Lubricating Oils Having Improved Friction Stability

Abstract

Lubricating oil compositions having excellent friction stability comprise a base lubricating oil, an oil soluble source of phosphorus and a defined polyalkylene polyamine-based friction modifier that has been reacted with an acylating agent to convert at least one secondary amine group into an amide.

1 . A lubricating oil composition comprising a base lubricating oil, at least one oil soluble phosphorus containing compound and at least one polyalkylene polyamine-based friction modifier comprising at least one hydrocarbyl substituent wherein the, or each, hydrocarbyl substituent comprises between 6 and 30 carbon atoms 1  and wherein at least one secondary amino group present in the polyamine chain of the friction modifier has been acylated to the corresponding amide group. 
   
   
       2 . A composition comprising:
 (a) a major amount of a base lubricating oil; and   (b) a friction stability improving effective amount of an additive combination comprising:
 (i) at least one friction modifier comprising the reaction product of an acylating agent R 3 COX (wherein R 3  is a hydrocarbyl group and X is a leaving group) with one or more compounds selected from the group of compounds (I), (II) and (III), where (I), (II), and (III) are represented by the structures: 
   
     
       
         
         
             
             
         
       
     
     wherein R is a C 6  to C 30  alkyl or alkenyl group; R 1  is a polyalkylene polyamine group represented by structure (IV): 
     
       
         
         
             
             
         
       
     
     wherein n and m are each independently integers from 1 to 6; and R 2  is an alkyl or aryl group or their heteroatom containing derivatives, or is selected from the structures V, VI and VII below; and 
     
       
         
         
             
             
         
       
       
         (ii) at least one oil-soluble phosphorus-containing compound. 
       
     
   
   
       3 . The composition according to  claim 2  wherein the friction modifier (b)(i) comprises the reaction product represented by one or more of the structures (VIII), (IX) and (X): 
     
       
         
         
             
             
         
       
     
     wherein R, R 2 , R 3 , n and m are as defined in  claim 2  and wherein p+q=m, with the proviso that p≧1. 
   
   
       4 . The composition according to  claim 1  wherein the composition is a power transmission fluid. 
   
   
       5 . An additive composition comprising a friction modifier comprising at least one hydrocarbyl substituent wherein the, or each, hydrocarbyl substituent comprises between 6 and 30 carbon atoms, and wherein at least one secondary amino group present in the polyamine chain of the friction modifier has been acylated to the corresponding amide group in combination with an oil soluble phosphorus containing compound. 
   
   
       6 . The composition according to  claim 5  wherein the phosphorus compound is an ester of phosphoric or phosphorous acid. 
   
   
       7 . A method of imparting friction stability to lubricating oils, comprising adding a friction modifier comprising at least one hydrocarbyl substituent wherein the, or each, hydrocarbyl substituent comprises between 6 and 30 carbon atoms, and wherein at least one secondary amino group present in the polyamine chain of the friction modifier has been acylated to the corresponding amide group to a lubricating oil.