Additive composition for lubricating oil

Abstract

An additive composition is provided for a lubricating oil that is easy to produce, does not have adverse effects, such as causing rubber seals to swell, and is excellent in storage stability. The additive composition contains a metal salt of a phosphorus-containing compound represented by formula (1) in an amount of 10 to 90 percent by mass of the composition, contained in a hydrocarbon solvent selected from a mineral oil, a hydrocarbon synthetic oil and a mixture thereof, the hydrocarbon solvent having a 100° C. kinematic viscosity of 0.5 to 4.5 mm 2 /s, a % C A of 3 or less, and a sulfur content of 0.05 percent by mass or less: wherein X 1 and X 2 are each independently oxygen or sulfur, R 1 , R 2 , R 3 , and R 4 are each independently a straight-chain alkyl group having 3 to 12 carbon atoms, the average of the carbon number is 5 or greater, and M is a divalent metal atom.

1 . An additive composition for a lubricating oil, comprising a metal salt of a phosphorus-containing compound represented by formula (1) in an amount of 10 to 90 percent by mass on the basis of the composition, contained in a hydrocarbon solvent selected from a mineral oil, a hydrocarbon synthetic oil and a mixture thereof, the hydrocarbon solvent having a 100° C. kinematic viscosity of 0.5 to 4.5 mm 2 /s, a % C A  of 3 or less, and a sulfur content of 0.05 percent by mass or less: 
       
         
           
           
               
               
           
         
       
       wherein X 1  and X 2  are each independently oxygen or sulfur, R 1 , R 2 , R 3 , and R 4  are each independently a straight-chain alkyl group having 3 to 12 carbon atoms, the average of the carbon number is 5 or greater, and M is a divalent metal atom. 
     
     
         2 . A process for producing an additive composition for a lubricating oil, comprising dissolving a metal salt of a phosphorus-containing compound represented by formula (1) in an amount of 10 to 90 percent by mass on the basis of the composition in a hydrocarbon solvent selected from a mineral oil, a hydrocarbon synthetic oil and a mixture thereof, the hydrocarbon solvent having a 100° C. kinematic viscosity of 0.5 to 4.5 mm 2 /s, a % C A  of 3 or less, and a sulfur content of 0.05 percent by mass or less: 
       
         
           
           
               
               
           
         
       
       wherein X 1  and X 2  are each independently oxygen or sulfur, R 1 , R 2 , R 3 , and R 4  are each a straight-chain alkyl group having 3 to 12 carbon atoms, the average of the carbon number is 5 or greater, and M is a divalent metal atom. 
     
     
         3 . A lubricating oil composition comprising the additive composition for a lubricating oil according to  claim 1 .