Fatty-acid soaps processability

T. J. Farrell, C. C. Nunn, Fatty acid soap/fatty acid bars which process and have good lather, US Patent 6 846 787 B1 (2005). 

W. Narath, G. Omoski, J. Corr, Enhanced processing of synthetic bar compositions comprising amphoterics based on minimal levels of fatty acid soap and minimum ratios of saturated to unsaturated soap, US Patent No. 6 121 216 (2000). 

The alkali-metal salts of fatty acids - soaps - are the oldest synthetic surfactants and they have been prepared in various forms and in varying purity since pre-historic times. The technology has progressed from boiling animal fats with wood ash to an ultra-efficient high volume process, with a very extensive knowledge and literature base. 

The paper industry uses large amounts of the sodium salt of rosin as paper size, which accounts for the greatest single use of rosin. The synthetic rubber industry is the second most important user of rosin. In making styrene-butadiene rubber, disproportionated rosin soaps are used alone or in combination with fatty acid soaps as emulsifiers in the polymerization process. Disproportionation decreases the number of double bonds in the abietic acid of the rosin, making a more stable material. 

Fig. 36.2). The methyl ester process for soap manufacture is typically more capital and cost intensive versus the more traditional fats/oils saponification and fatty acid neutralization processes. 

Butadiene-Styrene Rubber occurs as a synthetic liquid latex or solid rubber produced by the emulsion polymerization of butadiene and styrene, using fatty acid soaps as emulsifiers, and a suitable catalyst, molecular weight regulator (if required), and shortstop. It also occurs as a solid rubber produced by the solution copolymerization of butadiene and styrene in a hexane solution, using butyl lithium as a catalyst. Solvents and volatiles are removed by processing with hot water or by drum drying. 

The ester bonds in fats and oils can be hydrolyzed in the presence of base to produce soaps which are the sodium salts of fatty acids. Soap making is an ancient process which has changed little over millenia. 

Fatty Acids. The above process is an old and direct method by which to make soap but if fatty acids are wanted, and their use is increasing, the addition of alkali must be avoided unless subsequent treatment with acid at additional expense iis to be incurred. For making these fatty acids several processes may be used, the autoclave and the traditional Twitched method, which are batch operations, and the more modem continuous-countercurrent procedures developed by Colgate-Palmolive-Peet and by The Procter Gamble Company. Darkening of the resulting products from this type of operation is retarded by the use of hydroxy aromatic compounds as stabilizers. ... 

In case of using mixtures of two and more collectors, the selective hydrophobisation is accomplished simultaneously both due to chemisorption and physical adsorption. It is shown in [69] that the simultaneous use of fatty acids and hydrocarbon oils for calcium phosphate flotation from quartz different processes are observed. Fatty acid soaps form chemical compounds on the surface of the material floated, after which the hydrocarbon oil physically adsorbs. It has been experimentally established that hydrocarbon oil is transferred from quartz particles to the surface of floated phosphate. When using mixtures of anionics and nonionics, hydrophobisation of particle surfaces is also accomplished both due to the formation of chemical compounds and physical adsorption which is confirmed by measurements of the zeta-potential of the particles floated [70]. 

A relatively new field is the use of flotation in wet textile processes [73]. The ( -potential of cotton fibres in aqueous solutions is negative, therefore they are effectively floated by cationics like quaternary ammonium salts, e.g. dodecyl trimethyl ammonium chloride. Sysilia et al. [74] have established, by measuring the electrokinetic potential, a clear rule between the positive surface charge of chromite and flotation efficiency. At low pH, chromite was effectively floated by fatty acid soaps, the ions of which are negatively charged under these conditions. The surfactant adsorption is reversible which is indicative of its physical nature. 

Other Chemical Methods These methods rely chiefly on destroying the foam stabilizer or neutralizing its effect through methods other than displacement and are applicable when the process will permit changing the chemical environment. Forms stabilized with alkali esters can be broken by acidification since the equivalent free acids do not stabilize foam. Foams containing sulfated and sulfonated ionic detergents can be broken with the addition of fatty-acid soaps and calcium salts. Several theories have been proposed. One su ests that the surfactant is tied up in the foam as double calcium salts of both the sulfonate and the soap. Another suggests that calcium soaps oriented in the film render it inelastic. 

Fatty acid soaps are now used only as minor ingredients, and function as defoamers in the washing machines. Soaps also aid in the cleaning process, but with hard water, they leave encrustation of soap scum on fabrics. 

Such a hydrolysis is termed saponification since it produces soaps, which are sodium and potassium salts of the fatty acids. The process of fat breakdown may take place naturally xmder the influence of enzymes, collectively known as lipases, when it is termed lipolysis.The enzymes may have a certain specificity and preferentially catalyse hydrolysis at particular positions in the molecule. Removal of the fatty acid residue attached to carbon atom 2 of an acylglycerol is more difficult than those at positions 1 and 3. Under natural conditions, the products of lipolysis are usually mixtures of mono- and diacylglycerols with free fatty acids. Most of these acids are odourless and tasteless, but some of the lower ones, particularly butyric and caproic, have extremely powerful tastes and smells when such a breakdown takes place in an edible fat, it may frequently be rendered completely imacceptable to the consumer. The lipases are mostly derived from bacteria and moulds, which are chiefly responsible for this type of spoilage, commonly referred to as randdity. Extensive lipolysis of dietary fats takes place in the duodenum and during their absorption from the small intestine. Lipolysis also precedes the hydrogenation of fats in the rumen, and the oxidation of fats in the body. 

Resin Recovery Process. Typically, the polymer is recovered by the addition of coagulants which destabilize the ABS latex. Different coagulants are used depending on the surfactant. Thus, strong and weak acids work well with fatty acid soaps, and metal salts are used with acid stable soaps (106). The use of nonionic coagulants has also been reported (107,108). Acrylic latices have been... 

The soap which is removed in the refining process is diluted with water and acidified to form fatty acids. The fatty acids are centrifuged to remove the aqueous phase, dried and used for production of fatty acids, soap or feed manufacturing. This product is called acid oil or acidulated soap stock by the oil industry (Bimbo and Crowther, 1991). 

Free Fatty Acid Soap bars are intrinsically alkaline in nature on account of the physical properties of soap in water and the process utilized in its manufacture, which yields base... 

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