膜法制备乳状液研究进展

膜法制乳是靠膜两侧的压差使分散相通过微孔膜,以小液滴的形式分散在连续相中而形成乳状液的方法。与转-定体系、高压均化等传统方法相比,该法液滴尺寸均一、节能、剪应力小,可应用于化妆品、食品、医药等领域,其中一些应用已经工业化。液滴从膜孔中形成和分离依赖于各种过程参数(如过膜压差、膜表面连续相的剪切应力)、膜材料和结构。很多实验研究集中在膜乳化过程参数的影响上,膜乳化过程的机理尚需进一步完善。     

SPG膜乳化与界面聚合法制备单分散多孔微囊膜

小粒径单分散中空储库结构微囊膜的制备具有重要学术意义和实用价值。为此采用了SPG(Shirasu-Porous-Glass)膜乳化法和界面聚合法，对小粒径单分散多孔微囊膜的制备进行了较系统的实验研究，以期为进一步制备多孔内接枝环境感应型功能凝胶开关的小粒径单分散微囊型靶向式药物载体提供基体。研究结果表明，采用SPG膜乳化法可制得单分散性良好的乳液液滴，进而采用界面聚合法可得到单分散微囊。用膜乳化方法易于控制乳液液滴及微囊的大小，在研究中SPG膜乳化法制备的乳液液滴及微囊的平均粒径大约是所用膜孔径的3．6倍。微囊膜的多孔性可以靠改变溶剂和单体的成分来进行控制，扫描电镜检测结果表明所制备出的不同粒径级别的单分散微囊膜均具有良好的多孔结构。     

陶瓷微滤膜分散传质性能

引　言近年来 ,国内外对膜法制乳的研究已做了相当多的工作[1～ 7] ,并取得了良好的结果 .膜法制乳即以微滤膜为分散介质制备乳液的方法[8] .研究结果证明 ,采用膜分散制乳的方法可以得到液滴直径小且均一的稳定的乳液 .由于微滤膜的孔隙率较大 ,这种方法所需压力很小 ,能耗小 ,粒径可小于 10 μｍ,这是传统的分散方法无法达到的 .由此可见 ,膜法分散是理想的分散方法 .目前工业中的萃取操作多采用传统的分散法 ,分散的液滴粒径大 (1ｍｍ左右 ) ,比表面积小 ,滴内传质速度小 ,萃取效率低 .而膜法分散应用于萃取 ,传质面积和滴内传质速度比传…     

产品开发

正新型微流控液滴包裹技术研发前景好新型微流控液滴包裹技术,与传统液滴包裹技术相比,其优点是:操作灵活、可控性强、可通过改变通道数量、结构等方式制备双乳、复乳液滴,每层液滴的尺寸和数量还可通过调节流量等参数进行调控。因此新型微流控液滴包裹技术研发和应用具有非常广阔的前景,可应用于生物医学、食品科学、化妆品、医药等诸多领域。新型微流控液滴包裹技术主要包括膜乳化包裹、外力驱动乳化包裹、微通道乳化包裹等。     

聚醚砜超滤膜乳化法制备乳化柴油

采用平均孔径为25 nm的聚醚砜超滤(UF)膜,以去离子水为分散相,以0#柴油为连续相,分别以Tween-20和Span-80为分散相及连续相的乳化剂,采用膜乳化法制备W/O型乳化柴油。UF膜乳化法制备的乳液比传统乳化方法稳定时间提高2～2.5倍,而相同条件下乳化剂用量减少了50%～65%。此外,考察了UF膜法制备乳化柴油过程中的各工艺参数对乳液液滴大小、分布及稳定性的影响规律,结果表明:当乳化剂质量分数高于0.5%,连续相流速在2.0～5.0 m/s范围内,跨膜压差为0.02 MPa时,乳液分散系数α达到0.12～0.3,液滴尺寸为30～65 nm。     

高压脉冲电场中乳化油最佳破乳电场参数

合理的电场参数是确保高压脉冲电场实现乳化油液高效破乳脱水的重要前提,目前关于电场参数的理论研究鲜有报道。通过建立乳化油液滴在高压脉冲电场中的振动动力学模型,研究液滴振动幅频特性,得到液滴共振频率及共振振幅。在此基础上,根据乳化油系统物性参数,结合液滴最大稳态拉伸变形条件,利用作图法可计算出乳化油最佳破乳电场频率与电场强度的值。实验结果表明,计算得到的最佳破乳电场参数能够实现乳化液滴高效结聚。因此,利用非线性振动动力学确定的乳化油最佳破乳电场参数是合理可靠的。     

微孔膜乳化过程中乳滴大小的控制

微孔膜乳化法作为一种新型获得高质量单分散稳定乳液的简单有效方法,近来受到了越来越广泛的关注和重视。综述了微孔膜乳化过程中控制乳滴大小的工艺方法和各种影响因素。     

有机硅改性苯丙乳液的研制

通过预乳化种子乳液聚合和水解抑制技术，利用活性有机硅单体改性苯丙乳液，制得了稳定性和成膜性能优异的硅丙乳液；对制备过程中的聚合方式、工艺参数、有机硅种类及用量、加入方式等因素进行了探讨。结果表明：有机硅宜选用空间位阻较大的乙烯基三异丙氧基硅烷，且在壳层聚合时加入，用量应控制在8％～10％。较佳的聚合工艺为：种子聚合温度80℃，预乳化液滴加时间1．5h；壳层聚合温度75～80℃，滴加时间5h。     

一种新型的制乳技术--膜法制乳

乳液在工业中有着广泛的应用,传统的制备乳液的方法多种多样,但主要采用的方法是机械搅拌或高压分散,这种方法能耗大,制乳效果差,制得的乳液液滴不均匀。膜法制乳的方法是靠膜两侧的压差使分散相以微小液滴的形成通过微孔膜,并分散在连续相中,从而乳状液。     

稠油O/W型乳状液微观现象研究

新滩稠油O/W乳状液是由含水较高的W/O乳状液直接转相形成的,利用微观摄像技术对其微观结构进行了研究。研究发现,乳状液中含有一定量的W/O/W液滴,其数量的多少与乳化剂浓度和含水量的大小有一定关系。液滴的形状大多数是等轴球形,既有液滴单个的乳滴存在,又有相互接触的乳滴簇存在,有乳滴形成乳滴簇的过程,也有乳滴簇分离的过程。乳滴大小分布模式基本相似,但对于具体的乳状液来说还是有差别。乳滴的大小分布受乳化剂浓度、油水性质含水量和放置时间等的影响。乳状液随时间表现出的性质主要是其微观结构变化的结果。液滴的大小分布情况和存在方式,在一定程度上影响乳状液的稳定性和流变行为。     

Stirred tank membrane emulsification using flat metallic membranes: A dimensional analysis

The performance of a membrane emulsification unit, using flat membranes in a stirred tank, has been examined by dimensional analysis. The dimensionless numbers were defined in terms of shear and membrane pore size. Dimensionless droplet size prediction models based on simple force balances were used to select the most representative dimensionless numbers including operating parameters. Oil-in-water emulsions were produced with tailor-made metallic membranes with pore sizes of 30 and 50 μm. Results showed that monodisperse emulsions were produced with span values around 0.5, significantly lower than when a rotor-stator homogenizer is used. The influence of the selected operating parameters (impeller rotational speed, continuous phase viscosity and dispersed phase flux) on droplet size distribution was studied and experimental results were compared with droplet size prediction models. Impeller rotational speed and membrane pore size were the key parameters influencing emulsion droplet size and monodispersity. A correlation based on the Euler dimensionless number, including all the operating parameters is proposed.     

Preparation of water-in-oil and ethanol-in-oil emulsions by membrane emulsification

In this work, water-in-oil emulsions (W/O) and ethanol-in-oil emulsions (E/O) emulsions were prepared successfully by membrane emulsification. The emulsifiers selected were PGPR and MO-750 for the W/O and E/O emulsions, respectively. For W/O emulsions prepared with an oil pre-filled membrane, the dispersed flux was lower and the droplet size sharper than that obtained with a water pre-filled membrane. On the contrary, for E/O emulsions prepared with the membrane pre-filled with oil, the dispersed phase (ethanol) rapidly pushed out the oil from the membrane pores. Therefore, the pre-treatment of the membrane had almost no effect on the dispersed phase flux and on the droplet size. The droplet size distribution of the E/O emulsion was close to that obtained with a classical homogenizer. The dispersed phase fluxes were high and no fouling was observed for our experimental conditions (1.6 l emulsion, 10 wt% ethanol). These results confirm that membrane emulsification could be an interesting alternative for the preparation of E/O emulsions for the purpose of biodiesel fuels, considering the scale-up ability of membranes and their potentiality for industrial processes.     

二次膜射流乳化法制备单分散乳状液研究

为解决传统膜乳化法制备单分散O/W型乳状液中存在的粒径和通量的矛盾,介绍了采用二级陶瓷膜乳化在射流条件下制备单分散O/W乳状液的方法。2套一体式陶瓷膜乳化装置被串联使用,一级膜乳化采用孔径为0.16μm的ZrO2陶瓷膜,二级膜乳化采用孔径为1.5μm的-αA l2O3陶瓷膜。以甲苯/水体系为研究对象,阴离子表面活性剂(SDS)和非离子表面活性剂(乳化剂OP)分别被用作乳化剂。2种情况下均可获得单分散的乳液,能耗分别是1.53×105J/m3和1.21×105J/m3。因此,该方法可在较低的能耗下制备单分散乳液。     

Emulsification using tubular metallic membranes

Tubular metallic membranes with pore diameters of 5 and 10 μm have been used in a cross-flow unit to prepare monodisperse oil-in-water emulsions (O/W) with span values as low as 0.67, significantly lower than for emulsions prepared with a rotor–stator homogenizer. The influence of typical operating parameters (continuous phase flow rate and transmembrane pressure) on droplet size distribution was studied. The smallest droplets were obtained at low transmembrane pressures and high continuous phase flow rates. The droplet production with tubular metallic membranes was higher than with other types of tubular membranes, such as SPG or ceramic.Experimental results were compared with those obtained in a stirred tank unit operating under similar conditions and using flat metallic membranes with the same pore diameter. Droplet size prediction models based on simple force balances were applied to compare theoretical and experimental droplet diameters. The droplet formation regime (dripping, jetting) was also studied for both types of membranes.     

陶瓷微滤膜制备水包油型乳液的研究

乳液制备一直是化工领域中的一个重要的研究课题,本文选择水－正丁醇实验体系,以十二烷基碘酸钠为乳化剂,分别采用０．２μｍ和０．８μｍ的陶瓷膜为分散介质制备水包油型乳液。实验研究了压力、连续相流量等因素对乳液粒径大小、分布和分散相通量的影响。结果表明,用微滤膜可以制得分布均匀的乳状液。微滤膜的孔径较小时,连续相流量和膜两侧压差对于乳液粒径和粒径分布没有明显的影响;当膜孔径增大后,乳液滴的直径分布变宽,     

High throughput membrane emulsification using a single-pass annular flow crossflow membrane

Membrane emulsification has the potential to revolutionize the energy-efficient production of uniform emulsions and dispersions, relevant to diverse fields from pharmaceutical active ingredient controlled release particles to Fast Moving Consumer Goods. A novel highly robust single-pass continuous phase crossflow system has been developed providing dispersed phase concentrations up to 40% vol/vol and dispersed phase fluxes up to 5,730 L m⁻² hr⁻¹, from a single 100 mm long membrane tube. Extensive results of two oil-in-water systems (vegetable oil and PolyCaproLactone dissolved in DiChloroMethane) and one water-in-oil system (sodium silicate solution) are reported, using hydrophilic and hydrophobic membranes respectively. Mathematical models are validated enabling comprehensive engineering analysis of processes including predicted droplet size, membrane pressure drops, and energy requirement for dispersion production. Surfactant depletion, pore utilization, and droplet interaction at the membrane surface were investigated to provide a comprehensive analysis of the capabilities of novel annular-flow membrane emulsification for high throughput emulsion generation.     

A STUDY OF SILICONE OIL-IN-WATER EMULSIONS

Emulsions of silicone oil-in water were formed using a Brinkmann Polytron homogenizer with Igepal CO-530 as an emulsifier. Silicone viscosities ranged from 10 to 33,000 mPa.s at 25°C. Rheological characteristics and particle size analyses of silicone oil-in-water emulsions were studied. At high volume fraction of the dispersed phase (70%-75%), silicone oil-in-water emulsions were stable. At lower volume fractions (50%-60%), emulsions formed were less stable and the two phases easily separated in a few days. The emulsions formed with high volume fraction silicone oil show highly non-Newtonian behavior (shear thinning). Emulsions made with low viscosity oils had lower viscosities than those made from high viscosity oils. Relative viscosity-concentration data could be correlated by the Frankel and Acrivos Equation. Increasing the emulsifier concentration of 70% oil-in-water emulsions resulted in a decrease in mean droplet size and an increase in emulsion viscosity. Increasing the intensity of agitation also resulted in higher viscosity and smaller droplet size until a critical energy input above which droplet size increased. Emulsification with low shear mixing provides more control in decreasing mean droplet size with time.     

Evolution of the microstructure and rheology of O/W emulsions during the emulsification process

This paper deals with the influence that the processing variables and the nature of the low-molecular-weight emulsifier used exert on the evolution of the droplet size distributions and linear viscoelasticity functions of concentrated oil-in-water emulsions during the emulsification process, and the way these variables affect the final characteristics of the emulsions. With this aim four different surfactants and two impeller geometries were used. Influences of the emulsification time, agitation speed and temperature of emulsification were studied. From the experimental results obtained, a correlation between the plateau modulus, a linear viscoelastic parameter related to the strength of the interdroplet interactions, and the volume diameter is proposed.     

微孔膜制乳技术基本规律研究

在对制乳技术进行充分调研的基础上 ,选择水 -正丁醇和水 -煤油为实验体系 ,以十二烷基磺酸钠、Span85等表面活性剂为乳化剂。在 0 .2 μm的陶瓷膜中研究了压力、连续相流量等因素对乳液粒径大小、分布和分散相通量的影响。实验结果表明 ,用微孔膜可以制得分布均匀的乳状液。乳化剂的类型与用量对乳液的性质有显著影响。微孔膜对低界面张力及界面张力中等的体系可制得粒径小、分布窄的O/W乳液。连续相流量和膜两侧压差对于乳液粒径和粒径分布没有明显的影响 ;分散相通量随压差的增大而明显增大 ,但连续相流速对分散相通量影响不大。