EP4284904A1

EP4284904A1 - Professional machine dishwash detergent liquid

Info

Publication number: EP4284904A1
Application number: EP22700934.7A
Authority: EP
Inventors: Liam Edward DAVIES-MCGRAA; Marina MIXTRO SERRASQUEIRO
Original assignee: Unilever Global IP Ltd; Unilever IP Holdings BV
Current assignee: Unilever Global IP Ltd; Unilever IP Holdings BV
Priority date: 2021-01-29
Filing date: 2022-01-14
Publication date: 2023-12-06
Also published as: ZA202306564B; CN116745398A; WO2022161793A1; AR124702A1

Abstract

An aqueous liquid professional machine dishwash detergent comprising from 10 to 40 wt.% of alkali metal hydroxide; and from 0.1 to 10 wt. % of alkali metal silicate; and at most 5 wt. % of bleach activator; and at most 0.5 wt. % of bleach catalyst; and at most 0.1 wt. % of enzyme; and at most 1 wt. % of phosphate; and optionally builder; and optionally surfactant; and wherein the pH of a 1 wt.% solution of the detergent in water at 25 degrees Celsius and in otherwise standard conditions provides a pH of at least 10.5.

Description

PROFESSIONAL MACHINE DISHWASH DETERGENT LIQUID

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an aqueous liquid detergent for use in a professional machine dishwasher which provides reduced foaming. The invention further relates to a method of professional machine dishwashing.

BACKGROUND OF THE INVENTION

Professional machine dishwash machines are distinct from domestic dishwash machines and used for example used in restaurants and canteens of office buildings, factories, schools and the like. Such machines require high throughput capacity and must be able to effectively clean large volumes of dishware in a short space of time. To achieve this, they tend to operate at high wash temperatures with very short total washcycles times which typically are no more than 15 minutes. Such machines require specialized detergent products to effectively clean large volumes of (dish) ware in such short periods. The detergent products themselves are also sold in large volume containers which ideally can be auto-dosed (e.g. are liquid). The detergent products tend to provide quite high main-wash alkalinity and are often consider not suitable for domestic use from a safety point of view.

One recurring problem when using detergents in professional dishwash machines is that of foam formation. The foaming can result from a variety of factors. One is the saponification of fats during the wash by the high temperature and highly alkaline conditions in the wash. Another can stem from recycling of rinse water for the subsequent main wash cycles which carries over surfactants present in the rinse agent.

Finding a suitable solution to the problem of foaming is made more challenging as consumers of professional machine dishwash detergents desire products which have a reduced environmental impact, and which have short ingredient lists.

It is therefore an object of the current invention to provide an aqueous liquid detergent suitable for use in a professional machine dishwasher which has improved anti-foaming properties, preferably which has a short ingredient list and/or has a low or reduced environmental impact.

SUMMARY OF THE INVENTION

The object of the invention has been achieved in a first aspect by an aqueous liquid professional machine dishwash detergent comprising

• from 10 to 40 wt.% of alkali metal hydroxide; and

• from 0.1 to 10 wt. % of alkali metal silicate; and

• at most 5 wt. % of bleach activator; and

• at most 0.5 wt. % of bleach catalyst; and

• at most 0.1 wt. % of enzyme; and

• at most 1 wt. % of phosphate; and

• optionally builder; and

• optionally surfactant; and wherein the pH of a 1 wt.% solution of the detergent in water at 25 degrees Celsius and in otherwise standard conditions provides a pH of at least 10.5.

It was surprisingly observed that in particular the use of alkali metal silicates in a professional machine dishwash detergent can reduce foaming problems. In particular it was observed that the presence of alkali metal silicates in the amount of from 0.1 to 10 wt. % results in faster dissipation of any foam formed. It was furthermore unexpectedly observed that effective cleaning of dishware in professional dishwash machines could be achieved with little or no enzyme, bleach catalyst, bleach activator and surfactant.

The invention in a further aspect relates to a professional method for machine dishwashing comprising the steps of:

• adding from 1 to 10 ml of the liquid detergent according to any of the preceding claims per litre of total water used in the main wash of the professional dishwash machine;

• cleaning dishware in the main-wash cleaning step at a water temperature of at least 60 degrees Celsius; and

• subjecting dishware to a rinse step at a temperature of at least 60 degrees Celsius. In yet another aspect the invention relates to the use of alkali metal silicate in a liquid detergent suitable for professional machine dishwashing to reduce foaming. Indeed, the anti-foaming properties of alkali metal silicates has not been recognized in the field of professional machine dishwashing as far as the inventors are aware. The invention thus also relates to the use of alkali metal silicate in a professional machine dishwashing method to reduce foaming.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

Weight percentage (wt.%) is based on the total weight of the detergent composition unless otherwise indicated or as made clear from the context. It will be appreciated that the total weight amount of ingredients will not exceed 100 wt. %. Whenever an amount or concentration of a component is quantified herein, unless indicated otherwise, the quantified amount or quantified concentration relates to said component per se, even though it may be common practice to add such a component in the form of a solution or of a blend with one or more other ingredients. It is furthermore to be understood that the verb "to comprise" and its conjugations is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. Finally, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one". Unless otherwise specified all measurements are taken at standard conditions. Whenever a parameter, such as a concentration or a ratio, is said to be less than a certain upper limit it should be understood that in the absence of a specified lower limit the lower limit for said parameter is 0.

Alkali metal silicate

The professional machine dish wash detergent according to the invention comprises from 0.1 to 10 wt. % of alkali metal silicate. A more beneficial amount is from 0.5 to 7 wt. %, even more preferred is from 1.0 to 5 wt. % and still even more preferred is from 1.5 to 3.5 wt. %. The more preferred amounts were, in succession of preference, observed to provide an improved optimization between anti-foaming capacity and formulation stability. In particular, higher amounts of alkali metal silicate have a greater propensity to precipitate from the liquid.

Sodium silicate is a generic name for chemical compounds with the formula Na₂xSiyO₂y₊x or (Na₂O)_x (SiO₂)_y such as sodium metasilicate Na₂SiO₂, sodium orthosilicate Na4SiO4, and sodium pyrosilicate NaeShO?. The anions are often polymeric. These compounds are generally colorless transparent solids or white powders, and soluble in water in various amounts. Sodium silicate is also the technical and common name for a mixture of such compounds, chiefly the metasilicate, also called waterglass, water glass, or liquid glass.

The silicate which is beneficially used in the detergent composition of the invention is characterized by the general formula SiO₂:M₂O, where ‘M’ indicates an alkali metal atom. ‘M’ typically is Na, K or Li. In industry, the various grades of alkali metal silicate are characterized by their SiO₂:M₂O weight ratio. The ratio can vary between 0.5 (i.e. half the weight of SiO₂ versus that of M₂O and 4 (i.e. four times the weight of SiO₂ versus that of M₂O). Best results in terms of optimizing anti-foaming and detergent stability were found when using an alkali metal silicate having such a formula, preferably when in the detergent, and advantageously having a ratio of 1.0 to 3.5, more preferably a ratio of 1.5 to 3.0. The alkali metal may be based on potassium or sodium, whereof sodium is the more preferred alkali metal species.

Alkali metal hydroxide

The professional machine dishwash detergent comprises relatively large amounts of alkali metal hydroxide to provide quite alkaline conditions of the wash liquor in the main wash. Preferred alkali metal hydroxides are selected from the list of sodium hydroxide, potassium hydroxide and combinations thereof. The amount of alkali metal hydroxide in the detergent composition of the invention is from 10 to 40 wt. %, preferably from 12 to 30 wt. %, more preferably from 13 to 25 wt. % and even more preferably from 15 to 20 wt. %. Bleach

The detergent of the invention preferably comprises from 1 to 25 wt. %, more preferably from 5 to 20 wt. % and even more preferably from 8 to 15 wt. % of bleach. Inorganic and/or organic bleaches can be used. Bleach may be selected from peroxides, organic peracids, salts of organic peracids and combinations thereof.

Examples of peroxides are acids and corresponding salts of monopersulphate, perborate monohydrate, perborate tetrahydrate, and percarbonate. Organic peracids 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-1 , 4- dioic acid.

Preferably, the bleach is selected from peroxides (including peroxide salts such as sodium percarbonate), organic peracids, salts of organic peracids and combinations thereof. More preferably, the bleach is a peroxide. Most preferably, the bleach is a percarbonate. Further preferred, the bleach is a coated percarbonate.

Bleach Activators

The detergent of the invention may contain one or more bleach activators such as peroxyacid bleach precursors. 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 sul phonate (SBOBS) and the cationic peroxyacid precursor (SPCC) as described in US-A-4, 751 ,015. The detergent of the invention however preferably comprises at most 5 wt. % of bleach activator, more preferably at most 3 wt. %, even more preferably at most 2 wt. % and still even more preferably at most 1 wt. %. Advantageously the detergent composition comprises essentially no bleach activator. In particular it was found that the presence of bleach activator provided little or no further cleaning effect for the cleaning of dishes in professional dish wash machines. Hence not including bleach activator was surprisingly found to enable keeping the ingredient list shorter without much impact on cleaning efficiency of the professional machine dish wash detergent composition.

Bleach catalyst

Bleach catalysts function by oxidizing typically via peroxide or a peracid to form a bleaching species. They require the presence of an oxidizable soil so that they can be reduced back to the starting bleach activator state.

A suitable bleach catalyst is a manganese complex of formula (A):

[L_nMn_mXp]^zYq

.wherein Mn is manganese, which can be in the II, III, IV or V oxidation state or mixtures thereof; n and m are independent integers from 1-4; X represents a coordination or bridging species; p is an integer from 0-12; Y is a counter-ion, the type of which is dependent on the charge z of the complex which can be positive, zero or negative; q = z/[charge Y]; and L is a ligand being a macrocyclic organic molecule of the general formula: wherein R¹ and R² can each be zero, H, alkyl or aryl optionally substituted; t and t’ are each independent integers from 2-3; each D can independently be N, NR, PR, O or S, where R is H, alkyl or aryl, optionally substituted; and s is an integer from 2-5.

Such bleach catalysts are described in EP0458397A2. The preferred features of the manganese-based bleach catalyst described therein are preferred for any manganese- based bleach catalyst used in the detergent according to the invention. The preferred features referred to are those mentioned on pages 3 to 8 of EP0458397A2 insofar as relating to manganese-based bleach catalysts. The amount of bleach catalyst in the detergent composition of the invention is at most 0.5 wt. %. The detergent composition of the invention however preferably comprises at most 0.1 wt. % of bleach catalyst, more preferably at most 0.05 wt. %, even more preferably at most 0.01 wt. %, still even more preferably at most 0.001 wt. %. Advantageously the detergent composition comprises essentially no bleach catalyst. In particular it was found that the presence of bleach catalyst provided little or no further cleaning effect for the cleaning of dishes in professional dish wash machines. Hence not including bleach catalyst was surprisingly found to enable keeping the ingredient list shorter without much impact on cleaning efficiency of the professional machine dish wash detergent. Moreover, bleach catalysts are typically poorly biodegradable, hence having reduced (or even no) amounts of bleach catalyst can further reduce the environmental impact of the detergent according to the invention.

Surfactant

The detergent of the invention may comprise surfactant. The nonionic and anionic surfactants of the surfactant system may be chosen from the surfactants described "Surface Active Agents" Vol. 1 , by Schwartz & Perry, Interscience 1949, Vol. 2 by Schwartz, Perry & Berch, Interscience 1958, in the current edition of "McCutcheon’s Emulsifiers and Detergents" published by Manufacturing Confectioners Company or in "Tenside-Taschenbuch", H. Stache, 2nd Edn., Carl Hauser Verlag, 1981. Preferably the surfactants used are saturated.

Non-ionic surfactants

The detergent according to the invention may comprise from 0.1 to 15 wt. % of a nonionic surfactant or a mixture of two or more non-ionic surfactants. If nonionic surfactant is present advantageously a combination of at least two nonionic surfactants is used. Examples of nonionic surfactants that may be employed include the condensation products of hydrophobic alkyl, alkenyl, or alkyl aromatic compounds bearing functional groups having free reactive hydrogen available for condensation with hydrophilic alkylene oxide, such as ethylene oxide, propylene oxide, butylene oxide, polyethylene oxide or polyethylene glycol to form nonionic surfactants. Examples of such functional groups include hydroxy, carboxy, mercapto, amino or amido groups. Examples of useful hydrophobes of commercial nonionic surfactants include C8-C18 alkyl fatty alcohols, C8-C14 alkyl phenols, C8-C18 alkyl fatty acids, C8-C18 alkyl mercaptans, C8-C18 alkyl fatty amines, C8-C18 alkyl amides and C8-C18 alkyl fatty alkanolamides. Accordingly, suitable ethoxylated fatty alcohols may be chosen from ethoxylated cetyl alcohol, ethoxylated ketostearyl alcohol, ethoxylated isotridecyl alcohol, ethoxylated lauric alcohol, ethoxylated oleyl alcohol and mixtures thereof. Examples of suitable nonionic surfactants for use in the invention are found in the low- to non-foaming ethoxylated/ propoxylated straight-chain alcohols of the Plurafac™ LF series, supplied by the BASF and the Synperonic™ NCA series supplied by Croda. Also of interest are the end-capped ethoxylated alcohols available as the SLF 18 series from BASF and the alkylpolyethylene glycol ethers made from a linear, saturated CIGCIS fatty alcohol of the Lutensol™ AT series, supplied by BASF. Other suitable nonionics to apply in the composition of the invention are modified fatty alcohol polyglycolethers available as Dehypon™ E127, Dehypon™ 3697 GRA or Dehypon™ Wet from BASF/Cognis. Also suitable for use herein are nonionics from the Lutensol™ TO series of BASF, which are alkylpolyethylene glycol ethers made from a saturated iso-C13 alcohol.

Amineoxide surfactants may also be used in the present invention as anti-redeposition surfactant. Examples of suitable amineoxide surfactants are C10-C18 alkyl dimethylamine oxide and C10-C18 acylamido alkyl dimethylamine oxide.

Anionic surfactants

If an anionic surfactant is used, the total amount present preferably is less than 5 wt. %, and more preferably not more than 2 wt. %. Examples of suitable anionic surfactants are methylester sulphonates or sodium lauryl sulphate.

The total amount of surfactant in the detergent composition of the invention is preferably at most 5 wt. %, more preferably at most 3.0 wt. %, even more preferably at most 1.5 wt. %, still even more preferably at most 1.0 wt. % and still even more preferably at most 0.5 wt.%. Advantageously the detergent according to the invention comprises essentially no surfactant. In particular it was found that the presence of surfactant provided little or no further cleaning effect for the cleaning of dishes in professional dish wash machines. Hence not including surfactant was surprisingly found to enable keeping the ingredient list shorter without much impact on cleaning efficiency of the professional machine dish wash detergent composition. Moreover, most current surfactants are not derived from renewable sources and/or are poorly biodegradable. Hence having reduced (or even no) amounts of surfactant can further reduce the environmental impact of the detergent composition of the invention.

Enzymes

The professional detergent composition according to the invention may comprise enzyme. Examples of enzymes suitable for use in the cleaning compositions of this invention include lipases, cellulases, peroxidases, proteases (proteolytic enzymes), amylases (amylolytic enzymes) and others. Well-known and preferred examples of these enzymes are proteases, amylases, cellulases, peroxidases, mannanases, pectate lyases and lipases and combinations thereof. The enzymes most commonly used in detergent compositions are proteolytic and amylolytic enzymes. Enzymes may be added in liquid or in encapsulated form. In a preferred embodiment of this invention the enzymes are present in encapsulated form. Well know enzyme stabilizers such as polyalcohols/borax, calcium, formate or protease inhibitors like 4-formylphenyl boronic acid may also be present in the composition

Suitable levels of protease are from 0.1 to 10 mg, more preferably from 0.2 to 5 mg, most preferably 0.4 to about 4 mg active protease per gram of the detergent composition. Preferred levels of amylase are from 0.01 to 5, more preferably from 0.02 to 2, most preferably from 0.05 to about 1 mg active amylase per gram of the detergent composition.

However, it was found that the addition of enzymes to the detergent according to the invention provides little or no added cleaning benefit when used in a professional machine dishwasher. Therefore, advantageously the detergent according to the invention comprises essentially no enzymes, which will further aid in providing a shorter ingredient list. Dispersing polymers

The detergent composition according to the invention may comprise dispersing polymer. Dispersing polymers as are beneficially chosen from the group of anti-spotting agents and/or anti-scaling agents. Examples of suitable anti-spotting polymeric agents include hydrophobically modified polycarboxylic acids such as Acusol™460 ND (ex Dow) and Alcosperse™747 by Nouryon, whereas also synthetic clays, and preferably those synthetic clays which have a high surface area can be useful to reduce spotting, in particular those formed where soil and dispersed remnants are present at places where the water collects on the glass and spots formed when the water subsequently evaporates.

Suitable anti-scaling agents are water soluble dispersing polymers prepared from an allyloxybenzenesulfonic acid monomer, a methallyl sulfonic acid monomer, a copolymerizable nonionic monomer and a copolymerizable olefinically unsaturated carboxylic acid monomer as described in US5547612 or known as acrylic sulphonated polymers as described in EP851022. Polymers of this type include polyacrylate with methyl methacrylate, sodium methallyl sulphonate and sulphophenol methallyl ether such as Alcosperse™240 supplied (Nouryon). Also suitable is a terpolymer containing polyacrylate with 2-acrylamido-2 methylpropane sulphonic acid such as Acumer 3100 supplied by Dow. As an alternative, polymers and co-polymers of acrylic acid having a molecular weight between 500 and 20,000 can also be used, such as 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 e.g. Sokolan ™ PA 25 from BASF or Acusol™425 from Dow. Also suitable are polycarboxylates co-polymers derived from monomers of acrylic acid and maleic acid, such as CP5 from BASF. The average molecular weight of these polymers in the acid form preferably ranges from 4,000 to 70,000. Modified polycarboxylates like Sokalan™ CP50 from BASF or Alcoguard™4160 from Nouryon may also be used. Mixture of anti-scaling agents may also be used. Particularly useful is a mixture of organic phosphonates and polymers of acrylic acid. It is preferable that the level of dispersing polymers is at most 6 wt. %, more preferably at most 5 wt. %, and even more preferably is at most 4 wt. %, where suitable lower levels are at least 0.1 wt. %, at least 0.5 wt. % and 1.0 wt. %. Advantageously however the detergent according to the invention comprises essentially no dispersing polymer. This since it was found that additional of such polymers provides but little or no added benefit when the detergent is used in a professional machine dishwasher. Hence in order to keep the ingredient list as short as possible and to further reduced the amount of poorly biodegradable ingredients in the composition the detergent according to the invention preferably comprises essentially no dispersing polymer.

Anti-scaling agents which surprisingly were found to provide a significant cleaning benefit in professional machine dishwash methods are organic phosphonates, amino carboxylates, polyfunctionally-substituted compounds, and mixtures thereof.

Particularly preferred anti-scaling agents are organic phosphonates such as a-hydroxy- 2 phenyl ethyl diphosphonate, ethylene diphosphonate, hydroxy 1,1 -hexylidene, vinylidene 1,1 -diphosphonate, 1 ,2-di hydroxyethane 1,1- diphosphonate and hydroxyethylene 1,1 -diphosphonate. Most preferred is hydroxy-ethylene 1,1- diphosphonate (HEDP) and 2-phosphono-butane, 1,2,4-tricarboxylic acid (Bayhibit ex Bayer). Hydroxy-ethylene 1,1- diphosphonate is sometime also abbreviated as EHDP.

The detergent according to the invention beneficially comprises from 0.1 to 5 wt. % of HEDP, more preferably from 0.5 to 4 wt. %, even more preferably from 1.0 to 3.0 wt. % and still more advantageously from 1.5 to 2.5 wt. %.

Glass corrosion inhibitors and anti-tarnishing agents

Glass corrosion inhibitors can prevent the irreversible corrosion and iridescence of glass surfaces in machine dishwash detergents. The claimed composition may suitably contain glass corrosion inhibitors. Suitable glass corrosion agents can be selected from the group the group consisting of salts of zinc, bismuth, aluminum, tin, magnesium, calcium, strontium, titanium, zirconium, manganese, lanthanum, mixtures thereof and precursors thereof. Most preferred are salts of bismuth, magnesium or zinc or combinations thereof. Usual preferred levels of glass corrosion inhibitors in the present composition are 0.01-2 wt. %, more preferably 0.01- 0.5 wt. %. Anti-tarnishing agents may prevent or reduce the tarnishing, corrosion or oxidation of metals such as silver, copper, aluminum and stainless steel. Anti-tarnishing agents such as benzotriazole or bisbenzotriazole and substituted or substituted derivatives thereof and those described in EP723577 (Unilever) may also be included in the composition. Other anti-tarnishing agents that may be included in the detergent composition are mentioned in WO 94/26860 and WO 94/26859. Suitable redox active agents are for example complexes chosen from the group of cerium, cobalt, hafnium, gallium, manganese, titanium, vanadium, zinc or zirconium, in which the metal are in the oxidation state of II, II, IV V or VI.

In view of reducing the environmental impact of the detergent composition of the invention the detergent composition is preferably free of zinc and/or bismuth. In the context of his invention alkali metal silicates are not considered glass corrosion inhibitors or anti-tarnish agents.

Builders

The builder materials may be selected from 1) calcium sequestrant materials, 2) precipitating materials, 3) calcium ion-exchange materials and 4) mixtures thereof. Water used to provide a wash liquor in the dishwasher usually contains calcium, magnesium, and metallic cations (iron, copper, and manganese). Builders remove the hard water ions typically through precipitation, chelation, or ion exchange. In addition, they help remove soil by dispersion. A beneficial amount of builder in view of the aqueous liquid detergent according to the invention is from 2 to 30 wt. %, more preferably from 4 to 15 wt. %, even more preferably from 5 to 12 wt. % and still even more preferably from 6.0 to 10 wt. %.

Examples of precipitating builder materials include sodium carbonate. Examples of calcium ion-exchange builder materials include the various types of water-insoluble crystalline or amorphous aluminosilicates, of which zeolites are the best known representatives, e.g. zeolite A, zeolite B (also known as zeolite P), zeolite C, zeolite X, zeolite Y and also the zeolite P-type as described in EP-A-0,384,070. Zeolite and carbonate (carbonate (including bicarbonate and sesquicarbonate) are preferred builders, whereof carbonate is the more preferred. The detergent may contain as builder a crystalline aluminosilicate, preferably an alkali metal aluminosilicate, more preferably a sodium aluminosilicate. This is typically present at a level of less than 15 wt. %. Aluminosilicates are materials having the general formula:

0.8-1.5 M₂O. AI₂O₃. 0.8-6 SiO₂ where M is a monovalent cation, preferably sodium. These materials contain some bound water and are required to have a calcium ion exchange capacity of at least 50 mg CaO/g. The preferred sodium aluminosilicates contain 1.5-3.5 SiO₂ units in the formula above. They can be prepared readily by reaction between sodium silicate and sodium aluminate, as amply described in the literature. The ratio of surfactants to alumuminosilicate (where present) is preferably greater than 5:2, more preferably greater than 3:1.

Alternatively, or additionally to the aluminosilicate builders, phosphate builders may be used. In this art the term ‘phosphate’ embraces diphosphate, triphosphate, and phosphonate species. Preferably the machine dish wash detergent is non-phosphate- built (i.e. contains less than 1 wt. % of phosphate). Preferably the detergent composition according to the invention comprises essentially no diphosphate and/or triphosphate.

Aminopolycarboxylates are well known in the detergent industry and sometimes referred to as aminocarboxylate chelants. They are generally appreciated as being strong builders. Examples include glutamic acid N,N-diacetic acid (GLDA), methylglycinediacetic acid (MGDA), ethylenediaminedisuccinic acid (EDDS), iminodisuccinic acid (IDS), iminodimalic acid (IDM), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), hydroxyethyliminodiacetic acid (HEIDA) aspartic acid diethoxysuccinic acid (AES) aspartic acid-N,N-diacetic acid (ASDA) , hydroxyethylenediaminetetraacetic acid (HEDTA), hydroxyethylethylene-diaminetriacetic acid (HEEDTA) , iminodifumaric (IDF), iminoditartaric acid (IDT), iminodimaleic acid (IDMAL), ethylenediaminedifumaric acid (EDDF), ethylenediaminedimalic acid (EDDM), ethylenediamineditartaric acid (EDDT), ethylenediaminedimaleic acid and (EDDMAL), dipicolinic acid.

Preferred aminopolycarboxylate builders are GLDA, MGDA and/or EDDS, of which GLDA and MGDA are the more preferred, and GLDA is even more preferred. In particular GLDA can be dissolved in high amounts in the detergent product while maintaining a good pourability, hence making the product more advantageous to use in auto-dosing machine dish wash systems.

In the context of this invention alkali metal silicates are not considered as being builders.

Perfume and colorants

The detergent according to the invention may comprise one or more colorants, perfumes or a mixture thereof. Colorants are beneficially present in an amount of from 0.0001 to 8 wt. %, more preferably from 0.001 to 4 wt. % and even more preferably from 0.001 to 1.5 wt. %.

Perfume may be present in the range from 0.1 to 1 wt. %. Many suitable examples of perfumes are provided in the CTFA (Cosmetic, Toiletry and Fragrance Association) 1992 International Buyers Guide, published by CFTA Publications and OPD 1993 Chemicals Buyers Directory 80th Annual Edition, published by Schnell Publishing Co. In perfume mixtures preferably 15 to 25 wt. % are top notes. Top notes are defined by Poucher (Journal of the Society of Cosmetic Chemists 6(2):80 [1955]). Preferred topnotes are selected from citrus oils, linalool, linalyl acetate, lavender, dihydromyrcenol, rose oxide and cis-3-hexanol. It is however noted that another typical difference between domestic and professional machine dishwash detergents is that perfumes in the latter are usually not preferred. Hence perfumes are preferably essentially absent in the detergent according to the invention. Not adding perfume to the detergent according to the invention further aids in reducing the number of ingredients. Form of the detergent product

The professional machine dish wash detergent product of the invention is in the form of a pourable aqueous liquid. As such the preferred amount of water is from 40 to 90 wt. %, more preferably from 50 to 85 wt. %, even more preferably from 55 to 80 wt. % and still even more preferably from 60 to 75 wt. %. These amounts of water refer to the total amount of water in the detergent product irrespective of how it is added (e.g. as pure water or as present as part of an added ingredient make-up).

Given the short wash cycle times of a professional machine dishwasher highly alkaline wash liquors are important for the adequate cleaning of the dishware. Hence the detergent composition according to the invention is such that it provides a pH of at least 10.5 when a 1 wt.% solution of the detergent in water is provided at 25 degrees Celsius and in otherwise standard conditions. Preferably said pH is from 11.0 to 14.5, more preferably from 11.5 to 14.0, even more preferably from 12.0 to 13.8 and advantageously is from 12.2 to 13.5.

Professional machine dishwashers are required to handle large throughputs of dishes to be cleaned in short amount of time. In order to achieve this, it is therefore important that the detergent according to the invention is packaged in relatively large volumes (e.g. as compared to conventional domestic use detergent packaged). This reduces the chance of the detergent pack being empty during the peaks of machine dish cleaning activity. Hence it highly advantageous that the detergent according to the invention is packaged in a container with from 1 to 50, preferably 2 to 30, more preferably 4 to 20 and even more preferably from 8 to 15 litres of the detergent liquid.

As mentioned, many professional dishwash machines have the option to auto-dose liquid detergent automatically. This not only saves time for the user, who no longer needs time to dose detergent between each successive wash-cycle, but also is important from a safety point of view. As mentioned, professional machine dish wash detergents tend to be more alkaline in nature then domestic detergents and hence skin-contact with a professional machine dishwash detergent can be more hazardous. Hence advantageously the machine dishwash detergent according to the invention is packaged in a bottle which is suitably adapted for auto-dosing. The preferred packaging form is that of a bottle-container more preferably having a pouring spout. Further advantageous are containers (preferably bottles) which have a gripping handle. This to accommodate easy transport (as the detergents are often packed in large volumes) and to further reduce the chance of accidental spillage and skin-contact.

As indicated, part of the invention is the recognition that several ingredients known from domestic dishwash detergents provide little or no added benefit when used in professional dishwashers. This finding beneficially enables to further optimize the detergent according to the invention by restricting the number of ingredients whilst still providing on-par cleaning effectiveness. Restricting the number of ingredients in the detergent composition is not only beneficiary from a consumer perspective, but also in the sense that it makes the production of the detergent less technically complex. It will also further enhance general detergent stability as there are fewer interactions (chemical or otherwise) possible if fewer ingredients are present. Preferably the detergent composition contains (excluding water, dye and perfumes for accounting purposes) at most 8, more preferably at most 6, even more preferably at most 5 and still more beneficially at most 4 ingredients.

Method of professional dishwashing

One aspect of the invention relates to a professional method for machine dishwashing comprising the steps of:

• adding from 1 to 10 ml of the liquid detergent according to any of the preceding claims per litre of total water used in the main wash of the professional dishwash machine; and

• subjecting dishware to a rinse step at a temperature of at least 60 degrees Celsius.

It will be appreciated that these methods steps are executed in this order.

A professional dishwash machine is different from those used in domestic settings. A professional dishwash machine is designed for peak dishwash needs and should be capable of cleaning at least 100, preferably 200, more preferably 500 and even more preferably at least 800 dishes per hour. Another conventional way of assessing the throughput capacity is based on the number of racks per hour which can be cleaned by a professional dishwash machine. A professional dishwash machine preferably is capable of washing at least 10 racks per hours, more preferably at least 20 racks per hours, even more preferably at least 50 racks per hours and still even more preferably at least 100 racks per hour.

One typical difference between domestic and professional dishwash machines is that the latter often does not use an active drying step. Drying of ware in a professional machine is typically accomplished by exposure of hot ware to the open air. This can reduce the time before another batch of dishes can be loaded in the machine. Hence preferably the method for a professional dishwash machine according to the invention does not comprise an active drying step. Active drying is can be accomplished by actively circulating hot air in the still closed wash compartment of a machine dishwasher. Hence the preferred method according to the invention is to include a passive drying step which advantageously includes exposure of hot ware to the open air. ‘Hot ware’ referring a temperature of the dishware above ambient temperature, and which is often at least above 50 degrees Celsius upon the moment of opening of the dishwash machine.

The main wash cycle is conducted at the relatively high temperature at least of 60 degrees Celsius, but preferably is in the range of from 62 to 90 degrees Celsius, more preferably of from 63 to 87 degrees Celsius, even more preferably of from 65 to 85 degrees Celsius and still even more preferably is in the range of from 70 to 80 degrees Celsius.

Furthermore, the rinse cycle in professional machines is also typically conducted at quite high temperatures which is at least 60 degrees, but preferably is in the range of from 62 to 90 degrees Celsius, more preferably of from 63 to 87 degrees Celsius, even more preferably of from 65 to 85 degrees Celsius and still even more preferably is in the range of from 70 to 80 degrees Celsius. Preferably also, the rinse cycle involves steam at least at some point of the cycle, to further aid in drying the ware when subsequently exposed to the open air.

The professional dishwash machines can vary in length of their respective cycle-times for the main wash and the rinse cycle time. Preferably each separately is at most 10 minutes, at most 8 minutes, at most 6 minutes, at most 5 minutes, at most 3 and even more preferably at most 2 minutes. The total ware-wash time (including both the main and rinse cycle) is preferably at most 15 minutes, more preferably at most 10 minutes, at most 8 minutes, at most 6 minutes, at most 5 minutes, at most 3 and even more preferably at most 2 minutes. In general, the shorter cycles times, the more preferred these are for professional dish wash machines.

A further characteristic of professional machine dishwashers is their relatively low water per dish ratio. This has advantages in reducing water usage, but also saves energy in water heating. One way this can be accomplished is to recycle rinse water for use as water for the main wash. This can however make any foaming problems worse as said rinse water usually contains surfactants as drying agents. Of course, the short washcycle times and the general absence of an active drying step means in general there is a propensity of surfactants to be present in the main wash cycle, even if not present in the neat detergent composition.

In order to combine short ware-wash time with overall ware throughput efficiency it is preferred that the professional machine is provided with either a main wash liquor storage tank suitable for supplying wash liquor for multiple washes and/or an autodosing system for the detergent.

Use of alkali metal silicates

The invention in another aspect relates to the use of alkali metal silicates in a liquid detergent suitable for professional machine dishwashing to reduce foaming.

Although alkali metal silicates are known in domestic detergents as protective agents for dishware, their use in professional machines is less well known. In particular, the dishware used by e.g. restaurants is typically less sensitive to corrosion by design and hence there is little need to include corrosion protective agents in the professional machine dishwash detergents. Furthermore, their anti-foaming activity is unanticipated, let alone in the context of the operation of professional machine dishwashers.

The invention thus also relates to the use of alkali metal silicate in a professional machine dishwashing method to reduce foaming.

Unless stated otherwise or is apparent from the context of the description, preferred embodiments mentioned for one aspect of the invention applies mutated mutandis to the other aspects of the invention as well. The below examples are meant to be illustrative and not limiting.

EXAMPLES

Example 1

Professional machine dishwash detergents were made with a composition as set out in Table 1 below, where the Example 1 composition is according to the invention and the Comparative 1 composition is not according to the invention.

Table 1 - compositions of professional machine dish wash detergents. Amounts are given in weight % actives based on the weight of the total detergent.

¹added as silicic acid sodium salt (CAS no: 1344-09-8).

Method to test effects of foam formation

The detergents according to Table 1 were mixed with water in an amount of 4 ml/L. Subsequently a rinse aid product (with a formulation as in Table 2), was added in a concentration of 4 ml/L as well. The resulting mixture was placed in a 1000ml volume plastic cylinder. The top of the cylinder was sealed and the cylinder was inverted 15 times. At the end of this inversion process foam developed in about the same amount for each composition tested. The speed at which the foam column dissipated in the cylinder was followed over time, the results of which are given in Table 3.

Table 2: Rinse aid formulation composition. Amounts are given in weight % actives based on the weight of the total rinse aid composition.

¹Plurafac LF300: fatty alcohol alkoxylate non-ionic surfactant (Supplier: BASF) Table 3: Dissipation of the foam as function of time, wherein the foam height is given in %, relative to that of the initial foam height (which is set to 100%).

What can be seen from the results is that the Example 1 composition which comprises 5 wt. % sodium disilicate effectively reduces any initial foam formation at a much quicker rate than the Comparative composition which does not include any sodium silicate. This is highly beneficial in professional machine dish wash machines which use very short cycle times to accommodate a high throughput of dishware.

Claims

1. An aqueous liquid professional machine dishwash detergent comprising

• from 10 to 40 wt.% of alkali metal hydroxide; and

• from 0.1 to 10 wt. % of alkali metal silicate; and

• at most 5 wt. % of bleach activator; and

• at most 0.5 wt. % of bleach catalyst; and

• at most 0.1 wt. % of enzyme; and

• at most 1 wt. % of phosphate; and

• optionally builder; and

• optionally surfactant; and wherein the pH of a 1 wt.% solution of the detergent in water at 25 degrees Celsius and in otherwise standard conditions provides a pH of at least 10.5, wherein the alkali metal silicate has a SiC^IV O weight ratio of from 1.5 to 4.

2. A professional machine dishwash detergent liquid according to claim 1 , wherein the amount of surfactant is at most 5 wt. %, preferably 3 wt. %, more preferably 1.5 wt. % even more preferably 1.0 wt. % and still even more preferably is at most 0.5 wt. % and advantageously the detergent comprises essentially no surfactant.

3. A professional machine dishwash detergent liquid according to claim 1 or claim 2, comprising from 2 to 30 wt. % of builder, preferably from 4 to 15 wt. % and more preferably from 5 to 12 wt. %, wherein the builder is not alkali metal silicate.

4. A professional machine dishwash detergent liquid according to any preceding claim, wherein the builder is selected from a) aminopolycarboxylate, b) citric acid and/or its alkalimetal salt or c) carbonate or mixtures thereof, preferably wherein the builder comprises builders from a) and b); a) and c) or b) and c); and even more preferably wherein the builders from a) comprise GLDA, MGDA or mixtures thereof.

5. A professional machine dishwash detergent liquid according to any preceding claim, wherein the amount of water is from 40 to 90 wt. %, preferably from 50 to 85 wt. %, more preferably from 55 to 80 wt. % and even more preferably from 60 to 75 wt. %. A professional machine dishwash detergent liquid according to any preceding claim, wherein the amount of alkali metal hydroxide in the detergent composition of the invention is from 12 to 30 wt. %, more preferably from 13 to 25 wt. % and even more preferably from 15 to 20 wt. %. A professional machine dishwash detergent liquid according to any preceding claim, wherein the pH of a 1 wt.% solution of the detergent in water at 25 degrees Celsius and in otherwise standard conditions provides a pH of from 11.0 to 14.5, preferably from 11.5 to 14.0, more preferably from 12.0 to 13.8 and even more preferably is from 12.2 to 13.5. A professional machine dishwash detergent liquid according to any preceding claim, wherein the detergent liquid is packaged in a container with from 1 to 50, preferably 2 to 30, more preferably 4 to 20 and even more preferably from 8 to 15 litres of the detergent liquid. A professional method for machine dishwashing comprising the steps of:

• adding from 1 to 10 ml of liquid detergent according to any of the preceding claims per litre of total water used in the main wash of the professional dishwash machine;

• subjecting dishware to a rinse step at a temperature of at least 60 degrees Celsius. A professional method for machine dishwashing according to claim 9, wherein the dishwasher is suitable for cleaning at least 200 dishes per hour, preferably at least 500 dishes per hour. A professional method for machine dishwashing according to claim 9 or claim 10, wherein the method includes automatic recycling of rinse-water for use as water for the subsequent main wash. A professional method for machine dishwashing according to any one of claims 9 to

11 , wherein the method does not contain an active drying step. A professional method for machine dishwashing, according to anyone of claims 9 to

12, wherein the detergent liquid is automatically dosed. Use of alkali metal silicate in a liquid detergent suitable for professional machine dishwashing to reduce foaming. Use of alkali metal silicate in a professional machine dishwashing method to reduce foaming.