Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR THE PROD1~'r'rnN Og A DETERGENT COMPOSITION
' The present invention relates to a process for the
production of a detergent composition. In particular the
invention is concerned with a process for the production of a
detergent composition having a medium bulk density without
the use of a spray-drying step involving a high shear mixing
step and a very low shear mixing step and to detergent
compositions thereby produced.
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
crutcher slurry which is then sprayed into a spray-drying
tower and contacted with hot air to remove water whereby
detergent particles, often referred to as a "base" powder are
obtained. The particles so obtained, have a high porosity.
Thus powders produced by this method typically have a bulk
density of 300 to 550 g/1 or even up to 650 g/l.
Spray-dried powders generally provide good powder
delivery characteristics such as dispensing and dissolution.
However, the capital and operating costs of the spray-drying
process are high. Nevertheless there remains a significant
consumer demand for such low density powders.
In recent years, detergent powders having a high bulk
density have been produced by mechanical mixing processes.
Bulk densities of 700 to 900 g/1 and even higher have been
obtained. Typically such powders are produced by densifying
a spray-dried base powder in one or more mechanical mixers,
optionally with the addition of further components, or by
mixing the components of the composition in a continuous or
batch mixing process without the use of a spray-drying step.
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EP 367 339 (Unilever) discloses a process for the
production of a detergent composition having a high bulk
density in which a particulate starting material is treated
in a high speed mixer, a moderate speed mixer wherein the
material is brought into or maintained in a deformable state,
and then dried and/or cooled. The starting material may be a
spray-dried base powder or the components of the composition
may be employed without a prior spray-drying step in the
detergent production process.
Powders having a high bulk density have a low packing
volume which is advantageous for storage and distribution
operations and also for the consumer. Furthermore, if a
spray-drying step is not employed, the capital and operating
costs are typically much lower and the process uses less
energy and so provides an environmental benefit. The
avoidance of a spray-drying step in the detergent production
process is therefore desirable.
However, such high density powders typically have a much
lower porosity than a conventional spray-dried powder which
may impair the delivery of the powder into the wash liquor.
Additionally, the production of powders having a low to
medium bulk density, for example less than about 700 g/1, has
not hitherto been readily achievable on a commercial scale
without the use of a spray-drying step.
EP 544 365 (Unilever) is concerned with the production
of a high bulk density detergent composition and refers to
the bulk density of a detergent powder being dependent upon
the bulk density of the starting materials in the case of a
mixing process.
Treating a porous spray-dried material in a mechanical
mixing process typically leads to an increase in bulk density
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as the powder porosity is reduced. However, we have found
that a powder having a surprisingly low bulk density, for
' example less than 700 g/l, may be obtained by a process in
which a spray-drying step is not employed, involving a high
shear mixing step and a very low shear mixing step if a
component having a low bulk density is incorporated in the
very low shear mixing step. Further, such a powder exhibits
good powder properties.
A first aspect of the invention provides a process for
the production of a detergent composition or component having
a bulk density of less than 700 g/1 which. does not comprise a
spray-drying step and which process comprises mixing a
particulate starting material with a liquid binder in a mixer
granulator, preferably having both a stirring and a cutting
action, to form granules wherein the starting material and/or
binder comprises a non-soap detergent active or a precursor
thereof, feeding the said granules to a very low shear mixing
zone and contacting the granules with a particulate material
having a bulk density of not more than 700g/1 to produce a
detergent composition or component having a bulk density of
less than 700 g/l.
A second aspect of the invention provides a detergent
composition or component having a bulk density of less than
700 g/1 obtainable by a process which does not comprise a
spray-drying step and which comprises mixing a particulate
starting material with a liquid binder in a mixer/granulator,
preferably having both a stirring and cutting action, to form
granules and feeding the said granules to a ve
ry low shear
mixing zone and contacting the granules with a particulate
material having a bulk density of not more than 700g/1.
Unless stated otherwise, ~ figures are on a weight basis
and based on the total weight of the detergent composition or
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component prior to the optional addition of post-dosed
ingredients.
Suitably the detergent composition has a bulk density of
400 to 680 g/1, preferably 450 to 680 g/1 and more preferably
500 to less than 650 g/l. =t is further preferred that the
detergent composition has a particle porosity of at least 0.2
and more preferably at least 0.25. The porosity may be
determined by a mercury porosimetry method.
The component incorporated in the very low shear zone
has a bulk density of not more than 700 g/1, and suitably has
a bulk density of 200 to 600 g/1, preferably 250 to 550 g/1
and especially 350 to 500 g/1.
This low bulk density component is desirably an
aluminosilicate, for example zeolite 4A or zeolite A24 or a
salt, preferably an inorganic salt. Salts, preferab:Ly
sodium, of phosphates, for example tripolyphosphate,
carbonate, bicarbonate and sulphate are especially suitable.
Desirably the low bulk density component constitutes the
detergency builder, or part thereof in the composition. 2f
desired, this component may be a non-builder material, in
which case the particulate starting material will suitably
comprise a builder.
It is especially preferred that the low bulk density
component comprises sodium tripolyphosphate having a bulk
density of 380 to 500 g/1. This compares to a typical bulk
density of 800 to 1000 g/1 for tripolyphosphate
conventionally employed in detergent compositions.
Suitably the level of the low bulk density compt>nent is
selected according to the desired density of the detergent
composition. Preferably it is present at a level of 5 to
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65 wt ~, preferably 10 to 40 wt ~ and optimally 10 to 30 wt
of the composition.
If desired part of the low bulk density component may be
' 5 introduced into the high speed mixer/granulator. In a
preferre-d embodiment, the level of this component in the very
low shear mixing zone is at least 10g by~weight based on the
detergent composition and additionally up to 80~ of the total
amount of the low bulk density component may be dosed into
the high speed mixer/granulator although it is preferred that
up to 60~, more preferably 5 to 50~, especially 20 to 45~ of
the low density material (as a percentage of the total amount
of this material) be dosed into the high speed mixer
granulator.
The process may be continuous but is preferably batch-
wise.
A preferred type ofmixer/granulator for use in the
process of the invention is bowl-shaped and preferably has a
substantially vertical stirrer axis. Especially preferred
are mixers of the Fukae (Trade Mark) FS-G series manufactured
by Fukae Powtech Kogyo Co., Japan; this apparatus is
essentially in the form of a bowl-shaped vessel accessible
via a top port, provided near its base with a stirrer having
a substantially vertical axis, and a cutter positioned on a
side wall. The stirrer and cutter may be operated
independently of one another, and at separately variable
speeds.
Other similar mixers found to be suitable for use in the
process of the invention are the Diosna (Trade Mark) V series
ex Dierks & Sohne, Germany; and the Pharma Matrix (Trade
Mark) ex T K Fielder Ltd., England. Other similar mixers
believed to be suitable for use in the process of the
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invention include the Fuji (Trade Mark) VG-C series ~ex Fuji
Sangyo Co., Japan; and the Roto (Trade Mark) ex Zanchetta &
Co srl, Italy.
Another mixer found to be suitable for use in the
process of the invention is the Lddige (Trade Mark) 1.~'M series
batch mixer ex Morton Machine Co. Ltd., Scotland. This
differs from the mixers mentioned above in that its stirrer
has a horizontal axis.
Granulation is preferably effected by running the mixer
using both stirrer and cutter; a relatively short residence
time (for example, 5-8 minutes for a 35 kg batch) is
generally sufficient. The final bulk density can be
controlled by choice of residence time.
Suitably the stirrer is operated at a rate of 25 to 80
rpm, preferably 30 to 75 rpm. Independently the cutter is
suitably operated at a rate of 200 to 2500 rpm, preferably
300 to 2200 rpm. A batch process typically involves pre-
mixing of solid components, addition of liquids, granulation,
optional addition of a layering material suitable for
controlling the granulation end-point, and product discharge.
The rate of stirring and/or cutting is suitably adjusted
according to the stage of the process.
The presence of a liquid binder is necessary for
successful granulation. The precise nature of the binder is
not critical provided that it enables successful granulation
to be achieved. Suitably the binder comprises one or more of
the following: liquid detergent-active compound(s),
precursors thereof, water, solutions, non-aqueous or aqueous,
of other ingredients or mixtures thereof. If water is
employed the level is desirably controlled so that the
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moisture content of the detergent composition is not more
than 10~ by weight and preferably not more than 6%.
The mixing step is preferably carried out at a
controlled temperature somewhat above ambient, preferably
above 30°C. Suitably the temperature is within the range 30
to 55°C although higher temperatures may be suitable, for
example, where heat of reaction is generated by in situ
neutralisation.
The very low shear mixing zone may be located within the
r
same apparatus as the high speed mixer granulation but
desirably is in a separate apparatus for example a rotating
bowl mixer and preferably a fluid bed. The fluid bed is
suitably operated at a temperature of 30 to 90°C and at a
superficial air velocity of about 0.25 to 1.2 ms-'. Suitable
fluid beds are available from, for example NIRO~". The air
flow in the fluid bed may be adjusted according to the
desired level of shear and agitation of the low bulk density
component. Suitably the low bulk density component is dosed
into the bed and gently agitated using a small air flow which
is then increased prior to feeding in the granules from the
high speed mixer/granulator.
r 5 The detergent composition suitably comprises anionic
detergent active. This may be incorporated as a pre-
neutralised material, desirably as a component of the
particulate starting material, or may be neutralised in situ.
In the latter case the acid precursor of the active is
preferably neutralised using a solid neutralising agent, for
example carbonate (preferably sodium carbonate), which is
desirably a component of the particulate starting material.
The detergent active material present in the composition
may be selected from anionic, ampholytic, zwitterionic or
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nonionic detergent active materials or mixtures thereof.
Examples of suitable synthetic anionic detergent compounds
are sodium and potassium (C9-C2o) benzene sulphonates,
particularly sodium linear secondary alkyl (Clo-Cls) benzene
sulphonates; sodium or potassium alkyl sulphates; and sodium
alkyl glyceryl ether sulphates, especially those ethers of
the higher alcohols derived from tallow or coconut oil and
synthetic aicohols derived from petroleum. Suitable
nonionics which may be employed include, in particular the
reaction products of compounds having a hydrophobic group and
a reactive hydrogen atom, for example, aliphatic alcohols,
acids, amides or alkyl phenols with alkylene oxides,
especially ethylene oxide either alone or with propylene
oxide. Specific nonionic detergent compounds are alkyl (C6-
C22) phenol ethylene oxide condensates, generally having 5 to
EO, ie 5 to 25 units of ethylene oxide per molecule, and
the condensation products of aliphatic (C8-Cl8) primary or
secondary linear or branched alcohols with ethylene oxide,
generally 5 to 40 EO. The level of detergent active material
20 present in the composition may be in the range from 1 to 50~
by weight depending on the desired applications. Nonionic
material may be present in the particulate starting material
at a level which is preferably less than 10~ by weight, more
preferably less than 5~ by weight and/or employed as the
25 liquid binder optionally with another liquid component, for
example water.
2n a preferred embodiment of the invention, the
particulate starting material comprises one or more of a
carbonate salt at a level.of 5 to 60 wt ~, a zeolite at a
level of 5 to 60 wt ~ and, if present as the low bulk density
component, a phosphate salt at a level of 5 to 20~ by weight
of the total quantity of starting material.
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Suitably the particulate starting material constitutes
30 to 70~ of the detergent composition.
Optionally, a layering material may be employed during
the high speed mixing step to control granule formation and
reduce or prevent over-agglomeration. Preferably a layering
material is introduced into the very low shear mixing step.
Suitable materials include aluminosilicates, for example
zeolite 4A and A24. The layering material is suitability
present at a level of 1 to 4 wt ~ based on the co
mposition.
The composition may be used as a complete composition in
its own right or may be mixed with other components or
mixtures and thus may form a major or minor part of a final
product. The composition may be blended with for example a
spray-dried base powder.
Conventional additional components such as enzymes,
bleach and perfume may also be admixed with the composition
as desired to produce a fully formulated product.
The invention is further illustrated by the following
non-limiting Examples.
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Example 1 and A (Comnarativ~Z
A detergent composition was prepared by dosing the
following components into a Fukae FS3500 mixer (in the
5 following sequence):
Sodium Tripolyphosphate (400- 80(kg)
440g/1)
Fluorescer 1
10 SCMC 12
Sodium Carbonate 530
LAS acid 170 l
Fatty acid (pRISERENE"" 4918)/ 40/30
Nonionic mixture
The process conditions employed are summarised below:
Process step Stirrer(rnm) Cutter(r~m)
Solids premix 40 0
Liquids addition 75 1900
Granulation 70 1900
Discharge 30-45 1500
The mixer was operated at a temperature of 30-35°C. The
mixer was operated for sufficient time to effect granulation
in the granulation step (end point 60 amps) and the product
was discharged over 240 seconds.
130kg of sodium tripolyphosphate (bd 400-440g/1) was
dosed into a NIRO fluid bed and 'bubbled' at a low air
velocity. Prior to discharge of the granules from the Fukae
mixer, the air flow was increased to about 11000 m3/hr and
the granules were fed into the fluid bed.
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20kg of zeolite 4A was then dosed into the fluid bed as
a layering material. The detergent composition was then
discharged from the fluid bed at a temperature below 30°C.
' S For comparative purposes the above procedure was
repeated to produce Composition A, but conventional density
STP (about 800g/1) was substituted for the low density STP.
All of the STP was dosed into the Fukae mixer and none into
the fluid bed.
The properties of the two powders were measured and the
results are detailed below:
Bulk density (g/1) 520 775
Dynamic
Flow Rate (ml/s) >90 >90
Mean particle size (l.un) 520 750
Both powders were crisp and free flowing and white/cream
in colour.
The results demonstrate that a medium bulk density
powder is obtainable without the need for a spray-drying step
in the production process. A reduction in bulk density may
be expected to have an adverse effect on powder properties
(compression, UCT). However these properties remain at an
acceptable level for the powder of Example 1.
