The invention relates to stable deodorant glycolic sticks comprising a magnesium salt and its preparation and uses.

BACKGROUND OF THE INVENTION

Body odor is caused by degradation of sweat by bacteria. Currently, body odor can be treated using aluminum salts, which act on the odor as an active bactericide and in sweat reduction as an antiperspirant. Fighting odor is critical for the Body Hygiene metier. Other antiodor actives are also available in the market, like zinc gluconate, and technologies like glycolic sticks, however, they do not reach the level of efficacy of aluminum salts.

Even though there is no approved scientific evidence that aluminum salts are harmful to health, they have a reputation of “nasties.” Magnesium salts such as magnesium oxide and magnesium hydroxide have been shown to have the same level of antiodor efficacy as aluminum salts in aerosols. Magnesium oxide and magnesium hydroxide are very difficult to stabilize and generate a good dispersion to be used in deodorant glycolic sticks. The addition of magnesium oxide or magnesium hydroxide to a glycolic stick formula may increase the pH of the glycolic stick formula, therefore further work is necessary. There remains a need for stable deodorant glycolic sticks comprising a magnesium salt instead of an aluminum salt.

SUMMARY OF THE INVENTION

The present invention relates to stable deodorant glycolic sticks comprising a magnesium salt and methods of preparing or using the glycolic sticks. The inventors have unexpectedly discovered that the stable deodorant glycolic sticks have a good sensorial profile, improved stability, great dispersion, optimal hardness, excellent payload, and an antiodor efficacy as deodorant glycolic sticks with an aluminum salt.

A stable deodorant glycolic stick is provided. The stick comprises about 0.5-10 wt% of a magnesium salt, a solvent and a surfactant. The stick is free of an aluminum salt and has a pH no greater than about 11 . The glycolic composition is prepared without precipitation by (a) dispersing the magnesium salt in a dispersion with an agitation at about 300-700 rpm for about 5-15 minutes at about 85°C to form a glycolic composition, and (b) cooling the glycolic composition at about 1 -5°C. The dispersion comprises the solvent and the surfactant. The magnesium salt may be dispersed in the dispersion with an agitation at about 500 rpm for about 10 minutes to form the glycolic composition. The glycolic composition may be cooled at about 4°C.

The magnesium salt may be magnesium oxide or magnesium hydroxide. The magnesium salt may be present at about 1 -10 wt%.

The solvent may consist of propylene glycol and water. The propylene glycol may be present at about 50-80 wt%. The propylene glycol may be present at about 50 wt%. Where propylene glycol is present at about 50 wt%, the stick may further comprise glycerine.

The surfactant may consist of sodium stearate and steareth-100. The sodium stearate may be present at about 3-1 1 wt%. The steareth-100 may be present at about 1 -4 wt%.

The stick may be free of a fragrance, a clay or both.

A treatment method of treating body odor on skin is further provided. The treatment method comprises applying to the skin the stable deodorant stick of the present invention in an amount effective for providing an antiodor effect to the skin.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides stable deodorant glycolic sticks comprising a magnesium salt and methods of preparing or using the glycolic sticks. Magnesium salts such as magnesium oxide and magnesium hydroxide are in a powder form. It is very difficult to disperse magnesium oxide and magnesium hydroxide well during formulation without precipitation of the magnesium oxide or magnesium hydroxide, for example, in the form of aggregates. Surprisingly, the inventors have discovered a novel method to make stable deodorant sticks with magnesium salts having the same or improved properties such as a sensorial profile, hardness, payload and antiodor efficacy as deodorant glycolic sticks with an aluminum salt. Unless stated otherwise, all wt% figures herein are relative to the total weight of a composition, formula or deodorant stick.

Unless stated otherwise, a wt% figure for an ingredient of a composition is relative to the total weight of the composition.

The term “antiperspirant” used herein refers to a cosmetic composition comprising ingredients that control perspiration and therefore body odor. An antiperspirant can prevent sweat from reaching the skin surface and reduce bacteria that cause body odor. An antiperspirant is applied to skin, for example, of an armpit, to reduce or prevent sweat formation on the skin. An antiperspirant may be in the form of a stick, aerosol (or spray), roll-on, wipe or cream.

The term “deodorant” used herein refers to a cosmetic composition comprising ingredients that control body odor caused by degradation of sweat by bacteria, but not perspiration. A deodorant can inhibit growth of the bacteria or kill the bacteria and thereby reduce or prevent the body odor. Among various deodorant active ingredients, aluminum salts are commonly used and most effective bactericides. A deodorant may be in the form of a stick, aerosol (or spray), roll-on, wipe or cream.

The terms “antiodor efficacy” and “efficacy of a deodorant” are used herein interchangeably and refer to the effectiveness of a deodorant in controlling body odor caused by degradation of sweat by bacteria.

The term “stable” used herein refers to a physical or chemical property of a cosmetic composition such as a deodorant anhydrous stick that does not change significantly over time. For example, no significant amount of precipitation, color change or exudation of an oil (e.g., less than about 10, 5, 1 , 0.5 or 0.1 wt%) is observed in a deodorant anhydrous stick during a predetermined time period, for example, within about 1 , 3, 6, 12, 18 or 24 months.

The invention provides a stable deodorant glycolic stick. The stick comprises a magnesium salt, a solvent and a surfactant. The magnesium salt is present at about 0.5-10 wt%. The stick is free of an aluminum salt and has a pH no greater than about 1 1 , for example, no greater than about 10. The glycolic composition is prepared without precipitation by dispersing the magnesium salt in a dispersion with an agitation at about 300-700 rpm for about 5-15 minutes at, for example, about 85°C to form the glycolic composition and cooling the glycolic composition at about 1 -5°C. The dispersion comprises the solvent and the surfactant.

The magnesium salt may be dispersed in the dispersion with an agitation at about 500 rpm for about 10 minutes to form the glycolic composition. The glycolic composition may be cooled for about 0.5-2 hours, for example, about 1 hour. The glycolic composition may be cooled at about 4°C.

The magnesium salt may be selected from the group consisting of magnesium oxide, magnesium hydroxide and a combination thereof. The stick may comprise about 1 -10 wt%, about 1 -5 wt%, about 2-4 wt%, or about 1 , 2, 3, 4 or 5 wt% or the magnesium salt. The solvent may be any cosmetically acceptable substance in which the magnesium salt is dissolved without precipitation. The solvent may be propylene glycol, water or a combination thereof. The stick may comprise about 30-80 wt%, about 50- 80 wt%, or about 45, 50, 55, 60, 65, 70, 75 or 80 wt%, of the propylene glycol. The stick may comprise about 70-80 wt%, for example, about 75 wt%, of the propylene glycol. The stick may comprise about 45-55 wt%, for example, about 50 wt% of the propylene glycol. Where the propylene glycol is present at about 45-55 wt%, for example, about 50 wt%, the stick may further comprise glycerine.

The surfactant may be any cosmetically acceptable compound suitable for lowering the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. The surfactant may be sodium stearate, steareth-100 or a combination thereof. The stick may comprise about 3-1 1 wt, for example, about 5-10 wt%, of the sodium stearate, about 1 -4 wt%, for example, about 1 -3 wt% of the steareth-100, or a combination thereof.

The stable deodorant glycolic stick of the present invention may be free of a fragrance, a clay or both.

For each stable deodorant anhydrous stick of the present invention, a method of preparing the stick without precipitation is provided. The method comprises mixing water and propylene glycol to form a mixture, adding a surfactant into the mixture to form a dispersion, and adding and dispersion a magnesium salt into the dispersion with an agitation in a range from about 300 rpm to about 700 rpm (e.g., about 500 rpm) to form a glycolic composition. The magnesium salt may be magnesium oxide, magnesium hydroxide or a combination thereof. The method further comprises cooling the glycolic composition at a temperature in a range from about 1 °C to about 10°C (e.g., about 4°C) and then using the glycolic composition after cooling to make a stable deodorant glycolic stick free of an aluminum salt and having a pH no greater than about 10. After the addition of the magnesium salt, the time and the speed of the agitation as well as the cooling are very important to prevent precipitation of the magnesium salt. The method may further comprise storing the deodorant glycolic stick without precipitation at about 1 -10°C (e.g., about 4°C).

The water and the propylene glycol may be mixed at a temperature up to about 70°C, 80°C or 90°C, for example, up to about 80°C, with an agitation in a range from about 200 rpm to about 600 rpm, for example, about 400 rpm. The surfactant may comprise a first surfactant and a second surfactant. The first surfactant may be added and dispersed into the solvent for about 1 -20 minutes (e.g., about 5 minutes) to form a first dispersion, and a second surfactant may be added and dispersed into the first dispersion with an agitation in a range from about 300 rpm to about 700 rpm (e.g., about 500 rpm) for about 1 -30 minutes (e.g., about 10 minutes). The first surfactant may be sodium stearate and the second surfactant may be steareth-100.

A method of treating body odor on skin is further provided. The treatment method comprises applying to the skin the stable deodorant stick of the present invention in an amount effective for providing an antiodor effect to the skin. The antiodor effect may last for at least about 8, 16, 24, 48 or 72 hours.

Example 1. Preparation of stable deodorant glycolic sticks

Stable deodorant glycolic sticks free of an aluminum salt were prepared. Water and propylene glycol were added into a THERMOMIX® blender and mixed at a temperature up to 80°C with an agitation of around 400 rpm. Sodium stearate was added and dispersed for 5 minutes. Steareth-100 was then added and melt for 5 minutes with an agitation of 500 rpm. Finally, magnesium oxide was added and dispersed with an agitation of 500 rpm for 10 minutes to prepare a deodorant glycolic formula.

Differently than a cooling process of glycolic sticks with an aluminum salt at room temperature, to avoid precipitation of magnesium oxide, the deodorant glycolic formula was kept in a refrigerator or cooling tunnel at 4°C for 1 hour before being poured to make deodorant glycolic sticks. The deodorant glycolic sticks were stored in a refrigerator. Table 1 shows the concentration (wt%) of each ingredient in deodorant glycolic sticks A-H.

Table 1. Deodorant glycolic sticks Example 2. Characteristics of deodorant glycolic sticks

Deodorant glycolic stick B prepared in Example 1 was stable. No aggregates or precipitates were observed deodorant glycolic stick B for two (2) months at 45°C, which is equivalent to two (2) years of shelf life. Deodorant glycolic stick B had a pH of about 10. Compared with deodorant glycolic sticks with an aluminum salt as a benchmark, deodorant glycolic stick B showed a superior antiodor performance. Other deodorant glycolic sticks prepared in Example 1 are expected to be stable having similar characteristics as deodorant glycolic stick B.

The term “about” as used herein when referring to a measurable value such as an amount, a percentage, and the like, is meant to encompass variations of ±20% or ±10%, more preferably ±5%, even more preferably ±1%, and still more preferably ±0.1% from the specified value, as such variations are appropriate.

Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims without departing from the invention.