Fundamental Research On Synthetic Rubber Production With Supercritical Fluid

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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