EP1232240B1

EP1232240B1 - Detergent compositions

Info

Publication number: EP1232240B1
Application number: EP00983174A
Authority: EP
Inventors: Peter Willem Unilever Research Vlaardingen APPEL; Erik C. Unilever Research Vlaardingen BERDEN; Jelles V. Unilever Research Vlaardingen BOSKAMP; Henning Wagner
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1999-11-26
Filing date: 2000-11-24
Publication date: 2004-09-15
Anticipated expiration: 2020-11-24
Also published as: DE60010117D1; DE60013889D1; DE60013889T2; CN1425060A; CA2389975A1; ATE276351T1; EP1232241B1; BR0015904A; CA2389984A1; ES2225276T3; ES2215782T3; WO2001038478A1; ATE264908T1; AU2002301A; EP1232241A1; GB9928078D0; WO2001038479A1; EP1232240A1; TR200401112T4; DE60010117T2

Abstract

A multi-region detergent tablet of compressed particulate composition is provided comprising a detergent active compound, a detergency builder, particles which contain sodium tripolyphosphate with a content of the Phase I form which is more than 40 % by weight of the sodium tripolyphosphate in the said particles, at least one salt which is fully hydrated and optionally other detergent ingredients, where in one or more of the regions which contains the particles which contain sodium tripolyphosphate there is less than 10 % by weight of that region of fully hydrated salts, and there is at least one region containing at least 10 % by weight of that region of fully hydrated salts.

Description

This invention relates to detergent compositions in the form of tablets for cleaning, and in particular tablets for fabric washing and tablets for machine dish washing. It is known to make such tablets by compressing or compacting a quantity of detergent composition in particulate form.
It is desirable that tablets should have adequate mechanical strength when dry, before use, yet disintegrate and disperse/dissolve quickly when added to wash water. It has not proved simple to achieve both properties simultaneously. As more pressure is used when a tablet is compacted, so the tablet density and strength rise, but the speed of disintegration/dissolution when the tablet comes into contact with wash water goes down.
Our European published application EP-A-839906 describes tablets of a compacted, particulate detergent composition intended for fabric washing in which the tablet comprises particles containing sodium tripolyphosphate with a substantial content of the phase I form, and this tripolyphosphate is partially hydrated so as to contain water of hydration in an amount between 1% and 5% by weight of the sodium tripolyphosphate in those particles.
It is demonstrated by examples in that patent application that tablets incorporating particles with a substantial content of the Phase I form of sodium tripolyphosphate and with some partial hydration of the tripolyphosphate disintegrate and dissolve in use much more quickly than comparative tablets using sodium tripolyphosphate with a higher content of the Phase II form. Consequently, it is possible to achieve tablets which disintegrate rapidly at the time of use.
Typically these tablets will contain base powder particles which incorporate organic detergent-active surfactant together with some tripolyphosphate detergency builder, separate particles containing sodium tripolyphosphate which is rich in the Phase I form and also partially hydrated, and thirdly particles of other ingredients. A substantial proportion of the other ingredients is constituted by peroxygen bleach which may be sodium percarbonate.
Such tablets have been marketed commercially. For use one or two tablets are placed in a net bag, closed with a drawstring. The bag containing these tablets is placed in the washing machine, with fabrics to be washed.
Our co-pending WO 01/02524 discloses machine dish washing tablets comprising less than 5wt% of surfactant and particles of solid tripolyphosphate as described above. The examples in this application also demonstrate an improvement in dissolution time for tablets containing sodium tripolyphosphate rich in Phase I and partially hydrated rather than sodium tripolyphosphate with a higher content of Phase II form. The tablets exemplified in this co-pending application contain a considerable amount of sodium disilicate as a detergency builder, as well as a peroxygen bleach, sodium perborate, and sodium carbonate.
EP-A-957159 (Chimiotechnic SA) discloses three layered detergent tables which may comprise particles of solid tripolyphosphate in the outer two layers.
We have now surprisingly found that it is beneficial to partially or completely separate any salts which can be further hydrated ('further hydratable salts') in a tablet, from the sodium tripolyphosphate which is rich in the Phase I form and which may also be partially hydrated. By this separation, it has been found possible to increase the dissolution speed of the detergent tablets containing these components.
This separation of ingredients can be accomplished by isolating most, if not all, of the further hydratable salts, in a region of the tablet which may be a layer, core or insert, while the sodium tripolyphosphate which is rich in the Phase I form is in another region of the tablet.
Therefore, according to the present invention, there is provided a detergent tablet of compressed particulate composition comprising a detergent-active compound, a detergency builder, particles which contain sodium tripolyphosphate with a content of the Phase I form which is more than 40% by weight of the sodium tripolyphosphate in the said particles, at least one salt which can be further hydrated, and optionally other detergent ingredients, where the tablet comprises a plurality of discrete regions, characterised in that in one or more of the discrete regions containing said particles which contain sodium tripolyphosphate there is less than 10% by weight of that region of further hydratable salts (other than said sodium tripolyphosphate), and there is at least one discrete region containing at least 10% by weight of that region of further hydratable salts (other than said sodium tripolyphosphate).
It is envisaged that all of the discrete regions containing said particles which contain sodium tripolyphosphate will contain less than 10% by weight of that region of further hydratable salts (other than sodium tripolyphosphate). However, this may not be the case, particularly if there is a very small discrete region containing said particles which contain sodium tripolyphosphate, or the discrete regions contain a minor amount of sodium tripolyphosphate, for example less than 5% by weight.
The region containing at least 10% by weight of further hydratable salts may also contain a disintegrant system which does not comprise said particles which contain said sodium tripolyphosphate.
It is further preferred that there is less than 5% by weight, or even no further hydratable salts in the regions of the tablet containing said particles of sodium tripolyphosphate.
Preferably the sodium tripolyphosphate in the said particles has a content of the Phase I form which is at least 50% by weight of the sodium tripolyphosphate in the said particles. It is also preferred that the amount of water of hydration in the sodium tripolyphosphate particles lies in a range from 0.5% to 5% by weight, preferably 2 to 4%, of the sodium tripolyphosphate in those particles.
Features of this invention, suitable materials and further preferences will now be described in more detail.

Sodium Tripolyphosphate with High Phase I Content

As discussed in EP-A-839906, sodium tripolyphosphate can be converted to the phase I form by heating to above the transition temperature at which phase II anhydrous sodium polyphosphate is transformed into the phase I form. A process for the manufacture of particles containing a high proportion of the phase I form of sodium tripolyphosphate by spray drying below 420°C is given in US-A-4536377.
Suitable material is commercially available. Suppliers include Rhone-Poulenc, Courbevoie, France and Albright & Wilson, Warley, West Midlands, UK. The sodium tripolyphosphate is preferably partially hydrated, but the phase I anhydrous form should also be present. Thus, the sodium tripolyphosphate in the particles may incorporate from 0.5% up to, at least, 5% (by weight of the sodium tripolyphosphate in these particles) of water of hydration. The extent of hydration is desirably from 1% to 4%, 5% or 7% by weight.
The sodium tripolyphosphate in these particles is preferably hydrated by a process which leads to a homogeneous distribution of the water of hydration within the tripolyphosphate.
This can be accomplished by exposing anhydrous sodium tripolyphosphate to steam or moist air. The particles preferably consist solely of sodium tripolyphosphate with a high content of the phase I form. However, it may be preferred that only at least 80% or 90% by weight of the particles is sodium tripolyphosphate. It is possible that only at least 50% by weight of the particles are sodium tripolyphosphate.
The particles preferably contain sodium tripolyphosphate in a porous form so as to have high surface area. This can be achieved by spray drying the tripolyphosphate as a mixture with a blowing agent, that is a compound such as ammonium carbonate which decomposes to yield a gas during the course of the spray drying. This gives the dried material a porous structure, with higher surface area than hollow beads of tripolyphosphate obtained without blowing agent.
The bulk density of the sodium tripolyphosphate particles is preferably 0.75 kg/m³ or less, more preferably from 0.52 to 0.72 kg/m³.
The particles which contain or consist of sodium tripolyphosphate may have a small mean particle size, such as not over 300µm, better not over 250µm. Small particle size can if necessary be achieved by grinding.
Uniform prehydration and high phase I content promote rapid hydration when the tripolyphosphate comes into contact with water. A standard test for the rapidity of hydration is the Olten test. It is desirable that in such a test the tripolyphosphate reaches 90% of the final value (ie 90% of complete hydration when exposed to water at 80°C) within 60 seconds.
"Rhodiaphos HPA 3.5" is a grade of sodium tripolyphosphate from Rhone-Poulenc which has been found to be particularly suitable. It consists of porous particles of small particle size (mean size below 250 µm) with 70% phase I and prehydrated with 3.5% water of hydration.
Preferably the said particles containing sodium tripolyphosphate with more than 40% of phase I material provide sodium tripolyphosphate, including the phase I tripolyphosphate, in a quantity which is from 20% up to 45% or 50%, or even 60% by weight of the whole tablet. A quantity of at least 30% has been found useful in some tablets. The amount of these particles in any one region of the tablet may be higher then these limits, in order to provide a suitable level of particles in the whole tablet.
The remainder of the tablet composition may include additional sodium tripolyphosphate not in the form discussed above, such as anhydrous sodium tripolyphosphate with a high content of the phase II form, hydrated sodium tripolyphosphate or some combination of the two.
The total quantity of sodium tripolyphosphate, in all forms, present in the tablet composition of a laundry tablet will generally lie in a range up to 70% by weight of the tablet. This may also be the case for a machine dish wash tablet, although a range of up to 60% by weight of the tablet is preferred for this type of tablet. Therefore it will be appreciated that the overall quantity of sodium tripolyphosphate may be provided at least partially by other material in addition to the said particles.

Salts which can be further hydrated

These salts are those which are not in their maximum hydration state, i.e. those salts which can take up water as water of hydration, and include the class of salts known as persalts. Usually, salts can only take up water as water of hydration if they are present in a hydration state which is less than their most thermodynamically stable hydration state at ambient temperature. These further hydratable salts include carbonates, percarbonates, perborate monohydrates, sulphates, citrates and acetates.
Many carbonates naturally display a range of hydration states. For example, sodium carbonate may be anhydrous, or may have one, seven or ten water molecules present as water of hydration. Both potassium and magnesium carbonates also have a variety of hydration states. Thus, as long as some of the carbonate present is not in its maximum hydration state, the salt will be further hydratable. Carbonates (in particular sodium and potassium carbonates) are often included in detergent tablets in order to control the pH of the composition when it dissolves. They also function, to some extent, as detergency builders, particularly in machine dish washing tablets.
Percarbonates are carbonate salts where at least one molecule of hydrogen peroxide is present instead of or in addition to water of hydration. They exhibit similar properties to carbonates in terms of their ability to take up water as water of hydration. Percarbonates (particularly sodium percarbonate) are used as bleaches in detergent tablets - they function by acting as a source of hydrogen peroxide.
Perborates may exist in a range of hydration states, and are similar in structure to percarbonates in that they have hydrogen peroxide present instead of, or in addition to, water of hydration. For example, sodium perborate exists in a monohydrated or tetrahydrated form both of which are suitable for use in detergent formulations. Therefore it can be seen that sodium perborate monohydrate is a further hydratable salt. Perborates are used as bleaches in detergent tablets (see below).
Sulphates can have different hydration states. Sodium sulphate may be anhydrous, heptahydrated or decahydrated, whilst magnesium sulphate may be anhydrous or heptahydrated. Sulphates may be included in detergent tablets as fillers.
Sodium acetate may exist in a range of hydration states from 0 (anhydrous) to 3 (trihydrate). Anhydrous sodium acetate may be present as a disintegration aid (see below).
In general, the further hydratable salts suitable for use in detergent tablets are sodium salts, persalts, and less preferably potassium carbonate.

Discrete Regions

The discrete regions may be in the form of layers, and a tablet with two layers is one preferred embodiment of the present invention. One layer of this two-layer tablet contains granules of sodium tripolyphosphate rich in Phase I form and also partially hydrated, whilst the other layer contains hydratable salts and/or persalts and optionally another disintegrant.
Each layer of such a tablet is preferably substantially homogeneous, that is to say, is the compaction product of a single particulate composition, although that particulate composition may have been prepared by mixing a number of components and all its particles will not necessarily be identical. Typically, such a two-layer tablet is made on a tableting press by part filling the die with the composition of the first layer, pressing this layer, and then adding the composition of the second layer before pressing the tablet for a second time. It is preferred that the two layers of this tablet are not equal in size - a weight ratio range of 10:90 to 40:60 is preferable, and a ratio range of 20:80 to 30:70 is more preferred, with a ratio of 25:75 being most preferred. A discrete region typically has a minimum weight of 5g.
It is preferred that the layer or layers containing the particles of sodium tripolyphosphate make up at least 50 wt% of the tablet, and that the layer (or layers) which contain the hydratable salts and/or persalts make up at least 15% by weight of the whole tablet.
An alternative preferred embodiment of the invention is a tablet which has a pair of opposite faces spaced apart from each other and joined by a peripheral surface of the tablet, wherein the tablet is subdivided into at least two regions which are each visible at a said face. One such tablet is one having a central core passing through the whole tablet. One particular method of manufacturing such tablets is described in our copending application, WO 00/44869.
Other forms of discrete regions are known for detergent tablets and are included in the present invention, and include cores which do not pass all the way through the tablet and a central region completely enclosed by an outer region.

Detergent-active compounds

In laundry detergent tablets, detergent-active compounds are suitably present in an amount of from 2% or 5% up to 50 wt%, more preferably from 5% or 8% up to 40 wt% of the whole tablet. These will most usually be anionic and nonionic surfactants and mixtures of the two. Amphoteric (including zwitterionic) and less commonly cationic detergents can also be used.

Anionic Surfactant Compounds

Synthetic (i.e. non-soap) anionic surfactants are well known to those skilled in the art. The anionic surfactant may comprise, wholly or predominantly, linear alkyl benzene sulphonate of the formula
where R is linear alkyl of 8 to 15 carbon atoms and M⁺ is a solubilising cation, especially sodium.
Primary alkyl sulphate having the formula ROSO₃ ^- M⁺ in which R is an alkyl or alkenyl chain of 8 to 18 carbon atoms especially 10 to 14 carbon atoms and M⁺ is a solubilising cation, is also commercially significant as an anionic surfactant and may be used in this invention.
Frequently, such linear alkyl benzene sulphonate or primary alkyl sulphate of the formula above, or a mixture thereof will be the desired non-soap anionic surfactant and may provide 75 to 100 wt% of any anionic non-soap surfactant in the composition.
Examples of other non-soap anionic surfactants include olefin sulphonates; alkane sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates.
One or more soaps of fatty acids may also be included in addition to non-soap anionic surfactant. Examples are sodium soaps derived from the fatty acids from coconut oil, beef tallow, sunflower or hardened rapeseed oil.

Nonionic surfactant compounds

Nonionic surfactant compounds include in particular the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example, aliphatic alcohols, acids, amides or alkyl phenols with alkylene oxides, especially ethylene oxide.
Specific nonionic surfactant compounds are alkyl (C_8-22) phenol-ethylene oxide condensates, the condensation products of linear or branched aliphatic C_8-20 primary or secondary alcohols with ethylene oxide, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylene-diamine.
Especially preferred are the primary and secondary alcohol ethoxylates, especially the C_9-11 and C_12-15 primary and secondary alcohols ethoxylated with an average of from 3 to 20 moles of ethylene oxide per mole of alcohol.

Amphoteric surfactants

Amphoteric surfactants which may be used jointly with anionic or nonionic surfactants or both include amphopropionates of the formula:
where RCO is a acyl group of 8 to 18 carbon atoms, especially coconut acyl.
The category of amphoteric surfactants also includes amine oxides and also zwitterionic surfactants, notably betaines of the general formula
where R₄ is an aliphatic hydrocarbon chain which contains 7 to 17 carbon atoms, R₂ and R₃ are independently hydrogen, alkyl of 1 to 4 carbon atoms or hydroxyalkyl of 1 to 4 carbon atoms such as CH₂OH,
Y is CH₂ or of the form CONHCH₂CH₂CH₂ (amidopropyl betaine);
Z is either a COO^- (carboxybetaine), or of the form CHOHCH₂SO₃ - (sulfobetaine or hydroxy sultaine).
Another example of amphoteric surfactant is amine oxide of the formula
where R₁ is C₁₀ to C₂₀ alkyl or alkenyl
R₂, R₃ and R₄ are each hydrogen or C₁ to C₄ alkyl while n is from 1 to 5.
In machine dish washing tablets, detergent-active compounds are preferably present in an amount of 5 wt% of the total composition or less.
Typically the detergent-active compound is a low to non foaming nonionic surfactant, which may be an alkoxylated nonionic surface-active agent wherein the alkoxy moieties are selected from the group consisting of ethylene oxide, propylene oxide and mixtures thereof. This nonionic surfactant is used to improve the detergency without excessive foaming, however, an excessive proportion of nonionic surfactant should be avoided. Preferably the level of nonionic surfactant is at least 0.1% by weight, more preferably at least 0.5% by weight.
Examples of suitable nonionic surfactants for use in machine dish washing tablets of the invention are the low-to non-foaming ethoxylated straight-chain alcohols. Preferred nonionic surfactants are Plurafac LF series ex BASF, the Synperonic series ex ICI; Lutensol® LF series, ex BASF Company and the Triton® DF series, ex Rohm & Haas Company.
Other surfactants such as anionic surfactant may be used but may require the additional presence of an antifoam to suppress foaming. If an anionic surfactant is used it is advantageously present at levels of 2 wt% or below.

Detergency builder

The detergent tablets of the invention contain one or more detergency builders, in addition to the sodium tripolyphosphate builder of the invention. These builders may be either water-soluble or water-insoluble, and a mixture of the two is also included within the scope of the present invention.

Water-insoluble builders

Alkali metal aluminosilicates are strongly favoured as environmentally acceptable water-insoluble builders for fabric washing. Alkali metal (preferably sodium) aluminosilicates may be either crystalline or amorphous or mixtures thereof, having the general formula: 0.8 - 1.5 Na2O.Al2O3. 0.8 - 6 SiO2. xH2O
These materials contain some bound water (indicated as "xH2O") and are required to have a calcium ion exchange capacity of at least 50 mg CaO/g. The preferred sodium aluminosilicates contain 1.5-3.5 SiO₂ units (in the formula above). Both the amorphous and the crystalline materials can be prepared readily by reaction between sodium silicate and sodium aluminate, as amply described in the literature.
Suitable crystalline sodium aluminosilicate ion-exchange detergency builders are described, for example, in GB 1429143 (Procter & Gamble). The preferred sodium aluminosilicates of this type are the well known commercially available zeolites A and X, the zeolite P described and claimed in EP 384070 (Unilever) which is also referred to as zeolite MAP and mixtures thereof. Zeolite MAP is available from Crosfields under their designation Zeolite A24.
Conceivably, water-insoluble detergency builder could be a crystalline layered sodium silicate as described in US 4664839.
NaSKS-6 is the trademark for a crystalline layered silicate marketed by Hoechst (commonly abbreviated as "SKS-6").
NaSKS-6 has the delta-Na₂SiO₅ morphology form of layered silicate. It can be prepared by methods such as described in DE-A-3,417,649 and DE-A-3,742,043. Other such layered silicates, which can be used have the general formula NaMSi_xO_2x+1.yH₂O wherein M is sodium or hydrogen, x is a number from 1.9 to 4, preferably 2, and y is a number from 0 to 20, preferably 0.
Crystalline layered silicate may be used in the form of granules which also contain citric acid.

Water-soluble builders

Suitable organic builders include the carboxylate or polycarboxylate builders containing from one to four carboxy groups, particularly selected from monomeric polycarboxylates or their acid forms, homo or copolymeric polycarboxylic acids or there salts in which the polycarboxylate comprises at least two carboxylic radicals selected from each other by not more than two carbon atoms. Preferred carboxylates include the polycarboxylate materials described in US-A-2,264,103, including the water-soluble alkali metal salts of mellitic acid and citric acid (citrate), gluconic acid, dipicolinic acid, oxydisuccinic acid and alkenyl succinates, glycerol mono- di- and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates and hydroxyethyliminodiacetates.
The water-soluble salts of polycarboxylate polymers and copolymers, such as are described in US-A-3,308,067 are also be suitable for use with the invention. Of the builder materials listed in the above paragraph, the preferred polycarboxylates are hydroxycarboxylates containing up to three carboxy groups per molecule, especially citric acid or its salt, particularly sodium citrate.
Further soluble detergency builder salts which can be used with the present invention are poly-valent inorganic and poly-valent organic builders, or mixtures thereof. Nonlimiting examples of suitable water-soluble, inorganic alkaline detergency builder salts include the alkali metal (generally sodium) carbonates (see above), bicarbonates, borates, phosphates, and polyphosphates, phosphono carboxylates. Specific examples of such salts include the sodium and potassium tetraborates, carbonates, bicarbonates, orthophosphates and hexametaphosphates. Other suitable detergency builders include organic alkaline compounds such as water-soluble amino polyacetates, e.g. nitrilotriacetates and N-(2-hydroxyethyl)nitrilodiacetates; and water-soluble salts of phytic acid, e.g. sodium and potassium phytates.
Preferably, the total amount of builders in the composition including the particles containing sodium tripolyphosphate (having a water of hydration in an amount from 1% to 5% by weight and wherein at least 50% by weight of the sodium tripolyphosphate within the particles is of a phase I form) for fabric laundry tablets is from 5 or 30% to 70% by weight, whereas for machine dish washing tablets is from 5 or 40% to about 80% by weight.

Bleach Material

Bleach material may preferably be incorporated in composition for use in processes according to the present invention. These materials may be incorporated in solid form or in the form of encapsulates and less preferably in dissolved form.
The bleach material may be a chlorine- or bromine-releasing agent or a peroxygen compound. Peroxygen based bleach materials are however preferred for use in detergent tablets of the invention.

Inorganic peroxygen bleaches

Inorganic peroxygen-generating compounds are most preferably used as the bleaching material of the present invention, and salts (especially sodium salts) of perborate monohydrate and percarbonate have been mentioned above. Sodium perborate tetrahydrate can also be used as a peroxygen bleach, but is not a salt which can be further hydrated.

Organic peroxy acids

Organic peroxy acids can be used as the bleach material. The peroxyacids suitable for use in the present invention are solid and, preferably, substantially water-insoluble compounds. By "substantially water-insoluble" is meant herein a water-solubility of less than about 1% by weight at ambient temperature. In general, peroxyacids containing at least 7 carbon atoms are sufficiently insoluble in water for use herein.
Monoperoxy acids useful herein include alkyl peroxy acids and aryl peroxyacids such as peroxybenzoic acid and ring-substituted peroxybenzoic acids (e.g. peroxy-alpha-naphthoic acid); aliphatic and substituted aliphatic monoperoxy acids (e.g. peroxylauric acid and peroxystearic acid); and phthaloyl amido peroxy caproic acid (PAP).
Typical diperoxy acids useful herein include alkyl diperoxy acids and aryldiperoxy acids, such as 1,12-di-peroxy-dodecanedioic acid (DPDA); 1,9-diperoxyazelaic acid, diperoxybrassylic acid, diperoxysebacic acid and diperoxy-isophthalic acid; and 2-decyldiperoxybutane-1,4-dioic acid.

Chlorine & Bromine bleaches

Among suitable reactive chlorine- or bromine-oxidizing materials are heterocyclic N-bromo and N-chloro imides such as trichloroisocyanuric, tribromoisocyanuric, dibromoisocyanuric and dichloroisocyanuric acids, and salts thereof with water-solubilising cations such as potassium and sodium. Hydantoin compounds such as 1,3-dichloro-5,5-dimethyl-hydantion are also quite suitable.
Particulate, water-soluble anhydrous inorganic salts are likewise suitable for use herein such as lithium, sodium or calcium hypochlorite and hypobromite. Chlorinated trisodium phosphate and chloroisocyanurates are also suitable bleaching materials.
Encapsulation techniques are known for both peroxygen and chlorine bleaches, e.g. as described in US-A-4,126,573, US-A-4,327,151, US-A-3,983,254, US-A-4,279,764, US-A-3,036,013 and EP-A-0,436,971 and EP-A-0,510,761. However, encapsulation techniques are particularly useful when using halogen based bleaching systems.
For chlorine bleaches, the compositions of the invention may comprise from 0.5% to 3% AvCl (available Chlorine). For peroxygen bleaching agents a suitable range are also from 0.5% to 3% AvOx (available Oxygen). Preferably the amount of bleach material in the wash liquor is at least 12.5 x 10^-4 % and at most 0.03% AvOx by weight of the liquor.

Bleach activator

Detergent tablets of the present invention which contain an inorganic peroxygen bleaching material such as sodium percarbonate or sodium perborate preferably also contain a bleach activator. Bleach activators have been widely disclosed in the art. Preferred examples include peracetic acid precursors, for example tetraacetylethylene diamine (TAED), and perbenzoic acid precursors. The quaternary ammonium and phosphonium bleach activators disclosed in US 4751015 and US 4818426 (Lever Brothers Company) are also of interest. Another type of bleach activator which may be used, but which is not a bleach precursor, is a transition metal catalyst as disclosed in EP-A-458397, EP-A-458398 and EP-A-549272.
It is preferred that the bleach activator is present in a different region of the tablet to the bleach, and in particular alkali metal percarbonate/perborate monohydrate (if present). Thus it may be present in the region containing the particles of sodium tripolyphosphate which is rich in Phase I form, especially if the tablet has only two discrete regions, e.g. layers.
In terms of tablet composition, bleach activator is usually present in an amount from 1 to 10% by weight of the tablet, possibly less in the case of a transition metal catalyst which may be used as 0.1% or more by weight of the tablet.

Heavy Metal Chelating Agent

A detergent tablet of the invention may also include a heavy metal chelating agent, which may also act as a bleach stabiliser. Such components will also chelate non-heavy metals to a limited extent, and similarly builders such as tripolyphosphate will chelate heavy metals to a limited extent.
Preferred chelating agents include organic phosphonates, amino carboxylates, polyfunctionally-substituted compounds, and mixtures thereof.
Particularly preferred chelating agents are organic phosphonates such as ethylenediamine tetramethylene phosphonate; _-hydroxy-2 phenyl ethyl diphosphonate; methylene diphosphonate; ethylene diphosphonate; hydroxy-1,1-hexylidene; vinylidene-1,1-diphosphonate; 1,2-dihydroxyethane-1,1-diphosphonate; and hydroxy-ethylene-1,1-diphosphonate. Most preferred is hydroxy-ethylene-1,1-diphosphonate; 2-phosphono-1,2,4-butanetricarboxylic acid or salts thereof.
Another possible chelating agent is ethylenediamine disuccinate (EDDS).
If present it is preferable if the level of chelating agent is from 0.5 to 3 wt% of the total composition.

Disintegrant Systems

As mentioned above, the region of the tablet which does not include the sodium tripolyphosphate rich in Phase I form may contain a further disintegrant system. This is particularly preferred in discrete regions which contain more than 5% detergent active compounds, which is generally the case for laundry detergent tablets. The further disintegrant system helps such regions to disperse quickly, which counters the binding effect of the detergent active compound.
The further hydratable salt may in fact be a disintegrant itself, or be part of a disintegrant system.
There are a number of laundry tablet disintegrant systems other than forms of sodium tripolyphosphate. It is preferred that the region containing hydratable salts and/or persalts includes a disintegration promoting system or agent using material other than salts which take up water of hydration, thus it may be a material which is either fully hydrated, e.g sodium acetate trihydrate, or does not hydrate e.g. bentonite clay. However, the hydratable salts may well themselves act as disintegration aids, e.g. anhydrous sodium acetate.
Suitable disintegrants may preferably be present in the region as at least 15 or 20% by weight of the region, possibly at least 25% up to 50 or 60%.
Suitable disintegrants may be grouped into the following classes: swelling (physical) disintegrants; effervescent disintegrants; and materials of high solubility.

Swelling disintegrant

Swelling disintegrants include organic materials such as starches, for example, corn/ maize, rice and potato starches and starch derivatives, such as Primojel™, carboxymethyl starch and Explotab™, sodium starch glycolate; celluloses, for example, Arbocel®-B and Arbocel®-BC (beech cellulose), Arbocel®-BE (beech-sulphite cellulose), Arbocel®-B-SCH (cotton cellulose), Arbocel®-FIC (pine cellulose) as well as further Arbocel® types (Arbocel®-TF-30-HG) from Messrs Rettenmaier and cellulose derivatives, for example Courlose™ and Nymcel™, sodium carboxymethyl cellulose, Ac-di-Sol™, cross-linked modified cellulose, and Hanfloc™, microcrystalline cellulosic fibres; and various synthetic organic polymers, notably polyethylene glycol and cross-linked polyvinyl pyrrolidone, for example Polyplasdone™, XL or Kollidon™ CL.
Inorganic swelling disintegrants include bentonite clay.

Effervescent disintegrants

Effervescent disintegrants include weak acids or acid salts, for example, citric acid (preferred), malic acid or tartaric acid, in combination with alkali metal carbonate or bicarbonate; these may suitably be used in an amount of from 1 to 25 wt%, preferably from 5 to 15 wt%. Further examples of acid and carbonate sources and other effervescent systems may be found in Pharmaceutical Dosage Forms: Tablets, Volume 1, 1989, pages 287-291 (Marcel Dekker Inc, ISBN 0-8247-8044-2).

Materials of High Solubility

Highly water soluble materials, which are one of the two possibilities are compounds, especially salts, with a solubility at 20°C of at least 50 gms per 100 gms of water.
A solubility of at least 50 grams per 100 grams of water at 20°C is an exceptionally high solubility: many materials which are classified as water soluble are less soluble than this.
Some highly water-soluble materials which may be used are listed below, with their solubilities expressed as grams of solid to form a saturated solution in 100 grams of water at 20°C:-

Material Water Solubility (g/100g)

Sodium citrate dihydrate 72

Potassium carbonate 112

Urea >100

Sodium acetate trihydrate 76

Magnesium sulphate 7H₂O 71

Potassium acetate >200
Particularly preferred materials are sodium acetate trihydrate and sodium citrate dihydrate.
As different disintegrants are found in different regions of the tablets, the tablets may provide for the sequential release of components of the tablet into the wash liquor. By placing different types of component in the different regions, such a tablet may be able to deliver detergent actives first, and fabric softeners later.
Further examples of disintegrants falling into the above categories, particularly swelling disintegrants, are known for use in pharmaceutical tablets.

Silica material for Machine Dish Washing Tablet

Dish washing tablets may preferably contain silica material. Suitable forms of silica include amorphous silica, such as precipitated silica, pyrogenic silica and silica gels, such as hydrogels, xerogels and aerogels, or the pure crystal forms quartz, tridymite or crystobalite, but the amorphous forms of silica are preferred. Suitable silicas may readily be obtained commercially. They are sold, for example under the Registered Trade Name Gasil 200 (ex Crosfield, UK).
Preferably, the silica is in the product in such a form that it can dissolve when added to the wash liquor. Therefore, addition of silica by way of the addition of anti-foam particles of silica and silicone oil is not preferred.
The particle size of the silica material of the present invention may be of importance, especially as it is believed that any silica material that remains undissolved during the washing process, may deposit on the glass at a later stage. Therefore, it is preferred that silica material are used that have a particle size (as determined with a Malvern Laser, i.e. "aggregated" particles size) of at most 40 µm, more preferably at most 30µm, most preferably at most 20µm provides better results in the wash. In view of incorporation in a cleaning composition, it is preferred that the particle size of the silica material is at least 1µm, more preferably at least 2µm, most preferably at least 5µm.
Preferably, the primary particle size of the silica is in general less than about 30nm, in particular less than about 25nm. Preferably, elementary particles size are less than 20nm or even 10nm. There is no critical lower limit of the elementary particle size; the lower limit is governed by other factors such as the manner of manufacture. In general commercial available silicas have elementary particle sizes of 1 nm or more.
Preferably, the silica material is present in the wash liquor at a level of at least 2.5x10^-4%, more preferably at least 12.5x10^-4%, most preferably at least 2.5x10^-3% by weight of the wash liquor and preferably at most 1x10^-1%, more preferably at most 8x10^-2%, most preferably at most 5x10^-2% by weight of the wash liquor.
Preferably, the level of dissolved silica material in the wash liquor is at least 80 ppm, more preferably at least 100 ppm, most preferably at least 120 ppm and preferably at most 1,000 ppm. It is noted that for the silica material to be effective, the lower level of dissolved silica material depends on the pH value, i.e. thus at pH 6.5, the level is preferably at least 100 ppm; at pH 7.0 preferably at least 110 ppm; at pH 7.5 preferably at least 120 ppm; at pH 9.5 preferably at least 200 ppm; at pH 10 preferably at least 300 ppm; at pH 10.5 preferably at least 400ppm.
Preferably, the silica material is present in the cleaning composition at a level of at least 0.1%, more preferably at least 0.5%, most preferably at least 1% by weight of the cleaning composition and preferably at most 10%, more preferably at most 8%, most preferably at most 5% by weight of the cleaning composition.

Silicates

The composition of the invention optionally comprises alkali metal silicates. The alkali metal silicate has some detergency builder properties, and particularly for machine dish washing may provide pH adjusting capability and protection against corrosion of metals and against attack on dishware, including fine china and glassware benefits. The presence of such alkali metal silicates in detergent tablets may be advantageous in providing protection against the corrosion of metal parts in washing machines, and also in aiding the detergency builder and in adjusting the alkalinity of the wash liquor.
If silicates are present in machine dish washing tablets, they are preferably included at a level of from 1% to 30%, preferably from 2% to 20%, more preferably from 3% to 10%, based on the weight of the composition.
In laundry tablets, preferred amounts of silicate are between 1 and 6 % by weight, which may be achieved through the base powder or by post dosing.
The ratio of SiO₂ to the alkali metal oxide (M₂O, where M=alkali metal) is typically from 1 to 3.5, preferably from 1.6 to 3, more preferably from 2 to 2.8. Preferably, the alkali metal silicate is hydrous, having from 15% to 25% water, more preferably, from 17% to 20%.
The highly alkali metasilicates can in general be employed, although the less alkaline hydrous alkali metal silicates having a SiO₂:M₂O ratio of from 2.0 to 2.4 are, as noted, greatly preferred. Anhydrous forms of the alkali metal silicates with a SiO₂:M₂O ratio of 2.0 or more are also less preferred because they tend to be significantly less soluble than the hydrous alkali metal silicates having the same ratio.
Sodium and potassium, and especially sodium, silicates are preferred. A particularly preferred alkali metal silicate is a granular hydrous sodium silicate having a SiO₂:Na₂O ratio of from 2.0 to 2.4 available from Ak30 PQ Corporation, especially preferred is Britesil H20 and Britesil H24. Most preferred is a granular hydrous sodium silicate having a SiO₂:Na₂O ratio of 2.0. While typical forms, i.e. powder and granular, of hydrous silicate particles are suitable, preferred silicate particles having a mean particle size between 300 and 900 microns and less than 40% smaller than 150 microns and less than 5% larger than 1700 microns. Particularly preferred is a silicate particle with a mean particle size between 400 and 700 microns with less than 20% smaller than 150 microns and less than 1% larger then 1700 microns. Compositions of the present invention having a pH of 9 or less preferably will be substantially free of alkali metal silicate.

Water Soluble Polymeric Polycarboxylic Compounds

A water soluble polymeric polycarboxylic compound may be present in the composition, and is advantageously present in a dish wash composition. They inhibit unwanted deposition from the wash liquor onto the material being washed, either laundry or dish ware, and also onto machine parts.
Preferably these compounds are homo- or co-polymers of polycarboxylic compounds, especially co-polymeric compounds in which the acid monomer comprises two or more carboxyl groups separated by not more than two carbon atoms. Salts of these materials can also be used.
Particularly preferred polymeric polycarboxylates are co-polymers derived from monomers of acrylic acid and maleic acid. the average molecular weight of these polymers in the acid form preferably ranges from 4,000 to 70,000.
Another type of polymeric polycarboxylic compounds suitable for use in the composition of the invention are homopolymeric polycarboxylic acid compounds with acrylic acid as the monomeric unit. The average weight of such homopolymers in the acid form preferably ranges from 1,000 to 100,000 particularly from 3,000 to 10,000.
Acrylic sulphonated polymers as described in EP 851 022 (Unilever) are also suitable.
Preferably, this polymeric material is present at a level of at least 0.1%, more preferably at levels from 1 wt% to 7 wt% of the total composition.

Polymer Binder

Tablets of this invention, and in particular laundry tablets, may include an organic water-soluble polymer, serving as a binder when the particles are compacted into tablets. This polymer may be a polycarboxylate included as a supplementary builder, as mentioned earlier. It may be applied as a coating to some or all of the constituent particles prior to compaction.
As taught in our EP-A-522766, such polymers can function to enhance tablet disintegration at the time of use, as well as acting as a binder to enhance tablet strength prior to use.
It is preferred that such a binder material, if present, should melt at a temperature of at least 35°C, better at 40°C or above, which is above ambient temperatures in many temperate countries. For use in hotter countries it will be preferred that the melting temperature is somewhat above 40°C, so as to be above the ambient temperature.
For convenience the melting temperature of the binder material should be below 80°C.
Preferred binder materials are synthetic organic polymers of appropriate melting temperature, especially polyethylene glycol. Polyethylene glycol of average molecular weight 1500 (PEG 1500) melts at 45°C and has proved suitable. Polyethylene glycol of higher molecular weight, notably 4000 or 6000, can also be found.
Other possibilities are polyvinylpyrrolidone, and polyacrylates and water-soluble acrylate copolymers.
The binder may suitably be applied to the particles by spraying, e.g. so as a solution or dispersion. It may be applied to particles which contain organic surfactant. As an alternative, the binder may be provided in a powder form, and be dispersed into the composition to be tableted. If used, the binder is preferably used in an amount within the range from 0.1 to 10% by weight of the tablet composition, more preferably the amount is at least 1% or even at least 3% by weight of the tablets. Preferably the amount is not over 8% or even 6% by weight unless the binder serves some other additional function.

Enzymes

The detergent tablets of the invention may also contain one of the detergency enzymes well known in the art for their ability to degrade and aid in the removal of various soils and stains. Suitable enzymes include the various proteases, cellulases, lipases, amylases, and mixtures thereof, which are designed to remove a variety of soils and stains from fabrics and dishes. Examples of suitable proteases are Maxatase (Trade Mark), as supplied by Gist-Brocades N.V., Delft, Holland, and Alcalase (Trade Mark), and Savinase (Trade Mark), as supplied by Novo Industri A/S, Copenhagen, Denmark. Detergency enzymes are commonly employed in the form of granules or marumes, optionally with a protective coating, in amount of from 0.1% to 3.0% by weight of the composition; and these granules or marumes present no problems with respect to compaction to form a tablet.

Other Laundry Detergent Ingredients

The laundry detergent tablets of the invention may also contain a fluorescer (optical brightener), for example, Tinopal (Trade Mark) DMS or Tinopal CBS available from Ciba-Geigy AG, Basel, Switzerland. Tinopal DMS is disodium 4,4'bis-(2-morpholino-4-anilino-s-triazin-6-ylamino) stilbene disulphonate; and Tinopal CBS is disodium 2,2'-bis-(phenyl-styryl) disulphonate.
An antifoam material is advantageously included, especially if the detergent tablet is primarily intended for use in front-loading drum-type automatic washing machines. Suitable antifoam materials are usually in granular form, such as those described in EP 266863A (Unilever). Such antifoam granules typically comprise a mixture of silicone oil, petroleum jelly, hydrophobic silica and alkyl phosphate as antifoam active material, sorbed onto a porous absorbed water-soluble carbonate-based inorganic carrier material. Antifoam granules may be present in an amount up to 5% by weight of the composition.
Further ingredients which can optionally be employed in the laundry detergent tablet of the invention include antiredeposition agents such as sodium carboxymethylcellulose, straight-chain polyvinyl pyrrolidone and the cellulose ethers such as methyl cellulose and ethyl hydroxyethyl cellulose, fabric-softening agents; heavy metal sequestrants such as EDTA; perfumes; and colorants or coloured speckles.

Other Dish Washing Detergent Ingredients

Anti-tarnishing agents such as benzotriazole and those described in EP 723 577 (Unilever) may be included in dish washing detergent tablets of the present invention.
Optional ingredients in dish washing detergents tablets are, for example, buffering agents, reducing agents, e.g., borates, alkali metal hydroxide and the well-known enzyme stabilisers such as the polyalcohols, e.g. glycerol and borax; anti-scaling agents; crystal-growth inhibitors, threshold agents; thickening agents; perfumes and dyestuffs.
Reducing agents may e.g. be used to prevent the appearance of an enzyme-deactivating concentration of oxidant bleach compound. Suitable agents include reducing sulphur-oxy acids and salts thereof. Most preferred for reasons of availability, low cost, and high performance are the alkali metal and ammonium salts of sulphuroxy acids including ammonium sulphite ((NH₄)₂SO₃), sodium sulphite (Na₂SO₃), sodium bisulphite (NaHSO₃), sodium metabisulphite (Na₂S₂O₃), potassium metabisulphite (K₂S₂O₅), lithium hydrosulphite (Li₂S₂O₄), sodium sulphite being particularly preferred. Another useful reducing agent, though not particularly preferred for reasons of cost, is ascorbic acid. The amount of reducing agents to be used may vary from case to case depending on the type of bleach and the form it is in, but normally a range of 0.01% to 1.0% by weight, preferably from 0.02% to 0.5% by weight, will be sufficient.

Particle Size and Distribution

The discrete regions of a detergent tablet of this invention are each a matrix of compacted particles. Preferably the particulate composition has an average particle size in the range from 200µm to 2000µm, more preferably from 250µm to 1400µm. Fine particles, smaller than 180µm or 200µm may be eliminated by sieving before tableting, if desired, although we have observed that this is not always essential.
While the starting particulate composition may in principle have any bulk density, the present invention is especially relevant to tablets made by compacting powders of relatively high bulk density, because of their greater tendency to exhibit disintegration and dispersion problems. Such tablets have the advantage that, as compared with a tablet derived from a low bulk density powder, a given dose of composition can be presented as a smaller tablet.
Thus the starting particulate composition may suitably have a bulk density of at least 400g/litre, preferably at least 500g/litre, and advantageously at least 700g/litre.
Granular detergent compositions of high bulk density prepared by granulation and densification in a high-speed mixer/granulator, as described and claimed in EP 340013A (Unilever), EP 352135A (Unilever), and EP 425277A (Unilever), or by the continuous granulation/densification processes described and claimed in EP 367339A (Unilever) and EP 390251A (Unilever), are inherently suitable for use in the present invention.
A spray-dried base powder may also be used, and this can results in a powder to be tableted having a bulk density of 600 to 700 g/litre.

Porosity

The step of compacting the particles reduces the porosity of the composition. Porosity is conveniently expressed as the percentage of volume which is air.
The air content of a tablet or region of a tablet can be calculated from the volume and weight of the tablet or region, provided the air-free density of the solid content is known. The latter can be measured by compressing a sample of the material under vacuum with a very high applied force, then measuring the weight and volume of the resulting solid.
The percentage air content of a tablet or region of a tablet varies inversely with the pressure applied to compact the composition while the strength of the tablet or region varies with the pressure applied to bring about compaction. Thus the greater the compaction pressure, the stronger the tablet or region becomes but the smaller the air volume within.
The invention may be applied when compacting particulate detergent composition to give tablets with a wide range of porosities. Specifically included among possible porosities is a porosity of up to 38% air volume, e.g. from 10 or 15 better 25% up to 35% air by volume in the tablet.

Tablet Size and Density

The size of a tablet will suitably range from 10 to 160 grams, preferably from 15 to 60 g, depending on the conditions of intended use, and whether it represents a dose for an average load in a fabric washing or dishwashing machine or a fractional part of such a dose. In particular, a machine dish wash tablet is preferably from 15 to 30 g. The tablets may be of any shape. However for ease of packaging they are preferably blocks of substantially uniform cross-section, such as cylinders or cuboids. The overall density of a tablet preferably lies in a range from 1040 or 1050gm/litre, possibly 1100gm/litre, up to 1450gm/litre or 1700gm/litre, or more. The tablet density may well lie in a range up to 1350 to 1400gm/litre for a laundry tablet and in a range from 1300 to 1600gm/litre for a machine dish wash tablet.
Embodiments of the present invention will now be described by way of example only.

Example 1

46g cylindrical laundry detergent tablets having the following formulations were prepared on a rotating table tableting machine from Fette. Two tablets of the invention were made with two layers, the thicker of which contained the Rhodiaphos HPA 3.5, the other sodium percarbonate and a effervescent disintegrant system. The thicker layer was 80% of the tablet (36.8g), the thinner layer 20% (9.2g). Two comparative tablets were made having a single layer, but having the same composition as the two two-layer tablets. All the tablets contained the same base powder, which had the following formulation

Component	% wt
Na-LAS	23.55
Nonionic surfactant	10.42
Soap	0.72
AA/MA copolymer (70:30)	3.22
Sodium tripolyphosphate (builder)	40.63
Sodium silicate	8.63
Sodium carboxy methyl cellulose	0.67
Moisture	12.15
Total	100.00

The strength of the tablets, in their dry state, as made on the press, was determined as the force, expressed in Newtons, needed to break the tablet, as measured using an Instron type universal testing instrument to apply compressive force on a diameter (i.e. perpendicular to the axis of a cylindrical tablet).
The rate of disintegration of the detergent tablet was assessed by means of the "still water grid test": the tablet is placed on a 10 x 9 cm metal grid with a mesh size of 1.2 x 1.2 cm and placed into a beaker containing 1 litre of still water at 20°C. The disintegration time was the time taken for no residue to be left on the grid. The test was repeated 4 times. The results are shown in the tablet below:

Tablet A I B II

Strength (N) 40 40 40 40

Disintegration Time (mins) 1.0-1.3 1.75-2.0 0.7-1.0 1.75-2.4

Example 2

42g cylindrical detergent tablets having the following formulations were prepared on a rotating table tableting machine from Fette. Four tablets of the invention were made with two layers, the thicker of which contained the Rhodiaphos HPA 3.5, the other a further hydratable salt (selected from sodium percarbonate, anhydrous sodium carbonate, sodium perborate monohydrate and anhydrous sodium sulphate) and a swelling disintegrant system (Nylin LX-16 available from FMC). The thicker layer was 75% of the tablet (31.5g), the thinner layer 25% (10.5g). Four comparative tablets were made having a single layer, but having the same composition as the respective two-layer tablets. All the tablets were made to have a strength of 35 N when tested as in example 1. All the tablets contained the same base powder, which had the same formulation as in example 1.

The tablets had the formulations below:

Component	wt. %
	Tablets C to F	Tablets III to VI
	Thick layer	Thin layer	Overall
Base Powder	40.00	40.00	40.00	40.00
Further Hydratable Salt	-	54.00	13.50	13.50
TAED granules (83% active)	4.00	-	3.00	3.00
Rhodiaphos HPA 3.5	48.00	-	36.00	36.00
Anti-foam granule	4.00	-	3.00	3.00
Fluorescer	2.00	-	1.50	1.50
Dequest 2047 (EDTMP)	1.00	-	0.75	0.75
Soil-release polymer	1.00	-	0.75	0.72
Blue Dye	-	0.10	0.03	0.03
Swelling Disintegrant	-	5.90	1.48	1.48
Total	100	100	100	100

Further hydratable salts:
Tablets C & III sodium percarbonate
Tablets D & IV anhydrous sodium carbonate
Tablets E & V sodium perborate monohydrate
Tablets F & VI anhydrous sodium sulphate
The rate of disintegration of the tablets was measured as in Example 1, and the results are shown in the table below:

Tablet Disintegration Time (s)

C 178

III 354

D 187

IV 375

E 208

V 519

F 329

VI 384

Example 3

42g cylindrical detergent tablets having the following formulations were prepared on a rotating table tableting machine from Fette. Four tablets of the invention were made with two layers, the thicker of which contained the Rhodiaphos HPA 3.5 and a minor proportion of sodium percarbonate, the other the major proportion of sodium percarbonate and a swelling disintegrant system selected from Nylin XL-16 (available from FMC) and Arbocel (available from Rettenmaier). The thicker layer was 75% of the tablet (31.5g), the thinner layer 25% (10.5g).

Two comparative tablets were made having a single layer, but having the same composition as the respective two-layer tablets. All the tablets were made to have a strength of 35 N when tested as in example 1.
All the tablets contained the same base powder, which has the formulation:

Component	% wt
Na-LA,S	21.0
Nonionic surfactant	9.5
Soap	1.5
Zeolite A24	47.0
Sodium carbonate	7.0
Sodium acetate trihydrate	6.0
Sodium carboxy methyl cellulose	1.0
Water & minor ingredients	7.0
Total	100.00

Disintegrant: Tablets G, H and VII - Nylin LX16
Tablets J, K and VIII - Arbocel

The dispensing behaviour of tablets G, J, VII and VIII was measured by placing two tablets of each type in a washing machine dispenser. The dispenser was of the type used in a Philips washing machine (AWB 126/127). Water at 10°C flowing at a rate of 5 litres per minute was passed through the dispenser for two minutes, The amount of wet residue was measured, and the average of three runs is shown below:

Tablet Residue (%)

G 4

VII 84

J 0

VIII 27

Example 4

25g cuboid machine dish wash detergent tablets having the following formulations were prepared on a rotating table tableting machine from Fette. Four tablets of the invention were made with two layers, the thicker of which contained the Rhodiaphos HPA 3.5 and optionally a minor proportion of sodium perborate monohydrate and sodium carbonate, the other the major proportion (or all) of these salts. The thicker layer was 75% of the tablet, the thinner layer 25%.
Two comparative tablets were made having a single layer, but having the same composition as the respective two-layer tablets.

Claims

A detergent tablet of compressed particulate composition comprising a detergent active compound, a detergency builder, particles which contain sodium tripolyphosphate with a content of the Phase I form which is more than 40% by weight of the sodium tripolyphosphate in the said particles, at least one salt other than said sodium tripolyphosphate which can be further hydrated and optionally other detergent ingredients, where the tablets comprise a plurality of discrete regions, characterised in that in one or more of the discrete regions containing said particles which contain sodium tripolyphosphate there is less than 10% by weight of that region of further hydratable salts, and there is at least one discrete region containing at least 10% by weight of that region of further hydratable salts.
A detergent tablet according to claim 1, wherein the further hydratable salt is selected from a carbonate, percarbonate, monohydrated perborate, sulphate, acetate or citrate, or a mixture of these.
A detergent tablet according to claim 2, wherein the further hydratable salt is selected from a sodium salt or persalt or potassium carbonate.
A detergent tablet according to any one of the preceding claims, wherein the sodium tripolyphosphate in the said particles contains water of hydration in an amount between 1% and 5% by weight of that sodium tripolyphosphate.
A detergent tablet according to any one of the preceding claims, wherein said regions containing said particles which contain sodium tripolyphosphate contain no further hydratable salts.
A detergent tablet according to any one of the preceding claims, wherein the sodium tripolyphosphate in said particles have a content of the Phase I form which is at least 50% by weight of the sodium tripolyphosphate in the said particles.
A detergent tablet according to any one of the preceding claims wherein the amount of water of hydration in the sodium tripolyphosphate particles lies in a range between 2% and 4% by weight of the sodium tripolyphosphate in those particles.
A detergent tablet according to any one of the preceding claims wherein the amount of sodium tripolyphosphate is less than 70% by weight of the overall composition.
A detergent tablet according to any one of the preceding claims, wherein the region containing at least 10% by weight of further hydratable salts contains a disintegrant system which does not incorporate said particles which contain said sodium tripolyphosphate.
A detergent tablet according to claim 9, wherein the disintegrant is a swelling disintegrant.
A detergent tablet according to claim 9, wherein the disintegrant is an effervescent disintegrant.
A detergent tablet according to claim 9, wherein the disintegrant is a material of a high water solubility.
A detergent tablet according to any one of the preceding claims wherein the tablet contains between 2 and 40% by weight detergent active compound and 5 to 70% by weight of detergency builder.
A detergent tablet according to any one of claims 1 to 12, wherein the tablet contains less than 5% by weight of detergent active compound and 5 to 70% by weight of detergency builder.