HYDRAULIC OIL COMPOSITION

摘要

PURPOSE:To obtain a hydraulic oil which is less apt to be emulsified upon water inclusion by incorporating a specific barium sulfonate, an alkali metal borate hydrate, and a specific zinc dialkyldithiophosphate into a base oil. CONSTITUTION:A barium sulfonate (A) represented by formula I (wherein R2 and R2 are each a 1-20C primary or secondary alkyl) is incorporated in an amount of 0.5-5wt.% into a mineral or synthetic base oil together with 0.001-0.1wt.% alkali metal borate hydrate (B) in terms of boron amount and 0.05-5 wt.& zinc dialkyldithiophosphate (C) represented by formula II (wherein R<3> to R<6> each has the same meaning as R<1> or R<2>) to obtain a hydraulic oil. The compound (A) has been used as a rust preventive. The compound (B) is usually obtained as a suspension from neutral calcium sulfonate and an ash-free dispersant such as succinimide. This oil is less apt to be emulsified upon inclusion of water or an aqueous hydraulic fluid, is thermally stable and color-fast, and is usable for long.