| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject polyester useful for, e.g. gas barriering containers by treating a polyethylene terephthalate(PET) oligomer in two stages, esterification and then polycondensation in the presence of a polycondensation catalyst. SOLUTION: This high-molecular-weight copolyester is obtained by a two- stage process; esterification for at least 0.5 h as the first stage of (A) a PET oligomer having a number-average molecular weight of 2,000 or less with (B) isophthalic acid at an isophthalic acid component/terephthalic acid component molar ratio of 95/5 to 15/85, and ethylene glycol, and (C) 1×10<-4> to 200×10<-4> mols of phosphoric acid (ester) per mol of the acid component; and polycondensation as the second stage, effected in the presence of a polycondensation catalyst with (E) an Sb compound, Co compound and Zn compound added to levels which satisfy the relationships shown by formulae I to VI (unit: 10<-4> /acid, mol/mol), to a number-average molecular weight of at least 10,000. This copolyester is excellent in color tone, resistance to heat and impact, and transparency.
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