Transmission oil formulation for reducing fuel consumption

Abstract

The present invention relates to a transmission oil formulation comprising a base oil and a copolymer obtained by free-radical polymerization from a monomer composition. The invention also relates to the use of the transmission oil formulation as transmission oil for reducing the fuel consumption of motor vehicles.

1 : A transmission oil formulation comprising
 (i) a base oil having a kinematic viscosity at 100° C. of at least 1.5 mm 2 /s to ASTM D445 and an aromatics content of less than 15% by weight to ASTM D 2007; and   (ii) a copolymer obtained by free-radical polymerization from a monomer composition, said monomer composition comprising the following monomers:   (A) 30% to 50% by weight of an ester of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene, where the hydroxylated hydrogenated polybutadiene has a number-average molar mass M n  to DIN 55672-1 of 4000 to 6000 g/mol;   (B1) 0.2% to 50% by weight of methyl(meth)acrylate;   (B2) 0.2% to 50% by weight of butyl(meth)acrylate;   (B3) 0.2% to 5% by weight of C5-C30 alkyl(meth)acrylates;   (C) 10% to 50% by weight of styrene monomers having 8 to 17 carbon atoms; and   (D) 0% to 5% by weight of further free-radically polymerizable comonomers,   where the sum total of the proportions by weight of monomers (B1), (B2) and (B3) is at least 10% by weight.   
     
     
         2 : The transmission oil formulation as claimed in  claim 1 , characterized in that the monomer composition comprises
 as monomer (B1) 0.2% to 45% by weight of methyl methacrylate;   as monomer (B2) 0.2% to 45% by weight of n-butyl methacrylate and/or n-butyl acrylate; and
 as monomer (B3) 0.2% to 5% by weight of C12-C14 alkyl(meth)acrylates. 
   
     
     
         3 : The transmission oil formulation as claimed in  claim 1 , characterized in that the hydroxylated hydrogenated polybutadiene is a hydroxyethyl- or hydroxypropyl-terminated hydrogenated polybutadiene. 
     
     
         4 : The transmission oil formulation as claimed in  claim 1 , characterized in that the copolymer has an iodine number to DIN 53241-1:1995-05 of up to 5 g of iodine per 100 g of copolymer. 
     
     
         5 : The transmission oil formulation as claimed in  claim 1 , characterized in that the further free-radically polymerizable comonomers are selected from the group consisting of maleic anhydride, (di)alkyl fumarates, (di)alkyl maleates, aminoalkyl(meth)acrylates, aminoalkyl(meth)acrylamides, hydroxyalkyl(meth)acrylates, carbonyl-containing (meth)acrylates, heterocyclic(meth)acrylates, heterocyclic vinyl compounds and mixtures thereof. 
     
     
         6 : The transmission oil formulation as claimed in  claim 1 , characterized in that the copolymer has a molar branching level of 1.0 to 3.1 mol %. 
     
     
         7 : The transmission oil formulation as claimed in  claim 1 , characterized in that the base oil has a proportion of aromatic carbon atoms of not more than 2%. 
     
     
         8 : The transmission oil formulation as claimed in  claim 1 , characterized in that the base oil is a group III oil as defined by the American Petroleum Institute. 
     
     
         9 : The transmission oil formulation as claimed in  claim 1 , characterized in that the transmission oil formulation comprises 60% to 99.9% by weight of component (i) based on the total weight of the transmission oil formulation. 
     
     
         10 : The transmission oil formulation as claimed in  claim 1 , characterized in that the transmission oil formulation comprises 0.1% to 40% by weight of component (ii) based on the total weight of the transmission oil formulation. 
     
     
         11 : The transmission oil formulation as claimed in  claim 1 , characterized in that the transmission oil formulation additionally comprises, as component (iii), a second polymer selected from the group of the hydrogenated polybutadienes, hydroxylated hydrogenated polybutadienes or (meth)acrylic esters thereof, polyalkyl(meth)acrylates and mixtures thereof. 
     
     
         12 : The transmission oil formulation as claimed in  claim 11 , characterized in that the transmission oil formulation comprises 0% to 3% by weight of component (iii) based on the total weight of the transmission oil formulation. 
     
     
         13 : The transmission oil formulation as claimed in  claim 1 , characterized in that the transmission oil formulation additionally comprises, as component (iv), further additives selected from the group consisting of dispersants, defoamers, detergents, antioxidants, antiwear additives, extreme pressure additives, friction modifiers, anticorrosion additives, dyes and mixtures thereof. 
     
     
         14 : The use of a transmission oil formulation as claimed in  claim 1  as transmission oil for reducing the fuel consumption of motor vehicles. 
     
     
         15 : The use as claimed in  claim 14 , characterized in that the transmission oil formulation is used as transmission oil for automatic transmission systems.