EP4402237A1

EP4402237A1 - An alkaline hard surface cleaning composition

Info

Publication number: EP4402237A1
Application number: EP22785958.4A
Authority: EP
Inventors: Manoj Vilas Dagaonkar; Somnath Ghosh
Original assignee: Unilever Global IP Ltd; Unilever IP Holdings BV
Current assignee: Unilever Global IP Ltd; Unilever IP Holdings BV
Priority date: 2021-09-14
Filing date: 2022-09-12
Publication date: 2024-07-24
Anticipated expiration: 2042-09-12
Also published as: ZA202401378B; WO2023041471A1; EP4402237B1; EP4402237C0

Abstract

The present invention relates to an aqueous alkaline composition comprising calcium-based anionic surfactant for cleaning hard surfaces. It provides an aqueous hard surface cleaning composition comprising: (i) calcium salt of linear alkyl benzene sulphonic acid; (ii) 21 to 50 wt% of an abrasive particle; (iii) alkoxylated fatty alcohol; and (iv) magnesium oxide; wherein (a) the composition has a pH in the range of 9 to 12 at 20 °C; (b) the composition comprises an amount of magnesium salt of linear alkyl benzene sulphonic acid that is 0 to 1 wt% of the amount of said calcium salt; (c) the composition comprises less than 1 wt% sodium salt of linear alkyl benzene sulphonic acid; (d) the composition has a viscosity in the range 500 to 2000 mPa.S at 20 S-1 shear rate and 25°C; (e) said abrasive has a Moh's index in the range 0.5 to 7 and comprises at least calcite; and (f) the amount of surfactant on the surface of the abrasive particles is 0 to 10 % of the total surfactant of the composition; and (g) said alkoxylated fatty alcohol has and HLB value in the range 11 to 20, carbon chain length 12 to 16 and ethoxylation degree of 5 to 8.

Description

AN ALKALINE HARD SURFACE CLEANING COMPOSITION

Field of the Invention

The present invention relates to a hard surface cleaning composition. In particular, it relates to an alkaline hard surface cleaning composition comprising calcium-based anionic surfactant.

Background of the Invention

Hard surface cleaning compositions are available in various formats. There was a time when powders were widely used. Then came bars which were shaped like soap bars. Bars are being gradually replaced by liquids and pastes. Often liquids are preferred due to ease of application and uniform spreading on hard surfaces.

Conventional liquid hard surface cleaning compositions may contain anionic surfactant, nonionic surfactant, abrasives, and other minors such as fragrance, antimicrobial agent, colourant etc. Calcium based anionic surfactant such as Calcium-LAS (Linear Alkyl benzene Sulphonate) is one of the examples suitable for such compositions. Typically, the compositions are stored and used over a period, hence, they may further contain preservatives. ‘Preservative’ herein refers to a class of compound being present in a composition, inhibits microbial growth over time. It is observed that certain compounds, e.g, benzisothiazolinone (BIT), octylisothiazolinone (OIT), methylchloroisothiazolinone (MCIT), methylisothiazolinone (MIT) (commonly known as ‘IT’ based preservatives) works as effective preservative, however, may cause skin sensitization or skin allergies. Thus, it is desired to have compositions free of those compounds without compromising cleaning efficacy and preservation performance.

In the context of preservatives, it is observed that all preservatives are not efficient in wide range of pH, or in other words, there are preservatives which are effective only in select pH range. Even certain preservatives may not be compatible with all type of formulations or ingredients therein. Thus, formulating a stable composition with select preservative for a particular format is a challenging task.

In this context, WO 2018/091226 describes a calcium-LAS based composition containing abrasive particle, alkoxylated fatty alcohol and having pH in the range 6 to 8 at 20° C. The composition is suitable for cleaning hard surfaces. It further describes the composition in terms of amount of surfactant deposited on the abrasives, HLB values and carbon chain length of alkoxylated fatty alcohol, and restricting the amount of magnesium-LAS, sodium-LAS. It also describes a method for preparing a composition comprising Ca-LAS by reacting LAS acid with calcium oxide and/or calcium hydroxide.

Although prior art document provides a calcium-based anionic surfactant containing cleaning composition, it is not stable beyond the pH range 6 to 8. Thus, adding a preservative which is effective in alkaline pH or acidic pH to such composition, would result either inefficient preservation efficacy or affect stability of the composition.

Therefore, there is need to formulate an improved calcium- based anionic surfactant containing composition, which is free of harmful preservative (‘IT’ based) yet stable and efficacious.

Surprisingly, the present inventors have found that a composition comprising a calcium based anionic surfactant, magnesium oxide and having pH in the range 9 to 12, which also contain abrasive particle and select non-ionic surfactant, provides a stable composition free of harmful preservatives (‘IT’ based) yet efficacious.

Summary of the Invention

In first aspect, the present invention provides an aqueous hard surface cleaning composition comprising:

(i) calcium salt of linear alkyl benzene sulphonic acid;

(ii) 21 to 50 wt% of an abrasive particle;

(iii) alkoxylated fatty alcohol; and

(iv) magnesium oxide; wherein

(a) the composition has a pH in the range of 9 to 12 at 20 °C;

(b) the composition comprises an amount of magnesium salt of linear alkyl benzene sulphonic acid that is 0 to 1 wt% of the amount of said calcium salt;

(c) the composition comprises less than 1 wt% sodium salt of linear alkyl benzene sulphonic acid;

(d) the composition has a viscosity in the range 500 to 2000 mPa.S at 20 S'¹ shear rate and 20°C;

(e) said abrasive has a Moh’s index in the range 0.5 to 7; and comprises at least calcite; (f) the amount of surfactant on the surface of the abrasive particles is 0 to 10 % of the total surfactant of the composition; and

(g) alkoxylated fatty alcohol has and HLB value in the range 11 to 20, carbon chain length 12 to 16 and ethoxylation degree 5 to 8.

Also, in accordance with the present invention there is provided a method of preparing the composition of the present invention, said method comprising a step of preparing calcium salt of linear alkyl benzene sulphonic acid by reacting linear alkyl benzene sulphonic acid with calcium oxide and/or calcium hydroxide.

Detailed Description of the Invention

Any feature of one aspect of the present invention may be utilized in any other aspect of the invention. The word “comprising” is intended to mean “including” but not necessarily “consisting of” or “composed of.” In other words, the listed steps or options need not be exhaustive. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word “about”. Numerical ranges expressed in the format " x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "x to y", it is understood that all ranges combining the different endpoints are also contemplated. Unless specified otherwise, amounts as used herein are expressed in percentage by weight based on total weight of the composition and is abbreviated as “wt%”. The use of any and all examples or exemplary language e.g. “such as” provided herein is intended merely to better illuminate the invention and does not in any way limit the scope of the invention otherwise claimed. Room temperature is defined as a temperature of about 25 degrees Celsius.

Hard surfaces include floors, walls, tiles, windows, cupboards, sinks, showers, shower, wash basins, WCs, fixtures and fittings made of different materials like ceramic, vinyl, no-wax vinyl, linoleum, melamine, glass, Formica®, vitroceramic, plastified wood, metal or any painted or varnished or sealed surface. It also includes household appliances including, but not limited to refrigerators, freezers, washing machines, automatic dryers, ovens, microwave ovens and dishwashers. The term dishes include glasses, pots, pans, baking dishes and flatware made from ceramic, china, metal, glass, plastic (polyethylene, polypropylene, polystyrene), wood, enamel, Inox®, teflon, or any other material commonly used in the making of articles used for eating and/or cooking.

Calcium salt of linear alkyl benzene sulphonic acid

The aqueous hard surface cleaning composition of the present invention comprises calcium salt of linear alkyl benzene sulphonic acid (abbreviated as Ca-LAS).

Ca-LAS is formed by neutralising linear alkyl benzene sulphonic acid (LAS acid) with a calcium salt. Preferably the calcium salt is calcium hydroxide or calcium oxide. Preferably the LAS acid is neutralised with the calcium salt in absence of abrasive particles. Ca-LAS works as primary surfactant in the composition for cleaning benefit.

It is preferred that the composition according to the present invention comprises 0.1 to 15 wt% of calcium salt of linear alkyl benzene sulphonic acid, more preferably 0.5 to 10 wt%, even more preferably 1 to 5 wt% and most preferably 2 to 4 wt%.

Often dolomite is used as source of calcium salt for neutralising LAS acid, which may leave a part of magnesium salt of linear alkyl benzene sulphonic acid (Mg-LAS) in addition to Ca-LAS. However, dolomite is naturally occurring minerals and often varies in its specification, particularly in the relative ratio of components therein, which may affect the product performance. Therefore, according to the present invention it is preferred to use non-dolomite source of calcium salt for neutralising LAS acid.

Magnesium salt of linear alkyl benzene sulphonic acid is in an amount not more than 1 wt% of the amount of said calcium salt. For example, if the total amount of Ca-LAS is 15 wt%, then the maximum amount of Mg-LAS is 0.15 wt%, which amounts to not more than 1 wt% of the amount of the calcium salt.

It is preferred that the composition does not contain magnesium salt of linear alkyl benzene sulphonic acid.

Thus, the amount of magnesium salt of linear alkyl benzene sulphonic acid is from 0 to 1 wt% of the amount of the calcium salt.

Alkoxylated fatty alcohol The composition comprises one or more alkoxylated fatty alcohol. These are non-ionic surfactants. The HLB of the alkoxylated fatty alcohol is in the range of 11 to 20 and the carbon chain length of said fatty alcohol is in the range of 12 to 16. All non-ionic surfactants have an HLB value. The higher the number, the more hydrophilic the surfactant. On the other hand, surfactants having lower HLB value are more lipophilic.

Alkoxylated fatty alcohols lend stability to the composition. It is particularly preferred that the degree of ethoxylation in said alkoxylated fatty alcohol is from 5 to 8 moles of ethylene oxide units. Alkoxylated fatty alcohols having a degree of ethoxylation from 5 to 8 show particularly good technical effect by stabilizing the composition which is stored at temperatures higher or lower than the normal room temperature (i.e., a temperature around 20 °C).

It is preferred that the composition comprises 0.05 to 10 wt% of alkoxylated fatty alcohol, more preferably 0.1 to 8 and most preferably 1 to 5 wt%. A combination of one or more such non- ionic surfactants may also be used.

Preferably the ratio calcium salt linear alkyl benzene sulphonic acid to alkoxylated fatty alcohols is 1 :1 to 2:1.

Abrasive particles

The composition comprises abrasive particles having a Moh’s Index of 0.5 to 7 and comprises at least calcite.

The composition according to the present invention comprises 21 to 50 wt% abrasive particles, preferably 23 to 47 wt% and more preferably 25 to 45 wt%. The abrasive particles suitable for the invention also include bentonite, china clay, dolomite or feldspar but any other suitable abrasive particles, which may present in addition to calcite.

It is preferred that the abrasive particles comprise at least calcite and preferably in an amount of at least 50 wt% of the total amount of abrasives in the composition.

It is preferred that the average particle size of abrasive particles is in the range 0.5 to 400 pm, more preferably 10 to 200 pm.

One of the goals of the present invention is to provide a composition free of harmful preservatives. In this context, it is observed that most of the preservatives, leaving beside the ‘IT’ based, are more effective either in alkaline pH or acidic pH. Thus, the composition may be formulated as acidic or alkaline pH for better preservative benefit. However, the composition according to the present invention comprises abrasive particles, such as calcite, which may react in acidic pH. Therefore, it is not preferable to formulate the composition in acidic pH.

The composition according to the present invention is alkaline in nature. The composition has a pH in the range of 9 to 12 at 20 °C. More preferably the composition has pH in the range 9.5 to 11 .5, most preferably in the range 10 to 11 at 20 °C.

Preservatives

The composition may comprise one or more preservatives. Preservatives helps in inhibition of microbial growth in storage, thereby increase shelf-life of the composition.

It is observed that all preservatives are not efficient in wide range of pH, even they may not be compatible with all type of formulations or ingredients there. There are preservatives which are effective only in select pH range.

The composition is alkaline and has pH in the range 9 to 12 at 20 °C. Preservatives which are effective in this pH range are suitable for the invention. Most preferred preservative is phenoxyethanol.

Preferably the composition is free of ‘IT’-based preservative, such as Benzisothiazolinone (BIT), Octylisothiazolinone (OIT), Methylchloroisothiazolinone (MCIT), Methylisothiazolinone (MIT) etc.

Magnesium oxide

The composition according to the present invention comprises magnesium oxide. It is observed that a Ca-LAS based composition having alkoxylated fatty alcohol, abrasive particles in alkaline pH tends to become unstable over a period on storage and pH of such composition drops over the period, which may affect the efficacy of the composition. In the present invention, magnesium oxide helps in stabilising the composition and maintaining the pH in different storage conditions.

Preferably magnesium oxide is added in the composition post neutralisation of LAS acid.

It is preferred that the composition comprises 0.01 to 2 wt% magnesium oxide, more preferably the composition comprises 0.02 to 1 wt% and most preferably 0.05 to 0.5 wt% magnesium oxide.

Most hard surface cleaning compositions like dish wash composition and kitchen cleaners need a certain viscosity inter alia for ease of application and spreadability.

The composition according to the invention has a viscosity of 500 to 2000 mPa.S at 20 S'¹ and 20 °C.

The viscosity may be measured by any suitable method. It is preferably measured at 20 °C at a shear rate from 1 s^-1 to 50 s’¹, using a Haake® AR1000 Rheometer with cone and plate assembly.

It will be understood that any known method can be used to build the required viscosity, including for example by using the abrasive particles present in the composition.

The composition preferably comprises a polymer. The purpose of the polymer is to provide some viscosity to the composition. It is preferred that the polymer is a water-swellable polymer or an associative polymer. It is preferred that the polymer provides the desired viscosity when the pH of the composition is in the range of 9 to 12. Whenever the polymer is present, it is preferred that the amount thereof is 0.005 to 10 wt%. It is preferred that the polymer is one or more of polyacrylic acid, polyacrylates, cross-linked acrylates, guar gum or its derivatives, starch-acrylic grafted copolymers, hydrolysate of starch-acrylonitrile grafted copolymers, crosslinked polyoxyethylene, cross-linked methyl cellulose, sodium carboxymethylcellulose or partially cross-linked water-swellable polymers of polyethylene oxides and polyacrylamide or isobutylene/maleic acid copolymer. Whenever present, it is preferred that the composition comprises 0.008 wt% to 5 wt% polymer, more preferably 0.01 wt% to 2.5 wt% of the polymer. A particularly preferred polymer is Acusol® 880/882/883.

Amount of water

The composition according to the present invention is aqueous, i.e. , water based. It is preferred that the composition comprises 20 to 80 wt% water and more preferably 30 to 75 wt%, even more preferably 40 to 70 wt% and most preferably 50 to 60 wt%.

The composition may contain other ingredients which are disclosed hereinafter.

Other surfactants

The composition according to the present invention may further contain other surfactants.

However, the composition comprises less than 1 wt% sodium salt of linear alkyl benzene sulphonic acid (Na-LAS). Any excess amount of Na-LAS could tend to destabilise the composition due to exchange of calcium ions with the sodium ions.

The cleaning composition may further comprise other anionic surfactants, amphoteric and zwitterionic surfactants, provided they do not interfere with the performance or stability of the composition. It is preferred that the amount of such other surfactants is in the range 0.1 to 20 wt%.

Preferably the composition comprises less than 1 wt% cationic surfactant.

It is further preferred that in the composition, the total amount of surfactants is not greater than 40 wt%. In other words, the Active Detergent (AD) level is not greater than 40 wt%. The term total surfactant means the sum of all surfactants contained in the composition, which includes calcium salt of linear alkyl benzene sulphonic acid. Preferably the AD level is not more than 30 wt%, with a preferred level being not more than 20 wt%, and even more preferred not more than 10 wt%.

Suitable amphoteric surfactants are derivatives of aliphatic secondary and tertiary amines containing an alkyl group of 8 to 20 carbon atoms and an aliphatic group substituted by an anionic water-solubilising group, for instance sodium 3-dodecylamino-propionate, sodium 3- dodecylaminopropane-sulphonate and sodium N 2-hydroxy-dodecyl-N-methyltaurate.

Examples of suitable zwitterionic surfactants include derivatives of aliphatic quaternary ammonium, sulphonium and phosphonium compounds having an aliphatic group of from 8 to 18 carbon atoms and an aliphatic group substituted by an anionic water-solubilising group, for instance betaine and betaine derivatives such as alkyl betaine, in particular C12-C16 alkyl betaine, 3-(N,N-dimethyl-N-hexadecylammonium)-propane 1 -sulphonate betaine, 3- (dodecylmethyl-sulphonium)-propane 1 -sulphonate betaine, 3-(cetylmethyl-phosphonium)- propane-1 -sulphonate betaine and N,N-dimethyl-N-dodecyl-glycine. Other well-known betaines are the alkylamidopropyl betaines e.g., those wherein the alkylamido group is derived from coconut oil fatty acids or alcohols.

Further examples of suitable surfactants can be found in the well-known textbooks: 'Surface Active Agents' Vol.1 , by Schwartz & Perry, Interscience 1949; 'Surface Active Agents' Vol.2 by Schwartz, Perry & Berch, Interscience 1958; the current edition of 'McCutcheon's Emulsifiers and Detergents' published by Manufacturing Confectioners Company; 'Tenside-Taschenbuch', H. Stache, 2nd Edn., Carl Hauser Verlag, 1981.

Other ingredients

The composition according to the present invention may include additional ingredients to improve or enhance the in-use performance.

Such ingredients include colour, fragrance, soil suspending agents, detersive enzymes, compatible bleaching agents, freeze-thaw stabilisers, bactericides, preservatives, hydrotrope, and perfumes.

Product Form

It is preferred that the composition according to the present invention is liquid or cream or paste form, which may be directly applied to the hard surface. An example of a commercial cream is Cl F® from Unilever. Packaging

The composition according to the invention can be packaged in any suitable container. Preferably, the composition is packaged in a plastic bottle with a detachable closure /pouring spout. The bottle may be rigid or deformable. A deformable bottle allows the bottle to be sgueezed for dispensing. If clear bottle is used, they may be made of PET or Polyethylene. Preferably, if non-transparent bottle is used, they may be made of high-density polyethylene (HDPE). The bottle may be provided with one or more labels, or with a shrink-wrap sleeve, which is desirably at least partially transparent, for example 50% of the area of the sleeve is transparent. The adhesive used for any transparent label should preferably not adversely affect the transparency. The composition can also be packed in other formats like sachets and pouches.

Method of preparing the composition

Conventional methods to prepare Ca-LAS containing cleaning compositions include the step of neutralizing acid-LAS with Dolomite or e.g., calcite. This way any deliberate excess of the neutralizing agent (i.e. , Dolomite or calcite) will act as the abrasive in the final composition.

We have found that these methods may not always result in a composition comprising abrasive particles with the reguired cleaning properties, as the surface of the remaining abrasive particles will be covered with a substantial amount of the total surfactant present in the composition. In some cases, this could be as much as more than 10, 20 or even 30 wt% of the total amount of surfactant in the composition.

In the composition of the present invention, the amount of surfactant on the surface of the abrasive particles is from 0 to 10 wt% of the total surfactant of the composition. Preferably 0.1 to 8 wt%, more preferably 0.5 to 6 wt% and even more preferably 1 to 4 wt% of the total surfactant of the composition.

The amount of surfactant present on the surface of the abrasive particles can be determined by following way:

To segregate the abrasive particles, present in the composition, the composition is centrifuged twice at 7500 rpm for 20 min. The particles are removed from the supernatant and washed thoroughly with DI water to ensure removal of all soluble ingredients deposited on the particle. The washed particles are then dried in a hot air oven. The dried particles are washed with methyl alcohol to extract the calcium salt of linear alkyl benzene sulfonate from the surface of the particles. The stock solution comprising methyl alcohol and leached calcium salt of linear alkyl benzene sulfonate is titrated against 0.4 mM 30 hyamine solution in presence of chloroform and mixed indicator. Based on the volume of hyamine solution required for the titration, the amount of surfactant present in the stock solution is determined. Based on this, the amount of surfactant deposited on the particle surface is calculated. The percentage of surfactant deposited on the particle is then calculated using the formula below:

Surfactant deposited on the particle surface = (amount of surfactant deposited on the particle surface/total amount of surfactant present in the composition) *100 %.

As such the present invention further provides a method of preparing a composition of the present invention comprising a step of preparing the calcium salt of linear alkyl benzene sulphonic acid by reacting linear alkyl benzene sulphonic acid with calcium oxide and/or calcium hydroxide. Preferably said step of preparation of Ca-LAS takes place in the absence of the abrasive particles, present in the final composition.

The invention will now be further described with reference to the following non-limiting examples.

Examples

Preparation of compositions

Examples were prepared according to the recipe provided in table 1.

Table 1

¹Acusol 882 or 823 neutralized with sodium hydroxide; ²Silicon DB 310

A thickener premix was prepared by neutralising Acusol 882 or 823 with sodium hydroxide in water for 10 minutes and was kept aside. In a separate mixer, water at 50 °C is mixed with calcium hydroxide, followed by LAS acid was added and mixed for 10 minutes. Subsequently magnesium oxide was added to the mixer and followed by calcium carbonate and silicon antifoam agent and was stirred for 5 min. The thickener premix was then added to the mixer and followed by non-ionic surfactant (alcohol ethoxylate 7 EO), coconut fatty acid or alcohol were added to the mixture. The preservative was added and stirred for 5 min. The composition was decanted and stored in an appropriate container.

Evaluation of preservation efficacy:

Protocol for preservation test:

The objective of preservative challenge test is to determine the susceptibility of a product to microbial contamination. The method includes a broad spectrum of organisms, namely, Group I: Gram Negative Bacteria -Non-fermenters; Group II: Gram Negative Bacteria- Fermenters, Group III: Gram positive Bacteria - Cocci, Group IV: Yeast and Group V: Mould.

99 ml of each composition was challenged (spiked) with 1 ml of each inoculum at a time and incubated for 28 days. Re-challenge was done with Group I, II and III and total viable count (TVC) was taken after 7, 14, 21 and 28 days. No rechallenge for Group III and IV. For the product to pass the preservative challenge test, there should be complete kill for Group I, II and III and no re-growth on 14 and 28 days. For group IV and V, 2 log reductions on day 7 and no- regrowth on 14 and 28 day was the pass criteria. Results are summarised in table 2 Table 2

From table 2, it is evident that Ex-1 and Ex-2, which are according to the present invention pass the challenge test, whereas Ex-A could not. pH stability of the compositions:

Each composition was stored in airtight HDPE containers under accelerated storage condition at 37 °C and were monitored for change in pH after every 4 weeks for a total period of 13 weeks. The results are shown in Table 3.

The pH was tested in a standard pH meter at 20 °C.

Table 3

It is evident from table 3, the pH of Ex- 1, Ex-2 are maintained in the range of 10.0 to 11.5, whereas pH of the Ex-B drops significantly in the storage period.

Evaluation of cleaning efficacy:

To determine the cleaning performance a model bathroom soil composition containing calcium stearate was sprayed on enamel tiles for uniform deposition and then baked at a certain temperature for a fixed amount of time. 5 g of the composition was spread on the model bathroom soil uniformly. A pressure of 340 g/cm² was applied on the soil through a head, covered with a cloth as an implement. The soiled plate was then scrubbed in a cleaning equipment for fixed rotations. After cleaning, the tile was rinsed under running water. The tile was weighed after drying and the % soil removal was calculated gravimetrically. The results can be found in Table 4. As can be seen in Table 4, no significant effect on bathroom soil removal was observed as per the new invention in spite of change in pH from neutral to alkaline. able 4

From table 4, it is evident that cleaning efficacy of Ex-1 and Ex-2 are at par with or better than the comparative example Ex-A.

Claims

1. An aqueous hard surface cleaning composition comprising:

(i) calcium salt of linear alkyl benzene sulphonic acid;

(ii) 21 to 50 wt% of an abrasive particle;

(iii) alkoxylated fatty alcohol; and

(iv) magnesium oxide; wherein

(a) the composition has a pH in the range of 9 to 12 at 20 °C;

(e) said abrasive has a Moh’s index in the range 0.5 to 7 and comprises at least calcite;

(f) the amount of surfactant on the surface of the abrasive particles is 0 to 10 wt% of the total surfactant of the composition; and,

(g) said alkoxylated fatty alcohol has a HLB value in the range 11 to 20, carbon chain length 12 to 16 and a degree of ethoxylation 5 to 8.

2. Composition as claimed in claim 1 comprising a ratio of calcium salt of linear alkyl benzene sulphonic acid to alkoxylated fatty alcohol of 1 :1 to 2:1.

3. Composition as claimed in claim 1 or 2 comprising 20 to 80 wt% water.

4. Composition as claimed in any one of claims 1 to 3 comprising 0.1 to 15 wt% calcium salt of linear alkyl benzene sulphonic acid.

5. Composition as claimed in any one of claims 1 to 4 comprising 0.05 to 10 wt% alkoxylated fatty alcohol.

6. Composition as claimed in any one of claims 1 to 5 wherein said abrasive further comprises at least one of bentonite, china clay, dolomite or feldspar. Composition as claimed in any one of claims 1 to 6 comprising 0.01 to 2 wt% magnesium oxide. Composition as claimed in any one of claims 1 to 7 wherein said composition comprises less than 1 wt% cationic surfactant. Composition as claimed in any one of claims 1 to 8 wherein the total amount of surfactant in said composition is not more than 40 wt%. Composition as claimed in any one of claims 1 to 9 comprising a preservative. Composition as claimed in claim 10, wherein the preservative is phenoxyethanol. Method of preparing a composition as claimed in any one of claims 1 to 11 comprising a step of preparing calcium salt of linear alkyl benzene sulphonic acid by reacting linear alkyl benzene sulphonic acid with calcium oxide and/or calcium hydroxide. Method as claimed in claim 12 wherein said step of preparing takes place in the absence of the abrasive particles, present in the final composition.