Method of forming fine polymer particles and polymer-encapsulated

Abstract

A polyamide polymer and one of methanol, ethanol and 2-propanol are formed into a solution by heating at 70 degrees Celsius for approximately two hours, the resulting solution is cooled to precipitate the polymer as particles from said solution. Alternatively, a non-solvent to said polymer may be added to effect precipitation of said polymer particles. The solvent is removed and the particles isolated and dried to form a dry powder. Fine particulate material such as a pigment, may be included with the polymer and solvent in formation of the solution. The resulting solution may be cooled at a rapid rate to precipitate the particles as polymer-encapsulated pigment particles of generally uniform size and morphology, the surface characteristics such as surface area being controlled. The precipitated polymer particles may be classified when dispersed in a dispersant medium, as mono-dispersed particles. The polymer-encapsulated pigment particles are isolated, dried and may be redispersed in a dispersant medium along with a charge control agent and a steric stabilizer to form a liquid toner for electrophotographic imaging. Alternatively, the solvent can be removed by washing with a non-solvent, the charge control agent added with the dispersant to form the liquid toner. Particles other than pigment may be polymer-encapsulated using the precipitation method disclosed. The non-solvent may be any solvent which has a poor thermodynamic quality for the polymer.