Metallocene polyethylene random copolymers

COC is a relatively new commercial polymer. Four commercial sources are available under the TOPAS , ApeF, Zeonor and Zeonex , and Arton product names, supplied by Topas Advanced Polymers, Mitsui Chemicals, Zeon Chemical and Japan Synthrtic Rubber. COC is a random copolymer of ethylene and norbomene. Norbomene is synthesized via Diels-Alder reaction of ethylene and cylopentadiene. Polymerization of ethylene and norbomene using metallocene catalysts produces cyclic olefin copolymer. Large bulky cyclic rings randomly distributed in a polyethylene backbone prevent crystallization of the ethylene, creating an amorphous morphology. 

The sheer size and value of the polyethylene industry ensure that there is continued research, progress, and development in catalysis, for their potential commercial impact. Although this whole subject is not within the scope of this chapter, we mention a couple of aspects of the progress, which offer the potential to impact this industry. In 1995, DuPont introduced work, carried out with them at the University of North Carolina—via the largest patent applicafion ever in the USA. They disclosed what are described as post-metallocene catalysts. These are transition and late transition metal complexes with di-imine ligands, which form part of the DuPont Versipol technology. Such catalysts create highly branched to exceptionally linear ethylene homopolymers and linear alpha-olefins. Late transition metals offer not only the potential for the incorporation of polar comonomers, which until now has only been possible in LDPE reactors, but also their controlled sequence distribution, compared to the random composition of free radical LDPE copolymers. Such copolymers account for over 1 million tons per annum [20]. Versipol has so far only been cross-licensed and used commercially by DuPont Dow Elastomers (a former joint venture, now dissolved) in an EPDM plant. 

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