The third compound promoted ethylene homopolymerization and copolymerization with 1-octene by using metallocene catalyst

In order to improve the polymerization behavior and polymer properties, hindered phenol is added as the third compound in a mature metallocene catalyst system, Ph 2 C(Cp)(Flu)ZrCl 2 -MAO, for ethylene (co)polymerization in this study. The steric hindered phenols reduce the chain transfer ability of free trimethylaluminum in the system. At the same time, the chemical environment surrounding the active center was changed, giving it greater steric hindrance. It results the increases of molecular weight of ethylene homopolymer and ethylene-1-octene copolymer (from 61.4k to max. 208.8k for ethylene homopolymerization and from 49.6k to max. 100.3k). And the activity for ethylene homopolymerization slightly increased (from 498 to max. 654 kg-PE/mol-cat/hr) and that for ethylene/1-octene decreased (from 1128 to min. 870 kg-copolymer/mol-cat/hr). The incorporation of 1-octene increased only in one polymerization (from 15.3 to 16.8 mol%), while others decreased (to min. 11.5 mol%). It is also found that the introduction of the third compound changed the distribution of monomers in the polymer chain, therefore it is believed that the third compound is involved in the formation of active center. These changes are closely related to the structure and dosage of steric hindered phenols.