Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-07-27
2002-08-20
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...
C510S334000, C510S446000, C510S478000, C510S488000, C510S501000, C510S507000, C510S509000
Reexamination Certificate
active
06436889
ABSTRACT:
This invention relates to detergent compositions in the form of tablets for use in fabric washing. Such tablets have the advantage that they do not require the user to measure out a volume of powder or liquid. Instead one or several tablets provide an appropriate quantity of composition for washing a single load in a washing machine or possibly by hand. They are thus easier for the consumer to handle and dispense.
Detergent compositions in tablet form have been described in a number of documents and are sold commercially.
Such tablets are generally made by compressing or compacting a quantity of detergent composition in particulate form. It is desirable that tablets should have adequate mechanical strength when dry, before use, yet disintegrate and disperse/dissolve quickly when added to wash water. Prior literature, including our EP-A-522766, has pointed out that there is difficulty in achieving both properties simultaneously, especially with compositions containing insoluble detergency builder such as aluminosilicate. As more pressure is used when a tablet is compacted, so the tablet density and strength rise, but there is also a reduction in the speed of disintegration/dissolution when the tablet comes into contact with wash water at the time of use. Organic detergent-active serves as a binder, but a typical quantity of such detergent can also retard disintegration and dissolution of a tablet.
It is possible to improve the speed of disintegration of tablets when placed in wash water, while retaining strength, by including a material of high solubility in water. Some tablets which have been sold commercially incorporate urea for this purpose. Our EP-A-711827 teaches the use of sodium citrate, and our later EP-A-838 519 discloses the use of sodium acetate trihydrate for the same purpose. However, such disintegration aids have no other function in the wash liquor after acting as a disintegration aid. There is therefore, furthermore, a need to provide a tablet which has acceptable disintegration and tablet characteristics and which has a high level of functional ingredients.
Certain clays with ion exchange properties are known to be effective as fabric softeners, and are described in U.S. Pat. No. 4,062,647, EP 26528-A, U.S. Pat. No. 3,959,155 and U.S. Pat. No. 3,936,537. Also clays have been disclosed for use as bodying agents in detergent laundry bars (as described in GB 2 145 109) and also for use in clear personal wash bars (as described in EP 210 842). A few documents have mentioned the possible use of such clay minerals in tablets, in certain limited circumstances.
WO 96/14384 is principally concerned with detergent compositions in powder form. It teaches the placing of a clay mineral in close proximity to, and preferably in the same granule as, an organic peroxyacid bleach to prevent patchy discolouration by the bleach. It also briefly mentions the possibility of using such a system in tablets.
JP 09/087696 discloses compacted particulate material tablets which are based on nonionic surfactant. These tablets contain a clay mineral and a disintegration parameter.
WO96/24656 describes the synergistic fabric softening effect achieved by a combination of a clay mineral with zeolite MAP (a zeolite P with silicate to aluminium ratio no greater than 1.33), and again mentions the possibility of using this system in tablets.
We have now found that smectite clay minerals can be incorporated in tablets as a partial replacement for the materials of high solubility which have been taught as aids to the rapid disintegration of tablets. When this is done, there is little or no adverse effect on the combination of strength and speed of disintegration.
In consequence, there can be a net benefit. The clay can provide a benefit of fabric softening or conditioning and serves to replace another material which does not give a benefit after the tablets have disintegrated.
The present invention provides a tablet of a compacted particulate composition for use in fabric washing which contains detergent-active, detergency builder and other ingredients, characterised in that the tablet contains:
(i) a smectite clay mineral; and
(ii) a material with a water-solubility which exceeds 50 gm per 100 gm of water at 20° C., and
(iii) 0.5 to 40% by weight of an anionic surfactant.
This combination of the material of high water-solubility with the smectite clay mineral acts to aid disintegration of a tablet in which they are present, without significantly reducing the strength of the tablet.
In a second aspect, the invention further provides the use of a smectite clay mineral in a tablet of compacted particulate composition for use in fabric washing as a tablet disintegration aid.
Most preferably the smectite clay is used in combination with a material of a water-solubility as stated above.
All percentages referred to herein are to percentages by weight based on the total weight of the composition unless otherwise stated.
Preferably, the tablet contains from 5 to 50 wt % detergent-active, from 15% to 70 wt % detergency builder, from 0.5% to 40 wt % of the smectite clay mineral and from 5% to 40 wt % of the material with water-solubility which exceeds 50 gm per 100 gm of water at 20° C. The upper limit of the amount of the material with high water-solubility may be 30 wt %, more preferably 20 or 15 wt %. The lower limit may be 8 wt % or even 10 wt %. The total amount of the clay mineral and the material of high water-solubility may be between 5.5 and 40 wt %, preferably no more than 25 or 30 wt %. The lower limit may be as high as 10% or 15 wt %.
It is further preferred that the smectite clay mineral is a fabric softening smectite clay with a ion exchange capacity of at least 50, or more preferably 70 meq/100 g of dry clay. The cation exchange capacity of a clay relates to the expandable properties of the clay and to the charge of the clay, and is conventionally measured by electrodialysis or by exchange with ammonium ions followed by titration. These procedures are set out in Grimshaw, “The Chemistry and Physics of Clays”, pp. 264-265, Interscience (1971).
Another preferred feature of the present invention is that the tablets contain from 15 to 60 wt % of water-insoluble builder.
It is further preferred that the ratio of clay mineral to material with a water-solubility which exceeds 50 gm per 100 gm of water at 20° C. is between 1:1 and 1:10.
Materials for use in this invention, and preferred amounts and other features which may be used will be discussed in more detail below.
Smectite Clay Minerals
This invention utilises smectite clay minerals to promote disintegration of a tablet in water. Smectites are 2:1 clay minerals in which aluminium oxide or magnesium are present in a silicate lattice.
Suitable smectite clay minerals include montmorillonite, beidellite, hectorite, nontronite, saponite and sauconite, particularly those having an alkali or alkaline earth metal ion between the clay mineral layers. Montmorillonite is the preferred mineral, and clays which contain a majority of montmorillonite, such as bentonite, are a preferred source of this clay mineral. It may be preferred that the clay is at least 90% montmorillonite. Bentonites containing calcium or sodium montmorillonite (known as calcium or sodium bentonites) are particularly preferred.
Suitable bentonite clays are sold under the trade names of Laundrosil DW, M630 Agglomerat and EX 0276 Agglomerat clays available from Süd Chemie, Germany, Detercal G1 FC and Detercal G2 FC clays, available from Laviosa, Italy, Bentonite QPC 200G and QTIC 200G clay available from Colin Stewart Minerals, UK.
It is preferred that the majority of the clay particles have a particle size between 0.35 mm and 0.71 mm. It is further preferred that 90% of the clay particles have diameters between 0.35 mm and 0.71 mm.
The clay mineral is preferably present at a level from 0.5 to 40% by weight of the tablet, these percentages referring to the level of the clay mineral per se. The upper limit on the level of clay mineral may be as low as 8 wt %, 10 wt %, 15 wt %, 20 wt % or
Sta Mirjam
Westerhout Ronaldus Wilhelmus
Douyon Lorna M.
Mitelman Rimma
Unilever Home & Personal Care USA , division of Conopco, Inc.
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