Study on the Industrial Production of Organic Fine Powders Using Supercritical Carbon Dioxide

用于聚合物微粉化的常规方法具有若干缺点。近年来，超临界流体（SCF）的PGSS（Particles from Gas Saturated Solutions，气体饱和溶液中的颗粒）工艺作为解决这些缺点的一种方法引起了人们的广泛关注。SCF溶解在熔融聚合物中，高压混合物通过喷嘴快速减压。通过膨胀过程中的冷却作用，聚合物固化，导致通过沉淀形成颗粒。由于PGSS过程不需要在SCF相中溶解聚合物，因此该过程可以应用于广泛的聚合物，并且该应用被研究用于药物、催化剂、涂料、生物聚合物和食品。本文主要研究了超临界流体初始温度、压力、超临界流体浓度和喷嘴结构对超临界流体微粒化的影响 关于我们 尺寸、粒度分布和所得颗粒的形状。用超临界二氧化碳对聚乙二醇（PEG）和聚酯进行了实验研究。结果表明，在温度高于313 K、压力高于10 MPa、CO2浓度高于70 wt%的条件下，可快速得到平均分子量为4000的PEG微粒。随着温度的降低、压力的升高和CO_2浓度的增加，平均粒径减小。根据能量平衡法模拟了减压过程中温度和压力的变化路径，发现随着温度的降低、压力的降低和CO2浓度的增加，聚合物处于液态的时间缩短，平均粒径减小，形状向非球形转变。然而，在这个模拟中的压力的影响是相反的实验结果，这被认为是在喷嘴中的混合物的速度的变化的原因。少

Conventional processes for micronization of polymers have several disadvantages. Recently, PGSS (Particles from Gas Saturated Solutions) process that uses supercritical fluids (SCF) attracts much attention as a solution of the disadvantages. SCF is dissolved in a molten polymer and the high-pressure mixture is rapidly depressurized through a nozzle. By cooling effect in course of expansion the polymer is solidified leading to particle formation by precipitation. Since PGSS process do not require the dissolution of polymers in SCF phase, this process can be applied to wide range of polymers and the application is investigated to pharmaceuticals, catalysts, paints, biopolymers, and foods. However, researches of this process are scare for polymers and mechanism of micronization and effect of process parameters are not known enough.The objective of the present work is to investigate the effect of initial temperature, pressure, SCF concentration and nozzle structure on the average particle … More size, particle size distribution and shape of resulting particles. Experiments were carried out for poly (ethylene glycol) (PEG) and polyester with supercritical carbon dioxide. As the results, fine particles of PEG with average molecular weight of 4000 could be obtained quickly at temperatures higher than 313 K, pressures higher than 10 MPa and CO_2 concentrations higher than 70 wt%. The average diameter decreased with decreasing temperature, increasing pressure, and increasing CO_2 concentration. By simulating the path of temperature and pressure during the decompression based on the energy balance, it was found that the period when the polymer is in liquid state decreased with decreasing temperature, decreasing pressure and increasing CO_2 concentration, and therefore the average diameter decreased and the shape changed to non-sphere. However, the effect of pressure in this simulation was opposite to the experimental results and the reason for this was considered to the change in the velocity of the mixture in the nozzle. Less