Background and Prior art In the manufacture of detergent compositions by casting, the formulated system is taken to a fluid state by raising the temperature, filled into moulds, and cooled. This technology is commonly employed for manufacturing transparent personal wash tablets that contain among other ingredients (such as soap and synthetic surfactants) typically 15-50% of expensive alcoholic ingredients such as ethanol, polyhydric alcohols, sugars, etc. , at the time of casting.

It is preferable to develop cast compositions comprising high levels of water, air, and liquid benefit agents to obtain low cost yet high performing bars. It enables one to manufacture detergent bars cost effectively. It is important to deliver sensory and in-use properties such as lather, cleaning, economy, product feel and skin feel in such bars.

Detergent formulations where high levels of water or other liquid benefit agents are incorporated could pose a problem as the physical properties of the bar such as hardness is low.

Detergent bars require an acceptable physical strength so that they retain their structural integrity during handling, transport and use. The hardness of the bars, at the time of manufacture and subsequently, is an important property.

The prior art (US-A-5,340, 492, US-A-4,165, 293, WO-96/04361, our co-pending application (717/Bom/99)), generally teaches the use of additives such as polyols or salting-in-electrolytes or other bar appearance aids in melt cast compositions comprising fatty acid soap, detergent active, very high levels of water or liquid benefit agents to enhance the rigidity of the bar.

WO-02/053689 teaches a melt cast detergent composition with a solids content less than 30%, exhibiting a yield stress >75kPa at a temperature range 20-40°C, without the addition of any bar firmness aids such as polyols or salting-in-electrolytes.

It has been observed that the rate of wear is very high for bars comprising high levels of water or other liquids, consequently the economy of the bar in use is poor. Enhancing hardness of the bar alone addresses the problem in handling, storage and transportation but does not essentially take care of economy in use and other in-use properties. The problem of poor economy is particularly significant in fabric wash scenario.

It is an object of the present invention to incorporate low levels of selected surfactants into the melt cast compositions comprising high levels of water and other liquid benefit agents to enhance the hardness and significantly reduce the rate of wear for laundry applications. It has been possible to achieve the above objective by incorporating 0. 5-5% by weight of an ester of sulphosuccinic acid in a melt cast detergent composition using nil or very low levels of additives, and high levels of water or other liquid benefit agents.

Description of the invention Accordingly, in a first aspect the present invention provides a melt cast solid shaped detergent composition with a solid content less than 30% by weight, comprising: i. 2-50% by weight saturated fatty acid soap comprising one or more salts of C6-C24 fatty acids, ii. 2-40% by weight of non-soap detergent active species, of which 0.5-5% by weight of the composition is an ester of sulphosuccinic acid and iii. 30-80% by weight water and, optionally, other liquid benefit agents.

It is desirable that said solid shaped detergent composition is a tablet composition.

Preferably, the saturated fatty acid soap in said solid shaped detergent composition comprises a salt of C16 fatty acid. More preferably, the saturated fatty acid soap is present in said solid shaped detergent composition at a concentration of 10-30% by weight.

The additives generally employed in the prior art are ethanol, propylene glycol and other polyols, salting-in-electrolytes, etc. The present invention preferably avoids the use of any of these in the composition.

According to another aspect of the invention, there is provided a process for manufacturing a solid shaped detergent composition, comprising the steps of: i. making a melt of a detergent composition according to the present invention; ii. pouring the said melt into a mould to obtain the desired shape; and

iii. cooling the mould under quiescent conditions to bring about solidification.

Preferably, the said process comprises the additional step of sealing the mould after the melt has been poured thereinto and before cooling the mould, whereby the mould is a pre-formed polymeric mould. When applying this preferred process of the invention, a so-called cast-in-pack solid shaped detergent composition can be suitably manufactured.

According to a further embodiment of the present invention there is provided a continuous process for casting, comprising the steps of: i. filling a continuous tube of flexible material formed online and sealed at the bottom end, with a melt having a detergent composition according to the invention, where the tube acts as a sleeve to the composition, and simultaneously conveying through a cross section constraining guide to achieve desired area of cross section of the filled sleeve that is independent of the perimeter; ii. sealing the filling end of the filled tubular sleeve without air entrapment to obtain a cast-in-sleeve melt; iii. solidifying and simultaneously shaping the said melt by cooling the said filled sleeve on a suitable mould to obtain a cast-in-sleeve log; iv. cutting the said shaped and solidified cast composition into billets/tablets ; and v. optionally, flow wrapping the said logs/billets/tablets.

Detailed description of the Invention The present invention relates to a melt-cast detergent composition with a solid content of less than 30% by weight and very high levels of water or other liquid benefit agents, that exhibits enhanced hardness and shows low rate of wear. These properties are desirable features of bars for certain applications such as fabric washing.

Fatty acid soap The saturated fatty acid soap present in the composition of the invention comprises one or more salts of saturated C6-C24 fatty acids. Preferably, the soap comprises a salt of C16 fatty acid.

The soap employed may be a sodium, potassium, magnesium, aluminium, calcium or lithium salt of saturated fatty acids. It is especially preferred to apply a sodium or potassium salt of saturated fatty acid. It is particularly preferred that the saturated fatty acid soap is sodium palmitate.

The saturated fatty acid soap is present in the composition of the invention at a concentration of 2-50% by weight, preferably 10-30% by weight.

Detergent Active Preferably, the composition according to the invention comprises a non-soap detergent active that is selected from anionic, non-ionic, cationic, amphoteric or zwitterionic surfactants or their mixtures. More preferably, the non-soap detergent active is an anionic surfactant.

It is however essential that the composition of the invention comprises 0.5-5% by weight of a detergent active that is a sodium or potassium salt of an ester of sulphosuccinic acid.

Sulphosuccinates These are esters of sulphosuccinic acid. The acid groups can be either monoesters or diesters and the general structures of these are presented below. The monoesters are also called half esters. CH2COOR CH2COOR I I NaS03CHCOONa NaS03CHCOOR Monoester Diester The most common diesters are made from Cg and Cg alcohols and the monoesters from C12-Cl8 alcohols. A few of the examples of sulphosuccinates are dialkylsulphosuccinate, fatty alcohol ether sulphosuccinate which could be a monoester or a diester and is always a monoester if the alcohol is ethoxylated, sodium di (2-ethylhexyl) sulphosuccinate, disodium coco alcohol ethoxylate (3) monosulphosuccinate.

It is particularly preferred that the sulphosuccinates for use according to the present invention are sodium lauryl sulphosuccinate and sodium oleate sulphosuccinate.

Anionic surfactants Suitable anionic detergent active compounds are water soluble salts of organic sulphuric reaction products having in the molecular structure an alkyl radical containing from 8 to 22 carbon atoms, and a radical chosen from sulphonic acid or sulphuric acid ester radicals and mixtures thereof. Some examples of synthetic anionic detergent active compounds are linear alkyl benzene sulphonate, Sodium lauryl sulphate, Sodium

lauryl ether sulphate, Alpha olefin sulphonate, alkyl ether sulphate, Fatty methyl ester sulphonate, Alkyl isothionate, etc.

The cations most suitable in above detergent active species are sodium, potassium, ammonium, and various amines e. g. monoethanol amine, diethanolamine and triethanolamine.

Nonionic surfactants Suitable non-ionic detergent active compounds can be broadly described as compounds produced by the condensation of alkylene oxide groups, which are hydrophilic in nature, with an organic hydrophobic compound which may be aliphatic or alkyl aromatic in nature. The common non-ionic surfactants are the condensation products of aliphatic alcohols having from 8 to 22 carbon atoms in either straight or branched chain configuration with ethylene oxide, such as a coconut oil ethylene oxide condensate having from 2 to 15 moles of ethylene oxide per mole of coconut alcohol. Some examples of non-ionic surfactants are Alkyl phenol ethylene oxide (EO) condensate, Tallow alcohol 10 EO condensate, Alkyl de-methyl amine oxides, Lauryl mono- ethanolamide, Sugar esters, etc.

Other surfactants Some examples of amphoteric detergent active are Coco amidopropyl betaine, Cocobetaine, etc.

It is also possible optionally to include cationic or zwitterionic detergent actives in the compositions according to the invention.

Further examples of suitable detergent-active species are given in the following reference :"Handbook of Surfactants", M. R.

Porter, Chapman and Hall, New York, 1991.

The detergent active to be employed in the detergent composition of this invention is preferably an anionic surfactant and will generally be present at a concentration of from 2 to 40% by weight.

Liquid benefit agents According to a preferred aspect of the invention, liquid benefit materials such as moisturisers, emollients, fabric conditioners, etc. are incorporated in the composition. Examples of moisturisers and humectants include polyols, glycerol, cetyl alcohol, carbopol 934, ethoxylated castor oil, paraffin oils, lanolin and its derivatives.

Optional ingredients Other optional ingredients such as salting-in-electrolytes, polyols, fillers, colour, perfume, opacifier, preservatives, one or more water insoluble particulate materials such as talc, kaolin, polysaccharides and other conventional ingredients may also be incorporated in the composition.

Process A melt of the detergent composition comprising 2-50% by weight of saturated fatty acid soap, 2-40% by weight of non-soap detergent active wherein 0. 5-5% by weight of the composition is an sodium/potassium salt of ester of sulphosuccinic acid and 30-80% water or other liquid benefit agents is prepared. This melt is poured into any suitable mould or a pre-formed polymeric mould to obtain the desired shape, the mould is

sealed, and cooled under quiescent conditions to bring about solidification.

The above composition is preferably characterised in that the said composition does not show pure lyotropic liquid crystalline phase in the temperature range 20-100°C and forms an isotropic liquid phase or a dispersion of lyotropic liquid crystalline phase in the continuum of isotropic liquid in the temperature range 40-100°C.

The mould may be suitably selected to produce near net shape tablet or to produce bars/blocks. The bars/blocks may be further shaped into a detergent article.

If the solid detergent article is produced using a near net shape thermoformed polymer, the mould is sealed to obtain a cast-in pack detergent composition. To obtain cast-in pack detergent composition the mould is preferably sealed immediately after filling the mould.

The composition can be prepared in bar form using a continuous process, comprising steps of: i. filling a continuous tube of flexible material formed online and sealed at the bottom end, with a melt of a castable composition, where the tube acts as a sleeve to the composition, and simultaneously conveying through a cross section constraining guide to achieve desired area of cross section of the filled sleeve that is independent of the perimeter; ii. sealing the filling end of the filled tubular sleeve without air entrapment to obtain a cast-in-sleeve melt;

iii. solidifying and simultaneously shaping the said melt by cooling the said filled sleeve on a suitable mould to obtain a cast-in-sleeve log; iv. cutting the said shaped and solidified cast composition into billets/tablets; and v. optionally flow wrapping the said logs/billets/ tablets.

The bars may be dehydrated after demoulding to obtain aerated, low density bars.

The invention will now be illustrated with respect to the following non-limiting examples.

Example 1 Demonstration of the effect of ester of sulphosuccinic acid on bar properties. i. Preparation of Detergent Tablet A melt having one of the detergent compositions as presented in Table 1, and having an elevated temperature of 80°C is poured into a rectangular mould of dimensions 75mm (L) x 55mm (W) x 40mm (H). The composition was allowed to cool to bring about solidification and a detergent tablet was obtained. The yield stress and rate of wear were measured using the procedure described below and the results are presented in table 1. ii. Yield Stress Measurement The detergent tablets were then kept in oven maintained at 25°C for 4 hours and allowed to equilibrate. The yield stress of the tablets at 25°C was measured using a automatic penetrometer using the procedure described below.

The automatic penetrometer used for yield stress measurements was model PNR 10 from M/s Petrotest Instruments GmbH. Standard Hollow Cone (part &num 18-0101, as per ASTM D 217-IP 50) along with Plunger (part &num 18-0042) was used for the measurements.

The cone consisted of a conical body of brass with detachable, hardened steel tip. The total mass of the cone was 102.5 g.

The total mass of the movable plunger was 47.5 g. Total mass of cone and plunger that fall on the detergent tablet was therefore 150 g. Additional weights of 50 g and 100 g (making the total weight falling on the sample 200 g and 250 g, respectively) were also used. The yield stress values of the sample at 25°C were measured using the standard procedure comprising following steps: The detergent tablet was placed on the table of the penetrometer.

The measuring device of the penetrometer was lowered so that the tip of the penetrometer touched the tablet but did not penetrate it.

The measurement operation was started by pressing"start"key.

The penetration depth was read in mm as indicated on the display.

The measured penetration depth value was used to calculate the yield stress of the detergent tablet using the following equation : Yield stress = Applied force / (Projected area of the cone) = (m x g) x 103 / [# (p tan 1/2 # + 1/2 tip diameter) 2] wherein: yield stress is measured in kPa, m : total mass falling on the flat surface of the bar in kg g : acceleration due to gravity in m/s

p : penetration achieved in mm 9 : Cone angle (30°), and tip diameter = 0.359 mm According to the above equation it follows that if the measured penetration depth is <10 mm for 200 g total mass falling on the sample then the yield stress of the detergent tablet is > 75 kPa. The penetration values reported in the tables 1-3 are for 200g total mass falling on the detergent tablet. iii. Protocol to Measure Intrinsic Rate of Wear The bars were cut to the following size : 6.5 cm (length) x 5.5 (width) x 4.5 cm height. The initial weight of the bar (W1) was taken. The fabric was wet using a 24FH water and the bar was rubbed on the fabric. The number of rubs being maintained uniform the experiment was conducted as a replicated trial.

The weight of the bar was measured (W2). Intrinsic rate of wear = W1-W2. s Table 1 Composition % weight 1.1 1.2 1.3 1.4 Sodium Palmitate (NaP) 18 18 18 18 Sodium Linear Alkyl Benzene 13 11 11 9 Sulphonate (NaLAS) Disodium Lauryl Sulphosuccinate--2 2 (LSS) Water 69 71 69 71 Bar Properties Penetration (mm) 7.8 8.5 4.5 5. 1 Y. S (kPa) 121 103 321 257 pH 9. 8 9. 8 9. 9 9. 8 Intrinsic Rate of Wear (g) 47 43 26 31

The data presented in Table 1 shows that incorporation of 2% (by weight) of lauryl sulphosuccinate helps in processing bar with high levels of water and improves the hardness of the bar significantly. It also reduces the rate of wear of the bar significantly.

Example 2 Effect of chemical nature and levels of the ester of sulphosuccinic acid on bar properties.

The bars of composition as described in Table 2 were prepared by using the process described in Example 1. The effect of incorporating different types of the ester of sulphosuccinic acid and the level at which they are incorporated was tested on the processability and rigidity by measuring the yield stress using the procedure described above and the data is presented in table 2.

Table 2 Composition % weight 2.1 2. 2 2. 3 2. 4 2. 5 2. 6 2. 7 2. 8 Sodium 18 18 18 18 18 18 13 13 Palmitate (NaP) Sodium Linear 13 10.5 10 6 6 11 10 8 Alkyl Benzene Sulphonate Disodium Lauryl-0. 5 1 5 7--2 Sulphosuccinate Disodium Oleate-----2-- Sulphosuccinate (OSS) Water 69 71 71 71 69 69 77 77 Bar Properties Penetration 7. 8 6. 7 5. 4 6.4 9.4 5.6 10.6 6.3 (mm) Y. S (Kpa) 121 159 238 173 85 224 68 178 pH 9. 8 9.6 9. 8 9. 8 9.8 9.7 9.8 9.7 The data presented in Table 2 show that irrespective of the nature of the ester there is improvement in the processability and rigidity of the bar. It also demonstrates that the

selective range of 0.5-5% of the ester gives the benefit and the bars become soft when the level is increased beyond 5% by weight of the composition. The data shown in Table 2 also demonstrates that the use of sulphosuccinates helps in obtaining rigid bars in compositions containing low levels of structurant (13% NaP) as well as high levels of structurant (18% NaP) Example 3: Demonstration using different types of detergent actives: The bars of composition as described in Table 3 were prepared by using the process described in Example 1. The effect of incorporating different types of detergent actives was tested on the processability and rigidity by measuring the yield stress using the procedure described above and the data is presented in Table 3.

Table 3 Composition % weight 3. 1 3. 2 3.3 3.4 3.5 3. 6 3. 7 3.8 3.9 NaP 18 18 18 18 18 18 18 18 18 Alpha olefin----11 9 13 11 11 sulphonate (AOS) Sodium Oleate 5 5 5 5----- (NaOl) Sodium lauryl 6 4--- ether sulphate (SLES) NaLAS - - 8 6 - - - - - LSS 2-2-2 2- ost------2 Water 71 71 69 69 71 71 69 69 69 Bar Properties Penetration (mm) 7. 61 4.41 6. 5 4.6 6.7 5.75 6.89 4.68 5.63 Y. S (Kpa) 127 336 169 313 160 211 152 303 219

The data presented in Table 3 show that the nature of the detergent active used does not have an influence on the bar properties so long as the required amounts of the ester of sulphosuccinic acid is present in the formulation.