FIELD OF THE INVENTION This invention relates to a process to manufacture an antiperspirant composition. More particularly, the invention is directed to a process to manufacture solid cosmetic antiperspirant compositions in the form of a stick.

BACKGROUND OF THE INVENTION

Antiperspirant compositions are applied to the underarm area. It is desirable to include ingredients that provide a skin care benefit to this underarm area. The difficulty with formulating antiperspirant products to provide a skin care benefit is that many skin care benefit agents from the cosmetics field are difficult to formulate into antiperspirant products due to incompatibility with common ingredients in antiperspirants, such as the antiperspirant active, or have negative interactions such that sensory problems are introduced into the product.

One such class of ingredients is the hydroxyalkyl ureas. WO 2008/145582 A1 discloses on page 15 an antiperspirant incorporating hydroxyethyl urea in combination with glycerol.

A problem with inclusion of this class of materials is that the resulting product feels gritty to the user, which is undesirable for a product that is applied to the skin.

We have found that a stable non-gritty solid antiperspirant product containing a hydroxyalkyl urea can be provided by application of specific process steps. SUMMARY OF THE INVENTION

In a first aspect, the invention is directed to process of manufacture of a solid cosmetic antiperspirant composition in the form of a stick comprising from 0.0005 to 3 wt.% of a hydroxyalkyl urea, the process comprising the steps of:-

(a) providing a stick dispenser comprising a stick barrel;

(b) providing a first mixture comprising a solvent and gellant and heating the mixture to a temperature above the melting point of the gellant;

(c) providing a second mixture comprising a hydroxyalkyl urea and a carrier material selected from the group consisting of: a natural oil that comprises a triglyceride of an unsaturated carboxylic acid, and polyalkylene glycols having a molecular weight of up to 650 Daltons, and heating this mixture to a temperature of 65°C or above;

(d) mixing together of the first and second mixtures;

(e) addition of an antiperspirant active to the mixture (d); and,

(f) filling a stick barrel with the mixture (e).

Preferably the first mixture is heated to a temperature of from 65°C to 120°C, preferably 70°C to 100°C, more preferably 80°C to 95°C

Preferably for step d), each of the two mixtures is at a temperature of 60°C to 100°C, preferably 65°C to 90°C, more preferably 75°C to 85°C.

Preferred hydroxyalkyl ureas have the following formula:

wherein R-i , R ₂ , R3 and R each independently represent: Hydrogen, a C-i- alkyl, or a C2-6 hydroxyalkyl group, with the proviso that at least one of the groups R-i, R2, R3 and R ₄ is a C2-6 hydroxyalkyl group. A particularly preferred hydrox alkyl urea is a hydroxyethyl urea of structure:

Preferably the natural oil comprises a triglyceride of an unsaturated carboxylic acid containing 1 , 2, or 3 olefinic bonds.

Preferably the natural oil comprises a triglyceride of an unsaturated carboxylic acid containing from 14 to 22 carbon atoms, preferably 16-20 carbon atoms, more preferably 18 carbons Preferably the natural oil comprises sunflower seed oil.

Preferably the polyalkylene glycol carrier material is selected from the group consisting of: polybutylene glycol, polypropylene glycol, polyethylene glycol and mixtures thereof.

The polyalkylene glycol carrier material has a molecular weight of up to 650 Daltons, preferably from 360 to 460 Daltons.

Preferably the carrier material is selected from: sunflower seed oil; and, polyethylene glycol having a molecular weight of from 360 to 460 Daltons and mixtures thereof. Preferably the antiperspirant stick composition comprises no more than 1 wt.% of water, more preferably the stick composition is anhydrous.

Preferably the hydroxyalkyl urea is included at a level of from the hydroxyalkyl urea is included at a level of from 0.0005 to 2.5 wt.%, more preferably from 0.001 to 2 wt.%.

A preferred antiperspirant active comprises an aluminium salt, preferably an aluminium/zirconium tetrachlorohydrex glycine complex.

The invention further relates in a second aspect to a solid antiperspirant stick obtained by the process of the first aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term "comprising" means including, made up of, composed of, consisting and/or consisting essentially of.

All percentages quoted are wt.% based on total amount in the composition unless otherwise stated.

The invention is based on the finding that a stable non-gritty solid antiperspirant stick product containing a hydroxyalkyl urea can be provided by way of the process steps outlined herein.

Antiperspirant Active

The composition comprises from 0.1 to 40 wt.%, preferably from 5 to 40 wt.% of antiperspirant active. Antiperspirant active is preferably incorporated in an amount of at least 5 wt.%, more particularly from 20 to 30 wt.% of the composition. More preferably the antiperspirant active is present in an amount of from 22 to 27 wt.% of the composition.

Antiperspirant actives for use herein are often selected from astringent active salts, including, in particular, aluminium, zirconium and mixed

aluminium/zirconium salts, including both inorganic salts, salts with organic anions and complexes. Preferred astringent salts include aluminium, zirconium and aluminium/zirconium halides and halohydrate salts, such as chlorohyd rates and activated aluminium chlorohyd rates.

Aluminium halohydrates are usually defined by the general formula

Al2(OH) _x Qy ^» wH ₂ O in which Q represents chlorine, bromine or iodine, x is variable from 2 to 5 and x+y=6 while wH ₂ O represents a variable amount of hydration. Zirconium actives can usually be represented by the empirical general formula: ZrO(OH)2n-nzB _z ^» wH ₂ 0 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 chloride, other halide, sulfamate, sulfate and mixtures thereof. Possible hydration to a variable extent is represented by wH ₂ O. In one embodiment 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. Aluminium zirconium 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- -phenylalanine, dl- valine, dl-methionine and β-alanine, and preferably glycine which has the formula CH ₂ (NH ₂ )COOH.

It is highly desirable to employ complexes of a combination of aluminium halohydrates and zirconium chlorohyd rates together with amino acids such as glycine, examples of which are disclosed in U.S. Pat. No. 3,792,068 (Luedders et al).

Certain of those Al/Zr complexes are commonly called AZG in the literature. AZG actives generally contain aluminium, zirconium and chloride with an Al/Zr ratio in a range from 2 to 10, especially 2 to 6, an AI/CI ratio from 2.1 to 0.9 and a variable amount of glycine. Actives of this type are available from suppliers that include Summit Reheis. In one preferred embodiment the active is enhanced activity or activated aluminium/zirconium halohydrate, in particular, activated aluminium- zirconium tetrachlorohydrex glycine (AAZG).

Other actives which may be utilized include astringent titanium salts, for example those described in GB 2299506A.

The proportion of solid particulate antiperspirant salt in a suspension composition normally includes the weight of any water of hydration and any complexing agent that may also be present in the solid active.

In one or more embodiments it is desirable that the mean particle size of the antiperspirant salts is within the range of 0.1 to 100 micron with a mean particle size that is often from 3 to 30 microns, more particularly from 5 to 35 microns, and certain embodiments of interest from 10 to 25 microns. The particulate antiperspirant active may be present in the form of hollow spheres or dense particles (by which is meant particles which are not hollow) at the discretion of the manufacturer. To reduce the appearance of visible deposits on the skin to which the composition is applied or on clothing which comes into contact with the composition, it is preferable for the particles to be substantially free from hollows. Hollows can be eliminated by crushing the spheres.

The most preferred antiperspirant salt is an aluminium/zirconium

tetrachlorohydrex glycine complex.

Hydroxyalkyl Urea

Hydroxyalkyl ureas may be derived from urea (NH ₂ CONH ₂ ). Preferred hydroxyalkyl ureas have the formula:

wherein R-i , R ₂ , R3 and R ₄ each independently represent: Hydrogen, a C-i- alkyl, or a C _2- 6 hydroxyalkyl group, with the proviso that at least one of the groups R-i, R ₂ , R3 and R ₄ is a C _2- 6 hydroxyalkyl group.

A particularly preferred hydrox alkyl urea is hydroxyethyl urea, of structure:

H The hydroxyalkyl urea is present at a level of from 0.0005 to 3 wt.%, preferably from 0.0005 to 2.5 wt.%, more preferably from 0.001 to 2 wt.%, most preferably from 0.01 to 2 wt.%. Preferably the hydroxyalkyl urea is included is included as a premix with the carrier material.

Carrier Material

The carrier material is selected from the group consisting of: a natural oil that comprises a triglyceride of an unsaturated carboxylic acid, and polyalkylene glycols having a molecular weight of up to 650 Daltons.

Preferably the natural oil comprises a triglyceride of an unsaturated carboxylic acid containing 1 , 2, or 3 olefinic bonds.

Preferably the natural oil comprises a triglyceride of an unsaturated carboxylic acid containing from 14 to 22 carbon atoms, preferably 16-20 carbon atoms, more preferably 18 carbon atoms. Preferably the natural oil comprises sunflower seed (Helianthus annuus) oil.

Preferably the polyalkylene glycol carrier material is selected from the group consisting of: polybutylene glycol, polypropylene glycol, polyethylene glycol and mixtures thereof.

The polyalkylene glycol carrier material has a molecular weight of up to 650 Daltons, preferably from 360 to 460 Daltons.

Preferably the carrier material is selected from: sunflower seed oil, polyethylene glycol having a molecular weight of from 360 to 460 Daltons and mixtures thereof. The preferred level of carrier material present in the composition is from 0.1 to 10 wt.%, preferably from 0.5 to 7.5 wt.% A preferred ratio of hydroxyalkyl urea to carrier material is from 1 :5 to 2:1 , more preferably 1 :2.5 to 1 :1 .

Form of the Invention

The process is for the manufacture of a solid antiperspirant composition in the form of a stick.

Preferably the stick composition comprises no more than 1 wt.% of water, more preferably the stick composition is anhydrous. The stick composition is solid, in that it retains its shape in the form of a stick without lateral support. The solid form is usually provided by way of a gellant.

The hardness of solid sticks is commonly measured using a conventional penetrometer test in which a Seta needle weighing 50g and having a tip angle of 9° 10' +/- 15' is allowed to drop for 5 seconds from surface contact with the test material. Desirably, the needle penetrates less than 30mm, preferably less than 20mm and especially up to 15mm, by virtue of the concentration of gellant or gellant mixture employed to solidify the composition. An alternative method of measuring hardness employs a Stable Micro Systems TA.XT2i Texture Analyzer and Texture Expert Exceed™ software to generate the motion profile of a spherical probe employed in the method. A specific protocol involves a metal sphere, of diameter 9.5mm, is attached to the underside of a 5kg load cell, and positioned just above the sample surface. Under control of Expert Exceed™ software, the sphere is indented into the sample at an indentation speed of 0.05mm/s for a distance of 7 mm and reversed to withdraw the sphere from the sample at the same speed. Data comprising time(s) distance (mm) and force (N) is acquired at a rate of 25 Hz. The hardness H at a penetration of 4.76 mm is calculated using the formula:

H=F/A

in which H is expressed in N/mm ² , F is the load at the same travelled distance in N, and A is the projected area of the indentation in mm ² . This area can be calculated geometrically and is equal to the area of a diametral plane of the sphere, i.e., π x (4.76) ² mm ² . A measured hardness of at least 0.5N/mm ² indicates a solid stick.

Preferred gelling agents comprise: from 10 to 25 wt.% of a fatty alcohol wax; and, from 1 to 15 wt.% of hydrogenated castor oil. In the stick composition, one or more further ingredients may be included, such as further oils, non-volatile emollient oil, silicone elastomers, gellants and fragrances.

Suitable solvents include silicone oils, which may be volatile or non-volatile.

Particularly useful volatile oils are linear siloxanes containing from 3 to 9 silicon atoms, and cyclic siloxanes having from 4 to 6 silicon atoms, commonly referred to as cyclomethicone (e.g. cyclopentasiloxane, known as D5). Examples of commercially available volatile silicone oils include oils having grade designations 344, 345, 244, 245 and 246 from Dow Corning Corporation. Particularly useful non-volatile silicone oils are polyalkyl siloxanes. Commercially available non-volatile silicone oils include products available under the trademarks Dow Corning 556 and Dow Corning 200 series

Solvents may be included at levels of from 5 to 75 wt.%, preferably 10 to 60 wt.%, more preferably 15 to 55 wt.%, or even 18 to 50 wt.%. Suitable non-volatile emollient oils include the non-volatile silicone oils as previous described. Preferred non-volatile emollient oils are hydrocarbon oils, ester oils and ether oils.

Particularly preferred non-volatile emollient oils are Cs to Cie alkyl benzoate esters and PPG-14 butyl ether.

Non-volatile emollients, if present, may be present at a level of from 5 to 35 wt.%, preferably from 10 to 25 wt.%.

Silicone elastomers otherwise known as crosslinked dimethicone may be included, and are particularly useful in soft solid compositions,. Elastomers tend to thicken oils, often by absorbing them and swelling. The elastomer is typically crosslinked by reacting a silicone hydride with an α-ω olefinically unsaturated dialkylene. If present, the elastomer is advantageously present at a concentration of at least 0.1 % up to 8%, and especially from 0.5% to 5% by weight of the antiperspirant composition. Elastomers are commercially available, for example from Dow Corning Inc and Shinetsu, and typically are supplied in a carrier oil that is frequently a cyclomethicone.

Preferred gellants include fatty alcohols having a melting range of from 55 to 75°C, and in many desirable embodiments, in the range of from 58 to 73°C. One or a blend of fatty alcohols can be employed, such as cetyl alcohol, stearyl alcohol, eicosyl alcohol and behenyl alcohol, or mixtures of any two or more thereof. Commercial fatty alcohols, though nominally and predominantly one specified alcohol often comprise a minor fraction, such as up to 5 or 6% by weight in total, of homologues differing by 2, 4 or even 6 carbons. When present, fatty alcohol is preferably present at a level of from 10 to 30 wt.%, preferably 1 1 to 20 wt.%, more preferably from 12.5 to 18.5 wt.% Alternative gellants include waxes, preferably having a melting point in the range of from 70 to 95°C and especially from 75 to 90°C. Such waxes are often selected from hydrocarbon waxes and ester waxes, that can be derived from natural sources or synthesised. Suitable hydrocarbon waxes include mineral wax, microcrystalline wax, Montana wax, paraffin wax, and low molecular weight polyethylene, such as from 300 to 600 Daltons. Suitable ester waxes can be derived from unsaturated natural oils, such as plant-originating triglyceride oils by hydrogenation and optionally dehydroxylation (where the substituent contains at least one hydroxyl group as in castor oil). Suitable ester waxes include castor wax, candelilla wax, carnauba wax, beeswax and spermeceti wax. Natural waxes such as beeswax include a range of different chemical classes. Synthetic esters often comprise aliphatic monoesters containing at least 30 carbons, and indeed may be isolated natural products such as beeswax, or be derived from them or be the same compounds.

For solid sticks, a highly preferred gelling system is based on a fatty alcohol with a co-gellant wax as described above. Preferably the fatty alcohol would be present at a level of from 1 1 to 20 wt.%, and the wax would be present at a level of from 2 to 8 wt.%.

The most preferred gellant system for solid sticks is to use stearyl alcohol as the fatty alcohol in combination with hydrogenated castor oil as the wax co-gellant. The composition can contain as perfume: free fragrance, a profragrance, encapsulated fragrance or fragrance that is associated with a host substrate such as cyclodextrin, or a mixture of any two or more of such perfume options.

Perfume (fragrance) if present, may be present at a level of from 0.25 to 2.5 wt.%. Dispensers

The compositions produced herein are suitable for dispensing from known cosmetic dispensers for solid antiperspirant formulations such as stick or soft solid dispensers. Such dispensers commonly comprise a barrel, often of round or oval transverse cross section, having an opening at a first end through which the composition is dispensed and an elevator at an opposed second end that can be advanced towards the first end. The elevator fits within the barrel. Commonly, the first end can be covered with a cap, conveniently dimensioned to push it over the exterior of the barrel.

For sticks, the opening is the full cross section of the barrel. The elevator can be advanced by insertion of finger within the barrel or by co-operation between a threaded spindle and aperture in the elevator, the spindle being rotated by either an externally protruding rotor wheel or by a pawl arrangement. Suitable dispensers for firm sticks are described, for example in US 4,232,977,

US 4, 605,330, WO 09 818695, WO 09 603899, WO 09 405180, WO 09 3251 13, WO 09 305678, EP 1 040 445, US 5,997,202, US 5,897,263, US 5,496,122, US 5,275,496, US 6,598,767, US 6,299,369, or WO 2002/03830. Examples

Examples according to the invention are denoted with a number; examples not according to the invention are denoted with a letter.

Incorporation of Hydroxyethyl Urea (HEU) in a Solid Stick

The hydroxyethyl urea was sourced from Hydrovance as a 45-55% weight active in aqueous solution. Before use, it was freeze dried to yield a solid, which was then used in the formulations. Table 1 - Base Formulation

The general method of preparation of the sticks was as follows:-

1 . Oils (cyclomethicone, alkyl benzoate, PPG-14 butyl ether, dimethicone, optional PEG-8 if included) and BHT were added together into an appropriate vessel, silica then added;

2. Contents of vessel were sheared until homogeneous (e.g. 7000rpm for 5 minutes);

3. Stearyl alcohol, wax, steareth 100 and polyethylene added to vessel;

4. Vessel heated to ca. 85°C to ensure complete dissolution of the waxes, and mixed (e.g. 250rpm using a Heidolph mixer) for 10 minutes;

5. Contents of vessel allowed to cool to 78°C, prior to slow addition of antiperspirant active. Contents of vessel mixed (e.g. 350rpm using a Heidolph mixer) 6. Temperature maintained above 70°C for at least 5 minutes following addition of all of the antiperspirant active

7. Fragrance (and optional sunflower seed oil if included) added at 65°C

8. Formulation poured directly into stick barrel at ca. 62°C and allowed to set.

Sticks made to the base formulation (both with and without optional PEG-8 and sunflower seed oil individually or together) using the above process proved to be non-gritty. To these base stick forming process, attempts were made to incorporate hydroxyethyl urea (HEU), either alone - as a solid, or as a melt; or with a carrier material. The point of addition of the HEU in the process was also assessed. The sticks were assessed as to whether they formed a stable product, and if so, their level of grittiness.

Grittiness test

The resulting stick was tested for grit by a trained assessor. The assessment involved running an index finger over the domed surface of the stick formulation. The formulation was further assessed by removal of the domed surface of stick using a sharp knife, with the assessment involving running an index finger over the freshly cut stick surface of the stick formulation. These tests were repeated by running the stick over the back of the hand. The stick was then either assessed as gritty or non-gritty, and in some cases even lumpy. The gritty and lumpy sticks are unacceptable sticks for consumer use.

Addition of HEU

HEU was added as:-

1 . Solid;

2. Melt (HEU alone);

3. Melt (with carrier material) Solid HEU was heated up to ca. 85°C to provide HEU in a molten state prior to addition. HEU was added at 4 different points in the process:-

A. With Oils (HEU added with oils in general method)

B. With Gellant (HEU added with gellant in general method)

C. After Gellant, but before Antiperspirant Active addition (HEU added after gellant/oil mixture is heated in step 4 in general method)

D. After Antiperspirant Active (HEU added after antiperspirant active added in in general method)

Table 1 - HEU addition alone, either as solid or as a melt

Point of Addition 12 week stability

C

B After D

Exp % HEU A

with Gellant/ After 25°C 45°C Code HEU Form with Oils

Gellant before Active

Active

a 4 Solid X Unstable Unstable b 2 Solid X Gritty Gritty c 4 Solid X Gritty Gritty d 4 Solid X Lumps Lumps e 4 Solid X Gritty Gritty f 4 Solid X Gritty Gritty g 4 Melt X Lumps Lumps

Lumps

h 4 Melt X Lumps

Gritty

4 Melt X Lumps Gritty j 2 Melt X Gritty Gritty

Gritty k 4 Melt X Lumps

Lumps These tests indicated that it was not possible to add HEU alone, either in the solid form; or as a melt to result in a stable stick that was not gritty or lumpy.

Table 2 - HEU addition as a melt with a carrier material

Glycerol has a Hildebrand solubility parameter of 16.3

PEG-8 has a Hildebrand solubility parameter of 1 1 .3

Sunflower Seed Oil has a Hildebrand solubility parameter of ca. 8 These tests show that by incorporating HEU in a melt with a carefully selected carrier material, a stable, non-gritty stick can be made. Only materials with a Hildebrand solubility parameter of from 7 to 15 resulted in an acceptable non-gritty stick. Glycerol is outside this range, and resulted in an unacceptable gritty stick. The melt must be added at a specific point in the process, namely after the addition of oils and gellant with mixing, but before the addition of antiperspirant active.

An example method of preparation of the sticks is as follows:-

1 . Oils (cyclomethicone, alkyl benzoate, PPG-14 butyl ether, dimethicone) and BHT were added together into an appropriate vessel, silica then added;

2. Contents of vessel were sheared until homogeneous (e.g. 7000rpm for 5 minutes);

3. Stearyl alcohol, wax, steareth 100 and polyethylene added to vessel;

4. Vessel heated to ca. 85°C to ensure complete dissolution of the waxes, and mixed (e.g. 250rpm using a Heidolph mixer) for 10 minutes;

5. HEU added along with carrier material (triglyceride, polyalkylene glycol or a mixture thereof) and heated to ca. 85°C

6. Contents of vessel allowed to cool to 78°C, prior to slow addition of

antiperspirant active. Contents of vessel mixed (e.g. 350rpm using a Heidolph mixer)

7. Temperature maintained above 70°C for at least 5 minutes following

addition of all of the antiperspirant active

8. Fragrance added at 65°C

9. Formulation poured directly into stick barrel at ca. 62°C and allowed to set.

This process allows incorporation of HEU at levels of 0.0005 to 3 wt.% in a solid antiperspirant stick. Table 3 - Stick examples according to the Invention