Stabilizing compositions for lubricating oils

Abstract

Stabilising compositions for lubricant base stocks and lubricant formulations are composed of a mixture of (a) at least one aromatic aminic amine antioxidant optionally blended with at least one hindered phenolic antioxidant and (b) at least one neutral organo phosphate or phosphite, optionally blended with at least one acid organo phosphate or phosphite. These stabilising composition mixtures are characterised by their stabilising capacity which is considerably higher than that of either the single antioxidants or the single phosphate or phosphite additives. These stabilising compositions can be used in all fields where the single components of the mixtures are generally used and where deterioration due to oxidation processes takes place.

1 . A stabilising composition comprising a mixture of: 
 (a) at least one aromatic aminic antioxidant having the general formula:                           wherein R 1  and R 2  are the same or different and may be H, an alkyl group with 4 to 9 carbon atoms or an aralkyl group with 8 carbon atoms and m and n are 0 to 2 but m+n is not greater than 3, either alone or optionally blended with at least one hindered phenolic antioxidant selected from those corresponding to one of the following general formulae:                           wherein R 3 , R 4 , R 5  and R 6  are the same or different and may be an alkyl group with 1 to 4 carbon atoms and X is —S— or —CH 2 — or —CH 2 CH 2 —S—CH 2 CH 2 — or —CH 2 —S—CH 2 — or —CH 2 CH 2 CO 2 CH 2 CH 2 —S—CH 2 CH 2 CO 2 CH 2 CH 2 —                          wherein R 7  is an alkyl group with 6 to 20 carbon atoms; and                           with (b) at least one neutral organo phosphate or phosphite optionally mixed with at least one acid organo phosphate or phosphite selected from those corresponding to the following general formulae 
 (i) neutral triaryl phosphates:  
                     
  wherein R 8 , R 9  and R 10  are the same or different and may be H, CH 3 , isopropyl or tertiary butyl and m is 0 to 2;  
 (ii) neutral trialkyl phosphates:  
                     
  wherein R 11 , R 12  and R 13  are all the same and are alkyl groups with 4 to 12 carbon atoms;  
 (iii) neutral alkyl aryl phosphates:  
                     
  wherein R 14  is different from R 15  and R 16  and R 14  is an alkyl group with 4 to 12 carbon atoms and R 15  is phenyl or substituted phenyl with 7 to 10 carbon atoms and R 16  may be an alkyl group with 4 to 12 carbon atoms or phenyl or substituted phenyl with 7 to 10 carbon atoms;  
 (iv) alkyl acid phosphates:  
                     
  wherein R 17  is an alkyl group with 5 to 12 carbon atoms and m is 1 or 2 and n is 1 or 2 but m+n is not greater than 3;  
 (v) neutral triaryl phosphites:  
                     
  wherein R 18 , R 19 , R 20  are the same or different and are H or alkyl with 1 to 9 carbon atoms.  
 (vi) neutral trialkyl phosphites  
                     
  wherein R 21 , R 22 , and R 23  are the same or different and are alkyl groups with 1 to 18 carbon atoms.  
 (vii) neutral alkyl aryl phosphites:  
                     
  wherein R 24  and R 25  are the same or different and are alkyl groups with 1 to 12 carbon atoms or R 24  is phenyl or substituted phenyl where R26 is alkyl with 1 to 9 carbon atoms.  
 (viii) alkyl acid phosphites:  
                     
  wherein R 27  may be an alkyl group with 4 to 18 carbon atoms, phenyl or substituted phenyl with 7 to 10 carbon atoms and m is 1 or 2, n is 1 or 2 but m+n is not greater than 3,  
  and wherein the antioxidants and the phosphate(s) and/or phosphite(s) are utilised in a weight ratio from 10:1 to 1:10.  
   
     
     
         2 . The stabilising composition in accordance with  claim 1  wherein the antioxidant(s) and the phosphate(s) and/or phosphite(s) are utilised in a weight ratio from 1:1 to 1:5.  
     
     
         3 . The stabilising composition in accordance with  claim 1  or  claim 2  which has been prepared by heating the antioxidant(s) and the phosphate(s) and/or phosphite(s) for 0.2 to 6 hours at a temperature between 40° C. and 150° C.  
     
     
         4 . A lubricant base stock or lubricant composition stabilised by the stabilised composition of any one of  claims 1  to  3 .