| 摘要 |
<p>The elimination of impurities, for example monomeric substances of low molecular weight, solvents or the like, from polymer plastics is performed by mixing in extraction gas in a first extruder (1), in a super-critical state. The mixture is transferred into a second extruder (18), where, in a first separating zone (26), it is freed by a counterflow process of the major portion of the extraction gas carrying the impurities, through a draw-off orifice (25). In a downstream vacuum zone (31), a residual separation takes place. The high pressure in the first extruder is maintained by a counter- pressure valve (17) in the connecting line (16) between first extruder and second extruder. By the separation of contaminated extraction gas and plastic melt in a closed space, namely the second extruder (18), an orderly discharge of extraction gas on the one hand and plastic melt on the other hand is possible. …<IMAGE>… </p> |
