Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
1997-06-30
2002-10-22
Russell, Jeffrey E. (Department: 1653)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S056000, C424S059000, C424S061000, C424S070110, C424S070170, C514S772300, C514S844000, C514S880000
Reexamination Certificate
active
06468549
ABSTRACT:
The invention relates to a cosmetic or dermatological composition containing an acidic aqueous medium and at least one crosslinked poly(2-acrylamido-2-methylpropanesulphonic acid) polymer which is neutralized to at least 90%.
The invention also relates to the use of this composition in the cosmetic treatment of keratinous substances, in particular of the skin, hair and mucous membranes, in particular to a non-therapeutic process for depigmentation of the skin.
At different periods in their life, some people witness the appearance on the skin, and more particularly on the hands, of darker or more highly colored blemishes which give the skin a heterogeneous appearance. These blemishes are generally due to significant production of melanin in the epidermis or the dermis of the skin.
These blemishes can be related to a number of phenomena and more especially to aging. In some cases, these blemishes can become cancerous. It is consequently increasingly sought to decrease, indeed remove, these blemishes. Use is made of organic active principles, such as kojic acid, caffeic acid or salicylic acid and its derivatives, in treating these blemishes.
Damaged hair can also be treated with compositions based on acidic active principles, in order to tone it up, to restore its vigor and to strengthen the keratinous fibers.
Compositions conventionally used in the cosmetic or dermatological fields are water-in-oil (W/O) emulsions, oil-in-water (O/W) emulsions or aqueous gels in which it is often difficult, indeed even impossible, to incorporate organic acid active principles, such as kojic acid, caffeic acid or salicylic acid and its derivatives.
These acidic active principles generally have a tendency to recrystallize or to degrade. This results in a more or less significant loss in effectiveness of these compositions, according to the degree of recrystallization or degradation, which goes against the desired objective. In addition, this recrystallization or degradation can modify the overall stability of these compositions as well as their appearance, which can dissuade the user from employing these specific treatment compositions.
The use is known, in dissolving some of these active principles, of W/O or O/W emulsions in which the aqueous phase exhibits an acidic pH. For these emulsions to be stable (non separation of the aqueous and oily phases), it is necessary to use emulsifiers (or surfactants). Unfortunately, these surfactants are often irritating to the skin. In addition, these emulsions often lack freshness on application, which can interfere with their uses during warm periods of the year or in hot countries. An aqueous gel is much more appreciated under these conditions of use. However, its very large amount of water does not allow active principles exhibiting a degree of lipophilic nature to be introduced therein. Moreover, the stability of these gels is mediocre.
The need thus remains for a stable composition having the appearance of a gel, which can be used in particular in the cosmetic or dermatological fields, Which makes possible sufficient solubilization of the acidic a-active principles generally used in these fields for the purpose of maximum effectiveness.
With this objective, the use has already been envisaged, in European Patent Application EP-A-680,748, of acidic compositions in the gel form containing crosslinked cationic copolymers or homopolymers which are substantially soluble in aqueous media, and in particular in water, and which are composed of units resulting from the reaction between (i) a cationic monomer containing ethylenic unsaturation or a cationic mixture of monomers containing ethylenic unsaturation and (ii) a crosslinking agent containing ethylenic polyunsaturation. These gelling agents make it possible to stabilize and to dissolve these acidic active principles in compositions containing aqueous media rich in organic solvent.
The use has also already been envisaged, in European Patent Application EP-A-642,781, as gelling and stabilizing agents, of a crosslinked anionic copolymer which is substantially soluble in water and which is composed of units deriving from the reaction between (i) acrylamide, (ii) 2-acrylamido-2-methylpropanesulphonic acid and (iii) at least one compound containing olefinic polyunsaturation (crosslinking agent) in acidic oil-in-water emulsions containing acidic organic active principles.
These two polymer families exhibit the disadvantage, however, of not allowing the production of spontaneously transparent gels, which is harmful to the aesthetic appearance of the final product. Moreover, in the presence of certain acidic organic active principles, such as glycolic acid, these polymers lose their thickening or gelling power and do not allow formulations of high and stable viscosity to be obtained.
The inventors have discovered, surprisingly, a new family of thickening or gelling polymers allowing acidic cosmetic and dermatological formulations to be obtained in the form of transparent and homogeneous gels making it possible to attain high viscosities which are stable over time at room temperature or at higher temperatures.
Moreover, these polymers make it possible to dissolve and stabilize acidic organicactive principles in a cosmetic or dermatological composition containing an acidic aqueous medium at pH values of less than or equal to 5.
In particular, they make it possible to dissolve and to stabilize organic acid active principles in a cosmetic or dermatological composition containing an acidic aqueous medium rich in organic solvent. Compositions containing an aqueous medium rich in organic solvent is understood to mean a composition containing at least 45% by weight of organic solvent with respect to the total weight of the composition.
Finally, these polymers make it possible to produce gels which are transparent, non-runny, non-stringy, soft and smooth on application.
Thus, a subject of the invention is a cosmetic or dermatological composition containing a cosmetically acceptable acidic aqueous medium and at least one crosslinked poly(2-acrylamido-2-methyl-propanesulphonic acid) polymer neutralized to at least 90%.
The composition of the invention has a certain consistency or behavior; it is not stringy, i.e., it does not form strings when taken with the finger. It is more preferably provided in the form of a gel.
The pH of the aqueous medium is advantageously less than or equal to 5 and in practice preferably in the range from 1 to 4. Above the pH value of 6, the formulation no longer exhibits difficulties.
The crosslinked and virtually or completely neutralized poly(2-acrylamido-2-methylpropanesulphonic acid) polymers in accordance with the invention are water-soluble or swellable in water. They are in general characterized in that they comprise, distributed randomly:
(a) from 90 to 99.9% by weight of units of the following formula (1):
in which X
+
denotes a cation or a mixture of cations, it being possible for at most 10 mol % of the cations X
+
to be protons H
+
; and
(b) from 0.01 to 10% by weight of crosslinking units originating from at least one monomer having at least two olefinic double bonds; the proportions by weight being defined with respect to the total weight of the polymer.
The polymers of the invention preferentially contain a number of units of formula (1) in an amount which is sufficiently high to obtain a hydrodynamic volume of the polymer, in solution in water, having a radius ranging from 10 to 500 nm, with a homogeneous and unimodal distribution.
The more particularly preferred polymers according to the invention comprise from 98 to 99.5% by weight of units of formula (1) and from 0.2 to 2% by weight of crosslinking units.
X
+
represents a cation or a mixture of cations selected in particular from a proton, an alkali metal cation, a cation equivalent to that of an alkaline-earth metal or the ammonium ion. More particularly, 90 to 100 mol % of the cations are NH
4
+
cations and 0 to 10 mol % are protons (H
+
).
The crosslinking monomers having at least two olefini
Dupuis Christine
Hansenne Isabelle
Lorant Raluca
Maubru Mirelle
Sebillote-Arnaud Laurence
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
L'Oreal
Russell Jeffrey E.
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