Compositions – Heat-exchange – low-freezing or pour point – or high boiling... – Organic components
Patent
1998-08-11
2000-04-04
Skane, Christine
Compositions
Heat-exchange, low-freezing or pour point, or high boiling...
Organic components
252 75, 252394, 422 13, 422 16, C09K 500, C23F 1114
Patent
active
060457198
DESCRIPTION:
BRIEF SUMMARY
Use of quaternized imidazoles as corrosion inhibitors for non-ferrous metals, and coolant compositions and antifreeze concentrates comprising them
The present invention relates to the use of specific quaternized imidazoles as corrosion inhibitors for preventing the corrosion of nonferrous metals. The invention also relates to antifreeze concentrates and to ready-to-use aqueous coolant compositions comprising these quaternized imidazoles, and to a method of treating aqueous liquids with these quaternized imidazoles in order to reduce the corrosion of nonferrous metals.
Antifreeze for the cooling circuits of internal-combustion engines, as in automobiles, generally contains an alkylene glycol, especially ethylene glycol or propylene glycol, as the principal component. For use in the cooling system these are diluted with water and are intended to provide not only for protection from frost but also for good heat dissipation. Alkylene glycol/water mixtures, however, are highly corrosive at the operating temperatures of internal-combustion engines, and therefore the various metals and their alloys present in the cooling system must be provided with sufficient protection against a wide variety of types of corrosion, such as pitting, crevice corrosion, erosion or cavitation. For use as corrosion inhibitors in such cooling systems the prior art already includes a multiplicity of individual chemicals.
As far as temperature stress on the heat transfer faces, pressure, flow rate and the selection of appropriate materials are concerned, the operating conditions in modern internal-combustion engines nowadays place very much greater demands on the anticorrosion capacity of the coolant than was previously the case. In addition to the known materials, such as copper, brass, soft solder, steel and gray cast iron, aluminum alloys are being used to an increasing extent. Consequently, more of the recent patent literature describes specific combinations of long-known active substances, each claimed to have its own specific spectrum of action.
For instance, EP-B 229 440 (1) describes the combination of the salt of an aliphatic monobasic C.sub.3 -C.sub.16 acid, the salt of a dibasic C.sub.5 -C.sub.16 -hydrocarbon acid and a hydrocarbon-triazole as an effective inhibitor formulation in a liquid-alcoholic freezing-point reducer for protecting aluminum alloys against pitting. It is additionally possible to employ other customary inhibitors, such as alkali metal borate, silicate, benzoate, nitrate, nitrite or molybdate, and/or a hydrocarbazole.
EP-A 564 721 (2) discloses antifreeze compositions, in particular for car radiator protection, which comprise a combination of the salt of an aliphatic monobasic C.sub.5 -C.sub.16 acid, a hydrocarbon-triazole and imidazole as effective inhibitor formulation in a liquid-alcoholic freezing-point reducer. The imidazole concerned includes unsubstituted imidazole and also alkyl- and aryl-substituted imidazole.
A deficiency of the known inhibitor combinations is that, as far as nonferrous metal protection is concerned, they lose marks at elevated temperatures. For example, the hydrocarbon-triazoles which are employed predominantly in this context, for example benzotriazole and toluotriazole, lose their effectiveness above about 130.degree. C.
It is an object of the present invention, therefore, to find substances which raise the high-temperature protection afforded to nonferrous metals by customary inhibitor systems without a drop in protection for the other metals, especially aluminum alloys.
We have found that this object is achieved by the extensive replacement, in customary inhibitor systems, of the hydrocarbon-triazoles, such as benzotriazole or toluotriazole, by quaternized imidazoles, resulting in a marked improvement in the protection afforded to nonferrous metals, especially copper, brass and bronze, under high temperature stress.
It has been found that quaternized imidazoles of the general formula I ##STR2## where R.sup.1 and R.sup.3 independently of one another are saturated or unsaturate
REFERENCES:
patent: 2875210 (1959-02-01), Bollenback et al.
patent: 4452758 (1984-06-01), Wilson et al.
patent: 4622158 (1986-11-01), Walsh
Chemical Abstracts, AN 80:133872, "Synthesis and homopolymerization of vinylimidazolium salts", Salamone et al, No Month Available 1973.
Derwent Publication Ltd., London. GB, & JP 06 157 471, Jun. 3, 1994.
Gillich Michael
Gunther Wolfgang
Meszaros Ladislaus
Oppenlander Knut
Pfitzner Klaus
BASF - Aktiengesellschaft
Skane Christine
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