Processes for preparing an aqueous dispersion of composite particles to prepare an aqueous composition aqueous dispersion of composite particles coating composition pigment suspension and process for preparing an aqueous dispersion of composite particles

摘要

Inorganic material particles such as titanium dioxide (10) pigment particles (12) are dispersed in an aqueous medium with a polyelectrolyte pigment dispersant (20). A selected, relatively hard, polymeric latex (40), which adsorbs onto the surface of the inorganic material particles in the presence of the pigment dispersant, is added, as well as a film-forming binder (64) to give a formulated coating composition. The strongly adsorbing polymeric latex can include residues of polymerized itaconic acid or dihydrogen phosphate functional groups, or have a high level of acid functional groups or acid functional groups distributed preferentially at the surface of the latex. The adsorbed latex particles space the inorganic particles apart in the coating film (60), improving performance properties. Alternatively, a single selected polymeric latex is 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 is employed.