The invention relates to stable deodorant emulsion sticks comprising a magnesium salt and uses thereof.

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.

Deodorant products are available in the form of solid emulsion compositions such as water-in-oil emulsion (also known as reversed emulsion) for topical application to skin, for example, of an armpit. It is often challenging to obtain emulsion deodorant sticks with desirable mechanical properties, for example, sufficient hardness and sufficient deposition when applied.

Even though there is no approved scientific evidence that aluminum salts are harmful to health, they have a reputation of “nasties”. Other effective deodorant active substances have been explored. 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 however very difficult to stabilize in an deodorant emulsion sticks with desirable mechanical properties.

There remains a need for stable, well dispersed, hard and integrate deodorant emulsion sticks comprising a magnesium salt instead of, for example, an aluminum salt.

SUMMARY OF THE INVENTION

The present invention relates to stable deodorant emulsion sticks comprising a magnesium salt and uses thereof. The inventors have unexpectedly discovered that the stable deodorant anhydrous sticks have a good sensorial profile, improved stability, great dispersion, optimal hardness, excellent payload, and a statistically superior antiodor efficacy.

A stable deodorant emulsion stick is provided. The stick comprises about magnesium hydroxide and a combination thereof, about 0.5-4 wt% of a surfactant selected from the group consisting of PEG/PPG-18/18 dimethicone, cetyl PEG/PPG- 10/1 dimethicone, polyglyceryl-3 diisostearate and a combination thereof, about 14-17 wt% of an oil selected from the group consisting of isopropyl palmitate, dimethicone and a combination thereof, about 8-10 wt% of a wax, a filler, and water. The stick is free of an aluminum salt and comprises a reversed emulsion.

The stick may comprise about 2-3 wt% of the magnesium salt.

The surfactant may be a combination of PEG/PPG-18/18 dimethicone, cetyl PEG/PPG-10/1 dimethicone and polyglyceryl-3 diisostearate. The stick may comprise about 0.2-1 wt% of PEG/PPG-18/18 dimethicone, about 0.5-2.5 wt% of cetyl PEG/PPG-10/1 dimethicone, about 0.2-0.4 wt% of polyglyceryl-3 diisostearate, or a combination thereof.

The oil may be a combination of isopropyl palmitate and dimethicone. The stick may comprise about 8-10 wt% of isopropyl palmitate, about 6-7 wt% of dimethicone, or a combination thereof.

The wax may be polyethylene.

The stick may further comprise a preservative selected from the group consisting of phenoxyethanol, pentylene glycol and a combination thereof.

The may be free of beheneth-10, a fragrance or a combination thereof. The stick may be free of a clay. The stick may have a pH no more than 10.

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

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides stable deodorant emulsion sticks comprising a magnesium salt and uses thereof. Magnesium salts such as magnesium oxide and magnesium hydroxide are in a powder form. Addition of magnesium oxide into a deodorant emulsion stick formula has been found to break the emulsion structure. Surprisingly, the inventors have discovered a balance of surfactants to make stable, well dispersed, hard and integrated deodorant sticks, which comprise a reversed emulsion. The resulting deodorant emulsion sticks with magnesium salts show good 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.

An emulsion is a mixture of two liquids that are normally immiscible (unmixable or unblendable). An emulsion may be direct (i.e., oil dispersed in water, o/w), reversed (i.e., water dispersed in oil, w/o) or bicontinuous. One or more surfactants may be used to promote formation of an emulsion in a formula. A direct surfactant promotes formation of a direct emulsion. Examples of direct surfactants include beheneth-10. A reserved surfactant promotes formation of a reversed emulsion in a formula. Examples of reserved surfactants include PEG/PPG-18/18 dimethicone, cetyl PEG/PPG-10/1 dimethicone, and polyglyceryl-3 diisostearate. The emulsion structure in a formula may be observed under microscope or determined in a droplet test. In the droplet test, conductivity of the formula is determined. A formula having low or no conductivity and/or interaction with water comprises a reversed emulsion.

A stable deodorant emulsion stick is provided. The stick comprises a magnesium salt, a surfactant, an oil, a wax, a filler, and water. The stick is free of an aluminum salt and comprises a reversed emulsion.

The stick may comprise the magnesium salt at a concentration of about 1 -6 wt% or about 2-3 wt%. The magnesium salt may be selected from the group consisting of magnesium oxide, magnesium hydroxide and a combination thereof. The magnesium salt may be magnesium oxide. The stick may comprise about 2-3 wt% of magnesium oxide.

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 effective for maintaining the reversed emulsion in the stick. The surfactant may be selected from the group consisting of PEG/PPG-18/18 dimethicone, cetyl PEG/PPG- 10/1 dimethicone, polyglyceryl-3 diisostearate and a combination thereof. The stick may comprise about 0.5-4 wt% of the surfactant. The surfactant may be PEG/PPG- 18/18 dimethicone, cetyl PEG/PPG-10/1 dimethicone, polyglyceryl-3 diisostearate, or a combination thereof. The stick may comprise about 0.2-1 wt% of PEG/PPG-18/18 dimethicone, about 0.5-2.5 wt% of cetyl PEG/PPG-10/1 dimethicone, about 0.2-0.4 wt% of polyglyceryl-3 diisostearate, or a combination thereof.

The stick may be free of a direct surfactant. The direct surfactant may be beheneth-10. The stick may be free of beheneth-10.

The oil may be any cosmetically acceptable fatty substance suitable for providing emolience to the stick and effective for keeping the same or similar deposit quantity of the stick when applied despite of the hardness of the stick. The oil may be liquid at room temperature (25°C) and atmospheric pressure (760 mmHg, i.e., 105 Pa). The oil may be mineral oil, animal oil, plant oil, synthetic oil or a combination thereof. The oil may be chosen from silicones like D5, dimethine, vegetable oils, petroleum based oils like petrolatum, esters, or combinations thereof. The oil may be selected from the group consisting of isopropyl palmitate, dimethicone and a combination thereof. The stick may comprise about 14-17 wt% of the oil. The oil may be isopropyl palmitate, dimethicone or a combination thereof. The stick may comprise about 8-10 wt% of isopropyl palmitate, about 6-7 wt% of dimethicone, or a combination thereof.

The wax may be any cosmetically acceptable polymer suitable as a structuring agent responsible for harness of the stick. The wax may be chosen from animal, fossil, plant, mineral and synthetic waxes. For example, the wax may be chosen from vegetable waxes, fatty alcohols, paraffin waxes, or combinations thereof. The stick may comprise about 8-10 wt% of the wax. The wax may be polyethylene.

The filler may be any cosmetically acceptable compound suitable for increasing bulk, weight, viscosity, opacity, or strength of the stick. The filler may be solid at room temperature (25°C) and atmospheric pressure (760 mmHg, i.e., 105 Pa). The stick may comprise about 0.1 -0.3 wt% of the filler. The filler may be perlite.

The stick may be free of a fragrance. The presence of a fragrance may cause a color change in the stick.

The stick of the present invention may comprise no more than about 70 wt% water, may be free of a clay, and/or may have a pH no more than about 10, for example, about 4-10, 5-9 or 6-8.

The stable deodorant emulsion stick free of an aluminum salt of the present invention may be prepared without precipitation. The oils and the surfactants may be mixed with an agitation in a range from about 500 rpm to about 900 rpm (e.g., about 700 rpm for about 10 minutes) to form a mixture. The mixture may be heated to a temperature in a range from about 50°C to about 70°C (e.g., about 60°C) with an agitation in a range from about 800 rpm to about 1200 rpm (e.g., about 1000 rpm) for about 5-20 minutes (e.g., about 10 minutes) to form a first reversed emulsion. A filler (e.g., perlite) may be added to the first reversed emulsion at a temperature in a range from about 60°C to about 80°C (e.g., about 70°C) with an agitation in a range from about 800 rpm to about 1200 rpm (e.g., about 1000 rpm) to form a second reversed emulsion. A wax may be added and melted in the second reversed emulsion at a temperature in a range from about 80°C to about 99°C (e.g., about 90°C) with an agitation in a range from about 500 rpm to about 700 rpm (e.g., about 600 rpm) to form a third reversed emulsion. The magnesium salt may be added and dispersing in the third reversed emulsion to form a deodorant reversed emulsion. The deodorant reversed emulsion may be heated to, for example, about 100°C before being used to make the stable deodorant emulsion stick. The stick may be stored without precipitation at about 1 -5°C, for example, about 4°C. A method of preparing a stable deodorant emulsion stick free of an aluminum salt is also provided. The stick comprises a reversed emulsion. The composition comprises a magnesium salt, a surfactant, a wax, an oil, a filler and water. The magnesium salt is selected from the group consisting of magnesium oxide, magnesium hydroxide and a combination thereof. The surfactant may be present in an effective amount for maintaining the reversed emulsion. The method comprises (a) mixing the water, the oil and the surfactant with an agitation in a range from about 500 rpm to about 900 rpm, whereby a mixture is formed, (b) heating the mixture to a first temperature in a range from about 50°C to about 70°C with an agitation in a range from about 800 rpm to about 1200 rpm for about 5-20 minutes, whereby a first reversed emulsion is formed, (c) adding the filler to the first reversed emulsion at a second temperature in a range from about 60°C to about 80°C with an agitation in a range from about 800 rpm to about 1200 rpm, whereby a second reversed emulsion is formed, (d) adding to and melting the wax in the second reversed emulsion at a third temperature in a range from about 80°C to about 99°C with an agitation in a range from about 500 rpm to about 700 rpm, whereby a third reversed emulsion is formed, (e) adding and dispersing the magnesium salt in the third reversed emulsion, whereby a deodorant reversed emulsion is formed, (f) heating the deodorant reversed emulsion, and (g) using the deodorant reversed emulsion after heating to make the stable deodorant emulsion stick. The method may further comprise storing the stick without precipitation at a temperature in a range from about 1 °C to about 10°C.

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 deodorant emulsion sticks

Deodorant emulsion sticks free of an aluminum salt were prepared. Water, oils (e.g., isopropyl palmitate and dimethicone) and surfactants (e.g., PEG/PPG-18/18 dimethicone, cetyl PEG/PPG-10/1 dimethicone, polyglyceryl-3 diisostearate and/or beheneth-10) were added into a THERMOMIX® blender and mixed with an agitation of 700 rpm for 10 minutes. The temperature was increased to 60°C and the mixture was agitated for 10 minutes with 1000 rpm. The emulsion reversed and the bulk became thicker. Then, the temperature was further increased to 70°C with the same agitation and perlite was added. The wax (e.g., polyethylene) was added to the formula and the temperature was increased to 90°C to let it melt for 10 minutes with an agitation of 600 rpm. Preservatives (i.e., phenoxyethanol and pentylene glycol) were added. Lastly, a magnesium salt (i.e., magnesium oxide) was added and dispersed for 10 minutes to make a deodorant emulsion formula. The deodorant formula was heated to 100°C before being poured to make deodorant emulsion sticks. Table 1 shows the concentration (wt%) of each ingredient in deodorant emulsion sticks A, B, C and D. The deodorant emulsion sticks were then stored immediately in a refrigerator or cooling tunnel at 4°C to avoid precipitation of the magnesium salt.

Table 1. Deodorant emulsion sticks

Example 2. Characteristics of deodorant emulsion sticks

Compared with deodorant glycolic sticks with an aluminum salt as a benchmark, deodorant emulsion sticks A, B and C, not deodorant emulsion stick D, showed a good sensorial profile, improved stability, dispersion, optimal hardness, payload, freshness and a statistically superior antiodor efficacy.

The deodorant emulsion sticks were tested in a droplet test to determine if they comprised a reversed emulsion. Deodorant emulsion sticks A, B and C showed low conductivity and did not interact with water, indicating that the presence of a reversed emulsion in deodorant emulsion sticks A, B and C. Deodorant emulsion stick D showed high conductivity and interacted with water, indicating the absence of a reversed emulsion from deodorant emulsion stick D. In a sensorial test, deodorant emulsion sticks A, B and C showed a similar sensorial profile as the benchmark.

In a hardness test using a texturometer equipment, deodorant emulsion sticks A, B and C showed similar characteristics as the benchmark. In a payload test, deodorant emulsion sticks A, B and C showed similar characteristics as the benchmark.

In antiodor tests, deodorant emulsion sticks A, B and C showed a statistically superior efficacy than the benchmark.

Deodorant emulsion stick A was stable and no precipitation was observed for at least 6 months. Deodorant emulsion sticks B and C showed color change and this instability was due to the fragrance in the sticks.

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.