GB2219002A - Processing of liquid cleaning products - Google Patents

Abstract

A process for controlling the size of solid particles during manufacture of a substantially non-aqueous liquid cleaning product comprising a dispersion of solid particles in a liquid solvent phase, said process comprising the steps of:- a) passing said dispersion through a mill; b) measuring the particle size in the dispersion after it has passed through the mill; and c) using the particle size measurement for controlling the operation of the mill; wherein during said process, said dispersion contains a deflocculant at the time it is subjected to the particle size measurement. o

Description

PROCESSING OF LIQUID CLEANING PRODUCTS The present invention relates to a process for controlling the size of solid particles during manufacture of substantially non-aqueous liquid products of the kind comprising a dispersion of solid particles in a liquid solvent phase.

In such products, the particles are conventionally less than 100 microns in average diameter, most preferably less than 10 microns. The particle size has a profound effect on the product properties, especially on its viscosity , both long and short term, and on its tendency to phase separation (sedimentation). Therefore, it is desirable to control the particle size as tightly as possible during manufacture.

During manufacture, the particles are milled to the appropriate size, either in the dry form, prior to dispersion in the liquid solvent phase, or more preferably they are wet-milled after dispersion in the latter phase.

Whilst it ought in theory to be possible to measure the particles when they are so dispersed, unfortunately this is not possible with the particle sizes used and at the typical solids volume fraction levels.

The reason is that in such systems, the particles form a loosely aggregated network of particle flocs, as is known from e.g. patent specification EP-A-30 096. It is not possible to distinguish individual particles within the flocs.

Whilst such aggregated systems could be greatly diluted (i.e. the solids volume fraction reduced considerably) until the flocs break up and the individual particle sizes then measured, that only amounts to a batch sampling technique and is unsuitable for on-line control.

The applicants have now found that continuous control of particle size during manufacture is possible by effecting the steps of:a) passing said dispersion through a mill; b) measuring the particle size in the dispersion after it has passed through the mill; and c) using the particle size measurement for controlling operation of the mill; wherein during said process, said dispersion contains a deflocculant at the time it is subjected to the particle size measurement.

The term 'deflocculant' will be defined and deflocculants described in detail hereinbelow. However, their importance in the process of the present invention is that they appear to break-up the particle flocs so that the size of the discrete particles can then be measured.

It is preferred that the particle size be measured using an optical technique (i.e. using radiation of visible wavelength), most preferably a light scattering measurement. However, any suitable method known to those skilled in the art of measurement and control may be employed. Thus, for example, a Malvern particle size analyser may be used. This, in principle, operates as follows.

A helium-neon laser with associated beam expander, delivers parallel monochromatic light which irradiates the particles in the dispersion. Scattered rays are collected by a lens although those resulting from wide scatter are not. The unscattered (direct) beam falls on an obscuration detector as a reference. The scattered beam is received by a multi-element detector in the focal plane of the lens. From the measured scatter, the average particle size is calculated in known manner.

The output of measured average particle size from the analyser is fed to a computer. Atorque meter also provides the computer with a measure of the ball mill shaft torque. The computer also receives the output from a mass flow meter. From these inputs, the computer is then calibrated to correlate the average particle size and the operational parameters.

Once the computer is so calibrated, it can control the speed of the ball mill motor to achieve a pre-selected average particle size. If that size is too large, the motor is run faster and vice versa. A tachometer may be used to display the speed of revolution of the motor.

In general, the solids content of the product may be within a very wide range, for example, from 1-90%, usually from 10-80% and preferably from 15-70%, especially 15-50% by weight of the final composition. The alkaline salt should be in particulate form and have an average particle size of less than 300 microns, preferably less than 200 microns, more preferably less than 100 microns, especially less than 10 microns. The particles may even be of sub-micron size.

Preferably the milling step or at least a final milling step is effected by using a ball mill, the particle size measurement being used to control the energy input thereto. The way in which the output of the particle size measurement is used will follow known control techniques but for example may be effected using a standard PI (two-term) or PID (three-term) controller.

In a typical preferred total manufacturing sequence, it is preferred that all raw materials should be dry and (in the case of hydratable salts) in a low hydration state, e.g. anhydrous phosphate builder, sodium perborate monohydrate and dry calcite abrasive, where these are employed in the composition. The dry, substantially anhydrous solids are blended with the solvent in a dry vessel. In order to minimise the rate of sedimentation of the solids, this blend is passed through a combination of mills, e.g. a colloid mill, a corundum disc mill, a horizontal or vertical agitated ball mill, to achieve a particle size of 0.1 to 100 microns, preferably 0.5 to 50 microns, ideally 1 to 10 microns.A preferred combination of such mills is a colloid mill followed by a horizontal ball mill since these can be operated under the conditions required to provide a narrow size distribution in the final product.

The dry ingredients (including the deflocculant) may be mixed in any desired order. However, the deflocculant is preferably incorporated in the initial mix of solvent and solids or it may be added immediately prior to the ball milling step, or fed separately, immediately into the ball mill. It is also possible to add different deflocculants or portions of the same deflocculant or deflocculant mix at any combination of such stages.

Whilst the majority of particles, the size of which it is intended to control, should be subjected to such milling with the deflocculant, others may be added at a later stage. This may be because these post-dosed particles are already of known size, because they comprise a temperature sensitive ingredient, because they constitute only a minor fraction of the total solids in the final product, or for a combination of these factors.

During the milling procedure, the energy input results in a temperature rise in the product and the liberation of air entrapped in or between the particles of the solid ingredients. It is therefore highly desirable to mix any heat sensitive ingredients into the product after the milling stage and a subsequent cooling step. It may also be desirable to de-aerate the product before addition of these (usually minor) ingredients and optionally, at any other stage of the process. Typical ingredients which might be added at this stage are perfumes and enzymes, but might also include highly temperature sensitive bleach components or volatile solvent components which may be desirable in the final composition. However, it is especially preferred that volatile material be introduced after any step of aeration. Suitable equipment for cooling (e.g. heat exchangers) and de-aeration will be known to those skilled in the art.

It follows that all equipment used in this process should be completely dry, special care being taken after any cleaning operations. The same is true for subsequent storage and packing equipment.

The deflocculant will be any material defined as such, according to the applicants' aforementioned unpublished European Patent Application. It may be any deflocculant specifically described there as such, or it may be any material known before but not previously recognised as a deflocculant. Thus, is it appropriate to explain deflocculant here by way of relevant passages reproduced from the latter unpublished application.

Liquid cleaning products which are non-aqueous dispersions comprise a non-aqueous liquid (solvent) phase which can be a liquid surfactant, an organic non-aqueous non-surfactant liquid, or a mixture of such materials.

Many do contain a surfactant as a dispersed or dissolved solid, or more often, as all or part of said liquid phase.

These surfactant compositions are liquid detergent products, e.g. for fabrics washing or hard surface cleaning. However, the wider term 'liquid cleaning product' also includes non-surfactant liquids which are still useful in cleaning, for example non-aqueous bleach products or those in which the liquid phase (solvent) consists of one or more light, non-surfactant solvents for greasy stain pre-treatment of fabrics prior to washing.

Such pre-treatment products can contain solid bleaches, dispersed enzymes and the like.

As well as the solvent phase, such non-aqueous dispersions also contain dispersed particulate solids.

These are small (e.g. 10 microns) particles of solid material which are useful in cleaning and could be solid surfactants, builders, bleaches, enzymes or any other such solids known to those skilled in the art.

The particles can be maintained in dispersion (i.e.

resist settling, even if not perfectly) by a number of means. For example, settling may be inhibited purely by virtue of the relative small size of the particles and the relatively high viscosity of the solvent phase. In other words, the particles settle very slowly at a rate predicted by Stokes' law or due to the formation of a loosely aggregated network of particle flocs. This effect is utilised in the compositions described in patent specifications EP-A-30 096 and GB 2 158 838A. However, there have been several proposals to utilise additional means to enhance solid-suspending properties in such non-aqueous liquids.These are somewhat analogous to so-called external structuring techniques used in aqueous systems; i.e., in addition to the particulate solids and the liquid solvent phase in which they are to be suspended, an additional dispersant is used which by one means or another, acts to aid stable dispersion or suspension of the solids for a finite period.

An early means attempted for the stabilisation of a dispersion of solids in non-aqueous system was to use nonionic surfactant as the solvent and to add an inorganic carrier material as the dispersant, in particular highly voluminous silica. This acts by forming a solid-suspending network. This silica was highly voluminous by virtue of having an extremely small particle size, hence high surface area. This is described in GB patent specifications 1,205,711 and 1,270,040. A gross problem with these compositions is setting upon prolonged storage.

A similar structuring has been effected using fine particulate chain structure-type clay, as described in specification EP-A-34,387.

Later, another substance used as a dispersant for particles in nonionic-based non-aqueous compositions was a hydrolyzable co-polymer of maleic anhydride with ethylene or vinylmethylether, which co-polymer is at least 30% hydrolyzed. This is described in specification EP-A-28,849. A problem with these compositions is the difficulty in controlling manufacture to obtain reproducible product stability.

In the context of those earlier known systems, the -applicants' unpublished European Patent Application explains the action of deflocculants as follows. For deflocculation to occur, an appropriate combination of solids, solvent and deflocculant must be identified. The deflocculant can be solid or liquid before it is added to the remainder of the composition. It can be mono-functional (i.e. act only to deflocculate the particulate solids) or it can be bi-functional (i.e. also have properties beneficial in the relevant cleaning application, e.g. a surfactant). Many of the deflocculants described are inorganic or organic acids (including the free acid form of anionic surfactants). Two mentioned as particularly preferred are dodecyl benzene sulphonic acid (as the free acid) and lecithin.

In these deflocculated systems, the solvent/deflocculant combinations seem to result in a repulsive force between particles placed in the solvent, which may only be an apparent effect and represents a theory by which the applicants found it convenient to describe the phenomenon. It was not presented as in any way defining or restricting the scope of the invention.

It could be that the apparent force is merely a reduction in or destruction of the affinity between individual particles, so that instead of agglomerating to form flocs, they sediment-out in the solvent phase slower by virtue of their smaller size, as predicted by Stokes' law. The apparent force may also be sufficient to mitigate or completely counteract any network formation by the particles, which would otherwise lead to setting (solidification). Setting can be partly or wholly reversible, or irreversible, depending on the degree of network formation and the force applied in an attempt to break it down. The apparent force could also be of sufficient strength that the repulsion between the particles will inhibit sedimenting, i.e. it could be a positive suspending force.It may be that the way which the apparent force acts could vary according to the quantities and types of the materials (solvents, solids and structurants) used, or there could be a spectrum with all of these effects occurring simultaneously, each to a different relative degree.

The applicants' unpublished European Patent Application categorises three forms of deflocculated system.

The first of these entails systems in which the size of particles is small enough and the solvent viscous enough that the particles settle very slowly and no more phase separation is observed than 1% by volume in 1 week, preferably in 1 month, preferably 3 months. Such products are most suited where low volume fractions of solids are required, yet only minimal visible phase separation is tolerable over the period from manufacture, through storage, until use.

The second form is where low volume fractions of solids are required but visible phase separation can be tolerated. Here the particle size/solvent viscosity combination results in rapid settling, in particular a phase separation df more than 1% by volume in one week.

However, the liquid can be made substantially homogeneous, e.g. by stirring or shaking just prior to use.

In both of the above-mentioned product forms, the deflocculant confers the advantage of inhibiting setting of the bulk of the liquid by network formation or the formation of a compacted settled solids layer which is not readily re-dispersible in the solvent. Whatever the rate of sedimentation of solids in either product form, this rate is minimised by the deflocculation effect preventing individual particles from agglomerating into larger flocs which then settle more rapidly.

The third product form corresponds to the composition of the final settled layer which will develop eventually if liquids of either of the first two product forms are left to stand. The minimum volume which this layer assumes will be approached asymptotically with progression of time. However, for all practical purposes, after standing a sample of either of the first two product forms for sufficient time, the volume of the settled layer will not substantially decrease further. The composition of that layer can then be analysed by means which will be known to those skilled in the art and this substantially constitutes the composition of a liquid of the third product form.

A product in the latter category can be formulated by dispersing all major solids in excess solvent and with an amount of deflocculant which can be optimised by a means which will be described hereinbelow. Thus, this dispersion can be left to assume the final settled volume, the composition of which is then analysed. In a new composition made-up according to this latter formulation, all minor ingredients can be dissolved and/or dispersed and the sample stored to determine compatibility of the components, optionally followed by minor adjustments in amounts and types of solids, solvents and structurant to achieve the required balance of rheology, performance and manufacturing cost.

The aforementioned unpublished European Application also sets-out a method by which combinations of solids, solvent and deflocculant in which deflocculation occurs can be identified. First, one chooses the solvent and solids according to the intended product form and action.

The solids are preferably selected in the form of a powder with a very small particle size, say less than 10 microns.

If not already available in such fine form, the solids can be taken in coarser form and ground by appropriate means, such as in a suitable ball mill. The solids are then added progressively (with stirring) to the solvent until sufficient are added, that a substantial viscosity rise is apparent (i.e. the mixture thickens visibly). A sample potential deflocculant is then added progressively until deflocculation is detected. If it is not observed at any level of potential structurant, that material is unsuitable in that particular solids/solvent system and another should be tried.

In its most marked degree, deflocculation is apparent by a readily discernable thinning (viscosity reduction) at some point during addition of structurant whilst stirring.

However, the main means of quantitative detection of deflocculation is identification of a viscosity reduction at low shear rates (e.g. at or around 5 s 1) as measured in a suitable rheometer. Preferably, at at least some structurant level, at such a shear rate, a viscosity reduction of 25% should be observed, although 50% reduction or even of a whole order of magnitude is even more indicative of a structurant with good deflocculant properties. Although the deflocculants reduce the viscosity of the system, many products according to the invention are still quite viscous at low shear rates (e.g.

> 1 Pas) but they are very shear thinning and so are relatively pourable.

Once a suitable deflocculant has been identified (for use in a composition according to any aspect of the invention), the optimum amount of structurant can be determined by varying the amount of structurant added to the pre-selected solids/solvent combination and measuring the sedimentation rate at each value. Sedimentation rate can be measured by standing the liquid in a measuring cylinder or other suitable vessel and determining the rate of sinking of the upper surface of the settled layer.

Having selected a viable solids/solvent/deflocculant combination, an appropriate final product can then be formulated.

In their unpublished European application, the present applicants indicate prior disclosures where certain other materials have been specifically included in nonionic surfactant solvents as dispersants for solid particles. Thus according to GB 2 158 453 A, one such agent is an organic phosphorus compound having an acidic -POH group. This is also essentially disclosed in J 61 227 832. According to GB 2 172 897 A, the dispersant (there called an anti-settling agent) may be the aluminium salt of a higher aliphatic carboxylic acid, or as described in GB 2 179 346 A, a cationic quaternary amine salt surfactant, urea, or a substituted-urea or -guanidine. Substituted-ureas are also described as such dispersants in J 61 227 829, whilst comparable use of substituted-urethanes is the subject of J 61 227 830.

According to the some of these disclosures, such anti-settling agents increase the yield value of the composition. This suggests that the ultimate mechanism of action of these previously known dispersants may be somewhat different from many of those claimed in the unpublished European application, although some may be 'deflocculants' in as much as they fulfil the test prescribed in the latter document.

The unpublished European application also refers to disclosures where certain materials have been included in non-aqueous liquid detergents having a solvent phase of mainly surfactant material, without it being realised previously that these materials act as dispersants, perhaps even as deflocculant dispersants, in those particular systems. In other words these are materials included in the composition purely with the intention of aiding product performance (i.e. improved dispensing and/or cleaning performance).

Thus, anti-gelling agents which.improve product dispersability on contact with water are claimed in GB 2 158 454 A. These agents are polyether carboxylic acids. However, GB 2 177 716 A, claims anti-gelling use of aliphatic linear dicarboxylic acids containing at least about 6 aliphatic carbon atoms or aliphatic monocyclic dicarboxylic acids in which one of the carboxylic acid groups is bonded directly to a ring carbon atom and the other is bonded to the monocyclic ring through an alkyl or alkenyl chain of at least about 3 carbon atoms. In addition, according to DE 3 704 903 A, a combination or complex of a quaternary ammonium salt cationic surfactant and an acid-terminated nonionic (optionally in excess, thereby said to control viscosity) produces a fabric softening effect.

Furthermore, 61 227 828, claims use of fatty acid alkanolamide di-esters of dicarboxylic acids actually as dispersants. Analogous dispersants but where the ester is formed with a carboxylated polymer, optionally only partially esterified (including salt forms thereof) is the subject of J 61 227 832.

Certain builder systems which may or may not act as dispersants/deflocculants are also known. Those where the builder is heptonic acid or alginic acid alkali metal salt are described in GB 2 178 753 A whereas those with aluminosilicatel nitrilotriacetate (NTA) combinations are described in GB 2 178 954 A, whilst GB 2 180 551 A, describes systems wherein the builder is an alkali metal salt of a lower polycarboxylic acid. In GB 2 187 199 A, the builder disclosed is a linear long chain (20-30 phosphorus atoms) condensed polyphosphoric acid or an alkali-metal or ammonium salt thereof. Also, the aforementioned GB 2 158 545 A, and GB 2 158 838 A, describe use of sequestrant sodium salts, namely of certain acetic or phosphonic acid derivatives, which have some acidic character, as is common to many of the present applicants' own deflocculants.

Returning now to the present invention, all of the compositions to be subjected to the process are liquid cleaning products. They may be formulated in a very wide range of specific forms, according to the intended use.

They may be formulated as cleaners for hard surfaces (with or without abrasive) or as agents for warewashing (cleaning of dishes, cutlery etc) either by hand or mechanical means, as well as in the form of specialised cleaning products, such as for surgical apparatus or artificial dentures. They may also be formulated as agents for washing and/or conditioning of fabrics.

In the case of hard-surface cleaning, the compositions may be formulated as main cleaning agents, or pre-treatment products to be sprayed or wiped on prior to removal, e.g. by wiping off or as part of a main cleaning operation.

In the case of warewashing, the compositions may also be the main cleaning agent or a pre-treatment product, e.g applied by spray or used for soaking utensils in an aqueous solution and/or suspension thereof.

Typical are those products which are formulated for the cleaning and/or conditioning of fabrics because for those, in that there is a very great need to be able to incorporate substantial amounts of various kinds of solids. These compositions may for example, be of the kind used for pre-treatment of fabrics (e.g. for spot stain removal) with the composition neat or diluted, before they are rinsed and/or subjected to a main wash.

The compositions may also be formulated as main wash products, being dissolved and/or dispersed in the water with which the fabrics are contacted. In that case, the composition may be the sole cleaning agent or an adjunct to another wash product. Within the context of the present invention, the term 'cleaning product' also embraces compositions of the kind used as fabric conditioners (including fabric softeners) which are only added in the rinse water (sometimes referred to as 'rinse conditioners').

Thus, the compositions will contain at least one agent which promotes the cleaning and/or conditioning of the article(s) in question, selected according to the intended application. Usually, this agent will be selected from surfactants, enzymes, bleaches, microbiocides, (for fabrics) fabric softening agents and (in the case of hard surface cleaning) abrasives. Of course in many cases, more than one of these agents will be present, as well as other ingredients commonly used in the relevant product form.

The compositions will be substantially free from agents which are detrimental to the article(s) to be treated. For example, they will be substantially free from pigments or dyes, although of course they may contain small amounts of those dyes (colourants) of the kind often used to impart a pleasing colour to liquid cleaning products, as well as fluorescers, bluing agents and the like.

All ingredients before incorporation will either be liquid, in which case, in the composition they will constitute all or part of the solvent, or they will be solids, in which case, in the composition they will either be dispersed as deflocculated particles in the solvent or they will be dissolved in the solvent. Thus as used herein, the term solids is to be construed as referring to materials in the solid phase which are added to the composition and are dispersed therein in solid form, those solids which dissolve in the solvent and those in the liquid phase which solidify (undergo a phase change) in the composition, wherein they are then dispersed.

Some liquids are alone, unlikely to be suitable to perform the function of solvent for any combination of solids and dispersant/deflocculant. However, they will be able to be incorporated if used with another liquid which does have the required properties, the only requirement being that where the solvent comprises two or more liquids, they are miscible when in the total composition or one can be dispersible in the other, in the form of fine droplets.

Thus, where surfactants are solids, they will usually be dissolved or dispersed in the solvent. Where they are liquids, they will usually constitute all or part of the solvent. However, in some cases the solvents may undergo a phase change in the composition, Also, as mentioned earlier above, some surfactants are also eminently suitable as deflocculants. In general, they may be chosen from any of the classes, sub-classes and specific materials described in 'Surface Active Agents' Vol. I, by Schwartz & Perry, Interscience 1949 and 'Surface Active Agents' Vol. II by Schwartz, Perry & Berch (Interscience 1958), in the current edition of "McCutcheon's Emulsifiers & Detergents" published by the McCutcheon division of Manufacturing Confectioners Company or in 'Tensid-Taschenbuch', H. Stache, 2nd Edn., Carl Hanser Verlag, Mdnchen & Wien, 1981.

Liquid surfactants are an especially preferred class of material to use in the solvent phase, especially polyalkoxylated types and in particular polyalkoxylated nonionic surfactants.

As a general rule, the applicants have found that the most suitable liquids to choose as the organic solvents are those having polar molecules. In particular, those comprising a relatively lipophilic part and a relatively hydrophilic part, especially a hydrophilic part rich in electron lone pairs, tend to be well suited. This is completely in accordance with the observation that liquid surfactants, especially polyalkoxylated nonionics, are one preferred class of solvent.

Nonionic detergent surfactants are well-known in the art. They normally consist of a water-solubilizing polyalkoxylene or a mono- or di-alkanolamide group in chemical combination with an organic hydrophobic group derived, for example, from alkylphenols in which the alkyl group contains from about 6 to about 12 carbon atoms, dialkylphenols in which each alkyl group contains from 6 to 12 carbon atoms, primary, secondary or tertiary aliphatic alcohols (or alkyl-capped derivatives thereof), preferably having from 8 to 20 carbon atoms, monocarboxylic acids having from 10 to about 24 carbon atoms in the alkyl group and polyoxypropylenes. Also common are fatty acid mono- and dialkanolamides in which the alkyl group of the fatty acid radical contains from 10 to about 20 carbon atoms and the alkyloyl group having from 1 to 3 carbon atoms.In any of the mono- and dialkanolamide derivatives, optionally, there may be a polyoxyalkylene moiety joining the latter groups and the hydrophobic part of the molecule. In all polyalkoxylene containing surfactants, the polyalkoxylene moiety preferably consists of from 2 to 20 groups of ethylene oxide or of ethylene oxide and propylene oxide groups.

Amongst the latter class, particularly preferred are those described in the applicants' published European specification EP-A-225,654, especially for use as all or part of the solvent. Also preferred are those ethoxylated nonionics which are the condensation products of fatty alcohols with from 9 to 15 carbon atoms condensed with from 3 to 11 moles of ethylene oxide. Examples of these are the condensation products of Cull 13 alcohols with (say) 3 or 7 moles of ethylene oxide. These may be used as the sole nonionic surfactants or in combination with those of the described in the last-mentioned European specification, especially as all or part of the solvent.

Another class of suitable nonionics comprise the alkyl polysaccharides (polyglycosides/oligosaccharldes) such as described in any of specifications US 3,640,998; US 3,346,558; US 4,223,129; EP-A-92,355; EP-A-99,183; EP-A-70,074, '75, '76, '77; EP-A-75,994, '95, '96.

Nonionic detergent surfactants normally have molecular weights of from about 300 to about 11,000.

Mixtures of different nonionic detergent surfactants may also be used, provided the mixture is liquid at room temperature. Mixtures of nonionic detergent surfactants with other detergent surfactants such as anionic, cationic or ampholytic detergent surfactants and soaps may also be used. If such mixtures are used, the mixture must be liquid at room temperature.

Examples of suitable anionic detergent surfactants are alkali metal, ammonium or alkylolamaine salts of alkylbenzene sulphonates having from 10 to 18 carbon atoms in the alkyl group, alkyl and alkylether sulphates having from 10 to 24 carbon atoms in the alkyl group, the alkylether sulphates having from 1 to 5 ethylene oxide groups, olefin sulphonates prepared by sulphonation of C 10-C24 alpha-olefins and subsequent neutralization and hydrolysis of the sulphonation reaction product.

Other surfactants which may be used include alkali metal soaps of a fatty acid, preferably one containing 12 to 18 carbon atoms. Typical such acids are oleic acid, ricinoleic acid and fatty acids derived from caster oil, rapeseed oil, groundnut oil, coconut oil, palmkernal oil or mixtures thereof. The sodium or potassium soaps of these acids can be used. As well as fulfilling the role of surfactants, soaps can act as detergency builders or fabric conditioners, other examples of which will be described in more detail hereinbelow. It can also be remarked that the oils mentioned in this paragraph may themselves constitute all or part of the solvent, whilst the corresponding low molecular weight fatty acids (triglycerides) can be dispersed as solids or function as structurants.

Yet again, it is also possible to utilise cationic, zwitterionic and amphoteric surfactants such as referred to in the general surfactant texts referred to hereinbefore. Examples of cationic detergent surfactants are aliphatic or aromatic alkyl-di(alkyl) ammonium halides and examples of soaps are the alkali metal salts of C12-C24 fatty acids. Ampholytic detergent surfactants are e.g. the sulphobetaines. Combinations of surfactants from within the same, or from different classes may be employed to advantage for optimising structuring and/or cleaning performance.

Non-surfactants which are suitable as solvents include those having the preferred molecular forms referred to above although other kinds may be used, especially if combined with those of the former, more preferred types. In general, the non-surfactant solvents can be used alone or with in combination with liquid surfactants. Non-surfactant solvents which have molecular structures which fall into the former, more preferred category include ethers, polyethers, alkylamines and fatty amines, (especially di- and tri-alkyl- and/or fatty- Nsubstituted amines), alkyl (or fatty) amides and mono- and di- N-alkyl substituted derivatives thereof, alkyl (or fatty) carboxylic acid lower alkyl esters, ketones, aldehydes, and glycerides.Specific examples include respectively, di-alkyl ethers, polyethylene glycols, alkyl ketones (such as acetone) and glyceryl trialkylcarboxylates (such as glyceryl tri-acetate), glyceroi, propylene glycol, and sorbitol.

Many light solvents with little or no hydrophilic character are in most systems, unsuitable on their own (i.e. deflocculation will not occur in them). Examples of these are lower alcohols, such as ethanol, or higher alcohols, such as dodecanol, as well as alkanes and olefins. However, they can be combined with other solvent materials which are surfactants or non-surfactants having the aforementioned 'preferred' kinds of molecular structure. Even though they appear not to play a role in the deflocculation process, it is often desirable to include them for lowering the viscosity of the product and/or assisting soil removal during cleaning.

The compositions may also contain the organic solvent (whether or not comprising liquid surfactant) in an amount of at least 10% by weight of the total composition. The amount of the solvent present in the composition may be as high as about 90%, but in most cases the practical amount will lie between 20 and 70% and preferably between 20 and 50% by weight of the composition.

The deflocculant may be any of those referred to in the published prior art or any described in the applicants unpublished European patent application as related above.

Of these deflocculants, especially preferred are acids.

In the narrowest sense, these are regarded as substances which in aqueous media are capable of dissociating to produce hydrogen ions (H+), which in aqueous systems can be regarded as existing in the form H3 0 . However, in the content of the present invention, the definition also extends to those materials which are capable of losing a proton (H+) and are often termed 'Bronsted Acids', and even those according to the widest definition, that is, a substance which can accept a pair of electrons. Such an acid according to this definition is often called a Lewis acid.

Bronsted acids constitute a preferred group of the acid deflocculants, especially inorganic mineral acids and alkyl-, alkenyl-, aralkyl- and aralkenyl-sulphonic or mono-carboxylic acids and halogenated derivatives thereof, as well as acidic salts (especially alkali metal salts) of these.

Some typical examples from within the latter group include the alkanonic acids such as acetic, propionic and stearic and their halogenated counterparts such as trichloracetic and trifluoracetic as well as the alkyl (e.g. methane) sulphonic acids and aralkyl (e.g.

paratoluene) sulphonic acids.

Examples of suitable inorganic mineral acids and their salts are hydrochloric, carbonic, sulphurous, sulphuric and phosphoric acids; potassium monohydrogen sulphate, sodium monohydrogen sulphate, potassium monhydrogen phosphate, potassium dihydrogen phosphate, sodium monohydrogen phosphate, potassium dihydrogen pyrophosphate, tetrasodium monohydrogen triphosphate.

In addition to the acids and acidic salts, other organic acids may also be used as deflocculants, for example formic, lactic, citric, amino acetic, benzoic, salicylic, phthalic, nicotinic, ascorbic, ethylenediamine tetraacetic, and aminophosphonic acids, as well as longer chain fatty carboxylates and triglycerides, such as oleic, stearic, lauric acid and the like. Peracids such as percarboxylic and persulphonic acids may also be used.

The class of acid deflocculants further extends to the Lewis acids, including the anhydrides of inorganic and organic acids. Examples of these are acetic anhydride, maleic anhydride, phthalic anhydride and succinic anhydride, sulphur-trioxide, diphosphorous pentoxide, boron trifluoride, antimony pentachloride.

One particularly suitable sub-class of deflocculants comprises the anionic surfactants of formula (I) R-L-A-Y (I) wherein R is a linear or branched hydrocarbon group having from 8 to 24 carbon atoms and which is saturated or unsaturated; L is absent or represents -0-, -S-, -Ph-, or -Ph-O (where Ph represents phenylene), or a group of formula -CON(R -CON(R1)R2- or -COR-, wherein R represents a straight or branched C14 alkyl group and R represents an alkylene linkage having from 1 to 5 carbon atoms and is optionally substituted by a hydroxy group; A is absent or represents from 1 to 12 independently selected alkenyloxy groups; and Y represents -SOjH or -CH2 SO 3H or a group of formula -CH(R3)COR4 wherein R represents -OSO3H or -SO3H and R4 5 independently represents -NH2 or a group of formula -OR where R5 respresents hydrogen or a straight or branched C14 alkyl group and salts, particularly metal, more especially alkali metal salts thereof. However, the free acid forms thereof are the most preferred.

Especially preferred of the free acid forms are those wherein L is absent or represents -0-, -Ph- or -Ph-O-; A is absent or represents from 3 to 9 ethoxy, i.e. -(CH2)20- or propoxy, i.e. -(CH2)3O- groups or mixed ethoxy/propoxy groups; and Y represents -S03H or -CH2SO3H.

The alkyl and alkyl benzene sulphates, and sulphonates, as well as ethoxylated forms thereof, and also analogues wherein the alkyl chain is partly unsaturated, are particularly preferred.

As well as anionic surfactants, zwitterionic-types can also be used as structurants/deflocculants. These may be any described in the aforementioned general surfactant references. One preferred example is lecithin which is a material having both acidic and basic sites on the molecule and contains a phosphorous linkage of formula -O-P(-O) (O) -0-.

The level of the deflocculant material in the composition can be optimised by the means hereinbefore described but in very many cases is at least 0.01%, usually 0.18 and preferably at least 1% by weight, and may be as high as 158 by weight. For most practical purposes, the amount ranges from 2-12%, preferably from 4-10% by weight, based on the final composition.

The compositions may also contain one or more other functional ingredients, for example selected from detergency builders, bleaches or bleach systems, and (for hard surface cleaners) abrasives.

The detergency builders are those materials which counteract the effects of calcium, or other ion, water hardness, either by precipitation or by an ion sequestering effect. They comprise both inorganic and organic builders. They may also be sub-divided into the phosphorus-containing and non-phosphorus types, the latter being preferred when environmental considerations are important.

In general, the inorganic builders comprise the various phosphate-, carbonate-, silicate-, borate- and aliminosilicate-type materals, particularly the alkali-metal salt forms. Mixtures of these may also be used.

Examples of phosphorus-containing inorganic builders, when present, include the water-soluble salts, especially alkali metal pyrophosphates, orthophosphates, polyphosphates and phosphonates. Specific examples of inorganic phosphate builders include sodium and potassium tripolyphosphates, phosphates and hexametaphosphates.

Examples of non-phosphorus-containing inorganic builders, when present, include water-soluble alkali metal carbonates, bicarbonates, borates, silicates, metasilicates, and crystalline and amorphous alumino silicates. Specific examples include sodium carbonate (with or without calcite seeds), potassium carbonate, sodium and potassium bicarbonates, silicates and zeolites.

Examples of organic builders include the alkali metal1 ammonium and substituted, citrates, succinates, malonates, fatty acid sulphonates, carboxymethoxy succinates, ammonium polyacetates, carboxylates, polycarboxylates, aminopolycarboxylates, polyacetyl carboxylates and polyhydroxsulphonates. Specific examples include sodium, potassium, lithium, ammonium and substituted ammonium salts of ethylenediaminetetraacetic acid, nitrilotriacetic acid, oxydisuccinic acid, melitic acid, benzene polycarboxylic acids and citric acid. Other examples are organic phosphonate type sequestering agents such as those sold by Monsanto under the tradename of the Dequest range and alkanehydroxy phosphonates.

Other suitable organic builders include the higher molecular weight polymers and co-polymers known to have builder properties, for example appropriate polyacrylic acid, polymaleic acid and polyacrylic/polymaleic acid co-polymers and their salts, such as those sold by BASF under the Sokalan Trade Mark.

The aluminosilicates are an especially preferred class of non-phosphorus inorganic builders. These for example are crystalline or amorphous materials having the general formula: Naz (AlO2)z (SiO2)y x H20 wherein Z and Y are integers of at least 6, the molar ratio of Z to Y is in the range from 1.0 to 0.5, and x is an integer from 6 to 189 such that the moisture content is from about 4% to about 20% by weight (termed herein, 'partially hydrated'). This water content provides the best rheological properties in the liquid. Above this level (e.g. from about 19% to about 28% by weight water content), the water level can lead to network formation.

Below this level (e.g. from 0 to about 6% by weight water content), trapped gas in pores of the material can be displaced which causes gassing and tends to lead to a viscosity increase also. However, it will be recalled that anhydrous materials (i.e. with 0 to about 6% by weight of water) can be used as structurants. The preferred range of aluminosilicate is from about 12% to about 30% on an anhydrous basis. The aluminosilicate preferably has a particle size of from 0.1 to 100 microns, ideally betweeen 0.1 and 10 microns and a calcium ion exchange capacity of at least 200 mg calcium carbonate/g.

Suitable bleaches include the halogen, particularly chlorine bleaches such as are provided in the form of alkalimetal hypohalites, e.g. hypochlorites. In the application of fabrics washing, the oxygen bleaches are preferred, for example in the form of an inorganic persalt, preferably with an precursor, or as a peroxy acid compound.

In the case of the inorganic persalt bleaches, the precursor makes the bleaching more effective at lower temperatures, i.e. in the range from ambient temperature to about 600C, so that such bleach systems are commonly known as low-temperature bleach systems and are well known in the art. The inorganic persalt such as sodium perborate, both the monohydrate and the tetrahydrate, acts to release active oxygen in solution, and the precursor is usually an organic compound having one or more reactive acyl residues, which cause the formation of peracids, the latter providing for a more effective bleaching action at lower temperatures than the peroxybleach compound alone.

The ratio by weight of the peroxy bleach compound to the precursor is from about 15:1 to about 2:1, preferably from about 10:1 to about 3.5:1. Whilst the amount of the bleach system, i.e. peroxy bleach compound and precursor, may be varied between about 5% and about 35% by weight of the total liquid, it is preferred to use from about 6% to about 30% of the ingredients forming the bleach system.

Thus, the preferred level of the peroxy bleach compound in the composition is between about 5.5% and about 27% by weight, while the preferred level of the precursor is between about 0.58 and about 40E, most preferably between about 1% and about 5% by weight.

Typical examples of the suitable peroxybleach compounds are alkalimetal peroborates, both tetrahydrates and monohydrates, alkali metal percarbonates, persilicates and perphosphates, of which sodium perborate is preferred.

Precursors for peroxybleach compounds have been amply described in the literature, including in British patent specifications 836,988, 855,735, 907,356, 907,358, 907,950, 1,003,310, and 1,246,339, US patent specifications 3,332,882, and 4,128,494, Canadian patent specification 844,481 and South African patent specification 68/6,344.

The exact mode of action of such precursors is not known, but it is believed that peracids are formed by reaction of the precursors with the inorganic peroxy compound, which peracids then liberate active-oxygen by decomposition.

They are generally compounds which contain N-acyl or O-acyl residues in the molecule and which exert their activating action on the peroxy compounds on contact with these in the washing liquor.

Typical examples of precursors within these groups are polyacylated alkylene diamines, such as N,N,N,N-tetraacetylethylene diamine (TAED) and N,N,N1 1 N,N,N ,N -tetraacetylmethylene diamine (TAMED) acylated glycolurils, such as tetraacetylgylcoluril (TAGU); triacetylcyanurate and sodium sulphophenyl ethyl carbonic acid ester.

A particularly preferred precursor is N,N,N ,N -tetra- acetylethylene diamine (TAED).

The organic peroxyacid compound bleaches are preferably those which are solid at room temperature and most preferably should have a melting point of at least 500C. Most commonly, they are the organic peroxyacids and water-soluble salts thereof having the general formula

wherein R is an al-kylene or substituted alkylene group containing 1 to 20 carbon atoms or an arylene group containing from 6 to 8 carbon atoms, and Y is hydrogen, halogen, alkyl, aryl or any group which provides an anionic moiety in aqueous solution.

Another preferred class of peroxygen compounds which can be incorporated to enhance dispensing/dispersibility in water are the anhydrous perborates described for that purpose in the applicants' European patent specification EP-A-217,454.

When the composition contains abrasives for hard surface cleaning (i.e. is a liquid abrasive cleaner), these will inevitably be incorporated as particulate solids. They may be those of the kind which are water insoluble, for example calcite. Suitable materials of this kind are disclosed in the applicants' patent specifications EP-A-50,887; EP-A-80,221; EP-A-140,452; EP-A-214,540 and EP 9,942, which relate to such abrasives when suspended in aqueous media. Water soluble abrasives may also be used.

The compositions optionally may also contain one or more minor ingredients such as fabric conditioning agents, enzymes, perfumes (including deoperfumes), micro-biocides, colouring agents, fluorescers, soil-suspending agents (anti-redeposition agents), corrosion inhibitors, enzyme stabilizing agents, and lather depressants.

The composftions are substantially non-aqueous, i.e.

they little or no free water, preferably no more than 5%, preferably less than 3%, especially less than 1% by weight of the total composition. It has been found by the applicants that the higher the water content, the more likely it is for the viscosity to be too high, or even for setting to occur.- However, this may at least in part be overcome by use of higher amounts of, or more effective deflocculants or other dispersants.

Since the objective of a non-aqueous liquid will generally be to enable the formulator to avoid the negative influence of water on the components, e.g.

causing incompatibility of functional ingredients, it is clearly necessary to avoid the accidental or deliberate addition of water to the product at any stage in its life.

For this reason, special precautions are necessary in manufacturing procedures and pack designs for use by the consumer.

The following compositions are typical of those which may be subjected to the process of the present invention.

Compositions (% by weight) A B C D E F G Solvent Plurafac RA30 36.1 34.1 37.0 - - - Dobanol 91-6 - - - 36.6 36.6 - Dobanol 91-ST - - - - - 36.6 36.6 Glyceryl Triacetate 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Deflocculant ABSA 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Solids STP 0.aq 30.0 30.0 29.3 30.0 30.0 30.0 30.0 Soda Ash 4.0 - 4.0 - - - - Na Perborate 13.4 13.0 15.05 15.0 13.0 15.0 13.0 Mono.Hy.

Na Peroxoborate 2.1 2.0 - - 2.0 - 2.0 TAED 4.0 4.0 4.0 4.0 4.0 4.0 4.0 Minors* ----------------- balance ------------------ * Enzyme, bleach stabiliser, corrosion inhibitor, anti-redeposition agent, fluorescer, perfume.

Compositions (8 by weight) A B C D E F Solvent Plurafac RA30 38.6 38.6 38.6 36.2 - Glyceryl 5.0 5.0 5.0 5.0 - Tri-Acetate Dobanol 91-6 - - - - 41.3 Synperonic A3 - - - - - 12.4 Synperonic A5 - - - - - 28.9 Monoethanolamine - - - - 0.5 0.5 Deflocculant ABSA 1.0 1.0 - 1.0 2.3 2.3 Lecithin - - 1.0 - - Solids Hydrated Zeolite - 24.0 24.0 - - Activated Zeolite 24.5 - - - - - Sokalan CP5 5.5 5.5 5.5 - - Versa TL3 - - - 0.5 - Soda Ash - 4.5 4.5 29.9 42.2 42.2 Calcite Socal U3 - - - 6.0 6.8 6.8 Na perborate Mono.hy. 13.0 15.0 15.0 13.0 6.0 6.0 Na Peroxoborate 2.0 - - 2.0 0.9 0.9 TAED 4.0 4.0 4.0 4.0 - - Minors* -------------- balance --------------- * Enzyme, bleach stabiliser, corrosion inhibitor, anti-redeposition agent, fluorescer, perfume.

Commercial Materials Synperonic A3: nonionic surfactant comprising C13-15 fatty alcohol alkoxylated with an average of 3 moles of ethylene oxide (ex ICI).

Synperonic A5: nonionic surfactant comprising C13-15 fatty alcohol alkoxylated with an average of 5 moles of ethylene oxide (ex ICI).

Dobanol 91-5T nonionic surfactant comprising Cog 11 fatty alcohol alkoxylated with an average of 5 moles of ethylene oxide (ex Shell).

Dobanol 91/6: nonionic surfactant comprising Cm 11 fatty alcohol alkoxylated with an average of 6 moles of ethylene oxide (ex Shell).

Plurafac RA30: nonionic surfactant comprising C13-15 fatty alcohol and alkoxylated with an average of 4-5 moles of ethylene oxide and 2-3 moles of propylene oxide (ex ICI).

Versa TL3: polystyrene maleic anhydride sulphonate sodium salt (ex National Adhesives and Resins Limited).

Sokalan CP5: acrylic acid/maleic acid co-polymer, average molecular weight 70,000, acrylic acid:maleic acid ratio 1:1,

Claims (6)

1. CLAIMS 1. A process for controlling the size of solid particles during manufacture of a substantially non-aqueous liquid cleaning product comprising a dispersion of solid particles in a liquid solvent phase, said process comprising the steps of:a) passing said dispersion through a mill; b) measuring the particle size in the dispersion after it has passed through the mill; and c) using the particle size measurement for controlling the operation of the mill; wherein, during said process, said dispersion contains a deflocculant at the time it is subjected to the particle size measurement.
2. 2. A process according to claim 1, wherein the particle size measurement is performed using an optical technique.
3. 3. A process according to claim 2, wherein the optical technique comprises detecting light scattered by the particles.
4. 4. A process according to any preceding claim, wherein the mill is a ball mill and the particle size measurement is used for controlling the energy input thereto.
5. 5. A process according to any preceding claim, comprising admixing one or more heat sensitive components with the dispersion after the milling step.
6. 6. A process according to any preceding claim, wherein the deflocculant is dodecyl benzene sulphonic acid.