In-line monitoring of a copolymerization reaction

Beyers et aV° in the Polymer Research Division of BASF-AG used in-line transflectance NIR to monitor methyl methacrylate (MMA) and iV,7V-dimethylacrylamide (DMAAm) monomers in a copolymerization reaction. The work in this paper is of interest as it illustrates an example of calibration development done off-line with a very limited number of prepared calibration samples. The value of the measurement is to control the end properties of the products resulting from the copolymerization reaction. The end properties are related to many parameters including the intramolecular chemical composition distribution (CCD). The 

000 Designed E xperimen Process J Upsets Line dOut [  

Parameter Model name Range Number of PLS factors / val Accuracy (SEP) Precision  

To control the CCD, the anthors chose a closed-loop control strategy with in-line NIR used to measure the monomer concentrations. The closed-loop control strategy nses the NIR in-line measurement to provide close to real-time information abont the concentration of both reactants and prodncts in the reactor. One prerequisite of this control strategy is that the sampling rate be faster than the kinetics of the reaction. 

Monitoring the MMA/DMAAm reaction is challenging becanse both monomers have very similar NIR spectra, and because other interfering snbstances are present in the reaction mixtnre. The anthors prepared calibration samples gravimetrically and made the NIR measurements at reaction temperatnres. The calibration sets consisted of only five or six samples, which is considerably fewer than standard recommendations for NIR chemometric model development. The final models for MMA and DMAAm were validated with an internal validation set as well as an external reaction validation. The performance of the models is summarized in Table 15.6. This table inclndes a measurement of the standard deviation of an external GC method 

---