| 摘要 |
PROBLEM TO BE SOLVED: To obtain a hydraulic working oil composition for a buffer, having an excellent friction reducing effect by mixing a base oil with a phosphoric ester compound, an alkanolamine and a sorbitan ester in a specified mixing ratio. SOLUTION: A base oil comprising a mineral or synthetic oil and having a kinetic viscosity of about 1-20mm<2> /s at 100 deg.C is mixed with 0.1-5wt.%, based on the total composition, at least one phosphoric ester compound selected from among phosphoric esters and acid phosphoric esters represented by formula I, phosphorous esters and acid phosphorous esters represented by formula II (wherein R<1> and R<4> are each a 6-20 C hydrocar on group; R<2> , R<3> , R<5> and R<6> are each H, a 4-20 C alkyl, a 6-20 C aryl or the like), phosphoric ester amine salts and phosphorous ester amine salts. The obtained mixture is then mixed with 0.005-2wt.% alkanolamine (e.g. diethanolamine compound) and 0.005-5wt.% sorbitan ester represented by any one of formulas III to IV (wherein R<8> to R<15> are each H or an acyl), a cleaning dispersant, an antioxidant, etc., to obtain a hydraulic working oil composition for a buffer. |
