High solids content miniemulsion polymerization of vinyl acetate in a continuous stirred tank reactor

The dynamics of high solids content miniemulsion polymerization of vinyl acetate produced in a continuous stirred tank reactor (CSTR), under different emulsification processes and hydrophobes were studied. In order to gain more insight into the process, a previous kinetic study in a batch reactor was performed. In addition, the rheological behavior of latexes produced by miniemulsion was compared with those obtained by conventional emulsion. From the experiments made in batch mode, it was observed that poly(vinyl acetate) or polystyrene as the sole hydrophobes were able to create miniemulsions as far as the time elapsed between sonication and polymerization was small. The same behavior was observed in the CSTR, where the feasibility of those systems to eliminate the oscillatory performance of CSTR reactors, also at high solids content was demonstrated. The sonication itself or the sole presence of hydrophobe - without sonication - was not enough to avoid the oscillatory behavior. Further, it was shown that the viscosity of miniemulsions at the beginning of the CSTR process is notably lower than emulsions, thus preventing the initial mixing and heating problems. (C) 2000 Elsevier Science Ltd. All rights reserved.