Lubricating oil composition, method for manufacturing lubricating oil composition, and drive system apparatus

Abstract

To provide a lubricating oil composition having excellent viscosity characteristics and a property of difficulty in evaporation, which contains a base oil having a kinematic viscosity at 40° C. of 4.0 mm2/s or more and less than 6.0 mm2/s, a kinematic viscosity at 100° C. of 1.0 mm2/s or more and less than 2.0 mm2/s and a flash point of 140° C. or more, and a viscosity index improver, and has a Brookfield viscosity at −40° C. of 750 mPa·s or less, a kinematic viscosity at 60° C. of 5.5 mm2/s or more, and a NOACK value at 145° C. for 1 hour of 10% by mass or less.

1 . A lubricating oil composition, comprising:
 a base oil having a kinematic viscosity at 40° C. of 4.0 mm 2 /s or more and less than 6.0 mm 2 /s, a kinematic viscosity at 100° C. of 1.0 mm 2 /s or more and less than 2.0 mm 2 /s and a flash point of 140° C. or more; and   a viscosity index improver,   wherein the lubricating oil composition has a Brookfield viscosity at −40° C. of 750 mPa·s or less, a kinematic viscosity at 60° C. of 5.5 mm 2 /s or more, and a NOACK value at 145° C. for 1 hour of 10% by mass or less.   
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the base oil has a kinematic viscosity at 100° C. of 1.5 mm 2 /s or more and less than 2.0 mm 2 /s. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the base oil is a mineral oil, and a feedstock oil of the mineral oil contains a gas oil fraction obtained by hydrocracking of a heavy gas oil. 
     
     
         4 . The lubricating oil composition according to  claim 3 , wherein the feedstock oil has a paraffin content (% C P ) of 60 or more. 
     
     
         5 . The lubricating oil composition according to  claim 3 , wherein the feedstock oil has an aromatic content (% C A ) of 10.0 or less. 
     
     
         6 . The lubricating oil composition according to  claim 3 , wherein the feedstock oil has a proportion of a n-paraffin component of 1% by volume or more and 50% by volume or less based on 100% by volume of the total amount of an aromatic component, a naphthene component, a n-paraffin component, and an isoparaffin component. 
     
     
         7 . The lubricating oil composition according to  claim 3 , wherein the feedstock oil has a 10% distillation temperature of 250° C. or more, and a 90% distillation temperature of 320° C. or more, as measured by the distillation test according to HS K2254. 
     
     
         8 . The lubricating oil composition according to  claim 3 , wherein the feedstock oil has a kinematic viscosity at 40° C. of 4.0 mm 2 /s or more and 6.0 mm 2 /s or less, and a kinematic viscosity at 100° C. of 1.0 mm 2 /s or more and 2.0 mm 2 /s or less. 
     
     
         9 . The lubricating oil composition according to  claim 1 , wherein the viscosity index improver is a polymethacrylate. 
     
     
         10 . The lubricating oil composition according to  claim 9 , wherein the polymethacrylate has a mass average molecular weight of 30,000 or more and 350,000 or less. 
     
     
         11 . The lubricating oil composition according to  claim 1 , wherein a content of the viscosity index improver is 2.5% by mass or more and 7.4% by mass or less based on a total amount of the composition. 
     
     
         12 . The lubricating oil composition according to  claim 1 , which has a flash point of 120° C. or more and 180° C. or less. 
     
     
         13 . The lubricating oil composition according to  claim 1 , which is adapted to function as a lubricating oil composition to be applied to a drive system apparatus. 
     
     
         14 . The lubricating oil composition according to  claim 1 , which is adapted to function as a lubricating oil composition to be applied to a shock absorber for a four-wheel vehicle. 
     
     
         15 . A method for producing a lubricating oil composition having a Brookfield viscosity at −40° C. of 750 mPa·s or less, a kinematic viscosity at 60° C. of 5.5 mm 2 /s or more, and a NOACK value at 145° C. for 1 hour of 10% by mass or less, the method comprising blending a base oil having a kinematic viscosity at 40° C. of 4.0 mm 2 /s or more and less than 6.0 mm 2 /s, a kinematic viscosity at 100° C. of 1.0 mm 2 /s or more and less than 2.0 mm 2 /s and a flash point of 140° C. or more, and a viscosity index improver. 
     
     
         16 . A drive system apparatus, comprising the lubricating oil composition of  claim 1 . 
     
     
         17 . The drive system apparatus according to  claim 16 , which is a shock absorber for a four-wheel vehicle.