Ionic liquids as lubricating oil base stocks, cobase stocks and multifunctional functional fluids

Abstract

A composition including an ionic liquid alkylammonium salt (e.g., tetraalkylammonium cation and bis(2-ethylhexyl)phosphate anion), or an ionic liquid imidazolium salt (e.g., 1,3-dialkylimidazolium cation and bis(2-ethylhexyl)phosphate anion), that have a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks. The disclosure also relates to a lubricating oil base stock and lubricating oil containing the composition, a multifunctional functional fluid containing the composition, and a method for improving solubility of an ionic liquid in a lubricating oil by using as the lubricating oil a formulated oil including a lubricating oil base stock as a major component, and an ionic liquid alkylammonium salt cobase stock, or an ionic liquid imidazolium salt cobase stock, as a minor component.

What is claimed is: 
     
         1 . A composition comprising:
 (i) an ionic liquid alkylammonium salt represented by the formula
   R 4 N + ,[C 8 H 17 O] 2 P(O) 2   −   (1)
 
   
       wherein R is independently hydrogen, C 1  to C 16  straight chain alkyl, branched chain alkyl, cycloalkyl, alkyl substituted cycloalkyl, cycloalkyl substituted alkyl, or, optionally, two R groups comprise a cyclic structure including the nitrogen atom and 4 to 12 carbon atoms; wherein said ionic liquid alkylammonium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks; or
 (ii) an ionic liquid imidazolium salt represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 3  are independently a C 1  to C 24  straight chain or branched chain alkyl group, a C 6  to C 10  aryl group, a C 7  to C 12  arylalkyl group, a C 7  to C 12  alkylaryl group, a C 2  to C 8  alkenyl group, a C 1  to C 8  alkoxy group, a C 2  to C 8  alkinyl group, or a C 2  to C 8  acyl group; and R 2 , R 4  and R 5  are hydrogen; wherein said ionic liquid imidazolium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks. 
     
     
         2 . The composition of  claim 1  represented by the formula 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         3 . The composition of  claim 1  wherein, in formula (1), R is independently C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 H 13 , C 8 H 17 , C 10 H 21 , C 12 H 25 , C 14 H 29 , or C 16 H 33 ; and wherein, in formula (2), R 1  is CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 H 13 , C 8 H 17 , C 10 H 21 , or C 12 H 25 , and R 3  is C 10 H 21 , C 12 H 25 , C 14 H 29 , C 16 H 33 , C 18 H 37 , or C 20 H 41 . 
     
     
         4 . The composition of  claim 1  wherein said ionic liquid alkylammonium salt of formula (1) has a solubility in one or more Group I-V base stocks of at least 5%, and said ionic liquid imidazolium salt of formula (2) has a solubility in one or more Group I-V base stocks of at least 5%. 
     
     
         5 . The composition of  claim 1  wherein said one or more Group I-V base stocks comprise a Group V base stock. 
     
     
         6 . The composition of  claim 1  which has an onset of thermal decomposition temperature greater than 250° C. 
     
     
         7 . The composition of  claim 1  having a viscosity (Kv 100 ) from 2 to 400 at 100° C., and a viscosity index (VI) from 100 to 300. 
     
     
         8 . A lubricating oil base stock comprising:
 (i) an ionic liquid alkylammonium salt represented by the formula
   R 4 N + ,[C 8 H 17 O] 2 P(O) 2   −   (1)
 
   
       wherein R is independently C 1  to C 16  straight chain alkyl, branched chain alkyl, cycloalkyl, alkyl substituted cycloalkyl, cycloalkyl substituted alkyl, or, optionally, two R groups comprise a cyclic structure including the nitrogen atom and 4 to 12 carbon atoms; wherein said ionic liquid alkylammonium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks; or
 (ii) an ionic liquid imidazolium salt represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 3  are independently a C 1  to C 24  straight chain or branched chain alkyl group, a C 6  to C 10  aryl group, a C 7  to C 12  arylalkyl group, a C 7  to C 12  alkylaryl group, a C 2  to C 8  alkenyl group, a C 1  to C 8  alkoxy group, a C 2  to C 8  alkinyl group, or a C 2  to C 8  acyl group; and R 2 , R 4  and R 5  are hydrogen; wherein said ionic liquid imidazolium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks. 
     
     
         9 . A lubricating oil comprising a lubricating oil base stock as a major component, and an ionic liquid alkylammonium salt cobase stock or an ionic liquid imidazolium salt cobase stock, as a minor component; wherein said ionic liquid alkylammonium salt is represented by the formula
   R 4 N + ,[C 8 H 17 O] 2 P(O) 2   −   (1)
   
       wherein R is independently C 1  to C 16  straight chain alkyl, branched chain alkyl, cycloalkyl, alkyl substituted cycloalkyl, cycloalkyl substituted alkyl, or, optionally, two R groups comprise a cyclic structure including the nitrogen atom and 4 to 12 carbon atoms; wherein said ionic liquid alkylammonium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks; and said ionic liquid imidazolium salt is represented by the formula 
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 3  are independently a C 1  to C 24  straight chain or branched chain alkyl group, a C 6  to C 10  aryl group, a C 7  to C 12  arylalkyl group, a C 7  to C 12  alkylaryl group, a C 2  to C 8  alkenyl group, a C 1  to C 8  alkoxy group, a C 2  to C 8  alkinyl group, or a C 2  to C 8  acyl group; and R 2 , R 4  and R 5  are hydrogen; wherein said ionic liquid imidazolium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks. 
     
     
         10 . The lubricating oil of  claim 9  wherein the lubricating oil base stock comprises a Group I, II, III, IV or V base oil stock. 
     
     
         11 . The lubricating oil of  claim 9  wherein the lubricating oil base stock is present in an amount from 50 weight percent to 99 weight percent, and the ionic liquid alkylammonium salt cobase stock or the ionic liquid imidazolium salt cobase stock is present in an amount from 1 weight percent to 50 weight percent, based on the total weight of the lubricating oil. 
     
     
         12 . The lubricating oil of  claim 9  wherein the cobase stock is represented by the formula 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         13 . The lubricating oil of  claim 9  wherein, in formula (1), R is independently C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 H 13 , C 8 H 17 , C 10 H 21 , C 12 H 25 , C 14 H 29 , or C 16 H 33 ; and wherein, in formula (2), R 1  is CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 H 13 , C 8 H 17 , C 10 H 21 , or C 12 H 25 , and R 3  is C 10 H 21 , C 12 H 25 , C 14 H 29 , C 16 H 33 , C 18 H 37 , or C 20 H 41 . 
     
     
         14 . The lubricating oil of  claim 9  wherein said ionic liquid alkylammonium salt of formula (1) has a solubility in one or more Group I-V base stocks of at least 5%, and said ionic liquid imidazolium salt of formula (2) has a solubility in one or more Group I-V base stocks of at least 5%. 
     
     
         15 . The lubricating oil of  claim 9  wherein the lubricating oil further comprises one or more of a viscosity improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, and anti-rust additive. 
     
     
         16 . A multifunctional functional fluid comprising:
 (i) an ionic liquid alkylammonium salt represented by the formula
   R 4 N + ,[C 8 H 17 O] 2 P(O) 2   −   (1)
 
   
       wherein R is independently C 1  to C 16  straight chain alkyl, branched chain alkyl, cycloalkyl, alkyl substituted cycloalkyl, cycloalkyl substituted alkyl, or, optionally, two R groups comprise a cyclic structure including the nitrogen atom and 4 to 12 carbon atoms; wherein said ionic liquid alkylammonium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks; or
 (ii) an ionic liquid imidazolium salt represented by the formula 
 
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 3  are independently a C 1  to C 24  straight chain or branched chain alkyl group, a C 6  to C 10  aryl group, a C 7  to C 12  arylalkyl group, a C 7  to C 12  alkylaryl group, a C 2  to C 8  alkenyl group, a C 1  to C 8  alkoxy group, a C 2  to C 8  alkinyl group, or a C 2  to C 8  acyl group; and R 2 , R 4  and R 5  are hydrogen; wherein said ionic liquid imidazolium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks. 
     
     
         17 . The multifunctional functional fluid of  claim 16  which is represented by the formula 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         18 . The multifunctional functional fluid of  claim 16  wherein, in formula (1), R is independently C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 H 13 , C 8 H 17 , C 10 H 21 , C 12 H 25 , C 14 H 29 , or C 16 H 33 ; and wherein, in formula (2), R 1  is CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 , C 5 H 11 , C 6 H 13 , C 8 H 17 , C 10 H 21 , or C 12 H 25 , and R 3  is C 10 H 21 , C 12 H 25 , C 14 H 29 , C 16 H 33 , C 18 H 37 , or C 20 H 41 . 
     
     
         19 . The multifunctional functional fluid of  claim 16  wherein said ionic liquid alkylammonium salt of formula (1) has a solubility in one or more Group I-V base stocks of at least 5%, and said ionic liquid imidazolium salt of formula (2) has a solubility in one or more Group I-V base stocks of at least 5%. 
     
     
         20 . A method for improving solubility of an ionic liquid in a lubricating oil by using as the lubricating oil a formulated oil comprising a lubricating oil base stock as a major component, and an ionic liquid alkylammonium salt cobase stock or an ionic liquid imidazolium salt cobase stock, as a minor component; wherein said ionic liquid alkylammonium salt is represented by the formula
   R 4 N + ,[C 8 H 17 O] 2 P(O) 2   −   (1)
   
       wherein R is independently C 1  to C 16  straight chain alkyl, branched chain alkyl, cycloalkyl, alkyl substituted cycloalkyl, cycloalkyl substituted alkyl, or, optionally, two R groups comprise a cyclic structure including the nitrogen atom and 4 to 12 carbon atoms; wherein said ionic liquid alkylammonium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks; and said ionic liquid imidazolium salt is represented by the formula 
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 3  are independently a C 1  to C 24  straight chain or branched chain alkyl group, a C 6  to C 10  aryl group, a C 7  to C 12  arylalkyl group, a C 7  to C 12  alkylaryl group, a C 2  to C 8  alkenyl group, a C 1  to C 8  alkoxy group, a C 2  to C 8  alkinyl group, or a C 2  to C 8  acyl group; and R 2 , R 4  and R 5  are hydrogen; wherein said ionic liquid imidazolium salt has a structure sufficient to exhibit at least partial solubility in one or more Group I-V base stocks.