固定床中PET固相聚合的研究

SOLID STATE POLYMERIZATION OF PET IN FIXED BED REACTOR

本文利用固定床反应器对N_2保护下的PET固相聚合反应进行研究,在低于粘结点温度下预聚合之后再实施高温聚合,可消除切片粘结,提高反应速率及产品质量。建立了化学反应和扩散过程共同控制下的动力学模型,其计算结果表明从粒子中心到表面,固相聚合表现反应速率和分子量随副产物小分子(乙二醇和水)的浓度减小而增大,并且描述了反应温度、载气中小分子含量和预聚体切片粒径对反应的影响,为优化工艺操作,提高产品质量提供了理论依据。

The PET Solid State Polymerization was studied in a fixed bed reactor with nitrogen, as carrying gas, flowing through it. In order to avoid sticking between chips, prepolymerization had been done at a temperature below the sticking point for certain time before the SSP happened at high temperature. The kinetics of PET SSP in a single chip was appropriately simulated with a model combining diffusion rate with reaction rate. The model indicates that the SSP reaction rate from the core to the surface of the chip increases steadily. This is due to gradual reduction of the concentrations of byproducts such as ethylene glycol and water.The effects of the reaction temperature, the concentration of byproducts in the inert carrying gas stream and the particle size on the SSP reaction can also be explained by using this model.