Particle features of poly(vinyl chloride) resins prepared by a new heterogeneous polymerization process

The heterogeneous polymerization of vinyl chloride monomer (VCM), with n‐butane as the reaction medium, was used to prepare poly(vinyl chloride) (PVC) resins. The particle features of the resulting resins and the particle formation mechanism of the polymerization process were investigated. The PVC resins prepared by the new polymerization process had a volume‐average particle size comparable to that of suspension PVC resins and a lower number‐average particle size. From scanning electron micrographs, it could be seen that the new PVC resins had a regular particle shape and a smooth surface with no obvious skin. They also had a high porosity. The new PVC resins were composed of individual and loosely aggregated primary particles. The diameter of the primary particles in the top layer of the grains was smaller than that of the primary particles in the center part of the grains. On the basis of the particle features of these PVC resins, a particle formation mechanism for the new polymerization process was proposed. PVC chains precipitate from a VCM/n‐butane mixed medium to form primary aggregates at a very low conversion, and the primary aggregates of the PVC chains aggregate to form primary particles, which further aggregate to form grains. The primary particles and grains grow by the capture of newly formed PVC chains and their primary aggregates and by polymerization occurring inside the aggregates. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 954–958, 2003     

Die Herstellung von Thermoplastisch verarbeitbarem tieftemperatur-Masse-Polyvinylchlorid

A mass polymerisation process for the manufacture of thermoplastically processable poly(vinylchloride) at low temperatures has been developed on a pilot plant scale. The new resins are superior to conventional PVC by a 10 to 15°C higher softening point. Low temperature PVC with a degree of polymerisation of about 10³ may be processed by extrusion, calendering, injection and blow moulding. Crucial steps on the course to technical realization were the search for economically reasonable, active chain transfer agents and the development of a polymer with suitable particle size distribution by pre-polymerisation.     

Emulsion Polymerisation of Styrene and Vinyl Acetate

Kinetic data on the emulsion polymerisation of styrene are discussed in the light of the Smith-Ewart theory as modified by Gardon. It is shown that at least in the beginning of the reaction serious discrepances exist between experimental results and the theoretical concept. An electrolytic effect in cationic emulsifier systems was found. Emulsion polymerisation of vinyl acetate was investigated and the mechanism is discussed. The polymerisation of vinyl acetate in aqueous solution without added emulsifier begins as a true solution polymerisation but very soon changes to a suspension polymerisation. The latex particles formed are an order of magnitude larger than those obtained in the emulsion polymerisation and have a very narrow size distribution. There seems to be a very short period of particle formation in this system.     

分散剂和非离子型表面活性剂对悬浮聚氯乙烯树脂颗粒特性的影响

研究了聚乙烯醇(PVA)分散剂和非离子型表面活性剂对悬浮聚氯乙烯(PVC)树脂颗粒特性的影响。结果表明随着PVA醇解度的增加，PVC树脂的颗粒规整性和表现密度增加，孔隙率和吸油率降低；随着非离子型表面活性剂添加量的增加，PVC树脂的平均粒径和吸油率增大。从PVA和表面活性剂在水一油两相分配出发，讨论了PVA醇解度和添加非离子型表面活性剂对PVC树脂的颗粒特性影响机理。     

Thermal characterization of poly(vinyl chloride) samples prepared by living radical polymerization: Comparison with poly(vinyl chloride) prepared by free radical polymerization

Poly(vinyl chloride) (PVC) samples were synthesized by a living radical polymerization (LRP) method and compared with commercial PVC prepared by the conventional free radical polymerization (FRP). The differences were assessed, for the first time, in terms of viscosimetry parameters and thermal analysis. The LRP method used to prepare the PVC‐LRP samples is the only one available to obtain this polymer free of structural defects, being of commercial interest in a view of preparing a new generation of PVC‐based polymer with outstanding performance. The polymerization temperature selected (35°C) to prepare the LRP samples is currently used in the industry to prepare PVC‐FRP grades with moderate to high molecular weight. Since the thermal stability is a direct consequence of the polymer structure, this study is of vital importance to understand the potential of new PVC‐LRP. The thermoanalytical measurements demonstrate an enhanced thermal stability of PVC‐LRP when compared with its FRP counterpart. The PVC‐LRP sample with very low molecular weight reveals a higher thermal stability than the most stable PVC‐FRP sample. It is the first report dealing with thermal analysis of PVC prepared by LRP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of fine fiberglass‐resin powders from waste printed circuit boards by different milling methods for reinforcing polypropylene composites

In this study, different milling methods were used to prepare fine fiberglass‐resin powders (FRP) from waste printed circuit boards for the sake of obtaining high‐performance polypropylene (PP)/FRP composite. The processability and appearance of composites can be greatly improved through further milling of FRP; smaller average particle size and narrower particle size distribution can be obtained by pan milling as compared with jet milling and planetary ball milling. Mechanical test results showed that fine FRP prepared by pan milling could be used as reinforcing fillers in the PP composites and possessed better mechanical properties than other two milling methods. The mechanical properties was also confirmed by scanning electron microscopy studies which indicated that the dispersion of FRP and interfacial adhesion between fiberglass and PP matrix was much better by pan milling. Meanwhile, the heterogeneous nucleation effect of FRP by pan milling was more obvious. The above results indicate that solid‐state shear is a new method for producing fine FRP and high‐performance PP composites filled with FRP. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42494.     

超细空心微珠填充聚氯乙烯复合材料的研究

选用三种不同粒径(2μm、3．8μm和11μm)的空心微珠制备了聚氯乙烯／空心微珠(PVC／GB)复合材料。研究了GB的粒径、表面处理剂及其用量对复合材料力学性能、介电性能和阻燃性等的影响，并与PVC／超细CaCO3复合材料的性能进行了对比。结果表明，经硅烷偶联剂处理的GB与PVC基体之间存在良好的界面粘附作用；在体积分数0～11％范围内，粒径为3．8μm的GB能同时提高PVC复合材料的力学性能、介电性能和阻燃性能，且GB改性效果明显优于超细CaCO3填充体系。该复合材料能作为轻质、高强度和阻燃的电缆护套材料使用。     

聚氯乙烯糊树脂颗粒形态与增塑糊性能关系的研究

用激光散射法对聚氯乙烯糊树脂 (PPVC)浆料粒径及其分布和粉料颗粒粒径及其强度进行了测定和研究。结果表明 :初级粒子的粒径大小和分布是决定 PPVC树脂糊性能的关键因素 ;在一定范围内 (3 0～ 60μm) ,二次粒子颗粒强度即二次粒子的解碎程度是影响 PPVC树脂成糊性能的重要因素之一     

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。     

Structural heterogeneities of suspension poly(vinyl chloride). II. Formation of compact glassy particles and the cause of their difficult processing

By modifying the polymerization process of suspension polymerization of vinyl chloride, poly(vinyl chloride) (PVC) samples were prepared containing various amounts of compact glassy particles. It was found that these particles probably arise by a different polymerization mechanism than usual suspension particles, namely, as a result of the nonhomogeneous distribution of initiator in vinyl chloride drops of the polymerization system. It was proved experimentally that the lower heat stability of difficultly processible particles is due to a side reaction between the initiator radical and the PVC polymer chain which causes dehydrochlorination of PVC already under polymerization conditions. This reaction may also explain the yet unknown mechanism of formation of internal double bonds in PVC produced by the radical polymerization of vinyl chloride. In conclusion, the difficult processibility of compact glassy particles is discussed as a consequence of the insufficient drying of these particles in the usual drying process.     

原料粒度对合成碳化硅的影响研究

以轮胎半焦为碳源,石英砂为硅源,在1520℃下通过碳热还原法制备了碳化硅。采用XRD、SEM和红外光谱仪等对不同原料粒度条件下制备的碳化硅进行了表征,探究了原料粒度对合成碳化硅物相、形貌、粒度和反应程度的影响规律。结果表明：原料粒度对碳化硅的合成反应进行程度及产物碳化硅的物相组成、形貌、粒度均有十分重要的影响。在一定粒度范围内,随着石英砂粒度的减小,碳化硅晶型变完整,且晶须逐渐减少,碳化硅的粒径分布没有明显变化;随着轮胎半焦粒度的增大,产物物相逐渐变为单一,碳化硅的粒径和晶须所占的比例逐渐减小。此外,通过对产物中C/Si 比的测定和存在中间产物SiO的证实,推测出了碳化硅颗粒的生成机理为气-固（VS）反应,而碳化硅晶须的生成机理为气-气（VV）反应。     

The dyeing of nylon with a microencapsulated disperse dye

Melamine resin microcapsules containing CI Disperse Blue 56 were prepared by in situ polymerisation. The microcapsules were characterised by their thermal properties and morphology, such as particle size and particle size distribution. The dyeing behaviour of the microcapsules on nylon 6.6 was evaluated. The microencapsulated dye exhibited good build-up, levelness and fastness properties. It has been demonstrated that microencapsulated disperse dye can be used to replace commercial disperse dyes in dyeing polyamide fabric without dyeing additives, and the resulting effluent can be easily recycled after filtration.     

引发剂对氯乙烯微悬浮聚合转化率和聚氯乙烯粒径分布的影响

分别采用水溶性过硫酸铵(APS)和油溶性偶氮二异庚腈(ABVN)引发剂进行氯乙烯(VC)微悬浮聚合,并与APS引发的VC乳液聚合以及ABVN引发的VC悬浮聚合情况进行比较,考察了引发剂类型对聚氯乙烯(PVC)乳胶粒子粒径分布和增塑糊流变特性的影响。结果表明:引发剂浓度相同时,VC微悬浮聚合转化率大于悬浮聚合,而小于VC乳液聚合;APS引发微悬浮聚合得到的PVC乳胶粒子存在数目较多的纳米级粒子,而ABVN引发微悬浮聚合得到的PVC基本不存在纳米级粒子;引发剂和分解产生的初级自由基在水相/油相/胶束中的分配和成核机理不同是导致上述差异的主要原因。ABVN引发微悬浮聚合得到的PVC树脂成糊后呈剪切增稠特性,而APS引发微悬浮聚合得到的PVC树脂成糊后呈剪切变稀特性,且糊黏度较大。     

氯乙烯SET-DT悬浮聚合动力学和成粒过程的相互关系

以碘仿为引发剂、连二亚硫酸钠/碳酸氢钠为催化体系、聚乙烯醇(PVA)和/或纤维素衍生物(MC)为分散体系,进行氯乙烯单电子转移-蜕化链转移(SET-DT)活性自由基悬浮聚合,采用在线示踪气相色谱法和激光粒度分析系统研究分散剂种类和浓度、搅拌转速等对聚合动力学和单体液滴/聚合物颗粒粒径分布的影响。发现在相同搅拌转速下,以MC为分散剂的氯乙烯聚合速率最大,以PVA为分散剂时反应速率最小;分散剂种类固定时,聚合速率随分散剂浓度增大而增大。SET-DT悬浮聚合过程中,水相连二亚硫酸钠分解产生的自由基向单体液滴的扩散速率与液滴粒径分布和皮膜结构有关,因此聚合成粒过程影响聚合动力学。尽管不同条件下的聚合均经历液-液分散、液滴黏并、树脂颗粒稳定(转化率>30%)等成粒阶段,但各阶段的液滴/颗粒平均尺寸随分散体系和搅拌转速的变化而变化,引起聚合速率变化;采用MC为分散剂得到的PVC树脂皮膜少,有利于水相产生的自由基向单体相的扩散,聚合速率大。     

Transitional emulsion polymerisation: Zero-one to pseudo-bulk

The transitional behaviours of emulsion polymerisation for styrene and butyl acrylate (BA) monomers from zero-one to pseudo-bulk regime were mechanistically investigated. A dynamic mathematical model, which incorporates cross-over mechanism from zero-one to pseudo-bulk kinetics was developed for emulsion polymerisation and compared with experimental data for conversion, particle size and molar mass. Particles smaller than cross-over size follow zero-one kinetics and particles greater than cross-over size, they follow pseudo-bulk kinetics. In our mechanistic approach, particles nucleated from micelles, grow until the cross-over size is attained, based on zero-one kinetics, and subsequently continue to grow based on pseudo-bulk kinetics. Key findings from our work are that the developed transitional model predictions agree reasonably with experimental data on process and product attributes such as conversion, average molecular weight, molecular weight distribution (MWD), average particle size and particle size distribution (PSD). Optimal strategies for semibatch operation was developed using reaction temperature and monomer feed rate as process variables with specified initial conditions.     

Plastisols of poly(vinyl chloride); particle size distribution,morphology, rheology,and mechanism of aging

Plastisols of poly(vinyl chloride) (PVC) are suspensions of fine resin particles in plasticizer with about a 50% resin volume fraction. Typically, the gross particle size ranges from about 15 to 0.2 μm and smaller, where the common practice of spray drying these resins dictates that the size ranges include agglomerates as well as the ultimate particles. In this work we have related the particle size distribution to the dynamic mechanical behavior with model plastisols prepared from various particle-size fractions of a commercial resin. This relationship, together with the microscopic observation of the particle dispersions, provided an interpretation of the plausible mechanisms of the viscoelastic response. The morphological observation of the particle aggregates, the changes of the particle size distribution during the aging, and the above viscoelastic study have established that deagglomeration is the dominant cause of the increase of viscosity during aging.     

Dispersion polymerisation in organic media

The development of a technique for the direct preparation of polymer dispersions of controlled particle size in organic media is described. This method of dispersion polymerisation involves the polymerisation of a monomer dissolved in an organic liquid to produce insoluble polymer dispersed in the continuous phase. An amphipathic graft or block copolymer is used as the dispersant. The general features of the process, including the method used for stabilising the polymer dispersions and the mode of particle formation and growth, are reviewed.     

国产HPMC分散剂在127m3釜上生产PVC树脂的应用总结

上海氯碱化工股份有限公司在127m^3聚合釜中成功试用了国产HPMC分散剂,以替代价格昂贵的进口HPMC分散剂。共进行了50釜的应用试验,试生产了B、D、F三种牌号PVC树脂。通过分析B、D、F三种牌号PVC树脂的常规质量(如,表观密度、VCM残留量、“鱼眼”数及挥发分)、塑化性能、增塑剂吸收量及粒径分布,发现除了F牌号PVC树脂的平均粒径及粒径分布略微变宽、三目集中率略有偏低外,B、D牌号树脂的性能及F牌号树脂的其它性能均无明显变化。同时还指出,F牌号PVC树脂的粒径大小与分布可通过调整分散剂的用量来解决。     

Miniemulsion polymerisation in pseudo-bulk regime: Mathematical modelling, prediction and optimal strategy of operation

A dynamic mathematical model based on pseudo-bulk kinetics was developed for styrene miniemulsion polymerisation and validated using experimental data. Key findings are that the developed model match reasonably with experimental data and is able to predict the polymerisation attributes and product properties such as fractional conversion, average molecular weight, molecular weight distribution (MWD), average particle size and particle size distribution (PSD) in miniemulsion polymerisation. Optimal strategy of semibatch operation was developed using reaction temperature and monomer feed rate as process variables with specified initial conditions.     

Utilizing cellulose ethers as suspension agents in the polymerization of vinyl chloride

Proper choice of a suspending agent will help the PVC manufacturer achieve control of resin particle size, particle size distribution, and resin bead porosity. The results of research work at Dow has revealed that certain properties of cellulsoe ethers (a hydroxypropyl methylcellulose ether structure) are useful in helping control the properties of the PVC resin. In vinyl chloride polymerizations, cellulose ethers act as both an emulsifier; and during the polymerization, as a protective colloid to prevent excessive coalescence of the monomer droplets. The average particle size of the organic droplets in the aqueous phase during the PVC polymerization reaction is a function of the interfacial tension, intensity of agitation, viscosity of the two phases, and the volume fraction of the dispersed phase. The average particle size of the PVC resin was found to be a direct function of the interfacial tension multiplied by the 0.2 power of the gel strength of the cellulose ether solution. The interfacial tension of the cellulose ether solution/organic interface is probably the most important factor in determining the resin particle size. Particle size distribution widens with an increase in interfacial tension. Resin bead porosity is also important and is directly related to the solubility of the cellulose ethers in the organic phase. This observation supports the proposed seed stabilization theory that can explain the formation of a porous resin bead. The use of a proper suspension agent like cellulose ethers with or without a secondary surfactant will help control important properties of the PVC resin product. Control of the average molecular wight, degree of substitution, and grouping distribution on the cellulose chain of the cellulose ether suspension agent (all of which affect interfacial tension) is important for the PVC manufacturer.