Process for preparing aqueous polymer dipersores styrene-butadiene iii.

Process for preparing an aqueous polymer dispersion of styrene-butadiene by polymerisation in aqueous emulsion radical of a monomer mixture M comprising - from 40 to 80% by weight styrene, by way of monomer M1, - from 20 to 60% by weight of butadiene as monomer M2, and - from 0 to 40% by weight, based on 100% by weight of the monomers, of ethylenically unsaturated comonomers M3 other than styrene and butadiene, by a method with feeding monomers in the presence of 0.05 to 0.5% by weight, based on 100% by weight of the monomers of at least one hydrocarbon with CH 6-20 carbon atoms, which are chosen from the compounds which form a pentadienyl radical or 1-phenylallyl radical by abstraction of a hydrogen atom, and alphamethylstyrene dimer, characterized in that provided in the polymerization vessel at least 30% of the hydrocarbon HC and the remaining amount of hydrocarbon HC is fed to the polymerization reaction during its course.