JP3405383B2 - Electrophotographic developer carrier and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier for electrophotographic development which has stable triboelectric charging properties and excellent durability, and a method for producing the same.

[0002]

2. Description of the Related Art Selenium and OPC are used in electrophotography.
A photoconductive substance such as (organic semiconductor) or α-Si is used as a photoconductor, an electrostatic latent image is formed by various means, and a magnetic brush developing method or the like is used for this latent image to determine the polarity of the latent image. On the other hand, a method is generally adopted in which charged toner is attached by electrostatic force to visualize the toner.

As is well known, carrier particles called carriers are used in this developing process, and a proper amount of positive or negative electricity is imparted to the toner by frictional charging, and a magnet is incorporated by utilizing magnetic force. The toner is conveyed to the developing area near the surface of the photoreceptor on which the latent image is formed, via the developing sleeve.

In recent years, the electrophotographic method has been widely used in copiers and printers, and it is required to be able to handle various documents such as thin lines, small letters, photographs and color originals. Further, with the increase in speed and continuity, durability as a developer is also required, and it is considered that these demands will be further increased in the future.

Further, as is well known, the developer is required to have durability such that the chargeability of the toner and carrier does not change during use. For example, the toner is strongly adhered to the surface of carrier particles. There is a phenomenon that the chargeability of the original carrier is lost (so-called toner spent) or the coating resin layer on the surface of the carrier particles peels off with time, and as a result, the toner cannot be appropriately charged. It is a problem.

As a measure against the former, a means of coating the surface of the carrier particles with a fluororesin or silicone resin having a low surface energy is adopted, but as a measure against the latter, such a measure is not taken at present. Is.

In particular, carriers such as ferrite and iron powder are
The adhesiveness between the particle surface and the coating resin is not so good, the coating resin is gradually peeled off during use, the chargeability is changed, and as a result, problems such as image disturbance and carrier adhesion are caused.

On the other hand, a so-called binder type carrier in which magnetic powder is dispersed in a resin has been developed in order to solve these problems, but the content of the magnetic powder cannot be increased or the resin is limited. There is a problem such as.

The inventors of the present invention have disclosed in Japanese Patent Laid-Open No. 3-220068.
JP-A-4-100850, JP-A-4-86749
Japanese Patent Application Laid-Open No. 5-237369 and Japanese Patent Application Laid-Open No. 5-237369 disclose inventions aimed at solving the above problems.

The composite particles composed of the magnetic powder and the phenol resin in the inventions described in the above publications have several times better adhesiveness to the coating resin than the above-mentioned ferrite or iron powder, so that they are coated during use. Although the problem of resin peeling hardly occurs, there is a possibility that problems may occur when used in high-speed machines, and there is a demand for a binder-type carrier having better adhesiveness.

At present, as the developer, a two-component type developer comprising a toner and a carrier having different charge polarities is used, but recently, a negatively chargeable toner and a positively chargeable carrier are used in combination. Two-component developers have come into use. Although coating with a resin or the like has been performed in order to impart a positive charging property to the carrier, it cannot be said to be sufficient. Therefore, in order to enhance the negative chargeability of the toner, the carrier is required to have higher positive chargeability.

Further, the carrier has been required to have a certain level of electrical resistivity, specifically 10 ⁹
An electric resistance value of about 10 ¹⁴ Ωcm is required. That is, when the electric resistance value is as low as 10 ⁶ Ωcm like the iron powder carrier, the carrier is attached to the image portion of the photoconductor by the charge injection from the sleeve, or the latent image charge escapes through the carrier, and There are problems such as image distortion and image loss. On the other hand, if the insulating resin is thickly coated, the electric resistance value becomes too high, the carrier charges are less likely to leak, and the charge amount of the toner also becomes higher, resulting in an edged image. On the other hand, on a large-area image surface, the image density in the central portion becomes very low. Therefore, a moderately high electric resistance 10 ⁹ to 1
A carrier having 0 ¹⁴ Ωcm is desired.

Therefore, the carrier for the electrophotographic developer is
It can be said that it is required that there is no change in the physical properties of the carrier particle surface, such as peeling of the coating resin layer, that the particle size can be controlled, and that the specific gravity is appropriate.

Several attempts have heretofore been made with respect to carriers for electrophotographic developers, which are composed of a composite particle powder composed of a phenol resin and iron oxide particle powder. For example, composite particle powder composed of ferromagnetic fine particle powder and hardened phenol resin (Japanese Patent Laid-Open No. 2-220068),
There is a composite particle powder (JP-A-3-192268) in which the particle surface of a composite core particle composed of a ferromagnetic fine particle powder and a hardened phenol resin is coated with a melamine resin.

[0015]

A spherical composite particle powder having a high electric resistance value and a positive charging property and excellent in peeling durability of a coating resin is currently most demanded. It cannot be said that the composite particle powder described in each publication sufficiently satisfies these various characteristics.

That is, since the composite particle powder described in JP-A-2-220068 does not have a resin coating layer containing an amino group, sufficient electric resistance and positive chargeability cannot be obtained.

Since the composite particle powder described in JP-A-3-192268 has a melamine resin coating containing an amino group, it can form an electric resistance value and a positive chargeability to some extent, but constitutes a composite core particle. Since the phenol resin and the melamine resin forming the coating layer on the particle surface of the core particles are different, the adhesion of the resin is weak and the peeling durability of the coating resin is poor.

Therefore, the present invention is to provide a carrier for an electrophotographic developer comprising a spherical composite particle powder having a high electric resistance value and a positive charging property and excellent in peeling durability of a coating resin. Subject.

[0019]

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

That is, the present invention has an average particle size of 1 to 1000.
A carrier for an electrophotographic developer composed of spherical composite particles of [mu] m, the core particles spherical composite particle, the particle surface of the spherical composite core particles consisting of a phenolic resin and cured with iron oxide particles It has a coating layer consisting of a phenol resin containing a cured amino group that is continuous with the resin inside and the content of iron oxide particles is 80 to 99% by weight.
The carrier for electrophotographic developer, iron oxide particle powder, and phenol, wherein the content of the amino group in the coating layer is 70 to 1500 mg / kg of the spherical composite particles in terms of nitrogen atoms. And aldehydes are reacted in an aqueous medium in the presence of a basic catalyst to produce spherical composite core particles composed of iron oxide particle powder and a cured phenolic resin, and further, the spherical composite core particles and By adding a basic catalyst containing an amino group to an aqueous medium containing the remaining unreacted phenols to react the unreacted phenols, the spherical composite core particles containing an amino group on the particle surface. A method for producing a carrier for an electrophotographic developer, which comprises obtaining a spherical composite particle powder coated with a phenol resin.

The present invention will be described in detail below. First, the spherical composite particle powder according to the present invention will be described.

The spherical composite particle powder according to the present invention has an average particle size of 1 to 1000 μm, preferably 10 to 200 μm.
m. If the average particle size is less than 1 μm, secondary agglomeration tends to occur, and if it exceeds 1000 μm, the mechanical strength is weak and a clear image cannot be obtained. The shape of each composite particle constituting the composite particle powder according to the present invention is spherical.

Each spherical composite particle constituting the spherical composite particle powder according to the present invention comprises a spherical composite core particle portion composed of iron oxide particle powder and a hardened phenol resin, and a hardened amino group on the surface of the particle. And a coating layer portion made of a phenol resin containing a large amount of. The weight ratio of the spherical composite core particle portion to the coating layer portion is 1000: 1 to 5
It is 0: 1, preferably 1000: 5 to 50: 1. The content of iron oxide particles in the spherical composite particles is 80 to 99.
% By weight. If it is less than 80% by weight, sufficient specific gravity cannot be obtained. If it exceeds 99% by weight, the resin content is insufficient and sufficient strength cannot be obtained.

The content of the amino group in the coating layer portion is 70 to 70 in terms of nitrogen atom based on the spherical composite particles.
1500 mg / kg, preferably 80-1200 mg / kg
It is kg. When it is less than 70 mg / kg, the positive charging property is not sufficient. When it exceeds 1500 mg / kg, the hygroscopicity of the spherical composite particle powder becomes high, and for example,
This may cause a problem in environmental stability of charging.

The spherical composite particle powder according to the present invention preferably has a bulk density of 2.5 g / cm ³ or less. It is more preferably 2.0 g / cm ³ or less. The specific gravity is 2.5 to 5.2, preferably 2.5 to 4.5.

The spherical composite particle powder according to the present invention has an electric resistance of 10 ⁹ to 10 ¹⁴ Ωcm, preferably 10 ¹⁰ to ¹⁰ 10.
It is ¹⁴ Ωcm.

The spherical composite particle powder according to the present invention is excellent in positive charging property. Specifically, it is as described in the embodiments and examples of the present invention described later.

The spherical composite particle powder according to the present invention has good peeling durability of the coating layer on the particle surface. That is,
The electrification amount and the electric resistance value do not change by the forced durability test described later. Specifically, the rate of change (ΔR / R) in electric resistance value is −10 to + 10%, preferably −
It is 5 to + 5%. Change rate (ΔQ / Q) of charge amount is -1
It is 0 to + 10%, preferably -5 to + 5%.

Next, a method for producing the spherical composite particle powder according to the present invention will be described.

The phenols used in the present invention include, in addition to phenol, alkylphenols such as m-cresol, p-tert-butylphenol, o-propylphenol, resorcinol and bisphenol A, and a part of the benzene nucleus or alkyl group or Examples thereof include compounds having a phenolic hydroxyl group such as halogenated phenols, all of which are substituted with chlorine atoms or bromine atoms, and among these, phenol is most preferable. When a compound other than phenol is used as the phenol, particles may be difficult to form, or even if particles are formed, the particles may have an irregular shape. Therefore, phenol is most preferable in consideration of the shape property.

Examples of the aldehydes used in the present invention include formaldehyde and furfural in the form of either formalin or paraaldehyde, and formaldehyde is particularly preferable.

The molar ratio of aldehydes to phenols is preferably 1 to 4, particularly preferably 1.2 to 3. The molar ratio of aldehydes to phenols is 1
If it is smaller, the particles are less likely to be formed, or even if they are produced, the curing of the resin is less likely to proceed, so that the strength of the produced particles tends to be weak. On the other hand, the molar ratio of aldehydes to phenols is 4 If it is larger than this, unreacted aldehydes remaining in the aqueous medium after the reaction tends to increase.

As the basic catalyst used in the present invention, a basic catalyst used in ordinary resol resin production can be used. Examples thereof include aqueous ammonia, hexamethylenetetramine, and alkylamines such as dimethylamine, diethyltriamine, and polyethyleneimine. The molar ratio of these basic catalysts to phenols is 0.02 to
0.3 is preferable. When it is less than 0.02, curing does not proceed sufficiently and granulation is not performed. If it exceeds 0.3, the structure of the phenol resin is affected and the granulation property deteriorates, making it difficult to obtain a large particle size.

The iron oxide powder particles used in the present invention include:
Magnetic iron oxide particle powder such as magnetite and maghemite,
Spinel ferrite particle powder containing one or more kinds of metals other than iron (Mn, Ni, Zn, Mg, Cu, etc.),
Magnetoplumbite-type ferrite particle powder such as barium ferrite, fine particle powder of iron having an oxide layer on its surface and its alloy, and the like can be used. In addition, non-magnetic iron oxide particles such as hematite, goethite, wustite and the like can be used, and in some cases, they can be used as a mixture with the magnetic iron oxide particles. Preferred are magnetic iron oxide particles such as magnetite and maghemite, and non-magnetic iron oxide particles such as hematite and goethite. More preferred are magnetic iron oxide particles such as magnetite and maghemite. The shape of the particles may be any of granular, spherical and acicular.

The iron oxide particles have a particle size of 0.1 to
10 μm is desirable, and considering the dispersion of fine particles in an aqueous medium and the strength of the resulting composite particles,
It is preferably 0.05 to 5 μm.

The iron oxide particle powder used in the present invention is preferably lipophilicized in advance, and when iron oxide particle powder that is not lipophilicized is used, a spherical composite is used. It may be difficult to obtain.

The lipophilic treatment is carried out by treating the iron oxide particle powder with a coupling agent such as a silane coupling agent or a titanate coupling agent, or by dispersing the iron oxide particle powder in an aqueous solvent containing a surfactant. Then, there is a method of adsorbing a surfactant on the particle surface.

The silane coupling agents include those having a hydrophobic group, an amino group and an epoxy group, and the silane coupling agents having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane and vinyl.
Examples include tris (β-methoxy) silane.

As the silane coupling agent having an amino group, γ-aminopropyltriethoxysilane, N-
There are β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and the like.

As the silane coupling agent having an epoxy group, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, etc. There is.

Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, and the like.

As the surfactant, commercially available surfactants can be used, and those having a functional group capable of binding to the iron oxide particles and the hydroxyl groups on the particle surface are desirable,
Speaking of ionicity, cationic or anionic one is preferable.

The object of the present invention can be achieved by any of the above-mentioned treatment methods, but treatment with a silane coupling agent having an amino group or an epoxy group is preferable in consideration of the adhesiveness with a phenol resin.

When the above-mentioned phenols and aldehydes are reacted in the presence of a basic catalyst, the amount of iron oxide particle powder coexisted is 75 to 99% by weight with respect to the total amount of iron oxide particle powder, phenols and aldehydes. %, Preferably 78 to 99% by weight, and more preferably 80 to 99% by weight in consideration of the strength of the composite particles produced.

The reaction in the present invention is carried out in an aqueous medium, and it is preferable that the solid content concentration in the aqueous medium is 30 to 95% by weight, particularly 60 to 90% by weight. Preferably.

In the reaction for producing the spherical composite core particles, phenols, aldehydes, water and iron oxide particle powder are charged into a reaction vessel, and after sufficiently stirring, a basic catalyst is added and the temperature is raised with stirring. , The reaction temperature is 70 to 90 ° C., preferably 8
The temperature is adjusted to 3 to 87 ° C. to cause curing of the phenol resin. At this time, in order to obtain spherical composite core particles having a high sphericity, it is desirable to raise the temperature gently. The rate of temperature increase is preferably 0.5 to 1.5 ° C / min, more preferably 0.8 to 1.2 ° C / min.

After curing as described above, the reaction mass was heated to 40 ° C.
When cooled below, an aqueous dispersion containing spherical composite core particles in which iron oxide particle powder is uniformly dispersed in a cured phenol resin matrix is obtained.

Next, the reaction for forming a coating layer made of a phenol resin containing a hardened amino group on the surface of the spherical composite core particles is carried out by newly adding amino to the aqueous dispersion containing the spherical composite core particles. A basic catalyst having a group and water are added and the temperature is raised to adjust the reaction temperature to 70 to 90 ° C., preferably 83 to 87 ° C. to react unreacted phenols remaining in the aqueous medium. The spherical composite core particles are cured and adsorbed on the surface of the particles. To the unreacted phenols remaining in the aqueous medium after the formation of the spherical composite core particles, by adding a predetermined amount of a basic catalyst having an amino group in excess of the usual amount, the basic catalyst is added to the phenol resin. A large amount of amino groups are taken in, and a coating layer made of a phenol resin containing a large amount of amino groups can be formed. In order to obtain spherical composite particles with high sphericity,
It is desirable to raise the temperature gently. The rate of temperature increase is preferably 0.5 to 1.5 ° C / min, more preferably 0.8 to 1.2 ° C / min.

The aqueous dispersion containing the spherical composite particles is separated by filtration and centrifugal separation to obtain a solid-liquid solution, which is then washed and dried to obtain a composite in which iron oxide particle powder is uniformly dispersed in the phenol resin matrix. A spherical composite particle powder having a coating layer composed of a phenol resin containing an amino group on the particle surface of the body core particle is obtained.

As the basic catalyst having an amino group used in the reaction for forming the coating layer composed of the phenol resin having an amino group, among the basic catalysts used in the usual production of resole resins, one having an amino group is used. Can be used. Examples thereof include aqueous ammonia, hexamethylenetetramine, and alkylamines such as dimethylamine, diethyltriamine, and polyethyleneimine. The amount of the basic catalyst having an amino group used in this case is preferably 0.03 to 0.5, more preferably 0.04 to 0.5 in terms of the molar ratio to the phenol added first in the reaction for forming the composite core particles. It is 0.5. When it is less than 0.03, the coating layer is not sufficiently formed, and moreover, the phenol resin cannot contain sufficient amino groups. 0.5
If it exceeds, it is impossible to form a uniform coating layer on the surface of the particles.

The amount of water added together with the basic catalyst is preferably such that the solid content concentration in the aqueous medium after addition of water is 30.
˜80% by weight, more preferably 60 to 90% by weight.

As described above, once the reaction temperature is 40 ° C.
It is also possible to add water and the basic catalyst directly without cooling below. Furthermore, in addition to the basic catalyst, a phenol resin component such as phenols and aldehydes may be added and reacted.

In any of the above reactions, spherical particles are easily produced by using a hydrophilic organic compound such as carboxymethyl cellulose or polyvinyl alcohol or a fluorine compound such as calcium fluoride as the suspension stabilizer.

In the production method of the present invention, the unreacted phenols and aldehydes remaining in the wastewater are greatly reduced, so that the COD (chemical oxygen demand) value in the wastewater is also low and the wastewater treatment cost is reduced. It can be significantly reduced.

[0055]

The composite particle powder composed of the ferromagnetic fine particle powder and the hardened phenol resin described in the above-mentioned JP-A-2-220068 does not have a coating layer composed of the phenol resin, and therefore has sufficient electric resistance and positive charging property. Was not obtained, and moreover, a considerable amount of unreacted phenols remained in the aqueous medium after the formation of the composite particles, and there was a problem that the COD value in the waste water became high.

Further, the composite particle powder described in JP-A-3-192268, in which a coating layer made of a melamine resin is formed on the particle surface of a composite core particle made of a ferromagnetic fine particle powder and a hardened phenol resin, Sufficient positive charge,
Although the electric resistance value was obtained, the resin constituting the core particles and the resin constituting the coating layer were different, and therefore the adhesion of the resin was insufficient and the peeling durability was insufficient.

Therefore, the coating layer is formed of the same resin, that is, a phenol resin, and in the coating method, the core particles are taken out after the core particles are formed and before the coating layer is formed in the conventional method. By drying the particle surface of the core particles, the coating layer formed thereafter becomes discontinuous, and the peeling durability is not sufficient even if the resin of the core particles and the resin of the coating layer are the same. The method of continuously forming the coating layer was investigated. As described above, since a considerable amount of unreacted phenols and aldehydes remain in the aqueous medium after the core particles are prepared, it is possible to form a coating layer made of a phenol resin by adding a basic catalyst. The inventor found out.

According to the production method of the present invention, the phenol resin of the coating layer contains more amino groups than usual, so that the positive charging property is good, the electric resistance value is high, and the core particles and the coating layer are coated. Since the layer and the resin constituting the layer are continuous, the peeling durability of the coating resin is improved even against stress in the developing machine, and a spherical composite particle powder showing stable chargeability over time is obtained. To be

The carrier for an electrophotographic developer according to the present invention has good miscibility with a toner, and as a result can accelerate the charging speed of the toner, and on the other hand, has a specific gravity that does not damage the toner. By this, it is possible to suppress spent formation.

[0060]

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

The average particle size in the embodiments of the present invention, the examples described later and the comparative examples is shown by a value measured by a laser diffraction type particle size distribution meter (manufactured by Horiba Ltd.),
The particle morphology of the particles was observed with a scanning electron microscope (S-800, manufactured by Hitachi, Ltd.).

The nitrogen atomic weight is measured by the Kjeldahl method (JI
SK0102) and analyzed and quantified.

The saturation magnetization is measured by a vibrating sample magnetometer VSM-3.
External magnetic field of 10k using S-15 (manufactured by Toei Industry Co., Ltd.)
It is shown by the value measured under Oe.

The true specific gravity is shown by a value measured by a multi-volume densitometer (manufactured by Micromeritics).

The electric resistance value (volume specific resistance value) is shown by a value measured by a high resistance meter 4329A (manufactured by Yokogawa Hewlett Packard).

The toner charge amount is 95% of this composite particle powder.
5 parts by weight of a commercially available toner CLC-200 black were thoroughly mixed and measured with a blow-off charge amount measuring device TB-200 (manufactured by Toshiba Chemical Co.).

The peeling durability of the coating resin was examined by the following forced durability test. 50 g of composite particle powder 100
It is put in a cc glass sample bottle, covered with a lid, and then shaken for 10 hours in a paint conditioner (RED DEVIL). For each sample before and after shaking, the rate of change of the charge amount Q and the volume specific resistance value R (Δ
The peeling durability of the coating resin was estimated by the size of (R / R, ΔQ / Q). Here, the larger the rate of change, the more the coating resin was peeled off.

The chemical oxygen demand (COD value) can be measured by
Performed in accordance with JIS K0102.17, product 1 kg
Value in the total amount of wastewater at the end of the manufacturing process (mg / k
It was evaluated as g).

Average particle size of 0.2 in a Henschel mixer
After charging 400 g of spherical magnetite particle powder of 4 μm and stirring well, a silane coupling agent (KBM
-403; Shin-Etsu Chemical Co., Ltd.) 2.0 g was added to about 1
By raising the temperature to 00 ° C. and thoroughly mixing and stirring for 30 minutes, iron oxide particle powder consisting of magnetite particles coated with a coupling agent was obtained.

Separately, in a 1-liter four-necked flask, 50 g of phenol, 70 g of 37% formalin, 400 g of iron oxide particle powder subjected to lipophilic treatment, 10 g of 28% ammonia water,
While stirring 50 g of water, the temperature was raised to 85 ° C. over 40 minutes,
The mixture was reacted and cured at the same temperature for 180 minutes to generate composite core particles composed of iron oxide particle powder and cured phenol resin.

Next, the content in the flask was cooled to 50 ° C., 8 g of 28% ammonia water and 50 g of water were added,
The temperature was raised to 85 ° C. for 30 minutes and the reaction was carried out at the same temperature for 60 minutes to obtain composite particles in which the particle surface of the composite core particles was coated with a phenol resin having many amino groups. Thirty
After cooling to ° C, the supernatant was removed, and the lower layer precipitate was washed with water and air-dried.

The CO of the wastewater at the end of this process
D (chemical oxygen demand) value is 1k of spherical composite particle powder
It was 2869 mg / kg with respect to g, which was a lower value than the COD value of the waste water at the end of the process shown in Comparative Example 1 below.

Then, this is depressurized (5 mmHg or less).
Then, it was dried at 150 to 160 ° C. to obtain a spherical composite particle powder.

The obtained spherical composite particle powder had an average particle diameter of 33 μm, and had a spherical shape close to a true sphere, as shown in the scanning electron micrograph (× 2000) of FIG. The coating resin layer of the phenol resin was continuous and uniform with the resin in the core particles from the scanning electron micrograph (× 15000) of the particle cross section of FIG.

The spherical composite particle powder as a carrier for an electrophotographic developer has excellent durability and stable triboelectrification. That is, the specific gravity is 3.56, the volume resistivity value is 2.0 × 10 ¹² Ωcm, and the toner charge amount is −3.
7 μC / g, the amino group content in the coating resin layer is 160 mg / kg in terms of nitrogen atoms. Further, the peeling durability of the coating resin layer is such that the change rate (ΔR / R) of the volume resistivity value is 0.
%, The rate of change in charge amount (ΔQ / Q) is 0%, which is excellent in peeling durability of the coating resin layer.

[0076]

EXAMPLES Next, examples and comparative examples will be given.

Examples 1 to 3 and Comparative Examples 1 to 4; Examples 1 to 3 In the production reaction of the composite core particles, the type and amount of iron oxide particle powder, the type and amount of lipophilic treatment agent, and phenols. , The amount of aldehydes, the amount of basic catalyst and the amount of water,
Spherical composite particle powder was obtained in the same manner as in the embodiment of the present invention, except that the type and amount of the basic catalyst containing an amino group added in forming the coating layer were changed. The production conditions at this time are shown in Table 1, and various properties of the obtained spherical composite particle powder are shown in Table 2.

Comparative Example 1 Up to formation of spherical composite core particles was carried out in the same manner as in the embodiment of the present invention, and the subsequent formation reaction of the coating layer was not carried out.
After cooling to 0 ° C., the supernatant was removed, and the lower layer precipitate was washed with water and air-dried.

Then, this is depressurized (5 mmHg or less).
Then, it was dried at 150 to 160 ° C. to obtain a spherical composite particle powder. The COD value of the wastewater at the end of this process is
6400 mg / kg for 1 kg of spherical composite particle powder
Met. Table 2 shows various properties of the obtained spherical composite particle powder.

Comparative Examples 2 to 4 In the formation reaction of the composite core particles, the type and amount of the iron oxide particle powder, the type and amount of the lipophilic treatment agent, the amount of phenols, the amount of aldehydes and the basic catalyst were used. The composite core particles were produced in the same manner as in the embodiment of the present invention except that the amount and the amount of water were variously changed, the subsequent formation reaction of the coating layer was not performed, and the supernatant liquid was cooled to 30 ° C. Was removed, and the precipitate in the lower layer was washed with water and air dried.

Then, this is depressurized (5 mmHg or less).
Then, it was dried at 150 to 160 ° C. to obtain a spherical composite particle powder. The production conditions at this time are shown in Table 1, and various properties of the obtained spherical composite particle powder are shown in Table 2.

[0082]

[Table 1]

[0083]

[Table 2]

[0084]

EFFECTS OF THE INVENTION The spherical composite particle powder according to the present invention has a high electric resistance value and a positive charging property, and since it is excellent in peeling durability of the coating resin, it has excellent durability and stable triboelectric charging. Since it has the property, it is suitable as a carrier for an electrophotographic developer. Further, in the production method according to the present invention, residual unreacted phenols and aldehydes are reduced, so that COD in wastewater can be reduced.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph (× 200) showing a particle structure of a spherical composite particle powder according to an embodiment of the present invention.
0)

FIG. 2 is a scanning electron micrograph (× 15) showing a particle cross-sectional structure of the spherical composite particle powder according to the embodiment of the present invention.
000)

Claims (2)

(57) [Claims] 1. A carrier for an electrophotographic developer comprising a spherical composite particle powder having an average particle diameter of 1 to 1000 μm, the spherical composite particle comprising a spherical oxide particle powder and a cured phenol resin. On the surface of the composite core particles
It has a coating layer consisting of a phenol resin containing a cured amino group that is continuous with the resin in the core particles, and the content of the iron oxide particle powder is 80 to 99% by weight. A carrier for an electrophotographic developer, which has a group content of 70 to 1500 mg / kg based on the spherical composite particles in terms of nitrogen atoms. 2. Iron oxide particle powder, phenols and aldehydes are reacted in an aqueous medium in the presence of a basic catalyst to form spherical composite core particles composed of iron oxide particle powder and a hardened phenol resin. Further, by adding a basic catalyst containing an amino group to an aqueous medium containing the spherical composite core particles and remaining unreacted phenols to react the unreacted phenols, the spherical composite A method for producing a carrier for an electrophotographic developer, which comprises obtaining a spherical composite particle powder in which a particle surface of a core particle is coated with a phenol resin containing an amino group.