Copolymerization of ethylene and alpha-olefins with combined metallocene catalysts. III. Production of polyolefins with controlled microstructures

The distributions of the molecular weight (MWD) and chemical composition of polyolefins can be controlled by the combination of two or more metallocen es from the knowledge of the behavior of each individual metallocene. Polyo lefins with bimodal MWDs and a higher comonomer content in high molecular w eight chains have physical properties suitable for advanced applications su ch as pipes for gas and water distributions. With conventional Ziegler-Natt a catalysts, this type of polymer resin is produced only by tandem reactor technology in which two or more polymerization reactors are used in series. With combined metallocene catalysts, similar polymer resins can be produce d in a single reactor. The versatility of these combined metallocene cataly sts is investigated in this article. (C) 2000 John Wiley & Sons, Inc. J Pol ym Sci A: Polym Chem 38: 1427-1432, 2000.