EP0980419A1

EP0980419A1 - Hard surface cleaning composition

Info

Publication number: EP0980419A1
Application number: EP98924259A
Authority: EP
Inventors: Giles James Crowley; George Hunter Cullen; Alexander Martin
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1997-05-02
Filing date: 1998-04-23
Publication date: 2000-02-23
Also published as: AU7651698A; JP2001523292A; ZA983667B; WO1998050510A1; PL336659A1; AU722809B2; AR012507A1; CA2288303A1; GB9709065D0; BR9809320A; HUP0002976A2

Abstract

The invention provides a hard surface cleaning composition of pH 7-13 comprising: a) a surfactant selected from the group comprising anionic sulphate, anionic sulphonate, alkyl poly glycoside and mixtures thereof, b) a sequestering agent for Group II metals, and c) a solvent selected from the group comprising hexanol, methyl digol.

Description

HARD SURFACE CLEANING COMPOSITION

Technical Field

The present invention relates to a composition for hard surface cleaning.

Background to the Invention

There is a general need for compositions which assist in the removal of 'soap scum' and limescales from bathroom and kitchen fittings and tiles. Limescale mainly comprises calcium and magnesium carbonates, and can contain lesser amounts of soap scum, protein, particulates and other soils. Limescale is formed on evaporation of water containing said soils. While the deposit formed by evaporation is initially paste-like, it hardens with time to form a recalcitrant deposit. Conventional cleaning compositions are generally buffered at alkaline pH so as to attack fatty soils. Limescale is resistant to the action of alkali and specialist cleaning compositions, of acid pH, are generally used to remove it. 'Soap-scum' is a deposit formed by the reaction of soaps with metal ions. Soap-scum differs from limescale in that it is removed better under alkaline conditions and acid cleaners are generally poor at removing soap-scum.

Although such compositions have been in existence for some years, it has recently become apparent that many formulations have the ability. o cause surface damage either through enamel etching by acidic formulations or via stress cracking of plastics induced by components, such as solvents and nonionic surfactants which are typically present in the cleaning compositions. There is consequently a need for cleaning compositions which are effective for the removal of limescale and other related soils but which do not suffer from the above-mentioned disadvantages.

Brief Description of the Invention

We have now determined that a well-defined group of solvents at relatively low levels are particularly effective solvents for soil removal in the presence of a sequestering agent in combination with anionic surfactants and/or alkyl poly glycoside nonionic surfactants and at non-acidic pH .

Accordingly, the present invention provides a hard surface cleaning composition of pH 7-13 comprising:

a) a surfactant selected from the group comprising anionic sulphate, anionic sulphonate, alkyl poly glycoside and mixtures thereof,

b) a sequestering agent for Group II metals and

c) a solvent selected from the group comprising hexanol, methyl digol, methanol and mixtures thereof.

Without wishing to limit the scope of the invention by reference to any theory of operation, it is believed that improved cleaning is obtained for example with short chain nonionic surfactants which give low contact angles on surfaces such as perspex. It is believed that these low contact angle surfactants can wet the soil and allow the penetration of the sequestering agent into to soil such that the sequestering agent can attack the calcium bridges which bind the soil together and to the surface.

However, short chain nonionic materials which are known for their low contact angles are believed to be particularly damaging to surfaces. The anionic and glycoside surfactants employed in the compositions of the present invention are believed to be less damaging but have high contact angles and consequently wet soils and surfaces poorly. In the compositions of the invention, it is believed that either wetting is improved by the addition of, for example, hexanol as solvent or that overall desorption of the soil particles is effected by the addition of, for example, methanol.

It should be noted that for the series of short chain alcohols there is considerable variation in the effect on soil removal which these materials have. Detachment of soil particles slows dramatically if methanol is replaced by ethanol, propanol or butanol with the effect becoming progressively larger until with butanol the desorption of soil is actually worse than with no solvent at all. At longer chain lengths the effect appears to be one of improved wetting and penetration into the soil of the solvent, surfactant and sequesterant which causes a break-up of the soil particle rather than a desorption of the particle as a whole. It is therefore believed that there are at least two different mechanisms acting in the removal of these soils, both of which show reduced efficacy with alcoholic solvents in the range ethanol to butanol. Detailed Description of the Invention

The invention is described in further detail below with especial reference to preferred features including levels and natures of components.

Surfactants :

Typically, the compositions of the invention comprise total surfactant levels of 2-8% on product, preferably around 4% on product. In this specification all levels of components are given as %wt on product unless stated as otherwise.

Suitable anionic surfactants for use in the compositions of the invention include: secondary alkane sulphonates, fatty acid ester sulphonates, dialkyl sulphosuccininates , alpha- olefin sulphonates, primary alkyl sulphates, alkylbenzene sulphonates and alkyl ether sulphates .

The most preferred anionic is primary alkyl sulphate (PAS) and this preferably comprises the major part (i.e. 50% or more) of the surfactant present. Preferably the PAS comprises a mixture of materials of the general formulation:

ROSO.M

wherein R is a C₈ to Cι_δ primary alkyl group and M is an equivalent cation. This class of surfactant is not only particularly efficient in cleaning hard surfaces but is also readily broken down in the environment and can be obtained from natural sources. The cation M is preferably an alkali metal or ammonium or substituted ammonium. Sodium is preferred as cation. We have found that combinations of methanol and/or methyl digol and PAS show a much more rapid removal of soil particles by desorption than other anionic detergents. No such benefit is seen with cationic or nonionic surfactants. While it might be suspected that the solvents are acting a hydrotropes this particular benefit is not seen with other hydrotropes when these replace the solvent.

Preferred alkyl polyglycosides (APG's) have an alkyl chain comprising C₆-i6 and it is preferred that more than 50%wt of the APG present in the compositions of the invention comprises a C₆-ιo alkyl APG. It is particularly preferred that the APG as a chain length of around C8. The preferred degree of polymerisation is 1.1-1.6, more preferably 1.3- 1.5. Suitable materials include GLUCOPON 225 and GLUCOPON 600 (both RTM ex HENKEL) . It was noted that compositions which comprise both the APG surfactant and hexanol spread over surfaces with particular ease to give very thin surface films.

Where mixtures of anionics and APG's are used it is preferred that the weight ratio of APG to anionic lies in the range 1:10-10:1 as anionic :APG.

It is preferred that the compositions of the invention are free of ethoxylated alcohol nonionic surfactants.

Sequestering Agents:

The sequestering agents present in the composition of the invention are preferably organic and include the di and tricarboxylic acids such as adipate, glutarate, succinate, maleate and citrate.

It is particularly preferred to use a sequestering agent with a pK_Ca>5. Suitable sequestering materials include nitrillo triacetic acid (NTA) , methylglycine diacetic acid (MGDA) and ethylene diamine tetraacetic acid (EDTA) .

Preferred sequesterants are of the general formula:

R-CH (COOH) -N- (CH2COOH) 2

where R=CH3 , CH2COOH or CH20H.

MGDA ia particularly preferred.

Typical levels of the sequestering agent in the compositions of the invention are l-10%wt, more preferably 2-7%wt, most preferably 2.5-6 or around 4%wt on product.

Solvents :

Hexanol is the preferred solvent at levels of 0.5-2%, more preferably 0.5-1%. At levels of hexanol above 2% surface damage can occur and usage at this level should be avoided for surfaces which are sensitive to this solvent.

When methanol and/or methyl digol are used, solvent levels can be 1-5%, with levels of 1-3% being preferred. Care should be taken when using methanol due to it's toxicity and flammability . It is particularly preferred that the compositions of the invention are free of solvents selected from the group comprising propylene glycol n-butyl ether and 2-butoxy ethanol .

Thickeners :

We have found it be advantageous to thicken the products of the invention so as to prevent run-off from sloping or vertical surfaces. Preferred final product viscosities are in the range 6-15 centipoise with viscosities of 8-10 centipoise being particularly preferred.

Preferred thickeners are polymers giving the required viscosity provided that they are compatible with the ionic strength of the composition. Preferably the thickeners are non-charged polymers or nonionic/anionic saccharide polymers. These are preferably polysaccharrides and particularly xanthan gums and/or nonionic guar gums. Materials sold under the tradename KELZAN are especially suitable, as are materials sold under the tradename TYLOSE, such as TYLOSE H4000P. Charged thickener species are less preferred as these can salt out of solution, however it is envisaged that charged polymers, for example polyacrylates could be used when low levels of MGDA are present.

Typical levels of polymer are 0.05-0.5%, preferably around 0.1%. Polymer was found to be particularly effective in maintaining a stiff foam in the products of the invention which also contained APG. Minors :

Hydrotrope can be present in the compositions as required to improve the low temperature stability of the composition. Suitable hydrotropes include the aromatic sulphonates, particularly benzene, toluene and cumene sulphonates at preferred levels of 0-6%wt, more preferably 1-2%.

pH regulants can be present to bring the compositions to the preferred pH of 9-12, more preferably to around pH 10. This can however be achieved without buffering systems in the presence of a sequesteran . The alkaline pH is particularly preferred in the presence of the sequestering agents with a pK_a>5 as these are believed to be most effective in a fully ionised form and generally ionise at markedly alkaline pH.

The preferred delivery form for the compositions of the invention is in the form of a clinging foam or other slow- draining product form, preferably delivered to the surface being cleaned in the form of a spray.

Particularly preferred compositions comprise:

a) 2-8% of a surfactant selected from the group comprising anionic sulphate, anionic sulphonate, alkyl poly glycoside and mixtures thereof,

b) 2-10% of a sequestering agent for Group II metals and

c) 1-5% of a solvent selected from the group comprising hexanol, methyl digol, methanol and mixtures thereof, provided that the hexanol level is less than 2% on product . In order that the present invention can be better understood it will be described hereinafter with reference to the following non-limiting examples.

Examples :

The following materials were used in the examples, the formulations of which are given in Tables 1 and 2, and the identities of which is listed below.

Surfactants :

Empicol LX 28 [TM] Sodium C12-14 primary alkyl sulphate (PAS) : ex Albright &

Wilson; Glucopon 225 CS UP [TM] C8-10 alkyl glycoside with a

DP of 1.6: ex. Henkel; Imbentin 91-35 OFA [TM] CIO E5 nonionic surfactant: ex

Dr W Kolb AG;

D Dehydol 04 [TM] C8 E4 nonionic surfactant: ex

Henkel

Sequesterants:

M Trilon ES 9964 [TM) Methylglycinediacetic acid (MGDA) : ex BASF;

C Citric acid; Solvents :

MeOH Methanol

HEX Hexanol

0 Octanol

IP Isopropanol

IMS Industrial Methylated Spirits (denatured ethanol

AMP 2 -amino-2-methyl-1-propanol

NB n-butanol

TB t-butanol

DG Diethylene glycol H- (-O-CH2CH₂) ₂-OH: ex Dow,•

PnB Dowanol PnB [TM] C₄Ho-0-CH(CH₃)-CH₂-OH: ex

Dow;

MD Methyl Digol [TM] CH₃- (-0-CH₂CH₂) 2-OH: ex.

Hopkin and Williams;

Minors :

K Clear Kelzan [TM] Xanthan Gum: ex Kelco International ; scs Eltesol SC 40 [TM] Sodium cumene sulphonate: ex Albright and Wilson;

Compositions were made up by simple mixing of the components in the levels indicated in Tables 1A, IB, 1C and 2A & 2B below, in water. Tables 1A, IB & 1C show comparative examples while Tables 2A & B show compositions according to the present invention.

In Tables 1A, IB, 1C and 2A & B ' Al ' is the level of surfactant present and 'A2' the level of any further main surfactant species. The type and level of sequesterant is identified in the column headed 'Seq' and the solvent type and level is given for each formulation. 'C is a cleaning score further described below; 'V the viscosity of the product and 'Per' and 'Ena' the contact angles on perspex and enamel respectively as described below. The tables also provide observations which include the time to soil deflocculation or break-up as seen under the microscope.

Cleaning data were obtained by soiling Perspex [TM] tiles with an 'Artificial Sebum¹ soil made up of:

Glycerol trioleate 400g 19. .95%

Oleyl oleate 246g 12. .3%

Squalene 180g 8. .97%

Oleic acid 184g 9. .18%

Linoleic acid 20g 0. .99%

Glycerol tripalmitate 400g 19. .95%

Tetracosane 24g 1. .19%

Steryl stearate 246g 12, .27%

Cholesterol 84g 4. .19% n-Eicosane 25g 1, .25%

Laurie acid 8g 0. .4%

Myristic acid 48g 2 .4%

Palmitic acid 112g 5 .6%

Stearic acid 23g 1 .15%

Total 2005g

To prepare this soil one weighs out glycerol trioleate, puts this into 4 litre beaker which is placed on a steam bath, weighs out oleyl oleate and adds this to the beaker. Keeping mixture at medium meat, one continues to add ingredients ensuring that any powders are dissolved before adding more. Before adding n-eicosane, it was heated on a water bath to melt. When all have been added and dissolved, one removes the beaker from the bath and allows it to cool. One then pours the cooled sebum into a polythene bag inserted into a 2.5 litre container and puts this into a refrigerator to solidify.

The Perspex substrates used are 10 x 10 cm black Perspex [TM] (ex. ICI) tiles and are prepared in the following way:

1. The protective backing film is first removed from the tiles .

2. The tiles are then placed on the WIRA (Wool Industries Research Abrasion Tester) machine for uniform scratching. The total pressure applied is 252.5g.cm² on a 3.8cm² head (this equates to a total assembly mass of 959.6g applied to an area of 3.8cm²) . A piece of P600 grade wet and dry abrasive paper is fitted to the head and the tiles are scratched for 34 cycles on each side of the tiles.

3. After the scratching, the tiles are then numbered for identification purposes.

4. The tiles are then cleaned with either 10% nonionic or hand dishwash liquid to remove perspex residues and grease. The tiles are then rinsed and finally cleaned in methylated spirits to ensure that they are absolutely clean.

5. Tiles can be cleaned and reused. To do this the tiles must be washed in washing up liquid and then soaked in ethanolic potassium hydroxide for one hour or more. The tiles are then rinsed and washed in methylated spirits before being allowed to dry.

Soil is applied to the Perspex tiles as follows: for each set of ten tiles:

i. 5g coco soap (commercial 'Shield' (TM) soap was used), 0.75g 'Artificial Sebum' and 70-80g (normally 75g) distilled water are all placed in a 250cm³ beaker.

ii. Ingredients are then stirred using a Heidolph (TM) stirrer at full speed (approx. 2000RPM) for 5 minutes at room temperature. A thick foam or mousse should be produced.

iii. The prepared soil is then added to 7.5 litres of tap water (approximately 10°FH see note below) and quickly stirred in until large amounts of foam have subsided and a scum is produced.

iv. The tiles are then dipped in the soil whilst being suspended from a rack. The soiled tiles are then left in racks overnight (approx 15 hours) at room temperature to dry and age.

Cleaning is spray on/rinse off only. No mechanical effort is applied. Formulations can be delivered to both vertical surfaces or horizontal surfaces, as differences are seen due to drainage rates and viscosity effects.

1. Each of the formulations is applied by a manually operated spray pack, in this case a finger pump type spray with about 3 to 8 sprays given per soiled surface (back and front) . The typical amount of formulation delivered is 0.12-0.15g per spray.

2. The formulation is left in contact with the tiles for either 30 seconds or 1 minute.

3. The tile is rinsed under the tap until it is as clean as possible, in all cases the same flow rate of water is used and the rinsing process is carried out at the same distance from the tap.

Once the tiles have dried, the performance of the cleaners can then be assessed by means of subjective visual examination. This is done by assigning a cleaning score to each tile on a scale of 1 to 6 as follows:

0 - No effect/Heavy soiling

1 - Very poor 2 - Poor

3 - Average

4 - Good

5 - Very Good

6 - Completely clean/No soil remaining

Relative cleaning performance between experiments can be measured and the use of a control or controls between experiments has shown that the assessments are consistent and reproducible. JIF BATHROOM (TM) was used as such a control. All results are given as normalised results using a score for JIF BATHROOM of 2.66 which was the average of many trials. As noted above these scores are recorded in the tables in column 'C¹. It has been established that the water hardness of the bulk 7.5 litres that the soap/sebum mousse is added to, has a major effect on the soil and the subsequent cleaning performance of formulations. The water hardness is therefore best maintained at 10°FH. Small variations either higher or lower than this value make the soil much easier to remove and hence discrimination between formulations is reduced.

Contact angle measurements were performed using the Kruss Goniometer (at room temperature) and either a perspex or a calcium stearate on enamel substrate. In either case, a small volume of the test liquor (10 uL or less) is applied to the surface and the contact angle was measured at both 30 and 120 seconds. Contact angles are recorded in the tables under 'Per' for perspex and 'Ena' for calcium stearate on enamel. The enamel tiles used were white titanium enamelled 10cm x 10cm (ex. Enamel Signs Co. Smethwick, West Midlands, England, United Kingdom) . The enamel tile preparation method is as follows:

1. Tiles are washed and scrubbed with Jif LAC [TM] (a liquid abrasive cleaner) and hot water. They are then rinsed.

2. Tiles are then cleaned with hand dishwash liquid and rinsed.

3. A heaped spatula (approximately 5g) of fine calcite powder is placed on the tiles and they are then scrubbed with a damp cloth. 4. The tiles are then rinsed with de ineralised water. The tiles are deemed to be clean if the surface is completely hydrophillic (ie: the water forms a constant film and does not bead) .

5. The tiles are dried and then wiped with a paper tissue before use.

For coating with calcium stearate the treatment solution contains 12.9% Calcium Stearate ( ex. Fisons, Technical

Grade Reagent; made up to 100% with isopropyl alcohol. This mixture is mixed using a Silverson stirrer/homogeniser at full speed for 5 minutes. The soil is sprayed on to the tiles to give a nominal coverage of 2.28mg/cm2 ( without solvent ). This gives a coverage of 0.0176g/cm2 when spraying the tile ( i.e. with solvent present ). The coated tiles are placed in an oven at 180 degrees Celsius for 35 minutes. The tiles are then allowed to cool to room temperature before use.

Viscosity was measured so as to give only a guide and a relative measure of viscosity. A U-tube Viscometer was employed and used in accordance with International Standards ISO 3104-1976 and 3105-1976. All measurements were made at 25°C.

Optical microscopy observations were obtained on transparent (unscratched) Perspex slides (occasionally glass slides) which were soiled according to the method described earlier for dipped soap/sebum (1:0.15). lOul of each formulation was applied to the soil. The interaction of test liquors with larger flocculated soil particles were examined under a X20 lens (and recorded on video) where the particles were remote from the edge of the liquid droplet to avoid evaporation/triple interface effects. Attempts to examine soil/surfactant interactions on enamel were unsuccessful as the soil could not be viewed in light reflection mode when immersed in cleaning fluid.

Table 1A; Comparative examples

Table IB; Comparative examples

Table IC; Comparative examples

Table 2A: Embodiments of the invention

Table 2B: Embodiments of the invention

From the results in Tables 1A, IB, IC and 2A & 2B it can be seen that the formulations according to the present invention show rapid release of soil from surfaces and give acceptable cleaning performance.

Claims

CLAIMS :

1. A hard surface cleaning composition of pH 7-13 comprising:

b) a sequestering agent for Group II metals and

2. A composition according to claim 1 which comprises a total surfactant level of 2-8%wt on product.

3. A composition according to claim 1 wherein the major part of the surfactant present is primary alkyl sulphate comprising a mixture of materials of the general formulation:

ROS0₃M

wherein R is a C₈ to C₁₈ primary alkyl group and M is an equivalent cation.

4. A composition according to claim 1 comprising alkyl polyglycosides wherein more than 50%wt of the APG present in the compositions comprises C₆-╬╣o alkyl APG and wherein the degree of polymerisation is 1.1-1.6.

5. A composition according to claim 1 or 2 wherein the surfactant comprises a mixture of anionics and alkylpolyglucosides (APG) and wherein the weight ratio of APG to anionic lies in the range 1:10-10:1 as anionic :APG.

6. A composition according to claim 1-5 which is free of ethoxylated alcohol nonionic surfactants.

7. A composition according to claim 1-6 wherein the sequestering agent has a pK_Ca>5.

8. A composition according to claim 7 wherein the sequestering agent is of the general formula:

R-CH (COOH) -N- (CH2COOH) 2

where R=CH3 , CH2COOH or CH20H.

9. A composition according to claims 1-8 which comprises hexanol at levels of 0.5-2%wt

10. A composition according to claims 1-9 which comprises methanol and/or methyl digol at levels of l-5%wt

11. A composition according to claims 1-10 which is free of solvents selected from the group comprising propylene glycol n-butyl ether and 2-butoxy ethanol.

12. A composition according to claims 1-11 having a final product viscosity in the range 6-15 centipoise which comprises a polymer thickener.

13. A composition according to claim 1 which comprises:

a) 2-8% of a surfactant selected from the group comprising anionic sulphate, anionic sulphonate, alkyl poly glycoside and mixtures thereof, b) 2-10% of a sequestering agent for Group II metals and

c) 1-5% of a solvent selected from the group comprising hexanol, methyl digol, methanol and mixtures thereof, provided that the hexanol level is less than 2% on product.