Lubricant composition

Abstract

A lubricant composition comprising a major amount of an oil of lubricating viscosity and a minor amount of: (A) an oil-soluble or oil-dispersible salt of a dihydrocarbylthiophosphoric acid, which acid is derivable from the reaction of a phosphorus sulfide and (I) compound (P) having at least two groups independently selected from hydroxyl (OH) and sulfhydryl (SH), wherein there is at least four, preferably at least five, atoms, separating two groups, preferably any two groups, in compound (P), or (II) a mixture of two or more compounds comprising compound (P) as defined in (I) and one or more compounds, wherein each or the compound has at least one group selected from hydroxyl (OH) and sulfhydryl (SH); and (B) an oil-soluble or oil-dispersible molybdenum compound. Such a composition has been found to demonstrate improved friction-reducing performance.

What is claimed is:  
     
         1 . A lubricant composition comprising a major amount of an oil of lubricating viscosity and, added thereto or admixed therewith, a minor amount of: 
 (A) an oil-soluble or oil-dispersible salt of a dihydrocarbylthiophosphoric acid, which acid is derived or derivable from the reaction of a phosphorus sulfide and 
 (I) at least one compound (P) having at least two groups independently selected from hydroxyl (OH) and sulfhydryl (SH), wherein there is at least four atoms, separating two groups in compound (P), or  
 (II) at least one compound (P) as defined in (I) and at least one compound (M), which is different from compound (P) and, has at least one group selected from hydroxyl (OH) and sulfhydryl (SH); and  
   (B) an oil-soluble or oil-dispersible molybdenum compound.    
     
     
         2 . The lubricant composition claimed in  claim 1 , wherein the dihydrocarbylthiophosphoric acid is derived or derivable from the reaction of a phosphorus sulfide and a mixture of two or more compounds as defined in  claim 1 , provided that the mixture comprises compound (M) having one group selected from hydroxyl (OH) and sulfhydryl (SH) and compound (P) as defined in  claim 1 .  
     
     
         3 . The lubricant composition claimed in  claim 1 , wherein there is a mixture of of at least one compound (P) and at least one compound (M), wherein the amount of the compound (P), based on the hydroxyl (OH) and sulfhydryl (SH) groups, present in the mixture is at most 50 mole %, based on the total hydroxyl (OH) and sulfhydryl (SH) groups in the mixture.  
     
     
         4 . The lubricant composition claimed in  claim 2 , wherein the amount of the compound (P), based on the hydroxyl (OH) and sulfhydryl (SH) groups, present in the mixture is at most 50 mole %, based on the total hydroxyl (OH) and sulfhydryl (SH) groups in the mixture.  
     
     
         5 . The lubricant composition claimed in  claim 1 , wherein compound (P) comprises at least two hydroxyl groups.  
     
     
         6 . The lubricant composition claimed in  claim 1 , wherein there are at least six atoms separating two groups in compound (P).  
     
     
         7 . The lubricant composition claimed in  claim 1 , wherein at least one atom separating two groups in compound (P) is selected from oxygen, sulfur and nitrogen.  
     
     
         8 . The lubricant composition claimed in  claim 2 , wherein the compound (M) is an aliphatic mono-alcohol.  
     
     
         9 . The lubricant composition claimed in  claim 1 , wherein the compound (P) is derived from the reaction of a glycol and an alkylene oxide.  
     
     
         10 . The lubricant composition claimed in  claim 1 , wherein the dihydrocarbylthiophosphoric acid is a salt of a moiety selected from an amine, ammonia and a metal selected from alkali metal, alkaline earth metal and transition metal.  
     
     
         11 . The lubricant composition claimed in  claim 1 , wherein the molybdenum compound is a trinuclear molybdenum compound.  
     
     
         12 . The lubricant composition claimed in  claim 1 , wherein the lubricant composition has at most 0.15 mass % of phosphorus, based on the mass of the lubricant composition.  
     
     
         13 . An additive concentrate composition suitable for preparing a lubricant composition comprising a diluent fluid and, added thereto or admixed therewith, (A) and (B) as defined in  claim 1 .  
     
     
         14 . A process for making a lubricant composition as claimed in  claim 1  comprising blending a major amount of an oil of lubricating viscosity and a minor amount of (A) and (B).  
     
     
         15 . A method of lubricating a surface comprising supplying to the surface a lubricant composition as claimed in  claim 1 .  
     
     
         16 . An oil-soluble or oil-dispersible salt of a dihydrocarbylthiophosphoric acid, which acid is derived or derivable from the reaction of a phosphorus sulfide and 
 (I) at least one compound (P′) having at least two groups independently selected from hydroxyl (OH) and sulfhydryl (SH), wherein there is at least four atoms separating two groups in compound (P′) and at least one atom separating two groups in compound (P′) is selected from oxygen, sulfur and nitrogen, or    (II) a mixture of at least two compounds comprising compound (P′) as defined in (I) and at least one compound (M), which is different from compound (P′) and has at least one group selected from hydroxyl (OH) and sulfhydryl (SH).    
     
     
         17 . An additive comprising the oil-soluble or oil-dispersible salt as claimed in  claim 16 , and optionally a diluent fluid.  
     
     
         18 . An additive concentrate composition comprising a diluent fluid, and added thereto or admixed therewith, an additive as claimed in  claim 17  and one or more co-additives.  
     
     
         19 . A lubricant composition comprising a major amount of an oil of lubricating viscosity, and added thereto or admixed therewith, a minor amount of an additive as claimed in  claim 17 .  
     
     
         20 . A dihydrocarbylthiophosphoric acid, which acid is derived or derivable from the reaction of a phosphorus sulfide and 
 (I) at least one compound (P′) having at least two groups independently selected from hydroxyl (OH) and sulfhydryl (SH), wherein there is at least four atoms separating two groups in compound (P′) and at least one atom separating two groups in compound (P′) is selected from oxygen, sulfur and nitrogen, or    (II) a mixture of at least two compounds comprising compound (P′) as defined in (I) and at least one compound (M), which is different from compound (P′) and has at least one group selected from hydroxyl (OH) and sulfhydryl (SH).