Low melt flow index resins for injections-stretch-blow-moulding

A method for preparing vials comprising:

• providing a Ziegler-Natta formed random copolymer of propylene and from 2 to 3.5 wt. % ethylene exhibiting a melt index (MI2) of from 1 to 3 dg/min., wherein an entirety of the random copolymer is prepared with a Ziegler-Natta catalyst;
• and
• two-stage injection-stretch-blow-moulding the random copolymer to form a vial, wherein the two-stage injection-stretch-blow-moulding includes forming a perform at a preform injection temperature of at least 330° C. and a mould filling rate over gate diameter ratio that is at least 5 cc/s/mm;
• and wherein the two-stage-stretch-blow moulding comprises the following steps:
• providing the preform by injection moulding on a multi-cavity mould;
• cooling the preform to room temperature;
• transporting the preform to the stretch-blow moulding machine;
• re-heating the preform in the stretch-blow moulding machine;
• optionally passing the heated preform through an equilibration zone to allow the heat to disperse evenly through the preform wall;
• optionally, submitting the preform to a pre-blow step;
• and
• stretching the preform axially by a centre rod and simultaneously orienting the preform radially by high pressure air, wherein a ratio of the centre rod diameter to the diameter of the preform is within 3% of 2/3.