Note: Descriptions are shown in the official language in which they were submitted.
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Henkel KGaA
TTP-]?atentabteilung/Dr. Fabry 445/55-APG/FAG
13th September, 1995
Patent Application
H 2044
A process for the production of water- and
dust-free sugar ~urfactant granules
Field of the Invention
This invention relates to a process for the simul-
taneous drying and granulation of water-containing sugar
surfactant pastes using a lhin-layer evaporator.
Prior Art
Sugar surfactants, for example alkyl
oligoglucosides or fatty acid-N-alkyl glucamides, are
distinguished by excellent detergent properties and high
ecotoxicological compatibility. For this reason, these
classes of nonionic surfactants are acquiring increasing
significance. Although, hitherto, they have generally
been used in liquid formulations, for example
dishwashing detergents or hair shampoos, there is now
also a market need for solid, water-free formulations
which may even be incorporated, for example, in powder-
form detergents or syndet soaps.
On an industrial scale, liquid surfactant formula-
tions are generally dried by conventional spray drying,
in which the water-containing surfactant paste is
sprayed in the form of fine droplets at the head of a
tower, the droplets encountering hot drying gases
flowing in countercurrent. Unfortunately, this
technology cannot readily be applied to sugar surfactant
pastes because the temperatures required for drying are
above the caramelization temperature, i.e. the
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decomposition temperature of the sugar surfactants. In
short, the conventional drying of sugar surfactant
pastes results in the formation of carbonized products,
in addition to which caking occurs on the walls of the
spray drying tower so that they have to be cleaned at
considerable expense at short intervals.
Attempts have been made in the past to overcome
this problem. For example, German patent application
DE-A1 41 02 745 (Henkel) clescribes a process in which a
small quantity of 1 to 5~ by weight of alkyl glucosides
is added to fatty alcohol pastes which are then
conventionally spray dried. Unfortunately, the process
can only be carried out in the presence of a large
quantity of inorganic salts. According to German patent
application DE-A1 41 39 551 (Henkel), pastes of alkyl
sulfates and alkyl glucosides which may contain at most
only 50~ by weight of the sugar surfactant are sprayed
in the presence of mixtures of soda and zeolites.
However, this process only gives compounds with a low
surfactant concentration and an inadequate apparent
density. Finally, International patent application WO
95/14519 (Henkel) reports on the drying of sugar
surfactant pastes wit:h superheated steam.
Unfortunately, this is technically very complicated. In
fact, there has not yet been a reliable process which
enables high-quality, substantially water-free sugar
surfactant powders or granules to be produced, but which
does not entail the use of carriers during the drying
process. Another problem of known processes is that
they do not lead to the particularly preferred heavy
powders with an apparent density above 500 g/l and, at
the same time, a greatly reduced dust content. However,
it is precisely these two parameters which are so
important on economical, applicational and safety
grounds.
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Accordingly, the complex problem addressed by the
present invention was to convert water-containing sugar
surfactant pastes with minimal outlay on equipment and
without any need for inorganic or organic carriers into
substantially water-free and dust-free granules which
would be distinguished simultaneously by acceptable
color quality, by high apparent density, by good flow
properties, by satisfactory stability in storage and, in
comparison with known products, by at least comparable
lo performance properties.
Description of the Invention
The present invention relates to a process for the
production of water-free and dust-free sugar surfactant
granules of high apparent density, in which water-con-
taining pastes of
a) alkyl and/or alkenyl oligoglycosides and/or
b) fatty acid-N-alkyl po:Lyhydroxyalkylamides
with a solids content of at least 20~ by weight and
preferably in the range from 25 to 75~ by weight are
dried in a horizontally arranged thin-layer evaporator
with rotating fittings to a residual water content below
2~ by weight, preferably helow 1.5~ by weight and, more
preferably, below 1~ by weight and, at the same time,
converted into particulate form.
It has surprisingly been found that a horizontally
arranged thin-layer evaporator is eminently suitable for
converting water-containing sugar surfactant pastes into
dry, light-colored, free-flowing and non-tacky granules
without any risk of product discoloration and caking on
the walls. The products have a high apparent density of
550 to 650 g/l and an average particle diameter of 2.0
to 2.8 mm which leads to a reduction in the unwanted
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absorption of water and in the caking of the particles.
High stability in storage is also achieved in this way.
At the same time, the particles are dust-free, i.e. the
percentage of particles smaller than 200 ~m in diameter
is less than 5~ by weight:. This discovery is all the
more surprising insofar as, although evaporators of the
type mentioned are known in principle for the drying of
anionic surfactant pastes r the powders obtained do not
meet the requirements mentioned either in regard to
their apparent density or in regard to their dust and
residual water contents.
Alkyl and/or alkenyl oligoqlycosides
Alkyl and alkenyl oligoglycosides are known
nonionic surfactants corresponding to general formula
(I):
R O-[G]p (I)
in which R1 is an alkyl and/or alkenyl radical containing
4 to 22 carbon atoms, G is a sugar unit containing 5 or
6 carbon atoms and p is a number of 1 to 10. They may
be obtained by the relevant methods of preparative
organic chemistry. EP-A1-0 301 298 and WO 90/03977 are
cited as representative of the extensive literature
available on this subject.
The alkyl and/or alkenyl oligoglycosides may be
derived from aldoses or ketoses containing 5 or 6 carbon
atoms, preferably glucose. Accordingly, the preferred
alkyl and/or alkenyl oligoglycosides are alkyl and/or
alkenyl oligoglucosides.
The index p in general formula (I) indicates the
degree of oligomerization (DP degree), i.e. the
distribution of mono- and oligoglycosides, and is a
number of 1 to 10. Whereas p in a given compound must
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always be an integer and, above all, may assume a value
of 1 to 6, the value p for a certain alkyl oligogly-
coside is an analytically determined calculated quantity
which is generally a broken number. Alkyl and/or
alkenyl oligoglycosides having an average degree of
oligomerization p of 1.1 to 3.0 are preferably used.
Alkyl and/or alkenyl oligoglycosides having a degree of
oligomerization of less than 1.7 and, more particularly,
between 1. 2 and 1. 4 are preferred from the applicational
point of view.
The alkyl or alkenyl radical R1 may be derived from
primary alcohols containing 4 to 11 and preferably 8 to
10 carbon atoms. Typical examples are butanol, caproic
alcohol, caprylic alcohol, capric alcohol and undecyl
alcohol and the technical mixtures thereof obtained, for
example, in the hydrogenation of technical fatty acid
methyl esters or in the hydrogenation of aldehydes from
Roelen's oxosynthesis. Alkyl oligoglucosides having a
chain length of C8 to C10 (DP = 1 to 3), which are
obtained as first runnings in the separation of
technical Ca18 coconut oil fatty alcohol by distillation
and which may contain less than 6-g6 by weight of C12
alcohol as an impurity, and also alkyl oligoglucosides
based on technical Cg/11 oxoalcohols (DP = 1 to 3) are
preferred.
In addition, the alkyl or alkenyl radical R1 may
also be derived from primary alcohols containing 12 to
22 and preferably 12 to 14 carbon atoms. Typical
examples are lauryl alcohol, myristyl alcohol, cetyl
alcohol, palmitoleyl alcohol, stearyl alcohol,
isostearyl alcohol, oleyl alcohol, elaidyl alcohol,
petroselinyl alcohol, arachyl alcohol, gadoleyl alcohol,
behenyl alcohol, erucyl alcohol, brassidyl alcohol and
technical mixtures thereof which may be obtained as
3 5 described above. Alkyl oligoglucosides based on
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hydrogenated C12/14 coconut oil fatty alcohol having a DP
of 1 to 3 are preferred.
Fatty acid N-alkyl polyhydroxyalkylamides
Fatty acid N-alkyl polyhydroxyalkylamides are
nonionic surfactants corresponding to formula (II):
R3
R2CO-N-[Z] (II)
in which R2CO is an aliphatic acyl radical containing 6
to 22 carbon atoms, R3 is hydrogen, an alkyl or
hydroxyalkyl radical containing 1 to 4 carbon atoms and
[Z] is a linear or branched polyhydroxyalkyl radical
containing 3 to 12 carbon atoms and 3 to 10 hydroxyl
groups.
The fatty acid N-alk:yl polyhydroxyalkylamides are
known compounds which may normally be obtained by reduc-
tive amination of a reducing sugar with ammonia, an
alkylamine or an alkanolamine and subsequent acylation
with a fatty acid, a fatty acid alkyl ester or a fatty
acid chloride. Processes for their production are
described in US 1,985,424, in US 2,016,962 and in US
2,703,798 and in International patent application WO
92/06984. An overview of this subject by H. Kelkenberg
can be found in Tens. Surf. Det. 25, 8 (1988).
The fatty acid N-alk.yl polyhydroxyalkylamides are
preferably derived from reducing sugars containing 5 or
6 carbon atoms, more particularly from glucose. Accord-
ingly, the preferred fatty acid N-alkyl
polyhydroxyalkylamides are fatty acid N-alkyl glucamides
which correspond to formula (III):
R3 OH OH OH
R2CO-N-CH2-CH-CH-CH-CH-CH2OH (III)
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OH
Preferred fatty acid N-alkyl polyhydroxyalkylamides
are glucamides corresponding to formula (III) in which R3
is hydrogen or an alkyl ~roup and R2CO represents the
acyl component of caproic acid, caprylic acid, capric
acid, lauric acid, myristic acid, palmitic acid, palm-
itoleic acid, stearic acid, isostearic acid, oleic acid,
elaidic acid, petroselic acid, linoleic acid, linolenic
acid, arachic acid, gadoleic acid, behenic acid or
erucic acid or technical mixtures thereof. Fatty acid
N-alkyl glucamides (III) obtained by reductive amination
of glucose with methylamine and subsequent acylation
with lauric acid or C12/l4 coconut oil fatty acid or a
corresponding derivative are particularly preferred. In
addition, the polyhydroxyalkylamides may also be derived
from maltose and palatinose.
Drying and granulation in a so-called flash dryer
The simultaneous drying and granulation process
takes place in a horizontally arranged thin-layer evapo-
rator with rotating fittings of the type marketed, for
example, by the VRV company under the name of "flash
dryer". In simple terms, the flash dryer is a tube
which can be heated to different temperatures over
several zones. The paste--form starting material, which
is introduced by a pump, is projected onto the heated
wall by one or more shafts fitted with paddles or
plowshares as rotating f:ittings and is dried on the
heated wall in a thin layer typically with the thickness
of 1 to 10 mm. According to the invention, it has been
found to be of advantage to apply a temperature gradient
of 170~C (product entrance) to 20~C (product exit) to the
thin layer evaporator. To this end, the first two zones
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of the evaporator for example may be heated to 160~C and
the last zone to 20~C. H:igher drying temperatures have
not been found to be of advantage in view of the thermal
lability of the starting materials. The thin-layer
evaporator is operated at atmospheric pressure. Air is
passed through in countercurrent (throughput 50 to 150
m3/h). The gas entry temperature is generally in the
range from 20 to 30~C while the exit temperature is in
the range from 90 to 110~C.
The water-containing sugar surfactant pastes which
may be used as starting materials may have a solids
content above 20~ by weight and preferably in the range
from 25 to 75~ by weight. Typically, their solids
content is of the order of 30 to 50~ by weight. The
throughput is of course dependent on the size of the
dryer, but is typically in the range from 5 to 15 kg/h.
It is advisable to heat the pastes to 40 to 60~C during
their introduction.
In addition, after drying, it has proved to be of
considerable advantage to transfer the granules, which
still have a temperature of around 50 to 70~C, to a
conveyor belt, preferably in the form of a vibrating
shaft, and rapidly to cool them thereon, i.e. over a
period of 20 to 60 seconds, to temperatures of around 30
to 40~C using ambient air. In order further to improve
their resistance to the unwanted absorption of water,
the granules may also be subsequently dusted with 0.5 to
2~ by weight of silica powder.
Industrial Applications
The granules obtainable by the process according to
the invention may be subsequently mixed with other
ingredients of powder-form surface-active formulations,
for example tower powders for detergents. In addition,
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the powders may readily be incorporated in aqueous
preparations. In fact, where the powders are used, no
differences in performance properties are observed in
relation to the water-containing starting pastes. The
granules may also readily:be incorporated in syndet soap
formulations, for example together with fatty acids,
fatty acid salts, starch, polyglycol and the like.
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Examples
Example 1
The granules were produced in a flash dryer of the
type manufactured by VRV ',.p.A., Milan, Italy. This is
5 a horizontally arranged thin-layer evaporator (length
1100 mm, internal diameter 155 mm) with four shafts and
22 paddles of which the distance from the wall is 2 mm.
The dryer had three separate heating and cooling zones
and a total heat exchange area of, in all, 0. 44 m2 . The
dryer was operated at normal pressure. An aqueous paste
- heated to 50~C - of a cocoalkyl oligoglucoside (Plan-
taren(~' APG 1200, solids content around 50~ by weight)
was pumped into the thin-layer evaporator at a
throughput of 11. 5 kg/h by a vibrating pump. Heating
15 zones 1 and 2 of the thin-layer evaporator had been
adjusted to 160~C while its cooling zone 3 had been
adjusted to 20~C. The rotor speed was 24 m/s. Air was
passed through the flash dryer at a rate of around 110
m3/h. The gas exit temperature was around 65~C. The
20 predried granules which still had a temperature of
around 60~C were transferred to a vibrating chute
(length 1 m), exposed to ambient air and cooled to
around 4 0~C in 30 s. The granules were then dusted with
around 1~ by weight of silica powder (Sipernat~' 50 S).
25 Dry, pure white granules which were still free flowing
and lump-free even after prolonged storage in air were
obtained and, after incorporation in shampoo formu-
lations, did not show any differences in relation to a
paste-form comparison product. The characteristic data
of the granules are set out: in Table 1:
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Table 1
Characteristic data of the flash dryer granules
Parameter Granules
Particle size distribution [~ by weight]
< 1.0 mm 1.2
1.0 mm 47.8
2.5 mm 16.5
3.2 mm 16.2
4.0 mm 11.3
5.0 mm 4.7
6.2 mm 2.3
Residual water content (Fischer method)
[~ by weight] 1.0
Apparent density [g/l] 590
Example 2
The procedure was as in Example 1 except that the
glucoside was replaced by cocofatty acid-N-methyl gluc-
amide. The temperature in the two heating zones of the
flash dryer was increased to 170~C. Pure white, free-
flowing lump-free granules with an apparent density of
600 g/l and a residual water content of 0.8~ by weight
were again obtained.
