CLEANING COMPOSITION COMPRISING MONOALKYL CATIONIC SURFACTANTS

Abstract: The specification disloses improved compositions which both clean a surface and are believed to deposit thereupon a layer of cationic surfactant which assists the release of soil subsequently deposited upon said surface. These comprise a surfactant mixture, wherein said surfactant mixture itself comprises: a) at least 65 wt.% on total surfactant of nonionic surfactant; b) less than 1 wt.% on total surfactant of anionic surfactant; c) 0.1-35 wt.% on total surfactant of a cationic surfactant which is a mono fatty alkyl quaternary ammonium compound wherein the alkyl chains comprise at least 10 % of C18-C26 alkyl groups; wherein said composition further comprises, at least 0.5 wt.% of an organic amine having a pKa of at least 8.0.

Description: CLEANING COMPOSITION COMPRISING MONOALKYL CATIONIC SURFACTANTS Technical Field The present invention relates to an alkaline cleaning composition for hard surfaces, wherein said composition comprises both a fatty alkyl cationic surfactant and a nonionic surfactant. Background to the Invention In traditional cleaning of hard surfaces such as wood, glazed tiles, painted metal and the like, it is known to follow soil removal using surfactant or solvent based compositions with the application of a lacquer, wax or polish as a separate operation so as to seal and protect the surface and reduce the rate of soil redeposition. This two-step cleaning and sealing operation is time-consuming and complex. It has been proposed to include a range of soil release agents, including polymers, siloxanes and dialkyl quaternary cationic surfactants in cleaning compositions so as to provide a secondary cleaning benefit. It is believed that these soil release agents function by deposition of a layer of of polymer, siloxane or surfactant on the surface during cleaning. This layer of material is believed to facilitate further cleaning operations by reducing the extent to which soil adheres to the surface. It is preferable that these compositions are strongly alkaline, so as to assist cleaning. Of these materials the quaternary, cationic surfactants are available at the lowest cost. These quaternary salts generally comprise a quaternised nitrogen with one or two pendant fatty alkyl chains and three or two pendant lower alkyl chains. In the case of those compositions which comprise dialkyl quaternary cationic surfactants, it has been found difficult to stabilize the products against flocculation and or phase-separation due to the interaction of the components present. Consequently, a technical problem exists as regards the stable formulation of strongly alkaline cleaning compositions which contain an effective level of a quaternary nitrogen containing, soil release agent. Brief Description of the Invention We have devised stable, alkaline organic amine containing compositions which both clean a surface and are believed to deposit thereupon a layer of relatively long chain mono-fatty alkyl cationic surfactant which assists the release of soil subsequently deposited upon the said surface. It is believed that stability in such compositions is brought about by the combined use of the alkaline organic amine and the mono-fatty alkyl cationic surfactant. Accordingly, the present invention provides an aqueous, hard- surface cleaning composition comprising a surfactant mixture, wherein said surfactant mixture comprises: at least 65%wt on total surfactant of nonionic surfactant, less than l%wt on total surfactant of anionic surfactant, c) 0.1-35%wt on total surfactant of a cationic surfactant which is a mono fatty alkyl quaternary ammonium compound wherein the alkyl chains comprise at least 10%wt of C18-C26 alky groups, wherein, said composition further comprise, at least 0.5%wt of of an organic amine having a pKa of at least 8.0. It is believed that the cationic surfactants present in the compositions of the present invention modify the surface energy of surfaces to which the composition is applied so as to raise the contact angle of soil subsequently deposited on the modified surface. Detailed Description of the Invention In order that the present invention may be further understood it will be described in greater detail below with particular reference to preferred components and formulation details. Cationic surfactants: A range of cationic mono-fatty alkyl quaternary ammonium compounds find useful appliaction in the compositions of the present invention. Particularly suitable cationic surfactants are of the general formula: [R 1 R 2 R 3 R 4 N] wherein R l t R 2 and R 3 are independently C j _ 6 alkyl, R 4 is a fatty alkyl chain and X is an monovalent anion equivalent, the distribution of chain lengths in the material being such that in at least 10%wt of the material the fatty alkyl chain comprises C18-26 carbon atoms. It is preferable that less than 60% of the material comprises mono-fatty alkyl quaternary ammonium compounds in which the fatty alkyl chain is C16 or shorter. It is believed that these longer chain mono fatty alkyl quaternary materials give better performance in terms of secondary cleaning benefits than shorter mono fatty alkyl chain materials. It has also been found that use of the mono fatty alkyl chain materials allows more scope for formulation than the use of the corresponding dialkyl fatty chain materials. Halide, particularly chloride or bromide, is a suitable counter-ion. The fatty alkyl chain can be derived from synthetic or natural feedstocks. If the fatty alkyl chain is derived from natural feedstocks it will generally comprise a mixture of materials with a range of alkyl chain lengths in the fatty-alkyl chain. Preferably the fatty alkyl chains are fully saturated. It is envisaged that saturated alkyl chains will show effective properties due to packing of the alkyl chains at surfaces and interfaces. Preferably, the cationic surfactant comprises a cation of the formula given above wherein R j =R 2 =R 3 =CH 3 . Materials of this general nature, in which the lower alkyl groups are methyl groups are available in the marketplace. A particularly preferred material is trimethyl behenyl ammonium bromide. We have determined that this material will flocculate over time in the presence of significant quantities of inorganic salts, including alkali's such as sodium hydroxide and sodium or potassium carbonate. As is further described herein, this difficulty is avoided in the compositions of the present invention. Nonionic Surfactants : It is essential that the compositions of the present invention comprise a nonionic surfactant. The presence of nonionic surfactant is believed to contribute significantly to the cleaning effectiveness of the compositions of the invention. Suitable nonionic detergent active compounds can be broadly described as compounds produced by the condensation of alkylene oxide groups, which are hydrophilic in nature, with an organic hydrophobic compound which may be aliphatic or alkyl aromatic in nature. The length of the hydrophilic or polyoxyalkylene radical which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements . Particular examples include the condensation product of aliphatic alcohols having from 6 to 22 carbon atoms in either straight or branched chain configuration with ethylene oxide, such as a coconut oil ethylene oxide condensate having from 2 to 15 moles of ethylene oxide per mole of coconut alcohol; condensates of alkylphenols whose alkyl group contains from 6 to 12 carbon atoms with 5 to 25 moles of ethylene oxide per mole of alkylphenol; condensates of the reaction product of ethylenediamine and propylene oxide with ethylene oxide, the condensates containing from 40 to 80% of polyoxyethylene radicals by weight and having a molecular weight of from 5,000 to 11,000; tertiary amine oxides of structure R 3 N0, where one group R is an alkyl group of 8 to 18 carbon atoms and the others are each methyl, ethyl or hydroxy-ethyl groups, for instance dimethyldodecylamine oxide; tertiary phosphine oxides of structure R,P0, where one group R is an alkyl group of from 10 to 18 carbon atoms, and the others are each alkyl or hydroxyalkyl groups of 1 to 3 carbon atoms, for instance dimethyldodecylphosphine oxide; and dialkyl sulphoxides of structure R 2 S0 where the group R is an alkyl group of from 10 to 18 carbon atoms and the other is methyl or ethyl, for instance methyltetradecyl sulphoxide; fatty acid alkylolamides; alkylene oxide condensates of fatty acid alkylolamides and alkyl mercaptans . Particularly preferred nonionic surfactants are the ethoxylated alcohols having 6-14 carbons and 2-9 moles of ethoxylation. Suitable materials include IMBENTIN 91/35 OFA (TM) , a C 9.n nonionic having on average five moles of ethoxylation and NONIDET 91-6T (TM) a topped C 9 _ n nonionic with an average of six moles of ethoxylation. Many more nonionic surfactants are known to the skilled worker, as set forth in M.J.Schick 'Nonionic Surfactants', Marcel Dekker (1967) and subsequent editions of the same work. The amount of nonionic detergent active to be employed in the composition of the invention will generally be from 1 to 30%wt, preferably from 2 to 20%wt, and most preferably from 5 to 10%wt. It is particularly preferred that the ratio of nonionic surfactant to anionic and cationic surfactant is such that > 75% of the total surfactant present in the composition is nonionic. It is essential that the compositions of the present invention only comprise low levels of anionic detergent actives or that these actives are absent in so far as is practical. It is believed that the presence of anionic detergents will cause the formation of a complex between the cationic and anionic detergents which will reduce the effectiveness of the compositions. The overall surfactant content of compositions according to the present invention will generally be 1 to 30%wt. Organic Amine: It is essential that the compositions of the invention comprise at least 0.5%wt of an organic amine, with a pK a of at least 8.0. This component is believed to function as ester- cleavage agent which assists cleaning of recalcitrant soils such as the pyrolised soils which are produced when fatty and/or proteinaceous foodstuffs are heated at the surface. When organic amines with a lower pK a such as aniline are used they are ineffective in assisting cleaning. When inorganic alkali's are present at significant levels, the quaternary material described above flocculates, and the composition phase-separates. It is preferred that the composition comprises 1-10% of an alkanolamine, with levels of 2-6%wt being particularly preferred. Particularly suitable alkanolamines include: 2- amino-2-methyl-1-propanol, mono-ethanolamine and di- ethanolamine . 2-amino-2-methyl-l-propanol is the most preferred organic amine. Preferably the compositions of the present invention comprise less than 1% of electrolyte salts, including sodium and/or potassium carbonates, bicarbonates and/or hydroxides. Minors and other components: A plurality of minor components can be present in the compositions of the present invention. The composition according to the invention can contain other ingredients which aid in their cleaning performance and/or improve the physical properties of the composition. These components are not essential to the functioning of the invention. Hydrophobic oils are optional components of compositions according to the present invention. Suitable oils include oils which rapidly dissolve triglyceride. When oils are present preferred oils include limonene, para-cymene, di-butyl ether and butyl butyrate. A further optional ingredient for compositions according to the invention is a suds regulating material, which can be employed in those compositions according to the invention which have a tendency to produce excessive suds in use. Examples of suds regulating materials are organic solvents, hydrophobic silica and silicone oils or hydrocarbons. Solvents are optional components of compositions according to the present invention. Where solvents are present, preferred solvents are of the form R : -0- (E0) m - (PO) n -R 2 , wherein R x and R 2 are independently C2-6 alkyl or H, but not both hydrogen, m and n are independently 0-5. More preferably, the solvent is selected from the group comprising di-ethylene glycol mono n- butyl ether, mono-ethylene glycol mono n-butyl ether, propylene glycol n-butyl ether, isopropanol, ethanol, butanol and mixtures thereof. Alternative solvents include the pyrrolid (in) ones, for example N-methyl pyrrolidinone. We have determined that the inclusion of a long-chain fatty alcohol, particularly C16 or longer, more preferably C16-C20 such as tallow alcohol gives an improvement in cleaning performance. Typically, these alcohols will be present at levels of 0.001-2%, and preferably less than 1%. Compositions according to the invention can also contain, in addition to the ingredients already mentioned, various other optional ingredients such as pH regulants, colourants, optical brighteners, soil suspending agents, detersive enzymes, compatible bleaching agents, gel-control agents, freeze-thaw stabilisers, bactericides, preservatives, detergent hydrotropes, perfumes and opacifiers. It has been found convenient to deliver products according to the invention in the form of a relatively low dosage of product in a relatively fine mist. This has the significant advantage that only low levels of product need be employed. Preferably compositions according to the invention are packaged in a container adapted to produce a spray of 0.1-1.5ml of product per spraying operation, said spray having an average drop size in the range 30-300 microns. We have determined that it is particularly advantageous to include a polymer in the compositions of the present invention so as to reduce the level of formation of exceptionally fine droplets when the composition is sprayed as a relatively fine mist. Suitable polymers include polyvinyl pyrrolidone, available in the marketplace as Polymer PVP K-90. Suitable levels of PVP polymer range upwards from 50ppm. Levels of 300-2000ppm are particularly preferred. Particularly preferred compositions have a pH of >10 and comprise, in admixture with water, : a) 3-15% nonionic surfactant (preferably, C9-C12 E05-8 nonionic surfactant) b) 2-10% solvent (preferably, diethylene glycol mono-n-butyl ether) c) 2-6% alkanolamine (preferably, 2-amino-2-methyl-l- propanol ) d) 0-2000ppm polymer (preferably, PVP) , and f) 0.1-4% of a cationic surfactant comprises a cation of the general formula: [R t R 2 R 3 R 4 N] + X " wherein R ι r R 2 and R 3 are independently C j.6 alkyl, R 4 is a fatty alkyl chain comprising at least 10% C18-26 carbon atoms and X is an monovalent anion equivalent. In order that the present invention may be better understood it will be described hereinafter by way of non-limiting example. EXAMPLES Aqueous compositions comprising nonionic surfactant, and a relatively low level of cationic surfactant were prepared as in Tables 1 below: using the following materials (all compositions are given in terms of wt% unless otherwise stated) : NONI : NONIDET 91-6T (TM: ex. Nippon Shell): a C9-C11 ethoxylated alcohol with 6 moles of ethoxylation, and topped to reduce the quantity of low ethoxylates, VBM: Behenyl trimethyl ammonium chloride (ex Nippon Oils & Fats) , DIGOL: Butyl Digol (TM) : diethylene glycol mono n-butyl ether, AMP: 2-amino-2-methyl-l-propanol, CTAB:Cetyl trimethyl ammonium bromide (ex: BDH), DEA: Diethanolamine CARB: Potassium Carbonate POL: PVP K-90 (TM ex. International Speciality Polymers ) 2HT: NISSAN CATION 2ABTN (TM ex: Nippon Oils & Fats) : di hardened tallow dimethyl ammonium chloride. All samples contained 0.1% polyvinyl pyrrolidone, available in the marketplace as Polymer PVP K-90 (TM) and 0.2% of a perfume. For example 1, the required amounts of all of the ingredients were mixed at room temperature. For examples 2 & 5 VBM was added to hot water at 80C and stirred using a Heidolph mixer at 80C for 2 hours, to give a 15.5% solution by weight. The required amount of this solution (still at 80C) was then added to the required amount of a solution containing all the remaining ingredients, at room temperature, and the solution stirred for a further 10 minutes. For example 3, equal amounts of nonionic surfactant (NONI) and dihardened tallow dimethyl ammonium chloride were melted together at 60C. The required amount of this comelt was added (still at 60C) to the required amount of a solution containing all the remaining ingredients, at room temperature, and the solution stirred for a further 30 minutes. For example 4 the required amounts of all of the ingredients were mixed at room temperature. The solution was then warmed briefly to 60 C to homogenise. In order to measure cleaning results the following experiments were performed. lOOg of 1.5 poise dehydrated castor oil (ex. SEATONS) was weighed into a glass jar. To this was added 0.2g Fat Red (TM) dye (ex. SIMGA) and the mixture was stirred vigorously (2000 RPM) for 6 hours using a Heidolph stirrer. The stirred mixture was refrigerated when not in use. Vitreous enamel tiles (380x300mm) were cleaned using a fresh damp J-CLOTH (TM) using, in sequence, JIF cream (TM) , then a commercially available brand of hand dishwashing liquid and finally calcite powder. After drying residual calcite was removed by buffing with a paper towel . lml of the compositions listed in Table 1 was wiped onto the cleaned tiles using a fresh damp J-CLOTH. The tiles were rinsed with tap water for 15 seconds to remove excess composition and allowed to drain. Tiles were soiled over a 215x150mm area using a DeVilbiss (TM) gravity feed spray gun (MODEL MPS-514/515) using compressed air at 25 psi, by spraying from 27 cm for 35 seconds. The soiled tiles were laid horizontally in an oven at 85 Celcius and thermally aged for 1.5 hours and then stored overnight . Tiles were cleaned by hand using damp J-cloths and the compositions listed in Table 1. The effort required to clean the tiles was determined as 'ETh' in Table 1. ETh measurements are expressed in Newton. seconds, higher values indicate that more effort was required to clean the tile. Stability was determined by placing samples on storage at 5, 25 an 37 Celcius for three months. In the cases indicated as unstable in Table 1 a cloudy precipitate was formed under one or more of the storage conditions. From the results in Table 1 it can be seen that the lowest effort cleaning score were obtained with example 2, which is an embodiment of the invention using the longer chain fatty alkyl containing quaternary cationic VBM. Examples 3 and 4 also showed an improvement over the control formulation provide as example 1. It can be seen that this improvment was either slight, as with the shorter fatty alkyl chain (CTAB: as used in example 4) or that product stability on storage was lost, as with the di fatty alkyl material (2HT: as used in example 3) . Example 5 shows that the combination of an alkaline salt with VBM did not lead to a stable product . Further results are shown in Table 2 below. The same raw materials were used as described above. ETh is as described above. Sample 11 was prepared as sample 1. Samples 6, 7, 9 and 10 were prepared as samples 2 and 5. Sample 8 was prepared as sample 3. 'WIRA' are the % soil removal using a Wool Industries Research Association Abrasion Tester. To obtain these results 10cm by 10cm stainless steel tiles were cleaned using calcite followed by a rinse in deionised water. 25g of salad oil (ex Nisshin, Japan) , 5g of plain flour (Homepride [RTM] , ex Dalgety, UK) and 75g of acetone were mixed together for two minutes using a high shear Silverson [RTM] mixer. This mixture was then sprayed using a Humbrol [RTM] airbrush paint sprayer onto the cleaned tiles, using a circular mask, to give 5.5cm diameter patches of soil. The acetone was allowed to evaporate to give 0.04-0.05g of soil per tile. The soiled tiles were heated at 175 Celcius for 34 minutes and left overnight prior to cleaning. The soil tile was placed in the 'WIRA' tester and 0.5ml of test product applied. The tile was then cleaned using a 'J-cloth' [RTM] (ex. Johnson and Johnson, UK) , folded to give eight layers, at a head pressure of 657g/cm 2 , for one full cycle (17 passes of the head) . This procedure was repeated to give a total of three full cycles, using a fresh J-cloth and 0.5ml of test product each time. After all three cycles the soiled tile was removed, rinsed and allowed to dry at 50 Celcius for 30 minutes. The total mass of soil removed was then calculated and expressed as a percentage of the original soil mass. This is given as 'WIRA' in Table 2. CB is the contact angle on glass which has been contacted with the composition according to the example, using bromonaphthalene . Table 2 Examples 6, 7 and 10 are in accordance with the invention, whereas the remaining examples are comparative. Example 11 is a commercially successful kitchen cleaner. From Table 2, it can be seen that a larger cleaning effort (ETh) is required when no quaternary cationic is present (example 11), or when the quaternary cationic has a short chain (example 8) . The WIRA results, for which higher scores are better, show that the presence of organic amines AMP (example 6 and 10) or DEA (example 7) give a significantly more effective composition than one in which the amine is absent (example 9) . CB data demonstrates that the compositions of the invention modify the surface energy (which may be calculated from the contact angle) as compared with a known kitchen cleaning formulation (example 11) which contains no quaternary cationic. The modification of surface energy ia less for the CTAB based formulations (example 8) . Overall, it can be seen that examples 6 and 7 with clean a surface with reduced effort and leave the surface energy modified so as to prevent or reduce re-soiling. Example 8 is less effective especially as regards thermally aged soils. The formulation of example 9 will attack the thermally aged soil used to determine ETh but is poor as a general cleaner. Example 10 is acceptable but it is preferable that carbonate is absent.

Claims: CLAIMS 1. An aqueous, hard-surface cleaning composition comprising a surfactant mixture, wherein said surfactant mixture comprises: a) at least 65%wt on total surfactant of nonionic surfactant, b) less than l%wt on total surfactant of anionic surfactant, c) 0.1-35%wt on total surfactant of a cationic surfactant which is a mono fatty alkyl quaternary ammonium compound wherein the alkyl chains comprise at least 10%wt of C18-C26 alkyl groups wherein, said composition further comprise, at least 0.5%wt of of an organic amine having a pKa of at least 8.0. 2. Composition according to claim 1 wherein the mono fatty alkyl quaternary ammonium compound is of the general formula: [R 1 R 2 R 3 R < N] 4 X ' wherein R 1# R 2 and R 3 are independently C^ alkyl, R 4 is a fatty alkyl chain and X is an monovalent anion equivalent, the distribution of chain lengths in the material being such that less than 60% of the material comprises mono-fatty alkyl quaternary ammonium compounds in which the fatty alkyl chain is C16 or shorter. 3. Composition according to claim 2 wherein R 1 =R 2 =R 3 =CH 3 . 4. Composition according to any one of claims 1-3 wherein the mono fatty alkyl quaternary ammonium compound is trimethyl behenyl ammonium halide. 5. Composition according to claim 1 wherein the ratio of nonionic surfactant to anionic and cationic surfactant is such that > 75% of the total surfactant present in the composition is nonionic. 6. Composition according to claim 1 comprising 2-10% of an organic amine. 7. Composition according to claim 1 wherein the organic amine is selected from the group comprising 2-amino-2- methyl-1-propanol, mono-ethanolamine and di-ethanolamine. 8. Composition according to claim 1, packaged in a container adapted to produce a spray of 0.1-1.5ml of product per spraying operation, said spray having an average drop size in the range 30-300 microns. 9. Composition according to claim 1 of pH >10 which comprises, in admixture with water, : a) 3-15% nonionic surfactant b) 2-10% solvent c) 2-6% organic amine d) 0-2000ppm polymer, and e) 0.1-4% of a cationic surfactant comprises a cation of the general formula: [R j R 2 R 3 R 4 N] * X " wherein R l t R 2 and R 3 are independently C 6 alkyl, R 4 is a fatty alkyl chain comprising at least 10% C18-26 carbon atoms and X is an monovalent anion equivalent. 10. A method for cleaning hard surfaces which comprises the step of treating the surface with a composition according to any one of claims 1-9, by spraying said composition onto the surface.

Inventors: LEACH MATTHEW JAMES, NIWATA YOSHIHISA, LEACH, MATTHEW, JAMES, NIWATA, YOSHIHISA
Applicants: LEACH MATTHEW JAMES, NIWATA YOSHIHISA, UNILEVER NV, UNILEVER PLC, LEACH, MATTHEW, JAMES, NIWATA, YOSHIHISA, UNILEVER N.V.
Application year: 1997
Main classification: C11D1
IPC codes: C11D1, C11D3