Sunscreen having disappearing color

INTRODUCTION TO THE INVENTION
The invention relates to compositions for skin application, to protect against the effects of ultraviolet radiation exposure.
Sunscreens are substances or compositions applied to the skin to protect the skin from damage, such as sunburn, due to excessive exposure to ultraviolet radiation. The typical commercial product is an emulsion, such as an emulsion having a continuous (external) aqueous phase and a discontinuous (internal) oily phase; such "oil-in-water" emulsions have a particularly pleasing feel when applied to the skin, since the sensation is one of applying an aqueous material. Most of such products are sold in the form of lotions. When uniformly applied to the body, sunscreens can be highly effective in protecting against damage. However, less effective protection can occur when areas of the body are unevenly covered because the sunscreen is hard to see while being spread onto the skin. Children may be at greater risk of damage than adults, since self-applied coverage on children's skin tends to be more incomplete, uneven or inconsistent, and children tend to be less aware of their sunburn condition until it becomes serious.
PCT International Patent Application WO 94/26233 teaches that phenolphthalein, an acid-base indicator, can be added to sunscreens to create a disappearing pink coloration, provided the sunscreens are formulated at a pH greater than 9.0. However, phenolphthalein can induce skin rashes and eruptions. Additionally, formulations with this pH are too highly alkaline and can be irritating to the skin.
PCT International Patent Application WO 95/28912 teaches composite UV sunblock compositions that may contain colored particles. However, when the sunscreen of WO 95/28912 is topically applied to the skin, the skin remains visibly colored.
U.S. Pat. No. 5,747,011 relates to a colored sunscreen composition which "disappears" when dried on the skin or rubbed into the skin. The composition incorporates water-soluble dyes, as the color formers. However, it has been discovered that some common fabrics can be indelibly stained by at least some of the dyes, when the composition contacts the fabrics. Results of a staining test are reported in an article in Consumer Reports, May 1998, pages 20-23.
Accordingly, it was sought to provide a colored sunscreen formulation which could be readily visualized while the sunscreen is being applied to the skin, but would substantially disappear when rubbed into the skin, and which has a reduced potential for permanent fabric staining.
SUMMARY OF THE INVENTION
It has been surprisingly and unexpectedly found that although the inclusion of particulate ultramarine pigments in a sunscreen emulsion can render the sunscreen visually colored as it is being spread onto the skin, such coloration will substantially disappear when the sunscreen emulsion is rubbed into the skin.
Thus, in one embodiment, the present invention is directed toward a colored sunscreen emulsion comprising:
a) at least one ultramarine pigment that imparts a color other than white to the emulsion, but when the emulsion is rubbed into the skin, the color substantially disappears;
b) at least one sunscreen active agent in an amount effective to protect skin against the actinic radiation of the sun;
c) at least one emulsifier; and
d) sufficient water to form the colored emulsion.
The amount of the ultramarine pigment in the emulsion can range from about 0.5 to about 10 weight percent of the emulsion, preferably from about 1 to about 5 weight percent of the emulsion.
Optionally, the colored, sunscreen emulsion can contain one or more additional ingredients, including emollients, waterproofing agents, dry-feel modifiers, insect repellents, antimicrobial preservatives and/or fragrances.
In another embodiment, the present invention is directed towards a method for protecting the skin against sunburn comprising topically applying the sunscreen emulsion as described above to the skin.
An advantage of the present invention is that it provides a sunscreen and a method for protecting against sunburn that enables the user to apply the sunscreen more completely and uniformly to the skin, thus providing more effective protection against skin damage.
A second advantage of the present invention is that it provides a sunscreen with a color indicator which has a low fabric staining potential, and for which those stains that form can easily be removed from fabrics.
A third advantage of the present invention is that it provides a colored sunscreen and a method for protecting against sunburn which is more enjoyable for children to use because of the attractiveness and appealing nature of the color indicator.
DETAILED DESCRIPTION OF THE INVENTION
In the present specification, the terms "emulsion," "formulation" and "composition" can be used interchangeably. The emulsion of the present invention contains one or more particulate ultramarine pigments, one or more sunscreen actives, one or more emulsifiers, water; and may optionally contain one or more emollients, humectants, dry-feel agents, waterproofing agents, insect repellents, preservatives, antioxidants, chelating agents and fragrances.
Ultramarine Pigments
Particulate ultramarine pigments are well known as an ingredient in water-resistant cosmetics, particularly eye liners and shadows, mascara, foundations and other products. The pigments are complex sodium aluminum sulfosilicates having a structure related to zeolites and empirical formulas approximating Na.sub.7 Al.sub.6 Si.sub.6 O.sub.24 S.sub.3 ; ultramarines are synthetically prepared by heat treatment (such as at temperatures about 700-800.degree. C.) and very slow subsequent cooling of mixtures of kaolin, silica, sulfur, sodium carbonate, sodium sulfate and a reducing agent such as rosin or charcoal pitch. The color is determined by formulation parameters, firing temperature and time, cooling rate and other factors, including any final chemical treatments which may be employed. Commercially available colors include green, blue, violet, red, rose and pink; the available products are usually in the form of very small particles, at least about 99.8 percent of which will pass through a 325 mesh (0.044 mm) sieve. Representative ultramarine products are those available from Whittaker, Clark & Daniels, Inc., South Plainfield, N.J. U.S.A.
Ultramarine pigments are quite insoluble in water and organic solvents, but (unless specially treated to provide acid resistance) are readily decomposed by acidic substances. Thus, the inventors have discovered that residual fabric stains caused by contact with ultramarine-containing sunscreen emulsions can be removed by treatment of the stained areas with dilute or weak acids, such as hydrochloric acid, sulfuric acid, acetic acid, lemon juice, citric acid or boric acid, either used alone or as a pretreatment with subsequent normal cleaning procedures. Suitable ultramarine pigments for use in the present invention are those which are substantially decolorized by contact with 5 percent acetic acid for less than about one hour. In general, fabrics (including carpets and other commodities fabricated from synthetic and natural fibers) will not incorporate ultramarine stains if a sunscreen formulation is not allowed to remain in contact with the fabric for sufficient time to permit separation of the phases in the emulsion, such as occurs upon evaporation of water; the sunscreen should be rinsed from the fabric (such as with water, or a soap or detergent solution) as soon as possible. However, even if the contact is not appreciated until after fabric staining has occurred, dilute or weak acid applications can be used to remove the stain. Of course, the fabric should be tested in an inconspicuous location for compatibility with specific acids, before stain removal treatment is attempted.
It is desirable to use pigments which form colors easily visualized when a sunscreen-effective amount of the formulation is spread onto the skin. Generally preferred colors include blue, purple, violet, green and aqua, all of which colors contrast with the skin quite vividly.
The sunscreen emulsion should contain the ultramarine pigment in an amount sufficient to enable the sunscreen to be readily visualized when initially applied to the skin, but which allows the color to substantially disappear when the sunscreen emulsion is rubbed into the skin. One or more ultramarine pigments can be employed in the composition, in an amount totaling about 0.5 to about 10 percent by weight of the sunscreen composition, preferably from about 1 to about 5 percent, and more preferably from about 1 to about 3 percent if the pigment has sufficient color intensity to function at such lower levels.
Sunscreen Active Ingredients
The compositions of the present invention can contain a sunscreening effective amount of one or more oil-soluble or water-soluble sunscreening UV-B active agents or a mixture of one or more UV-B actives and one or more UV-A actives. UV-A type sunscreening actives protect against long wavelength actinic radiation of the sun in the 320 to 400 nm range and UV-B type sunscreening actives protect against shorter wavelength actinic radiation of the sun in the 290-320 nm range.
Typical sunscreen actives include: aminobenzoic acid at up to about 15 weight percent; cinoxate at up to about 3 weight percent; avobenzone at up to about 3 weight percent or about 2 to 3 percent in admixture with one or more other sunscreen active agents; diethanolamine methoxycinnamate at up to about 10 weight percent or about 8 to 10 percent in admixture; digalloyl trioleate at up to about 5 weight percent or about 2 to 5 percent in admixture; dioxybenzone at up to about 3 weight percent alone or in admixture; ethyl 4-[bis(hydroxypropyl)]-aminobenzoate at up to about 5 weight percent or about 1 to 5 percent in admixture; glyceryl aminobenzoate at up to about 3 weight percent or about 2 to 3 percent in admixture; homosalate at up to about 15 weight percent or about 4 to 15 percent in admixture; lawsone at up to about 0.25 weight percent, together with dihydroxyacetone at up to about 3 weight percent, alone or in admixture; menthyl anthranilate at up to about 5 weight percent or about 3.5 to 5 percent in admixture; octocrylene at up to about 10 weight percent or 7 to about 10 percent in admixture; octyl methoxycinnamate at up to about 7.5 weight percent or about 2 to 7.5 percent in admixture; octyl salicylate at up to about 5 weight percent or about 3 to 5 percent in admixture; oxybenzone (benzophenone-3) at up to about 6 weight percent or about 2 to 6 percent in admixture; padimate O at up to about 8 weight percent or about 1.4 to 8 percent in admixture; phenylbenzimidazole sulfonic acid at up to about 4 weight percent or about 1 to about 4 percent in admixture; red veterinary petrolatum at up to about 100 percent or at least about 30 percent in admixture; sulisobenzone at up to about 10 weight percent or about 5 to 10 percent in admixture; titanium dioxide at up to about 25 weight percent or about 2 to 25 percent in admixture; and trolamine salicylate at up to about 12 weight percent or about 5 to 12 percent in admixture.
Typical suitable UV-B type sunscreening actives include benzophenone-3; benzophenone-8; substituted para-aminobenzoates; alkyl esters of p-methoxycinnamate, including octyl p-methoxycinnamate, available from Givaudan Corp., Clifton, N.J. U.S.A. under the tradename Parsol MCX; and octyl salicylate available from Harmann and Riemer, Springfield, N.J. U.S.A. The amount of UV-B type sunscreening active should be sufficient to give an SPF of 2 to at least 15.
Typical suitable UV-A type sunscreening actives include oxybenzone and avobenzone. Sunscreen emulsions containing mixtures of UV-B and UV-A type sunscreen actives should be able to provide an SPF value between about 2 and about 50, or higher.
Except as noted otherwise, one or more sunscreen actives can be employed in the present composition in amounts up to about 35 weight percent, preferably about 12 to about 30 weight percent of the sunscreen composition, more preferably from about 5 to about 30 weight percent.
Emulsions/Emulsifiers
A stable emulsion is a mixture of two immiscible liquids, i.e. liquids that are not mutually soluble, but which can form a fluid in which very small droplets of one component are stably dispersed throughout the other liquid, giving the mixture the appearance of a homogeneous fluid. Emulsions can include particulate materials and materials which are solid or solid-like at room temperature, but which will liquefy at higher temperatures used during formation of the emulsion. The presence of an emulsifier enhances the ability of one of the immiscible liquids to remain in a continuous form, while allowing the other immiscible liquid to remain in a dispersed droplet form. Thus, one function of an emulsifier, a stabilizing compound, is to assist in the production of a stable emulsion. A secondary function of emulsifiers is to provide a thickening or "bodying" to an emulsion. Typically, emulsifiers are molecules with non-polar and polar parts that are able to reside at the interface of the two immiscible liquids. As used herein in reference to the emulsifiers, the term "HLB value" means the hydrophilic/lipophilic balance. The HLB value has been used by those skilled in the emulsion art as an approximate guide for selecting emulsifiers useful for preparing the various types of emulsions: emulsifiers having HLB values at least about 7 are commonly used to prepare oil-in-water emulsions.
An oil-in-water (o/w) emulsion is a mixture where water-insoluble droplets (the discontinuous phase) are dispersed in a continuous aqueous phase. A water-in-oil (w/o) emulsion is a mixture where water droplets (the discontinuous phase) are dispersed in a continuous oily phase. Preferably, but not necessarily, the composition of the present invention is an oil-in-water emulsion where the water-insoluble actives are dispersed in the oil phase, prior to mixture with the aqueous phase. The type of emulsion formed, oil-in-water (o/w) or water-in-oil (w/o), is sometimes determined by the volume ratio of the two liquids provided the ratio is sufficiently high. For example, with 5% by volume aqueous phase and 95% by volume oily phase (an oil:water phase ratio of 19), the emulsion likely will become w/o. For moderate ratios (such as <3), the type of emulsion is decided by several factors, such as order of addition or type of emulsifier. One liquid slowly added to a second liquid with agitation usually results in the second liquid being the continuous phase. Another factor is preferred solubility of the emulsifier, the phase in which the emulsifier is soluble most probably will be continuous.
More complex emulsions such as double emulsions are formed where droplets of an emulsion are dispersed in a continuous phase. For example, in an oil-in-water-in-oil (o/w/o) emulsion, the water in a continuous water phase containing dispersed oil droplets is itself dispersed in a continuous oil phase. Similarly, in a water-in oil-in-water (w/o/w) emulsion, the oil in a continuous phase containing dispersed water droplets is itself dispersed in a continuous water phase. These more complex emulsions, however, are not commonly used for products such as sunscreens.
Typical suitable emulsifiers having an HLB value about 1 to about 7 include, without limitation, sorbitan monooleate, sorbitan sesquioleate, sorbitan isostearate, sorbitan trioleate, PEG-22/dodecyl glycol copolymer, PEG45/dodecyl glycol copolymer, polyglyceryl-3-diisostearate, polyglycerol esters of oleic/isostearic acid, polyglyceryl-6 hexaricinolate, polyglyceryl-4 oleate, polyglyceryl-4 oleate/PEG-8 propylene glycol cocoate, oleamide DEA, sodium glyceryl oleate phosphate and hydrogenated vegetable glycerides phosphate.
Emulsifiers useful in the present invention may be anionic, cationic or non-ionic, and either liquid or solid at room temperature. Emulsifiers which are salts may be formed in-situ when their constituents (such as stearic acid and triethanolamine, which form TEA-stearate) are present together in the formulation. Suitable emulsifiers further include, without limitation, sorbitan esters such as sorbitan isostearate available as Crill 6, tradename of Croda Inc. of New York, N.Y. U.S.A.; polyglyceryl-3 distearate available as Cremophor GS-32, tradename of BASF, Parsippany, N.J. U.S.A.; and carbomer, which is a homopolymer of acrylic acid crosslinked with an allyl ether of sucrose, available as Carbopol 941, tradename of B.F. Goodrich, Cleveland, Ohio U.S.A. Other useful emulsifiers include ceteareth-15, cetyl alcohol, cetyl phosphate, dimethicone copolyol phosphate, glyceryl isostearate, hydrogenated lecithin, laureth-12, PEG-20 distearate, PEG-8 oleate, PEG-40 sorbitan diisostearate, polyglyceryl-10 distearate, polysorbate 20, polysorbate 80, PPG-7 lauryl ether, sodium laureth sulfate, sorbitan sesquioleate and acrylates/C.sub.10-30 alkyl acrylate crosspolymer; these are only representatives from some of the useful emulsifier chemical classes.
During preparation of the emulsion, an acid or a base may be added to adjust the pH of one or more ingredients, e.g. to adjust the viscosity of a polymeric thickener, prior to its inclusion in the sunscreen composition. For example, triethanolamine, a base, can be used to increase the pH of the water phase and consequently modify the desired viscosity of the emulsion. The sunscreen typically has a pH of about 4 to about 9, preferably from about 6.5 to about 7.5; more preferably the pH of the sunscreen is approximately neutral, i.e. about 7.
Conveniently, one or more emulsifiers can be used in the compositions of the present invention in amounts ranging from about 0.05 to about 20 weight percent of emulsion, preferably from about 0.1 to about 15 percent, more preferably from about 5 to about 10 percent.
Water
Water is employed in amounts effective to form the emulsion. It is generally preferred to use water which has been purified by processes such as deionization or reverse osmosis, to improve the batch-to-batch formulation inconsistencies which can be caused by dissolved solids in the water supply. The amount of water in the emulsion or composition can range from about 2 to 95 weight percent, preferably from about 40 to 85 percent.
Emollients
An emollient is an oleaginous or oily substance which helps to smooth and soften the skin, and may also reduce its roughness, cracking or irritation. Typical suitable emollients include mineral oil having a viscosity in the range of 50 to 500 centipoise (cps), lanolin oil, coconut oil, cocoa butter, olive oil, almond oil, macadamia nut oil, aloe extracts such as aloe vera lipoquinone, synthetic jojoba oils, natural sonora jojoba oils, safflower oil, corn oil, liquid lanolin, cottonseed oil and peanut oil.
Other suitable emollients include squalane, castor oil, polybutene, odorless mineral spirits, sweet almond oil, avocado oil, calophyllum oil, ricin oil, vitamin E acetate, olive oil, silicone oils such as dimethylpolysiloxane and cyclomethicone, linolenic alcohol, oleyl alcohol, the oil of cereal germs such as the oil of wheat germ, isopropyl palmitate, octyl palmitate which is commercially available as Lexol EHP, tradename of Inolex Co. of Philadelphia, Pa. U.S.A., isopropyl myristate, hexadecyl stearate, butyl stearate, decyl oleate, acetyl glycerides, the octanoates and benzoates of (C.sub.12 -C.sub.15) alcohols, the octanoates and decanoates of alcohols and polyalcohols such as those of glycol and glycerol, ricinoleates and esters such as isopropyl adipate, hexyl laurate and octyl dodecanoate.
Other suitable emollients which are solids or semi-solids at ambient temperatures may be used. Such solid or semi-solid cosmetic emollients include hydrogenated lanolin, hydroxylated lanolin, acetylated lanolin, petrolatum, isopropyl lanolate, butyl myristate, cetyl myristate, myristyl myristate, myristyl lactate, cetyl alcohol, isostearyl alcohol and isocetyl lanolate. One or more emollients can optionally be included in the sunscreen emulsion in an amount ranging from about 10 to about 50 weight percent, preferably about 20 to about 40 percent.
Humectants
A humectant is a moistening agent that promotes retention of water due to its hygroscopic properties. Suitable humectants include glycerin, polymeric glycols such as poyethylene glycol and polypropylene glycol, mannitol and sorbitol. One or more humectants can optionally be included in the in the sunscreen in amounts from about 1 to 10 weight percent.
Dry-feel Modifier
A dry-feel modifier is an agent which when added to a emulsion, imparts a "dry feel" to the skin when the emulsion dries. Dry-feel modifiers may also reduce sunscreen migration on the skin. Dry feel modifiers can include starches, talc, kaolin, chalk, zinc oxide, silicone fluids, inorganic salts such as barium sulfate and sodium chloride, C.sub.6 to C.sub.12 alcohols such as octanol; sulfonated oils; surface treated silica, precipitated silica, fumed silica such as an Aerosil.RTM. available from Degussa Inc. of New York, N.Y. U.S.A.; dimethicone, a mixture of methylated linear siloxane polymers, available as DC200 fluid, tradename of Dow Corning, Midland, Mich. U.S.A. One or more dry-feel modifiers can optionally be included in the sunscreen in amounts ranging from 0.01 to about 20 weight percent, preferably from about 0.5 to about 6 weight percent.
Waterproofing Agents
A waterproofing agent is a hydrophobic material that imparts film forming and waterproofing characteristics to an emulsion. Typical suitable waterproofing agents include copolymers derived from polymerization of octadecene-1 and maleic anhydride in accordance with the published procedures in U.S. Pat. Nos. 3,860,700 and Re. 28,475. A preferred waterproofing agent is a polyanhydride resin, also known as PA-18, tradename of the Chevron Chemicals Co., San Francisco, Calif. U.S.A. Another preferred waterproofing agent is a copolymer of vinyl pyrollidone and eicosene monomers such as Ganex Polymer, tradename of ISP Inc. of Wayne, N.J. U.S.A.
The waterproofing agent is used in amounts effective to allow the sunscreen to remain effective on the skin after exposure to circulating water for at least 80 minutes using the procedures described by the U.S. Food and Drug Administration in "Sunscreen Drug Products for OTC Human Use," Federal Register, Vol. 43, Aug. 25, 1978, Part 2, pp. 38206-38269. One or more waterproofing agents can optionally be included in the sunscreen composition in an amount ranging from about 0.01 to about 10 weight percent, preferably about 1 to about 10 percent.
Insect Repellents
Sunscreen products are typically used by persons contemplating outdoor activities, in which contact with bothersome or potentially harmful insects is possible. Therefore, it is frequently desired to incorporate one or more insect repelling agents into the products. The most widely used active ingredient for personal care products is N.N-Diethyl-m-toluamide, frequently called "DEET" and commercially available in the form of a concentrate containing at least about 95 percent DEET. Other synthetic chemical repellents include dimethyl phthalate, ethyl hexanediol, indalone, di-n-propylisocinchoronate, bicycloheptene, dicarboximide and tetrahydrofuraldehyde. Certain plant-derived materials also have insect repellent activity, including citronella oil and other sources of citronella (including lemon grass oil), limonene, rosemary oil and eucalyptus oil. Choice of an insect repellent for incorporation into the sunscreen emulsion will frequently be influenced by the odor of the repellent. The amount of repellent agent used will depend upon the choice of agent; DEET is useful at high concentrations, such as up to about 15 percent or more, while some of the plant-derived materials are typically used in much lower amounts, such as 0.1 percent or less.
Antimicrobial Preservative
An antimicrobial preservative is a substance or preparation which destroys, or prevents or inhibits the proliferation of, microorganisms in the sunscreen composition, and which may also offer protection from oxidation. Preservatives are frequently used to make self-sterilizing, aqueous based products such as emulsions. This is done to prevent the development of microorganisms that may be in the product from growing during manufacturing and distribution of the product and during use by consumers, who may further inadvertently contaminate the products during normal use. Typical preservatives include the lower alkyl esters of para-hydroxybenzoates (parabens), especially methylparaben, propylparaben, isobutylparaben and mixtures thereof, benzyl alcohol and benzoic acid. One or more antimicrobial preservatives can optionally be included in the sunscreen composition in an amount ranging from about 0.001 to about 10 weight percent, preferably about 0.05 to about 2 percent.
Antioxidants
An antioxidant is a natural or synthetic substance added to the sunscreen to protect from or delay its deterioration due to the action of oxygen in the air (oxidation). Anti-oxidants prevent oxidative deterioration which may lead to the generation of rancidity and nonenyzymatic browning reaction products. Typical suitable antioxidants include propyl, octyl and dodecyl esters of gallic acid, butylated hydroxyanisole (BHA, usually purchased as a mixture of ortho and meta isomers), butylated hydroxytoluene (BHT), nordihydroguaiaretic acid, vitamin E, vitamin E acetate, vitamin C and alkylated parabens such as methylparaben and propylparaben. One or more antioxidants can optionally be included in the sunscreen composition in an amount ranging from about 0.001 to about 5 weight percent, preferably about 0.05 to about 2 percent.
Chelating Agents
Chelating agents are substances used to chelate or bind metallic ions, such as with a heterocylic ring structure so that the ion is held by chemical bonds from each of the participating rings. Suitable chelating agents include ethylene diaminetetraacetic acid (EDTA), EDTA disodium, calcium disodium edetate, EDTA trisodium, EDTA tetrasodium and EDTA dipotassium. One or more chelating agents can optionally be included in the sunscreen in amounts ranging from about 0.001 to about 0.1 weight percent.
Fragrances
Fragrances are aromatic substances which can impart an aesthetically pleasing aroma to the sunscreen composition. Typical fragrances include aromatic materials extracted from botanical sources (i.e. rose petals, gardenia blossoms, jasmine flowers, etc.) which can be used alone or in any combination to create essential oils. Alternatively, alcoholic extracts may be prepared for compounding fragrances. However, due to the relatively high costs of obtaining fragrances from natural substances, the modern trend is to use synthetically prepared fragrances, particularly in high-volume products. One or more fragrances can optionally be included in the sunscreen composition in an amount ranging from about 0.001 to about 10 weight percent, preferably about 0.05 to about 5 percent.
Dispensers
The sunscreen emulsions of the present invention containing the disappearing color indicator can be stored or dispensed in any container suitable for convenient delivery, i.e. pouring or spraying. Such containers can include but are not limited to jars, bottles, lotion pumps, pump spray bottles and aerosols.
Application Method
To achieve the maximum possible uniformity of application to the skin, the sunscreen lotions of the invention should be spread onto exposed skin in sufficient amounts to yield a distinctly visible uniform layer of colored lotion. After it is visually verified that the desired coverage has been obtained, the lotion should be rubbed into the skin to cause the visible color to disappear. As with most sunscreen products, it is recommended that the sunscreen be applied shortly (e.g., 15 minutes) prior to commencing exposure to ultraviolet radiation; this permits the emulsion to break apart, due to evaporation of its contained water, and frees the active ingredients from the formulation.
The visualization and disappearance of the sunscreen on the skin can be evaluated using visual, chromatographic and pantone matching systems.
To evaluate the color indicator on the skin, it is helpful to have an objective, instrumental measurement of colors and intensities. Accordingly, a method has been developed using the Minolta Chroma Meter Model CR-200, which uses reflected light from a surface and gives results in terms of the CIE (International Commission on Illumination) tristimulus values. These values are subsequently transformed mathematically into the L* a* b* color space, wherein the magnitudes of changes in hue and intensity of color correspond closely with those perceived by the human eye.
L*, being achromatic, ranges from black (L*=0) to white (L*=100); this term is called "metric lightness" and is a measure of how light or dark a color is, relative to a matching shade of gray. Hue is measured in terms of the chromaticity coordinates a* and b*, where a* indicates redness (a* >0) and b* indicates yellowness (b* >0). The values of a* and b* can be plotted with a* as the x-axis and b* as the y axis, to give quantitative color information: "metric chroma" is the length of a line from the origin (a*=0, b*=0) to the point of a sample reading, while "metric hue angle" is the angle between the a* axis and the metric chroma line. Metric chroma indicates the strength of a color response (i.e., the extent to which a color differs from its matching shade of gray). Metric hue angle quantifies hue in degrees, with larger values indicating more yellow hues and smaller values indicating more red (or less yellow) hues.
The meter can be used to measure a base line skin tone as well as residual color left on the skin after rubbing a sunscreen formulation into the skin with a number of subjects, to establish a target value for disappearance of color applied to the skin.
Definitions and suppliers of many of the ingredients mentioned above or used in the following illustrative examples may be found in J. M. Nikitakis et al., Eds., CTFA International Cosmetic Ingredient Dictionary, Fourth Ed., The Cosmetic, Toiletry and Fragrance Association, Washington, D.C. U.S.A., 1991. Percentages given in this specification are, unless the context clearly dictates otherwise, percent by weight.

EXAMPLE 1
A kilogram batch of a sunscreen emulsion having an SPF value of 30 and a violet color is prepared according to the invention, using the following components:
______________________________________Component Grams______________________________________Part AWater 410.65Carbomer 941 0.24Part BSorbitol, 70% aqueous solution 48.5Methylparaben 1.94Disodium EDTA 0.1Triethanolamine 21.83Part CAloe vera lipoquinone 0.49Vitamin E 0.97Octadecene/maleic anhydride copolymer 29.1Jojoba oil 0.49Stearic acid 19.4Polyglyceryl-3 distearate 29.1Sorbitan isostearate 38.8Octyl methoxycinnamate 72.8Homomenthyl salicylate 77.6Benzophenone-3 58.2Octyl salicylate 28.5Propylparaben 0.97Dimethicone 3.88Part DOctyl salicylate 20Barium sulfate 16.98Part EWater 10Imidazolidinyl urea 1.94Part FFragrance 5.82Benzyl alcohol 9.7Part GWater 62Ultramarine Violet 30______________________________________
The emulsion is prepared using the following procedure: (1) mix the Part A components and stir to obtain a clear, lump-free mixture, then add the Part B components with continuous stirring and heat the mixture to 77-82.degree. C.; (2) in a separate vessel, mix all components of Part C (except for the octadecene/maleic acid copolymer), heat to 82-85.degree. C., then add the copolymer in small increments and stir to dissolve; (3) in a separate vessel, combine the components of Part D and mix until uniform, then add the mixture to the components of step 2; (4) using vigorous agitation, add the mixture of step 3 to the mixture of step 1, and continue mixing as the combination cools to 49-52.degree. C.; (5) with stirring, sequentially add the pre-combined components of Parts F and G to the step 4 combination, then add sufficient water to compensate for evaporative losses during the procedure; and (6) cool the emulsion to ambient temperature.
The violet sunscreen is easily visualized when spread onto the skin, but substantially disappears when rubbed into the skin.
EXAMPLE 2
A pink sunscreen emulsion is prepared, using the components and procedure of the preceding example, except that cosmetic ultramarine pink is substituted for the ultramarine violet. The pink sunscreen is easily visualized when spread onto the skin, but substantially disappears when rubbed into the skin.
EXAMPLE 3
A kilogram batch of a sunscreen emulsion having an SPF value of 40 and a blue color is prepared according to the invention, using the following components:
______________________________________Component Grams______________________________________Part AWater 500.65Carbomer 941 0.25Part BMethylparaben 2Disodium EDTA 0.1Triethanolamine 22.5Part CAloe vera lipoquinone 0.5Vitamin E 1Octadecene/maleic anhydride copolymer 30Jojoba oil 0.5Stearic acid 20Polyglyceryl-3 distearate 30Sorbitan isostearate 40Octyl methoxycinnamate 75Homomenthyl salicylate 80Benzophenone-3 60Octyl salicylate 50Propylparaben 1Dimethicone 4Part DFragrance 5Benzyl alcohol 10Part ESorbitol, 70% aqueous solution 50Ultramarine blue 5Barium sulfate 12.5______________________________________
The emulsion is prepared using the following procedure: (1) mix the Part A components and stir to obtain a clear, lump-free mixture, then add the Part B components with continuous stirring and heat the mixture to 77-82.degree. C.; (2) in a separate vessel, mix all components of Part C (except for the octadecene/maleic acid copolymer), heat to 82-85.degree. C., then add the copolymer in small increments and stir to dissolve; (3) in a separate vessel, combine the components of Part E and mix under high shear conditions until a uniform dispersion is obtained; (4) using vigorous agitation, add the mixture of step 2 to the mixture of step 1, and continue mixing as the combination cools to 49-52.degree. C.; (5) with stirring, sequentially add the pre-combined components of Parts D and E to the step 4 combination, then add sufficient water to compensate for evaporative losses during the procedure; and (6) cool the emulsion to ambient temperature.
The blue sunscreen is easily visualized when spread onto the skin, but substantially disappears when rubbed into the skin.
EXAMPLE 4
A staining test is performed to compare the discoloration potential of ultramarine pigment-containing sunscreen lotion, with that of emulsions prepared using water-soluble dyes.
Violet, rose, blue and pink-blue ultramarine formulations according to the present invention, and similarly prepared formulations using either 0.04 weight percent of a mixture of external D&C Violet #2 and D&C Red #33 (purple color) or 0.0067 weight percent of FD&C Blue #1 (light blue color) dyes as the colorants, are applied to pieces of off-white nylon carpeting having no stain-resistant coating. Approximately 2 mL of emulsion are spread onto about 25 cm.sup.2 of carpet, and the emulsions are rubbed into the fibers. After drying for about an hour, the carpet pieces are cleaned with an aqueous solution of liquid soap, carbonated water, or one of two commercial carpet cleaning products.
Each of the emulsions made with an ultramarine pigment is completely removed from the carpet by the aqueous soap solution, leaving no visible coloration. However, light stains remain on the carpet pieces after attempting to remove either of the dye-containing emulsions with each of the cleaners.
EXAMPLE 5
The potential of ultramarine pigments to stain fabrics is demonstrated, by applying ultramarine-colored sunscreen emulsions to pieces of cotton, nylon and nylon/Lycra blend woven fabric samples, rubbing the emulsions into the fabrics and allowing the samples to dry under ambient room conditions for at least 24 hours. The samples are then laundered in an home automatic washer, using a consumer detergent product and, for some samples, a consumer stain pretreatment product.
Conventional laundering completely removes the ultramarine stains from nylon, and in some cases, from the nylon/Lycra fabric blends. Although cotton and some nylon/Lycra blends have residual staining, soaking the stained fabric in vinegar is found to completely remove those stains. However, subjecting the stained fabrics to treatments with chlorine and perborate bleaches will not remove the stains.
The required soaking time for removal of residual purple ultramarine stains (from a sunscreen emulsion containing 0.2 percent ultramarine blue and 1.2 percent ultramarine violet) from cotton fabric is determined, as a function of vinegar concentration. The following table shows the approximate elapsed soaking time needed for stain removal, at various dilutions of vinegar (about 5 percent acetic acid) with tap water:
______________________________________ Vinegar:Water Hours______________________________________ 1:320 16 1:160 3 1:80 3 Undiluted <0.25______________________________________
Although the soaking time needed to remove stains caused by other ultramarine pigments may vary, it will typically not be necessary to contact the stain with undiluted vinegar longer than about one hour to accomplish complete visual disappearance.

Number	Name	Date
5523075	Fuerst et al.	Jun 1996
5567420	McEleney et al.	Oct 1996
5747011	Ross et al.	May 1998

Sunscreen having disappearing color

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