Oce-van Der Grinten N.v.

Wilhelmus J VanRhijn

Roelof R Hendriksma

Toner powders having excellent flow and non-agglomerating properties, and being readily removable from the imaging medium in use for indirect electrophotographic copying, are provided in the form of substantially spherical resin particles, containing additives or not as desired, which particles have been formed from irregularly shaped resin particles heated in a liquid dispersion containing hydrophobic silica particles smaller than 100 nanometers in diameter. The toner particles may be thus formed so as to carry on their surface or dispersed therein electrically conductive particles, such as carbon black, rendering them attractable by electrical inductance. The toner can be prepared simply by heating and stirring irregularly shaped resin particles and hydrophobic silica particles in a liquid carrier, such as water or a mixture of water and a water miscible organic solvent, that does not dissolve the resin, with heating to a temperature at which the resin particles soften until they become spherical or almost so, followed by cooling of the dispersion and separating and drying the toner particles.

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Venlo, Netherlands

Wilhelmus J VanRhijn