Abstract:
A shaving cream composition and method is provided wherein the cream composition is packaged in an aerosol dispenser and includes a propellant system of dimethyl ether and hydrocarbon, an anionic surfactant, a fatty alcohol and a hydrophobic emollient. Total weight ratio of all hydrophobic emollients to all anionic surfactants ranges from about 50:1 to greater than about 1:1. An improved shaving experience is achieved through use of the dimethyl ether/hydrocarbon propellant, fatty alcohol and high level of hydrophobic emollient.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to shaving compositions delivered as aerosols exhibiting enhanced foaming qualities.  
           [0003]    2. The Related Art  
           [0004]    Shaving is an inherently abrasive treatment of the skin. Cosmetic foams have been created to lubricate the cutting process. Lubrication markedly reduces the trauma induced by a razor.  
           [0005]    Emollient ingredients of shaving creams are substantial contributors to reduction of irritation caused by the razor action.  
           [0006]    Emollients have long been incorporated into cleansing compositions. For instance, U.S. Pat. No. 5,002,680 (Schmidt et al.) discloses a mild skin-cleansing aerosol mousse. Nice skinfeel after washing is imparted to the skin through a combination of mild surfactants, skinfeel polymers and high levels of moisturizing emollients. Similar skin cleansing compositions have been reported in U.S. Pat. No. 6,407,044 B2 (Dixon) wherein a hydrocarbon propellant system was used to generate a cleansing foam.  
           [0007]    A problem with use of high levels of emollients is that they depress foam formation often even collapsing the bubbles. Systems are needed which foam well despite the presence of high levels of emollient oils.  
         SUMMARY OF THE INVENTION  
         [0008]    A shaving cream composition is provided which includes:  
           [0009]    (i) from about 1 to about 20% of a propellant comprising dimethyl ether and hydrocarbons in a relative weight ratio of about 5:1 to about 1:5;  
           [0010]    (ii) from about 0.5 to about 25% of an anionic surfactant;  
           [0011]    (iii) from about 0.05 to about 20% of a C 12 -C 24  fatty alcohol;  
           [0012]    (iv) from about 5 to about 40% of a hydrophobic emollient;  
           [0013]    wherein a total weight ratio of all hydrophobic emollients to all anionic surfactants present in the composition ranges from about 50:1 to greater than about 1:1.  
         DETAILED DESCRIPTION OF THE INVENTION  
         [0014]    Now it has been found that a combination of factors can influence generation of a rich, long lasting shaving foam despite the presence of very high emollient levels. One factor is utilization of fatty alcohols which were found to interact with the surfactants to create small sustainable bubbles. Another factor is the use of dimethyl ether as at least one component of the propellant system. Fatty alcohol, dimethyl ether and the emollient all combine to provide a rich lasting foam that also delivers substantial emollient to the interface between skin and razor.  
           [0015]    Accordingly, a first aspect of the present invention is that of a propellant. The propellant is present in amounts from about 1 to about 20%, preferably from about 3 to about 15%, optimally from about 5 to about 10% by weight of the composition. The propellant is a mixture of dimethyl ether and a C 3 -C 6  hydrocarbon. Suitable hydrocarbons include n-butane, isobutane, n-propane, isopropane, n-pentane, isopentane and mixtures thereof. Amounts of the dimethyl ether and total hydrocarbon are present in a relative weight ratio ranging from about 5:1 to about 1:5, preferably from about 4:1 to about 1:4, optimally from about 2:1 to about 1:2, and most optimally from about 1:1 to about 1:1.5.  
           [0016]    Another component of the present invention is that of one or more anionic surfactants. These will be present in amounts from about 0.5 to about 25%, preferably from about 1 to about 15%, more preferably from about 3 to about 10%, optimally from about 4 to about 8% by weight of the composition.  
           [0017]    Anionic surfactants useful herein include: acyl isethionates, acyl sarcosinates, alkylglycerylether sulfonates, alkyl sulfates, acyl lactylate, methylacyl taurates, paraffin sulfonates, linear alkyl benzene sulfonates, N-acyl glutamates, alkyl sulfosuccinates, alpha sulfo fatty acid esters, alkyl ether carboxylates, alkyl phosphate esters, ethoxylated alkyl phosphate esters, alpha olefin sulphates, the alkyl ether sulfates (with 1 to 12 ethoxy groups) and mixtures thereof, wherein said surfactants contain C8 to C22 alkyl chains and wherein the counterion is preferably selected from the group consisting of Na, K, NH 4 , N(CH 2 CH 2 OH) 3 . Most preferred are lauryl ether sulfates.  
           [0018]    Although soaps (i.e. salts of C 10 -C 22  fatty acids) are often used in shaving formulations, these materials are relatively irritating to the skin. For purposes of this invention, amounts of the soap advantageously is limited to no more than about 10%, ordinarily no more than about 2%, and preferably less than 10% or especially less than 0.1% by weight of the composition. Similarly, unsaponified soaps which are known as C 10 -C 24  fatty acids advantageously can also be avoided because of their acidity and foam inhibiting properties, particularly stearic acid. Levels of fatty acid, particularly stearic acid, is best held to less than 1%, preferably less than 0.8%, optimally less than 0.1% by weight of the composition. Under some circumstances, an amine neutralized fatty acid such as triethanolammonium stearate can be employed, particularly at levels from about 0.2 to about 1% by weight.  
           [0019]    Amphoteric surfactants may be included in compositions of this invention. Amounts may range from about 0.5 to about 15%, preferably from about 1 to about 10%, optimally from about 3 to about 6% by weight. Illustrative of the amphoteric surfactant are cocoamidopropyl betaine, lauroamphoacetates and diacetates, alkyl dimethylamine oxides and combinations thereof. Particularly preferred are combinations of anionic and amphoteric surfactants, especially present in relative weight ratios of total anionic to total amphoteric surfactant ranging from about 10:1 to about 1:1, preferably about 3:1 to about 1.5:1.  
           [0020]    The pH of the composition may range from about 4.5 to about 12.5. However, the pH is preferably near neutral and may range from about 6.5 to about 9.5, preferably from about 6.7 to about 8.5, optimally from about 7 to about 7.5.  
           [0021]    Another component of compositions according to this present invention is a C 12 -C 24  fatty alcohol. This material may be present in an amount from about 0.05 to about 20%, preferably from about 0.2 to about 8%, more preferably from about 0.5% to about 5%, optimally from about 1 to about 3% by weight of the composition.  
           [0022]    Illustrative fatty alcohols include stearyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, behenyl alcohol and combinations thereof.  
           [0023]    Hydrophobic emollients are an important component of the present invention. These materials may be present from about 5 to about 40%, preferably from about 8 to about 30%, more preferably from about 10 to about 25%, optimally from about 15 to about 20% total hydrophobic emollient by weight of the composition.  
           [0024]    Hydrophobic emollients may be in the form of natural oils (particularly vegetable oils), synthetic esters, hydrocarbons and silicone oils.  
           [0025]    Natural oils include triglycerides such as sunflower seed oil, cottonseed oil, safflower oil, olive oil, rapeseed oil, canola oil, linseed oil, shea nut oil, palm oil, corn oil, babassu oil, peanut oil, sesame oil and combinations thereof. Chemically modified versions of vegetable oils may also be utilized. For instance, suitable may be brominated soybean oil and maleated soybean oil. Lanolin oils are another category of natural oils suitable for the present invention. Particularly useful is lanolin alcohol.  
           [0026]    Synthetic esters may include:  
           [0027]    (1) Alkenyl or alkyl esters of fatty acids having 10 to 20 carbon atoms. Examples thereof include isopropyl palmitate, isopropyl oleate, methyl palmitate, isoarachidyl neopentanoate, isononyl isonanonoate, oleyl myristate, oleyl stearate, and oleyl oleate.  
           [0028]    (2) Wax esters such as beeswax, spermaceti wax and tribehenin wax.  
           [0029]    (3) Sterols esters, of which cholesterol fatty acid esters are examples thereof.  
           [0030]    (4) Sugar ester of fatty acids such as sucrose polybehenate and sucrose polycottonseedate.  
           [0031]    Silicone oils may be divided into the volatile and nonvolatile variety. The term “volatile” as used herein refers to those materials which have a measurable vapor pressure at ambient temperature. Volatile silicone oils are preferably chosen from cyclic (cyclomethicone) or linear polydimethylsiloxanes containing from 3 to 9, preferably from 4 to 5, silicon atoms.  
           [0032]    Nonvolatile silicone oils useful as an emollient material include polyalkyl siloxanes, polyalkylaryl siloxanes and polyether siloxane copolymers. The essentially nonvolatile polyalkyl siloxanes useful herein include, for example, polydimethyl siloxanes with viscosities of from about 5×10 −6  to 0.1 m 2 /s at 25 C. Among the preferred nonvolatile emollients useful in the present compositions are the polydimethyl siloxanes having viscosities from about 1×10 −5  to about 4×10 −4  m 2 /s at 25 C.  
           [0033]    Another class of nonvolatile silicones are emulsifying and non-emulsifying silicone elastomers. Representative of this category is Dimethicone/Vinyl Dimethicone Crosspolymer available as Dow Corning 9040, General Electric SFE 839, and Shin-Etsu KSG-18. Silicone waxes such as Silwax WS-L (Dimethicone Copolyol Laurate) may also be useful.  
           [0034]    Hydrocarbons which are suitable as hydrophobic emollients include petrolatum, mineral oil, C 11 -C 13  isoparaffins, polyalphaolefins, and especially isohexadecane, available commercially as Permethyl 101A from Presperse Inc.  
           [0035]    Advantageously the total weight ratio of all hydrophobic emollients to all anionic surfactants may range from about 50:1 to greater than about 1:1, preferably from about 30:1 to about 2:1, optimally from about 5:1 to about 1.5:1.  
           [0036]    Hydrophilic emollients may also be included in compositions of this invention. These type are usually polyhydric alcohols which include glycerol, polyalkylene glycols and more preferably alkylene polyols and their derivatives, including propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol and derivatives thereof, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1,3-butylene glycol, isoprene glycol, 1,2,6-hexanetriol, ethoxylated glycerol, propoxylated glycerol and mixtures thereof. The amount of hydrophilic emollient may range anywhere from about 0.5 to about 30%, preferably between about 1 and about 10% by weight of the composition. When both hydrophobic and hydrophilic emollients are present they may range from about 20:1 to greater than about 1:1 in weight ratio.  
           [0037]    Preservatives may also desirably be incorporated into the compositions of this invention to protect against the growth of potentially harmful microorganisms. Preservatives which have more recently come into use include hydantoin derivatives, propionate salts, and a variety of quaternary ammonium compounds. Cosmetic chemists are familiar with appropriate preservatives and routinely choose them to satisfy the preservative challenge test and to provide product stability. Particularly preferred preservatives are phenoxyethanol, methyl paraben, propyl paraben, imidazolidinyl urea, sodium dehydroacetate and benzyl alcohol. The preservatives should be selected having regard for the use of the composition and possible incompatibilities between the preservatives and other ingredients in the emulsion. Preservatives are preferably employed in amounts ranging from 0.01% to 2% by weight of the composition.  
           [0038]    Skin conditioners may be incorporated into compositions of this invention. For instance, these materials can be cationic polysaccharides and particularly cationic guar gums with number average molecular weights ranging from 1000 to 3 million; polymers formed from acrylic and/or methacrylic acid; cationic polymers of dimethyl dialkyl ammonium salts and acrylic acids; cationic homopolymers of dimethyl dialkylammonium salts; cationic polyalkylene and ethoxy polyalkylene imines; polyethylene glycol of molecular weight from 100,000 to 4 million; and combinations thereof. Particularly suitable are sodium polyacrylate, hydroxyethyl cellulose and combinations thereof. Most particularly useful are quaternary materials identified by the CTFA names of polyquaternium-3, polyquaternium-5, polyquaternium-6, polyquaternium-7, polyquaternium-10, polyquaternium-11 and polyquaternium-24. Most preferred is guar hydroxypropyl trimonium chloride sold as Jaguar C13S by Rhone Poulenc. Amounts of the conditioners may range from about 0.01 to about 2%, preferably from about 0.1 to about 1%, optimally from about 0.2 to about 0.8% by weight of the composition.  
           [0039]    Sunscreen actives may be included in the compositions. Particularly preferred are Parsol MCX®, Parsol 1789® and benzophenone-3. Inorganic sunscreen actives may be employed such as microfine titanium dioxide, zinc oxide, polyethylene and various other polymers. Amounts of the sunscreen agents when present may generally range from 0.1 to 15%, preferably from 2 to 8%, optimally from 3 to 6% by weight.  
           [0040]    Anti-microbial agents which are intended for deposition onto body surfaces may also be formulated into the compositions. Illustrative are the aluminum salts including aluminum chlorohydrate, aluminum zicronium tetrachlorohydrex glycinate, zinc phenosulfonate, chlorhexidine, hexetidine, zinc citrate, 2,4,4′-trichloro-2′-hydroxydiphenyl ether (triclosan) and 3,4,4′-trichlorocarbanilide (triclocarbon). Amounts of the anti-microbials may be utilized at levels from about 0.0001 to about 15%, preferably from about 0.1 to about 5% by weight.  
           [0041]    Compositions of the present invention may include vitamins. Illustrative vitamins are Vitamin A (retinol), Vitamin B 2 , Vitamin B 6 , Vitamin C, Vitamin E and Biotin. Derivatives of the vitamins may also be employed. For instance, Vitamin C derivatives include ascorbyl tetraisopalmitate, magnesium ascorbyl phosphate and ascorbyl glycoside. Derivatives of Vitamin E include tocopheryl acetate, tocopheryl palmitate and tocopheryl linoleate. DL-panthenol and derivatives may also be employed. Total amount of vitamins when present in compositions according to the present invention may range from 0.001 to 10%, preferably from 0.01% to 1%, optimally from 0.1 to 0.5% by weight.  
           [0042]    A variety of herbal extracts may optionally be included in compositions of this invention. Illustrative are green tea, chamomile, licorice and extract combinations thereof. The extracts may either be water soluble or water-insoluble carried in a solvent which respectively is hydrophilic or hydrophobic. Water and ethanol are the preferred extract solvents.  
           [0043]    Colorants, fragrances, opacifiers and abrasives may also be included in compositions of the present invention. Each of these substances may range from about 0.05 to about 5%, preferably between 0.1 and 3% by weight.  
           [0044]    Compositions of the present invention will contain water in amounts ranging from about 10% to about 92%, preferably from about 30 to about 70%, optimally from about 40 to about 60% by weight.  
           [0045]    Hydrophobic emollients are delivered to the shaving surface by the composition in average droplet size ranging from about 0.00001 to about 350, more preferably from about 0.0001 to about 5, optimally from about 0.001 to about 1 micron in diameter.  
           [0046]    The term “comprising” is meant not to be limiting to any subsequently stated elements but rather to encompass non-specified elements of major or minor functional importance. In other words the listed steps, elements or options need not be exhaustive. Whenever the words “including” or “having” are used, these terms are meant to be equivalent to “comprising” as defined above.  
           [0047]    Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material ought to be understood as modified by the word “about”.  
           [0048]    All documents referred to herein, including patents, patent applications and printed publications, are hereby incorporated by reference in their entirety in this disclosure.  
           [0049]    The following examples will more fully illustrate the embodiments of this invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight unless otherwise illustrated. 
       
    
    
     EXAMPLES 1-8  
       [0050]    Shaving creams according to the present invention are detailed in the Table below.  
                                                                                                           Example (Weight %)            Ingredient   1   2   3   4   5   6   7   8                    Sunflower Seed   24.0   24.0   16.0   16.0   12.0   12.0   19.5   19.5       Oil       Lanolin   1.0   1.0   1.0   1.0   1.0   1.0   1.0   1.0       Alcohol/       Cholesterol       Cocoamide   1.8   1.8   1.8   2.5   2.5   2.5   2.5   2.5       Monoethanol-       amide       Myristyl   1.9   1.9   1.9   2.8   1.9   2.8   2.0   3.0       Alcohol       Lauryl Alcohol   —   —   —   —   0.9   —   1.0   —       Petrolatum   3.5   3.5   3.5   3.5   4.5   4.5   1.5   7.5       Glycerol   5.4   5.4   5.4   5.4   5.4   5.4   5.4   5.4       Cocoamido-   3.2   6.3   3.2   6.3   3.2   3.2   3.2   3.2       propyl Betaine       Sodium   6.3   3.2   6.3   3.2   6.3   6.3   6.3   6.3       Laureth       Sulphate       Guar   0.1   0.1   0.3   0.3   0.3   0.3   0.4   0.5       Hydroxy-       propyl       Trimonium       Chloride       Isopropyl   1.4   1.4   1.4   1.4   2.7   2.7   2.7   2.7       Palmitate       Tetrasodium   0.02   0.02   0.02   0.02   0.02   0.02   0.02   0.02       EDTA       DMDM   0.05   0.05   0.05   0.05   0.05   0.05   0.05   0.05       Hydantoin       Etidronic Acid   0.02   0.02   0.02   0.02   0.02   0.02   0.02   0.02       Fragrance   1.0   1.0   1.0   1.0   1.0   1.0   1.0   1.0       Dimethyl   3.0   2.0   2.0   3.0   2.0   1.0   2.0   2.0       Ether       Propane   0.5   0.5   0.5   0.5   1.5   0.5   0.5   2.5       Isobutane   2.5   0.5   2.5   0.5   2.5   3.5   2.0   0.5       Water   to   to   to   to   to   to   to   to           100   100   100   100   100   100   100   100                  
 
         [0051]    The shaving creams outlined in the Table are packaged in an aerosol metal can fitted with a conventional aerosol spray head with nozzle. Prior to use, instructions on the can request a user to thoroughly shake the combination before expressing the foam by pressing downward on the spray head. After the cream has been placed on a human face, underarm or legs, a razor is applied over the skin area to remove hair by cutting. These formulations are particularly suitable for legs and underarm.  
       EXAMPLE 9  
       [0052]    This Example evaluates the effect of different propellant mixtures on the quality of the foam. The formula detailed in the Table below was utilized for evaluations under this Example.  
                                                                 INGREDIENT   WEIGHT %                                        Sunflower Seed Oil   21.3           Petrolatum   5.7           Glycerin   3.7           Sodium Lauryl Ether Sulphate (3 EO)   6.6           Cocoamidopropyl Betaine   3.3           Water   Balance                      
 
         [0053]    The formula of shaving cream outlined above was packaged in aerosol metal canisters fitted with a conventional aerosol spray head with nozzle. Each canister was also filled with a propellant in equal weight throughout. Identity of the propellant is found in the Table below. Samples were evaluated in a Compression (Squeeze) Test and measured for the Liquid Fraction of the foam.  
         [0054]    Measurement of Liquid Fraction of Foam  
         [0055]    Liquid volume fractions of foams were obtained by weighing a known volume of foam. The weight of the foam essentially can all be attributed to its liquid fraction as the remaining volume of foam consists of air. To measure the liquid fraction, foam was expelled from a sample canister into a plastic Petri dish having a volume of 5.2 ml. The level of the foam was carefully adjusted to the height of the dish with a metal spatula so that the foam was contained within the volume of the dish. The weight of the dish with the foam was recorded. After subtracting the weight of the dish, the weight of the foam was used to calculate the liquid phase volume. The weight of the foam is divided by the density of the formulation to obtain the volume of the liquid portion of the formula. The liquid fraction is then the volume of the liquid divided by the total volume of foam (in these tests, 5.2 ml). Samples were measured in triplicate.  
         [0056]    Rheology of Foams—Compression (Squeeze) Test  
         [0057]    The Compression Test measures the force required to compress the foam generated from a formulation expelled from a canister. Measurements were performed using a Rheometric Scientific ARES controlled strain rheometer (SR-5, Rheometric Scientific, Piscataway, N.J.). The rheometer was set up with parallel plates 50 mm in diameter with a gap of 2.0 mm between the plates. Foams were loaded between the parallel plates and then tests were formed using programmed extension mode which subjects the foams to an axial deformation applied at a programmed rate. The foam samples were compressed at controlled rate of 0.25 mm/second, brought back to initial state at a rate of 0.33 mm/sec and then extended at a rate of 0.25 mm/sec. Tests were performed at 25° C. The output is the normal force (grams) associated with the compression and extension of the foams.  
         [0058]    Higher force values reflect a more rigid, better foam quality. When product is expelled from a canister, some is in gaseous form and some extrudes as a liquid. The greater the amount of liqued, the lower the foam quality.  
                                                                                                                                                                             Liquid Fraction   Compression Test                            Aver-   Std   Normal               Sam-       Propellant   %   age   dev   Force   Aver-   Std            ple   Can   DME   A70*   w/w   %   %   (g)   age   dev                    A   1   100   0   25.93   26.39   1.94   111   210.3   117.5           2           24.72           180           3           28.51           340       B   1   80   20   16.97   16.96   0.38   502   431.0   67.0           2           17.33           369           3           16.57           422       C   1   66   33   18.05   17.14   0.85   419   435.7   36.9           2           17.00           478           3           16.37           410       D   1   33   66   5.53   10.64   4.60   500   517.3   28.3           2           11.94           550           3           14.45           502       E   1   20   80   4.24   7.36   3.91   505   514.0   50.1           2           11.75           568           3           6.08           469       F   1   0   100   5.24   5.65   0.74   539   499.0   45.2           2           6.51           450           3           5.20           508                          
 
         [0059]    Sample A was found to deliver a dead non-springy foam. This is evidenced by the relatively low compression test average of 210.3 g force. Samples B through E were able to be worked during hand washing and did not break into undesirable smaller segments of foam. The working ability is attributed to the relatively high level of liquid fraction. By contrast, Sample F was extremely fluffy, containing too much air and did not wash-off well from the skin. It is evident that such as in Samples B through E combinations of dimethyl ether and hydrocarbon are necessary to obtain a satisfactory shaving cream product.