Formation of microcapsules by interfacial cross-linking of emulsifier, and resulting microcapsules

A process for the formation of pressure-rupturable, oil-containing microcapsules, which comprises admixing:

• (A) a water-immiscible, oily material containing a capsule wall-forming material consisting essentially of an oil-soluble, non-polymeric cross-linking agent selected from the group consisting of a polyfunctional isocyanate and an orthoester of a Group IV element;
• and
• (B) an aqueous solution of an organic, polymeric, emulsifying agent comprising starch having ether-linked aralkyl groups,
• said admixing being conducted under conditions to form an oil-in-water emulsion, wherein said oily material containing said cross-linking agent is dispersed in the form of an oil phase of microscopic, oily emulsion droplets in an aqueous, continuous phase, said emulsifying agent aiding in the formation of said emulsion and possessing cross-linkable hydroxyl groups capable of reacting with said cross-linking agent to form a cross-linked capsule wall at the oil/water interface, reacting said cross-linking agent with the hydroxyl groups of said polymeric emulsifying agent thereby surrounding each of said droplets with a solid, cross-linked capsule wall, said polymeric emulsifying agent being the major wall former, said emulsifying agent being employed in a ratio of at least one part by weight of said polymeric emulsifying agent per part by weight of said cross-linking agent.