Halogen free ionic liquids as lubricant or lubricant additives and a process for the preparation thereof

Abstract

A lubricant or lubricant additive composed of halogen-, phosphorus- and sulphur-free ionic liquids containing fatty acid anions exhibit superior friction-reducing and anti-wear properties. Preferably, the lubricant composition comprises a base oil and an ionic liquid or mixed of two or more ionic liquids having concentration of 0.5 wt. % or more. These halogen-, phosphorus- and sulphur-free ionic liquids as lubricant or lubricant additive have minimal hazardous and corrosion effect to the environment and engineering surfaces, respectively. General chemical formula of fatty acid anion is represented as RCOO − ; whereas R may be C 4 to C 30 straight chain alkyl, branched alkyl, cycloalkyl, alkyl substituted cycloalkyl, cycloalkyl substituted alkyl, alkenyl (single or more double bonds) includes with or without branched structure and may contain heteroatom.

We claim: 
     
         1 . A lubricant or lubricant additive(s) composition comprising an ionic liquid(s), wherein anions in the ionic liquid(s) are fatty acids of the general formula RCOO , wherein R is selected from C 4  to C 30  straight chain alkyl, branched alkyl, straight or branched alkenyl, cycloalkyl, alkyl substituted cycloalkyl, cycloalkyl substituted alkyl; alkyl or alkenyl group(s) containing heteroatom selected from —OH, —CN, —C—O —C—; and cations in the ionic liquids are selected from the group consisting of 
       
         
           
           
               
               
           
         
         wherein R 1  to R 12  is similar or different from one another, selected from the group consisting of hydrogen, —OH, C 1  to C 18  alkyl group(s) including straight chain or branched structures, C 2  to C 12  alkenyl group(s) including straight chain or branched structures, wherein the alkyl or alkenyl group(s) optionally contain heteroatom, C 7  to C 12  arylalkyl group(s), C 7  to C 12  alkylaryl group(s). 
       
     
     
         2 . The composition as claimed in  claim 1 , wherein the ionic liquids are substatntially or completely free of halogen, phosphorous, and/or sulphur. 
     
     
         3 . The composition as claimed in  claim 1 , wherein ionic liquid are selected from Tetrabutylammonium oleate (TBA-OL), 1-Hexyl-methylimidazolium oleate (HMIM-OL) and Tetrabutylammonium linoleate (TBA-LN), Tetrabutylammonium caprylate, Tetrabutylammonium caprate, Tetrabutylammonium laurate, Tetrabutylammonium myrisate, Hexyldimethylcyclohexylammonium oleate and Dioctylmethylpentylammonium oleate. 
     
     
         4 . The composition as claimed in  claim 1 , further comprising one or more additives selected from dispersants, corrosion inhibitors, detergents, antioxidants, anti-wear and extreme pressure additives, viscosity improvers, fiction improvers, oiliness improver, metal deactivator, demulsifiers, pour point depressants, foam inhibitors, seal-swelling agents, antimicrobial. 
     
     
         5 . The lubricant or lubricant additive composition as claimed in  claim 1  is having high friction reducing and anti-wearing properties. 
     
     
         6 . A lubricating oil comprising the lubricant additive composition as claimed in any of the preceding claims and a base lubricating oil. 
     
     
         7 . The lubricating oil as claimed in  claim 6 , wherein the concentration of ionic liquid (s) as lubricant additive(s) in the base lubricant oil(s) is in the range of 0.5 to 10 wt. %. 
     
     
         8 . The lubricating oil as claimed in  claim 6  or  7 , wherein the base lubricant oil(s) is selected from synthetic, minerals and native base stock (s) or base oil (s). 
     
     
         9 . The lubricating oil as claimed in  claim 8 , wherein the synthetic oils is selected from the group consisting of polymerized and interpolymerized olefins: polyalphaoelefin (PAO) derived from olefins, diol or triol or polyol esters or polyphenyl ether or alkylated di- or triphenyl ether, alkylated naphthalenes, alkylated benzene, polyglycols, polyalkylglycols, silicon oils, perfluoropolyethers; mineral base oil (s) is selected from Group I (solvent refined mineral oils), Group II (hydrocracked mineral oils), Group III (severely hydrocracked oils, also referred to as synthetic or semi oils), Group V (esters, napthenes, and others); native oil(s) as lube base stock (s) is selected from animal and vegetable oils,which are predominantly composed of triglycerides with minor components of mono- and diglycerides. 
     
     
         10 . A process for the preparation of lubricant or lubricant additive composition comprising ionic liquid(s) as claimed in  claim 1 , wherein the said process comprises the steps of:
 a) mixing sodium salt of fatty acid in an aqueous solution of tetraalkylammonium halide or di-/tri-alklyimidazolium tetrafluoroborate in 1:1 molar ratio with stirring at a temperature ranging between 20-100° C. for a period of time ranging between 4 to 48 hours to get organic layer in reaction mixture; and   b) extracting the organic layer as obtained in step (a) using dichloromethane followed by washing with water then removing dichloromethane under reduced pressure subsequently drying under reduced pressure to get lubricant or lubricant additive composed of ionic liquid.