CHARACTERIZATION OF OLIGOMERIC BY-PRODUCTS PRODUCED DURING THE HIGH-PRESSURE POLYMERIZATION OF ETHYLENE

The characterization of oligomeric compounds separated from waste mate rial produced in the high-pressure, free-radical ethylene polymerizati on process is reported. A solid wax layer, constituting 11% (w/w) of t he total waste material, was analysed by Fourier transform infrared (F TIR) spectroscopy and gas chromatography/mass spectrometry (GC-MS) and was found to contain mostly short-branched C-18-C-26 paraffins. An oi l fraction constituting 64% (w/w) of the material was identified by FT IR and NMR analyses as a polyether of complex structure. Both the wax and the oil fractions contain a degree of unsaturation. The molecular weight characteristics of the polyether were determined by gel permeat ion chromatography and found to be M(n) = 1716 Da, M(w) = 1926 Da, dis persity M(w)/M(n) = 1.22, using polystyrene standards to calibrate the chromatographic column. A liquid fraction constituting about 25% (w/w ) of the waste was separated from the oil layer by distillation. It wa s identified by FTIR and GC-MS analyses as mainly propan-1-one. This c ompound is used both as a solvent for the initiator and as a chain tra nsfer agent in the low-density polyethylene (LDPE) polymerization proc ess.