Polyethylene Terephthalate (PET) is one of the major polymers produced worldwide representing about 18 % of world polymer production and comes in third after Polyethylene and Polypropylene. The main downstream industries based on PET are production of polyester fibers, accounting for around 65% of global consumption, and PET bottle resins consuming around 30%.
PET is produced from high purity ethylene glycol (EG) and Terephthalic acid (TPA). All PET resin manufacture processes are using the same reaction path as shown in the figure bellow :
The conventional PET process consists of two discrete plant sections. The first part consists of melt phase reaction used to produce copolymers with an intrinsic viscosity (IV) suitable for textile applications. But when very high molecular weights are desired, as is the case for bottle grade PET resins, the polymerization may be carried out in stages. The traditional Buhler process integrates four typical stages for producing bottle grade PET : crystallization, annealing, solid state polymerization (SSP) and cooling. New technologies are currently replacing this design with a tendency to reduce the number of units involved
and thus the global process cost.
A radical approach that is rapidly becoming more and more employed is Eastman IntegRex technology (illustrated in figure 2). The main unit is a tubular reactor that leads to a significant reduction of energy, raw materials consumptions, operation costs and capital costs.