Composition for cooling and lubricating a propulsion system of an electric or hybrid vehicle

1. A method for cooling and lubricating a propulsion system of an electric or hybrid vehicle, comprising a step of bringing at least one mechanical component of said system into contact with a composition comprising:

(i) from 60% to 99.5% by weight of at least one synthetic base oil, based on a total weight of the composition, the synthetic base oil having a kinematic viscosity of from 1.5 to 8 mm 2 /s, measured at 100° C. according to standard ASTM D445; and

(ii) at least one diester of formula (I), different than the synthetic base oil (i):

R a —C(O)—O—([C(R) 2 ] n —O) s —C(O)—R b   (I)

in which:

R represents, independently of one another, a hydrogen atom or a linear or branched (C 1 -C 5 )alkyl group;

s has a value of 1 or 2;

n has a value of 1, 2 or 3; wherein, when s is different from 1, n may be identical or different; and

R a and R b , which may be identical or different, represent independently of one another, saturated or unsaturated, linear or branched, hydrocarbon groups having a linear chain with 2 to 11 carbon atoms,

wherein when s has a value of 1 and n has a value of 3, at least one of the R groups bound to the carbon in the beta position of the oxygen atoms of the ester groups represents a hydrogen atom.

2. The method as claimed in claim 1 , in which the diester of formula (I) is a diester of formula (I′):

R a —C(O)—O—([C(R) 2 ] n —O)—([C(R′) 2 ] m —O) s-1 —C(O)—R b   (I′)

in which:

R and R′ represent, independently of one another, a hydrogen atom or a linear or branched (C 1 -C 5 )alkyl group;

s has a value of 1 or 2;

n has a value of 2;

m has a value of 2;

R a and R b , which may be identical or different, represent independently of one another, saturated or unsaturated, linear or branched, hydrocarbon groups having a linear chain with 2 to 11 carbon atoms;

wherein, when s has a value of 2, at least one of the groups R or R′ represents a linear or branched (C 1 -C 5 )alkyl group.

3. The method as claimed in claim 1 , wherein the diester or diesters of formula (I) are present in an amount ranging from 1 to 30 wt %, relative to the total weight of the composition.

4. The method as claimed in claim 1 , in which the composition further comprises at least one additive chosen from hydrocarbon-containing fluids having a boiling point greater than or equal to 50° C., radical inhibitors, friction modifiers, detergents, antiwear additives, extreme-pressure additives, dispersants, antioxidants, pour-point improvers, antifoaming agents, or mixtures thereof.

5. The method as claimed in the claim 1 , wherein said at least one mechanical component is a battery, and the battery is immersed or semi-immersed, static or circulating, in said composition.

6. The method as claimed in claim 1 , wherein said at least one mechanical component is a battery, and the composition is brought into direct contact with the battery by injection, jet, spraying, or misting.

7. The method as claimed in claim 1 , wherein the synthetic base oil has a kinematic viscosity, measured at 100° C. according to standard ASTM D445, from 1.5 to 2.1 mm 2 /s.

8. The method as claimed in claim 1 , wherein the composition comprises from 90% to 97% by weight of the synthetic base oil.

9. The method as claimed in claim 1 , in which the diester or diesters of formula (I) are present in an amount ranging from 10 to 25 wt %, relative to the total weight of the composition.

10. The method as claimed in claim 1 , wherein at least one mechanical component of said system is at least one battery cell.

11. The method as claimed in claim 1 , wherein at least one mechanical component of said system is a lithium-ion or nickel-cadmium battery.

12. A method for extending the oil-changing interval of a propulsion system of an electric or hybrid vehicle comprising a step of adding into a composition comprising:

from 60% to 99.5% by weight of at least one synthetic base oil, based on a total weight of the composition, the synthetic base oil having a kinematic viscosity of from 1.5 to 8 mm 2 /s, measured at 100° C. according to standard ASTM D445; and

a diester of formula (I):

R a —C(O)—O—([C(R) 2 ] n —O) s —C(O)—R b   (I)

in which:

R represents, independently of one another, a hydrogen atom or a linear or branched (C 1 -C 5 )alkyl group;

s has a value of 1 or 2;

n has a value of 1, 2 or 3; wherein, when s is different from 1, n may be identical or different; and

R a and R b , which may be identical or different, represent independently of one another, saturated or unsaturated, linear or branched, hydrocarbon groups having a linear chain with 2 to 11 carbon atoms,

wherein when s has a value of 1 and n has a value of 3, at least one of the R groups bound to the carbon in the beta position of the oxygen atoms of the ester groups represents a hydrogen atom.

13. The method as claimed in claim 12 , wherein the diester of formula (I) is a diester of formula (I′):

R a —C(O)—O—([C(R) 2 ] n —O)—([C(R′) 2 ] m —O) s-1 —C(O)—R b   (I′)

in which:

R and R′ represent, independently of one another, a hydrogen atom or a linear or branched (C 1 -C 5 )alkyl group;

s has a value of 1 or 2;

n has a value of 2;

m has a value of 2;

R a and R b , which may be identical or different, represent independently of one another, saturated or unsaturated, linear or branched, hydrocarbon groups having a linear chain with 2 to 11 carbon atoms;

wherein, when s has a value of 2, at least one of the groups R or R′ represents a linear or branched (C 1 -C 5 )alkyl group.

14. The method as claimed in claim 12 , wherein the diester or diesters of formula (I) are present in an amount ranging from 1 to 30 wt %, relative to the total weight of the composition.