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

悬浮聚合通常是在釜式聚合反应器中用搅拌器将单体分散在水中进行的，但得到的聚合物粒子具有较宽的尺寸分布，需要对聚合物粒子进行分类。因此，在聚合过程中通常要求节能、节材。我们从实验和理论上研究了单个喷嘴在液体中形成气泡的行为。将这一研究扩展到两相气泡的形成，即在温度低于分散液体沸点的连续液体中的单个喷嘴上相变汽泡的形成。本研究在非球形气泡形成模型的基础上，对恒流条件下两相气泡的体积和形状进行了数值模拟。在该模型中，以气泡颈长等实验数据作为气泡…的条件不需要更多的分离，如果气泡的颈部关闭，气泡自然会分离。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气泡内汽相与连续液相间的温差、气相通过喷嘴的流量和喷嘴内径。这一两相气泡形成模型很好地预测了两相气泡完全凝聚时的液滴大小。基于对两相气泡形成的基本认识，我们尝试用高温玻璃制成的循环鼓泡塔式聚合反应器来生产尺寸均匀的聚合物粒子。该反应器由蒸馏部分、单体汽泡形成部分和单体聚合部分组成的下降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，单体液体被加热和汽化，从而在成型部分的恒流喷嘴处形成单体蒸汽气泡。聚合部分采用锥形管。为了保证聚合过程中单体液滴的稳定，循环连续相的表观速度由循环泵控制。用该反应器生产醋酸乙烯酯聚合物粒子，考察了原料的投加顺序，选择了合适的投料顺序。用数码显微镜测量了聚合物粒子的大小和尺寸分布。并与传统的搅拌釜聚合法进行了比较，得到了较好的聚醋酸乙烯酯颗粒尺寸分布。较少

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