Foams amphoterics

Foaming. Amphoterics are excellent foamers and foam stabilizers under a variety of conditions. Foamability is essentially insensitive to water hardness. All of these characteristics have their implications on the designs of the production processes of the various amphoterics in the detergent market. 

Amphoteric 400 Is an extremely low foam amphoteric designed for use In hard surface alkaline or acid cleaning formulations where no foam Is desired, such as In continuous metal cleaning with pressure spray. It also has application In machine dishwashing compounds, again where no foam Is desired. Amphoteric 400 is an Imlnodlproplonate amphoteric supplied as a 50% solution of the partial sodium salt. 

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). 

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. 

The foam-holding characteristics of foam from surfactants in oil field jobs can be tailored by adding an imidazoline-based amphoacetate surfactant. Amphoacetates are a special class of amphoteric tensides (Figure 16-1). Imidazoles, such as 2-heptylimidazoline, are reacted with fatty acids under the ring opening. For alkylation, the imidazoline is reacted with, for example, chloroacetate [493]. 

A foam can be generated by using an inert gas and a fluorocarbon surfactant solution in admixture with an amphoteric or anionic hydrocarbon surfactant solution. A relatively small amount of the fluorocarbon surfactant is operative when mixed with the hydrocarbon surfactant and foamed. The foam has better stability than a foam made with hydrocarbon surfactant alone when in contact with oil [1491]. 

Even if this class covers the smallest market segment, amphoteric surfactants still remain useful because of their unique properties, which justifies their comparably high manufacturing costs. Since they have partial anionic and cationic character, they can be compatible, under specific conditions, with both anionic and cationic surfactants. They can function in acid or basic pH systems and, at their isoelectric point, they exhibit special behaviour. Many amphoteric surfactants demonstrate exceptional foaming and detergency properties combined with antistatic effects. 

Long-lasting foam Use anionic or amphoteric surfactants, or a mixture of the two for high foaming... 

Adsorption can be measured by direct or indirect methods. Direct methods include surface microtome method [46], foam generation method [47] and radio-labelled surfactant adsorption method [48]. These direct methods have several disadvantages. Hence, the amount of surfactant adsorbed per unit area of interface (T) at surface saturation is mostly determined by indirect methods namely surface and interfacial tension measurements along with the application of Gibbs adsorption equations (see Section 2.2.3 and Figure 2.1). Surfactant structure, presence of electrolyte, nature of non-polar liquid and temperature significantly affect the T value. The T values and the area occupied per surfactant molecule at water-air and water-hydrocarbon interfaces for several anionic, cationic, non-ionic and amphoteric surfactants can be found in Chapter 2 of [2]. 

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. 

Antaron FC-34 [BASF]. TM for a high-foaming, water-soluble, amphoteric surfactant with soaplike qualities, a complex fatty amido compound 40% active. 

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). 

Copious foam usually requires the use of high-foaming surfactants, typically anionic or amphoteric surfactants or a mixture of surfactants. Long-lasting foam often requires the use of foam stabilizers in addition to surfactant mixtures. 

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