Semi-permanent hair dyes

The nitro group is commonly encountered as a substituent in dyes and pigments of most chemical classes, but it acts as the essential chromo-phore in only a few dyes. Nitro dyes are a small group of dyes of some importance as disperse dyes for polyester and as semi-permanent hair dyes. Picric acid, 139, was historically the first nitro dye, although it was... 

Figure 2.14 Correlation between calculated and experimental series of nitroarylamine semi-permanent hair dyes.

The semi-permanent hair-dye products, available to professional hairdressers or directly to the consumer for home use, are often products to be applied to the wet hair after shampooing and rinsed out carefully after waiting for 10-30 min. They are available in all kinds of presentations lotions, gels, creams, foaming preparations, etc. 

Uses Weak cationic surfactant for semi-permanent hair color systems Lowenol Copolymer 725 [Lowenstein Dyes Cosmetics]... 

Hair dyes are of three kinds temporary, semi-permanent, and permanent. The first kind are easily washed out of the hair, the second will survive several washings but eventually fade, and the third are locked fast within the hair shaft and disappear only as the hair grows... 

Semi-permanent dyes are smaller molecules and these can pass through the outer layer of the hair, known as the cuticle, and move into the inner cortex, there to remain until they gradually leach out again and are washed away. A combination of dyes is generally required to produce the desired shade and those commonly used are listed in the Glossary. 

Colorants for other purposes, such as hair dyes, are not so strictly regulated. The ones used in semi-permanent dyes are 2-nitro-i,4-diaminobenzene, (orange/red), 2-amino-4-nitrophenol (yellow), 1,4-diaminoanthraquinone (violet), and 1,4,5,8-tetra-aminoanthaquinone (blue), and a combination of these will produce the desired shade. 

Hair dyes. Primary intermediates and couplers used in semi-permanent and permanent hair-colouring procedures. Allergies were described to ... 

Uses dyestuff used to dye furs brown and reddish-brown dye intermediate in semi-permanent and permanent hair coloring products (produces brown and red shades on the hair) in different hair-dyeing preparations. 2-NITRO-P-PHENYLENEDIAMINE A... 

Semi-permanent dyes are usually applied to natural, unbleached hair after shampooing. The formulations use mixtures of dyes, blended to the desired shade. It is common to use several dyes of similar colour but with different molecular sizes to provide even coloration. Larger dye molecules tend to be retained by the more damaged tip of the hair, but do not penetrate so readily into the roots, while smaller molecules penetrate the entire hair fibre but wash out of the more porous tip. 

The ROK Ministry of Health and Welfare (MOHW) has published a positive list of active ingredients authorized in oxidation dyes, semi-permanent dyes and bleaching products (MOHW Decree 1995/68). It is fairly similar to the Japanese list for oxidation dyes, but 19 hair dyes and 3 bleaching active ingredients have been added by modification of the Decree on 23 August 2004. 

According to how long-lasting they are, hair-dye prodncts may be classified into three gronps temporary, semi-permanent, and permanent hair colonrs. The two formers are based into a non-oxidation mechanism, whereas the last is based mainly on oxidation reactions although other chemicals which impart progressive permanent hair colonr do not follow this mechanism. They are discnssed below. 

Apart from the paper pubhshed by Scarpi et al. (1998) which deals with semi-permanent triphenylmethane, azo and anthraquinone dyes, all the others deal mainly with oxidative hair dyes. This is because oxidative hair dyes seem to be the most interesting topic at the moment. Also, as many triphenylmethane, azo and anthraquinone dyes are used as cosmetic colorants, the papers published on this matter and reviewed in Section 4.2 will be useful to determine these substances in hair-dye products. 

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