Patent ID: 8258234

Claim:
A process which comprises preparing an aqueous dispersion comprising composite particles comprising addition polymer and finely divided inorganic solid, in which process ethylenically unsaturated monomers are dispersely distributed in an aqueous medium and polymerized by free-radical aqueous emulsion polymerization initiated by at least one free-radical polymerization initiator in the presence of at least one dispersely distributed, finely divided inorganic solid and at least one dispersant, wherein a) the inorganic solid has an average particle diameter of >0 nm and ≦100 nm, b) 1 to 1000 parts by weight of inorganic solid are used per 100 parts by weight of monomers, c) 0.01 to 10 parts by weight of a silane compound are used per 100 parts by weight of monomers, the silane compound having at least one Si—OH group or at least one functional group which is hydrolyzed in deionized water at a temperature ≦100° C. to form an Si—OH or an Si—O—Si group, and the silane compound having no free-radically copolymerizable ethylenically unsaturated group, and d) at least a portion of the inorganic solid is included in an initial charge in an aqueous polymerization medium in the form of an aqueous dispersion of solids, then e) at least a portion of the silane compound but less than 100% thereof is metered into the aqueous polymerization medium over a period of ≧5 and ≦240 minutes, subsequently f) optionally ≦20% by weight of the monomers are added to the aqueous polymerization medium and free-radically polymerized, and subsequently g) any remainder of the inorganic solid, the remainder of the silane compound, and any remainder or the total amount of the monomers are metered into the aqueous polymerization medium under polymerization conditions.