Use of dialkylene glycol ester to increase the oxidation resistance of a lubricant composition

Abstract

The present invention relates to the use of at least one diester having formula (I) in a lubricant composition containing at least one base oil, so as to increase the oxidation resistance of said lubricant composition or to decrease the oxidation level of said lubricant composition,Ra—C(O)—O—([C(R)2]n—O)s—C(O)—Rb   (I)

1 .- 8 . (canceled) 
     
     
         9 . A method to increase the oxidation resistance of a lubricant composition comprising at least one base oil, comprising the addition to said lubricant composition of at least one diester of formula (I)
   R a —C(O)—O—([C(R) 2 ] n —O) s —C(O)—R b    (I)
   where:   R, each independently, are a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms;   s is 1 or 2;   n is 1, 2 or 3, on the understanding that when s differs from 1, the n values can be the same or different;   Ra and Rb, the same or different, are each independently linear or branched, saturated or unsaturated hydrocarbon groups having a linear sequence of 6 to 18 carbon atoms;   provided that when s is 2, and n all the same are 2, at least one of the R groups is a linear or branched alkyl group having 1 to 5 carbons atoms; and   provided that when s is 1, and n is 3, at least one of the R groups linked to the carbon at beta position of the oxygen atoms of the ester functions, represents a hydrogen atom.   
     
     
         10 . A method for decreasing the oxidation level of a lubricant composition comprising at least one base oil, comprising the addition to said lubricant composition of at least one diester of formula (I)
   R a —C(O)—O—([C(R) 2 ] n —O) s —C(O)—R b    (I)
   where:   R, each independently, are a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms;   s is 1 or 2;   n is 1, 2 or 3, on the understanding that when s differs from 1, the n values can be the same or different;   Ra and Rb, the same or different, are each independently linear or branched, saturated or unsaturated hydrocarbon groups having a linear sequence of 6 to 18 carbon atoms;   provided that when s is 2, and n all the same are 2, at least one of the R groups is a linear or branched alkyl group having 1 to 5 carbon atoms; and   provided that when s is 1, and n is 3, at least one of the R groups linked to the carbon at beta position of the oxygen atoms of the ester functions, represents a hydrogen atom.   
     
     
         11 . The method of  claim 9 , wherein when s differs from 1 all the n values are the same. 
     
     
         12 . The method of  claim 9 , wherein n is 2 or 3. 
     
     
         13 . The method of  claim 9 , wherein at least one of the R groups is a linear or branched alkyl group having 1 to 5 carbon atoms. 
     
     
         14 . The method of  claim 9 , wherein the diester of formula (I) of the invention is a diester of following formula (I′):
   R a —C(O)—O—([C(R) 2 ] n —O)—([C(R′) 2 ] m —O) s-1 —C(O)—R b    (I′)
 
 where: 
 R and R′ each independently are a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms; 
 s is 1 or 2; 
 n is 2; 
 m is 2; 
 Ra and Rb, the same or different, are each independently linear or branched, saturated or unsaturated hydrocarbon groups having a linear sequence of 6 to 18 carbon atoms; 
 provided that when s is 2, at least one of the groups R or R′ is a linear or branched alkyl group having 1 to 5 carbon atoms. 
 
     
     
         15 . The method of  claim 9 , wherein the diester is a compound of formula (I″a)
   R a —C(O)—O—CHR 1 —CHR 2 —O—CHR 3 —CHR 4 —O—C(O)—R b    (I″a)
 
 where: 
 
       one of the groups R 1  and R 2  is a linear or branched alkyl group having 1 to 5 carbon atoms, the other representing a hydrogen atom; 
       one of the groups R 3  and R 4  is a linear or branched alkyl group having 1 to 5 carbon atoms, the other representing a hydrogen atom. 
     
     
         16 . The method of  claim 9 , wherein the diester of formula (I) is added in a proportion of 10 to 70% by weight relative to the total weight of the lubricant composition. 
     
     
         17 . The method of  claim 10 , wherein when s differs from 1 all the n values are the same. 
     
     
         18 . The method of  claim 10 , wherein n is 2 or 3. 
     
     
         19 . The method of  claim 10 , wherein at least one of the R groups is a linear or branched alkyl group having 1 to 5 carbon atoms. 
     
     
         20 . The method of  claim 10 , wherein the diester of formula (I) of the invention is a diester of following formula (I′):
   R a —C(O)—O—([C(R) 2 ] n —O)—([C(R′) 2 ] m —O) s-1 —C(O)—R b    (I′)
 
 where: 
 R and R′ each independently are a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms; 
 s is 1 or 2; 
 n is 2; 
 m is 2; 
 Ra and Rb, the same or different, are each independently linear or branched, saturated or unsaturated hydrocarbon groups having a linear sequence of 6 to 18 carbon atoms; 
 provided that when s is 2, at least one of the groups R or R′ is a linear or branched alkyl group having 1 to 5 carbon atoms. 
 
     
     
         21 . The method of  claim 10 , wherein the diester is a compound of formula (I″a)
   R a —C(O)—O—CHR 1 —CHR 2 —O—CHR 3 —CHR 4 —O—C(O)—R b    (I″a)
 
 where: 
 
       one of the groups R 1  and R 2  is a linear or branched alkyl group having 1 to 5 carbon atoms, the other representing a hydrogen atom; 
       one of the groups R 3  and R 4  is a linear or branched alkyl group having 1 to 5 carbon atoms, the other representing a hydrogen atom. 
     
     
         22 . The method of  claim 10 , wherein the diester of formula (I) is added in a proportion of 10 to 70% by weight relative to the total weight of the lubricant composition.