Note: Descriptions are shown in the official language in which they were submitted.
-1- 2040050
A PROCESS FOR PREPARING GRANULES FOR DETERGENT
COMPOSITIONS
This invention relates to a process for preparing
granules for incorporation into detergent composltions
and, ln particular, to a process for preparing granules
comprising a zeolite; and to detergent composition
containing the granules produced by the process.
It is generally desirable that the components of a
detergent composition should be in granule form becau~e
the bulk density of a granular composition is hlgher
than that of a finely divided powder with the result
that a given weight of the composition can be packed
into a smaller container when the composition is
granular than when it is in powder form.
The granules should be free flowing and should
also be resistant to crushing and abrasion so that they
can withstand handling and transportation in
contalners. They should also be relatively white in
colour and will typically have sizes in the range of
~0 from 0.75mm to 2.0mm.
Zeolite, which is a cation exchanging
aluminosilicate, is included in detergent compositions
to perform the function of a builder or scavenger of
metal cations, especially calcium and magnesium ions,
from the washing water, which ions, if allowed to
remain in solution, would impair the effectiveness of
the surfactant present in the detergent composition.
Until recent years the function of the builder in
detergent compositions has been fulfilled by water-
soluble condensed phosphate salts, for example sodiumhexametaphosphates, but the discharge of large
quantities of phosphates into rivers is damaging to the
environment, and there is therefore a growing trend
towards replacing phosphate builders with zeolites. A
zeolite with a particularly advantageous cation
exchange capacity is known as zeolite A or zeolite 4A,
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and it is this zeolite which is commonly found in
detergent compositlons. Zeolite A is generally
available in commerce in the form of a fine powder
having particles of size of the order of a few microns,
but it has hitherto been found difficult to form the
zeolite into granules of suitable size which are
sufficiently coherent to withstand handling and
transportation in packages without the use of
additional blnding materials which add to the expense
and are undesirable in the complete detergent
compositions. An attempt to overcome this problem is
disclosed in EP-A-0279040 in which the detergent
builder is prepared by spray-drying a feed suspension
containing the zeolite and bentonite.
A smectite clay, for example bentonite, is often
included in a detergent composition. The clay may be
included on account of its fabric softening properties,
or as a stabilising agent for the detergent
compositlon, but the use of the clay brings with it the
disadvantage that the clay i8 somewhat dark in colour
and therefore imparts an undeslrable dark colouration
to the compositlon containing lt.
According to one aspect of the invention there is
provided a process for preparing a granule for
incorporation ln a detergent composition, which process
comprises the steps of
(a) tumbling together in a rotating pan a finely
divlded, particulate smectite clay and a finely
divided, particulate zeolite in a weight ratio of
from 1:9 to 9:1 whilst sufficient water is added
slowly to the resultant mixture to bind the
particles together to form granules of a mixture
of said smectite clay and said zeolite; and
(b) drying the resultant granules to reduce the
water content to not more than 20~ of the total
weight of the granules.
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The process of the invention preferably includes
the further step of:
(c) sieving the dried granules to yield a product
comprising granules having sizes in ~he range from
0.75mm to 2.Omm.
Granules prepared in accordance with the invention
are solid and will comprlse the smectlte clay and -
zeolite in a weight ratio of from 1:9 to 9:1.
The present invention also provides a detergent
lQ composition which includes granules prepared in
accordance with the process of the present invention.
The detergent composition will contain a surfactant and
optionally other ingredients in amounts known Der se.
The smectite clay may be montmorillonite,
saponite, hectorite, nontronite or beidellite, but is
most conveniently a bentonite clay which is a naturally
occurring clay of volcanic origins consisting
predominantly of montmorillonite.
The weight ratio of zeollte to smectite clay
charged to the pan may preferably be in the range of
from 2:8 to 8:2, more preferably 3:7 to 7:3, especially
7:3.
The smectite clay in its initial, finely divided,
particulate form preferably has a particle size
distribution such that substantially all of it passes
through a No. 60 mesh British Standard sieve (nominal
aperture O.250mm).
The zeolite is most advantageously a synthetic
zeolite such as zeolite A which has a chemical
composition corresponding to the approximate formula:-
1.0+0.2 Na20. Al203. 1.9+0.1 SiO2, 0-5.1H20
and an apparent pore width of approximately 4 Angstrom
units. Preferably, the initlal~ finely divided,
particulate ~eolite has a particle size distribution
such that lt consists predominantly of particles having
sizes in the range from 1 to 10 microns.
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The granules of the present inven~ion may also
incorporate minor proportions of other ingredients, and
up to 20% of the total weight of the granules may be
water (as residual water derived either from the water
binder added or moisture present in either of the clay
or zeolite components). No additional liquid binder
material is essential to form the granules; i.e. t~-
water used in step (a) is preferably the sole liquid
binder employed. The size of the final granules, after
sieving is preferably from 0.75mm to 2.Omm, most
preferably from O.85mm to 1.7mm. Also, the granulPs
preferably should not contain more than about 7% by
weight of particles smaller than 0.15mm.
In the process of the invention, the sme~tite clay
and the zeolite are preferably tumbled together in a
pan granulator. The Eirich pan granulator is an
example of a particularly suitable device. The
quantities of zeolite and smectite clay added to the
pan are those necessary to give the desired proportions
of each component in the resultant granules and this
will normally mean that from 10 to 90% by weight of
smectite clay and from 90 to 10% by weight of zeolite
are added, based on the total weight of smectite clay
and zeolite. The water is preferably added in the form
of a fine spray and in an amount such that it
constitutes preferably at least 10~ and preferably no
more than 40~ of the total weight of the granules
formed in step (a) of the process. Thus, for every 100
parts by weight of smectite clay/zeolite mixture
charged to the pan, from about 11 to about 67 parts by
weight of water may be employed.
The granules may conveniently be thermally dried
in step (b) in, for example, a fluidised bed dryer.
The process of the present invention provides
granules which are sufficiently coherent to withstand
handling and transportation in containers without the
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use of an additional binding materlal. It is bslleved
that the smectite clay itself acts as a binder which
makes it possible to form coherent granules containlng
a zeollte. The granules of the invention also have the
advantages of being relatively light in colour compared
wlth the smectite clay on its own.
~ typical, conventional detergent composition ~
containQ the following ingredients normally in amounts
ln the ranges given below:-
Inaredient % bY weiaht
Anionic surfactant 1 - 30
Nonionic surfactant 1 - 17
Suds controlling agent O - 0.6
Zeolite A 1 - 45
Sodium carbonate 10 - 35
Bleaching agent O - 5
Smectite clay 1 - 5
Cellulose ether O - 0.5
Enzymes O - 2.5
Optlcal brightening agent 0.05 - 0.25
Sodium silicate O -25
Formulation aid O - 1
Water to 100
With the present inventlon, at least part of the
Zeolite A and at least part of the smectite clay in the
foregoing composition can be replaced by granules in
accordance with the present invention.
The anionic surfactant may be, for example, an
alkyl benzene sulphonate or a fatty alcohol ether
sulphate.
The nonionlc surfactant may be, for example, an
alkyl polyethyleneglycol ether or a nonylphenol
polyethyleneglycol ether.
The suds controlling agent may be, for example, a
soap, a silicone oil or a paraffin.
The bleaching agent may be, for example, sodium
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perborate or sodlum percarbonate.
The invention is illustrated by the following
Example.
EXAMPLE
A bentonite clay having a particle size
distribution such that 99% by weight passed a No. 60
mesh British Standard sieve (nominal aperture 0.25~mm)
and 85% by weight passed a No. 200 mesh 8ritish
Standard sieve (nominal aperture 0.076mm) and a zeolite
A powder having a particle size distribution such that
70% by weight consisted of particles in the range from
2 to 6 microns were loaded into the pan of an Eirich
granulator in the proportions 70% by weight of zeolite
and 30% by welght of bentonite. The pan was set in
motion at a speed of 46 rpm and the agitator at a speed
of 1429m.min~~ and the clay and zeolite were mixed in a
substantially dry state for 15 seconds. During the
next lO seconds, with the pan and agitator rotating at
the same speeds, sufficient water was sprayed on to the
mlxture of clay and zeolite to give a final water
content of the granules of 33~ by weight. Finally the
moist granules were tumbled in the pan of the
granulator for a further 75 seconds at the same speed
settings for the pan and for the agitator.
The moist granules were then dried in a fluidised
bed dryer at a temperature of 80C for a time
sufficient to reduce the water content of the granules
to 14* by weight. The granules were then screened on a
sieve having a nominal aperture size of 1.2mm and the
granules passing through the sieve were retained as the
product. The starting materials and the product
granules were tested for bulk density and for
reflectance to violet light of wavelength 457nm and the
results obtained are set forth in the followlng Table:
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TABI,E
Bulk % reflectance to light
density of 457nm wavelenth
(q.cm~3l ~owder
qranule
Bentonite 0.70 76.0 53.0
Zeol$te A 0. 50 94.5
Bentonite/zeollte A
granule 0.73 - 77.1
The granules were found to be sufficiently
coherent to be able to withstand bulk handling and
transportation in containers, and the reflectance to
violet light of 457nm wavelength of 77.1% was
sufficiently high to give the granules an acceptably
light colour such that they would not impair the white
appearance of a detergent composition in which they
were incorporated.
