Processing HDPE powder for extrusion blow-moulding - by processing at 210-290 deg. C with specified mechanical energy input divided between crystalline-molten transition and molten states

摘要

A process is claimed for processing high-density polyethylene powder (HDPE) (I), which is obtd. by gas-phase polymerisation with organo-Cr catalysts, has MFI 210 N = 12-32 g/10 mins. with ratio MFI-210N/MFI-21N = 50-100, and is suitable for prodn. of hollow prods. by extrusion blow-moulding. The powder is processed at 210-290 deg.C, with an effective mechanical energy input of 0.6-1.55 MJ/kg, 30-55% of which is concentrated in the partly-crystalline/molten-amorphous transition zone and 30-55% in the molten amorphous state. Effective mechanical energy input is pref. 0.75-1.30 MJ/kg, with 35-50% of the energy conc. in each of the above zones. The process enables the processing of HDPE powder to make it suitable for the problem-free prodn. of high-strength, stress crack-resistant hollow mouldings on modern blow-moulding equipment; this is achieved by modifying crucial properties such as percent swell amd melt viscosity.