Refrigeration compressor lubricant

1. A lubricant and refrigerant combination, comprising:

a lubricant composition, comprising a mixture of:

(a) about 30 to about 70% by weight of the mixture of one or more first ester compounds having a structure

wherein each of R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 is independently H or methyl; each of a, b, c, x, y, and z is independently an integer and a+x, b+y, and c+z are each independently an integer 1 to about 20; and R 7 , R 8 , and R 9 are each independently selected from the group consisting of straight-chain and branched alkyl, and straight-chain and branched alkenyl groups having 3 to about 8 carbon atoms that may be substituted or unsubstituted; and

(b) from about 30 to about 70% by weight of the mixture of one or more second ester compounds having a structure

wherein each of R 11 and R 12 is independently H or methyl; each of m and n is independently an integer and m+n is an integer 1 to about 10; and R 10 and R 13 are each independently selected from the group consisting of straight-chain and branched alkyl, and straight-chain and branched alkenyl groups having 3 to about 8 carbon atoms that may be substituted or unsubstituted, wherein the lubricant composition is free of lubricant compounds other than the the first ester compound or compounds (a) and the second ester compound or compounds (b); and

a refrigerant composition selected from the group consisting of R410a, R32, and HFO refrigerants, combinations of these refrigerants, and combinations or refrigerants comprising at least one of these refrigerants, wherein the lubricant and refrigerant combination has a minimum miscibility temperature of about −40° C. or lower.

2. A lubricant composition according to claim 1 , wherein

(a) each of a+x, b+y, and c+z is independently an integer 1 to about 10, or

(b) m+n is an integer about 2 to about 8, or

(c) each of a+x, b+y, and c+z is independently an integer 1 to about 10 and m+n is an integer about 2 to about 8.

3. A lubricant composition according to claim 1 , wherein

(a) each of R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 is H, or

(b) each of R 11 and R 12 is H, or

(c) each of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 11 , and R 12 is H.

4. A lubricant and refrigerant combination, comprising:

a lubricant composition, comprising a mixture of:

(a) about 20 to about 80% by weight of the mixture of one or more first ester compounds having a structure

wherein x, y, and z are each independently an integer 2 to about 8 and R 7 , R 8 , and R 9 are each independently selected from the group consisting of straight-chain and branched alkyl and straight-chain and branched alkenyl groups having 3 to about 8 carbon atoms that may be substituted or unsubstituted; and

(b) from about 20 to about 80% by weight of the mixture of one or more second ester compounds having a structure

wherein m is an integer 1 to about 10 and R 10 and R 13 are each independently selected from the group consisting of straight-chain and branched alkyl, and straight-chain and branched alkenyl groups having 3 to about 8 carbon atoms that may be substituted or unsubstituted, wherein the lubricant composition is free of lubricant compounds other than the first ester compound or compounds (a) and the second ester compound or compounds (b); and

a refrigerant composition selected from the group consisting of R410a, R32, and HFO refrigerants, combinations of these refrigerants, and combinations or refrigerants comprising at least one of these refrigerants, wherein the lubricant and refrigerant combination has a minimum miscibility temperature of about −55° C. or lower.

5. A lubricant composition according to claim 1 , wherein the composition meets one or both of the conditions

(a-1) R 7 , R 8 , and R 9 together have an average of about 5 to about 7 carbon atoms and

(a-2) R 10 and R 13 together have an average of about 5 to about 7 carbon atoms.

6. A lubricant composition according to claim 1 , wherein the mixture consists of about 40 to about 60% by weight of the one or more first ester compounds (a) and about 40 to about 60% by weight of the one or more second ester compounds (b).

7. A lubricant composition according to claim 1 , wherein a major portion by weight of the mixture is the one or more first ester compounds (a).

8. A lubricant according to claim 1 , wherein at least one of the first and second ester compounds is an ester of n-pentanoic acid, 2-methylbutanoic acid, n-hexanoic acid, n-heptanoic acid, 3,3,5-trimethylhexanoic acid, 2-ethylhexanoic acid, n-octanoic acid, n-nonanoic acid, or combinations thereof.

9. A lubricant according to claim 1 , wherein at least one of the first and second ester compounds is an ester of n-butyric acid, isobutyric acid, n-pentanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, 2-ethylhexanoic acid, 3,3,5-trimethylhexanoic acid, n-nonanoic acid, or combinations thereof.

10. A lubricant according to claim 1 , wherein the first ester compound or compounds (a) comprise a glycerol ethoxylate triester and the second ester compound or compounds (b) comprise at least one of a triethylene glycol diester and a tetraethylene glycol diester.

11. A lubricant composition according to claim 1 , further including an additive or additives selected from the group consisting of antioxidants, anti-wear agents, extreme-pressure agents, oiliness agents, antifoaming agents, metal inactivating agents, viscosity index improvers, pour point depressants, detergent dispersants, stabilizers, metal passivators, corrosion inhibitors, flammability suppressants, acid scavengers, and combinations thereof.

12. A lubricant composition according to claim 11 , comprising about 0.1 to about 5% by weight of the additive or additives.

13. A lubricant composition according to claim 11 , wherein the additive is selected from the group consisting of diaryl sulfides, arylalkyl sulfides, dialkyl sulfides, diaryl disulfides, arylalkyl disulfides, dialkyl disulfides, diaryl polysulfides, arylalkyl polysulfides, dialkyl polysulfides, dithiocarbamates, derivatives of 2-mercaptobenzothiazole, derivatives of 2,5-dimercapto-1,3,4-thiadiazole, and combinations thereof.

14. A lubricant composition according to claim 11 , wherein the additive is selected from the group consisting of 2,5-bis(n-octyldithio)-1,3,4-thiadiazole, dioctyl disulfide, and combinations thereof.

15. A lubricant and refrigerant combination according to claim 1 , having a minimum miscibility temperature of about −55° C. or lower.

16. A compression-type heat transfer device comprising a lubricant and refrigerant combination composition according to claim 1 .

17. A lubricant and refrigerant combination, comprising:

a lubricant composition comprising:

(a) about 20 to about 80% by weight of one or more first ester compounds comprising a glycerol ethoxylate ester formed by esterification with 3,3,5-trimethylhexanoic acid; and

(b) about 20 to about 80% by weight of one or more second ester compounds comprising a triethylene glycol ester formed by esterification with 3,3,5-trimethylhexanoic acid, a tetraethylene glycol ester formed by esterification with 3,3,5-trimethylhexanoic acid, or a combination of the triethylene glycol ester formed by esterification with 3,3,5-trimethylhexanoic acid and the tetraethylene glycol ester formed by esterification with 3,3,5-trimethylhexanoic acid, wherein the first ester compound or compounds (a) and the second ester compound or compounds (b) together form greater than or equal to about 50% by weight of the lubricant composition; and

a refrigerant composition selected from the group consisting of R410a, R32, and HFO refrigerants, combinations of these refrigerants, and combinations or refrigerants comprising at least one of these refrigerants, wherein the lubricant and refrigerant combination has a minimum miscibility temperature of about −55° C. or lower.

18. A lubricant and refrigerant combination according to claim 17 , wherein the one or more second ester compounds comprises a tetraethylene glycol ester of 3,3,5-trimethylhexanoic acid.