GB1446914A - Container forming process - Google Patents

Abstract

1446914 Blow-moulding; orientation MONSANTO CO 24 Aug 1973 40244/73 Heading B5A A biaxially oriented thermoplastic container is formed by extruding a tubular parison, closing a first mould thereon to thereby pinching its lower end, blowing the parison against the cooled surfaces of the mould cavity to form a pre-form having a cooled surface, transferring the pre-form to a zone where the entire wall thickness is reduced in temperature and stretching it longitudinally to orient it and finally blowmoulding the pre-form in a cooled blow-mould. A parison (12, Fig. 1, not shown) is extruded from extrusion head (14) having an axially movable mandrel (16), movement of which may be programmed to produce a varying wall thickness as at 81, Fig. 2. The parison is then enclosed in halves 34, 36, Fig. 2, of a first blowmould 32, and pinched shut by portions 118, 120 thereof. The parison is blow-moulded in cavity 38 by air from a needle 50 mounted on a piston 52 moved when air is supplied through duct 54, into pre-form 80 having neck threads 39 and shoulder 41. Mould 32 is cooled at 43. The pre-form is then gripped about its upper flash portion (51, Fig. 3, not shown) by means (74) and transferred automatically or manually to temperature conditioning means (56) having a housing (58) with inlet (60) and outlet (62) for conditioning air and holders (64) for the preforms on a rotary carrier plate (66). The cooled pre-form is then transferred to a final blowmould 82, Fig. 4, having halves 86, 88, cooling ducts 92, and a shaft 96 having a central duct 100 for blowing air. The pre-form 80 is stretched longitudinally by foot 98 of shaft 96 and blowmoulded against cavity 84. The mould is sealed by resilient member 102 mounted on retaining ring 104 and compressively seated on the upper surface 106 of the mould. The material is preferably a polymer comprising at least 60% by wt. of polymerized nitrile monomer, e.g. acrylonitrile or methacrylonitrile, the remainder including at least one polymerized ethylenically unsaturated monomer, e.g. styrene. Many other comonomers may be used. Many impact-modifying resins may be incorporated.