To obtain the subject fluid comprising a specific naphthenic ring-contg. ester, exhibiting excellent power transmission and the outstanding ability as a fluid for hydraulic pressure control or wet clutch friction control as well, and therefore useful in e.g. automotive stepless speed change gears.
This fluid for traction drive comprises (A) a compound of formula I [R1 to R6 are each H or a (naphthenic ring contg.) 1-8C alkyl] and, as necessary, furthermore (B) a mineral oil or a synthetic oil 150-800 in molecular weight, (C) a viscosity index improver [e.g. a (hydrogenated) ethylene-α-olefin copolymer with a number-average molecular weight of 800-150,000], (D) an ash-free dispersant and phosphorus-based additive, (E) a friction regulator having 6-30C alkyl or alkenyl group in the molecule but containing no ≥31C hydrocarbon group, and/or (F) a metal-based cleaning agent with a total base value of 20-450 mgKOH/g; by the way, the component A is prepared, for example, by reaction between formic acid and a compound of formula II.
KONO JUNYA
SHIRAHAMA SHINICHI
OKAWA TETSUO
