Reduction of residual monomer in latex products by enhanced polymerization and extraction in supercritical carbon dioxide

One of the most important environmental incentives for the polymer industry is to reduce the residual monomer content in polymer products. In addition to the conventional techniques for the reduction of residual monomer, a process based on supercritical carbon dioxide (scCO(2)) can be a viable alternative as both further polymerization and extraction of the monomer can occur. In this work, the reduction of methyl methacrylate (MMA) in a PMMA latex was chosen as a representative model system. Pulsed electron beam experiments were performed to study the effect of scCO(2) on the monomer concentration inside the polymer particles during the polymerization reaction. The partitioning behavior of MMA between water and scCO(2) was measured in a high-pressure extraction unit as a function of pressure and temperature. The obtained results show that the extraction of MMA is the predominant effect as compared to the enhancement of polymerization through plasticization.