Method for reducing deposit formation in lubricant compositions

Abstract

The deposit forming tendency of Group II, III and IV lubricating base oils is reduced by the use of synergistic mixtures of diphenylamines or phenyl-α-naphthylamines with triarylphosphites.

1 . A method for reducing deposit formation in a lubricating base oil selected from the group consisting of Group II, III, IV oils and mixtures thereof comprising adding to the oil an effective amount of a mixture of triaryl phosphites represented by Formula I with diphenylamines or phenyl-α-naphthylamines represented by Formula II and III respectively, 
     
       
         
         
             
             
         
       
     
     wherein R 1  is H or a hydrocarbyl group having from 1 to about 8 carbon atoms and R 2  is H or a hydrocarbyl group of from 1 to about 12 carbon atoms and R 3  is a hydrocarbyl group of from 1 to 12 carbon atoms or NHR 4  where R 4  is a hydrocarbyl group of from 1 to about 12 carbon atoms. 
   
   
       2 . The method of  claim 1  wherein the weight ratio of diphenylamine or phenyl-α-naphthylamine to the triaryl phosphite in the mixture is in the range of from about 5:1 to about 1:5. 
   
   
       3 . The method of  claim 2  wherein the amount of the mixture added to the base oil is in the range of about 0.1 wt % to about 2 wt % based on the total weight of the composition. 
   
   
       4 . The method of  claim 3  wherein R 1  is tert-butyl, R 2  is H and R 3  is octyl. 
   
   
       5 . The method of  claim 4  wherein the oil is a Group III oil. 
   
   
       6 . The method of  claim 5  wherein the Group III oil is a GTL oil. 
   
   
       7 . A lubricating composition having reduced deposit forming tendency as evidenced by the Hot Tube Test, comprising:
 a major amount of an oil of lubricating viscosity selected from the group consisting of Group II, III, IV oils and mixtures thereof; and   a minor amount of a mixture of triaryl phosphites represented by Formula I with diphenylamines or phenyl-α-naphthylamines represented by Formula II and III respectively.   
     
       
         
         
             
             
         
       
     
     wherein R 1  is H or a hydrocarbyl group having from 1 to about 8 carbon atoms and R 2  is H or a hydrocarbyl group of from 1 to about 12 carbon atoms and R 3  is a hydrocarbyl group of from 1 to 12 carbon atoms or NHR 4  where R 4  is a hydrocarbyl group of from 1 to about 12 carbon atoms. 
   
   
       8 . The composition of  claim 7  wherein the weight ratio of diphenylamine or phenyl-α-naphthylamine to triaryl phosphite in the mixture is in the range of from about 5:1 to about 1:5. 
   
   
       9 . The composition of  claim 8  wherein the amount of the mixture is in the range of from about 0.1 wt % to about 2 wt %, based on the total weight of the composition. 
   
   
       10 . The composition of  claim 9  wherein R 1  is tert-butyl, R 2  is H and R 3  is octyl. 
   
   
       11 . The composition of  claim 10  wherein the base oil is a Group III base oil. 
   
   
       12 . The composition of  claim 11  wherein the Group III base oil is a GTL oil. 
   
   
       13 . A method for reducing deposit formation in a lubricating base oil selected from the group consisting of Group II, III, IV oils and mixtures thereof comprising adding to the oil an effective amount of a mixture of triaryl phosphites represented by Formula I with diphenylamines or phenyl-α-naphthylamines represented by Formula II and III respectively, 
     
       
         
         
             
             
         
       
     
     wherein R 1  is H or a hydrocarbyl group having from 1 to about 8 carbon atoms and R 2  is H or a hydrocarbyl group of from 1 to about 12 carbon atoms and R 3  is a hydrocarbyl group of from 1 to 12 carbon atoms or NHR 4  where R 4  is a hydrocarbyl group of from 1 to about 12 carbon atoms and wherein the weight ratio of diphenylamines or phenyl-α-naphthylamines to triaryl phosphites is in the range of about 5:1 to about 1:5.