EP0301884A1

EP0301884A1 - Liquid detergent compositions

Info

Publication number: EP0301884A1
Application number: EP88307008A
Authority: EP
Inventors: Mario Bulfari; Johannes Cornelis Van De Pas; Anthony John Roberts; John Mark Saunders; Bryan Cecil Smith
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1987-07-31
Filing date: 1988-07-29
Publication date: 1989-02-01
Also published as: ES2038761T3; DE3867361D1; GB8718215D0; EP0301884B1

Abstract

An aqueous liquid detergent composition with a pH of 12 or less at 1% weight concentration in water and a viscosity no greater than 1.5 Pas at a shear rate of 21s<-><1>, said composition comprising at least 1% by weight of dissolved electrolyte and at least 1% by weight of a surfactant system which consists of one or more detergent surfactants, which surfactant system somewhere between 0.0001% and 5% weight concentration alone in water has a cloudy phase somewhere in the temperature range of 40 DEG C down to the freezing point of the surfactant system at that concentration in water.

Description

This invention relates to aqueous liquid detergent compositions for washing fabrics.
The applicants have discovered that such detergent liquids can demonstrate one or more surprising advantages selected from fabric softening, improved stability with pourability, enhanced cleaning and other benefits if formulated according to a special definition set-forth hereinbelow.
One approach to providing a softening benefit in liquid laundering agents has been to incorporate a swelling bentonite clay, as described in UK Patent Specification GB-A-2,168,717. However, this has a tendency to increase the product viscosity to an unacceptable level unless an additional agent, namely a low molecular weight polyacrylate, is also incorporated. Moreover, although some fabric softening benefit can be obtained from these clays, it is generally some way short of that which can be obtained by the application of softening materials to fabrics in the rinse step of a laundering process, i.e. using conventional rinse conditioners.
The present invention now provides an aqueous liquid detergent composition with a pH of 12 or less at 1% weight concentration in water and a viscosity no greater than 1.5 Pas at a shear rate of 21s⁻¹, comprising at least 1% by weight of dissolved electrolyte and at least 1% by weight of a surfactant system which consists of one or more detergent surfactants, which surfactant system somewhere between 0.0001% and 5% weight concentration alone in water has a cloudy phase somewhere in the temperature range of 40°C down to the freezing point of the surfactant system at that concentration in water.
The detergent surfactants which make up the surfactant system maybe selected from known anionic, nonionic, zwitterionic and amphoteric detergent surfactants, for example as chosen from the classes, sub-classes and specific examples of such detergent surfactants described in Surface Active Agents Vol. I by Schwartz and Perry, Interscience (1949) and Vol II by Schwartz, Perry and Berch, Interscience (1958), in the current edition of "McCutcheon's Emulsifiers & Detergents" published by the McCutcheon division of Manufacturing Confectioners Company or in 'Tensid-Taschenbuch', H.Stache, 2nd ed., Carl Hanser Verlag, München & Wien, 1981.
An alternative aspect of the present invention provides an aqueous liquid detergent composition with a pH of 12 or less at 1% weight concentration in water and a viscosity no greater than 1.5 Pas at a shear rate of 21s⁻¹, comprising at least 1% by weight of dissolved electrolyte and at least 1% by weight of a surfactant system which consists of one or more detergent surfactants including a nonionic detergent surfactant which somewhere between 0.0001% and 5% weight concentration alone in water has a cloudy phase somewhere in the temperature range of 40°C down to the freezing point of the nonionic detergent surfactant at that concentration in water.
It should be noted that this cloud point requirement for the nonionic detergent surfactant applys regardless of whether when with any other detergent surfactants which make up the surfactant system, the total surfactant system also then exhibits such cloudy phase formation as defined. When the surfactant system comprises a nonionic detergent surfactant according to the definition of the alternative aspect of the invention, any other detergent surfactant of a kind referred to previously, may also be present including one or more others of the nonionic type.
In either aspect of the invention, the aqueous concentration at which the cloudy phase exists at one or more temperatures in the range of 40°C down to the freezing point of the surfactant system in distilled water, may be a specific concentration, or more often, will span a range of such concentrations. This concentration is preferably 3% and/or 1% and/or 0.1% and/or 0.01% by weight.
When regarded from the point of view of a fixed relevant aqueous concentration, the surfactant system or the nonionic detergent surfactant, as appropriate, has a cloudy phase somewhere in the temperature range from 40°C, preferably 15°C, most preferably 10°C down to the freezing point in distilled water at that concentration. In practice, this means that it has a cloud point of not more than 40°C, preferably 15°C, most preferably 10°C. In other words, it is clear from the freezing point up to the cloud point which is the onset of turbidity, i.e. at 40°C or less. In fact, many will be cloudy right down to the freezing point of the composition. As used herein, the term cloudy phase includes 'cloud phase' and all other turbid phases e.g. lamellar phase, as will be known to those skilled in the art. Cloud phase and cloud point have the meanings ascribed to them in Surface Active Ethylene Oxide Adducts by N. Schonfeldt, Pergamon Press 1969, pp 145 to 154. In general terms, the cloud point of a surfactant material is the temperature at which association between the surfactant and water molecules through hydrogen bonding breaks down, leading to the separation of surfactant rich and water rich phases and a consequential increase in turbidity or cloudiness.
The cloud point correlates approximately to the hydrophilic - lipophilic balance (HLB) of the surfactant system. Preferably, the surfactant system, or one nonionic detergent surfactant which is part of that system, has an HLB equal to or less than 10.5, especially less than 10.0 or even below 9.5. However, the HLB should preferably be above 6.0, most preferably above 7.5.
Suitable nonionic detergent surfactants which may be used include in particular the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example aliphatic alcohols, acids, or alkyl phenols with alkylene oxides, especially ethylene oxide either alone or with propylene oxide. Specific nonionic detergent compounds are alkyl (C₆ - C₂₂) phenols-ethylene oxide condensates, the condensation products of aliphatic (C₈ -C₁₈) primary or secondary linear or branched alcohols with ethylene oxide, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylenediamine. Other so-called nonionic detergent compounds include long chain tertiary amine oxides, long chain tertiary phosphine oxides and dialkyl sulphoxides.
Where, for example, alkylene oxides adducts of fatty materials are used as the nonionic detergent compounds, the number of alkylene oxide groups per molecule has a considerable effect upon the cloud point as indicated by the Schonfeldt reference mentioned above. The chain length and nature of the fatty material is also influential, and thus the preferred number of alkylene oxide groups per molecule depends upon the nature and chain length of the fatty material.
We have found for example that where the fatty material is a fatty alcohol having about 13 to 15 carbon atoms, the adduct having 3 ethylene oxide (EO) groups per molecule has a cloud point of less than 0°C and is therefore suitable for use in the present invention. A similar detergent surfactant having 7 ethylene oxide groups per molecule has a cloud point of about 48°C and is therefore unsuitable. Further ethoxylation raises the cloud point still higher. Thus the similar detergent surfactant with 11 ethylene oxide groups per molecule has a cloud point higher than 80°C. However, we have found that for many common ethoxylated fatty alcohol nonionics (ie. with typical fatty residues), the required cloud point can be achieved if the average degree of ethoxylation per molecule is less than 56% by weight and/or the average number of EO groups per molecule is six or less, typically about 3.
Such nonionic detergent surfactants are known per se from a variety of references such as GB-A-1 241 754 or US 4 537 708. The former reference, whilst mentioning the possibility of liquids, discloses no example of a stable, pourable liquid. The latter discloses slurries containing sodium tripolyphosphate and at least 13% by weight of detergent surfactants. Such slurries have unacceptably high viscosities in the context of the present invention. It can also be noted that UK patent specification GB-A-2 153 839 discloses examples of aqueous liquid detergent compositions which contain some low-detergency, foam boosting surfactants of the long-chain ethanolamide or diethanolamide kind which are not detergent surfactants as defined herein.
However, when it is desired to formulate with a surfactant system comprising a nonionic detergent surfactant having a cloud point defined according to the alternative aspect of the invention, then the presence of other nonionic detergent surfactants will not necessarily cause loss of cloudiness of the whole system, under the relevant conditions, for example because of non-ideal mixing of components in the product, which is a condition which can remain even after transport or prolonged storage, or because of the properties of the surfactant system as a whole.
Thus, whilst a 1:1 molar mixture of such 3EO and 11EO ethoxylated alcohols may well have an HLB close to that of the 7EO material, the 7EO material alone would give a clear solution below 15°C, passing to a cloudy condition above about 48°C, whilst the mixture could be cloudy below 15°C. In the context of the present invention therefore, the use of the 7EO material alone would be unsuitable while the mixture of 3EO and 11EO materials would be suitable.
The anionic detergent surfactants are usually water-soluble alkali metal salts of organic sulphates and sulphonates having alkyl radicals containing from about 8 to about 22 carbon atoms, the term alkyl being used to include the alkyl portion of higher acyl radicals. Examples of suitable synthetic anionic detergent compounds are sodium and potassium alkyl sulphates, especially those obtained by sulphating higher (C₈ -C₁₈) alcohols produced for example from tallow or coconut oil, sodium and potassium alkyl (C₉ -C₂₀) benzene sulphonates, particularly sodium linear secondary alkyl (C₁₀ -C₁₅) benzene sulphonates; sodium alkyl glyceryl ether sulphates, especially those ethers of the higher alcohols derived from tallow or coconut oil and synthetic alcohols derived from petroleum; sodium coconut oil fatty monoglyceride sulphates and sulphonates; sodium and potassium salts of sulphuric acid esters of higher (C₈ -C₁₈) fatty alcohol-alkylene oxide, particularly ethylene oxide, reaction products; the reaction products of fatty acids such as coconut fatty acids esterified with isethionic acid and neutralised with sodium hydroxide; alkane monosulphonates such as those derived by reacting alpha-olefins (C₈ -C₂₀) with sodium bisulphite and those derived from reacting paraffins with SO₂ and Cl₂ and then hydrolysing with a base to produce a random sulphonate; and olefin sulphonates, which term is used to describe the material made by reacting olefins, particularly C₁₀ -C₂₀ alpha-olefins, with SO₃ and then neutralising and hydrolysing the reaction product. The preferred anionic detergent compounds are sodium (C₁₁ -C₁₅) alkyl benzene sulphonates and sodium (C₁₆ -C₁₈) alkyl sulphates.
It is also preferred in many cases to include an alkali metal soap of a fatty acid, especially a soap of an acid having from 12 to 18 carbon atoms, for example oleic acid, ricinoleic acid, and fatty acids derived from castor oil, rapeseed oil, groundnut oil, coconut oil, palmkernel oil or mixtures thereof. The sodium or potassium soaps of these acids can be used, the potassium soaps being preferred.
In the definition of the present invention, the requirement of a pH of 12 or less at 1% aqueous dilution is to exclude a number of disadvantages. First, a major benefit of many compositions according to the present invention is a fabric softening effect. Very alkaline wash solutions tend to have a harshening effect. There can also be disadvantages in terms of safety and of adverse effects on the stability of any enzymes which optionally may be present.
The present invention also requires the compositions to have a viscosity no greater than 1.5 Pas at a shear rate of 21s⁻¹. However, at the latter shear rate, many practical embodiments will have a viscosity no greater than 1.25 Pas, preferably 1.0 Pas, 900 mPas, or even 850 mPas.
This low viscosity may be achieved by incorporating sufficient hydrotrope in the composition to render the system isotropic. Hydrotropes are water soluble compounds which serve to increase the solubility of surfactants in aqueous solution and are well known in the art. Typical examples are lower alkanols such as ethanol, alkanolamines, e.g. triethanolamine, salts of aralkyl sulphonates and those with ureum types of molecule.
Alternatively, the composition as a whole (as opposed to the diluted surfactant system) is anisotropic (structured) and comprises a lamellar phase formed by the surfactant system, preferably as lamellar droplets dispersed in an aqueous continuous phase which contains the dissolved electrolyte. In that case, to achieve the required low viscosity, the composition should be formulated as described hereinbelow.
Of the structured compositions, those which are capable of suspending solid particles are generally preferred, especially those which actually contain such particles in suspension. Structuring is brought about by the interaction of the surfactant molecules in the presence of water and the dissolved electrolyte, for example as described in Chapter 2, entitled 'Detergents' by H A Barnes, in K Walters (Ed.), 'Rheometry: Industrial Applications', J Wiley & Sons, Letchworth 1980.
To achieve the required low viscosity in the lamellar structured embodiments, the composition either includes at least one special viscosity-reducing polymer (as defined hereinbelow) and/or at least one of the following three rules must be applied.
The first rule is that the surfactant system also should contain an anionic detergent surfactant and that the anionic:nonionic weight ratio should be 6:1 or less of the anionic, but most frequently, 4:1 or less.
Here, it can be noted that European Patent Specification EP-A-38,101 describes structured liquids based on a blend of anionic and nonionic surfactants with an alkali metal soap incorporated to ensure stability. However, we have now found that many of those compositions of the present invention which are structured, can be formulated stably without soap, for example where the ratio of anionic to nonionic surfactants is from 6:1 to 1:2, preferably from 4:1 to 1:1, especially from 3:1 to 4:3. Also, when soap is included, stability can be obtained for a greater range of anionic/nonionic blends, than with the prior art compositions. In this context, the anionics may (for example) be as described in the aforementioned EP-A-38,101.
The second rule is that the weight ratio of the surfactant system to water is 5:1 or less of the surfactant system.
The third rule is that any suspended solids should contribute no more than 15%, preferably no more than 10% by volume of the total composition.
In these lamellar structured embodiments, most preferably any two of the three rules are applied, especially all three.
The special viscosity reducing polymer(s) can be selected from one of two classes, or from both.
The first class of special viscosity reducing polymers comprises those polymers which would be only partly dissolved in the aqueous continuous phase as described in our UK patent application no. 8718216. This allows a viscosity reduction (due to the polymer which is dissolved) whilst incorporating a sufficiently high amount to achieve a secondary benefit, especially building, because the part which is not dissolved does not bring about the instabilty that would occur if substantially all were dissolved.
Examples of partly dissolved polymers include many of the polymer and co-polymers salts already known as detergency builders. For example, may be used (including building and non-building polymers) polyethylene glycols, polyacrylates, polymaleates, polysugars, polysugarsulphonates and co-polymers of any of these. Preferably, the partly dissolved polymer comprises a co-polymer which includes an alkali metal salt of a polyacrylic, polymethacrylic or maleic acid or anhydride. Preferably, compositions with these co-polymers have a pH of above 8.0. In general, the amount of viscosity reducing polymer can vary widely according to the formulation of the rest of the composition. However, typical amounts are from 0.5 to 4.5% by weight.
The second class of special viscosity reducing polymers comprises those polymers which are substantially totally soluble in the aqueous phase and have an electrolyte resistance of more than 5 grams sodium nitrilotriacetate in 100ml of a 5% by weight aqueous solution of the polymer, said soluble polymer also having a vapour pressure in 20% aqueous solution, equal to or less than the vapour pressure of a reference 2% by weight or greater aqueous solution of polyethylene glycol having an average molecular weight of 6000; said soluble polymer having a molecular weight of at least 1000. Use of such polymers is generally described in our UK patent application No. 8718217.
The incorporation of the soluble polymer permits formulation with improved stability at the same viscosity (relative to the composition without the soluble polymer) or lower viscosity with the same stability. The soluble polymer can also reduce viscosity drift, even when it also brings about a viscosity reduction.
It is especially preferred to incorporate the soluble polymer with a partly dissolved polymer which has a large insoluble component. That is because although the building capacity of the partly dissolved polymer will be good (since relatively high quantities can be stably incorporated), the viscosity reduction will not be optimum (since little will be dissolved). Thus, the soluble polymer can usefully function to reduce the viscosity further, to an ideal level.
The soluble polymer can, for example, be incorporated at from 0.05 to 20% by weight, although usually, from 0.1 to 2.5% by weight of the total composition is sufficient, and especially from 0.2 to 1.5% by weight. Often, levels above these can cause instability. A large number of different polymers may be used as such a soluble polymer, provided the electrolyte resistance and vapour pressure requirements are met. The former is measured as the amount of sodium nitrilotriacetate (NaNTA) solution necessary to reach the cloud point of 100ml of a 5% solution of the polymer in water at 25°C, with the system adjusted to neutral pH, i.e. about 7. This is preferably effected using sodium hydroxide. Most preferably, the electrolyte resistance is 10g NaNTA, especially 15g. The latter indicates a vapour pressure low enough to have sufficient water binding capability, as generally explained in the applicants' specification GB-A-2 053 249. Preferably, the measurement is effected with a reference solution at 10% by weight aqueous concentration, especially 18%.
Typical classes of polymers which may be used as the soluble polymer, provided they meet the above requirements, include polyethylene glycols, Dextran, Dextran sulphonates, polyacrylates and polyacrylate/maleic acid co-polymers. Whether a particular polymer is partly soluble or substantially totally soluble will depend on the formulation of the remainder of the composition, but in particular on the type and amount of dissolved electrolyte.
The soluble polymer must have an average molecular weight of at least 1000 but a minimum average molecular weight of 2000 is preferred.
The compositions of the present invention may also contain other ingredients, especially ingredients useful in the washing of fabrics. Thus, a fully formulated fabric washing product may be so obtained.
The electrolyte is preferably at least 10% by weight of the composition, most preferably at least 10% of the composition being electrolyte which is dissolved. In any case, the electrolyte may be partially or totally, a water-soluble builder salt. Where all or part of the electrolyte is not a builder salt, then it will simply be another water soluble electrolyte. In the case of systems which suspend solids, these solids will generally be excess of water soluble builder salt beyond the solubility limit of the dissolved builder salt acting as electrolyte (although of course some or all of the electrolyte may not be dissolved builder salt). It is possible to suspend builders which are not water soluble and so cannot constitute all or part of the electrolyte. A prime example of these builders comprises the aluminosilicates.
To give a guide as to preferred levels of ingredients, it is therefore convenient to refer to the total amount of electrolyte and builder, although it will be appreciated from the previous paragraph that some or all of the electrolyte can be builder and vice versa. In this context, the total amount of these substances will hereinafter be referred to under the general term electrolyte/builder material. However, the preferred amounts of both detergent active material and electrolyte/builder material will differ between those compositions which are structured prior to dilution (whether or not solids are suspended) and those (hydrotroped) systems which are unstructured pre-dilution.
The total amount of detergent active material in the structured liquids is preferably from 2% to 50% by weight of the composition, most preferably from 5% to 40%, especially from 7.5% to 30% and typically from 10% to 20%. For the unstructured liquids, the amount is preferably from 5% to 70%, most preferably from 10% to 65%, especially from 15% to 60% and typically from 20% to 50%.
In the lamellar structured liquids, the total amount of electrolyte/builder material is preferably from 1% to 70% by weight of the composition, most preferably from 2% to 50%, especially from 5% to 40% and typically from 10% to 30%. In the unstructured liquids, the amount is preferably from 0.5% to 40%, most preferably from 1% to 30%, especially from 1.5% to 20% and typically from 2% to 15%.
In both the structured and unstructured liquids optionally, other conventional ingredients are also included.
When the compositions of the invention, contain a detergency builder material this may be any material capable of reducing the level of free calcium ions in the wash liquor and will preferably provide the composition with other beneficial properties such as the generation of an alkaline pH, the suspension of soil removed from the fabric and the dispersion of any fabric softening clay material which may be included in the composition.
Examples of phosphorus-containing inorganic detergency builders, when present, include the water-soluble salts, especially alkaline metal pyrophosphates, orthophosphates, polyphosphates and phosphonates. Specific examples of inorganic phosphate builders include sodium and potassium tripolyphosphates, phosphates and hexametaphosphates.
Examples of non-phosphorus-containing inorganic detergency builders, when present, include water-soluble alkali metal carbonates, bicarbonates, silicates and crystalline and amorphous alumino silicates. Specific examples include sodium carbonate (with or without calcite seeds), potassium carbonate, sodium and potassium bicarbonates and silicates.
Examples of organic detergency builders, when present, include the alkaline metal, ammonium and substituted ammonium polyacetates, carboxylates, polycarboxylates, polyacetyl carboxylates and polyhydroxsulphonates. Specific examples include sodium, potassium, lithium, ammonium and substituted ammonium salts of ethylenediaminetetraacetic acid, nitrilotriacetic acid, oxydisuccinic acid, melitic acid, benzene polycarboxylic acids and citric acid.
As stated, apart from the water, detergent active material and electrolyte/builder material, a number of optional conventional ingredients may also be present. Examples of such conventional ingredients which may be present in the composition include the lather boosters (foam-boosting surfactants) such as alkanolamides, particularly the mono- and di-ethanolamides derived from palm kernel fatty acids and coconut fatty acids, lather depressants, oxygen-releasing bleaching agents such as sodium perborate and sodium percarbonate, peracid bleach precursors, chlorine-releasing bleaching agents such as trichloroisocyanuric acid, inorganic salts such as sodium sulphate, and, usually present in very minor amounts, fluorescent agents, perfumes, enzymes such as lipases (e.g. Lipolase (Trade Mark) ex Novo), proteases and amylases, germicides and colourants. Fabric softening clay materials may also be included to boost the softening effect produced by the present invention.
The invention will now be illustrated by the following non-limiting examples.

Example 1 - Determination of Cloud Point for Various Surfactant Systems

Concentrated systems comprising the detergent surfactants (with predetermined ratios) were prepared at a concentration of approximately between 20% and 40% w/w in water. From this sample, 50 grams were taken and diluted with water whilst stirring, until a clear solution was obtained. The water must be added slowly because it may take some time for the detergent active material to disintegrate/dissolve. There may be a point at the onset of clarity when turbidity is no longer visible to the unaided eye but ordered phases still just exist. In that case, the precise point where a truly clear solution is first created may be determined by detecting the point where streaming birefringence disappears, or by any other electronic detection system for detecting turbidity, e.g. scattering measurements.
The percentage level of detergent surfactant (%DS) at which a clear solution is first obtained is expressed by the simple formula
where A = grams of concentrated detergent surfactant solution
B = %w/w of detergent surfactant present in the concentrated solution
C = grams of water added until a clear solution is first obtained
The results obtained for the various blends are shown in Table I.
In Table I, compositions 3-7 and 10, 11 are all in accordance with the present invention.

Example 2 - Lamellar Structured Compositions with Electrolyte/Builder and Minors

The compositions of Example 2 were tested by mechanical means for assessing softening. Compositions 2.2 and 2.3 according to the present invention gave superior softening performance relative to reference composition 2.1.

Example 3: Isotropic Composition with Electrolyte and Minors

This was a clear isotropic liquid with pH = 9.3
This composition according to the invention gave a cloudy phase on dilution to low concentrations in water at 5°C (but not at 20°C). A similar reference composition with C₁₃₋₁₅ alcohol 7EO in place of the 3EO nonionic gave no cloudy phase even in water/ice mixture.
The above composition according to the invention gives fabric softening performance comparable to compositions 2.2 and 2.3 in Example 2.

Example 4 - Lamellar Structured Liquid with Electrolyte/Builder, Minors and Viscosity Reducing Polymers

In a variant of the above formulation, 0.2% by weight of a polyethylene glycol, average MW 2,500 was added to the composition as a substantially totally soluble viscosity reducing polymer.

Claims

1. An aqueous liquid detergent composition with a pH of 12 or less at 1% weight concentration in water and a viscosity no greater than 1 Pas at a shear rate of 21s⁻¹, said composition comprising at least 1% by weight of dissolved electrolyte and at least 1% by weight of a surfactant system which consists of one or more detergent surfactants, which surfactant system somewhere between 0.0001% and 5% weight concentration alone in water has a cloudy phase somewhere in the temperature range of 40°C down to the freezing point of the surfactant system at that concentration in water.

2. A composition according to Claim 1, in which the surfactant system comprises a nonionic detergent surfactant which has an HLB of equal to or less than 10.5

3. A composition according to either preceding claim, in which the surfactant comprises a nonionic detergent surfactant which has an HLB of less than 9.5.

4. A composition according to any of claims 1 to 3, in which the surfactant system comprises a nonionic detergent surfactant which has an HLB greater than 7.5.

5. A composition according to any preceding claim, wherein the surfactant system comprises a nonionic detergent surfactant which is an ethoxylated fatty alcohol having an average degree of ethoxylation less than 56% by weight.

6. A composition according to claim 5, wherein the nonionic detergent surfactant is an ethoxylated fatty alcohol having an average of six or less ethoxy groups per molecule.

7. The composition according to claim 6, wherein the number of ethoxy groups is about three.

8. A composition according to any preceding claim, wherein the said concentration at which the cloudy phase exists is 3% by weight.

9. A composition according to any preceding claim, wherein the said concentration at which the cloudy phase exists is 1% by weight.

10. A composition according to any preceding claim, wherein the said concentration at which the cloudy phase exists is 0.1% by weight.

11. A composition according to any preceding claim, wherein the said concentration at which the cloudy phase exists is 0.01% by weight.

12. A composition according to any preceding claim, wherein the cloud point of the surfactant system is not more than 15°C.

13. A composition according to claim 12, wherein the cloud point is not more than 10°C.

14. A composition according to any preceding claim, having a viscosity of 1.25 Pas or less at a shear rate of 21 s⁻¹.

15. A composition according to claim 14, wherein the viscosity is 1.0 Pas or less.

16. A composition according to claim 15, wherein the viscosity is 850 mPas or less.

17. A composition according to any preceding claim, further comprising sufficient hydrotrope to render the composition isotropic.

18. A composition according to any of claims 1-13, wherein the surfactant system in the composition is in the form of a lamellar phase.

19. A composition according to claim 18, wherein the lamellar phase comprises lamellar droplets which are dispersed in an aqueous continuous phase containing the dissolved electrolyte.

20. A composition according to claim 18 or claim 19, wherein the composition is capable of suspending particulate solids.

21. A composition according to any of claims 18-20, further comprising particulate solids in suspension.

22. A composition according to claim 21, wherein the suspended solids constitute 15% or less by volume of the total composition.

23. A composition according to claim 22, wherein the suspended solids constitute 10% or less by volume of the total composition.

24. A composition according to any of claims 18-23, wherein the surfactant system comprises both anionic and nonionic detergent surfactants in an anionic to nonionic weight ratio of 6:1 or less of the anionic.

25. A composition according to claim 24, wherein the ratio is 4:1 or less of the anionic.

26. A composition according to any of claims 18-25, wherein the weight ratio of the surfactant system to water is 5:1 or less of the surfactant system.

27. A composition according to any preceding claim, comprising at least 10% by weight of electrolyte.

28. A composition according to any preceding claim, comprising at least 10% by weight of electrolyte which is dissolved.

29. A composition according to any preceding claim, further comprising a fatty mono- or di-ethanolamide foam-boosting surfactant.

30. A method of washing fabrics, comprising contacting said fabrics with a 5% by weight, or lower, aqueous wash solution of a composition according to any preceding claim.