TECHNICAL FIELD

The present invention relates generally to cosmetic formulations and more specifically, to a novel formulation which may be applied to human (or other animals) for hardening and/or strengthening the finger or toe nails.

BACKGROUND ART

It is known to include various ingredients in nail coating formulations for the general purpose for hardening and/or strengthening finger and/or toe nails. Formaldehyde, acetic aldehyde and glutaraldehyde have all been used for this purpose; however, these ingredients suffer from certain undesirable side effects including irritation of the skin tissue surrounding the nail (i.e. the cuticle area), allergenic reactions to people having sensitive skin, and a bothersome residual odor all of which limit the use of these ingredients in cosmetic nail coating compositions.

DISCLOSURE OF THE INVENTION

Nail coating formulations are provided having a nail hardening/strengthening ingredient, specifically, isobutyraldehyde, in a concentration of about 5Ϊ or less based upon the weight of the formulation whereby surprisingly nail hardening and strengthening efficacy 1s achieved without the negative side effects of irritation, allergenic reactions, and a bothersome residual odor.

BEST MODE FOR CARRYING OUT THE INVENTION

The nail hardening or strengthening agent contemplated by the present invention may be used in any of the well known forms of "nail coatings" used in the cosmetic industry such as base coats, top coats, pigmented or colorless lacquers or enamels, frosts, creams, menders, strengtheners, and the like. Generally, a typical nail coating has as its basic constituents a film former (nitrocellulose) a resin (toluene- sulfona ide formaldehyde), a solvent (butyl or ethyl acetate), and a plasticizer (dibutyl phthalate). If color is desired a suitable pigment or combination of different pigments and suspension material (clay) also are added. In a manner well understood in the art of formulating nail coatings, the relative proportions of the various basic ingredients mentioned above may be adjusted for optimizing selected characteristics of the nail coating such as its hardeness, strength, gloss, resistance to chipping, flexibility and so on.

In accordance with the present invention, a "nail hardening or strengthening" agent is added to the basic composition described above to improve the hardeness or strength of nails to which the coating is applied. Hardness and strength imparted to the nail helps resist nail breakage, splitting and chipping. Not only does the hardened, stronger nail provide a better supporting surface for the nail coating, leading to a longer effective lifetime for the nail coating, but moreover, hardened or stronger nails resist the tendency to curl as they grow longer. Under current standards of beauty, straight nails as opposed to curled nails generally are considered more aesthetically appealing.

The specific nail hardening or stengthening agent of the present invention comprises isobutyraldehyde, a member of the aldehyde family having branched methyl groups (CH,) and having the formula: (CH,) ₂ CHCHO. So far as applicants are aware isobutyraldehyde has never been used as a nail hardener or strengthening agent. This ingredient is commercially available as a colorless liquid from a variety of sources including, for example, Eastman Chemicals, Rochester, New York. Without being resistricted to any particular theory, it is believed that the isobutyraldehyde reacts with the keratin or other proteinaceous substances in the nail to effect a cross-linking thereof, thereby leading to an increase in strength and/or in the hardeness of the nail.

When adding the isobutylaldehyde ingredient to a nail coating formulation in accordance with the invention up to about 54 by weight may be employed. However, it has been discovered that when employed at lower amounts, say, about 14 of the composition by weight, strengthening and hardening efficacy still is achieved yet the negative side effects associated with other aldehydes in nail coating formulations are minimized, if not eliminated entirely. Therefore, an amount of isobutyraldehyde in the nail coating formulation of 14 or less by weight is mostly preferred. More specifically, at this mostly preferred amount no irritation of skin tissue surrounding the nail of the cuticle area fs experienced, the ingredient is non-sensitive to allergy prone individuals, and disagreeable odor retention is absent.

In use, the nail coating formulation including isobutyraldehyde as an active nail hardening or strengthening ingredient in accordance with the invention may be applied to the nails by following the use

instructlons for the particular nail coating involved. Repeated applications of the nail coating including the isobutyraldehyde ingredient will cause the nails to become strengthened and more hardened compared to their preappH cation condition.

The foregoing advantages and other aspects of the invention are further illustrated by the following actual examples which are not to be construd as limiting.

EXAMPLE I The efficacy of using isobutyraldehyde to strengthen and/or harden

10 nails was tested by measuring the force to depress (bend) a clipped nail sample a fixed distance on a Diastron Rheometer (Diastron Ltd., Surrey, England). All tests were conducted in-vitro on fingernails clipped from young adults. All clipped nail tests samples were washed, for 2 minutes in acetone, and equilibrated (hydrated) at 1004 relative humidity for 24 hours. Baseline (pre-test) measurements were then taken prior to treatment. In a first test, the nail clipping samples were treated by being soaked for 30 minutes in a bath of 1004 isobutyraldehyde, followed by a 5 minute water rinse. The treated samples showed an average increase in rigidity of 61.84 over the baseline measurement. In a second test, lower concentrations of isobutyraldehyde (14 and 54 aqueous) were tested by soaking nail clipping samples repeatedly for 30 minutes at a time with no after rinse. Following eight such treatments to simulate repeated application the increase in rigidity

EXAMPLE II

A "base coat" composition having the following ingredients was formulated:

41.960004 Ethyl Acetate

23.970004 Butyl Acetate

11.480004 Heptane

9.860004 Nitrocellulose

5.220004 Isopropyl Alcohol

4.000004 To luenesulfonamide/ Formaldehyde Resin

2.000004 Dibutyl Phthalate 1.000004 Isobutyraldehyde

.400004 Benzophenone-1

.050004 Sucrose Benzoate/Sucrose Acetate

Isobutyrate/Butyl Ben∑yl

.020004 Acrylates Copolymer

.020004 Calcium Pantothenate

.020004 Dimethicone (and) TrimethylsHoxyHlicate Total 100.000004

A sample of the above formulation (e.g. .5 oz. ) was placed in an unmarked vial. In a separate unmarked vial was placed the same formulation without the 14 isobutyraldehyde ingredient (Qs: ethyl acetate). The two vials were then tested for olfactory quality by a trained fragrance evaluator. The formulation of the Example including the 14 isobutyraldehyde was found not to have a pugent or unpleasant odor. Compared to the odor eminating from the other unmarked vial

(without the 14 isobutyraldehyde ingredient) the former had a sweeter more fragrant note.

EXAMPLE III Utilizing the nail coating of Example II, a Draize-Shelanski allergeniclty assay was preformed on a randomly selected human population of 103 subjects. During the induction phase, (i.e. nine 24 hours periods with a 24 hour hiatus between each application)

-6- measured as follows:

54 Isobutyraldehyde (aqueous) 160.34

14 Isobutyraldehyde (aqueous) 11.74

In the third test, a nail coating vehicle comprising a blend of solvents only (ethyl acetate 2 parts, butyl acetate 1 part) was compared to the same vehicle containing 14 isobutyraldehyde. Treatment consisted of a 5 minute soak followed by no rinse. The following increase over the base¬ line measurement was observed after 6 and then 10 such treatments:

6 10 6 -1- 10 (Avg.) Vehicle alone 6.94 10.84 8.94

Vehicle plus 14 isobutyraldehyde 19.34 13.14 16.24

The foregoing tests demonstrate that isobutyraldehyde is effective to increase^the rigidly of clipped nail samples. The tests also proved that at a level of 14 an increase in rigidly is achieved, especially after repeated applications.

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14 reactions of mild erethyma was observed. During the challenge phase (2 weeks later) zero (0) occurances of sensitivity was observed. This test proved that the nail coating of Example II failed to produce any allergenic reactions or challenges among the test population; and that the formulation was essentially non-irritating during the induction phase.

EXAMPLE IV An aqueous solution of 14 isobutyraldehyde was tested for primary irritation using a single occlusive patch applied repeatedly (4X times) to the same skin site on the backs of 20 randomly selected human subjects under the supervision of a dermatologist. Seventeen (17) of the subjects showed no reaction whereas three (3) subjects showed barely perceptible erythema. Results of this test demonstrate that the 14 isobutyraldehyde solution was essentially non irritating.

It is evident from the forgoing that the present invention provides a "nail coating" composition effective to strengthen or harden nails without the undue side effects of allergenic reaction and irritation. In addition, use of isobutyraldehyde, the active ingredient according to the present invention, provides the further advantage of avoiding any disagreeable residual odor as is the case with prior nail hardening compositions employing other aldehydes (e.g. formaldehyde).

Although the present invention has been fully described above with reference to actual Examples thereof, this was done merely for the sake of illustrating preferred embodiments of the Invention as required by

statute. Obviously, many changes, modifications, and alterations may be made without departing from the principles of the invention. Accordingly, it is desired that the present invention be limited only by the true spirit and scope of the annexed claims.