Note: Descriptions are shown in the official language in which they were submitted.
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C 7212 (R)
PROCESS FOR PREP~RING
HIGH BULK DENSITY DETERGENT POWDERS CONTAINING CLAY
l~NlCAL FIELD
The present invention relates t~ a process for preparing a
granular detergent composition or componenk having a high
bulk density and good powder pr~perties. ~ore in particular,
it relates to a process for the preparation o~ a granular
detergent composition having good powder dissolution
properties and a good softening in the wash performance.
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 550 g/l
and above.
Generally spe~ki ng, 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 that 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 ca~e of a spray-
drying process. Both factors can only be vaxied within a
limited range. For exampIe, the bulk density of a dry-mixed
powder can be increased by increasing its content o~
relatively dense sodium sulphate, but the latter does not
contribute to the detergency of the powder, so that its
overall properties as a w~hing powder will generally be
adversely affected.
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Therefore, a substantial increase in bulk density can only be
achieved by additional processinc~ steps which lead to
densification of the detergent powders. There are several
processes known in the art leading to such densification.
Particular attention has thereby been paid to the
densification of spray-dried powclers by post-tower treatment.
For instance, the Japanese patent application 61 069897 (Kao), published
April 10,1986 discloses a process in which ia spray-dried delergent
powder containing a high level of' anionic surfactant and a
low level of builder ~zeolite) is, subjected successively to a
pulverizing and a granulating tre!atment in a high-speed
mixer/granulator. The granulation is carried out in the
presence of an "agent for improving surface properties" and
optionally a binder.
It is also known to incorporate smectite clays into
detergent powders for obtaining a fabric-softening effect.
Furthermore, the British patent specification 2,063,289
(Unilever), published June 2, 1981 discloses that detergent powders
containing less than 20% by weight of a phosphate salt and more than
20% by weight of anionic surfactant may be rendered crisp and free-
flowing by addition of 1-15% of bentonite or kaolin to the
crutcher slurry.
One of the inherent problems of detergent compositions
having a high bulk density is, however, that their
dissolving behaviour is usually reduced relative to a
corresponding composition having a lower bulk density. This
may be attributed to the lower particle porosity of the
powder.
We have now surprisingly found th,at the admixture of a
swelling clay to a particulate detergent starting material
followed by treating the mixture in a high-speed
mixer/granulator having both a stirring action and a cutting
action provides a high bulk density detergent powder having
much better dissolution propertie~s and softening properties
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than when the clay is admixed to the crutcher slurry followed
by spray-drying.
D~ lON OF THE lNVhN'l'lON
In a ~irst aspect, the present invention provides a process
for the preparation of a granular detergent composition or
component having a ~ulk density o~ at least 550 g/l, which
comprises the steps of adding up to 35% by weight of a
swellin~ clay to a particulate starting material comprising:
(a) from 10 to 70% by weight of non-soap detergent
active materlal, and
~ b) at least 10% by weight o~ water-soluble crystalline
inorganic salts, including sodium tripolyphosphate and/or
sodium carbonate,
thè weight ratio of (a) to ~b) being at most 2.5,
and treating the mixture in a high speed mixer/granulator
having both a stirring action and a cutting action.
DET~ILED DES~RIPTION OF THE lNv~:hllON
In the process of the present invention, a particulate
starting material is admixed with a swelling clay and
treated in a high-speed mixer/granulator.
The ~tarting material for the process according to the
invention comprises (a3 from 10 to 70% by weight of non-soap
detergent active material, and (b) at least 15% by weight of
water-soluble crystalline inorganic salts, including sodium
tripolyphosphate and/or sodium carbonate, the weight ratio of
(a~ to (b) being at most 2~5. Preferably the ratio of (a) to
~b) is from 0.1 to 2.0, even mor~ preferably from 0.1 to 0.4.
The starting material comprises the compounds usually found
in detergent compositions such as deter~ent active
materials, builders, and so forth, all well known in th~ art.
The detergent active material may be selected ~rom non-soap
anionic, ampholytic, zwitterionic or nonionic detergent
active materials or mixtures thereo~. Particularly pre~erred
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are all anionic or mixtures with nonionic deteryent active
materials such as a mixtur~ of an alkali metal salt of an
alkyl benzene sulphonate together with an alkoxylated
alcohol.
The preferred detergent compounds wh~ch can be used are
synthetic anionic and nonionic compounds. The former are
usually water-soluble;alkali metal salts of organic
sulphates and sulphonates having alkyl radicals containing
lQ ~rom about 8 to about 22 earbon atoms, the term alkyl being
used to include the alkyl portion of higher acyl radicals.
Examples of suitable synthetic anionic detergent compounds
are sodium and potassium alkyl sulphates, especially those
obt~in~ by sulphating hiyher (C8-C18) alcohols, produced for
example from tallow or coconut oil, sodium and potassium
alkyl (Cg-C20) ~enzene sulphonates, particularly sodium
linear secondary alkyl ~C10-Cl5) benzene sulphonates; sodium
alkyl glyceryl ether sulphates, especially those ethers of
the higher alcohols derived from tallow or coconut oil and
synthetic alcohols derived from petroleum; sodium coconut oil
~atty monoglyceride sulphates and sulphonates; sodium and
potassium salts o~ sulphuric acid esters of higher ~C8-C18)
~atty ~lcohol-alkylene oxide, particularly ethylene oxide,
reaction products; the reaction products o~ ~akty acids such
as coconut fatty acids esterified with isethionic aaid and
neutralized with sodium hydroxide; sodium and potassium
salts of ~atty acid amides of methyl taurine; alkane
monosulphonates such as those derived by reacting alpha
olefins (C8-C2~ with sodium bisulphite and those derived
from reacting paraffins with S02 and Cl2 and then hydrolysing
with a base to produce a random sulphonate; and olefin
sulphonates, whioh term is used to describe the material made
~y reacting ole~ins, particularly C10-C20 alpha-olefins, with
S03 and then neutralizing and hydrolysing the reaction
product. The preferred anionic detergent compounds are sodium
~Cll-C15) alkyl benzene sulphonates and sodium (C16-C18)
alkyl sulphatesO
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Suitable nonionic detergent compounds which may be used
include, in particular, ~he 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
coompounds are alkyl (C6-C22) phenols-ethylene oxida
con~n~Ates, generally 5 to 2S EO, i.e. 5 to 25 units of
ethylene oxide per molecule, the conden~ation products of
aliphatic (C8-C18) primary or secondary linear or branched
alcohols with ethylene oxide, generally 5 to 40 EO, and
products made by condensation o~ ethylene oxide with the
reaction products of propylene oxide and ethylenediamine.
Other so-called nonionic detergent compounds include long-
chain tertiary amine oxides, long-chain tertiary phosphine
oxides and dialkyl sulphoxides.
Mixtures of detergent compounds, for example, mixed anionic
or mixed anionic and nonionic compounds, may be used in the
detergent compositions, particularly in the latter case to
provide controlled low sudsing properties. ~his is beneficial
for compositions intended for use in suds-intolerant
automatic w~in~ machines.
Amounts of amphoteric or zwitterionic detergent compounds can
also be used in ~he compositions of the invention but this in
not normally desired owing to their relatively high cost. If
any amphoteric or zwitterionic detergent compounds are used,
it is generally in small amounts in compositions ~ased on the
much more commonly used synthetic anionic and/or nonionic
detergent compounds.
The detergency builder may be any material capable of
reducing the level of free calcium ions in the wa~h liquor
and will preferably provide the composition with other
beneficial properties such as the generation of an alkaline
pH, the suspension o~ soil removed ~rom the fabric and the
s~lcpencîon of the fabric-softening clay material. The level
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of the det~rgency builder may be ~rom 10% to 70% by weight,
most preferably from 25% to 50% by weight.
Examples of detergency builders include precipitating
builders such as the alkali metal carbonates, bicarbonates,
orthophosphates, seguestering builders such as the alkali
metal tripolyphosphates or nitrilotriacetates, or ion
exchange builders such as the amorphous alkali metal
aluminosilicates or the zeolites.
The starting material may be prepared by any suitable
method, such as spray-drying or dry mixing. A suitable
particulate material may also be prepared by a dry
neutralization process in which a liquid acid anionic
sur~actant precursor is reacted with a solid alkaline
inorganic component, such as carbonate~ Such dry
neutralization processes are for example disclosed in the
British Patents 2 166 452 (Kao~, 1 404 317 ~Bell~ or l 369
269 (Colgate).
In the process of the invention, the starting material is fed
into a high-speed mixer/granulator having both a stirring
action and a cutting action. The preferred type of high speed
mixer/granulator for use in the process of the invention is
bowl-shaped and has a substantially vertical stirrer axis. It
is especially preferred when the mixer/granulator
additionally has cutter mean~ positioned on a side wall~
These stirrer and cutter means may advantageou~ly be operated
~ndependently o~ one another, and at separately variable
spee~. It is also preferred if the vessel of the mixer is
equipped with a jacket ~or cooling or heating purposes, If
n~ce~.sAry, cooling may be effect~d by means o~ a cryogenic
un1t~
3S Example~ of preferred mixers are the Fukae ~Trade Mark) FS-G
s ries manufactured by Fukae Powtech Kogyo Co., Japan, e.g.
the Fuk~e FS30. This apparatus is ~s~entially in the form of
a ~owl-shaped vessel accessible via a top port, provided near
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its base with a stirrer having a substantially v~rtical axis,
and a cutter on a side wall.
~ similar mixer manufactured in India is the Sapphire (Trade
Mark) RMG series of rapid mixer/granulators, which, like the
Fukae mixer, is available in a range of different sizes. This
apparatus is essentially in the form of a bowl-shaped vessel
rai~ed up pneumatically to seal ayainst a ~ixed lid~ A three-
bladed stirrer and a four-bladed shutt~r share a single
substantially vertical axis of rotation mounted on the lid.
The stirrer and cutter may be operated independently of one
another, the stirrer at speeds of 75 rpm or 150 rpm, and the
cutter at speeds o~ 1440 xpm or 2880 rpm. The vessel can be
~itted with a water jacket which may be used to cool or heat
the content of the vessel.
The Sapphire RMG-100 mixer, which is suitable Por handling a
60 kg batch of detergent powder, has a bowl o~ about 1 meter
diameter and 0O3 meters deep; the working capacity is 200
liters. The stirrer blades are of 1 meter diameter and the
cutter blades are of 0.1 met~r diameter.
Other similar mixers found to be suitable for use in the
process of the invention include th~ Diosna (Trade Mark) V
series ex Dierks and Sohne, Germany, and the Pharma Matrix
~Trade ~ark) ex T.~. Fielder Ltd, England. Other mixers
b~lieved to be suitable for use in the procass of ~he
invention are the Fuji (Trade Mark) VG C series ex Fuji
Sangyo Co., Japan; and the Roto (Trade Mark) ex Zanche~ta
Co. srl, Italy.
~et another mixer found to be suita~le for use in the
process of the invention is the Lodige (Trade Mark) FM
series batch mixer ex Morton Machine Co. Ltd, Scotland. l~his
35 diff~3rs from the mixers mentioned above in that its stirrer
has a horizontal axis.
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These apparatus (which may be continuous or batch fed)
essentially consist o~ a large, static hollow cylinder and a
rotating shaft in the middle. The shaft has several different
types of blades mounted thereon. The rotation speed, which
may be variable, will depend on the degree of densification
and the particle size desired. The blades on the sha~t
provide a thorough mixing action of the solids and the
liquids which may be admixed at this stage. The mean
residence time is somewhat dependent on the rotational speed
of the shaft and the position of the blades with continuous
plant. High-~peed cutter blade5, independently driven, may
also be incorporated in this type of mixer operating
normally to the main agi~ator, e.g. Lodige (Trade Mark) K~
series or Drais (Trade Mark) KT series.
The use of the high-speed mixer/granulator is essential to
obtain granulation and den~ification. Before the granulation
of the starting material takes place, a pretreatment may be
carried out, for example a pulverization step. Whether this
is nece~s~ry is dependent, amongst other things~ on the
method of preparing of the starting material, its particle
size and moisture content. For example, ~pray-dried powders
are more likely to require a pulverization pretreatment than
dry-mixed powders. In order to carry out the pulverization a
suitable stirringtcutting regime must be chosen which will
generally be characterized by relatively high speeds for both
the stirrer and the cutter and a relatively short residence
time, for example of 1 to 4 minutes.
The granulation step is similarly carried out by running the
stirrer and the cutter at a relatively high speed, but here
the presence of a liquid binder is necessary. The preferred
binder is water~ The amount of b~nder added should preferably
not exceed about 6 % by weight, because higher levels may
adversely af~ect the flow properties o~ the final product.
The liquid binder may be added be~ore or during granulation,
preferably by spraying it in while the apparatus is running.
The starting material may also already con~ain suf~icient
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moisturef such that addition o~ ~urther liquid binder is not
necassary. In this case, pulverization and granulation may be
carried out as a single operation.
Aecording to a preferred embodiment of the invention, the
granulation is carried out at a temperature above ambient,
such as a temperature above 30 or 45 ~C. For exampla, a
spray-dried detergent;base powder leaving ~he ~ower at a
temperature of approximately 45~C or above ~ay be fed
directly into the process of the present invention. Of
course, the spray-dried powder may be cooled first, e.g. by
means of an airlift.
In the process of the present invention, a swelling clay is
added to the mixer/granulator in an amount of up to 35% by
weight of the starting material. ~he swelling clay material
may be any such material capable of providing a fabric-
softening benefit. Usually the~e materials will be of natural
origin cont~ining a three-layer swellable smectite clay.
Preferably, the clay is o~ the calcium and/or sodium
montmorillonite type.
The effectivenes~ of a clay-con~ ;ng material as a fabric
so~tener will depend amon~st other things on the level of
smectite clay. Impurities such as calcite, feldspar and
silica will oft~n be present. Relatively impure clays can be
used, provided that such impurities are tolerable in the
composition.
The level of the fabric-softening clay material in the
composition should be sufficient to proYide a softening
benefit. Amounts from 1.5~ to 35~ by weight, pref~rably from
4% to 20% by weight, calculated on the basis of the clay
mineral E~ se were found to be ef~ectiveO
In addition to the detergent active material, the detergency
builder and the clay-conta;ning material~ the compositions
according to the invention optionally may contain other
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ingredients usually found in detergent compositions, in the
amounts in which such additives are normally employed in
fabric-washing detergent compositions. Examples sf such
additives include the lather boosters such as alkanolamides,
particularly the monoethanolamides derived from palm kernel
fatty a~ids and coconut ~atty acids, lather depressants,
oxygen releasing bleaching agents such a5 sodium perborate
and sodium percarbonate, peracid bleach precursors, chlorine
releasing bleaching agents such as trichloroisocyanuric acid,
fillers such as sodium sulphate, and, usually present in very
minor amounts, fluorescent agents, perfumes, enzymes such as
proteases, lipases and amylase~, germicides and colorants~
The process of the pre~ent invention enables th~ preparation
of detergent compositions having a high bulk density o~ at
least 550 g/l. It is a surprising advantage of the process of
the invention that the bulk density of thP obtained powders
is higher than when the clay is a~ ;~e~ to the crutcher
slurry prior to spray-drying of the starting material.
2~
A further advantage of the process of the invention is that
the so~tening action of the final detergent powder is
improved relative to when the clay is admixed to the
crutch~r slurry followed by spray drying. Thi~ e~fect of the
present process can be established by methods used for
assessment of softening delivery as they have previously been
described in the art.
It is a further advantage of the process of the present
invention that the storage stability of the final detergent
powder is improved. This can be e~tablished by means of the
Uncon~ined Compressibility Test (UCT). In this kest the
detergen~ powder is placed in a cylinder having a diameter of
13 cm and a height of 15 cm. Subsequently, a weight o~ 10 kg
is placed on top of the powder. After 5 minutes the weight is
removed and the walls of the cylinder are taken away. Then an
increasing load is placed on top o~ the column o~ compressed
detergent powder and the weight (in kg) is determine~ at
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which the column disintegrates. This value is a function of
the stickiness of the detergent powder and proved to be a
good measure for the storage stability.
The invention will now ~ ~urther illustrated by the
following non-li~iting examples, in which parts and
percentages are by weiqht unless otherwise indicated.
ln the Exampl~s which follow, the following abbreviations are
used fox the materials employed:
LAS : Linear ~lkyl benzene sulphonate
STP : Sodium tripolyphosphate
Silicate : Sodium alkaline silicate
Carbonate : Sodium carbonate
Sulphate : Sodium sulphate
Clay : Calcium or sodium montmorillonite
EXAMPLES 1~3
The following deterge~t powders were prepared by spray-
drying aqueous slurries. The compositions (in % by weight) of
the powders thus obtained are given bPlow.
TABLE 1
Example 1 2 3
LAS 31 34 34
total NSD ~a) 31 34 34
STP 41 46 46
Silicate 5 6 6
Carbonate 8 - 9
Sulpha~e 10 - -
total 5alts (b) 64 52 61
35 Clay 10
Water 5 4 5
Ratio (a):(b) 0.48 0.65 0.~6
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The compocition of Example 2 ~ontained a Ca-clay (Prassa ex
Colin Stewart Minerals, U.X.) which was added to the
crutcher slurry and spray-dried. Sodium carbonate was in
this case omitted from the sluxry to maintain it at a
sufficiently low ViSC05ity to aid in spray-drying. Example 3
wa a spray-dried powder without clay but i~cluding
carbonate. ~ .
The compositions of Examples 2 and 3 had a higher percentage
by weight o~ LAS, STP and silicate than the composition of
Example 1 to allow for dilution on post~dosing of either
carbonate or clay, respectively, during the densification/
gxanulation step.
The powders were added (10 kg - Example 1; 9.2 kg - Example
2; 9.0 kg Example 3) to a Fukae FS-30 high-speed mixer/
gra~ulator. The powders were pulverized for 2 minutes at 70~C
with a stirrer rotation of 300 rpm and a cutter rotatio~ of
3000 rpm. Subsequently, 0.8 kg sodium carbonata and 1.0 kg
Ca~¢lay wer~ added to the densified powders of Examples 2 and
3. Gxanulation was then e~fected by addition of about 150 ml
water over a time period of one minute at a ~tirrer rotation
speed of 275 rpm and a cutter rotation speed of 3000 rpm. The
resulting powd~rs were sieved for oversize (>1700 ~m~. The
composition ~in % by weight) of th~ powders was as follows:
TABL~ 2
Exam~les 1 2 3
LAS 31 31 31
STP 41 41 41
Silicate 5 5 5
Carbonate 8 8 8
Clay - 10 lO
35 Sulphate 10 - -
Wat~r 5 5 5
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The powdar properties of the sieved ma~erials are given ~elow
in Ta~le 3.
TABLE 3
Examples 1 2 3
Bulk Density (g/l) 965 738 980
Dynamic ~low Rate
(c~3/ ) 149 145 150
UCT ~2.9 8.2 2.9
Particle Si2e (~m) 870 699 856
N 2.33 1.45 2.70
wherein UCT is ~ unconfined compressibility and N is the
distribution o~ mean particle size.
The dissolution propert.ies of the concentrated powders
described in Tables 2 and 3 and the respective undensified
control powders were measured by standard conductometric
teçhniques. A sieved fraction of the powder samples ( 500 +
425 ~m) was used to ~nsure that the dissolution behaviour o~
a c- ~-rable particle size range was compared. In order to
compensate for inevitable differences in powder properties
such as bulk density, etc., the rate of dissolution was
compared to the ratio SA~/SAb where ~A is the sur~ace area
per unit weight of a given granulated powder (g3 or
l~n~en~ified base (b)~ The ratio SAg/SAb therefore represents
a ~cale of concentration. The surface area per kg (SAI ~or a
specific powder was calculated (assuming spherical particles)
from the formula:
SA = 6 /(BD x dm)
where BD stands for bulk density and dm for mean diam~ter
~m)-
The results of the dissolution experiments are ~iven in
Table 4 anq are graphically 5hown in Figure 1. In the Figure,
a linear relationship i~ observed between the dissolutionrate and the ratio SAg/SAb for the concentrated powders from
Examples 1 and 2 and the unconcentr~ted base powder of
Example 1. This indicates that the dissolution rate is a
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function of the surface area available for mass transfer. The
Figure shows for Example 3, whereby the clay was post-dosed
prior to granulation, that the dissolution rate is higher
than expected for a comparable powder. This illustrates that
S the clay is contributing to improved dissolution properties
TABLE 4
Examples ~ 1 2 3
Dissolution Rate (s-l~ ~.92 2.54 2.85
S ~ /SAb 0.23 0.47 0.31
~ Softness o 75.3 99.5
Also shown in Table 4 are the softening pxoperties of the
various compositions. The softening delivery o~ concentrated
powders of Examples 1-3 was measured on terry toweling
fabric. Tergo~ometer washes at a powder concen~ration of 3.6
g/l were performed for 30 minutes with a cloth to liquor
weight ratio o~ 1:20. The relative softening delivery was
measured according to standard practice by a trained panel of
ten people, as described in the art.
The superior ~oftening delivery of the composition o~
Example 3 according to the invention (in which ~he clay was
post-dosed during granulation) may'also be illustrated by a
further comparative experiment whereby the clay powder was
added to Example 1 during the wash at concentrations
equivalent to Example 3.
When the clay was added separately to the wash using the
composition of Example 1, a softness value of 9705 was
found. Comparison of this value with the softness value of
99.5 found for Example 3 indicates that essentially the full
softenin~ performanc~ is delivered by the process of the
invention. However, when the clay was added to the crutcher
slurry prior to spray drying as in Example 2, a much lower
softness value of 75.3 was found.
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