PETG/PCTG industrial synthesis methods

PETG/PCTG industrial production technology includes DMT method and PTA method.

1) DMT method

DMT method uses dimethyl terephthalate (DMT), ethylene glycol (EG), 1.4-cyclohexane dimethanol (CHDM) as raw materials, DMT and EG, CHDM two mixed alcohols maintain a certain molar ratio of alkyd acid, after transesterification reaction to generate BHET (bishydroxyethyl terephthalate) and BHCT (bis(hydroxymethylmethyl terephthalate) monomer, and then condensed to make copolyester PETG.

2) PTA method

PTA method used terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexane dimethanol (CHDM) as raw materials, PTA and EG, CHDM two mixed alcohols to maintain a certain molar ratio of alkyd, molar ratio of alkyd acid limited by equipment and process conditions, different molar ratio can be selected, after esterification reaction to generate BHET (bishydroxyethyl terephthalate) and BHCT (bis(hydroxymethylmethylmethyl terephthalate) monomer, and then polycondensed to make copolyester PETG.

Compared with the DMT method, the PTA method does not need to recover methanol, which can simplify the recovery process and equipment, improve production efficiency, reduce environmental pollution, and the production process is reasonable, so the PTA method has greater advantages than the DMT method. And with the development of PTA in recent years, PTA is far easier to obtain than DMT, and PTA method will be the main method of PETG production in the future, which is the future development direction.