Lubricating Composition Containing a Compound Derived from a Hydroxy-carboxylic Acid

Abstract

The invention relates to a lubricating composition comprising (a) a compound derived from a hydroxy-carboxylic acid, and (b) an oil of lubricating viscosity. The invention further provides for the use of the lubricating composition for lubricating a limited slip differential.

1 - 22 . (canceled) 
     
     
         23 . A method of lubricating a limited slip differential comprising supplying to the limited slip differential a lubricating composition comprising (a) a derivative of a hydroxy-carboxylic acid, and (b) an oil of lubricating viscosity, wherein derivative of a hydroxy-carboxylic acid is represented by Formula 1a or 1b: 
       
         
           
           
               
               
           
         
       
       wherein
 n′ is 0 to 10 for Formula (1b), and 1 to 10 for Formula (1a); 
 p is 1 to 5; 
 Y and Y′ are independently —O—, >NH, >NR 3 , or an imide group formed by taking together both Y and Y′ groups in (1b) or two Y groups in (1a) and forming a R 1 —N<group between two >C═O groups; 
 X is independently —CH 2 —, >CHR 4 , >CR 4 R 5 , >CHOR 6 , >C(OH)CO 2 R 6 , >C(CO 2 R 6 ) 2 , —CH 3 , —CH 2 R 4  or CHR 4 R 5 , —CH 2 OR 6 , —CH(CO 2 R 6 ) 2 ,═C—R 6  (where equals three valences, and may only apply to Formula (1a) or mixtures thereof to fulfill the valence of Formula (1a) and/or (1b)); 
 R 1  and R 2  are independently hydrocarbyl groups; 
 R 3  is a hydrocarbyl group; 
 R 4  and R 5  are independently keto-containing groups, ester groups or hydrocarbyl groups, or —OR 6 , or —CO 2 R 6 , or —OH; and 
 R 6  is independently hydrogen or a hydrocarbyl group. 
 
     
     
         24 . The method of  claim 23 , wherein the derivative of a hydroxy-carboxylic acid is a derivative of a hydroxy-polycarboxylic acid. 
     
     
         25 . The method of  claim 24 , wherein the derivative of a hydroxy-polycarboxylic acid is selected from the group consisting of a hydroxy-carboxylic acid di-ester, a hydroxy-carboxylic acid di-amide, a hydroxy-carboxylic acid imide, a hydroxy-carboxylic acid di-imide, a hydroxy-carboxylic acid ester-amide, a hydroxy-carboxylic acid ester-imide, and a hydroxy-carboxylic acid imide-amide. 
     
     
         26 . The method of  claim 24 , wherein the derivative of a hydroxy-polycarboxylic acid is selected from the group consisting of a hydroxy-carboxylic acid imide, a hydroxy-carboxylic acid di-imide, a hydroxy-carboxylic acid ester-imide, and a hydroxy-carboxylic acid imide-amide. 
     
     
         27 . The method of  claim 24 , wherein the derivative of a hydroxy-polycarboxylic acid is selected from the group consisting of a hydroxy-carboxylic acid imide and a hydroxy-carboxylic acid di-imide. 
     
     
         28 . The method of  claim 24 , wherein the derivative of a hydroxy-polycarboxylic acid is a derivative of tartaric acid, an imide derivative of citric acid, or mixtures thereof. 
     
     
         29 . The method of  claim 24 , wherein the derivative of a hydroxy-polycarboxylic acid is an imide derivative of tartaric acid, an imide derivative of citric acid, or mixtures thereof. 
     
     
         30 . The method of  claim 24 , wherein the derivative of a hydroxy-polycarboxylic acid is an imide derivative of tartaric acid, or mixtures thereof. 
     
     
         31 . The method of  claim 23 , wherein the derivative of a hydroxy-carboxylic acid is present in an amount in the range of 0.2 wt % to 3 wt % of the lubricating composition 
     
     
         32 . The method of  claim 23 , wherein the derivative of a hydroxy-carboxylic acid is present at greater than 0.2 wt % to 3 wt % of the lubricating composition. 
     
     
         33 . The method of  claim 23 , further comprising a sulphur-containing compound. 
     
     
         34 . The method of  claim 33 , wherein the sulphur-containing compound is a dimercaptothiadiazole or derivative, or mixtures thereof. 
     
     
         35 . The method of  claim 33 , wherein the sulphur-containing compound is a polysulphide or a sulphurised olefin. 
     
     
         36 . The method of  claim 23 , wherein the lubricating composition further comprises a phosphorus-containing compound, and wherein the phosphorus containing compound is an amine salt of a phosphoric acid ester. 
     
     
         37 . The method of  claim 36 , wherein the amine salt of a phosphoric acid ester is an amine salt of either (i) a hydroxy-substituted di-ester of phosphoric acid, or (ii) a phosphorylated hydroxy-substituted di- or tri-ester of phosphoric acid. 
     
     
         38 . The method of  claim 23 , wherein the lubricating composition further comprises a boron-containing compound, and wherein the boron-containing compound is a borated dispersant, a borate ester or a borated phospholipid. 
     
     
         39 . The method of  claim 23 , wherein the lubricating composition has a sulphur content in the range of 0.3 wt % to 5 wt %. 
     
     
         40 . The method of  claim 23 , wherein the hydroxy-carboxylic acid comprises a monohydroxy monocarboxylic acid. 
     
     
         41 . The method of  claim 23 , wherein the monohydroxy monocarboxylic acid comprises glycolic acid. 
     
     
         42 . The method of  claim 23 , wherein the derivative of the hydroxy-carboxylic acid is an amide. 
     
     
         43 . The method of  claim 23 , wherein the amide is the condensation product of glycolic acid with a hydrocarbyl amine containing 1-150 carbon atoms.