Reconstituted thermoplastic sheets prodn. - in which assorted film waste is reduced, mixed, hot-pressed between cauls and cooled to release

摘要

Thermoplastic materials, and partic. waste, is reconstituted into sheets by measuring out, distributing over an area, and densifying hot. The material is reduced and laid between two metal cauls at over 120 deg.C (pref. over 200 deg.C); it heats up and is pressed at 6 kp/cm2, air is removed, and the controlled-dimension sheet is cooled under pressure to permit release from the cauls. Various polymers can be used without binder, prods. are dense, rigid, physiologically neutral sheets suitable for use in drainage/soil improvement, process can use e.g. bag scrap. In the plant a conveyor passes to and through a hot and a cold press, both working at over 6 kp/cm2. Different kinds of scrap thermoplastic materials are reduced and mixed together beforehand, fed on to a bottom caul, and distributed evenly. A second press caul is laid on top. The conveyor moves this press load stepwise into the hot press, occluded air in the material escapes from between its (e.g.) strips. The cauls adhere to the densified sheet produced, and a subsequent cooling station is therefore necessary for their release.