Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO92/18602 PCT/US92/02879
2lasl6s
CHEMICAL STRUCTURING OF SURFACTANT PASTES TO FORM HIGH
ACTIVE SURFACTANT GRANULES
FIELD OF THE INVENTION
The present invention relates to a process for preparing
compositions comprising condensed detergent granules.
BACKGROUND OF THE INVENTION
Granular detergent compositions have so far been
principally prepared by spray drying. In the spray drying
process the detergent components, such as surfactants and
builders, are mixed with as much as 35-50% water to form a
slurry. The slurry obtained is heated and spray dried, which
is expensive. A good agglomeration process, however, could
be less expensive.
WOg2/1~02 ~ PCT/US92/02879
21 a~1 6~ 2
Spray drying requires 30-40 wt. % of the water to be
removed. The equipment used to produce spray dry is
expensive. The granule obtained has good solubility but a
low bulk density, so the packing volume is large. Also, the
flow properties of the granule obtained by spray drying are
adversely affected by large surface irregularities, and thus
the granulate has a poor appearance. There are other known
disadvantages in preparing granular detergents by spray
drying.
There are many prior art nonspray-drying processes which
produce detergent granules. They have drawbacks as well.
Most require more than one mixer and a separate granulation
operation. Others require use of the acid form of the
surfactant to work. Some others require high temperatures
which degrade the starting materials. High active surfactant
paste is avoided in these processes because of its
stickiness.
EP-A-0 110 731, published August 13, 1984, discloses
processes for making detergent powders by mixing surfactant
solutions in a neat phase, with builder powders in order to
form a solid without any evaporative drying. Processes for
solid bars or blocks for milling are described, but there is
no teaching of paste conditioning to directly form high
active granules by agglomeration.
EP-A-0 345 090, published December 6, 1989, discloses a
process for manufacturing particulate detergent compositions
comprising contacting detergent acid with neutralizing agents
and providing particulates by contacting the detergent acid
with a particulate neutralizing agent or detergent salt with
carrier in an absorption zone.
EP-A-0 349 201, published January 3, 1990, discloses a
process for preparing condensed detergent granules by finely
dispersing dry detergent builders and a high active
surfactant put into a uniform dough which is subsequently
chilled and granulated using fine dispersion to form uniform,
free flowing granular particles.
WO92/1&~2 2 1 0 8 1 6 5 PCT/US92/02879
EP-0 390 251, published October 3, 1990, discloses a
process for the continuous preparation of a granular
detergent or composition comprising steps of treating,
firstly, particulate starting material of detergent
surfactant and builders in a high-spead mixer, secondly in a
moderate-speed granulator/densifier and thirdly in a
drying/cooling apparatus, with the addition of powder in the
second or between the first and second step to reduce the
amount of oversize particles.
A. Davidsohn and B.M. Mildwidsky, Synthetic Detergents,
John Wiley & Sons 6th edition, 1978, discloses general
detergency teachings, including the manufacturing of finished
detergent products.
High shear and cold mixing processes per se are known,
but they require an extra grinding step or some other action.
E.g., some use a dry neutralization technique of mixing an
acid form of the surfactant with sodium carbonate. See U.S.
Pat. No. 4,515,707, Brooks, issued May 7, 1985; Japanese
laid-open Appln. No. 183540/1983, Kao Soap Co., Ltd., filed
Sept. 30, 1983: and Japanese Sho. 61-118500, Lion K.K., June
5, 1986. Typically, excess carbonate is required (2-20 molar
excess) to assure reasonable conversion of the surfactant
acids. Excess carbonate adversely drives up the wash water
pH to the very alkaline range which can be undesirable,
particularly for some low-phosphate formulas.
The use of a surfactant acid generally requires
immediate use or cool temperature storage, for highly
reactive acids such as the alkyl sulfate acids are subject to
degradation unless cooled, they tend to undergo hydrolysis
during storage, forming free sulfuric acid and alcohol. In
practical terms, such prior art processes require close-
coupling of surfactant acid production with granulation which
requires an additional capital investment.
A second route, well known in the field and described in
the patent literature, is the in-situ neutralisation of the
anionic surfactant acid with caustic solutions (e.g. 50%
WO92/1~02 PCT/US92/02879
21!~'8~L66 4
NaOH) or caustic powders (e.g. Na2CO3) right before or in ~1~e
course of the granulation step. In this situation,
precautions are needed to ensure complete neutralisation of
the acid to avoid undesirable effects on the rest of the
surfactant matrix upon storage/or during the wash. The
resulting particle is a highly dense granule which can be
incorporated into granular detergents.
While this second route uses lower temperatures and less
drastic shear conditions than crutching and spray drying, it
has many limitations. On one side the need to carry out a
chemical reaction (neutralization) during or right before the
granulation step limits considerably the range of processing
conditions that can be used (temperature, chemicals, etc.).
The very low pH of the anionic surfactant acid prevents the
incorporation of chemicals sensitive to these acidic
conditions. But above all, in the case of those anionic
surfactants which are not chemically stable in the acid form
or phy~-cally unstable, this process requires the close
coupling of the sulphation/sulphonation unit with the
neutralization/granulation step. This results in
considerable limitations in the logistics and/or the design
of the facilities for these processes as well as an important
increase in the complexity and difficulty of the control
systems for the overall process.
The present invention brings solutions to the problems
mentioned above and provides with a more flexible and
versatile route to the processing of granular detergents.
The present invention is based on an agglomeration/
granulation step that is completely uncoupled from the
sulphation/sulphonation process. To obtain the greatly
increased surfactant activity of the agglomerates, the
present invention enables the increase in the ratio o~ paste
to powder that can be formed into crisp granules. This is
achieved by a chemical and/or physical structuring of the
paste, such as the addition of specific chemical structuring
agents and/or moisture removal, temperature control. The
basis of the invention is the introduction of the anionic
WO92/1~02 5- 2 1 0 8 ~ PCT/US92/02879
surfactant in an aqueous, highly concentrated solution of
its salt, most preferably of its sodium salt. These high
active (low moisture) surfactant pastes are of a high
viscosity but remain pumpable at temperatures at which the
surfactants are stable. This guarantees the ability to
transport and transfer the chemical from the manufacturing
location to the granulation site and to be able to have
adequate storage facilities prior to the formation of a
particle. For those cases where both the
sulphation/sulphonation is already immediately preceding the
granulation step, it provides the possibility to install
intermediate buffer tanks that simplifies the control of the
whole unit. In the case of some anionic surfactants or
mixtures of them where highly viscous liquid crystal phases
occur, this technology requires that either lower viscous
phases can be formed (e.g. neat phases) or that some
viscosity modifiers are used (e.g. hydrotropes).
The present invention also describes a process for carrying
out the conditioning of the paste. It has been discovered
that the addition of the chemical structuring agents, the
control of temperature and/or the removal of water from the
paste is critical to physical properties such as viscosity,
melting point and stickiness which in turn determine the
characteristics of the detergent granules made by
mixing/granulation of the paste. It has been found that a
very effective way to achieve this paste conditioning is to
use an extruder.
An important object of the present invention is to make
a dense, concentrated detergent granular product by an
agglomeration process as opposed to a spray-drying process.
Other objects of the present invention will be apparent in
view of the following.
2 ~ 0 8 ~ 6 6
SUMMARY OF THE INVENTION
The present invention relates to an economical process
for making a dense, concentrated detergent granular product,
and particularly, compositions comprising very high active
condensed detergent granules, wherein said process comprises
high active paste agglomeration steps coupled with chemical
treatment of the resultant paste.
The present invention relates to a process for making a
concentrated granular detergent composition comprising the
processing stages of: (i) neutralising anionic surfactant acid
or acids in an excess of alkali to form a high active (at
least 40% by weight of anionic surfactant) paste, said paste
having a viscosity of at least 1-Pa.s when measured at 70~C
and a shear rate of 25 s-1; (ii) maintaining said paste without
further processing; (iii) conditioning said paste by raising
the apparent viscosity of said paste at said temperature and
said shear rate; and (iv) forming high active detergent
granules in a high shear mixer/granulator in the presence of
an effective amount of detergent powder.
Any other surfactants, if present, are selected from the
group of anionic, nonionic, zwitterionic, ampholytic and
cationic surfactants and mixtures thereof. In a preferred
process said chemical structuring agent is added in a
continuous proces~.
The present invention is based on a process for producing
high active surfactant pastes, having an
agglomeration/granulation step that is completely uncoupled
from the sulphation/sulphonation process, and, additionally, a
chemical conditioning of the pastes produced by said process
to obtain high active granules. Conditioning of a paste means
the modifying its physical characteristics to form
~B
WO92/1~02 PCT/US92/02879
7 21~8~16S
higher active agglomerates which otherwise are not easily
obtainable under normal operating conditions. The present
invention is particularly applicable to all neutralized AS
aqueous pastes. It may prove applicable to a wide variety of
surfactants (e.g. Coco, Tallow, ... etc). In one embodiment
of the present invention, the introduction of the anionic
surfactant in an aqueous, highly concentrated solution of
its salt, preferably its sodium salt. These high active
(and, preferably, low moisture) surfactant pastes are of a
high viscosity but remain pumpable at temperatures at which
the surfactants are stable. In other embodiments of the
present invention, anionic surfactants or mixtures comprising
at least one anionic surfactant, where highly viscous liquid
crystal phases occur, requires that either lower viscous
phases be formed or that some viscosity modifiers are used.
On a more preferred embodiment organic and/or inorganic
compounds that alters the physical structure and/or physical
characteristics of the surfactant paste are added to the
paste. It has been found that the addition to the surfactant
paste reduces the stickiness of the paste, increases its
viscosity and increases its softening point. This allows for
more paste to be added during the agglomeration process thus
leading to higher active agglomerates i.e. more than 50%.
This method of treating the surfactant paste can be performed
batchwise and continuous, preferably continuously.
In a preferred embodiment of the invention an extruder
is used to condition the paste. The extruder is a versatile
piece of equipment which enables two or more pastes to be
mixed and/or the chemical structuring agents to be added to,
and mixed with the viscous paste. Furthermore it enables
moisture to be removed under vacuum, and it enables control
of paste temperature.
Conditioning of the paste, as defined herein, means: a)
increasing its apparent viscosity, b) increasing its
effective melting point, c) increasing the "hardness" of the
paste and d) decreasing the stickiness of the granules
formed. The hardness/softness of the paste may be measured by
a softness penetrometer according to ASTM D 217-IP50 or ISO
WO92/1~02 PCT/US92/02879
2I 081 6~ 8
2137. Paste hardness measured in this way should be less th~an
2 cm, preferably less than 1 cm.
This paste conditioning may be achieved by i) cooling,
ii)drying, iii) adding of structurants (usually electolytes)
to the high active detergent paste. A paste useful for this
invention will consist of at least 40% by weight of salts of
anionic surfactants, which has a viscosity of at least 10
Pa.s when measured at 70~C and a shear rate of 25s~1.
The Chemical Structuring Agents
Various chemical structuring agents, when added to the
surfactant paste, result in a modification of the chemical
and/or physical characteristics of the paste to form very
high active agglomerates. These agents may be in a solid,
liquid or solution form, depending on their specific chemical
properties. Examples of agents useful in the present
invention include 50% NaOH (aq), 50% KOH (aq), NaCl,
phosphonate, silicate, silica, starch, polymers and
copolymers, nonionic surfactant and urea. The agents above
can be used independently or in combination with each other,
in accordance with their compatability.
The Pastes
One or various aqueous pastes of the salts of anionic
surfactants is preferred for use in the present invention,
preferably the sodium salt of the anionic surfactant. In a
preferred embodiment, the anionic surfactant is preferably as
concentrated as possible, (that is, with the lowest possible
moisture content that allows it to flow in the manner of a
liquid) so that it can be pumped at temperatures at which it
remains stable. While granulation using various pure or
mixed surfactants is known, for the present invention to ~e
of practical use in industry and to result in particles of
adequate physical properties to be incorporated into granular
detergents, an anionic surfac~ant must be part of the paste
in a concentration of above 10%, preferably from 10-95%, more
preferably from 20-95%, and most preferably from 40%-95%.
W O 92/18602 PC~r/US92/02879
9 . '21 ~81 6 r~
.
It is preferred that the moisture in the surfactant
aqueous paste is as low as possible, while maintaining paste
fluidity, since low moisture leads to a higher concentration
of the surfactant in the finished particle. Preferably the
paste contains between 5 and 40% water, more preferably
between 5 and 30% water and most preferably between 5% and
20% water. A highly attractive mode of operation for
lowering the moisture of the paste prior to entering the
agglomerator without problems with very high viscosities is
the installation, in line, of an atmospheric or a vacuum
flash drier whose outlet is connected to the agglomerator.
It is preferable to use high active surfactant pastes to
minimize the total water level in the system during mixing,
granulating and drying. Lower water levels allow for: (1) a
higher active surfactant to builder ratio, e.g., 1:1; (2)
higher levels of other liquids in the formula without causing
dough or granular stickiness; (3) less cooling, due to higher
allowable granulation temperatures; and (4) less granular
drying to meet final moisture limits.
Two important parameters of the surfactant pastes which
can affect the mixing and granulation step are the paste
temperature and viscosity. Viscosity is a function, among
others, of concentration and temperature, with a range in
this application from about 10,000 cps to 10,000,000 cps.
Preferably, the viscosity of the paste entering the system is
from about 20,000 to about 100,000 cps. and more preferably
from about 30,000 to about 70,000 cps. The viscosity of the
paste of this invention is measured at a temperature of 70~C.
The paste can be introduced into the mixer at an initial
temperature between its softening point (generally in the
range of 40-60~C) and its degradation point (depending on the
chemical nature of the paste, e.g. alkyl sulphate pastes tend
to degrade above 75-85~C). High temperatures reduce
viscosity simplifying the pumping of the paste but result in
lower active agglomerates. The use of in-line moisture
-
WO92/1~02 PCT/US92/02879
210~166 10
reduction steps (e.g. flash drying), however, require the use
of higher temperatures (above 100~C). In the present
invention, the activity of the agglomerates is maintained
high due to the elimination of moisture.
The introduction of the paste into the mixer can be done
in many ways, from simply pouring to high pressure pumping
through small holes at the end of the pipe, before the
entrance to the mixer. While all these ways are viable to
manufacture agglomerates with good physical properties, it
has been found that in a preferred embodiment of the present
invention the extrusion of the paste results in a better
distribution in the mixer which improves the yield of
particles with the desired size. The use of high pumping
pressures prior to the entrance in the mixer results in an
increased activity in the final agglomerates. By combining
both effects, and introducing the paste through holes
(extrusion) small enough to allow the desired flow rate but
that kecp the pumping pressure to a maximum feasible in the
system, highly advantageous results are achieved.
Hiqh Active Surfactant Paste
The activity of the aqueous surfactant paste is at least
30% and can go up to about 95%; preferred activities are :
50-80% and 65-75%. The balance of the paste is primarily
water but can include a processing aid such as a nonionic
surfactant. At the higher active concentrations, little or
no builder is required for cold granulation of the paste.
The resultant concentrated surfactant granules can be added
to dry builders or powders or used in conventional
agglomeration operations. The aqueous surfactant paste
contains an organic surfactant selected from the group
consisting of anionic, zwitterionic, ampholytic and cationic
surfactants, and mixtures thereof. Anionic surfactants are
preferred. Nonionic surfactants are used as secondary
surfactants or processing aids and are not included herein as
an "active" surfactant. Surfactants useful herein are listed
in U.S. Pat. No. 3,664,961, Norris, issued May 23, 1972, and
W092/18602 i 2 1 0 8 1 6 S PCT/US92/02879
11 ~
in U.S. Pat. No. 3,919,678, Laughlin et al., issued Dec. 30,
1975. Useful cationic surfactants also include those
described in U.S. Pat. No. 4,222,905, Cockrell, issued Sept.
16, 1980, and in U.S. Pat. 4,239,659, Murphy, issued Dec. 16,
1980. However, cationic surfactants are generally less
compatible with the aluminosilicate materials herein, and
thus are preferably used at low levels, if at all, in the
present compositions. The following are representative
examples of surfactants useful in the present compositions.
Water-soluble salts of the higher fatty acids, i.e.,
"soaps", are useful anionic surfactants in the compositions
herein. This includes alkali metal soaps such as the sodium,
potassium, ammonium, and alkylammonium saits of higher fatty
acids containing from about 8 to about 24 carbon atoms, and
preferably from about 12 to about 18 carbon atoms. Soaps can
be made by direct saponification of fats and oils or by the
neutralization of free fatty acids. Particularly useful are
the sodium and potassium salts of the mixtures of fatty acids
derived from coconut oil and tallow, i.e., sodium or
potassium tallow and coconut soap.
Useful anionic surfactants also include the water-
soluble salts, preferably the alkali metal, ammonium and
alkylolammonium salts, of organic sulfuric reaction products
having in their molecular structure an alkyl group containing
from about 10 to about 20 carbon atoms and a sulfonic acid or
sulfuric acid ester group. (Included in the term "alkyl" is
the alkyl portion of acyl groups.) Examples of this group of
synthetic surfactants are the sodium and potassium alkyl
sulfates, especially those obtained by sulfating the higher
alcohols (C8-C18 carbon atoms) such as those produced by
reducing the glycerides of tallow or coconut oil; and the
sodium and potassium alkyl benzene sulfonates in which the
alkyl group contains from about 9 to about 15 carbon atoms,
in straight or branched chain configuration, e.g., those of
the type described in U.S. Pat. Nos. 2,220,099 and 2,477,383.
Especially valuable are linear straight chain alkyl benzene
sulfonates in which the average number of carbon atoms in the
WO92/1~02 PCT/US92/02879
21~8166 12
alkyl group is from about 11 to 13, abbreviated as Cll-C13
-LAS.
Other anionic surfactants herein are the sodium alkyl
glyceryl ether sulfonates, especially those ethers of higher
alcohols derived from tallow and coconut oil; sodium coconut
oil fatty acid monoglyceride sulfonates and sulfates; sodium
or potassium salts of alkyl phenol ethylene oxide ether
sulfates containing from about 1 to about 10 units of
ethylene oxide per molecule and wherein the alkyl groups
contain from about 8 to about 12 carbon atoms; and sodium or
potassium salts of alkyl ethylene oxide ether sulfates
containing from about 1 to about 10 units of ethylene oxide
per molecule and wherein the alkyl group contains from about
10 to about 20 carbon atoms.
Other useful anionic surfactants herein include the
water-soluble salts of esters of alpha-sulfonated fatty acids
containing from about 6 to 20 carbon atoms in the fatty acid
group and from about 1 to 10 carbon atoms in the ester group;
water-soluble salts of 2-acyloxy-alkane-1-sulfonic acids
containing from about 2 to 9 carbon atoms in the acyl group
and from about 9 to about 23 carbon atoms in the alkane
moiety; alkyl ether sulfates containing from about 10 to 20
carbon atoms in the alkyl group and from about 1 to 30 moles
of ethylene oxide; watersoluble salts of olefin sulfonates
containing from about 12 to 24 carbon atoms; and beta-
alkyloxy alkane sulfonates containing from about 1 to 3
carbon atoms in the alkyl group and from about 8 to about 20
carbon atoms in the alkane moiety. Although the acid salts
are typically discussed and used, the acid neutralization cam
be performed as part of the fine dispersion mixing step.
The preferred anionic surfactant pastes are mixtures of
linear or branched alkylbenzene sulfonates having an alkyl of
10-16 carbon atoms and alkyl sulfates having an alkyl of 10-
18 carbon atoms. These pastes are usually produced by
reacting a liquid organic material with sulfur trioxide to
produce a sulfonic or sulfuric acid and then neutralizing the
WO92/1~02 PCT/US92/02879
2 1 ~ ~ 1 6 ~ 13
acid to produce a salt of that acid. The salt is the
surfactant paste discussed throughout this document. The
sodium salt is preferred due to end performance benefits and
cost of NaOH vs. other neutralizing agents, but is not
required as other agents such as KOH may be used.
Water-soluble nonionic surfactants are also useful as
secondary surfactant in the compositions of the invention.
Indeed, preferred processes use anionic/nonionic blends. A
particularly preferred paste comprises a blend of nonionic
and anionic surfactants having a ratio of from about 0.0l:l
to about l:l, more preferably about 0.05:l. Nonionics can be
used up to an equal amount of the primary organic surfactant.
Such nonionic materials include compounds produced by the
condensation of alkylene oxide groups (hydrophilic in nature)
with an organic hydrophobic compound, which may be aliphatic
or alkyl aromatic in nature. The length of the
polyoxyalkylene group which is condensed with any particular
hydrophobic group can be readily adjusted to yield a water-
soluble compound having the desired degree of balance between
hydrophilic and hydrophobic elements.
Suitable nonionic surfactants include the polyethylene
oxide condensates of alkyl phenols, e.g., the condensation
products of alkyl phenols having an alkyl group containing
from about 6 to 16 carbon atoms, in either a straight chain
or branched chain configuration, with from about 4 to 25
moles of ethylene oxide per mole of alkyl phenol.
Preferred nonionics are the water-soluble condensation
products of aliphatic alcohols containing from 8 to 22 carbon
atoms, in either straight chain or branched configuration,
with from 4 to 25 moles of ethylene oxide per more of
alcohol. Particularly preferred are the condensation
products of alcohols having an alkyl group containing from
about 9 to 15 carbon atoms with from about 4 to 25 moles of
ethylene oxide per mole of alcohol: and condensation products
of propylene glycol with ethylene oxide.
92/18602 ~0 816 G 14 PCT/US92/02879
Semi-polar nonionic surfactants include water-soluble
amine oxides containing one alkyl moiety of from about 10 to
18 car~on atoms and 2 moieties selected from the group
consisting of alkyl groups and hydroxyalkyl groups containing
from 1 to about 3 carbon atoms; water-soluble phosphine
oxides containing one alkyl moiety of about 10 to 18 carbon
atoms and 2 moieties selected from the group consisting of
alkyl groups and hydroxyalkyl groups containing from about 1
to 3 carbon atoms; and water-soluble sulfoxides containing
one alkyl moiety of from about 10 to 18 carbon atoms and a
moiety selected from the group consisting of alkyl and
hydroxyalkyl moieties of from about 1 to 3 carbon atoms.
Ampholytic surfactants include derivatives of aliphatic
or aliphatic derivatives of heterocyclic secondary and
tertiary amines in which the aliphatic moiety can be either
straight or branched chain and wherein one of the aliphatic
substituents contains fr~n about 8 to 18 carbon atoms and at
least one aliphatic substituent contains an anionic water-
solubilizing group.
Zwitterionic surfactants include derivatives of
aliphatic quaternary ammonium phosphonium, and sulfonium
compounds in which one of the aliphatic substituents contains
from about 8 to 18 carbon atoms.
Particularly preferred surfactar~-- herein include linear
alkylbenzene sulfonates containing from about 11 to 14 carbon
atoms in the alkyl group: tallow alkyl sulfates; coconutalkyl
glyceryl ether sulfonates; alkyl ether sulfates wherein the
alkyl moiety contains from about 14 to 18 carbon atoms and
wherein the average degree of ethoxylation is from about 1 to
4; olefin or paraffin sulfonates containing from about 14 to
16 carbon atoms; alkyldimethylamine oxides wherein the alkyl
group contains from about 11 to 16 carbon atoms;
alkyldimethylammonio propane sulfonates and
alkyldimethylammonio hydroxy propane sulfonates wherein the
alkyl group contains from about 14 to 18 carbon atoms; soaps
of higher fat~v acids containing from about 12 to 18 carbon
WO92/1~02 ~2 1 0 8 1 6 6
atoms; condensation products of C9-C15 alcohols with from
about 3 to 8 moles of ethylene oxide, and mixtures thereof.
Useful cationic surfactants include. Useful cationic
surfactants include water-soluble quaternary ammonium
compounds of the form R4R5R6R7N+X-, wherein R4 is alkyl
having from 10 to 20, preferably from 12-18 carbon atoms, and
R5, R6 and R7 are each Cl to C7 alkyl preferably methyl; X~
is an anion, e.g. chloride. Examples of such trimethyl
ammonium compounds include C12_14 alkyl trimethyl ammonium
chloride and cocalkyl trimethyl ammonium methosulfate.
Specific preferred surfactants for use herein include:
sodium linear Cll-C13 alkylbenzene sulfonate; ~-olefin
sulphonates; triethanolammonium Cll-C13 alkylbenzene
sulfonate; alkyl sulfates, (tallow, coconut, palm, synthetic
origins, e.g. C45, etc.); sodium alkyl sulfates; MES; sodium
coconut alkyl glyceryl ether sulfonate; the sodium salt of a
sulfated condensation product of a tallow alcohol with about
4 moles of ethylene oxide; the condensation product of a
coconut fatty alcohol with about 6 moles of ethylene oxide;
the condensation product of tallow fatty alcohol with about
11 moles of ethylene oxide; the condensation of a fatty
alcohol containing from about 14 to about 15 carbon atoms
with about 7 moles of ethylene oxide; the condensation
product of a C12-C13 fatty alcohol with about 3 moles of
ethylene oxide; 3-(N,N-dimethyl-N-coconutalkylammonio)-2-
hydroxypropane-l-sulfonate; 3-(N,N-dimethyl-N-
coconutalkylammonio)-propane-1-sulfonate; 6- (N-
dodecylbenzyl-N,N-dimethylammonio) hexanoate;
dodecyldimethylamine oxide; coconutalkyldimethylamine oxide;
and the water-soluble sodium and potassium salts of coconut
and tallow fatty acids.
(As used herein, the term "surfactant" means non-
nonionic surfactants, unless otherwise specified. The ratio
of the surfactant active (excluding the nonionic(s)) to dry
detergent builder or powder ranges from 0.005 to 19:1,
preferably from 0.05 to 10:1, and more preferably from 0.1:1
WO92/18602 PCT/US92/02879
21081~6 16
to 5:1. Even more preferred said surfactant active to
builder ratios are 0.15:1 to 1:1; and 0.2:1 to 0.5:1).
The Extruder
The extruder fulfils the functions of pumping and mixing the
viscous surfactant paste on a continuous basis. A basic
extruder consists of a barrel with a smooth inner cylindrical
surface. Mounted within this barrel is the extruder screw.
There is an inlet port for the high active paste which, when
the screw is rotated, causes the paste to be moved along the
length of the barrel.
The detailed design of the extruder allows various functions
to be carried out. Firstly additional ports in the barrel may
allow other ingredients, including the chemical structuring
agents to be added directly into the barrel. Secondly a
vacuum pump and a seal around the shaft of the screw allows a
vacuum to be drawn which enables the moisture level to be
reduced. Thirdly means for heating or cooling may be
installed in the wall of the barrel for temperature control.
Fourthly, careful design of the extruder screw promotes
mixing of the paste both with itself and with other
additives.
A preferred extruder is the twin screw extruder. Thi~ type of
extruder has two screws mounted in parallel within tne same
barrel, which are made to rotate either in the same direction
(co-rotation) or in opposite directions (counter-rotation).
The co-rotating twin screw extruder is the most preferred
piece of equipment for use in this invention.
An extruder is particularly useful in this invention because
the paste can be effectively cooled by adding liquid nitrogen
or solid carbon dioxide into the barrel (this may be
considered surprising, because normally an extruder heats its
contents as a result of the mechanical energy input to
overcome viscous shear forces) and at the same time p mps the
increasingly viscous (colder) paste out of the extruder and
into the mixer/agglomerator were granulation takes place.
WO92/1~02 PCT/US92/02879
17' ~2iO81B~
Suitable twin screw extruders for use in the present
invention include those supplied by : APV Baker, (CP series);
Werner and Pfleiderer, (Continua Series); Wenger, (TF
Series); Leistritz, (ZSE Series); and Buss, (LR Series).
The extruder allows the paste to be conditioned by
moisture and temperature reduction. Moisture may be removed
under vacuum, preferably between O mmHg (gauge) and -55 mmHg
(gauge), (o - 7.3 kPa below atmospheric pressure).
Temperature may be reduced by the addition of solid
carbon dioxide or liquid nitrogen directly into the extruder
barrel. Preferably liquid nitrogen is used at up to 30~ by
weight of the paste.
Powder stream
Although the preferred embodiment of the process of the
present invention involves introduction of the anionic
surfactant in via pastes as described above, it is possible
to have a certain amount via the powder stream, for example
in the form of blown powder. In these embodiments, it is
necessary that the stickiness and moisture of the powder
stream be kept at low levels, thus preventing increased
"loading" of the anionic surfactant and, thus, the production
of agglomerates with too high of a concentration of
surfactant. The liquid stream of a preferred agglomeration
process can also be used to introduce other surfactants
and/or polymers. This can be done by premixing the
surfactant into one liquid stream or, alternatively by
introducing various streams in the agglomerator. These two
process embodiments may produce differences in the properties
of the finished particles (dispensing, gelling, rate of
dissolution, etc.), particularly, if mixed surfactants are
allowed to form prior to particle formation. These
differences can then be exploited to the advantage of the
intended application for each preferred process.
WO92/18602 2 1 0 8 i ~ ~ 18 PCT/US92/02879
It has also been observed that by using the presently
described technology, it has been possible to incorporate
higher levels of certain chemicals (e.g. nonionic, citric
acid) in the final formula than via any other known
processing route without detrimental effects to some key
properties of the matrix (caking, compression, etc.).
The Fine Dispersion Mixinq and Granulation
The term "fine dispersion mixing and/or granulation," as
used herein, means mixing and/or granulation of the above
mixture in a fine dispersion mixer at a blade tip speed of
from about 5m/sec. to about 50 m/sec., unless otherwise
specified. The total residence time of the mixing and
granulation process is preferably in the order of from 0.1 to
10 minutes, more preferably 0.1-5 and most preferably 0.2-4
minutes. The more preferred mixing and granulation tip
speeds are about 10-45 m/sec. and about 15-40 m/sec.
The ratio of paste to powder should be chosen in order to
maintain visible, discrete particles at all stages of the
process. These particles may be sticky at higher temperatures
but must be substantially free flowing so that the mixing and
granulation steps can be carried out simultaneously, or
immediately sequentially without causing blockage of the
mixer/granulator.
Any apparatus, plants or units suitable for the
processing of surfactants can be used for carrying out the
process according to the invention. Suitable apparatus
includes, for example, falling film sulphonating reactors,
digestion tanks, esterification reactors, etc. For mixing/
agglomeration any of a number of mixers/agglomerators can be
used. In one preferred embodiment, the process of the
invention is continuously carried out. Especially preferred
are mixers of the FukaeR FS-G series manufactured by Fukae
Powtech Kogyo Co., Japan; this apparatus is essentially in
the form of a bowl-shaped vessel accessible via a top port,
provided near its base with a stirrer having a substantially
W O 92/18602 2 i O g 1 6 ~ PC~r/US92/02879
19
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. The vessel can be
fitted with a cooling jacket or, if necessary, a cryogenic
unit.
Other similar mixers found to be suitable for use in the
process of the invention inlcude DiosnaR V series ex Dierks &
Sohne, Germany; and the Pharma MatrixR ex T K Fielder Ltd.,
England. Other mixers believed to be suitable for use in the
process of the invention are the FujiR VG-C series ex Fuji
Sangyo Co., Japan; and the RotoR ex Zanchetta & Co srl,
Italy.
Other preferred suitable equipment can include EirichR,
series RV, manufactured by Gustau Eirich Hardheim, Germany;
LodigeR, series FM for batch mixing, series Baud KM for
continuous mixing/agglomeration, manufactured by Lodige
Machinenbau GmbH, Paderborn Germany; DraisR T160 series,
manufactured by Drais Werke GmbH, Mannheim Germany; and
WinkworthR RT 25 series, manufactured by Winkworth Machinery
Ltd., Bershire, England.
The Littleford Mixer, Model #FM-130-D-12, with internal
chopping blades and the Cuisinart Food Processor, Model #DCX-
Plus, with 7.75 inch (19.7 cm) blades are two examples of
suitable mixers. Any other mixer with fine dispersion mixing
and granulation capability and having a residence time in the
order of 0.1 to 10 minutes can be used. The "turbine-type"
impeller mixer, having several blades on an axis of rotation,
is preferred. The invention can be practiced as a batch or a
continuous process.
Operatinq Temperatures
Preferred operating temperatures should also be as low
as possible since this leads to a higher surfactant
WO92/1~02 210 81~ ~ PCT/US92/02879
concentration in the finished particle. Preferably the
temperature during the agglomeration is less than lO0~C, more
preferably between lO and 90~C, and most preferably between
20 and 80~C. Lower operating temperatures useful in the
process of the present invention may be achieved by a variety
of methods known in the art such as nitrogen cooling, cool
water jacketing of the equipment, addition of solid CO2, and
the like; with a preferred method being solid CO2, and the
most preferred method being nitrogen cooling.
A highly attractive option in a preferred embodiment of
the present invention to further increase the concentration
of surfactant in the final particle, is accomplished by the
addition to a liquid stream containing the anionic surfactant
and/or other surfactant, of other elements that result in
increases in viscosity and/or melting point and/or decrease
the stickiness of the paste. In a preferred embodiment of
the process of the present invention the addition of these
element_ an be done in line as the paste is pumped into the
agglomerator. Example of these elements can be various
powders, described in more detail herein.
Final Agqlomerate Composition
The present invention produces granules of high density
for use in detergent compositions. A preferred composition
of the final agglomerate for incorporation into granular
detergents has a high surfactant concentration. By
increasing the concentration of surfactant, the
particles/agglomerates made by the present invention are more
suitable for a variety of different formulations. These high
surfactants containing particle agglomerates require fewer
finishing techniques to reach the final agglomerates, thus
freeing up large amounts of processing aids (inorganic
powders, etc.) that can be used in other processing steps of
the overall detergent manufacturing process (spray drying,
dusting off, etc).
WO92/18602 2 1 0 8 1 6 S
The granules made according to the present invention are
large, low dust and free flowing, and preferably have a bulk
density of from about 0.4 to about 1.2 g/cc, more preferably
from about 0.6 to about 0.8 g/cc. The weight average
particle size of the particles of this invention are from
about 200 to about 1000 microns. The preferred granules so
formed have a particle size range of from 200 to 2000
microns. The more preferred granulation temperatures range
from about 10~C to about 60~C, and most preferably from about
20~C to about 50~C.
DrYinq
The desired moisture content of the free flowing granules of
this invention can be adjusted to levels adequate for the
intended application by drying in conventional powder drying
equipment such as fluid bed dryers. If a hot air fluid bed
dryer is used, care must be exercised to avoid degradation of
heat sensitive components of the granules. It is also
advantageous to have a cooling step prior to large scale
storage. This step can also be done in a conventional fluid
bed operated with cool air. The drying/cooling of the
agglomerates can also be done in any other equipment suitable
for powder drying such as rotary dryers, etc.
For detergent applications, the final moisture of the
agglomerates needs to be maintained below levels at which the
agglomerates can be stored and transported in bulk. The
exact moisture level depends on the composition of the
agglomerate but is typically achieved at levels of 1-8% free
water (i.e. water not associated to any crystalline species
in the agglomerate) and most typically at 2-4%.
Deterqency Builders and Powders
Any compatible detergency builder or combination of
builders or powder can be used in the process and
compositions of the present invention.
WO92/1~02 PCT/US92/02879
~I~'816~ 22
The detergent compositions herein can contain
crystalline aluminosilicate ion exchange material of the
formula
NaZ[(A102)Z (SiO2)y]-XH20
wherein z and y are at least about 6, the molar ratio of z to
y is from about 1.0 to about 0.4 and z is from about 10 to
about 264. Amorphous hydrated aluminosilicate materials
useful herein have the empirical formula
MZ(zAlo2 YSiO2)
wherein M is sodium, potassium, ammonium or substituted
ammonium, z is from about 0.5 to about 2 and y is 1, said
material having a magnesium ion exchange capacity of at least
about 50 milligram equivalents of CaC03 hardness per gram of
anhydrous aluminosilicate. Hydrated sodium Zeolite A with a
particle size of from about 1 to 10 microns is preferred.
The aluminosil :~te ion exchange builder materials
herein are in hydra~ed form and contain from about 10% to
about 28% of water by weight if crystalline, and potentially
even higher amounts of water if amorphous. Highly preferred
crystalline aluminosilicate ion exchange materials contain
from about 18% to about 22% water in their crystal matrix.
The crystalline aluminosilicate ion exchange materials are
further characterized by a particle size diameter of from
about 0.1 micron to about 10 microns. Amorphous materials
are often smaller, e.g., down to less than about 0.01 micron.
Preferred ion exchange materials have a particle size
diameter of from about 0.2 micron to about 4 microns. The
term "particle size diameter" herein represents the average
particle size diameter by weight of a given ion exchange
material as determined by conventional analytical techniques
such as, for example, microscopic determination utilizing a
scanning electron microscope. The crystalline
aluminosilicate ion exchange materials herein are usually
further characterized by their calcium ion exchange capacity,
which is at least about 200 mg equivalent of CaCO3 water
hardness/g of aluminosilicate, calculated on an anhydrous
basis, and which generally is in the range of from about 300
mg eq./g to about 352 mg eq./g. The aluminosilicate ion
8 1 0 8 ~ 6 6
- 23
exchange materials herein are still further characterized by
their calcium ion exchange rate which is at least about 2
grains Ca+~/gallon/minute/gram/gallon of aluminosilicate
(anhydrous basis), and generally lies within the range of from
about 2 grains/gallon/minute/gram/gallon to about 6
grains/gallon/minute/gram/gallon, based on calcium ion
hardness. Optimum aluminosilicate for builder purposes
exhibit a calcium ion exchange rate of at least about 4
grains/gallon/minute/gram/gallon.
The amorphous aluminosilicate ion exchange materials
usually have a Mg+t exchange of at least about 50 mg eq. CaCO3/g
(12 mg Mg~'/g) and a Mg~' exchange rate of at least about 1
grain/gallon/minute/gram/gallon. Amorphous materials do not
exhibit an observable diffraction pattern when examined by Cu
radiation (1.54 Angstrom Units).
Aluminosilicate ion exchange materials useful in the
practice of this invention are commercially available. The
aluminosilicates useful in this invention can be crystalline
or amorphous in structure and can be naturally occurring
aluminosilicates or synthetically derived. A method for
producing aluminosilicate ion exchange materials is discussed
in U.S. Patent No. 3,985,669, Krummel et al., issued Oct. 12.
1976. Preferred synthetic crystalline aluminosilicate ion
exchange materials useful herein are available under the
designations Zeolite A, Zeolite B, and Zeolite X. In an
especially preferred embodiment, the crystalline
aluminosilicate ion exchange material has the formula
Nal2 [ (Al02) 12 (si~2) 12] ~ XH2~
wherein x is from about 20 to about 30, especially about 27
and has a particle size generally less than about 5 microns.
The granular detergents of the present invention can
contain neutral or alkaline salts which have a pH in solution
of seven or greater, and can be either organic or inorganic in
nature. The builder salt assists in providing the desired
density and bulk to the detergent granules herein. While
. ~
1.~,
Z~Q8~ 66
_ 24
some of the salts are inert, many of them also function as
detergency builder materials in the laundering solution.
Examples of neutral water-soluble salts include the
alkali metal, ammonium or substituted ammonium chlorides,
fluorides and sulfates. The alkali metal, and especially
sodium, salts of the above are preferred. Sodium sulfate is
typically used in detergent granules and is a particularly
preferred salt. Citric acid and, in general, any other
organic or inorganic acid may be incorporated into the
granular detergents of the present invention as long as it is
chemically compatible with the rest of the agglomerate
composition.
Other useful water-soluble salts include the compounds
commonly known as detergent builder materials. Builders are
generally selected from the various water-soluble, alkali
metal, ammonium or substituted ammonium phosphates,
polyphosphates, phosphonates, polyphosphonates, carbonates,
silicates, borates, and polyhydroxysulfonates. Preferred are
the alkali metal, especially sodium, salts of the above.
Specific examples of inorganic phosphate builders are
sodium and potassium tripolyphosphate, pyrophosphate,
polymeric metaphosphate having a degree of polymerization of
from about 6 to 21, and orthophosphate. Examples of
polyphosphonate builders are the sodium and potassium salts of
ethylene diphosphonic acid, the sodium and potassium salts of
ethane 1-hydroxy-1,1-diphosphonic acid and the sodium and
potassium salts of ethane, 1,1,2-triphosphonic acid. Other
phosphorus builder compounds are disclosed in U.S. Patent Nos.
3,159,581; 3,213,030; 3,422,021; 3,422,137; 3,400,176 and
3,400,148.
Examples of nonphosphorus, inorganic builders are sodium
and potassium carbonate, bicarbonate, ses~uicarbonate,
tetraborate decahydrate, and silicate having a molar ratio of
SiO2 to alkali metal oxide of from about 0.5 to about 4.0,
preferably from about 1.0 to about 2.4. The compositions
. ~
~.,
WO92/1~02 PCT/US92/0287~
2~ 210816~
' 1 , ; .
made by the process of the present invention does not require
excess carbonate for processing, and preferably does not
contain over 2% finely divided calcium carbonate as disclosed
in U.S. Pat. No. 4,196,093, Clarke et al., issued Apr.l,
1980, and is preferably free of the latter.
As mentioned above powders normally used in detergents
such as zeolite, carbonate, silica, silicate, citrate,
phosphate, perborate, etc. and process acids such as starch,
can be used in preferred embodiments of the present
invention.
Polymers
Also useful are various organic polymers, some of which
also may function as builders to improve detergency.
Included among such polymers may be mentioned sodium carboxy-
lower alkyl celluloses, sodium lower alkyl celluloses and
sodium hydroxy-lower alkyl celluloses, such as sodium
carboxymethyl cellulose, sodium methyl cellulose and sodium
hydroxypropyl cellulose, polyvinyl alcohols (which often also
include some polyvinyl acetate), polyacrylamides,
polyacrylates and various copolymers, such as those of maleic
and acrylic acids. Molecular weights for such polymers vary
widely but most are within the range of 2,000 to 100,000.
Polymeric polycarboxyate builders are set forth in U.S.
Patent 3,308,067, Diehl, issued March 7, 1967. Such
materials include the water-soluble salts of homo-and
copolymers of aliphatic carboxylic acids such as maleic acid,
itaconic acid, mesaconic acid, fumaric acid, aconitic acid,
citraconic acid and methylenemalonic acid.
optionals
Other ingredients commonly used in detergent
compositions can be included in the compositions of the
present invention. These include flow aids, color speckles,
bleaching agents and bleach activators, suds boosters or suds
WO92/1~02 PCT/US92/02879
21081~S 26
suppressors, antitarnish and anticorrosion agents, soil
suspending agents, soil release agents, dyes, fillers,
optical brighteners, germicides, pH adjusting agents,
nonbuilder alkalinity sources, hydrotropes, enzymes, enzyme-
stabilizing agents, chelating agents and perfumes.
The detergent granules of the present invention are
particularly useful in a pouched through-the-wash product.
Materials like sodium perborate tetrahydrate and monohydrate
can be included as part of the granular detergent
compositions of this invention. Pouched through-the-wash
products are disclosed in the art, e.g., those disclosed in
commonly assigned U.S. Pat. No. 4,740,326, Hortel et al.,
issued April 26, 1988. Another useful pouch has at least one
of its walls constructed of a finely apertured polymeric
film. The terms "LAS" and "AS" as used herein mean,
respectively, "sodium lauryl benzene sulfonate" and "alkyl
sulfate." "MES" means sodium methyl ester sulphonate. The
terms like "C45" mean Cl4 and Cl5 alkyl, llnl ~ss otherwise
specified. TAS means Tallow alkyl sulphate.
The invention will be better understood in view of the
following nonlimiting examples. The percentages are on a
before drying weight basis, unless otherwise specified. The
tables are followed with additional processing disclosure.
Exam~le l
This Example describes the process in batch mode in a pilot
plant scale high shear mixer, an Eirich RV02. The mixer is
filled first with a mixture of the powders to be used, in
this particular case a 2:l ratio of Zeolite A to finely
divide. -arbonate or Zeolite A to finely divided citrate.
The sur~actant is an aqueous paste of C45AS with a detergent
activity of 78% and a water content of 13%. In this Example,
a 50% solution of NaOH (0.6 kg), is added to the paste (3 kg)
in the mixer (the Eirich RV 02) before starting the
granulation. Upon mixing, the paste solidifies and is ground
by the mixer at 2500 rpm. The process is stopped and the
WO92/1~02 PCT/US92/02879
27~ 1~ a1 6 S
powders (1.050 kg) are added. The mixer is operated until
granulation takes place. The process is then stopped and the
agglomerates are dried in a fluid bed and classified through
mesh sieves. The agglomerates made have a detergent activity
of 60% and a density of 600 g/L. They show excellent
physical properties.
Example 2
This Example is similar to Example 1. The powder mixture
again a 2:1 ratio of Zeolite A to finely divided carbonate.
The surfactant is an aqueous paste of C4sAS with a detergent --
activity of 78% and a water content of 13%. In this Example,both the powders (1.05 kg) and the paste (3 kg) are added to
the mixer (the Eirich RV02) before starting the granulation.
A certain amount (2 kg) of dry ice is also added to the mixer
to lower the temperature below -15~C. The mixer is then
started at a speed of 1600 (2500) rpm. At first, at the low
temperature achieved, the mixture is in the form of a fine
powder. The mixer is operated until the temperature raises
to the point (12~C) where granulation occurs. The process is
then stopped and the agglomerates are dried in a fluid bed
and classified through mesh sieves. The agglomerates made
have a detergent activity of 60% and a density of 625 g/L.
They show excellent physical properties.
Exam~le 3
This Example describes the process in batch mode in a lab
scale high shear mixer (food processor). The mixer is filled
first with a mixture of the powders to be used, in this
particular case a 2:1 ratio of Zeolite A to finely divided
sodium carbonate. The surfactant is an aqueous paste of C45
AS with detergent activity of 72% and a water content of 24%.
In this Example, silica powder (40 g), is added to the paste
(400 g) in the mixer prior to starting granulation. Upon
mixing, the paste stiffens. The process is stopped and the
powders (105 g) are added to the paste (335 g). The mixer is
operated until granulation takes place. The process is then
WO92/1~02 PCT/US92/02879
~10816fi 28
stopped and the agglomerates are dried in a fluid bed and
classified through mesh sieves. The agglomerates made have a
detergent activity of 55-60% and a density of 650 g/L. they
show excellent physical properties.
Exam~le 4
This example describes the process of paste conditioning in
continuous mode in a pilot plant twin screw extruder, Werner
and Pfleiderer C58 with a barrel in six sections, followed by
immediate granulation of the paste exiting the extruder in a
lab scale high shear mixer. The surfactant is an aqueous
paste of sodium linear alkyl benzene sulphonate (NaLAS) with
a detergent activity of 78% and a water content of 18%. The
paste is introduced into the extruder at a temperature of
70OC and at a flow rate of 150 kg/hr. The paste exiting the
extruder is agglomerated in the lab scale high shear mixer
with a ratio of 2:1 by weight of zeolite A to finely divided
carbonate powders. The paste is added to the bed of powders
until agglomerates of average particle size between 400 and
800 ~m are obtained. The agglomerates are then dried in a
fluid bed and analysed for LAS content (described herein as
activity).
The paste is simply pumped through the extruder which is
operated between 100 and 120 rpm. The paste exiting the
extruder is still at 70~C and the activity of the resulting
agglomerates is 32%.
Example 5
Agglomerates are made using the same equipment and weight
ratios as described in example 4. In this example the paste
is cooled while being pumped through the extruder by means of
cooling coils containing city water at 15~C in the first two
sections of the barrel and chilled glycol at -20~C in the
last four sections of the barrel. The exit temperature of the
paste at steady state conditions is 30~C and the activity of
the resulting agglomerates is 45%.
WO92/1~02 - PCT/US92/02879
29 210816
ExamPle 6
Agglomerates are made using the same equipment and weight
ratios as described in example 4. In this example, a solid
powder of a copolymer of maleic and acrylic acids is added to
the paste at the inlet of the extruder. Without any cooling,
the paste temperature exiting the extruder is 68~C and the
activity of the resulting agglomerates is 3B%. When cooling
is applied to the extruder barrel, in the same way as
described in example 5, the paste exit temperature is 30~C
and the activity of the resulting agglomerates is 54%.
Example 7
Agglomerates are made using the same equipment and weight
ratios as described in example 4. However in this example the
NaLAS is replaced by a surfactant paste containing 60% by
weight of sodium alkyl sulphate with a carbon chain length of
Cl4-Cl5 and containing 25% water. The inlet temperature is
again 70~C.
The paste is simply pumped through the extruder and exits at
a temperature of 70~C. The activity of the resulting
agglomerates is 36%.
ExamPle 8
Agglomerates are made using the same equipment and weight
ratios as described in example 7, also using the alkyl
sulphate paste of that example. However in this example, a
vacuum is applied through a vacuum port in one of the barrels
by using a vacuum capable of delivering 70mbar of vacuum. At
the same time cooling is applied through the internal coils
in the extruder with the use of glycol at -20~C in all
sections of the barrel. The paste exiting the extruder has an
activity of 72~C and a water content of 22% and a temperature
of 25~C. The agglomerates made with this paste have an alkyl
sulphate activity of 60%.
Example 9
WO92/18602 PCT/US92/02879
210816~
Agglomerates are made using the same equipment and weight
ratios as described in example 7, also using the alkyl
sulphate paste of that example. In this example the paste was
cooled by passing glycol at -20~C through the cooling coils
and additionally by injecting liquid nitrogen into the fourth
section of the barrel at a rate of 15kg/hr. The paste coming
out of the extruder had a temperature of 15~C and the
resulting agglomerates had an alkyl sulphate activity of 65%.
