Patent ID: 8715522

Claim:
A refrigerator oil composition, comprising: a base oil; and a polyalkylene glycol (PAG) block copolymer; wherein the PAG block copolymer is represented by formula (1): R 1 [(OR 2 ) m (OE) n OR 3 ] 1 (1) where: R 1 represents a hydrocarbon residue having 1 to 10 carbon atoms; R 2 represents a butylene group; E represents an ethylene group; R 3 represents a hydrogen atom; m and n each represent a positive integer, the ratio of min being 95/5 to 50/50; and l represents an integer in a range of 1 to 100; and wherein the base oil is mineral oil and/or synthetic base oil, and the synthetic base oil is at least one compound selected from the group consisting of alkyl benzene, alkyl naphthalene, poly-α-olefin, polyvinyl ether, polyalkylene glycol, polycarbonate, and an ether-base compound represented by formula (2): R a -[(OR b ) n -(A)-(OR c ) k]x -R d (2) where: Ra and Rd each represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms or a hydrocarbon group having 2 to 6 bonding sites and 1 to 10 carbon atoms; Rb and Rc each represent an alkylene group having 2 to 4 carbon atoms; n and k each represent an integer in a range of 0 to 20; x represents an integer in a range of 1 to 6; and (A) represents a polymerization site comprising three or more monomer units each represented by formula (3): where: R 4 , R 5 and R 6 each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R 4 , R 5 and R 6 being allowed to be mutually the same or different; R 7 represents a divalent hydrocarbon group having 1 to 10 carbon atoms or a divalent ether-bonded oxygen-containing hydrocarbon group having 2 to 20 carbon atoms; R 8 represents a hydrogen atom, or a hydrocarbon group having 1 to 20 carbon atoms; m represents a number whose average value is in a range of 0 to 10; when plural m are present, the plural m are allowed to be mutually the same or different per unit; R 4 to R 8 each are allowed to be mutually the same or different per unit; when plural R 7 O are present, the plural R 7 O are allowed to be mutually the same or different; and when k and n in formula (2) both represent 0, one of plural m in formula (3) represents an integer of 1 or more.