PET polymer is produced by the reaction of terephthalic acid (TA) and ethylene glycol (EG) and subsequent polymerisation of the oligomer produced. There are 2 main reactions to the process.
The esterification reaction takes place in a reactor incorporating a heat exchanger and vapour separator connected with a recirculation pipe. This enables good mixing at high recirculation rates with no moving parts – no pumps, no motors, no agitators to cause mechanical failures. The reactor is continuously fed with a slurry of TA and excess glycol.
EG and TA are reacted to form oligomer and water. The water and glycol vapour from the reactor are separated by distillation and the glycol fed back to the feed vessel. Typical reaction conditions are 280°C to 300°C and atmospheric pressure. The feed to the reactor has an excess of glycol to promote the reversible reaction typically in the molar ratio 2:1.
The resultant oligomer is continuously fed forward to the pre-polymeriser reactor. Here the oligomer travels up the reactor where it is reacted in the presence of a catalyst under vacuum conditions and temperatures up to 300°C to produce pre-polymer and glycol. The glycol and other volatiles are removed from the system through a series of spray condensers and the glycol is recycled back to the slurry feed system.
Pre-polymer is the fed to the finisher reactor where the final polymerisation takes place under vacuum conditions and temperatures up to 300°C. Here the polymer viscosity is increased to the required specification. The polymer is then chipped
IPT has a range of polymerisation technology capacities and has licensed the largest single stream CP plant in the world. With its 3-vessel technology IPT has achieved over 1500 tpd of resin production. IPT offers split lines fed from a single esterifier that can give customers increased flexibility of products and additive packages for each line.
IPT's technology provides high quality products with additive packages that can be tailored to customers' requirements and those of their customers. IPT's knowledgeable team of engineers and chemists can help manufacturers get the most from their plant by optimising process conditions.