Abstract:
Disclosed are improved oil and water emulsions and improved oil and water emulsification systems. Also disclosed are methods and compositions for increasing the sun protection factor of oil and water sunscreen emulsions comprising adding a phthalic acid derivative to an oil and water sunscreen emulsion in an amount effective to increase the sun protection factor of the emulsion, the phthalic acid derivative having the general formula:  
                         
 
     where  
     R represents an organic substituent, X represents a cation; and m is an integer satisfying the valency of X.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to skin-care products in general and specifically to sunscreen formulations comprising an emulsion of water and at least one oil. In particular, it relates to oil and water emulsions containing organic sunscreens or containing organic and/or inorganic (physical) sunscreen components. It further relates to suncare/skincare compositions capable of providing a high degree of protection from the harmful effects of ultraviolet radiation, such as sunburn and sun-induced premature aging.  
           [0003]    2. Description of the Related Art  
           [0004]    Ultraviolet radiation (UVR) is defined as radiation beyond the visible portion of the electromagnetic spectrum at its violet end. UVR consists of wavelengths from 200 to 400 nm and is subdivided into three bands from longer to shorter wavelengths as ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC), respectively.  
           [0005]    Human skin has a limited capacity to adapt to certain UV radiation when exposure to solar radiation is increased gradually. However, this protective mechanism fails when exposure increases abruptly. The sunburn response is generally associated with UVB exposure. Recent work, however has shown that large doses of UVA have detrimental effects on skin as well.  
           [0006]    The damaging effects of sunlight on skin are well documented. The combination of a diminished ozone layer with the growing tendency for people to engage in outdoor activities is believed to increase the occurrence of skin cancer and also to accelerate premature aging of the skin.  
           [0007]    As the body of evidence regarding the harmful effects of UV radiation grows, the cosmetic industry continues to formulate new products for providing enhanced protection against UVB and UVA radiation. Sunscreen agents or sunfilters are now incorporated into a variety of products for everyday use. These include moisturizers, creams, lotions, foundations, lipsticks, and other miscellaneous skin care products as well as shampoos and mousses. Such formulations are designed to at least partially protect human skin and hair from UV radiation.  
           [0008]    The protective strength of a particular sunscreen agent on the skin depends on a variety of factors. Among these factors are distribution (or deployment) of the sunscreen molecules on the skin, the spectral UV properties of the sunscreen, the photostability of the sunscreen, the chemical structure, the concentration of the sunscreen, the penetration of the sunscreens into the stratum comeum, and the spreading properties of the vehicle and the subsequent adherence to skin.  
           [0009]    Deployment of the sunscreen molecules over the surface of the skin determines to a major extent the protection delivered by various sunscreen formulations. Sunscreen formulations should be designed such that when applied to skin they deliver a film that covers both the peaks and the valleys of skin. Ideally, the sunscreen formulation can be applied to yield a film of uniform thickness on the skin with the sunscreen molecules homogeneously distributed within the film. The vehicle (the non-sunscreen component of the formulation) determines the manner in which the sunscreen molecules are deployed on the skin. In addition, the vehicle also controls to a large extent the ability of a sunscreen to protect skin after prolonged water exposure. Beyond protecting the skin from UV radiation, other formulation attributes such as product mildness and cosmetic elegance are also important to consumers.  
           [0010]    The most common formulation type for topical sunscreens is an emulsion. Sunscreen products may be manufactured as either oil-in-water (O/W) or water-in-oil (W/O) emulsions. Consequently, it is important that the emulsification system be capable of creating stable emulsions with a variety of polar and non-polar sunscreen agents as well as cosmetic oils.  
         SUMMARY OF THE INVENTION  
         [0011]    There exists a need for efficient emulsifying systems with improved mildness. Cosmetic chemists have devoted much effort towards developing methods and compositions for improving the SPF (“sun protection factor”) efficiency of sunscreen vehicles, i.e. delivering higher sun protection factor with a given amount of sunscreening agent. The present invention provides novel methods and compositions for unexpectedly improving the sun protection factor of formulations employing in some embodiments, relatively low levels of various organic and/or inorganic (physical) sunscreen components. The invention also provides methods and compositions for emulsifying various oils and active ingredients (such as, for example, organic and physical sunscreens, vitamins, moisturizers, and antioxidants).  
           [0012]    More specifically, the invention provides methods and compositions for increasing the sun protection factor of an oil and water sunscreen emulsion. The invention comprises adding a phthalic acid derivative to an oil and water sunscreen emulsion in an amount effective to increase the sun protection factor of the emulsion. The emulsions of the invention may be oil-in-water or water-in-oil emulsions. Such emulsions are typically prepared by preparing and combining water and oil phases to produce an emulsion.  
           [0013]    The phthalic acid derivatives useful in the invention are encompassed by the general structure shown below in Formula I:  
                         
 
           [0014]    R represents C 8 -C 40  alkyl, C 8 -C 40  alkenyl, alkylaryl where the alkyl portion is C 8 -C 40  alkyl, aryl, C 3 -C 7  cycloalkyl, or R 1 —O—R 2  where R 1  and R 2  independently represent C 1 -C 22  alkyl, C 1 -C 22  alkenyl, alkylaryl where the alkyl portion is C 1 -C 22  alkyl, aryl, or C 3 -C 7  cycloalkyl;  
           [0015]    X represents a cation; and  
           [0016]    m is an integer satisfying the valency of X.  
           [0017]    The emulsions of the invention may be prepared by adding the phthalic acid derivative to either the water phase or the oil phase prior to preparing the emulsion.  
           [0018]    The compositions of the invention provide important advantages. Reduced levels of emulsifiers in the compositions of the invention, i.e., less than 1%, result in stable formulations employing various oils. Other advantages are increased sun protection factor efficiency, increased mildness to human skin and scalp, and an absence of soaping and minimal whitening when applied to the skin. Further, the inventive compositions are easy to spread, adhere well to the skin, and are waterproof.  
           [0019]    As can be seen in the examples, the compositions of the present invention yield higher sun protection factors (SPFs) than do compositions without the phthalic acid derivative but having the same amount of active sunscreen agents. Consequently, sunscreen formulations prepared according to the invention require less of an active sunscreen agent to achieve SPFs similar to conventional sunscreen formulations. In addition, since the active sunscreen agent contributes a major portion of the cost of the final formulation, significant cost savings can be realized with this invention. Further, because high levels of organic sunscreens can irritate skin of certain individuals, formulations of the invention are generally more mild than conventional formulations having similar SPFs, due to the decreased concentration of organic sunscreens and the inherent mildness of the emulsification system.  
           [0020]    In another aspect, the invention provides water and oil emulsification, preferably oil-in- water, systems comprising:  
           [0021]    (a) a phthalic acid derivative of formula I; and  
           [0022]    (b) a secondary emulsifier which is  
           [0023]    (1) a polyacrylic acid-based emulsifier;  
           [0024]    (2) a polyglycerol ester;  
           [0025]    (3) a phospholipid; or  
           [0026]    (4) a carboxylic copolymer containing a crosslinking monomer selected from the group consisting of triallylisocyanurate, triallyl trimellitate and glyoxal bis(diallyl acetal) in combination with an ethoxylated glyceride surfactant ester with an HLB value greater than 10; or  
           [0027]    (5) a mixture thereof.  
           [0028]    Emulsions prepared according to the invention using the emulsification system comprising the phthalic acid derivative of formula I and the secondary emulsifier are typically liquid crystalline gel networks at room temperature. This emulsification system of the invention functions best at pHs of at least 7.  
           [0029]    The invention further provides sunscreen compositions comprising a sunscreen compound and an effective emulsifying amount of the water and oil emulsification system containing the polyacrylic acid emulsifier or fatty acid phosphate ammonium salt emulsifiers.  
           [0030]    Emulsification systems of the present invention also function as general emulsifiers for other non-sunscreen ingredients. These emulsification systems allow for formulation of a broad range of oils and active ingredients. The emulsification systems disclosed herein are highly versatile, requiring no more than about 3% by weight of total emulsifying system in a particular formulation. Use of the present emulsification systems in finished personal care products allows for the formulation of multi-functional products, and provides enhanced mildness to such products. The emulsifying systems are generally considered non-irritating. More specifically, the emulsification systems are intrinsically mild and allow for reduced levels of emulsifiers in finished personal care products, as compared to traditional emulsification systems disclosed in the art.  
           [0031]    The emulsification systems of the present invention function as rheology modifiers and general emulsifiers for oil in water formulations. The emulsification systems function most efficiently at pH&gt;7.0, and are insoluble in water at room temperature. Accordingly, they typically impart water resistance to various formulations.  
           [0032]    Without being bound by any particular theory, emulsification systems of the present invention generally provide rigidity at the oil/water interface, preventing coalescence. The resulting emulsion behaves like a liquid crystalline gel network at room temperature. Additionally, the emulsion systems generally display thixotropic characteristics, eliminating the need for hydrocolloid thickeners. When the emulsification systems are utilized to emulsify/suspend materials in various personal care products, application of shear during spreading of the product, on the skin for example, breaks the emulsion into a continuous film, allowing for the uniform distribution of the emulsification system within the film, and does not re-emulsify the oil with water.  
           [0033]    The current emulsification systems emulsify oils over a wide range of HLB&#39;s (generally from 5 to 12.0), in addition to various “SPF efficient” oils, and combinations of inorganic and organic sunscreens, both oil and water soluble. The emulsification systems are capable of emulsifying from about 7.5-45% oil utilizing lower levels of the emulsification system, as compared to traditional emulsifiers know in the art. The emulsification systems of the present invention are easy to assemble and are cost effective, whereby enhanced efficiency allows for use of reduced sunscreen actives.  
         DETAILED DESCRIPTION OF THE INVENTION  
         [0034]    Compositions according to the invention comprise an oil and water emulsion. Such oil and water emulsions comprise oil components, water, and, optionally, water soluble components. These compositions comprise at least one oil and an efficient emulsifying system. In certain aspects, these inventive compositions further comprise at least one sunscreen compound and a sun protection factor enhancement system. Preferred sunscreen compositions comprise a combination of sunscreen components. The sun protection factor enhancement system includes a phthalic acid derivative of Formula I above, a low hydrophilic/lipophilic balance (HLB) emulsifier and/or a polyacrylic acid based emulsifier.  
           [0035]    The oil components include various cosmetic oils and other oil soluble ingredients (e.g., vitamins, moisturizers, and antioxidants) and/or sunscreen agents and oil soluble low HLB emulsifiers or polymeric emulsifiers. The oil components include various cosmetic oils and other oil soluble ingredients (e.g. polymers, waxes) the sunscreen agents, the sunscreen enhancing system. The phthalic acid derivative may be incorporated into the emulsion either by way of the oil phase of the emulsion or alternatively by way of the water phase of the emulsion.  
           [0036]    The oil component forming the vehicle may comprise one or more hydrophobic materials. These materials are hydrophobic oils that are insoluble in water. Representative oils suitable for use in the inventive compositions include, but are not limited to isopropyl palmitate (IPP), octyl isononanoate (OIN), octyl dodecyl neopentanoate (e.g. Elefac I-205), isohexadecane (e.g. Permethyl 101A), hydrogenated vegetable oil (e.g. Vegepure). Other suitable oils include mineral oil, petrolatum, isopropyl myristate, triglycerides, and various silicones including dimethicones and cyclomethicones, etc.  
           [0037]    The sun protection factor enhancement system typically includes a low HLB emulsifier such as, for example, glycerol esters including glycerol monostearate (GMS) and glycerol monooleate (GMO), ethylene glycol distearate (EGDS), PEG esters such as polyethylene glycol monostearate, polyglyceryl esters such as polyglyceryl-10-decaoleate (e.g. Drewpol), and silicone emulsifiers such as polysiloxane based water-in-oil emulsifiers (e.g. Abil EM-90). These low HLB emulsifiers have HLB&#39;s of from about 1 to 6, and preferably from about 1.5 to about 3.8.  
           [0038]    Polyglycerol esters, e.g., Drewpol® available from Stepan Company, Northfield, Ill., are prepared by the esterification of polyglycerol with fatty acid. These products range from hydrophillic monoesters to lipophilic deca-esters. The polyglycerol esters are effective nonionic emulsifiers in both oil-in-water and water-in-oil emulsions. Preferred polyglycerol esters include Drewpol 10-8-0 (Polyglyceryl-10-monooctaoleate); Drewpol 3-1-SH (Polyglyceryl-3-mono-hydrogenated shortening); and Drewpol 6-2-SK (Polyglyceryl-6-dishortening kosher).  
           [0039]    As noted above, the sun protection factor enhancement system also includes a phthalic acid derivative of formula I that may be added with the oils or with the water. The phthalic acid derivative is present in the final sunscreen emulsions in an amount of about 0.1 to about 15% by weight of the emulsion. Preferred sunscreen emulsions of the invention comprise about 0.5 to 10% of the phthalic acid derivative by weight of the emulsion. Most preferred sunscreen emulsions of the invention comprise about 0.5 to 5% of the phthalic acid derivative by weight of the emulsion.  
           [0040]    Preferred compounds of Formula I are those where R represents straight or branched chain alkyl groups having from about 8-22 carbon atoms; m is 1; and X is sodium, potassium, ammonium, mono-, di-, or trialkanolamonium, more preferably ethanolammonium, mono-, di-, or trialkylammonium, more preferably ethanolammonium. Yet more preferred compounds of Formula I are those where R represents straight or branched chain alkyl having from about 12-20 carbons atoms; m is 1; and X is sodium, potassium, or triethanolammonium.  
           [0041]    Representative cations, i.e., “X” groups, include Mg ++ , Ca ++ , Na +, K   + , NH 4   + , and R 1 R 2 R 3 NH + , where R 1 , R 2 , and R 3  independently represent C 1-6  straight or branched chain alkyl groups or C 1-6  straight or branched chain alkylol groups.  
           [0042]    Representative phthalic acid derivatives of formula I suitable for use in the sunscreen compositions include, for example, sodium soyaamido benzoate, sodium oleylarnido benzoate, potassium cocoamido benzoate, and sodium stearylamido benzoate. Suitable phthalic acid derivatives are commercially available from Stepan Company, Northfield, Ill.  
           [0043]    As noted above, the invention also provides a water and oil emulsification system consisting essentially of a phthalic acid derivative of formula I and a secondary emulsifier which is (I) a polyacrylic acid-based emulsifier; (2) a polyglycerol ester, e g., the Drewpol materials described above; (3) a phospholipid, e.g., lecithin; or (4)a carboxylic copolymer containing a crosslinking monomer selected from the group consisting of triallylisocyanurate, triallyl trimellitate and glyoxal bis(diallyl acetal) in combination with an ethoxylated glyceride surfactant ester with an HLB value greater than 10; or (5) a mixture of any of secondary emulsifiers 1-4.  
           [0044]    This water and oil emulsification system is capable of emulsifying from 7.5 to 45% by weight of oil using no more than about 5% by weight of the emulsification system. The system is capable of achieving stable emulsification using just 3% total emulsification system. Thus, in preferred embodiments, the emulsion is a oil-in-water emulsion comprising from about 0.5 to 5%, preferably 2-4%, and more preferably about 3%, by weight of the emulsion of the emulsification system comprising the phthalic acid derivative and the secondary emulsifier. Preferred emulsions are formulated to have a final pH of greater than about 7.  
           [0045]    In the compositions of the invention, the effective amount of the water and oil emulsification system containing the secondary emulsifier is generally from about 0.5 to 5% by weight of the composition. More preferably, the composition comprises about 1-3% by weight of the emulsification system containing the secondary emulsifier.  
           [0046]    The polyacrylic acid-based emulsifiers are described in U.S. Pat. Nos. 4,758,641 and 5,004,557, both of which patents are incorporated herein by reference in their entirety. A highly preferred emulsifier herein is commercially available under the trademark Pemulen from The B. F. Goodrich Company. Pemulen® polymeric emulsifiers are high molecular weight polyacrylic acid polymers. The structure of Pemulen® includes a small portion that is oil-loving (lipophilic) and a large water-loving (hydrophilic) portion. A particularly preferred polyacrylic-acid based emulsifier is acrylates/C 10-30  alkyl acrylate crosspolymer, commercially available from the B. F. Goodrich Company as Pemulen®.  
           [0047]    Where the secondary emulsifier is the polyacrylic acid-based emulsifier, the composition comprises at least about 0.5% by weight of the phthalic acid derivative and at least about 0.05% by weight of the polyacrylic acid-based emulsifier. In the compositions comprising this emulsification system, the oil phase is from about 10-50% by weight of the composition. The oil phase of these compositions comprises at lease one oil selected from the group of dimethicones, cyclomethicones, C 12 -C 22  alcohols, and C 5 -C 10  alkyl esters of C 8 -C 18  fatty acids.  
           [0048]    The secondary emulsifier may also be a carboxylic copolymer emulsifier. Such carboxylic copolymer emulsifiers are carboxylic copolymers containing a crosslinking monomer selected from the group consisting of triallylisocyanurate, triallyl trimellitate and glyoxal bis(diallyl acetal) in combination with an ethoxylated glyceride surfactant ester with an HLB value greater than 10.  
           [0049]    The carboxylic copolymer contains a crosslinking monomer selected from the group consisting of triallylisocyanurate, triallyl trimellitate and glyoxal bis(diallyl acetal) in combination with an ethoxylated glyceride surfactant ester with an HLB value greater than 10.  
           [0050]    A preferred carboxylic copolymer is a crosslinked carboxylic copolymer comprising  
           [0051]    (i) an unsaturated carboxylic acid;  
           [0052]    (ii) an additional comonomer containing a polymerizable ethylenically unsaturated group;  
           [0053]    (iii) a crosslinking monomer selected from the group consisting of triallylisocyanurate, triallyl trimellitate, and glyoxal bis(diallyl acetal); and  
           [0054]    (iv) an ethoxylated glyceride compound of the formula  
                         
 
           [0055]    wherein R represents an alkyl group of from C 8  to C 18  and the sum of x+y is from 20 to 300.  
           [0056]    The particularly preferred carboxylic copolymer comprises  
           [0057]    (a) from about 70% to 99% by weight, based on the weight of the carboxylic copolymer, of at least one unsaturated carboxylic acid;  
           [0058]    (b) from about 0.2 to about 29%, based on the weight of the carboxylic copolymer, of a monomer containing a polymerizale ethylenically unsaturated group;  
           [0059]    (c) from about 0.8% to about 1.2% by weight, based on the weight of the carboxylic copolymer, of at least one crosslinking monomer selected from the group consisting of triallylisocyanurate, triallyl trimellitate, and glyoxal bis(diallyl acetal); and  
           [0060]    (d) from about 0.1 to about 1.0% by weight, based on the weight of the carboxylic copolymer, of an ethoxylated glyceride of the formula  
                         
 
           [0061]    wherein R represents an alkyl group of from C 8  to C 18  and the sum of x+y is from 20 to 300.  
           [0062]    In preferred embodiments, the polymerizable ethylenically unsaturated group is not selected from the group consisting of alkyl acrylates, alkyl methacrylates, acrylic acid esters derived from a polyalkylene glycol and methacrylic acid esters derived from a polyalkylene glycol.  
           [0063]    The carboxylic copolymers used in the invention may be prepared according to the methods set forth in U.S. Pat. No. 5,416,158, which is incorporated herein in its entirety. Suitable carboxylic copolymers are commercially available from Rheox, Inc., Hightstown, N.J., USA, as Rheolate. The most preferred carboxylic copolymer is available from Rheox as Rheolate 5000.  
           [0064]    Optionally, the secondary emulsifier(s) may be combined with a low HLB emulsifier as necessary.  
           [0065]    Where the secondary emulsifier is the polyacrylic acid-based emulsifier, better emulsions are obtained with pH adjustment of the water phase to activate the polyacrylic acid. Preferably, the water phase is adjusted with an aqueous base such as 10% aq. NaOH or KOH to about pH 7. Resulting emulsions prepared using this emulsifier system preferably have pH values of from about 7.5 to 7.7.  
           [0066]    The level of oil components in the emulsion is generally from about 1 to 65% by weight of the emulsion. More preferred formulations of the invention comprise about 5-40% by weight of the oil components. Most preferred formulations of the invention comprise about 10-30% by weight of the oil components.  
           [0067]    The sunscreen component for use in the inventive compositions may be a single sunscreen or a mixture of more than one sunscreen. The sunscreens may be organic or inorganic sunscreens, or a combination of organic and inorganic sunscreens. Suitable sunscreens are those capable of blocking, scattering, absorbing or reflecting UV radiation. Inorganic sunscreens, often referred to as physical sunscreens, typically scatter, reflect and absorb UV radiation while organic sunscreens I 10 generally absorb UV radiation. Representative sunscreen components capable of protecting human skin from the harmful effects of UV-A and UV-B radiation ate set forth below in table 1.  
                   TABLE 1                       CTFA Name   FDA Name/Chemical name                   Benzophenone-3   Oxybenzone/2-Hydroxy-4-methoxy           benzophenone       Octylmethoxycinnamate   2-Ethylhexyl-p-methoxy cinnamate       Benzophenone-4   Sulisobenzone/2-Hydroxy-4-methoxy           benzophenone-5-sulfonic acid       Octylsalicylate   2-Ethylhexyl salicylate       Triethanolamine salicylate   Triethanolamine o-hydroxybenzoate       Glyceryl PABA   Glyceryl p-aminobenzoate       Padimate O   Octyldimethyl p-aminobenzoate       Homosalate   Homomenthyl salicylate       PABA   p-Aminobenzoic acid       Padimate A   Amyldimethyl PABA       Benzophenone-8   Dioxybenzone       Octocrylene   2-Ethyl-hexyl-2-cyano-3,3-diphenylacrylate       Phenyl Benzimidazole   2-Phenylbenzimidazole-5-sulfonic acid       sulfonic acid       Titanium dioxide   Titanium dioxide       Melanin coated titanium       dioxide       Zinc oxide   Zinc oxide       Avobenzone   Butyldibenzomethane                  
 
           [0068]    Preferred sunscreens and sunscreen combinations are ethyl hexyl-p-methoxy-cinnamate (commerically available from Givaudan as Parsol MCX), Benzophenone-3 (Oxybenzone commercially available from Haarmann &amp; Reimer), 2-phenylbenzimidazole-5-sulfonic acid (commercially available as Eusolex 232 from Rona), Avobenzone (4-tert-Butyl-4′-methoxy-dibenzoylmethane, commercially available from Roche as Parsol 1789), and octyldimethyl p-amino benzoic acid (octyl dimethyl PABA commercially available from Haarmann &amp; Reimer).  
           [0069]    Preferred inorganic (physical) sunscreens include appropriately sized particles of micronized titanium dioxide (TiO 2 ) and zinc oxide (ZnO). In addition, these particles may have various surface treatments to render the surface non-reactive and/or hydrophobic. Inorganic sunscreens may be added to the inventive formulations on a dry basis or as predispersed slurries.  
           [0070]    In the case of predispersed slurries, well dispersed sluries are preferred. Representative non-limiting examples of currently preferred inorganic sunscreens include a slurry of 40% by weight of aluminum stearate coated micronized titanium dioxide in Octyl dodecylneopentanoate (commercially available as TiOSperse I from Collaborative Laboratories); a slurry containing 40% by weight of a mixture of TiO 2  and aluminum stearate in caprylic/capric triglyceride (commercially available as TiOSperse GT from Collaborative Laboratories); a 40% slurry of glycerol coated TiO 2  in butylene glycol and glycerin (commercially available as TiOSperse BUG/Gly from Collaborative Laboratories); melanin coated TiO 2  (commercially available from MelCo); ultrafine silicone coated TiO 2  (commercially available as UV-Titan from Presperse, Inc.); ZnO and Dimethicone coated ZnO (commercially available as Z-cote HP1 from SunSmart, Inc.); a 60% TiO 2 , aluminum stearate, an trifluoromethyl-C 1-4  alkyldimethicone in octyl dodecylneopentanoate (commercially available as ON60TA from Kobo Products, Inc.); and a 40% TiO 2  slurry in octyl palmitate (commercially available as Tioveil OP from Tioxide Specialties, Ltd.).  
           [0071]    The sunscreen emulsions are typically prepared by combining water and aqueous components (the “water phase”) with any oil components (the “oil phase”) where each of the phases have been optionally heated to about 70-80° C., preferably heating the resulting mixture, and subsequently mixing, preferably at an elevated temperature such as, for example, about 70-80° C., to prepare the emulsion. After cooling, a preservative may optionally be added and the pH adjusted as necessary, with, for example, citric acid.  
           [0072]    The oil phase used to prepare the emulsion includes the low HLB emulsifier and/or the polymer emulsifier, various oils, and, optionally, any sunscreen component(s). The phthalic acid derivative may be present in the water phase, the oil phase, or in both, prior to combining the phases to prepare the emulsion.  
           [0073]    The pH of the resulting sunscreen formulations is normally between about 6 and 9, preferably between about 7 and 8, and most preferably between about 7.5 and 8.  
           [0074]    The sunscreen compositions of the invention are preferably oil-in-water emulsions. However, the invention also encompasses water-in-oil emulsions.  
           [0075]    All documents, e.g., patents and journal articles, cited above or below are hereby incorporated by reference in their entirety.  
           [0076]    In the following examples, all amounts are stated in percent by weight of active material unless indicated otherwise.  
           [0077]    One skilled in the art will recognize that modifications may be made in the present invention without deviating from the spirit or scope of the invention. The invention is illustrated further by the following examples which are not to be construed as limiting the invention or scope of the specific procedures or compositions described herein.  
         In Vitro Determination of Sun Protection Factor (SPF) of Sunscreen Formulations  
         [0078]    The following method for determining SPF for the formulations of the invention employs a synthetic substrate (Vitro-Skin™) that mimics the surface properties of human skin.  
           [0079]    1. A series of 6 cm by 9 cm pieces of Vitro-Skin™ are placed in a humidity controlled chamber for about 16 hours. The humidity control chamber contains a solution of about 70% water and 30% glycerin and is maintained at 23° C.  
           [0080]    2. 100 μl of the sunscreen formulation to be tested is drawn into a calibrated positive-displacement pipette.  
           [0081]    3. A 6 cm×9 cm piece of Vitro-Skin™ substrate is removed from the hydration chamber and placed on a plastic-covered foam block such that the skin topography side (the dull or non-shiny side) is away from the foam block. The 100 μl of sample sunscreen formulation is pipetted evenly across a 6×8 cm section of the substrate by dotting it approximately at 30 equally spaced points across the substrate.  
           [0082]    4. The sample sunscreen formulation is then rubbed into the substrate and with sufficient force to slightly deform the plastic covered flexible foam. The product is then allowed to dry for 15 minutes after which the substrate is trimmed and then mounted on a 6 cm×6 cm slide. A second piece of substrate (untreated) is removed from the hydration chamber and mounted on a separate 35 mm slide mount to be used as a control.  
           [0083]    5. Sun protection factors are then determined using an Optometrics SPF-290 instrument. The control (untreated piece of substrate) is then placed above the integrating sphere of the instrument and a reference scan is obtained by recording the photocurrent at 5 nm increments between 290 and 400 nm. The in vitro sun protection factor for each formulation according to the invention is then determined by placing the product treated substrate above the integrating sphere. The sample scan is then obtained by recording the photocurrent at 5 nm increments between 290 and 400 nm. Monocromatic Protection Factors (MPF) are subsequently calculated by taking the ratio of the photocurrent untreated vs. treated at each wavelength.  
         In Vivo Determination of Waterproof Sun Protection Factor (SPF) of Sunscreen Formulations  
         [0084]    The following method is used to determining the in vivo waterproof SPF for the formulations of the invention. The method employs a 150 watt xenon arc solar simulator commercially available as Model 12S, 14S, or 600 from Solar Light Co., Philadelphia, Pa., as a source of ultraviolet radiation. These models have a continuous emission spectrum in the UV-B range from 290-320 nm.  
           [0085]    UV radiation is continuously monitored during a period of exposure using a Model DCS-1 Sunburn UV Meter/Dose Controller System (available from Solar Light Co.). Measurements are taken at a position within 8 mm of the skin surface. The field of iradiation is 1 cm in diameter.  
           [0086]    The procedure for this study is essentially as described in the Federal Register, 43: 38264-38267(1978).  
           [0087]    A single test site area is used to determine a subjects minimal erythema dose (MED). This is accomplished by exposing the subject back to a series of timed incremental UV exposures at 25% intervals. An individual subjects MED is the shortest time of exposures that produces minimally perceptible erythema at 16 to 24 hours post irradiation. The test area is defined as the infrascapular area of the back to the right and left of the midline. A 8% homosalate standard is delivered to the test site through plastic volumetric syringe. The homosalate standard is evenly applied to a rectangular area measuring about 5 cm×10 cm for a final concentration of 2.0 mg/cm 2 .  
           [0088]    Fifteen minutes after the application of the homosalate standard, a series of UV light exposures in 25% increments calculated from previously determined MED&#39;s bracketing the intended SPF were administered from the solar simulator to subsites within the treated area. On the actual day of testing another series of exposures similar to the one given on the previous day was administered to an adjacent untreated site of unprotected skin to re-determine the MED. An adjacent test site was then selected for a static determination of the test substance, conducted as above, prior to the immersion test.  
           [0089]    WATERPROOF DETERMINATION  
           [0090]    The following determination indicates the substantivity of a sun protection emulsion and its ability to resist water immersion  
           [0091]    On the day of the test, after exposure of the homosalate standard, MED&#39;s and static determination, another area measuring 5 cm×10 cm is designated. The test formulation is spread uniformly over the area at a concentration of 2.0 mg/cm 2  and allowed a fifteen minute drying period as before. Another adjacent site is selected for determination of a waterproof sunscreen standard. The standard has a known waterproof sun protection factor bracketing the expected sun protection factor of the test formulation.  
           [0092]    The following immersion schedule is employed:  
           [0093]    20 minutes of moderate activity in water.  
           [0094]    20 minutes rest period out of the water.  
           [0095]    20 minutes of moderate activity in water.  
           [0096]    20 minutes rest period out of the water.  
           [0097]    20 minutes of moderate activity in water.  
           [0098]    20 minutes rest period out of the water.  
           [0099]    20 minutes of moderate activity in water.  
           [0100]    Immersion is achieved indoors in a circulating whirlpool tub having a 1 h.p. pump operating at 3450 RPM delivering 8 g.p.m. through 8-1.5 cm diameter ports. The water is maintained at an average temperature of 75-80° F. The test area was air dried prior to exposure from the solar simulator. A second series of exposures on the test formulation is administered to the protected area, again using 25% increments. The exact series of exposures employed is determined by the controlled MED and the expected SPF of the product as defined above.  
           [0101]    Sixteen to twenty four hours post exposure, the subjects are evaluated for delayed erythemic response. The smallest exposure or least amount of energy required to produce erythema (MED) in the treated site is recorded. SPF is then calculated according to the following equation:  
       SPF   =       MED                 Protected                 Skin       MED                 Unprotected                 Skin                             
 
       
    
    
     EXAMPLE 1  
       [0102]    [0102]                                                       The following sunscreen formulations are prepared essentially as described       above.                Formulation No.            Component   1 1     2               Stearic acid    3.0   —       Triethanolamine    1.5   —       Carbopol 934 2      0.2   —       Stearyl amido benzoate, sodium salt   —    2.0       Glycerol mono stearate    1.0    1.0       Elefac I-205 3      8.0    8.0       2-Ethylhexyl-p-methoxy cinnamate    5.0    5.0       2-Phenyl-benzimidazole-5-sulfonic acid    1.0    1.0       TioSperse I 4  (% active TiO 2  in formulation)   10.0 (4.0)   10.0 (4.0)       Water   Q.S. to 100   Q.S. to 100       Stability 5     stable   stable       pH    7.55    7.6       Sun Protection Factor   15.5   23.8       (in vitro)                    
         [0103]    1 Comparative example.  
         [0104]    2 A homopolymer of acrylic acid crosslinked with an allyl ether of pentaerythritol or an allyl ether of sucrose, commercially available from BF Goodrich.  
         [0105]    3 Octyl dodecyl neopentanoate, commercially available from Bernel, Inc.  
         [0106]    4 A 40% by weight slurry of TiO 2  coated with aluminum stearate in Elefac I-205, commercially available from Collaborative Laboratories, Inc.  
         [0107]    5 Emulsion stability was evaluted via multiple criteria; specifically: l)oven stability at 42° C. for 1 month, 2) comparison of emulsion micrographs obtained on day one vs. two weeks vs. one month, 3) measurement of conductivity and 4) Theological profile. Stable indicates that all criteria were satisfied.  
       EXAMPLE 2  
       [0108]    The following sunscreen formulations are prepared essentially as described above.  
                                                           Waterproof sunscreen formulations                Formulation No.            Component   3 6     4   5               Stearic acid    3.0   —   —       Triethanolamine    1.5   —   —       Carbopol 934    0.1   —   —       Stearyl amido benzoate,        2.0    2.0       sodium salt       Glycerol mono stearate    1.0    1.0    1.0       Elefac I-205    8.0    8.0    8.0       2-Ethylhexyl-p-methoxy    3.5    3.5    3.5       cinnamate       Benzophenone-3    1.5    1.5    1.5       Tiosperse I (% active TiO 2  in   10.0 (4.0)   10.0 (4.0)   10.0 (4.0)       formulation)       Ganex V-220 7              0.5       water   Q.S. to 100   Q.S. to 100   Q.S. to 100       stability   stable   stable   stable       pH    7.6    7.65    7.6       sun protection factor (in vitro)   14   22.1   22       Waterproof sun protection   15.3   21.8   22.7       factor (in vivo)                  
 
         [0109]    6 Comparative example.  
         [0110]    7 A polymer of vinylpyrrolidone and eicosene monomers, commercially available from GAF.  
       EXAMPLE 3  
       [0111]    The following sunscreen formulations are prepared essentially as described above.  
                                                                     Formulation No.                    Component   6 8     7                       Stearic acid    3.0   —           Triethanolamine    1.5   —           Carbopol 934 9      0.2   —           Stearyl amido benzoate, sodium        2.0           salt           glycerol mono stearate    1.0    1.0           Elefac I-205   10.0   10.0           2-ethylhexyl-p-methoxy    7.5    7.5           cinnamate           Benzophenone-3    3.0    3.0           2-Phenyl-benzimidazole-5-    1.0    1.0           sulfonic acid           Water   Q.S.   Q.S.           stability   stable   stable           pH    7.65    7.6           sun protection factor   28.7   34.2           (in vitro)                      
 
         [0112]    8 Comparative example.  
         [0113]    9 A homopolymer of acrylic acid crosslinked with an allyl ether of pentaerythritol or an allyl ether of sucrose, commercially available from Goodrich.  
       EXAMPLE 4  
       [0114]    Formulations 8-10 are prepared essentially as follows:  
         [0115]    Water and stearyl amido benzoate, sodium salt, are combined at room temperature and heated with mixing to about 75-80° C. An oil phase is prepared by combining the oil phase components and mixing with heating to about 77-82° C. When preparing compositions containing titanium dioxide, a slurry of titanium dioxide is added to a mixture of completely solubilized oil phase components at a temperature of about 55-60° C.; the mixture is then heated to about 75-80° C. and homogenized. Subsequently, the oil phase is added to the water phase with constant mixing. The resulting mixture is mixed at 75° C. for about 30 minutes and then allowed to cool with continuous mixing to about at least 30° C. At a temperature below 50° C., a preservative is optionally added and the pH is optionally adjusted with, for example, citric acid.  
                                                                                                   Formulation No.            Components   4 10     8   5 10     9   10                    Stearyl amido benzoate,   2   2   2   2   2       sodium salt       Glycerol mono stearate   1   1   1   1   1       Elefac I-205   8   8   8   8   8       2-Ethylhexyl p-methoxy   3.5   3.5   3.5   3.5   3.5       cinnamate       Benzophenone-3   1.5   1.5   1.5   1.5   1.5       TioSperse I (% active   10 (4)   10 (4)   10 (4)   10 (4)   10       TiO 2  in formulation)       Cetyl alcohol       1           1       Ganex V-220           0.5       Xantham Gum               0.1   0.2       Magnesium Aluminum               0.3   0.5       Silicate       Water   Q.S. to   Q.S. to   Q.S. to   Q.S. to   Q.S. to           100%   100%   100%   100%   100%       SPF(in vitro)   22.1   19.1   22.0   —   25.2                          
 
         [0116]    From the above examples, it is apparent that the sunscreening enhancement is not affected by the addition of different ingredients to formulations.  
         [0117]    General Procedure for Examples 5-12  
         [0118]    Water Phase: Water is added to amido benzoate at ambient temperature. The mixture is mixed and heated to about 80° C. until sufficiently clear to see the agitator shaft. Additional components are added where called for to the mixture with heating as required to maintain 80° C. Where necessary, 10% aq. NaOH may be used to adjust the pH of the water phase prior to combination with the oil phase.  
         [0119]    Oil Phase: Oil phase components are mixed with heating to about 80-82° C. Where a physical sunscreen, e.g., Titanium dioxide or Zinc oxide, is added, additional mixing may be necessary to adequately disperse the material. A Bamix 2 speed M122 mixer may be employed.  
         [0120]    Emulsion: Oil phase at about 80° C. is added to 80° C. water phase with increasing agitation, i.e., to about 5000 rpm (using a Silverson homogenizer) or 500 rpm (using a turbine agitator). The resulting mixture is mixed at 75-80° C. for about 5 minutes with homogenization or about 30-40 minutes with a turbine agitator. Cooling to about 30° C. is carried out with reduced agitation to form what is believed to be a liquid crystalline gel network. After mixture is below about 50° C., Glydant or Germaben II may be added and pH may be adjusted as necessary to about 7.5 to 7.7 with, e.g., 10% citric acid or stearic acid.  
       EXAMPLE 5  
       [0121]    [0121]                                                             Formulation No.                Component   5-1                       Water phase               water   Q.S.           Na 2  EDTA    0.1           Stearyl amido benzoate, sodium    2           salt           Xanthan gum (2% solution in   15           water)           Oil Phase           Elefac I-205 (Octyl dodecyl    9           neopentanoate)           Octyl isononanoate    6           2-Ethylhexyl-p-    7.5           methoxycinnamate           silicone coated Zinc oxide    5           Glycerol mono stearate    1           cetyl alcohol    1.75           cyclomethicone   1 (optional)                        
         [0122]    Alternate Mode of Preparation  
         [0123]    Water Phase: Water and EDTA are combined in the emulsification vessel giving a solution of pH 4.9. The temperature is raised to about 75° C. with mixing at which time the amido benzoate is added. The mixture initially cools and gels moderately. Heating is continued to about 70° C.; the pH is about 7.65. Xanthan gum is added slowly and the mixture heated again to about 80-82° C.  
         [0124]    Oil Phase: Elefac 1-205 and Ethylhexyl-p-methoxycinnamate are combined in a separate vessel and heated with mixing to about 45° C., mixed for about 10 minutes, after which time the temperature is increased to about 65° C. and the zinc oxide added. Glycerol mono stearate and cetyl alcohol are then added and the temperature increased further to about 82° C.  
         [0125]    Emulsion: The oil phase is added to the water phase with 500 rpm agitation, mixed for about minutes, and homogenized at 5000 rpm for an additional 5 minutes. The mixture is at a temperature of about 62° C. after the homogenization. After cooling, 1 g of cyclomethicone may be added.  
       EXAMPLE 6  
       [0126]    [0126]                                                                                                   Formulation No.           (% by weight of composition)            Component   6-1   6-2   6-3   6-4   6-5                    Water phase                           water   73.8   69   68.6   69.2   68.3       Na 2  EDTA   0.1   0.1   0.1   —   0.1       Stearyl amido benzoate,   2   1   1.2   1.5   1.5       sodium salt       Pemulen TR-1   —   —   —   0.075   0.1       (acrylates/C 10-30  alkyl       acrylate crosspolymer)       Oil Phase       Elefac I-205 (Octyl dodecyl   6   12   12   10   12       neopentanoate)       octyl methoxycinnamate   7.5   7.5   7.5   7.5   7.5       silicone coated Zinc oxide   5   5   5   5   5       cetyl alcohol   1.75   1.75   1.75   1   1.75       Ganex V-220   0.75   0.75   0.75   —   0.75       dimethicone   3   3   3   3   3       Pemulen TR-1   0.1   0.1   0.15   —   —       (acrylates/C 10-30  alkyl       acrylate crosspolymer)       Panalane 11     —   —   —   0.75   —       Soya oil   —   —   —   2   —       Emulsion pH   —   8.68   8.78                            
         [0127]    The formulations of the following examples are prepared essentially as described above in Example 5 with the following modifications: Where Pemulen is added to the water phase, it is added initially with the water and homogenized at about 5000 rpm. Where Pemulen is added to the oil phase, it is added prior to the addition of the Zinc oxide.  
       EXAMPLE 7  
       [0128]    [0128]                                                                     Formulation No.           (% by weight of composition, unless           noted otherwise)            Component   7-1   7-2   7-3   7-4               Water phase                       water   68.3   Q.S.   Q.S.   Q.S.       Na 2  EDTA    0.1       Stearyl amido benzoate,    1.5    1    1.5    2       sodium salt       Pemulen TR-1        0.1    0.2    0.1       (acrylates/C 10-30  alkyl       acrylate crosspolymer)       Oil Phase       Elefac I-205 (Octyl dodecyl   12       neopentanoate)       octyl isononanoate           15   15       octyl methoxycinnamate    7.5       silicone coated Zinc oxide    5    2    5    5       cetyl alcohol    1.75    1.75    1.75    1.75       Ganex V-220    0.75        0.5    0.5       dimethicone    3    3    3    3       Pemulen TR-1    0.1       (acrylates/C 10-30  alkyl       acrylate crosspolymer)       Isopropyl palmitate       12                    
       EXAMPLE 8  
       [0129]    [0129]                                                                     Formulation No.           (% by weight of composition, unless noted           otherwise)            Component   8-1   8-2   8-3   8-4               Water phase                       water   77.25   77.25   76.25   79.4       Stearyl amido benzoate,    1    1    2    1       sodium salt       Oil Phase       octyl methoxycinnamate       silicone coated Zinc oxide    2    2    2    2.1       cetyl alcohol    1.75    1.75    1.75    1.80       dimethicone    3    3    3    3.1       Stearic Acid    3 12      3 13      3 14      0.24       Isopropyl palmitate   12   12   12   12.3       Emulsion pH    8.58    9.7    9.4    7.22                    
         [0130]    [0130] 
       EXAMPLE 9  
       [0131]    [0131]                                                                                                                   Formulation No.           (% by weight of composition,           unless noted otherwise)            Component   9-1   9-2   9-3   9-4   9-5   9-6   9-7                    Water phase                                   water   Q.S.   Q.S.   86.5   Q.S.   Q.S.   Q.S.   Q.S.       Na 2  EDTA   0.05   0.05               0.05   0.05       Stearyl amido   2   1.5               2   2       benzoate, sodium salt       Pemulen TR-1           0.1   0.1   0.1       (acrylates/C 10-30  alkyl       acrylate crosspolymer)       Oil Phase       Parsol MCX   5   5               5   5       (2-Ethylhexyl-       4-methoxycinnamate)       Parsol 1789   2   2               2   2       (4-tert-Butyl-4′-       methoxy-       dibenzoylmethane)       caprylic/capric   5   5               8       triglyceride       Octyl isononanoate   3   3                   8       Glycerol mono stearate   1   —               1   1       dimethicone               3   3       silicone coated               2   2       Zinc oxide       Pemulen TR-2   —   0.1       cetyl alcohol   1   1   1.75   1.75   1.75   1   1       isopropyl palmitate           12   12   12       Emulsion pH   7.7   6.76   9.3 15         7.6 16     7.67   7.74                                    
       EXAMPLE 10  
       [0132]    [0132]                                                                                                           Formulation No.           (% by weight of composition,           unless noted otherwise)            Component   10-1   10-2   10-3   10-4   10-5   10-6                    Water phase                               water   Q.S.   Q.S.   87.15   82.15   Q.S.   Q.S.       Stearyl amido benzoate,   2   1           0.5   0.5       sodium salt       Pemulen TR-2           0.1   0.1   0.1   0.1       (acrylates/C 10-30  alkyl       acrylate crosspolymer)       Oil Phase       Glycerol mono stearate           1   1       dimethicone       3       3       silicone coated Zinc oxide       2       2       cetyl alcohol   1.75   1.75   1.75   1.75   1.75   1.75       isopropyl palmitate   12   12   10   10   10   10       Emulsion pH   9   10.25   6.85   6.85       7.4 17                              
       EXAMPLE 11  
       [0133]    [0133]                                                                                                           Formulation No.           (% by weight of composition,           unless noted otherwise)            Component   11-1   11-2   11-3   11-4   11-5   11-6                    Water phase                               water   81.65   81.95   82.4   82   81.75   81.65       Na 2  EDTA       Stearyl amido benzoate,   1   0.8   0.5   0.8   1   0.5       sodium salt       PemulenTR-2   0.1   0.1   0.1   0.05       0.3       (acrylates/C 10-30  alkyl       acrylate crosspolymer)       Oil Phase       Glycerol mono stearate   0.5   0.4   0.25   0.4   0.5   1       cetyl alcohol   1.75   1.75   1.75   1.75   1.75   1.75       isopropyl palmitate   15   15   15   15   15   15       Emulsion pH   7.2   7.31   6.81   7.56 18     8.63   6.91                            
       EXAMPLE 12  
       [0134]    [0134]                                                               (Ampbisol Systems)                Formulation No.           (% by weight of composition, unless noted           otherwise)            Component   12-1   11-2   12-3   12-4               Water phase                       water   Q.S.   Q.S.   Q.S.   Q.S.       Stearyl amido benzoate,            2           sodium salt       Oil Phase       Octyl isononanoate   15   15   15   15       Glycerol mono stearate        1    1           Amphisol (Bis (2-    2    2        2       hydroxyethyl)-ammonium       hexadecyl hydrogen       phosphate)       Pemulen TR-2                0.1       Emulsion pH       Emulsion Stability   &gt;7   &gt;7   &gt;7   &gt;7                    
       EXAMPLE 13  
       [0135]    [0135]                                                                                           Formulation No.           (% by weight of composition, unless           noted otherwise)            Component   13-1   13-2   13-3   13-4                    Water phase                       water   67.7   57 g +   50 g +   50 g +               20 g 19     20.4 g   20.4 g       Na 2  EDTA       Stearyl amido benzoate,   5.5     2 g     2 g     2 g       sodium salt       Drewpol 10-8-0 20     3.3       Drewpol 3-1-SH 21             1       Drewpol 6-2-SK 22                 1       Oil Phase       Octyl isononanoate   15       Lecithin   1.1       Glycerol mono stearate         1 g       glycerin           7   7       Behenyl alcohol       1.5 g   1   1       isopropyl palmitate        15 g   15   15       Emulsion pH       Emulsion Stability                                                    
       EXAMPLE 14  
       [0136]    [0136]                                                             Formulation No.           (% by weight of com-           position, unless noted           otherwise)                Component   14-1                       Water phase 1               water   20 g           Na 2  EDTA    0.1           Allantoin    0.3           Glycerin    4           Water Phase 2           Stearyl amido benzoate,    2           sodium salt           Rheolate 5000    0.5           water   56.1 g           Oil Phase           Elefac I-205   15           Drewpol 6-2-SK    1           Behenyl alcohol    1           Emulsion pH           Emulsion Stability                        
         [0137]    Procedure: Water in Oil emulsion A prepared as described above by combining Water Phase 1 and Oil phase. Emulsion A then added to Water Phase 2 with agitation to prepare oil in water emulsion.  
         [0138]    Alternatively, Water phase 2 may be added to Water Phase 1 prior to combining with the oil phase.  
         [0139]    From the foregoing, it will appreciated that although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of the invention.