| 摘要 |
1493528 Screw mixers BASF AG 10 April 1975 [11 April 1974 19 Feb 1975 6 March 1975] 14728/75 Heading BIC A process for the admixture of one or more additives to a plastics material, with simultaneous removal of volatile constituents comprises separately feeding the additive(s) and a plastics melt, solution or dispersion into a horizontal devolatilizing extruder, heating, mixing and conveying the charge whilst vapourizing the volatile constituents, and extruding the mixture, wherein taken in sequence in the direction of flow, the additive(s) are first introduced into the devolatilizing extruder from above, 4 and the plastics material is then introduced from below 6, the bulk of the volatile constituents being withdrawn from the devolatilizing extruder by way of an orifice 8 located substantially vertically above the point at which the plastics material is fed in. The extruder may be a single-or, as shown, double-screw extruder with contra-rotating screws 3 arranged to touch or intermesh and to draw material downwards into the gap between them. The plastics material is preheated in a heat exchanger 5 and fed at superatmospheric pressure to the feed point 6, which may comprise nozzle-like holes or elongate slits, preferably having a variable throttle device. Pressure at the volatiles removal orifice 8 is maintained at or below atmospheric by pumping. Further orifices 9, 10 for the removal of volatile constituents may be provided and an entraining agent e.g. superheated steam, inert gases or readily volatile organic solvents may be introduced from below, at a feed point 7. Plastics materials and additives which may be used in the process are listed and particular examples giving comparative results with conventional processes are given.
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