Personal care products amphoteric surfactants

In the 1970s and 1980s, a number of amphoteric surfactants were introduced to the market that were based on alkyl polyamines, primary amines upon which is condensed acrylonitrile, then hydrogenated to produce an alkyl propylenediamine and, with additional cycles, alkyl polyamines. These, in turn, are alkylated with sodium chloroacetate to produce alkyl polyamine polycarboxylates. Some of these products find utility in laundry applications, in personal care products and as industrial foamers. 

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... 

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). 

As shown in Figure 22.1, 7% of total surfactants are used in cosmetics and pharmaceuticals, especially in personal care products such as shampoos, bath preparations or toothpastes. Surfactants are important in their function as emulsifiers in creams and lotions. A great variety of anionic, nonionic, cationic and also amphoteric surfactants are used here. 

Amphoterics are excellent foamers and foam stabilizers under a variety of conditions. Their foamability is essentially insensitive to water hardness. Capitalizing on these properties, amphoterics were among the many specialty surfactants commercialized after World War II [2]. Since then, these surfactants have been used in personal care products because of their unsurpassed mildness and low eye-sting properties. Today, most mild skin cleansers and shampoos contain an amphoteric surfactant as a major component. 

TOMAH Amphoteric N is a unique amphoteric surfactant with exceptionally high foaming properties in the presence of many other surfactants and components typically used in shampoos and personal care products. Amphoteric N is a modified dipropionate amphoteric supplied as a 35% aqueous solution of the partial sodium salt. Amphoteric N is CTFA listed as Sodium C12-15 Alkoxypropyl Iminodipropionate. 

Amphoterics are usually used in conjunction with other surfactants (anionics or nonionics) to boost desired properties such as foam or detergency. Since the optimal surface activity of amphoterics takes place around neutral pH, they are particularly appreciated in personal care products (shower gels, foam baths, shampoos, etc.) for their mildness and skin compatibility. 

Applications. Amphoterics of this class are mainly used in personal care products. Polycarboxylates deliver reduced eye irritation and provide hair conditioning benefits zwitterionic forms are substantive on the hairs. In household products, they are especially suitable in built liquids with high electrol)de contents (i.e., containing the so-called builders )- These surfactants are also used as foaming agents in fire-fighting foam production appliances. 

Table 4 Performance Characteristics and Application of Cationic and Amphoteric Surfactants in Personal Care Products...

Primarily owing to cost or even tradition, other surfactants, snch as ethoxy-lated amines, amides, and amphoterics, have not been used generally in laundry detergents. However, these specialty surfactants have been included in a number of other household cleaners, industrial formulations, and personal-care products. 

Amphoteric surfactants can function either as anionic or cationic surfactants, depending on the pH of the system. They contain both anionic and cationic functions in the same moiecuie. More costiy to produce than ionic surfactants, amphoteric surfactants represent oniy about 3% of surfactant voiume in Europe and less than 1% in the United States. They are less irritating than other materials and are largely used in personal care products. A distinction can be made between amphoteric and zwitterionic surfactants. This distinction does not affect their analysis. For the analyst, a more important distinction is between am-photerics with a secondary or tertiary amine group and those containing a quaternary amine function. The former only have cationic properties when protonated at low pH, while the quaternary amines have cationic properties even under alkaline conditions. 

A secondary surfactants group with increasing economical importance are the A -(2-aminoethyl)-2-aminoethanol (aminoethylethanolamine)-derived amphoterics. Because the intermediate in the synthesis of these surfactants is a substituted imidazoline, they are also classified as being imidazoline-derived. Historically, these mild surfactants have been the first to offer the possibility for the production of non-eye-stinging shampoos. Still today, aminoethylethanolamine-derived amphoterics are mainly used in personal care formulations where mild properties are desired, whereas industrial applications play only a minor role. 

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. 

---