Method and apparatus for the manufacture of a aufgeschaeumten cell - the form body made of a foamable, thermoplastic starting material, preferably synthetic resin

摘要

A shaped cellular thermoplastic article is formed by feeding granules of an expandable thermoplastic material into a mould chamber which defines the shape of the article at a temperature below the softening point of the thermoplastic material, heating the granules to 5-10 DEG F. above the softening point of the thermoplastic material by means of high-frequency electrical energy, allowing the heated particles to expand and fuse together under a vacuum of from 15 to 30 inches of mercury and, thereafter, removing the shaped article from the mould. If desired the expanded contents of the mould may be allowed to cool under vacuum and then cooled completely with air under pressure before discharging the mould. Preferred expandable thermoplastic materials, with high power-loss factor, are homo-polymers of styrene containing up to 10% of wood flour or walnut shell flour or copolymers of styrene with, for example, tri-methylol-propane monoallyl ether. Polystyrene, polyethylene, polypropylene, poly(alkyl - substituted - styrene), polyacrylic esters, polymethacrylic esters and copolymers of styrene with a -methyl-styrene or alkyl - substituted - styrene may be used in conjunction with a coating of a high power-loss factor material.