Surfactant-free emulsion polymerisation of methyl methacrylate and methyl acrylate using intensified processing methods

The feasibility of enhancing the latex yield and colloid characteristics in the surfactant-free emulsion polymerisation (SFEP) of methyl methacrylate (MMA) and methyl acrylate (MA) through the use of intensified processing technologies is reported in this paper. The effects of high power ultrasonic energy as a well-established technique for mixing and mass transfer enhancements were compared with thermal initiation in a conventional mechanically agitated reactor. Although increases in ultrasonic power input resulted in higher rates of reaction and larger particles in the MMA polymerisation, reaction yields were nevertheless found to be low compared with the thermally initiated stirred tank reactor experiments. This was attributed to the low frequency ultrasound used (24 kHz) that was observed to provide excellent emulsification but was ineffective in terms of radical generation. The results for a thermally initiated SFEP of MA in a narrow channel reactor as an example of a continuous flow reactor technology showed that reaction rates were comparable with those achieved in the stirred tank reactor but at only a fraction of the specific power input whilst smaller particles with a tighter distribution are generated. These effects highlight the process intensification characteristics of the narrow channel reactor for the SFEP of MA.