Two=stage serial extruder - comprises preliminary extruder and second stage extruder with screw having rows of ribs at front end the parameters of which can be changed at each step

摘要

A two stage serial extruder for mfg high quality polymer prods. comprises a preliminary and a second stage extruder. The preliminary extruder has (i) a conveyer screw length, 5-9 times the screw dia.; (ii) a mixing screw with a hexagonal section and a pitch 1-3 times the screw dia. and (iii) a dosing screw with a channel depth specifically suited to a given purpose e.g. 0.07-0.11 screw dia. A second stage extruder has a screw with channel depth according to purpose and a front section with rows of ribs which alternate with corresp. rows of ribs on the inner surface of the cylinder. A second stage extruder with a high mixing/kneading ability has rows of axial ribs alternating with ribless sections. The rib configuration parameters in each step are identical, while at least one of the parameters e.g. rib groove depth and breadth rib numbers and axial length can be varied in each step. USE/ADVANTAGE - For prodn. of film, sheet, tubing in rubbers or plastics. Gives higher mixing efficiency and therefore a higher quality prod.