CN1222848A - Vitamin C Delivery System - Google Patents

Abstract

The present invention provides cosmetic compositions comprising ascorbic acid (vitamin C) dissolved by cross-linked non-emulsifying silicone in a volatile silicone carrier medium. Cosmetic properties are also improved by the presence of a cross-linked non-emulsifying silicone elastomer.

Description

Vitamin C Delivery System

Background of the invention

Scope of the invention

The present invention relates to cosmetic products that can stably store ascorbic acid and then deliver it to the skin.

related fields

Ascorbic acid, also commonly known as vitamin C, has long been recognized as an active that benefits the appearance of the skin. Vitamin C has been reported to increase collagen production in human skin tissue. Wrinkles and fine lines are thus reduced. For a healthier and younger appearance. Vitamin C has also been found useful as a UV blocker or absorber. The property of vitamin C to interfere with the melanin formation process is exploited as a composition for whitening or bleaching the skin. Additionally, it is believed that ascorbic acid interacts with the human immune system to reduce skin sensitivity to harmful chemicals. Decreased vitamin C concentrations on the skin were also associated with increased skin tension. Overall, vitamin C or ascorbic acid provided significant benefits when applied topically.

The downside is that vitamin C is an extremely unstable substance. Although it is readily soluble in water, oxidation occurs rapidly in aqueous media. The reported solubility of asbic acid in non-aqueous media is relatively low, thus preventing any significant level of active concentration in anhydrous systems.

Various methods to overcome the above-mentioned problems have been sought in the art. One approach is to prepare derivatives of ascorbic acid. These derivatives have better stability than the parent compound and are converted to the parent acid at the site of action by biotransformation or chemical hydrolysis. For example, US Patent 5,137,723 (Yamamoto et al.) and US Patent 5,078,989 (Ando et al.) provide glycosylate and ester derivatives, respectively.

US Patent 4818521 (Tamabuchi) introduces the background technology of so-called two-pack type (two-pack type) cosmetics, wherein vitamin C powder and other ingredients are packed in different containers respectively, just mix before using cosmetics. The hybrid approach and high cost of packaging are reported to be disadvantages of this system. This patent provides a stable oil-in-water weakly acidic emulsion, wherein ascorbic acid and stabilizing oil have been pre-mixed.

Maintaining a pH below about 3.5 is also proposed in US Patent 5,140,043 (Darr et al.) as a means of stabilizing aqueous ascorbic acid compositions.

Water-compatible alcohols such as propylene glycol, polypropylene glycol, and glycerin have been suggested as co-carriers with water to improve stability. A description of this method can be found in US Patent 4,983,382 (Wilmott and Znaiden). A mixture of water and a water-miscible organic solvent is used as a stable system. At least about 40% of the organic solvent must be ethanol and the balance may be selected from such alcohols as propylene glycol, glycerol, dipropylene glycol and polypropylene glycol.

Japanese Patent 44-22312 (Shionogi) describes increasing the stability of vitamin C in predominantly aqueous media by means of various diols. These glycols include polyethylene glycol, ethylene glycol, diethylene glycol and even ethanol. These formulations are for ingestion.

US Patent 4372874 (Modrovich) reports the incorporation of relatively large amounts of ascorbic acid into polar water-miscible organic solvents such as dimethylsulfoxide. The water content is kept below 0.5% by adding a granular desiccant to the carrier. Although highly polar systems such as dimethyl sulfoxide are effective, it and related carriers have toxicity problems.

It is therefore an object of the present invention to provide a delivery system for ascorbic acid wherein the compound is water miscible and stable against both hydrolysis and oxidation during storage.

Another object of the present invention is to provide a delivery system which facilitates the penetration of ascorbic acid into human skin without its irritating effects.

It is a further object of the present invention to provide a system for delivering ascorbic acid to provide cosmetic benefits and smooth skin feel.

These and other objects of the invention will become more apparent from the following summary, detailed description and examples.

SUMMARY OF THE INVENTION

Cosmetic compositions are provided comprising:

(i) 0.001-50% ascorbic acid;

(ii) 0.1-30% cross-linked non-emulsifying silicone elastomer; and

(iii) 10-80% volatile silicone.

Detailed description of the invention

It has now been found that ascorbic acid is stable to decomposition and can be stably suspended in systems containing crosslinked non-emulsifying silicone elastomers and volatile silicones.

Ascorbic acid is available from several sources including Roche Chemicals. The amount of this material used may be in the range of 0.001-50%, preferably 0.1-10%, most preferably 1-10% by weight.

The crosslinked non-emulsifying silicone elastomers of the present invention should have a number average molecular weight in excess of 10,000, preferably in excess of 1,000,000 and most preferably in the range of 10,000 to 20 million. The term "non-emulsifying" is defined as a silicone lacking polyoxyalkylene units. Preferred crosslinked non-emulsifying silicone elastomers are formed by reacting divinyl monomers with the Si-H linkages of the silicone backbone. An exemplary elastomer is a material with the CTFA designation cross-linked stearoylmethyl-dimethylsiloxane copolymer available from Grant Industries as Gransil SR-CYC (25-35% active elastomer). Inc., Elmwood park, New Jersey. Supplies of related elastomers are also available from the General Electric Company.

The amount of high elasticity may range from 0.1-30%, preferably 1-15%, most preferably 3-10% by weight.

The third base material of the present invention is a volatile silicone. Exemplary of such materials are cyclomethicone fluids having the formula [(CH ₃ ) ₂ SiO)] _x cyclomethicone, where X is an integer of 3-6. The cyclosiloxane has a boiling point below 250°C and a viscosity at 25°C of less than 10 centipoise. The common name for this raw material is cyclomethylacetone. Tetramers and pentamers of cyclomethylacetone are commercially available from Dow Corning Corporation as DC244 and DC344.

Volatile silicones are used in the range of 10-80%, preferably 20-70%, most preferably 30-65% by weight.

The composition of the present invention may further include a pharmaceutically acceptable carrier. Generally, the carrier should be an ingredient capable of dissolving the vitamin C and all other ingredients of the composition. The amount of carrier used is in the range of 1-70%, preferably 10-60%, most preferably 20-50% by weight.

Pharmaceutically acceptable carriers can be selected from water, polyols, silane fluids, esters and mixtures thereof. When water is present it may range from 0.5-20%, preferably 1-10%, usually 2-6%, most preferably less than 5% by weight of the composition.

The composition of the invention has the advantage that one or more polyols are also present as a carrier. Illustrative examples are propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1,3-butanediol, 1,2,6-hexanetriol, propane Triols, ethoxylated glycerol, propoxylated glycerol, and mixtures thereof. The most preferred polyol is a mixture of polyethylene glycol (molecular weight range 200-2000) and propylene glycol. Preferably the weight ratio of polyethylene glycol to propylene glycol ranges from 5:1 to 1:10, preferably from 2:1 to 1:5, most preferably from 1:1 to 1:2. The amount of polyol used is in the range of 1-50% by weight of the composition, preferably 10-40% by weight, most preferably 25-35% by weight.

Silicone oils are also included as carriers in the compositions of the present invention. These oils should be non-volatile. Examples of such non-volatile silicone oils for use in the compositions of the present invention are polyalkylsiloxanes, polyalkylarylsiloxanes and polyethersiloxane copolymers. Basic nonvolatile polyalkylsiloxanes useful herein include, for example, polydimethylsiloxanes having viscosities of from about 5 to about 100,000 centistokes at 25°C. Such polyalkylsiloxanes include the Viscasil series (available from General Eleetric Company) and the Dow Corning 200 series (available from Dow Corning Corporation). Polyalkylaryl siloxanes include poly(methylphenyl)siloxanes, which have a viscosity of about 15-65 centistokes at 25°C. For example, it is available as SF1075 Tolyl Fluid (available from the General Electric Company) and 556 Cosmetic Grade Fluid (available from DowComing Corporation). Useful polyether siloxane copolymers include, for example, polyoxyalkylene ether copolymers having a viscosity of about 1200-1500 centistokes at 25°C. Such a fluid is available as SF-1066 silicone surfactant (available from General Eleetric Company). Cetyl dimethicone copolyol and cetyl dimethicone are particularly preferred because these materials also have emulsifying and lubricating properties. The former material is available from Goldschmidt AG under the trade name AbilEM-90. Non-volatile silicones are used in the range of 0.1-40%, preferably 0.5-25% by weight of the composition.

Esters can also be incorporated into cosmetic compositions as pharmaceutically acceptable carriers. The amount used is in the range of 0.1-50% by weight of the composition. where the esters are:

(1) Fatty acid alkyl esters having 10 to 20 carbon atoms. Used herein are the methyl, isopropyl and butyl esters of fatty acids. Examples include hexyl laurate, isohexyl laurate, isohexyl palmitate, isopropyl palmitate, decyl oleate, isodecyl oleate, cetyl stearate, decyl stearate, Isopropyl Stearate, Diisopropyl Adipate, Diisohexyl Adipate, Dicetyl Adipate, Diisopropyl Sebacate, Lauryl Lactate, Myristyl Lactate and cetyl lactate. Particular preference is given to C ₁₂ -C ₁₅ alcohol esters of benzoate.

(2) Fatty acid alkenyl esters having 10 to 20 carbon atoms. Examples thereof include oleyl myristate, oleyl stearate, and oleyl myristate.

(3) Ether-esters such as ethoxylated fatty alcohol fatty acid esters.

(4) Polyol ethers. Ethylene glycol mono- and di-fatty acid esters, diethylene glycol mono- and di-fatty acid esters, ethylene glycol (200-6000) mono- and di-fatty acid esters, propylene glycol mono- and di-fatty acid esters, mono oil Polypropylene Glycol 2000 Monostearate, Polypropylene Glycol 2000 Monostearate, Ethoxypropylene Glycol Monostearate, Mono- and Di-Glycerol Fatty Acids, Polyglycerol Poly-Fatty Ester, Ethoxyl Monostearate Glycerol ester, 1,3-butanediol monostearate, 1,3-butanediol distearate, polyoxyethylene polyol fatty acid ester, sorbitan fatty acid ester and polyoxyethylene Ethyl sorbitan fatty acid ester is a suitable polyol ester.

(5) Wax esters such as beeswax, spermaceti, myristyl myristate, stearyl stearate.

(6) Sterol esters, examples of which are liposterol fatty acid esters.

Minor amounts of additive ingredients are also included in the cosmetic compositions of the present invention. These ingredients are selected from preservatives, fragrances, defoamers, opacifiers, toners, and mixtures thereof, each in an effective amount to perform its respective function.

The following examples will more fully illustrate the embodiments of the invention. All parts, percentages and ratios referred to herein and in the appended claims are by weight unless otherwise indicated.

Example 1

The effect of crosslinking non-emulsifying silicone elastomers was evaluated by comparing the experiments with the control formulations listed in Table 1.

Table Ⅰ

Test formula Element Example number (weight %) 1 1A (control) Cyclomethicone 36.0 60.0 Gransil SR CYL 24.0 -- polyethylene glycol 200 19.25 19.25 Dimethyl Isosorbide 10.0 10.0 ascorbic acid 5.0 5.0 Sodium chloride 1.0 1.0 Cetyl Dimethicone Copolyol 0.8 0.8 water 4.0 4.0

Formula 1 is an emulsion with a homogeneous and stable cream-like consistency and cosmetic effects. After comparison, Formula 1A cannot form an emulsion.

Example 2-5

A series of other examples were prepared. Their compositions are listed in Table II. These formulations provide ascorbic acid with good storage stability and acceptance by cosmetic consumers.

Table II Element Example number (weight %) 2 3 4 5 Cyclomethicone 42.0 41.6 40.0 42.0 Gransil SR CYL 18.0 17.9 17.3 18.0 Propylene Glycol 16.8 14.8 17.5 15.0 polyethylene glycol 200 11.0 13.7 13.5 13.5 ascorbic acid 5.0 5.0 5.0 5.0 Dimethyl Isosorbide 2.0 2.0 2.0 2.0 Cetyl Dimethicone Copolyol 0.8 0.8 0.8 0.8 water balance balance balance balance

Example 6-12

These series of examples illustrate the scope of the invention and set forth various concentrations of ascorbic acid, cyclomethylacetone and silicone elastomer.

Table III Element Example number (weight %) 6 7 8 9 10 11 12 Cyclomethi-cone 36.0 36.0 36.0 40.0 40.0 45.0 32.0 Gransil SRCYL 24.0 24.0 24.0 20.0 20.0 15.0 27.0 Butanediol 17.5 -- 17.5 -- -- -- 29.0 Propylene Glycol -- 17.5 -- -- -- -- -- polyethylene glycol 200 10.0 -- -- 17.5 12.0 10.0 10.0 polyethylene glycol 800 -- 10.0 10.0 10.0 12.0 10.0 -- Dimethyl Isosorbide 2.0 2.0 2.0 4.0 8.0 10.0 1.0 ascorbic acid 1.0 1.0 1.0 4.0 4.0 8.0 0.5 CetylDimethiconeCopolyol 0.8 0.8 0.8 0.8 0.8 -- -- water balance balance balance balance balance balance balance

The foregoing description and examples illustrate selected embodiments of the invention. Accordingly, various changes and modifications proposed by those skilled in the art are within the spirit and purview of the present invention.

Claims (3)

1. cosmetic composition comprises:

(ⅰ) ascorbic acid of 0.001-50%;

(ⅱ) the crosslinked non-emulsifying silicone elastomer of 0.1-30%; With

(ⅲ) volatile siloxane of 10-80%.

2. according to the compositions of claim 1, wherein said crosslinked non-emulsifying silicone elastomer is that the Si-H by divinyl monomer and siloxane main chain connects the key reaction and forms.

3. according to the compositions of claim 1 or claim 2, wherein said volatile siloxane is a Cyclomethicone.