EP1397477A1

EP1397477A1 - Detergent compositions

Info

Publication number: EP1397477A1
Application number: EP02745551A
Authority: EP
Inventors: Antonio Reckitt Benckiser Italia CORDELLINA; Luca Rosa Fauzza
Original assignee: Reckitt Benckiser NV
Current assignee: Reckitt Benckiser NV
Priority date: 2001-06-22
Filing date: 2002-06-20
Publication date: 2004-03-17
Also published as: GB2376692A; WO2003000835A1; GB0115328D0

Abstract

This invention relates to laundry detergent compositions which contain sufficient clay that the compositions provide a distinct softening effect, and in particular it relates to such compositions in the form of tablets with a fast disintegration time and good physical properties required for storing, shipping and handling.

Description

Detergent Compositions

It is known to provide detergent compositions in the form of tablets made by compacting a particulate detergent composition. Usually a small amount of binder is included in the composition in order to promote the integrity of the tablets.

Although it is necessary that the tablets should have good integrity before use, it is necessary also that they should disintegrate rapidly during use, when contacted with wash water. It is known to include a disintegrant which will promote disintegration of the tablet. Various classes of disintegrant are known, including the class in which disintegration is caused by swelling of the disintegrant. Various swelling disintegrants have been proposed in the literature, with the preference being directed predominantly towards starches, celluloses and water soluble organic polymers. Inorganic swelling disintegrants such as bentonite clay have also been mentioned, for instance in EP-A-466,484.

In that disclosure, the same material acts as binder and disintegrant. It is also mentioned therein that the disintegrant may give supplementary building, anti- redeposition or fabric softening properties. The amount of disintegrant is preferably 1 to 5 %. It is proposed in EP-A-466,484 that the tablet may have a heterogeneous structure comprising a plurality of discrete regions, for example layers, inserts or coatings.

In WO 98/40463 it is proposed to introduce the disintegrant substantially only in granular form. JP-A-9/87696 is concerned with tablets containing a non-ionic detergent composition with a non-ionic surfactant as the main component and in particular is concerned with preventing the non-ionic surfactant from oozing out of the tablets during storage, and it is also concerned with the fact that the non-ionic surfactant causes a loss in the softening effect that would be expected when a softening clay is included. It describes the formulation of the tablets containing finely divided clay material, together with a finely divided oil absorbing carrier, and a disintegrant.

WO 0066695 discloses a 2 layer softening laundry detergent tablet with a higher concentration of a clay in one layer than in the second layer. A flocculant is concentrated in the second layer to aid dispersibility.

We have found that is possible to produce laundry tablets capable of delivering a softening effect, an additional benefit well perceived by consumers; the new tablets have good characteristics in term of stability and easy disintegration for dosing in the drawer of washing machines.

The goal is reached through the incorporation of at least one type of clay, preferably the clay is a smectite clay, with the characteristics defined below. Clays are well known as being capable of imparting, among other properties, a softening effect to garments. But only a few particular grades have the right properties.

Once the right grade is chosen the main hurdle is the incorporation of it into the formula without adversely affecting the physical properties of the tablet. We have assessed that the best way to incorporate a clay into the formula is in the granular form. We have found that the pure granular form doesn't represent the best option since the final formula is not easily tabletted. Clay containing tablets don't show the same physical characteristics of as the same tablets without clay, i.e. the disintegration time is much higher.

Therefore, further investigations have been conducted on coated clays: surprisingly, among all alternatives, clay coated with an aluminosilicate, preferably zeolite, gave tablets with good disintegration properties. An additional beneficial effect is on the aesthetics of the tablet since the coating covers the grey cast produced on uncoloured products typical of using pure clay.

Therefore, we present as a feature of the invention a fabric softening laundry tablet comprising;

i) at least 5 % w/w, of the total composition, of a granular coated clay;

ii) from 1 % to 35 % w/w, of the total composition, of a bleaching agent or a bleaching composition comprising 1 % to 35 %, of the total composition, one bleaching agent and at least one bleaching activator;

iii) 0 % to 3 % w/w of an enzyme; iv) at least 5 % w/w of a detergent builder; v) at least 3 % w/w of a surfactant; and a water content of less than 10 %w/w.

The amount of coated clay in the tablet is usually at least 5 % by weight of the tablet, preferably at least 8 % by weight, more preferably at least 10 % by weight of the tablet but usually less than 35 %, more preferably less than 30 %, most preferably less than 20 % by weight.

There is preferably at least 5 % by weight non-ionic and/or anionic surfactant in the tablet.

The tablet is usually made by compression of particulate material. The tablets of the invention are of a size which is convenient for dosing in a washing machine. The preferred size is 30 to 40 g and the size can be selected in accordance with the intended wash load and the design of the washing machine which is to be used.

Clays

The clay is preferably mainly in the form of granules, with at least 50 % (and preferably at least 70 % or at least 90 %) being in the form of granules having a size of at least 100 μm up to 1400 μm, preferably up to 1250 μm, preferably 200- 1200 μm. Preferably the amount of clay in the granules is at least 50 %, usually at least 70 % or 90 % of the weight of the granules.

The coating for the granules of clay may be a coating of an ingredient of the detergent composition, such as a builder, a surfactant or a binder, preferably a builder. In a preferred feature the granules are coated with, for example, zeolite and preferably zeolite A. Coating techniques that can be used are readily known in the art and include spray coating, co-melt extrusion, coaservation and fluid bed coating techniques.

Ideally the coating present on the clay should be at least 5 % by weight of the tablet, preferably at least 8 % by weight, more preferably at least 10 % by weight of the granule, ideally less than 35 %, more preferably less than 30 %, most preferably less than 20 % by weight. At such levels the coatings produce more evenly shaped granules which aid the flowability of the granules, which is especially important in tabletting machines, in addition even coverage of the clay granule with an ingredient of the detergent composition allows for a more even integration of the clay granules into the composition.

The granular clay materials used to provide the fabric softening properties of the instant compositions can be described as expandable, three-layer clays, i.e., alumino- silicates and magnesium silicates, having an ion exchange capacity of at least 50 meq/lOOg of clay. The term "expandable" as used to describe clays relates to the ability of the layered clay structure to be swollen, or expanded, on contact with water. The three-layer expandable clays used herein are those materials classified geologically as smectites.

There are two distinct classes of smectite-type clays; in the first, aluminium oxide is present in the silicate crystal lattice; in the second class of smectites, magnesium oxide is present in the silicate crystal lattice. The general formulas of these smectites are Al₂(Si₂Os)₂(OH)₂ and Mg₃(Si₂O₅)(OH)₂ for the aluminium and magnesium oxide type clay respectively. It is to be recognised that the range of the water of hydration in the above formulas can vary with the processing to which the clay has been subjected. This is immaterial to the use of the smectite clays in the present invention in that the expandable characteristics of the hydrated clays are dictated by the silicate lattice structure. Furthermore, atom substitution by iron and magnesium can occur within the crystal lattice of the smectites, while metal cations such as Na⁺, Ca ^{" "}, as well as H⁺, can be co-present in the water of hydration to provide electrical neutrality. Except as noted hereinafter, such cation substitutions are immaterial to the use of the clays herein since the desirable physical properties of the clays are not substantially altered thereby.

As noted herein above, the clays employed in the compositions of the instant invention contain cationic counterions such as protons, sodium ions, potassium ions, calcium ion, magnesium ion and the like. It is customary to distinguish between clays on the basis of one cation predominantly or exclusively absorbed. For example, a sodium clay is one in which the absorbed cation is predominantly sodium and is preferred. Such absorbed cations can become involved in exchange reactions with cations present in aqueous solutions. A typical exchange reaction involving a smectite-type clay is expressed by the following equation:

smectite clay (Na) + NH₄OH_smectite clay (NH₄) + NaOH. Since in the foregoing equilibrium reaction, one equivalent weight of ammonium ion replaces an equivalent weight of sodium, it is customary to measure cation exchange capacity (sometimes termed "base exchange capacity") in terms of milliequivalents per 100 g of clay (meq/100 g). The cation exchange capacity of clays can be measured in several ways, including by electrodialysis, by exchange with ammonium ion followed by titration or by a methylene blue procedure, all as fully set forth in Grimshaw, "The Chemistry and Physics of Clays", pp. 264/265, h terscience (1971). The cation exchange capacity of a clay mineral relates to such factors as the expandable properties of the clay, the charge of the clay, which, in turn, is determined at least in part by the lattice structure, and the like.

Any of the smectite-type clays having a cation exchange capacity of at least 50 meq/100 g are useful herein, certain clays are preferred.

The smectite clays used in the compositions herein are all commercially available. Such clays include, for example, bentonite, montmorillonite, volchonskoite, nontronite, hectorite, saponite, and vermiculite. The clays herein are available under various tradenames, for example, Volclay from American Colloid Ltd., Steebent HW from Steetley Bentonite Ltd., Detercal from Laviosa Chimica S.p.a., Laundrosil from Sϋd-Chemie. It is to be recognised that such smectite-type minerals obtained under the foregoing tradenames can comprise mixtures of the various discrete mineral entities. Such mixtures of the smectite minerals are suitable for use herein. A preferred smectite clay is bentonite.

Manufacture

A preferred method of manufacturing the laundry tablets of the present invention comprising the steps of

i) pelletising a flowable tower spray powder and a flowable detergent builder in a pellet mill to form a premix (preferably with a aluminosilicate content of at least 30 % w/w (weight of aluminosilicate/weight of pellets); and

ii) mixing the pellets with the other ingredients.

Preferably the tower spray powder is made up of the following constituents (weight/weight of tower spray powder):

20-60% anionic surfactant; 0-15% processing aid; 0-25% further zeolite; 12-45% inorganic alkali metal, preferably sodium, salt; and 0-20% additional constituent(s).

More preferably, the tower spray powder comprises 30-50% of one or more anionic surfactant.

Preferably an alkali metal salt of an alkylbenzene sulphonic acid (for example an LAS) is present in the pellets, preferably wholly derived from the tower spray powder.

Preferably an alkali metal salt of an alkylbenzene sulphonic acid (for example an LAS) is not present in the zeolitic powder which is to be palletised. Preferably no anionic surfactant is present in the zeolitic powder which is to be pelletised.

Preferably an alkali metal salt of an alkylbenzene sulphonic acid (for example an LAS) is not present in the post-mixed ingredients to be mixed with the pellets.

Preferably the pellets do not contain any anionic sulphate surfactant.

Preferably the post-mixed ingredients include an anionic sulphate surfactant, suitably providing 2-10%, preferably 3-7%, of the final cleaning agent (weight/weight).

A processing aid may be included, in the tower spray and/or the zeolitic powder and/or in the post-mixed ingredient(s), in order to improve the efficiency of a later pelletisation step and/or of a later tabletting step, where provided. A suitable processing aid preferably functions as a plasticiser or lubricant. Examples include a soap, preferably a solid soap; a nonionic surfactant; an acrylic polymer or copolymer, for example an acrylic/ maleic anhydride copolymer; starch or a derivative thereof; gelatin; polyvinyl alcohol; and water. Preferred are a soap; a nonionic surfactant; an acrylic polymer or copolymer; and water.

The tower spray powder may include further zeolite, but this is not essential. When there is thus an input of further zeolite, the further zeolite preferably provides 4-30%, more preferably 6-20%, of the cleaning agent (weight/weight). Preferably, when there is a further input of zeolite it is less than the input of zeolite from the zeolite powder added to the tower spray powder.

It should be noted that both the tower spray powder and the flowable zeolitic powder are preferably macroscopically dry when delivered to the pellet mill. Preferably, both are free-flowing. The amount of liquid components present (if any) must not be such that the respective powders become damp, or sticky, or prone to form lumps. Zeolite for use in the present invention is desirably stored in conditions which discourage water take-up from the atmosphere; for example it can be stored in closed or sealed plastic sacks.

The tower spray powder and the zeolitic powder are preferably mixed upstream of the pellet mill in a separate unit, for example a vertical mixer/granulator, a horizontal mixer/granulator or a tumbler unit, all of which are conventional. Preferably, no heating is provided during this step.

Preferably the zeolite content of the pellets is at least 35%, more preferably at least 40%. Most preferably, it is at least 45% and, especially, at least 50%.

Preferably, the zeolite content of the pellets does not exceed 80%, more preferably 70%, most preferably the zeolite content of the pellets does not exceed 65%. Pelletisation can be performed in a standard pellet mill, e.g. a Kahl mill or a UMT mill: the process is efficient and unproblematic. This was unexpected given the failure we encountered in trying to extrude such materials.

Further information on pellet mills is readily available. Examples of patents concerning rotary pellet mills include DE 3813081, DE 3806945 and DE 3432780.

Preferably external heat is not provided in the pelletising step. We have found that the temperature of the material being pelletised rises moderately, typically to temperatures in the range 30-55°C, without detriment.

For the pelletisation step, the tower spray powder and the flowable zeolitic powder, as defined above, are preferably mixed together without any further material.

The pellets which are products of the pellet mill are chopped strands, "shaved" from the outer wall of the pellet mill as pelletisation proceeds. Based on our work to date it does not seem necessary from a technical standpoint to treat the pellets in any way before mixing them with post-mixed ingredients, to form the end laundry cleaning agent. However, they could if wished, primarily for aesthetic reasons, be given a simple mechanical treatment in a "ploughshare" shovel mixer, to reduce their mean aspect ratio, to be as close as possible, what may be considered to be the aesthetic ideal, 1:1 (pellet length:maximum diameter). We have found it easy to reduce the mean aspect ratio of the as-formed pellets, by feeding them straight from the pellet mill into the shovel mixer, preferably when the pellets are still warm.

Alternatively or additionally pellets may be spheronized. Preferably, however, the pellets are not spheronized.

Alternatively or additionally pellets may be dusted with a powder to aid flowability. This could suitably be zeolite, for example zeolite A. Preferably, however, the pellets are not dusted. Suitably the mean aspect ratio of the pellets used in the post-mixing is in the range 0.5-5:1, more preferably 0.8-3:1 (pellet length:maximum diameter). Preferably the pellets are circularly cylindrical and so the aspect ratio denotes length:diameter. Preferably the pellets from the pellet mill are given a mechanical treatment to reduce their mean aspect ratio, to be within this range.

The pellets are intended as a universal base material to which the post-mixing ingredient(s) can be added, for example to make a heavy duty laundry detergent product, or a colour care laundry detergent product. Thus, the pellets themselves preferably do not contain any of the "specialist" ingredients which are characteristic of such products. In particular, the pellets preferably do not contain any enzymes, bleaching compounds or bleach activators.

The post-mixing ingredient(s) will depend on the target use for the laundry cleaning agent - for example for general purpose laundry; for heavy duty/white clothes. Typically the ratio of the pellets to the post-mixing ingredient(s) is in the range of 20-80 : 80-20 (weight/weight). Preferably the ratio is in the range of 40-70 : 60-30. Most preferably, the ratio is in the range 50-60 : 50-40.

The post-mixing ingredient(s) suitably include one or more of the following: a surfactant, for example an anionic and/or nonionic surfactant; sodium bicarbonate; sodium carbonate; sodium citrate; an anti-foaming agent; an enzyme; a bleaching agent; a bleach activator; a stabiliser, for example of the phosphonate type as defined above; a soil release polymer; a soil redeposition inhibitor; an optical brightener; a colorant; and a fragrance.

Preferably the clay is added as a post-mixing ingredient.

Generally the surfactant component of the post-mixing ingredient(s) is relatively small, suitably making up not more than 10% of the total weight of post-mixing ingredient(s). As mentioned above the post-mixing ingredients may include an alcohol sulphate and this is preferably the only anionic surfactant component, and preferably the only surfactant component, in the post-mixing ingredient(s). In the case of a heavy duty cleaning agent the major complement of post-mixing ingredient(s) is a bleaching agent, for example sodium percarbonate, and a bleach activator, for example TAED; together preferably constituting at least 50% of the weight of post-mixing ingredient(s).

A particulate laundry cleaning agent may be made by simple mixing of the pellets and the post-mixing ingredient(s), for example in a tumbler unit. The bulk density of the resulting particulate material is typically high, suitably at least 750g/l, preferably at least 800 g/1. Although such particulate material is itself of potential utility as a washing powder, preferred laundry cleaning agents of the present invention are laundry tablets. Therefore, the invention preferably includes the step, after the step of mixing the pellets with the other ingredients, of pressing the particulate material to form a tablet.

Pressing the pellets and other ingredients to form tablets is a straightforward step, using standard equipment, for example a commercially available Korsch or Bonals press. It is preferred that when tablets are to be produced, one of the post-mixing ingredient(s) is a disintegrant, for example a rapidly water-swellable material, especially a water-swellable cellulosic material. Preferably the disintegrant provides less than 10% of the total weight of the tablets of the present invention and preferably not more than 8%.

Preferably the tablets produced in accordance with the present invention have a density of at least 1 kg/1. More preferably, the tablets have a density of at least 1.1 kg/1 and most preferably at least 1.15 kg/1.

Preferably the tablets have a hardness of at least 50 N, preferably at least 80 N, as measured by a dynamometer as the maximum force required to break the upper surface of the tablet when a perpendicular force is applied to the centre of it, by a vertically orientated cylinder of diameter 0.5cm. Preferably the tablets have a disintegration time of not more than 30 seconds, more preferably not more than 25 seconds, most preferably not more than 20 seconds, as measured by a standard method in which a laundry tablet is placed in a stainless steel mesh ladle, with mesh holes approximately 5mm x 5mm, and then successively lowered into and raised from a transparent tank containing 800 ml water at 20°C at a frequency of 60 immersions per minute. When no solid residue of the tablet can be seen within the ladle, the time is recorded ("disintegration time").

Preferably the pellets, and the other ingredients of the washing powder or of the particulate material to be tabletted, are of size such that at least 90 wt% thereof are in the size range 150-1200 μm, more preferably in the size range 250-1000 μm (as determined by standard mesh test, employing ASTM sieves and a Retsch vibrator with predetermined amplitude and working time).

If necessary the pellets and/or the particulate material resulting from the post-mixing may be graded, and overly large or small particles removed, for example for recycling.

When manufactured by the method described herein it will be appreciated that the laundry tablets may have an exceptional combination of beneficial properties, namely high density, high zeolite content and a low amount of disintegrant (all of which would normally lead to long disintegration time); and yet, unexpectedly, exhibit a short disintegration time.

Preferably the solid laundry cleaning agents of the present invention contain no phosphate detergents.

Preferably the amount of surfactants in the cleaning agent is at least 10% by weight. Preferably it does not exceed 30%, more preferably 25%, by weight. Preferably the zeolite content of the cleaning agent is at least 15% by weight, more preferably at least 20%, most preferably at least 25%, and, especially at least 25%.

Tablet Manufacture

Detergent tablets of the present invention can be prepared simply by mixing the solid ingredients together and compressing the mixture in a conventional tablet press as used, for example, in the pharmaceutical industry. Preferably the principal ingredients, in particular gelling surfactants, are used in particulate form. Any liquid ingredients, for example surfactant or suds suppressor, can be incorporated in a conventional manner into the solid particulate ingredients.

The tablets may be manufactured by using any compacting process, such as tabletting, briquetting, or extrusion, preferably tabletting. Suitable equipment includes a standard single stroke or a rotary press (such as Courtoy(R), Korsch(R), Manesty(R), or Bonals(R)).

Detergent Builders

Suitable organic and inorganic builders are soluble and/or insoluble components showing a mildly acidic, neutral or alkaline reaction which are capable of precipitating or complexing calcium ions. Suitable and, in particular, ecologically safe builder systems, such as finely cristalline, synthetic water-containing zeolites type, which have a calcium binding power of 100 to 200 mg CaO/g are preferably used.

Preferred synthetic crystalline aluminosilicate ion exchange materials useful herein are available under the designations Zeolite A, Zeolite P, and Zeolite X. Natural zeolites include analcite, chabazite, heulandite, stilbite, fayisite, natrolite and thomsite. hi an especially preferred embodiment, the crystalline aluminosilicate ion exchange material has the formula:

Na₁₂[(AlO₂)ι₂(SiO₂)₁₂].xH₂O wherein x is from about 20 to about 30, especially about 27. This material is known as Zeolite A. Dehydrated zeolites (x = 0 - 10) may also be used herein. Preferably, the aluminosilicate has a particle size of about 0.1-10 microns in diameter. The detergent builder, preferably an aluminosilicate builder may be present in either or both layers, in at least 5 % by weight, preferably at least 15 % by weight, preferably at least 20 % by weight. A preferred range is 5 % to 40 % by weight. Other suitable builder constituents which may be used in particular together with the zeolite include (co)polymeric polycarboxylates, such as polyacrylates, polymethacrylates and, in particular, copolymers of acrylic acid with maleic acids, preferably those of 50% to 10% of maleic acid. The molecular weight of homopolymers in generally in the range from 1000 to 100000 while the molecular weight of the copolymers is in the range from 50000 to 120000, based on free acid. A particularly preferred acrylic acid/maleic acid copolymer has a molecular weight of 50000 to 100000.

Useful organic builders are, for example, polycarboxylic acids used in the form of their sodium salts, such as citric acid.

Suitable inorganic non-complexing salts are the bicarbonates, carbonates, borates or silicates of the alkali metals which are also known are "washing alkalis"

The level of builder can vary widely depending upon the end use of the composition.

Surfactants

Non limiting examples of surfactants include anionic surfactants alkali metal salts, ammonium salts, amine salts, aminoalcohol salts or magnesium salts of one or more of the following compounds: alkylsulphonates, alkylamide sulphonates, alkylarylsulphonates, olefinsulphonates, alkylamide sulphonates, alkyl sulfosuccinates, alkyl ether sulfosuccinates, alkylamide sulfosuccinates, alkyl sulfosuccinamate, alkyl sulfoacetates, acyl sarconsinates, acyl isothionates and N-acyl taurates. Generally, the alkyl or acyl group in these various compounds comprises a carbon chain containing 8 to 22, preferably, 12 to 20, carbon atoms. Other anionic surfactants which may be used include salts (having cations as described above) of fatty acids, individually or as mixtures, including salts of oleic and stearic acids, and of acids of palm kernel oil, coconut oil and tallow; and lactylates whose acyl group contains 8 to 20 carbon atoms. Especially useful are solid soaps, and preferably solid alkali metal salts of Cι_6-18 saturated fatty acids, especially of tallow fatty acids, as these are useful also as processing aids.

Suitable nonionic surfactants include alkoxylated alcohols, particularly alkoxylated fatty alcohols. These include ethoxylated and propoxylated fatty alcohols, as well as ethoxylated and propoxylated alkyl phenols, both having alkyl groups, suitably linear or secondary, of from 7 to 18, more preferably 8 to 16 carbon chains in length, and an average of 2 to 20 moles, preferably 2 to 10, most preferably 4 to 6 moles of alkylene oxide per mole of alcohol or phenol. Ethoxylated compounds are generally preferred.

Another class of nonionic surfactants that may be used are sorbitan esters of fatty acids, typically fatty acids having from 10 to 24 carbon atoms, for example sorbitan mono oleate.

Other classes of nonionic surfactants that may be used are amine oxides and polyhydroxy fatty acid amides.

In preferred embodiments, the tablet comprises at least 3 % by weight of surfactant, more preferably at least 5 % by weight, even more preferably at least 8 % by weight, and most preferably between 5 % and 20 % by weight of surfactant. The amount of anionic is preferably at least 1.5 times, generally at least 2 or 3 times, the total amount of other surfactants.

Bleach Among the compounds yielding H₂O₂ in water which serve as bleaches, sodium perborate tetrahydrate (NaB0₂-H₂O₂-3H₂O) and sodium perborate monohydrate (NaB0₂-H O) are particularly important. Other useful bleaches are, for example, peroxycarbonate (Na₂CO T.5H₂0₂), peroxypyrophosphates, citrate perhydrates and H 0₂-yelding paracidic salts and peracids, such as perbenzoates, peroxaphtalates, diperazelaic acid or diperdodecandioic acid.

When present, bleaching agents will typically be at levels of from about 1 % to about 30 %, more typically from about 5 % to about 20 %, of the detergent composition, especially for fabric laundering. To obtain an improved belaching effect where washing is carried out at temperatures of 60°C and lower, bleach activators may be incorporated in the preparations. Examples of suitable bleach activators are N-acyl or O-acyl compounds which from organic peracids with H₂O₂, preferably N, N'-tetraacylated diamines, such as TAED (N,N,N',N'-tetraacetyl ethylendiamine), also carboxylic anhydride and esters of polyols, such as glucose pentaacetate.

The detergent compositions herein may contain bleaching agents or bleaching compositions containing a bleaching agent and one or more bleach activators. If present, the amount of bleach activators will typically be from about 0.1 % to about 10%, more typically from about 0.5 % to about 6 % of the composition.

Enzymes

Suitable enzymes are enzymes from the class of proteases, lipases and amylases or mixture thereof. Enzymes obtained from bacterial strains pr fungi, such as Bacillus subtilis, Bacillus licheniformis and Stretomyces griseus, are particularly suitable. The enzymes may be absorbed onto supports and/or encapsulated in shell forming substances to prevent them against premature decomposition.

The compositions herein will typically comprise from about 0.001 % to about 3 %, preferably 0.01 %-l % by weight of a commercial enzyme preparation. Additional constituents of the detergent composition may be selected from a stabilizer, particularly for per compounds or enzymes. Suitable stabilizers are salts of polyphosphonic acids, such as l-hydroxyethane-l,l-diphosphonic acid (HEDP), diethylenetriaminopentamethylene phosphonic acid (DETPMP), ethylenediaminotetramethylene phosphonic acid (EDTMP) and aminotrimethylene phosphonic acid (ATP).

Another useful additional constituent of the cleaning agent is an optical brightener, for example a suitable stilbene compound, in particular diaminostilbene disulfonic acid or a derivative thereof, especially an alkali metal salt. An optical brightener may conveniently be delivered via the tower spray powder.

Another possible additional constituent of the cleaning agent is a soil redeposition inhibitor, for example one or more of polyvinyl pyrollidone, carboxymethyl- cellulose-sodium salt (CMC) or methylcellulose (MC). A soil redeposition inhibitor may conveniently be delivered via the tower spray powder.

Examples

Preparation of Tower Spray Powder

A tower spray powder having the following ingredients was prepared in the conventional manner, in a vertical tower, from an aqueous slurry.

Preparation of Pellets

The tower spray powder was mixed in equal weight with dry, virgin zeolite A powder in a concrete mixer. The zeolite had been stored in sealed plastic sacks and nothing was added to it before the mixing. The mixed material was fed into a Kahl pellet mill operated at 100 rpm to yield circularly cylindrical pellets, 1.3mm in diameter and approximately 8- 10mm in mean length. The temperature of the pellets as they issued from the pellet mill was about 30-40°C. They were passed directly to a Lδdige batch mixer, in which a short treatment with rotating ploughshare shovels reduced the mean length of the pellets to approximately 2-4 mm. At this point they were graded using a sieve, to remove powder for recycling.

Pellets produced as described above were post-mixed with the following ingredients in a standard concrete mixer in the proportions stated to yield a high density washing powder.

The final product contained the following

¹ Laundrosil PRW 414, supplied by Siid-Chemie.

The resulting mixture was fed repetitively to a Korsch tablet press, and pressed into white monolayer tablets of circularly cylindrical shape, having the following characteristics:

Size 21 mm height x 44mm diameter Density 1.17 kg/1 Hardness 90N (measured as described above)

Disintegration time 20 seconds (measured as described above) Weight: 37.5g

Claims

1. A fabric softening laundry tablet comprising;

i) at least 5 % w/w, of the total composition, of a granular coated clay;

2. A fabric softening laundry tablet as claimed in claim 1 wherein the amount of coated clay in the tablet is at least 5 % by weight of the tablet, preferably at least 8 % by weight, more preferably at least 10 % by weight of the tablet

3. A fabric softening laundry tablet as claimed in claim 2 wherein the amount of coated clay in the tablet is less than 35 %, more preferably less than 30 %, most preferably less than 20 % by weight of the tablet.

4. A fabric softening laundry tablet as claimed in any claim from 1 to 3 wherein the clay is mainly in the form of granules, with at least 50 % (and preferably at least 70 % or at least 90 %) being in the form of granules having a size of at least 100 μm up to 1400 μm.

5. A fabric softening laundry tablet as claimed in any claim from 1 to 4 wherein the clay is coated with an ingredient of the tablet.

6. A fabric softening laundry tablet as claimed in claim 5 wherein at least 50 %, usually at least 70 % or 90 % of the weight of the granule is clay.

7. A fabric softening laundry tablet as claimed in any claim from 1 to 5 wherein at least 5 % by weight of the tablet, preferably at least 8 % by weight, more preferably at least 10 % by weight of the granule is the coating.

8. A fabric softening laundry tablet as claimed in any claim from 1 to 7 wherein the coating is an aluminosilicate, preferably zeolite.

9. A method of manufacturing a laundry tablet as claimed in any claim from 1 to 8 comprising the steps of

i) pelletising a flowable tower spray powder and a flowable detergent builder in a pellet mill to form a premix (preferably with an aluminosilicate content of at least 30 % w/w (weight of aluminosilicate/weight of pellets)); and

ii) mixing the pellets with the other ingredients.

10. A method as claimed in claim 1 wherein the pellets have a zeolite content of at least 40%.

11. A method as claimed in claim 1 or 2 wherein the zeolitic content of the pellets does not exceed 80%.