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 styrene and methyl acrylate has been investigated. A special tubular reactor, the pulsed packed column (PPC), has been used. The PPC combines intensive radial mixing with limited axial mixing, thus providing good heat transfer to the reactor wall and proper emulsification for low net flow rates. A simple backmixing model was developed for feed stream mixing in the PPC. A combination of this backmixing model with a simple mechanistic model for emulsion copolymerisation was used to calculate the CCD of the PPC product. Experimental 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-batch process. The two processes are similar in terms of conversion; however, the CCD of the PPC product shows a characteristic difference. In the PPC some copolymer with an intermediate chemical composition is formed through backmixing of side feed streams. This work demonstrates that the PPC is a promising alternative for semi-batch processes, although some product characteristics will be slightly different.