Kinetic and Active Centre Studies on the Polymerization of Propylene using MgCl2 Supported Ziegler – Natta Catalysts and 1,3 Diether Donors

All polymerization experiments were carried out in a Buchi glass reactor capable of operating at propylene pressures of 1-7 atmospheres. Two types of MgCl 2 supported catalysts with controlled morphology were studied, viz., catalyst systems containing either a 1,3 diether (Catalysts A and D), 9,9-bis (methoxymethyl) fluorene, or a simple diester (Catalysts B, C and E) such as diisobutylphthalate, used as reference systems. The kinetic behaviours of these catalysts were investigated for propylene polymerization. The 1,3-diether based systems proved to be excellent catalyst systems for propylene polymerization showing high polymerization activities and stable rate-time profiles and produced spherical polymer particles. Catalyst pre-treatment was found to play an important role in controlling the morphology of the final polymer. A tritiated alcohol radio-quenching technique was used to determine the concentrations active centres: values of 7.5 and 5.1 mol/mol % respectively were obtained for catalysts A and D and 3.5, 2.9 and 2.2 mol/mol % respectively were obtained for catalysts B, C and E. Catalysts A and D showed very high polymerization activities and also higher C o * values. All polymers produced were characterized by SEM, DSC, extraction and molecular weight determinations.