Lubricants for refrigeration systems
View Patent ↗A polyol ester suitable for use as a lubricant or a lubricant base stock has a kinematic viscosity at 40° C. less than or equal to 22 cSt and a viscosity index of greater than or equal to 140. The ester comprises a reaction product of (a) at least one polyhydric alcohol having at least 2 primary hydroxyl groups, (b) at least one monocarboxylic acid having 2 to 15 carbon atoms and (c) at least one polycarboxylic acid having 2 to 15 carbon atoms, wherein the number of acid groups derived from the polycarboxylic acid(s) is at least 25% of the total number of acid groups derived from the monocarboxylic and polycarboxylic acids.
1. A polyol ester suitable for use as a lubricant or a lubricant base stock, the ester having a kinematic viscosity at 40° C. less than or equal to 22 cSt and a viscosity index of greater than or equal to 140 and the ester comprising a reaction product of
(a) at least one polyhydric alcohol having at least 2 primary hydroxyl groups selected from pentaerythritol, dipentaerythritol, tripentaerythritol, tetrapentaerythritol, trimethylolpropane, trimethylolethane, neopentyl glycol and mixtures thereof,
(b) at least one monocarboxylic acid having 2 to 15 carbon atoms wherein from about 25 mole % to about 100 mole % of the at least one monocarboxylic acid, based on total moles of monocarboxylic acid, is one or more linear monocarboxylic acids, and
(c) at least one polycarboxylic acid having 2 to 15 carbon atoms, wherein the number of acid groups derived from the polycarboxylic acid(s) is 25 to 50% of the total number of acid groups derived from the monocarboxylic and polycarboxylic acids.
2. The ester of claim 1 , wherein said at least one polyhydric alcohol is selected from trimethylolpropane, neopentyl glycol and mixtures thereof.
3. The ester of claim 1 , wherein said at least one polyhydric alcohol is neopentylglycol.
4. The ester of claim 1 , wherein said at least one monocarboxylic acid has 5 to 11 carbon atoms.
5. The ester of claim 1 , wherein said at least one monocarboxylic acid has 6 to 10 carbon atoms.
6. The ester of claim 1 , wherein said at least one monocarboxylic acid is selected from butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, 3- methylbutanoic acid, 2-methylbutanoic acid, 2-ethylhexanoic acid, 2,4-dimethylpentanoic acid, 3,3,5-trimethylhexanoic acid, benzoic acid and mixtures thereof.
7. The ester of claim 6 , wherein said at least one monocarboxylic acid comprises a mixture of at least one linear monocarboxylic acid selected from pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid
and at least one branched monocarboxylic acid selected from 3-methylbutanoic acid, 2-methylbutanoic acid, 2-ethylhexanoic acid, 2,4-dimethylpentanoic acid, and 3,3,5-trimethylhexanoic acid.
8. The ester of claim 7 , wherein said at least one linear monocarboxylic acid comprises n-heptanoic acid.
9. The ester of claim 7 , wherein said mixture comprises about 25 mole % to about 75 mole % of said at least one linear monocarboxylic acid.
10. The ester of claim 6 , wherein (b) comprises n-heptanoic acid.
11. The ester of claim 6 , wherein said at least one polycarboxylic acid comprises adipic acid.
12. The ester of claim 1 , wherein said at least one polycarboxylic acid has 4 to 10 carbon atoms.
13. The ester of claim 1 , wherein said at least one polycarboxylic acid comprises adipic acid.
14. The ester of claim 1 and having a kinematic viscosity at 40° C. less than or equal to 20 cSt.
15. A lubricant blend comprising a mixture of the polyol ester of claim 1 and a further polyol ester having a different kinematic viscosity than said first mentioned polyol ester.
16. The blend of claim 15 wherein said further polyol ester consists essentially of a reaction product of at least one polyhydric alcohol having at least 2 primary hydroxyl groups and at least one monocarboxylic acid.
17. The blend of claim 15 wherein said further polyol ester has a kinematic viscosity at 40° C. greater than or equal to 40 cSt.
18. A working fluid comprising a halogenated hydrocarbon refrigerant and the polyol ester of claim 1 .
19. The working fluid of claim 18 wherein the refrigerant is a hydrofluorocarbon, a fluorocarbon or a mixture thereof.
20. The ester of claim claim 1 comprising a reaction product of (a) neopentylglycol, (b) at least one monocarboxylic acid having 5 to 9 carbon atoms wherein from about 25 mole % to about 100 mole % of the at least one monocarboxylic acid, based on total moles of monocarboxylic acid, is one or more linear monocarboxylic acids, and (c) at least one polycarboxylic acid selected from succinic acid, glutaric acid, adipic acid and mixtures thereof, wherein the number of acid groups derived from the polycarboxylic acid(s) is 25% to 50 of the total number of acid groups derived from the monocarboxylic and polycarboxylic acids.
21. The ester of claim 20 , wherein said at least one polycarboxylic acid comprises adipic acid.
22. A lubricant blend comprising a mixture of the polyol ester of claim 20 and a further polyol ester having a different kinematic viscosity than said first mentioned polyol ester.
23. The blend of claim 22 wherein said further polyol ester consists essentially of a reaction product of at least one polyhydric alcohol having at least 2 primary hydroxyl groups and at least one monocarboxylic acid.
24. The blend of claim 22 wherein said further polyol ester has a kinematic viscosity at 40° C. greater than or equal to 40 cSt.
25. A working fluid comprising a halogenated hydrocarbon refrigerant and the polyol ester of claim 20 .
26. The working fluid of claim 25 wherein the refrigerant is a hydrofluorocarbon, a fluorocarbon or a mixture thereof.
27. The ester of claim 20 , wherein said at least one monocarboxylic acid is selected from pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, 3-methylbutanoic acid, 2-methylbutanoic acid, 2-ethylhexanoic acid, 2,4-dimethylpentanoic acid, 3,3,5-trimethylhexanoic acid, and mixtures thereof.
28. The ester of claim 27 , wherein said at least one monocarboxylic acid comprises n-heptanoic acid and 2-methylbutanoic acid and/or 3,3,5-trimethylhexanoic wherein of about 25 mole% to about 75 mole% of said at least one monocarboxylic acid is n-heptanoic acid.
29. The ester of claim 28 , wherein wherein said at least one polycarboxylic acid comprises adipic acid.
30. A working fluid comprising a halogenated hydrocarbon refrigerant and the polyol ester of claim 28 .
31. The working fluid of claim 30 wherein the refrigerant is a hydrofluorocarbon, a fluorocarbon or a mixture thereof.
32. The ester of claim 27 , wherein said at least one monocarboxylic acid consistis of n-heptanoic acid.
33. The ester of claim 32 , wherein wherein said at least one polycarboxylic acid comprises adipic acid.
34. A working fluid comprising a halogenated hydrocarbon refrigerant and the polyol ester of claim 32 .
35. The working fluid of claim 34 wherein the refrigerant is a hydrofluorocarbon, a fluorocarbon or a mixture thereof.