Alkali decomposition of poly(ethylene terephthalate) with sodium hydroxide in nonaqueous ethylene glycol: A study on recycling of terephthalic acid and ethylene glycol

Abstract

Pellets of poly(ethylene terephthalate) (PET; 0.48–1.92 g) were heated in anhydrous ethylene glycol (EG; 5 mL) with 2-equivs of NaOH at 150°C for 80 min or 180°C for 15 min to convert them quantitatively to disodium terephthalate (Na2-TPA) and EG. The disodium salt was precipitated quantitatively in pure state from the EG solution and separated readily. The other product EG, being the same component to the solvent, remains in the solution and can be obtained after distillation as a part of the solvent. The rate of decomposition was significantly accelerated by the addition of ethereal solvents to EG, such as dioxane, tetrahydrofuran, and dimethoxyethane. The reaction system is simple; no water and no extra reagent other than NaOH and EG are used. A few recycling systems of PET can be designed on the basis of the present alkali decomposition reaction. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 595–601, 1997