Emulsification description

In terms of the process, very little has been achieved. The mass transfer limitations still exist although emulsification has solved the problem partially, but not without creating another problem downstream in separation of the product from the rest of the stream and the issue still needs further work. The IP portfolio contains very few real process concepts. The patented material refers to a BDS process several times, but the process referred to, is no more than a simple description of the pH, temperature, etc., and the particular use of a given biocatalyst in an application. Some protected subject matter concerns the integration of a bioprocess into the flow sheet of the refinery, but again those are no more than theoretical scheme proposed for implementation, with no actual evidence with real feedstocks. 

Considerable progress has been achieved in understanding the technology from the experimental point of view, with the establishment of many empirical correlations. On the other hand, their theoretical interpretation by means of reliable models is not accordingly advanced. The first model devoted to membrane emulsification, based on a torque balance, was proposed in 1998 by Peng and Williams [13], that is, ten years later the first experimental work was published, and still nowadays, a theoretical study aiming at a specific description of the premix membrane emulsification process is not available. 

In this chapter, a description of membrane emulsification basic concepts, empirical correlations, theoretical studies, as well as most common applications have been discussed. 

The adsorption of surfactants at the liquid/air interface, which results in surface tension reduction, is important for many applications in industry such as wetting, spraying, impaction, and adhesion of droplets. Adsorption at the liquid/liquid interface is important in emulsification and subsequent stabilization of the emulsion. Adsorption at the solid/liquid interface is important in wetting phenomena, preparation of solid/liquid dispersions, and stabilization of suspensions. Below a brief description of the various adsorption phenomena is given. 

To get a better idea of how to formulate the nanosized emulsion delivery systems suitable for parenteral, ocular, percutaneous, and nasal uses, the reader is referred to more detailed descriptions of methods of nanosized emulsion preparation [6, 116], A hot-stage high-pressure homogenization technique or combined emulsification technique (de novo production) is frequently employed in order to prepare nanosized emulsions with desired stability even after subjection to autoclave sterilization. Therefore, the steps involved in this technique in making blank anionic and cationic emulsions were arranged in the following order ... 

Emulsion polymerization involves the emulsification of monomers in an aqueous phase, and stabilization of the droplets by a surfactant. Usually, a water-soluble initiator is used to start the free-radical polymerization. The final product is a dispersion of submicrometer polymer particles, which is called latex. The locus of polymerization is the micelle. Typical applications are paints, coatings, adhesives, paper coatings and carpet backings. The latex particles can have different structures (see Fig. 2). Excellent text books on the applications and structure-property relationships exist [11-15]. Besides a full description of the kinetics and mechanism of emulsion polymerization [16], a textbook adapted for use as material for people entering the field is also available [17]. 

The theoretical description of the mutual approach and coalescence of two emulsion drops is the subject of Sec. IV the Bancroft rule on emulsification is interpreted and generalized in Sec. V and the kinetics of flocculation is considered in Sec. Vt, where the size of the aggregates needed for the creaming to start is estimated. 

Microfluidic devices can be used for either premix emulsification (a method in which a coarse emulsion is broken up by passing it through a geometry) or direct emulsification (a method in which oil and water are introduced separately in the device and the emulsion is formed at their point of contact). Depending on the surface properties of the microfluidic device or other microstructured devices (e.g., membrane) either oil in water (hydrophilic device) or water in oil (hydrophobic device), emulsions are formed. Also related products, such as double emulsions, particles, and capsules, are reported in literature. Eor an extensive description of the construction of various microfluidic devices for emulsion preparation, and the various products that have... 

In this chaptCT we focus our attention on key optical methods and nuclear magnetic resonance (NMR), which have been indispensable for quantitative descriptions of size and structure, and diffusivity, where size and structure play an important role. Whereas in the previous chapters we have tended to focus on the overall dynamics, we concentrate here at the smallest scale needed to understand what the fundammtal building blocks are in those systems. With the exception of NMR, the other methods are restricted to transparent systems. This can sometimes be a drawback, as in the study of water-in-crude oil emulsions, which are black in color. These are very important systems industrially and require de-emulsification. NMR techniques for measurement of drop size distributions in such emulsions, while beyond the scope of this chapter, have been reviewed by Pena and Hirasaki (2003). 

At first sight the process of generation of small particles by solvent displacement is deceptively simple after mixing of the two solvents, the organic substance (polymer or active principle) suddenly finds itself surrounded by a water-rich environment and, because of its low solubiUty in water, it precipitates, generating solid particles. An everyday occurrence of this process is the spontaneous emulsification of alcoholic drinks when diluted with water, such as Ouzo in Greece and Fastis in France. However, the detailed description of the mechanism is more complex and is still controversial. 

Although the exact explanation and theoretical description of the compatibilizers activity remains an open field of research, the morphology changes induced by effective compatibilization are qualitatively the same. The efficiency of a compati-bilizer can be determined from emulsification curves showing the size of the dispersed particles as a function of compatibUizer concentration [129,130]. 

Figure 7.25 Schematic description of the reaction mechanism for the encapsulation of retinol (vitamin A) in silica particles by the O/W/O emulsification method. (Adapted...

Nano-emulsions are defined as a class of emulsions with uniform and extremely small droplet size (typically in the range 20-500 nm). The formation of kinetically stable liquid/hquid dispersions of such small sizes is of great interest from fundamental and applied viewpoints. In this review, nanoemulsion formation, with special emphasis on low-energy emulsification methods, is first discussed. This is followed by a description of nano-emulsion properties, focusing on their kinetic stability. Finally, relevant industrial applications of nano-emulsions in the preparation of latex particles, in personal-care formulations, and as drug dehvery systems are reported. 

In this chapter, different methods for nano-emulsion formation, with special emphasis on low-energy emulsification methods, are discussed in Section 11. This is followed by a description of nano-emulsion stability (Section 111). Finally, the most relevant applications of nano-emulsions are reviewed... 

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