JPH0683099A - Electrophotographic developer - Google Patents

Abstract

PURPOSE:To obtain excellent flowability and to reduce secular changes of an electrophotographic developer, and also to make it hardly influenced by environment by using organo-polysiloxane having an epoxy group as a substituent together with polyalkyleneimine. CONSTITUTION:A powdery metal oxide is surface treated by concurrently using organo-polysiloxane having an epoxy group as a substituent and polyalkyleneimine. At this time the surface of the powdery metal oxide is provided effectively with positive electrostatic chargeability by the polyalkyleneimine which is firmly fixed through the organo-polysiloxane having high physical adhesion, on the surface of the powdery metal oxide by allowing to react the epoxy group in the organo-polysiloxane with the amino group in the polyalkyleneimne. At the same time the surface of this powdery metal oxide is provided with hydrophobic property by the organo-polysiloxane. At this time, the electrophotographic developer which contains particularly the powdery metal oxide having a >=60% hydrophobicity determined by the transmissivity method and alumina or titania as the metal oxide, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer containing a hydrophobic metal oxide powder for the purpose of improving powder fluidity.

[0002]

2. Description of the Related Art The so-called hydrophobic metal oxide powder obtained by hydrophobizing the surface of the metal oxide powder with an organic substance is used in electrophotography, electrostatic recording, etc.
It is widely used as an agent for improving cleaning properties.
In these applications, the triboelectrification property of the metal oxide powder itself to the carrier iron or iron oxide is one of the important properties, and its hydrophobicity and triboelectrification property are simultaneously controlled by various treatment agents. ing. Among them, as a method of reducing the negative chargeability or imparting the positive chargeability to the metal oxide powder, a method of treating the surface of the powder with an amine-based organic compound is generally used. It is used. However, when a low molecular weight compound such as a quaternary ammonium salt is used as the amine-based organic compound, the reproducibility of the obtained charge amount is low because the bondability with the surface is low, and the environment is particularly susceptible to moisture. Such problems are likely to occur. On the other hand, when treated with an amino group-substituted silane coupling agent or an amino-modified polysiloxane, these treatment agents chemically or physically bond strongly to the surface of the metal oxide powder, so that an effective positive The chargeability can be obtained. However, these treatment agents are relatively expensive and it is difficult to finely control the charge amount because there are few types of products on the market.

On the other hand, polyalkyleneimine is an inexpensive organic compound having a high molecular weight and is expected as a material for improving the above problems of the treating agent. However, when the metal oxide powder is actually treated with polyalkyleneimine, it is not possible to obtain a high positive charge amount while maintaining low hydrophobicity and affinity with the surface. Therefore, the metal oxide powder treated with polyalkyleneimine has not been practically used in a developer for electrophotography for the purpose of improving fluidity.

[0004]

It is an object of the present invention to contain a metal oxide powder having a controlled charge amount and a sufficient hydrophobicity by using polyalkyleneimine which is an inexpensive material.
An object is to provide an electrophotographic developer having stable chargeability and excellent fluidity.

[0005]

In order to solve the above problems and obtain an excellent hydrophobic metal oxide powder,
As a result of earnest studies, a metal oxide powder having a sufficient charge controllability and a sufficient hydrophobicity was obtained by surface-treating a metal oxide powder using an organopolysiloxane having an epoxy group as a substituent simultaneously with a polyalkyleneimine. It was found that an oxide powder was obtained, and that by containing this powder, the fluidity of the developer was improved and a stable charging property was obtained, and the object of the present invention was achieved. That is, by reacting an epoxy group in the organopolysiloxane with an amino group in the polyalkyleneimine, the polyalkyleneimine is firmly attached to the surface of the metal oxide powder through the organopolysiloxane having high physical adhesiveness. The above preferable result was achieved by immobilizing and effectively giving a positive charging property, and at the same time, the surface of the metal oxide powder was made hydrophobic by the organopolysiloxane.

A feature of the present invention is that an electrophotographic developer containing a metal oxide powder treated with an organopolysiloxane having an epoxy group as a substituent and a polyalkyleneimine, particularly measured by a transmittance method. Developer for electrophotography, which contains a metal oxide powder having a hydrophobized ratio of 60% or more, wherein the metal oxide is silica, alumina or titania. And a treating agent other than an organopolysiloxane having an epoxy group as a substituent are used together as a hydrophobizing agent to provide the electrophotographic developer.
The present invention will be described in more detail below.

The organopolysiloxane having an epoxy group as a substituent used in the present invention means a modified silicone having an appropriate number of epoxy groups in the molecule which are reactive with an amino group in polyalkyleneimine. However, it is not particularly limited except that it has fluidity such that it can be uniformly attached to the surface of the metal oxide powder.
It is preferable to use one having a viscosity of about 0 to 10,000 cs. As a commercially available material, K manufactured by Shin-Etsu Silicone Co., Ltd.
F-101, KF-102, KF-103, KF-10
5, X-22-169AS; Toray Dow Corning Silicone SF8411, SF8413 and the like are exemplified. The polyalkyleneimine used in the present invention may be polyethyleneimine, polypropyleneimine, etc. which are generally used for industrial purposes (average molecular weight: several hundreds to 100,000), and practically about 30%. Most preferably, a polyethyleneimine aqueous solution having a concentration of is used.

The metal oxide powder used in the present invention can be selected according to the application, but especially silica,
Alumina or titania is preferred for applications such as improving fluidity. The particle size can also be selected according to the use, but those having a specific surface area of 50 m ² / g or more are particularly preferable for the above use. The metal oxide may be a complex oxide or a mixture. Even if only an organopolysiloxane having an epoxy group as a substituent and a polyalkyleneimine are used, it is possible to impart practically sufficient hydrophobicity to the metal oxide powder. But to get higher hydrophobicity,
In order to save the amount of the organopolysiloxane having an epoxy group as a substituent, it is desirable to use a hydrophobizing agent other than the organopolysiloxane having an epoxy group as a substituent in combination. Dimethylpolysiloxane and polymethylhydrosiloxane are particularly preferable as the hydrophobizing agent other than the organopolysiloxane having the epoxy group as a substituent.

The amount of the treatment agent suitable for obtaining the hydrophobic metal oxide powder constituting the present invention depends on the type of the metal oxide powder to be treated, the specific surface area and the type of the treatment agent and is not particularly limited. . However, since excessive use of polyalkyleneimine causes a decrease in hydrophobicity, polyalkyleneimine is usually not more than 20% by weight without water, and particularly preferably 12% with respect to the weight of the metal oxide powder to be treated. It is desirable to use an amount of less than or equal to%. The amount of the organopolysiloxane having an epoxy group as a substituent depends on the epoxy group pigment, but for the purpose of fixing the polyalkyleneimine, it is 5 to 150% based on the weight of the polyalkyleneimine containing no water. , Particularly preferably 50-100%
It is desirable to use an amount of The higher the degree of hydrophobicity of the metal oxide powder obtained as a result of such treatment, the lower the hygroscopicity of the metal oxide powder and the smaller the change in the charge amount of the toner with respect to humidity, and The effect of preventing aggregation is enhanced and the utility value is high, but in practice, the value of the hydrophobicity ratio measured by the transmittance method described below is 60% or more,
It is desirable to have a value of 70% or more.

The method of measuring the triboelectric charge amount with respect to iron is specified in the literature, for example, "Coloring Material" 55 [9] 630-636.1982. The transmittance method is a method for experimentally obtaining the hydrophobicity of the treated metal oxide powder, and comprises the following steps. 1.0 g of the treated metal oxide powder and 100 ml of water are put in a separating funnel for extraction and shaken vigorously for 5 minutes. Then let stand for 1 minute and withdraw a small amount of suspension from the bottom of the separatory funnel. The transmittance of this liquid for light of 550 nm is represented by the transmittance of pure water as 100%, and the value is defined as the hydrophobicity of the metal oxide.

A conventionally known method is applied to the treatment of the metal oxide powder used in the present invention. That is, while mechanically and sufficiently stirring the metal oxide powder to be treated, an organopolysiloxane having an epoxy group as a substituent, a polyalkyleneimine, and an organopolysiloxane having an epoxy group as a substituent, if necessary, are added thereto. Other organopolysiloxanes are added dropwise or by spraying. At this time, it is possible to add all the treating agents at the same time, but first add an organopolysiloxane having an epoxy group as a substituent and an organopolysiloxane other than an organopolysiloxane having an epoxy group as a substituent, and then add The method of adding polyalkyleneimine is
The reproducibility of the obtained charging property is high and it is particularly preferable. It is also possible to use a solvent such as alcohol, ketone or hydrocarbon as a diluent depending on the viscosity of the polyalkyleneimine and the organopolysiloxane used. After the treatment agent is added, the reaction is completed by heating under a nitrogen stream at a temperature in the range of 100 to 250 ° C., particularly preferably in the range of 130 to 170 ° C. to remove the solvent. Further, depending on the kind of the metal oxide powder, when the dry treatment as described above is difficult, it is possible to perform the treatment under a wet condition using a considerable amount of a solvent. The hydrophobic metal oxide obtained by such a method is added to the toner by a conventionally known method. The amount added is 0.1 with respect to the toner.
It is practically desirable to be in the range of ˜20%, particularly in the range of 0.1 to 3%. The toner prepared in this manner is further mixed with iron powder or iron oxide powder to prepare a developer.

[0012]

INDUSTRIAL APPLICABILITY The hydrophobic metal oxide powder constituting the present invention can be made stronger by using the organopolysiloxane having an epoxy group as a substituent together with the polyalkyleneimine so that the polyalkyleneimine becomes stronger. It is fixed on the body surface. As a result, in addition to having excellent fluidity, the developer containing this hydrophobic metal oxide has a characteristic that it shows little change with time and is stable and not easily affected by environment such as humidity. .

[0013]

DETAILED DESCRIPTION OF THE INVENTION Examples and comparative examples are shown below for the purpose of facilitating the understanding of the present invention, but these do not limit the present invention at all.

Example 1 Heat-dried silica powder (“Aerosil # 130” manufactured by Nippon Aerosil Co., Ltd. specific surface area 13)
0 m ² / g) 10 g was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Epoxy modified polysiloxane (Shin-Etsu Chemical Co., Ltd. “KD-101” (2,000 cs)) 0.50 g Dimethyl polysiloxane (Shin-Etsu Chemical Co., Ltd. “KF-96” (50 cs) ) 1.00 g n-propanol 5.0 ml After completion of spraying, the mixture was further stirred at room temperature for 5 minutes, and then externally heated under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The hydrophobicity of the obtained powder by the transmittance method and the triboelectrification amount for iron were 87% and +198 μC /, respectively.
It was g. Next, 18% carbon and 5% nigrosine were dispersed in a styrene-acrylic resin material, pulverized, and then 10-
A toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of the resin powder obtained by classification into 20 μm. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer is + 17μ
It was C / g. When this developer was put into a commercially available copying machine and a life test was conducted, no fog occurred on the image even after copying about 29,000 sheets or more. Further, a good image was shown even in an environment of high temperature and high humidity (28 ° C., 85% RH). The triboelectric charge amount of the developer prepared without adding the metal oxide powder was +16 μC / g.

Comparative Example 1 Silica powder dried by heating (“Aerosil # 130” manufactured by Nippon Aerosil Co., Ltd. specific surface area 13)
0 m ² / g) 10 g was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Dimethylpolysiloxane ("KF-96" (50cs) manufactured by Shin-Etsu Chemical Co., Ltd.) 1.00 g n-Propanol 5.0 ml After spraying, stir at room temperature for 30 minutes. After that, external heating was performed under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 30 minutes, and then allowed to cool to room temperature. The hydrophobicity of the obtained powder was 87%, and the amount of triboelectricity with respect to iron was 97 μC / g.

Next, 18% carbon and 5% nigrosine were dispersed in a styrene-acrylic resin material, and after pulverization, 10 to 10
A toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of the resin powder obtained by classification into 20 μm. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer is + 16μ
It was C / g. When this developer was put in a commercially available copying machine and a life test was conducted, fog occurred on the image after about 16,000 sheets. The triboelectric charge amount of the developer prepared without adding the metal oxide powder was +17 μC / g.

Example 2 Heat-dried alumina powder (“Aluminum oxide C” manufactured by Nippon Aerosil Co., Ltd.)
10 g of a specific surface area of 90 m ² / g) was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Epoxy-modified polysiloxane (Shin-Etsu Chemical "KF-101" (2,000cs)) 0.50g Dimethylpolysiloxane (Shin-Etsu Chemical "KF-96" (50cs) ) 1.00 g n-propanol 5.0 ml After completion of spraying, the mixture was further stirred at room temperature for 5 minutes, and then externally heated under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The hydrophobicity of this powder by the transmittance method and the amount of triboelectricity with respect to iron were 68% and 140 μC / g, respectively. Next, 18% carbon and 5% nigrosine were dispersed in a styrene-acrylic resin material, and after crushing, 10 to 20 μm
A toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of the resin powder obtained by classification. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer is +16 μC / g
Met. When this developer was put into a commercially available copying machine and a life test was conducted, no fog occurred on the image even after copying about 23,000 sheets. Higher temperature and humidity (28
Good images were shown even under the environment of 85 ° C. and 85% RH. The triboelectric charge amount of the developer prepared without adding the metal oxide powder was +16 μC / g.

Example 3 Heat-dried titania powder (“Titanium oxide P2” manufactured by Nippon Aerosil Co., Ltd.)
10 g of 5 "specific surface area 80 m ² / g) was charged into a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 2.00 g Epoxy-modified polysiloxane (Shin-Etsu Chemical "KF-101" (2,000cs)) 0.50g Dimethylpolysiloxane (Shin-Etsu Chemical "KF-96" (50cs) ) After spraying 1.00 g of acetone 5.0 ml, the mixture was further stirred at room temperature for 5 minutes, and then externally heated under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The hydrophobicity of this powder by the transmittance method and the amount of triboelectricity with respect to iron were 72% and 100 μC / g, respectively. Next, 18% carbon and 5% nigrosine were dispersed in a styrene-acrylic resin material, and after crushing, 10 to 20 μm
A toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of the resin powder obtained by classification. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer is +17 μC / g
Met. When this developer was put into a commercially available copying machine and subjected to a life test, no fog occurred on the image even after copying about 28,000 sheets. Higher temperature and humidity (28
Good images were shown even under the environment of 85 ° C. and 85% RH. The triboelectric charge amount of the developer prepared without adding the metal oxide powder was +16 μC / g.

[Example 4] Heat-dried silica powder ("Aerosil # 130" specific surface area 13 manufactured by Nippon Aerosil Co., Ltd.)
0 m ² / g) 10 g was placed in a stainless steel container, and a treating agent having the following composition was sprayed while stirring at room temperature under a nitrogen atmosphere. Treatment agent Polyethyleneimine (30% aqueous solution) 0.40 g Epoxy-modified polysiloxane (Shin-Etsu Chemical Co., Ltd. “KF-101” (2,000cs)) 0.50 g Methylhydropolysiloxane (Shin-Etsu Chemical Co., Ltd. “KF-99”) 1 0.00 g n-propanol 5.0 ml After spraying was completed, the mixture was further stirred at room temperature for 5 minutes, and then externally heated under a nitrogen stream. The temperature was raised to 150 ° C. over 40 minutes, held at this temperature for 60 minutes, and then allowed to cool to room temperature. The hydrophobicity of the obtained powder by the transmittance method and the amount of triboelectricity with respect to iron were 93% and -98 µC / g, respectively.
Met. Next, disperse 18% carbon and 5% nigrosine in a styrene-acrylic resin material, grind, and then
A toner was prepared by mixing 1 g of the above metal oxide particles with 100 g of the resin powder obtained by classification into 20 μm. Further, 30 g of this toner was added to 1000 g of iron oxide powder to prepare a developer. The triboelectric charge of this developer is -14μ.
It was C / g. When this developer was put into a commercially available copying machine and a life test was conducted, no fog was generated on the image even after copying about 26,000 sheets. Further, a good image was shown even in an environment of high temperature and high humidity (28 ° C., 85% RH). The triboelectric charge of the developer prepared without adding the metal oxide powder was -14 μC / g.

Claims (4)

[Claims] 1. An electrophotographic developer containing an organopolysiloxane having an epoxy group as a substituent and a metal oxide powder having a coating of polyalkyleneimine. 2. The electrophotographic developer according to claim 1, wherein the metal oxide powder has a hydrophobicity of 60% or more as measured by a transmittance method. 3. The electrophotographic developer according to claim 1, wherein the metal oxide is silica, alumina or titania. 4. The electrophotographic developer according to claim 1, wherein a hydrophobizing agent other than the organopolysiloxane having an epoxy group as a substituent is also used as a treating agent.