JPH0561253A - Production of electrostatic charge developing toner - Google Patents

Abstract

PURPOSE:To obtain the dry toner having a excellent characteristic by adding water-soluble nigrosine into a water phase and subjecting a polymerizable monomer to a suspension polymn. in an aq. medium, thereby efficiently preventing the generated emulsion polymn. CONSTITUTION:The polymerizable monomer, coloring agents and charge control agent, etc., which are the essential components of the toner constituting an oil phase are prepd. as a dispersion and after a polymn. initiator is added and dissolved in the prepn. and thereafter, the suspension is dispersed and suspended in the water phase. A dispersion stabilizer consisting of a water-soluble high polymer, such as polyvinyl alcohol or hardly water-soluble inorg. powder, such as tricalcium phosphate and a surfactant, such as dodecyl sodium sulfate, and the water-soluble nigrosine as a polymn. inhibitor of the water phase are added to the water phase. The dispersed suspension is heated to polymerize the polymerizable monomer. The emulsion polymn. generated in the water phase is efficiently prevented in this way and the electric resistance, triboelectrostatic charge characteristic, weatherability, and flowability are improved. The toner with which the excellent image quality is obtainable is thus obtd.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a toner, especially a dry toner, for developing an electrostatic latent image in electrophotography, electrostatic recording and electrostatic printing.

[0002]

2. Description of the Related Art A dry toner is a conventional toner in which a thermoplastic resin is melted and a coloring agent such as a dye or a pigment is added thereto, and if necessary, a magnetic material,
Add friction charge control agent, anti-offset agent, lubricant, etc.,
After thoroughly kneading, solidify by cooling, finely pulverize this,
It has been manufactured by classifying it to the required particle size. However,
There are various problems with the method described above. First,
Polymerization equipment for resin production, equipment for kneading, grinding,
A device associated with many processes such as a device for classification is required, and the number of processes is large and the energy consumption is large, which causes a cost increase. Secondly, it is difficult to obtain a uniform mixture in the kneading step, and particularly the conditions for uniform dispersion are delicate. Thirdly, in order to obtain a clear and fog-free image, it is necessary to remove fine powders and coarse powders produced as a by-product in the pulverization process, which is not only complicated but also the yield of the obtained toner is reduced. Bad things exist as a drawback that leads to higher costs. Fourthly, since the obtained toner is pulverized, it has an irregular shape, and has poor fluidity of the toner, and carriers and photoconductors caused by fine powder generated by re-pulverization by stirring during development. There is a decrease in durability due to filming. As means for compensating for and improving these drawbacks, Japanese Patent Publication No. 36-10231.
No. 47/518305/47/148
No. 95 and the like disclose methods for producing a toner by a suspension polymerization method, and these methods improve the above-mentioned problems, but cause problems associated with the suspension polymerization method. In the suspension polymerization method, a colorant, a charge control agent or the like and a polymerizable monomer containing a radical polymerization initiator are used as a water-soluble polymer, a poorly water-soluble inorganic powder, or a dispersion stabilizer such as a water-soluble surfactant alone or Toner particles can be obtained by using together and dispersing in an aqueous phase dissolved or dispersed in water by a dispersing means such as a homomixer to obtain a particle size of 3 to 20 μm, and then heating to perform polymerization. When the oil phase is dispersed in the water phase, the monomer is dissolved in a trace amount of the aqueous phase, and further, the water-soluble polymer used as a dispersion stabilizer and a trace amount of the emulsion are emulsified by the surfactant, which causes emulsion polymerization by heating, and the fine particles Adheres to the toner surface,
There is a problem that not only the electrical characteristics such as electric resistance and triboelectricity are deteriorated, but also the filterability of the toner is remarkably lowered, and it becomes extremely difficult to separate the toner from the aqueous phase. Therefore, in order to prevent the occurrence of emulsion polymerization by adding to a water phase, JP-A-56-156839 discloses the addition of a hageronide such as an alkali metal, an alkaline earth metal or a transition metal. However, it requires a relatively large amount of addition, which affects the electrical resistance of the toner. or,
JP-A-61-255353 discloses the addition of a water-soluble mercaptan compound, but this also requires the addition of a relatively large amount, which also affects the polymerization of the monomer in the oil phase. In addition, Japanese Patent Publication No. 63-58355 discloses the addition of nitrite and water-soluble molybdic acid, but similarly, there is a problem in the influence on electrical characteristics.

[0003]

DISCLOSURE OF THE INVENTION The present invention efficiently prevents emulsion polymerization occurring in the aqueous phase, improves electrical properties, particularly electrical resistance, triboelectrification properties, weather resistance and fluidity, and provides excellent images. It is intended to provide a manufacturing method capable of efficiently manufacturing an electrostatic charge developing toner having high quality.

[0004]

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention have made earnest studies and, as a result, have found that an aqueous medium containing a dispersion stabilizer containing a polymerizable monomer containing a property-imparting agent such as coloring. In the method for producing a toner for electrostatic charge development in which suspension polymerization is carried out in a medium, by adding water-soluble nigrosine to an aqueous medium to carry out polymerization, there is no effect on the electrical properties of the toner produced or the polymerizability of monomers. The inventors have found that the emulsion polymerization in the aqueous phase can be effectively prevented without giving it to the present invention. Aqueous nigrosine has a high affinity with water, and a trace amount of it has an effect of preventing emulsion polymerization, so that it is considered that a toner having excellent properties can be obtained. Hereinafter, the manufacturing method of the present invention will be specifically described. The oil phase is a main component of toner, such as a weighting monomer, a colorant such as a pigment or a dye, a charge control agent and, if necessary, a crosslinking agent, a chain transfer agent, an offset preventing agent, a magnetic powder, a prepolymer, an oligomer or a polymer. Etc. and a polymerization initiator as an essential component. The components constituting the oil phase excluding the polymerization initiator are prepared as a uniform dispersion by means of a ball mill, a sand mill, etc., and then the polymerization initiator is added and dissolved, and then a homomixer, an ultrasonic homomixer, a pressure homogenizer. And the like are dispersed and suspended in the water phase. In the aqueous phase, polyvinyl alcohol, a water-soluble polymer such as hydroxyethyl cellulose or a poorly water-soluble inorganic powder such as tricalcium phosphate and sodium dodecyl sulfate, a dispersion stabilizer comprising a surfactant such as sodium dodecylbenzenesulfonate, Water-soluble nigrosine, which is a feature of the present invention, is added as a polymerization inhibitor for the aqueous phase. The dispersed suspension is transferred to a polymerization device equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe, and a thermometer, and after replacement with nitrogen, the polymerizable monomer is polymerized to form a toner. It After completion of polymerization, by filtration and centrifugal sedimentation,
After separating the toner particles, washing with water is repeated several times and then drying to obtain a toner powder.

The materials to be used include, as the polymerizable monomer, styrenes such as styrene, α-methylstyrene, vinyltoluene and parachlorostyrene, methyl (meth) acrylate, ethyl (meth) acrylate,
N-butyl (meth) acrylate, 2- (meth) acrylic acid
(Meth) acrylic acid alkyl ester such as ethylhexyl Vinyl acetate, vinyl propionate and other vinyl esters, methyl vinyl ether, ethyl vinyl ether and other vinyl esters, acrylonitrile, methacrylonitrile and other vinyl nitriles, butadiene, isoprene and other dienes And halogenated vinyl such as vinyl chloride and vinylidene chloride are used. Further, a monomer having a triboelectrifying functional group such as acrylic acid, 2-oxyethyl succinic acid (meth) acrylic acid, trifluoroethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and aminostyrene. May be copolymerized. As the cross-linking agent, divinylbenzene, ethylene glycol dimethacrylate, butanediol dimethacrylate, trimethylol, propanetrimethacrylate, etc. are used. These crosslinking agents are used in an amount of 0.01 to 15% by weight, preferably 0.1 to 10% by weight, of the polymerizable monomer. As the chain transfer agent, n dodecyl mercaptan, tert dodecyl mercaptan and the like are used in an amount of 0.01 to 3% by weight of the monomer.
As the pigments and dyes, carbon black, phthalocyanine pigments, monoazo dyes / pigments, disazo dyes / pigments, trisazo dyes / pigments and the like are used. It is preferable to improve the dispersibility of carbon black by surface modification such as graft treatment and addition of a dispersant. As the charge control agent, an azo complex dye, a salicylic acid metal salt as a negative charge control agent, a nigrosine dye as a positive charge control agent, a quaternary ammonium salt compound, or the like which is commonly used can be used. As the anti-offset agent, low molecular weight polyethylene, polyolefin such as polypropylene, synthetic / natural wax such as paraffin wax and carnauba wax, fatty acid ester, fatty acid amide and the like are used.
In addition, in order to improve the characteristics, an oligomer or a polymer such as an epoxy resin, a polyester or a silicone resin can be used by dissolving or dispersing it in a monomer. As the magnetic powder, fine powder of magnetite, ferrite or the like is used, but it is preferable to use it as a lipophilic substance after surface modification. Examples of the polymerization initiator include azo compounds such as 2,2′-azobis- (2,4-dimethylvaleronitrile) and 2,2′-azobisisobutyronitrile, lauroyl peroxide,
A radical polymerization initiator such as a peroxide compound such as benzoyl peroxide is used. These polymerization initiators are used in an amount of 0.2 to 5% by weight of the monomer. As a water-soluble polymer used as a dispersion stabilizer, polyvinyl alcohol, particularly saponification degree 70 to 90%, viscosity (20 ° C, 4%)
5-60 cps partially saponified is preferred. These water-soluble polymers are used in the range of 0.1 to 3% by weight. or,
As the poorly water-soluble inorganic powder, tricalcium phosphate is preferable, and it is used in the range of 0.1 to 10% by weight with respect to water. Further, it is preferable to use an anionic surfactant such as sodium dodecyl sulfate or dodecylbenzene sulfonic acid in combination with the poorly water-soluble inorganic powder. These surfactants are used in the range of 0.1 to 3% by weight with respect to water.
Water-soluble nigrosine used as an emulsion polymerization inhibitor, which is a feature of the present invention, is a dye represented by CI50430 and is 0.005 to 0.1% by weight, preferably 0.001 to 0.07% by weight in the aqueous phase.
Used at a concentration of. If the concentration is less than 0.005% by weight, the effect of inhibiting emulsion polymerization is poor, and if it exceeds 0.1% by weight, the oil phase is affected. Since the water-soluble nigrosine has such an extremely low concentration, it does not affect the triboelectric chargeability of the produced toner.

[0006]

EXAMPLES Examples and comparative examples will be described below. Parts indicate parts by weight. Example 1 To 30 parts of styrene, 15 parts of carbon black (Raven 410, manufactured by Columbia Chemicals) and 0.25 part of 2,2'-azobisisobutyronitrile were added, and after replacement with nitrogen, 80
Heated at ° C for 6 hours. After cooling, 92 parts of styrene and 53 parts of n-butyl methacrylate were added and uniformly dissolved. To this carbon black dispersion, 3.5 parts of Spiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.) was added and dispersed with a ball mill for 20 hours. 40 parts of this dispersion was mixed with 2,2'-azobis (2,4-
1 part of dimethyl valeronitrile) was added to prepare an oil phase. On the other hand, 3.2 parts of partially saponified polyvinyl alcohol (Kuraray Poval 217) and 0.08 part of water-soluble nigrosine were dissolved in 156.8 parts of ion-exchanged water to prepare an aqueous phase. The oil phase was added to the water phase, and the mixture was dispersed with a TK homomixer (manufactured by Tokushu Kika Co., Ltd.) at 4000 rpm for 10 minutes, and then transferred to a separable flask equipped with a stirrer, a cooling tube and a thermometer, and after replacement with nitrogen, 60 The mixture was heated and stirred at 8 ° C for 8 hours. After the polymerization, a filter paper with 1 μm of retained particles was used for suction filtration, and it could be easily filtered. After this, after washing with water three times,
Vacuum drying was performed at 40 ° C. to obtain a toner. This toner has a volume average particle diameter of 9.5 μm and a volume resistivity of 5.5 × 1.
The powder had a flowability of 0 ¹⁰ Ωcm and a charge amount of −20.1 μc / g. When this toner was mixed with a silicone-coated ferrite carrier in an amount of 3% and subjected to a development test with FT5510 (manufactured by Ricoh), a clear image was obtained.

Example 2 Example 2 was repeated except that the aqueous phase was changed to 160 parts of ion-exchanged water, 6 parts of calcium phosphate, 3 parts of sodium dodecylbenzenesulfonate and 0.1 part of water-soluble nigrosine. It was as good as No. 1. The particle diameter of this toner is 10.5 μm, and the volume resistivity is 4.7 × 10.
^The charge amount was ¹⁰ Ωcm and -19.8 μc / g. When a developer was prepared and developed in the same manner as in Example 1, a clear image was obtained.

Comparative Example 1 Suspension polymerization was carried out in the same manner as in Example 1 except that water-soluble nigrosine was not added to the aqueous phase, and suction filtration was carried out using 1 μ of filter paper. It became impossible. Therefore, centrifugal sedimentation was carried out to separate polymer particles, washing with water and centrifugal sedimentation were repeated twice, followed by washing with water and suction filtration. Although filtration was gradually possible, it was vacuum dried at 40 ° C. After that, crushing was tried, but it could not be crushed into single particles, and no toner was obtained. When observed under a microscope, the emulsion-polymerized particles adhered to the entire surface of the polymerized particles.

Comparative Example 2 Polymerized particles were obtained in the same manner as in Example 1 except that 3 parts of ferric chloride was added instead of the water-soluble nigrosine in the aqueous phase. The filterability was good when 1 μ of filter paper was used. The volume average particle diameter of this toner is 9.6 μm,
Volume resistivity is 5.9 × 10 ⁹ Ωcm, charge amount is -1
It was 5.8 μc / g. When a developer was prepared and a development test was conducted in the same manner as in Example 1, an unclear image with a low image density was obtained.

[0010]

As described above, according to the present invention, an oil phase comprising a polymerizable monomer containing a characteristic imparting agent such as a colorant is added to a dispersion stabilizer and water-soluble nigrosine in an aqueous medium. By carrying out suspension polymerization, it is possible to effectively prevent emulsion polymerization that occurs in the aqueous phase, and to efficiently produce a toner having excellent environmental stability and electrostatic properties.

Claims (1)

[Claims] 1. A process for producing a toner for electrostatic charge development, which comprises subjecting a polymerizable monomer containing a characteristic-imparting agent such as a colorant to suspension polymerization in an aqueous medium containing a dispersion stabilizer to obtain a water-soluble toner in an aqueous medium. A method for producing a toner for electrostatic charge development, characterized in that polymerization is carried out by adding a polymerizable nigrosine.