Production of uniform-sized polymer particles by bubble column type polymerization reactor

在罐式聚合反应器中，悬浮聚合通常是用搅拌器将单体分散在水中进行，而聚合得到的聚合物颗粒尺寸分布较广，需要对聚合物颗粒进行分类。因此，通常要求在聚合过程中节约能源和材料。本文从实验和理论两方面研究了单喷嘴浸没在液体中的气泡形成行为。本研究扩展到两相气泡的形成，即单喷嘴浸没在温度低于分散液体沸点的连续液体中的相变蒸汽气泡的形成。本研究在非球形气泡形成模型的基础上，采用恒流条件下的理论模型模拟了两相气泡的体积和形状。在该模型中，气泡颈部的长度等实验数据作为气泡的条件，如果气泡颈部闭合，则不需要更多的分离，气泡自然分离。计算结果较好地说明了实验结果。影响两相气泡形成过程的参数有两相气泡内气相与连续液相的温差、蒸汽通过喷嘴的流量和喷嘴内径。该两相气泡形成模型较好地预测了两相气泡完全凝结时液滴的大小。基于对两相气泡形成的基本认识，我们尝试用热玻璃制成的循环泡柱式聚合反应器制备尺寸均匀的聚合物颗粒。该反应器由由静止部分、单体汽泡形成部分和单体聚合部分组成的下水管部分和控制循环连续相温度的提升管部分组成。在静止部分，对单体液体进行加热汽化，使单体蒸汽泡在形成部分的恒流喷嘴处形成。聚合部分采用锥形管。为了使单体液滴保持在聚合部分，循环连续相的表面速度由循环泵控制。为了在该反应器中生产醋酸乙烯聚合物颗粒，研究了原料的添加顺序，选择了合适的添加顺序。用数码显微镜对所得聚合物颗粒的大小和粒径分布进行了测量。并与传统搅拌槽聚合反应器进行了比较，得到了醋酸乙烯聚合物颗粒明显的粒径分布。少

The suspension polymerization has been done normally by dispersing monomer in the water with stirrer in a tank polymerization reactor, whereas the polymer particles obtained have rather broad size distribution and the classification of polymer particles is necessary. Therefore, it is usually requested to save energy and material in the polymerization process. We have studied experimentally and theoretically the behavior of bubble formation at a single nozzle submerged in liquid. This research was extended to the two-phase bubble formation, that is, the vapor bubble formation with phase change at the single nozzle submerged in continuous liquid whose temperature is lower than the boiling point of dispersed liquid. In this research, the volume and shape of two-phase bubble were simulated by the theoretical model based on our non-spherical bubble formation model under the constant flow condition. In this model, the experimental data such as a length of bubble neck as a condition of bubble … More detachment does not need and the bubble naturally detaches if the neck of the bubble closed. The calculated results elucidate relatively well the experimental ones. The parameters which affect two-phase bubble formation process are temperature difference between vapor phase inside the two-phase bubble and continuous liquid phase, vapor flow rate through the nozzle and nozzle inner diameter. This two-phase bubble formation model predicts well the droplet size at complete condensation from two-phase bubble.Based on this fundamental understanding of two-phase bubble formation, we tried to produce the uniform-sized polymer particles by the circulating bubble column type polymerization reactor made of pyrex glass. This reactor is constructed from the downcomer part composed of the still part, the formation part of monomer vapor bubble and the polymerization part of monomer, and the riser part where the temperature of the circulating continuous phase is controlled. In the still part, the monomer liquid was heated and vaporized so that the monomer vapor bubbles were formed at the constant flow nozzle in the formation part. The tapered pipe was used for the polymerization part. To keep the monomer droplet in this polymerization part, the superficial velocity of the circulating continuous phase was controlled by the circulation pump. To produce vinyl acetate polymer particles by this reactor, the order of feed materials addition was investigated and the appropriate order was selected. The size and size distribution of the polymer particles obtained were measured with digital microscope. The sharp size distribution of vinyl acetate polymer particle was obtained by this reactor was compared with that by the conventional stirred tank polymerization reactor. Less