Efficient Depolymerization and Recycling of Poly(trimethylene terephthalate) Using 1,3-Propanediol as Reaction Media
摘要
The chemical depolymerization of poly(trimethylene terephthalate) (PTT) in 1,3- propanediol (1,3-PDO) was investigated in this study. After depolymerization, the bis-(3-hydroxypropyl terephthalate) (BHPT) was recovered, which can be directly utilized as monomer in the synthesis of PTT. Zinc acetate (Zn(OAc)2) was found to be the most suitable catalyst in the depolymerization of PTT in 1,3-PDO since a high monomer yield was achieved and no side reactions were triggered during the depolymerization process. The reaction parameters for depolymerization in the presence of Zn(OAc)2 catalyst was optimized. Under the optimized depolymerization conditions: reaction temperature of 220 °C, catalyst concentration of 0.2 wt% and a ratio of 1,3-PDO to PTT of 8:1, the recovered BHPT monomer yield was 83 mol% within 45 min. Then, the recovered BHPT monomer was directly regenerated into PTT though a single polycondensation process. Comparing with PTT synthesized from virgin dimethyl terephthalate (DMT), the regenerated PTT shows a better quality in terms of color.