US 3527559 A
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United States Patent 3,527,559 DENSE AQUEOUS AEROSOL FOAM DEPILATORY COMPOSITIONS CONTAINING A MIXTURE OF ALKALINE METAL AND ALKALI METAL THIO- GLYCOLATES AND A FATTY ALCOHOL-ALKYL- ENE OXIDE WAX EMULSIFYING AGENT Robert A. Sliwinski, Elgin, Ill., assignor to Standard Pharmacal Corporation, Elgin, Ill., a corporation of Illinois No Drawing. Filed Jan. 5, 1967, Ser. No. 607,398 Int. Cl. A61k 7/14 US. Cl. 8-161 6 Claims ABSTRACT OF THE DISCLOSURE An aqueous formulation of an alkaline earth metal thioglycolate and an alkali metal thioglycolate with a fatty alcohol-alkylene oxide wax which, in combination with a volatile liquid propellant, forms an aerosol foam of relatively high density which is effective as a depilatory.
BRIEF SUMMARY OF THE INVENTION This invention relates to a depilatory composition. More particularly, this invention relates to an aqueous depilatory composition which produces a dense aerosol foam when sprayed on the skin.
Depilatory compositions containing substituted organic thiols, particularly salts of thioglycolic acid, are well known in the art and are commercially available as pastes, creams or powders, the latter being admixed with water to form a paste just prior to use. Pastes and creams are disadvantageous because they are messy to apply and are difficult to apply uniformly to the skin. It has long' been desired to prepare aerosol depilatory compositions which could be sprayed on the skin, but heretofore effective depilatory preparations of this type have not been available.
Broadly, my invention is based on the discovery that an aqueous solution of salts of thioglycolic acid containing a nonionic emulsifying agent can be propelled by a volatile halogenated hydrocarbon liquid or a volatile hydrocarbon liquid through a small orifice in the form of an aerosol foam of high density. This foam can be sprayed on the skin in a form which does not break down and form a liquid, the foam being stable on the skin for the period of time (four to fifteen minutes) required for depilatory action, and can then be readily washed or wiped from the skin. It is necessary that the foam be of reasonably high density in order to apply sufficient thioglycolate to the hair for depilatory action. Low density foams such as those of shaving creams are inadequate for this purpose since they do not supply sufficient thioglycolate to the hair and are not stable for a sufficient period of time to exert effective 'depilatory action.
DETAILED DESCRIPTION OF THE INVENTION In accordance with my invention, an aqueous preparation containing about 2% to about 7% (by weight) of an alkaline earth metal thioglycolate, about 2% to about 10% (by Weight) of an alkali metal thioglycolate and about 1% to about 8% (by weight) of a nonionic emulsifying agent in the form of a fatty alcohol-alkylene oxide wax, having a pH of about 11.5-13.5, can be propelled by a volatile halogenated hydrocarbon liquid and/or volatile hydrocarbon liquid propellant to form an aerosol foam of high density (0.1 to 0.2 gram per cubic centimeter) which is readily sprayed on the skin and has high depilatory efficiency. This preparation is stable for extended periods of time. The preferred density of the ice foam is from about 0.12 to 0.17 gram per cubic centimeter. In the aerosol formulation, the aqueous composition of thioglycolic acid salts and nonionic emulsifying agent forms approximately to 97% of the material in the aerosol container, the balance of the material being a volatile liquid propellant such as a halogenated hydrocarbon or a hydrocarbon.
The amount of thioglycolate should be in the range from about 4% to about 15% of the weight of the aqueous depilatory preparation. Below about 4% concentration, the thioglycolates are effective but not practical because the period of time required for depilatation is too long. Above 10% concentration certain thioglycolates, such as the calcium, strontium and barium salts, tend to become insoluble in the aqueous composition and may cause valve clogging in the aerosol container. Calcium thioglycolate is the preferred depilatory material and its solubility in water is about 7% at ordinary temperature. Consequently, its preferred concentration is the range of about 4% to 7% (by weight). Calcium thio glycolate can be purchased on the market at a high state of purity (95-98%) and for this reason is a preferred component. Thioglycolic acid ranging from 70% to 95% is also commercially available and can be used as a starting material. It can be converted to the calcium salt by reaction with lime or an alkali metal salt by reaction with alkali. The barium and strontium salts can be produced by reaction with barium hydroxide and strontium hydroxide, respectively.
The nonionic wax emulsifying agent which is a component of the depilatory preparation is the reaction product of a fatty alcohol and an alkylene oxide. The preferred preparation is the product of stearyl alcohol and ethylene oxide in the form of a creamy, wax-like solid having a melting range from about 48 to about 52 C., a saponification value of 9.0-l4.0 and a maximum iodine value of about 3.5. In a 3% aqueous solution this product has a pH value from 5.5 to 7.0. It does not deteriorate on heating to 150 C. for two hours and has only a slight weight loss (2-3%) with slight hardening of the wax. Other suitable nonionic emulsifying waxes can be prepared from other fatty alcohols such as oleyl alcohol, cetyl alcohol, lauryl alcohol and similar aliphatic alcohols containing 12 to 24 carbon atoms per molecule by reaction with an alkylene oxide such as ethylene oxide or propylene oxide. The reaction is carried out to the extent that a creamy, wax-like water-emulsifiable material is produced.
My invention is disclosed in further detail by means of the following examples which are provided for the purpose of illustration only. It will be readily understood by those skilled in the art that various modifications in materials, quantities and operating conditions can be made within the general disclosure of this application without departing from the invention herein. In the examples the amounts of materials and percentages are by weight.
EXAMPLE 1 Forty parts of stearyl alcohol-ethylene oxide wax of MP. 48-52 C. was suspended in 150 parts of water and the mixture heated to 75 to C. to melt and emulsify the wax. Then 600 parts of cold water was added rapidly to reduce the temperature of the mixture to about 25 C., after which 50 parts of powdered calcium thioglycolate trihydrate was dissolved in the emulsion followed by 50 parts of thioglycolic acid. Then sufficient 40% sodium hydroxide solution was added to bring the pH to 12.0 to 12.5. Finally, sufiicient water was added to make 1,000 parts.
An aerosol can was filled with a mixture containing parts by weight of the foregoing aqueous concentrate and 10 parts of propellant made up to 60% difluorodichloromethane and 40% tetrafluorodichloroethane. The
aerosol valve had a small orifice 0.02 inch in diameter and could be used continuously without clogging. The density of the foam produced by this formulation was approximately 0.13 gram per cubic centimeter.
EXAMPLE 2 Eight parts of finely powdered magnesium-aluminum silicate was suspended in 200 parts of water. Thirty-five parts of oleyl alcohol-ethylene oxide wax (melting from 50 to 55 C.) was emulsified by stirring in 175 parts of water at 70 C. The two suspensions were mixed with stirring. Fifty parts of calcium thioglycolate trihydrate was dissolved in the mixture, then 50 parts of thioglycolic acid was added. The pH of the mixture was adjusted to 12.0 to 12.5 with 40% sodium hydroxide solution. Then sufiicient water was added to make 1,000 parts.
An aerosol can was filled with '85 parts of the foregoing aqueous concentrate and 15 parts of propellant made up of 40% diiiuorodichloromethane and 60% tetrafluorodichloroethane. The density of the foam produced by this formulation was approximately 0.16 gram per cubic centimeter.
Another useful aerosol preparation was made by filling an aerosol can with 95 parts of the foregoing aqueous concentrate and 5 parts of isobutane. It produced a foam with a density of about 0.14 gram per cubic centimeter.
1. A depilatory preparation, adapted for dispensing as a dense foam from a pressurized aerosol container, comprising about 2% to about 7% by weight of an alkaline earth metal thioglycolate, about 2% to about 10% by weight of an alkali metal thioglycolate and about 1% to about 8% by weight of a C to C fatty alcohol-alkylene oxide wax nonionic emulsifying agent wherein alkylene oxide is selected from the group consisting of ethylene oxide and propylene oxide, and the balance water, at a pH in the range from about 11.5 to about 13.5, said depilatory preparation comprising approximately 75- 97% of the material in an aerosol container, the balance being a volatile liquid propellant.
2. A depilatory composition as defined by claim 1 wherein the lakaline earth metal thioglycolate is calcium thioglycolate.
3. A depilatory composition as defined by claim 2 wherein the lakali metal thioglycolate is sodium thioglycolate.
4. A depilatory composition as defined by claim 3 wherein the fatty alcohol-alkylene oxide wax is a stearyl alcohol-ethylene oxide wax.
5. A depilatory composition as defined by claim 4 wherein the stearyl alcohol-ethylene oxide wax has a melting range of 4852 C.
6. A depilatory composition, adapted for dispensing as a dense foam from a pressurized aerosol container, comprising a mixture of sodium and calcium thioglycolates, the total thioglycolates amounting to about 5% to about 10% of the Weight of the composition, and about 3% to about 5% by weight of stearyl alcohol-ethylene oxide wax nonionic emulsifying agent of MP. about 48- 52 C., and the balance water, at a pH in the range of about 11.5-13.5, said depilatory preparation comprising approximately -97% of the material in an aerosol container, the balance being a volatile liquid propellant.
References Cited UNITED STATES PATENTS 2,352,524 6/1944 Evans et a1. 8-161 2,823,168 2/1958 Stonehill 8-161 3,194,736 7/1965 Braun et al. 8-161 3,384,548 5/1968 Zviak et a1. 424-47 ALBERT T. MEYERS, Primary Examiner D. M. STEPHENS, Assistant Examiner U.S. Cl. X.R. 424-47
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