Hydrophilic emulsifiers

Natural Ethoxylated Fats, Oils, and Waxes. Castor oil (qv) is a triglyceride high in ticinoleic esters. Ethoxylation in the presence of an alkaline catalyst to a polyoxyethylene content of 60—70 wt % yields water-soluble surfactants (Table 20). Because alkaline catalysts also effect transestenfication, ethoxylated castor oil surfactants are complex mixtures with components resulting from transesterrfication and subsequent ethoxylation at the available hydroxyl groups. The ethoxylates are pale amber Hquids of specific gravity just above 1.0 at room temperature. They are hydrophilic emulsifiers, dispersants, lubricants, and solubilizers used as textile additives and finishing agents, as well as in paper (qv) and leather (qv) manufacture. 

The choice of coagulant for breaking of the emulsion at the start of the finishing process is dependent on many factors. Salts such as calcium chloride, aluminum sulfate, and sodium chloride are often used. Frequentiy, pH and temperature must be controlled to ensure efficient coagulation. The objectives are to leave no uncoagulated latex, to produce a cmmb that can easily be dewatered, to avoid fines that could be lost, and to control the residual materials left in the product so that damage to properties is kept at a minimum. For example, if a significant amount of a hydrophilic emulsifier residue is left in the polymer, water resistance of final product suffers, and if the residue left is acidic in nature, it usually contributes to slow cure rate. 

An emulsion is a suspension of one liquid in a second, immiscible, liquid. Emulsifiers are agents that facilitate the formation of emulsions and play a role in stabilizing the emulsion so formed. There are two main types of emulsions oil in water and water in oil. Predominantly hydrophilic emulsifiers (for example, PI88) will stabilize the former predominantly hydrophobic emulsifiers (for example, P181) will stabilize the latter. 

There is a common rule, called Bancroft s rule, that is well known to people doing practical work with emulsions if they want to prepare an O/W emulsion they have to choose a hydrophilic emulsifier which is preferably soluble in water. If a W/O emulsion is to be produced, a more hydrophobic emulsifier predominantly soluble in oil has to be selected. This means that the emulsifier has to be soluble to a higher extent in the continuous phase. This rule often holds but there are restrictions and limitations since the solubilities in the ternary system may differ from the binary system surfactant/oil or surfactant/water. Further determining variables on the emulsion type are the ratios of the two phases, the electrolyte concentration or the temperature. 

Sorbitan fatty acid esters are produced by polymerization of ethylene oxide to sorbitan fatty acid esters. The resulting polyoxyethylene sorbitan esters are nonionic hydrophilic emulsifiers. They are used in bakery products as antistaling agents. They ate known as polysorbates with a number as indication of the type of fatty acid used (e.g., lauric, stearic, or oleic acid). 

Water-removable ointments and creams are basically hydrophilic-type emulsions. They are prepared by fusion followed by mechanical addition approach. Hydrocarbon components are melted together and added to the aqueous phase that contains water-soluble components with constant stirring until the mixture congeals. A hydrophilic emulsifying agent is included in the aqueous phase in order to obtain stable oil-in-water dispersion. Sodium lauryl sulfate is used in the preparation of hydrophilic ointment USP. 

A hydrophilic emulsifier, functions as a co-emulsifier for petroleum oils, fats, solvents and waxes in household products, industrial lubricants and textile dye carriers. It is also used as a dispersant for pigments in coatings, a solubilizer for oils and fragrances, and as an emulsifier for aliphatic alcohols in tobacco sucker control concentrates. 

These products are frequently used in conjunction with more hydrophilic emulsifiers, particularly their polyoxyethylene derivatives. When used alone or with other emulsifiers, they are very effective for the preparation of both W/O and O/W emulsions. 

Is a moderately hydrophilic emulsifier which is primarily used as a lubricant component and scrooping agent for textile fibers and yarn, applied either from aqueous or emulsifiable mineral oil systems. It also functions as a viscosity control agent for plastisols. 

Is a strongly hydrophilic emulsifier, stabilizer, antlgellant, and lubricant. It is used as an emulsifier for glycerol monostearate and other waxy esters in the production of concentrated, pourable textile lubricants and softeners, and as a stabilizer and antlgellant for starch solutions. Other applications Include its use as a nonabrasive coating for glass bottles,... 

Is a very hydrophilic emulsifier used for preparing solubilized oils. It is also used as a viscosity modifier and as a softener or plasticizer in acrylic or vinyl resin emulsions,... 

A moderately hydrophilic emulsifier and lubricant, is used as an emulsifier for solvents in pesticide carriers and metal cleaners. In the textile industry it is used in the formulation of specialty detergents and dyeing assistants. It is also used as an emulsifier for neatsfoot oil in leather fat liquoring and as a rewetting agent for paper. 

Is a strongly hydrophilic emulsifier, dispersant, solubilizer and detergent. It is used as a stabilizer and anticoagulant for natural and synthetic latices and dye pastes, as a dyeing assistant for wool/acrylic blends, and as a detergent and lubricant for fiber/fabric scouring. TRYCOL 5972 is also used as an emulsifier for waxes used in coating citrus fruits. HLB 15.8... 

Is a moderately hydrophilic emulsifier used in textile applications as an emulsifier for resin finishing and softener-lubricant systems. It is a good co-emulslfier in dye carrier solvent systems and for lanolin. 

A hydrophilic emulsifier, is a highly effective anti-precipitant for mixed dye baths, a superior leveling agent for acid dyes, and a migrating agent for dispersed dyes. TRYMEEN 6606 is also an intermediate for quaternary ammonium compounds and a versatile antistat for processing synthetic fibers. 

Is an 80% aqueous solution of a strongly hydrophilic emulsifier that is used as an antistatic additive for commercial carpet maintenance. It is also used as a dyeing assistant and as a stabilizer for natural and synthetic latices to prevent coagulation by acids. 

Is a strongly hydrophilic emulsifier and antistat used as an emulsifier in metal buffing compounds. In latex rubber compounding it is used to emulsify stearic acid and to prevent premature coagulation in mild acid or salt baths. 

In semisolid emulsions, excess cetyl alcohol combines with the aqueous emulsifier solution to form a viscoelastic continuous phase that imparts semisolid properties to the emulsion and also prevents droplet coalescence. Therefore, cetyl alcohol is sometimes referred to as a consistency improver or a bodying agent , although it may be necessary to mix cetyl alcohol with a hydrophilic emulsifier to impart this property. 

Two-step Procedure of Emulsification. W/O/W emulsions can be prepared by the method of a two-step procedure. The first step is made for providing an ordinary W/0 emulsion by use of hydrophobic emulsifier. The W/0 emulsion is then mixed with an aqueous solution of hydrophilic emulsifier as the second step procedure for obtaining W/O/W-type dispersion. 

Figure 5. Plot of the W/O/W-type dispersion formation against the weight ratio of Span 80 to the hydrophilic emulsifiers in the final form of the samples. "Reproduced with permission from Ref. U. Copyright 1976, Academic Press. "...

The selection of emulsifiers to prepare food emulsions is mainly based on their HLB number. This index is based on the relative percentage of hydrophilic to lipophilic groups within the emulsifier molecule. Lower HLB numbers indicate a more lipophilic emulsifier, while higher numbers indicate a more hydrophilic emulsifier. Emulsifiers showing HLB numbers between 3 and 6 are best for water-in-oil (W/O) emulsions, and emulsifiers with numbers between 8 and 18 are best for O/W emulsions. 

Soaps of 12-hydroxystearate, derived from castor oil, have superb thickening and lubricity properties and are hence used in greases. Sulphated castor oil is used in a mineral-based lubricant for pre-sizing polyester fibres and thus minimising abrasion. Ethoxlyated castor oil is a hydrophilic emulsifier which has found use in metalworking fluids. 

The presence of emulsifiers (materials that promote emulsion formation) influences the ability to form an emulsion between petroleum and water. Emulsifiers act by lowering the interfacial tension between the phases and creating a strong adsorbed layer around the surface of the internal phase. Emulsifiers that are soluble in water (hydrophilic) promote the creation of oil in water emulsion. Alkaline soaps, starch and so on are such hydrophilic emulsifiers. Hydrophobic emulsifiers (i.e. soluble in petroleum) promote the formation of water in oil emulsions. Hydrophobic emulsifiers include resins dispersed in particle form within soot, clay and other substances. Petroleum emulsions can be characterized using properties such as viscosity, dispersion, density, electrical properties and stability. The viscosity of petroleum emulsion changes within wide ranges and depends on the viscosity of petroleum, temperature, and amounts of petroleum and water. 

In early reports on the formation of double emulsions only one set of emulsifiers and an inversion process were used. Such preparations were done in one step, but the stability was in most cases questionable. It was difficult to control the distribution of the emulsifiers within the two interfaces. There was fast migration of the emulsifiers between the phases that destabilized the emulsions. In most recent emulsion formulations the emulsions are prepared in two steps. At first, a high-shear homogenization is applied to the water that is added to the solution of the oil and the hydrophobic emulsifiers, to obtain a stable W/0 emulsion. In the second step the W/0 emulsion is gently added with stirring (not homogenization) to the water and hydrophilic emulsifiers solution (Fig. 2). The droplet size distribution of a typical classical double emulsion ranges from 10 to 50 pm. 

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