Method of Lubricating an Automotive or Industrial Gear

Abstract

The disclosed technology relates to a lubricant composition for automotive or industrial gears, as well as axles and bearings, the lubricant composition containing an oil of lubricating viscosity and a metal alkylthiophosphate compound, such as zinc dialkyldithiophosphate, as well as a method of obtaining extreme pressure performance in automotive or industrial gears, axles and bearings at lower sulfur content than is typical, by lubricating such automotive or industrial gears, axles and bearings with a lubricant composition containing a metal alkylthiophosphate compound, such as zinc dialkyldithiophosphate.

1 . A lubricant composition comprising
 a. an oil of lubricating viscosity;   b. 0.5 to 2.0 wt % of an amine alkyl(thio)phosphate compound, and   c. 0.2 to 0.8 wt % of a metal alkylthiophosphate   
       wherein the lubricant comprises a total sulfur level of about 2 to about 5 wt %. 
     
     
         2 . The lubricant composition of  claim 1 , wherein the amine alkyl(thio)phosphate comprises an amine phosphate. 
     
     
         3 . The lubricant composition of  claim 2 , where the amine phosphate comprises a substantially sulfur-free alkyl phosphate amine salt wherein at least about 30 mole percent of the phosphorus atoms are in an alkyl pyrophosphate salt structure and at least about 80 mole percent of the alkyl groups are secondary alkyl groups of about 3 to about 12 carbon atoms. 
     
     
         4 . The lubricant composition of  claim 2 , where the amine phosphate comprises a substantially sulfur-free alkyl phosphate amine salt wherein at least about 30 mole percent of the phosphorus atoms are in an alkyl pyrophosphate salt structure and at least about 25 mole percent of the alkyl groups in such a sulfur-free alkyl phosphate can be primary alkyl groups of about 3 to about 12 carbon atoms 
     
     
         5 . The lubricant composition of  claim 1  wherein the amine comprises 2-ethylhexylamine. 
     
     
         6 . The lubricant composition of  claim 1  wherein the amine comprises an N-hydrocarbyl-substituted γ- or δ-amino(thio)ester. 
     
     
         7 . The lubricant composition of  claim 1  wherein the amine phosphate is present at from 0.5 to 2.0 weight percent. 
     
     
         8 . The lubricant composition of  claim 1 , wherein the amine alkyl(thio)phosphate comprises an amine alkylthiophosphate. 
     
     
         9 . The lubricant composition of  claim 8 , wherein the alkylthiophosphate of the amine alkylthiophosphate comprises a dialkyldithiophosphate. 
     
     
         10 . The lubricant composition of  claim 8 , wherein the amine comprises a C 8  to C 20  alkylamine. 
     
     
         11 . The lubricant composition of  claim 8 , wherein the amine alkylthiophosphate is present at from 0.5 to 2.0 weight percent. 
     
     
         12 . The lubricant composition of  claim 1 , wherein the metal alkylthiophosphate comprises zinc dialkyldithiophosphate. 
     
     
         13 . The lubricant composition of  claim 12 , wherein the zinc dialkyldithiophosphate comprises, consists essentially of, or consists of a secondary zinc dialkyldithiophosphate. 
     
     
         14 . The lubricant of  claim 13 , wherein the alkyl of the zinc dialkyldithiophosphate comprises 3 to 6 carbon atoms. 
     
     
         15 . The lubricant composition of  claim 12 , wherein the zinc dialkyldithiophosphate provides from 0.02 to 0.2 wt % zinc to the lubricant composition. 
     
     
         16 . The lubricant composition of  claim 1  further comprising less than 6 wt % of an organo-sulfide. 
     
     
         17 . The lubricant of  claim 17 , wherein the organo-sulfide comprises 2,5-dimercapto-1,3,4-thiadiazole. 
     
     
         18 . (canceled) 
     
     
         19 . The lubricant composition of  claim 1 , wherein the lubricant comprises a total phosphorus level of about 0.01 to about 0.5 wt %. 
     
     
         20 . A method of reducing the roughness of a metal surface comprising placing the metal surface under boundary lubrication conditions and providing to the metal surface a lubricant composition comprising:
 a. an oil of lubricating viscosity;   b. 0.5 to 2.0 wt % of an amine alkyl(thio)phosphate compound, and   c. 0.2 to 0.8 wt % of a metal alkylthiophosphate, wherein the lubricant comprises a total sulfur level of about 2 to about 5 wt %.   
     
     
         21 . The method of  claim 20 , wherein the metal surface comprises the surface of an axle. 
     
     
         22 . The method of  claim 20 , wherein the metal surface comprises the surface of a bearing. 
     
     
         23 . The method of  claim 20 , wherein the metal surface comprises the surface of a gear. 
     
     
         24 . A method of improving the operating temperatures of a gear at high load and low speed conditions comprising lubricating the gear with a lubricant composition comprising:
 a. an oil of lubricating viscosity;   b. 0.5 to 2.0 wt % of an amine alkyl(thio)phosphate compound, and   c. 0.2 to 0.8 wt % of a metal alkylthiophosphate, wherein the lubricant comprises a total sulfur level of about 2 to about 5 wt %, and operating the gear.   
     
     
         25 . A method of improving the operating efficiency of a used gear comprising lubricating the gear with a lubricant composition comprising:
 a. an oil of lubricating viscosity;   b. 0.5 to 2.0 wt % of an amine alkyl(thio)phosphate compound, and   c. 0.2 to 0.8 wt % of a metal alkylthiophosphate, wherein the lubricant comprises a total sulfur level of about 2 to about 5 wt %, and operating the gear.