Estolide compositions exhibiting high oxidative stability
Provided herein are estolide compositions having high oxidative stability, said compositions comprising at least one compound of formula: in which n is an integer equal to or greater than 0; m is an integer equal to or greater than 1; R 1 , independently for each occurrence, is selected from optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched; R 2 is selected from hydrogen and optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched; and R 3 and R 4 , independently for each occurrence, are selected from optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched. Also provided herein are uses for the compositions and methods of preparing the same.
1. A composition comprising a combination of an estolide base oil and at least one amine antioxidant, said combination having a time of at least 1000 minutes when tested in a rotating pressurized vessel oxidation test using ASTM Method 2272-11,
wherein the estolide base oil has an acid value equal to or less than 0.2 mg KOH/g, and comprises at least one estolide compound selected from compounds of Formula I:
wherein
x is, independently for each occurrence, an integer selected from 0 to 20;
y is, independently for each occurrence, an integer selected from 0 to 20;
n is an integer greater than or equal to 0;
R 1 is an optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched; and
R 2 is an optionally substituted alkyl that is saturated or unsaturated, and branched or unbranched,
wherein each fatty acid chain residue of said at least one estolide compound is independently optionally substituted.
2. The composition according to claim 1 , wherein
x is, independently for each occurrence, an integer selected from 1 to 10;
y is, independently for each occurrence, an integer selected from 1 to 10;
n is an integer selected from 0 to 8;
R 1 is an optionally substituted C 1 to C 22 alkyl that is saturated or unsaturated, and branched or unbranched; and
R 2 is an optionally substituted C 1 to C 22 alkyl that is saturated or unsaturated, and branched or unbranched,
wherein each fatty acid chain residue is unsubstituted.
3. The composition according to claim 2 , wherein
x+y is, independently for each chain, an integer selected from 13 to 15; and
n is an integer selected from 0 to 6.
4. The composition according to claim 1 , wherein R 2 is an unsubstituted alkyl that is saturated or unsaturated, and branched or unbranched.
5. The composition according to claim 1 , wherein R 2 is a branched or unbranched C 1 to C 20 alkyl that is saturated or unsaturated.
6. The composition according to claim 5 , wherein R 2 is selected from C 6 to C 12 alkyl.
7. The composition according to claim 1 , wherein R 1 is a branched or unbranched C 1 to C 20 alkyl that is saturated or unsaturated.
8. The composition according to claim 1 , wherein said composition has an EN selected from an integer or fraction of an integer that is equal to or less than 2, wherein EN is the average number of linkages in compounds according to Formula I.
9. The composition according to claim 8 , wherein said estolide base oil has a kinematic viscosity equal to or less than 55 cSt when measured at 40° C.
10. The composition according to claim 9 , wherein said estolide base oil has a pour point equal to or lower than −25° C.
11. The composition according to claim 1 , wherein said combination has a time of at least 1200 minutes when tested in a rotating pressurized vessel oxidation test using ASTM Method 2272-11.
12. The composition according to claim 1 , wherein the at least one amine antioxidant is selected from one or more diphenylamine antioxidants.
13. The composition according to claim 12 , wherein the at least one amine antioxidant is selected from one or more alkylated diphenylamine antioxidants.
14. The composition according to claim 13 , wherein the at least one amine antioxidant is selected from one or more of a nonylated diphenylamine, an octylated diphenylamine, or a butylated diphenylamine.
15. The composition according to claim 1 , wherein said composition further comprises at least one lubricating oil selected from one or more of a Group I oil, a Group II oil, a Group III oil, a polyalphaolefin, a polyalkylene glycol, or an oil soluble polyalkylene glycol.
16. The composition according to claim 1 , wherein said at least one amine antioxidant comprises 0.01 to 5 wt. % of the combination.
17. The composition according claim 1 , wherein the composition is substantially free of fatty acids.
18. The composition according to claim 3 , wherein x is, independently for each occurrence, an integer selected from 7 and 8.
19. The composition according to claim 3 , wherein y is, independently for each occurrence, an integer selected from 7 and 8.
20. The composition according to claim 3 , wherein R 1 is an unsubstituted alkyl that is saturated and branched or unbranched.
21. The composition according to claim 1 , further comprising at least one phenolic antioxidant.
22. The composition according to claim 1 , wherein said combination has a time of at least 1400 minutes when tested in a rotating pressurized vessel oxidation test using ASTM Methods 2272-11.
23. The composition according to claim 1 , wherein said composition further comprises at least one additive selected from one or more of an antimicrobial agent, an extreme pressure agent, a cold flow modifier, a friction modifier, a viscosity modifier, a pour point depressant, a metal chelating agent, a metal deactivator, an antifoaming agent, or a demulsifier.
24. The composition according to claim 1 , wherein the combination of the estolide base oil and the at least one amine antioxidant comprises at least 50 wt. % of the composition.
25. The composition according to claim 1 , wherein said composition comprises
50 to 70 wt. % of the estolide base oil;
25 to 49.99 wt. % of a lubricating oil; and
0.01 to 5 wt. % of the at least one amine antioxidant.
26. The composition according to claim 1 , wherein said composition comprises a hydraulic fluid, a passenger car motor oil, or a crankcase oil.
27. The composition according to claim 15 , wherein the at least one lubricating oil is an oil soluble polyalkylene glycol.
28. The composition according to claim 27 , wherein the oil soluble polyalkylene glycol is prepared by a process that includes reacting an alcohol with a mixed butylene oxide and propylene oxide feed.
29. The composition according to claim 28 , wherein the ratio of butylene oxide to propylene oxide is from about 3:1 to about 1:3.
30. The composition according to claim 20 , wherein the estolide base oil has an acid value equal to or less than 0.1 mg KOH/g.