JP2001271005A - Iron oxide particle, iron oxide powder comprising the same iron oxide particle, toner for electrostatic copying, carrier for developing electrostatic latent image, black pigment and method for producing iron oxide particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an iron oxide particle having a high blackness degree, excellent in dispersibility and comprising a carbonaceous component more firmly and uniformly treated on the particle surface, to provide a method for producing the iron oxide particle and further to obtain an iron oxide powder comprising the iron oxide particle, a toner comprising the iron oxide powder, a carrier and a black pigment powder comprising the iron oxide powder. SOLUTION: This iron oxide particle is characterized in that a carbonaceous component having 0.05-1 μm average particle diameter in an amount of 0.1-30 wt.% based on the total amount of the iron oxide particle expressed in terms of carbon atom sticks to the particle surface and the elimination rate of the carbonaceous component is <=15% when water is used as a dispersion medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to iron oxide particles having high blackness and a method for producing the same, and further relates to an iron oxide powder containing the iron oxide particles, a toner for electrostatic copying using the iron oxide powder, The present invention relates to a carrier for developing an electrostatic latent image and a black pigment.

[0002]

2. Description of the Related Art Iron oxide particles produced by an aqueous solution reaction have been widely used because of their magnetic properties and blackness.

[0003] In particular, in recent years, materials utilizing iron oxide particles have been widely used as materials for magnetic toners of electrophotographic copying machines and printers.

[0004] Various general developing characteristics are required for magnetic toners. In particular, toner materials corresponding to high resolution of digital copying machines and printers have been demanded.

That is, in addition to conventional characters, output of graphics and photographs is also required. In particular, some printers are required to have a capacity of 2400 dots or more per inch, and fine lines in development are required. Improvements in reproducibility and halftone dot reproducibility have been strongly demanded.

[0006] In addition, the particle size of the toner has also been reduced, and a toner having a high blackness has been required.

Further, with the improvement of low-temperature fixability for high-speed output, etc., the demand on the resin side for forming the toner has also been increased. High dispersibility has also become an important required characteristic in development.

Japanese Patent Application Laid-Open No. 53-94932 discloses a method utilizing iron oxide particles as an electrophotographic material.
Various improvements have been made to the particles, including the publication of Japanese Patent Application Laid-Open Publication No. H10-26095.

On the other hand, carbon black as a powder for a black pigment is already widely used as a pigment for a non-magnetic black toner because of its high blackness.

Attempts have also been made to compound iron oxide particles and carbon black particles.
JP-A-163927, JP-A-5-66609, JP-A-11-194532, JP-A-11-3054
No. 80 describes a magnetic material for toner.

Japanese Patent Application Laid-Open No. 54-163927 discloses that carbon black is suspended in an aqueous solution of iron salt, and an alkali is gradually added to convert the iron salt into triiron tetroxide. A method for producing a black pigment having magnetism, comprising coprecipitating carbon black and separating and collecting a coprecipitate, is described. According to this method, a pigment excellent in both blackness and magnetism can be obtained.

Japanese Patent Application Laid-Open No. 5-66609 discloses that at least a magnetic substance obtained by heating magnetite with a reducing gas and then a CO ₂ gas to form a coating of carbon black by a decomposition reaction of CO ₂ and a binder resin are used. A magnetic toner characterized by being contained is described. According to the publication, a magnetic substance whose surface is coated with carbon black by a decomposition reaction of CO ₂ can be obtained.

Furthermore, Japanese Patent Application Laid-Open No. 5-61258 discloses an electrostatic image developing method characterized in that magnetite is coated with a resin in which carbon-deposited magnetite is formed by depositing carbon on the surface. The carrier is listed. According to this, the carbon-deposited magnetite is subjected to a heat treatment of the magnetite with a reducing gas, followed by a heat treatment in a CO ₂ gas atmosphere to thereby reduce CO _2.
It is described as being obtained by causing a dispersion reaction of No. ₂ and depositing and forming a carbon component on the magnetite surface. In addition, by performing such a treatment, the carbon coating layer on the surface of the carbon-deposited magnetite has a specific resistance several orders of magnitude lower than that of magnetite, and therefore, the desired electric conductivity can be obtained by adding a relatively small amount to the carrier coat resin. It is described that the resulting toner has an effect of alleviating the accumulation of excessive charge of the toner, and a uniform and stable charging property can be obtained.

Further, Japanese Patent Application Laid-Open No. 7-72654 discloses that in a magnetic toner containing magnetic iron oxide, the volume resistivity of the magnetic iron oxide is 5 × 10 ³ to 1 × 10 ⁸ Ωcm.
Is disclosed. According to the publication, it is described that when the volume resistivity of iron oxide is high, the charge amount tends to be unnecessarily high, and the image density tends to decrease, especially when repeatedly used under low temperature and low humidity. Therefore, it is considered that the volume resistivity, that is, the electric resistance of iron oxide is preferably low to some extent.

Japanese Patent Application Laid-Open No. 11-194532 discloses a black toner characterized in that a toner having at least a binder resin and a colorant contains at least magnetic carbon black composite particles as the colorant. ing. According to the publication, a fuel is burned to form a high-temperature combustion gas stream, and a hydrocarbon material is spray-injected into the high-temperature combustion gas stream to cause a pyrolysis reaction, thereby producing carbon black. In a method for producing carbon black in which water is sprayed and cooled in a high-temperature gas stream and then carbon black is separated and collected, a magnetic transition metal compound is spray-injected from two positions of an upstream region and a downstream region of the high-temperature combustion gas. Then, composite particles composed of the generated carbon black and magnetic metal fine particles,
It is said that magnetic carbon black composite particles can be obtained by performing a heat treatment at a temperature of 400 to 900 ° C. in a non-oxidizing atmosphere.

Furthermore, Japanese Patent Application Laid-Open No. H11-305480 discloses that an organosilane compound formed from alkoxysilane is coated on the surface of a magnetic iron oxide powder having an average particle size of 0.055 to 0.95 nm. A black magnetic composite powder in which carbon black fine powder having an average particle size of 0.002 to 0.05 μm is adhered to the silane compound coating, and the amount of the carbon black fine powder adhered to 100 parts by weight of the magnetic iron oxide powder There is described a black magnetic powder for black magnetic toner, which is 1 to 25 parts by weight based on the weight of the black magnetic powder. According to the publication, carbon black particles can be sufficiently adhered to the extent that blackness and fluidity can be improved by performing an organosilane treatment.

When such a black composite magnetic material is used for toner, it is important to increase the degree of blackness, but at the same time, it is possible to solve the problems of image density and fog in an environmental system and a transfer system. Is required.

That is, required as a magnetic toner,
There is a demand for high fluidity, optimization of electrical properties such as toner electrical resistance and chargeability, and high dispersibility of the composite magnetic material in thermoplastic resin during toner production.

This is because, when a large amount of carbon black is used on the surface of a magnetic material to determine the degree of blackness, a decrease in electric resistance, a deterioration in dispersibility, and the like occur, and as a result, the uniformity as a toner is impaired, and the image density becomes insufficient And fog are high.

Furthermore, since there is a high market demand for inexpensive products as electrophotographic materials, and there is a demand for regulations on the use of environmentally harmful substances, manufacturing costs are reduced while complying with regulations on chemicals used. There has been a demand for a method capable of stably producing a large amount in a short time.

Iron oxide particles having a high blackness as described above, having excellent dispersibility when formed into a toner, and adaptable to the environment and cost, and a method for producing the same have not yet been obtained.

That is, the above-mentioned Japanese Patent Application Laid-Open No. 54-16392
In the method disclosed in JP-A-H7 (7), that is, when carbon black is suspended in an aqueous solution of iron salt and an alkali is gradually added to convert iron salt to triiron tetroxide, the carbon black is rapidly precipitated with ferrous hydroxide. The fine carbon black particles cannot be uniformly and stably adhered to the surface of the iron oxide particles which are optically effective and are fixed, and it is difficult to obtain sufficient hiding power and coloring power as a pigment.

In the method described in JP-A-5-66609, that is, the method of coating carbon black on the surface of particles by a dry method using CO ₂ gas, a uniform carbon black component is coated on the surface of particles. Adhesion is possible, but if the heat treatment time and temperature are not adjusted, magnetite will be reduced, and the electrical resistance of the magnetic material will be reduced more than necessary, and the energy cost of dry heat treatment is lower than that of wet treatment. The problem is that it is enormous.

In Japanese Patent Application Laid-Open No. 5-61258,
It describes the function of adjusting the electrification of carbon-deposited magnetite by depositing and coating carbon components.However, the cost is high because the iron oxide particles are dry-processed, and the carbon component on the surface of the iron oxide particles is further reduced. It is not clear whether it has sufficient adhesive strength.

In the method described in Japanese Patent Application Laid-Open No. 11-194532, that is, the method of producing a magnetic material simultaneously with the production of carbon black in a high-temperature region, the characteristics of the composite particles greatly change depending on conditions such as spraying conditions and temperature control. There is a possibility, and the cost is high due to a high-temperature reaction such as a combustion method, so that the method is not industrially easy to carry out.

Further, in the method disclosed in JP-A-11-305480, that is, the method in which carbon black fine particles are adhered by mixing and stirring after organosilane treatment, only a dry mixing operation is performed, which is advantageous in terms of cost. Although carbon black particles can be attached to the surface of the iron oxide particles, it is difficult to uniformly and firmly attach the carbon black particles to the surface of the iron oxide particles because the carbon black particles, which are fine particles, have a high cohesive force. In addition, there is a problem of environmental load due to the use of organosilane, and it cannot be said that it sufficiently satisfies the demands of the market.

Accordingly, an object of the present invention is to provide a high blackness,
And iron oxide particles having a carbon-based component more firmly and uniformly treated on the surface of the particles and a method for producing the same.Moreover, an iron oxide powder containing the iron oxide particles, and an iron oxide powder containing the iron oxide particles. An object of the present invention is to provide a toner, a carrier and a black pigment powder contained therein.

[0028]

As a result of the study, the present inventors have found a method for more firmly and uniformly attaching a carbon-based component to the surface of iron oxide particles, and have found that the above object can be achieved.

That is, the present invention has been made on the basis of the above findings, and has an average particle diameter of 0.05 to 1 μm and a carbon-based component on the particle surface in terms of carbon atoms, based on the total amount of iron oxide particles. An object of the present invention is to provide iron oxide particles which are attached at 0.1 to 30% by weight and have a carbon-based component desorption rate of 15% or less when water is used as a dispersion medium.

In the present invention, the surface of the particles containing the carbon-based component is preliminarily subjected to alkali treatment and / or oxidation treatment to activate the surface, and then added to an aqueous suspension of iron oxide particles to add acid or alkali. The present invention provides a method for producing iron oxide particles, wherein particles containing a carbon-based component are adhered to the surface of iron oxide particles by adjusting the pH to 5 to 12 by using the particles.

[0031]

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, and include those containing various effective elements such as silicon, aluminum, and titanium, or those coated with these effective elements. .
As for the shape of the iron oxide particles, various shapes such as a spherical shape, a polyhedron such as a hexahedron and an octahedron, and a needle shape are known. In the present invention, any shape can be used. Here, the iron oxide powder or the magnetite powder means an aggregate of iron oxide particles or magnetite particles.

The iron oxide particles of the present invention have an average particle size of 0.0
The particle size is 5 to 1 μm, and a carbon-based component is attached to the particle surface in an amount of 0.1 to 30% by weight in terms of carbon atoms based on the total amount of iron oxide particles. Here, the term “adhesion” means that the carbon-based component is hardly detached from the iron oxide particles due to mechanical and / or chemical external factors. Therefore, these particles were simply physically mixed. Different from the ones.

The average particle size of the iron oxide particles in the present invention is as follows:
As described above, the thickness is 0.05 to 1 μm, and preferably 0.1 to 1 μm.
08 to 0.5 μm, more preferably 0.1 to 0.3 μm
m. The size of the iron oxide particles is important in evaluating blackness, and is also a factor in evaluating the optimal absorption / scattering effect with respect to the wavelength of visible light. Therefore, it is important to define the size of the primary particles, and it is desirable that the particle size distribution of the primary particles is excellent and that the particles do not aggregate. That is, it is needless to say that monodisperse particles are preferable. If the average particle size of the iron oxide particles is less than 0.05 μm, it is difficult to obtain a sufficient monodispersion, and optical transparency is caused, resulting in poor blackness. If the average particle size of the iron oxide particles exceeds 1 μm, the reflection becomes dominant over the optical absorption, and the blackness is reduced under white light.

The carbon-based component adhering to the particle surface is
As will be described later, it is preferable that the surface of the carbon-based component can be chemically exposed, and the one having a large optical absorption effect among the optical characteristics with respect to the particle diameter of the iron oxide particles is preferable. More specifically, with respect to the iron oxide particles, the size of the carbon component is as small as 1/5 or less, and the dispersibility is high.
Those having high surface activity are preferred. Typical examples of such substances include coke and artificial graphite obtained by a liquid phase carbonization method, activated carbon and carbon fiber obtained by a solid phase carbonization method,
Examples thereof include carbon black, pyrolytic carbon, highly oriented graphite, and vapor grown carbon fiber obtained by a gas phase carbonization method. Further, so-called activated carbon can be used for such a carbon-based component. In the present invention, it is preferable to select and use a particle size that satisfies the optical characteristics of such a carbon-based component. It is also a desirable method to select and use fine particles such as carbon black.

It is important that the iron oxide particles of the present invention have a carbon-based component desorption rate of 15% or less when water is used as a dispersion medium. The desorption rate of the carbon-based component is determined based on the amount of the carbon-based component adhered, how much the iron oxide particles are dispersed in water, and how much the carbon-based component is depleted against mechanical external factors such as ultrasonic waves. Evaluation is made as to whether the components have adhesiveness. Therefore, in this evaluation, the desorption rate is preferably as low as 15% or less, more preferably 10% or less.

It is important to note that the iron oxide particles of the present invention are more robust because both the iron oxide particles and the carbon-based component whose surface is chemically activated, which will be described later, are hydrophilic. The reason is that the desorption rate becomes small due to the adhesion. Therefore, as described in JP-A-11-305480, this is different from the method of increasing the adhesive force using an organosilane compound generated from alkoxysilane in order to firmly adhere the carbon black particles.

When carbon black particles are selected as the carbon component, the particle size of the carbon black is 1 to
It is preferably 100 nm, more preferably 5 nm.
５０50 nm. Thereby, the blackness of the iron oxide particles can be further increased, and at the same time, the adhesion between the iron oxide particles can be reduced, and the dispersibility of the iron oxide particles can be improved.

As such carbon black particles, commercially available carbon black particles may be used. For example, carbon black manufactured by Mitsubishi Chemical Corporation # 52, # 50, # 4
7, # 45, # 45L, # 44, # 40, # 33, # 3
2, # 30, # 25, # 20, # 10, # 5, CF9,
# 95, # 260, # 1000, # 990, # 980,
# 970, # 960, # 950, # 900, # 850,
MCF88, MA600, # 750B, # 650B, #
2700B, # 2650, # 2600, # 2450B,
# 2400B, # 2350, # 2300, # 2200B
And in Cabot Special Black, MONARCH 1400; 1300; 1100;
1000: 900, VULCAN, XC72R, MOG
LL, REGAL 400R, REGAL 660
R, ELFTEX-8, BLACK PEARLS 1
400; 1300; 1100; 1000; 900, VU
LCAN XC72, BLACK PEARLS-L,
REGAL 400, REGAL 660 and the like. In addition, a combination of such carbon black particles and adjusted to desired pigment properties can also be used in the present invention.

In the present invention, it is desirable to use a carbon-based component whose surface is chemically activated. In general, carbon-based materials such as carbon black and graphite are constituted by carbon-carbon bonds, but active points such as carbon-oxygen, carbon-hydroxyl group, and carbon-carboxylic acid group as terminal groups on the material surface. It is known that there is. Therefore, the present inventors presumed that by increasing the number of active points, a hydroxyl group or the like existing on the surface of the iron oxide particles could be chemically bonded to the carbon-based material. Further, by increasing the number of active sites, the hydrophilicity of the carbon-based component is increased as described above, so that the carbon-based component is more firmly and uniformly attached to the iron oxide particles manufactured by a wet method in a dispersed state using water as a medium. It was presumed that it could be processed.

Further, the present inventors have found that the use of an alkali and / or an oxidizing agent as a method for chemically activating the surface of a carbon-based component improves the adhesion to iron oxide particles. Was found. This is a method of treating a carbon-based component with an alkali such as alkali hydroxide and ammonia, a method using an oxidizing agent such as dichromate, permanganate, hydrogen peroxide and benzoyl peroxide, and a combination thereof. It has been found that the method improves the adhesion between the iron oxide and the carbon-based component. Although it is not clear why the carbon-based component subjected to such a surface treatment can be attached to the surface of the iron oxide particles, the present inventors have found that the carbon-carbon bond is formed by an oxidizing agent or air. Oxidized by oxygen, an active site such as a carbon-hydroxyl group or a carbon-carboxylic acid group is generated, and a hydrogen atom of the above-mentioned hydroxyl group or carboxylic acid group is removed by alkali treatment, and the state of an alkoxide ion or a carboxylate anion Was added to the iron oxide slurry, and the carbon-based component adhered to the surface of the iron oxide particles via these anions and was neutralized, thereby stabilizing the surface of the iron oxide particles. It was presumed that binding could occur. By making such improvements,
Sufficient adhesion strength can be imparted to the carbon-based component without performing a treatment with organosilane or the like, which has a problem on the environment, as disclosed in JP-A-11-305480.

In addition, the iron oxide particles of the present invention are JIS K
It is desirable that the L value by a color difference meter by a method according to the pigment dispersion method described in 5101-1991 is 12 or less. In the evaluation method based on the L value, the lower the L value, the higher the blackness.
The following are preferable, and a more preferable L value is 11 or less,
More preferably, it is 10 or less.

The iron oxide particles of the present invention have a specific surface area of preferably 3 to 30 m ² / g, more preferably 5 to 30 m ² / g.
２５25 m ² / g. In addition, as for magnetic characteristics, when the external magnetic field is 796 kA / m, it is 70 Am ² / kg or more.
It is more preferably at least 75 Am ² / kg. Further, the pH of the powder is preferably 5 to 10. Further, the electric resistance value is preferably about the same as or lower than ordinary iron oxide particles, and more specifically, 1 × 10 ⁵ Ωcm or less,
Preferably 1 × 10 ⁴ Ωcm or less, more preferably 5 ×
It is 10 ³ Ωcm or less. This can prevent an adverse effect on an image due to excessive charging when the toner or carrier is formed using the iron oxide particles of the present invention. Also,
The oil absorption is also preferably low for dispersibility with the resin, and more specifically, 30 m for an octahedral magnetic material.
1/100 g or less, preferably 28 ml / 100 g or less, more preferably 25 ml / 100 g or less.
In the case of a spherical magnetic material, the volume is 20 ml / 100 g or less, preferably 18 ml / 100 g or less, and more preferably 16 ml / 100 g or less. Thereby, high dispersibility at the time of kneading to the resin can be ensured.

Furthermore, the present invention is an iron oxide powder containing the iron oxide particles in an amount of 1% by weight or more. The above-mentioned iron oxide particles may be appropriately mixed with iron oxide particles to which no carbon-based component is adhered, and may be used by adjusting the mixing ratio so as to have appropriate characteristics for various uses. The iron oxide powder obtained by the blending has a saturation magnetization value of 796 kA / m and a magnetic characteristic of 70 Am ² / kg or more, more preferably 75 Am ² / kg or more when the external magnetization is 796 kA / m. Further, the FeO content is at least 18% by weight, more preferably at least 20% by weight, based on the weight of iron oxide.

The iron oxide powder whose composition ratio has been adjusted as described above is suitable for use as a toner for electrostatic copying, a carrier for developing an electrostatic latent image, and a black pigment. For example, as an electrostatic copying toner, an iron oxide powder containing iron oxide particles to which the carbon-based component of the present invention is adhered, a thermoplastic binder resin, an additive such as a charge control agent, a wax, and a fluidity imparting agent In addition to the iron oxide powder containing iron oxide particles to which the carbon-based component is adhered, known materials and processing methods can be arbitrarily selected and used. As an example thereof, JP-A-11-194532 and the like can be mentioned.

In the method for producing the iron oxide particles of the present invention, it is an important requirement that the treatment is first performed by a wet method.
According to this method, the carbon-based component can be uniformly attached to the fine iron oxide particles. As in the prior art, when adhered by a dry method, particularly small carbon-based component particles have a strong cohesive force and enhance the dispersibility of these particles even with a strong disperser or pulverizer. It is difficult. Therefore, by dispersing by the wet method, it becomes possible to loosen the aggregated particles, and further, in a state where the iron oxide particles are sufficiently dispersed, the carbon-based component can be adhered, so that a uniform treatment is performed for the first time. The present inventors have found that this is possible. In the present invention, such manufacturing processes as uniform dispersion and adhesion by the wet method can be performed consistently, and continuous production is also possible. In the case of dispersing such particles, not only water but also a liquid at room temperature such as alcohol can be used. More preferably, a method using water capable of pH adjustment as a dispersion medium as described later is more uniform and cost-effective. Is preferred.

When the carbon-based component is adhered, it is preferable that the surface of the carbon-based component is previously subjected to an alkali treatment and / or an oxidation treatment to enhance the chemical activity in view of the uniform treatment and the adhesion strength of the particles. . It is not clear why such a pretreatment is effective, but this treatment increases the number of chemically active sites such as carboxyl groups and hydroxyl groups exposed on the surface of the carbonaceous component. It is presumed that the adsorption force on the surface of the iron oxide particles can be further increased.

As the treatment for increasing the activity of the surface of the carbon-based component, the oxidation treatment includes a gaseous oxidizing agent such as oxygen or ozone.
An inorganic oxidizing agent such as nitric acid, hydrogen peroxide, an aqueous solution of permanganate and an aqueous solution of dichromate, and an organic oxidizing agent such as benzoyl peroxide can be appropriately used. When treating a carbon-based component with such an oxidizing agent, it is preferable to adjust the treatment time, the treatment temperature, the concentration of the treatment liquid, and the like. For example, when nitric acid is used as the oxidizing agent, the concentration of the aqueous nitric acid solution is 0.1 mol / dm ³ or more, the processing temperature is 20 ° C. to 100 ° C., and the processing time is 5 minutes to 5 minutes.
It is preferable to perform the treatment by appropriately selecting about 12 hours.

In the case of performing the alkali treatment, it is more preferable to perform the treatment on the carbon-based component that has been subjected to such an oxidation treatment. In the case of performing the alkali treatment, a gas such as ammonia, an aqueous solution of an alkali hydroxide, an aqueous solution of an alkaline earth metal hydroxide, an aqueous solution of an alkali metal carbonate, an aqueous solution of an alkaline earth metal carbonate, or the like can be optionally used. As a preferable treatment method, it is preferable to appropriately select an alkali concentration, a treatment temperature, a treatment time and the like. For example, when treating with an aqueous solution of sodium hydroxide, the concentration is set to 0.1.
001 mol / dm ³ or more, processing temperature is 20 to 100
It is preferable to appropriately select from about 5 minutes to 12 hours as the processing temperature.

The carbon-based component treated as described above is added to the suspension of the iron oxide particles, and the pH is adjusted with an acid or an alkali to adhere the carbon-based component to the surface of the iron oxide particles. Can be. The range for adjusting the pH is preferably pH 5 to 12, more preferably 6 to 9, and furthermore pH
The rate of change is preferably adjusted at a slow rate of 5 minutes / pH, more preferably at least 10 minutes / pH,
The retention time at the target final pH is preferably 5 minutes or more. By this method, the carbon-based component can be uniformly attached to the surface of the iron oxide particles, the chemically active sites exposed on the surface of the carbon-based component can be stabilized, and the adhesion to the surface of the iron oxide particles can be further improved. Can be higher.

Further, the outermost surface of the iron oxide particles of the present invention may be treated with a fatty acid or a titanate-based and / or silane-based coupling agent, if necessary.

[0051]

EXAMPLES The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited to these examples.

[0052] [Preparation of magnetite slurry] Fe ²⁺
50 dm aqueous ferrous sulfate solution containing 2.0 mol / dm ^3
3, was mixed and stirred aqueous sodium hydroxide solution 50 dm ³ of 4.0 mol / dm ^3. The temperature of the ferrous hydroxide slurry thus obtained and the pH of the slurry were adjusted to 80 ° C and 6 ° C, respectively.
-9, air was blown while stirring was continued, the particle shape was spherical, the specific surface area by the BET method was 5.5 m ² / g,
Observation with a scanning electron microscope yielded a magnetite slurry (A) having an average Feret diameter of 100 particles of 0.23 μm.

[0053] was similarly mixed and stirred to respectively 50 dm ³ and 51Dm ³ to an aqueous solution of ferrous and aqueous sodium hydroxide sulfate. The temperature of the ferrous hydroxide slurry thus obtained was maintained at 80 ° C. and the pH of the slurry at 10, air was aerated while stirring was continued, and the particle shape was hexahedral, BET
The specific surface area by the method was 6.0 m ² / g, and the average of the Feret diameter of 100 particles was 0.2 when observed by a scanning electron microscope.
A magnetite slurry (B) having a size of 5 μm was obtained.

[0054] Furthermore, it was mixed and stirred so as to become an aqueous solution of ferrous and aqueous sodium hydroxide sulfate respectively 50 dm ³ and 52dm ^3. The temperature of the ferrous hydroxide slurry thus obtained was 80 ° C. and the pH of the slurry was 1
Maintained at 1.5, air was aerated while stirring was continued, the particle shape was octahedral, and the specific surface area by the BET method was 6.8 m ^2.
/ G, by observation with a scanning electron microscope, a magnetite slurry (C) having an average Feret diameter of 100 particles of 0.21 μm was obtained.

[Example of treatment of carbon black] Carbon black # 44 (hydrophilicity, particle size: 24, manufactured by Mitsubishi Chemical Corporation)
nm, specific surface area 110 m ^{2 /} g, pH 8.0) to 10 m
ol / dm ³ in an aqueous sodium hydroxide solution at 50 ° C.
After maintaining for 30 minutes, the surface treatment of the carbon-based component was performed to obtain a carbon black slurry (a).

The carbon black # 44 manufactured by Mitsubishi Chemical Corporation was dispersed in an aqueous nitric acid solution (concentration: 3 mol / dm ³ ), kept at 50 ° C. for 30 minutes, and then decanted with pure water to remove nitric acid. This was removed to obtain a carbon black slurry (b).

Further, the carbon black slurry (b) was maintained in a 10 mol / dm ³ aqueous solution of sodium hydroxide at 50 ° C. for 30 minutes to perform a surface treatment of the carbon component to obtain a carbon black slurry (c). Was.

Example 1 As shown in Table 1, a magnetite slurry (A) was added to a carbon black slurry (a).
Is 3.2 as carbon with respect to the total amount of magnetite particles.
% By weight. The temperature of the mixed slurry was adjusted to 50 ° C., the pH was adjusted to 6.5 with sulfuric acid while stirring, and this state was maintained for 30 minutes. The obtained mixed slurry was subjected to ordinary filtration, washing, drying, and pulverization to obtain a magnetite powder subjected to a carbon black treatment. The obtained magnetite powder was evaluated by the following method. Table 2 shows the obtained results. FIG. 1 shows an SEM photograph (× 40000) of this magnetite powder.

<Evaluation Method> (1) Specific Surface Area The specific surface area by nitrogen gas was measured using a 2200 type BET meter manufactured by Shimadzu-Micromeritech. (2) Magnetic properties Using a vibration type magnetometer VSM-P7 manufactured by Toei Kogyo, 79
Saturation magnetization (σs), remanence magnetization (σr) and coercive force (Hc) in an external magnetic field of 6 kA / m and 79.6 kA / m
Was measured. (3) pH Measured according to the method described in JIS K 5101-1991 26 (3.1). (4) Oil absorption The oil absorption was measured according to the method described in JIS K 5101-199121. (5) Electric Resistance 10 g of a sample was placed in a holder, and a pressure of 60 MP was applied to form a tablet having a diameter of 25 mm.
The measurement was performed under the pressure of P. The electrical resistance was determined from the thickness and cross-sectional area of the sample used for the measurement and the resistance. (6) Paint colorimetry It measured by the method based on JISK5101-1991. First, 10 g of magnetite powder and 60 g of a resin solution prepared by adjusting styrene-acrylic resin (TB-1000F, manufactured by Sanyo Chemical Co., Ltd.): Toluene = 1: 2 into a glass bottle having an inner volume of 120 ml, and 90 g of 1 mmφ glass beads were further added. Put in and disperse with paint shaker, then 4
It was applied to a mirror-coated paper using a mil applicator, dried, and then measured with the above color difference meter. (7) Desorption rate of carbon-based components 5 g of a sample was placed in 100 ml of pure water, and dispersed in an ultrasonic cleaning tank (Silent Sonic UC-602 type) manufactured by Sharp Corporation for 5 minutes. The resulting dispersion was allowed to stand for 3 minutes, the supernatant was immediately discarded, and the precipitated magnetite particles were collected by filtration and dried to obtain a sample after ultrasonic dispersion treatment. The carbon-based component content of the sample before and after the ultrasonic dispersion treatment was measured using a carbon in metal analyzer (EMIA-1) manufactured by Horiba, Ltd.
10), the combustion temperature is 1250 ° C, and JIS
Z-2615 (general rules for the method of determining carbon in metallic materials) 6.10
The carbon-based component desorption rate before and after ultrasonic dispersion was evaluated by the following equation. Carbon-based component desorption rate (%) = 100− [Carbon content (% by weight) of sample after ultrasonic treatment / carbon content (% by weight) of sample before ultrasonic treatment] × 100 carbon black slurry When dispersed by the present evaluation method using (a) to (c), carbon black particles did not precipitate even after being allowed to stand for 3 minutes. As a result, the carbon black particles desorbed by the ultrasonic dispersion do not precipitate. Therefore, by collecting the precipitated magnetite, it is possible to evaluate only the carbon-based component adhered and remaining on the surface of the magnetite particles.

[Evaluation of Tonerization] Using the magnetite powder subjected to the carbon black treatment obtained in Example 1, an electrophotographic toner was manufactured according to the following formulation. 100 parts by weight of magnetite powder of Example 1 100 parts by weight of styrene-acrylic thermoplastic resin (TB-1000F, manufactured by Sanyo Chemical Co., Ltd.) 1 part by weight of wax (Viscol 550P manufactured by Sanyo Chemicals, Inc.) 2 parts by weight of charge control agent (Orient Chemical Co., Ltd., Bontron S-34)

After mixing the above sample with a Henschel mixer, the mixture was melt-kneaded at 180 ° C. with a biaxial kneader. The obtained kneaded material was cooled to room temperature, coarsely pulverized with a bantam mill, finely pulverized with a jet mill, and averaged with a wind classifier (Turbo Classifier TC-15M, manufactured by Nisshin Engineering Co., Ltd.). A 7 μm powder was obtained.
To this powder was added 2% by weight of silica fine particles (R-972, manufactured by Nippon Aerosil Co., Ltd.) as a fluidizing agent to prepare a developing toner. Using an LBP printer (manufactured by Canon Co., Ltd., LBP-320), the obtained toner was changed to low-temperature and low-humidity (10 ° C., 20% RH), normal temperature and normal humidity (23 ° C., 55% RH), and high temperature. High humidity (35 ° C, 85%
RH), and the initial image density of the solid black portion and the image density after 1k printing were measured using a Macbeth densitometer (RD91).
Measured in 8). Table 3 shows the obtained results.

[Evaluation of Carrier Formation] Using the magnetite powder subjected to the carbon black treatment obtained in Example 1, the carrier for developing an electrostatic latent image was evaluated according to the following formulation. -100 parts by weight of the magnetite powder of Example 1-400 parts by weight of a styrene-acrylic thermoplastic resin (TB-1000F, manufactured by Sanyo Chemical Co., Ltd.)

After mixing the above materials with a Henschel mixer, melt kneading was performed at 200 ° C. with a biaxial kneader. The obtained kneaded material was cooled to room temperature, coarsely pulverized by a bantam mill, then finely pulverized by a jet mill, and averaged to 30 μm by an air classifier (Turbo Classifier TC-15M, manufactured by Nisshin Engineering Co., Ltd.). Was obtained. This powder was mixed with 10% by weight of the toner produced in the above-mentioned evaluation of toner formation to obtain a developer.
30 g of this developer was placed in a poly bottle, and the temperature was 23 ° C. and 55% R
The mixing was continued at a rotation of 120 rpm by a ball mill rotating device under the environment of H. Samples at the mixing time of 5 minutes and 4 hours were collected from the polybin, and the charge amount was measured by a blow-off method using a charge amount measurement device (TB-200, manufactured by Toshiba Chemical Co., Ltd.). In each of the samples, when the charge amount was 3 μC / g or less, it was judged that the stability was excellent.
In the case where the charge stability was exceeded, it was judged that there was no charge stability, and the charge stability was evaluated as x. Table 3 shows the obtained results.

[Evaluation of Pigment] Using the magnetite powder subjected to the carbon black treatment obtained in Example 1, a black pigment was evaluated according to the following formulation. 20 g of titanium oxide powder for white pigment (R-820, manufactured by Ishihara Sangyo Co., Ltd.)
0.8g of magnetite powder, steel ball (6mm
φ) 100g into a glass pot and shaker (5
After mixing at 00 rpm for 5 minutes, the mixed powder was formed into pellets, and the color was measured using a color difference meter (manufactured by Tokyo Denshoku Co., Ltd., color analyzer TC-1800). Table 3 shows the obtained results.

Examples 2 to 8 As shown in Table 1, various types of carbon black treatment were performed by changing the type of magnetite, the type and amount of treated carbon black, and the final pH as a treatment condition. To give a magnetite powder. This magnetite powder was evaluated according to Example 1, and the obtained results are shown in Tables 2 and 3. 2 and 3 show SEM photographs (× 40000) of the magnetite powders of Examples 2 and 3, respectively.

[Comparative Examples 1 and 2] As shown in Table 1, the magnetite slurries (A) and (C) were subjected to ordinary filtration, washing, drying, and pulverization. Evaluation was performed according to Example 1, and the obtained results are shown in Tables 2 and 3.

[Comparative Examples 3 and 4] # 44 was dispersed in pure water as a carbon black powder, and added to the magnetite slurry (A) or (B) to adjust the pH of the mixed slurry to 8.5. Filtration, washing, drying, and pulverization were performed according to Example 1. The obtained magnetic material was evaluated according to Example 1, and the obtained results are shown in Tables 2 and 3.

Comparative Example 5 As shown in Table 1, a magnetite powder treated with carbon black was obtained in the same manner as in Example 4 except that the final pH at the time of carbon black treatment was changed to 3. This magnetite powder was evaluated according to Example 1, and the obtained results are shown in Tables 2 and 3.

Comparative Example 6 Using # 44 as the carbon black particles as they were, they were mixed and consolidated in a dry process to physically attach the carbon black particles. Specifically, the magnetite slurry (A) is subjected to ordinary filtration, washing, drying, and pulverization, and the obtained magnetite powder and carbon black powder are weighed, and a Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.) is used. After mixing for 30 minutes by using a sand mill (MPUV-2, manufactured by Yodo Casting Co., Ltd.), the throughput is 6 kg at a processing rate of 10 kg / batch, a linear pressure of 80 kg / cm, and a rotation speed of 8.5 rpm.
The treatment was performed for 0 minutes. The obtained magnetite powder was evaluated according to Example 1, and the obtained results were shown in Tables 2 and 3.
Shown in In addition, an SEM photograph of this magnetite powder (×
1000) is shown in FIG.

[0070]

[Table 1]

[0071]

[Table 2]

[0072]

[Table 3]

As is clear from Table 2, the Example has a lower desorption rate of the carbon-based component and a higher adhesion strength between the carbon black particles and the magnetite particles than the Comparative Example. In addition, even when the same amount of carbon black particles were adhered, in the case of Examples 2 and 6 in which the carbon black particles were subjected to the oxidation treatment and the alkali treatment, in Examples 1 and 4 in which only the alkali treatment was performed. It can be seen that the desorption rate of this carbon-based component is lower than in such a case. In addition, the magnetite particles subjected to such treatment showed a tendency to decrease in oil absorption and electric resistance, which is presumed to be because carbon black particles were uniformly contained in the gaps between the magnetite particles. did. On the other hand, Comparative Examples 3 to 6
It can be seen that the desorption rate of the carbon-based component is high, and in particular, dry physical treatment alone cannot provide sufficient adhesion strength of the carbon-based component. In the dry physical treatment, it was presumed that a phenomenon in which the electrical resistance was increased was observed because the magnetite particles were subjected to surface oxidation and the carbon black particles having low electrical resistance could not be uniformly surface-treated. In Comparative Examples 3 and 4, carbon black particles whose surfaces were not chemically treated were used, so that sufficient adhesion to the surface of the iron oxide particles could not be obtained, so that the desorption rate was somewhat high. Met.

Further, as is clear from Table 3, the examples have higher image density stability in toner evaluation and a sufficient blackness as compared with the comparative examples. It is presumed that the uniformity of the charging property and the electric resistance was sufficiently achieved because the carbon black particles were uniformly attached to the surface of the magnetite particles. On the other hand, in the comparative example, it was difficult to obtain a sufficient image density with the carbon black untreated product, and the decrease in image density particularly under high temperature and high humidity was conspicuous.

In addition, the carrier stability in the evaluation of carrier formation was high in the examples, but the carrier particles having high stability were obtained. In Comparative Examples 3 to 6, especially in Comparative Example 6 in which the adhesion strength of the carbon black particles was low, the chargeability was high. The stability was low.

Regarding these evaluation results, the present inventors have found that when carbon black particles are subjected to hot melt kneading with a binder component such as a resin, the carbon black particles are separated from the magnetite particle surface, It is presumed that this phenomenon occurred due to agglomeration between magnetite particles and lack of uniformity as a powder.

In the pigment evaluation, the carbon black particles are subjected to an oxidation treatment and an alkali treatment in advance,
It can be seen that the blackness is further improved. This is presumably because the uniform treatment of carbon black particles has been improved by this chemical pretreatment. On the other hand, especially in the case of Comparative Example 6 in which the physical treatment was performed, the dispersibility of the consolidation treatment was not sufficient, and the carbon black treatment could not be further uniformly performed. Therefore, the undispersed portion of the magnetite particles could be visually confirmed. , A high blackness as a pigment could not be obtained.

When observed with a SEM at a magnification of 40,000, carbon black particles did not adhere to the surface of most of the magnetite particles, and when observed at a magnification of 1,000, undispersed carbon black particles became island-like as shown in FIG. It turned out to be scattered.

[0079]

As described above, the iron oxide particles of the present invention have a high blackness and excellent dispersibility because they can be more firmly and uniformly adhered in a wet process by a carbon-based component having a surface activated in advance. It is suitable for applications such as material powder for magnetic toner for electrostatic copying, carrier powder for electrostatic latent image development, and black pigment powder for paint.

[Brief description of the drawings]

FIG. 1 is a SEM photograph (× 40000) of the magnetite powder obtained in Example 1.

FIG. 2 is an SEM photograph (× 40000) of the magnetite powder obtained in Example 2.

FIG. 3 is an SEM photograph (× 40000) of the magnetite powder obtained in Example 3.

FIG. 4 is an SEM photograph (× 1000) of the magnetite powder obtained in Comparative Example 6.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 9/09 G03G 9/08 361 9/107 9/10 311 F term (Reference) 2H005 AA02 AB02 BA02 CA21 CB03 CB18 DA04 EA05 EA07 EA10 4G002 AA04 AA12 AB02 AE01 AE03 4J037 AA15 CA02 DD05 DD07 DD17 EE02 EE28 EE43 FF05

Claims (8)

[Claims] 1. An average particle diameter of 0.05 to 1 μm, wherein a carbon-based component is attached to the particle surface in an amount of 0.1 to 30% by weight based on the total amount of iron oxide particles in terms of carbon atoms, and Iron oxide particles characterized by having a carbon-based component desorption rate of 15% or less when water is used as a dispersion medium. 2. The carbon-based component having an average particle size of 1 to 10
The iron oxide particles according to claim 1, which are surface-activated carbon black particles having a thickness of 0 nm. 3. The iron oxide particles according to claim 1, wherein the L value measured by a color difference meter based on the coloring power measurement method described in JIS K 5101-1991 is 12 or less. 4. The iron oxide particles according to claim 1, wherein
Iron oxide powder, characterized in that it contains at least% by weight. 5. An electrostatic copying toner containing the iron oxide powder according to claim 4. 6. A carrier for developing an electrostatic latent image, comprising the iron oxide powder according to claim 4. 7. A black pigment containing the iron oxide powder according to claim 4. 8. The surface of particles containing a carbon-based component is previously surface-activated by alkali treatment and / or oxidation treatment, and then added to an aqueous suspension of iron oxide particles, and the pH is adjusted using an acid or alkali. A method for producing iron oxide particles, wherein particles containing a carbon-based component are attached to the surface of iron oxide particles by adjusting the particle size to 5 to 12.