Summary: A Ziegler‐Natta‐catalyst was used in ultra low‐yield slurry prepolymerization followed by liquid propylene (main) polymerizations. Complete catalyst disintegration down to 1.5–2 µm particle size is observed at prepolymerization yields of 10 g per g cat. The initial (main) polymerization rate increased up to 55% and the final average particle diameter can be controlled between 50 and 1 500 µm at main polymerization yields of 20 kg PP per g cat · hr−1. Tension generation within the particle and the absence of a polymer layer explains these results.
Surface SEM. Top: Catalyst surface covered with polyhexene. Bottom: Cracks on catalyst surface after washing with hexane.
