| abstract |
Titanium dioxide particles are dispersed in an aqueous medium with a polymeric latex which adsorbs to the surface of the titanium dioxide to give a low-viscosity slurry or pigment grind of composite titanium dioxide-polymeric latex particles. A high glass transition polymeric latex can be used as the dispersant, and a low glass transition temperature binder latex can be added. The zeta potential of the polymeric latex can be at least about 30 millivolts more negative than the zeta potential of the titanium dioxide. The adsorbed polymeric latex provides more optimal spacing of the titanium dioxide particles in films formed from coating compositions formulated using the composite particles, and consequently greater film opacity and hiding at a given pigment volume concentration. Coatings formulated using the composite particles can be prepared to give the same hiding as coatings including titanium dioxide dispersed with conventional polyelectrolyte pigment dispersants, but with lower levels of costly titanium dioxide. Alternatively, a single selected polymeric latex can be used to both strongly adsorb to the pigment particles and to serve as binder, or a mixture of a selected, strongly adsorbing polymeric latex having a low effective glass transition temperature and a conventional binder latex can be employed. |