Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR PREPARING GRANULAR DETERGENT
COMPOSITIONS
FIELD OF THE INVENTION
The present invention relates to a process for preparing a
granular detergent composition with good. powder properties.
More particularly, the invention is directed to a process in
which a liquid binder is contacted with a solid particulate
material in a gas fluidisation granulator under controlled
process conditions.
BACKGROUND OF THE INVENTION
In recent years, there has been much interest in the
production of detergent products by processes which employ
mainly mixing, without the use of spray-drying. In this
type of process, the various components are dry-mixed and
optionally granulated with a liquid binder. Liquid binders
typically used in such granulation processes are anionic
surfactants, acid precursors of anionic surfactants,
nonionic surfactants, or any mixture thereof.
If substantially mechanical mixing is employed in the
granulation process, then granular detergent products having
a high bulk density, typically greater than 700 or 800 g/1,
tend to be produced. If however the granulation process
involves mixing by means of gas fluidisation, then products
with medium to low bulk densities tend to be generated, for
example from 300 to 750 g/1.
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Liquid binders are generally pumped into the mixer to
contact the solid particulate material. Liquid binders must
therefore be of low enough viscosity to allow for ready
pumping. It is also important that the liquid binder is
properly adsorbed and absorbed by the solid particulate
material and that the liquid binder does not "bleed" from
the product granules, especially upon storage.
When powders to be formulated contain particulate components
with low liquid carrying capacities, mixing processes
employing liquid binders can have a deleterious effect on
the requirement to produce free-flowing powders with good
granularity and low moisture content. Soft granules tend to
be formed in the resultant product with poor powder
behaviour due to the low adhesive forces of wet particle
surfaces and hence poor granule structure. Problems can
also be encountered with the build-up of hard lumps due to
brisk exothermic hydration and crystal bridge formation.
PRIOR ART
Such problems have been addressed by using a liquid binder
containing a structurant as described in W098/11198
(Unilever). This document discloses formulating a liquid
binder with a structurant so as to remain pumpable at a
temperature at which the liquid binder is formed and then
admixing the liquid binder with a solid component at a lower
temperature at which the structurant causes solidification
of the mixture.
W098/58048 (Unilever) describes a granulation process in
which a liquid binder is sprayed onto a fluidising
particulate material in a gas fluidisation granulator.
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C3933 (C) WO
Amended 16 July 2001.
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During the pxocess, the temperature of the fluidising gas,
and preferably also the bed temperature, is lowered or
elevated. However, W098/58048 fails to make any correlation
between the temperature of the fluidising gas and/or the bed
temperature and the nature of the liquid binder being
sprayed onto the fluidising particulate material.
Surprisingly, we have found that when a liquid binder is
being contacted with a solid particulate material in a gas
fluidisation granulation process, the resulting powder
properties are significantly improved if the temperature in
the granulator is controlled relative to viscosity
properties of the liquid binder. More specifically, we have
found that the powder flaw properties and storage
properties, in particular cohesiveness levels, are improved.
DEFINITION OF THF INVENTTON
1n a first aspect, this inventian provides process for
preparing a granular detergent product comprising contacting
a particulate solid material with a spray of liquid binder
whilst fluidising the solids in gas fluidisation granulator,
wherein the temperature of the fluidisation gas is elevated
so as to be within plus or.minus 25°C and preferably within
plus or minus 15°C, of the temperature at which the liquid
binder exhibits a viscosity of lPa.s at 50s'1.
In a second aspect, this invention provides a process for
preparing a granular detergent product comprising contacting
a particulate solid material with a spray of liquid binder
whilst fluidising the solids in a gas fluidisation
granulator, wherein the bed temperature is elevated sa as to
AMENDED SHEET
Emufaub~crm
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be within 35°C, preferably within 25°C and more preferably
within 15°C, of the pumpable temperature (as hereinafter
defined) of the liquid binder.
In a third aspect this invention provides a granular
detergent product of bulk density less than 900 g/1 obtained
according to the process of the invention.
The "pumpable temperature" of the liquid binder is defined
herein as the temperature at which the liquid binder
exhibits a viscosity of 1 Pa.s at 50 s-1 .
DETAINED DESCRIPTION OF THE INVENTION
Definitions
Hereinafter, in the context of this invention, the term
"granular detergent product" encompasses granular finished
products for sale, as well as granular components or
adjuncts for forming finished products, e.g. by post-dosing
to or with, or any other form of admixture with further
components or adjuncts. Thus a granular detergent product
as herein defined may, or may not contain detergent-active
material such as synthetic surfactant and/or soap. The
minimum requirement is that it should contain at least one
material of a general kind of conventional component of
granular detergent products, such as a surfactant (including
soap), a builder, a bleach or bleach-system component, an
enzyme, an enzyme stabiliser or a component of an enzyme
stabilising system, a soil anti-redeposition agent, a
fluorescer or optical brightener, an anti-corrosion agent,
an anti-foam material, a perfume or a colourant.
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However, in a preferred embodiment of this invention
granular detergent products contain detergent-active
material such as synthetic surfactant and/or soap at a level
of at least 5 wto, preferably at least 10 wto of the
product.
As used hereinafter, the term "powder" refers to materials
substantially consisting of grains of individual materials
and mixtures of such grains. As used hereinafter, the term
"granule" refers to a small particle of agglomerated smaller
particles, for example, agglomerated powder particles. The
final product of the process according to the present
invention consists of, or comprises a high percentage of
granules. However, additional granular and or powder
materials may optionally be post-dosed to such a product.
As used herein, the terms "granulation" and "granulating"
refer to a process in which, amongst other things, particles
are agglomerated.
For the purposes of this invention, the flow properties of
the granular product are defined in terms of the dynamic
flow rate (DFR), in ml/s, measured by means of the following
procedure. A cylindrical glass tube of internal diameter of
mm and length of 600 mm is securely clamped with its
longitudinal axis in the vertical position. Its lower end
is terminated by a cone of polyvinyl chloride having an
internal angle of 15° and a lower outlet orifice of diameter
30 22.5 mm. A first beam sensor is positioned 150 mm above the
outlet, and a second beam sensor is positioned 250 mm above
the first sensor.
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To determine the dynamic flow rate, the outlet orifice is
temporarily closed and the cylinder filled with the granular
detergent product to a point about 10 cm above the upper
sensor. The outlet is opened and the flow time t (seconds)
taken for the powder level to fall from the upper sensor to
the lower sensor measured electronically. This is repeated
2 or 3 times and an average time taken. If V is the volume
(ml) of the tube between the upper and lower sensors, the
DFR is given by V/t.
The unconfined compressibility test (UCT) provides a measure
of the cohesiveness or "stickiness" of a product and can
provide a guide to its storage properties, for example, in
silos. UCT may be measured on both fresh and weathered
powders but the UCT value is of especial significance in
indicating the likely storage behaviour of a powder.
The principle of the test is to compress the granular
detergent product into a compact and then measure the force
required to break the compact. This is carried out using an
apparatus comprising a cylinder of diameter 89 mm and height
114 mm (3.5 x 4.5 inches), a plunger and plastic discs and
weights of predetermined weight as follows.
The cylinder, positioned around a fixed locating disc and
secured with a clamp, is filled with granular detergent
product and the surface leveled by drawing a straight edge
across it. A 50 g plastic disc is placed on top of the
granular product, the plunger lowered and a 10 kg weight
placed slowly on top of the upper plunger disc. The
weight is left in position for 2 minutes after which time
the 10 kg weight is removed and plunger raised. The clamp
is removed from the cylinder and the two halves of the
cylinder carefully removed to leave a compact of granular
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product. If the compact is unbroken, a second 50 g
plastic disc is placed on top of the first and left for
approximately ten seconds. If the compact is still
unbroken, a 100 g disc is placed on top to the plastic
discs and left for ten seconds. If the compact is still
unbroken, the plunger is lowered very gently onto the
discs and 250 g weights added at ten second intervals
until the compact collapses. The total weight of plunger,
plastic discs and weights at collapse is recorded.
The cohesiveness of the powder is classified by the weight
required to break the compact as follows. The greater the
weight required, the higher the UCT level and the more
cohesive ("sticky") the powder.
"Fines", according to this invention, are defined as
particles with a diameter of less than 180 microns.
"Coarse" material, according to this invention, is defined
as those particles with a diameter greater than 1400
microns.
Levels of fine and coarse particles can be measured using
sieve analysis.
Unless specified otherwise, values relating to powder
properties such as bulk density, DFR, moisture content etc.
relate to the weathered granular detergent product.
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Amended 16 July 2001
_ g _
Th~ Psocess
The process of this invention is carried out using a gas
fluidisation granulator. A gas fluidisation granulator is
sometimes called a "fluidised bed" granulator or mixer_
This ie nat strictly accurate since such mixers can be
operated with a gas flow rate so high that a classical
'bubbling" fluid bed does not form.
1o The gas fluidiaation granulation and agglomeration process
step is preferably carried out substantially as described in
W098/58046 and W098/58047 (Unilever).
The gas fluidisation apparatus basically comprises a chamber
in which a stream of gas (hereinafter referred to ws the
fluidisation gas), usually air, is used to cause turbulent
flow of particu7.ate solids to form a "cloud" of the solids
and liquid binder is sprayed onto or into the cloud to
Contact the individual particles. As the process
progresses, individual particles of solid starting materials
become agglomerated, due to the liquid binder, to form
granules.
The gas fluidisation granulator is typically operated at a
superficial air velooity of about 0.1-1.2 ms-l, either under
positive or negative relative pressure and with an air inlet
temperature (ie fluidisation gas temperature) ranging from -
10°C or 5°C up to 100°C. It may be as high as
200°C in some
cases.
The fluidisation gas temperature, and thus preferably the
bed temperature, may be changed during the granulation
AMENDED SHEET
Empfanss~em io.~vi
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process as described in W098/58048. It may be elevated for
a first period, e.g. at up to 100°C or even up to 200°C and
then at one or more other stages (before or after), it may
be reduced to just above, at, or below ambient, e.g. to 30°C
or less, preferably 25°C or less or even as low as 5°C or
less or -10°C or less.
When the process is a batch process, the temperature
variation will be effected over time. If it is a continuous
process, it will be varied along the "track" of the
granulator bed (i.e. in the direction of powder flow through
the granulator bed). In the latter case, this is
conveniently effected using a granulator of the "plug flow"
type, ie one in which the materials flow through the reactor
from beginning to end.
In a batch process, the fluidisation gas temperature may be
reduced over a relatively short period of time, for example
10 to 500 of the process time. Typically, the gas
temperature may be reduced for 0.5 to 15 minutes. In a
continuous process, the gas temperature may be reduced along
a relatively short length of the "track" of the granulator
bed, for example alonct 10 to 50% of the track. In both
cases, the gas may be pre-cooled.
Preferably, the fluidisation gas temperature, and preferably
also the bed temperature, is not lowered until agglomeration
of the fluidising particulate solid material is
substantially complete.
In addition to the fluidisation gas, a gas fluidisation
granulator may also employ an atomising gas stream. Such an
atomising gas stream is used to aid atomisation of the
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liquid binder from the nozzle onto or into the fluidising
solids. If an atomising gas stream is employed, it may
generally be operated at a pressure of from 2 to 5 bar.
The atomising gas stream, usually air, may also be heated.
According to one aspect of the invention, the temperature of
the fluidisation gas is elevated so as to be within (plus or
minus) 35°C, preferably within 25°C, more preferably within
15°C, most preferably within 10°C and advantageously within
5°C, of the pumpable temperature (as defined) of the liquid
binder.
In a preferred embodiment, the atomisation gas temperature
is also elevated so as to be within (plus or minus) 35°C,
preferably within 25°C, more preferably within 15°C, most
preferably within 10°C and advantageously within 5°C, of the
pumpable temperature of the liquid binder.
Alternatively, in another aspect of the invention, the bed
temperature in the gas fluidisation chamber is elevated so
as to be within (plus or minus) 35°C, preferably within 25°C,
more preferably within 15°C, most preferably within 10°C and
advantageously within 5°C, of the pumpable temperature of the
liquid binder.
It is highly preferred that the temperature of the
fluidising gas, and preferably also the atomising gas,
and/or the temperature of the bed be elevated for at least
part of the time and preferably for substantially the entire
time the liquid binder is being sprayed onto the fluidising
solids.
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It is especially preferred that the temperature of the
fluidising gas, and preferably also the atomising gas,
and/or the temperature of the bed be elevated and maintained
at around or near the pumpable temperature of the liquid
binder.
The elevation in temperature, relative to the pumpable
temperature of the liquid binder, of the fluidising gas, and
preferably also the atomising gas, and/or the temperature of
the bed, has been found to be especially beneficial when the
liquid binder is a structured blend.
As used herein, the term "bed temperature" refers to the
temperature of the fluidising gas around the solid
particulate material. The bed temperature can be measured,
for example, using a thermocouple probe. Whether there is a
discernible powder bed or no discernible powder bed (ie
because the mixer is being operated with a gas flow rate so
high that a classical "bubbling" fluid bed is not formed),
the "bed temperature" is taken to be the temperature as
measured at a point inside the fluidisation chamber about 15
cm from the gas distributor plate.
Whether the gas fluidisation granulation process of the
present invention is a batch process or a continuous
process, solid particulate material may be introduced at any
time during the time when liquid binder is being sprayed.
In the simplest form of process, solid particulate material
is first introduced to the gas fluidisation granulator and
then sprayed with the liquid binder. However, some solid
particulate material could be introduced at the beginning of
processing in the gas fluidisation apparatus and the
remainder introduced at one or more later times, either as
one or more discrete batches or in continuous fashion.
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The gas fluidisation granulator may optionally be of the
kind provided with a vibrating bed, particularly for use in
continuous mode.
Optional Drying and/or cooling
For use, handling and storage, the granular detergent
product must be in a free flowing state. Therefore, in a
final step, the granules can be dried and/or cooled if
necessary. This step can be carried out in any known
manner, for instance in a fluid bed apparatus (drying and
cooling) or in an airlift (cooling). Drying and/or cooling
can be carried out in the same fluid bed apparatus as used
for the final agglomeration step simply by changing the
process conditions employed as will be well-known to the
person skilled in the art. For example, fluidisation can be
continued for a period after addition of liquid binder has
been completed and the air inlet temperature can be reduced.
Other optional process steps
In a refinement of the process of the present invention, the
solid particulate material may be treated in one or more
mixers and/or granulators prior to the gas fluidisation
granulator. For example, a solid particulate material may
be mixed and optionally contacted with a liquid binder, in a
separate premixing step, e.g. in a low-, moderate- or high-
shear mixer. If liquid binder is added in a premixing step,
then a partially granulated material is formed. The latter
can then be sprayed with further liquid binder in the gas
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fluidisation granulator, to form the granulated detergent
product.
In this respect, it is possible to precede the fluid bed
granulation step with one or more separate mixing or
granulation steps. Suitable mixers and granulators will be
well-know to the person skilled in the art. For example,
solid particulate material may first be treated with liquid
binder in a high-speed mixing step, which is then followed
by a moderate-speed mixing step, prior to the gas
fluidisation step.
Examples of suitable pre-granulation processes are described
in EP 367339, EP 420317, W096/04359, W098/58046 and
W098/58047 (Unilever), but other granulation and mixing
processes are equally as appropriate as will be evident to
the person skilled in the art.
The process of the invention can be carried out either in a
batchwise or continuous manner. In a preferred embodiment,
the entire process is continuous.
The liquid binder
In the process of this invention, liquid binder is added
during the gas fluidisation granulation step, and also may
be added in other optional preceding process steps.
If there is more than one granulation step, or more than one
point of addition or time of addition, then the liquid
binder added at each step or point or time may be the same
or different and more than one liquid binder may be added in
any one step or at any one point or time.
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The liquid binder is sprayed into the gas fluidisation
granulator.
The liquid binder can comprise one or more components of the
granular detergent product. Suitable liquid components
include anionic surfactants and acid precursors thereof,
nonionic surfactants, fatty acids, water and organic
solvents.
The liquid binder can also comprise solid components
dissolved in or dispersed in a liquid component, such as,
for example, inorganic neutralising agents and detergency
builders. The only limitation is that with or without
dissolved or dispersed solids, the liquid binder should be
pumpable and capable of being delivered to the mixer and/or
granulator in a fluid, including paste-like, form.
It is preferred that the liquid binder comprises an anionic
surfactant. The content of anionic surfactant in the liquid
binder may be as high as possible, e.g. at least 98 wto of
the liquid binder, or it may be less than 75 wt%, less than
50 wto or less than 25 wto. It may, of course constitute 5
wt% or less or not be present at all.
Suitable anionic surfactants are well-known to those skilled
in the art. Examples suitable for incorporation in the
liquid binder include alkylbenzene sulphonates, particularly
linear alkylbenzene sulphonates having an alkyl chain length
of C$-C15; primary and secondary alkyl sulphates,
particularly C12-Ci5 primary alkyl sulphates; alkyl ether
sulphates; olefin sulphonates; alkyl xylene sulphonates;
dialkyl sulphosuccinates; and fatty acid ester sulphonates.
Sodium salts are generally preferred.
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It is very much preferred to form some or all of any anionic
surfactant in situ in the liquid binder by reaction of an
appropriate acid precursor and an alkaline material such as
an alkali metal hydroxide, e.g. NaOH. Since the latter
normally must be dosed as an aqueous solution, that
inevitably incorporates some water. Moreover, the reaction
of an alkali metal hydroxide and acid precursor also yields
some water as a by-product.
However, in principle, any alkaline inorganic material can
be used for the neutralisation but water-soluble alkaline
inorganic materials are preferred. Another preferred
material is sodium carbonate, alone or in combination with
one or more other water-soluble inorganic materials, for
example, sodium bicarbonate or silicate. If desired, a
stoichiometric excess of neutralising agent may be employed
to ensure complete neutralisation or to provide an
alternative function, for example as a detergency builder,
e.g. if the neutralising agent comprises sodium carbonate.
Organic neutralising agents may also be employed.
Of course, if the liquid binder contains an acid precursor
of an anionic surfactant, the acid precursor can be
neutralised or neutralisation completed in situ in the mixer
and/or granulator by either contacting with a solid alkaline
material or adding a separate liquid neutralising agent to
the mixer and/or granulator. However, neutralisation in the
mixer and/or granulator is not a preferred feature of this
invention.
The liquid acid precursor may be selected from linear alkyl
benzene sulphonic (LAS) acids, alphaolefin sulphonic acids,
internal olefin sulphonic acids, fatty acid ester sulphonic
acids and combinations thereof. The process of the
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invention is especially useful for producing compositions
comprising alkyl benzene sulphonates by reaction of the
corresponding alkyl benzene sulphonic acid, for instance
Dobanoic acid ex Shell. Linear or branched primary alkyl
sulphates (PAS) having 10 to 15 carbon atoms can also be
used.
In a preferred embodiment, the liquid binder comprises an
anionic surfactant and a nonionic surfactant. The weight
ratio of anionic surfactant to nonionic surfactant is in the
range from 10:1 to 1:15, preferably from 10:1 to 1:10, more
preferably 10:1 to 1:5. If the liquid binder comprises at
least some acid precursor of an anionic surfactant and a
nonionic surfactant, then the weight ratio of anionic
surfactant, including the acid precursor, to nonionic
surfactant can be higher, for example 15:1.
The nonionic surfactant component of the liquid binder may
be any one or more liquid nonionics selected from primary
and secondary alcohol ethoxylates, especially C8-C2o
aliphatic alcohols ethoxylated with an average of from 1 to
20 moles ethylene oxide per mole of alcohol, and more
especially the Clo-C15 primary and secondary aliphatic
alcohols ethoxylated with an average of from 1 to 10 moles
of ethylene oxide per mole of alcohol. Non-ethoxylated
nonionic surfactants include alkylpolyglycosides, glycerol
monoethers, and polyhydroxyamides (glucamide).
In a preferred embodiment the liquid binder is substantially
non-aqueous. That is to say, the total amount of water
therein is not more than 15 wto of the liquid binder,
preferably not more than 10 wto. However, if desired, a
controlled amount of water may be added to facilitate
neutralisation. Typically, the water may be added in
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amounts of 0.5 to 2 wt% of the final detergent product.
Typically, from 3 to 4 wto of the liquid binder may be water
as the reaction by-product and the rest of the water present
will be the solvent in which the alkaline material was
dissolved. The liquid binder is very preferably devoid of
all water other than that from the latter-mentioned sources,
except perhaps for trace amounts/impurities.
Alternatively, an aqueous liquid binder may be employed.
This is especially suited to manufacture of products which
are adjuncts for subsequent admixture with other components
to form a fully formulated detergent product. Such adjuncts
will usually, apart from components resulting from the
liquid binder, mainly consist of one, or a small number of
components normally found in detergent compositions, e.g. a
surfactant or a builder such as zeolite or sodium
tripolyphosphate. However, this does not preclude use of
aqueous liquid binders for granulation of substantially
fully formulated products. In any event, typical aqueous
liquid binders include aqueous solutions of alkali metal
silicates, water soluble acrylic/maleic polymers (e. g.
Sokalan CP5) and the like.
The liquid binder may optionally comprise dissolved solids
and/or finely divided solids which are dispersed therein.
The only limitation is that with or without dissolved or
dispersed solids, the liquid binder should be pumpable and
sprayable at temperatures of 50°C or greater or at any rate,
60°C or greater e.g. 75°C. Preferably it is solid at below
50°C, preferably at 25°C or less. The liquid binder is
preferably at a temperature of at least 50°C, more preferably
at least 60°C when fed into the mixer or gas fluidisation
granulator.
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According to the present invention, liquid binders are
considered readily pumpable if they have a viscosity of no
greater than 1 Pa.s at a shear rate of 50 s-1 and at the
temperature of pumping. Liquid binders of higher viscosity
may still in principle be pumpable, but an upper limit of
1 Pa.s at a shear rate of 50 s-1 is used herein to indicate
easy pumpability.
The viscosity can be measured, for example, using a Haake
VT500 rotational viscometer. The viscosity measurement may
be carried out as follows. A SV2P measuring cell is
connected to a thermostatic waterbath with a cooling unit.
The bob of the measuring cell rotates at a shear rate of 50
s-1. Solidified blend is heated in a microwave to 95°C and
poured into the sample cup. After conditioning for 5
minutes at 98°C, the sample is cooled at a rate of +/- 1°C
per minute. The temperature at which a viscosity of 1 Pa.s
is observed, is recorded as the "pumpable temperature".
The "pumpable temperature" of the liquid binder is therefore
defined herein as the temperature at which the liquid binder
exhibits a viscosity of 1 Pa.s at 50 s-1 .
A definition of solid can be found in the Handbook of
Chemistry and Physics, CRC Press, Boca Raton, Florida, 67th
edition, 1986.
Structured blends
In a preferred embodiment of this invention, the liquid
binder contains a structurant and liquid binders which
contain a structurant are referred to herein as structured
blends. All disclosures made herein with reference to
liquid binders apply equally to structured blends.
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In the context of the present invention, the term
"structurant" means any component which enables the liquid
component to achieve solidification in the granulator and
hence good granulation, even if the solid component has a
low liquid carrying capacity.
Structurants may be categorised as those believed to exert
their structuring (solidifying) effect by one of the
following mechanisms, namely: recrystallisation (e. g.
silicate or phosphates); creation of a network of finely
divided solid particles (e. g. silicas or clays); and those
which exert steric effects at the molecular level (e.cr.
soaps or polymers) such as those types commonly used as
detergency builders. One or more structurants may be used.
Structured blends provide the advantage that at lower
ambient temperatures they solidify and as a result lend
structure and strength to the particulate solids onto which
they are sprayed. It is therefore important that the
structured blend should be pumpable and sprayable at an
elevated temperature, e.g. at a temperature of at least 50°C,
preferably of at least 60°C, and yet should solidify at a
temperature below 50°C, preferably below 35°C so as to impart
its benefit.
Typically, in the high-speed and moderate- or low-speed
mixers the temperature is more than 10°C, preferably more
than 20°C below the temperature at which the blend is
prepared and pumped into the granulator.
The structurants cause solidification in the liquid binder
component preferably to produce a blend strength as follows.
The strength (hardness) of the solidified liquid component
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can be measured using an Instron pressure apparatus. A
tablet of the solidified liquid component, taken from the
process before it contacts the solid component, is formed of
dimensions 14 mm in diameter and 19 mm in height. The
tablet is then destroyed between a fixed and a moving plate,
the moving plate moving towards the fixed plate. The speed
of the moving plate is set to 5 mm/min, which causes a
measuring time of about 2 seconds. The pressure curve is
logged on a computer. Thus, the maximum pressure (at the
moment of tablet breaking) is given and the E-modulus is
calculated from the slope.
For the solidified liquid component, Pmax at 20°C is
preferably a minimum of 0.1 MPa, more preferbaly 0.2 MPa,
e.g. from 0.3 to 0.7 M Pa. At 55°C, a typical range is from
0.05 to 0.4 M Pa. At 20°C, Em°d for the liquid blend is
preferably a minimum of 3 M Pa, e.g. from 5 to 10 M Pa.
The structured blend is preferably prepared in a shear
dynamic mixer for premixing the components thereof and
performing any neutralisation of anionic acid precursor.
Soaps represent one preferred class of structurant,
especially when the structured blend comprises a liquid
nonionic surfactant. In many cases it may be desirable for
the soap to have an average chain length greater than the
average chain length of the liquid nonionic surfactant but
less than twice the average chain length of the latter.
It is very much preferred to form some or all of any soap
structurant in situ in the liquid binder by reaction of an
appropriate fatty acid precursor and an alkaline material
such as an alkali metal hydroxide, e.g. NaOH. However, in
principle, any alkaline inorganic material can be used for
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the neutralisation but water-soluble alkaline inorganic
materials are preferred. In a liquid binder comprising an
anionic surfactant and soap, it is preferred to form both
the anionic surfactant and soap from their respective acid
precursors. All disclosures made herein to formation of
anionic surfactant by in situ neutralisation in the liquid
binder of their acid precursors equally apply to the
formation of soap in structured blends.
If desired, solid components may be dissolved or dispersed
in the structured blend. Typical amounts of ingredients in
the essential structured blend component as % by weight of
the structured blend are as follows:
preferably from 98 to 10 wt% of anionic surfactant,
more preferably from 70 to 300, and especially from 50
to 30 wt%;
preferably from 10 to 98 wt% of nonionic surfactant,
more preferably from 30 to 70 wto, and especially from
to 50 wto~
preferably from 2 to 30 wto of structurant, more
preferably from 2 to 200, yet more preferably from 2 to
15 wto, and especially from 2 to 10 wto.
In addition to the anionic surfactant or precursor thereof,
nonionic surfactant and structurant, the structured blend
may also contain other organic solvents.
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Solid particulate material
The solid particulate materials of this invention may be
powdered and/or granular. As such, the solid particulate
material may be any component of the granular detergent
product that is available in particulate form. Preferably,
the solid particulate material with which the liquid binder
is admixed comprises a detergency builder. In a
particularly preferred embodiment of this invention, the
solid starting material comprises builders selected from
crystalline and amorphous aluminosilicates.
Product
The present invention also encompasses a granular detergent
product resulting from the process of the invention (before
any post-dosing or the like).
Granular detergent products according to the invention have
a bulk density of less than 900 g/1, preferably less than
800 g/1, more preferably less than 750 g/1, and yet more
preferably less than 700 g/1. The bulk density may be as
low as 300 g/1, however it is preferably greater than 400
g/1. Preferably it is in the range of 400-800 g/1, more
preferably 400-750 g/1, and yet more preferably 400-700 g/1.
The product will have a bulk density determined by the exact
nature of the process but can be controlled to a certain
degree by selecting appropriate premixing steps, as will be
evident to the person skilled in the art.
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The granular detergent products of the process of this
invention are low in fines, possess good flow properties and
have low UCT levels.
Preferably less than 15 wto, and more prefertably less than
wt% of the granules have a diameter of less 180 microns,
more preferably less than 8 wto, and most preferably less
than 5 wto.
10 The granular product is considered to be free flowing if it
has a DFR of at least 80 ml/s. Preferably the granular
products of this invention have DFR values of at least 80
ml/s, preferably at least 90 ml/s, more preferably at least
100 ml/s, and most preferably at least 110 ml/s.
The granular detergent product preferably has a UCT level of
less than 1500 g, more preferably less than 1000 g, yet more
preferably less than 900 g, yet more preferably less than
700g, and most preferably less than 500 g.
Finally, the granules may be distinguished from granules
produced by other methods by using mercury porosimetry. The
latter technique is ideal for characterising granules that
have been prepared by a process involving gas fluidisation
agglomeration.
Detergent compositions and ingredients
As previously indicated, a granular detergent product
prepared by the process of the invention may itself be a
fully formulated detergent composition, or may be a
component or adjunct which forms only a part of such a
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composition. This section relates to final, fully formed
detergent compositions.
The total amount of detergency builder in the final
detergent composition is suitably from 10 to 80 wt%,
preferably from 15 to 60 wt%. The builder may be present in
an adjunct with other components or, if desired, separate
builder particles containing one or more builder materials
may be employed.
15
This invention is especially applicable to use where the
solid starting material comprises builders selected from
crystalline and amorphous aluminosilicates, for example
zeolites as disclosed in GB-A-1 473 201; amorphous
aluminosilicates as disclosed in GB-A-1 473 202; and mixed
crystalline/amorphous aluminosilicates as disclosed in GB 1
470 250; and layered silicates as disclosed in EP-B-164 514.
Aluminosilicates, whether used as layering agents and/or
incorporated in the bulk of the particles may suitably be
present in a total amount of from 10 to 60 wto and
preferably an amount of from 15 to 50 wto based on the final
detergent composition. The zeolite used in most commercial
particulate detergent compositions is zeolite A.
Advantageously, however, maximum aluminium zeolite P
(zeolite MAP) described and claimed in EP-A-384 070 may be
used. Zeolite MAP is an alkali metal aluminosilicated of
the P type having a silicone to aluminium ratio not
exceeding 1.33, preferably not exceeding 1.15, and more
preferably not exceeding 1.07.
Other suitable builders include hydratable salts, preferably
in substantial amounts such as at least 25% by weight of the
solid component, preferably at least 10% by weight.
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Hydratable solids include inorganic sulphates and
carbonates, as well as inorganic phosphate builders, for
example, sodium orthophosphate, pyrophosphate and
tripolyphosphate.
Other inorganic builders that may be present include sodium
carbonate (as mentioned above, an example of a hydratable
solid), if desired in combination with a crystallisation
seed for calcium carbonate as disclosed in GB-A-1 437 950.
As mentioned above, such sodium carbonate may be the residue
of an inorganic alkaline neutralising agent used to form an
anionic surfactant in situ.
Organic builders that may be present include polycarboxylate
polymers such as polyacrylates, acrylic/maleic copolymers,
and acrylic phosphinates; monomeric polycarboxylates such as
citrates, gluconates, oxydisuccinates, glycerol mono-, di-
and trisuccinates, carboxymethyloxysuccinates,
carboxymethyloxymalonates, dipicolinates,
hydroxyethyliminodiacetates, aminopolycarboxylates such as
nitrilotriacetates (NTA), ethylenediaminetetraacetate (EDTA)
and iminodiacetates, alkyl- and alkenylmalonates and
succinates; and sulphonated fatty acid salts. A copolymer
of malefic acid, acrylic acid and vinyl acetate is especially
preferred as it is biodegradable and thus environmentally
desirable. This list is not intended to be exhaustive.
Especially preferred organic builders are citrates, suitably
used in amounts of from 2 to 30 wto, preferably from 5 to
25 wto; and acrylic polymers, more especially acrylic/maleic
copolymers, suitably used in amounts of from 0.5 to 15 wto,
preferably from 1 to 10 wto. The builder is preferably
present in alkali metal salt, especially sodium salt, form.
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The granular detergent compositions may contain, in addition
to any anionic and/or nonionic surfactants of the liquid
binder, one or more other detergent-active compounds which
may be chosen from soap and non-soap anionic, cationic,
nonionic, amphoteric and zwitterionic surfactants, and
mixtures thereof. These may be dosed at any appropriate
stage before or during the process. Many suitable
detergent-active compounds are available and are fully
described in the literature, for example, in "Surface-Active
Agents and Detergents", Volumes I and II, by Schwartz, Perry
and Berch. The preferred detergent-active compounds that
can be used are soaps and synthetic non-soap anionic and
nonionic compounds.
The detergent compositions may also contain a bleach system,
desirably a peroxy bleach compound, for example, an
inorganic persalt or organic peroxyacid, capable of yielding
hydrogen peroxide in aqueous solution. The peroxy bleach
compound may be used in conjunction with a bleach activator
(bleach precursor) to improve bleaching action at low wash
temperatures. An especially preferred bleach system
comprises a peroxy bleach compound (preferably sodium
percarbonate optionally together with a bleach activator).
Usually, any bleach and other sensitive ingredients, such as
enzymes and perfumes, will be post-dosed after granulation
along with other minor ingredients.
Typical minor ingredients include sodium silicate; corrosion
inhibitors including silicates; antiredeposition agents such
as cellulosic polymers; fluorescers; inorganic salts such as
sodium sulphate, lather control agents or lather boosters as
appropriate; proteolytic and lipolytic enzymes; dyes;
coloured speckles; perfumes; foam controllers; and fabric
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softening compounds. This list is not intended to be
exhaustive.
Optionally, a "layering agent" or "flow aid" may be
introduced at any appropriate stage in the process of the
invention. This is to improve the granularity of the
product, e.g. by preventing aggregation and/or caking of the
granules. Any layering agent flow aid is suitably present
in an amount of 0.1 to 15 wto of the granular product and
more preferably in an amount of 0.5 to 5 wto.
Suitable layering agents/flow aids include crystalline or
amorphous alkali metal silicates, aluminosilicates including
zeolites, citrates, Dicamol, calcite, diatomaceous earths,
silica, for example precipitated silica, chlorides such as
sodium chloride, sulphates such as magnesium sulphate,
carbonates such as calcium carbonate and phosphates such as
sodium tripolyphosphate. Mixtures of these materials may be
employed as desired.
Zeolite MAP, as well as being a preferred builder, is
especially useful as a layering agent. Layered silicates
such as SKS-6 ex Clariant are also useful as layering
agents.
Powder flow may also be improved by the incorporation of a
small amount of an additional powder structurant, for
example, a fatty acid (or fatty acid soap), a sugar, an
acrylate or acrylate/maleate polymer, or sodium silicate
which is suitably present in an amount of from 1 to 5 wto.
In general, additional components may be included in the
liquid binder or admixed with the solid starting material at
an appropriate stage of the process. However, solid
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components can be post-dosed to the granular detergent
product.
The granular detergent composition may also comprise a
particulate filler (or any other component which does not
contribute to the wash process) which suitably comprises an
inorganic salt, for example sodium sulphate and sodium
chloride. The filler may be present at a level of 5 to 70
wt% of the granular product.
The invention will now be described in more detail in the
following non-limiting Examples, in which parts and
percentages are by weight unless otherwise stated. Examples
denoted by a number are in accordance with the invention,
while those denoted by a letter are comparative.
L~ V T l~tT~T L~ G~
Example 1 and Comparative Example A
A granular detergent product base powder of the following
formulation was prepared: wt%
Sodium linear alkylbenzene
sulphonate (Na-LAS) 12.40
Nonionic surfactant 7E0 12.81
Soap 1.73
Zeolite MAP 36.10
Light soda ash 24.96
SCMC 0.81
Sodium citrate 3.33
Moisture, salts, NDOM 7.86
100.00
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The base powder in Example 1 was prepared as follows:
(i) mixing and granulating the solid particulate materials
with a liquid binder in a high-speed mixer (Lodige
Recycler CB 30) for about 15 seconds,
(ii) transferring the material from step (i) to a moderate-
speed mixer (Lodige Ploughshare KM 300) for about 3
minutes,
(iii)transferring the material from the step (ii) to a
fluid bed operating as a gas fluidisation granulator,
adding further liquid binder and granulating, and
(iv) finally drying/cooling the product in the fluid bed.
The fluid bed in step (iii) was operated under the following
conditions during the period when the liquid binder was
being sprayed into the fluidising solids.
Fluidisation gas temperature: 75°C
Atomisation gas temperature . hot
Atomisation air pressure . 3.5 bar.
The liquid binder used in steps (i) and (iii) was a
structured blend comprising the anionic surfactant, nonionic
surfactant and soap components of the base powder. The
blend was prepared by mixing 38.44 parts by weight of LAS
acid precursor and 5.20 parts by weight fatty acid precursor
of the soap in the presence of 41.60 parts by weight
nonionic surfactant in a blend-loop and neutralising with
14.75 parts of a sodium hydroxide solution. The blend
temperature in the loop was controlled by a heat-exchanger.
The neutralising agent was a sodium hydroxide solution. The
resulting blend had the following composition .
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Sodium linear alkylbenzene sulphonate 39.9
Nonionic surfactact (7E0) 41.6
Soap 5.6
Water 12.9
The pumpable temperature of the structured blend was 75°C.
The weight ratio of blend added in the recycler and gas
fluidisation granulator was 67:33.
The base powder of Comparative Example A was prepared in the
same way except that the fluidisation gas and atomisation
gas temperatures were ambient.
The resulting powder properties as recorded in Table 1
clearly demonstrate the benefit of elevating the temperature
of the fluidising gas and atomising gas when spraying on a
liquid binder. The UCT level of Example 1 is considerably
better than that of Example A.
Table 1
Example 1 Comparative Example A
BD (g/1) 652 593
DFR(ml/s) 131 117
UCT(g) 200 950
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Example 2 and Comparative Example B
A granular detergent product base powder of the following
formulation was prepared:
wt o
Na-LAS 12.9
Nonionic 7E0 14.5
Soap 2.0
Zeolite A24 51.7
Light soda ash 9.1
SCMC 0.95
Moisture, salts, NDOM 8.85
100.00
The base powder of Example 2 was prepared as in Example 1
except that the weight ratio of blend added in the recycler
and gas fluidisation granulator was 80:20.
The formulation of the blend was as follows:
Sodium linear alkylbenzene sulphonate 39.7
Nonionic surfactant (7E0) 44.7
Soap 6.0
Water 9.6
Its pumpable temperature was 73°C.
The base powder of Comparative Example B was prepared by the
same method as Example 2 except that the fluidisation gas
temperature was at ambient (the atomisation gas temperature
remaining hot). Details of the powder properties are given
in Table 2.
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Comparing Example 2 with Example B, it can clearly be seen
that elevating the fluidising gas temperature leads to a
clear improvement in the UCT levels of the powder. The
visible properties of powders also showed a marked
improvement. Example B appeared quite sticky, whereas
Example 2 appeared to be very well granulated, not coarse
and not sticky.
Table 2
Example 2 Comparative Example B
BD (g/1) 634 554
DFR (ml/s) 131 130
UCT (g) 450 1950
Example 3
The procedure of Example 2 was repeated with both the
fluidising and atomising air temperatures elevated. The
powder had the following properties:
BD (g/1) 648
DFR (ml/s) 132
UCT (g) <200
