| 摘要 |
PROBLEM TO BE SOLVED: To obtain a hydraulic oil which does not wither plants and does not affect natural environment by formulating a surface active agent with an ester of an aliphatic fatty polyol, as a basic oil, showing good biodegradation. SOLUTION: A hydraulic oil is obtained by formulating 0.5-50 pts.wt. of a surface active agent including an anionic surface active agent, a cationic surface active agent and a nonionic surface active agent and, if necessary, additives including 0.1-5.0 pts.wt. of a rust preventive agent, 0.1-2.0 pts.wt. of an anti-oxidant, 0.1-1.0 pt.wt. of a defoaming agent, 0.1-2.0 pts.wt. of an extreme pressure agent, a metal-inactivating agent, an abrasion resistant agent, an abrasion-controlling agent, a viscosity improving agent or the like with 100 pts.wt. of an ester of an aliphatic fatty polyol or the like as a basic oil showing good biodegradation. An aliphatic polyol ester to be used includes synthetic esters such as a trimethylolpropanetrioleate, a neopentylglycolidioleate or the like and natural oils such as a rape oil, a peanut oil or the like. |
