Note: Descriptions are shown in the official language in which they were submitted.
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'29374-55 (S)
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Non-Thickening De-Icing and Anti-Icing Composition
Comprising an Alkoxylated Fatty Alcohol and an Arylsulfonate
Description
De-icing compositions and anti-icing composit~.ons for
aircraft (called simply de-icing compositions or de-icing
liquids in the following for brevity) are employed for
removal of ice, snow and/or frost from certain aircraft
surfaces and for avoiding such deposits on these sur-
faces. The period of time within which the de-icing
liquid provides protection against reformation of ice,
snow and/or frost on the aircraft is called the re-icing
protection time or holdover time.
GB-A 1 026 150 describes a de-icing liquid which essen-
tially comprises glycol and water as the main constitu-
ents and a comparatively small amount of a tertiary amine
from the group consisting of ethoxylated fatty amines and
at least one corrosion inhibitor. Reference is also made
in US-A 3 412 030 to the intensifying action of water
soluble surfactants in the thawing or melting of snow and
ice.
US-A 4 585 571 describes a de-icing composition which
essentially comprises glycol as the main component and a
combination of three specific surfactants, in particular
an anionic surfactant from the group consisting of fatty
acid diamines, a hydrophilic surfactant from the group
consisting of mono- or polyalcoholamines and an
anionicaily hydrophilic surfactant from the group con-
sisting of sulfated or sulfonated compounds as a coupling
agent for the hydrophobic radicals in the fatty acid
diamine and the hydrophilic alcoholamine. Although this
de-icing liquid is said to have a longer-lasting protec-
tion against re-icing, it nevertheless leaves something
to be desired, inter alia because of the complicated
surfactant system.
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A number of publications in the field of de-icing and
anti-icing liquids for aircraft which address, inter
alia, increasing the holdover time recommend thickeners
for this purpose, because experts are evidently convinced
that an increased holdover time can be achieved only with
the aid of thickeners, cf., for example, US-A 4 358 389,
DE-A-31 42 059 (Derwent reference AN 44404K/19),
US-A 4 744 913 and EP-B 0 360 183 (Derwent reference
AN 90/092789/13). The de-icing compositions described
here thus comprise essentially glycol and water, at least
one thickener, for example from the group consisting of
polyacrylates, at least one surfactant, for example from
the group consisting of alkylarylsulfonates and oxy-
alkylated alcohols, corrosion inhibitors and, if appro-
priate, pH regulators. These thickened de-icing
compositions, which are pseudoplastic liquids having
non-Newtonian flow properties, are distinguished by a
considerably longer re-icing protection time compared
with the non-thickened compositions.
Two types of aircraft de-icing liquids are specified in
"Recommendations for De-/Anti-Icing of Aircraft on the
Ground'° (March 1993 edition) of the Association of
European Airlines (AEA). AEA Type I liquids comprise
essentially glycol, water and corrosion inhibitors, and
if appropriate surfactants and pH regulators, and AEA
Type II liquids comprise a thickener in addition to
these. De-icing liquids of the AEA Type I are also the
so-called "Military Specification Fluids" with sodium
di(2-ethylhexyl)sulfosuccinate as the surfactant.
The most important technical properties of aircraft de-
icing compositions are the longest possible protection
against re-icing of the wings before take-off under
extreme weather conditions and good flow of the de-icing
composition from the body and wings during take-off of
the aircraft. Furthermore, the properties of the de-icing
liquids should not be impaired during storage at tempera -
tures of up to 100°C and during shearing of the liquid by
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pumps and spray cans. While the thickened de-icing
compositions thus adequately meet the requirements in
respect of holdover time, they flow from the wings in
general more slowly than the non-thickened compositions.
Because of their polymeric thickener, Type II de-icing
compositions are also considerably more sensitive to
shearing and heat, so that special technically
complicated spray equipment is needed during their use.
In contrast, non-thickened Type I de-icing comlpositions
in general are insensitive to shearing and temperature
and flow from the wings more quickly during take-off.
However, they have the considerable disadvantage of only
a short protection time against re-icing. In the test
methods described for determination of the holdover time
in the AEA recommendations mentioned, that is to say in
the "Water Spray Endurance Test" (which simulates freez-
ing rain) and in the "High Humidity Endurance Test"
(which simulates formation of frost), a protection time
of only at least 3 minutes and, respectively, 20 minutes
is therefore required for Type I liquids, but a protec-
tion time of at least 30 minutes and, respectively,
240 minutes is required for Type II liquids under the
same conditions.
The object of the invention is accordingly to discover an
AEA Type I de-icing composition which is built up in a
simple manner and has a prolonged holdover time. The
novel de-icing liquid should thus combine in it the
advantages of Type I and Type II liquids, without having
their adverse properties. It should furthermore be such
that the spent liquid can be processed in a simple manner
and reused.
The de-icing composition and anti-icing composition
according to the invention, for aircraft, which is based
on glycols and water essentially comprises
a) 60 to 97% by weight, preferably 80 to 95o by weight,
of at least one glycol from the group consisting of
alkylene glycols having 2 to 3 carbon atoms and
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oxyalkylene glycols having 4 to 6 carbon atoms,
b) 0.01 to 1% by weight, preferably 0.1 to 0.5% by
weight, of at least one nonionic surfactant from the
group consisting of fatty alcohols and fatty
alcohols which are alkoxylated with a low molecular
weight alkoxide and have 1 to 10 alkoxide units,
preferably 1 to 8 alkoxide units,
c) 0 . O1 to 0 . 8% by weight, preferably 0 . 03 to 0 .5 % by
weight, of at least one corrosion inhibitor and
d) water as the remainder to make up 1000 by weight,'
the percentages by weight being based on the weight of
the composition.
It has furthermore been found that an even higher hold-
over time value can be achieved if a combination of the
nonionic surfactant b) mentioned and an anionic
surfactant b') from the group consisting of alkali metal
alkylarylsulfonates is employed as the surfactant compo-
nent in an amount of likewise 0.01 to to by weight,
preferably 0.1 to 0.5% by weight. The two surfactant
compounds b) and b'), where surfactant b') above all acts
as a spreading agent, are preferably employed in a weight
ratio of about 1 . (0.5 to 1), and particularly prefer-
ably in a weight ratio of about 1 . 1.
Component a) of the liquid according to the invention is
preferably ethylene glycol, propylene glycol (1,2-
propylene glycol or 1,3-propylene glycol), diethylene
glycol, dipropylene glycol or a mixture of two or more of
these glycols, propylene glycols being particularly
preferred. The glycols are used above all for lowering
the freezing point and, alongside water, are the main
component of the liquid.
Component b) is a fatty alcohol, that is to say an
alcohol having 6 to 24 carbon atoms in the alkyl radical,
preferably 8 to 18 carbon atoms, or an alkoxylate thereof
having 1 to 10 molecules, preferably 1 to 8 molecules, of
a low molecular weight alkylene oxide in the alkoxylated
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fatty alcohol. The low molecular weight alkylene oxide is
preferably ethylene oxide, propylene oxide or a mixture
thereof, ethylene oxide being preferred. The said alkyl
radical in the fatty alcohal can be straight-chain or
branched, straight-chain radicals being preferred, and
saturated or unsaturated with preferably 1 to 3 double
bonds. Examples which may be mentioned are: octyl, decyl,
dodecyl, isotridecyl and stearyl alcohol, and furthermore
oleyl, coconut alkyl and tallow alkyl alcoho 1.
I0 Component b) can also be a mixture of the fatty alcoho is
and/or fatty alcohol alkoxylates mentioned, thus, f or
example, a fatty alcohol mixture having a C12-alkyl
radical and C14-alkyl radical (C12/C14-fatty alcohol) .
Component b') is preferably a potassium and/or sodium
alkylarylsulfonate having one ar more, preferably one or
two, sulfonate groups (S03R or S03Na groups) , one or
more, preferably one or two, alkyl groups having 5 to
18 carbon atoms, preferably 12 to 18 carbon atoms, and
one or more, preferably one or two, benzene rings. Alkali
metal (potassium and/or sodium) alkylbenz enesulfonates
having 12 to 18 carbon atoms in the alkyl group are
preferred. Since hydrocarbon mixtures such as are
obtained, for example, as fractions in the processing of
crude oil are also used as starting subs tances in the
preparation of alkylarylsulfonates, the alkyl group can
also represent such mixtures. The number of carbon atoms
here is preferably 12 to 18 (that is to say an average
number of 15) .
Component c) comprises corrosion inhibitor s such as are
customary for liquids based on glycol s and water.
Suitable corrosion inhibitors are alkali metal phos-
phates, lower alkyl phosphates, such as ethyl phosphate,
dimethyl phosphate, isopropyl phasphate and the like,
imidazoles, such as 1H-imidazole, me thylimidazole,
benzimidazole and the like, and triazo les, such as
benzotriazole and tolyltriazole, the tr iazoles being
pref erred.
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Component d) is water. Completely desalinated water is
preferably employed.
The pH of AEA Type I de-icing liquids should be 6.5
to 10, preferably 7 to 9. If the liquid according to the
invention does not in any case have such a value, it can
easily be established by suitable pH regulators. In
general, it will be necessary to add a basic compound to
the liquid. Suitable basic compounds are those from the
group consisting of alkali metal hydroxides, such as NaOH
and KOH, alkylamines, such as butylamine, hexylamine,
octylamine and isononylamine, and alkanolamines, such as
mono-, di- and triethanolamine. The alkali metal hydrox-
ides are preferred.
The de-icing composition and anti-icing composition
according to the invention are prepared by mixing the
individual (known and commercially obtainable) components
together in any desired sequence, which can be carried
out, for example, in a tank fitted with a stirrer.
The de-icing composition according to the invention has
all the advantages of non-thickened de-icing liquids, and
moreover has a holdover time which is considerably above
the value required of AEA Type I liquids. It thus
combines both the advantages of nonthickened and those of
thickened liquids. This is an unexpected result. Until
recently, experts in fact evidently assumed that a longer
holdover time in liquids based on glycols and water can
be achieved only with the aid of thickeners.
When used for de-icing and preserving the aircraft
surfaces to be treated, the de-icing composition is
employed either as such, that is to say in concentrated
form, or as a dilution with water, preferably in a ratio
of 1 . 1. The de-icing agent can be applied to the
surfaces to be treated by spraying on with the customary
equipment, such as spray cans and the like.
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The invention will now be illustrated in more detail by
examples and comparison examples.
Example 1
A de-icing composition and anti-icing composition
according to the invention was prepared by mixing the
following components (concentrate):
80.00 by weight of 1,2-propylene glycol
0.05% by weight of benzotriazole
0.25% by weight of sodium alkylbenzenesulfonate having
an average number of carbon atoms in
the alkyl group of 15
0.200 by weight of C1z/Ci4-fatty alcohol ethoxyla ted
with 2 mol of ethylene oxide
0.015% by weight of potassium hydroxide
19.485% by weight of water.
This de-icing composition has a pH of 9. The holdover
time was determined by the "AEA Water Spray Endurance
Test" (Test 1) and by the "AEA High Humidity Endurance
Test" (Test 2), and in particular for the concentrated
formulation and the formulation diluted 1 . 1 with water.
The values are summarized below:
Example 1 Test 1 Test 2
concentrated 12 minutes greater than 180 minutes
50 . 50 7 minutes greater than 50 minutes
Comparison Example 1
Example 1 was repeated, but omitting the ethoxyla ted
fatty alcohol. The following components were thus mixed:
80.00% by weight of 1,2-propylene glycol
0.050 by Weight of benzotriazole
0.25% by weight of alkylbenzenesulfonate from
Example 1
0.015% by weight of potassium hydroxide
19.685% by weight of water.
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Testing of the composition of pH 9 was carried out as in
Example l:
Comparison Test 1 Test 2
Example 1
concentrated 5 minutes 25 minutes
50 . 50 3 minutes 20 minutes
Example 2
In this example according to the invention, the following
components were mixed:
90.000 by weight of diethylene glycol
0.040 by weight of benzotriazole
0.25% by weight of alkylbenzenesulf onate from
Example 1
0 . 2 0 % by weight of C12/Ci4' fatty alcohol ethoxylated
with 2 mol of ethylene oxide
0.0150 by weight of potassium hydroxide
9.495% by weight of water.
Testing of the composition of pH 9 was carried out as in
Example 1:
Example 2 Test 1 Tes t 2
concentrated 11 minutes greater than 180 minutes
50 . 50 5 minutes greater than 60 minutes
Comparison Example 2
Example 2 was repeated, but omitting the ethoxylated
fatty alcohol. The following components wer a thus mixed:
90.00% by weight of diethylene glycol
0.040 by weight of benzotriazole
0.250 by weight of alkylbenzenesulf onate from
Example I
0.015% by weight of potassium hydroxide
9 . 6 9 5 o by weight of water .
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Testing of the composition of pH 9 was carried out as in
Example 1:
Comparison Test 1 Test 2
Example 2
concentrated 4 minutes 45 minutes
50 . 50 3 minutes 23 minutes
Example 3
A de-icing composition and anti-icing composition
according to the invention was prepared by mixing the
following components:
90.00% by weight of diethylene glycol
0.04% by weight of benzotriazole
0.250 by weight of alkylbenzenesulfonate from
Example 1
0.400 by weight of tallow fatty alcohol ethoxylated
with 8 mol of ethylene oxide
0.0150 by weight of potassium hydroxide
9 . 2 95 % by weight of water .
This de-icing composition has a pH of 9. It was tested
only by the more important Test 1:
. Example 3 Test 1
concentrated 16 minutes
50 . 50 4 minutes
Example 4
In this example according to the invention, the following
components were mixed:
90.00% by weight of diethylene glycol
0.04% by weight of benzotriazole
0.250 by weight of alkylbenzenesulfonate from
Example 1
0.40% by weight of coconut fatty alcoho 1 ethoxylated
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with 5 mol of ethylene oxide
0.015% by weight of potassium hydroxide
9 .295 o by weight of water.
This de-icing composition has a pH of 9. It was tested
only by the more important Test l:
Example 4 Test 1
concentrated 17 minutes
50 . 50 4 minutes
