METHOD FOR PRODUCING AN AQUEOUS POLYMER DISPERSION FROM VINYLAROMATIC COMPOUND AND CONJUGATED ALIPHATIC DIENE

The present invention relates to a process for producing an aqueous polymer dispersion by free-radically initiated aqueous emulsion polymerization, by polymerizing, in an aqueous medium,(a) 40 to 75 parts by weight of at least one vinylaromatic compound and(b) 24.9 to 59.9 parts by weight of at least one conjugated aliphatic diene(c) 0.1 to 10 parts by weight of at least one monomer comprising acid groups and(d) 0 to 20 parts by weight of at least one other monoethylenically unsaturated monomer,the amounts of the monomers (a) to (d) adding up to 100 parts by weight, in a monomer feed process in the presence of a free-radical initiator, with the proviso thatthe vinylaromatic compound is metered in under polymerization conditions in a continuous mass flow over a period of at least 120 minutes,the metering of the conjugated aliphatic diene is started at a time at which at least 5% and not more than 30% of the vinylaromatic compound has already been metered in in a continuous mass flow andoptionally, the polymerization is initiated in an aqueous polymerization mixture comprising up to 5% of the vinylaromatic compound and comprising no aliphatic diene,and also to the aqueous polymer dispersions produced by the process and to the use of these as a binder, adhesive, sizing agent for fibers, for the production of coatings or for the production of a paper coating slip.