WO2001000766A1

WO2001000766A1 - Dish washing process and compositions relating thereto

Info

Publication number: WO2001000766A1
Application number: PCT/EP2000/004427
Authority: WO
Inventors: Alan Digby Tomlinson
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 1999-06-25
Filing date: 2000-05-15
Publication date: 2001-01-04
Also published as: AU4405600A; ZA200109843B; EP1190029A1; BR0011929A; AR024455A1

Abstract

A process for washing articles in a mechanical washing machine in which no salt is added to the machine. The process involves treating the articles with a wash liquor comprising a dishwashing composition when undiluted said composition comprising 55 wt. % or greater of an inorganic poly-valent builder; followed by treating the article with a rinsing solution comprising a rinse aid, the rinse aid when undiluted comprising at least 20 wt. % of a water soluble builder or salt thereof; wherein no salt is added to the machine.

Description

DISH WASHING PROCESS AND COMPOSITIONS RELATING THERETO

Technical Field

The present invention is in the field of machine dishwashing. More specifically, the invention encompasses automatic dishwashing detergents and rinse aids and a process for using them.

Background of the Invention

To wash articles in a commercially available dish washing machine entails using three product types. Salt is added to the salt compartment to soften the water, a dish-washing formulation is used to clean the articles and a rinse aid is used to ensure that the articles are rinsed with no streaks or smears .

The salt in the machine does not have to be replaced every wash, however it is inconvenient for consumers replace the salt .

The present invention relates to a process of washing dishes that obviates the need for salt in a machine dish-washing formulation. Description of the Invention

Accordingly, the present invention provides a process for washing articles m a mechanical washing machine comprising the steps of: (I) treating the articles with a wash liquor comprising a dishwashing composition, when un-diluted said composition comprising 55 wt % or greater of an inorganic poly-valent builder (n) followed by treating the article with a rinsing solution comprising a rmse aid, the rmse aid when undiluted comprising at least 20 wt . % of a water soluble builder or salt thereof; (in) wherein no salt is added to the machine .

Detailed Description of the Invention

Dish Washing Composition

Builder material

The detergency builder salt for use with the present invention is a poly-valent inorganic builder. Preferably the builder is water-soluble. Non-limitmg examples of suitable, inorganic builder salts include the alkali metal, phosphates, polyphosphates, and tripolyphosphates. Specific examples of such salts include the sodium and potassium, tripolyphosphates, orthophosphates and hexametaphosphates . Sodium tripolyphosphate is particularly preferred as a builder. The level of inorganic builder is 55 wt. % or greater. Most preferably the level of builder is from 58 wt.% to 65 wt.%. Particularly suitable for use with the invention is sodium tripolyphosphate, which 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/M³ or less, more preferably from 0.52 to 0.72 Kg/M³.

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 Rhodia 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 detergency builder system may additionally comprise a bicarbonate salt, preferably sodium or potassium bicarbonate most especially sodium bicarbonate. Bicarbonate salts are particularly preferred as builders as they also have a buffering capacity.

The builder may further comprise a carboxylate or polycarboxylate builder 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.

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.

Mixtures of organic and/or inorganic builder salts can be used herein.

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 sizes 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. When silicates are present, the Si0₂ 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 Si0₂ to the alkali metal oxide (M₂0, 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 Si0₂:M₂0 ratio of from 2.0 to 2.4 are, as noted, greatly preferred. Anhydrous forms of the alkali metal silicates with a Si0₂:M₂0 ratio of 2.0 or more are also less preferred because they tend to be signi icantly 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 Si0₂:Na0 ratio of from 2.0 to 2.4 available from PQ Corporation, named Britesil H20 and Britesil H24. Most preferred is a granular hydrous sodium silicate having a Si0₂:Na₂0 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 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 10² to 10⁶ Maltose units/kg. For proteolytic enzymes the final composition will have proteolytic enzyme activity of from 10⁶ to 10⁹ 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 onopersulphate, 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 an 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 m the composition of the invention are homo- polymeric polycarboxylic acid compounds with acrylic acid as the monomeπc unit. The average weight of such homo- polymers m the acid form preferably ranges from 1,000 to 100,000 particularly from 3,000 to 10,000.

Acrylic sulphonated polymers as described m 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.

Chelatmg Agent

A chelatmg agent may be present the composition. If present it is preferable if the level of chelatmg agent is from 0.5 to 3 wt.% of the total composition.

Preferred chelatmg agents include organic phosphonates, ammo carboxylates, polyfunctionally-substituted compounds, and mixtures thereof .

Particularly preferred chelatmg agents are organic phosphonates such as α-hydroxy-2 phenyl ethyl diphosphonate, ethylene diphosphonate, hydroxy 1 , 1-hexylιdene, v ylidene 1,1 diphosphonate, 1,2 dihydroxyethane 1,1 diphosphonate and hydroxy-ethylene 1,1 diphosphonate. Most preferred is hydroxy-ethylene 1,1 diphosphonate. 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 )₂S0₃), sodium sulphite (Na₂S0₃) , sodium bisulphite (NaHS0₃) , sodium metabisulphite (NaS₂0₃) , potassium metabisulphite (K₂S₂0₅) , lithium hydrosulphite (Li₂S₂0₄) , 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 m mechanical dish washing machines wherein the wash liquor has a low pH. By "low pH" is meant here that the pH of the wash liquor is preferably higher than about 6.5, more preferably 7.5 or higher, most preferably 8.5 or higher. Preferably the pH is lower than about 10.5, more preferably lower than about 10, more preferably lower than about 9.5. The most advantageous pH range is from 8.5 to 10.

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.

Rmse Aid

The rmse aid for use m the invention comprises a water soluble acid builder or salt, preferably organic acids including, for example, carboxylic acids, such as citric and succimc acids, polycarboxylic acids, such as polyacrylic acid, and also acetic acid, boric acid, malomc acid, adipic acid, fumaπc acid, lactic acid, glycolic acid, tartaπc acid, tartronic acid, maloic acid, their derivatives and any mixtures of the foregoing. - I S

The level of water soluble builder salt in the composition is at least 20wt% of the total composition, preferably at least 25 wt.%, more preferably at least 30 wt.%, most preferably at least 35 wt.%

Suitable water-soluble monomeric or oligomeric carboxylate builders can be selected from a wide range of compounds but such compounds preferably have a first carboxyl logarithmic acidity/constant (pKi) of less than 9, preferably of between 2 and 8.5, more preferably of between 2.5 and 7.5.

The carboxylate or polycarboxylate builder can be monomeric or oligomeric in type although monomeric polycarboxylates are generally preferred for reasons of cost and performance. Monomeric and oligomeric builders can be selected from acyclic, alicyclic, heterocyclic and aromatic carboxylates .

Suitable carboxylates containing one carboxy group include the water-soluble salts of lactic acid, glycolic acid and ether derivatives thereof. Polycarboxylates containing two carboxy groups include the water-soluble salts of succinic acid, malonic acid, (ethylenedioxy) diacetic acid, maleic acid, diglycolic acid, tartaric acid, tartronic acid and fumaric acid, as well as the ether carboxylates and the sulfinyl carboxylates. Polycarboxylates containing three carboxy groups include, in particular, water-soluble citrates, aconitrates and citraconates as well as succinate derivatives such as the carboxymethyloxysuccinates , lactoxysuccinates , and aminosuccinates , and the oxypolycarboxylate materials such as 2-oxa-l , 1 , 3-propane tricarboxylates. The carboxylate or polycarboxylate builder compounds described above can also have a dual function as pH controlling agents.

Polycarboxylates containing four carboxy groups include oxydisuccinates , 1 , 1 , 2 , 2 -ethane tetracarboxylates, 1,1,3,3- propane tetracarboxylates and 1 , 1 , 2 , 3-propane tetracarboxylates. Polycarboxylates containing sulfo substituents include the sulfosuccinate derivatives, and the sulfonated pyrolysed citrates.

Alicyclic and heterocyclic polycarboxylates include cyclopentane-cis , cis , cis-tetracarboxylates , cyclopen- tadienide pentacarboxylates, 2 , 3 , 4 , 5-tetrahydroturan - cis, cis, cis-tetracarboxylates, 2 , 5-tetrahydrofuran - cis - dicarboxylates , 2 , 2 , 5 , 5-tetrahydrofuran - tetracarboxylates, 1, 2 , 3 , 4 , 5 , 6-hexane - hexacarboxylates and carboxymethyl derivatives of polyhydric alcohols such as sorbitol, mannitol and xylitol. Aromatic polycarboxylates include mellitic acid, pyromellitic acid and the phthalic acid derivatives disclosed in British Patent No. 1,425,343.

Of the above, the preferred polycarboxylates are hydroxycarboxylates containing up to three carboxy groups per molecules, more particularly citrates or citric acid.

As an alternative to the above phosphonates may be used.

The parent acids of the monomeric or oligomeric polycarboxylate chelating agents or mixtures thereof with their salts, e.g. citric acid or citrate/citric acid mixtures are also contemplated as components of builder systems of rinse compositions in accordance with the present invention.

The surfactant system most preferably comprises low foaming nonionic surfactant, selected for its wetting ability, preferably selected from ethoxylated and/or propoxylated nonionic surfactants, more preferably selected from nonionic ethoxylated/propoxylated fatty alcohol surfactants.

The surfactant system is typically present at a level of from 1% to 40% by weight, more preferably 1.5 % to 30% by weight, most preferably from 5% to 20% by weight of the compositions. If an anionic surfactant is used it is advantageously present at levels of 1 wt% or below.

The compositions of the invention may contain organic solvents, particularly when formulated as liquids or gels.

The compositions in accord with the invention preferably contain a solvent system present at levels of from 1% to

30% by weight, preferably from 3% to 25% by weight, more preferably form 5% to 20% by weight of the composition.

The solvent system may be a mono or mixed solvent system.

Preferably, at least the major component of the solvent system is of low volatility. Suitable organic solvent for use herein has the general formula RO (CH₂C (Me) HO) _nH, wherein R is an alkyl, alkenyl, or alkyl aryl group having from 1 to 8 carbon atoms, and n is an integer from 1 to 4. Preferably, R is an alkyl group containing 1 to 4 carbon atoms, and n is 1 or 2. Especially preferred R groups are n-butyl or isobutyl . Preferred solvents of this type are 1 -n-butoxypropane-2-ol (n = 1) : and 1 (2-n-butoxy-l -methylethoxy) propane-2 -ol (n = 2), and mixtures thereof .

Other solvents useful herein include the water-soluble CARBITOL⁷ solvents or water-soluble CELLOSOLVE⁷ solvents. Water-soluble CARBITOL⁷ solvents are compounds of the 2- (2 alkoxyethoxy) ethanol class wherein the alkoxy group is derived from ethyl, propyl or butyl; a preferred water- soluble carbitol is 2 (2-butoxyethoxy) ethanol also known as butyl carbitol. Water-soluble CELLOSOLVE⁷ solvents are compounds of the 2 -alkoxyethoxy ethanol class, with 2- butoxyethoxyethanol being preferred.

Other suitable solvents are benzyl alcohol, and diols such as 2 -ethyl -1 , 3 -hexanediol and 2 , 2 , 4-trimethyl-l , 3- pentanediol .

Hydrotropes may be present and are typically present at levels of from 0.5% to 20%, preferably from 1% to 10%, by weight .

Useful hydrotropes include sodium, potassium, and ammonium xylene sulfonates, sodium, potassium, and ammonium toluene sulfonate, sodium potassium and ammonium cumene sulfonate, and mixtures thereof .

In a highly preferred aspect of the invention, the compositions have a pH as a 1% solution in distilled water at 20°C of less than 7, preferably from 0.5 to 6.5, most preferably from 0.5 to 1.0.

Product Form

The dish washing composition for use in the invention may be in any product form, however it is preferred if it granular. Granular in the context of the present invention includes both powdered material and tablets. Tablets are particularly preferred.

The rinse aid is preferably a liquid.

Dishwash compositions according to the present invention may be dosed in the wash liquor at levels of from 10 g/1 to 2.5 g/i.

Rinse aid composition according to the present invention may be dosed in the final rinse liquor at levels 1 g/1 or less.

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. All percentages are on a weight basis

EXAMPLE I

Table 1

The compositions were tested in a robotised Miele G5953C (total water hardness 28°FH, including temporary hardness of 18°FH) . The compositions were dosed at a level of 20 g/wash; the main wash time was 20 minutes; the drying time with open door was 10-20 minutes; the washing temperature was up to 65°C;

30 washes were carried out by loading the machine with glass, and plastics,

Rinse aid was added to the rinse via the rinse and dispenser. The rinse aid had the following formulation:

Nonionic surfactant LF400s (ex BASF) 14.55%; sodium Xylene sulphonate 5%; citric acid 40% and water to 100%.

Overall appearance

Overall appearance was measured by placing the tested articles on a black cloth under a reflected artificial daylight source (Kelvin temperature 2300°K) ; placed 2 metres above the articles. A subjective scoring system on a 1-9 scale was used

1 as new - 9 extremely poor.

The overall appearance was a combination of white filming due to calcium salt deposits, spots, streaks and glass corrosion. The results are given in table 3

TABLE 3

Claims

1. A process for washing articles in a mechanical washing machine comprising the steps of:

i) treating the articles with a wash liquor comprising a dishwashing composition when undiluted said composition comprising 55 wt. % or greater of an inorganic poly-valent builder;

ii) followed by treating the article with a rinsing solution comprising a rinse aid, the rinse aid when undiluted comprising at least 20 wt. % of a water soluble builder or salt thereof;

iii) wherein no salt is added to the machine.

2. A process according to claim 1 in which the water poly- valent builder is sodium tripolyphosphate.

3. A process according to claim 1 or 2 in which the water soluble acid builder is citric acid or citrate.

. A process according to claim any preceding claim in which the rinse aid comprises 30 wt% or greater of water soluble acid builder or salt thereof.

5. A process according to any preceding claim in which the dish washing composition comprises a silica or silicate material . A process according to any preceding claims wherein the temperature of the wash liquor is at least 40°C.

Machine dishwash compositions for use in any of the above claimed processes, said dish washing composition being in tablet form and rinsing composition being in liquid form.