Field of Invention

The present invention concerns antiperspirant compositions and methods of reducing perspiration. It is particular concerned with such compositions and methods that do not involve the use of aluminium salts.

Background

Traditionally, antiperspirant compositions use astringent aluminium or aluminium-zirconium salts to deliver their antiperspirant benefit. These antiperspirant salts function by blocking the top part of sweat glands and thereby reducing the release of sweat from these glands.

Many parties have investigated alternative, non-aluminium antiperspirant actives and compositions. Some of these have involved reducing the production of sweat by the secretory coil of the sweat glands; however, actives functioning in this manner may be considered therapeutic in nature, which may be undesirably for formulations intended for use as cosmetic products.

Alternative non-aluminium antiperspirant actives and compositions that function by blocking the sweat glands have also been devised.

WO 2010/145905 (Unilever, 2010) discloses the use lamellar phase stabilised oil-in-water emulsions as antiperspirant agents.

EP 550,960 A1 (Unilever, 1992) discloses the use as an antiperspirant active of an amphiphilic material which forms, upon contact with perspiration, a water-insoluble liquid crystal phase of greater than one dimensional periodicity.

WO 2018/111664 (Colgate, 2018) discloses antiperspirant compositions comprising a zinc- based antiperspirant active, a thickener comprising a C14-C22 fatty acid salt and a carrier comprising a polyhydric alcohol, optionally with water.

WO 2019/206466 (Beiersdorf, 2019) discloses antiperspirant compositions comprising alkaline earth metal salts and carboxylic acids, but is silent on the use of zinc salts. WO 2020/094568 (Unilever. 2020) discloses oil-in-water emulsions comprising liquid fatty acids and water-soluble metal salts capable of forming a water-insoluble salt with the liquid fatty acid.

Summary of Invention

It is an objective of the present invention to reduce perspiration from the surface of the human body, particularly in the underarm regions, otherwise known as the axillae.

It is a further objective of the present invention to reduce perspiration from the surface of the human body without the use of astringent aluminium or zirconium salts.

In a first aspect of the invention, there is provided an ethanolic solution comprising a liquid C10-C22 fatty acid and a water-soluble zinc salt.

In preferred embodiments, the water-soluble zinc salt is capable of forming a solid, waterinsoluble salt with the liquid C10-C22 fatty acid at a pH of greater than 6, particularly at a temperature of 37°C.

In a second aspect of the invention, there is provided a method of reducing perspiration comprising the topical application of an ethanolic solution according to the first aspect of the invention.

In a third aspect of the invention, there is provided a method of manufacture of an antiperspirant composition comprising the steps of dissolving a liquid C10-C22 fatty acid in an ethanolic solution and adding a water-soluble zinc salt to the ethanolic solution, before or after the liquid C10-C22 fatty acid is dissolved therein, the water-soluble zinc salt being capable of forming a water-insoluble salt with the C10-C22 fatty acid at a pH of greater than 6.

The method of reducing perspiration is generally on the skin of the human body, in particular the axillae.

Generation of an active antiperspirant agent occurs in situ, i.e. the water-insoluble zinc salt of the C10-C22 fatty acid is formed on the skin of the human body; in particular, in the sweat ducts present in the skin of the human body, especially in the axillae. Generation of the active antiperspirant agent is “pH-triggered”, being caused by the pH of the sweat on the skin being relatively high, typically pH ca. 6 to 7. This enables the water- soluble zinc salt to form a gel with the fatty acid and lead to an antiperspirancy benefit.

Detailed description

Herein, all amounts, parts, percentages, and ratios are by weight and relate to the total composition, unless otherwise indicated. This also applies to the examples.

Herein, the term comprising is used non-exhaustively.

Herein, preferences expressed with regard to one aspect of the invention apply, to the extent possible, with regard to any other aspect of the invention.

Herein, preferences expressed with regard to one feature are preferably used in combination with preferences expressed for one or more other features.

Herein, when a component is referred to in the singular, it is to be understood that multiple components of the type referred to could be present and all should be included in calculating any amount or ratio specified.

Herein, states of matter such as solid, liquid and gas relate to the specified state of matter at 25°C and atmospheric pressure. For example, the “liquid” C10-C22 fatty acid used in the present invention is liquid at 25°C and one atmosphere pressure.

Herein, quoted viscosities are measured at 37°C and at a shear rate of 0.01 s’ ¹ .

Herein, the terms gel and gelation refer to states of matter and formations of states of matter that might comprise crystalline solids, amorphous solids, or viscous states of matter capable of blocking sweat glands. The gel referred to is typically of viscosity of at least 2 Pa.s, preferably at least 5 Pa.s, more preferably at least 10 Pa.s, and most preferably at least 100 Pa.s. The “gel” may be a solid, crystalline or amorphous, or may have a viscosity of up to 1000 Pa.s.

Herein, references to “compositions” [of the invention] equate to “ethanolic solutions” [of the invention]. Herein, “ethanolic solution” refers to a solution having ethanol as a major component, typically present at 25% or greater, preferably present at 50% or greater and more preferably present at 60% or greater.

Ethanol is an essential component of compositions of the invention. Preferably, ethanol comprises at least 25%, more preferably at least 50% and most preferably at least 60% by weight of the total composition, excluding any volatile propellant that may be present therein.

In preferred compositions, the ethanol is accompanied by water. Particularly preferred compositions are homogeneous aqueous-ethanol solutions. The ratio of ethanol to water is preferably from 1 : 1 to 4: 1 , more preferably from 3: 2 to 7: 2 and most preferably from 2: 1 to 3: 1 . These ratios are found to give the best solubilisation of both the unsaturated fatty acid and the water-soluble zinc salt. In addition, the presence of water reduces any possible irritancy problems with the compositions.

The C10-C22 fatty acid used in accordance with the invention must be a liquid. Such fatty acids are typically unsaturated, meaning that they have one or more unsaturated carboncarbon bonds.

Preferably, the C10-C22 fatty acid used in accordance is liquid at 20°C and more preferably it is liquid at 10°C. Having a relatively low melting point for the fatty acid can enhance the low temperature storage stability for compositions of the invention.

The C10-C22 fatty acid preferably has from 14 to 20 carbon atoms, more preferably from 16 to 18 carbon atoms and most preferably 18 carbon atoms. Preferred C18 fatty acids are unsaturated, having at least one double bond. Particularly preferred fatty acids are oleic, linoleic, linolenic and ricinoleic acid. Especially preferred are oleic and ricinoleic acid.

Mixtures of C10-C22 fatty acids may be used in some embodiments.

The total amount of C10-C22 fatty acid in compositions of the invention is preferably from 3%, more preferably from 4.5% and most preferably from 6%. Independently and in conjunction with each of the preferred lower levels indicated above, the total amount of C10-C22 fatty acid is preferably up to 15%, more preferably up to 12.5% and most preferably up to 10%. In certain preferred embodiments, the total amount of C10-C22 fatty acid is from 5 to 10%.

The total amount of zinc salts in compositions of the invention is preferably from 0.75%, more preferably from 1.0% and most preferably from 1.3%. Independently and in conjunction with each of the preferred lower levels indicated above, the total amount of water-soluble zinc salt is preferably up to 3.0%, more preferably up to 2.5% and most preferably up to 2%.

In certain preferred embodiments, the total amount of water-soluble zinc salts is from 1.5 to 2.0%.

The molar ratio of the C10-C22 fatty acid to the cation of the water-soluble zinc salt (divided by its valence), is preferably selected to be from 1 : 2 to 2: 1 , more preferably from 2: 3 to 3: 2 and most preferably about 1 : 1. In this way, neither too much of the C10-C22 fatty acid nor too much of the water-soluble zinc salt is wasted. To clarify, these ratios may be expressed as preferably from 33: 67 to 67: 33; more preferably from 40: 60 to 60: 40 and most preferably about 503: 50.

The molar ratio of the water-soluble zinc salt to the C10-C22 fatty acid is preferably selected to be from. 1 : 4 to 1 : 1 , more preferably from 1 : 3 to 2: 3 and most preferably about 1 : 2. To clarify, these ratios may be expressed as preferably from 20: 80 to 50: 50; more preferably from 25: 75 to 40: 60 and most preferably about 33: 67.

In preferred embodiments, the water-soluble zinc salt is solubilised in the ethanolic solution.

The ability of the water-soluble zinc salt to form a water-/nso/c/b/e salt with the C10-C22 fatty acid at a pH of greater than 6 is a key feature of the present invention. This may be tested by bringing together the components at a pH of greater than 6 and a temperature of 20°C, 25°C or 37°C. In a preferred method of testing, the components are co-formulated at a pH of 3.5 and the pH of the mixture is then adjusted to greater than 6 using a base.

Herein, “water-insoluble” means having a solubility in water of less than 10 g/L at 25°C, preferably less than 1 g/L. An emulsifier is an optional component of the composition of the invention. Any emulsifier capable of emulsifying the C10-C22 fatty acid in water at a temperature of 20°C may be used. Mixtures of emulsifiers may also be used.

When employed, the emulsifier or mixture of emulsifiers preferably comprises a nonionic emulsifier. In certain preferred embodiments, a mixture of emulsifiers is used, such as a mixture of nonionic emulsifiers or a mixture of a nonionic emulsifier and an anionic emulsifier.

The total amount of emulsifier in compositions of the invention may be from 0.5%, preferably from 1.0% and most preferably from 1.3%. Independently and in conjunction with each of the preferred lower levels indicated above, the total amount of emulsifier is preferably up to 10%, more preferably up to 7.5% and most preferably up to 5%.

The ratio of the emulsifier to the C10-C22 fatty acid is preferably from 1 : 10, more preferably from 1 : 8 and most preferably from 1 : 6. Independently and in conjunction with each of the preferred ratios indicated above, the ratio of the emulsifier to the C10-C22 fatty acid is preferably up to 2: 3, more preferably up to 1 : 2 and most preferably up to 1 : 3.

In certain preferred embodiments, the emulsifier may comprise a polyglyceryl ester, such as polyglyceryl-3 stearate. When the emulsifier comprises such materials, the ratio of the emulsifier to the C10-C22 fatty acid is preferably from 1 : 10, more preferably from 1 : 7 and most preferably from 1 : 4. Independently and in conjunction with each of the preferred ratios indicated above, the ratio of the emulsifier to the C10-C22 fatty acid is preferably up to 1 : 1 , more preferably up to 9: 11 and most preferably up to 2: 3. In an especially preferred embodiment, the ratio of the polyglyceryl ester containing emulsifier to the C10-C22 fatty acid is from 1 : 4 to 2: 3, i.e. from 20: 80 to 40: 60.

In certain preferred embodiments, the emulsifier comprises a linear alkyl ethoxylate, such as Steareth-20. Preferred linear alkyl ethoxylates have at least 10 ethoxylate units per molecule and particularly preferred linear alkyl ethoxylates have at least 15 ethoxylate units per molecule.

When the emulsifier consists of only linear alkyl ethoxylate, the ratio of the emulsifier to the C10-C22 fatty acid is preferably from 5: 95 to 30:70, more preferably from 10: 90 to 28:72 and most preferably from 15: 85 to 25: 75. The preferred emulsifiers and preferred ratios of emulsifier to the C10-C22 fatty acid are important for the stability of the composition, by which is meant its phase stability, i.e. its lack of phase separation over an extended period.

A preferred additional feature is a thickener. A thickener serves to increase the viscosity of compositions of the invention and can enhance the consumer appeal thereof. The thickener can also aid the phase stability of the composition and/or the ability of the composition to be retained within a roll-on dispenser without leakage.

Thickeners suitable for use with the present invention include cationic and nonionic polymers, particularly naturally derived cationic and nonionic polymeric thickeners, examples including guar gum and derivatives and cellulose derivatives, such as hydroxyethylcellulose. Especially preferred thickeners are cationic polymers, in particular guar gum and/or derivatives thereof.

A thickener is typically employed at from 0.1 to 10% of the total composition. In preferred embodiments, the thickener is present at from 0.2 to 5% and in more preferred embodiments it is present at from 0.3 to 3% of the total composition.

In a preferred embodiment, the composition of the invention is stored in a roll-on dispenser and is dispensed therefrom. Compositions of the invention are particularly suited to being stored and dispensed from a roll-on dispenser designed to be kept in an inverted position for extended periods. For the avoidance of doubt, “an inverted position” for a roll-on dispenser is with the roll-on applicator, usually a ball, located below the reservoir containing the composition.

A thickener is a preferred component of compositions to be stored and dispensed from a rollon dispenser.

In another preferred embodiment, the composition of the invention is stored in a pump spray or squeeze spray dispenser and is dispensed therefrom.

A preservative is a preferred additional component in compositions of the invention. A preservative serves to reduce or eliminate microbial contamination of compositions of the invention. Preservatives are typically employed at a total level of from 0.05 to 3%, preferably at from 0.1 to 2% and most preferably at from 0.4 to 1%.

Suitable preservatives for use with the present invention include 2-phenoxyethanol, iodopropynyl butylcarbamate, C1-C3 alkyl parabens, sodium benzoate, caprylyl glycol and EDTA. Particularly preferred preservatives are 2-phenoxyethanol, iodopropynyl butylcarbamate, sodium benzoate, caprylyl glycol and EDTA and especially preferred are 2- phenoxyethanol and iodopropynyl butylcarbamate.

An antimicrobial deodorant active is a preferred an additional component in compositions of the invention. Such components serve to reduce or eliminate body odour by reducing or otherwise impeding the function of microbes on the skin of the body responsible for malodour generation.

The antimicrobial deodorant active may also be a preservative for the composition.

When employed, the anti-microbial deodorant agent is typically incorporated into the composition at from 0.01% to 3% and particularly at from 0.03% to 0.5%.

Preferred anti-microbial deodorant agents have a minimum inhibitory concentration (MIC) of 1 mg. ml ^-1 or less, particularly 200 pg. ml' ¹ or less, and especially 100 pg. ml' ¹ or less. The MIC of an anti-microbial agent is the minimum concentration of the agent required to significantly inhibit microbial growth. Inhibition is considered “significant” if an 80% or greater reduction in the growth of an inoculum of Staphylococcus epidermidis is observed, relative to a control medium without an anti-microbial agent, over a period of 16 to 24 hours at 37°C. Details of suitable methods for determining MICs can be found in “Antimicrobial Agents and Susceptibility Testing”, C.Thornsberry, (in “Manual of Clinical Microbiology”, 5 ^th Edition, Ed. A. Balows et al, American Society for Microbiology, Washington D.C., 1991). A particularly suitable method is the Macrobroth Dilution Method as described in Chapter 110 of above publication (pp. 1101-1111) by D. F. Sahm and J. A. Washington II. MICs of antimicrobials suitable for inclusion in the compositions of the invention are triclosan: 0.01-10 pg. ml' ¹ (J. Regos et al., Dermatologica (1979), 158: 72-79) and farnesol: ca. 25 pg. ml' ¹ (K. Sawano, T. Sato, and R. Hattori, Proceedings of the 17 ^th IFSCC International Conference, Yokahama (1992) p.210-232). By contrast ethanol and similar alkanols have MICs of greater than 1 mg. ml' ¹ . Suitable organic anti-microbials are bactericides, for example quaternary ammonium compounds, like cetyltrimethylammonium salts; chlorhexidine and salts thereof; and diglycerol monocaprate, diglycerol monolaurate, glycerol monolaurate, and similar materials, as described in “Deodorant Ingredients”, S. A. Makin and M.R. Lowry, in “Antiperspirants and Deodorants”, Ed. K. Laden (1999, Marcel Dekker, New York). More preferred antimicrobials for use in the compositions of the invention are polyhexamethylene biguanide salts (also known as polyaminopropyl biguanide salts), an example being Cosmocil CQ™ available from Zeneca PLC, preferably used at up to 1% and more preferably at 0.03% to 0.3% by weight; 2',4,4'-trichloro,2-hydroxy-diphenyl ether (triclosan), preferably used at up to 1% by weight of the composition and more preferably at 0.05-0.3%; and 3,7,11- trimethyldodeca-2,6,10-trienol (farnesol), preferably used at up to 1% by weight of the composition and more preferably at up to 0.5%.

Other suitable organic antimicrobial agents are transition metal chelators, as described in W001/52805, for example. Transitional metal chelators having a binding coefficient for iron(lll) of greater than 10 ²⁶ , for example diethylenetriaminepentaacetic acid and salts thereof are preferred.

Antioxidants may be advantageously employed in certain compositions, in particularly those comprising unsaturated fatty acid. Antioxidants that may be used include butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and pentaerythrityl tetra-di-t-butyl hydroxyhydrocinnamate. Antioxidants may be used at from 0.05 to 5%, in particular at from 0.075 to 2.5% and especially at from 0.1 to 1%.

Certain sensory modifiers are further desirable components. Such materials are preferably used at a level of up to 20% by weight of the composition. Emollients, humectants, volatile oils, non-volatile oils, and particulate solids which impart lubricity are all suitable classes of sensory modifiers. Examples of such materials include cyclomethicone, dimethicone, dimethiconol, isopropyl myristate, isopropyl palmitate, talc, finely-divided silica (e.g. Aerosil 200), particulate polyethylene (e.g. Acumist B18), polysaccharides, corn starch, C12-C15 alcohol benzoate, PPG-3 myristyl ether, octyl dodecanol, C7-C14 isoparaffins, di-isopropyl adipate, isosorbide laurate, PPG-14 butyl ether, glycerol, hydrogenated polyisobutene, polydecene, titanium dioxide, phenyl trimethicone, dioctyl adipate, and hexamethyl disiloxane. Fragrance is also a desirable additional component. Suitable materials include conventional perfumes, such as perfume oils and also include so-called deo-perfumes, as described in EP 545,556 and other publications. Levels of incorporation are preferably up to 4% by weight, particularly from 0.1% to 2% by weight, and especially from 0.7% to 1.7% by weight.

Examples

Table 1 gives details of Example 1 and Comparative Examples A and B. These examples and comparative examples each had the same molar concentration of divalent metal ion.

Table 1

Example 1 was prepared as follows. The Klucel was dispersed in the water and ethanol using a magnetic stirrer until the Klucel was fully swollen. The zinc chloride was then dissolved into the mixture with magnetic stirring. Finally, the oleic acid was dissolved into the mixture, again with magnetic stirring.

Comparative Example A was prepared as follows. A pre-mix containing half of the total water, the preservatives and Jaguar S thickener was prepared. The Jaguar S was sheared into the vessel containing the other ingredients using a Silverson L4RT homogeniser. Once prepared this was left overnight at ambient temperature to allow the mixture to become fully swollen. The remaining half of the water was placed in a separate vessel along with the calcium chloride dihydrate and Steareth-20. This was heated to 70°C whilst stirring. The oleic acid was then added and the mixture was homogenised to produce a homogeneous milky white pre-mix. The two pre-mixes described above were then combined and homogenised.

Example 1 gave a significant Sweat Weight Reduction (SWR) of 44% in a standard hot room test performed on the backs of multiple panellists. Comparative Example A gave a SWR benefit of 5%, which was not statistically significant. This shows the benefit of ethanolic systems comprising zinc salts and oleic acid over emulsion systems comprising calcium salts and oleic acid.

In a further study, Example 1 and Comparative Example B were flooded with model sweat. Example 1 solidified in 20-30 seconds in the model sweat, whereas Comparative Example B took 3-4 hours to solidify. This illustrates the greater speed to gelation and potential sweat duct blockage for the composition of the invention over an analogous calcium chloride plus oleic acid composition.

Stability studies on Example 1 revealed that it had good stability, maintaining rheological stability for 12 weeks at 45°C.

Table 2 gives details of other examples according to the invention that may be prepared in analogous manner to Example 1.

Table 2