Drug – bio-affecting and body treating compositions – Anti-perspirants or perspiration deodorants
Reexamination Certificate
2001-07-26
2004-06-15
Qazi, Sabiha (Department: 1616)
Drug, bio-affecting and body treating compositions
Anti-perspirants or perspiration deodorants
C424S065000, C424S066000, C424S067000, C424S085100, C424S085100, C424S401000
Reexamination Certificate
active
06749841
ABSTRACT:
TECHNICAL FIELD
The invention is in the field of antiperspirant compositions.
BACKGROUND OF THE INVENTION
Antiperspirant stick compositions are usually anhydrous. They are typically solidified with waxes or various other types of gelling agents such as fatty alcohols, amino acid amides, and the like. One problem with such sticks is that they may be greasy and leave an undesirable residue on underarms and clothing.
The traditional drawbacks with wax-based antiperspirant sticks are remedied with aqueous based antiperspirant sticks gelled with polysaccharide gellants as taught in U.S. Pat. Nos. 6,033,651 and 6,171,581. Such formulas are unique to the antiperspirant market. They provide superior wetness protection and provide a sheer, cool-feeling application on the skin with little or no residue. One problem with such sticks is that the polysaccharide gellants that contribute to the desirable tactile properties tend to lose gel strength over time, which in turn contributes to stick breakage. Gel strength is a measure of the strength of a gelled solid. In antiperspirant solid sticks the gel strength must be carefully monitored to provide a commercially acceptable product. If gel strength is too hard the stick does not have adequate payoff. If the gel strength is not adequate the stick will break too easily. To further complicate the situation, the gel strength of a stick immediately after manufacture may be adequate, but due to the interaction between the various ingredients found within the stick the gel strength decreases over time.
The need gap in the antiperspirant solid stick market is to produce a solid stick that exhibits superior efficacy, sheer application, and minimal residue. In order to be commercially acceptable such sticks must exhibit stability and long term gel strength.
It is an object of the invention to provide solid antiperspirant stick compositions having a long term gel strength.
It is a further object of the invention to provide a method for improving gel strength and inhibiting loss of gel strength in an aqueous acidic composition gelled with polysaccharide gellants comprising adding a gel strengthening effective amount of a gel degradation inhibitor.
SUMMARY OF THE INVENTION
The invention is directed to a method for inhibiting loss of gel strength in an acidic aqueous based solid antiperspirant composition gelled with one or more polysaccharides comprising adding to said composition an effective amount of a gel degradation inhibitor.
The invention is also directed to a method for preparing an aqueous based antiperspirant composition having improved gel strength comprising the steps of:
a) preparing a water phase by combining antiperspirant salts, one or more polysaccharide gellants, a gel degradation inhibitor, and water and heating to a temperature sufficient to form a homogeneous mixture;
b) preparing an oil phase by combining at least one oil with one or more compatible ingredients,
c) emulsifying the water phase into the oil phase.
The invention is also directed to a method for preparing an aqueous based solid antiperspirant composition having improved gel strength comprising the steps of:
a) preparing a first aqueous phase comprised of antiperspirant salts, water, and a gel degradation inhibitor and mixing well to form a homogeneous solution,
b) preparing a second aqueous phase comprising water and at least one polysaccharide gellant,
c) preparing an oil phase comprising at least one oil in combination with one or more oil compatible ingredients,
d) emulsifying the second aqueous phase (b) into the oil phase (c) to form an emulsion; and
e) emulsifying the first aqueous phase (a) into the mixture of (d) to form a water and oil emulsion solid antiperspirant composition.
one or more polysaccharide gellants, and a gel degradation inhibitor and heating to a temperature sufficient to form a homogeneous mixture,
The invention is also directed to acidic aqueous based solid antiperspirant composition gelled with one or more water soluble polysaccharide gelling agents, wherein the improvement comprises including in the water phase an effective amount of a gel degradation inhibitor in the form of a water soluble metal salt.
DETAILED DESCRIPTION
All percentages mentioned herein are percentages by weight unless otherwise indicated.
The pH values of the solutions are measured at 15% w/w @25° C.
The term “gel strength” means the strength of a gel composition measured in grams per centimeter squared (gm/cm
2
). Preferably, the gel strength is measured using a TA.XT2i analyzer with a cylindrical probe having a diameter of 2 inches. A circle about 1 cm. in diameter and 1 cm. in height is cut from a gel and placed on a glass slide beneath the elevated probe. The machine is activated and the probe falls on gel. The gel strength of the sample is the maximum force in grams/cm
2
required to fracture the gel sample.
I. The Method of the Invention
Typically aqueous based solid antiperspirant sticks contain efficacious levels of astringent antiperspirant salts which are acidic in nature. The acidity contributes to the effectiveness of such salts in inhibiting perspiration. However, antiperspirant salts are very difficult to formulate because their inherent acidity reduces the pH of the stick which in turn may have a negative impact on other ingredients in the stick which may be pH labile. Increasing the pH of the antiperspirant stick by including other neutralizing ingredients in the stick, or reacting the antiperspirant salts themselves with a neutralizing agent, may reduce the incompatibility between the low pH salts and other ingredients in the stick but the effectiveness of the antiperspirant salts on inhibiting perspiration is then compromised. It has been discovered that antiperspirant salts that are too neutralized are not as effective in inhibiting perspiration. Thus, a certain balance must be maintained between formula stability and efficacy.
It has been found that aqueous based antiperspirant stick compositions gelled with polysaccharides are particularly susceptible to stick degradation, e.g. the sticks lose a significant amount of gel strength within one week (especially at elevated temperature) after they are poured because polysaccharide gellants readily hydrolyze in acidic media. Certain tests on such sticks show that the aqueous-based antiperspirant sticks gelled with polysaccharides lose as much as 33% of their original gel strength when stored at 40° C. for one week, and as much as 65% of their original gel strength when stored at 40° C. for five weeks. Typically the pH of these antiperspirant sticks is in the range of 3.2 to 3.5.
In the method of the invention, the loss in gel strength over time can be minimized by including at least one gel degradation inhibitor in the aqueous based antiperspirant compositions gelled with polysaccharides, preferably in the aqueous phase. Most suitable gel degradation inhibitors are those materials which are capable of increasing the pH of the antiperspirant composition to a range of about 4.2 to 4.5. Examples of suitable gel degradation inhibitors include water soluble inorganic or organic bases that are stable (i.e. do not precipitate the antiperspirant salts), and are capable of increasing the pH of the compositions at least ½ unit. The following materials may be suitable gel degradation inhibitors: salts of alkali and alkaline earth metals, urea, imidazole, tris buffers, N,N-tetrakis-2-hydroxypropyl-ethylenediamine, EDTA, alkali and alkaline earth metals reacted with amino acids, and so on. Further examples of such gel degradation inhibitors include sodium hydroxide, potassium hydroxide, zinc glycinate, and the like. Particularly preferred is zinc glycinate.
In a more preferred embodiment of the claimed method, the gel degradation inhibitor is added at certain times during manufacture of the compositions. In the case where the compositions are a single phase gel, the antiperspirant salts, agarose, water, and gel degradation inhibitor are combined and heated to 80° C. with stirring to dissolve all componen
Carpio Leandro Gimpaya
Franco Philip
Joshi Vijay Kumar
Blackburn Julie
Qazi Sabiha
Revlon Consumer Products Corporation
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