Patent ID: 7196146

Claim:
A process for preparing an aqueous styrene-butadiene polymer dispersion, comprising: polymerizing, in an aqueous emulsion containing a free radical initiator, by a monomer feed technique, in a polymerization vessel a monomer mixture comprising from 40 to 80% by weight of styrene as 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 monomers, of ethylenically unsaturated comonomers M3 other than styrene and butadiene, the emulsion also containing from 0.05 to 0.5% by weight, based on 100% by weight of monomers, of at least one hydrocarbon compound selected from the group consisting of compounds having from 6 to 20 carbon atoms, which upon abstraction of a hydrogen atom, form a pentadienyl or 1 -phenylallyl radical, and α-methylstyrene dimer, wherein during the supply of monomer mixture to the polymerization vessel, raising, at a point in time when at least 70% of the monomers to be polymerized have been supplied to the polymerization reaction medium, the concentration of butadiene in the monomer feed for a period of at least 1% of the total feed time by at least 10% by weight, based on monomers in the feed.