Patent ID: 7071270

Claim:
A process for obtaining an aqueous dispersion of copolymers comprising polymerizing a blend of monomers comprising butadiene and at least one monomer selected from the group consisting of styrene, acrylic esters and vinyl nitriles, as an aqueous emulsion in the presence of one or more free-radical initiator(s), wherein said initiator(s) comprise an azocarboxylic acid ester of formula (I): wherein: R 1 , R 2 , R 3 and R 4 , which may be identical or different, are independently selected from the group consisting of: linear or branched alkyls containing from 1 to 9 carbon atoms and preferably from 1 to 4 carbon atoms, optionally substituted with one or more substituents selected from hydroxyl, C 1 to C 6 alkoxy and halogen substituents; C 3 to C 12 cycloalkyls, optionally substituted with one or more substituents selected from C 1 to C 6 alkyl, C 1 to C 6 alkoxy, hydroxyl and halogenated groups; aralkyls optionally substituted with one or more C 1 to C 6 alkyl, C 1 to C 6 alkoxy, hydroxyl and halogenated groups; aryls optionally substituted with one or more substituents selected from C 1 to C 6 alkyl, C 1 to C 6 alkoxy, hydroxyl and halogenated groups, wherein one or more of the combinations R 1 –R 2 and R 3 –R 4 optionally forms an aliphatic ring; and wherein R″ and R′ are identical or different and are independently selected from the group consisting of unsubstituted linear or branched C 1 to C 10 aliphatic radicals.