Depilatory composition

Abstract

A depilatory composition comprising: (a) a synthetic oil; (b) a source of alkalinity; (c) a depilatory agent; (d) water; and (e) a C8-20 alkyl hydroxyalkyl cellulose; and wherein the composition has a pH in the range of 10-12.9 at 30°C ± 0.5°C measured as a 10% w / v aqueous solution or as a neat composition is provided. The synthetic oil is selected from mineral oil, silicone, white oil, PPG-Stearyl ethers, synthetic squalane or combinations thereof. The source of alkalinity is preferably potassium hydroxide. The depilatory agent is preferably potassium thioglycolate. The C8-20 alkyl hydroxyalkyl cellulose is preferably cetyl hydroxyethyl cellulose. The use of a C8-20 alkyl hydroxyalkyl cellulose to provide a storage stable depilatory composition is provided, wherein the composition is stable for at least one week at a temperature of above freezing to up to 50°C. The use of the depilatory composition to remove hair from the body is provided. A method of hair removal using the depilatory composition is provided. A preferred composition comprises (a) mineral oil; (b) potassium hydroxide; (d) water; and (e) cetyl hydroxyethyl cellulose.

Description

Technical Field The present invention relates to storage stable depilatory compositions and methods of their use. The compositions provide effective hair removal within an acceptable contact time yet are well tolerated by the skin. Background Compositions for removing superfluous hair from mammals are well known. Such compositions include depilatory compositions which comprise a compound that degrades the keratin within the hair thus weakening it and allowing for removal. The depilatory compositions are applied to the area containing the superfluous hair, allowed to remain thereon to degrade the hairs and then removed from the area together with the degraded hairs. Depilatory compositions of this type typically comprise depilatory compounds which have a thiol group, such as potassium thioglycolate, and typically contain potassium hydroxide to provide a high pH which aids hair removal efficacy. Depilatory compositions typically have a pH in the range of from 10 to 12.9. Depilatory compositions are often stored at temperatures ranging from not far above freezing, for example in a refrigerator or in a cold warehouse, up to 50°C in hotter climates around the world. The range of temperatures to which a depilatory composition is subjected to during storage may have a negative impact on it resulting in, for example, coalescence, creaming, syneresis, coagulation, and / or phase separation. Such compositions are thereby rendered unsuitable for use. The presence of alkaline salts and the high pH also make depilatory compositions susceptible to phase separation especially at elevated temperatures. There remains a need for depilatory compositions which are storage stable (also referred to herein as stable on storage). In particular, there remains a need for depilatory compositions which are stable on storage when exposed to elevated temperatures up to 50°C (such as temperatures in the range of from above freezing up to 50°C) and which show for example good pH stability, do not phase separate and / or maintain an acceptable viscosity upon storage. There is also a need to provide depilatory compositions which do not thicken unacceptably during production as this can lead to production and processing difficulties. There is also a need to provide depilatory compositions which do not thicken unacceptably during storage at the above-mentioned temperatures as this can lead to difficulties in applying the compositions to the skin, and / or, in decanting the compositions from their packaging. An object of the present invention is to provide depilatory compositions comprising a depilatory agent which addresses one or more of the above disadvantages. Another object of the present invention is to provide depilatory compositions which storage stable. A particular objective is to provide depilatory compositions which show good pH stability, do not phase separate, maintain an acceptable viscosity and / or do not thicken unacceptably during production or during storage e.g. at the above-mentioned temperatures. Another object of the present invention is to provide depilatory compositions which are stable on storage at temperatures in the range of from above freezing to up to 50°C for more than one week. It is a further object of the present invention to provide storage stable depilatory compositions which exhibit good hair removal properties with a contact time of 10 minutes or less. Surprisingly, it has been found that one or more of the aforementioned disadvantages can be addressed by the inclusion of a Cg-Cao alkyl hydroxyalkyl cellulose, especially cetyl hydroxyethyl cellulose, in depilatory compositions comprising a depilatory agent and which compositions have a pH at 30°C the range of from 10 to 12.9. EP2355788A2 discloses a depilatory composition comprising a depilatory agent, an emollient selected from at least one of mineral oil, silicone oil, a source of alkalinity and water. No examples are given of a depilatory composition comprising an C8-C20 alkyl hydroxyalkyl cellulose. EP3348250A1 discloses a depilatory cream composition comprising, a depilatory agent, an emollient selected from at least one of mineral oil, silicone oil and emollient esters, and a silicone wax, a talc and / or polyamide resin. No examples are given of a depilatory composition comprising a C8-C20 alkyl hydroxyalkyl cellulose. Statement of invention In a first aspect, the present invention provides a depilatory composition comprising: (a) a synthetic oil, (b) a source of alkalinity, (c) a depilatory agent, (d) water, and, (e) a C8-C20 alkyl hydroxyalkyl cellulose, having a pH in the range of from 10 to 12.9 at 30°C ±0.5°C measured as a 10% w / v aqueous solution or as a neat composition. It has been found that depilatory compositions of the present invention remain stable on storage for at least one week, particularly at least two weeks, such as for five or six weeks at elevated temperatures up to 50°C. Furthermore, depilatory compositions according to the present invention provide for good hair removal properties yet are well tolerated by the skin. Compositions of the present invention provide for good hair removal within acceptable contact times with the skin / hair which further reduces the risk of skin irritation / damage. Typically, a contact time of 10 minutes or less is required for the compositions of the present invention to provide for effective hair removal and contact times of 8 minutes or less, and even 7 minutes or less, can be provided according to some embodiments of the invention. In a second aspect, the present invention provides the use of a C8-C20 alkyl hydroxyalkyl cellulose to provide a storage stable depilatory composition, which composition is stable for at least one week at temperatures of from above freezing to up to 50°C. Depilatory compositions of the present invention have been found to be storage stable for at least one week at temperatures in the range from above freezing to 50°C, such as in the range of from 5°C to 50°C, preferably 5°C to 40°C, such as at 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C and typically for up to 2, 5 or 6 weeks. A third aspect the invention provides the use of a depilatory composition according to any one of the preceding claims, to remove hair by applying the depilatory composition to part of a human body from which it is desired to remove hair and allowing the depilatory composition to contact the hair for a sufficient time to sufficiently degrade the hair to allow for its removal. According to a fourth aspect of the present invention there is provided a method of hair removal from human skin which includes the steps of: (i) applying a composition according to the invention to the skin of a human where superfluous hair is present; (ii) allowing the composition to remain in contact with the superfluous hair for a predetermined time; and (iii) subsequently removing the composition and superfluous degraded hair from the skin. The predetermined contact time is in the range of from 1 to 10 minutes. According to a fifth aspect of the present invention there is provided a method of producing a depilatory composition comprising combining a C8-C20 alkyl hydroxyalkyl cellulose with a composition comprising a synthetic oil. Detailed Description Definitions By the term "depilatory agent" as used herein is meant a compound which acts upon the keratin in the hair to chemically degrade it by breaking down the disulphide bonds in the keratin. This chemical degradation weakens the hair and allows for the degraded, and thus weakened, hair to be removed. It does not include rosin materials or waxes or any other ingredient(s) which do / does not exert a chemical-degradation action on the hair, but which rather, provide(s) an epilatory effect by adhering to the hair. By the term "bodily surface" as used herein is meant an external surface of a mammal including but not limited to the head, face, and body. Mucosal membranes are not included within this definition of "bodily surface". By the term "storage stable" as used herein is meant that a composition shows less than 10% by volume, or no, phase separation upon storage for the stated amount of time. The compositions furthermore preferably substantially maintain their pH, viscosity and / or colour upon storage for the stated amount of time. The pH of the compositions as referred to herein is the pH of the composition at 30°C ±0.5°C. The pH is measured as a neat composition or as a 10% w / v aqueous solution. Unless otherwise stated all amounts are given herein as wt% based on the total weight of the composition. Synthetic Oil Depilatory compositions of the present invention comprise a synthetic oil. The synthetic oil may be any synthetic oil suitable for use in depilatory compositions of the present invention. Suitable synthetic oils include mineral oil (such as heavy mineral oil and light mineral oil), silicone oils (such as polydimethylsiloxane, polymethyl phenyl siloxane and cyclic polysiloxanes), white oil, PPG-Stearyl Ethers (such as PPG-15 Stearyl Ethers and PPG-11 Stearyl Ethers) and synthetic squalene. Combinations of these oils may also be used. Most preferably the synthetic oil is a mineral oil. Depilatory compositions of the present invention may comprise of from 0.1 to 10 wt% of synthetic oil, preferably of from 0.25 to 7 wt% of synthetic oil, more preferably of from 0.5 to 5.0 wt%, most preferably if from 1.0 to 4 wt%, and especially of from 1.5 to 3.5 wt%, such as 1.75 to 3 wt%. Preferably compositions of the present invention comprise synthetic oil in an amount of for example, 1.25,1.50,1.75,1.80, 1.85,1.90, 1.95, 2.00, 2.25, 2.50, 2.75, 3.00, 3.25, 3.35, 3.75, 4.00, 4.25, 4.50, 4.75 or 5.00 wt%. Source of alkalinity Depilatory compositions of the present invention comprise a source of alkalinity. This source may include hydroxides, such as hydroxides of alkali and alkaline earth metals. Suitable hydroxides include sodium hydroxide, potassium hydroxide, calcium hydroxide and magnesium hydroxide or combinations thereof. Preferably, the source of alkalinity is potassium hydroxide. Alternatively, potassium hydroxide is employed together with calcium hydroxide. The source of alkalinity may be present in a total amount of from 0.01 to 5 wt%, preferably of from 0.1 to 4 wt%, for example, of from 0.2 to 2 or 3 wt%. When calcium hydroxide and potassium hydroxide are employed together, calcium hydroxide may be present in an amount of from 0.1 to 5 wt%, preferably of from 1 to 4 wt%, such as of from 1.5 to 3 wt%, and potassium hydroxide may be present in an amount of from 0.05 to 1.5, more preferably of from 0.1 to 1 wt%, most preferably of from 0.2 to 0.5 wt%. The amount of the alkali metal hydroxide added will depend upon the desired pH of the depilatory composition and other formulation considerations. However, it has been found that good hair removal properties and acceptable contact times combined with the compositions being well tolerated by the skin are achieved with compositions according to the invention which contain the above amounts of the alkali metal hydroxide. Depilatory Agent The depilatory agent present in the depilatory compositions of the present invention may be any compound which provides for the removal of hair by a chemical reaction, such as by degrading the keratin present in the hair. It is preferred that the depilatory active contains a thiol group and most especially that the depilatory active which contains a thiol group is selected from one or more of the group consisting of potassium thioglycolate, calcium thioglycolate, thioglycolic acid, dithioerythritol, thioglycerol, thioglycol, thioxanthine, thiosalicylic acid, N-acetyl-L-cysteine, lipoic acid, sodium dihydrolipoate 6,8-dithiooctanoate, sodium 6,8-diothiooctanoate, a hydrogen sulphide salt, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, ammonium thioglycolate, glyceryl monothioglycolate, monoethanolamine thioglycolate, monoethanolamine diammoniumdithiodiglycolate, ammonium thiolactate, monoethanolamine thiolactate, thioglycolamide, homocysteine, cysteine, glutathione, dithiothreitol, dihydrolipoic acid, 1,3-dithiopropanol, thioglycolamide, thioglycol-hydrazine, keratinase, guanidine thioglycolate, and cysteamine. It is preferred that the depilatory agent comprises potassium thioglycolate. According to one embodiment of the invention the depilatory agent comprises at least one of potassium thioglycolate, calcium thioglycolate and thioglycolic acid, in particular at least one of potassium thioglycolate and thioglycolic acid. Typically, the compositions include a thioglycolic acid salt, such as potassium thioglycolate and / or calcium thioglycolate. Whilst the compositions are typically prepared using the thioglycolates, during storage at least some of the thioglycolate is converted to thioglycolic acid. The depilatory agent is preferably present in an amount of from 0.5 to 10 wt% more preferably 1.0 to 9 wt%, such as 1.5 to 7 wt%, based on the total weight of the depilatory composition. It is preferred that the compositions of the invention comprise potassium thioglycolate and / or sodium thioglycolate and / or thioglycolic acid in the aforementioned amounts (in total if more than one of these are present). It is especially preferred that the compositions comprise the aforementioned amounts of potassium thioglycolate and / or thioglycolic acid Water Composition of the present invention comprise water. Suitably water is added to make up the balance of the overall composition to 100 wt%. The compositions may comprise of from 30 to 95 wt% water, preferably of from 40 to 90 wt%, more preferably of from 45 to 85 wt%, most preferably of from 45 to 80 wt%, such as of from 50 to 75 wt%, for example of from 55 to 70 wt%. Typically 40, 45, 50, 55, 60, 65 or 70 wt% water is present in the depilatory compositions of the present invention. Cg-C20 alkyl hydroxyalkyl cellulose Depilatory compositions of the present invention comprise C8-C20 alkyl hydroxyalkyl cellulose or mixtures thereof. Suitably the C8-C20 alkyl hydroxalkyl cellulose is selected from C10-C18 alkyl hydroxyalkyl cellulose, such as C12-C18 alkyl hydroxyalkyl cellulose suitably C12-Ci6 alkyl hydroxyalkyl cellulose, most preferably C14-C16 alkyl hydroxyalkyl cellulose and especially Cie (cetyl) hydroxyalkyl cellulose. The hydroxyalkyl group is preferably chosen from hydroxyethyl and hydroxypropyl groups. Either of these groups may be used in combination with any of the alkyl chains in the aforementioned C8-C20 alkyl chains. Suitably the C8-C20 alkyl hydroxalkyl cellulose is selected from C8-C20 alkyl hydroxyethyl cellulose or C8-C20 alkyl hydroxypropyl cellulose, preferably from C10-C18 alkyl hydroxyethyl cellulose or C10-C18 alkyl hydroxypropyl cellulose, more preferably C12-C18 alkyl hydroxyethyl cellulose or C12-C18 alkyl hydroxypropyl cellulose suitably C12-C16 alkyl hydroxyethyl cellulose or C12-Ci6 alkyl hydroxyethyl cellulose, most preferably C14-C16 alkyl hydroxyethyl cellulose or C14-Ci6 alkyl hydroxypropyl cellulose and especially Cie (cetyl) hydroxyalkyl cellulose. Suitably the C8-C20 alkyl hydroxyalkyl cellulose is cetyl hydroxyethyl cellulose, stearyl hydroxyethyl cellulose, cetearyl hydroxyethyl cellulose, lauryl hyroxyethyl cellulose, myristyl hydroxyethyl cellulose, cetyl hydroxypropyl cellulose, stearyl hydroxypropyl cellulose, cetearyl hydroxypropyl cellulose, lauryl hyroxypropyl cellulose, myristyl hydroxypropyl cellulose, hydroxypropyl ethyl cellulose or hydroxyethyl ethyl cellulose, or, combinations thereof. cetyl hydroxyethyl cellulose is especially preferred according to the present invention. Suitably, the depilatory compositions of the present invention may comprise of from 0.001 to 5 wt% of the Cg-Czo alkyl hydroxyalkyl cellulose, preferably of from 0.01 to 2 wt%, more preferably of from 0.01 to 1.5 wt%, such as of from 0.02 to 1 wt%, most preferably 0.02 to 0.5 wt%. Preferably depilatory compositions of the present invention may comprise 0.02, 0.05, 0.1, 0.20, 0.30, 0.40, 0.45 or 0.50 wt% of the C8-C20 alkyl hydroxyalkyl cellulose. In particular, these amounts of cetyl hydroxymethyl cellulose, cetyl hydroxyethyl cellulose, cetyl hydroxypropyl cellulose, cetyl hydroxybutyl cellulose or cetyl hydroxypentyl cellulose or combinations thereof may be included in the compositions of the invention. Most preferably depilatory compositions of the present invention comprise cetyl hydroxyethyl cellulose in an amount stated above. pH Depilatory compositions of the present invention have a pH in the range of from 10 to 12.9. Preferably the depilatory compositions have a pH in the range of from 11.0 to 12.7, more preferably in the range of from 11.2 to 12.6, most preferably in the range of from 11.5 to 12.5, for example in the range of from 11.5 to 12.5 including all ranges in between, such as, 11.1, 11.2, 11.3,11.4, 11.5, 11.6, 11.7,11.8,11.9, 12.0, 12.1,12.2, 12.3,12.4, 12.5,12.6, 12.7. The pH values of the compositions are those as measured at 30°C ± 0.5°C. The pH may be measured as a neat sample or as a 10% w / v aqueous solution. When the pH is measured as a neat composition, the pH will typically be slightly higher than that of a 10% w / v solution of the same composition and will usually vary between 0.1 to 0.3 pH units compared to the pH of the 10% w / v solution. The pH of the compositions of the invention should ideally be within the above ranges when measured at 30°C ±0.5°C both as a neat composition and as a 10% w / v aqueous solution. Form of the compositions Depilatory compositions of the present invention may be of any suitable form. Preferred forms of the compositions include gels, mousses, foams, creams, lotions, or oil-water emulsions. The form may be chosen according to the intended area of application for the compositions. Especially preferred forms of the compositions include oil-water emulsions, creams, mousses, and foams. Especially preferred compositions include oil-water emulsions and creams. Optional Ingredients Depilatory compositions of the present invention may comprise additional optional ingredients. Such optional ingredients may vary according to the physical format of the compositions and other formulation considerations. Depilatory compositions of the present invention may comprise one or more surfactant(s). The surfactant may be anionic, cationic, or non-ionic. It is preferably non-ionic. Examples of suitable surfactants include cetearyl phosphate, cetearyl glucoside, ceteareth 20, steareth 2 or steareth 21. When present, surfactants are preferably present in an amount of from 0.5 to 10 wt relative to the weight of the depilatory composition, more preferably from 0.6 to 2.0 wt%. Depilatory compositions of the present invention may further comprise fatty alcohols such as cetearyl alcohol, cetyl alcohol, behenyl alcohol, stearyl alcohol which act as coemulsifiers. These co-emulsifiers may be present in amount of 0.5 to 10 wt%, more preferably 2 to 6 wt%. These ingredients do not form part of the synthetic oil used in the compositions of the invention. Depilatory compositions of the present invention may further comprise a humectant. Suitable humectants include polyols, such as glycerin, propylene glycol and butylene glycol. Glycerin is preferred. The humectant may be present in an amount of 0.001 to 10 wt%, preferably by 0.5 to 5 wt%, most preferably 1.0 to 4.0 wt%. Optionally, depilatory compositions of the present invention may comprise an accelerator to accelerate the keratin degradation reaction. Suitable accelerators include urea, thiourea, dimethyl isosorbide, ethoxydiglycol and methyl propyl diol. Preferably the accelerator is urea or methyl propyl diol. The depilatory composition according to the invention preferably comprises of from 0.5 to 15 wt% of an accelerator, more preferably 1 to 12 wt%, even more preferably 1.5 to 10%, for example 2 to 8 wt%, such as, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0,10.0,11.0 or 12.0 wt%. Depilatory compositions of the present invention may comprise other optional ingredients, such as pigments and fillers, such as clays. Examples of suitable clays include, kaolin, bentonite, sodium magnesium silicate, magnesium trisilicate and titanium dioxide. Preferably depilatory compositions of the present invention comprise a clay of the aforementioned types, especially kaolin. When present the clay, especially kaolin, is preferably present in an amount of from 0.01 to 10 wt%, more preferably of from 0.1 to 5 wt%, most preferably of from 0.15 to 2wt%, for example of from 0.2 to lwt%, such as 0.01, 0.02, 0.05,1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 or 5.0 wt%. Pigments may be included in any suitable amount. Typically pigments, if present, may be included in an amount of from 0.001 to 1 wt%, preferably of from 0.002 to 0.5 wt%, such as from 0.002 to 0.1 wt% Depilatory compositions of the present invention may comprise a chelating agent, such as sodium gluconate, EDTA or tetrasodium EDTA. The chelating agent may be present in an amount of less than 1 wt%, preferably 0.01 to 0.5 wt%, for example 0.05 to 0.1 wt%. Depilatory compositions may also include an additive that inhibits phase separation. Suitable additives include polymers or copolymers of acrylic acid, for example, an acrylate copolymer. Such additives may be present in an amount of up to 2 wt%, preferably less than 1 wt%, more preferably less than 0.5 wt%, for example 0.1 to 0.4 wt%. Optionally, compositions of the present invention may comprise skin care additives such as aloe vera and Vitamin E. Such additives are typically employed in amounts of less than 1 wt%, for example, 0.1 to 0.5 wt% of the composition. According to one aspect of the present invention, the depilatory composition comprises: (a) 0.01 to 10 wt% synthetic oil, (b) 0.1 to 10 wt% potassium hydroxide, (c) 0.5 to 10 wt% potassium thioglycolate and / or thioglycolic acid, (d) at least 40 wt% water, (e) 0.01 to 5 wt% C8-C20 alkyl hydroxyethyl cellulose, and having a pH in the range of from 10 to 12.9 at 30°C as measured as a 10% w / v aqueous solution or as a neat composition. According to another aspect of the present invention, the depilatory composition comprises: (a) 0.01 to 10 wt% mineral oil, (b) 0.1 to 10 wt% potassium hydroxide, (c) 0.5 to 10 wt% potassium thioglycolate and / or thioglycolic acid (d) at least 40 wt% water, (e) 0.01 to 5 wt% C8-C20 alkyl hydroxyethyl cellulose, and having a pH in the range 10 to 12.9 at 30°C as measured as a 10% w / v aqueous solution or as a neat composition. According to a preferred aspect of the present invention, the depilatory composition comprises: (a) 0.5 to 7 wt% mineral oil, (b) 0.1 to 1 wt% potassium hydroxide, (c) 0.5 to 7 wt% potassium thioglycolate and / or thioglycolic acid, (d) at least 60 wt% water, (e) 0.05 to 3 wt% cetyl hydroxyethyl cellulose, and having a pH in the range 10.5 to 12.8 at 30C as measured as a 10% w / v aqueous solution or as a neat composition. In another preferred aspect of the present invention, the depilatory composition comprises: (a) 1.5 to 3.5 wt% mineral oil, (b) 0.05 to 1.0 wt% potassium hydroxide, (c) 0.5 to 7 wt% potassium thioglycolate and / or thioglycolic acid, (d) at least 65 wt% water, (e) 0.025 to 0.5 wt% cetyl hydroxyethyl cellulose, and having a pH in the range 11.0 to 12.7 at 30C as measured as a 10% w / v aqueous solution or as a neat composition. In another preferred aspect of the present invention, the depilatory composition comprises: (a) 1.7 to 1.9 wt% mineral oil, (b) 0.2 to 1.0 wt% potassium hydroxide, (c) 0.5 to 7 wt% potassium thioglycolate and / or thioglycolic acid, (d) at least 65 wt% water, (e) 0.05 to 0.3 wt% cetyl hydroxyethyl cellulose, and having a pH in the range 11.0 to 12.7 at 30C as measured as a 10% w / v aqueous solution or as a neat composition. The present invention also provides a method of removing hair from a bodily surface of a mammal, such as the head, body or face by i) applying a composition according to the invention to a bodily surface of the mammal, from where it is desired to remove hair, ii) allowing the composition to contact the bodily surface for a period of time from 1 to 10 minutes, iii) and subsequently removing the composition and degraded hair from the bodily surface. The depilatory compositions of the present invention of the invention may be applied and removed by any suitable method according to the type of composition. Such methods are well known in the art. For example, a cream or lotion may be applied to the area to be treated either by hand or with the aid of a device (such as a spatula, roll-on, tube applicator or similar device). Mousse or foam compositions may be applied directly from a dispensing device such as an aerosol can or pump dispenser. After the required contact time between the unwanted hairs and the depilatory composition of the invention has elapsed and the unwanted hairs have been degraded, the depilatory composition and the degraded hairs may be removed by any suitable means, for example, in the same way as in which the composition was applied. Typically, a spatula or similar device especially one with a substantially straight edge, or a flexible object such as a foam / tissue / cloth / wipe type object may be used to remove the depilatory composition and the degraded hairs. This is achieved simply by moving the spatula or flexible object around the area to which the depilatory composition has been applied to 'scoop' up the same. In this way the depilatory composition is lifted from the area to which it has been applied and can be removed. Any residual composition may be removed by, for example, rinsing with water. Alternatively, the composition may be rinsed away with water. The depilatory compositions of the present invention are typically allowed to contact the bodily surface, e.g. skin or hair, for at least 1 minute, preferably at least 3 minutes, such as 4 minutes. However, to reduce any potential skin irritation from the use of the compositions of the invention it is preferred that the contact time is 10 minutes or less, preferably 8 minutes or less, such as 7 minutes or less. Preferred contact times for the compositions of the invention and the hair to be removed are in the range of from 2 to 8 minutes, more preferably 3 to 7 minutes, such as 4 to 7 minutes (including ranges therebetween). It has been found that the compositions of the invention provide effective hair removal yet are well tolerated by the skin when these contact times are used. Ideally depilatory compositions of the present invention remove as high a percentage as possible of unwanted hair in a single treatment. As the application method, and result achieved, can very slightly with the user (as this is influenced by hair type treated, application method, contact time and personal levels of expectation etc.) it is generally considered that hair removal results above about 50% would be considered as acceptable by the user. Hair removal results higher than this are preferred such as at least 55%, more preferably at least 65%, even more preferably at least 70%, or even more preferably at least 75% and ideally above 80%, 85% or 90%. The invention will now be described in more detail with reference to the following nonlimiting examples. Further examples within the scope of the present invention will be apparent to the person skilled in the art. Examples The following examples illustrates comparative compositions and preferred embodiments of the invention. It is to be understood that these examples are provided by way of illustration only and that further useful compositions falling within the scope of the present invention and the claims may be readily produced by one skilled in the art without deviating from the scope and spirit of the invention. Method The compositions in Table 1 were produced using the following method of preparation: 1. Mix together the mineral oil, Steareth 2, Steareth 21, modified paraffin wax (if used) and cetearyl alcohol with heating to a minimum of 75°C to ensure they are fully dissolved. 2. Separately, thoroughly mix together the calcium hydroxide, kaolin and sodium gluconate in the main volume of the water (approximately 45-50% of the formulation quantity) ensuring the ingredients are fully dispersed, then heat to 70-75°C. 3. Emulsify the composition from step 1 into the mixture from step 2 when both are at the stated temperature and mix until uniformity of the composition is achieved. 4. Commence cooling of the mixture from step 3. When the temperature has reached approximately 60°C add the glycerol and mix until uniform. 5. When the mixture in step 4 reaches approximately 50°C, add a premixed gel phase of C8-C20 hydoxyalkyl cellulose (or the HPMC) in 20 wt% water to the batch and again mix until uniform. 6. When the temperature of the mixture reaches below 45°C add any fragrance, dyes and the cosmetic / emotive ingredients (e.g. aloe barbadensis (vera) one by one and mix until uniform. 7. Once the temperature of the composition reaches 38°C or below, add the potassium thioglycolate followed by the potassium hydroxide. 8. Finally, homogenise the composition to ensure uniformity and then cool to below 30°C with stirring. Table 1. Compositions Composition Number wt% based on the total weight of the composition Comparative Compositions Compositions of the invention Ingredient 1 2 3 4 5 6 7 8 9 Calcium hydroxide 3.33 3.33 3.33 3.33 3.33 3.30 2.50 3.33 2.50 Sodium gluconate 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Glycerol 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 Kaolin 0.20 0.20 0.20 0.20 0.20 0.20 0.50 0.20 0.50 *Cetyl HEC 0.20 0.25 0.20 0.05 0.10 0.10 **HPMC K15M 0.25 ***HPMC K4M 0.40 0.20 ****Potassium hydroxide (as a 50% solution) 0.80 0.80 0.80 0.80 0.80 0.80 0.20 0.40 0.20 Cetearyl alcohol 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 Aloe barbadensis 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Mineral oil 1.75 1.75 1.75 1.75 1.75 3.00 1.75 1.75 1.75 Paraffin wax 0.50 Steareth-21 1.83 1.83 1.83 1.83 1.83 1.83 2.10 1.83 2.10 Streareth -2 0.833 0.833 0.833 0.833 0.833 0.833 0.833 0.833 0.833 Fragrance 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.75 1.50 Dye 0.023 0.002 *****Potassium thioglycolate (as a 44% solution) 12.90 12.90 12.90 12.90 12.90 12.90 10.00 12.90 10.00 Deionised water to 100% To 100 To 100 To 100 To 100 To 100 To 100 To 100 To 100 To 100 *Cetyl hydroxyet lyl cellulose, Natrosol™ Plus 330 CS, availab e from Ashlanc TM 5 **Hydroxy propyl methyl cellulose, Methocel™ K15M, available from International Flavours &Fragrances, Inc (IFF). *** Hydroxy propyl methyl cellulose, Methocel™ K4M, available from IFF. ****Concentration of active is 0.4 wt% for compositions 1 to 6, 0.1 wt% for compositions 7 and 9 and 0.2 wt% for composition 8. 10 *****Concentration of active is 5.7% wt% for compositions 1 to 5 and 7, and 4.44 wt% for compositions 7 and 9. Temperature Stability Testing Viscosity, pH, appearance and thiogylcolic acid levels were measured initially and after certain storage periods to assess temperature stability of the compositions. Samples of compositions 1 to 9 were sealed in plastic HDPE and aluminium barrier tubes and placed inside temperature-controlled rooms and ovens at each of 5°C, 40°C and 50°C for a maximum of 6 weeks. Samples were evaluated at various timepoints within the 6 weeks. Final assessments were performed at 6 weeks and 50°C conditions for all compositions. Viscosity Testing Viscosity measurements were carried out within the temperature range of 20 ± 3°C using a Brookfield DVii+ viscometer, using a T-bar spindle D at 5rpm, with a 150ml stability pot with a 5cm diameter. A helipath was associated with the viscometer and was turned on and 5 measurements were taken; one at each of 30, 35, 40, 45 and 50 seconds. The Helipath stand is designed for the measurement of non-flowing substances. It consists of T-shaped mobiles and a drive motor oscillating at constant speed, mounted on the rack of the viscometer and generating a helical movement to allow measurement of very viscous products, such as creams, without forming a hole. The drive motor slowly lowers or raises the viscometer so that the T-bar spindle creates a helical path through the test sample thus eliminating the problem of channelling. A mean average of the 5 viscosity measurements above was calculated and represents product viscosity. Viscosity measurements were carried out on the compositions stored at 5°C, 40°C and 50°C at week 1 of storage and at 5°C and 50°C at week 6 of storage. pH Testing The pH of the compositions was measured using combined electrode with standard KCI electrolyte and a fixed joint diaphragm and a combined temperature sensor with a potassium glass sensor. pH measurements were carried out at 30°C ± 0.5°C and were measured either neat or as a 10% w / v aqueous solution of the sample, as stated according to the results. Formulations were transferred to a container either neat or as a 10% aqueous solution, placed in a water bath and allowed to equilibrate to 30°C ± 0.5°C for at least 30 minutes. The pH electrode was plunged into the sample until the pH value settled. Frequent probe cleaning, calibration and buffer checks were performed to ensure consistent and reliable results. Thioglycolic acid Testing Thioglycolic acid (TGA) content was measured via iodometric titration using a platinum electrode. The compositions were diluted by adding 1.4g to 40g of water and fully solubilised in water. Appearance - Phase separation Organoleptic tests were performed by removing the compositions from temperature-controlled rooms and ovens and they were acclimatised at room temperature for 24h. To assess a composition it was gently squeezed out of its original packaging onto a white tray and assessed visually and by smell for emulsion stability, appearance of water droplets, odour and colour. Appearance assessments were carried out on compositions stored at 5°C, 40°C and 50°C at week 1 of storage and at 5°C and 50°C at week 6 of storage. To assess the appearance, a water separation assessment score was recorded (to note the absence of presence of water droplets) using the following appearance scoring system: 1. No water drops (pass) 2. 1-3 water drops (pass) 3. 4-5 water drops (pass) 4. 6+water drops (fail) The results of the water separation assessment (appearance) are given in Table 2. Compositions 1, 2 and 3 are the comparative compositions in Tables 2 to 5. Results Table 2. Appearance Composition Number Appearance score - (Water droplet) 1 2 3 4 5 6 7 8 9 1 Week 5°C 1 1 1 1 - 1 - - - 40°C 1 1 1 1 - 1 - - - 50°C 1 1 1 1 1 1 - - - 6 Weeks 5°C 1 1 1 1 - 1 - - - 50°C 4 split 4 split 4 split 1 * 1 1 1 1 1 (- not tested), (*3 samples scored 1,1 sample scored 3) The results in Table 2 demonstrate that comparative compositions 1, 2, 3 which contain HPMC had all separated at 6 weeks storage at 50°C. Compositions 4 to 9 (according to the invention) that comprise cetyl hydroxyethyl cellulose had not separated at 6 weeks storage at 50°C. These results demonstrate the good storage stability at 50°C for the compositions of the invention, whereas, the comparative compositions had all split and were not storage stable. Compositions 4 and 6 were the only compositions of the invention which was tested for storage stability at 5°C. Both compositions exhibited good storage stability at 5°C. The viscosity of the comparative examples and of the compositions of the invention was measured using the method described above. Viscosity measurements were taken on samples which had been stored at the stated temperature for the stated time in Table 3. Table 3. Viscosity Composition Number Viscosity (Cps) 1 2 3 4 5 6 7 8 9 Initial 71360 87360 70400 141400 174880 185400 93973 108527 114480 1 Week 5°C 51360 30800 30560 123600 - 109580 - - - 40°C 73680 43920 42720 164806 - 171800 - - - 50°C 24640 26320 - 170800 139000 160000 - - - 6 Weeks 5°C - - - - - - - - - 50°C split split split 145800 140600 158100 87800 91713 89567 (- not tested) The results in Table 3 demonstrate that compositions 4, 5, 6, 7, 8 and 9 of the invention (comprise Cetyl hydroxyethyl cellulose showed little or no change in viscosity (only small 5 variations in viscosity which were within the acceptable error margins) after 6 weeks storage at 50°C. This demonstrates the excellent elevated temperature storage stability properties of the compositions of the invention. The comparative compositions had all split during storage for 6 weeks and so no viscosity measurements could be made for them. The pH of the comparative examples and of the compositions of the invention was 10 measured using the method described above. The results are given in Table 4. Table 4. pH Composition Number pH 1* 2* 3* 4* 5* 6* 7t 8+ 9+ Initial pH 12.24 12.33 12.35 12.32 12.28 12.28 12.47 12.46 12.48 6 Weeks 5°C - - - - - - - - 50°C split split split 12.23 12.23 12.22 12.46 12.47 12.47 (*measured as a 10% w / v aqueous solution, + measured neat, - not tested) The results in Table 4 demonstrate that the pH of the compositions of the invention was 15 not affected on storage for 6 weeks at 50°C. The comparative compositions had all split during storage for 6 weeks and so no pH measurements could be made for them. The Thioglycolic acid (TGA) content of the comparative examples and of the compositions of the invention was measured using the method described above. The results are given in Table 5. Table 5. Thioglycolic Acid Composition Number TGA% 1 2 3 4 5 6 7 8 9 Initial 3.87 3.89 3.73 3.95 - 3.92 3.05 3.93 3.02 6 Weeks 5°C - - - - - - - - - 50°C split split split 3.95 4.03 3.76 3.00 3.97 3.00 5 (- not tested) The results demonstrate that the level of thioglycolic acid (TGA) did not drop significantly upon storage for 6 weeks at 50°C for the compositions of the invention. The comparative compositions had all split during storage for 6 weeks and so no measurement of the level of TGA was possible for those compositions. 10 Compositions according to the invention have been showed to exhibit superior storage stability (including appearance / water droplet presence, viscosity, pH and stability of TGA content) compared to the comparative examples which do not comprise a synthetic oil together with a C8-C20 alkyl hydroxyalkyl cellulose. Hair Removal Efficacy Test 15 The depilatory compositions in Table 6 are compositions according to the invention and were made using the above method of manufacture. The Frescolat™ MGA Plus is added in step 6 of the above method. They were tested for hair removal efficacy (expressed as a mean result) using the method below. Table 6. Compositions Composition Number wt% Ingredient 10 11 12 13 14 Mineral Oil 1.750 1.750 1.850 1.750 1.850 Cetyl Hydroxyethyl cellulose* 0.200 0.200 0.200 0.225 0.200 Glycerin BP 1.000 1.000 3.500 1.000 2.000 Steareth-2 0.833 0.833 0.833 0.833 0.833 Steareth-21 1.830 1.830 1.830 1.830 1.830 Potassium Hydroxide 50% 0.800 0.800 0.800 0.800 0.800 Kaolin 0.200 0.200 0.200 0.200 0.200 Calcium hydroxide 2.500 3.330 3.330 2.500 3.330 Cetearyl Alcohol 30 / 70 6.000 6.000 6.000 6.000 6.000 Sodium gluconate 0.100 0.100 0.100 0.100 0.100 Potassium thioglycolate 10.00 12.90 12.90 10.00 12.90 Aloe Vera 0.010 0.010 0.010 0.010 0.010 Fragrance 0.650 0.750 0.750 0.650 0.750 Fragrance (mint) 0.100 Frescolat™ MGA Plus** 0.750 Deionised Water To 100 To 100 To 100 To 100 To 100 *Natrosol ™ Plus 330 CS available from Ashland™ . ** a cooling agent mixture of menthone glycerin acetal and menthol available from Symrise. 5 Method Hair removal tests were carried out on the lower leg of participants. The total number of test participants was 41. Six test sites, (3 per leg), of 10 cm x 5 cm were marked out. Hairs longer that 5mm were 10 trimmed to equal length of approximately 3mm. Macrophotographs were taken of each test site prior to application of the depilatory cream formulation. Each of the depilatory cream compositions were applied by trained personnel to the test sites in a randomised rotation. One site was left untreated. The depilatory cream 15 compositions were left in contact with the skin for either 4.5 minutes, 5.5 minutes or 6.5 minutes depending upon the amount of depilatory active in the composition. The application times are based on minimum application times for creams depilatories. 1.5 minutes is added to represent the time it takes on average to apply cream to both lower legs. After the relevant contact time was reached, the depilatory cream composition was removed with a spatula. A second macrophotograph was taken of each test site after removal. The number of hairs before application and after removal of the depilatory cream 5 composition were counted and the percentage hair removed determined. The success criteria for a composition to be considered as passing the hair removal test was at least 70% hair removal: this being considered as an acceptable level of hair removal for the consumer. The results of the hair removal tests are given in Table 7. 10 Table 7 - Hair Removal Test Results Formulation Test Time (mins) Mean Reduction % Std Deviation % Lower confidence interval % 10 5 89.46 8.68 86.31 6 92.41 7.18 89.92 11 3 90.74 9.65 87.32 4 90.15 9.75 86.69 12 3 78.83 17.10 72.63 4 89.60 7.56 86.92 13 5 88.08 11.23 84.01 6 94.10 8.17 91.32 14 3 88.89 8.42 85.97 4 91.82 6.47 89.53 It can be seen from the results that the mean reduction in hair was high across all of compositions 10 to 14 with a mean reduction greater than 80% hair removal in 3 minutes, at lower confidence interval 5% significance. The mean of all hair removal test results 15 combined was 89.4% mean reduction in hair presence. All compositions tested resulted in excellent hair removal at 3 minutes contact time with the skin and hairs.

Claims

1. A depilatory composition comprising:(a) a synthetic oil,(b) a source of alkalinity,(c) a depilatory agent,(d) water, and,(e) a C8-C20 alkyl hydroxyalkyl cellulose, andhaving a pH in the range 10 to 12.9 at 30°C ±0.5°C measured as a 10% w / v aqueous solution or as a neat composition.

2. A depilatory composition according to claim 1, wherein the synthetic oil is selected from mineral oil, silicone, white oil, PPG-Stearyl Ethers, synthetic squalane or combinations thereof.

3. A depilatory composition according to either one of claim 1 or 2, wherein the synthetic oil is mineral oil.

4. A depilatory composition according to any one of the preceding claims, wherein the composition comprises synthetic oil in an amount of from 0.01 to 10 wt%.

5. A depilatory composition according to any one of the preceding claims, wherein the source of alkalinity comprises potassium hydroxide.

6. A depilatory composition according to any one of the preceding claims, wherein the source of alkalinity is present in a total amount of from 0.01 to 5 wt%.

7. A depilatory composition according to any one of the preceding claims, wherein the depilatory agent is potassium thioglycolate.

8. A depilatory composition according to any one of the preceding claims, wherein the composition comprises of from 0.5 to 10 wt% depilatory agent.

9. A depilatory composition according to any one of the preceding claims, wherein the composition comprises of from 30 to 95 wt% water.

10. A depilatory composition according to any one of the preceding claims, wherein the Cg-C20 alkyl hydroxyalkyl cellulose is selected from C10-C18 alkyl hydroxyalkyl celluloses.

11. A depilatory composition according to Claim 10, wherein the C10-C18 alkyl hydroxyalkyl cellulose is Cis alkyl hydroxyalkyl cellulose.

12. A depilatory composition according to Claim 11, wherein the Cie alkyl hydroxyalkyl cellulose is cetyl hydroxyethyl cellulose.

13. A depilatory composition according to any one of the preceding claims, wherein the Cg-C20 hydroxyalkyl cellulose is present in an amount of from 0.001 to 5 wt %.

14. A depilatory composition according to any one of the preceding claims, comprising:(a) 1.7 to 1.9 wt% mineral oil,(b) 0.2 to 1.0 wt% potassium hydroxide,(c) 0.5 to 7 wt% potassium thioglycolate and / or thioglycolic acid,(d) at least 65 wt% water,(e) 0.05 to 0.3 wt% cetyl hydroxyethyl cellulose, andhaving a pH in the range 11.0 to 12.7 at 30C as measured as a 10% w / v aqueous solution or as a neat composition.

15. A depilatory composition according to any one of the preceding claims, wherein the composition has a pH in the range of from 11.0 to 12.7.

16. A depilatory composition according to any one of the preceding claims, which composition is storage stable at 50°C for at least one week.

17. The use of a C8-C20 alkyl hydroxyalkyl cellulose to provide a storage stable depilatory composition, which composition is stable for at least one week at temperatures of from above freezing to up to 50°C.

18. The use of a depilatory composition according to any one of the preceding claims, to remove hair by applying the depilatory composition to part of a human body from which it is desired to remove hair and allowing the depilatory composition to contact the hair for a sufficient time to sufficiently degrade the hair to allow for its removal.

19. A method of hair removal from human skin which includes the steps of:(i) applying a composition according to any one of Claims 1 to 16 of the invention to the skin of a human where superfluous hair is present;(ii) allowing the composition to remain in contact with the superfluous hair for a predetermined time; and(iii) subsequently removing the composition and superfluous degraded hair from the skin.

20. A method as claimed in claim 19, wherein the contact time on the skin is from 1 to 10 minutes.

21. A method of producing a depilatory composition comprising combining a C8-C20 alkyl hydroxyalkyl cellulose with a composition comprising a synthetic oil.Application No: GB2315807.4 Examiner: Dr Alistair LongshawClaims searched: 1-16, 18-20 (in full) and 17, 21 Date of search: 7 March 2024(in part)Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance v A 1-21 Mintel GNPD (mintel.com), Record ID 10724054, "2 Minute Cream Hair Remover", Reckitt Benckiser, April 2023 - See whole document, especially Product Description and Ingredient List X 1-21 WO 2015 / 149975 Al (L'OREAL) - See whole document, especially paragraphs [0001], [0006]-[0009], [00146]-[0184], [00192]-[00196], [00227]; and Examples 1 and 3 A - CN 115607462 A (SHANGHAI FEICHUANG TECHNOLOGY AND TRADE CO., LTD.) - See especially paragraphs [0027]-[0030], [0034], [0038]-[0040] and [0049] A - CN 112156039 A (GUANGZHOU DOVE COSMETICS CO., LTD.) - See especially paragraphs [0005]-[0017], [0055]-[0061]Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From A61K 0008 / 92 01 / 01 / 2006 A61K 0008 / 06 01 / 01 / 2006 A61K 0008 / 19 01 / 01 / 2006 A61K 0008 / 46 01 / 01 / 2006 A61K 0008 / 73 01 / 01 / 2006 A61Q 0009 / 04 01 / 01 / 2006