1.  Field of the Invention
The invention relates to lubricant compositions.  More particularly, it relates to a group of N-alkylalkylenediamine amides and to their use in lubricants as multipurpose additives.  The invention is especially concerned with internal combustion engines. 
2.  Discussion of Related Art
As those skilled in this art know, additives impart special properties to lubricants.  They may give the lubricants new properties or they may enhance properties already present.  One property all lubricants have in common is the reduction of friction between materials in contact.  Nonetheless, the art constantly seeks new materials to enhance the friction properties of the lubricant. 
A lubricant, even without additives, when used in an internal combustion engine, for example, will not only reduce friction, but in the process will also reduce consumption of the fuel required to run it.  When oils appeared to be inexhaustable, and cheap, some attention was given to increasing frictional properties, but most of the advances in this area came as a result of additives being placed in lubricants for other purposes.  Recent events, however, have spurred research programs designed specifically to find materials capable of reducing friction. 
The use of amides in lubricants is known (see U.S. Pat.  No.  3,884,822, for example, which discloses lubricants containing the product of reaction between an amino pyridine and oleic acid), no art teaches or suggests that the amides of this invention are useful for the purposes disclosed herein. 
U.S. Pat.  No.  3,778,372 discloses that compositions prepared by contacting and reacting formic acid or a formic acid producing compound with alkylene polyamines of specific structural formulas are useful as rust inhibitors.  These compositions are not disclosed to be effective as lubricity enhancers in lubricants. 
It has now been determined that reaction products of diamines of a certain structural formula with carboxylic acids such as formic acid provide improved lubricity when added to lube oils.