Lubricant composition comprising a dispersant, a trinuclear molybdenum compound and a different other antioxidant

Abstract

This invention relates to a diesel engine lubricant composition comprising a base stock, a dispersant and an antioxidant comprising an oil soluble trinuclear organomolybdenum compound of the generic formula (I): Mo 3 S x —(Q), wherein x is from 4 to 10 and Q is a core group, which may be a ligand, and at least one other compound selected from a phenolic and an aminic compound. The composition is capable of controlling the viscosity of the lubricant in the presence of soot and to retain the dispersancy of the dispersant. The compositions of the present invention minimise wear in engines and undesirable emission from exhaust caused by incomplete combustion from vehicles which use diesel engines and lubricants therefor. The combination of antioxidants perform better at controlling soot induced viscosity increase than the individual compounds.

1 . A diesel engine lubricant composition comprising a base stock, a dispersant and an antioxidant comprising an oil soluble trinuclear organomolybdenum compound of the generic formula: 
       Mo 3 S x —(Q)  (I) 
       wherein x is from 4 to 10 and Q is a core is a core group, which may be a ligand, and at least one other compound selected from a phenolic and an aminic compound.  
     
     
         2 . A composition according to  claim 1  wherein said composition comprises a major amount of a natural or synthetic lubricating oil having a kinematic viscosity of 3.5 to 25 cSt at 100° C.  
     
     
         3 . A composition according to any one of the preceding Claims wherein the trinuclear molybdenum compounds are of formula (I) 
       Mo 3 S x —(Q)  (I) 
       wherein x is 7 and Q is a core group.  
     
     
         4 . A composition according to any one of the preceding Claims wherein the core group Q is a ligand capable of rendering the organomolybdenum compound of formula (I) oil soluble and ensuring that said molybdenum compound is substantially charge neutral.  
     
     
         5 . A composition according to any one of the preceding Claims wherein the phenolic compound is a hindered phenol.  
     
     
         6 . A composition according to any one of the preceding Claims wherein the aminic compound is selected from one or more of diaryl amines, aryl naphthyl amines and alkyl derivatives of diaryl amines and the aryl naphthyl amines of the formulae (VII) or (VIII) below wherein each of R 4  and R 5  is a hydrogen atom or represents the same or different alkyl groups from 1-8 carbon atoms.  
       
         
           
           
               
               
           
         
       
     
     
         7 . A composition according to any one of the preceding Claims wherein the antioxidant which comprises the trinuclear organomolybdenum compound and at least one other compound selected from a phenolic and/or an aminic compound form a minor component of the total lubricant composition.  
     
     
         8 . A composition according to any one of the preceding Claims wherein the antioxidant which comprises the trinuclear organomolybdenum compound and an aminic compound form a minor component of the total lubricant composition.  
     
     
         9 . A composition according to any one of the preceding Claims wherein the trinuclear organomolybdenum compound is present in said composition in an amount of about 0.05 to about 5.00 wt % of the total composition.  
     
     
         10 . A composition according to any one of the preceding Claims wherein the amount of phenolic and/or aminic compounds present in said composition is about 0.10 to about 3.0 wt % of the total composition.  
     
     
         11 . A method of controlling the soot induced viscosity of diesel engine lubricant compositions diesel engine lubricant compositions comprising a base stock and a dispersant with an effective amount of an antioxidant characterised in that the antioxidant comprises an oil soluble trinuclear organomolybdenum compound of the generic formula: 
       Mo 3 S x —(Q)  (I) 
       wherein x is from 4 to 10, preferably 7, and Q is a core group, which may be a ligand, and at least one other compound selected from a phenolic and an aminic compound.