GB2179053A - Heavy-duty detergent gel compositions - Google Patents

Abstract

Built or unbuilt fabric washing detergent compositions comprise stable transparent, translucent or opaque hexagonal phase gels contain an anionic surfactant which is "secondary", i.e. its polar head group is either positioned non-terminally on a hydrophobic chain or carries two or more hydrophobic chains; optionally a further surfactant which is nonionic or non-"secondary"; a material (the "additive") capable of forcing the surfactant system into hexagonal phase; water; and an enzyme, fluorescer, bleach, photobleach, deoperfume or germicides. A particulate water-insoluble bleach may be present as a suspended solid. Gels of the invention may contain alkylbenzene sulphonate as the "secondary" surfactant and urea as the "additive". Bleaches may be organic peroxyacids such as 1,12-diperoxydodecanedioic acid.

Description

SPECIFICATION Detergent compositions Technical field The present invention relates to detergent compositions in the form of a stable transparent, translucent or opaque water-soluble gel which is wholly or predominantly in hexagonal liquid crystal form. The compositions of the invention are especially suitable for heavy duty fabric washing.

Background and prior art Detergent compositions in hexagonal or middle phase are disclosed in US 2 580 713 (Wood/Procter & BR< Gamble).

GB 2155 031A (Unilever), published on 18 September 1985, describes and claims an aqueous detergent composition comprising or consisting of a gel wholly or predominantly in hexagonal liquid crystal form, the gel comprising: (a) a surfactant system having a Krafft point below ambient temperature, said system being incapable of forming hexagonal phase spontaneously, and consisting essentially of: (i) 30 to 100% by weight of an anionic or cationic surfactant, having a polar head group and one or more linear or branched aliphatic or araliphatic hydrocarbon chains containing in total at least 8 aliphatic carbon atoms, the polar head group being positioned non-terminally in a single hydrocarbon chain or carrying more than one hydrocarbon chain; or two or more such surfactants of the same charge type; and (ii) optionally 0 to 70% by weight of a further surfactant selected from surfactants of the same charge type as (i) but having a polar head group positioned terminally in a linear or branched aliphatic or araliphatic hydrocarbon chain containing at least 8 aliphatic carbon atoms; nonionic surfactants; and mixtures thereof; (b) an "additive" which is a water-soluble non-micelle-forming or weakly micelle-forming material capable of forcing the surfactant system (a) into hexagonal phase, the additive being nonionic or of the same charge type as the surfactant (a) (i); and (c) water.

There are disclosed in the above-mentioned application unbuilt compositions consisting essentially of the ingredients listed above: compositions additionally containing water-soluble and water-insoluble builders; and compositions additionally containing abrasives. All these compositions are especially well-suited to hard surface cleaning.

It has now been discovered that this type of composition can also tolerate effective amounts of the adjuncts, especially bleaches, enzymes, fluorescers and antiredeposition agents, nowadays considered indispensible in heavy-duty fabric washing formulations. In general these adjuncts can be included in the gel, but oxygen bleaches are conveniently held in suspension as insoluble solids.

The present invention represents a further development of the invention of the aforementioned GB 2 155 031 A, and provides a composition as defined above in which the 'secondary' surfactant is anionic, and which additionally contains one or more fabric washing adjuncts selected from bleaches, enzymes, fluorescers, antiredeposition agents, deoperfumes, germicides, and mixtures of any two or more of these. The adjuncts are present in amounts effective for them to fulfil their functions, and these will clearly vary from one adjunct to another.

Definition of the invention The present invention provides a built or unbuilt aqueous fabric washing detergent composition comprising a gel wholly or predominantly in hexagonal liquid crystal form, the gel comprising: (a) a surfactant system having a Krafft point below ambient temperature, said system being incapable of forming hexagonal phase spontaneously, and consisting essentially of: (i) 30 to 100% by weight of a surfactant having an anionic head group and one or more linear or branched aliphatic or araliphatic hydrocarbon chains containing in total at least 8 aliphatic carbon atoms, the anionic head group being positioned non-terminally in a single hydrocarbon chain or carrying more than one hydrocarbon chain; or two or more such surfactants; and (ii) optionally 0 to 70% by weight of a further surfactant selected from anionic surfactants having a head group positioned terminally in a linear or branched aliphatic or araliphatic hydrocarbon chain containing at least 8 aliphatic carbon atoms; nonionic surfactants; and mixtures thereof; (b) an additive which is a water-soluble non-micelle-forming or weakly micelle-forming material capable of forcing the surfactant system (a) into hexagonal phase, the additive being nonionic or anionic; (c) water, the composition further comprising one or more fabric washing adjuncts selected from enzymes, fluorescers, bleaches, photobleaches, antiredeposition agents, deoperfumes, germicides, and mixtures of any two or more of these.

In a preferred embodiment of the invention, the composition contains a particulate water-insoluble bleach suspended therein.

Disclosure of the invention The detergent gels of the invention are characterised by being wholly or predominantly in hexagonal liquid crystal form. This crystal form, also known as "middle" phase, may be recognised by various microscopic techniques, of which X-ray diffraction is the most definitive: hexagonal phase compositions give rise to a characteristic X-ray diffraction pattern unique to this liquid crystal form. The ratio between the Bragg spacings in the X-ray pattern is

see, for example, "Liquid Crystals and Plastic Crystals", edited by G W Gray and P A Winsor (Ellis Horwood Ltd.

1974), volume 2, chapter 4, page 88.

Of the three liquid crystal forms - lamellar, hexagonal and cubic - hexagonal phase is intermediate in rigidity, but rigidity or viscosity is not an infallible means of distinguishing hexagonal phase gels from other gels because, for example, softer lamellar phase gels can be thickened with polymers or electrolytes to produce products of comparable viscosity. The products of the invention are inherently stiff gels, and require no thickening agent.

Preferred embodiments are transparent or translucent, and are sufficiently attractive in appearance for packaging in transparent containers.

The compositions of the invention contain three essential components in addition to the fabric washing adjuncts present in the gel or as a separate phase: a surfactant system consisting at least in part of "secondary" anionic surfactant; an "additive"; and water. Builder, perfume, colour, buffer and other conventional minor ingredients may also be present subject to certain restraints on electrolyte level discussed below.

The compositions of the invention may consist entirely of hexagonal phase gel, but it is also possible for other phases, for example, solid particles or droplets of immiscible liquid, to be present, provided that a stable gel can still be obtained; and indeed any bleach present must be in the form of a separate suspended phase. Generally the weight ratio of other phase to gel should not exceed 1.5:1.

The surfactant system (a) For the purposes of the present invention, surfactants of the type (a) (i), in which the head group is non-terminal, will be referred to as "secondary", while surfactants in which the head group occupies a terminal position on the hydrocarbon chain, such as the charged surfactants defined under (a) (ii), will be referred to as "primary". In the gels of the invention, a "secondary" surfactant is always present, and a "primary" surfactant of the same charge type or a nonionic surfactant may optionally be present.

The ''secondary" surfactant (a) (i) In a "secondary" anionic surfactant, the polar head group is either attached to the hydrophobic hydrocarbon chain in a non-terminal position, or itself occupies a non-terminal position within the chain, that is to say, two or more shorter chains are directly attached to the head group itself. The first type of "secondary" surfactant will generally conform to the general formula I

wherein Y is the anionic head group, for example, a sulphonate or sulphate group, in combination with solubilising cation; R1 and R2 are aliphatic or araliphatic hydrocarbon chains the shorter of which contains at least 2 aliphatic carbon atoms; and X is a linking group such as

the total number of aliphatic carbon atoms in R1, R2 and X being at least 8, preferably 10 to 28.

Examples of this first type of "secondary" anionic surfactant include alkylbenzene sulphonates, secondary alkane sulphonates and secondary alkyl sulphates. All these materials are generally random mixtures of isomers, and will include some material that is not "secondary", that is to say, with a terminally or next-to-terminally positioned head group; for the purposes of the present invention, however, it is only necessary for the average

constitution of the material to be "secondary".

The second type of "secondary" surfactant will generally conform to the general formula II wherein Y is the anionic head group in combination with a solubilising cation, and R3 and R4 are aliphatic or araliphatic hydrocarbon chains together containing at least 8, preferably 10 to 28, aliphatic carbon atoms, the shorter of the chains R3 and R4 containing at least 2 aliphatic carbon atoms.

Examples of this second type of "secondary" surfactant are dialkyl sulphosuccinates.

The upper limit for the total number of carbon atoms in the hydrocarbon chains of both the first and second types of "secondary" surfactants is in practice set by the requirement that the surfactant system as a whole must have a Krafft point below ambient temperature; this is essential for hexagonal phase formation. The lower limit of 8 aliphatic carbon atoms represents the minimum level of surface activity useful for detergent products.

Preferred examples of "secondary" anionic surfactants that may be used in the gels of the invention include secondary alkane sulphonates, secondary alkyl sulphates, dialkyl sulphosuccinates and alkylbenzene sulphonates. These materials may have straight or branched alkyl chains. Of these materials, two classes are of especial interest: the linear or branched alkylbenzene sulphonates containing an average of 8 to 15 alkyl carbon atoms, preferably 10 to 13; and the linear or branched di(C4-CrO)alkyl sulphosuccinates, and more especially the linear di(C4-C8)alkyl sulphosuccinates.

The counterion of the "secondary" anionic surfactant may be any solubilising cation, provided that the Krafft point condition is satisfied. Examples include alkali metal, such as sodium, potassium, lithium or caesium; alkaline earth metal, such as magnesium; ammonium; and substituted ammonium, such as mono-, di- or trialkylamine or mono-, di- or trialkanolamine. Trialkanolamine salts, for example, triethanolamine salts, have the special advantage of a buffering action to pH 7-9 (the pK of triethanolamine is 8) which can be useful if components unstable at high or low pH are present. A further advantage of trialkanolamines accrues from their high molecular weight, which for a given composition reduces the water content and thereby increases the concentration of surfactant and "additive".In practice this increases the range of compositions over which robust commercial gels can be prepared. Sodium salts, on the other hand, are easy to prepare by neutralisation with caustic soda. The choice of cation is therefore very much a matter of preference.

The auxiliary surfactant (a) (ii) As already indicated, the surfactant system of the compositions of the invention may optionally contain a further surfactant, (a) (ii), which is either a "primary" anionic surfactant or a nonionic surfactant. Mixtures are also possible. The further surfactant (a) (ii) contains at least 8 aliphatic carbon atoms, preferably from 10 to 20 aliphatic carbon atoms.

If the "secondary" surfactant (a) (ii) is of the type where the head group is randomly distributed about the hydrocarbon chain, as in alkylbenzene sulphonates, or is positioned asymmetrically in the chain, as in (for example) a branched-chain sulphosuccinate monoester, the surfactant (a) (ii) can be omitted entirely, although its presence may aid processing or provide other ancillary benefits. In terms of the general formulae I and II above, those "secondary" surfactants are materials in which R, and R2, or R3 and R4, are of lengths that differ significantly from one another. On the other hand, if the "secondary" surfactant (a) (i) is a highly symmetrical material in which R, and R2, or R3 and R4, are of approximately the same chain length, a "primary" or nonionic surfactant (a) (ii) may be essential in order to obtain hexagonal phase at all.Dialkyl sulphosuccinates fall into this class.

Preferred surfactants (a)(ii) are ethoxylated nonionic surfactants, notably ethoxylated aliphatic alcohols and ethoxylated alkyl phenols. These generally contain at least 8 aliphatic carbon atoms, preferably 10 to 20, the limits being determined, as with the "secondary" surfactant (a) (i), by surface activity and the Krafft point of the whole surfactant system. The average degree of ethoxylation may range, for example, from 5 to 30: the longer the hydrocarbon chain, the larger the number of ethoxy groups that can be tolerated.

A second group of preferred surfactants (a) (ii) is constituted by the alkyl ether sulphates. Chain length, degree of ethoxylation and cation may be chosen according to the criteria already advahced for the other surfactants mentioned.

A third group of "primary" surfactants (a) (ii) is constituted by the soaps of fatty acids. Chain length and cation may again be chosen according to previously indicated criteria. Soaps are not preferred for use in high-foaming compositions, but are useful in low foaming fabric washing compositions because they behave both as surfactants and as builders.

Amounts of surfactant The gels of the invention preferably contain from 15 to 70% by weight of the total surfactant system, more preferably from 25 to 60% by weight, based on the gel phase alone and excluding any other phases, such as suspended solid, that might be present.

The surfactant system (a) itself consists to an extent of 30 to 100% by weight of the "secondary" surfactant (a) (i), preferably from 35 to 90% by weight. The auxiliary surfactant constitutes from 0 to 70% by weight, preferably from 10 to 65% by weight, of the surfactant system (a).

The surfactant system may also contain minor amounts, for example, up to 25% by weight, of fatty acid monoand diethanolamides, in order to enhance foaming performance. These may, for example, constitute up to 10% by weight of the composition as a whole.

The additive (b) The second essential component in the gels of the invention is the "additive" (b). Without this material the transition into the hexagonal phase will not take place. The additive is a water-soluble non-micelle-forming or weakly micelle-forming material capable of forcing the "secondary" surfactant into hexagonal phase. The mechanism of action of the "additive" is not clearly understood; it is possible that it acts so as to increase micelle or liquid crystal curvature, but the scope of the invention is not to be limited by this hypothesis. Empirically it has been observed that some materials useful as hydrotropes in light-duty liquid detergent compositions may behave as additives" in the sense of the present invention.These are generally molecules containing a large polar group and, optionally, a small hydrophobic group, such as an aliphatic or araliphatic chain containing not more than 6, preferably 4 or less, aliphatic carbon atoms. The larger the polar head group, the larger the hydrophobe that can be tolerated.

The polar group of the additive may carry an ionic charge, but if so this must be of the same polarity as that of the surfactant or surfactants, that is to say, anionic. Materials that are in effect short-chain analogues of the "secondary" surfactants themselves may advantageously be used. For example, the lower aryl or alkylaryl sulphonates, such as toluene and xylene sulphonates, may be used as "additives" for compositions based on detergent-chain-length alkylbenzene sulphonates. They are also useful in conjunction with other sulphonates, for example, secondary alkane sulphonates, of which they are not exact structural analogues, and in conjunction with sulphates, for example, secondary alkyl sulphates.Thus one preferred type of "additive" has the same or a similar polar head group as the surfactant (a) (i) but has a relatively short hydrocarbon chain containing at most 6, and preferably not more than 4, aliphatic carbon atoms.

A second preferred type of "additive" is a highly polar but uncharged material. This type is typified by the lower amides, containing the - CON - group. Common features of this second type appear to be an ability to raise the dielectric constant of water combined with a structure-breaking effect on water. The preferred material, which is both cheap and environmentally unobjectionable, is urea, Short-chain urea homologues and analogues, for example, methyl and ethyl ureas, thiourea, formamide and acetamide, are possible alternatives, but these are of less interest than the urea itself in view of various drawbacks such as cost, toxicity or simply a lesser effectiveness as an "additive".

If the "additive" (b) is urea, a buffering agent is advantageously present in order to minimise hydrolysis, especially alkaline hydrolysis, of the urea. A suitable buffer is boric acid, preferably used in an amount of less than 3% by weight, more preferably from 1 to 2% by weight. As also mentioned earlier, buffering may instead be achieved by including triethanolamine as a countercation in the surfactant system. The buffering capability and greater electrolyte tolerance of triethanolamine as countercation allow the possibility of incorporating significant quantities of builder electrolytes such as sodium tripolyphosphate in combination with pH-sensitive additives such as urea.

The "additive" is preferably used in an amount of from 1 to 45% by weight, more preferably from 5 to 35% by weight, based on the gel phase alone.

The water (c) The third essential component of the gels of the invention is water. The relative proportions of the three ingredients for any particular surfactant and any particular additive required for hexagonal phase formation can be inferred from the relevant triangular phase diagram, which will be discussed in more detail below. They will obviously depend on the chemical nature of the surfactant system and the additive.

Water is preferably present in an amount of at least 20% by weight, more preferably from 25 to 55% by weight, based on the gel phase alone.

The fabric washing adjuncts (dJ The compositions of the invention also contain one or more fabric washing adjuncts selected from enzymes, fluorescers, bleaches, photobleaches, antiredeposition agents, deoperfumes, germicides and mixtures of any two or more of these, present in the gel phase, or as suspended solid; and combinations of these.

Fabric washing adjuncts that may be present in the gel phase itself, such as enzymes, fluorescers, photobleaches, antiredeposition agents, deoperfumes and germicides, may suitably be used in total amounts of from 0.001 to 10% by weight, based on the gel phase.

Particular water-insoluble bleach, present as a suspended solid, may suitably be used in amounts of from 1 to 10% by weight, more preferably from 3 to 8% by weight based on the total composition (gel plus solid).

However, as described below, bleach levels can more usefully be defined in terms of available oxygen.

Enzymes that may usefully be included are proteases, for example, alcalase and savinase; amylase; and lipases.

They are advantageously used at levels amounting to from 1 to 15 glycine units/mg, preferably from 4 to 10 glycine units/mg, in the whole composition.

Suitable fluorescers will be well known to those skilled in the art. They may be exemplified by the anionic stilbene derivatives, such as diaminostilbenedisulphonate cyanuric chloride derivatives and naphthotriazoylstilbene sulphonate derivatives.

Specific commercially available fluorescers suitable for use in the present invention are: Tinopal (Trade Mark) CBS-X ex Ciba-Geigy, which is 4, 4'-di(2-sulphostyryl)diphenyl, disodium salt.

Tinopal RBS-200 ex Ciba-Geigy, which is 4-(napthotriazol-2-yl)stilbene 2-sulphonate, sodium salt.

Tinopal AMS ex Ciba-Geigy, which is disodium 4,4'-bis(2-phenylamino-4-morpholino-1 ,3,5-triazin-6-yl amino) stilbene-2,2'-disulphonate; and Blancophor (Trade Mark) MBBH ex Bayer AG.

Tinopal AMS and Blancophor MBBH are diaminostilbenedisulphonate-cyanuric chloride derivatives, while Tinopal RBS is a naphthotriazoylstilbene sulphonate derivative.

Other suitable fluorescers are listed in EP 72 1 66A (Procter & Gamble).

Fluorescers are suitably incorporated in the compositions of the present invention at levels of from 0.03 to 0.5% by weight, preferably from 0.08 to 0.2% by weight.

Suitable photobleaches are water-soluble metallated phthalocyanines and naphthalocyanines, for example aluminium and zinc phthalocyanine sulphonates, preferably used in an amount of from 0.001 to 0.1% by weight, more preferably from 0.002 to 0.01% by weight.

Suitable antiredeposition agents include anionic cellulosic polymers, for example, sodium carboxymethyl cellulose. These are advantageously used at levels of from 0.05 to 2% by weight, preferably from 0.08 to 1.5% by weight.

Preferred germicides are formaldehyde, conveniently used as formalin (37% aqueous formaldehyde solution), and chlorinated phenols. These are suitably used at levels of from 0.05 to 1% by weight, preferably from 0.1 to 0.5% by weight.

Deoperfumes are disclosed in GB 2016507,GB 1 596792and GB 2012302 (all Unilever). Theyare suitably used at levels of from 0.05 to 1% by weight, preferably from 0.1 to 0.5% by weight.

All the aforementioned fabric washing adjuncts may be incorporated in the gels of the invention without destabilising the hexagonal phase. Some bleaching agents may also be incorporated in the gels of the invention, notwithstanding their electrolytic nature, provided that the level used is not too high. One example of such a bleach is sodium sulphate, which may be used as a mild stain removal agent as described in GB 1 417 840 and British Patent Application No. 86 01645 (both Unilever). Sodium sulphite is preferably used in an amount of from 1 to 20% by weight more preferably from 5 to 15% by weight.

An alternative approach is to use a bleaching agent that is substantially water-insoluble and will remain stably suspended in the gel. The water solubility of the bleaching agent should be less than 1% by weight at ambient temperature.

A preferred class of water-insoluble bleaching agents is constituted by organic peroxyacids containing at least 7 carbon atoms. These materials, which are sufficiently insoluble under acidic conditions, have the general formula III

wherein R5 is an alkylene or substituted alkylene group containing from 6 to about 20 carbon atoms or a phenylene or substituted phenylene group, and Z is hydrogen, halogen, alkyl, aryl or

The organic peroxyacids usable in the present invention can contain either one or two peroxy groups and can be either aliphatic or aromatic. When the organic peroxyacid is aliphatic, the unsubstituted acid has the general formula IV

wherein Z can be, for example, H, CH3, CH2CI, COOH, or COOOH; and n is an integer from 6 to 20.

When the organic peroxyacid is aromatic, the unsubstituted acid has the general formula V:

wherein Z is hydrogen, alkyl, alkylhalogen or halogen, or COOH or COOOH.

Typical monoperoxyacids useful in the invention include alkyl peroxyacids, alkenyl peroxyacids and arylperoxyacids, such as: (i) peroxybenzoic acid and ring-substituted peroxybenzoic acids, for example, peroxy-alpha-naphthoic acid; (ii) aliphatic and substituted aliphatic monoperoxy acids, for example, peroxylauric acid and peroxystearic acid.

Typical diperoxyacids useful in the invention include alkyl diperoxyacids, alkenyl diperoxyacids and aryldiperoxyacids, such as (iii) 1,1 2-diperoxydodecanedioic acid; (iv) 1,9-diperoxyazelaic acid; (v) diperoxybrassilic acid; diperoxysebacic acid and diperoxyisophthalic acid; (vi) 2-decyldiperoxybutane-1 ,4-dioic acid.

An especially preferred bleaching agent for use in the compositions of the invention is 1,12diperoxydodecanedioic acid (DPDDA).

In order to obtain good peroxyacid bleach stability during storage, it is advantageous to include within the gel a buffer capable of maintaining the pH below about 6, preferably between 3 and 4.5; this overrides any buffering for maximum urea stability as mentioned previously. Suitable buffers include low molecular weight polybasic organic acids such as citric acid.

DPDDA and other solid organic peroxyacids are commercially available as granules, normally containing high proportions of inorganic salts. To avoid destabilisation of the gel, steps should be taken substantially to remove any inorganic salts before the peroxyacids are mixed with other ingredients to form the compositions of the invention. This can conveniently be done by slurrying the granules in water and filtering off the insoluble peroxyacid.

After such treatment DPDDA, for example, will have an available oxygen content of about 12% by weight.

Peroxyacid bleaches such as DPDDA are suitably used in the compositions of the invention at levels of from 0.1 to 2% by weight, preferably from 0.3 to 1% by weight, of available oxygen. For DPDDA of 12% available oxygen content, therefore, this amounts to about 0.8 to 17% by weight, preferably from 2.5 to 8.5% by weight, of DPDDA itself. These percentages are based on the total composition (gel plus suspended solid).

Other optional ingredients The compositions of the invention can advantageously contain inorganic or organic builders, for example, phosphates, citrates or nitrilotriacetates. Preferred builders are alkali metal tripolyphosphates and pyrophosphates. Care must be taken not to raise the electrolyte level to an extent sufficient to disrupt the gel but this can be compensated for by the addition of more "additive". Compositions in which the surfactant system is wholly or partially in the form of a salt of a large non-metallic cation, such as triethanolamine, will generally tolerate higher levels of such builders than will sodium-salt-based formulations. The same applies to other electrolytic fabric washing adjuncts, for example, the sodium sulphite mentioned previously.

Water-soluble organic builders that are micelle-forming, notably soap, can be incorporated at rather higher levels if desired, because they form part of the hexagonal phase structure. Soap is of course also functioning here as a "primary" cosurfactant.

The compositions of the invention may if desired contain other suspended solids in addition to the bleach already discussed. Other solids that might be present include insoluble inorganic builders such as zeolite, and partially soluble builder salts such as sodium tripolyphosphate or sodium or potassium pyrophosphate at concentrations above their solubility limits, provided that the surfactant system and counterion selected will tolerate this.

Preparation of compositions For mixtures of any particular surfactant system, "additive" and water a triangular phase diagram can be constructed from which the compositional requirements for hexagonal phase formation can be inferred. Samples at various ratios are prepared by mixing, and the phases present can be recognised without difficulty by visual appearance, gross flow properties, appearance in polarised light, and texture observed in a polarising microscope. A similar exercise can be carried out to determine the levels of additional ingredients that can be tolerated.

Compositions of the invention are conveniently prepared by mixing a "surfactant part" with an "additive part".

The "surfactant part" contains the surfactants, water, the fabric washing adjuncts(s), and any other optional ingredients such as suspended solids, buffer, perfume and colourants. The "additive part" comprises either neat "additive" (for example, urea powder), a slurry or, preferably, a concentrated solution of the "additive" in water.

In the preferred case, the "additive"is used neat or dissolved in as little water as necessary, and the water, or the remaining water, is included in the "surfactant part".

Hexagonal phase gels are stiff and difficult to handle at ambient temperatures; processing can, however, be facilitated by heating the mixture as this reduces the stiffness of the hexagonal phase. For certain formulations heating can take the mixture temporarily out of the hexagonal phase region, and hence processing becomes relatively easier; temperature effects are discussed in more detail below. The hexagonal phase will form when the mixture cools down to ambient temperature. If the "additive" is urea, the temperature should be kept below 70"C, preferably below 55"C, to avoid significant hydrolytic decomposition of the urea to give ammonia.

Some fabric washing adjuncts, notably peroxyacid bleaches and enzymes, are temperature-sensitive, and should not be added while the composition is at elevated temperatures.

Because the hexagonal phase gels of the invention are so stiff, aeration during preparation can present a problem; air entrained during the mixing process tends to remain trapped in the gel, spoiling its appearance. This problem can be alleviated by operating under vacuum. Certain compositions, which can be temporarily taken out of hexagonal phase by raising the temperature, can be deaerated by holding them at this elevated temperature for a sufficient length of time. The deaerated hexagonal phase will reform on cooling.

Preferred embodiments Gels of the invention in which the "secondary" surfactant is an alkylbenzene sulphonate are of especial interest. Both linear and branched material, having an average of 8 to 1 5 alkyl carbon atoms, preferably 10 to 13 carbon atoms, may be used. Preferred "additives" for use in conjunction with alkylbenzene sulphonates are sodium toluene and xylene sulphonates and, above all, urea.

Gels of the invention which contain alkylbenzene sulphonate may advantageously be prepared by a variant of the process described in which the "surfactant part" is prepared by in-situ neutralisation of the alkylbenzene sulphonic acid, for example, with sodium hydroxide solution, with an amine such as triethanolamine, or with magnesium oxide.

The more branched the alkyl chain of the alkylbenzene sulphonate, the more urea will be required. The upper limit for urea content is limited by its solubility (about 55% by weight in pure water); other more soluble additives can be used at higher levels.

In this embodiment, the surfactant system preferably contains from 45-100% alkylbenzene sulphonate, 0-55% ethoxylated nonionic surfactant and/or alkyl ether sulphate, and 0-25% fatty acid mono- or diethanolamide.

Preferred compositions based on alkylbenzene sulphonates contain the following proportions of ingredients: Weight % of gel alkylbenzene sulphonate: 20-60, preferably 20-55 ethoxylated nonionic surfactant and/or alkyl ether sulphate: 0-30, preferably 0-20 fatty acid diethanolamide 0-10 urea: 1-45, preferably 8-30 phosphate builder: 0-15 boric acid (buffer): 0-2 water: 20-65, preferably 25-45 plus fabric washing adjuncts as specified previously.

Compositions based on C4-Cao dialkyl sulphosuccinates are also of interest. Especially preferred ingredients, on grounds of foaming performance, are Cb-C8 dialkyl sulphosuccinates, for example, those described and claimed in GB 2108 520A, GB 2105 325A and GB 2133 793A (Unilever). These are preferably linear.

A "primary" or nonionic surfactant (a) (ii) appears to be essential when the "secondary" surfactant is a dialkyl sulphosuccinate. This is preferably an alkyl ether sulphate, if very high foaming performance is required.

In this embodiment, the surfactant system may advantageously contain 30-60% by weight of dialkyl sulphosuccinate, 40-70% by weight of alkyl ether sulphate and/or ethoxylated nonionic surfactant, and 0-25% by weight of fatty acid mono- or diethanolamide.

Preferred compositions may contain, for example, 15-20% by weight of dialkyl sulphosuccinate, 20-25% by weight of alkyl ether sulphate, 10-20% by weight of urea, and 40-50% by weight of water, plus the fabric washing adjuncts and the usual minor ingredients. As with previous compositional limits, the percentage base here does not include any suspended solid that might be present.

Examples The invention is further illustrated by the following non-limiting Examples, in which parts and percentages are by weight unless otherwise stated, and refer to 100% active material.

Examples 1 to 18 Compositions were prepared from the ingredients shown in the relevant Tables, in which all percentages are based on 100% active ingredient. The materials used were as follows: Linear alkylbenzene sulphonate: Petrelab (Trade Mark) 550 ex Petresa, sodium or triethanolamine (TEA) salt Fluorescer:Tinopal (Trade Mark) CBS-X ex Ciba-Geigy Photobleach: aluminium phthalocyanine sulphonate ex Ciba Geigy Antiredeposition agent: sodium carboxymethyl cellulose ex Courtaulds (62% active matter) Enzyme: alcalase solution ex Novo, activity 1600 glycine units/mg Deoperfume: ex PPF International Germicide: formalin (37%) The unbuilt compositions of Examples 1 to 8 were were prepared by a method involving in-situ neutralisation of the alkylbenzene sulphonic acid.The sodium sulphate (used to lower the gel melting point), boric acid, and (if present) sodium carboxymethyl cellulose, were dissolved in water; a predetermined amount of sodium hydroxide solution was added (calculated to give a final pH in the gel of 7.0); the sulphonic acid was added and mixed until homogeneity was attained; when the temperature reached about 60"C, urea powder was added and dissolved; the fabric washing adjunct(s) was or were added and dissolved; and the mixture was cooled to ambient temperature. When enzyme was included (Examples 3, 7 and 8) its addition was delayed until the mixture had been cooled to room temperature.

In the unbuilt composition of Example 9 and the built compositions of Examples 10 to 18, buffering was effected by means of triethanolamine (TEA) instead of boric acid. The builder used in Examples 10 to 18 was sodium tripolyphosphate.

The composition of Example 9 was prepared as follows. Sodium hydroxide and TEA (predetermined amounts to give a final pH in the gel of 7.0) were mixed with water; the sulphonic acid was added and mixed to homogeneity; thereafter the same procedure as for the unbuilt compositions of Examples 1 to 8 was followed.

The compositions of Examples 10 to 18 were prepared as follows: sodium tripolyphosphate was dissolved or slurried in water; the sodium hydroxide and TEA were then added and the same procedure as for Example 9 was followed.

The compositions of Examples 1 to 18 were stable translucent hexagonal phase gels.

EXAMPLES 1 TO 9 1 2 3 4 5 6 7 8 9 Linear alkylbenzene sulphonate Na salt 40 40 40 40 40 40 40 40 19 TEA salt - - - - - - - - 16 Urea 20 20 20 20 20 20 20 20 25 Boric acid 1 1 1 1 1 1 1 1 - Sodium sulphate 1 1 1 1 1 1 1 1 Fluorescer 0.1 - - - - - 0.1 0.1 Photobleach - - - - - 0.006 - 0.006 Sodium sulphite - - - - - - - - 10 Sodium carboxymethyl cellulose 1 1 1 Alcalase solution" - - 0.5 - - - 0.5 0.5 Deoperfume - - - 0.3 - - 0.3 0.3 Formalin - - - - 0.75 - 0.75 0.75 Water to 100% "8 glycine units/mg in the whole composition EXAMPLES 10 TO 18 10 11 12 13 14 15 16 17 18 Linear alkylbenzene sulphonate: Na salt 19 19 19 19 19 19 19 19 19 TEA salt 16 16 16 16 16 16 16 16 16 Urea 25 25 25 25 25 25 25 25 25 Sodium tripolyphosphate 10 10 10 10 10 10 10 10 10 Fluorescer 0.1 - - - - - - 0.1 0.1 Photobleach - - - - - 0.006 - - 0.006 Sodium sulphite - - - - - - 5 - 5 Sodium carboxymethyl celiulose 1 1 1 Alcalase solution - - 0.5 - - - - 0.5 0.5 Deoperfume - - - 0.3 - - - 0.3 0.3 Formalin - - - - 0.75 - - 0.75 0.75 Water to 100% Example 19 A bleaching detergent composition was prepared from the following ingredients: Linear alkylbenzene sulphonate (Na salt) (Petrelab 550) 40 Urea 20 Citric adic (buffer) 1 DPDDA (12%ago2) 5 Water to 100 DPDDA granules ex Degussa, containing 85% inorganic salts, were slurried in water and the insoluble DPDDA filtered off. The weight given above refers to the DPDDA itself, and amounts to an available oxygen level of 0.6% by weight in the whole composition.

The composition was prepared as follows. Water, citric acid and alkylbenzene sulphonic acid were mixed; sodium hydroxide was added in a predetermined amount calculated to give a final pH of 3.5; at a temperature of about 60"C urea powder was added and dissolved; the mixture was cooled to ambient temperature to form a gel; and finally the DPDDA was added and dispersed by stirring.

The product was a stable translucent hexagonal phase gel.

Claims (12)

1. A built or unbuilt aqueous fabric washing detergent composition comprising a gel wholly or predominantly in hexagonal liquid crystal form, the gel comprising: (a) a surfactant system having a Krafft point below ambient temperature, said system being incapable of forming hexagonal phase spontaneously, and consisting essentially of: i) 30 to 100% by weight of a surfactant having an anionic head group and one or more linear or branched aliphatic or araliphatic hydrocarbon chains containing in total at least 8 aliphatic carbon atoms, the anionic head group being positioned non-terminally in a single hydrocarbon chain or carrying more than one hydrocarbon chain; or two or more such surfactants; and ii) optionally 0 to 70% by weight of a further surfactant selected from anionic surfactants having a head group positioned terminally in a linear or branched aliphatic or araliphatic hydrocarbon chain containing at least 8 aliphatic carbon atoms; nonionic surfactants; and mixtures thereof; (b) an additive which is a water-soluble non-micelle-forming or weakly micelle-forming material capable of forcing the surfactant system (a) into hexagonal phase, the additive being nonionic or anionic; and (c) water, the composition further comprising one or more fabric washing adjuncts selected from enzymes, fluorescers, bleaches, photobleaches, antiredeposition agents, deoperfumes, germicides, and mixtures of any two or more of these.

2. A detergent composition as claimed in claim 1, having suspended therein a particulate water-insoluble bleach.

3. A detergent composition as claimed in claim 2, which includes as particulate water-insoluble bleach an organic peroxyacid containing 7 or more carbon atoms, together with a buffer whereby a pH not exceeding 6 is maintained.

4. A detergent composition as claimed in claim 3, which includes as bleach 1,1 2-diperoxydodecanedioic acid.

5. A detergent composition as claimed in any one of claims 2 to 4, containing from 1 to 10% by weight of the particulate water-insoluble bleach.

6. A detergent composition as claimed in any one of claims 1 to 5, wherein the surfactant (a) (i) comprises a linear or branched alkylbenzene sulphonate containing an average of from 8 to 15 alkyl carbon atoms.

7. A detergent composition as claimed in any one of claims 1 to 6, wherein the additive (b) is urea.

8. A detergent composition as claimed in any one of claims 1 to 7, which further comprises a builder selected from alkali metal tripolyphosphates and pyrophosphates.

9. A detergent composition as claimed in any one of claims 1 to 8, comprising from 15 to 70% by weight of the surfactant system (a); from 1 to 45% by weight of the additive (b); at least 20% by weight of water; from 0.001 to 10% by weight of fabric washing adjuncts; and optionally an effective amount of a builder.

10. A detergent composition as claimed in any one of claims 1 to 9, wherein the anionic surfactant (a) (i) is present at least partially in trialkanolamine salt form.

11. A detergent composition as claimed in claim 1, wherein the gel incorporates one or more fabric washing adjuncts selected from enzymes, fluorescers, antiredeposition agents, deoperfumes, germicides and mixtures of two or more of these, and/or has suspended therein a particulate water-insoluble bleach.

12. An aqueous composition comprising a gel wholly or predominantly in hexagonal liquid crystal form, substantially as described in any one of the Examples herein.