Lubricant base oil

Abstract

A lubricant base oil may contain at least one ester compound (A) selected from a diester (A1) having 24 or more carbon atoms and a triester (A2) having 24 or more carbon atoms and at least one base oil (B) selected from a mineral oil (B1) and a synthetic oil (B2) other than an ester synthetic oil. A lubricating oil composition may contain such a lubricant base oil.

1 . A lubricant base oil, comprising:
 an ester compound (A) comprising a diester (A1) having 24 or more carbon atoms and/or a triester (A2) having 24 or more carbon atoms; and   a base oil (B) comprising a mineral oil (B1) and/or a synthetic oil (B2) other than an ester synthetic oil.   
     
     
         2 . The lubricant base oil of  claim 1 , wherein having a density at 15° C. of less than 0.850 g/cm 3 . 
     
     
         3 . The lubricant base oil of  claim 1 , wherein the ester compound (A) is present in a range of from 1 to 90 mass %, based on a total lubricant base oil mass. 
     
     
         4 . The lubricant base oil of  claim 1 , wherein the diester (A1) is present and has 26 or more carbon atoms. 
     
     
         5 . The lubricant base oil of  claim 1 , wherein the diester (A1) is present and comprises a compound (A11) of formula (a1-1): 
       
         
           
           
               
               
           
         
         wherein 
         R 1  and R 2  are each independently a monovalent chain hydrocarbon group, and 
         A 1  is a divalent hydrocarbon group having 5 or more carbon atoms. 
       
     
     
         6 . The lubricant base oil of  claim 1 , wherein the triester (A2) comprises a compound (A21) of formula (a2-1): 
       
         
           
           
               
               
           
         
         wherein 
         R 3 , R 4 , and R 5  are each independently a monovalent chain hydrocarbon group, and 
         A 2  is a trivalent hydrocarbon group having 5 or more carbon atoms. 
       
     
     
         7 . The lubricant base oil of  claim 1 , wherein the ester compound (A) comprises the diester (A1). 
     
     
         8 . The lubricant base oil of  claim 1 , wherein the ester compound (A) comprises the synthetic oil (A2). 
     
     
         9 . A lubricating oil composition, comprising:
 the lubricant base oil of  claim 1 .   
     
     
         10 . The composition of  claim 9 , further comprising:
 a pour point depressant;   a viscosity index improver;   an antioxidant;   an extreme pressure agent;   a metallic detergent;   an ashless dispersant;   a metal deactivator;   a corrosion inhibitor;   a rust inhibitor; and   a defoamer.   
     
     
         11 . The composition of  claim 9 , further comprising:
 a fatty acid amide in less than 1.0 mass %, based on a total lubricating oil composition mass.   
     
     
         12 . The composition of  claim 9 , wherein a volume change rate of a nitrile rubber for test, as measured by immersing the nitrile rubber for test in the lubricating oil composition under conditions at 100° C. for 144 hours by a rubber immersion test method in accordance with JIS K6258, is less than 10%. 
     
     
         13 . The lubricant base oil of  claim 1 , wherein the ester compound (A) comprises the diester (A1) and the synthetic oil (A2).