Metallocene polyethylene composition distribution

General Description The fundamental attribute of ExxonMobil Exceeds metallocene-catalyzed linear low density polyethylene (mEEDPE) is a consistent, uniform distribution of polymer molecules based on single-site catalysts. This uniformity eliminates molecular extremes (narrowing the molecular weight and composition distribution), resulting in a range of property improvements. 

We will introduce this approach in the case of the 2D CLD/DBD computation for mixed-metallocene polymerization of ethylene. Subsequently, we present applications of the approach to the 3D problems of radical polymerization of vinyl acetate (CLD/DBD/number of terminal double bonds distribution), AB radical copolymerization (CLD/comonomer composition distribution/sequence length distribution), and finally the 2D problem of radical polymerization of polyethylene, where random scission is a complicating factor. 

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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