Abstract:
A sunscreen composition containing a UV-A dibenzoylmethane derivative, such as 4-(1,1-dimethylethyl)-4&#39;-methoxydibenzoylmethane (PARSOL® 1789), and a stabilizer/solubilizer for the dibenzoylmethane derivative having formula (I): ##STR1## These long branched chain alkyl salicylates having a C 4  branch at the 2 position are quite effective in stabilizing the dibenzoylmethane derivative UV-B filter compounds making them more effective; effective for longer periods of time.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 08/967,121 filed Nov. 12, 1997 now U.S. Pat. No. 5,788,954 which is a continuation-in-part of application Ser. No. 08/752,585 filed Nov. 21, 1996 now U.S. Pat. No. 5,783,173. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to an ultra-high SPF, stable sunscreen composition for topical application to human skin to protect the skin against UV radiation damage. More particularly, the present invention is directed to the use of a long chain (C 12 , C 16  and/or C 18 ) branched alkyl salicylate that is surprisingly effective in stabilizing dibenzoylmethane derivatives, particularly 4-(1,1-dimethylethyl)-4&#39;-methoxydibenzoylmethane (PARSOL® 1789) such that the PARSOL® 1789 is a more effective sunscreen, having a surprisingly increased sunscreen protection factor (SPF) and such that the PARSOL® 1789 is more effective over a longer period of time so that the sunscreen composition need not be applied to the skin as frequently. Additional UW-A and/or UV-B sunscreen agents can be included, such as oxybenzone (UV-A/UV-B) and/or octyl salicylate (UV-B), to increase the SPF to a value of at least 25, preferably at least 30, while maintaining the stabilization of the dibenzoylmethane derivative UV-A sunscreen agent, e.g., PARSOL® 1789. In a preferred embodiment, the composition also includes one or more branched chain alkyl benzoates for solvent/emollient properties that provides an exceptionally elegant skin feel. 
     BACKGROUND OF THE INVENTION AND PRIOR ART 
     It is well known that ultraviolet light having a wavelength between about 280 nm or 290 nm and 320 nm (UV-B) is harmful to human skin, causing burns that are detrimental to the development of a good sun tan. UV-A radiation, while producing tanning of the skin, also can cause damage, particularly to very lightly colored, sensitive skin, leading to reduction of skin elasticity and wrinkles. 
     Therefore, a sunscreen composition should include both UV-A and UV-B filters to prevent most of the sunlight within the full range of about 280 nm to about 400 nm from damaging human skin. 
     The UV-B filters that are most widely used commercially in sunscreen compositions are paramethoxycinnamic acid esters, such as 2-ethylhexyl paramethoxycinnamate, commonly referred to as octyl methoxycinnamate or PARSOL® MCX, having an ethyl radical extending from the 2 position of the hexyl long chain backbone; oxybenzone; and octyl salicylate. 
     The UV-A filters most commonly used in commercial sunscreen compositions are the dibenzoylmethane derivatives, particularly 4-(1,1-dimethylethyl)-4&#39;-methoxydibenzoylmethane (PARSOL® 1789), and 4-isopropyl dibenzoylmethane (EUSOLEX 8020). Other dibenzoylmethane derivatives described as UV-A filters are disclosed in U.S. Pat. Nos. 4,489,057; 4,387,089 and 4,562,067 and 5,670,140, hereby incorporated by reference. It is also well known that the above described and most commonly used UV-A filters, particularly the dibenzoylmethane derivatives, such as PARSOL® 1789, suffer in photochemical stability when combined with the above-described most commercially used UV-B filters. Accordingly, when a UV-B filter, such as 2-ethylhexyl paramethoxycinnamate (PARSOL® MCX), oxybenzone and/or octyl salicylate, is combined with the dibenzoylmethane derivative UV-A compounds, such as PARSOL® 1789, the PARSOL® 1789 becomes less photochemically stable necessitating repeated, frequent coatings over the skin for sufficient UV radiation protection. 
     In accordance with the principles of the present invention, it has been found, quite surprisingly, that by including a C 12 , C 16 , C 18  branched chain salicylate of formula (I), preferably C 12  branched chain salicylate, into a cosmetic sunscreen formulation containing a UV-A dibenzyolmethane derivative, particularly PARSOL® 1789, and/or 4-isopropyl dibenzoylmethane (EUSOLEX 8020), the dibenzyolmethane derivative is photochemically stabilized so that the dibenzyolmethane derivative-containing sunscreen composition with or without additional sunscreen agents, such as oxybenzone and/or octyl methoxycinnamate (ESCALOL 567), is more effective for filtering out UV-A radiation; the composition filters UV-A radiation for longer periods of time; and, therefore, the sunscreen formulation need not be applied to the skin as frequently while maintaining effective skin protection against UV-A radiation: ##STR2## 
     In the preferred embodiment, the sunscreen composition also contains about 1% to about 10% by weight of one or more alkyl benzoate solvent/emollient compounds having formula (II): ##STR3## 
     By the addition of UV-B filter compounds, such as octyl methoxycinnamate, octyl salicylate, and/or oxybenzone, the cosmetic sunscreen formulation can maintain surprisingly effective skin protection against UV radiation both in the UV-A and UV-B range, with or without common sunscreen additives, such as benzophenone 3, octocrylene, and/or titanium dioxide. The composition reaches a surprisingly high SPF without solid additives, such as titanium dioxide, thereby providing an exceptionally elegant feel that can be applied easily in a continuous coating for complete coverage and sunscreen protection. The ratio of UV-A to UV-B filter compounds is in the range of about 0.1:1 to about 3:1, preferably about 0.1:1 to about 0.5:1, most preferably about 0.2:1 to about 0.2:1. Quite surprisingly, the compositions of the present invention maintain a high SPF, e.g., higher than 25, preferably at least 30, without solid blocking compounds, such as TiO 2 . 
     SUMMARY OF THE INVENTION 
     In brief, the present invention is directed to sunscreen compositions containing a dibenzoylmethane derivative UV-A filter compound, such as 4-(1,1-dimethylethyl)-4&#39;-methoxydibenzoylmethane (PARSOL® 1789), and a salicylate stabilizer/solubilizer for the dibenzoylmethane derivative having formula (I): ##STR4## 
     In accordance with a preferred embodiment of the present invention, the composition also includes about 1% to about 10% by weight of one or more branched chain alkyl benzoates for solvent/emollient properties having formula (II): ##STR5## 
     Surprisingly, it has been found that these long branched-chain alkyl salicylates, such as butyloctyl salicilate, having at least C 4  branches at the 2 position, are quite effective in stabilizing the dibenzoylmethane derivative UV-A filter compounds making them more effective; effective for longer periods of time; and, therefore, the sunscreen composition need not be reapplied as frequently to maintain effective UV radiation skin protection. 
     Accordingly, one aspect of the present invention is to provide a stable, moisturizing sunscreen composition that includes a stabilizer/solubilizer salicylate compound having formula (I), capable of stabilizing a dimethylbenzoyl derivative UV-A filter, particularly PARSOL® 1789: ##STR6## 
     Another aspect of the present invention is to provide photochemical stabilizer compounds for dimethylbenzoyl derivatives, particularly PARSOL® 1789, and methods of manufacturing the stabilizer compounds, capable of stabilizing the dimethylbenzoyl derivatives, and capable of increasing the sunscreen protection factor (SPF) achievable for sunscreen compositions containing the dimethylbenzoyl derivatives to a SPF of at least 20, particularly 25-35 SPF. 
     Another aspect of the present invention is to provide a stable, moisturizing sunscreen composition that has a SPF of at least 25, without a sunscreen composition additive selected from the group consisting of benzophenone 3, octocrylene or other substituted dialkylbenzalmalonates or substituted dialkylmalonates, or solid blocking agents such as TiO 2 , zinc oxide, or phenyl benzimidazole sulfonic acid. It should be understood however, that these sunscreen composition additives can be included in the composition of the present invention without detrimental effect. 
     Still another aspect of the present invention is to provide an improved, stable, moisturizing sunscreen composition containing 2-butyloctyl benzoate and/or 2-hexyldecyl benzoate, particularly a 40%, 60% by weight mixture, respectively, having a refractive index of at least about 1.40, particularly about 1.45 to about 1.48, that provides an exceptionally elegant skin feel to the moisturizer/sunscreen composition. 
     Another aspect of the present invention is to provide an improved, stable, moisturizing sunscreen composition containing butyloctyl salicylate, having a refractive index of about 1.49, that increases the effectiveness of dimethylbenzoyl derivative sunscreen compounds, particularly 4-(1,1-dimethylethyl)-4&#39;-methoxydibenzoylmethane (PARSOL® 1789), in SPF and in duration. 
     Still another aspect of the present invention is to provide a composition that conditions the skin in providing emollient, humectant and/or occlusive properties and maintains the skin soft, smooth and pliable while enhancing the appearance of dry skin with reduced flaking. 
     Another aspect of the present invention is to provide a homogenous composition that provides a high SPF, of at least 25, preferably at least 30, e.g. 25-35, and provides emollient and humectant skin care properties while including a very low concentration of surface active agents, less than about 1% by weight, preferably less than about 0.8% by weight, more preferably less than about 0.7% by weight, while emulsifying an oil phase of the composition, wherein the oil phase comprises at least about 25%, preferably at least about 30% by weight of the composition so that the composition is less irritating to sensitive skin. 
     Still another aspect of the present invention is to provide a sunscreen composition containing a combination of acrylate/C 10-30  alkyl acrylate block copolymers, e.g., PEMULEN TR-1 and PEMULEN TR-2, in a weight ratio of TR-1 greater than TR-2, preferably in a weight ratio of 1.2-3:1 TR-1:TR-2, more preferably about 2:1, for use in emulsification of the oil phase of at least 25% by weight, preferably at least 30% by weight, and increased viscosity, while maintaining a completely non-greasy after feel. The more hydrophobic PEMULEN TR-2 include a molar ratio of C 10-30  alkyl acrylate to acrylate of about twice as high as the ratio of C 10-30  alkyl acrylate to acrylate of PEMULEN TR-1 to provide more hydrophobicity and better oil emulsification. 
     Another aspect of the present invention is to provide a composition that has a high SPF, particularly useful for daywear/skincare, as well as beachwear/suncare that can be applied to the skin, particularly the face, to provide a cosmetically elegant appearance with a superb skin feel, which can be worn all day and is capable of receiving makeup thereover, and makeup can be applied more easily and more smoothly over the composition than directly over the face, thereby requiring less makeup for complete face coverage. 
     Another aspect of the present invention is to provide a moisturizing sunscreen composition containing a combination of hydrophobic and hydrophilic acrylate/C 10-30  alkyl acrylate crosspolymers (PEMULEN TR-1 and PEMULEN TR-2 from B.F. Goodrich) emulsifier that provides excellent emulsification of the substantial oil phase of the moisturizing sunscreen composition while maintaining a high SPF. It has been found that the acrylate/C 10-30  alkyl acrylate crosspolymers in a preferred weight ratio of 2:1 TR-1:TR:2 emulsify the compositions of the present invention such that the composition can be spread over the skin without gas bubbles or voids while providing a non-greasy after feel, and providing sufficient viscosity, and complete emulsification of the oil phase of the composition so that complete coverage of the skinis achieved, without interfering with the high SPF provided by the sunscreen and stabilizer compounds of the composition. 
     Still another aspect of the present invention is to provide a moisturizing sunscreen composition that provides an SPF of at least 25, including about 3-6% by weight octyl salicylate, and contains less than 4%, preferably about 3% by weight avobenzone (PARSOL® 1789). 
     Another aspect of the present invention is to provide a moisturizing sunscreen composition that provides an SPF of at least 25 while incorporating less than about 8% by weight octyl methoxycinnamate, and about 2-4% by weight oxybenzone. 
     The above and other aspects and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The sunscreen compositions of the present invention include about 0.5% to about 5%, preferably about 0.5% to about 3% of a dibenzoylmethane derivative UV-A filter compound, such as 4-(1,1-dimethylethyl)-4&#39;-methoxy-dibenzoylmethane (PARSOL® 1789) and about 1% to about 10% by weight of a branched chain salicylate stabilizer/solubilizer for the dibenzoylmethane derivative, having formula (I): ##STR7## 
     The compounds of formula (I) are formed by typical esterification and transesterification reactions as follows: ##STR8## 
     
         ______________________________________Loading Formula For Butyloctyl Salicylate(preferred Formula (I)) SynthesisREACTANTS          WEIGHT %______________________________________Hydroxybenzoic Acid              40.32-Butyloctanol (ISOFOL 12)              59.7M.S.A.* (99.9%)    0.2Sodium Hypophosphite              0.015**______________________________________ *Methane sulfonic acid catalyst **Based on the weight of hydroxybenzoic acid 
    
     Preferably, the compositions of the present invention include one or more branched chain alkyl benzoates of formula (II) that act as solvents and emollients in the composition: ##STR9## 
     The benzoates of formula (II) can be synthesized as follows: ##STR10## 
     
         ______________________________________Loading Formula For 40% 2-ButyloctylBenzoate/60% 2-Hexyldecyl BenzoateREACTANTS        WEIGHT %______________________________________Methylbenzoate   40.82-Butyloctyl alcohol            22.4 lbs.(ISOFOL 12)2-Hexyldecyl alcohol            36.8 lbs.(ISOFOL 16)Catalyst Fascat 9102*            0.03%**Sodium Hypophosphite            0.015%**SORBAMOL         1.5%**Dicalite         0.75%**______________________________________ *Butyltin tris 2ethylhexanoate catalyst **Based on the weight of methyl benzoate + alcohols 
    
     After loading the raw materials, agitation, nitrogen sparge and heat were turned on in a glass reaction kettle. Sodium hypophosphite was added on loading. At 290° F. the catalyst was added and heating was continued. Reaction started in the 380°-385° F. range as manifested by the evolution of MeOH. The overhead temperature was maintained at 140°-145° F. during the generation of MeOH. This was accomplished by controlling the reflux at 1:2 ratio. The reflux ratio indicates one fraction of the overhead product is taken out as a distillate product and two fractions goes back to the reaction kettle as reflux. This is the ratio found to be ideal to control the overhead temperature. 
     Heat was continued to a maximum reaction temperature of 420° F. When the overhead temperature dropped to 130°-135° F., the column was switched off and the reaction was continued on by-pass. Kettle samples were checked for acid value, color and percent alcohol. Vacuum was applied when the methyl alcohol content dropped to 2% by weight. Partial vacuum was applied initially to prevent foam over, then gradually increased to full as conditions permitted. Stripped for methylbenzoate until 0.10% by weight. At this time methylbenzoate odor was very faintly detectable. Cooled down the glass-lined reaction kettle to 180° F. 
     It is preferred to treat the product with a color body-absorbing compound, such as an activated charcoal or acid-activated calcium montmorillonite clay, to improve the color. The product required three separate activated charcoal treatments using 1% charcoal (based on batch initial weight) for each treatment to bring color down to 30-40 APHA. On the other hand, only one treatment with an acid-activated calcium montmorillonite clay (SORBAMOL) was required, in an amount of 1.2% based on the initial weight of the batch, to improve color to 20 APHA. All post treatment decolorizing steps were done at 180° F. and mixed for one hour, and then the batch was filtered with Dicalite. 
     The finished product was then analyzed and the results are as follows: 
     
         ______________________________________Appearance        Clear______________________________________Acid Value        0.01Color, APHA       30-40Water, %          0.03Saponification Value             175.7Specific Gravity  0.92Refractive Index  1.48______________________________________ 
    
     One or more of the compounds of formula (I) are combined with moisturizers, emollients, solvents, lubricants, emulsifiers and/or other common cosmetic formulation ingredients for solubility of the formula (I) compound(s), one or more emulsifiers, thickening agents, and to provide other skin enhancement, e.g., moisturizing and humectant properties. The compositions can be produced as oily lotions, gels, solid sticks, emulsions, aerosols, and all other forms of cosmetic compositions. The compositions of the following examples provide exceptional skin feel, moisturizing and humectant properties in comparison to typical prior art sunscreen compositions. 
     
         __________________________________________________________________________EXAMPLE 1                           PREFERREDPHASE    CHEMICAL NAME TRADE NAME                      RANGE                           RANGE  % WW                                      FUNCTION__________________________________________________________________________A.  Octyl methoxycinnamate             Escalol 557.sup.7                       0-10                             1-9  7.50                                      Sunscreen                                      (UV-B)A.  Octyl salicylate             Dermoblock OS.sup.4                       0-10                             1-8  5.00                                      Sunscreen                                      (UV-B)A.  Butyloctyl salicylate             HallBrite ™ BHB.sup.1 *                       1-15                             1-10 5.00                                      Cosolvent,                                      emollientA.  Hexyldecyl benzoate &amp;             HallStar ™ AB.sup.1 *                       0-10                             1-7  2.00                                      Cosolvent,    Butyloctyl benzoate                    emollientA.  Isopropyl myristate             HallStar ™ IPM.sup.1 *                      0-5    1-4  3.00                                      Cosolvent,                                      emollientA.  Avobenzone    Parsol ® 1789.sup.3                      0.5-5                           0.5-3  3.00                                      Sunscreen                                      (UV-A)A.  Oxybenzone    Escalol 567.sup.7                       0-10                           0.1-7  4.00                                      Sunscreen                                      (UV-A/UV-B)B.  Sorbitan oleate             Span 80.sup.5                      0-2  0.1-1  0.40                                      Particle                                      size reducerB.  Dimethicone copolyol             Silwet L-7087.sup.8 *                      0-2  0.01-1 0.20                                      LubricantB.  PVP/Eicosene copolymer             Ganex V-220.sup.7                      0-2  0.01-2 0.75                                      Moisture                                      barrierC.  Silica        Aerosil R972.sup.11                      0-2  0.1-1  0.50                                      ThixotropeD.  Acrylates/C.sub.10-30 alkyl acrylates             PEMULEN TR-1,                      0-5  0.1-2  0.30                                      Emulsifier    crosspolymer  PEMULEN TR-2.sup.9D.  Carbomer      Carbopol Ultrez.sup.9                      0-5  0.1-2  0.20                                      Thickener,                                      stabilizerE.  Deionized water             Water    50-90                             60-80                                  Q.S.                                      Solvent,                                      carrierE.  Disodium EDTA Disodium EDTA                      0-1  0.01-1 0.10                                      ChelatorE.  Hydroxypropyl methylcellulose             Primaflow                      0-2  0.01-1 0.20                                      Film former             MP3295A.sup.10F.  Glycerin      Glycerin*                       0-10                             1-8  4.00                                      HumectantF.  Butylene glycol             1,3 Butane diol*                      0-5  1.4    2.00                                      Humectant,                                      solventF.  Phenoxyethanol( )methyl-             Phenonip.sup.2                      0-5  0.1-5  0.50                                      Preservative    paraben( )ethylparaben( )propyl-    paraben( )butylparabenF.  Panthenol &amp; Propylene glycol             D-Panthenol 50-P.sup.8                      0-5  0.1-5  0.50                                      MoisturizerF.  Triethanolamine (99%)             Triethanolamine*                      0-1  0.01-2 0.25                                      Neutralizer__________________________________________________________________________ .sup.1. C. P. Hall .sup.2. Nipa .sup.3. Roche .sup.4. Alzo .sup.5. ICI .sup.6. OSI .sup.7. ISP .sup.8. BASF .sup.9. B. F. Goodrich .sup.10. Aqualon .sup.11. DeGussa *Available from C. P. Hall **SPF determined on human subjects by Harrison Research Laboratories, Union, NJ. Report available upon request. REF: CAG257, 78 SPF30a.FRM 
    
     Preferred Mixing Sequence For All Examples 
     1. Blend &#34;A&#34; oils. In turn, dissolve Avobenzone and Oxybenzone. Add &#34;B&#34; ingredients, heating oil phase to 35° C. to 40° C. to dissolve PVP/eicosene copolymer. Thoroughly wet and disperse Silica in oil. This is best done with high shear such as produced by a rotor/stator head. Fifteen (15) minutes before emulsification, disperse Pemulen TR-1 (0.20%), Pemulen TR-2 (0.10%), and Carbomer in oil phase. 
     2. Dissolve half of the disodium EDTA (0.05%) in the water. Add Hydroxypropyl methylcellulose to water with sitrring. Pre-blend &#34;F&#34; ingredients, then add to water to complete water phase. 
     3. With vortex stirring, add Oil Phase (&#34;A&#34;, &#34;B&#34;, &#34;C&#34;, &#34;D&#34;) all at once to Water Phase (&#34;E&#34;, &#34;F&#34;). This may be done at room temperature or up to 40° C. Stir/blend for fifteen (15) minutes. Adjust viscosity as necessary by adding some or all of remaining disodium EDTA in a step-wise fashion. Continue stirring/blending until creamy smooth. 
     In order to demonstrate that the branched chain salicylates of formula (I) photostabilize the dibenzoylmethane derivative UV-A filter compounds, such as PARSOL® 1789, two sunscreen formulations were prepared containing 2% avobenzone (dibenzoylmethane derivative--UV-A filter) incorporated in an oil phase consisting of 8% C 12-15  alkyl benzoate and an equal amount of another ester: octyl palmitate (Formulation A) or butyloctyl salicylate (Formulation B). Slides 7 mm square were prepared for each formulation by placing approximately 100 μl on a skin-like substrate (Vitro-skin, IMS) and spreading the material with a finger cot according to the established protocol. Measurements were made of each formulation using a Labsphere UV Transmittance Analyzer and the results were recorded. The slides were then placed in sunlight for two hours, following which measurements were again taken and the results were recorded. 
     The results were: 
     
         ______________________________________Before SunExposure       Formulation A                     Formulation B______________________________________Sun Protection 2.9        8.0FactorUVA Absorbance 88.26%     88.63%UVB Absorbance 62.87%     86.78%After SunExposure       Formulation A                     Formulation BSun Protection 0.9        4.8FactorUVA Absorbance 0.0%       32.66%UVB Absorbance 23.25%     83.75%______________________________________ 
    
     As demonstrated by the data, Formulation B, containing butyloctyl salicylate, retains 60% of its Sun Protection Factor (SPF), 38% of is UV-A absorbance, and 97% of its UV-B absorbance following two hours of exposure to sunlight. In contrast, the formulation containing octyl palmitate retains only 31% of its SPF, none of its UV-A absorbance, and only 37% of its UV-B absorbance. The addition of butyloctyl salicylate to a formulation containing avobenzone clearly contributes to the photostability of the avobenzone and the maintenance of the efficacy of the formulation.