Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1998-04-10
2001-02-27
Medley, Margaret (Department: 1714)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S228000, C510S230000, C510S231000, C510S233000, C510S375000, C510S378000, C510S402000
Reexamination Certificate
active
06194368
ABSTRACT:
The present invention relates to a dishwasher detergent in the form of a tablet comprising a bleach and a bleach activator and also other customary constituents.
Conventional detergents for the machine cleaning of dishes are generally pulverulent, granular or liquid products. Cleaning compositions in the form of tablets have likewise been known for some years. In principle, products in the form of tablets have a number of advantages over pulverulent and liquid products: they do not require accurate measurement of the amount to be used and are therefore easier to handle and introduce into the dishwasher, they are more compact and therefore require less packing material and storage space and they are safer to use in the household since spillage of the often aggressive substances is not possible.
However, it has been found that cleaning compositions in tablet form can have a poorer cleaning action than those in powder form. This can be attributed to the fact that in pressed tablets the individual constituents are significantly more closely joined together than in, powders, so that negative interactions which individual constituents can exercise on one another can occur to a greater degree. But, partial inactivation of individual constituents can result. The applicant has now found that such a problem also occurs in the combined use of bleaches and bleach activators with silver/copper corrosion inhibitors.
A further problem which occurs in the case of dishwasher detergents in tablet form and which impairs washing performance is that such dishwasher detergents are less effective than comparable powders, since the tablets dissolve more slowly and therefore are available in the washing liquor only later than when powders are used. This problem occurs particularly in the case of dishwasher detergents containing a bleach, since when said compositions are used in tablet form the concentration of the bleach necessary for bleaching is reached only relatively late in the washing process. As a solution to this problem, it is proposed in EP-A 504 091 that a certain combination of alkali metal carbonate, polycarboxylate, a polyfunctional carboxylic acid, sodium silicate, a nonionic surfactant and the bleach be used so that the bleaching effect of the pressed tablets is retained.
EP-A 634 478 discloses dishwasher detergents comprising nitrogen-containing corrosion inhibitors and an oxygen-liberating bleach. According to the statements of this document, the dishwasher detergents can be present in any form and tablets too are mentioned in passing, with the difficulties which can occur in the formulation of corrosion inhibitors with bleaches or bleach activators obviously not having been recognized.
EP-A 481 547 discloses that during storage of a dishwasher detergent and in the aqueous cleaning solution in a dishwasher, enzymes are deactivated in the presence of a chlorine bleach. As a solution to this problem, EP-A 481 547 discloses a dishwasher detergent comprising enzymes and chlorine bleaches in the form of a tablet having at least three layers and a complex structure, comprising an inner layer, a barrier layer and an outer layer. The enzymes and the chlorine bleaches are thus separated in various layers of the tablet. This complex structure of the cleaning composition tablets is supposed to ensure that, on the one hand, no interface exists during storage between the layer containing the chlorine bleach and the layer containing the enzyme and, on the other hand, the two layers are not dissolved simultaneously but rather are dissolved in succession and therefore the chlorine bleach and the enzyme are not simultaneously present in the washing water of the dishwasher.
EP-A 1481 793 discloses cleaning compositions in tablet form which contain sodium percarbonate as bleach and are to be used in textile washing machines. In order to be able to obtain a storage-stable tablet which comprises not only sodium percarbonate but also other constituents which can interact with the bleach, it is proposed that percarbonate be separated in the tablet from the other constituents, for example in two layers. The tablets thus produced are, in addition, said to have an increased dissolution rate in the washing liquor.
EP-A 481 792 discloses a product in tablet form for the treatment of fabrics in washing machines, which product comprises, to improve the bleaching action, a combination of a per-salt and a bleach activator, with the bleach activator having to have a certain rate constant for the hydrolysis of the per-salt.
DE-A 25 27 534 discloses a multilayer cleaning tablet for dentures, with the first layer containing an enzyme and dissolving before the second layer containing active oxygen. By this means the enzyme can act at first without being deactivated by the active oxygen liberated.
It is an object of the present invention to provide a dishwasher detergent in the form of a tablet which comprises not only a bleach, a bleach activator and other customary constituents but also a silver/copper corrosion inhibitor which prevents the tarnishing of nonferrous metals on the dishes to be cleaned, with the silver/copper corrosion inhibitor not impairing the effectiveness of the tablet, but giving at least as good a washing performance as in the case of a comparable powder, preferably even better.
It is a further object of the invention to provide a dishwasher detergent in the form of a tablet which comprises not only a bleach, a bleach activator and other customary constituents but also a silver/copper corrosion inhibitor which prevents the tarnishing of nonferrous metals on the dishes to be cleaned, with the composition, although it is in tablet form and the individual constituents of the washing liquor are therefore available only in a later stage of the washing process, displaying a washing performance which is at least as good, preferably better, as that of the composition in powder form.
It has now surprisingly been found that tablets which consist of at least two layers and in which the silver/copper corrosion inhibitor is not present together with the bleach and the activator in one layer have an undiminished or even improved cleaning action compared with powders of the same composition, despite the fact that the tablet dissolves only during the course of the washing process and the constituents of the composition are therefore available only in a later stage of the washing process.
Furthermore, these effects occur not only in dishwasher detergents after a certain storage time, but surprisingly also in dishwasher detergents directly after manufacture, so that the effects occur independently of interactions which can take place in the composition during storage.
The present invention accordingly provides a dishwasher detergent in the form of a tablet comprising a bleach, a bleach activator and other customary constituents and additionally contains a silver/copper corrosion inhibitor, where the tablet consists of at least two layers and the silver/copper corrosion inhibitor is not present together with the bleach and the bleach activator in one layer.
Preferably, the tablet of the invention does not dissolve completely in the liquor of the dishwasher in less than three minutes.
For the purposes of the present invention, “dissolve completely” means that the tablets have disintegrated to the extent that in agitated water at 40° C. they can pass through a basket having 4 mm openings.
The bleaches present in the dishwasher detergents of the invention are preferably chlorine-free bleaches which liberate active oxygen, for example inorganic perhydrates or organic peracids and their salts.
Examples of inorganic perhydrates are perborates, percarbonates and persulfates such as peroxo monopersulfates. The inorganic perhydrates are normally alkaline metal salts such as lithium, sodium, potassium, or rubidium salts, in particular the sodium salts. The inorganic perhydrates can be present in the detergent as crystalline solids without further protection. However, for certain perhydrates it is advantageous to use them as g
Höflinger Wilfried
Magg Harald
Robinson Paul
Sandmann Brigitte
Wäschenbach Guido
Joh A. Benckiser GmbH
Medley Margaret
Oppenheimer Wolff & Donnelly LLP
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