POLYMERS COMPRISED OF POLYETHYLENE AND MONO-OLEFINS AND METHODS OF MAKING THE SAME

摘要

Disclosed are polymer compositions comprised of copolymers of polyethylene with mono-olefins that exhibit low levels of long chain branching, as indicated by the narrow theological breadths combined with the high molecular weight (M w) values of the polymers. These characteristics, among others, are realized by methods of preparing polymerization catalysts disclosed herein. These methods include treating chromium-based catalysts, having an alumina support, with sulfate to avoid sintering of the alumina. Methods of calcining the alumina support are further disclosed as well as the catalyst compositions, comprised of chromium and a sulfate-treated alumina support, which exhibit increased catalyst activity.