聚对苯二甲酸乙二醇酯(PET)是热塑性聚酯中最常用的一类,具有良好的力学性能、耐磨性、耐热性、尺寸稳定性等.基于杜邦公司的"三釜"工艺,设计了由 3 个反应釜和 2 个分离器组成的带有循环生产的 PET 模拟流程,并进行了对苯二甲酸(TPA)/乙二醇(EG)进料量、酯化釜内部压力与温度以及酯化釜/终聚釜停留时间对产品聚合度和分子量的影响分析.结果表明:若要得到高聚合度的 PET,应该使用多个反应釜串联的方式;在流程中,由于循环的存在,选择TPA与EG的进料质量比为2.54∶1,压力为1.013～202.650 kPa,最优操作温度为 260～280℃;在实际生产中,初期应该使用较高的压力,之后逐级降低反应压力,形成一定的差压;在反应初期应尽量降低反应温度,到了反应中后期,可逐级提升反应温度;延长体系在终聚釜中的停留时间,可大幅度提高产品的聚合度.此结果可为下一步工业优化生产提供可靠的模型基础.
Simulation of Stepwise Polymerization Process of Polyethylene Terephthalate
Polyethylene terephthalate(PET)is the most commonly used type of thermoplastic polyester,with good mechanical properties,abrasion resistance,heat resistance,dimensional stability,etc.Based on DuPont's"three-pot"process,a cycled PET production simulation process consisting of three reactors and two separators was designed,and the effect of the TPA/EG feed volume,the internal pressure/temperature of the esterification reactor,and the residence time of the esterification/final polymerization reactor on the degree of polymerization and molecular weight of the product was investigated.The results showed that,to obtain PET with high degree of polymerization,multiple reactors in series should be used;in this process,due to the existence of circulation,the feed ratio of TPA to EG was selected to be 2.54∶1 and the pressure was 1.013～202.650 kPa,and the best operating temperature was 260～280℃;in actual production,higher pressure should be used in the initial stage,and then the reaction pressure should be gradually reduced to form a certain differential pressure;the reaction temperature should be reduced as much as possible in the initial stage of the reaction;in the middle and late stages of the reaction,the reaction temperature should be gradually increased;extending the residence time of the system in the final polymerization reactor could greatly increase the degree of polymerization of the product.This result can provide a reliable model basis for the next industrial optimization production.
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