Lubricant composition for high-temperature applications

Abstract

A lubricant composition is provided that has reduced deposit formation and a low evaporation allowing for improved performance in high temperature applications relative to conventional high temperature lubricants. The high temperature lubricant composition includes a base oil, wherein the base oil includes at least one polyol ester and at least one pyromellitate ester. In some embodiments, the lubricant composition further includes one or more additives selected from the group of an extreme-pressure additive, an anti-wear additive, an anti-rust additive, a corrosion inhibitor, and an antioxidant, or a combination thereof. Further provided are methods for lubricating an apparatus using the lubricant composition, methods for improving the operational lubrication of a conventional high temperature lubricant, and methods of preparing the high temperature lubricant composition of the present invention.

1 . A lubricant composition, comprising:
 a base oil comprising a mixture of at least one polyol ester and at least one pyromellitate ester, wherein the polyol ester is present in an amount of about 36% to about 86% by weight of the lubricant composition and the pyromellitate ester is present in an amount of about 10% to about 60% by weight of the lubricant composition and   at least one additive,   
       wherein after at least 44 hours at a temperature of 240° C., the lubricant composition has a liquid fraction of at least about 50 percent, total deposit formation no greater than 2.75, and residue formation no greater than 30 percent. 
     
     
         2 . The lubricant composition of  claim 1 , wherein the at least one polyol ester comprises a pentaerythritol ester, a dipentaerythritol ester, or a mixture thereof. 
     
     
         3 . The lubricant composition of  claim 1 , wherein the at least one polyol ester comprises a dipentaerythritol ester having a structure according to the following formula: 
       
         
           
           
               
               
           
         
         wherein each R group is a linear or branched, saturated alkyl group having between about 4 and about 10 carbon atoms. 
       
     
     
         4 . The lubricant composition of  claim 4 , wherein at least one R group is a linear, saturated alkyl group, and wherein at least one R group is a branched, saturated alkyl group. 
     
     
         5 . The lubricant composition of  claim 1 , wherein the pyromellitate ester has a structure according to the following formula: 
       
         
           
           
               
               
           
         
         wherein R 1  is a branched or unbranched, saturated alkyl group having about 3 to about 15 carbon atoms. 
       
     
     
         6 . The lubricant composition of  claim 1 , wherein the pyromellitate ester is selected from the group consisting of tetraisopropyl pyromellitate, tetra 2-ethylhexyl pyromellitate, tetraheptyl pyromellitate, tetraoctyl pyromellitate, tetranonyl pyromellitate, tetradecyl pyromellitate, tetraisodecyl pyromellitate, tetra isononyl pyromellitate, tetra isooctyl pyromellitate, tetrabutyl pyromellitate, tetra isobutyl pyromellitate, and combinations thereof. 
     
     
         7 . The lubricant composition of  claim 1 , further having a kinematic viscosity at about 40° C. of about 90 to about 250 centistokes. 
     
     
         8 . The lubricant composition of  claim 1 , wherein the additive is selected from the group consisting of an extreme pressure additive, an anti-wear additive, an anti-rust additive, and a corrosion inhibitor. 
     
     
         9 . The lubricant composition of  claim 1 , wherein the additive is an antioxidant. 
     
     
         10 . The lubricant composition of  claim 9 , wherein the antioxidant is selected from the group consisting of a diphenyl amine, a naphthyl phenyl amine, a phenol, a thiophenol, a thiocarbamate, a triazole, a tocopherol, a phosphite, and a combination thereof. 
     
     
         11 . A lubricant composition, comprising:
 a base oil comprising:
 about 36 percent to about 86 percent of at least one polyol ester comprising a pentaerythritol ester, a dipentaerythritol ester, or a mixture thereof; 
 about 10 percent to about 60 percent of at least one pyromellitate ester having a structure according to the following formula: 
   
       
         
           
           
               
               
           
         
         wherein R 1  is a branched or unbranched, saturated alkyl group having about 3 to about 15 carbon atoms, and 
         one or more additives, 
       
       wherein after at least 44 hours at a temperature of 240° C., the lubricant composition has a liquid fraction of at least about 50 percent, total deposit formation no greater than 2.75, and residue formation no greater than 30 percent. 
     
     
         12 . The lubricant composition of  claim 11 , further having a kinematic viscosity at about 40° C. of about 90 to about 250 centistokes. 
     
     
         13 . The lubricant composition of  claim 11 , wherein the one or more additives is selected from the group consisting of an extreme pressure additive, an anti-wear additive, an anti-rust additive, and a corrosion inhibitor. 
     
     
         14 . The lubricant composition of  claim 1 , wherein the one or more additives are an antioxidant. 
     
     
         15 . The lubricant composition of  claim 14 , wherein the antioxidant is selected from the group consisting of a diphenyl amine, a naphthyl phenyl amine, a phenol, a thiophenol, a thiocarbamate, a triazole, a tocopherol, a phosphite, and a combination thereof. 
     
     
         16 . A method for lubricating an apparatus operated at high-temperatures, comprising:
 applying a high temperature lubricant composition to the apparatus, wherein the lubricant composition comprises,   a base oil comprising a mixture of at least one polyol ester and at least one pyromellitate ester, wherein the polyol ester is present in an amount of about 36% to about 86% by weight of the lubricant compositions and the pyromellitate ester is present in an amount of about 10% to about 60% by weight of the lubricant composition and   at least one additive,   
       wherein after at least 44 hours at a temperature of 240° C., the lubricant composition has a liquid fraction of at least about 50 percent, total deposit formation no greater than 2.75, and residue formation no greater than 30 percent.