VERFAHREN ZUR HERSTELLUNG EINES RISSFREIEN HOCH MOLEKULARORIENTIERTEN GEBLASENEN BEHAELTERS

Mfr. of molecularly highly oriented blow-moulded containers e.g. bottles, free from cracks, from nitrile-contg. polymer, comprises (a) shaping a seamless comparison closed at 1 end, in an injection-mould with an extrusion die that has a cavity surrounding a coaxial core pin; (b) injecting polymer melt under pressure into the extrusion die cavity; removing the parison from the core pin; and (c) transferring the hot parison immediately to a temp. controlled conditioning pin in contact with the inner surface with the inner surface of the parison and a temp. controlled cavity in contact with the outer surface of the parison. Thus the parison is temp. conditioned within the orientation temp. range for the polymer. The so-conditioned parison is then blow-moulded, the polymer an orientation relaxation stress (sic), in a circumferential direction, of at least 35.2 kg/cm. Used e.g. in mfr. of plastics bottles for carbonated beverages. The prods. are free from stress cracks and unsightly stress marks.