| abstract |
(57) [Abstract] [Problem] Excellent heat resistance, transparency, gas barrier property, etc. Provided is a method for producing a copolyester suitable for use in bottles, films, fibers, sheets, foams and the like. SOLUTION: Terephthalic acid as a dicarboxylic acid component, As a diol component, ethylene glycol is used as a main component, When producing a polyester in which 3 to 15 mol% of a 2,6-naphthalenedicarboxylic acid component is copolymerized with respect to all dicarboxylic acid components, bis (β-hydroxyethyl) terephthalate and / or its low polymer is A naphthalenedicarboxylic acid dialkyl ester and ethylene glycol are added, an ester exchange reaction is performed in the presence of a titanium compound or a tin compound, and then a polycondensation reaction is performed. |