Method for the production of ABS compositions having an improved surface

A process for producing a composition comprising

• A) 0 to 98 parts by weight, based on the sum total of A and B, of a thermoplastic polymer or a mixture of a plurality of thermoplastic polymers different from B and
• B) 2 to 100 parts by weight, based on the sum total of A and B, of
• B1) at least one graft polymer prepared in an emulsion polymerization process,
• B2) optionally at least one graft polymer prepared by the bulk, suspension or solution polymerization process,
• B3) optionally at least one rubber-free vinyl (co)polymer and
• C) 0 to 30 parts by weight, based on the sum total of A and B, of at least one commercially available polymer additive,
• where the sum total of parts by weight A and B is 100,
• component B, comprises at least one inorganic salt consisting of a cation selected from the group of the alkali metals, alkaline earth metals and aluminum and an anion selected from the group consisting of chloride, sulfate, nitrate, phosphate, acetate and formate, in a concentration of the salt or salt mixture of 100 to 5000 mg/kg based on the composition, and
• wherein
• a) in a first process step the entirety of the component(s) containing the salt from B, optionally together with a portion or the entirety of the remaining components from B, A and C is processed in a compounding system, preferably an extruder, to give a polymer blend melt, then this polymer melt is discharged from the extruder and, in the form of polymer strands prior to pelletization or alternatively in the form of pellets after the pelletization, is contacted with water completely by contact with liquid water in a water bath, a water-filled pipe system or a dip bath,
• b) in a second process step the pellets which have been contacted with water in this way are separated from water not adhering to the surface of the pellets and then are stored under surface-moist conditions,
• c) in a third process step the pellets thus stored under moist conditions are melted and kneaded in the molten state and/or
• d) in a fourth process step the component thus prepared is mixed with the remaining components of the composition, the mixture is melted again and kneaded, and the components of the mixture are interdispersed in this way,
• where a reduced pressure is applied at least in one of steps c) and d) and, in this way, the water introduced into the process in process step a) is removed again from the product, and where the mean storage time of the surface-moist pellets in step b) is at least 24 h.