PURPOSE: To provide a process for producing a polyethylene terephthalate having high quality and polymerization degree without generating flow failure at a gas-liquid interface in polymerization reaction.
CONSTITUTION: The polycondensation reaction after an esterification reaction is divided into a former-stage polycondensation step to get a polyethylene terephthalate having an intrinsic viscosity [η] of 0.4-0.9dλ/g and a latter-stage polycondensation step to get a polyethylene terephthalate having an intrinsic viscosity [η] of 0.8-1.3dλ/g. The latter-stage polycondensation is carried out by a stirring polymerizer having plural rotary shafts 12, 13 and stirring blades composed of paddles 21-26 and 31-36 perpendicularly attached to the rotary shafts interposing gaps in the direction of the shaft and scrapers 41-46 and 51-56 attached to the tip ends of the paddles and having a length nearly corresponding to the dimension of the gaps. The stirring blade has an L/D ratio of 2-10, preferably 4-8 wherein D is rotary diameter of the blade and L is the length of the blade in longitudinal direction.
SHIMADA TAKAFUMI
KONDO MASAMI