Melt Polycondensation In A Rotating Disc Reactor

熔融缩聚技术在聚合物工业中用于合成热塑性塑料和特种聚合物。例如，饱和聚酯(如聚对苯二甲酸乙二酯-PET和聚对苯二甲酸丁二醇酯-PBT)、聚酰胺、聚芳酸酯和聚碳酸酯可在半间歇或连续缩聚反应器中生产。其中许多过程的特点是多个反应阶段和复杂的反应网络，从而产生各种不想要的副产物。纯熔融单体在没有添加溶剂的情况下聚合--比其他工业聚合过程更环保。该方法也是有利的，因为聚合物可以直接造粒或纺丝成纤维。工业熔融缩聚过程的一个共同特点是，使用多个串联的反应器来使用多个反应阶段。对于聚酯生产，顺序反应程序包括：(A)在连续搅拌釜式反应器中合成单体、低分子量低聚物和低分子量预聚体，和(B)然后在提供大的汽液表面积的终凝聚合反应器(通常是旋转圆盘反应器)中将预聚体聚合成更高分子量的聚合物。最终聚合物产品的性能主要是在这一结束聚合阶段调节的，因此该反应器的优化设计和操作是重要的，也是本研究的目的。具体地说，PI将解决以下问题：(1)影响旋转圆盘上聚合物膜形成的主要因素是什么？膜设计/操作变量与膜厚之间的定量关系是什么？(2)冷凝副产物气泡在传质过程中的作用是什么？如何量化气泡对总的气液传质速率的影响？(3)相邻圆盘之间发生了什么相互作用？搅拌轴上多个圆盘的最佳布局是什么？圆盘在液池中的最佳浸入角度是多少？(4)反应器中液体(聚合物熔体)的整体流动模式是什么？(5)连续精整反应器是如何在稳态和暂态下，在不同的反应堆运行条件和进料条件下表现如何？哪些聚合物的性能受哪些反应堆变量的影响最大？在设计产品质量控制系统时，应如何将聚合物性能参数与反应器操作条件配对？实验工作和反应堆模型都将完成。*/

Melt condensation polymerization techniques are used in the polymer industry for the synthesis of thermoplastics and specialty polymers. For example, saturated polyesters (such as poly(ethylene terephthalate) - PET and poly(butylene terephthalate) - PBT), polyamides, polyarylates, and polycarbonates are manufactured in either semi-batch or continuous polycondensation reactors. Many of these processes are characterized by multiple reaction stages and complex reaction networks that give rise to various unwanted side products. The pure molten monomers are polymerized in the absence of added solvents - a more environmentally friendly process than other industrial polymerization processes. The process is also advantageous because the polymers can be directly pelletized or spun into fibers. A common feature of industrial melt polycondensation processes is that multiple reaction stages are employed using several reactors in series. For PET production, the sequential reaction procedure includes: (a) monomers, low molecular weight oligomers, and low molecular weight prepolymers are synthesized in continuous stirred tank reactors, and (b) the prepolymers are then polymerized to higher molecular weight polymers in finishing polymerization reactors (often rotating disc reactors) where large vapor-liquid surface areas are provided. The final polymer product properties are mostly regulated in this finishing polymerization stage, therefore the optimal design and operation of this reactor is important and is the objective this research. Specifically, the PI will address the following questions: (1) What are the major factors that affect the formation of polymer films on a rotating disc? What are the quantitative relations between the disc design/operating variables and film thickness? (2) What is the role of gas bubbles of condensation byproducts in the mass transfer process? How can one quantify the effect of gas bubbles on the total vapor- liquid mass transfer rate? (3) What interactions occur between the neighboring discs and what will be the optimal layout of multiple discs on the agitator shaft? What will be the optimal angle of disc immersion in the liquid pool? (4) What is the overall liquid (polymer melt) flow pattern in the reactor? (5) How does the continuous finishing reactor behave under various reactor operating conditions and feed conditions at steady state and transient state? What polymer properties are most strongly influenced by what reactor variables? How should one pair the polymer property parameters with reactor operating conditions for the design of product quality control systems? Both experimental work and reactor modeling will be done.***//