Method for producing an aqueous polymer dispersion from vinylaromatic compound and conjugated aliphatic diene

A process for producing an aqueous polymer dispersion by free- radically initiated aqueous emulsion polymerization, which comprises 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 that
• the vinylaromatic compound is metered 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 a continuous mass flow and
• optionally, the polymerization is initiated in an aqueous polymerization mixture comprising up to 5% of the vinylaromatic compound and comprising no aliphatic diene.