| 摘要 |
A problem of the invention is to provide a process for producing a polyester with high molecular weight and high quality and having practicality as a container material, etc., which is able to achieve the production for a relatively short period of time of solid phase polycondensation without using a complicated melt polycondensation reaction device and consequently at a low cost and with good efficiency. The invention is concerned with a continuous production process for continuously producing a polyester including an esterification step, a melt polycondensation step, a granulation step and a solid phase polycondensation step, wherein at least two kinds of a catalyst 1 and a catalyst 2 which are satisfied with the following requirements (1) to (3) are successively added as catalysts in two arbitrary different places prior to the granulation step; an intrinsic viscosity of the polyester prepolymer granule obtained in the granulation step is 0.18 dL/g or more and not more than 0.35 dL/g; and an intrinsic viscosity of the polyester obtained in the solid phase polycondensation step is 0.70 dL/g or more: (1) an activity ratio (K1) of the catalyst 1 is 0.5 or more, (2) an activity ratio (K2) of the catalyst 2 is less than 0.6, and (3) K1>K2 wherein the catalytic activity ratio is an index of a ratio of esterification reaction catalytic activity to the total sum of esterification reaction catalytic activity and ester exchange reaction catalytic activity of the catalyst and is defined according to a method described in the description.
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