Process for producing ABS graft copolymers

A process for the production of a graft copolymer composition comprising:

• B:
• from 90 to 100% by weight of at least one graft copolymer B comprising:
• B1:
• from 40 to 85% by weight, based on the graft copolymer B, of at least one graft base B1 which is obtained via emulsion polymerization of:
• B11:
• from 50 to 100% by weight, based on the graft base B1, of butadiene,
• B12:
• from 0 to 50% by weight, based on the graft base B1, of at least one other monomer B12 selected from the group consisting of styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, isoprene, chloroprene, C1-C4-alkylstyrene, C1-C8-alkyl (meth)acrylate, alkylene glycol di(meth)acrylate, and divinylbenzene;
• where the entirety of B11+B12 provides precisely 100% by weight;
• and
• B2:
• from 15 to 60% by weight, based on the graft copolymer B, of a graft shell B2 which is obtained via emulsion polymerization, in the presence of the at least one graft base B1, of:
• B21 from 50 to 95% by weight, based on the graft shell B2, of a monomer B21 selected from the group consisting of styrene and mixtures of styrene with at least one other monomer selected from the group consisting of α-methylstyrene, p-methylstyrene, and C1-C8-alkyl (meth)acrylate;
• B22 from 5 to 50% by weight, based on the graft shell B2, of a monomer B22 selected from the group consisting of acrylonitrile and mixtures of acrylonitrile with at least one other monomer selected from the group consisting of methacrylonitrile, anhydrides of unsaturated carboxylic, acids and imides of unsaturated carboxylic acids;
• where the entirety of graft base B1 and graft shell B2 provides precisely 100% by weight;
• and
• K1:
• from 0 to 10% by weight of at least one other component K1,
• comprising the steps of:
• a) production of the graft copolymer B comprising emulsion polymerization of the graft shell B2 in the presence of the at least one graft base 131, where the graft copolymer B is obtained in the form of a latex L;
• b) precipitation of the latex L of the at least one graft copolymer B after emulsion polymerization via addition of at least one precipitation solution F comprising at least one salt and/or at least one acid, where a precipitation solution F1 and a portion of the latex L1 are mixed in a first container H1 at a temperature T1 in the range from 30 to 80° C., and the mixture of latex L1 and precipitation solution F1 is passed into at least two further containers H2 and H3 with temperatures T2 and T3 in the range from 60 to 130° C., where optionally further portions of the latex L2 and/or L3 and optionally further precipitation solutions F2 and/or F3 are added,
• where the volume V1 of the first container H1 is less than or equal to 30% of the volume V2 of the second container H2;
• c) mechanical dewatering of the precipitated graft copolymer B from step b), where an extracted serum S and a graft copolymer B are obtained, where the residual moisture content of the graft copolymer B is less than or equal to 25% by weight;
• and
• d) optionally drying of the dewatered graft copolymer B from step c).