GB1435646A - Method and apparatus for making oriented hollow plastic articles - Google Patents

Abstract

1435646 Injection blow-moulding E I VALYI 5 March 1974 [5 March 1973] 9906/74 Heading B5A Molecularly oriented hollow articles are made by injection-moulding a parison on a blow core, removing the blow core with the parison thereon from the parison die, partially expanding the parison and axially extending it while maintaining a positive pressure therein before final blow-moulding. As shown in Fig. I, the apparatus comprises a two-part injection mould 10 co-operating at 13 with injection nozzle 14. The parison neck is defined by neck ring parts 52, 53. The blow core 15 is mounted on rod 16 and has blowing passages 19 and its anterior portion 15a is axially extensible on piston rod 20. A pre-forming mould 21 and a final blow mould 25 may be in one or two parts. In the position shown, plastics is injected through nozzle 14 to form parison 31. The injection mould 10 is opened and the blow core 15 with the neck ring 52/53 and parison 31 retracted. Preform mould 21 is then aligned with the parison 31 (Fig. 2, not shown), the core 15 engaged therein and the parison 31 blowmoulded therein (Fig. 3, not shown). The core 15 with the neck ring 52/53 and partially expanded parison 31 are then retracted, mould 21 returned, and the parison 31 stretched axially by extension of core portion 15a (Fig. 4, not shown). Alternatively, the whole core 15 may be axially extended. The parison may alternatively be partially expanded and axially extended in the final blow mould or without any mould. The axially stretched, partially expanded parison 31 is then finally blowmoulded in blow mould 25 (Fig. 5, not shown). After cooling, neck ring parts 52/53 are separated and the blow mould 25 returned to the discharge position (Fig. 6, not shown) while the blow core is returned to the injection mould for a further cycle. The article may be ejected from the blow mould or preforming mould by air or ejector pins through opening (88<SP>1</SP>) or 88. The parison which may be multilayered may be cooled or heated as desired before axial stretching and the process may be continuous or intermittent. The blow core may also be rotated to injection, preforming and final blow moulding stations. The plastics material may be polyolefines, e.g. polyethylene, polypropylene or copolymers thereof, polyvinyl chloride, polystyrene, acrylonitrile and methacrylonitrile polymers, polyvinylidine chloride, polycarbonate, polyester, polyamide, &c.