Patent ID: 6936576

Claim:
A refrigerating machine oil for a carbon dioxide refrigerant, comprising polyalkylene glycol represented by the following general formula (1): R 1 {—(OR 2 ) n —OH} m (1) wherein a number average molecular weight of said polyalkylene glycol is not less than 500 nor more than 5000, wherein a rate of ethylene group among said alkylene group in said polyalkylene glycol is more than 0 and not more than 80 mol %, and wherein a rate of molecules in which the alkylene group bonded to a terminal hydroxyl group in said polyalkylene glycol is an ethylene group, is not more than 20 mol %, wherein said polyalkylene glycol has a first polymer chain selected from an ethylene oxide homopolymer chain and a copolymer chain of ethylene oxide and one or more alkylene oxides except for ethylene oxide, and a second polymer chain of one or more alkylene oxides except for ethylene oxide, the one end of the first polymer chain being bonded to R 1 , the other end of the first polymer chain being bonded to one end of the second polymer chain; and the other end of the second polymer chain being bonded to a terminal hydroxyl group.