| 摘要 |
PROBLEM TO BE SOLVED: To stably produce a copolyester in a short time at a low cost, while recycling ethylene isophthalate cyclic dimer [hereinafter (EI)2] as a raw material, by adding a specific amount of (EI)2 to polyethylene terephthalate oligomers and subjecting the mixture to a polymerization reaction. SOLUTION: This method for producing a copolyester having an isophthalic acid(IPA) component/terephthalic acid(TPA) component molar ratio of 60/40 to 10/90 comprises adding 5-30 mol.% of (EI)2 to polyethylene terephthalate (TPA) oligomers and subjecting the mixture to a polycondensation reaction. A polycondensation catalyst used in the reaction includes antimony compounds, germanium compounds, cobalt compounds and titanium compounds. The reaction is preferably carried out under a reduced pressure of <=0.9 hPa at 260-300 deg.C. The PET oligomers used as a raw material are obtained from the TPA and ethylene glycol by a conventional method.
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