The effect of Lewis Bases as a component of the solid catalyst (internal base) and of the cocatalyst (external base) on propylene polymerization for different $MgCl_2$-supported catalysts was studied. The catalysts were prepared by recrystallization and/or ball-milling method.
The crystalline structure, polymerization activity, polymer stereospecificity and morphology for the prepared catalysts were investigated and compared with others.
Optimum activity, the highest stereospecificity, enhanced surface area and desirable polymer morphology were observed for the catalyst to which ethyl benzoate was added during recrystallization stage.
IR and XRD analysis showed the possibility that $TiCl_4$ Lewis Base complex could be existent on the surface and a certain new compound be formed, for the recrystallized catalysts.
The decay of polymerization rate of the recrystallized catalyst was more marked than that of the ball-milled catalysts. Also, the recrystallized catalyst showed slightly higher stereospecificity and lower activity.
In accordance with the change of concentration of external Lewis Bases, the change of activity, polymer stereospecificity and molecular weight occurred. The case of 2,2,6,6-TMPip did not show remarkable tendency but, when methyl-p-toluate was added at 0.1 MPT/A1 mole ratio, the highest stereospecificity (>95% I.I.) was observed.
Also, external Lewis Bases did not have conspicuous effect on kinetic behavior and polymer morphology.
