An Analysis upon Concept and Technology of Polymerization: Principles and Mechanisms

Effects of Reactants and Operating Mechanisms on Suspension Polymerization

Abstract

The versatility of polymerization resides not only in the different types of reactants which can be polymerized but also in the variations allowed by copolymerization and stereoselective polymerization. Industrial suspension polymerization usually proceeds via a free-radical mechanism to produce polymer beads. The size distribution of the polymer beads is often similar to that of the polymerizing drops in the reactor. That distribution is determined by the operating mechanisms of drop breakage and of drop coalescence. Consequently, the value of the Reynolds Number is significant and a potential change in flow regime must be considered in reactor scale-up. The choice of suspending agent, which can be a watermiscible polymer or a finely divided particulate solid, can affect both the drop size and the properties of the final product. High monomer conversions are attainable but reaction kinetics can be affected by increases in drop viscosity during the polymerization. Drop mixing, which sometimes takes place, can be slow so that non-uniformity occurs in the final product. With copolymerization, complications can arise if the initiator, or one of the monomers, is partially soluble in the continuous phase. Adverse environmental impact of suspension polymerization can be avoided by cleaning and/or recycling of the continuous phase when it leaves the reactor.