GB2389856A

GB2389856A - Removal of stains from plastics

Info

Publication number: GB2389856A
Application number: GB0213971A
Authority: GB
Inventors: Daniele Fregonese; Chris Efstathios Housmekerides; Marcus Richter
Original assignee: Reckitt Benckiser NV
Current assignee: Reckitt Benckiser NV
Priority date: 2002-06-18
Filing date: 2002-06-18
Publication date: 2003-12-24
Also published as: GB0213971D0

Abstract

A process for removing coloured stains from a plastics substrate comprises the step of contacting the substrate with an aqueous liquor comprising a composition containing a component with a peroxide value of 0.05-40. The component preferably comprises an unsaturated carbon-carbon bond and an allylic hydrogen. Typically, the component is a terpene having 1-10 isoprene units. The terpene may be squalene, farnesol, citral, or neral. The aqueous liquor may further contain a carrier, e.g. paraffin, as well as a bleach. Dishwashing compositions containing the component in combination with a bleach or a surfactant are also disclosed. The use of squalene in a dishwashing process to enhance the removal of coloured food stains from a plastics substrate is also claimed.

Description

. :;: ':e ':::.; 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 lo liquor comprising a component having a peroxide value of O.OS to 40.

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 5 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.

20 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 25 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. Tupperware items), plastic dishes and plastic elements of the dishwasher.

30 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.

35 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

/. / 5 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. 0 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 Is 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 25 317 Bl).

Still another drawback of diacy1 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 Bl. According to this 30 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 35 ingredients which are capable of delivering a good performance in relation with the removal of coloured food stains from plastic, when the dishwashing detergent

:: It. I:::: 44 5 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 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 15 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 JO stains from plastic is proposed, which is characterized in that the stained plastic is treated in a dishwashing machine 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 25 of oxygen that reacts with a composition / 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 composition / 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 30 mg of sample.

It has been found that a composition having a peroxide value in the range of 0.05 to 40 is particularly effective at removing coloured stains (particularly food stains such as those caused by tomatoes) from plastic. Without wishing to be bound by theory it 35 is proposed that in use, in the presence of oxygen, oxygen containing groups such as 2

B t À e t e t 5 peroxide and hydroxyl form in the composition. lt is hereby suggested that these 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 IO, more preferably 0.05 to 5, more preferably from 0.05 to 3, and most preferably from 0.5 to 0 2.5.

The desired peroxide value of the composition may be obtained by the use of an active component (hereafter the "component"). In order to provide a peroxide value the component may contain an (or more preferably a plurality of) unsaturated carbon-carbon bonds. Most preferably the carboncarbon bonds are singly unsaturated (i.e. carbon-carbon double bonds, "c=c"). It has been found that when 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 20 below.

02 0 it< HIGH {ca. 50D,'o) ÀlIIAL - ti. i 1 9 >A 13 OOH (ca. 50Y Thus it is preferred that the component has an allylic hydrogen. Such as 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 terpenes).

25 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 30 ingredients normally used for dish cleaning or rinsing.

f À : I:

5 It is paticularly 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 lo 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 15 rinse liquor (either alone or in combination with conventional rinse ingredients) during the rinse cycle in a dishwashing machine.

Although it is within the scope of the presence invention to use the component at any desired level which achieves the desired peroxide value, it has been observed that a 20 concentration in the washing or rinsing liquor comprised between 15 and 1000 ppm is normally enough 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 like the length and temperature of the washing or rinsing process and/or the composition of the detergent used in conjunction with the 25 component.

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

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

3s The carrier preferably has one or more of the following characteristics a) It is inert

:: lll I:. le::: s 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 active component e) It is compatible with bleach and other ingredients used in dishwashing 10 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 t 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, meadofoarn seed oil, linseed oil, walnut oil, sesame oil and disteloel. Mixtures of more than one carrier may be used. A preferred carrier is paraffin oil (a hydrocarbon having a boiling range of 140 - 300 centigrade - otherwise known as kerosene).

20 Other similar hydrocarbons (and substituted hydrocarbons) such as C5 C20 aliphatic hydrocarbons are also considered to be suitable in this application. Paraffin oil has been shown to display excellent comparability with the preferred active components, especially squalene.

25 It has been observed that although the 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 30 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 dichloroisocyanurate, hydrogen peroxide and inorganic peroxides 35 such as percarbonates, perforates, persulfates, etc; organic peroxides such as diacyl, and tetraacyl peroxides; peracids such as diperoxyazelaic all of them optionally

t: P:'::: s combined with bleach activators. 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 component to bleach in the aqueous liquor is between 4:1 and 400:1.

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.

15 The composition preferably further comprises (a) a bleach and (b) a detergency builder. 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 1itres of 20 water per washing cycle resulting 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.

25 According to a third aspect of the present invention a dishwasher additive composition is proposed which comprises at least 2% w/w of a component having a peroxide value in the range 0.05 to 40 and a bleach.

It will be appreciated that details described above in reference to the first aspect of 30 the invention shall apply mutatis mutandis 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 combination with conventional detergent formulations, it is contemplated that the Is additive compositions, which are essentially intended to improve stains removal from plastic, can nevertheless provide additional benefits such as softening of dried-on or

l l J l 5 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. Obviously when the compositions of the invention are formulated as detergent 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.

It is hereby furler contemplated to use the active component as a machine cleaner (such as a dishwasher cleaner). Thus in accordance with a fourth aspect of the 20 present invention there is provided a dishwasher cleaning composition comprising a component having a peroxide value in the range of 0.05 to 40 and a surfactant.

Preferred surfactants include citric acid and citrate.

25 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 30 with conventional dishwashing processes.

The evaluation method consist in the following steps: À Preparation of stained plastic articles À Washing of the stained articles in dishwasher with the compositions of the 35 invention À Colorimetric assessment of the degree of stain removal.

:: l(t ':; d; l' 9- 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 lo SGS5602 machine with water of 2 of German hardness at 55 C using a Calgonit Powerball tablet dishwashing detergent.

The reflectance (Ro) of the washed containers was measured with a spectrophotometer (Mahlo0 color guide 45/0).

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

Method of stain removal: The different compositions where evaluated using a dishwasher (GE Quiet Power 3 a) and both the pre-wash cycle and the main wash cycle were run with water at 55 C.

5 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 30 spectrophotometer (Mahlo09 color guide 45/0).

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

( t d #l ldd 4 (d TSR1 = Ro Rf * 100 Ro - Ri Obviously 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 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.

Examples:

Example 1

To evaluate the performance of compositions according to the invention in 5 comparison with state-of-the art compositions, a base gel dishwashing detergent was used for both pre-wash and wash cycles and to this different terpene was added as! shown in table I. Containers, which had been stained with tomato, as described above were washed in 20 a dishwasher (GE Quiet Power 3 0) 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

B E F H l TerBene Peroxide Amount of Amount of Amount of Amount of Amount of Soil Number Detergent Detergent in Terpene sodium sodium removal I in pre-wash main wash added to hypochlorite hypochlorite % cycle (g) cycle (8) pre-wash (g) added to added to main pre-wash (g) wash (g) l Famesol 45 60 8 0.22 0.36 45 Citral 2 45 60 0.22 0.36 40 Neral 45 60 8 0. 22 0.36 40 Squalene 1.2 45 60 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.

( ÀI ÀtItl tide Example 2

To evaluate the perfonnance 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 I o 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 some other it was 60 C. In each of the examples different amounts of sodium hypochlorite and squalene were added to any of the detergents for the pre-wash and wash cycles as 5 indicated in table II. 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 J

Example Temp Amount of Amount of Amount of Amount of Amount of Amount of TSR] (.C) Detergent in Detergent in squalene squalene sodium hype- sodium pre-wash main wash added to pre- added to chlorite added hypo- chlorite cycle (g) cycle (g) wash (g) main wash to pre-wash (g) added to (B) main wash (g) Comp 1 55 45 60 0,27 0,36 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 j 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 9 60 37 60 0,22 0,36 79

60 37 60 8 0,22 0,36

: l'' I' À -I t-: - d d t 5 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 D

Example Temp Amount of Amount of Amount of Amount of Amount of Amount of TSRI ( C) Detergent in Detergent in squalene paraffin sodium hypo- sodium pre-wash main wash added to pre- added to pre- chlorite added hypo-chlorite cycle (g) cycle (g) wash (g) wash (g) to pre-wash (B.) added to main wash 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 O,65 S2

5 55 45 60 2,70 1,30 0,22 0,36 71

6 SS 45 60 4,05;4,00 1,95;4,00 73,72

Addition of paraffin improves the efficacy of the squalene.

ll d44 6 d e d 5 Example 3

To evaluate the perfonnance of an active component in combination with various carriers a base gel dishwashing detergent was used (as shown below).

Componento/o De-hardened water61,31 19 Monopropylen glycol1,850 i Isothiazolinone0,100 Polyacrylic acid1,250 Trisodimn citrate N 156032,800 Calcium chloride0,500 Speckles with amilase0,500 Nonionic EO/PO LF 5000, 200 I Perfume Centauro FC-11 360,050 Savinase 16.0L.EX0,650 Purastar ST 15000L0,550 Sodium hydroxid L (50%)0,23 Acid Blue 90,00075 To this detergent lg of squalene was added in combination with 4g of carriers as shown in Table III.

The containers were soiled (60g tomatosoil) and washed as described above.

I td e d tet ed tt 4t 5 Table Ill

Carrier S ualene Amount (g) Soil Removal (%) l None q - I u None _ 45 Paraffm oil I 65 Meadafoam seed oil 10673 I 38 Meadofoam seed oil BW801 I 22 Olive Oil I 19 Sunflower Oil I 50 Maize Oil I 38 Rape Seed Oil I 31 Distelol 1 40 Linseed Oil I 29 Soya Oil I 36 Peanut Oil I 44 Walnut Oil 1 35 Sesame Oil I 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 0 presence of radical quenchers (such as vitamin E) within these carriers.

Claims

r d 4 4 d e t t .:: c: 4: s Claims

1. A process for removing coloured stains from plastic by contacting the plastic with an aqueous liquor comprising a composition including a component having a peroxide value in the range of 0.05 to 40.

2. A process according to claim 1, wherein the peroxide value of the component is from 0.05 to 10.

3. A process in accordance with claim 1 or 2, wherein the peroxide value of the Is component is between 0.05 to 5.

4. A process in accordance with any one of claims I to 3, wherein the peroxide value of the component is between 0.05 to 3.

20

5. A process in accordance with any one of claims 1 to 4, wherein the component comprises an unsaturated carbon-carbon bond.

6. A process in accordance with claim 5 wherein the component comprises an allylic hydrogen.

7. A process in accordance with claim 5 or claim 6, wherein the component is a terpene.

8. A process in accordance with claim 7, wherein the terpene has from I to 10 30 isoprene units.

9. A process in accordance with claim 7, wherein the terpene has from 2 to 9 isoprene units.

3s

10. A process in accordance with claim 7, wherein a terpene has from 3 to 7 isoprene units.

/ t d ti4 5

11. A process in accordance with claim 7, wherein the terpene has 6 isoprene units.

12.A process in accordance with any one of claims 1 to 11, wherein the component is squalene.

13. A process in accordance with any one of claims 1 to 12 wherein the composition comprises a carrier.

14. A process in accordance with claim 13, wherein the carrier is present in the

15 composition in a ratio of 0.5 to 10 times the amount of component present.

IS. A process as claimed in claim 13, wherein the carrier is present in an amount of between 1 to 8 times the amount of component present in the composition.

20

16. A process as claimed in any one of claims 13 to 15 wherein the carrier is a hydrocarbon.

17. A process as claimed in any one of claims 13 to 16, wherein the carrier is paraffin.

18. A process according to any one of the preceding claims, wherein the aqueous liquor comprises from 1 S to 1000 ppm of the component.

19. A process according to any of the preceding claims, wherein the aqueous 30 liquid comprises a bleach.

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

35

21. A process according to any of the preceding claims, wherein the ratio of component to bleach is between 4:1 and 400:1.

( tes d44l s

22. An automatic dishwashing detergent composition comprising a component having a peroxide value in the range of 0.05 to 40.

23. An automatic dishwashing detergent composition comprising at least 0. 5 % lo w/w of a component having a peroxide value in the range of 0.05 to 40.

24. A dishwasher additive composition comprising at least 2% w/w of a component having a peroxide value in the range of COOS to 40 and a bleach.

5

25. A composition as claimed in claim 22, 23 or 24 and further as claimed in any one of claims 1 to 21.

26. Use of squalene in a dishwashing process to enhance the removal of coloured food stains from plastic.

27. A dishwasher cleaning formulation comprising a component having a peroxide value of from 0.05 to 40 and a surfactant.

28. A formulation as claimed in claim 27 wherein the surfactant is citric acid or 25 citrate.