CONTINUOUS EMULSION COPOLYMERIZATION OF ACRYLONITRILE AND BUTADIENE. COMPUTER SIMULATION STUDY FOR REDUCING THE OFF-SPEC RUBBER PRODUCED BETWEEN STEADY STATES

MINARI, ROQUE J; GUGLIOTTA, LUIS M; VEGA, JORGE R; MEIRA, GREGORIO R

Buenes Aires (Argentina)

Congreso; XXII Congreso Interamericano de Ingeniería Química - V Congreso Argentino de Ingeniería Química; 2006

This theoretical article investigates an emulsion copolymerization of acrylonitrile (A) and butadiene (B) carried out in an industrial train of 8 continuous stirred-tank reactors, with the aim of reducing the off-spec product generated in the transitions during changes between steady states (SSs) of two different grades (BJLT and AJLT). These grades exhibit different average values of copolymer composition, molecular weights, and levels of branching. The transitions between the so called Normal SS and Improved SS were simulated. In the Normal SSs, all the reagents are fed into the first reactor. The Improved SSs include intermediate constant additions of A, B, and chain transfer agent (CTA) along the train, and produce a better rubber quality from the point of view of reducing degree of branching, molecular weight polydispersity and compositional drift, and increasing rubber production. For reducing the off-spec product, optimal control strategies were developed. For the transitions between Normal SSs, “bang-bang” feed profiles of A, B, and CTA into the first reactor were proposed, reducing the off-spec product by more than 35% with respect to a simultaneous step change in all of reagents feeds. For transitions between Improved SSs, the intermediate feeds of A, B, and CTA were manipulated through delayed step changes or “bang-bang” profiles delayed along the reactor train. Both strategies considerably reduced the off-spec product with respect to simultaneous step changes in all of reagents.