Note: Descriptions are shown in the official language in which they were submitted.
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C7292 (R)
DETERGENT COMPOSITIONS AND PROCESS FOR PREPARING THEM
TECHNICAL FIELD
The present invention relates to a process for the
preparation of a granular detergent composition having a
high bulk density and good powder properties. More in par-
ticular, it relates to a process for the continuous
preparation of such detergent compositions, especially those
with high detergent activity. Moreover, it relates to a
granular detergent composition obtainable by the process of
the present invention.
BACKGROUND AND PRIOR ART
Recently there has been considerable interest within the
detergents industry in the production of detergent powders
having a relatively high bulk density, for example 600 g/l
and above.
Generally speaking, there are two main types of processes by
which detergent powders can be prepared. The first type of
process involves spray-drying an aqueous detergent slurry in
a spray-drying tower. In the second type of process, the
various components are dry-mixed and optionally agglomerated
with liquids, e.g. nonionics.
The most important factor which governs the bulk density of
a detergent powder is the bulk density of the starting
materials in the case of a dry-mixing process, or the
chemical composition of the slurry in the case of a spray-
drying process. Both factors can only be varied within alimited range.
Therefore, a substantial increase in bulk density can only
be achieved by additional processing steps which lead to the
densification of the detergent powder. There are several
processes known in the art leading to such densification.
Particular attention has thereby been paid to the den-
sification o~ spray-dried powders by post-tower treatment.
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In view of increased environmental concern, it is desirable
to produce high density detergent powder containing alkyl
sulphate as an active detergent component. The reason is
that this type of active detergent material is readily
biodegradable and therefore environmentally friendly.
EP-A-337,330 (Henkel) relates to a continuous process for
obtaining high bulk density detergent powder containing a
considerable amount of anionic and nonionic surfactant
material, said process comprising treating spray~dried
detergent material in a high-speed mixer under addition of
nonionic material, whereby the mean residence time in the
mixer is from 10-60 seconds. Alkyl sulphate is not mentioned
in this document.
EP-A-265,203 (Unilever) discloses li~uid surfactant com-
positions comprising an anionic and a nonionic surfactant.
This patent document also discloses the use of these com-
positions which comprises spraying these compositions onto a
solid particulate absorbent material. In this document alkyl
sulphate is explicitly mentioned as a possible anionic
surfactant which could effectively be applied in the surfac-
tant composition which is sprayed onto the absorbent
material.
The disadvantages of this route are the limited level of
active detergent material which can be dosed in this way and
the necessity that the particulate solid material to which
the liquid surfactant compositions are added, is an absor-
bent material. Furthermore, at increased levels of active
detergen~ material sticky detergent powder having
deteriorated powder properties could easily be produced in
this way.
It has also been proposed to make high active alkyl sulphate
conta;n;ng granules and to postdose these granules to an
essentially anionic-free concentrated base powder.
This method of producing high active alkyl sulphate con-
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taining detergent particles is, however, not attractive. Thereason is that it involves the separate drying of a hydrous
alkyl sulphate paste which requires considerable amounts of
energy, or, alternatively, as described in EP-A-402,112
(P&G), the incorporation into said high active detergent
particles of non-detergent active, less biodegradable ad-
ditives such as ethoxylated nonionic surfactant material
including at least 9 ethylene oxide groups.
It is an object of the present invention to pro~ide a
process for obtaining high bulk density granular detergent
compositions having a bulk density of at least 650 g/l and a
high active detergent content. It is also an object to
provide an environmentally friendly, low energy process for
the preparation of a high bulk density granular detergent
composition having a high active detergent content. It is a
further object to provide a process for obtaining a deter-
gent composition comprising alkyl sulphate as one of the
active detergent constituents.
We have now found that these and other objects can be
achieved if a liquid surfactant system comprising alkyl
sulphate and an alkoxylated nonionic surfactant is thorough-
ly mixed with particulate starting material during treatment
of this starting material in a high speed mixer/densifier.
DEFINITION OF THE INVENTION
In a first aspect, the present invention provides a process
for the preparation of a granular detergent composition
having a bulk density of at least 650 g/l, which comprises
treating a particulate starting material in a high speed
mixer/d~nsifier, characterised in that 0.1 to 50% by weight
as calculated on the granular detergent composition of a
liquid surfactant composition is mixed with the starting
material during this treating process, said surfactant com-
position comprising
(a) a sodium or potassium salt of an alkyl sulphate in an
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4 ~7292 (R)
amount from 5 to 60% by weight;
(b) an alkoxylated nonionic surfactant in an amount from 40
to 95% by weight,
(c) the balance being water in an amount from O to less than
20~ by weight.
In a second aspect, the invention provides a granular deter-
gent composition obtainable by this process and having a
particle porosity of less than 10%, preferably less than 5~.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is concerned with a process for the
preparation of a high bulk density powder having a high
active detergent content. An important characteristic of the
present process is that the detergent material remains
throughout the process in particulate or granular form.
Caking, balling an dough formation are avoided and the final
product does not require an additional step in which the
particle size is reduced.
During the process of the invention, a liquid surfactant
composition comprising alkyl sulphate and an
alkoxylated,preferably ethoxylated, nonionic surfactant is
thoroughly mixed with a particulate starting material in a
high-speed mixer/densifier. This is essentially an ag-
glomeration process, wherein the particulate starting
material is agglomerated by the liquid surfactant material,
resulting in detergent particles containing the particulate
starting material and a surfactant phase. Generally, this
surfactant phase acts as a binder for the particulate star-
ting material.
The advantage of this agglomeration process over a process
wherein the liquid surfactant composition is absorbed into
the particulate starting material is the fact that by ag-
glomerating much higher levels of liquid surfactant materialcan be incorporated in the detergent powder to be obtained,
while maintaining good powder properties.
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C7292 (R)
This agglomeration process can be carried out either as a
continuous or as a batch process. For economic reasons, it
is preferred to carry out the process of the invention con-
tinuously in a high-speed mixer/densifier, whereby the mean
residence time is from about 5-30 seconds.
Furthermore, it is important that the agglomeration process
is a well controlled, robust process resulting in detergent
powder with the desired particle size and with powder
properties which are comparable to those of detergent pow-
ders currently on the market . For obtaining detergent
powder with good powder properties, it has been found effec-
tive to add to the liquid surfactant composition one or more
components with such a composition that a significant vis-
cosity increase of the resulting total liquid composition isobtained. The addition of these components raises the
afore-mentioned viscosity generally by at least a factor 5,
pre~erably by at least a factor 10, a viscosity increase by
at least a factor 100 being most preferred (when measured in
a Haake viscometer at a shear rate between 0.1 and 20 S1).
As a result of this viscosity increase, the agglomeration
process appeared to be better controllable resulting in
better powder properties of the detergent material produced
in this way.
Examples of such viscosity raising components are water and,
particularly, fatty acid in combination with a
stoichiometric amount of alkaline material ( SUC]I as caustic
soda~ sufficient to neutralize the fatty acid which obvious-
ly results in the formation of soap.
For obtaining a very high bulk density powder, the detergentpowder obtained by the process of the invention may be
further treated in a second step in a moderate speed
granulator/densifier, whereby it is brought into or main-
tained in a deformable state, the mean residence time being
from 1-10 minutes, and thereafter in a third step in a
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drying and/or cooling apparatus, as described in EP-A-
367,339.
Pàrticulate startinq material
The process of the present invention is very flexible with
respect to the chemical composition of the particulate
starting material. This material comprises the compounds
usually found in detergent compositions such as builders and
detergent active materials. Phosphate containing as well as
zeolite containing compositions and compositions having
either high or low active detergent content may be used as
particulate starting material.
The detergency builder present in the starting material may
be any material capable of reducing the level of free cal-
cium ions in the wash liquor and will preferably provide the
composition with other beneficial properties such as the
generation of an alkaline Ph, the suspension of soil removed
from the fabric and the suspension of fabric softening clay
material. Examples of suitable builders include
precipitating builders such as the alkali metal carbonates,
bicarbonates, orthophosphates, sequestering builders such as
the alkali metal tripolyphosphates or nitrilotriacetates, or
ion exchange builders such as the amorphous alkali metal
alumino-silicates or the zeolites.
The process is also suitable for producing calcite/sodium
carbonate built detergent compositions.
Preferably, the builder material applied in the process of
the present invention consists of fine particles, desirably
with a particle size of less than 10 microns. When very high
bulk density detergent powder is prepared, part of the
builder material amounting to about 0.5-10% by weight as
calculated on the total granular composition is preferably
added during the second step when the detergent powder is
further treated in a moderate speed granulator/densifier, as
mentioned above. This process is disclosed in more detail by
EP-A-390,251.
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The level of builder material present in the starting
material is preferably such that its content as calculated
on the total granular composition is in the range from 10 to
70% by weight, most preferably from 30 to 60% by weight.
The detergent active material present in the starting
material may be selected from anionic, ampholytic, zwit-
terionic or nonionic detergent active materials or mixtures
thereof. Examples of suitable synthetic anionic detergent
compounds are sodium and potassium (C9-C2~ benzene sul-
phonates, particularly sodium linear secondary alkyl (C1D_
C~5) benzene sulphonates; and sodium alkyl glyceryl ether
sulphates, especially those ethers of the higher alcohols
derived from tallow or coconut oil and synthetic alcohols
derived from petroleum. Suitable nonionics which may be used
as constituents of the particulate starting material
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 com-
pounds are alkyl (C~-C22) phenol ethylene oxide condensatesl
generally having 5 to 25 EO, i.e. 5 to 25 units of ethylene
oxide per molecule, and the condensation products of
aliphatic (C8-C18) primary or secondary linear or branched
alcohols with ethylene oxide, generally 5 to 40 EO.
The level of detergent active material present in the star-
ting material may be in the range from 0 to 30% by weight.
This level is preferably less than 10% by weight, more
preferably less than 5~ by weight.
Other examples of materials which may be present in the
particulate starting material include fluorescers; polycar-
boxylate polymers; antiredeposition agents, such as carboxy
methyl cellulose; fatty acids; fillers, such as sodium
sulphate; clays such as kaolin or bentonite.
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The particulate starting material for the process of the
invention may be prepared by any suitable method, such as
spray-drying or dry-mixing. The components of the starting
material may also effectively be added separately to the
mixer/densifier. It is considered to be one of the ad~
vantages of the process of this invention that high bulk
density, high active detergent powders may be prepared from
dry-mixed or untreated starting materials, without the need
for expensive spray-drying e~uipment. On the other hand, it
may also be desirable that one or more of the ingredients of
the starting material are adjuncts of liquids onto solid
components, prepared by spray-drying, granulation or via in-
situ neutralization in a high-speed mixer.
The liquid surfactant system
The liquid surfactant composition which is mixed into the
particulate starting material in the mixer/densifier
comprises an anionic surfactant (which is a sodium or potas-
sium salt of an alkyl sulphate), an alkoxylated nonionic
surfactant and water. The amount of the liquid surfactant
composition which is applied is such that its content as
calculated on the total granular detergent obtained is in
the range from 0.1 to 50% by weight, preferably from 20 to
50 % by weight, more preferably from 25 to 50 % by weight.
Preferred surfactant compositions according to the invention
contain not more than 30% by weight of alkyl sulphate, and
as little water as possible. Compositions in which the
weight ratio of alkyl sulphate to alkoxylated nonionic
surfactant ranges from 0.125:1 to 0.5:1 are of especial
interest.
The nonionic surfactant is preferably an ethoxylated or
mixed ethoxy-propoxylated primary or secondary aliphatic
alcohol. Most preferred are ethoxylated primary alcohols,
especially C8-C15 primary alcohols ethoxylated with from 2 to
25 moles of ethylene oxide per mole of alcohol.
The anionic surfactant component o~ the liquid surfactant
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composition is a sodium or potassium alkyl sulphate salt.
Suitable alkyl sulphates are sodium C12-C18 alkyl sulphates,
especially the primary alkyl sulphates, although other alkyl
sulphates outside this carbon chain length range, and potas-
sium alkyl sulphates may also be used.
As described above, it is preferred to add to the liquid
surfactant composition one or more components with such a
composition, that a significant viscosity increase of the
resulting total liquid composition is obtained. The total
level of these components may be as high as 20% by weight as
calculated on the total liquid composition, said level being
preferably in a range of from 2 to 10% by weight.
The densification process and the final densified powder
It was found to be essential for obtaining an optimal den-
sification to subject the particulate starting material to a
three-step densification process, as extensively disclosed
in EP-A-367,339.
The densified powder thus obtained has preferably a particle
porosity of less than 10%, more preferably less than 5%.
This powder may be used as a dPtergent powder in its own
right. Generally, however, various additional ingredients
may be added to give a more efficient product. The amount of
post-dosed material will generally range from about 10 to
200~ by weight, calculated on the weight of the densified
powder.
Examples of materials which may be postdosed to the den-
sified powder include enzymes, bleaches, bleach precursors,
bleach stabilizers, lather suppressors, perfumes and dyes.
Liquid or pasty ingredients may conveniently be absorbed on
to solid porous particles, generally inorganic, which may
then be postdosed to the densified powder obtained by the
process of the invention~
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C7292 (R)
The process of the invention is further illustrated by the
following non-limitin~ Examples, in which parts and per-
centages are by weight unless otherwise indicated. In the
Examples the following abbreviations are used:
PAS : Primary alkyl sulphate, sodium salt of
C1z-C18 primary alkyl sulphate
NI : Clz-C14 Nonionic surfactant (ethoxylated
alcohol containing on average 5 E0 groups,
ex Kolb
Carbonate : Sodium carbonate, ex AKZO
Silicate : Sodium alkaline silicate
Zeolite : Zeolite A4 ~Wessalith [trade mark]),ex
Degussa.
15 Soap : Sodium salt o~ C16-C22 fatty acid, ex
Unichema
Polymer : Sokalan CP5/7 [trademark] type of polymer,
ex BASF
Sulphate : Sodium sulphate.
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11 C7292 (R)
COMPARATIVE EXAMPLES A B
The following zeolite-containing detergent granules were
prepared by spray-drying aqueous slurries. The compositions
(in % by weight) of the porous granules thus obtained are
shown in Table 1.
TABLE 1
10 Examples R B
Zeolite 4A 76.7
Sulphate 8.3 71.2
Carbonate - 25.4
Polymer - 1.7
15 Moisture 15.0 1.7
100.0 100.0
The granules were free flowing and had a mean particle size
of ca. 300 microns.
The granules were fed directly into a continuous low speed
mixer, The rotational speed was in both cases about 30 rpm.
The mean residence time of the granules in the mixer was
approximately 2 minutes.
In this apparatus, a mixture of 20 wt% PAS and 80 wt% non-
ionic was sprayed onto these granules until the granule~
were almost saturated. At this stage, the free-flowiness of
the granular detergent material started to decline.
The following compositions and physical properties o~ the
resulting detergent granules were obtained:
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TABLE 2
Examples A B
Compositions:
Zeolite 4A 57.6
5 Sulphate 6.2 53.4
Carbonate - 19.0
Polymer - 1.3
Moisture 11.2 1.3
PAS 5.0 5.0
10 Nonionic 3E0 20.0 20.0
100. 0 100. 0
Physical properties:
Bulk density (g/l)830 690
15 Dynamic Flow Rate (ml/s) 85 103
Particle size (microns) 320 270
It can be seen that the r~ level of detergent active
material which can be sprayed-on in view of the obtainable
powder properties, is 25 % by weight. Furthermore, it can be
derived by comparing the particle size of the detergent
granules before and after treatment in the mixer, that no
agglomeration has occurred.
EXAMPLE 1
Several detergent componen~s of which the solid components
have a particle size lower than 200 microns, were fed into a
high speed batch mixer/densifier. The mean residence time of
the granular detergent mixture in the batch mixer/densifier
was approximately 3 minutes.
The composition of the granular detergent powder leaving the
batch mixer/densifier is given in Table 3.
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13 C7292 (R)
TABLE 3
Example
Zeolite 4A 43.7
5 Carbonate 16.2
PAS 8.3
Nonionic 19.5
Water 12.3
_____
100. 0
The thus obtained granular detergent compositions had good
powder properties (DFR was 101 ml/s) and a bulk density of
about 770 g/l .
It can be seen that the level of the active detergent
material present in the detergent powder obtained (i.e.:
27.8 % by weight) is higher than the levels obtained in the
comparative examples.
EXAMPLES 2,3
Several detergent components of which the solid materials
have a particle size lower than 200 microns, were fed into a
Lodige (Trade Mark) Recycler CB30, a continuous high speed
mixer/densifier. The rotational speed was 1600 rpm. The
mean residence time of the granular mixtures in the Lodige
~ecycler was approximately 10 seconds.
The compositions of the granular material leaving the Lodige
Recycler are given in Table 4.
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14 C7292 (R)
TABLE ~
Examples 2 3
Compositions:
Zeolite 4A 52.6 47.1
Carbonate - 8.0
PAS 8.5 8.3
NI 19.4 18.8
Soap 2.9 2.9
10 Water 16.4 14.9
____ _____
100.0 100.0
The thus obtained granular detergent compositions had good
powder properties, a bulk density of about 700 g/l and a
particle size of 500-600 microns.
It can be seen that the levels of the active detergent
material present in the detergent powders obtained are
respectively 30.8 % by weight and 30.0 % by weight. These
active detergent levels are much higher than the levels
obtained in the comparative examples and also higher than
the active detergent level obtained in example 2. This is
the result of incorporating into the liquid surfactant com-
position fed into the Recycler, fatty acid in combination
with a stoichiometric amount of caustic soda, as viscosity
raising material. It is clear that during the
mixing/densifying process soap is formed from this material.
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