Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR THE PRODUCTION OF A DETERGENT COMPOSITION
Technical field
The present invention relates to a process for the
production of a detergent composition. In particular the
invention is concerned with a process for the production of
a detergent composition having a medium or low bulk density.
Background to the invention
Conventionally, detergent compositions have been produced by
a spray-drying process in which the components of the
composition are mixed with water to form an aqueous crutcher
slurry which is then sprayed into a spray-dying tower and
contacted with hot air to remove water whereby detergent
particles, often referred to as a abase" powder are
obtaa.ned. The particles so obtained, have a high porosity.
Thus powders produced by this method typically have a bulk
density of 300 to 550 g/1 or even up to 650 g/1.
Spray-dried powders generally provide good powder delivery
characteristics such as dispensing and dissolution.
However, the capital and operating costs of the spray-drying
process are high. Nevertheless there remains a significant
consumer demand for such low density powders.
In recent years, detergent powders having a high bulk
density have been produced by mechanical mixing processes.
Bulk densities of 700 to 900 g/I and even higher have been
obtained. Typically such powders are produced by densifying
a spray-dried base powder in one or more mechanical mixers,
optionally with the addition of further components, or by
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WO 98124876 PGT/EP97/06073
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mixing the components of the composition in a continuous or
batch mixing process without the use of a spray-drying step.
Powders having a high bulk density have a low packing volume
which is advantageous for storage and distribution
operations and also for the consumer. Furthermore, if a
spray-drying step is not employed, the capital and operating
costs are typically much lower and the process uses less
energy and so provides an environmental benefit. The
avoidance of a spray-drying step in the detergent production
process is therefore often desirable.
However, such high density powders typically have a much
lower porosity than a conventional spray-dried powder which
may impair the delivery of the powder into the wash liquor.
Additionally, the production of powders having a low to
medium bulk density, for example less than about 700 g/1,
has not hitherto been readily achievable on a commercial
scale without the use of a spray-drying step.
EP-A-367 339 discloses a process for the production of a
detergent composition having a high bulk density in which a
particulate starting material is treated in a high speed
mixer, a moderate speed mixer wherein the material is
brought into or maintained in a deformable state, and then
dried and/or cooled. The starting material may be a spray-
dried base powder or the components of the composition may
be employed without a prior spray-drying step in the
detergent production process.
WO 97/02338 (Unilever , unpublished at the priority date of
the present application) discloses that a low bulk density,
for example less than 700 g/l, may be obtained by a process
in which a spray-drying step is not employed, if the
composition is formulated with a component having a low bulk
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density. However, this process is relatively unsuitable for
use with starting materials which are either available
commercially in a form in which the particle density is high
or which are themselves produced by spray-drying (the latter
normally producing relatively porous particles).
EP-A-544 365 discloses granulation of porous spray-dried
detergent free starting material of 300 micron particle size
in a "recycler" high speed mixer/densifier with a liquid
binder comprising a primary alcohol sulphate anionic
surfactant, a nonionic surfactant and water.
We have now found that medium or low bulk density powders may
be obtained by a new process of mechanical mixing of a powder
which contains little or no detergent active material and
which consists of particles having a predetermined average
particle size and a high particle porosity together with a
liquid component comprising a detergent active material or a
precursor therefore.
Definition of the invention
Thus, a first aspect of the present invention provides a
process for the production of a detergent composition having
a bulk density of no more than 750 g/l, e.g. no more than 700
or 650 g/1, the process comprising mixing a particulate
starting material which contains no more than loo by weight
of the starting material of a detergent active material and
which starting material has a d5o average particle diameter of
from 100um to 1000um and a particle porosity of at least 0.4,
together with a liquid component comprising a detergent
active material or a precursor therefore in a
mixer/granulator having both a stirring and a cutting action,
the stirrer is operated at a rate of 25 to 250 rpm and the
cutter is operated at a rate of 300 to 3000 rpm.
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Detailed description of the invention
The present invention derives from t:~e unexpected
observation that the bulk density cf the resultant product
is dependent upon the rotational speed of mixing. This is
also a function of the particular mixer of choice but
essentially, the lower the speed of the mixer, the lower the
bulk density of the product.
I0 This new process has two distinct but separate advantages.
The first advantage is that by choosing a powder starting
material which already possesses the required average
particle size and porosity medium or low bulk density
powders may be prepared.
The second advantage is obtainable in :«anufacturing
scenarios where both spray-drying and mechanical mixture
agglomeration facilities are available. By affording the
possibility of using a spray-dried product as a starting
material in a mechanical agglomeration process, the present
invention provides a further degree of flexibility in such a
modular approach to the production of detergent powder
products. As used herein, the abbreviation "NTR" means
"non-tower route", i.e. a powder produced by mixing rather
than in a spray-drying tower even if the starting materials
are themselves produced by saray drying.
Suitably, the detergent composition resulting from the
process of the present inv~r.tion hus a bulk density of 400
to 650 g/1, preferably a5G to 650 g/1 and more preferably
500 to 600 g/1. It is fur~her preferred that the resultant
detergent composition has a Darticle porosity Of at least
0.2 and more preferably at least 0.25.
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Suitably, the particulate starting material is dosed at a
level of from 10 to 75 wt%, preferably from 20 to 40 wt%, of
the composition resulting from the mechanical mixing
process.
Instead of expressing particle size distributions in terms
of average (e. g. d~~? particle diameters, if they are capable
of being fitted to a Rosin-Rammler distribution, they may be
expressed in terms of their Rosin Rammler number. This is
calculated by fitting the particle size distribution to an
n-power distribution according to the following formula:-
~r
R = 100 * ~p _ I~
~r
where R is the cumulative percentage of powder above a
certain size D. D~ is the average granule size and n is a
measure of the particle size distribution. Dr and n are the
Rosin Rammler fits to a measured particle size distribution.
A high n value means narrow particle size distribution and
low values mean a broad particle size distribution.
The process may be a continuous process or may be performed
?,~r~-h-w; ca
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A suitable type of mixer/granulator for use in the
process of the invention is bowl-shaped and preferably has a
substantially vertical stirrer axis. Especially preferred
are mixers of the Fukae (Trade Mark) FSOG series
manufactured by Fukae Powtech Kogyo Co., Japan; thi s
apparatus is essentially in the form of a bowl-shaped vessel
accessible via a top part, provided near its base with a
stirrer having a substantially vertical axis, and a cutter
positioned on a side wall. The stirrer and cutter may be
operated independently of one another, and at separately
variable speeds.
Other similar mixers found to be suitable for use in the
process of the invention are the Diosna (Trade Mark) V
series ex Dierks & Sohne, Germany; and the Pharma Matrix
(Trade Mark) ex T K Fielder Ltd., England. Other similar
mixers suitable for use in the process of the invention
include the Fuji (Trade Mark) VG-C series ex Fuji Sangyo
Co., Japan; and the Roto (Trade Mark) ex Zanchetta & Co srl,
Italy.
Granulation is effected by running the mixer using both stirrer
and cutter; a relatively short residence time (for example, 5-8
minutes for a 35 kg batch) is generally sufficient. the final
2~ bulk density can be controlled by choice of residence time and
stirrer rate.
Suitably the stirrer is operated at a rate of 25 to 250 rpm,
e.g. from 100 rpm to 200 rpm or even as low as 30 to 50 rpm.
However, this speed is dependent on the size of the
apparatus. Independently tha cutter is suitably operated at
a rate of 300 to 3000 rpm. For example, 300 to 2200 rpm. A
batch prOCeS~ typically involves pre-mixing of solid
components, addition
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of liquids, granulation, optional addition of a layering
material suitable for controlling the granulation end-point,
and product discharge. The rate of stirring and/or cutting
is suitably adjusted according to the stage of the process.
The mixing step is preferably carried out at a controlled
temperature somewhat above ambient, preferably above 3G°C.
Suitably the temperature is within the range 30 to 45°C.
The amount of detergent active material in the particulate
starting material is no more than 10% by weight of that
material. However, the amount of detergent active material
in the particulate starting material is suitably no more
than 5% by weight thereof and preferably no more than 1% by
weight thereof. The particulate starting material may be
substantially or totally free of any detergent active
material. Suitably, the particulate starting material may
be one prepared by spray-drying. However, starting
materials having the reguired parameters may be obtained by
other means, e.g. involving granulation.
The ds~ average particle diameter of the particulate starting
material is from 100um to 1000um. This is important for
controlling the particle size distribution in the final
product. Preferably though, this average particle diameter
is from 150um to 800um, especially from 200um to 700um.
Preferably, 90o by weight of the particles in the starting
material have a particulate diameter in the region of 100um
to 1000um.
The particle porosity of the particulate starting material
is at least 0.4 but is preferably at least 0.45, e.g. from
0.45 to 0.55. Most preferably it is at least 0.50. In any
event, such particulate starting material may comprise a
spray-dried material, that is to say some or all of the
starting material is formed by a spray-drying process.
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The measurement of particle porosity is based on the well
known Kozeny-Carman relation for air flow through a packed
bed of powder:
evh 1~172bed Dp2 E3bed
=k
OP 4'1'~ ~1-~bed~ 2
In which: ~, - air flow
DP - pressure drop over the bed
Z O Dbea - bed diamet er
h - bed height _
Dp - particle diameter
abed - bed porosity
gas viscosity
I5 k - empirical constant, equal to 180 for
granular solids
The bulk density of a powder can be described by the
following equation:
Bulk Dens ity = rsol ' ( 1 - Ebed ) ' ( 1 - ~particle )
In which: rsol - solids density of the materials in
the particle
t - particle porosity
particle
Based on these equations, the particle porosity can be
derived from the following experiments:
A glass tube with a diameter of I6.3 mm, containing a glass
filter (pore diameter 40-90~1m) as support for the powder, is
filled with a known amount of powder (particle size between
355 and 710~1m). The height of the powder bed is recorded.
An air flow of 375 cm3/min is flowed through the bed of
powder. The pressure drop over the bed is measured. The
pressure drop over the empty tube should also be measured at
the specified air flow.
This measurement is repeated with the same quantity of
powder, but now a more dense bed packing is achieved by
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gentle tapping of the tube containing the powder. Again the
pressure drop is measured at the specified air flow.
In order to be able to derive the particle porosity from
these measurements, also the solids density of the particles
is needed (eq. 2). This is measured using helium
pycnometry, e.g. by using a penta pycnometer supplied by
Quantachrome.
Based on the above described measurements and equations, the
particle porosity can easily be derived.
For the purposes of the present invention, powder flow is
defined in terms of the dynamic flow rate (DFR), in mI/s,
measured by means of the following procedure. The apparatus
used consists of a cylindrical glass tube having an internal
diameter of 35 mm and a length of 600 mm. The tube is
securely clamped in a position such that its longitudinal
axis is vertical. Its lower end is terminated by means of a
smooth cone of polyvinyl chloride having an internal angle
of 15° and a Lower outlet orifice of diameter 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.
To determine the DFR of a powder sample, the outlet orifice
is temporarily closed, for example, by covering with a piece
of card, and powder is poured through a funnel into the top
of the cylinder until the powder level is about 10 cm higher
than the upper sensor; a spacer between the funnel and the
tube ensures that filling is uniform. The outlet is then
opened and the time ~ (seconds) taken for the powder level
to fall from the upper sensor to the lower sensor is
measured electronically. The measurement is normally
repeated two or three times and an average value taken. If
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~1 is t he volume (ml) of the tube between the upper and lower
sensor s, the DFR (ml/s) is given by the following equation:
DFR - V ml/s
t
The averaging and calculation are carried out electronically
and a direct read-out of the DFR value obtained.
The particulate starting material preferably comprises a
builder, most preferably aluminosilicate, for example -
zeolite 4A or zeolite A24 or a salt, preferably an inorganic
salt. Salts, preferably sodium, of phosphates, for example
sodium tripolyphosphate (STP), carbonate, bicarbonate and
sulphate are also suitable.
Other solid materials (if required) may also be incorporated
in the particulate starting material, although they may
alternatively or additionally be dosed at any appropriate
stages) of the mechanical mixing.
The liquid component preferably contains at least one liquid
nonionic surfactant. It may also contain one or more acid
precursors of anionic surfactants and/or fatty acids. The
acid precursors) can then be neutralised to form the
corresponding anionic surfactants) and the fatty acids)
saponified by dosing one or more suitable alkaline materials
at an appropriate stage during the mechanical mixing
process. Suitable alkaline materials include alkali metal
carbonates, e.g. Na_.CO;, and hydroxides, e.g. NaOH. Such
alkaline materials may be dosed in solid form or as aqueous
solutions. It is also possible to partially
neutralise/saponify such precursors or ratty acids in the
liquid component prier to the mecr.~:nical mixi:~g step.
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The detergent composition suitably comprise anionic
detergent active. This may be incorporated as a pre-
neutralised material, desirably as a component of the
particulate starting material, or may be neutralised in
situ. In the latter case the acid precursor of the active
is preferably neutralised using a solid neutralising agent,
for example carbonate, which is desirably a component of the
particulate starting material.
The detergent active material present in the composition may
be selected for anionic, cationic, ampholytic, zwitterionic
or nonionic detergent active materials or mixtures thereof.
Examples of suitable synthetic anionic detergent compounds
are sodium and potassium (C.:-C..") benzene sulphonates,
25 particularly sodium linear secondary alkyl (C1~,-C,5) benzene
sulphonates (LAS); sodium or potassium alkyl sulphates
(PAS); 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 employed include, in
particular the reaction products of compounds having a
hydrophobic group and a reactive hydrogen atom, for example,
aliphatic alcohols, acids, amines or alkyl phenols with
alkylene oxides, especially ethylene oxide either alone or
with propylene oxide. Specific nonionic detergent compounds
are alkyl (C~-C,:) phenol ethylene oxide condensates,
generally having 5 to 25 EO, i.e. 5 to 25 units of ethylene
oxide per molecule, and the condensation products of
aliphatic (Cp-C,~) primary or secondary linear or branched
alcohols with ethylene oxide, generally 5 to 50 EO.
The level of detergent active material present in the
composition may be in the range from 1 to 50~ by weight
depending on the desired applications. Nonionic material
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may be present in particulate starting material at a level
which is less than 10~ by weight more preferably less than
5% by weight and/or employed as the liquid binder in the
mixing process optionally with another liquid component, for
example water.
Suitably the particulate starting material constitutes 30 to
700 of the detergent composition.
Optionally, a layering material may be employed during the
mixing step to control granule formation and reduce or
prevent over-agglomeration. Suitable materials include
aluminosilicates, for example zeolite 4A. The layering
material is suitably present at a level of 1 to 4 wt %.
The composition may be used as a complete composition in its
own right or may be mixed with other components or mixtures
and thus may form a major or minor part of a final product.
The composition may be blended with for example a spray-
dried base powder. Conventional additional components such
as enzymes, bleach and perfume may also be admixed with the
composition as desired to produce a fully formulated
product.
The present invention will now be further illustrated by the
following non-limiting Examples.
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EXAMPLE S
All Examples used the following equipment: A Fukae FS30 for
batch NTR experiment .
Unless stated otherwise herein, all amounts expressed as
percentages are on a weight basis and based on the total
weight of the detergent composition or component prior to
the addition of any post-dosed ingredients.
production of zeolite-NTR powders according to the invention
The following slurries were spray dried to produce powders
of high porosity and low bulk density (BD):
Slurry 1 Slurry 2
(wt~) (wt%)
Zeolite A24 40.0 43.8
LAS 0.0 1.3
Sokalan CP5 10.0 5.0
water 50.0 49.9
The resulting powders had the following properties:
Properties Base Powder 1 Base Powder
2
BD, [g/1] 629 370
DFR, [ml/s] 115 88
dsa [um] 210 279
RRd [um] 242 299
RRn [-] 2.7 2,4
Moisture Content [s] 5-7 7
Particle Porosity 0.51 0.70
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RRd - Rosir_ Rammler diameter
RRn - Rosin Rammler number
Sokalan CP5 is a polyacrylate/polymaleate copolymer.
The sp ray-dried zeolite-based porous carriers were
subsequently used as base powders in NTR processes as
described in Examples 1 and 2.
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Examples 1 & 2
Bath base powders were used in a batch NTR trial on a Fukae.
Formulation Example 1 Example 2 Reference
(wt%) (wto) (wt~)
Base Powder 1 43.4
Base Powder 2 46.4
Zeolite A24 46.4
PAS adjunct 31.9 33.8 33.9
Nonionic 7E0 9.4 10.0 10.0
Nonionic 3E0 6.3 6.6 6.6
Fatty acid 2.5 2.6 2.6
NaOH 0.6 0.7 0.7
Zeolite A24 layering 5.6 0.0 0.0
Premix
Agitator rpm 200
Chopper rpm 3000
Time [sec] 10
Granulation
Agitator rpm 100
Chopper rpm 3000
Time [min] 1-0.5 1 1
Layering [sec] 10
Powder properties
DFR [ml/s] 140 90 55
RRd [um] 492-574 366 1015
RRn 2.6 1.9 1.6
The PAS adjunct used in the trial had the following
composition: PAS 45 wto
Zeolite 38 wt%
Carbonate 9 wto
Water + other components 8 wt%
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Production of ATP-NTR gowder~ according to the invention
The following slurries were spray dried to produce powders
of high porosity and low BD:
Composition Wt~
STP (Rhodiaphos H5) 38.8
LAS 1.1
50~ NaOH soln 0.3
45°s Alkaline silicate soln 12.0
Water 47.9
The resulting powder had the following properties:
Properties
BD [g/lJ 404
DFR [ml/sJ 111
dso [uml
303
RRd (umJ 349
RRn [ - ] 2 . 9
Moisture content [oJ 5.9
Particle porosity 0.67
The spray-dried STP-based carrier was used to formulate
powders in Examples 3 and 4.
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Examples 3 & 4
The STP-based carrier was used in a batch NTR process using
a Fukae FS30 mixer as follows:
Example 3 Example 4 Reference
(kg) (kg)
Standard STP 0 0 4.7
Spray-dried STP carrier 4.7 4.7 0
Sodium carbonate 5.2 5.2 5.2
Zeolite 4A (Wessalith 1.0 1.0 1.0
P)
LAS acid 3.3 3.3 3.3
Zeolite 4A layering 0 0.3 0
Pre-mixing
Pre-mix time (sec.) 10 10 10
RPM (agitator/chopper) 100/3000 100/3000 100/3000
Mixing
RPM (agitator) 100 200 100
RPM (chopper) 3000 3000 3000
Mixing time (sec) 120 120 220
Pow der properties
BD [g/1] 576 688 846
DFR [ml/s] 110 119 132
RRd (um] 486 373 680
RRn [-] 1.72 1.70 1.19
Again the powders produced with porous carriers have a lower
BD and a narrower particle size distribution as indicated by
the higher RRn value.
