| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a high-molecular weight polytrimethylene terephthalate(PTT) good in tone of color and small in generating amount of cyclic oligomers. SOLUTION: Phosphoric acid or an ester thereof in an amount of 1×10-4-200×10-4 mol based on 1 mol acid components is added to a polyester oligomer, and the resultant oligomer is subjected to an esterification reaction or an ester-interchange reaction of >=0.5 h. A polycondensation catalyst is added to the resultant product, and the obtained mixture is subjected to a polycondensation at 230-250 deg.C polycondensation temperature until the degree of the reducing pressure in the polycondensation satisfies the formula (1): 0.0266X-5.852<=Y<=0.0225X2-11.993X+1605.1 (1) [wherein, X is the polycondensation temperature ( deg.C); and Y is the degree of the reducing pressure in the polycondensation (hPa)], and the intrinsic viscosity becomes >=0.70.
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