On-Line Monitoring and Composition Control of the Emulsion copolymerization of VeoVA 9 and butyl acrylate by raman spectroscopy

摘要

The batch and semi-continuous emulsion copolymerization of n-butyl acrylate and vinyl neononanoate (VeoV A 9) were mon- itored by remote on-line Raman spectroscopy. Monomer con- centrations were calculated in real-time by a classical least squares (CLS) approach using the vinyl regions of the Raman spectra. During the batch copolymerization, conversion and copolymer composition calculated from on-line data showed good agreement with off-line gravimetry and NMR results, indi- cating that the CLS procedure indeed enables the calculation of individual monomer concentrations and on-line characterization of the copolymer formed. Real-time analysis of the data enabled control of the copolymer composition by suggesting how one of the comonomers should be added in a semi-continuous polymerization. NMR and gradient polymer elution chromatogra- phy corroborated the Raman results for the copolymer composi- tion. Further, it was shown that only at high conversions (>80%) monomer partitioning influences the copolymerization behavior, since both monomers have a low solubility in water. The results demonstrate that Raman spectroscopy is very well suited as on-line sensor in emulsion copolymerization processes.