Moulding hygroscopic plastics material

摘要

A method for moulding hygroscopic plastics material in a clean room environment comprises drawing granules of hygroscopic plastics material from a supply container 10 into a hopper loader 13 by means of a vacuum drawn on the hopper loader 13 by a plant room vacuum pump. The granules are then delivered into a drying hopper 15 and air from the drying hopper 15 is drawn by a dessicator vacuum pump in a closed loop to substantially remove moisture from the air in a dessicator 22. Heated air from the dessicator 22 is delivered to the granules in the drying hopper 15 to substantially remove moisture from the granules. On removal of moisture from the granules in the drying hopper 15, the dessicated granules are drawn to a hopper loader 1 of a moulding machine in the clean room environment by means of a main vacuum pump 30. The main vacuum pump 30 draws air in a closed loop from the hopper loader 1 of the moulding machine through a dust separator 31 and a filter 32 and draws the dessicated granules from the drying hopper 15 to the hopper loader 1. Positive pressure in the dessicated granules stream is released prior to delivery to the hopper loader 1 to maintain the integrity of the clean room environment.