Continuous monitoring of polymerization processes is a fast and efficient means of investigating the conditions within a reactor in near real time. During the reaction, a small, continously flowing stream of the polymerization mixture is removed from the reactor. This liquid stream is then diluted as necessary and sent through a series (or train) of detectors (selected according to the requirements of the analysis). The data obtained shows the state of the contents of the reactor in near real time, and can be further manipulated to allow calculations of conversions and other relevant information.
A continuous monitoring PL-PMC system was set up to monitor the formation of a block polymer of styrene and methylmethacrylate. The reaction was carried out under a blanket of nitrogen at 40% solids content (assuming that the reaction proceeded to completion). During the analysis, a controlled, continuous stream of sample from the polymerization reaction was automatically extracted, diluted and pumped through a 'train' of analytical detectors comprising refractive index, ultra violet, viscometry and light scattering detectors.
In this application, the aim of monitoring the experiment was to determine the absolute molecular weight of the forming polymer together with information on the depletion rate of the two monomers and the percentage conversion of the block copolymer.
After the addition of initiator, the outputs of all detectors varied with reaction time. The UV signal decreased as styrene was consumed. The RI, Viscometer and LS signals increased as the polymer molecular weight (Mw is obtained by ratio-ratioing the signals from the RI and LS detectors) and conversion level of the block polymer increased. The reaction was followed, essentially, to 100% conversion over the course of 750 minutes. Clearly, the ACOMP technique is capable of real time monitoring of the entire polymerization process from initiation through conversion to accurate determination of the end point and has significant implications for process economics and product quality.
Manufactured by PL under license from Symyx US No. 6,260,407. Use of this instrument may also be covered by one or more of US Patent Numbers 6,406,632, 6, 475,391, 6,265,266 and 6,454,947. Additional US and foreign patents pending.