JPH0723971B2 - Manufacturing method of dry type one-component electrophotographic developer with less surface deposit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a dry one-component type electrophotographic developer with less surface deposit.

[Problems to be Solved by Prior Art and Invention]

Conventionally, a dry one-component type electrophotographic developer (hereinafter referred to as a developer) is prepared by heating, melting, kneading and dispersing a magnetic substance in a synthetic resin, and then classifying it into a predetermined particle size by a fine pulverizer and a classifier. Manufactured by the method.

Developers produced by conventional manufacturing methods generally have the following drawbacks.

(1) Since it has undergone the crushing process, the particle size distribution is wide, the yield that matches the predetermined particle size is small, and the manufacturing cost is high.

(2) Since the process is long and complicated, it is not suitable for high-mix low-volume production.

(3) Since the shape is irregular, it is likely to be pulverized further inside the copying machine to form fine powder.

(4) So-called fog, in which the generated fine powder adheres to the white background, is likely to occur.

(5) Inorganic substances that are difficult to be compatible with the resin are easily exposed, and the fluidity of the powder is impaired.

(6) The exposed inorganic substance makes the electric resistance value of the developer unstable.

(7) Since the particle shape is indefinite, electrical polarization occurs inside the developer, and tailing easily occurs around the black solid portion.

(8) As a result, the life of the developer is shortened.

As a means for improving these drawbacks, JP-A-53-17735
There has been proposed a method for producing a developer by a polymerization method as disclosed in Japanese Patent Publication No.

According to this method, a developer having a well-formed shape and a narrow particle size distribution can be produced depending on the selection of conditions. However, as a result of using a polymerization dispersion stabilizer as disclosed in JP-A-54-84731, in order to meet the demand for reducing the particle size to a practical range as quickly as possible, the particles are There is a problem that it remains adsorbed on the surface and contaminates the developer.

In addition, for the purpose of improving the wetting of magnetic materials, colorants, charge control agents, charge control agents, etc., which are difficult to finely disperse in polymerizable monomers, for example, “Modern Industrial Chemistry” Vol. 16, page 65 (published by Asakura Shoten) Surfactants may also be used, as described. However, when a surfactant is used, an emulsion polymer is produced as a by-product, and the emulsion polymer produced as a by-product remains on the surface of the particles refined by dispersion polymerization and contaminates the developer. When this pollution occurs, the following adverse effects occur.

(1) The emulsion polymer adhering to the surface of the particles adheres to the photoreceptor by repeated use of the developer and changes the surface potential characteristics.

(2) The blackness of the developer is lowered, which in turn lowers the image density.

(3) Moisture resistance of the developer is reduced.

(4) The fluidity of the developer is impaired.

(5) As a result, the life of the developer is shortened.

The present invention has solved the problems of the conventional developer as described above, that is, the developer in which the filler is sufficiently dispersed inside, the surface is smooth and the flowability is excellent, and the developer is suitable for high speed copying,
This is done in order to obtain a developer whose surface is not contaminated, has a high degree of blackness, is excellent in moisture resistance, and has a long life.

[Means for solving problems]

The present invention is a method in which a surfactant, an emulsion polymerization inhibitor, and a polymerization dispersion stabilizer are allowed to coexist in an aqueous medium in a certain ratio, and then a developer is produced by a special dispersion polymerization method, whereby A developer in which a filler such as a magnetic material is finely dispersed inside the developer particles while preventing the coalescence of the particles and the emulsion polymerization, resulting in prevention of contamination of the surface of the developer particles by the emulsion polymer. Further, it is possible to sufficiently remove the polymerization dispersion stabilizer and the like adhering to the surface of the developer particles by washing with a solvent containing alcohol after polymerization, and a developer with stable quality can be produced. It was made by the finding that the surfactant was 0.01 to 1% (wt%, the same applies hereinafter) emulsion polymerization inhibitor.
Dispersion polymerization method in which a magnetic material as a developer raw material is dispersed in an aqueous liquid containing 0.1 to 10% and a polymerization dispersion stabilizer and a developer raw material containing a polymerizable monomer and a polymerization initiator is added. The method for producing a dry one-component type electrophotographic developer having a small amount of surface deposits by producing composite particles by the method described above and then washing with a medium containing alcohol.

〔Example〕

In the present invention, an aqueous solution containing 0.01 to 1% of a surfactant, 0.1 to 10% of an emulsion polymerization inhibitor and 0.1 to 10% of a polymerization dispersion stabilizer is used.

Examples of the surfactant include higher fatty acid salts that are anionic surfactants, alkyl sulfate ester salts, alkylbenzene sulfonates, and the like, nonionic surfactants such as polyoxyethylene alkyl ether, sorbitan fatty acid esters, and cationic surfactants. Examples include surfactants such as alkyl amine salts and quaternary ammonium salts, and amphoteric surfactants such as alkyl betaine. These surfactants may be used alone or in combination of two or more of the same type. When two or more different types of surfactants are used in combination, it is preferable to limit the use to those of a type that does not react when used in combination. The number of carbon atoms in the alkyl chain is generally 8 to 24, more typically 12 to 18.

The amount of the surfactant used is 0.01 to 1%, preferably 0.02 to 0.1% in the aqueous liquid, and when the amount is less than 0.01%,
The wettability, which is the purpose of use, is not sufficiently exerted, and if it exceeds 1%, the dispersion stability of the particles becomes poor, and agglomeration occurs between the particles.

Examples of the emulsion polymerization inhibitor include metal salts of group I and metal salts of group II of the periodic table of the elements, specifically sodium, potassium, cadmium, magnesium, calcium, copper, zinc and the like hydrochloride, sulfuric acid. Examples include salts and nitrates. These may be used alone or in combination of two or more. Among the above emulsion polymerization inhibitors, sodium chloride and sodium sulfate are particularly preferable from the viewpoint of exhibiting the effect even in a small amount.

The amount of the emulsion polymerization inhibitor used is 0.1 to 10%, preferably 0.1 to 2% in the aqueous liquid, and if it is used in excess of 10%, even the desired polymerization reaction may be suppressed, and the developer may be used. The appropriate amount varies depending on the type. On the other hand, the amount used is 0.1
If it is less than%, the effect of preventing emulsion polymerization is not sufficiently exhibited.

As the polymerization dispersion stabilizer, generally used water-soluble polymers such as polyvinyl alcohol, polyethylene oxide, methyl cellulose, hydroxyethyl cellulose and the like can be mentioned as typical specific examples. These may be used alone or in combination of two or more.

Among the polymerization dispersion stabilizers, polyvinyl alcohol,
Incompletely saponified polyvinyl alcohol is preferred.

The amount of the polymerization dispersion stabilizer used is 0.1 to 10%, preferably 1 to 5% in the aqueous liquid, and when the amount used is less than 0.1%, the dispersed state of the particles decreases, and aggregation occurs between the particles. If it exceeds 10%, the amount of the polymerization dispersion stabilizer remaining on the particle surface increases, and it becomes difficult to obtain a stable quality product.

In the present invention, a magnetic material that is a developer raw material is dispersed in the above-mentioned aqueous liquid, and a developer raw material containing a polymerizable monomer and a polymerization initiator is added, and the stirring speed is preferably 10
Composite particles are produced by a dispersion polymerization method at 00 rpm or more.

Typical examples of the magnetic material include iron trioxide, γ-iron sesquioxide, manganese ferrite, nickel ferrite and cobalt ferrite. These magnetic materials may be used as they are, or may be surface-treated with a silane coupling agent, oleic acid, or the like, if necessary. These may be used alone or in combination of two or more.

The average particle size of the magnetic material is preferably about 0.01 to 1 μm in order to finally obtain developer particles of 1 to 30 μm. The content of the finally obtained developer in the developer is preferably about 30 to 70%, more preferably about 40 to 60% in order to obtain a developer having good deviations in magnetic properties and fixing properties.

The dispersion amount of the magnetic material in the aqueous solution is usually 15 to
It is about 35%, preferably about 20 to 30% in order to obtain a developer having good magnetic properties and fixing properties.

As the polymerizable monomer that can be used in the present invention, any monomer can be used as long as it gives a thermoplastic resin by polymerization, and among them, a vinyl-based monomer is typical, and for example, styrene. General-purpose polymerizable monomers such as butyl acrylate, butyl methacrylate, and methyl methacrylate are inexpensive and easy to use industrially. These polymerizable monomers may be used alone or may be used in combination of two or more kinds simultaneously or sequentially, but in view of easy control of charging performance and fixing performance of the obtained developer, combination is possible. Is generally used.

The polymerization initiator may be used without particular limitation as long as it is a commonly used oil-soluble polymerization initiator, but depending on the type of carbon black generally used as a colorant or an electrical resistance control agent, a peroxide-based polymerization initiator may be used. In some cases, an azo polymerization initiator may be preferable.

The developer raw material containing the polymerizable monomer and the polymerization initiator, in addition to these components, a chain transfer agent such as lauryl mercaptan, a colorant, a plasticizer, a cross-linking agent, a charge control agent, an electric resistance control agent, etc. May be added.

Other components (chain transfer agent, colorant, plasticizer, cross-linking agent, charge control agent, electric resistance control agent) other than the magnetic substance, the polymerizable monomer, and the polymerization initiator used as the raw material of the developer, if necessary. Etc.), the chain transfer agent is preferably 0.1 to 15% with respect to the polymerizable monomer, and more preferably 1
~ 10%, plasticizer, the cross-linking agent is preferably 0.1 to 20% to the polymerizable monomer, more preferably 1 to 10%,
It is preferably 0.1 to 10%, and more preferably 1 to 5% with respect to the developer capable of obtaining a colorant, a charge control agent, and an electric resistance control agent. First, the magnetic material is dispersed in an aqueous liquid using a developer raw material so as to have such a composition, and under stirring, the components of the residue are added under the condition that the gas phase part of the reaction vessel is replaced with nitrogen gas. By carrying out dispersion polymerization,
Composite particles are produced in which the filler is sufficiently dispersed inside the particles to serve as a developer.

The polymerization temperature is generally 40 to 100 ° C, but 55 to 85 ° C is more preferable from the viewpoint of controlling the polymerization rate.

The composite particles thus obtained are separated from the dispersion liquid containing about 20 to 80%, preferably about 40 to 60% by a method such as centrifugation or vacuum filtration, and then washed with a medium containing alcohol. Then, a dry type one-component type electrophotographic developer having less adherence on the surface of the present invention is produced.

The medium containing alcohol is one type of alcohol that can dissolve polyvinyl alcohol and the like such as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, butanol, and can be removed by washing with water, or Including 2 or more, 10% or more,
It is preferably an alcohol solution of 30% or more.

The method of washing the composite particles with a medium containing alcohol is not particularly limited, and a small amount of the emulsion polymer or polyvinyl alcohol attached to the composite particles is removed, unless the composite particles are destroyed, any A method can also be adopted. As a specific example of such a method, for example, a method of immersing the composite particles in a medium containing alcohol to wash the composite particles,
There is a method of washing under stirring. If necessary, such cleaning methods may be combined, or the same method may be repeatedly applied.

In this way, the developer according to the present invention can be obtained in which the surface of the composite particles has little deposit, that is, the surface is not contaminated.

The surface of the developer according to the present invention obtained as described above has almost no dispersion stabilizer or the like attached to it, so that a developer having excellent moisture resistance, excellent fluidity and long life can be obtained. .

Although it has not been clarified exactly what mechanism the characteristics of the developer according to the present invention have, it is considered as follows.

Generally, a polymerization dispersion stabilizer is used to control the particle size of the composite particles to a particle size practical for a developer. The polymerization dispersion stabilizer used is adsorbed around the oil droplets generated by the shearing force, and prevents the oil droplets from coalescing. The oil droplets are polymerized into polymer particles. However, the polymerization dispersion stabilizer adsorbed on the polymer particles cannot be easily removed by simple washing with water. However, washing with a solvent containing an appropriate alcohol changes the compatibility of the polymerization dispersion stabilizer and removes it from the polymer particles.

On the other hand, when a surfactant that improves the wettability of the surface of the filler is used in order to obtain a developer in which the filler such as a magnetic material is sufficiently dispersed inside the polymerized particles, emulsion polymerization micelles in an aqueous medium other than the above action are used. Are also formed, and the surface of the composite particles is contaminated by the emulsion polymer thus formed. However, when the surfactant and the emulsification inhibitor are used in appropriate concentrations, the emulsion polymerization micelles are destroyed by the action of the emulsion polymerization inhibitor with almost no sacrifice of the wettability of the filling surface. Generation of an emulsion polymer is suppressed and contamination is prevented.

Next, the method of the present invention will be explained based on examples, but the present invention is not limited thereto.

Example 1 In a 500 ml separable flask, 230 parts of ion-exchanged water and amphoteric surfactant (Amphitol 86B manufactured by Kao Soap Co., Ltd.) 0.1
92 parts, 100 parts of 10% polyvinyl alcohol (Nippon Gosei Kagaku Kogyo Co., Ltd. Gohsenol KP-08) aqueous solution and 1.12 parts of sodium sulphate were added, and after sufficiently stirring, ferric oxide (KN manufactured by Toda Kogyo Co., Ltd.) -320) 72 parts was added and dispersed under stirring.

Separately, 57.6 parts of styrene monomer, 19.2 parts of n-butyl methacrylate, 1.6 parts of diethylaminoethyl methacrylate, 1.6 parts of glycidyl methacrylate, 1.6 parts of 2-hydroxyethyl methacrylate, and 3.2 parts of dye (Bontron NO1 manufactured by Orient Chemical Co., Ltd.) , Carbon black (furnace black # 4 manufactured by Mitsubishi Kasei Co., Ltd.)
4) A monomer mixture liquid was prepared by uniformly mixing 3.2 parts, 4 parts of lauryl mercaptan and 6 parts of 2,2'-azobis (2,4-dimethylvaleronitrile).

After replacing the gas phase part of the separable flask with nitrogen gas, the above monomer mixture was added and dispersed at a rotation speed of 1200 rpm by a turbine propeller, and then the temperature was raised to 65 ° C. under stirring and the reaction was carried out for 2 hours. After that, further raise the temperature to 80 ℃,
The treatment was carried out for 3 hours to complete the polymerization reaction.

After cooling the polymerization solution, the particles produced were separated by vacuum filtration, washed thoroughly with water, and ethanol: water was added at a volume ratio of 1: 1.
It was washed several times with the mixed solvent of, and washed again with water to replace the residual ethanol. After dehydration by filtration, it was air-dried to obtain a developer.

The particle size of the obtained developer was 15 μm as measured by a Coulter counter, the shape was substantially spherical, and the fluidity was excellent, and the value of the repose angle test method was 38.2 °. Furthermore, when the surface was observed with a SEM (Scanning Electron Microscope), the surface was smooth and no adhesion of contaminants was observed. The powder did not block even when left at 38 ° C and 80% RH for 10 days. Furthermore, the image characteristics were examined with a Sharp SF-730 copier.
6. The image quality was good with a white background density of 0.01 and good contrast.

Example 2 A developer was prepared and evaluated in the same manner as in Example 1 except that 24 parts of sodium chloride was used instead of 1.12 parts of sodium sulfate used in Example 1.

The average particle size of the obtained developer was 25 μm, the shape was substantially spherical, the flowability was excellent, and the value of the repose angle test method was 38.8 °. When the surface was observed by SEM, the surface was smooth like the one obtained in Example 1 and no adhesion of contaminants was observed. Further, even if it was left for 10 days under the conditions of 30 ° C. and 80% RH, blocking of the powder did not occur.

Example 3 A 500 ml separable flask was charged with 284 parts of ion-exchanged water, 0.016 part of sodium dodecylbenzenesulfonate, 40 parts of 10% polyvinyl alcohol (Gosenol KP-08 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 1.28 parts of sodium sulfate. After adding and stirring thoroughly, ferric oxide (KN- manufactured by Toda Kogyo Co., Ltd.)
320) 72 parts were added and dispersed under stirring.

Separately, 57.6 parts of styrene monomer, 19.2 parts of n-butyl methacrylate, 3.2 parts of aniline blue, carbon black (Furnace Black # manufactured by Mitsubishi Kasei Co., Ltd.)
50) 3.2 parts, 4 parts of lauryl mercaptan and 8 parts of 2,2'-azobisisobutyronitrile were uniformly mixed to prepare a liquid.

After replacing the gas phase part of the separable flask with nitrogen gas, the above-mentioned monomer mixture liquid was added and dispersed at a rotation speed of 1300 rpm by a turbine propeller, and then the temperature was raised to 65 ° C. under stirring and the reaction was carried out for 2 hours.

The produced particles were washed with an ethanol-water mixed solvent in the same manner as in Example 1 to obtain a developer.

The average particle size of the obtained developer was 18 μm, the shape was substantially spherical, the flowability was excellent, and the value of the repose angle test method was 38.0 °. Also, when the surface was observed by SEM, the surface was smooth and no adhesion of contaminants was observed. When the image characteristics were examined with a Sharp SF-730 copying machine in the same manner as in Example 1, the image density was 1.17, and the image quality was excellent with little fog.

Comparative Example 1 A developer was prepared and evaluated in the same manner as in Example 1 except that the particles produced after the polymerization in Example 1 were washed using only water. Had a sticky surface, and when air-dried, cake-like lumps partially formed. When the solidified particles were disentangled and observed by SEM, it was confirmed that gelatinous polyvinyl alcohol remained.

When the fluidity of the obtained developer was measured, it was significantly disturbed, and blocking occurred between the magnet roller and the doctor sleeve, and it was impossible to convey. The angle of repose test method resulted in clogging of the funnel, and it was impossible to measure.

Comparative Example 2 A developer was prepared in the same manner as in Example 2 except that polyvinyl alcohol, which is the polymerization dispersion stabilizer used in Example 2, was not added. As a result, the dispersion stability of the entire polymerization system became poor, and the polymer became lumpy, and the reaction could not proceed any further.

Comparative Example 3 A developer was manufactured in the same manner as in Example 1 except that the surfactant used in Example 1 was not added.

Although the polymerization reaction itself could be carried out without any trouble, the shape of the particles produced was indefinite, and when observed by SEM, there was a filler exposed on the surface of the developer. In addition, a liberated fine magnetic material was confirmed. When the image characteristics of the obtained developer were examined, the image was remarkably fogged and the white background density increased to 0.13. The value of the angle of repose test was 41.2 °, which was also inferior to that of Example 1 in terms of powder fluidity. When left at 30 ° C. and 80% RH, blocking was observed after 3 days.

Comparative Example 4 A developer was produced in the same manner as in Example 3 except that the emulsion polymerization inhibitor sodium sulfate used in Example 3 was not added, and the aqueous phase after polymerization was significantly clouded.

When the obtained developer was observed by SEM, an adhering substance was recognized on the surface, the color tone of the particles after drying did not have a sufficient blackness, probably because of the influence of the color tone of the emulsion polymer, It was grayish. The value of the angle of repose test was 42.2 °, which was also inferior to that of Example 3 in terms of powder fluidity. When it was left under the conditions of 30 ° C. and 80% RH, blocking occurred already after 1 day, and the fluidity as a powder was lost.

〔The invention's effect〕

When a developer is produced by the method of the present invention, a developer whose surface is not contaminated can be obtained. A developer with a smooth surface and a well-filled dispersion inside can be obtained. A developer with high blackness can be obtained. A developer with excellent properties is obtained. It has excellent fluidity, a developer suitable for high-speed copying is obtained, and a developer with a long life is obtained.

Claims (1)

[Claims] 1. A surfactant of 0.01 to 1% by weight and an emulsifying agent of 0.
Disperse a magnetic material as a developer raw material in an aqueous liquid containing 1 to 10% by weight and a polymerization dispersion stabilizer 0.1 to 10% by weight, and add and disperse the developer raw material containing a polymerizable monomer and a polymerization initiator. A method for producing a dry type one-component type electrophotographic developer, in which composite particles are produced by a polymerization method and then washed with a medium containing alcohol to reduce surface deposits.