Emulsion copolymerization in continuous reactors

The kinetics and mass transfer phenomena associated with emulsion copolymerization in a seed-fed continuous stirred-tank reactor (CSTR) operating at steady state were examined in this work. The goal was to develop a mathematical model to predict the particle size distribution, copolymer composition, and conversion of the effluent latex from a seed-fed CSTR operating at steady state.;Published theories for the prediction of the number of free radicals per particle for emulsion copolymerization in a batch reactor were modified for the broad particle size distribution of a latex produced in a CSTR. An age distribution analysis was used to relate particle size and growth rate to the time spent by the particle in the CSTR. The model accounts for the absorption of aqueous-phase free radicals by particles. The diffusion of monomer free radicals from the particles is also accounted for by the model.;Monomer partitioning between the particles, aqueous phase, and monomer droplets (when present) was calculated using published thermodynamic theories. The thermodynamic interaction parameters required for these calculations were determined by fitting the thermodynamic relations to experimental styrene, methyl acrylate, and acrylonitrile partitioning data.;Emulsion copolymerization experiments with styrene-methyl acrylate were carried out in a tubular reactor-CSTR system. The low-conversion seed latex was produced in the tubular reactor and fed to the first of two CSTR's in series. The seed latex for styrene-acrylonitrile experiments was produced in a batch reactor. The seed latex, emulsified monomer-water mixture, and initiator solution were fed to the first of two CSTR's in series.;The free radical desorption process has been quantified for the emulsion copolymerization of styrene-methyl acrylate and styrene-acrylonitrile. This was accompished by varying the desorption parameter until the deviation between simulated PSD and experimental PSD was minimized.;A kinetic model for aqueous-phase polymerization during seed emulsion copolymerization was derived. An expression for the concentration of radicals in the aqueous phase was derived from a balance on radicals in the aqueous phase. The rate of aqueous-phase polymerization and copolymer composition can be calculated with the model.