Lubricant composition for automotive transmission having improved anticorrosion properties

Abstract

A lubricating composition includes at least one base oil, at least one dispersant and at least one phosphite polymer having formula (I) wherein each of the R 1 , R 2 , R 3 and R 4 can be independently selected from the C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers and Y—OH groups; Y is selected from among the C2-C40 alkylene, C2-C40 alkyl lactone —R 7 —N(R 8 )—R 9 — groups, R 7 , R 8 and R 9 are independently selected from among hydrogen, C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers; m is an integer from 2 to 100; and n is an integer from 1 to 1000.

1 . A lubricant composition comprising:
 at least one base oil;   at least one dispersant; and   at least one phosphite polymer of formula (I):   
       
         
           
           
               
               
           
         
         where: 
         each of R 1 , R 2 , R 3  and R 4  can each be independently selected from among the following groups: C 1 -C 20  alkyl, C 3 -C 22  alkenyl, C 6 -C 40  cycloalkyl, C 7 -C 40  cycloalkenyl, C 1-20  methoxy alkyl glycol ethers and Y—OH; 
         Y is selected from among the following groups: C 2 -C 40  alkylene, C 2 -C 40  alkyl lactone, —R 7 —N(R′)—R 9 — where R 7 , R 8  and R 9  are each independently selected from among hydrogen, C 1 -C 20  alkyl, C 3 -C 22  alkenyl, C 6 -C 40  cycloalkyl, C 7 -C 40  cycloalkenyl, C 1-20  methoxy alkyl glycol ethers, 
         m is an integer ranging from 2 to 100; and 
         n is an integer ranging from 1 to 1000. 
       
     
     
         2 . The lubricant composition according to  claim 1 , wherein the polymer of formula (I) has a weight average molecular weight lower than 30000 g/mol. 
     
     
         3 . The lubricant composition according to  claim 1 , wherein the phosphite polymer represents from 0.01 to 10% by weight of the total weight of the lubricant composition. 
     
     
         4 . The lubricant composition according to  claim 1 , wherein the dispersant is a boron-containing dispersant. 
     
     
         5 . The lubricant composition according to  claim 1 , comprising from 5 to 9150 ppm by weight of phosphorus, relative to the total weight of the lubricant composition. 
     
     
         6 . The lubricant composition according to  claim 1 , further comprising at least one antiwear additive selected from among phosphorus antiwear additives, sulfur antiwear additives, sulfur-phosphorus antiwear additives, phosphorus-amine antiwear additives, sulfur-amine antiwear additives, and mixtures thereof. 
     
     
         7 . The lubricant composition according to  claim 1 , comprising from 5 to 4000 ppm by weight of sulfur, relative to the total weight of the lubricant composition. 
     
     
         8 . The lubricant composition according to  claim 1 , comprising:
 70 to 99% by weight of one or more base oils; and   0.01 to 10% by weight of phosphite polymer;   0.01 to 5% by weight of dispersant(s) preferably including at least one boron-containing dispersant;   optionally, 0.01 to 5% by weight of antiwear additive(s) selected from among phosphorus antiwear additives, sulfur antiwear additives, sulfur-phosphorus antiwear additives, phosphorus-amine antiwear additives, sulfur-amine antiwear additives and mixtures thereof; and   optionally 1 to 30% by weight of one or more functional additives,   relative to the total weight of the lubricant composition.   
     
     
         9 . A method for improving the anticorrosion properties of a lubricant composition comprising at least one base oil, the method comprising adding a phosphite polymer in combination with a dispersant into the lubricant composition, said phosphite polymer replying to formula (I): 
       
         
           
           
               
               
           
         
         where:
 each of R 1 , R 2 , R 3  and R 4  can each be independently selected from among the following groups: C 1 -C 20  alkyl, C 3 -C 22  alkenyl, C 6 -C 40  cycloalkyl, C 7 -C 40  cycloalkenyl, C 1-20  methoxy alkyl glycol ethers and Y—OH (acting as terminal group); 
 Y is selected from among the following groups: C 2 -C 40  alkylene, C 2 -C 40  alkyl lactone, —R 7 —N(R 8 )—R 9 — where R 7 , R 8  and R 9  are each independently selected from among hydrogen, C 1 -C 20  alkyl, C 3 -C 22  alkenyl, C 6 -C 40  cycloalkyl, C 7 -C 40  cycloalkenyl, C 1-20  methoxy alkyl glycol ethers; 
 m is an integer ranging from 2 to 100; and 
 n is an integer ranging from 1 to 1000. 
 
       
     
     
         10 . A method for lubricating at least one mechanical part of an automotive vehicle, the method comprising contacting the composition according to  claim 1  with the at least one mechanical part of an automotive vehicle. 
     
     
         11 . The lubricant composition according to  claim 1 , wherein the polymer of formula (I) has a weight average molecular weight ranging from 3000 to 20000 g/mol. 
     
     
         12 . The lubricant composition according to  claim 1 , wherein the dispersant is selected from among boronated and optionally phosphorated succinimides. 
     
     
         13 . The lubricant composition according to  claim 1 , wherein the dispersant is selected from among boronated and optionally phosphorated polyisobutylene succinimides. 
     
     
         14 . The lubricant composition according to  claim 1 , comprising from 5 to 4500 ppm by weight of phosphorus, relative to the total weight of the lubricant composition. 
     
     
         15 . The lubricant composition according to  claim 1 , comprising from de 7 to 1000 ppm by weight of sulfur, relative to the total weight of the lubricant composition. 
     
     
         16 . The lubricant composition according to  claim 1 , comprising from de 10 to 800 ppm by weight of sulfur, relative to the total weight of the lubricant composition. 
     
     
         17 . The lubricant composition according to  claim 6 , comprising from 0.01 to 5% by weight of the at least one antiwear additive, relative to the total weight of the lubricant composition. 
     
     
         18 . The lubricant composition according to  claim 8 , wherein the functional additives are selected from among viscosity index improver additives, antioxidant additives, defoaming additives, dispersants, detergents, viscosity modifying additives, and mixtures thereof. 
     
     
         19 . The method according to  claim 10 , wherein the mechanical part of an automotive vehicle is contained in a transmission component of an automotive vehicle. 
     
     
         20 . The method according to  claim 19 , wherein the mechanical part of an automotive vehicle contained in a transmission component of an automotive vehicle is a gear of an automotive vehicle.