Lubricating Composition

Abstract

The present invention relates to a lubricating composition containing a dispersant, a corrosion inhibitor and an antioxidant. The invention further provides a method for lubricating a mechanical device with the lubricating composition.

What is claimed is: 
     
         1 . A method for lubricating a hydraulic system comprising supplying to the hydraulic an ashless lubricating composition comprising:
 (a) about 0.01 to about 2 wt % of a dispersant;   (b) about 0.05 to about 1 wt % of an antioxidant;   (c) about 0.0001 wt % to about 0.1 wt % of a corrosion inhibitor;   (d) an oil of lubricating viscosity; and   (e) about 0.05 wt % to about 5 wt % of an antiwear agent mixture comprising:
 (i) an ammonium or amine salt of a phosphorus-containing acid or ester, and 
 (ii) an amide-containing dithiophosphorus acid ester. 
   
     
     
         2 . The method of  claim 1 , wherein the dispersant is a borated dispersant. 
     
     
         3 . The method of  claim 1 , wherein the antioxidant comprises (i) a hindered phenol or (ii) an alkylated diphenylamine. 
     
     
         4 . The method of  claim 1 , wherein the corrosion inhibitor comprises (i) a 2,5-bis(alkyl-dithio)-1,3,4-thiadiazole, (ii) a benzotriazole containing a hydrocarbyl substitution on at least one of the following ring positions 4- or 5- or 6- or 7-, or (iii) a benzotriazole containing a hydrocarbyl substitution on at least one of the following ring positions 1- or 2-. 
     
     
         5 . The method of  claim 1 , wherein the lubricating composition further comprises about 0.05 wt % to about 1.5 wt % of an antiwear agent. 
     
     
         6 . The method of  claim 1 , wherein the amide-containing dithiophosphorus acid ester is prepared by the addition of dithiophosphoric acid to an acrylamide chosen from acrylamide, methacrylamide, methylenebisacrylamide, or methylenebismethacrylamide. 
     
     
         7 . The method of  claim 1 , wherein the amide-containing dithiophosphorus acid ester is a methylenebisacrylamide, or methylenebismethacrylamide product prepared from prepared by the addition of a dithiophosphoric acid to acrylamide or methacryalamide to form an adduct; and subsequent reaction of the adduct with formaldehyde to make the amide-containing dithiophosphorus acid ester.