Method for producing caoutchouc particles

A process for preparing rubber particles K comprising in polymerized form

• A) from 80 to 100% by weight, based on K, of butadiene or isoprene or mixtures thereof (diene monomers A), and
• B) from 0 to 20% by weight, based on K, of one or more monoethylenically unsaturated comonomers B
• by emulsion polymerization in the presence of an emulsifier or a mixture of different emulsifiers selected from the group consisting of alkali metal salts of alkyl- or alkylarylsulfonic acids, alkyl sulfates, fatty alcohol sulfonates, salts of higher fatty acids with 10 to 30 carbon atoms, sulfosuccinates, ether sulfonates and resin soaps, and a polymerization initiator, which comprises
• 1) initially introducing a mixture M1 comprising, based on M1,
• M1a) from 20 to 100% by weight of the water needed to prepare the emulsion (emulsion water), and
• M1b) from 0.1 to 100% by weight of the emulsifier,
• 2) subsequently adding a mixture M2 comprising, based on M2,
• M2a) from 90 to 100% by weight of one or more monomers selected from styrene, α-methylstyrene, butadiene, n-butyl acrylate, methyl methacrylate and acrylonitrile, and
• M2b) from 0 to 10% by weight of one or more copolymerizable monomers,
• the monomers M2a) and M2b) being added alternatively in monomeric form with subsequent in situ polymerization to give a seed latex, or as a mixture of polymerized and monomeric form, and the seed latex polymer having a weight-average molecular mass of more than 20,000,
• 3) then starting the polymerization of the resulting mixture in the presence of the polymerization initiator at temperatures of from 5 to 95° C.,
• 4) simultaneously or subsequently adding a mixture M3 comprising
• M3a) from 0 to 100% by weight, based on B, of the comonomers B, and
• M3b) from 0 to 25% by weight, based on A, of the diene monomers A,
• 5) simultaneously or subsequently metering in a mixture M4 comprising
• M4a) the remaining 75 to 100% by weight, based on A, of the diene monomers A, and
• M4b) the remaining 0 to 100% by weight, based on B, of the comonomers B,
• and carrying out polymerization, and
• 6) subsequently ending the polymerization at a conversion above 90 and below 95%, based on the sum of the monomers,
• the remaining 0 to 80% by weight of the emulsion water and the remaining 0 to 99.9% by weight of the emulsifier being added individually or separately from one another in one or more of steps 2) to 5).