Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2001-01-25
2003-04-08
Dawson, Robert (Department: 1712)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C556S444000, C556S445000, C568S673000, C528S031000, C528S015000, C528S025000, C525S474000, C525S477000, C524S081000, C524S261000, C524S027000, C524S588000, C514S553000, C514S725000, C523S105000
Reexamination Certificate
active
06544532
ABSTRACT:
The invention relates to a composition comprising an active principle, unstable in oxidizing medium, which is stabilized, to the use of the said composition, in particular in the cosmetics field, and to a process for the treatment of human skin using such a composition.
The invention also relates to the use of a crosslinked organopolysiloxane elastomer comprising an oxyalkylene group, for the purpose of stabilizing an active principle which is unstable in oxidizing medium.
It is known to introduce active principles into cosmetic and/or dermatological compositions for the purpose of contributing specific treatments to the skin and/or hair, for example for cleansing the skin, for combating drying, ageing or pigmentation of the skin, for treating acne or certain skin disorders (eczema, psoriasis), for combating excess weight, for promoting restructuring of the skin or its cell replacement, or for treating seborrhoea of the hair.
For example, attempts have been made for a long time to formulate ascorbic acid (or vitamin C) and retinol (vitamin A) in the cosmetic and dermatological fields, in various pharmaceutical dosage forms, because of their numerous beneficial properties. In particular, ascorbic acid stimulates the synthesis of connective tissue and in particular of collagen, reinforces the defences of cutaneous tissue against external attacks, such as ultraviolet radiation and pollution, compensates for vitamin E deficiency in the skin, depigments the skin and has a role in combating free radicals. Due to its properties, ascorbic acid is effective in cleansing the skin and also in combating signs of ageing of the skin, for example in improving the radiance of the complexion and softening fine lines and wrinkles of the skin.
Furthermore, the effects of retinol on cell differentiation make it possible to envisage, inter alia, its use in effectively combating the appearance of wrinkles and fine lines, in effectively combating skin dryness or in effectively combating roughness and/or stiffness of the skin. Repeated application of cosmetic compositions comprising retinol makes it possible, inter alia, to erase wrinkles, to smooth the skin or to repair small tears in the epidermis.
Unfortunately, these active principles are unstable in oxidizing medium and therefore very sensitive to certain environmental parameters, such as, for example, light, oxygen and water. The result of this is therefore a rapid decomposition of these active principles when they are in contact, in particular, with one of these parameters, which runs counter to the desired effectiveness.
In the state of the art, this problem has been dealt with in various ways. Thus, to decrease or slow down the decomposition of ascorbic acid in solution, the document U.S. Pat. No. 5,140,043 recommends stabilizing it by introducing it into aqueous/alcoholic solutions formed of at least 80% water and having a pH of less than 3.5. Due to the high acidity of these solutions, their use in the cosmetics field is difficult to envisage. This is because repeated application of these solutions can disturb the balance of the skin and in particular irritate, indeed even give a burning feeling to, the skin.
Other methods of stabilizing ascorbic acid have been envisaged, in particular by coating (technique disclosed in the document FR-A-1,600,826) or by granulating ascorbic acid (technique illustrated in the document JP-A-53-127819, for the farm produce industry). However, these techniques are, on the one hand, expensive and can, on the other hand, detrimentally affect ascorbic acid, for example during heating, and/or result in compositions which are of little use cosmetically, as is the case with granules.
In addition, the document U.S. Pat. No. 5,853,741 discloses the stabilization of ascorbic acid by non-emulsifying silicone elastomers known under the trade references Gransils from the company Grand Industrie. The disadvantage of these products is that they introduce an oily and greasy effect, without a fresh effect, which does not allow them to be used or only allows them to be used with difficulty in a hot and humid environment and/or by users with greasy skin. Furthermore, these polymers are completely water-repellant and difficult to incorporate in an aqueous phase. Due to their high incompatibility with water and in particular with sweat, the latter is not absorbed by these polymers and even has a tendency to “form beads” at the surface of the skin when the latter perspires.
The stabilization of retinol has also formed the subject of much research. Thus, the document WO-A-93/00085 discloses W/O emulsions comprising retinol and a stabilizing system composed of a chelating agent and an antioxidant. The document EP-A-209,509 has also made known the use of certain polyamino compounds as antioxidants. However, none of the compounds of the prior art makes it possible to obtain satisfactory stabilization of retinol.
The need therefore remains for a composition, which can be used in particular in the cosmetics field, in which an active principle which is unstable in oxidizing medium is stabilized, which is comfortable during application and which does not cause any irritation of the skin after application.
The Applicant Company has now found a composition which overcomes the disadvantages of the prior art.
A subject-matter of the present invention is a composition comprising, in a physiologically acceptable medium, at least one active principle which is unstable in oxidizing medium and an oily phase comprising particles of a crosslinked solid organopolysiloxane elastomer comprising at least one oxyalkylene group, the said composition not being an O/W/O or W/O/W triple emulsion.
By virtue of the presence of the particles of organopolysiloxane elastomer comprising an oxyalkylene group in the composition of the invention, active principles which are unstable in oxidizing medium, such as ascorbic acid and retinol, exhibit better stability and therefore better effectiveness than in a composition not comprising them.
The invention also relates to the use of particles of a crosslinked solid organopolysiloxane elastomer comprising at least one oxyalkylene group for the stabilization of an active principle which is unstable in oxidizing medium.
The term “physiologically acceptable medium” is understood to mean, in the composition of the invention, a non-toxic medium capable of being applied to the skin (including the inside of the eyelids) or the lips of human beings.
The term “solid elastomer” is understood to mean a flexible and deformable material having viscoelastic properties and in particular the consistency of a sponge or of a flexible sphere. Its modulus of elasticity is such that this material is resistant to deformation and has a limited ability to expand and to contract. This material is capable of returning to its original shape after it has been stretched. This elastomer is formed of polymeric chains of high molecular weight, the mobility of which is limited by a uniform network of crosslinking points.
The organopolysiloxanes of the composition of the invention comprise one or more oxyalkylene and in particular oxyethylene (OE) groups, for example from 1 to 40 oxyalkylene units, preferably from 1 to 20 and better still from 10 to 20 oxyalkylene units, which can form polyoxyalkylene and in particular polyoxyethylene chains. These groups can be pendant, at the chain end or intended to connect two parts of the silicone structure. The silicon atoms carrying these groups advantageously number from approximately 1 to 10 and better still from 1 to 6.
Although the invention relates more especially to organopolysiloxanes comprising oxyethylene groups(s) (namely, groups only comprising oxyethylene groups as oxyalkylene groups), it can also relate to organopolysiloxanes comprising oxypropylene group(s), that is to say only comprising oxypropylene groups as oxyalkylene groups. The organopolysiloxanes can also comprise both one or more oxyethylene (OE) group(s), for example 1 to 20, and one or more oxypropylene (OP) group(s), for example 0 to 20;
Jager-Lezer Nathalie
Lorant Raluca
Dawson Robert
L'Oreal
Peng Kuo-Liang
LandOfFree
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