Poly ethylene terephthalate production and modeling

Stage including cage reactors, rotating disk reactors, wiped film reactors and extruder type reactors. 

When polyesters are made using melt-phase polymerization, small amounts of cyclic oligomers (1.4—1.8 wt%) are produced, which are in equilibrium with the linear polymer chains [23]. These oligomers, which can migrate to the surface of molded products and interfere with their appearance, can be removed from solid polymer pellets using solvent extraction processes. Unfortunately, the oligomers quickly reappear (due to transesterification reactions) if the polymer is remelted for further processing. 

1 Developing mathematical model equations for production processes 

To explore the difference between these two approaches, consider the following esterification reaction (more precisely known as ester interchange reaction) where dimethyl terephthalate (DMT) is reacted with ethylene glycol (EG) in presence of metal acetate catalyst  

In modeling the polycondensation kinetics, there is also a question of how we define the reaction rate constants. In the above reaction represented by a functional-group modeling framework, the forward rate constant k is the reaction rate constant for reaction of a methyl ester group with a hydroxyl group, not the reaction rate constant for DMT and ethylene glycol molecules. For example, the above reaction can be represented as follows  

---