DISH WASHING COMPOSITIONS

Abstract: A tablet comprising: a) Particles containing sodium tripolyphosphate having a water of hydration in an amount from 1 % to 5 % by weight and wherein at least 50 % by weight of the sodium tripolyphosphate within the particles is of a phase I form; b) 0.1 to 2 wt.% of the total composition of a ketone which has at least 25 carbon atoms and; c) 0.5 to 10 wt.% of the total composition of an anionic surfactant.

Description: DISH WASHING COMPOSITIONS Technical Field The present invention is in the field of machine dishwashing. More specifically, the invention encompasses automatic dishwashing tablets . Background of the Invention A re-current problem with tablets is to obtain a tablet that dissolves quickly when added to the main wash of the machine but with sufficient strength so it does not crumble on storage or handling. Attempts to optimize the performance of tablet technology have primarily been directed towards modification of the dissolution profile of tablets. This is deemed especially important for those tablets that are placed in the dispenser of the machine so that they come into contact with a water spray at the very beginning of the wash process . EP-A-264, 701 describe machine dishwashing tablets comprising anhydrous and hydrated metasilicates, anhydrous triphosphate, active chlorine compounds and a tabletting aid consisting of a mixture of sodium acetate and spray-dried sodium zeolite. The specification teaches in warm water at least 65% of the tablet is available for the cleaning stage of the wash. DE-A-4229650 describes a tablet comprising tripolyphosphate hexahydrate and water-free silicate and optional cleaning components and tabletting auxiliaries. The tablets are said to exhibit rapid dissolution. The technology of the present invention provides fast dissolving tablets that clean well and do not crumble. Description of the Invention Accordingly, the present invention provides a tablet comprising: a) particles containing sodium tripolyphosphate having a water of hydration in an amount from 1% to 5% by weight and wherein at least 50% by weight of the sodium tripolyphosphate within the particles is of a phase I form; b) 0.1 to 2 wt . % of the total composition of a ketone which has at least 25 carbon atoms and; c) 0.5 to 10 wt. % of the total composition of an anionic surfactant In the most preferred aspect of this invention the tablet is for use in a machine dishwasher. Detailed Description of the Invention I . Sodium Tripolyphosphate with High Phase I Content Sodium tripolyphosphate of the present invention can be converted to the phase I form by heating to above the transition temperature at which phase II anhydrous sodium polyphosphate is transformed into the phase I form. A process for the manufacture of particles containing a high proportion of the phase I form of sodium tripolyphosphate by spray drying below 420°C is given in US-A-4536377. Suitable material is commercially available. Suppliers include Rhodia, Courbevoie, France and Albright & Wilson, Warley, West Midlands, UK. The sodium tripolyphosphate should be partially hydrated, but the phase I anhydrous form should also be present. Thus, the sodium tripolyphosphate in the particles may incorporate up to 5% (by weight of the sodium tripolyphosphate in these particles) of water of hydration. The extent of hydration is desirably from 1% to 4% or 5% by weight. This degree of hydration in general means that the sodium tripolyphosphate is partially hydrated. The sodium tripolyphosphate in these particles is preferably hydrated by a process, which leads to a homogeneous distribution of the water of hydration within the tripolyphosphate . This can be accomplished by exposing anhydrous sodium tripolyphosphate to steam or moist air. The particles preferably consist solely of sodium tripolyphosphate with a high content of the phase I form. The phase I content of the sodium tripolyphosphate being measured by X-ray diffraction, or IR. The particles preferably contain sodium tripolyphosphate in a porous form so as to have high surface area. This can be achieved by spray drying the tripolyphosphate as a mixture with a blowing agent, that is a compound such as ammonium carbonate, which decomposes to yield a gas during the course of the spray drying. This gives the dried material a porous structure, with higher surface area than hollow beads of tripolyphosphate obtained without blowing agent. The bulk density of the of sodium tripolyphosphate particles is preferably 0.75 Kg/M 3 or less, more preferably from 0.52 to 0.72 Kg/M 3 . The particles which contain or consist of sodium tripolyphosphate preferably have a small mean particle size, such as not over 300μm, better not over 250μm. Small particle size can if necessary be achieved by grinding. Uniform prehydration, 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 Rhodea 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 and prehydrated with 3.5% water of hydration. Preferably the said particles containing sodium tripolyphosphate with more than 50% of phase I material provide this phase I tripolyphosphate as at least 3% by weight of the tablet or region thereof . More preferably they provide sodium tripolyphosphate, including the phase I tripolyphosphate, in a quantity which is from 30% up to 40% or 60% by weight of the tablet or region thereof. The remainder of the tablet composition may include additional sodium tripolyphosphate. This may be in any form, including anhydrous sodium tripolyphosphate with a high content of the phase II form, hydrated sodium tripolyphosphate or some combination of the two. The total quantity of sodium tripolyphosphate, in all forms, present in the composition of a tablet or a region thereof will generally lie in a range from 15% to 85% by weight, more preferably at al level of 30 to 75 wt%. It is especially preferable if the total level of phosphate is greater than 60-wt% of the tablet. Surfactant material An anionic surfactant is present as an essential feature of the invention. Suitable anionic surfactants are listed in standard texts such as Surfactants in Consumer Products; Theory, Technology and Application, J. Falbe, ed. Springer-Verlag 1987 and Handbook of Surfactants, M.R. Porter, Blackie & Son, 1991. Preferred anionic surfactants include the conventional Cll- C18 alkyl benzene sulfonates and primary, secondary and random alkyl sulfates, the C 8 -C 18 alkyl alkoxy sulfates and the C 8 -Ci 8 alpha-sulfonated fatty acid esters and the like. Especially preferred is the sodium salt of a Cι 0 -C 22 sulphate, such as sodium lauryl sulphate (SLS) . It is preferred if at least 90 wt%, more preferably 95 wt%, most preferably of the anionic surfactant is in powdered form and has a particle size such that the length of the particles is at least double the width of the particles, more preferably the length of the particles is at least three times the width of the particles. It is also advantageous if the length of the particles of anionic surfactant is at least 1400 microns and the width is a maximum of 250 microns. It is also advantageous if the anionic surfactant is in powdered form and has a density at 25°C from 0.25 to 0.6 g/cm, preferably 0.4 to 0.6 g/cm. The anionic surfactant is present at levels from 0.5 to 10 wt% of the total composition, more preferably from 0.5 to 3 wt%. Other surfactant systems comprising surfactants selected from nonionic, cationic, ampholytic and zwitterionic surfactants and mixtures thereof may also be present in the composition at levels of 5 wt% of the total composition or less . Suitable low to non-foaming nonionic surfactants, include any alkoxylated nonionic surface-active agent wherein the alkoxy moiety is selected from the group consisting of ethylene oxide, propylene oxide and mixtures thereof. This nonionic surfactant is used to improve the detergency. Preferably the level of nonionic surfactant is at least 0.1% by weight, more preferably at least 0.5% by weight. Examples of suitable nonionic surfactants for use in the invention are the low- to non-foaming ethoxylated straight- chain alcohols preferred nonionic surfactants are Plurafac LF series ex BASF, the Synperonic series ex ICI; Lutensol ® LF series, ex BASF Company and the Triton ® DF series, ex Rohm & Haas Company. The Ketone , The ketones of the present invention are obtained by the ketonization of Cι 6 -C 2 2 carboxylic acids, carboxylic acid salts and mixtures thereof. The long-chain ketones may be prepared as described in US-A- 4,937,011. The ketones are prepared by catalytic elimination of C0 2 from higher monocarboxylic acids, more particularly relatively high molecular weight fatty acids or salts thereof. Preferred ketones are those obtained by the reaction of linear or branched, saturated or unsaturated carboxylic acids or carboxylic acid mixtures in which the carboxylic acids or some of them contain more than 12 carbon atoms and in particular, have a carbon chain-length of C X to C 30 and, on ketonization, react with water with elimination of carbon dioxide. Particularly preferred ketones are those obtained by the ketonization of Cι 6 -C 2 2 carboxylic acids or carboxylic acid salts and mixtures thereof as described in US-A-4,937,011. Mixtures of symmetrical and asymmetrical ketones are formed in which the asymmetrical ketones, commensurate with the material used, may have chain lengths other than C i4 or C 12 provided that a relatively long-chain radical is present in the molecule so that the total number of carbon atoms on average is at least about 25. Examples are heptacosanone- 14, hentriacontanone-16, pentatriacontanone-18 , nonatriacontanone-20, triatetracontanone-22 or nonacossanone-15, tri-triacontanone-17, heptatriacontanone- 19, hentetracontanone-21 and the like. Ketones or ketone mixtures useful in the present invention are normally solid at room temperature and have melting points in the range from 60° to 105°C. To make them easier to process and to improve their foam-inhibiting effect, it is preferred to disperse the ketones in a liquid carrier. In addition to water, suitable liquid phases are preferably organic carriers which have a low pour point or melting point of lower than about 5°C . It is also preferable to use free-flowing carriers or carrier mixtures which have a comparatively high viscosity and contribute stabilization of the dispersions. The liquid carrier phase may also have a foam-inhibiting effect or may be used solely as a carrier for the foam inhibitor of the invention. Particularly useful organic carrier liquids, which have an additional foam-inhibiting effect, are mineral oils having a boiling point above 140°C and branched alcohols containing 8 to 24 carbon atoms, such as 2-hexyl-l-decanol or 2-octyl-2- dodecanol . Other useful foam-inhibiting carrier liquids are liquid esters of branched or unsaturated fatty acids containing 8 to 18 carbon atoms with monohydric or polyhydric alcohols, for example glycol diesters or glycerol triesters of oleic acid, isostearic acid; esters based on branched-chain or unsaturated, liquid fatty alcohols containing 8 to 18 carbon atoms, for example isotridecyl alcohol or oleyl alcohol . Mixtures of these carriers may also be used. It is preferred to use organic carriers in which the ketones are soluble at elevated temperature and precipitate in finely divided form on cooling. To this end, the components are heated, a solution formed and then rapidly cooled with intensive stirring. Stable dispersions of finely divided foam inhibitors are formed. However, dispersions may also be prepared by stirring the finely ground, wax-like ketone or ketone mixture into the liquid phase. The dispersions to be processed preferably contain from about 5 to about 15% by weight of the ketone or mixtures of ketones. The carrier/ketone combination is present in the detergent composition in an amount of from 0.1 to 2 wt.%. In addition, the dispersion of the ketone in the liquid carrier may be stabilized by suitable additives. Suitable additives are, for example, magnesium stearate, calcium stearate or aluminum stearate in quantities of from about 0.3 to 3.0% by weight. Commercially available ketones of the type described above are available under the Dehypon Series from Henkel Kommanditgesellschaft auf Aktien, Germany. Builder material In addition to sodium tripolyphosphate builder of the invention further builders may be present. Suitable additional builders are the carboxylate or polycarboxylate builders containing from one to four carboxy groups, particularly selected from monomeric polycarboxylates or their acid forms, homo or copolymeric polycarboxylic acids or there salts in which the polycarboxylate comprises at least two carboxylic radicals selected from each other by not more than two carbon atoms . Preferred carboxylates include the polycarboxylate materials described in US-A-2 , 264 , 103 , including the water-soluble alkali metal salts of mellitic acid and citric acid, dipicolinic acid, oxydisuccinic acid and alkenyl succinates. The water-soluble salts of polycarboxylate polymers and copolymers, such as are described in US-A-3 , 308, 067 are also be suitable for use with the invention. Of the builder materials listed in the above paragraph, the preferred polycarboxylates are hydroxycarboxylates containing up to three carboxy groups per molecule, especially citric acid or its salt, particularly sodium citrate. If present it is preferable if the carboxylate builder is present at a level of at least 20-wt% of the total formulation, more preferably at a level greater than 30-wt%. Further soluble detergency builder salts which can be used with the present invention are poly-valent inorganic and poly-valent organic builders, or mixtures thereof. Non- limiting examples of suitable water-soluble, inorganic alkaline detergency builder salts include the alkali metal carbonates, bicarbonates, borates, phosphates, polyphosphates, tripolyphosphates, and phosphono carboxylates. Specific examples of such salts include the sodium and potassium tetraborates , carbonates, bicarbonates tripolyphosphates, orthophosphates and hexametaphosphates . Other suitable detergency builders organic alkaline compounds such as water-soluble amino polyacetates, e.g. sodium and potassium ethylenediamine tetraacetates, nitrilotriacetates and N- (2 -hydroxyethyl) nitrilodiacetates; water-soluble salts of phytic acid, e.g. sodium and potassium phytates; water-soluble polyphosphonates, including sodium, potassium and lithium salts of ethane-1- hydroxy-1, 1-diphosphonic acid; sodium, potassium and lithium salts of methylenediphosphonic acid and the like. It is to be understood that, while the alkali metal salts of the foregoing inorganic and organic poly-valent anionic builder salts are preferred for use herein from an economic standpoint, the ammonium, alkanolammonium, e.g. triethanol- ammonium, diethanolammonium, and the like, water-soluble salts of any of the foregoing builder anions are useful herein. Mixtures of organic and/or inorganic builder salts can be used herein. Preferably, the total amount of builders in the composition including the particles containing sodium tripolyphosphate (having a water of hydration in an amount from 1% to 5% by weight and wherein at least 50% by weight of the sodium tripolyphosphate within the particles is of a phase I form) is from 30 to 80% by weight, more preferably from 40 to about 70% by weight. Silica material Suitable forms of silica include amorphous silica, such as precipitated silica, pyrogenic silica and silica gels, such as hydrogels, xerogels and aerogels, or the pure crystal forms quartz, tridymite or crystobalite, but the amorphous forms of silica are preferred. Suitable silicas may readily be obtained commercially. They are sold, for example under the Registered Trade Name Gasil 200 (ex Crosfield, UK) . Preferably, the silica is in the product in such a form that it can dissolve when added to the wash liquor. Therefore, addition of silica by way of addition anti-foam particles of silica and silicone oil is not preferred. The particle size of the silica material of the present invention may be of importance, especially as it is believed that any silica material that remains undissolved during the washing process, may deposit on the glass at a later stage. Therefore, it is preferred that silica material are used that have a particle size (as determined with a Malvern Laser, i.e. "aggregated" particles size) of at most 40 μm, more preferably at most 30μm, most preferably at most 20μm provides better results in the wash. In view of incorporation in a cleaning composition, it is preferred that the particle size of the silica material is at least lμm, more preferably at least 2μm, most preferably at least 5μm. Preferably the primarily particle size of the silica is in general less than about 30nm, in particular less than about 25nm. Preferably, elementary particles size are less than 20nm or even lOnm. There is no critical lower limit of the elementary particle size; the lower limit is governed by other factors such as the manner of manufacture, etc. In general commercial available silicas have elementary particle sizes of 1 nm or more. Preferably, the silica material is present in the wash liquor at a level of at least 2.5xl0 " %, more preferably at least 12.5xl0 "4 %, most preferably at least 2.5xl0 "3 % by weight of the wash liquor and preferably at most lxl0 "1 %, more preferably at most 8xl0 "2 %, most preferably at most 5xl0 "2 % by weight of the wash liquor. Preferably, the level of dissolved silica material in the wash liquor is at least 80 ppm, more preferably at least 100 ppm, most preferably at least 120 ppm and preferably at most 1,000 ppm. It is noted that for the silica material to be effective, the lower level of dissolved silica material depends on the pH value, i.e. thus at pH 6.5, the level is preferably at least 100 ppm; at pH 7.0 preferably at least 110 ppm; at pH 7.5 preferably at least 120 ppm; at pH 9.5 preferably at least 200 ppm; at pH 10 preferably at least 300 ppm; at pH 10.5 preferably at least 400ppm. Preferably, the silica material is present in the cleaning composition at a level of at least 0.1%, more preferably at least 0.5%, most preferably at least 1% by weight of the cleaning composition and preferably at most 10%, more preferably at most 8%, most preferably at most 5% by weight of the cleaning composition. Silicates The composition optionally comprises alkali metal silicates. The alkali metal may provide pH adjusting capability and protection against corrosion of metals and against attack on dishware, including fine china and glassware benefits. If silicates are present, they are preferably included at a level of from 1% to 30%, preferably from 2% to 20%, more preferably from 3% to 10%, based on the weight of the composition. The ratio of Si0 2 to the alkali metal oxide (M 2 0, where M=alkali metal) is typically from 1 to 3.5, preferably from 1.6 to 3, more preferably from 2 to 2.8. Preferably, the alkali metal silicate is hydrous, having from 15% to 25% water, more preferably, from 17% to 20%. The highly alkali metasilicates can in general be employed, although the less alkaline hydrous alkali metal silicates having a Si0 2 :M 2 0 ratio of from 2.0 to 2.4 are, as noted, greatly preferred. Anhydrous forms of the alkali metal silicates with a Si0 2 :M 2 0 ratio of 2.0 or more are also less preferred because they tend to be significantly less soluble than the hydrous alkali metal silicates having the same ratio. Sodium and potassium, and especially sodium, silicates are preferred. A particularly preferred alkali metal silicate is a granular hydrous sodium silicate having a Si0 2 :Na 2 0 ratio of from 2.0 to 2.4 available from Ak30 PQ Corporation, especially preferred is Britesil H20 and Britesil H24. Most preferred is a granular hydrous sodium silicate having a Si0 2 :Na 2 0 ratio of 2.0. While typical forms, i.e. powder and granular, of hydrous silicate particles are suitable, preferred silicate particles having a mean particle size between 300 and 900 microns and less than 40% smaller than 150 microns and less than 5% larger than 1700 microns. Particularly preferred is a silicate particle with a mean particle size between 400 and 700 microns with less than 20% smaller than 150 microns and less than 1% larger then 1700 microns. Compositions of the present invention having a pH of 9 or less preferably will be substantially free of alkali metal silicate. Enzymes Enzymes may be present in the compositions of the invention. Examples of enzymes suitable for use in the cleaning compositions of this invention include lipases, peptidases, amylases (amylolytic enzymes) and others which degrade, alter or facilitate the degradation or alteration of biochemical soils and stains encountered in cleansing situations so as to remove more easily the soil or stain from the object being washed and to make the soil or stain more removable in a subsequent cleansing step. Preferred Examples of these enzymes are lipases, amylases and proteases . The enzymes most commonly used in machine dishwashing compositions are amylolytic enzymes. Preferably, the composition of the invention also contains a proteolytic enzyme . Enzymes may be present in a weight percentage amount of from 0.2 to 5% by weight. For amylolytic enzymes, the final composition will have amylolytic activity of from 10 2 to 10 δ Maltose units/kg. For proteolytic enzymes the final composition will have proteolytic enzyme activity of from 10 s to 10 9 Glycine Units/kg. Bleach Material Bleach material may optionally and preferably be incorporated in composition for use in processes according to the present invention. These materials may be incorporated in solid form or in the form of encapsulates and less preferably in dissolved form. The bleach material may be a chlorine- or bromine-releasing agent or a peroxygen compound. Peroxygen based bleach materials are however preferred. Organic peroxy acids or the precursors therefor are typically utilized as the bleach material. The peroxyacids usable in the present invention are solid and, preferably, substantially water-insoluble compounds. By "substantially water-insoluble" is meant herein a water-solubility of less than about 1% by weight at ambient temperature. In general, peroxyacids containing at least about 7 carbon atoms are sufficiently insoluble in water for use herein. Inorganic peroxygen-generating compounds are also typically used as the bleaching material of the present invention. Examples of these materials are salts of monopersulphate, perborate monohydrate, perborate tetrahydrate, and percarbonate . Monoperoxy acids useful herein include alkyl peroxy acids and aryl peroxyacids such as peroxybenzoic acid and ring-substituted peroxybenzoic acids (e.g. peroxy-alpha- naphthoic acid) ; aliphatic and substituted aliphatic monoperoxy acids (e.g. peroxylauric acid and peroxystearic acid) ; and phthaloyl amido peroxy caproic acid (PAP) . Typical diperoxy acids useful herein include alkyl diperoxy acids and aryldiperoxy acids, such as 1, 12-di-peroxy- dodecanedioic acid (DPDA) ; 1, 9-diperoxyazelaic acid, diperoxybrassylic acid, diperoxysebacic acid and diperoxy- isophthalic acid; and 2-decyldiperoxybutane-l, 4-dioic acid. Peroxyacid bleach precursors are well known in the art. As non-limiting examples can be named N,N,N' ,N' -tetraacetyl ethylene diamine (TAED) , sodium nonanoyloxybenzene sulphonate (SNOBS) , sodium benzoyloxybenzene sulphonate (SBOBS) and the cationic peroxyacid precursor (SPCC) as described in US-A-4 , 751, 015. If desirably a bleach catalyst, such as the manganese complex, e.g. Mn-Me TACN, as described in EP-A- 0458397, or the sulphonimines of US-A-5, 041, 232 and US-A-5 , 047 , 163 , is to be incorporated, this may be presented in the form of a second encapsulate separately from the bleach capsule or granule. Cobalt catalysts can also be used. Among suitable reactive chlorine- or bromine-oxidizing materials are heterocyclic N-bromo and N-chloro imides such as trichloroisocyanuric, tribromoisocyanuric, dibromoisocyanuric and dichloroisocyanuric acids, and salts thereof with water-solubilizing cations such as potassium and sodium. Hydantoin compounds such as 1, 3-dichloro-5, 5- dimethyl-hydantoin are also quite suitable. Particulate, water-soluble anhydrous inorganic salts are likewise suitable for use herein such as lithium, sodium or calcium hypochlorite and hypobromite. Chlorinated trisodium phosphate and chloroisocyanurates are also suitable bleaching materials. Encapsulation techniques are known for both peroxygen and chlorine bleaches, e.g. as described in US-A-4 , 126, 573 , US- A-4,327,151, US-A-3 , 983 , 254 , US-A-4 , 279, 764 , US-A-3 , 036 , 013 and EP-A-0,436, 971 and EP-A-0, 510 , 761. However, encapsulation techniques are particularly useful when using halogen based bleaching systems. Chlorine bleaches, the compositions of the invention may comprise from about 0.5% to about 3% avCl (available Chlorine) . For peroxygen bleaching agents a suitable range are also from 0.5% to 3% AvO (available Oxygen). Preferably, the amount of bleach material in the wash liquor is at least 12.5xl0 "4 % and at most 0.03% AvO by weight of the liquor. Water Soluble Polymeric Polycarboxylic Compounds A water soluble polymeric polycarboxylic compound is advantageously present in the dish wash composition. Preferably these compounds are homo- or co-polymers of polycarboxylic compounds, especially co-polymeric compounds in which the acid monomer comprises two or more carboxyl groups separated by not more than two carbon atoms. Salts of these materials can also be used. Particularly preferred polymeric polycarboxylates are co- polymers derived from monomers of acrylic acid and maleic acid. the average molecular weight of these polymers in the acid form preferably ranges from 4,000 to 70,000. Another type of polymeric polycarboxylic compounds suitable for use in the composition of the invention are homo- polymeric polycarboxylic acid compounds with acrylic acid as the monomeric unit. The average weight of such homo- polymers in the acid form preferably ranges from 1,000 to 100,000 particularly from 3,000 to 10,000. Acrylic sulphonated polymers as described in EP 851 022 (Unilever) are also suitable. Preferably, this polymeric material is present at a level of at least 0.1%, more preferably at levels from 1 wt% to 7 wt% of the total composition. Chelating Agent A chelating agent may be present in the composition. If present it is preferable if the level of chelating agent is from 0.5 to 3 wt% of the total composition. Preferred chelating agents include organic phosphonates, amino carboxylates, polyfunctionally-substituted compounds, and mixtures thereof . Particularly preferred chelating agents are organic phosphonates such as -hydroxy-2 phenyl ethyl diphosphonate, ethylene diphosphonate, hydroxy 1, 1-hexylidene, vinylidene 1,1 diphosphonate, 1,2 dihydroxyethane 1,1 diphosphonate and hydroxy-ethylene 1,1 diphosphonate. Most preferred are hydroxy-ethylene 1,1 diphosphonate and 2 phosphono-1 , 2 , 4 butanetricarboxylic acid or salts there of. Anti-tarnishing Agents Anti-tarnishing agents such as benzotriazole and those described in EP 723 577 (Unilever) may also be included. Optional Ingredients Optional ingredients are, for example, buffering agents, reducing agents, e.g., borates, alkali metal hydroxide and the well-known enzyme stabilisers such as the polyalcohols, e.g. glycerol and borax; anti-scaling agents; crystal-growth inhibitors, threshold agents; thickening agents; perfumes and dyestuffs and the like. Reducing agents may e.g. be used to prevent the appearance of an enzyme-deactivating concentration of oxidant bleach compound. Suitable agents include reducing sulphur-oxy acids and salts thereof. Most preferred for reasons of availability, low cost, and high performance are the alkali metal and ammonium salts of sulphuroxy acids including ammonium sulphite ((NH 4 ) 2 S0 3 ), sodium sulphite (Na 2 S0 3 ) , sodium bisulphite (NaHS0 3 ) , sodium metabisulphite (Na 2 S 2 0 3 ) , potassium metabisulphite (K 2 S 2 0 5 ) , lithium hydrosulphite (Li 2 S 2 0 4 ) , etc., sodium sulphite being particularly preferred. Another useful reducing agent, though not particularly preferred for reasons of cost, is ascorbic acid. The amount of reducing agents to be used may vary from case to case depending on the type of bleach and the form it is in, but normally a range of about 0.01% to about 1.0% by weight, preferably from about 0.02% to about 0.5% by weight, will be sufficient. pH of wash liquor The invention relates to washing processes in mechanical dish washing machines in which the pH of the wash liquor is preferably higher than about 8, more preferably 9 or higher, most preferably 10 or higher. Preferably the pH is lower than about 12. The most advantageous pH range is from 9.5 to 11. Temperature of washing process The present invention preferably relates to processes of mechanically washing soiled articles with a wash liquor at a temperature of at least 40°C, more preferably at least 50 °C, most preferably at least 55°C. The invention will now be illustrated by the following non limiting Examples. Examples of the invention are illustrated by a number, comparative Examples are illustrated by a letter. The following compositions were compressed to give tablets The mass of all the tablets was 25g. SLS is sodium lauryl sulphate Sokalan PA 25 CL is a polyacrylate . - Dehypon 2429 is a long chain ketone in a fatty alcohol carrier. The strength of the tablet was on a MTS Synergie 100. This machine uses a loadcell of 500 N maximum capacity. The initial -and secondary crosshead speeds are set at 25 mm/min, with a deformation limit of 200%. Break-sensitivity is 10%. The tablet is broken standing upright with its small side surfaces between the upper and lower plates The dissolution time was measured in a Bauknecht GSF 1161 (at 55°C) machine, loaded with on-glaze decorated porcelain, glass, plates plus cutlery stainless steel articles and plastics. The tablet to be tested was placed on the floor of the machine and the weight of the tablet recorded as a function of time. Table 2 shows that the tablets of the invention are stronger than the comparative tablet. Table 2 Both tablets were made with a press force of 8 newtons If the SLS is in the form of needles, that is if the length of the particles is at least 1400 microns and the width is a maximum of 250 microns, the disintegration time of the tablet is decreased as shown in the table below. Table 3 shows the time taken for 100 % of the tablet to disintegrate. (Both tablets pressed using 6 tons) . Table 3 The tablet strength is increased if a solvent such as polybutylene diol is included. Table 4 Press force used to manufacture the tablets is 6 Tonnes.

Claims: CLAIMS A tablet comprising a) particles containing sodium tripolyphosphate having a water of hydration in an amount from 1% to 5% by weight and wherein at least 50% by weight of the sodium tripolyphosphate within the particles is of a phase I form; b) 0.1 to 2 wt . % of the total composition of a ketone which has at least 25 carbon atoms and; c) 0.5 to 10 wt.% of the total composition of an anionic surfactant 2. A tablet according to claim 1 in which the level of anionic surfactant is from 0.5wt% to 3.0wt% of the total composition. 3. A tablet according to claim 1 or claim 2 in which the anionic surfactant is the sodium salt of a Cι 0 -C 22 sulphate . 4. A tablet according to any preceding claim in which the anionic surfactant is in powdered form and has a particle size such that length of the particle is at least 1400 microns and the width of the particle is less or equal to 250 microns. A tablet according to any preceding claim in which the anionic surfactant is in powdered form and has a density at 25°C from 0.4 to 0.6 g/cm. 6. A tablet according to any preceding claim in which the ketone is obtained by the ketonization of Cι 6 -C 2 2 carboxylic acids, carboxylic acid salts and mixtures thereof . 7. A tablet according to claim 4, wherein the ketone is elected from the group consisting of heptacosanone-14 , hentriacontanone-16 , pentatriacontanone-18 , nonatriacontanone-20, triatetracontanone-22 or nonacossanone-15, tri-triacontanone-17, heptatriacontanone-19, hentetracontanone-21 and mixtures thereof . 8. A tablet according to any preceding claim in which at least 60% by weight of the sodium tripolyphosphate within the particles is of a phase I form. 9. A tablet according to any preceding claim in which particles containing sodium tripolyphosphate having a water of hydration in an amount from 2% to 4% by weight. 10. A tablet according to any preceding claim, in which the tablet includes other sodium tripolyphaste, in addition to the sodium tripolyphosphate in the particles. 11. Use of a tablet according to any preceding claim for cleaning objects in a dishwasher.

Inventors: TOMLINSON ALAN DIGBY, TOMLINSON, ALAN, DIGBY
Applicants: LEVER HINDUSTAN LTD, UNILEVER NV, UNILEVER PLC, HINDUSTAN LEVER LIMITED
Application year: 2001
Main classification: C11D17
IPC codes: C11D1, C11D3, C11D17