WO2002087516A2

WO2002087516A2 - Antiperspirant formulations

Info

Publication number: WO2002087516A2
Application number: PCT/EP2002/004509
Authority: WO
Inventors: Charles Herbert Maxwell Moore
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 2001-05-01
Filing date: 2002-04-23
Publication date: 2002-11-07
Also published as: GB0110681D0; WO2002087516A3; AU2002302569A1

Abstract

An antiperspirant stick formulation in which a particulate antiperspirant salt is suspended in a water-immiscible carrier oil of which the major fraction is a hydrocarbon oil, the carrier oil being solidified by a mixture of C14 to C22 linear aliphatic monohydric alcohols, of which mixture the C14 to C16 alcohols representing from 15 to 65% by weight.Preferred formulations also contain minor fractions of castor wax and talc.

Description

Antiperspirant Formulations

The present invention relates to antiperspirant formulations and in particular to anhydrous stick formulations.

During the course of exercise, muscles generate heat and humans have evolved a cooling mechanism in which an aqueous fluid is perspired through eccrine glands in skin. Although such glands are distributed over much of the body, they have a particularly high concentration in certain regions of the body such an in the armpits, (axillae) so that accordingly in such regions, perspiration can become particularly noticeable. Perspiration can also be triggered by emotional stimuli, such as in frightening situations. Many societies seek to avoid the appearance of excess perspiration, for example in axillae, so that an industry has developed to prevent or ameliorate localised perspiration.

Applicators for antiperspirant formulations to control or eliminate localised sweating commonly fall into one of two types, namely non-contact or contact applicators. Non- contact applicators have a number of consumer-perceived benefits such as being particularly hygienic to employ, but some consumers prefer to apply an active substance more precisely and accordingly choose contact applicators.

Contact formulations commonly fall within three classes, namely lotions which are applied often via a roll ball applicator or possibly via a pad or tissue, creams or soft solids which flow when subjected to gentle pressure and are commonly dispensed from a container onto a distributing surface such as a dome and thirdly firm solids which retain their integrity when subjected to gentle pressure. The instant invention is particularly directed to stick formulations. Antiperspirant stick formulations share a number of common features. They contain an antiperspirant active material, which is distributed throughout the stick, a carrier fluid and a structurant, sometimes called a gellant, which transforms the carrier fluid into a solid mass at ambient temperature. However, even within that class of formulations, there are several variations possible. Some formulations employ a hydrophilic carrier in which the antiperspirant active is usually dissolved to at least a substantial extent. Other formulations include a water-immiscible carrier in which the antiperspirant active is commonly suspended in particulate form, and yet others can comprise an emulsion of a hydrophilic phase and a water- immiscible phase.

When the carrier fluid is a water- immiscible oil, it can be structured by various types of structurant, including polymeric materials, fibre-forming gellants and waxes. The present invention is directed particularly to anhydrous stick formulations in which the water-immiscible oil is structured by waxes. For many years, various different classes of waxes have been used or proposed for use to structure anhydrous antiperspirant sticks. Such waxes have included aliphatic monohydric linear fatty alcohols containing at least 12 carbons up to about 24 carbons, of which the most commonly employed alcohol was stearyl alcohol. Whilst several others were named as alternatives to stearyl alcohol, in patent specifications of the last decade, few antiperspirant stick formulations containing them have been found in the course of making the present invention.

Various different classes of oils have been proposed as a carrier fluid in antiperspirant sticks, including silicone oils, especially volatile silicone oils, hydrocarbon oils, and various water-immiscible esters, ethers and alcohols. The choice of carrier fluid has been one which a manufacturer of antiperspirant formulations has made in the light of the target market for the formulation, including such factors as the climate of the territory and the desired sensory characteristics of the stick. Many current formulations on the market employ volatile silicone oils as the main carrier fluid, but this can increase the risk of solvent losses in tropical or sub-tropical climates.

Accordingly, a programme of research was conducted into formulations which employed alternative oils as the main carrier fluid.

What has been found is that some anhydrous stick formulations employing stearyl alcohol as structurant for sticks employing a hydrocarbon oil as the main carrier suffer from a lack of consistency. In particular, such sticks have included many spots, or regions of differing crystallisation. Consistency of a formulation is regarded by manufacturers as being important, in order to guarantee the provision of a product having the same characteristics each time the product is bought, and a constancy of product quality as the same stick is employed. Varying crystallisation affects the physical characteristics of the stick, such as its localised appearance or hardness. Thus it can not only create a stick with a dappled appearance, commonly considered by many cinge a varied performance.

The present inventors have found that there is also a second potential problem for sticks which employ hydrocarbon oils as the main carrier fluid and which are structured with aliphatic monohydric alcohols. This is a problem which is especially pertinent for products intended for employment in warmer climates, such as tropical or adjacent sub-tropical regions. If certain of those alcohols are employed, the stick becomes too soft during storage and use and in the extreme, might even melt sufficiently to leak from the applicator container in which the formulation is transported and sold. Accordingly, is addressing the desire to produce a stick in which the problem of inconsistency is ameliorated or eliminated, the need to preserve a stick that can readily be transported must also be borne in mind.

Wax structured cosmetic sticks are described in the following US patent specifications, amongst others : -

USP 4049792 (Elsnau) USP 4126679 (Davy et al) USP 4425328 (Nabial) USP 4725432 (May) USP 4822603 (Farris et al) and USP4944937 (McCall)

Other specifications disclosing the use of fatty alcohols as structurant include WO 97/16161 and CA 2054478, both assigned to Unilever and CA 1266003 assigned to Procter & Gamble. These other specifications employed a volatile silicone (often called therein a cyclomethicone) as the main or sole carrier fluid and thus provide no teaching of direct relevance to solving the problems identified above in relation to the manufacture of sticks which employ a hydrocarbon as the main carrier fluid.

It is an object of the present invention to provide a wax- based stick employing a hydrocarbon oil as the main carrier fluid which at least ameliorates stick unevenness for alcohol-structured antiperspirant sticks. Summary of the Present Invention

According to the present invention, there is provided an anhydrous antiperspirant stick formulation comprising a particulate antiperspirant salt, a water-immiscible oil and a structurant for the oil in which the water-immiscible oil comprises at least 50% by weight of a hydrocarbon oil, and the structurant comprises a mixture of C14 to C22 linear aliphatic monohydric alcohols of which an alcohol containing up to 16 carbons comprises from 15 to 65% by weight of said mixture .

By the use of a mixture of monohydric linear aliphatic alcohols to structure the water-immiscible oil comprising hydrocarbon oil as the main constituent of the carrier fluid, but by also limiting the proportion of the lower- molecular weight fraction in said mixture, it is possible not only to ameliorate or eliminate the problem of uneven stick consistency indicated above, but also address the difficulties of stick melting. The selection of the window for the lower alcohol proportion in the mixture is of importance. Too low a ratio does not solve the problems the instant inventors are addressing. Thus, for example, a weight ratio of 2 parts cetyl alcohol to 13 parts stearyl alcohol, as in US4944937, is too low, whereas if the mixture were to contain mainly cetyl alcohol, it would be too high, possibly exhibiting undesirable softness and/or excessive deposition on topical application to the skin.

In a second and related aspect there is provided a process for manufacturing an anhydrous antiperspirant stick comprising the steps of : -

a) to c) being in any order, a) introducing into a water-immiscible oil or blend of oils, which comprises at least 50% by weight of a hydrocarbon oil, a structurant comprising a mixture of C14 to C22 linear aliphatic monohydric alcohols of which an alcohol containing up to 16 carbons comprises from 15 to 65% by weight of said mixture ;

b) heating to an elevated temperature at which the structurant is soluble in the oil or blend of oils, c) introducing into oil or blend of oils a particulate antiperspirant salt;

followed by:

d) optionally introducing into a mould, which preferably is a dispensing container, a fluid mass comprising the particulate antiperspirant salt dispersed in a solution of the structurant in the water-immiscible oil or oils and f) cooling or permitting the fluid mass to cool to a temperature at which the oil is structured.

In a third and also related aspect there is provided a cosmetic method for controlling perspiration which comprises applying topically to skin an anhydrous antiperspirant stick formulation comprising a particulate antiperspirant salt, a water-immiscible oil and a structurant for the oil in which the water-immiscible oil comprises at least 50% by weight of a hydrocarbon oil, and the structurant comprises a mixture of C14 to C22 linear aliphatic monohydric alcohols of which an alcohol containing up to 16 carbons comprises from 15 to 65% by weight of said mixture. Detailed Description and Preferred Embodiments of the Present Invention

In the present invention, the oily carrier fluid, as described more fully hereinbelow, for a suspended particulate antiperspirant salt is structured by a waxy structurant which comprises a mixture of C14 to C22 linear aliphatic monohydric alcohols of which an alcohol containing up to 16 carbons comprises from 15 to 65% by weight of said mixture.

The choice of materials constituting the waxy structurant represents a key aspect of the present invention and the solution to the various problems in stick production highlighted hereinabove.

The invention employs a mixture of linear monohydric aliphatic alcohols. In particular, it employs a combination in which significant weight proportions are present of both a lower and a higher molecular weight alcohol. The combination comprises a mixture of aliphatic alcohol containing up to 16 carbon atoms (lower) and aliphatic alcohol containing more than 16 carbon atoms (higher) . It is especially desirable that the aliphatic alcohol containing up to 16 carbon atoms comprises cetyl alcohol. It is furthermore especially desirable that the aliphatic alcohol containing more than 16 carbon atoms comprises stearyl alcohol and/or behenyl alcohol. An especially desirable combination comprises cetyl with stearyl and/or behenyl alcohols.

The lower alcohol is preferably present in a weight proportion of at least 20%, particularly at least 25% of the mixture of alcohols and especially at least 30%. It is highly desirably present in a weight proportion of the mixture of alcohols of not more than 55% and particularly not more than 50%. In some particularly desirable embodiments, the lower alcohol, eg cetyl alcohol comprises from 33 to 45 weight % of the mixture. The higher alcohol constitutes the balance of the mixture.

The total proportion of waxy structurant in the formulation is normally at least 10% by weight thereof, and commonly not more than 30 weight %. In many instances, the weight proportion of said waxy structurant is at least 15% and is conveniently not more than 25% by weight. The aforementioned mixture of linear alcohols can constitute all the waxy structurant, if desired.

It is especially desirable to employ an additional waxy structurant such as one having a melting point of a least 65°C, such as from 65 to 95°C. Within that class of higher melting point waxy structurants, it is preferable to choose materials having a melting point of at least 75°C. The structurant normally comprises at least 5% by weight of the mixture of linear aliphatic alcohols and preferably comprises a major weight fraction of the mixture of aliphatic alcohols and a minor fraction of the higher melting point wax. The components of the wax structurant are more preferably present in a weight ratio of alcohol mixture to higher melting point wax of from 2.5:1 to 4.5:1 and especially from 3:1 to 4:1. It will be understood that the combination of the chosen mixture of aliphatic alcohols with the higher melting point wax is particularly suitable for amelioration of product inconsistency identified hereinabove .

The higher melting point wax can comprise paraffin waxes (having an appropriate melting point) , synthetic waxes such as Fischer-Tropsch waxes, microcrystalline wax, beeswax, spermaceti, carnauba, candellila, montan, ceresin, ozekerite, baysberry or hydrogenated castor oil, sometimes called castor wax. Some preferred higher melting point waxes of the foregoing list comprise hydrogenated plant oils, of which a particularly desirable example comprises castor wax.

In a number of the invention formulations herein, the blend of structurant waxes comprises cetyl alcohol, stearyl alcohol and castor wax in a weight ratio of 4 to 6 : 7 to 10 : 3 to 5 respectively.

The water-immiscible oil or oils preferably comprises at least 25% and especially at least 30% by weight of the formulation. Normally, it constitutes not more than 65% and preferably not more than 50% by weight of the formulation.

In some highly desirable formulations the water-immiscible oil comprises from 35 to 45% by weight of the formulation.

The water-immiscible oil and structurant waxes are preferably present in a weight ratio to each other of from

1.25:1 to 3:1, and particularly from 1.5:1 to 2.5:1.

The choice of water-immiscible oil represents a second key factor in the present invention. Subject to the requirement that at least 50% by weight of the water-immiscible oil is a liquid hydrocarbon, it can be any oil which is liquid in the absence of structurant at 20°C and which is immiscible in water. Such materials are commonly other liquid hydrocarbons, or silicone oils and water-immiscible fatty aliphatic alcohols, fatty alcohol ethers or fatty acid or fatty alcohol esters or aromatic esters. In the context of the water-immiscible oils herein, fatty indicates a residue containing at least 10 carbon atoms. Liquid hydrocarbons employable herein include liquid aliphatic hydrocarbons such as mineral oils or hydrogenated polyisobutene, often selected to exhibit a low viscosity. Further examples of liquid hydrocarbons are polydecene and paraffins and isoparaffins of at least 10 carbon atoms, as well as polyisobutene. Isoparaffins commonly have an average carbon content of between 15 and 30 carbon atoms, for example those available under the trademark ISOPAR (grades L and M) and polyisobutene commonly contains from 10 to 250 isobutene units. Suitable isoparaffins or polyisobutene are available from Presperse under their trademark Permethyl, grades 99A, 101A, 102A, 104A, 106A or 108A. It is particularly preferred to employ a mineral oil and/or isoparaffin. It is highly desirable that the hydrocarbon oil comprises at least 75% by weight of the water-immiscible oils and especially at least 90% by weight of the oil blend. In at least some embodiments, the oil blend is free from any other oil . Herein in the context of the oils, free indicates that less than about 2% by weight of such component oil is present, preferably less than about 1%, and ideally no more than a trace amount, if any. Advantageously, it has been found that such formulations demonstrate noticeably low visible deposits when the formulation is applied to skin.

Alternative water-immiscible oils can be contemplated for the remaining minor fraction of the oil blend and particularly at zero or only a small fraction of the blend as indicated above. Such other oils can vary the attributes of the formulation.

Other water-immiscible oils can include silicone oils, such as a volatile or non-volatile liquid silicone, i.e. liquid polyorganosiloxane . To class as "volatile" herein such a material has a measurable vapour pressure at 20 or 25°C. Typically the vapour pressure of a volatile silicone lies in a range from 1 or 10 Pa up to 2 kPa at 25°C.

Volatile polyorganosiloxanes are commonly polydimethyl- siloxanes, and can be linear dimethicone) or cyclic

(cyclomethicone) or mixtures thereof. Preferred volatile silicone oils comprise from 4 to 6 silicon atoms, especially cyclomethicones . Volatile silicone oils normally by themselves exhibit viscosities of below 10⁵ m²/sec (10 centistokes) , and particularly above 10^"7 m²/sec (0.1 centistokes) , the linear siloxanes normally exhibiting a viscosity of below 5 x 10^"6 m²/sec (5 centistokes) . Nonvolatile silicone oils commonly comprise higher molecular weight dimethicones or alternatively or additionally, comprise polysiloxanes substituted by a aryl group, such as polymethylphenylsiloxanes . Commercially available nonvolatile silicone oils include Dow Corning 556 and Dow Corning 200 series.

Nonetheless, many preferred formulations according to the present invention are free or substantially free from volatile silicone oils, such as below 5% by weight of the carrier liquids, and alternatively or additionally in many instances substantially may be free from non-volatile silicone oils.

Other water-immiscible oils include liquid branched aliphatic monohydric alcohols containing at least 10 and preferably up to 30 carbon atoms.

Suitable aliphatic esters contain at least one long chain alkyl group, such as esters derived from C_λ to C₂₂ alkanols esterified with a C₈ to C₂₂ alkanoic acid or C₆ to Cι₀ alkanedioic acid. The alkanol and acid moieties or mixtures thereof are preferably selected such that they each have a melting point of below 20°C. These esters include isopropyl myristate, lauryl myristate, behenyl behenate, isopropyl palmitate, diisopropyl sebacate and diisopropyl adipate .

Suitable liquid aromatic esters, preferably having a melting point of below 20°C, include fatty alkyl benzoates. Examples of such esters include suitable C₈ to Cι₈ alkyl benzoates or mixtures thereof .

The liquid aliphatic ethers are desirably derived from at least one fatty alcohol, such as myristyl ether derivatives e.g. PPG-3 myristyl ether or lower alkyl ethers of polygylcols such as PPG- 14 butyl ether. Such liquid ethers preferably have a melting point of below 20°C.

In some highly desirable embodiments herein, the formulation comprises : from 35 to 45 % by weight of said mineral oil from 4.5 to 6.5% by weight cetyl alcohol from 7.5 to 10% by weight stearyl alcohol and/or behenyl alcohol and from 3.5 to 4.5% by weight castor wax.

The proportion of particulate antiperspirant salt included in the formulation is commonly selected in the range of from 1 to 30% by weight, and in many instances is at least 5% by weight. Good antiperspirant efficacy is often achievable when the formulation contains from 15 to 26% by weight of the antiperspirant salt.

The antiperspirant active employed herein is desirably an aluminium and/or zirconium astringent salt. Preferred astringent salts include aluminium, zirconium and aluminium/zirconium halides and particularly halohydrate salts, such as chlorohydrates . Aluminium halohydrates are usually defined by the general formula Al₂ (OH) _xQ_y . wH₂0 in which Q represents chlorine, bromine or iodine, x is variable from 2 to 5 and x + y = 6 while wH₂0 represents a variable amount of hydration. The chlorohydrates are especially favoured. In many halohydrates, x represents 3 or 4. Especially effective aluminium halohydrate salts, known as activated aluminium chlorohydrates, are described in EP-A-6739 (Unilever NV et al) , the contents of which specification is incorporated herein by reference.

Zirconium actives can usually be represented by the empirical general formula:

ZrO (OH) _n-_nzB_z . wH₂0 in which z is a variable in the range of from 0.9 to 2.0 so that the value 2n-nz is zero or positive, n is the valency of B, and B is selected from the group consisting of halide, especially chloride, sulphamate, sulphate and mixtures thereof. Hydration is possible to a variable extent and is represented by wH₂0. Preferably B represents chloride and the variable z lies in the range from 1.5 to 1.87. In practice, such zirconium salts are usually not employed by themselves, but as a component of a combined aluminium and zirconium-based antiperspirant.

The above aluminium and zirconium salts may have coordinated and/or bound water in various quantities and/or may be present as polymeric species, mixtures or complexes. In particular, zirconium hydroxy salts often represent a range of salts having various amounts of the hydroxy group. Zirconium aluminium chlorohydrate may be particularly preferred.

Antiperspirant complexes based on the above-mentioned astringent aluminium and/or zirconium salts can be employed. The complex often employs a compound with a carboxylate group, and advantageously this is an amino acid. Examples of suitable amino acids include dl-tryptophan, dl-β- phenylalanine, dl-valine, dl-methionine and β-alanine, and preferably glycine which has the formula CH₃CH (NH₂) C0₂H. Certain highly efficacious examples of complexes are disclosed in US-A-3792068 (Luedders et al) . Various Al/Zr complexes, commonly called ZAG in the literature, contain aluminium, zirconium and chloride with an Al/Zr ratio in a range from 2 to 10, especially 2 to 6, an Al/Cl ratio from 2.1 to 0.9 and a variable amount of glycine.

In calculating the proportion of particulate astringent antiperspirant salt in the formulation, the weight of any water of hydration is normally included.

The choice of antiperspirant active salt is at the discretion of the formulation manufacturer. In some formulations, an aluminium chlorohydrate is preferable, whereas in other formulations a ZAG can be preferred.

In addition to the particulate antiperspirant active, it is often desirable to incorporate an additional particulate material, inert to the oil. Such additional particulates can alter the appearance and/or feel of the formulation. Such additional material can be organic or inorganic or a mixture of both. Suitable organic particulate materials include starch, such as corn starch, or aluminium starch succinate (Dri-Flo™) or particulate polyethylene or particulate metallic stearates. Inorganic particulate materials can include silicates including complex silicates such as talc. Other suitable silicates can include magnesium silicate and aluminum silicates. Materials such as starch and talc can provide an attractive white appearance, and very finely divided materials such as talc or fine polyethylene can impart a silky feel.

The proportion of such additional particulate material in the formulation is at the discretion of the formulator.

Desirably, the proportion is at least 1% and especially at least 5% by weight and is commonly not more than 30% by weight of the formulation. In several preferred embodiments, the proportion of such additional particulate materials is from 10 to 20% by weight of the formulation.

It is particularly desirable for the formulation to contain at least 15% by weight of particulate materials, and commonly not more than 45%, including the antiperspirant salt and additional particulate materials. A preferred range for the combined weight of particulate materials is from 20% by weight and the same or a further preferred range is up to 40% by weight of the formulation.

The particulate materials commonly have a mean particle size of below 40 μm and in many instances from 1 to 25μm.

A yet further preferred component of the formulation comprises a wash-off aid. The wash-off aid is preferably present at a concentration of from at least 0.2% by weight and often not more than 10% by weight of the formulation. Preferred proportions of wash-off aid comprise at least 0.5% and particularly at least 1%, such as up to 5% w/w of the formulation. Expressed in alternative fashion, the wash-off aid is desirably present in a weight ratio of at least 1 part of wash-off aid per 100 parts of the water-immiscible oil, and especially at least 1 part of aid per 40 parts of oil w/w. Parts of wash-off aid and oil herein are by weight. Commonly, the wash-off aid is present at not more than 1 part per 5 parts of the oil and in many instances in not more than 1 part per 10 parts of the oil. The wash-off aid is especially desirable when the oil comprises no more than 25% by weight of volatile oils, for example when it comprises mineral oil.

The wash-off aid herein conveniently can comprise a surface active agent and especially a non- ionic surface active agent or mixture of surface active agents. Preferred non-ionic surface active agents are either esters or ethers. Especially preferred agents comprise polyethylene oxide (POE) or polypropylene oxide (POP) or mixed POE/POP derivatives of fatty alcohols or fatty acids, optionally containing an embedded polyhydric alcohol residue, such as a residue from glycol, glycerol or sorbitol . The average number of POE or POP units in such agents is commonly selected in the range of from 2 to 50 units and in many instances up to 25 units. The eventual average can be achieved employing a single surfactant or by a mixture of surfactants of differing average unit number. The fatty residue in the alcohol or acid moiety commonly contains on average at least 12 carbons and especially up to about 30 carbons. Many suitable surfactants, the fatty residue contains from 14 to 22 carbons, such as an average of C14, C16, C20 or C22, or especially C18. The spread of chain lengths of the fatty residue is often narrow, such as +/- 3 or even 2 carbons about the average value. Particularly preferred surfactants include steareth-n and ceteareth-n or mixtures of any two or more steareth-n or ceteareth-n surfactants, where n is an integer from 2 to 25.

The invention emulsions can comprise, if desired, one or more optional ingredients.

Optional ingredients in compositions of this invention can include deodorants, for example at a concentration of up to about 10% w/w. Suitable deodorant actives can comprise microbicides, including particularly bactericides, such as chlorinated aromatics, including triclosan, Triclorban™, and chlorhexidine and biguanide salts such as those available under the trade mark Cosmosil™.

Herein, an alternative or complementary expression of the present invention, there is provided an anhydrous antiperspirant formulation which essentially comprises in combination from 25 to 60% hydrocarbon oil, from 10 to 25% of an aliphatic linear monohydric alcohol containing from 14 to 22 carbon atoms or mixture of said alcohols, from 3 to 5% of a higher melting wax (melting at a temperature of at least 65°C, from 1% to 30% of a particulate antiperspirant active, from 5 to 15% of a further particulate material and from 0.5 to 5% by weight of a non-ionic wash-off aid, %s being by weight based on the formulation and optionally up to 0.5% by weight of an antioxidant. Preferences for the indicated constituents for such formulations can be in accordance with the foregoing description.

Other optional ingredients include skin benefit agents such as glycerol, and allantoin or lipids, for example in an amount of up to 5%; oil-soluble colorants; skin cooling agents such as menthol and menthol derivatives, often in an amount of up to 2%, all of these percentages being by weight of the formulation. A commonly employed ingredient is a perfume, which is normally present at a concentration of from 0 to 4% and in many formulations from 0.25 to 2% by weight thereof.

The formulations described herein can be produced by any method that has been described previously for preparing an anhydrous stick formulation in which a particulate antiperspirant active is suspended in a water-immiscible oil that is structured into a solid mass by incorporation of a wax or mixture of waxes.

In general, the preparative process comprises introducing the wax or mixture of waxes into the water-immiscible oil or blend of oils and both heating and agitating the resultant mass until the waxes dissolve in the oil forming an homogenous blend. The waxes can be pre-melted if desired. The oil/wax mass is preferably heated to above the melting point of the wax having the highest melting point . In many instances, this is a temperature in the region of from 75 or 80°C to 90°C.

In a separate step, the antiperspirant actives are introduced into the formulation. Although this can be before the mass of oil and wax is heated, it occurs preferably after the mass has been homogenised, and in many instances can occur after the mass has cooled somewhat . A temperature range of below 70°C has been recommended, but a temperature of over 70°C is often acceptable.

The further ingredients of the formulation are introduced at a time of convenience to the producer. Thus, for example, it can be particularly convenient to introduce particulate materials together with the antiperspirant active, and wash- off aids into the oil together with the wax. Any temperature sensitive ingredients, of which perfume can be one, are most preferably added last.

When the formulation has been produced in a fluid form, it is then packaged. This is the commonly achieved by introducing the fluid material into a mould, which is preferably the eventual dispensing container, and thereafter cooled or allowed to cool to below the solidification temperature of the wax, which commonly is at least about 50°C. Alternatively, the formulation could be shaped and cooled into a bar, which is thereafter cut or otherwise fashioned into sticks of the appropriate size which are subsequently wrapped.

The formulations herein are capable of being dispensed using stick dispensers such as those described in WO0008970. The dispenser commonly contains from 10 to lOOg formulation.

The invention formulations can be applied to skin in the conventional manner by wiping the sticks across the surface of the skin, and particularly in the axilla.

Having described the invention in general terms, a specific embodiment thereof will now be described in greater detail by way of example only.

Example 1

In this Example, the formulation described in Table 1 below was made by the following process :-

The oil was introduced into the vessel to provide a carrier. The waxes and wash-aids were introduced into the carrier and the waxes dissolved by heating and stirring to a temperature of 80°C to 100°C which was above the melting point of the highest melting point wax (MP80) . The resultant mobile mixture was then allowed to cool under gentle stirring to the region of about 70 to 75°C, and the particulate antiperspirant active and other particulate material were then stirred in and fully dispersed. When the mixture had reached a temperature of about 5-10 degrees C above its gelling point, the perfume and antioxidant was introduced with stirring and the still mobile mixture was then poured into stick barrels of a conventional dispenser for sticks and allowed to cool in a laboratory environment (ambient temperature of about 23°C) and solidify.

The amount of product deposited (payoff) and the visibility of the deposit were measured using the procedures summarised below, and the results included in Table 1.

Table 1

The antiperspirant stick in Example 1 has an even consistency with relatively few spots or localised regions of differing crystallisation and has a pleasing white appearance with good wash-off properties. The stick is acceptably hard as shown by the amount of product deposited. Moreover, it exhibited good storage and transportation properties as indicated by its high Drop Point temperature of 63°C, rendering the formulation advantageous for transportation and storage within tropical or sub-tropical climates, by not melting at 50°C. Furthermore, in conjunction with its pleasing white appearance, the formulation exhibited only low visible residues when applied to human skin, not only on initial application, but also during a representative period after application (6 hours) . Comparative testing against antiperspirant stick products commercially available in South East Asia or Australasia confirms that the invention formulation exhibits only low visible deposits.

An alternative formulation having similar properties is obtained by substituting behenyl alcohol for stearyl alcohol in the Example 1 formulation.

Procedures - Measurement of Deposits

1. Top of stick was cut with a knife to yield a flat surface for application. One cm of stick was exposed then sample was tared on balance.

2. A weighed strip of abrasive paper ( (Wet&Dry™ lOOOgrit) of width 2.5 cm and length 25 cm was placed on level bench and swiped once with the inverted upright sample, keeping the rate of movement and pressure as even as possible. This amounted to a 20cm application.

3. The sample was swiped across the surface of the abrasive strip a further three times.

4. After the fourth swipe, the weight of product that had been applied to the abrasive strip was measured.

Measurement of visibility of deposits.

1. A sample of antiperspirant formulation was applied to the abrasive strip using method steps 1-4 above.

2. A Minolta Chromameter™ was set to read in the LAB mode. 3. "L" value, a measure of the lightness (whiteness) of residue was measured on five sites in the central 20 cm part of the abrasive strip application area, one minute (for the initial reading) and 6hrs after the 4^th swipe.

The drop point temperature is the minimum temperature at which it is desirable to fill containers using a conventional cast fill process.

Claims

An anhydrous antiperspirant stick formulation comprising a particulate antiperspirant salt, a water- immiscible oil and a structurant for the oil in which the water-immiscible oil comprises at least 50% by weight of a hydrocarbon oil, and the structurant comprises a mixture of C_i4 to C₂₂ linear aliphatic monohydric alcohols of which an alcohol containing up to 16 carbons comprises from 15 to 65% by weight of said mixture .

An antiperspirant composition according to claim 1 in which the alcohol containing up to 16 carbon atoms is cetyl alcohol.

An antiperspirant formulation according to either preceding claim in which the mixture of aliphatic alcohols comprises stearyl alcohol and/or behenyl alcohol .

An antiperspirant formulation according to claim 3 in which the mixture comprises a mixture of cetyl alcohol with stearyl alcohol and/or behenyl alcohol .

An antiperspirant formulation according to any preceding claim in which the alcohol containing up to 16 carbons comprises from 33 to 45% by weight of the mixture .

An antiperspirant formulation according to any preceding claim in which the structurant comprises from 10 to 30% and preferably from 15 to 22.5% by weight of the formulation. An antiperspirant formulation according to any preceding claim in which the structurant comprises a combination of a mixture of linear monohydric alcohols and a wax having a melting point of from 65 to 95°C and preferably from 75 to 85°C.

An antiperspirant formulation according to claim 7 in which the mixture of monohydric alcohols and the high melting point wax are present in a weight ratio in the range of from 2.5:1 to 4.5:1 and preferably from 3:1 to 4:1.

An antiperspirant formulation according to claim 7 or 8 in which the high melting point wax comprises castor wax.

An antiperspirant formulation according to any preceding claim in which the structurant comprises cetyl alcohol, stearyl alcohol and castor wax in a weight ratio of 4 to 6 : 7 to 10 : 3 to 5 respectively.

An antiperspirant formulation according to any preceding claim in which at least 90% by weight of the oil comprises the hydrocarbon oil.

An antiperspirant formulation according to any preceding claim in which the hydrocarbon oil is a mineral oil .

An antiperspirant formulation according to claim 11 or 12 in which the oil is free from volatile silicone oil.

An antiperspirant formulation according to any preceding claim in which the oil comprises from 30 to 70% and preferably from 35 to 50% by weight of the formulation.

An antiperspirant formulation according to claim 14 which comprises from 35 to 45 % by weight of said mineral oil; from 4.5 to 6.5% by weight cetyl alcohol; from 7.5 to 10% by weight stearyl alcohol and/or behenyl alcohol; from 3.5 to 4.5% by weight castor wax.

An antiperspirant formulation according to any preceding claim which contains at least 15% by weight particulate antiperspirant salt.

An antiperspirant formulation according to any preceding claim in which the antiperspirant salt comprises an aluminium chlorohydrate, optionally activated, or an aluminium/zirconium chlorohydrate, or either complexed with an amino acid, preferably glycine .

An antiperspirant formulation according to any preceding claim which contains particulate materials other than an antiperspirant salt, preferably in an amount of at least 5% by weight of the formulation.

An antiperspirant formulation according to claim 16 in which said other particulate material is talc.

An antiperspirant formulation according to any preceding claim which contains a wash-off aid, preferably in an amount of from 0.5 to 5% by weight of the formulation. An antiperspirant formulation according to claim 20 in which the wash-off aid comprises a nonionic ester or ether surfactant, preferably containing at least one alkyl C₁₂ to C₂₄ residue and at least one hydrophylic group containing from 2 to 30 ethylene oxide units.

An anhydrous antiperspirant formulation according to any preceding claim which comprises in combination from 25 to 60% hydrocarbon oil, from 10 to 25% of an aliphatic linear monohydric alcohol containing from 14 to 22 carbon atoms or mixture of said alcohols, from 3 to 5% of a higher melting wax (melting at a temperature of at least 65°C, from 1% to 30% of a particulate antiperspirant active, from 5 to 15% of a further particulate material and from 0.5 to 5% by weight of a non- ionic wash-off aid, %s being by weight based on the formulation.

An antiperspirant formulation according to any preceding claim which comprises :- from 20 to 26% by weight of aluminium chlorohydrate; from 10 to 20% talc and; from 1.5 to 4% by weight of a nonionic surfactant wash- off aid comprising a C16 to C22 aliphatic acyl group and from 2 to 25 ethylene oxide units.

A process for producing an anhydrous antiperspirant formulation comprising the steps of : - a) to c) being in any order, a) introducing into a water-immiscible oil or blend of oils comprising at least 50% by weight of a hydrocarbon oil, a structurant comprising a mixture of C_ι4 to C₂₂ linear aliphatic monohydric alcohols of which an alcohol containing up to 16 carbons comprises from 15 to 65% by weight of said mixture; b) heating to an elevated temperature at which the structurant is soluble in the oil or blend of oils, c) introducing into oil or blend of oils a particulate antiperspirant salt;

followed by:

A cosmetic method of controlling perspiration which comprises applying topically to skin an anhydrous antiperspirant stick formulation comprising a particulate antiperspirant salt, a water-immiscible oil and a structurant for the oil in which the water- immiscible oil comprises at least 50% by weight of a hydrocarbon oil, and the structurant comprises a mixture of C_i4 to C₂₂ linear aliphatic monohydric alcohols of which an alcohol containing up to 16 carbons comprises from 15 to 65% by weight of said mixture .

An antiperspirant formulation substantially as described herein with respect to Example 1.

An anhydrous antiperspirant formulation in which an oil is structured with a combination of wax structurants employing any feature described herein which is novel or any combination of features described herein which is novel.