Polyester - PET

Polyester has a wide range of properties which can be utilized in a variety of applications ranging from filaments and fibres through technical yarns to containers, films and mouldings.

Process description

Polyethylene terephthalate polymer (PET) is produced from purified terephthalic acid (PTA) and ethylene glycol (EG) in a series of subsequent chemical reactions. PTA is initially esterified with EG at temperatures of 250 - 270 °C and a higher pressure to produce an esterification product (prepolymer) and water, which is withdrawn from the process by distillation.

During the polycondensation reaction the low molecular esterification product is converted into a high molecular polymer, i.e. the length of the molecular chain is increased to approx. 100 or more repeating units. This is achieved at a higher product temperature of up to 280 - 290 °C and lower pressure of approx. 100 Pa. During the catalytic reaction, excess EG is evaporated and returned to the reaction later on.

The high viscous polymer melt obtained may optionally be transferred into POY, FDY or technical yarn direct spinning machines, directly to bottle resin (MTR®), directly to preforms (MTP®), directly to cast film (MTF®) and/or converted into PET chips by pelletizing.

Continued R&D focuses on replacing the conventional heavy metal catalyst due to concerns about health and the environment.

Commercial experience

Uhde Inventa-Fischer built the world’s first industrial PET plant starting from PTA. We have:

  • long-standing experience in PET processes (since the 1960's).
  • patent coverage on technology and equipment.
  • high quality single stream CP plants of up to 800 mt/d in operation.
  • supplied more than 150 PET plants worldwide.