Note: Descriptions are shown in the official language in which they were submitted.
- 131 6G~S
- 1 - 3-15152JMAC 1873/-
Corrosion-inhibiting aqueous coat;ng compositions
The present invention relates to aqueous coating
compositions which, by virtue of containing certain compounds,
are capable of inhibiting the corrosion of metallic sub-
strates, especially ferrous metals. The compounds are
aliphat;c or cycloaliphatic carboxylic acids containing a
heterocyclic radical.
Protection against corrosion is one of the most
important duties of organic coating compositions for metal
substrates. Many suggestions for improving the protection
of coatings against corrosion are to be found in the litera-
ture, for example in H. Kittel, Lehrbuch der Lacke und Be-
schichtungen ("Textbook of Paints and Coatings"), volume V,
Stuttgart l977, 46-103. On the one hand, the barrier function
of the coating composition can be improved, in order to keep
corrosive agents, such as oxygen, water and ions, away from
the metal surface~ On the other hand, it is possible to employ
corrosion-inhibiting pigments which intervene chemically or
electrochemically in the corrosion process, for example by
the formation of insoluble deposits with corrosion products
or by passivation (polarisation~ of the metal surface. Metal
chromates and lead compounds rank amongst the most effective
corrosion-inhibiting pigments. Much use has been made of metal
chromates, particularly because they inhibit both anodic and
cathodic corrosion. Nowadays there are certain objections to
the use of chromates owing to their potential carcinogenic
action. Similarly, there are objections to the use of lead
compounds owing to their chronic toxicity.
Metal salts of organic compounds have also been
frequently suggested as corrosion inhibitors. Thus, for
example, European Patent Specification 3,817 recommends the
use of zinc or lead salts of hydroxy or mercapto compounds of
5-membered or 6-membered heterocyclic compounds containing
the characteristic group
~ 1 3 1 6 6 ~?~
-- 2 --
-N=gH or -N=~-
Typical examples of these are the Zn or Pb salts of 2-mer-
captobenzthiazole.
In a separate patent Application, certain heterocyclic
carboxylic acids and salts thereof have been described which
can be used as corrosion inhibitors for coating compositions,
which makes it possible to formulate highly effective
corrosion-inhibiting paints which are free from chromates and
lead.
Organic corrosion inhibitors of this type are not
pigments, and their use in coating compositions therefore
permits a free choice of pigments or extenders. In the fieLd
of coating composit;ons, however, here has hitherto been doubt
whether the addition of organic corrosion inhibitors on their
own makes possible adequate protection, in practice, against
corros;on (Farbe und Lack _ ~1981) 787).
The tw;n factors of env;ronment protection and of
economy of natural resources are fundamental to any modern
chemical manufacture. In the case of surface coatings
manufacture, these factors have influenced a trend away from
the expensive, hazardous and polluting hydrocarbon solvents
towards water-borne coatings.
It has now been found that certain heterocyclic
carboxylic ac;ds and their salts are effective corrosion
inhibitors in such water-borne coatings.
It is surprising, therefore, that the organic
corrosion inhibitors used according to the invention have a
corrosion-inhibit;ng effect in aqueous coat;ng compos;tions
which is in certain cases equal to that of chromate or lead
pigments, or even surpasses the latter.
The present invention relates, therefore, to an
aqueous corrosion-inhibiting coating composition containing
a) an aqueous film-form;ng b;nder and
.. . .
1 3 1 66~5
-- 3 --
b) as the corrosion inhibitor, an effective amount of an
aliphatic or cycloaliphatic di-, tri- or tetra-carboxYlic
acid which is substituted in its aliphatic or cycloaliphatic
radical by at least one group of the formula I
s-
R
in which X is oxygen, sulfur or NH and each R independently
of the others is hydrogen, alkyl, halogenoalkyl, alkoxy,
alkylthio, alkylsulfonyl, cycloalkyl, phenyl, alkylphenyl,
phenylalkyl, halogen, -CN, -NO2, -COOH, -COOalkyl, -OH or a
primary, secondary or tertiary amino or carbamoyl group, and
aLso base addition salts of these compounds.
Depending on whether X is oxygen, sulfur or NH, these
are derivatives of benzoxazole, benzthiazole or benzimidazole.
The benzthiazole derivatives are preferred.
As alkyl, alkoxy, alkylthio or alkylsulfonyl, R
preferably contains 1-12 C atoms, especially 1-6 C atoms.
Examples of these are methyl, ethyl, propyl, isopropyl,
n-butyl, isobutyl, tert.-butyl, pentyl, hexyl, octyl, nonyl,
decyl, undecyl, dodecyl and the corresponding alkoxy,
alkylthio and alkylsulfonyl radicals. As cycloalkyl, R
preferably contains 5-8 C atoms. Examples of these are
cyclopentyl, cyclohexyl or cyclooctyl.
As halogenoalkyl, R preferably contains 1-4 C atoms
and 1-3 fluorine or chlorine atoms. Examples of these are
chloromethyl, fluoromethyl, difluoromethyl, trifluoromethyl
or 2-chloroethyl~
As alkylphenyl, R preferably contains 7-16 C atoms
and can be, for example, tolyl, xylyl, 4-isopropylphenyl,
. .
. . . .
1 3 1 6 G ~ ~
-- 4 --
4-tert.-butylphenyl, 4-octylphenyl or 4-decylphenyl. As
phenylalkyl, R preferably conta;ns 7-9 C atoms and can be,
for example, benzy(, 1-phenylethyl, 2-phenylethyl, a,-di-
methylbenzyl or 3-phenylpropyl.
As halogen, R ;s preferably fluorine, chlorine or
bromine. If R is -COOalkyl, the alkyl group preferably has
1-4 C atoms.
As an amino group or carbamoyl group, R preferably
has up to 20 C atoms. Examples of these are the groups
NH2~ -NHCH3, -NHC12H1s~ -NH-cyclohexyl, -NH-phenyl, -N~CH3)2,
-N~C4Hg)2, -N~cH3)~benzyl)~ morpholino, piperidino,
-CONH2, -CONHphenyl, -CONHCgH17, -CON~C2Hs)2,
-C~N~CH2CH20H)2, morpholinocarbonyl or piper;dinocarbonyl.
Preferably, one of the substituents R is hydrogen,
C1-C4-alkyl, C1-C4-alkoxy or an amino group, and the
other three Rs are hydrogen. It is part;cularly preferable
for all four Rs to be hydrogen.
The component b) is preferably a d;carboxylic ac;d
or a salt thereof. The substituent of the formula I is
preferably in the beta-position in relation to a carboxyl
group.
The component b) is preferably an aliphatic poly-
carboxylic acid which has 2-20 C atoms or a cycloaliphatic
polycarboxylic ac;d which has 4-12, in particular 5-8, C atoms
and which is substituted by a group of the formula I. In
addition to the group of the formula I, the carboxylic acid
can also have other substituents, for example hydroxyl,
alkoxy, halogen or aryl.
Components b) which are preferred are compounds of
the formula II
`I/' ` ~ ~ II
1 31 6&~,5
-- 5 --
in which X and R have the meaning g;ven above, n is zero or
one and R1, R2, R3 and R4 indepPndently of one another are
hydrogen, alkyl, hydroxyalkyl, halogenoalkyl, alkoxyalkyl,
carboxyalkyl, carboxyl or phenyl or phenylalkyl which is
unsubstituted or monosubstituted or disubstituted, or Ri
and R2 or R1 and R3 together are linear or branched alky-
lene which can be substituted by 1 or 2 carboxyl groups, or
R1 and R2 together are a direct bond, and at least two of
the substituents R1, R2, R3 and R4 are acarboxyl or car-
boxyalkyl group, and also base addition salts of these
compounds.
As alkyl, R1, R2, R3 and R4 are preferab~y
ct-cl8-alkYl~ for example methyl, ethyl, n-propyl, isopro-
pyl, n-butyl, isobutyl, tert.-butyl, pentyl, hexyl, octyl,
dodecyl or octadecy~. As hydroxyalkyl or halogenoalkyl,
these subst;tuents preferably have 1-4 C atoms. Examples
of these are hydroxymethyl, 1-hydroxyethyl, 2-hydroxyethyl,
2-hydroxypropyl, 3-hydroxypropyl, chloromethyl, bromoethyl
or bromo;sopropyl. As alkoxyalkyl, these subst;tuents pre-
ferably have 2-1û C atoms. Examples of these are methoxy-
methyl, 1-methoxyethyl, 2-ethoxypropyl, 1-methoxybutyl, n-
butoxymethyl or 4-isopropoxybutyl.
As carboxyalkyl, R1, R2, R3 and R4 are preferably
C2-C12-carboxyalkyl, for example carboxymethyl, 1-carboxy-
ethyl, 2-carboxyethyl, 3-carboxypropyl, 2-carboxy;sopropyl,
1-carboxybutyl, 2-carboxybutyl, 1-, 2- or 3-carboxyhexyl,
1,2-dicarboxyethyl or 2,3,4-tricarboxyl-1-butyl. As sub-
stituted or unsubstituted phenyl or phenylalkyl, the same
substituents can be, for example, 4-chlorophenyl, 3-nitro-
phenyl, tolyl, xylyl, 3-methoxyphenyl, 4-isopropylphenyl,
3-carboxyethyl, 4-hydroxypheny~, 4-bromobenzyl, 4-tert.-
butylbenzyl, 2-phenylethyl or 3-phenylpropyl, but are pre-
ferably phenyl or benzyl.
~ f R1 and R2 or R1 and R3 together are alkylene,
they form, together ~;th the C atoms to which they are
linked, a cycloalkane ring, preferably a cyclopentane or
cyclohexane ring, wh;ch can be substituted by alkyl groups,
1 31 6~')'',5
- 6 -
preferably ~1-C4-alkyl groups, or by 1 or 2 carboxyl
groups.
If R1 and R2 together are a direct bond, the com-
pounds of the formula II are unsaturated carboxylic acids.
R1, R2, R3 and R4 are preferably hydrogen, C1-C4-
alkyl, carboxyl or C2-C6-carboxyalkyl. It ;s part;cularly
preferable for R4 to be a carboxyl group.
Base addition salts are metal, ammonium or organic
ammonium salts, ;n part;cular salts of alkal; metals, alka-
line earth metals, metals of the groups tIB, IIIA or ~III
of the per;odic system of the elements, ammonium salts or
salts of organ;c amines. Examples of these are, in par-
ticular, sodium, potass;um, calcium, magnesium, zinc, alu-
minium, ammonium, trialkylammonium and tris-thydroxyethyl)-
ammonium salts.
The following are examples of corrosion inhibitors
of the component b):
benzthiazol-2-ylthiomalonic acid,
benzthiazol-2-ylth;osuccinic ac;d,
5-methylbenzth;azol-2-ylth;osuccinic acid,
6-ethylbenzth;azol-2-ylthiosuccinic acid,
4-;sopropylbenzth;azol-2-ylth;osucc;n;c acid,
7-t-butylbenzthiazol-2-ylthiosucc;n;c acid,
5-n-hexylbenzth;azol-2-ylthiosuccinic acid,
6-(1,1,3,3-tetramethylbutyl)-benzthiazol-2-ylth;osuccinic
acid,
6-cyclohexylbenzthiazol-2-ylthiosuccinic acid,
1 31 66~5
- 7 -
7-benzylbenzth;azol-2-ylth;osuccinic acid,
b-methoxybenzthiazol-2-ylthiosuccinic acid,
~S-ethoxybenzthiazol-2-ylthiosuccinic acid,
7-ethoxybenzthiazol-Z-ylth;osuccinic acid,
5-methoxybenzthiazol-2-ylthiosuccinic acid,
4-methylthiobenzthiazol-2-ylthiosuccinic acid,
4-fluorobenzthiazol-2-ylthiosuccin;c acid,
5-chlorobenzthiazol-2-ylthiosuccinic acid,
7-bromobenzth;azol-2-ylthiosuccinic acid,
6-chlorobenzthiazol-2-ylthiosuccinic acid,
4-phenylbenzthiazol-2-ylthiosuccinic acid,
5-trifluoromethylbenzthiazol-2-ylthiosuccinic acid,
S-carboxybenzthiazoi-2-ylthiosuccinic ac;d,
6-methylsulfonylbenzthiazol-2-ylthiosuccinic acid,
5-cyanobenzth;azol-2-ylthiosuccinic acid,
6-n;trobenzth;azol-2-ylth;osuccin;c ac;d,
S-cyanobenzthiazol-2-ylthiosuccin;c acid,
7-hydroxybenzthiazol-2-ylthiosucc;nic acid,
6-chloro-4-methylbenzth;azol-2-ylthiosucc;nic acid,
S-chloro-6-n-butylbenzthiazol-2-ylthiosuccinic acid,
4-bromo-5-n-hexylbenzthiazol-2-ylthiosuccinic acid,
5-nitro-6-n-propylbenzthiazol-2-ylthiosuccinic acid,
S-bromo-6-n-propoxybenzthiazol-2-ylthiosuccinic acid,
6-aminobenzthiazol-2-ylthiosuccinic acid,
6-methylaminobenzthiazol-2-ylthiosuccinic acid,
5-dimethylaminobenzth;azol-2-ylth;osucc;n;c ac;d,
7-phenylaminobenzthiazol-2-ylthiosuccinic acid,
6-diphenylaminobenzthiazol-2-ylthiosuccinic acid,
4-benzylaminobenzthiazol-2-ylth;osuccinic acid,
4-morpholinobenzth;azol-2-ylth;osucc;nic acid,
5-carbamoylbenzthiazol-2-ylthiosuccin;c acid,
5-methylcarbamoylbenzth;azol-2-ylthiosuccin;c acid,
S-diethylcarbamoylbenzthiazol-2-ylthiosucc;n;c acid,
6-phenylcarbamoylbenzth;azol-2-ylthiosuccinic acid,
5,6-dimethylbenzthiazol-2-ylth;osucc;nic acid,
4,5,6-triethylbenzth;azol-2-ylth;osuccinic acid,
4,5,6,7-tetramethylbenzth;azol-2-ylthiosucc;n;c acid,
- 8 - 13~ 6~
1-(benzthiazol-2-ylthio)-propane-1,2-dicarboxylic acid,
3-(benzthiazol-2-ylthio)-propane-1,2-dicarboxylic acid,
3-(6-trifluoromethylbenzthiazol-2-ylthio)-proPane-1,2-di-
carboxylic acid,
3-(6-methoxycarbonylbenzthiazol-2-ylthio)-propane-1,2-di-
carboxylic acid,
3-(6-aminobenzthiazol-2-ylthio)~propane-1,2-dicarboxylic
acid,
3-(5-ethylaminobenzth;azol-2-ylthio)-propane~1,2~dicarboxy-
l;c ac;d,
3-(4-dibutylaminobenzthiazol-2-ylth;o)-propane-1,2-dicar-
boxylic ac;d,
4-(morphol;nobenzth;azol-2-ylthio)-propane-1,2-dicarboxylic
ac;d,
1-(4-phenylbenzth;azol-2-ylth;o)-propane-1,2-dicarboxylic
ac;d,
1-~benzth;azol-2-ylth;o)-propane-1,3-dicarboxylic acid,
1-(6-ethylbenzth;azol-2-ylth;o)-propane-1,3-d;carboxylic
acid,
2-(benzthiazol-2-ylthio)~propane-1,3-dicarboxylic acid,
2-(5-carboxybenzthiazol-2-ylthio)-propane-1,3-dicarboxylic
ac;d,
3-(benzthiazol-2-ylthio)-3-phenylpropane-1,2-dicarboxylic
acid,
3-(benzthiazol-2-ylthio)-3-(4-carboxyphenyl)-propane-1,2-
dicarboxyl;c acid,
3-(benzthiazol-2-ylth;o)-3-(2,4-d;carboxylphenyl)-propane-
1,2-dicarboxylic acid,
3-(benzthiazol-2-ylthio)-3,3-diphenylpropane-1,2-dicarboxy-
l;c ac;d,
1-(benzthiazol-2-ylthio)-butane-1,2-dicarboxyl;c acid,
1-~4-methoxy-6-hydroxybenzthiazol-2-ylthio)-butane-1,2-di-
carboxylic acid,
3-(4,5-dimethyl-7-propoxybenzthiazol-2-ylthio)-propane-1,2-
dicarboxylic acid,
1-(benzthiazol-2-ylthio)~2-methylpropane~1,2~dicarboxylic
acid~
:. -
1 31 6635
_ 9 _
2-tbenzthiazol-2-ylthio)-butane-2,3-dicarboxyl;c acid~
1-~benzthiazol-2-ylthio)-butane-2,4-dicarboxylic acid,
4-(benzthiazol-2-ylthio)-butane-1,2,3-tricarboxylic acid,
4-(benzthiazol-2-ylthio)-butane~1,4-dicarboxylic acid,
1-(benzthiazol-2-ylthio)-pentane-1,5-dicarboxylic acid,
3-(benzthiazol-2-ylthio)-hexane~1,2~dicarboxylic acid,
8-(benzthiazol-2-ylthio)-octane-1,3,5,7~tetracarboxylic
acid,
1-(benzthiazol-2-ylthio)-cyclohexane~1,2-dicarboxylic acid,
~-(benzthiazol-2-ylthio)-cyclohexane~1,2-dicarboxylic ac;d,
1-(benzth;azol-2-ylthio)-propane-1,2,3-tricarboxylic acid,
1-(benzthiazol-2-ylthio)-3-chloropropane-1~2~dicarboxylic
acid,
1-(benzth;azol-2-ylthio)-3-methoxypropane-1,2-dicarboxylic
acid,
1-(benzthiazol-2-ylthio)-3-hydroxypropane-1,2-dicarboxylic
ac;d,
1-(benzth;azol-2-ylth;o)-2-phenylsucc;nic acid,
1-(benzthiazol-2-ylthio)-2-benzylsucc;nic acid,
1-~benzthiazol-2-ylthio)-3-methylbutane-1,3-dicarboxylic
acid,
3-(benzthiazol-2-ylthio)-hexane-3,4-dicarboxylic acid,
2,3-bis-~benzthiazol-2-ylthio)-butane-1,4-dicarboxylic
acid,
disodium benzthiazol-2-ylthiosuccinate,
dlpotassium benzthiazol-2-ylthiosuccinate,
calcium benzthiazol-2-ylthiosuccinate,
zinc benzthiazol-2-ylthiosuccinate,
cobalt benzthiazol~2~ylthiosuccinate,
alumin;um benzthiazol-2-ylthiosuccinate,
ammon;um benzth;azol-2-ylth;osuccinate,
bis-methylammonium benzthiazol-2-ylthiosuccinate,
bis-triethanolammon;um benzth;azol-2-ylthiosuccinate,
b;s-octylammonium benzth;azol-2-ylth;osuccinate,
bis-cyclohexylammonium benzthiazol-2-ylthiosuccinate,
diethylammonium benzthiazol-2-ylthiosuccinate,
tributylam~onium benzthiazol~2~ylthiosuccinate,
1 ~1 66~
- 10 -
d;sodium 3-(benzthiazol-2-ylthio)~propane-1,2-dicarboxylate,
dipotassium 3-(benzthiazol~2~ylthio)~propane-1,2~dicarboxy~
late,
calcium 3-~benzthiazol-2-ylthio)-propane-1,2-dicarboxy-
late,
zinc 3-(benzthia2ol-2-ylthio)-propane-l~2-dicarboxylate~
aluminium 3-(benzthiazol~2-ylthio)-propane-1,2-dicarboxy-
late,
ammonium 3-(benzth;azol-2-ylthio)-propane~1,2~dicarboxy-
late,
bis-methylammon;um 3-(benzthiazol-2-ylthio)-propane-1,2-d;-
carboxylate,
bis-(tr;ethanolammonium) 3-(benzth;azol-2-ylthio)-propane-
1,2-dicarboxylate,
benzoxazol-2-ylthiomalon;c acid,
benzoxazol-2-ylth;osucc;n;c acid,
5-methylbenzoxazol-2-ylth;osùcc;nic acid,
6-ethylbenzoxazol-2-ylth;osucc;nic ac;d,
4-;sopropylbenzoxazol-2-ylth;osucc;nic acid,
7-t-butylbenzoxazol-2-ylth;osucc;n;c ac;d,
5-n-hexylbenzoxazol-2-ylth;osucc;n;c ac;d,
6-C1,1,3,3-tetramethylbutyl~-benzoxazol-2-ylthiosucc;n;c
ac;d,
6-cyclohexylbenzoxazol-2-ylth;osucc;n;c ac;d,
~-benzylbenzoxazol-2-ylth;osucc;n;c ac;d,
6-methoxybenzoxazol-2-ylth;osucc;n;c acid,
7-ethoxybenzoxazol-2-ylthiosuccinic ac;d,
1 31 6~S5
-- 1 1 --
6-ethoxybenzoxazol-2-ylthiosucc;nic acid,
S-methoxybenzoxazol-2-ylthiosuccinic acid,
S-ethoxycarbonylbenzoxazol-2-ylthiosuccinic acid,
4-methylthiobenzoxazol-2-ylthiosuccinic acid,
6-methylsulfonylbenzoxazol-2-ylthiosuccinic acid,
4-fluorobenzoxazol-2-ylthiosuccinic acid,
S-chlorobenzoxazol-2-ylthiosuccinic acid,
7-bromobenzoxazol-2-ylthiosuccinic ac;d,
6-chlorobenzoxazol-2-ylthiosuccinic acid,
4-phenylbenzoxazol-2-ylth;osucc;n;c acid,
6-nitrobenzoxazol-2-ylthiosuccin;c ac;d,
5-cyanobenzoxazol-2-ylth;osuccinic acid,
S-carboxybenzoxazol-2-ylthiosuccinic acid,
7-hydroxybenzoxazol-2-ylthiosuccin;c acid,
6-chloro-4-methylbenzoxazol-2-ylth;osuccinic acid,
5-chloro-6-n-butylbenzoxazol-2-ylth;osuccinic acid,
4-bromo-5-n-hexylbenzoxazol-2-ylth;osuccinic ac;d,
S-nitro-6-n-propylbenzoxazol-2-ylth;osucc;n;c acid,
5-bromo-6-n-propoxybenzoxazol-2-ylth;osucc;nic ac;d,
6-am;nobenzoxazol-2-ylth;osucc;n;c ac;d,
6-methylam;nobenzoxazol-2-ylth;osucc;nic acid,
S-d;methylaminobenzoxazol-2-ylthiosuccinic acid,
7-phenylam;nobenzoxazol-2-ylthiosuccinic acid,
6-diphenylaminobenzoxazol-2-ylth;osuccinic acid,
4-benzylaminobenzoxazol-2-ylthiosuccinic acid,
4-morpholinobenzoxazol-2-ylthiosuccinic acid,
5-carbamoylbenzoxazol-2-ylthiosuccinic acid,
S-methylcarbamoylbenzoxazol-2-ylthiosuccinic acid,
S-diethylcarbamoylbenzoxazol-2-ylthiosuccinic acid,
6-phenylcarbamoylbenzoxazol-2-ylthiosuccinic acid,
5,6-dimethylbenzoxazol-2-ylthiosuccinic acid,
4,5,6-triethylbenzoxazol-2-ylthiosuccinic acid,
4,5,6,7-te~ramethylbenzoxazol-2-ylthiosuccin;c acid,
1-(benzoxazol-2-ylthio)-propane-1,2-dicarboxylic acid,
1-(4-phenylbenzoxazol-2-ylthio)-propane-1,2-dicarboxyl;c
acid,
3-~benzoxazol-2-ylthio~-propane-1,2-d;carboxylic acid,
1 31 66~,5
- 12 -
3-(6-tr;fluoromethylbenzoxazol-2-ylthio)-propane-1-2-dicar-
boxylic acid,
3-(6-methoxycarbonylbenzoxazol-2-ylthio)-propane-1,2-dicar-
boxylic acid,
3-(6-aminobenzoxazol-2-ylthio)-propane-1,2-dicarboxylic
acid,
3-(5-ethylaminobenzoxazol-2-ylthio)-propane-1,2-dicarboxy-
lic acid,
3-(4-dibutylaminobenzoxazol-2-ylthio)-propane-1,2-dicar-
boxylic acid,
4-tmorpholinobenzoxazol-2~ylthio)~propane~1,2~dicarboxylic
acid,
1-(benzoxazol-2-ylthio)-propane-1,3-dicarboxylic acid,
1-~6-ethylbenzoxazol-2-ylthio)-propane-1,3-dicarboxylic
acid,
2-~benzoxazol-2-ylthio)-propane-1,3-d;carboxylic acid,
2-~5-carboxybenzoxazol-2-ylth;o)-propane-1,3-dicarboxylic
acid,
3-(benzoxazol-2-ylth;o~-3-phenylpropane-1,2-d;carboxylic
acid,
3-(benzoxazol-Z-ylth;o)-3-(4-carboxyphenyl~-propane-1,2-di-
carboxylic ac;d,
3-(benzoxazol-2-ylthio~-3-(2,4-dicarboxyphenyl)-propane-
1,2-dicarboxylic acid,
3-(benzoxazol-2-ylthio)-3,3-diphenylpropane-1,2-dicarboxy-
l;c acid,
1-(benzoxazol-2-ylthio)-butane-1,2-dicarboxylic acid,
1-(4-methoxy-6-hydroxybenzoxazol-2-ylthio)-butane-1,2-di-
carboxylic acid,
3-(4,5-dimethyl-7-propoxybenzoxazol-2-ylthio~-propane-1,2-
dicarboxylic acid,
1-(benzoxazol-2-ylthio~-2-methylpropane-1,2-d;carboxylic
acid,
2-(benzoxazol-2-ylthio)-butane-2,3-dicarboxylic acid,
1-(benzoxazol-2-ylthio)-butane-2,4-dicarboxylic acid,
4-~benzoxazol-2-ylthio~-butane-1,2,3-tricarboxylic acid,
4-(benzoxazol-2-ylthio)-butane-1,4-dicarbo%ylic acid,
1 31 66~,5
- 13 -
1-~benzoxazol-2-ylthio)-pentane-1,5-dicarboxylic acid,
3-(benzoxazol-2-ylthio)-hexane-1,2-dicarboxylic asid,
~-(benzoxazol-2-ylthio)-octane-1,3,5,7-tetracarboxylic
acid,
1-(benzoxazol-2-rlthio)-cyclohexane-1,2-dicarboxylic acid,
4-(benzoxazol-2-ylthio)-cyclohexane-1,2-dicarboxylic acid,
1-(benzoxazol-2-ylthio)~propane-1,2,3-tricarboxylic acid,
1-(benzoxazol-2-ylthio)~3~chloropropane-1,2-dicarboxylic
acid,
1-~benzoxazol-2-ylthio)-3-methoxypropane-1,2~dicarboxylic
acid,
1-(benzoxazol-2-ylthio)-3-hydroxypropane-1,2-dicarboxylic
acid,
1-(benzoxazol-2-ylthio)-2-phenylsucçinic acid,
1-~benzoxazol-2-ylthio)-2-benzylsuccinic acid~
1-tbenzoxazol-2-ylth;o)-3-methylbutane-1,3-dicarboxylic
acid,
3-~benzoxazol-Z~ylthio)~hexane-3,4~dicarboxyl;c acid,
2,3-bis-~benzoxazol-2-ylthio)-butane-1,4-dicarboxylic acid,
disodium benzoxazol-2-ylth;osuccinate,
dipotassium benzoxazol-Z-ylthiosuccinate,
calcium benzoxazol-2-ylthiosuccinate,
zinc benzoxazol-2-ylthiosuccinate,
cobalt benzoxazol-2-ylthiosuccinate,
ammonium benzoxazol-2-ylthiosuccinate,
bis-methylammonium benzoxazol-2-ylthiosuccinate,
bis-triethanolammonium benzoxazol-2-ylthiosuccinate,
bis-octylammon;um benzoxazol-2-ylthiosuccinate,
bis-cyclohexylammonium benzoxazol-2-ylthiosuccinate,
diethylammoniùm benzoxazol-2-ylthiosuccinate,
tributylammonium benzoxazol-2 ylthiosucc;nate,
disodium 3-(benzoxazbl-2-ylthio)-propane-1,2-dicarboxylate,
dipotassium 3-(benzoxazol-2-ylthio)-propane-1,2-dicarboxy-
late,
calcium 3-(benzoxazol-2-ylthio)-propane-1,2-dicarboxyLate,
zinc 3-(benzoxazol-2-ylthio~-propane-1,2-dicarboxylate,
ammon;um 3-(benzoxazol-2-ylthio)-propane-1,2-dicarboxylate,
1 31 66'',5
- 14 -
bis-methylammonium 3-(benzoxazol-2-ylthio)~Propane-l~2-d
carboxyLate,
b;s-triethanoLammonium 3-~benzoxazoL-2-yLthio)~Propane-l,Z-
dicarboxylate,
benzimidazol-2-ylthiomalon;c acid,
benzimidazol-2-ylthiosuccinic acid,
5 (or 6)-methylbenzim;dazol-2-ylth;osuccinic acid,
6 (or 5)-ethylbenzimidazol-2-ylthiosuccin;c acid,
4 (or 7)-isopropylbenzimidazol-2-ylthiosuccinic acid,
? tor 4)-t-butylbenz;midazol-2-ylth;osucc;nic acid,
S ~or 6)-hexylbenzim;dazol-2-ylth;osuccin;c acid,
6 (or S)-Ct,1,3,3-tetramethylbutyl~-benzimidazol-2-ylthio-
succinic acid,
7 (or 4)-benzylbenzimidazol-2-ylthiosuccinic acid,
6 (or 5)-methoxybenzimidazol-2-ylthiosuccinic acid,
5-ethoxycarbonylbenzimidazol-2-ylthiosuccinic acid,
6 (or 5)-ethoxybenzimidazol-2-ylth;osucc;n;c ac;d,
7 ~or 4)-ethoxybenzimidazol-2-ylthiosuccinic acid,
4 (or 7)-fluorobenzimidazol-2-ylthiosuccinic acid,
5 tor 6)-chlorobenz;midazol-2-ylthiosuccinic acid,
7 (or 4)-bromobenzim;dazol-2-ylthiosuccin;c acid,
6 ~or 5)-nitrobenzimidazol-2-ylthiosuccinic acid,
S ~or 6)-methylsulphonylbenz;midazol-2-ylthiosuccin;c
acid~
1-(benzimidazol-2-ylthio)-2-phenylsuccinic acid,
S (or 6)-chloro-4 (or 7)-methylbenzimidazol-2-ylthiosuc-
cinic acid,
1 31 66~5
, 5
S (or 6)-chloro-6 tor 5)-n-butylbenzimidazol-2-ylth;osuc-
cinic acid,
4 tor 7)-bromo-5 (or 6)-n-hexylbenzimidazol-2-ylthiosuc-
cinic acid,
S (or 6)-nitro-6 tor 5)-n-propylbenzimidazol-2-ylthiosuc-
cinic acid,
5 tor 6)-bromo-6 (or 5)-n-propoxybenzimidazol-2-ylthiosuc-
cinic acid,
5,6-dimethylbenzimidazol-2-ylthiosuccinic acid,
4,5,6-triethylbenzimidazol-2~ylthiosuccinic acid,
4,5,6,7-tetramethylbenzim;dazol~2~ylthiosuccinic acid,
5 (or 6)-aminobenzimidazol-2-ylthiosuccinic acid,
t1- benzim;dazol-2-ylthio)-propane-1,2-dicarboxylic acid,
1-(4 (or 7)-phenylbenzim;dazol-2-ylthio)-propane-1,2-dicar-
boxyl;c ac;d,
1-(benz;m;dazol-2-ylth;o)-propane-1,3-dicarboxyl;c acid,
1-(6 (or 5)-ethylth;obenzim;dazol-2-ylth;o)-propane-1,3-di-
carboxyl;c ac;d,
2-(benzimidazol-2-ylthio)-propane-1,3-dicarboxylic acid,
2-t5 (or 6)-carboxybenzim;dazol-2-ylthio)-propane-1,3-di-
carboxyl;c ac;d,
3-tbenzimidazol-2-ylthio)-propane-1,2-dicarboxylic acid,
3-(5 (or 6)-aminobenzimidazol-2-ylthio)-propane-1,2-dicar-
boxyl;c acid,
3-t5 tor 6)-ethoxycarbonylbenzimidazol-2-ylthio)-propane-
1,2-dicarboxylic acid,
3-t5 tor 6)-trifluoromethylbenzimidazol-2-ylthio)-propane-
1,2-dicarboxylic acid,
3-(4 (or 7)-dipropylaminobenzimidazol-2-ylthio)-propane-
1,2-dicarboxylic ac;d,
3-(4 (or 7~-morphol;nobenz;midazol-2-ylth;o)-propane-1,2-
dicarboxylic acid,
3-(5 (or 6)-carbamoylbenzimidazol-2-ylthio)-propane-1,2-di-
carboxylic ac;d,
3-(4 tor 7)-cyanobenzim;dazol-2-ylthio)-propane-1,2-dicar-
boxylic acid,
3-(benzim;dazol-2-ylthio)-3-phenylpropane-1,2-dicarboxylic
1 31 6G',5
- ~6 -
acid,
3-(benzimidazol-2-ylthio)-3-(4-carboxyphenyl)-propane-1,2-
dicarboxylic acid,
3-~benzimidazol-2-ylthio)-3-~2,4-dicarboxyphenyl)-propane-
1,2-dicarboxylic acid,
3-~benzimidazol-2-ylthio)-3,3-diphenylpropane-1,2-dicar-
boxylic acid,
1-~benzimidazol-2-ylthio)-butane-1,2-dicarboxylic acid,
1-~4 (or 7)-methoxy-6 (or 5)-hydroxybenzimidazol-2-ylthio)-
butane-1,2-dicarboxylic acid,
4-(benz;midazol-2-ylthio)-butane-1,2,3-tr;carboxylic acid,
1-(4 (or 7)-methyl-7 ~or 4)-propoxybenzimidazol-2-ylthio)-
propane-2,3-dicarboxylic acid,
1-(benzimidazol-2-ylth;o)-2-methylpropane-1,2-dicarboxylic
acid,
2-(benzimidazol-2-ylthio)-butane-2,3-dicarboxylic acid,
1-(benz;midazol-2-ylthio)-butane-2,4-dicarboxylic acid,
4-(benz;m;dazol-2-ylth;o)-butane-1,4-dicarboxyl;c acid,
1-~benzimidazol-2-ylthio)-pentane-1,5-dicarboxylic acid,
3-(benz;midazol-2-ylth;o)-hexane-1,2-d;carboxylic acid,
8-(benzim;dazol-2-ylthio)-octane-1,3,5,7-tetracarboxylic
ac;d,
1-~benzimidazol-2-ylthio)-cyclohexane-1,2-dicarboxylic
ac;d,
4-(benzimidazol-2-ylthio)-cyclohexane-1,2-dicarboxylic acid,
1-~benzimidazol-2-ylthio)-propane-1,2,3-tricarboxylic acid,
1-(benzimidazol-2-ylthio)-3-chloropropane-1,2-dicarboxylic
acid,
1-~benzimidazol-2-ylthio)~3-methoxypropane-1,2~dicarboxylic
ac;d,
1-(benzimidazol-2-ylthio)-3-hydroxypropane-1,2-d;carboxylic
acid,
1-(benzimidazol-2-ylthio)-3-methylbutane-1,3-dicarboxylic
acid,
3-~benzimidazol-2-ylthio)-hexane-3,4-dicarboxylic acid,
disodium benzimidazol-2-ylthiosuccinate,
dipotassium benzimidazol-2-ylthiosuccinate,
1 31 66~ ~
21489-6829
- 17 -
calc~um ben2imida20l-2-ylthiosuccinate,
2~nc benzlmidazol-2-ylthiosuccinate,
cobalt ben2imidazol-2-ylthiosuccinate,
ammonium benz~midazol-2-ylthiosuccinate,
b1s-methylammon1um benz~midazol-2-ylthiosuccinate,
b1s-triethanolammonium benzim1dazol-2-ylthiosuccinate,
bis-octylammonium benzim~dazol-2-ylthiosuccinate,
bis-cyclohexylammon~um benzlmida20l-2-ylthiosuccinate and
d;ethylammonium ben21m1dazol-2-ylthiosuccinate.
tO The compounds of the formula II which are
used ln accord~nce uith the ~nventlon as corros~on 1nhlb1-
tors are knoun compound ; The
preparatlon of the compounds tan be effected in accordance
u~th a proces~ of European Patent Applicat~on Publ.
No. 129506, by reactlng a compound of the formula III
R\t~ ~./ ~ III
R
ln uhlch A ls a leavlng group, for example Cl, Or, I or p-
tosyloxy, ulth a compound ot the tormula
~R
1n ~h~ch 11 ~s hydrogen or a catlon, for example an alkall
metal cat10n, ~lkallne earth metal cat~on or ammon~um cat-
20 lon. Alternativelr, a compound of the formula IV
1316~ 5
- 18 -
I ll ~ -S-M IV
R ~ ~
can be reacted with a compound of the formula
Compounds of the formula ~I in which X ;s sulfur or
NH and R4 ;s carboxyl can aLso be prepared by reacting IV,
;n wh;ch M ;s hydrogen and X is S or NH, with an a, ~-un-
saturated ac;d o~ the formula
l 2
=c~
R COOH
in accordance with a process which ;s the subject of
Europ. Patent Application Publ. No. 126030.
The component a) can be any des;red film-former,
such as those wh;ch are known as binders for aqueous
coating compGs;tions e.g. dispersion paints, emulsion paints
or electrodepositable paints. The aqueous binder used
as component a) may be one or more water-soluble or water-
dispersible synthetic polymer. Examples of such
polymers are alkyd, polyester, acrylic, polyurethane,
epoxide, phenoplast or aminoplast resins
and mixtures of these resins,and homo- or copolymers of
vinyl ethers, vinyl esters, styr-ene, vinylidene chloride
and v;nyl chloride.
The water-borne binder may be optionally crosslinked
with aminoplast resins, phenoplast resins, blocked
isocyanates, epoxy resins, Mannic h bases of phenols or
activated carboxylic esters.
: -
1 3 1 66~,5
- 19 -
There are several methods available for rendering these
binders suitable for use in water-borne paints. These
methods, which are well known to those skilled in the
coatings art, include the incorporation of basic or acidic
functional groups which are then neutralised prior to
d;lution with water~
In addition to the components a) and b), the coat-
ing composition can also contain further components, for
example pigments, dyes, extenders and other additives such
as are customary for water-borne coating compositions. The pigments
can be organic, inorganic or metallic pigments, for example
titanium dioxide, iron oxide, aluminium bronze, phthalocya-
nine blue etc. It is also possible to use concomitantly
anti-corrosion pigments, for example pigments containing
phosphates or borates, metal pigments and metal oxide pig-
ments (see Farbe und Lack 88 (1982), 183) or the ~igments
described in European Patent A 54,267. Examples of exten-
ders hhich can be used concomitantl~ are talc, chalk, alu-
mina, baryte, mica or silica. ~xamples of 'urtner addi-
tives are flow control auxiliaries, dispersing agents,
th;xotropic agents, adhesion promoters, an.ioxidants, light
stabilisers or curing catalysts.
Particular importance attaches to the addi;ion of
basic extenders or pigments. In certain binder systems,
for example in acrylic and alkyd resins, these produce a
synergistic effect on the inhibition of corrosion.
Examples of such basic extenders or pigments are calcium
carbonate, magnesium carbonate, zinc oxide, zinc carbonate,
zinc phosphate, magnesium oxide, aluminium oxide, aluminium
phosphate or mixtures thereof. Examples of pigments are
those based on aminoanthraquinone.
The corrosion inhibitors according to the invention
can also first be applied to such basic extenders or pig-
ments, for example by chemisorption from an aqueous solu-
tion, and the preparations thus obtained can be added to
the coating composition.
1 31 66~5
- 20 -
In a further preferred embodiment of the invention
the corrosic,n inh;bitors are used together ~ith basic ion
exchangers or an ion exchanger of this type is first
treated with a solution of the inhibitor, and this prepara-
tion is then added to the coat;ng compos;tion. Examples of
basic ion exchangers are all typical anion exchangers, such
as those available commercially, for example under the
names Dowex R 1 or 11 or Amberlite R IRA.
Finally, the corrosion inhibitor can also be app-
lied to a neutral carrier. Suitable carriers are, in par-
ticular, pulverulent extenders or pigments. This technique
is described in greater detail in German Offenlegungs-
schrift 3,122,907.
In addition to the component b), the coating
composition can also contain another organic, metal-organic
or inorganic corrosion inhibitor, for exam?le salts of
nitro;sophthalic acid, tannin, phosphoric esters, technical
amines, substituted benztriazoles or subs~ituted phenols,
such as are described in German Offenlegungsschrift
3,146,~65~
The coating compositions according to the invention
are preferably used as a primer on metallic substrates, in
particular on iron, steel, copper and aluminium. Here they
can function as so-called conversion coa;ings, in that
chemical reactions take place at the interface ~etween the
metal dn the coating. The coating compositions may also
find application ;n can coating processes. The application
of the coatings can be effected by the customary methods,
such as spraying, brushing, roller-coating or dipping.
One preferred method is electrodeposition which may be
either anodic or cathodic, but is preferably cathodic.
1 3 1 6 6 ~
- 21 -
Depending on whether the film-former is a resin which dries
phys;cally or can be cured by heat or radiation, t~e
cur;ng of the coatings is carried out at room temperature,
by stoving or by irradiation.
The corrosion inhibitors can be added to the coat-
ing composition during the preparation of the latter, for
example during the distribution of the pig~ent by grinding
or the ;nhibitors are dissolved beforehand in a solvent and
the solution is stirred into the coating composition. The
innibitor is used in an amount of û.1 - 2û,. by ~eight, pre-
ferably û.5 - 5,'. by weight, based on the solids content of
the ~o~tinq composition.
Example_ A water-based maintenance primer is prepared by
mixing the follow;ng components (A) and (B)
~A) Pigment Paste
14.6 9 TiO2-Pigment (Ti-Pure ~ R-96û, Du Pont de
Nemours Co)
1.4 9 35 % aqueous solution of an dispersing agent
(Dispersing Agent QR 681 M, Rohm & Haas)
0.2 g pigment wetting agent (Triton ~ CF 10, Rohm
& Haas)
4.7 9 dist. water
0.2 9 antifoaming agent (Colloids 643, Colloids Inc.)
1.2 9 zinc oxide
5.1 9 micronized CaC03 (Millicarb ~ , Pluss-Staufer)
27.4 9
1 31 6~5
~B) Binder Dispers;on
64.4 9 43 % aqueous dispersion of an acrylic resin
tPrimal ~ MV 23, Rohm & Haas)
1.0 g 2-butoxyethoxy-ethanol
2.7 9 ethylene glycol
0.2 9 mildewcide agent CSkane ~ M-8, Rohm & Haas)
0.4 9 antifoaming agent (Colloids 643, Colloids Inc.)
0.2 9 thickener (Primal ~ ICS-1, Rohm & Haas)
1.1 9 rheology modifier (Primal ~ RM-8, Rohm & Haas)
2.6 9 dist. water
72.6 9
The mixed primer has a solid content of 48 %. To this
dispersion are added the corrosion inhibitors indicated in
the follow;ng table.
The primer is applied to phosphatised iron sheets in a
thickness of 100~um. The samples are baked at 130C for
20 m;nutes and are afterwards tested by a salt spray test
according to ASTM method B-117 for a duration of 600 hours.
The condition of the coating is assessed at the cross-cut
and on 'he whole surface according to DIN methods 53 209
and 53 210.
The coating is removed by treatment with concentrated NaOH
solution and the corrosion of the metal is assessed according
to DIN method 53 167. In both cases the assessment is made
on the basis of a 6-stage scale.
The sum of the assessment of coating and metal is the
corrosion protection ~alue ~CP).
i. ,
I
1 3 1 6 6 ~ '
- 23 -
*) Assessment Assessment
Corrosion Inhibitor Amount of coating of metal CP
-
none - 3.6 3.9 7.5
Benzthiazol-2-ylthio-
succinic acid-zinc
salt 2 % 3.7 4.3 8.0
-NH4 salt 2 % 4.1 4.3 8.4
3 % 4.3 5.2 9.5
3-~Benzthiazol-2-
ylthio)-propane-1,2-
dicarboxylic ac;d-NH4
salt 5 % 4.4 4.5 8.9
) related to the solid coating
