In-line monitoring of styrene1,3 butadiene emulsion polymerization by ATR-FTIR spectroscopy

Abstract

Synthetic rubber is a highly valuable commodity polymer. One important synthetic rubber product is styrene-butadiene rubber (SBR). It is principally made via the emulsion copolymerization of styrene and butadiene monomers and the product is referred to as emulsion polymerized SBR or E-SBR. It is one of the most widely used polymers in the world today. Typical E-SBR applications include pneumatic tires and tubes; heels and soles for footwear; and gaskets. This study focused on demonstrating and validating the use of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy to the in-line monitoring of E-SBR copolymerization. Based on this objective, a series of styrene/1, butadiene emulsion copolymerizations of different monomer feed ratios were carried out in a 12L stainless steel reactor using a typical industrial recipe. A special sample-taking valve was developed to account for the presence of the 1,3 butadiene (a gaseous monomer at atmospheric conditions). Monomer conversion was monitored off-line using gravimetry combined with proton nuclear magnetic resonance (1H-NMR) spectroscopy and in-line using ATR-FTIR spectroscopy. The in-line ATR-FTIR monitoring was accomplished with a ReactIR(TM) 1000 probe. It was found that a multivariate statistical analysis (Partial Least Squares) was necessary to achieve good results. A comparison of the off-line and in-line results was made and it was demonstrated that no significant differences existed between the two methods. This confirmed the reliability of ATR-FTIR as a tool for monitoring monomer conversion and polymer composition for the E-SBR process.