| 摘要 |
PROBLEM TO BE SOLVED: To produce a polyethylene terephthalate copolyester which has isophthalic acid-derived comonomer units, is excellent in clarity and color tone, and is suitable for direct blow molding or for producing thick-walled molded articles by using an antimony trioxide catalyst. SOLUTION: A copolyester comprising ethylene terephthalate units and ethylene isophthalate units in a molar ratio of (98/2)-(85/15) is produced by adding phosphoric acid in an amt. of 1×10<-4> to 2×10<-3> mol (per mol of the acid component for producing the copolyester) to an oligmer having an average degree of polymn. of 10 or lower, then subjecting the oligomer to reaction at 200-280 deg.C for 0.5-4 hr, adding antimony trioxide as the polymn. catalyst to the reaction mixture to cause melt polymn., and subjecting the resulting product to solid phase polymn.
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