WO2013160023A1

WO2013160023A1 - Externally structured aqueous isotropic liquid laundry detergent compositions

Info

Publication number: WO2013160023A1
Application number: PCT/EP2013/055648
Authority: WO
Inventors: Jonathan BEST; Adam Jan Kowalski; Philip Michael Ryan; Alastair Richard Sanderson
Original assignee: Unilever Plc; Unilever N.V.; Conopco, Inc., D/B/A Unilever
Priority date: 2012-04-23
Filing date: 2013-03-19
Publication date: 2013-10-31
Also published as: EP2841546A1; AR090780A1; IN2014MN02040A; CN104364362A; ZA201407636B; BR112014026300A2

Abstract

An externally structured aqueous isotropic liquid laundry detergent composition comprising: -at least 10 wt% water, -at least 10 wt% of a mixed surfactant system comprising anionic surfactant, -an external structuring system comprising from 0.025 to 0.15 wt% insoluble cellulosic fibre comprising at least 50 wt% activated citrus fibre, -at least 0.01 wt% suspended non-clay solid particles, characterised in that the external structuring system further comprises at least 0.1 wt% water-swellable clay.

Description

EXTERNALLY STRUCTURED AQUEOUS ISOTROPIC LIQUID LAUNDRY

DETERGENT COMPOSITIONS

TECHNICAL FIELD

This invention relates to externally structured aqueous isotropic liquid laundry detergent compositions comprising surfactant and suspended particles.

BACKGROUND

It is desirable to be able to include particulate materials into liquid detergent compositions, for example encapsulated perfume or visual cues. Advantageously, the liquid should have rheology that provides a yield stress (also known as critical stress) so that the particles remain stably suspended and dispersed.

It has been proposed to use external structurants in aqueous detergent liquids to give the required rheology and suspending duty.

Hydrogenated castor oil (HCO) may be converted into an external structurant by crystallising it in the liquid, or in part of the liquid. This crystallisation process may impose formulation constraints, especially when using high surfactant levels.

HCO structured liquids are slightly cloudy, which is undesirable when visual cues are suspended in the liquid. Because the HCO structurant is formed by cooling, its performance is reduced if the liquid is subjected to extreme temperatures, either in the supply chain, or in the hands of consumers. When encapsulated perfume microcapsules are added to concentrated surfactant solutions comprising HCO microcapsules have been found to undergo agglomeration into clumps during the incorporation step. These agglomerates remain undispersed in the liquid. This increases visibility of the microcapsules. It also causes uneven dosing of their contents per wash, as liquid is removed from the container.

An alternative to HCO is a structuring network formed from insoluble cellulosic fibre. One such external structuring system uses microfibrous cellulose (MFC) either on its own as in US2007/0197779), or in combination with HCO, as in WO2010/048154. However, MFC suffers from other disadvantages. The first is that due to its very low incorporation levels it can fail to remain evenly dispersed through the liquid if air micro bubbles form and get trapped by the structuring network to buoy the MFC up. This may happen, for example, when air is released during thermal cycling of a stored product. Combining it with HCO has the same disadvantages of the HCO system due to the need to keep the HCO in the correct crystalline state to provide the structuring effect. Citrus fibres and their uses for structuring of foodstuffs and personal care compositions are described in US2004/0086626 and US2009/269376. It is suggested that material may be suspended in the structured compositions.

The compatibility of an activated citrus fibre structured liquid detergent

composition with cleaning and care enzymes is described in

PCT/EP201 1 /067549. Its use with cationic deposition polymer (Jaguar

quaternised guar gum) for anti-dandruff shampoo is disclosed in WO2012/019934. The combination of MFC and citrus fibres is disclosed in US 7981855, which discloses detergent liquid surfactant compositions comprising up to 15 wt% surfactant, including at least 1 % anionic surfactant, up to 2 wt% bacterial cellulose, preferably MFC, and from 0.001 to 5 wt% citrus fibres. This

combination when used at levels sufficient to suspend particles in the liquid also traps air and becomes destabilised.

We have found that whenever insoluble cellulosic fibres, especially activated citrus fibres, are used at a sufficiently high level to provide a sufficient yield stress to suspend particles in isotropic laundry detergent compositions in a stable and dispersed way, then the fibre structuring network also traps air bubbles, particularly very fine micro bubbles. Such air bubbles may have come out of solution due to thermal cycling of the product, or may have formed during manufacture and filling of the composition into its container. Reducing the level of insoluble cellulosic fibre to allow all the air to be released due to its own buoyancy leads to failure of the external structuring network. It is thought that this failure occurs because the external structuring network fails to fill the full volume of the liquid and sinks leaving a clear unstructured layer at the top of the container.

High water binding capacity citrus fibres are available for example as "Herbacel AQ plus citrus fibre", from HerbaFoods.

An alternative system aimed at suspending solid particles is a combination of clay and a rheology modifying polymer, as disclosed in EP1402877 (Rohm and Haas) and Research Disclosure, June 2000, No. 434, pages 1032-1033. Clay on its own is incapable of forming a stable structuring system in an aqueous isotropic laundry liquid composition. Thickening polymers have to be used at relatively high levels to provide the necessary synergy with the clay. Furthermore these polymers have been found to have negative effects on cleaning in laundry compositions and have unwanted interactions with other components normally found in liquid detergents. They are costly and introduce manufacturing complexity.

It is an object of the present invention to provide an external structuring system suitable for use in aqueous isotropic detergent liquid compositions that provides stable suspension of particles, for example encapsulated perfume, whilst not becoming destabilised by air bubbles. SUMMARY OF THE INVENTION

According to the present invention there is provided an externally structured aqueous isotropic liquid laundry detergent composition comprising:

- at least 10 wt% water,

- at least 10 wt% of a mixed surfactant system comprising anionic surfactant,

- an external structuring system comprising from 0.025 to 0.15 wt% insoluble cellulosic fibre comprising at least 50 wt% activated citrus fibre,

- at least 0.01 wt% suspended non-clay solid particles,

characterised in that the external structuring system further comprises at least 0.1 wt% water-swellable clay.

Preferably the liquid composition has a yield stress of at least 0.08 Pa at 25 °C. The yield stress is more preferably at least 0.1 Pa, even at least 0.15 Pa at 25 °C. The viscosity of the liquid composition at 20 ^s"1 and 25 °C is preferably at least 0.2 Pa.s.

The insoluble cellulosic fibre preferably comprises at least 90 wt% activated citrus fibre and most preferably it is 100% activated citrus fibre. Activated citrus fibre is very robust in the presence of other detergent ingredients, especially enzymes. Preferably the composition comprises at least 0.05 wt% activated citrus fibre, more preferably at least 0.07 wt%.

The suspended non-clay solid particles are neither liquid nor gas. They may, however, comprise liquids or gasses contained in a solid shell or matrix. The shell or matrix may be rigid or deformable. Preferably the liquid comprises at least 0.1 wt%, even at least 0.2 wt% of the suspended non-clay solid particles. Preferred non-clay solid particulate materials are microcapsules. The microcapsules may have a melamine formaldehyde shell. Other suitable shell material may be selected from (poly)urea, (poly)urethane, starch/ polysaccharide, aminoplasts and xyloglucans. Mixtures of different types of microcapsules may be combined as convenient and desirable.

The microcapsules may be perfume encapsulates. The average particle diameter of the microcapsules preferably lies in the range from 1 to 100 micrometer and at least 90 wt% of the microcapsules has a diameter in this range. Preferably, 90 wt% of the microcapsules have a diameter in the range 2 to 50 micrometers, even more preferably 5 to 50 micrometers. Most preferred are microcapsules with diameters less than 30 micrometers.

An alternative, or additional, non-clay solid particulate material comprises visual cues, preferably cues formed from a film material comprising a polymer, so as to have maximum visual impact from a low weight of cue material. Visual cues made from film may be from 2 to 5 mm in diameter (largest dimension).

Preferably the clay has a particle size less than 250 micron, more preferably less than 100 micron. The D₅₀ particle size of the clay is preferably less than 50 micron. The clay may either be used as a dry raw material or in a gel or form which is easier to disperse into the CFF and water premix.

Preferably the total of insoluble cellulosic material, comprising activated citrus fibre, and clay in the external structuring system lies in the range 0.10 to 0.80 wt%. Insoluble cellulosic fibres, preferably comprising at least 50 wt% activated citrus fibre, more preferably at least 90 wt% and most preferably comprising 100% activated citrus fibre can give excellent suspending properties to isotropic detergent liquid compositions. However air is also readily entrained via mixing, transportation and filling processes. The late stage introduction of air during filling is hard to solve by use of degassing equipment. Air entrainment is a big problem when high shear dispersal is used to activate the fibres that will form the external structuring network. Possibly this is due to micronized air which is formed during the activation and which seems to be particularly hard to release from external structuring systems comprising 100% insoluble cellulosic fibre networks with high enough yield stresses to suspend solid materials. This air can accumulate in sufficient amounts to "float" the structuring network.

For example, when the 0.25 wt% activated citrus fibre required for suspending of perfume microcapsules is used as an external structuring system in a laundry detergent liquid it also suspends entrained air and this suspended air causes the fibre network of the external structuring system to rise. This in turn causes an inhomogeneous liquid with poorly dispersed microcapsules. Reduction of the amount of activated citrus fibre results in insufficient ability to suspend either itself or to suspend microcapsules in a dispersed form, because the external structuring system sinks.

It is well known that clay cannot normally suspend itself as a colloidal dispersion in a high surfactant liquid. However, we have found that the combination of low levels of insoluble cellulosic fibre, preferably activated citrus fibre, with otherwise non-suspending water swellable clay provides a storage stable structuring system that allows microcapsules to remain fully dispersed and does not suffer from destabilisation due to trapped air. The coloration of the liquid is also improved compared to the use of (higher levels of) activated citrus fibre alone. DETAILED DESCRIPTION OF THE INVENTION

Water

The detergent compositions are aqueous and water forms the majority of the solvent in the composition. Hydrotropes such as propylene glycol and glycerol/glycerine may be included as co-solvents in a lesser amount than the water. Water is needed in the composition in order to keep the surfactant, any polymers, soluble builders, enzymes etc in solution. The water amount stated includes both free and any bound water. The amount of water in the composition is preferably at least 20 wt%, more preferably at least 30 wt%.

Mixed surfactant system

Due to the robust properties of the novel external structuring system there are few limitations on the type or the amount of the mixed surfactant system. Synthetic surfactants preferably form a major part of the surfactant system. Mixtures of synthetic anionic and nonionic surfactants, or a wholly anionic mixed surfactant system or admixtures of anionic surfactants, nonionic surfactants and amphoteric or zwitterionic surfactants may all be used according to the choice of the formulator for the required cleaning duty and the required dose of the detergent composition.

The surfactants forming the mixed surfactant system may be chosen from the surfactants described in 'Surface Active Agents' Vol. 1 , by Schwartz & Perry, Interscience 1949, Vol. 2 by Schwartz, Perry & Berch, Interscience 1958, 'McCutcheon's Emulsifiers and Detergents' published by Manufacturing

Confectioners Company or in Tenside Taschenbuch', H. Stache, 2nd Edn., Carl Hauser Verlag, 1981 . The amount of surfactant in the composition may range from 3 to 75 wt%, preferably 10 to 60 wt%, more preferably from 16 to 50 wt%. The skilled worker will appreciate that the optimum surfactant concentration will largely depend on the product type and the intended mode of use. The anionic surfactant may include soap (salt of fatty acid). A preferred soap is made by neutralisation of hydrogenated coconut fatty acid, for example Prifac® 5908 (ex Croda). Mixtures of saturated and unsaturated fatty acids may also be used.

Nonionic detergent surfactants are well-known in the art. A preferred nonionic surfactant is a C12-C18 ethoxylated alcohol, comprising 3 to 9 ethylene oxide units per molecule. More preferred are C12-C15 primary, linear ethoxylated alcohols with on average 5 to 9 ethylene oxide groups, more preferably on average 7 ethylene oxide groups.

Examples of suitable synthetic anionic surfactants include sodium lauryl sulphate, sodium lauryl ether sulphate, ammonium lauryl sulphosuccinate, ammonium lauryl sulphate, ammonium lauryl ether sulphate, sodium cocoyl isethionate, sodium lauroyl isethionate, and sodium N-lauryl sarcosinate. Mostly preferred the synthetic anionic surfactants comprise the synthetic anionic surfactant linear alkylbenzene sulphonate (LAS). Another synthetic anionic surfactant suitable in the present invention is sodium alcohol ethoxy-ether sulphate (SAES), preferably comprising high levels of sodium C12 alcohol ethoxy-ether sulphate (SLES). It is preferred for the composition to comprise LAS.

A preferred mixed surfactant system comprises synthetic anionic with nonionic detergent active materials and optionally amphoteric surfactant, including amine oxide.

Another preferred mixed surfactant system comprises two different anionic surfactants, preferably linear alkyl benzene sulphonate and a sulphate, for example LAS and SLES. Synthetic anionic surfactants can be present, for example, in amounts in the range from about 5% to about 70 wt% of the mixed surfactant system.

The detergent compositions may further comprise an amphoteric surfactant, wherein the amphoteric surfactant is present in a concentration of 1 to 20 wt%, preferably 2 to 15 wt% more preferably 3 to 12 wt% of the mixed surfactant system. Typical examples of suitable amphoteric and zwitterionic surfactants are alkyl betaines, alkylamido betaines, amine oxides, aminopropionates,

aminoglycinates, amphoteric imidazolinium compounds, alkyldimethylbetaines or alkyldipolyethoxybetaines.

Insoluble cellulosic fibres

The external structuring system is composed of the water swellable clay in association with one or more insoluble cellulosic fibres comprising at least 50 wt% activated citrus fibre, more preferably comprising 90 wt% activated citrus fibre and most preferably comprising 100 wt% activated citrus fibre. The original fibres may be partially soluble so all quantities given in this specification include both insoluble and soluble fractions. The fibres may all be of one type or may be used as a mixed fibre system. Preferred fibres are the microfibrous celluloses produced from bacteria and the naturally derived fibres from plants. Activated citrus fibre is used due to its very high water absorbency. In general the higher the water absorbency the more preferred is the fibre or fibre mixture. Many of the comments about processing of citrus fibre may also apply to other types of insoluble cellulosic fibres.

Activated Citrus fibre

The albedo of citrus fruits is used to make powdered citrus fibre. It has a 'spongy microstructure'. Citrus fruits (mainly lemons and limes) are dejuiced to leave the insoluble plant cell wall material and some internally contained sugars and pectin. It is dried and sieved and then washed to increase the fibre content. Dried materials are large (100's micron cell fragment, consisting of tightly bound/ bonded fibrils). After milling a powdered citrus fibre material is obtained. The process used leaves much of the natural cell wall intact while the sugars are removed. The resulting highly swelling citrus fibre materials are typically used as food additives and have been used in low fat mayonnaise. The pH of the dispersed powder is acidic.

Microscopy shows that powdered citrus fibre is a heterogeneous mixture of particles with various sizes and shapes. The majority of the material consists of aggregated lumps of cell walls and cell wall debris. However, a number of tubelike structures with an open diameter of about 10 micron, often arranged in clusters, can be identified. These, so called, xylem vessels are water transport channels that are mainly located in the peel of citrus fruits. The xylem vessels consist of stacks of dead cells, joined together to form relatively long tubes, 200 to 300 micron long. The outsides of the tubes are reinforced by lignin, which is often laid down in rings or helices, preventing the tubes from collapse due to the capillary forces acting on the tube walls during water transport.

A preferred type of powdered citrus fibre is Herbafoods' Herbacel AQ+ type N citrus fibre. This citrus fibre has a total (soluble and insoluble) fibre content of greater than 80% and soluble fibre content of greater than 20%. It is supplied as a fine dried powder with low colour and has a water binding capacity of about 20 kg water per kg of powder.

To obtain adequate structure powdered citrus fibre is activated (hydrated and opened up structurally) via a high shear dispersion at a low concentration in water to form a premix. Because the dispersed activated citrus fibre is biodegradable, it is advantageous to include a preservative into the premix. The shear should not be high enough to lead to defibrillation. If a high-pressure homogeniser is used it should be operated between 200 and 600 bar. The more shear that is applied the less dense the resulting particles. Whilst the morphology is changed by the high shear, process aggregate size appears not to be changed. The fibres break down and then fill the water phase. The shear also rubs loose the outer parts of the cell walls and these are able to form a matrix that structures the water outside of the volume of the original fibre.

An activated citrus fibre structuring premix may alternatively be made by milling using a high shear mixer, such as a Silverson. The premix may be passed through several sequential high-shear stages in order to ensure full hydration and dispersal of the citrus fibre to form the activated citrus fibre dispersion. The premix may be left to hydrate further (age) after the high shear dispersal. The activated premix is preferably used fresh.

High Pressure Homogenised premixes are preferred over milled premixes, as they are more weight effective to provide sufficient suspending duty to liquids.

Increasing the homogenisation pressure gives further increased weight efficacy to the premix. A suitable operational pressure is about 500 barg.

The level of activated citrus fibre in a premix preferably lies in the range 1 to 5 wt%, more preferably 1 .5 to 2.5 wt%. The concentration of activated citrus fibre in the pre-mix depends on the ability of the equipment to deal with the higher viscosity due to higher concentrations. Preferably the amount of water in the premix is at least 20 times greater than the amount of citrus fibres, more preferably at least 25 times even as much as 50 times. It is advantageous that there is excess water in order to hydrate the activated citrus fibre fully.

Preferred premixes have a measured yield stress of at least 70 Pa measured using an Anton Paar serrated cup and bob geometry at 25 °C. When added to a detergent liquid composition activated citrus fibre boosts the yield stress and the pour viscosity of the composition at 20 ^s"1 and the composition is a shear thinning liquid. Yield stress and viscosity at 20 ^s"1 increase generally in line with the level of activated citrus fibre.

Activated citrus fibre is compatible with enzymes used in laundry and household care detergent compositions.

The premix may either be added to the detergent liquid as a post dosed

ingredient, or alternatively the composition can be formed by starting with the premix and then adding the other ingredients to it. Some high shear is required to disperse the premix in the composition fully but the duty is not as demanding as for the premix preparation. The insoluble cellulosic fibre comprising activated citrus fibre, should be used at a high enough level to ensure that the external structuring network does not settle under its own weight. If the network settles then any suspended solid particles settle with the network. To avoid air entrapment in the structuring network the amount of activated fibre is preferably reduced to close to the minimum required to suspend the solid particles, for example encapsulated perfume. The clay portion of the external structuring system assists in reduction of the level of the activated fibre needed.

Water-swellable Clay

Suitable water swellable clays are hydrous aluminium phylosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations. Clays form flat hexagonal sheets similar to the micas. Clays are ultrafine-grained (normally considered to be less than 2 micrometres in size on standard particle size classifications). Clays are commonly referred to as 1 :1 or 2:1 . Clays are fundamentally built of tetrahedral sheets and octahedral sheets. A 1 :1 clay consists of one tetrahedral sheet and one octahedral sheet, and examples include kaolinite and serpentine. A 2:1 clay consists of an octahedral sheet sandwiched between two tetrahedral sheets and examples are illite, smectite, and attapulgite.

The Smectite group includes dioctahedral smectites such as montmorillonite and nontronite and trioctahedral smectites for example saponite. Also, bentonite, pyrophylite, hectorite, sauconite, talc, beidellite. Other 2:1 clay types include sepiolite or attapulgite, clays with long water channels internal to their structure. Phylosilicates include: Halloysite, Kaolinite, Illite, Montmorillonite,

Vermiculite, Talc, Palygorskite, Pyrophylite . Montmorillonite is a smectite phylosilicate (Na,Ca)₀.33(AI,Mg)₂(Si₄O ₀)(OH)2'nH₂O. Montmorillonite is a very soft phylosilicate group of minerals that typically form in microscopic crystals to form a clay. Montmorillonite, is a 2:1 clay, meaning that it has 2 tetrahedral sheets sandwiching a central octahedral sheet. The particles are plate-shaped with an average diameter of approximately one micrometre. Montmorillonite is the main constituent of bentonite - a volcanic ash weathering product. Hectorite is a natural smectite clay with high silica content. Natural hectorite is a rare soft, greasy, white clay mineral.

Suitable water-swellable clays include: smectites, kaolins, ilites, chlorites and attapulgites. Specific examples of such clays include bentonite, pyrophylite, hectorite, saponite, sauconite, nontronite, talc and beidellite as smectite type clays. The water-swellable clay is preferably a smectite-type clay.

Montmorillonite clays, even in the presence of stabilising agents are sensitive to ionic strength. They lose their liquid structuring efficiency at high electrolyte levels normally present in many detergent compositions. Clays tend to collapse onto themselves or flocculate under these conditions. If this collapse occurs during storage the liquid will lose its physical stability, suffer syneresis and /or settling of solids.

The preferred water-swellable clay is a smectite-type clay, selected from the group consisting of Laponites, aluminium silicate, bentonite and fumed silica.

Most preferred commercial synthetic hectorites are the Laponites from Rockwood. Particularly preferred synthetic hectorites are: Laponite S, Laponite RD, Laponite RDS, Laponite XLS and Laponite EL. Most preferred is Laponite EL. Laponite RD, XLG, D, EL, OG, and LV: are all lithium magnesium sodium silicates.

Other synthetic hectorite type clays include: Veegum Pro and Veegum F from RT Vanderbilt and the Barasymacaloids and Proaloids from Baroid division of

National Lead Company. Synthetic smectites are synthesised from a combination of metallic salts such as salts of sodium, magnesium and lithium with silicates, especially sodium silicates, at controlled ratios and temperature. This produces an amorphous precipitate which is then partially crystallised. The resultant product is then filtered washed dried and milled to give a powder containing platelets which have an average platelet size of less than 100 nm. Platelet size refers to the longest lineal dimension of a given platelet. Synthetic clay avoids the use of impurities found in natural clay.

Laponite is synthesised by combining salts of sodium magnesium and lithium with sodium silicate at carefully controlled rates and temperatures. This produces an amorphous precipitate which is then partially crystallised by a high temperature treatment. The resulting product is filtered, washed, dried and milled to a fine white powder. The size of the clay is important. Thus the very fine synthetic hectorites are especially preferred because of their small particle size. Particle size is the size of a discreet grain of moistened clay. A suitable particle size is 0.001 to 1 micron, more preferably 0.005 to 0.5 micron and most preferably from 0.01 to 0.1 micron. The clay may be ground or crushed to bring the average size within the desired range.

Laponite has an average platelet size maximum dimension less than 100 nm. Laponite has a layer structure, which in dispersion in water, is in the form of disc- shaped crystals each being about 1 nm thickness and about 25 nm diameter.

Small platelet size provides good sprayability, rheology and clarity. Preferably the clay has a particle size range in the colloidal range. Typically such clays provide a clear solution when they are hydrated, possibly because the clay particles do not scatter light when the clay is hydrated and exfoliates. Other larger clays will provide low shear viscosity build as required but the compositions will lack clarity. The clay is present in the composition in an amount of at least 0.05 wt%.

Preferably at least 0.1 wt%, more preferably at least 0.2 wt%.

Preferably the clay is present in an amount of no more than 0.7 wt%, more preferably no more than 0.6 wt%, most preferably no more than 0.5 wt%.

Use of sol grade of synthetic clay decreases batch time which can be

advantageous.

Most preferred as the water swellable clay is the synthetic clay supplied under the name Laponite EL from Rockwood. It combines a very small grain size with a tolerance to high ionic strength as found in detergent liquids. Laponite EL forms a dispersion in water and has a high surface charge. This is said to give it improved tolerance to electrolyte (including anionic surfactant). Laponite EL is available in both powder and sol forms. Either is suitable for use in the detergent liquid compositions. Laponite has a layer structure which, in dispersion in water, is in the form of discshaped crystals. It can be envisaged as a two dimensional "inorganic polymer" where the empirical formula forms a unit cell in the crystal having six octahedral magnesium ions sandwiched between two layers of four tetrahedral silicon atoms. These groups are balanced by twenty oxygen atoms and four hydroxyl groups. The height of the unit cell represents the thickness of the Laponite crystal. The unit cell is repeated many times in two directions, resulting in the disc shaped appearance of the crystal. It has been estimated that a typical Laponite crystal contains up to 2000 of these unit cells. Macromolecules of this particle size are known as colloids. Natural clay mineral thickeners such as bentonite and hectorite have a similar disc shaped crystal structure but are more than one order of magnitude larger in size. The primary particle size of Laponite is much smaller than either natural hectorite or bentonite. The idealised structure would have a neutral charge with six divalent magnesium ions in the octahedral layer, giving a positive charge of twelve. In practice, however, some magnesium ions are substituted by lithium ions (monovalent) and some positions are empty. The clay has a negative charge of 0.7 per unit cell, which becomes neutralised during manufacture as sodium ions are adsorbed onto the surfaces of the crystals. The crystals become arranged into stacks which are held together electrostatically by sharing of sodium ions in the interlayer region between adjacent crystals. At 25^QC in tap water and with rapid agitation, this process is substantially complete after 10 minutes. High shear mixing, elevated temperature or chemical dispersants are not required. A dilute dispersion of Laponite in deionised water may remain a low viscosity dispersion of non-interacting crystals for long periods of time. The crystal surface has a negative charge of 50 to 55 mmol.100^9"1. The edges of the crystal have small localised positive charges generated by absorption of ions where the crystal structure terminates. This positive charge is typically 4 to 5 mmol.100^9"1. The addition of polar compounds in solution (e.g. simple salts, surfactants, coalescing solvents, soluble impurities and additives in pigments, fillers or binders etc.) to the dispersion of Laponite will reduce the osmotic pressure holding the sodium ions away from the particle surface. This causes the electrical double layer to contract and allows the weaker positive charge on the edge of the crystals to interact with the negative surfaces of adjacent crystals. The process may continue to give a "house of cards" structure which, in a simple system of Laponite, water and salt, is seen as a highly thixotropic gel. This gel consists of a single flocculated particle held together by weak electrostatic forces.

Suspended non-clay particles

The composition comprises suspended non-clay particles. These particles are preferably solid; that is to say they are neither liquid nor gas. However, within the term solid we include particles with either rigid or deformable solid shells which may then contain fluids. For example the solid particles may be microcapsules such as perfume encapsulates, or care additives in encapsulated form. The particles may take the form of insoluble ingredients such as silicones, quaternary ammonium materials, insoluble polymers, insoluble optical brighteners and other known benefit agents as described, for example, in EP1328616. The amount of suspended particles may be from 0.001 to up to 10 or even 20 wt%. One type of solid particle to be suspended is a visual cue, for example the type of flat film cue described in EP131 19706. The cue may itself contain a segregated component of the detergent composition. Because the cue must be water-soluble, yet insoluble in the composition, it is conveniently made from a modified polyvinyl alcohol that is insoluble in the presence of the mixed surfactant system. In that case, the detergent composition preferably comprises at least 5 wt% anionic surfactant.

The suspended non-clay particles can be any type. This includes perfume encapsulates, care encapsulates and/ or visual cues or suspended solid opacifier such as mica or other suspended pearlescent materials and mixtures of these materials. The closer the match of the density of the suspended particles to that of the liquid and the thicker the liquid before addition of the external structurant, the greater the amount of particles that may be suspended. Typically, up to 5 wt% of suspended particles may be suspended stably using the mixed external structuring system; however, amounts up to 20 wt% are possible.

Suspension is achieved through providing a yield stress. The yield stress needs to be larger than the stress imposed on the network by the microcapsules or cues otherwise the network is disrupted and the particles can sink or float depending on whether or not they are denser than the base liquid. Perfume microcapsules are almost neutrally buoyant and small, so the required yield stress is low. Air bubbles are bigger and have the biggest density difference and so require a high yield stress (>0.5 Pa, depending on bubble size). If the yield stress is not too high the air bubbles can escape by floating and disengaging from the surface.

Microcapsules preferably comprise a solid shell. Microcapsules carrying an anionic charge should be well dispersed to avoid agglomeration issues.

Microcapsules with a cationic charge may also be used. The microcapsule may have a melamine formaldehyde shell. Other suitable shell material may be selected from (poly)urea, (poly)urethane, starch/ polysaccharide, xyloglucan and aminoplasts.

The average particle diameter of the microcapsules lies in the range from 1 to 100 micrometer and at least 90 wt% of the microcapsules preferably has a diameter in this range. More preferably, 90 wt% of the microcapsules have a diameter in the range 2 to 50 micrometers, even more preferably 5 to 50 micrometers. Most preferred are microcapsules with diameters less than 30 micrometers.

It is advantageous to have a very narrow particle size distribution, for instance 90 wt% of microcapsules in the range 8 to 1 1 microns. Microcapsules in the range 2 to 5 microns cannot be dispersed so effectively due to the high surface area of the smaller particles. Preferably the composition comprises at least 0.01 wt% of microcapsules, preferably with an anionic charge. Such microcapsules may deliver a variety of benefit agents by deposition onto substrates such as laundry fabric. To obtain maximum benefit they should be well dispersed through the liquid detergent composition and the vast majority of the microcapsules must not be significantly agglomerated. Any microcapsules that become agglomerated during manufacture of the liquid remain so in the container and will thus be dispensed unevenly during use of the composition. This is highly undesirable. The contents of the

microcapsules are normally liquid. For example, fragrances, oils, fabric softening additives and fabric care additives are possible contents. Preferred

microcapsules are particles termed core-in-shell microcapsules. As used herein, the term core-in-shell microcapsules refers to encapsulates whereby a shell which is substantially or totally water-insoluble at 40 °C surrounds a core which comprises or consists of a benefit agent (which is either liquid or dispersed in a liquid carrier).

Suitable microcapsules are those described in US-A-5 066 419 which have a friable coating, preferably an aminoplast polymer. Preferably, the coating is the reaction product of an amine selected from urea and melamine, or mixtures thereof, and an aldehyde selected from formaldehyde, acetaldehyde,

glutaraldehyde or mixtures thereof. Preferably, the coating is from 1 to 30 wt% of the particles.

Core-in-shell microcapsules of other kinds are also suitable for use in the present invention. Ways of making such other microcapsules of benefit agents such as perfume include precipitation and deposition of polymers at the interface such as in coacervates, as disclosed in GB-A-751 600, US-A-3 341 466 and

EP-A-385 534, as well as other polymerisation routes such as interfacial condensation, as described in US-A-3 577 515, US-A-2003/0125222,

US-A-6 020 066 and WO-A-03/101606. Microcapsules having polyurea walls are disclosed in US-A-6 797 670 and US-A-6 586 107. Other patent applications specifically relating to use of melamine-formaldehyde core-in-shell microcapsules in aqueous liquids are WO-A-98/28396, WO02/074430, EP-A-1 244 768,

US-A-2004/0071746 and US-A-2004/0142868.

Perfume encapsulates are a preferred type of microcapsule suitable for use in the present invention.

A preferred class of core-in-shell perfume microcapsule comprises those disclosed in WO 2006/066654 A1 . These comprise a core having from about 5% to about 50 wt% of perfume dispersed in from about 95% to about 50 wt% of a carrier material. This carrier material preferably is a non-polymeric solid fatty alcohol or fatty ester carrier material, or mixtures thereof. Preferably, the esters or alcohols have a molecular weight of from about 100 to about 500 and a melting point from about 37°C to about 80 °C, and are substantially water-insoluble. The core comprising the perfume and the carrier material are coated in a substantially water-insoluble coating on their outer surfaces. Similar microcapsules are disclosed in US 5,154,842 and these are also suitable. The microcapsules may attach to suitable substrates, e.g. to provide persistent fragrance that is desirably released after the cleaning process is complete.

Liquid detergent compositions The detergent compositions have sufficient yield stress, also called critical stress, of at least 0.08 Pa, preferably at least 0.09 Pa, more preferably at least 0.1 Pa, even at least 0.15 Pa measured at 25 °C. These increasing levels of yield stress are capable of suspending particles of increasingly different density from the bulk liquid. A yield stress of 0.09 Pa has been found sufficient to suspend most types of perfume encapsulates. Pure clay is unstable and cannot provide effective structuring of an aqueous isotropic detergent liquid composition. The mixed external structuring system also stays dispersed; neither floating (to give bottom clear layer separation) nor sinking (to give top clear layer separation). This self suspension is achieved by ensuring that the structuring system wants to occupy all the volume of the detergent liquid. This is a function of the amounts of clay and cellulosic fibre used. To obtain this from activated citrus fibre alone has been found to generate a yield stress so high that air bubbles are suspended and these then destabilise the structuring network. The detergent liquid may be formulated as a concentrated detergent liquid for direct application to a substrate, or for application to a substrate following dilution, such as dilution before or during use of the liquid composition by the consumer or in washing apparatus. Cleaning may be carried out by simply leaving the substrate in contact for a sufficient period of time with a liquid medium constituted by or prepared from the liquid cleaning composition. Preferably, however, the cleaning medium on or containing the substrate is agitated. Product Form

The liquid detergent compositions are preferably concentrated liquid cleaning compositions. The liquid compositions are pourable liquids. Throughout this specification, all stated viscosities are those measured at a shear rate of 20 ^s"1 and at a temperature of 25 °C unless stated to be otherwise. This shear rate is the shear rate that is usually exerted on the liquid when poured from a bottle. The liquid detergent compositions according to the invention are shear- thinning liquids. Manufacturing process

At the higher levels of insoluble cellulosic fibre required to suspend heavier particles the amount of water that may be removed from the base to make up the premix separately becomes too large so post dosing of a structuring premix is not a viable option. Instead structured detergent compositions may be prepared starting with the activated fibre to which the other ingredients are added in their normal order of addition. In addition to enabling the incorporation of the higher level of activated fibre into the detergent liquid this has the further advantage that dispersion of the activated fibre by high shear continues during the addition of the later ingredients (including the later added clay) rather than as a post shearing step, thereby reducing the batch time. We have found that the best practice is to de-aerate the liquid composition before filling it into containers. However, the external structuring system allows for more process flexibility and this step is not essential.

Optional ingredients

The preferred cellulosic material is activated citrus fibre and that type of fibre has been found to be compatible with usual ingredients that may be found in detergent liquids. Among which there may be mentioned, by way of example: polymeric thickeners; enzymes, particularly: lipase, cellulase, protease, mannanase, amylase and pectate lyase; cleaning polymers, including ethoxylated polyethylene imines (EPEI) and polyester soil release polymers; chelating agents or

sequestrants, including HEDP (1 -Hydroxyethylidene -1 ,1 ,-diphosphonic acid) which is available, for example, as Dequest® 2010 from Thermphos; detergency builders; hydrotropes; neutralising and pH adjusting agents; optical brighteners; antioxidants and other preservatives, including Proxel®; other active ingredients, processing aids, dyes or pigments, carriers, fragrances, suds suppressors or suds boosters, chelating agents, clay soil removal/ anti-redeposition agents, fabric softeners, dye transfer inhibition agents, and transition metal catalyst in a composition substantially devoid of peroxygen species.

These and further possible ingredients for inclusion are further described in WO2009 153184.

Packaging

The compositions may be packaged in any form of container. Typically a plastic bottle with a detachable closure/pouring spout. The bottle may be rigid or deformable. A deformable bottle allows the bottle to be squeezed to aid dispensing. If clear bottles are used they may be formed from PET. Polyethylene or clarified polypropylene may be used. Preferably the container is clear enough that the liquid, with any visual cues therein, is visible from the outside. The bottle may be provided with one or more labels, or with a shrink wrap sleeve which is desirably at least partially transparent, for example 50% of the area of the sleeve is transparent. The adhesive used for any transparent label should not adversely affect the transparency. EXAMPLES

The invention will now be further described with reference to the following non- limiting examples. Rheology Flow Curve Measurement

Rheology flow curves are generated using the following three step protocol :-

Instrument - Paar Physica - MCR300 with Automatic Sample Changer (ASC) Geometry - CC27, profiled DIN concentric cylinder

Temperature - 25 °C Step 1 - Controlled stress steps from 0.01 to 400 Pa; 40 steps logarithmically spaced in stress with 40 s being spent at each point to measure the shear rate (and hence viscosity); Step 1 is terminated once a shear rate of 0.1 ^s"1 is reached.

Step 2 - Controlled shear rate steps from 0.1 to 1200 ^s"1 ; 40 steps logarithmically spaced in shear rate with 6 seconds being spent at each point to determine the stress required to maintain the shear rate and hence the viscosity.

Step 3 - Controlled shear rate steps from 1200 to 0.1 ^s"1 ; 40 steps logarithmically spaced in shear rate with 6 seconds being spent at each point to determine the stress required to maintain the shear rate and hence the viscosity.

The results of the first two steps are combined being careful to remove any overlap and to ensure that the required shear rates were achieved at the start of the step.

The yield stress in Pa is taken to be the value of the stress at a shear rate of 0.1 ^s"1. I.e. the equivalent of the y-axis intercept in a Herschel-Buckley plot of shear stress vs. shear rate. The yield stress was taken as the point at which the data cut the viscosity = 10 Pa.s and the pour viscosity was taken as the viscosity at 20 ^s"1, both at 25 °C. The abbreviated names used in these examples have the following meanings:

ACF is HPH activated citrus fibre 2 wt% premix (500 Barg).

Water is Demineralised water.

Glycerol is hydrotrope.

MPG is Monopropylene Glycol (hydrotrope).

Nl is Neodol 25-7 nonionic ex Shell.

NaOH is 50% sodium hydroxide base.

LAS is linear alkyl benzene sulphonate anionic surfactant.

MEA is Monoethanolamine base.

TEA is Triethanolamine base.

Prifac 5908 is saturated fatty acid (soap) ex Croda

SLES(3EO) is SLES 3EO anionic surfactant.

Dequest 2066 is Diethylenetriamine penta(methylene phosphonic acid (or

Heptasodium DTPMP) sequestrant ex Thermphos.

Dequest 2010 is HEDP (1 -Hydroxyethylidene -1 ,1 ,-diphosphonic acid)

sequestrant ex Thermphos.

EPEI is ethoxylated polyethyleneimine PEI600EO20 Sokalan HP20 ex BASF.

Perfume encaps is Oasis Cap Det B72 ex Givaudan.

Preservative is Proxel GXL™ antimicrobial preservative, 20% solution of

1 ,2 benzisothiazolin-3-one in dipropylene glycol and water ex

Arch Chemicals.

Perfume is free oil perfume.

Laponite EL is water swellable synthetic hectorite clay ex Rockwood. Laponite RD is water swellable synthetic hectorite clay ex Rockwood. Micro is ISP white microbeads (visual cues).

Viscolam CK57 is a crosslinked thickening polymer ex Lamberti.

Xpect®1000L is pectate lyase ex Novozymes.

Protease is Relase Ultra 16L EX ex Novozymes. L blend is a blend of 3 parts Stainzyme (amylase) to 1 part Mannaway (mannanase) ex Novozymes.

Activated Citrus Fibre Premix

A 2 wt% activated citrus fibre premix was prepared using the materials given Table 1 , according to the following method.

Table 1

The demineralised water was stirred using an agitator stirrer with overhead drive operated at 160 rpm. The Proxel GXL preservative was added. Then Herbacel AQ plus N Citrus Fibre (ex: Herbafoods) was added gradually to ensure no clumping. Stirring was continued for a further 15 minutes to allow the fibres to swell sufficiently prior to the activation stage. The activation stage was carried out by high pressure homogenisation (HPH) at 500 barg.

Detergent liquids Detergent liquids as specified in the following examples were made using the 2 wt% activated citrus fibre premix described above. Sufficient freshly made premix was added to a mixer to give the required level of activated citrus fibre in the finished composition and it was milled for 10 minutes. The mill was then stopped and Laponite clay was added at the required level while stirring with a dual blade impeller. The mix was then stirred at 300 rpm for a further 15 minutes. The remaining ingredients to make up the liquid were then combined with this mix. The fragrance encapsulates were combined last, when used. Dispersion was carried out using an in-line Silverson (L5T).

Example 1 and Comparative example A

Fabric washing liquids were prepared according to Table 2. A comparative liquid A with 0.25 wt% ACF and no clay was also prepared. Example 1 was made both with and without the perfume encapsulates.

Table 2

The yield stress for Example 1 with no perfume encapsulates was 0.17 Pa.

The yield stress for Example 1 with 1 .25% perfume encapsulates was 0.24 Pa, with no evidence of creaming or sedimentation. The non-clay suspended particles are contributing to the yield stress which assists in their own suspension. The compositions were storage stable for at least 12 weeks at temperatures from 5 to 50 °C. The activated citrus fibre and clay combination Example 1 gave significantly lower air retention (air perceivably disengages within minutes) compared to the comparative example A structured using 0.25 wt% activated citrus fibre in the same fabric washing liquid composition given in Table 2 (air retained > 6 months and bottom clear layer separation). It is not feasible to lower the level of activated citrus fibre to less than 0.25 wt% in this liquid, as there would then be insufficient activated citrus fibre to support itself, i.e. the structuring network sediments to give top clear layer separation. Examples 2 and 3

We repeated Example 1 substituting Laponite EL for the Laponite RD. For this example 2 the level of clay used was up to 0.6 wt% and the level of activated citrus fibres was consequently as low as 0.05%. The resulting detergent compositions were found to be stable for at least 8 weeks. We also used a combination of 0.1 %CP, 0.4 % Laponite EL clay in this detergent base as

Example 3 to suspend encaps stably for up to 12 weeks under various storage conditions. For the clay sol Laponite RD, we see performance improvements (i.e. higher yield stress values) compared to the same levels of powdered Laponite EL clay.

Example 4

We modified Example 3 by post dosing the premix of the clay and the activated citrus fibre to an already mixed but unstructured detergent liquid. We found that use of sol grade clay was better than powder clay for this process variant. Late addition of the structurant to the detergent base allows formulation flexibility and reduces impact on batch cycle time. Example 5

A detergent base as detailed in Table 3 was structured with a combination of 0.1 wt % activated citrus fibre and 0.2 wt% Laponite EL clay. It was stable at all temperatures tested (5°C to 50°C) and the 0.3 wt% perfume encapsulates remained evenly dispersed. No air entrainment was observed for this liquid.

Table 3

Ingredient %

Water and minors^* 58.464

Laponite EL (Liq.) 0.200

ACF 0.100

Perfume encapsulates 0.300

Glycerol 5.000

MPG 2.000

NaOH 1 .200

TEA 1 .690

Nl 13.720

LAS Acid 9.150

Prifac 5908 1 .500

SLES 3EO 4.570

Dequest 2066 0.340

Proxel GXL 0.016

Perfume 1 .000

Enzymes 0.750 Example 6

This composition held perfume microcapsules in stable suspension for many weeks and did not suffer from network destabilisation due to air micro bubbles attaching themselves to the citrus fibre network and causing it to float. A similar comparative formulation, identical except for the lack of any water swellable clay did not maintain the perfume encapsulates in stable suspension.

Table 4

Ingredient %

Water 37.21

Laponite EL 0.20

ACF 0.10

Fluorescer and colorants 0.25

MPG 8.00

Nl 8.40

Viscolam CK57 1 .00

MEA 6.20

LAS acid 1 1 .20

TEA 4.00

Citric Acid 2.50

Prifac 5908 3.50

Dequest 2010 1 .50

Sodium Sulphite 0.25

SLES 3EO 8.40

EPEI 3.00

Perfume encapsulates 0.30

Free oil perfume 1 .39

L-Blend Stainzyme/Mannaway

1 .20

6.0/2.0

Xpect 1000L 0.40

Relase Ultra 16L EX 1 .00 Examples 7-18

Table 5 lists further laundry detergent liquid compositions with the clay and activated citrus pulp external structuring system that have sufficient measured yield stress to stably suspend the stated particles. None of the compositions suffered from stability problems resulting from trapped air bubbles.

Table 5

*colorant, fluorescer, enzyme

Table 5 (continued)

*colorant, fluorescer, enzyme

Claims

1 . An externally structured aqueous isotropic liquid laundry detergent composition comprising:

- at least 10 wt% water,

- at least 10 wt% of a mixed surfactant system comprising anionic surfactant,

- at least 0.01 wt% suspended non-clay solid particles,

2. A composition according to claim 1 which comprises at least 0.05 wt% insoluble cellulosic fibre and more preferably at least 0.07 wt%.

3. A composition according to claim 1 in which the insoluble cellulosic fibre comprises 100 wt% activated citrus fibre.

4. A composition according to any preceding claim with a viscosity at 20 ^s"1 and 25 °C of at least 0.2 Pa.s.

5. A composition according to any preceding claim in which the clay has d₅o particle size less than 50 micron.

6. A composition according to any preceding claim in which the total of insoluble cellulosic fibre and clay in the external structuring system lies in the range 0.10 to 0.80 wt%.

7. A composition according to any preceding claim in which the liquid comprises at least 0.1 wt %, preferably at least 0.2 wt%, of the suspended non- clay solid particles.

8. A composition according to any preceding claim in which the non-clay solid particles comprise visual cues, preferably cues formed from a film material comprising a polymer.

9. A composition according to any preceding claim in which the suspended non-clay solid particles have an average particle diameter in the range, 4 to 100, preferably 5 to 50 micron.

10. A composition according to claim 8 in which the non-clay solid particles are perfume encapsulates.

1 1 . A composition according to any preceding claim which comprises as the major part by weight of the non-clay solid particles, microcapsules with an average particle diameter in the range from 1 to 100 micrometer, wherein at least 90 wt% of the microcapsules have a diameter in this range.

12. A composition according to any preceding claim which has a yield stress of at least 0.08 Pa at 25 °C.