EXTRUDING A SHEET OF MIXED PIGMENT AND REGRIND/VIRGIN PLASTICS,FOR THERMOFORMING

摘要

The components of the mixture are delivered from respective separate pigment, and regrind and virgin plastics hoppers 7, 8 6 into an infeed hopper 10, thence by delivery auger 15 into an extruder screw 5 which has a primary helical flight 41 and, in a transition zone 35, a secondary flight 46 which defines a channel 47 in which the material is thoroughly mixed. The diameter of the secondary helical flight 46 is approximately 99.17% of the diameter of the primary helical flight 41 and this achieves efficient material transfer into the channel 47 with reduced shearing and improved pumping action. The combination of the reduced diameter of the secondary flight 46 and the delivery auger 15 achieved efficient handling of materials with a high content of regrind material and change-over from one mix to another is achieved quickly with minimum wastage. IMAGE