Compositions – Frost-preventing – ice-thawing – thermostatic – thermophoric,...
Patent
1998-12-04
2000-05-09
Green, Anthony
Compositions
Frost-preventing, ice-thawing, thermostatic, thermophoric,...
106 13, C09K 318
Patent
active
060599898
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a deicing composition based on alkali metal acetates, alkali metal formates or a mixture of the two for traffic areas. The invention also relates to a method of melting snow and ice on traffic areas using said composition.
DESCRIPTION OF THE RELATED ART
Snow and/or ice on roads, cycleways, footpaths, bridges, sportsgrounds, airfields and the like (called traffic areas below) lead to a substantial impairment in the progress of the traffic and in transport safety. It has therefore long been known to apply to such areas a composition for melting or thawing snow and ice.
The requirements to be met by a deicing composition are multifaceted. The materials from which the areas in question are constructed, for example concrete, must not be damaged, let alone destroyed, by the deicing composition. It is also essential to rule out a corrosive action on metals, inter alia. Since the composition may enter the wastewater, biodegradability is a further requirement. It is also essential that very rapid thawing is achieved. From the economic standpoint, finally, it is necessary that only a small amount of deicing composition is required and that it does not cost much.
The prior art describes numerous alkali metal salts and alkaline earth metal salts of inorganic and organic acids as deicing agents, examples being sodium chloride, calcium chloride, sodium formate, calcium formate, sodium acetate, magnesium acetate, sodium lactate and the like. These deicing agents, especially the acetates and formates, do indeed meet several of the abovementioned requirements; however, with regard to corrosion they leave much to be desired. For instance, especially on light metals such as aluminum and magnesium, they have a more or less strong corrosive effect, which is particularly disadvantageous in view of means of transport such as cars, motorbikes, aircraft and the like.
Attempts have already been made to solve the above-mentioned problems with the aid of inhibitors. Thus EP-A 0 375 214 describes a liquid deicer consisting essentially of from 45 to 60% by weight of an alkali metal acetate and/or alkali metal formate, from 0.1 to 0.4% by weight of an alkali metal phosphate, from 0.2 to 0.6% by weight of an alkali metal nitrite, and water as a remainder to 100% by weight, the percentages by weight being based on the weight of the deicer. However, the inhibitor effect of alkali metal phosphate and alkali metal nitrite leaves much to be desired, especially with regard to magnesium; a further disadvantage is the nitrite content.
DE-A 40 34 217 describes a liquid or solid deicing composition based on water-soluble alkali metal salts of formic acid and/or acetic acid, the corrosion inhibitor system consisting of water-soluble polycarboxylic acids and water-soluble silicates and/or carbonates of alkali metals or of ammonium. This chloride- and nitrite-free deicing composition is said to attack neither constructions of concrete, bitumen or stone, nor metallic materials such as iron, copper, aluminum or zinc. The anticorrosive effect is based on the combination of a water-soluble polycarboxylic acid, such as succinic acid, citric acid or tartaric acid, with a water-soluble silicate and/or carbonate. In the case of light metals, it too leaves much to be desired.
Mention may also be made of U.S. Pat. No. 4,803,007, in which a deicing composition is described which is based on sodium chloride and which employs, as corrosion inhibitor, a mixture of a divalent metal salt and an alkali metal polyphosphate. Divalent metals mentioned include calcium, magnesium and barium and, as counterions, borates, metasilicates and sulfates. This inhibitor combination acts in particular to counter corrosion to ferrous metals, but less so with respect to the corrosion of light metals such as magnesium.
SUMMARY OF THE INVENTION
It has now been found that a mixture of alkali metal phosphates and alkali metal silicates is a particularly effective light metal corrosion inhibitor for a deicing composition based on alk
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Becker Wilfried
Stankowiak Achim
Clariant GmbH
Dearth Miles B.
Green Anthony
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