Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Heterogeneous arrangement
Reexamination Certificate
2000-11-21
2004-01-20
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Heterogeneous arrangement
C510S509000, C510S510000, C023S3130FB
Reexamination Certificate
active
06680288
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for preparing a free-flowing, storage-stable granular detergent composition. More particularly, the invention is directed to a process involving granulation of a particulate material with a liquid binder and treating the resulting granules with an amount of water.
BACKGROUND OF THE INVENTION
The handling and storage properties of modern detergent powders have gained increasing importance in recent years. The detergent industry has been put under increasing pressure to satisfy both external consumer demands and expectations, and in addition, internal demands to cut the cost of production and to improve the management of manufacturing and supply chain.
An important criterion in the management of manufacturing and supply chain is the ability to handle and store powders. A serious problem which can arise during storage is caking of the powder, for example in big bags or silos. This can lead to hold-ups in the supply chain, and, if the powder has deteriorated to a significant degree, the discarding of the powder.
Therefore, it is very important that powders are free-flowing and do not cake upon storage (i.e. they should not be “sticky”). It is also important that powders do not contain a significant amount of fine particles as large levels of fines can have a deleterious effect of the flow-properties of a powder. Furthermore, fines have a tendency to “settle”, aggregating at the bottom of, for example, a storage vessel. Conventionally, detergent compositions have been produced by a spray-drying process in which the components of the composition are mixed with water to form an aqueous slurry which is then sprayed into a tower and contacted with hot air to remove water. In recent years, there has been much interest in the production of detergent products produced by processes which employ non-spray-drying (“non-tower”) techniques. In these type of processes, the various components are generally mixed, for example by mechanical agitation or gas fluidisation, and granulated with the addition of a liquid binder. Liquid binders typically used in such granulation processes are anionic surfactants, acid precursors of anionic surfactants, nonionic surfactants, fatty acids or salts thereof, water or any mixture thereof.
Spray-drying tends to produce dry, relatively non-sticky powders. In contrast, powders produced by non-tower granulation techniques tend to be much more sensitive to problems of stickiness and caking upon storage. The amount of liquid binder added in a non-tower granulation process usually represents an important factor in determining the quality of the product. Too much binder can lead to lumping and a sticky product, and too little can lead to incomplete granulation.
There are several well-known techniques which manufacturers use to help prevent powders caking and lumping, and also to aid the flow properties of powders. For example, it is well-known to coat sticky or moist granules with a finely divided solid such as an aluminosilicate. This is often referred to as “layering”.
Granulated powders are also often put through a drying step in order to improve their flow and storage properties. However, the very step of drying can create problems in itself. During drying, depending on the absorbency of the solid components and on the nature of the liquid constituents, the liquid binder constituents can become mobile and start to move to the surface of, and eventually bleed from, the granulates. This can lead to caking and lumping both during the drying process and upon storage of the powder.
We have found that powders produced by non-tower processes and containing a hydratable salt, such as for example a phosphate detergency builder such as sodium tripolyphosphate (STPP), are prone to problems of “stickiness”, leading to reduced flowability, and caking upon storage. Furthermore, “drying” and layering do not automatically produce “non-sticky” powders with good flow properties. Hence there is still a need for cost-effective methods for improving the handling and storage properties of these powders.
PRIOR ART
W097/34991 (Henkel) describes a processes for the manufacture of detergent powders in which water is used as a granulation aid. According to this document, the risk of lumping and bleeding of any nonionic surfactant, even during the drying stage is minimised by treating the granulated product either before or during drying with an aqueous solution or an aqueous dispersion of one or more non-surfactant washing- or cleaning agent constituents. The resulting powders are free flowing, do not cake and have good storage stability. The aqueous solution contains 25-50, preferably 30-40 wt % of the non-surfactant washing- or cleaning agent, for example sodium silicate, and is used in amounts of 1-15, preferably 2-8 wt %.
It is also known to spray an aqueous solution of nonionic surfactant into a fluid bed granulator during the granulation process, as disclosed in U.S. Pat. No. 3,714,051.
EP-A-0 643 129 discloses a process in which detergent composition ingredients are granulated in a process in which the components are mixed in a high shear mixer followed by a moderate speed mixer, wherein water is sprayed on at the rear of the moderate speed mixer, followed by dosing of a zeolite layering agent.
We have now found a simpler and cheaper method of improving the handling and storage properties of powders containing a hydratable salt. Surprisingly, we have found that the handling and storage properties of such powders can be improved merely by treating the product of a granulation process with an amount of water. More specifically, we have found that powders with very good flow properties, low levels of fines and a low level of “stickiness” can be obtained from the process of the present invention.
DEFINITION OF THE INVENTION
In a first aspect, this invention provides a process for preparing a granular detergent product in which a particulate material comprising a hydratable salt is granulated with a liquid binder, characterised in that the resulting granules are treated in a low shear mixer with from 0.5 to 20 wt % of water, based on the total amount of untreated granules, in such a manner that little or no further agglomeration takes place.
In a second aspect, this invention provides a granular detergent product obtained according to the process of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
Hereinafter, in the context of this invention, the term “granular detergent product” encompasses granular finished products for sale, as well as granular components or adjuncts for forming finished products, e.g. by post-dosing to or with, or any other form of admixture with further components or adjuncts. Thus a granular detergent product as herein defined may, or may not contain detergent-active material such as synthetic surfactant and/or soap. The minimum requirement is that it should contain at least one material of a general kind of convenbonal component of granular detergent products, such as a surfactant (including soap), a builder, a bleach or bleach-system component, an enzyme, an enzyme stabiliser or a component of an enzyme stabilising system, a soil anti-redeposition agent, a fluorescer or optical brightener, an anti-corrosion agent, an anti-foam material, a perfume or a colourant.
However, in a preferred embodiment of this invention granular detergent products contain detergent-active material such as synthetic surfactant and/or soap at a level of at least 5 wt %, preferably at least 10 wt % of the product.
As used hereinafter, the term “powder” refers to materials substantially consisting of grains of individual materials and mixtures of such grains. As used hereinafter, the term “granule” refers to a small particle of agglomerated smaller particles, for example, agglomerated powder particles. The final product of the process according to the present invention consists of, or comprises a high percentage of granules. However, additional granular and or powder materials may optionally be post-dosed to
Groot Andreas Theodorus
van Pomeren Roland Wilhemus
Douyon Lorna M.
Mitelman Rimma
Unilever Home & Personal Care USA , division of Conopco, Inc.
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