Fundamental Research On Synthetic Rubber Production With Supercritical Fluid

这项工作是超临界流体应用于合成橡胶生产过程的基础性研究。研究内容如下：1)超临界流体去除聚合物溶液中的溶剂和未反应单体；2)超临界流体中的溶液聚合。本工作使用的超临界流体是超临界CO2，因为它的临界温度为31℃，所以它允许我们在室温附近操作，并可以通过降低压力很容易地自我去除。溶解实验是用超临界萃取仪进行的。以聚丁二烯为聚合物样品，正己烷为溶剂。在40℃和150 Mpa下进行的萃取实验表明，超临界CO_2能有效去除正己烷，在S/F为100时，可使聚合物溶液中正己烷的浓度降低到1wt%。用一种新的实验…测定了无限稀态下超临界二氧化碳与聚合物之间的分配平衡系数更多的器械。用平衡系数来评价聚合物产品中的残留溶剂是必不可少的。在压力8-20 Mpa，温度80-140℃范围内，用三根填充柱进行了实验，得到的数据表明，重量分配系数在1-2范围内，并随温度和压力的增加而增大。用一个既适用于CO2，又适用于聚合物的状态方程对数据进行关联，并用实验数据确定了其方程参数。利用优化后的参数，我们可以预测聚合物溶液在较宽的溶剂浓度范围内的分配平衡，并设计出超临界CO2聚合物生产中的脱溶过程。作为第一次尝试，以AIBN为引发剂，通过改变4个反应时间，在70℃、0.1、8、15和20 Mpa的条件下，进行了苯乙烯的自由基聚合。通过称量生成的聚合物来确定单体转化率。结果表明，0.1 Mpa和8 Mpa下的聚合反应与本体聚合和有机溶剂中的聚合反应非常相似，而15和20 Mpa下的反应速度较慢，这可能是由于CO2在反应溶液中起到了稀释剂的作用。从相对分子质量来看，由于高相对分子质量聚合物在CO2中的溶解度较小，在聚合过程中发生了聚合物沉淀。这一讨论部分得到了模拟结果的部分支持，并用有机溶剂的速率常数的文献数据进行了验证。值得注意的是，反应体系的相行为是解释超临界流体中聚合反应机理的关键。较少

This work was conduted as a fundamutl study of applying supercritical fluid to synthetic rubber production processes. The researchtopicsare followings ; 1) removal of solventand unreactedmonomer from polymer solution with supercriticalfluid , 2) solution polymerizationin supercriticalfluid.The supercriticalfluid usedin this work is supercritical CO2 sinceit allows for us to operate around room temperature due to its critical temperatureof 31C and to removeitself easily via decreasingpressure.Desolvation experimentwas performedwith a supercriticalextraction apparatus. Polybutadiene was used as a polymer sample and n-hexane as a solvent. The extractionat 40C and 150 Mpa revealed that supercritical CO2 can removefairly amount of n-hexane and reduce the concentration of n-hexanein polymersolution upto 1wt % at S/F of 100. Partition equilibrium coefficient between supercritical CO2 and polymer has been measured at infinitely dilute state via chromatography technique with a new experimental … More apparatus. The equilibirum coefficient was indispensableto evaluate the remaing solvent in polymer products. Experiments were carried out with three packed columnspreparedin this study in the pressure range of 8-20Mpa and at temperatures of 80-140C.The obtained data showed that the weight baed partition coefficientsare in the range of 1-2 and increased with temperature and pressure. An equation of state which can be applied to both CO2 anf polymer, was used for correlation the data, and its equation paraneters were determined with the experimentaldata. With the optimized parameterswe can predictthe partition equilibria in the wide range of solvent concentration in polymer solution and design the desol vation process in polymer Production with supercritical CO2.As a firstattempt, radical polymerization of stirenein supercritical CO2 was conducted with AIBN as an initiator at 70C and 0.1,8,15 and 20 Mpa by varying the 4 reaction time. The monomer conversion was determinedby weighing the produced polymer. The conversiondata suggested that the polymerizationat 0.1,8Mpa is quite similar to bulk polymerization of stireneand that in organic solvent while the reaction ratesat 15 and 20 Mpa are slow, which may be attributableto CO2 playing a role as a dilutantin the reactionsolution. Accordingto the molecularweight, the polymer pricipitation took place in the course of polymerzation because of small solubility of high molecaular weightpolymer into CO2. This discussion was partly supportedby the simulation results with the literaturedata for rate constantspropsed for or ganic solvents. It should be noted that the phase behavior of reaction systemis key to elucidate the mechanism of polymerization in supercritical fluids. Less