Skin moisturizing microemulsions

Abstract: The present invention provides microemulsions, con­ taining moisturizing agents or sunscreens, suitable for cos­ metic uses. Also disclosed are methods of moisturizing dry skin using the microemulsions containing moisturizing agents. Further, there are provided methods of potentiating the effects of macroemulsion moisturizing creams and lotions by the prior application of the described micro­ emulsions.

Description: An emulsion is a dispersed system containing at least two immiscible liquid phases, one of which is dispersed in the form of small droplets throughout the other, and an emulsifying agent in order to improve the stability of the system. There are two types of emulsions depending on the droplet size of the liquids present in the emulsions. Light does not pass through macroemulsions because the droplets have average diameters of about 10 to about 1000 µm. These emulsions typically appear milky white. Microemulsions are stable systems consisting of droplets which are significantly smaller, being approximately 0.2 µm, or smaller, in diameter on the average. As such, microemulsions are translucent, and routinely transparent, in appearance. Microemulsions are an extraordinary type of emulsion that form spontaneously. Products consisting of these systems are valued for their stability and small particle size, thus affording microemulsions a special consideration in the market place. Additional information on microemulsions and their properties may be obtained from Emulsions and Emulsion Technology Part I, ed. Kenneth J. Lissant, Marcel Dekker, Inc., New York, Chapter 3 "Microemulsions" (1974) an Microemulsions Theory and Practice ed. Leon M. Prince, Academic Press, Inc. (1977). Emulsions have a variety of uses, most notably as vehicles for the delivery of medicines. In particular, microemulsions are known to deliver pharmacologically active agents as disclosed in U.K. Patent No. 2,098,865. Microemulsions are also known to provide injectable compositions containing an anaesthetic, as disclosed in U.S. Patent No. 3,917,830, and are known as carriers for oxygen absorbing fluorinated organic compounds, as disclosed in U.S. Patent No. 3,778,381. Jayakrishnan et al. in J . Soc . Cosmet . Chem . 34, 335-350 (1983) disclose the delivery of hydrocortisone with microemulsions. EP-A-0125779 describes skin care formulations comprising a water-in-mineral oil emulsion and which incorporate organopolysiloxane-polyoxyalkylene block copolymers as emulsifiers. US-A-4,052,331 discloses emulsifiers for use in transparent microemulsions or gels. GB-A-2,113,568 relates to an emulsifying system for cosmetic or pharmaceutical emulsoids or gels and which is based on a fatty acid or a protein condensate thereof. GB-A-2,155,337 describes a topical delivery system, formed of a water-in-volatile silicone emulsion, which includes an interior aqueous phase and an exterior silicone phase containing the active ingredient. Chemical Abstracts, vol. 93, 1980, No. 173618 (f) refers to a transparent multi-component face lotion composition which includes a polysiloxane and water. US-A-3,392,040 discloses silicone compositions comprising an aqueous dispersion of a solution of an organo-silicon polymer dissolved in a C₁-C₃ alkyl C₈-C₁₄ alkanoate. The present invention provides a stable water-in-oil or oil-in-water microemulsion non-irritating moisturizing composition which when applied to skin promotes the penetration of moisturizers into the skin and leaves little residue on the surface of the skin following its application comprising from 1% by weight to 46% by weight of moisturizer, from 14% by weight to 90% by weight of microemulsion forming surfactant, from 1% by weight to 79% by weight of polysiloxane and from 2% by weight to 54% by weight of skin humectant, and a sunscreen, said composition having an average droplet size in the range of 0.001 µm to 0.2 µm in diameter. The present invention further provides a method for cosmetically moisturizing skin which comprises administering to the skin a microemulsion composition of the aforementioned type. In one embodiment of this method, the microemulsion composition is first applied to skin in need of cosmetic moisturizing and a macroemulsion moisturizing composition is subsequently applied to the skin. This approach has been found to potentiate the effect of the macroemulsion moisturizing composition. A preferred composition is one which comprises from 5% by weight to 35% by weight of moisturizers, from 20% by weight to 80% by weight of surfactants, from 10% by weight to 70% by weight of polysiloxane compounds and from 5% to 50% by weight of skin humectants. Finally, the present invention provides a water-in-oil microemulsion composition comprising from 1.0% by weight to 8.0% by weight of a sunscreen, from 1% by weight to 46% by weight of moisturizer, from 15.0% by weight to 79.0% by weight of a microemulsion forming surfactant, from 15.0% by weight to 79.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant and having an average droplet size in the range of 0.001 µm to 0.2 µm in diameter. Typically, one of the two immiscible liquids in an emulsion is aqueous while the other is an oil. Emulsions may be classified depending on which liquid forms the dispersed phase and which liquid forms the dispersion medium. An emulsion in which oil is dispersed as droplets throughout the aqueous phase is termed an oil-in-water emulsion. When water is the dispersed phase and an oil is the dispersion medium, a water-in-oil emulsion exists. Whether the aqueous phase or the oil phase becomes the dispersed phase, or is the dispersion medium, depends primarily on the emulsifying agent used and the relative amounts of the two liquid phases The emulsions contemplated for use in the methods of the present invention include both water-in-oil microemulsions, wherein the continuous phase is oil, and oil-in-water microemulsions, wherein the continuous phase is water. The preferred microemulsions contemplated for use in the instantly claimed methods are water-in-oil microemulsions. As noted above, the present invention provides a method of moisturizing human skin comprising administering to said skin a microemulsion composition comprising one of the compositions noted above. In particular, the method may comprise administering to the skin a composition comprising a sunscreen and one of the following: a) from 1.0% by weight to 36.0% by weight of a fatty alcohol, from 23.5% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 28.0% by weight of a polysiloxane, and from 2.0% by weight to 36.0% by weight of a skin humectant; b) from 1.0% by weight to 46.0% by weight of an animal oil, from 14.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 35.0% by weight of a polysiloxane, and from 2.0% by weight to 18.0% by weight of a skin humectant; c) from 1.0% by weight to 31.0% by weight of a triglyceride, from 37.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 35.0% by weight of a polysiloxane, and from 2.0% by weight to 24.0% by weight of a skin humectant; d) from 1.0% by weight to 41.0% by weight of a fatty diester, from 23.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane, and from 2.0% by weight to 42.0% by weight of a skin humectant; e) from 1.0% by weight to 41.0% by weight of a branched chain fatty ester, from 18.5% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane and from 2.0% by weight to 54.0% by weight of a skin humectant; f) from 1.0% by weight to 6.0% by weight of a fatty acid, from 60.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 5.0% by weight of a polysiloxane, and from 2.0% by weight to 26.0% by weight of a skin humectant; g) from 1.0% by weight to 41.0% by weight of a tribasic acid ester, from 23.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane, and from 3.0% by weight to 33.0% by weight of a skin humectant; h) from 3.0% by weight to 35.0% by weight of a vegetable oil, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant, from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant; i) from 5.0% by weight to 35.0% by weight of a long chain hydrocarbon, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant, from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant; and j) from 5.0% by weight to 35.0% by weight of a straight chain fatty ester, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant, from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant. The present invention also provides a method of moisturizing human skin comprising administering to said skin a microemulsion comprising one of the compositions discussed above, followed by subsequent application of a macroemulsion moisturizing composition. Also encompassed within the present invention is a water-in-oil microemulsion composition comprising a sunscreen and one of the following: a) from 1.0% by weight to 36.0% by weight of a fatty alcohol, from 23.5% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 28.0% by weight of a polysiloxane, and from 2.0% by weight to 36.0% by weight of a skin humectant; b) from 1.0% by weight to 46.0% by weight of an animal oil, from 14.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 35.0% by weight of a polysiloxane, and from 2.0% by weight to 18.0% by weight of a skin humectant; c) from about 1.0% by weight to 31.0% by weight of a triglyceride, from 37.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 35.0% by weight of a polysiloxane, and from 2.0% by weight to 24.0% by weight of a skin humectant; d) from 1.0% by weight to 41.0% by weight of a fatty diester, from about 23.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane, and from 2.0% by weight to 42.0% by weight of a skin humectant; e) from 1.0% by weight to 41.0% by weight of a branched chain fatty ester, from 18.5% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane, and from 2.0% by weight to 54.0% by weight of a skin humectant. f) from 1.0% by weight to 6.0% by weight of a fatty acid, from about 60.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 5.0% by weight of a polysiloxane, and from 2.0% by weight to 26.0% by weight of a skin humectant; g) from 1.0% by weight to 41.0% by weight of a tribasic acid ester, from 23.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane, and from 3.0% by weight to 33.0% by weight of a skin humectant; h) from 3.0% by weight to 35.0% by weight of a vegetable oil, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant, from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant; i) from 5.0% by weight to 35.0% by weight of a long chain hydrocarbon, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant, from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant; and j) from 5.0% by weight to 35.0% by weight of a straight chain fatty ester, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant. from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant; Another water-in-oil microemulsion of the invention comprises from 1.0% by weight to 8.0% by weight of a sunscreen, from 1% by weight to 46% by weight of moisturizer, from 15.0% by weight to 79.0% by weight of a microemulsion forming surfactant, from 15.0% by weight to 79.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant. The composition will preferably contain from 2.0% by weight to 6.0% by weight of a sunscreen, from 20.0% by weight to 35.0% by weight of a microemulsion forming surfactant, from 20.0% by weight to 55.0% by weight of a polysiloxane, and from 20.0% by weight to 35.0% by weight of a skin humectant. The oil-in-water and water-in-oil microemulsions employed may contain one or more ingredients which provide skin moisturizing microemulsions. These ingredients may be selected from fatty alcohols, animal oils, triglycerides, fatty diesters, branched chain fatty esters, fatty acids, tribasic acid esters, vegetable oils, long chain hydrocarbons, and straight chain fatty esters. Typical "fatty alcohols" useful in preparing the skin moisturizing microemulsions of the present invention contain one hydroxy group. Examples of such fatty alcohols may include behenyl alcohol, cetyl alcohol, isocetyl alcohol, isostearyl alcohol, lauryl alcohol, 2-octyldodecanol, oleyl alcohol, myristyl alcohol, and stearyl alcohol. "Animal oils" may include, for example, cod liver oil, lanolin oil, mink oil, orange roughy oil, and shark liver oil. Typical "triglycerides" may include caprylic/capric triglycerides, triisononanoin, triisostearin, trilaurin, trilinolein, and triolein. Examples of typical "fatty diesters" may include dibutyl adipate, dibutyl sebacate, dicetyl adipate, diethyl sebacate, dihexyl adipate, diisocetyl adipate, diisopropyl adipate, diisopropyl dimerate, diisopropyl sebacate, diisostearyl adipate, dioctyl adipate, dioctyl sebacate, and dioctyl succinate. "Branched chain fatty esters" may include 2-ethylhexyl isononanoate, 2-ethylhexyl myristate, 2-ethylhexyl oxystearate, 2-ethylhexyl palmitate, 2-ethylhexyl pelargonate, 2-ethylhexyl stearate, isocetyl isodecanoate, isocetyl palmitate, isodecyl isononanoate, isononyl isononanoate, isopropyl isostearate, isopropyl laurate, isopropyl linoleate, isopropyl myristate, isopropyl oleate, isopropyl palmitate, isopropyl stearate, isostearyl isostearate, isostearyl lactate, isostearyl neopentanoate, isostearyl palmitate, isotridecyl isononanoate, and tocopheryl linoleate. Exarnples of acceptable "fatty acids" may include isostearic acid, lauric acid, linoleic acid, linolenic acid, and oleic acid. Typical "tribasic acid esters" may include triisocetyl citrate, triisopropyl trilinoleate, triisostearyl trilinoleate, trilauryl citrate, and trioctyl citrate. "Vegetable oils" may include almond oil, apricot kernel oil, avocado oil, castor oil, coconut oil, corn oil, evening primrose oil, jojoba oil, olive oil, safflower oil, sesame oil, soybean oil, and wheat germ oil. Exarnples of useful "long chain hydrocarbons" may include squalane and squalene. "Straight chain fatty esters" useful in the present invention may include lauryl lactate, lauryl myristate, lauryl palmitate, lauryl stearate, myristyl lactate, myristyl myristate, myristyl neopentanoate, myristyl propionate, myristyl stearate, oleyl erucate. oleyl linoleate, oleyl myristate, oleyl oleate, oleyl stearate, stearyl lactate, and stearyl oleate. Preferred ingredients for use in the microemulsions of the present invention are fatty alcohols, such as isocetyl alcohol, cetyl alcohol, myristyl alcohol, and 2-octyldodecanol; animal oils, such as lanolin oil; triglycerides, such as caprylic/capric triglycerides; fatty diesters, such as diisopropyl sebacate and diisopropyl dimerate; branched chain fatty esters, such as isopropyl isostearate and isopropyl myristate; fatty acids, such as isostearic acid; and tribasic acid esters, such as triisocetyl citrate, Those skilled in the art will recognize that other moisturizing agents may be used and that the moisturizers above are merely exemplary. One or more sunscreens are incorporated into the present microemulsions. A variety of sunscreens may be employed including the p-aminobenzoic acid derivatives such as p-(2-ethylhexyl)dimethylaminobenzoate, and benzophenone derivatives such as (2-hydroxy-4-methoxyphenyl)phenylmethanone. The exact amount of sunscreen employed in the present compositions will vary depending on the degree of protection desired from the sun's harmful rays. A variety of microemulsion forming surfactants may be employed in the compositions of the invention. As used "microemulsion forming surfactant" is a surfactant selected from sorbitans, such as polysorbate 21 and polysorbate 60; poloxamers, such as Pluronic L-31; poloxamines, such as Tetronic 304; ethoxylated fatty alcohols, such as Brij; esters of phosphoric acid, such as PPG-10 cetyl ether phosphate and PPG-5 ceteth-10 phosphate; PEG castor oils, such as PEG-30 castor oil: polyoxyethylene alkylphenyl ethers, such as octoxynol-9 and nonoxynol-9; lanolin ethoxylates, such as PPG-20 lanolin ether and laneth-10 acetate; the sodium laureth sulfates; the glucose surfactants PPG-10 methyl glucose ether and PPG-20 methyl glucose ether; the sucrose ester sucrose ricinoleate; sodium lauryl sulfate; and sodium dodecyl sulfate. A particularly useful non-ionic emulsifier is Polawax or Ritachol® 1000, [R.I.T.A. Chemicals, Crystal Lake. III.]. A preferred group of microemulsion forming surfactants are the sorbitans, the sodium laureth sulfates, sodium lauryl sulfate and sodium dodecyl sulfate. A variety of polysiloxane compounds may be employed in the compositions of the present invention. These polysiloxanes may be volatile or non-volatile and include the cyclic dimethyl polysiloxanes having from three to six silicon atoms, such as cyclomethicone, as well as linear polysiloxanes having a viscosity of ten centistokes, or less, at room temperature (25°C), and mixtures thereof. A preferred polysiloxane employed in the compositions of the invention is cyclomethicone. The compositions of the invention will also contain one or more suitable skin compatible humectants. These humectants are polar in nature and may include deionized water, as well as polyhydric alcohols such as propylene glycol, glycerine, or sorbitol or other polyhydric alcohols. All cosmetic compositions must be protected against the growth of potentially harmful microorganisms, and therefore preservatives are added as a routine. While it is in the aqueous phase that microorganisms tend to grow, microorganisms can also reside in the oil phase. As such, preservatives which have solubility in both water and oil are preferably employed in the present compositions. Generally from one tenth of one percent by weight to one percent by weight of preservatives are adequate. The traditional preservatives for cosmetics and pharmaceuticals are alkyl esters of para-hydroxybenzoic acid. Other preservatives which have more recently come into use include hydantoin derivatives, propionate salts, and a variety of quaternary ammonium compounds. Cosmetic chemists are familiar with appropriate preservatives and routinely choose them to satisfy the preservative challenge test and to provide product stability. Particularly preferred preservatives for a preferred emulsion product of this invention are methyl and propyl parahydroxybenzoates, imidazolidinyl urea, and quaternium-15. The preservatives should be selected having regard for the use of the composition and possible incompatibilities between the preservatives and the other ingredients in the emulsion. The microemulsion compositions of the invention may also contain one or more pigments to color the composition, and a fragrance, such as Firmenich and Co. 66.001/NY/G fragrance oil, to make the composition soothing to the olfactory system. The amount of these ingredients present in the composition will depend on the specific effect desired. The compositions of the invention may be prepared by procedures well known to formulation chemists. Typically, an oil phase is prepared by combining all hydrophobic components, as well as the water-insoluble solids, in a container and heating the resulting mixture under agitation until all the ingredients are dissolved. In a separate container, an aqueous phase is prepared by combining all of the hydrophilic components, as well as the oil-insoluble solids, and heating the resulting mixture under constant stirring until the mixture is homogeneous. The microemulsion forming surfactant, or surfactants, are separately combined and mixed until homogeneous, and heat may be applied if necessary. The three phases thus prepared are combined and stirred until homogeneous and the solution becomes clear when allowed to stand at room temperature. The composition is finally allowed to stand for approximately 24 hours in order for the composition to achieve equilibrium. The composition may be transferred to appropriate containers for storage until needed for application to individuals in need of a microemulsion of the invention. As noted above, the compositions of the invention are translucent, and typically transparent because the average droplet size of a microemulsion being very small (compared to the macroemulsion average droplet size of about 10 µm or more in diameter) will not reflect light. As such, the compositions of the invention will have a droplet size in the range of about 0.001 µm to about 0.2 µm in diameter, more typically in the range of about 0.001 µm to about 0.14 µm in diameter. The compositions of the invention are useful for a variety of purposes, especially for protecting the skin's surface from, for example, the sun, wind, or rain. The present microemulsions are particularly well suited for moisturizing skin and this is the primary use contemplated for the microemulsions. To assist in protecting skin from the sun, a sunscreen is incorporated into the microemulsions of the invention. In addition, the microemulsion compositions employed in the present invention provide superior results when applied to skin since they leave little residue on the surface of the skin following their application. Further, the compositions are generally not irritating to the skin when formulated with the proper balance of nonionic surfactants. It is important from a commercial standpoint that the compositions of the invention remain stable over a range of temperatures and under various conditions. For example, these compositions may be used under warm, humid conditions in the summer, or under cold, dry conditions in the winter. While such stability is important from an esthetic point of view, this generally does not substantially affect the operability of the microemulsions of the invention. As noted above, the microemulsions described are useful in moisturizing human skin. Therefore, one embodiment of the present invention is a method of moisturizing human skin comprising administering to the skin a microemulsion as described. The particular quantity of microemulsion administered, of course, will be determined by the particular circumstances surrounding its use, including the microemulsion administered, the condition of the skin, the age of the user, the degree of moisturization desired, and similar considerations, The microemulsions are administered transdermally. Typically, a single application of the microemulsion will be applied topically to cover adequately the affected area of the skin. Subsequent applications may be made as needed to maintain the desired level of moisturization of the skin. The microemulsions employed in the present invention are particularly important because of their ability to increase the rate of penetration of the incorporated moisturizing agents into the areas of skin in need of moisturizing. Tests have been conducted in laboratory animals comparing microemulsions containing a radiolabeled ingredient with commercially available macroemulsion moisturizers, These tests have shown that greater amounts of the radiolabeled material reach the dermis and epidermis of the skin faster for the microemulsion moisturizer. Tests on laboratory animals have indicated also that the microemulsions employed in the present invention cause epidermal thickening. Epidermal thickening can lead to a highly desirable increase in skin resilience and elasticity. Also discovered is that the present microemulsions have the ability to potentiate the effect of subsequently applied macroemulsion moisturizers. By first applying to the skin a microemulsion of the invention, followed by application of a macroemulsion moisturizing composition, the microemulsion has been shown to enhance the penetration of the subsequently applied moisturizing composition. Thus, the rate of penetration of a particular macroemulsion moisturizing composition is increased as compared to the rate of penetration of that moisturizing composition alone. As such, the present invention provides, as an additional embodiment, a method of potentiating a macroemulsion moisturizing composition wherein a microemulsion is first applied to the skin followed by the application of a macroemulsion moisturizing composition. Macroemulsion moisturizing compositions are well known in the art. As described previously a macroemulsion consists of an oil-in-water or water-in-oil emulsion wherein the average droplet size is from about 10 µm to about 1000 µm in diameter. Such emulsions exist in both lotion and cream form and are often opaque or white in appearance due to the larger droplet size. Macroemulsion moisturizing compositions encompassed within the presently disclosed potentiation method are emulsions of the above size which have a moisturizing effect and will be familiar to those skilled in the art. The following Examples illustrate formulations and methods for their preparation. Example 1 An oil phase was prepared by combining 1000 g (25.0%) of Silicone 344 Fluid (cyclomethicone from Dow Corning Corp., Midland, Michigan), 788 g (19.7%) of Robane (squalane from Robeco Chemicals, Inc., New York, New York), 80 g (2.0%) of Polawax or Ritachol 1000 (non-ionic emulsifier from R.I.T.A. Chemicals Corp., Crystal Lake, III.), and 120 g (3.0%) of isopropyl myristate and stirring the resulting mixture under heat until homogeneous. To the oil phase was added 6 g (0.15%) of methylparaben and 6 g (0.15%) of propylparaben and the resulting mixture was heated, at about 50°C, until the two paraben derivatives were dissolved. In a separate container a water phase was prepared by dissolving 8 g (0.2%) of Germall 115 (imidazolidinyl urea from Sutton Laboratories, Inc., Chatham, New Jersey) in a solution of 80 g (2.0%) of glycerine and 912 g (22.8%) of deionized water, The water and oil phases were combined. To the resulting mixture was added 1000 g (25.0%) of Tween 21 (polysorbate 21 from ICI Americas, Inc., Wilmington, Delaware) at room temperature and the mixture was allowed to equilibrate overnight prior to transferring the resulting water-in-oil microemulsion composition into appropriate containers for storage. Example 2 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil Silcone 344 Fluid 800 20.0 Robane 588 14.7 Ritachol 1000 80 2.0 isopropyl myristate 120 3.0 jojoba oil 400 10.0 Water deionized water 832 20.8 glycerine 160 4.0 methylparaben 6 0.15 propylparaben 6 0.15 Germall 115 8 0.2 Surfactant T-Maz 21 (poly-sorbate 21 from Mazer Chemicals Inc., Gurnee, Illinois) 1000 25.0 Example 3 A water-in-oil microemulsion was prepared containing the following ingredients according to the general procedure of Example 1. Phase Ingredient Weight (g) Weight % Oil Silcone 344 Fluid 200 20.0 Robane 129 12.9 jojoba oil 100 10.0 isopropyl myristate 30 3.0 propylparaben 1 0.1 propylene glycol 20 2.0 myristyl alcohol 10 1.0 cetyl alcohol 6 0.6 polysorbate 60 4 0.4 Water deionized water 244 24.4 Germall 115 3 0.3 methylparaben 3 0.3 Surfactant polysorbate 21 250 25.0 Example 4 Following the procedure outlined in Example 3, the following ingredients were formulated to provide a water-in-oil microemulsion Phase Ingredient Weight (g) Weight % Oil Silcone 344 Fluid 800 20.0 Robane 594 14.85 isopropyl myristate 120 3.0 jojoba oil 400 10.0 Water glycerine 80 2.0 deionized water 904 22.6 propylparaben 6 0.15 methylparaben 6 0.15 Germall 115 8 0.20 Surfactant sodium dodecyl sulfate 2 0.05 T-Maz 21 1080 27.0 Example 5 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil cyclomethicone 24.22 24.22 isocetyl alcohol 31.98 31.98 propyl paraben 0.1 0.1 Water deionized water 16.98 16.98 propylene glycol 1.41 1.41 Dowicil 200 (quaternium-15) 0.2 0.2 methyl paraben 0.1 0.1 Surfactant polysorbate 21 23.15 23.15 polysorbate 60 0.37 0.37 myristyl alcohol 0.93 0.93 cetyl alcohol 0.56 0.56 Example 6 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil cyclomethicone 15.09 15.09 lanolin oil 19.92 19.92 propyl paraben 0.10 0.10 Water deionized water 13.45 13.45 propylene glycol 1.13 1.13 Dowicil 200 0.20 0.20 methyl paraben 0.10 0.10 Surfactant polysorbate 21 46.30 46.30 polysorbate 80 0.74 0.74 myristyl alcohol 1.85 1.85 cetyl alcohol 1.12 1.12 Example 7 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil cyclomethicone 18.96 18.96 caprylic/capric triglyceride 25.04 25.04 propyl paraben 0.10 0.10 Water deionized water 9.76 9.76 propylene glycol 0.83 0.83 Dowicil 200 0.20 0.20 methyl paraben 0.10 0.10 Surfactant polysorbate 21 41.67 41.67 polysorbate 60 0.67 0.67 myristyl alcohol 1.67 1.67 cetyl alcohol 1.00 1.00 Example 8 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil cyclomethicone 21.12 21.12 diisopropyl sebacate 27.88 27.88 propyl paraben 0.10 0.10 Water deionized water 19.02 19.02 propylene glycol 1.58 1.58 Dowicil 200 0.20 0.20 methyl paraben 0.10 0.10 Surfactant polysorbate 21 27.78 27.78 polysorbate 60 0.44 0.44 myristyl alcohol 1.11 1.11 cetyl alcohol 0.67 0.67 Example 9 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil cyclomethicone 17.76 17.76 isopropyl isostearate 23.44 23.44 propyl paraben 0.10 0.10 Water deionized water 30.85 30.85 propylene glycol 2.54 2.54 Dowicil 200 0.20 0.20 methyl paraben 0.10 0.10 Surfactant polysorbate 21 23.15 23.15 polysorbate 60 0.37 0.37 myristyl alcohol 0.93 0.93 cetyl alcohol 0.56 0.56 Example 10 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil cyclomethicone 4.56 4.56 isostearic acid 6.02 6.02 propyl paraben 0.10 0.10 Water deionized water 17.7 17.7 propylene glycol 1.47 1.47 Dowicil 200 0.20 0.20 methyl paraben 0.10 0.10 Surfactant polysorbate 21 64.68 64.68 polysorbate 60 1.03 1.03 myristyl alcohol 2.58 2.58 cetyl alcohol 1.56 1.56 Example 11 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil cyclomethicone 21.12 21.12 triisocetyl citrate 27.88 27.88 propyl paraben 0.10 0.10 Water deionized water 19.02 19.02 propylene glycol 1.58 1.58 Dowicil 200 0.10 0.10 methyl paraben 0.20 0.20 Surfactant polysorbate 21 27.78 27.78 polysorbate 60 0.44 0.44 myristyl alcohol 1.11 1.11 cetyl alcohol 0.67 0.67 Example 12 A water-in-oil microemulsion composition containing the following ingredients was prepared according to the procedure of Example 1: Phase Ingredient Weight (g) Weight % Oil cyclomethicone 21.03 21.03 diisopropyl dimerate 27.77 27.77 propyl paraben 0.10 0.10 Water deionized water 23.82 23.82 propylene glycol 1.97 1.97 Dowicil 200 0.20 0.20 methyl paraben 0.10 0.10 Surfactant polysorbate 21 23.15 23.15 polysorbate 60 0.37 0.37 myristyl alcohol 0.93 0.93 cetyl alcohol 0.56 0.56 Example 13 An oil phase was prepared by combining 0.49 g (0.49%) of cetyl alcohol, 0.81 g (0.81%) of myristyl alcohol, 0.15 g (0.15%) of methylparaben, 0.15 g (0.15%) of propylparaben, 0.32 g (0.32%) of polysorbate 60, 2.17 g (2.17%) of isocetyl alcohol, and 2.17 g (2.17%) of 2-octyldodecanol, and heating the resulting mixture with agitation until all solids had dissolved, The remainder of the oil phase ingredients were added; 25.93 g (25.93%) cyclomethicone, 12.08 g (12.08%) squalane, 3.12 g (3.12%) jojoba oil, 3.12 g (3.12%) isopropyl myristate, 3.12 (3.12%) p-(2-ethylhexyl)dimethylaminobenzoate, and the mixture stirred until homogeneous. To the oil phase was added 21.66 g (21.66%) polysorbate 21 and 0.25 g (0.25%) fragrance oil and the resulting mixture stirred until homogeneous. A water phase was prepared in a separate container by combining 18.79 g (18.79%) deionized water, 0.20 g (0.20%) quaternium-15, 0.22 g (0.22%) sodium lauryl sulfate, 0.83 g (0.83) butylene glycol, 1.00 g (1.00%) 2-phenoxyethanol, 1.25 g (1.25%) propylene glycol, and 2.17 g (2.17%) sodium laureth sulfate (30% by weight in water), and heating the resulting mixture under agitation until homogeneous. The water phase was added to the previously prepared mixture and the resulting composition was stirred until homogeneous. Once the mixture was homogeneous the composition was stored at room temperature until ready for use. Two water-in-oil microemulsions of the invention were prepared containing a sunscreen. The preparation of these compositions is illustrated below. Example 14 An oil phase was prepared by combining 260 g (26.0%) of Silicone 344 Fluid, 157 g (15.7%) of Robane, 30 g (3.0%) of isopropyl myristate, 30 g (3.0%) of Escalol 507 (p-(2-ethylhexyl)dimethylaminobenzoate) and 20 g (2.0%) of (2-hydroxy-4-methoxyphenyl)phenylmethanone, and heating the resulting mixture with agitation until homogeneous. To the oil phase was added 1.5 g (0.15%) of propylparaben, and the resulting mixture was stirred until the propylparaben was dissolved. A water phase was prepared in a separate container by combining 248 ml (24.8%) of water and 1.5 g (0.15%) of methylparaben with 2.0 g (0.2%) of Germall 115 and heating the resulting mixture under agitation until homogeneous. The oil and water phases were combined and 250 g (25.0%) of T-Maz 21 was added thereto. The resulting composition was stirred until homogeneous and stored at room temperature until ready for use. Example 15 An oil phase was prepared by combining 1040 g (26.0%) of Silicone 344 Fluid, 628 g (15.7%) of Robane, 120 g (3.0%) of isopropyl myristate, 120 g (3.0%) of Escalol 507 and 80 g (2.0%) of (2-hydroxy-4-methoxyphenyl)phenylmethanone in a suitable container. The mixture was heated and stirred until homogeneous. To the oil phase was added 6 g (0.15%) of methylparaben and 6 g (0.15%) of propylparaben with stirring until the mixture was homogeneous. A water phase was prepared in a separate container by combining 992 g (24.8%) of water with 8 g (0.20%) of Germall 115 and 8 g (0.2%) of sodium dodecyl sulfate. The oil and water phases were combined and 992 g (24.8%) of Tween 21 was added thereto. The mixture was stirred until homogeneous and stored at room temperature until ready for use. Certain of the compositions prepared above were tested to demonstrate efficacy as moisturizing agents. The test was conducted on dry skin, and the compositions to be tested were used over a 3-week period, followed by a two-week regression period. Thirty-two subjects were used in the study to test the efficacy of the formulations. Subjects were divided into two groups of 16 and each member of one group randomly received the formulation of Example 1 on one leg and the formulation of Example 2 on the other leg. In the second group subjects randomly received the formulation of Example 4 on one leg. The study was carried out for seven weeks. For the first two weeks, skin was allowed to dry. For the next three weeks treatment was conducted, and the final two weeks were a regression period. Subjects with obvious skin conditions, extensive varicose veins, deep suntans, or conditions on their legs other than dry skin were excluded from the study. Subjects ranged in age from 18 to 45 years. Evaluations were performed blind by the same evaluator, when possible. Evaluations were done 7, 5 and 3 days before application, the initial day of treatment prior to application, and 1, 2, 3, 4, 7, 9, 10, 11, 15, 16, 17, 18, 21, 22, 23, 24, 25, 28, 30, 32 and 35 days after the initial application. Test formulations were applied to the leg(s) twice each day for three weeks, once in the morning in the laboratory and each evening at home on weekdays. All week-end applications (morning and evening) were performed at home. No other skin moisturizers except the test formulations were allowed during the course of the study. In addition, the subjects were not allowed to swim or sunbathe. Showers, baths, and water contact to the legs were also not allowed the mornings that evaluations were performed. Evaluations were performed according to the following scale: 0 = smooth, no evidence of dryness 1 = slightly dry skin 2 = moderately dry skin; peeling 3 = severely dry skin; faking, peeling 4 = extremely dry skin; faking, peeling and/or fissures Results (mean dryness scores) of each of the formulations were compared to the untreated control and to the positive control groups. In addition, each product was evaluated for significant change from day 0 for each evaluation day in the study. This data is presented below in Table I as the average of the 16 subjects employed. Moisturization study Days After First Application Formulation of Example No. 1 2 4 0 3.0 3.0 3.0 1 2.0 1.8 2.3 2 0.9 0.8 1.3 3 0.3 0.4 0.8 4 0.5 0.3 0.6 7 0.1 0.1 0.7 9 0.5 0.4 0.4 10 0.3 0.2 0.5 11 0.1 0 0.5 15 0.9 0.7 1.3 16 0.2 0.2 0.8 17 0.2 0.3 0.4 18 0.1 0.1 0.3 21 0.1 0.1 0.3 22 0.5 0.3 0.9 23 0.2 0.3 1.3 24 0.5 0.3 1.1 25 0.5 0.4 1.1 28 0.9 0.6 1.6 30 1.1 1.0 1.9 32 1.8 1.8 2.3 35 2.4 2.4 2.8 The data generated from the preceding experiment indicate the effectiveness of the formulae of Examples 1 and 2 as moisturizers. The formula of Example 4 demonstrated moderate effectiveness as a moisturizer.

Claims: A stable water-in-oil or oil-in-water microemulsion non-irritating moisturizing composition which when applied to the skin promotes the penetration of moisturizers into the skin and leaves little residue on the surface of the skin following its application comprising from 1% by weight to 46% by weight of moisturizer, from 14% by weight to 90% by weight of microemulsion forming surfactant, from 1% by weight to 79% by weight of polysiloxane, from 2% by weight to 54% by weight of skin humectant, and a sunscreen, said composition having an average droplet size in the range of 0.001 um to 0.2 um in diameter. A microemulsion composition of Claim 1 comprising from 1% by weight to 8% by weight of a sunscreen, from 1% to 46% by weight of moisturizer, from 15% by weight to 79% by weight of a polysiloxane compound, from 15% by weight to 79% by weight of a microemulsion forming surfactant, and from 5% to 50% by weight of skin humectants. A composition as claimed in Claim 1 or claim 2, comprising as additional ingredients from 0.1% by weight to 1.0% by weight of preservatives. A composition of claim 3 consisting of: Ingredient Weight % cyclomethicone 26.0 squalane 15.7 isopropyl myristate 3.0 p-(2-ethylhexyl)dimethylaminobenzoate 3.0 benzophenone-3 2.0 water 24.8 polysorbate 21 25.0 methylparaben 0.15 propylparaben 0.15 imidazolidinyl urea 0.2 A composition as claimed in Claim 3 consisting of: Ingredient Weight % cyclomethicone 26.0 squalane 15.7 isopropyl myristate 3.0 p-(2-ethylhexyl)dimethylaminobenzoate 3.0 benzophenone-3 2.0 water 24.8 polysorbate 21 24.8 sodium dodecyl sulfate 0.2 methylparaben 0.15 propylparaben 0.15 imidazolidinyl urea 0.2 A moisturizing microemulsion composition as claimed in Claim 1 which comprises a sunscreen and: a) from 1.0% by weight to 36.0% by weight of a fatty alcohol, from 23.5% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 28.0% by weight of a polysiloxane, and from 2.0% by weight to 36.0% by weight of a skin humectant; b) from 1.0% by weight to 46.0% by weight of an animal oil, from 14.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 35.0% by weight of a polysiloxane, and from 2.0% by weight to 18.0% by weight of a skin humectant; c) from 1.0% by weight to 31.0% by weight of a triglyceride, from 37.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 35.0% by weight of a polysiloxane, and from 2.0% by weight to 24.0% by weight of a skin humectant; d) from 1.0% by weight to 41.0% by weight of a fatty diester, from 23.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane, and from 2.0% by weight to 42.0% by weight of a skin humectant; e) from 1.0% by weight to 41.0% by weight of a branched chain fatty ester, from 18.5% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane, and from 2.0% by weight to 54.0% by weight of a skin humectant; f) from 1.0% by weight to 6.0% by weight of a fatty acid, from 60.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 5.0% by weight of a polysiloxane, and from 2.0% by weight to 26.0% by weight of a skin humectant; g) from 1.0% by weight to 41.0% by weight of a tribasic acid ester, from 23.0% by weight to 90.0% by weight of a microemulsion forming surfactant, from 1.0% by weight to 31.0% by weight of a polysiloxane, and from 3.0% by weight to 33.0% by weight of a skin humectant; h) from 3.0% by weight to 35.0% by weight of a vegetable oil, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant, from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant; i) from 5.0% by weight to 35.0% by weight of a long chain hydrocarbon, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant; or j) from 5.0% by weight to 35.0% by weight of a straight chain fatty ester, from 20.0% by weight to 80.0% by weight of a microemulsion forming surfactant, from 10.0% by weight to 70.0% by weight of a polysiloxane, and from 5.0% by weight to 50.0% by weight of a skin humectant. A composition as claimed in claim 6 which consists of: Ingredient Weight % cyclomethicone 25.93 p-(2-ethylhexyl)dimethylaminobenzoate 3.12 fragrance oil 0.25 squalane 12.08 jojoba oil 3.12 isopropyl myristate 3.12 myristyl alcohol 0.81 cetyl alcohol 0.49 isocetyl alcohol 2.17 2-octyldodecanol 2.17 deionized water 18.79 propylene glycol 1.25 butylene glycol 0.83 polysorbate 21 21.66 polysorbate 60 0.32 sodium laureth sulfate (30% by weight in water) 2.17 sodium lauryl sulfate 0.22 2-phenoxyethanol 1.00 quaternium-15 0.20 methyl paraben 0.15 propyl paraben 0.15 A method for cosmetically moisturizing skin which comprises administering to said skin a microemulsion composition as claimed in any one of claims 1 to 7. A method as claimed in claim 8 in which a macroemulsion moisturizing composition is subsequently applied to the skin. Use of a microemulsion as claimed in any one of claims 1 to 7 in a method for cosmetically moisturizing skin.

Inventors: LINN EDWARDS EON-CHAO, WEST MICHAEL PHILBERT, YORK THOMAS OLIVER, LINN, EDWARDS EON-CHAO, WEST, MICHAEL PHILBERT, YORK, THOMAS OLIVER
Applicants: UNILEVER NV, UNILEVER N.V.
Application year: 1986
Main classification: A61K7
IPC codes: A61K8, A61Q19, A61K9, C08L83