Tpa-zro<inf>2</inf>-sio<inf>2</inf>-catalyzed polyesterification of tmp polyester

Abstract

A series of tungstophosphoric acid (TPA)-ZrO2-SiO2particles (30 wt% TPA) with various ZrO2contents were prepared by sol-gel method. Using heptanoic acid (HA) as an end-capping agent, trimethylolpropane (TMP) polyester plasticizers were prepared by the TPA-ZrO2-SiO2-catalyzed polyesterification of TMP and adipic acid (AA). The particles were characterized by means of inductively coupled plasma atomic emission spectroscopy (ICP- AES), X-ray diffraction (XRD), fourier transform infrared (FT-IR), ultraviolet-visible diffuse reflectance (UV-VIS DR) and transmission electron microscopy (TEM). TPA with 200 nm microspheric particles were mostly embedded into the network of ZrO2-SiO2mixed oxide. Mole ratio of ZrO2: SiO2was 3:7 resulted in the most suitable composition for the catalyzed polyesterification. Excess ZrO2induced destruction of the ZrO2-SiO2framework whilst some TPA only adsorbed on the support surfaces. TPA-3Z-7S exhibited high catalytic activity and better controllable of the weight average molecular weight (MW) distribution of the TMP polyesters. Under the optimal reaction condition the TMP polyester with MW between ca. 600- 3800 was achievable prepared with excellent yield (up to 93%).