Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Heterogeneous arrangement
Reexamination Certificate
2000-09-11
2002-08-06
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Heterogeneous arrangement
C510S495000, C264S117000, C023S3130FB
Reexamination Certificate
active
06429184
ABSTRACT:
The present invention relates to a process for the production of granular detergent compositions.
It is long known in the art to obtain detergent powders by spray drying. However, the spray-drying process is both capital and energy intensive and consequently the resultant product is expensive.
More recently, there has been much interest in production of granular detergent products by processes which employ mainly mixing, without the use of spray drying. These mixing techniques can offer great flexibility in producing powders of various different compositions from a single plant by post-dosing various components after an initial granulation stage.
A known kind of mixing process, which does not involve spray drying, employs a moderate-speed granulator (a common example often colloquially being called a “ploughshare”), optionally preceded by a high-speed mixer (a common example often colloquially being called a “recycler” due to its recycling cooling system). Typical examples of such processes are described in our European patent specifications EP-A-367 339, EP-A-390 251 and EP-A-420 317. These moderate-speed and high-speed mixers exert relatively high levels of shear on the materials being processed.
Until recently, there has been less effort in developing use of low-shear mixers or granulators. One type of low-shear equipment is a gas fluidisation granulator. In this kind of apparatus, a gas (usually air) is blown through a body of particulate solids onto which is sprayed a liquid component. A gas fluidisation granulator is sometimes called a “fluidised bed” granulator or mixer. However, this is not strictly accurate since such mixers can be operated with a gas flow rate so high that a classical “bubbling” fluid bed does not form.
Although low-shear granulators can give good control of bulk density, there is still a need for greater flexibility and in particular, for producing lower bulk density powders. Processes involving low-shear granulation are quite varied.
Indian Patent No. 166307 (Unilever) describes use of an internal recirculating gas fluidisation granulator and explains that use of a conventional fluidised bed will lead to a lumpy and sticky product.
East German Patent No. 140 987 (VEB Waschmittelwerk) discloses a continuous process for the production of granular washing and cleaning compositions, wherein liquid nonionic surfactants or the acid precursors of anionic surfactants are sprayed onto a fluidised powdered builder material, especially sodium tripolyphosphate (STPP) having a high phase II content to obtain a product with bulk density ranging from 530-580 g/l.
WO96/04359 (Unilever) discloses a process whereby low bulk density powders are prepared by contacting a neutralising agent such as an alkaline detergency builder and a liquid acid precursor of an anionic surfactant in a fluidisation zone to form detergent granules.
We have now found that in systems where a liquid binder is sprayed onto a powdered and/or granular solid in a low shear granulator, the droplet size in the spray relative to the particle size of the solids, determines granule size, bulk density and the yield of the process. Thus, the present invention provides a process for the production of a granular detergent product, the process comprising spraying droplets of a liquid binder to contact a particulate solid starting material in a low-shear granulator, wherein the d
3,2
average droplet diameter of the liquid binder is not greater than 10 times, preferably not greater than 5 times, more preferably not greater than 2 times and most preferably not greater than the d
3,2
average particle diameter of that fraction of the total solid starting material which has a d
3,2
particle diameter of from 20 &mgr;m to 200 &mgr;m, provided that if more than 90% by weight of the solid starting material has a d
3,2
average particle diameter less than 20 &mgr;m then the d
3,2
average particle diameter of the total solid starting material shall be taken to be 20 &mgr;m and if more than 90% by weight of the solid starting material has a d
3,2
average particle diameter greater than 200 &mgr;m then the d
3,2
average particle diameter of the total solid starting material shall be taken to be 200 &mgr;m.
In the context of the present 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 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 conventional 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.
As used herein, the term “powder” refers to materials substantially consisting of grains of individual materials and mixtures of such grains. The term “granule” refers to a small particle of agglomerated powder materials. 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 such a product.
The solid starting materials of the present invention are particulate and may be powdered and/or granular.
All references herein to the d
3,2
average of solid starting materials refers to the d
3,2
average diameter only of solids immediately before they are added to the low-shear granulation process per se. For example, hereinbelow it is described how the low-shear granulator may be fed by at least partially pre-granulated solids from a premixer. It is very important to note that “solid starting material” is to be construed to comprise all of the material from the premixer which is fed to the low-shear granulation process but does not include all solids as dosed to the premixer and/or direct to any other processing stage up to processing or after the end of processing in the low-shear granulator. For example, a layering agent or flow aid added after the granulation process in the low-shear granulator does not constitute a solid starting material.
The process of the present invention may be carried out in either batch or continuous mode of operation as desired.
Whether the low-shear granulation process of the present invention is a batch process or a continuous process, solid starting material may be introduced at any time during the time when liquid binder is being sprayed. In the simplest form of process, solid starting material is first introduced to the low-shear granulator and then sprayed with the liquid binder. However, some solid starting material could be introduced at the beginning of processing in the low-shear granulator and the remainder introduced at one or more later times, either as one or more discrete batches or in continuous fashion. However, all such solids fall within the definition of “solid starting material”.
The d
3,2
diameter of the solid starting materials is that obtained by, for example, a conventional laser diffraction technique (e.g. using a Helos Sympatec instrument) or sieving as would be well-known to the skilled person.
Suitably, the solid starting material(s) have a particle size distribution such that not more than 5% by weight of the particles have a particle size greater than 250 &mgr;m. It is also preferred that at least 30% by weight of the particles have a particle size below 100 &mgr;m, more preferably below 75 &mgr;m. However the present invention is also usable with larger fractions of solid starting materials (i.e. >5% more than 250 &mgr;m, optionally also <30% below 100 &mgr;m or 75 &mgr;m) but this increases the chance of some crystals o
Akkermans Johannes Hendrikus
Edwards Michael Frederick
Groot Andreas Theodorus
Montanus Cornelis Paulus
Pomeren Roland Wilhelmus
Douyon Lorna M.
Lever & Brothers Company, division of Conopco, Inc.
Mitelman Rimma
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