EP3558223A1

EP3558223A1 - Antiperspirant formulation

Info

Publication number: EP3558223A1
Application number: EP17825142.7A
Authority: EP
Inventors: Adeline Mary COULSON; Aline Moreira DE SOUZA
Original assignee: Croda International PLC
Current assignee: Croda International PLC
Priority date: 2016-12-22
Filing date: 2017-12-08
Publication date: 2019-10-30
Also published as: GB201621967D0; WO2018114387A1

Abstract

A clear antiperspirant stick formulation and a method of making the formulation. The formulation comprising antiperspirant actives selected from any known actives, and particularly aluminium chlorohydrates or zirconium salts. The formulation also comprising a gelling agent being a hydrocarbon-polyether-polyamide-polyether-hydrocarbon block copolymer, and a liquid vehicle and/or solvent. The formulation may be used in conventional antiperspirant dispensing containers.

Description

Antiperspirant Formulation

Field of Invention The present invention relates to an antiperspirant formulation, and in particular to an antiperspirant formulation which is clear. The antiperspirant formulation is preferably clear in stick form.

Background

There are numerous antiperspirant products in use throughout the world today, such as aerosol sprays, pump sprays, roll-ons, creams and stick forms. The actual antiperspirant formulation, which may be applied in one or more of the above forms, can vary greatly, but generally comprises at least one antiperspirant active ingredient and a suitable carrier, which may for example be an appropriate emulsion, solvent or powder. Suitable solvents include water, glycol, and alcohol. In addition, the antiperspirant formulation normally contains perfume, which may or may not have deodorant properties. One particular type of antiperspirant formulation is a solid or gel oil in water emulsion primarily for use in sticks. There is a commercial need for improved aesthetics for such formulations. Unfortunately, if the vehicle is an emulsion, a solid or gelled formulation will usually be cloudy, hazy or otherwise unaesthetically pleasing. Thus, there is a requirement for a stable solid or gel emulsion antiperspirant formulation that has pleasing aesthetic properties, in particular which is not cloudy or hazy. Summary of the Invention

It is an object of the present invention to provide an antiperspirant formulation which reduces or substantially overcomes at least one of the aforementioned problems or other disadvantages associated with the prior art.

According to a first aspect of the present invention, there is provided a clear or transparent antiperspirant stick formulation comprising:

a) an antiperspirant active agent;

b) a block copolymer gelling agent having the formula hydrocarbon-polyether- polyamide-polyether-hydrocarbon; and

c) a liquid vehicle. In this embodiment, optionally, a solvent may also be present in the formulation.

According to a second aspect of the present invention, there is provided a clear or transparent antiperspirant stick formulation comprising:

a) an antiperspirant active agent;

c) a solvent. In this embodiment, optionally, a liquid vehicle may also be present in the formulation.

Optionally one or more of the following ingredients including mixtures thereof and multiples of any single ingredient may also be included in formulations of the present invention:

I ) an agent for reducing malodor;

2) a stabilizing agent;

3) an antibacterial agent;

4) an agent for reducing skin irritation;

5) a bio-active agent;

6) an emollient;

7) a detackifier;

8) a sun screen;

9) an insect repelling agent;

1 0) an anti-syneresis agent;

I I ) an anti-irritant;

1 2) a fragrance; and

13) a coloring.

In one aspect, the block copolymer gelling agent may also include one or more of a diacid, diamine or hydrocarbon-terminated polyether.

In various aspects, the polyamide block of the block copolymer includes blocks of the hydrocarbon diradical, preferably dimer acid-derived, e.g., wherein the R³ group includes a diradical that results when two carboxylic acid groups are removed from dimer acid; R⁴ is selected from a hydrocarbon and a polyether diradical; the polyether block includes blocks of the formula (R²— Oy, where R² is a hydrocarbon; C_{1 -2}2 hydrocarbon radicals are located at either end of the copolymer, where the hydrocarbon radical may optionally be selected from alkyl, aralkyl, aryl, and alkaryl radicals. In other aspects, the copolymer has the

0 0 o o

R^!-£- O— R² - ZC-(-R³— CNH- R⁴— HNC-)- R³— CZ- R²— 0 R¹ formula ^x y ^z wherein, independently at each occurrence, R is selected from C_{1 -2}2 hydrocarbon radicals;

R² is selected from C 2-6hydrocarbon diradicals; R³ is selected from C₂-52 hydrocarbon diradicals, where at least 50% of the R³ diradicals have at least 34 carbons; R⁴ is selected from C₂-36 hydrocarbon diradicals and C4-C₁₀₀ polyether diradicals; Z is selected from O and NH ; x is an integer from 2 to 1 00; y is an integer from 1 to 1 0; Z is NH ; R² is a C₂ hydrocarbon diradical; and at least 80% of the R³ diradicals have at least 34 carbon atoms. Detailed description

Clear:

The present invention provides for a clear antiperspirant formulation. When used herein, the term clear is intended to have its usual dictionary definition. Accordingly, a clear antiperspirant formulation allows for ready viewing of objects behind it, like glass. Conversely, a translucent antiperspirant formulation, although allowing light to pass through it, would cause scattering of the light passing through it, making it impossible to clearly identify objects behind it.

The clarity of a formulation may be measured instrumentally by measuring the % transmittance of light through the formulation on a Jenway 6300 spectrophotometer at a wavelength of 410nm in a plastic 1 cm path length cuvette. Preferably, a clear or transparent formulation according to the present invention has a light transmittance measured according to this method of at least 75% transmittance, preferably at least 80% transmittance, and most desirably at least 85% transmittance, when compared to water at 1 00% transmittance.

AP agent:

The first component of the clear antiperspirant stick formulation is an antiperspirant active agent. The antiperspirant active used in formulations according to the invention may be any of the known actives. Examples of suitable antiperspirant actives include aluminium chloride; aluminium bromide; aluminium sulphate; aluminium chlorohydrate; zirconyl chloride; zirconyl hydroxide; zirconyl hydroxychloride; aluminium chloridehydroxyallantoinate; complexes of aluminium hydroxide, zirconyl chloride and aluminium chlorohydrate; complexes of aluminium hydroxide, zirconyl hydroxychloride, and aluminium chlorohydrate; complexes of dihydroxyaluminium glycinate, zirconyl chloride and/or zirconyl hydroxychloride and aluminium chlorohydrates; complexes of zirconyl chloride and/or zirconyl hydroxychloride and aluminium chlorohydrate; complexes of zirconyl chloride and/or zirconyl hydroxychloride with aluminium chlorohydrate and an amino acid, such as glycine; and mixtures thereof. Particularly preferred antiperspirant actives are those having high antiperspirant activity, such as aluminium chlorohydrates and aluminium zirconium salts.

The antiperspirant active agent is preferably present in aqueous solution. Preferably the antiperspirant active agent is present in a 50% by weight aqueous solution. Preferably, therefore, the formulation comprises an aqueous antiperspirant agent solution, most preferably a 50% by weight aqueous antiperspirant agent solution, i.e. where the antiperspirant active agent is present in solution with an equal weight of water.

A particularly surprising feature of the present invention is that clear formulations can be achieved at high concentrations of antiperspirant active agent. Thus, the concentration of the antiperspirant active agent present in the formulation according to the present invention can range from as little as 0.5% to as much as 30% by weight based on the total weight of the formulation. Preferably, the antiperspirant active agent is present in the formulation from 5% by weight, more preferably from 10% by weight, most preferably from 15% by weight, up to 28% by weight, more preferably up to 25% by weight, most preferably up to 22% by weight based on the total weight of the formulation. Weights given here are based on total antiperspirant agent solids. Therefore, where a formulation comprises an antiperspirant agent which is present in a 50% by weight aqueous solution, the antiperspirant agent solution is preferably present in the formulation at a concentration of from 1 % by weight, more preferably from 10% by weight, more preferably from 20% by weight, most preferably from 30% by weight, up to 60% by weight, more preferably up to 56% by weight, more preferably up to 50% by weight, most preferably up to 44% by weight based on the total weight of the formulation. Most preferably, the formulation comprises 40% by weight based on the total weight of the formulation of a 50% aqueous solution of antiperspirant agent (i.e. 20% by weight antiperspirant solids). The amount of antiperspirant active agent present in a formulation according to the present invention may vary according to the other components present in the formulation, and the clarity of the formulation. Gelling agent:

The second component of the clear antiperspirant stick formulation is a block copolymer gelling agent having the formula hydrocarbon-polyether-polyamide-polyether-hydrocarbon. This component imparts structure to the formulation. Preferably, it is the only structurant in the formulation.

Preferably, the block copolymer component of the formulation is a hydrocarbon-terminated block copolymer of the formula (1 ) hydrocarbon-polyether-polyamide-polyether-hydrocarbon (1 )

In formula (1 ), a hydrocarbon group contains only carbon and hydrogen atoms. A polyether groups contains 2 or more ether groups, i. e., groups of the formula hydrocarbon-O- hydrocarbon, where the hydrocarbon of one ether group can also serve as the hydrocarbon of another ether group. A polyamide group contains 2 or more amide groups, i. e., groups of the formula hydrocarbon-C(=0)-NR-hydrocarbon, where the hydrocarbon of one amide group may, or may not, also serve as the hydrocarbon of another amide group, and R is hydrogen or a hydrocarbon. Essentially, R in the amide group is determined by the choice of diamine used in the preparation of the polyamide block of the block copolymer of the present invention. In one aspect, at least one amide group of the polyamide is flanked by polyether groups, while in another aspect all of the amide groups in the polyamide block are flanked by hydrocarbon groups.

Suitable hydrocarbon groups are formed from one or more of aliphatic and aromatic moieties. Suitable aliphatic moieties are alkyl, alkylene, alkenyl, alkenylene, alkynyl, alkylnylene, cycloalkyl, cycloalkylene, cycloalkenyl, cycloalkenylene, cycloalkynyl, and cycloalkynylene moieties. Aromatic moieties are also referred to herein as aryl groups. The hydrocarbon groups that terminate the block copolymers of the present invention will be referred to herein as R . As used herein, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, and cycloalkynyl are monovalent radicals, while alkylene, alkenylene, alkynylene, cycloalkylene, cycloalkenylene, and cycloalkynylene are polyvalent radicals. As used herein alkyl, alkylene, cycloalkyl, and cycloalkylene are saturated radicals, while alkenyl, alkenylene, alkynyl, alkylnylene, cycloalkenyl, cycloalkenylene, cycloalkynyl, and cycloalkynylene are unsaturated radicals. The alkyl, alkylene, alkenyl, alkenylene, alkynyl, and alkynylene moieties may be straight chain or branched. The cycloalkyl, cycloalkenyl, cycloalkynyl, cycloalkylene, cycloalkenylene and cycloalkynylene moieties may be monocyclic or polycyclic, where a polycyclic moiety may be, for example, bicyclic or tricyclic.

Exemplary alkyl moieties are methyl, ethyl, propyl, hexyl, and 2-ethylhexyl. Exemplary alkylene moieties are methylene (-CH₂-), methylidene (=CH₂), and ethylene (-CH₂CH₂-). Exemplary cycloalkyl groups are cyclohexyl and norbornyl.

Suitable aromatic moieties are monocyclic or polycyclic. An exemplary monocyclic aryl group is phenyl, while exemplary polycyclic aryl groups are naphthyl and fulverenyl. The aromatic moiety may be monovalent, e.g., phenyl, or polyvalent, e.g., phenylene.

The hydrocarbon group may be a combination of aromatic and aliphatic groups. For example, benzyl (phenyl-CH₂-, an arylalkylene group), tolyl (CH₃-phenylene-, an alkylarylene group), and xylyl (CH₃)₂ phenylene-, a dialkylarylene group). The hydrocarbon group may be a combination of two or more aromatic groups, e.g.,biphenyl (phenyl- phenylene-, an arylarylene group).

The R group necessarily contains at least one carbon. In one embodiment, the R group contains 1 -32 carbons. In one embodiment, the R alkyl group contains 1 -12 carbons. In one embodiment, R is an alkyl group containing 1 -4 carbons. In one embodiment, the R group is an alkyl group. In one embodiment, the R alkyl group is straight-chained. In one embodiment, the R alkyl group is branched. In one embodiment, R is methyl.

The block copolymer of formula (1 ) contains at least two polyether blocks. As its name implies, a polyether block contains a plurality of ether groups, i.e., groups of the formula - C-0-C-. In other words, a polyether block contains the repeating formula -O-R²- where R² is a hydrocarbon group. In one aspect, R² is an alkylene group. The alkylene group R² may be aliphatic (saturated and/or unsaturated) or aromatic, straight chain and/or branched, independently at each occurrence in the polyether block. In one aspect, R² has 1 -6 carbons at each occurrence in the polyether block, while in another aspect R² has 2-4 carbons at each occurrence. In one aspect, R² has the formula -CH₂-CH(R^2a)- wherein R^2a is selected from hydrogen, methyl and ethyl.

In one aspect, the polyether component of the block copolymer has a molecular weight (measured as either number or weight average) of less than 10,000. In another aspect, the molecular weight is between 100 and 4,000.

The block copolymer of formula (1 ) contains a polyamide block. As its name implies, the polyamide block contains a plurality of amide groups, i. e., groups of the formula -NH- C(=0)- and/or -C(=0)-NH-. In the polyamide block, two or more amide groups are separated by hydrocarbon groups, e. g., alkylene groups and/or polyether groups.

In one aspect, the polyamide block contains -C(=0)-R³-C(=0)- moieties wherein R³ is a hydrocarbon group. In one aspect, the polyamide block includes R³ groups having at least 30 carbons. In one aspect, the polyamide block includes R³ groups having 30-42 carbons.

In one aspect, the polyamide block includes R³ groups that are formed from fatty acid polymerization. Fatty acids derived from vegetable oils, tallow, and tall oil (the latter are known as tall oil fatty acids, or TOFA) are commonly subjected to thermal polymerization, typically in the presence of a clay catalyst, to provide a commercially-available product known as dimer acid. These fatty acids contain 18 carbons, so that corresponding dimer acid consists mainly of C₃₆ dicarboxylic acids. This dimer acid may be denoted by the structure HOOC-C₃₄-COOH, where the C₃₄ group is an exemplary R³ group of the present invention. C₃₄ is a mixture of isomeric structures, as more fully described in detailed descriptions of dimer acid, as found in, for example, Naval Stores - Production, Chemistry and Utilization, D.F. Zinkel and J. Russel (eds.), Pulp. Chem. Assoc..Inc., 1989, Chapter 23.

Suitable polymerized fatty acids are available commercially as, for example, SYLVADYM™ dimer acid and UNIDYME™ dimer acid, both from Arizona Chemical, company of International Paper, (Jacksonville, FL), EMPOL™ dimer acid from Henkel Corporation, Emery Oleochemicals Division (Cincinnati, OH); and PRIPOL™ dimer acid from Croda International pic. Dimer acid, as commercially available, typically contains some byproducts of the fatty acid polymerization process. One common byproduct is so-called trimer acid, which results when three fatty acid molecules react together to form a C₆₄ tricarboxylic acid. It may happen, in the preparation of a block copolymer of the present invention, that two of the carboxylic acid groups of trimer acid will react with, e.g., a diamine, leaving one carboxylic acid group unreacted. When this occurs, the block copolymer will contain a carboxylic acid- substituted R³ group, which is technically not a hydrocarbon. Accordingly, while block copolymers of the present invention contain hydrocarbon groups between two NHC(=0) groups, they may also contain some, typically a minor amount, of carboxylic acid- substituted hydrocarbon groups between two NHC(=0) groups. For convenience; as used herein, C₃₄ refers to the incorporation of dimer acid into a polyamide block, where C₃₄ includes the reaction product of some trimer acid that may be a by-product in the commercial dimer acid.

In one aspect, in the block copolymers of formula (1 ) each of the C(=0) groups is bonded to C₃₄, i.e., the block copolymer is formed from dimer acid as the exclusive polyacid reactant. However, in another aspect, the polyamide block includes both C₃₄ and "co- diacid"-derived R³ groups. Thus, the polyamide block may be formed by reacting both dimer acid and co-diacid with a diamine. However, in a preferred embodiment of the invention, dimer acid is used without any co-diacid in preparing the polyamide block of the block copolymer.

As used herein, a co-diacid is a compound of formula HOOC-R³-COOH where R³ is not C₃₄ as defined above. In one aspect, the polyamide block in copolymers of formula (1 ) includes R³ groups having 2-32 carbons, which are referred to herein a co-diacid R³ groups. Suitable co-diacid R³ groups include ethylene (from, e.g., succinic acid) and n-butylene (from, e.g., adipic acid).

In one aspect, the C₃₄ R³ groups constitute at least 50 mol% of the total of the R³ groups. In other aspects, the C₃₄ R³ groups constitute at least 60 mol%, or 70 mol%, or 80 mol%, or 90 mol%, or 95 mol% of the R³ groups. Stated another way, dimer acid contributes at least 50% of the diacid equivalents, or at least 60-%, or 70%, or 80%, or 90%, or 95% of the diacid equivalents in the polyamide block of the copolymer of formula (1 ).

In one aspect, the polyamide block contains -NH-R⁴-NH- moieties wherein R⁴ is a hydrocarbon group. In one aspect, the R⁴ hydrocarbon groups has 1 -20 carbons. In one aspect, the polyamide block includes R⁴ groups having 1 -10 carbons. In one aspect, the R⁴ group is an alkylene group. In one aspect, R⁴ is a straight-chained alkylene group. In one aspect, the polyamide block includes R⁴ groups having 2 carbons, while in another aspect at least 50% of the R⁴ groups have 2 carbons, while in another aspect all of the R⁴ groups have 2 carbons. In one aspect, the polyamide block contains -NH-R⁴-NH- moieties wherein R⁴ is a polyether group. As defined above, a polyether block contains a plurality of ether groups, i.e., groups of the formula -C-0-C-. In other words, a polyether block contains the repeating formula -O-R²- where R² is a hydrocarbon group. In one aspect, R² is an alkylene group. The alkylene group R² may be aliphatic (saturated and/or unsaturated) or aromatic, straight chain and/or branched, independently at each occurrence in the polyether block. In one aspect, R² has 1 -6 carbons at each occurrence in the polyether block, while in another aspect R² has 2-4 carbons at each occurrence. In one aspect, R² has the formula -CH₂- CH(R^2a)- wherein R^2a is selected from hydrogen, methyl and ethyl. In one aspect, the polyether component of the R⁴ potion of the block copolymer of the present invention has a molecular weight (number or weight average) of less than 10,000. In another aspect, the molecular weight is between 100 and 4,000.

Compounds of the formula H₂N-R⁴-NH₂ are commonly known as diamines, and are available from a large number of vendors. Compounds of the formula HOOC-R³-COOH are commonly known as diacids, or dibasic acids, and are likewise available from a large number of vendors. Aldrich (Milwaukee, Wl; www.sigma-aldrich.com); EM Industries, Inc. (Hawthorne, NY; http://www.emscience.com); Lancaster Synthesis, Inc. (Windham, NH; http://www.lancaster.co.uk) are three representative vendors.

In formula (1 ), the bond '-' between hydrocarbon and polyether represents a C bond where the carbon is contributed by the hydrocarbon and the oxygen is contributed by the polyether. In formula (1 ), in one aspect, the bond between polyether and polyamide is C-NH-C(=0)-C where C-NH may be seen as being contributed by the polyether and C(=0)-C may be seen as being contributed by the terminal acid group of a polyamide. Block copolymers according to this aspect may be formed by, for example, reacting an amino and hydrocarbon terminated polyether of the formula R -(0-R²-)NH₂ with a carboxylic acid terminated polyamide of the formula HOOC-NH-R⁴-NH- etc. so as to form R -(0-R²-)N- C(=0)-R⁴. Thus, an amide group may be present as the link between polyether and polyamide in formula (1 ).

In formula (1 ), in one aspect, the bond between polyether and polyamide is C-C(=0)-NH-C where C-C(=0) may be seen as being contributed by the polyether and NH-C may be seen as being contributed by the terminal amine group of a polyamide. Block copolymers according to this aspect may be formed by, for example, reacting a carboxylic acid and hydrocarbon terminated polyether of the formula R -(OR²-)COOH with an amine terminated polyamide of the formula H₂N-R⁴-NH-C(=0)-R³- etc. so as to form R -(0-R²-)- C(=0)-NH-R⁴-NH-C(=0)-R³- etc. Thus, once again, an amide group may be present as the link between polyether and polyamide in formula (1 ). However, urethane groups are preferably not a part of the block copolymer of the present invention.

In formula (1 ), in one aspect, the bond between polyether and polyamide is C-0-C(=0)-C where C may be seen as being contributed by the polyether and C(=0) may be seen as being contributed by the terminal acid group of a polyamide. Block copolymers according to this aspect may be formed by, for example, reacting a hydroxyl and hydrocarbon terminated polyether of the formula R -(0-R²-)OH with a carboxylic acid terminated polyamide of the formula HOOC-NH-R⁴-NH-etc. so as to form R -(0-R²-)0-C(=0)-R⁴. Thus, an ester group may be present as the link between polyether and polyamide in formula (1 ). In various aspects of the invention, the block copolymer contains 0 ester groups (e.g., when the polyether is amine terminated rather than hydroxyl terminated), or no more than 1 ester group (when a mixture of amine terminated and hydroxyl terminated polyether are used), or no more than 2 ester groups.

In one aspect, the present invention provides a formulation comprising a hydrocarbon- terminated polyether-polyamide block copolymer of the present invention having an acid number of less than 25, or less than 20, or less than 15, or less than 10. The hydrocarbon- terminated polyether-polyamide block copolymer of formula (1 ) does not have any free carboxylic acid groups, and accordingly has an acid number of zero. However, when prepared from diacid, diamine and hydrocarbon-terminated polyether according to a process described herein, some of the diacid may not react with the diamine and/or polyether, and according the final product may have some unreacted carboxylic acid that will be responsible for the product having an acid number greater than zero. Preferably, the product has a minor amount of this unreacted diacid, and thus has only a small acid number. Esterification catalysts may be used to encourage all of the diacid to react with hydroxyl groups, so as to minimize the amount of free acid, i. e., to reduce the acid number of the product.

In one aspect, the present invention provides a formulation comprising a hydrocarbon- terminated polyether-polyamide block copolymer of the present invention having an amine number of less than 25, or less than 20, or less than 15, or less than 10, or less than 5 or less than 2 or less than 1 . The hydrocarbon-terminated polyether-polyamide block copolymer of formula (1 ) does not have any free amine groups, and accordingly has an amine number of zero. However, when prepared from diacid, diamine and hydrocarbon- terminated polyether according to a process described herein, some of the diamine may not react with the diacid, and according the final product may have some unreacted amine groups that will be responsible for the product having an amine number greater than zero. Preferably, the product has a minor amount of this unreacted diamine, and thus has only a small amine number. Amidification catalysts may be used to encourage all of the diamine to react with carboxyl groups, so as to minimize the amount of free amine, i. e., to reduce the amine number of the product.

In one aspect, the hydrocarbon-terminated polyether-polyamide block copolymer has a softening point of 50-150^ (Ring and Ball, or Mettler). In another aspect, the softening point is 75-125 *Ό, while in another aspect the softening point is 75-100°C, while in another aspect the softening point is 80-120 °C.

In one aspect, the hydrocarbon-terminated polyether-polyamide block copolymer has a weight or number average molecular weight of 2,000 to 30,000. The molecular weight is measured by preparing a solution of the copolymer or formulation in a suitable solvent, e. g., tetrahydrofuran (THF) and identifying the retention time of the copolymer by gel permeation chromatography, and comparing that retention time to the retention times of solutions of polystyrene having known molecular weight characterizations. In one aspect, the copolymers have a weight or number average molecular weight of greater than 1 ,000. Among other features, the hydrocarbon termination on the polyether reactant allows for control of the molecular weight of the copolymer. If both ends of the polyether reactant were reactive, e.g., the polyether contained hydroxyl functionality at both ends, then the polyether could not be utilized as a terminator in the preparation of copolymers of the present invention.

In one aspect, the hydrocarbon-terminated polyether-polyamide block copolymer has a viscosity, as measured on the neat copolymer or formulation at 160°C, of less than 5,000 centipoise (cPs, or cps), or less than 4,000 cPs, or less than 3,000 cPs, or less than 2,000 cPs, or less than 1 ,000 cPs Typically, the copolymer and formulations will have a melt viscosity, as measured on the neat copolymer or formulation at 160°C, of more than 50 cPs, typically more than 500 cPs.

The block copolymers described herein may be prepared by any method known in the art. In particular, the block copolymers of the present invention may be prepared by one of the methods described in EP1358248, the contents of which is herein incorporated by reference.

The block copolymer gelling agent is preferably present in the formulation at a concentration which will gel the formulation sufficiently to form a stick, that is, the formulation has sufficient structural rigidity to harden and produce a solid structure which will retain its shape on standing. Preferably, the block copolymer gelling agent is present in the formulation at a concentration of between 2% and 50% by weight based on the total weight of the formulation. More preferably, the block copolymer gelling agent is present in the formulation at a concentration of at least 4%, preferably at least 6% and most preferably at least 8% by weight based on the total weight of the formulation. More preferably, the block copolymer gelling agent is present in the formulation at a concentration of up to 40%, preferably up to 35% and most preferably up to 30% by weight based on the total weight of the formulation.

The concentration of the block copolymer gelling agent present in the formulation will vary depending on the presence and concentration of other components in the formulation.

Liquid vehicle:

When a liquid vehicle is present in the formulation, the liquid vehicle is preferably water. When present, the concentration of the liquid vehicle present in the antiperspirant formulation is preferably in the range from 0.1 % to 60% by weight based on the total weight of the formulation. Preferably, the liquid vehicle is present in the formulation at a concentration of at least 10% by weight, preferably at least 15% by weight based on the total weight of the formulation. Preferably, the liquid vehicle is present in the formulation at a concentration of up to 50% by weight, preferably up to 45% by weight based on the total weight of the formulation. The liquid vehicle corresponds to added water in the formulation. This does not take into account any water that may be present as a result of any other component in the formulation being present in an aqueous solution. Therefore, it follows that according to an embodiment of the present invention, there is provided a clear or transparent antiperspirant stick formulation that comprises no added water.

Solvent:

In an embodiment of the present invention, the antiperspirant stick formulation comprises a solvent. As used herein, the term solvent includes any substance which is a liquid at a temperature between 10-60^, and which forms a gel upon being combined with a block copolymer of the present invention. As used herein, the term solvent will be used to encompass oils and other fluids that may be gelled by the block copolymer of the invention, and is not otherwise limited.

The solvent is a liquid at room temperature or slightly above room temperature. A preferred solvent is a polar solvent, where exemplary polar solvents include glycols, ethers, glycol ethers (i.e., polyalkyleneglycol ethers), and polyols. The polar solvent may be a mixture of solvents.

The solvent must also be selected so that it is non-reactive with the block copolymer gelling agent. It is added in sufficient quantity to form the cosmetic formulation, for example, in an amount of from 0.1 % to 60% by weight based on the total weight of the formulation. Preferably, the solvent is present in the formulation at a concentration of at least 10% by weight, preferably at least 20% by weight based on the total weight of the formulation. Preferably, the solvent is present in the formulation at a concentration of up to 55% by weight, preferably up to 50% by weight based on the total weight of the formulation. Examples of suitable solvents that can be used in the formulation of the present invention include (but are not limited to):

(a) dihydroxy aliphatic alcohols containing from 3 to 6 carbon atoms, such as 1 ,3-propylene glycol, 1 ,2-propylene glycol, 1 ,3-butylene glycol, 1 ,4-butylene glycol and hexylene glycol;

(b) various liquid polyethylene and polypropylene glycols, such a dipropylene glycol, tripropylene glycol, tetrapropylene glycol and methyl propane diol (also called 2-methyl-1 ,3- propanediol or, more commonly, MPDiol) from Arco Chemical Company, Newtown Square, Pa.; and

(c) mixtures of the individual groups or individual solvents within a single group listed above.

Particularly preferred solvents include propylene glycol, dipropylene glycol, butylene glycol, hexylene glycol, PPG-10 butanediol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol and MPDiol; and mixtures thereof. Most preferred is propylene glycol. In order to prepare a gel from a solvent and block copolymer, the two components are mixed together and heated until homogeneous. A temperature within the range of about 80-150°C is typically sufficient to allow the block copolymer to completely dissolve in the solvent. A lower temperature may be used if a solution can be prepared at the lower temperature. Upon cooling, the mixture forms the gelled formulation of the invention. Optional components may be added to the molten formulation, and are dispersed and/or dissolved to provide a homogeneous formulation prior to cooling of the molten formulation.

The solvent and liquid vehicle combination forms the base matrix of the solid stick when combined with the gelling agent. The solvent and liquid vehicle combination desirably also solubilizes the antiperspirant active, to form a clear product, and can also solubilize other components, in order to produce miscible products which can be formed into transparent or clear gels.

Optional Additives:

Optionally, the antiperspirant formulation may comprise additional additives. These additives may be selected from amongst agents for reducing malodor, stabilizing agents, antibacterial agents, agents for reducing skin irritation, bio-active agents, emollients, detackifiers, sun screens, insect repellants, anti-syneresis agents, anti-irritants, fragrances and colourants.

A stabilizing agent may be included in the clear antiperspirant stick formulation. Examples of suitable stabilizing agents include cosmetically acceptable alkali metal salts, bases, amines and other nitrogen containing compounds, particularly guanidine carbonate. Agents for reducing malodor that may be present in the antiperspirant stick formulation include sodium bicarbonate and antibacterial agents. Illustrative antibacterial agents that can be utilized according to the present invention include Triclosan, benzethonium chloride, zinc phenolsulfonate and Triclocarban. Typically, formulations according to the present invention may contain up to about 2% antibacterial agents, preferably about 0.1 % to 1 .5%, by weight, of the total weight of the formulation.

Suitable emollients may be selected from the group consisting of emollient oils such as a liquid mixture of hydrocarbons which are liquids at ambient temperatures (such as petroleum distillates and light mineral oils), mineral oil, plant and animal oils; fatty acids; fatty alcohols; Guerbet alcohols; lanolin and its derivatives and silicone oils.

When non-polar oils are used it may be desirable to use relatively high concentrations of emulsifier, particularly high HLB emulsifier, in order to achieve suitably satisfactory emulsification, particularly to obtain small oil droplets. The concentration of the emulsifier may vary widely. The emulsifier concentration is preferably in the range from 0.5 to 25%, more preferably 1 .5 to 15%, particularly 2.5 to 10%, and especially 3 to 5% by weight of the total formulation.

Suitable humectants include cosmetically acceptable ingredients, for example glycerin, PEG-6, and sorbitol.

Suitable surfactants include cosmetically acceptable ingredients, for example nonionic surfactants such as glyceryl laurate, laureth-3, oleth-10, sorbitan laurate; anionic surfactants such as DEA-oleth-10 phosphate, cocoyl sarcosine, sodium cocoylisethionate; cationic surfactants such as cocamidopropylaimine oxide, dicetyldimonium chloride; and amphoteric surfactants such as cocamidopropyl hydroxysultaine, oleyl betaine, disodium cocoamphodiacetate.

Suitable detackifiers include silicone fluids such as phenyl trimethicone (for example, DOW CORNING. RTM. 556 Fluid (Dow Corning Corporation, Midland, Mich.), isopropyl esters, triglycerides, and isostearate esters, dimethyl sebacate, dipropyl sebacate.

Suitable sun screens include octyl methoxycinnamate, aminobenzoic acid, octyl salicylate, oxybenzole and cosmetically acceptable ultraviolet light absorbers.

Suitable bug repelling agents include N,N-diethyl-m-toluamide ("DEET") and citronella. Suitable antisynerisis agents include fumed silica, acrylic polymers and, for deodorants, pectins and gelatins. Suitable anti-irritants include high molecular weight glycols, for example, di-, tri- and tetrapropylene glycols and mixtures thereof, benzyl alcohol, and aloe vera.

The formulation of suitable fragrances may vary over a wide range, and is usually a complex mixture of many individual fragrance ingredients, which may themselves be a single chemical species or a mixture of materials. Fragrances normally employed in antiperspirant formulations, which are well known to the person skilled in the art, may be used. The concentration of the fragrance present in the antiperspirant formulation is suitably greater than 0.3%, preferably in the range from 0.5 to 5%, more preferably 0.7 to 3%, particularly 0.9 to 2%, and especially 1 .0 to 1 .5% by weight of the total formulation.

Suitable bio-active agents include plant and flower oils and extracts, and essential oils. For example, the formulation may include oils and extracts such as those available from Crodarom, for example aloe vera, Delice Fraicheur™, Crodarom™ Nordic Cotton, Crodarom™ Blue Lotus and/or Phytofleur™ Tiare.

The invention also includes a method of making such clear antiperspirant stick formulations. The method comprises the steps of:

a) heating the block copolymer gelling agent to a temperature of 85°C, or a temperature above its melting point;

b) combining the block copolymer gelling agent at temperature with the solvent, where present;

c) separately combining the antiperspirant active agent with the liquid vehicle, where present, and heating to the same temperature as the block copolymer gelling agent;

d) combining the block copolymer gelling agent and solvent, where present, with the antiperspirant active agent and liquid vehicle, where present, at temperature; and e) allowing the formulation to cool.

Preferably, the block copolymer gelling agent and solvent, where present, with the antiperspirant active agent and liquid vehicle, where present, are combined slowly whilst stirring. Preferably, the formulation is dispensed into the desired antiperspirant stick receptacle before the temperature of the formulation falls below the melting point of the block copolymer gelling agent. Preferably, the formulation is dispensed into the desired antiperspirant stick receptacle at a temperature of approximately 60°C to 75°C, more preferably at approximately 70 °C.

Throughout the present specification, where formulations are described as including or comprising specific components, it is contemplated by the inventors that formulations of the present invention also consist essentially of, or consist of, the recited components. Accordingly, throughout the disclosure any described formulation can consist essentially of, or consist of, the recited components.

The antiperspirant solid gel stick formulation according to the present invention is used as such stick formulations are conventionally used. Specifically, the formulation can be filled into a dispensing container as done conventionally, with the formulation hardening in such container. The formulation is used by elevating and exposing the stick out of the dispensing container, as done conventionally, and applying the product to, for example, axillary regions of the body, so as to provide antiperspirant protection. The invention is illustrated by the following non-limiting examples.

Examples

Examples 1 -4

Four antiperspirant stick formulations were prepared with the components and concentrations set out in Table 1 below. The formulations were each prepared according to the following method. The Part A components were pre-mixed in a vessel and heated in a water bath with over-head stirring to a temperature of 85^. Separately, the Part B components were combined in another vessel and heated in a water bath to a temperature of 85°C. The vessels were removed from the water baths and the Part B components were added to the Part A components slowly, with stirring. The formulation was stirred without the application of any further heat to allow the formulation to start to cool. The formulation was stirred until the temperature fell to 70 *Ό, at which point the formulation was poured into an antiperspirant stick container and allowed to cool fully without any further agitation. Table 1 : Formulations of Examples 1 to 4

The formulations of Examples 1 to 4 provided antiperspirant stick formulations with the desired structural rigidity. Examples 1 and 2 were clear formulations which were found to have a well-liked skin feel in a panel test, Example 1 providing a slightly softer feel than Example 2.

Any or all of the disclosed features, and/or any or all of the steps of any method or process described, may be combined in any combination.

Each feature disclosed herein may be replaced by alternative features serving the same, equivalent or similar purpose. Therefore, each feature disclosed is one example only of a generic series of equivalent or similar features. The above statements apply unless expressly stated otherwise. The term specification, for these purposes, includes the description and any accompanying claims, abstract and drawings.

Claims

1 . A clear or transparent antiperspirant stick formulation comprising:

a) an antiperspirant active agent;

c) a liquid vehicle and/or a solvent.

2. The formulation according to claim 1 , wherein the block copolymer gelling agent also includes one or more of a diacid, diamine or hydrocarbon-terminated polyether.

3. The formulation according to either claim 1 or claim 2, wherein the polyamide block of the block copolymer includes blocks of the formula

where

R³ is a hydrocarbon diradical, preferably dimer acid-derived;

R⁴ is selected from a hydrocarbon and a polyether diradical;

the polyether block includes blocks of the formula (-R²— Oy, where

hydrocarbon; and

where C_{1 -2}2 hydrocarbon radicals are located at either end of the copolymer, and the hydrocarbon radical is selected from alkyl, aralkyl, aryl, and alkaryl radicals.

4. The formulation according to any preceding claim, wherein the copolymer has the formula wherein, independently at each occurrence

R is selected from C_{1 -2}2 hydrocarbon radicals;

R² is selected from C₂.₆ hydrocarbon diradicals;

R³ is selected from C₂-₅₂ hydrocarbon diradicals, where at least 50% of the

R³ diradicals have at least 34 carbons; R⁴ is selected from C₂-₃₆ hydrocarbon diradicals and C4-C100 polyether diradicals; Z is selected from O and NH;

x is an integer from 2 to 100;

y is an integer from 1 to 10; and

Z is NH; R² is a C₂ hydrocarbon diradical.

5. The formulation according to any preceding claim, wherein said formulation has a light transmittance of at least 75%.

6. The formulation according to any preceding claim, wherein the antiperspirant active is present in an aqueous solution at least 50% by weight.

7. The formulation according to any preceding claim, wherein the concentration of the antiperspirant active agent present in the formulation is in the range from 0.5% to 30% by weight based on the total weight of the formulation.

8. The formulation according to any preceding claim, wherein the hydrocarbon-terminated polyether-polyamide block copolymer has a weight or number average molecular weight of 2,000 to 30,000.

9. The formulation according to any preceding claim, wherein the hydrocarbon-terminated polyether-polyamide block copolymer has a viscosity, as measured on the neat copolymer or formulation at 160 *Ό, of less than 5,000 centipoise.

10. The formulation according to any preceding claim, wherein block copolymer gelling agent is present in the formulation at a concentration of between 2% and 50% by weight based on the total weight of the formulation.

1 1 . The formulation according to any preceding claim, wherein the liquid vehicle is water.

12. The formulation according to any preceding claim, wherein the solvent is a polar solvent selected from glycols, ethers, glycol ethers (i.e., polyalkyleneglycol ethers), and polyols.

13. The formulation according to any preceding claim, wherein the formulation comprises additional additives selected from agents for reducing malodor, stabilizing agents, antibacterial agents, agents for reducing skin irritation, bio-active agents, emollients, detackifiers, sun screens, insect repellants, anti-syneresis agents, anti-irritants, fragrances and colourants.

14. A method of making clear antiperspirant stick formulations according to any of claims 1 to 13, said method comprising the steps of:

a) heating the block copolymer gelling agent to a temperature of 85 *Ό, or a temperature above its melting point;

d) combining the block copolymer gelling agent and solvent, where present, with the antiperspirant active agent and liquid vehicle, where present, at temperature; and

e) allowing the formulation to cool.