| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing an alkylene naphthalate copolyester excellent in performance such as a heat resistance, mechanical strengths, gas barrier property, etc., in a good efficiency, and further a method for producing the above copolyester by using the waste materials of the polyester resins such as the polyethylene naphthalate, etc., as raw materials in a good efficiency. SOLUTION: This method for producing the alkylene naphthalate copolyester (A) containing 5-60 mol% alkylene naphthalate unit, is characterized by adding a polyester (C) containing >=90 mol% alkylene naphthalate unit and an alkylene glycol having 0.5-5.0 fold (in a mass ratio) amount based on the total acid component of the (C), to (B) a carboxylate consisting of an acid component other than the naphthalene dicarboxylate, a glycol component and its low molecular weight polymer, performing a depolymerization and then performing a polycondensation reaction.
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