Patent ID: 7153929
Filing Date: 2006-12-26
Classification: B01D,B01J,C08F

Abstract:
1. A process for the preparation of rubber-free copolymers of ethylenically unsaturated monomers selected from the group consisting of styrenes and vinyl cyanides containing 65 wt. % to 80 wt. % styrene and 20 wt. % to 35 wt. % vinyl cyanide with a low residual monomer content, wherein concentration takes place in two steps, characterized in that solutions of the rubber-free copolymers are brought to concentrations of greater than or equal to 99.8% in a first step of concentration by introducing energy with simultaneous evaporation in tubes in a tube evaporator and, in a second step without intermediate heating, further removal of the monomers is carried out in a strand evaporator.