Method for producing an aqueous dispersion of particles composed of a polymer and a fine-particle inorganic solid

A process for preparing an aqueous dispersion of particles composed of addition polymer and finely divided inorganic solid (composite particles), in which process at least one ethylenically unsaturated monomer is dispersely distributed in aqueous medium and is polymerized by the method of free-radical aqueous emulsion polymerization by means of at least one free-radical polymerization initiator in the presence of at least one dispersely distributed, finely divided inorganic solid and at least one anionic, cationic and nonionic dispersant, wherein

• a) a stable aqueous dispersion of said at least one inorganic solid is used, said dispersion having the characteristic features that at an initial solids concentration of ≧1% by weight, based on the aqueous dispersion of said at least one inorganic solid, it still contains in dispersed form one hour after its preparation more than 90% by weight of the originally dispersed solid and its dispersed solid particles have a diameter ≦100 nm,
• b) the dispersed particles of said at least one inorganic solid exhibit a nonzero electrophoretic mobility in an aqueous standard potassium chloride solution at a pH which corresponds to the pH of the aqueous reaction medium before the beginning of dispersant addition,
• c) at least one anionic, cationic or nonionic dispersant is added to the aqueous solid-particle dispersion before the beginning of the addition of said at least one ethylenically unsaturated monomer,
• d) then from 0.01 to 30% by weight of the total amount of said at least one monomer are added to the aqueous solid-particle dispersion and polymerized to a conversion of at least 90%,
• and
• e) thereafter the remainder of said at least one monomer is added under polymerization conditions at the rate at which it is consumed.