Receiving of Therephthalic Acid from Polyethylene Terephthalate waste by depolymerization in the melt

Abstract

The technological method of terephthalic acid receiving by depolymerization of polyethylene terephthalate (PET) in the melt has been developed as the result of research. Mechanism of depolymerization is studied by mean of DSC analysis. It was established, that PET depolymerization in melt can be reached at atmospheric pressure, and temperature range 140-160°C during a short time with the yield of terephthalic acid close to 95- 98%. Sodium or potassium hydroxide is more suitable reagents for PET depolymerization regarding technological point of view. The best found amount of alkali to be added to the polymer is 120% from stoichiometrically necessary quantity. Electrolytic method is more prominent for terephthalic acid precipitation because at the time of terephthalic acid receiving, sodium or potassium hydroxide can be regenerated by electrolysis and used in cycle. Possible use of catalyst – zinc acetate which is added into the melt to increase the degree of PET depolymerization is shown. The quantity of zinc acetate of 1% from polymer weight amount was found as optimum.