Low traction/energy efficient liquid crystal base stocks

Abstract

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy or alkylthio group having from 2 to 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricating oil base stock has a kinematic viscosity of 2 cSt to 200 cSt at 40° C., and 1 cSt to 25 cSt at 100° C. Also, this disclosure relates to low traction/energy efficient liquid crystal base stocks containing liquid crystals.

1 . A lubricating oil base stock comprising one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula:
   R1-(A) m -Y—(B) n —R2
   
       wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy, or alkylthio group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricating oil base stock has a kinematic viscosity of about 2 cSt to about 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 25 cSt at 100° C., as determined according to ASTM D445. 
     
     
         2 . The lubricating oil base stock of  claim 1  wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, the friction coefficient is less than about 0.02. 
     
     
         3 . The lubricating oil base stock of  claim 1  wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a temperature of 80° C., and over a pressure of 0.6-1.4 GPa, the friction coefficient is less than about 0.02. 
     
     
         4 . The lubricating oil base stock of  claim 1  wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a pressure of 1 GPa, and over a temperature of 0° C. to 150° C., the friction coefficient is less than about 0.025. 
     
     
         5 . The lubricating oil base stock of  claim 1  wherein, in elastohydrodynamic lubrication (EHL) film measurements of the lubricating oil base stock over a 10-1000 mm/s rolling speed using a mini-traction machine (MTM), at a temperature of 40° C. or 100° C., the EHL film thickness is greater than about 8 nm. 
     
     
         6 . The lubricating oil base stock of  claim 1  wherein the one or more liquid crystals are represented by the formula: 
       
         
           
           
               
               
           
         
       
     
     
         7 . The lubricating oil base stock of  claim 1  wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene. 
     
     
         8 . The lubricating oil base stock of  claim 1  further comprising one or more viscosity modifiers to form a bimodal blend. 
     
     
         9 . The lubricating oil base stock of  claim 8  wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.02. 
     
     
         10 . The lubricating oil base stock of  claim 8  wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.025. 
     
     
         11 . The lubricating oil base stock of  claim 8  wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.01. 
     
     
         12 . The lubricating oil base stock of  claim 8  wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.02. 
     
     
         13 . The lubricating oil base stock of  claim 8  wherein the viscosity modifier comprises a polymer thickening agent comprising a co-oligomer of 1-propylene and ethylene. 
     
     
         14 . A method for improving wear control, while maintaining or improving energy efficiency, in an engine or other mechanical component lubricated with a lubricating oil, by using as the lubricating oil a formulated oil, said formulated oil having a composition comprising at least one lubricating oil base stock; wherein the at least one lubricating oil base stock comprises one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula:
   R1-(A) m -Y—(B) n —R2
   
       wherein R1 and R2 are the same or different and are a substituted or unsubstituted, hydrocarbon, alkoxy, or alkylthio group having from about 2 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —OCOO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricating oil base stock has a kinematic viscosity of about 2 cSt to about 200 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 25 cSt at 100° C., as determined according to ASTM D445; and
 wherein wear control is improved and energy efficiency is maintained or improved as compared to wear control and energy efficiency achieved using a lubricating oil containing a lubricating oil base stock other than the lubricating oil base stock comprising one or more liquid crystals. 
 
     
     
         15 . The method of  claim 14  wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1 GPa, the friction coefficient is less than about 0.02. 
     
     
         16 . The method of  claim 14  wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a temperature of 80° C., and over a pressure of 0.6-1.4 GPa, the friction coefficient is less than about 0.02. 
     
     
         17 . The method of  claim 14  wherein, in friction coefficient measurements of the lubricating oil base stock by a mini-traction machine (MTM) at a 30% slide-to-roll ratio (SRR), a pressure of 1 GPa, and over a temperature of 0° C.-150° C., the friction coefficient is less than about 0.025. 
     
     
         18 . The method of  claim 14  wherein, in elastohydrodynamic lubrication (EHL) film measurements of the lubricating oil base stock over a 10-1000 mm/s rolling speed using a mini-traction machine (MTM), at a temperature of 40° C. or 100° C., the EHL film thickness is greater than about 8 nm. 
     
     
         19 . The method of  claim 14  wherein the one or more liquid crystals are represented by the formula: 
       
         
           
           
               
               
           
         
       
     
     
         20 . The method of  claim 14  wherein the one or more liquid crystals are selected from the group consisting of 4′-n-octyl-4-cyano-biphenyl, 4-(trans-4-heptylcyclohexyl)-pentylbenzene, 4-(trans-4-heptylcyclohexyl)-propylbenzene, and 4-(trans-4-propylcyclohexyl)-ethylbenzene. 
     
     
         21 . The method of  claim 14  wherein the lubricating oil comprises a bimodal blend of the at least one lubricating oil base stock comprising the one or more liquid crystals, and one or more viscosity modifiers. 
     
     
         22 . The method of  claim 21  wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.02. 
     
     
         23 . The method of  claim 21  wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 40° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.025. 
     
     
         24 . The method of  claim 21  wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 0.75 GPa, the friction coefficient is less than about 0.01. 
     
     
         25 . The method of  claim 21  wherein, in friction coefficient measurements of the bimodal blend by a mini-traction machine (MTM) over 0-100% slide-to-roll ratio (SRR), a temperature of 100° C., and a pressure of 1.25 GPa, the friction coefficient is less than about 0.02. 
     
     
         26 . The method of  claim 21  wherein the viscosity modifier comprises a polymer thickening agent comprising a co-oligomer of 1-propylene and ethylene. 
     
     
         27 . The method of  claim 14  wherein the lubricating oil further comprises one or more of an antiwear additive, viscosity modifier, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, or anti-rust additive. 
     
     
         28 . The method of  claim 14  wherein the lubricating oil is a passenger vehicle engine oil (PVEO).