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

悬浮聚合通常通过在釜式聚合反应器中用搅拌器将单体分散在水中来进行，然而所获得的聚合物颗粒具有相当宽的粒度分布，并且聚合物颗粒的分级是必要的。因此，通常要求在聚合过程中节能、节材。本文从实验和理论上研究了单喷嘴浸没在液体中时气泡的形成行为。本文将研究扩展到两相气泡的形成，即在温度低于分散液沸点的连续液体中，单喷嘴处发生相变的汽泡形成。本文在非球形气泡形成模型的基础上，采用理论模型对恒流条件下两相气泡的体积和形状进行了模拟。在该模型中，将实验数据如汽泡颈长度作为汽泡产生的条件 关于我们 不需要分离，并且如果气泡的颈部闭合，则气泡自然分离。计算结果较好地解释了实验结果。影响两相气泡形成过程的参数有两相气泡内汽相与连续液相的温差、通过喷嘴的蒸汽流量和喷嘴内径。该两相气泡形成模型能较好地预测两相气泡完全冷凝时的液滴尺寸。基于对两相气泡形成的基本认识，我们尝试用耐热玻璃制成的循环式鼓泡塔聚合反应器制备尺寸均匀的聚合物颗粒。该反应器由降液管部分和提升管部分构成，降液管部分由蒸馏器部分、单体蒸气泡形成部分和单体聚合部分组成，提升管部分控制循环连续相的温度。在蒸馏器部分中，单体液体被加热并蒸发，使得在形成部分中的恒流喷嘴处形成单体蒸气泡。锥形管用于聚合部分。为了保持单体液滴在该聚合部分中，通过循环泵控制循环连续相的表观速度。为了通过该反应器生产乙酸乙烯酯聚合物颗粒，研究了进料的添加顺序并选择了合适的顺序。用数字显微镜测量所获得的聚合物颗粒的尺寸和尺寸分布。与传统的搅拌釜式聚合反应器相比，该反应器获得的醋酸乙烯酯聚合物粒子的粒度分布较窄。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