Modeling of Continuous Dispersion Copolymerization of Styrene and Acrylonitrile in a Polyol Medium

Abstract

Acrylonitrile and styrene radical copolymerization in a dispersed medium has been investigated. Experiments were carried out in a continuous stirred-tank reactor in the presence of a stabilizing agent elaborated in situ during polymerization. The continuous phase was a polyol. The numerous elementary chemical mechanisms concerning the copolymerization as well as synthesis and grafting of the stabilizing agent together with several physical phenomena clearly show the complexity of the process. Using justified assumptions and a simplified kinetic scheme, a tendency model of the process was developed, using mass balances and thermodynamics. Its unknown parameters were identified by use of an evolutionary algorithm and experimental data resulting from an adapted experimental strategy. This model was then validated and allowed to forecast, with an acceptable order of magnitude, the number and weight average molecular weights, monomers and transfer agent conversions, amounts of solids, copolymer composition, amounts of grafted copolymer, and average particle diameters versus the operating conditions.

Graft Copolymerization of Styrene and Acrylonitrile in the Presence of Poly(propylene glycol): Kinetics and Modeling

“…Initiator and chain‐transfer agent (CTA) are assumed to partition evenly between each phase. The critical chain length ( j cr ) assumption is used and radical desorption from the dispersed phase into the continuous phase is neglected. All macromer and PPG are considered to exist in the continuous phase 9. All SAN is considered to be in the dispersed phase. The terminal model is used although the penultimate effect is often significant in copolymerization of St and AN 51, 52.…”

“…All SAN is considered to be in the dispersed phase. The terminal model is used although the penultimate effect is often significant in copolymerization of St and AN 51, 52. The polymeric radicals undergo termination exclusively by recombination 9, 29 A narrow molecular weight distribution (MWD) of PPG and macromer is assumed. The number of SAN chains per graft copolymer is one 9…”

“…The polymeric radicals undergo termination exclusively by recombination 9, 29 A narrow molecular weight distribution (MWD) of PPG and macromer is assumed. The number of SAN chains per graft copolymer is one 9 …”

“…Similar to conventional dispersion polymerization,6–8 graft copolymerization of St and AN in the presence of poly(propylene glycol) (PPG) starts from a homogeneous system, and becomes heterogeneous soon after the beginning due to the limited miscibility between PPG and poly(St ‐co‐ AN) (SAN) 9. After the phase separation, the heterogeneous polymerization and partition behaviors of the reactants make the kinetics very complicated.…”

“…In general, partition coefficients of small molecular weight species between a dispersed phase and a continuous phase are determined by phase equilibria 9, 10. Some phase equilibrium models have been developed to estimate partition coefficients of small molecular weight species in heterogeneous polymerization systems, such as dispersion polymerization of St in alcohol and/or water,11–13 dispersion polymerization of methyl methacrylate (or vinylidene fluoride) in supercritical carbon dioxide,14–16 two‐phase polymerization of acrylamide in aqueous poly(ethylene glycol) solution,17 and emulsion polymerization of St and AN 18.…”