WO2009034360A2

WO2009034360A2 - Shampoo

Info

Publication number: WO2009034360A2
Application number: PCT/GB2008/003125
Authority: WO
Inventors: John Hawkins
Original assignee: Chartered Brands Limited
Priority date: 2007-09-15
Filing date: 2008-09-15
Publication date: 2009-03-19
Also published as: EP2200568A2; CN101951869A; WO2009034360A3

Abstract

A shampoo suspending medium comprises: A. a higher HLB surfactant with an HLB greater than 37, such as alkyl ether sulphate; B. a surfactant with an HLB lower than 30, in a proportion to the higher HLB surfactant sufficient to provide a total surfactant with a mean HLB between 13 and 37; and C. sufficient of a carbohydrate and/or electrolyte structurant to form a stable system. The composition is capable of suspending selenium sulphide or cationic surfactants. Mica can be co-suspended with selenium sulphide in an anti-dandruff shampoo to provide a more homogeneous looking composition.

Description

SHAMPOO

The invention relates to structured aqueous shampoos having suspending properties. Formulating suspensions of water insoluble, or sparingly soluble solids and/or liquids in aqueous shampoos presents a long-standing problem.

Formulators need to be able to suspend a variety of such ingredients. For example oils, anti-dandruff agents, such as selenium sulphide, hair conditioners including cationic polymers, and opacifiers such as mica are widely used. There is therefore a need to disperse them in aqueous shampoos. The latter, desirably, also comprise anionic and /or amphoteric surfactants, such as alkyl ether sulphates, or betaines, which are high foaming and mild to the skin.

Cationic polymers, such as poly(diallyldimethylammonium) chloride, referred to hereinafter as "polyquaternium", are widely used as hair conditioners. There is therefore a need to disperse them in aqueous shampoos. Cationic polymers are, however liable to interact with anionic or amphoteric surfactants. Formulators have serious problems dispersing them in shampoo active systems to form stable homogeneous dispersions.

Selenium sulphide is widely used as an anti-dandruff agent, but presents problems of formulation. It is a dense, water-insoluble solid, with a strong, unattractive orange colour. Attempts to maintain selenium sulphide in suspension have generally involved the use of polymeric thickeners. It has also been proposed to suspend selenium sulphide in structured surfactant systems. However due to its high density, some sedimentation is usually observed. Even the most effective suspending systems have not been able to avoid an appearance of inhomogeneity.

We have discovered novel structured surfactant suspending systems that are capable of suspending cationic polymers and dense particles such as selenium sulphide stably, without sedimentation, using shampoo surfactants which give dense stable foams with good wetting and feel. The term "structured system" as used herein means a pourable composition comprising water, surfactant, any structurants, which may be required to impart suspending properties to the surfactant, and optionally other dissolved matter, which together form a mesophase, or a dispersion of a mesophase in a continuous aqueous medium, and which has the ability to immobilise non-colloidal, water- insoluble particles, while the system is at rest, thereby forming a stable, pourable suspension.

A number of attempts have been made to mask the colour and curdled appearance of selenium sulphide suspensions. For example products are widely sold which are loaded with high levels of titanium oxide and blue pigment. This approach is only partially successful, and neither of the above masking additives is particularly desirable in a shampoo. Other approaches such as fine milling, and the use of pearlisers such as glycol stearates have proved unsuccessful.

Hitherto the only successful approach to marketing selenium sulphide shampoos has been to use opaque bottles so that the lack of aesthetic appeal is not apparent, at least at the point of sale.

We have found that systems which are capable of suspending selenium sulphide are capable of co-suspending mica to form homogeneous suspensions with an attractive appearance.

We have discovered that the addition of mica to selenium sulphide suspensions not only masks the appearance of the sulphide very effectively, but also confers an attractive nacreous sheen. Moreover the mica can be tinted to match different hair shades, making it a positively desirable ingredient.

"Mica" is used herein broadly, where the context permits, to include natural mica, artificially coated mica, and synthetic, mica-like, pearlescent, mineral flakes such as calcium aluminium borosilicate, which can be coated to give similar effects to coated mica. Mica is one of a large number of lamellar solids known to be capable of imparting a pearly appearance to liquids, but in practice its use in aqueous formulations has been restricted because, like selenium sulphide, it is difficult to suspend. Pearl shampoos are therefore normally formulated with glycol stearates, which are self-suspending.

It is particularly surprising that selenium sulphide and mica, each of which is difficult to suspend individually to form a homogeneous suspension, can be co-suspended in this way to produce a strikingly enhanced visual effect.

Attempts to solve the problem of dispersing water insoluble materials in water have generally involved either using gums or other polymeric thickeners to raise the viscosity of the liquid medium, or else forming colloidal dispersions.

Gums and polymeric thickeners, which increase the viscosity of the liquid medium, retard, but do not prevent sedimentation, and at the same time make the composition harder to pour. They do not provide stable suspensions.

Colloidal dispersions contain particles of about 1 micron or smaller, which are prevented from sedimenting by Brownian motion. Such systems are obviously incapable of dispersing relatively coarse particles. They are moreover not fully stable, because the dispersed particles tend to grow in size, due to agglomeration and Ostwald ripening, until they are too large to be maintained in suspension.

An alternative to the above methods of suspension would be the use of a structured suspending system. Structured suspending systems depend on the rheological properties of the suspending medium to immobilise the particles, irrespective of size. This requires the suspending medium to exhibit a yield point, which is higher than the sedimenting or creaming force exerted by the suspended particles, but low enough to enable the medium to flow under externally imposed stresses, such as pouring and stirring, like a normal liquid. The structure reforms sufficiently rapidly to prevent sedimentation, once the agitation caused by the external stress has ceased. Three main types of structured system have been employed in practice, all involving an L_α-phase, in which bilayers of surfactant are arranged with the hydrophobic part of the molecule on the interior and the hydrophilic part on the exterior of the bilayer (or vice versa). The bilayers lie side by side, e.g. in a parallel or concentric configuration, sometimes separated by aqueous layers. L_α-phases (also known as G- phases) can usually be identified by their characteristic textures under the polarising microscope and/or by x-ray diffraction, which is often able to detect evidence of lamellar symmetry. Such evidence may comprise first, second and sometimes third order peaks with a d-spacing (2π/Q, where Q is the momentum transfer vector) in a simple integral ratio 1:2:3. Other types of symmetry give non-integral ratios. The d-spacing of the first peak in the series corresponds to the repeat spacing of the bilayer system. Most surfactants form an L_α-phase either at ambient or at some higher temperature when mixed with water in certain specific proportions. However such conventional L_α-phases do not usually function as structured suspending systems. Useful quantities of solid render them unpourable and smaller amounts tend to sediment.

The main types of structured system used in practice are based on dispersed lamellar, spherulitic and expanded lamellar phases. Dispersed lamellar phases are two phase systems, in which the surfactant bilayers are arranged as parallel plates to form domains of L_α-phase, which are interspersed with an aqueous phase to form an opaque gel-like system. They are described in EP 0 086614.

Spherulitic phases comprise well-defined spheroidal bodies, usually referred to in the art as spherulites, in which surfactant bilayers are arranged as concentric shells. The spherulites usually have a diameter in the range 0.1 to 15 microns and are dispersed in an aqueous phase in the manner of a classical emulsion, but interacting to form a structured system. Spherulitic systems are described in more detail in EP 0 151 884. Many structured systems are intermediate between dispersed lamellar and spherulitic, involving both types of structure. Usually systems having a more spherulitic character are preferred because they tend to have lower viscosity. A variant on the spherulitic system comprises prolate or rod shaped bodies sometimes referred to as batonettes. These are normally too viscous to be of practical interest. -S-

Both of the foregoing systems comprise two phases. Their stability depends on the presence of sufficient dispersed phase to pack the system so that the interaction between the spherulites or other dispersed mesophase domains prevents separation. If the amount of dispersed phase is insufficient, e.g. because there is not enough surfactant or because the surfactant is too soluble in the aqueous phase to form sufficient of a mesophase, the system will undergo separation and cannot be used to suspend solids. Such unstable systems are not "structured" for the purpose of this specification.

A third type of structured system comprises an expanded L_α-phase. It differs from the other two types of structured system in being essentially a single phase, and from conventional L_α-phase in having a wider d-spacing. Conventional L_α-phases, which typically contain 60 to 75% by weight surfactant, have a d-spacing of about 4 to 7 nanometers. Attempts to suspend solids in such phases result in stiff pastes which are either non-pourable, unstable or both. Expanded L_α-phases with d-spacing greater than 8, e.g. 10 to 15 nanometers, form when electrolyte is added to aqueous surfactants at concentrations just below those required to form a normal L_α-ρhase, particularly to surfactants in the H-phase.

The H-phase comprises surfactant molecules arranged to form cylindrical rods of indefinite length. It exhibits hexagonal symmetry and a distinctive texture under the polarising microscope. Typical H-phases have so high a viscosity that they appear to be curdy solids. H-phases near the lower concentration limit (the Li/H-phase boundary) may be pourable but have a very high viscosity and often a mucus-like appearance. Such systems tend to form expanded L_α-phases particularly readily on addition of sufficient electrolyte.

Expanded L_α-phases are described in more detail in EP 0 530 708. In the absence of suspended matter they are generally translucent, unlike dispersed lamellar or spherulitic phases, which are normally opaque. They are optically anisotropic and have shear-dependent viscosity. In this they differ from Li -phases, which are micellar solutions or microemulsions. Li-phases are clear, optically isotropic and are usually substantially Newtonian. They are unstructured and cannot suspend solids.

Some Li -phases exhibit small angle x-ray diffraction spectra, which show evidence of hexagonal symmetry and/or exhibit shear dependent viscosity. Such phases usually have concentrations near the Li/H-phase boundary and may form expanded L_α-phases on addition of electrolyte. However in the absence of any such addition of electrolyte they lack the yield point required to provide suspending properties, and are not, therefore, "structured systems" for the purpose of this specification.

Expanded L_α-phases of the above type are usually less robust than spherulitic systems. They are liable to become unstable at low temperatures. Moreover they frequently exhibit a relatively low yield stress, which may limit the maximum size of particle that can be stably suspended.

Most structured surfactants require the presence of a structurant, as well as surfactant and water in order to form structured systems capable of suspending solids. The term "structurant" is used herein to describe any non-surfactant capable, when dissolved in water, of interacting with surfactant to form or enhance (e.g. increase the yield point of,) a structured system. It is typically a surfactant-desolubiliser, e.g. an electrolyte. However, certain relatively hydrophobic surfactants such as isopropylamine alkyl benzene sulphonate can form spherulites in water in the absence of electrolyte. Such surfactants are capable of suspending solids in the absence of any structurant, as described in EP 0 414 549.

It is known from WO 01/05932 that carbohydrates can interact with surfactants to form suspending structures. Such systems generally exhibit even greater d-spacings than the electrolyte-structured expanded L_α-phases, described in EP 0 530 708. The d- spacings of the sugar-structured systems, described in WO 01/05932, are typically greater than 15nm, and may, for example, be as high as 50nm. Such systems can be obtained in a clear or translucent form by suitable choice of surfactant and carbohydrate concentration. The structured surfactant systems available hitherto have failed to combine adequate suspending power to suspend particles such as selenium sulphide or cationic polymer, with the foaming characteristics required of a shampoo.

The invention provides a novel aqueous suspending system, which comprises:

A. an anionic, non-ionic or amphoteric surfactant having an HLB greater than 37;

B. sufficient of an anionic, amphoteric or non-ionic surfactant having an HLB less than 30 to provide a mean HLB between 13 and 36.5; and

C. sufficient carbohydrate and/or electrolyte to form a structured suspending system.

According to a further embodiment the invention provides a shampoo containing suspended particle of anti-dandruff agent, such as selenium sulphide and/or of a cationic polymer.

The invention also provides the use of mica to improve the appearance of aqueous selenium sulphide suspensions. Preferably the mica is coated with a metal oxide or silica.

According to a fourth embodiment the invention provides an anti-dandruff shampoo, which comprises an aqueous suspending medium for selenium sulphide having an effective amount of selenium sulphide suspended therein, characterised in that the suspension additionally comprises sufficient suspended mica to provide a more homogeneous-looking product.

Preferably the aforesaid aqueous suspending medium for selenium sulphide comprises a surfactant and sufficient of an electrolyte or carbohydrate structurant to form a structured surfactant suspending system.

According to a fifth embodiment, the invention provides a clear, transparent container, containing an anti-dandruff shampoo as aforesaid. In the following discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

The composition of the invention is a shampoo, which preferably comprises surfactants suitable for the cleaning of hair. The surfactant system is typically a high foaming mild surfactant, which may be anionic, non-ionic, amphoteric, zwitterionic or cationic. Mixtures of anionic with non-ionic, zwitterionic and/or amphoteric surfactants are particularly preferred.

Preferably the surfactant comprises at least one high HLB surfactant, which is preferably an anionic surfactant, and which has an HLB greater than 37, more preferably greater than 38, most preferably greater than 39.Typically the high HLB surfactant has an HLB less than 80, more preferably less than 50, most preferably less than 45. We prefer that the high HLB surfactant constitutes more than 50% by weight of the total surfactant, more preferably at least 60%, most preferably at least 70%.

The surfactant preferably comprises at least one lower HLB surfactant, e.g. having an HLB less than 35, preferably less than 30, more preferably less than 20, even more preferably lower than 15. The lower HLB surfactant preferably has an HLB greater than 0.5, more preferably greater than 1. Preferred examples include surfactants having an HLB greater than 5, but less than 12 more preferably less than 10, in particular sarcosinates, alkyl sulphates, hydroxysultaines, and diethanolamides, such as coconut diethanolamide.

We particularly prefer that the surfactant should comprise low HLB non-ionic foam boosters having an HLB between 0.5 and 5, including fatty acids such as oleic acid, fatty alcohols such as oleyl alcohol, acetylated monoglycerides, glyceryl diesters, such as glyceryl dioleate, sorbitan triesters such as sorbitan trioleate and sorbitan tristrearate. For the avoidance of doubt the term "surfactant", as used herein, includes low HLB foam boosters wherever the context permits

The low HLB surfactant should preferably be present in a sufficient proportion to the higher HLB surfactant to provide a mean HLB between 13 and 36.5, more preferably above 15, still more preferably above 20, even more preferably above 25, most preferably above 27, but preferably less than 36, more preferably less than 35, most preferably less than 34.

The preferred high HLB anionic surfactants comprise alkyl ether sulphates. The latter are preferably the products obtained by:

(1) ethoxylating a natural fatty or synthetic alcohol having an average of more than 8, preferably more than 10, more preferably more than 12, but less than 30, preferably less than 25, more preferably less than 20, most preferably less than 15 carbon atoms with an average of at least 0.5, preferably more than 1, more preferably more than 1.5, but less than 40, preferably less than 30, more preferably less than 20, even more preferably less than 10, more preferably still less than 5, most preferably less than 3 ethyleneoxy groups;

(2) optionally, stripping any unreacted alcohol;

(3) reacting the ethoxylated product with a sulphating agent; and

(4) neutralising the resulting alkyl ether sulphuric acid with a base.

Suitable alkyl ether sulphates also include alkyl glyceryl sulphates, and random- or block-copolymerised alkyl ethoxy/propoxy sulphates. Other anionic surfactants, typically of lower HLB, which may be present include, for example: Gio-jo e.g. Ci_2-18 alkyl sulphate; G10--20 alkyl benzene sulphonate; G₈^o β-g- Cio-2₀ aliphatic soaps, such as dodecanoates, myristates, stearates, isostearates, oleates, linoleates, linolenates, behenates, erucates, palmitates, coconut and tallow soaps; olefin sulphonates; paraffin sulphonates; taurides; isethionates; ether sulphonates; ether carboxylates; aliphatic ester sulphonates, e.g. alkyl glyceryl sulphonates; sarcosinates; sulphosuccinates; or sulphosuccinamates.

A mixture of alkyl ether sulphate and sarcosinate is particularly preferred.

The cation of the anionic surfactant is typically sodium and/or ammonium. However it may alternatively or additionally comprise potassium, lithium, calcium, magnesium, ammonium, or an alkyl or hydroxyalkyl ammonium having up to 6 aliphatic carbon atoms including ethylammonium, isopropylammonium, monoethanolammonium, diethanolammonium, and triethanolammonium, or a mixture of any of the foregoing.

The surfactant may optionally comprise non-ionic surfactants such as amine oxides, polyglyceryl fatty esters, fatty acid ethoxylates, fatty acid monoalkanolamides, fatty acid dialkanolamides, fatty acid alkanolamide ethoxylates, propylene glycol monoesters, fatty alcohol propoxylates, alcohol ethoxylates, alkyl phenol ethoxylates, fatty amine alkoxylates and fatty acid glyceryl ester ethoxylates. Other non-ionic compounds suitable for inclusion in compositions of the present invention include mixed ethylene oxide/ propylene oxide block copolymers, ethylene glycol monoesters, alkyl polyglycosides, alkyl sugar esters including alkyl sucrose esters and alkyl oligosaccharide esters, sorbitan esters, ethoxylated sorbitan esters, alkyl capped polyvinyl alcohol and alkyl capped polyvinyl pyrrolidone. The surfactant may comprise an amphoteric or zwitterionic surfactant. The former may comprise so-called imidazoline betaines, also called amphoacetates, which were traditionally ascribed the zwitterionic formula:

CH₂ — ^: — CH₂

N ^"1N — CH₂COO-

\ c/ |

R¹ R

because they are obtained by reacting sodium chloracetate with an imidazoline. It has been shown, however, that they are actually present, at least predominantly, as the corresponding, amphoteric, linear amidoamines:

RCONH CH₂CH₂N CH₂ CH₂OH

I

CH₂COO-,

which are usually obtained commercially in admixture with the dicarboxymethylated form:

RCON CH₂CH₂N CH₂CH₂OH

I I

CH₂COO- CH₂COO-

R preferably has at least 8, more preferably at least 10 carbon atoms but less than 25, more preferably less than 22, even more preferably less than 20, most preferably less than 18. Typically R represents a mixture of alkyl and alkenyl groups, obtained, for example, from coconut or palm oil, and having sizes ranging from 8 to 18 carbon atoms, with 12 predominating, or a fraction of such a feedstock, such as lauryl (>90%C₁₂). The zwitterionic surfactant is preferably a betaine or sulphobetaine, e.g. one with the formula R"R'₂ NCH₂COOH₃ where R' is an aliphatic group having 1 to 4 carbon atoms and R" is an aliphatic group having from 8 to 25 carbon atoms, preferably a straight or branched chain alkyl or alkenyl group, or more preferably a group of the formula RCONR' (CH₂)_ni where R and R' have the same significance as before, and n is an integer from 2 to 4.

We prefer that R' is a methyl, carboxymethyl, ethyl, hydroxyethyl, carboxyethyl, propyl, isopropyl, hydroxypropyl, carboxypropyl, butyl, isobutyl or hydroxybutyl group.

The surfactant may comprise cationic surfactants such as fatty alkyl trimethylammonium or benzalkonium salts, amidoamines or imidazolines.

Preferably the total surfactant is present in a proportion of at least 2, more preferably at least 7, still more preferably at least 9, most preferably at least 10% by weight based on the total weight of the formulation, but less than 30, more preferably less than 25, most preferably less than 23% by weight.

We particularly prefer that the surfactant comprises A. an ether sulphate and B. a sarcosinate, betaine or sulphobetaine in a ratio of A:B from 1:1 to 4:1, preferably 1.5:1 to 3:1.

The anti-dandruff shampoo of the invention has suspending properties, sufficient to suspend an anti-dandruff agent such as selenium sulphide. It should be capable of maintaining at least the major portion of the solid in suspension for at least three months. This may be achieved by the conventional method of adding thickening polymers, such as xanthan gum or ethylene glycol stearates. However we prefer suspending systems that give no sedimentation after three months. To achieve this, it is generally necessary to use a structured suspending system, and in particular a novel suspending system as herein described. We particularly prefer the use of sugar structured surfactant systems in the present invention. We have also found that use of clear suspending systems, such as those of WO 01/05932 or WO 00/63079, provide mica suspensions, which are particularly attractive, visually.

The sugar is preferably a mono or, more preferably, disaccharide sugar, most preferably sucrose, but could for example be fructose, maltose, glucose or invert sugar. Other sugars, which can be used, include, for example, mannose, ribose, galactose, lactose, allose, altrose, talose, gulose, idose, arabinose, xylose, lyxose, erythrose, threose, acrose, rhamnose, fucose, glyceraldehyde, stachyose, agavose and cellobiose or a tri- or tetra-saccharide.

Alternatively, or additionally, the composition may contain an electrolyte as structurant. The concentration of electrolyte and/or sugar is preferably sufficient to provide a structured suspending system. The amount required depends on the nature and concentration of the surfactant. Typically, in the case of electrolyte alone, this is greater than 4, preferably greater than 5, more preferably greater than 6, most preferably greater than 7% by weight, based on the weight of the formulation, but less than 20, more preferably less than 15, most preferably less than 12%. In the case of sugar, the amount required is typically greater than 20%, preferably more than 30% most preferably more than 40%, but preferably less than 60% by weight.

The electrolyte is typically sodium and/or ammonium chloride, but could, for example, alternatively or additionally be or comprise, sodium carbonate, potassium chloride, sodium, phosphate, or sodium citrate.

For many shampoo applications high levels of electrolyte are undesirable. They may be unacceptably harsh on the hair. Instead of, or in addition to, using electrolyte to improve stability, it is often preferred to increase the proportion of low HLB surfactant until a stable formulation is obtained. The compositions of the invention are preferably substantially free from electrolyte.

As used herein "substantially free" means that they do not contain electrolyte in quantities sufficient to confer a suspending structure on the shampoo surfactant in the absence of the low HLB surfactant. Generally the lower the electrolyte content, the better the foaming properties. We prefer that the concentration of electrolyte is less than 7%, more preferably less than 5%, still more preferably less than 3%, even more preferably less than 1%, most preferably less than 0.1% by weight of the composition.

According to a preferred embodiment, therefore our invention therefore provides a substantially electrolyte-free structured aqueous shampoo composition comprising:

(1) A high foaming anionic, amphoteric and/or zwitterionic shampoo surfactant; and

(2) Sufficient of a low HLB surfactant to provide a structured suspending system. Preferably the low HLB surfactant comprises a non-ionic surfactant, which is preferably a low HLB foam booster having an HLB less than 5.

The optimum amount of electrolyte and/or low HLB surfactant can be determined by making incremental additions and measuring the yield point, e.g. using a rheometer, to determine where the maximum yield point is obtained.

Instead of measuring the yield point, a quick indication of the optimum amount is obtained by measuring conductivity. This falls with the addition of electrolyte or low HLB surfactant, to a minimum, located within a shallow trough, and then rises to a peak. The preferred range is usually within +/-2%, preferably +1-1%, of the first such minimum. Another quick indication of the formation of a structured system is to shake air into the composition and observe the bubbles, which show no tendency to rise in a structured system.

The shampoo preferably contains a cationic polymer, which may for example comprise a polyquaternium polymer, present in an amount effective for hair treatment. Typically this requires at least 0.01%, preferably at least 0.05%, more preferably at least 0.1%, most preferably at least 0.2% by weight of the polymer. While it is technically possible to suspend much larger concentrations of polymer, e.g. more than 10%, for reasons of cost effectiveness we prefer to use less than 5%, more preferably less than 2%, still more preferably less than 1%, most preferably less than 0.5% by weight of the polymer.

The anti-dandruff shampoo of the invention preferably contains at least an effective amount, preferably more than 0.05, more preferably more than 0.1, most preferably more than 0.5%, by weight, based on the total weight of the composition, of selenium sulphide. The upper limit, technically, is largely dependant upon what viscosity can be tolerated, however the more selenium there is present, the more mica will be required to mask it. This, as well as economic considerations, dictates a practical concentration less than 7%, preferably less than 5%, more preferably less than 3%, most preferably less than 2% by weight of the composition.

The particle size of the selenium sulphide is preferably greater than 0.1 μm, more preferably greater than 1 μm, more preferably still, greater than 10 μm. The particles are preferably less than lmm, more preferably less than 0.75mm, still more preferably less than 0.5mm, most preferably less than 0.1mm.

The proportion of mica required to give a homogeneous appearance will depend on the amount of selenium sulphide, but is typically at least 0.01, preferably at least 0.05, more preferably at least 0.1, most preferably at least 0.2% by weight of the composition. To avoid excessive cost, and also viscosity, it is preferred that the concentration of mica is less than 5, more preferably less than 2, still more preferably less than 1, most preferably less than 0.5% by weight of the composition.

We particularly prefer the use of coated mica, and especially mica coated with metal oxides such as iron oxide, titanium oxide, stannic oxide aluminium oxide and or silica. Such products are available in a number of different shades, some of which are especially suitable for hair shampoos. The mica preferably has a particle size greater than lμm, more preferably greater than 5 μm, most preferably greater than 10 μm, but less than 200 μm, more preferably less than 100 μm, most preferably less than 50 μm. The composition preferably contains effective amounts of hair conditioners such as oleyl alcohol, ethyl oleate, oleyl ethoxylate or glycerol, e.g. in proportions greater than 0.05, preferably greater than 0.1, more preferably greater than 0.5, most preferably greater than 0.7 % by weight of the composition, but less than 10, preferably less than 5, more preferably less than 3, most preferably less than 2%.

The product preferably contains a buffer, such as a citrate/ citric acid buffer. The pH is preferably greater than 4, more preferably greater than 5. Where the ingredients are sufficiently stable, the pH is still more preferably greater than 6, most preferably greater than 6.5, but less than 9, more preferably less than 8, most preferably less than 7.5. In the case of selenium sulphide the Ph needs to be lower to ensure stability, e.g. below 6.

The product may optionally contain other common ingredients of shampoos, such as, essential oils, fragrances, pigments, dyes, antiseptics and topical medicaments.

The product is suitable for marketing in clear containers, such as glass or plastic bottles, or plastic tubes or sachets.

The invention will be illustrated by the following examples, in which all proportions are % by weight unless stated to the contrary.

EXAMPLE I

The above composition was a stable, mild, high foaming structured liquid. The mean HLB of the surfactants was 33. The suspending system, in the absence of solid was clear. The suspension was stable after two months and had a particularly desirable golden lustre. It was especially suitable for washing blond hair.

EXAMPLE II

The following formulation was prepared by adding the following ingredients to water in the order shown, with gentle stirring, to avoid air entrainment. The ether sulphate and alkyl sulphate were each added as a 28% w/w aqueous solution. The surfactants had a mean HLB of 28.

Samples were prepared using three different tints of oxide-coated mica to give shampoo formulations suitable for blond, brunette and red hair respectively. The shampoos were stable, pourable and had a particularly fine pearly lustre, compared with conventional pearl shampoo based on ethylene glycol stearates as the pearlising agent. The presence of the selenium sulphide was not detectable.

EXAMPLE III

The above composition was a stable, mild, high foaming structured liquid. The surfactant had a mean HLB of 33. On stirring with 1% of micronized selenium sulphate (median particle size 5μm), a suspension was obtained, which showed no separation after six months storage at laboratory ambient temperature. Small angle X- ray diffraction and electron microscopy confirmed a spherulitic structure. In the absence of mica, the formulation had an unattractive mottled appearance.

EXAMPLE IV

1 An aqueous solution of ₅-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

2 Ex Merck.

The above composition was a fully stable, homogeneous-looking, spherulitic liquid, with an attractive metallic gold sheen. The surfactant had a mean HLB of 32. No sedimentation was observed after six months storage.

EXAMPLE V

A cationic polymer formulation was prepared by adding the following ingredients, except the ammonium chloride, to water in the order shown, with gentle stirring, and then blending with a high shear mixer. The mixture was allowed to deaerate for two hours. Finally the ammonium chloride was added with gentle stirring to avoid excessive air entrainment. The ether sulphate and alkyl sulphate were each added as a 28% w/w aqueous solution.

A stable, pourable lamellar suspension, showing low intensity scattering between 4 and 20nm, was obtained.

EXAMPLES VI and VII

Electrolyte-free formulations were prepared by adding the following ingredients to water in the order shown, with gentle stirring at room temperature until homogeneous.

The formulations were buffered to pH 5.5 with a citrate buffer. They formed suspensions with 10% coated mica, which were stable at room temperature and at 45^°C after two months. The Examples had a viscosity of approximately 3 Ps at 21s^"1 shear.

Claims

1. An aqueous suspending system, which comprises: (A) an anionic, non-ionic and/or amphoteric surfactant having an HLB greater than 37; (B) sufficient of an anionic, amphoteric and/or non-ionic surfactant having an HLB less than 30 to provide a mean HLB between 13 and 36.5; and (C) sufficient carbohydrate and/or electrolyte to form a structured suspending system.

2. An aqueous suspending system according to claim 1 characterised in that the surfactant (A) comprises an alkyl ether sulphate.

3. An aqueous suspending system according to either of claims 1 and 1, characterised in that the surfactant (A) constitutes at least 60% by weight of the total surfactant.

4. An aqueous suspending system according to any of claims 1 to 3, characterised in that the surfactant (B) comprises a surfactant having an HLB between 5 and 15.

5. An aqueous suspending system according to any of claims 1 to 4 characterised in that the surfactant (B) comprises at least one surfactant selected from sarcosinates, hydroxysultaines, alkyl sulphates, alkyl diethanolamides.

6. An aqueous suspending system according to any of claims 1 to5 characterised in that the surfactant (B) comprises at least one low HLB foam booster having an HLB between 0.5 and 5.

7. An aqueous suspending system according to claim 6 characterised in that the low HLB foam booster is non-ionic.

8. An aqueous suspending system according to claim 7 characterised in that the low HLB foam booster is oleyl alcohol or oleic acid.

9. A substantially electrolyte-free aqueous suspending system according to any foregoing claim.

10. A shampoo comprising an aqueous suspending system according to any foregoing claim characterised in that it contains suspended selenium sulphide and/or cationic polymer.

11. The use of an aqueous suspending system according to any of claims 1 to 9 to suspend selenium sulphide.

12. The use of an aqueous suspending system according to any of claims 1 to 9 to co-suspend selenium sulphide and mica.

13. The use of mica to impro ve the appearance of aqueous selenium sulphide suspensions.

14. An anti-dandruff shampoo, which comprises an aqueous suspending medium for selenium sulphide having an effective amount of selenium sulphide suspended therein, characterised in that the suspension additionally comprises sufficient suspended mica to provide a more homogeneous-looking product.

15. A shampoo according to claim 14 characterised in that said aqueous suspending medium comprises sufficient of a surfactant and an electrolyte and/or carbohydrate structurant to form a structured surfactant suspending system.

16. A clear transparent container containing an anti-dandruff shampoo according to either of claims 14 and 15.