Patent ID: 6696533
Filing Date: 2004-02-24
Classification: C08F

Abstract:
A process of free-radically initiated aqueous emulsion polymerization for preparing an aqueous polymer dispersion, where compounds having at least one ethylenically unsaturated group are emulsified in an aqueous medium by means of dispersants and are free-radically polymerized in the presence of a stable N-oxyl radical, which comprisesa) using as free-radical polymerization initiator a peroxide, a hydroperoxide and/or an azo compound whose molal solubility at 25Â° C. and 1 bar in water is greater than or equal to the corresponding molal solubility of tert-butyl hydroperoxide in water and whose dissociation temperature in the polymerization medium is <100Â° C., b) conducting the free-radically initiated aqueous emulsion polymerization at a polymerization temperature of more than 100Â° C., and c) conducting the free-radically initiated aqueous emulsion polymerization at pressures which are above the vapor pressure of the polymerization mixture present within the polymerization vessel, said pressures being established by means of an inert gas or molecular oxygen prior to heating the polymerization mixture to the polymerization temperature.