Hydroxychroman Derivatives As Engine Oil Antioxidants

Abstract

A lubricant and concentrate composition comprises a hydroxychroman derived antioxidant and a method for improving the performance of a lubricant composition, especially a lubricant composition for an internal combustion engine, comprising the use of a lubricant containing said antioxidant.

1 . A lubricant composition comprising an oil of lubricating viscosity and an antioxidant having the formula: 
       
         
           
           
               
               
           
         
       
       wherein each R 1  is independently —OR 2 , —NH 2 , —NR 2 R 2 , —SR 2  or —R 2 ; each R 2  is independently a hydrogen, a hydrocarbyl group, or a —C(═O)—X—R 3  group where X is O, NR 3  or S and each R3 is independently a hydrogen or a hydrocarbyl group; and n is 0 or 1; and where the two adjacent R 1  groups are hydrocarbyl groups, they may be linked to form a ring. 
     
     
         2 . The lubricant composition of  claim 1  wherein the antioxidant is a chromanol having a hydroxy group located on the aromatic ring. 
     
     
         3 . The lubricant composition of  claim 1  wherein the antioxidant is a 2,3-dihydrobenzofuranol having a hydroxy group located on the aromatic ring. 
     
     
         4 . The lubricant composition of  claim 1  wherein: (i) at least one R 1  group of the antioxidant is a hydrocarbyl group, (ii) at least one R 2  group of the antioxidant is a hydrocarbyl group, or (iii) combinations thereof. 
     
     
         5 . The lubricant composition of  claim 1  wherein at least one of the R 1  groups adjacent to the hydroxy group is a hydrocarbyl group. 
     
     
         6 . The lubricant composition of  claim 1  wherein each R 1  is independently a hydrogen or hydrocarbyl group containing from 1 to 20 carbon atoms and each R 2  is independently a hydrogen or hydrocarbyl group containing from 1 to 15 carbon atoms. 
     
     
         7 . The lubricant composition of  claim 1  wherein the antioxidant has the formula: 
       
         
           
           
               
               
           
         
       
       wherein R 1  is hydrocarbyl group containing from 1 to 10 carbon atoms; and each R 2  is independently a hydrogen or hydrocarbyl group containing from 1 to 10 carbon atoms. 
     
     
         8 . The lubricant composition of  claim 1  wherein the composition contains no more than 1200 ppm phosphorus. 
     
     
         9 . The lubricant composition of  claim 8  wherein the composition has a sulfur content of no more than 0.4 percent by weight and a sulfated ash content of no more than 1.0 percent by weight. 
     
     
         10 . The lubricant composition of  claim 8  further comprising a zinc dialkyldithiophosphate at a level of no less than 300 ppm. 
     
     
         11 . The lubricant composition of  claim 1  further comprising an aminic antioxidant. 
     
     
         12 . The lubricant composition of  claim 1  further comprising a friction modifier. 
     
     
         13 . A method of lubricating an internal combustion engine comprising the steps of: (I) supplying to said engine a lubricant composition comprising an oil of lubricating viscosity and an antioxidant having the formula: 
       
         
           
           
               
               
           
         
       
       wherein each R 1  is independently —OR 2 , —NH 2 , —NR 2 R 2 , —SR 2  or —R 2 ; each R 2  is independently a hydrogen, a hydrocarbyl group, or a —C(═O)—X—R 3  group where X is O, NR 3  or S and each R3 is independently a hydrogen or a hydrocarbyl group; and n is 0 or 1; and where the two adjacent R 1  groups are hydrocarbyl groups, they may be linked to form a ring.