Aggregation Behaviors of Colloidal Particles for Production of Polyester-Based Chemically Prepared Toner

High performance, full color electrophotographic printers are gaining acceptance in many office environments. In this study, we controlled the aggregation of three different colloidal dispersions using four different multivalent metallic coagulants over a wide pH range to develop a polyester-based chemically prepared toner (CPT). The quantity of the each metallic coagulant required to achieve a narrow particle size distribution at the target mean aggregate size reached an optimum operation limit that, when exceeded produced a viscous, inoperative, sludge in the reactor. The optimal pH condition for each coagulant system was mainly dependent on the electrostatic balance produced by the deprotonation of the exposed carboxylic acid groups on the polyester resin particles at a pH between 5.5 and 6.5. Additional electrostatic interactions between the polyester colloidal dispersions and the monovalent cation (M1⁺) metallic coagulation system at high electrolyte concentrations created a favorable environment to reproduce core-toner particles with a narrow particle distribution at the target mean size.

By manipulating the aggregation process, the individual nano-dispersions coalesced in an aqueous environment to form a polyester-resin based chemical toner that was uniform in particle size and had low total VOC level. The printing and image performance of this toner using a color laser printing system meet the specifications of major OEM printer engine manufactures.