Automatic dishwashing detergents (ADD) used for washing tableware (i. e. glassware, china, silverware, pots and pans, plasticware, etc. ) in the home or institutionally in machines especially designed for the purpose have long been known. The particular requirements of cleaning tableware and leaving it in a sanitary, essentially spotless, residue-free state has resulted in so many particular ADD compositions that the body of art pertaining thereto is now recognised as quite distinct from other cleaning product art.

There is an area where dish-cleaning products still fail to deliver the perfect results that the users of ADD products have come to expect from these products. This area is namely the cleaning of plastic, which have been stained by coloured soils coming from their contact with food. In effect, it has been observed that some coloured foods 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 ADD products. Examples of plastic surfaces, which get stained by coloured food, are plastic

containers for food (i. e. Tupperwaree items), plastic dishes and plastic elements of the dishwasher.

It has surprisingly been observed by the experts in the field that, although the food ingredients responsible for the staining are normally bleached effectively 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 of food coloured stains from plastic in dishwashing machines. These solutions are based on the use of very strong oxidants. One example of such an oxidant is described in PCT application number 95/19132 Al where it is proposed to use diacyl or tetraacyl peroxides as bleaching species to enhance the removal of bleachable 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 which 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 both the strong oxidants and the bleach sensitive ingredients. Examples of such measures are the segregation of the incompatible ingredients in different phases of the formulations (i. e. in different regions of a tablet), coating one of the ingredients or maintaining

it in an isolated state (i. e. by insolubilisation in a liquid matrix) to reduce its interaction with the rest of the formulation.

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 WO 93/07086 that they are used in the form of their clathrates with urea or that they are formulated by forming particles with a stabilizing additive (EP 0 796 317 B1).

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 EP 0 821 722 B1.

According to this document the alternative of using diacyl peroxides of smaller particles size 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 removal of coloured food stains from plastic, when the dishwashing detergent comprising them are used to treat the stained plastic in an automatic dishwashing machine.

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

The inventors have now surprisingly found that the above- mentioned objectives can be achieved when a composition containing a species capable of absorbing oxygen, at least temporarily, 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 used in 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 characterised in that the stained plastic is treated with an aqueous liquor comprising a composition including a component having a peroxide value in the range of 0.05 to 40.

In the context of this invention the peroxide value is a value that defines the amount of oxygen that reacts with a component. The peroxide value may be determined using the Wheeler Method (as described in C-VI 69-98 Beath, Wiley WCH Berlin 2000). In this method the component to be evaluated is tested in a titration involving potassium iodide/sodium sulphite in a solution of glacial acetic acid and isoctane. The peroxide value is usually expressed in mmol per mg of sample.

It has been found that a component having a peroxide value in the range of 0.05 to 40 is particularly effective at removing coloured stains (particularly

coloured food stains such as those caused by tomatoes) from plastic. Without wishing to be bound by theory it is proposed that in use, in the presence of oxygen, the component reacts with oxygen to form oxidising/reactive oxygen containing groups such as peroxide and hydroxyl therein. It is hereby suggested that these"active" species are active in affecting the stains in the plastic.

Preferably the peroxide value is from 0.05 to 20, more preferably 0.05 to 10, more preferably 0.05 to 5, more preferably from 0.05 to 3, and most preferably from 0.5 to 2.5.

In order to provide a peroxide value the component may contain an unsaturated carbon-carbon bond. Most preferably the carbon-carbon bond is singly unsaturated (i. e. a carbon-carbon double bond,"C=C").

It has been found that when the component comprises a plurality of carbon-carbon double bonds wherein the carbon-carbon double bonds are arranged so as to provide an allylic hydrogen particularly high stain removing efficacy is achieved. It is suggested that this efficacy arises from the relative ease of activation of the allylic hydrogen as shown below. oh - 12 10 OOH 9 \ y . llylischtH __ _ _, \ 9 \ 13-OOH (ca. 50%) II Thus it is most preferred that the component has an allylic hydrogen. Such an allylic hydrogen may be found in the molecule isoprene. Therefore most preferably the component is based on a polymer of isoprene (commonly referred to as the class of terpenes). The terpene may be formed from 1 to 10 isoprene molecules, more preferably 2 to 9, more preferably 3 to 7, and most preferably 6 isoprene molecules. The most preferred form of the component is squalene, a terpene containing 6 molecules of isoprene. Squalene is particularly preferred as not only has it been found to display good stain removal but also it has been found to be highly compatible with the ingredients normally used for dish cleaning or rinsing.

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 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 rinse liquor (either alone or in combination with conventional rinse ingredients) during the rinse cycle in a dishwashing machine.

In 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.

Although it is within the scope of the presence invention to use the peroxide component at any desired level, it has been observed that a concentration in the washing or rinsing liquor between 15 and 1000 ppm is sufficient to improve the removal of coloured food soils comprising natural dyestuffs from plastic substrates. The degree of improvement is of course influenced by a number of factors such as the length and temperature of the washing

or rinsing process and/or the composition of the detergent used in conjunction with the component.

It has been observed that a carrier may be employed to increase the efficacy of the composition, and more particularly that of the peroxide component.

Preferably the carrier is present in the composition in an amount of (based upon the amount of peroxide component) of between 0.5 to 10 times (both amounts being expressed in weight) the amount of the peroxide component, with more preferably 1 to 8 times and most preferably 1 to 4 times.

The carrier preferably has one or more of the following characteristics:- a) It is inert b) It is apolar c) It is slightly viscous, with a viscosity of less than 300 cp, more preferably 95-100 cp. d) It is compatible with the peroxide component e) It is compatible with bleach and other ingredients used in dishwashing compositions f) It has density of between 0. 77-1 g/cm3, more preferably 0. 85-0. 87 g/cm3.

The density/viscosity of the carrier is most important.

Carriers which are too dense/too viscous may not be effectively discharged during operation of the dishwasher. Preferred carriers 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, meadofoam seed oil, linseed oil, walnut oil, sesame oil and thistle oil. Mixtures of more than one carrier may be used.

A preferred carrier is paraffin oil (a hydrocarbon having a boiling range of 140-300°C-otherwise known as kerosene). Paraffin oil has been shown to display excellent compatibility with the preferred peroxide components, especially squalene. Other similar hydrocarbons (and substituted hydrocarbons) such as C5- C20 aliphatic hydrocarbons are also considered to be suitable in this application.

It has been observed that although the peroxide component in itself is able to deliver good performance in the removal of coloured stains from plastic, the presence of bleach increases its efficiency.

Thus, 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 peroxide component. The bleach is preferably an organic or inorganic oxidising material, such as those which are conventionally used in detergents. Preferred examples of bleaches include; chlorinated bleaches such as sodium hypochlorite or dichloroisocyanurate; hydrogen peroxide and inorganic peroxides such as percarbonates and perborates, persulfates organic peroxides such as diacyl, and tetraacyl peroxides; and peracids such as diperoxyazelaic acid. The bleach may be used in combination with a bleach activator.

It is a preferred execution of the present invention that the bleach is present in the aqueous liquor at a concentration of at least 15 ppm. It has also been found that particularly good results are obtained when the ratio of the peroxide component to bleach in the aqueous liquor is between 4: 1 and 400: 1.

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 silica gel, polyacrylates, xanthan gum and (for aqueous solutions) high ionic strength.

According to a second aspect of the present invention there is provided an automatic dishwashing detergent composition comprising at least 0.5% w/w of a component having a peroxide value in the range of 0.05 to 40.

It will be appreciated that details described above in reference to the first aspect of the invention shall apply mutatis mutandis to the second aspect of the invention.

The composition may comprise a complete dishwashing detergent. As dishwashing detergents are normally dosed at levels comprised between 15 and 120 grams per washing cycle and dishwashers employ an average of 5 to 10 litres of water per washing cycle this results in a concentration of detergent ranging from 3,000 to 12,000

ppm. As a consequence a detergent with at least 0. 5% w/w of a component having a peroxide value in the range 0.05 to 40 is providing an aqueous liquor for treating plastic having a concentration of that component of at least 15 ppm.

When the composition is formulated as a complete dishwashing detergent composition, it preferably includes a number of conventional detergents such as those belonging to the classes of surfactants, builders, bleaches, bleach activators or bleach catalysts, enzymes, solvents, fillers, tarnishing or corrosion controlling ingredients, perfumes and dyes.

Preferred surfactants include citric acid and citrate.

The composition may comprise an additive to be used in combination with conventional detergent formulations.

The additive composition, essentially intended to improve stains removal from plastic, maybe used to 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 contain other ingredients selected from the group comprising builders, solvents, enzymes and other conventional ingredients of normal use in dishwashing compositions. The additive composition generally includes a higher amount of peroxide component.

Preferably the amount of peroxide component is at least 2% w/w

It is hereby further contemplated to use the composition as a machine cleaner (such as a dishwasher cleaner).

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.

The present invention is further illustrated with reference to the following non-limiting Examples Method of evaluation of coloured 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 compositions and processes.

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

Preparation of standard soiled plastic articles : Commercially available plastic containers made of isotactic polypropylene, as offered in the US market by

Curver-Rubbermaid, where washed twice in a Bosch SGS5602 machine with water of 2° of German hardness at 55 °C using a Calgonit Powerball'E'tablet dishwashing detergent.

The reflectance (Ro) 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 under identical conditions but replacing the detergent by 50g of Ketchup (Rantomato@) and the reflectance of the stained containers (Ri) was measured again with the same apparatus.

Method of stain removal: The compositions were evaluated using a dishwasher (GE Quiet Power 3 ) with both the pre-wash cycle and the main wash cycle run with water at 55°C. The soiled containers where placed vertically (with their mouth looking to the side) 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 (Rf) of the base of the containers was determined using a spectrophotometer (Mahloo color guide 45/0).

The parameter TSRI (tomato stain removal index) was calculated using the following formula:

TSRI = Ro Rf 8100 Ro-Ri A perfect stain removal is characterised by a treated article having a reflectance as high as that of the unstained original article and thus a TSRI of 100. An article where no stain removal had been achieved would show a reflectance identical to that of the stained container and thus a TSRI of 0.

Examples : Example 1 To evaluate the performance of compositions according to the invention in comparison with state-of-the art compositions, a base gel dishwashing detergent was used for both pre-wash and wash cycles and to this base detergent a different terpene was added as shown in Table I.

Containers, which had been stained with tomato, as described above were washed in a dishwasher (GE Quiet Power 3 using a certain amount of gel dishwashing 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 A B C D E F G H Terpene Peroxide Detergent Detergent Terpene NaOCl NaOCI Soil Number in pre-in main added to added to added to remo wash wash pre-pre-main wash val % cycle (g) cycle (g) wash (g) wash (g) (g) Farnesol 2 45 60 8 0. 22 0. 36 45 Citral 2 45 60 8 0. 22 0. 36 40 Neral 2 45 60 8 0. 22 0. 36 40 Squalene 1. 2 45 60 8 0. 22 0. 36 80 45 60 15

These results clearly show that terpene addition greatly enhances removal of tomato stains on plastic.

Furthermore squalene exhibits the greatest enhancement.

Example 2 To evaluate the performance of compositions according to the invention in comparison with state-of-the art compositions, a base gel dishwashing detergent was used for both pre-wash and wash cycles and to this detergent different amount of hypochlorite bleach and of squalene were added as shown in Table II.

In some tests the temperature of the incoming water was 55°C a while in others it was 60°C. The results expressed as TSRI can be found in column J of the table.

The TSRI was determined as explained above but without performing the step of treating the articles with the pretreater and it a value of 15 was obtained.

Table II A B C D F G H I J Example Temp Detergent Detergent Squalene Squalene NaOCI NaOCI TSRI (°C) in pre-in main added to added to added to added to wash wash pre-wash main pre-wash main wash cycle (g) cycle (g) (g) wash (g) (g) (g) Comp 1 55 45 60-0, 27 0, 36 15 Comp 2 55 45 60--0, 54 0, 72 29 3 55 37 60 4 - 0,22 0,36 50 4 55 37 60 5---52 5 55 37 60 5-0, 22 0, 36 71 6 55 37 60 8 - - - 58 7 55 37 60 8-0, 22 0, 36 81 Comp 8 60 37 60 - - 0,22 0,36 15 9 60 37 60 5-0, 22 0, 36 79 11 60 37 60 8-0, 22 0, 36 83

These results clearly show that addition of squalene in a dishwashing process significantly improves the removal of tomato stains on plastic and that the improvement is bigger in the presence of bleach.

Further tests were carried out with a carrier. These are

shown in Table IIa Table IIa A B C D F G H I J Example Temp Detergent Detergent Squalene Paraffin NaOCl NaOCI TSRI (°C) in pre-in main added to added to added to added to wash wash pre-wash pre-wash pre-wash main wash cycle (g) cycle (g) (g) (g) (g) (g) 1 55 45 60 0, 27 0, 36 15 2 55 45 60 4 0, 27 0, 36 50 3 55 45 60 6-0, 27 0, 36 74 4 55 45 60 1, 35 0, 65--52 5 55 45 60 2, 70 1, 30 0, 22 0, 36 71 6 55 45 60 4, 05; 4,00 1, 95 ; 4, 00--73, 72

These results clearly show that addition of paraffin improves the efficacy of the squalene.

Example 3 To evaluate the performance of an active component in combination with various carriers a base gel dishwashing

detergent was used (as shown below). The containers were soiled (60g tomato soil) and washed as described above. Component De-hardened water 61,3119 Monopropylene glycol 1,850 Preservative 0,100 Polyacrylic acid 1,250 Trisodium citrate N 1560 32,800 Calcium chloride 0,500 Speckles with amilase 0,500 Nonionic EO/PO LF 500 0, 200 Perfume 0,050 Savinase 16. OL. EX 0,650 Purastar ST 15000L 0, 550 Sodium hydroxid L (50%) 0,23 Acid Blue 9 0, 00075

To this detergent ig of squalene was added in combination with 4g of carriers as shown in Table III.

Table III Carrier Squalene Amount (g) Soil Removal None-10 None 1 45 Paraffin oil 1 65 Meadofoam seed oil 1 38 10673 Meadofoam seed oil 1 22 BW801 Olive Oil 19 Sunflower Oil 1 50 Maize Oil 38 Rape Seed Oil 1 31 Thistle Oil 1 40 Linseed Oil 1 29 Soya Oil 1 36 Peanut Oil 1 44 Walnut Oil 1 35 Sesame Oil 1 38

These results clearly show that certain carriers (particularly paraffin oil and also sunflower oil) were able to enhance the efficacy of squalene in the removal of tomato stains on plastic. Other carriers were much less effective, actually as result of the presence of radical quenchers (such as vitamin E) within these carriers. This is particularly true of olive oil.

Example 4 To evaluate the performance of a machine cleaner in accordance with the invention a machine cleaner base

formulation was prepared as below. Component % Nonionic Surfactant1 0. 10 Sodium Cumenesulphate2 (SCS) 2.00 Monopropylene Glycol 2.00 Anhydrous Citric Acid 25.00 Dye (Fishin 38 693) 0.20 Water 70. 70

1: An ethylene oxide based surfactant.

2: Used as a 40% solution.

From the base formulation 250ml machine cleaning formulations were made up using the additives in Table IV below (with the remainder being base formulation).

Table IV Formulation Squalene (g) Paraffin (g) Added SCS (g) I 4 4 - II 4 4 (-2)

Additionally other machine cleaner formulations were prepared which did not contain any of the machine cleaner base. These formulations are shown in Table IVa.

Table IVa Formulation Squalene (g) Paraffin (g) Citric Acid (g) III 4 4- Il 4 4 62. 5

Dishwashers which had been stained with tomato, as described above, were operated using the machine cleaner formulations over a long-wash cycle (on an empty machine) at 60°C.

The results are shown below. Formulation % Stain Removal zu II 10 III 77 IV 81.5

These results are clearly show that the activity of squalene/paraffin is enhanced by the presence of citric acid.