Method of moulding heat-expandable thermoplastic polymeric resinous granules involving enhanced distribution of the hot gaseous medium in the mold cavity
Abstract
Abstract HEAT-EXPANDED BEADS OF THERMO-PLASTIC MATERIAL SUCH AS POLYSTYRENE ARE MOULDED BY STEAM HEATING IN A METAL MOULD AND VENTING THE INTERIOR OF THE MOULD THROUGH APERTURES IN PLUGS SET INTO PORTS IN THE WALL OF THE MOULD. THE PLUGS ARE MADE OF LOW HEAT CONDUCTIVITY MATERIAL, FOR EXAMPLE NYLON, TO PREVENT THE APERTURES BEING BLOCKED BY FUSION OF THE BEADS IN CONTACT WITH THE PLUGS DUE TO HEAT CNDITION FROM THE WALL OF THE MOULD. THE STEAM MAY BE INTRODUCED INTO THE MOULD THROUGH APERATURES IN NYLON PLUGS SET IN PORTS IN THE WALL OF THE MOULD, THE LOW HEAT CONDUCTIVITY OF THE NYLON PREVENTING THE STEAM RAISING THE PLUGS TO A TEMPERATURE AT WHICH THE BEADS WOULD BURN ONTO THE PLUGS. THE SAME PLUGS MAY BE USED TO INTRODUCE STEAM INTO THE MOULD AND THEN VENT THE INTERIOR OF THE MOULD.
Inventors
- 👤 R Cotterell
Bibliographic Details
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