Butadiene polymerization using neodymium versatate-based catalysts: catalyst optimization and effects of water and excess versatic acid

The polymerization of 1,3-butadiene (Bd) in a stirred batch reactor with th e ternary catalytic system Nd(versatate)(3)/Al2Et3Cl3/Al(i-Bu)(2)H in cyclo hexane at 70 degrees C has been studied with initial emphasis on the effect s of the order of addition of the catalyst components, the concentrations o f Al2Et3Cl3 and Al(i-Bu)(2)H. Using in situ catalyst activation, the optimu m concentration ratios of Nd(versatate)(3)/ Al2Et3Cl3/Al(i-Bu)(2)H = 1:1:25 at a catalyst concentration of 0.11 mmol Nd/100 g Bd was established and u sed to determine the influence of water and excess versatic acid ([versatic acid]/[Nd]-3) on polymerization performance. It was found that the optimum catalyst characteristics were obtained when [H2O][Nd] = 0.11; higher and l ower amounts of water decreased conversion, broadened the molecular weight distribution and increased the molecular weight. Increasing the level of ex cess versatic acid above [excess versatic acid/Nd] = 0.22 resulted in lower conversions, broader molecular weight distributions and higher molecular w eights. Polybutadiene cis-1,4 contents were consistently high for all polym erizations (ca. 98%) and were found to be independent of the water content and excess acid level. (C) 2000 Elsevier Science Ltd. All rights reserved.