in an external magnetic field of 10 kOe, the magnetite particles having an adhering layer made of a hydrophobizing agent as an upper layer. Hc (Oe) is the following relational expression with the average particle diameter d (μm): 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207
-322.7 × d, and the amount of the elemental sulfur contained in the magnetic powder is 0.35% by weight or less. Powder.

A magnetic toner using the magnetic iron oxide particle powder for any one of the above magnetic toners.

The structure of the present invention will be described in more detail as follows. First, the magnetic iron oxide particle powder for magnetic toner according to the present invention will be described.

The composition of the magnetic iron oxide particles according to the present invention is magnetite particles ( (FeO) x.Fe ₂ O ₃ ,
0 <x ≦ 1), and as a metal element other than iron, M
One or more metal elements selected from n, Zn, Ni, Cu, Al and Ti may be contained in an amount of 10 atomic% or less with respect to Fe. The particle shape is spherical, as shown in the transmission electron micrograph of FIG. 1 below.

The magnetic iron oxide particle powder according to the present invention has an average particle diameter of 0.05 to 0.30 μm. When the average particle size is less than 0.05 μm, the number of particles in the unit volume becomes too large, and the number of contact points between particles increases, so that the adhesive force between the powder layers becomes large. Dispersibility into the inside becomes poor. If it exceeds 0.30 μm,
The number of magnetic iron oxide particles contained in one toner particle decreases, and the distribution of the magnetic iron oxide particles in each toner particle becomes uneven, resulting in impaired uniformity of toner charging.

The magnetic iron oxide particle powder according to the present invention has a sphericity Φ represented by the following formula of 0.95 to 1.00.
When it is less than 0.95 , the spherical property is poor and the fluidity is poor. Further, the sphericity Φ defined by the following formula is 1.
It does not exceed 00.

Sphericity Φ = w / l l: average major axis diameter of magnetic iron oxide particles in projection w: average minor axis diameter of magnetic iron oxide particles in projection

The magnetic iron oxide particle powder according to the present invention comprises Fe
^{The 2+} content is 12 to 24% by weight, preferably 17 to 24% by weight, based on the total weight of the magnetic iron oxide particles. 12% by weight
When it is less than 1, a sufficient blackness cannot be obtained. If it exceeds 24% by weight, it tends to be oxidized, resulting in poor environmental stability.

The magnetic iron oxide particle powder according to the present invention comprises Si
Is 1.7 to 4.5 at%, preferably 2.0
˜4.0 at%. When the Si content is less than 1.7 at%, hexahedral particles having curved ridges are obtained, resulting in poor fluidity. If it exceeds 4.5 atomic%, the amount of SiO _{2 on} the particle surface may increase,
In addition, since SiO ₂ separates from the particles, the hygroscopicity of the toner becomes high and the environmental stability deteriorates. The larger the amount of deposited SiO ₂ on the particle surface, the better the fluidity of the toner because the adhesive force decreases, but considering the hygroscopicity, the amount of SiO ₂ deposited on the particle surface is 0.01 to
4.0% by weight is preferred.

The magnetic iron oxide particle powder according to the present invention has a sulfur element content of 0.35% by weight or less, preferably 0.2.
It is 5% by weight or less. If it exceeds 0.35% by weight, a large amount of elemental sulfur is incorporated into the crystal during the production reaction,
This indicates that the residual magnetism remains, and therefore the crystal magnetic anisotropy is inferior and the coercive force is considered to be low.

The magnetic iron oxide particle powder according to the present invention has an oxide, hydroxide or hydrous oxide of one or more elements selected from Mn, Zn, Ti, Zr, Si and Al on the particle surface. Alternatively, it is preferable to have a coating layer made of any of these.

The amount of the selected element oxide, hydroxide, hydrous oxide, or mixture thereof selected is preferably 0.01 to 20% by weight.

The magnetic iron oxide particle powder according to the present invention preferably has a hydrophobic treatment agent adhered to the particle surface. The hydrophobizing agent is one or more selected from coupling agents, silicone compounds and higher fatty acids.

Examples of coupling agents include silane coupling agents, titanate coupling agents, aluminate coupling agents and the like. The silicone compound is silicone oil or the like. Examples of higher fatty acids include stearic acid, isostearic acid, palmitic acid, isopalmitic acid, and oleic acid.

The amount of the hydrophobicizing agent deposited is preferably 0.
1 to 4.0% by weight, more preferably 0.1 to 2.
It is 0% by weight. If it is less than 0.1% by weight, the hydrophobicity is not sufficient, and if it exceeds 4.0% by weight, it is present independently on the surface other than the magnetic iron oxide particle surface, which is not preferable. Further, since the SiO ₂ on the particle surface is covered, the effect of improving the fluidity cannot be obtained, which is not preferable.

The magnetic iron oxide particle powder according to the present invention has one or more non-magnetic oxide fine particles or non-magnetic hydrous oxide particles selected from Fe, Mn, Zn, Ti, Zr, Si and Al on the particle surface. Fine particles (hereinafter, referred to as “non-magnetic oxide fine particles or non-magnetic hydrous oxide fine particles of a specific element”) are preferably fixed.

The non-magnetic oxide particles or non-magnetic hydrous oxide particles of the specific element are hematite (α-Fe).
₂ O ₃ ) fine particles, titanium oxide (TiO ₂ ) fine particles, zirconia fine particles, silica (SiO ₂ ) fine particles, alumina (Al ₂ O ₃ ) fine particles, non-magnetic oxide fine particles, goethite (α-FeOOH) fine particles, Pidcrosite (γ-FeOOH) fine particles, agenite (β-FeOOH)
OH) fine particles such as ferric hydroxide fine particles, AlOOH fine particles, and TiO (OH) ₂ fine particles such as non-magnetic hydroxide fine particles can be used.

The particle diameter of the non-magnetic oxide fine particles or non-magnetic hydrous oxide fine particles of the specific element is 0.01 to 0.1 μm.
m, preferably 0.02-0.06 μm. 0.0
When it is less than 1 μm or when it exceeds 0.1 μm, the dispersibility is not improved, and particularly when it exceeds 0.1 μm, sufficient fixation cannot be achieved. The particle shape of the non-magnetic oxide particles or non-magnetic hydrous oxide particles of the specific element may be any of granular, needle-like, spindle-like, plate-like, columnar and the like.

Regarding the particle size of the non-magnetic oxide particles or non-magnetic hydrous oxide particles of the specific element, the particle size of the magnetic particle powder is defined as (a), and the non-magnetic oxide particles or non-magnetic hydrous oxide of the specific element are used. When the fine particles are granular, the particle diameter is (b),
1/100 ≦ (b) / (a), where (c) is the major axis diameter or plate surface diameter in the case of needles, spindles, plates, and columns, and its minor axis diameter or thickness is (d). ≦ 1/3 1/100 ≦ (c) / (a) ≦ 1 1/100 ≦ (d) / (a) ≦ 1/3 1/100 ≦ (d) / (c) <1 Those are preferable. More preferably, 1/50 ≦ (b) / (a) ≦ 1/5 1/50 ≦ (c) / (a) ≦ 1/2 1/50 ≦ (d) / (a) ≦ 1/5 1 The range is / 10 ≦ (d) / (c) <1.

When (b) / (a) <1/100, the effect of improving the dispersibility cannot be obtained. 1/3 <
In the case of (b) / (a), it becomes difficult to fix the non-magnetic oxide particles or non-magnetic hydrous oxide particles of the specific element.

When (c) / (a) <1/100, the effect of improving dispersibility cannot be obtained. 1 <(c) / (a)
In this case, it becomes difficult to fix the non-magnetic oxide particles or non-magnetic hydrous oxide particles of the specific element.

When (d) / (a) <1/100, the effect of improving dispersibility cannot be obtained. 1/3 <(d) /
In the case of (a), it becomes difficult to fix the non-magnetic oxide fine particles or non-magnetic hydrous oxide fine particles of the specific element.

When (d) / (c) <1/100, the non-magnetic oxide fine particles or non-magnetic hydrous oxide fine particles of the specific element are easily broken or cracked during the fixing process, and become fine powder to disperse. It is not preferable because it causes the deterioration of sex.

The fixed amount of the non-magnetic oxide fine particles or non-magnetic hydrous oxide fine particles of the specific element is preferably 0.1 to 10.
It is 20% by weight, more preferably 0.5 to 10% by weight. When it is less than 0.1% by weight, the dispersibility is not sufficiently improved. When it exceeds 20% by weight, the magnetization value decreases and the image quality deteriorates.

The magnetic iron oxide particle powder according to the present invention comprises 10
The coercive force Hc (Oe) at kOe is the average particle diameter d (μm).
The following relational expression with 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207-32
It is in a range satisfying 2.7 × d 2. There is a close relationship between the coercive force value and the particle size, and as shown in FIG. 2, the coercive force value increases as the particle size decreases. When the coercive force value exceeds the upper limit of the above expression for the particle diameter d, the magnetic stress becomes too strong, and when it is used as a magnetic toner, it is difficult to transfer it from the sleeve onto the photosensitive drum. Will not be obtained. Further, when the coercive force value is less than the lower limit value of the above formula for the particle diameter d, the magnetic stress becomes weak, scattering easily occurs on the photosensitive drum, and fog occurs.

The magnetic iron oxide particle powder according to the present invention has a saturation magnetization value of 80 to 92 emu / g, preferably 82 to 90.
It is in the range of emu / g. The value of 92 emu / g is a theoretical value of magnetite, and it does not exceed this value. 80
If it is less than emu / g, the amount of Fe ^{2+ in} the particles decreases, and the particles become reddish.

The magnetic iron oxide particle powder according to the present invention has a compressibility as an index of fluidity of 45 or less, preferably 43 or less. When it exceeds 45, the fluidity is not preferable.

The magnetic iron oxide particles according to the present invention have a repose angle θ which is another index of fluidity of 45 ° or less, preferably 43 ° or less. When it exceeds 45 °, the fluidity is not preferable.

The magnetic iron oxide particle powder according to the present invention preferably has an oil absorption of 20 ml / 100 g or less.

The magnetic iron oxide particle powder according to the present invention preferably has a hydrophobicity (Vm / Vm ⁰ ) of less than 1, more preferably 0.98 or less, still more preferably 0.96 or less. Here, Vm is the water monomolecular adsorption amount (mg / g) after the hydrophobic treatment, and Vm ⁰ is the water monomolecular adsorption amount (mg / g) before the hydrophobic treatment.

Next, a method for producing the magnetic iron oxide particle powder for magnetic toner according to the present invention as described above will be described.

In the present invention, water obtained by reacting a ferrous salt aqueous solution with an aqueous solution of an alkali hydroxide of 0.80 to 0.99 equivalent to the ferrous salt in the ferrous salt aqueous solution. 70 to 1 in a ferrous salt reaction aqueous solution containing ferrous oxide colloid
A first-step reaction in which an oxygen-containing gas is aerated to generate magnetite particles while being heated to a temperature range of 00 ° C., and 1.00 equivalent or more of alkali hydroxide with ^respect to residual Fe ²⁺ after completion of the first-step reaction In the method for producing magnetite particle powder, which comprises a two-step reaction of adding an aqueous solution and aerating an oxygen-containing gas while heating to a temperature range of 70 to 100 ° C. to generate magnetite particles, In an aqueous solution of either an alkaline aqueous solution or a ferrous salt aqueous solution containing the ferrous hydroxide colloid, water-soluble silicate is added in advance by 1.7 to 6.5 atomic% in terms of Si in terms of Si, and placed. And, by adjusting the pH to 8.0 to 9.5 by adding an aqueous solution of an alkali hydroxide at the start of the aeration of the oxygen-containing gas in the first step reaction, and aerating the oxygen-containing gas, Exhibit Jo, moreover, to obtain a magnetic iron oxide particles for magnetic toner having a high coercive force.

The aqueous ferrous salt solution used in the present invention may be an aqueous ferrous sulfate solution or an aqueous ferrous chloride solution.

The aqueous alkali hydroxide solution used in the present invention is an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, or an aqueous solution of an alkaline earth metal hydroxide such as magnesium hydroxide or calcium hydroxide. ,
Further, an aqueous solution of an alkali carbonate such as sodium carbonate, potassium carbonate or ammonium carbonate, and aqueous ammonia can be used.

The amount of the alkali hydroxide aqueous solution used before pH adjustment in the first-step reaction is 0.80 to 0.99 equivalents to Fe ²⁺ in the ferrous iron salt aqueous solution. The range is preferably 0.90 to 0.99 equivalents. 0.80
If it is less than the equivalent, goethite is mixed in the product,
The desired magnetite particles cannot be obtained as a single phase. When it exceeds 0.99 equivalents, the particle size distribution becomes large, and particles having a uniform particle size cannot be obtained.

The reaction temperature in the first-step reaction is 70 to
It is 100 ° C. If the temperature is lower than 70 ° C., acicular goethite particles are mixed. Magnetite particles are also produced when the temperature exceeds 100 ° C., but this is not industrially easy because an apparatus such as an autoclave is required.

The oxidizing means is an oxygen-containing gas (eg air).
Is aerated in the liquid.

As the water-soluble silicate used in the present invention, sodium silicate, potassium silicate and the like can be used. The addition amount of the water-soluble silicate is 1.7 to 6.5 atomic% in terms of Si with respect to Fe. It is preferably 2.0 to 4.5 atom%. If it is less than 1.7 atomic%, the ridge line becomes curved hexagonal particles or square hexahedral particles, resulting in poor fluidity. On the other hand, 6.5
If it exceeds atomic%, the amount of SiO _{2 on the} surface of the particles may increase in the case of performing a neutralization operation after completion of the reaction to be described later, and since SiO ₂ is precipitated separately from the particles, the toner If it is set to high, the hygroscopicity becomes high and the environmental stability becomes poor. The larger the amount of deposited SiO ₂ on the particle surface, the better the fluidity of the toner because the adhesive force decreases, but considering the hygroscopicity, the SiO ₂ deposited on the surface of the particle
The amount is preferably 0.01 to 4.0% by weight.

The water-soluble silicate in the present invention is involved in the shape of the produced magnetite particles. Therefore, the addition timing of the water-soluble silicate is the ferrous salt containing the ferrous hydroxide colloid. It is necessary to ventilate an oxygen-containing gas into the reaction aqueous solution before generating magnetite particles, and add it to either an alkali hydroxide aqueous solution or a ferrous iron reaction aqueous solution containing a ferrous hydroxide colloid. can do. When the water-soluble silicate is added to the aqueous solution of ferrous salt, the water-soluble silicate is added and, at the same time, it is precipitated as SiO ₂ separately from the ferrous salt, thus achieving the object of the present invention. Can not do it.

In the first-step reaction, an aqueous alkali hydroxide solution is added at the start of aeration of oxygen-containing gas to adjust the pH of the suspension to a range of 8.0 to 9.5. The pH is more preferably in the range of 8.3 to 9.3. When the suspension pH is less than 8.0, sulfate ions are easily adsorbed on the generated crystal surface, and the amount of sulfur element taken into the crystal is increased, so that the crystal magnetic anisotropy is low and the coercive force is low. It will be low. When the suspension pH exceeds 9.5, angular octahedral particles are generated, resulting in poor fluidity.

The amount of the aqueous alkali hydroxide solution used in the second-step reaction is 1.00 equivalent or more with respect to the Fe ²⁺ remaining at the start of the second-step reaction. If it is less than 1.00 equivalent, the entire amount of remaining Fe ²⁺ is not precipitated. Practically, an amount of 1.00 equivalent or more considering industrial properties is preferable.

The reaction temperature of the second-step reaction may be the same as that of the first-step reaction. The oxidizing means may be the same.

It should be noted that, after the addition of the raw materials and the first-step reaction, and between the first-step reaction and the second-step reaction, sufficient agitation may be carried out for a required time as necessary.

After the completion of the second-step reaction, if necessary, the pH
By neutralizing to 6 to 7.5, preferably pH 6.5 to 7.5, the silicate remaining in the solution can be deposited on the particle surface.

Oxides, hydroxides, hydrous oxides or oxides of one or more elements selected from Mn, Zn, Ti, Zr, Si and Al on the surface of the magnetic iron oxide particles according to the present invention. The formation of the coating layer consisting of any of the mixture of the above, the solution of the inorganic compound of the selected element is added to the aqueous suspension of the magnetic iron oxide particles powder or the aqueous suspension after the completion of the second step reaction. The pH can be adjusted to a known pH range in which the additive element precipitates as an oxide, a hydroxide, a hydrous oxide, or the like.

When the magnetic iron oxide particle powder that has been once dried is used as the aqueous suspension of the magnetic iron oxide particle powder, a sufficiently dispersed aqueous suspension is used to form a more uniform coating layer. Needed to get. When the aqueous suspension of the magnetic iron oxide particle powder after the completion of the second-step reaction is used as it is, it is more industrial because the above-mentioned dispersion step is not required.

Mn, Zn, Ti, Zr, Si, Al
The inorganic compound such as may be a water-soluble inorganic compound.
As the Mn compound, manganese sulfate, manganese chloride or the like can be used. As the Zn compound, zinc sulfate, zinc chloride or the like can be used. As the Ti compound, titanyl sulfate,
Titanium chloride or the like can be used. As the Zr compound, zirconium chloride, zirconium sulfate or the like can be used. Si
As the compound, No. 3 water glass, sodium silicate, potassium silicate or the like can be used. As the Al compound, aluminum sulfate, aluminum chloride, aluminum nitrate, sodium aluminate or the like can be used.

The addition amount of the inorganic compound of the selected element is preferably 0.01 to 20% by weight. 0.01
If it is less than wt%, the effect of improving the dispersibility cannot be sufficiently obtained. If it exceeds 20% by weight, hydroxides, hydrous oxides, or a mixture thereof are formed alone in addition to the particle surface. Further, it is preferable not to completely cover the Si component on the particle surface from the viewpoint of improving fluidity.

The adjusted pH after the addition of the aqueous solution of the inorganic compound of the selected element is in the range of pH 8.5 or higher in the case of Mn and in the range of pH 6.5 to 14 in the case of Zn. In the case of, the pH is 3 or more, in the case of Zr, the pH is 2 or more, and in the case of Si, the pH is 9 or less,
In the case of Al, the pH is in the range of 4-12.

The application of the hydrophobizing agent to the magnetic iron oxide particles in the present invention can be carried out by treating the magnetic iron oxide particle powder with the hydrophobizing agent by either dry treatment or wet treatment. It is preferable to use a dry process.

The hydrophobizing agent is one or more selected from coupling agents, silicone compounds and higher fatty acids. Examples of coupling agents include silane coupling agents, titanate coupling agents, aluminate coupling agents, and the like. The silicone compound is silicone oil or the like. Examples of higher fatty acids include stearic acid, isostearic acid, palmitic acid, isopalmitic acid, and oleic acid.

The amount of the hydrophobizing agent added is preferably 0.1 to 4.0% by weight, more preferably 0.1 to 2.0% by weight, based on the magnetic particle powder. When it is less than 0.1% by weight, the effect of hydrophobization is not sufficient, and 4.
If it exceeds 0% by weight, the SiO ₂ on the particle surface is covered, which is not preferable.

For the hydrophobic treatment, a wheel type kneader, a raider, a Henschel mixer, etc. can be used.

In the present invention, non-magnetic oxide fine particles or non-magnetic hydrous oxide fine particles of a specific element are fixed to the particle surface of the magnetic iron oxide particles by the non-magnetic property of the specific element with respect to the obtained magnetite particle powder. Oxide fine particles or non-magnetic hydrous oxide fine particles are preferably added in an amount of 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, and the mixture is compressed, sheared and spatulated using a wheel-type kneader or a raker. It can be done by stroking. If it is less than 0.1% by weight, the fluidity of the obtained particle powder is not improved, and 2
When it exceeds 0% by weight, the saturation magnetization is lowered and the image quality is lowered, which is not preferable.

As the wheel type kneader, those having effects of compression, shearing and spatula are preferable, and Simpson mix muller, multi-mill, backflow kneader, Erich mill, etc. can be used, but wet pan mill, melanger, whirl mix. Neither the kneader nor the quick kneader can be applied because they have only a compression and spatula action and no shearing action.

The linear load in the case of processing with a wheel type kneader is preferably in the range of 10 to 200 kg / cm. More preferably, it is in the range of 20 to 150 kg / cm. If the linear load is less than 10 kg / cm, it becomes difficult to fix the non-magnetic oxide fine particles or non-magnetic hydrous oxide fine particles of the specific element on the particle surface of the magnetic particles, and 200 kg / c
If it exceeds m, the magnetic iron oxide particles are destroyed, which is not preferable.

The time for processing with a wheel type kneader is preferably in the range of 10 to 120 minutes. It is more preferably in the range of 20 to 90 minutes. If it is less than 10 minutes, it becomes difficult to fix the non-magnetic oxide fine particles or the non-magnetic hydrous oxide fine particles to the particle surface of the magnetic iron oxide particles.
Fixing is possible even if it exceeds 0 minutes, but it is not industrial.

Next, the magnetic toner according to the present invention will be described.

The magnetic toner according to the present invention has a volume average diameter of 3 to 15 μm, preferably 5 to 12 μm.

The magnetic toner according to the present invention comprises the above magnetic iron oxide particle powder for magnetic toner and a binder resin, and optionally contains a releasing agent, a coloring agent, a charge control agent, and other additives. You may. The ratio of the binder resin to the magnetic iron oxide particle powder for magnetic toner is 10 to 900 parts by weight, preferably 10 to 400 parts by weight, relative to 100 parts by weight of the magnetic iron oxide particle powder. .

As the binder resin used in the magnetic toner according to the present invention, a vinyl polymer obtained by polymerizing or copolymerizing vinyl monomers such as styrene, alkyl acrylate and alkyl methacrylate can be used. Examples of the monomer styrene constituting the binder resin include styrene and its substitution products, and examples of the acrylic acid alkyl ester include acrylic acid, methyl acrylate, and the like.
Examples include ethyl acrylate and butyl acrylate. The copolymer preferably contains 50 to 95% by weight of a styrene component.

Further, as the binder resin, a polyester resin, an epoxy resin, a polyurethane resin or the like can be used if necessary.

The magnetic toner according to the present invention can be prepared by a known method such as mixing, kneading and pulverizing. Specifically, the magnetic iron oxide particle powder and the binder resin, if necessary, can be used. Depending on the colorant, release agent, charge control agent, other additives, etc., first thoroughly mix with a mixer, and then melt and knead the resin etc. with a heating kneader to compatibilize the magnetic iron oxide. After the particles and the like are dispersed and solidified by cooling, the resin kneaded product obtained is pulverized and classified to obtain a magnetic toner.

As the mixer, a Henschel mixer, a ball mill, or the like can be used.
As the heating and kneading machine, a roll mill, a kneader, a twin screw type, an extruder or the like can be used. The pulverization can be performed by a pulverizer such as a cutter mill or a jet mill, and the classification can be performed by a known method.

As another method for obtaining the magnetic toner according to the present invention, there is a suspension polymerization method or an emulsion polymerization method. In the suspension polymerization method, a polymerizable monomer, magnetic iron oxide particle powder for magnetic toner, and coloring are used. Agent, a polymerization initiator if necessary, a cross-linking agent, a charge control agent, and a monomer composition in which other additives are dissolved or dispersed are added to an aqueous phase containing a suspension stabilizer while stirring. It can be granulated and polymerized to form toner particles.

In the emulsion polymerization method, a suitable particle size is obtained by adding an emulsifier in the process of dispersing a monomer, magnetic iron oxide particle powder for a magnetic toner, a coloring agent, a polymerization initiator, etc. in water to carry out polymerization. Toner particles can be formed.

[0084]

BEST MODE FOR CARRYING OUT THE INVENTION A typical embodiment of the present invention is as follows.

In the following embodiments, examples and comparative examples, the average particle size is the average of the numerical values measured from electron micrographs, and the specific surface area is the value measured by the BET method. For magnetic characteristics, "Vibration sample magnetometer VSM-3S-15" (manufactured by Toei Industry Co., Ltd.) was used.
An external magnetic field of 10 KOe was applied for measurement.

The particle shape is determined by a scanning electron microscope (Hitachi S-
800).

The sphericity Φ of the magnetic iron oxide particle powder is measured by
A projection type transmission electron microscope (JEOL JEM-10
0S) In the photograph, magnetic iron oxide particles were randomly added to 250
The average major axis diameter l and the average minor axis diameter w are obtained by extracting more than one,
It was calculated by the following formula.

Sphericity Φ = w / l l: average major axis diameter of magnetic iron oxide particles in projection w: average minor axis diameter of magnetic iron oxide particles in projection

The amount of Si in the magnetic iron oxide particles is a value measured by using a "fluorescent X-ray analyzer 3063M type" (manufactured by Rigaku Denki Kogyo Co., Ltd.) according to "General rules for fluorescent X-ray analysis" of JIS K0119. Indicated.

The Fe ²⁺ content is shown by the value obtained by the following chemical analysis method. That is, in an inert gas atmosphere, phosphoric acid and sulfuric acid were added to 0.5 g of magnetic particle powder in an amount of 2:
25 cc of the mixed solution containing 1 is added to dissolve the magnetic particles. After adding a few drops of diphenylamine sulfonic acid as an indicator to the diluted solution of the dissolved aqueous solution, redox titration was performed using an aqueous potassium dichromate solution. The time point when the diluted solution had a purple color was taken as the end point, and the value was calculated from the amount of the aqueous solution of potassium dichromate used until reaching the end point.

Mn, Zn, Ti, Z deposited on the particle surface
Regarding the amounts of r, Si, and Al, J was measured using a fluorescent X-ray analyzer 3063M type (manufactured by Rigaku Denki Kogyo Co., Ltd.).
It is measured by performing fluorescent X-ray analysis in accordance with "General rules for fluorescent X-ray analysis" of IS-K-0119, and the amount of deposition on the particle surface is calculated by subtracting the content measured in advance before deposition. did. If the deposition amount is very small, the "inductively coupled plasma emission spectroscopy analyzer SPS400
0 "(manufactured by Seiko Denshi Kogyo Co., Ltd.).

The amount of the hydrophobizing agent deposited was shown as a value converted from the amount of carbon measured using "Horiba Metal Carbon Sulfur Analyzer EMIA-2200" (manufactured by HORIBA, Ltd.).

Fe, Mn on the particle surface of the magnetic iron oxide particles,
The amount of non-magnetic oxide fine particles or non-magnetic hydrous oxide fine particles of an element selected from Zn, Ti, Zr, Si and Al was determined by using a fluorescent X-ray analyzer 3063M type (manufactured by Rigaku Denki Kogyo Co., Ltd.). It is measured by performing fluorescent X-ray analysis according to "General rules for fluorescent X-ray analysis" of JIS-K-0119, and the content of the particle surface adhered is subtracted by subtracting the content measured in advance before fixation. It was calculated.
When the amount of fixation was very small, it was measured using "inductively coupled plasma emission spectroscopic analyzer SPS4000" (manufactured by Seiko Denshi Kogyo KK).

The fluidity of the magnetic iron oxide particle powder can be estimated by the degree of compression and the angle of repose θ.

The degree of compression is represented by a value calculated by measuring the bulk density (ρa) and tap density (ρt) and substituting these values into the following formula. Compressibility = [(ρt−ρa) / ρt] × 100 Incidentally, the smaller the compressibility is, the more excellent the fluidity is.

The bulk density (ρa) is JIS-51.
01 pigment test method), tap density (ρt)
Is 20 g of magnetic iron oxide particle powder 10 g after the measurement of the bulk density.
After gently filling the cc graduated cylinder with a funnel and then letting it fall naturally from a height of 25 mm 600 times, the amount (cc) of the magnetic iron oxide particles powder filled is graduated. Was read from the scale and the value was calculated by substituting this value into the following formula. Tap density (g / cc) = 10 (g) / capacity (cc)

The angle of repose θ was measured as follows. First, the sample powder is passed through a 710 μm sieve in advance. A repose angle measuring table having a radius of 3 cm is installed, and the sample powder previously sieved once is dropped onto a 710 μm sieve installed 10 cm above the table. The height x is measured when the sample powder comes to form a cone on the table, the sample powder is further dropped, and the height x of the cone is measured again. If there is no difference in the height x measured twice, x is substituted into the following formula to obtain the value of the angle of repose θ. tan θ = x / 3 Note that the smaller the angle of repose θ, the better the fluidity.

The oil absorption of the magnetic iron oxide particles is JIS-
It was measured by the pigment test method of K-5101.

The degree of hydrophobization (Vm / Vm ⁰ ) was measured by measuring the adsorption amount (Vm ⁰ and Vm) of water vapor monomolecules before and after the hydrophobization treatment using a “water vapor adsorbing device BELSORP18” (manufactured by Bell Japan Ltd.) It is shown by the ratio (Vm / Vm ⁰ ) of the values.
The water vapor monomolecular adsorption amount is 120 ° C for the magnetic particle powder.
Is a value obtained from the BET formula by degassing for 2 hours, measuring the water vapor adsorption isotherm at an adsorption temperature of 25 ° C.

The volume average diameter of the toner is Couter C
outer TA-II (Couter Elect
tronics Co. ) Was used for the measurement. The fluidity of the toner is determined by powder tester PT-E (Hosokawa).
Micron Co. ) Was used for the measurement.

<Production of Magnetite Particle Powder> Fe
26.7 l of ferrous sulfate aqueous solution containing ²⁺ 1.5 mol / l
Was added to 22.3 l of a 3.4N aqueous sodium hydroxide solution prepared in advance in the reactor (for Fe ²⁺ , 0.
This corresponds to 95 equivalents. ), A pH of 6.8 and a ferrous hydroxide suspension containing a ferrous hydroxide colloid were produced at 90 ° C. At this time, No. 3 water glass (S
iO ₂ 28.8% by weight) 250.3 g (Si with respect to Fe
This corresponds to 3.00 atom% in conversion. ) Was diluted with water to 1 liter and added to a sodium hydroxide aqueous solution before adding the ferrous sulfate aqueous solution. To the ferrous salt suspension containing the above ferrous hydroxide colloid, 1.2 l of 3.5N sodium hydroxide aqueous solution was added to adjust the pH of the suspension to 8.9, and then the temperature was 90 ° C. In the above, 100 l / min of air was aerated for 80 minutes to produce a ferrous salt aqueous solution containing magnetite nucleation particles.

Then, the ferrous salt suspension containing the magnetite nucleus crystal particles was added to an 18N aqueous solution of sodium hydroxide 10
Add ml (corresponding to 2.25 equivalents to the remaining Fe ²⁺ ), 100 l / min at pH 10 and temperature 90 ° C.
Of air for 30 minutes to generate magnetite particles. The alkaline solution containing the magnetite particles was neutralized to pH 7.0 with a dilute sulfuric acid solution to precipitate the silicate remaining in the reaction solution on the surface of the magnetite particles. The produced particles were washed with water, separated by filtration, dried and pulverized by a conventional method.

As is clear from the electron micrograph (× 200000) shown in FIG. 1, the obtained magnetite particles have a spherical particle shape and an average particle diameter of 0.15 μm.
The sphericity Φ was 1.0. Further, this magnetite particle powder was found to contain 2.61 atomic% of Si with respect to Fe as a result of fluorescent X-ray analysis, and the amount of Fe ²⁺ was 19.3% by weight as a result of redox titration. It had a sufficient blackness. The content of elemental sulfur was 0.14% by weight. As for the magnetic characteristics, the coercive force was 114 Oe and the saturation magnetization value was 86.0 emu / g. The amount of monomolecular adsorption of water was 3.07 mg / g (Vm ⁰ ).

<Adhering Treatment> An aqueous suspension (pH 10 to 1) containing 1 kg of magnetic iron oxide particle powder after the completion of the second step reaction.
1) At a temperature of 80 ° C., 0.1% by weight of aluminum sulfate in terms of Al with respect to the particles while stirring.
After dropping an aqueous solution containing 7 g, the pH was adjusted to 7 and
Stir for minutes. Then, the mixture was filtered, washed with water, and then dried at 60 ° C. to obtain magnetite particle powder in which an adhered layer made of aluminum hydroxide was formed on the particle surface.

The magnetite particle powder having the adhered layer of aluminum hydroxide formed on the surface of the obtained particles has a BET specific surface area of 14.1 m ² / g and a compressibility of 3
7, the oil absorption amount is 17 ml / 100 g, and the adhered layer made of aluminum hydroxide on the surface of the particles is 0.
The content was 10% by weight.

<Production of Toner> The above-obtained magnetite particle powders were mixed in the following proportions, heated and melted in a kneader for 10 minutes to disperse the magnetite particles in a resin, and after cooling and solidification, the resin obtained was obtained. The kneaded product was pulverized and classified to obtain a magnetic toner. The volume average diameter of the obtained magnetic toner was 12 μm. The liquidity index was 90. Toner mixing ratio: Styrene-acrylic resin 100 parts by weight Negative charge control agent 0.5 parts by weight Release agent 6 parts by weight Magnetite particle powder 60 parts by weight

[0107]

First, the most important point in the present invention is 0.8% of the ferrous salt aqueous solution and the ferrous salt in the ferrous salt aqueous solution.
An oxygen-containing gas is bubbled through a ferrous salt reaction aqueous solution containing a ferrous hydroxide colloid obtained by reacting with 0 to 0.99 equivalents of an alkaline hydroxide aqueous solution while heating in a temperature range of 70 to 100 ° C. The first-stage reaction to generate magnetite particles and the residual Fe ²⁺ after the first-stage reaction is 1.0
Add 0 equivalents or more of an aqueous alkali hydroxide solution to 70 to 1
A method for producing magnetite particle powder, which comprises a two-step reaction with a second-step reaction in which an oxygen-containing gas is aerated to produce magnetite particles while being heated to a temperature range of 00 ° C.,
A water-soluble silicate in advance in an aqueous solution of either the aqueous solution of the alkali hydroxide or the aqueous solution of the ferrous salt containing the ferrous hydroxide colloid is 1.7 to 10 in terms of Si with respect to Fe.
The amount of the oxygen-containing gas was adjusted by adjusting the pH to 8.0 to 9.5 by adding 6.5 atomic% and adding an aqueous solution of alkali hydroxide at the start of aeration of the oxygen-containing gas in the first step reaction. By aeration, it exhibits a spherical shape, and since it has a high coercive force, it has high fluidity when used as small-sized magnetic toner particles, and has high resolution due to suppression of fog, and The fact is that magnetic iron oxide particles for magnetic toner having excellent blackness can be obtained.

The present inventors have found that the coercive force of the obtained magnetite particles depends on the content of the elemental sulfur in the magnetite crystal particles. That is, when a large amount of elemental sulfur is contained in the crystal, it is considered that a large amount of elemental sulfur due to sulfate ions was incorporated during the production reaction as described later, and the crystallinity is poor due to poor crystallinity. When the coercive force is low and the elemental sulfur is almost absent in the crystal, the crystallinity is good and the crystal magnetic anisotropy is good, and the coercive force is high.

In the case where 0.80 to 0.99 equivalent of an aqueous solution of alkali hydroxide with respect to Fe ²⁺ is added as in the conventional Japanese Patent Publication No. 3-9045, the pH value is
It is less than 8.0, and if the magnetite particle formation reaction is carried out as it is, sulfate ions in the reaction suspension are adsorbed by the magnetite crystal particles that are generated and taken into the interior along with crystal growth, resulting in poor crystallinity. It was.
In the present invention, by adjusting the pH to a range of 8.0 to 9.5 and then carrying out the reaction, it is difficult for the sulfate ion to be adsorbed to the generated magnetite crystal particles, and the sulfur element taken into the crystal is small, Therefore, it is considered that magnetite particles having a high coercive force were obtained because the crystallinity was good and the crystal magnetic anisotropy was also good.

The magnetic iron oxide particle powder according to the present invention has a spherical shape and thus is excellent in fluidity, and since it contains a small amount of sulfur element, it is excellent in crystal magnetic anisotropy and thus has a high retention. When the magnetic toner has a magnetic force and has a small particle size, fog is suppressed, so that the resolution is high, the Fe ²⁺ content is sufficiently large, and the blackness is excellent.

[0111]

EXAMPLES Next, examples and comparative examples will be described.

[0112] Examples 1 27 Comparative Examples 1 to 4; <magnetite generation of particles> Magnetite 1-5, Comparative Examples 1-4 ferrous salt type aqueous solution, the addition amount of the water glass, the first stage reaction Magnetite particle powder in the same manner as the embodiment of the present invention except that the pH at the start, the kind of the aqueous alkali hydroxide solution in the first-step reaction, the reaction temperature, and the neutralization pH after the end of the second-step reaction were variously changed. Got Table 1 shows the main production conditions at this time, and Table 2 shows various characteristics of the generated magnetite particle powder.

[0113]

[Table 1]

[0114]

[Table 2]

The amount of water adsorbed on the monomolecular layer in Comparative Example 1 was 4.86 mg / g, which was higher in hygroscopicity than the magnetite particle powder of magnetite 1 .

There is a close relationship between the coercive force value and the particle size.
Generally, the smaller the particle size, the larger the coercive force value tends to be. FIG. 2 shows the relationship between the coercive force value and the particle diameter of the magnetic iron oxide particle powder for magnetic toner according to the present invention. In FIG. 2, the mark ● indicates the embodiment of the present invention and the magnet.
The spherical magnetite particle powders of Nettite 1 to 5 are indicated by ∘, the magnetic iron oxide particles of Comparative Example 3 of the present invention are indicated by ∘, and the triangle is indicated by JP-B-3-9045.
The magnetic iron oxide particle powders obtained in Examples 1 and 10 of Japanese Patent Laid-Open No. 7-105
The magnetic iron oxide particle powder obtained in Example 2 of Japanese Patent Publication No. 98-9898, and the symbol ▲ indicates Example 1 and Comparative Example 5 of Japanese Patent Publication No. 25747/1996 (JP-A-5-213620). This is for the magnetic iron oxide particle powder obtained in.

It was confirmed that the magnetic iron oxide particle powder according to the present invention has a larger coercive force value with the same particle diameter as compared with the conventional spherical magnetite particle powder. The magnetic iron oxide particle powder obtained in the present invention is within the range shown by the solid line in the figure. In the figure, the straight line A is the expression 147-32.
Shown as 2.7 × d. In the figure, the straight line B is the equation 207-3.
It is shown by 22.7 × d. In the figure, only the magnetite particle powder before surface treatment is shown, but since the particle size and coercive force of the magnetite particle powder after surface treatment hardly change, the magnetite after surface treatment shown below is shown. The average particle diameter of the particle powder and the coercive force have the same relationship as before the surface treatment.

<Deposition Treatment> Example 1 Aqueous suspension (pH 10 to 11) containing 1 kg of magnetic iron oxide particle powder after the completion of the second step reaction in the above-mentioned embodiment.
25.4 g of aluminum sulfate containing 0.2% by weight of Al in terms of Al at a temperature of 80 ° C. with stirring.
After adding dropwise an aqueous solution containing, the solution was adjusted to pH 7 and stirred for 30 minutes. Then, the mixture was filtered, washed with water, and then dried at 60 ° C. to obtain magnetite particle powder in which an adhered layer made of aluminum hydroxide was formed on the particle surface.

The magnetite particle powder obtained by forming an adherent layer of aluminum hydroxide on the surface of the obtained particles contained 0.20% by weight in terms of Al in terms of Al.

Example 2 Deposition was performed in the same manner as in Example 1 except that the addition amount of the adherend was changed. Table 3 shows the conditions and various characteristics of the obtained magnetic iron oxide particle powder.

[0121]

[Table 3]

<Hydrophobic treatment> Example 3 A wheel-type kneading machine was used, in which 10 kg of magnetite particle powder before surface treatment obtained in the embodiment and 15 g of a silane coupling agent A-143 (manufactured by Nippon Unica Co., Ltd.) were used. (Product name: Sand Mill Co., Ltd. Matsumoto Foundry Iron Works)
The hydrophobization treatment was performed by operating for one hour.

Examples 4 to 17 Hydrophobization treatment was carried out in the same manner as in Example 3 except that the type of powder to be treated, the type of hydrophobizing agent and the addition amount were variously changed. Table 4 shows the conditions and various properties of the obtained magnetic iron oxide particle powder. As a hydrophobizing agent other than the above, a titanate coupling agent Blenact TT
S (manufactured by Ajinomoto Co., Inc.) and isopalmitic acid (manufactured by Nissan Chemical Co., Ltd.) were used.

[0124]

[Table 4]

<Fixing Treatment of Non-Magnetic Oxide Fine Particles etc.> Example 18 10 kg of magnetite particle powder before surface treatment obtained in the embodiment and 300 g of granular TiO ₂ fine powder having a particle diameter of 0.04 μm were mixed. Then, this mixture was put into a Simpson mix muller and treated with a linear load of 50 kg for 30 minutes to fix the TiO ₂ fine powder to the surface of the magnetite particles.

Examples 19 to 23 Hydrophobization treatment was carried out in the same manner as in Example 18 except that the kind of the powder to be treated, the kind of the non-magnetic oxide particles or the non-magnetic hydrous oxide particles and the addition amount were variously changed. went. Table 5 shows the conditions and various characteristics of the obtained magnetic iron oxide particle powder.

[0127]

[Table 5]

<Adhesion treatment + hydrophobization treatment> Example 24 Magnetite particle powder 10k having an adhesion layer made of aluminum hydroxide on the surface of the particles obtained in the embodiment
g 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 Iron Works), and operated for 1 hour. A hydrophobic treatment was performed.

Examples 25 to 27 Examples 25 to 27 were carried out except that the type of powder to be treated having the adhered layer on the surface of the particles, the type of the hydrophobizing agent and the addition amount were variously changed.
Hydrophobization treatment was carried out in the same manner as in Example 24 . Table 6 shows the conditions and various characteristics of the obtained magnetic iron oxide particle powder.

[0130]

[Table 6]

[0131]

The magnetic iron oxide particle powder for magnetic toner according to the present invention has a spherical shape and a particle size of 0.05 to 0.3.
Since it is a fine particle of 0 μm and has a high coercive force, it has high fluidity when made into a small-diameter magnetic toner particle,
Fog is suppressed, resulting in high resolution and excellent blackness. Furthermore, when oil absorption is small or the particle surface is hydrophobic, good mixing with the resin results in good magnetic properties for electrophotography. Most suitable as magnetic powder for toner.

[Brief description of drawings]

FIG. 1 is an electron micrograph (× 200000) showing a particle structure of a spherical magnetite particle powder obtained in an embodiment of the present invention.

FIG. 2 shows the relationship between the average particle diameter d (μm) and the coercive force Hc (Oe) of the magnetic iron oxide particle powder for magnetic toner according to the present invention.

Continuation of the front page (56) Reference JP 63-17222 (JP, A) JP 58-135137 (JP, A) JP 58-80648 (JP, A) JP 8-278660 (JP , A) JP-A-8-101529 (JP, A) JP-A-8-50369 (JP, A) JP-A-7-175262 (JP, A) JP-A-7-110598 (JP, A) JP-A-7-110598 (JP, A) 6-273974 (JP, A) JP 6-250436 (JP, A) JP 6-194869 (JP, A) JP 4-362954 (JP, A) JP 3-221965 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (5)

(57) [Claims] 1. An average particle size of 0.05 to 0.30 μm
And has a sphericity Φ of 0.95 to 1.0, contains 1.7 to 4.5 atomic% of silicon in terms of Si , and has Mn, Zn, Ti, Zr, Si on the particle surface. A magnetite particle having an adherent layer made of an oxide, a hydroxide, a hydrous oxide of one or more elements selected from Al, or a mixture thereof, in an external magnetic field of 10 kOe of the particle. Coercive force Hc (Oe) is average particle diameter d
(Μm), the following relational expression, 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207
-322.7 × d, and the amount of the elemental sulfur contained in the magnetic powder is 0.35% by weight or less. Powder. 2. An average particle size of 0.05 to 0.30 μm
And has a sphericity Φ of 0.95 to 1.0, contains 1.7 to 4.5 atom% of silicon with respect to Fe in terms of Si , and has a hydrophobic treatment agent adhered to the particle surface. It is a magnetite particle, and the coercive force Hc (Oe) in the external magnetic field 10 kOe of the particle is the following relational expression with the average particle diameter d (μm): 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207
-322.7 × d, and the amount of the elemental sulfur contained in the magnetic powder is 0.35% by weight or less. Powder. 3. An average particle size of 0.05 to 0.30 μm
And has a sphericity Φ of 0.95 to 1.0, contains 1.7 to 4.5 atom% of silicon in terms of Si , and Fe, Mn, Zn, Ti, Zr, and Magnetite particles to which non-magnetic oxide particles or non-magnetic hydrous oxide particles of one or more elements selected from Si and Al are fixed, and the coercive force Hc (Oe ) Is the following relational expression with the average particle diameter d (μm): 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207
-322.7 × d, and the amount of the elemental sulfur contained in the magnetic powder is 0.35% by weight or less. Powder. 4. An average particle size of 0.05 to 0.30 μm
And has a sphericity Φ of 0.95 to 1.0, contains 1.7 to 4.5 atomic% of silicon with respect to Si in terms of Si, and contains Mn, Zn, Ti, Zr as a lower layer on the surface of the particles. Si, A
1 has one or more kinds of oxides selected from 1 or 2 or more elements, a hydroxide, a hydrous oxide, or a mixture thereof, and further has a hydrophobic treatment agent as an upper layer. Magnetite particles having a coercive force Hc (Oe) in an external magnetic field of 10 kOe with an average particle diameter d (μm), 147-322.7 × d ≦ Hc _{(10 kOe)} ≦ 207
-322.7 × d, and the amount of the elemental sulfur contained in the magnetic powder is 0.35% by weight or less. Powder. 5. A magnetic toner using the magnetic iron oxide particle powder for a magnetic toner according to claim 1.