Synthesis and properties of poly(butylene succinate): Efficiency of different transesterification catalysts

The efficiency of organometal‐ (Ti, Zr, Sn, Hf, and Bi) and metal oxide‐ (Ge and Sb) based catalysts was investigated during the transesterification step of the synthesis of poly(butylene succinate) (PBS). PBS was prepared from succinic acid and 1,4‐butanediol via a two‐stage melt polycondensation process. The catalytic efficiency of the organometal catalysts was as follows: Ti≫Zr∼ Sn>Hf>Sb>Bi. The germanium and antimony metal oxides displayed desirable catalytic efficiency when were associated with hydroxy acids (lactic acid or glycolic acid), which acted as chelating agents. However, this catalytic system exhibited lower efficiency compared to the titanium system. Furthermore, at high concentrations of hydroxy acids the overall transesterification rate decreased. This effect can be explained by the substitution of PBS hydroxyl end groups by a lactic or glycolic unit, both of which are less reactive during the transesterification reaction. The role of catalytic residues during the storage and processing of PBS was also studied. The reduced viscosity of the PBS samples did not vary when processing at 190 °C from 1 to 10 minutes. However, when stored under ambient conditions, all PBS samples were prone to significant hydrolytic degradation, especially those containing a titanium catalyst. This behavior indicates that zirconium‐ and germanium‐based catalysts could be interesting substitutes for titanium‐based catalysts. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. Among the organometal‐ (Ti, Zr, Sn, Hf, and Bi) and metal oxide‐ (Ge and Sb) based catalysts studied during the transesterification step of the synthesis of poly(butylene succinate), Ti‐based catalyst exhibited the highest activity. In case of metal oxides‐ (Ge and Sb) based catalysts, the catalytic efficiency was improved when hydroxy acids (lactic acid or glycolic acid) were used as chelating agents. However, when the concentration of hydroxy acid was too high the catalytic activity decreased. The following order of catalytic activity was found: Ti > Ge > Zr ˜ Sn > Hf > Sb > Bi.