Patent ID: 8648022

Claim:
A hydraulic fluid composition which comprises (A) a refrigerant consisting of difluoromethane and (B) a lubricating oil which comprises, as a base oil, a polyoxyalkylene glycol derivative with a kinematic viscosity of 3 to 2,000 mm 2 /s at 40° C. and, as a main component thereof, having at least one constituting unit represented by general formula (III): wherein R 7 to R 10 each independently represent hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms or a group represented by general formula (IV): wherein R 11 and R 12 each independently representing hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms, R 13 representing an alkylene group having 2 to 5 carbon atoms, a substituted alkylene group having an alkyl group as a substituent and 2 to 5 carbon atoms in an entire group or a substituted alkylene group having an alkoxyalkyl group as a substituent and 4 to 10 carbon atoms in an entire group, R 14 representing a monovalent hydrocarbon group having 1 to 10 carbon atoms and n representing an integer of 0 to 20; and at least one of R 7 to R 10 represents a group represented by general formula (IV).