Patent ID: 6359106
Filing Date: 2002-03-19
Classification: C08G

Abstract:
A process for continuously producing polybutylene terephthalate, which comprises a first step of reacting an aromatic dicarboxylic acid comprising terephthalic acid as a main ingredient or a derivative thereof with a glycol comprising 1,4-butanediol as a main ingredient in a first reactor, thereby producing an oligomer with an average degree of polymerization of 2.2 to 5, a second step of polycondensing the oligomer from the first step in a second reactor, thereby preparing a low polymerization product with an average degree of polymerization of 25 to 40, and a third step of further polycondensing the low polymerization product from the second step in a third reactor to an average degree of polymerization of 70 to 130, thereby producing a high molecular weight polyester, with good heat stability and excellent hydrolysis resistance, the third reactor being a horizontal cylindrical vessel type reactor having an inlet and an outlet for a process solution at lower parts on one end and on another end in the longitudinal direction of the vessel proper, respectively, and an outlet for volatile matters at the upper part of the vessel proper, and a stirring rotor rotating in the proximity of the inside wall of the vessel proper being provided in the longitudinal direction of the vessel proper, the stirring rotor being made of a plurality of stirring blade blocks in accordance with the viscosity of the process solution, and the stirring blades being without any rotating shaft along the center of the stirring rotor.