US2352524A - Depilatory - Google Patents

Description

Patented June 27, 1944 DEPILATORY Ralph L. Evans, Bay Shore, and Everett G. Mc- Donough, Yonkers, N. Y., assignors to Sales atfiiiates, Inc., New York, N. Y., a corporation of New York No Drawing. Application June 20, 1938, Serial No. 214,742

17 Claims.

Our invention relates to the removal of hair from the living body, the products commonly employed being known as depilatories.

The practice of removing hair from the skin of certain parts of the body has been followed for many years. Various methods such as shaving, abrading, plucking, electrolysis, etc., have been resorted to, but the method most popular for removal of hair from the arms, armpits and legs, particularly of women, employs preparations whose chemical action on the hair fibre sufficiently weakens it so that the hair above the skin surface may be wiped or washed off in a few minutes after applying. These preparations are known as depilatories and are sold in liquid, paste or powder form. The latter is made into a paste by addition of sufficient water in order to be used.

These chemical preparations contain as their effective ingredients, one or more of the alkali or alkaline-earth salts of hydrogen sulfide. Such salts have a tendency to hydrolyze and have an appreciable vapor pressure due to the hydrogen sulfide gas. Their use in any product imparts to it the disagreeable odor that is reminescent of rotten eggs. All attempts to mask the odor result in failure. The use of heavy perfume and gaseous absorbents, such as clays and charcoals, only serve to minimize the objectionable odor. If the alkalinity is increased, the odor is reduced but the possible danger due to irritation of the skin is increased. If the sulfide is oxidized to an odorless form, its odor is destroyed, but also the effectiveness of the product is lost.

Another disadvantage that accompanies the use of these sulfides is that when present in a paste they impart to it an unattractive greenishcast. probably due to the formation of insoluble co ored metallic sulfides.

Besides the disgusting odor that accompanies the use of hydrogen sulfide salts is the fact that the liberated or free hydrogen sulfide that escapes into the room is toxic to breathe and although in such dilution it is probably not dangerous, nevertheless, together with its nauseating odor it has caused certain individuals to become ill.

Also the escape of this hydrogen sulfide gas into the home causes black coating of most metal utensi s. such, for example, as silverware or jewelrr. Also it is retained and imparts its loathsome odor to fabrics and rugs, etc.

The object of our invention is the production of depilating preparations which have none of these disadvantages. There are no objectionable odors, a white paste is produced, a delicate perfume may be used and silverware or other metals are not tarnished if brought in contact with the preparation. Depilating preparations made in accordance with our invention will remove hair quickly (within 5 to 10 minutes), depending on coarseness of the hair, safely ,(without injury to the skin), and effectively (no stubble left).

We have found that an effective depilatory can be had by proper formulation if we use a substance which may be looked upon as a hydrogen sulfide derivative, since it is a replacement of one of the hydrogen atoms of H--SH with an organic group. For example,

(ethyl mercaptan) or (benzyl mercaptan) can be used.

However, we have found that simple mercaptans are of no value commercially since they possess a nauseating odor far greater, in most instances, than hydrogen sulfide.

We have found that the odor can be minimized by having the molecule contain other groups. For example, the other group may be an hydroxy group, such as represented by H H HO-C-O-SH H H (p-mercaptoethanol), or an ether, ketone,.aldehyde, etc. However, we have found that even with these groups included there is still a pronounced disagreeable odor, unless the molecule is loaded with more than one group, in which case the molecular weight increase will make it necessary to use a greater percentage of the material in order to obtain the effect of the SH group. Also the cost of manufacturing such complicated structure is expensive.

We have found, however, that the odor can be rendered negligible if in place of groups such as described above, and known as non-polar, we use polar groups. Polar groups differ from non-p0- lar in that in solution they ionize. Probably-the reason for the effectiveness of the polar groups is due to the fact that they possess a large stray. electric field, which results in holding about the mercaptan molecule a number of water molecules as a loose hydration, tending thus to prevent vaporization and odor. Polar groups we have found less odorous salt in an alkaline medium. Also we have found these salts-in an alkaline medium serve to give an easily controlled buflered solution at a desired pH value. Also we have found that depilatories made with mercaptans containing polar groups, and particularly acid-acting groups, tend to produce less damage to the epidermis or skin irritation. In other words, we have found that when used in depilatories that the unsubstituted mercaptans do the most damage to the epidermis, that the mercaptans containing non-polar groups are next in order of action and that the least damaging to the skin are the mercaptans containing polar groups.

A depilatory to achieve its purpose must destroy hair without damaging or even irritating the outermost layers of the skin. The difllculty of accomplishing this object appears almost insurmountable when one realizes the close chemical relation that exists between the outer skin (epidermis) and hair. Further, in a; commercially successful preparation the depilatory must remove even the most resistant and coarse hair and yet not injure or irritate the most delicate and sensitive skin: Further, the depilation must take place in a very short time, not to exceed about thirty minutes, not only because the user will be annoyed the longer the time but also because with longer contacts there is the tendency to do skin damage because of (a) penetration into and action on the skin of the depilatory solution and (b) evaporation of water from a paste depilatory to form a crust that abrades the tenderized skin on removal.

We found that in order to obtain a desirable depilating action the depilatory solution and the depilatory paste must conform to certain general formulation.

1) Preferably the pH value should not be less than pH 9.0 and no greater than pH 12.5. Below pH 9.0 the depilating action is too slow and as the pH increases beyond pH 12.5 the skin damage becomes increasingly more pronounced and the skin irritation more severe.

.(2) We have found that primarily the damage to the skin is due to (a) long contacts and (1)) high alkalinity. We have found that we can overcome this by establishing certain general rules of formulation. We have found that when the concentration of the mercaptan is less than 0.1 mole per liter of solution it is necessary for us to increase the alkalinity to such a high concentration in order to efiect hair destruction that skin damage and irritation results. Further, we have found that the mercaptan need not exceed 1.5 moles per liter. This is particularly true of mercaptans containing polar groups and especially those containing acid-acting polar groups for at higher concentration (than 1.5 moles) in the same alkalinity the action is no faster in destroying hair and is no less irritating to the skin. The most desirable results are achieved when the solution contains about 0.5 mole of the mercaptan per liter of solution.

(3) We have found that not all alkaline materials are satisfactory for supplying the necessary alkalinity. We can not, for example, use

bases that are volatile, such as ammonia, methylamine, or ethylamine for they tend to destroy and irritate the epidermis. Also we have found that the base must have an ionization constant greater than 2.0x 10-. For example, ethanolamine, having an ionization constant of 1.5x 10- is of practically no value, even in concentrations high enough to give skin injury, whereas ethylenediamine having an ionization constant of 8.5 10- is active. The hydroxides of the alkali metals and the alkaline earth metals are effective, if they in) not form too insoluble salts with the mercaptan. For example, barium hydroxide forms a fairly insoluble salt with mercapto-acetic acid rendering inefl'ective and depilating action.

(4) In using the hydroxides of the alkali met: als or the alkaline earth metals to obtain the proper alkalinity we have found a slightly greater than equivalence of the alkaline material to the mercaptan (and the acidic groups it contains) gives depilating action without irritation. Increasing the alkalinity at a given concentration of mercaptan increases the speed of depilation but also increases the irritation to the skin. We have found that in order to prevent skin injury, it is desirable that the concentration of the alkaline material in solution be not greater than twice the equivalent concentration of the mercaptan (and the acid groups it contains). For example, in one liter of solution, if with 0.2 mole of mercapto-acetic acid is used 0.5 mole of sodium hydroxide (1.25 equivalents) good results are obtained, yet a smaller amount of mercapto-acetic (0.1 mole) with the same amount (0.5mole) or (2.5 equivalents) of sodium hydroxide concentration gives skin irritation and damage. We have found that the alkaline-earth hydroxides are thus more desirable to use than the alkali hydroxides because of their decreased solubility, since only a slight excess of the free alkaline-earth hydroxide remains in solution with that required for neutralizing the mercaptan and acid-acting groups it contains. Calcium hydroxide is therefore particularly useful since by its lower solubility, even with a large excess as in a paste depilatory, it furnishes only a slight excess of free hydroxide in solution but has a ready insoluble reservoir for keeping constant the alkalinity of the solution. Thus, the stronger and more soluble bases such as strontium hydroxide or sodium hydroxide may be used in suflicient amount to neutralize the acidity (or part of the acidity) of the mercaptan (and any acid-acting groups it contained) while lime paste or calcium hydrate may be used to supply the slight excess of alkalinity and an alkalinity reservoir.

(5) Because of the difllculty of localizing the liquid depilating medium we have found a paste medium to be far more satisfactory. Although a paste can be made by using a large excess of the insoluble alkaline-supplying material, such as calcium hydrate, nevertheless, we find that other fillers are desirable additions, due to the fact that the use of depilatories containing only such materials as calcium hydrate are dimcult to remove if allowed to dry on the skin due to a cementing effect. Also we have found there is no need for an excessively large reservoir of insoluble alkalinity and the substitution of inert fillers for part of it not only increases the ease of removal but also reduces the tendency to irritate. We have found that almost any non-reactive insoluble powders can be used as the pasteforming ingredient butwe prefer white finely ground powders, such as precipitated chalk, magnesium oxide, clays, tales and pyrophyllites. One of the advantages 01 our depilatory is that unlike hydrogen sulfide depilatories there is no development of blue color formed because of the use of these paste-forming materials in our depilatory. Although the amount of filler to be used will vary, the percentage will probably be in the range from 20 to 50%.

(6) We have found, however, that unless we are exceedingly careful in formulation, there is either a slight separation of water or a stiffening of the cream on standing. The possibility of these two undesirable results occurring we have found can be prevented by the addition of ingredients to increase the viscosity of the solution. Materials which may be used are the natural gums. For example, tragacanth, karaya, quince seed extraction may be used to prevent this tendency to change in consistency by increasing the viscosity of the depilatory solution, and we have found that in our depilatory they are more stable than in the hydrogen sulfide depilatory. We have found, however, two groups of materials that are even more satisfactory. One group is the water-dispersible poly-vinyl alcohols and the other is the water-dispersible cellulose ethers, such as methyl cellulose. These materials are stable and allow wide percentagg variations. The higher the percentage of these viscosity-increasing materials the less filler there need be used, but at too high percentage the depilatory will not spread easily. The range of from 1 to 10% will usually give satisfactory results.

(8) We have found that we have a much wider choice of perfume materials than heretofore possible with other depilatories. Heretofore, the

hydrogen sulfide in an alkaline medium tended to produce malodorous organic sulfur compounds by reacting with the perfume constituents. We have found that in our depilatory the perfume is remarkably stable. This, coupled with the fact that there is no offensive odor to cover, allows us to use less perfume, a wider variety in selecting perfume materials, and more fragrant yp been the basic constituents as much for their powerful (and to some, offensive) odor as for their stability and the percentage of perfume usually as great as 3%. We have found we can use 1% or less of light fragrant compounded fioral odors.

It must be pointed out at this point that various attempts have been made to form odorless depilatories but they all have had to use a very high alkalinity. The result has been that this high alkalinity while decreasing the offensive odor has increased the tendency to irritate the skin. Solutions of alkali metal hydroxide, alone, with hydrogen sulfide, or with materials such as divalent tin compounds, have been used but when the concentration of the alkali is sufficiently high to overcome the odor or to effectively depilate it is also sufficiently high to cause skin irritation. The pHs of such solutions are greater than lime putty and are above pH 12.5. Aside from irritation danger there are few perfume materials stable at this high pH. With our invention we are able to obtain an odorless depilatory at pH 12.5 or less that is non-irritating and in which many perfume materials are remarkably stable.

Although we prefer to remove hair with a depilatory made according to the above formulation we have found that there are various other methods of depilating hair with our invention.

Heretofore, ionones and geraniols have For example, we know that the mercaptan may be used separately from the alkaline medium- In Strontium hydrate grams CaO do 12 Colloidal clay do 102 Methyl cellulose do 11 Mercapto-acetic acid ccs 12 Water do 300 Perfume cc-.. 0.8

While we have described examples of our invention and have outlined advantages of our invention over the art, we do not wish to limit ourselves to the exact materials Or proportions outlined in the preceding. A variety of materials of like or similar properties may be used in lieu of those described herein and the proportions may be widely varied, without departing from the scope of our invention or the spirit of the appended claims.

This application is a continuation in part of tour application Serial No. 167,934, filed October What we claim is:

l. A depilatory to effect removal of hair without irritation or injury to the epidermis comprising the formula Strontium hydrate grams 50 Calcium oxide do 12 Colloidal clay do 102 Methyl cellulose do 11 Mercapto-acetic acid ccs 12 Water do 300 Perfume M 0.8

a the amount of thioglycollic acid being suflicient to render the hair removable after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount sufficient to give the preparation a pH value between about 10 and.

3. A creamy depilatory for use in removing hu man hair from the body, comprising a preparation containing a substantial amount of a non- .depilating vehicle carrying a mercapto-carvalue between about 10 and 12.5.

4. A depilatory for use in removing human hair from the body, comprising a preparation containing a substantial amount of a non-depilating ve-"i hicle carrying a mercapto-carboxylic acid, and

an excess oi. an alkaline reacting material, said preparation being adapted to be spread upon the human skin and around the hair,- the amount of said mercapto-carboxylic acid being suflicient toline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of such acid being sufficient to render the hair removable after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount suiiicient to give the preparation a pH value between about 12 and 12.5.

6. A depilatory for use in removing human -hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a mercaptan, and an excess of an alkaline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of mercaptan being suflicient to render the hair removable after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount sufllcient to give the preparation a pH value between 9 and about 12.5.

7. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a mercaptan, and an excess of an alkaline reacting material, said creamy preparation being adaptedto be spread upon the human skin and around the hair, the amount of mercaptan being sufllcient to render the hair removable after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount sufficient to give the preparation a pH value not greater than 12.5.

8. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a subtituted mercaptan, and an excess of an alkaline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of substituted mercaptan being suificient to render the hair removable after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount sufiicient to give the preparation a pH value between 9 and about 12.5.

9. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a mercaptan having polar group, and an excess of an alkaline reacting material, said creamy prepration being adapted to be spread upon the human skin and around the hair, the amount of mercaptan having polar-group being sumcient to render the hair removable after contact therewith within'a short time and without irritation to the skin, and the alkaline reacting material being present in an amount suflicient to give the preparation a pH value between 9 and about 12.5.

10. A depilatory for use inrcmoving human hair from the body, comprising a creamy preparation containing a substantial amount, of a creamy non-depilating vehicle carrying a merhair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a substituted mercaptan and an excess of an alkaline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of substituted mercaptan being not less than 0.1 mole per liter of solution to efiect removal of the hair after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount suflicient to give the preparation a pH value between 9 and about 12.5.

12. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a substituted mercaptan and an excess of an alkaline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of substituted mercaptan being not less than 0.1 mole per liter of solution to efiect removal of the hair after contact therewith within a short time and without irritation to the skin, and the alkaline reacting-material being present in an amount not greater than twice the acidic equivalents of said mercaptan, and sufiicient to give the preparation a pH between 9 and about 12.5.

,13. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying asubstituted mercaptan and an excess of a non-volatile alkaline reacting material having a dissociation constant greater than 2.0x 10 said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of substituted mercaptan being not less than 0.1 mole per liter of solution to effect removal of the hair after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount not greater than twice the acidic equivalents of said mercaptan, and suflicient to give the preparation a pH value between 9 and about 14. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a mercaptan having non-polar group, and an excess of an alkaline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of mercaptan having non-polar group being sufficient to render the hair removable after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount suficient to give the preparation a pH value between 9 and about 12.5.

15. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a mercaptan having hydroxy group, and an excess of an alkaline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of mercaptan having hydroxy group being suflicient to render the hair removable after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount suflicient to give the preparation a pH value not less than 9.

16. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a -niercaptoethanol and an excess of an alkaline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of mercapto-ethanol being sufficient to render the hair removable after contact therewith within a short time and without irritation to the skin, and an alkaline reacting material being present in an amount suflicient to give the preparation a pH value not less than 9.

17. A depilatory for use in removing human hair from the body, comprising a creamy preparation containing a substantial amount of a creamy non-depilating vehicle carrying a salt of mercaptan and an excess of an alkaline reacting material, said creamy preparation being adapted to be spread upon the human skin and around the hair, the amount of said salt of mercaptan being suiificient to render the hair removable after contact therewith within a short time and without irritation to the skin, and the alkaline reacting material being present in an amount suflicient to give the preparation a pH value not less than 9.

RALPH L. EVANS. EVERETT G. McDONOUGH.

I Certificate of Correction Patent No. 2,352,524 June 27, 1944. RALPH L. EVANS ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 26, claim 15; and second column, line 11, claim 16; and line 25, claim 17, for not less than 9 read not greater than about 12.5 and that the said Letters Patent should be read with tihese cosrtgctions therein that the same may conform to the record of the case in the atent ce.

Signed and sealed this 24th day of September, A. D.-1946.

LESLIE FRAZER,

First Assistant Commissioner of Patents.

DISCLAIMER 2,352,524.Ralph L. Evans, Bay Shore, and Everett G. McDrmough, Yonkers, N. Y. DEPILATORY. Patent dated June 27, 1944. Disclaimer filed Feb. 6, 1947, by the assignee, Sales Afiil'iates, Inc. Hereby enter this disclaimer to claims 6, 7, and 17 of the above-identified patent.

[Qfiicial Gazette March 4, 1947.]