Moisture-resistant skin treatment compositions

Abstract

Skin treatment compositions such as sun screen compositions and moisturizer compositions are provided which include a secondary amide, such as N-stearyl stearamide, to impart moisture resistance or substantivity to the compositions.

Description

FIELD OF THE INVENTION

The present invention relates to skin treatment compositions, such as sun screen compositions and moisturizer compositions, which have improved substantivity.

BACKGROUND OF THE INVENTION

The market place is flooded with sun screen and sun block formulations. These products provide excellent protection against severe sun burning of exposed skin and contain chemicals which can absorb ultraviolet light at various wavelengths, such as 2-hydroxy-4-methoxybenzophenone, or an opaque substance that physically reflects or scatters ultraviolet light, such as zinc oxide or titanium dioxide. Most of these formulations offer protection from the sun for extended periods so long as they remain on exposed areas and are not washed off by bathing. Unfortunately, bathing in pool water and ocean water will usually result in most conventional sun screen and sun block formulations being washed away from the skin thereby leaving exposed areas of skin. Attempts have been made at formulating sun screen products which are moisture resistant. For example, see U.S. Pat. No. 3,666,732.

U.S. Pat. No. 4,597,963 to Deckner discloses moisture-resistant skin treatment composition, such as sunscreen compositions, containing a polyvinyl alkyl or alkenyl ester, such as polyvinyl stearate to impart moisture resistance or substantivity.

DESCRIPTION OF THE INVENTION

In accordance with the present invention, moisture resistant skin treatment compositions, such as sun screen and sun block formulations, and moisturizer formulations are provided, which compositions have improved moisture resistance and substantivity due to the presence therein of one or more secondary amides, which contain water, emollients, emulsifiers, thickeners, preservatives, coloring agents, fragrances, antioxidants and the like and one or more known ultraviolet absorbing compounds (in the case of sun screen or sun block formulations). In fact, the moisturizer compositions of the invention will be similar in composition to the sun screen or sun block formulations except for the presence or absence of the ultraviolet absorbing compound.

The formulation of the invention is preferably a oil-in-water type emulsion since this type of emulsion affords better cosmetic feel to the product. However, the product could also be formulated as a water-in-oil emulsion, cream base, or oil base. Depending upon the choice of ingredients, the formulation has a semi-solid cream-like consistency which can be packaged in a plastic squeeze tube or it has a lotion type consistency which can be packaged in a plastic squeeze container. The container can include a flow-type cap or pump-type dispenser.

The essence of the present invention resides in the use of one or more secondary amides as defined hereinafter to enhance the moisture resistance of the particular composition involved. Thus, the composition of the invention, regardless of whether it is a sun screen, sun block, moisturizer, etc. will contain from about 0.5 to about 10% and preferably about 1 to about 8% by weight (based on the total weight of the formulation) of secondary amide. Where amounts less than 0.5% by weight secondary amide are employed, the moisture resistance imparted will be minimal and unacceptable, whereas, where amounts greater than 10% by weight are employed, increase in moisture resistance imparted will be minimal and unwarranted considering the expense of raw materials involved.

The secondary amides useful in the present invention to impart improved substantivity to sun screen compositions will have the structure ##STR1## wherein R.sub.1 and R.sub.2 may be the same or different and represent saturated or unsaturated fatty acid residues containing from 8 to 36 carbons and preferably 12 to 22 carbons, and zero to three double bonds, and zero or one or more hydroxyl groups. These amides are commercially available and may be prepared by conventional techniques.

Examples of secondary fatty amides suitable for use herein include, but are not limited to, N-stearyl stearamide, N-stearyl erucamide, N-stearyl 12-hydroxystearamide, N-erucyl erucamide, N-oleyl palmitamide, N-oleyl hydroxypalmitamide, N-stearyl oleamide, N-erucyl stearamide, N-stearyl hydroxyoleamide, N-oleyl oleamide, N-palmitylpalmitamide, N-oleyl hydroxyoleamide, N-behenylbehenamide, N-behenylerucamide, N-oleyl hydroxystearamide, N-oleylstearamide, N-oleylbehenamide, N-erucylbehenamide, N-caprylstearamide, N-lauryl myristamide, N-margarylarachidamide, N-lauryl hydroxymyristamide, N-tricosanyl nonadecanamide and the like.

Where the formulation is a sun screen or sun block formulation, it will contain one or more known ultraviolet absorbing agents, preferably at least one compound which absorbs in the UV-B region (wavelength 290 to 320 nanometers) and at least one compound which absorbs in the UV-A region (wavelength 320 to 400 nanometers). The total amount of UV absorbing agents included within the formulation will be from about 3% to about 15% by weight, which amount will determine whether it is a sun screen or sun block.

Suitable UV-A absorbing agents include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (Tinuvin P); 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole (Spectra-Sorb UV 5411); 2,4-dihydroxybenzophenone (Uvinul 400); 2-hydroxy-4-methoxybenzophenone (oxybenzone, Spectra-Sorb UV9, Uvinul M-40); 2,2', 4,4'-tetrahydroxybenzophenone (Uvinul D50); 2,2'-dihydroxy-4,4'-dimethoxybenzophenone (Uvinul D49); 2,2'-dihydroxy-4-methoxybenzophenone (dioxybenzone, Spectra-Sorb UV24); 2-ethylhexyl-4-phenyl-benzophenone carbonate (Eusolex 3573); 2-hydroxy-4-methoxy-4'-methylbenzophenone (mexenone, Uvistat 2211); 2-hydroxy-4-(n-octyloxy)benzophenone (octabenzone, Spectra-Sorb UV531); 4-phenylbenzophenone (Eusolex 3490); and 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate (Uvinul N539). The UV-A absorbing agent or agents are present in the final product at from about 0.5% to about 10% by weight of the formulation. The amount will vary according to the particular agent selected and whether the formulation is intended to minimize or permit tanning. The preferred UV-A absorbing agent is 2-hydroxy-4-methoxybenzophenone alone or in combination with 2,2'-dihydroxy-4-methoxybenzophenone.

Suitable UV-B absorbing agents include 4-(dimethylamino)benzoic acid, ethyl ester; 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester (Escalol 507); 4-(dimethylamino)benzoic acid, pentyl ester (Escalol 506); glyceryl p-aminobenzoate (Escalol 106); isobutyl p-aminobenzoate (Cycloform); and isopropyl p-aminobenzoate. The UV-B absorbing agent or agents are present in the final product at from about 1% to about 15% by weight of the formulation. The amount will vary according to the particular agent selected and degree of protection desired in the final product. The preferred UV-B absorbing agent is 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester.

The formulation also contains from about 50% to about 90% and preferably from about 60 to about 80% by weight of water, from about 1% to about 20% and preferably from about 1 to about 10% by weight of emollients, from about 1% to about 10% and preferably from about 1 to about 5% by weight of emulsifiers, from about 0.05 to about 2% and preferably from about 0.1 to about 1% by weight of preservatives and antioxidants, and less than about 1% by weight of fragrance and coloring agents.

Suitable emollients include mineral oil, avocado oil, squalane, octyl palmitate, cocoa butter, sesame oil, petrolatum, propylene glycol dicaprylate/dicaprate, isopropyl myristate, etc. The formulation will preferably contain a mixture of several of these emollients or others which are approved for cosmetic use.

Suitable emulsifiers include polyethylene glycol 20 sorbitan monolaurate (Polysorbate 20), diethanolamine cetyl phosphate, glyceryl stearate, polyethylene glycol 100 stearate, polyethylene glycol 20 stearyl ether (Brij 78, Steareth 20), polysorbate 80 (Tween 80), etc. The formulation will preferably contain a mixture of two or more of these emulsifiers or others which are approved for cosmetic use.

Suitable preservatives include imidazolidinyl urea (Germall 115), methylparaben (Tegosept M), quaternium-15 (N-(3-chloroallyl)hexaminium chloride, Dowcil 200), propylparaben (Tegosept P), dimethyldimethoyl hydantoin, benzyl alcohol and/or phenoxyethanol, etc., and the preferred antioxidant is a mixture of butylated hydroxyanisole, propylene glycol, propyl gallate and citric acid (Tenox 2). The formulation will preferably contain the antioxidant mixture and one or more of the preservatives or any other preservatives and antioxidants approved for cosmetic use.

As discussed above, by varying the percentage of ingredients the formulation can be obtained in a lotion or semi-solid form. For example, in formulation the product as a lotion, water would be included at from about 60% to 65% by weight of the final product and one or more humectants such as propylene glycol, glycerin, 1,3-butylene glycol, sorbitol, polyethylene glycols (for example, Carbowax 400), could be included at up to about 7.5% by weight of the final product.

The composition of the invention will optionally include a thickener in an amount within the range of from about 0.05 to about 1% and preferably from about 0.05 to about 0.3% by weight. A preferred thickener suitable for use herein is Carbopol 940 or Carbomer 940 which is hydrophilic acrylic polymer cross-linked with a polyfunctional agent and employed with an organic or inorganic base, preferably triethanolamine. Other examples of thickeners which may be employed herein include, but are not limited to, stearic acid, magnesium aluminum silicate, stearoxydimethicone, hydroxyethyl cellulose, hydroxypropyl cellulose or xanthan gum.

Skin conditioning agents which may optionally be present in the composition of the invention include allantoin, d- or dl-panthenol, hydrolyzed animal protein and the like. Such conditioning agents may be present in an amount within the range of from about 0.01 to about 5% and preferably from about 0.05 to about 2% by weight depending upon the ultimate use of the skin preparation.

The process techniques will vary depending upon the particular ingredients present. In a preferred process, thickener such as stearic acid, emulsifier such as polysorbate 20 laurate (Tween 20) and glyceryl monostearate and sodium lauryl sulfate (Tegacid special), emollient, such as dimethicone (Silicon 225), preservative, such as propyl paraben, and sun screen agents (where present) are blended together with moderate mixing to form a first non-aqueous blend. A second blend of deionized water, gum thickener, such as Carbopol 940 and other water-soluble ingredients, if desired, and a third blend of humectant, for example, a polyethylene glycol (such as Carbowax 400) and preservative, such as methyl paraben and benzyl alcohol are formed. The first non-aqueous blend is sweep mixed into the second and third blends to form an emulsion. Thereafter, a blend of a small amount of deionized water and triethanolamine (neutralizer for Carbopol 940, if necessary) and other water-soluble ingredients which can be included with this aqueous phase is added to the emulsion with mixing. Aqueous secondary amide is then added and the final blend is cooled to room temperature, homogenized, stored or packaged.

Preferred sun block formulations offering maximum protection according to this invention include from about 60% to about 80% by weight of water, from about 1% to about 10% by weight of a secondary amide, such as N-stearyl stearamide, from about 2.5% to about 3.5% by weight of UV-A absorbing agents selected from 2-hydroxy-4-methoxybenzophenone (oxybenzone) and 2,2'-dihydroxy-4-methoxybenzophenone (dioxybenzone), from about 5% to about 10% by weight of the UV-B absorbing agent 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester (Escalol 507), from about 1 to about 5% by weight of humectants, from about 1% to about 5% by weight of emollients, from about 1% to about 5% by weight of emulsifiers, from about 0.1 to about 0.5% by weight thickeners, and up to about 1% by weight of combined preservatives, antioxidants, and fragrances.

Most preferably the maximum protection formulation will contain about 70% by weight of deionized water, about 4% by weight of N-stearyl stearamide, about 3% by weight of 2-hydroxy-4-methoxybenzophenone, up to about 1% by weight of 2,2'-dihydroxy-4-methoxybenzophenone, about 8% by weight of 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester, about 3% by weight of emollients, about 5% by weight of emulsifiers, about 0.35% by weight thickener, and up to 1% by weight of combined preservatives, antioxidants, and fragrances.

Preferred sunscreen formulations which protect but still permit gradual tanning according to this invention contain from about 55% to about 65% by weight of water, from about 1 to about 10% by weight of secondary amide, up to about 1% by weight of 2-hydroxy-4-methoxybenzophenone (oxybenzone), from about 3% to about 5% by weight of 4-(dimethylamino)benzoic acid, 2-ethylhexylester (Escalol 507), up to about 7.5% by weight of humectants, from about 1 to about 10% by weight of emollients, from about 1% to about 5% by weight of emulsifiers, and up to about 1% by weight of combined preservatives, antioxidants, fragrances, and up to about 1% by weight of thickeners.

The most preferred sunscreen formulation which still permits tanning is a lotion containing from about 70% to about 72% by weight of deionized water, about 4% by weight of a secondary amide, about 0.5% by weight of 2-hydroxy-4-methoxybenzophenone, about 4% by weight of 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester, about 3% by weight of glycerin or propylene glycol, about 3% to about 8% by weight of emollients, from about 2% to about 5% by weight of emulsifiers, and up to about 1% by weight of combined preservatives, anitoxidants and fragrances and about 0.5% thickener.

Preferred moisturizer compositions will be similar to the sunscreen and sun block formulations set out above without the sunscreen agents.

The following Examples represent preferred embodiments of the invention. Unless otherwise indicated, all temperatures are expressed in degrees Centigrade.

EXAMPLE 1

A sun screen composition having improved substantivity having the following composition is prepared as described below.

______________________________________ Parts byIngredient Weight______________________________________Sun screen Base formulation* 90N--Stearyl stearamide (Kemamide S-180) 4Deionized water 6*Sunscreen Base formulationIngredient % w/w______________________________________Phase ADeionized water 75Carbopol 940 (acrylic acid 0.4polymer-thickener)Phase BCarbowax 400 (PEG-400 humectant) 2Benzyl alcohol (preservative) 0.5Tegosept M (methyl paraben - 0.2preservative)Phase CTegacid special (glyceryl stearate 1.5and sodium lauryl sulfate -emulsifier)Cetyl alcohol (thickener-emollient) 1.6Stearic acid (thickener) 3.5Uvinul M-40/Spectra-Sorb 3UV-9 (benzophenone 3)Escalol 507 (octyldi- (sun screens) 8methyl p-aminobenzoicacidTween 20 (Polysorbate 120-emulsifier)Tegosept P (propyl 0.1paraben-preservative)Phase DDeionized water 2Triethanolamine 99% 1.5Phase EGlydant (dimethyldimethoyl 0.001hydantoin - preservative)______________________________________

The Phase A ingredients are homomixed for 15 minutes. Thereafter, a mix of the Phase B ingredients is sweep mixed into Phase A. A mixture of Phase C ingredients, heated at 80.degree. C., is then added to the above mix with fast mixing to form an emulsion. The mix is then combined with Phase D with mixing and thereafter Phase E is added and the mixture is cooled to 30.degree. C. to form the sun screen cream base formulation.

Next, the N-stearyl stearamide-water mix is heated at 100.degree. C. and one-third of the sun screen base formulation is mixed therewith at 100.degree. C. for 10 minutes. Thereafter, the remainder of the sun screen base formulation is mixed therewith at 60.degree. C. for 15 minutes. The batch is cooled and hand homogenized to form the sun screen composition of the invention which has improved substantivity.

EXAMPLE 2

A water-resistant sun block formulation (in the form of a oil-in-water type emulsion in thick lotion form) in accordance with the present invention having a sun protection factor (SPF) value of 15 having the following composition was prepared as described below.

The SPF value is determined by dividing minimal erythema dose (MED) for protected skin after the application of 2 mg/cm.sup.2 of the formulation by the MED for unprotected skin.

______________________________________Ingredient Parts by Weight______________________________________Blend IGlyceryl monostearate and Sodium 3lauryl sulfate (Tegacidspecial)(thickener andauxiliary emulsifier)Stearic acid (thickener and 3emollient)2-Hydroxy-4-methylbenzophenone 3(UVinul M40 - sunscreen)4-(Dimethylamino)benzoic acid, 82-ethylhexyl ester (Escalol 507 -sunscreen)Dimethicone (Silicone 225 - 0.5emollient)Polysorbate 20 laurate 1(Tween 20 - emulsifier)Propylparaben (Tegosept P - 0.1preservative)Blend IIDeionized water 72Acrylate polymer (Carbopol 0.3940 - gum thickener)Blend IIIPolyethylene glycol 400 (Carbowax 1400 - humectant)Methylparaben (Tegosept M - 0.2Preservative)Benzyl alcohol (Preservative) 0.5Blend IVDeionized water 8Triethanolamine 1N--Stearyl stearamide 4______________________________________

Aqueous Blend II is prepared by dispersing the acrylate polymer in the deionized water. Blend III (prepared by simple mixing of ingredients) is then mixed with Blend II. The combined Blend II-III is then heated to 75.degree. C.

Blend I is formed by simple mixing of the ingredients in a separate vessel while heating to 75.degree. C.

Blend I (heated at 75.degree. C.) is then added to the combined Blend II-III (also at 75.degree. C.) with sweep mixing.

The combined Blend I-II-III is heated at 75.degree. C. for 30 minutes, allowed to air cool to 60.degree. C., and then Blend IV (prepared by simple mixing of ingredients) is added with sweep mixing. The resulting batch is then allowed to air cool to 30.degree. C. to form the sun block formulation of the invention.

EXAMPLE 3

A sun screen formulation in accordance with the present invention having the following composition and having a sun protection factor (SPF) value of 8 is prepared as described below.

The ingredients are listed on a parts by weight basis and the chemical, CTFA, and/or trade name are included. This formulation is an oil-in-water type emulsion in a thick lotion form.

______________________________________Ingredient Parts by Weight______________________________________Blend IADeionized water 69.2Acrylate polymer (Carbopol 940- 0.35gum thickener)Blend IBGlycerine (humectant) 1Deionized water 0.1Methylparaben (Tegosept M, 0.25preservative)Blend IICetyl alcohol (thickener 5emollientPolysorbate 60 (Tween 60, 2emulsifier)Glyceryl monostearate (Tegin, 2thickener)Cetyl palmitate (Kessco X653, 1emollient)Dimethicone (Silicone 200 1(350 c.s.) emollient)Petrolatum (emollient) 0.5Propylparaben (Tegosept P, 0.1preservative)4-(Dimethylamino)benzoic acid, 4.252-ethylhexyl ester (Escalol 507,sun screeen)2-Hydroxy-4-methoxybenzophenone/ 1.22,2'-dihydroxy-4-methoxy-benzo-phenone (Uvinul M-40/Spectra-SorbUV-9)Blend IIIDeionized water 2Sodium hydroxide 0.16Perfume oil 0.45Blend IVDeionized water 2Potassium sorbate (Sorbistat-K, 0.2preservative)Imidazolidinyl urea (Germall 115, 0.45preservative)N--Palmityloleamide 5______________________________________

Aqueous Blend IA is prepared by dispersing the acrylate polymer in the deionized water. Blend IB (prepared by simple mixing of ingredients) is then mixed with Blend IA. The combined Blend IA-B is then heated to 75.degree. C.

Blend II is formed by simple mixing of the ingredients in a separate vessel while heating at 75.degree. C.

Blend II (heated at 75.degree. C.) is then added to the combined Blend IA-B (also at 75.degree. C.) with sweep mixing.

The combined Blend IA-B-II is heated at 75.degree. C. for 30 minutes, allowed to air cool to 60.degree. C. and then Blends III and IV (each prepared by simple mixing) together with the perfume oil are added with sweep mixing.

The resulting batch is then allowed to air cool to 30.degree. C. to form the sun screen formulation of the invention.

EXAMPLE 4

A sunscreen formulation having a sun protection factor value of 4 having the following composition is prepared as described below. The ingredients are listed on a parts by weight basis and both the CFTA and trade name are included. This formulation is an oil-in-water type emulsion having a lotion consistency.

______________________________________Ingredient Parts by Weight______________________________________Blend IADeionized water 74Acrylate polymer (Carbopol 940- 0.2gum thickener)Blend IBPropylene glycol (humectant) 2Methylparaben (Tegosept M, 0.2preservative)Blend IIPolyethylene glycol 23 - lauryl ether 2(Brij 35, Laureth 23,auxiliary emulsifier)Sorbitan stearate (Arlacel 60, 1emulsifier)4-(Dimethylamino)benzoic acid, 32-ethylhexyl ester (Escalol 507,sun screen, UV-B)C.sub.12 -C.sub.15 alcohol benzoate (Finsolv 3TN, emollient)Dimethicone (Silicone 225, 1emollient)Propylparaben (Tegosept P, 0.1preservative)Cetyl alcohol (thickener, 2.5emollient)Blend IIIDeionized water 1Triethanolamine 0.2Dimethyldimethoyl hydantoin 0.2(Glydant, preservative)N--behenylerucamide 4.5______________________________________

Aqueous Blend IA is prepared by dispersing the acrylate polymer in the deionized water. Blend IB (prepared by simple mixing of ingredients) is then mixed with Blend IA. The combined Blend IA-B is then heated to 75.degree. C.

Blend II is formed by simple mixing of the ingredients in a separate vessel while heating at 75.degree. C.

Blend II (heated at 75.degree. C.) is then added to the combined Blend IA-B (also at 75.degree. C.) with sweep mixing.

The combined Blend IA-B-II is heated at 75.degree. C. for 30 minutes, allowed to air cool to 60.degree. C. and then Blend III (prepared by simple mixing) is added with sweep mixing.

The resulting batch is then allowed to air cool to 30.degree. C. to form the sun screen formulation of the invention.

EXAMPLE 5

A moisturizer formulation having the following composition is prepared as described below. The ingredients are listed on parts by weight basis and both the CTFA and trade name are included. The formulation is an oil-in-water type emulsion and is in the form of a lotion.

______________________________________Ingredient Parts by Weight______________________________________Blend IDeionized water 74.3Magnesium aluminum silicate 0.2(Veegum R, thickener)dl-Panthenol (skin conditioner) 0.5Allantoin (skin conditioner) 0.2N--Stearyl stearamide 4Blend IIPolyethylene glycol (Carbowax 400, 2humectant)Xanthan gum (Keltrol F, 0.2thickener)Methylparaben (Tegosept M, 0.2preservative)Blend IIIIsopropyl palmitate (emollient) 2.5Cetearyl octanoate (Purcellin oil, 4emollient)Propylene glycol dicaprate/ 8dicaprylate (Standamul 302emollient)Propylparaben (Tegosept P, 0.1preservative)Stearic acid (thickener) 2Cetyl alcohol 0.5Polyethylene glycol 100 stearate 2and glycerol monostearate (1:1)(Arlacel 165, emulsifier)Polyethylene glycol 20 stearyl 2ether (Brij 78, emulsifier)Component IVDimethyldimethoyl hydantoin 0.3(Glydant, preservative)______________________________________

Aqueous Blend IA is prepared by mixing the ingredients in the deionized water. Blend II (prepared by simple mixing of ingredients) is then mixed with Blend I. The combined Blends I-II is then heated to 75.degree. C.

Blend III is formed by simple mixing of the ingredients in a separate vessel while heating at 75.degree. C.

Blend III (heated at 75.degree. C.) is then added to the combined Blend I-II-III (also at 75.degree. C.) with sweep mixing.

The combined Blend I-II-III is heated at 75.degree. C. for 30 minutes, allowed to air cool to 60.degree. C. and then component IV is added with sweep mixing.

The resulting batch is then allowed to air cool to 30.degree. C. to form the moisturizer formulation of the invention.

Claims

1. A moisture-resistant skin treatment composition in the form of a sun screen composition or moisturizer composition, in the form of an oil-in-water emulsion or a water-in-oil emulsion, consisting essentially of from about 50 to about 90% by weight water, from about 1 to about 10% by weight emollient, from about 1 to about 10% by weight emulsifier, a preservative and a secondary amide having the structure ##STR2## wherein R.sub.1 and R.sub.2 may be the same or different and represent saturated or unsaturated fatty acid residues containing 8 to 36 carbons and 0 to 3 double bonds, and 0 or 1 hydroxyl groups, in an amount within the range of from about 0.5 to about 10% by weight based on the total composition to impart moisture-resistance to said composition.

2. The composition as defined in claim 1 wherein R.sub.1 and/or R.sub.2 contains from about 12 to about 22 carbons.

3. The composition as defined in claim 1 wherein said secondary amide is N-stearyl stearamide, N-stearyl erucamide, N-erucyl erucamide, N-oleyl palmitamide, N-stearyl oleamide, N-erucyl stearamide, N-oleyl oleamide, N-palmityl palmitamide, N-behenylbehenamide, N-behenylerucamide, N-oleylstearamide, N-oleylbehenamide or N-erucylbehenamide, or N-stearyl hydroxystearamide.

4. The composition as defined in claim 1 wherein the secondary amide is N-stearyl stearamide.

5. The composition as defined in claim 1 in the form of a moisture-resistant sun screen composition and includes from about 1 to about 15% by weight of at least one ultraviolet absorbing agent.

6. The composition as defined in claim 1 wherein the ultraviolet absorbing agents include one or more UV-A absorbing and one or more UV-B absorbing agents.

7. The composition as defined in claim 6 wherein the UV-A absorbing agent or agents are present at from about 0.5% to about 10% by weight and the UV-B absorbing agent or agents are present at from about 3% to about 10% by weight.

8. The composition as defined in claim 7 wherein the UV-A absorbing agent is one or more selected from the group consisting of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole; 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole; 2,4-dihydroxybenzophenone; 2-hydroxy-4-methoxybenzophenone; 2,2', 4,4'-tetrahydroxybenzophenone; 2,2'-dihydroxy-4,4'-dimethoxybenzophenone; 2,2'-dihydroxy-4-methoxybenzophenone; 2-ethylhexyl-4-phenylbenzophenone carbonate; 2-hydroxy-4-methoxy-4'-methylbenzophenone; 2-hydroxy-4-(n-octyloxy)benzophenone; 4-phenylbenzophenone; and 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate and the UV-B absorbing agent is one or more selected from the group consisting of 4-(dimethylamino)benzoic acid, ethyl ester; 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester; 4-(dimethylamino)benzoic acid, amyl ester; glyceryl p-aminobenzoate; isobutyl p-aminobenzoate; and isopropyl p-aminobenzoate.

9. The composition as defined in claim 7 wherein the UV-A absorbing agent is 2-hydroxy-4-methoxybenzophenone alone or in combination with 2,2'-dihydroxy-4-methoxybenzophenone and the UV-B absorbing agent is 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester.

10. The composition as defined in claim 1 wherein water is present in an amount of from about 50 to about 90% by weight, emollients are present in an amount of from about 1 to about 10% by weight, emulsifiers are present in an amount of from about 1 to about 5% by weight, thickeners are present in an amount of from about 0.1 to about 1% by weight, humectants are present in an amount of from about 1 to about 5% by weight, preservatives are present in an amount of from about 0.5 to about 1% by weight.

11. The composition as defined in claim 5 offering maximum ultraviolet protection and moisture resistance comprising from about 60% to about 80% by weight of water, from about 2% to about 7% by weight of secondary amide, from about 1% to about 5% by weight of 2-hydroxy-4-methoxybenzophenone alone or in combination with 2,2'-dihydroxy-4-methoxybenzophenone, from about 5% to about 10% by weight of 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester, from about 1% to about 10% by weight of emollients, from about 1% to about 5% by weight of emulsifiers, and up to about 1% by weight of combined preservatives, antioxidants and fragrances.

12. The composition of claim 11 comprising about 73% by weight of deionized water, about 4% by weight of N-stearyl stearamide, about 2% to about 4% by weight of 2-hydroxy-4-methoxy-benzophenone, up to about 1% by weight of 2,2'-dihydroxy-4-methoxybenzophenone, about 8% by weight of 4-(dimethylamino)benzoic acid, 2-ethylhexyl ester, from about 3% to about 8% by weight of emollients, from about 2% to about 4% by weight of emulsifiers, and up to about 1% by weight of combined preservatives, antioxidants and fragrances.

13. The composition as defined in claim 1 further including a thickener in an amount within the range of from about 0.05 to about 1% by weight.

14. The method of enhancing the moisture resistant properties of a sun screen composition which contains one or more ultraviolet absorbing agents which comprises including at least about 0.5 by weight of a secondary amide having the structure ##STR3## wherein R.sub.1 and R.sub.2 are the same or different and represent saturated or unsaturated fatty acid residues containing from 8 to 36 carbons, and 0 to 3 double bonds and 0 or 1 hydroxyl groups.

15. The method as defined in claim 14 wherein the sun screen composition contains from about 3% to about 15% by weight of ultraviolet absorbing agents and the secondary amide is included at from about 0.5 to about 10% by weight of the composition.

16. The method as defined in claim 14 wherein the secondary amide is N-stearyl stearamide, N-stearyl erucamide, N-erucyl erucamide, N-oleyl palmitamide, N-stearyl oleamide, N-erucyl stearamide, N-oleyl oleamide, N-palmityl palmitamide, N-behenylbehenamide, N-behenylerucamide, N-oleylstearamide, N-oleylbehenamide, N-erucylbehenamide or N-stearyl hydroxystearamide.

17. The method as defined in claim 16 wherein the secondary amide is N-stearyl stearamide.

18. The composition as defined in claim 1 further including a thickener in an amount within the range of from about 0.05 to about 1% by weight.