On‐line monitoring of all‐acrylic emulsion polymerization reactors by Raman spectroscopy

Fourier Transform Raman spectroscopy was used as an on‐line sensor in order to monitor high solids content (50 wt%) n‐BA/MMA emulsion copolymerization reactions. Due to the similarity of the chemical structure of the monomers, no separate bands could be detected for each monomer, and therefore a multivariate calibration technique was required (Partial Least Squares Regression, PLSR). Using experimental data from several semi‐batch reactions independent PLSR models were built for the solids content, cumulative copolymer composition and unreacted amounts of n‐BA and MMA. Those models were experimentally validated by monitoring reactions not used for calibration. It is demonstrated that FT‐Raman spectroscopy can be successfully applied to on‐line monitor emulsion polymerization reactors. This technique also shows a high potential for process control purposes because independent information about several molecular properties can be obtained from a single apparatus.