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)2H, for the stereospecific polymerization of 1,3-butadiene (Bd) has been studied at a catalyst concentration of 0.11 mmol Nd per 100 g Bd. The effects of the concentration of SiCl4 following in situ activation, preformed at 20 °C in the presence and absence of isoprene and the substitution of Al(iso-Bu)2H with AlEt3 as alkylating agent, were established and compared to the performance of NdV3-based catalyst systems incorporating ethylaluminium sesquichloride (EASC), diethylaluminium chloride (DEAC) and t-butyl chloride (t-BuCl) as chloride sources. Comparable catalytic activity between the control catalysts based on EASC, DEAC and t-BuCl and the studied NdV3/SiCl4/Al(iso-Bu)2H system was achieved once the optimum concentration ratios of NdV3/SiCl4/Al(iso-Bu)2H = 1:1:25 were applied in conjunction with preforming the catalyst components in the presence of isoprene for 72 h at 20 °C. Polybutadiene cis-1,4 contents were consistently high (about 97 %) for all polymerizations.