Synergistic additive combination for industrial gear oils

Abstract

The invention relates to industrial gear oil compositions that have been specially designed to have improved friction and/or antiwear properties. That is the industrial gear oil compositions of the invention provide good performance and/or protection in the areas of friction and/or antiwear due to the use of a synergistic combination of additives. The industrial gear oil compositions of the invention utilize a combination of certain phosphorus-containing compounds and derivatives of a hydroxy-carboxylic acid, to provide a synergistic improvement in friction and/or antiwear properties.

1 . An industrial gear oil composition comprising:
 (a) an oil of lubricating viscosity;   (b) a phosphorus-containing compound; and   (c) a derivative of a hydroxy-carboxylic acid;   where component (b) is present in the industrial gear oil composition at more than 0.3 percent by weight; and   where component (b) and component (c) combined are present in the industrial gear oil composition at 0.6 percent by weight or more.   
     
     
         2 . The industrial gear oil composition of  claim 1 , wherein the oil of lubricating viscosity comprises a mineral base oil. 
     
     
         3 . The industrial gear oil composition of  claim 1 , wherein the oil of lubricating viscosity comprises a synthetic base oil. 
     
     
         4 . The industrial gear oil composition of  claim 1 , wherein the phosphorus-containing compound comprises an alkyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, phosphonates, or some combination thereof. 
     
     
         5 . The industrial gear oil composition of  claim 1 , wherein the phosphorus-containing compound comprises alkyl phosphites. 
     
     
         6 . The industrial gear oil composition of  claim 1 , wherein (c), the derivative of a hydroxy-carboxylic acid, comprises a compound derived from a hydroxy-carboxylic acid represented by the formula: 
       
         
           
           
               
               
           
         
       
       wherein: a and b may be independently integers of 1 to 5; X may be an aliphatic or alicyclic group, or an aliphatic or alicyclic group containing an oxygen atom in the carbon chain, or a substituted group of the foregoing types, said group containing up to 6 carbon atoms and having a+b available points of attachment; each Y may be independently —O—, >NH, or >NR 3  or two Y's together representing the nitrogen of an imide structure R 4 —N< formed between two carbonyl groups; and each R 3  and R 4  may be independently hydrogen or a hydrocarbyl group, provided that at least one R 1  and R 3  group may be a hydrocarbyl group; each R 2  may be independently hydrogen, a hydrocarbyl group or an acyl group, further provided that at least one —OR 2  group is located on a carbon atom within X that is α or β to at least one of the —C(O)—Y—R 1  groups, and further provided that at least on R 2  is hydrogen. 
     
     
         7 . The composition of  claim 1 , wherein (c), the derivative of a hydroxy-carboxylic acid, comprises a compound derived from a hydroxy-carboxylic acid represented by the formula: 
       
         
           
           
               
               
           
         
         wherein each R 5  is independently H or a hydrocarbyl group, or wherein the R 5  groups together form a ring; 
         where the hydroxy-carboxylic acid is reacted with an alcohol and/or an amine, via a condensation reaction, to form the derivative of the hydroxy-carboxylic acid. 
       
     
     
         8 . The composition of  claim 1 , wherein the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid or citric acid. 
     
     
         9 . The industrial gear oil composition of  claim 1 , wherein the composition further comprises (d), one or more additional additives;
 wherein component (d) comprises one or more sulfurized olefins, phosphoric acid esters, thiophosphates, thiophosphoric acid esters and/or amine salts thereof, thiadiazoles and/or substituted thiadiazole, tolyltriazoles and/or substituted triazoles, polyethers, alkenyl amines and/or polyolefin amide alkenamines, ester copolymers, carboxylic esters, dispersants, anitfoams, hydrocarbon polymers, a sulfurized fatty ester, and or any combination thereof.   
     
     
         10 . The industrial gear oil composition of  claim 1 , wherein the weight ratio of component (b) to component (c) in the industrial gear oil composition is from 2.5:1 to 30:1. 
     
     
         11 . The industrial gear oil composition of  claim 1 , wherein component (b) is present from 0.3 to 10 percent by weight of the overall industrial gear oil composition; and
 wherein component (c) is present from 0.1 to 10 percent by weight of the overall industrial gear oil composition.   
     
     
         12 . A process of making an industrial gear oil composition comprising the step of: (1) mixing the following components:
 (a) an oil of lubricating viscosity;   (b) a phosphorus-containing compound; and   (c) a derivative of a hydroxy-carboxylic acid;   where component (b) is present in the industrial gear oil composition at more than 0.3 percent by weight; and   where component (b) and component (c) combined are present in the industrial gear oil composition at 0.6 percent by weight or more;   resulting in an industrial gear oil composition.   
     
     
         13 . The process of  claim 11 , wherein the oil of lubricating viscosity comprises a mineral base oil, a synthetic base oil, or a combination thereof;
 wherein the phosphorus-containing compound comprises an alkyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, or some combination thereof;   wherein the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid or citric acid; and   wherein step (1) optionally further comprises mixing (d), one or more additional additives into the industrial gear oil composition;   wherein component (d) comprises one or more sulfurized olefins, phosphoric acid esters, thiophosphates, thiophosphoric acid esters and/or amine salts thereof, thiadiazoles and/or substituted thiadiazole, tolyltriazoles and/or substituted triazoles, polyethers, alkenyl amines and/or polyolefin amide alkenamines, ester copolymers, carboxylic esters, dispersants, anitfoams, hydrocarbon polymers, a sulfurized fatty ester, and or any combination thereof.   
     
     
         14 . A method of improving the friction and antiwear properties of an industrial gear oil composition comprising the step of: (1) adding to an industrial gear oil composition, which comprises (a) an oil of lubricating viscosity, the following components:
 (b) a phosphorus-containing compound; and   (c) a derivative of a hydroxy-carboxylic acid;   where component (b) is present in the industrial gear oil composition at more than 0.3 percent by weight; and   where component (b) and component (c) combined are present in the industrial gear oil composition at 0.6 percent by weight or more;   resulting in an industrial gear oil composition with improved friction and antiwear properties of the composition.   
     
     
         15 . The method of  claim 13 , wherein the oil of lubricating viscosity comprises a mineral base oil, a synthetic base oil, or a combination thereof;
 wherein the phosphorus-containing compound comprises an alkyl phosphite, a phosphoric acid ester, an amine salt of a phosphoric acid ester, or some combination thereof;   wherein the derivative of hydroxycarboxylic acid includes an imide, a di-ester, a di-amide, an imide amide, an imide ester or an ester-amide derivative of tartaric acid or citric acid; and   wherein step (1) optionally further comprises mixing (d), one or more additional additives into the industrial gear oil composition;   wherein component (d) comprises one or more sulfurized olefins, phosphoric acid esters, thiophosphates, thiophosphoric acid esters and/or amine salts thereof, thiadiazoles and/or substituted thiadiazole, tolyltriazoles and/or substituted triazoles, polyethers, alkenyl amines and/or polyolefin amide alkenamines, ester copolymers, carboxylic esters, dispersants, anitfoams, hydrocarbon polymers, a sulfurized fatty ester, and or any combination thereof.   
     
     
         16 . (canceled)