Viscosity amphoteric surfactants

Surfactant adsorption on the reservoir surface is another important factor to be considered when using foams in EOR processes is discussed in [258]. Adsorption experiments with surfactants of different structures were performed on cores of a number of materials (quartz, sandstones, kaolin, calcite and others), both clean and modified (impregnated) with hydrocarbons of various structure ( light oil, high-viscosity oil, asphaltenes). Minimum adsorption, as well as maximum oil recovery based was observed when using amphoteric surfactants as well as surfactant mixtures, e.g. diphenyl ether disulfonate - a-olefin sulfonate (DPES-AOS). 

Zwitterionic and amphoteric surfactants are typically used as secondary surfactants. The existence of secondary surfactants obviously implies that there are primary surfactants. The latter are mostly the anionic alkyl sulfates and alkylether sulfates, but also include different types of sulfonates. These very often are the main components of a formulation and provide the basic properties of detergency, wetting and foaming. In modem formulations, however, their base properties are not sufficient and need to be improved by secondary surfactants. Improvement is especially needed with respect to mildness, but foaming and viscosity are also enhanced by the use of secondary surfactants. This is where zwitterionic... 

It is generally known that aqueous solutions of true amphoterics can be difficult to thicken. Viscosity control is best achieved by using either the amphoteric salts or by combining with anionic surfactants. The traditional thickening aids, the alkanolamides, are not particularly effective with amphoterics. Nonionic surfactants offer the best thickening support for amphoteric surfactants, especially those based on fatty acids or alcohols ethoxy-lated with 50-200 moles of ethylene oxide, but like all nonionics, they could exert a foam depressing effect if used at a higher level. When amphoteric surfactants are combined with anionic surfactants, the traditional alkanolamides are effective. The final pH adjustment can also make a difference to the viscosity of the product. 

Other hard surface applications rely on amphoteric surfactants to enhance viscosity in highly acidic or alkaline formulations. Some liquid toilet bowl cleaners, for instance, are formulated within a pH range of 2-4 (83). Amphoteric surfactants have been demonstrated to provide good gellation and stability in compounds containing peracetic acid (84). 

The formulation class (tooth paste, shampoo, fabric softener, etc.) provides basic information about the components present. Standard shampoo formulations contain two types of surfactants (either two anionic or one anionic and one amphoteric surfactant) foam booster (nonionic surfactant) conditioner, viscosity improver, opacifier, dye, perfume, chelate, and preservatives. Normally, formulated products are available as liquid, solid, emulsion, dispersion, etc, with a great number of components (in some cosmetic products there may be 20 components) and some of them, such as the preservatives, are found at low concentrations. 

Amphoteric surfactants are divided into two groups based on their response to pH. One class of compounds that contain carboxylated imidazoles and A-alkyl betaines are zwitterionic at pHs at, and above, their isoelectric points and cationic at lower pHs. Sulfobetaines and phosphobetaines, on the other hand, exhibit zwitterionic characteristics as the anionic portion is dissociated at all pHs. Although the former are the major ingredients in many baby shampoos or those products that provide mildness, they also function as foam and viscosity enhancers when utilized as secondary surfactants, having good water solubility over a wide pH range. ° ... 

Likewise, thickened aqueous hypochlorite compositions rely on these surfactants to accomplish the same purpose at alkaline pH levels of 11 or higher [47]. Desired viscosity for such formulas may range from 150 to 3000 cP. This would not only permit easy dispensing, but provides good coating action necessary for cleaning toilet bowls, bathroom tiles, and shower walls [48]. Effective viscosity control is also necessary to suspend abrasives found in scouring cleansers. Finally, the choice of the particular amphoteric surfactant is an important factor in the preparation of low solvent hard surface cleaners [49-50]. 

A characteristic example in the field of cosmetics is the separation and determination of surfactants in shampoos, which contain various combinations of anionic, cationic, nonionic, and amphoteric surfactants. The surfactant combination is designed to influence the essential characteristics of the shampoo cleansing, foam, conditioning, and viscosity. Laurylether sulfates and alkylben-zene sulfonates are common anionic surfeictants used in shampoos to provide lather and cleansing. The only required sample preparation step is the dilution of the product to be analyzed in deionized water and subsequent membrane filtration (0.45 pm) prior to injection. Figure 10.200 illustrates the gradient... 

An amphoteric surfactant with special conditioning, foaming and viscosity-building properties. Especially effective with AOS and compatible with all anionics. Uses include shampoos,... 

The polymer-surfactant complex has high surfeice viscosity and elasticity (i.e. surfeice viscoelasticity), both will enhance the foam stability (see below). The amphoteric surfactants such as betaines and the phospholipid surfeictants when used in conjunction with alkyl sulfeites or alkyl ether sulfeites can also enhance the foam stability. All these molecules strengthen the film of surfactant at the air/water interface, thus modifying the lather from a loose lacy structure to a rich, dense, small bubble size, luxurious foam. Several foam boosters have been suggested and these include fatty acid alkanolamide, amine oxides. Fatty alcohol and fatty acids can also act as foam boosters when used at levels of 0.25-0.5 %. Several approaches have been considered to explain foam stability (a) Surface viscosity and elasticity theory The adsorbed surfeictant film is assumed to control the mechanical-dynamical properties of the surface layers by virtue of its surface viscosity and elasticity. This may be true for thick films (> 100 nm) whereby intermolecular forces are less dominant. Some correlations... 

Chem. Descrip. Sodium lauroamphoacefate Ionic Nature Amphoteric Chem. Analysis 44% solids CAS 68608-66-2 EINECS/ELINCS 271-794-6 Uses Surfactant, foam booster for baby shampoos Features Mild good lathering provide more viscosity than other amphoteric surfactants... 

Secondary surfactants, which include nonionics, amphoterics, and some of the less widely used anionics, are often employed in a formulation to improve foam quality and stability, to provide additional detergency, and to enhance viscosity. Some of them are also used to reduce eye irritation in mild or baby shampoos. 

Amphoteric/betaine surfactants have been used in a wide variety of products including household, l l, and personal-care detergents [13,14]. Some of their advantages include mildness, stability in acidic and alkaline formulations, hydrotroping and coupling properties, synergism with other surfactants, foam stabilization, and viscosity modification. 

Esumi and Ogawa [150] studied micellar solutions of an amphoteric fiuorinated surfactant, [N- [3 [ [Tridecafluoroocty 1) sulfony 1 ] amino]propyl] -iV,A-dimethy 1am-monio]acetate [C6F,3C2H4S02NH(CH2)3N+(CH3)2C00", FOSAB], and its mixtures with LiFOS and LiDS by surface tension, fluorescence probing, and viscosity measurements. At cmc and at 25°C, the surface tension value for FOSAB... 

Shampoos normally contain a blend of cleansing agents (usually two anionic surfactants or an amphoteric and an anionic), foam booster (also a surfactant, most often an alkanola-mide), conditioner, viscosity improver (inorganic salts or cellulose derivatives), opacifier, dye, perfume, biostats (often esters of p-hydroxybenzoic acid), and perhaps chelates (EDTA or citric acid). Propylene glycol or glycerin may be present to adjust solubility and viscosity. Depending on current fashion, other compounds will be present, such as vitamins and food or herb extracts (26,27). 

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