Cleaning compositions

Details Cleaning compositions Cleaning compositions

1998-06-04

2002-04-16

Delcotto, Gregory (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

Heterogeneous arrangement

C510S305000, C510S309000, C510S312000, C510S320000, C510S374000, C510S446000, C510S447000, C510S470000, C510S471000, C510S473000

Reexamination Certificate

active

06372707

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to cleaning compositions in the form of tablets for use in fabric washing.
BACKGROUND AND SUMMARY OF PRIOR ART
Detergent compositions in tablet form are described, for example, in GB 911204 (Unilever), U.S. Pat. No. 3,953,350 (Kao), JP 60-015500A (Lion) and EP-A-711827 (Unilever); and are sold commercially in Spain. 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 detergent 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 the 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.
It can be difficult, to obtain both tablet strength and an ability to disperse and dissolve quickly in the wash liquor. Tablets formed using only a light compaction pressure tend to crumble and disintegrate on handling and packing; while more strongly compacted tablets may be sufficiently cohesive but then fail to disintegrate or disperse to an adequate extent in the wash.
This problem has proved especially acute with tablets formed by compressing powders containing surfactant and built with insoluble detergency builder such as sodium aluminosilicate (zeolite).
It is known to include materials whose function is to enhance disintegration of tablets when placed in wash water. Some tablets which are sold commercially incorporate urea for this purpose. Urea has a very high solubility in water exceeding 100 gms per 100 ml water at 20° C.
SUMMARY OF THE INVENTION
We have now found that the disintegration of tablets of cleaning composition can be accelerated by incorporating in the tablet a quantity of a water-insoluble but water-swellable polymeric material.
However, we have observed that particles of water-swellable but water-insoluble material which are effective to cause tablet disintegration are liable to be retained on the washed laundry as visible residues.
We therefore propose, in the present invention, that the disintegration and dissolution of tablets is brought about by a combination of two materials. One is a water-swellable but water-insoluble polymeric material. The other is a water-soluble compound which enhances dissolution.
According to the present invention, there is provided a tablet of compacted particulate cleaning composition, containing overall from 5 to 50 wt % surfactant and from 5 to 80 wt % detergency builder wherein the tablet or a discrete region thereof which contains surfactant and detergency builder also contains (i) water-insoluble, water-swellable polymeric material, and (ii) particles functioning to aid and dissolution/disintegration and 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.
As will be explained further below, these disintegration-promoting particles can also contain other forms of . tripolyphosphate or other salts within the balance of their composition.
DETAILED DESCRIPTION AND EMBODIMENTS
A tablet of the invention may be either homogeneous or heterogeneous. In the present specification, the term “homogeneous” is used to mean a tablet produced by compaction of a single particulate composition, but does not imply that all the particles of that composition will necessarily be of identical composition. The term “heterogeneous” is used to mean a tablet consisting of a plurality of discrete regions, for example layers, inserts or coatings, each derived by compaction from a particulate composition. In a heterogenous tablet according to the present invention, each discrete region of the tablet will preferably have a mass of at least 5 gm.
In a heterogeneous tablet, at least one of the discrete regions contains the said swellable polymeric material and disintegration-promoting particles together with surfactant and detergency builder in accordance with the invention.
A preferred tablet or a discrete region thereof contains from 2 or 5 wt % up to 40 or 50 wt %, or 8 to 49 wt % surfactant, from 5 or 10 up to 60 or 80 wt % detergency builder and from 0.5 to 10 wt %, or 0.1 to 8 wt % of the water-insoluble but swellable polymeric material. Where a tablet is heterogenous, these percentage ranges for surfactant and builder may apply to the overall composition of the tablet, as well as to at least one discrete region of the tablet.
If the material in the disintegration-promoting particles can function as a detergency builder, (as is the case with sodium tripolyphosphate) then of course it contributes to the total quantity of detergency builder in the tablet composition.
The quantity of disintegration-promoting particles is suitably from 5 or 8 wt % up to 25 or 40 wt % of the tablet or region thereof. Benefits from water-insoluble, swellable polymeric material can be obtained when it is present in amounts from 0.5 better 0.9 up to at least 2.7 or 3.5 wt % of the tablet or region thereof. It may possibly be used in larger amounts such as up to 5 or 8 wt %.
In a heterogenous tablet, the polymeric material may be incorporated in some only of a plurality of discrete regions (eg. in only one of two) while other region(s) contain a lesser concentration, or more, of the polymeric material. Such an arrangement may be used to cause the regions of the tablet to disintegrate and dissolve (in so far as their constituents are soluble) at different rates.
The Water-swellable Polymer
Suitable water-swellable polymeric materials preferably have sufficient water-absorptivity that they can absorb at least four times their own weight of water, ie. a water uptake of at least 4 gm per gm.
A number of such materials are known, and are generally based on cellulose which may be chemically modified to enhance its water uptake capacity. Sometimes such modified celluloses have ionic substituents but for this invention it is preferred that any substituents are nonionic.
Surprisingly, we have found that such a material is more effective if it has a relatively large particle size. We therefore prefer that the polymeric material has a particle dimension of at least 400 preferably at least 500 micrometers. Such polymeric material with a particle dimension of at least 400 micrometers is preferably an agglomerate of smaller particles whose largest dimension is no greater than 150 or 200 micrometers, better no greater than 50 micrometers. This makes it possible for at least some of the polymer particles to break up during a wash cycle, and not remain as visible residues in fabrics. While this is advantageous, we have observed that since particles nevertheless remain intact and can be observed as residues.
The material may exist as relatively rounded particles, or as relatively flat particles such as flakes or discs. In the latter case a dimension (diameter) of the flakes will be larger, perhaps substantially larger, than the diameter of a sphere with the same volume.
The largest dimension of particles of the polymeric material may be determined by sieve analysis, and the shape of the particles can be observed under a microscope.
It is customary to use sodium carboxymethylcellulose (SCMC) in detergent compositions, usually as not more than 3 wt % of the composition. We have found that such quantities of SCMC are generally ineffective to promote tablet disintegration.
We have found it desirable to use swellable polymeric materials with little or no ionic character. Such materials may be polysaccharides with little or no ionic substitution.
The absence or near absence of ionic substitution can be e

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