Lubricating oil composition

Abstract

A lubricating oil composition comprising: boron atoms from about 5-75 ppm; and 100% by mass being (i) 90 to 10% of a (co)polymer of specified kinematic viscosity and acid values, primarily derived from 1-decene, (ii) 5 to 85% of a (co)polymer having specified kinematic viscosity and molecular weight distribution, mostly derived from 1-octene, and (iii) 5 to 15% of a fatty acid ester.

1 . A lubricating oil composition comprising the following (i) to (iii), having a kinematic viscosity at 40° C. of not less than 30 mm 2 /s but not more than 750 mm 2 /s and containing boron atoms in an amount of not less than 5 ppm but not more than 75 ppm,
 (i) 90 to 10% by mass of a (co)polymer having a kinematic viscosity at 100° C. of not more than 45 mm 2 /s and having an acid value of less than 0.1 mgKOH/g, not less than 60% by mol of its constituent units being derived from 1-decene, 
 (ii) 5 to 85% by mass of a (co)polymer having a kinematic viscosity at 100° C. of not less than 35 mm 2 /s but not more than 1,500 mm 2 /s and having a molecular weight distribution, as measured by gel permeation chromatography, of not more than 1.8, not less than 90% by mol of its constituent units being derived from 1-octene, and 
 (iii) 5 to 15% by mass of a fatty acid ester having a kinematic viscosity at 100° C. of not more than 20 mm 2 /s, 
 with the proviso that the total amount of (i) to (iii) is 100% by mass. 
 
     
     
         2 . The lubricating oil composition as claimed in  claim 1 , which further comprises one or more kinds of extreme pressure agents. 
     
     
         3 . The lubricating oil composition as claimed in  claim 1 , wherein the kinematic viscosity of the lubricating oil composition at 40° C. is not less than 190 mm 2 /s but not more than 750 mm 2 /s. 
     
     
         4 . The lubricating oil composition as claimed in  claim 1 , wherein the kinematic viscosity of the lubricating oil composition at 40° C. is not less than 288 mm 2 /s but not more than 352 mm 2 /s, and a kinematic viscosity decrease ratio of the lubricating oil composition at 40° C. after a KRL shear stability test, as measured in accordance with DIN 52350-6, is less than 10%. 
     
     
         5 . The lubricating oil composition as claimed in  claim 1 , wherein the kinematic viscosity of the (co)polymer (ii) at 100° C. is not less than 150 mm 2 /s but not more than 1,200 mm 2 /s. 
     
     
         6 . The lubricating oil composition as claimed in  claim 1 , wherein the kinematic viscosity of the (co)polymer (i) comprising 1-decene at 100° C. is not more than 11 mm 2 /s. 
     
     
         7 . A gear for a wind power generator, which is filled with the lubricating oil composition as claimed in  claim 1 .