Bimodal polyethylene - Interplay of catalyst and process

HDPE specialities having tailored bimodal molecular mass distributions suit able for applications as e.g. pipe or film material are formed in the Hosta len(R)-BM low pressure slurry process. A cascade of two STHD (stirred tank heavy diluent) reactors is used to produce at extremely different reaction conditions in each step of the polymerization an in situ polyethylene blend consisting of a low molecular mass homopolymer and a high molecular mass c opolymer. This way, a resin having a very broad molecular mass distribution and an inverse comonomer distribution is obtained. High impact strength, s tress crack resistance, stiffness, tensile strength, and good processabilit y are combined and materials showing outstanding properties are achieved.