Patent Description:
It is well known that certain metal compounds, notably calcium and magnesium compounds, when present in water, have a significant effect on the properties of the water. When Calcium and Magnesium are present at a significant level the water is generally referred to as "hard". Water hardness is a measure of Ca<NUM>+ and Mg<NUM>+ concentration in the water and is often indicated in terms of °fH (degrees of French Hardness), which is defined as <NUM>/L CaCOs. Hard water, e.g. having more than <NUM>°fH, contains a significant loading of soluble calcium and magnesium compounds and may require a large amount of soap or detergent in order to form a lather. Scale deposits can readily form from such water, for example on heating or pH change or evaporation. These can be incrustations, which are left on a surface that has come into contact with the hard water. Particular issues arise in ware washing machines, such as dish and clothes washing machines. In particular, scale incrustations may be left on the surfaces of the machines as well as the items washed therein. In particular, issues arise with incrustation of heating elements, which reduce their life span and efficiency. A further issue arises in that scale incrustation can be found on the surface of clothes washed in the clothes washing machines which are perceptible to the wearer as feeling harsh to the touch.

There have been many proposals for removal of metal ions from aqueous solutions. In the industrial context proposals have included filter beds and polymeric filters for capturing heavy metal ions from an aqueous solution flowing within a passageway. In the domestic context chelating compositions or complexing agents can be added to an aqueous washing solution and these can capture metal ions, such as calcium ions. Examples of chelating compositions are given in <CIT>. Further, relevant documents are <CIT>, <CIT>, <CIT>.

Typically, in ware washing machines cleaning compositions are provided which are "built" which provide a water softening effect and an increase to the efficiency of the detergent used therein. However, such compositions are not effective for softening the water in the rinse cycle of ware washing machines since such compositions are pumped out of the machine along with the dirty water prior to the rinse cycle. Therefore, scale deposits may build up on the hard surfaces of the washing machine such as the heating element, as well as the fabric of the items being worked.

Historically, phosphate-based compounds have been the mainstay of complexing agents, but there is an increasing environmental and regulatory drive to develop phosphate-free detergents. Amino carboxylic complexing agents such as methylglycine-N,N-diacetic acid (MGDA) and L-glutamic acid-N,N-diacetic acid (GLDA) and salts thereof are known to be very effective builder replacements for phosphates in detergent formulations. Their excellent cleaning performance, even in hard water conditions, confers advantages over other P-free builders. However, in water-softener compositions comprising only GLDA at low concentrations, there will still be considerable encrustations deposited on, for example, heating elements.

It is an object of the present invention to provide a composition that when used in a washing and/or rinsing operation in a washing machine leads to a reduced heating element incrustation and reduced laundry ash deposition on garments.

It is another object of the present invention to provide a method of removing and preventing deposition of limescale in a clothes washing machine.

It is another object of the present invention to provide a method of softening the water in the main and/or in the rinse cycle of a clothes washing machine.

In a first aspect, the present invention relates to a liquid water softener composition comprising:.

The present invention further relates to a method of removing and preventing the deposition of limescale in a clothes washing machine and the use of the composition in the main wash or/and rinse cycle of a clothes washing machine. The essential features of the invention are set out in independent claims <NUM>, <NUM>, <NUM>. Further preferred embodiments are described in dependent claims <NUM>-<NUM>.

The formation of limescale in the washing process is made possible by the presence of anions like Carbonate or Phosphate, which can be found in most detergents where they are used as builders and source of alkalinity. An additional source of carbonate can come via bicarbonate in the water supply. At higher temperatures bicarbonate undergoes a reaction whereby it converts to carbonate. Carbonate and Phosphate can react with Ca/Mg coming from the water to create limescale.

In order to prevent the build-up of scale in the wash over time it is important to avoid precipitates of Ca- and Mg-Carbonate/Phosphate from forming and growing. Consequently, a complexing system is necessary that prevents formation, growth and deposition of insoluble precipitates.

The composition according to the invention softens hard water, by neutralizing Ca and Mg ions and keeping them in solution, therefore, avoiding that they bind to carbonate and form limescale. It also limits the further growth of limescale crystals eventually deposited.

The composition according to the invention is eco-friendly as it comprises biodegradable polymer agents. The present inventors have observed that the ratio of the at least one monomeric polycarboxylate to the at least one organic acid together with the at least one amino carboxylic complexing agent lead to a composition that is effective in protecting a clothes washing machine against limescale and dirt. The composition is also effective against deposition of inorganic incrustations in garments. Therefore, the composition is a water softener composition.

In one embodiment, the ratio in weight of the at least one monomeric polycarboxylate to the at least one organic acid is between <NUM>:<NUM> and <NUM>:<NUM>, preferably between <NUM>:<NUM> and <NUM>:<NUM>, more preferably about <NUM>:<NUM>.

The at least one amino carboxylic complexing agent is selected from the group consisting of methyl glycine diacetic acid (MGDA), glutamic acid diacetic acid (GLDA), their salts and combinations thereof, preferably wherein the at least one amino carboxylic complexing agent is glutamic acid diacetic acid (GLDA). The composition may comprise at least <NUM> wt. % of said at least one monomeric polycarboxylate, based on the total weight of the composition, preferably at least <NUM> wt. %, more preferably between <NUM> wt. % and <NUM> wt. %, even more preferably between <NUM> wt. % and <NUM> wt. %, such as for example between <NUM> wt. % and <NUM> wt.

The at least one monomeric polycarboxylate is selected from the group consisting of, citrates, gluconates, oxydisuccinates, glycerol mono- di- and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates, hydroxyethyliminodiacetates, iminodisuccinates, and combinations thereof, preferably the at least one monomeric polycarboxylate is a citrate, more preferably trisodium citrate.

The at least one organic acid is selected from the group consisting of citric, acetic, formic, glycolic and oxalic acid, and combinations thereof; preferably the at least one organic acid is citric acid.

A preferred composition, which is specially effective against limescale and dirt deposition on the solid surfaces of a clothes washing machine and against deposition of inorganic incrustations in garments, comprises glutamic acid diacetic acid (GLDA), trisodium citrate, and citric acid, wherein the ratio in weight of the trisodium citrate : citric acid is between <NUM>:<NUM> and <NUM>:<NUM>, preferably between <NUM>:<NUM> and <NUM>:<NUM>, more preferably between <NUM>:<NUM> and <NUM>:<NUM>, most preferably about <NUM>:<NUM>.

Optionally, the composition may comprise a "pH buffering means", which is any compound which when mixed with another solution of higher pH makes the resulting solution able to resist a decrease in hydrogen ion concentration. Suitable pH buffers may be based upon citric, acetic, phosphoric, or boric acid, or any other buffer systems described in literature. The composition may comprise between <NUM> wt. % and <NUM> wt. % of the pH buffering means, based on the total weight of the composition.

The composition is neutral or acidic, therefore, the composition has a pH of less than <NUM>, preferably less than <NUM>, more preferably between <NUM> and <NUM>, even more preferably between <NUM> and <NUM>.

The composition may further comprise a suspending agent, which prevents redeposition of limescale particles eventually formed and of dirt removed from a garment by a laundry detergent. This suspending agent may be of natural source, such as a natural sourced polymer, for example a polysaccharide. The composition may then further comprise at least one homogeneous polysaccharide constituted of a single species of monosaccharides, preferably having at least <NUM> carboxyl groups per monosaccharide unit, more preferably at least <NUM> carboxyl groups per monosaccharide unit, even more preferably at least <NUM> carboxyl groups per monosaccharide unit. The at least one homogeneous polysaccharide constituted of a single species of monosaccharides may be selected from the group consisting of glucosans, modified starches, cellulose and its derivatives, fructosans and combinations thereof; preferably selected from the group of inulin and its derivatives; more preferably selected from dicarboxy and carboxymethyl inulin, and combinations thereof; even more preferably wherein the at least one homogeneous polysaccharide constituted of a single species of monosaccharides is carboxymethyl inulin.

The composition may comprise effective amounts of the polysaccharide in order to achieve a suspending effect. For example, the composition may comprise at least <NUM> wt. % of said at least one homogeneous polysaccharide constituted of a single species of monosaccharides, based on the total weight of the composition, preferably at least <NUM> wt. %, more preferably between <NUM> and <NUM> wt. %, even more preferably between <NUM> and <NUM> wt. %, such as for example between <NUM> and <NUM> wt.

The composition of the invention may be liquid or gel, and it may comprise at least <NUM> wt. % water, based on the total weight of the composition, preferably at least <NUM> wt. %, more preferably between <NUM> wt. % and <NUM> wt. %, even more preferably between <NUM> wt. % and <NUM> wt. %, such as for example <NUM> wt. % and <NUM> wt.

The composition is substantially free from surfactant and the composition is substantially free from any fabric softening actives, and/or bleach. By substantially free we mean less than 5wt. %, of each and any combination or all of the ingredients listed above, based on the total weight of the composition, preferably less than <NUM> wt. %, more preferably less than <NUM> wt. %, most preferably less than <NUM> wt. %, for example less than <NUM> wt. It will be understood that the composition is substantially free from surfactant, meaning that no surfactant is intentionally added to the formulation.

The composition may further comprise preservative, for example, to inhibit the growth of moulds and yeasts. Examples of suitable preservatives are lactic acid, potassium sorbate and sodium benzoate.

In a second aspect, the invention relates to a method of removing and preventing the deposition of limescale in a clothes washing machine by providing a composition according to the first aspect of the invention.

The method according to the second aspect is preferably carried out while the machine is being used for washing clothes. This mean that the composition may be added together with a detergent composition having as primary goal to remove dirt and grim from the garments being washed.

In a third aspect, the invention relates to a use of the composition according to the first aspect of the invention for softening the water in the main wash and/or the rinse cycle of a clothes washing machine.

In the methods the composition may be provided in a sustained release manner through the wash and rinse cycle in a single product. Delayed release of the composition could be used such that the composition is released during the rinse cycle only, or substantially most of the composition (greater than <NUM>%) is released into the rinse cycle.

The composition may be provided together with a detergent, wherein said detergent may be in powder, granular or tablet form.

The invention will be further described, by way of example, with the reference to the following non-limiting embodiments.

Table <NUM> shows compositions, in which compositions C1-C3 are comparative compositions and compositions E1-E4 are compositions according to the invention.

Batches of garments including standard cloth fabrics Empa <NUM>, WfK 10A and Honey Comb, were washed with a commercial laundry detergent (Dash Powder with Actilift, P&G, Italy) and with combinations of the commercial laundry detergent (Dash Powder with Actilift, P&G, Italy) and the compositions of Table <NUM>. Each batch of garments was washed <NUM> times in a washing machine using the following washing protocol:.

Table <NUM> shows the performance, considering heating element encrustation and laundry ash, of the commercial laundry detergent and the combinations of the commercial laundry detergent and the compositions of Table <NUM>. In table <NUM>, examples with an asterisk (*) are comparative examples.

The heating element encrustation is the encrustation deposited on the heating element and is determined by weighing the heating element before and after <NUM> washes. The difference in weight represents the heating element encrustation.

The laundry ash refers to the amount of inorganic incrustations in each batch of garments. This is determined by burning the batch of garments at <NUM> and by weighing the remaining ashes.

From the results shown in Table <NUM> it is demonstrated that the compositions according to the invention lead to a lower heating element encrustation and to a lower laundry ash deposition on garments.

When the compositions according to the invention are used, the heating element incrustation is reduced by at least <NUM>% with respect to the commercial laundry detergent alone, and by at least <NUM>% with respect to the combination of the commercial detergent and the comparative compositions.

Furthermore, when the compositions according to the invention are used, the laundry ash is reduced by at least <NUM>% with respect to the combination of the commercial detergent and the comparative compositions.

Claim 1:
Liquid water softener composition comprising:
- at least one amino carboxylic complexing agent selected from the group consisting of methyl glycine diacetic acid (MGDA), glutamic acid diacetic acid (GLDA), their salts and combinations thereof;
- at least one monomeric polycarboxylate selected from the group consisting of, citrates, gluconates, oxydisuccinates, glycerol mono- di- and trisuccinates, carboxymethyloxysuccinates, carboxymethyloxymalonates, dipicolinates, hydroxyethyliminodiacetates, iminodisuccinates, and combinations thereof;
- and at least one organic acid selected from the group consisting of citric, acetic, formic, glycolic and oxalic acid, and combinations thereof;
wherein the ratio in weight of the at least one monomeric polycarboxylate to the at least one organic acid is between <NUM>:<NUM> and <NUM>:<NUM>;
wherein the composition has a pH of less than <NUM>; and
wherein the composition is substantially free from surfactant.