有机蒙脱土对PET后缩聚反应的影响

Study on the Influence of Nanoclay on Polycondensation of Poly-(ethylene terephthalate)

实验研究了有机蒙脱土对PET后缩聚反应过程的影响。结果表明有机蒙脱土对PET缩聚反应的前期有加速作用,但由于对气液传质过程有阻碍作用,导致了PET后缩聚反应的速度下降。蒙脱土的存在还使缩聚过程中二甘醇(DEG)基团及端羧基基团浓度上升。根据缩聚反应机理建立了PET后缩聚过程的数学模型,并依据实验结果拟合出缩聚反应动力学参数及气液传质系数。模型计算结果能较好地反映PET后缩聚过程中特性粘数的变化及DEG基团的生成规律,但对端羧基浓度的变化存在较大的偏差。

The influence of nanoclay on the polycondensation of Poly(ethylene terephthalate) (PET) was studied. The results showed that with the addition of nanoclay into the polycondensation system, the reaction rate increases in the early stage, while decreases in the later stage. It was also found that the contents of diethylene glycol (DEG) groups and the end-acid groups increased during the polycondensation, due to the presence of nanoclay. A kinetic model and a mass transfer model for the polycondensation process were developed on the basis of reaction mechanism. Using the models established for the PET polycondenzation process with or without the nanoclay, the parameters, ki, Ki', Ei, Ai, Kla, were estimated, and it was found that the coefficient of mass transfer greatly decreased by adding nanoclay. According to the calculating results, it shows that the models fit well with the changes of the intrinsic viscosity and the formation of the DEG group content for the PET polycondenzation process. However, there are errors in calculating the changes of the end-acid group content with the models in which the thermal depolymerization of PET has not been considered.