The present invention relates to cosmetic and pharmaceutical oil-in-water emulsions which have a mattifying effect when applied to the skin. The invention comprises a hydrophilic, non-organically modified magnesium aluminum silicate or a bentonite clay and a polyol in the water phase; and a volatile, skin-compatible, lipophilic solvent and a high melting point lipophilic plasticizer in the oil phase. A preferred surfactant system to stabilize the emulsion includes non-toxic metal alkyl sulfates and/or sucrose esters.

SUMMARY OF THE INVENTION

The claimed invention is a novel alcohol-free or low-alcohol, oil-in-water emulsion for application to the skin which imparts rapid, uniform and long-lasting mattification with desirable aesthetics and feel. The novel mattifying emulsion comprises a hydrophilic, non-organically modified magnesium aluminum silicate or a bentonite clay and a polyol in the water phase; and a volatile, skin-compatible, lipophilic solvent and a high melting point lipophilic plasticizer in the oil phase. Preferably, the surfactant system used to stabilize the emulsion includes non-toxic metal alkyl sulfates and/or sucrose esters.

DETAILED DESCRIPTION OF INVENTION

Emulsions are formed from at least two liquid phases, typically oil and water, which are immiscible in each other. The oil phase is comprised of ingredients which are substantially insoluble in water. Such water-insoluble ingredients are also described as lipophilic. In an oil-in-water emulsion, the inner oil phase is finely dispersed in the outer, continuous aqueous phase. Surface active ingredients, known as surfactants, are added to the emulsion to provide a uniform fine dispersion of the inner phase ingredients and to retard or prevent coalescence and eventual separation of the emulsion into its constituent phases.

The mattifying oil-in-water emulsion of the present invention is preferably alcohol-free, but may also comprise low levels of volatile alcohol. In both cases, the emulsions have an outer (aqueous) phase in which an inner (oil) phase is finely dispersed by gentle, skin-compatible surfactants. The emulsion comprises: a volatile, skin-compatible, lipophilic solvent; a high melting point lipophilic plasticizer; a hydrophilic, non-organically modified magnesium aluminum silicate or a bentonite clay; an emulsifier system; and a polyol. As detailed below, the aqueous phase preferably comprises: (i) from about 2% to about 6% by weight of a hydrophilic mattifying ingredient, which is either a hydrophilic, non-organically modified magnesium aluminum silicate or a bentonite clay; and (ii) from about 0.50% to about 5.0% by weight of a polyol, preferably from about 2% to about 3%. The oil phase comprises (i) from about 3% to about 30% by weight of a volatile, skin-compatible, lipophilic solvent, preferably from about 5% to about 25%, and most preferably from about 15% to about 20%; and (ii) from about 0.5% to about 6% by weight of a high melting point lipophilic plasticizer. In a preferred embodiment, the ratio of the high melting point lipophilic plasticizer to mattifying ingredient is approximately one to one.

The surfactant system of the present invention comprises from about 0.1% to about 2.0% by weight of the total composition, preferably from about 0.2% to about 1.0%. Preferred surfactants are non-toxic metal alkyl sulfates and/or sucrose esters.

A low-alcohol embodiment of the present invention comprises the above-described aqueous and oil phases and surfactant system, and additionally comprises from about 2% to about 5% by weight of C.sub.2 and C.sub.3 alcohols.

The aqueous phase of the emulsion of the present invention includes water, which is preferably deionized, distilled or similarly purified.

Mattifying ingredients suitable for use in compositions of the present invention are readily available. Preferred mattifying ingredients usable in the present invention include non-organically modified magnesium aluminum silicates and bentonite clays, with non-organically modified magnesium aluminum silicates being most preferred. One such magnesium aluminum silicate is sold under the tradename Matte Lite-239 by MMP, Inc., South Plainfield, N.J. Bentonite clays usable in the present invention include, for example, Bentonite USP brands manufactured by Whittaker Clark & Daniels of South Plainfield, N.J. or Polargel brands manufactured by American Colloid Company of Belle Fourche, S.D. Other mattifying ingredients which can be used in the present invention include hydrophobic starches, such as aluminum starch octenyl succinate, micronized zinc oxide, micronized titanium dioxide, kaolin, micas, and the like. A commercially available hydrophobic starch suitable for the present invention is marketed under the trade name Dry-Flo by National Starch & Chemical, Bridgewater, N.J. The mattifying effect of compositions of the present invention lasts from between about 3 hours to at least about 12 hours, depending on the oiliness of the skin. For oily skin, the duration of mattification is from about 3 hours to about 8 hours, preferably. For normal skin, the mattifying effect lasts from about 8 hours to about 12 or more hours, preferably.

Polyols available for use in compositions of the current invention are also widely available commercially and include, for example, glycerin and sorbitol. Preferred polyols are glycerin, propylene glycol, 1,3 butylene glycol or sorbitol. A more preferred polyol is glycerin. Other polyols which may be used in the present invention include hexylene glycol, polymeric polyols such as polypropylene glycol, and polyethylene glycol. Surprisingly, the polyol, in combination with the high melting point lipophilic plasticizer described below, allows for a more uniform mattification without the residual white splotches common in prior art compositions. Uniform matte appearance without whitening is especially important in color cosmetics and sunscreens.

Volatile, skin-compatible lipophilic solvents which can be used in the oil phase of the present invention include volatile silicones, such as cyclomethicone, isododecane, or mixtures thereof. Preferred cyclomethicones suitable for use in the invention are cyclopentasiloxane, cyclohexasiloxane, cycoltetrasiloxane or dimethicone (0.65 centistokes). A preferred isododecane usable in the present invention is sold under the tradename Permethyl 99A, by Presperse Inc., Piscataway, N.J.

As discussed above, low levels of volatile ethyl and, preferably, propyl alcohols may also be used in the invention. These alcohols provide a vehicle for carrying pharmaceutically active ingredients including, for example, salicylic acid, and also provide another means to modulate application properties.

The high melting point lipophilic plasticizer appears to coat or "plasticize" the surface of the non-organically modified magnesium aluminum silicate or bentonite clays, thus aiding in preventing the mattifying ingredients from being oxidized and thereby whitened. Solid fatty alcohols having from 14 to 30 carbon atoms per molecule may be used as the plasticizer in the present invention. Preferred fatty alcohols are from 16 to 22 carbon atoms per molecule in length. The most preferred fatty alcohols are preferred cetyl and cetearyl fatty alcohols. These fatty alcohols also provide a desirable semi-occlusive moisturizing action. Other plasticizers usable in the present invention include monodiglycerides, such as glycerol monostearate, and high-melting point esters, such as stearyl stearate, cetyl palmitate or behenyl stearate.

Preferred surfactants usable in the present invention include a non-toxic metal salt of an n-alkyl sulfate, a sucrose ester, or a combination of both. These surface active agents provide uniform dispersion and emulsification of the previously described lipophilic components. Alkyl sulfates suitable for use as surfactants in the present invention have from 12 to 22 carbon atoms per molecule. Preferred metals are sodium or potassium, with sodium as the most preferred. A preferred alkyl sulfate is sodium cetearyl sulfate. Preferred sucrose esters include sucrose stearate, sucrose oleate, sucrose laurate and isostearate. A more preferred sucrose ester is sucrose stearate, which is sold under the tradename Sisterna SP 70-C. A preferred surfactant system is about 0.25 % sucrose stearate by weight and about 0.25% by weight sodium cetearyl sulfate. Use of these preferred surfactants produces formulations with very desirable mildness characteristics.

Surprisingly, compositions containing the preferred sucrose esters described above as the sole emulsifier produced a less thixotropic composition than those also comprising alkyl sulfates. These unexpected improved flow characteristics allow the emulsion of the present invention to be more conveniently dispensed as a flowable lotion (e.g, in pumps) for easier application. For systems where greater fluidity and reduced viscosity is desired, a particularly preferred embodiment comprises about 0.50% by weight of sucrose stearate as the sole emulsifier.

Surfactants which are anionic, nonionic, cationic or amphoteric in character and combinations thereof can also be used in the present invention. Anionic-type surfactants may include fatty acid soaps, sodium lauryl sulfate, sodium lauryl ether sulfate, mono and dialkyl phosphates and sodium fatty acyl isothionate. Illustrative of the nonionic surfactants are alkoxylated compounds based upon fatty alcohols, fatty acids and sorbitan. Copolymers of polyoxypropylene-polyoxyethylene, sold under the Pluronic tradename by BASF Corp., Mount Olive, N.J., as well as non-ethoxylated, nonionic emulsifiers, such as sucrose laurate, sucrose oleate, alkyl polyglucosides, polygylceryl-4 palmitate, polyglyceryl-10laurate can be utilized. Amphoteric surfactants suitable for use in the invention include dialkylamine oxide and betaines, such as cocoamido propyl betaine.

Compositions of the present invention exhibit long-lasting, uniform mattification, without whitening, and can be used as a vehicle for a variety of products in which an oil-in-water vehicle is appropriate. The invention can therefore be employed in a wide range of cosmetic and pharmaceutical products, including, but not limited to, matte make-up compositions, oil absorbing face masks, matte anti-acne oil absorption vehicles, matte after shave balms or lotions, fragrance delivery vehicles, sunscreens, foot creams, and other dermatologic vehicles.

In order to produce the desired products, the basic components of the invention described above may be combined with other cosmetic and pharmaceutical ingredients which are well known to cosmetic and pharmaceutical chemists. Examples of such additional components include, but are not limited to, antiseborrheic agents, anti-acne agents, antioxidants, skin lightening agents, depigmenting agents, anti-wrinkle agents, vitamins, sunscreen agents, self-tanning agents, topical analgesics, anti-inflammatory agents, antipruritic agents deodorants, as well as purely cosmetic ingredients, such as pigments, water soluble emollients, humectants, stabilizers and fragrances. Sunscreen agents which do not whiten are most suitable for use in the present invention and include micronized titanium dioxide, micronized zinc oxide or avobenzone which is commercially available under the tradename Parsol 1789. Preferred pigments in makeup emulsions of the present invention are iron oxides and titanium dioxides.

The oil-in-water emulsion of the present invention is prepared according to principles and techniques generally known to those skilled in the cosmetic and pharmaceutical arts. Ingredients which are miscible (e.g., disodium EDTA or other chelating agent) or dispersible (e.g., hydrophilic mattifying ingredient) in the water phase are mixed together with propeller agitation. In order to accelerate hydration of the mattifying ingredient, the above mixture is preferably heated to a temperature of about 60.degree. C. and processed with a high speed homogenizer. It is preferable to hydrate non-organically modified magnesium aluminum silicate with a Silverson L4RT homogenizer (manufactured by A. Silverson Machines, Ltd., Chesham, England) operating at 5500 6500 rpm for about ten minutes at about 60.degree. C. Other mixers such as a colloid mill or propeller mixer may also be used, although the latter would considerably increase processing time. A colloid mill with a narrow orifice may be preferred when adding high pigments loads.

Polyol, emulsifier (i.e., non-toxic metal alkyl sulfate and/or sucrose ester) and high melting point lipophilic plasticizer (e.g., cetyl alcohol) are then added to the above water phase mixture. It is preferable to incorporate these ingredients while mixing with medium propeller agitation and heating until a temperature is reached at which the emulsifiers melt, typically from about 65.degree. C. to about 85.degree. C. The speed of propeller mixing should be sufficient to create a vortex but not so fast as to cause aeration. Alternatively, the emulsifier and plasticizer may be melted in separate vessels and mixed with the polyol and other water phase ingredients using a rotating static mixer, a colloid mill, or an in-line homogenizer.

The emulsion is then allowed to cool to about 55.degree. C. while being further mixed with a high speed homogenizer, at which point the volatile, skin-compatible, lipophilic solvent (e.g., cyclomethicone) is added. Low levels of volatile ethyl and/or propyl alcohol may also be added at this stage of processing. Mixing with the homogenizer continues until viscosity begins to build up, normally about 50.degree. C. At this point, it is preferable to switch to a medium paddle or side-sweep mixer in order to remove air that may have been incorporated during homogenization. Once the mixture has cooled down further, to about 45.degree. C., preservatives as well as any water lost through evaporation may be added. Fragrance and other temperature sensitive active ingredients may also be added once the emulsion is below about 45.degree. C. Sweep mixing and cooling are continued, preferably until about 32.degree. C., at which time processing is stopped.

Homogenizers, mixers and mills which are suitable for use in the process described above are well known to artisans of ordinary skill in the art.
 

Claim 1 of 25 Claims

1. A mattifying oil-in-water emulsion composition suitable for application to the skin comprising: (a) from about 3% to about 30% by weight of a volatile, skin-compatible, lipophilic solvent; (b) from about 0.5% to about 6% by weight of plasticizer selected from the group consisting of solid fatty alcohols having from 14 to 30 carbon atoms per molecule, monodiglycerides, stearyl stearate, cetyl palmitate, and behenyl stearate; (c) from about 2% to about 6% by weight of a hydrophilic, non-organically modified magnesium aluminum silicate or a bentonite clay; (d) from about 0.1% to about 2.0% by weight of the total composition of a surface active agent; and (e) from about 0.50% to about 5.0% by weight of the total composition of a polyol.

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