The invention relates to a builder system for use in detergent compositions. The invention more particularly relates to a builder system that ensures faster removal of Calcium ions from washing solutions while being less expensive than Phosphate and Zeolite based building systems.

Soaps which are alkali metal salts of fatty acids have traditionally been used for personal washing applications. Soaps have also been used for washing laundry. When washing laundry with soaps, the efficiency of washing is lower when washed in hard water. Hard water refers to water having high levels of dissolved Calcium and Magnesium salts. The dissolved Calcium and Magnesium ions react very quickly with the alkali metal cation (sodium or potassium) of the soap, leading to formation of Calcium soap which is insoluble in water and therefore leading to poor detergency. With the advent of synthetic detergents which are alkali metal salts of long chain acids of petroleum origin, the same problem persists. Most popular synthetic detergents include linear alkyl benzene sulphonates, alpha olefin sulphonates, and primary alkyl sulphates which belong to the class of anionic surfactants. Surfactants of the non-ionic, cationic, amphoteric and zwitterionic character are also known.

Cleaning performance of most synthetic surfactants are also affected by the washing in hard water.

Compounds that react preferentially with the dissolved Calcium and Magnesium ions present in hard water, thereby maintaining the desired high concentration of the detergent in its active form, have been used in detergent compositions. Such compounds or mixture of compounds are known as detergency builders. Commonly known detergency builders are alkali metal carbonates, silicates, phosphates and structured compounds like Zeolites. Alkali metal carbonates like Sodium Carbonate, commonly referred to as soda ash is a very inexpensive and widely used builder in low cost detergent formulations. Premium detergents use builders like phosphates and/or Zeolites since they have better building properties but are more expensive. There has been continuous work to develop more efficient and faster building systems using less expensive materials. Further, use of phosphates in detergents, is believed by many to be responsible for the eutrophication of rivers and other natural waters bodies. Thus a lot of effort has been made to develop faster building systems using sodium carbonate as the main raw material.

EP0234818 (Unilever, 1987) discloses a detergent composition containing (i) a detergent active system comprising a mixture of (a) an anionic non-soap detergent active; (b) a non-ionic detergent active; and (c) soap; (ii) a watersoluble alkali metal carbonate; and (iii) a water-insoluble particulate carbonate material which is a seed crystal for Calcium carbonate; characterised in a specific combination of weight ratios of the various detergent actives. The builder system in this publication is a mixture of soda and Calcium carbonate. There have been many improvements to this technology and many products launched which are improvements over this basic technology where combination of soda and Calcium carbonate is used. The present inventors have determined that the best building systems available presently using sodium carbonate as the basic builder still do not provide the desired fast building and there is scope for improvement on this technology which can be perceived by the consumers in the cleanliness of their washed laundry or in terms of costs of the products. The present inventors have found that use of the specific builder system disclosed in EP0234818 along with a specific co-builder provides for very fast building never before achieved with similar systems.

US7186677 (Henkel, 2007) describes a method for producing surfactant granules having good solubility and varying bulk densities comprising (a) providing a mixture of anionic surfactant acids and builder acids having a weight ratio of 1:100 to 1:20 of builder acid to surfactant acid; and (b) contacting the mixture with at least one solid neutralising agent. The builder acid is selected from citric, tartaric, succinic, malonic, adipic, maleic, fumaric, oxalic, gluconic, nitrilotriacetic, aspartic, ethylenediaminetetracetic, among many other acids wherein the builder acid has a particle size below 200 µm.

The use of a combination of calcium carbonate and sodium carbonate in a builder system for detergent compositions is known from CA 979772, US 4473485, WO 9840455 and CA 991942.

It is thus an object of the present invention to provide for a builder system for a detergent composition that provides faster building as compared to at least some of the prior art for similar systems.

It is another object of the present invention to provide for a builder system for a detergent composition that provides for fast building while having a lower cost as compared to at least some of the prior art systems.

The invention provides for a builder system for a detergent composition comprising:

1. (i) a water soluble alkali metal carbonate;
2. (ii) 5% to 50% by weight of the builder system, a seed for precipitating Calcium carbonate, which is Calcium carbonate; and
3. (iii) a co-builder which is a di-carboxylic acid or a salt thereof, wherein said co-builder has an average particle size less than 150 microns.

It is preferred that the water solubility of the co-builder is more than 1 g/l at 25°C.

Particularly preferred di-carboxylic acids are oxalic, malonic and succinic acid.

The invention relates to a builder system for a detergent composition. One component of the builder system is a water soluble alkali metal carbonate. The alkali metal is preferably sodium or potassium, sodium being preferred. Thus the most preferred alkali metal carbonate is sodium carbonate. The alkali metal carbonate is preferably present in an amount in the range of 10% to 90%, more preferably 25% to 90%, most preferably 45% to 80% by weight of the builder system.

Another important element of the builder system of the invention is a seed for precipitating Calcium carbonate. By "a seed for precipitating Calcium carbonate" is meant a compound which has the ability to act as a seed for precipitation of Calcium carbonate in aqueous media. The seed for precipitating Calcium carbonate is a substantially water insoluble particulate material. This water insoluble particulate material may be present in the builder system or generated insitu when the builder system is dispersed in water. The more preferred aspect provides for the substantially water insoluble particulate material to be present in the builder system. The substantially water insoluble particulate material is Calcium carbonate. Calcium carbonate may be calcite, or aragonite; and is more preferably Calcite. Calcite is preferably High Surface Area Calcite. Preferably the Calcium carbonate seed has a surface area greater than 20 m²/g, more preferably greater then 30 m²/g, most preferably greater than 60 m²/g. The seed for precipitating Calcium carbonate is present in an amount in the range of 5% to 50%, more preferably from 10% to 40%, most preferably from 15% to 30% by weight of the builder system.

The builder system of the invention comprises a co-builder which is a di-carboxylic acid or a salt thereof. The co-builder preferably has water solubility of more than 1 g/l at 25°C. Preferred di-carboxylic acids are chosen from oxalic acid, malonic acid or succinic acid, most preferred being oxalic acid. The preferred salts of the di-carboxylic acid are alkali metal or ammonium salts, alkali metal salts being more preferred. The co-builder is present in an amount in the range of 2% to 20%, more preferably from 4% to 12% by weight of the builder system. The invention works best when the co-builder is present as a powder i.e in a low particle size form. The average particle size of the co-builder is less than 150 microns, more preferably less than 75 microns. Ideally, the co-builder is molecularly dispersed in the detergent composition in which the builder system is present. This can be achieved by dissolving the co-builder in water and spraying the solution onto the detergent composition or the builder system and then drying to the desired moisture content.

The builder system of the invention provides for relatively fast building kinetics, faster than prior art systems. The builder system ensures that the Ca²⁺ ion concentration in input water reduces from about 200 ppm to less than, or about, 1.2 ppm, more preferably to less than, or about, 1.0 ppm, further more preferably less than, or about, 0.5 ppm, optimally less than, or about, 0.3 ppm, in about 30 seconds. The builder system of the invention is preferably substantially free of phosphate builders. Further, more preferably the builder system is substantially free of Zeolite builders.

According to another aspect of the invention, there is provided a process to prepare a builder system for a detergent composition comprising mixing powders of a water soluble alkali metal carbonate, 5% to 50% by weight of the builder system a seed for precipitating Calcium carbonate, which is Calcium carbonate; and a co-builder which is a dicarboxylic acid or a salt thereof.

In the above process, the powders of the co-builder have an average particle size less than 150 microns, more preferably less than 75 microns.

In a preferred aspect, the process of the invention comprises:

1. (i) dissolving dicarboxylic acid or salts thereof in water to form a solution;
2. (ii) dry mixing powders of a water soluble alkali metal carbonate with 5% to 50% by weight of the builder system a seed for precipitating Calcium carbonate, which is Calcium carbonate to form a powder mix; and
3. (iii) mixing said solution from step (i) with the powder mix of step (ii).

The solution is preferably sprayed onto the powder mix during the mixing step (iii).

According to another aspect of the present invention, there is provided a detergent composition comprising (i) the builder system according to the invention and (ii) a surfactant selected from any one of the anionic, non-ionic, cationic, zwitterionic or amphoteric class. The builder system of the invention may be present in an amount in the range of 5% to 80%, more preferably 15% to 60%, most preferably 25% to 50% by weight of the detergent composition. Suitable surfactants are compounds commonly used as surface-active agents given in the well-known textbooks "Surface Active Agents", Volume I by Schwartz and Perry and "Surface Active Agents and Detergents", Volume II by Schwartz, Perry and Berch.

According to another aspect of the present invention there is provided a process to prepare a detergent composition comprising dry mixing powders of a surfactant selected from any one of the anionic, non-ionic, cationic, zwitterionic or amphoteric class with the powders of the builder system of the present invention.

According to yet another aspect of the present invention there is provided a process to prepare a detergent composition comprising the steps of:

1. (i) dissolving a dicarboxylic acid or salts thereof in water to form a solution;
2. (ii) dry mixing powders of a surfactant selected from any one of the anionic, non-ionic, cationic, zwitterionic or amphoteric class with a water soluble alkali metal carbonate and 5% to 50% by weight of the builder system a seed for precipitating Calcium, which is Calcium carbonate, to form a powder mix; and
3. (iii)mixing said solution from step (i) with the powder mix of step (ii).

Preferably the process comprises a step of drying the detergent composition to moisture content of less than 10%.

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

These are examples as per prior art builder systems.

Various builder compositions were prepared and added to hard water containing 200 ppm Calcium ions at concentrations as shown in Table -1. Disodium oxalate, when used, was added after crushing to powder to an average particle size of about 145 microns. The building kinetics was studied by measuring the Ca²⁺ ion concentration, at various time periods and the data is presented in Table -1. The method of determining Ca²⁺ concentration is given below:

The method involved titration with EDTA (di sodium salt of Ethylene Diamine Tetra Acetic acid) using EBT (Eriochrome Black - T) as indicator. About 2 ml of the Calcium ion solution was pipetted out into a 150 ml conical flask. The solution was diluted with about 10 ml water. To this was added 5 ml of Ammonia-Ammonium chloride pH 10 buffer. Further, about 35 mg of 1% EBT in potassium nitrate solution was added. A wine red colour was obtained. A standardized EDTA solution was added dropwise from a burette with constant stirring. As more EDTA was added the colour gradually changed from wine red to violet. The end point was identified by a sudden colour change from violet to blue. The Calcium ion concentration was calculated by using the formula: $${\mathrm{Ca}}^{2+}\mathrm{ion\; concentration}=\frac{\mathrm{volume\; of\; EDTA\; X\; strength\; of\; EDTA}}{\mathrm{volume\; of\; Calcium\; solution\; taken}\mathrm{.}}$$ Comparative Example Sodium carbonate, g/l HSAC g/l Disodium Oxalate, g/l Time, s Concentration of Calcium ions, ppm A 1.5 0 0 60 10.4 B 1.5 0 0 300 1.8 C 1.5 0.5 0 60 4.7 E 1.5 0.5 0 120 1.2 F 1.5 0 0.4 30 3.6 G 1.5 0 0.4 60 1.7 Note: HSAC means High Surface Area Calcite with surface area of (20-30) m²/g.

The comparative examples of the prior art are able to bring the Ca²⁺ ion concentration down from 200 ppm to a minimum of about 1.2 to 2 ppm and the time required is about 1 to 2 minutes (Best being Comparative Examples E and G).

These are examples as per the invention having a combination of sodium carbonate, HSAC and di sodium oxalate.

Various builder compositions were prepared and added to hard water containing 200 ppm Calcium ions at concentrations as shown in Table -2. In Examples 1 to 5, the builder system was a dry mix of the sodium carbonate and High Surface Area Calcite (HSAC) to which a solution of disodium oxalate in water was sprayed and mixed. In Example 6, the disodium oxalate granules were first crushed to a powder to an average particle size of about 145 microns. The disodium oxalate powder was then dry mixed with the sodium carbonate and HSAC. The building kinetics was studied by measuring the Ca²⁺ ion concentration, at various time periods. The results are summarized in Table -2 Example Sodium carbonate, g/l HSAC, g/l Disodium Oxalate, g/l Time, s Concentration of Calcium ions, ppm 1 1.5 0.5 0.1 30 1.2 2 1.5 0.5 0.1 60 0.7 3 1.5 0.5 0.15 30 1.0 4 1.5 0.5 0.15 60 0.4 5 1.5 0.5 0.3 30 0.28 6 1.5 0.5 0.3 30 0.96

The data in Table-2 when compared to data in Table - 1 indicates that the builder system of the invention provides for relatively faster building kinetics as compared to builder systems of the prior art.

These are examples pertaining to the performance of builder systems as per the invention (Examples 7, 8) as compared to prior art building system (Comparative Example - H).

Various builder compositions were prepared and added to hard water containing 200 ppm Calcium ions at concentrations (in grams per litre or g/l) as shown in Table -3. The building efficacy was studied by measuring the Ca²⁺ ion concentration, 2 minutes after addition of the compositions and the data is presented in Table -3. The method of determining Ca²⁺ concentration is same as given earlier: Example Sodium carbonate, g/l HSAC, g/l Oxalic acid, g/l Concentration of Calcium ions, ppm Comparative Example H 1.5 0.5 0 1.2 Example 7 1.5 0.5 0.3 0.4 Example 8 1.5 0.5 0.42 0.28 Note: Oxalic acid was used in the above experiments in a particle size of < 0.075 mm.

The data in Table-3 indicates that inclusion of a dicarboxylic acid viz. Oxalic acid in a Sodium Carbonate/Calcite building system provides for more efficient building as compared to builder system of the prior art.

These examples relate to the cleaning performance of fabrics cleaned with detergent compositions of the invention compared to commercial detergent products.

Detergent compositions were used to clean various test monitors as shown in Table -4. WFK10D (composite soil on cotton fabric) had an initial reflectance of about 45, WFK20D (composite soil on poly-cotton fabric) of about 40 and WFK30D (composite soil on polyester fabric) of about 40. All detergent compositions had sodium linear alkyl benzene sulphonate as the active surfactant at about 0.7 g/l in the wash liquor. The builder systems of the various detergent compositions in the wash liquor were as follows:

• SURF EXCEL^™ : 1.02 g/l STPP + 0.89 g/l sodium carbonate + 0.07 g/l HSAC
• RIN ADVANCED^™ : 0.16 g/l STPP + 1.4 g/l sodium carbonate + 0. 3 g/l HSAC
• Examples 9 to 11: 1.5 g/l sodium carbonate + 0.5 g/l HSAC+ 0. 4 g/l disodium oxalate.
• STPP is sodium tri poly phosphate.

The cost of the compositions as per the invention (Examples 9 to 11) is comparable to the RIN ADVANCED^™ composition and about 30% lower than the SURF EXCEL^™ composition. The water used for cleaning had hardness value of 48 FH. The protocol used for cleaning is given below.

The experiments were carried out in a Tergo-to-meter. The various compositions were dissolved in the tergo-o-meter pot for 10 minutes at 90 rpm speed. The test monitors were soaked in the solution for 15 minutes followed by 30 minutes of wash cycle in the pot at 90 rpm. The test monitors were then rinsed three times at a liquid to cloth ratio of 25.

The test monitors were then dried. The reflectance of the monitors was then measured. Average of reflectance data (ΔR 460) on three different monitors was taken.

The data on the reflectance is given in Table -4 below. Examples Product Test Monitor ΔR 460 Comparative Example I SURF EXCEL^™ WFK10D 20.0 Comparative Example J RIN ADVANCED^™ WFK10D 17.4 Example 9 As per invention WFK10D 19.6 Comparative Example K SURF EXCEL^™ WFK20D 14.9 Comparative Example L RIN ADVANCED^™ WFK20D 12.2 Example 10 As per invention WFK20D 17.8 Comparative Example M SURF EXCEL^™ WFK30D 16.7 Comparative Example N RIN ADVANCED^™ WFK30D 14.3 Example 11 As per invention WFK30D 19.2

The data in Table -4 indicates that detergent composition according to the invention provides same or superior cleaning as compared to one of the best commercial detergent product SURF EXCEL^™, but at lower cost. Further the detergent composition of the invention provides superior cleaning for all test monitors as compared to RIN ADVANCED^™, at same cost.