EP1412468A1

EP1412468A1 - Detergent compositions

Info

Publication number: EP1412468A1
Application number: EP02747473A
Authority: EP
Inventors: Olaf Cornelis P. Unilever R & D Vlaardingen BEERS; Erik Ch. Unilever R & D Vlaardingen BERDEN; Manoe Unilever R & D Vlaardingen HEXSPOOR; Christophe M. B. Unilever Philippines Inc JOYEUX
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2001-08-01
Filing date: 2002-07-25
Publication date: 2004-04-28
Also published as: WO2003014286A1

Abstract

A detergent tablet comprising water swellable detergency builder and organic surfactant, a detergent base powder and optionally post dosed materials and wherein the base powder is obtainable by a process comprising the steps: (i) mixing and agglomerating a liquid binder comprising organic surfactant with a solid starting material in a high-speed mixer; (ii) mixing the material from step (i) in a moderate- or low-speed mixer; (iii) feeding the material from step (ii) and a liquid binder into a gas fluidisation granulator and further agglomerating, and (vi) optionally, drying and/or cooling. The detergent tablets show good retention of strength properties upon storage.

Description

DETERGENT COMPOSITIONS

This invention relates to detergent tablets, especially those for use in the washing of fabrics. These tablets are intended to disintegrate completely when placed in water and thus to be consumed in a single use .

Detergent compositions in tablet form and intended for fabric washing have been described in a number of patent documents including, for example EP-A-711827, WO-98/42817 and WO-99/20730 (Unilever) and are now sold commercially. Tablets have several advantages over powdered products: they do not require measuring and are thus easier to handle and dispense into the washload, and they are more compact, hence facilitating more economical storage.

Tablets of a detergent composition have frequently been made by compressing or compacting a composition in particulate form; tablets of the present invention are also made this way. 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. Additionally the tablets should exhibit good storage stability especially with respect to strength.

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. Tableting 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 whilst providing tablets which exhibit good storage stability.

Organic surfactants function as a binder in detergent tablets and help to plasticise the tablets. However, they 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 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 already known to make tablets from compositions which consist of (i) base-powder particles which contain organic surfactant and other materials including detergency builder materials and (ii) various post-dosed ingredients, including water-soluble salts.

It is well known that detergent tablets, like detergent compositions generally, can be made using water-soluble or water-insoluble detergency builder. The water-soluble builder commonly used is sodium tripolyphosphate . However it may be necessary to restrict the amount of this material in order to meet regulatory constraints on the amount of phosphate in detergent compositions.

The alternative of using a water-insoluble detergency builder, such as zeolite, also encounters problems in that it can be even more difficult to make tablets with satisfactory strength and speed of disintegration. Such builders generally swell on contact with water and this usually leads to reduced strength of the tablet upon storage. Current practice in the commercial market in Europe is that when zeolite is used as the detergency builder, some expedient is adopted to assist disintegration. One possibility, is to use a tablet core which is not very strong, but dissolves rapidly, and enclose it in a soluble coating to strengthen the weak tablet core.

Other tablets which have been sold commercially and are exemplified in EP-A-838519 contain a highly soluble salt to promote disintegration. They also utilise zeolite MAP which aids disintegration because it swells on contact with water.

WO 00/53716 (Henkel) discloses washing tablets comprising non- ionic surfactants, phosphate builders and Faujasite type zeolites, where the ratio of non-ionic surfactants: zeolite is between 1: 20 and 1:1.

WO 01/04256 (Henkel) discloses an auxiliary disintegration agent for shaped bodies, said agents comprising 20 to 95% wt phosphate and 0.1 to 9%wt zeolite.

WO 00/77147 (Unilever) discloses a process for producing granular detergent compositions wherein a liquid binder is contacted with a solid starting material in a high-speed mixer and the resulting mixture treated in a medium- or low-speed mixer and finally in a gas fluidisation granulator, where more liquid binder is added.

WO 01/68795 (Unilever) discloses particulate detergent compositions comprising zeolite builder and which may be produced by the process disclosed in WO 00/77147. WO 00/77140 (Unilever) discloses non-spray dried granular components for zero phosphate detergent compositions.

The stability upon storage of detergent tablets comprising organic surfactant and water swellable detergency builders, for example zeolites, is often found to be inadequate. The strength of such tablets often falls rapidly upon storage and i the tablets are not able to withstand the stresses and strains exerted upon them during transport and handling, resulting in tablets which are prone to crumbling or breakage before use.

This problem is especially problematic with detergent compositions comprising zeolite MAP which has a greater tendency to swell upon contact with water than most other zeolites.

It is an aim of the invention to address one or more of the aforementioned technical problems.

We have now discovered how to provide a tablet, which comprises a water swellable detergency builder (such as zeolite) and organic surfactant and which has good strength both immediately after production and upon storage.

Broadly, the present invention addresses one or more of the aforementioned technical problems encountered in producing the detergent tablets from a detergent base powder composition which comprises a water swellable detergency builder and an organic surfactant by producing the base powder by the process as described herein.

We have found that detergent tablets of a particulate detergent composition comprising water swellable detergency builder and base powder particles comprising organic surfactant and made from the process as herein-described, exhibit good retention of strength upon storage. The storage stability has been found to be especially good at storage conditions of 37 °C, 70% relative humidity, 50 °C, 50% relative humidity and at 37 °C in closed systems .

For the purpose of this invention the reference to tablets of particulate detergent materials also refers to tablets which have a region of particulate detergent material . For example a region constituting from 50-100 wt% of the tablet.

Thus according to a first aspect of this invention, there is provided a detergent tablet of compacted particulate detergent material comprising water swellable detergency builder and organic surfactant wherein the particulate detergent material comprises a detergent base powder and optionally post dosed materials and further wherein the base powder is obtainable by a process comprising the steps :

(i) mixing and agglomerating a liquid binder comprising organic surfactant with a solid starting material in a highspeed mixer;

(ii) mixing the material from step (i) in a moderate- or low-speed mixer;

(iii) optionally feeding the material from step (ii) and a liquid binder into a gas fluidisation granulator and further agglomerating, and (iv) optionally, drying and/or cooling.

According to a second aspect of this invention, there is provided a detergent tablet of compacted particulate detergent material comprising water swellable detergency builder, water soluble detergency builder and organic surfactant wherein the particulate detergent material comprises a detergent base powder and post dosed materials added thereto and further wherein the base powder is obtainable by a process comprising the steps :

(ii) mixing the material from step (i) in a moderate- or low-speed mixer;

(iii) optionally feeding the material from step (ii) and a liquid binder into a gas fluidisation granulator and further agglomerating, and

(iv) optionally, drying and/or cooling, and further wherein the post dosed materials comprise a water soluble builder which is sodium tripolyphosphate .

In a third aspect there is provided a method of making a detergent tablet or region thereof of compacted particulate detergent material comprising water swellable detergency builder and organic surfactant comprising the steps of producing a detergent base powder by the steps:

(i) mixing and agglomerating a liquid binder comprising organic surfactant with a solid starting material in a high-speed mixer;

(ii) mixing the material from step (i) in a moderate- or low-speed mixer;

(iii) optionally feeding the material from step (ii) and a liquid binder into a gas fluidisation granulator and further agglomerating, and (iv) optionally, drying and/or cooling, then optionally mixing the base powder with the post dosed materials to form a particulate detergent material and compacting a quantity of the particulate detergent material in a mould to form the tablet or region thereof . The detergent tablets of the invention are produced from a particulate detergent composition comprising a base powder portion comprising organic surfactant and made according to the process described below and in WO 00/77147, and, optionally, although usually, post dosed materials added to the base powder portion to produce the particulate detergent composition. A water swellable detergency builder is also present in the detergent tablets and may be present either in the base powder particles or added as a post dosed material. Preferably the water swellable detergency builder is present in the base powder particles.

The invention is especially applicable to tablets comprising zeolite, especially zeolite MAP, as the water swellable detergency builder. In a preferred embodiment of the invention zeolite is present in the base powder and the post dosed ingredients mixed therewith to produce the composition to be compacted into a tablet comprise a water soluble builder such as sodium tripolyphosphate . The tripolyphosphate used is preferably at least 50% by weight is in the Phase I form.

Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of 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.

A detergent tablet may be made from one or more compositions and so 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 necessarily 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 each discrete region of the tablet will preferably have a mass of at least 10% of the whole tablet, which may be a mass of at least 4gm.

For a heterogeneous tablet having more than one discrete region, for example a tablet with two layers of different composition, it is possible that one region will be provided by a composition in accordance with this invention while another region will be provided by some other composition. It is also possible that two regions would be provided by different compositions both of which however, embody the present invention.

Process to produce the base powder The process used to produce the base powder particles is fully described in WO 00/77147 (Unilever) the contents of which is incorporated herein by reference .

The process is carried out using a high-speed mixer, a moderate- or low-speed mixer and optionally, although usually, a gas fluidisation granulator.

The high- and moderate- or low-speed mixers: Steps (i) and (ii) The mixers suitable for use in the process whether of high-, moderate- or low-speed, are fully described in WO 00/77147 as are suitable operating conditions for these mixers and are applicable to the present invention. All operating conditions disclosed in WO 00/77147 are incorporated herein by reference.

The operating conditions disclosed in WO 00/77147 include the following operating conditions.

The minimum tip speed of the tools in the high-speed mixer being preferably at least 5 m/s with the maximum tip speed preferably no greater than 60 m/s. The high-speed mixer is preferably operated at a minimum Froude Number of at least 5 and with a maximum Froude Number preferably no greater than 750. The Froude number is calculated as in WO 00/77147.

The maximum tip speed of the tools in the moderate- or low- speed mixer is preferably less than 15 m/s and the minimum tip speed is preferably at least lm/s. The moderate- or low-speed mixer is preferably operated at a maximum Froude Number of less than 30 and the minimum Froude Number is preferably at least 0.15.

In specifying any particular preferred tip speed range herein no particular maximum tip speed or Froude Number is associated with any particular minimum tip speed or Froude Number.

The essential difference between the moderate- or low-speed mixer and the high-speed mixer in the process is that the moderate- or low-speed mixer operates at a lower tip speed and/or lower Froude number, preferably both.

In addition to the stirring/mixing action of the tools, the moderate- or low-speed mixer may contain cutters as disclosed in WO 00/77147. The residence time in the high-speed mixer should be relatively short, preferably from about 1 to 60 seconds. The residence time in the moderate- or low-speed mixer should generally be longer that that in the high-speed mixer. Preferably it is in the range of from about 30 seconds to 10 minutes.

The temperature in the high- and moderate- or low-speed mixers can be elevated and/or lowered by any appropriate means . The process in the mixers can be batch or continuous, however it is preferably continuous.

The gas fluidisation granulator : Step (iii)

The optional third step of the process utilises a gas fluidisation granulator. In practice this step is usually employed. In this kind of apparatus, a gas (usually air) is blown through a body of particulate solids into or onto which is sprayed a liquid component. The gas fluidisation granulation and agglomeration process step is preferably carried out substantially as described in WO98/58046 and WO98/58047 (Unilever) , the contents of which are hereby incorporated by way of Reference .

The gas fluidisation apparatus basically comprises a chamber in which a stream of gas (hereinafter referred to as the fluidisation gas) , usually air, is used to cause turbulent flow of particulate solids to form a "cloud" of the solids and liquid binder is sprayed onto or into the cloud to contact the individual particles. As the process progresses, individual particles of solid starting materials become agglomerated, due to the liquid binder, to form granules. The gas fluidisation granulator is typically operated at a superficial air velocity of about 0.1-1.2 ms^"1, either under positive or negative relative pressure and with an air inlet temperature (ie fluidisation gas temperature) ranging from -10°C or 5°C up to 100°C. It may be as high as 200°C in some cases.

The fluidisation gas temperature, and thus preferably the bed temperature, may be changed during the granulation process as described in WO98/58048. It may be elevated for a first period, e.g. at up to 100°C or even up to 200°C and then at one or more other stages (before or after) , it may be reduced to just above, at, or below ambient, e.g. to 30°C or less, preferably 25°C or less or even as low as 5°C or less or -10°C or less.

In a preferred embodiment, the fluidisation gas temperature, and preferably also the bed temperature, is elevated for a first period and subsequently lowered in a second period.

Further details are given in WO 00/77147 and apply equally to the process used according to the present invention, including with respect to batch and continuous processes.

Preferably, the fluidisation gas temperature, and preferably also the bed temperature, is not lowered until agglomeration of the fluidising particulate solid material is substantially complete.

In addition to the fluidisation gas, a gas fluidisation granulator may also employ an atomising gas stream as described in WO 00/77147.

In a preferred embodiment, the bed temperature is maintained at around or near the pumpable temperature (as defined hereinbelow) of the liquid binder for at least part of the time and preferably for substantially the entire time the liquid binder is being sprayed onto the fluidising solids. This is especially preferred when the liquid binder is a structured blend (as described hereinbelow) .

Alternatively, it is preferred that one, and preferably both of the fluidisation gas temperature and the atomisation gas temperature be elevated to a temperature which is within 15°C (plus or minus) , and preferably within 10°C of the pumpable temperature of the liquid binder, especially when the liquid binder is a structured blend. The temperature should be elevated for at least part of, and preferably for subtantially all of the period over which the liquid binder blend is being sprayed onto the fluidising material.

In a preferred embodiment, one, and preferably both of the fluidisation gas temperature and the atomisation gas temperature are elevated so as to be at least at the pumpable temperature of the liquid binder, especially when the liquid binder is a structured blend.

As used herein, the "bed temperature" is measured according to the definition set out in WO 00/77147.

The gas fluidisation granulator may optionally be of the kind provided with a vibrating bed, particularly for use in continuous mode.

Optional drying and/or cooling : Step (iv)

For use, handling and storage, the granular detergent product must be in a free flowing state. Therefore, in a final step, the granules can be dried and/or cooled if necessary. This step can be carried out in any known manner, for instance in a fluid bed apparatus (drying and cooling) or in an airlift (cooling) . Drying and/or cooling can be carried out in the same fluid bed apparatus as used for the final agglomeration step simply by changing the process conditions employed as will be well-known to the person skilled in the art.

In a preferred embodiment, the entire process is continuous.

The liquid binder

In the process, the liquid binder is added in steps (i) and optionally also in step (iii) and comprises an organic surfactant. Liquid binder may also be added in step (ii) but it is preferred that little or no liquid is added. If added during step (ii) , it is preferred that of the total amount of liquid binder added in the process, less than 10 wt%, preferably less than 5 wt% is added in step (ii) .

The liquid binder added at each step may be the same or different and more than one liquid binder may be added in any one step.

The weight ratio of binder added in step (i) to that added in step (iii) is preferably in the range from 20:1 to 1:20, preferably from 10:1 to 1:10 and more preferably from 9:1 to 1:2. Preferably, of the total amount of liquid binder added in steps (i) and (iii) , at least 5 wt%, more preferably at least 10 wt% is added in step (iii) .

Generally, for the same process conditions, the higher the weight ratio of liquid binder added in step (i) to step (iii) , the higher the resulting bulk density. The bulk density of the granular detergent product can thus be controlled to a certain degree by altering the ratio of binder addition. The liquid binder may simply be pumped into the mixer of step (i) , and optionally the mixer of step (ii) , or may be introduced as a spray. The liquid binder is sprayed into the gas fluidisation granulator of step (iii) .

The liquid binder comprises organic surfactant and preferably one or more other components of the detergent tablet . Especially preferred suitable liquid components include anionic surfactants and acid precursors thereof, nonionic surfactants, fatty acids, water and organic solvents.

The liquid binder can also comprise solid components dissolved in or dispersed in a liquid component, such as, for example, inorganic neutralising agents and detergency builders. The only limitation is that with or without dissolved or dispersed solids, the liquid binder should be pumpable and capable of being delivered to the mixer and/or granulator in a fluid, including paste-like, form.

It is especially preferred that the liquid binder comprises an anionic surfactant. The content of anionic surfactant in the liquid binder may be as high as possible, e.g. at least 98 wt% of the liquid binder, or it may be less than 75 wt%, less than 50 wt% or less than 25 wt%. It may, of course constitute 5 wt% or less or not be present at all.

Suitable anionic surfactants are well-known to those skilled in the art and also are referred to below under the section "Organic surfactant".

It is very much preferred to form some or all of any anionic surfactant in situ in the liquid binder by reaction of an appropriate acid precursor and an alkaline material such as an alkali metal hydroxide, e.g. NaOH. Since the latter normally must be dosed as an aqueous solution, that inevitably incorporates some water. Moreover, the reaction of an alkali metal hydroxide and acid precursor also yields some water as a by-product .

However, in principle, any alkaline inorganic material can be used for the neutralisation but water-soluble alkaline inorganic materials are preferred. Another preferred material is sodium carbonate, alone or in combination with one or more other water-soluble inorganic materials, for example, sodium bicarbonate or silicate. If desired, a stoichiometric excess of neutralising agent may be employed to ensure complete neutralisation or to provide an alternative function, for example as a detergency builder, e.g. if the neutralising agent comprises sodium carbonate. Organic neutralising agents may also be employed.

Of course, if the liquid binder contains an acid precursor of an anionic surfactant, the acid precursor can be neutralised or neutralisation completed in situ in the mixer and/or granulator by either contacting with a solid alkaline material or adding a separate liquid neutralising agent to the mixer and/or granulator. However, neutralisation in the mixer and/or granulator is not a preferred feature of this invention.

The liquid acid precursor is preferably selected from linear alkyl benzene sulphonic (LAS) acids, alphaolefin sulphonic acids, internal olefin sulphonic acids, fatty acid ester sulphonic acids and combinations thereof. The process is especially useful for producing compositions comprising alkyl benzene sulphonates by reaction of the corresponding alkyl benzene sulphonic acid, for instance Dobanoic acid ex Shell. Linear or branched primary alkyl sulphates (PAS) having 10 to 15 carbon atoms can also be used.

In a preferred embodiment, the liquid binder comprises an anionic surfactant and a nonionic surfactant in the ratios referred to below under the heading "Organic surfactant". If the liquid binder comprises at least some acid precursor of an anionic surfactant and a nonionic surfactant, then the weight ratio of anionic surfactant, including the acid precursor, to nonionic surfactant can be higher, for example 15:1.

The nonionic surfactant component of the liquid binder may be any one or more liquid nonionics selected from those referred to below under the heading "Organic surfactant". Non- ethoxylated nonionic surfactants include alkyl polyglycosides, glycerol monoethers, and polyhydroxyamides (glucamide) .

In a preferred embodiment the liquid binder is substantially non-aqueous, that is, the total amount of water therein is not more than 20 wt% of the liquid binder, preferably not more than 15 wt% and more preferably not more than 10 wt%. However, if desired, a controlled amount of water may be added to facilitate neutralisation. Typically, the water may be added in amounts of 0.5 to 2 wt% of the final detergent product. Typically, from 3 to 4 wt% of the liquid binder may be water as the reaction by-product and the rest of the water present will be the solvent in which the alkaline material was dissolved. The liquid binder is very preferably devoid of all water other than that from the latter-mentioned sources, except perhaps for trace amounts/impurities .

Alternatively, an aqueous liquid binder may be employed. This is especially suited to manufacture of products which are adjuncts for subsequent admixture with other components to form a fully formulated detergent product. Such adjuncts will usually, apart from components resulting from the liquid binder, mainly consist of one, or a small number of components normally found in detergent compositions, e.g. a surfactant or a builder such as zeolite or sodium tripolyphosphate. However, this does not preclude use of aqueous liquid binders for granulation of substantially fully formulated products. In any event, typical aqueous liquid binders include aqueous solutions of alkali metal silicates, water soluble acrylic/maleic polymers (e.g. Sokalan CP5) and the like.

The liquid binder may optionally comprise dissolved solids and/or finely divided solids which are dispersed therein. The only limitation is that with or without dissolved or dispersed solids, the liquid binder should be pumpable and sprayable at temperatures of 50°C or greater or at any rate, 60°C or greater e.g. 75°C. Preferably it is solid at below 50°C, preferably at 25°C or less. The liquid binder is preferably at a temperature of at least 50°C, more preferably at least 60°C when fed into the mixer or gas fluidisation granulator.

According to the invention, liquid binders are considered readily pumpable if they have a viscosity of no greater than 1 Pa.s at a shear rate of 50 s^"1 and at the temperature of pumping. Liquid binders of higher viscosity may still in principle be pumpable, but an upper limit of 1 Pa.s at a shear rate of 50 s^_1 is used herein to indicate easy pumpability.

The viscosity can be measured, for example, using a Haake VT500 rotational viscometer as described in WO 00/77147. The "pumpable temperature" of the liquid binder is therefore defined herein as the temperature at which the liquid binder exhibits a viscosity of 1 Pa.s at 50 s^"1 .A definition of solid can be found in the Handbook of Chemistry and Physics, CRC Press, Boca Raton, Florida, 67th edition, 1986.

Structured liquid binder blends

In a preferred embodiment of this invention, the liquid binder further comprises a structurant . Liquid binders which comprise a structurant are referred to herein as structured blends. All disclosures made herein with reference to liquid binders apply equally to structured blends.

In the context of the present invention, the term "structurant" means any component which enables the liquid component to achieve solidification in the granulator and hence good granulation, even if the solid component has a low liquid carrying capacity.

Structurants may be categorised as those believed to exert their structuring (solidifying) effect by one of the following mechanisms, namely: recrystallisation (e.g. silicate or phosphates) ; creation of a network of finely divided solid particles (e.g. silicas or clays); and those which exert steric effects at the molecular level (e.g. soaps or polymers) such as those types commonly used as detergency builders . One or more structurants may be used.

Structured blends provide the advantage that at lower ambient temperatures they solidify and as a result lend structure and strength to the particulate solids onto which they are sprayed. It is therefore important that the structured blend should be pumpable and sprayable at an elevated temperature, e.g. at a temperature of at least 50°C, preferably of at least 60°C, and yet should solidify at a temperature below 50°C, preferably below 35°C so as to impart its benefit.

Typically, in the high-speed and moderate- or low-speed mixers the temperature is more than 10°C, preferably more than 20°C below the temperature at which the blend is prepared and pumped into the granulator.

The structurants cause solidification in the liquid binder component preferably to produce a blend strength as follows. The strength (hardness) of the solidified liquid component can be measured using an Instron pressure apparatus as described in WO 00/77147. A tablet of the solidified liquid component, taken from the process before it contacts the solid component, is formed of dimensions 14 mm in diameter and 19 mm in height. The tablet is then destroyed between a fixed and a moving plate, the moving plate moving towards the fixed plate. The speed of the moving plate is set to 5 mm/min, which causes a measuring time of about 2 seconds. The pressure curve is logged on a computer. Thus, the maximum pressure (at the moment of tablet breaking) is given and the E-modulus is calculated from the slope.

For the solidified liquid component, P_max at 20 °C is preferably a minimum of 0.1 MPa, more preferbaly 0.2 M Pa, e.g. from 0.3 to 0.7 M Pa. At 55°C, a typical range is from 0.05 to 0.4 M Pa. At 20°C, E_mod for the liquid blend is preferably a minimum of 3 M Pa, e.g. from 5 to 10 M Pa.

The structured blend is preferably prepared in a shear dynamic mixer for premixing the components thereof and performing any neutralisation of anionic acid precursor. Soaps represent one preferred class of structurant, especially when the structured blend comprises a liquid nonionic surfactant. In many cases it may be desirable for the soap to have an average chain length greater than the average chain length of the liquid nonionic surfactant but less than twice the average chain length of the latter.

It is very much preferred to form some or all of any soap structurant in situ in the liquid binder by reaction of an appropriate fatty acid precursor and an alkaline material such as an alkali metal hydroxide, e.g. NaOH. However, in principle, any alkaline inorganic material can be used for the neutralisation but water-soluble alkaline inorganic materials are preferred. In a liquid binder comprising an anionic surfactant and soap, it is preferred to form both the anionic surfactant and soap from their respective acid precursors . All disclosures made herein to formation of anionic surfactant by in situ neutralisation in the liquid binder of their acid precursors equally apply to the formation of soap in structured blends.

If desired, solid components may be dissolved or dispersed in the structured blend. The structured blend component preferably comprises, as % by weight of the structured blend, from 98 to 10 wt% of anionic surfactant, more preferably from 70 to 30%, and especially from 50 to 30 wt%; from 10 to 98 wt% of nonionic surfactant, more preferably from 30 to 70 wt%, and especially from 30 to 50 wt%; from 2 to 30 wt% of structurant, more preferably from 2 to 20%, yet more preferably from 2 to 15 wt%, and especially from 2 to 10 wt%.

The structured blend may also contain other organic solvents. Solid starting material

The solid starting materials of this invention are particulate and may be powdered and/or granular. As such, the solid starting material may be any component of the granular detergent product that is available in particulate form.

Preferably, the solid starting material with which the liquid binder is admixed comprises a detergency builder, especially a water swellable detergency builder such as a zeolite and especially zeolite MAP as referred to hereinbelow. Thus the water swellable builder can be present as the solid starting material in the process to make the base powder particles, or it can be added separately if another solid material is used as the solid starting material. It is especially preferred that the water swellable detergency builder is present at least in part as the solid starting material, more preferably at least 50%wt is present in the solid staring material, better at least 80%wt.

If the solid starting material comprises or substantially consists of an aluminosilicate builder, the weight ratio of liquid binder to the solid component is preferably from 0.2:1 to 0.8:1. If the solid component comprises or substantially consists of a phosphate builder, this ratio is preferably from

0.2:1 to 5:1.

Base powder and post dosed materials

Preferably the tablet or a region thereof is compacted from a composition which comprises 25 or 35% to 95 or 98% by weight of the base powder particles and 2 or 5% to 65 or 75% by weight of post dosed materials mixed therewith. It is further preferred that the composition comprises 30%, 33% or 40% to 60% or 70% by weight of base powder particles and 30% or 40% to 60%, 67%, or 70% by weight of post dosed materials.

It is especially preferred that the detergent tablets comprise zeolite, especially zeolite MAP, as the water swellable detergency builder and that the post dosed materials comprise from 5 to 60% by weight based on the total weight of the detergent tablet of water soluble builder, especially sodium tripolyphosphate having at least 50% of its own weight in the Phase I form.

The process described herein can be modified to include water soluble builders such as sodium tripolyphosphate among the solids supplied to the granulation process to produce base powder particles which comprise organic surfactant, water swellable detergency builder and water soluble builders. It is most preferred that the base powder particles comprise less than 10% by weight of water soluble builder and that the majority thereof is added as post dosed material.

The base powder particles may have average particle size in the range from 200 to 2000μm, more preferably from 250 to 1400μm. Fine particles, such as those smaller than 180μm or 200μm and oversized particles may be eliminated by sieving before tableting, if desired, although we have observed that this is not always essential.

Organic surfactant One or more organic surfactants are present in the detergent tablets. At least a part of the organic surfactant is added as a part of the liquid binder used to produce the base powder particles as disclosed in the method of making the base powder particles above .

Preferably the organic surfactants provide from 7 to 40% by weight of the total composition, more preferably from 8, 10 or 12% by weight up to 40% by weight. More organic surfactant may be present in the base powder particles or in the post dosed material.

Organic surfactant may be present solely in the base powder particles, or some may additionally be present as a part of the post dosed materials. Preferably the amount of organic surfactant outside the base powder particles is not more than 10% by weight of the composition of the tablet or region thereof, that is, at least 90% of the organic surfactant in the composition is contained in the base powder particles.

The organic surfactant preferably comprises anionic surfactant, either alone or mixed with nonionic surfactant.

Anionic surfactant may be present in an amount from 0.5 to 40% by weight, preferably from 2% or 4% up to 30% or 40% by weight of the total composition.

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

It is preferred that the organic surfactant comprises alkylbenzene sulphonates, particularly sodium linear alkylbenzene sulphonates having an alkyl chain length of C₈-Cι₅.

Such linear alkyl benzene sulphonates may provide 75 to 100 wt% of any anionic non-soap surfactant in the composition.

Further anionic surfactants which may be used are fatty acyl ester sulphonates of formula:

RCH-C0₂- 2M⁺

so₃-

in which R is an alkyl or alkenyl chain of 8 to 18 carbon atoms and M⁺ is a solubilising cation.

Various other anionic surfactants are available and can be used. Examples include olefin sulphonates of formula:

R CH-R¹ M⁺ I so₃- in which R is alkyl of 6 to 18 carbon atoms R¹ is methyl or ethyl and M⁺ is a solubilising cation.

The amount of non-soap anionic surfactant preferably lies in a range from 5 or 10% to 20 or 25 %wt of the overall tablet composition. The amount of non-soap anionic surfactant in the base powder particles preferably lies in a range from 10 to 40%wt of the weight of the particles themselves, preferably 15 to 35%wt, more preferably 18 to 30wt%.

Primary alkyl sulphate having the formula;

ROS0₃ ^" 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 a commercially significant anionic surfactant.

It is highly desirable to include one or more soaps of fatty acids. These are discussed above with respect to structurants These are preferably sodium soaps derived from naturally occurring fatty acids, for example, the fatty acids from coconut oil, beef tallow, sunflower or hardened rapeseed oil.

Suitable non-ionic 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 non-ionic surfactant compounds are alkyl (C₈-₂₂) phenol- ethylene oxide condensates, the condensation products of linear or branched aliphatic C_8-2o 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_n and C₁₂-i5 primary and secondary alcohols ethoxylated with an average of from 2 to 20 moles of ethylene oxide per mole of alcohol, preferably 5 to 9 moles. Of these the C₉-n and C1₂-₁5 primary and secondary alcohols ethoxylated with an average of from 5 , 6 , 7 or 8 moles of ethylene oxide per mole of alcohol are especially preferred.

It is also preferred that the compositions comprise less than 2% by weight, more preferably less than 1 % by weight, based upon the total weight of the composition, of C₉_u and/or C₁₂-₁₅ primary and secondary alcohols ethoxylated with an average of 4 or less moles of ethylene oxide per mole of alcohol. Most preferably the compositions are substantially free of said primary and secondary ethoxylated alcohols.

The amount of non-ionic surfactant may lie in a range from 2 to 40%, better 2.5 or 3% up to 20% by weight of the composition. Many non-ionic surfactants are liquids and may be absorbed onto particles of the composition, prior to compaction into tablets.

When both anionic and nonionic surfactants are used as the organic surfactant, the weight ratio of anionic surfactant: nonionic surfactant is preferably in the range from 4:1 to 1:2, more preferably 3:1 to 1.1.5, most preferably 2.5:1 to 1:1.2.

A mixture of a linear alkylbenzene sulphonate having an alkyl chain length of C₈-C_15/ especially sodium, with a C₉-_n or C12-₁5 primary or secondary alcohol ethoxylated with an average of from 5 to 9 moles of ethylene oxide per mole of alcohol is especially preferred.

Amphoteric surfactants which may be used include amphopropionates of the formula:

O CH₂CH₂OH

II I

RC— NH— CH₂CH₂— N-CH₂CH₂C0₂Na

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 CH0HCH₂S0₃ - (sulfobetaine or hydroxy sultaine) .

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

where R_x is Cι₀ to C₂o alkyl or alkenyl; R₂, R₃ and R₄ are each hydrogen or Ci to C₄ alkyl, while n is from 1 to 5.

Cationic 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 X^" is a counterion.

The amount of amphoteric surfactant, if any, may be from 3% to 20 or 30% by weight of the tablet or region thereof, the amount of cationic surfactant, if any, may be from 0.5% to 10 or 20% by weight of the tablet or region thereof .

The base powder particles may provide at least 50% by weight or even more such as at least 52 or at least 55% of the tablet or tablet region. In such a case the concentration of surfactant in the tablet or region may be substantial such as from 15% to 40% by weight of the tablet or tablet region. It is preferred that the amount of total organic surfactant in the tablet or region thereof is at least 10% or 12% by weight in any event.

Water swellable detergency builder

The water swellable detergency builder may be any detergency builder which swells upon contact with water. The water swellable detergency builder may be present as post dosed material but it is preferred that the base powder particles comprise a proportion of thereof. Preferably at least 50% by weight of the water swellable builder is present in the base powder particles, more preferably at least 75% by weight. It is especially advantageous that substantially all the water swellable detergency builder is present in the base powder particles.

Water insoluble builders, especially aluminosilicates, most especially zeolites, are preferred.

Alkali metal aluminosilicates are strongly favoured as environmentally acceptable water-insoluble softening agents (detergency 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.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. They remove calcium ions from water by ion exchange .

The aluminosilicate detergency builder may be zeolite P, A, X or Y and mixtures thereof, with zeolites P and A being preferred.

Zeolite A is widely available commercially and can be used in this invention. Zeolite P is especially preferred. A type of zeolite P known as zeolite MAP, or maximum aluminium zeolite P, is the subject of EP-A-384070 and is available as DOUCIL A24 ex Ineos Silicas. Zeolite MAP shows greater swelling characteristics on contact with water than many other zeolites and thus the present invention is especially applicable to detergent tablets comprising zeolite MAP.

The base powder particles preferably contain the water swellable detergency builder in an amount from 20 or 30% to 40 or 55% by weight of these particles .

It is preferred that the base powder particles comprise a greater percentage by weight of a water swellable builder such as zeolite than of a water soluble builder such as sodium tripolyphosphate when both types of builder are present in the base powder particles.

Materials which may be used in the detergent tablets of the invention will now be discussed in greater detail, and specific possibilities will be mentioned by way of example. Optional water soluble detergency builder

The preferred water soluble builder is a phosphate, especially a tripolyphosphate, most especially an alkali metal tripolyphosphate such as sodium tripolyphosphate .

Sodium tripolyphosphate is very well known as a water soluble 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. The resulting product is generally a mixture of the Phase I and Phase II forms. A process for the manufacture of particles containing a high proportion of the Phase I form sodium tripolyphosphate by spray drying below 420°C is given in US-A-4536377.

Phase I material is known to hydrate to the hexahydrate more rapidly than phase II material. It is also known to dissolve somewhat more rapidly when there is no obstacle to dispersion in the solution. However, during dissolution, this phase I material can form a viscous or solid mass which, in a confined space can hinder dissolution. For instance when making a slurry for spray drying, phase I tripolyphosphate can form so-called "grit", which is a mass of interlocked crystals.

The tripolyphosphate used is preferably at least partially in the Phase I form , more preferably at least 50% by weight is in the Phase I form, better at least 70% by weight. It is especially preferred that substantially all the sodium tripolyphosphate is in the phase I form. Preferably this sodium tripolyphosphate is also partially hydrated. The extent of hydration is desirably at least 0.5%wt. The sodium tripolyphosphate may incorporate from 0.5% up to 10% (by weight of the sodium tripolyphosphate) of water of hydration, e.g. from 1% to 4% or 5% by weight, preferably from 2% to 4%.

Suitable sodium tripolyphosphate is commercially available. Suppliers include Courbevoie, France and Rhodia, UK.

The sodium tripolyphosphate in the tablet or region thereof may consist partly of sodium tripolyphosphate which contains the Phase I form and partly of some other form of sodium tripolyphosphate provided the overall amount of tripolyphosphate complies with the requirement that at least 50% of it is in the Phase I form. For instance, the base powder particles might contain sodium tripolyphosphate in which the content of Phase I form was well above 50% by weight while the tablet or region thereof also contains additional sodium tripolyphosphate which is in the anhydrous Phase II form.

The sodium tripolyphosphate is preferably hydrated by a process which leads to a homogenous distribution of the water of hydration within the tripolyphosphate. This can be accomplished by exposing anhydrous sodium tripolyphosphate to steam or moist air.

The sodium tripolyphosphate is preferably in a porous form so as to have high surface area. This can be achieved by spray drying the tripolyphosphate. Porosity can be enhanced 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 higher surface area than porous beads of tripolyphosphate obtained without blowing agent .

Particles of (sodium) tripolyphosphate preferably have a small mean particle size, such as not over 300μm, preferably 280μm or below. Small particle size can, if necessary, be achieved by grinding.

Uniform prehydration, high Phase I content, porosity and small particle size all 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 (i.e. 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 Rhodia-Chemie which has been found to be particularly suitable. It consists of porous particles of small particle size (mean size below 250μm) with 70% Phase I form and prehydrated with 3.5% water of hydration.

Preferably the total amount of water soluble builder, e.g. sodium tripolyphosphate, in the composition is at least 15% by weight, better in a range of from 20, 25 or 30 % to 50% by weight .

If base powder particles include some water soluble builder, especially sodium tripolyphosphate, then it is typically in an amount of from 7-40% by weight based on the weight of the particles. However it is preferred that the base powder particles contain less than 10% by weight of water soluble builder, more preferably less than 5%wt, especially less than 2%wt and most especially that the particles are substantially free of said water soluble builder.

Where the water soluble detergency builder is also present in the detergent tablet, the preferred ratio of soluble builder : water swellable builder lies in the range of from 3:1 to 1:2.5, better 2.5:1 to 1:1.5, especially 2.2:1 to 1:1. It is preferred that the base powder particles comprises a greater amount of the water swellable detergency builder than water soluble builder if both types of builder are used in these particles.

The post dosed material preferably comprises at least 60% by weight, more preferably at least 80% by weight, and especially substantially all of any sodium tripolyphosphate present in the tablet or region thereof.

Optional water soluble disintegration material

The tablets of the invention optionally comprise from 2% to 10% by weight of a material, such as a salt, which has a solubility in deionised water at 20°C of at least 50 grams per 100 grams of de-ionised water. Preferably amounts of from 2 to 5 or 7% by weight are used. The highly soluble material may be included in the base powder particles or as part of the post dosed material .

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 required to form a saturated solution in 100 grams of water at 20°C:- Material Water Solubility (g/lOOg)

Sodium citrate dihydrate 72

Potassium carbonate 112 Sodium acetate 119

Sodium acetate trihydrate 76

Magnesium sulphate 7H₂0 71

Urea >100

The solubilities of some other common materials at 20°C are:-

Material Water Solubility (g/lOOg)

Sodium chloride 36

Sodium sulphate decahydrate 21.5 Sodium carbonate anhydrous 8.0

Sodium percarbonate anhydrous 12

Sodium perborate anhydrous 3.7

Sodium tripolyphosphate anhydrous 15

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 salt) . However, the said particles may contain material of such solubility in a mixture with other material, provided that material of the specified solubility provides at least 40% by weight of these particles.

Preferred materials are sodium acetate in a partially or fully hydrated form such as sodium acetate trihydrate, urea or sodium citrate dihydrate. Optional water-swellable disintegrant

Another material which may be present is a water-swellable but dispersible disintegrant material which does not have detergency building properties. This is typically a water- insoluble, water-swellable disintegrant material.

A number of water-insoluble, water-swellable materials are known to be useful as tablet disintegrants . Although insoluble, these materials are generally dispersible in water. A discussion of such materials is found in "Drug Development and Industrial Pharmacy", Volume 6, pages 511-536 (1980) . Such materials are mostly polymeric in nature and many of them are of natural origin. Such disintegrants include starches, for example, maize, rice and potato starches, and starch derivatives, such as Primojel™, and Explotab™, which are both forms of sodium carboxymethyl starch also known as 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 from

Rettenmaier and cellulose derivatives, from example Courlose™ and Nymcel™, sodium carboxymethyl cellulose, Ac-di-Sol™ cross- linked modified cellulose, and Hanfloc™ microcrystalline cellulosic fibers; and various synthetic organic polymers. 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. Suppliers of water-swellable disintegrant materials include Rettenmaier in Germany and FMC Corporation in USA.

The water swellable disintegrant material which is incorporated into the tablet composition preferably has a mean particle size in a range of from 250_;αm to l,500μm, more preferably from 700μm to l,100μm.

Optional bleach system Tabletted compositions according to the invention may be bleach-free or may contain a bleach system. If present, 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. Preferred inorganic persalts are sodium perborate monohydrate and tetrahydrate, and sodium percarbonate . If any peroxygen compound is present, the amount is likely to lie in a range from 5 to 50% by weight of the composition, preferably 10 to 20 or 25%.

Bleach activators may also be referred to as bleach precursors. Preferred examples include peracetic acid precursors, for example, tetraacetylethylene diamine (TAED) and perbenzoic acid precursors. N-ackyl ammonium acetonotriles as described in WO 96/40061 and US 6 225 274, sodium nonanoyloxy benzene sulphonate (SNOBS) and (6-nonanamidocaproyl) oxy benzene sulphonate (Na.COBS) as described in US 6 207 632 and EP 170 386 may be used. The quaternary ammonium and phosphonium bleach activators disclosed in US 4751015 and US 4818426 (Lever Brothers Company) are also of interest. A suitable bleach activator which is not a bleach precursor, is a transition metal catalyst as disclosed in EP-A-458397, EP-A-458398 and EP- A-549272. A bleach system may also include a bleach stabiliser (heavy metal sequestrant) such as ethylenediamine tetramethylene phosphonate, diethylenetriamine pentamethylene phosphonate or ethylene diamine di-succinate .

If a bleach system is present, the peroxygen bleach and/or bleach activator is preferably included as a post-dosed component .

Other optional materials

One or more polycarboxylate polymers may be included, 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. Amounts of from 0.5 to 5% by weight of the composition are typical.

Tablets may contain one of the detergency enzymes known 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™, as supplied by Gist-Brocades N.V., Delft, Holland and Alcalase™, and Savinase™, 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; and these granules or marumes present no problems with respect to compaction to form a tablet.

Tablets may also contain a fluorescer (optical brightener) , for example, Tinopal™ 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 may be included. 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, 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.

It may also be desirable to include an alkali metal silicate, particularly sodium ortho-, meta- or disilicate in amounts of for example 0.1 to 10 wt% to provide protection against corrosion of metal parts in washing machines, some measure of building and processing benefits in manufacture of the tablets. A composition for fabric washing will generally not contain more than 15 wt% silicate.

Further ingredients which can employed in fabric washing detergent tablets of the invention include anti-redeposition 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.

The above ingredients may be incorporated amongst the post- dosed constituents of the composition. Some of them, notably fluorescer, polycarboxylate polymers and anti-redeposition agents may be incorporated into the granulated base powder particles. Any constituents which are liquids such as nonionic detergents or perfumes may be incorporated within the granulated particles or may be sprayed onto those particles or the overall mixture. Preferably perfumes are sprayed onto the overall mixture so that they are the last ingredient added to the overall composition before tableting.

Tableting Tableting entails compaction of a particulate composition to produce a tablet. A variety of known tableting machinery can be used. Generally it will function by stamping a quantity of the particulate composition which is confined in a die.

The mould in which the tablet is formed may be provided by an aperture within a rigid structure and a pair of dies which can be urged into the aperture towards each other, thereby compacting the contents of the aperture. A tableting machine may have a rotary table defining a number of apertures each with a pair or associated dies which can be driven into an apertures. Each die may be provided with an elastomeric layer on its surface which contacts the tablet material, as taught in WO 98/46719 or WO 98/46720.

Tableting 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 tableting at a temperature which is above ambient, the particulate composition is preferably supplied to the tableting machinery at an elevated temperature. This will of course supply heat to the tableting 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 60g, 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 invention will now be further illustrated with reference to the following non-limiting examples.

EXAMPLES a. Detergent tablet formulations and preparation.

Two sets of detergent tablets were prepared having the formulations as given in table 1. The base powder was produced from the ingredients listed above the term "base powder". When the base powder was mixed with the post dosed ingredients listed below the term "base powder", the resulting composition comprised the percentages by weight as given in the table .

Table 1

* C8-15 linear alkyl benzene sulphonate *² Maximum aluminium zeolite P ex Ineos Silicas, UK *³ Rhodiaphos HPA 3.5 ex Rhodia-Chemie, with over 70% Phase I Form and prehydrated with 3.5% water of hydration.

The base powder for both examples was made by; (i) mixing and granulating solid starting materials consisting of zeolite, light soda ash and sodium carboxymethylcellulose (SCMC) with the structured liquid binder as described below in a L dige Recycler (CB 30) (ii) transferring the material from the Recycler to a LUdige

Lδdige Ploughshare (KM 300) mixer (iii) transferring the material from the Ploughshare to a Vometec (Trade mark) fluid bed operating as a gas fluidisation granulator, adding further liquid binder and agglomerating, and (iv) finally drying/cooling the product in the fluid bed.

The conditions in steps (i) to (iii) were as follows: (i) Lδdige Recycler (CB 30)

Residence time : about 15 seconds Shaft rotation speed : 1000 rpm Tip speed : 15.7 m/s

Froude number : 168

(ii) Lδdige Ploughshare (KM 300) Residence time : about 3 minutes

Shaft rotation speed : 100 rpm

Choppers : Switched off

Tip speed : 2.62 m/s

Froude number : 2.8 Liquid binder : None added

(iii) Fluid bed (Batch Vomotec apparatus, batch size 10 kg:)

Superficial air velocity 1.0 m/s

FLuidisation gas temperature: 75°C

Atomisation gas temperature : Hot Atomisation air pressure : 3.5 bar

Height of nozzle

(above distributor plate) : 47 cm

Rate of spray-on of binder: 800 g/min

The liquid binder used in steps (i) and (iii) was a structured blend comprising the anionic surfactant, nonionic surfactant and soap components of the base powder. The blend was prepared by mixing 16.25 parts by weight of LAS acid precursor and 1.77 parts by weight fatty acid precursor of the soap in the presence of 13.14 parts by weight of the nonionic surfactant in a blend-loop and neutralising with 4.82 parts of a sodium hydroxide solution. The blend temperature in the loop was controlled by a heat-exchanger. The neutralising agent was a sodium hydroxide solution. The resulting blend had the following composition :

% by weight Sodium linear alkylbenzene sulphonate 48.25

Nonionic surfactant (7EO) 36.52

Soap 5.28

Water 9.95

The base powder was mixed with the post dosed ingredients by conventional mixing techniques.

Approximately 39.5 gram portions of the composition were compacted into tablets of 44mm diameter using a Korsch Rotary Tablet Press sufficient force applied to produce a tablet of the strengths below;

Example 1 - 50N strength

Example 2A - 5ON strength Example 2B - 65N strength

Example 2C - 8ON strength

The strength of the tablets was measured by compressing them radially, between the platens of a universal materials testing machine until fracture of the tablet occurred. Comparative Example A

Comparative detergent tablets were prepared having the formulation given in table 2. The base powder was prepared by a conventional granulation process where a liquid binder mixture was not used and step (i) described for the preparation of examples 1 and 2 was not used.

Table 2

Approximately 42 gram portions of the composition were compacted into tablets of 44mm diameter using a Korsch Rotary Tablet Press hand press with sufficient force applied to produce a tablet of 65 N. The strength of the tablets was measured as described for examples 1 and 2.

b. Storage tests

The strength upon storage of the tablets according to the invention and the comparative tablets was tested as below.

A batch of tablets from each of examples 1, 2 and comparative example A were packaged in flow-wrap packaging and stored in normal carton packs at the stated temperature and humidity for the given storage times. The initial strength of the tablets in each batch was measured and at the storage times stated, a tablet was selected and its strength tested.

The T=0 column shows the initial strength values determined for the tablets. The figures given at T=2 , T=4 or T=8 columns are the strength values after 2, 4 or 8 weeks respectively. The values in brackets show the strength values after the given storage time expressed as a percentage of its original (T=0) value .

50°C, 50% relative humidity storage

37 °C, Closed system

The tablets of the invention show better strength retention in all storage tests than the comparative tablets and especially for the closed systems.

Claims

1. A detergent tablet or region thereof of compacted particulate detergent material comprising water swellable detergency builder and organic surfactant wherein the particulate detergent material comprises a detergent base powder and optionally post dosed materials and further wherein the base powder is obtainable by a process comprising the steps :

(ii) mixing the material from step (i) in a moderate- or low-speed mixer;

(iii) feeding the material from step (ii) and a liquid binder into a gas fluidisation granulator and further agglomerating, and

(v) optionally, drying and/or cooling.

2. A tablet according to claim 1 wherein the water swellable detergency builder comprises zeolite.

3. A tablet according to claim 2 wherein the zeolite comprises maximum aluminium zeolite P.

4. A tablet according to any one of the preceding claims wherein the material from step (ii) of the process to produce the base powder is fed into step (iii) .

5. A tablet according to any one of the preceding claims wherein the liquid binder comprises one or more anionic surfactants or precursors thereof.

6. A tablet according to claim 5 wherein the liquid binder comprises linear alkylbenzene sulphonates and/or alkyl benzene sulphonic acids

7. A tablet according to any one of the preceding claims wherein the liquid binder comprises one or more nonionic surfactants .

8. A tablet according to claim 7 wherein the nonionic surfactant is C₉-n or C₁₂-₁₅ primary or secondary alcohol ethoxylated with an average of from 2 to 20 moles of ethylene oxide per mole of alcohol .

9. A tablet according to any one of the preceding claims wherein the liquid binder is a structured blend.

10. A tablet according to claim 9 wherein the structured blend comprises a soap structurant.

11. A tablet according to any one of the preceding claims wherein the liquid binder comprises soap, linear alkylbenzene sulphonate having an alkyl chain length of C₈- Ci₅, and C₉_n or C₁₂-i5 primary or secondary alcohol ethoxylated with an average of from 5 to 9 moles of ethylene oxide per mole of alcohol .

12. A tablet according to any one of the preceding claims wherein the liquid binder is at a temperature of at least 50°C when fed into step (i) and/or (iii) of the process.

13. A tablet according to any one of the preceding claims wherein the tablet comprises anionic surfactant and nonionic surfactant in weight ratio of anionic surfactant : nonionic surfactant of from 4:1 to 1:2.

14. A tablet according to any one of the preceding claims wherein the tablet further comprises a water soluble builder.

15. A tablet according to any one of the preceding claims wherein the post dosed material comprises water soluble builder which comprises sodium tripolyphosphate comprising at least 50% by weight in the Phase I form and or which is partially hydrated.

16. A detergent tablet or region therof of compacted particulate detergent material comprising water swellable detergency builder, water soluble detergency builder and organic surfactant wherein the particulate detergent material comprises a detergent base powder and post dosed materials added thereto and further wherein the base powder is obtainable by a process comprising the steps:

(ii) mixing the material from step (i) in a moderate- or low-speed mixer;

(iii) feeding the material from step (ii) and a liquid binder into a gas fluidisation granulator and further agglomerating, and (iv) optionally, drying and/or cooling, and further wherein the post dosed materials comprise a water soluble builder which is sodium tripolyphosphate.

17. A method of making a detergent tablet or region thereof of compacted particulate detergent material comprising water swellable detergency builder and organic surfactant comprising the steps of producing a detergent base powder by the steps :

(ii) mixing the material from step (i) in a moderate- or low-speed mixer;

(iii) feeding the material from step (ii) and a liquid binder into a gas fluidisation granulator and further agglomerating, and (iv) optionally, drying and/or cooling, then optionally mixing the base powder with the post dosed materials to form a particulate detergent material and compacting a quantity of the particulate detergent material in a mould to form the tablet or region thereof .