Encapsulation by cross-linking of anionic polymers by ph induced dissociation of cation-chelate complexes

Abstract

Microencapsulation methods are provided using encapsulant, fiber or film forming compositions of a cross-linkable anionic polymer, a multivalent cation salt, a chelating agent, and a volatile base. During the formation of this composition, the generally acidic chelating agent is titrated with a volatile base to an elevated pH to improve ion-binding capability. Multivalent cations are sequestered in cation-chelate complexes. Cross-linkable polymers in this solution will remain freely dissolved until some disruption of equilibrium induces the release of the free multivalent cations from the cation-chelate complex. Vaporization of the volatile base drops the pH of the solution causing the cation-chelate complexes to dissociate and liberate multivalent cations that associate with the anionic polymer to form a cross-linked matrix. During spray-drying, the formation of a wet particle, polymer cross-linking, and particle drying occur nearly simultaneously.