USING VISCOSITY METERS TO CONTROL BATCH POLYMERIZATION REACTIONS

摘要

Viscosity is one of the physical properties most extensively measured. Most of those measurements are made in laboratories where many technologies and suppliers are available while, on the other hand, monitoring of process viscosity has long been overlooked. Recent years though have seen an increase in the use of process equipment which can be attributed to the complexity of measuring viscosity and the crucial information it provides to many processes but also to the fact that companies try to automate more their processes. The importance of viscosity lays in the fact that many products have strict requirements to meet quality specifications and that the efficiency of many processes is influenced by the viscosity of the products being processed. Viscosity is also in many cases, used as an intermediate to monitor other properties of a product that correlate easily to viscosity. In the case of polymers, viscosity can reflect the average molecular weight of the polymer or the concentration in a suspension/emulsion type polymerization. In this paper, we will present a sensor to measure viscosity that has been in use for 30 years and received many improvements and modifications over time to push further the limits of its use: The MIVI sensor. Due to the vibration at resonance technology it is based on and its design, this sensor achieves high repeatability and high sensitivity in very difficult environments while maintaining very low maintenance needs. We will then look into how the use of this equipment provides valuable information in batch polymerization to monitor and control the whole process. We will develop with some examples of applications and expand on some of the correlations used in those particular cases. Finally, we will give a brief introduction about one of the new features of this sensor, i.e.: measurement of combined viscosity and density.