| 摘要 |
PROBLEM TO BE SOLVED: To obtain a crystallization-suppressed PET using an inexpensive Sb catalyst as the catalyst. SOLUTION: The polyester has terephthalic acid as an acid component accounting for 95 mol.% or more of the total acid component, and ethylene glycol as a glycol component accounting for 95 mol.% or more of the total glycol component. The amount of Sb element contained in the polyester is from 60 ppm to 380 ppm, based on the total amount of the polyester. The thermal properties of this polyester satisfy formula I and formula II, and the limiting viscosity number of this polyester satisfies formula III. Formula I: 24.6/[η]+130.0<=Tcd<=24.6/[η]+142.0. Formula II: 34.5×[η]+130.0<=Tci<=34.5×[η]+142.0. [wherein Tcd( deg.C) is the peak temperature for crystallization heat upon temperature decrease, measured by DSC, and Tci( deg.C) is the peak temperature for crystallization heat upon temperature increase, measured by DSC]. Formula III: 0.50<=[η]<=1.10 [wherein [η] is a limiting viscosity number calculated from the solution viscosity which is determined at 35 deg.C using a phenol/tetrachloroethane (= at a 3/2 ratio) solvent].
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