Method of encapsulating finely divided solid particles and stable suspensions prepared thereby

Finely divided water-insoluble solid particles free of ionic charge, of about 0.01 µm upward, for example paint pigments, are uniformly encapsulated by admixing them, in an aqueous medium, with a water-insoluble monomer polymerizable to form a water-insoluble polymer free of ionic charge, in the presence of a non-ionic surface-active stabiliser, preferably a polyethoxylated alkyl phenol (at least C8-alkyl and preferably at least 40-50 EO groups), and then Initiating polymerization, usually with heating, with a redox system free of anionic groups. Naturally agglomerated particulate materials are effectively dispersed in situ during polymerization, thus eliminating preliminary grinding and/ or dispersion. Normal emulsion polymerisation conditions may be used, with usual emulsion-polymerization monomers free of ionic groups. The product is a suspension of polymer-encapsulated discrete particles exhibiting remarkable stability against flocculation or settling. White paint pigments, e.g. TiO., thus encapsulated exhibit increased hiding power, and colored pigments exhibit greater brilliance and color-depth in dried paintfilms. In both cases, the film has improved abrasion-resistance, and improved stain- resistance due to reduced porosity, as compared with conventional latex paints.