Lather stability

In the presence of excess fatty acid, different soap crystaUine phase compounds can form, commonly referred to as acid—soaps. Acid—soap crystals are composed of stoichiometric amounts of soap and fatty acid and associate in similar bilayer stmctures as pure soap crystals. There are a number of different documented acid—soap crystals. The existence of crystals of the composition 2 acid—1 soap, 1 acid—1 soap, and 1 acid—2 soap has been reported (13). The presence of the acid—soaps can also have a dramatic impact on the physical and performance properties of the finished soap. The presence of acid—soaps increases the plasticity of the soap during processing and decreases product firmness, potentially to the point of stickiness during processing. Furthermore, the presence of the acid—soap changes the character of the lather, decreasing the bubble size and subsequently increasing lather stability and creaminess. 

These surfactants, in conjunction with soap, produce bars that may possess superior lathering and rinsing in hard water, greater lather stability, and improved skin effects. Beauty and skin care bars are becoming very complex formulations. A review of the literature clearly demonstrates the complexity of these very mild formulations, where it is not uncommon to find a mixture of synthetic surfactants, each of which is specifically added to modify various properties of the product. For example, one approach commonly reported is to blend a low level of soap (for product firmness), a mild primary surfactant (such as sodium cocoyl isethionate), a high lathering or lather-boosting cosurfactant, e.g., cocamidopropyl betaine or AGS, and potentially an emolhent-like stearic acid (33). Such benefits come at a cost to the consumer because these materials are considerably more expensive than simple soaps. 

U.S. 6503873 (2002) Crudden et al. (Hampshire Chem) JV-acyl ethylenediaminetriacetic acid (ED3A) (Na or K lauroyl) A novel chelating surfactant product ultra-mild detergent compositions in combination with alkyl sulfates excellent lather stability... 

N-acyl ED3A chelating surfactants are capable of very dramatic, highly synergistic lather enhancement on mixed surfactant systems particularly in the presence of divalent connterions. The lather stability on mixtnres of SLES (3 moles EO) and Na LEDS A at a constant concentration of 1% in the presence and absence of water hardness is presented in Figure 5. Synergistic lather enhancement is evident when the system composition passes 30% LED3A. 

When Na LED3A was added to a commercial baby shampoo (Fig. 6), the lather stability was enhanced nearly sevenfold in soft water and in water containing 200 ppm water hardness. The two factors which lead to the formation of stable lather are low surface tension and high snrface viscosity. Since synergy in surface tension is not evident in the mixtnres, it is likely that synergistic lather enhancement is due to increase of surface viscosity and formation of more stable surface films which are... 

Uses Foam and lather stabilizer, vise, booster for shampoos, liq. dishwashing prods., hand soaps, and other personal care or household prods. does not contain propylene glycol or other diluents... 

Because the core of an aqueous micelle is extremely hydrophobic, it has the abiHty to solubiHze oil within it, as weU as to stabilize a dispersion. These solubilization and suspension properties of surfactants are the basis for the cleansing abiHty of soaps and other surfactants. Furthermore, the abiHty of surfactants to stabilize interfacial regions, particularly the air—water interface, is the basis for lathering, foaming, and sudsing. 

Cocamide DEA (or MEA or TEA) is used as a foaming agent, to make lather. The other surfactants generate a certain amount of suds, but this foaming agent is added to get the amount just right. In addition to its foam-stabilizing effects, it is also a viscosity booster—it s thick. 

Since we want the texture of products like shaving cream to stay stable, and since shampoo advertisers like to pretend that unnecessary extra lather is an important selling point, foam stabilizers are helpful in preventing foams from breaking down. 

Odor and color stability problems were also related to the alkyl chains used for SAI. These could be traced to the oxidation of unsaturated carbons, such as oleic acid (Ci8 fatty acid with a single double bond between carbon 9 and 10, i.e. bond position 9 counted from the carboxyl carbon), linoleic acid (Cis fatty acid with two double bonds at position 9 and 12), and linolenic acid (Cis fatty acid with three double bonds at position 9, 12, and 15). Natural coconut fatty acid contains about 6% oleic acid, about 3% linoleic acid, and less than 1% linolenic acid. Tallow fatty acid contains nearly 44% oleic and about 6% of other unsaturates [20]. Partial hydrogenation of the coconut fatty acid used in the manufacture of SCI served to eliminate linoleic and linolenic acids for improved odor stability, while not eliminating oleic acid, which is important for good lather. 

Consumer-acceptable lather requires the consideration of a variety of lathering attributes, such as the speed with which lather is generated, volume, quality (i.e., loose or creamy), and the stability of the lather. In general, the use of fatty acids of C10 C12 chain length provides a voluminous lacey foam and fatty acids of longer chain length, from C16 to Clg, contribute to a richer, creamier foam. 

Amine oxides are also employed to improve foam characteristics and stabilize lather, especially at moderately acidic pH values. CAP (cocamidopropyl) amine oxide is one of the most commonly used amine oxides. These materials act as nonionics at the near-neutral pH encountered in shampoos but are easily protonated at acidic pH. As a result, they sometimes behave as cationics and act as conditioning and antistatic agents as well in a properly formulated system [13,19],... 

U.S. 5302323 (1994) Hartung et al. (Abbott Lab.) 0.5-2.5% selenium sulfide two suspending agents di(hydrogenated) tallow phthalic acid amide and one selected from hydroxypropylbmethylcellulose and Mg Al silicate pH 4.0-6.5 buffer system with Na citrate and citric acid at least 18% anionic surfactant Improved pH stability, suspension stability, lathering, and conditioning (three-in-one)... 

For more complex shampoos, including emulsions, a variety of thickeners is available besides salt, including gums, associative thickeners, synthetic polymers, and long-chain alcohols (Section II.C.2). These materials are used to attain a desired viscosity, to stabilize a product, and to attain a desirable rheological profile. Since they affect product structure, they can also affect lather. Viscosity modifiers, therefore, should be chosen to give the best mix of lather and rheological properties. 

In the laboratory, lather properties of liquid hand soap and shower gel are measured as flash foam (speed of foam generation), maximum foam (quantity and stability), and foam creaminess (drainage time). 

A) Titration with calcium chloride. As was indicated above, these phosphates are widely used in laundry operation and in soap powders, to prevent the calcium and magnesium ions of hard water from giving a precipitate with the soap. The value of a particular phosphate for this purpose depends not only on the amount of calcium or magnesium the phosphate can take up to form a complex ion but also on the stability of this complex. In the procedure to be described, the amount of calcium salt needed to destroy a lather of soap and water containing phosphate is measured. This procedure gives an estimate of the calciumbinding power of the phosphate for this particular application. 

The presence of the cationic polymer in a typical cleansing system can be expected to affect the lather characteristics of the system. While the polymer can stabilize and enhance the lather under nonprecipitation conditions by increasing the surface viscosity in the liquid film lamellae, it may reduce/destroy the lather under precipitation conditions by lowering the levels of surfactant available in the solution phase. (See Section III.)... 

The lather shave cream is a concentrated dispersion of alkali metal soap in a glycerol-water mixture. This formulation has adequate physical stability, particularly if the manufacturing process is carefully optimised. Phase separation of the formulation may occur at elevated temperatures. 

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