DSC AND C-13 NMR-STUDIES OF ETHYLENE-PROPENE COPOLYMERS PREPARED BY AHIGHLY-ACTIVE AND STEREOSPECIFIC CATALYST

Ethylene-propene copolymers (EPR) were synthesized at different feed c ompositions using a highly active and isospecific MgCl2-supported Ti-b ased catalyst. The thermal behavior of EPR was studied by differential scanning calorimetry, the heterogeneity by fractionation, and the cha in structure by C-13 NMR using the method of substituent chemical shif t. The results show that EPR of very low crystallinity (1,0 wt.-%) can be obtained at high propene content in the feed with a heptane-insolu ble fraction of only 0,9 wt.-%. Thus, a high isotacticity in propylene sequences and a high randomness in EPR can be achieved at the same ti me, and producing high-impact poly(propylene) in a reactor is possible with this catalyst. Sequence distribution and length distribution of ethylene sequences indicate that EPR is produced at multiple active si tes, and each site is dominated not only by a first-order Markovian mo del but also by unsteady diffusion factors.