Compositions for improved friction durability in power transmission fluids

Abstract

The present invention discloses compositions and methods for improving steel-on-steel friction in power transmission fluids through the use of a sufficient amount of a thiadiazole or derivatives thereof.

1 . A power transmitting fluid for use in a transmission having a steel-on-steel contact, comprising: 
 (a) a major amount of a base oil; and    (b) at least one thiadiazole or derivative thereof present in an amount of about 0.05 wt % or more,    wherein the fluid has improved steel-on-steel friction properties.    
     
     
         2 . The fluid of  claim 1 , wherein the thiadiazole comprises one or more of (a) 2-hydrocarbyldithio-5-mercapto-1,3,4-thiadiazole, 2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazole, and mixtures thereof; (b) 2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazole; and (c) products from combining an oil soluble dispersant with 2,5-dimercapto-1,3,4-thiadiazole (DMTD); and (d) mixtures thereof.  
     
     
         3 . The fluid of  claim 1 , wherein the thiadiazole is substituted with at least one linear, branched or cyclic saturated or unsaturated hydrocarbon group.  
     
     
         4 . The fluid of  claim 1 , wherein the thiadiazole is present in an amount of from about 0.095 wt % to about 5 wt %.  
     
     
         5 . The fluid of  claim 1 , wherein the thiadiazole is present in an amount of from about 0.3 wt % to about 0.5 wt %.  
     
     
         6 . The fluid of  claim 1 , wherein the transmission comprises one or more of a belt-type continuously variable transmission (CVT), chain-type CVT, and toroidal CVT.  
     
     
         7 . The fluid of  claim 1 , wherein the improved steel-on-steel friction properties are improved relative to a fluid not comprising the cited amount of the thiadiazole.  
     
     
         8 . The fluid of  claim 1 , wherein the base oil comprises one or more of natural lubricating oils, synthetic lubricating oils, and mixtures thereof.  
     
     
         9 . A continuously variable transmission lubricated with the fluid of  claim 1 .  
     
     
         10 . A method of lubricating a transmission having steel-on-steel contact, comprising adding to, and operating in, the transmission a fluid as set forth in  claim 1 .  
     
     
         11 . An additive composition for use in a transmission having a steel-on-steel contact, comprising at least one thiadiazole or derivative thereof present in an amount of about 0.5 wt % or more, wherein the fluid has improved steel-on-steel friction properties.  
     
     
         12 . The additive composition of  claim 11 , wherein the thiadiazole comprises one or more of (a) 2-hydrocarbyldithio-5-mercapto-1,3,4-thiadiazole, 2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazole, and mixtures thereof; (b) 2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazole; and (c) products from combining an oil soluble dispersant with 2,5-dimercapto-1,3,4-thiadiazole (DMTD); and (d) mixtures thereof.  
     
     
         13 . The additive composition of  claim 11 , wherein the thiadiazole is present in an amount of from about 0.95 wt % to about 10 wt %.  
     
     
         14 . The additive composition of  claim 11 , wherein the thiadiazole is present in an amount of from about 3 wt % to about 5 wt %.  
     
     
         15 . The additive composition of  claim 11 , wherein the transmission comprises one or more of a belt-type continuously variable transmission (CVT), chain-type CVT, and toroidal CVT.  
     
     
         16 . The additive composition of  claim 11 , wherein the improved steel-on-steel friction properties are improved relative to a fluid not comprising the cited amount of the thiadiazole.  
     
     
         17 . A continuously variable transmission lubricated with the additive composition of  claim 11 .  
     
     
         18 . A method of lubricating a transmission having steel-on-steel contact, comprising adding to, and operating in, the transmission a additive composition as set forth in  claim 11 .  
     
     
         19 . A method of making a power transmitting fluid having steel-on-steel friction-improving capabilities, comprising adding to a major amount of a base oil a thiadiazole in an amount of about 0.05 wt % or more.  
     
     
         20 . A power transmitting fluid for use in a transmission having a steel-on-steel contact, comprising: 
 (a) a major amount of a base oil; and    (b) at least one thiadiazole or derivative thereof present in an amount sufficient to provide a coefficient of friction of about 0.085 or greater in a steel-on-steel application.    
     
     
         21 . The fluid of  claim 20 , wherein the thiadiazole or derivative thereof is present in an amount sufficient to provide a coefficient of friction of about 0.09 or greater in a steel-on-steel application.