Twin tool system for moulding expanded thermoplastics - for improved thermal efficiency and quicker cycles

摘要

Mouldings of expanded plastics materials produced by (a) injecting a predetermined quantity of non-expanded pellets into a (steam-) heated mould to expand and partially melt and agglomerate the pellets, (b) extracting the soft preform from the hot mould to relax in a controlled atmos., (c) loading the preform into a cooler mould, and (d) extracting the chilled moulding for cooling to ambient temp. Suitable for producing shaped packaging or moulded thermal insulation from expanded polystyrene. Use of two tools avoids transfer and waste associated with changing the temp. of a single tool for the thermal cycle necessary to expand, fuse and chill a moulding of material which is a poor heat transfer medium and of low mass c.f. with the mass of the tool. Can also reduce cycle times. Tool designs are simplified for hot or cold duties independently.