Characterization and purification of by-product polyethylene wax from slurry high density polyethylene process

Polyethylene wax is one of the main byproducts of low pressure slurry high density polyethylene (HDPE) process.This wax is being produced in an amount of about 8-10 kilogram per ton of the polyethylen product,depending on the catalyst used and the process conditions. This wax is almost soluble in hexane at high temperatures and pressures. After solvent recovery and wax drying in wax removal unit, the wax contains different kinds and amounts of volatile compounds. In this research characterization, two byprodut waxes obtained from ethylene polymerization (two flaky waxes dried by water jet) were studied. Solvent extraction method is used for purification of waxes to produce narrow molecular weight(MW) waxes. Differential Scanning Calorimetry (DSC) and High Temperature Gel Permeation Chromatography(GPC) were used to invesigate the efficiency of purification process.The results showed that sharp melting point and narrow molecular weight frations have been produced from soft paraffin like waxes to hard ones.

Keywords:

polyethylene wax , By-product , Slurry Process , Solvent Extraction