Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Heterogeneous arrangement
Reexamination Certificate
1998-05-26
2001-02-20
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Heterogeneous arrangement
C510S276000, C510S444000, C510S507000, C510S512000
Reexamination Certificate
active
06191095
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a medium to low bulk density particulate detergent composition.
BACKGROUND
Particulate detergent compositions of medium to low bulk density may be manufactured by the spray-drying process, or by agglomeration in low shear mixers such as a fluidised bed, or pan granulator and may be used as a “base powder” for a detergent composition. In the spray-drying process, a slurry of components such as anionic detergent active, builder material and optionally nonionic detergent active is manufactured and then dried by spraying it in atomised form into a co- or countercurrent stream of air at high temperature. The resultant particulate compositions may be used directly as a detergent composition or other components can be post-dosed, for example heat or moisture sensitive components, to provide a complete powder composition. The spray-dried granules are found in practice to have bulk densities less than 600 g/l, but the postdosed components may raise the bulk density of the composition to around 700 g/l.
Such low to medium bulk density detergent compositions can be sticky particularly in moist environments and particularly where they have a moderate to high content of organic detergent surfactant. Moderate to high quantities of anionic surfactant can give particular problems. This can make them difficult to handle and process, as they become less free-flowing and tend to form lumps. Such compositions may also have poor storage stability, tending to form cakes on storage, leading to poor product quality.
Particulate composition flow properties can be measured for example by dynamic flow rate and/or the compressibility. Compressibility can be measured by the tests described below. High compressibilities imply poor flow properties. Compositions having in excess of 10% by weight of organic detergent surfactant generally have a compressibility in the range of 20 to 25%. The compressibility of such compositions can under certain conditions be reduced to just above 17%, but further reduction is very difficult without reducing the surfactant level.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a particulate detergent composition having a medium to low bulk density (preferably a bulk density of less than 700 g/l, more preferably less than 600 g/l ) and a moderate to high organic detergent surfactant content (preferably at least 10% by weight, more preferably at least 15% by weight and especially at least 20% by weight) and which has improved properties such as lower stickiness, improved storage stability and lower caking tendency.
It is further desired to reduce the compressibility of the detergent composition without reducing the content of organic surfactant. It is further desired that the particulate detergent composition should retain its improved properties even in conditions of increase ambient temperature and humidity.
The inventors have discovered that, if at least a proportion of the base powder is reformulated so that its compressibility is below 17%, the properties of the detergent composition can be improved.
Here, the term “base powder” is used to signify granular components manufactured by spray-drying or spray-drying followed by densification or manufactured by agglomeration. The base powder comprises structured particles containing detergent active and builder which form the base of any detergent composition.
It has been found by the inventors that improved properties can be obtained if the quantity of the base powder having a compressibility above a certain value is kept at a low level. In the present invention, compressibility is measured by compressing a known volume of particulate detergent composition by application of a standard weight, at defined conditions of temperature and humidity, after which the volume reduction is noted. The method used in the invention is described further below.
Accordingly, the present invention provides a particulate detergent composition having a bulk density of 700 g/l or less and comprising a base powder, the composition comprising builder and at least 10% by weight of organic detergent surfactant, characterised in that less than 80% by weight, preferably less than 66% by weight, of the base powder has a compressibility (measured as described below at 20-25° C. and about 40% relative humidity) of 17% or more.
A base powder of the present invention will comprise particulate composition comprising builder and detergent surfactant selected from anionic surfactant, nonionic surfactant or mixtures thereof. The base powder may include other components as discussed below.
According to the present invention, the base powder will comprise at least two different components. At least one of these components will have a compressibility below 17%. As will be described further below, any given component of the base powder may not include both detergent active and builder, but the base powder as a whole will.
More particularly, therefore, the present invention provides a particulate detergent composition having a bulk density of 700 g/l or less and comprising at least 10 wt % of organic detergent surfactant, the composition comprising a base powder which contains detergency builder and organic detergent surfactant selected from anionic surfactant, nonionic surfactant and mixtures thereof and which consists of structured particles, characterised in that the base powder is composed of at least two different granular components, and at least one of these components has a compressibility (measured at 20-25° C. and about 40% relative humidity) of less than 17%, whereby less than 80% by weight, preferably less than 66% by weight, of the total base powder has a compressibility of 17% or more.
As previously indicated, the composition preferably contains at least 15% by weight of detergent surfactant. The invention is of especial interest as a means for formulating compositions containing very high levels of detergent surfactant, for example, at least 20% by weight.
The base powder preferably comprises granules having an average particle size of greater than 200 micrometers.
The invention further provides a process for manufacturing a particulate detergent composition as defined above, comprising separately preparing granular components and dry-mixing the granular components.
Compressibility
The method of measuring compressibility used in the present invention is as follows.
The experiment is carried out at 20-25° C. and a relative humidity of about 40%. These values represent typical ambient conditions in a northern European indoor laboratory environment. The exact relative humidity at which the measurement is carried out is not critical, provided that it is not so high that the samples take up moisture.
The apparatus comprises a perspex cylinder with an internal diameter of 54 mm and a height of 170 mm. The side of the cylinder is graduated in millimeters. A piston is provided which fits the internal diameter of the perspex cylinder.
The top of the piston has means to support a weight, whereby pressure can be applied to detergent powder contained in the perspex cylinder. The combined mass of the piston and the weight is 25 kg.
To measure the compressibility of a sample, the perspex cylinder is filled with particulate detergent composition (herein after “powder”). The top of the layer of powder is levelled by removing superfluous powder with a straight-edge. Thus, a standard volume of powder is tested. The initial volume is measured by means of the scale on the side of the cylinder. The piston and weight are then lowered onto the surface of the powder and are allowed to rest freely on the powder for 60 seconds. The volume of the powder after 60 seconds is measured by means of the scale on the side of the cylinder.
The volume reduction is used to calculate the compressibility using the following equation:
Compressibility
(
in
%
)
=
(
initial
volume
-
final
volume
)
initial
volume
×
100
Components having a compress
Emery William Derek
Instone Terry
Liem Seeng Djiang
Verschelling Gilbert Martin
Douyon Lorna M.
Lever Brothers Company, a Division of Conopco, Inc.
Mitelman Rimma
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