| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic oil composition high in sludge resistance and excellent in frictional characteristic. SOLUTION: The composition is based on one or more oils selected from the group consisting of mineral oil, fatty oil, and synthetic oil, and contains (A) 0.01-5 mass% of a phenolic oxidation inhibitor and/or an aminic oxidation inhibitor, (B) 0.01-10 mass% of a phosphorus compound and/or a sulfur compound, and (C) 0.001-5 mass% of a compound by formula (1) described below, but does not contain zinc dithiophosphate practically. The formula (1) is R1- CH2COOH [wherein, R1 is an alkyl group having 7-29 carbons, an alkenyl group having 7-29 carbons, or a group described by formula (2): R2-C6H4O- (wherein, R2 is an alkyl group having 1-20 carbons or a hydrogen)]. |
