Water-in-oil systems

M. Ramesh and A. Sivakumar. Hydrophobic demulsifiers for oil-in-water systems. Patent CA 2124301, 1994. 

Shorter chain sodium alkylbenzene/alkylxylene sulphonates (sodium salts) are used as emulsifiers for oil in water systems. Cutting fluids are often made by diluting an oil-based concentrate containing a petroleum sulphonate with water, at the point of use. The petroleum... 

Flexible macromolecules, such as proteins, and small molecules, such as surfactants, are amphipathic and may form a layer at the oil-water interface. These molecules may also partly stabilize emulsions by forming a physical barrier to close contact, thereby reducing the attractive van der Waals forces to ineffective levels (Dalgleish, 1989). Repulsion can arise in either of two ways and physico-chemical calculations are available for both mechanisms in oil-in-water systems. Either the approaching protein-coated particles will tend to compress or alternatively interpenetrate the adsorbed protein layer on adjacent particles. The optimum structure of the stabilizing protein will be dealt with in the section on protein as an ingredient. 

Since aqueous solutions are extremely sensitive to salts, the active catalyst system is not suitable with an all aqueous system it is only suitable for oil-in-water system. Characteristics of oil-in-water emulsion systems have been discussed by Parikh (1 5). 

Interfacial Metal Ion Complexatlon. Complexatlon of copper (II) ion by oil soluble ligands has been implicated in metallo-porphyrin formation in benzene in water MB s, but not apparently in the mineral oil in water system (vide supra). Therefore, an electrochemical study of the interaction of quinoline and copper ion was undertaken. 

The first part of the book discusses formation and characterization of the microemulsions aspect of polymer association structures in water-in-oil, middle-phase, and oil-in-water systems. Polymerization in microemulsions is covered by a review chapter and a chapter on preparation of polymers. The second part of the book discusses the liquid crystalline phase of polymer association structures. Discussed are meso-phase formation of a polypeptide, cellulose, and its derivatives in various solvents, emphasizing theory, novel systems, characterization, and properties. Applications such as fibers and polymer formation are described. The third part of the book treats polymer association structures other than microemulsions and liquid crystals such as polymer-polymer and polymer-surfactant, microemulsion, or rigid sphere interactions. 

Is a primary emulsifier for water in oil systems and an effective co-emulsifier for oil in water systems for mineral oil, fats, and waxes. It is also a versatile coupling agent for water soluble materials in O/W systems. Suggested applications include its use as a W/O emulsifier for consumer household aerosols and as an O/W co-emulsifier for cosmetics, industrial oils and textile oils. 

In an inverse latex, these electrostatic forces are quite difFerent. For water-in-oil emulsions, Albers and Overbeek (J, 2, 3) found that, with ionic emulsifiers, flocculation was promoted by gravity because of the diffuse nature of the electric double layer relative to that of oil-in-water systems and, with nonionic emulsifiers,... 

Conventionally, polycarbophil is used as a thickening agent at very low concentrations (less than 1 %) to produce a wide range of viscosities and flow properties in topical lotions, creams, and gels, in oral suspensions, and in transdermal gel reservoirs. It is also used as an emulsifying agent in topical oil-in-water systems. 

Many modern dermatological formulations are washable oil-in-water systems. Simple aqueous lotions are also used as they have a cooling effect on the skin. Ointments are used for the application of insoluble or oil-soluble medicaments and leave a greasy film on the skin, inhibiting loss of moisture and encouraging the hydration of the keratin layer. Aqueous creams combine the characteristics of the lotions and ointments. A classification of semisolid bases is given in Fig. 9.24. 

The amount of flavouring substance bound by fat or oil depends on the chain length of the volatile compound within a homologous series. Thus, for instance, the distribution coefficient in oil-in-water systems increases with the increasing chain length of... 

Fig. 5.23 Distribution coefficients of aliphatic alcohols in an oil-in-water system [47]...

Scheme 6 Similar to the process in Scheme 5, where emulsification of the polymer/drug organic solution takes place forming an oil-in-water system. The alternative is the dissolution of the polymer and drag in an aqueous phase, which is added to an organic phase to form a water-in-oil emulsion. In both cases, the internal phase is then evaporated leaving the polymer-drag particles.

Both interfacial polycondensation and polyaddition involve two reactants dissolved in a pair of immiscible liquids, one of which is preferably water, which is normally the continuous phase, and the other one is the dispersed phase, which is normally called the oil phase. The polymerization takes place at the interface and controlled by reactant diffusion. Researches indicate that the polymer film occurs and grows toward the organic phase, and this was visually observed by Yuan et al. In most cases, oil-in-water systems are employed to make microcapsules, but water-in-oil systems are also common for the encapsulation of hydrophilic compounds. Even oil-in-oil systems were applied to prepare polyurethane and polyurea microcapsules. ... 

Core/wall ratio cannot only decide the wall thickness of a microcapsule but also the effectiveness of the microencapsulation." The work" on the microencapsulation of xylitol by poly (urethane-urea), which was performed in a water-in-oil system, indicates that the most proper core/wall ratio is 77/23 in terms of high encapsulation yield and xylitol loading content. Another work on the microencapsulation of perfume by polyurea, which was performed in a oil-in-water system, found that with the decrease of the core/wall ratio, the size of the formed microcapsule increased even the original droplet size is roughly the same. An outward diffusion mechanism was proposed to explain... 

This section describes the horseradish peroxidase-catalyzed synthesis of both homo- and copolymers of aromatic polymers based on phenols, naphthols, aniline, and their derivatives. Syntheses of novel optically active polymers are studied by changing the environment in which the enzyme functions, along with the organization of the monomers in the reaction mixture. To this objective, enzyme-catalyzed polymer syntheses are carried out in bulk monophasic conditions in which the solvent is miscible with water, biphasic solvent systems in which the solvents used for the syntheses are not miscible with water, and oil-in-water system in the presence of a detergent called reverse micelles. These experimental approaches are shown schematically in Fig. 4. 

Three different stabilizing systems were chosen for the experiments presented in this paper (i) surfactants for inverse (water-in-oil) systems possessing low HLB values (Span 80, HLB 4.3) (ii) surfactants for oil-in-water systems with high HLB values (Tween 80, HLB 15), and (iii) a mixture of surfactants for both systems (Tween 80 and Span 80 in the ratio of 3 2 w/w). Ligure 2a shows the average diameter of the miniemulsion droplets in Miglyol 812N, plotted as a function of the surfactant type and concentration. 

The ALKAZINE imidazolines are specialty surfactants, which, when neutralized to a pH of 8.5 or lower, function as cationic emulsifiers for oil-in-water systems. 

The use of NMR self-diffusion coefficients clearly demonstrated that a water-in-oil type microemulsion exists. The transition from water-in-oil to bicontinuous microemulsion and finally to an oil-in-water system by increasing the water-IL content can be detected by considering the change in the diffusion coefficients. 

Microemulsions in equilibrium with excess oil or water are classified according to the scheme introduced by Winsor. These two-phase regions are sketched in Fig. 3.18. A Winsor I microemulsion is an oil-in-water system with excess oil, a Winsor II microemulsion is a water-in-oil system with excess water and a Winsor III microemulsion is a middle phase system, with an excess of both water and oil. Winsor III microemulsions are thus used in tertiary oil recovery. Transitions between these phases formed using non-ionic surfactants can be controlled by variation of the HLB through temperature, whereas for ionic surfactants transitions can be driven by changing salt concentration. The temperature at which a microemulsion contains equal amounts of water and oil is termed the phase inversion temperature (PIT). 

Many pharmaceutical emulsions are semi-solid oil-in-water systems, prepared with mixed emulsifiers [92]. Often combinations of anionic, cationic or non-ionic surfactants with a fatty alcohol are used as the emulsifying system. Emulsifying... 

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