PURPOSE: To obtain spherical particles having submicron diameters and suitable for use under high speed high pressures by emulsifying a solution containing cellulose triacetate and a surfactant in a soluble solvent in an aqueous medium. removing the solvent for forming particles. and subsequently saponifying the particles.

CONSTITUTION: A solution containing cellulose triacetate and a surfactant in a soluble solvent is emulsified in an aqueous medium, and subsequently subjected to the removal of the soluble solvent to produce the particles of the cellulose triacetate. which are hydrolyzed. The cellulose triacetate has preferably an acetylation degree of 60%, and the solvent is preferably dichloromethane. The surfactant is preferably a polyglycerol acid ester.