Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Nitrogen containing other than solely as a nitrogen in an...
Reexamination Certificate
1999-09-03
2001-10-16
Cintins, Marianne M. (Department: 1614)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Nitrogen containing other than solely as a nitrogen in an...
C514S238200, C514S727000
Reexamination Certificate
active
06303656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition which stably comprises urea and which is intended, in particular, for use in the fields of cosmetics and/or dermatology. The invention also relates to a use of this composition for the care, the treatment, the protection and/or hydration of human skin, of mucous membranes and/or keratin fibers, and for the treatment of dry skin.
2. Discussion of the Background
In cosmetic or dermatological compositions, moisturizers, i.e., hygroscopic substances which allow the water content in the skin to be retained and thus the suppleness and the touch of the skin to be affected advantageously, are widely used. Such moisturizers are also useful for hydrating the skin and, in particular for treating dry skin.
Among the many moisturizers, urea is particularly important. Urea is a component of the NMF (natural moisturizer factor) and has a softening effect on the corneal layers of the skin.
However, the disadvantage of urea is that it is generally not stable in an aqueous environment, where it degrades into carbon dioxide and ammonia. This leads to a rise in pH of the composition containing it and the release of an odor, which make the use of such compositions very unsatisfactory.
It has therefore been attempted for a long time to formulate urea in cosmetically acceptable compositions in a form which is stable over at least several months. Thus, document JP51048441 describes the stabilization of urea in a glycine/sodium hydroxide buffer at a pH of 6 to 9. However, the use of such a buffer has the disadvantage of making the composition containing it sticky when applied to the skin.
Accordingly, there remains therefore the need for stable urea-based compositions which have satisfactory cosmetic properties.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a stable moisturizing composition contains urea.
It is another object of the present invention to provide a moisturizing composition which contains urea and water.
It is another object of the present invention to provide a method of moisturizing skin with a composition containing urea.
In a surprising and unexpected manner, the Inventor has discovered that it is possible to formulate compositions which comprise urea and which are stable over time and pleasant to use, by using an N-substituted aminosulfonic acid.
Accordingly, the objects of the invention, and others, may be accomplished with a composition comprising urea and at least one N-substituted aminosulfonic acid.
The objects of the invention may also be accomplished with a method of treating body skin and/or facial skin, comprising applying the composition to body skin and/or facial skin.
The objects of the invention may also be accomplished with a method of treating dry skin, comprising applying the composition to dry skin.
The objects of the invention may also be accomplished with a method of moisturizing skin comprising applying a composition comprising urea and at least one N-substituted aminosulfonic acid to dry skin.
The objects of the invention may also be accomplished with a method of preparing the inventive composition comprising combining urea and at least one N-substituted aminosulfonic acid.
An advantage of the composition according to the invention is that it can comprise stable urea after storage at 45° C. over 2 months. Another advantage of the composition according to the invention is that it is particularly well tolerated by the skin and the keratin fibers and that it is extremely suitable for a topical use, in particular a cosmetic and/or dermatological use.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
The N-substituted aminosulfonic acid of the inventive composition generally constitutes a buffer with a pKa at approximately 20° C. ranging from 6 to 7.8, preferably 6.3 to 7.6. These ranges include all specific pHs and subranges therebetween, such as 6.1, 6.2, 6.4, 6.5, 6.8, 7.0, 7.2 and 7.5.
The N-substituted aminosulfonic acid can be chosen, in a preferred embodiment, from the amino derivatives of alkylsulfonic acids, where the alkyl group preferably has 1 to 6 carbon atoms, more preferably 2 to 3 carbon atoms. Amino derivatives of ethanesulfonic acid and propanesulfonic acid are particularly preferred.
Specific examples of N-substituted aminosulfonic acids include are N,N-bis[2-hydroxyethyl]-2-aminoethanesulfonic acid (pKa=7.17), N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (pKa=7.55), 3-[N-morpholino]propanesulfonic acid (pKa=7.15), piperazine-N,N′-bis[2-ethanesulfonic] acid (pKa=6.82), 3-[N-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid (pKa=7.6), 2-[N-morpholino]ethanesulfonic acid (pKa=6.15), N-(2-acetamido)-2-aminoethanesulfonic acid (pKa=6.88), N-tris(hydroxymethyl)methyl -2-aminoethanesulfonic acid (pKa=7.5). A mixture of these acids may also be used. The pKa values given hereinabove are those determined at approximately 20° C. at a concentration of 0.1 M.
The quantity of N-substituted aminosulfonic acid(s) is preferably high enough to achieve the intended result, i.e., stabilization of the urea in the composition. This quantity may range, for example, from 0.1 to 20% by weight, preferably 0.5 to 15% by weight, based on the total weight of the composition. These ranges include all specific values and subranges therebetween, such as 0.2, 1, 2, 5, 8, 10, 12 and 18% by weight.
The quantity of urea in the composition may vary within a wide range. For a cosmetic and/or dermatological application, the urea is preferably present in a quantity which generally ranges from 0.1 to 20% by weight, preferably 0.5 to 15% by weight, based on the total weight of the composition. These ranges include all specific valves and subranges therebetween, such as 0.2, 1, 2, 5, 8, 10, 12 and 18% by weight.
In a preferred embodiment, the inventive composition contains water. The amount of water in the composition may vary widely. For example, the composition may contain 0.5 to 99.5% water by weight, based on the total weight of the composition. This range includes all specific values and subranges therebetween, such as 1, 2, 5, 10, 20, 25, 30, 40, 50, 60, 70, 80, 90, 95, 98, and 99% by weight, based on the total weight of the composition.
The composition preferably has a pH of approximately 7 to ensure better stability of the urea. By a pH of approximately 7 there is understood a pH which ranges from 6.5 to 7.5. The pH of the composition preferably ranges from 6.8 to 7.2. The pH may be adjusted by any suitable means which is known and, depending on the circumstances, by an inorganic acid or organic acid such as hydrochloric acid or citric acid, or an inorganic or organic base, such as sodium hydroxide and triethanolamine. Depending on the pH, the N-substituted aminosulfonic acid can be in partial salt form.
It is known that urea undergoes less degradation when the composition comprising it has a pH of 7. However, even at this pH, an unavoidable degradation takes place over time. In the composition according to the invention, the degradation of urea is avoided owing to the presence of the N-substituted aminosulfonic acid.
The composition of the invention may be, in a preferred embodiment, a cosmetic or dermatological composition, and thus comprises a physiologically acceptable carrier, i.e., one that is compatible with the skin, the mucous membranes, including lips and/or the keratin fibers (hair, eyelashes). This composition may be present in any pharmaceutical form for topical use which are normally employed, for example, in the form of an aqueous or oily solution, an aqueous or oily suspension or a dispersion of the lotion or serum type, or emulsions obtained by dispersing a fatty phase in an aqueous phase (O/W) or the other way round
Cintins Marianne M.
Kim Vickie
L'Oreal
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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