Retrofitting of industrial olefin polymerization plants: Producing broad MWDs through multiobjective periodic operation

The drop-in of metallocene catalysts (MCs) in existing industrial polymeriz ation plants is the current goal of most polymer producers. However, the na rrow molecular weight distribution (MWD) of the polymers produced by NICs p revent them of moving into commodities market dominated by conventional Zie gler-Natta catalysts, where ease of processing is an essential property. Br oader MWDs may be obtained through mixing of different iMCs or blending of different resins, but resin-compatibility problems and complex undesirable catalyst interactions pose technological problems that have yet to be solve d. For these reasons, modern olefin polymerization plants have to work with both catalysts to respond to market demands, resulting in costly operation s of grade/catalyst change. In this article, we describe how periodic contr ol of short residence-time reactors operating with an MC (Me2Si(2-Me-Benz[e ]Ind)(2)ZrCl2/MAO) can lead to polymers with broad MWD and, consequently, t o high processability. (C) 2000 John Wiley & Sons, Inc.