A method for the synthesis of polyethylene terephthalate

By using the deacetyl ester exchange method of ethylene glycol diacetate (EGDA) with terephthalic acid to synthesize PET, the problems of diethylene glycol generation and ethylene glycol evaporation were solved, the oxidation resistance and yellowing resistance of PET were improved, and efficient and low-cost polyester production was achieved.

CN118772383BActive Publication Date: 2026-07-14UNIV OF SCI & TECH OF CHINA
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Patent Information

Application Number
CN202310361484.1
Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Filing Date
2023-04-03
Publication Date
2026-07-14
Estimated Expiration
2043-04-03

AI Technical Summary

Technical Problem

The existing direct esterification method in PET polyester production has a high chance of diethylene glycol formation, which affects the quality of polyester. Furthermore, the evaporation of ethylene glycol can easily lead to side reactions and impurities, making it difficult to reuse. This results in poor oxidation and light resistance of the polyester, as well as high production costs.

Method used

PET was synthesized by ethylene glycol diacetate (EGDA) as a polymerization raw material and terephthalic acid in the presence of a catalyst via deacetyl ester exchange. This avoided undesirable condensation reactions. Low-boiling-point EGDA was used for easy removal without impurities. Catalysts such as antimony trioxide and stabilizer triethyl phosphoroacetate were used to optimize the reaction conditions.

Benefits of technology

It improves the oxidation resistance and yellowing resistance of PET, with a molecular weight exceeding 15,000, meeting fiber-grade requirements. EGDA can be directly reused, reducing production costs and process complexity.

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Abstract

The application discloses a synthesis method of polyethylene terephthalate, which utilizes terephthalic acid and ethylene glycol diacetate as polymerization raw materials, and obtains polyethylene terephthalate through de-acetate exchange polymerization under the action of a catalyst. In the method, the non-expected condensation mode (such as forming a diethylene glycol fragment) does not appear to affect the polymer performance; and because EG is not used, the tolerance to oxygen is stronger during the reaction process, and the produced PET will be more resistant to oxidation and yellowing. On the other hand, the boiling point of EGDA is lower than that of EG, so that EGDA is easier to separate from the system in theory, and the evaporated EGDA can be directly used for the next polymerization without other impurities.
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