Emulsion saponifications

A recent study of emulsion saponification (Lachampt, Zviak, and Rossignol, 64) has shown that at relatively low temperatures the speed of saponification increases with the fineness of the emulsion. Complete saponification occurs in two minutes with an emulsion in which the droplets are about 1 y in diameter. While for weak soda concentrations the reaction never proceeds to completion, with sufficiently strong sodium hydroxide the reaction reaches its end point whatever the coarseness of the emulsion. The presence of sodium chloride hinders the overall reaction. Catalysts such as fatty acids and 2-naphthol function by stabilizing the emulsion, permitting the interfacial area to remain large when otherwise the emulsion droplets would coalesce with consequent reduction in reaction rate. 

Paste rosin sizes are supplied as viscous pastes containing 60—80% solids. These sizes may contain unmodified or fortified rosin that has reacted (ie, been fortified) with either maleic anhydride [108-31-6] or fumaric acid [110-17-8] (see Fig. 3). In either case, the unmodified or fortified rosin is treated with aqueous alkaH so that the degree of neutralization, ie, saponification, varies from 75—100% depending on the physical state desired for the commercial product. Before use, the paste size must be converted to a stable, dilute rosin size emulsion by careful sequential dilution with warm water foUowed by cold water, with good agitation. 

The hydrophile—hpophile balance (HLB) is an empirical system based on the fact that oil—water (o/w) emulsions are best stabilized by water-soluble-emulsifiers and water—oil (w/o) emulsions are best stabilized by oil-soluble ones (3). The HLB scale mns from 0—20 and is based on the ratio of the saponification number of ester, A, to the acid number of recovered acid, where HLB = 20 1-Sj A). The dispersibiUty of an emulsifier in water is related to HLB value. 

Water-in-oil macroemulsions have been proposed as a method for producing viscous drive fluids that can maintain effective mobility control while displacing moderately viscous oils. For example, the use of water-in-oil and oil-in-water macroemulsions have been evaluated as drive fluids to improve oil recovery of viscous oils. Such emulsions have been created by addition of sodium hydroxide to acidic crude oils from Canada and Venezuela. In this study, the emulsions were stabilized by soap films created by saponification of acidic hydrocarbon components in the crude oil by sodium hydroxide. These soap films reduced the oil/water interfacial tension, acting as surfactants to stabilize the water-in-oil emulsion. It is well known, therefore, that the stability of such emulsions substantially depends on the use of sodium hydroxide (i.e., caustic) for producing a soap film to reduce the oil/water interfacial tension. 

It is liquid-liquid reactions involving phase transfer catalysts which generally benefit from the use of ultrasound. Sonication produces homogenisation - i. e. very fine emulsions - which greatly increase the reactive interfacial area and allows faster reaction at lower temperatures. Davidson has reported an example of this with the ultrasonically enhanced saponification of wool waxes by aqueous sodium hydroxide using tetra n-heptyl ammonium bromide as a PTC [124]. 

The CSTR is particularly useful for reaction schemes that require low concentration, such as selectivity between multiple reactions or substrate inhibition in a chemostat (see Section IV). The reactor also has applications for heterogeneous systems where high mixing gives high contact time between phases. Liquid-liquid CSTRs are used for the saponification of fats and for suspension and emulsion polymerizations. Gas-liquid mixers are used for the oxidation of cyclohexane. Gas homogeneous CSTRs are extremely rare. 

The large areas of the oil-water interfaces in an emulsion have proved important in several chemical operations—emulsion polymerizations, saponifications, and the condensation of peptides. The particular influence of the interface depends on many different factors, including the increased opportunity offered for reaction between oil-soluble and water-soluble components, the possibility that the surface may bear an electrical charge, and the uniform orientation of the superficial reactant molecules under the action of the directive forces of the two different liquids. 

Those fata taken in with the food are unaltered by the digestive fluids, except in that they are freed from tiieir enclosing membranes in the stoniAcb, until they reach the duodenum here, under the influence of the pancreatic juice, the major port is converted into a fine emulsion, in which form it is absorbed by the ueteals. A smaller portion ia saponified, and the products of the saponification, free fatty acids, soaps, and glycerin. Sub uentiy absorbed ig lacteals and blood-vessels. 

PTC incorporated with other methods usually greatly enhances the reaction rate. Mass transfer of the catalyst or the complex between different phases is an important effect that influences the reaction rate. If the mass transfer resistance cannot be neglected, an improvement in the mass transfer rate will benefit the overall reaction rate. The application of ultrasound to these types of reactions can be very effective. Entezari and Keshavarzi [12] presented the utilization of ultrasound to cause efficient mixing of the liquid-liquid phases for the saponification of castor oil. They used cetyltrimethylammo-nium bromide (CTAB), benzyltriethylammonium chloride (BTEAC), and tetrabutylammonium bromide (TBAB) as the catalysts in aqueous alkaline solution. The more suitable PT catalyst CTAB can accumulate more at the liquid-liquid interface and produces an emulsion with smaller droplet size this phenomenon makes the system have a high interfacial surface area, but the degradation of CTAB is more severe than that of BTEAC or TBAB because of more accumulation at the interface of the cavity under ultrasound. 

Fatty adds are predominantly used as intermediates. Main applieations are water soluble soaps for household eleaning, personal care, industrial and institutional (I I) cleaning and synthetic rubber manufacturing by emulsion polymerization. Soaps are made by reaction of fatty acids with caustic alkalis, alkali carbonate or ammonia or (>90%) by direct saponification of the triglyceride oil. Another important group of fatty add soaps are dry, water-insoluble metal soaps used as lubricants or stabilizers for PVC and other plastics and aqueous calcium stearate dispersions applied as paper coating... 

Methyl acetate and the more valuable butyl acetate find a ready market as solvents. During the transesterification, a highly viscous gel phase occurs at yields between 45% and 75%. To prevent the formation of this gel phase, it was proposed to work continuously in very dilute solutions, to work with poly(vinyl acetate) in hydrocarbon emulsions, or that kneaders or masticators should be used. One can avoid these difficulties with poly(vinyl formiate), which is easily saponified in hot water. Monomeric vinyl formiate is, however, difficult to produce because of its great susceptibility to hydrolysis. In addition, the formic acid liberated during the saponification is very corrosive. 

On the other hand, emulsion losses are higher when using dilute solutions. Similarly, a large excess (30-50%) has a high purifying action but a greater tendency to saponification. Emulsions are more likely to be encountered with low excess lye usage (5-15%). 

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