Background of the inventionThe preparation of polydienes e.g cis-polybutadiene (BR), on the basis of metal - organic Ziegler- Natta catalysts is a process which has bern used on the industriak scale for a long time. The commercially available grades are charac - terized by different microstructures. The high-cis grades have cis contents of over 90% and vinyl contents of up to 4%: Nd-BR (97% cis, 2% trans, 1% vinyl), Ni-BR (96% cis, 2% trans, 2% vinyl) Co-BR (95%, 3% trans, 2% vinyl)(Ullmanns Encyklopdie der technischen Chemie (Ullmann's Encyclo-paedia of Chemical Technology) Verlag Chemie, Weinheim, 4th edition, volume 13, pages 602-604.Li-BR, on the other hand, is prepared by an anionic process using lithium alkyl catalysts. The trans content exceeds the cis content is this case (35% cis, 55% trans, 10% vinyl)
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