Development of Highly Precise Controlling Methods for Polymer Microspher by Taking Advantage of Nonlinear Dynamics

本研究试图利用连续乳液聚合过程中的非线性动力学来控制乳液的粒径分布。当在低于乳化剂临界胶束浓度的条件下，在CSTR中进行醋酸乙烯乳液聚合时，在与时间无关的稳态操作中获得的单体转化率在临界反应温度或平均停留时间下从0急剧上升到60%以上。在非稳态操作中，平均停留时间或反应温度在两个值之间交替切换，一个值使单体转化率为零，另一个值在通常的稳态操作中使单体转化率很高。周期开关操作在时间上引起了单体转换的振荡。粒径分布随开关操作同步变化。研究表明，通过调整平均停留时间或反应温度的时间变化的频率或幅度，可以控制粒径分布。本研究发现，即使单体转化率保持在稳定状态，粒径分布也会在非常大的时间周期内振荡。研究表明，振荡是由聚合反应和乳胶颗粒聚集之间的竞争性相互作用引起的。为了改变胶乳颗粒的胶体稳定性，在某些情况下加入了非离子表面活性剂。非离子表面活性剂和阴离子表面活性剂的混合物对抑制振荡非常有效。为了利用粒径的振荡，在两个连续搅拌釜串联系统中进行醋酸乙烯乳液聚合。通过改变叶轮的转速和平均停留时间可以控制其振荡行为。用两个CSTR串联的研究表明了生产各种聚分散乳胶颗粒的可能性。少

This research attempted to take advantage of the nonlinear dynamics in continuous emulsion polymerization processes in order to control latex particle size distribution. When the emulsion polymerization of vinyl acetate was conducted in a CSTR under conditions below the critical micelle concentration of the emulsifier, the monomer conversion attained in a time-independent steady-state operation showed a drastic rise from 0 to over 60% at a critical reaction temperature or mean residence time. The mean residence time or the reaction temperature was switched alternately between two values in the non-steady-state operation, one giving zero monomer conversion and the other a high monomer conversion in the usual steady-state operation. The periodic-switching operation induced oscillations in monomer conversion in time. The particle size distribution varied synchronously with the switching operation. This research showed the possibility of controlling the particle size distribution by adjust … More ing the frequency and/or the amplitude of the temporal variation of the mean residence time or reaction temperature. This research found that even while the constant monomer conversion was maintained at the steady state, the particle size distribution oscillated with a very large time period. This research revealed that the oscillations occur by a competitive interaction between polymerization reaction and aggregation of latex particles. In order to vary the colloidal stability of latex particles, a nonionic surfactant was added in some cases. It was found that using a mixture of a nonionic surfactant and an anionic surfactant was very effective for suppressing the oscillations. In order to take advantage of the oscillations of particle size, emulsion polymerization of vinyl acetate was performed in a system of two continuous stirred tank reactors in series. The oscillatory behavior could be controlled by varying the rotational speed of the impeller and the mean residence time. The research using two CSTR in series indicated the possibility of producing various poly-dispersed latex particles. Less