Other amphoteric surfactants

The chemical literature and patent art disclose a great variety of amphoteric surface active molecules. The author has attempted to address only those that are of economic importance today. Not all of the current commercial products fall into the categories above, so a few additional ones are mentioned here. 

Mona Industries received a series of patents in the 1980s for betaines and imidazoline-based surfactants similar to the hydroxysultaines and hydroxypropylsulfonates discussed earlier but alkylated with a propanechlorohydrin phosphate rather than the CHPS [9]. These amphoteric surfactants were demonstrably mild and were thought to have some 

Amphoteric surfactants have a variety of roles in industry today. They continue to be among the mildest surfactants available for the formulation of personal care products and are incorporated into products that demand the least irritation potential such as facial cleansers, feminine hygiene washes, no rinse cleansers such as baby wipes, geriatric products and so 

Their ability to render compatible various surfactants and other types of surfactants into strong solutions of electrolyte make them invaluable in the formulation of strong detergent products where mildness is not an issue. 

In addition, because they are generally based on aminoacid structures, they are among the most biodegradable surfactants available to the formulator. Products based on amphoteric surfactants are usually readily biodegradable, thus having a minimal impact on the environment. 

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N-alkyl (3-alanine derivatives, the monopropionates , have distinct isoelectric points while most other amphoteric surfactants do not. The isoelectric point is the pH at which the molecule is internally neutralized, existing as a zwitterion. Aqueous solubility and the propensity to foam are lowest at the isoelectric point. 

Other amphoteric surfactants include the betaines derived from imidazolines, which absorb UV light and the lecithins or phosphati-dicholines, which are naturally occurring phospholipids [7]. Multifunctional surfactants associating a nonionic moiety with a charged one are considered ionic surfactants. 

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... 

As mentioned above, the betaine surfactants can be considered to be special members of the ring-opened, imidazoline surfactants. However, they do not exhibit many of the characteristics of other amphoteric surfactants, especially with regard to their solubility and electrical nature in alkaline solution. Even at high pH, the betaines do not acquire any significant anionic character, and they appear to... 

Major industrial uses for chloroacetic acid are in the manufacture of cellulose ethers (mainly carboxymethylceUulose, CMC), herbicides, and thioglycolic acid. Other industrial uses include manufacture of glycine, amphoteric surfactants, and cyanoacetic acid. 

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]. 

Numerous laboratory sorption studies have been conducted for the most common surfactants non-ionics, such as AE and alkylphenol ethox-ylates (APEOs) anionics such as LAS, secondary alkane sulfonates (SASs) and sodium dodecylsulfates (SDS) and on different natural sorbents [3,8,15-17], Until now, cationic and amphoteric surfactants have received less study than the other types, probably because they represent only 5 and 2%, respectively, of the total surfactant consumption in Western Europe (1998) [18]. 

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]. 

These imidazoline compounds have proved very useful as intermediates to amphoteric surfactants. Products made from them, alkylated with sodium chloroacetate or methyl acrylate were patented by Hans Mannheimer who founded Miranol Company in the USA during the 1950s [2]. Miranol Company became the major vendor of imidazoline derived amphoteric surfactants in the world. Other imidazolines are used to produce amphoteric surfactants, such as alkyl aminoethyl imidazoline, but those products are of less economic significance. 

The other major class of fatty imidazoline derived amphoteric surfactants is the amphopropionates. Again, the ampho portion of the name indicates that they are derived from imidazolines but, rather than being alkylated with sodium chloroacetate, they are carboxy-lated with an acrylate via the Michael reaction. A primary or secondary amine is added across the double bond of the acrylate to yield the beta-alanine derivative. 

Amphoteric Surfactant A surfactant molecule for which the ionic character of the polar group depends on solution pH. For example, lauramidopropylbetaine, CnH23CONH(CH2)3N (CH3)2CH2COO", is positively charged at low pH but is electrically neutral, having both positive and negative charges at intermediate pH. Other combinations are possible, and... 

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. 

A saturated bromine aqueous solution can also be used to determine the type of amphoteric surfactant. Add 5 ml of 1 % sample solution to 1.5 ml saturated bromine aqueous solution. Observe the colour of the precipitate. Heat the mixture and observe the change in the precipitate. If the precipitate is a yellow to yellow-orange colour and is dissolved to form a yellow solution after heating, the sample is an imidazoline or alanine type of amphoteric surfactant. If the precipitate is a white to yellow colour and insoluble after heating, the sample is the other type of amphoteric surfactant. 

Amphoteric surfactants are sometimes referred to as 2witterionic molecules. They are soluble in water, but their solubility shows a minimum at the i.e.p. Amphoterics show excellent compatibility with other surfactants, forming muKd micelles they are also chemically stable both in acids and alkalis. The surface activity of amphoterics varies widely, and depends on the distance between the charged groups. Amphoterics display a maximum in surface activity at the i.e.p. 

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). 

We have already mentioned that xanthan gum solutions are tolerant to both acids and bases. Solutions of xanthan gum also have excellent compatibility with many surfactants, water-miscible solvents, and other thickeners. As an anionic polysaccharide, xanthan gum is most stable with anionic surfactants (up to 20% active), nonionic surfactants (up to 40% active), and amphoteric surfactants (up to... 

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