Clear solid topical deodorant compositions comprising a water-insoluble ester of a water-soluble acid

A clear solid topical deodorant composition comprising 50 to 98% by weight of at least one water-insoluble ester of a water-soluble acid having solubility in water of greater than 50% w/w at 20.degree. C., 2 to 6% by weight of dibenzylidine sorbitol, 0 to 44% by weight of one or more optional ingredients, said composition being substantially free of water and of water-miscible solvents which are liquid at ambient temperature. In one embodiment, the water-insoluble liquid ester is present at 85-98% by weight of the composition.

FIELD OF THE INVENTION 
Improved clear solid compositions, substantially free of water, for topical 
application and delivery of a deodorant effect to the skin, optionally 
further comprising additional active compounds, and further imparting a 
pleasant skin feel. 
BACKGROUND OF THE INVENTION 
Underarm odor is the result of attack by microorganisms upon the excretion 
products of the sweat glands and sebaceous glands in the skin. There are 
two types of sweat glands in the underarm, i.e., eccrine and apocrine. 
Eccrine glands are numerous and secrete a clear aqueous sweat directly 
onto the skin surface, thereby serving a thermoregulatory function. The 
secretions of eccrine glands are not responsible for underarm odor except 
that they provide a warm, moist environment which encourage the growth of 
microorganisms. Apocrine glands, which are larger and fewer, are usually 
associated with sebaceous glands. The function of these glands is not 
understood, but their milky secretions contain nutrients for 
microorganisms. It is believed that the characteristic underarm odor is 
produced by the odorous products of microorganisms, and by the action of 
esterases, elaborated upon the skin by microorganisms, upon apocrine 
secretions 
Underarm odor can be controlled in a variety of ways. Washing of the 
underarms controls odor only if washings are repeated throughout the day. 
Such repeated washing is not practicable; consequently, practically all 
adults in this country use a topical product to control underarm odor. 
There are two classes of topical products which are effective in 
controlling underarm odor, i.e., antiperspirants and deodorants. 
Antiperspirants work by reducing the flow of eccrine perspiration to 
reduce wetness in the underarm area and by inhibiting the growth of 
microorganisms. Antiperspirant compositions are conventionally available 
in aerosol, roll-on and stick product forms. Clear antiperspirants 
typically comprise an antiperspirant active such as aluminum hydroxy 
chloride in a solvent, typically a lower monohydric alcohol or lower 
polyglycol, plus a gelling agent. Due to their acidic pH, these 
antiperspirant compositions inhibit microorganism growth and also 
chemically neutralize the odorous products formed by these microorganisms. 
(Dibenzylidine sorbitol ("DBS"), a gelling agent which has been 
conventionally used to gel clear cosmetic compositions such as 
antiperspirants, is stable in alkaline neutral or slightly acidic 
compositions. In additions to gelling, or solidifying, topical 
compositions, DBS frequently imparts transparency or translucency to these 
compositions). 
Despite their microorganism-inhibiting acidity, conventional antiperspirant 
compositions have been found to have numerous shortcomings. The most 
siw.about.yvysant shortcoming is that the antiperspirant active may 
irritate the skin of some users. Furthermore, when non-volatile glycols, 
for example, propylene glycol, are used as the solvent, the composition 
can impart an unpleasant stickiness to the skin. When components of the 
solvent are volatile, these components may evaporate during storage, 
leading to a drying of the composition or even to physical shrinkage in 
the product's size. Further, these compositions typically must include a 
stabilizer ingredient. Finally, high temperatures are required to 
solubilize dibenzylidine sorbitol as the gelling agent in certain 
formulations. 
Deodorant compositions, also available in aerosol, roll-on and stick 
product forms, typically comprise an antimicrobial agent to inhibit the 
growth of microorganisms and a fragrance to mask odor. Conventional 
deodorant active ingredients include bacteriostatic quaternary ammonium 
compounds such as cetyl trimethyl-ammonium bromide and benzalkonium 
chloride, as well as zinc salts such as zinc citrate. In deodorant stick 
compositions, the antimicrobial agent and fragrance are carried in a low 
volatility solvent, such as propylene glycol, and solidified by a gelling 
agent such as a soap. DBS is a suitable alternative gelling agent. When 
DBS is so used, deodorant compositions further include an emollient such 
as di-n-butyl-phthalate and a polar solvent such as ethanol, as described 
in U.S. Pat. No. 4,816,261. 
These conventional deodorant compositions have several shortcomings. The 
glycol and soap in these compositions create an unpleasant sticky feel on 
the skin. To retain their solidity, the conventional deodorant 
compositions must have an alkaline pH, because soap compounds are 
chemically stable only in alkaline formulations. Consequently, 
conventional deodorant compositions do not impart an acidic pH to the 
skin, and so are unable to exploit the benefits of an acidic composition, 
i.e., inhibiting microorganism growth and chemically neutralizing the 
odorous products of microorganisms. Further, the antimicrobial actives of 
several deodorants have been found to irritate the skin of a significant 
number of users. As with antiperspirant compositions described above, the 
presence of volatile solvents can lead to drying and shrinking of the 
solid composition upon storage. Moreover, when the gelling agent is DBS, a 
high heat of processing (i.e., up to 170.degree. C.) is necessary. The 
presence of phthalate esters as emollients in deodorant compositions 
solidified by DBS also requires high processing temperatures, e.g., 
170.degree. C., to fully dissolve and disperse all components through the 
solvent. Still further, when the deodorant composition includes a 
phthalate ester as an emollient, there is the possibility of imparting a 
toxic effect to the skin from these esters. The resulting gels also are 
easily fractured and are opaque instead of clear. Finally, the deodorant 
effect from conventional deodorant compositions is short lived. 
Certain esters of low molecular weight, water soluble acids such as 
hydroxycarboxylic acids, are known to have the ability to reduce the 
growth of microorganisms on the skin. Examples of such esters are glyceryl 
triacetate and triethyl citrate. Without in any way restricting the 
invention, it is believed that esterases elaborated by microorganisms on 
the skin hydrolyze the water-insoluble esters, when such esters are 
applied topically, to release water soluble acids. The resulting lowered 
skin pH inhibits the growth of the microorganisms and chemically 
neutralizes odorous products of microorganisms and of the action of 
bacterial esterases on apocrine secretions. The ability of microorganisms 
to produce underarm odor is thus reduced. Although the skin's natural 
buffering ability eventually neutralizes these acids and esterases again 
become active, the hydrolysis of the remaining esters on the skin again 
lowers skin pH to inactivate the esterases and prevent or delay 
development of unpleasant odor. Optionally, these esters of water soluble 
acids may be delivered to the skin with an anti-oxidant to enhance the 
deodorant effect, as described in Cosmetics and Toiletries, 95, July 1980, 
48-50. 
It would be desirable to produce a solid topical deodorant composition 
which produces an acid pH on the skin. Such a composition would allow one 
to exploit the inhibition of microorganism growth and chemical 
neutralyzation of odorous products which an acidic pH causes. It would 
additionally be desirable that this deodorant composition produce no 
unpleasant skin feel, not dry out, and not require the presence of 
co-solvents or stabilizing agents therein or the use of high processing 
temperatures in its manufacture. Finally, because consumers have exhibited 
a strong preference for clear (i.e., transparent or translucent) cosmetic 
compositions, including deodorant compositions, it would be desirable for 
this deodorant composition to be clear. 
SUMMARY OF THE INVENTION 
It has now been found that by combining a high level of certain 
water-insoluble esters of water-soluble acids with DBS in a composition 
which is substantially free of water and of water-miscible solvents which 
would be liquid at ambient temperature, there is produced a clear solid 
topical deodorant composition. Replacing conventional deodorant solvents 
and gelling agents with the water-insoluble esters and DBS respectively, 
produces a clear solid topical deodorant composition which generates the 
acidic pH advantage of antiperspirant compositions without the 
disadvantages of conventional deodorant compositions. 
The presence of the clear solid topical deodorant composition at a high 
level produces a topical acidic pH when the one or more water-insoluble 
esters hydrolyzes on the skin. This topical acidic pH inhibits bacterial 
esterases and neutralizes the odorous products of microorganisms. Further, 
due to the absence of the conventional active ingredients of deodorant or 
antiperspirant compositions, as well as of phthalate ester emollients, the 
possibility of skin irritation or toxicity is virtually eliminated. The 
solid topical deodorant composition is also clear and thus significantly 
more attractive to the consumer than conventional white, opaque products. 
The clear solid topical deodorant composition further imparts a pleasant, 
soft feel to the skin, rather than an unpleasant stickiness. Producing the 
composition requires heating its components at significantly lower 
temperatures than manufacturing conventional deodorant compositions. 
Finally, although the composition as formulated is substantially free of 
water and of water-miscible solvents, it is not necessary to exclude all 
water from the final product. The clear solid topical deodorant 
composition needs no packaging barriers to water vapor, or desiccants. 
Instead, there may be up to approximately 3% by weight of water in the 
composition before the advantages described are reduced or lost. 
This clear solid topical deodorant composition comprises 50 to 98% by 
weight of at least one water-insoluble ester of a water-soluble acid 
having solubility in water of greater than 50% w/w at 20.degree. C., 2 to 
6% by weight of dibenzylidine sorbitol ("DBS"), and 0 to 44% by weight of 
one or more optional ingredients. The composition is substantially free of 
water or water-miscible solvents which are liquid at ambient temperature. 
The water-soluble acid may suitably be selected from the group consisting 
of acetic, propionic, butyric, citric, tartaric, adipic, malic and maleic 
acids. The at least one water-insoluble esters which produce an acidic 
topical pH when hydrolyzed upon the skin is selected from the group 
consisting of one of said water-soluble acids esterified with a low 
molecular weight alcohol selected from the group consisting of ethanol, 
propanol, isopropanol, glycerol, propylene glycol, butylene glycol and 
dipropylene glycol. 
One embodiment of the clear solid topical deodorant composition comprises a 
single water-insoluble ester. In another, the one or more water-insoluble 
ester is present at 85 to 98% by weight and the one or more optional 
ingredients is present at 0 to 5% by weight. 
Suitable water-insoluble esters include triethyl citrate, glyceryl 
triacetate, tributyl citrate, and glyceryl tripropionate, and 
water-insoluble liquid esters. 
The limited water solubility of the esters of water soluble acids is 
important to the clear solid topical deodorant compositions. Water soluble 
solvents such as lower aliphatic alcohols (e.g., ethanol) are volatile, 
causing the product to dry out on storage. Non-volatile glycols such as 
propylene glycol leave sticky, inelegant residues on the skin. However, 
the esters of water soluble acids having limited water solubility are not 
sticky upon application to moist underarms, but leave a pleasant soft feel 
on the skin in addition to providing long lasting deodorant activity. 
The optional ingredients of the clear solid topical deodorant composition 
are selected from the group consisting of coloring agents, fragrances, 
antimicrobial agents, topical anesthetics, topical analgesics, 
anti-oxidants, sunscreens and insect repellents. In a further embodiment, 
the clear deodorant composition may be employed as a cosmetic/therapeutic 
topical composition when the one or more active ingredients are selected 
from the group consisting of topical anesthetics, topical analgesics, 
anti-oxidants, sunscreens and insect repellents. 
In another embodiment, the clear solid topical deodorant composition 
comprises 96% by weight of triethyl citrate, 3% by weight of DBS, 0.25% by 
weight of a topical antimicrobial agent, and 0.75% by weight of a 
fragrance. In a further embodiment, this composition comprises 50% by 
weight of triethyl citrate, 46.50% by weight of glyceryl tripropionate, 
2.5% by weight of DBS, and 1.00% by weight of fragrance. 
There is further provided a method of making the clear solid topical 
deodorant composition described above. The steps of this method comprise 
forming a liquid phase comprising the one or more water-insoluble esters 
of a water soluble acid having solubility in water of greater than 50% w/w 
at 20.degree. C., and the optional ingredients, if any; heating this 
liquid phase to 100.degree. C.; slowly adding DBS to this liquid phase 
with vigorous agitation; agitating the resulting mixture for 10 to 30 
minutes while maintaining the liquid phase temperature in the range of 
100.degree. to 140.degree. C. until a clear solution results; cooling this 
clear solution to 80.degree. to 90.degree. C. while stirring and adding in 
any remaining ingredients; and pouring the clear solution into molds.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The at least one water-insoluble ester of water-soluble acids which acts as 
the solvent as well as the deodorizing active ingredient of the clear 
solid topical deodorant compositions have the following properties. They 
are water-insoluble esters of low molecular weight water soluble acids, 
such as hydroxy carboxylic acids. The water-insoluble esters are less than 
10% soluble by weight in water at 20.degree. C. Suitable water-insoluble 
esters include triethyl citrate, glyceryl triacetate, tributyl citrate and 
glyceryl tripropionate. Further suitable water-insoluble esters include 
those which are liquid at ambient temperature. It is noted that esters of 
phthalate compounds are not considered suitable for the present 
composition due to the possibility that they may impart toxicity to the 
skin. The one or more water-insoluble ester is present in the clear solid 
topical deodorant compositions at from 50 to 98% by weight or 
alternatively at from 85 to 98% by weight. With these high levels of 
water-insoluble ester, the clear solid topical deodorant composition 
delivers to the skin a substantial amount of deodorant active ingredient. 
The gelling agent of the present composition is DBS. One commercially 
available DBS is Millithix 925 produced by Milliken Chemical of 
Spartanburg, S.C., USA. DBS may be incorporated in the composition at from 
2 to 6% by weight. At less than about 2% by weight, the DBS is considered 
to impart insufficient gelling activity, so that the composition is 
considered insufficiently hard for spreading on the skin. Amounts of DBS 
greater than 6% by weight do not significantly improve the composition. 
Accordingly, amounts of DBS above 6% by weight in the clear solid topical 
deodorant compositions are considered superfluous. 
The clear solid topical deodorant compositions are substantially free of 
water and of water-miscible solvents which are liquid at ambient 
temperature. By "substantially free of water," it is understood that these 
compositions have no more than 3% by weight of water therein. Similarly, 
there is no more than approximately 3% by weight of water-miscible 
solvents which are liquid at ambient temperature in the clear solid 
topical deodorant composition. Since water up to the 3% by weight level is 
permissible in the present composition, it is not necessary during 
manufacturing or storage of the clear solid topical deodorant composition 
to take steps to preclude water or water vapor from entering the 
composition or employ packaging which seals out water vapor. 
The clear solid topical deodorant compositions are "clear" and "solid", as 
these terms are understood by persons skilled in the art; that is, these 
compositions are transparent or translucent, and are sufficiently hard to 
maintain their shape, without cracking of shattering, when spread over the 
skin. 
One embodiment of the clear solid topical deodorant composition consists 
essentially of 50 to 98% by weight of one or more water-insoluble esters 
of watersoluble acids, 2 to 6% by weight of dibenzylidine sorbitol, and 0 
to 44% by weight of one or more optional ingredients, said composition 
being substantially free of water or water-miscible solvents which are 
liquid at ambient temperature. 
Among the optional ingredients suitable for inclusion in the clear solid 
topical deodorant composition are coloring agents, fragrances, 
antimicrobial agents, topical anesthetics, topical analgesics, 
antioxidants, sunscreens and insect repellents. One or more of each of 
these optional ingredients may be present in the composition. Coloring 
agents and fragrances suitable for the composition are those known to 
persons skilled in the art. The antimicrobial agents considered suitable 
for inclusion in the clear composition are those conventionally used in 
deodorant compositions. The topical anesthetics (e.g., benzocaine), 
topical analgesics (e.g., methyl salicylate), antioxidants (e.g., vitamin 
E), sunscreens and insect repellents which are suitable for the 
composition are those considered suitable by persons skilled in the art. 
It is further understood that the amount of these optional ingredients to 
be included in the composition is the amount that is considered suitable 
by persons skilled in the art. 
Unlike conventional methods for manufacturing deodorant compositions, the 
method disclosed herein uses processing temperatures of no more than 
100.degree. to 150.degree. C., or 100.degree. to 140.degree. C. It is 
particularly noted that the step of adding the DBS to the liquid phase in 
this method is to be performed slowly. If the DBS is added quickly, it may 
clump and so require an extended time in which to be dispersed through the 
liquid phase. 
______________________________________ 
EXAMPLE I 
Deodorant Stick: % w/w 
______________________________________ 
Triethyl Citrate 95.75 
DBS 3.00 
Triclosan 0.25 
Fragrance 1.00 
100.00% 
______________________________________ 
EXAMPLE II 
Deodorant Stick: % w/w 
______________________________________ 
Triethyl Citrate 50.00 
Glyceryl Tripropionate 
46.50 
DBS 2.50 
Fragrance 1.00 
100.00% 
______________________________________ 
EXAMPLE III 
Antifungal Stick: % w/w 
______________________________________ 
Tolnaftate 1.0 
Glyceryl Triacetate 
95.5 
DBS 3.5 
100.0% 
______________________________________ 
EXAMPLE IV 
Topical Anesthetic: 
% w/w 
______________________________________ 
Benzocaine 20.0 
Triethyl citrate 76.0 
DBS 4.0 
100.0% 
______________________________________ 
EXAMPLE V 
Topical Analgesic: % w/w 
______________________________________ 
Menthol 16.0 
Triethyl citrate 80.0 
DBS 4.0 
100.0% 
______________________________________ 
EXAMPLE VI 
Topical Analgesic: % w/w 
______________________________________ 
Methyl salicylate 10.0 
Menthol 16.0 
Triethyl citrate 70.0 
DBS 4.0 
100.0% 
______________________________________ 
The compositions of Examples I-VI above are made according to a process 
comprising the following steps: 
A. heating a liquid phase (water-insoluble ester plus optional ingredients) 
to 100.degree. C.; 
B. adding the DBS, with vigorous agitation, by slowly sifting the DBS into 
the vortex of the liquid; 
C. agitating the resulting solution for 10 to 30 minutes at temperatures in 
the range 100.degree.-140.degree. C. until the solution is clear; 
D. cooling the solution with stirring to 80.degree.-90.degree. C. then 
mixing them to dissolve; and 
E. pouring the cooled solution into stick molds and cooling it there. 
The invention now being fully described, it will be apparent to one of 
ordinary skill in the art that many changes and modifications may be made 
thereto without departing from the spirit or scope of the invention as set 
forth herein.