Fluorocarbon elastomers are commonly used in assembling internal combustion engines. The seals are used to prevent leakage of lubricants at the point where moving parts, such as the crankshaft, leaves the engine.
It is well known that the fluorocarbon elastomers are subject to attack by basic amine compounds which are usually present in lubricating oil compositions. This attack consists of base-promoted dehydrofluorination and cross-linking of the elastomer leading to, in essence, further curing of the material. This attack by the dispersants causes a loss of both elasticity and tensile strength in the elastomer. The seal eventually deteriorates to a point to where it fails to adequately prevent leakage of the lubricant from the crankcase.
U.S. Pat. No. 3,422,017 discloses load carrying oil additives which are the reaction product of primary, secondary or tertiary monoamines containing up to 30 carbon atoms and fluorophosphoric acid.
U.S. Pat. No. 4,379,064 teaches a method of mild oxidation of basically reacting polyamine crankcase dispersants in order to passivate the dispersant to fluorocarbon compositions used in engines.
U.S. Pat. No. 3,502,677 discloses additives for lubricating oil compositions which are the reaction product of an alkenyl succinimide and a phosphorus acid-producing compound. Suitable phosphorus acid-producing compounds disclosed in this reference include, among others, phosphoric acids, phosphorus acids, phosphonyl acids, phosphinyl acids and the halides thereof.
It has now been discovered that carboxylic amide dispersants containing basic nitrogen groups may be passivated to fluorocarbon elastomers used in engines by reacting said dispersants with a fluorine-containing acid selected from the group consisting of fluorophosphoric acid, boron trifluoride, fluoboric acid and the ammonium salts or complexes thereof.
The passivation of these dispersants is accomplished by reducing the total base of the dispersant by 50% to 90% of its original value.