Antiwear hydraulic fluid composition with useful emulsifying and rust prevention properties

Abstract

Disclosed are antiwear hydraulic fluid compositions comprising (a) a major amount of a base oil of lubricating viscosity and (b) a minor amount of at least one oil soluble detergent additive comprising a salt of an alkyl-substituted hydroxybenzoic acid or a sulfurized derivative thereof, wherein said salt is selected from the group consisting of alkali metal salts, alkaline earth metal salts, ammonium salts or substituted ammonium salts, and further wherein said antiwear hydraulic fluid compositions have a Carboxylate Index of greater than levels disclosed herein.

Description

FIELD OF THE INVENTION [0001]The present invention relates to detergents utilized in antiwear hydraulic fluid compositions. In particular, the present invention relates to antiwear hydraulic fluid compositions which can be useful for certain mobile equipment applications (e.g., hydraulic fluids for construction equipment).BACKGROUND OF THE INVENTION [0002]Hydraulic fluids need to protect equipment from rust. To achieve this they are formulated with rust inhibitors. Typical rust inhibitors are metal sulfonates or succinic acid derivatives. Hydraulic fluids are also typically designed to separate readily from water (demulsify). Often, metallic rust inhibitors act to improve the demulsifying characteristics of the fluids.[0003]Japanese Patent Publication No. JP1999311187A describes a composition containing (A) a base fluid of a sulfur content of up to 100 ppm, (B) 0.2-1 wt. % of zinc dithiophosphate, (C) 0.2-1 wt. % of an alkaline earth metal salt of salicylic acid and (D) 0.001-0.5 wt...

AI Technical Summary

Benefits of technology

[0008]Surprisingly, we have found that salts as described above exhibit excellent emulsifying and rust inhibition characteristics. This combined performance is unexpected when compared to other detergents. One advantage of the present invention is the reduction or removal of conventional rust inhibitors, such as metallic naphthalene sulfonic acid salts, (e.g., NA-SUL® from King Industries).

is the reduction or removal of conventional rust inhibitors, such as metallic naphthalene sulfonic acid salts, (e.g., NA-SUL® from King Industries).

Problems solved by technology

These include fluids with enhanced detergent and dispersant characteristics (e.g., so called HLPD and HVLPD fluids as defined by the German DIN 51 502 standard) and hydraulic fluids for certain mobile equipment applications (e.g., hydraulic fluids for Caterpillar equipment, building machinery, excavators, hydraulic hoists, lifting platforms, presses, and the like), wherein water separated from the fluid may not be adequately removed from the equipment leading to poor lubrication.

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