Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2000-05-01
2001-05-15
Martin, Roland (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
Reexamination Certificate
active
06232030
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for manufacturing a toner usable in electrophotographic method, electrostatic printing method, magnetic recording method, and the like.
BACKGROUND ART
Elements relating to the performance of color toners include color strength and transmittance. Although the color strength and the transmittance are affected by the amount of a colorant, these properties are also greatly affected by the dispersibility of the colorant in the color toner particles. In a process for manufacturing a color toner by pulverization method, the dispersion states of the various raw materials in the color toner particles are substantially determined by the steps of mixing raw materials, and kneading the mixture.
In order to solve the above problem, Japanese Patent Laid-Open No. Hei 6-161154 discloses a technique for dispersing a water-insoluble dye and/or pigment in a resin binder by flushing method. In addition, Japanese Patent Laid-Open No. Hei 6-11895 discloses a technique of a melt-kneading process divided into two steps, comprising granulating a raw material mixture in the first kneading step; and adding additives such as a resin binder to dilute and mix the mixture in the second kneading step. However, in these attempts, there also arise some problems that specialized plurality of steps are necessitated, and that the number of steps are very large, thereby making the process complicated.
In addition, in a process using an extruder as that described in Japanese Patent Gazette No. 2677685, there arises a problem that sufficient dispersion of a colorant, a charge control agent, a wax, and the like required for a color toner cannot be carried out as the temperature of the composition increases by kneading heat.
Also, there are numerous prior arts disclosing that a wax is used as an offset inhibitor by blending it in the toner. However, as the amount of the wax blended increases, the wax in the toner is poorly dispersed, so that the wax deposits on the photoconductor in the developer device, and that the level of the triboelectric charges is lowered with the passage of time, thereby making it less likely to carry out stable development.
In order to solve these problems, Japanese Patent Laid-Open No. Hei 6-161153 discloses a technique of kneading the mixture at a set temperature (Ts), wherein the set temperature is within the range of Tm−20° C.≦Ts≦Tm+20° C., wherein Tm is a melting temperature of the resin binder. However, in order to sufficiently disperse the wax blended into the toner, it is necessary to apply a strong kneading force. When a twin-screw kneader described in Japanese Patent Laid-Open No. Hei 6-161153, since the temperature of the kneaded mixture increases by 20° to 60° C. or so from the set temperature owing the generated kneading heat, the wax is re-agglomerated, and a strong kneading force cannot be applied, so that there arises a defect that a toner having excellent dispersibility of the wax cannot be obtained. Especially, this phenomenon is markedly found when a wax having a low melting point (83° C.), such as carnauba wax, is used. On the other hand, when the set temperature is lowered in consideration of the kneading heat, there arises a defect that the resin does not melt, so that kneading cannot be carried out.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a process for manufacturing a toner having excellent dispersibility of a colorant and/or a wax, and a process for manufacturing a toner in which the dispersibility of the charge control agent and the wax is controlled.
These objects and other objects of the present invention will be apparent from the following description.
Specifically, the present invention relates to:
[1] a process for manufacturing a toner comprising the step of melt-kneading a composition comprising a resin binder and a colorant using an open roller-type continuous kneader having heating and cooling functions;
[2] the process according to item [1] above, wherein a plurality of feed openings are provided for melt-kneading along a shaft direction of a roller of the kneader, and wherein melt-kneading is carried out by continuously feeding 6 to 70% by weight of a resin binder to be blended at a position of 0 L to 0.5 L from a roller end at inlet side of the kneader, L being a roller length, and continuously feeding 50 to 100% by weight of a colorant at a position 0 L to 0.5 L;
[3] the process according to item [1] above, wherein a composition comprising a resin binder, a colorant, and a wax, wherein the content of the wax is 3 to 20 parts by weight, based on 100 parts by weight of the resin binder, is melt-kneaded using the kneader under the conditions that a temperature of a kneaded mixture during melt-kneading is [Tm−20° C.] to [Tm+20° C.], wherein Tm is a melting temperature of the resin binder; and
[4] the process according to item [1] above, wherein a plurality of feed openings are provided for melt-kneading along a shaft direction of a roller of the kneader, and wherein melt-kneading is carried out by continuously feeding a kneaded mixture previously prepared by melt-blending a colorant with a resin binder, a resin binder, and a charge control agent, at a position of 0 L to 0.9 L from a roller end at inlet side of the kneader, L being a roller length.
BEST MODE FOR CARRYING OUT THE INVENTION
The resin binder usable in the present invention is not particularly limited, and those known resin binders for black toners or for color toners can be used. For instance, there may be used resin binders such as polyester resins and vinyl resins described at Page 3, Column 4, Line 37 to Page 6, Column 10, Line 10 of Japanese Patent Laid-Open No. Hei 7-98518; and resin binders obtained by mixing a releasing agent with a raw material monomer mixture, and carrying out polymerization reaction.
The content of the resin binder is preferably from 55 to 98% by weight, more preferably from 80 to 95% by weight, of the composition.
The colorant is not particularly limited, and those known colorants for black toners or for color toners can be used. The colorant includes black colorants, yellow pigments, red or crimson pigments, blue pigments, green pigments, and the like, and these colorants may be used alone, or in admixture of two or more kinds.
The content of the colorant is preferably from 2 to 15% by weight, more preferably from 3 to 10% by weight, of the composition.
In addition, the open roller-type continuous kneader having heating and cooling functions usable in the present invention includes an open roller-type continuous kneader comprising two rollers provided in proximity with and in parallel to each other. Each roller can be heated or cooled by passing through a heating medium. Specifically, one roller is a heat roller, and the other roller is a cooling roller, to thereby carry out temperature regulation.
The gap between the two rollers is preferably from 0.1 to 10 mm, more preferably from 0.1 to 3 mm. The structure, the size, the material, and the like of each roller is not particularly limited, and the roller surface may be smooth, or it may be wavy or rugged.
In addition, the number of rotations of the roller is preferably at a peripheral speed of from 2 to 100 m/min, and the ratio of the number of rotations of two rollers (number of rotations of the cooling roller
umber of rotations of the heat roller) is preferably from 1/10 to 9/10.
Also, a desired kneading force can be obtained by appropriately adjusting the kneading temperature and the number of rotations of the roller.
Incidentally, in order to feed the raw materials into the open roller-type continuous kneader, there may be employed, for instance, a table feeder, and the like.
In addition, before feeding the raw materials, each of the raw materials may be previously mixed by using a mixer. The mixer is not particularly limited, and the mixer include high-speed agitation mixers such as Henschel mixer (manufa
Hattori Toshihiro
Otani Yasuhisa
Birch & Stewart Kolasch & Birch, LLP
Kao Corporation
Martin Roland
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