苯乙烯悬浮聚合工艺条件研究

通过悬浮聚合法制取了聚苯乙烯(PS)。主要研究了引发剂用量、搅拌速度、温度、分散剂用量以及水和单体的比对苯乙烯悬浮聚合的影响。结果表明:在苯乙烯20mL,引发剂过氧化二苯甲酸用量0.9g,搅拌速度250r/min,反应时间2.5h左右,反应温度82~85℃,水和单体比为5∶1(体积比)的实验条件下,当分散体系为MgCl(21mol/L)溶液1mL、NaOH(1mol/L)溶液2mL时,可制得合适颗粒尺寸、透明度良好、产率高达99.1%的聚苯乙烯。     

氯乙烯悬浮聚合复合引发剂体系的中试研究

提出了生产3种牌号PVC树脂的复合引发剂配方。中试结果表明:采用悬浮法生产S-700、S-1000和S-1300 PVC树脂时宜分别采用Tx-36和Tx-23、EHP和Tx-99、Tx-99和Tx-23复合过氧化物引发剂体系,聚合时间可控制在3.2~3.8 h,反应过程平稳,反应速率快,生产的PVC树脂质量优良。     

氢氧化镁在苯乙烯悬浮聚合中的应用研究

利用NaOH和MgCl_2反应制备悬浮聚合分散剂氢氧化镁,以过氧化二苯甲酰(BPO)为引发剂,进行苯乙烯(St)悬浮聚合。研究了分散剂用量、引发剂用量、水和单体比、搅拌速度、反应温度及反应时间对聚苯乙烯(PS)珠粒大小、均匀程度和产率的影响。结果表明:氢氧化镁作为分散剂有很好的稳定作用,当苯乙烯为12 mL,适宜的反应温度为95℃;MgCl_2(1 mol/L)4 mL,NaOH (1 mol/L)8 mL;BPO 0.35g;V(水)∶V(St)=4.0∶1;搅拌速度300 r/min,反应时间80 min,制得的PS珠粒透明度良好,颗粒大小均匀,粒径在1～2 mm,收率可以达到90%。     

苯乙烯悬浮聚合实验的改进研究

悬浮聚合实验是一个经典的高分子化学教学实验,国内高校开设该实验,普遍选用聚乙烯醇PVA-1799作为分散剂、苯乙烯为单体,悬浮聚合制备聚苯乙烯微球。但该实验悬浮体系不稳定,致使实验成功率不高。为改进此状况,在不改变悬浮聚合的本质与实验步骤的前提下,作者在分散剂PVA-1799中加入10%的PVA-1788,以提高实验悬浮体系的稳定性,实验成功率提升至90%以上。实验的成功极大调动了学生做实验的积极性和学习热情。改进后的实验,有利于学生加深理解悬浮聚合的本质,以及与乳液聚合的区别,可将其作为大学高分子化学实验课程的教学内容。     

苯乙烯悬浮聚合工艺条件优化

研究了影响苯乙烯悬浮聚合的主要因素。探讨了引发剂用量、搅拌速度、反应温度、分散剂用量、水和单体的体积比对苯乙烯悬浮聚合的影响。结果表明,在苯乙烯用量为20 mL、水与单体的体积比为5∶1(即水用量为100mL)、分散剂聚乙烯醇用量为0.073 g、引发剂过氧化二苯甲酰用量为0.7 g、搅拌速度为400 r.min-1、反应温度为80~85℃的最佳悬浮聚合条件下,得到了颗粒尺寸适中、透明度良好、产率高达98.95%的聚苯乙烯。     

在无机分散剂存在下苯乙烯悬浮聚合宏观成粒的特征

以苯乙烯悬浮聚合为体系,考察羟基磷酸钙(HAP)或HAP与聚乙烯醇(PVA)复合为分散剂体系时,各种因素如分散剂浓度、油水比、搅拌速度等与瞬时液滴大小及分布之间的关系,并分析讨论瞬时液滴分散、合并的过程特征.结果表明,悬浮苯乙烯液滴聚合宏观成粒的特征与分散剂的分散机理无关,仅体现液滴分散、合并的过程特点.当采用分批加分散剂时,实验观察到瞬时液滴大小分布呈由单峰过渡到双峰,再发展成单峰分布的特征,从而找出了以分批加分散剂方式制备窄分布聚合物颗粒的理论依据.     

TCP为分散剂时苯乙烯悬浮聚合分散特性因素对瞬间液滴的影响

以磷酸三钙(Tripotassium Phosphate or TCP)为苯乙烯悬浮聚合的分散剂,实验研究了分散剂的用量、表面活性剂的浓度、油水比、电介质盐及搅拌转速等因素对液滴聚合增长的影响。着重分析在无机分散剂存在下,液滴分散、合一的特点。从而关联出了瞬间液滴平均直径的准数方程:(d)_(32)/D=1.86(Ф)~(0.388)We~(-0.444)(μ_d/μ_c)~(0.103)     

无外加表面活性剂的苯乙烯悬浮聚合

针对传统悬浮聚合制备聚苯乙烯颗粒粒径分布宽、有效粒子收率低的问题,采用过硫酸铵/磷酸钙复合分散剂体系,在无外加表面活性剂情况进行苯乙烯悬浮聚合,制备了聚苯乙烯珠粒。通过对聚合稳定性、聚苯乙烯珠粒粒径及分布的测定与分析,考察了磷酸钙、过硫酸铵的用量及比例对悬浮聚合的影响,并分析了过硫酸胺对悬浮聚合的分散稳定机理。结果表明,当过硫酸铵和磷酸钙的用量分别为单体质量的0.01%和1.00%时,悬浮聚合体系稳定,得到的粒子透明性好,平均粒径为1.35 mm,粒径分布窄;通过改变过硫酸铵和磷酸钙的用量,可以调节聚苯乙烯珠粒的平均粒径。     

基于均匀设计的苯乙烯分散聚合反应研究

本文基于均匀设计方法对苯乙烯的分散聚合反应进行了试验设计,并通过回归分析,建立了聚苯乙烯粒子相关性能参数(聚苯乙烯粒子分子量、粒径大小及分布)和各变量(单体浓度、稳定剂用量、引发剂用量和反应介质溶度参数)之间的回归方程。根据回归方程进行了分散聚合反应的配方优化,得到了约束条件下的苯乙烯分散聚合反应配方,实测值与预测值比较结果表明,回归方程的预测值与优化配方制备的PS粒子的各项性能实测值存在一定的偏差(相对偏差在15%以内),但仍对试验配方设计有一定的指导作用。     

Semibatch styrene suspension polymerization processes

Emulsion and suspension polymerization processes have widely been studied for more than 40 years. Although both polymerization processes are performed in heterogeneous media, each one presents its own typical characteristics, such as the particle size distribution, molecular weight distribution, polymer particle nucleation rate, and polymerization rate. In this study, semibatch styrene suspension polymerizations were carried out with feed compositions typical of emulsion processes. The initial reactor charge resembled the recipe of standard styrene suspension polymerizations, and the emulsion polymerization constituents were added during the batch. The influence of the moment at which the emulsion feed was started on the course of the polymerization and the effects of the feed on the polymer properties were analyzed. The polymer particle morphology and the average molecular weights changed very significantly with the emulsion feed time, and the changes could lead to the production of broad molecular weight distributions. Core–shell polymer particles could also be obtained, with the core being formed of polymer particles originating from the suspension polymerization process and the shell being formed of polymer particles originating from the emulsion polymerization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3021–3038, 2003     

氯乙烯悬浮聚合分散体系的中试研究

通过大量试验分析了HPMC-E50和HPMC-F50在氯乙烯悬浮聚合中对PVC树脂的影响,从而确定了复合分散体系的质量分数以及分散剂的配比。结果表明,PVA和HPMC-E50复合分散体系的分散能力优于PVA和HPMC-F50复合分散体系;在悬浮聚合中,PVA和HPMC-E50复合分散体系与VCM的比例以0.05%~0.06%为宜;在PVA和HPMC-E50复合分散体系中,HPMC-E50所占比例以40%~60%为宜。     

Applied kinetics of styrene suspension polymerization

In order to describe the kinetics of styrene suspension polymerization, it was proposed to apply the concept of the organized space of experiment formed by the results of kinetic experiments at different combinations of initial conditions, the properties of which can be determined using factor analysis. For this purpose, a 5 × 5 matrix of experiments performed at five temperatures and five initiator concentrations was implemented. Using the reduction of the obtained curves to the unified dimensionless time scale and performing the merge and ordering operation on the curves, it was shown that the introduction of seven empirical parameters was sufficient for the complete characterization of the entire space. A semi-empirical dependence of the monomer conversion on the dimensionless time was obtained; it was adequate to the experiment.     

磁场引发苯乙烯分散聚合反应的研究

本文采用苯乙烯的分散聚合反应体系为研究对象,在无外加温度、压力及其它物理手段的前提下,直接利用磁场在室温条件下引发苯乙烯的分散聚合反应,成功制备出了聚苯乙烯微球。研究结果表明,交变磁场作用引发苯乙烯分散聚合生成了聚苯乙烯,其重均分子量Mw=96856,数均分子量Mn=13162。所制备的聚苯乙烯微球的粒径为1—2μm,恒定磁场条件下制备的聚苯乙烯微球重含有部分不成形的杂质,而交变磁场条件下制备的聚苯乙烯微球的球形度规整,表面光滑,无缺陷和杂质。     

Modeling of semibatch styrene suspension polymerization processes

We developed a mathematical model to describe the behavior of semibatch styrene suspension polymerization processes, where the constituents of a typical emulsion polymerization process are added into the reaction vessel during the course of a typical suspension reaction. This technique was recently described for the production of core–shell polymer particles. The model assumes that the nucleated emulsion particles can agglomerate with the sticky and much bigger suspension particles and that the agglomeration rate constant is a function of the internal states of the suspended droplets. The proposed model presented good agreement with experimental conversion, average molecular weight, and molecular weight distribution data. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1950–1967, 2005     

氯乙烯悬浮法聚合分散体系综述

简单介绍了国内外氯乙烯悬浮聚合分散体系应用情况及常用的聚乙烯醇及纤维素类分散剂的品种和规格。具体分析了影响聚乙烯醇及羟丙基甲基纤维素分散剂分散能力及保胶能力的因素。指出了PVC生产中应用分散剂时的一般规律,并探讨了不同搅拌强度、转化率和充N2压力下分散剂的不同应用对聚合体系的作用情况。     

Study of suspension polymerization of styrene with a circular loop reactor

A circular loop reactor was devised and used to study the suspension polymerization of styrene. The transient droplet diameter distributions and the final particle size distributions were measured by changing the impeller diameter and the impeller speed. The effects of the impeller diameter on the size distributions and mean sizes of the final polymer particles were investigated. In the case of lower mixing power, the mean polymer droplet diameters depend upon impeller diameter in the early stage of polymerization, but become almost identical irrespective of the impeller diameter after the middle stage. In the case of higher mixing power, the mean polymer droplet diameters are almost identical irrespective of the impeller diameter throughout polymerization. The final mean particle sizes are correlated only with mixing power.     

Unsteady stirring method used in suspension polymerization of styrene

An unsteady stirring method, that is, coreverse rotation with different periodic intervals, was adopted to the suspension polymerization of styrene. Experiments were carried out in a 0.5‐L flat‐bottom flask with a six‐blade Rushton turbine. Parameters affecting the final particle size and the particle size distribution under the unsteady stirring conditions, such as the agitation speed and the periodic interval, had been studied in detail, and the results were compared with those under a steady stirring one. The experimental results showed that the average particle size decreased and the uniformity final particle size distribution could be significantly improved when unsteady stirring approach is used. These were explained as the result of the decrease of the coalescence rate during the suspension polymerization when the unsteady stirring method was used. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1431–1438, 2000     

Unsteady stirring method staged used in suspension polymerization of styrene

The results of an unsteady stirring method staged, used in the suspension polymerization of styrene in a lab‐scale batch reactor, are presented. Variation of droplet size during the whole polymerization process under the unsteady stirring condition, compared with that under a steady stirring condition, was found to be small. According to the variable droplet size character, two methods were used to divide the polymerization process into four stages and the unsteady stirring method was used in only one stage of each experimental run. By these operations, the optimum operation of obtaining large particle product with uniform particle size distribution was achieved. The results suggest that controlling the droplet coalescence process is more important than controlling the initial droplet size distribution to obtain uniform final particle products. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1873–1881, 2001