SKIN AND HAIR-CARE COMPOSITIONS

Abstract: A skin- or hair-care composition containing silica additionally comprises a C₂₋₄ alkyl ester of a di, tri- or tetrabasic carboxylic acid or hydroxy-carboxylic acid (optionally acetylated). The alkyl ester may be dissolved in an aqueous solvent system.

Description: This invention relates to improvements in or relating to skin- and hair-care compositions containing silica. The incorporation of silica into skin- and hair-care compositions for other purposes is known. For example, EP-A-0 118 180 discloses the use of silanised silica gel as an anti-seborrheic agent, and EP-A-0 117 621 discloses its use in a deodorant. FR-A-2192799, FR-A-2192 798 and US-A-3903258 disclose antiperspirant compositions in which aluminium salts are dispersed in liquid esters including, inter alia, triethylcitrate and triethyl acetyl citrate. The examples show the use of small amounts (0.35% by wt) of silica as a suspending agent. GB-A-1461991 describes similar compositions in which the carrier is an ester of formula R-OOC-R₁-COOR, where R is an alkyl group having 2 to 6 carbon atoms and R₁ is a hydroxy substituted saturated alkylene radical having 4 to 8 carbon atoms and 2 6o e hydroxyl groups. The examples disclose use of 0.2% by weight silica as a suspending agent. A disadvantage of previously proposed compositions that are not loaded with antiperspirant salts is that the level of silica has been limited by its tendency to become visible as an unsightly residue on hair or areas of dry (non-greasy) skin. It has now surprisingly been found that this problem can be overcome by the incorporation into the composition of esters of citric, tartaric and succinic acid. Such esters are commercially available, and some, the α-hydroxy derivatives, have been proposed for use in the treatment of skin disorders such as dandruff. They have also been used as carriers for antiperspirant salts, as described above. They are non-volatile and have the texture of a light oil. However, they are soluble to varying degrees in aqueous alcohols, and most show significant water solubility. Furthermore, they have been found to have the same refractive index as commercially available silicas. As a result, when the silica particles are coated with one of these esters, during which process any air pockets are automatically excluded, they become transparent. The present invention is based on these findings. A first aspect of the invention therefore provides a skin- or hair-care composition comprising at least 0.5% w/w silica, a C₂₋₄ alkyl ester of citric, tartaric or succinic acid, wherein any hydroxy residue is optionally acetylated, and an aqueous carrier therefor. Preferred alkyl esters include ethyl and butyl. Advantageously, the ester is selected from triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, diethyl tartrate and diethyl succinate. Preferably the ester is triethyl citrate or tributyl citrate or their acetylated derivatives. A particular advantage of the esters of the invention is that, unlike other commonly available oils, they have a significant degree of solubility in aqueous solvent systems. Also, unlike many carboxylic acid esters, such as ethyl lactate, they are resistant to hydrolysis when suspended in water or aqueous alcohols. Thus they can be formulated into a stable non-oily composition. Thus, a further aspect of the invention provides a skin- or hair-care composition comprising at least 0.5% w/w silica, and an ester as defined above dissolved in an aqueous solvent system. Typically the aqueous solvent system is an aqueous alkanol or water, preferably aqueous ethanol. Preferably ethanol is included in the composition at from 2% to 80% w/w, more preferably 10% to 70% w/w, especially about 30% w/w in antisebborheic and anti-acne preparations, and about 70% w/w in deodorant preparations. On application to the skin or hair, the aqueous solvent system evaporates. Once out of solution, the ester becomes associated with the silica particles and masks them by rendering them transparent as described above. The association is particularly strong in the case of hydrophobic silicas such as silanised silica gel, making it particularly suitable for incorporation into compositions of the type described in EP-A-0 118 180. Surprisingly, it has been found that the anti-seborrheic properties of silanised silica gel remain largely unaffected by adsorption of the esters of the invention in the amounts required to mask the presence of the silica. As indicated above, the silica in the compositions of the invention is preferably a hydrophobic silica such as silanised silica gel. However, it is envisaged that the improvement of the present invention may be applied to any skin- or hair-care composition containing silica, for example as a microencapsulating agent for other active ingredients, or as a deodorant ingredient in which particulate silica is included to increase the evaporative surface area and rapidly remove sweat. The discovery on which the present invention is based has been found to apply to a wide range of commercially available hydrophilic and hydrophobic silicas, including silica gels and precipitated silicas such as pyrogenic (fumed) silica; examples include Cab-O-Sil M-5, Sipernat D10, Sipernat D17 and Aerosil R972 (all Trade Marks). Suitably the silica has a mean particle size of 0.1 to 20µm, the particles consisting of aggregates of smaller particles. Preferably the composition comprises at least 0.5% w/w of the silica, more preferably about 2%. The proportion of silica will not normally exceed 10% w/w, more preferably about 5% w/w. The amount of ester will normally be selected to give an ester:silica ratio of at least 1:1, preferably about 2:1. Thus, the composition will typically contain at least 1% w/w, preferably about 4% w/w, ester. In the above-mentioned aqueous compositions of the invention, the amount of ester will not normally exceed the solubility limit thereof, which will obviously vary according to the ester used, the solvent system used, and the other ingredients present, and may be as high as 30% w/w. However, it is normally preferred that the ester be present in an amount of up to 20% w/w, more preferably up to 10% w/w. As used herein, 'skin- or hair-care composition' denotes any composition which is to be applied to the skin and/or hair for its beneficial therapeutic and/or cosmetic properties, including organoleptic properties. Suitably the composition is presented in a conventional skin- or hair-care form, for instance as a roll-on formulation, gel, cream, lotion or stick, and will contain conventional carriers and diluents known to be suitable for each particular presentation. The compositions may also comprise optional accessory ingredients such as perfume, colouring and preserving agents, keratolytics, antibacterials and antimicrobial agents such as Irgasan or chlorhexidine including its salts such as chlorhexidine gluconate. Preferably the composition is presented as an aqueous ethanolic gel. A process for the preparation of a composition of the invention comprises admixing the ingredients thereof in the required proportions. A method for the therapeutic and/or cosmetic treatment of skin and/or hair comprises applying a composition according to the invention to the skin and/or hair. The antiseborrheic compositions of the invention are typically applied to the skin, usually the face, on a regular (1-3 times per day) basis. They can be formulated as a leave-on product or as a wipe-on, wipe-off cleansing product which is optionally impregnated into absorbent material for use as swabs. The following Examples illustrate the invention: Example 1 Oil-free Gel (for seborrhea) Example 2 Antimicrobial Gel (for mild acne) Example 3 Roll-on Lotion (deodorant) Example 4 Matting Emulsion

Claims: A skin-care or hair-care composition comprising at least 0.5% w/w silica, a C₂₋₄ alkyl ester of citric, tartaric or succinic acid, optionally acetylated at any hydroxy residue, and an aqueous carrier. A composition according to claim 1, in which the aqueous carrier is an aqueous solvent system. A composition according to claim 2, in which the aqueous solvent system is an aqueous lower alkanol or water. A composition according to claim 3, in which the aqueous solvent system is aqueous ethanol. A composition according to any preceding claim, comprising up to 10% w/w silica. A composition according to claim 4, comprising 2 to 5% w/w silica. A composition according to any preceding claim, in which the ester is selected from triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, diethyl tartrate and diethyl succinate. A composition according to any preceding claim, in which the silica has a mean particle size of 0.1 to 20µm, the particles consisting of aggregates of smaller particles. A composition according to any preceding claim, in which the ester: silica ratio is at least 1:1. A composition according to any preceding claim, in which the silica is a hydrophobic silica. A composition according to claim 10, in which the silica is silanised silica gel. The use of a C₂₋₄ alkyl ester of citric acid, tartaric acid or succinic acid, optionally acetylated at any hydroxy residue, in a skin-care or hair-care composition comprising at least 0.5% w/w silica in an aqueous carrier, to mask the presence of silica on evaporation of the carrier.

Inventors: FAIRHURST, EDGAR BEECHAM PRODUCTS, POILE, STEVEN BEECHAM PRODUCTS, SAYERS, HELEN BEECHAM PRODUCTS
Applicants: BEECHAM GROUP PLC
Application year: 1989
Main classification: A61K7
IPC codes: A61Q19, A61Q1, A61K8, A61Q17, A61Q5, A61Q15