Multiple screw extruder implemented with vacuum vent and screws configured to densify, or extract fluid from, material processed by the extruder

Abstract

A multiple screw extruder () combines application of vacuum to a vacuum vent () positioned between material feed locations () of the extruder and use of specially configured extruder screws () to extract gases, primarily air, out of the extruder to densify the materials introduced into it and to extract unwanted fluid from material introduced for mixture with molten polymeric material flowing through the extruder. The multiple screw extruder is operationally versatile in that it is capable of carrying out the material densification and fluid extraction processes either separately or simultaneously. Implementation of the disclosed vacuum feed technology provides an increase in rate of extrudate throughput as compared with that achievable by implementation of atmospheric venting () in a conventionally configured extruder ().