text: Aqueous based and non-aqueous functional fluids have been employed in such diverse uses as hydraulic fluids, metal working fluids, heat transfer fluids, electronic coolants, damping fluids and lubricants. To meet such diverse uses functional fluids are often tailored to have sets of properties and performance characteristics specific to the intended use of the fluid. Among the principle uses of functional fluids is their application as hydraulic fluids and metal working fluids. In metal working applications they find use in drilling, tapping, drawing, turning, milling, broaching, grinding, bending, rolling and the like metal working operations. The stability and lubricating characteristics of the functional fluid as a whole and the various components of the fluid play a major role in the performance and utility of the fluid in hydraulic and metal working applications. High stability for the fluid and its components during storage and use as well as high lubricity of the fluid are important and desirable characteristics in the use of the fluid as a hydraulic fluid or metal working fluid.
  In recent years aqueous based functional fluids have gained in importance because of their safety, environmental, disposal, flammability, performance and economic advantages over non-aqueous functional fluids. These advantages are particularly significant in view of the strong emphasis currently being placed on safety and environmental considerations, especially in metal working operations. The economic advantages of aqueous functional fluids over non-aqueous functional fluids have become important in view of the supply problems and increasing price of non-aqueous functional fluids.
  However, to derive the greatest benefit from these advantages of aqueous functional fluids, such fluids should exhibit high stability during storage and use, as well as provide a high degree of lubricity. Thus the aqueous functional fluid should be highly resistant to separation of one or more components from the mixture and resistant to undesirable breakdown (e.g. degradation) of the components of the fluid, especially undesirable degradation of a lubricant component of the fluid. Separation and undesirable degradation of components (especially a lubricant component) of an aqueous functional fluid reduces the effectiveness and useful life of the fluid leading to such undesirable effects as (1) excessive wear of metallic components of hydraulic systems (e.g. pumps and valves) and metal working equipment (e.g. cutting tools, rolls and dies) and (2) metal working products which have poor surface finish and incorrect dimensions. Although many aqueous functional fluids have been proposed by the art and a number of such fluids have been and are being used today in such applications as hydraulics and metal working those fluids have exhibited stability and/or lubricity problems which tend to limit or preclude their effective utilization. Improvements in aqueous functional fluids have therefore been continuously sought by persons skilled in the art.
  It is therefore an object of this invention to overcome the disadvantages of prior art aqueous functional fluids and provide a stable, lubricating aqueous functional fluid.
  Another object of this invention is to provide a novel lubricant for use in forming a stable, lubricating aqueous functional fluid.
  It is a further object of this invention to provide a stable, lubricating aqueous functional fluid containing a novel polyamide lubricant.