Cosmetic composition

Abstract: An aqueous cosmetic emulsion is provided that includes an isoparaffin and an alkyl phosphate salt wherein the relative ratio of isoparaffin to alkyl phosphate salt ranges from about 40:1 to 1:1 The combination of isoparaffin with alkyl phosphate salt provides an unexpected thickening effect and results in a non-greasy product relative to a mineral oil bearing formula.

Description: The invention relates to a cosmetic emulsion with a special thickening agent that provides a product having improved aesthetics and skin feel. Various emollient creams and lotions have been used to alleviate the signs and symptoms of dry skin. The application of these products helps return skin to a normal, moisturized condition by the process of occlusion and humectancy. Historically, a performance dichotomy has always existed, wherein those ingredients such as glycerin and petroleum jelly found to be effective in the treatment of dry skin, have been cosmetically unacceptable due to their heaviness. This is especially true with increasing concentration of these materials in a finished emulsion product. Therefore, ingredients such as mineral and silicone oils are used by formulators to increase lubricity of a formulation, thereby decreasing the perception of heaviness related to the materials such as glycerin and petroleum jelly. U.S. Patent 3,818,105 (Coopersmith et al.) teaches the usefulness of C₁₂-C₁₄ isoparaffinic hydrocarbons as effective skin lubricants in cosmetic perparations. These hydrocarbons were disclosed as being typically admixed with water, monoalkanols, organic esters, polyhydroxy compounds, lanolin, minerals, colorants, surfactants, waxes and perfumes. Example 5 reports a hand cleaner composition whose major ingredients are isoparaffin, oleic acid and nonylphenol (10) ethoxylate, the latter a nonionic surfactant. U.S. Patent 3,634,265 (Merritt) reports use of a liquid isoparaffinic hydrocarbon as a solvent for skin contaminents in a skin cleaner emulsion. Among the further components listed are a light mineral oil, a long-chain alkanoic acid neutralized with an alkanolamine, an anionic surfactant, a protective colloid and deionized water. EP 227 012 describes gel like compositions, which may be for example creams, which comprise water, monoalkyl phosphates, polyhydric alcohols, and oil substances, such as squalahe. While the aforementioned art has recognized the usefulness of isoparaffinic hydrocarbons, as lubricants or solvents, there has been no mention as to how these materials affect product viscosities. Often one of the more difficult problems in formulating high water systems is the search for thickening agents which provide the correct viscosity but do not detract from skin performance properties. Some thickeners provide sufficient body but impart unacceptable greasiness. Moreover, one ingredient frequently renders another physically incompatible resulting in phase separation of the composition. Examples of the aforementioned patents suggest use of rather high levels (greater than 10%) of isoparaffin and no higher than 60% water. According to the present invention, an aqueous cosmetic emulsion is provided comprising the following components: i) an isoparaffin; and ii) a C₈ to C₂₂ alkyl phosphate salt; wherein the isoparaffin and alkyl phosphate salt are present in a respective weight ratio of from about 40:1 to about 1:1. Such a cosmetic emulsion, when applied to the skin, can have sufficient viscosity to render it aesthetically pleasing while at the same time avoiding a greasy feeling that some thickeners would normally impart. Certain forms of the invention provide a hand and body lotion. This can be of proper pH for such a product and can have good phase stability. As just mentioned, the emulsions of this invention can display a viscosity which is pleasing to the consumer. The inventors have found that isoparaffins have exceptional thickening properties even though present at relatively low concentration in the aqueous system. Furthermore the inventors have discovered that certain types of surfactants interact with isoparaffins to improve the thickening effect of the latter. Also noted has been the critical nature of the relative ratios of the oil to the surfactant. A still further discovery has been the reduction in greasiness through use of isoparaffins as replacement for straight-chain hydrocarbon oil. Isoparaffins contemplated for use in the present invention are largely saturated aliphatic hydrocarbons generally with highly branched structures and having from 11 to 13 carbon atoms per molecule. Preferably the isoparaffins are selected from one or a mixture of isomeric species including: It will be apparent that these materials all have a plurality of chain branches per molecule - indeed the compounds mentioned all have at least three side chains. A particularly preferred type of isoparaffin is a material known as Isopar L, sold by the Exxon Company, Houston, Texas. The material is a clear, odorless and colorless thin liquid with a flash point of 61°C. Isopar L has an average molecular weight of 171 and a viscosity of 2.6 centistokes at 15.5°C. Isoparaffin normally will be incorporated into the compositions of this invention in an amount from about 0.5 to about 5% by weight of the total. Preferably this material will be present in an amount from about 1% to about 3%, optimally between about 1 and about 2% by weight of the total formulation. As mentioned earlier, a second critical component of the composition is the presence of a selected surfactant, namely an alkyl phosphate salt. More particularly, the surfactant should be a salt of a C₈-C₂₂ alkyl phosphate. Illustrative surfactants include salts of cetyl phosphate, myristyl phosphate, lauryl phosphate and stearyl phosphate. Salt counterions may notably be selected from alkalimetal, ammonium, and substituted ammonium, especially trialkylammonium and di- or tri- alkanolammonium, cations. Particularly preferred is diethanolammonium cetyl phosphate, commercially available under the trademark Amphisol from the Givaudan Corporation. Usual amounts of alkyl phosphate salt will range from about 0.1% to about 3% by weight of the total formulation. Particularly preferred is a concentration from about 0.25% to about 1%, optimally between about 0.25% and 0.5%. For the present invention it is important to incorporate isoparaffin and alkyl phosphate salt in a relative weight ratio which falls within the range from about 40:1 to about 1:1, preferably from about 20:1, better 10:1, to about 4:1, optimally between about 10:1 and about 6:1. By selection of isoparaffin and alkyl phosphate salt as well as careful control of the relative ratios, it has become possible to thicken an aqueous system with a minimum amount of oily material. Consumer acceptable viscosities are herewith achieved which may range from 3500 mPas (35 units) to about 9000 mPas (90 units) preferably from about 5000 mPas (50 units) to about 7000 mPas (70 units) as measured with a Brookfield Viscometer LVT Model using #4 spindle at 60 rpm at 25°C @15 revolutions. Water is of course a major component of the compositions of this invention. The amount of water will generally range in amount anywhere from about 50% up to about 95% by weight of the total formulation. Preferably the amount of water will be present in amount from about 80% to about 92%, optimally between about 87 and 90% by weight. Beyond the aforementioned essential components, the cosmetic compositions of the present invention may also contain other ingredients typically found in such formulations. Besides isoparaffin there may also be included from 0.1 to 2% of mineral oil comprising liquid hydrocarbons that are substantially non-isoparaffinic. For emulsification and emollient purposes there may be incorporated from 0.1% of a wax (e.g. carnauba or microcrystalline polyethylene wax), a lanolin derived material (e.g. Acetulan which is a 9:1 mixture of cetyl acetate and acetyl lanolin alcohol available from Amerchol), stearols (e.g. glycerol monostearate and stearamide AMP and mixtures thereof sold by the Van Dyke Co. under the mark Cerasynt IP), fatty alcohols (e.g. stearic acid available under the trademark Neofat) and mixtures of these ingredients. There may also be present from 0.01 to 2% of adjunct water-phase thickening agents such as Veegum, a magnesium aluminum silicate sold by the Vanderbilt Chemical Co., and Carbopol 934, a cross-linked polyacrylate polymer available from the B.F. Goodrich Co. Proteins as well as silicone oils may be included to improve skin feel. Other minor but important functional ingredients such as colorant, fragrance and preservative are normally also included, each present in an effective amount to accomplish its function. Suitable preservatives include the methyl and propyl parabens and sodium ethylenediaminetetraacetates. All the foregoing materials are more fully illustrated in Cosmetics, Science & Technology , 2 ed., Ed. Board - M.S. Balsom et al. and Cosmetic and Toileting Formulations , E.W. Flick, Noyes Publications, 1984; Compositions of the present invention generally have a cream or lotion consistency and may be in the form of either an oil-in-water or water-in-oil emulsion. The former type emulsion having a continuous water phase is the preferred embodiment since it has more pleasing cosmetic properties. These compositions are useful in the treatment of dry skin. They can be applied to the skin in an amount sufficient to meet an individual user's needs and desires. The following examples will more fully illustrate the embodiments of the invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight unless otherwise indicated. EXAMPLE 1 A variety of compositions were prepared having the following base formula. These were used for viscosity and skin feel tests set out as Examples 2 and 3 below. As already mentioned, Amphisol is diethanolammonium cetyl phosphate, Isopar L is isoparaffin and Veegum is magnesium aluminium silicate. EXAMPLE 2 A series of skin feel tests were conducted employing the base formula of Example 1. Results of these tests are reported in Tables I through V. Each table sets out a comparative trial of two compositions, one containing Isopar L, the other containing mineral oil, and both containing an equal amount of Amphisol. From the foregoing results it is evident that at ratios of hydrocarbon to surfactant of 40:1 to 1:1 isoparaffin-type hydrocarbon is much preferred over mineral oil. EXAMPLE 3 Viscosity effects from the interaction of Amphisol with mineral oil versus that of isoparaffin are herein reported. The base formula of Example 1 was employed for these tests. As can be seen in Tables VI through IX, the combination of Amphisol with Isopar L is much more effective as a thickening agent than the Amphisol combination with mineral oil. This thickening effect was unexpected because mineral oil itself has a viscosity of 1900 mPas (19.0 Brookfield units) as compared with the much lighter Isopar L having 280 mPas (2.8 Brookfield unit) viscosity. EXAMPLE 4 Illustrated here is the effect of substituting surfactants other than Amphisol in the base formula of Example 1. Table X demonstrates that the cationic surfactant Arosurf and nonionic surfactant Brij 35 do not interact with Isopar L to thicken the base formula relative to that of mineral oil. The mineral oil formula has higher viscosity in both instances. Only Anionic surfactants such as lauryl ether sulfate, lauryl sulfate and DEA cetyl phosphate appear to interact with Isopar L to thicken the base formula. However, it is only with the DEA cetyl phosphate, i.e. Amphisol, that there is achieved a viscosity higher than 3500 mPas (35 Brookfield Units). Viscosities lower than 3500 mPas. (35 Brookfield Units) are undesirably watery in hand or body cosmetic lotions.

Claims: An aqueous cosmetic emulsion comprising: i) a saturated liquid isoparaffin of average chain length C₁₁-C₁₃. ii) a C₈ to C₂₂ alkyl phosphate salt; wherein the isoparaffin and alkyl phosphate salt are present in a respective weight ratio of from 40:1 to 1:1. An aqueous cosmetic emulsion according to claim 1 wherein the ratio ranges from 10:1 to 4:1. An aqueous cosmetic emulsion according to claim 1 or claim 2 wherein the emulsion has a viscosity ranging from 3500 mPas (35 units) to 9000 mPas (90 Brookfield units) as measured with a Brookfield Viscometer Model LVT using a #4 spindle rotating at 60 rpm at 25°C. An aqueous cosmetic emulsion according to claim 3 wherein the viscosity ranges from 5000 mPas (50 units) to 7000 mPas (70 Brookfield units). An aqueous cosmetic emulsion according to any one of the preceding claims wherein the alkyl phosphate salt is a cetyl phosphate salt. An aqueous cosmetic emulsion according to claim 5 wherein the salt is diethanolamine cetyl phosphate. An aqueous cosmetic emulsion according to any one of the preceding claims wherein the isoparaffin is present in an amount from 0.5% to 5% by weight. An aqueous cosmetic emulsion according to any one of the preceding claims wherein water is present in an amount from 50 to 95% by weight and the alkyl phosphate salt is present in an amount from 0.1 to 3% by weight. An aqueous cosmetic emulsion according to any one of the preceding claims wherein the isoparaffin is present in an amount from 1% to 2% by weight. An aqueous cosmetic emulsion according to any one of the preceding claims wherein water is present from 80% to 92% by weight. Use in an aqueous cosmetic emulsion composition of a saturated liquid isoparaffin of average chain length C₁₁-C₁₃ and a C₈ to C₂₂ alkyl phosphate salt, wherein the isoparaffin and the alkyl phosphate salt are present in a respective weight ratio of from 40:1 to 1:1, to improve the thickening properties of the composition.

Inventors: CHENEY MICHAEL CHARLES, GHOSH DIPAK KANTI, WILLIAMS LORRAINE, ZIEGLER PHILIP DALE, CHENEY, MICHAEL CHARLES, GHOSH, DIPAK KANTI, WILLIAMS, LORRAINE, ZIEGLER, PHILIP DALE
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1990
Main classification: A61K7
IPC codes: A61K8, A61Q19