Continuous emulsion copolymerization of acrylonitrile and butadiene: Computer simulation study for improving the rubber quality and increasing production

This theoretical article investigates an industrial emulsion copolymerization of acrylonitrile (A) and butadiene (B), for the production of grades BJLT and AJLT of a nitrile rubber (NBR). The simulated process involves a train of eight continuous stirred-tank reactors operating at 10 °C. The product quality is determined by its molecular structure (average copolymer composition, average molecular weights, and average level of branching), and by its final latex characteristics (number particle concentration and number-average particle diameter). The mathematical model by Vega et al. [Vega, J. R., Gugliotta, L. M., Bielsa, R. O., Brandolini, M. C., & Meira, G. R. (1997). Emulsion copolymerization of acrylonitrile and butadiene, mathematical model of an industrial reactor. Industrial and Engineering Chemistry Research, 36, 1328] for the semibatch process was extended to investigate three alternative steady-state (SS) operations of a continuous reactor train. When all the reagents are fed into the first reactor (Normal SS), then a deteriorated quality compared with respect to the equivalent batch process is produced (with increased polydispersities and degrees of branching). This can be improved by admitting intermediate feeds of A and chain transfer agent (CTA) along the train. If in addition, constant B feeds are admitted, then it is possible to eliminate the compositional drift, to generate predetermined profiles of the average molecular weights, and to increase the rubber production by over 10% with respect to the Normal SS. The best improvements were observed for grade AJLT.