Application of IR spectroscopy and multivariate calibration to monitor the fusion synthesis of Ca- and Ca/Mg-resinates Original Research Article

The application of FTIR spectroscopy was studied in mid-infrared region (MIR) and near-infrared (NIR) region in fusion synthesis of Ca-resinates as well as Ca/Mg-resinates. Predictive calibration models based on partial least squares (PLS) regression were developed to describe the relationship between the spectra and the acid value of laboratory scale synthesized Ca-resinates. The relationship between the spectra and the viscosity of 50 wt% toluene solution of industrially processed Ca/Mg-resinates was also modelled with PLS. The results showed that both the calibration models can be applied to monitor the fusion resinate process. However, it was observed that pre-processing of the spectra with multiplicative scatter correction was necessary before the calibration. In acid value calibrations, linear PLS was sufficient for calibration, even when different rosin grades were used in the syntheses. For the solution viscosity calibrations, non-linear PLS had to be applied to obtain satisfactory calibration models. The models in the MIR and NIR regions were observed to be equally good for the calibration.