Economic plasticisation of plastic granules and complete or preshredded plastic products

摘要

A process for plasticising plastic granules as well as complete or pre-shredded plastic components and semi-finished products involves preheating the materials to their softening region before and/or during transport to either a screw extruder (22) or injection moulding machine (24). Heating is effected in one or more stages (10,12) which integrate the usual processing stages, e.g. drying, with plasticisation and utilise various different energy-saving methods. At the screw machine (22,24) the prewarmed materials are immediately plasticised by mechanical energy in a shortened feed section of the compression zone or where increased throughput is required processed in a less shortened or non-shortened feed zone. Continuous material flow in the screw machine can be ensured by various measures (20) at the feed zone. Preferably process stages such as screw plasticisation and/or milling are eliminated when processing fully homogenised materials, e.g. components of one type or production scrap. Initial material heating is by hot air, irradiation or similar type of system and can be carried out either: (a) in a drying and/or metering unit: (b) by utilising waste heat from the screw machine to assist the preheating or (c) by the use of directly supplied heat, e.g. from a gas burner. The plastic may be heated outside the screw machine to a temperature below the softening region and then processed in a screw machine with a grooved feed zone.