Refrigerator oil and refrigerator working fluid composition

1. A refrigerating machine oil consisting of a base oil and an additive;

wherein the base oil consists of at least one ester of a fatty acid and a polyhydric alcohol, the ester having a carbon/oxygen molar ratio of 4.0 to 5.0, and the fatty acid comprises a branched fatty acid having 4 to 9 carbon atoms in a proportion of 50 to 100 mol %,

wherein the additive consists of

an acid scavenger, and

at least one additive selected from the group consisting of an oxidation inhibitor, an extreme-pressure agent, an oily agent, an anti-foaming agent, a metal deactivator, an anti-wear agent, a viscosity index improver, a pour point depressant, and a detergent dispersant, and

wherein the refrigerating machine oil is used with a trifluoroethylene refrigerant.

2. A working fluid composition for a refrigerating machine consisting of:

a refrigerating machine oil according to claim 1 ; and

a refrigerant comprising 20 mass % to 60 mass % of trifluoroethylene with respect to the total amount of the refrigerant.

3. A working fluid composition for a refrigerating machine according to claim 2 ,

wherein the additive consists of at least one selected from the group consisting of an acid scavenger, an oxidation inhibitor, an anti-foaming agent, a metal deactivator, a viscosity index improver, a pour point depressant and a detergent dispersant; and

the oxidation inhibitor consists of at least one selected from N,N′-diphenylphenylenediamine, p-octyldiphenylamine, p,p′-dioctyldiphenylamine, N-phenyl-1-naphthyamine, N-phenyl-2-naphthylamine, N-(p-dodecyl)phenyl-2-naphthylamine, di-1-naphthylamine, di-2-naphthylamine, N-alkylphenothiazine, 6-(t-butyl)phenol, 2,6-di-(t-butyl) phenol, (4-methyl-2,6-di-(t-butyl)phenol), and 4,4′-methylenebis(2,6-di-t-butylphenol).

4. A working fluid composition for a refrigerating machine comprising:

a refrigerant comprising 20 mass % to 60 mass % of trifluoroethylene with respect to the total amount of the refrigerant, and

a refrigerating machine oil comprising:

an additive comprising an acid scavenger; and

a base oil comprising an ester of a fatty acid and a polyhydric alcohol, the ester having a carbon/oxygen molar ratio of 4.0 to 5.0;

wherein a content of the additive is 5 mass % or less with respect to the total amount of the refrigerating machine oil, and

the fatty acid comprises a branched fatty acid having 4 to 9 carbon atoms in a proportion of 50 to 100 mol %.

5. A working fluid composition for a refrigerating machine according to claim 4 ,

wherein the polyhydric alcohol comprises at least one selected from the group consisting of neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, and dipentaerythritol; and

the branched fatty acid comprises at least one selected from the group consisting of isobutanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid.

6. A working fluid composition for a refrigerating machine according to claim 5 ,

wherein the fatty acid consists of at least one fatty acid selected from the group consisting of isobutanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid.

7. A working fluid composition for a refrigerating machine according to claim 5 ,

wherein the refrigerant comprises:

trifluoroethylene; and

at least one refrigerant selected from the group consisting of difluoromethane (HFC-32), pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1,2,3,3-hexafluoropropane (HFC-236ea), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa), 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,3,3-pentafluorobutane (HFC-365mfc), 1,2,3,3,3-pentafluoropropene (HFO-1225ye), 1,3,3,3-tetrafluoropropene (HFO-1234ze), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1,2,3,3 -tetrafluoropropene (HFO-1234ye), and 3,3,3 -trifluoropropene (HFO-1243zf).

8. A working fluid composition for a refrigerating machine according to claim 7 ,

wherein the acid scavenger comprises at least one compound selected from the group consisting of a glycidyl ether epoxy compound, a glycidyl ester epoxy compound, an oxirane compound, an alkyloxirane compound, an alicyclic epoxy compound, an epoxidized fatty acid monoester, an epoxidized vegetable oil, a dialkylcarbodiimide, a diphenylcarbodiimide, and a bis(alkylphenyl)carbodiimide.

9. A working fluid composition for a refrigerating machine according to claim 7 ,

wherein the glycidyl ether epoxy compound comprises at least one compound selected from the group consisting of n-butylphenyl glycidyl ether, i-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, tert-butylphenyl glycidyl ether, pentylphenyl glycidyl ether, hexylphenyl glycidyl ether, heptylphenyl glycidyl ether, octylphenyl glycidyl ether, nonylphenyl glycidyl ether, decylphenyl glycidyl ether, decyl glycidyl ether, undecyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, 2-ethylhexyl glycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether, sorbitol polyglycidyl ether, polyalkylene glycol monoglycidyl ether, and polyalkylene glycol diglycidyl ether,

the glycidyl ester epoxy compound comprises at least one compound selected from the group consisting of glycidyl benzoate, glycidyl neodecanoate, glycidyl-2,2-dimethyloctanoate, glycidyl acrylate, and glycidyl methacrylate,

the dialkylcarbodiimide comprises at least one compound selected from the group consisting of diisopropylcarbodiimide and dicyclohexylcarbodiimide, and

the bis(alkylphenyl)carbodiimide comprises at least one compound selected from the group consisting of ditolylcarbodiimide, bis(isopropylphenyl)carbodiimide, bis(diisopropylphenyl)carbodiimide, bis(triisopropylphenyl)carbodiimide, bis(butylphenyl)carbodiimide, bis(dibutylphenyl)carbodiimide, and bis(nonylphenyl)carbodiimide.

10. A working fluid composition for a refrigerating machine according to claim 7 ,

wherein the acid scavenger comprises at least one compound selected from the group consisting of 2-ethylhexyl glycidyl ether, glycidyl neodecanoate, diisopropylcarbodiimide, and bis(diisopropylphenyl)carbodiimide.

11. A working fluid composition for a refrigerating machine according to claim 5 ,

wherein the refrigerant comprises trifluoroethylene and difluoromethane.