Catalysts For Synthesis Of Poly (Trimethylene Terephthalate) By Direct Esterification

Poly(trimethylene terephthalate) is a relatively new semicrystalline thermoplastic polyerster. As its excellent performance, this polymer has been widely used in the fiber and engineering plastic areas. However, the local production of PTT doesn't go well, due to the intrinsic viscosity of the PTT is not high as been used for spinnings. The viscosity of PTT has relation with catalysts, reaction conditions, reactors and so on. Among these, the catalyst is the key factor. Therefore, two types of catalysts were designed, prepared and used as catalyst for the PTT synthesis in this paper.The first type is organic tin catalyst, such as stannous oxalate, stannous malonate and stannous succinate, which are prepared by stannous chloride and the corresponding acids. The catalysts were characterized by FT-IR and NMR. The results of experiment show that the yield of stannous oxalate is higher than others. The reason may be that malonic acid and succinic are not easily form coordinating bond between acid and tin ion, with structure of the flexible methylene, leading to a larger space resistance. These catalysts for PTT synthesis have some activities, but the activities are not high enough.The second type is composite catalysts, such as SnO2-SiO2 complex and SnO2-TiO2 complex, which are prepared by flame hydrolysis. The catalysts were characterized by SEM. The performance of composite catalysts for PTT synthesis was also investigated. The experiment results show that two types of catalysts for PTT synthesis have activities. But it lower than organic tin catalysts.In addition, the effection of catalyst amount, ratio of PDO/PTA, reaction temperature etc. on the reaction rate of esterification and performance of the PTT were also investigated.