Lubricating and cooling fluid for an electric motor system

1. A method for lubricating gears and clutches in an electric motor system, wherein the electric motor system comprises a sump, copper windings in a stator, gears and clutches, and simultaneously cooling a motor thereof, the method comprising:

operating an electric motor system, containing a lubricating and cooling fluid, such that a temperature of the lubricating and cooling fluid in a sump of the electric motor system is between 70° C. and 125° C. and the temperature of copper windings in a stator of the electric motor system is between 150° C. and 180° C.;

lubricating gears and clutches in the electric motor system with the lubricating and cooling fluid and simultaneously cooling the motor in the electric motor system by contacting the copper windings with the lubricating and cooling fluid; and

wherein the lubricating and cooling fluid comprises:

an oil of lubricating viscosity comprises an API Group III base oil, API Group IV base oil, or mixtures thereof;

at least one thiadiazole or hydrocarbyl-substituted derivatives thereof delivering about 1000 to about 1500 ppm sulfur to the lubricating and cooling fluid;

a dispersant system including comprising (1) a first dispersant obtained from polyisobutylene having a number average molecular weight of about 1500 to about 2500 and delivering up to about 700 ppm nitrogen to the lubricating and cooling fluid and (i1) a second dispersant having a number average molecular weight of about 1000 or less and delivering up to about 150 ppm nitrogen to the lubricating and cooling fluid;

an alkoxylated aliphatic amine delivering up to about 20 ppm nitrogen to the lubricating and cooling fluid;

an ether amine delivering up to about 20 ppm nitrogen to the lubricating and cooling fluid; and

wherein at least one of the first dispersant and the second dispersant is borated and phosphorylated such that a total amount of boron and phosphorus in the dispersant system relative to the nitrogen in the dispersant system is from about 0.5 to about 0.7 and wherein the first and second dispersants deliver up to about 100 ppm of total boron and phosphorus per 1000 number average molecular weight of the combined polyisobutylene moieties used in the dispersant system. first and second dispersants deliver up to about 100 ppm of total boron and phosphorus per 1000 number average molecular weight of the combined polyisobutylene moieties used in the dispersant system.

2. The method of claim 1 , where the at least one thiadiazole or hydrocarbyl-substituted derivatives thereof includes one or more compounds having a structure of Formula I:

wherein

each R 1 i is independently hydrogen or sulfur;

each R 2 is independently an alkyl group;

n is an integer of 0 or 1 and if R 1 is hydrogen then the integer n of the adjacent R 2 moiety is 0 and if R 1 is sulfur then the n of the adjacent R 2 moiety is 1; and

wherein at least one R l is sulfur.

3. The method of claim 2 , wherein the at least one thiadiazole or hydrocarbyl-substituted derivatives thereof is a thiadiazole mixture of 2,5-bis-(nonyldithio)-1,3,4-thiadiazole, and 2,5-mono-(nonyldithio)-1,3,4-thiadiazole.

4. The method of claim 1 , wherein the lubricating and cooling fluid further comprises a fatty diamine delivering up to about 3 ppm nitrogen to the lubricating and cooling fluid.

5. The method of claim 4 , wherein the combination of the alkoxylated aliphatic amine, the ether amine, and the fatty diamine deliver nitrogen in amounts of about 30 ppm or less nitrogen to the lubricating and cooling fluid.

6. The method of claim 5 , wherein the alkoxylated aliphatic amine is a di(hydroxyalkyl) aliphatic tertiary amine comprising hydroxyalkyl groups each containing from 2 to 4 carbon atoms, and further comprising an acyclic hydrocarbyl group containing from 16 to 25 carbon atoms.

7. The method of claim 6 , wherein the ether amine comprises isodecyloxypropylamine.

8. The method of claim 7 , wherein the fatty diamine comprises n-oleyl-1,3-diaminopropane.

9. The method of claim 5 , wherein the lubricating and cooling fluid further comprises a sulfurized ester delivering about 300 ppm or less sulfur and wherein the alkoxylated aliphatic amine and the ether amine each deliver up to about 15 ppm nitrogen to the lubricating and cooling fluid and wherein the at least one thiadiazole or hydrocarbyl-substituted derivatives thereof is a thiadiazole mixture of 2,5-bis-(nonyldithio)-1,3,4-thiadiazole, and 2,5-mono-(nonyldithio)-1,3,4-thiadiazole, and wherein the combination of the thiadiazole mixture and the sulfurized ester deliver about 1400 to about 1800 ppm sulfur to the lubricating and cooling fluid.

10. The method of claim 1 , wherein the first dispersant is present in an amount to deliver up to about 500 ppm nitrogen to the lubricating and cooling fluid.

11. The method of claim 10 , wherein the second dispersant is present in an amount to deliver up to about 115 ppm nitrogen to the lubricating and cooling fluid.

12. The method of claim 11 , wherein the first dispersant is obtained from polyisobutylene having a number average molecular weight of about 2000 to about 2400 and the second dispersant is obtained from polyisobutylene having a number average molecular weight of about 950.

13. The method of claim 12 , wherein the first dispersant delivers boron and phosphorus in amounts of about 100 ppm or less boron and about 250 ppm or less phosphorus to the lubricating and cooling fluid.

14. The method of claim 1 , wherein the oil of lubricating viscosity includes the Group III base oil.

15. The method of claim 1 , wherein the oil of lubricating viscosity includes a gas-to-liquid (GTL) base oil.

16. The method of claim 1 , wherein the oil of lubricating viscosity includes a polyalphaolefin (PAO) base oil.

17. The method of claim 1 , wherein the lubricating fluid has an initial electrical conductivity of about 60 nS/M or less, as measured by a modified ASTM D2624-15 using the lubricating and cooling fluid at 20 Hz and at 100° C.

18. The method of claim 1 , wherein the lubricating and cooling fluid further comprises a sulfurized ester delivering about 180 to about 300 ppm sulfur to the lubricating and cooling fluid.

19. The method of claim 18 , wherein the combination of the at least one thiadiazole or hydrocarbyl-substituted derivatives thereof and the sulfurized ester deliver about 1400 to about 1800 ppm sulfur to the lubricating and cooling fluid.

20. The method of claim 18 , wherein the sulfurized ester comprises sulfurized transesterified triglycerides.

21. A lubricating and cooling fluid for an electric motor system , wherein the electric motor system comprises a sump, copper windings in a stator, gears and clutches, the lubricating and cooling fluid comprising:

a majority base oil of lubricating viscosity comprising an API Group III base oil, an API Group IV base oil, or mixtures thereof;

at least one thiadiazole or hydrocarbyl-substituted derivatives thereof delivering about 1000 to about 1500 ppm sulfur to the lubricating and cooling fluid;

a dispersant system comprising (i) a first dispersant obtained from polyisobutylene having a number average molecular weight of about 1500 to about 2500 and delivering nitrogen in amounts of about 700 ppm or less nitrogen to the lubricating and cooling fluid and (ii) a second dispersant obtained from polyisobutylene having a number average molecular weight of about 1000 or less and delivering nitrogen in amounts of about 150 ppm or less nitrogen to the lubricating and cooling fluid;

an alkoxylated aliphatic amine delivering up to about 20 ppm nitrogen to the lubricating and cooling fluid;

an ether amine delivering up to about 20 ppm nitrogen to the lubricating and cooling fluid;

wherein at least one of the first dispersant and the second dispersant is borated and phosphorylated such that a total amount of boron and phosphorus in the dispersant system relative to the nitrogen in the dispersant system is from about 0.5 to about 0.7 and wherein the first and second dispersants deliver up to about 100 ppm of total boron and phosphorus per 1000 number average molecular weight of the combined polyisobutylene moieties used in the dispersant system;

wherein the lubricating and cooling fluid has an electrical conductivity of 60 nS/M or less, as measured by ASTM D2624-15 at 20 Hz and at 100° C.

22. The lubricating and cooling fluid of claim 21 , where the at least one thiadiazole or hydrocarbyl-substituted derivatives thereof includes one or more compounds having a structure of Formula I:

wherein

each R 1 is independently hydrogen or sulfur;

each R 2 is independently an alkyl group;

n is an integer of 0 or 1 and if R 1 is hydrogen then the integer n of the adjacent R 2 moiety is 0 and if R 1 is sulfur then the n of the adjacent R 2 moiety is 1; and

wherein at least one R l is sulfur.

23. The lubricating and cooling fluid of claim 21 , wherein the at least one thiadiazole or hydrocarbyl-substituted derivatives thereof comprises a thiadiazole mixture of 2,5-bis-(nonyldithio)-1,3,4-thiadiazole, and 2,5-mono-(nonyldithio)-1,3,4-thiadiazole.

24. The lubricating and cooling fluid of claim 21 wherein the fluid further comprises a fatty diamine delivering up to about 3 ppm nitrogen to the lubricating and cooling fluid.

25. The lubricating and cooling fluid of claim 24 , wherein the combination of the alkoxylated aliphatic amine, the ether amine, and the fatty diamine deliver up to about 30 ppm of nitrogen to the lubricating and cooling fluid.

26. The lubricating and cooling fluid of claim 25 , wherein alkoxylated aliphatic amine is a di(hydroxyalkyl) aliphatic tertiary amine comprising hydroxyalkyl groups each containing from 2 to 4 carbon atoms, and further comprising an acyclic hydrocarbyl group containing from 16 to 25 carbon atoms.

27. The lubricating and cooling fluid of claim 26 , wherein the ether amine is isodecyloxypropylamine.

28. The lubricating and cooling fluid of claim 27 , wherein the fatty diamine is n-oleyl-1,3-diaminopropane.

29. The lubricating and cooling fluid of claim 25 , further comprising a sulfurized ester delivering about 300 ppm or less sulfur to the lubricating and cooling fluid and wherein the alkoxylated aliphatic amine and ether amine each deliver up to about 15 ppm nitrogen to the lubricating and cooling fluid and wherein the at least one thiadiazole or hydrocarbyl-substituted derivatives thereof is a thiadiazole mixture of 2,5-bis-(nonyldithio)-1,3,4-thiadiazole and 2,5-mono-(nonyldithio)-1,3,4-thiadiazole and wherein the combination of the thiadiazole mixture and the sulfurized ester deliver about 1400 to about 1800 ppm sulfur to the lubricating and cooling fluid.

30. The lubricating and cooling fluid of claim 21 , wherein the first dispersant is present in an amount to deliver up to about 500 ppm nitrogen to the lubricating and cooling fluid.

31. The lubricating and cooling fluid of claim 30 , wherein the second dispersant is present in an amount to deliver up to about 115 ppm nitrogen to the lubricating and cooling fluid.

32. The lubricating and cooling fluid of claim 31 , wherein the first dispersant is obtained from polyisobutylene having a number average molecular weight of about 2000 to about 2400 and the second dispersant is obtained from polyisobutylene having a number average molecular weight of about 950.

33. The lubricating and cooling fluid of claim 32 , wherein the first dispersant delivers boron and phosphorus in amounts of about 100 ppm or less boron and about 250 ppm or less phosphorus to the lubricating fluid.

34. The lubricating and cooling fluid of claim 21 , wherein the first dispersant is obtained from polyisobutylene having a number average molecular weight of about 2000 to about 2400 and the second dispersant is obtained from polyisobutylene having a number average molecular weight of about 950.

35. The lubricating and cooling fluid of claim 21 wherein the base oil includes Group III base oil.

36. The lubricating and cooling fluid of claim 21 wherein the base oil includes gas-to-liquid (GTL) base oil.

37. The lubricating and cooling fluid of claim 21 wherein the base oil includes a polyalphaolefin (PAO) base oil.

38. The lubricating and cooling fluid of claim 21 , wherein the lubricating fluid further comprises a sulfurized ester delivering about 180 to about 300 ppm sulfur to the lubricating fluid.

39. The lubricating and cooling fluid of claim 38 , wherein the combination of the at least one thiadiazole or hydrocarbyl-substituted derivatives thereof and the sulfurized ester deliver about 1400 to about 1800 ppm sulfur to the lubricating fluid.