Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
2000-06-08
2002-11-26
Douyon, Lorna M (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Solid, shaped macroscopic article or structure
C510S294000, C510S298000, C510S344000, C510S462000, C510S464000
Reexamination Certificate
active
06486118
ABSTRACT:
This invention relates to detergent compositions in the form of tablets. These tablets may be used in fabric washing. These tablets are intended to disintegrate when placed in water and thus are intended to be consumed in a single use.
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 now sold 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.
Detergent tablets are generally made by compressing or compacting a detergent powder, which includes organic surfactant as detergent active and also contains detergency builder.
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. Although it is desirable that tablets have adequate strength when dry, yet disperse and dissolve quickly when brought into contact with wash water, it can be difficult to obtain both properties together. 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. Tableting will often be carried out with enough pressure to achieve a compromise between these desirable but antagonistic properties. However, it remains desirable to improve one or other of these properties without detriment to the other so as to improve the overall compromise.
The problem has proved especially acute with tablets formed by compressing powders containing surfactant and built with insoluble detergency builder such as sodium aluminosilicate (zeolite).
A number of documents have taught 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. Such documents include WO 98/40462, 98/40463, 98/55575, 98/55582 and 98/55583.
These documents disclose use of cellulosic material derived from timber and subjected to a substantial amount of pretreatment before incorporation into tablets. In some instances the cellulosic fibres are separated from the raw material, dispersed in water and then recovered using a process analogous to papermaking. Wo 98/40462 mentions the use of a material known in the papermaking industry as “Thermomechanical pulp”. Fibres obtained from timber by mechanical processing combined with dispersion in water generally contain 35% or more of cellulose and 30% or less of lignin.
Cellulose fibres may be chemically treated to remove this lignin as is done when making high quality white paper. In the papermaking industry the resulting purified fibres are referred to a “chemical fibres”.
The use of cruder cellulosic particles such as sawdust or wood flour was suggested many years ago in U.S. Pat. No. 2,560,097, but this was in the context of one-use tablets for hand cleansing, where the material serves as a filler and the tablets were disintegrated in use by handling.
Some tablets which are sold commercially are compacted from a composition which includes particles which contain both surfactant and detergency builder, and other particles which consist of material which is readily water-soluble. This material functions to enhance disintegration of tablets when placed in wash water. For example, EP-A-838519 teaches the use of sodium acetate trihydrate for this purpose. Tablets containing this material can be formulated and compacted so as to disintegrate within an acceptably short time when placed in the drum of a washing machine together with laundry.
It would be desirable to achieve a further increase in the speed of disintegration of tablets, compared to those currently sold commercially, so as to achieve even more reliable disintegration in use and/or to permit the tablets to be placed in the dispenser drawer of a washing machine if the user so desires.
Surprisingly we have found that the disintegration in water of tablets containing particles in which organic surfactant is mixed with other material can be increased using material of vegetable origin which has been processed to suitable size without dispersing the fibres in liquid and recovering them. The improvement in disintegration can be achieved together with adequate mechanical strength.
So, according to a first aspect of this invention there is provided a tablet of compacted particulate composition containing;
(a) particles which contain organic surfactant together with detergency builder, and
(b) water-insoluble but water-swellable particles of plant material which contain both cellulose and lignin, obtainable by fragmentation of plant material without separation of its fibres into a liquid dispersion.
The composition is likely to contain particles of other ingredients as well. These, or some of them, may take the form of particles which contain water-soluble salt as at least 50% of their own weight.
The particles of plant material preferably have a mean size, before contact with water, in a range from 250 to 1,500 micrometers, more preferably 400 up to 1,500 micrometers. The mean particle size may be in a range from 250 or 400 up to 1,100 micrometers. Particularly preferred is a mean particle size in a range from 700 to 1,000 micrometers. The material may be sieved so that all of its particles fall within one of these size ranges. In any event, particles larger than 2,000 micrometers are preferably removed, such as by sieving.
The water-insoluble but water-swellable particles may be obtained by breaking up plant material and collecting particles of the desired size, or by comminuting plant material of larger particle size.
One possible form of cellulosic plant material is woodchips or sawdust, which may be milled to a smaller particle size within the preferred range above.
Another possible form of cellulose-containing plant material which may be used is particles of coconut husk material, sometimes known as coir.
Consequently, in a second aspect this invention provides a tablet of compacted particulate composition containing organic surfactant and detergency builder wherein the tablet or a discrete region of the tablet contains disintegration-promoting particles of coconut husk material, which is of course water-insoluble. We have discovered that is it strongly water-swellable.
Forms of this invention, preferred and optional features, and materials which may be used, will now be discussed in greater detail.
Discrete Regions/Whole Tablets
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 of which is a matrix of particles 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 3 gm.
In a heterogeneous tablet, at least one of its discrete regions contains the said swellable disintegration-promoting particles, and usually will also contain surfactant and detergency builder. For example, there is provided a tablet which contains a pluarity of discrete regions at least one of which contains a greater concentration of the water-insoluble water-swellable disintegration disintegration promoting particles than another region of the tablet.
Proportions
Tablets of this invention will generally contain, overall, from 5 to 50% by weight of organic surfactant and from 5 to 80%
Boskamp Jelles Vincent
Loomans Paulus Jacobus
Douyon Lorna M
Mitelman Rimma
Unilever Home & Personal Care USA , division of Conopco, Inc.
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