JP3081008B2 - Method for producing toner for electrostatic charge development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a toner for developing an electrostatic latent image in electrophotography, electrostatic recording and electrostatic printing, and more particularly to a method for producing a dry toner.

[0002]

2. Description of the Related Art These dry toners are prepared by melting a thermoplastic resin, adding a coloring agent such as a dye and a pigment, and if necessary, a magnetic substance, a triboelectric charge controlling agent, an offset preventing agent, a lubricant and the like, and sufficiently kneading. After cooling, the mixture is solidified by cooling, finely pulverized, and then classified to a required particle size to produce a product. However, the above-described method has various disadvantages. Firstly, it requires equipment for many processes such as a polymerization device for resin production, a device for kneading, a device for pulverization and classification, etc. Is the cause. Secondly, it is difficult to obtain a uniform mixture in the kneading step, and in particular, the conditions for uniformly dispersing are delicate. Third, in order to obtain a clear and fog-free image, it is necessary to remove fine powder and coarse powder by-produced in the pulverization process, which is not only complicated, but also results in poor toner yield. This is a disadvantage that leads to increased costs. Fourthly, since the obtained toner is pulverized, it has an irregular shape, poor fluidity of the toner, carrier and photoreceptor 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 the above-mentioned disadvantages, Japanese Patent Publication No. 36-10231, Japanese Patent Publication No. 47-518305, Japanese Patent Publication No. 51-14895, and the like describe a method for producing a toner by a suspension polymerization method. Although an improvement over the noted disadvantages, there are problems associated with the suspension polymerization process.

In the suspension polymerization method, a vinyl monomer containing a coloring agent, a magnetic substance, a charge controlling agent, an anti-offset agent, etc. and a radical polymerization initiator is mixed with a water-soluble polymer, a poorly water-soluble inorganic powder, a water-soluble surfactant. A high-speed shearing force is applied by a homomixer or the like to a water phase dissolved or dispersed in water using a dispersion stabilizer such as an agent alone or in combination, and after being dispersed to a particle size of 3 to 30 μm, polymerization is carried out by heating. Then, toner particles can be obtained, but a hydrophilic suspension stabilizer adheres to the surface of the obtained toner particles and needs to be removed. On the other hand, as a suspension stabilizer, polyvinyl alcohol (hereinafter abbreviated as PVA) is useful because it is excellent in dispersibility of an oil phase in an aqueous phase and polymerization stability. Cannot be completely removed from For this reason, the electric resistance of the toner surface decreases, and the toner is easily affected by the environment.
Further, even if a charge control agent is added to the inside of the toner, the effect cannot be sufficiently exhibited. To solve these problems, JP-A-53-17736 and JP-A-59-123 have been proposed.
No. 853, JP-A-59-152446, JP-A-59-152446
No. 152452 discloses that the suspension-polymerized toner surface is treated with a silane coupling agent or a titanate coupling agent to remove the influence of the dispersion stabilizer remaining on the toner surface, thereby improving the weather resistance. Not only is the coupling agent relatively expensive, but its effect is not sufficient. JP-A-1-137268 discloses a method of treating a toner obtained by suspension polymerization with aldehydes. However, even with this method, it is difficult to completely hydrophobize the toner, although the degree of hydrophilicity is reduced. Japanese Patent Application Laid-Open No. 1-257859 discloses a method for improving the weather resistance by saponifying polyvinyl alcohol remaining on the toner surface and then treating the surface by mechanical impaction. Although this method considerably improves the environmental resistance, it is not preferable because the process is complicated.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner for developing an electrostatic charge which is excellent in electric characteristics, particularly electric resistance, triboelectricity, environmental resistance and fluidity, and which can form a clear image by a simple method. To be manufactured by

[0005]

Means for Solving the Problems In order to solve such a problem, the present inventors have intensively studied a method for removing polyvinyl alcohol used as a dispersion stabilizer during suspension polymerization in a simple step, and as a result, the present invention has been reached. That is, the present invention, as a property imparting agent , a partially saponified polyvinyl alcohol-based dispersion stabilizer polymerizable monomer containing at least a colorant , and
Partially saponified polyvinyl alcohol having a saponification degree of 70 to 90%
In a method for producing a toner for electrostatic charge development, which is subjected to suspension polymerization in an aqueous medium containing a rucohol-based dispersion stabilizer, the polymer particles obtained by adding an oil-soluble fluorine-based surfactant to a polymerizable monomer are alkali or alkaline. A method for producing a toner for electrostatic charge development, characterized by treating with an acid. According to the present invention, PVA remaining on the toner surface can be completely removed. Although the reason for this is not clear, polyvinyl alcohol used as a dispersion stabilizer during suspension polymerization is strongly adsorbed or chemically bonded to the toner surface and cannot be completely removed by repeated washing with water. Polyvinyl alcohol (hereinafter abbreviated as PVA) is particularly preferably used because partially saponified PVA has excellent dispersion stability, but the vinyl acetate portion of the partially saponified PVA serves as an adsorption site and is difficult to remove only by washing with water. Treatment with alkali or acid was found to hydrolyze the vinyl acetate moiety and remove a significant portion of the PVA, but not completely. However, by adding an oil-soluble fluorine-based surfactant to the oil phase, the adsorption force of PVA to the toner surface is weakened by the fluorine-based surfactant mainly present on the toner surface, and is easily removed by treatment with an alkali or an acid. It is thought that it will be.

Hereinafter, a method for producing a toner according to the present invention will be described. The oil phase is a main component of the toner, such as polymerizable monomers, pigments, dyes and other colorants, charge control agents and, if necessary, crosslinking agents, chain transfer agents, offset inhibitors, magnetic powders, prepolymers, oligomers and polymers, etc. And a polymerization initiator as an essential component and an oil-soluble fluorine-based surfactant which is a feature of the present invention. The components constituting the oil phase excluding the polymerization initiator are adjusted as a uniform dispersion by means such as a ball mill and a sand mill, and then the polymerization initiator is added and dissolved, and then dispersed using a homomixer ultrasonic homomixer pressure homogenizer or the like. It is dispersed and suspended in an aqueous phase by an apparatus. The aqueous phase comprises polyvinyl alcohol as a dispersion stabilizer and, if necessary, an aqueous emulsion polymerization inhibitor. The dispersion suspension is transferred to a polymerization apparatus equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe, and a thermometer, and after the replacement with nitrogen, the polymerizable monomer is polymerized by heating to form a toner. After completion of the polymerization, the toner particles are separated by filtration, centrifugal sedimentation or the like, added to an aqueous solution of an alkali or acid, heated, solid-liquid separated, and washed with water. Alternatively, the toner may be separated from the aqueous phase, washed with water, and treated with an alkali or an acid. In terms of the materials used, polymerizable monomers include styrenes such as styrene, α-methylstyrene, vinyltoluene, and parachlorostyrene; methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylic. N-butyl, alkyl (meth) acrylates such as 2-ethylhexyl (meth) acrylate, vinyl esters such as vinyl acetate and vinyl propionate, vinyl esters such as methyl vinyl ether and ethyl vinyl ether, acrylonitrile, methacrylonitrile Such as vinyl nitriles, butadiene,
Dienes such as isoprene, and vinyl halides such as vinyl chloride and vinylidene chloride are used. Also, acrylic acid, (meth) acrylic acid 2-oxyethylsuccinic acid,
A monomer having a triboelectrically functional group such as trifluoroethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, or aminostyrene may be copolymerized.

As a crosslinking agent, divinylbenzene, ethylene glycol dimethacrylate, butanediol dimethacrylate, trimethylolpropane trimethacrylate and the like are used. These crosslinking agents are used in the polymerizable monomer.
It is used in an amount of from 0.01 to 15% by weight, preferably from 0.1 to 10% by weight. Examples of the chain transfer agent include n-dodecyl mercaptan, tert-dodecyl mercaptan, and the like.
To 3% by weight. Pigments and dyes include carbon black and phthalocyanine pigments, monoazo dyes and pigments, disazo dyes and pigments, trisazo dyes and pigments,
Anthraquinone dyes and pigments are used. It is preferable to improve the dispersibility of carbon black by surface modification such as grafting, addition of a dispersant, and the like. Usable charge control agents include azo complex dyes and salicylic acid metal salts as negative charge control agents, and nigrosine dyes and quaternary ammonium salt compounds as positive charge control agents. Examples of the anti-offset agent include low molecular weight polyethylene, polyolefins such as polypropylene, paraffin wax, synthetic and natural waxes such as carnauba wax,
Fatty acid esters, fatty acid amides and the like are used. In order to improve other properties, oligomers or polymers such as epoxy resins, polyesters, and silicone resins can be dissolved or dispersed in monomers. As the magnetic powder, a fine powder such as magnetite / ferrite is used, but it is preferable to use the magnetic powder after lipophilicity by surface modification. Examples of the polymerization initiator include azo compounds such as 2,2'-azobis-2,4-dimethylvaleronitrile and 2,2'-azobisisobutyronitrile, and peroxide compounds such as lauroyl peroxide and benzoyl peroxide. Is used. These polymerization initiators may be used in the form of monomeric 0.1.
It is used in an amount of 2 to 5% by weight.

The oil-soluble fluorine-based surfactant added to the oil phase, which is a feature of the present invention, includes esters, ethers, amidesulfonamides and perfluoroalkyls having a lipophilic group such as a perfluoroalkyl group and a perfluoroalkenyl group. An oligomer having a group or a perfluoroalkenyl group can also be used. The amount of the fluorinated surfactant added to the oil phase is 0.1 to 2% by weight, preferably 0.2 to 1% by weight and 0.1% or less has no effect.
Even if it uses above, the effect does not change. Polyvinyl alcohol used as a dispersion stabilizer is particularly preferably a saponification degree of 70 to 90.
% And a viscosity (20 ° C., 4%) of 5 to 60 cps are preferred. The polyvinyl alcohol concentration in the aqueous phase is 0.1 to
3% by weight, preferably 0.5 to 3% by weight, and the ratio of the oil phase to the aqueous phase is preferably 1/10 to 5/10. As the alkali used for the treatment of the toner after the polymerization, an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide is preferably used. The concentration of the alkali metal hydroxide is 0.1N to 1.N.
0N, hydrochloric acid or sulfuric acid is used as the acid. The concentration of the acid is the same as in the case of the alkali. Further, at the time of saponification, an alcohol such as methanol or ethanol may be added. The saponification temperature is 20 ° C to 70 ° C, preferably 30 ° C to
At 50 ° C., the treatment time is 0.5 to 10 hours. After saponification, if necessary, neutralize with acid or alkali and wash with water,
After drying, a toner is obtained.

[0009]

Embodiments will be described below with reference to embodiments. Parts represent parts by weight. Example 1 15 parts of carbon black (manufactured by Raven 410 Columbia Chemicals) and 0.25 parts of 2,2'-azobisisobutyronitrile were added to 30 parts of styrene, and the mixture was replaced with nitrogen.
For 6 hours. After cooling, 92 parts of styrene and 53 parts of n-butyl methacrylate were added and uniformly dissolved. This carbon black dispersion is charged with a charge control agent (Spiron Black TR
H Hodogaya Chemical Co., Ltd.)
Time dispersed. Take 40 parts of this dispersion, add and dissolve an oil-soluble fluorine-based surfactant (MegaFac F172, manufactured by Dainippon Ink) and 1 part of 2,2'-azobis-2,4-dimethylvaleronitrile, and dissolve the oil phase. Was prepared. On the other hand, 3.2 parts of partially saponified polyvinyl alcohol (Kurarepovar 217E) was dissolved in 156.8 parts of ion-exchanged water to prepare an aqueous phase. The oil phase was added to the aqueous phase and dispersed at 4,000 rpm for 10 minutes with a TK homomixer (manufactured by Tokushuki Kagaku Kogyo Co., Ltd.). The mixture was heated and stirred at 8 ° C. for 8 hours. After the polymerization, the polymer particles were separated from the aqueous phase by centrifugal sedimentation, added to 100 parts of a 0.75 N aqueous sodium hydroxide solution, and heated at 40 ° C. for 1 hour with stirring. After cooling, the mixture was filtered with suction to obtain polymer particles.
Vacuum drying was performed at 0 ° C. to obtain a toner. This toner has an average volume particle size of 10.1 μm and a volume resistivity of 5.0 × 10 ¹⁰ Ω.
cm, and the charge amount was -20.5 μc / g. 3% of the obtained toner is mixed with a silicone-coated carrier,
When a development test was conducted at T5510 under conditions of 90% RH and 30 ° C., a clear image was obtained.

Example 2 After suspension polymerization under the same conditions as in Example 1, polymer particles were separated from the aqueous phase by centrifugal sedimentation, added to a 0.8 N aqueous sulfuric acid solution, and heated at 40 ° C. for 10 hours with stirring. . Thereafter, washing and drying were performed in the same manner as in Example 1. The volume average particle diameter of the obtained toner is 10.0 μm, and the volume resistivity is 4.8 × 10
^The charge amount at ¹⁰ Ωcm was −19.2 μc / g. A developer was prepared in the same manner as in Example 1, and a development test was performed under the same conditions. As a result, a clear image was obtained.

Example 3 A toner was obtained in the same manner as in Example 1 except that the oil-soluble fluorine-based surfactant was changed to Megafac F183 (manufactured by Dainippon Ink). This toner has a volume average particle size of 9.8 μm and a volume resistivity of 4.5 × 10 ¹⁰ Ωcm.
The charge amount at% RH was -18.9 μc / g. A developer was prepared in the same manner as in Example 1, and a development test was performed under the same conditions. As a result, a clear image was obtained.

Comparative Example 1 A toner was obtained in the same manner as in Example 1, except that no oil-soluble fluorine-based surfactant was added. This toner has a volume average particle size of 9.7 μm and a volume resistivity of 8.8 μm.
The charge amount at 0 × 10 ⁹ Ωcm, ° C.% RH is -16.
It was 5 μc / g. In a development test similar to that in Example 1, an unclear image having a low image density was obtained.

Comparative Example 2 A toner was obtained in the same manner as in Example 1 except that the heat treatment with alkali was not performed. The particle size of this toner is 9.8 μm, and the volume resistivity is 5.2 × 10 ⁹ Ωcm.
In a development test similar to that of Example 1, an unclear image having a low image density was obtained with a charge amount of -15.0 μc / g.

[0014]

As described above, according to the present invention, an oil-soluble fluorine-based surfactant is added to an oil phase comprising a polymerizable monomer containing a colorant or other property imparting agent, and a partially saponified polyvinyl alcohol is added. Is used as a dispersion stabilizer, polymerized particles obtained by suspension polymerization in an aqueous medium are heated with an alkali or acid aqueous solution, and are subjected to saponification to provide excellent environmental resistance and triboelectric charging in a simple manner. Toner can be obtained.

Claims (2)

(57) [Claims] 1. A method for producing a toner for electrostatic charge development in which a polymerizable monomer containing at least a colorant as a property imparting agent is suspension-polymerized in an aqueous medium containing a partially saponified polyvinyl alcohol-based dispersion stabilizer. A method for producing a toner for electrostatic charge development, comprising treating an polymer particle obtained by adding an oil-soluble fluorine-based surfactant to a polymerizable monomer with an alkali or an acid. 2. A partially saponified polymer having a saponification degree of 70 to 90%.
Claims characterized by using a vinyl alcohol
2. A method for producing a toner for electrostatic charge development according to item 1.