Dispersant Combination for Improved Transmission Fluids

Abstract

A lubricant composition of an oil, a dispersant viscosity modifier of a poly(meth)acrylate copolymer having a nitrogen-containing monomer in an amount to provide at least about 0.4 percent by weight nitrogen to the copolymer, and a succinimide dispersant prepared in the substantial absence of chlorine gives good performance as a transmission fluid.

1 . A lubricant composition comprising:
 (a) an oil of lubricating viscosity;   (b) a dispersant viscosity modifier comprising a poly(meth)acrylate copolymer containing nitrogen derived from a nitrogen-containing monomer in an amount to provide at least about 0.4 percent by weight nitrogen to said dispersant viscosity modifier; and   (c) a succinimide dispersant prepared from reaction of an amine with a hydrocarbyl-substituted succinic acylating agent prepared by reaction of a polyalkene, at least about 70 percent of the chains thereof containing a terminal vinylidene end group, with maleic anhydride in the substantial absence of chlorine.   
   
   
       2 . The composition of  claim 1  further comprising (d) a phosphorus acid. 
   
   
       3 . The composition of  claim 1  wherein the dispersant viscosity modifier comprises about 0.4 to about 1.2 weight percent nitrogen atoms. 
   
   
       4 . The composition of  claim 1  wherein the dispersant viscosity modifier contains about 2.5 to about 6 percent by weight units derived from said nitrogen-containing monomer 
   
   
       5 . The composition of  claim 1  wherein the nitrogen-containing monomer comprises 3-dimethylaminopropyl methacrylamide, N-vinylpyrrolidone, or dimethylaminoethyl methacrylate. 
   
   
       6 . The composition of  claim 1  wherein the dispersant viscosity modifier is a copolymer derived from monomers comprising C 6 -C 18  alkyl methacrylates and 3-dimethylaminopropyl methacrylate. 
   
   
       7 . The composition of  claim 6  wherein the C 6 -C 18  alkyl methacrylates comprise 2-ethylhexyl methacrylate. 
   
   
       8 . The composition of  claim 6  wherein monomers of the dispersant viscosity modifier further comprise a C 1 -C 4  alkyl methacrylate. 
   
   
       9 . The composition of  claim 1  wherein the amount of the dispersant viscosity modifier is about 0.5 to about 10 weight percent. 
   
   
       10 . The composition of  claim 1  wherein the succinimide dispersant contains at least one succinic moiety which is attached to the hydrocarbyl substituent through a non-cyclic linkage. 
   
   
       11 . The composition of  claim 1  wherein the hydrocarbyl substituent of the succinimide dispersant is a polyisobutene substituent. 
   
   
       12 . The composition of  claim 1  wherein the amine portion of the succinimide dispersant comprises a poly(alkyleneamine). 
   
   
       13 . The composition of  claim 1  wherein the succinimide dispersant is borated. 
   
   
       14 . The composition of  claim 13  wherein the boron content of the succinimide dispersant is about 0.1 to about 1 weight percent. 
   
   
       15 . The composition of  claim 1  wherein the succinimide dispersant is further treated with terephthalic acid. 
   
   
       16 . The composition of  claim 1  wherein the nitrogen content of the succinimide dispersant is about 0.8 to about 2.0 weight percent. 
   
   
       17 . The composition of  claim 1  wherein the succinimide dispersant is present in an amount of about 0.1 to about 10 weight percent. 
   
   
       18 . A composition prepared by admixing the components of  claim 1 . 
   
   
       19 . A method of lubricating a transmission, a gear box, a transfer case, or a chain, comprising supplying thereto the lubricant composition of  claim 1 .