FIELD OF THE INVENTION
The present invention relates to a novel nail enamel composition with improved thixotropic properties as well as improved clarity in the bottle. More specifically, the invention relates to the use of a urea-modified compound as a thixotropic agent in a nail enamel composition.
BACKGROUND OF THE INVENTION
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 to thicken the composition in order to allow better spreading on the nail. The thixotropic agent also acts to suspend the colorant.
The classic thixotropic agent used in the prior art is a bentonite clay. Aromatic organic solvents in particular 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 from liquid to gel after standing. A composition containing such a gel thus exhibits relatively good dispersion stability without sedimentation or separation over a long period. Further, such compositions do not require the vigorous shaking that other compositions often require after extended periods of storage.
The clay thixotropes, however, 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 diminishes 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
In order to achieve these and other advantages, 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:
wherein R represents CnH2n+1— or CmH2m−1(CpH2pO)r—; n represents an integer having a value of from 4 to 22; m represents an integer having a value of from 1 to 18; p represents an integer having a value of from 2 to 4; and r represents an integer having a value of from 1 to 10.
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, results in a clear suspension with improved gloss. 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 novel urea-modified thixotrope are easy to produce consistently at optimum conditions because their creation does not require high shear processing.
Reference will now be made in detail to the present preferred embodiment(s) of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
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 present inventors have found that the use of such a thixotropic agent gives nail enamel compositions with higher gloss, high clarity, improved aesthetics in the bottle, excellent thixotropic properties, and improved application properties.
The urea-modified thixotropic agents used in the present invention are urea urethanes having the following formula:
wherein R represents CnH2n+1— or CmH2m+1(CpH2pO)r—; n represents an integer having a value of from 4 to 22; m represents an integer having a value of from 1 to 18; p represents an integer having a value of from 2 to 4; and r represents an integer having a value of from 1 to 10.
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 BYK®-410 and is generally described in U.S. Pat. No. 4,314,924. The at least one urea-modified thixotropic agent is preferably present in an amount of from about 0.05 to about 0.40% relative to the weight of the composition. More preferably, the at least one urea-modified thixotropic agent is present in an amount of from about 0.25 to about 0.35% 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 comprises 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 selected from conventional silica or bentonite clay agents. Particularly preferred 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, acrylate/vinyl acetate copolymers, acrylonitrile/butadiene copolymers, and ethylene/vinyl acetate copolymers.
The primary film-forming agent is preferably nitrocellulose, which is known to give hardness and resistance to abrasion. If a second film-forming substance is present, this second film-forming substance is preferably selected from cellulose acetate butyrate, polyesters, polyurethanes, and acrylates. The film-forming substance is preferably present in an amount of from about 5% to about 20% by weight relative to the weight of the composition, and more preferably 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 preferably contains 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, tricresyl phthalate, butyl phthlate, 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 slearate, and dibutyl tartrate. Particularly preferred as a plasticizer in the present invention is the mixture of acetyl tributyl citrate and N-ethyl tosyl amide. The plasticizer is preferably present in an amount of from about 3% to about 12% by weight relative to the weight of the composition.
The solvents useful in the present invention are cosmetically acceptable organic solvents including, but not limited to toluene, xylene, alkyl acetates such as ethyl acetate and butyl acetate; ketones such as acetone or methyl ethyl ketone; alkanes such as hexane or heptane; alkyl alcohols such as ethanol, isopropanol, and butanol; glycol ethers; N-methyl pyrrolidone; and alkyl lactates. A preferred solvent is alkyl acetate. The solvent or mixture of solvents is preferably present in an amount of from about 40% to about 80% by weight relative to the weight of the composition, and more preferably from about 65% to about 78%.
The nail enamel composition of the invention also preferably contains at least one coloring agent. Conventional coloring agents can be used, and preferred coloring agents 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 are preferred 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. Pat. Nos. 3,438,796; 4,410,570; 4,434,010; 4,838,648; 4,930,866; 5,171,363; 5,364,467; 5,569,535; 5,607,904; 5,624,486; 5,658,976; 5,688,494; 5,766,335; N. Häberle 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. 110-113; 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.
Preferably, the coloring agent is present in the nail enamel composition in an amount up to about 5% by weight relative to the total weight of the composition. More preferably, 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, hardening agents such as silica and formaldehyde/glyoxal, UV absorbers, and fibers such as nylon or aramide fibers. Any art-recognized UV absorber can be used, both organic and inorganic. Preferred inorganic UV absorbers include titanium dioxide and zinc oxide, both of which may be used in nanoparticulate form. Preferred 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.