Production apparatus of toner for developing electrostatic images, production method thereof, and toner for developing electrostatic images

#This invention relates to a production method and production apparatus of a toner for developing electrostatic images. To state it in more detail, this invention relates to a production method and a production apparatus of a toner for developing electrostatic images wherein toner particles are obtained through a process of practicing the removal of impurities attached to the surface of toner particles by the concentration of the slurry composed of particles produced at the time of toner particle production, and to a toner for developing electrostatic latent images obtained by said production method.

#In recent years, it is disclosed in the publication of the unexamined patent application 2000-214629 that, as regards a toner obtained by a polymerization process based on a suspension polymerization method or an emulsion polymerization method, because the particle diameter and shape can be controlled during polymerization process in an aqueous medium, it can be obtained a toner composed of toner particles having a small size, a uniform size distribution, and a round shape with no protrusion on the particles; because of its reproducibility of fine lines and a high resolution, it is remarked as a toner capable of reproducing small dots for a digital image.

#As described in the above, as regards a polymerization toner, toner particles are produced by a polymerization process in an aqueous medium, and from particles produced in a slurry state, toner particles dispersed in an aqueous medium are obtained. In order to extract the produced toner particles from the aqueous medium, slurry concentration for removing water from the aqueous medium in a slurry state containing particles is repeated. In the aqueous medium which is a dispersion medium of the slurry of dispersed particles, impurities such as free releasing agent particles and particles of their decomposition products leaving from the surface of the toner particles are contained. Therefore, because these impurities are adhering on the surface of the toner particles separated from the aqueous medium, it is necessary that the toner particles after separation are well washed to remove these impurities from the surface of the toner particles.

#FIG. 1 is a structural drawing of a cross-section of a centrifugal precipitating apparatus of a disk type to be desirably used in this invention;

#FIG. 2 is a drawing showing the movement of particles in slurry and a dispersion medium containing impurities in a centrifugal precipitating apparatus of a disk type to be used in this invention;

#FIG. 3(a) and FIG. 3(b) each is a drawing showing the automatic discharging caused by the opening and closing of the junction portion of a centrifugal precipitating apparatus of a disk type to be used in this invention;

#A centrifugal precipitating apparatus of a disk type to be used desirably as a concentration means according to this invention makes toner particles in slurry in a moment precipitate by the action of a centrifugal force to carry out slurry concentration, and at the same time, automatically discharges the concentrated slurry out of the apparatus.

#It has already been stated that the idea of this invention was found by the inventors remaking the difference in the specific weight between the toner particles and the impurities in the slurry. That is, the inventors remarked that the specific weight of the impurities composed of free releasing agent particles etc. remaining on the surface of particles is not so much different from the specific weight of water, and found that it is possible to remove the impurities from the surface of particles with certainty even with the precipitation distance of particles made shorter by a large margin on the premise of the difference in the specific weight between the both.

#FIG. 1 shows an example of a centrifugal precipitating apparatus of a disk type to be desirably used in this invention, and is a cross-sectional view of the main body of said apparatus at a plane containing its axis.