JP2000335920A - Iron oxide particles and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an iron oxide particle hardly applying a load on a toner particle itself, having a low toner stress, consequently capable of preventing falling off of magnetic particles from a magnetic toner, having a good balance of magnetic characteristics and also excellent packing properties and blendability with a resin, and to provide a method for producing the iron oxide particle. SOLUTION: This iron oxide particle comprises >=95 wt.% of at least one kind of Mg, Na, K, Ca, Li, Ti, S, Al, Si, B and C at a part within 80 wt.% from the surface of particle in the particle and >4 and <5.2 true specific gravity at 20 deg.C. Preferably, the content of Mg, Na, K, Ca, Li, Ti, S, Al, Si, B or C per component is preferably <=5 wt.% based on the total of the iron oxide particle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to iron oxide particles suitable for use as a material powder for a magnetic toner for electrostatic copying, a material powder for an electrostatic copying carrier, a black pigment powder for a paint, and a method for producing the same.

[0002]

2. Description of the Related Art
Iron oxide particles are widely used as a material powder for magnetic toners in various fields, especially in dry-type electronic copiers and printers. Iron oxide alone is magnetite (Fe ₃ O ₄ ), and maghemite (γ-Fe ₂ O) is a ferrite. ₃₎ or berthollide compound of intermediate composition _{(FeOx · Fe 2 O 3,} 0 <x
<1) and the like are used.

One of the characteristics required of the magnetic toner is that the magnetic powder such as the iron oxide particles contained in the magnetic toner does not easily fall off the magnetic toner.

[0004] Regarding the required characteristics, see JP-A-9-24.
No. 1025 discloses that magnetic particles exposed on the surface of toner particles easily fall off from the toner due to friction or the like. In particular, in the case of a small particle size toner, the number of magnetic particles exposed on the surface increases and drops off from the surface of the toner particles. Not only do the magnetic particles become finer, deteriorating the environment inside the device, and not only hinder uniform charging of the toner, but also cause problems such as falling off magnetic particle powder scattered during electrostatic development, lowering developability. It is described that magnetic particles which are hard to fall off even when exposed to the surface of toner particles and have excellent durability are strongly required.

In response to this request, Japanese Patent Laid-Open No. 9-241
No. 025 and JP-A-10-182163,
A magnetic iron oxide particle having convex protrusions and having a spinous shape is disclosed.

According to the above technique, it is possible to prevent the magnetic particles from falling off from the magnetic toner, but the magnetic particles exposed on the surface of the magnetic toner are liable to damage the photosensitive drum because of the convexity in shape. The problem derives. In addition, there is a limit in overcoming such a problem only by the shape.

On the other hand, another characteristic required of the magnetic toner is that the toner stress is low, and it goes without saying that the raw material used for the magnetic toner largely depends on it.

It is known that the force acting on the toner particles includes gravity, inertia force, polarization force, magnetic force, etc. Among them, in the toner bottle and the copying mechanism, the frictional charge is applied to the toner particles. Physical loads mainly due to gravity, inertia force, etc., such as agitation near the sleeve, scattering / collision between the photosensitive member and the sleeve, pressure load between particles, and the like are generated.

As a result, the toner particles are broken more than necessary, which is a distant cause of the generation of fine powder as disclosed in Japanese Patent Application Laid-Open No. 9-241025.

That is, iron oxide particles that not only prevent the magnetic particles from dropping off from the magnetic toner but also are durable because the above-mentioned load is not easily applied, that is, have low toner stress, are required.

On the other hand, important properties required for the iron oxide particles used in the magnetic toner are that the magnetic properties are balanced, the mixing property with the resin is excellent, and the filling of the magnetic toner. It is also mentioned that it has excellent properties.

Accordingly, it is an object of the present invention to provide a toner which is less likely to be subjected to a load, has a low toner stress, and can prevent the magnetic particles from falling off from the magnetic toner. It is an object of the present invention to provide iron oxide particles having excellent properties and mixing properties with a resin, and a method for producing the same.

[0013]

In general, a magnetic toner is produced by adding an inorganic material such as a pigment and a magnetic material to an organic material such as a thermoplastic resin, a charge control agent, and other external additives. In the case of iron oxide particles, it can be said that the material has both properties of a pigment and a magnetic material. Therefore, if an inorganic material having a large specific gravity is used in the manufactured magnetic toner or if the amount of the inorganic material is increased, the specific gravity of the toner tends to increase. A magnetic toner having a large toner specific gravity has advantages such as improved fluidity, but has a disadvantage that it is more susceptible to a physical load such as contact between particles or contact between particles and a copying mechanism or collision.

On the other hand, in order to improve the initial dispersibility of the iron oxide particles in the resin during the production of the toner, the mixing property of the iron oxide particles in the resin is important. Smaller is better and will eventually result in improved dispersibility.

The inventors of the present invention have conducted intensive studies based on the above fact, and as a result, it has been found that the above-mentioned object can be achieved by using a specific element contained in a certain portion of the particle and having a low specific gravity. Was found.

The present invention has been made based on the above-mentioned findings, and includes Mg, Na, K, Ca, Li, Ti, S,
At least one of Al, Si, B, and C is contained in a portion within 80% by weight of the particle surface in an amount of 95% by weight or more, and the true specific gravity at 20 ° C is more than 4 and less than 5.2. An object of the present invention is to provide a characteristic iron oxide particle.

Further, as a preferred method for producing the iron oxide particles of the present invention, the present invention provides a method for neutralizing and mixing an aqueous ferrous salt solution and an aqueous alkaline solution, and then oxidizing the resulting slurry containing ferrous hydroxide colloid. In the method for producing iron oxide particles, Mg, Na, K, C is added to the slurry containing the ferrous colloid.
a method for producing iron oxide particles, wherein a soluble inorganic compound salt containing at least one of a, Li, Ti, S, Al, Si, B and C or an aqueous solution thereof is gradually added during the oxidation reaction. Is provided.

[0018]

Embodiments of the present invention will be described below. The iron oxide particles referred to in the present invention preferably contain magnetite as a main component. In the following description, magnetite particles, which are typical iron oxide particles, will be described. Further, when referring to iron oxide particles or magnetite particles, it means either individual particles or their aggregates depending on the content.

The magnetite particles of the present invention contain M
g, Na, K, Ca, Li, Ti, S, Al, Si,
95% or more of at least one of B and C is contained in a portion within 80% by weight of the particle surface. Although magnetite particles having a small true specific gravity can be produced by containing other elements, it is preferable to use these elements from the viewpoint of environmental load and economy.

When these elements are contained in a portion exceeding 80% by weight from the particle surface in an amount exceeding 5% by weight, these elements are excessively taken into the center of the magnetite particles, and a sufficient saturation magnetization as a magnetic material is obtained. No longer available.

The true specific gravity of the magnetite particles of the present invention is 4
And less than 5.2, preferably 4.2 to 5, more preferably 4.3 to 4.9. When the true specific gravity is 4 or less, a large amount of components other than magnetite that lowers the specific gravity are contained, so that the magnetic properties cannot be balanced. When the true specific gravity is 5.2 or more, conventional magnetite particles, Further, since components other than magnetite having a large specific gravity are contained, magnetite particles having low toner stress cannot be obtained.

In the magnetite particles of the present invention, the content of the above elements is preferably 5% by weight or less, more preferably 3% by weight or less, most preferably 1.5% by weight or less based on the total amount of magnetite particles per component. is there. When the content of the element per one component exceeds 5% by weight, although the toner stress is reduced, the balance of magnetic properties is lost, the tap density is reduced, and the filling property is also poor.

The average particle size of the magnetite particles of the present invention is preferably from 0.05 to 1 μm, more preferably from 0.1 to 0.5 μm, most preferably from 0.1 to 0.3 μm.
m. Average particle size of magnetite particles is 0.05μm
If it is less than 1, the magnetic agglomeration of the magnetite particles is remarkable, which adversely affects the effect of preventing the magnetic particles from falling off the magnetic toner. The average particle size of the magnetite particles is 1 μm.
When the ratio exceeds, the exposure of the magnetite particles to the surface of the magnetic toner becomes excessive, and the photosensitive drum is easily damaged.

The tap density of the magnetite particles of the present invention is preferably from 0.3 to 2 g / cm ³ , more preferably from 0.5 to 2 g / cm ³ , and most preferably from 0.7 to 1.
8 g / cm ³ . If the tap density of the magnetite particles is less than 0.3 g / cm ³ , the filling and dispersibility of the magnetite particles in the toner resin will be poor, causing variations in the magnetic properties of the magnetic toner particles, If the tap density exceeds 2 g / cm ³ ,
Since the compressibility is high, the handling property of the magnetic material becomes poor, such as a noticeable seizure of the powder in the hopper.

The magnetite particles of the present invention have a saturation magnetization of 70 to 92 emu / g when an external magnetic field of 10 kOe is applied.
Is preferred. More preferably, 75 to 90 emu / g,
Most preferably, it is 80 to 90 emu / g. If the saturation magnetization is less than 70 emu / g, image deterioration is likely to occur due to poor triboelectricity of the magnetic toner.
mu / g is the theoretical value of magnetite particles,
There are no magnetite particles satisfying this condition below 5.2.

The shape of the magnetite particles of the present invention is not particularly limited as long as it can impart characteristics suitable for toner. preferable.

Next, a preferred method for producing the magnetite particles of the present invention will be described. The magnetite particles of the present invention, after neutralization and mixing with an aqueous ferrous salt solution and an aqueous alkali solution, when oxidizing a slurry containing the obtained ferrous hydroxide colloid to produce magnetite particles, the ferrous colloid is used. The slurry containing Mg, Na, K, Ca, Li, T
It is obtained by gradually adding a soluble inorganic compound salt containing at least one of i, S, Al, Si, B and C or an aqueous solution thereof during the oxidation reaction.

As a method for producing magnetite particles, not only a wet method but also a dry method can be considered. Basically, the above-mentioned wet method is more economically advantageous and produces uniform magnetite particles having a small specific gravity. It is suitable to do.

Further, Mg, Na, K, Ca, Li, T
It is important to add the soluble inorganic compound salt containing at least one of i, S, Al, Si, B, and C or the aqueous solution thereof gradually during the oxidation reaction as described above. Other methods, such as batch addition to a slurry containing ferrous hydroxide colloid before the oxidation reaction or addition after the oxidation reaction, are likely to cause uneven distribution of the above elements in the particles, control of particle size and magnetic properties. It is not preferable in terms of balance. By adopting the production method in the present invention, it is possible to more uniformly contain each of the above-described elements in the magnetite particles, and if the reaction atmosphere is set according to the reactivity of each of the above-described elements to be subjected to the reaction. Good.

At this time, when the pH at the time of the oxidation reaction is less than 8.0, spherical magnetite particles are obtained.
In the case of 9.5, hexahedral magnetite particles can be obtained, and in the case of exceeding 9.5, octahedral magnetite particles can be obtained. It is possible.

Examples of the aqueous ferrous salt solution used in the present invention include an aqueous ferrous sulfate solution and an aqueous ferrous chloride solution. Examples of the aqueous alkali solution used in the present invention include aqueous hydroxide solutions of alkali metals such as sodium hydroxide and potassium hydroxide, aqueous hydroxide solutions of alkaline earth metals such as magnesium hydroxide and calcium hydroxide, and sodium carbonate. And aqueous solutions of alkali carbonates such as potassium carbonate and ammonium carbonate, and aqueous ammonia.

Mg, Na, K, Ca, Li, T
The soluble inorganic compound salt containing at least one of i, S, Al, Si, B, and C may be a water-soluble, acid / alkali-soluble sulfate compound, nitrate compound, chloride, or the like, but is preferably used. May be used that matches the liquid properties.

[0033]

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

[Example 1] <Production of magnetite particles> As shown in Table 1, F
e ²⁺ 50 liters of an aqueous solution of ferrous sulfate containing 2.0 mol / l and 45 liters of a 4.0 mol / l aqueous solution of sodium hydroxide are mixed, and while maintaining the temperature at 80 ° C., 40 liters / minute of air And the oxidation reaction was allowed to proceed.

On the way, while checking the progress of the reaction based on the concentration of unreacted ferrous hydroxide, 8 liters of a 0.1 mol / l aqueous solution of titanium sulfate is used from the time when the progress has progressed 50% from the beginning of the reaction. Was gradually added until the progress rate reached 80%. The pH during this addition was maintained at 6.5 using aqueous sodium hydroxide.

The slurry containing the magnetite particles after the reaction was washed, filtered, dried and pulverized by a conventional method.

The magnetite particles thus obtained were measured or analyzed for the average particle size, magnetic properties, true specific gravity, tap density, and chemical components by the following methods, and the results are shown in Table 2.

(1) Average Particle Size The Feret diameter of the particles on the transmission electron micrograph (magnification: 30,000) was measured, and the average value was taken. (2) Magnetic properties Using a vibration sample type magnetometer VSM-P7 manufactured by Toei Industry,
The saturation magnetization, residual magnetization, and coercive force were measured at an applied magnetic field of 10 kOe. (3) Tap density Measured with a powder tester PT-E type manufactured by Hosokawa Micron. (4) True Specific Gravity Measured at room temperature and 20 ° C. using a multi-volume density meter 1305 manufactured by Shimadzu Corporation. (5) Chemical component analysis The total content of elements was measured by dissolving a sample and performing plasma photosensitivity analysis (ICP). Further, element content sites within 80 wt% from the particle surface, 1N-H ₂ Sample 25g
The solution was gradually dissolved at 60 ° C. in an aqueous solution of SO _{4, and} during the dissolution process, 20 ml of each solution was collected, insoluble components were filtered off with a membrane filter, and the dissolved components were quantified by ICP. Each element at the time when Fe dissolved 80% by weight with respect to Fe when the magnetite particles were completely dissolved was analyzed. (6) Mixability with Resin 30 g of a sample was put into a 500 ml polybin, and further, a resin powder (TB-1000F, manufactured by Sanyo Chemical Co., Ltd.) was pulverized with a bantam mill, and a resin powder under the sieve was used using a 1 mm sieve. Use 30 g gently. Cover the polybin and slowly rotate and stir at 5 seconds / revolution with a V-type mixer. 10
When rotated, stop rotating and stirring, gently take out the contents on white paper, and visually check the mixing state. The color of the mixture was confirmed, and the mixture was evaluated as ○ when there was no unevenness in the mixed state and uniformly mixed, Δ when there was slight unevenness, and X when there was large unevenness and insufficient mixing.

<Production of Magnetic Toner> Powder was mixed by a mixer with the following composition and melt-kneaded in a biaxial kneader for 10 minutes. After cooling, the kneaded material was coarsely pulverized and finely pulverized (fine mill). Further, this was classified by air to produce a magnetic toner.

・ Styrene-acrylic resin 100 parts by weight (TB-1000F, manufactured by Sanyo Kasei Co., Ltd.) ・ 1 part by weight of negative charge control agent (Bontron S-34, manufactured by Orient Chemical Co., Ltd.) ・ 2 parts by weight of release agent ( (Viscol 550P manufactured by Sanyo Chemical Co., Ltd.) ・ 100 parts by weight of magnetite particles

With respect to the obtained magnetic toner, image evaluation (image density and fog) and evaluation of fine particles falling off magnetite particles from the toner were evaluated by the following methods. The results are shown in Table 2.

(7) Image Evaluation (Image Density and Fog) The one-component developer composed of the magnetic toner obtained above was actually photographed using a commercially available laser beam printer, and the image density was measured with a Macbeth densitometer. The level of no fog was evaluated as ◎, the level slightly observed was evaluated as ○, the level considerably observed was evaluated as Δ, and the level of fog that was not practically used was evaluated as x. (8) Evaluation of magnetite particle-dropped fine powder from magnetic toner The container containing 20 g of the magnetic toner obtained above was shaken with a paint shaker for 1 hour, and the presence or absence of the dropped fine powder was examined.

[Examples 2 to 8 and Comparative Examples 1 to 6] The types and amounts of the aqueous ferrous salt solution and the aqueous alkali solution, the types, concentrations, amounts, timings and reaction conditions of the additives are shown in Table 1. Except for the above, magnetite particles were obtained in the same manner as in Example 1. Further, a magnetic toner was obtained in the same manner as in Example 1 using the magnetite particles.

The properties and properties of the magnetite particles and the magnetic toner were measured or analyzed in the same manner as in Example 1, and the results are shown in Table 2.

[0045]

[Table 1]

[0046]

[Table 2]

As is clear from Table 2, Examples 1 to 8
Showed better magnetic property balance, lower true specific gravity, and better mixability with resin than Comparative Examples 1 to 6. In the evaluation after toner formation, the image density is good, the fog is small, and the magnetite fine powder falling from the magnetic toner is small.

[0048]

As described above, the iron oxide particles of the present invention hardly apply a load to the toner particles themselves, have low toner stress, prevent the magnetic particles from falling off from the magnetic toner, and balance the magnetic characteristics. Since it is excellent in removal property, filling property and mixing property with resin, it is suitable for uses such as material powder for electrostatic copying magnetic toner, material powder for electrostatic copying carrier, or black pigment powder for paint. Further, the iron oxide particles can be easily produced on an industrial scale by the production method of the present invention.

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[Procedure amendment]

[Submission date] April 21, 2000 (200.4.2
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

The present invention has been made based on the above-mentioned findings, and includes Mg, Na, K, Ca, Li, Ti, S,
Containing Al, Si, B, at least one or more of C
And contained at a site within 80% by weight of the particle surface.
The total amount of the above elements is relative to the total amount of the elements contained in the particles.
To have 95 wt% or more and a true specific gravity of greater than 4 at 20 ° C., there is provided iron oxide particles and less than 5.2.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

Further, as a preferred method for producing the iron oxide particles of the present invention, the present invention provides a method for neutralizing and mixing an aqueous ferrous salt solution and an aqueous alkaline solution, and then oxidizing the resulting slurry containing ferrous hydroxide colloid. In the method for producing iron oxide particles, Mg, Na, K, C is added to the slurry containing the ferrous colloid.
When gradually adding a soluble inorganic compound salt or an aqueous solution thereof containing at least one of a, Li, Ti, S, Al, Si, B and C during the oxidation reaction , the addition is started.
At the earliest, after the oxidation reaction rate 20% or more, at the end of the addition
At the earliest period it is intended to provide a process for the production of iron oxide particles, characterized in der Rukoto 80% after the oxidation reaction rate.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

The magnetite particles of the present invention contain M
g, Na, K, Ca, Li, Ti, S, Al, Si,
The total amount of the above elements contained in at least 80% by weight of the particle surface containing at least one of B and C
But Der Ru 95 weight% or more, based on the total amount of elements contained in the particles. Although magnetite particles having a small true specific gravity can be produced by containing other elements, it is preferable to use these elements from the viewpoint of environmental load and economy.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

When these elements are contained in a portion exceeding 80% by weight from the particle surface in an amount exceeding 5% by weight based on the total amount of the elements contained in the particles, excessive amounts of these elements are present at the center of the magnetite particles. It is taken in, and sufficient saturation magnetization as a magnetic material cannot be obtained.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

Next, a preferred method for producing the magnetite particles of the present invention will be described. The magnetite particles of the present invention, after neutralization and mixing with an aqueous ferrous salt solution and an aqueous alkali solution, when oxidizing a slurry containing the obtained ferrous hydroxide colloid to produce magnetite particles, the ferrous colloid is used. The slurry containing Mg, Na, K, Ca, Li, T
When gradually adding a soluble inorganic compound salt or an aqueous solution thereof containing at least one of i, S, Al, Si, B, and C during the oxidation reaction , the addition start time is early.
Even after the oxidation reaction rate of 20%,
It can be obtained by setting the oxidation reaction rate to 80% or less .

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

Further, Mg, Na, K, Ca, Li, T
The time when the soluble inorganic compound salt containing at least one of i, S, Al, Si, B, and C or the aqueous solution thereof is added is as described above when gradually adding during the oxidation reaction.
The oxidation reaction rate is 20% or less at the earliest when the addition is started.
At the end of the addition, the oxidation reaction rate is 80% or more at the earliest
It is important to. Other methods, such as batch addition to a slurry containing ferrous hydroxide colloid before the oxidation reaction or addition after the oxidation reaction, are likely to cause uneven distribution of the above elements in the particles, control of particle size and magnetic properties. It is not preferable in terms of balance. By adopting the production method in the present invention, it is possible to more uniformly contain each of the above-described elements in the magnetite particles, and if the reaction atmosphere is set according to the reactivity of each of the above-described elements to be subjected to the reaction. Good.

Continued on the front page F term (reference) 2H005 AA02 AB02 BA03 CB03 EA02 EA05 EA07 EA10 4G002 AA04 AA06 AA08 AA12 AB05 AD04 AE01 AE03

Claims (6)

[Claims] 1. The method according to claim 1, wherein Mg, Na, K, Ca, Li,
95% by weight of at least one of Ti, S, Al, Si, B, and C at a site within 80% by weight of the particle surface
Contains, and the true specific gravity at 20 ° C. exceeds 4,
Iron oxide particles having a particle size of less than 5.2. 2. The method of claim 1, wherein the Mg, Na, K, Ca, Li, T
The iron oxide particles according to claim 1, wherein the content of i, S, Al, Si, B, and C is 5% by weight or less based on the total amount of iron oxide particles per component. 3. The iron oxide particles according to claim 1, having an average particle size of 0.05 to 1 μm. 4. The iron oxide particles according to claim 1, wherein the tap density is 0.3 to 2 g / cm ³ . 5. The iron oxide particles according to claim 1, wherein the saturation magnetization when applying an external magnetic field of 10 kOe is 70 to 92 emu / g. 6. A method for producing iron oxide particles in which a slurry containing a ferrous hydroxide colloid is oxidized after neutralization and mixing with an aqueous ferrous salt solution and an alkaline aqueous solution, the slurry containing the ferrous colloid is provided. In addition, Mg, Na, K, Ca, L
A method for producing iron oxide particles, characterized by gradually adding a soluble inorganic compound salt containing at least one of i, Ti, S, Al, Si, B and C or an aqueous solution thereof during an oxidation reaction.