Biodegradable lubricating oil composition

Abstract

[PROBLEMS] To provide a biodegradable lubricating oil composition which has excellent biodegradability, a high viscosity index, a low pour point, a high flash point, being satisfactory with lubricity, oxidative stability, property of preventing the corrosion of iron and non-ferrous metals, and suitability for use with sealing materials. [MEANS FOR SOLVING THE PROBLEMS] A biodegradable lubricating oil composition comprising (A) a synthetic ester base oil comprising at least 50 mass % hindered ester of an aliphatic monocarboxylic acid with an aliphatic hindered polyol which has one or more quaternary carbon atoms per molecule and in which at least one of the quaternary carbon atoms has one to four methylol groups bonded thereto and (B) ingredients which are (a) 0.1 to 5.0 mass % phenolic antioxidant, (b) 0.01 to 2.0 mass % calcium sulfonate having a low base number, and (c) 0.01 to 1.0 mass % triazole compound, and has the degree of biodegradation of 60% or higher when examined by the test for the degree of microbial degradation of chemical substances according to the OECD Test Guideline 301C method.

1 . A biodegradable lubricating oil composition comprising (A) a synthetic ester base oil comprising at least 50 mass % hindered ester of an aliphatic monocarboxylic acid with an aliphatic hindered polyol which has one or more quaternary carbon atoms per molecule and in which at least one of the quaternary carbon atoms has one to four methylol groups bonded thereto and (B) ingredients which are (a) 0.1 to 5.0 mass % phenolic antioxidant, (b) 0.01 to 2.0 mass % calcium sulfonate having a low base number, and (c) 0.01 to 1.0 mass % triazole compound, and has the degree of biodegradation of 60% or higher when examined by the test for the degree of microbial degradation of chemical substances according to the OECD Test Guideline 301C method. 
   
   
       2 . The biodegradable lubricating oil composition according to  claim 1 , wherein the 96-h LC 50  value of the acute toxicity test for Japanese medaka ( Oryzias latipes ) according to the JIS K 0102 test method is 100 mg/L or more. 
   
   
       3 . The biodegradable lubricating oil composition according to  claim 1 , wherein a viscosity index is 130 or more, a pour point is 40° C. or less, and a flash point is 250° C. or more. 
   
   
       4 . The biodegradable lubricating oil composition according to  claim 1 , wherein the aliphatic hindered polyol is a compound represented by general formula (I): 
     [Formula I] 
     
       
         
         
             
             
         
       
     
     (wherein R 1  and R 2  represent independently a hydrocarbon group having 1 to 6 carbon atoms or a methylol group, and n is an integer of 0 to 4). 
   
   
       5 . The biodegradable lubricating oil composition according to  claim 4 , wherein the aliphatic hindered polyol is trimethylolpropane, neopentyl glycol, pentaerythritol, or a dehydrated condensate thereof. 
   
   
       6 . The biodegradable lubricating oil composition according to  claim 1 , wherein the aliphatic monocarboxylic acid is a saturated or unsaturated monocarboxylic acid having 6 to 22 carbon atoms. 
   
   
       7 . The biodegradable lubricating oil composition according to  claim 1 , wherein the calcium sulfonate as the component (B) (b) having a low base number has the total base number in the range from 0 to 100 mg KOH/g. 
   
   
       8 . The biodegradable lubricating oil composition according to  claim 1 , which contains 0.1 to 5.0 mass % of an extreme-pressure agent and/or an antiwear agent as a component (B) (d).