Abstract: The method of decreasing unreacted monomer in vinyl polymer of the present invention is a method comprising adding a water-soluble inorganic salt that is able to solubilize unreacted monomer contained in vinyl polymer to an aqueous dispersion in which particles of vinyl polymer are dispersed in an aqueous medium, followed by solubilizing the unreacted monomer and removing the unreacted monomer together with the aqueous medium. According to this method, the amount of unreacted monomer present in a polymer can be efficiently and reliably decreased at low cost without requiring a special apparatus or thermal energy, etc. In addition, the toner resin of the present invention has for its constituent component a vinyl polymer in which the amount of unreacted monomer has been decreased by the method described above.

Abstract: A negatively chargable toner for electrophotography, comprising a binder, a coloring agent and a charge control agent, the charge control agent comprising a copolymer of 1 to 30% by weight of a sulfoalkyl (meth)acrylic acid monomer represented by a specific chemical formula and 99 to 70% by weight of other vinyl monomer copolymerizable therewith, the amount of the charge control agent being from 0.1 to 10 parts by weight for 100 parts by weight of the binder. The toner can be charged immediately, can stably maintain the toner properties, in particular, under the conditions of high temperatures and high humidities, can produce a good image that is free from toner scattering, fogging and the like, and can be made into a color toner capable of clearly forming a colored image.

Abstract: A process for producing a composite resin for a toner, comprising the steps of: mixing, in water, (a) a low-molecular weight polymer powder comprising particles, not less than 80% by weight of the particles having a diameter of from 20 to 2000 microns with (b) a high-molecular weight polymer emulsion; subjecting the thus obtained mixture to a coagulation treatment; and heating the resulting mixture to obtain a composite resin in which the low-molecular weight polymer particle and the high-molecular weight polymer are fixed and homogeneously mixed with each other.

Abstract: A process for producing a resin composition which comprises suspension-polymerizing at least one vinyl monomer in an aqueous medium in the presence of a dispersing agent, said suspension polymerization being carried out using a nonionic dispersant as said dispersing agent in the presence of a high-molecular-weight vinyl polymer having a weight average molecular weight of at least 500,000 obtained by emulsion polymerization.