| 摘要 |
PROBLEM TO BE SOLVED: To obtain a lube base oil which is satisfactory in low-temperature fluidity, volatile loss, and viscosity index and has an excellent lubricity in a wide temperature range for a long term by incorporating a synthetic lube base oil specified in volatile loss, fluidity, and viscosity index into the same. SOLUTION: This synthetic lube base oil exhibits a volatile loss, when heated at 180 deg.C for 500 hr, of 35 wt.% or lower, a pour point of -40 deg.C or lower, a viscosity index of 135 or higher, and a kinematic viscosity at 40 deg.C of 10-100 mm2/sec. Preferably, the lube base oil contains at least 70 wt.% ester which has an acid value of 1 mgKOH/g or lower and a hydroxyl value of 10 mgKOH/g or lower and is prepared by reacting a tri- or tetrahydric alcohol with a carboxylic acid mixture comprising 0.5-20 mol% 16C or 18C branched saturated fatty acid, 50-96.5 mol% n-heptanoic acid, and 3-40 mol% at least one branched saturated fatty acid selected from among isoheptanoic, 2-ethylhexanoic, and isononanoic acids. This lube base oil is used in a temperature range of -60 to 250 deg.C.
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