1978 Volume 35 Issue 12 Pages 787-794
Polycondensation of bis (2-hydroxyethyl) terephthalate (BHET) was studied in the presence of mixed complexes [M (II) (acac) 2 (BHET); M=Mn, Co, Zn] which were prepared by the reaction of BHET with bivalent metal acetylacetonates [M (II) (acac) 2 (H2O) 2] inacetone. The structure of the mixed complexes was speculated from the measurements of infrared spectra, reflectance curves, thermal analysis and elemental analysis. Polycondensation was initiated when the acetylacetone was released from the mixed complex by the ligand exchange reaction. The rate of polycondensation was found to be proportional to the square of the hydroxyl group concentration. The both rate of polycondensation and of the side reaction which leads to the formation of an ester diethylene glycol increased as the kind of metals in the catalyst changed in the following order: Mn (II) <Co (II) <Zn (II). It was concluded on the bases of the kinetics of the reaction and the structure of the complexes that increased nucleophilicity of the hydroxyl groups due to the coordinaton of BHET to the metal plays an important role in accelerating the reactions.
