GB589148A - Improvements relating to injection-moulding of organic thermoplastic materials - Google Patents

Abstract

589,148. Injection-mouldjng. BRITISH CELANESE, Ltd. Dec. 11, 1944, No. 24792. Convention date, Dec. 9, 1943. [Class 87 (ii)] The material, immediately before introduction into the injection cylinder, is preheated by highfrequency alternating electromotive force, and from the cylinder the material is forced into an unheated mould. Fig. 1 shows an apparatus for doing this, comprising a preheating cylinder 6, made of low-loss material, in which the material is heated between a high tension electrode 11 and the earthed injection cylinder 13. The electrode 11 is a metal facing on a plunger 10 of non-conducting material which slides through a cross-head 14. The preheating occurs whilst a previously-ejected charge is cooling in the mould, the injection plunger 20 being then to the right. When the moulded charge has cooled, the plunger 20 returns to the left and plunger 10 forces the preheated material into the injection cylinder. Cold material is fed into the preheating cylinder from a hopper 1 by a piston 3, the hopper itself reciprocating into and out of feeding position on a slideway 8. The injection lever is heated by a coil 25. The mould is cooled by water &c. circulated therethrough. The material moulded may be cellulose derivatives or acrylic or vinyl resins. The Specification as open to inspection under Sect. 91 states that the material, after pre-heating, may be extruded through a die instead of injected into mould, and that the material may be phenol-formaldehyde, ureaformaldehyde, glycerol-phthalic anhydride or polymerized allyl resin, or polystyrene. This subject-matter does not appear in the Specification as accepted.