Ethylene-propylene copolymerization was carried out over $MgCl_2$-supported $TiCl_4$ catalyst with two different reaction schemes; i.e., stopped-flow copolymerization(SFC), continuouslypurged copolymerization (CPC). Two types of $MgCl_2$-supported $TiCl_4$ catalysts were tested; one was prepared by ball-milling, while the other was prepared by recrystallization of the alcoholic $MgCl_2$ solution. The effects of aging time, Al/Ti mole ratio and external Lewis base on the propylene content in copolymer were also examined. The reactivity ratios for each monomer were evaluated by Fineman-Ross and Kelen-$T\ddot{u}d\hat{o}s$ methods. It was found that the SFC resulted in smaller value of ethylene reactivity ratio($r_K$) and larger value of propylene reactivity ratio ($r_p$) than CPC. The yield and the propylene content of copolymer were almost independent of aging time up to 80 minutes but decreased for longer aging time. Those are attributed to the different extent of interaction between catalytic titanium sites and aluminum alkyls. The maximum yields obtained with ball-milled catalyst shifted to the lower range of comonomer content with the increasing Al/Ti mole ratio, but those with recrystallized catalyst did not. It seems to be attributed to the significant differences of the catalyst morphology.
