Process parameter optimization through Design of Experiments in synthesis of high cis-polybutadiene rubber

• The polymerization of butadiene was investigated with a neodymium-based catalyst system using DOE.
• The optimum conditions for the polymerization were determined using developed models.
• The developed model equations for active catalyst phase and reaction phase were validated.
• The developed models can turn out to be very effective to predict the response for given set of operating conditions.

The neodymium octanoate (Nd), diethylaluminum chloride (DEAC) and triethylaluminum (TEAL)-based catalyst system was studied for polymerization of 1,3-butadiene (BD). The present paper deals with the identification of linear, square and interaction effects of the process parameters on conversion, molecular weight and microstructure of the polybutadiene rubber and consequently the optimization of polymerization process using statistical tool, Design of Experiments. The process comprises of two steps: (1) active catalyst formulation and (2) polymerization of BD. Both steps were optimized sequentially using Box–Behnken design (BBD) and each BBD has three independent variables. In both designs and models, the proposed correlations represent the experimental data adequately for response variables viz. conversion, molecular weight and cis-content. Optimum catalyst formulation was observed to be BD/Nd, DEAC/Nd and TEAL/Nd molar ratio of 902.88, 1.74 and 27.51, respectively. Optimum polymerization conditions were monomer concentration 22%, reaction time 3.3 h and reaction temperature 42 °C for the said catalyst system.