Monitoring of polymer content in an emulsion polymerization using spatially resolved spectroscopy in the near infrared region and Raman spectroscopy

Abstract

The potential of spatially resolved spectroscopy (SRS) for in situ monitoring is evaluated in this work. SRS is based on near‐infrared spectroscopy. It is well adapted to heterogeneous systems and collects information about both physical and chemical properties. In this work, the polymer content in emulsion copolymerization is predicted using SRS. The reaction was first carried out in batch mode for particle nucleation followed by semi‐continuous monomer addition under starved conditions to allow particle growth. SRS and Raman spectroscopy are compared, and the advantages and disadvantages of both methods are highlighted, revealing that each method has its own benefits. Different operating conditions were varied, including the monomer ratio, the surfactant mass fraction, and the agitation speed. Regression models were developed using partial least square for both techniques.

Online Monitoring of the Particle Size in Semibatch Emulsion Copolymerization Using Spatially Resolved Spectroscopy and Raman Spectroscopy

“…However, the magnitude of the variations is different from the one observed with the particle size, which should allow distinguishing between them by calibration. The impact of concentration on the spectra is not investigated further here as monitoring of the solids content by SRS has already been studied in a previous work and its feasibility was demonstrated …”

“…A multiangle probe Sam-Flex (Indatech, Chauvin Arnoux) was connected to a spectrometer from Indatech (Hyternity), which is composed of an NIR InGaAs camera. The measurement is done simultaneously with a 3 mm pathlength at four angles, which are positioned as follows: one angle in the transmission direction at 180° (according to the light source), two angles in the scattering directions at 175 and 170°, and one angle in the backscattering direction at 30° . From this configuration, the 175° angle can be thought to be more sensitive to simple scattering, while the angle at 170° is more sensitive to the multiple scattering and the angle at 30° is more sensitive to backscattering.…”

“…A data preprocessing approach was employed, including data smoothing using a Savitzky–Golay filter with 15 points averaged with a polynomial of second order, followed by a first-order derivative. A prediction model of the particle size was then developed based on partial least-squares (PLS) regression using the nonlinear iterative partial least-squares (NIPALS) algorithm .…”

In-line Monitoring of Microgel Synthesis: Flow versus Batch Reactor

“…In-line measurements via Raman spectroscopy are nondestructive, need no preparation, and are only slightly affected by scattering of water below a Raman shift of 2750 cm –1 . Thus, Raman spectroscopy represents an established process analytical technology (PAT) tool for various applications in polymerization, most prominently in emulsion polymerization − and precipitation polymerization. , …”

Inline Raman Spectroscopy of an Emulsion Copolymerization in an Industrial Pilot Plant Using Indirect Hard Modeling

“…These works use either peak integration methods, i.e., analyzing single peaks or PLS regression. In [11], both Raman and spatially resolved near infrared spectroscopy are used to monitor the polymer content in a copolymerization system operated in semi-batch. PLS regression is used to analyze the spectra, but no individual monomer contents are predicted.…”