Hair dyes – Ypatent

Books: The Science of Hair Care, published in the series “Dermatology” 1986

Companies: BASF SE Aveda (hair care products)

Natural hair dyes such as henna and mineral salts are still used, but hair dyeing increasingly involves careful chemical manipulation of the chemistry of hair fibers through bleacing or enyhancement of natural colors.

Hair dyeing compositions are usually sold in the form of aqueous solutions or emulsions, which are as concentrated as possible and contain, in addition to the actual dyes, for example fatty acid alcohols and/or other oily componetns, emulsifers as well as surface active agents and optionally alcohols.

Classification of Hair Dyes

Temporary Hair dyes (class 1):

These types of dyes generally do not function non-oxidatively. The molecules of the dye arrange theselves on the keratin surface or they penetrate the hair only for a marginal distance. They are too large to completely permeate the hair. The dye layer can thus be removed by washing.

In general, acidic dyes with only low affinity for hair and which ratehr deposit on the hair surface are used in temperorary hair dyeing compositiosn (Barg (US 2011/0192416)

Semi-permanent hair dyes (class 2): (“colorations”)

Semi-permanent hair dyes can penetrate into the hair, because they contain smaller dye molecules than temperory hair colorations. They generaly have to be renewed after 8-10 washes.

Dyes in colorations are generally either positively charged and thus bind to negatively charged surface gorups of the hair, or they are small molecules that can penetrate the cuticula. (Barg (US 2011/0192416)

–Cationic dyeing agents: include triphenylmethan dyes such as for example Basic Blue 26, Basic violet 2 (b) aromatic systems substituted with quaternary nitrogen groups sucha s basic yello/red/blue/brown as well as (c) direct dyeing agetns cotnainign a heterocycle having at least one quaternary nitrogen atom such as basic yellow 87, basic organe 31, basic red 51. A particularly preferred cationic direct dyeing agent is distrbuted as Arianors (Barg (US 2011/0192416)

Permanent hair dyes (claim3 ): (“self-oxidizing dyes”)

Permanent hair dyes may not be washed out. These dyes contain a “eveloper” generally an oxidizing chemical and on the other hand an alkaline component as part of the dyeing paste, usually ammonia or ammonia subsitute such as mono-ethanolamine. These compounds render the ahir fiber cuticula permeable for the colorless dye precursors, facilitating the development of the final dyes inside the hair and at the same time bring out a lightening through the influence of the peroxide. As soon as the dyeing paste containing g the alkline ingredient is brought into contact with the devleopers, hydrogen peroxide is deprotonated, diffuses through the cuticula and reaches the interior fo the hair, where the melanin is found. The alkaline peroxide destrosy the melanin and oxidizes the initially collorless precursors of the dye yielding the final dye molecuels, which are too large to exit the hair. Permanent hair dydes have been implicated in the cause of cancer of the bladder (Barg (US 2011/0192416)

Natural Dyes

Natural dyes include henna red, henna neutral, henna black, chamomile blossom, sandalwood, black tea, black alder tree bark, sage, logwood, madder root, catechu, sedre and alkanna root. (Barg (US 2011/0192416)

Radico (sells natural hair dyes; discloses that some of the ingredients even promote hair growth)

Patented Products

Hair Dyes with Hydrophobins:

Hydrophobins are a class of small, cystein rich proteins of about 100-150 amino acids which occur in anture only in flamentous fungi. They are amphiphilic and may form a water insoluble layer on the surface of an object. Their natural functions comprse the coating of fungal spores to prevetn them from sticking to each other, the coating of air hyphae to reduce the surface tension of water thus making the uptake of water easier and possibly transmission of signals between a fungus and its environment. (Barg (US 2011/0192416)

(Barg (US 2011/0192416) discloses the use of hydrophobin for the non-permanent dyeing of keratin, particularly of hair. Berg found that the intensity of non-permanent dyeing against washing out is increased upon use of hydrophbins.

Gradual Coloring of Hair:

Combe (just for men dye) US 4,104,021 (process for dyeing hair in which the depth of shade is gradually increased in successive treatments).