(79d) Polycondensation Process System Design and Scale-up Challenges

Polycondensation reactions have many industrial applications and are commonly employed in syntheses of polymers such as polyesters. A typical Polycondensation process takes place at relatively high temperature and can involve exothermic and/or endothermic reactions. Small molecules are formed by the condensation reaction and are usually removed by distillation in order to drive the reaction to completion and to isolate the products. Once the small molecules are removed, the bulk of the product can become very viscous even at high temperature.  The viscosity of molten raw materials and products can range from water-like to more than 10,000 Centipoises.

An institution actively engaged in development and scale up of specialty polymer can benefit from having versatile Bench Engineering and Pilot Plant process systems custom designed and built specifically for carrying out Polycondensation. A typical Polycondensation reaction system should incorporate the following components and features:

-          A reactor which can handle a broad range of mixing (low to very high viscosity materials) and heat transfer (exotherm and endotherm) requirements, as well as having adequate numbers of nozzles sized for feeding bulky raw materials and discharging viscous products

-          Auxiliary equipment including:
High-temperature, high-power circulation baths for the reactor and condensers
Refrigerated water or glycol supply system(s) for condensers and receivers

Atmospheric, or preferably, vacuum distillation equipment such as reflux and take-off condensers, packed columns, vacuum pump, splitter and phase separation equipment

Vessels and pumps for feeding and collecting raw materials, products and byproducts

-          Process Monitoring, Control and Data Acquisition components and systems for monitoring and control of process parameters, including temperature, pressure, viscosity/torque/power, flow and agitator speeds

-          Sampling and analytical instruments for end point determination

-          Post reaction processing equipment such as chilled rolls or belts

In this presentation, examples of several custom Bench Engineering and Pilot Plant process system, ranging in size from less than 1 litre to over 1,000 litres, which were designed and built specifically for carrying out a broad range of Polycondensation reactions in a materials research centre are described. Challenges and lessons learned from designing, operating and scale-up of Polycondensation processes using these custom reaction systems should interest those who are involved with development and scale-up of polymer syntheses.