IMPROVEMENTS RELATING TO LIGHT DUTY CLEANING

Abstract: The present invention is concerned with improvements relating to light duty cleaning and in particular to improvements relating to manual dish-washing. The invention provides a process which comprises the steps of: a) treating an adsorbent carrier such as a cloth or more preferably a sponge with a surfactant composition which is capable of thickening on the addition of water, b) treating the combination of the carrier and surfactant composition with water, and c) subsequent to step (b) performing a cleaning operation with the carrier. An advantage of this process is that the surfactant composition thickens within the carrier and is retained therein to provide an extended release of surfactant from the carrier.

Description: IMPROVEMENTS RELATING TO LIGHT DUTY CLEANING Technical Field The present invention is concerned with improvements relating to light duty cleaning and in particular to improvements relating to manual dishwashing. Background of the Invention It is known that the viscosity of certain surfactant solutions can be influenced by the concentration of electrolyte in the surfactant solution. WO 93/08247 (Clorox: 1991) discloses that surfactant systems containing alkyl ether sulphate systems can be thickened with the addition of an appropriate amount of electrolyte. EP 574086 (Colgate: 1992) discloses how the salts in a composition may affect the viscosity of the composition. Such technology is known and used in the formulation of shampoo and other personal washing compositions where the concentration of electrolyte and surfactant is often selected to give a peak viscosity for the surfactant system chosen. It is known that the addition of excess electrolyte does not result in further thickening but 'salts-out' the surfactant and results in a lowering of viscosity. It is known to prepare compositions which contain an excess of electrolyte such that they become thicker on dilution. EP 254653 (Cotelle SA and Henkel: 1986) relates to dilution-thickening concentrates in general and covers compositions which are thickened with excess NaCl. WO 95/02664 (Jeyes Group: 1993) discloses a liquid concentrate for dilution with water to give a thickened product. The concentrate comprises: an alkyl ether sulphate, optional further anionic or nonionic or amphoteric, optional cationic alone or in combination with nonionic, electrolyte and/or hydrotrope. The compositions disclosed in the above-mentioned documents can be sold as concentrates and are intended for dilution before use to give a thickened composition. Such rheological properties are considered advantageous for the cleaning of hard surfaces as they prevent the product running off the surface. With shampoo compositions, it is also advantageous for the product to thicken in the presence of water such that it is not washed of the skin rapidly. In the art of manual dishwashing it is known to prepare a very dilute solution of surfactant (typically less that 0.1%wt surfactant in water) and immerse the articles to be cleaned in this solution. This is known as 'bowl-washing' in the art. Dilution-thickening hand dishwashing compositions are known. Liquid dilution-thickening compositions are known for use in hand dishwash processes of the "bowl-washing" type. WO 93/03129 (Unilever: 1991) discloses a concentrated light duty liquid which contains: a mixture of anionic and nonionic, and 3-6 carbon alkane diol solvent as a hydrotrope. In a further method of manual dishwashing it is known to apply a concentrated surfactant composition directly into the articles to be cleaned. Compositions useful for this purpose may take the form of gels or pastes and may be applied to the surface of the articles with a cloth or sponge. In a second, alternative method, it is known to prepare a washing solution and transfer this to the surface of the articles, using an adsorbent carrier. For the purposes of the present invention the term adsorbent carriers includes articles such as a cloth or sponge. The operative consideration is that the carrier can be used to carry the washing solution to the articles to be cleaned. One difficulty with this second alternative method is that the surfactant content of the carrier rapidly becomes depleted in use and needs to be replenished. In order to solve this problem it has been known to provide carriers which comprise a support means such as steel wool and a solid surfactant composition impregnated thereupon. These gradually release surfactant over a period of time. However, once the surfactant is exhausted it is generally not possible to replenish the supply. Brief Description of the Invention We have now determined that the time for which the carrier can be used before the surfactant borne thereupon is exhausted can be significantly increased by use of method wherein the surfactant composition is thickened on dilution, within the carrier. This enables the carrier to be treated with surfactant which thickens within the carrier so as to replenish the store of surfactant held therein. Accordingly, the present invention provides a cleaning process which comprises the steps of: a) treating an adsorbent carrier with a surfactant composition which is capable of thickening on the addition of water, b) treating the combination of the carrier and surfactant composition with water, and, c) subsequent to steps (a) and (b) performing a cleaning operation with the carrier. It is believed that the use of a dilution thickening composition in combination with a carrier causes the surfactant to be retained on the carrier and released over a significantly longer period of time. Therefore in the method of the present invention the increased viscosity on dilution of selected compositions is beneficially combined with the delivering features of a porous substrate to extend the working lifetime of the substrate during the cleaning process The present invention also provides a kit of parts comprising: a) a surfactant composition which is capable of thickening on the addition of water, and, b) an adsorbent carrier. The invention is described in more detail below with particular reference to manual dishwashing processes. While the preferred cleaning process according to the present invention is a manual dishwashing process other cleaning processes including personal washing are not intended to be excluded from the scope of the invention. Detailed Description of the Invention Typically, the compositions of the present invention comprise at least one surfactant whose solution viscosity is strongly influenced by the prevailing electrolyte concentration. While other means by which the viscosity can be increased on dilution are known, the use of an electrolyte is preferred. In preferred embodiments of the invention the thickening of the diluted concentrate is effected by the presence of selected surface active agents whose thickening effect, in the concentrate, is reduced by the presence of an excess of dissolved electrolyte. Thus, upon dilution of the concentrate, the concentration of dissolved electrolyte is reduced and the surface active agent component is then capable of exerting its thickening effect. In practical embodiments of the invention, the carrier, which is preferably a sponge, is treated with the surfactant composition either by dipping at least a part of the carrier in the composition or by otherwise exposing the carrier to the surfactant composition, such as by pouring or otherwise dispensing the surfactant composition onto the carrier. The combination of the carrier and the composition is treated with water, either by dipping the combination into water or by the simple expedient of starting with a wet carrier. As a result of the dilution of the electrolyte which occurs, the electrolyte concentration falls below that which is sufficient to prevent the surfactants from thickening and the viscosity of the surfactant composition rises. As described above, this increase in viscosity causes the surfactant to be retained on the carrier and released over a significantly longer period of time. Preferred surfactant concentrations range from 2-40%wt on product. Levels of total surfactant in the range 7.5- 30%wt are particularly preferred. Preferred electrolyte concentrations range from l-20%wt with levels of 4-9%wt being particularly preferred. Surfactants In a preferred embodiment of the present invention the surfactants include at least one anionic, zwitterionic or amphoteric surfactant. Particularly preferred surfactants include one or more of ethoxylated alkyl ether sulphate, lauryl sulphate and amido propyl betaine. Amongst the most preferred electrolyte sensitive surfactants are alkyl ether sulphates of the general formula: R-0-(CH 2 -CH 2 0) n SO ? - where R is C 8 . 18 alkyl and n is 1 - 5. Preferably, R is lauryl- . The alkyl ether sulphate surfactants are preferably present at a level of 2-30%wt. A particular preferred electrolyte sensitive surfactant is lauryl ammonium ether sulphate. Conveniently, this component is present in the formulations of the invention at levels of 2-20%wt, more preferably 3-7%wt on product for relatively dilute products or 8-18% for concentrates. It is possible to use other anionic surfactant in combination with the ether sulphate surface active agents. Anionic surfactants which may be used in combination with the ether sulphate surface active agents include alkylaryl sulphonates, alcohols sulphates, phosphate esters, sulphosuccinates, sulphosuccinamates, alkane sulphonates, olefin sulphonates, petroleum sulphonates, sarcosinates, taurates, isethionates, and soaps. Particular examples of these classes of anionic surfactants include those sold under the trade names Eltesol SX30[TM] (sodium xylene sulphonate) , E picol L2[TM] (sodium lauryl sulphate), Triton H55[TM] (potassium phosphate ester), Marlinat DF8 (sodium sulphosuccinate) , Hostapur SAS 30X[TM] (sodium alkane sulphonate), Hostapur OS[TM] (sodium olefin sulphonate), Petronate S[TM] (sodium petroleum sulphonate), Hamposyl L30[TM] (sodium lauroyl sarcosinate) , Fenopon T33 [TM] (sodium N-methyl-N-oleyl taurate) , and Fenopon AC 78[TM] (sodium coconut isethionate) . Preferred amongst these surfactants additional are alcohol sulphates, particularly C 8-18 alcohol sulphates and alkyl benezene sulphonates. Typical levels of alcohol sulphates in compositions of the present invention range from 5-15%wt on product, more preferably 6-10%wt on product. Typical levels of alkyl benzene sulphonate in compositions of the present invention range from 10-30% on product. It is possible to use nonionic surfactant in combination with the ether sulphates surface active agents. One particular class of nonionic surfactants for use in combination with the ether sulphate surface active agents comprises the amine oxides of the formula: in which R_ is a long chain alkyl group, typically containing 8 to 20 carbon atoms; and R 2 and R 3 are the same or different, lower alkyl group, typically containing 1-4 carbon atoms. Particular examples of this class of nonionic surfactants are alkyl dimethyl amine oxides such as sold under the trade name "Empigen OB" [TM] by Albright & Wilson. Other classes of nonionic surface active agents which may be employed comprise polyalkoxylated fatty alcohols and their esters; polyalkoxylated fatty acids; polyalkoxylated alkyl phenols; alkanolamides; polyalkoxylated alkanolamides, glucosides, polyglucosides, sucrose and sugar esters, fatty esters, ethoxylated alkanolamides, ethoxylated long chain amines; alkyl amines, alkyl polyglucosides and alkyl polyglycosides. Particular examples of these classes of nonionic surfactants are those sold under the trade names Synperonic A[TM] (alcohol ethoxylates) , Crodet L24[TM] (polyoxyethylene-24-lauric acid), Synperonic NP[TM] (nonyl phenyl ethoxylates), Empilan CME[TM] (coconut monoethanolamide) , Triton CG110[TM] (alkyl glucoside) , Glucam E10[TM] (10 mole ethoxylate of methyl glucoside), Crodesta SL 40 [TM] (sucrose cocoate) , Empilan MAA[TM] (ethoxylated coconut monoethanolamide), Ethomeen C12 [TM] (ethoxylated coconut amine), and Tagosoft 16B[TM] (cetyl isooctanoate) . Suitable amphoteric surfactants for use in combination with the ether sulphate surfactants include alkyl betaines, alkyl aminopropionates, alkyl iminodipropionates; alkyl glycinates; carboxyglycinates; alkyl imidazolines sulphobetaines; alkyl polyaminocarboxylates and polyamphocarboxyglycinates. Particular examples of such amphoteric surfactants are those sold under the trade names Tegobetain A4080[TM] (alkyl dimethyl betaine) , Ampholax XCU[TM] (coco- amphoglycolate) , Amphotensid CT[TM] (alkyl imidazoline based amphoteric), Ampholax XCO 30 [TM] (coco- amphocarboxyglycinate) and Sandobet SC[TM] (cocoa ide- sulphobetaine) ; and sodium N-coco-aminopropionate, disodium N-coco-iminodiproprionate, and cocoglycinate. Preferred amongst these surfactants are betaines, preferably alkyl amido propyl betaines with an alkyl chain length of C 8 -C 18 . Coco amido propyl betaine is particularly preferred. Typical levels of betaine in compositions according to the present invention range from 0.5-5.0%wt, more preferably l-3%wt on product. Suitable cationic surfactants for use in the concentrates of the invention includes alkyl quaternary ammonium halides; primary, secondary and tertiary amines and their salts; and polyamines. Particular examples of such cationic surfactants are those sold under the trade names Empigen BAC[TM] (alkyl dimethyl benzalkonium chloride), Armac 1[TM] (tallow amine acetate-amine salts), Synprolam 35N3 [TM] (N-alkyl propane propane diamine) , and Synprolam 35X10 [TM] (10 mole ethoxylated primary amine). Alternatives to the use of anionic containing systems are known. For example, nonionic surfactants can be used in combination with the cationic surfactant. In such systems the nonionic surfactant is preferably a nonionic surfactant as described above for use in combination with the ether sulphates. Electrolytes Where the surfactants are sensitive to the presence of electrolyte, a broad range of electrolytes can be employed, provided that the electrolyte causes thickening of the surfactant at a first concentration and thinning of the surfactant, relative to the viscosity peak at a second, higher concentration. Preferred electrolytes of present inventions are NaCl, MgCl 2 , MgS0 4 and mixtures thereof. Other water-soluble electrolytes may be employed, including builders such as sodium, sodium phosphates and alkali metal silicates. Typical electrolyte concentration is from 4.0 to 30% %w/w, preferred electrolyte concentration is from 4-15 %w/w, particularly preferred concentration is from 4-10% %w/w. Carriers Preferred carriers comprise a porous or fibrous material. Typical examples of porous materials are sponges which can be natural and/or synthetic. Typical examples of fibrous materials are cloths, which can be woven and/or non-woven. Synthetic sponges as are widely available in the marketplace are particularly preferred. Additional Components Other components which may be present include non- bleaching germicides or disinfectants and weak or strong acids which may serve as limescale removing agents e.g. glycollic acid, citric acid, hydrochloric acid and sulphuric acid. The compositions useful in present invention can include, optionally, perfumes, solvents, colorants and mixtures thereof. It is also possible for the compositions of the invention to contain a compound which provides a particularly unpleasant taste so as to prevent inadvertent consumption of the product. Preservatives and other antimicrobial components are optional components of the compositions according to the invention. Typical antimicrobial agents include formaldehyde. It is possible to include polymers in the composition of the invention. Guar gum is a suitable polymer. Typical inclusion levels of polymer range from 0.001-2%. Hydrotropes are another optional component of the present invention. Ethanol is a suitable hydrotrope as are the xylene, cumeme and benzene sulphonates. Preferably ethanol is present at a level of up to 10%wt, preferable up to a level of 6%wt. Preferred compositions according to the present invention are dilution thickening and comprise: 2.0-10%wt C8-C18 alkyl ether sulphate, 5.0-15%wt C8-C18 alkyl sulphate, 0.5-5.0%wt C8-C18 alkyl amidopropyl betaine, 7.5-30.0%wt electrolyte, and, up to 6%wt ethanol to 100% water and minors Other preferred compositions comprise 2-15%wt C8-C18 alkyl ether sulphate, 3-16%wt alkyl benzene sulphonate (as the TEA salt) 7-14%wt alkyl benzene sulphonate (as the Na salt), 0.5-10%wt electrolyte, and, 0.5-10%wt hydrotrope. to 100% water and minors One particularly preferred composition according to the present invention comprises: 8-18%wt C8-C18 alkyl ether sulphate 0.5-5%wt amidopropyl betaine 0.5-10%wt electrolyte, and, to 100% water and minors In the last above-mentioned composition it is particularly preferred that the minors comprise: 0.01-l%wt guar gum 0.001-0.l%wt formaldehyde 0.001-0.l%wt butylated hydroxytoluene 0.1-5%wt perfume Examples The following examples will further illustrate a preferred embodiment of present invention. However, it is understood that following examples are given by way of illustration and not limitation. Typical examples of porous and/or fibrous material useful in the present invention are synthetic sponges, available in the marketplace from the Minesota Mining and Manufacturing (3M) company. EXAMPLE I A series of illustrative and comparative examples using the method of present invention were prepared and the results are shown in Table 2 below. The formulations used are given in Table 1 below. Dilution viscosity profiles of the composition according to the present invention are given in Table 3. Table 1 I II LES-Na(*) 5.0 5.0 LS-NH4(**) 7.0 7.0 CAPB ( * * * ) 1.5 1.5 NaCl 1.0 0.5 Ethanol 1.0 0.5 * - lauryl ether sulphate as sodium salt ** - lauryl sulphate as ammonium salt *** - amido propyl betaine based on coco fatty acid Compositions were prepared by simple mixing of the components listed in Table 1 to form compositions I and II. Composition I is a composition for use in the method of the present invention and composition II is a control. Both compositions had an initial viscosity of 600cp as measured using a Haake viscometer at 75.04 reciprocal seconds shear rate. The product retention was measured by applying first 3 g of the composition I or II plus, subsequently, 15 g of water to a sponge. After application the sponge was manually compressed to as to generate foam and expel a washing liquor which was allowed to fall into a beaker. The sponge was then treated with a further 15 g of water and the process repeated, each time gathering the liquor in a fresh beaker, until no further foam was generated as the liquor was expelled. The contents of the beakers was subjected to chemical analysis to determine the surfactant concentration. The concentrations are given in table 2 below. Table 2 SURFACTANT RELEASED (concentration in ppm) SOLUTION I II 1 1645 6999 2 6792 7055 3 5901 2090 4 1802 966 5 936 464 10 177 86 15 48 60 20 33 36 25 21 29 From the results in Table 2 it can be seen that the composition I showed a clear retention of the product on the sponge and an extended release of the surfactant from the sponge: i.e. with composition I, which embodies the invention, a more extended washing procedure could be conducted without excessive wastage of the surfactant containing product. Table 3 below gives viscosity/dilution data for the compositions I and II. It can be seen that composition I exhibits an increase in viscosity as it is diluted. Whereas composition II shows a continuous fall in viscosity with dilution. Table 3 Active concentration Viscosity (cp) (%) I II 620 13.5 12.5 1 045 - 11.5 1 685 - 11.0 410 10.5 1 549 10.0 366 9.5 275 9.0 275 8.5 1 123 8.0 149 7.5 794 7.0 54 6.5 484 6.0 20 5.5 193 5.0 14 4.5 19

Claims: CLAIMS 1. A cleaning process which comprises the steps of: a) treating an adsorbent carrier with a surfactant composition which is capable of thickening on the addition of water, b) treating the combination of the carrier and surfactant composition with water, and, c) subsequent to step (b) performing a cleaning operation with the carrier. 2. Process according to claim 1 wherein the surfactant composition comprises at least one surfactant whose solution viscosity is strongly influenced by the prevailing electrolyte concentration. 3. Process according to claim 2 wherein said at least one surfactant is present in the surfactant composition at a level of 2-40%wt. 4. Process according to claim 2 wherein the surfactant composition comprises electrolyte at a level of 4- 20%wt. 5. Process according to claim 2 wherein said surfactant composition comprises one or more alkyl ether sulphates of the general formula: R-O- (CH,-CH 2 0) n S0 3 - where R is C 8-1 <, alkyl and n is 1 - 5. 6. Process according to claim 2 wherein said surfactant composition comprises an alkyl amido propyl betaines with an alkyl chain length of C 8 -C 18 . 7. Process according to claim 2 wherein said surfactant composition comprises an electrolyte selected from the group comprising NaCl, MgCl 2 , MgS0 4 and mixtures thereof. 8. Process according to claim 1 wherein the surfactant composition comprises: a) 2.0-10%wt C8-C18 alkyl ether sulphate, b) 5.0-15%wt C8-C18 alkyl sulphate, c) 0.5-5.0%wt C8-C18 alkyl amidopropyl betaine, d) 7.5-30.0%wt electrolyte, and, e) optionally, up to 6%wt ethanol. 9. A manual dishwashing process which comprises the steps of, treating an adsorbent carrier with a surfactant composition which comprises: a) 2.0-10%wt C8-C18 alkyl ether sulphate, b) 5.0-15%wt C8-C18 alkyl sulphate, c) 0.5-5.0%wt C8-C18 alkyl amidopropyl betaine, d) 7.5-30.0%wt electrolyte, and, e) optionally, up to 6%wt ethanol, subsequently treating the combination of the carrier and surfactant composition with water, and, thereafter performing a manual dishwashing operation with the carrier. 10. A kit of parts comprising: a) a surfactant composition which is capable of thickening on the addition of water, and, b) an adsorbent carrier.

Inventors: HELFANT BEATRICE MICHELIN, LUNA AMAURI ZANINI, LUPPY EDUARDO JR, MARCHANT PABLO ANDRES MARQUES, HELFANT, BEATRICE, MICHELIN, LUNA, AMAURI, ZANINI, LUPPY, EDUARDO, JR., MARCHANT, PABLO, ANDRES, MARQUES
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1996
Main classification: C11D17
IPC codes: C11D1, C11D3, C11D11, C11D17