ETHYLENE-PROPYLENE COPOLYMERS BY A SUPPORTED ZIEGLER-NATTA CATALYST BASED ON TICL4 MGCL2/

Ethylene-propylene copolymers have been prepared by using Ziegler-Natt a catalysts based on TiCl4, MgCl2, PCl3 and (n-Bu)(3)PO4. The catalyst s TiCl4/MgCl2/PCl3 and TiCL4/MgCl2/(n-Bu)(3)PO4 were prepared by react ing TiCl4 with pretreated MgCl2. The support was prepared by ball mill ing of MgCl2 with varied amounts of PCl3 or (n-Bu)(3)PO4. The addition of PCl3 has remarkably increased the MgCl2 surface area in comparison with (n-Bu)(3)PO4. The effects of PCl3 and (n-Bu)(3)PO4 on ethylene h omopolymerization, ethylene-propylene copolymerization and on copolyme r properties were evaluated. The catalyst system containing PCl3 permi tted to synthesize propylene-ethylene copolymers with up to 75 % (w/w) of propylene and provided control of copolymer crystallinity. The red uction of the copolymer molecular weight distribution suggested that P Cl3 acted as an internal donor, poisoning some active catalytic sites.