Patent Picks—Azo Quinolinium, Permanent Waving, Anionic Surfactants, Cassia Derivatives and More for Hair Care

By: Katie Anderson (Schaefer), Cosmetics & Toiletries magazine

Posted: November 9, 2011

Azo quinolinium compounds comprising a disulphide/thiol unit, compositions containing same, process for dyeing keratin fibres and device
European Patent EP2201070
Publication Date: Nov. 09, 2011
Assignee: L'Oréal

The present invention relates to thiol/disulphide azo quinolinium compounds for dyeing keratin fibres. It is a known practice to dye keratin fibres, and in particular human keratin fibres such as the hair, with dye compositions containing direct dyes. These compounds are colored or coloring molecules which have an affinity for the fibres.

It is known practice, for example, to use direct dyes of the nitrobenzene type, anthraquinone dyes, nitropyridine dyes, or dyes of the azo, xanthene, acridine, azine or triarylmethane type. These dyes are normally applied to the fibres, optionally in the presence of an oxidizing agent, if it is desired to obtain a simultaneous lightening effect on the fibres. Once the leave-on time has elapsed, the fibres are rinsed, optionally washed and dried. The colorings, which result from the use of direct dyes, are temporary or semi-permanent colorings since the nature of the interactions which bind the direct dyes to the keratin fibre, and their desorption from the surface and/or from the core of the fibre, are responsible for their weak dyeing power and their relatively poor resistance to washing and perspiration.

In order to increase the fastness of direct colourings, it is known practice to use disulphide dyes. However, some disulphide dyes have performance levels that are insufficient in particular in terms of selectivity, uptake, stability or resistance to outside attacks such as bad weather, shampooing operations, light or sweat, which brings about a change in color over time. Color change is a particularly embarrassing problem when it occurs after shampooing and/or exposure to light.

The aim of the present invention is therefore to provide disulphide or thiol dyes that do not have the drawbacks of existing direct dyes. In particular, one of the aims of the present invention is to provide dyes which make it possible to obtain natural shades which are resistant to outside attacks and which do not change color over time. This aim is achieved with the present invention, a subject of which is a process for dyeing keratin materials, in particular human keratin materials such as the hair, which comprises applying, to the keratin materials, a dye composition comprising, in a suitable cosmetic medium, at least one disulphide or thiol azo quinolinium dye and also the addition salts thereof with an organic or mineral acid, and the solvates, hydrates, tautomers and optical and geometrical isomers thereof.