Drug – bio-affecting and body treating compositions – Live hair or scalp treating compositions – Shaving preparation
Reexamination Certificate
1996-10-11
2001-03-20
Levy, Neil S. (Department: 1616)
Drug, bio-affecting and body treating compositions
Live hair or scalp treating compositions
Shaving preparation
C424S400000, C424S401000, C514S557000
Reexamination Certificate
active
06203784
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to compositions for the treatment of hair and, in particular, to hair treatment compositions having improved rinsing properties. The invention relates especially to depilatory compositions, but will also find application in perming compositions.
Depilatory compositions are conventionally applied to the skin in the form of a cream, lotion, gel or mousse. After a period of time, the depilatory composition is removed by suitable means, such as by the use of a spatula. The active depilatory ingredient of the composition is conventionally an alkali metal salt or alkaline earth metal salt of an alpha or beta mercapto-carboxylic acid, such as potassium or calcium thioglycolate. These materials act by penetrating the hair and destroying the cystine bonds between the hair molecules. This weakens the hair to such an extent that the action of scraping and wiping away the depilatory composition causes the hair to break off at skin level, so that the hair may be removed.
A particular problem with compositions of this type is that the composition is difficult to remove completely from the skin and cannot be removed easily by simply rinsing away the composition. A heavy or vigorous mechanical scrubbing or scraping action is required, for example with a spatula, which can be a cause of considerable discomfort and inconvenience. Accordingly, the present invention seeks to provide hair treatment compositions, in particular depilatory compositions, having improved rinsing properties.
For conventional depilatory compositions in the form of a cream, lotion, gel or mousse, the emulsion is normally stabilized by including a relatively high amount of thickener in the composition. For example, conventional thickeners, which will be well known to those skilled in the art, are generally present at levels of up to 30% w/w. Alternatively, depilatory creams, lotions and gels can be formulated to give a stable emulsion by including high levels of fatty materials in the depilatory composition. In such compositions, either no thickener is present, or a small amount of thickener may be present.
In both cases, however, good rinsability of the depilatory composition from the skin will not be achieved. In the case where a high level of thickener is present, there will be such strong steric interactions between the polymeric materials in the emulsion that it is not possible to remove the depilatory composition quickly and easily from the skin by the mechanical action of water together with a light rubbing action. Where high levels of fatty materials are present, the texture or “body” of the depilatory composition will be too strong to allow the composition to be rinsed simply from the skin.
For example, International Patent Publication Ser. No. WO 93/08791 (The Boots Company PLC) describes depilatory formulations including, inter alia, smectite or kaolin clays such as bentonite. The clays are said to improve the feel of the depilatory composition on the skin and to reduce the unpleasant smell associated with the depilatory agent. However, the compositions described in WO 93/08791 would not have the improved rinsability of the depilatory compositions of the present invention. That is, the compositions described in WO 93/08791, containing the levels of thickeners and fatty materials as specified, would not be able to be rinsed simply from the skin by the mechanical action of water together with a light rubbing action.
However, in accordance with the present invention, we have found that it is possible to formulate a depilatory composition which is sufficiently stable to provide a good depilatory product, but which has weak enough steric interactions between the polymeric materials in the composition to provide improved rinsing properties.
SUMMARY OF THE INVENTION
It has now been found surprisingly that the incorporation in a hair treatment composition of a viscosity enhancer which imparts a shear sensitive structure to the composition (hereinafter called a thixotropic agent) provides such improved rinsing properties. The incorporation of a thixotropic agent in a depilatory composition allows the composition to be rinsed off the skin simply, for example, by the mechanical action of water from a shower together with a light rubbing action. The need for heavy scrubbing or scraping with a spatula or the like is thus avoided. The sensitivity of the composition to shear forces can be made so acute that the mere mechanical action on the skin of water from the shower is sufficient for effective removal of the composition, but such a degree of shear sensitivity may adversely affect other properties of the composition.
Accordingly, the first aspect of the present invention provides a depilatory composition including a functional amount of a thixotropic agent, which composition has a shear sensitive structure.
By this we mean that the sensitivity of the depilatory composition of the present invention to shear forces is such that the mechanical action on the skin of water alone, or the mechanical action on the skin of water together with a light rubbing action, is sufficient to remove the composition from the skin.
In accordance with a second aspect of the present invention there is provided the use, in a depilatory composition, of a functional amount of a thixotropic agent effective to impart a shear sensitive structure to the composition.
DETAILED DISCLOSURE
The compositions of the invention may include any suitable mineral or organic thixotropic agent, but particularly preferred thixotropic agents include smectite clays, synthetic hectorite clays such as Laponite LS from Laporte, colloidal montmorillonites such as those available under the trade name Gelwhite from Southern Clay Products Inc, USA and Laporte, silicoaluminate clays such as the collidal magnesium aluminium silicate derived from natural smectic clay obtainable as Veegum from Vanderbilt Products (USA) and xanthan gums such as Keltrol T from Kelco.
The thixotropic agent is preferably present in an amount of 0.25% to 6% w/w, most preferably 0.25% to 2% w/w, and especially 0.25% to 1% w/w.
The compositions of the invention preferably include 1.5% to 8% w/w (most preferably 2.5% to 5% w/w) of an active depilatory agent. In the compositions of the invention, the depilatory agent will preferably act by reducing disulfide bonds in the hair and in principle any suitable reducing agent may be used. Suitable examples include mercaptans and sulfides such as organic sulfides, especially alkyl sulfides. Preferred depilatory agents are alkaline salts of thioglycolic acid such as the lithium, sodium, potassium or calcium salts. The potassium and calcium salts, alone or in mixture, are particularly preferred. Other suitable depilatory agents include thioglycerol, mercapto propionic acid and dithioerythritol.
Optionally, the compositions of the invention may further include an accelerator to facilitate the action of the depilatory agent, preferably in an amount of 3% to 10% w/w and particularly preferably not less than 5% w/w. A preferred accelerator is urea.
Additional polymeric thickening agents may be included in the compositions of the invention in amounts of 0 to 2% w/w, preferably 0 to 0.5% w/w, especially 0.1% w/w. Appropriate thickening agents can also contribute to the stability of the composition.
The compositions of the invention will preferably have a pH of at least 10.5, particularly preferably 11.5 to 12.7 (whilst the pH could be higher than 12.7, the latter value is the highest permitted in Europe). Suitable materials for achieving the desired pH include calcium hydroxide (at a concentration of 2% to 4% w/w) or alkaline silicates such as meta- or trisilicates.
The compositions of the invention will also desirably include texturizing agents to provide the composition with a desired texture or “body” whereby the depilatory composition can be maintained on the skin in contact with the hair and in the correct quantity to achieve a satisfactory degree of hair digestion in a suitable time. Suitable materials for
Delagneau Hubert
Ledon Philippe
Martin Georges
Fish & Richardson P.C.
Levy Neil S.
Reckitt Benckiser France
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