Melamine formaldehyde microencapsulation in aqueous solutions containing high concentrations of organic solvent

Abstract

A process for making melamine-formaldehyde microcapsules in an aqueous solution containing a high concentration of a water miscible or water soluble organic solvent is provided. The aqueous solution is prepared and a water insoluble melamine-formaldehyde pre-condensate is dissolved therein by adjusting the temperature and organic solvent concentration of the aqueous solution such that the melamine-formaldehyde pre-condensate is barely soluble therein. A substance to be encapsulated, preferably an oily solution containing a dyestuff precursor, is dispersed into the aqueous solution to form an emulsion, the melamine-formaldehyde pre-condensate being insoluble in the substance to be encapsulated. The melamine-formaldehyde pre-condensate is separated from the aqueous solution onto droplets of the substance to be encapsulated and the self-condensation reaction of the phase-separated melamine-formaldehyde pre-condensate initiated to form capsule walls around the droplets, thereby producing melamine-formaldehyde microcapsules in the aqueous solution containing a high concentration of a water miscible or water soluble organic solvent.

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