| 摘要 |
<p>The invention relates to copolymers of unsaturated monomers, devoid of rubber, which are selected from the group of styrenes and vinyl cyanides. Said copolymers contain between 65 and 80 % by weight, preferably between 68 and 77 % by weight styrene and between 20 and 35 % by weight, preferably between 23 and 32 % by weight acryl nitrile. The invention also relates to a method and a device for producing said copolymers. A mild, two-stage evaporation treatment allows copolymers with few residual monomers, namely less than 20, preferably 10 ppm of acryl nitrile, less than 200, preferably 100 ppm of styrene and less than 200, preferably 100 ppm of ethyl benzole to be obtained. In addition, in a first stage of a mild concentration process, solutions of the product are reduced to concentrations greater than/or equal to 99.8 % by the supply of energy and simultaneous evaporation and additional monomers are then eliminated in a second stage, without intermediate heating.</p> |
