Japan successfully developed polyester recycling process
TSK Corporation recently introduced a recycled polyester (PET) waste process that recovers terephthalic acid (PTA) and ethylene glycol (EG) from waste PET bottles.
The process uses ethylene glycol as a solvent to disperse the fragments of PET resin and react with sodium carbonate at 170-185°C and 0.1 MPa. PET is depolymerized into EG and PTA, and the latter is formed into sodium terephthalate (NaTP). . Since NaTP is insoluble in EG, the resulting EG can be recycled after being separated by filtration and distillation. NaTP dissolves in water. Sulfuric acid was added in two steps slightly above 90°C and PTA crystals were obtained in sodium sulfate solution. Crystal filtration and washing give PTA with a purity of more than 99.9% and sodium sulfate can be recovered.
TSK has completed a pilot test of 100 tons/year, with a PTA recovery rate of approximately 98%. Because the process is carried out at low pressure and the reaction time is short, investment costs are low. Estimated investment of 8000 tons/year of industrialized equipment is about 11 million US dollars. This process saves PET disposal costs and is economically viable.