| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a copolyester by copolymerizing an isophthalic acid component and a polyethylene glycol while suppressing the formation of foreign matter by the deterioration of the polyester. SOLUTION: The method for producing the copolyester includes adding polyethylene glycol having a number average molecular weight of 500-2,000, and a phosphorus compound represented by general formula (1) (wherein, R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>are each a≥1C hydrocarbon; X is carbonyl or ester; and n is 0 or 1) in an amount of 1-100 ppm expressed in terms of the phosphorus atom based on the obtained polyester before the start of polycondensation reaction when producing the polyester by subjecting a dicarboxylic acid or an ester-forming derivative thereof, and a diol or an ester-forming derivative thereof to esterification or ester-interchange reaction, and subjecting the resultant product to the polycondensation reaction in the presence of a polycondensation catalyst to provide the polyester copolymerized with the isophthalic acid component and the polyethylene glycol, and having the melting point of≤230°C and the glass transition temperature of 50-65°C. COPYRIGHT: (C)2010,JPO&INPIT
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