Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-05-12
2002-05-14
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S349000, C510S376000, C510S392000, C510S446000
Reexamination Certificate
active
06387861
ABSTRACT:
This invention relates to tablets of compacted particulate detergent composition suitable for washing fabrics.
Detergent compositions in tablet form have been described in a number of documents including, for example, GB 911204 (Unilever), WO 90/02165 (Henkel) and EP-A-711827 (Unilever) and are sold now commercially. Tablets have several advantages over powdered products: they do not require measuring and are thus easier to handle and dispense into the washload, and they are more compact, hence facilitating more economical storage.
One issue that has been considered in the formulation of detergent tablets is the incorporation of bleaching ingredients, especially when the presence of bleach-sensitive ingredients such as enzymes and perfume is also desired. In a compressed tablet, the ingredients are much more intimately associated with one another than in a powder, and it would be foreseen that any adverse interactions and instability will be exacerbated.
It has become commonplace to use an inorganic peroxygen bleach jointly with a bleach activator. The latter is usually an organic compound which reacts with the peroxygen bleach in the wash liquor to generate a bleaching species such as peracetic acid which is effective at lower wash temperature than the bleach.
EP 737 738 (Clean tabs) discloses bleach tablets comprising coated sodium percarbonate and a bleach activator (TAED). However, this document does not teach the separation of the percarbonate and the bleach activator. The bleach tablets are intended to be used together with usual textile detergent compositions.
EP 0 481 793A (Unilever) is aimed at solving the particular storage problems that arise when sodium percarbonate, Na
2
CO
3
.1.5H
2
O
2
, is included in a tablet formulation. This persalt is less stable than sodium perborate in the presence of moisture, and hence more readily undergoes premature decomposition in which hydrogen peroxide is liberated and this decomposes readily. The solution proposed is to separate the sodium percarbonate from any other ingredient of the composition detrimental to its stability by segregation in a discrete region of the tablet.
This segregation can be achieved by isolating the percarbonate in a region of the tablet which may be a layer, core or insert, while other ingredients are present in other region(s), which may be other layers or the main body or matrix of the tablet. Alternatively, it is suggested that the percarbonate is present in regions which are relatively large granules or noodles distributed throughout the main body or matrix of the tablet, the granules or noodles being protected by coating or encapsulation with a water-soluble material.
Examples in the application demonstrated that percarbonate decomposition occurs even in the absence of bleach activator and is reduced when the percarbonate is segregated into discrete region(s).
EP 481 792 (Unilever) discloses a laundry detergent tablets containing a particulate bleaching composition which may comprise a bleach activator.
GB 911 204 (Unilever) discloses layered detergent tablets containing persalt bleach, for example, sodium perborate, and certain bleach activators, for example, sodium acetoxybenzene sulphonate and phthalic anhydride. To avoid destabilisation, the bleach activator is segregated from the remaining tablet ingredients, including persalt bleach.
Segregation is achieved by putting the bleach activator in a separate section or layer.
In contrast, EP 395 333A (Unilever) disclosed detergent tablets containing sodium perborate in conjunction with one or more bleach-sensitive ingredients—tetraacetylethylenediamine (TAED) or similar bleach activator, enzyme, fluorescer, or any combination of these—as well as detergent-active compound, detergency builders and optionally other ingredients. The persalt is not segregated from the bleach-sensitive ingredients.
This document taught that segregation of bleach activator from the perborate bleach was not necessary for TAED and similar activators. When compositions were prepared containing both perborate and TAED together, and then stored either as powders or as tablets compacted from those powders, a loss of bleaching activity during storage was observed but there was no significantly greater loss in tablets. In a number of instances the tablets showed better bleaching after storage than did powders where the ingredients are not in such close proximity.
This document also showed a similar finding when enzymes were incorporated in powders with the bleaching system and a comparison was made of enzyme stability both in these powders and in tablets compacted from the powders. During storage the decomposition of enzyme in tablets, where the compaction had necessarily brought the enzyme into closer proximity with the bleaching system was not significantly greater and in some cases was less than observed with powders.
WO 99/35225 and WO 99/35229 to WO 99/35236 (Henkel) all disclose segregation of ingredients within double layer laundry detergent tablets.
Surprisingly, it has now been found that the stability of the bleach sensitive ingredients can be further increased by encapsulating the sodium percarbonate and in addition segregating these sensitive ingredients from (encapsulated) sodium percarbonate, even though stability of percarbonate is not much affected by such “double segregation”. Therefore, in a first aspect, the present invention provides a tablet of compacted particulate detergent composition comprising a detergent-active compound, a detergency builder, a bleach system comprising sodium percarbonate in the form of particles having a coating of water-soluble material together with bleach activator which is preferably at least one bleach activator selected from N-diacylated and N,N′-polyacylated amine bleach activators, and optionally other detergent ingredients, which tablet comprises a plurality of discrete regions, each of which is at least 10% of the total weight of the tablet, and wherein the bleach activators and the particles containing the sodium percarbonate within a water-soluble coating are concentrated in respective different regions of the tablet.
In a second aspect, the present invention provides a tablet of compacted particulate detergent composition comprising a detergent active compound, a detergency builder, a bleach system comprising sodium percarbonate in the form of particles having a coating of water-soluble material, at least one enzyme and optionally other detergent ingredients, where the tablet comprises a plurality of discrete regions each of which is at least 10% of the total weight of the tablet and wherein the said enzyme and the particles containing the sodium percarbonate within a water-soluble coating are concentrated in respective different regions of the tablet.
It will be appreciated that in this invention both bleach activator and enzyme may be incorporated in the same region(s) of the tablet while sodium percarbonate is concentrated in a different region or regions.
Preferably a region or regions in which sodium percarbonate is concentrated contain at least 80% better at least 90% or 95% of the sodium percarbonate present in the tablet and better still all of it. It is preferred that such regions contain at most 20% of all the bleach activator and/or at most 20% of a detergent enzyme present in the tablet, more preferably less than this. Correspondingly a region or regions in which bleach activator is concentrated or in which an enzyme is concentrated preferably contain at least 80% of the bleach activator or respectively enzyme present in the tablet more preferably at least 90% or 95% of the bleach activator or enzyme and at most 20% preferably at most 10% or 5% of the percarbonate present in the tablet.
If more than one enzyme is used in a tablet, it is possible but not preferred, to segregate one enzyme but not segregate another enzyme from the coated percarbonate. Preferably all the enzyme types present are segregated together so that one or more regions contain at least 90 or 95% of all enzyme but not more than 20% of
Lammers Rene
Liem Seeng Djiang
Niemantsverdriet Robert Ernst
Van Asperen Anja Leonarda M
Van der Goot Atze Jan
Douyon Lorna M.
Mitelman Rimma
Unilever Home & Personal Care USA , division of Conopco, Inc.
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