Continuous Emulsion Styrene-Butadiene Rubber (SBR) Process: Computer Simulation Study for Increasing Production and for Reducing Transients between Steady States

The industrial production of two styrene-butadiene rubber (SBR) grades is optimized by means of a representative mathematical model. The emulsion process involves a train of seven continuously stirred-tank reactors. In the simulations, intermediate feeds of comonomers and chain transfer agent (CTA) are admitted. The steady-state (SS) productions can be increased by ~8%, while maintaining the required final values of conversion, particle diameter, and molecular characteristics (Mn, Mw, and the average number of branches per molecule). For the same rubber grade, the polymer production can be changed with negligible generation of intermediate off-specs, by regulating the global calorimetric conversion. For changes of grade at a fixed polymer production, transient profiles of the intermediate CTA feeds are proposed. For changes of production and grade, a sequential (rather than a simultaneous) transition seems preferable.