Method of preparing microcapsules

Abstract

Void-containing microcapsules are prepared by a method featuring gellation of an organic polymer with the simultaneous precipitation of an organic liquid non-solvent. The method involves the preparation of a solution containing an organic polymer, a good solvent for the polymer and an organic liquid non-solvent which is miscible with the polymer solvent. The solution is then atomized into a bath containing a liquid which is miscible with the good polymer solvent but which is immiscible with the organic liquid non-solvent. The bath liquid extracts out the good polymer solvent, causing gellation of polymer around discrete droplets of the organic liquid non-solvent, which simultaneously precipitates out of the solution as the good polymer solvent is extracted, thereby producing microcapsules having encapsulated therein the non-solvent. The organic liquid non-solvent can then be removed as by evaporation to provide void-containing microcapsules. These void-containing microcapsules may be employed as opacifying agents. In addition to producing void-containing microcapsules, this method can be utilized to produce microcapsules in which pigments are entrapped in the voids or the polymeric walls of the microcapsules or in which certain non-solvents which serve a secondary function remain entrapped in the microcapsules. Such non-solvents include, for instance, vitamins, minerals, biocides, perfumes, chemical reactants, fertilizers, and the like.