Lubricating oil composition for refrigerating machines

1. A refrigerant composition, comprising:

(a) a lubricating oil composition comprising

(a1) a base oil; and

(a2) an additive comprising a coumarin compound; and

(b) a refrigerant,

wherein:

the coumarin compound is selected from the group consisting of 10-oxo-2,3,5,6-tetrahydro-4H,10H-11-oxa-3a-aza-1H-benzo[de]anthracene-9-carboxylic acid ethyl, and 7-diethylamino-4-methylcoumarin; and

a content of the coumarin compound ranges from 0.001 mass % to mass %, based on the total amount of the lubricating oil composition (a).

2. The refrigerant composition of claim 1 , wherein:

the lubricating oil composition is adapted to function as a lubricating oil for a refrigerating machine; and

the refrigerant comprises at least one of a saturated hydrofluorocarbon compound (saturated HFC), carbon dioxide (CO 2 ), a hydrocarbon (HC) having 5 or less carbon atoms, ammonia, and a fluorine-containing organic compound represented by formula (A):

C p O q F r R s   (A);

R represents Cl, Br, I or hydrogen;

p is an integer of 1 to 6;

q is an integer of 0 to 2;

r is an integer of 1 to 14; and

s is an integer of 0 to 13,

with a proviso that when q is 0, p is an integer of 2 to 6 and one or more unsaturated carbon-carbon bonds are contained in a molecule of the fluorine-containing organic compound.

3. The refrigerant composition of claim 2 , wherein the refrigerant is a saturated HFC having 1 to 3 carbon atoms or an unsaturated HFC having 3 carbon atoms and having a carbon-carbon double bond.

4. The refrigerant composition of claim 1 ,wherein:

the base oil comprises at least one compound selected from the group consisting of an alkylbenzene, an alkylnaphthalene, a poly-alpha-olefin, a polyvinylether, a polyalkylene glycol, a polycarbonate, a polyol ester and an ether compound represented by formula (1):

Ra—[(ORb) n -(B)—(ORc) k]x -Rd  (1);

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 bonds and having 1 to 10 carbon atoms;

Rb and Rc each represent an alkylene group having 2 to 4 carbon atoms;

n and k each are an integer of 0 to 20;

x is an integer of 1 to 6;

(B) represents a polymer portion having 3 or more monomer units represented by formula (2):

R 4 , R 5 and R 6 each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms and are 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 is a number with an average of 0 to 10 and plural m are mutually the same or different in each unit;

R 4 to R 8 are mutually the same or different in each unit;

plural R 7 O are mutually the same or different; and

m the formula (2) is an integer of 1 or more when k and n in the formula (1) are both 0.

5. The refrigerant composition of claim 1 , wherein the base oil (a1) has a kinematic viscosity at 100 degrees C ranging from 1 mm 2 /s to 50 mm 2 /s.

6. The refrigerant composition of claim 1 , wherein the lubricating oil composition (a) comprises at least another additive selected from the group consisting of an extreme pressure agent, an oiliness agent, an antioxidant, an acid scavenger, a metal deactivator and an antifoaming agent.

7. The refrigerant composition of claim 1 , wherein the lubricating oil composition is adapted to function as a lubricating oil for refrigerating equipment selected from the group consisting of an open-type automobile air-conditioner, an electric automobile air-conditioner, a gas heat pump, other air-conditioning equipment, a refrigerating machine, a vending machine, a showcase, a water-heating system and a refrigerating/heating system.

8. The refrigerant composition of claim 1 , wherein the refrigerant comprises an unsaturated fluorocarbon compound.

9. The refrigerant composition of claim 1 , wherein the refrigerant comprises a propene substituted with 1 to 5 fluorine atoms.

10. The refrigerant composition of claim 1 , wherein the refrigerant comprises a combination of a saturated hydrofluorocarbon refrigerant having 1 or 2 carbon atoms and an unsaturated hydrofluorocarbon refrigerant having 3 carbon atoms.

11. The refrigerant composition of claim 1 , wherein the base oil comprises at least one compound selected from the group consisting of a polyvinylether, a polyalkylene glycol, a polyol ester and an ether compound represented by formula (1):

Ra—[(ORb) n -(B)—(ORc) k]x -Rd  (1);

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 bonds and having 1 to 10 carbon atoms;

Rb and Rc each represent an alkylene group having 2 to 4 carbon atoms;

n and k each are an integer of 0 to 20;

x is an integer of 1 to 6;

(B) represents a polymer portion having 3 or more monomer units represented by formula (2):

R 4 , R 5 and R 6 each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms and are 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 is a number with an average of 0 to 10 and plural m are mutually the same or different in each unit;

R 4 to R 8 are mutually the same or different in each unit;

plural R 7 O are mutually the same or different; and

m in the formula (2) is an integer of 1 or more when k and n in the formula (1) are both 0.

12. The refrigerant composition of claim 1 , wherein the base oil comprises at least one compound selected from the group consisting of a polyvinylether, a polyvinylether-polyalkyleneglycol copolymer and a polyolester.

13. The refrigerant composition of claim 1 , wherein the base oil comprises at least one compound selected from the group consisting of a polyoxypropylene glycol dimethyl ether, a polyoxypropylene glycol monomethyl ether, a poly(oxyethylene) (oxypropylene)glycol dimethyl ether, a poly(oxyethylene)(oxypropylene) glycol monomethyl ether, a polyoxypropylene glycol monobutyl ether and a polyoxypropylene glycol diacetate.

14. The refrigerant composition of claim 1 , wherein the refrigerant comprises 2,3,3,3-tetrafluoropropene.

15. The refrigerant composition of claim 1 , wherein the coumarin compound is 10-oxo-2,3,5,6-tetrahydro-4H,10H-11-oxa-3a-aza-1H-benzo[de]anthracene-9-carboxylic acid ethyl.

16. The refrigerant composition of claim 1 , wherein the coumarin compound is 7-diethylamino-4-methylcoumarin.