This article theoretically investigates the reduction of off-specs generated during changes of grade in an emulsion copolymerization of acrylonitrile (A) and butadiene (B) performed in an industrial train of eight continuous stirred tank reactors (CSTRs). The investigated nitrile rubber (NBR) grades exhibit differences in the copolymer composition, molecular weights, and levels of branching. In the Normal plant configuration, all the reagents are fed into the first reactor. In the Improved plant configuration, intermediate additions of A, B, and chain-transfer agent (CTA) are admitted'along the train for increasing production and reducing chain branching, polydispersity, and compositional drift. Optimal transitions between the Normal steady states and the Improved steady states were calculated. They involved changes between two typical copolymer grades and the application of "bang-bang" feed profiles onto A, B, and CTA. According to the model, the bangbang strategies reduce the off-specs 35%-60%, with respect to simultaneous step changes in all of the reagents.