Structural interpretation of the interfacial properties of aqueous solutions of methylcellulose and hydroxypropyl methylcellulose

Interfacial properties of aqueous solutions of methyl and hydroxypropyl methyl ethers of cellulose are important in foam and emulsion stability, detergency and many other applications involving surface activity of these cellulose ethers. Interfacial tensions of aqueous solutions of these cellulose ethers are measured using a spinning drop interfacial tensiometer. A general correlation is found between interfacial tension and the degree of substitution of methoxyl and hydroxypropyl groups. From thermodynamic considerations it is proposed that these cellulose ethers, for a constant degree of substitution, should exhibit the lowest interfacial tension values for a polymer having the most uniform distribution of substituent groups along the backbone. Other factors which influence the interfacial tension values are surface gelation of adsorbed polymer, molecular weight, concentration of cellulose ether in water phase, ageing time, temperature, and the type of organic phase.     

Influences of some polymerization conditions on particle properties of suspension poly(vinyl chloride) resin

Effects of polymerization temperature, conversions, and nonionic surfactant on the particle properties of suspension poly(vinyl chloride) (PVC) resins were investigated. It was shown that polymerization temperature has no significant influences on the mean particle size of PVC resin, and that the cold plasticiser absorption (CPA) of resin decreases linearly with the increase of polymerization temperature. Agglomeration of VCM droplets finishes before 20% conversion, and the mean particle size keeps almost constant at later stages of the polymerization process, but the CPA continues decreasing with the increase of conversion. Scanning Electron Microscopy (SEM) micrographs show that the degree of agglomeration of primary particles increases with polymerization temperature and conversion. Addition of nonionic surfactant to the VCM suspension system, as a secondary suspending agent, has a great influence on the particle properties of PVC resin. The particle size and CPA increase as the concentration of nonionic surfactant increases. The nonionic surfactant with a greater HLB value is more effective in raising the mean particle size, but is less effective in raising the CPA. It is considered that the added nonionic surfactant would be absorbed faster on the VCM/water interface than the poly(vinyl alcohol) (PVA), which was used as the primary suspending agent. Because the colloid protection ability of the nonionic surfactant is less than that of PVA, droplets become less resistant to coalescence, and the mean particle size of the final PVC resin increases consequently. The increase of porosity is caused by the combined effects of increased coalescence of VCM droplets and the nonionic surfactant's steric effect inside the droplets. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1544–1552, 2002     

国产聚乙烯醇助分散剂对悬浮法聚氯乙烯树脂颗粒特性的影响

在聚乙烯醇／羟丙基甲基纤维素复合主分散体系基础上加入聚乙烯醇助分散剂。对比研究了国内外同类型聚乙烯醇对分散体系界面张力、保胶能力和聚氯乙烯树脂颗粒形态的影响。结果发现：随着聚乙烯醇助分散剂含量增加,分散剂水溶液一三氯乙烯界面张力和保胶能力降低,聚氯乙烯树脂平均粒径和增塑剂吸收量增加,初级粒子聚集程度降低。     

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。     

VCM／VAC共聚掺混树脂的合成及性能研究

本文介绍用特殊悬浮法合成共聚掺混树脂的方法,并讨论了粒经、掺混树脂含量等因素对糊性能的影响.结果表明,通过使用多元混合引发剂和悬浮剂及加入适量的助分散剂、界面活性剂、调粒剂等,并通过控制搅拌速率、温度等工艺条件能有效地控制粒子的粒径、粒度分布及粒子形状,从而制得具有良好性能和粒度均匀的掺混树脂;在一定的粒径范围内(25～40μm),掺混树脂的平均粒径越大,对降低糊粘度的效果越好;增加掺混树脂的含量对降低初始糊粘度更为有利,在PVC糊树脂中加入一定量的掺混树脂可降低塑化温度,缩短塑化时间,从而改善了PVC糊树脂的加工性能.     

Influences of individual and composed poly(vinyl alcohol) suspending agents on particle morphology of suspension poly(vinyl chloride) resin

Effects of individual and composed poly(vinyl alcohol) (PVA) suspending agents on the particle morphology of poly(vinyl chloride) (PVC) resins were investigated and discussed in the view of PVA absorption at the oil/water interface and interfacial behavior. It was shown that the percentage and surface coverage of PVA at the oil/water interface decreased with the increase of the degree of hydrolysis (DH) of PVA in the DH range of 70–98 mol %, while the interfacial tension of VC/PVA aqueous solution increased linearly with the increase of DH of PVA. PVC resin with more regular particle shape, increased agglomeration and fusion of primary particles, lower porosity and higher bulk density, was prepared by using PVA with a higher DH as a suspending agent. This was caused by the occurrence of drop coalescence at the very early stage of VC polymerization, the increase of particle shrinkage, and the lower colloidal protection to primary particles. It was also shown that the interfacial tension of VC/water in the presence of composed PVA suspending agents varied linearly with the weight composition of the composed PVA suspending agents. The particle properties of PVC resin prepared by using the composed PVC suspending agents were usually situated in between the properties of PVC resins prepared by using the corresponding individual PVA suspending agent. The particle morphology and properties of PVC resin could be controlled by the suitable choice of the composed PVA suspending agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3848–3855, 2003     

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。     

Suspension stabilizers for PVC production III: Control of resin porosity

Suspension PVC resins were prepared using dispersant systems based on a cellulose derivative, Methocel F50, and two poly(vinyl alcohol)s; Gohsenol GH20 and Rhodoviol 5/270. Ammonium laurate and Span 20 were tested as secondary dispersants. The resins were characterized by mercury porosimetry. The results showed that the porosity of the resins increased in the series Gohsenol < Methocel < Rhodoviol. This order seems to follow the order of increasing surface activity. A closer analysis of the data clearly showed, however, that porosity control in S-PVC manufacture is not due to a pure interfacial tension mechanism, not even in those cases where the dispersant systems do not contain any monomer-soluble components. Other possible mechanisms by which suspension stabilizers may affect resin porosity are briefly commented upon.     

Performance relationships in PVC–plasticizer dry blending

The phenomenon of plasticizer acceptance by poly(vinyl chloride) (PVC) in hotprocess dry blending is examined via scanning electron microscopy, mercury intrusion porosimetry, and torque rheometer measurements. The effects of granule porosity, resin molecular weight, and synthesis recipe in PVC manufacture by the suspension process are related to the rate of plasticizer acceptance. For a PVC resin to dry blend, i.e., to become a free-flowing powder when mixed with plasticizer under hot-processing conditions, the resin granules must be porous. Porosity arises from interstices between primary PVC particles. At a given granule porosity, an increase in primary particle agglomeration adversely affects dry blend performance. At constant molecular weight and for resins manufactured by a given recipe, dry-blend performance is quantitatively described by granule porosity. With an increase in resin molecular weight, a greater granule porosity is required to maintain an equivalent dry-blend time (DBT). Accordingly, for most suspending agent recipes, DBT is dependent directly upon granule porosity and inversely upon molecular weight. However, if the suspending agent used in resin manufacture is an excessively rapid film former, dry-blend performance with molecular weight variation is dependent upon the suspending agent's concentration, not upon granule porosity, which must be adequate, nor upon the resin's molecular weight. An interfacial film-forming suspending agent enhances fusion of primary PVC particles at the suspension granule—water interface, increasing the granule's “pericellular membrane” thickness. This membrane, a PVC skin, does not significantly influence dry-blend performance with low- or intermediate-viscosity plasticizers. The particle skin does impede dry-blend rates with high-viscosity, poorly solvating plasticizers, but this effect can be negated in part by increasing the diameter of pore openings in the topographical skin. Dry blending occurs below the glass transition temperature (T_g) of PVC with low-viscosity plasticizers and above the T_g with high-viscosity, poorly solvating modifiers. The influence of resin and plasticizer variables indicates the dry-blend phenomenon to be a diffusion-controlled process. The rate of dry blending is dependent upon two mechanisms: (1) the rate of pore penetration—which exposes the plasticizer to a much greater surface area than if it remained exterior, encapsulating the granule—and (2) the rate of plasticizer diffusion into the PVC matrix.     

The influence of poly(vinyl alcohol) suspending agents on suspension poly(vinyl chloride) morphology

The requirements for PVC suspension resin have changed considerably in the last few years, so much so that few companies have products on their ranges that are more than 4 or 5 years old. The suspending agent has a crucial influence on the morphology of the resin, so the changes in resin characteristics have largely been achieved by changes in the suspending agent systems. After a brief review of the mechanism of PVC suspension polymerisation, the properties of polymers made using PVOH suspending agents are related to changes in the latter. The effect of variations in PVAc degree of hydrolysis and viscosity are related to changes in surface tension. Methods of achieving higher porosity by using low hydrolysis co-suspending agents are described. It is shown that higher bulk densities can be achieved by delayed addition of the PVOH. Levels of conjugated unsaturation and copolymer distributions are also shown to have important influences.     

偏氯乙烯-氯乙烯悬浮共聚树脂的颗粒特性

在5L聚合釜中制备了偏氯乙烯(VDC)一氯乙烯(VC)共聚树脂,研究了起始搅拌转速、分散剂配比、水油比和助剂对共聚树脂颗粒特性的影响。实验结果表明,随着起始搅拌转速的增加,树脂粒径增大,而粒径分布变宽;增加复合分散剂中纤维素醚K的配比,树脂的平均粒径增大;增加水油比,树脂颗粒的粒径变小,分布变窄;聚合前加入助剂环氧大豆油(ESO)对树脂颗粒的粒径及分布影响不大。本实验制备的树脂颗粒形态规整,与日本同类产品相近。     

氯化专用聚氯乙烯树脂颗粒特性的研究——非离子型表面活性剂和链转移剂的影响

水相悬浮法生产氯化聚氯乙烯(CPVC)时,氯化速度和氯化均匀性取决于Cl2在聚氯乙烯(PVC)颗粒中的扩散程度,因而需要有能满足氯化要求的PVC专用树脂。采用以聚乙烯醇(PVA)和羟丙基甲基纤维素(HPMC)为主的复合分散剂,考察Span系列非离子表面活性剂、链转移剂等对PVC颗粒特性的影响。实验结果表明,表面活性剂的加入使PVC树脂增塑剂吸收率、平均粒径和比表面积增大,粒径分布变窄,而表观密度下降;随着链转移剂的加入,PVC树脂增塑剂吸收率、平均粒径和表观密度都增加。     

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。     

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.     

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。     

Effect of the phase ratio on the particle properties of poly(vinyl chloride) resins produced by suspension polymerization

The effects of the dispersed phase to continuous phase ratio (weight of VCM (gr)/weight of water (gr) (φ = g_VCM/g_water)) on the particle properties of a poly(vinyl chloride) (PVC) suspension were investigated experimentally. A series of experiments were performed with different φ values in a pilot‐scale reactor. The cold plasticizer absorption of the resin decreased with φ. Scanning electron micrographs showed that by the reduction of φ, many of the produced particles had a regular shape, a smooth surface, and greater porosity. An increase in φ caused a wider and multimodal particle size distribution of the produced PVC particles. The mean particle size and bulk density also increased with φ, whereas the molecular weight and polydispersity index did not change. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of thermally-responsive hydroxypropyl methylcellulose gel beads

Thermally responsive gels of hydroxypropyl methylcellulose (HPMC) were produced in spherical form by a suspension crosslinking technique. The suspension crosslinking of HPMC with divinylsulfone was accomplished by dispersing aqueous polymer droplets, containing all of the reactants, in a continuous organic phase. The gel beads were characterized in terms of their swelling properties and particle size distribution. The swelling degrees at 25°C of different formulations of the gel beads ranged from 12 to 123 times their dry volume and shrank to 4 to 18 times dry volume at 75°C. The spherical beads were made in diameters ranging from 500 to 3000 μ. Bead size generally decreased with use of a larger impeller, suspending at high stirring speeds, or at a lower phase ratio. As bead size decreased, the size distribution also narrowed. When compared with bulk HPMC gels, the gel beads demonstrated the same swelling properties and crosslinked network formation. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1279–1290, 1997     

Reactive polymers. XXXII. Effect of composition of polymerization feed on morphology and some physical properties of macroporous suspension copolymers glycidyl methacrylate–ethylene dimethacrylate

The effects of inert solvent concentration of crosslinking agent and initiator and polymerization temperature on specific surface area, porosity, penetration modulus, stress at break, and inner and surface morphology of the copolymer glycidyl methacrylate–ethylene dimethacrylate were investigated. There is a direct influence of interfacial tension between the continuous and dispersed phases in suspension at the beginning of polymerization on the morphology of the bead, and hence on the resulting physical characteristics of the structure.     

Inverse suspension polymerization of sodium acrylate

A superwater-absorbent sodium polyacrylate was synthesized by inverse suspension polymerization, using Span60 as the dispersant, cyclohexane as the organic phase, N,N′-methylene bisacrylamide as the crosslinking agent, and potassium persulfate as the initiator. The effect of reaction conditions such as reaction time, crosslinking agent, and dispersant on deionized-water and saline solution absorbability, average particle size, and distribution of the sol–gel of the resin is discussed. The deionized-water and saline solution absorbabilities of sodium polyacrylate prepared at proper conditions were 300–1200 and 50–120, respectively; the number-average particle size was 10–50 μm and the gel portion was 20–85% by weight. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 789-794, 1997     

颗粒特性对聚氯乙烯树脂基本性能的影响

研究了牌号为QS-800F的聚氯乙烯(PVC)树脂的颗粒形态及其粒径分布、颗粒微观结构对QS-800F树脂基本性能的影响,并与国内应用较好的同类型树脂进行了对比分析.结果表明,QS-800F树脂具有良好的颗粒形态,粒径分布适中,颗粒表皮多为不连续结构,颗粒内部孔隙率高,具有很高的增塑剂吸收值和较强的增塑剂吸收能力.