Additive composition for transmission oil

Abstract

Disclosed are additive compositions for transmission oils comprising an oil dispersion of a hexagonal boron nitride and a polymethacrylate, a dispersant polymethacrylate or a dispersant olefin copolymer viscosity index improver, as well as lubricating oil compositions containing the same.

1 . An additive composition for a transmission oil comprising: 
 a) an oil dispersion of hexagonal boron nitride; and    b) a viscosity index improver selected from the group consisting of 
 i) a polymethacrylate,  
 ii) a dispersant polymethacrylate, and  
 iii) a dispersant olefin copolymer.  
 wherein the weight ratio of the oil dispersion of hexagonal boron nitride to the viscosity index improver is in the range of from about 99:1 to about 1:99.  
   
     
     
         2 . The additive composition according to  claim 1 , wherein the weight ratio of the oil dispersion of hexagonal boron nitride to the viscosity index improver copolymer is in the range of from about 5:95 to about 95:5.  
     
     
         3 . The additive composition according to  claim 1 , wherein the oil dispersion of hexagonal boron nitride has a particle size distribution wherein 90% or greater of the particles are less than about 0.5 microns.  
     
     
         4 . The additive composition according to  claim 1 , wherein the oil dispersion of hexagonal boron nitride contains an oil of lubricating viscosity and from about 1 to about 50 wt % of hexagonal boron nitride solids, based on the total weight of the oil dispersion.  
     
     
         5 . The additive composition according to  claim 4 , wherein the oil dispersion of hexagonal boron nitride further contains a surfactant as a stabilizer.  
     
     
         6 . The additive composition according to  claim 1 , wherein the oil dispersion of hexagonal boron nitride is present in the additive composition in the range of from about 10 to about 90 wt %, based on the total weight of the additive composition.  
     
     
         7 . The additive composition according to  claim 1 , wherein the polymethacrylate contains short chain, intermediate chain or long chain hydrocarbon side chains.  
     
     
         8 . The additive composition according to  claim 1 , wherein the dispersant polymethacrylate contains short chain, intermediate chain or long chain dispersant hydrocarbon side chains.  
     
     
         9 . The additive composition according to  claim 1 , wherein the dispersant olefin copolymer is a dispersant ethylene-propylene olefin copolymer.  
     
     
         10 . The additive composition according to  claim 1 , further comprising an oil dispersion of hydrated alkali metal borate.  
     
     
         11 . The additive composition according to  claim 10 , wherein the alkali metal in the hydrated alkali metal borate is sodium or potassium.  
     
     
         12 . The additive composition according to  claim 11 , wherein the alkali metal is potassium.  
     
     
         13 . The additive composition according to  claim 10 , wherein the hydrated alkali metal borate is hydrated potassium triborate.  
     
     
         14 . The additive composition according to  claim 10 , wherein the oil dispersion of hydrated alkali metal borate contains a hydrated alkali metal borate, a dispersant and an oil of lubricating viscosity.  
     
     
         15 . The additive composition according to  claim 14 , wherein the oil dispersion of hydrated alkali metal borate contains from about 10 to about 75 wt % of the hydrated alkali metal borate, based on the total weight of the oil dispersion.  
     
     
         16 . The additive composition according to  claim 15 , wherein the oil dispersion of hydrated alkali metal borate contains from about 2 to about 40 wt % of the dispersant, based on the total weight of the oil dispersion.  
     
     
         17 . The additive composition according to  claim 16 , wherein the oil dispersion of hydrated alkali metal borate further contains a detergent.  
     
     
         18 . The additive composition according to  claim 17 , wherein the oil dispersion of hydrated alkali metal borate contains from about 0.2 to about 10 wt % of the detergent, based on the total weight of the oil dispersion.  
     
     
         19 . The additive composition according to  claim 10 , wherein the oil dispersion of hydrated alkali metal borate is present in the additive composition in the range of from about 10 to about 90 wt %, based on the total weight of the additive composition.  
     
     
         20 . A lubricating oil composition comprising a major amount of a transmission oil of lubricating viscosity and an effective synchronizer sticking reducing amount of an additive composition comprising: 
 a) an oil dispersion of hexagonal boron nitride; and    b) a viscosity index improver selected from the group consisting of 
 i) a polymethacrylate,  
 ii) a dispersant polymethacrylate, and  
 iii) a dispersant olefin copolymer,  
 wherein the weight ratio of the oil dispersion of hexagonal boron nitride to the viscosity index improver is in the range of 99:1 to about 1:99.  
   
     
     
         21 . The lubricating oil composition according to  claim 20 , wherein the weight ratio of the oil dispersion of hexagonal boron nitride to the viscosity enhancing copolymer is in the range of from about 5:95 to about 95:5.  
     
     
         22 . The lubricating oil composition according to  claim 20 , wherein the lubricating oil composition contains from about 1 to about 20 wt % of the additive composition, based on the total weight of the lubricating oil composition.  
     
     
         23 . The lubricating oil composition according to  claim 20 , wherein the transmission oil is a manual transmission gear oil.