对位芳纶（PPTA）是一种高强度、高模量、化学稳定性好、低密度的高性能材料，被广泛应用在航天航空材料、防弹材料、增强材料等领域。由于国外技术垄断，我国当前仍未真正实现对位芳纶国产化。对位芳纶聚合过程反应速率快、体系粘度大、反应放热量大、反应和传质耦合，导致过程控制复杂，而之前国内研究者多以条件优化为主，缺乏过程的基础理论研究。根据对位芳纶聚合过程的特点，本文针对性地提出利用微化工系统高效的传质传热效率、准确停留时间控制的特点，在微化工系统中实现对位芳纶的可控制备。同时研究了对位芳纶聚合过程的基本原理，为其工业化生产提供理论基础。对位芳纶由对苯二胺和对苯二甲酰氯经过缩聚反应得到，该聚合过程属于芳香胺和芳香酰氯之间的反应。本文以苯胺和苯甲酰氯为模型体系，研究了芳香胺和芳香酰氯类的反应机理，同时建立动力学模型，并在微化工系统中测定反应速率常数、活化能、指前因子等动力学参数。在芳香胺和芳香酰氯反应过程中，由于芳香胺和副产物氯化氢的可逆结合作用，导致过程整体达到高收率需要的时间较长。提出在反应体系中加入弱碱性物质氨气实现反应过程强化的方法。氨气主要用于中和副产物氯化氢，抑制副反应发生。研究了氨气强化的机理，建立强化过程的动力学模型，并得到相关动力学参数。在微化工系统中实现对位芳纶的制备，通过热重、红外光谱、X光衍射、偏光显微、元素分析等众多分析方法，验证微化工系统中合成对位芳纶聚合产物的可靠性。通过对微化工系统中聚合条件优化，实现一定链长对位芳纶的可控制备。在此基础上，将微化工系统与传统搅拌釜结合，在微化工系统中实现单体的均匀混合，再在搅拌釜中延长反应停留时间，可以实现重均分子量在15000左右的对位芳纶聚合产物的制备。最后，为解决单体对苯二甲酰氯连续进料问题，提出利用非均相合成的方法制备对位芳纶。首先在N-甲基吡咯烷酮和石蜡油非均相体系中，通过乳液法制备得到重均分子量10000左右对位芳纶产物，验证非均相合成的可行性。同时，首次提出利用氯仿带入单体对苯二甲酰氯的方法，可以在不影响最终聚合反应性能的条件下实现单体对苯二甲酰氯的连续化进料。
Poly(p-phenylene terephthalamide) (PPTA) is a kind of high-performance polymer with high strength, high modulus, good chemical stability, and low density. It is widely used in aerospace, ballistic, and reinforcement fields. Due to the monopoly of foreign technology, China has not yet actually realized the domestic production of PPTA. The polycondensation of PPTA has the characteristics of fast reaction rate, high viscosity, high reaction heat, and complex coupling of reaction and mass transfer, leading to complicated process control. Previously researchers mostly focused on condition optimization and lacked basic theoretical research of the process. According to the characteristics of the PPTA polycondensation, this work adopted a microstructured chemical system to achieve preparation of PPTA, which has high mass transfer and heat transfer efficiency, and accurate residence time control. At the same time, the basic principles of the PPTA polycondensation were also studied to provide a theoretical basis for its industrial production.PPTA is prepared through polycondensation of p-phenylenediamine (PPD) and terephthaloyl chloride (TPC). The polycondensation is the reaction between an aromatic amine and an aromatic acyl chloride. The reaction of aniline with benzoyl chloride was selected as a model system to study the reaction mechanism between aromatic amines and aroyl chlorides. A kinetic model was established and parameters such as reaction rate constants, activation energy and pre-exponential factor were determined in a microstructured chemical system. In the reaction between aromatic amines and aromatic acyl chlorides, it takes a long time for the overall process to reach a high yield due to the reversible by-reaction between aromatic amines and hydrogen chloride.In order to solve this problem, ammonia was used to enhance the reaction process. Ammonia was mainly used to neutralize hydrogen chloride, reducing side reactions. In addition, the mechanism of process intensfication was further studied, and a kinetic model was established.PPTA was successfully prepared in a microsturctured chemical system. The reliability of the product was proved by many means, such as thermogravimetry, infrared spectroscopy, X-ray diffraction, polarized light microscopy, elemental analysis and so on. Through the optimization of the experimental conditions, PPTA with a certain chain length could be prepared controllably. Further, through the combination of a microstructured chemical system and a conventional stirred tank, uniform mixing of monomers was achieved in the microstructured chemical system, and reaction residence time was further extended in a stirred tank. As a result, PPTA with an Mw of about 15000 was obtained. Finally, in order to achieve continuous feed of TPC, PPTA was prepared in a heterogeneous method. Firstly, the preparation of PPTA with an Mw of about 10000 was achieved in N-methylpyrrolidone and paraffin oil system, which verified the reliability of heterogeneous preparatioin methods. Further, we proposed the method of feeding TPC with chloroform. Continuous feed of monomer could be achieved without affecting the properties of the final polymer product.
