Encapsulated solid hydrophilic particles

Abstract

A process of forming a population of microcapsules is described comprising a solid hydrophilic core material and a wall material at least partially surrounding the core material. The microcapsule population is formed by providing an anionic, or optionally a cationic, solid hydrophilic core material; providing an oil continuous phase which is low boiling and preferably nonflammable, the oil continuous phase comprising one or more esters with chain length up to about 18 carbons. A mixture is formed by dispersing the solid hydrophilic material in the oil continuous phase. Either an oil soluble or dispersible amine acrylate or methacrylate, along with acid, or alternatively acid acrylate or methacrylate along with base is added. A multifunctional acrylate or methacrylate monomer or oligomer is provided and an initiator. Optionally a surfactant is also added to form the mixture. Emulsification is achieved by subjecting the mixture to high shear agitation and heating the mixture for a time sufficient to enable the acid or amine acrylate or methacrylate and the multifunctional acrylate or methacrylate to form a prepolymer which migrates to the anionic or cationic solid hydrophilic material, thereby forming prepolymers adhered to the hydrophilic core materials. Temperature is held or heating continued for a time sufficient to enable the prepolymer to flow onto and coalesce into a continuous film surface coating on the hydrophilic core material. Heating is carried out or light exposure or both for a time and temperature sufficient to cross link the prepolymers.