BACKGROUND Various nail enamel compositions are known in the art. Nail enamel compositions typically contain, in an organic solvent or mixture of solvents, film-forming ingredients, plasticizing ingredients, and colorants. Generally, the composition also contains a thixotropic agent, which may act to thicken the composition in order to allow better spreading on the nail. The thixotropic agent may also act to suspend the colorant.

The classic thixotropic agent used in the prior art is a bentonite clay.

Aromatic organic solvents in particular may cause these clays to swell, thus providing a gel with good thixotropic properties, i. e., rendering the composition capable of passing from a gelled state to a liquid state simply by stirring and capable of going from liquid to gel after standing. A composition containing such a gel thus may exhibit relatively good dispersion stability without sedimentation or separation over a long period. Further, such compositions may not require the vigorous shaking that other compositions often require after extended periods of storage.

The clay thixotropes, however, may produce cloudy suspensions, rendering the composition opaque and often giving it a more or less yellowish color inside the bottle, unpleasant to the eye. Although this opacity is generally masked by the presence of colorants and/or pigments in the composition, the use of the clay thixotropes may diminish gloss in the final formulated nail enamel product. Thus the need remains for a thixotropic agent that will not affect the glossiness of the nail enamel and yet will have sufficient thixotropic properties such that the stability of the composition is not compromised.

SUMMARY OF THE INVENTION Accordingly, the present invention is drawn to a novel nail enamel composition containing, in a cosmetically acceptable solvent, at least one film-forming substance and at least one urea-modified thixotropic agent wherein the urea-modified thixotropic agent is a urea urethane having the following formula : R-O-CO-NH-R'-NH-CO-NH-R"-NH-CO-NH-R'-NH-CO-OR wherein R is chosen from CnH2n+1- and CmH2m+1 (CpH2pO)r-; n is an integer having a value of from 4 to 22; m is an integer having a value of from 1 to 18 ;. p is an integer having a value of from 2 to 4; and r is an integer having a value of from 1 to 10; R'is chosen from: and R"is chosen from: In one embodiment, the cosmetically acceptable solvent is a solvent system comprising diacetone alcohol and at least one additional solvent chosen from C,-C6 alkyl acetates and C,-C6 alkyl alcohols.

The nail enamel composition of the invention may also contain a plasticizer and optionally a coloring agent.

The present inventors have discovered that the use of a urea-modified thixotropic agent in place of, or in conjunction with, the clay thixotropes of the prior art, may result in a clear suspension with improved gloss and have further discovered that the clarity of the suspension may be further enhanced when the urea-modified thixotropic agent is present in a solvent system comprising diacetone alcohol and at least one additional solvent chosen from C1-C6 alkyl acetates and C1-C6 aikyl alcohols. In general, nail enamel compositions containing clay thixotropes only are difficult to process because their creation requires a great deal of high shear. Also, since the clay thixotropes are naturally occurring products, they can vary in quality and consistency. In contrast, the presently claimed compositions utilizing the urea-modified thixotrope, and in one embodiment, the urea-modified thixotrope in a specific solvent system, may be easy to produce consistently at optimum conditions because their creation may not require high shear processing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the embodiment (s) of the invention.

The presently claimed invention is drawn to a nail enamel composition which contains, in a cosmetically acceptable solvent, at least one film-forming substance and at least one urea-modified thixotropic agent. The use of such a thixotropic agent can give nail enamel compositions at least one of higher gloss, high clarity, improved aesthetics in the bottle, excellent thixotropic properties, and improved application properties. It has been discovered that at least one of these properties may be even more greatly enhanced where the cosmetically acceptable solvent is a solvent system comprising diacetone alcohol and at least one additional solvent chosen from C,-C6 alkyl acetates and C,-C6 alkyl alcohols.

The urea-modified thixotropic agents used in the present invention are urea urethanes having the following formula: R-O-CO-NH-R'-NH-CO-NH-R"-NH-CO-NH-R'-NH-CO-OR wherein R is chosen from CnH2n+,-and CmH2m+, (CpH2pO) r-; n is an integer having a value of from 4 to 22; m is an integer having a value of from 1 to 18; p is an integer having a value of from 2 to 4; and r is an integer having a value of from 1 to 10; R'is chosen from: and R"is chosen from: Such a urea-modified product can be purchased from BYK-Chemie in a dilute solution with N-methyl-pyrrolidone as solvent under the trade name of By@-410 and is generally described in U. S. Patent No. 4,314,924, the disclosure of which is hereby incorporated by reference herein. In one embodiment, the at least one urea-modified thixotropic agent may be present in an amount of from about 0.05 to about 1.00% relative to the weight of the composition. In another embodiment, the at least one urea-modified thixotropic agent may be present in an amount of from about 0.25 to. about 0.75% relative to the weight of the composition.

The nail enamel composition of the invention may contain at least one additional thixotropic agent, used in conjunction with the at least one urea- modified agent. When such an additional thixotropic agent is present, the composition may comprise from about 0.10 to about 0.30% of the at least one urea-modified thixotropic agent relative to the weight of the composition and up to about 1.0% of the additional thixotropic agent. The additional thixotropic agent (s) may be chosen from conventional silica and bentonite clay agents.

In one embodiment, the additional thixotropic agent is stearalkonium hectorite, sold by RHEOX as BENTONE 27.

Film forming substances useful in the present invention include, but are not limited to, conventional film-forming agents such as nitrocellulose, other cellulose derivatives, such as cellulose acetate, cellulose acetate butyrate, and ethyl cellulose ; polyesters; resins, such as polyurethane resins, alkyd resins, and polyvinyl resins such as polyvinyl acetate, polyvinyl chloride, polyvinylbutyrate ; (meth) acrylic and vinyl copolymers such as styrene/butadiene copolymers, acrylatelvinyl acetate copolymers, acrylonitrile/butadiene copolymers, and ethylene/vinyl acetate copolymers.

In one embodiment, the primary film-forming agent may be nitrocellulose, which is known to give hardness and resistance to abrasion. If a second film-forming substance is present, this second film-forming substance may, for example, be chosen from cellulose acetate butyrate, polyesters, polyurethanes, and acrylates. In one embodiment, the film- forming substance may be present in an amount of from about 5% to about 20% by weight relative to the weight of the composition, for example, from about 10% to about 14%. Suitable modifiers for the primary film-forming agent include arylsulfonamide resins such as arylsulfonamide formaldehyde or epoxy resins.

The presently claimed composition also may contain at least one plasticizer. Plasticizers useful in the presently claimed nail enamel composition include plasticizers commonly employed in nail varnish compositions. These plasticizers encompass, but are not limited to, dibutyl phthalate, dioctyl phthalate, : tricresyi phthafate, butyt phthfate, dibutoxy ethyl phthalate, diamylphthalate, tosyl amide, N-ethyl-tosyl amide, sucrose acetate isobutyrate, camphor, castor oil, citrate esters, glyceryl diesters, glyceryl triesters, tributyl phosphate, tri-phenyl phosphate, butyl glycolate, benzyl benzoate, butyl acetyl ricinoleate, butyl stearate, and dibutyl tartrate. In one embodiment, a plasticizer used in the present invention may be the mixture of acetyl tributyl citrate and N-ethyl tosyl amide. The plasticizer may, for example, be present in an amount of from about 3% to about 12% by weight relative to the weight of the composition.

The cosmetically acceptable solvents useful in the present invention are cosmetically acceptable organic solvents including, but not limited to toluene, xylene, Cl-C., alkyl acetates, such as ethyl acetate, propyl acetate, and butyl acetate; ketones such as acetone or methyl ethyl ketone; alkanes such as hexane or heptane; C1-C6 alkyl alcohols such as ethanol, isopropanol, and butanol ; glycol ethers; N-methyl pyrrolidone ; diacetone alcohol, and alkyl lactates. In one embodiment, the invention uses a solvent system comprising diacetone alcohol and at least one additional solvent chosen from C1-C6 alkyl acetates andC,-C6alkyl alcohols. In another embodiment, the solvent system comprises diacetone alcohol, at least one C1-C6 alkyl acetate and at least one Cl-C., alkyl alcohol. The solvent or mixture of solvents may be present, in one embodiment, in an amount of from about 40% to about 80% by weight relative to the weight of the composition, and, in another embodiment, from about 65% to about 78%.

The nail enamel composition of the invention may also contain at least one coloring agent. Conventional coloring agents can be used, and examples include inorganic pigments such as titanium dioxide, iron oxides, titanated mica, iron oxide coated mica, ultramarine, chromium oxide, chromium hydroxide, manganese violet, bismuth oxychloride, guanine, and aluminum ; pearlescent materials ; and organic coloring agents such as ferric ammonium ferrocyanide, and D&C Red Nos. 6,7,34, Blue No. 1, Violet No. 2, and Yellow No. 5.

The inorganic pigments may be surface-treated as is customary to prevent migration or striation. Silicones and polyethylenes are most often used as the coatings for inorganic pigments and thus may be used according to the present invention. Colorant materials may also include chips or powder of mica or diamonds in the nail composition. Also useful are specialty materials giving rise to two-tone color effects such as liquid crystal silicones or multi-lamellar metallic particulates, which generally can be mixed with pigments or dyes to obtain a broader spectrum of brilliant color and increased luminous reflectance. Such materials are described in, e. g., U. S. Patent No.

3,438,796; U. S. Patent No. 4,410,570; U. S. Patent No. 4,434,010 ; U. S.

Patent No. 4,838,648; U. S. Patent No. 4,930,866; U. S. Patent No.

5,171,363; U. S. Patent No. 5,364,467; U. S. Patent No. 5,569,535; U. S.

Patent No. 5,607,904; U. S. Patent No. 5,624,486; U. S. Patent No. 5,658,976; U. S. Patent No. 5,688,494; U. S. Patent No. 5,766,335; N. Haberle et al., "Right and Left Circular Polarizing Colorfilters made from Crosslinkable Cholesteric LC-Silicones,"Conference Record of the 1991 International Display Research Conference (IEEE), pp. 57-59 ; R. Maurer et al.,"Polarizing Color Filters made from Cholesteric LC-Silicones,"SID 90 Digest (1990), pp.

1 10-113 ; H.-J. Eberle et al.,"Inverse Angle Dependence of the Reflection Colours of Cholesteric Polymeric Liquid Crystals Mixed with Pigments,"Liquid Crystals, 5 (3), (1989), pp. 907-916; J. Pinsl et al.,"Liquid Crystalline Polysiloxanes for Optical Once-Write Storage,"J. Molec. Electr., Vol. 3 (1987), pp. 9-13; and D. Makow,"Reflection and Transmission of Polymer Liquid-Crystal Coatings and their Application to Decorative Arts and Stained Glass,"Color Res. Applic. Vol. 11, No. 3, (1986), pp. 205-208, all of which are incorporated herein by reference in their entirety.

In one embodiment, the coloring agent may be present in the nail enamel composition in an amount up to about 5% by weight relative to the total weight of the composition. In another embodiment, the coloring agent is present in an amount of from 2% to 3% by weight.

The composition according to the invention may also include additives recognized by a person skilled in the art as being capable of incorporation into such a composition. For example, the composition may include at least one cosmetically active compound, which may be selected from vitamins, minerals, moisturizers, flavoring compounds, fragrances, masking agents, hardening agents such as silica and formaldehyde/glyoxal, UV absorbers, and fibers such as nylon and aramide fibers. Any art-recognized UV absorber can be used, both organic and inorganic. In one embodiment, inorganic UV absorbers include titanium dioxide and zinc oxide, both of which may be used in nanoparticulate form. In another embodiment organic UV absorbers include octocrylene, octylmethoxy cinnamate, and benzophenone.

Additional additive ingredients may include keratin and its derivatives, melanin, collagen, cystine, chitosan and its derivatives, ceramides, biotin, oligoelements, protein hydrolysates, and phospholipids.

A person skilled in the art can, without undue experimentation, select those optional additional compounds and/or their quantity, so that the advantageous properties of the composition according to the invention are not, or are not substantially, impaired by the inclusion of such additives.

The composition according to the invention may be prepared by a person skilled in the art on the basis of his or her general knowledge and according to the state of the art.

The composition according to the invention may be in the form of a product to be applied to the nails, such as a top coat, a base coat, or a pigmented nail lacquer or varnish.

The invention will be further clarified by the following examples, which are intended to be illustrative of the invention, but not limiting thereof.

EXAMPLES Example 1 Three compositions were formulated as set forth in the following table.

The amounts listed are in grams. COMPOSITIONS INGREDIENTS 1 2 3 Ethyl Acetate 25.65 21 23.65 Butyl Acetate 25 24 25 Propyl Acetate 20 15 20 Nitrocellulose 10 14.7 10 Isopropyl Alcohol 5 5 5 Sucrose Acetate Isobutyrate 5--5 N-Ethyl Tosylamide 5 7.5 5 Tosylamide Epoxy Resin 2 9 2 Acrylates Copolymer 1.5--1.5 StearalkoniumHectorite 1 COMPOSITIONS INGREDIENTS 1 2 3 Etocrylene 0.5 0.5 0.5 Benzophenone-1 0.1 0.1 0.1 Colorants/Pearls-2 2 Modified Urea-Urethane (BYK 410) 0. 25 0.2 0. 25 Each of compositions 1-3 were visually compared with a"classic"nail enamel composition, i. e., one containing only the traditional clay-based thixotrope. The comparisons are described below.

Composition 1, which was a formulation according to the invention but which contained no colorants, i. e., was a clear top coat enamel. This formulation exhibited significantly improved body and viscosity, while maintaining excellent clarity, when compared to the"classic"composition.

Composition 2 was similar to composition 1 but did not contain sucrose acetate isobutyrate, one of the plasticizers, or acrylates copolymer, one of the film-formers. Composition 2 did contain, however, pigments and pearlescent colorants and, in addition to the urea-urethane (BYK-410) as a thixotrope, contained a clay-based thixotrope, stearalkonium hectorite. The result was a pigmented/pearlescent nail enamel with no perceptible (visual) differences over the"classic"compositions.

Finally, composition 3 was an inventive pigmented/pearlescent nail enamel utilizing only the modified urea-urethane as the thixotrope. This product displayed improved bottle aesthetics (gloss) and a smoother finish on the nail versus a"classic"nail enamel which utilized the clay type thixotropes.

Overall, the inventive compositions had higher gloss ; better stability, i. e., even with pigments that are normally difficult to suspend; and improved application properties, e. g., almost no brush marks were perceptible on the nail after the composition dried, when compared to the"classic"compositions.

Example 2 Four compositions were formulated as set forth in the following table.

The amounts listed are in grams. COMPOSITIONS INGREDIENTS 4 5 6 7 Ethyl Acetate 24.8 22. 8 24.4 23.8 Butyl Acetate 20.7 19.7 20.7 20.7 Propyl Acetate 9.7 9.7 9.7 9.7 Nitrocellulose 14 14 14 14 Isopropyl Alcohol 1. 03 1. 03 1.03 1.03 Butyl Alcohol 9 9 9 9 Diacetone Alcohol 4.5 4.5 4.5 4.5 Acrylates Copolymer 4.42 4.42 4.42 4.42 Triphenyl Phosphate 4.57 4.57 4.57 4.57 Tosylamide Epoxy Resin 2.4 2.4 2.4 2.4 Polyester Resin 2.4 2.4 2.4 2.4 Acetyl Tributyl Citrate 2 2 2 2 Polyethylene Teraphthalate--3--- D&C Red #6 Barium Lake--0. 3 D&C Red #34 Calcium Lake--0. 1- D&C Red #7 Calcium Lake---0. 1 Mica (Splendid Violet)---0. 7 Ferric Ammonium Ferrocyanide------0. 02 Modified Urea-Urethane (BYK 410) 0.5 0.5 0. 5 0.5 Compositions 5,6, and 7 are almost identical to inventive composition 4, but each contains a different colorant or additive.

Specifically, composition 5 is a translucent nail enamel containing polyethylene teraphthalate, commonly known as"glitter"and having a particle size ranging from 100 microns to 0.32 cm. This composition displayed improved particle suspension and bottle aesthetics when compared to the "classic"composition. This example illustrates the ability of the present inventive compositions to suspend large particles even without the presence of the traditional clay or silica thixotropes, i. e., using only the modified urea- urethane thixotrope and a solvent system comprising at least one C1-C6 alkyl acetate, at least one C1-C6 alkyl alcohol, and diacetone alcohol.

Composition 6 contains two red pigments. Composition 7 contains pearlescent pigments. Like the other inventive composition, suspension, gloss, and stability were all improved for compositions 6 and 7.

Overall, the inventive compositions had higher gloss ; better stability, i. e., even with pigments that are normally difficult to suspend; and improved application properties, e. g., almost no brush marks were perceptible on the nail after the composition dried, when compared to the"classic"compositions.