Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1994-09-19
1995-09-19
Bell, Mark L.
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106311, 106494, 106498, 106502, 106504, 8405, 8406, 8414, 8416, 8423, 424 707, 424 709, A61K 713
Patent
active
054512549
DESCRIPTION:
BRIEF SUMMARY
The subject of the present invention is a fine dispersion of melanin pigments, the process for its preparation and its use in cosmetics.
Melanin pigments are pigments which are known per se. More particularly, they are pigments which are at the origin of the coloration of hair, skin or hairs of human or animal origin. They may also be prepared by synthesis, in particular by oxidation of indole derivatives such as, more particularly, 5,6-dihydroxyindole.
Melanin pigments having a small particle size are particularly valuable insofar as they have a good covering power, which makes it possible for them to be used in lower concentrations compared with pigments having a larger particle size with a view to obtaining the same coloration.
The value of pigments having a small particle size also resides in their cosmetic characteristics, especially regarding the feel. The compositions based on pigments of small particle size have, in effect, a softer feel.
The known melanin pigments generally have a particle size between 100 and 150 microns and must be ground, for example in a mortar, by a grinder, by micronization or by other grinding techniques, in order to obtain particles having a particle size between 15 and 25 microns.
In order to obtain a smaller particle size, it is again necessary to grind these pigments, which is generally carried out in aqueous medium. However, a reagglomeration of the various particles is observed following this grinding and even after drying of the pigment.
The cosmetic compositions containing pigments presented in this manner often have poor cosmetic characteristics, insofar as the particles are relatively large and irregular. Due to the agglomeration, the compositions are visually appealing, often poorly stable and cover poorly.
The Applicant has observed that by carrying out the grinding of the melanin pigment in a specific medium, it was possible to obtain a fine dispersion of a melanin pigment, which is stable with time and does not reagglomerate. Moreover, the dispersion thus obtained has the advantage of being able to be used as it is in cosmetic compositions without it being necessary to isolate, dry and resuspend the pigment.
Moreover, these dispersions have improved antioxidant properties.
A subject of the invention is thus a stable dispersion of melanin pigments, having a very fine particle size, of low dispersity in a medium as defined below.
Another subject of the invention consists of the process for the preparation of such a dispersion.
A subject of the invention is also the use of this dispersion in the preparation of cosmetic compositions and the cosmetic compositions using this dispersion.
Other subjects of the invention will become apparent on reading the description and the examples which follow.
The process for the preparation of the dispersions of melanin pigments in accordance with the invention consists in grinding a melanin pigment in a liquid medium consisting of: carbon atoms; or a C.sub.2 -C.sub.6 polyol, an ester of a C.sub.1 -C.sub.6 aliphatic acid or an aromatic acid and a C.sub.8 -C.sub.22 fatty alcohol, an ester of a C.sub.8 -C.sub.22 fatty acid and a C.sub.8 -C.sub.22 fatty alcohol, an ester of a polyacid and a C.sub.6 -C.sub.22 alcohol, a diester of a hydroxylated fatty acid; and an emulsifying agent.
The melanin pigment is present in the liquid phase used during the grinding step at a concentration generally between 5 and 50% and preferably between 15 and 35%.
The process is implemented at a temperature between room temperature and 110.degree. C. The grinding means preferably consist of a grinder containing beads. Zirconium oxide beads, glass beads or sand are more particularly used.
The duration of the grinding depends on the nature of the pigment, the size of the melanin pigment particles, the nature of the liquid medium and the grinding parameters. The duration is generally between 15 minutes and 24 hours and more preferably between 30 minutes and 9 hours.
A grinder containing beads sold under the name DYNOMILL, type KDL Special, for which the bead
REFERENCES:
patent: 5205837 (1993-04-01), Andrean et al.
Andrean Herve
Candau Didier
Mellul Myrian
Papantoniou Christos
Piot Bertrand
"L'Oreal"
Bell Mark L.
Hertzog Scott L.
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