Cosmetic composition of a water-free thixotropic nail polish with a nail hardener, use and method of implementation

Description

FIELD OF THE INVENTION

[0001] The invention relates to the field of cosmetic compositions for nails, more particularly to cosmetic compositions intended to strengthen and harden nails, as well as the use of a nail hardening agent, and the associated method. STATE OF THE ART

[0002] It is well known that nails, which are made of keratin, are sometimes weakened, brittle, split or cracked. In addition to the deterioration of the aesthetic appearance of these nails, this results in significant inconvenience for the person in their daily life, mainly when these defects concern the nails of the hands: catching in textiles, clothing, or worsening of cracks during each grip.

[0003] Until now, various solutions have been found to this problem, but these are either imperfect or generate other disadvantages. These include: The use of formaldehyde, in proportions of up to 5% by weight in cosmetic compositions, has been known for a long time. However, this compound is now very closely monitored due to its toxic effects on the body, with proven carcinogenic effects. This molecule is also a powerful allergen.

[0004] The use of glyoxal, a dialdehyde, was described in patent GB 2,196,978 as early as 1986. However, this product is harmful by inhalation, irritates the skin and eyes, and can cause skin sensitization.

[0005] Citral (in the form of a mixture of its two isomers geranial and neral), described in patent EP 1 408 917, is certainly also recognized for its action as a nail hardener, but can cause sensitization through contact with the skin and is classified among the detected allergens (according to the list of allergenic substances cited in the 7th amendment of European directive 76 / 768 / EEC). It is therefore used less and less in cosmetics. In addition, these molecules contain a double bond, which makes citral sensitive to UV, and therefore prone to yellowing.

[0006] In patent EP 2 413 887 it was proposed to use, as a hardening agent for nails, mono-aldehyde of formula (I): R-CHO, R being a linear C 5 -C 12 alkyl radical, or a C 5 -C 12 alkenyl with a double bond not conjugated with the aldehyde group -CHO, not belonging to the list of allergenic substances cited in the 7th amendment of European directive 76 / 768 / EEC. However, these aldehydes, such as hexanal, have a strong odor, especially in varnish in liquid form, which limits their use and their concentration in said cosmetic compositions for nails.

[0007] This list of disadvantages relating to aldehydes used in cosmetic compositions for nails has prompted those skilled in the art to seek other types of non-aldehyde molecules to harden and strengthen the strength of human nails.

[0008] Among other nail hardeners, US4,919,920 describes the incorporation of iodine or fluorine in the form of ions into an aqueous cosmetic composition without organic solvent, possibly in the presence of a polyol such as glycerin. Such use is not suitable for nail polishes that include a significant phase of organic solvents. Iodine can also cause allergies in some users. EP0755676 describes the use of monocarboxylic acids as a hardening agent.

[0009] There is therefore a real need to find a nail hardening compound that overcomes the aforementioned drawbacks and that can be used in various cosmetic compositions, such as varnish compositions, varnish undercoats, or peelable varnishes for example. AIMS OF THE INVENTION

[0010] A first aim of the invention is therefore to provide a nail polish composition incorporating a compound intended to strengthen the structure of the keratin of the nail by hardening it, not having the drawbacks mentioned above. Another aim of the invention is to provide a compound which is not sensitive to aging, and in particular to yellowing, at the concentrations at which it is effective as a nail hardener, in a cosmetic varnish composition.

[0011] Another object of the invention is to provide a nail hardening compound which does not have an unpleasant odor for the user, at the concentrations at which it is effective as a nail hardener, in a cosmetic varnish composition.

[0012] Another aim of the invention is to provide a thixotropic nail polish composition, i.e. fluid when applied but having a higher viscosity at rest, incorporating a nail hardening compound which does not modify the thixotropic properties of said polish. DESCRIPTION OF THE INVENTION

[0013] To this end, the present invention provides a non-aqueous thixotropic cosmetic nail polish composition containing a film-forming agent comprising nitrocellulose, at least one organic solvent, and a thixotropic agent, characterized in that it contains sorbic acid or one of its salts at a concentration of less than 1% by weight and in that the thixotropic agent, present at a concentration of between 0.1 and 4% by weight of the composition, is a clay modified with a quaternary amine, neutralized by a strong acid at a concentration of less than 0.1% by weight of the composition.

[0014] The varnish composition is of the solvent type, that is to say based mainly (containing more than 50% by weight) on organic solvents. By non-aqueous, or essentially non-aqueous, is meant here a varnish composition whose water content does not exceed 3% by weight, preferably less than or equal to 2% by weight, and more preferably less than or equal to 1%.

[0015] Sorbic acid is not a toxic or allergenic product: in fact, this molecule is frequently used as a preservative (E200) in the food industry, as an antimicrobial agent to inactivate or inhibit the growth of mold and bacteria in food compositions containing a significant aqueous fraction.

[0016] Furthermore, this molecule, despite the presence of two double bonds, does not generate yellowing over time or an unpleasant odor for the user at concentrations less than or equal to 1% by weight. Thus, sorbic acid can be used in a cosmetic composition for nails. In addition, sorbic acid and its salts have the advantage of not presenting any danger to health (sensitization, allergy, toxicity, or carcinogenic effect, unlike certain active ingredients of the prior art).

[0017] Advantageously, said cosmetic composition contains a concentration of sorbic acid or one of its salts less than or equal to 0.5% by weight. More advantageously, the cosmetic composition contains a concentration of sorbic acid or one of its salts of between 0.01% and 0.5% by weight, more preferably between 0.05% and 0.1% by weight.

[0018] The thixotropic agent of the varnish composition according to the invention is a clay modified with a quaternary amine, the clay preferably being chosen from bentonite or hectorite. However, these thixotropic agents comprising quaternary amine grafts are particularly sensitive to the presence of acids, thereby modifying their thixotropic behavior. However, it has been found that, even in the form of free acid, sorbic acid has no adverse effect on the stability of the varnish composition, nor on its thixotropic character.

[0019] The concentration of thixotropic agent is advantageously between 0.5 and 3% by weight, preferably between 1 and 2% by weight of the composition.

[0020] The strong acid neutralizing the clay modified with a quaternary amine is advantageously phosphoric acid, preferably at a concentration less than or equal to 0.05% by weight, preferably less than or equal to 0.03% by weight of the composition. At such concentrations, the phosphoric acid, while allowing the thixotropic action of the clay, does not discolor the pigments that may be present in the varnish composition.

[0021] Advantageously, the nitrocellulose concentration is between 8 and 30% by weight, preferably between 10 and 25% by weight, more preferably between 12 and 20% by weight of the composition. Other cellulose derivatives as film-forming agents are excluded, due to their poor adhesion to the nail.

[0022] The cosmetic composition according to the invention may be a cosmetic composition in the form of a colored or colorless nail polish, a varnish undercoat, or a peelable varnish. It is of course possible to incorporate colorants, pigments and / or pearlescent agents into these cosmetic compositions to produce nail polishes of different colors and appearances.

[0023] The inventors have surprisingly found that the sorbic acid present in such a thixotropic nail polish composition confers strengthening and hardening properties to said nails. In the cosmetic nail polish composition according to the invention, sorbic acid or one of its salts is thus advantageously used as a hardening agent for the nails.

[0024] This use is non-therapeutic. Certain organic acids, or their salts, are already known (in particular from document US 2008 / 0193508) as antifungal agents, in particular against nail fungus, i.e. for therapeutic use.

[0025] The present invention therefore also relates to the use of sorbic acid, or one of its salts, as a nail hardening agent in a cosmetic composition as described above applied to nails free from fungal infection.

[0026] The composition may contain a concentration of sorbic acid or one of its salts less than or equal to 0.5% by weight, and advantageously a concentration of sorbic acid or one of its salts of between 0.01% and 0.5% by weight, more preferably of between 0.05% and 0.1% by weight.

[0027] Indeed, it has also been found that the hardening properties of sorbic acid on nails are present even at very low concentrations, less than or equal to 0.1% by weight (see examples 1-2 below).

[0028] According to the present invention, sorbic acid as a nail hardening agent is incorporated into a film-forming cosmetic composition, such as a colored or colorless nail polish, a nail polish primer, or a peelable nail polish. Film-forming cosmetic compositions, such as nail polishes, are preferred because they can remain on the nail for a long time.

[0029] Sorbic acid applied to healthy nails, i.e. nails free from fungal infection, can nevertheless be active at several levels on nail defects: cracked nails, thin nails, brittle nails, split nails, nail hardness, nail fragility, without causing allergic reactions.

[0030] The present invention also relates to a method for strengthening and hardening nails, free from fungal infection, in particular cracked, thin, brittle, soft or split nails, consisting of topically applying to said nails a cosmetic nail polish composition as described above, containing sorbic acid or one of its salts.

[0031] The following examples illustrate, in a non-limiting manner, the present invention. In all the formulations, the concentration of the different constituents is expressed as % by weight of the total weight of the cosmetic composition. EXAMPLES

[0032] Various cosmetic compositions in the form of organic solvent-based nail polishes were prepared and applied to nails. The following tests were carried out on these polishes: Gloss: On a Leneta plate, 100µm of varnish was applied. After drying, the gloss was measured at an index angle of 60°, using a MINOLTA 268 Glossmeter. Flexibility: On an aluminum plate covered with a 300µm wet varnish, a slow stamping is carried out and the penetration depth is measured (ISO1520). Varnish hardness: was measured using a Persoz pendulum on a glass plate covered with a 100µm wet varnish, after drying at room temperature, according to ISO1522. Adhesion: a "Cross hatch test" is carried out on the glass plate. A score of 0 corresponds to no loss of adhesion. A score of 5 corresponds to a total loss of adhesion. Dry extract: In a dish, between 0.5 and 1g of varnish is poured. This plate is then placed in an oven for 3 hours at 100°C, then weighed to calculate the dry extract of the varnish. Yellowing stability: The varnishes are packaged in glass bottles and stored in an oven at 50°C for 1 month. The color of the varnish is then compared to a reference varnish that does not contain a hardening agent.Sedimentation stability: A tinted varnish composition containing mother-of-pearl and a coloring solution is prepared and placed in an oven for 1 month at 45°C. A visual observation is made to check whether the mother-of-pearl has sedimented or not. Color stability: A tinted varnish containing a mixture of the following pigments: titanium dioxide, Red 34 and Ferric Blue ferrocyanide, is placed in an oven at 45°C for 30 days. The stability of this color and more specifically the appearance or absence of syneresis are observed. Odor: The odor of the varnish is compared to that of a varnish not containing a hardening agent. Viscosity: The viscosity of the product is measured at 25°C using a Brookfield viscometer. Measurements are taken after one minute of rotation at 6 rpm, then after one minute at 60 rpm, and finally after one minute at 6 rpm. Values are given in mPa.s. Examples 1 to 3, comparative example 4

[0033] Cosmetic compositions in the form of organic solvent-based nail polish were prepared from the constituents presented in Table 1 below. These compositions contained variable concentrations of sorbic acid, between 0.05 and 1% by weight. Table 1 Composition Ex. 1 Ex. 2 Ex. 3 Ex. Comp. 4 Butyl acetate 42,52 42,47 42,07 41,57 Ethyl acetate 20,6 20,6 20,6 20,6 Nitrocellulose 14 14 14 14 Polyester resin 9,5 9,5 9,5 9,5 Acetyltributyl citrate 6 6 6 6 Isopropyl alcohol 6 6 6 6 Stearalkonium bentonite 1,3 1,3 1,3 1,3 Phosphoric acid 0,03 0,03 0,03 0,03 Sorbic acid 0,05 0,1 0,5 1 Results Stability OK OK OK Yellowing Hardness of varnish(s) 240 248 243 235 Viscosity (mPa.s) 6 rpm 3300 3250 3290 3320 60 rpm 1030 1020 1040 1030 6 rpm 2100 2090 2120 2140 Dye stability No syneresis No syneresis No syneresis No syneresis Membership 0 0 0 0

[0034] The polyester resin in Table 1 above is an adipic acid / neopentyl glycol / trimellitic anhydride copolymer diluted to 70% solids in butyl acetate.

[0035] Nitrocellulose is wetted 70% in isopropanol.

[0036] These cosmetic compositions are in the form of a varnish, colorless and transparent after application to the nail, having a dry extract content equal to 24% by weight (measured at 100°C). One or more coloring materials chosen from pigments, soluble dyes and decorative particles, such as mother-of-pearl and glitter, may be added.

[0037] It is noted that the maximum quantity of sorbic acid that can be incorporated into the varnish, without causing yellowing, is less than 1% by weight.

[0038] Furthermore, sorbic acid at these concentrations below 1% by weight does not have an unpleasant odor for the user. It also has no influence on the viscosity of the varnish composition or its stability. Comparative examples 5-6 and 9, and example 7 - In vivo tests :

[0039] Four varnish compositions according to Example 1, each containing 0.05% by weight of hardening agent, and a reference varnish composition without hardening agent were each subjected to in vivo tests on panels of 30 people aged at least 20 years for three weeks to evaluate their efficacy and tolerance. None of the people tested had any lesions in the target areas (here the edges of the fingernails), nor any dermatological condition, nor any fungal infection of the nails. The varnish was applied under normal conditions of use (i.e. one application every three days, after removing the previous varnish).

[0040] Comparative composition 5 contained 0.05% hexanal, comparative composition 6 contained 0.05% by weight of citral, comparative composition 9 0.05% by weight of caproic acid and composition 7 according to the present invention 0.05% by weight of sorbic acid. Varnish composition 8 was without hardening agent (reference composition).

[0041] The respective compositions as well as the results of the physical tests and those observed by the panelists are grouped in Table 2 below. Table 2 Compositions Ex.5 Comp. Ex. 6 Comp. Ex. 7 Ex. 8 (Ref.) Ex. 9 Comp. Butyl acetate 42,53 42,52 42,52 42,57 42,52 Ethyl acetate 20,6 20,6 20,6 20,6 20,6 Nitrocellulose 14 14 14 14 14 Polyester resin 9,5 9,5 9,5 9,5 9,5 Acetyltributyl citrate 6 6 6 6 6 Isopropyl alcohol 6 6 6 6 6 Stearalkonium bentonite 1,3 1,3 1,3 1,3 1,3 Phosphoric acid 0,03 0,03 0,03 0,03 0,03 Hexanal 0,05 - - - - Citral - 0,05 - - - Sorbic acid - - 0,05 - - Caproic acid 0,05 Test results Brilliance 86,7 87,1 87 86,9 Flexibility 4,5 4,4 4,6 4,4 4,4 Hardness of the varnish(s) 236 233 240 238 235 Adhesion 0 0 0 0 0 Dry extract 28,1 28,3 27,9 28 28,1 Stability OK OK OK Reference OK Smell Forte Light and pleasant Absence Reference Absence Nail hardness Number of people answering Yes 23 18 25 12 14 Percentage 76,7 60,0 83,3 40,0 46,7

[0042] No clinical signs of intolerance were observed or experienced by the individuals tested. No allergy symptoms were noted.

[0043] Additionally, over 83% of subjects reported an overall improvement in the quality and hardness of their nails. These results demonstrate the in vivo nail hardening properties of sorbic acid, even at a low concentration (0.05% by weight) in the nail polish composition. Examples 11 and 12 - Comparative Examples 10 and 13: Sedimentation stability and color retention

[0044] To check the stability to sedimentation, two coloring materials were added to the base varnish composition according to claim 2: on the one hand, a Mother of pearl : Titanium mica marketed under the name Flamenco gold, 6-48µm, by the company BASF, and on the other hand the Pigment Red 34 : Organic pigment marketed by the SUN Chemical company.

[0045] This pigment was ground for incorporation. The grinding protocol included mixing the solvents with the pigment, stirring to deagglomerate the pigment, and then incorporating the nitrocellulose. Once the nitrocellulose was dissolved, the plasticizer was incorporated while stirring for 20 minutes. The resulting mixture was then ground in a ball mill.

[0046] Pigment Red 34 was thus ground with the following constituents (% by weight): Table 3 Butyl acetate 30 Ethyl acetate 30 Plasticizer (ATC) 10 Red 34 10 Nitrocellulose 20

[0047] The following shade was achieved on each of the tests described below: Base coat composition 95% by weight Solution containing Red 34 3% by weight Titanium mica (Flamenco gold, 6-48µm, from BASF) 2% by weight

[0048] The stability of the compositions thus prepared was evaluated by visual observation after storage for one month at 45°C. Table 4 Composition Ex. 2 Ex. 10 (comp.) Ex. 11 Ex. 12 Ex. 13 (comp.) Butyl acetate 42,47 42,52 42,49 42,45 42,4 Ethyl acetate 20,6 20,6 20,6 20,6 20,6 Nitrocellulose 14 14 14 14 14 Polyester resin 9,5 9,5 9,5 9,5 9,5 Acetyl tributyl citrate 6 6 6 6 6 Isopropyl alcohol 6 6 6 6 6 Stearalkonium bentonite 1,3 1,3 1,3 1,3 1,3 Phosphoric acid 0,03 0,01 0,05 0.1 Citric acid 0.03 Sorbic acid 0,1 0.1 0,1 0.1 0.1 Results Stability to yellowing OK OK OK OK OK Hardness of varnish(s) 248 242 240 240 237 Viscosity (mPa.s) 6 rpm 3250 1400 1890 4090 5630 60 rpm 1020 980 1010 1080 1120 6 rpm 2090 1230 1460 2530 3250 Membership 0 0 0 0 0 Stability of the shade described above Stable Sedimentation of mother-of-pearl Stable Stable Fading of the tint Conclusions:

[0049] Sedimentation is observed in the presence of citric acid replacing phosphoric acid.

[0050] Phosphoric acid at 0.1% by weight in the varnish bleaches the Red 34 pigment.

Claims

1. Nonaqueous thixotropic cosmetic nail varnish composition containing a film-forming agent comprising nitrocellulose, at least one organic solvent, and a thixotropic agent, characterized in that said composition contains sorbic acid or one of its salts at a concentration of less than 1% by weight, and in that the thixotropic agent, present at a concentration of between 0.1% and 4% by weight of the composition, is a clay modified with a quaternary amine, neutralized by a strong acid at a concentration of less than 0.1% by weight of the composition.

2. Cosmetic nail varnish composition according to Claim 1, characterized in that it contains a concentration of sorbic acid or one of its salts of less than or equal to 0.5% by weight, preferably of between 0.01% and 0.5% by weight, more preferably of between 0.05% and 0.1% by weight.

3. Cosmetic nail varnish composition according to either of Claims 1 and 2, characterized in that the thixotropic agent is a clay modified with a quaternary amine, the clay being chosen from bentonite or hectorite.

4. Cosmetic nail varnish composition according to any one of the preceding claims, characterized in that the concentration of thixotropic agent is between 0.5% and 3% by weight, preferably between 1% and 2% by weight, of the composition.

5. Cosmetic nail varnish composition according to any one of the preceding claims, characterized in that the strong acid which neutralizes the clay modified with a quaternary amine is phosphoric acid, preferably at a concentration of less than or equal to 0.05% by weight, preferably of less than or equal to 0.03% by weight, of the composition.

6. Cosmetic nail varnish composition according to any one of the preceding claims, characterized in that the concentration of nitrocellulose is between 8% and 30% by weight, preferably between 10% and 25% by weight, more preferably between 12% and 20% by weight, of the composition.

7. Cosmetic nail varnish composition according to any one of the preceding claims, characterized in that the sorbic acid or one of its salts is used as a hardening agent for the nails.

8. Cosmetic nail varnish composition according to any one of the preceding claims, characterized in that the composition is a cosmetic composition in the form of a coloured or colourless nail varnish, of a varnish base coat, or of a peelable varnish.

9. Use of sorbic acid, or of one of its salts, as a nail-hardening agent, at a concentration of less than 1% by weight, in a cosmetic composition according to any one of the preceding claims applied to nails free from fungal infection.

10. Use according to Claim 9, characterized in that the cosmetic composition contains a concentration of sorbic acid or of one of its salts of less than or equal to 0.5% by weight.

11. Use according to either of Claims 9 and 10, characterized in that the cosmetic composition contains a concentration of sorbic acid or of one of its salts of between 0.01% and 0.5% by weight, more preferably of between 0.05% and 0.1% by weight.

12. Method for strengthening and hardening nails free from fungal infection, in particular cracked, thin, brittle, soft or split nails, consisting in topically applying to said nails a cosmetic varnish composition according to any one of Claims 1 to 8.