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AssigneeAgfa-Gevaert
InventorsDaniel Maurice Timmerman, Victor Jan Thijs, Walter Frans De Winter, Frans Henri Claes, Hubert Vandenabeele
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Polymeric particles are homogeneously dispersed in aqueous medium by a process which comprises dissolving a water-insoluble film-forming polymer in a water-insoluble, ethylenically unsaturated monomer which is liquid at room temperature. The solution formed is dispersed by stirring in an aqueous solution of a hydrophilic colloid and of a dispersing agent, stirring being continued until a stable dispersing of polymer-in-monomer solution droplets having a diameter between 1 and 10 microns, preferably between 1 and 6 micron, in said aqueous solution is obtained. While continuously stirring the dispersion in the presence of a free-radical forming polymerisation initiator, the dispersion is heated at the decomposition temperature of said polymerisation initiator to effect polymerisation of the water-insoluble, liquid monomer and to form an aqueous dispersion of solvent-free polymer particles. The homogeneously dispersed polymer particles are used in hydrophilic coating compositions as matting agents, particularly in protective layers for photographic materials formed of these hydrophilic coating compositions.
Hydrophilic coating composition containing an aqueous binder solution and a homogeneous aqueous dispersion of polymer particles, said dispersion prepared by dissolving a water-insoluble, film-forming polymer in a water-insoluble ethylenically unsaturated monomer which is liquid at room temperature to provide a solution thereof, dispersing by stirring the solution thus formed in an aqueous solution of a hydrophilic colloid and dispersing agent, the stirring being continued until a stable dispersion of polymer-in-monomer solution droplets having a diameter between 1 and 10 micron is formed in said aqueous solution and, while continuously stirring in the presence of a free-radical forming polymerization initiator, heating the dispersion to the decomposition temperature of said polymerization initiator to effect polymerization of said water-insoluble liquid monomer and to form an aqueous dispersion of solvent-free polymer particles, said unsaturated monomer being selected so as to be a solvent at room temperature for said film-forming polymer, and to provide upon said polymerization in the presence of said film-forming polymer, polymer particles having a glass transition temperature of at least 60.degree.C., and said binder of said aqueous binder solution when in an aqueous solution being compatible with said dispersion.
Dependencies are inferred from the claim text.