Lubricating oil composition

Abstract

The present invention provides a lubricating oil composition comprising a base oil made of synthetic oil and/or mineral oil, admixed with an antioxidant and a polymethacrylate having a phosphate ester added to a terminal position. In a further aspect the present invention provides the use of the lubricating oil composition as a transmission oil, in particular as an automatic transmission oil.

1 . A lubricating oil composition comprising a base oil made of synthetic oil and/or mineral oil, admixed with an antioxidant and a polymethacrylate having a phosphate ester added to a terminal position.  
   
   
       2 . A lubricating oil composition according to  claim 1 , wherein the antioxidant is selected from the group comprising a phenolic antioxidant and an amine antioxidant, or a combination thereof.  
   
   
       3 . A lubricating oil composition according to  claim 1 , further comprising a compound selected from the group comprising an alkaline earth metal salt of a sulphonate, phenate or a salicylate; preferably an alkyl salicylic acid alkaline earth metal salt.  
   
   
       4 . A lubricating oil composition according to any one of the preceding claims, wherein said polymethacrylate comprises an oil-soluble copolymer having a weight average molecular weight of 3,000-500,000 obtainable by copolymerising at least one species of a monomer represented by following general formula (1) and at least one species of a monomer represented by general formula (2): 
       CH2═C(R 1 )—Q—(Z—A 1 )m—X  (1) CH2═C(R 3 )—CO—(O—A 2 )n—OR 4   (2) wherein X is a polar group represented by formula —(O)a—P(═O)b(OR 2 ) 2 , wherein either one of a and b is 1 and the other is 0 or 1, and the two R 2 s are the same or different and denote H, a C 1-24  alkyl group, a group represented by formula —(A 1 —Z) m —Q—C(R 1 )═CH 2  or a cation of formula M 1 /ff, wherein M is a cation with a valency of f (monovalent or divalent);    wherein R1 is H or a methyl group, Z is —O— or —NH—, A 1  is a C 2-18  alkylene group, m is 0 or 1 or an integer of 2-50, and Q is —CO— or a divalent hydrocarbon group of carbon number 1-22, and when m is 0, then Q is a divalent hydrocarbon group of carbon number 1-22; and    wherein R 3  is H or a methyl group, n is 0 or an integer of 1-30, A 2  is a C 2-18  alkylene group and R 4  is an aliphatic hydrocarbon group of carbon number 1-32, an alicyclic hydrocarbon group of carbon number 5-7 or a C7-32 aralkyl group, and when present in plurality, A 1 , Z, Q, R 1 , m and A 2  each independently may be the same or different.    
   
   
       5 . A lubricating oil composition according to  claim 4 , wherein, in formula (1), R 2  in X of formula —(O)a—P(═O)b(OR 2 ) 2,  is a C 1-24  alkyl group, preferably C 1-4  alkyl group, and in particular a methyl or ethyl group.  
   
   
       6 . A lubricating oil composition according to any one of the preceding claims, comprising a base oil made of synthetic oil and/or mineral oil, admixed with a phenolic antioxidant and a polymethacrylate having a phosphate ester added to a terminal position.  
   
   
       7 . A lubricating oil composition according to any one of the preceding claims, comprising a base oil made of synthetic oil and/or mineral oil, admixed with an amine antioxidant, an alkyl salicylic acid alkaline earth metal salt and a polymethacrylate having a phosphate ester added to a terminal position.  
   
   
       8 . A lubricating oil composition according to any one of the preceding claims, wherein the base oil is a Fischer-Tropsch derived base oil.  
   
   
       9 . Use of the lubricating oil composition according to  claim 1  as a transmission oil, in particular as an automatic transmission oil.  
   
   
       10 . Method of improving the lubrication in a transmission device, in particular an automatic transmission device, by lubricating said transmission device with a lubricating oil composition according to  claim 1.