Cosmetic Composition for Rejuvenation of Skin Without Skin Irritation

1. Field of the Invention

This invention relates to cosmetic compositions, and, more particularly, to a cosmetic composition for rejuvenating the appearance of skin with substantially no skin irritation, in the form of a lotion, creme, solution or gel, which includes an aqueous, alcoholic or aqueous-alcoholic solution of a polymer having a carboxylic acid funcitionality, at a pH of 1.5 to 5.

2. Description of the Prior Art

Cosmetic compositions having an alpha- or beta-hydroxy acid (AHA/BHA) as the active ingredient are well-known in the art. These compositions are useful for treatment of the skin, particularly for anti-aging, improvement in skin tone, reduction of fine line, enhancement of moisture, and development of a smooth skin. Application of such compositions generally results in a younger-looking skin as new cells replace the old. Smith, in Soap/Cosmetics/Chemical Specialties, September 1993, page 54, addressed the question of whether an AHA must be in the acid form to be effective in promoting exfoliation and skin renewal. Various AHA and BHA compounds were examined for their ability to increase cell renewal at different pHs, with similar results observed for all acids tested. As the pH increased, the ability to stimulate cell renewal diminished; in fact, at a pH above 6, very little stimulation of cell turn over was observed with any AHA material. For the acids tested, a maximal stimulation of renewal was observed at a pH of about 3, as shown in Table 1 below.

Accordingly, to achieve improvement in skin condition, it has been found necessary for the user to tolerate the skin irritation caused by the acid present in the product. Thus, skin irritation is a major concern to formulators of alpha and beta-hydroxy acid-containing products, particularly at acid loading levels which can deliver faster and more effective skin peeling. More irritation, however, is perceived by the user as being a more effective treatment.

Scott and Yu, in EP 671162, have described an amphoteric composition containing AHAs and their esters and salts for topical application for the treatment of cosmetic conditions and dermatological disorders. The inclusion of an amphoteric compound in the composition provided a stable composition having a pH closer to that of skin.

Accordingly, it is an object of this invention to provide a cosmetic composition for the rejuvenation of skin and its appearance, with substantially no irritation during use.

Another object of this invention is to provide a cosmetic composition for the rejuvenation of skin and its appearance, which includes as the active ingredient therein a polymer having a carboxylic acid functionality, at a predetermined pH level, where effective cell renewal and exfoliation is achieved without skin irritation.

These and other objects and features of the invention will be made apparent from the following description thereof.

A cosmetic composition for rejuvenating the appearance of skin with substantially no skin irritation, in the form of a lotion, creme, solution or gel, includes an aqueous, alcoholic or aqueous-alcoholic solution of a polymer having a carboxylic acid functionality, the solution having a pH of 1.5 to 5.

The active ingredient in the cosmetic composition of the invention is a polymer having a carboxylic acid functionality, including homopolymers, copolymers and terpolymers which has the following general formula set forth below: ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3 are each independently selected from the group of --H, --C.sub.1 to C.sub.4 alkyl, --(CH.sub.2).sub.p COOR.sub.4, C.sub.6 H.sub.4 COOR.sub.4 and CH(R.sub.5)(CH.sub.2).sub.p COOR.sub.4 where R.sub.4 is hydrogen or C.sub.1 to C.sub.4 alkyl; R.sub.5 is hydrogen, --OH or --CO-- and p has a value of from 0 to 4, and mixtures thereof, with the proviso that at least one of R.sub.1, R.sub.2 and R.sub.3 contains a carboxyl group; n is an integer from 10 to 10,000, preferably 100 to 1000; Y is a monomer unit derived from an unsaturated ether, hydrocarbon, alcohol, ester, ketone or amide, including a vinyl C.sub.1 to C.sub.4 alkyl ether, C.sub.2 to C.sub.4 alkene, C.sub.1 to C.sub.4 ester, styrene, itaconic mono- or di- ester, vinyl pyrrolidone, vinyl caprolactam, acrylic acid, methacrylic acid, (meth)acrylamide, alkyl maleate, alkyl (meth)acrylate and mixtures thereof; and m is an integer from 0 to 10,000.

When m=0, the active ingredient is a homopolymer; when Y is present, m is a positive integer from 1 to 10,000, preferably 100 to 1000, and copolymers and terpolymers are provided.

The mole ratio of m to n in the polymer of this invention preferably is between 0:20 and 20:2 which includes homopolymers, copolymers and terpolymers of unit n and copolymers, terpolymers and interpolymers of units m and n. Further, the total number of units m+n in the polymer is preferably between 3 and 100,000, most preferably between 100 and 10,000.

The above co- and ter- polymers of m and n can be branched or linear and the monomer units can be combined in a random, graft or alternating structure.

Examples of polymers which are suitably employed as the active ingredient in the composition of the present invention include the homopolymers of acrylic acid, methacrylic acid, maleic acid, allyl acetic acid, 4-vinylbenzoic acid, itaconic acid, crotonic acid, N-vinyl succinimidic acid, 2-carboxyethyl acrylic acid, and vinyl ether.

Examples of suitable copolymers and terpolymers for use herein include those of acrylic/itaconic acids, methacrylic/itaconic acids, acrylic/methacrylic acids, methacrylic/maleic/acrylic acids, a vinyl alkyl ether/maleic acid, styrene/maleic acid, ethylene/maleic acid, vinyl pyrrolidone/acrylic acid, vinyl acetate/butyl maleate/isobornyl acrylate/acrylic acid, isobornyl salicylate/acrylic acid, maleic acid/vinyl pyrrolidone/vinylcaprolactam/dimethylaminoethylmethacryla te, methyl vinylether/monoalkyl maleate/acrylic acid/methacrylic acid, vinyl pyrrolidone/2-carboxyethyl acrylate/acrylic acid and vinyl pyrrolidone/allyl acetic acid/maleic acid.

The above defined polymers, copolymers and terpolymers also may be crosslinked by reaction with a conventional polyfunctional crosslinking agent, such as a diene, a polyalkylether, a polyvinylether, dialdehyde, a polyalcohol, and the like. Suitably the polymer can be crosslinked by the addition of 0.5-3% of a suitable crosslinker.

In the skin treatment compositions of this invention, such polymers are employed within a critical solution pH range of 1.5 to 5, preferably between about 2 and about 4.5. Above pH 5, little if any cell renewal or exfoliation is achieved; below pH 1.5, noticeable skin irritation results. If the pH is below 1.5, conventional bases can be used to partially neutralize the composition, i.e. increase the pH as desired.

The present polymers are generally employed as a solution, cream, gel or paste in a formulation including a diluent such as water, alcohol, aqueous-alcohol, glycol or other inactive carrier; which includes between about 0.1 and about 25 wt. % of the polymer, preferably about 1 to about 15 wt. % of the polymer.

In addition to the diluent, formulations of the polymer may also contain other standard adjuvants such as an emolient, moisturizer, thickener, emulsifier, neutralizer, coloring agent, UV absorber or filter, preservative and/or gelling agent such as those described below. When employed in the formulation, each of these adjuvants generally are present in an amount of between about 0.1 to 10 wt. % of the formulation.

Emollient

Suitable emollients for use herein include, for example, optionally hydroxy-substituted C.sub.8 -C.sub.50 unsaturated fatty acids and esters thereof, C.sub.1 -C.sub.24 esters of C.sub.8 -C.sub.30 saturated fatty acids such as isopropyl myristate, cetyl palmitate and octyldodecylmyristate (Wickenol 142), beeswax, saturated and unsaturated fatty alcohols such as behenyl alcohol and cetyl alcohol, hydrocarbons such as mineral oils, petrolatum, squalane, fatty sorbitan esters, lanolin and lanolin derivatives, such as lanolin alcohol ethoxylated, hydroxylated and acetylated lanolins, cholesterol and derivatives thereof, animal and vegetable triglycerides such as almond oil, peanut oil, wheat germ oil, linseed oil, jojoba oil, oil of apricot pits, walnuts, palm nuts, pistachio nuts, sesame seeds, rapeseed, cade oil, corn oil, peach pit oil, poppyseed oil, pine oil, castor oil, soybean oil, avocado oil, safflower oil, coconut oil, hazelnut oil, olive oil, grapeseed oil, and sunflower seed oil and C.sub.1 -C.sub.24 esters of dimer and trimer acids such as diisopropyl dimerate, diisostearylmalate, diisostearyldimerate and triisostearyltrimerate.

Suitable emollients for use herein include isocetyl alcohol, octyl palmitate, isostearyl neopentanoate and isocetyl stearyl stearate, natural or synthetic oils selected from mineral, vegetable, and animal oils, fats and waxes, fatty acid esters, fatty alcohols, alkylene glycol and polyalkylene glycol ethers and esters, fatty acids and mixtures thereof.

Preferred emollients are selected from hydrocarbons such as isohexadecane, mineral oils, petrolatum, squalane, lanolin alcohol, and stearyl alcohol. These emollients may be used independently or in mixtures and may be present in the composition of the present invention in an amount from about 1% to about 30% by weight, and preferably are present in an amount from about 5% to about 15% by weight of the total composition.

Emulslfier

Suitable emulsifiers for use herein include glyceryl stearate and laureth 23, PEG 20 stearate, and mink-amidopropyl dimethyl 2-hydroxyethylammonium chloride.

Moisturizer

Typical moisturizers are glycerin, petrolatum and maleated vegetable oil.

Thickener

The compositions of the invention can also contain a hydrophilic gelling agent at a level from about 0.01% to about 10%, preferably from about 0.02% to about 2%, and especially from about 0.02% to about 0.5%. The gelling agent preferably has a viscosity (1% aqueous solution, 20.degree. C., Brookfield RVT) of at least about 4000 mPa.s, more preferably at least about 10,000 mPa.s and especially at least 50,000 mPa.s.

Suitable hydrophilic gelling agents can generally be described as water-soluble or colloidally water-soluble polymers, and include cellulose ethers (e.g. hydroxyethyl cellulose, methyl cellulose, hydroxypropylmethyl cellulose), polyvinylalcohol, polyquaternium-10, guar gum, hydroxypropyl guar gum and xanthan gum.

Among suitable hydrophilic gelling agents are acrylic acid/ethyl acrylate copolymers and the carboxyvinyl polymers sold by the B.F. Goodrich Company under the trademark of Carbopol.RTM. resins. These resins consist essentially of a colloidally water-soluble polyalkenyl polyether crosslinked polymer of acrylic acid crosslinked with from 0.75% to 2.00% of a crosslinking agent such as polyallyl sucrose or polyally pentaerythritol. Examples include Carbopol 934, Carbopol 940, Carbopol 950, Carbopol 980, Carbopol 951 and Carbopol 981. Carbopol 934 is a water-soluble polymer of acrylic acid crosslinked with about 1% of a polyallyl ether of sucrose having an average of about 5.8 allyl groups for each sucrose molecule. Also suitable for use herein are hydrophobically-modified crosslinked polymers of acrylic acid having amphipathic properties available under the Trade Name Carbopol 1382, Carbopol 1342 and Pemulen TR-1 (CTFA Designation: Acrylates/10-30 Alkyl Acrylate Crosspolymer). A combination of the polyalkenyl polyether cross-linked acrylic acid polymer and the hydrophobically modified crosslinked acrylic acid polymer is also suitable for use herein. Other suitable gelling agents suitable for use herein are oleogels such as trihydroxystearin and aluminum magnesium hydroxy stearate.

Preferred thickeners for use herein include crosslinked maleic anhydride-alkyl methylvinylethers, and copolymers, sold as Stabileze.RTM. QM (International Specialty Products (ISP)). Also useful are Carbomer.RTM., natural gums, highly crosslinked polymethacrylate copolymer such as Microsponges.RTM. 5647, which take the form of generally spherical particles of crosslinked hydrophobic polymer having a pore size of from about 0.01 to about 0.05 .mu.m and a surface area of 200-300 m.sup.2 /g. Again, it is preferably loaded with humectant in the levels described above.

Neutralizer

Neutralizing agents suitable for use in neutralizing acidic group containing hydrophilic gelling agents herein include sodium hydroxide, potassium hydroxide, ammonium hydroxide, monoethanolamine, diethanolamine and triethanolamine, and aminomethyl propanol.

Other Optional Components

Another optional but preferred component of the composition is one or more preservatives. The preservative concentration in the composition, based on the total weight of that composition, is in the range of between about 0.05% and about 1.0% by weight, preferably between abut 0.1% and abut 0.4% by weight. Suitable preservatives for use herein include sodium benzoate and propyl paraben, and mixtures thereof.

The composition may also contain additional materials such as, for example, fragrances, fillers such as nylon, sun-screens, electrolytes such as sodium chloride, proteins, antioxidants and chelating agents as appropriate.

Another optional component is one or more ultraviolet absorbing agents. Ultraviolet absorbing agents, often described as sunscreening agents, can be present in a concentration in the range of between about 1% and about 25% by weight, based on the total weight of composition. Preferably, the UV absorbing agents constitute between about 2% and 15% by weight. More preferably, the UV absorbing agents can be present in the composition in a concentration range of between about 4% and about 10% by weight. Of the ultraviolet absorbing agents suitable for use herein, benzophenone-3, benzophenone-4, octyl dimethyl PABA (Padimate O), octyl methoxy cinnamate, octyl salicylate, octocrylene, p-methylbenzylidene camphor, butyl methoxy dibenzoyl methane (Parsol 1789), titanium dioxide, zinc oxide and mixtures thereof are particularly preferred.

The cosmetic compositions of the present invention are useful in the epidermal treatment to achieve cell renewal, skin smoothing, exfoliation, removal of skin blemishes such as freckles, warts, ichthyosis, keratoses, melasma, age spots and other undesirable skin pigmentation. The polymers therein are also useful in the treatment of acne, psoriasis, clogged pores and general improvement of skin tone. The crosslinked polymers described herein additionally provide a moisturizing effect. Many other benefits and uses will become apparent from the above disclosure.

The present polymers provides many advantages for such uses over the non-polymeric acid compounds (AHA or BHA) of the prior art. Specifically, their large molecular size as compared to such compounds prevents penetration through the pores of the skin. Accordingly, skin irritation and toxicity are substantially avoided or minimized during use. Furthermore, polymers containing a carboxylic acid functionality are less acidic than their monomers and thus can be employed in combination with other treating agents, if desired.

Single applications of the skin care compositions containing the instant polymers provides immediate effect in smoothing, moisturizing and toning the skin. Conversely, exfoliation, cell renewal, etc. may require multiple applications of daily or weekly frequency, depending on the skin type of the consumer. Generally, such applications for 0.5 to 6 weeks show a marked effect for skin treatments usually requiring stronger action.

Having generally described the invention, reference is now had to the accompanying examples which illustrate preferred embodiments but which are not to be construed as limiting to the scope of the invention as more broadly set forth above and in the appended claims.

This example is a comparative cell renewal study of (A) an acid polymer of the invention and (B) a non-polymeric acid compound, against (C) an untreated control, measured by the disappearance of dansyl chloride from the stratum corneum on human skin. Such disappearance of the fluorescent dye is an accepted marker for the transit of cells through the horny epidermal layer, and is therefore a function of the new cell production rate.

In this experiment, the (A) polymer is a 1:1 maleic acid/methyl vinyl ether copolymer (GANTREZ.RTM. S-93, ISP, as a aqueous solution, with a pH of 2.1); (B) is lactic acid, as a 10% aqueous solution; and (C) is dansyl chloride (5-dimethylaminonaphalene-1-sulfonyl chloride), as a 5% petrolatum composition.

Method

50 microliters (.mu.l) of each test sample was applied to separate sites of the skin of 26 female test subjects (5 times a week for 4 weeks). Particularly, Compositions A, B and C were separately tested on the outer, upper arms above the elbow fold of each subject. The test sites were cleansed with 70% isopropyl alcohol. The test sites, 5 cm.times.5 cm, were initially outlined with gentian violet surgical marker on the first day of testing and a 2 cm space was left between test sites.

In three separate areas, approximately 0.2 g dansyl was placed in a 2 cm.times.2 cm area in the center of the test site. The control patch site areas were kept dry for 24 hours after which the patches were removed and excess dansyl chloride wiped off. The penetration of the dansyl chloride was confirmed by examination for the presence of fluorescence under ultraviolet illumination using a Wood's light (model SL-3660 Long Wave Ultra Violet, Black Light Eastern Corp., Westbury, Long Island, N.Y.).

On a randomized basis, 50 .mu.l of each test material A and B was evenly spread over a dansyl chloride treated site, and after 24 hour intervals, the results were observed and recorded.

Each of the 26 subjects tested was evaluated for the degree of fluorescent brightness and assigned values of 1 to 5, namely

5=uniform, very bright;

4=uniform moderate brightness

3=faded yet visible fluorescence

2=faded spotty brightness

1=no brightness

The brightness values in following Table 2 represent the total of individual value ratings assigned to each subject in the group of 26 subjects tested. A lower value indicates a higher cell renewal.

The experimental results in Table 2 establishes that a polymer having a carboxylic acid functionality has the same cell renewal efficacy as a non-polymer alpha-hydroxy acid, and both are substantially more effective than the control sample.

A comparative test was conducted to determine the extent of reduction of irritation during use of the polymers of the invention (Test Samples A) vs. alpha- and beta-hydroxy acids (Test Samples B), below.

In this study, a panel of 12 volunteers was selected from people who previously reported moderate stinging following application of a standard lactic acid solution. These people were asked to report their reactions to standard Test Sample B aqueous solutions of lactic acid, glycolic acid, salicyclic acid and citric acid, and also to aqueous and undiluted Test Sample A solutions of poly(methylvinyl ether/maleic acid, poly(vinylpyrrolidone/acrylic acid, and polyacrylic acid at a pH of about 2.5. These materials were randomly applied with a cotton-tipped applicator to either the left or right naso-labial fold. Subjective reactions were reported on a PDI scale of 0-3, with 0 being no irritation, 10 seconds, 21/2 and 5 minutes after application. The results are given in Table 3 below.

The invention will now be illustrated by the following examples.

A skin creme composition containing poly(methylvinylether/maleic acid) (Gantrez.RTM. S-93) was formulated as follows:

Procedure

(1) Add Plasdone.RTM. K 29/32 to water-mix until totally dissolved.

(2) Add Stabtleze.RTM. QM to water mix, then heat to 75.degree. C. and mix until hydrolyzed.

(3) Cool to 60.degree. C. add Suttocide.RTM. A.

(4) Add Gantrez.RTM. S-93/Na0H.

(5) Add oil phase at 60.degree. mix for 10 minutes.

(6) Homogenize 15 minutes.

(7) Cool to 40.degree., add preservative.

(8) Adjust for water loss.

A skin creme composition containing polyacrylic acid was prepared as follows.

Procedure

Add polyacrylic acid to water--mix until completely dissolved; then add Stabileze.RTM. QM mix well, heat to 75.degree. C., forming a smooth, white mixture; cool to 60.degree. C.; add Suttocide.RTM. A, keeping temperature at 60.degree. C.; add oil phase at 60.degree. C.; mix for 10 minutes, homogenize 15 minutes, a thin water-like consistency; cool; add the neutralizer to bring pH to 4.0.

A skin care facial toner composition containing Gantrez.RTM. S-93 was prepared as described in Example 4 above. The compositions included:

An after-sun gel composition containing a Gantrez.RTM. S-93 polymer was prepared as follows:

Procedure

(1) At room temperature add ingredients of water phase in order listed. Mix until completely uniform between additions. Do not aerate.

(2) Add premix to water phase slowly. Do not aerate.

(3) Add polymer of invention.

(4) At 85.degree. C. add ingredients of the oilphase to separate vessel in order listed. Mix until uniform between additions.

(5) While in liquid form, add oil phase to water phase in desired design.

Procedure

(1) Heat water to 85.degree. C.

(2) Disperse hydroxyethylcellulose in water until clear and uniform. Add Ganex.RTM. P 904 followed by Gantrez.RTM. S-95.

(3) Add paraben premix.

(4) Heat oil phase to 85.degree. C. and mix until uniform.

(5) Add oil phase to water phase. Mix well with sweep blade.

(6) Homogenize.

(7) Cool to 40.degree. C. while mixing.

(8) Add remaining ingredients in order listed, mixing well between additions.

Procedure

(1) Completely disperse Carbomer in water with heat to 85.degree. C. Add poly(maleic acid).

(2) Add propylene glycol premix. Then TEA premix.

(3) Heat oil phase to 85.degree. C. Mix until uniform.

(4) Add oil phase to water phase. Mix until uniform with a sweep blade.

(5) Homogenize.

(6) Cool to 45.degree. C. while mixing with a sweep blade.

(7) Add imidazolidinyl urea premix. Mix until uniform.

(8) Add remaining ingredients in order listed. Mix well.

Note: cream will become lustrous overnight.

Procedure

(1) Heat Phase A with agitation to 85.degree. C., mix until uniform (40-45 minutes).

(2) Lower temperature to 60.degree. C. Add Phase B.

(3) Heat Phase C to 85.degree. C., mix until uniform.

(4) Reduce heat to 60.degree. C.

(5) Add Phase C to Phase A/B while homogenizing for approximately 5-10 minutes, being careful not to aerate the batch.

(6) Remove. Add Phase D using a sweep blade.

(7) Sweep to 25.degree. C.

(8) Adjust pH to 3.5 with NaOH (10% aq.)

Procedure

(1) Prepare premix with roller mill.

(2) Disperse the gum cold with high speed mixing, then add propylene glycol and lactic acid. Heat to 75.degree. C.

(3) Heat Phase B to 80.degree. C. add premix.

(4) Add Phase B to Phase A, mix for approximately 10 minutes.

(5) Place under homogenizer and mix for approximately 15 minutes.

(6) Remove. Mix to 40.degree. C. using sweep blade.

(7) Add Phase C, then add Phase D.

(8) Mix to 25.degree. C. using sweep blade.

Procedure

(1) Mix Carbomer.RTM. and deionized water at 85.degree. C. until uniform. Add polyacrylic acid and mix until uniform.

(2) Add preservative premix.

(3) Slowly add triethanolamine premix.

(4) In separate vessel mix oil phase until uniform at 85.degree. C.

(5) Add oil phase to water phase slowly. Mix at 85.degree. C. until uniform.

(6) Homogenize.

(7) Mix while cooling to 45.degree. C.

(8) Add imidazolidinyl urea premix.

(9) Add remaining ingredients one at a time, stirring well between additions.

Example 7 was repeated except that Gantrez.RTM. S-95 was substituted for Gantrez.RTM. S-97.

Example 7 was repeated except that poly(maleic acid) was substituted for Gantrez.RTM. S-95.

Example 7 was repeated except that polyitaconic acid was substituted for Gantrez.RTM. S-95.

Example 7 was repeated except that a mixture of Gantrez.RTM. S-91 and poly(maleic acid) were used as the exfoliating polymers.

Procedure

1. Prepare a mixture of lightly crosslinked PVP in an aqueous solution of Gantrez.RTM. S-91 with stirring for 10 minutes at 40.degree.-50.degree. C. until thickening occurs.

2. Add glycerine slowly over 10 minutes with stirring. Stir until uniform gel is obtained.

3. Add remaining ingredients, mixing thoroughly after each addition.

Procedure

1. Prepare hydrogel by adding lightly crosslinked PVP in ethanol, water, glycerine, lactic acid, then heat to 40.degree.-50.degree. C. in suitable enclosed vessel with stirring for 15 minutes.

2. Start cooling.

3. Add remaining ingredients with stirring. Mix thoroughly after each addition, until uniform gel is obtained.

Procedure

1. Prepare a spray gel by adding lightly crosslinked PVP in water, ethanol, Gantrez S-91 and P(VP-VA) S-60 for 15 minutes, then heat to 45.degree. C.-60.degree. C. in suitable enclosed vessel with stirring for 30 minutes.

2. Start cooling.

3. Add remaining ingredients with stirring. Mix thoroughly after each addition, until uniform. Suggested Pump:--CalmarMistette, Mark II, 0.20 ml/stroke, yellow orifice (high viscosity).

While the invention has been described with particular reference to certain embodiments thereof, it will be understood that many alterations and modifications may be made which are considered within the scope of this invention and which will become apparent from the foregoing disclosure.