Process for coating pigment particles with organic polymers

Claim 1

A PROCESS FOR THE COATING OF TITANIUM DIOXIDE PIGMENT PARTICLES TO FORM DISCRETE PIGMENT PARTICLES INDIVIDUALLY COATED WITH ORGANIC POLYMERS WHICH COMPRISES THE STEPS OF: A. ADDING TO A WATER SLURRY OF TITANIUM DIOXIDE PIGMENT PARTICLES WHEREIN SAID PARTICLE COMPRISE 70% BY WEIGHT OF SAID SLURRY, A POLYANIONIC DISPERSING AGENT SELECTED FROM THE GROUP CONSISTING OF SODIUM HEXAMETAPHOSPHATE, POTASSIUM TRIPOLYPHOSPHATE, AND SODIUM SALT OF POLYCARBOXYLIC ACID IN AN AMOUNT EQUIVALENT TO THE DISPERSANT DEMAND OF THE PARTICLES TO FORM A WATER DISPERSION WHEREIN THE DISPERSANAT DEMAND IS FROM A WATER DISPERSION WEIGHT PERCENT OF THE AMOUNT OF PARTICLES AND THEREBY MAINTAINING SAID DISPERSANT AT A MINIMUM VISCOSITY; B. DILUTING SAID WATER DISPERSION WITH AN AQUEOUS MEDIUM UNTIL SAID PARTICLES COMPRISE FROM 15 TO 30% BY WEIGHT OF SAID DISPERSION; C. ADDING AN ANCHORING AGENT TO SAID DISPERSION; SAID ANCHORING AGENT COMPRISING AN ORGANIC VINYL MONOMER CONTAINING POLAR GROUPS WHICH ARE ADSORBED ON THE SURFACE OF SAID PARTICLES; SAID ANCHORING AGENT BEING CAPABLE OF POLYMERIZATION WITH VINYL MONOMERS; D. ADDING AN ORGANIC VINYL MONOMER TO SAID DISPERSION; E. POLYMERIZING SAID MONOMER AND SAID ANCHORING AGENT IN THE PRESENCE OF A POLYMERIZATION CATALYST THEREBY COATING SAID INDIVIDUAL AND DISCRETE PIGMENT PARTICLES WITH THE FORMED ORGANIC POLYMERS; F. AND FILTERING AND DRYING THE PRODUCT OF STEP (E).