Method of fatigue control

Abstract

This invention relates to a method comprising (a) employing a composition comprising (i) an oil of lubricating viscosity; and (ii) a salt of a nitrogen containing poly(meth)acrylate and a phosphorus acid ester; and (b) lubricating a gear with such composition resulting in control of gear fatigue.

1 . A method comprising (a) employing a composition comprising (i) an oil of lubricating viscosity; and (ii) a salt of a nitrogen containing poly(meth)acrylate and a phosphorus acid ester; and (b) lubricating a gear with such composition resulting in control of gear fatigue.  
   
   
       2 . The method of  claim 1 , wherein the phosphorus acid ester comprises a phosphorodithioic acid or a dithiophosphoric acid mixtures thereof.  
   
   
       3 . The method of  claim 2 , wherein the phosphorus acid ester is a dihydrocarbyl phosphorodithioic acid or a dihydrocarbyl dithiophosphoric acid containing about 3 to about 30 carbon atoms in each hydrocarbyl group mixtures thereof.  
   
   
       4 . The method of  claim 1 , wherein the poly(meth)acrylate is prepared from a reaction of of (a) from about 60% to about 99.9% by weight of alkyl (meth)acrylate ester monomers containing from about 8 to about 40 carbon atoms in the alkyl group and (b) from about 0% to about 39.9% by weight of alkyl (meth)acrylate ester monomers containing from about 1 to about 7 carbon atoms in the alkyl group and (c) from 0% to about 39.9% by weight of one or more other comonomers such as a vinyl aromatic monomer; (d) and a nitrogen containing monomer.  
   
   
       5 . The method of  claim 1 , wherein the poly(meth)acrylate is prepared from a reaction of of (a) from about 75% to about 94.9% by weight of alkyl (meth)acrylate ester monomers containing from about 12 to about 18 carbon atoms in the alkyl group and (b) from about 5% to about 25% by weight of alkyl (meth)acrylate ester monomers containing from 1 to aobut 4 carbon atoms in the alkyl group; and (d) a nitrogen containing monomer.  
   
   
       6 . The method of  claim 1 , wherein the poly(meth)acrylate is prepared from a reaction of of (meth)acrylate ester monomers containing (a) from about 8 to about 24 carbon atoms in the ester group and (b) from about 6 to about 11 carbon atoms in the ester group and which have 2-(C 1 -4 alkyl)-substituents; (c) a nitrogen containing monomer; and (d) optionally a (meth)acrylate ester containing from about 1 to about 7 carbon atoms in the ester group and which are different from (meth)acrylate esters (a) and (b) or a vinyl aromatic compound.  
   
   
       7 . The method of  claim 1 , wherein the nitrogen containing poly(meth)acrylate is from an amino alkyl (meth)acrylic amide, dialkyl amino alkyl (meth)acrylate or mixtures thereof.  
   
   
       8 . The method of claim 1   1 , wherein the polymethacrylate has a weight average molecular weight in the range from about 10,000 to about 350,000.  
   
   
       9 . The method of  claim 1 , wherein the method of gear fatigue controls at least one of micropitting, pitting and spalling.  
   
   
       10 . The method of  claim 1 , wherein the oil of lubricating viscosity is a Group III or IV base oil.  
   
   
       11 . The method of  claim 10 , wherein the oil of lubricating viscosity is a Group IV base oil.  
   
   
       12 . A method comprising (a) employing a composition comprising (i) about 60 wt % to about 99.5 wt % of an oil of lubricating viscosity; and (ii) about 0.5 wt % up to about 40 wt % of a salt of a nitrogen containing poly(meth)acrylate and a phosphorus acid ester; and (b) lubricating a gear with the compostion resulting in control of gear fatigue.