Additive package for high temperature synthetic lubricants

Abstract

An improved additive package including at least a polymeric amine antioxidants and a borated extreme pressure/antiwear agent for a polyol ester lubricant suitable for use in high temperature applications is provided. The lubricant fluid includes a base stock that is the reaction product of a polyol and monocarboxylic acid mixture including a major proportion of 3,5,5-trimethylhexanoic acid (iso-C 9 acid). The additive package may be added in up to about 20 percent by weight of the lubricant to provide a viscosity of the lubricant at 40° C. of at least about 140 cSt and at 100° C. of no less than about 15.0 cSt. Greases are formed by adding a thickener to a high viscosity lubricating fluid.

1 . An additive package for a polyol ester base stock suitable for high temperature use, comprising: 
 at least one oligomeric aromatic amine antioxidant, and    at least one borated extreme pressure/antiwear agent.    
     
     
         2 . The additive package of  claim 1 , wherein the oligomeric aromatic amine antioxidant is the reaction product of alkylated diphenylamine, an alkylated phenylnaphthylamine and an ester base stock.  
     
     
         3 . The additive package of  claim 1 , wherein the borated extreme pressure/antiwear agent is at least one of a borated amine, potassium tetraborate, borates of Group 2a alkaline earth metals, stable borates of transition metals, including zinc, copper and tin, and boric acid.  
     
     
         4 . The additive package of  claim 1 , wherein the oligomeric aromatic amine antioxidant is the reaction product of alkylated diphenylamine, an alkylated phenylnaphthylamine and an ester base stock and the borated extreme pressure/antiwear agent is at least one of a borated amine, potassium tetraborate, borates of Group 2a alkaline earth metals, stable borates of transition metals, including zinc, copper and tin, and boric acid.  
     
     
         5 . A synthetic ester based lubricant fluid, comprising 
 (A) an ester base stock that is the reaction product of: 
 (i) pentaerythritol, and  
 (ii) a monocarboxylic acid mixture including at least 60 weight percent iso-C 9  acid; and  
   (B) an effective amount of an additive package including: 
 at least one oligomeric aromatic amine antioxidant, and  
 at least one borated extreme pressure/antiwear agent;  
   the lubricant fluid having a viscosity at 40° C. of at least about 120 cSt.    
     
     
         6 . The synthetic lubricant fluid of  claim 5 , wherein the additive package is present in an amount between 5 to 15 weight percent, based on the total weight of the fluid.  
     
     
         7 . The synthetic lubricant fluid of  claim 5 , wherein the antioxidant is present in an amount between about 1 to 10 weight percent, based on the total weight of the fluid.  
     
     
         8 . The synthetic lubricant fluid of  claim 5 , wherein the borated antiwear agent is present in an amount between about 0.1 to 5 weight percent based on the total weight of the fluid.  
     
     
         9 . The synthetic lubricant fluid of  claim 5 , wherein the borated extreme pressure agent is selected from the group consisting of borated amines, potassium tetraborate, borates of Group 1a alkali metals, borates of Group 2a alkaline earth metals, stable borates of transition metals, such as zinc, copper and tin, and boric acid.  
     
     
         10 . The synthetic lubricant fluid of  claim 5 , wherein the oligomeric aromatic amine is the reaction product of alkylated diphenylamine, an alkylated phenylnaphthylamine and an ester base stock.  
     
     
         11 . The additive package of  claim 5 , wherein the oligomeric aromatic amine antioxidant is the reaction product of alkylated diphenylamine, an alkylated phenylnaphthylamine and an ester base stock and the borated extreme pressure/antiwear agent is at least one of a borated amine, potassium tetraborate, borates of Group 2a alkaline earth metals, stable borates of transition metals, including zinc, copper and tin, and boric acid.  
     
     
         12 . The synthetic lubricant fluid of  claim 5 , wherein the polyol is at least 85 weight percent pentaerythritol.  
     
     
         13 . The synthetic lubricant fluid of  claim 5 , wherein the polyol is about 98 percent pentaerythritol.  
     
     
         14 . The synthetic lubricant fluid of  claim 5 , wherein the straight chain acid is a mixture including at least 75 weight percent iso-C 9  acid and the balance C 7  and C 8-10  straight chain acids.  
     
     
         15 . The synthetic lubricant fluid of  claim 5 , further including an effective amount of a corrosion inhibitor.  
     
     
         16 . The synthetic lubricant fluid of  claim 5 , wherein the corrosion inhibitor is benzotriazole.  
     
     
         17 . The synthetic lubricant fluid of  claim 5 , wherein the balance of the monocarboxylic acid is normal C 7  to C 10  acids.  
     
     
         18 . The synthetic lubricant fluid of  claim 17 , wherein the acid mixture is at least about 66 percent iso-C 9  acid.  
     
     
         19 . A synthetic ester base lubricant fluid, comprising 
 (A) an ester base stock that is the reaction product of: 
 (i) dipentaerythritol, and  
 (ii) a monocarboxylic acid mixture including at least about 60 weight percent iso-C 9  acid and straight chain C 7  and C 8-10  acids; and  
   (B) an effective amount of an additive package including: 
 at least one oligomeric aromatic amine antioxidant and  
 a borated extreme pressure/antiwear agent;  
   to yield the lubricant fluid having a viscosity at 40° C. of at least about 120 cSt.    
     
     
         20 . The synthetic ester lubricant of  claim 19 , wherein the dipentaerythritol is at least about 85 weight percent dipentaerythritol.  
     
     
         21 . The synthetic ester lubricant fluid of  claim 19 , wherein the antioxidant is present in an amount between about 3 to 8 weight percent, based on the total weight of the fluid.  
     
     
         22 . The synthetic ester lubricant fluid of  claim 19 , wherein the borated antiwear agent is present in an amount between about 0.5 to 4 weight percent based on the total weight of the fluid.  
     
     
         23 . The synthetic ester lubricant fluid of  claim 5 , further including a thickening agent to form a grease.  
     
     
         24 . The synthetic ester lubricant fluid of  claim 22 , wherein the thickening agent is a polyurea.  
     
     
         25 . The synthetic ester lubricant fluid of  claim 19 , further including a thickening agent to form a grease.  
     
     
         26 . The synthetic ester lubricant fluid of  claim 25 , wherein the thickening agent is a polyurea present between about 20 to 25 weight percent of the total weight of the lubricant.