Prepolymerization and morphology. Study on the factors determining powder morphology in propylene polymerization.

Due to the developments in catalysis and the use of improved and dedicated catalysts in modern polymerization processes, the variety of different grades of polyolefins produced (and with that the variety of possible applications) has increased rapidly over the past decades. Combined with the low prices of these polymers, this has lead to a huge growth rate of the annual worldwide production capacity for polyolefins. The more modern processes almost always utilize a number of different polymerization reactors in series, often being a combination of one or two liquid phase reactors and one or two gas phase reactors. At the same time, the developments ask for improved control on particle morphology. Improved powder morphology will decrease the presence of fines, it will reduce the chance of wall sheeting in the gas phase reactors and increase the ease of transport and other handling properties of the powder. Next to that, when producing high-impact polypropylene, control on internal particle morphology will allow control of the distribution of the rubbery phase in the homopolymer matrix. In this work a Ziegler-Natta catalyst of the fourth generation was used, of TiCl4 on a MgCl2 support, with Al(Eth)3 as cocatalyst and di-cyclopentyl di-methoxy silane as external electron donor.