Dishwash composition comprising rinse-activatable antifoam

Abstract

The invention is in the field of hard surface cleaning compositions. There is need for compositions that foam copiously during the washing/cleaning stage. However, during the rinse stage, the foam should rinse-off as quickly as possible in minimum number of rinses-cycles so that the process becomes sustainable. Disclosed is an aqueous cleaning composition, having a pH of 6.5 or lower, comprising (i) 3.0 to 25.0% by weight alkyl ethoxy sulphate; (ii) 1.0 to 5.0% by weight amphoteric surfactant; (iii) 0.1 to 1.0% by weight fatty acids being saturated non-hydroxy C.sub.8-12 fatty acid and a saturated non-hydroxy C.sub.14-18 fatty acid, where ratio of amount of said C.sub.8-12 fatty acid to that of said C.sub.14-18 fatty acid is from 1:0.1 to 1:10 parts by weight; and (iv) 0.5 to 5% by weight non-ionic surfactant, wherein (iii) and (iv) together an antifoaming system, and wherein amount of non-alkoxylated anionic surfactant in said composition in less than 1.0% by weight.

Claims

1. An aqueous cleaning composition, having a pH of 6.5 or lower, comprising: (i) 3.0 to 25.0% by weight alkyl ethoxy sulphate; (ii) 1.0 to 5.0% by weight amphoteric surfactant; (iii) 0.1 to 1.0% by weight fatty acids being saturated non-hydroxy C.sub.8-12 fatty acid and a saturated non-hydroxy C.sub.14-18 fatty acid, where ratio of amount of said C.sub.8-12 fatty acid to that of said C.sub.14-18 fatty acid is from 1:0.1 to 1:10 parts by weight; and (iv) 0.5 to 5% by weight non-ionic surfactant, wherein (iii) and (iv) together form an antifoaming system, and wherein amount of non-alkoxylated anionic surfactant in said composition in less than 1.0% by weight.

2. A composition as claimed in claim 1 wherein ratio of the amount of said amphoteric surfactant to that of said alkyl ethoxy sulphate is 1:4 to 1:8 parts by weight.

3. A composition as claimed in claim 1 comprising 0.25 to 1.0% by weight of said fatty acids.

4. A composition as claimed in claim 1 wherein ratio of amount of said C.sub.8-12 fatty acid to that of said C.sub.14-18 fatty acid is from 1:0.5 to 1:2 parts by weight.

5. A composition according as claimed in claim 1 wherein said composition comprises 0.5 to 3.0% by weight non-ionic surfactant.

6. A composition as claimed in claim 1 wherein said alkyl ethoxy sulphate contains 1 to 3 ethylene oxide units per molecule.

7. A composition as claimed in claim 1, wherein said amphoteric surfactant is coco amido propyl betaine.

8. A method of cleaning a hard surface, comprising the steps of: (v) applying thereto a neat or diluted form of a composition according to claim 1; (vi) cleaning said surface with an implement; and (vii) rinsing said surface with water.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Compositions in accordance with this invention are aqueous. The term ‘aqueous’ implies that the compositions comprise 40 to 95% by weight water. It is preferred that the compositions comprise 50 to 90% by weight water and more preferably 70 to 85% by weight water, the balance being the essential and other optional ingredients of the invention.

(2) Aqueous hard surface cleaning compositions invariably contain surfactants or surface-active agents. These may be anionic, non-ionic, cationic or zwitterionic. Surfactants are necessary to clean the articles which may be soiled dishes or kitchen ware. The total amount thereof may vary and it depends on the intended application as well the selling price of the product.

(3) The compositions in accordance with this invention are generally suited for cleaning hard surfaces. The hard surface could be any household or industrial surface, but household surfaces are specifically considered and the invention is explained further with reference to this application, in particular, dish washing. Typical hard surfaces include glass, wood, tiles and other ceramic materials, metal surfaces, polished stones and polished concrete; more preferably stone or concrete kitchen tops, hobs, chimneys, platforms, sink, glass windows and cooker tops and tiles.

(4) Dishwash compositions are available in various formats. These include powders, pastes, liquids and bars. Of all these formats, powders contain the least amount of surfactants while liquids contain the most.

(5) The total surfactant content of a composition is expressed as the Active Detergent (AD) level. Powders are usually 2 to 4 AD products whereas dishwash or detergent liquids usually are 5 to 30 AD products.

(6) In addition to surfactants, which determine the AD level, such compositions also contain other additives like foam boosters, foam suppressants (or antifoam agents), hydrotropes, polymers, colour and perfume.

(7) Cleaning compositions like detergents and dishwash compositions usually contain a combination of surfactants where each surfactant has a definite purpose. The primary purpose of any surfactant is to act on soil/dirt on soiled articles.

(8) Surfactants generate foam and the amount of foam or the foam volume varies according to type(s) of the surfactants present. Usually the anionic surfactants foam the most. Detergent and dishwash composition contain substantial amount of anionic surfactants. Therefore, such compositions tend to generate copious amount of foam during the washing stage at which the articles come in contact with the composition, either in neat form or the diluted form (i.e., diluted with water).

(9) The volume of foam is usually associated with the efficacy of the product. Consumers prefer high-foaming products.

(10) On the other hand, after the wash-cycle is over, the articles need water for rinsing. Generally, the articles are rinsed three to four times, and sometimes even up to six times. Each rinse cycle requires a fresh load of clean water.

(11) It is known to include materials that reduce the formation of foam, either during the washing stage or during the rinse cycles. This allows the foam to subside as quickly as possible. In other words, the motive is to reduce the number of rinse-cycles.

(12) Compositions in accordance with this invention provide high foam-volume during the washing or the pre-rinse stage but require lesser than the usual number of rinse-cycles for the foam to subside almost completely. The solution lies in use of a rinse-activatable antifoaming system comprising combination of fatty acids and non-ionic surfactant as defined in accordance with this invention.

(13) Surfactants in the Composition for Basic Cleaning

(14) Compositions in accordance with this invention comprise two different types of surfactants, which together may constitute a surfactant system meant for basic cleaning.

(15) Alkyl Ethoxy Sulphate

(16) The compositions contain in accordance with this invention comprise 3.0 to 25.0% by weight alkyl ethoxy sulphate. Such ethoxylated surfactants account for a significant amount of the total surfactant content. Therefore, they may be said to be primary surfactants.

(17) The primary surfactant is a surfactant of the formula, R.sub.1—(OR′).sub.n—O—SO.sub.3.sup.−M.sup.+, where, R.sub.1 is saturated or unsaturated C.sub.8-C.sub.16, preferably C.sub.12-C.sub.14 alkyl chain; preferably, R.sub.1 is a saturated C.sub.8-C.sub.16, more preferably a saturated C.sub.12-C.sub.14 alkyl chain; R′ is ethylene; n is from 1 to 22. M.sup.+ is a suitable cation, which provides charge neutrality, preferably sodium, calcium, potassium, or magnesium, more preferably a sodium cation.

(18) Preferably the alkyl ethoxy sulphate contains 1 to 3 ethylene oxide units per molecule (n=1 to 3). In particular it is preferred that the alkyl ethoxy sulphate is sodium lauryl ether sulphate having 1 to 2 ethylene oxide units per molecule.

(19) It is preferred that compositions in accordance with the invention comprise 8.0 to 18.0% by weight alkyl ethoxy sulphate.

(20) Amphoteric Surfactant

(21) The compositions in accordance with this invention also comprise 1.0 to 5.0% by weight amphoteric surfactant. Preferred amphoteric surfactants include cocoamidopropyl betaine (CAPB), coco amido propyl amine oxide (CAPAO), cocodiethanol amide (CDEA) and cocomonoethanol amide (CMEA). As the amphoteric surfactants constitute minor portion of the total surfactant content, it may be termed secondary surfactant. It is particularly preferred that the amphoteric surfactant is coco amido propyl betaine.

(22) It is particularly preferred that ratio of the amount of amphoteric surfactant to that of alkyl ethoxy sulphate is 1:4 to 1:8 parts by weight. More particularly this ratio is 1:4 to 1:6 parts by weight. It is further preferred that the total amount of surfactant (AD) consisting of alkyl ethoxy sulphate and amphoteric surfactant is 8 to 25% by weight.

(23) Combination of Fatty Acids as the Rinse Activatable Antifoam Agents

(24) The compositions of the present invention comprise 0.1 to 1.0% by weight of a combination of fatty acids containing a saturated non-hydroxy C.sub.8-12 fatty acid and a saturated non-hydroxy C.sub.14-18 fatty acid, where ratio of amount of C.sub.8-12 fatty acid to that of C.sub.14-18 fatty acid is from 1:0.1 to 1:10 parts by weight. It is preferred that ratio of the amount of C.sub.8-12 fatty acid to that of C.sub.14-18 fatty acid is from 1:0.5 to 1:2 parts by weight.

(25) It is particularly preferred that the compositions comprise 0.25 to 1.0% by weight of said fatty acids.

(26) Said fatty acids are part of an antifoaming system together with non-ionic surfactant.

(27) Without wishing to be bound by theory, it is believed that when C.sub.8-12 and C.sub.14-18 fatty acids are used in combination, the chain lengths of these fatty acids play a role on the flash foam and the antifoam activity during rinse. The C.sub.8-12 component ensures there is no adverse effect on the flash (initial) foam while C.sub.14-18 triggers the antifoam activity only during rinse. Individually, the fatty acids either destroy the initial foam or do not reduce the foam to a sufficient extent during rinse stage.

(28) The fatty acids used in the present invention are saturated. Saturated lauric (C.sub.12) and stearic acid (C.sub.18) from each type are preferred.

(29) It is preferred that the saturated non-hydroxy C.sub.14-18 fatty acid is a single fatty acid. Alternatively, it could a mixture of two or more C.sub.14-18 fatty acids. Hysteric acid is commercially available mixture and its composition is approximately 1:1 mixture of palmitic acid (C.sub.16) and stearic acid (C.sub.18). Such mixtures are preferred in view of their commercial availability.

(30) Non-Ionic Surfactant

(31) Compositions in accordance with this invention also include 0.5 to 5% by weight non-ionic surfactant which forms part of the antifoaming system. It is preferred that compositions in accordance with this invention comprise 0.5 to 3.0% by weight non-ionic surfactant.

(32) Preferred nonionic surfactants include condensation products of a higher alcohol (e.g., an alkanol containing about 8 to 18 carbon atoms in a straight or branched chain configuration) with about 5 to 30 moles of ethylene oxide; for example lauryl or myristyl alcohol condensed with about 16 moles of ethylene oxide (EO). Particularly preferred is Lauryl alcohol condensed with 5, 7 or 9 moles of ethylene oxide (Laureth 5, Laureth 7 and Laureth 9). Condensates of 2 to 30 moles of ethylene oxide with sorbitan mono- and tri C.sub.10-C.sub.20 alkanoic acid esters having HLB of 8 to 15 also may be used as nonionic surfactant. These surfactants are well known and are available under the Tween® trade name. Suitable surfactants include polyoxyethylene (4) sorbitan monolaurate, polyoxyethylene (4) sorbitan monostearate, polyoxyethylene (20) sorbitan trioleate and polyoxyethylene (20) sorbitan tristearate.

(33) The term ‘non-soap anionic surfactants’ is known to persons who are skilled in the art of detergent manufacture. Soaps are salts, usually sodium salts, of fatty acids and they constitute a class of anionic surfactants. Soaps are prepared by neutralisation of fatty acids with an alkali or by transesterification of oils, generally vegetable oils.

(34) The amount of non-alkoxylated anionic surfactant in said composition in less than 1.0% by weight. Such surfactants include alkylbenzene sulphonates, alpha olefin sulphonates, ester sulphonates and primary non-ethoxylated alkyl sulphates.

(35) The pH of the Composition

(36) The pH of the compositions in accordance with this invention is 6.5 or lower, like e.g. from 2 to 6.5, preferably 4.5 to 6.5, more preferably 5 to 6.5 and most preferably 5.5 to 6.

(37) Foaming Ability of the Compositions

(38) The foaming ability of the compositions in accordance with the invention could be determined by any suitable method known in the art.

(39) The Cylinder Shake method is usually most suited for such applications. This procedure is utilized to determine foamability and how quickly the foam subsides.

(40) A fixed amount of the composition (diluted with water) is poured into a graduated cylinder. A stopper is applied. The cylinder is inverted a number of times and then the foam volume is determined in ml.

(41) Preferably, the foam volume is determined as follows:

(42) A test solution of the concerned composition (6.25 g/1) is prepared using 24 F.H. [French Hardness] water at 40° C. Fifty ml of this solution is transferred to a 250 ml graduated glass cylinder. The solution is shaken by first covering the cylinder with its lid and by inverting the cylinder ten times. Then it is placed on the flat surface for one minute to allow the layers to separate. Thereafter, the solution is shaken one more time to allow the foam to even out.

(43) The foam volume is recorded after excluding the amount of aliquot water as the initial foam (washing/pre-rinse stage).

(44) To measure the foam at the end of each rinse cycle, the aliquot water is decanted along the sides of the cylinder while allowing the foam to be retained therein. Fifty ml of fresh 40° C. 24 F.H. water is added along the sides of the cylinder. The solution is shaken and the foam volume is measured again as described earlier. The rinse-cycle is repeated until the foam subsides.

(45) The initial foam volume of a control composition i.e., composition devoid of fatty acids, is taken to be the standard or desired volume.

(46) The initial foam is measured in the case of each experimental composition and is compared against the foam volume of the control composition. While a difference of 20 units in the volume is acceptable, any greater difference is not.

(47) Accordingly in a preferred aspect of the invention is disclosed an aqueous cleaning composition, having a pH of 6.5 or lower, comprising: (i) 3.0 to 25.0% by weight alkyl ethoxy sulphate; (ii) 1.0 to 5.0% by weight amphoteric surfactant; (iii) 0.1 to 1.0% by weight fatty acids being saturated non-hydroxy C.sub.8-12 fatty acid and a saturated non-hydroxy C.sub.14-18 fatty acid, where ratio of amount of said C.sub.8-12 fatty acid to that of said C.sub.14-18 fatty acid is from 1:0.1 to 1:10 parts by weight; and (iv) 0.5 to 5% by weight non-ionic surfactant,

(48) wherein (iii) and (iv) together form an antifoaming system, and

(49) wherein amount of non-alkoxylated anionic surfactant in said composition is less than 1.0% by weight and wherein foam volume of said composition during pre-rinse stage as determined by Cylinder Shake method described herein, is at least 140 ml and said foam volume subsides to 20 ml or less that that within four rinse-cycles.

(50) Optional Ingredients

(51) In addition to the ingredients described earlier, the compositions in accordance with the invention may comprise other known ingredients such as thickeners, colorants, preservatives, polymers, anti microbial agents, perfumes, pH adjusters, sequesterants, alkalinity agents and hydrotropes.

(52) Use and Method

(53) The method of cleaning any hard surface such as soiled dishes using the compositions of the invention is not different from the usual method. In particular, such a method includes a step of contacting a soiled article, such as a plate, with an efficacious amount of the composition of the invention; preferably with the help of a scrubber or implement such as sponge. It is followed by scouring the article with a pad or cloth;

(54) followed by scrubbing it and later by rinsing with water until foam subsides to 20 ml or less than that within four rinse-cycles.

(55) Accordingly, in another aspect of the invention, is disclosed a sustainable method of cleaning a hard surfaces comprising the steps of: (i) applying thereto a neat or diluted form of a composition according to the first aspect; (ii) cleaning said surface with an implement; and (iii) rinsing said surface with water.

(56) While the aqueous cleaning compositions according to the invention are generally suitable for use in dish wash applications for manual or machine assisted cleaning, the compositions could also be used for related applications like fabric cleaning and general hard surface cleaning.

(57) The invention will be explained with the help of the following non-limiting examples.

EXAMPLES

(58) Two different dishwash compositions containing just basic minimum ingredients (therefore termed herein as base compositions BC1 and BC2) were prepared. The compositions were prepared because they represent widely used dishwash compositions. The formulations are included in Table 1.

(59) TABLE-US-00001 TABLE 1 Table 1: Formulations of Base Composition BC1 BC1 BC2 Ingredient % by weight % by weight Sodium Lauryl ether sulphate 1EO 9.0 18.0 (on 100% active basis) Coco Amido Propyl Betaine 1.5 3.0 (On 100% active basis) Water and other minors to 100 to 100 pH 5.5 5.5 Total Active Detergent level (AD) 10.5 21.0

(60) For the purpose of experiments on foamability, varying levels of saturated non-hydroxy fatty acid and non-ionic surfactant were added to each of the base compositions. Details are shown in Tables 2 and 3. All the formulations were subjected to foam volume tests.

(61) All observations pertaining to the experiments on Base Composition 1 are summarised in Tables 2, 3 and 5. All observations pertaining to the experiments on Base Composition 2 are summarised in Table 6.

(62) Note: In all the tables that follow, PR means foam volume at pre-rinse stage

Example 1: Synergistic Effect of the Claimed Ingredients

(63) TABLE-US-00002 TABLE 2 Exam- Foam volume ple PR at rinse-cycle no. Details of the formulation 0 1 2 3 4 1 BC1 135 135 135 110 80 2 BC1 containing 0.5 wt % C.sub.12-18 130 130 120 90 60 EO7 3 BC1 containing 0.25 wt % Lauric 130 130 110 75 40 acid and 0.25 wt % Stearic acid 4 BC1 containing 0.25 wt % Lauric 140 120 90 50 10 acid and 0.25 wt % Stearic acid and 0.5 wt % C.sub.12-18 EO7

(64) The data presented in table 1 indicates that the base composition retains its tendency to foam substantially even after four rinses. Inclusion of non-ionic surfactant does not improve the situation but it does not adversely affect the initial foam either (Example 2).

(65) Addition of fatty acids reduces the amount of foam (at the end of rinse 4) to 40 ml but that is also not good enough reduction. On the other hand, the composition in accordance with the invention (Example 4) has substantially reduced tendency to foam after four rinses.

Example 2: Effect of % by Weight of the Non-Ionic Surfactant

(66) The compositions and the observations are shown in Table 3.

(67) TABLE-US-00003 TABLE 3 Foam volume Example PR at rinse-cycle no. Details of formulations 0 1 2 3 4 5 5 BC1 containing 0.25 wt % Lauric 130 115 90 50 20 — acid and 0.25 wt % Stearic acid and 0.5 wt % C.sub.12-18 EO7 6 BC1 containing 0.25 wt % Lauric 130 110 80 50 18 — acid and 0.25 wt % Stearic acid and 1.0 wt % C.sub.12-18 EO7 7 BC1 containing 0.25 wt % Lauric 130 110 80 40 10 — acid and 0.25 wt % Stearic acid and 2.0 wt % C.sub.12-18 EO7 8 BC1 containing 0.25 wt % Lauric 130 120 90 50 10 — acid and 0.25 wt % Stearic acid and 3.0 wt % C.sub.12-18 EO7 9 BC1 containing 0.25 wt % Lauric 120 120 100 60 20 — acid and 0.25 wt % Stearic acid and 4.0 wt % C.sub.12-18 EO7 10 BC1 containing 0.25 wt % Lauric 120 110 90 50 20 — acid and 0.25 wt % Stearic acid and 5.0 wt % C.sub.12-18 EO7 11 BC1 containing 0.25 wt % Lauric 120 110 100 70 30 14 acid and 0.25 wt % Stearic acid and 6.0 wt % C.sub.12-18 EO7 12 BC1 containing 0.25 wt % Lauric 120 100 70 50 40 12 acid and 0.25 wt % Stearic acid and 7.0 wt % C.sub.12-18 EO7 13 BC1 containing 0.25 wt % Lauric 100 100 80 50 30 10 acid and 0.25 wt % Stearic acid and 10.0 wt % C.sub.12-18 EO7 14 BC1 containing 0.25 wt % Lauric 110 110 100 70 40 12 acid and 0.25 wt % Stearic acid and 20.0 wt % C.sub.12-18 EO7

(68) The data in Table 3 indicates that even as high as 3 wt % non-ionic surfactant could be safely included without loss of performance.

(69) It is noted that examples 4 and 5 concern the same composition showing the same trend in foam volume decrease and required number of rinses.

Example 3: Effect of Unsaturation

(70) In this experiment, an unsaturated fatty acid was included instead of the saturated fatty acids. Details of the formulation and the observations are shown in Table 4.

(71) TABLE-US-00004 TABLE 4 Foam volume Example PR at rinse-cycle no. Details of the formulation 0 1 2 3 4 15 BC1 containing 0.5 wt % oleic 100 100 80 40 12 acid and 0.5 wt % C.sub.12-18 EO7

(72) The data in Table 4 indicates that although the composition has reduced tendency to foam at the end of four rinses, there is substantial reduction in the amount of initial foam, making such fatty acids unsuitable for the purpose.

Example 4: Effect of % by Weight of Saturated Fatty Acids

(73) In this experiment, compositions with differing amount of saturated fatty acids were prepared, keeping the amount of non-ionic surfactant constant across all formulations. Details are summarised in Table 5.

(74) TABLE-US-00005 TABLE 5 Foam volume Example PR at rinse-cycle no. Details of the formulation 0 1 2 3 4 16 BC1 containing 0.25 wt % Lauric acid 140 140 110 60 20 and 0.25 wt % Stearic acid and 0.5 wt % C.sub.12-18 EO7 17 BC1 containing 0.5 wt % Lauric acid 130 110 80 40 8 and 0.5 wt % Stearic acid and 0.5 wt % C.sub.12-18 EO7 18 BC1 containing 1.0 wt % Lauric acid 110 100 70 30 10 and 1.0 wt % Stearic acid and 0.5 wt % C.sub.12-18 EO7

(75) The intended technical effects can be obtained so long as the total amount of fatty acids is up to 1% by weight. An increase affects the initial foam (Example 18).

Example 4: Experiments Conducted on Base Composition 2

(76) The details are summarised in Table 6.

(77) TABLE-US-00006 TABLE 6 Exam- Foam volume ple PR at rinse-cycle no. Details of the formulation 0 1 2 3 4 19 BC2 140 150 140 80 40 20 BC2 + 0.25 wt % Lauric acid + 0.25 130 120 66 20 4 wt % Stearic acid + 0.5 wt % C.sub.12-18 EO7 21 BC2 + 0.5 wt % Lauric acid + 0.5 125 90 35 4 wt % Stearic acid + 1 wt % C.sub.12-18 EO7 22 BC2 + 0.75 wt % Lauric acid + 0.75 70 30 4 wt % Stearic acid + 1.5 wt % C.sub.12-18 EO7

(78) This base composition per-se foams substantially, as is the case with the other base composition. Addition of 0.5% by weight fatty acids (total) provides the desired technical effect. An increase up to 1% by weight also provides the intended technical effects. However, more amount affects the initial foam (Example 22).

(79) The disclosed examples meet the need for compositions which have more efficient rinse-activatable antifoaming system.

(80) The disclosed examples provide a cleaning composition, especially a dishwashing composition, which provides more foam during the washing or the pre-rinse stage but which requires lesser than the usual number of rinse-cycles for the foam to subside.