S S

4.2 Hair Conditioning Agents

Quaternized polymers and silicone polymers are the two categories of conditioning agents most commonly found in the two-in-one shampoos. Very often they are used in together to take advantage of their combined hair conditioning benefits.

4.2.1 Quaternized Polymers

The quaternized polymers suitable for formulating two-in-one shampoos are polyquaternium-10 (polymer JR), polyquaternium-11 (Guafquat), polyquater-nium-7 (Merquat 550), guar hydroxypropyltrimethylammonium chloride, and polyquaternium-15. Polyquaternium-10 is a polymeric quaternium ammonium salt of hydroxethylcellulose. Polyquaternium-11 is quaternary ammonium polymer derived from diethyl sulfate and a copolymer of vinyl pyrrolidone and dimethyl aminoethylmethacrylate. Polyquaternium-7 is a polyquaternium salt from the reactions of acryamide and dimethyl diallyl ammonium chloride. Guar hydroxypropyltrimethylammonium chloride is polysaccharide quaternized with hydroxypropyltrimonium chloride. The chemical structures of these polymers are as follows.

Polyquaternium-10:

{Hydroxyehtyl Cellulose)-CH3-CHOH-CH2-CH - N+ - CHjCr nch3

Polyquaternium-7:

Polyquaternium-7:

Polyquaternium-11:

Polyquaternium-11:

Guarhydroxypropyltrimethylammonium chloride: „TI

Guarhydroxypropyltrimethylammonium chloride: „TI

(Polysaccharide galactommannan) - CHOH-CH2-CH - N+ - CH3C1"

Silicone Polymers. The silicone polymer most frequently used in two-in-one shampoos is dimethicone, while amodimethicone and dimethicone copolyol are also found occasionally. Dimethicone is an oil that is practically insoluble in water, making it a real challenge to use in shampoo formulations. The amo-dimethicone and dimethicone copolyol are modified dimethicone with organo-functional groups to increase the solubility and facilitate formulation [75]. The chemical structures of these three silicone polymers are as follows.

Dimethicone:

Amodimethicone:

Dimethicone copolyol:

4.3 Foam Boosters

Having a rich and copious foam in a shampoo is essential to consumer acceptance. Foam boosters are ingredients included in a shampoo to improve its lathering characteristics. Many of the anionic surfactants are good foamers, but the foams are mostly lacy and loose, especially in the presence of sebum or other oily materials. The function of foam boosters in two-in-one shampoos is particularly important when silicones are routinely used as conditioning agents. The two types foam booster most commonly used are discussed.

4.3.1 Fatty Acid Alkanolamides

The nonionic surfactants available as lauramide diethanolamine, cocamide diethanolamine, and cocamide monoethanolamine are fatty acid alkanolamides. These three surfactants alone at one point were believed to make up over 80% of the foam booster used for shampoos [73]. Of the three, the lauramide monoethanolamine is used more frequently because of the regulatory issue regarding the potential for V-nitrosamine formation from diethanolamines. The chemical structures of these three alkanolamides are as follows.

Lauramide diethethanolamine:

CH3 (CH2) 10CON (CH2CH2OH) 2

Cocamidediethanol amine:

RCON (CHjCHJOH) 2

Cocamidemonoethanol amine:

RCONH-CH2CH2OH

where R is a coconut acid radical.

4.3.2 Betaines and Amine Oxides

Materials also found to be effective foam boosters for shampoos include betaines and amine oxides. Both are ionic surfactants that tend to display cationic characteristics under the pH values at which shampoos are normally formulated. The important betaine and amine oxides used in shampoos as foam boosters are cocamidopropyl betaine, cocamidopropyl hydroxysultaine, lauramine oxide, dihydroxyethyl C12-15 alkoxypropylamine oxide, and cocamidopropylamine oxide (see structures that follow).

Cocamidopropyl betaine:

Cocamidopropyl hydroxysultaine:

Lauramine oxide:

Cocamine oxide:

Dihydroxyethyl C12-15 alkoxypropylamine oxide:

where R is a coconut acid radical.

The uses of amine oxides have been somewhat restrained by the concern that some of them (such as lauramine oxide and stearamine oxide) are potential precursors of N-nitrosamine [76,77].

4.4 Preservatives

Effective preservatives for shampoos are essential to protect against microbial growth that could cause spoilage of the product, or more importantly, pose a health hazard to consumers. For two-in-one shampoos, the choice of a proper preservative system is even more critical because xof the incorporation of conditioning agents, such as silicone or hydrolyzed proteins, that are believed to support the growth and propagation of microorganisms, in particular the gram-negative family of Pseudomonas [78-80]. Formaldehyde used to be popular but has been largely replaced because of toxicological concerns. Other compounds that are found to be effective preservatives and are frequently used in shampoos [76,81] |

are methyl and propyl parahydroxy benzoates alone or in combination with imi-dazolidinyl urea, methylisothiazolinone, methyloldiethylhydantoin (DMDMH), ^

methychloroisothiazolinone, and N-(3-chloroallyl)-hexaminium chloride (quater- a nium 15). The selection of a suitable preservative, however, must be customized J

t for a specific shampoo formulation to achieve the proper trade-off between efficacy, safety, and compatibility [82-86].

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