Polymerization of butadiene using neodymium versatate-based catalyst systems: preformed catalysts with SiCl4 as halide source

The ternary neodymium versatate (NdV3)-based catalyst system, NdV3/SiCl4/Al (iso-Bu)(2)H, for the stereospecific polymerization of 1,3-butadiene (Bd) h as been studied at a catalyst concentration of 0.11 nmol Nd per 100 g Bd. T he efdects of the concentration of SiCl4 following in situ activation, pref ormed at 20 degrees C in the presence and absence of isoprene and the subst itution of Al(iso-Bu)(2)H with AlEt3 as alkylating agent, were established and compared to the performance of NdV3-based catalyst systems incorporatin g ethylaluminium sesquichloride (EASC), diethylaluminium chloride (DEAC) an d t-butyl chloride (t-BuCl) as chloride sources. Comparable catalytic activ ity between the control catalysts based on EASC, DEAC and t-BuCl and the st udied NdV3/SiCl4/Al(iso-Bu)(2)H system was achieved once the optimum concen tration ratios of NdV3/SiCl4/Al(iso-Bu)(2)H = 1:1:25 were applied in conjun ction with preforming the catalyst components in the presence of isoprene f or 72 h at 20 degrees C. Polybutadiene cis-1,4 contents were consistently h igh (about 97%) for all polymerizations. (C) 2000 Society of Chemical Indus try.