Abstract: There is provided a method for producing a polyethylene terephthalate for molding which has a low content of cyclic trimer. The present invention is a method for producing a polyethylene terephthalate for molding which comprises (1) a condensation step of condensing bis(2-hydroxyethyl)terephthalate having an ion content of 10 ppm or less and an acid value of 30 mgKOH/g or less to produce an oligomer having an average polymerization degree of 4 to 10, (2) a melt-polymerization step of melt-polymerizing the oligomer to produce a prepolymer having an intrinsic viscosity of 0.50 to 0.65, and (3) a solid-state polymerization step of crystallizing pellets of the prepolymer and then solid-state polymerizing the prepolymer at a temperature of 190 to 230° C. to produce a polyethylene terephthalate having an intrinsic viscosity of not lower than 0.65; and a polyethylene terephthalate for molding which is obtained by the method and has specific properties.

Abstract: A method is disclosed for efficiently obtaining BHET of high purity from an EG (ethylene glycol) solution containing crude BHET (bis(2-hydroxyethyl)terephthalate), especially a decomposition product solution obtained by decomposing a polyester containing PET (polyethylene terephthalate) as a main component, by use of EG, while minimizing by-production of impurity components such as DEG (diethylene glycol), DEG ester and oligomers. The decomposition product solution is subjected to crystallization and solid-liquid separation under specific temperature conditions. Further, in accordance with the invention, a method of purifying BHET is taught which comprises evaporation steps of evaporating low-boiling-point components from the decomposition product solution under specific conditions so as to obtain a melt solution and a molecular distillation step of distilling the obtained melt solution under specific conditions so as to obtain a specific fraction.