WO2005079730A1

WO2005079730A1 - Hair conditioning compositions and methods of manufacture

Info

Publication number: WO2005079730A1
Application number: PCT/EP2005/001452
Authority: WO
Inventors: Peter Simon Carew; Michael James Cooke
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 2004-02-21
Filing date: 2005-02-10
Publication date: 2005-09-01
Also published as: GB0403879D0; WO2005079730A8

Abstract

Hair-care compositions comprising an L-beta phase at 25°C have i) from 0.1% to 10% by weight of a cationic surfactant, ii) a fatty material selected from fatty alcohol, fatty acid, ethoxylated fatty alcohol and mixtures thereof, iii) 60% by weight or more of water; wherein the weight ratio of fatty alcohol to cationic surfactant is from 4:1 to 12:1 having less than 0.5% by weight of discrete particles of fatty material have improved conditioning properties. A process for their manufacture involves mixing an aqueous phase with the molten fatty material such that the resulting mix is 5°C or more lower in temperature than the chain melting temperature of the L-beta phase.

Description

HAIR CONDITIONING COMPOSITIONS AND METHODS OF MANUFACTURES

Field of the invention The invention is concerned with rinse-off hair conditioner compositions which comprise both a cationic surfactant and a fatty alcohol. In particular it is concerned with compositions having low levels of particles of fatty alcohol, and with methods for manufacturing such , compositions.

Background to the invention

Rinse-off hair conditioner compositions are typically applied to the hair immediately after shampooing and rinsing the hair. After application of the hair conditioner, the hair is then rinsed again before drying.

Such compositions comprise one or more conditioning agents. The purpose of the conditioning agent is to make the hair easier to comb when wet and more manageable when dry, e.g. less static and fly-away. They also make the hair feel softer. Typically, these conditioning agents are either water-insoluble oily materials which act by spreading on the hair in the form of a film, or cationic surfactant materials or polymers, which adsorb onto the hair surface.

The present invention is concerned with hair conditioning compositions which comprise a cationic surfactant and a fatty alcohol dispersed in an aqueous phase in the form of a lamellar L-beta surfactant. Typically, the fatty material is solid at 20°C. The combined use of fatty alcohols and cationic surfactants in conditioning compositions is believed to be especially advantageous, because this leads to the formation of a structured lamellar liquid crystalline phase (so called L-beta phase) , in which the cationic surfactant and part of the fatty material is dispersed.

A typical process for forming such a composition involves separately heating an aqueous dispersion or solution of the cationic surfactant, and the fatty alcohol to a temperature above the melting point of the fatty alcohol (typically 80 °C) . The two components are then mixed together such that droplets of fatty material are dispersed as an emulsion in the surfactant solution. Upon cooling the emulsion, the surfactant and fatty material self-assemble into a lamellar liquid crystalline phase (L-beta phase) at some temperature lower than the melting point of the fatty material but higher than 20 °C. However, the interaction between the two components, which takes place at the interface between the particles of fatty alcohol and the surfactant solution, is limited by diffusion.

In order to form a suitable lamellar phase, a certain ratio of fatty material to cationic surfactant is needed in the lamellar phase. If too low a ratio of fatty alcohol is used, this can lead to problems of irritancy from the composition in use. In practice, using the typical process, an excess of fatty material must be employed in order to achieve the correct ratio of fatty material to cationic surfactant in the lamellar phase. This leads to excess fatty material being present in the compositions made by the typical process. These particles of excess fatty material, which are dispersed through the lamellar phase, are undesirable as they disrupt the long range structure of the lamellar phase and are not in a form useful for conditioning the hair.

In an attempt to improve the interaction of the fatty material with the cationic surfactant, the cooled dispersion can be subjected to further shear at room temperature or lower. This can lead to the removal of some of the fatty material into the lamellar phase, and to a small improvement in conditioning performance, but it has been found that an excess of fatty material is still needed in order to obtain the desired ratio of surfactant to fatty material in the lamellar phase. Moreover, the lamellar phase resulting from shearing at low temperature is found to be lacking in long range crystalline structural order, as measured by x-ray diffraction.

Hence there is a need for lamellar hair conditioner compositions comprising cationic surfactant and fatty material in the form of a lamellar liquid crystal, where the composition is substantially free of discrete particles of fatty alcohol even when the fatty alcohol is present by weight in excess of the cationic surfactant.

There is also a need for hair conditioning compositions which provide improved hair conditioning performance with low irritancy. Summary of the invention

It has now been found that hair conditioning compositions comprising cationic surfactant and fatty alcohol in a lamellar liquid crystalline phase can be obtained which are substantially free of discrete particles of fatty alcohol, yet which have sufficient fatty alcohol in the lamellar phase to prevent irritancy. Moreover, it has been found that such compositions give a considerable benefit in conditioning performance over compositions which have discrete particles of fatty material present.

In a first aspect, the invention concerns a hair-care composition comprising an L-beta lamellar liquid crystalline phase at 25°C, the composition comprising i) from 0.1% to 10% by weight of cationic surfactant ii) a fatty material selected from fatty alcohol, fatty acid, ethoxylated fatty alcohol and mixtures thereof, iii) 60% by weight or more of water;

wherein the weight ratio of fatty material to cationic surfactant is from 4:1 to 12:1, characterised in that the composition comprises less than 0.5% by weight of discrete particles consisting essentially of the fatty material.

Such fatty particle free compositions were previously unobtainable by known process routes, and in a second aspect, the invention is concerned with the process by which such compositions may be obtained. This aspect of the invention is a process for forming a hair-care composition which comprises an L-beta lamellar liquid crystalline phase at_,25°C, comprising the steps of: i) preparing an aqueous dispersion of a cationic surfactant at a temperature less than the chain melting temperature of the L-beta phase, ii) preparing a melt of a fatty material at a temperature above its melting point, iii) intimately mixing the melt and the aqueous dispersion to form a dispersion wherein the mean droplet diameter, D3,2 of the fatty material after mixing is 10 micrometres or less,

such that the mean temperature during mixing is at least 5°C lower than the chain melting temperature of the L-beta phase.

Detailed description of the invention

By water insoluble it is meant that a material has a solubility in water of 0.1% or less by weight of water at 25°C. By non-volatile it is meant that a material has a vapour pressure of less than 1000 Pa at 25°C.

Viscosities, except where otherwise specified, are dynamic viscosities. These may be measured using a cone and plate -1 rheometer at 25°C and at a shear rate of 0.01s Where particles are referred to in the description, the broad definition of particles is meant, indicating that a material is present in a divided form. If the material is a liquid, the particles will be in the form of droplets.

Particle sizes can be measured by photomicroscopy, using image analysis followed by calculation of the mean D3_f2 particle diameter.

Aqueous Composition

Compositions according to the invention comprise water. Suitably compositions according to the invention comprise 60 or more, preferably 65 or more, more preferably 70 or more percent by weight of water.

Conditioning Surfactant

Hair conditioner compositions according to the invention comprise one or more conditioning surfactants which are cosmetically acceptable and suitable for topical application to the hair.

Suitable conditioning surfactants are selected from cationic surfactants, used singly or in admixture. Cationic surfactants useful in compositions of the invention contain amino or quaternary ammonium hydrophilic moieties which are positively charged when dissolved in the aqueous composition of the present invention. Examples of suitable cationic surfactants are those corresponding to the general formula:

[N(Rι) (R₂) (R₃) (R₄)] (X) in which Ri, R2, R3, and R4 are independently selected from (a) an aliphatic group of from 1 to 22 carbon atoms, or (b) an aromatic, alkoxy, polyoxyalkylene, alkylamido, hydroxyalkyl, alkoylalkyl, aryl or alkylaryl group having up to 22 carbon atoms; and X is a salt-forming anion such as those selected from halogen, (e.g. chloride, bromide), acetate, citrate, lactate, glycolate, phosphate nitrate, sulphate, and alkylsulphate radicals. The aliphatic groups can contain, in addition to carbon and hydrogen atoms, ether linkages, and other groups such as amino groups. The longer chain aliphatic groups, e.g., those of about 12 carbons, or higher, can be saturated or unsaturated. ^■ • Preferred cationic surfactants for conditioner compositions of the present invention are so-called monoalkyl quaternary ammonium compounds in which R has an alkyl chain length from C16 to C22 and R2, R3 and R4 have 2 or less carbon atoms.

Other preferred cationic surfactants are so-called dialkyl quaternary ammonium compounds in which Ri and R2 independently have an alkyl chain lengths from C16 to C22 and R₃ and R₄ have 2 or less carbon atoms.

Examples of suitable cationic surfactants include quaternary ammonium compounds, particularly trimethyl quaternary compounds .

Preferred quaternary ammonium compounds include cetyltrimethylammonium chloride, behenyltrimethylammonium chloride (BTAC) , cetylpyridinium chloride, tetramethylammonium chloride, tetraethylammonium chloride, octyltrimethylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octyldimethylbenzylammonium chloride, decyldimethylbenzylammonium chloride, stearyldimethylbenzylammonium chloride, didodecyldimethylammonium chloride, dioctadecyldimethylammonium chloride, tallowtrimethylammonium chloride, cocotrimethylammonium chloride, PEG-2 oleylammonium chloride and salts of these, where the chloride is replaced by halogen, (e.g., bromide), acetate, citrate, lactate, glycolate, phosphate nitrate, sulphate, or alkylsulphate. Further suitable cationic surfactants include those materials having the CTFA designations Quaternium-5, Quaternium-31 and Quaternium-18. Mixtures of any of the foregoing materials may also be suitable. Particularly useful quaternary ammonium cationic surfactants for use in hair conditioners of the invention are cetyltrimethylammonium chloride, available commercially, for example as GENAMIN CTAC, ex Hoechst Celanese and Arquad 16/29 supplied by Akzo Nobel, and behenyltrimethylammonium chloride (BTAC) such as Genamin KDM-P supplied by Clariant.

Another suitable cationic conditioning surfactant is a dialkoylalkyl dimethylammonium halide. An example of such a compound has the CTFA designation dipalmitoyethyldimethylammonium chloride.

Further suitable cationic systems are primary, secondary, and tertiary fatty amines used in combination with an acid to provide the cationic species. The alkyl groups of such amines preferably have from 12 to 22 carbon atoms, and can be substituted or unsubstituted.

Particularly useful are amido substituted tertiary fatty amines, in particular tertiary amines having one C₁₂ to C₂₂ alkyl or alkenyl chain. Such amines, useful herein, include stearamidopropyIdimethylamine, stearamidopropyidiethylamine, stearamidoethyldiethylamine, steara idoethyldimethylamine, palmitamidopropyld imethylamine, palmitamidopropyldiethylamine, palmitamidoethyldiethylamine, palmitamidoethyldimethylamine, behenamidopropyldimethylamine, behenamidopropyldiethylamine, behenamidoethyldiethylamine, behenamidoethyldimethylamine, arachidamidopropyldimethylamine, arachidamidopropyldiethylamine, arachidamidoethyldiethylamine, arachidamidoethyldimethylamine, diethylaminoethylstearamide. Also useful are dimethylstearamine, dimethylsoyamine, soyamine, myristylamine, tridecylamine, ethylstearylamine, N- tallowpropane diamine, ethoxylated (with 5 moles of ethylene oxide) stearylamine, dihydroxyethylstearylamine, and arachidyl behenylamine .

As stated previously, these amines are typically used in combination with an acid to provide the cationic species. The preferred acid useful herein includes L- glutamic acid, lactic acid, hydrochloric acid, malic acid, succinic acid, acetic acid, fumaric acid, tartaric acid, citric acid, L- glutamic hydrochloride, and mixtures thereof; more preferably L-glutamic acid, lactic acid, citric acid. Cationic amine surfactants included among those useful in the present invention are disclosed in U.S. Patent 4,275,055 to Nachtigal, et al., issued June 23, 1981.

The molar ratio of protonatable amines to H from the acid is preferably from about 1:0.3 to 1:1.2, and more preferably from about 1:0.5 to about 1:1.1.

In the conditioners of the invention, the level of cationic surfactant is preferably from 0.1 to 10, more preferably 0.2 to 5, most preferably 0.25 to 4 percent by weight of the total composition.

Fatty Materials

Conditioner compositions of the invention comprise fatty materials. The combined use of fatty materials and cationic surfactants in conditioning compositions is believed to be especially advantageous, because this leads to the formation of a structured lamellar or liquid crystal phase, in which the cationic surfactant is dispersed.

By "fatty material" is meant a fatty alcohol, an alkoxylated fatty alcohol (preferably ethoxylated) , a fatty acid or a mixture thereof.

Preferably, the alkyl chain of the fatty material is fully saturated.

Representative fatty materials comprise from 8 to 22 carbon atoms, more preferably 16 to 22. Examples of suitable fatty alcohols include cetyl alcohol, stearyl alcohol and mixtures thereof. The use of these materials is also advantageous in that they contribute to the overall conditioning properties of compositions of the invention.

Alkoxylated, (e.g. ethoxylated or propoxylated) fatty alcohols having from about 12 to about 18 carbon atoms in the alkyl chain can be used in place of, or in addition to, the fatty alcohols themselves. Suitable examples include ethylene glycol cetyl ether, polyoxyethylene (2) stearyl ether, polyoxyethylene (4) cetyl ether, and mixtures thereof.

The level of fatty material required in conditioners of the invention is dependent upon the level of cationic surfactant in the composition. The weight ratio of fatty alcohol to cationic surfactant should be from 4:1 to 12:1, preferably from 5:1 to 10:1, most preferably from 6:1 to 8:1. The compositions of the invention are characterised in that they are substantially free of discrete particles of free fatty material, by which it is meant that the compositions contain less than 0.5% by weight of such material, preferably less than 0.2%, more preferably less than 0.1%.

A suitable method for measuring the amount of discrete fatty material is differential scanning calorimetry. The area under a peak on the DSC trace at the melting point of the free fatty material can be measured, and this indicates the amount of the free fatty material present as discrete particles in the composition.

Optional ingredients

Conditioning Oil

An optional but preferred component of compositions according to the invention is a hydrophobic conditioning oil. In order for such an oil to exist in discrete droplets in the compositions according to the invention, it must be water- insoluble. By water-insoluble is meant that the solubility in water at'25°C is 0.01% by weight or less.

It is preferred if the conditioning oil is non-volatile, by which it is meant that the vapour pressure of the oil at 25°C is less than 10 Pa.

As used herein, the term "conditioning oil" includes any material, which is used to give a particular conditioning benefit to hair. For example, suitable materials are those which deliver one or more benefits relating to shine, softness, combability, wet-handling, anti-static properties, protection against damage, body, volume, stylability and manageability.

Preferred conditioning oils will have a viscosity of less than 5 Pa.s, more preferably less than 1 Pa.s, and most preferably less than 0.5 Pa.s, e.g. 0.1 Pa. s .

Oily and fatty materials with higher viscosities may be used. For example, materials with viscosities as high as 65 Pa.s may be used.

Suitable hydrophobic conditioning oils are selected from hydrocarbon oils, fatty esters, silicone oils and mixtures thereof.

Hydrocarbon oils include cyclic hydrocarbons, straight chain aliphatic hydrocarbons (saturated or unsaturated) , and branched chain aliphatic hydrocarbons (saturated or unsaturated) . Straight chain hydrocarbon oils will preferably contain from about 12 to about 30 carbon atoms. Branched chain hydrocarbon oils can and typically may contain higher numbers of carbon atoms. Also suitable are polymeric hydrocarbons of alkenyl monomers, such as C₂-C₆ alkenyl monomers. These polymers can be straight or branched chain polymers. The straight chain polymers will typically be relatively short in length, having a total number of carbon atoms as described above for straight chain hydrocarbons in general. The branched chain polymers can have substantially higher chain length. The number average molecular weight of such materials can vary widely, but will typically be up to about 2000, preferably from about 200 to about 1000, more preferably from about 300 to about 600.

Specific examples of suitable hydrocarbon oils include paraffin oil, mineral oil, saturated and unsaturated dodecane, saturated and unsaturated tridecane, saturated and unsaturated tetradecane, saturated and unsaturated pentadecane, saturated and unsaturated hexadecane, and mixtures thereof. Branched-chain isomers of these compounds, as well as of higher chain length hydrocarbons, can also be used. Exemplary branched-chain isomers are highly branched saturated or unsaturated alkanes, such as the permethyl-substituted isomers, e.g., the permethyl- substituted isomers of hexadecane and eicosane, such as 2, 2, 4, 4, 6, 6, 8, 8-dimethyl-10-methylundecane and 2, 2, 4, 4, 6, 6-dimethyl-8-methylnonane, sold by Permethyl Corporation. A further example of a hydrocarbon polymer is polybutene, such as the copolymer of isobutylene and butene. A commercially available material of this type is L-14 polybutene from Amoco Chemical Co. (Chicago, 111., U.S.A.).

Particularly preferred hydrocarbon oils are the various grades of mineral oils. Mineral oils are clear oily liquids obtained from petroleum oil, from which waxes have been removed, and the more volatile fractions removed by distillation. The fraction distilling between 250°C to 300°C is termed mineral oil, and it consists of a mixture of hydrocarbons ranging from C₁₆H₃₄ to C₂₁H₄₄. Suitable commercially available materials of this type include Sirius M85 and Sirius M125, all available from Silkolene.

Suitable fatty esters are characterised by having at least 10 carbon atoms, and include esters with hydrocarbyl chains derived from fatty acids or alcohols, e.g., monocarboxylic acid esters, polyhydric alcohol esters, and di- and tricarboxylic acid esters. The hydrocarbyl radicals of the fatty esters hereof can also include or have covalently bonded thereto other compatible functionalities, such as amides and alkoxy moieties, such as ethoxy or ether linkages .

Monocarboxylic acid esters include esters of alcohols and/or acids of the formula R " COOR in which R' and R independently denote alkyl or alkenyl radicals and the sum of carbon atoms in R" and R is at least 10, preferably at least 20.

Specific examples include, for example, alkyl and alkenyl esters of fatty acids having aliphatic chains with from about 10 to about 22 carbon atoms, and alkyl and/or alkenyl fatty alcohol carboxylic acid esters having an alkyl and/or alkenyl alcohol-derived aliphatic chain with about 10 to about 22 carbon atoms, benzoate esters of fatty alcohols having from about 12 to 20 carbon atoms.

The monocarboxylic acid ester need not necessarily contain at least one chain with at least 10 carbon atoms, so long as the total number of aliphatic chain carbon atoms is at least 10. Examples include isopropyl isostearate, hexyl laurate, isohexyl laurate, isohexyl palmitate, isopropyl palmitate, decyl oleate, isodecyl oleate, hexadecyl stearate, decyl stearate, isopropyl isostearate, dihexyldecyl adipate, lauryl lactate, myristyl lactate, cetyl lactate, oleyl stearate, oleyl oleate, oleyl myristate, lauryl acetate, cetyl propionate, and oleyl adipate.

Di- and trialkyl and alkenyl esters of carboxylic acids can also be used. These include, for example, esters of C₄-C₈ dicarboxylic acids such as C₁-C₂₂ esters (preferably Ci-Cς) of succinic acid, glutaric acid, adipic acid, hexanoic acid, heptanoic acid, and octanoic acid. Examples include diisopropyl adipate, diisohexyl adipate, and diisopropyl sebacate. Other specific examples include isocetyl stearoyl stearate, and tristearyl citrate.

Polyhydric alcohol esters include alkylene glycol esters, for example ethylene glycol mono and di-fatty acid esters, diethylene glycol mono- and di-fatty acid esters, polyethylene glycol mono- and di-fatty acid esters, propylene glycol mono- and di-fatty acid esters, polypropylene glycol monooleate, polypropylene glycol monostearate, ethoxylated propylene glycol monostearate, polyglycerol poly-fatty acid esters, ethoxylated glyceryl monostearate, 1,3-butylene glycol monostearate, 1,3-butylene glycol distearate, polyoxyethylene polyol fatty acid ester, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters and mono-, di-and triglycerides.

Particularly preferred fatty esters are mono-, di- and triglycerides, more specifically the mono-, di-, and tri- esters of glycerol and long chain carboxylic acids such as ₁-C₂₂ carboxylic acids. A variety of these types of materials can be obtained from vegetable and animal fats and oils, such as coconut oil, castor oil, safflower oil, sunflower oil, cottonseed oil, corn oil, olive oil, cod liver oil, almond oil, avocado oil, palm oil, sesame oil, peanut oil, lanolin and soybean oil. Synthetic oils include triolein and tristearin glyceryl dilaurate.

Specific examples of preferred materials include cocoa butter, palm stearin, sunflower oil, soyabean oil and coconut oil.

The oil may be blended with other materials in the discrete droplets present in compositions according to the invention.

It is preferred that the 0_3^2 mean particle diameter of the hydrophobic conditioning oil droplets in the composition is less than 100 microns, more preferably less than 40 microns, even more preferably less than 10 microns and most preferably less than 2 microns. Larger particle diameters lead to problems in stabilising the composition from separation of components. Practical difficulties in making emulsion droplets with a median diameter of 0.02 microns or less are know n to those skilled in the art. Thus it is preferred if the volume-based median diameter 0₃,₂ is greater than 0.02 microns, more preferably greater than 0.03 microns, even more preferably greater than 0.1 microns. Preferred ranges of mean diameter can be formed by combining any of the preferred minimum diameters with any of the preferred maximum diameters.

Mean droplet diameter 0₃,₂ may be measured by means of a laser light scattering technique, for example using a 2600D Particle Sizer from Malvern Instruments.

The total amount of hydrophobic conditioning oil present in composition is preferably from 0.1% to 10 % by weight of the total composition more preferably from 0.2% to 6%, most preferably 0.5% to 4 %.

Silicone Conditioning oils

Preferred hydrophobic conditioning oils which may be used in compositions according to the invention are silicones.

Suitable silicones for use as conditioning oils include polydiorganosiloxanes, in particular polydimethylsiloxanes which have the CTFA designation dimethicone. Also suitable for use in compositions of the invention are polydimethyl siloxanes having hydroxyl end groups, which have the CTFA designation dimethiconol.

It is preferred if the silicone oil also comprises a functionalised silicone.

Suitable functionalised silicones include, for example, amino-, carboxy-, betaine-, quaternary ammonium-, carbohydrate-, hydroxy- and alkoxy-substituted silicones. Preferably, the functionalised silicone contains multiple substitutions.

For the avoidance of doubt, as regards hydroxyl-substituted silicones, a polydimethylsiloxane merely having hydroxyl end groups (which have the CTFA designation dimethiconol) is not considered a functionalised silicone within the present invention. However, a polydimethylsiloxane having hydroxyl substitutions along the polymer chain is considered a functionalised silicone.

Preferred functionalised silicones are amino-functionalised silicones. Suitable amino functionalised silicones are described in EP 455,185 (Helene Curtis) and include trimethylsilylamodimethicone as depicted below, and are sufficiently water insoluble so as to be useful in compositions of the invention:

Si(CH3)3 - 0 - [Si(CH₃)₂ - 0 - ]_x - [Si (CH3) (R - NH - CH₂CH₂ NH₂) - 0 -]_y - Si (CH₃)₃

wherein x + y is a number from about 50 to about 500, and the weight percent amine functionality is in the range of from about 0.03% to about 8% by weight of the molecule, and wherein R is an alkylene group having from 2 to 5 carbon atoms. Preferably, the number x + y is in the range of from about 100 to about 300, and the weight percent amine functionality is in the range of from about 0.03% to 8% by weight of the molecule.

As expressed here, the weight percent amine functionality is measured by titrating a sample of the amino-functionalised silicone against alcoholic hydrochloric acid to the bromocresol green end point. The weight percent amine is calculated using a molecular weight of 45 (corresponding to

CH₃- CH₂-NH₂) .

Suitably, the weight percent amine functionality measured and calculated in this way is in the range from 0.03% to 8%, preferably from 0.5% to 4%.

By "amino functional silicone" is meant a silicone containing at least one primary, secondary or tertiary amine group, or a quaternary ammonium group. Examples of suitable amino functional silicones include: polysiloxanes having the CTFA designation "amodimethicone" . Specific examples of amino functional silicones suitable for use in the invention are the aminosilicone oils DC-8220, DC-8166, DC-8466, and DC-8950-114 (all ex Dow Corning), and GE 1149-75, (ex General Electric Silicones) . Suitable quaternary silicone polymers are described in EP-A-0 530 974. A preferred quaternary silicone polymer is K3474, ex Goldschmidt.

Another preferred functional silicone for use as a component in the hydrophobic conditioning oil is an alkoxy-substituted silicone. Such molecules are known as silicone copolyols and have one or more polyethyleneoxide or polypropyleneoxide groups bonded to the silicone polymer backbone, optionally through an alkyl linking group.

A non-limiting example of a type of silicone copolyol useful in compositions of the invention has a molecular structure according to the formula depicted below: Si ( CH₃ ) ₃ [ 0-Si ( CH₃ ) (A) ] _p - [ O-Si ( CH₃ ) ( B ) ] _q - 0 - Si ( CH₃ ) ₃

In this formula, A is an alkylene chain with from 1 to 22 carbon atoms, preferably 4 to 18, more preferably 10 to 16.

B is a group with the structure: - (R) - (EO) _r (PO) _S-0H wherein

R is a linking group, preferably an alkylene group with 1 to

3 carbon atoms. Preferably R is -(CH₂)₂ ^— • The mean values of r and s are 5 or more, preferably 10 or more, more preferably 15 or more. It is preferred if the mean values of r and s are 100 or less. In the formula, the value of p is suitably 10 or more, preferably 20 or more, more preferably 50 or more and most preferably 100 or more. The value of q is suitably from 1 to 20 wherein the ratio p/q is preferably 10 or more, more preferably 20 or more. The value of p + q is a number from 11 to 500, preferably from 50 to 300.

Suitable silicone copolyols have an HLB of 10 or less, preferably 7 or less, more preferably 4 or less. A suitable silicone copolyol material is DC5200, known as Lauryl PEG/PPG - 18/18 methicone (INCI name), available from Dow Corning.

It is preferred to use a combination of functional and nonfunctional silicones as the hydrophobic silicone conditioning oil.

The viscosity of the droplets hydrophobic silicone conditioning oil, measured in isolation from the rest of the composition (i.e. not the viscosity of any pre-formed emulsion, but of the hydrophobic conditioning oil itself) is 2 -1 preferably in the range from 5,000 mm sec to 2,000,000 9 —1 mm sec at 25 °C. Suitable methods for measuring the kinematic viscosity of silicone oils are known to those skilled in the art, e.g. capillary viscometers. For high viscosity silicones, a constant stress rheometer can also be used to measure dynamic viscosity which is related to kinematic viscosity by the density of the silicone.

Process

Compositions according to the invention may be made by a process comprising the steps of: i) preparing an aqueous dispersion of a cationic surfactant at a temperature less than the chain melting temperature of the L-beta phase, ii) preparing a melt of a fatty material at a temperature above its melting point, iii) intimately mixing the melt and the aqueous dispersion to form a dispersion, wherein the mean droplet diameter, 0_{3 2} of the fatty material after mixing is 10 micrometres or less,

such that the mean temperature during mixing is at least 5°C lower than the chain melting temperature of the L-beta phase. Other optional ingredients such as conditioning oils may be added either after step (iii) or after step (iv) of the process .

In order for the process to give a composition which is substantially free discrete particles of fatty material, the mixing must be such that the fatty material is dispersed in the dispersion with a mean particle diameter (0_{3 2}) of 10 micrometres or less, preferably 2 micrometres or less, more preferably 1 micrometre or less.

This may be monitored by sampling the dispersion immediately after the mixing stage, and examining a thin section of the sample on a microscope slide at room temperature. The sample should be photographed microscopically within 1 minute of sampling such that the diameter of any discrete particles of fatty material may be measured using image analysis software to derive the mean 0_{3 2} particle diameter.

In order to achieve the dispersion of fatty material required for the invention, a suitable high shear mixer must be used. Many such mixers are commercially available, such as toothed wheel rotor/stator mixers. A particularly preferred mixing unit suitable for the process of the TM invention is a model A dual feed high pressure Sonolator such as is available from the Sonic corporation USA. The apparatus operates by forcing two independent streams of liquid (in this case the aqueous cationic surfactant and the melt of fatty material, through a nozzle. Intensive mixing is provided by the nozzle and can be controlled by selection of nozzle orifice cross sectional area.

Preferably, the temperatures of the aqueous phase and the melt are selected such that after the intensive mixing and dispersion, the dispersion is at a temperature close to ambient temperature such that the composition can be immediately packaged. For example, the aqueous phase may be at 5 to 15 °C while the molten fatty material is at 60 to 75°C.

The chain melting temperature of the L-beta phase is the temperature at which the material transforms from an L-beta phase to an L-alpha lamellar phase on heating. This is suitably measured by differential scanning calorimetry, and is the temperature at which the L-beta-L-alpha transition starts to take place on heating.

Without wishing to be limited by any scientific explanation, it is thought that by dispersing the particles of fatty material in an aqueous medium at a temperature below their melting point, contrary to conventional practice, they can be provided in a form such that the interaction between fatty material and cationic surfactant can proceed to completion.

Claims

1. A hair-care composition comprising an L-beta lamellar liquid crystalline phase at 25°C, the composition comprising i) from 0.1% to 10% by weight of a cationic surfactant, ii) a fatty material selected from fatty alcohol, fatty acid, ethoxylated fatty alcohol and mixtures thereof, iii) 60% by weight or more of water; wherein the weight ratio of fatty material to cationic surfactant is from 4:1 to 12:1, characterised in that the composition comprises less than 0.5% by weight of discrete particles consisting essentially of the fatty material.

2. A composition according to claim 1 wherein the fatty material is a fatty alcohol with from 16 to 22 carbon atoms .

3. A composition according to claim 1 or claim 2 wherein the cationic surfactant is according to the formula:

[N(Rι) (R₂) (R₃) (R4)l (X) in which Ri, R₂, R₃, and R₄ are independently selected from (a) an aliphatic group of from 1 to 22 carbon atoms and/or (b) an aromatic, alkoxy, polyoxyalkylene, alkylamido, hydroxyalkyl, alkoylalkyl, aryl or alkylaryl group having up to 22 carbon atoms; and X is a salt- forming anion selected from halogen, acetate, citrate, lactate, glycolate, phosphate, nitrate, sulphate, and alkylsulphate radicals.

A process for forming a hair-care according to claims 1 to 3, comprising the steps of:

i) preparing an aqueous dispersion of a cationic surfactant at a temperature less than the chain melting temperature of the L-beta phase,

ii) preparing a melt of a fatty material at a temperature above its melting point, and

iii) intimately mixing the melt and the aqueous dispersion to from a dispersion wherein the mean droplet diameter, D_{3 2} of the fatty material after mixing is 10 micrometres or less,

wherein the mean temperature during mixing is at least 5°C lower than the chain melting temperature of the L- beta phase. A process according to claim 4 wherein the aqueous dispersion is at a temperature of 20°C or less and wherein the melt of fatty material is at a temperature of 60°C or more.