Polymerization of chloroprene

Process for the preparation of chloroprene polymers by aqueous emulsion polymerization of phenothiazine compound-stabilized chloroprene or of a mixture of chloroprene and up to 20% by weight of at least one or more monomers which can be copolymerized with chloroprene, using a polymerization initiator comprising sodium dithionite or a mixture of sodium dithionite with formamidinesulphinic acid or with potassium peroxodisulphate or with formamidinesulphinic acid and potassium peroxodisulphate or with potassium peroxodisulphate and sodium anthraquinone-.beta.-sulphinate or with formamidinesulphinic acid and potassium peroxodisulphate and sodium anthraquinone-.beta.-sulphonate, in the presence of oxygen and a chain transfer agent, 20 to 80% by weight of the total amount of chain transfer agent being present before or at the commencement of polymerization and the remaining amount being added in one or more parts at monomer conversions above 20%, characterized in that 30 to 90% of the initiators are present at the commencement of polymerization and the remainder is added in portions during the polymerization, only further sodium dithionite being added at a conversion>60% in the case of an initiator combination.