Moisture-Resistant Skin Treatment Compositions

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

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.