EP1373456A1

EP1373456A1 - Cleaning tablets

Info

Publication number: EP1373456A1
Application number: EP01997535A
Authority: EP
Inventors: Jelles V Unilever Research Vlaardigen BOSKAMP; Somdath Unilever Research Vlaardingen CHOENNIE
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2000-11-24
Filing date: 2001-11-01
Publication date: 2004-01-02
Also published as: AU2002219081A1; ATE293680T1; AU2002217008A1; DE60110251D1; WO2002042406A1; EP1337618B1; EP1337618A1; ES2239176T3; DE60110251T2; WO2002042404A1

Abstract

The invention provides a tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder, wherein the tablet or a discrete region thereof contains 1 to 20 %wt based on the total weight of the tablet of a disintegration system comprising;a) water-swellable disintegrant granules with a mean particle size of between 500-1000 micrometers, and b) a hydrophilic starch having a mean particle size of 250 micrometers or below, a solubility in water of less than 1g/100g of water at 20 DEG C and a development of expansion force of 2.0 Newtons/second or less.The tablets exhibit good disintegration properties and use ingredients from renewable sources. A method of making the tablets is also provided.

Description

CLEANING TABLETS

The present invention relates to cleaning compositions in the form of tablets. These tablets are intended to disintegrate when placed in water and thus are intended to be consumed in a single use. The tablets may be suitable for use in machine dishwashing, the washing of fabrics or other cleaning tasks.

Products in tablet form have several advantages over powdered products: for example, they do not require measuring and are thus easier to handle and dispense into the washload. Furthermore they are more compact, hence facilitating more economical storage .

Detergent compositions in tablet form and intended for fabric washing have been described in a number of patent documents including, for example GB 911204 (Unilever) , US 3953350 (Kao) ,

EP-A-711827, WO-98/42817 and O-99/20730 (Unilever) and are now sold commercially. Tablets of composition suitable for machine dishwashing have been disclosed in EP-A-318204 and US- A-5691293 and are sold commercially.

Tablets of a cleaning composition are generally made by compressing or compacting a composition in particulate form. Although it is desirable that tablets have adequate strength when dry, yet disperse and dissolve quickly when brought into contact with water, it can be difficult to obtain both properties together. Tablets formed using a low compaction pressure tend to crumble and disintegrate on handling and packing; while more forcefully compacted tablets may be sufficiently cohesive but then fail to disintegrate or disperse to an adequate extent in the wash. Tabletting will often be carried out with enough pressure to achieve a compromise between these desirable but antagonistic properties. However, it remains desirable to improve one or other of these properties without detriment to the other so as to improve the overall compromise between them. US-A-3018267 (Procter & Gamble) taught that the force, and hence pressure, applied when compacting a composition into tablets should be limited, or else the tablets would take too long to dissolve.

If a tablet contains organic surfactant, this can function as a binder, plasticising the tablet. However, it can also retard disintegration of the tablet by forming a viscous gel when the tablet comes into contact with water. Thus, the presence of surfactant can make it more difficult to achieve both good strength and good speed of disintegration: the problem has proved especially acute with tablets formed by compressing powders containing surfactant and built with insoluble detergency builder such as sodium aluminosilicate (zeolite) .

It is known to include highly soluble materials whose function is to enhance disintegration of tablets when placed in wash water. Some tablets which are sold commercially incorporate urea for this purpose. Urea has a very high solubility in water exceeding lOOg s per 100ml water at 20°C. EP-A-711827 (Unilever) teaches the use of sodium citrate for this purpose and EP-A-838519 (Unilever) teaches the use of sodium acetate trihydrate for this purpose.

Some of these highly soluble materials, for example sodium acetate, are hygroscopic which necessitates careful handling of the material during the production and storage of the laundry tablets. Therefore, it is desirable to use a tablet disintegrant material which is not hygroscopic and which does not require the same careful handling during production or storage of the tablet .

Generally the above soluble compounds are produced by synthetic reactions. Alternatives to these soluble compounds are always being sought from ^Λrenewable' sources in order to increase the ^natural' content of detergent tablets. A more ^Λnatural' product is becoming increasingly desired by consumers.

A number of documents have taught that the disintegration of tablets of cleaning composition can be accelerated by incorporating a quantity of a water-insoluble but water- swellable material serving to promote disintegration when the tablet is placed in water at the time of use. Two such documents are O98/40462 (Rettenmaier and Henkel) and WO98/40463 (Henkel) .

EP 1 043 391 (Stockhausen GmbH) discloses detergent tablets comprising water-swellable disintegrant granules and micro- crystalline cellulose having a particle size of 200 microns.

EP 0 846 756 (Procter & Gamble Company) discloses a detergent tablet comprising CMC disintegrant and perfume capsules for which the encapsulant material is starch.

Tablets comprising an optical brightener and about 60 to 95% by weight of potato starch are disclosed in DE 2 263 940 and DE 23 62 595 (both Henkel GmbH) . Very high levels of starch are used in these tablets and there is no teaching of the advantages when such materials are used with water-swellable materials. It is therefore an aim of the present invention to address one or more of the above mentioned problems. In particular, the present invention seeks to provide an alternative tablet to those known, which tablet has satisfactory disintegration efficiency and tablet strength, and/or, wherein a substantial proportion of the disintegration system in the tablet is derived from enewable' sources.

We have now found that the above can be achieved by using a disintegration aid system comprising particular water swellable disintegration granules of a given mean particle size and/or particular hydrophilic starches or celluloses having a given mean particle size.

This result is surprising because, amongst other things, the hydrophilic starches and celluloses used according to the invention have an extremely low solubility in water and are preferably water insoluble . Thus it would not be expected that the level of the ingress of water into the tablet caused by these materials would be sufficient to aid good disintegration. Rather, it would be expected that the ingress of water would be much slower than that achieved with the materials of very high water solubility which are conventionally used as disintegration aids and thus comparable disintegration would not be achieved.

The invention also or alternatively allows a lower level of synthetic chemicals to be included in detergent tablets whilst maintaining satisfactory tablet disintegration properties and performance. Furthermore, the disintegration system according to the invention does not present any significant difficulties when being handled in the factory. In some instances the total level of disintegration aids in the tablets may be reduced by the present invention.

We have found that two different measures of tablet strength are relevant to properties observed by a consumer. Force to cause fracture is a direct assessment of strength and indicates the tablets' resistance to breakage when handled by a consumer at the time of use. The amount of energy (or mechanical work) put in prior to fracture is a measure of table deformability and is relevant to the tablets' resistance to breakage during transport .

Both properties are relevant to consumers' perception of tablets: consumers want tablets to be strong enough to handle, to reach them intact, and to disintegrate quickly and fully at the time of use. The present invention makes it possible to achieve a good combination of disintegration and strength properties whilst making use of, at least in part, renewable materials.

Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts oϊ material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about." All amounts are by weight, unless otherwise specified.

Thus according to a first aspect of the invention, there is provided a tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder, wherein the tablet or a discrete region thereof contains 1 to 20%wt based on the total weight of the tablet of a disintegration system comprising; a) water-swellable disintegrant granules with a mean particle size of between 500-1000 micrometers, and b) a hydrophilic starch or cellulose having a mean particle size of 150 micrometers or below, a solubility in water of less than lg/lOOg of water at 20°C and a development of expansion force of 2.0 Newtons/second or less.

Tablets according to the invention have the advantage that they exhibit good disintegration and strength properties and comprise an acceptable level of a disintegration system without needing to rely upon high levels of synthetic ingredients in order to achieve this. Furthermore the disintegrant system is convenient to handle during the production of the tablets.

According to a second aspect the invention there is provided a disintegrant system for a tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder, the disintegration system comprising; a) water-swellable disintegrant granules with a mean particle size of between 500-1000 micrometers, and b) a hydrophilic starch or cellulose having a mean particle size of 150 micrometers or below, a solubility in water of less than lg/lOOg* of water at 20°C and a development of expansion force of 2.0 Newtons/second or less.

According to a third aspect the invention there is provided a process for making a tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder which process comprises; 1) mixing 1 to 20%wt based on the total weight of the tablet of a disintegration system comprising; a) water-swellable disintegrant granules with a mean particle size of between 500-1000 micrometers, and b) a hydrophilic starch or cellulose having a mean particle size of 150 micrometers or below, a solubility in water of less than lg/lOOg of water at 20°C and a development of expansion force of 2.0 Newtons/second or less, with 2) other constituents of a detergent composition including non- soap surfactant and detergency builder, placing a quantity of resulting particulate composition within a mould and compacting that composition within the mould.

According to a forth aspect the invention there is provided a tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder, wherein the tablet or a discrete region thereof contains 1 to 20%wt based on the total weight of the tablet of a disintegration system comprising; a) water-swellable disintegrant granules with a mean particle size of between 600-900 micrometers, and b) a hydrophilic starch or cellulose having a mean particle size of 250 micrometers or below, a solubility in water of less than lg/lOOg of water at 20°C and a development of expansion force* of 2.0 Newtons/second or less.

Forms of this invention, including preferred and optional features, and materials which may be used, will now be discussed in greater detail.

A tablet of the present invention may be either homogeneous or heterogeneous. In the present specification, the term

"homogeneous" is used to mean a tablet produced by compaction of a single particulate composition, but does not imply that all the particles of that composition will be of identical composition. The term "heterogeneous" is used to mean a tablet consisting of a plurality of discrete regions, for example layers, inserts or coatings, each derived by compaction from a particulate composition. In a heterogeneous tablet according to the present invention, each discrete region of the tablet will preferably have a mass of at least 5gm.

Unless otherwise stated, all percentages herein are to percentages by weight based upon the total weight of the tablet, or region thereof.

Tablet disintegration system

A tablet according to the invention comprises non-soap surfactant and detergency builder and the tablet or a discrete region thereof contains 1 to 20%wt, based on the total weight of the tablet, of a tablet disintegration system as described herein.

The tablet disintegration system comprises a first component (a) which is a water swellable disintegrant granule and a second component (b) which is a hydrophilic starch or cellulose having a mean particle size of 150 micrometers or below , said starch or cellulose'^' acting as a pathway for the ingress of water into the tablet.

The tablet, or a discrete region thereof, contains 1 to 20% wt in total of said disintegration system based on the total weight of the tablet or region thereof. Preferably the tablet, or a discrete region thereof, comprises 5 or 8%wt to 16%wt of the disintegration system. Good results have been obtained by using a total amount of the disintegrant system which lies in the range of 8 to 15%wt, even better in the range of more than 8.5 to 13%wt, e.g. 8.5% to 12.5%wt based on the total weight of the tablet or region thereof.

(a) water swellable disintegrant granule A number of water-insoluble, water-swellable materials are known to be useful as tablet disintegrants, in particular for pharmaceutical tablets. A discussion of such materials is found in "Drug Development and Industrial Pharmacy", Volume 6, pages 511-536 (1980) . Suppliers of water-swellable disintegrant materials include J Rettenmaier & Sδhne in Germany and FMC Corporation in USA.

The total amount of water-swellable disintegrant granules in the tablet is preferably between 0.5 and 13%wt based on the total weight of the tablet, more preferably between 1 and ll%wt, such as between 2 and 9%wt depending upon the type of granule used. For example, water-swellable disintegrant granules comprising polymeric disintegrant material have been found to give good results when included in the tablets at levels of from 2 to 7%wt, especially 3 to 6%wt. However for non-polymeric disintegrant material, the amounts are typically higher, for example 5 to 13%wt, preferably 6 to ll%wt.

The disintegrant granule according to the invention swells upon contact with water. It is much preferred that the granule is made from a material that itself is a water swellable material before being granulated to produce the water-swellable disintegrant granule. However, the granule may be made from a material that itself shows negligible swelling characteristics unless granulated possibly to a specific particle size. For example micro-crystalline cellulose when granulated to a suitable average particle size, e.g. 700 to 1000 micrometers may be used provided that the granule itself is water swellable.

The disintegrant system of the invention comprises water- swellable disintegrant granules with a mean particle size of between 500-1000 micrometers. Preferably the water-swellable disintegrant granules have a mean particle size in the range of from 550 to 950 micrometers, more preferably 600 to 900 micrometers, such as 650 to 850 micrometers.

The particle size as referred to herein is measured by sieving the granules and collecting the sievings. The weight of the sieved fractions is plotted against the particle size of the fractions and the weight average mean particle size is then calculated following the method defined in Rosin and Rammler, J. Inst. Fuel, 1_, 29-36 (1933) to give the weight average particle size. All particle sizes referred to herein are to weight average particle sizes determined by this method unless otherwise stated.

The water-swellable disintegrant granules preferably have a solubility in water of less than 2g/l00g of water at 20°C, more preferably of less than lg/lOOg, most preferably of less than 0.5g/l00g. Especially preferred are water insoluble water swellable disintegrant granules.

The water-swellable disintegrant granules comprise one or more disintegrant materials. The granules may consist essentially of one or more disintegrant materials which are either water- swellable per se or which are water-swellable when granulated. Alternatively the granules may comprise one or more of ^■ said materials mixed with other materials as carriers. The disintegrant granules may comprise polymeric material as the disintegrant material. Many of these polymeric materials are of natural origin even if they have subsequently undergone chemical processing. It is especially preferred that the water-swellable disintegrant granules comprise cellulose.

Suitable disintegrant granules include those made from starches, for example, maize, rice and potato starches and starch derivatives, such as Primojel™, or Explotab™, both of which are sodium starch glycolate also known as sodium carboxymethyl starch; 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 from Rettenmaier and cellulose derivatives, for example Courlose™ and Nymcel™, sodium carboxymethyl cellulose, Ac-di-Sol™ cross- linked modified cellulose, microcrystalline cellulosic fibres and cross-linked cellulose; and various synthetic organic polymers. These materials are referred to herein as disintegrant materials regardless of whether they have disintegration properties per se, or, whether they act as a disintegrant only when granulated to form the water-swellable disintegrant granule". '

Cellulose-containing fibrous materials originating from timber may be compacted wood pulps. So-called mechanical pulps generally incorporate lignin as well as cellulose whereas chemical pulps generally contain cellulose but little of the original lignin remains. Pulp obtained by a mixture of chemical and mechanical methods may retain some but not all of the original lignin. Cellulose based materials include Nilyn LX-16 which is a water-insoluble compacted cellulose based disintegrant, commercially available from FMC. A strongly swelling disintegrant material may come from a category referred to in the art as a 'super-disintegrant' . Such super disintegrants tend to be cross-linked synthetic or natural polymers and include cross-linked forms of carboxymethyl cellulose, cellulose, starch, polyvinylpyrrolidone and polyacrylate . Cross-linked forms of carboxymethyl cellulose are especially preferred.

Any of these materials which are starch may be present in/as the disintegrant granule a) in addition to being present in/as component b) of the disintegrant system, provided, they are included in different forms that fulfil the criteria for both components a) and b) .

The disintegrant granules may consist of a water-absorbent carrier material which may swell on initial contact with water, mixed with a minor proportion of disintegrant material. The disintegrant material may swell more strongly than the carrier material on contact with water. It may take up more water than the carrier material, or swell more rapidly or both. The proportions in the disintegrant granule are preferably from 75 to 90, 95 or 99.9%wt^ifof the carrier material, from 0.1 to 15%wt of the disintegrant material and from 0% to 24.9%wt of other material based on the total weight of the disintegrant particles. It is especially preferred that the proportions are from 75%wt to 99.9%wt of the carrier material, from 0.1 to 10% of the disintegrant material and from 0% to 24.5%wt of other material based on the total weight of the disintegrant particles. The carrier materials are preferably selected from compounds which contain hydroxy groups. A carrier material may itself be a water-insoluble, and somewhat water-swellable, material. Such materials include starches, for example, maize, rice and potato starches, celluloses, micro-crystalline cellulosic fibres and some synthetic organic polymers .

The disintegrant granules may also contain up to 15% or 20% by weight of a water-soluble polymer which acts as a binder, e.g. polyethylene glycol.

An apparatus for measuring increase in volume (swelling) is illustrated in "The Mechanisms of Disintegrant Action". Kanic & Rudnic, Pharmaceutical Technology, April 1984, pages 50-63. This article also refers to papers describing other types of apparatus for measuring swelling.

Another parameter which can be used to characterise swellable materials is the force which they exert if they are allowed to take up water whilst confined within an enclosure.

We have found that materials and particles which swell on contact with water are ' effective as disintegrants if there is a rapid development of force when they come into contact with water. We have carried out measurements using a relatively simple piece of apparatus shown in the attached drawing and an Instron materials testing machine type 5566 from Instron, UK (herein after referred to as "the Instron machine").

The apparatus consists of a cylinder (10) with internal diameter 25mm and a length of 20mm. This cylinder is perforated by a ring of holes (12) adjacent one end. There are 36 of these holes, of 1mm diameter, with centers 2.5mm from the end of the cylinder.

This end of the cylinder is glued to the base of a glass container (14) of internal diameter 73mm.

To test a sample of powdered disintegrant, 1.5 gram of the disintegrant is placed in the cylinder and gently tapped so that it forms a level bed (16) which is usually 6mm to 10mm deep depending on the bulk density of the powder.

A plunger (18) of the Instron machine is moved into the upper set of the cylinder, over this powder bed. Under computer control of the Instron machine the plunger is applied to the top of the powder bed (16) with a force of 1 Newton.

50ml of distilled water at 22°C is tipped into the annular space (20) around the cylinder. This water passes through the holes (12) into the powder bed. The Instron machine is programmed to hold the plunger in position against the swelling bed of powder, and the force required for this is recorded.

It is especially preferred that the disintegrant material used in the disintegrant granule when tested per se, has the ability to absorb at least twice its own volume of water and has a development of expansion force which exceeds 1.5 Newton/second. It is especially preferred that the disintegrant material has a development of expansion force of greater than 2.2 Newtons/second, such as 2.5 Newtons/second or greater.

Specifically, a super-disintegrant may take up more than twice and possibly more than 2.5 or 3 times its own volume of water, and/or develop expansion force exceeding 1.5 Newton/second whist a carrier for it takes up less water by volume than the super-disintegrant and develops less expansion force.

The development of swelling force has been measured for a number of materials, as set out in the following table. The data is taken from C. Caramella et al ; The role of swelling in the disintegration process Int. J. Pharm. Tech. & Prod. Mfr. 5 (2) , 1 - 5, (1984) .

The significant parameter is the maximum slope of a graph of expansion force against time . Measurement of swelling can be recorded with the same apparatus. The plunger is again applied to the top of a bed of the dry powder, and pressed against it with a force of 1 Newton. 50ml of water is poured in as before. The Instron machine is programmed to allow expansion of the bed of powder, while maintaining a force on it of 1 Newton. Displacement of the plunger is recorded.

The water swellable disintegrant granules may be made by mixing the disintegrant material with the carrier material, if any, compacting the mixture, and if necessary comminuting the compacted mixture into granules.

Mixing of these materials can be carried out by standard apparatus for mixing particulate solids. Other ingredients can be incorporated at this stage. If a polymeric binder is incorporated, it can be added in particulate form during this mixing operation. Alternatively, if it can be melted, the molten polymer can be sprayed on to the mixture or on to one particulate ingredient of the mixture.

Compaction of the mixture can be brought about by forcing it between a pair of rollers. Suitable apparatus - a roller compactor - has a feed screw which delivers the mixture to the nip of the rollers. The speed of the feed screw, and hence the amount of material delivered to the nip of the rollers should be high enough to force an unbroken stream of material through the rollers, but not so high that the material is converted into a dough.

The sheet of material which issues from the rollers is then broken up and milled to the required particle size. Manufacturers of both roller compactor and milling machinery include Hosokawa Bepex located at Heilbronn, Germany, Alexanderwerk located at Remschied, Germany and Fitzpatrick located at Elmhurst, USA.

(b) hydrophilic starch or cellulose

The second component of the disintegration system is a hydrophilic starch or cellulose having a mean particle size of 150 micrometers or below, preferably 100 micrometers or below. Mean particle sizes in the range 2 to 70 micrometers have been found to be particularly suitable. For example, starches or celluloses having mean particle sizes of 5 or 10 to 30 or 50 micrometers have been found to be especially suitable. Maize starch (which has a mean particle size of approximately 15 micrometers) has been found to be beneficial according to the present invention. The mean particle sizes herein are measured according to the method stated above .

The hydrophilic starch or cellulose has a solubility in water of less than lg/lOOg of water at 20°C, preferably less than 0.5g/l00g, more preferably less than 0.2g/l00g. Water insoluble starches or cellulose are especially preferred.

The hydrophilic starch or cellulose has a development of expansion force, as defined above, of 2.0 Newtons/second or less, preferably of 1.8 Newtons/second or less, more preferably of 1.5 Newtons/second or less, such as 1.3 Newtons/second or less. The development of expansion forces of some hydrophilic starches and celluloses suitable for use as component b) in the disintegration system are given in the table above in the description of the disintegration granule. The tablet preferably comprises 1 to 15%wt of the hydrophilic starch or cellulose based on the total weight of the tablet, more preferably 2 or 3 to 12%wt, even more preferably 4 to 10%wt. Amounts between 4 and 8%wt have been found to be very effective, such as 4.5 to 7.5%wt. We have found especially good results using about 4% wt of the disintegrant granule with about 6 to 8%wt of starch or cellulose and using about 5%wt of the disintegrant granule with about 4-6%wt of starch or cellulose.

The hydrophilic starch or cellulose is preferably a native starch or cellulose. By the term native' as used herein is meant a starch or cellulose which is natural in origin.

If the hydrophilic material is a native starch, the material can be any commercially available native starch. Native sources of starch include potato, tapioca, maize, rice, wheat, barley, triticale, millet, arrowroot, banana, sweet potato starches or high amylose starches like amylomaize, wrinkled pea starch, mung bean starch or amylopectin rice starches like waxy maize, waxy barley, waxy wheat, waxy rice, amylopectin potato, ^' amylopectin tapioca, amylopectin sweet potato or amylopectin banana stach. Amylopectin starches may be derived from plants that selectively produce amylopectin such as waxy cereals or amylose-free potato mutants and/or genetically modified plant varieties such as potatoes modified to selectively produce amylopectine. Preferably the native starch is maize, tapioca, rice or potato starch, most preferably maize or potato starch. If the hydrophilic material is a native cellulose, the material can be any commercially available native cellulose. Suitable hydrophilic cellulosic materials include micro-crystalline cellulose, alpha -cellulose, citric acid intra cross linked cellulose and sulphur grafted cellulose.

The hydrophilic starch or cellulose may be used as the material per se. Alternatively it may be combined, for example co- granulated, with a carrier material. Suitable carrier materials are described above for the water swellable disintegrant granule. If a carrier material is present, then the combination of the hydrophilic material and the carrier should still have a mean particle size of 150 micrometers or below.

Without wishing to be bound by theory, it is believed that the hydrophilic starches or cellulose are suitable for use in the disintegration system of the present invention because they combine rapid water uptake with a limited increase of the viscosity of the penetrating water.

According to the invention a mixture of different starches, different celluloses or mixtures of starches and celluloses may be used. In particular mixtures of native and non-native starches or celluloses may be used. Non-native starches or celluloses include chemically or physically modified materials even if of native origin, e.g. pregelatinised starch.

Surfactant Compounds

Compositions which are compacted to form tablets, or discrete regions thereof, of this invention contain one or more non-soap surfactants. In a fabric washing composition, these preferably provide from 5 to 50% by weight of the composition of the tablet or region thereof, more preferably from 8 or 9% by weight of the composition up to 35% or 40% by weight. If the tablet is composed of more than one discrete region, then these preferred amounts of surfactant may apply to the tablet as a whole or to a discrete region thereof.

The organic surfactant may be present as a component in granulated particles in an amount between 10 and 70% by weight of the particles, more preferably 15 to 50% by weight based on the total weight of the granulated particles. All the surfactant in the composition may be contained within these particles. The surfactant may be anionic (soap or non-soap) , cationic, zwitterionic, amphoteric, nonionic or a combination of these.

In a fabric washing tablet, anionic surfactant may be present in an amount from 0.5 to 50% by weight, preferably from 2% or 4% up to 30% or 35% or 40% by weight of the tablet or region thereof .

In a machine dishwashing composition, organic surfactant is likely to constitute from 0.5 to 8%, more likely from 0.5 to 5% of the composition of the tablet or region thereof and is likely to consist of' nonionic surfactant, either alone or in a mixture with anionic surfactant .

Synthetic (i.e. non-soap) anionic surfactants are well known to those skilled in the art. Examples include alkyl benzene sulphonates, particularly sodium linear alkyl benzene sulphonates having an alkyl chain length of C₈-Cι₅; olefin sulphonates; alkane sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates . 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 commercially significant as an anionic surfactant.

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, is also a commercially significant anionic surfactant.

Frequently, such linear alkyl benzene sulphonate or primary alkyl sulphate of the formula above, or a mixture thereof will be the desired anionic surfactant and may provide 75 to 100 wt% of any anionic non-soap surfactant in the composition. In some forms of this invention the amount of non-soap anionic surfactant lies in a range from 5 to 20 or 25 wt% of the tablet or region thereof .

It may also be desirable to include one or more soaps of fatty acids. These are preferably sodium soaps derived from naturally occurring fatty acids, for example, the fatty acids from coconut oil, beef tallow, sunflower or hardened rape seed oil.

Suitable nonionic surfactant compounds which may be used 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 (C₈-22. phenol- ethylene oxide condensates, the condensation products of linear or branched aliphatic C₈-₂o 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 C₉_u and C12-15 primary and secondary alcohols ethoxylated with an average of from 5 to 20 moles of ethylene oxide per mole of alcohol.

In certain forms of this invention the amount of nonionic surfactant lies in a range from 4 to 40%, better 4 or 5 to 30% by weight of the composition of the tablet or region thereof. Many nonionic surfactants are liquids. These may be absorbed onto particles of the composition prior to compaction into tablets.

Amphoteric surfactants which may be used jointly with anionic or nonionic surfactants or both include amphopropionates of the formula;

O OfeCHOH

II I

RC-NH-CH₂CH₂~N-C bCH₂C Na 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 (a idopropyl betaine) ; Z is either a COO^" (carboxybetaine) , or of the form CHOHCH₂S0₃ - (sulfobetaine or hydroxy sultaine) .

Another example of amphoteric surfactant is amine oxide of the formula;

where R_x is C_L0 to C₂o alkyl or alkenyl; R₂, R₃ and R₄ are each hydrogen or C_x to C₄ alkyl, while n is from 1 to 5.

Ca ionic surfactants may possibly be used. These frequently have a quaternised nitrogen atom in a polar head group and an attached hydrocarbon group of sufficient length to be hydrophobic . A general formula for one category of cationic surfactants is ;

where each R independently denotes an alkyl group or hydroxyalkyl group of 1 to 3 carbon atoms and R_h denotes an aromatic, aliphatic or mixed aromatic and aliphatic group of 6 to 24 carbon atoms, preferably an alkyl or alkenyl group of 8 to 22 carbon atoms and ^" is a counterion.

The amount of amphoteric surfactant, if any, may possibly be from 3% to 20 or 30% by weight of the tablet or region of a tablet; the amount of cationic surfactant, if any, may possibly be from 1% to 10 or 20% by weight of the tablet or region of a tablet .

Detergency Builder

A tablet according to the present invention comprises a detergency builder hich serves to remove or sequester calcium and/or magnesium ions in the water. Thus the builder acts as a water softener. In detergent tablets the amount of builder is likely to be from 5% to 80%, more usually 10% or 15% to 60% by -weight of the tablet .

The detergency builder may be present in granulated particles in an amount of from 20 to 80% by weight, more preferably 30 to 60% by weight of the granulated particles. Detergency builders may be provided wholly by water soluble materials, or may be provided in a large part or even entirely by water-insoluble material with water-softening properties.

Alkali metal aluminosilicates are strongly favoured as environmentally acceptable detergency builders for fabric washing, and are preferred in this invention. Alkali metal (preferably sodium) aluminosilicates may be either crystalline or amorphous or mixtures thereof, having the general formula:

0.8 - 1.5 Na₂O.Al₂0₃. 0.8 - 6 Si0₂. xH₂0

These materials contain some bound water (indicated as xH₂0) 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 Si0₂ 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 materials are described, for example, in GB 1 429 143 (Procter & Gamble) . The preferred sodium aluminosilicates of this type are the well known commercially available zeolites A and X, the newer zeolite P described and claimed in EP 384 070 (Unilever) and mixtures thereof. This form of zeolite P is also referred to as "zeolite MAP". One commercial form of it is denoted "zeolite A24" .

Conceivably a detergency builder could be a layered sodium silicate as described in US 4 664 839. NaSKS-6 is the trademark for a crystalline layered silicate marketed by Hoechst (commonly abbreviated as "SKS-6") . NaSKS-6 has the delta-Na₂Si0₅ 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, such as those having the general formula NaMSi_x0_2x+ι.yH₂0 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 can be used.

The less preferred category of water-soluble phosphorus- containing inorganic softeners includes the alkali-metal orthophosphates, metaphosphates, pyrophosphates and polyphosphates . Specific examples of inorganic phosphate detergency builders include sodium and potassium tripolyphosphates, orthophosphates and hexametaphosphates .

Non-phosphorus water-soluble detergency builders may be organic or inorganic. Inorganics that may be present include alkali metal (generally sodium) carbonate; while organics include polycarboxylate polymers, such as polyacrylates, acrylic/maleic copolymers, and acrylic phosphonates, monomeric polycarboxylates such as citrates, gluconates, oxydisuccinates, glycerol mono- di- and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates and hydroxyethyliminodiacetates.

Tablet compositions preferably include polycarboxylate polymers, more especially polyacrylates and acrylic/maleic copolymers which have some function as water-softening agents and also inhibit unwanted deposition onto fabric from the wash liquor.

Where the tablet contains water soluble builder it is preferably present in an amount of from 10 to 80% by weight based on the total weight of the tablet or region thereof. Where the tablet contains water in-soluble builder it is preferably present in an amount of from 5 to 80% by weight based on the total weight of the tablet or region thereof.

Tablets comprising from 4 to 50% by weight of surfactant and from 5 to 80% by weight of builder are especially preferred for fabric washing tablets. Tablets comprising from 1 to 5% by weight of surfactant and from 50 to 98% by weight of detergency builder are especially preferred for machine dishwashing tablets.

For the avoidance of doubt, where a tablet is heterogeneous, the percentage ranges for the components referred to herein may apply to the overall composition of the tablet, as well as to at least one region of the tablet.

Optional Water-Soluble Disintegration-Promoting Particles A tablet or a region of a tablet may additionally contain water-soluble particles to further promote disintegration in addition to the claimed disintegration system. It is preferred that such disintegration-promoting particles make up from 2%, 3%, 5%, 8% or 10% up to 15% by weight of the composition of the tablet or region thereof .

Such water-soluble particles typically contain at least 40% by weight (of their own weight) of one or more materials which is other than soap or organic surfactant and which has a solubility in deionised water of at least 30g/l00g at 20°C.

More preferably this water-soluble material is selected from compounds containing at least 40% (by weight of the particles) of one or more materials selected from the group consisting of; compounds with a water-solubility exceeding 50 grams/100 grams in water at 20°C; or sodium tripolyphosphate containing at least 50% of its own weight of the phase I anhydrous form, or sodium tripolyphosphate which is partially hydrated so as to contain water of hydration in an amount which is at least 0.5% by weight of the sodium tripolyphosphate in the particles, preferably which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate in the particles .

As will be explained further below, these disintegration- promoting particles can also contain other forms of tripolyphosphate or other salts within the balance of their composition.

If the material in such water-soluble disintegration-promoting particles can function as a detergency builder, (as is the case with sodium tripolyphosphate) then of course it contributes to the total quantity of detergency builder in the tablet composition.

A solubility of at least 50 g/lOOg of deionised 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 lOOg of deionised water at 20°C:- Material Water Solubility (g/lOOg)

Sodium citrate dihydrate 72

Potassium carbonate 112

Urea >100

5 Sodium acetate 119 Sodium acetate trihydrate 76

Magnesium sulphate 7H₂0 71

By contrast the solubilities of some other common materials at 10 20°C are:-

Material Water Solubility (g/lOOg)

Sodium chloride 36

Sodium sulphate decahydrate 21.5

15 Sodium carbonate anhydrous 8.0

Sodium percarbonate anhydrous 12

Sodium perborate anhydrous 3.7

Sodium tripolyphosphate anhydrous 15

20 Preferably this highly water soluble material is incorporated as particles of the material in a substantially pure form (i.e. each such particle contains over 95% by weight of the material) . However,* the said particles may contain material of such solubility in a mixture with other material, provided that

25 material of the specified solubility provides at least 50% by weight of these particles.

Preferred water-soluble materials having a solubility exceeding 50 g/lOOg of deionised water at 20°C are sodium citrate 30 dihydrate, urea, sodium acetate and sodium acetate trihydrate. The sodium acetate may be in a partially or fully hydrated form. It may be preferred that the highly water-soluble material is a salt which dissolves in water in an ionised form. As such a salt dissolves it leads to a transient local increase in ionic strength which can assist disintegration of the tablet by preventing nonionic surfactant from swelling and inhibiting dissolution of other materials.

Specifically, tablets of this invention may contain water- soluble salt, with a solubility exceeding 50g/100g of deionised water at 20°C, both as a small percentage within the said granulated particles and as separate particles which are mixed with them.

Within granulated particles which may contain surfactant and/or builder, such highly water soluble salt may be present in an amount from 1 to 25 or 30% by weight of those particles, preferably from 3 or 5 to 10% or 15% thereof, while an amount from 1, 2 or 5% up to 15% by weight of the whole tablet formulation of highly soluble salts may be added to those particles before tabletting.

Another possibility, _* which is less preferred, is that the said particles which promote disintegration are particles which contain sodium tripolyphosphate with more than 50% (by weight of the particles) of the anhydrous phase I form, and, which is partially hydrated so as to contain water of hydration in an amount which is at least 1% by weight of the sodium tripolyphosphate .

Sodium tripolyphosphate is very well known as a sequestering builder in detergent compositions. It exists in a hydrated form and two crystalline anhydrous forms. These are the normal crystalline anhydrous form, known as phase II which is the low temperature form, and phase I which is stable at high temperature. The conversion of phase II to phase I proceeds fairly rapidly on heating above the transition temperature, which is about 420°C, but the reverse reaction is slow.

Consequently phase I sodium tripolyphosphate is metastable at ambient temperature .

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-4 536 377. These particles should also contain sodium tripolyphosphate which is partially hydrated. The extent of hydration should be at least 1% by weight of the sodium tripolyphosphate in the particles. It may lie in a range from 1 to 4%, or it may be higher. Indeed fully hydrated sodium tripolyphosphate may be used to provide these particles.

The remainder of the tablet composition used to form the tablet or region thereof may include additional sodium tripolyphosphate. This may be in any form, including sodium tripolyphosphate with a high content of the anhydrous phase II form. Suitable material is commercially available. Suppliers include Rhone-Poulenc, France and Albright & Wilson, UK.

Some countries require that phosphate is not used. For such countries, a zero phosphate tablet in accordance with this invention may utilise a suitable amount, e.g. 15% by weight or more of disintegration-promoting material with solubility of at least 50g/100g at 20°C. Other countries permit the use, or at least some limited use, of phosphates, making it possible to use some sodium tripolyphosphate . Water-soluble disintegration-promoting particles are preferably stable up to at least 20% relative humidity, preferably at least 30% and more preferably at least 60% relative humidity, stability being measured at 25°C in the manner described hereinbelow and as described in WO 01/51600 (Procter and Gamble Company) .

The stability of the disintegration-promoting particles can be determined using dynamic vapor sorption isotherms.

This test measures the equilibrium moisture uptake at constant temperature as a function of relative humidity (RH) . The RH is increased in incremental steps and at each level the sample is given time to equilibrate thereafter the sample is weight to determine the mass increase due to water sorption. The measurements may be performed using a DVS-1 instrument, supplied by Surface Measurement Systems Ltd. The instrument comprises mass flow meters to regulate the wet/dry air ratios and a Cahn D-200 microbalance . The instrument is housed in an incubator to ensure all parts of the systems are at the same temperature. The test is run using 15 mg samples with the RH ranging from 0 to 80% at 25°C. The disintegration-promoting particles are considered to be stable up to a relative humidity x if the percent increase in weight of the dissolution aid is less than 5%, preferably less than 1% for sorption over the relative humidity range from 0 to x% .

Optional Water-soluble organic polymer Tablets of the present invention may include a water-soluble organic polymer which is solid at 25°C to act as a binder for the particulate composition when compacted. This may be included in granulated particles containing organic surfactant and/or detergency builder.

The term "solid" is used here to denote materials which have the appearance of an immobile solid at 25°C and can be handled as solids. They contrast with liquids which, even if viscous, can be seen to be capable of fluid flow. Organic polymers are generally amorphous materials which are strictly classified as super-cooled liquids - but of such high viscosity that for practical purposes they are solid.

The terms water-soluble is used herein to indicate that when the polymer is placed in water it appears, on visual inspection, to dissolve. Whether the solution is a true isotropic solution or has some colloidal character is not important to this invention.

It is preferred that the polymer material should melt at a temperature of at least 35°C, better 40°C or above, which is above ambient temperatures in many temperate countries. For use in hotter countries it will be preferable that the melting temperature is somewhat above 40°C, so as to be above the ambient temperature-'.

Some polymers which may be used are solids at temperatures up to 100 °C, that is to say they retain a solid appearance even though they are in an amorphous state . They may soften and melt to a mobile liquid on heating further, or may decompose without melting on heating sufficiently in excess of 100 °C. Such polymers will generally be added as a powder during the course of granulation. Another possibility would be addition as a solution in a volatile organic solvent, but that is not preferred. Other polymers which may be used melt to liquid form at temperatures not exceeding 80 °C and may be sprayed as molten liquid onto the surfactant and builder mixture during the course of granulation.

Organic polymers are in general amorphous solids. A significant parameter characterising amorphous solids is their glass transition temperature. When an amorphous hydrophilic polymer absorbs moisture, the moisture acts as a plasticiser and lowers the glass transition temperature of the polymer. Suitable polymers may have a glass transition temperature, when anhydrous, which is from 300 to 500K (i.e. approximately 25°C to 225 °C) but may be incorporated in a moisture-containing state so that their glass transition temperature is lower.

A preferred polymer is polyethylene glycol. Preferred polymer materials are synthetic organic polymers 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 can also be used (PEG 4000 melts at 56°C and PEG 6000 at 58°C). Other possibilities are podyvinylpyrrolidone, and polyacrylate and water-soluble acrylate copolymers.

The amount of water-soluble polymer included in particles which may also contain organic surfactant and detergency builder is preferably between 0.2% or 0.5% or 1% and 15% by weight of the particles, possibly at least 1.5 or 3%. Further preferred is that the amount is not over 7 or 10% by weight. Alternatively, the amount of water-soluble polymer present may be defined in terms of the whole composition of the tablet or region thereof, in which case, it is desirably present in an amount of between 0.5% and 10% by weight, more preferably at least 1, 2 or 5% by weight. Possibly the amount of polymer does not exceed 7% by weight of the whole composition.

Optional Bleach System

Tabletted compositions according to the invention may contain a bleach system. This preferably comprises one or more peroxy bleach compounds, for example, inorganic persalts or organic peroxyacids, which may be employed in conjunction with activators to improve bleaching action at low wash temperatures. If any peroxygen compound is present, the amount is likely to lie in a range from 10 to 25% by weight of the composition of the tablet or region thereof.

Preferred inorganic persalts are sodium perborate monohydrate and tetrahydrate, and sodium percarbonate, advantageously employed together with an activator. Bleach activators, also referred to as bleach precursors, have been widely disclosed in the art. Preferred examples include peracetic acid precursors, for example, tetraacetylethylene diamine (TAED) , now in widespread commercial use in conjunction with sodium perborate; and perbenzoic acid precursors . The quaternary ammonium and phosphonium bleach activators disclosed in US 4 751 015 and US 4 818 426 (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-458 397, EP-A-458 398 and EP-A-549 272. A bleach system may also include a bleach stabiliser (heavy metal sequestrant) such as ethylenediamine tetramethylene phosphonate and diethylenetriamine pentamethylene phosphonate. Optional Other Ingredients

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. 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 about 0.1% to about 3.0% by weight of the composition of the tablet or region thereof; and these granules or marumes present no problems with respect to compaction to form a tablet .

The 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 if organic surfactant is present, especially if a 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 266 863A (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 of the tablet or region thereof .

It may also be desirable that a tablet of the invention includes an amount of an alkali metal silicate, particularly sodium ortho-, meta- or disilicate. The presence of such alkali metal silicates at levels, for example, of 0.1 to 10 wt%, may be advantageous in providing protection against the corrosion of metal parts in washing machines, besides providing some degree of building to the composition and giving processing benefits in manufacture of the particulate material which is compacted into tablets. A composition for fabric washing will generally not contain more than 15wt% silicate. A tablet for machine dishwashing will frequently contain at least 20wt% silicate.

Bulk Density and Granulation of detergent powder

While the starting particulate composition from which the tablets are produced may in principle have any bulk density, the present invention may be especially relevant to tablets of detergent composition 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, 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 400 g/litre, preferably at least 500 g/litre, and possibly at least 600 g/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-A-340 013 (Unilever) , EP-A-352 135 (Unilever) , and EP-A-425 277 (Unilever) , or by the continuous granulation/densification processes described and claimed in EP-A-367 339 (Unilever) and EP-A-390 251 (Unilever) , are inherently suitable for use in the present invention.

Another particularly suitable process for the preparation of a high-bulk density detergent powder is described in WO-A- 98/11193 (Unilever) . In this document, a feedstock of the starting acid for production of the anionic surfactant is partially neutralised, for example by sodium hydroxide, before being fed into a high-speed mixer densifier (e.g. Lodige CB 30 Recycler) where the partially neutralised acid feedstock is completely neutralised, whilst being mixed with the majority of other components of the detergent base powder granule. This powder can be further densified by treating in a moderate speed mixer (e.g. Lodige KM 300 mixer) , before which stage further detergency builder may be added. The water-soluble polymer material is preferably added before the further densification step, although it may be added in the first mixer. The water- soluble polymer material may be heated to a temperature considerably above its melting point to obtain a free-flowing liquid. The resulting powder can be cooled and dried using a fluid bed, after which any desired particle size control can be exercised.

Any separate particles containing further components of the finished formulation can be mixed with the base powder prior to compaction. Particle Size Control

Particle sizes can be controlled in the manufacturing process of any particles included in the composition. Oversize particles are usually removed by sieving (for example by a

Mogensen screen) at the end of the production process, followed by milling and recycling of the removed oversize fraction. Undersize particles can also be removed by sieving, or if the manufacturing process employs a fluidised bed, undersized particles may be entrained in the air stream and subsequently recovered from it for recycling to the granulation stage.

It is preferred that the average particle size of granulated particles forming the particulate composition from which the tablet is formed is between 400 and 1100 micrometers, preferably between 500 and 1000 micrometers. Preferably no more than 5% of these particles is smaller than 200 micrometers while no more than 5% is larger than 1400 micrometers.

Materials which are mixed with the granulated particles may also comply with these requirements concerning particle size.

Tabletting

Tabletting entails compaction of a particulate composition. A variety of tabletting machinery is known, and can be used. Generally it will function by stamping a quantity of the particulate composition which is confined in a die. Tabletting may be carried out at ambient temperature or at a temperature above ambient which may allow adequate strength to be achieved with less applied pressure during compaction. In order to carry out the tabletting at a temperature which is above ambient, the particulate composition is preferably supplied to the tabletting machinery at an elevated temperature. This will of course supply heat to the tabletting machinery, but the machinery may be heated in some other way also.

If any heat is supplied, it is envisaged that this will be supplied conventionally, such as by passing the particulate composition through an oven, rather than^' by any application of microwave energy.

The size of a tablet will suitably range from 10 to 160 grams, preferably from 15 to 60 grams, 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. 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 for fabric washing preferably lies in a range from 1040 or 1050g/litre up to 1400g/litre preferably at least HOOg/litre up to 1400g/litre. The tablet density may well lie in a range up to no more than 1350 or even 1250g/litre. The overall density of a tablet of some other cleaning composition*, such as a tablet for machine dishwashing or as a bleaching additive, may range up to 1700g/litre and will often lie in a range from 1300 to 1550g/litre.

The invention also provides a process for making a tablet according to the invention which comprises mixing the disintegrant system with other constituents of a detergent composition including organic surfactant and detergency builder, placing a quantity of resulting particulate composition within a mould and compacting that composition within the mould. Tablet testing - disintegration

The speed of disintegration of tablets was measured by means of a test procedure under static conditions in which a pre-weighed tablet was placed on a metal grid with 1 X 1 cm mazes and the tablet and grid was then immersed in a suitable amount of 15° FH (French Hardness) tap water at 10°C or 20°C so that the tablet when immersed is covered by 2cm of water. After 60 seconds the metal grid is carefully taken out of the water and the wet tablet residue is weighed. If the tablet had fully disintegrated in this time then the time taken for 100% disintegration is recorded. It is preferred that the tablets exhibit 70% by weight or more disintegration in the above test, more preferably 75% or more, most preferably 80% or more.

Tablet Strength

The strength of the tablets, in their dry state as made on the compaction press, can be determined according to their diametrical fracture stress DFS, which is calculated from the equation:

2F„

DFS = max πDt

where DFS is the diametrical fracture stress in Pascals, F_max is the applied load in Newtons to cause fracture, D is the tablet diameter in meters and t is the tablet thickness in meters. The test is carried out using an Instron type universal testing instrument to apply compressive force on a tablet diameter (i.e. perpendicular to the axis of a cylindrical tablet).

It is preferred that tablets have a DFS of at least 20kPa more preferably at least 25kPa, such as 30kPa or above. EXAMPLES

The invention will be further described by reference to the following examples. Further examples within the scope of the present invention will be apparent to the person skilled in the art .

Preparation of a stock granulated powder

A stock granular detergent powder was made having the composition in table 1 by granulating the first eight ingredients together in the correct proportions under high shear followed by densification under reduced shear to produce a granular component. The post-dosed ingredients were added to the granular composition to produce the overall composition in Table 1.

Table 1; Stock powder formulation

Zeolite A24 is maximum aluminium zeolite P ex Crosfields .

NDOM is non detergent organic matter

,3 Sokalan HP23 is a grafted co-polymer of polyethylene oxide and polyvinylacetate available from BASF coated percarbonate available from Interox Dequest 2047 is ethylene diamine tetra methylene phosphonate available from Monsanto Dequest 2016 is ethylene hydroxy diphosphonate available from Monsanto

Comparative Examples A to D The stock composition of table 1 was mixed with swelling polymeric disintegrant granule*⁷, starch*⁸ and/or acetate to form comparative examples A, B and D as shown in table 2 which have the approximate compositions given in table 3. All amounts in table 2 are given* as parts by weight . Example C was made from the stock powder formulation only.

Table 2; preparation of comparative examples A to D.

Water Swellable disintegrant granule*⁷ was Nilyn LX-16 ex FMC Corporation, USA; a water-insoluble compacted cellulosic disintegrant granule.

Maize starch*⁸ ex Roquette Freres, Lestrem, France and having a mean particle size of approximately 15 micrometers.

Table 3; Composition of comparative examples A, B and D.

40g portions of each comparative composition were made into cylindrical tablets of 44.7 mm diameter and height 19-20 mm using a Graseby Specac laboratory tabletting machine. The compaction pressure used for each tablet was adjusted so that the tablets were all compacted to the same diametrical fracture stress of 30 kPa. The strength of the tablets, in their dry state as made on the press, was determined as their diametrical fracture stress DFS by the method detailed in the description above .

Examples 1 to 4

Examples 1 to 4 are examples according to the invention. The stock particulate composition of table 1 was mixed with varying amounts of a swelling polymeric disintegrant granule*⁷, and starch*⁸ to form examples 1 to 4 as shown in table 4 which have the approximate compositions given in table 5. All amounts in table 4 are given as parts by weight . These particulate compositions were compressed as detailed below to produce the tablets of the invention.

Table 4; preparation of examples 1 to .

Thus Examples 1 to 4 had the following approximate overall compositions as given in table 5. To 100 parts of examples 3 and 4, 3 parts by weight of Polyeythylene glycol 1500 was added at a level of 3 parts by weight to allow a DFS of 30 kPa to be obtained. Thus examples 1 and 2 are as % by weight and examples 3 and 4 as parts by weight with a total of 103 parts by weight.

Table 5; Composition* of examples 1 to 4

These compositions were compacted and the tablet strength determined according to the methods given above for comparative examples A to D.

Disintegration Results of comparative examples A to D and examples 1 to 4.

The speed of disintegration of tablets was measured under static conditions. A pre-weighed tablet was placed on a metal grid with 1 X 1 cm mazes and the tablet and grid was then immersed in 15° French Hardness tap water at 20°C so that 2cm of water was above the top of the immersed tablet. After 60 seconds the metal grid was carefully taken out of the water and seconds the metal grid was carefully taken out of the water and the wet tablet residue is weighed. If the tablet had fully disintegrated in this time then the time taken for 100% disintegration is recorded. The results are given in table 6.

Table 6; disintegration results of examples 1-4 and comparative examples A to D.

disintegration results in t is range were obtained.

The above results show that with the disintegration system of the invention good disintegration of a detergent tablet can be obtained in an acceptable time. In the absence of acetate or a polymeric material that acts as a hydrophilic pathway, the disintegrant granule gives reasonable disintegration (Example A) . Adding in 6%wt of maize starch improves the disintegration characteristics of the tablet, especially for Examples 1 and 2. Comparative example B shows excellent disintegration but has a total of 25.0%wt of the tablet formulation of sodium acetate and disintegrant granule (as a disintegration system) and additionally 3.7%wt of sodium citrate which may help with disintegration. Examples 1 to 4 comprise only between 10% and 16%wt of the tablet formulation of maize starch and disintegrant granule (as a disintegration system) and additionally 4.14-4.44%wt of sodium citrate which may help with disintegration. In the absence of the disintegrant granule, sodium acetate or starch, disintegration is poor (examples D and E) .

Comparative Examples E to I

The stock particulate composition of table 1 was mixed with varying amounts of a swelling polymeric disintegrant granule*⁷ and/or acetate to form comparative examples E to I as shown in table 7 and which have the approximate compositions given in table 8. All amounts in table 7 are given as parts by weight.

Table 7; preparation of comparative examples E to I .

Thus Comparative Examples E to I had the following approximate overall compositions as given in table 8. Table 8; Composition of comparative examples E to I .

Examples 5 and 6

Examples 5 and 6 are examples according to the invention. The stock particulate composition of table 1 was mixed with varying amounts of a swelling polymeric disintegrant granule*⁷, and starch*⁸ (as used above) to form examples 5 and 6 shown in table 9 which have the approximate compositions given in table 10. All amounts in table 9 are given as parts by weight. These particulate compositions were compressed as detailed below to produce the tablets of the invention.

Table 9; preparation of examples 5 and 6.

Thus Examples 5 and 6 had the following approximate overall compositions as given in table 10.

Table 10; overall compositions of examples 5 and 6.

Disintegration Results of comparative examples E to I and examples 5 and 6.

The speed of disintegration of the tablets was measured as for the examples above. The results are given in table 11.

Table 11; disintegration results of examples 5 and 6 and comparative examples E to I .

The above results show that with the disintegration system of the invention good disintegration of a detergent tablet can be obtained in an acceptable time . In the absence of acetate or a material that acts as a hydrophilic pathway, the disintegrant granule gives reasonable disintegration (Example E) . A comparison of Examples 5 and 6 with examples F and G respectively shows that using starch in place of acetate gives comparable disintegration characteristics. Comparative example I exhibits excellent disintegration but has a total of 26.0%wt of the tablet formulation of sodium acetate and disintegrant granule (as a disintegration system) and additionally 3.64%wt of sodium citrate which may help with disintegration. Examples 5 and 6 comprise only between 9 and ll%wt of the tablet formulation of maize starch and disintegrant granule (as a disintegration system) and additionally 4.39-4.49%wt of sodium citrate which may help -with disintegration.

Claims

1. A tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder, wherein the tablet or a discrete region thereof contains 1 to 20%wt based on the total weight of the tablet of a disintegration system comprising; a) water-swellable disintegrant granules with a mean particle size of between 500-1000 micrometers, and b) a hydrophilic starch or cellulose having a mean particle size of 150 micrometers or below, a solubility in water of less than lg/lOOg of water at 20°C and a development of expansion force of 2.0 Newtons/second or less .

2. A tablet according to claim 1 wherein the water-swellable disintegrant granules have a solubility in water of less than 0.5g/l00g of water at 20°C.

3. A tablet according to either claim 1 or claim 2 wherein the water-swellable disintegrant granules comprise polymeric material .

4. A tablet according to claim 3 wherein the water-swellable disintegrant granules comprise cellulose.

5. A tablet according to any one of the preceding claims wherein the disintegrant granules comprise 75 to 99.9%wt carrier material, 0.1 to 10%wt disintegrant material, and 0% to 24.5%wt of other material based on the total weight of the disintegrant particles.

6. A tablet according to any one of the preceding claims comprising between 1 and 11% by weight based on the total weight of the tablet of water-swellable disintegrant granules .

7. A tablet according to any one of the preceding claims wherein the water-swellable disintegrant granules have a mean particle size in the range from 600 to 900 micrometers .

8. A tablet according to any one of the preceding claims wherein the water-swellable disintegrant granules comprises disintegrant material, the disintegrant material having a development of expansion force of greater than 2.2 Newtons/second.

9. A tablet according to any one of the preceding claims comprising 1 to 15%wt of the hydrophilic starch or cellulose.

10. A tablet according to any one of the preceding claims wherein the hyd ophilic starch or cellulose has a mean particle size of 100 micrometers or below.

11. A tablet according to any one of the preceding claims wherein the hydrophilic starch or cellulose has a development of expansion force of 1.5 Newtons/second or less.

12. A tablet according to any one of the preceding claims wherein the hydrophilic starch or cellulose is a native starch or cellulose.

13. A tablet according to claim 12 wherein the native starch is maize, tapioca, rice or potato starch.

1 . A tablet according to claim 12 wherein the native cellulose is micro-crystalline cellulose, alpha - cellulose, citric acid intra cross linked cellulose or sulphur grafted cellulose.

15. A tablet according to any one of the preceding claims wherein the tablet or a discrete region thereof comprises said disintegration system in an amount of from 8 to 16% by weight based on the total weight of the tablet or region thereof .

16. A tablet according to any one of the preceding claims wherein said tablet further comprises water-soluble disintegration-promoting particles containing at least 40% (by weight of the particles) of one or more materials selected from the group consisting of

• compounds with water-solubility exceeding 50 grams per 100 grams water at 20°C

• sodium tripolyphosphate containing at least 50% of its own weight of the phase I anhydrous form

• sodium tripolyphosphate which is partially hydrated so as to contain water of hydration in an amount which is at least 0.5% by weight of the sodium tripolyphosphate in the particles.

17. A tablet according to claim 16, wherein said compounds with water-solubility exceeding 50 grams per 100 grams water are chosen from sodium acetate trihydrate, sodium acetate, sodium citrate dihydrate or urea.

18. A tablet according to either claim 16 or 17, wherein the tablet contains from 2 to 10 wt% of said water-soluble disintegration-promoting particles .

19. A tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder, wherein the tablet or a discrete region thereof contains 1 to 20%wt based on the total weight of the tablet of a disintegration system comprising; b) water-swellable disintegrant granules with a mean particle size of between 600-900 micrometers, and b) a hydrophilic starch or cellulose having a mean particle size of 250 micrometers or below, a solubility in water of less than lg/lOOg of water at 20°C and a development of expansion force of 2.0 Newtons/second or less.

20. A disintegrant system for a tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder, the disintegration system comprising; a) water-swellable disintegrant granules with a mean particle size of between 500-1000 micrometers, and b) a hydrophilic starch or cellulose having a mean particle size of 150 micrometers or below, a solubility in water of less than lg/lOOg of water at 20°C and a development of expansion force of 2.0 Newtons/second or less.

1. A process for making a tablet of compacted particulate detergent composition comprising non-soap surfactant and detergency builder which process comprises;

1) mixing 1 to 20%wt based on the total weight of the tablet of a disintegration system comprising; a) water-swellable disintegrant granules with a mean particle size of between 500-1000 micrometers, and b) a hydrophilic starch or cellulose having a mean particle size of 150 micrometers or below, a solubility in water of less than lg/lOOg of water at 20°C and a development of expansion force of 2.0 Newtons/second or less, with

2) other constituents of a detergent composition including non-soap surfactant and detergency builder, placing a quantity of resulting particulate composition within a mould and compacting that composition within the mould.