DETERGENT TABLETS

Abstract: A detergent tablet (1) having a top and bottom horizontal surface (2, 3), these surfaces (2, 3) having a convex profile.

Description: DETERGENT TABLETS Technical Field The present invention is in the field detergent tablets. More specifically, the invention encompasses automatic dishwashing tablets and a process for preparing them. 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 wash, without the need to flow-wrap the tablets so they do not crumble on transport and storage. 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 machine such 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. The technology of the present invention provides tablets, which are aesthetically pleasing, do not crumble on storage and yet dissolve rapidly Description of the Invention Accordingly, the present invention provides A detergent tablet (l),for use in an automatic dish washing machine or washing machine for laundry, having a top and bottom horizontal surface (2,3), these surfaces (2,3) having a convex profile. Use of a convex shape for a dish wash tablet to give the tablet strength on storage yet fast dissolution in use is also described. Detailed Description of the Invention The tablets of the present invention have two horizontal surfaces with a convex shape, it is however highly preferable if they also have a vertical surface (4) . The vertical surface may be curved but is preferably straight. It is further preferable if the height of the vertical surface (5) is less than the depth greatest width (6) of the horizontal surface. It is desirable if the horizontal surfaces of the tablet are non-circular in shape. Especially preferred are tablets in which at least one end is tapered, particularly those that can be described as having a tear drop shape. Tablets having this shape are convenient to pack into cartons, and are highly preferred by the consumer. It is preferred if the tablet has a strength from 50 to 300 newtons (N) as measured on a MTS Synergie 100 using a loadcell of 500 N maximum capacity. The initial -and secondary crosshead speeds being set at 25 mm/min, with a deformation limit of 200%. The tablets of the invention preferably have a mass of greater than 8g, more preferably from 12 to 30g, most preferably 15 to 27g. Tablet with a mass of 18, 20 or 25g are particularly useful . Preferably the tablets are prepared from dense powder. Dish Washing Composition Builder material The compositions of the invention contain a builder. The builder may be a phosphate or non-phosphate builder. Compositions of the invention comprising a water-soluble phosphate builder typically contain this builder at a level of from 1 to 90% by weight, preferably from 10 to 80% by weight, most preferably from 20 to 80% by weight of the composition. Specific examples of water-soluble phosphate builders are the alkali metal tripolyphosphates, sodium, potassium and ammonium pyrophosphate, sodium and potassium orthophosphate, sodium polymeta/phosphate in which the degree of polymerization ranges from about 6 to 21, and salts of phytic acid. Sodium or potassium tripolyphosphate is most preferred. In a preferred composition sodium tripolyphosphate with high Phase I Content is used. Sodium tripolyphosphate with high Phase I can be prepared 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 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 40% of phase I material. A further preferred embodiment is a mixture of phase II and phase I sodium tripolyphaspate, preferably in the dration of 6:4 to 4:6 of phase I to phase II. The compositions of the present invention may comprise a water-soluble nonphosphate builder. This is typically present at a level of from 1 to 90% by weight, preferably from 10 to 80% by weight, most preferably from 20 to 70% by weight of the composition. Suitable examples of non-phosphorus-containing inorganic builders include water-soluble alkali metal carbonates, bicarbonates, sesquicarbonates, borates, silicates, including layered silicates such as SKS-6 ex. Hoechst, metasilicates, and crystalline and amorphous aluminosilicates . Specific examples include sodium carbonate (with or without calcite seeds) , potassium carbonate, sodium and potassium bicarbonates, silicates including layered silicates and zeolites . Organic detergent builders can also be used as nonphosphate builders in the present invention. Examples of organic builders include alkali metal citrates, succinates, malonates, fatty acid sulfonates, fatty acid carboxylates, nitrilotriacetates, oxydisuccinates, alkyl and alkenyl disuccinates, oxydiacetates, carboxymethyloxy succinates, ethylenediamine tetraacetates, tartrate monosuccinates, tartrate disuccinates, tartrate monoacetates, tartrate diacetates, oxidized starches, oxidized heteropolymeric polysaccharides, polyhydroxysulfonates, polycarboxylates such as polyacrylates, polymaleates, polyacetates, polyhydroxyacrylates, polyacrylate/poly aleate and polyacrylate/ polymethacrylate copolymers, acrylate/maleate/vinyl alcohol terpolyτners, aminopolycarboxylates and polyacetal carboxylates, and polyaspartates and mixtures thereof. Such carboxylates are described in U.S. Patent Nos . 4,144,226, 4,146,495 and 4,686,062. Alkali metal citrates, nitrilotriacetates, oxydisuccinates, acrylate/maleate copolymers and acrylate/maleate/vinyl alcohol terpolymers are especially preferred nonphosphate builders. 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. When silicates are present, the Si0 2 level should be from 1% to 25%, preferably from 2% to 20%, more preferably from 3% to 10%, based on the weight of the ADD. 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 :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. 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 to make the soil or stain more removable in a subsequent cleansing step. Both degradation and alteration can improve soil removal. Well-known and 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 6 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. In general the level of bleach material is preferably greater than 0.5 wt% of a bleaching material. 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. 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. 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, is preferably used to improve the detergency without excessive foaming. However, an excessive proportion of nonionic surfactant should be avoided. Normally, an amount of 15% by weight or lower, preferably 10% by weight or lower, more preferably 7% by weight or lower, most preferably 5% by weight or lower and preferably 0.1% by weight or higher, more preferably 0.5% by weight or higher is quite sufficient, although higher level may be used. Examples of suitable nonionic surfactants for use in the invention are the low- to non- foaming ethoxylated straight- chain alcohols of the Plurafac ® RA series, supplied by the Eurane Company; of the Lutensol ® LF series, supplied by the BasF Company and of the Triton ® DF series, supplied by the Rohm & Haas Company. Other surfactants such as anionic surfactant may be used but may require the additional presence of antifoam to surpress foaming. If an anionic surfactant is used it is advantageously present at levels of 2 wt% or below. 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 (EHDP) . 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 liquor It is prefererable the pH of the wash liquor is higher than 6.5, more preferably 7.5 or higher, most preferably 8.5 or higher. Preferably the pH is lower than 12, more preferably lower than 11. The invention will now be illustrated by the following non- limiting Examples. Examples of the invention will be illustratd by a number, Examples of the invention will be illustrated by a letter. Tablets having the shape shown in figure 1 were prepared having a formulation within the following range: 1 is nonionic surfactant ex BASF 2 is maleic and acrylic copolymer (mwt 50,000) acrylic acid polymer mwt 4,000. To process the tablets all dry ingredients were mixed together, while spraying on the nonionic and perfume. The resulting powder was then tabletting on a rotary tabletting machine using force between 50 and 200 kn. The tablets handled well on storage and performed well in the wash. To show the improved friability of the pebble shaped tablet Examples were made having the following formulation: This powder was tabletted on a rotary press at compaction forces between 60 and 150 kN to prepare Example A and Example 2. Example A round tablets: 32 mm in diameter; height 16 mm; flat top and bottom surface. Example 2 pebble shape: length: 40 mm; width: 29 mm; vertical height : 8 mm; total height including bulged surface: 17 mm. Tablet strength and friability were measured after the test runs. The results were as follows: Tablet properties Strength is measured on a TS 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 . Friability testing - For this test a square box of 10.5 cm/side was connected to motor running at 50 rpm at a horizontal angle of approx. 15°. Five tablets were pre- weighed ( Ml) . The tablets were put in the box and the motor was turned on for a period of three minutes . After the test run the tablets were weighed again ( M2) . The following equation is used to calculate the friability: ( 1-M2)/M1*100% The invention will now be furthe illustrated by the following non-limiting drawings: Figure 1 depicts a tablet according to the invention Figure 2 depicts the shape of the horizontal plane of figure 1 of the tablet. Figure 3 is a vertical cross-section of the tablet of figure 1, taken along the line I-I. In figure 1, a tablet (1) has a top horizontal surface (2) and a bottom horizontal surface (3) . The tablet has a vertical edge (4) , Figure 2 shows the point that the horizontal surface has its greatest width (6) should be taken as a plane ignoring the degree of curvature of the tablet . Figure 3 demonstrates the height (5) of the vertical edge (4) .

Claims: CLAIMS 1) A detergent tablet (1) , for use in an automatic dish washing machine or washing machine for laundry, having a top and bottom horizontal surface (2,3), these surfaces (2,3) having a convex profile. 2) A tablet according to claim 1 in which the horizontal surfaces are non-circular in shape. 3) A tablet according to claim 1 or claim 2 having two horizontal surfaces and a vertical surface (4) . 4) A tablet according to claim 1, in which at least one end is tapered. 5) A tablet according to claim 1 or 2 having a tear drop shape 6) A tablet according to any preceding claim having a tablet strength from 50 to 300 newtons (N) 7) A tablet according to any preceding claim having a mass greater than 8g 8) A tablet according to any preceding claim comprising from 0.1 to 5 wt% of a surfactant. 9) A tablet according to any preceding claim comprising from 10 wt% to 80 wt% of a builder. 10) A tablet according to claim 9 in which the builder is sodium tripolyphosphate with high phase I content. 11) A tablet according to any preceding claim comprising greater than 0.5 wt% of a bleaching material. 12) Use of a convex shape for a dish wash tablet to give the tablet strength on storage yet fast dissolution in use .

Inventors: COSTELLO NORA ANN, EUSER HUUG, COSTELLO, NORA, ANN, EUSER, HUUG
Applicants: COSTELLO NORA ANN, EUSER HUUG, LEVER HINDUSTAN LTD, UNILEVER NV, UNILEVER PLC, COSTELLO, NORA, ANN, EUSER, HUUG, HINDUSTAN LEVER LIMITED
Application year: 2000
Main classification: C11D17
IPC codes: C11D17