HIGH TEMPERATURE FUNCTIONAL FLUIDS

摘要

It has now been discovered that functional fluids characterized as effective over a wide range of temperature including very high temperatures can be prepared which comprise (A) a major amount of at least one synthetic base oil; and minor amounts of (B) at least one phenolic compound selected from the group consisting of (B-1) metal-free, hindered phenols substituted with at least one alkyl group containing at least about 6 carbon atoms, and alkylene coupled derivatives thereof; (B-2) neutral and basic alkaline earth metal salts of hindered phenols which are not alkylene- or sulfur-coupled; (B-3) metal-free alkyl phenol sulfides or neutral and basic alkaline earth metal salts of alkyl phenol sulfides; and (B-4) neutral and basic alkaline earth metal salts of alkylene-coupled phenols; and (C) at least one non-phenolic antioxidant. When the phenolic compound (B) is a metal-free or neutral phenolic compound, it is preferred to include as an additional component, (D) at least one basic alkali metal salt or alkaline earth metal salt of a sulfonic or carboxylic acid, or mixtures thereof. In one preferred embodiment, the high temperature functional fluids of the invention are free of ashless dispersants or metal salts of dihydrocarbyl dithiophosphoric acids, or both. The lubricating compositions of the present invention are particularly useful at high temperatures such as above 260 DEG C including high temperature applications of up to about 370 DEG C or even 540 DEG C or higher. The functional fluids of the invention retain their lubricating properties and are thermally stable at the very high temperatures.