GB2390853A - Cleaning composition containing hydrophobic component - Google Patents

Abstract

A process for removing stains from a plastic substrate comprises the step of contacting the substrate with an aqueous liquor containing a composition which comprises a hydrophobic component with a density of 0.6-1 g/cm<3>. The hydrophobic component may have a viscosity less than 300 cp and may be present in the liquor in an amount of 15-10000 ppm. Typically, the hydrophobic component is a hydrocarbon oil, such as paraffin, and/or an edible oil. The edible oil may be olive oil, sunflower oil, maize oil, rape oil, soya oil, peanut oil, meadowfoam seed oil, linseed oil, walnut oil, sesame oil, or thistle oil. The aqueous liquor may further contain a bleach, whereby the ratio of the hydrophobic component to the bleach may be 4:1 to 1400:1. A dishwashing composition containing the hydrophobic component is also disclosed.

Description

s Detergent Composition The present invention relates to a process of

removing coloured stains from plastic by treating the substrate in an automatic dishwashing machine with an aqueous liquor comprising a hydrophobic component having a density of from 0.6 to 1/cm h Automatic dishwashing detergents (ADL)) used for washing tableware (i.e. glassware, china, silverware pots and pans, plasticware, etc.) in the home or institutionally in machines especially designed t'or the purpose have long been known. The particular requirements of cleaning tableware and leaving, it in a 5 sanitary, essentially spotless, residue-l'ree state has resulted in so many particular Al)D compositions that the body of art pertaining thereto is now recognized as quite distinct from other cleaning product art.

There is an area where dish-cleaning products still flail to deliver the perfect results so that the users ot'ADO products have come to expect from these products. This area is namely the cleaning of plastic, which have been stained by coloured snails coming from their contact with food. In eft'ect, it has been observed that slime coloured Mods when left in more or less}prolonged contact with plastic, can stain the plastic and that these stains are very stubborn and cannot be completely removed with conventional o: Al)D products. Examples ot' plastic surfaces, which get stained by coloured food. are plastic containers for flood (i.e. 'I'upperware'9 items), plastic dishes and plastic elements of the dishwasher.

It has surprisingly been observed by the experts in the field that. although the tood

30 ingredients responsible for the staining are normally bleached eft'cctively by strong, oxidants in solution (i.e. sodium hypochlorite bleaches). once they have caused a stain in plastic the stain is no longer bleachable with the strong oxidants.

Some solutions have been proposed in the art to improve the removal ot' food 5 coloured stains from plastic in dishwaslling machines. These solutions are based on the use of very strong oxidants. ()ne example ol' such an oxidant is described in 1'(1'1'

application number 95/19132 A1 where it is proposed to use cliacyl or tetraacyl peroxides as bleaching species to enhance the removal of blcachablc food soils from plastic. This solution presents however a number of drawbacks. One of the major drawbacks when using not only diacyl or tetraacyl peroxides but also other strong oxidants is the limited compatibility of these ingredients with bleach sensitive ingredients whicl1 are desirable in ADD formulations (i.e. enzymes, perfumes, etc.). As a consequence it is normally necessary to take special measures to assure the stability of the formulation comprising troth the strong oxidants and the bleach sensitive ingredients. Examples ts of such measures are the segregation of the incompatible ingredients in different phases ot the formulations (i.e. in different regions ol a tablet), coating one of the ingredients or maintaining it in an isolated state (i.e. by insolubilisation in a litlui matrix) to reduce its interaction with the rest of the formulation.

so Another drawback of using diacyl or tetraacyl peroxides (and also other strong, oxidants) is their lack of stability at high temperatures for which reason it has been proposed in W() 93/07086 that they are used in the form of their clathrates with urea or that they are formulated by forming particles with a stabilize additive (EST' () 7')6 317 Bl).

Still another drawback of diacyl peroxides is that when used in dishwashing; processes at their conventional granulometry of 400 to 700 microns, a problem of residue formation occurs as reported by lop 0 821 722 P. 1. According, to this document the alternative of using, diacyl peroxides of smaller particles size 30 incorporated into granular detergent compositions will generate segregation problems. Due to the above mentioned difficulties an unmet need remains to find alternative ingredients which are capable of delivering a good performance in relation with the -s removal of coloured food stains from plastic, when the dishwashinL: detergent comprising them are used to treat the stained plastic in an automatic dishwashing

i 5 machine. It would also be an additional advantage that the alternative ingredients be fully compatible with the conventional detergent ingredients (i.c. with ingredients incompatible with oxidants) and thus could be easily incorporated into dishwasllblg detergent formulations.

lo 'I he inventors have now surprisingly found that the above-mentioned objectives can be achieved when a composition containing a hydrophobic species having a density less than or equal to water is delivered to washing liquors in a method of treating stained plastic in a dishwashing machine. The composition may be delivered to the washing liquor through the use of a specially formulated additive to be usccl in 5 addition to conventional dishwashing detergents or in the alternative it can be incorporated in conventional dishwashing detergents or rinse aids.

According to one aspect of the present invention a process of removing coloured stains from plastic is proposed, which is characterized in that the stained plastic is 3, treated in a dishwashing machine with an aqueous liquor comprising a composition including a hydrophobic component having a density oI' from 0.6 to I g/cm3.

It has been found that a composition comprising a hydrophobic component having u density ot't'rom 0.6 to I g/cm is particularly effective at removing coloured stains 25 (particularly food stains such as those caused by tomatoes) from plastic. Without wishing to be bound by theory it is proposed that in use, the hydrophobic component liberates the food stain I'rom the plastic, then by virtue of the low density ol the hydrophobic component (in comparison to a typical wash liquor) the hydrophobic component floats on the wash liquor, taking the stain with it. I'he stain is thus 30 ef'l'ectivcly distanced from the article being cleaned.

Although it is within the scope of the presence invention to use the hydrophobic component at any desired level which achieves the desired peroxide value, it has been observed that a concentration in the washing or rinsing liquor comprised 35 between l 5 and l 0000 PPM is normally enough to improve the removal of coloured food soils comprising natural dyestuffs from plastic substrates. The degree of

s improvement is of course influenced by a number of factors like the length and temperature of' the washing or rinsing process and/or the composition of the detergent used in conjunction with the component.

It is preferred that the density of the hydrophobic component is in the range of 0.65 o to 0.95g/cm3, more preferably of 0.7 to 0.92/cm3, more preferably 0.75 to ().92g/cm3, more preferably 0.8 to 0.92g/cm3 more preferably 0.85 to 0.92/cm;, more preferably 0.85 to 0.87g/cm3.

It has been observed that the hydrophobic component should not be too viscous as I s otherwise it may not be ef'fcctively discharged during operation of the dishwasher.

I'rcferably the viscosity of the hydrophobic component is less than 300cp. more preferably between 50 to 250 cp, more preferably between 75 to 15() cp and most preferably from 95 to 1()0 cp.

To 'I'he hydrophobic material preferably has one or more of the t'ollowing characteristics: a) It is inert b) It is apolar c) It is compatible with bleach and other ingredients used in dishwashing As compositions. I'referred hydrophobic components include hydrocarbon oils and edible oils such as vegetable and / or nut oils such as olive oil, sunflower oil, maize oil, rape oil, soya oil, peanut oil, meadof'oam seed oil, linseed oil, walnut oil' sesame oil and disteloel.

So Mixtures of more than one carrier may be used Most preferably the hydrophobic component is parathion oil (a hydrocarbon having, a boiling range of 14() - 3()() centigrade - otherwise known as kerosene). ()ther similar hydrocarbons (and substituted hydrocarbons) such as C5 - Cat, aliphatic hydrocarbons are also considered to be suitable in this application. Paraffin oil has been shown to display as excellent compatibility with other active components. especially bleach.

s lt has been observed that although the hydrophobic component in itself' is able to deliver good performance in the removal of coloured stains from plastic, the presence of bleach increases its efficiency It is proposed that the bleach is able to act on the stain after liberation by the hydrophobic component when the hydrophobic component is floating on the wash liquor.

I'hus. in particularly preferred embodiments of the present invention the aqueous liquor used in the stain removing process of the present invention comprises a bleach in addition to the component. In the context of' the present invention a bleach is any organic or inorganic oxidising material which is conventionally used in detergents.

Non-limiting examples of such materials are chlorinated bleaches such as sodium hypochlorite or dichloroisoeyanurate, hydrogen peroxide and inorganic peroxides such as percarbonates, perforates, persulfates, etc; organic peroxides such as diacyl, and tetraacyl peroxides; peracids such as diperoxyazelaic all of them optionally combined with bleach activators. It is a preferred execution of the present invention 20 that the bleach is present in the aqueous liquor at a concentration of at least 15 I'l'M.

It has also been tound that particularly good results are obtained when the ratio of the hydrophobic component to bleach in the aqueous liquor is between 4:1 and 140():1.

95 It is particularly advantageous that, at the same time that coloured stains are removed from plastic, other cleaning tasks are also performed (i.e. removal of proteinic or starchy stains) both on plastic substrates and on other items optionally present in the dishwashing machine (i.e. china, dishware, glassware, cutlery, etc.). It is advantageous that the composition is added to the washing liquor in the dishwasher 30 in a single composition (complete detergent with stain removal capacity) or alternatively as a separate product (being added as a stain removal booster) together with a conventional detergent.

In one embodiment of the present invention the composition may be added to, the 35 rinse liquor (either alone or in combination with conventional rinse ingredients) luring the rinse cycle in a dishwashing machine.

( ln an alternative embodiment the composition may be used in a pre-wash and / or main wash cycle in addition to / as an alternative to being used in the rinse cycle. It is also contemplated to use the composition as a pre-treater, namely the composition may be used to treat a soiled article before it is added to a dishwashing machine.

The composition may comprise a thickener so that the composition is in the form of a paste / gel. It is understood that such viscous gels / pastes are pleasing to consumers yet are easily dispersed in solution to provide good cleaning results. Suitable examples of thickeners include polyacrylates, xanthan gum and silica (the latter two thickeners being especially suitable tor high ionic strength aqueous solutions).

According to a second aspect of the present invention there is provided an automatic dishwashing detergent composition comprising at least 0.5 X, w/w ol a hydrophobic component having a density in the range of O.6 to l. Og/cm;.

2n The composition preferably further comprises a bleach.

Oishwashing detergents are normally dosed at levels comprised between 15 and 120 grams per washing cycle and dishwashers employ an average ot 5 to 10 1itres of 5 water per washing cycle resulting in a concentration of detergent ranging from 0()() to 12,0()() ppm. As a consequence a detergent with at least 0.5%w/w ot a hydrophobic component having a density in the range of 0.6 to l.Og/cm3 is providing an aqueous liquor for treating plastic having a concentration of that component of at least 15 ppm.

According to a third aspect ot the present invention a dishwasher additive composition is proposed which comprises at least 2% w/w of a component having a hydrophobic component having a density in the range of 0.6 to l.Og/cm3 and a bleach.

5 It will he appreciated that details described above in reference to the first aspect of the invention shall apply mutoti.s mutcncli.s to the second and third aspects of' the invention. In the case the compositions of the invention are formulated as additives to be used in in combination with conventional detergent formulations' it is contemplated that the additive compositions, which are essentially intended to improve stains removal throne plastic, can nevertheless provide additional benefits such as softening of' dried-on or burnt-on food or boosting the performance of the detergent composition in any other performance area. To this effect it is foreseen that the additive composition may ls contain other ingredients selected from the group comprising builders. solvents, enzymes and other conventional ingredients of normal use in dishwashing compositions. (obviously when the compositions of' the invention are formulated as detergent 20 compositions, they will include in addition to the peroxide component any other conventional detergent ingredient including but not limited to compounds belonging; to the classes of surfactants, builders, bleaches, bleach activators or bleach catalysts, enzymes, solvents, fillers, tarnishing or corrosion controlling ingredients, perfumes and dyes.

2s It is hereby further contemplated to use the active component as u machine cleaner (such as a dishwasher cleaner). Thus in accordance with a fourth aspect of the present invention there is provided a dishwasher cleaning composition comprising a hydrophobic component having a density in the range of 0.6 to 1.0/cm and a 30 surfactant.

The dishwasher cleaning composition may be used as a pre-treater, i.e. before the machine is operated or alternatively in one or more of the dishwasher cleaning programs. Preferred suri;actants include citric acid and citrate.

g- Mcthol of evaluation of colourel food soil removal: A method for the evaluation of coloured food soil removal from plastic has been developed and is used to evaluate the results obtained with the process and compositions of the present invention and to compare them with the results obtained with conventional dishwashing processes.

The evaluation method consist in the following steps: Preparation of stained plastic articles ts Washing of the stained articles in dishwasher with the compositions of the i nvention Colorimetric assessment of the degree of stain removal.

I'reparation of standard soiled plastic articles: 2(1 Commercially available plastic containers made of isotactic polypropylene as offered in the US market by Curver-Rubbermaid@, where washed twice in a Bosch biC, 85602 machine with water of 2 of German hardness at 55 C using a ('algonit Powerball tablet dishwashing detergent.

I he reflectance (Rat) of the washed containers was measured with a spectrophotometer (Mahlo" color guide 45/0).

The same containers were subsequently washed twice in the same dishwasher and 30 under identical conditions but replacing the detergent by 50 g. of Ketcllup (Rantomato@) and the reflectance of the stained containers (Rj) was measured again with the same apparatus.

it/ s Mcthod of stain removal: 1 he different compositions where evaluated using a dishwasher (GE Quiet Power 0') and both the pre-wash cycle and the main wash cycle were run with water at 55 ('.

The soiled containers where placed vertically (with their mouth looking to the side) lo on the lower rack of the dishwasher and the compositions to be tested where dosed in the corresponding pre-wash and main wash compartments of the machine. After the completion of the machine program the stained containers where taken out of the machine and the reflectance (Rig of the base of the containers was determined using a speetrophotometer (Mahlo color guide 45/0).

The parameter TSRI (tomato stain removal index) was calculated using the following formula: TORI _ Ro- RJ * 100 Ro - Ri JO Obviously a perfect stain removal is characterized by a treated article having a reflectance as high as that of the unstained original article and thus a TSRI of 1()0.

An article were no stain removal would have been achieved would show a reflectance identical to that of the stained container and thus a TSRI of 0.

25 Examples:

Examrle I l o evaluate the performance of compositions according; to the invention in comparison with state-of-the art compositions, a base gel dishwashing detergent was 30 used for both pre-wash and wash cycles and to this different hydrophobic component was added as shown in table 1.

(containers. which had been stained with tomato' as described above were washed in a dishwasher (GF. Quiet Power 3 a') using a certain amount oi gel dishwaslling

detergent (as indicated in column C) for the pre-wash cycle and a different amount of detergent was used in the main wash cycle (indicated in column D).

Table I

[] (' 1. l: (:i I tydrophobic Amount of Amount or Amount of Amount of Amount of Soil ( omponent Dclergenl De(crgent hi I Iydr, pilobi sodium sodium removal in pre-wash main wash c hypuchloritc hylxcilkritc 'M cycle (g) cycic (a) ( Opponent added to added to main added to prc-wash (g) wash (g) I,rc-wash (g) ParaHb, 45 6() ().22 ().3(. 67 Olive Oil 45 6(, ().22 ().36 55 Soya ()il 45 60 () .22 ().36 60/63 lo These results clearly show that addition of a hydrophobic component greatly enhances removal of tomato stains on plastic. Furthermore paraffin exhibits the greatest enhancement.

Claims (16)

( 5 CLAIMS

1. A process for removing coloured stains from plastic by contacting the plastic with an aqueous liquor comprising a composition including; a hydrophobic component having a density of Prom ().6 tol gram/cm3.

2. AL process according to claim 1, wherein the density of the hydrophobic component is in the range of ().65 to 0.95 grams cm3. more preferably ().7 to 0.92 grams cm3, more preferably 0.75 to 0.92 grams cm3. more preferably (1.8 to 0.92 grams cm3, more preferably 0.85 to 0.92 grams cm3, and [llOSt preferably from 0.85 to ().87 grams cm3.

3. A process in accordance with claim 1 or 2, wherein the viscosity ol' the hydrophobic component is less than 300 cp' more preferably betwocn 5() - 25() cp, more preferably between 75 to 150 cp' end most preferably t'rom 95-1()() 2() cp.

4. A process in accordance with any one of claims 1 to 3 wherein the concentration of' the hydrophobic component in the washing liquor is bctwccn 15 and 10000 ppm.

5. A process in accordance with any one of claims 1 to 4, wherein the hydrophobic component is a hydrocarbon oil, an edible oils or a mixture thereof so

6. A process in accordance with claim 5 wherein the edible <ail is olive tail.

sunflower oil,,maizc oil, rape oil, soya oil, peanut oils meadowfoam seed oil.

linseed oil, walnut oil, sesame oil, thistle oil or a mixture thereof.

7. A process in accordance with claim 5' wherein the hydrophobic component is 3> paraffin oil.

s

8. A process according to any of the preceding claims, wherein the aqueous liquid comprises a bleach.

9. A process according to any one of the preceding claims, wherein the aqueous liquid comprises more than 10 ppm of bleach.

10. A process according to any of the preceding claims, wherein the ratio of hydrophobic component to bleach is between 4:1 and 1400:1.

11. A process according to any one of the preceding claims wherein the s composition comprises a thickener.

12. An automatic dishwashing detergent composition comprising a hydrophobic component having a density in the range of 0.6 to I gram cm i.

So

13. An automatic dishwashing detergent composition comprising at least 0.5% w/w of a hydrophobic component having a density in the range ot 0.(, to I gram crn3.

14. A dishwasher additive composition comprising at least 2% w/w of a 25 hydrophobic component having a density in the range of 0.6 to I gram cm3 and a bleach.

15. A composition as claimed in claim 13. 14 or 15 and further as claimed in any one of claims I to 12.

16. Use of a hydrophobic component having a density of from 0.6 to I gram cmi in a dishwashing process to enhance the removal of coloured tood stains from plastic.