Ashless lubricant composition

Abstract

A lubricant composition with improved antioxidant capability is provided by way of an additive composition containing a metal free sulfur-containing compound, an aromatic amine, and a hindered amine. Particularly effective metal-free sulfur-containing compounds include ashless dithiocarbamates, such as methylenebis(dibutyldithiocarbamate), and sulfurized fatty acids.

1 . A lubricating composition comprising at least 90% by weight of a lubricant basestock, and an antioxidant additive composition comprising:
 (a) a metal-free sulfur-containing compound at between about 0.001 and 10%, chosen from the group consisting of sulfurized fatty acids, ashless dithiocarbamates, tetraalkylthiuram disulfides, and thiadiazoles,   (b) a hindered amine at between about 0.001 and 10%, and   (c) a diaryl amine at between about 0.001 and 10%.   
   
   
       2 . The lubricant composition according to  claim 1 , wherein the additive composition comprises:
 (a) the metal-free sulfur-containing compound at between about 0.1 and 1.0%,   (b) the hindered amine at between about 0.05 and 1.0%, and   (c) the diaryl amine at between about 0.1 and 1.0%.   
   
   
       3 . The lubricant composition according to  claim 2 , wherein the additive composition comprises:
 (a) the metal-free sulfur-containing compound at between about 0.25 and 0.5%,   (b) the hindered amine at between about 0.1 and 0.5%, and   (c) the diaryl amine at between about 0.25 and 0.5%.   
   
   
       4 . The lubricant composition according to  claim 3 , wherein the additive composition comprises:
 (a) the metal-free sulfur-containing compound at about 0.5%,   (b) the hindered amine at about 0.1%, and   (c) the diaryl amine at about 0.4%.   
   
   
       5 . The lubricant composition according to  claim 1 , wherein the metal-free sulfur-containing compound is chosen from the group consisting of ashless dithiocarbamates and sulfurized fatty acids. 
   
   
       6 . The lubricant composition according to  claim 5 , wherein the ashless dithiocarbamate is methlyenebis(dibutyldithiocarbamate) or sulfurized fatty acids. 
   
   
       7 . The lubricant composition according to  claim 1 , wherein the sulfur-containing compound is methlyenebis(dibutyldithiocarbamate) and the hindered amine is 4-piperidol-2,2,6,6-tetremethyl-RPW stearin (fatty acids mixture). 
   
   
       8 . The lubricant composition according to  claim 2 , wherein the sulfur-containing compound is methlyenebis(dibutyldithiocarbamate). 
   
   
       9 . The lubricant composition according to  claim 3 , wherein the sulfur-containing compound is methlyenebis(dibutyldithiocarbamate). 
   
   
       10 . The lubricant composition according to  claim 4 , wherein the sulfur-containing compound is methlyenebis(dibutyldithiocarbamate). 
   
   
       11 . The lubricant composition according to  claim 1 , wherein the additive composition comprises:
 (a) methlyenebis(dibutyldithiocarbamate at about 0.5%,   (b) 4-piperidol-2,2,6,6-tetremethyl-RPW stearin (fatty acids mixture) at about 0.1%, and   (c) the diaryl amine at about 0.4%.   
   
   
       12 . The lubricant composition according to  claim 1 , wherein the sulfur-containing compound is sulfurized fatty acid. 
   
   
       13 . The lubricant composition according to  claim 1 , wherein the sulfur-containing compound is sulfurized fatty acid and the hindered amine is 4-piperidol-2,2,6,6-tetremethyl-RPW stearin (fatty acids mixture). 
   
   
       14 . The lubricant composition according to  claim 2 , wherein the sulfur-containing compound is sulfurized fatty acid. 
   
   
       15 . The lubricant composition according to  claim 3 , wherein the sulfur-containing compound is sulfurized fatty acid. 
   
   
       16 . The lubricant composition according to  claim 1 , wherein the additive composition comprises:
 (a) sulfurized fatty acid at about 0.5%,   (b) 4-piperidol-2,2,6,6-tetremethyl-RPW stearin (fatty acids mixture) at about 0.1%, and   (c) the diaryl amine at about 0.4%.