Patent ID: 6833401
Filing Date: 2004-12-21
Classification: C04B,C08F,C08L,C09D,C09J

Abstract:
A process for preparing an aqueous dispersion of composite particles composed of addition polymer and finely divided inorganic solid, comprising:polymerizing a mixture of ethylenically unsaturated monomers dispersely distributed in an aqueous medium by 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, which is characterized by (a) and (b) which follow, and at least one dispersant, wherein a) the aqueous dispersion of said at least one inorganic solid is stable in that it has an initial solids concentration of &gE;1% by weight, based on the aqueous dispersion of said at least one solid, and 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 weight-average diameter &lE;100 nm, b) the dispersed particles of said at least one inorganic solid exhibit a non-zero electrophoretic mobility in an aqueous standard potassium chloride solution at a pH which corresponds to the pH of the aqueous reaction medium at the beginning of the emulsion polymerization, and c) the mixture of ethylenically unsaturated monomers of the polymerization medium contains >0 and &lE;4% by weight, based on its overall amount, of at least one ethylenically unsaturated monomer A, that is at least one acid group and/or its corresponding anion containing monomer, if the dispersed particles of said at least one inorganic solid have an electrophoretic mobility with a positive sign under the abovementioned conditions, or at least one amino, amido, ureido or N-heterocyclic group and/or its ammonium derivatives alkylated or protonated on the nitrogen containing monomer, if the dispersed particles of said at least one inorganic solid have an electrophoretic mobility with a negative sign under the above-mentioned conditions.