Lubricant for gears

Abstract

The invention provides a lubricating oil for gears which contains an α-olefin polymer having a viscosity index of 175 or higher and which has a viscosity index of 170 or higher. The lubricating oil for gears which has high shear stability and high oxidation resistance and which prevents malfunction during start-up at low temperature.

1 . A lubricating oil for gears which contains an α-olefin polymer having a viscosity index of 175 or higher and which has a viscosity index of 170 or higher. 
     
     
         2 . A lubricating oil for gears which contains an α-olefin polymer having a viscosity index of 180 or higher and which has a viscosity index of 175 or higher. 
     
     
         3 . A lubricating oil for gears according to  claim 1  or  2 , wherein the α-olefin polymer is produced by polymerizing a C6 to C20 α-olefin. 
     
     
         4 . A lubricating oil for gears according to any of  claims 1  to  3 , wherein the α-olefin polymer is produced in the presence of a metallocene catalyst. 
     
     
         5 . A lubricating oil for gears according to  claim 4 , wherein the metallocene catalyst includes (A) a transition metal compound represented by formula (I): 
       
         
           
           
               
               
           
         
       
       (wherein each of R 1  to R 6  represents a hydrogen atom, a halogen atom, a C1 to C20 hydrocarbyl group, or a C1 to C20 organic group containing at least one element selected from among a halogen atom, a silicon atom, an oxygen atom, a sulfur atom, a nitrogen atom, and a phosphorus atom; at least one group selected from among R 1  to R 3  is a hydrogen atom; at least one group selected from among R 4  to R 6  is a hydrogen atom; each of R a  and R b  represents a divalent group formed though bonding of two cyclopentadienyl rings via 1 to 3 atoms; each of X 1  and X 2  represents a hydrogen atom, a halogen atom, a C1 to C20 hydrocarbyl group, or a C1 to C20 organic group containing at least one element selected from among a halogen atom, a silicon atom, an oxygen atom, a sulfur atom, a nitrogen atom, and a phosphorus atom; and M represents a transition metal belonging to group 4 to group 6 in the periodic table) and (B) an organic aluminumoxy compound (b-1) and/or an ionic compound (b-2) which can transform into a cation through reaction with the transition metal compound. 
     
     
         6 . A lubricating oil for gears according to any of  claims 1  to  5 , which is a lubricating oil for use with a step-up gear for wind power generation.