| abstract |
A process for continuously producing a polyester, comprising the steps of esterification, melt polycondensation, granulation and solid-phase polycondensation, wherein as a catalyst, at least two catalysts, catalyst 1 and catalyst 2, satisfying the following requirements (1) to (3) are sequentially added at arbitrary different two points prior to the granulation step, and wherein the polyester prepolymer granules obtained by the granulation step and the polyester obtained by the solid-phase polycondensation step have an intrinsic viscosity of 0.18 to 0.35 dL/g and ≥ 0.70 dL/g, respectively. (1) Activation of catalyst 1 (K1) is ≥ 0.5; (2) Activation of catalyst 2 (K2) is < 0.6; and (3) K1>K2. The above activation of catalyst means an index for the ratio of esterification reaction catalyst activity to the total of esterification reaction catalyst activity and transesterification reaction catalyst activity of the catalyst, and is defined in the manner set forth in the description. |