Bimodal polyethylene for pipe applications obtained by chromium oxide/metallocene binary catalysts [PE]

Two stage cascade polymerization process is the most employed technology for production of bimodal polyethylene using only one optimized catalyst. However, such schemes are inherently more complex and therefore, there are many advantages of using single reactor bimodal technology : lower investment costs, easier and simpler control, less process complexity, intimate mixing of high and low molecular weight components, etc. For this single reactor bimodal technology, a greatly advanced catalyst design is required. In this work, a novel chromium oxide/metallocene hybrid catalyst has been developed by supporting a MAO/metallocene system on different chromium containing-mesoporous supports. The hydrogen effect over this hybrid catalyst as well as over the parent physical mixture is explored and finally, properties of the synthesized bimodal polyethylenes are compared to a conventional bimodal polyethylene PE100. Results indicate that the synthesized binary systems lead to polymers with higher average molecular weight, crystallinity and melting point than PE100 with even better processability. Keywords : bimodal polyethylene, PE-100, binary catalysts, chromium, metallocene.