DISH WASHING COMPOSITIONS

Abstract: A machine dish washing tablet comprising less than 5 wt% of the total composition of a surfactant and 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.

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 Machine dishwashing tablets are popular with the consumer, as they have several advantages over powdered products in that they do not require measuring and they are compact and so easy to store. However, a re-current problem with machine dish washing tablets is to obtain a tablet that dissolves quickly when added to the main wash of the machine, the tablets frequently crumble on storage and so are not pleasant to touch or easy to dose. However, if a harder tablet that does not crumble is produced complete dissolution may not occur during the main wash cycle. If part of the tablet is still available for dissolution in the rinse, serious spotting and filming problems can occur. 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 describes machine dish washing 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 which are more aesthetically pleasing and more consumer friendly than conventional tablets by virtue of the virtual absence of fines on the tablet surface. A further advantage is that these tablets do not crumble. Description of the Invention Accordingly, the present invention provides a machine dish washing tablet comprising a) less than 5 wt% of the total composition of a surfactant and; b) 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. 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 (ie 90% of complete hydration when exposed to water at 80 °C) within 60 seconds. "Rhodiaphos HPA 3.5" is a grade of sodium tripolyphosphate from 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 60% by weight. Surfactant material A surfactant system comprising a surfactant selected from nonionic, anionic, cationic, ampholytic and zwitterionic surfactants and mixtures thereof is preferably present in the composition at levels of 5 wt% of the total composition or less. Typically the surfactant is a low to non foaming nonionic surfactant, which includes 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 without excessive foaming, however, an excessive proportion of nonionic surfactant should be avoided. Preferably the level of nonionic surfactant is at least 0.1% by weight, more preferably at least 0.5% by weight . Examples of suitable nonionic surfactants for use in the invention are the low- to non- foaming ethoxylated straight - chain alcohols preferred nonionic surfactants are Plurafac LF series ex BASF, the Synperonic series ex ICI; Lutensol ® LF series, ex BASF Company and the Triton ® DF series, ex Rohm & Haas Company. Other surfactants such as anionic surfactant may be used but may require the additional presence of an antifoam to surpress foaming. If an anionic surfactant is used it is advantageously present at levels of 2 wt% or below. 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, 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 "4 %, 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 6 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 diperox - 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 ' % 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 α-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 is hydroxy-ethylene 1,1 diphosphonate, 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-deacti ating 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 results show that tablets made with the phosphate of the invention are stronger than the comparative Example with currently used phosphate. Furthermore tablets with the phosphate of the invention, having low levels of nonionic surfactant have faster dissolution than tablets with no or higher levels of nonionic surfactant. In the table below Sokalan PA 25 CL is a polyacrylate ex. BASF, Plurafac CF 403 is a nonionic surfactant ex. BASF.

Claims: CLAIMS 1. A machine dish wash tablet comprising: a) less than 5 wt% of the total composition of a surfactant and; b) 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. 2. A machine dish washing tablet according to claim 1 in which the level of surfactant is from 0.5wt% to 3.0wt% of the total composition. 3. A machine dish washing tablet according to claim 1 or claim 2 in which the surfactant is an alkoxylated nonionic surface-active agent wherein the alkoxy moiety is selected from the group consisting of ethylene oxide, propylene oxide and mixtures thereof. 4. A machine dish washing 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. 5. A machine dish wash tablet according to any prceding claim in which particles containing sodium tripolyphosphate having a water of hydration in an amount from 2% to 4% by weight. A tablet according to any preceding claim in which said particles have a mean particle size not greater than 300 μm. A tablet according to any preceding claim, wherein said particles provide phase I sodium tripolyphosphate as at least 8% by weight of the tablet or region thereof. A tablet according to any preceding claim, in which the tablet includes other sodium tripolyphaste, in addition to the sodium tripolyphosphate in the particles. A tablet according to any preceding claim, in which the tablet includes other sodium tripolyphosphate, in addition to the sodium tripolyphosphate in the particles .

Inventors: TOMLINSON ALAN DIGBY, TOMLINSON, ALAN, DIGBY
Applicants: LEVER HINDUSTAN LTD, TOMLINSON ALAN DIGBY, UNILEVER NV, UNILEVER PLC, HINDUSTAN LEVER LIMITED, TOMLINSON, ALAN, DIGBY
Application year: 2000
Main classification: C11D3
IPC codes: C11D3, C11D17