Pigment encapsulation by emulsion polymerisation,redespersible in water

Emulsion Polymerization was carried out in the presence of inorganic pigments such as TiO2, black FexOy, yellow FexOy, and red FexOy, and NP 30 as surfactants, and water soluble AZO compounds or KPS as initiator. Monomers with specific hydrogen bonding interaction must be used in the initial steps of polymerisation, methylmethacrylate and vinylacetate being the most convenient. Then a semi continuous feed of a mixture of monomers was carried out in starved conditions. In order to make the covered pigments water-redispersible a mixture of hydrophobic and hydrophilic monomers should be chosen with proper pH conditions. The amount of surfactant has to be chosen so that no agglomeration of the covered pigments take place. The covered pigments were dried upon lyophylisation, then formulation of powder paints was carried out using commercial powder binders and other additives. Good properties of the paints, such as brightness were obtained in that way.