Formation of microcapsules by interfacial cross-linking, microcapsules produced, and microcapsular dispersion

摘要

Pressure-rupturable, oil-containing microcapsules are produced by admixing a water-immiscible, oily material containing an oil-soluble, non- polymeric polyfunctional isocyanate cross-linking agent, and an aqueous solution of a polymeric emulsifying agent in the form of a water- soluble polymer containing recurring --NH.sub.2 or ═NH groups or a water- soluble natural gum containing recurring hydroxy groups. An oil-in- water emulsion is formed containing the isocyanate dispersed in the form of microscopic emulsion droplets in the aqueous continuous phase containing the emulsifying agent, and a solid capsule wall is formed by the cross- linking of the emulsifying agent by the isocyanate. Emulsions utilizing the natural polymeric emulsifying agents preferably contain a viscosity lowering agent in the form of a urea-formaldehyde or alkali metal periodate in order to obtain a higher solids coat weight while at an efficient coating viscosity.