Note: Descriptions are shown in the official language in which they were submitted.
CA 02269398 1999-04-15
Clariant GmbH 1998DE415 Dr.KM/sch
Description
Anti-icing composition for aircraft
The present invention relates to an anti-icing composition for aircraft and
the use of
fluorescent dyes or optical brighteners in anti-icing compositions for
aircraft.
Deicing and anti-icing compositions for aircraft (called deicing compositions
or
deicing fluids below) are used for removing ice, snow and/or frost from
aircraft
surfaces and for avoiding such deposits on these surfaces. In wintry weather
conditions, complete deicing of aircraft prior to take-off using deicing
compositions
and complete protection of the surface against re-icing are of crucial
importance for
5 ensuring smooth and safe running of air traffic.
International standards ISO 11075/11078 and AMS 1424A/1428B distinguish
between type I, type II and type IV fluids. Type I fluids essentially comprise
glycol,
water, corrosion inhibitors) surfactants, pH regulators and optionally a dye
for
improved recognition on the aircraft surface. Type II and type IV fluids
additionally
comprise a water-soluble polymer as thickener to achieve a highly viscous
pseudoplastic consistency, which ensures long-term protection against re-icing
(holdover time) on the aircraft surface.
An aircraft deicing composition is described, for example, in DE-A-24 23 893
and in
EP-B-0 050 700, US-4 358 389, EP-B-0 231 869 and EP-B-0 360 183. It
essentially
comprises:
a) from 35 to 95% by weight of at least one glycol from the group consisting
of
alkylene glycols hawing from 2 to 3 carbon atoms and oxalkylene glycols
having from 4 to 6 carbon atoms
b) from 0.02 to 1.5% by weight of at least one surfactant from the group
consisting of anionic and nonionic surfactants
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c) at least one corrosipn inhibitor in an effective amount
d) at least one basic compound from the group consisting of alkali metal
carbonates, alkali metal hydroxides and amines for setting a pH of from
7 to 11
e) optionally (in the case of type II and type IV deicing compositions) from
0.05
to 3% of at least one water-soluble polymer as thickener
f) water as the remaining amount up to 100% by weight, based on the finished
deicing composition.
0 Deicing compositions are usually applied down onto the aircraft surface by
spraying
the aircraft from a tanker vehicle from a lifting platform.
As is stated in ARP 4737 from the American Federal Aviation Administration
(FAA),
the complete removal of any ice and snow from the aircraft surface and the
complete
coverage with deicing fluid are of crucial importance for a safe take-off. In
order to
make it easier to detect whether the surrface is completely covered with
deicing
compositions, the deicing fluids have for some time been colored using
standard
commercial dyes. For example) AMS 14288 prescribes a green coloration for
type IV fluids. In the normally poor light conditions which prevail during
application of
deicing compositions and of course at night, these dyes represent only a
limited
safety advantage.
The object on which this invention is based was thus to find dyes which are
suitable
for use in deicing fluids and which permit detection of the application of the
deicing
fluid even in poor light conditions.
Surprisingly, it has been found that optical brighteners achieve this object.
The invention thus provides for the use of optical brighteners in aircraft
deicing
compositions for improving detection of the application of deicing
compositions in
poor visibility conditions and at night on the surface of aircraft.
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The invention also provides an anti-icing composition for aircraft, comprising
water,
one or more glycols, one or more corrosion inhibitors, one or more
surfactants, one
or more pH regulators and one or more dyes, wherein the composition
additionally
comprises an optical brightener which absorbs ultraviolet light and displays a
fluorescence in the visible spectral region.
The invention further provides a method for the deicing of aircraft by
applying an
anti-icing composition, wherein the anti-icing composition comprises an
optical
brightener, and wherein the complete wetting of the aircraft is established by
irradiating with ultraviolet light and observing the fluorescence.
In a preferred embodiment of the invention, the anti-icing composition
comprises
from 0.05 to 3% by weight, based on the anti-icing composition, of a water-
soluble
polymer as thickener.
Optical brighteners can generally be referred to as substances which absorb in
the
ultraviolet wavelength region and re-emit some of the absorbed electromagnetic
radiation in the wavelength region of visible light. Preferred ultraviolet
wavelengths
are between 350 and 380 nm. Typical compounds for this application are of an
anionic, cationic or nonionic nature.
Examples of suitable anionic optical brighteners are given below.
1 i(S03M)(0_3) 1
- (S03M)(0_3)
~N N
N/ ~~'-NH / ~ - / ~ NH~/ ~N
(1)
~N N
1 (S03M) (S03M) R1- (S03M)(0_3)
(S03M)(0-3)
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in which R' is in each case independently OH, NH2 , O-(C,-C4)-alkyl, O-aryl,
NH-(C,-
C4)-alkyl, N-((C,-C,)-alkyl)2, N-((C,-C4)-alkyl)-((C,-C4)-hydroxyalkyl), N-
((C,-C4)-
hydroxyalkyl)Z, NH-aryl, morpholino, S-(C,-C4)-alkylaryl or CI, and M is Na+,
K+, NH4+
or NH~4_a~Ra in which a = 1) 2 or 3 and R = C,-C4-hydroxyalkyl, in particular
C2-hydroxyalkyl, the stoichiometric indices of the sulfonate groups being
dependent
on the type of radical R', namely on the number of such groups this radical
can
carry;
Ar2
R2
0 \CH ~ N (2)
/CH-N-Ark
R2,
in which Ar' and Arz independently of one another are substituted or
unsubstituted
5 aryl radicals, and R2 and R2', which can be identical or different, are
hydrogen,
(C,-C4)-alkyl or phenyl;
Ar3
R2
\CH ~ N (3)
CH-N-Ar4
20 2, ~
R
in which Ar3 and Ar4 independently of one another are phenyl) Biphenyl or
naphthyl
radicals which can carry further substituents such as hydroxyl, (C,-Cs)-alkyl,
(C,-C6)-
alkoxy, halogen, hydroxyalkyl, amino, alkylamino, acylamino, carboxyl,
25 alkoxycarbonyl, sulfonic acid, sulfonic esters, alkylsulfonyl,
arylsulfonyl) sulfonyl and
sulfonamide groups;
/
(R3)m
30 R2HC ~N (4)
R2~HC N
R4
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in which R3 is halogen or (C,-C6)-alkyl, R" is a substituted or unsubstituted
(C,-Cs)-
alkoxycarbonyl, (C,-Cs)-alkylsulfonyl, sulfonamide or sulfonic acid group, and
m is
zero, 1, 2 or 3;
5
CI
~\N
N~
(5)
S02 CH2 C(CH3)2 S03M
CI
~\N
N
(6)
S02 CH2 CH2 S03M
CI
(7)
S02 CH2 CH2 S03M
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MS03
Aryl / N\ ~ ~ N Aryl
N
N, ~N ~ Ca)
S03M
R5 R5
(9)
0 J n
(S03M)1-2 (S03M)1_2
where RS = H, alkyl, oxalkyl, halogen, CN, COO-(C,-C4)-alkyl or CO-N[(C,-C4)-
alkyl]z
andn=Oor1;
5
(M03S)n (S03M)n
S03M \
~N\ (
20 ~ NON ~ ~ CH CH ~ ~ N 10)
N N
S03M
(S03M)n
i
~N\
CH CH ~ ~ N
~N ~ ~ (11)
S03M
in which n is 0 or 1,
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/ \ CH CH / ~ / ~ CH CH
(12)
S03M S03M
CI / ~ / ~ / ~ CH = CH / \ CI
CH = CH
( 13)
S03M S03M
CH = CH / ~ / ~ CH = CH / \ (14)
U
S03M S03M
S03M S03M
~ / ~ ~ ~ , (1
-O- ~ ~ ~O~ a
S03M S03M
CH3 / CH3
~ / ~ ~ ~ , (1
O
CH3 CH3
CH3 CH3 CH3 CH3
(17)
S03M O U ~ ~O v ~03M
CA 02269398 1999-04-15
/ \ / \ ~ ~ ~ (18)
(S03M)3_4
The optical brighteners of a cationic nature are preferably compounds with a
pyrazoline base structure which are in salt form, i.e. acid addition salts.
Suitable
acids for this purpose are those which have colorless anions, such as, for
example,
C,-C3-alkanoates, C,-C4-alkanephosphates, C,-C4 alkanesulfonates, CZ C3-
hydroxyalkanoates, phosphite, sulfamate, halides, methosulfate, p-
toluenesulfonate,
preferably those which have good solub~lities in water, for example
Ars
(19)
HZC~ N
H2C--~-N Ar6
R6
in which Ar5 and Are independently of one another are substituted or
unsubstituted
aryl radicals, and R6 is hydrogen, C,-C4 alkyl or phenyl.
Of particular interest are compounds of the formula
Ar7
(20)
H2C~ N
H2C--~--N Ar8
R8
in which Ar, and Are independently of one another are phenyl, Biphenyl or
naphthyl
radicals which can carry further substituents such as hydroxyl, (C,-C6)-alkyl,
(C,-Cs)-
alkoxy, halogen, hydroxyalkyl, amino, alkylamino, acylamino, carboxyl,
alkoxycarbonyl, sulfonic acid, sulfonic esters, alkylsulfonyl, arylsulfonyl,
sulfonyl and
CA 02269398 1999-04-15
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sulfonamide groups, and R6 is as defined above.
Particular preference is given to compounds of the formula
i
(R7)m
(21 )
HzCI ~ N
H2C -~-- N
Rg
R$
in which R' is hydrogen, halogen or C,-Cs-alkyl, Re is a substituted or
unsubstituted
C,-C6-alkoxycarbonyl, C,-Cg-alkylsulfonyl, sulfonamide or sulfonic acid group,
and m
is zero, 1, 2 or 3) and RB is as defined above.
Particular preference is also given to compounds of the formula
n+
r9
(22)
HZCI ~ N
HzC~N / \ S~2 - R10 - N R9
R6 I
R9 nA-
in which Ars is a group of the formulae
CI
R11
R~ , ( \ , or ~ ,
i i
R12 3
23a 23b 23c 23d
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R'° is substituted or unsubstituted C,-Cs alkylene,
C,-C6-alkylene-O-C,-C6-alkylene, C,-Cg alkylene-CONH-C,-C6-alkylene, C,-C6-
alkylene-COO-C,-C6 alkylene, -NH-Cz-C4 alkylene or -Cz-CQ hydroxyalkylene-NH-
Cz-
C4-alkylene, R9 is independently of one another hydrogen, C,-C6-alkyl, Cz-C6-
5 hydroxyalkyl, or in each case two radicals R9 together with the N atom are a
morpholino, pyrrolidino, piperidino, N-alkylpiperazino or N-
hydroxyethylpiperazino
group, R" and R'z independently of one another are hydrogen, methyl or
chlorine,
R6 and R' are as defined above, n is zero or 1, and A is a colorless anion.
10 Suitable and preferred pyrazoline brighteners are especially the compounds
of the
following formula
Ark 0
(24)
M2CI w N
HZC N ~ ~ S02 - R13
in which Ar'° is a 4-chlorophenyl group and R'3 is a group of the
following formulae:
-NHz, -CzH4N(CH3)z, -CHzCHCH3N(CH3)z, -Czl"'~aOCzE.I4N(CH3)z, _
CHCH3CH2N(CH3)z or Ar'° is a 2-methyl-4,5-dichlorophenyl group and R'3
is a group
of the formula -CZH4N(CH3)z) (CHz)X -OCOR'4 or (CHz)X OR'S, X is a number from
1
to 4, R'4 is C,-Cg-alkyl, preferably C,-C3-alkyl or C,-C6-hydroxyalkyl,
preferably C,-C3-
hydroxyalkyl, and R'S is hydrogen or C,-Cg-alkyl, preferably C,-C3-alkyl.
Suitable C,-C6-alkyl radicals are unbranched and branched alkyl radicals, such
as
the methyl, ethyl, propyl, butyl, pentyl and hexyl radicals. The same applies
to the
C,-C8-alkoxy groups and the C,-Cg-alkylene groups.
Other compounds of a cationic nature are benzimidazole-benzofuran derivatives
or
benzimidazole-benzoxazole derivatives of the formula
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R18
1 ~ S02CH3
X N
\~/
R16 ~ ~ N ~ (25)
17
R
in which X' is N or CH, R'6 is C,- to C4 alkoxy, and R" and R'8 independently
of one
another are C,- to C4-alkyl, and A is a colorless anion.
Other compounds of a cationic nature are based on coumarin:
.~ n
(26)
R21
in which R'9 is H, CI or CHZCOOH, R2° is H, phenyl, COO-(C,- to C4
alkyl) or a group
of the formula
CH3
N~> (27)
N
and R2' is O-C,-C4 alkyl, N-(C,-C4 alkyl)2, NH-CO-(C,-C4-alkyl) or a group of
the
formulae
2 5 R22 /
N ~ N CH3 N R25
-N~~ ~N -N ~ -N ~ or
, , ~
R24 N R26
R23
28a 28b 28c 28d
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in which R22 and R23 independently of one another are phenyl, mono- or
disulfonated
phenyl, phenylamino, morpholino, -N(CHZCH20H)2, -N(CH3)(CHZCHZOH), -NH2,
-N(C,-C4-Alkyl), -OCH3, -CI, NH-CH2CHZS03H or -NH-CHZCHZOH, and R24, Rzs and
Rzs are H, C,-C4-alkyl or phenyl.
The optical brighteners of a nonionic nature preferably conform to the
following
formulae:
R27 R28
X3 X3
~ O j~- X 2-~ O U (291
in which R2' and RZ$ independently of one another are H or (C,-Cs)-alkyl, X3
is N or
CH and X2 is a bond via 1,4-naphthyl, 2,5-thiophene, 2,5-furan, 1,4-phenyl,
ethylene,
stilbene, styryl or imidazo~yl units,
5
R29
N / ~ CH CH / \ B
X4 ~ ~ ~ n
R30
where X4 is O or S, R29 in the 5-position is a hydrogen or chlorine atom, a
methyl or
phenyl group and R3° is a hydrogen atom, or R29 and R3° are both
a methyl group in
5,6- or 5,7-position, n is 0 or 1, and B is a cyano or carbo-(C,-C4)-alkoxy
group or a
group of the formulae
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~~ -O ~O-N
O Rs2
N~Rs, N~Rs, N-N
(31 a) (31 b) (31 c)
R~
N Rs3
N-
(31 d)
(31 e)
in which R3' is (C,-C6)-alkyl, (C,-Cg)-chloroalkyl, (C,-C4)-alkoxy-(C,-C4)-
alkyl,
hydroxy-(C,-C4)-alkyl or a group of the formula -(CH2CH20)~-R35, n is 2 or 3
and R3s
is hydrogen or (C,-C4)-alkyl, R32 is phenyl) halophenyl, (C,-C4)-alkylphenyl
or (C,-C4)-
5 alkoxyphenyl, R33 is (C,-C;,)-alkyl and R34 is cyano or carbo-(C,-C4)-
alkoxy. In
formula 31 e, the semicircle which has been drawn in indicates that a double
bond is
present) in each case between 2 of the nitrogen atoms, and consequently the
radical
R33 adopts a correspondingly suitable position for valence saturation.
Other preferred optical brighteners of a nonionic nature are:
CN CN
CH CH / \ CH CH ~ (32)
where the CN groups are identical or different and can be in the ortho, meta
or para
position,
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-alkyl
N ~N
_ ~O-alkyl
~.--~ N (33)
R36
R38
(~)
R37
5
where R36 is hydrogen or alkoxy, R3' is alkoxy and R3° is alkyl,
alkoxyalkyl or
dialkylaminoalkyl,
R40
(35)
R2g O O
R7
~ (36)
i
O O
N(R~2)2
where R39 is phenyl or the group of the formula
I
(37)
-N~
N
CA 02269398 1999-04-15
and R4° is a group of the formulae
N alkyl
N
-N , ~ \
5 'N~ / ~ °~ N'N
(38a) (38b)
and R'z is as defined above,
N O
(39)
'
N
(C~-C~-alkyl-OOC-- - O CH=CH2-COO-(C~-C~-alkyl (40)
The use of such optical brighteners in small concentrations in aircraft
deicing
compositions makes it possible, by virtue of the fluorescence effect triggered
by UV
light irradiation) to easily check, even in darkness, whether all of the
surfaces of an
aircraft are coated with anti-icing composition. This represents a safety
advantage
prior to the aircraft taking off. The invention is now illustrated in more
detail by
reference to examples.
Example 1:
Into 1000 g of a thickened aircraft anti-icing composition consisting of
a) 500 g of 1,2-propylene glycol,
b) 2 g of sodium alkylbenzenesulfonate as surfactant
c) 1 g of benzotriazole as corrosion inhibitor
d) 3.3 g of crosslinked polyacrylic acid as thickener
e) 1.2 g of sodium hydroxide to adjust the pH to from 7.0 to 7.5
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f) 0.05 g of green water-soluble dye and
g) water as residual amount up to 1000 g were dissolved
h) 0.05 g of an optical brightener of the formula
H-CH2 - CH2 - OH
N
NH~/ N (41 ).
N-
S03Na NH
S03Na
The deicing composition was poured onto an aluminum surface and illuminated in
darkness with UV light of a wavelength of 350 nm. Complete coverage of the
aluminum surface with deicing composition and thus complete protection against
icing could be unambiguously observed from the blue green-white fluorescence.
On
illumination with visible light, differentiation between aluminum surfaces
coated with
deicing compositions and unprotected aluminum surfaces was possible only to an
inadequate degree.
Comparative Example 1:
The thickened deicing composition from Example 1, consisting of components a)
to
g) without the addition of the optical brightener h) was poured onto an
aluminum
surface. It was not possible to unambiguously assess complete coverage of the
aluminum surface on illumination with visible light or UV light.
Example 2:
Into 1000 g of a thickened aircraft deicing composition comprising
a) 600 g of monoethylene glycol,
b) 2 g of fatty alcohol ethoxylate as surfactant
c) 1 g of tolyltriazole end 1 g of sodium phosphate as corrosion inhibitors
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d) 2.5 g of xanthan as thickener and
e) water as residual amount up to 1000 g were dissolved
f) 0.05 g of a brightener as in Example 1.
The deicing composition was heated to 70°C and sprayed onto an aluminum
surface
covered with 1 mm of ice until the ice had melted and a protective film of
deicing
composition remained on the surface. By illuminating with UV light of a
wavelength
of 350 nm, it was clearly possible to observe from the white fluorescence
complete
coverage of the aluminum surface with deicing composition and thus complete
protection against re-icing. On illumination with visible light,
differentiation between
aluminum surfaces coated with deicing composition and iced aluminum surfaces
was possible only to an inadequate degree.
Comparative Example 2:
The thickened deicing composition from Example 2, consisting of components a)
to
e) without the addition of the optical brightener f) was heated to 70°C
and sprayed
onto an aluminum surface coated with 1 mm of ice until the ice had melted and
a
protective film of deicing composition remained on the surface. Merely by
omitting
component f), in darkness it was not possible to differentiate between
aluminum
surfaces coated with deicing composition and iced aluminum surfaces by
illumination with UV light. On illumination with visible light, a
differentiation between
aluminum surfaces coated with deicing composition and iced aluminum surfaces
was possible only to an inadequate degree.
Example 3:
The procedure was as in Example 1. The optical brightener used was 0.05 g of a
brightener of the formula
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CI
,N
N
(42)
H3
O
S02 - CH2 - CH2 - N~ - H COOH
CH3
0
Complete coverage of the AI surface with deicing composition was observed from
the bluish fluorescence.
Example 4:
5 The procedure was as in Example 1, but 350 mg of the brightener of the
formula
X x
~N ~ ~ ~ O (43)
O ~' O
were dissolved in 500 ml of propylene glycol with slight heating. Complete
coverage
of the AI surface with deicing composition was observed from the bluish
fluorescence.
