| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | October 22, 2002 |
| PATENT TITLE |
Sunscreen composition containing sol-gel microcapsules |
| PATENT ABSTRACT |
The present invention generally relates to safe and stable sunscreen compositions comprising of at least one sunscreen active ingredient in the form of an inert sol-gel microcapsules encapsulating ultraviolet absorbing compounds in any acceptable cosmetic vehicle. The composition according to the present invention can comprise several ultraviolet absorbers that may be encapsulated in the same sol-gel microcapsule or in different capsules. The hydophobicity/hydrophilicity character of the sol-gel microcapsules can be controlled by selecting suitable sol-gel precursors and suitable reaction conditions and can be chosen to be compatible with the cosmetic vehicle to be used in the sunscreen composition, thus, the present invention facilitates an easy incorporation of the composite sol-gel encapsulated sunscreen in all types of cosmetic vehicles including oil free compositions, with no necessary steps of heating or high shear forces. The sunscreen compositions of the present invention can comprise any acceptable UVA and/or UVB absorbing compounds at any desired ratio to obtain a desired accumulative ultraviolet screening spectrum. |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | April 24, 2001 |
| PATENT REFERENCES CITED |
"Contact and photocontact sensitivity to sunscreens--review of a 17-year experience and of the literature", S. Schauder and H. Ippen, European UV Sunfilters, Conference Proceedings, Paris 17-18, Nov. 1998, p. 14. "Sunlight-induced mutagenicity of a common sunscreen ingredient", Knowland et al, FEBS Letters, 324, 309-313, 1993. "Photosensitization of Guanine-Specific DNA Damage by 2-Phenylbenzimidazole and the Sunscreen Agent 2-Phenylbenzimidazole-5-sulfonic Acid", C. Stevenson and R.J.H. Davies, Chem. Res. Toxicol, 12, 38-45 1999. "Photocatalytic Degradation of Organic Contaminants: Halophenls and Related Model Compounds", U. Stafford, K.A. Gray and P.V. Kamat, Heterogeneous Chem. Rev. 3, 77-104, 1996. "Uric acid photo-oxidation assay: in vitro comparison of sunscreening agents", W.C. Dunlap et al, Int. J. Cosmetic. Sci. 20, 1-18, 1998. "Sun Protection--The influencing Factors in Creating Effective Products" W. Johncock, Mar. 1999, London |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A safe and stable sunscreen composition, comprising at least one sunscreen active ingredient and a cosmetically acceptable vehicle, wherein said sunscreen active ingredient is in the form of sol-gel microcapsules containing at least one sunscreen compound; and the at least one sunscreen compound is selected from the group consisting of sodium 3, 4-dimethoxyphenylglyoxylate, benzophenone-4, diethanolamine methoxycinnamate, Bisymi-dazylate (2,2-(1,4-Phenylene)bis)-1H-benzimidazole-4,6-disulfonic acid, monosodium salt)), camphor benzlakonium methosulfate, terephthalidene dicamphor sulfonic acid, benzylidene camphor sulfonic acid, octyltriazone, methylene bis-benzotriazolyl tetramethylbutyl phenol, Aniso-triazine (2,4-bis-{-phenyl}-6-(4-methoxy-phenyl)-(1,3,5)-triazine), Dioctyl butamido triazone, 3-benzylidene camphor, Drometrizole trisiloxane, Dimethico-diethyl-benzal-malonate, polyacrylamidomethyl benzylidene camphor, and mixtures thereof. 2. Sol-gel microcapsules encapsulating at least one sunscreen compound for use as a sunscreen active ingredient, wherein said at least one encapsulated sunscreen compound comprises at least one of isopentyl 4-methoxycinnamate, diethanolamine methoxycinnamate, 2-ethoxyethyl-p-methoxycinnamate, ethylhexyl-a-cyano-b-phenyl cinnamate, and mixtures thereof. 3. Sol-gel microcapsules encapsulating at least one sunscreen compound for use as a sunscreen active ingredient, wherein said sol-gel microcapsules co-encapsulating a sunscreen compound selected from the group consisting of 2-ethylhexyl 4-methoxycinnamate, isopentyl 4-methoxycinnamate, diethanolamine methoxycinnamate, 2-ethoxyethyl-p-methoxycinnamate, ethylhexyl-a-cyano-b-phenyl cinnamate and mixtures thereof together with a compound selected from the group consisting of Oxybenzone (benzophenone-3), benzophenone-4, benzophenone-8, benzophenone-1, benzophenone-2, benzophenone-5, benzophenone-9 and mixtures thereof. 4. Sol-gel microcapsules encapsulating at least one sunscreen compound for use as a sunscreen active ingredient, wherein said sol-gel microcapsules co-encapsulating a derivative of salicylate selected from the group consisting of Homosalate, octyl salycilate, 4-isopropylbenzyl salicylate, thiethanolamine salicylate, amyl salicylate, p-isopropyl phenyl salicylate, 4-isopropyl benzyl salicylate, and mixtures thereof together with a derivative of dibenzoylmethane selected from the group consisting of isopropyl dibenzoylmethane, 4,4'-methoxy-t-butyldibenzoylmethane and mixtures thereof. 5. Sol-gel microcapsules encapsulating at least one sunscreen compound for use as a sunscreen active ingredient, wherein said sol-gel microcapsules co-encapsulating a derivative of salicylate selected from the group consisting of Homosalate, octyl salycilate, 4-isopropylbenzyl salicylate, thiethanolamine salicylate, amyl salicylate, p-isopropyl phenyl salicylate, 4-isopropyl benzyl salicylate, and mixtures thereof together with a derivative of dibenzoylmethane selected from the group consisting of isopropyl dibenzoylmethane, 4,4'-methoxy-t-butyldibenzoylmethane and mixtures thereof and with a suitable cosmetic oil. 6. Sol-gel microcapsules according to claim 5, wherein the cosmetic oil is selected from the group consisting of Capric/caprylic triglyceride, octyl palmitate, C12-C15 alkyl benzoate, dioctyl maleate, propylene glycol dicaprylate/dicaprate, diisopropyls adipate, hexyl laurate, and mixtures thereof. 7. Sol-gel microcapsules encapsulating at least one sunscreen compound for use as a sunscreen active ingredient, wherein said sol-gel microcapsules co-encapsulating a derivative of salicylate selected from the group consisting of Homosalate, benzyl salicylate, octyl salicylate, triethanolamine salicylate, potassium salicylate, amyl salicylate, p-isopropyl phenyl salicylate, 4-isopropyl benzyl salicylate and mixtures thereof, together with a camphor derivative selected from the group consisting of 3-(4'-methylbenzylidene) camphor, 3-benzylidene camphor, 3-(4-methoxybenzylidene) camphor, and mixtures thereof. 8. Sol-gel microcapsules according to claim 7, further co-encapsulating a suitable cosmetic oil. 9. Sol-gel microcapsules encapsulating at least one sunscreen compound for use as a sunscreen active ingredient, wherein said sol-gel microcapsules encapsulating an aminobenzoic acid derivative selected from the group consisting of glyceril aminobenzoate, ethyl PABA, amyl dimethyl PABA, methyl anthranilate and mixtures thereof. 10. A safe and stable sunscreen composition comprising at least one sunscreen active ingredient and a cosmetically acceptable vehicle, wherein said sunscreen active ingredient is in the form of sol-gel microcapsules containing at least one sunscreen compound; the cosmetically acceptable vehicle contains at least one ultraviolet absorbing compound not enclosed within sol-gel microcapsules; and said at least one ultraviolet absorbing compound is water soluble. 11. A sunscreen composition according to claim 10, wherein the water soluble ultraviolet absorbing compounds are selected from the group consisting of 2-Phenylbenzimidazole-5-sulfonic acid, sodium 3, 4-dimethoxyphenylglyoxylate, benzophenone-4, diethanolamine mehtoxycinnamate, Bisymi-dazylate (2,2'-(1,4-Phenylene)bis)-1H-benzimidazole-4,6-disulfonic acid, monosodium salt)), camphor benzalkonium methosulfate, terephthalidene dicamphor sulfonic acid, and benzylidene camphor sulfonic acid. 12. A sunscreen composition according to claim 10, which is oil-free. 13. A safe and stable sunscreen composition comprising at least one sunscreen active ingredient and a cosmetically acceptable vehicle, wherein said sunscreen active ingredient is in the form of sol-gel microcapsules containing at least one sunscreen compound; the cosmetically acceptable vehicle contains at least one ultraviolet absorbing compound not enclosed within sol-gel microcapsules; and said at least one ultraviolet absorbing compound is a water insoluble micronized solid. 14. A sunscreen composition according to claim 13, wherein the water insoluble micronized solid ultraviolet absorbing compounds are selected from the group consisting of octyltriazone, methylene bis-benzotriazolyl tetramethylbutyl phenol, Aniso-triazine (2,4-bis-{[4-(2-Ethyl-hexyloxy)-2-hydroxy]-phenyl}-6-(4-methoxy-phenyl)-(1 ,3,5)-triazine), Dioxtyl butamido triazone, oxybenzone (benzophenone-3), benzophenone-1, benzophenone-2, benzophenone-6, benzophenone-8, 4,4'-methoxy-t-butyldibenzoylmethane, 4-isopropyl dibenzoylmethane, 4-methylbenzylidene camphor, 3-benzylidene camphor, Polyacrylamidomethyl benzylidene camphor, Drometrizole trisiloxane, and Dimethico-diethyl-benzal-malonate. 15. A sunscreen composition according to claim 13, which is oil-free. 16. Sol-gel microcapsules according to claim 2, wherein said at least one encapsulated sunscreen compound further comprises 2-ethylhexyl 4-methoxycinnamate. 17. Sol-gel microcapsules according to claim 9, further encapsulating at least one of 2-ethylhexyl N,N' dimethyl-4-aminobenzoate, and 4-aminobenzoic acid (PABA). 18. The sunscreen composition according to claim 1, wherein the at least one sunscreen compound further comprises at least one of 2-ethylhexyl 4-methoxycinnamate, 4-aminobenzoic acid, 2-ethylhexyl N,N-dimethyl-p-aminobenzoate, 2-cyano-3,3-diphenylacrylic acid 2-ethylhexyl ester (Octocrylene), 2-hydroxy-4-methoxy-benzophenone (Onzone), 2-phenylbenzimidizole-5-sulfonic acid, 3,3,5-trimethyl-cyclohexyl-salicylate (Homosalate), octyl salycilate, 4,4'-methoxy-t-butyldibenzoylmethane, 4-isopropyl dibenzoylmethane, 3-(4'-methylbenzyledene) camphor, 3-benzylidene camphor, triethanolamine salicylate, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 2,4-dihydroxybenzophenone, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 4-hydroxydibenzoylmethane, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 2-hydroxy-4-(2-hydroxyethoxy)benzophenone, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 4-(2-hydroxyethoxy)dibenzoylmethane. |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The present invention generally relates to safe and stable sunscreen compositions. More specifically the present invention relates to a sunscreen composition comprising at least one sunscreen active ingredient in the form of inert sol-gel microcapsules encapsulating UVB and/or UVA sunscreen compounds (ultraviolet absorbers), in any acceptable cosmetic vehicle. The composition according to the present invention can comprise several ultraviolet absorbers that may be encapsulated in the same sol-gel microcapsule or in different capsules. The encapsulation of the ultraviolet absorbers makes the composition safer for use, since the encapsulating sol-gel material forms a barrier that reduces or even prevents contact between the sunscreen compounds and human tissue. Hence, various adverse effects that are associated with the use of sunscreens, such as photoallergy and phototoxicity are prevented. Furthermore, the encapsulation reduces or even prevents cross reactivity between different sunscreen compounds when more than one such compound is present in the composition, between the sunscreen compounds and the packaging material and between the sunscreen compounds and any other component present in the composition. The present invention facilitates an easy incorporation of the composite sol-gel encapsulated sunscreen in all types of cosmetic vehicles including oil free compositions, with no necessary steps of heating or high shear forces. BACKGROUND OF THE INVENTION Sunscreens compositions are chemical compositions, which are usually applied topically to skin and hair in order to protect them from the damaging effects of the sun's radiation, especially against ultraviolet (UV) radiation. The damaging effects of sunlight exposure on skin and hair are well documented. These effects include increased incidence of skin carcinogenesis, pigmentation, anomalies and precancerous lesions such as actinic keratosis, melanoma and nonmelanoma skin cancers, as well as accelerated skin aging and undesirable changes in hair quality. In recent years, a growing number of studies show that damage is caused not only by the UVB irradiation (290-320 nm), but also by UVA irradiation (320-400 nm). The use of UV absorbing chemicals for human application is regulated by the health authorities. In the US and Australia sunscreens are regulated as over-the-counter (OTC) drugs, consequently introduction of new sunscreen active ingredients requires heavy investment of time and money. Most of the UV absorbing agents allowed for use are UVB absorbers. These include para amino benzoates, salicylates, cinnamates, anthranilate, camphors and miscellaneous chemicals. The number of UVA absorbers is more limited, with benzophcnones (UVB and UVA absorber) and dibenzoylmethanes (UVA absorber) being the most widely used. Recently new UV absorbers have entered the market. Examples of such UV absorbers are: Octyltriazone, Drometrizole trisiloxane, and Dimethico-diethyl-benzal-malonate. Some of the sunscreen active ingredients have been found to cause photoallergy and photosensitization reactions, encouraging the manufacturers to avoid using them. For example, growing public awareness to the photosensitization reactions of PABA and its derivatives has encouraged the use of PABA free products (see S. Schauder and H. Ippen, European UV Sunfilters, Conference Proceedings, Paris November 17-18 1998, p. 14). The production of another sunscreen, 4-isopropyl dibenzoyl methane was ceased in 1993 due to the high number of photoallergy incidents reported for this active ingredient (Ibid). Moreover, some of the reported cases of adverse reactions to sunscreen active ingredients relate the adverse reactions to cross reactivity of several sunscreen ingredients, as in the case of cross sensitization between different cinnamate derivatives (Ibid). Moreover, several research groups have demonstrated the photoinduced DNA damage and phototoxicity of several sunscreen agents, including Padimate-O (Knowland et al, FEBS Letters, 324, 309-313, 1993), Phenylbenzimidazole sulfonic acid (C. Stevenson and R. J. H. Davies, Chem. Res. Toxicol, 12, 38-45, 1999). Physical sunscreens such as titanium dioxide are known to be photocatalysts capable of rupturing covalent bonds (U Stafford, K. A. Gray and P. V. Kamat, Heterogeneous Chem Rev. 3, 77-104, 1996), and have been shown to produce reactive oxygen species under illumination (W. C. Dunlap et al, Int. J. Cosmetic. Sci. 20, 1-18, 1998). With the growing demand for higher SPF values and for broad-spectrum protection, manufacturers are forced to combine several active ingredients at increased concentrations (often the maximum permitted concentrations), hence the problem of cross reactivity between sunscreen active ingredients is becoming more severe. An example for cross reactivity effects is the photoinduced interaction between butyl methoxydibenzoylmethane (also known as 4,4'-methoxy-t-butyldibenzoylmethane or BMDBM), an excellent UVA absorber, with the most widely used UVB absorber octyl methoxycinnamate (R. M. Sayre et. al, 26.sup.th Annual Meeting if the American Society for Photobiology, Abstr. No. SPM-A7). This cross reactivity contributes significantly to the photochemical instability of both the UVB and the UVA active ingredients. Another problem associated with BMDMB that presents a number of composition problems, is its tendency to react with active methylene groups such as those present in formaldehyde releasing preservatives at temperatures above 30.degree. C., thus restricting the use of such preservatives (W. Johncock, Sun Protection The Influencing Factors in Creating Effective Products, March 1999 London, March 1999 and references therein). Another problem, associated with the use of high sunscreen compounds concentrations, is the tendency of some of these ingredients to crystallize at certain pH range, or if the amount of oil in the composition is not sufficient. Yet, another problematic aspect in sunscreen products is the selection of packaging material. Liquid UVB filters permeate into various plastic packaging materials (polystyrene as one example), and consequently cause decomposition or coloration of the packaging materials. UV absorbing liquids are able to permeate polymers like polystyrene, low density polyethylene and polyethylene terphthalate. This can cause fracturing of the packaging material, unacceptable colouring of white packaging material with time, and assay problems such as ensuring that the proper content of active ingredients are maintained upon storage. In the present invention it has been found that if the sunscreen active ingredients are introduced into the cosmetic vehicle in the form of sol-gel encapsulated sunscreen, cross reactivity of sunscreen active ingredients, e.g. butyl methoxydibenzoylmethane and octyl methoxycinnamate, can be reduced or even prevented. The separate encapsulation of sunscreen active ingredients in the sol-gel derived capsules creates a barrier that prevents cross interactions between these active ingredients. Furthermore, the encapsulation of UV absorbing liquids in sol-gel derived capsules reduces the contact between these liquids and the packaging material. Consequently, the problem of adverse reactions caused following permeation of the sunscreen active ingredients into the packaging material is diminished. Furthermore, the use of sol-gel encapsulated sunscreens facilitate the incorporation, in the same composition, of several components that are incompatible when simply dissolved in the composition, for example 2-phenyl benzimidizole-5-sulfonic acid with .alpha. or .beta. hydroxy acids. The present invention also allows easy incorporation of solid sunscreen active ingredient or active ingredients that tend to precipitate in various compositions, since even in a situation that solid is formed, the crystals are confined within the sol-gel capsules, hence, a pleasant non gritty feel and efficient spreading are maintained. Yet another advantage of the present invention is the ability to control the hydrophilicity/hydrophobicity character by choosing a suitable sol-gel encapsulating material, thus the encapsulated sunscreen can be conveniently introduced into the composition. It is an object of the present invention to provide safer sunscreen compositions by reducing or even preventing the contact of the light absorbing molecules (sunscreen compounds), or their possible light-induced degradation products, with human tissue. It is another object of this invention to provide a stable and safer sunscreen composition by reducing or even preventing cross reactivity between various ingredients present in the same composition. It is a further object of this invention to reduce or even to prevent the deleterious permeation of sunscreen active ingredient into plastic packaging materials which may result in fracturing of the packaging material, unacceptable colouring of white packaging material with time, and assay problems. It is a further object of this invention to provide the formulator with an easy-to-use sunscreen active ingredients, which can be incorporated easily, without applying heat or high shear forces, in any cosmetically accepted vehicle. Yet it is another object of the present invention to provide an easy incorporation of solid sunscreen active ingredient or of active ingredients that tend to precipitate, in various compositions, to thereby maintain a pleasant non gritty feel and efficient spreading. The compositions revealed by this invention are of general nature, and the method according to which they are prepared is applicable to any sunscreen compounds currently used, as well as to sunscreen compounds that will be introduced in the future. It is also applicable for other compounds that are regularly used in cosmetic compositions. Furthermore, because of the easy incorporation of the sunscreen active ingredients and the ability to control their hydrophilicity/hydrophobicity character and the capsules size, the cosmetic vehicle to be used with the sunscreen active ingredients is not limited to any group and can be any cosmetically acceptable vehicle. In the context of the present invention the term "sunscreen compound" refers to an ultraviolet (UVA and/or UVB) absorbing chemical that can be used in sunscreen composition. In the context of the present invention the term "sol-gel microcapsule" relates to a core material which is coated by a sol-gel coating matrix. In the context of the present invention the term "sunscreen active ingredient" refers to sol-gel microcapsules wherein the core material is a sunscreen compound. SUMMARY OF THE INVENTION The present invention relates to a sunscreen composition comprising as an active ingredient sol-gel derived microcapsules that encapsulate ultraviolet (UV) absorbing compounds and any cosmetically acceptable vehicle. The encapsulation of the UV absorbers forms a barrier between them and the human tissue, as well as between them and the other ingredients present in the formula and with the container in which the product is contained. The present invention further relates to sunscreen compositions in which cross reactivity between different sunscreen compounds, present in the same composition, is reduced or even prevented. The sunscreen active ingredient in the form of sol-gel microcapsules, is prepared by the method disclosed in U.S. patent application Ser. No. 09/372,176. The size of the microcapsules obtained by this method can be controlled to the range 0.01-100 .mu., preferably 0.1-10 .mu., by selecting suitable reaction conditions. The hydrophobicity/hydrophilicity character of the sol-gel microcapsules can be controlled by selecting suitable sol-gel precursors and suitable reaction conditions and can be chosen to be compatible with the cosmetic vehicle to be used in the sunscreen composition; therefore, the microcapsules can be incorporated easily into any acceptable cosmetic vehicle. The sunscreen active ingredient can be incorporated into the cosmetic vehicle in the form of an aqueous suspension of the sol-gel particles, or as a dried sol-gel powder. In a preferred embodiment of this invention, the sol-gel derived capsule materials consist of the encapsulated matter and silica or organically modified silica, in particular methyl modified silica. The sunscreen compound can be selected from any acceptable UVA absorber or UVB absorber or combination thereof. The compositions of the present invention can comprise a single active ingredient in the form of sol-gel microcapsules that encapsulate a single sunscreen compound or several sunscreen compounds together, or a combination of the active ingredients, to obtain a composition with the desired UV absorption spectrum. The concentration ratio of the active sunscreen ingredients present at the same composition is not limited and can be of any value. The sunscreen compositions according to the present invention can comprise about 1 to about 8 wt. %, in particular from about 10 to about 50 wt % (weight percent of the final composition), water suspension of sol-gel derived capsules, in any cosmetically acceptable vehicle, or can comprise about 1 to about 40 wt. %, in particular from about 5 to about 25 wt. % dry powder of sol-gel capsules, in any cosmetically acceptable vehicle. The present invention further relates to the sol-gel microcapsules encapsulating sunscreen compound for use as a sunscreen active ingredient in sunscreen compositions. This sunscreen active ingredient can be added to the cosmetic compositions at the end of the composition process, without the application of heat or shear forces. However, such steps of composition formation may be carried out if required for the purpose of formulating other constituents of the composition. The sunscreen active ingredient can be incorporated in any cosmetically acceptable oil-in-water or water-in-oil compositions; the final product may take the form of an oil, a gel, a solid stick, a lotion, a cream, a milk, an aerosol, a spray, a powder, a foam, a shampoo, a hair conditioner or lacquer or a make-up The compositions according to the present invention are of a general nature, and applicable to any sunscreen compounds currently used, as well as to compounds that will be introduced in the future. It is also applicable for other active ingredients that are regularly used in cosmetic compositions. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph of a supercoiled DNA remaining as a funciton of irradiation time with respect to some samples. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to stable and safer sunscreen compositions in which the contact between the sunscreen compounds and the human tissue, and the reactivity between sunscreen compound and other components present in the composition are reduced or even prevented, by encapsulation of the sunscreen compound/s in a sol-gel derived microcapsules. The selection of the cosmetic vehicle to be used in the composition is not limited and can be any cosmetically acceptable vehicle. The encapsulated sunscreen compound/s can be incorporated into the cosmetic vehicle in the form of an aqueous suspension of the sol-gel particles, or as a dried sol-gel powder. The sol-gel microcapsules are prepared by the method disclosed in U.S. patent application Ser. No. 09/372,176, i.e., by a) emulsifying hydrophobic solution comprising sol-gel precursors and at least one ultraviolet absorber in an aqueous solution under high shear forces and b) mixing and stirring the obtained emulsion with a second aqueous solution at a suitably selected pH to obtain the sol-gel microcapsules. The size of the microcapsules so obtained can be controlled to the range 0.01-100 .mu., preferably 0.1-10 .mu., by selecting suitable reaction conditions. The sol-gel precursors can be selected from metal or semi-metal alkoxide monomers, or metal ester monomers, or semi-metal ester monomers or monomers of the formula M(R).sub.n (P).sub.m, wherein M is a metallic or semi metallic element, R is a hydrolyzable substituent, n is an integer from 2 to 6, P is a non polymerizable substituent and m is and integer from 0 to 6, or partially hydrolyzed and partially condensed polymer thereof, or any mixture thereof. In a preferred embodiment of this invention, the sol-gel microcapsules are silica or organically modified silica microcapsules, produced through the sol-gel process disclosed in U.S. patent application Ser. No. 09/372,176. The term "organically modified silica microcapsules" refers to sol-gel microcapsules which are obtained when the sol-gel precursors are of the formula M(R).sub.n (P).sub.m, wherein M is Si, R is a hydrolyzable substituent, n is an integer from 2 to 5, P is a non polymerizable substituent and m is and integer from 1 to 6. Since the encapsulation process is general, the capsules may contain various sunscreen compounds or their mixtures. The hydrophilicity/hydrophobicity character of the capsules is determined by the encapsulating material, and not by the sunscreen compound which is encapsulated inside it. Hence, lypophilic sunscreen compounds, which normally can be dissolved only in hydrophobic, fat containing phases, are easily incorporated in the aqueous phase of any composition, be it o/w (oil in water) or w/o (water in oil) emulsions, or in oil-free compositions, e.g. gels. The compositions according to the present invention can comprise a hydrophilic composition as the cosmetic vehicle and water dispersible microcapsules encapsulating sunscreen compounds that are hydrophobic, water-insoluble. The invention further reveals that one or more sunscreen active ingredients are confined within particles of specific particle size, which is independent of the cosmetic vehicle, the composition preparation method, or the sunscreen concentration. This confinement prevents the rough feel and decreased coverage which are associated with undesired crystallization of sunscreen compounds, since in the event of crystallization the crystals are confined within the capsules, consequently the pleasant feel and efficient coverage are maintained. The aqueous suspensions of encapsulated sunscreens compounds may contain 1 to 50% wt. sunscreen compounds (a single sunscreen compound, or a combination of several sunscreens compounds together). In a preferred embodiment, the aqueous suspensions contain 20 to 40% wt. sunscreen compounds. The dried sol-gel silica powder may contain 1 to 85% wt. sunscreen compounds. In a preferred embodiment, the dried sol-gel silica powders contain 50 to 80% wt. sunscreen compound. The skilled formulator may use a suitable concentration of the aqueous suspension or the powder, to obtain the desired concentration of each sunscreen ingredient in the final composition. Thus, a cosmetic screening composition is obtained, which comprises in a cosmetically acceptable vehicle, about 1 to about 80%, in particular from about 10 to about 50% (w/w of the final composition) water suspension of the sol-gel derived capsules. In the same manner, a cosmetically acceptable screening composition may be obtained, comprising about 1 to about 40%, in particular from about 5 to about 25% (w/w of the final composition) dry powder of sol-gel derived capsules. The sol-gel containing suspension can easily be combined with o/w compositions at the end of the composition, by simple mixing or stirring with any suitable mixer or stirrer. No steps of heating or high shear force mixing are required in order to achieve good mixing. Nonetheless, the encapsulating material, being inert and stable, can sustain high shear forces such as those active in a homogenizer (Ultra Torax for example) and can sustain heating to 70.degree. C. for the typical time used in composition (up to 60 minutes), without any deterioration in the encapsulation or the capsules properties. Hence, if such processes are required for obtaining the desired formula, the aqueous suspension of the sol-gel derived sunscreen capsules can endure these processes. If w/o composition is prepared, the aqueous suspension is easily incorporated in the water phase by simple mixing or stirring. The combined water phases can then be handled as desired in a normal composition procedure known to the skilled formulator. In all these cases, several aqueous suspensions of sol-gel derived capsules containing different sunscreen active ingredients may be added together at any of these stages, in order to obtain formulae that contain several active ingredients in separate capsules, to reduce or even to prevent their cross reactivity. The sol-gel dried powder can also be easily combined with w/o compositions at the end of the composition, by simple mixing or stirring with any suitable mixer or stirrer. High shear forces may be applied to facilitate fast and efficient mixing of the powder in the cosmetic vehicle. Also, the powder may be re-suspended in the aqueous phase prior to mixing the composition to ease efficient dispersion. The inert nature and stability of the sol-gel derived capsules allows the formulator to utilize these tools without damaging the encapsulation or the capsules properties. The ease of composition when utilizing the sol-gel derived capsules is a unique advantage of this invention, and is an essential part of the innovation disclosed herein. Therefore, the composite encapsulated sunscreen active ingredient can be incorporated in cosmetically acceptable oil-in-water or water-in-oil compositions; the final product may take the form of an oil, a gel, a solid stick, a lotion, a cream, a milk, an aerosol, a spray, a powder, a foam, a shampoo, a hair conditioner or lacquer or a make-up. The composite encapsulated sunscreen active ingredient can be added to the cosmetic compositions at the end of the composition process, without the application of heat or shear forces. However, such steps of composition may be carried out if required for the purpose of formulating other constituents of the composition. It is further demonstrated and emphasized in the case of sunscreen active ingredients, which arc solid in nature, or tend to form crystals if the composition is not carefully balanced. Some examples of such active ingredient include benzophenones, dibenzoylmethanes, camphor and phenyl benzimidazole sulfonic acid in the presence of .alpha. and .beta. hydroxy acids. The encapsulation process confines these active ingredients, even in the event of crystallization, within the capsules. Consequently, the problems normally associated with crystals formation, i. e. rough feel and poor coverage, are prevented. The particle size of the capsules is determined in the encapsulation process, consequently it does not change as a result of the formula or the material encapsulated inside it, even in the event of crystal formation. An important feature of the capsules is their very efficient encapsulation of the lypophilic sunscreen compounds, which reduces or even prevents their leaching out into aqueous phases and into a large number of cosmetically acceptable oils. Thus, incorporation of incompatible active ingredients when each of them is encapsulated separately in the sol-gel capsules is a very efficient method to reduce or even to prevent their cross reactivity. Another important objective of this invention is to provide safer sunscreen products. As discussed in the background of this invention, several research groups around the world have demonstrated the potentially harmful effects of several sunscreen products on several in vitro models. It is also recognized that with the increased use of sunscreen product in the world, a growing number of incidents of photoallergy are being reported. In fact, some sunscreen products that are allowed for use by the regulations have been practically withdrawn from the market due to the high number of reported phoroallergy incidents related to them (Schauder and H. Ippen, European UV Sunfilters, Conference Proceedings, Paris November 17-18 1998, p. 14). With the encapsulated products, the contact between the active sunscreen molecules or its photodegradation products with the human tissue is eliminated. Consequently the harmful potential of the sunscreen active ingredients is dramatically minimized. It is a further object of this invention to provide a screening composition which reduces or even prevents the penetration by diffusion of sunscreen active ingredient into plastic containers, which may result in fracturing of the packaging material, unacceptable colouring of white packaging material with time, and assay problems. It has also been found that utilizing the encapsulated sol-gel sunscreen, active ingredients that form crystals in regular compositions can be easily used, as even in the event of crystallization the crystals are confined within the capsule, hence pleasant feel and efficient coverage are maintained. The sunscreen compound can be selected from the group consisting of 2-ethylhexyl 4-methoxyciinamate, 4-aminobenzoic acid, 2-ethylhexyl-N,N-dimethyl-4-aminobenzoate, 2-cyano-3,3-diphenylacrylic acid 2-ethylhexyl ester (Octocrylene), 2-hydroxy-4-methoxy-benzophenone (Oxybenzone) 2-phenylbenzimidizole-5-sulfonic acid, 3,3,5-trimethyl-cyclohexyl-salicilate (Homosalate) octyl salycilate, 4,4'-methoxy-t-butyldibenzoylmethane, 4-isopropyl dibenzoylmethane, 3-(4-methylbenzyledene) camphor, 3-benzylidene camphor, triethanolamine salicylate, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 2,4-dihydroxybenzophenone, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 4-hydroxyd ibenzoylmethane, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 2-hydroxy-4-(2-hydroxyethoxy)benzophenone, 4-N,N-(2-ethylhexyl)methyl aminobenzoic acid ester of 4-(2-hydroxyethoxy)dibenzoylmethane, sodium 3, 4-dimethoxyphenylglyoxylate, benzophenone-4, diethanolamine methoxycinnamate, Bisymi-dazylate (2,2-(1,4-Phenylene)bis)-1H-benzimidazole-4,6-disulfonic acid, monosodium salt)), camphor benziakonium methosulfate, terephthalidene dicamphor sulfonic acid, benzylidene camphor sulfonic acid, octyltriazone, methylene bis-benzotriazolyl tetramethylbutyl phenol, Aniso-triazinc (2,4-bis-{[4-(2-Ethyl-hexyloxy)-2-hydroxy]-phenyl}-6-(4-methoxy-phenyl)-(1 ,3,5)-triazine), Dioctyl butamido triazone, 3-benzylidene camphor, Drometrizole trisiloxane, Dimethico-diethyl-benzal-malonate, polyacrylamidomethyl benzylidene camphor, and mixtures thereof. The sunscreen compound can also include one or more of the following: ethylhexyl-a-cyano-b-phenyl cinnamate, triethanolamine salicylate, amyl salicylate, p-isopropyl phenyl salicylate, and 4-isopropyl benzyl salicylate. The sunscreen active ingredient can be in the form of a dried sol-gel powder. The cosmetic vehicle according to the present invention can be selected from the group consisting of fatty alcohols, fatty acids, fatty acids esters, fatty acid triglycerides, lanolin, natural or synthetic oils and waxes, water in oil and oil in water emulsions. The sunscreen composition can further comprise cosmetic adjuvants selected from thickeners, emollients, emulsifiers, humectants, surfactants, film forming agents, preservatives, antifoaming agents, fragrances, lower monoalcoholic polyols, propellants, colorants and pigments. The sunscreen composition according to the present invention can further contain additives selected from the group consisting of sunscreen actives, sunless tanning actives, skin lightening actives anti-acne actives, anti-skin wrinkling actives, vitamins, nonsteroidal anti-inflammatory actives, anesthetic actives, anti-pruritic actives, anti-microbial actives, and mixtures thereof wherein said additives are either dissolved in the cosmetic vehicle or are also in the form of sol-gel microcapsules. The sunscreen composition according to the present invention can further comprise physical sunblock active ingredients selected from the group consisting of titanium dioxide, zinc oxide, iron oxide, and mixtures thereof wherein said physical sunblock ingredients can be of any commercially available grade, including surface treated particles such as titanium dioxide, which has been surface treated with silica, alumina, stearic acid or mixtures thereof, or any other surface treatment. The sunscreen composition according to the present invention can further comprise .alpha. or .beta.-hydroxy acids such as salycilic acid, glycolic acid, lactic acid, retinoic acid and mixtures thereof. The present invention further relates to sol-gel microcapsules encapsulating at least one sunscreen compound for use as a sunscreen active ingredient in sunscreen products by easy incorporation into any cosmetically acceptable vehicle without the use of any shear forces. The sunscreen composition according to the present invention can further comprise one or more ultraviolet absorbing compounds, not enclosed within sol-gel microcapsules, that are water soluble. The sunscreen composition according to the present invention can also comprise water soluble ultraviolet absorbing compounds that are 2-Phenylbenzimidazole-5-sulfonic acid, sodium 3, 4-dimethoxyphenylglyoxylate, benzophenone-4, diethanolamine mehtoxycinnamate, Bisymi-dazylate (2,2'-(1,4-Phenylene)bis)-1H-benzimidazole-4,6-disulfonic acid, monosodium salt)), camphor benzalkonium methosulfate, terephthalidene dicamphor sulfonic acid, or benzylidene camphor sulfonic acid. The sunscreen composition according to the present invention can further be formulated such that it is oil-free. The sunscreen composition according to the present invention can also comprise one or more ultraviolet absorbing compounds, which are not enclosed within sol-gel microcapsules, that are water insoluble micronized solids. The sunscreen composition according to the present invention can further comprise water insoluble micronized solid ultraviolet absorbing compounds that are octyltriazone, methylene bis-benzotriazolyl tetramethylbutyl phenol, Aniso-triazine (2,4-bis-{[4-(2-Ethyl-hexyloxy)-2-hydroxy]-phenyl}-6-(4-methoxy-phenyl)-(1 ,3,5)-triazine), Dioxtyl butamido triazone, oxybenzone (benzophenone-3), benzophenone-1, benzophenone-2, benzophenone-6, benzophenone-8, 4,4'-methoxy-t-butyldibenzoylmethane, 4-isopropyl dibenzoylmethane, 4-methylbenzylidene camphor, 3-benzylidene camphor, Polyacrylamidomethyl benzylidene camphor, Drometrizole trisiloxane, or Dimethico-diethyl-benzal-malonate. Following are preferred embodiments for said sol-gel microcapsules: (One) Sol-gel microcapsules encapsulating 2-ethylhexyl 4-methoxycinnamate, as well as other cinnamate derivatives such as isopentyl 4-methoxycinnamate, diethanolamine methoxycinnamate, 2-ethoxyethyl-4-methoxycinnamate and mixtures thereof. (Two) Sol-gel microcapsules encapsulating Oxybenzone (benzophenone-3), as well as other benzophenone derivatives such as benzophenone-4, benzophenone-8, benzophenone-1, benzophenone-2, benzophenone-5, benzophenone-9 and mixtures thereof. (Three) Sol-gel microcapsules co-encapsulating 2-ethylhexyl 4-methoxycinnamate and oxybnezone, as well as as other cinnamate derivatives such as in preferred embodiment (a) and other benzophenone derivatives such as in preferred embodiment (b) and mixtures thereof. (Four) Sol-gel microcapsules co-encapsulating Homosalate and 4,4'-methoxy-t-butyldibenzoylmethane, as well as other derivatives of salicylate such as octyl salycilate, 4-isopropylbenzyl salicylate and dibenzoylmethanes such as isopropyl dibenzoyl methane and mixtures thereof. (Five) Sol-gel microcapsules co-encapsulating Homosalate and 4,4'-methoxy-t-butyldibenzoylmethane and a suitable cosmetic oil such as Capric/caprylic triglyceride, octyl palmitate, C12-C15 alkyl benzoate, dioctyl maleate, propylene glycol dicaprylate/dicaprate, diisopropyl adipate, hexyl laurate, and mixtures thereof, as well as other derivatives of salicylate and dibenzoylmethanes and mixtures thereof. (Six) Sol-gel microcapsules co-encapsulating 2-cyano-3,3-diphenylacrylic acid 2-ethylhexyl ester (Octocrylene), and 4,4'-methoxy-t-butyldibenzoylmethane, as well as other derivatives of dibenzoylmethane such as isopropyldibenzoylmethane and mixtures thereof. (Seven) Sol-gel microcapsules co-encapsulating 2-cyano-3,3-diphenylacrylic acid 2-ethylhexyl ester (Octocrylene) and 4,4'-methoxy-t-butyldibenzoylmethane and a suitable cosmetic oil such as Capric/caprylic triglyceride, octyl palmitate, C12-C15 alkyl benzoate, dioctyl maleate, propylene glycol dicaprylate/dicaprate, diisopropyls adipate, hexyl laurate, and mixtures thereof, as well as other derivatives of dibenzoylmethane such as isopropyl dibenzoylmethane and mixtures thereof. (Eight) Sol-gel microcapsules co-encapsulating Homosalate and 3-(4-methylbenzyledene) camphor, as well as other derivatives of salicylate such as octyl salicylate, 4-isopropylbenzyl salicylate and other camphor derivatives such as 3-benzylidene camphor and mixtures thereof. (Nine) Sol-gel microcapsules co-encapsulating Homosalate and 3-(4-methylbenzyledene) camphor and a suitable cosmetic oil such as Capric/caprylic triglyceride, octyl palmitate, C12-C15 alkyl benzoate, Dioctyl maleate, propylene glycol dicaprylate/dicaprate, diisopropyl adipate, hexyl laurate, and mixtures thereof, as well as other derivatives of salicylate such as octyl salicylate, 4-isopropylbenzyl salicylate and other camphor derivatives such as 3-benzylidene camphor and mixtures thereof. (Ten) Sol-gel microcapsules encapsulating 2-ethylhexyl N,N-dimethyl-p-aminobenzoate, as well as other aminobenzoic acid derivatives such as 4-aminobenzoic acid (PABA), glyceril amionobenzoate, menthyl anthranilate, ethyl PABA, amyl dimethyl PABA and mixtures thereof. The sunscreen composition according to the present invention can comprise any of the preferred embodiment (one) to (ten) or a combination thereof in any acceptable cosmetic vehicle. Following are preferred embodiments of sunscreen compositions according to the present invention: (Eleven) A sunscreen composition comprising of preferred embodiments (one) and (four) in any acceptable cosmetic vehicle (Twelve) A sunscreen composition comprising of preferred embodiments (one) and (five) in any acceptable cosmetic vehicle (Thirteen) A sunscreen composition comprising of preferred embodiments (one) and sol-gel microcapsules encapsulating cinoxate in any acceptable cosmetic vehicle. The compositions revealed by this invention are of general nature, and the method according to which they are prepared is applicable to any sunscreen compounds currently used, as well as to sunscreen compounds that will be introduced in the future. It is also applicable for other compounds that are regularly used in cosmetic compositions. Furthermore, because of the easy incorporation of the sunscreen active ingredients and the ability to control their hydrophilicity/hydrophobicity character and the capsules size, the cosmetic vehicle to be used with the sunscreen active ingredients is not limited to any group and can be any cosmetically acceptable vehicle. |
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