悬浮态乳液聚合条件对聚氯乙烯树脂颗粒特性的影响

Suspended emulsion polymerization of vinyl chloride was carried out in a 5 L autoclave. The influence of agitation, polymerization conversion, dispersant and surfactant on the average particle size (PS) and particle size distribution (PSD), particle morphology and porosity of polyvinyl chloride (PVC) resin was investigated. It showed that the agitator had great influence on the smooth operation of polymerization, PS and PSD. The PS increased and PSD became narrow as polymerization conversion became high. The porosity decreased with the increase of conversion. A convenient choice of additives, both dispersants and non-ionic surfactants, allows one to adjust PS and PSD. The PS decreased with the addition of polyvinyl alcohol or hydroxypropyl methylcellulose dispersants,and increased with the addition of Span surfactants. The addition of dispersants or surfactants also affected the morphology and porosity of resin, and PVC resin with looser agglomeration and homogeneous distribution of primary particles was prepared.     

Preliminary Design of a Loop Reactor for Bulk Propylene Polymerization

Some typical problems in the early design stages of a tubular loop reactor for bulk propylene polymerization are analyzed. Characteristic variables are identified, and a shortcut method for the preliminary estimation of the reactor dimensions is developed. the influences of process variables such as catalytic activity, suspended solid fraction, and average particle size are studied. In particular, a relationship between the average particle size in the reactor and the particle size at both the inlet and the outlet is obtained. the behavior of the reactor under different operating conditions is studied, and critical parameters are identified. Most relevant results are related to the importance of the particle size inside the reactor. the two goals of maximum yield and maximum productivity for a given loop reactor configuration cannot be achieved simultaneously: While catalyst yield increases with the third power of the average particle size in the reactor, the smaller the average particle size in the reactor, the greater the productivity. the steps to be followed for a preliminary design of a propylene polymerization, loop reactor are discussed. A priority list for the sequence of parameters to be adopted is proposed, according to the relative importance of the variables involved.     

搅拌对丁苯吡乳液聚合的影响

研究了搅拌对丁苯吡（简称ＶＰＬ）乳液聚合的影响。通过实验考察了不同搅拌器型式（折叶涡轮和Ｂｒｕｍａｇ－ｉｎ桨）和搅拌强度对ＶＰＬ浮液聚合流体混合、聚合反应速率、胶乳粒径和聚合稳定性的影响。结果表明,折叶涡轮搅拌器不适合ＶＰＬ乳液聚合,而Ｂｒｕｍａｇｉｎ桨比较适合ＶＰＬ乳液聚合;在ＶＰＬ乳液聚合中存在着最佳搅拌速度范围,并提出了最佳的搅拌控制方法。     

乳液聚合过程中搅拌对产品质量的影响

综述了乳液聚合过程中搅拌强度对乳胶粒径、聚合反应速率、乳液稳定性的影响及搅拌器形式的影响。指出应根据不同阶段采用最佳的搅拌控制方法。     

非均相聚合反应中乳化剂用量及搅拌状况对粒径大小的影响

以釜径为74mm,无挡板的玻璃搅拌釜为反应釜,恒温水浴为热源;自来水为冷却水组成了一套冷模的聚合反应实验装置,同时采用蜂蜡为分散相,去离子水为连续相,Span-80及Tween-60为乳化剂,以二叶平桨、二叶斜桨直边、二叶斜桨圆边及三叶后掠式搅拌桨叶为基准,分别研究了乳化剂用量及不同搅拌状况对粒径大小的影响。结果表明：在低转速下,三叶后掠式搅拌桨的搅拌效果最好;在一定范围内,同一转速下的树脂的平均粒径随乳化剂用量的增加而减小。     

Characterization of Miniemulsion Polymerization by Small-Angle Neutron Scattering

Summary Emulsion polymerization is one of the major techniques for the manufacture of adhesives, coatings, thermoplastics and elastomers. In miniemulsion polymerization, relatively stable oil droplets within a size range of 500 to 5000 ? are prepared by emulsifying a monomer in a medium, generally water, with the aid of a surfactant and a hydrophobic compound. Droplet size and size distribution are by far the most important parameters of miniemulsion because they affect directly both the miniemulsion stability and droplet nucleation. Therefore, the understanding of the mechanism ruling miniemulsion polymerization strongly depends on an accurate determination of the particle size. Small-angle neutron scattering has been used for the polymerization study of the 1,3,5-tris(trifluoropropylmethyl)cyclotrisiloxane (F₃). In particular, the shape and the size of the particles before and after the anionic polymerization were sought. Surprisingly, the sizes obtained are of the order of 250 ? which ranges this system rather into the microemulsion domain and the observed growth in the mean particle size (25%) implies that there is no full preservation of the particles during the polymerization reaction. On the other hand, the contribution to the scattering of a second population of smaller particles (38 ?) with a broad size distribution in the polymerized sample is attributed to secondary products leading to a 80% polymerization reaction yield.     

搅拌流化床干燥器流体力学性能研究

分析对比了搅拌流化床和普通流化床的流体力学特性,研究了搅拌转速,物料直径,物料密度和床载量对搅拌流化床床层压降和临界流化速度的影响,提出了临界流化速度的准数关联式,计算结果与实验数据吻合较好。     

悬浮四氟聚合反应釜的搅拌装置探讨

悬浮四氟聚合反应釜的上中央插入式搅拌器和底伸斜入式搅拌器相比,底伸斜入式搅拌器转速易提高,湍流强度与循环速率大,搅拌稳定性好,反应速率快,树脂产品性能提高。     

Modeling of the Suspension Polymerization Process Using a Particle Population Balance

On the basis of a population balance and the kinetic mechanism of free-radical suspension polymerization, a mathematical model of the suspension polymerization process is proposed. The population balance model which describes a mechanism involving the particle size distribution (PSD) in disperse systems leads to an integrodifferential equation. The basic numerical approach of this work is to use the finite-difference-differential technique with the logarithmic scale for particle size. The problem then was reduced to obtaining the numerical solution of a set of nonlinear ordinary differential equations. The numerical solutions were compared to experimental data, such as the reaction conversion which includes the gel effect and the particle size distributions, to yield the model parameters by Marquardt's method. The regression demonstrates reasonably good accuracy.     

A Novel Method to Model Emulsion Polymerization Kinetics: The Explicit Radical-Particle Size Distribution Approach

Abstract:

An alternative approach to model emulsion polymerization is presented that is capable of rigorously solving both particle and radical kinetics for emulsion polymerization: the explicit radical-particle size distribution approach. The method is based on a direct solution of all population balances and fully covers the strong influence of compartmentalization on rates of reactions between macroradicals and, consequently, on chain length averages. An essential and new feature is the compartmentalization factor (D_f), which accounts for compartmentalization in a transparent manner. The generic approach allows for studying the complete emulsion polymerization conversion range, including gel-effect, and the effect of various parameters on both chain length and particle size distribution. Well-known kinetic regimes for emulsion polymerization naturally arise as limiting cases from our model. The dynamic behavior of the model was studied by simulating several realistic seeded emulsion polymerization reactions for styrene. The model dealt with compartmentalization accurately and was able to correctly reproduce the dynamic behavior known to be typical for emulsion polymerization.     

乳液聚合成核阶段的模拟与分析

建立了乳液聚合成核阶段的Monte Carlo模型，并用计算机对一个体积为10^-17m^3的微型反应器中苯乙烯的乳液聚合进行了模拟。以计算机生成随机数作为自由基被胶束和乳胶粒捕获的几率，模拟了在微型反应器中每一个自由基的生成、被胶束或乳胶粒捕获的过程以及每一个乳胶粒的生成及增长过程。通过对每一个乳胶粒在增长过程中各参数的统计计算，研究了乳液聚合成核阶段诸参数(乳胶粒数目、乳胶粒直径与粒径分布、单体转化率、聚合反应速率等)与乳化剂浓度[S]及引发剂浓度[I]的关系。结果表明，苯乙烯的乳液聚合体系中乳胶粒数目与[S]^0.5996[I]^0.4016成正比：在成核阶段乳胶粒直径分布先变宽后变窄，乳液聚合过程中乳胶粒直径分布有自动变窄的趋势；成核阶段持续时间t12与[S]^0.60[I]^0.60成正比，成核阶段结束时的单体转化率X12与[S]^1.20[I]^0.20成正比。     

Experimental Validation of the Explicit Radical-Particle Size Distribution Approach for Modeling Emulsion Polymerization: The Seeded Emulsion Polymerization of Styrene

Abstract:

The objective of the present paper is to demonstrate that the explicit radical-particle size distribution approach correctly predicts the effect of compartmentalization on the overall reaction rates and therefore chain length averages. Modeling results for the seeded emulsion polymerization of styrene were compared with experimental results. Several experiments were carried out with systematically varied compartmentalization of radicals by varying seed latex particle numbers and the amount of initiator. The overall polymerization rate was measured using reaction calorimetry and the final particle size distribution was measured using Transmission Electron Microscopy. The results demonstrated that the model is able to predict successfully the rate of polymerization and particle size distributions as a function of time for all recipes. This proves that the model deals correctly with the effect of compartmentalization on overall reaction rates and thus on chain length averages. The work described in this paper demonstrates that the explicit radical particle size distribution approach is a powerful method for predicting emulsion polymerization kinetics and product properties, such as particle size distributions and chain length distributions.     

Relative shear stability of mini- and macroemulsion latexes

The shear stability of mini- and macroemulsion latexes is compared and quantitatively evaluated with respect to their particle-size distributions. The effect of a few externally added large particles on the shear stability of these two types of latexes was also investigated. All the latexes selected were in the colloidal size range (less than 1 micron). The original particle sizes for the macroemulsion latexes ranged from 141 to 241 nm, and those for the miniemulsion latexes ranged from 96 to 209 nm. The miniemulsion latexes were found to be more shear stable than were their macroemulsion latex counterparts over the particle-size range investigated. This trend was repeated even in the presence of a few large particles. Additionally, seeding experiments suggest that mini- and macroemulsion latexes incur different levels of shear aggregation due to inherent differences in their particle-size distributions. The shear rate used along with the particle size and number were quantitatively shown to significantly influence the aggregation process. Finally, a quantitative method for evaluating relative shear stability in emulsion polymerization was demonstrated, which, although not very rigorous, could serve as a starting point for further quantitative isolation and investigation of the various parameters that affect the shear aggregation process. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1317–1324, 1997     

丙烯酸酯微乳液聚合研究

重点研究以反应型乳化剂(DS6)为主组成复配乳化剂体系,进行间歇式微乳液聚合,通过控制聚合温度、加入功能单体等因素,制备出平均粒径小至21．6nm,粒径分布窄(Poly．=0．109),固含量可高达25％的聚合物(PMMA)微乳液,同时还发现,在这类体系中,其聚合动力学特征是：只存在着明显的增速期和减速期两个阶段。     

偏氟乙烯乳液聚合的气液传质效果影响因素研究

推导了表征气液传质效果的K值计算方法,并研究了聚合釜装填量、搅拌桨型和转速等因素对气液传质效果的影响。结果表明,随着聚合釜装填量和搅拌转速的增大,K值增大,气液传质效果提高;在搅拌转速大于500r/min的情况下,桨型采用上层二叶平桨、下层二叶斜桨的方式明显比单层的二叶斜桨或二叶平桨的K值大,气液传质效果好。确定了5L釜偏氟乙烯(VDF)乳液聚合必需的良好搅拌效果的条件:装填量3L,搅拌转速700r/min,桨型采用上层二叶平桨和下层二叶斜桨;VDF聚合速率达到115g/(L·h),合成出固体质量分数20%、粒径分布窄、稳定性好的聚偏氟乙烯(PVDF)乳液。     

乳液聚合法制备单分散性PS磁性微球的研究

用改进的乳液聚合法,以乙醇／水为反应介质,十二烷基苯磺酸钠为乳化剂,过硫酸钾为引发剂,制备出单分散性聚苯乙烯磁性微球。通过SEM观察其表面形貌、粒径大小及分布,表明具有良好的球形度和一定均匀性。为了制备出粒径小、粒径分布均匀的聚苯乙烯磁性微球,设计了正交实验来优化实验条件;探讨了反应聚合温度、引发剂用量、乳化剂用量及醇水比对微球粒径及粒径分布的影响。实验表明在实验范围内,较低的反应温度、较低的引发剂用量、较高的乳化剂用量、较低的醇水比有利于得到小粒径、高均匀性的PS磁性微球。     

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。     

新型氯乙烯非均相聚合动力学和成粒机理

对以正丁烷（But)为反应介质的新型氯乙烯（VC）非均相聚合动力学和成粒机理进行了研究，根据VC-But二元体系气液平衡方程，由聚合过程气相压力或组成变化计算VC聚合转化率，VC非均相聚合的诱导期不明显，自动加速现象一般发生在聚合前、中期，后期聚合速率较小，新型VC非均相聚合PVC树脂的体粒径与悬浮PVC树脂相当，数均粒径较小，PVC颗粒由基本不熔结的初级粒子组成，颗粒内部初级粒子分布密度大，粒径大，孔隙率高；而在颗粒表层初级粒子分布密度高，粒径小，孔隙率低；树脂的增塑剂吸收率远大于悬浮PVC树脂，根据PVC树脂的颗粒特性和PVC与VC／But混合液的溶解度参数差异，推断聚合成粒机理为：PVC分子链在很低转化率时就从聚合介质中沉析出来并聚集形成微区，初级粒子和颗粒；后期成粒过程包括颗粒内部初级粒子的增长和向表层的离心聚集，颗粒对新形成的大分子链及其初级聚集体的捕捉等。     

分散聚合法制备彩粉的粒径调控

采用分散聚合的方法制备出一种粒径在2～5μm之间,表面光滑、窄分布的彩粉.研究了引发剂、分散剂用量、分散介质中乙醇/水的比例、初始单体比及石蜡用量对彩粉粒径及粒径分布的影响.     

Calculation of the particle size distribution in suspension polymerization using a compartment-mixing model

A modelling strategy for effective estimation of the particle size distribution (PSD) in suspension polymerization is presented. The strategy consists of coupling a population balance equation (PBE) and a compartment-mixing (CM) model to account for the non-homogeneous mixing in the tank reactor. The values for the rate of energy dissipation of each compartment are estimated from Computational Fluid Dynamics (CFD) calculations and experimental reports on systems with the same agitator and geometric characteristics. Model predictions using the CM model are compared with predictions that assume homogeneous mixing and experimental data on PSD from styrene and divinylbenzene pilot-plant suspension polymerization reactors of 1 and 5 L with Rushton and PBT impellers.