Amphoteric shampoo

Chloroacetic acid can be esterified and aminated to provide useful chemical intermediates. Amphoteric agents suitable as shampoos have been synthesized by reaction of sodium chloroacetate with fatty amines (4,5). Reactions with amines (6) such as ammonia, methylamine, and trimethylamine yield glycine [66-40-6J, sarcosine [107-97-17, and carhoxymethyltrimethylammonium chloride, respectively. Reaction with aniline forms /V-phenylglycine [103-01 -5] a starting point for the synthesis of indigo (7). 

Shampoos based on lauryl sulfates can range from 6—17% of the active surfactant. However, though they are effective cleansers, the alkyl sulfates tend to be defatting. In an effort to make these shampoos more mild, many shampoos are now based on blends of amphoterics and alkyl sulfates or the less irritating alkyl ether sulfates. 

Amphoteric Detergents. These surfactants, also known as ampholytics, have both cationic and anionic charged groups ki thek composition. The cationic groups are usually amino or quaternary forms while the anionic sites consist of carboxylates, sulfates, or sulfonates. Amphoterics have compatibihty with anionics, nonionics, and cationics. The pH of the surfactant solution determines the charge exhibited by the amphoteric under alkaline conditions it behaves anionically while ki an acidic condition it has a cationic behavior. Most amphoterics are derivatives of imidazoline or betaine. Sodium lauroamphoacetate [68647-44-9] has been recommended for use ki non-eye stinging shampoos (12). Combkiations of amphoterics with cationics have provided the basis for conditioning shampoos (13). 

Baby Shampoos. These shampoos, specifically marketed for small children, feature a non-eye stinging quaHty. The majority of the products in this category are based on an amphoteric detergent system a system combining the use of an imidazoline amphoteric with an ethoxylated nonionic surfactant has been successfiiUy marketed (15,16). The sulfosuccinates also have been suggested for baby shampoo preparation because of thek mildness... 

Many of the surfactants made from ethyleneamines contain the imidazoline stmcture or are prepared through an imidazoline intermediate. Various 2-alkyl-imidazolines and their salts prepared mainly from EDA or monoethoxylated EDA are reported to have good foaming properties (292—295). Ethyleneamine-based imida zolines are also important intermediates for surfactants used in shampoos by virtue of their mildness and good foaming characteristics. 2- Alkyl imidazolines made from DETA or monoethoxylated EDA and fatty acids or their methyl esters are the principal commercial intermediates (296—298). They are converted into shampoo surfactants commonly by reaction with one or two moles of sodium chloroacetate to yield amphoteric surfactants (299—301). The ease with which the imidazoline intermediates are hydrolyzed leads to arnidoamine-type stmctures when these derivatives are prepared under aqueous alkaline conditions. However, reaction of the imidazoline under anhydrous conditions with acryflc acid [79-10-7] to make salt-free, amphoteric products, leaves the imidazoline stmcture essentially intact. Certain polyamine derivatives also function as water-in-oil or od-in-water emulsifiers. These include the products of a reaction between DETA, TETA, or TEPA and fatty acids (302) or oxidized hydrocarbon wax (303). The amidoamine made from lauric acid [143-07-7] and DETA mono- and bis(2-ethylhexyl) phosphate is a very effective water-in-od emulsifier (304). 

Cocamidopropyl betaine is an amphoteric detergent, a detergent that can act as an acid or a base. It does not irritate the skin or mucous membranes. It is used to thicken shampoos, and to reduce the irritation that would result if only more irritating detergents were used. It has antibiotic effects, and is used in personal sanitary products. It also has antistatic properties, making it an effective conditioning agent in shampoos. 

Sodium isethionate is an amphoteric detergent used in detergent bar soaps. It makes a dense lather in addition to the lather made by the soap. It is nondrying and mild on the skin. It works equally well in soft or hard water. It is also an antistatic agent in shampoos. 

Amphoteric surfactants are those that are an acid and a base at the same time (like water is). Cocamidopropyl betaine, for example, is used in shampoos to stabilize foam and thicken the mixture. 

In a patent survey [76] about shampoos over the period 1968-1978 the so-called cryptoanionic alkyl ether carboxylate based on tridecyl alcohol with 6.5 mol EO has been mentioned for a conditioning shampoo in combination with an amphoteric and cationic surfactant [77]. Because of the low interference with cationic surfactants no negative effect on the conditioning properties has been found [78]. 

Cocamidopropyl betaine (Table 1.4) is the most prominent representative of the class of amphoteric surfactants. Due to the synergism with other surfactants and its gentleness to the skin and mucous membranes, cocamidopropyl betaine performs well in shampoo and cosmetics where its dosage lies in the order of 1-5% [27]. 

Although these surfactants represent less than 1% of the U.S. production of surfactants, the market use is increasing dramatically because of their unique properties [353]. Of particular importance is the synergistic effect that amphoteric surfactants have when used in conjunction with other types of surfactants. The non-eye-stinging characteristic of these compounds has been responsible for the upsurge in the baby shampoo market over time [354,355]. 

Amphoteric surfactants are used in shampoos and can be used with alkalis for greasy surfaces as well as in acids for rusty surfaces. 

As mentioned above, most commercial products are based on either a lauric (mainly C-12) or a whole coconut distribution (C-8 to C-18, with approximately 50% C-12) since these alkyl distributions give the best detergency. Early on, the imidazoline derived amphoterics were characterized as exceptionally mild to the skin and eyes relative to most surfactants available at the time. This made them excellent candidates for use in baby shampoos, geriatric cleansing products, hand wash for medical facilities and so on. 

Over the years, optimized amphoacetates were developed that were intermediate between the 1 and 2-mol products. An effort was made to deliver more amphoteric surfactant and less by-products to the formulator. Most baby shampoos and body washes produced today are formulated with such optimized products, which are produced from an optimum ratio... 

Other European companies, such as ICI through Atlas and Tensia, Th. Goldschmidt, Rewo, and Servo, have particularly targeted the lucrative area of beauty care. In the United States, Miranol has been very successful with the amphoterics (imidazolines, betaines) for baby shampoos, an activity acquired by Rhone-Poulenc in 1989. 

Amphoteric surfactants. These compounds have the characteristics of both anionic detergents and cationic fabric softeners. They tend to work best at neutral pH, and are found in shampoos, skin cleaners, and carpet shampoos. They are very stable in strong acidic conditions and are favorably used with hydrofluoric acid. For example, compounds of alkyl-betain or alkylsulfobetaine type possess both anionic and cationic groups in the same molecule even in aqueous solution. These surfactants are rarely employed in laundry detergents because of their high costs [3, 4]. 

Cocamidopropyl betaine is the most commonly used amphoteric surfactant in shampoos, bath products, and other cosmetic products. It is popular because of its relatively low irritation potential. 

There is minimal absorption of anionic, nonionic, and amphoteric surfactants. Antidandruff shampoos may contain zinc pyridinethione and selenium... 

The change in charge with pH of amphoteric surfactants affects their properties, such as wetting, detergency, and foaming. Atthe i.e.p., the properties of amphoterics resemble those of nonionics very closely, but below and above the i.e.p. the properties shift towards those of cationic and anionic surfactants, respectively. Zwitterionic surfactants have excellent dermatological properties, and also exhibit low eye irritation consequently, they are frequently used in shampoos and other personal care products (e.g., cosmetics). 

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. 

Quaternized polymers have been found to improve wet combing and reduce static charge. In general, they can be formulated with anionic surfactants greater deposition occurs with a mixture of amphoteric and nonionic surfactants. Two of the most important examples are Polyquaternium-10, a quaternized hydroxyethylcel-lulose polymer, and Polyquaternium-7, a copolymer of diallyldimethylammonium chloride and acrylamide. These are the two most frequently used polymeric conditioning agents in commercial shampoos [46,47],... 

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