Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
1998-06-04
2002-03-19
Delcotto, Gregory (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Solid, shaped macroscopic article or structure
C510S305000, C510S309000, C510S312000, C510S320000, C510S374000, C510S440000, C510S447000, C510S470000, C510S471000, C510S473000
Reexamination Certificate
active
06358910
ABSTRACT:
FIELD OF INVENTION
This invention relates to cleaning compositions in the form of tablets, eg. for use in fabric washing or machine dishwashing.
BACKGROUND OF THE INVENTION AND SUMMARY OF PRIOR ART
Detergent compositions in tablet form are described, for example, in U.S. Pat. No. 3,953,350 (Kao) and EP-A-711827 (Unilever), and are sold commercially in Spain. Tablets for machine dishwashing are described in W096/28530 (P&G). Tablets have advantages over powdered products in that they do not require measuring and are thus easier to handle and dispense into the washload.
Tablets of a cleaning composition are generally made by compressing or compacting a quantity of the composition in particulate form. It is desirable that tablets have adequate strength when dry, yet disperse and dissolve quickly when added to wash water. In such tablets, any surfactant functions as a binder, plasticising the tablet. However, it can also retard disintegration of the tablet by forming a viscous gel when the tablet comes into contact with water.
There have been a number of proposals for tablets which are subdivided into separate regions (eg. layers) which differ in their composition. This has been done in order to isolate components of the tablet composition during storage of the tablet.
GB-A-911204 discloses tablets in which a detergent tablet contains peroxygen bleach and a bleach activator is confined to a separate layer of the tablet or insert within it.
GB-A-1423536 discloses tablets in which bleach activator is contained in separate, polymer-coated granules while the main part of the tablets includes a soluble or swellable starch.
EP-A-481793 discloses tablets in which sodium percarbonate is isolated in a discrete region of the tablet and enhance stability.
U.S. Pat. No. 3,962,107 discloses a denture cleaning tablet in which enzyme is contained in one layer of the tablet while peroxygen bleach is contained in another, slower-dissolving layer. Both layers contain effervescence producing materials.
U.S. Pat. No. 4,099,912 teaches that fabric washing should be performed using a plurality of tablets containing a plurality of different detergent composition components.
SUMMARY OF THE INVENTION
The present invention makes use of a water-swellable polymeric material to accelerate the disintegration of at least one region of a tablet, ahead of another region or regions.
According to the present invention there is provided a tablet of compacted particulate cleaning composition containing surfactant and detergency builder, and which has a plurality of discrete regions with differing compositions, characterised in that at least one said region of the tablet contains water-swellable polymer, preferably insoluble polysaccharide, in a concentration which is from 0.1 to 8 wt. % and which is greater than in at least one other region of the tablet, to promote disintegration of the first said region(s) before the said other(s).
DETAILED DESCRIPTION
As mentioned above, this invention relates to a tablet which is subdivided into a plurality of discrete regions. The regions of the tablet are most likely to be separate layers within a tablet. However, a discrete region of a tablet could be a core or an insert while another discrete region could be a shell or coating around such core or insert.
The first said region(s) of the tablets which disintegrate and dissolve ahead of other regions can contain an ingredient (eg. enzyme) which is intended to function in the wash liquor before another constituent, contained in the other region(s) of the tablets, is fully released into the wash liquor.
Another possibility is that the other region(s) of the tablet which disintegrate more slowly contain an ingredient which is intended to function towards the end of the wash cycle. For example this could be an antiredeposition polymer or soil suspending polymer. If this is released later in the wash cycle, the proportion of it which is taken up in surfactant micelles and effectively wasted will be minimised.
A further possibility is that a tablet has two layers dissolving at different rates which contain materials to give different values of pH in the wash liquor at different times during a wash cycle.
A tablet of this invention may be intended for use in machine dishwashing. Such a tablet is likely to contain surfactant in a low concentration such as 0.5 to 2 wt % based on the whole tablet, although higher-conecentraions ranging up to 10 wt % may be used. Such will typically contain salts, such as over 60 wt %, often over 85 wt % of the tablet.
Water soluble salts typically used in machine dishwashing compositions are phosphates (including condensed phosphates) carbonates and silicates, generally as alkali metal salts. Water soluble alkali metal salts selected from phosphates, carbonates and silicates may provide 60 wt % or more of a dishwashing composition.
In such a machine dishwashing tablet, a discrete region which disintegrates and dissolves first may be a pre-wash composition containing enzyme(s) and some water soluble salts.
Another possibility is that a tablet of this invention will be intended for fabric washing. In this event the tablet will be likely to contain at least 2 wt %, probably at least 5 wt %, up to 40 or 50 wt % surfactant based on the whole. tablet, and from 5 to 8 wt % detergency builder, based on the whole tablet.
In such a tablet a discrete region which disintegrates and dissolves first may be a pre-wash composition containing enzyme(s). Such a pre-wash composition will generally include detergency builder as 5 to 90% by weight of the discrete region.
The remainder of the composition may then be suitable for the main fabric wash, containing from 5, preferably 10 wt % up to 40% or 50% surfactant.
It will be appreciated that within this invention it is possible that the first said region, containing water-swellable polymeric material, does not itself contain surfactant or detergency builder. It could for example contain enzyme(s) and water-soluble carrier salts which have no function as water-softeners.
However, the first said region(s) which contains water-swellable polymer will often contain detergency builder salts and may contain at least some surfactant.
For instance, for fabric washing, a pre-wash composition, used to form a discrete region of a tablet, might contain enzyme(s), 5 to 90 wt % detergency builder and from 0 to 2% surfactant, together with at least 5 wt % of particles of water-swellable polymer.
In a second aspect, this invention provides a tablet of compacted particulate detergent composition containing surfactant and detergency builder, which has a plurality of discrete regions with differing compositions, characterised in that at least one region of the tablet has a composition which causes it to disintegrate ahead of at least one other region of the tablet, wherein the first said region contains enzyme in a quantity greater than in the other said region, and the other said region contains surfactant and/or bleach in a greater quantity than in the first said region.
The disintegration of the first said region is preferably promoted by incorporation of a water-swellable polymer. However, it could be promoted by incorporation of water soluble materials, more specifically by particles containing at least 40% (by weight of these particles (ii)) of one or more materials selected from
compounds with a water-solubility exceeding 50 grams per 100 grams water
phase I sodium tripolyphosphate or
sodium tripolyphosphate which is partially hydrated so as to contain water of hydration in an amount which is at least 0.5% by weight of the sodium tripolyphosphate in the particles.
There may be a substantial difference in the times for disintegration of the first said region(s) and the other said region(s). An addition of a tablet to water at 20° C. the said other region(s) may remain intact for at least 5 or even at least 10 minutes after disintegration of the first said region(s).
Materials which may be used in tablets of this invention will now be discussed in more detail.
The Water-swellable Polymer
Boskamp Jelles Vincent
Donker Cornelis Bernard
Lempers Edwin Leo
Delcotto Gregory
Lever Brothers Company, divison of Conopco, Inc.
Mitelman Rimma
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