Patent ID: 6149843
Filing Date: 2000-11-21
Classification: A01N,B01J

Abstract:
A process for preparing urea formaldehyde polymer or polyurea microcapsules containing a liquid comprising an effective amount of a particulate ultraviolet light protectant selected from titanium dioxide, zinc oxide and mixtures thereof suspended and thoroughly dispersed in the liquid, comprising the steps of (a) preparing a suspension of the protectant having an average particle size of from about 0.01 to about 2 microns in an organic liquid which is immiscible with water and a dispersant which serves to disperse the ultraviolet light protectant in the organic liquid, and to keep it in said liquid, but which does not allow it to be extracted into water, in which the protectant is thoroughly dispersed in the organic liquid; (b) introducing the suspension into water containing a protective colloid and optionally a surfactant capable of maintaining the organic liquid as droplets in the water without extracting the protectant from the organic liquid into the water, the organic liquid containing in solution one or more prepolymers which can react to form a polymer at the interface of the organic liquid and water; (c) mixing the suspension of organic liquid in the aqueous phase under high shear to form an oil in water emulsion; and (d) adjusting as necessary the temperature and/or pH of the oil in water emulsion such that a polymerization reaction takes place at the organic liquid/water interface to form the microcapsules.