Production of copolymers with a predefined intermolecular chemical composition distribution by emulsion polymerisation in a continuously operated reactor

The influence of residence time distribution on the intermolecular chemical composition distribution (CCD) for the emulsion copolymerisation of styren e and methyl acrylate has been investigated. A special tubular reactor, the pulsed packed column (PPC), has been used. The PPC combines intensive radi al mixing with limited axial mixing, thus providing good heat transfer to t he reactor wall and proper emulsification for low net flow rates. A simple backmixing model was developed for feed stream mixing in the PPC. A combina tion of this backmixing model with a simple mechanistic model for emulsion copolymerisation was used to calculate the CCD of the PPC product. Experime ntal and calculated results are in good agreement. Production of copolymer having a bimodal CCD in the PPC is compared to the performance of a semi-ba tch process. The two processes are similar in terms of conversion; however, the CCD of the PPC product shows a characteristic difference. In the PPC s ome copolymer with an intermediate chemical composition is formed through b ackmixing of side feed streams. This work demonstrates that the PPC is a pr omising alternative for semi-batch processes, although some product charact eristics will be slightly different. (C) 2001 Elsevier Science Ltd. All rig hts reserved.