It is well known in the art that limescale deposits can be chemically removed with acidic solutions, and a great variety of acidic cleaning compositions have been described for this purpose.
Furthermore, it is known in the art to use surfactants in such acidic compositions to lower the surface tension and to improve the wettability of the surfaces being cleaned. The presence of surfactants in such compositions helps to solubilize the soils and to improve the streaking profile of the acids, thereby also slowing down the limescale redeposition phenomenon.
However, the presence of surfactants causes the problem that a base odor is imparted to the compositions comprising them, thereby making them not attractive from a consumer point of view. This base odor, chemical in nature, can be due to the surfactant molecules themselves, to the presence of unreacted intermediates from the surfactant making process or to other impurities within the surfactant raw materials.
To overcome this problem it is well known in the art to add a perfume in surfactant-based compositions, one of its role being to effectively mask the surfactants base odor. However, it has been found that perfumes tend to deposit onto synthetic materials and are thus difficult to rinse off.
This is even more of a problem in applications such as the descaling of appliances including cooking appliances (e.g. coffee machine), beauty care appliances (e.g. dental jet machine) or any other appliance such as steam irons, kettles and the like, as said appliances comprise various synthetic surfaces. Indeed, during the descaling operation of such an appliance perfumes firstly tend to deposit onto the synthetic surfaces and then tend to be released during the normal use of said appliance. In other words, food or beverage can be contaminated during the normal use of a cooking appliance, when said normal use follows the descaling operation of said appliance with a composition comprising perfumes. This is highly undesirable from a consumer acceptance viewpoint. Thus it is desirable to use descaling compositions being free of perfumes.
It is therefore an object of the present invention to provide a composition comprising surfactants and an organic acid, for the removal of limescale deposits, said composition being free of perfume and possessing a superior limescale removing capacity while being also substantially odor-free.
It has now been found that compositions comprising an organic acid being substantially odor-free such as maleic acid together with a surfactant consisting of cationic, zwitterionic, amphoteric surfactants or mixtures thereof are substantially odor-free without the need of adding any further compound such as a perfume to mask the surfactants base odor. Indeed, we have found that cationic, zwitterionic, amphoteric surfactants or mixtures thereof do not impart a base odor to a composition, or to the surfaces treated with said composition, provided that the pH of the composition is neutral or maintained in the acidic range. Unexpectedly the compositions of the present invention comprising maleic acid and such a surfactant or mixtures thereof under neutral or acidic conditions, are substantially odor-free compared to the same compositions with equivalent amount of other surfactant types such as anionic, nonionic, amine oxide surfactants or mixtures thereof.
An advantage of the present invention is that said compositions are particularly suitable for applications in which the presence of perfume is not desirable including the descaling of appliances such as cooking appliances, beauty care appliances or any other appliance such as steam irons, kettles, coffee machines, tea pots and the like.
A further advantage is that the compositions of the present invention are also safe to a wide variety of materials used to manufacture said appliances, including synthetic materials as well as any type of metal (e.g. aluminum, stainless steel, chromed steel and the like).
European patent application No. 93870120.8 discloses an acidic composition comprising an acid for example maleic acid together with a thickening system comprising from 0.5% to 15% by weight of the total composition of a mixture of a nonionic surfactant and a cationic surfactant. No reference is made to the possibility to provide substantially odor-free surfactants based compositions due to the use of said cationic surfactants as the surfactant.
GB 2071 688 and EP 255 978 disclose acidic compositions comprising among other ingredients from 0.1% to 10% by weight of cationic surfactants and a strong inorganic acid. Organic acids and in particular maleic acid are not disclosed. No reference is made to the possibility to provide substantially odor-free surfactants based compositions due to the use of said cationic surfactants as the surfactant.